Merge branch 'maint'
[org-mode.git] / lisp / org-crypt.el
blobb02a7ceffbd9ce495d1ce66e12f38ebd26cf4899
1 ;;; org-crypt.el --- Public key encryption for org-mode entries
3 ;; Copyright (C) 2007-2013 Free Software Foundation, Inc.
5 ;; Emacs Lisp Archive Entry
6 ;; Filename: org-crypt.el
7 ;; Keywords: org-mode
8 ;; Author: John Wiegley <johnw@gnu.org>
9 ;; Maintainer: Peter Jones <pjones@pmade.com>
10 ;; Description: Adds public key encryption to org-mode buffers
11 ;; URL: http://www.newartisans.com/software/emacs.html
12 ;; Compatibility: Emacs22
14 ;; This file is part of GNU Emacs.
16 ;; GNU Emacs is free software: you can redistribute it and/or modify
17 ;; it under the terms of the GNU General Public License as published by
18 ;; the Free Software Foundation, either version 3 of the License, or
19 ;; (at your option) any later version.
21 ;; GNU Emacs is distributed in the hope that it will be useful,
22 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
23 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24 ;; GNU General Public License for more details.
26 ;; You should have received a copy of the GNU General Public License
27 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
29 ;;; Commentary:
31 ;; Right now this is just a set of functions to play with. It depends
32 ;; on the epg library. Here's how you would use it:
34 ;; 1. To mark an entry for encryption, tag the heading with "crypt".
35 ;; You can change the tag to any complex tag matching string by
36 ;; setting the `org-crypt-tag-matcher' variable.
38 ;; 2. Set the encryption key to use in the `org-crypt-key' variable,
39 ;; or use `M-x org-set-property' to set the property CRYPTKEY to
40 ;; any address in your public keyring. The text of the entry (but
41 ;; not its properties or headline) will be encrypted for this user.
42 ;; For them to read it, the corresponding secret key must be
43 ;; located in the secret key ring of the account where you try to
44 ;; decrypt it. This makes it possible to leave secure notes that
45 ;; only the intended recipient can read in a shared-org-mode-files
46 ;; scenario.
47 ;; If the key is not set, org-crypt will default to symmetric encryption.
49 ;; 3. To later decrypt an entry, use `org-decrypt-entries' or
50 ;; `org-decrypt-entry'. It might be useful to bind this to a key,
51 ;; like C-c C-/. I hope that in the future, C-c C-r can be might
52 ;; overloaded to also decrypt an entry if it's encrypted, since
53 ;; that fits nicely with the meaning of "reveal".
55 ;; 4. To automatically encrypt all necessary entries when saving a
56 ;; file, call `org-crypt-use-before-save-magic' after loading
57 ;; org-crypt.el.
59 ;;; Thanks:
61 ;; - Carsten Dominik
62 ;; - Vitaly Ostanin
64 (require 'org)
66 ;;; Code:
68 (declare-function epg-decrypt-string "epg" (context cipher))
69 (declare-function epg-list-keys "epg" (context &optional name mode))
70 (declare-function epg-make-context "epg"
71 (&optional protocol armor textmode include-certs
72 cipher-algorithm digest-algorithm
73 compress-algorithm))
74 (declare-function epg-encrypt-string "epg"
75 (context plain recipients &optional sign always-trust))
77 (defgroup org-crypt nil
78 "Org Crypt."
79 :tag "Org Crypt"
80 :group 'org)
82 (defcustom org-crypt-tag-matcher "crypt"
83 "The tag matcher used to find headings whose contents should be encrypted.
85 See the \"Match syntax\" section of the org manual for more details."
86 :type 'string
87 :group 'org-crypt)
89 (defcustom org-crypt-key ""
90 "The default key to use when encrypting the contents of a heading.
92 This setting can also be overridden in the CRYPTKEY property."
93 :type 'string
94 :group 'org-crypt)
96 (defcustom org-crypt-disable-auto-save 'ask
97 "What org-decrypt should do if `auto-save-mode' is enabled.
99 t : Disable auto-save-mode for the current buffer
100 prior to decrypting an entry.
102 nil : Leave auto-save-mode enabled.
103 This may cause data to be written to disk unencrypted!
105 'ask : Ask user whether or not to disable auto-save-mode
106 for the current buffer.
108 'encrypt : Leave auto-save-mode enabled for the current buffer,
109 but automatically re-encrypt all decrypted entries
110 *before* auto-saving.
111 NOTE: This only works for entries which have a tag
112 that matches `org-crypt-tag-matcher'."
113 :group 'org-crypt
114 :version "24.1"
115 :type '(choice (const :tag "Always" t)
116 (const :tag "Never" nil)
117 (const :tag "Ask" ask)
118 (const :tag "Encrypt" encrypt)))
120 (defun org-crypt-check-auto-save ()
121 "Check whether auto-save-mode is enabled for the current buffer.
123 `auto-save-mode' may cause leakage when decrypting entries, so
124 check whether it's enabled, and decide what to do about it.
126 See `org-crypt-disable-auto-save'."
127 (when buffer-auto-save-file-name
128 (cond
129 ((or
130 (eq org-crypt-disable-auto-save t)
131 (and
132 (eq org-crypt-disable-auto-save 'ask)
133 (y-or-n-p "org-decrypt: auto-save-mode may cause leakage. Disable it for current buffer? ")))
134 (message (concat "org-decrypt: Disabling auto-save-mode for " (or (buffer-file-name) (current-buffer))))
135 ; The argument to auto-save-mode has to be "-1", since
136 ; giving a "nil" argument toggles instead of disabling.
