lisp/epa-file.el

   1 ;;; epa-file.el --- the EasyPG Assistant, transparent file encryption
   2 ;; Copyright (C) 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   3
   4 ;; Author: Daiki Ueno <ueno@unixuser.org>
   5 ;; Keywords: PGP, GnuPG
   6 ;; Package: epa
   7
   8 ;; This file is part of GNU Emacs.
   9
  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.
  14
  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.
  19
  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/>.
  22
  23 ;;; Code:
  24
  25 (require 'epa)
  26 (require 'epa-hook)
  27
  28 (defcustom epa-file-cache-passphrase-for-symmetric-encryption nil
  29   "If non-nil, cache passphrase for symmetric encryption.
  30
  31 For security reasons, this option is turned off by default and
  32 not recommended to use.  Instead, consider using public-key
  33 encryption with gpg-agent which does the same job in a safer
  34 way."
  35   :type 'boolean
  36   :group 'epa-file)
  37
  38 (defcustom epa-file-select-keys nil
  39   "If non-nil, always asks user to select recipients."
  40   :type 'boolean
  41   :group 'epa-file)
  42
  43 (defvar epa-file-passphrase-alist nil)
  44
  45 (eval-and-compile
  46   (if (fboundp 'encode-coding-string)
  47       (defalias 'epa-file--encode-coding-string 'encode-coding-string)
  48     (defalias 'epa-file--encode-coding-string 'identity)))
  49
  50 (eval-and-compile
  51   (if (fboundp 'decode-coding-string)
  52       (defalias 'epa-file--decode-coding-string 'decode-coding-string)
  53     (defalias 'epa-file--decode-coding-string 'identity)))
  54
  55 (defun epa-file-passphrase-callback-function (context key-id file)
  56   (if (and epa-file-cache-passphrase-for-symmetric-encryption
  57            (eq key-id 'SYM))
  58       (progn
  59         (setq file (file-truename file))
  60         (let ((entry (assoc file epa-file-passphrase-alist))
  61               passphrase)
  62           (or (copy-sequence (cdr entry))
  63               (progn
  64                 (unless entry
  65                   (setq entry (list file)
  66                         epa-file-passphrase-alist
  67                         (cons entry
  68                               epa-file-passphrase-alist)))
  69                 (setq passphrase (epa-passphrase-callback-function context
  70                                                                    key-id
  71                                                                    file))
  72                 (setcdr entry (copy-sequence passphrase))
  73                 passphrase))))
  74     (epa-passphrase-callback-function context key-id file)))
  75
  76 ;;;###autoload
  77 (defun epa-file-handler (operation &rest args)
  78   (save-match-data
  79     (let ((op (get operation 'epa-file)))
  80       (if op
  81           (apply op args)
  82         (epa-file-run-real-handler operation args)))))
  83
  84 (defun epa-file-run-real-handler (operation args)
  85   (let ((inhibit-file-name-handlers
  86          (cons 'epa-file-handler
  87                (and (eq inhibit-file-name-operation operation)
  88                     inhibit-file-name-handlers)))
  89         (inhibit-file-name-operation operation))
  90     (apply operation args)))
  91
  92 (defun epa-file-decode-and-insert (string file visit beg end replace)
  93   (if (fboundp 'decode-coding-inserted-region)
  94       (save-restriction
  95         (narrow-to-region (point) (point))
  96         (insert (if enable-multibyte-characters
  97                     (string-to-multibyte string)
  98                   string))
  99           (decode-coding-inserted-region
 100            (point-min) (point-max)
 101            (substring file 0 (string-match epa-file-name-regexp file))
 102          visit beg end replace))
 103     (insert (epa-file--decode-coding-string string (or coding-system-for-read
 104                                                        'undecided)))))
 105
 106 (defvar epa-file-error nil)
