sudo/docs/sudoers.mdoc.in

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.\"	Todd C. Miller <Todd.Miller@sudo.ws>
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.nr SL @SEMAN@
.nr AA @AAMAN@
.nr BA @BAMAN@
.nr LC @LCMAN@
.nr PS @PSMAN@
.Dd July 14, 2024
.Dt SUDOERS @mansectform@
.Os Sudo @PACKAGE_VERSION@
.Sh NAME
.Nm sudoers
.Nd default sudo security policy plugin
.Sh DESCRIPTION
The
.Nm
policy plugin determines a user's
.Nm sudo
privileges.
It is the default
.Nm sudo
policy plugin.
The policy is driven by
the
.Pa @sysconfdir@/sudoers
file or, optionally, in LDAP.
The policy format is described in detail in the
.Sx SUDOERS FILE FORMAT
section.
For information on storing
.Nm
policy information
in LDAP, see
.Xr sudoers.ldap @mansectform@ .
.Ss Configuring sudo.conf for sudoers
.Nm sudo
consults the
.Xr sudo.conf @mansectform@
file to determine which plugins to load.
If no
.Xr sudo.conf @mansectform@
file is present, or if it contains no
.Em Plugin
lines,
.Nm
will be used for auditing, policy decisions and I/O logging.
To explicitly configure
.Xr sudo.conf @mansectform@
to use the
.Nm
plugin, the following configuration can be used.
.Bd -literal -offset 4n
Plugin sudoers_audit @sudoers_plugin@
Plugin sudoers_policy @sudoers_plugin@
Plugin sudoers_io @sudoers_plugin@
.Ed
.Pp
Starting with
.Nm sudo
1.8.5, it is possible to specify optional arguments to the
.Nm
plugin in the
.Xr sudo.conf @mansectform@
file.
Plugin arguments, if any, should be listed after the path to the plugin
(i.e., after
.Pa @sudoers_plugin@ ) .
The arguments are only effective for the plugin that opens (and parses) the
.Em sudoers
file.
.Pp
For
.Nm sudo
version 1.9.1 and higher, this is the
.Em sudoers_audit
plugin.
For older versions, it is the
.Em sudoers_policy
plugin.
Multiple arguments may be specified, separated by white space.
For example:
.Bd -literal -offset 4n
Plugin sudoers_audit @sudoers_plugin@ sudoers_mode=0400 error_recovery=false
.Ed
.Pp
The following plugin arguments are supported:
.Bl -tag -width 4n
.It error_recovery=bool
The
.Em error_recovery
argument can be used to control whether
.Nm
should attempt to recover from syntax errors in the
.Em sudoers
file.
If set to
.Em true
(the default),
.Nm
will try to recover from a syntax error by discarding the portion
of the line that contains the error until the end of the line.
A value of
.Em false
will disable error recovery.
Prior to version 1.9.3, no error recovery was performed.
.It ignore_perms=bool
The
.Em ignore_perms
argument can be used to disable security checks when loading the
.Em sudoers
file.
If enabled, the
.Em sudoers
file will be loaded regardless of the owner or file mode.
This argument is intended to be used for testing purposes and
should not be enabled on production systems.
.It ldap_conf=pathname
The
.Em ldap_conf
argument can be used to override the default path to the
.Pa ldap.conf
file.
.It ldap_secret=pathname
The
.Em ldap_secret
argument can be used to override the default path to the
.Pa ldap.secret
file.
.It sudoers_file=pathname
The
.Em sudoers_file
argument can be used to override the default path to the
.Em sudoers
file.
.It sudoers_uid=user-ID
The
.Em sudoers_uid
argument can be used to override the default owner of the sudoers file.
It should be specified as a numeric user-ID.
.It sudoers_gid=group-ID
The
.Em sudoers_gid
argument can be used to override the default group of the sudoers file.
It must be specified as a numeric group-ID (not a group name).
.It sudoers_mode=mode
The
.Em sudoers_mode
argument can be used to override the default file mode for the sudoers file.
It should be specified as an octal value.
.El
.Pp
For more information on configuring
.Xr sudo.conf @mansectform@ ,
refer to its manual.
.Ss User Authentication
The
.Nm
security policy requires that most users authenticate
themselves before they can use
.Nm sudo .
A password is not required
if the invoking user is
.Sy root ,
if the target user is the same as the invoking user, or if the
policy has disabled authentication for the user or command.
Unlike
.Xr su 1 ,
when
.Nm
requires
authentication, it validates the invoking user's credentials, not
the target user's (or
.Sy @runas_default@ Ns No 's)
credentials.
This can be changed via
the
.Em rootpw ,
.Em targetpw
and
.Em runaspw
flags, described later.
.Pp
If a user who is not listed in the policy tries to run a command
via
.Nm sudo ,
mail is sent to the proper authorities.
The address
used for such mail is configurable via the
.Em mailto
Defaults entry
(described later) and defaults to
.Em @mailto@ .
.Pp
No mail will be sent if an unauthorized user tries to run
.Nm sudo
with the
.Fl l
or
.Fl v
option unless there is an authentication error and
either the
.Em mail_always
or
.Em mail_badpass
flags are enabled.
This allows users to
determine for themselves whether or not they are allowed to use
.Nm sudo .
By default, all attempts to run
.Nm sudo
(successful or not)
are logged, regardless of whether or not mail is sent.
.Pp
If
.Nm sudo
is run by
.Sy root
and the
.Ev SUDO_USER
environment variable
is set, the
.Nm
policy will use this value to determine who
the actual user is.
This can be used by a user to log commands
through sudo even when a
.Sy root
shell has been invoked.
It also
allows the
.Fl e
option to remain useful even when invoked via a
sudo-run script or program.
Note, however, that the
.Em sudoers
file lookup is still done for
.Sy root ,
not the user specified by
.Ev SUDO_USER .
.Pp
.Nm
uses per-user time stamp files for credential caching.
Once a user has been authenticated, a record is written
containing the user-ID that was used to authenticate, the
terminal session ID, the start time of the session leader
(or parent process) and a time stamp
(using a monotonic clock if one is available).
The user may then use
.Nm sudo
without a password for a short period of time (@timeout@ minutes
unless overridden by the
.Em timestamp_timeout
option).
By default,
.Nm
uses a separate record for each terminal, which means that
a user's login sessions are authenticated separately.
The
.Em timestamp_type
option can be used to select the type of time stamp record
.Nm
will use.
.Pp
The
.Nm tsdump
utility, included with the sudo source distribution, can be used to
display the contents of a time stamp file.
See
.Xr sudoers_timestamp @mansectform@
for details of the time stamp file format.
.Ss Logging
By default,
.Nm
logs both successful and unsuccessful attempts (as well
as errors).
The
.Em log_allowed
and
.Em log_denied
flags can be used to control this behavior.
Messages can be logged to
.Xr syslog 3 ,
a log file, or both.
The default is to log to
.Xr syslog 3
but this is configurable via the
.Em syslog
and
.Em logfile
settings.
See
.Sx "EVENT LOGGING"
for a description of the log file format.
.Pp
.Nm
is also capable of running a command in a pseudo-terminal and logging
input and/or output.
The standard input, standard output, and standard error can be logged
even when not associated with a terminal.
For more information about I/O logging, see the
.Sx "I/O LOGGING"
section.
.Pp
Starting with version 1.9, the
.Em log_servers
setting may be used to send event and I/O log data to a remote server running
.Nm sudo_logsrvd
or another service that implements the protocol described by
.Xr sudo_logsrv.proto @mansectform@ .
.Ss Command environment
Since environment variables can influence program behavior,
.Nm
provides a means to restrict which variables from the user's
environment are inherited by the command to be run.
There are two
distinct ways
.Nm
can deal with environment variables.
.Pp
By default, the
.Em env_reset
flag is enabled.
This causes commands
to be executed with a new, minimal environment.
On AIX (and Linux
systems without PAM), the environment is initialized with the
contents of the
.Pa /etc/environment
file.
.if \n(LC \{\
On
.Bx
systems, if the
.Em use_loginclass
flag is enabled, the environment is initialized
based on the
.Em path
and
.Em setenv
settings in
.Pa /etc/login.conf .
.\}
The
.Ev HOME ,
.Ev MAIL ,
.Ev SHELL ,
.Ev LOGNAME
and
.Ev USER
environment variables are initialized based on the target user
and the
.Ev SUDO_*
variables are set based on the invoking user.
Additional variables, such as
.Ev DISPLAY ,
.Ev PATH
and
.Ev TERM ,
are preserved from the invoking user's environment if permitted by the
.Em env_check ,
or
.Em env_keep
options.
A few environment variables are treated specially.
If the
.Ev PATH
and
.Ev TERM
variables are not preserved from the user's environment, they will be set
to default values.
The
.Ev LOGNAME
and
.Ev USER
are handled as a single entity.
If one of them is preserved (or removed) from the user's environment,
the other will be as well.
If
.Ev LOGNAME
and
.Ev USER
are to be preserved but only one of them is present in the user's environment,
the other will be set to the same value.
This avoids an inconsistent environment where one of the variables
describing the user name is set to the invoking user and one is
set to the target user.
Environment variables with a value beginning with
.Ql ()
are removed unless both the name and value parts are matched by
.Em env_keep
or
.Em env_check ,
as they may be interpreted as functions by the
.Sy bash
shell.
Prior to version 1.8.11, such variables were always removed.
.Pp
If, however, the
.Em env_reset
flag is disabled, any variables not
explicitly denied by the
.Em env_check
and
.Em env_delete
options are allowed and their values are
inherited from the invoking process.
Prior to version 1.8.21, environment variables with a value beginning with
.Ql ()
were always removed.
Beginning with version 1.8.21, a pattern in
.Em env_delete
is used to match
.Sy bash
shell functions instead.
Since it is not possible
to block all potentially dangerous environment variables, use
of the default
.Em env_reset
behavior is encouraged.
.Pp
Environment variables specified by
.Em env_check ,
.Em env_delete ,
or
.Em env_keep
may include one or more
.Ql *
characters which will match zero or more characters.
No other wildcard characters are supported.
.Pp
By default, environment variables are matched by name.
However, if the pattern includes an equal sign
.Pq Ql =\& ,
both the variables name and value must match.
For example, a
.Sy bash
shell function could be matched as follows:
.Bd -literal -offset 4n
env_keep += "BASH_FUNC_my_func%%=()*"
.Ed
.Pp
Without the
.Ql =()*
suffix, this would not match, as
.Sy bash
shell functions are not preserved by default.
.Pp
The complete list of environment variables that are preserved or removed,
as modified by global Defaults parameters in
.Em sudoers ,
is displayed when
.Nm sudo
is run by
.Sy root
with the
.Fl V
option.
The list of environment variables to remove
varies based on the operating system
.Nm sudo
is running on.
.Pp
Other settings may influence the command environment:
.Bl -bullet -width 1n
.It
.Nm
options such as
.Em always_set_home ,
.Em secure_path ,
.Em set_logname ,
.Em set_home ,
and
.Em setenv .
.It
Command tags, such as
.Dv SETENV
and
.Dv NOSETENV .
Note that
.Dv SETENV
is implied if the command matched is
.Sy ALL .
.It
.Nm sudo
options, such as
.Fl E
and
.Fl i .
.El
.Pp
On systems that support PAM where the
.Sy pam_env
module is enabled for
.Nm sudo ,
variables in the PAM environment may be merged in to the environment.
If a variable in the PAM environment is already present in the
user's environment, the value will only be overridden if the variable
was not preserved by
.Nm .
When
.Em env_reset
is enabled, variables preserved from the invoking user's environment
by the
.Em env_keep
list take precedence over those in the PAM environment.
When
.Em env_reset
is disabled, variables present the invoking user's environment
take precedence over those in the PAM environment unless they
match a pattern in the
.Em env_delete
list.
.Pp
The dynamic linker on most operating systems will remove variables
that can control dynamic linking from the environment of set-user-ID
executables, including
.Nm sudo .
Depending on the operating
system this may include
.Ev _RLD* ,
.Ev DYLD_* ,
.Ev LD_* ,
.Ev LDR_* ,
.Ev LIBPATH ,
.Ev SHLIB_PATH ,
and others.
These type of variables are
removed from the environment before
.Nm sudo
even begins execution
and, as such, it is not possible for
.Nm sudo
to preserve them.
.Pp
As a special case, if the
.Fl i
option (initial login) is
specified,
.Nm
will initialize the environment regardless
of the value of
.Em env_reset .
The
.Ev DISPLAY ,
.Ev PATH
and
.Ev TERM
variables remain unchanged;
.Ev HOME ,
.Ev MAIL ,
.Ev SHELL ,
.Ev USER ,
and
.Ev LOGNAME
are set based on the target user.
On AIX (and Linux
systems without PAM), the contents of
.Pa /etc/environment
are also
included.
.if \n(LC \{\
On
.Bx
systems, if the
.Em use_loginclass
flag is
enabled, the
.Em path
and
.Em setenv
variables in
.Pa /etc/login.conf
are also applied.
.\}
All other environment variables are removed unless permitted by
.Em env_keep
or
.Em env_check ,
described above.
.Pp
Finally, the
.Em restricted_env_file
and
.Em env_file
files are applied, if present.
The variables in
.Em restricted_env_file
are applied first and are subject to the same restrictions as the
invoking user's environment, as detailed above.
The variables in
.Em env_file
are applied last and are not subject to these restrictions.
In both cases, variables present in the files will only be set to
their specified values if they would not conflict with an existing
environment variable.
.Sh SUDOERS FILE FORMAT
The
.Em sudoers
file is composed of two types of entries: aliases
(basically variables) and user specifications (which specify who
may run what).
.Pp
When multiple entries match for a user, they are applied in order.
Where there are multiple matches, the last match is used (which is
not necessarily the most specific match).
.Pp
The
.Em sudoers
file grammar will be described below in Extended Backus-Naur
Form (EBNF).
Don't despair if you are unfamiliar with EBNF; it is fairly simple,
and the definitions below are annotated.
.Ss Resource limits
By default,
.Nm
uses the operating system's native method of setting resource limits
for the target user.
On Linux systems, resource limits are usually set by the
.Pa pam_limits.so
PAM module.
On some BSD systems, the
.Pa /etc/login.conf
file specifies resource limits for the user.
On AIX systems, resource limits are configured in the
.Pa /etc/security/limits
file.
If there is no system mechanism to set per-user resource limits,
the command will run with the same limits as the invoking user.
The one exception to this is the core dump file size, which is set by
.Nm
to 0 by default.
Disabling core dumps by default makes it possible to avoid potential
security problems where the core file is treated as trusted input.
.Pp
Resource limits may also be set in the
.Em sudoers
file itself, in which case they override those set by the system.
See the
.Em rlimit_as,
.Em rlimit_core,
.Em rlimit_cpu,
.Em rlimit_data,
.Em rlimit_fsize,
.Em rlimit_locks,
.Em rlimit_memlock,
.Em rlimit_nofile,
.Em rlimit_nproc,
.Em rlimit_rss,
.Em rlimit_stack
options described below.
Resource limits in
.Nm
may be specified in one of the following formats:
.Bl -tag -width 6n
.It Dq value
Both the soft and hard resource limits are set to the same value.
The special value
.Dq infinity
can be used to indicate that the value is unlimited.
.It Dq soft,hard
Two comma-separated values.
The soft limit is set to the first value and the hard limit is set
to the second.
Both values must either be enclosed in a set of double quotes,
or the comma must be escaped with a backslash
.Pq Ql \e .
The special value
.Dq infinity
may be used in place of either value.
.It Dq default
The default resource limit for the user will be used.
This may be a user-specific value (see above) or the value of the
resource limit when
.Nm sudo
was invoked for systems that don't support per-user limits.
.It Dq user
The invoking user's resource limits will be preserved when running
the command.
.El
.Pp
For example, to restore the historic core dump file size behavior,
a line like the following may be used.
.sp
.Dl Defaults rlimit_core=default
.Pp
Resource limits in
.Nm
are only supported by version 1.8.7 or higher.
.Ss Quick guide to EBNF
EBNF is a concise and exact way of describing the grammar of a language.
Each EBNF definition is made up of
.Em production rules .
For example:
.Bd -literal -offset 4n
symbol ::= definition | alternate1 | alternate2 ...
.Ed
.Pp
Each
.Em production rule
references others and thus makes up a
grammar for the language.
EBNF also contains the following
operators, which many readers will recognize from regular
expressions.
Do not, however, confuse them with
.Dq wildcard
characters, which have different meanings.
.Bl -tag -width 4n
.It \&?
Means that the preceding symbol (or group of symbols) is optional.
That is, it may appear once or not at all.
.It *
Means that the preceding symbol (or group of symbols) may appear
zero or more times.
.It +
Means that the preceding symbol (or group of symbols) may appear
one or more times.
.El
.Pp
Parentheses may be used to group symbols together.
For clarity,
we will use single quotes
.Pq ''
to designate what is a verbatim character string (as opposed to a symbol name).
.Ss Aliases
There are four kinds of aliases:
.Em User_Alias ,
.Em Runas_Alias ,
.Em Host_Alias
and
.Em Cmnd_Alias .
Beginning with
.Nm sudo
1.9.0,
.Em Cmd_Alias
may be used in place of
.Em Cmnd_Alias
if desired.
.Bd -literal
Alias ::= 'User_Alias'  User_Alias_Spec (':' User_Alias_Spec)* |
          'Runas_Alias' Runas_Alias_Spec (':' Runas_Alias_Spec)* |
          'Host_Alias'  Host_Alias_Spec (':' Host_Alias_Spec)* |
          'Cmnd_Alias'  Cmnd_Alias_Spec (':' Cmnd_Alias_Spec)* |
          'Cmd_Alias'   Cmnd_Alias_Spec (':' Cmnd_Alias_Spec)*

User_Alias ::= NAME

User_Alias_Spec ::= User_Alias '=' User_List

Runas_Alias ::= NAME

Runas_Alias_Spec ::= Runas_Alias '=' Runas_List

Host_Alias ::= NAME

Host_Alias_Spec ::= Host_Alias '=' Host_List

Cmnd_Alias ::= NAME

Cmnd_Alias_Spec ::= Cmnd_Alias '=' Cmnd_List

NAME ::= [A-Z]([A-Z][0-9]_)*
.Ed
.Pp
Each
.Em alias
definition is of the form
.Bd -literal
Alias_Type NAME = item1, item2, ...
.Ed
.Pp
where
.Em Alias_Type
is one of
.Em User_Alias ,
.Em Runas_Alias ,
.Em Host_Alias ,
or
.Em Cmnd_Alias .
A
.Dv NAME
is a string of uppercase letters, numbers,
and underscore characters
.Pq Ql _ .
A
.Dv NAME
.Sy must
start with an
uppercase letter.
It is possible to put several alias definitions
of the same type on a single line, joined by a colon
.Pq Ql :\& .
For example:
.Bd -literal
Alias_Type NAME = item1, item2, item3 : NAME = item4, item5
.Ed
.Pp
It is a syntax error to redefine an existing
.Em alias .
It is possible to use the same name for
.Em aliases
of different types, but this is not recommended.
.Pp
The definitions of what constitutes a valid
.Em alias
member follow.
.Bd -literal
User_List ::= User |
              User ',' User_List

User ::= '!'* user name |
         '!'* #user-ID |
         '!'* %group |
         '!'* %#group-ID |
         '!'* +netgroup |
         '!'* %:nonunix_group |
         '!'* %:#nonunix_gid |
         '!'* User_Alias
.Ed
.Pp
A
.Em User_List
is made up of one or more user names, user-IDs
(prefixed with
.Ql # ) ,
system group names and IDs (prefixed with
.Ql %
and
.Ql %#
respectively), netgroups (prefixed with
.Ql + ) ,
non-Unix group names and IDs (prefixed with
.Ql %:
and
.Ql %:#
respectively), and
.Em User_Alias Ns es.
Each list item may be prefixed with zero or more
.Ql \&!
operators.
An odd number of
.Ql \&!
operators negate the value of
the item; an even number just cancel each other out.
User netgroups are matched using the user and domain members only;
the host member is not used when matching.
.Pp
A
.Em user name ,
.Em user-ID ,
.Em group ,
.Em group-ID ,
.Em netgroup ,
.Em nonunix_group
or
.Em nonunix_gid
may be enclosed in double quotes to avoid the
need for escaping special characters.
Alternately, special characters
may be specified in escaped hex mode, e.g., \ex20 for space.
When
using double quotes, any prefix characters must be included inside
the quotes.
.Pp
The actual
.Em nonunix_group
and
.Em nonunix_gid
syntax depends on
the underlying group provider plugin.
For instance, the QAS AD plugin supports the following formats:
.Bl -bullet -width 1n
.It
Group in the same domain: "%:Group Name"
.It
Group in any domain: "%:Group Name@FULLY.QUALIFIED.DOMAIN"
.It
Group SID: "%:S-1-2-34-5678901234-5678901234-5678901234-567"
.El
.Pp
See
.Sx "GROUP PROVIDER PLUGINS"
for more information.
.Pp
Quotes around group names are optional.
Unquoted strings must use a backslash
.Pq Ql \e
to escape spaces and special characters.
See
.Sx Other special characters and reserved words
for a list of
characters that need to be escaped.
.Bd -literal
Runas_List ::= Runas_Member |
               Runas_Member ',' Runas_List

Runas_Member ::= '!'* user name |
                 '!'* #user-ID |
                 '!'* %group |
                 '!'* %#group-ID |
                 '!'* %:nonunix_group |
                 '!'* %:#nonunix_gid |
                 '!'* +netgroup |
                 '!'* Runas_Alias |
                 '!'* ALL
.Ed
.Pp
A
.Em Runas_List
is similar to a
.Em User_List
except that instead
of
.Em User_Alias Ns es
it can contain
.Em Runas_Alias Ns es .
User names and groups are matched as strings.
In other words, two users (groups) with the same user (group) ID
are considered to be distinct.
If you wish to match all user names with the same user-ID (e.g.,
.Sy root
and
.Sy toor ) ,
you can use a user-ID instead of a name (#0 in the example given).
The user-ID or group-ID specified in a
.Em Runas_Member
need not be listed in the password or group database.
.Bd -literal
Host_List ::= Host |
              Host ',' Host_List

Host ::= '!'* host name |
         '!'* ip_addr |
         '!'* network(/netmask)? |
         '!'* +netgroup |
         '!'* Host_Alias |
         '!'* ALL
.Ed
.Pp
A
.Em Host_List
is made up of one or more host names, IP addresses,
network numbers, netgroups (prefixed with
.Ql + ) ,
and other aliases.
Again, the value of an item may be negated with the
.Ql \&!
operator.
Host netgroups are matched using the host (both qualified and unqualified)
and domain members only; the user member is not used when matching.
If you specify a network number without a netmask,
.Nm sudo
will query each of the local host's network interfaces and,
if the network number corresponds to one of the hosts's network
interfaces, will use the netmask of that interface.
The netmask may be specified either in standard IP address notation
(e.g., 255.255.255.0 or ffff:ffff:ffff:ffff::),
or CIDR notation (number of bits, e.g., 24 or 64).
A host name may include shell-style wildcards (see the
.Sx Wildcards
section below),
but unless the
.Em hostname
command on your machine returns the fully
qualified host name, you'll need to use the
.Em fqdn
flag for wildcards to be useful.
.Nm sudo
only inspects actual network interfaces; this means that IP address
127.0.0.1 (localhost) will never match.
Also, the host name
.Dq localhost
will only match if that is the actual host name, which is usually
only the case for non-networked systems.
.Bd -literal
digest ::= [A-Fa-f0-9]+ |
           [A-Za-z0-9\e+/=]+

