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1 ;;; epa-file.el --- the EasyPG Assistant, transparent file encryption -*- lexical-binding: t -*-
2 ;; Copyright (C) 2006-2015 Free Software Foundation, Inc.
4 ;; Author: Daiki Ueno <ueno@unixuser.org>
5 ;; Keywords: PGP, GnuPG
6 ;; Package: epa
8 ;; This file is part of GNU Emacs.
10 ;; GNU Emacs is free software: you can redistribute it and/or modify
11 ;; it under the terms of the GNU General Public License as published by
12 ;; the Free Software Foundation, either version 3 of the License, or
13 ;; (at your option) any later version.
15 ;; GNU Emacs is distributed in the hope that it will be useful,
16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 ;; GNU General Public License for more details.
20 ;; You should have received a copy of the GNU General Public License
21 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
23 ;;; Code:
25 (require 'epa)
26 (require 'epa-hook)
28 (defcustom epa-file-cache-passphrase-for-symmetric-encryption nil
29 "If non-nil, cache passphrase for symmetric encryption.
31 For security reasons, this option is turned off by default and
32 not recommended to use. Instead, consider using gpg-agent which
33 does the same job in a safer way. See Info node `(epa) Caching
34 Passphrases' for more information.
36 Note that this option has no effect if you use GnuPG 2.0."
37 :type 'boolean
38 :group 'epa-file)
40 (defcustom epa-file-select-keys nil
41 "Control whether or not to pop up the key selection dialog.
43 If t, always asks user to select recipients.
44 If nil, query user only when `epa-file-encrypt-to' is not set.
45 If neither t nor nil, doesn't ask user. In this case, symmetric
46 encryption is used."
47 :type '(choice (const :tag "Ask always" t)
48 (const :tag "Ask when recipients are not set" nil)
49 (const :tag "Don't ask" silent))
50 :group 'epa-file)
52 (defvar epa-file-passphrase-alist nil)
54 (eval-and-compile
55 (if (fboundp 'encode-coding-string)
56 (defalias 'epa-file--encode-coding-string 'encode-coding-string)
57 (defalias 'epa-file--encode-coding-string 'identity)))
59 (eval-and-compile
60 (if (fboundp 'decode-coding-string)
61 (defalias 'epa-file--decode-coding-string 'decode-coding-string)
62 (defalias 'epa-file--decode-coding-string 'identity)))
64 (defun epa-file-passphrase-callback-function (context key-id file)
65 (if (and epa-file-cache-passphrase-for-symmetric-encryption
66 (eq key-id 'SYM))
67 (progn
68 (setq file (file-truename file))
69 (let ((entry (assoc file epa-file-passphrase-alist))
70 passphrase)
71 (or (copy-sequence (cdr entry))
72 (progn
73 (unless entry
74 (setq entry (list file)
75 epa-file-passphrase-alist
76 (cons entry
77 epa-file-passphrase-alist)))
78 (setq passphrase (epa-passphrase-callback-function context
79 key-id
80 file))
81 (setcdr entry (copy-sequence passphrase))
82 passphrase))))
83 (epa-passphrase-callback-function context key-id file)))
85 ;;;###autoload
86 (defun epa-file-handler (operation &rest args)
87 (save-match-data
88 (let ((op (get operation 'epa-file)))
89 (if op
90 (apply op args)
91 (epa-file-run-real-handler operation args)))))
93 (defun epa-file-run-real-handler (operation args)
94 (let ((inhibit-file-name-handlers
95 (cons 'epa-file-handler
96 (and (eq inhibit-file-name-operation operation)
97 inhibit-file-name-handlers)))
98 (inhibit-file-name-operation operation))
99 (apply operation args)))
101 (defun epa-file-decode-and-insert (string file visit beg end replace)
102 (if (fboundp 'decode-coding-inserted-region)
103 (save-restriction
104 (narrow-to-region (point) (point))
105 (insert (if enable-multibyte-characters
106 (string-to-multibyte string)
107 string))
108 (decode-coding-inserted-region
109 (point-min) (point-max)
