143 lines
4.2 KiB
C
143 lines
4.2 KiB
C
/* Change the protections of file relative to an open directory.
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Copyright (C) 2006, 2009-2024 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* written by Jim Meyering and Paul Eggert */
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/* If the user's config.h happens to include <sys/stat.h>, let it include only
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the system's <sys/stat.h> here, so that orig_fchmodat doesn't recurse to
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rpl_fchmodat. */
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#define __need_system_sys_stat_h
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#include <config.h>
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/* Specification. */
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#include <sys/stat.h>
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#undef __need_system_sys_stat_h
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#if HAVE_FCHMODAT
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static int
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orig_fchmodat (int dir, char const *file, mode_t mode, int flags)
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{
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return fchmodat (dir, file, mode, flags);
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}
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#endif
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#ifdef __osf__
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/* Write "sys/stat.h" here, not <sys/stat.h>, otherwise OSF/1 5.1 DTK cc
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eliminates this include because of the preliminary #include <sys/stat.h>
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above. */
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# include "sys/stat.h"
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#else
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# include <sys/stat.h>
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#endif
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#include <intprops.h>
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/* Invoke chmod or lchmod on FILE, using mode MODE, in the directory
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open on descriptor FD. If possible, do it without changing the
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working directory. Otherwise, resort to using save_cwd/fchdir,
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then (chmod|lchmod)/restore_cwd. If either the save_cwd or the
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restore_cwd fails, then give a diagnostic and exit nonzero.
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Note that an attempt to use a FLAG value of AT_SYMLINK_NOFOLLOW
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on a system without lchmod support causes this function to fail. */
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#if HAVE_FCHMODAT
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int
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fchmodat (int dir, char const *file, mode_t mode, int flags)
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{
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# if HAVE_NEARLY_WORKING_FCHMODAT
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/* Correct the trailing slash handling. */
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size_t len = strlen (file);
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if (len && file[len - 1] == '/')
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{
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struct stat st;
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if (fstatat (dir, file, &st, flags & AT_SYMLINK_NOFOLLOW) < 0)
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return -1;
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if (!S_ISDIR (st.st_mode))
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{
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errno = ENOTDIR;
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return -1;
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}
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}
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# endif
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# if NEED_FCHMODAT_NONSYMLINK_FIX
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if (flags == AT_SYMLINK_NOFOLLOW)
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{
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# if HAVE_READLINKAT
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char readlink_buf[1];
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# ifdef O_PATH
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/* Open a file descriptor with O_NOFOLLOW, to make sure we don't
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follow symbolic links, if /proc is mounted. O_PATH is used to
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avoid a failure if the file is not readable.
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Cf. <https://sourceware.org/bugzilla/show_bug.cgi?id=14578> */
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int fd = openat (dir, file, O_PATH | O_NOFOLLOW | O_CLOEXEC);
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if (fd < 0)
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return fd;
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int err;
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if (0 <= readlinkat (fd, "", readlink_buf, sizeof readlink_buf))
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err = EOPNOTSUPP;
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else if (errno == EINVAL)
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{
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static char const fmt[] = "/proc/self/fd/%d";
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char buf[sizeof fmt - sizeof "%d" + INT_BUFSIZE_BOUND (int)];
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sprintf (buf, fmt, fd);
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err = chmod (buf, mode) == 0 ? 0 : errno == ENOENT ? -1 : errno;
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}
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else
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err = errno == ENOENT ? -1 : errno;
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close (fd);
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errno = err;
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if (0 <= err)
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return err == 0 ? 0 : -1;
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# endif
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/* O_PATH + /proc is not supported. */
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if (0 <= readlinkat (dir, file, readlink_buf, sizeof readlink_buf))
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{
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errno = EOPNOTSUPP;
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return -1;
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}
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# endif
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/* Fall back on orig_fchmodat with no flags, despite a possible race. */
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flags = 0;
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}
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# endif
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return orig_fchmodat (dir, file, mode, flags);
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}
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#else
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# define AT_FUNC_NAME fchmodat
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# define AT_FUNC_F1 lchmod
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# define AT_FUNC_F2 chmod
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# define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
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# define AT_FUNC_POST_FILE_PARAM_DECLS , mode_t mode, int flag
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# define AT_FUNC_POST_FILE_ARGS , mode
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# include "at-func.c"
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#endif
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