Merge branch 'maint'
[org-mode.git] / lisp / org-crypt.el
blob4439c947c0f943288a449ccf458920bd6f4c05d5
1 ;;; org-crypt.el --- Public Key Encryption for Org Entries -*- lexical-binding: t; -*-
2 ;; Copyright (C) 2007-2017 Free Software Foundation, Inc.
4 ;; Emacs Lisp Archive Entry
5 ;; Filename: org-crypt.el
6 ;; Keywords: org-mode
7 ;; Author: John Wiegley <johnw@gnu.org>
8 ;; Maintainer: Peter Jones <pjones@pmade.com>
9 ;; Description: Adds public key encryption to Org buffers
10 ;; URL: http://www.newartisans.com/software/emacs.html
11 ;; Compatibility: Emacs22
13 ;; This file is part of GNU Emacs.
15 ;; GNU Emacs is free software: you can redistribute it and/or modify
16 ;; it under the terms of the GNU General Public License as published by
17 ;; the Free Software Foundation, either version 3 of the License, or
18 ;; (at your option) any later version.
20 ;; GNU Emacs is distributed in the hope that it will be useful,
21 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
22 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23 ;; GNU General Public License for more details.
25 ;; You should have received a copy of the GNU General Public License
26 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
28 ;;; Commentary:
30 ;; Right now this is just a set of functions to play with. It depends
31 ;; on the epg library. Here's how you would use it:
33 ;; 1. To mark an entry for encryption, tag the heading with "crypt".
34 ;; You can change the tag to any complex tag matching string by
35 ;; setting the `org-crypt-tag-matcher' variable.
37 ;; 2. Set the encryption key to use in the `org-crypt-key' variable,
38 ;; or use `M-x org-set-property' to set the property CRYPTKEY to
39 ;; any address in your public keyring. The text of the entry (but
40 ;; not its properties or headline) will be encrypted for this user.
41 ;; For them to read it, the corresponding secret key must be
42 ;; located in the secret key ring of the account where you try to
43 ;; decrypt it. This makes it possible to leave secure notes that
44 ;; only the intended recipient can read in a shared-org-mode-files
45 ;; scenario.
46 ;; If the key is not set, org-crypt will default to symmetric encryption.
48 ;; 3. To later decrypt an entry, use `org-decrypt-entries' or
49 ;; `org-decrypt-entry'. It might be useful to bind this to a key,
50 ;; like C-c C-/. I hope that in the future, C-c C-r can be might
51 ;; overloaded to also decrypt an entry if it's encrypted, since
52 ;; that fits nicely with the meaning of "reveal".
54 ;; 4. To automatically encrypt all necessary entries when saving a
55 ;; file, call `org-crypt-use-before-save-magic' after loading
56 ;; org-crypt.el.
58 ;;; Thanks:
60 ;; - Carsten Dominik
61 ;; - Vitaly Ostanin
63 (require 'org)
65 ;;; Code:
67 (declare-function epg-decrypt-string "epg" (context cipher))
68 (declare-function epg-list-keys "epg" (context &optional name mode))
69 (declare-function epg-make-context "epg"
70 (&optional protocol armor textmode include-certs
71 cipher-algorithm digest-algorithm
72 compress-algorithm))
73 (declare-function epg-encrypt-string "epg"
74 (context plain recipients &optional sign always-trust))
75 (defvar epg-context)
78 (defgroup org-crypt nil
79 "Org Crypt."
80 :tag "Org Crypt"
81 :group 'org)
83 (defcustom org-crypt-tag-matcher "crypt"
84 "The tag matcher used to find headings whose contents should be encrypted.
86 See the \"Match syntax\" section of the org manual for more details."
87 :type 'string
88 :group 'org-crypt)
90 (defcustom org-crypt-key ""
91 "The default key to use when encrypting the contents of a heading.
93 This setting can also be overridden in the CRYPTKEY property."
94 :type 'string
95 :group 'org-crypt)
97 (defcustom org-crypt-disable-auto-save 'ask
98 "What org-decrypt should do if `auto-save-mode' is enabled.
100 t : Disable auto-save-mode for the current buffer
101 prior to decrypting an entry.
103 nil : Leave auto-save-mode enabled.
104 This may cause data to be written to disk unencrypted!
106 `ask' : Ask user whether or not to disable auto-save-mode
107 for the current buffer.
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 :version "24.1"
116 :type '(choice (const :tag "Always" t)
117 (const :tag "Never" nil)
118 (const :tag "Ask" ask)
119 (const :tag "Encrypt" encrypt)))
121 (defun org-crypt-check-auto-save ()
122 "Check whether auto-save-mode is enabled for the current buffer.
124 `auto-save-mode' may cause leakage when decrypting entries, so
125 check whether it's enabled, and decide what to do about it.
127 See `org-crypt-disable-auto-save'."
128 (when buffer-auto-save-file-name
129 (cond
130 ((or
131 (eq org-crypt-disable-auto-save t)
132 (and
133 (eq org-crypt-disable-auto-save 'ask)
134 (y-or-n-p "org-decrypt: auto-save-mode may cause leakage. Disable it for current buffer? ")))
135 (message "org-decrypt: Disabling auto-save-mode for %s"
136 (or (buffer-file-name) (current-buffer)))
137 ;; The argument to auto-save-mode has to be "-1", since
138 ;; giving a "nil" argument toggles instead of disabling.
139 (auto-save-mode -1))
140 ((eq org-crypt-disable-auto-save nil)
141 (message "org-decrypt: Decrypting entry with auto-save-mode enabled. This may cause leakage."))