 107 (defun epa-file--find-file-not-found-function ()
 108   (let ((error epa-file-error))
 109     (save-window-excursion
 110       (kill-buffer))
 111     (signal 'file-error
 112             (cons "Opening input file" (cdr error)))))
 113
 114 (defvar last-coding-system-used)
 115 (defun epa-file-insert-file-contents (file &optional visit beg end replace)
 116   (barf-if-buffer-read-only)
 117   (if (and visit (or beg end))
 118       (error "Attempt to visit less than an entire file"))
 119   (setq file (expand-file-name file))
 120   (let* ((local-copy
 121           (condition-case nil
 122               (epa-file-run-real-handler #'file-local-copy (list file))
 123             (error)))
 124          (local-file (or local-copy file))
 125          (context (epg-make-context))
 126          string length entry)
 127     (if visit
 128         (setq buffer-file-name file))
 129     (epg-context-set-passphrase-callback
 130      context
 131      (cons #'epa-file-passphrase-callback-function
 132            local-file))
 133     (epg-context-set-progress-callback context
 134                                        #'epa-progress-callback-function)
 135     (unwind-protect
 136         (progn
 137           (if replace
 138               (goto-char (point-min)))
 139           (condition-case error
 140               (setq string (epg-decrypt-file context local-file nil))
 141             (error
 142              (if (setq entry (assoc file epa-file-passphrase-alist))
 143                  (setcdr entry nil))
 144              ;; Hack to prevent find-file from opening empty buffer
 145              ;; when decryption failed (bug#6568).  See the place
 146              ;; where `find-file-not-found-functions' are called in
 147              ;; `find-file-noselect-1'.
 148              (when (file-exists-p local-file)
 149                (make-local-variable 'epa-file-error)
 150                (setq epa-file-error error)
 151                (add-hook 'find-file-not-found-functions
 152                          'epa-file--find-file-not-found-function
 153                          nil t))
 154              (signal 'file-error
 155                      (cons "Opening input file" (cdr error)))))
 156           (make-local-variable 'epa-file-encrypt-to)
 157           (setq epa-file-encrypt-to
 158                 (mapcar #'car (epg-context-result-for context 'encrypted-to)))
 159           (if (or beg end)
 160               (setq string (substring string (or beg 0) end)))
 161           (save-excursion
 162             ;; If visiting, bind off buffer-file-name so that
 163             ;; file-locking will not ask whether we should
 164             ;; really edit the buffer.
 165             (let ((buffer-file-name
 166                    (if visit nil buffer-file-name)))
 167               (save-restriction
 168                 (narrow-to-region (point) (point))
 169                 (epa-file-decode-and-insert string file visit beg end replace)
 170                 (setq length (- (point-max) (point-min))))
 171               (if replace
 172                   (delete-region (point) (point-max))))
 173             (if visit
 174                 (set-visited-file-modtime))))
 175       (if (and local-copy
 176                (file-exists-p local-copy))
 177           (delete-file local-copy)))
 178     (list file length)))
 179 (put 'insert-file-contents 'epa-file 'epa-file-insert-file-contents)
 180
 181 (defun epa-file-write-region (start end file &optional append visit lockname
 182                                     mustbenew)
 183   (if append
 184       (error "Can't append to the file"))
 185   (setq file (expand-file-name file))
 186   (let* ((coding-system (or coding-system-for-write
 187                             (if (fboundp 'select-safe-coding-system)
 188                                 ;; This is needed since Emacs 22 has
 189                                 ;; no-conversion setting for *.gpg in
 190                                 ;; `auto-coding-alist'.