110 (substring file 0 (string-match epa-file-name-regexp file))
111 visit beg end replace))
112 (insert (epa-file--decode-coding-string string (or coding-system-for-read
113 'undecided)))))
115 (defvar epa-file-error nil)
116 (defun epa-file--find-file-not-found-function ()
117 (let ((error epa-file-error))
118 (save-window-excursion
119 (kill-buffer))
120 (signal 'file-error
121 (cons "Opening input file" (cdr error)))))
123 (defvar last-coding-system-used)
124 (defun epa-file-insert-file-contents (file &optional visit beg end replace)
125 (barf-if-buffer-read-only)
126 (if (and visit (or beg end))
127 (error "Attempt to visit less than an entire file"))
128 (setq file (expand-file-name file))
129 (let* ((local-copy
130 (condition-case nil
131 (epa-file-run-real-handler #'file-local-copy (list file))
132 (error)))
133 (local-file (or local-copy file))
134 (context (epg-make-context))
135 (buf (current-buffer))
136 string length entry)
137 (if visit
138 (setq buffer-file-name file))
139 (epg-context-set-passphrase-callback
140 context
141 (cons #'epa-file-passphrase-callback-function
142 local-file))
143 (epg-context-set-progress-callback
144 context
145 (cons #'epa-progress-callback-function
146 (format "Decrypting %s" file)))
147 (setf (epg-context-pinentry-mode context) epa-pinentry-mode)
148 (unwind-protect
149 (progn
150 (if replace
151 (goto-char (point-min)))
152 (condition-case error
153 (setq string (epg-decrypt-file context local-file nil))
154 (error
155 (if (setq entry (assoc file epa-file-passphrase-alist))
156 (setcdr entry nil))
157 ;; If the decryption program can't be found,
158 ;; signal that as a non-file error
159 ;; so that find-file-noselect-1 won't handle it.
160 ;; Borrowed from jka-compr.el.
161 (if (and (eq (car error) 'file-error)
162 (equal (cadr error) "Searching for program"))
163 (error "Decryption program `%s' not found"
164 (nth 3 error)))
165 (when (file-exists-p local-file)
166 ;; Hack to prevent find-file from opening empty buffer
167 ;; when decryption failed (bug#6568). See the place
168 ;; where `find-file-not-found-functions' are called in
169 ;; `find-file-noselect-1'.
170 (setq-local epa-file-error error)
171 (add-hook 'find-file-not-found-functions
172 'epa-file--find-file-not-found-function
173 nil t)
174 (epa-display-error context))
175 (signal 'file-error
176 (cons "Opening input file" (cdr error)))))
177 (set-buffer buf) ;In case timer/filter changed/killed it (bug#16029)!
178 (setq-local epa-file-encrypt-to
179 (mapcar #'car (epg-context-result-for
180 context 'encrypted-to)))
181 (if (or beg end)
182 (setq string (substring string (or beg 0) end)))
183 (save-excursion
184 ;; If visiting, bind off buffer-file-name so that
185 ;; file-locking will not ask whether we should
186 ;; really edit the buffer.
187 (let ((buffer-file-name
188 (if visit nil buffer-file-name)))
189 (save-restriction
190 (narrow-to-region (point) (point))
191 (epa-file-decode-and-insert string file visit beg end replace)
192 (setq length (- (point-max) (point-min))))
193 (if replace
194 (delete-region (point) (point-max))))
195 (if visit
196 (set-visited-file-modtime))))
197 (if (and local-copy
198 (file-exists-p local-copy))
199 (delete-file local-copy)))
200 (list file length)))
201 (put 'insert-file-contents 'epa-file 'epa-file-insert-file-contents)
203 (defun epa-file-write-region (start end file &optional append visit lockname
204 mustbenew)
205 (if append
206 (error "Can't append to the file"))
207 (setq file (expand-file-name file))
208 (let* ((coding-system (or coding-system-for-write
209 (if (fboundp 'select-safe-coding-system)
210 ;; This is needed since Emacs 22 has
211 ;; no-conversion setting for *.gpg in
212 ;; `auto-coding-alist'.