142 ((eq org-crypt-disable-auto-save 'encrypt)
143 (message "org-decrypt: Enabling re-encryption on auto-save.")
144 (add-hook 'auto-save-hook
145 (lambda ()
146 (message "org-crypt: Re-encrypting all decrypted entries due to auto-save.")
147 (org-encrypt-entries))
148 nil t))
149 (t nil))))
151 (defun org-crypt-key-for-heading ()
152 "Return the encryption key for the current heading."
153 (save-excursion
154 (org-back-to-heading t)
155 (or (org-entry-get nil "CRYPTKEY" 'selective)
156 org-crypt-key
157 (and (boundp 'epa-file-encrypt-to) epa-file-encrypt-to)
158 (message "No crypt key set, using symmetric encryption."))))
160 (defun org-encrypt-string (str crypt-key)
161 "Return STR encrypted with CRYPT-KEY."
162 ;; Text and key have to be identical, otherwise we re-crypt.
163 (if (and (string= crypt-key (get-text-property 0 'org-crypt-key str))
164 (string= (sha1 str) (get-text-property 0 'org-crypt-checksum str)))
165 (get-text-property 0 'org-crypt-text str)
166 (setq-local epg-context (epg-make-context nil t t))
167 (epg-encrypt-string epg-context str (epg-list-keys epg-context crypt-key))))
169 (defun org-encrypt-entry ()
170 "Encrypt the content of the current headline."
171 (interactive)
172 (require 'epg)
173 (org-with-wide-buffer
174 (org-back-to-heading t)
175 (setq-local epg-context (epg-make-context nil t t))
176 (let ((start-heading (point)))
177 (org-end-of-meta-data)
178 (unless (looking-at-p "-----BEGIN PGP MESSAGE-----")
179 (let ((folded (outline-invisible-p))
180 (crypt-key (org-crypt-key-for-heading))
181 (beg (point)))
182 (goto-char start-heading)
183 (org-end-of-subtree t t)
184 (org-back-over-empty-lines)
185 (let ((contents (delete-and-extract-region beg (point))))
186 (condition-case err
187 (insert (org-encrypt-string contents crypt-key))
188 ;; If encryption failed, make sure to insert back entry
189 ;; contents in the buffer.
190 (error (insert contents) (error (nth 1 err)))))
191 (when folded
192 (goto-char start-heading)
193 (outline-hide-subtree))
194 nil)))))
196 (defun org-decrypt-entry ()
197 "Decrypt the content of the current headline."
198 (interactive)
199 (require 'epg)
200 (unless (org-before-first-heading-p)
201 (org-with-wide-buffer
202 (org-back-to-heading t)
203 (let ((heading-point (point))
204 (heading-was-invisible-p
205 (save-excursion
206 (outline-end-of-heading)
207 (outline-invisible-p))))
208 (org-end-of-meta-data)
209 (when (looking-at "-----BEGIN PGP MESSAGE-----")
210 (org-crypt-check-auto-save)
211 (setq-local epg-context (epg-make-context nil t t))
212 (let* ((end (save-excursion
213 (search-forward "-----END PGP MESSAGE-----")
214 (forward-line)
215 (point)))
216 (encrypted-text (buffer-substring-no-properties (point) end))
217 (decrypted-text
218 (decode-coding-string
219 (epg-decrypt-string
220 epg-context
221 encrypted-text)
222 'utf-8)))
223 ;; Delete region starting just before point, because the
224 ;; outline property starts at the \n of the heading.
225 (delete-region (1- (point)) end)
226 ;; Store a checksum of the decrypted and the encrypted
227 ;; text value. This allows reusing the same encrypted text
228 ;; if the text does not change, and therefore avoid a
229 ;; re-encryption process.
230 (insert "\n" (propertize decrypted-text
231 'org-crypt-checksum (sha1 decrypted-text)
232 'org-crypt-key (org-crypt-key-for-heading)
233 'org-crypt-text encrypted-text))
234 (when heading-was-invisible-p
235 (goto-char heading-point)
236 (org-flag-subtree t))
237 nil))))))
239 (defun org-encrypt-entries ()
240 "Encrypt all top-level entries in the current buffer."
241 (interactive)
242 (let ((org--matcher-tags-todo-only nil))
243 (org-scan-tags
244 'org-encrypt-entry
245 (cdr (org-make-tags-matcher org-crypt-tag-matcher))
246 org--matcher-tags-todo-only)))
248 (defun org-decrypt-entries ()
249 "Decrypt all entries in the current buffer."
250 (interactive)
251 (let ((org--matcher-tags-todo-only nil))
252 (org-scan-tags
253 'org-decrypt-entry
254 (cdr (org-make-tags-matcher org-crypt-tag-matcher))
255 org--matcher-tags-todo-only)))
257 (defun org-at-encrypted-entry-p ()
258 "Is the current entry encrypted?"
259 (unless (org-before-first-heading-p)
260 (save-excursion
261 (org-back-to-heading t)
262 (search-forward "-----BEGIN PGP MESSAGE-----"
263 (save-excursion (outline-next-heading)) t))))
265 (defun org-crypt-use-before-save-magic ()
266 "Add a hook to automatically encrypt entries before a file is saved to disk."
267 (add-hook
268 'org-mode-hook
269 (lambda () (add-hook 'before-save-hook 'org-encrypt-entries nil t))))
271 (add-hook 'org-reveal-start-hook 'org-decrypt-entry)
273 (provide 'org-crypt)
275 ;;; org-crypt.el ends here