lisp/gnus/encrypt.el

   1 ;;; encrypt.el --- file encryption routines
   2 ;; Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   3
   4 ;; Author: Teodor Zlatanov <tzz@lifelogs.com>
   5 ;; Created: 2003/01/24
   6 ;; Keywords: files
   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, or (at your option)
  13 ;; 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; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  23 ;; Boston, MA 02110-1301, USA.
  24
  25 ;;; Commentary:
  26
  27 ;;; This module addresses data encryption.  Page breaks are used for
  28 ;;; grouping declarations and documentation relating to each
  29 ;;; particular aspect.
  30
  31 ;;; Use in Gnus like this:
  32 ;;; (setq
  33 ;;;   nnimap-authinfo-file "~/.authinfo.enc"
  34 ;;;   nntp-authinfo-file "~/.authinfo.enc"
  35 ;;;   smtpmail-auth-credentials "~/.authinfo.enc"
  36 ;;;   ;; using the AES256 cipher, feel free to use your own favorite
  37 ;;;   encrypt-file-alist (quote (("~/.authinfo.enc" (gpg "AES256"))))
  38 ;;;   password-cache-expiry 600)
  39
  40 ;;; Then write ~/.authinfo.enc:
  41
  42 ;;; 1) open the old authinfo
  43 ;;; C-x C-f ~/.authinfo
  44
  45 ;;; 2) write the new authinfo.enc
  46 ;;; M-x encrypt-file-contents ~/.authinfo.enc
  47
  48 ;;; 3) verify the new authinfo is correct (this will show the contents in the minibuffer)
  49 ;;; M-: (encrypt-get-file-contents "~/.authinfo.enc")
  50
  51
  52 ;;; Code:
  53
  54 ;; autoload password
  55 (eval-and-compile
  56   (autoload 'password-read "password"))
  57
  58 (defgroup encrypt '((password-cache custom-variable)
  59                     (password-cache-expiry custom-variable))
  60   "File encryption configuration."
  61   :group 'applications)
  62
  63 (defcustom encrypt-file-alist nil
  64   "List of file names or regexes matched with encryptions.
  65 Format example:
  66  '((\"beta\"
  67     (gpg \"AES\"))
  68    (\"/home/tzz/alpha\"
  69     (encrypt-xor \"Semi-Secret\")))"
  70
  71   :type '(repeat
  72           (list :tag "Encryption entry"
  73            (radio :tag "What to encrypt"
  74                   (file :tag "Filename")
  75                   (regexp :tag "Regular expression match"))
  76            (radio :tag "How to encrypt it"
  77                   (list
  78                    :tag "GPG Encryption"
  79                    (const :tag "GPG Program" gpg)
  80                    (radio :tag "Choose a cipher"
  81                           (const :tag "3DES Encryption" "3DES")
  82                           (const :tag "CAST5 Encryption" "CAST5")
  83                           (const :tag "Blowfish Encryption" "BLOWFISH")
  84                           (const :tag "AES Encryption" "AES")
  85                           (const :tag "AES192 Encryption" "AES192")
  86                           (const :tag "AES256 Encryption" "AES256")
  87                           (const :tag "Twofish Encryption" "TWOFISH")
  88                           (string :tag "Cipher Name")))
  89                   (list
  90                    :tag "Built-in simple XOR"
  91                    (const :tag "XOR Encryption" encrypt-xor)
  92                    (string :tag "XOR Cipher Value (seed value)")))))
  93   :group 'encrypt)
  94
  95 ;; TODO: now, load gencrypt.el and if successful, modify the
  96 ;; custom-type of encrypt-file-alist to add the gencrypt.el options
  97
  98 ;; (plist-get (symbol-plist 'encrypt-file-alist) 'custom-type)
  99 ;; then use plist-put
 100
 101 (defcustom encrypt-gpg-path (executable-find "gpg")
 102   "Path to the GPG program."
