389 lines
14 KiB
EmacsLisp
389 lines
14 KiB
EmacsLisp
;;; epa-file.el --- the EasyPG Assistant, transparent file encryption -*- lexical-binding: t -*-
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;; Copyright (C) 2006-2024 Free Software Foundation, Inc.
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;; Author: Daiki Ueno <ueno@unixuser.org>
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;; Keywords: PGP, GnuPG
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;; Package: epa
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;; This file is part of GNU Emacs.
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;; GNU Emacs 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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;; GNU Emacs 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 GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;;; Code:
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(require 'epa)
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(require 'epa-hook)
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(eval-when-compile (require 'subr-x))
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;;; Options
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(defcustom epa-file-cache-passphrase-for-symmetric-encryption nil
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"If non-nil, cache passphrase for symmetric encryption.
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For security reasons, this option is turned off by default and
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not recommended to use. Instead, consider using gpg-agent which
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does the same job in a safer way. See Info node `(epa) Caching
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Passphrases' for more information.
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Note that this option has no effect if you use GnuPG 2.0."
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:type 'boolean
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:group 'epa-file)
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(defcustom epa-file-select-keys nil
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"Control whether or not to pop up the key selection dialog.
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If t, always ask user to select recipients.
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If nil, query user only when `epa-file-encrypt-to' is not set.
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If neither t nor nil, don't ask user. In this case, symmetric
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encryption is used."
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:type '(choice (const :tag "Ask always" t)
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(const :tag "Ask when recipients are not set" nil)
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(const :tag "Don't ask" silent))
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:group 'epa-file)
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;;; Other
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(defvar epa-file-passphrase-alist nil)
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(defun epa-file-passphrase-callback-function (context key-id file)
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(if (and epa-file-cache-passphrase-for-symmetric-encryption
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(eq key-id 'SYM))
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(progn
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(setq file (file-truename file))
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(let ((entry (assoc file epa-file-passphrase-alist))
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passphrase)
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(or (copy-sequence (cdr entry))
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(progn
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(unless entry
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(setq entry (list file))
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(setq epa-file-passphrase-alist
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(cons entry
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epa-file-passphrase-alist)))
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(setq passphrase (epa-passphrase-callback-function context
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key-id
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file))
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(setcdr entry (copy-sequence passphrase))
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passphrase))))
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(epa-passphrase-callback-function context key-id file)))
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;;; File Handler
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(defvar epa-inhibit nil
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"Non-nil means don't try to decrypt .gpg files when operating on them.")
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;;;###autoload
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(defun epa-file-handler (operation &rest args)
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(save-match-data
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(let ((op (get operation 'epa-file)))
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(if (and op (not epa-inhibit))
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(apply op args)
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(epa-file-run-real-handler operation args)))))
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(defun epa-file-run-real-handler (operation args)
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(let ((inhibit-file-name-handlers
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(cons 'epa-file-handler
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(and (eq inhibit-file-name-operation operation)
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inhibit-file-name-handlers)))
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(inhibit-file-name-operation operation))
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(apply operation args)))
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(defun epa-file-decode-and-insert (string file visit beg end replace)
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(save-restriction
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(narrow-to-region (point) (point))
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(insert string)
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(decode-coding-inserted-region
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(point-min) (point-max)
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(substring file 0 (string-match epa-file-name-regexp file))
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visit beg end replace)
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(goto-char (point-max))
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(- (point-max) (point-min))))
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(defvar epa-file-error nil)
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(defun epa-file--find-file-not-found-function ()
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(let ((error epa-file-error))
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(save-window-excursion
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(kill-buffer))
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(if (nth 3 error)
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(user-error "Wrong passphrase: %s" (nth 3 error))
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(signal 'file-missing
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(cons "Opening input file" (cdr error))))))
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(defun epa--wrong-password-p (context)
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"Return whether a wrong password caused the error in CONTEXT."
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(let ((error-string (epg-context-error-output context)))
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;; Use a strict regexp here that really only matches "wrong
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;; passphrase" errors to avoid hiding diagnostic information
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;; (bug#65316). Below regexp also can fail to match non-English
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;; messages, since at least the "decryption failed" part of it
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;; seems to be localized. But since this means false negatives
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;; this is probably OK.
