1 ;;; mml-smime.el --- S/MIME support for MML
3 ;; Copyright (C) 2000-2012 Free Software Foundation, Inc.
5 ;; Author: Simon Josefsson <simon@josefsson.org>
6 ;; Keywords: Gnus, MIME, S/MIME, MML
8 ;; This file is part of GNU Emacs.
10 ;; GNU Emacs is free software: you can redistribute it and/or modify
11 ;; it under the terms of the GNU General Public License as published by
12 ;; the Free Software Foundation, either version 3 of the License, or
13 ;; (at your option) any later version.
15 ;; GNU Emacs is distributed in the hope that it will be useful,
16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 ;; GNU General Public License for more details.
20 ;; You should have received a copy of the GNU General Public License
21 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
27 ;; For Emacs <22.2 and XEmacs.
29 (unless (fboundp 'declare-function) (defmacro declare-function (&rest r))))
31 (eval-when-compile (require 'cl))
36 (autoload 'message-narrow-to-headers "message")
37 (autoload 'message-fetch-field "message")
39 (defcustom mml-smime-use (if (featurep 'epg) 'epg 'openssl)
40 "Whether to use OpenSSL or EPG to decrypt S/MIME messages.
41 Defaults to EPG if it's loaded."
43 :type '(choice (const :tag "EPG" epg)
44 (const :tag "OpenSSL" openssl)))
46 (defvar mml-smime-function-alist
47 '((openssl mml-smime-openssl-sign
48 mml-smime-openssl-encrypt
49 mml-smime-openssl-sign-query
50 mml-smime-openssl-encrypt-query
51 mml-smime-openssl-verify
52 mml-smime-openssl-verify-test)
53 (epg mml-smime-epg-sign
58 mml-smime-epg-verify-test)))
60 (defcustom mml-smime-cache-passphrase mml-secure-cache-passphrase
61 "If t, cache passphrase."
65 (defcustom mml-smime-passphrase-cache-expiry mml-secure-passphrase-cache-expiry
66 "How many seconds the passphrase is cached.
67 Whether the passphrase is cached at all is controlled by
68 `mml-smime-cache-passphrase'."
72 (defcustom mml-smime-signers nil
73 "A list of your own key ID which will be used to sign a message."
75 :type '(repeat (string :tag "Key ID")))
77 (defun mml-smime-sign (cont)
78 (let ((func (nth 1 (assq mml-smime-use mml-smime-function-alist))))
81 (error "Cannot find sign function"))))
83 (defun mml-smime-encrypt (cont)
84 (let ((func (nth 2 (assq mml-smime-use mml-smime-function-alist))))
87 (error "Cannot find encrypt function"))))
89 (defun mml-smime-sign-query ()
90 (let ((func (nth 3 (assq mml-smime-use mml-smime-function-alist))))
94 (defun mml-smime-encrypt-query ()
95 (let ((func (nth 4 (assq mml-smime-use mml-smime-function-alist))))
99 (defun mml-smime-verify (handle ctl)
100 (let ((func (nth 5 (assq mml-smime-use mml-smime-function-alist))))
102 (funcall func handle ctl)
105 (defun mml-smime-verify-test (handle ctl)
106 (let ((func (nth 6 (assq mml-smime-use mml-smime-function-alist))))
108 (funcall func handle ctl))))
110 (defun mml-smime-openssl-sign (cont)
111 (when (null smime-keys)
112 (customize-variable 'smime-keys)
113 (error "No S/MIME keys configured, use customize to add your key"))
114 (smime-sign-buffer (cdr (assq 'keyfile cont)))
115 (goto-char (point-min))
116 (while (search-forward "\r\n" nil t)
117 (replace-match "\n" t t))
118 (goto-char (point-max)))
120 (defun mml-smime-openssl-encrypt (cont)
121 (let (certnames certfiles tmp file tmpfiles)
122 ;; xxx tmp files are always an security issue
123 (while (setq tmp (pop cont))
124 (if (and (consp tmp) (eq (car tmp) 'certfile))
125 (push (cdr tmp) certnames)))
126 (while (setq tmp (pop certnames))
127 (if (not (and (not (file-exists-p tmp))
130 (setq file (mm-make-temp-file (expand-file-name "mml."
