1 ;;; smime.el --- S/MIME support library
2 ;; Copyright (c) 2000, 2001, 2003 Free Software Foundation, Inc.
4 ;; Author: Simon Josefsson <simon@josefsson.org>
5 ;; Keywords: SMIME X.509 PEM OpenSSL
7 ;; This file is part of GNU Emacs.
9 ;; GNU Emacs is free software; you can redistribute it and/or modify
10 ;; it under the terms of the GNU General Public License as published
11 ;; by the Free Software Foundation; either version 2, or (at your
12 ;; option) any later version.
14 ;; GNU Emacs is distributed in the hope that it will be useful, but
15 ;; WITHOUT ANY WARRANTY; without even the implied warranty of
16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 ;; General Public License for more details.
19 ;; You should have received a copy of the GNU General Public License
20 ;; along with GNU Emacs; see the file COPYING. If not, write to the
21 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
22 ;; Boston, MA 02111-1307, USA.
26 ;; This library perform S/MIME operations from within Emacs.
28 ;; Functions for fetching certificates from public repositories are
29 ;; provided, currently only from DNS. LDAP support (via EUDC) is planned.
31 ;; It uses OpenSSL (tested with version 0.9.5a and 0.9.6) for signing,
32 ;; encryption and decryption.
34 ;; Some general knowledge of S/MIME, X.509, PKCS#12, PEM etc is
35 ;; probably required to use this library in any useful way.
36 ;; Especially, don't expect this library to buy security for you. If
37 ;; you don't understand what you are doing, you're as likely to lose
38 ;; security than gain any by using this library.
40 ;; This library is not intended to provide a "raw" API for S/MIME,
41 ;; PKCSx or similar, it's intended to perform common operations
42 ;; done on messages encoded in these formats. The terminology chosen
45 ;; The home of this file is in Gnus CVS, but also available from
46 ;; http://josefsson.org/smime.html.
48 ;;; Quick introduction:
50 ;; Get your S/MIME certificate from VeriSign or someplace. I used
51 ;; Netscape to generate the key and certificate request and stuff, and
52 ;; Netscape can export the key into PKCS#12 format.
54 ;; Enter OpenSSL. To be able to use this library, it need to have the
55 ;; SMIME key readable in PEM format. OpenSSL is used to convert the
58 ;; $ openssl pkcs12 -in mykey.p12 -clcerts -nodes > mykey.pem
61 ;; Now, use M-x customize-variable smime-keys and add mykey.pem as
64 ;; Now you should be able to sign messages! Create a buffer and write
65 ;; something and run M-x smime-sign-buffer RET RET and you should see
66 ;; your message MIME armoured and a signature. Encryption, M-x
67 ;; smime-encrypt-buffer, should also work.
69 ;; To be able to verify messages you need to build up trust with
70 ;; someone. Perhaps you trust the CA that issued your certificate, at
71 ;; least I did, so I export it's certificates from my PKCS#12
74 ;; $ openssl pkcs12 -in mykey.p12 -cacerts -nodes > cacert.pem
77 ;; Now, use M-x customize-variable smime-CAs and add cacert.pem as a
80 ;; You should now be able to sign messages, and even verify messages
81 ;; sent by others that use the same CA as you.
85 ;; Don't complain that this package doesn't do encrypted PEM files,
86 ;; submit a patch instead. I store my keys in a safe place, so I
87 ;; didn't need the encryption. Also, programming was made easier by
88 ;; that decision. One might think that this even influenced were I
89 ;; store my keys, and one would probably be right. :-)
91 ;; Update: Mathias Herberts sent the patch. However, it uses
92 ;; environment variables to pass the password to OpenSSL, which is
93 ;; slightly insecure. Hence a new todo: use a better -passin method.
95 ;; Cache password for e.g. 1h
97 ;; Suggestions and comments are appreciated, mail me at simon@josefsson.org.
101 ;; I would include pointers to introductory text on concepts used in
102 ;; this library here, but the material I've read are so horrible I
103 ;; don't want to recomend them.
105 ;; Why can't someone write a simple introduction to all this stuff?
106 ;; Until then, much of this resemble security by obscurity.
108 ;; Also, I'm not going to mention anything about the wonders of
109 ;; cryptopolitics. Oops, I just did.
113 ;;; Revision history:
115 ;; 2000-06-05 initial version, committed to Gnus CVS contrib/
116 ;; 2000-10-28 retrieve certificates via DNS CERT RRs
117 ;; 2001-10-14 posted to gnu.emacs.sources
123 (eval-when-compile (require 'cl))
126 "S/MIME configuration.")
128 (defcustom smime-keys nil
129 "*Map mail addresses to a file containing Certificate (and private key).
130 The file is assumed to be in PEM format. You can also associate additional
131 certificates to be sent with every message to each address."
132 :type '(repeat (list (string :tag "Mail address")
133 (file :tag "File name")
134 (repeat :tag "Additional certificate files"
135 (file :tag "File name"))))
138 (defcustom smime-CA-directory nil
139 "*Directory containing certificates for CAs you trust.
140 Directory should contain files (in PEM format) named to the X.509
141 hash of the certificate. This can be done using OpenSSL such as:
143 $ ln -s ca.pem `openssl x509 -noout -hash -in ca.pem`.0
145 where `ca.pem' is the file containing a PEM encoded X.509 CA
147 :type '(choice (const :tag "none" nil)
151 (defcustom smime-CA-file nil
152 "*Files containing certificates for CAs you trust.
