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: 7.3
   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 ;; TODO:
  61 ;;   - Allow symmetric encryption as well
  62
  63 ;;; Thanks:
  64
  65 ;; - Carsten Dominik
  66 ;; - Vitaly Ostanin
  67
  68 (require 'org)
  69
  70 ;;; Code:
  71
  72 (declare-function epg-decrypt-string "epg" (context cipher))
  73 (declare-function epg-list-keys "epg" (context &optional name mode))
  74 (declare-function epg-make-context "epg"
  75                   (&optional protocol armor textmode include-certs
  76                              cipher-algorithm digest-algorithm
  77                              compress-algorithm))
  78 (declare-function epg-encrypt-string "epg"
  79                   (context plain recipients &optional sign always-trust))
  80
  81 (defgroup org-crypt nil
  82   "Org Crypt"
  83   :tag "Org Crypt" :group 'org)
  84
  85 (defcustom org-crypt-tag-matcher "crypt"
  86   "The tag matcher used to find headings whose contents should be encrypted.
  87
  88 See the \"Match syntax\" section of the org manual for more details."
  89   :type 'string :group 'org-crypt)
  90
  91 (defcustom org-crypt-key nil
  92   "The default key to use when encrypting the contents of a heading.
  93
  94 This setting can also be overridden in the CRYPTKEY property."
  95   :type 'string :group 'org-crypt)
  96
  97 (defun org-crypt-key-for-heading ()
  98   "Return the encryption key for the current heading."
  99   (save-excursion
 100     (org-back-to-heading t)
 101     (or (org-entry-get nil "CRYPTKEY" 'selective)
 102         org-crypt-key
 103         (and (boundp 'epa-file-encrypt-to) epa-file-encrypt-to)
 104         (message "No crypt key set, using symmetric encryption."))))
 105
 106 (defun org-encrypt-entry ()
 107   "Encrypt the content of the current headline."
 108   (interactive)
 109   (require 'epg)
 110   (save-excursion
 111     (org-back-to-heading t)
 112     (let ((start-heading (point)))
 113       (forward-line)
 114       (when (not (looking-at "-----BEGIN PGP MESSAGE-----"))
 115         (let ((folded (org-invisible-p))
 116               (epg-context (epg-make-context nil t t))
 117               (crypt-key (org-crypt-key-for-heading))
 118               (beg (point))
 119               end encrypted-text)
 120           (goto-char start-heading)
 121           (org-end-of-subtree t t)
 122           (org-back-over-empty-lines)
 123           (setq end (point)
 124                 encrypted-text
 125                 (epg-encrypt-string
 126                  epg-context
 127                  (buffer-substring-no-properties beg end)
 128                  (epg-list-keys epg-context crypt-key)))
 129           (delete-region beg end)
 130           (insert encrypted-text)
 131           (when folded
 132             (goto-char start-heading)
 133             (hide-subtree))
 134           nil)))))
 135
 136 (defun org-decrypt-entry ()
 137   "Decrypt the content of the current headline."
 138   (interactive)
 139   (require 'epg)
 140   (unless (org-before-first-heading-p)
 141     (save-excursion
 142       (org-back-to-heading t)
 143       (forward-line)
 144       (when (looking-at "-----BEGIN PGP MESSAGE-----")
 145         (let* ((beg (point))
 146                (end (save-excursion
 147                       (search-forward "-----END PGP MESSAGE-----")
 148                       (forward-line)
 149                       (point)))
 150                (epg-context (epg-make-context nil t t))
 151                (decrypted-text
 152                 (decode-coding-string
 153                  (epg-decrypt-string
 154                   epg-context
 155                   (buffer-substring-no-properties beg end))
 156                  'utf-8)))
 157           (delete-region beg end)
 158           (insert decrypted-text)
 159           nil)))))
 160
 161 (defun org-encrypt-entries ()
 162   "Encrypt all top-level entries in the current buffer."
 163   (interactive)
 164   (org-scan-tags
 165    'org-encrypt-entry
 166    (cdr (org-make-tags-matcher org-crypt-tag-matcher))))
 167
 168 (defun org-decrypt-entries ()
 169   "Decrypt all entries in the current buffer."
 170   (interactive)
 171   (org-scan-tags
 172    'org-decrypt-entry
 173    (cdr (org-make-tags-matcher org-crypt-tag-matcher))))
 174
 175 (defun org-crypt-use-before-save-magic ()
 176   "Add a hook to automatically encrypt entries before a file is saved to disk."
 177   (add-hook
 178    'org-mode-hook
 179    (lambda () (add-hook 'before-save-hook 'org-encrypt-entries nil t))))
 180
 181 (add-hook 'org-reveal-start-hook 'org-decrypt-entry)
 182
 183 (provide 'org-crypt)
 184
 185 ;; arch-tag: 8202ed2c-221e-4001-9e4b-54674a7e846e
 186
 187 ;;; org-crypt.el ends here