lisp/org-crypt.el

   1 ;;; org-crypt.el --- Public key encryption for org-mode entries
   2
   3 ;; Copyright (C) 2007, 2009, 2010  Free Software Foundation, Inc.
   4
   5 ;; Emacs Lisp Archive Entry
   6 ;; Filename: org-crypt.el
   7 ;; Version: 7.5
   8 ;; Keywords: org-mode
   9 ;; Author: John Wiegley <johnw@gnu.org>
  10 ;; Maintainer: Peter Jones <pjones@pmade.com>
  11 ;; Description: Adds public key encryption to org-mode buffers
  12 ;; URL: http://www.newartisans.com/software/emacs.html
  13 ;; Compatibility: Emacs22
  14
  15 ;; This file is part of GNU Emacs.
  16 ;;
  17 ;; GNU Emacs is free software: you can redistribute it and/or modify
  18 ;; it under the terms of the GNU General Public License as published by
  19 ;; the Free Software Foundation, either version 3 of the License, or
  20 ;; (at your option) any later version.
  21
  22 ;; GNU Emacs is distributed in the hope that it will be useful,
  23 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  24 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  25 ;; GNU General Public License for more details.
  26
  27 ;; You should have received a copy of the GNU General Public License
  28 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  29
  30 ;;; Commentary:
  31
  32 ;; Right now this is just a set of functions to play with.  It depends
  33 ;; on the epg library.  Here's how you would use it:
  34 ;;
  35 ;; 1. To mark an entry for encryption, tag the heading with "crypt".
  36 ;;    You can change the tag to any complex tag matching string by
  37 ;;    setting the `org-crypt-tag-matcher' variable.
  38 ;;
  39 ;; 2. Set the encryption key to use in the `org-crypt-key' variable,
  40 ;;    or use `M-x org-set-property' to set the property CRYPTKEY to
  41 ;;    any address in your public keyring.  The text of the entry (but
  42 ;;    not its properties or headline) will be encrypted for this user.
  43 ;;    For them to read it, the corresponding secret key must be
  44 ;;    located in the secret key ring of the account where you try to
  45 ;;    decrypt it.  This makes it possible to leave secure notes that
  46 ;;    only the intended recipient can read in a shared-org-mode-files
  47 ;;    scenario.
  48 ;;    If the key is not set, org-crypt will default to symmetric encryption.
  49 ;;
  50 ;; 3. To later decrypt an entry, use `org-decrypt-entries' or
  51 ;;    `org-decrypt-entry'.  It might be useful to bind this to a key,
  52 ;;    like C-c C-/.  I hope that in the future, C-c C-r can be might
  53 ;;    overloaded to also decrypt an entry if it's encrypted, since
  54 ;;    that fits nicely with the meaning of "reveal".
  55 ;;
  56 ;; 4. To automatically encrypt all necessary entries when saving a
  57 ;;    file, call `org-crypt-use-before-save-magic' after loading
  58 ;;    org-crypt.el.
  59
  60 ;;; Thanks:
  61
  62 ;; - Carsten Dominik
  63 ;; - Vitaly Ostanin
  64
  65 (require 'org)
  66
  67 ;;; Code:
  68
  69 (declare-function epg-decrypt-string "epg" (context cipher))
  70 (declare-function epg-list-keys "epg" (context &optional name mode))
  71 (declare-function epg-make-context "epg"
  72                   (&optional protocol armor textmode include-certs
  73                              cipher-algorithm digest-algorithm
  74                              compress-algorithm))
  75 (declare-function epg-encrypt-string "epg"
  76                   (context plain recipients &optional sign always-trust))
  77
  78 (defgroup org-crypt nil
  79   "Org Crypt"
  80   :tag "Org Crypt"
  81   :group 'org)
  82
  83 (defcustom org-crypt-tag-matcher "crypt"
  84   "The tag matcher used to find headings whose contents should be encrypted.
  85
  86 See the \"Match syntax\" section of the org manual for more details."
  87   :type 'string
  88   :group 'org-crypt)
  89
  90 (defcustom org-crypt-key ""
  91   "The default key to use when encrypting the contents of a heading.
  92
  93 This setting can also be overridden in the CRYPTKEY property."
  94   :type 'string
  95   :group 'org-crypt)
  96
  97 (defcustom org-crypt-disable-auto-save 'ask
  98   "What org-decrypt should do if `auto-save-mode' is enabled.
  99
 100 t        : Disable auto-save-mode for the current buffer
 101            prior to decrypting an entry.
 102
 103 nil      : Leave auto-save-mode enabled.
 104            This may cause data to be written to disk unencrypted!
 105
 106 'ask     : Ask user whether or not to disable auto-save-mode
 107            for the current buffer.
 108
 109 'encrypt : Leave auto-save-mode enabled for the current buffer,
 110            but automatically re-encrypt all decrypted entries
 111            *before* auto-saving.
 112            NOTE: This only works for entries which have a tag
 113            that matches `org-crypt-tag-matcher'."
 114   :group 'org-crypt
 115   :type '(choice (const :tag "Always"  t)
 116                  (const :tag "Never"   nil)
 117                  (const :tag "Ask"     ask)
 118                  (const :tag "Encrypt" encrypt)))
 119
 120 (defun org-crypt-key-for-heading ()
 121   "Return the encryption key for the current heading."
 122   (save-excursion
 123     (org-back-to-heading t)
 124     (or (org-entry-get nil "CRYPTKEY" 'selective)
 125         org-crypt-key
 126         (and (boundp 'epa-file-encrypt-to) epa-file-encrypt-to)
 127         (message "No crypt key set, using symmetric encryption."))))