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(and (string-match
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"decryption failed: \\(Bad session key\\|Bad passphrase\\)"
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error-string)
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(match-string 1 error-string))))
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(defvar last-coding-system-used)
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(defun epa-file-insert-file-contents (file &optional visit beg end replace)
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(barf-if-buffer-read-only)
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(if (and visit (or beg end))
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(error "Attempt to visit less than an entire file"))
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(setq file (expand-file-name file))
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(let* ((local-copy
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(condition-case nil
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(epa-file-run-real-handler #'file-local-copy (list file))
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(error)))
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(local-file (or local-copy file))
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(context (epg-make-context))
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(buf (current-buffer))
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string length entry)
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(if visit
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(setq buffer-file-name file))
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(epg-context-set-passphrase-callback
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context
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(cons #'epa-file-passphrase-callback-function
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local-file))
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(epg-context-set-progress-callback
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context
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(cons #'epa-progress-callback-function
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(format "Decrypting %s" file)))
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(unwind-protect
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(progn
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(condition-case error
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(setq string (epg-decrypt-file context local-file nil))
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(error
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(if (setq entry (assoc file epa-file-passphrase-alist))
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(setcdr entry nil))
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;; If the decryption program can't be found,
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;; signal that as a non-file error
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;; so that find-file-noselect-1 won't handle it.
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;; Borrowed from jka-compr.el.
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(if (and (memq 'file-error (get (car error) 'error-conditions))
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(equal (cadr error) "Searching for program"))
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(error "Decryption program `%s' not found"
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(nth 3 error)))
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(let ((exists (file-exists-p local-file)))
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(when exists
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(if-let ((wrong-password (epa--wrong-password-p context)))
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;; Don't display the *error* buffer if we just
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;; have a wrong password; let the later error
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;; handler notify the user.
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(setq error (append error (list wrong-password)))
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(epa-display-error context))
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;; When the .gpg file isn't an encrypted file (e.g.,
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;; it's a keyring.gpg file instead), then gpg will
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;; say "Unexpected exit" as the error message. In
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;; that case, just display the bytes.
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(if (equal (caddr error) "Unexpected; Exit")
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(setq string (with-temp-buffer
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(insert-file-contents-literally local-file)
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(buffer-string)))
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;; Hack to prevent find-file from opening empty buffer
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;; when decryption failed (bug#6568). See the place
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;; where `find-file-not-found-functions' are called in
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;; `find-file-noselect-1'.
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(setq-local epa-file-error error)
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(add-hook 'find-file-not-found-functions
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'epa-file--find-file-not-found-function
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nil t)))
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(signal (if exists 'file-error 'file-missing)
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(cons "Opening input file" (cdr error))))))
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(set-buffer buf) ;In case timer/filter changed/killed it (bug#16029)!
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(setq-local epa-file-encrypt-to
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(mapcar #'car (epg-context-result-for
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context 'encrypted-to)))
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(if (or beg end)
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(setq string (substring string
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(or beg 0)
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(and end (min end (length string))))))
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(save-excursion
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;; If visiting, bind off buffer-file-name so that
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;; file-locking will not ask whether we should
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;; really edit the buffer.
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(let ((buffer-file-name
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(if visit nil buffer-file-name)))
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(setq length
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(if replace
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(epa-file--replace-text string file visit beg end)
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(epa-file-decode-and-insert
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string file visit beg end replace))))
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(if visit
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(set-visited-file-modtime))))
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(if (and local-copy
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(file-exists-p local-copy))
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(delete-file local-copy)))
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(list file length)))
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(put 'insert-file-contents 'epa-file 'epa-file-insert-file-contents)
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(defun epa-file--replace-text (string file visit beg end)
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;; The idea here is that we want to replace the text in the buffer
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;; (for instance, for a `revert-buffer'), but we want to touch as
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;; little of the text as possible. So we compare the new and the
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;; old text and only starts replacing when the text changes.
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(let ((orig-point (point))
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new-start length)
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(goto-char (point-max))
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(setq new-start (point))
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(setq length
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(epa-file-decode-and-insert
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string file visit beg end t))
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(if (equal (buffer-substring (point-min) new-start)
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(buffer-substring new-start (point-max)))
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;; The new text is equal to the old, so just keep the old.
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(delete-region new-start (point-max))
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;; Compute the region the hard way.
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(let ((p1 (point-min))
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(p2 new-start))
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(while (and (< p1 new-start)
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(< p2 (point-max))
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(eql (char-after p1) (char-after p2)))
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(cl-incf p1)
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(cl-incf p2))
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(delete-region new-start p2)
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(delete-region p1 new-start)))
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;; Restore point, if possible.