132 (with-current-buffer tmp
133 (write-region (point-min) (point-max) file))
134 (push file certfiles)
135 (push file tmpfiles)))
136 (if (smime-encrypt-buffer certfiles)
138 (while (setq tmp (pop tmpfiles))
141 (while (setq tmp (pop tmpfiles))
144 (goto-char (point-max)))
146 (defvar gnus-extract-address-components)
148 (defun mml-smime-openssl-sign-query ()
149 ;; query information (what certificate) from user when MML tag is
150 ;; added, for use later by the signing process
151 (when (null smime-keys)
152 (customize-variable 'smime-keys)
153 (error "No S/MIME keys configured, use customize to add your key"))
155 (if (= (length smime-keys) 1)
157 (or (let ((from (cadr (funcall (if (boundp
158 'gnus-extract-address-components)
159 gnus-extract-address-components
160 'mail-extract-address-components)
163 (message-narrow-to-headers)
164 (message-fetch-field "from")))
166 (and from (smime-get-key-by-email from)))
167 (smime-get-key-by-email
168 (gnus-completing-read "Sign this part with what signature"
169 (mapcar 'car smime-keys) nil nil nil
170 (and (listp (car-safe smime-keys))
171 (caar smime-keys))))))))
173 (defun mml-smime-get-file-cert ()
175 (list 'certfile (read-file-name
176 "File with recipient's S/MIME certificate: "
177 smime-certificate-directory nil t ""))))
179 (defun mml-smime-get-dns-cert ()
180 ;; todo: deal with comma separated multiple recipients
181 (let (result who bad cert)
184 (setq who (read-from-minibuffer
185 (format "%sLookup certificate for: " (or bad ""))
186 (cadr (funcall (if (boundp
187 'gnus-extract-address-components)
188 gnus-extract-address-components
189 'mail-extract-address-components)
192 (message-narrow-to-headers)
193 (message-fetch-field "to")))
195 (if (setq cert (smime-cert-by-dns who))
196 (setq result (list 'certfile (buffer-name cert)))
197 (setq bad (format "`%s' not found. " who))))
201 (defun mml-smime-get-ldap-cert ()
202 ;; todo: deal with comma separated multiple recipients
203 (let (result who bad cert)
206 (setq who (read-from-minibuffer
207 (format "%sLookup certificate for: " (or bad ""))
208 (cadr (funcall gnus-extract-address-components
211 (message-narrow-to-headers)
212 (message-fetch-field "to")))
214 (if (setq cert (smime-cert-by-ldap who))
215 (setq result (list 'certfile (buffer-name cert)))
216 (setq bad (format "`%s' not found. " who))))
220 (autoload 'gnus-completing-read "gnus-util")
222 (defun mml-smime-openssl-encrypt-query ()
223 ;; todo: try dns/ldap automatically first, before prompting user
226 (ecase (read (gnus-completing-read
227 "Fetch certificate from"
228 '("dns" "ldap" "file") t nil nil
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? "))))
239 (defun mml-smime-openssl-verify (handle ctl)
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
259 (if (not good-signature)
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"
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)))
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")
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"
293 (concat "Addresses in certificate: "
294 (mapconcat 'identity addresses ", "))
295 "No addresses found in certificate. (Requires OpenSSL 0.9.6 or later.)")