 191                                 (let ((buffer-file-name
 192                                        (file-name-sans-extension file)))
 193                                   (select-safe-coding-system
 194                                    (point-min) (point-max)))
 195                               buffer-file-coding-system)))
 196          (context (epg-make-context))
 197          (coding-system-for-write 'binary)
 198          string entry
 199          (recipients
 200           (cond
 201            ((listp epa-file-encrypt-to) epa-file-encrypt-to)
 202            ((stringp epa-file-encrypt-to) (list epa-file-encrypt-to)))))
 203     (epg-context-set-passphrase-callback
 204      context
 205      (cons #'epa-file-passphrase-callback-function
 206            file))
 207     (epg-context-set-progress-callback context
 208                                        #'epa-progress-callback-function)
 209     (epg-context-set-armor context epa-armor)
 210     (condition-case error
 211         (setq string
 212               (epg-encrypt-string
 213                context
 214                (if (stringp start)
 215                    (epa-file--encode-coding-string start coding-system)
 216                  (unless start
 217                    (setq start (point-min)
 218                          end (point-max)))
 219                  (epa-file--encode-coding-string (buffer-substring start end)
 220                                                  coding-system))
 221                (if (or epa-file-select-keys
 222                        (not (local-variable-p 'epa-file-encrypt-to
 223                                               (current-buffer))))
 224                    (epa-select-keys
 225                     context
 226                     "Select recipents for encryption.
 227 If no one is selected, symmetric encryption will be performed.  "
 228                     recipients)
 229                  (if epa-file-encrypt-to
 230                      (epg-list-keys context recipients)))))
 231       (error
 232        (if (setq entry (assoc file epa-file-passphrase-alist))
 233            (setcdr entry nil))
 234        (signal 'file-error (cons "Opening output file" (cdr error)))))
 235     (epa-file-run-real-handler
 236      #'write-region
 237      (list string nil file append visit lockname mustbenew))
 238     (if (boundp 'last-coding-system-used)
 239         (setq last-coding-system-used coding-system))
 240     (if (eq visit t)
 241         (progn
 242           (setq buffer-file-name file)
 243           (set-visited-file-modtime))
 244       (if (stringp visit)
 245           (progn
 246             (set-visited-file-modtime)
 247             (setq buffer-file-name visit))))
 248     (if (or (eq visit t)
 249             (eq visit nil)
 250             (stringp visit))
 251         (message "Wrote %s" buffer-file-name))))
 252 (put 'write-region 'epa-file 'epa-file-write-region)
 253
 254 (defun epa-file-select-keys ()
 255   "Select recipients for encryption."
 256   (interactive)
 257   (make-local-variable 'epa-file-encrypt-to)
 258   (setq epa-file-encrypt-to
 259         (mapcar
 260          (lambda (key)
 261            (epg-sub-key-id (car (epg-key-sub-key-list key))))
 262         (epa-select-keys
 263          (epg-make-context)
 264          "Select recipents for encryption.
 265 If no one is selected, symmetric encryption will be performed.  "))))
 266
 267 ;;;###autoload
 268 (defun epa-file-enable ()
 269   (interactive)
 270   (if (memq epa-file-handler file-name-handler-alist)
 271       (message "`epa-file' already enabled")
 272     (setq file-name-handler-alist
 273           (cons epa-file-handler file-name-handler-alist))
 274     (add-hook 'find-file-hook 'epa-file-find-file-hook)
 275     (setq auto-mode-alist (cons epa-file-auto-mode-alist-entry auto-mode-alist))
 276     (message "`epa-file' enabled")))
 277
 278 ;;;###autoload
 279 (defun epa-file-disable ()
 280   (interactive)
 281   (if (memq epa-file-handler file-name-handler-alist)
 282       (progn
 283         (setq file-name-handler-alist
 284               (delq epa-file-handler file-name-handler-alist))
 285         (remove-hook 'find-file-hook 'epa-file-find-file-hook)
 286         (setq auto-mode-alist (delq epa-file-auto-mode-alist-entry
 287                                     auto-mode-alist))
 288         (message "`epa-file' disabled"))
 289     (message "`epa-file' already disabled")))
 290
 291 (provide 'epa-file)
 292
 293 ;; arch-tag: 5715152f-0eb1-4dbc-9008-07098775314d
 294 ;;; epa-file.el ends here