213 (let ((buffer-file-name
214 (file-name-sans-extension file)))
215 (select-safe-coding-system
216 (point-min) (point-max)))
217 buffer-file-coding-system)))
218 (context (epg-make-context))
219 (coding-system-for-write 'binary)
220 string entry
221 (recipients
222 (cond
223 ((listp epa-file-encrypt-to) epa-file-encrypt-to)
224 ((stringp epa-file-encrypt-to) (list epa-file-encrypt-to))))
225 buffer)
226 (epg-context-set-passphrase-callback
227 context
228 (cons #'epa-file-passphrase-callback-function
229 file))
230 (epg-context-set-progress-callback
231 context
232 (cons #'epa-progress-callback-function
233 (format "Encrypting %s" file)))
234 (setf (epg-context-armor context) epa-armor)
235 (setf (epg-context-pinentry-mode context) epa-pinentry-mode)
236 (condition-case error
237 (setq string
238 (epg-encrypt-string
239 context
240 (if (stringp start)
241 (epa-file--encode-coding-string start coding-system)
242 (unless start
243 (setq start (point-min)
244 end (point-max)))
245 (setq buffer (current-buffer))
246 (with-temp-buffer
247 (insert-buffer-substring buffer start end)
248 ;; Translate the region according to
249 ;; `buffer-file-format', as `write-region' would.
250 ;; We can't simply do `write-region' (into a
251 ;; temporary file) here, since it writes out
252 ;; decrypted contents.
253 (format-encode-buffer (with-current-buffer buffer
254 buffer-file-format))
255 (epa-file--encode-coding-string (buffer-string)
256 coding-system)))
257 (if (or (eq epa-file-select-keys t)
258 (and (null epa-file-select-keys)
259 (not (local-variable-p 'epa-file-encrypt-to
260 (current-buffer)))))
261 (epa-select-keys
262 context
263 "Select recipients for encryption.
264 If no one is selected, symmetric encryption will be performed. "
265 recipients)
266 (if epa-file-encrypt-to
267 (epg-list-keys context recipients)))))
268 (error
269 (epa-display-error context)
270 (if (setq entry (assoc file epa-file-passphrase-alist))
271 (setcdr entry nil))
272 (signal 'file-error (cons "Opening output file" (cdr error)))))
273 (epa-file-run-real-handler
274 #'write-region
275 (list string nil file append visit lockname mustbenew))
276 (if (boundp 'last-coding-system-used)
277 (setq last-coding-system-used coding-system))
278 (if (eq visit t)
279 (progn
280 (setq buffer-file-name file)
281 (set-visited-file-modtime))
282 (if (stringp visit)
283 (progn
284 (set-visited-file-modtime)
285 (setq buffer-file-name visit))))
286 (if (or (eq visit t)
287 (eq visit nil)
288 (stringp visit))
289 (message "Wrote %s" buffer-file-name))))
290 (put 'write-region 'epa-file 'epa-file-write-region)
292 (defun epa-file-select-keys ()
293 "Select recipients for encryption."
294 (interactive)
295 (setq-local epa-file-encrypt-to
296 (mapcar
297 (lambda (key)
298 (epg-sub-key-id (car (epg-key-sub-key-list key))))
299 (epa-select-keys
300 (epg-make-context)
301 "Select recipients for encryption.
302 If no one is selected, symmetric encryption will be performed. "))))
304 ;;;###autoload
305 (defun epa-file-enable ()
306 (interactive)
307 (if (memq epa-file-handler file-name-handler-alist)
308 (message "`epa-file' already enabled")
309 (setq file-name-handler-alist
310 (cons epa-file-handler file-name-handler-alist))
311 (add-hook 'find-file-hook 'epa-file-find-file-hook)
312 (setq auto-mode-alist (cons epa-file-auto-mode-alist-entry auto-mode-alist))
313 (message "`epa-file' enabled")))
315 ;;;###autoload
316 (defun epa-file-disable ()
317 (interactive)
318 (if (memq epa-file-handler file-name-handler-alist)
319 (progn
320 (setq file-name-handler-alist
321 (delq epa-file-handler file-name-handler-alist))
322 (remove-hook 'find-file-hook 'epa-file-find-file-hook)
323 (setq auto-mode-alist (delq epa-file-auto-mode-alist-entry
324 auto-mode-alist))
325 (message "`epa-file' disabled"))
326 (message "`epa-file' already disabled")))
328 (provide 'epa-file)
330 ;;; epa-file.el ends here