org-crypt.el 9.32 KB
Newer Older
1 2
;;; org-crypt.el --- Public key encryption for org-mode entries

3
;; Copyright (C) 2007, 2009-2012  Free Software Foundation, Inc.
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

;; Emacs Lisp Archive Entry
;; Filename: org-crypt.el
;; Keywords: org-mode
;; Author: John Wiegley <johnw@gnu.org>
;; Maintainer: Peter Jones <pjones@pmade.com>
;; Description: Adds public key encryption to org-mode buffers
;; URL: http://www.newartisans.com/software/emacs.html
;; Compatibility: Emacs22

;; This file is part of GNU Emacs.
;;
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Right now this is just a set of functions to play with.  It depends
;; on the epg library.  Here's how you would use it:
;;
;; 1. To mark an entry for encryption, tag the heading with "crypt".
;;    You can change the tag to any complex tag matching string by
;;    setting the `org-crypt-tag-matcher' variable.
;;
;; 2. Set the encryption key to use in the `org-crypt-key' variable,
;;    or use `M-x org-set-property' to set the property CRYPTKEY to
;;    any address in your public keyring.  The text of the entry (but
;;    not its properties or headline) will be encrypted for this user.
;;    For them to read it, the corresponding secret key must be
;;    located in the secret key ring of the account where you try to
;;    decrypt it.  This makes it possible to leave secure notes that
;;    only the intended recipient can read in a shared-org-mode-files
;;    scenario.
47
;;    If the key is not set, org-crypt will default to symmetric encryption.
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
;;
;; 3. To later decrypt an entry, use `org-decrypt-entries' or
;;    `org-decrypt-entry'.  It might be useful to bind this to a key,
;;    like C-c C-/.  I hope that in the future, C-c C-r can be might
;;    overloaded to also decrypt an entry if it's encrypted, since
;;    that fits nicely with the meaning of "reveal".
;;
;; 4. To automatically encrypt all necessary entries when saving a
;;    file, call `org-crypt-use-before-save-magic' after loading
;;    org-crypt.el.

;;; Thanks:

;; - Carsten Dominik
;; - Vitaly Ostanin

(require 'org)

66 67
;;; Code:

68 69 70 71 72 73 74 75 76 77 78
(declare-function epg-decrypt-string "epg" (context cipher))
(declare-function epg-list-keys "epg" (context &optional name mode))
(declare-function epg-make-context "epg"
		  (&optional protocol armor textmode include-certs
			     cipher-algorithm digest-algorithm
			     compress-algorithm))
(declare-function epg-encrypt-string "epg"
		  (context plain recipients &optional sign always-trust))

(defgroup org-crypt nil
  "Org Crypt"
79
  :tag "Org Crypt"
80
  :group 'org)
81 82

(defcustom org-crypt-tag-matcher "crypt"
83 84 85
  "The tag matcher used to find headings whose contents should be encrypted.

See the \"Match syntax\" section of the org manual for more details."
86
  :type 'string
87
  :group 'org-crypt)
88

89
(defcustom org-crypt-key ""
90 91 92
  "The default key to use when encrypting the contents of a heading.

This setting can also be overridden in the CRYPTKEY property."
93
  :type 'string
94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117
  :group 'org-crypt)

(defcustom org-crypt-disable-auto-save 'ask
  "What org-decrypt should do if `auto-save-mode' is enabled.

t        : Disable auto-save-mode for the current buffer
           prior to decrypting an entry.

nil      : Leave auto-save-mode enabled.
           This may cause data to be written to disk unencrypted!

'ask     : Ask user whether or not to disable auto-save-mode
           for the current buffer.

'encrypt : Leave auto-save-mode enabled for the current buffer,
           but automatically re-encrypt all decrypted entries
           *before* auto-saving.
           NOTE: This only works for entries which have a tag
           that matches `org-crypt-tag-matcher'."
  :group 'org-crypt
  :type '(choice (const :tag "Always"  t)
                 (const :tag "Never"   nil)
                 (const :tag "Ask"     ask)
                 (const :tag "Encrypt" encrypt)))
118

Bastien Guerry's avatar
Bastien Guerry committed
119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147
(defun org-crypt-check-auto-save ()
  "Check whether auto-save-mode is enabled for the current buffer.

`auto-save-mode' may cause leakage when decrypting entries, so
check whether it's enabled, and decide what to do about it.