Digest_Spec ::= "sha224" ':' digest |
                "sha256" ':' digest |
                "sha384" ':' digest |
                "sha512" ':' digest

Digest_List ::= Digest_Spec |
                Digest_Spec ',' Digest_List

Cmnd_List ::= Cmnd |
              Cmnd ',' Cmnd_List

command name ::= regex |
                 file name

command ::= command name |
            command name args |
            command name regex |
            command name '""' |
            ALL

Edit_Spec ::= "sudoedit" file name+ |
              "sudoedit" regex |
              "sudoedit"

List_Spec ::= "list"

Cmnd ::= Digest_List? '!'* command |
         '!'* directory |
         '!'* Edit_Spec |
         '!'* List_Spec |
         '!'* Cmnd_Alias
.Ed
.Pp
A
.Em Cmnd_List
is a list of one or more commands, directories, or aliases.
A command is a fully qualified file name, which may include
shell-style wildcards (see the
.Sx Wildcards
section below),
or a regular expression that starts with
.Ql ^
and ends with
.Ql $
(see the
.Sx Regular expressions
section below).
A directory is a
fully qualified path name ending in a
.Ql / .
When you specify a directory in a
.Em Cmnd_List ,
the user will be able to run any file within that directory
(but not in any sub-directories therein).
If no command line arguments are specified, the user may run the
command with any arguments they choose.
Command line arguments can include wildcards or be a regular
expression that starts with
.Ql ^
and ends with
.Ql $ .
If the command line arguments consist of
.Ql \&"" ,
the command may only be run with
.Em no
arguments.
.Pp
If a
.Em Cmnd
has associated command line arguments, the arguments
in the
.Em Cmnd
must match those given by the user on the command line.
If the arguments in a
.Em Cmnd
begin with the
.Ql ^
character, they will be interpreted as a regular expression
and matched accordingly.
Otherwise, shell-style wildcards are used when matching.
Unless a regular expression is specified, the following characters must
be escaped with a
.Ql \e
if they are used in command arguments:
.Ql ,\& ,
.Ql :\& ,
.Ql =\& ,
.Ql \e .
To prevent arguments in a
.Em Cmnd
that begin with a
.Ql ^
character from being interpreted as a regular expression, the
.Ql ^
must be escaped with a
.Ql \e .
.Pp
There are two commands built into
.Nm sudo
itself:
.Dq list
and
.Dq sudoedit .
Unlike other commands, these two must be specified in the
.Em sudoers
file
.Em without
a leading path.
.Pp
The
.Dq list
built-in can be used to permit a user to list another user's privileges with
.Nm sudo Ns 's
.Fl U
option.
For example,
.Dq sudo -l -U otheruser .
A user with the
.Dq list
privilege is able to list another user's privileges even if they
don't have permission to run commands as that user.
By default, only root or a user with the ability to run any command as
either root or the specified
.Ar user
on the current host may use the
.Fl U
option.
No command line arguments may be specified with the
.Dq list
built-in.
.Pp
The
.Dq sudoedit
built-in is used to permit a user to run
.Nm sudo
with the
.Fl e
option (or as
.Nm sudoedit ) .
It may take command line arguments just as a normal command does.
Unlike other commands,
.Dq sudoedit
is built into
.Nm sudo
itself and must be specified in the
.Em sudoers
file
.Em without
a leading path.
If a leading path is present, for example
.Pa /usr/bin/sudoedit ,
the path name will be silently converted to
.Dq sudoedit .
A fully-qualified path for
.Nm sudoedit
is treated as an error by
.Nm visudo .
.Pp
A
.Em command
may be preceded by a
.Em Digest_List ,
a comma-separated list of one or more
.Em Digest_Spec
entries.
If a
.Em Digest_List
is present, the command will only match successfully if it can be verified
using one of the SHA-2 digests in the list.
Starting with version 1.9.0, the
.Sy ALL
reserved word can be used in conjunction with a
.Em Digest_List .
The following digest formats are supported: sha224, sha256, sha384, and sha512.
The string may be specified in either hex or base64 format
(base64 is more compact).
There are several utilities capable of generating SHA-2 digests in hex
format such as openssl, shasum, sha224sum, sha256sum, sha384sum, sha512sum.
.Pp
For example, using openssl:
.Bd -literal
$ openssl dgst -sha224 /bin/ls
SHA224(/bin/ls)= 118187da8364d490b4a7debbf483004e8f3e053ec954309de2c41a25
.Ed
.Pp
It is also possible to use openssl to generate base64 output:
.Bd -literal
$ openssl dgst -binary -sha224 /bin/ls | openssl base64
EYGH2oNk1JC0p9679IMATo8+BT7JVDCd4sQaJQ==
.Ed
.Pp
Warning, if the user has write access to the command itself (directly or via a
.Nm sudo
command), it may be possible for the user to replace the command after the
digest check has been performed but before the command is executed.
A similar race condition exists on systems that lack the
.Xr fexecve 2
system call when the directory in which the command is located
is writable by the user.
See the description of the
.Em fdexec
setting for more information on how
.Nm sudo
executes commands that have an associated digest.
.Pp
Command digests are only supported by version 1.8.7 or higher.
.Ss Defaults
Certain configuration options may be changed from their default
values at run-time via one or more
.Em Default_Entry
lines.
These may affect all users on any host
.Pq Sq Defaults ,
all users on a specific host
.Pq Sq Defaults@host ,
a specific user
.Pq Sq Defaults:user ,
a specific command
.Pq Sq Defaults!cmnd ,
or commands being run as a specific user
.Pq Sq Defaults>runasuser .
.Pp
White space is not permitted between
.Sq Defaults
and the
.Ql @ ,
.Ql \&: ,
.Ql \&! ,
or
.Ql >
characters.
While a comma-separated list may be used in place of a single value after the
.Ql @ ,
.Ql \&: ,
.Ql \&! ,
or
.Ql >
character, using an alias instead of a list is often improve readability.
Per-command entries may not include command line arguments.
If you need to specify arguments, define a
.Em Cmnd_Alias
and reference that instead.
.Bd -literal
Default_Type ::= 'Defaults' |
                 'Defaults@' Host_List |
                 'Defaults:' User_List |
                 'Defaults!' Cmnd_List |
                 'Defaults>' Runas_List

Default_Entry ::= Default_Type Parameter_List

Parameter_List ::= Parameter |
                   Parameter ',' Parameter_List

Parameter ::= Parameter '=' Value |
              Parameter '+=' Value |
              Parameter '-=' Value |
              '!'* Parameter
.Ed
.Pp
Parameters may be
.Sy flags ,
.Sy integer
values,
.Sy strings ,
or
.Sy lists .
Flags are implicitly boolean and can be turned off via the
.Ql \&!
operator.
Some integer, string and list parameters may also be
used in a boolean context to disable them.
Values may be enclosed
in double quotes
.Pq \&""
when they contain multiple words.
Special characters may be escaped with a backslash
.Pq Ql \e .
.Pp
To include a literal backslash character in a command line argument
you must escape the backslash twice.
For example, to match
.Ql \en
as part of a command line argument, you must use
.Ql \e\e\e\en
in the
.Em sudoers
file.
This is due to there being two levels of escaping, one in the
.Em sudoers
parser itself and another when command line arguments are matched by the
.Xr fnmatch 3
or
.Xr regexec 3
function.
.Pp
Lists have two additional assignment operators,
.Ql +=
and
.Ql -= .
These operators are used to add to and delete from a list respectively.
It is not an error to use the
.Ql -=
operator to remove an element
that does not exist in a list.
.Pp
Defaults entries are parsed in the following order: global, host,
user, and runas Defaults first, then command defaults.
If there are multiple Defaults settings of the same type, the last
matching setting is used.
The following Defaults settings are parsed before all others since
they may affect subsequent entries:
.Em fqdn ,
.Em group_plugin ,
.Em runas_default ,
.Em sudoers_locale .
.Pp
See
.Sx SUDOERS OPTIONS
for a list of supported Defaults parameters.
.Ss User specification
.Bd -literal
User_Spec ::= User_List Host_List '=' Cmnd_Spec_List \e
              (':' Host_List '=' Cmnd_Spec_List)*

Cmnd_Spec_List ::= Cmnd_Spec |
                   Cmnd_Spec ',' Cmnd_Spec_List

Cmnd_Spec ::= Runas_Spec? Option_Spec* (Tag_Spec ':')* Cmnd

Runas_Spec ::= '(' Runas_List? (':' Runas_List)? ')'

.ie \n(SL \{\
.ie \n(PS Option_Spec ::= (SELinux_Spec | Solaris_Priv_Spec | Date_Spec | Timeout_Spec | Chdir_Spec | Chroot_Spec)
.el Option_Spec ::= (SELinux_Spec | Date_Spec | Timeout_Spec | Chdir_Spec | Chroot_Spec)
.\}
.el \{\
.ie \n(AA \{\
.ie \n(PS Option_Spec ::= (AppArmor_Spec | Solaris_Priv_Spec | Date_Spec | Timeout_Spec | Chdir_Spec | Chroot_Spec)
.el Option_Spec ::= (AppArmor_Spec | Date_Spec | Timeout_Spec | Chdir_Spec | Chroot_Spec)
.\}
.el \{\
.ie \n(PS Option_Spec ::= (Solaris_Priv_Spec | Date_Spec | Timeout_Spec | Chdir_Spec | Chroot_Spec)
.el Option_Spec ::= (Date_Spec | Timeout_Spec | Chdir_Spec | Chroot_Spec)
.\}
.\}

.if \n(SL \{\
SELinux_Spec ::= ('ROLE=role' | 'TYPE=type')

.\}
.if \n(AA \{\
AppArmor_Spec ::= 'APPARMOR_PROFILE=profile'

.\}
.if \n(PS \{\
Solaris_Priv_Spec ::= ('PRIVS=privset' | 'LIMITPRIVS=privset')

.\}
Date_Spec ::= ('NOTBEFORE=timestamp' | 'NOTAFTER=timestamp')

Timeout_Spec ::= 'TIMEOUT=timeout'

Chdir_Spec ::= 'CWD=directory'

Chroot_Spec ::= 'CHROOT=directory'