 103   :type '(radio
 104           (file :tag "Location of the GPG executable")
 105           (const :tag "GPG is not installed" nil))
 106   :group 'encrypt)
 107
 108 (defvar encrypt-temp-prefix "encrypt"
 109   "Prefix for temporary filenames")
 110
 111 ;;;###autoload
 112 (defun encrypt-find-model (filename)
 113   "Given a filename, find a encrypt-file-alist entry"
 114   (dolist (entry encrypt-file-alist)
 115     (let ((match (nth 0 entry))
 116           (model (nth 1 entry)))
 117       (when (or (eq match filename)
 118                 (string-match match filename))
 119         (return model)))))
 120
 121 ;;;###autoload
 122 (defun encrypt-insert-file-contents (file &optional model)
 123   "Decrypt FILE into the current buffer."
 124   (interactive "fFile to insert: ")
 125   (let* ((model (or model (encrypt-find-model file)))
 126          (method (nth 0 model))
 127          (cipher (nth 1 model))
 128          (password-key (format "encrypt-password-%s-%s %s"
 129                                (symbol-name method) cipher file))
 130          (passphrase
 131           (password-read-and-add
 132            (format "%s password for cipher %s (file %s)? "
 133                    file (symbol-name method) cipher)
 134            password-key))
 135           (buffer-file-coding-system 'binary)
 136          (coding-system-for-read 'binary)
 137          outdata)
 138
 139     ;; note we only insert-file-contents if the method is known to be valid
 140     (cond
 141      ((eq method 'gpg)
 142       (insert-file-contents file)
 143       (setq outdata (encrypt-gpg-decode-buffer passphrase cipher)))
 144      ((eq method 'encrypt-xor)
 145       (insert-file-contents file)
 146       (setq outdata (encrypt-xor-decode-buffer passphrase cipher))))
 147
 148     (if outdata
 149         (progn
 150           (message "%s was decrypted with %s (cipher %s)"
 151                    file (symbol-name method) cipher)
 152           (delete-region (point-min) (point-max))
 153           (goto-char (point-min))
 154           (insert outdata))
 155       ;; the decryption failed, alas
 156       (password-cache-remove password-key)
 157       (gnus-error 5 "%s was NOT decrypted with %s (cipher %s)"
 158                   file (symbol-name method) cipher))))
 159
 160 (defun encrypt-get-file-contents (file &optional model)
 161   "Decrypt FILE and return the contents."
 162   (interactive "fFile to decrypt: ")
 163   (with-temp-buffer
 164     (encrypt-insert-file-contents file model)
 165     (buffer-string)))
 166
 167 (defun encrypt-put-file-contents (file data &optional model)
 168   "Encrypt the DATA to FILE, then continue normally."
 169   (with-temp-buffer
 170     (insert data)
 171     (encrypt-write-file-contents file model)))
 172
 173 (defun encrypt-write-file-contents (file &optional model)
 174   "Encrypt the current buffer to FILE, then continue normally."
 175   (interactive "sFile to write: ")
 176   (setq model (or model (encrypt-find-model file)))
 177   (if model
 178       (let* ((method (nth 0 model))
 179              (cipher (nth 1 model))
 180              (password-key (format "encrypt-password-%s-%s %s"
 181                                    (symbol-name method) cipher file))
 182              (passphrase
 183               (password-read
 184                (format "%s password for cipher %s? "
 185                        (symbol-name method) cipher)
 186                password-key))
 187              outdata)
 188
 189         (cond
 190          ((eq method 'gpg)
 191           (setq outdata (encrypt-gpg-encode-buffer passphrase cipher)))
 192          ((eq method 'encrypt-xor)
 193           (setq outdata (encrypt-xor-encode-buffer passphrase cipher))))
 194
 195         (if outdata
 196             (progn
 197               (message "%s was encrypted with %s (cipher %s)"
 198                        file (symbol-name method) cipher)
 199               (delete-region (point-min) (point-max))
 200               (goto-char (point-min))
 201               (insert outdata)
 202               ;; do not confirm overwrites
 203               (write-file file nil))
 204           ;; the decryption failed, alas
 205           (password-cache-remove password-key)
 206           (gnus-error 5 "%s was NOT encrypted with %s (cipher %s)"
 207                       file (symbol-name method) cipher)))
 208     (gnus-error 1 "%s has no associated encryption model!  See encrypt-file-alist." file)))
 209
 210 (defun encrypt-xor-encode-buffer (passphrase cipher)
 211   (encrypt-xor-process-buffer passphrase cipher t))
 212
 213 (defun encrypt-xor-decode-buffer (passphrase cipher)
 214   (encrypt-xor-process-buffer passphrase cipher nil))
 215
 216 (defun encrypt-xor-process-buffer (passphrase
 217                                         cipher
 218                                         &optional encode)
 219   "Given PASSPHRASE, xor-encode or decode the contents of the current buffer."
