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1 ;;; mml-smime.el --- S/MIME support for MML
2
3 ;; Copyright (C) 2000, 2001, 2002, 2003, 2004,
4 ;; 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
5
6 ;; Author: Simon Josefsson <simon@josefsson.org>
7 ;; Keywords: Gnus, MIME, S/MIME, MML
8
9 ;; This file is part of GNU Emacs.
10
11 ;; GNU Emacs is free software: you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation, either version 3 of the License, or
14 ;; (at your option) any later version.
15
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
20
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
23
24 ;;; Commentary:
25
26 ;;; Code:
27
28 ;; For Emacs < 22.2.
29 (eval-and-compile
30 (unless (fboundp 'declare-function) (defmacro declare-function (&rest r))))
31
32 (eval-when-compile (require 'cl))
33
34 (require 'smime)
35 (require 'mm-decode)
36 (require 'mml-sec)
37 (autoload 'message-narrow-to-headers "message")
38 (autoload 'message-fetch-field "message")
39
40 (defvar mml-smime-use 'openssl)
41
42 (defvar mml-smime-function-alist
43 '((openssl mml-smime-openssl-sign
44 mml-smime-openssl-encrypt
45 mml-smime-openssl-sign-query
46 mml-smime-openssl-encrypt-query
47 mml-smime-openssl-verify
48 mml-smime-openssl-verify-test)
49 (epg mml-smime-epg-sign
50 mml-smime-epg-encrypt
51 nil
52 nil
53 mml-smime-epg-verify
54 mml-smime-epg-verify-test)))
55
56 (defcustom mml-smime-verbose mml-secure-verbose
57 "If non-nil, ask the user about the current operation more verbosely."
58 :group 'mime-security
59 :type 'boolean)
60
61 (defcustom mml-smime-cache-passphrase mml-secure-cache-passphrase
62 "If t, cache passphrase."
63 :group 'mime-security
64 :type 'boolean)
65
66 (defcustom mml-smime-passphrase-cache-expiry mml-secure-passphrase-cache-expiry
67 "How many seconds the passphrase is cached.
68 Whether the passphrase is cached at all is controlled by
69 `mml-smime-cache-passphrase'."
70 :group 'mime-security
71 :type 'integer)
72
73 (defcustom mml-smime-signers nil
74 "A list of your own key ID which will be used to sign a message."
75 :group 'mime-security
76 :type '(repeat (string :tag "Key ID")))
77
78 (defun mml-smime-sign (cont)
79 (let ((func (nth 1 (assq mml-smime-use mml-smime-function-alist))))
80 (if func
81 (funcall func cont)
82 (error "Cannot find sign function"))))
83
84 (defun mml-smime-encrypt (cont)
85 (let ((func (nth 2 (assq mml-smime-use mml-smime-function-alist))))
86 (if func
87 (funcall func cont)
88 (error "Cannot find encrypt function"))))
89
90 (defun mml-smime-sign-query ()
91 (let ((func (nth 3 (assq mml-smime-use mml-smime-function-alist))))
92 (if func
93 (funcall func))))
94
95 (defun mml-smime-encrypt-query ()
96 (let ((func (nth 4 (assq mml-smime-use mml-smime-function-alist))))
97 (if func
98 (funcall func))))
99
100 (defun mml-smime-verify (handle ctl)
101 (let ((func (nth 5 (assq mml-smime-use mml-smime-function-alist))))
102 (if func
103 (funcall func handle ctl)
104 handle)))
105
106 (defun mml-smime-verify-test (handle ctl)
107 (let ((func (nth 6 (assq mml-smime-use mml-smime-function-alist))))
108 (if func
109 (funcall func handle ctl))))
110
111 (defun mml-smime-openssl-sign (cont)
112 (when (null smime-keys)
113 (customize-variable 'smime-keys)
114 (error "No S/MIME keys configured, use customize to add your key"))
115 (smime-sign-buffer (cdr (assq 'keyfile cont)))
116 (goto-char (point-min))
117 (while (search-forward "\r\n" nil t)
118 (replace-match "\n" t t))
119 (goto-char (point-max)))
120
121 (defun mml-smime-openssl-encrypt (cont)
122 (let (certnames certfiles tmp file tmpfiles)
123 ;; xxx tmp files are always an security issue
124 (while (setq tmp (pop cont))
125 (if (and (consp tmp) (eq (car tmp) 'certfile))
126 (push (cdr tmp) certnames)))
127 (while (setq tmp (pop certnames))
128 (if (not (and (not (file-exists-p tmp))
129 (get-buffer tmp)))
130 (push tmp certfiles)
131 (setq file (mm-make-temp-file (expand-file-name "mml."
