lisp/epa-file.el

   1 ;;; epa-file.el --- the EasyPG Assistant, transparent file encryption
   2 ;; Copyright (C) 2006, 2007, 2008 Free Software Foundation, Inc.
   3
   4 ;; Author: Daiki Ueno <ueno@unixuser.org>
   5 ;; Keywords: PGP, GnuPG
   6
   7 ;; This file is part of GNU Emacs.
   8
   9 ;; GNU Emacs is free software; you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation; either version 3, or (at your option)
  12 ;; any later version.
  13
  14 ;; GNU Emacs is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  21 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  22 ;; Boston, MA 02110-1301, USA.
  23
  24 ;;; Code:
  25
  26 (require 'epa)
  27 (require 'epa-file-hook)
  28
  29 (defcustom epa-file-cache-passphrase-for-symmetric-encryption nil
  30   "If non-nil, cache passphrase for symmetric encryption."
  31   :type 'boolean
  32   :group 'epa-file)
  33
  34 (defcustom epa-file-select-keys nil
  35   "If non-nil, always asks user to select recipients."
  36   :type 'boolean
  37   :group 'epa-file)
  38
  39 (defvar epa-file-passphrase-alist nil)
  40
  41 (eval-and-compile
  42   (if (fboundp 'encode-coding-string)
  43       (defalias 'epa-file--encode-coding-string 'encode-coding-string)
  44     (defalias 'epa-file--encode-coding-string 'identity)))
  45
  46 (eval-and-compile
  47   (if (fboundp 'decode-coding-string)
  48       (defalias 'epa-file--decode-coding-string 'decode-coding-string)
  49     (defalias 'epa-file--decode-coding-string 'identity)))
  50
  51 (defun epa-file-passphrase-callback-function (context key-id file)
  52   (if (and epa-file-cache-passphrase-for-symmetric-encryption
  53            (eq key-id 'SYM))
  54       (progn
  55         (setq file (file-truename file))
  56         (let ((entry (assoc file epa-file-passphrase-alist))
  57               passphrase)
  58           (or (copy-sequence (cdr entry))
  59               (progn
  60                 (unless entry
  61                   (setq entry (list file)
  62                         epa-file-passphrase-alist
  63                         (cons entry
  64                               epa-file-passphrase-alist)))
  65                 (setq passphrase (epa-passphrase-callback-function context
  66                                                                    key-id nil))
  67                 (setcdr entry (copy-sequence passphrase))
  68                 passphrase))))
  69     (epa-passphrase-callback-function context key-id nil)))
  70
  71 ;;;###autoload
  72 (defun epa-file-handler (operation &rest args)
  73   (save-match-data
  74     (let ((op (get operation 'epa-file)))
  75       (if op
  76           (apply op args)
  77         (epa-file-run-real-handler operation args)))))
  78
  79 (defun epa-file-run-real-handler (operation args)
  80   (let ((inhibit-file-name-handlers
  81          (cons 'epa-file-handler
  82                (and (eq inhibit-file-name-operation operation)
  83                     inhibit-file-name-handlers)))
  84         (inhibit-file-name-operation operation))
  85     (apply operation args)))
  86
  87 (defun epa-file-decode-and-insert (string file visit beg end replace)
  88   (if (fboundp 'decode-coding-inserted-region)
  89       (save-restriction
  90         (narrow-to-region (point) (point))
  91         (let ((multibyte enable-multibyte-characters))
  92           (set-buffer-multibyte nil)
  93           (insert string)
  94           (set-buffer-multibyte multibyte)
  95           (decode-coding-inserted-region
  96            (point-min) (point-max)
  97            (substring file 0 (string-match epa-file-name-regexp file))
  98            visit beg end replace)))
  99     (insert (epa-file--decode-coding-string string (or coding-system-for-read
 100                                                        'undecided)))))
 101
 102 (defvar last-coding-system-used)
 103 (defun epa-file-insert-file-contents (file &optional visit beg end replace)
 104   (barf-if-buffer-read-only)
 105   (if (and visit (or beg end))
 106       (error "Attempt to visit less than an entire file"))
 107   (setq file (expand-file-name file))
 108   (let* ((local-copy
 109           (condition-case inl
 110               (epa-file-run-real-handler #'file-local-copy (list file))
 111             (error)))
 112          (local-file (or local-copy file))
 113          (context (epg-make-context))
 114          string length entry)
 115     (if visit
 116         (setq buffer-file-name file))
 117     (epg-context-set-passphrase-callback
 118      context
 119      (cons #'epa-file-passphrase-callback-function
 120            local-file))
 121     (epg-context-set-progress-callback context
 122                                        #'epa-progress-callback-function)
 123     (unwind-protect
 124         (progn
 125           (if replace
 126               (goto-char (point-min)))
 127           (condition-case error
 128               (setq string (epg-decrypt-file context local-file nil))
 129             (error
 130              (if (setq entry (assoc file epa-file-passphrase-alist))
 131                  (setcdr entry nil))
 132              (signal 'file-error
 133                      (cons "Opening input file" (cdr error)))))
 134           (make-local-variable 'epa-file-encrypt-to)
 135           (setq epa-file-encrypt-to
 136                 (mapcar #'car (epg-context-result-for context 'encrypted-to)))
 137           (if (or beg end)
 138               (setq string (substring string (or beg 0) end)))
 139           (save-excursion
 140             (save-restriction
 141               (narrow-to-region (point) (point))
 142               (epa-file-decode-and-insert string file visit beg end replace)
 143               (setq length (- (point-max) (point-min))))
 144             (if replace
 145                 (delete-region (point) (point-max)))))
 146       (if (and local-copy
 147                (file-exists-p local-copy))
 148           (delete-file local-copy)))
 149     (list file length)))
 150 (put 'insert-file-contents 'epa-file 'epa-file-insert-file-contents)
 151
 152 (defun epa-file-write-region (start end file &optional append visit lockname
 153                                     mustbenew)
 154   (if append
 155       (error "Can't append to the file."))
