nndoc.el (nndoc-dissect-mime-parts-sub): Fix last change
[gnus] / lisp / mml-smime.el
1 ;;; mml-smime.el --- S/MIME support for MML
2
3 ;; Copyright (C) 2000-2013 Free Software Foundation, Inc.
4
5 ;; Author: Simon Josefsson <simon@josefsson.org>
6 ;; Keywords: Gnus, MIME, S/MIME, MML
7
8 ;; This file is part of GNU Emacs.
9
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.
14
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.
19
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/>.
22
23 ;;; Commentary:
24
25 ;;; Code:
26
27 ;; For Emacs <22.2 and XEmacs.
28 (eval-and-compile
29   (unless (fboundp 'declare-function) (defmacro declare-function (&rest r))))
30
31 (eval-when-compile (require 'cl))
32
33 (require 'smime)
34 (require 'mm-decode)
35 (require 'mml-sec)
36 (autoload 'message-narrow-to-headers "message")
37 (autoload 'message-fetch-field "message")
38
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."
42   :group 'mime-security
43   :type '(choice (const :tag "EPG" epg)
44                  (const :tag "OpenSSL" openssl)))
45
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
54          mml-smime-epg-encrypt
55          nil
56          nil
57          mml-smime-epg-verify
58          mml-smime-epg-verify-test)))
59
60 (defcustom mml-smime-cache-passphrase mml-secure-cache-passphrase
61   "If t, cache passphrase."
62   :group 'mime-security
63   :type 'boolean)
64
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'."
69   :group 'mime-security
70   :type 'integer)
71
72 (defcustom mml-smime-signers nil
73   "A list of your own key ID which will be used to sign a message."
74   :group 'mime-security
75   :type '(repeat (string :tag "Key ID")))
76
77 (defcustom mml-smime-sign-with-sender nil
78   "If t, use message sender so find a key to sign with."
79   :group 'mime-security
80   :version "24.4"
81   :type 'boolean)
82
83 (defcustom mml-smime-encrypt-to-self nil
84   "If t, add your own key ID to recipient list when encryption."
85   :group 'mime-security
86   :version "24.4"
87   :type 'boolean)
88
89 (defun mml-smime-sign (cont)
90   (let ((func (nth 1 (assq mml-smime-use mml-smime-function-alist))))
91     (if func
92         (funcall func cont)
93       (error "Cannot find sign function"))))
94
95 (defun mml-smime-encrypt (cont)
96   (let ((func (nth 2 (assq mml-smime-use mml-smime-function-alist))))
97     (if func
98         (funcall func cont)
99       (error "Cannot find encrypt function"))))
100
101 (defun mml-smime-sign-query ()
102   (let ((func (nth 3 (assq mml-smime-use mml-smime-function-alist))))
103     (if func
104         (funcall func))))
105
106 (defun mml-smime-encrypt-query ()
107   (let ((func (nth 4 (assq mml-smime-use mml-smime-function-alist))))
108     (if func
109         (funcall func))))
110
111 (defun mml-smime-verify (handle ctl)
112   (let ((func (nth 5 (assq mml-smime-use mml-smime-function-alist))))
113     (if func
114         (funcall func handle ctl)
115       handle)))
116
117 (defun mml-smime-verify-test (handle ctl)
118   (let ((func (nth 6 (assq mml-smime-use mml-smime-function-alist))))
119     (if func
120         (funcall func handle ctl))))
121
122 (defun mml-smime-openssl-sign (cont)
123   (when (null smime-keys)
124     (customize-variable 'smime-keys)
125     (error "No S/MIME keys configured, use customize to add your key"))
126   (smime-sign-buffer (cdr (assq 'keyfile cont)))
127   (goto-char (point-min))
128   (while (search-forward "\r\n" nil t)
129     (replace-match "\n" t t))
130   (goto-char (point-max)))
131
132 (defun mml-smime-openssl-encrypt (cont)
133   (let (certnames certfiles tmp file tmpfiles)
134     ;; xxx tmp files are always an security issue
135     (while (setq tmp (pop cont))
136       (if (and (consp tmp) (eq (car tmp) 'certfile))
137           (push (cdr tmp) certnames)))
138     (while (setq tmp (pop certnames))
139       (if (not (and (not (file-exists-p tmp))
140                     (get-buffer tmp)))
141           (push tmp certfiles)
142         (setq file (mm-make-temp-file (expand-file-name "mml."