132 mm-tmp-directory)))
133 (with-current-buffer tmp
134 (write-region (point-min) (point-max) file))
135 (push file certfiles)
136 (push file tmpfiles)))
137 (if (smime-encrypt-buffer certfiles)
138 (progn
139 (while (setq tmp (pop tmpfiles))
140 (delete-file tmp))
141 t)
142 (while (setq tmp (pop tmpfiles))
143 (delete-file tmp))
144 nil))
145 (goto-char (point-max)))
146
147 (defvar gnus-extract-address-components)
148
149 (defun mml-smime-openssl-sign-query ()
150 ;; query information (what certificate) from user when MML tag is
151 ;; added, for use later by the signing process
152 (when (null smime-keys)
153 (customize-variable 'smime-keys)
154 (error "No S/MIME keys configured, use customize to add your key"))
155 (list 'keyfile
156 (if (= (length smime-keys) 1)
157 (cadar smime-keys)
158 (or (let ((from (cadr (funcall (if (boundp
159 'gnus-extract-address-components)
160 gnus-extract-address-components
161 'mail-extract-address-components)
162 (or (save-excursion
163 (save-restriction
164 (message-narrow-to-headers)
165 (message-fetch-field "from")))
166 "")))))
167 (and from (smime-get-key-by-email from)))
168 (smime-get-key-by-email
169 (completing-read "Sign this part with what signature? "
170 smime-keys nil nil
171 (and (listp (car-safe smime-keys))
172 (caar smime-keys))))))))
173
174 (defun mml-smime-get-file-cert ()
175 (ignore-errors
176 (list 'certfile (read-file-name
177 "File with recipient's S/MIME certificate: "
178 smime-certificate-directory nil t ""))))
179
180 (defun mml-smime-get-dns-cert ()
181 ;; todo: deal with comma separated multiple recipients
182 (let (result who bad cert)
183 (condition-case ()
184 (while (not result)
185 (setq who (read-from-minibuffer
186 (format "%sLookup certificate for: " (or bad ""))
187 (cadr (funcall (if (boundp
188 'gnus-extract-address-components)
189 gnus-extract-address-components
190 'mail-extract-address-components)
191 (or (save-excursion
192 (save-restriction
193 (message-narrow-to-headers)
194 (message-fetch-field "to")))
195 "")))))
196 (if (setq cert (smime-cert-by-dns who))
197 (setq result (list 'certfile (buffer-name cert)))
198 (setq bad (format "`%s' not found. " who))))
199 (quit))
200 result))
201
202 (defun mml-smime-get-ldap-cert ()
203 ;; todo: deal with comma separated multiple recipients
204 (let (result who bad cert)
205 (condition-case ()
206 (while (not result)
207 (setq who (read-from-minibuffer
208 (format "%sLookup certificate for: " (or bad ""))
209 (cadr (funcall gnus-extract-address-components
210 (or (save-excursion
211 (save-restriction
212 (message-narrow-to-headers)
213 (message-fetch-field "to")))
214 "")))))
215 (if (setq cert (smime-cert-by-ldap who))
216 (setq result (list 'certfile (buffer-name cert)))
217 (setq bad (format "`%s' not found. " who))))
218 (quit))
219 result))
220
221 (autoload 'gnus-completing-read-with-default "gnus-util")
222
223 (defun mml-smime-openssl-encrypt-query ()
224 ;; todo: try dns/ldap automatically first, before prompting user
225 (let (certs done)
226 (while (not done)
227 (ecase (read (gnus-completing-read-with-default
228 "ldap" "Fetch certificate from"
229 '(("dns") ("ldap") ("file")) nil t))
230 (dns (setq certs (append certs
231 (mml-smime-get-dns-cert))))
232 (ldap (setq certs (append certs
233 (mml-smime-get-ldap-cert))))
234 (file (setq certs (append certs
235 (mml-smime-get-file-cert)))))
236 (setq done (not (y-or-n-p "Add more recipients? "))))
237 certs))
238
239 (defun mml-smime-openssl-verify (handle ctl)
240 (with-temp-buffer
241 (insert-buffer-substring (mm-handle-multipart-original-buffer ctl))
242 (goto-char (point-min))
243 (insert (format "Content-Type: %s; " (mm-handle-media-type ctl)))
244 (insert (format "protocol=\"%s\"; "
245 (mm-handle-multipart-ctl-parameter ctl 'protocol)))
246 (insert (format "micalg=\"%s\"; "
247 (mm-handle-multipart-ctl-parameter ctl 'micalg)))
248 (insert (format "boundary=\"%s\"\n\n"
249 (mm-handle-multipart-ctl-parameter ctl 'boundary)))