Tag_Spec ::= ('EXEC' | 'NOEXEC' | 'FOLLOW' | 'NOFOLLOW' |
              'LOG_INPUT' | 'NOLOG_INPUT' | 'LOG_OUTPUT' |
              'NOLOG_OUTPUT' | 'MAIL' | 'NOMAIL' | 'INTERCEPT' |
              'NOINTERCEPT' | 'PASSWD' | 'NOPASSWD' | 'SETENV' |
              'NOSETENV')
.Ed
.Pp
A
.Sy user specification
determines which commands a user may run
(and as what user) on specified hosts.
By default, commands are run as
.Sy @runas_default@
(unless
.Em runas_default
has been set to a different value)
but this can also be changed on a per-command basis.
.Pp
The basic structure of a user specification is
.Dq who where = (as_whom) what .
Let's break that down into its constituent parts:
.Ss Runas_Spec
A
.Em Runas_Spec
determines the user and/or the group that a command
may be run as.
A fully-specified
.Em Runas_Spec
consists of two
.Em Runas_List Ns s
(as defined above) separated by a colon
.Pq Ql \&:
and enclosed in a set of parentheses.
The first
.Em Runas_List
indicates which users the command may be run as via the
.Fl u
option.
The second defines a list of groups that may be specified via the
.Fl g
option (in addition to any of the target user's groups).
If both
.Em Runas_List Ns s
are specified, the command may be run with any combination of users
and groups listed in their respective
.Em Runas_List Ns s.
If only the first is specified, the command may be run as any user
in the list and, optionally, with any group the target user belongs to.
If the first
.Em Runas_List
is empty but the
second is specified, the command may be run as the invoking user
with the group set to any listed in the
.Em Runas_List .
If both
.Em Runas_List Ns s
are empty, the command may only be run as the invoking user and the
group, if specified, must be one that the invoking user is a member of.
If no
.Em Runas_Spec
is specified, the command may only be run as the
.Em runas_default
user
.Sy ( @runas_default@
by default) and the group,
if specified, must be one that the
.Em runas_default
user is a member of.
.Pp
A
.Em Runas_Spec
sets the default for the commands that follow it.
What this means is that for the entry:
.Bd -literal
dgb	boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
.Ed
.Pp
The user
.Sy dgb
may run
.Pa /bin/ls ,
.Pa /bin/kill ,
and
.Pa /usr/bin/lprm
on the host
.No boulder Ns \(em Ns but
only as
.Sy operator .
For example:
.Bd -literal
$ sudo -u operator /bin/ls
.Ed
.Pp
It is also possible to override a
.Em Runas_Spec
later on in an entry.
If we modify the entry like so:
.Bd -literal
dgb	boulder = (operator) /bin/ls, (root) /bin/kill, /usr/bin/lprm
.Ed
.Pp
Then user
.Sy dgb
is now allowed to run
.Pa /bin/ls
as
.Sy operator ,
but
.Pa /bin/kill
and
.Pa /usr/bin/lprm
as
.Sy root .
.Pp
We can extend this to allow
.Sy dgb
to run
.Pa /bin/ls
with either
the user or group set to
.Sy operator :
.Bd -literal
dgb	boulder = (operator : operator) /bin/ls, (root) /bin/kill,\e
	/usr/bin/lprm
.Ed
.Pp
While the group portion of the
.Em Runas_Spec
permits the
user to run as command with that group, it does not force the user
to do so.
If no group is specified on the command line, the command
will run with the group listed in the target user's password database
entry.
The following would all be permitted by the sudoers entry above:
.Bd -literal
$ sudo -u operator /bin/ls
$ sudo -u operator -g operator /bin/ls
$ sudo -g operator /bin/ls
.Ed
.Pp
In the following example, user
.Sy tcm
may run commands that access
a modem device file with the dialer group.
.Bd -literal
tcm	boulder = (:dialer) /usr/bin/tip, /usr/bin/cu,\e
	/usr/local/bin/minicom
.Ed
.Pp
In this example only the group will be set, the command still runs as user
.Sy tcm .
For example:
.Bd -literal
$ sudo -g dialer /usr/bin/cu
.Ed
.Pp
Multiple users and groups may be present in a
.Em Runas_Spec ,
in which case the user may select any combination of users and groups via the
.Fl u
and
.Fl g
options.
In this example:
.Bd -literal
alan	ALL = (root, bin : operator, system) ALL
.Ed
.Pp
user
.Sy alan
may run any command as either user
.Sy root
or
.Sy bin ,
optionally setting the group to operator or system.
.Ss Option_Spec
A
.Em Cmnd
may have zero or more options associated with it.
Options may consist of
.if \n(SL \{\
SELinux roles and/or types,
.\}
.if \n(AA \{\
AppArmor profiles,
.\}
.if \n(PS \{\
Solaris privileges sets,
.\}
start and/or end dates and command timeouts.
Once an option is set for a
.Em Cmnd ,
subsequent
.Em Cmnd Ns s
in the
.Em Cmnd_Spec_List ,
inherit that option unless it is overridden by another option.
Option names are reserved words in
.Em sudoers .
This means that none of the valid option names (see below) can be used
when declaring an alias.
.if \n(SL \{\
.Ss SELinux_Spec
On systems with SELinux support,
.Em sudoers
file entries may optionally have an SELinux role and/or type associated
with a command.
This can be used to implement a form of role-based access control (RBAC).
If a role or
type is specified with the command it will override any default values
specified in
.Em sudoers .
A role or type specified on the command line,
however, will supersede the values in
.Em sudoers .
.\}
.if \n(AA \{\
.Ss AppArmor_Spec
On systems supporting AppArmor,
.Em sudoers
file entries may optionally specify an AppArmor profile that should be
used to confine a command.
If an AppArmor profile is specified with the command, it will override
any default values specified in
.Em sudoers .
Appropriate profile transition rules must be defined to support the
profile change specified for a user.
.Pp
AppArmor profiles can be specified in any way that complies with the
rules of
.Xr aa_change_profile 2 .
For instance, in the following
.Em sudoers
entry
.Bd -literal
alice	ALL = (root)	APPARMOR_PROFILE=my-profile	ALL
.Ed
.Pp
the user
.Sy alice
may run any command as
.Sy root
under confinement by the profile
.Ql my-profile .
You can also stack profiles, or allow a user to run commands unconfined by
any profile.
For example:
.Bd -literal
bob	ALL = (root)	APPARMOR_PROFILE=foo//&bar	/usr/bin/vi
cathy	ALL = (root)	APPARMOR_PROFILE=unconfined	/bin/ls
.Ed
.Pp
These
.Em sudoers
entries allow user
.Sy bob
to run
.Pa /usr/bin/vi
as
.Sy root
under the stacked profiles
.Ql foo
and
.Ql bar ,
and user
.Sy cathy
to run
.Pa /bin/ls
without any confinement at all.
.\}
.if \n(PS \{\
.Ss Solaris_Priv_Spec
On Solaris systems,
.Em sudoers
file entries may optionally specify Solaris privilege set and/or limit
privilege set associated with a command.
If privileges or limit privileges are specified with the command
it will override any default values specified in
.Em sudoers .
.Pp
A privilege set is a comma-separated list of privilege names.
The
.Xr ppriv 1
command can be used to list all privileges known to the system.
For example:
.Bd -literal
$ ppriv -l
.Ed
.Pp
In addition, there are several
.Dq special
privilege strings:
.Bl -tag -width "basic"
.It none
the empty set
.It all
the set of all privileges
.It zone
the set of all privileges available in the current zone
.It basic
the default set of privileges normal users are granted at login time
.El
.Pp
Privileges can be excluded from a set by prefixing the privilege
name with either an
.Ql \&!
or
.Ql \-
character.
.\}
.Ss Date_Spec
.Nm
rules can be specified with a start and end date via the
.Dv NOTBEFORE
and
.Dv NOTAFTER
settings.
The time stamp must be specified in
.Dq Generalized Time
as defined by RFC 4517.
The format is effectively
.Ql yyyymmddHHMMSSZ
where the minutes and seconds are optional.
The
.Ql Z
suffix indicates that the time stamp is in Coordinated Universal Time (UTC).
It is also possible to specify a timezone offset from UTC in hours
and minutes instead of a
.Ql Z .
For example,
.Ql -0500
would correspond to Eastern Standard time in the US.
As an extension, if no
.Ql Z
or timezone offset is specified, local time will be used.
.Pp
The following are all valid time stamps:
.Bd -literal -offset 4n
20170214083000Z
2017021408Z
20160315220000-0500
20151201235900
.Ed
.Ss Timeout_Spec
A command may have a timeout associated with it.
If the timeout expires before the command has exited, the
command will be terminated.
The timeout may be specified in combinations of days, hours,
minutes, and seconds with a single-letter case-insensitive suffix
that indicates the unit of time.
For example, a timeout of 7 days, 8 hours, 30 minutes, and
10 seconds would be written as
.Ql 7d8h30m10s .
If a number is specified without a unit, seconds are assumed.
Any of the days, minutes, hours, or seconds may be omitted.
The order must be from largest to smallest unit and a unit
may not be specified more than once.
.Pp
The following are all
.Em valid
timeout values:
.Ql 7d8h30m10s ,
.Ql 14d ,
.Ql 8h30m ,
.Ql 600s ,
.Ql 3600 .
The following are
.Em invalid
timeout values:
.Ql 12m2w1d ,
.Ql 30s10m4h ,
.Ql 1d2d3h .
.Pp
This setting is only supported by version 1.8.20 or higher.
.Ss Chdir_Spec
The working directory that the command will be run in can be specified
using the
.Dv CWD
setting.
The
.Fa directory
must be a fully-qualified path name beginning with a
.Sq /
or
.Sq ~
character, or the special value
.Dq * .
A value of
.Dq *
indicates that the user may specify the working directory by running
.Nm sudo
with the
.Fl D
option.
By default, commands are run from the invoking user's current working
directory, unless the
.Fl i
option is given.
Path names of the form
.Pa ~user/path/name
are interpreted as being relative to the named user's home directory.
If the user name is omitted, the path will be relative to the runas
user's home directory.
.Pp
This setting is only supported by version 1.9.3 or higher.
.Ss Chroot_Spec
The root directory that the command will be run in can be specified
using the
.Dv CHROOT
setting.
The
.Fa directory
must be a fully-qualified path name beginning with a
.Sq /
or
.Sq ~
character, or the special value
.Dq * .
A value of
.Dq *
indicates that the user may specify the root directory by running
.Nm sudo
with the
.Fl R
option.
This setting can be used to run the command in a
.Xr chroot 2
.Dq sandbox
similar to the
.Xr chroot @mansectsu@
utility.
Path names of the form
.Pa ~user/path/name
are interpreted as being relative to the named user's home directory.
If the user name is omitted, the path will be relative to the runas
user's home directory.
.Pp
This setting is only supported by version 1.9.3 or higher.
.Ss Tag_Spec
A command may have zero or more tags associated with it.
The following tag values are supported:
.Dv EXEC ,
.Dv NOEXEC ,
.Dv FOLLOW ,
.Dv NOFOLLOW ,
.Dv LOG_INPUT ,
.Dv NOLOG_INPUT ,
.Dv LOG_OUTPUT ,
.Dv NOLOG_OUTPUT ,
.Dv MAIL ,
.Dv NOMAIL ,
.Dv INTERCEPT ,
.Dv NOINTERCEPT ,
.Dv PASSWD ,
.Dv NOPASSWD ,
.Dv SETENV ,
and
.Dv NOSETENV .
Once a tag is set on a
.Em Cmnd ,
subsequent
.Em Cmnd Ns s
in the
.Em Cmnd_Spec_List ,
inherit the tag unless it is overridden by the opposite tag (in other words,
.Dv PASSWD
overrides
.Dv NOPASSWD
and
.Dv NOEXEC
overrides
.Dv EXEC ) .
.Bl -hang -width 0n
.It Dv EXEC No and Dv NOEXEC
.sp
If
.Nm sudo
has been compiled with
.Em noexec
support and the underlying operating system supports it, the
.Dv NOEXEC
tag can be used to prevent a dynamically-linked executable from
running further commands itself.
.Pp
In the following example, user
.Sy aaron
may run
.Pa /usr/bin/more
and
.Pa /usr/bin/vi
on the host shanty, but shell escapes will be disabled.
.Bd -literal
aaron	shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
.Ed
.Pp
See the
.Sx Preventing shell escapes
section below for more details on how
.Dv NOEXEC
works and whether or not it will work on your system.
.It Dv FOLLOW No and Dv NOFOLLOW
.sp
Starting with version 1.8.15,
.Nm sudoedit
will not open a file that is a symbolic link unless the
.Em sudoedit_follow
flag is enabled.
The
.Dv FOLLOW
and
.Dv NOFOLLOW
tags override the value of
.Em sudoedit_follow
and can be used to permit (or deny) the editing of symbolic links
on a per-command basis.
These tags are only effective for the
.Em sudoedit
command and are ignored for all other commands.
.It Dv LOG_INPUT No and Dv NOLOG_INPUT
.sp
These tags override the value of the
.Em log_input
flag on a per-command basis.
For more information, see
.Sx "I/O LOGGING" .
.It Dv LOG_OUTPUT No and Dv NOLOG_OUTPUT
.sp
These tags override the value of the
.Em log_output
flag on a per-command basis.
For more information, see
.Sx "I/O LOGGING" .
.It Dv MAIL No and Dv NOMAIL
.sp
These tags provide fine-grained control over whether
mail will be sent when a user runs a command by
overriding the value of the
.Em mail_all_cmnds
flag on a per-command basis.
They have no effect when
.Nm sudo
is run with the
.Fl l
or
.Fl v
options.
A
.Dv NOMAIL
tag will also override the
.Em mail_always
and
.Em mail_no_perms
options.
For more information, see the descriptions of
.Em mail_all_cmnds ,
.Em mail_always ,
and
.Em mail_no_perms
in the
.Sx SUDOERS OPTIONS
section below.
.It Dv PASSWD No and Dv NOPASSWD
.sp
By default,
.Nm sudo
requires that a user authenticate
before running a command.
This behavior can be modified via the
.Dv NOPASSWD
tag.
Like a
.Em Runas_Spec ,
the
.Dv NOPASSWD
tag sets
a default for the commands that follow it in the
.Em Cmnd_Spec_List .
Conversely, the
.Dv PASSWD
tag can be used to reverse things.
For example:
.Bd -literal
ray	rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
.Ed
.Pp
would allow the user
.Sy ray
to run
.Pa /bin/kill ,
.Pa /bin/ls ,
and
.Pa /usr/bin/lprm
as
.Sy @runas_default@
on the machine
.Dq rushmore
without authenticating himself.
If we only want
.Sy ray
to be able to
run
.Pa /bin/kill
without a password the entry would be:
.Bd -literal
ray	rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
.Ed
.Pp
Note, however, that the
.Dv PASSWD
tag has no effect on users who are in the group specified by the
.Em exempt_group
setting.
.Pp
By default, if the
.Dv NOPASSWD
tag is applied to any of a user's entries for the current host,
the user will be able to run
.Ql sudo -l
without a password.
Additionally, a user may only run
.Ql sudo -v
without a password if all of the user's entries for the current
host have the
.Dv NOPASSWD
tag.
This behavior may be overridden via the
.Em verifypw
and
.Em listpw
options.
.It Dv SETENV No and Dv NOSETENV
.sp
These tags override the value of the
.Em setenv
flag on a per-command basis.
If
.Dv SETENV
has been set for a command, the user may disable the
.Em env_reset
flag from the command line via the
.Fl E
option.
Additionally, environment variables set on the command
line are not subject to the restrictions imposed by
.Em env_check ,
.Em env_delete ,
or
.Em env_keep .
As such, only trusted users should be allowed to set variables in this manner.
If the command matched is
.Sy ALL ,
the
.Dv SETENV
tag is implied for that command; this default may be overridden by use of the
.Dv NOSETENV
tag.
.It Dv INTERCEPT No and Dv NOINTERCEPT
.sp
If
.Nm sudo
has been compiled with
.Em intercept
support and the underlying operating system supports it, the
.Dv INTERCEPT
tag can be used to cause programs spawned by a command to be validated against
.Em sudoers
and logged just like they would be if run through
.Nm sudo
directly.
This is useful in conjunction with commands that allow shell escapes
such as editors, shells, and paginators.
There is additional overhead due to the policy check that may add
latency when running commands such as shell scripts that execute a
large number of sub-commands.
For interactive commands, such as a shell or editor,
the overhead is not usually noticeable.
.Pp
In the following example, user
.Sy chuck
may run any command on the machine
.Dq research
in intercept mode.
.Bd -literal
chuck	research = INTERCEPT: ALL
.Ed
.Pp
See the
.Sx Preventing shell escapes
section below for more details on how
.Dv INTERCEPT
works and whether or not it will work on your system.
.El
.Ss Wildcards
.Nm sudo
allows shell-style
.Em wildcards
(aka meta or glob characters)
to be used in host names, path names, and command line arguments in the
.Em sudoers
file.
Wildcard matching is done via the
.Xr glob 3
and
.Xr fnmatch 3
functions as specified by
.St -p1003.1 .
.Bl -tag -width "[!...]"
.It *
Matches any set of zero or more characters (including white space).
.It \&?
Matches any single character (including white space).
.It [...]
Matches any character in the specified range.
.It [!...]
Matches any character
.Em not
in the specified range.
.It \ex
For any character
.Sq x ,
evaluates to
.Sq x .
This is used to escape special characters such as:
.Ql * ,
.Ql \&? ,
.Ql [\& ,
and
.Ql ]\& .
.El
.Pp
.Bf -symbolic
These are not regular expressions.
.Ef
Unlike a regular expression there is no way to match one or more
characters within a range.
.Pp
Character classes may be used if your system's
.Xr glob 3
and
.Xr fnmatch 3
functions support them.
However, because the
.Ql :\&
character has special meaning in
.Em sudoers ,
it must be
escaped.
For example:
.Bd -literal -offset 4n
/bin/ls [[\e:\&alpha\e:\&]]*
.Ed
.Pp
Would match any file name beginning with a letter.
.Pp
A forward slash
.Pq Ql /
will
.Em not
be matched by
wildcards used in the file name portion of the command.
This is to make a path like:
.Bd -literal -offset 4n
/usr/bin/*
.Ed
.Pp
match
.Pa /usr/bin/who
but not
.Pa /usr/bin/X11/xterm .
.Pp
When matching the command line arguments, however, a slash
.Em does
get matched by wildcards since command line arguments may contain
arbitrary strings and not just path names.
.Pp
.Bf -symbolic
Wildcards in command line arguments should be used with care.
.Ef
.br
Wildcards can match any character, including white space.
In most cases, it is safer to use a regular expression to match
command line arguments.
For more information, see
.Sx Wildcards in command arguments
below.
.Ss Exceptions to wildcard rules
The following exceptions apply to the above rules:
.Bl -tag -width "sudoedit"
.It \&""
If the empty string
.Ql \&""
is the only command line argument in the
.Em sudoers
file entry it means that command is not allowed to be run with
.Em any
arguments.
.It sudoedit
Command line arguments to the
.Em sudoedit
built-in command should always be path names, so a forward slash
.Pq Ql /
will not be matched by a wildcard.
.El
.Ss Regular expressions
Starting with version 1.9.10, it is possible to use
regular expressions for path names and command line arguments.
Regular expressions are more expressive than shell-style
.Em wildcards
and are usually safer because they provide a greater degree of
control when matching.
The type of regular expressions supported by
.Nm
are POSIX extended regular expressions, similar to those used by the
.Xr egrep 1
utility.
They are usually documented in the
.Xr regex @mansectmisc@
or
.Xr re_format @mansectmisc@
manual, depending on the system.
As an extension, if the regular expression begins with
.Dq (?i) ,
it will be matched in a case-insensitive manner.
.Pp
In
.Em sudoers ,
regular expressions must start with a
.Ql ^
character and end with a
.Ql $ .
This makes it explicit what is, or is not, a regular expression.
Either the path name, the command line arguments or both may
be regular expressions.
Because the path name and arguments are matched separately, it is
even possible to use wildcards for the path name and regular
expressions for the arguments.
It is not possible to use a single regular expression to match
both the command and its arguments.
Regular expressions in
.Em sudoers
are limited to 1024 characters.
.Pp
There is no need to escape
.Em sudoers
special characters in a regular expression other than the pound sign
.Pq Ql # .
.Pp
In the following example, user
.Sy john
can run the
.Xr passwd 1
command as
.Sy @runas_default@
on any host but is not allowed to change
.Sy root Ns No 's
password.
This kind of rule is impossible to express safely using wildcards.
.Bd -literal -offset 4n
john	ALL = /usr/bin/passwd ^[a-zA-Z0-9_]+$,\e
              !/usr/bin/passwd root
.Ed
.Pp
It is also possible to use a regular expression in conjunction with
.Nm sudoedit
rules.
The following rule would give user bob the ability to edit the
.Pa /etc/motd ,
.Pa /etc/issue ,
and
.Pa /etc/hosts
files only.
.Bd -literal -offset 4n
bob    ALL = sudoedit ^/etc/(motd|issue|hosts)$
.Ed
.Pp
Regular expressions may also be used to match the command itself.
In this example, a regular expression is used to allow user
.Sy sid
to run the
.Pa /usr/sbin/groupadd ,
.Pa /usr/sbin/groupmod ,
.Pa /usr/sbin/groupdel ,
.Pa /usr/sbin/useradd ,
.Pa /usr/sbin/usermod ,
and
.Pa /usr/sbin/userdel
commands as
.Sy @runas_default@ .
.Bd -literal -offset 4n
sid    ALL = ^/usr/sbin/(group|user)(add|mod|del)$
.Ed
.Pp
One disadvantage of using a regular expression to match the command
name is that it is not possible to match relative paths such as
.Pa ./useradd
or
.Pa ../sbin/useradd .
This has security implications when a regular expression is used
for the command name in conjunction with the negation operator,
.Ql !\& ,
as such rules can be trivially bypassed.
Because of this, using a negated regular expression for the command name is
.Sy strongly discouraged .
This does not apply to negated commands that only use a regular
expression to match the command arguments.
See
.Sx Regular expressions in command names
below for more information.
.Ss Including other files from within sudoers
It is possible to include other
.Em sudoers
files from within the
.Em sudoers
file currently being parsed using the
.Em @include
and
.Em @includedir
directives.
For compatibility with sudo versions prior to 1.9.1,
.Em #include
and
.Em #includedir
are also accepted.
.Pp
An include file can be used, for example, to keep a site-wide
.Em sudoers
file in addition to a local, per-machine file.
For the sake of this example the site-wide
.Em sudoers
file will be
.Pa /etc/sudoers
and the per-machine one will be
.Pa /etc/sudoers.local .
To include
.Pa /etc/sudoers.local
from within
.Pa /etc/sudoers
one would use the following line in
.Pa /etc/sudoers :
.Bd -literal -offset 4n
@include /etc/sudoers.local
.Ed
.Pp
When
.Nm sudo
reaches this line it will suspend processing of the current file
.Pq Pa /etc/sudoers
and switch to
.Pa /etc/sudoers.local .
Upon reaching the end of
.Pa /etc/sudoers.local ,
the rest of
.Pa /etc/sudoers
will be processed.
Files that are included may themselves include other files.
A hard limit of 128 nested include files is enforced to prevent include
file loops.
.Pp
Starting with version 1.9.1, the path to the include file may contain
white space if it is escaped with a backslash
.Pq Ql \e .
Alternately, the entire path may be enclosed in double quotes
.Pq \&"" ,
in which case no escaping is necessary.
To include a literal backslash in the path,
.Ql \e\e
should be used.
.Pp
If the path to the include file is not fully-qualified (does not
begin with a
.Ql / ) ,
it must be located in the same directory as the sudoers file it was
included from.
For example, if
.Pa /etc/sudoers
contains the line:
.Bd -literal -offset 4n
@include sudoers.local
.Ed
.Pp
the file that will be included is
.Pa /etc/sudoers.local .
.Pp
The file name may also include the
.Ql %h
escape, signifying the short form of the host name.
In other words, if the machine's host name is
.Dq xerxes ,
then
.Bd -literal -offset 4n
@include /etc/sudoers.%h
.Ed
.Pp
will cause
.Nm sudo
to include the file
.Pa /etc/sudoers.xerxes .
Any path name separator characters
.Pq Ql /
present in the host name will be replaced with an underbar
.Pq Ql _
during expansion.
.Pp
The
.Em @includedir
directive can be used to create a
.Pa sudoers.d
directory that the system package manager can drop
.Em sudoers
file rules into as part of package installation.
For example, given:
.Bd -literal -offset 4n
@includedir /etc/sudoers.d
.Ed
.Pp
.Nm sudo
will suspend processing of the current file and read each file in
.Pa /etc/sudoers.d ,
skipping file names that end in
.Ql ~
or contain a
.Ql .\&
character to avoid causing problems with package manager or editor
temporary/backup files.
.Pp
Files are parsed in sorted lexical order.
That is,
.Pa /etc/sudoers.d/01_first
will be parsed before
.Pa /etc/sudoers.d/10_second .
Be aware that because the sorting is lexical, not numeric,
.Pa /etc/sudoers.d/1_whoops
would be loaded
.Em after
.Pa /etc/sudoers.d/10_second .
Using a consistent number of leading zeroes in the file names can be used
to avoid such problems.
After parsing the files in the directory, control returns to the
file that contained the
.Em @includedir
directive.
.Pp
Unlike files included via
.Em @include ,
.Nm visudo
will not edit the files in a
.Em @includedir
directory unless one of them contains a syntax error.
It is still possible to run
.Nm visudo
with the
.Fl f
flag to edit the files directly, but this will not catch the
redefinition of an
.Em alias
that is also present in a different file.
.Ss Other special characters and reserved words
The pound sign
.Pq Ql #
is used to indicate a comment (unless it is part of a #include
directive or unless it occurs in the context of a user name and is
followed by one or more digits, in which case it is treated as a
user-ID).
Both the comment character and any text after it, up to the end of
the line, are ignored.
.Pp
The reserved word
.Sy ALL
is a built-in
.Em alias
that always causes a match to succeed.
It can be used wherever one might otherwise use a
.Em Cmnd_Alias ,
.Em User_Alias ,
.Em Runas_Alias ,
or
.Em Host_Alias .
Attempting to define an
.Em alias
named
.Sy ALL
will result in a syntax error.
Using
.Sy ALL
can be dangerous since in a command context, it allows the user to run
.Em any
command on the system.
.Pp
The following option names permitted in an
.Em Option_Spec
are also considered reserved words:
.Dv CHROOT ,
.if \n(PS \{\
.Dv PRIVS ,
.Dv LIMITPRIVS ,
.\}
.if \n(SL \{\
.Dv ROLE ,
.Dv TYPE ,
.\}
.Dv TIMEOUT ,
.Dv CWD ,
.Dv NOTBEFORE
and
.Dv NOTAFTER .
Attempting to define an
.Em alias
with the same name as one of the options will result in a syntax error.
.Pp
An exclamation point
.Pq Ql \&!
can be used as a logical
.Em not
operator in a list or
.Em alias
as well as in front of a
.Em Cmnd .
This allows one to exclude certain values.
For the
.Ql \&!
operator to be effective, there must be something for it to exclude.
For example, to match all users except for
.Sy root
one would use:
.Bd -literal -offset 4n
ALL, !root
.Ed
.Pp
If the
.Sy ALL ,
is omitted, as in:
.Bd -literal -offset 4n
!root
.Ed
.Pp
it would explicitly deny
.Sy root
but not match any other users.
This is different from a true
.Dq negation
operator.
.Pp
Note, however, that using a
.Ql \&!
in conjunction with the built-in
.Sy ALL
alias to allow a user to run
.Dq all but a few
commands rarely works as intended (see
.Sx SECURITY NOTES
below).
.Pp
Long lines can be continued with a backslash
.Pq Ql \e
as the last character on the line.
.Pp
White space between elements in a list as well as special syntactic
characters in a
.Em User Specification
.Po
.Ql =\& ,
.Ql :\& ,
.Ql (\& ,
.Ql )\&
.Pc
is optional.
.Pp
The following characters must be escaped with a backslash
.Pq Ql \e
when used as part of a word (e.g., a user name or host name):
.Ql \&! ,
.Ql =\& ,
.Ql :\& ,
.Ql ,\& ,
.Ql (\& ,
.Ql )\& ,
.Ql \e .
.Sh SUDOERS OPTIONS
.Nm sudo Ns 's
behavior can be modified by
.Em Default_Entry
lines, as explained earlier.
A list of all supported Defaults parameters, grouped by type, are listed below.
.Pp
.Sy Boolean Flags :
.Bl -tag -width 16n
.It always_query_group_plugin
If a
.Em group_plugin
is configured, use it to resolve groups of the form
.Ql %group
as long as there is not also a system group of the same name.
Normally, only groups of the form
.Ql %:group
are passed to the
.Em group_plugin .
This flag is
.Em off
by default.
.It always_set_home
If enabled,
.Nm sudo
will set the
.Ev HOME
environment variable to the home directory of the target user
(which is the
.Em runas_default
user unless the
.Fl u
option is used).
This flag is largely obsolete and has no effect unless the
.Em env_reset
flag has been disabled or
.Ev HOME
is present in the
.Em env_keep
list, both of which are strongly discouraged.
This flag is
.Em off
by default.
.It authenticate
If set, users must authenticate themselves via a password (or other
means of authentication) before they may run commands.
This default may be overridden via the
.Dv PASSWD
and
.Dv NOPASSWD
tags.
This flag is
.Em on
by default.
.It case_insensitive_group
If enabled, group names in
.Em sudoers
will be matched in a case insensitive manner.
This may be necessary when users are stored in LDAP or AD.
This flag is
.Em on
by default.
.It case_insensitive_user
If enabled, user names in
.Em sudoers
will be matched in a case insensitive manner.
This may be necessary when groups are stored in LDAP or AD.
This flag is
.Em on
by default.
.It closefrom_override
If set, the user may use the
.Fl C
option which overrides the default starting point at which
.Nm sudo
begins closing open file descriptors.
This flag is
.Em off
by default.
.It compress_io
If set, and
.Nm sudo
is configured to log a command's input or output,
the I/O logs will be compressed using
.Sy zlib .
This flag is
.Em on
by default when
.Nm sudo
is compiled with
.Sy zlib
support.
.It exec_background
By default,
.Nm sudo
runs a command as the foreground process as long as
.Nm sudo
itself is running in the foreground.
When the
.Em exec_background
flag is enabled and the command is being run in a pseudo-terminal
(due to I/O logging or the
.Em use_pty
flag), the command will be run as a background process.
Attempts to read from the controlling terminal (or to change terminal
settings) will result in the command being suspended with the
.Dv SIGTTIN
signal (or
.Dv SIGTTOU
in the case of terminal settings).
If this happens when
.Nm sudo
is a foreground process, the command will be granted the controlling terminal
and resumed in the foreground with no user intervention required.
The advantage of initially running the command in the background is that
.Nm sudo
need not read from the terminal unless the command explicitly requests it.
Otherwise, any terminal input must be passed to the command, whether it
has required it or not (the kernel buffers terminals so it is not possible
to tell whether the command really wants the input).
This is different from historic
.Em sudo
behavior or when the command is not being run in a pseudo-terminal.
.Pp
For this to work seamlessly, the operating system must support the
automatic restarting of system calls.
Unfortunately, not all operating systems do this by default,
and even those that do may have bugs.
For example, macOS fails to restart the
.Xr tcgetattr 3
and
.Xr tcsetattr 3
functions (this is a bug in macOS).
Furthermore, because this behavior depends on the command stopping with the
.Dv SIGTTIN
or
.Dv SIGTTOU
signals, programs that catch these signals and suspend themselves
with a different signal (usually
.Dv SIGTOP )
will not be automatically foregrounded.
Some versions of the linux
.Xr su 1
command behave this way.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.8.7 or higher.
It has no effect unless I/O logging is enabled or the
.Em use_pty
flag is enabled.
.It env_editor
If set,
.Nm visudo
will use the value of the
.Ev SUDO_EDITOR ,
.Ev VISUAL
or
.Ev EDITOR
environment variables before falling back on the default editor list.
.Nm visudo
is typically run as
.Sy root
so this flag may allow a user with
.Nm visudo
privileges to run arbitrary commands as
.Sy root
without logging.
An alternative is to place a colon-separated list of
.Dq safe
editors int the
.Em editor
setting.
.Nm visudo
will then only use
.Ev SUDO_EDITOR ,
.Ev VISUAL
or
.Ev EDITOR
if they match a value specified in
.Em editor .
If the
.Em env_reset
flag is enabled, the
.Ev SUDO_EDITOR ,
.Ev VISUAL
and/or
.Ev EDITOR
environment variables must be present in the
.Em env_keep
list for the
.Em env_editor
flag to function when
.Nm visudo
is invoked via
.Nm sudo .
This flag is
.Em @env_editor@
by default.
.It env_reset
If set,
.Nm sudo
will run the command in a minimal environment containing the
.Ev TERM ,
.Ev PATH ,
.Ev HOME ,
.Ev MAIL ,
.Ev SHELL ,
.Ev LOGNAME ,
.Ev USER
and
.Ev SUDO_*
variables.
Any variables in the caller's environment or in the file specified
by the
.Em restricted_env_file
setting that match the
.Em env_keep
and
.Em env_check
lists are then added, followed by any variables present in the file
specified by the
.Em env_file
setting (if any).
The contents of the
.Em env_keep
and
.Em env_check
lists, as modified by global Defaults parameters in
.Em sudoers ,
are displayed when
.Nm sudo
is run by
.Sy root
with the
.Fl V
option.
If the
.Em secure_path
setting is enabled, its value will be used for the
.Ev PATH
environment variable.
This flag is
.Em @env_reset@
by default.
.It fast_glob
Normally,
.Nm sudo
uses the
.Xr glob 3
function to do shell-style globbing when matching path names.
However, since it accesses the file system,
.Xr glob 3
can take a long time to complete for some patterns, especially
when the pattern references a network file system that is mounted
on demand (auto mounted).
The
.Em fast_glob
flag causes
.Nm sudo
to use the
.Xr fnmatch 3
function, which does not access the file system to do its matching.
The disadvantage of
.Em fast_glob
is that it is unable to match relative paths such as
.Pa ./ls
or
.Pa ../bin/ls .
This has security implications when path names that include globbing
characters are used with the negation operator,
.Ql !\& ,
as such rules can be trivially bypassed.
As such, this flag should not be used when the
.Em sudoers
file contains rules that contain negated path names which include globbing
characters.
This flag is
.Em off
by default.
.It log_passwords
Most programs that require a user's password will disable echo before
reading the password to avoid displaying the plaintext password on
the screen.
However, if terminal input is being logged (see
.Sx "I/O LOGGING" ) ,
the password will still be present in the I/O log.
If the
.Em log_passwords
option is disabled,
.Nm
will attempt to prevent passwords from being logged.
It does this by using the regular expressions in
.Em passprompt_regex
to match a password prompt in the terminal output buffer.
When a match is found, input characters in the I/O log will be replaced with
.Ql *
until either a line feed or carriage return is found in the terminal input
or a new terminal output buffer is received.
If, however, a program displays characters as the user types
(such as
.Nm sudo
when
.Em pwfeedback
is set), only the
first character of the password will be replaced in the I/O log.
This option has no effect unless
.Em log_input
or
.Em log_ttyin
are also set.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.9.10 or higher.
.It fqdn
Set this flag if you want to put fully qualified host names in the
.Em sudoers
file when the local host name (as returned by the
.Ql hostname
command) does not contain the domain name.
In other words, instead of myhost you would use myhost.mydomain.edu.
You may still use the short form if you wish (and even mix the two).
This flag is only effective when the
.Dq canonical
host name, as returned by the
.Xr getaddrinfo 3
or
.Xr gethostbyname 3
function, is a fully-qualified domain name.
This is usually the case when the system is configured to use DNS
for host name resolution.
.Pp
If the system is configured to use the
.Pa /etc/hosts
file in preference to DNS, the
.Dq canonical
host name may not be fully-qualified.
The order that sources are queried for host name resolution
is usually specified in the
.Pa @nsswitch_conf@ ,
.Pa @netsvc_conf@ ,
.Pa /etc/host.conf ,
or, in some cases,
.Pa /etc/resolv.conf
file.
In the
.Pa /etc/hosts
file, the first host name of the entry is considered to be the
.Dq canonical
name; subsequent names are aliases that are not used by
.Nm .
For example, the following hosts file line for the machine
.Dq xyzzy
has the fully-qualified domain name as the
.Dq canonical
host name, and the short version as an alias.
.sp
.Dl 192.168.1.1 xyzzy.sudo.ws xyzzy
.sp
If the machine's hosts file entry is not formatted properly, the
.Em fqdn
flag will not be effective if it is queried before DNS.
.Pp
Beware that when using DNS for host name resolution, turning on
.Em fqdn
requires
.Nm
to make DNS lookups which renders
.Nm sudo
unusable if DNS stops working (for example if the machine is disconnected
from the network).
Just like with the hosts file, you must use the
.Dq canonical
name as DNS knows it.
That is, you may not use a host alias (CNAME entry) due to performance
issues and the fact that there is no way to get all aliases from DNS.
.Pp
This flag is
.Em @fqdn@
by default.
.It ignore_audit_errors
Allow commands to be run even if
.Nm
cannot write to the audit log.
If enabled, an audit log write failure is not treated as a fatal error.
If disabled, a command may only be run after the audit event is successfully
written.
This flag is only effective on systems for which
.Nm
supports audit logging, including
.Fx ,
Linux, macOS, and Solaris.
This flag is
.Em on
by default.
.It ignore_dot
If set,
.Nm sudo
will ignore "." or "" (both denoting the current directory) in the
.Ev PATH
environment variable; the
.Ev PATH
itself is not modified.
This flag is
.Em @ignore_dot@
by default.
.It ignore_iolog_errors
Allow commands to be run even if
.Nm
cannot write to the I/O log (local or remote).
If enabled, an I/O log write failure is not treated as a fatal error.
If disabled, the command will be terminated if the I/O log cannot be written to.
This flag is
.Em off
by default.
.It ignore_logfile_errors
Allow commands to be run even if
.Nm
cannot write to the log file.
If enabled, a log file write failure is not treated as a fatal error.
If disabled, a command may only be run after the log file entry is successfully
written.
This flag only has an effect when
.Nm
is configured to use file-based logging via the
.Em logfile
setting.
This flag is
.Em on
by default.
.It ignore_local_sudoers
If set via LDAP, parsing of
.Pa @sysconfdir@/sudoers
will be skipped.
This is intended for sites that wish to prevent the usage of local
sudoers files so that only LDAP is used.
This thwarts the efforts of rogue operators who would attempt to add roles to
.Pa @sysconfdir@/sudoers .
When this flag is enabled,
.Pa @sysconfdir@/sudoers
does not even need to exist.
Since this flag tells
.Nm sudo
how to behave when no specific LDAP entries have been matched, this
sudoOption is only meaningful for the
.Ql cn=defaults
section.
This flag is
.Em off
by default.
.It ignore_unknown_defaults
If set,
.Nm sudo
will not produce a warning if it encounters an unknown Defaults entry
in the
.Em sudoers
file or an unknown sudoOption in LDAP.
This flag is
.Em off
by default.
.It insults
If set,
.Nm sudo
will insult users when they enter an incorrect password.
This flag is
.Em @insults@
by default.
.It log_allowed
If set,
.Nm
will log commands allowed by the policy to the system audit log
(where supported) as well as to syslog and/or a log file.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.8.29 or higher.
.It log_denied
If set,
.Nm
will log commands denied by the policy to the system audit log
(where supported) as well as to syslog and/or a log file.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.8.29 or higher.
.It log_exit_status
If set,
.Nm
will log the exit value of commands that are run to syslog and/or a log file.