137 (auto-save-mode -1))
138 ((eq org-crypt-disable-auto-save nil)
139 (message "org-decrypt: Decrypting entry with auto-save-mode enabled. This may cause leakage."))
140 ((eq org-crypt-disable-auto-save 'encrypt)
141 (message "org-decrypt: Enabling re-encryption on auto-save.")
142 (org-add-hook 'auto-save-hook
143 (lambda ()
144 (message "org-crypt: Re-encrypting all decrypted entries due to auto-save.")
145 (org-encrypt-entries))
146 nil t))
147 (t nil))))
149 (defun org-crypt-key-for-heading ()
150 "Return the encryption key for the current heading."
151 (save-excursion
152 (org-back-to-heading t)
153 (or (org-entry-get nil "CRYPTKEY" 'selective)
154 org-crypt-key
155 (and (boundp 'epa-file-encrypt-to) epa-file-encrypt-to)
156 (message "No crypt key set, using symmetric encryption."))))
158 (defun org-encrypt-string (str crypt-key)
159 "Return STR encrypted with CRYPT-KEY."
160 ;; Text and key have to be identical, otherwise we re-crypt.
161 (if (and (string= crypt-key (get-text-property 0 'org-crypt-key str))
162 (string= (sha1 str) (get-text-property 0 'org-crypt-checksum str)))
163 (get-text-property 0 'org-crypt-text str)
164 (let ((epg-context (epg-make-context nil t t)))
165 (epg-encrypt-string epg-context str (epg-list-keys epg-context crypt-key)))))
167 (defun org-encrypt-entry ()
168 "Encrypt the content of the current headline."
169 (interactive)
170 (require 'epg)
171 (save-excursion
172 (org-back-to-heading t)
173 (let ((start-heading (point)))
174 (forward-line)
175 (when (not (looking-at "-----BEGIN PGP MESSAGE-----"))
176 (let ((folded (outline-invisible-p))
177 (epg-context (epg-make-context nil t t))
178 (crypt-key (org-crypt-key-for-heading))
179 (beg (point))
180 end encrypted-text)
181 (goto-char start-heading)
182 (org-end-of-subtree t t)
183 (org-back-over-empty-lines)
184 (setq end (point)
185 encrypted-text
186 (org-encrypt-string (buffer-substring beg end) crypt-key))
187 (delete-region beg end)
188 (insert encrypted-text)
189 (when folded
190 (goto-char start-heading)
191 (hide-subtree))
192 nil)))))
194 (defun org-decrypt-entry ()
195 "Decrypt the content of the current headline."
196 (interactive)
197 (require 'epg)
198 (unless (org-before-first-heading-p)
199 (save-excursion
200 (org-back-to-heading t)
201 (let ((heading-point (point))
202 (heading-was-invisible-p
203 (save-excursion
204 (outline-end-of-heading)
205 (outline-invisible-p))))
206 (forward-line)
207 (when (looking-at "-----BEGIN PGP MESSAGE-----")
208 (org-crypt-check-auto-save)
209 (let* ((end (save-excursion
210 (search-forward "-----END PGP MESSAGE-----")
211 (forward-line)
212 (point)))
213 (epg-context (epg-make-context nil t t))
214 (encrypted-text (buffer-substring-no-properties (point) end))
215 (decrypted-text
216 (decode-coding-string
217 (epg-decrypt-string
218 epg-context
219 encrypted-text)
220 'utf-8)))
221 ;; Delete region starting just before point, because the
222 ;; outline property starts at the \n of the heading.
223 (delete-region (1- (point)) end)
224 ;; Store a checksum of the decrypted and the encrypted
225 ;; text value. This allow to reuse the same encrypted text
226 ;; if the text does not change, and therefore avoid a
227 ;; re-encryption process.
228 (insert "\n" (propertize decrypted-text
229 'org-crypt-checksum (sha1 decrypted-text)
230 'org-crypt-key (org-crypt-key-for-heading)
231 'org-crypt-text encrypted-text))
232 (when heading-was-invisible-p
233 (goto-char heading-point)
234 (org-flag-subtree t))
235 nil))))))
237 (defun org-encrypt-entries ()
238 "Encrypt all top-level entries in the current buffer."
239 (interactive)
240 (let (todo-only)
241 (org-scan-tags
242 'org-encrypt-entry
243 (cdr (org-make-tags-matcher org-crypt-tag-matcher))
244 todo-only)))
246 (defun org-decrypt-entries ()
247 "Decrypt all entries in the current buffer."
248 (interactive)
249 (let (todo-only)
250 (org-scan-tags
251 'org-decrypt-entry
252 (cdr (org-make-tags-matcher org-crypt-tag-matcher))
253 todo-only)))
255 (defun org-at-encrypted-entry-p ()
256 "Is the current entry encrypted?"
257 (unless (org-before-first-heading-p)
258 (save-excursion
259 (org-back-to-heading t)
260 (search-forward "-----BEGIN PGP MESSAGE-----"
261 (save-excursion (outline-next-heading)) t))))
263 (defun org-crypt-use-before-save-magic ()
264 "Add a hook to automatically encrypt entries before a file is saved to disk."
265 (add-hook
266 'org-mode-hook
267 (lambda () (org-add-hook 'before-save-hook 'org-encrypt-entries nil t))))
269 (add-hook 'org-reveal-start-hook 'org-decrypt-entry)
271 (provide 'org-crypt)
273 ;;; org-crypt.el ends here