143                                                         mm-tmp-directory)))
144         (with-current-buffer tmp
145           (write-region (point-min) (point-max) file))
146         (push file certfiles)
147         (push file tmpfiles)))
148     (if (smime-encrypt-buffer certfiles)
149         (progn
150           (while (setq tmp (pop tmpfiles))
151             (delete-file tmp))
152           t)
153       (while (setq tmp (pop tmpfiles))
154         (delete-file tmp))
155       nil))
156   (goto-char (point-max)))
157
158 (defvar gnus-extract-address-components)
159
160 (defun mml-smime-openssl-sign-query ()
161   ;; query information (what certificate) from user when MML tag is
162   ;; added, for use later by the signing process
163   (when (null smime-keys)
164     (customize-variable 'smime-keys)
165     (error "No S/MIME keys configured, use customize to add your key"))
166   (list 'keyfile
167         (if (= (length smime-keys) 1)
168             (cadar smime-keys)
169           (or (let ((from (cadr (funcall (if (boundp
170                                               'gnus-extract-address-components)
171                                              gnus-extract-address-components
172                                            'mail-extract-address-components)
173                                          (or (save-excursion
174                                                (save-restriction
175                                                  (message-narrow-to-headers)
176                                                  (message-fetch-field "from")))
177                                              "")))))
178                 (and from (smime-get-key-by-email from)))
179               (smime-get-key-by-email
180                (gnus-completing-read "Sign this part with what signature"
181                                      (mapcar 'car smime-keys) nil nil nil
182                                      (and (listp (car-safe smime-keys))
183                                           (caar smime-keys))))))))
184
185 (defun mml-smime-get-file-cert ()
186   (ignore-errors
187     (list 'certfile (read-file-name
188                      "File with recipient's S/MIME certificate: "
189                      smime-certificate-directory nil t ""))))
190
191 (defun mml-smime-get-dns-cert ()
192   ;; todo: deal with comma separated multiple recipients
193   (let (result who bad cert)
194     (condition-case ()
195         (while (not result)
196           (setq who (read-from-minibuffer
197                      (format "%sLookup certificate for: " (or bad ""))
198                      (cadr (funcall (if (boundp
199                                          'gnus-extract-address-components)
200                                         gnus-extract-address-components
201                                       'mail-extract-address-components)
202                                     (or (save-excursion
203                                           (save-restriction
204                                             (message-narrow-to-headers)
205                                             (message-fetch-field "to")))
206                                         "")))))
207           (if (setq cert (smime-cert-by-dns who))
208               (setq result (list 'certfile (buffer-name cert)))
209             (setq bad (format "`%s' not found. " who))))
210       (quit))
211     result))
212
213 (defun mml-smime-get-ldap-cert ()
214   ;; todo: deal with comma separated multiple recipients
215   (let (result who bad cert)
216     (condition-case ()
217         (while (not result)
218           (setq who (read-from-minibuffer
219                      (format "%sLookup certificate for: " (or bad ""))
220                      (cadr (funcall gnus-extract-address-components
221                                     (or (save-excursion
222                                           (save-restriction
223                                             (message-narrow-to-headers)
224                                             (message-fetch-field "to")))
225                                         "")))))
226           (if (setq cert (smime-cert-by-ldap who))
227               (setq result (list 'certfile (buffer-name cert)))