If a command was terminated by a signal, the signal name is logged as well.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.9.8 or higher.
.It log_host
If set, the host name will be included in log entries written to
the file configured by the
.Em logfile
setting.
This flag is
.Em off
by default.
.It log_input
If set,
.Nm sudo
will run the command in a pseudo-terminal (if
.Nm sudo
was run from a terminal) and log all user input.
If the standard input is not connected to the user's terminal, due
to I/O redirection or because the command is part of a pipeline,
that input is also logged.
For more information about I/O logging, see the
.Sx "I/O LOGGING"
section.
This flag is
.Em off
by default.
.It log_output
If set,
.Nm sudo
will run the command in a pseudo-terminal (if
.Nm sudo
was run from a terminal) and log all output that is sent to the
user's terminal, the standard output or the standard error.
If the standard output or standard error is not connected to the
user's terminal, due to I/O redirection or because the command is
part of a pipeline, that output is also logged.
For more information about I/O logging, see the
.Sx "I/O LOGGING"
section.
This flag is
.Em off
by default.
.It log_server_keepalive
If set,
.Nm sudo
will enable the TCP keepalive socket option on the connection to the log server.
This enables the periodic transmission of keepalive messages to the server.
If the server does not respond to a message, the connection will
be closed and the running command will be terminated unless the
.Em ignore_iolog_errors
flag (I/O logging enabled) or the
.Em ignore_log_errors
flag (I/O logging disabled) is set.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.9.0 or higher.
.It log_server_verify
If set, the server certificate received during the TLS handshake
must be valid and it must contain either the server name (from
.Em log_servers )
or its IP address.
If either of these conditions is not met, the TLS handshake will fail.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.9.0 or higher.
.It log_stderr
If set,
.Nm sudo
will log the standard error if it is not connected to the user's terminal.
This can be used to log output to a pipe or redirected to a file.
This flag is
.Em off
by default but is enabled when either the
.Em log_output
flag or the
.Dv LOG_OUTPUT
command tag is set.
.It log_stdin
If set,
.Nm sudo
will log the standard input if it is not connected to the user's terminal.
This can be used to log input from a pipe or redirected from a file.
This flag is
.Em off
by default but is enabled when either the
.Em log_input
flag or the
.Dv LOG_INPUT
command tag is set.
.It log_stdout
If set,
.Nm sudo
will log the standard output if it is not connected to the user's terminal.
This can be used to log output to a pipe or redirected to a file.
This flag is
.Em off
by default but is enabled when either the
.Em log_output
flag or the
.Dv LOG_OUTPUT
command tag is set.
.It log_subcmds
If set,
.Nm
will log when a command spawns a child process and executes a program
using the
.Xr execve 2 ,
.Xr execl 3 ,
.Xr execle 3 ,
.Xr execlp 3 ,
.Xr execv 3 ,
.Xr execvp 3 ,
.Xr execvpe 3 ,
or
.Xr system 3
library functions.
For example, if a shell is run by
.Nm sudo ,
the individual commands run via the shell will be logged.
This flag is
.Em off
by default.
.Pp
The
.Em log_subcmds
flag uses the same underlying mechanism as the
.Em intercept
setting.
Some commands may not work properly when
.Em log_subcmds
is enabled, due to the way it intercepts sub-commands.
See
.Sx Preventing shell escapes
for more information on what systems support this option and its limitations.
This setting is only supported by version 1.9.8 or higher
and is incompatible with SELinux RBAC support unless the system supports
.Xr seccomp 2
filter mode.
.It log_ttyin
If set,
.Nm sudo
will run the command in a pseudo-terminal and log user keystrokes
sent to the user's terminal, if one is present.
This flag is
.Em off
by default but is enabled when either the
.Em log_input
flag or the
.Dv LOG_INPUT
command tag is set.
If no terminal is present, for example when running a remote command using
.Xr ssh 1 ,
this flag will have no effect.
.It log_ttyout
If set,
.Nm sudo
will run the command in a pseudo-terminal and log all output displayed
on the user's terminal, if one is present.
This flag is
.Em off
by default but is enabled when either the
.Em log_output
flag or the
.Dv LOG_OUTPUT
command tag is set.
If no terminal is present, for example when running a remote command using
.Xr ssh 1 ,
this flag will have no effect.
.It log_year
If set, the four-digit year will be logged in the (non-syslog)
.Nm sudo
log file.
This flag is
.Em off
by default.
.It long_otp_prompt
When validating with a One Time Password (OTP) scheme such as
.Sy S/Key
or
.Sy OPIE ,
a two-line prompt is used to make it easier
to cut and paste the challenge to a local window.
It's not as pretty as the default but some people find it more convenient.
This flag is
.Em @long_otp_prompt@
by default.
.It mail_all_cmnds
Send mail to the
.Em mailto
user every time a user attempts to run a command via
.Nm sudo
(this includes
.Nm sudoedit ) .
No mail will be sent if the user runs
.Nm sudo
with the
.Fl l
or
.Fl v
option unless there is an authentication error and the
.Em mail_badpass
flag is also set.
This flag is
.Em off
by default.
.It mail_always
Send mail to the
.Em mailto
user every time a user runs
.Nm sudo .
This flag is
.Em off
by default.
.It mail_badpass
Send mail to the
.Em mailto
user if the user running
.Nm sudo
does not enter the correct password.
If the command the user is attempting to run is not permitted by
.Nm
and one of the
.Em mail_all_cmnds ,
.Em mail_always ,
.Em mail_no_host ,
.Em mail_no_perms
or
.Em mail_no_user
flags are set, this flag will have no effect.
This flag is
.Em off
by default.
.It mail_no_host
If set, mail will be sent to the
.Em mailto
user if the invoking user exists in the
.Em sudoers
file, but is not allowed to run commands on the current host.
This flag is
.Em @mail_no_host@
by default.
.It mail_no_perms
If set, mail will be sent to the
.Em mailto
user if the invoking user is allowed to use
.Nm sudo
but the command they are trying is not listed in their
.Em sudoers
file entry or is explicitly denied.
This flag is
.Em @mail_no_perms@
by default.
.It mail_no_user
If set, mail will be sent to the
.Em mailto
user if the invoking user is not in the
.Em sudoers
file.
This flag is
.Em @mail_no_user@
by default.
.It match_group_by_gid
By default,
.Nm
will look up each group the user is a member of by group-ID to
determine the group name (this is only done once).
The resulting list of the user's group names is used when matching
groups listed in the
.Em sudoers
file.
This works well on systems where the number of groups listed in the
.Em sudoers
file is larger than the number of groups a typical user belongs to.
On systems where group lookups are slow, where users may belong
to a large number of groups, or where the number of groups listed
in the
.Em sudoers
file is relatively small, it may be prohibitively expensive and
running commands via
.Nm sudo
may take longer than normal.
On such systems it may be faster to use the
.Em match_group_by_gid
flag to avoid resolving the user's group-IDs to group names.
In this case,
.Nm
must look up any group name listed in the
.Em sudoers
file and use the group-ID instead of the group name when determining
whether the user is a member of the group.
.Pp
If
.Em match_group_by_gid
is enabled, group database lookups performed by
.Nm
will be keyed by group name as opposed to group-ID.
On systems where there are multiple sources for the group database,
it is possible to have conflicting group names or group-IDs in the local
.Pa /etc/group
file and the remote group database.
On such systems, enabling or disabling
.Em match_group_by_gid
can be used to choose whether group database queries are performed
by name (enabled) or ID (disabled), which may aid in working around
group entry conflicts.
.Pp
The
.Em match_group_by_gid
flag has no effect when
.Em sudoers
data is stored in LDAP.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.8.18 or higher.
.It intercept
If set, all commands run via
.Nm sudo
will behave as if the
.Dv INTERCEPT
tag has been set, unless overridden by an
.Dv NOINTERCEPT
tag.
Some commands may not work properly when
.Em intercept
is enabled, due to the way it intercept sub-commands.
See the description of
.Dv INTERCEPT and NOINTERCEPT
above as well as the
.Sx Preventing shell escapes
section at the end of this manual.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.9.8 or higher
and is incompatible with SELinux RBAC support unless the system supports
.Xr seccomp 2
filter mode.
.It intercept_allow_setid
On most systems, the dynamic loader will ignore
.Ev LD_PRELOAD
(or the equivalent) when running set-user-ID and set-group-ID
programs, effectively disabling intercept mode.
To prevent this from happening,
.Nm
will not permit a set-user-ID or set-group-ID program to be run in
intercept mode unless
.Em intercept_allow_setid
is enable.
This flag has no effect unless the
.Em intercept
flag is enabled or the
.Dv INTERCEPT
tag has been set for the command.
This flag is
.Em on
by default when the
.Em intercept_type
option is set to
.Em trace ,
otherwise it default to
.Em off .
.Pp
This setting is only supported by version 1.9.8 or higher.
.It intercept_authenticate
If set, commands run by an intercepted process must be authenticated
when the user's time stamp is not current.
For example, if a shell is run with
.Em intercept
enabled, as soon as the invoking user's time stamp is out of date,
subsequent commands will need to be authenticated.
This flag has no effect unless the
.Em intercept
flag is enabled or the
.Dv INTERCEPT
tag has been set for the command.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.9.8 or higher.
.It intercept_verify
If set,
.Nm sudo
will attempt to verify that a command run in intercept mode has
the expected path name, command line arguments and environment.
.Pp
The process will be stopped after
.Xr execve 2
has completed but before the new command has had a chance to run.
To verify the command,
.Nm sudo
will read the command's path from
.Pa /proc/PID/exe ,
the command line arguments and environment from the process's memory,
and compare them against the arguments that were passed to
.Xr execve 2 .
In the event of a mismatch, the command will be sent a
.Dv SIGKILL
signal and terminated.
.Pp
This can help prevent a time of check versus time of use issue with
intercept mode where the
.Xr execve 2
arguments could be altered after the
.Nm
policy check.
The checks can only be performed if the
.Xr proc @mansectform@
file system is available.
This flag has no effect unless the
.Em intercept
flag is enabled or the
.Dv INTERCEPT
tag has been set for the command and the
.Em intercept_type
option is set to
.Em trace .
.Pp
This setting is incompatible with programs that change their root directory via
.Xr chroot 2 .
If a program changes its root directory, path names will no longer match
those seen by the
.Nm sudo
parent process and sub-commands will be terminated before they have a chance
to run.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.9.12 or higher.
.It netgroup_tuple
If set, netgroup lookups will be performed using the full netgroup
tuple: host name, user name, and domain (if one is set).
Historically,
.Nm sudo
only matched the user name and domain for netgroups used in a
.Em User_List
and only matched the host name and domain for netgroups used in a
.Em Host_List .
This flag is
.Em off
by default.
.It noexec
If set, all commands run via
.Nm sudo
will behave as if the
.Dv NOEXEC
tag has been set, unless overridden by an
.Dv EXEC
tag.
See the description of
.Dv EXEC and NOEXEC
above as well as the
.Sx Preventing shell escapes
section at the end of this manual.
This flag is
.Em off
by default.
.It noninteractive_auth
If set, authentication will be attempted even in non-interactive mode
(when
.Nm sudo Ns 's
.Fl n
option is specified).
This allows authentication methods that don't require user interaction
to succeed.
Authentication methods that require input from the user's terminal
will still fail.
If disabled, authentication will not be attempted in non-interactive mode.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.9.10 or higher.
.It pam_acct_mgmt
On systems that use PAM for authentication,
.Nm sudo
will perform PAM account validation for the invoking user by default.
The actual checks performed depend on which PAM modules are configured.
If enabled, account validation will be performed regardless of whether
or not a password is required.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.8.28 or higher.
.It pam_rhost
On systems that use PAM for authentication,
.Nm sudo
will set the PAM remote host value to the name of the local host
when the
.Em pam_rhost
flag is enabled.
On Linux systems, enabling
.Em pam_rhost
may result in DNS lookups of the local host name when PAM is initialized.
On Solaris versions prior to Solaris 8,
.Em pam_rhost
must be enabled if
.Em pam_ruser
is also enabled to avoid a crash in the Solaris PAM implementation.
.Pp
This flag is
.Em off
by default on systems other than Solaris.
.Pp
This setting is only supported by version 1.9.0 or higher.
.It pam_ruser
On systems that use PAM for authentication,
.Nm sudo
will set the PAM remote user value to the name of the user that invoked sudo
when the
.Em pam_ruser
flag is enabled.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.9.0 or higher.
.It pam_session
On systems that use PAM for authentication,
.Nm sudo
will create a new PAM session for the command to be run in.
Unless
.Nm sudo
is given the
.Fl i
or
.Fl s
options, PAM session modules are run with the
.Dq silent
flag enabled.
This prevents last login information from being displayed for every
command on some systems.
Disabling
.Em pam_session
may be needed on older PAM implementations or on operating systems where
opening a PAM session changes the utmp or wtmp files.
If PAM session support is disabled, resource limits may not be updated
for the command being run.
If
.Em pam_session ,
.Em pam_setcred ,
and
.Em use_pty
are disabled,
.Em log_servers
has not been set and I/O logging has not been configured,
.Nm sudo
will execute the command directly instead of running it as a child
process.
This flag is
.Em @pam_session@
by default.
.Pp
This setting is only supported by version 1.8.7 or higher.
.It pam_setcred
On systems that use PAM for authentication,
.Nm sudo
will attempt to establish credentials for the target user by default,
if supported by the underlying authentication system.
One example of a credential is a Kerberos ticket.
If
.Em pam_session ,
.Em pam_setcred ,
and
.Em use_pty
are disabled,
.Em log_servers
has not been set and I/O logging has not been configured,
.Nm sudo
will execute the command directly instead of running it as a child
process.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.8.8 or higher.
.It pam_silent
If set, PAM authentication will be performed in silent mode.
This prevents PAM authentication modules from generating output.
In some cases, this may suppress important information about why
authentication failed.
For example, PAM modules such as
.Em pam_faillock
will only display a warning if
.Em pam_silent
is disabled.
This flag is
.Em on
by default.
.Pp
This setting is only supported by version 1.9.16 or higher.
.It passprompt_override
If set, the prompt specified by
.Em passprompt
or the
.Ev SUDO_PROMPT
environment variable will always be used and will replace the
prompt provided by a PAM module or other authentication method.
This flag is
.Em off
by default.
.It path_info
Normally,
.Nm sudo
will tell the user when a command could not be
found in their
.Ev PATH
environment variable.
Some sites may wish to disable this as it could be used to gather
information on the location of executables that the normal user does
not have access to.
The disadvantage is that if the executable is simply not in the user's
.Ev PATH ,
.Nm sudo
will tell the user that they are not allowed to run it, which can be confusing.
This flag is
.Em @path_info@
by default.
.It preserve_groups
By default,
.Nm sudo
will initialize the group vector to the list of groups the target user is in.
When
.Em preserve_groups
is set, the user's existing group vector is left unaltered.
The real and effective group-IDs, however, are still set to match the
target user.
This flag is
.Em off
by default.
.It pwfeedback
By default,
.Nm sudo
reads the password like most other Unix programs,
by turning off echo until the user hits the return (or enter) key.
Some users become confused by this as it appears to them that
.Nm sudo
has hung at this point.
When
.Em pwfeedback
is set,
.Nm sudo
will provide visual feedback when the user presses a key.
This does have a security impact as an onlooker may be able to
determine the length of the password being entered.
This flag is
.Em off
by default.
.It requiretty
If set,
.Nm sudo
will only run when the user is logged in to a real tty.
When this flag is set,
.Nm sudo
can only be run from a login session and not via other means such as
.Xr cron @mansectsu@
or cgi-bin scripts.
This flag is
.Em off
by default.
.It root_sudo
If set,
.Sy root
is allowed to run
.Nm sudo
too.
Disabling this prevents users from
.Dq chaining
.Nm sudo
commands to get a
.Sy root
shell by doing something like
.Ql sudo sudo /bin/sh .
Note, however, that turning off
.Em root_sudo
will also prevent
.Sy root
from running
.Nm sudoedit .
Disabling
.Em root_sudo
provides no real additional security; it exists purely for historical reasons.
This flag is
.Em @root_sudo@
by default.
.It rootpw
If set,
.Nm sudo
will prompt for the
.Sy root
password instead of the password of the invoking user
when running a command or editing a file.
This flag is
.Em off
by default.
.It runas_allow_unknown_id
If enabled, allow matching of runas user and group IDs that are
not present in the password or group databases.
In addition to explicitly matching unknown user or group IDs in a
.Em Runas_List ,
this option also allows the
.Sy ALL
alias to match unknown IDs.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.8.30 or higher.
Older versions of
.Nm sudo
always allowed matching of unknown user and group IDs.
.It runas_check_shell
If enabled,
.Nm sudo
will only run commands as a user whose shell appears in the
.Pa /etc/shells
file, even if the invoking user's
.Em Runas_List
would otherwise permit it.
If no
.Pa /etc/shells
file is present, a system-dependent list of built-in default shells is used.
On many operating systems, system users such as
.Dq bin ,
do not have a valid shell and this flag can be used to prevent
commands from being run as those users.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.8.30 or higher.
.It runaspw
If set,
.Nm sudo
will prompt for the password of the user defined by the
.Em runas_default
option (defaults to
.Sy @runas_default@ )
instead of the password of the invoking user
when running a command or editing a file.
This flag is
.Em off
by default.
.if \n(SL \{\
.It selinux
If enabled, the user may specify an SELinux role and/or type to use
when running the command, as permitted by the SELinux policy.
If SELinux is disabled on the system, this flag has no effect.
This flag is
.Em on
by default.
.\}
.It set_home
If enabled and
.Nm sudo
is invoked with the
.Fl s
option, the
.Ev HOME
environment variable will be set to the home directory of the target
user (which is the
.Em runas_default
user unless the
.Fl u
option is used).
This flag is largely obsolete and has no effect unless the
.Em env_reset
flag has been disabled or
.Ev HOME
is present in the
.Em env_keep
list, both of which are strongly discouraged.
This flag is
.Em off
by default.
.It set_logname
Normally,
.Nm sudo
will set the
.Ev LOGNAME
and
.Ev USER
environment variables to the name of the target user (the user specified by
.Em runas_default
unless the
.Fl u
option is given).
However, since some programs (including the RCS revision control system) use
.Ev LOGNAME
to determine the real identity of the user, it may be desirable to
change this behavior.
This can be done by negating the set_logname option.
The
.Em set_logname
option will have no effect
if the
.Em env_reset
option has not been disabled and the
.Em env_keep
list contains
.Ev LOGNAME
or
.Ev USER .
This flag is
.Em on
by default.
.It set_utmp
When enabled,
.Nm sudo
will create an entry in the utmp (or utmpx) file when a pseudo-terminal
is allocated.
A pseudo-terminal is allocated by
.Nm sudo
when it is running in a terminal and one or more of the
.Em log_input ,
.Em log_output ,
.Em log_stdin ,
.Em log_stdout ,
.Em log_stderr ,
.Em log_ttyin ,
.Em log_ttyout ,
or
.Em use_pty
flags is enabled.
By default, the new entry will be a copy of the user's existing utmp
entry (if any), with the tty, time, type, and pid fields updated.
This flag is
.Em on
by default.
.It setenv
Allow the user to disable the
.Em env_reset
option from the command line via the
.Fl E
option.
Additionally, environment variables set via the command line are
not subject to the restrictions imposed by
.Em env_check ,
.Em env_delete ,
or
.Em env_keep .
As such, only trusted users should be allowed to set variables in this manner.
This flag is
.Em off
by default.
.It shell_noargs
If set and
.Nm sudo
is invoked with no arguments it acts as if the
.Fl s
option had been given.
That is, it runs a shell as
.Sy root
(the shell is determined by the
.Ev SHELL
environment variable if it is set, falling back on the shell listed
in the invoking user's /etc/passwd entry if not).
This flag is
.Em off
by default.
.It stay_setuid
Normally, when
.Nm sudo
executes a command the real and effective user-IDs are set to the target
user
.Sy ( @runas_default@
by default).
This option changes that behavior such that the real user-ID is left
as the invoking user's user-ID.
In other words, this makes
.Nm sudo
act as a set-user-ID wrapper.
This can be useful on systems that disable some potentially
dangerous functionality when a program is run set-user-ID.
This option is only effective on systems that support either the
.Xr setreuid 2
or
.Xr setresuid 2
system call.
This flag is
.Em off
by default.
.It sudoedit_checkdir
If set,
.Nm sudoedit
will check all directory components of the path to be edited for writability
by the invoking user.
Symbolic links will not be followed in writable directories and
.Nm sudoedit
will refuse to edit a file located in a writable directory.
These restrictions are not enforced when
.Nm sudoedit
is run by
.Sy root .
On some systems, if all directory components of the path to be edited
are not readable by the target user,
.Nm sudoedit
will be unable to edit the file.
This flag is
.Em on
by default.
.Pp
This setting was first introduced in version 1.8.15 but initially
suffered from a race condition.
The check for symbolic links in writable intermediate directories
was added in version 1.8.16.
.It sudoedit_follow
By default,
.Nm sudoedit
will not follow symbolic links when opening files.
The
.Em sudoedit_follow
option can be enabled to allow
.Nm sudoedit
to open symbolic links.
It may be overridden on a per-command basis by the
.Dv FOLLOW
and
.Dv NOFOLLOW
tags.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.8.15 or higher.
.It syslog_pid
When logging via
.Xr syslog 3 ,
include the process ID in the log entry.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.8.21 or higher.
.It targetpw
If set,
.Nm sudo
will prompt for the password of the user specified
by the
.Fl u
option (defaults to the value of
.Em runas_default )
instead of the password of the invoking user
when running a command or editing a file.
This flag precludes the use of a user-ID not listed in the passwd
database as an argument to the
.Fl u
option.
This flag is
.Em off
by default.
.It tty_tickets
If set, users must authenticate on a per-tty basis.
With this flag enabled,
.Nm sudo
will use a separate record in the time stamp file for each terminal.
If disabled, a single record is used for all login sessions.
.Pp
This option has been superseded by the
.Em timestamp_type
option.
.It umask_override
If set,
.Nm sudo
will set the umask as specified in the
.Em sudoers
file without modification.
This makes it possible to specify a umask in the
.Em sudoers
file that is more permissive than the user's own umask and matches
historical behavior.
If
.Em umask_override
is not set,
.Nm sudo
will set the umask to be the union of the user's umask and what is specified in
.Em sudoers .
This flag is
.Em @umask_override@
by default.
.if \n(LC \{\
.It use_loginclass
If set,
.Nm sudo
will apply the defaults specified for the target user's login class
if one exists.
Only available if
.Nm sudo
is configured with the
.Li --with-logincap
option.
This flag is
.Em off
by default.
.\}
.It use_netgroups
If set, netgroups (prefixed with
.Ql + ) ,
may be used in place of a user or host.
For LDAP-based sudoers, netgroup support requires an expensive
sub-string match on the server unless the
.Sy NETGROUP_BASE
directive is present in the
.Pa @ldap_conf@
file.
If netgroups are not needed, this option can be disabled to reduce the
load on the LDAP server.
This flag is
.Em on
by default.
.It use_pty
If set, and
.Nm sudo
is running in a terminal, the command will be run in a new pseudo-terminal.
If the
.Nm sudo
process is not attached to a terminal,
.Em use_pty
has no effect.
.Pp
A malicious program run under
.Nm sudo
may be capable of injecting commands into the user's
terminal or running a background process that retains access to the
user's terminal device even after the main program has finished
executing.
By running the command in a separate pseudo-terminal, this attack is
no longer possible.
.Pp
A side effect of running the command in a new pseudo-terminal is
that input will be passed to the command even if it is non-interactive.
This means that, for example, keys pressed while a non-interactive
command is running will be consumed by
.Nm sudo
instead of being passed to the shell after the command exits.
.Pp
This flag is
.Em on
by default for
.Nm sudo
1.9.14 and above.
.It user_command_timeouts
If set, the user may specify a timeout on the command line.
If the timeout expires before the command has exited, the
command will be terminated.
If a timeout is specified both in the
.Pa sudoers
file and on the command line, the smaller of the two timeouts will be used.
See the
.Em Timeout_Spec
section for a description of the timeout syntax.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.8.20 or higher.
.It utmp_runas
If set,
.Nm sudo
will store the name of the runas user when updating the utmp (or utmpx) file.
By default,
.Nm sudo
stores the name of the invoking user.
This flag is
.Em off
by default.
.It visiblepw
By default,
.Nm sudo
will refuse to run if the user must enter a password but it is not
possible to disable echo on the terminal.
If the
.Em visiblepw
flag is set,
.Nm sudo
will prompt for a password even when it would be visible on the screen.
This makes it possible to run things like
.Ql ssh somehost sudo ls
since by default,
.Xr ssh 1
does
not allocate a tty when running a command.
This flag is
.Em off
by default.
.El
.Pp
.Sy Integers :
.Bl -tag -width 16n
.It closefrom
Before it executes a command,
.Nm sudo
will close all open file descriptors other than standard input,
standard output, and standard error (file descriptors 0-2).
The
.Em closefrom
option can be used to specify a different file descriptor at which
to start closing.
The default is 3.
.It command_timeout
The maximum amount of time a command is allowed to run before
it is terminated.
See the
.Em Timeout_Spec
section for a description of the timeout syntax.
.Pp
This setting is only supported by version 1.8.20 or higher.
.It log_server_timeout
The maximum amount of time to wait when connecting to a log server
or waiting for a server response.
See the
.Em Timeout_Spec
section for a description of the timeout syntax.
The default value is 30 seconds.
.Pp
This setting is only supported by version 1.9.0 or higher.
.It maxseq
The maximum sequence number that will be substituted for the
.Ql %{seq}
escape in the I/O log file (see the
.Em iolog_dir
description below for more information).
While the value substituted for
.Ql %{seq}
is in base 36,
.Em maxseq
itself should be expressed in decimal.
Values larger than 2176782336 (which corresponds to the
base 36 sequence number
.Dq ZZZZZZ )
will be silently truncated to 2176782336.
The default value is 2176782336.
.Pp
Once the local sequence number reaches the value of
.Em maxseq ,
it will
.Dq roll over
to zero, after which
.Nm
will truncate and reuse any existing I/O log path names.
.Pp
This setting is only supported by version 1.8.7 or higher.
.It passwd_tries
The number of tries a user gets to enter his/her password before
.Nm sudo
logs the failure and exits.
The default is @passwd_tries@.
.It syslog_maxlen
On many systems,
.Xr syslog 3
has a relatively small log buffer.
IETF RFC 5424 states that syslog servers must support messages of
at least 480 bytes and should support messages up to 2048 bytes.
By default,
.Nm
creates log messages up to 980 bytes which corresponds to the
historic
.Bx
syslog implementation which used a 1024 byte buffer
to store the message, date, hostname, and program name.
To prevent syslog messages from being truncated,
.Nm
will split up log messages that are larger than
.Em syslog_maxlen
bytes.
When a message is split, additional parts will include the string
.Dq Pq command continued
after the user name and before the continued command line arguments.
.Pp
This setting is only supported by version 1.8.19 or higher.
.El
.Pp
.Sy Integers that can be used in a boolean context :
.Bl -tag -width 16n
.It loglinelen
Number of characters per line for the file log.
This value is used to decide when to wrap lines for nicer log files.
This has no effect on the syslog log file, only the file log.
The default is @loglen@ (use 0 or negate the option to disable word wrap).
.It passwd_timeout
Number of minutes before the
.Nm sudo
password prompt times out, or 0 for no timeout.
The timeout may include a fractional component
if minute granularity is insufficient, for example 2.5.
The default is @password_timeout@.
.It timestamp_timeout
Number of minutes that can elapse before
.Nm sudo
will ask for a password again.
The timeout may include a fractional component if
minute granularity is insufficient, for example 2.5.
The default is @timeout@.
Set this to 0 to always prompt for a password.
If set to a value less than 0 the user's time stamp will not expire
until the system is rebooted.
This can be used to allow users to create or delete their own time stamps via
.Ql sudo -v
and
.Ql sudo -k
respectively.
.It umask
File mode creation mask to use when running the command.
Negate this option or set it to 0777 to prevent
.Nm
from changing the umask.
Unless the
.Em umask_override
flag is set, the actual umask will be the union of the
user's umask and the value of the
.Em umask
setting, which defaults to @sudo_umask@.
This guarantees that
.Nm sudo
never lowers the umask when running a command.
.Pp
If
.Em umask
is explicitly set in
.Em sudoers ,
it will override any umask setting in PAM or login.conf.
If
.Em umask
is not set in
.Em sudoers ,
the umask specified by PAM or login.conf will take precedence.
The umask setting in PAM is not used for
.Nm sudoedit ,
which does not create a new PAM session.
.El
.Pp
.Sy Strings :
.Bl -tag -width 16n
.if \n(AA \{\
.It apparmor_profile
The default AppArmor profile to transition into when executing the
command.
The default
.Em apparmor_profile
can be overridden for individual
.Em sudoers
entries by specifying the
.Dv APPARMOR_PROFILE
option.
This option is only available when sudo is built with AppArmor
support.
.\}
.It cmddenial_message
It set,
.Nm sudo
will display this message when a user is denied access to run the
specified command, but is listed in the
.Em sudoers
file for the host.
This can be used to provide additional, site-specific information
to the user when a command is denied by the security policy.
It does not override the standard warning the user receives when
a command is denied.
.It authfail_message
Message that is displayed after a user fails to authenticate.
The message may include the
.Ql %d
escape which will expand to the number of failed password attempts.
If set, it overrides the default message,
.Dq %d incorrect password attempt(s) .
.It badpass_message
Message that is displayed if a user enters an incorrect password.
The default is
.Dq @badpass_message@
unless insults are enabled.
.It editor
A colon
.Pq Ql :\&
separated list of editor path names used by
.Nm sudoedit
and
.Nm visudo .
For
.Nm sudoedit ,
this list is used to find an editor when none of the
.Ev SUDO_EDITOR ,
.Ev VISUAL
or
.Ev EDITOR
environment variables are set to an editor that exists and is executable.
For
.Nm visudo ,
it is used as a white list of allowed editors;
.Nm visudo
will choose the editor that matches the user's
.Ev SUDO_EDITOR ,
.Ev VISUAL
or
.Ev EDITOR
environment variable if possible, or the first editor in the
list that exists and is executable if not.
Unless invoked as
.Nm sudoedit ,
.Nm sudo
does not preserve the
.Ev SUDO_EDITOR ,
.Ev VISUAL
or
.Ev EDITOR
environment variables unless they are present in the
.Em env_keep
list or the
.Em env_reset
option is disabled.
The default is
.Pa @editor@ .
.It intercept_type
The underlying mechanism used by the
.Em intercept
and
.Em log_subcmds
options.
It has the following possible values:
.Bl -tag -width 6n
.It dso
Preload a dynamic shared object (shared library) that intercepts the
.Xr execve 2 ,
.Xr execl 3 ,
.Xr execle 3 ,
.Xr execlp 3 ,
.Xr execv 3 ,
.Xr execvp 3 ,
.Xr execvpe 3 ,
and
.Xr system 3
library functions.
A value of
.Em dso
is incompatible with
.Nm sudo Ns 's
SELinux RBAC support.
.It trace
Use
.Xr ptrace 2
to intercept the
.Xr execve 2
system call.
This is only supported on Linux systems where
.Xr seccomp 2
filtering is enabled.
If the
.Pa /proc/sys/kernel/seccomp/actions_avail
file is missing or does not contain a
.Dq trap
element, setting
.Em intercept_type
to
.Em trace
will have no effect and
.Em dso
will be used instead.
.El
.Pp
The default is to use
.Em trace
if it is supported by the system and
.Em dso
if it is not.
.It iolog_dir
The top-level directory to use when constructing the path name for
the input/output log directory.
Only used if the
.Em log_input
or
.Em log_output
options are enabled or when the
.Dv LOG_INPUT
or
.Dv LOG_OUTPUT
tags are present for a command.
The session sequence number, if any, is stored in the directory.
The default is
.Pa @iolog_dir@ .
.Pp
The following percent
.Pq Ql %
escape sequences are supported:
.Bl -tag -width 4n
.It %{seq}
expanded to a monotonically increasing base-36 sequence number, such as 0100A5,
where every two digits are used to form a new directory, e.g.,
.Pa 01/00/A5
.It %{user}
expanded to the invoking user's login name
.It %{group}
expanded to the name of the invoking user's real group-ID
.It %{runas_user}
expanded to the login name of the user the command will
be run as (e.g.,
.Sy root )
.It %{runas_group}
expanded to the group name of the user the command will
be run as (e.g.,
.Sy wheel )
.It %{hostname}
expanded to the local host name without the domain name
.It %{command}
expanded to the base name of the command being run
.El
.Pp
In addition, any escape sequences supported by the system's
.Xr strftime 3
function will be expanded.
.Pp
To include a literal
.Ql %
character, the string
.Ql %%
should be used.
.Pp
Any path name separator characters
.Pq Ql /
present in the user, group or host name will be replaced with an underbar
.Pq Ql _
during expansion.
.It iolog_file
The path name, relative to
.Em iolog_dir ,
in which to store input/output logs when the
.Em log_input
or
.Em log_output
options are enabled or when the
.Dv LOG_INPUT
or
.Dv LOG_OUTPUT
tags are present for a command.
.Em iolog_file
may contain directory components.
The default is
.Ql %{seq} .
.Pp
See the
.Em iolog_dir
option above for a list of supported percent
.Pq Ql %
escape sequences.
.Pp
In addition to the escape sequences, path names that end in six or
more
.Em X Ns s
will have the
.Em X Ns s
replaced with a unique combination of digits and letters, similar to the
.Xr mktemp 3
function.
.Pp
If the path created by concatenating
.Em iolog_dir
and
.Em iolog_file
already exists, the existing I/O log file will be truncated and
overwritten unless
.Em iolog_file
ends in six or
more
.Em X Ns s .
.It iolog_flush
If set,
.Nm sudo
will flush I/O log data to disk after each write instead of buffering it.
This makes it possible to view the logs in real-time as the program
is executing but may significantly reduce the effectiveness of I/O
log compression.
This flag is
.Em off
by default.
.Pp
This setting is only supported by version 1.8.20 or higher.
.It iolog_group
The group name to look up when setting the group-ID on new I/O log
files and directories.
If
.Em iolog_group
is not set,
the primary group-ID of the user specified by
.Em iolog_user
is used.
If neither
.Em iolog_group
nor
.Em iolog_user
are set, I/O log files and directories are created with group-ID 0.
.Pp
This setting is only supported by version 1.8.19 or higher.
.It iolog_mode
The file mode to use when creating I/O log files.
Mode bits for read and write permissions for owner, group, or other
are honored, everything else is ignored.
The file permissions will always include the owner read and
write bits, even if they are not present in the specified mode.
When creating I/O log directories, search (execute) bits are added
to match the read and write bits specified by
.Em iolog_mode .
Defaults to 0600 (read and write by user only).
.Pp
This setting is only supported by version 1.8.19 or higher.
.It iolog_user
The user name to look up when setting the user and group-IDs on new
I/O log files and directories.
If
.Em iolog_group
is set, it will be used instead of the user's primary group-ID.
By default, I/O log files and directories are created with user and
group-ID 0.
.Pp
This setting can be useful when the I/O logs are stored on a Network
File System (NFS) share.
Having a dedicated user own the I/O log files means that
.Nm
does not write to the log files as user-ID 0, which is usually
not permitted by NFS.
.Pp
This setting is only supported by version 1.8.19 or higher.
.It lecture_status_dir
The directory in which
.Nm sudo
stores per-user lecture status files.
Once a user has received the lecture, a zero-length file is
created in this directory so that
.Nm sudo
will not lecture the user again.
This directory should
.Em not
be cleared when the system reboots.
The default is
.Pa @vardir@/lectured .
.if \n(PS \{\
.It limitprivs
The default Solaris limit privileges to use when constructing a new
privilege set for a command.
This bounds all privileges of the executing process.
The default limit privileges may be overridden on a per-command basis in
.Em sudoers .
This option is only available if
.Nm
is built on Solaris 10 or higher.
.\}
.It log_server_cabundle
The path to a certificate authority bundle file, in PEM format,
to use instead of the system's default certificate authority database
when authenticating the log server.
The default is to use the system's default certificate authority database.