 128
 129 (defun org-encrypt-string (str crypt-key)
 130   "Return STR encrypted with CRYPT-KEY."
 131   ;; Text and key have to be identical, otherwise we re-crypt.
 132   (if (and (string= crypt-key (get-text-property 0 'org-crypt-key str))
 133            (string= (sha1 str) (get-text-property 0 'org-crypt-checksum str)))
 134       (get-text-property 0 'org-crypt-text str)
 135     (let ((epg-context (epg-make-context nil t t)))
 136       (epg-encrypt-string epg-context str (epg-list-keys epg-context crypt-key)))))
 137
 138 (defun org-encrypt-entry ()
 139   "Encrypt the content of the current headline."
 140   (interactive)
 141   (require 'epg)
 142   (save-excursion
 143     (org-back-to-heading t)
 144     (let ((start-heading (point)))
 145       (forward-line)
 146       (when (not (looking-at "-----BEGIN PGP MESSAGE-----"))
 147         (let ((folded (outline-invisible-p))
 148               (epg-context (epg-make-context nil t t))
 149               (crypt-key (org-crypt-key-for-heading))
 150               (beg (point))
 151               end encrypted-text)
 152           (goto-char start-heading)
 153           (org-end-of-subtree t t)
 154           (org-back-over-empty-lines)
 155           (setq end (point)
 156                 encrypted-text
 157                 (org-encrypt-string (buffer-substring beg end) crypt-key))
 158           (delete-region beg end)
 159           (insert encrypted-text)
 160           (when folded
 161             (goto-char start-heading)
 162             (hide-subtree))
 163           nil)))))
 164
 165 (defun org-decrypt-entry ()
 166   "Decrypt the content of the current headline."
 167   (interactive)
 168
 169   ; auto-save-mode may cause leakage, so check whether it's enabled.
 170   (when buffer-auto-save-file-name
 171     (cond
 172      ((or
 173        (eq org-crypt-disable-auto-save t)
 174        (and
 175         (eq org-crypt-disable-auto-save 'ask)
 176         (y-or-n-p "org-decrypt: auto-save-mode may cause leakage. Disable it for current buffer? ")))
 177       (message (concat "org-decrypt: Disabling auto-save-mode for " (or (buffer-file-name) (current-buffer))))
 178       ; The argument to auto-save-mode has to be "-1", since
 179       ; giving a "nil" argument toggles instead of disabling.
 180       (auto-save-mode -1))
 181      ((eq org-crypt-disable-auto-save nil)
 182       (message "org-decrypt: Decrypting entry with auto-save-mode enabled. This may cause leakage."))
 183      ((eq org-crypt-disable-auto-save 'encrypt)
 184       (message "org-decrypt: Enabling re-encryption on auto-save.")
 185       (add-hook 'auto-save-hook
 186                 (lambda ()
 187                   (message "org-crypt: Re-encrypting all decrypted entries due to auto-save.")
 188                   (org-encrypt-entries))
 189                 nil t))
 190      (t nil)))
 191
 192   (require 'epg)
 193   (unless (org-before-first-heading-p)
 194     (save-excursion
 195       (org-back-to-heading t)
 196       (let ((heading-point (point))
 197             (heading-was-invisible-p
 198              (save-excursion
 199                (outline-end-of-heading)
 200                (outline-invisible-p))))
 201         (forward-line)
 202         (when (looking-at "-----BEGIN PGP MESSAGE-----")
 203           (let* ((end (save-excursion
 204                         (search-forward "-----END PGP MESSAGE-----")
 205                         (forward-line)
 206                         (point)))
 207                  (epg-context (epg-make-context nil t t))
 208                  (encrypted-text (buffer-substring-no-properties (point) end))
 209                  (decrypted-text
 210                   (decode-coding-string
 211                    (epg-decrypt-string
 212                     epg-context
 213                     encrypted-text)
 214                    'utf-8)))
 215             ;; Delete region starting just before point, because the
 216             ;; outline property starts at the \n of the heading.
 217             (delete-region (1- (point)) end)
 218             ;; Store a checksum of the decrypted and the encrypted
 219             ;; text value. This allow to reuse the same encrypted text
 220             ;; if the text does not change, and therefore avoid a
 221             ;; re-encryption process.
 222             (insert "\n" (propertize decrypted-text
 223                                      'org-crypt-checksum (sha1 decrypted-text)
 224                                      'org-crypt-key (org-crypt-key-for-heading)
 225                                      'org-crypt-text encrypted-text))
 226             (when heading-was-invisible-p
 227               (goto-char heading-point)
 228               (org-flag-subtree t))
 229             nil))))))
 230
 231 (defun org-encrypt-entries ()
 232   "Encrypt all top-level entries in the current buffer."
 233   (interactive)
 234   (org-scan-tags
 235    'org-encrypt-entry
 236    (cdr (org-make-tags-matcher org-crypt-tag-matcher))))
 237
 238 (defun org-decrypt-entries ()
 239   "Decrypt all entries in the current buffer."
 240   (interactive)
 241   (org-scan-tags
 242    'org-decrypt-entry
 243    (cdr (org-make-tags-matcher org-crypt-tag-matcher))))
 244
 245 (defun org-crypt-use-before-save-magic ()
 246   "Add a hook to automatically encrypt entries before a file is saved to disk."
 247   (add-hook
 248    'org-mode-hook
 249    (lambda () (add-hook 'before-save-hook 'org-encrypt-entries nil t))))
 250
 251 (add-hook 'org-reveal-start-hook 'org-decrypt-entry)
 252
 253 (provide 'org-crypt)
 254
 255 ;; arch-tag: 8202ed2c-221e-4001-9e4b-54674a7e846e
 256
 257 ;;; org-crypt.el ends here