228             (setq bad (format "`%s' not found. " who))))
229       (quit))
230     result))
231
232 (autoload 'gnus-completing-read "gnus-util")
233
234 (defun mml-smime-openssl-encrypt-query ()
235   ;; todo: try dns/ldap automatically first, before prompting user
236   (let (certs done)
237     (while (not done)
238       (ecase (read (gnus-completing-read
239                     "Fetch certificate from"
240                     '("dns" "ldap" "file") t nil nil
241                     "ldap"))
242         (dns (setq certs (append certs
243                                  (mml-smime-get-dns-cert))))
244         (ldap (setq certs (append certs
245                                   (mml-smime-get-ldap-cert))))
246         (file (setq certs (append certs
247                                   (mml-smime-get-file-cert)))))
248       (setq done (not (y-or-n-p "Add more recipients? "))))
249     certs))
250
251 (defun mml-smime-openssl-verify (handle ctl)
252   (with-temp-buffer
253     (insert-buffer-substring (mm-handle-multipart-original-buffer ctl))
254     (goto-char (point-min))
255     (insert (format "Content-Type: %s; " (mm-handle-media-type ctl)))
256     (insert (format "protocol=\"%s\"; "
257                     (mm-handle-multipart-ctl-parameter ctl 'protocol)))
258     (insert (format "micalg=\"%s\"; "
259                     (mm-handle-multipart-ctl-parameter ctl 'micalg)))
260     (insert (format "boundary=\"%s\"\n\n"
261                     (mm-handle-multipart-ctl-parameter ctl 'boundary)))
262     (when (get-buffer smime-details-buffer)
263       (kill-buffer smime-details-buffer))
264     (let ((buf (current-buffer))
265           (good-signature (smime-noverify-buffer))
266           (good-certificate (and (or smime-CA-file smime-CA-directory)
267                                  (smime-verify-buffer)))
268           addresses openssl-output)
269       (setq openssl-output (with-current-buffer smime-details-buffer
270                              (buffer-string)))
271       (if (not good-signature)
272           (progn
273             ;; we couldn't verify message, fail with openssl output as message
274             (mm-set-handle-multipart-parameter
275              mm-security-handle 'gnus-info "Failed")
276             (mm-set-handle-multipart-parameter
277              mm-security-handle 'gnus-details
278              (concat "OpenSSL failed to verify message integrity:\n"
279                      "-------------------------------------------\n"
280                      openssl-output)))
281         ;; verify mail addresses in mail against those in certificate
282         (when (and (smime-pkcs7-region (point-min) (point-max))
283                    (smime-pkcs7-certificates-region (point-min) (point-max)))
284           (with-temp-buffer
285             (insert-buffer-substring buf)
286             (goto-char (point-min))
287             (while (re-search-forward "-----END CERTIFICATE-----" nil t)
288               (when (smime-pkcs7-email-region (point-min) (point))
289                 (setq addresses (append (smime-buffer-as-string-region
290                                          (point-min) (point)) addresses)))
291               (delete-region (point-min) (point)))
292             (setq addresses (mapcar 'downcase addresses))))
293         (if (not (member (downcase (or (mm-handle-multipart-from ctl) "")) addresses))
294             (mm-set-handle-multipart-parameter
295              mm-security-handle 'gnus-info "Sender address forged")
296           (if good-certificate
297               (mm-set-handle-multipart-parameter
298                mm-security-handle 'gnus-info "Ok (sender authenticated)")
299             (mm-set-handle-multipart-parameter
300              mm-security-handle 'gnus-info "Ok (sender not trusted)")))
301         (mm-set-handle-multipart-parameter
302          mm-security-handle 'gnus-details
303          (concat "Sender claimed to be: " (mm-handle-multipart-from ctl) "\n"
304                  (if addresses
305                      (concat "Addresses in certificate: "
306                              (mapconcat 'identity addresses ", "))
307                    "No addresses found in certificate. (Requires OpenSSL 0.9.6 or later.)")