This setting has no effect unless
.Em log_servers
is set and the remote log server is secured with TLS.
.Pp
This setting is only supported by version 1.9.0 or higher.
.It log_server_peer_cert
The path to the
.Nm sudo
client's certificate file, in PEM format.
This setting is required when the remote log server is secured
with TLS and client certificate validation is enabled.
For
.Nm sudo_logsrvd ,
client certificate validation is controlled by the
.Em tls_checkpeer
option, which defaults to
.Em false .
.Pp
This setting is only supported by version 1.9.0 or higher.
.It log_server_peer_key
The path to the
.Nm sudo
client's private key file, in PEM format.
This setting is required when the remote log server is secured
with TLS and client certificate validation is enabled.
For
.Nm sudo_logsrvd ,
client certificate validation is controlled by the
.Em tls_checkpeer
flag, which defaults to
.Em false .
.Pp
This setting is only supported by version 1.9.0 or higher.
.It mailsub
Subject of the mail sent to the
.Em mailto
user.
The escape
.Ql %h
will expand to the host name of the machine.
Default is
.Dq @mailsub@ .
.It noexec_file
As of
.Nm sudo
version 1.8.1 this option is no longer supported.
The path to the noexec file should now be set in the
.Xr sudo.conf @mansectform@
file.
.It pam_askpass_service
On systems that use PAM for authentication, this is the service
name used when the
.Fl A
option is specified.
The default value is either
.Ql sudo
or
.Ql @pam_login_service@ ,
depending on whether or not the
.Fl i
option is also specified.
See the description of
.Em pam_service
for more information.
.Pp
This setting is only supported by version 1.9.9 or higher.
.It pam_login_service
On systems that use PAM for authentication, this is the service
name used when the
.Fl i
option is specified.
The default value is
.Ql @pam_login_service@ .
See the description of
.Em pam_service
for more information.
.Pp
This setting is only supported by version 1.8.8 or higher.
.It pam_service
On systems that use PAM for authentication, the service name
specifies the PAM policy to apply.
This usually corresponds to an entry in the
.Pa pam.conf
file or a file in the
.Pa /etc/pam.d
directory.
The default value is
.Ql sudo .
.Pp
This setting is only supported by version 1.8.8 or higher.
.It passprompt
The default prompt to use when asking for a password; can be overridden via the
.Fl p
option or the
.Ev SUDO_PROMPT
environment variable.
The following percent
.Pq Ql %
escape sequences are supported:
.Bl -tag -width 4n
.It %H
expanded to the local host name including the domain name
(only if the machine's host name is fully qualified or the
.Em fqdn
option is set)
.It %h
expanded to the local host name without the domain name
.It %p
expanded to the user whose password is being asked for (respects the
.Em rootpw ,
.Em targetpw
and
.Em runaspw
flags in
.Em sudoers )
.It \&%U
expanded to the login name of the user the command will
be run as (defaults to
.Sy @runas_default@ )
.It %u
expanded to the invoking user's login name
.It %%
two consecutive
.Ql %
characters are collapsed into a single
.Ql %
character
.El
.Pp
On systems that use PAM for authentication,
.Em passprompt
will only be used if the prompt provided by the PAM module matches the string
.Dq "Password: "
or
.Dq "username's Password: " .
This ensures that the
.Em passprompt
setting does not interfere with challenge-response style authentication.
The
.Em passprompt_override
flag can be used to change this behavior.
.Pp
The default value is
.Ql "@passprompt@" .
.if \n(PS \{\
.It privs
The default Solaris privileges to use when constructing a new
privilege set for a command.
This is passed to the executing process via the inherited privilege set,
but is bounded by the limit privileges.
If the
.Em privs
option is specified but the
.Em limitprivs
option is not, the limit privileges of the executing process is set to
.Em privs .
The default privileges may be overridden on a per-command basis in
.Em sudoers .
This option is only available if
.Nm
is built on Solaris 10 or higher.
.\}
.if \n(SL \{\
.It role
The default SELinux role to use when constructing a new security
context to run the command.
The default role may be overridden on a per-command basis in the
.Em sudoers
file or via command line options.
This option is only available when
.Nm sudo
is built with SELinux support.
.\}
.It runas_default
The default user to run commands as if the
.Fl u
option is not specified on the command line.
This defaults to
.Sy @runas_default@ .
.It sudoers_locale
Locale to use when parsing the sudoers file, logging commands, and
sending email.
Changing the locale may affect how sudoers is interpreted.
Defaults to
.Ql C .
.It timestamp_type
.Nm
uses per-user time stamp files for credential caching.
The
.Em timestamp_type
option can be used to specify the type of time stamp record used.
It has the following possible values:
.Bl -tag -width 6n
.It global
A single time stamp record is used for all of a user's login sessions,
regardless of the terminal or parent process ID.
An additional record is used to serialize password prompts when
.Nm sudo
is used multiple times in a pipeline, but this does not affect authentication.
.It ppid
A single time stamp record is used for all processes with the same parent
process ID (usually the shell).
Commands run from the same shell (or other common parent process)
will not require a password for
.Em timestamp_timeout
minutes (@timeout@ by default).
Commands run via
.Nm sudo
with a different parent process ID, for example from a shell script,
will be authenticated separately.
.It tty
One time stamp record is used for each terminal,
which means that a user's login sessions are authenticated separately.
If no terminal is present, the behavior is the same as
.Em ppid .
Commands run from the same terminal will not require a password for
.Em timestamp_timeout
minutes (@timeout@ by default).
.It kernel
The time stamp is stored in the kernel as an attribute of the terminal
device.
If no terminal is present, the behavior is the same as
.Em ppid .
Negative
.Em timestamp_timeout
values are not supported and positive values are limited to a maximum
of 60 minutes.
This is currently only supported on
.Ox .
.El
.Pp
The default value is
.Em @timestamp_type@ .
.Pp
This setting is only supported by version 1.8.21 or higher.
.It timestampdir
The directory in which
.Nm sudo
stores its time stamp files.
This directory should be cleared when the system reboots.
The default is
.Pa @rundir@/ts .
.It timestampowner
The owner of the lecture status directory, time stamp directory and all
files stored therein.
The default is
.Sy root .
.if \n(SL \{\
.It type
The default SELinux type to use when constructing a new security
context to run the command.
The default type may be overridden on a per-command basis in the
.Em sudoers
file or via command line options.
This option is only available when
.Nm sudo
is built with SELinux support.
.\}
.El
.Pp
.Sy Strings that can be used in a boolean context :
.Bl -tag -width 12n
.It admin_flag
The
.Em admin_flag
option specifies the path to a file that is created the first time
a user that is a member of the
.Em sudo
or
.Em admin
groups runs
.Nm sudo .
Only available if
.Nm sudo
is configured with the
.Li --enable-admin-flag
option.
The default value is
.Pa ~/.sudo_as_admin_successful .
.It env_file
The
.Em env_file
option specifies the fully qualified path to a file containing variables
to be set in the environment of the program being run.
Entries in this file should either be of the form
.Ql VARIABLE=value
or
.Ql export VARIABLE=value .
The value may optionally be enclosed in single or double quotes.
Variables in this file are only added if the variable does not already
exist in the environment.
This file is considered to be part of the security policy,
its contents are not subject to other
.Nm sudo
environment restrictions such as
.Em env_keep
and
.Em env_check .
.It exempt_group
Users in this group are exempt from password and PATH requirements.
The group name specified should not include a
.Ql %
prefix.
This is not set by default.
.It fdexec
Determines whether
.Nm sudo
will execute a command by its path or by an open file descriptor.
It has the following possible values:
.Bl -tag -width 6n
.It always
Always execute by file descriptor.
.It never
Never execute by file descriptor.
.It digest_only
Only execute by file descriptor if the command has an associated digest
in the
.Em sudoers
file.
.El
.Pp
The default value is
.Em digest_only .
This avoids a time of check versus time of use race condition when
the command is located in a directory writable by the invoking user.
.Pp
.Em fdexec
will change the first element of the argument vector for scripts
($0 in the shell) due to the way the kernel runs script interpreters.
Instead of being a normal path, it will refer to a file descriptor.
For example,
.Pa /dev/fd/4
on Solaris and
.Pa /proc/self/fd/4
on Linux.
A workaround is to use the
.Dv SUDO_COMMAND
environment variable instead.
.Pp
The
.Em fdexec
setting is only used when the command is matched by path name.
It has no effect if the command is matched by the built-in
.Sy ALL
alias.
.Pp
This setting is only supported by version 1.8.20 or higher.
If the operating system does not support the
.Xr fexecve 2
system call, this setting has no effect.
.It group_plugin
A string containing a
.Nm
group plugin with optional arguments.
The string should consist of the plugin
path, either fully-qualified or relative to the
.Pa @plugindir@
directory, followed by any configuration arguments the plugin requires.
These arguments (if any) will be passed to the plugin's initialization function.
If arguments are present, the string must be enclosed in double quotes
.Pq \&"" .
.Pp
On 64-bit systems, if the plugin is present but cannot be loaded,
.Nm
will look for a 64-bit version and, if it exists, load that as a fallback.
The exact rules for this vary by system.
On Solaris, if the plugin is stored in a directory ending in
.Dq lib ,
.Nm
will create a fallback path by appending
.Dq /64
to the directory name;
.Pa @prefix@/lib/group_plugin.so
becomes
.Pa @prefix@/lib/64/group_plugin.so .
On Linux, a directory ending in
.Dq lib
will be transformed to
.Dq lib64
as the fallback path;
.Pa @prefix@/lib/group_plugin.so
becomes
.Pa @prefix@/lib64/group_plugin.so .
On all other systems, the fallback path is generated by adding a
.Dq 64
before the file extension;
.Pa group_plugin.so
becomes
.Pa group_plugin64.so .
.Pp
On AIX systems, the plugin may be either a shared object
ending in
.Ql .so
or an archive file containing a shared object ending in
.Ql .a
with the name of the shared object in parentheses at the end.
.Pp
For more information see
.Sx "GROUP PROVIDER PLUGINS" .
.It lecture
This option controls when a short lecture will be printed along with
the password prompt.
It has the following possible values:
.Bl -tag -width 6n
.It always
Always lecture the user.
.It never
Never lecture the user.
.It once
Only lecture the user the first time they run
.Nm sudo .
.El
.Pp
If no value is specified, a value of
.Em once
is implied.
Negating the option results in a value of
.Em never
being used.
The default value is
.Em @lecture@ .
.It lecture_file
Path to a file containing an alternate
.Nm sudo
lecture that will be used in place of the standard lecture if the named
file exists.
By default,
.Nm sudo
uses a built-in lecture.
.It listpw
This option controls when a password will be required when a user runs
.Nm sudo
with the
.Fl l
option.
It has the following possible values:
.Bl -tag -width 4n
.It all
All the user's
.Em sudoers
file entries for the current host must have
the
.Dv NOPASSWD
flag set to avoid entering a password.
.It always
The user must always enter a password to use the
.Fl l
option.
.It any
At least one of the user's
.Em sudoers
file entries for the current host
must have the
.Dv NOPASSWD
flag set to avoid entering a password.
.It never
The user need never enter a password to use the
.Fl l
option.
.El
.Pp
If no value is specified, a value of
.Em any
is implied.
Negating the option results in a value of
.Em never
being used.
The default value is
.Em any .
.It log_format
The event log format.
Supported log formats are:
.Bl -tag -width 4n
.It json
Currently, this is an alias for
.Em json_pretty .
In a future version of
.Nm sudo ,
.Em json
will be equivalent to
.Em json_compact .
JSON log entries contain the full user details as well as the execution
environment if the command was allowed.
.It json_compact
Log events in
.Dq compact
(minified) JSON format.
Each event is written as a separate JSON object on single line without
extraneous white space.
Due to limitations of the protocol, JSON events sent via
.Em syslog
may be truncated.
.It json_pretty
Log events in
.Dq pretty
JSON format.
When logging to a file, the entire file is treated as a single JSON
object consisting of multiple events, each event spanning multiple lines.
When logging via
.Em syslog ,
there is no difference between the
.Em json_pretty
and
.Em json_compact
formats.
.It sudo
Log events in traditional sudo-style format, see
.Sx "EVENT LOGGING"
for details.
.El
.Pp
This setting affects logs sent via
.Xr syslog 3
as well as the file specified by the
.Em logfile
setting, if any.
The default value is
.Em sudo .
.It logfile
Path to the
.Nm sudo
log file (not the syslog log file).
Setting a path turns on logging to a file;
negating this option turns it off.
By default,
.Nm sudo
logs via syslog.
.It mailerflags
Flags to use when invoking mailer.
Defaults to
.Fl t .
.It mailerpath
Path to mail program used to send warning mail (negate to prevent
.Nm sudo
from sending mail).
Defaults to the path to sendmail found at configure time.
.It mailfrom
Address to use for the
.Dq from
address when sending warning and error mail.
The address should be enclosed in double quotes
.Pq \&""
to protect against
.Nm sudo
interpreting the
.Ql @
sign.
Defaults to the name of the user running
.Nm sudo .
.It mailto
Address to send warning and error mail to (negate to prevent
.Nm sudo
from sending mail).
The address should be enclosed in double quotes
.Pq \&""
to protect against
.Nm sudo
interpreting the
.Ql @
sign.
Defaults to @mailto@.
.It rlimit_as
The maximum size to which the process's address space may grow (in bytes),
if supported by the operating system.
See
.Sx "Resource limits"
for more information.
.It rlimit_core
The largest size core dump file that may be created (in bytes).
See
.Sx "Resource limits"
for more information.
Defaults to 0 (no core dump created).
.It rlimit_cpu
The maximum amount of CPU time that the process may use (in seconds).
See
.Sx "Resource limits"
for more information.
.It rlimit_data
The maximum size of the data segment for the process (in bytes).
See
.Sx "Resource limits"
for more information.
.It rlimit_fsize
The largest size file that the process may create (in bytes).
See
.Sx "Resource limits"
for more information.
.It rlimit_locks
The maximum number of locks that the process may establish,
if supported by the operating system.
See
.Sx "Resource limits"
for more information.
.It rlimit_memlock
The maximum size that the process may lock in memory (in bytes),
if supported by the operating system.
See
.Sx "Resource limits"
for more information.
.It rlimit_nofile
The maximum number of files that the process may have open.
See
.Sx "Resource limits"
for more information.
.It rlimit_nproc
The maximum number of processes that the user may run simultaneously.
See
.Sx "Resource limits"
for more information.
.It rlimit_rss
The maximum size to which the process's resident set size may grow (in bytes).
See
.Sx "Resource limits"
for more information.
.It rlimit_stack
The maximum size to which the process's stack may grow (in bytes).
See
.Sx "Resource limits"
for more information.
.It restricted_env_file
The
.Em restricted_env_file
option specifies the fully qualified path to a file containing variables
to be set in the environment of the program being run.
Entries in this file should either be of the form
.Ql VARIABLE=value
or
.Ql export VARIABLE=value .
The value may optionally be enclosed in single or double quotes.
Variables in this file are only added if the variable does not already
exist in the environment.
Unlike
.Em env_file ,
the file's contents are not trusted and are processed in a manner
similar to that of the invoking user's environment.
If
.Em env_reset
is enabled, variables in the file will only be added if they are
matched by either the
.Em env_check
or
.Em env_keep
list.
If
.Em env_reset
is disabled, variables in the file are added as long as they
are not matched by the
.Em env_delete
list.
In either case, the contents of
.Em restricted_env_file
are processed before the contents of
.Em env_file .
.It runchroot
If set,
.Nm sudo
will use this value for the root directory when running a command.
The special value
.Dq *
will allow the user to specify the root directory via
.Nm sudo Ns 's
.Fl R
option.
See the
.Sx Chroot_Spec
section for more details.
.Pp
It is only possible to use
.Em runchroot
as a command-specific Defaults setting if the command exists with
the same path both inside and outside the chroot jail.
This restriction does not apply to global, host, or user-based
Defaults settings or to a
.Em Cmnd_Spec
that includes a
.Em Chroot_Spec .
.Pp
This setting is only supported by version 1.9.3 or higher.
.It runcwd
If set,
.Nm sudo
will use this value for the working directory when running a command.
The special value
.Dq *
will allow the user to specify the working directory via
.Nm sudo Ns 's
.Fl D
option.
See the
.Sx Chdir_Spec
section for more details.
.Pp
This setting is only supported by version 1.9.3 or higher.
.It secure_path
If set,
.Nm sudo
will use this value in place of the user's
.Ev PATH
environment variable.
There are two basic use cases for
.Em secure_path :
.Bl -enum -width 1n
.It
To make it possible for
.Nm sudo
to find system administrator commands located in directories that
may not be in the default user path, such as
.Pa /usr/sbin .
.It
To help protect scripts and programs that execute other commands without
first setting
.Ev PATH
to a safe value.
Otherwise, a user with limited privileges may be able to run arbitrary
commands by manipulating the
.Ev PATH
if the command being run executes other commands without using a
fully-qualified path name.
.El
.Pp
Users in the group specified by the
.Em exempt_group
option are not affected by
.Em secure_path .
This option is @secure_path_status@ by default.
.It syslog
Syslog facility if syslog is being used for logging (negate to
disable syslog logging).
Defaults to @logfac@.
.Pp
The following syslog facilities are supported:
.Sy authpriv
(if your
OS supports it),
.Sy auth ,
.Sy daemon ,
.Sy user ,
.Sy local0 ,
.Sy local1 ,
.Sy local2 ,
.Sy local3 ,
.Sy local4 ,
.Sy local5 ,
.Sy local6 ,
and
.Sy local7 .
.It syslog_badpri
Syslog priority to use when the user is not allowed to run a command or
when authentication is unsuccessful.
Defaults to @badpri@.
.Pp
The following syslog priorities are supported:
.Sy alert ,
.Sy crit ,
.Sy debug ,
.Sy emerg ,
.Sy err ,
.Sy info ,
.Sy notice ,
.Sy warning ,
and
.Sy none .
Negating the option or setting it to a value of
.Sy none
will disable logging of unsuccessful commands.
.It syslog_goodpri
Syslog priority to use when the user is allowed to run a command and
authentication is successful.
Defaults to @goodpri@.
.Pp
See
.Em syslog_badpri
for the list of supported syslog priorities.
Negating the option or setting it to a value of
.Sy none
will disable logging of successful commands.
.It verifypw
This option controls when a password will be required when a user runs
.Nm sudo
with the
.Fl v
option.
It has the following possible values:
.Bl -tag -width 6n
.It all
All the user's
.Em sudoers
file entries for the current host must have the
.Dv NOPASSWD
flag set to avoid entering a password.
.It always
The user must always enter a password to use the
.Fl v
option.
.It any
At least one of the user's
.Em sudoers
file entries for the current host must have the
.Dv NOPASSWD
flag set to avoid entering a password.
.It never
The user need never enter a password to use the
.Fl v
option.
.El
.Pp
If no value is specified, a value of
.Em all
is implied.
Negating the option results in a value of
.Em never
being used.
The default value is
.Em all .
.El
.Pp
.Sy Lists that can be used in a boolean context :
.Bl -tag -width 16n
.It env_check
Environment variables to be removed from the user's environment
unless they are considered
.Dq safe .
For all variables except
.Ev TZ ,
.Dq safe
means that the variable's value does not contain any
.Ql %
or
.Ql /
characters.
This can be used to guard against printf-style format vulnerabilities
in poorly-written programs.
The
.Ev TZ
variable is considered unsafe if any of the following are true:
.Bl -bullet -width 1n
.It
It consists of a fully-qualified path name,
optionally prefixed with a colon
.Pq Ql :\& ,
that does not match the location of the
.Pa zoneinfo
directory.
.It
It contains a
.Pa ..
path element.
.It
It contains white space or non-printable characters.
.It
It is longer than the value of
.Dv PATH_MAX .
.El
.Pp
The argument may be a double-quoted, space-separated list or a
single value without double-quotes.
The list can be replaced, added to, deleted from, or disabled by using
the
.Ql = ,
.Ql += ,
.Ql -= ,
and
.Ql \&!
operators respectively.
Regardless of whether the
.Em env_reset
option is enabled or disabled, variables specified by
.Em env_check
will be preserved in the environment if they pass the aforementioned check.
The global list of environment variables to check is displayed when
.Nm sudo
is run by
.Sy root
with the
.Fl V
option.
.It env_delete
Environment variables to be removed from the user's environment when the
.Em env_reset
option is not in effect.
The argument may be a double-quoted, space-separated list or a
single value without double-quotes.
The list can be replaced, added to, deleted from, or disabled by using the
.Ql = ,
.Ql += ,
.Ql -= ,
and
.Ql \&!
operators respectively.
The global list of environment variables to remove is displayed when
.Nm sudo
is run by
.Sy root
with the
.Fl V
option.
Many operating systems will remove potentially dangerous variables
from the environment of any set-user-ID process (such as
.Nm sudo ) .
.It env_keep
Environment variables to be preserved in the user's environment when the
.Em env_reset
option is in effect.
This allows fine-grained control over the environment
.Nm sudo Ns -spawned
processes will receive.
The argument may be a double-quoted, space-separated list or a
single value without double-quotes.
The list can be replaced, added to, deleted from, or disabled by using the
.Ql = ,
.Ql += ,
.Ql -= ,
and
.Ql \&!
operators respectively.
The global list of variables to keep
is displayed when
.Nm sudo
is run by
.Sy root
with the
.Fl V
option.
.Pp
Preserving the
.Ev HOME
environment variable has security implications since many programs use it
when searching for configuration or data files.
Adding
.Ev HOME
to
.Em env_keep
may enable a user to run unrestricted commands via
.Nm sudo
and is strongly discouraged.
Users wishing to edit files with
.Nm sudo
should run
.Nm sudoedit
(or
.Nm sudo Fl e )
to get their accustomed editor configuration instead of
invoking the editor directly.
.It log_servers
A list of one or more servers to use for remote event and I/O log storage,
separated by white space.
Log servers must be running
.Nm sudo_logsrvd
or another service that implements the protocol described by
.Xr sudo_logsrv.proto @mansectform@ .
.Pp
Server addresses should be of the form
.Dq host Ns Oo : Ns port Oc Ns Op (tls) .
The host portion may be a host name, an IPv4 address, or an IPv6 address
in square brackets.
.Pp
If the optional
.Em tls
flag is present, the connection will be secured
with Transport Layer Security (TLS) version 1.2 or 1.3.
Versions of TLS prior to 1.2 are not supported.
.Pp
If a port is specified, it may either be a port number or a well-known
service name as defined by the system service name database.
If no port is specified, port 30343 will be used for plaintext
connections and port 30344 will be used for TLS connections.
.Pp
When
.Em log_servers
is set, event log data will be logged both locally (see the
.Em syslog
and
.Em log_file
settings) as well as remotely, but I/O log data will only be logged remotely.
If multiple hosts are specified, they will be attempted in reverse order.
If no log servers are available, the user will not be able to run
a command unless either the
.Em ignore_iolog_errors
flag (I/O logging enabled) or the
.Em ignore_log_errors
flag (I/O logging disabled) is set.
Likewise, if the connection to the log server is interrupted while
.Nm sudo
is running, the command will be terminated unless the
.Em ignore_iolog_errors
flag (I/O logging enabled) or the
.Em ignore_log_errors
flag (I/O logging disabled) is set.
.Pp
This setting is only supported by version 1.9.0 or higher.
.It passprompt_regex
A list of POSIX extended regular expressions used to
match password prompts in the terminal output.
As an extension, if the regular expression begins with
.Dq (?i) ,
it will be matched in a case-insensitive manner.
Each regular expression is limited to 1024 characters.
This option is only used when
.Em log_passwords
has been disabled.
The default value is
.Dq [Pp]assword[: ]*
.Pp
This setting is only supported by version 1.9.10 or higher.
.El
.Sh GROUP PROVIDER PLUGINS
The
.Nm
plugin supports its own plugin interface to allow non-Unix
group lookups which can query a group source other
than the standard Unix group database.
This can be used to implement support for the
.Em nonunix_group
syntax described earlier.
.Pp
Group provider plugins are specified via the
.Em group_plugin
setting.
The argument to
.Em group_plugin
should consist of the plugin path, either fully-qualified or relative to the
.Pa @plugindir@
directory, followed by any configuration options the plugin requires.
These options (if specified) will be passed to the plugin's initialization
function.
If options are present, the string must be enclosed in double quotes
.Pq \&"" .
.Pp
The following group provider plugins are installed by default:
.Bl -tag -width 4n
.It group_file
The
.Em group_file
plugin supports an alternate group file that uses the same syntax as the
.Pa /etc/group
file.
The path to the group file should be specified as an option
to the plugin.
For example, if the group file to be used is
.Pa /etc/sudo-group :
.Bd -literal
Defaults group_plugin="group_file.so /etc/sudo-group"
.Ed
.It system_group
The
.Em system_group
plugin supports group lookups via the standard C library functions
.Xr getgrnam 3
and
.Xr getgrid 3 .
This plugin can be used in instances where the user belongs to
groups not present in the user's supplemental group vector.
This plugin takes no options:
.Bd -literal
Defaults group_plugin=system_group.so
.Ed
.El
.Pp
The group provider plugin API is described in detail in
.Xr sudo_plugin @mansectform@ .
.Sh EVENT LOGGING
.Nm
can log events in either JSON or
.Em sudo
format,
this section describes the
.Em sudo
log format.
Depending on
.Em sudoers
configuration,
.Nm
can log events via
.Xr syslog 3 ,
to a local log file, or both.
The log format is almost identical in both cases.
Any control characters present in the log data are formatted in octal
with a leading
.Ql #
character.
For example, a horizontal tab is stored as
.Ql #011
and an embedded carriage return is stored as
.Ql #015 .
In addition, space characters in the command path are stored as
.Ql #040 .
Command line arguments that contain spaces are enclosed in single quotes
.Pq '' .
This makes it possible to distinguish multiple command line arguments
from a single argument that contains spaces.
Literal single quotes and backslash characters
.Pq Ql \e
in command line arguments are escaped with a backslash.
.Ss Accepted command log entries
Commands that sudo runs are logged using the following format (split
into multiple lines for readability):
.Bd -literal -offset 4n
date hostname progname: username : TTY=ttyname ; CHROOT=chroot ; \e
    PWD=cwd ; USER=runasuser ; GROUP=runasgroup ; TSID=logid ; \e
    ENV=env_vars COMMAND=command
.Ed
.Pp
Where the fields are as follows:
.Bl -tag -width 12n
.It date
The date the command was run.
Typically, this is in the format
.Dq MMM, DD, HH:MM:SS .
If logging via
.Xr syslog 3 ,
the actual date format is controlled by the syslog daemon.
If logging to a file and the
.Em log_year
option is enabled,
the date will also include the year.
.It hostname
The name of the host
.Nm sudo
was run on.
This field is only present when logging via
.Xr syslog 3 .
.It progname
The name of the program, usually
.Em sudo
or
.Em sudoedit .
This field is only present when logging via
.Xr syslog 3 .
.It username
The login name of the user who ran
.Nm sudo .
.It ttyname
The short name of the terminal (e.g.,
.Dq console ,
.Dq tty01 ,
or
.Dq pts/0 )
.Nm sudo
was run on, or
.Dq unknown
if there was no terminal present.
.It chroot
The root directory that the command was run in, if one was specified.
.It cwd
The current working directory that
.Nm sudo
was run in.
.It runasuser
The user the command was run as.
.It runasgroup
The group the command was run as if one was specified on the command line.
.It logid
An I/O log identifier that can be used to replay the command's output.
This is only present when the
.Em log_input
or
.Em log_output
option is enabled.
.It env_vars
A list of environment variables specified on the command line,
if specified.
.It command
The actual command that was executed, including any command line arguments.
.El
.Pp
Messages are logged using the locale specified by
.Em sudoers_locale ,
which defaults to the
.Ql C
locale.
.Ss Denied command log entries
If the user is not allowed to run the command, the reason for the denial
will follow the user name.
Possible reasons include:
.Bl -tag -width 4
.It user NOT in sudoers
The user is not listed in the
.Em sudoers
file.
.It user NOT authorized on host
The user is listed in the
.Em sudoers
file but is not allowed to run commands on the host.
.It command not allowed
The user is listed in the
.Em sudoers
file for the host but they are not allowed to run the specified command.
.It 3 incorrect password attempts
The user failed to enter their password after 3 tries.
The actual number of tries will vary based on the number of
failed attempts and the value of the
.Em passwd_tries
option.
.It a password is required
The
.Fl n
option was specified but a password was required.
.It sorry, you are not allowed to set the following environment variables
The user specified environment variables on the command line that
were not allowed by
.Em sudoers .
.El
.Ss Error log entries
If an error occurs,
.Nm
will log a message and, in most cases, send a message to the
administrator via email.
Possible errors include:
.Bl -tag -width 4
.It parse error in @sysconfdir@/sudoers near line N
.Nm
encountered an error when parsing the specified file.
In some cases, the actual error may be one line above or below the
line number listed, depending on the type of error.
.It problem with defaults entries
The
.Em sudoers
file contains one or more unknown Defaults settings.
This does not prevent
.Nm sudo
from running, but the
.Em sudoers
file should be checked using
.Nm visudo .
.It timestamp owner (username): \&No such user
The time stamp directory owner, as specified by the
.Em timestampowner
setting, could not be found in the password database.
.It unable to open/read @sysconfdir@/sudoers
The
.Em sudoers
file could not be opened for reading.
This can happen when the
.Em sudoers
file is located on a remote file system that maps user-ID 0 to
a different value.
Normally,
.Nm
tries to open the
.Em sudoers
file using group permissions to avoid this problem.
Consider either changing the ownership of
.Pa @sysconfdir@/sudoers
or adding an argument like
.Dq sudoers_uid=N
(where
.Sq N
is the user-ID that owns the
.Em sudoers
file) to the end of the
.Nm
.Em Plugin
line in the
.Xr sudo.conf @mansectform@
file.
.It unable to open @sysconfdir@/sudoers
The
.Pa @sysconfdir@/sudoers
file is missing.
.It @sysconfdir@/sudoers is not a regular file
The
.Pa @sysconfdir@/sudoers
file exists but is not a regular file or symbolic link.
.It @sysconfdir@/sudoers is owned by uid N, should be 0
The
.Em sudoers
file has the wrong owner.
If you wish to change the
.Em sudoers
file owner, add
.Dq sudoers_uid=N
(where
.Sq N
is the user-ID that owns the
.Em sudoers
file) to the
.Nm
.Em Plugin
line in the
.Xr sudo.conf @mansectform@
file.
.It @sysconfdir@/sudoers is world writable
The permissions on the
.Em sudoers
file allow all users to write to it.
The
.Em sudoers
file must not be world-writable, the default file mode
is 0440 (readable by owner and group, writable by none).
The default mode may be changed via the
.Dq sudoers_mode
option to the
.Nm
.Em Plugin
line in the
.Xr sudo.conf @mansectform@
file.
.It @sysconfdir@/sudoers is owned by gid N, should be 1
The
.Em sudoers
file has the wrong group ownership.
If you wish to change the
.Em sudoers
file group ownership, add
.Dq sudoers_gid=N
(where
.Sq N
is the group-ID that owns the
.Em sudoers
file) to the
.Nm
.Em Plugin
line in the
.Xr sudo.conf @mansectform@
file.
.It unable to open @rundir@/ts/user-ID
.Nm
was unable to read or create the user's time stamp file.
This can happen when
.Em timestampowner
is set to a user other than
.Sy root
and the mode on
.Pa @rundir@
is not searchable by group or other.
The default mode for
.Pa @rundir@
is 0711.
.It unable to write to @rundir@/ts/user-ID
.Nm
was unable to write to the user's time stamp file.
.It @rundir@/ts is owned by uid X, should be Y
The time stamp directory is owned by a user other than
.Em timestampowner .
This can occur when the value of
.Em timestampowner
has been changed.
.Nm
will ignore the time stamp directory until the owner is corrected.
.It @rundir@/ts is group writable
The time stamp directory is group-writable; it should be writable only by
.Em timestampowner .
The default mode for the time stamp directory is 0700.
.Nm
will ignore the time stamp directory until the mode is corrected.
.El
.Ss Notes on logging via syslog
By default,
.Nm
logs messages via
.Xr syslog 3 .
The
.Em date ,
.Em hostname ,
and
.Em progname
fields are added by the system's
.Xr syslog 3
function, not
.Nm
itself.
As such, they may vary in format on different systems.
.Pp
The maximum size of syslog messages varies from system to system.
The
.Em syslog_maxlen
setting can be used to change the maximum syslog message size
from the default value of 980 bytes.
For more information, see the description of
.Em syslog_maxlen .
.Ss Notes on logging to a file
If the
.Em logfile
option is set,
.Nm
will log to a local file, such as
.Pa @log_dir@/sudo .
When logging to a file,
.Nm
uses a format similar to
.Xr syslog 3 ,
with a few important differences:
.Bl -enum
.It
The
.Em progname
field is not present.
.It
The
.Em hostname
is only logged if the
.Em log_host
option is enabled.
.It
The date does not include the year unless the
.Em log_year
option is enabled.
.It
Lines that are longer than
.Em loglinelen
characters (80 by default) are word-wrapped and continued on the
next line with a four character indent.
This makes entries easier to read for a human being, but makes it
more difficult to use
.Xr grep 1
on the log files.
If the
.Em loglinelen
option is set to 0 (or negated with a
.Ql \&! ) ,
word wrap will be disabled.
.El
.Sh I/O LOGGING
When I/O logging is enabled,
.Nm sudo
will runs the command in a pseudo-terminal, logging user input
and/or output, depending on which
.Nm
flags are enabled.
There are five distinct types of I/O that can be logged, each with
a corresponding
.Nm
flag.
.Bl -column "standard output" "log_output" "command output displayed to the screen"
.It Sy Type Ta Sy Flag Ta Sy Description
.It terminal input Ta log_ttyin Ta keystrokes entered by the user
.It terminal output Ta log_ttyout Ta command output displayed to the screen
.It standard input Ta log_stdin Ta input from a pipe or a file
.It standard output Ta log_stdout Ta output to a pipe or a file
.It standard error Ta log_stderr Ta output to a pipe or a file
.El
.Pp
In addition to flags described the above, the
.Em log_input
flag and
.Dv LOG_INPUT
command tag set both
.Em log_ttyin
and
.Em log_stdin .
The
.Em log_output
flag and
.Dv LOG_OUTPUT
command tag set
.Em log_ttyout ,
.Em log_stdout ,
and
.Em log_stderr .
.Pp
To capture terminal input and output,
.Nm sudo
run the command in a pseudo-terminal, logging the input and
output before passing it on to the user.
To capture the standard input, standard output or standard error,
.Nm sudo
uses a pipe to interpose itself between the input or output stream,
logging the I/O before passing it to the other end of the pipe.
.Pp
I/O can be logged either to the local machine or to a remote log server.
For local logs, I/O is logged to the directory specified by the
.Em iolog_dir
option
.Po
.Pa @iolog_dir@
by default
.Pc
using a unique session ID that is included in the
.Nm sudo
log line, prefixed with
.Ql TSID= .
The
.Em iolog_file
option may be used to control the format of the session ID.
For remote logs, the
.Em log_servers
setting is used to specify one or more log servers running
.Nm sudo_logsrvd
or another server that implements the protocol described by
.Xr sudo_logsrv.proto @mansectform@ .
.Ss I/O logging pitfals
When logging standard input, anything sent to the standard input
will be consumed, regardless of whether or not the command run via
.Nm sudo
is actively reading the standard input.
This may have unexpected results when using
.Nm sudo
in a shell script that expects to process the standard input.
For example, given the following shell script:
.Bd -literal -offset 4n
#!/bin/sh
sudo echo testing
echo done
.Ed
.Pp
It will behave as expected when the script is passed to the shell as a
an argument:
.Bd -literal -offset 4n
$ sh test.sh
testing
done
.Ed
.Pp
However, if the script is passed to the shell on the standard input, the
.Ql sudo echo testing
command will consume the rest of the script.
This means that the
.Ql echo done
statement is never executed.
.Bd -literal -offset 4n
$ sh -s < test.sh
testing
.Ed
.Pp
There are several ways to work around this problem:
.Bl -enum
.It
Redirect the standard input from
.Pa /dev/null
when running a command via
.Nm sudo
that does not need to read the standard input.
.Bd -literal -offset 4n
sudo echo testing < /dev/null
.Ed
.It
Pass the script to the shell by path name instead of via the standard input.
.Bd -literal -offset 4n
sh test.sh
.Ed
.It
Disable logging the standard input for commands that do not need
to read the standard input.
.Bd -literal -offset 4n
Defaults!/bin/echo !log_stdin
.Ed
.El
.Pp
Depending on the command, it may not be desirable to log the
standard input or standard output.
For example, I/O logging of commands that send or receive large
amount of data via the standard output or standard input such as
.Xr rsync 1
and
.Xr tar 1
could fill up the log file system with superfluous data.
It is possible to disable logging of the standard input and standard
output for such commands as follows:
.Bd -literal -offset 4n
Cmnd_Alias COPY_CMDS = /usr/bin/tar, /usr/bin/cpio, /usr/bin/rsync