250 (when (get-buffer smime-details-buffer)
251 (kill-buffer smime-details-buffer))
252 (let ((buf (current-buffer))
253 (good-signature (smime-noverify-buffer))
254 (good-certificate (and (or smime-CA-file smime-CA-directory)
255 (smime-verify-buffer)))
256 addresses openssl-output)
257 (setq openssl-output (with-current-buffer smime-details-buffer
258 (buffer-string)))
259 (if (not good-signature)
260 (progn
261 ;; we couldn't verify message, fail with openssl output as message
262 (mm-set-handle-multipart-parameter
263 mm-security-handle 'gnus-info "Failed")
264 (mm-set-handle-multipart-parameter
265 mm-security-handle 'gnus-details
266 (concat "OpenSSL failed to verify message integrity:\n"
267 "-------------------------------------------\n"
268 openssl-output)))
269 ;; verify mail addresses in mail against those in certificate
270 (when (and (smime-pkcs7-region (point-min) (point-max))
271 (smime-pkcs7-certificates-region (point-min) (point-max)))
272 (with-temp-buffer
273 (insert-buffer-substring buf)
274 (goto-char (point-min))
275 (while (re-search-forward "-----END CERTIFICATE-----" nil t)
276 (when (smime-pkcs7-email-region (point-min) (point))
277 (setq addresses (append (smime-buffer-as-string-region
278 (point-min) (point)) addresses)))
279 (delete-region (point-min) (point)))
280 (setq addresses (mapcar 'downcase addresses))))
281 (if (not (member (downcase (or (mm-handle-multipart-from ctl) "")) addresses))
282 (mm-set-handle-multipart-parameter
283 mm-security-handle 'gnus-info "Sender address forged")
284 (if good-certificate
285 (mm-set-handle-multipart-parameter
286 mm-security-handle 'gnus-info "Ok (sender authenticated)")
287 (mm-set-handle-multipart-parameter
288 mm-security-handle 'gnus-info "Ok (sender not trusted)")))
289 (mm-set-handle-multipart-parameter
290 mm-security-handle 'gnus-details
291 (concat "Sender claimed to be: " (mm-handle-multipart-from ctl) "\n"
292 (if addresses
293 (concat "Addresses in certificate: "
294 (mapconcat 'identity addresses ", "))
295 "No addresses found in certificate. (Requires OpenSSL 0.9.6 or later.)")
296 "\n" "\n"
297 "OpenSSL output:\n"
298 "---------------\n" openssl-output "\n"
299 "Certificate(s) inside S/MIME signature:\n"
300 "---------------------------------------\n"
301 (buffer-string) "\n")))))
302 handle)
303
304 (defun mml-smime-openssl-verify-test (handle ctl)
305 smime-openssl-program)
306
307 (defvar epg-user-id-alist)
308 (defvar epg-digest-algorithm-alist)
309 (defvar inhibit-redisplay)
310 (defvar password-cache-expiry)
311
312 (eval-when-compile
313 (autoload 'epg-make-context "epg")
314 (autoload 'epg-context-set-armor "epg")
315 (autoload 'epg-context-set-signers "epg")
316 (autoload 'epg-context-result-for "epg")
317 (autoload 'epg-new-signature-digest-algorithm "epg")
318 (autoload 'epg-verify-result-to-string "epg")
319 (autoload 'epg-list-keys "epg")
320 (autoload 'epg-decrypt-string "epg")
321 (autoload 'epg-verify-string "epg")
322 (autoload 'epg-sign-string "epg")
323 (autoload 'epg-encrypt-string "epg")
324 (autoload 'epg-passphrase-callback-function "epg")
325 (autoload 'epg-context-set-passphrase-callback "epg")
326 (autoload 'epg-configuration "epg-config")
327 (autoload 'epg-expand-group "epg-config")
328 (autoload 'epa-select-keys "epa"))
329
330 (defvar mml-smime-epg-secret-key-id-list nil)
331
332 (defun mml-smime-epg-passphrase-callback (context key-id ignore)
333 (if (eq key-id 'SYM)
334 (epg-passphrase-callback-function context key-id nil)
335 (let* (entry
336 (passphrase
337 (password-read
338 (if (eq key-id 'PIN)
339 "Passphrase for PIN: "
340 (if (setq entry (assoc key-id epg-user-id-alist))
341 (format "Passphrase for %s %s: " key-id (cdr entry))
342 (format "Passphrase for %s: " key-id)))
343 (if (eq key-id 'PIN)
344 "PIN"
345 key-id))))
346 (when passphrase
347 (let ((password-cache-expiry mml-smime-passphrase-cache-expiry))
348 (password-cache-add key-id passphrase))