308                  "\n" "\n"
309                  "OpenSSL output:\n"
310                  "---------------\n" openssl-output "\n"
311                  "Certificate(s) inside S/MIME signature:\n"
312                  "---------------------------------------\n"
313                  (buffer-string) "\n")))))
314   handle)
315
316 (defun mml-smime-openssl-verify-test (handle ctl)
317   smime-openssl-program)
318
319 (defvar epg-user-id-alist)
320 (defvar epg-digest-algorithm-alist)
321 (defvar inhibit-redisplay)
322 (defvar password-cache-expiry)
323
324 (eval-when-compile
325   (autoload 'epg-make-context "epg")
326   (autoload 'epg-context-set-armor "epg")
327   (autoload 'epg-context-set-signers "epg")
328   (autoload 'epg-context-result-for "epg")
329   (autoload 'epg-new-signature-digest-algorithm "epg")
330   (autoload 'epg-verify-result-to-string "epg")
331   (autoload 'epg-list-keys "epg")
332   (autoload 'epg-decrypt-string "epg")
333   (autoload 'epg-verify-string "epg")
334   (autoload 'epg-sign-string "epg")
335   (autoload 'epg-encrypt-string "epg")
336   (autoload 'epg-passphrase-callback-function "epg")
337   (autoload 'epg-context-set-passphrase-callback "epg")
338   (autoload 'epg-sub-key-fingerprint "epg")
339   (autoload 'epg-configuration "epg-config")
340   (autoload 'epg-expand-group "epg-config")
341   (autoload 'epa-select-keys "epa"))
342
343 (defvar mml-smime-epg-secret-key-id-list nil)
344
345 (defun mml-smime-epg-passphrase-callback (context key-id ignore)
346   (if (eq key-id 'SYM)
347       (epg-passphrase-callback-function context key-id nil)
348     (let* (entry
349            (passphrase
350             (password-read
351              (if (eq key-id 'PIN)
352                  "Passphrase for PIN: "
353                (if (setq entry (assoc key-id epg-user-id-alist))
354                    (format "Passphrase for %s %s: " key-id (cdr entry))
355                  (format "Passphrase for %s: " key-id)))
356              (if (eq key-id 'PIN)
357                  "PIN"
358                key-id))))
359       (when passphrase
360         (let ((password-cache-expiry mml-smime-passphrase-cache-expiry))
361           (password-cache-add key-id passphrase))
362         (setq mml-smime-epg-secret-key-id-list
363               (cons key-id mml-smime-epg-secret-key-id-list))
364         (copy-sequence passphrase)))))
365
366 (declare-function epg-key-sub-key-list   "ext:epg" (key))
367 (declare-function epg-sub-key-capability "ext:epg" (sub-key))
368 (declare-function epg-sub-key-validity   "ext:epg" (sub-key))
369
370 (defun mml-smime-epg-find-usable-key (keys usage)
371   (catch 'found
372     (while keys
373       (let ((pointer (epg-key-sub-key-list (car keys))))
374         (while pointer
375           (if (and (memq usage (epg-sub-key-capability (car pointer)))
376                    (not (memq (epg-sub-key-validity (car pointer))
377                               '(revoked expired))))
378               (throw 'found (car keys)))
379           (setq pointer (cdr pointer))))
380       (setq keys (cdr keys)))))
381
382 ;; XXX: since gpg --list-secret-keys does not return validity of each
383 ;; key, `mml-smime-epg-find-usable-key' defined above is not enough for
384 ;; secret keys.  The function `mml-smime-epg-find-usable-secret-key'
385 ;; below looks at appropriate public keys to check usability.
386 (defun mml-smime-epg-find-usable-secret-key (context name usage)
387   (let ((secret-keys (epg-list-keys context name t))
388         secret-key)
389     (while (and (not secret-key) secret-keys)
390       (if (mml-smime-epg-find-usable-key
391            (epg-list-keys context (epg-sub-key-fingerprint
392                                    (car (epg-key-sub-key-list
393                                          (car secret-keys)))))
394            usage)
395           (setq secret-key (car secret-keys)
396                 secret-keys nil)
397         (setq secret-keys (cdr secret-keys))))
398     secret-key))
399
400 (autoload 'mml-compute-boundary "mml")
401
402 ;; We require mm-decode, which requires mm-bodies, which autoloads
403 ;; message-options-get (!).