# Log input and output but omit stdin and stdout when copying files.
Defaults log_input, log_output
Defaults!COPY_CMDS !log_stdin, !log_stdout
.Ed
.Pp
However, be aware that using the
.Em log_input
flag or the
.Dv LOG_INPUT
command tag will also enable
.Em log_stdin .
Likewise, the
.Em log_ouput
flag or the
.Dv LOG_OUTPUT
command tag will enable
.Em log_stdout
and
.Em log_stderr.
Careful ordering of rules may be necessary to achieve the results
that you expect.
.Ss I/O log format
For both local and remote I/O logs, each log is stored in a separate
directory that contains the following files:
.Bl -tag -width "log.json"
.It Pa log
A text file containing information about the command.
The first line consists of the following colon-delimited fields:
the time the command was run, the name of the user
who ran
.Nm sudo ,
the name of the target user, the name of the target group (optional),
the terminal that
.Nm sudo
was run from, and the number of lines and columns of the terminal.
The second and third lines contain the working directory the command
was run from and the path name of the command itself (with arguments
if present).
.It Pa log.json
A JSON-formatted file containing information about the command.
This is similar to the
.Pa log
file but contains additional information and is easily extensible.
The
.Pa log.json
file will be used by
.Xr sudoreplay @mansectsu@
in preference to the
.Pa log
file if it exists.
The file may contain the following elements:
.Bl -tag -width 4n
.It timestamp
A JSON object containing time the command was run.
It consists of two values,
.Em seconds
and
.Em nanoseconds .
.It columns
The number of columns of the terminal the command ran on, or zero
if no terminal was present.
.It command
The fully-qualified path of the command that was run.
.It lines
The number of lines of the terminal the command ran on, or zero
if no terminal was present.
.It runargv
A JSON array representing the command's argument vector as passed to the
.Xr execve 2
system call.
.It runenv
A JSON array representing the command's environment as passed to the
.Xr execve 2
system call.
.It rungid
The group ID the command ran as.
This element is only present when the user specifies a group on the
command line.
.It rungroup
The name of the group the command ran as.
This element is only present when the user specifies a group on the
command line.
.It runuid
The user ID the command ran as.
.It runuser
The name of the user the command ran as.
.It submitcwd
The current working directory at the time
.Nm sudo
was run.
.It submithost
The name of the host the command was run on.
.It submituser
The name of the user who ran the command via
.Nm sudo .
.It ttyname
The path name of the terminal the user invoked
.Nm sudo
from.
If the command was run in a pseudo-terminal,
.Em ttyname
will be different from the terminal the command actually ran in.
.El
.It Pa timing
Timing information used to replay the session.
Each line consists of the I/O log entry type and amount of time
since the last entry, followed by type-specific data.
The I/O log entry types and their corresponding type-specific data are:
.Pp
.Bl -tag -width 4n -compact
.It 0
standard input, number of bytes in the entry
.It 1
standard output, number of bytes in the entry
.It 2
standard error, number of bytes in the entry
.It 3
terminal input, number of bytes in the entry
.It 4
terminal output, number of bytes in the entry
.It 5
window change, new number lines and columns
.It 6
bug compatibility for
.Nm sudo
1.8.7 terminal output
.It 7
command suspend or resume, signal received
.El
.It Pa ttyin
Raw input from the user's terminal, exactly as it was received.
This file is only present if the
.Em log_input
or
.Em log_ttyin
flags are set and
.Nm sudo
was run from a terminal.
No post-processing is performed.
For manual viewing, you may wish to convert carriage return characters
in the log to line feeds.
For example:
.Ql gunzip -c ttyin | tr \&"\er\&" \&"\en\&"
.It Pa stdin
The standard input when no terminal is present, or input redirected from
a pipe or file.
This file is only present if the
.Em log_input
or
.Em log_stdin
flags are set and the standard input is not connected to a terminal.
.It Pa ttyout
Output from the pseudo-terminal (what the command writes to the screen).
Terminal-specific post-processing is performed before the data is logged.
This means that, for example, line feeds are usually converted to
line feed/carriage return pairs and tabs may be expanded to spaces.
This file is only present if the
.Em log_output
or
.Em log_ttyout
flags are set and
.Nm sudo
was run from a terminal.
.It Pa stdout
The standard output when no terminal is present, or output redirected to
a pipe or file.
This file is only present if the
.Em log_output
or
.Em log_stdout
flags are set and the standard output is not connected to a terminal.
.It Pa stderr
The standard error when no terminal is present, or output redirected to
a pipe or file.
This file is only present if the
.Em log_output
or
.Em log_stderr
flags are set and the standard error is not connected to a terminal.
.El
.Pp
All files other than
.Pa log
are compressed in gzip format unless the
.Em compress_io
flag has been disabled.
Due to buffering, it is not normally possible to display the I/O logs in
real-time as the program is executing.
The I/O log data will not be complete until the program run by
.Nm sudo
has exited or has been terminated by a signal.
The
.Em iolog_flush
flag can be used to disable buffering, in which case I/O log data
is written to disk as soon as it is available.
The output portion of an I/O log file can be viewed with the
.Xr sudoreplay @mansectsu@
utility, which can also be used to list or search the available logs.
.Pp
User input may contain sensitive information such as passwords (even
if they are not echoed to the screen), which will be stored in the
log file unencrypted.
In most cases, logging the command output via
.Em log_output
or
.Dv LOG_OUTPUT
is all that is required.
When logging input, consider disabling the
.Em log_passwords
flag.
.Pp
Since each session's I/O logs are stored in a separate directory,
traditional log rotation utilities cannot be used to limit the
number of I/O logs.
The simplest way to limit the number of I/O is by setting the
.Em maxseq
option to the maximum number of logs you wish to store.
Once the I/O log sequence number reaches
.Em maxseq ,
it will be reset to zero and
.Nm
will truncate and reuse any existing I/O logs.
.Sh FILES
.Bl -tag -width 24n
.It Pa @sysconfdir@/sudo.conf
Sudo front-end configuration
.It Pa @sysconfdir@/sudoers
List of who can run what
.It Pa /etc/group
Local groups file
.It Pa /etc/netgroup
List of network groups
.It Pa @iolog_dir@
I/O log files
.It Pa @rundir@/ts
Directory containing time stamps for the
.Nm
security policy
.It Pa @vardir@/lectured
Directory containing lecture status files for the
.Nm
security policy
.It Pa /etc/environment
Initial environment for
.Fl i
mode on AIX and Linux systems
.El
.Sh EXAMPLES
Below are example
.Em sudoers
file entries.
Admittedly, some of these are a bit contrived.
First, we allow a few environment variables to pass and then define our
.Em aliases :
.Bd -literal
# Run X applications through sudo; HOME is used to find the
# .Xauthority file.  Other programs use HOME to locate configuration
# files and this may lead to privilege escalation!
Defaults env_keep += "DISPLAY HOME"