 220   (let* ((bs (buffer-substring-no-properties (point-min) (point-max)))
 221          ;; passphrase-sum is a simple additive checksum of the
 222          ;; passphrase and the cipher
 223         (passphrase-sum
 224          (when (stringp passphrase)
 225            (apply '+ (append cipher passphrase nil))))
 226         new-list)
 227
 228     (with-temp-buffer
 229       (if encode
 230           (progn
 231             (dolist (x (append bs nil))
 232               (setq new-list (cons (logxor x passphrase-sum) new-list)))
 233
 234             (dolist (x new-list)
 235               (insert (format "%d " x))))
 236         (progn
 237           (setq new-list (reverse (split-string bs)))
 238           (dolist (x new-list)
 239             (setq x (string-to-number x))
 240             (insert (format "%c" (logxor x passphrase-sum))))))
 241       (buffer-substring-no-properties (point-min) (point-max)))))
 242
 243 (defun encrypt-gpg-encode-buffer (passphrase cipher)
 244   (encrypt-gpg-process-buffer passphrase cipher t))
 245
 246 (defun encrypt-gpg-decode-buffer (passphrase cipher)
 247   (encrypt-gpg-process-buffer passphrase cipher nil))
 248
 249 (defun encrypt-gpg-process-buffer (passphrase
 250                                         cipher
 251                                         &optional encode)
 252   "With PASSPHRASE, use GPG to encode or decode the current buffer."
 253   (let* ((program encrypt-gpg-path)
 254          (input (buffer-substring-no-properties (point-min) (point-max)))
 255          (temp-maker (if (fboundp 'make-temp-file)
 256                          'make-temp-file
 257                        'make-temp-name))
 258          (temp-file (funcall temp-maker encrypt-temp-prefix))
 259          (default-enable-multibyte-characters nil)
 260          (args `("--cipher-algo" ,cipher
 261                  "--status-fd" "2"
 262                  "--logger-fd" "2"
 263                  "--passphrase-fd" "0"
 264                  "--no-tty"))
 265          exit-status exit-data)
 266
 267     (when encode
 268       (setq args
 269             (append args
 270                     '("--symmetric"
 271                       "--armor"))))
 272
 273     (if program
 274         (with-temp-buffer
 275           (when passphrase
 276             (insert passphrase "\n"))
 277           (insert input)
 278           (setq exit-status
 279                 (apply #'call-process-region (point-min) (point-max) program
 280                        t `(t ,temp-file) nil args))
 281           (if (equal exit-status 0)
 282               (setq exit-data
 283                     (buffer-substring-no-properties (point-min) (point-max)))
 284             (with-temp-buffer
 285               (when (file-exists-p temp-file)
 286                 (insert-file-contents temp-file))
 287               (gnus-error 5 (format "%s exited abnormally: '%s' [%s]"
 288                                     program exit-status (buffer-string)))))
 289           (delete-file temp-file))
 290       (gnus-error 5 "GPG is not installed."))
 291     exit-data))
 292
 293 (provide 'encrypt)
 294 ;;; encrypt.el ends here
 295
 296 ;; arch-tag: d907e4f1-71b5-42b1-a180-fc7b84ff0648