404 (declare-function message-options-set "message" (symbol value))
405
406 (defun mml-smime-epg-sign (cont)
407   (let* ((inhibit-redisplay t)
408          (context (epg-make-context 'CMS))
409          (boundary (mml-compute-boundary cont))
410          (sender (message-options-get 'message-sender))
411          (signer-names (or mml-smime-signers
412                            (if (and mml-smime-sign-with-sender sender)
413                                (list (concat "<" sender ">")))))
414          signer-key
415          (signers
416           (or (message-options-get 'mml-smime-epg-signers)
417               (message-options-set
418                'mml-smime-epg-signers
419                (if (eq mm-sign-option 'guided)
420                    (epa-select-keys context "\
421 Select keys for signing.
422 If no one is selected, default secret key is used.  "
423                                     signer-names
424                                     t)
425                  (if (or sender mml-smime-signers)
426                      (delq nil
427                            (mapcar
428                             (lambda (signer)
429                               (setq signer-key
430                                     (mml-smime-epg-find-usable-secret-key
431                                      context signer 'sign))
432                               (unless (or signer-key
433                                           (y-or-n-p
434                                            (format
435                                             "No secret key for %s; skip it? "
436                                             signer)))
437                                 (error "No secret key for %s" signer))
438                               signer-key)
439                             signer-names)))))))
440          signature micalg)
441     (epg-context-set-signers context signers)
442     (if mml-smime-cache-passphrase
443         (epg-context-set-passphrase-callback
444          context
445          #'mml-smime-epg-passphrase-callback))
446     (condition-case error
447         (setq signature (epg-sign-string context
448                                          (mm-replace-in-string (buffer-string)
449                                                                "\n" "\r\n")
450                                          t)
451               mml-smime-epg-secret-key-id-list nil)
452       (error
453        (while mml-smime-epg-secret-key-id-list
454          (password-cache-remove (car mml-smime-epg-secret-key-id-list))
455          (setq mml-smime-epg-secret-key-id-list
456                (cdr mml-smime-epg-secret-key-id-list)))
457        (signal (car error) (cdr error))))
458     (if (epg-context-result-for context 'sign)
459         (setq micalg (epg-new-signature-digest-algorithm
460                       (car (epg-context-result-for context 'sign)))))
461     (goto-char (point-min))
462     (insert (format "Content-Type: multipart/signed; boundary=\"%s\";\n"
463                     boundary))
464     (if micalg
465         (insert (format "\tmicalg=%s; "
466                         (downcase
467                          (cdr (assq micalg
468                                     epg-digest-algorithm-alist))))))
469     (insert "protocol=\"application/pkcs7-signature\"\n")
470     (insert (format "\n--%s\n" boundary))
471     (goto-char (point-max))
472     (insert (format "\n--%s\n" boundary))
473     (insert "Content-Type: application/pkcs7-signature; name=smime.p7s
474 Content-Transfer-Encoding: base64
475 Content-Disposition: attachment; filename=smime.p7s
476
477 ")
478     (insert (base64-encode-string signature) "\n")
479     (goto-char (point-max))
480     (insert (format "--%s--\n" boundary))
481     (goto-char (point-max))))
482
483 (defun mml-smime-epg-encrypt (cont)
484   (let* ((inhibit-redisplay t)
485          (context (epg-make-context 'CMS))
486          (config (epg-configuration))
487          (recipients (message-options-get 'mml-smime-epg-recipients))
488          cipher signers
489          (sender (message-options-get 'message-sender))
490          (signer-names (or mml-smime-signers
491                            (if (and mml-smime-sign-with-sender sender)
492                                (list (concat "<" sender ">")))))
493          (boundary (mml-compute-boundary cont))
494          recipient-key)
495     (unless recipients
496       (setq recipients
497             (apply #'nconc
498                    (mapcar
499                     (lambda (recipient)
500                       (or (epg-expand-group config recipient)
501                           (list recipient)))
502                     (split-string
503                      (or (message-options-get 'message-recipients)
504                          (message-options-set 'message-recipients
505                                               (read-string "Recipients: ")))
506                      "[ \f\t\n\r\v,]+"))))
507       (when mml-smime-encrypt-to-self
508         (unless signer-names
509           (error "Neither message sender nor mml-smime-signers are set"))
510         (setq recipients (nconc recipients signer-names)))
511       (if (eq mm-encrypt-option 'guided)