# User alias specification
User_Alias	FULLTIMERS = millert, mikef, dowdy
User_Alias	PARTTIMERS = bostley, jwfox, crawl
User_Alias	WEBADMIN = will, wendy, wim

# Runas alias specification
Runas_Alias	OP = root, operator
Runas_Alias	DB = oracle, sybase
Runas_Alias	ADMINGRP = adm, oper

# Host alias specification
Host_Alias	SPARC = bigtime, eclipse, moet, anchor :\e
		SGI = grolsch, dandelion, black :\e
		ALPHA = widget, thalamus, foobar :\e
		HPPA = boa, nag, python
Host_Alias	CUNETS = 128.138.0.0/255.255.0.0
Host_Alias	CSNETS = 128.138.243.0, 128.138.204.0/24, 128.138.242.0
Host_Alias	SERVERS = primary, mail, www, ns
Host_Alias	CDROM = orion, perseus, hercules

# Cmnd alias specification
Cmnd_Alias	DUMPS = /usr/bin/mt, /usr/sbin/dump, /usr/sbin/rdump,\e
			/usr/sbin/restore, /usr/sbin/rrestore,\e
			sha224:0GomF8mNN3wlDt1HD9XldjJ3SNgpFdbjO1+NsQ== \e
			/home/operator/bin/start_backups
Cmnd_Alias	KILL = /usr/bin/kill
Cmnd_Alias	PRINTING = /usr/sbin/lpc, /usr/bin/lprm
Cmnd_Alias	SHUTDOWN = /usr/sbin/shutdown
Cmnd_Alias	HALT = /usr/sbin/halt
Cmnd_Alias	REBOOT = /usr/sbin/reboot
Cmnd_Alias	SHELLS = /usr/bin/sh, /usr/bin/csh, /usr/bin/ksh,\e
			 /usr/local/bin/tcsh, /usr/bin/rsh,\e
			 /usr/local/bin/zsh
Cmnd_Alias	SU = /usr/bin/su
Cmnd_Alias	PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
.Ed
.Pp
Here we override some of the compiled in default values.
We want
.Nm sudo
to log via
.Xr syslog 3
using the
.Em auth
facility in all cases and for commands to be run with
the target user's home directory as the working directory.
We don't want to subject the full time staff to the
.Nm sudo
lecture and we want to allow them to run commands in a
.Xr chroot 2
.Dq sandbox
via the
.Fl R
option.
User
.Sy millert
need not provide a password and we don't want to reset the
.Ev LOGNAME
or
.Ev USER
environment variables when running commands as
.Sy root .
Additionally, on the machines in the
.Dv SERVERS
.Em Host_Alias ,
we keep an additional local log file and make sure we log the year
in each log line since the log entries will be kept around for several years.
Lastly, we disable shell escapes for the commands in the PAGERS
.Em Cmnd_Alias
.Po
.Pa /usr/bin/more ,
.Pa /usr/bin/pg
and
.Pa /usr/bin/less
.Pc .
This will not effectively constrain users with
.Nm sudo
.Sy ALL
privileges.
.Bd -literal
# Override built-in defaults
Defaults		syslog=auth,runcwd=~
Defaults>root		!set_logname
Defaults:FULLTIMERS	!lecture,runchroot=*
Defaults:millert	!authenticate
Defaults@SERVERS	log_year, logfile=@log_dir@/sudo.log
Defaults!PAGERS		noexec
.Ed
.Pp
The
.Em User specification
is the part that actually determines who may run what.
.Bd -literal
root		ALL = (ALL) ALL
%wheel		ALL = (ALL) ALL
.Ed
.Pp
We let
.Sy root
and any user in group
.Sy wheel
run any command on any host as any user.
.Bd -literal
FULLTIMERS	ALL = NOPASSWD: ALL
.Ed
.Pp
Full time sysadmins
.Po
.Sy millert ,
.Sy mikef ,
and
.Sy dowdy
.Pc
may run any command on any host without authenticating themselves.
.Bd -literal
PARTTIMERS	ALL = ALL
.Ed
.Pp
Part time sysadmins
.Sy bostley ,
.Sy jwfox ,
and
.Sy crawl )
may run any command on any host but they must authenticate themselves
first (since the entry lacks the
.Dv NOPASSWD
tag).
.Bd -literal
jack		CSNETS = ALL
.Ed
.Pp
The user
.Sy jack
may run any command on the machines in the
.Dv CSNETS
alias (the networks 128.138.243.0, 128.138.204.0, and 128.138.242.0).
Of those networks, only 128.138.204.0 has an explicit netmask (in
CIDR notation) indicating it is a class C network.
For the other networks in
.Dv CSNETS ,
the local machine's netmask will be used during matching.
.Bd -literal
lisa		CUNETS = ALL
.Ed
.Pp
The user
.Sy lisa
may run any command on any host in the
.Dv CUNETS
alias (the class B network 128.138.0.0).
.Bd -literal
operator	ALL = DUMPS, KILL, SHUTDOWN, HALT, REBOOT, PRINTING,\e
		sudoedit /etc/printcap, /usr/oper/bin/
.Ed
.Pp
The
.Sy operator
user may run commands limited to simple maintenance.
Here, those are commands related to backups, killing processes, the
printing system, shutting down the system, and any commands in the
directory
.Pa /usr/oper/bin/ .
One command in the
.Dv DUMPS
Cmnd_Alias includes a sha224 digest,
.Pa /home/operator/bin/start_backups .
This is because the directory containing the script is writable by the
operator user.
If the script is modified (resulting in a digest mismatch) it will no longer
be possible to run it via
.Nm sudo .
.Bd -literal
joe		ALL = /usr/bin/su operator
.Ed
.Pp
The user
.Sy joe
may only
.Xr su 1
to operator.
.Bd -literal
pete		HPPA = /usr/bin/passwd [A-Za-z]*, !/usr/bin/passwd *root*