 156   (setq file (expand-file-name file))
 157   (let* ((coding-system (or coding-system-for-write
 158                             (if (fboundp 'select-safe-coding-system)
 159                                 ;; This is needed since Emacs 22 has
 160                                 ;; no-conversion setting for *.gpg in
 161                                 ;; `auto-coding-alist'.
 162                                 (let ((buffer-file-name
 163                                        (file-name-sans-extension file)))
 164                                   (select-safe-coding-system
 165                                    (point-min) (point-max)))
 166                               buffer-file-coding-system)))
 167          (context (epg-make-context))
 168          (coding-system-for-write 'binary)
 169          string entry
 170          (recipients
 171           (cond
 172            ((listp epa-file-encrypt-to) epa-file-encrypt-to)
 173            ((stringp epa-file-encrypt-to) (list epa-file-encrypt-to)))))
 174     (epg-context-set-passphrase-callback
 175      context
 176      (cons #'epa-file-passphrase-callback-function
 177            file))
 178     (epg-context-set-progress-callback context
 179                                        #'epa-progress-callback-function)
 180     (epg-context-set-armor context epa-armor)
 181     (condition-case error
 182         (setq string
 183               (epg-encrypt-string
 184                context
 185                (if (stringp start)
 186                    (epa-file--encode-coding-string start coding-system)
 187                  (epa-file--encode-coding-string (buffer-substring start end)
 188                                                  coding-system))
 189                (if (or epa-file-select-keys
 190                        (not (local-variable-p 'epa-file-encrypt-to
 191                                               (current-buffer))))
 192                    (epa-select-keys
 193                     context
 194                     "Select recipents for encryption.
 195 If no one is selected, symmetric encryption will be performed.  "
 196                     recipients)
 197                  (if epa-file-encrypt-to
 198                      (epg-list-keys context recipients)))))
 199       (error
 200        (if (setq entry (assoc file epa-file-passphrase-alist))
 201            (setcdr entry nil))
 202        (signal 'file-error (cons "Opening output file" (cdr error)))))
 203     (epa-file-run-real-handler
 204      #'write-region
 205      (list string nil file append visit lockname mustbenew))
 206     (if (boundp 'last-coding-system-used)
 207         (setq last-coding-system-used coding-system))
 208     (if (eq visit t)
 209         (progn
 210           (setq buffer-file-name file)
 211           (set-visited-file-modtime))
 212       (if (stringp visit)
 213           (progn
 214             (set-visited-file-modtime)
 215             (setq buffer-file-name visit))))
 216     (if (or (eq visit t)
 217             (eq visit nil)
 218             (stringp visit))
 219         (message "Wrote %s" buffer-file-name))))
 220 (put 'write-region 'epa-file 'epa-file-write-region)
 221
 222 (defun epa-file-select-keys ()
 223   "Select recipients for encryption."
 224   (interactive)
 225   (make-local-variable 'epa-file-encrypt-to)
 226   (setq epa-file-encrypt-to
 227         (mapcar
 228          (lambda (key)
 229            (epg-sub-key-id (car (epg-key-sub-key-list key))))
 230         (epa-select-keys
 231          (epg-make-context)
 232          "Select recipents for encryption.
 233 If no one is selected, symmetric encryption will be performed.  "))))
 234
 235 ;;;###autoload
 236 (defun epa-file-enable ()
 237   (interactive)
 238   (if (memq epa-file-handler file-name-handler-alist)
 239       (message "`epa-file' already enabled")
 240     (setq file-name-handler-alist
 241           (cons epa-file-handler file-name-handler-alist))
 242     (add-hook 'find-file-hook 'epa-file-find-file-hook)
 243     (setq auto-mode-alist (cons epa-file-auto-mode-alist-entry auto-mode-alist))
 244     (message "`epa-file' enabled")))
 245
 246 ;;;###autoload
 247 (defun epa-file-disable ()
 248   (interactive)
 249   (if (memq epa-file-handler file-name-handler-alist)
 250       (progn
 251         (setq file-name-handler-alist
 252               (delq epa-file-handler file-name-handler-alist))
 253         (remove-hook 'find-file-hook 'epa-file-find-file-hook)
 254         (setq auto-mode-alist (delq epa-file-auto-mode-alist-entry
 255                                     auto-mode-alist))
 256         (message "`epa-file' disabled"))
 257     (message "`epa-file' already disabled")))
 258
 259 (provide 'epa-file)
 260
 261 ;; arch-tag: 5715152f-0eb1-4dbc-9008-07098775314d
 262 ;;; epa-file.el ends here