512           (setq recipients
513                 (epa-select-keys context "\
514 Select recipients for encryption.
515 If no one is selected, symmetric encryption will be performed.  "
516                                  recipients))
517         (setq recipients
518               (mapcar
519                (lambda (recipient)
520                  (setq recipient-key (mml-smime-epg-find-usable-key
521                                       (epg-list-keys context recipient)
522                                       'encrypt))
523                  (unless (or recipient-key
524                              (y-or-n-p
525                               (format "No public key for %s; skip it? "
526                                       recipient)))
527                    (error "No public key for %s" recipient))
528                  recipient-key)
529                recipients))
530         (unless recipients
531           (error "No recipient specified")))
532       (message-options-set 'mml-smime-epg-recipients recipients))
533     (if mml-smime-cache-passphrase
534         (epg-context-set-passphrase-callback
535          context
536          #'mml-smime-epg-passphrase-callback))
537     (condition-case error
538         (setq cipher
539               (epg-encrypt-string context (buffer-string) recipients)
540               mml-smime-epg-secret-key-id-list nil)
541       (error
542        (while mml-smime-epg-secret-key-id-list
543          (password-cache-remove (car mml-smime-epg-secret-key-id-list))
544          (setq mml-smime-epg-secret-key-id-list
545                (cdr mml-smime-epg-secret-key-id-list)))
546        (signal (car error) (cdr error))))
547     (delete-region (point-min) (point-max))
548     (goto-char (point-min))
549     (insert "\
550 Content-Type: application/pkcs7-mime;
551  smime-type=enveloped-data;
552  name=smime.p7m
553 Content-Transfer-Encoding: base64
554 Content-Disposition: attachment; filename=smime.p7m
555
556 ")
557     (insert (base64-encode-string cipher))
558     (goto-char (point-max))))
559
560 (defun mml-smime-epg-verify (handle ctl)
561   (catch 'error
562     (let ((inhibit-redisplay t)
563           context plain signature-file part signature)
564       (when (or (null (setq part (mm-find-raw-part-by-type
565                                   ctl (or (mm-handle-multipart-ctl-parameter
566                                            ctl 'protocol)
567                                           "application/pkcs7-signature")
568                                   t)))
569                 (null (setq signature (or (mm-find-part-by-type
570                                            (cdr handle)
571                                            "application/pkcs7-signature"
572                                            nil t)
573                                           (mm-find-part-by-type
574                                            (cdr handle)
575                                            "application/x-pkcs7-signature"
576                                            nil t)))))
577         (mm-set-handle-multipart-parameter
578          mm-security-handle 'gnus-info "Corrupted")
579         (throw 'error handle))
580       (setq part (mm-replace-in-string part "\n" "\r\n")
581             context (epg-make-context 'CMS))
582       (condition-case error
583           (setq plain (epg-verify-string context (mm-get-part signature) part))
584         (error
585          (mm-set-handle-multipart-parameter
586           mm-security-handle 'gnus-info "Failed")
587          (if (eq (car error) 'quit)
588              (mm-set-handle-multipart-parameter
589               mm-security-handle 'gnus-details "Quit.")
590            (mm-set-handle-multipart-parameter
591             mm-security-handle 'gnus-details (format "%S" error)))
592          (throw 'error handle)))
593       (mm-set-handle-multipart-parameter
594        mm-security-handle 'gnus-info
595        (epg-verify-result-to-string (epg-context-result-for context 'verify)))
596       handle)))
597
598 (defun mml-smime-epg-verify-test (handle ctl)
599   t)
600
601 (provide 'mml-smime)
602
603 ;;; mml-smime.el ends here