349 (setq mml-smime-epg-secret-key-id-list
350 (cons key-id mml-smime-epg-secret-key-id-list))
351 (copy-sequence passphrase)))))
352
353 (declare-function epg-key-sub-key-list "ext:epg" (key))
354 (declare-function epg-sub-key-capability "ext:epg" (sub-key))
355 (declare-function epg-sub-key-validity "ext:epg" (sub-key))
356
357 (defun mml-smime-epg-find-usable-key (keys usage)
358 (catch 'found
359 (while keys
360 (let ((pointer (epg-key-sub-key-list (car keys))))
361 (while pointer
362 (if (and (memq usage (epg-sub-key-capability (car pointer)))
363 (not (memq (epg-sub-key-validity (car pointer))
364 '(revoked expired))))
365 (throw 'found (car keys)))
366 (setq pointer (cdr pointer))))
367 (setq keys (cdr keys)))))
368
369 (autoload 'mml-compute-boundary "mml")
370
371 ;; We require mm-decode, which requires mm-bodies, which autoloads
372 ;; message-options-get (!).
373 (declare-function message-options-set "message" (symbol value))
374
375 (defun mml-smime-epg-sign (cont)
376 (let* ((inhibit-redisplay t)
377 (context (epg-make-context 'CMS))
378 (boundary (mml-compute-boundary cont))
379 signer-key
380 (signers
381 (or (message-options-get 'mml-smime-epg-signers)
382 (message-options-set
383 'mml-smime-epg-signers
384 (if (eq mm-sign-option 'guided)
385 (epa-select-keys context "\
386 Select keys for signing.
387 If no one is selected, default secret key is used. "
388 mml-smime-signers t)
389 (if mml-smime-signers
390 (mapcar
391 (lambda (signer)
392 (setq signer-key (mml-smime-epg-find-usable-key
393 (epg-list-keys context signer t)
394 'sign))
395 (unless (or signer-key
396 (y-or-n-p
397 (format "No secret key for %s; skip it? "
398 signer)))
399 (error "No secret key for %s" signer))
400 signer-key)
401 mml-smime-signers))))))
402 signature micalg)
403 (epg-context-set-signers context signers)
404 (if mml-smime-cache-passphrase
405 (epg-context-set-passphrase-callback
406 context
407 #'mml-smime-epg-passphrase-callback))
408 (condition-case error
409 (setq signature (epg-sign-string context
410 (mm-replace-in-string (buffer-string)
411 "\n" "\r\n")
412 t)
413 mml-smime-epg-secret-key-id-list nil)
414 (error
415 (while mml-smime-epg-secret-key-id-list
416 (password-cache-remove (car mml-smime-epg-secret-key-id-list))
417 (setq mml-smime-epg-secret-key-id-list
418 (cdr mml-smime-epg-secret-key-id-list)))
419 (signal (car error) (cdr error))))
420 (if (epg-context-result-for context 'sign)
421 (setq micalg (epg-new-signature-digest-algorithm
422 (car (epg-context-result-for context 'sign)))))
423 (goto-char (point-min))
424 (insert (format "Content-Type: multipart/signed; boundary=\"%s\";\n"
425 boundary))
426 (if micalg
427 (insert (format "\tmicalg=%s; "
428 (downcase
429 (cdr (assq micalg
430 epg-digest-algorithm-alist))))))
431 (insert "protocol=\"application/pkcs7-signature\"\n")
432 (insert (format "\n--%s\n" boundary))
433 (goto-char (point-max))
434 (insert (format "\n--%s\n" boundary))
435 (insert "Content-Type: application/pkcs7-signature; name=smime.p7s
436 Content-Transfer-Encoding: base64
437 Content-Disposition: attachment; filename=smime.p7s
438
439 ")
440 (insert (base64-encode-string signature) "\n")
441 (goto-char (point-max))
442 (insert (format "--%s--\n" boundary))
443 (goto-char (point-max))))
444
445 (defun mml-smime-epg-encrypt (cont)
446 (let ((inhibit-redisplay t)
447 (context (epg-make-context 'CMS))
448 (config (epg-configuration))
449 (recipients (message-options-get 'mml-smime-epg-recipients))
450 cipher signers
451 (boundary (mml-compute-boundary cont))
452 recipient-key)
453 (unless recipients
454 (setq recipients
455 (apply #'nconc
456 (mapcar
457 (lambda (recipient)
458 (or (epg-expand-group config recipient)
459 (list recipient)))
460 (split-string
461 (or (message-options-get 'message-recipients)
462 (message-options-set 'message-recipients
463 (read-string "Recipients: ")))
464 "[ \f\t\n\r\v,]+"))))
465 (if (eq mm-encrypt-option 'guided)