298 "---------------\n" openssl-output "\n"
299 "Certificate(s) inside S/MIME signature:\n"
300 "---------------------------------------\n"
301 (buffer-string) "\n")))))
304 (defun mml-smime-openssl-verify-test (handle ctl)
305 smime-openssl-program)
307 (defvar epg-user-id-alist)
308 (defvar epg-digest-algorithm-alist)
309 (defvar inhibit-redisplay)
310 (defvar password-cache-expiry)
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"))
330 (defvar mml-smime-epg-secret-key-id-list nil)
332 (defun mml-smime-epg-passphrase-callback (context key-id ignore)
334 (epg-passphrase-callback-function context key-id nil)
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)))
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)))))
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))
357 (defun mml-smime-epg-find-usable-key (keys usage)
360 (let ((pointer (epg-key-sub-key-list (car keys))))
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)))))
369 (autoload 'mml-compute-boundary "mml")
371 ;; We require mm-decode, which requires mm-bodies, which autoloads
372 ;; message-options-get (!).
373 (declare-function message-options-set "message" (symbol value))
375 (defun mml-smime-epg-sign (cont)
376 (let* ((inhibit-redisplay t)
377 (context (epg-make-context 'CMS))
378 (boundary (mml-compute-boundary cont))
381 (or (message-options-get 'mml-smime-epg-signers)
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. "
389 (if mml-smime-signers
392 (setq signer-key (mml-smime-epg-find-usable-key
393 (epg-list-keys context signer t)
395 (unless (or signer-key
397 (format "No secret key for %s; skip it? "
399 (error "No secret key for %s" signer))
401 mml-smime-signers))))))
403 (epg-context-set-signers context signers)
404 (if mml-smime-cache-passphrase
405 (epg-context-set-passphrase-callback
407 #'mml-smime-epg-passphrase-callback))
408 (condition-case error
409 (setq signature (epg-sign-string context
410 (mm-replace-in-string (buffer-string)
413 mml-smime-epg-secret-key-id-list nil)
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"
427 (insert (format "\tmicalg=%s; "
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
440 (insert (base64-encode-string signature) "\n")
441 (goto-char (point-max))
442 (insert (format "--%s--\n" boundary))
443 (goto-char (point-max))))
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))
451 (boundary (mml-compute-boundary cont))
458 (or (epg-expand-group config recipient)
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)
467 (epa-select-keys context "\
468 Select recipients for encryption.
469 If no one is selected, symmetric encryption will be performed. "
474 (setq recipient-key (mml-smime-epg-find-usable-key
475 (epg-list-keys context recipient)
477 (unless (or recipient-key
479 (format "No public key for %s; skip it? "
481 (error "No public key for %s" recipient))
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
490 #'mml-smime-epg-passphrase-callback))
491 (condition-case error
493 (epg-encrypt-string context (buffer-string) recipients)
494 mml-smime-epg-secret-key-id-list nil)
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))
504 Content-Type: application/pkcs7-mime;
505 smime-type=enveloped-data;
507 Content-Transfer-Encoding: base64
508 Content-Disposition: attachment; filename=smime.p7m
511 (insert (base64-encode-string cipher))
512 (goto-char (point-max))))
514 (defun mml-smime-epg-verify (handle ctl)
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
521 "application/pkcs7-signature")
523 (null (setq signature (or (mm-find-part-by-type
525 "application/pkcs7-signature"
527 (mm-find-part-by-type
529 "application/x-pkcs7-signature"
531 (mm-set-handle-multipart-parameter
532 mm-security-handle 'gnus-info "Corrupted")
533 (throw 'error handle))
534 (setq part (mm-replace-in-string part "\n" "\r\n")
535 context (epg-make-context 'CMS))
536 (condition-case error
537 (setq plain (epg-verify-string context (mm-get-part signature) part))
539 (mm-set-handle-multipart-parameter
540 mm-security-handle 'gnus-info "Failed")
541 (if (eq (car error) 'quit)
542 (mm-set-handle-multipart-parameter
543 mm-security-handle 'gnus-details "Quit.")
544 (mm-set-handle-multipart-parameter
545 mm-security-handle 'gnus-details (format "%S" error)))
546 (throw 'error handle)))
547 (mm-set-handle-multipart-parameter
548 mm-security-handle 'gnus-info
549 (epg-verify-result-to-string (epg-context-result-for context 'verify)))
552 (defun mml-smime-epg-verify-test (handle ctl)
557 ;;; mml-smime.el ends here