See `org-crypt-disable-auto-save'."
  (when buffer-auto-save-file-name
    (cond
     ((or
       (eq org-crypt-disable-auto-save t)
       (and
	(eq org-crypt-disable-auto-save 'ask)
	(y-or-n-p "org-decrypt: auto-save-mode may cause leakage. Disable it for current buffer? ")))
      (message (concat "org-decrypt: Disabling auto-save-mode for " (or (buffer-file-name) (current-buffer))))
      ; The argument to auto-save-mode has to be "-1", since
      ; giving a "nil" argument toggles instead of disabling.
      (auto-save-mode -1))
     ((eq org-crypt-disable-auto-save nil)
      (message "org-decrypt: Decrypting entry with auto-save-mode enabled. This may cause leakage."))
     ((eq org-crypt-disable-auto-save 'encrypt)
      (message "org-decrypt: Enabling re-encryption on auto-save.")
      (add-hook 'auto-save-hook
		(lambda ()
		  (message "org-crypt: Re-encrypting all decrypted entries due to auto-save.")
		  (org-encrypt-entries))
		nil t))
     (t nil))))

148
(defun org-crypt-key-for-heading ()
149
  "Return the encryption key for the current heading."
150 151
  (save-excursion
    (org-back-to-heading t)
152
    (or (org-entry-get nil "CRYPTKEY" 'selective)
153 154
        org-crypt-key
        (and (boundp 'epa-file-encrypt-to) epa-file-encrypt-to)
155
        (message "No crypt key set, using symmetric encryption."))))
156

157 158 159 160 161 162 163 164 165
(defun org-encrypt-string (str crypt-key)
  "Return STR encrypted with CRYPT-KEY."
  ;; Text and key have to be identical, otherwise we re-crypt.
  (if (and (string= crypt-key (get-text-property 0 'org-crypt-key str))
	   (string= (sha1 str) (get-text-property 0 'org-crypt-checksum str)))
      (get-text-property 0 'org-crypt-text str)
    (let ((epg-context (epg-make-context nil t t)))
      (epg-encrypt-string epg-context str (epg-list-keys epg-context crypt-key)))))

166 167 168 169 170 171
(defun org-encrypt-entry ()
  "Encrypt the content of the current headline."
  (interactive)
  (require 'epg)
  (save-excursion
    (org-back-to-heading t)
172 173 174
    (let ((start-heading (point)))
      (forward-line)
      (when (not (looking-at "-----BEGIN PGP MESSAGE-----"))
175
        (let ((folded (outline-invisible-p))
176 177 178 179 180 181 182 183 184
              (epg-context (epg-make-context nil t t))
              (crypt-key (org-crypt-key-for-heading))
              (beg (point))
              end encrypted-text)
          (goto-char start-heading)
          (org-end-of-subtree t t)
          (org-back-over-empty-lines)
          (setq end (point)
                encrypted-text
185
		(org-encrypt-string (buffer-substring beg end) crypt-key))
186 187 188 189 190 191
          (delete-region beg end)
          (insert encrypted-text)
          (when folded
            (goto-char start-heading)
            (hide-subtree))
          nil)))))
192 193

(defun org-decrypt-entry ()
194
  "Decrypt the content of the current headline."
195 196
  (interactive)
  (require 'epg)
197 198 199
  (unless (org-before-first-heading-p)
    (save-excursion
      (org-back-to-heading t)
200 201 202 203 204 205 206
      (let ((heading-point (point))
	    (heading-was-invisible-p
	     (save-excursion
	       (outline-end-of-heading)
	       (outline-invisible-p))))
	(forward-line)
	(when (looking-at "-----BEGIN PGP MESSAGE-----")
Bastien Guerry's avatar
Bastien Guerry committed
207
	  (org-crypt-check-auto-save)
208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234
	  (let* ((end (save-excursion
			(search-forward "-----END PGP MESSAGE-----")
			(forward-line)
			(point)))
		 (epg-context (epg-make-context nil t t))
		 (encrypted-text (buffer-substring-no-properties (point) end))
		 (decrypted-text
		  (decode-coding-string
		   (epg-decrypt-string
		    epg-context
		    encrypted-text)
		   'utf-8)))
	    ;; Delete region starting just before point, because the
	    ;; outline property starts at the \n of the heading.
	    (delete-region (1- (point)) end)
	    ;; Store a checksum of the decrypted and the encrypted
	    ;; text value. This allow to reuse the same encrypted text
	    ;; if the text does not change, and therefore avoid a
	    ;; re-encryption process.
	    (insert "\n" (propertize decrypted-text
				     'org-crypt-checksum (sha1 decrypted-text)
				     'org-crypt-key (org-crypt-key-for-heading)
				     'org-crypt-text encrypted-text))
	    (when heading-was-invisible-p
	      (goto-char heading-point)
	      (org-flag-subtree t))
	    nil))))))
235 236

(defun org-encrypt-entries ()
237
  "Encrypt all top-level entries in the current buffer."
238 239 240 241 242 243
  (interactive)
  (org-scan-tags
   'org-encrypt-entry
   (cdr (org-make-tags-matcher org-crypt-tag-matcher))))

(defun org-decrypt-entries ()
244
  "Decrypt all entries in the current buffer."
245
  (interactive)
246
  (org-scan-tags
247 248 249 250
   'org-decrypt-entry
   (cdr (org-make-tags-matcher org-crypt-tag-matcher))))

(defun org-crypt-use-before-save-magic ()
251
  "Add a hook to automatically encrypt entries before a file is saved to disk."
252 253
  (add-hook
   'org-mode-hook
254
   (lambda () (add-hook 'before-save-hook 'org-encrypt-entries nil t))))
255 256 257

(add-hook 'org-reveal-start-hook 'org-decrypt-entry)

258 259 260
(provide 'org-crypt)

;;; org-crypt.el ends here