466 (setq recipients
467 (epa-select-keys context "\
468 Select recipients for encryption.
469 If no one is selected, symmetric encryption will be performed. "
470 recipients))
471 (setq recipients
472 (mapcar
473 (lambda (recipient)
474 (setq recipient-key (mml-smime-epg-find-usable-key
475 (epg-list-keys context recipient)
476 'encrypt))
477 (unless (or recipient-key
478 (y-or-n-p
479 (format "No public key for %s; skip it? "
480 recipient)))
481 (error "No public key for %s" recipient))
482 recipient-key)
483 recipients))
484 (unless recipients
485 (error "No recipient specified")))
486 (message-options-set 'mml-smime-epg-recipients recipients))
487 (if mml-smime-cache-passphrase
488 (epg-context-set-passphrase-callback
489 context
490 #'mml-smime-epg-passphrase-callback))
491 (condition-case error
492 (setq cipher
493 (epg-encrypt-string context (buffer-string) recipients)
494 mml-smime-epg-secret-key-id-list nil)
495 (error
496 (while mml-smime-epg-secret-key-id-list
497 (password-cache-remove (car mml-smime-epg-secret-key-id-list))
498 (setq mml-smime-epg-secret-key-id-list
499 (cdr mml-smime-epg-secret-key-id-list)))
500 (signal (car error) (cdr error))))
501 (delete-region (point-min) (point-max))
502 (goto-char (point-min))
503 (insert "\
504 Content-Type: application/pkcs7-mime;
505 smime-type=enveloped-data;
506 name=smime.p7m
507 Content-Transfer-Encoding: base64
508 Content-Disposition: attachment; filename=smime.p7m
509
510 ")
511 (insert (base64-encode-string cipher))
512 (goto-char (point-max))))
513
514 (defun mml-smime-epg-verify (handle ctl)
515 (catch 'error
516 (let ((inhibit-redisplay t)
517 context plain signature-file part signature)
518 (when (or (null (setq part (mm-find-raw-part-by-type
519 ctl (or (mm-handle-multipart-ctl-parameter
520 ctl 'protocol)
521 "application/pkcs7-signature")
522 t)))
523 (null (setq signature (mm-find-part-by-type
524 (cdr handle)
525 "application/pkcs7-signature"
526 nil t))))
527 (mm-set-handle-multipart-parameter
528 mm-security-handle 'gnus-info "Corrupted")
529 (throw 'error handle))
530 (setq part (mm-replace-in-string part "\n" "\r\n" t)
531 context (epg-make-context 'CMS))
532 (condition-case error
533 (setq plain (epg-verify-string context (mm-get-part signature) part))
534 (error
535 (mm-set-handle-multipart-parameter
536 mm-security-handle 'gnus-info "Failed")
537 (if (eq (car error) 'quit)
538 (mm-set-handle-multipart-parameter
539 mm-security-handle 'gnus-details "Quit.")
540 (mm-set-handle-multipart-parameter
541 mm-security-handle 'gnus-details (format "%S" error)))
542 (throw 'error handle)))
543 (mm-set-handle-multipart-parameter
544 mm-security-handle 'gnus-info
545 (epg-verify-result-to-string (epg-context-result-for context 'verify)))
546 handle)))
547
548 (defun mml-smime-epg-verify-test (handle ctl)
549 t)
550
551 (provide 'mml-smime)
552
553 ;; arch-tag: f1bf94d4-f2cd-4c6f-b059-ad69492817e2
554 ;;; mml-smime.el ends here