%opers		ALL = (: ADMINGRP) /usr/sbin/
.Ed
.Pp
Users in the
.Sy opers
group may run commands in
.Pa /usr/sbin/
as themselves
with any group in the
.Dv ADMINGRP
.Em Runas_Alias
(the
.Sy adm
and
.Sy oper
groups).
.Pp
The user
.Sy pete
is allowed to change anyone's password except for
.Sy root
on the
.Dv HPPA
machines.
Because command line arguments are matched as a single,
concatenated string, the
.Ql *
wildcard will match
.Em multiple
words.
This example assumes that
.Xr passwd 1
does not take multiple user names on the command line.
On systems with GNU
.Xr getopt 3 ,
options to
.Xr passwd 1
may be specified after the user argument.
As a result, this rule will also allow:
.Bd -literal -offset 4n
passwd username --expire
.Ed
.Pp
which may not be desirable.
.Bd -literal
bob		SPARC = (OP) ALL : SGI = (OP) ALL
.Ed
.Pp
The user
.Sy bob
may run anything on the
.Dv SPARC
and
.Dv SGI
machines as any user listed in the
.Dv OP
.Em Runas_Alias
.Po
.Sy root
and
.Sy operator .
.Pc
.Bd -literal
jim		+biglab = ALL
.Ed
.Pp
The user
.Sy jim
may run any command on machines in the
.Em biglab
netgroup.
.Nm sudo
knows that
.Dq biglab
is a netgroup due to the
.Ql +
prefix.
.Bd -literal
+secretaries	ALL = PRINTING, /usr/bin/adduser, /usr/bin/rmuser
.Ed
.Pp
Users in the
.Sy secretaries
netgroup need to help manage the printers as well as add and remove users,
so they are allowed to run those commands on all machines.
.Bd -literal
fred		ALL = (DB) NOPASSWD: ALL
.Ed
.Pp
The user
.Sy fred
can run commands as any user in the
.Dv DB
.Em Runas_Alias
.Po
.Sy oracle
or
.Sy sybase
.Pc
without giving a password.
.Bd -literal
john		ALPHA = /usr/bin/su [!-]*, !/usr/bin/su *root*
.Ed
.Pp
On the
.Dv ALPHA
machines, user
.Sy john
may su to anyone except
.Sy root
but he is not allowed to specify any options to the
.Xr su 1
command.
.Bd -literal
jen		ALL, !SERVERS = ALL
.Ed
.Pp
The user
.Sy jen
may run any command on any machine except for those in the
.Dv SERVERS
.Em Host_Alias
(primary, mail, www, and ns).
.Bd -literal
jill		SERVERS = /usr/bin/, !SU, !SHELLS
.Ed
.Pp
For any machine in the
.Dv SERVERS
.Em Host_Alias ,
.Sy jill
may run
any commands in the directory
.Pa /usr/bin/
except for those commands
belonging to the
.Dv SU
and
.Dv SHELLS
.Em Cmnd_Aliases .
While not specifically mentioned in the rule, the commands in the
.Dv PAGERS
.Em Cmnd_Alias
all reside in
.Pa /usr/bin
and have the
.Em noexec
option set.
.Bd -literal
steve		CSNETS = (operator) /usr/local/op_commands/
.Ed
.Pp
The user
.Sy steve
may run any command in the directory /usr/local/op_commands/
but only as user operator.
.Bd -literal
matt		valkyrie = KILL
.Ed
.Pp
On his personal workstation, valkyrie,
.Sy matt
needs to be able to kill hung processes.
.Bd -literal
WEBADMIN	www = (www) ALL, (root) /usr/bin/su www
.Ed
.Pp
On the host www, any user in the
.Dv WEBADMIN
.Em User_Alias
(will, wendy, and wim), may run any command as user www (which owns the
web pages) or simply
.Xr su 1
to www.
.Bd -literal
ALL		CDROM = NOPASSWD: /sbin/umount /CDROM,\e
		/sbin/mount -o nosuid\e,nodev /dev/cd0a /CDROM
.Ed
.Pp
Any user may mount or unmount a CD-ROM on the machines in the CDROM
.Em Host_Alias
(orion, perseus, hercules) without entering a password.
This is a bit tedious for users to type, so it is a prime candidate
for encapsulating in a shell script.
.Sh SECURITY NOTES
.Ss Limitations of the So !\& Sc operator
It is generally not effective to
.Dq subtract
commands from
.Sy ALL
using the
.Ql !\&
operator.
A user can trivially circumvent this by copying the desired command
to a different name and then executing that.
For example:
.Bd -literal
bill	ALL = ALL, !SU, !SHELLS
.Ed
.Pp
Doesn't really prevent
.Sy bill
from running the commands listed in
.Dv SU
or
.Dv SHELLS
since he can simply copy those commands to a different name, or use
a shell escape from an editor or other program.
Therefore, these kind of restrictions should be considered
advisory at best (and reinforced by policy).
.Pp
In general, if a user has sudo
.Sy ALL
there is nothing to prevent them from creating their own program that gives
them a
.Sy root
shell (or making their own copy of a shell) regardless of any
.Ql !\&
elements in the user specification.
.Ss Security implications of Em fast_glob
If the
.Em fast_glob
option is in use, it is not possible to reliably negate commands where the
path name includes globbing (aka wildcard) characters.
This is because the C library's
.Xr fnmatch 3
function cannot resolve relative paths.
While this is typically only an inconvenience for rules that grant privileges,
it can result in a security issue for rules that subtract or revoke privileges.
.Pp
For example, given the following
.Em sudoers
file entry:
.Bd -literal
john	ALL = /usr/bin/passwd [a-zA-Z0-9]*, /usr/bin/chsh [a-zA-Z0-9]*,\e
              /usr/bin/chfn [a-zA-Z0-9]*, !/usr/bin/* root
.Ed
.Pp
User
.Sy john
can still run
.Ql /usr/bin/passwd root
if
.Em fast_glob
is enabled by changing to
.Pa /usr/bin
and running
.Ql ./passwd root
instead.
.Pp
Another potential issue is that when
.Nm sudo
executes the command, it must use the command or path specified by
the user instead of a path listed in the
.Em sudoers
file.
This may lead to a time of check versus time of use race condition.
.Ss Wildcards in command arguments
Command line arguments are matched as a single, concatenated string.
This mean a wildcard character such as
.Ql \&?
or
.Ql *
will match across word boundaries, which may be unexpected.
For example, while a sudoers entry like:
.Bd -literal -offset 4n
%operator ALL = /bin/cat @log_dir@/messages*
.Ed
.Pp
will allow command like:
.Bd -literal -offset 4n
$ sudo cat @log_dir@/messages.1
.Ed
.Pp
It will also allow:
.Bd -literal -offset 4n
$ sudo cat @log_dir@/messages /etc/shadow
.Ed
.Pp
which is probably not what was intended.
A safer alternative is to use a regular expression for matching
command line arguments.
The above example can be rewritten as a regular expression:
.Bd -literal -offset 4n
%operator ALL = /bin/cat ^@log_dir@/messages[^[:space:]]*$
.Ed
.Pp
The regular expression will only match a single file with a
name that begins with
.Pa @log_dir@/messages
and does not include any white space in the name.
It is often better to do command line processing outside of the
.Em sudoers
file in a scripting language for anything non-trivial.
.Ss Regular expressions in command names
Using a regular expression to match a command name has the same
security implications as using the
.Em fast_glob
option:
.Bl -bullet -width 1n
.It
It is not possible to reliably negate commands when the
path name is a regular expression.
.It
When
.Nm sudo
executes the command, it must use the command or path specified by
the user instead of a path listed in the
.Em sudoers
file.
This may lead to a time of check versus time of use race condition.
.El
.Pp
These issues do not apply to rules where only the command line
options are matched using a regular expression.
.Ss Preventing shell escapes
Once
.Nm sudo
executes a program, that program is free to do whatever
it pleases, including run other programs.
This can be a security issue since it is not uncommon for a program to
allow shell escapes, which lets a user bypass
.Nm sudo Ns 's
access control and logging.
Common programs that permit shell escapes include shells (obviously),
editors, paginators, mail, and terminal programs.
.Pp
There are four basic approaches to this problem:
.Bl -tag -width "intercept"
.It restrict
Avoid giving users access to commands that allow the user to run
arbitrary commands.
Many editors have a restricted mode where shell
escapes are disabled, though
.Nm sudoedit
is a better solution to
running editors via
.Nm sudo .
Due to the large number of programs that
offer shell escapes, restricting users to the set of programs that
do not is often unworkable.
.It intercept
On most systems,
.Nm sudo Ns 's
.Em intercept
functionality can be used to transparently intercept an attempt to
run a new command, allow or deny it based on
.Em sudoers
rules, and log the result.
For example, this can be used to restrict the commands run from
within a privileged shell or editor.
However, not all programs operate correctly when
.Em intercept
is enabled.
.Pp
There are two underlying mechanisms that may be used to implement
.Em intercept
mode:
.Em dso
and
.Em trace .
The
.Em intercept_type
setting can be used to select between them.
.Pp
The first mechanism,
.Em dso ,
overrides the standard C library functions that are used to execute a
command.
It does this by setting an environment variable (usually
.Ev LD_PRELOAD )
to the path of a dynamic shared object, or shared library,
containing custom versions of the
.Xr execve 2 ,
.Xr execl 3 ,
.Xr execle 3 ,
.Xr execlp 3 ,
.Xr execv 3 ,
.Xr execvp 3 ,
.Xr execvpe 3 ,
and
.Xr system 3
library functions that connect back to
.Nm sudo
for a policy decision.
Note, however, that this applies only to dynamically-linked
executables.
It is not possible to intercept commands for statically-linked executables
or executables that run under binary emulation this way.
Because most dynamic loaders ignore
.Ev LD_PRELOAD
(or the equivalent) when running set-user-ID and set-group-ID programs,
.Nm
will not permit such programs to be run in
.Em intercept
mode by default.
The
.Em dso
mechanism is incompatible with
.Nm sudo Ns 's
SELinux RBAC support (but see below).
SELinux disables
.Ev LD_PRELOAD
by default and interferes with file descriptor inheritance, which
.Nm sudo
relies on.
.Pp
The second mechanism,
.Em trace ,
is available on Linux systems that support
.Xr seccomp 2
filtering.
It uses
.Xr ptrace 2
and
.Xr seccomp 2
to intercept the
.Xr execve 2
system call instead of pre-loading a dynamic shared object.
Both static and dynamic executables are supported and it is compatible with
.Nm sudo Ns 's
SELinux RBAC mode.
Functions utilizing the
.Xr execveat 2
system call, such as
.Xr fexecve 3 ,
are not currently intercepted.
Programs that rely on
.Xr ptrace 2
themselves, such as debuggers and system call tracers
.Po
such as
.Xr strace 1
and
.Xr truss 1
.Pc
will be unable to function if
.Em intercept
is enabled in
.Em trace
mode.
This same restriction applies to the
.Em log_subcmds
sudoers option.
.Pp
The
.Em intercept
feature is known to work on Solaris, *BSD, Linux, macOS, HP-UX 11.x
and AIX 5.3 and above.
It should be supported on most operating systems that support the
.Ev LD_PRELOAD
environment variable or an equivalent.
It is not possible to intercept shell built-in commands or restrict
the ability to read or write sensitive files from within a shell.
.Pp
To enable intercept mode on a per-command basis, use the
.Dv INTERCEPT
tag as documented in the User Specification section above.
Here is that example again:
.Bd -literal
chuck	research = INTERCEPT: ALL
.Ed
.Pp
This allows user
.Sy chuck
to run any command on the machine
.Dq research
in intercept mode.
Any commands run via shell escapes will be validated and logged by
.Nm sudo .
If you are unsure whether or not your system is capable of supporting
.Em intercept ,
you can always just try it out and check whether or not external
commands run via a shell are logged when
.Em intercept
is enabled.
.Pp
There is an inherent race condition between when a command is checked against
.Nm
rules and when it is actually executed.
If a user is allowed to run arbitrary commands, they may be able
to change the
.Xr execve 2
arguments in the program after the
.Nm
policy check has completed but before the new command is executed.
Starting with version 1.9.12, the
.Em trace
method will verify that the command and its arguments have not
changed after
.Xr execve 2
has completed but before execution of the new program has had a chance to run.
This is not the case with the
.Em dso
method.
See the description of the
.Em intercept_verify
setting for more information.
.It log
There are two separate but related ways to log additional commands.
The first is to enable I/O logging using the
.Em log_output
flag.
This will log the command's output but will not create an event log
entry when the additional command is run.
The second is to enable the
.Em log_subcmds
flag in
.Em sudoers
which will create an event log entry every time a new command is run.
If I/O logging is also enabled, the log entry will include a time offset
into the I/O log to indicate when the command was run.
This offset can be passed to the
.Xr sudoreplay @mansectsu@
utility to replay the I/O log at the exact moment when the command was run.
The
.Em log_subcmds
flag uses the same mechanism as
.Em intercept
(see above) and has the same limitations.
.It noexec
.Nm sudo Ns 's
.Em noexec
functionality can be used to prevent a program run by
.Nm sudo
from executing any other programs.
On most systems, it uses the same
.Ev LD_PRELOAD
mechanism as
.Em intercept
(see above) and thus the same caveats apply.
The
.Em noexec
functionality
is capable of blocking execution of commands run via the
.Xr execve 2 ,
.Xr execl 3 ,
.Xr execle 3 ,
.Xr execlp 3 ,
.Xr exect 3 ,
.Xr execv 3 ,
.Xr execveat 3 ,
.Xr execvP 3 ,
.Xr execvp 3 ,
.Xr execvpe 3 ,
.Xr fexecve 3 ,
.Xr popen 3 ,
.Xr posix_spawn 3 ,
.Xr posix_spawnp 3 ,
.Xr system 3 ,
and
.Xr wordexp 3
functions.
On Linux, a
.Xr seccomp 2
filter is used to implement
.Em noexec .
On Solaris 10 and higher,
.Em noexec
uses Solaris privileges instead of the
.Ev LD_PRELOAD
environment variable.
.Pp
To enable
.Em noexec
for a command, use the
.Dv NOEXEC
tag as documented in the User Specification section above.
Here is that example again:
.Bd -literal
aaron	shanty = NOEXEC: /usr/bin/more, /usr/bin/vi
.Ed
.Pp
This allows user
.Sy aaron
to run
.Pa /usr/bin/more
and
.Pa /usr/bin/vi
with
.Em noexec
enabled.
This will prevent those two commands from
executing other commands (such as a shell).
If you are unsure whether or not your system is capable of supporting
.Em noexec
you can always just try it out and check whether shell escapes work when
.Em noexec
is enabled.
.El
.Pp
Restricting shell escapes is not a panacea.
Programs running as
.Sy root
are still capable of many potentially hazardous operations (such
as changing or overwriting files) that could lead to unintended
privilege escalation.
In the specific case of an editor, a safer approach is to give the
user permission to run
.Nm sudoedit
(see below).
.Ss Secure editing
The
.Nm
plugin includes
.Nm sudoedit
support which allows users to securely edit files with the editor
of their choice.
As
.Nm sudoedit
is a built-in command, it must be specified in the
.Em sudoers
file without a leading path.
However, it may take command line arguments just as a normal command does.
Wildcards used in
.Em sudoedit
command line arguments are expected to be path names, so a forward slash
.Pq Ql /
will not be matched by a wildcard.
.Pp
Unlike other
.Nm sudo
commands, the editor is run with the permissions of the invoking
user and with the environment unmodified.
More information may be found in the description of the
.Fl e
option in
.Xr sudo @mansectsu@ .
.Pp
For example, to allow user operator to edit the
.Dq message of the day
file on any machine:
.Bd -literal -offset 4n
operator ALL = sudoedit /etc/motd
.Ed
.Pp
The operator user then runs
.Nm sudoedit
as follows:
.Bd -literal -offset 4n
$ sudoedit /etc/motd
.Ed
.Pp
The editor will run as the operator user, not
.Sy @runas_default@ ,
on a temporary copy of
.Pa /etc/motd .
After the file has been edited,
.Pa /etc/motd
will be updated with the contents of the temporary copy.
.Pp
Users should
.Em never
be granted
.Nm sudoedit
permission to edit a file that resides in a directory the user
has write access to, either directly or via a wildcard.
If the user has write access to the directory it is possible to
replace the legitimate file with a link to another file,
allowing the editing of arbitrary files.
To prevent this, starting with version 1.8.16, symbolic links will
not be followed in writable directories and
.Nm sudoedit
will refuse to edit a file located in a writable directory
unless the
.Em sudoedit_checkdir
option has been disabled or the invoking user is
.Sy root .
Additionally, in version 1.8.15 and higher,
.Nm sudoedit
will refuse to open a symbolic link unless either the
.Em sudoedit_follow
option is enabled or the
.Em sudoedit
command is prefixed with the
.Dv FOLLOW
tag in the
.Em sudoers
file.
.Ss Time stamp file checks
.Nm
will check the ownership of its time stamp directory
.Po
.Pa @rundir@/ts
by default
.Pc
and ignore the directory's contents if it is not owned by
.Sy root
or if it is writable by a user other than
.Sy root .
Older versions of
.Nm sudo
stored time stamp files in
.Pa /tmp ;
this is no longer recommended as it may be possible for a user
to create the time stamp themselves on systems that allow
unprivileged users to change the ownership of files they create.
.Pp
While the time stamp directory
.Em should
be cleared at reboot time, not all systems contain a
.Pa /run
or
.Pa /var/run
directory.
To avoid potential problems,
.Nm
will ignore time stamp files that date from before the machine booted
on systems where the boot time is available.
.Pp
Some systems with graphical desktop environments allow unprivileged
users to change the system clock.
Since
.Nm
relies on the system clock for time stamp validation, it may be
possible on such systems for a user to run
.Nm sudo
for longer than
.Em timestamp_timeout
by setting the clock back.
To combat this,
.Nm
uses a monotonic clock (which never moves backwards) for its time stamps
if the system supports it.
.Pp
.Nm
will not honor time stamps set far in the future.
Time stamps with a date greater than current_time + 2 *
.Dv TIMEOUT
will be ignored and
.Nm
will log and complain.
.Pp
If the
.Em timestamp_type
option is set to
.Dq tty ,
the time stamp record includes the device number of the terminal
the user authenticated with.
This provides per-terminal granularity but time stamp records may still
outlive the user's session.
.Pp
Unless the
.Em timestamp_type
option is set to
.Dq global ,
the time stamp record also includes the session ID of the process
that last authenticated.
This prevents processes in different terminal sessions from using
the same time stamp record.
On systems where a process's start time can be queried,
the start time of the session leader
is recorded in the time stamp record.
If no terminal is present or the
.Em timestamp_type
option is set to
.Dq ppid ,
the start time of the parent process is used instead.
In most cases this will prevent a time stamp record from being reused
without the user entering a password when logging out and back in again.
.Sh DEBUGGING
Versions 1.8.4 and higher of the
.Nm
plugin support a flexible debugging framework that can help track
down what the plugin is doing internally if there is a problem.
This can be configured in the
.Xr sudo.conf @mansectform@
file.
.Pp
The
.Nm
plugin uses the same debug flag format as the
.Nm sudo
front-end:
.Em subsystem Ns @ Ns Em priority .
.Pp
The priorities used by
.Nm ,
in order of decreasing severity,
are:
.Em crit , err , warn , notice , diag , info , trace ,
and
.Em debug .
Each priority, when specified, also includes all priorities higher
than it.
For example, a priority of
.Em notice
would include debug messages logged at
.Em notice
and higher.
.Pp
The following subsystems are used by the
.Nm
plugin:
.Bl -tag -width "defaults"
.It Em alias
.Em User_Alias ,
.Em Runas_Alias ,
.Em Host_Alias
and
.Em Cmnd_Alias
processing
.It Em all
matches every subsystem
.It Em audit
BSM and Linux audit code
.It Em auth
user authentication
.It Em defaults
.Em sudoers
file
.Em Defaults
settings
.It Em env
environment handling
.It Em ldap
LDAP-based sudoers
.It Em logging
logging support
.It Em match
matching of users, groups, hosts, and netgroups in the
.Em sudoers
file
.It Em netif
network interface handling
.It Em nss
network service switch handling in
.Nm
.It Em parser
.Em sudoers
file parsing
.It Em perms
permission setting
.It Em plugin
The equivalent of
.Em main
for the plugin.
.It Em pty
pseudo-terminal related code
.It Em rbtree
redblack tree internals
.It Em sssd
SSSD-based sudoers
.It Em util
utility functions
.El
.Pp
For example:
.Bd -literal
Debug @sudoers_plugin@ @log_dir@/sudoers_debug match@info,nss@info
.Ed
.Pp
For more information, see the
.Xr sudo.conf @mansectform@
manual.
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr su 1 ,
.Xr fnmatch 3 ,
.Xr glob 3 ,
.Xr mktemp 3 ,
.Xr strftime 3 ,
.Xr sudo.conf @mansectform@ ,
.Xr sudo_logsrv.proto @mansectform@ ,
.Xr sudo_plugin @mansectform@ ,
.Xr sudoers.ldap @mansectform@ ,
.Xr sudoers_timestamp @mansectform@ ,
.Xr sudo @mansectsu@ ,
.Xr sudo_logsrvd @mansectsu@ ,
.Xr visudo @mansectsu@
.Sh AUTHORS
Many people have worked on
.Nm sudo
over the years; this version consists of code written primarily by:
.Bd -ragged -offset indent
.An Todd C. Miller
.Ed
.Pp
See the CONTRIBUTORS.md file in the
.Nm sudo
distribution (https://www.sudo.ws/about/contributors/) for an
exhaustive list of people who have contributed to
.Nm sudo .
.Sh CAVEATS
The
.Em sudoers
file should
.Sy always
be edited by the
.Nm visudo
utility which locks the file and checks for syntax errors.
If
.Em sudoers
contains syntax errors,
.Nm sudo
may refuse to run, which is a serious problem if
.Nm sudo
is your only method of obtaining superuser privileges.
Recent versions of
.Nm
will attempt to recover after a syntax error by ignoring the rest of
the line after encountering an error.
Older versions of
.Nm sudo
will not run if
.Em sudoers
contains a syntax error.
.Pp
When using netgroups of machines (as opposed to users), if you
store fully qualified host name in the netgroup (as is usually the
case), you either need to have the machine's host name be fully qualified
as returned by the
.Em hostname
command or use the
.Em fqdn
option in
.Em sudoers .
.Sh BUGS
If you believe you have found a bug in
.Nm ,
you can either file a bug report in the sudo bug database,
https://bugzilla.sudo.ws/, or open an issue at
https://github.com/sudo-project/sudo/issues.
If you would prefer to use email, messages may be sent to the
sudo-workers mailing list,
https://www.sudo.ws/mailman/listinfo/sudo-workers (public)
or <sudo@sudo.ws> (private).
.Pp
Please not report security vulnerabilities through public GitHub
issues, Bugzilla or mailing lists.
Instead, report them via email to <Todd.Miller@sudo.ws>.
You may encrypt your message with PGP if you would like, using
the key found at https://www.sudo.ws/dist/PGPKEYS.
.Sh SUPPORT
Limited free support is available via the sudo-users mailing list,
see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
search the archives.
.Sh DISCLAIMER
.Nm sudo
is provided
.Dq AS IS
and any express or implied warranties, including, but not limited
to, the implied warranties of merchantability and fitness for a
particular purpose are disclaimed.
See the LICENSE.md file distributed with
.Nm sudo
or https://www.sudo.ws/about/license/ for complete details.