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(if (< orig-point (point-max))
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(goto-char orig-point)
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(goto-char (point-max)))
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length))
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(defun epa-file-write-region (start end file &optional append visit lockname
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mustbenew)
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(if append
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(error "Can't append to the file"))
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(setq file (expand-file-name file))
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(let* ((coding-system (or coding-system-for-write
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(if (fboundp 'select-safe-coding-system)
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(let ((buffer-file-name file))
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(select-safe-coding-system
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(point-min) (point-max)))
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buffer-file-coding-system)))
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(context (epg-make-context))
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(coding-system-for-write 'binary)
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string entry
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(recipients
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(cond
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((listp epa-file-encrypt-to) epa-file-encrypt-to)
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((stringp epa-file-encrypt-to) (list epa-file-encrypt-to))))
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buffer)
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(epg-context-set-passphrase-callback
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context
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(cons #'epa-file-passphrase-callback-function
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file))
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(epg-context-set-progress-callback
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context
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(cons #'epa-progress-callback-function
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(format "Encrypting %s" file)))
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(setf (epg-context-armor context) epa-armor)
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(condition-case error
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(setq string
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(epg-encrypt-string
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context
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(if (stringp start)
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(encode-coding-string start coding-system)
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(unless start
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(setq start (point-min)
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end (point-max)))
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(setq buffer (current-buffer))
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(with-temp-buffer
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(insert-buffer-substring buffer start end)
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;; Translate the region according to
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;; `buffer-file-format', as `write-region' would.
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;; We can't simply do `write-region' (into a
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;; temporary file) here, since it writes out
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;; decrypted contents.
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(format-encode-buffer (with-current-buffer buffer
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buffer-file-format))
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(encode-coding-string (buffer-string)
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coding-system)))
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(if (or (eq epa-file-select-keys t)
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(and (null epa-file-select-keys)
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(not (local-variable-p 'epa-file-encrypt-to
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(current-buffer)))))
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(epa-select-keys
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context
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"Select recipients for encryption.
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If no one is selected, symmetric encryption will be performed. "
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recipients)
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(if epa-file-encrypt-to
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(epg--filter-revoked-keys
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(epg-list-keys context recipients))))))
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(error
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(epa-display-error context)
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(if (setq entry (assoc file epa-file-passphrase-alist))
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(setcdr entry nil))
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(signal 'file-error (cons "Opening output file" (cdr error)))))
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(epa-file-run-real-handler
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#'write-region
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(list string nil file append visit lockname mustbenew))
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(if (boundp 'last-coding-system-used)
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(setq last-coding-system-used coding-system))
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(if (eq visit t)
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(progn
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(setq buffer-file-name file)
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(set-visited-file-modtime))
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(if (stringp visit)
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(progn
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(set-visited-file-modtime)
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(setq buffer-file-name visit))))
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(if (or (eq visit t)
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(eq visit nil)
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(stringp visit))
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(message "Wrote %s" buffer-file-name))))
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(put 'write-region 'epa-file 'epa-file-write-region)
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;;; Commands
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(defun epa-file-select-keys ()
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"Select recipients for encryption."
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(interactive)
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(setq-local epa-file-encrypt-to
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(mapcar
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(lambda (key)
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(epg-sub-key-id (car (epg-key-sub-key-list key))))
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(epa-select-keys
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(epg-make-context)
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"Select recipients for encryption.
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If no one is selected, symmetric encryption will be performed. "))))
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;;;###autoload
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(defun epa-file-enable ()
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(interactive)
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(if (memq epa-file-handler file-name-handler-alist)
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(message "`epa-file' already enabled")
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(setq file-name-handler-alist
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(cons epa-file-handler file-name-handler-alist))
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(add-hook 'find-file-hook 'epa-file-find-file-hook)
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(setq auto-mode-alist (cons epa-file-auto-mode-alist-entry auto-mode-alist))
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(message "`epa-file' enabled")))
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;;;###autoload
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(defun epa-file-disable ()
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(interactive)
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(if (memq epa-file-handler file-name-handler-alist)
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(progn
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(setq file-name-handler-alist
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(delq epa-file-handler file-name-handler-alist))
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(remove-hook 'find-file-hook 'epa-file-find-file-hook)
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(setq auto-mode-alist (delq epa-file-auto-mode-alist-entry
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auto-mode-alist))
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(message "`epa-file' disabled"))
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(message "`epa-file' already disabled")))
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(provide 'epa-file)
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;;; epa-file.el ends here
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