153 File should contain certificates in PEM format."
154 :type '(choice (const :tag "none" nil)
158 (defcustom smime-certificate-directory "~/Mail/certs/"
159 "*Directory containing other people's certificates.
160 It should contain files named to the X.509 hash of the certificate,
161 and the files themself should be in PEM format."
162 ;The S/MIME library provide simple functionality for fetching
163 ;certificates into this directory, so there is no need to populate it
168 (defcustom smime-openssl-program
169 (and (condition-case ()
170 (eq 0 (call-process "openssl" nil nil nil "version"))
173 "*Name of OpenSSL binary."
177 ;; OpenSSL option to select the encryption cipher
179 (defcustom smime-encrypt-cipher "-des3"
180 "*Cipher algorithm used for encryption."
181 :type '(choice (const :tag "Triple DES" "-des3")
182 (const :tag "DES" "-des")
183 (const :tag "RC2 40 bits" "-rc2-40")
184 (const :tag "RC2 64 bits" "-rc2-64")
185 (const :tag "RC2 128 bits" "-rc2-128"))
188 (defcustom smime-dns-server nil
189 "*DNS server to query certificates from.
190 If nil, use system defaults."
191 :type '(choice (const :tag "System defaults")
195 (defvar smime-details-buffer "*OpenSSL output*")
199 (defalias 'smime-make-temp-file
200 (if (fboundp 'make-temp-file)
202 (lambda (prefix &optional dir-flag) ;; Simple implementation
204 (make-temp-name prefix)
205 (if (fboundp 'temp-directory)
207 temporary-file-directory))))))
209 ;; Password dialog function
211 (defun smime-ask-passphrase ()
212 "Asks the passphrase to unlock the secret key."
215 "Passphrase for secret key (RET for no passphrase): " t)))
216 (if (string= passphrase "")
222 (defun smime-call-openssl-region (b e buf &rest args)
223 (case (apply 'call-process-region b e smime-openssl-program nil buf nil args)
225 (1 (message "OpenSSL: An error occurred parsing the command options.") nil)
226 (2 (message "OpenSSL: One of the input files could not be read.") nil)
227 (3 (message "OpenSSL: An error occurred creating the PKCS#7 file or when reading the MIME message.") nil)
228 (4 (message "OpenSSL: An error occurred decrypting or verifying the message.") nil)
229 (t (error "Unknown OpenSSL exitcode") nil)))
231 (defun smime-make-certfiles (certfiles)
233 (append (list "-certfile" (expand-file-name (car certfiles)))
234 (smime-make-certfiles (cdr certfiles)))))
236 ;; Sign+encrypt region
238 (defun smime-sign-region (b e keyfile)
239 "Sign region with certified key in KEYFILE.
240 If signing fails, the buffer is not modified. Region is assumed to
241 have proper MIME tags. KEYFILE is expected to contain a PEM encoded
242 private key and certificate as its car, and a list of additional
243 certificates to include in its caar. If no additional certificates is
244 included, KEYFILE may be the file containing the PEM encoded private
245 key and certificate itself."
246 (smime-new-details-buffer)
247 (let ((keyfile (or (car-safe keyfile) keyfile))
248 (certfiles (and (cdr-safe keyfile) (cadr keyfile)))
249 (buffer (generate-new-buffer (generate-new-buffer-name " *smime*")))
250 (passphrase (smime-ask-passphrase))
251 (tmpfile (smime-make-temp-file "smime")))
253 (setenv "GNUS_SMIME_PASSPHRASE" passphrase))
256 (apply 'smime-call-openssl-region b e (list buffer tmpfile)
257 "smime" "-sign" "-signer" (expand-file-name keyfile)
259 (smime-make-certfiles certfiles)
261 (list "-passin" "env:GNUS_SMIME_PASSPHRASE"))))
263 (setenv "GNUS_SMIME_PASSPHRASE" "" t))
264 (with-current-buffer smime-details-buffer
265 (insert-file-contents tmpfile)
266 (delete-file tmpfile)))
268 (insert-buffer-substring buffer)
270 (when (looking-at "^MIME-Version: 1.0$")
271 (delete-region (point) (progn (forward-line 1) (point))))
273 (with-current-buffer smime-details-buffer
274 (goto-char (point-max))
275 (insert-buffer-substring buffer))
276 (kill-buffer buffer))))
278 (defun smime-encrypt-region (b e certfiles)
279 "Encrypt region for recipients specified in CERTFILES.
280 If encryption fails, the buffer is not modified. Region is assumed to
281 have proper MIME tags. CERTFILES is a list of filenames, each file
282 is expected to contain of a PEM encoded certificate."
283 (smime-new-details-buffer)
284 (let ((buffer (generate-new-buffer (generate-new-buffer-name " *smime*")))
285 (tmpfile (smime-make-temp-file "smime")))
288 (apply 'smime-call-openssl-region b e (list buffer tmpfile)
289 "smime" "-encrypt" smime-encrypt-cipher
290 (mapcar 'expand-file-name certfiles))
291 (with-current-buffer smime-details-buffer
292 (insert-file-contents tmpfile)
293 (delete-file tmpfile)))
295 (insert-buffer-substring buffer)
297 (when (looking-at "^MIME-Version: 1.0$")
298 (delete-region (point) (progn (forward-line 1) (point))))
300 (with-current-buffer smime-details-buffer
301 (goto-char (point-max))
302 (insert-buffer-substring buffer))
303 (kill-buffer buffer))))
305 ;; Sign+encrypt buffer
307 (defun smime-sign-buffer (&optional keyfile buffer)
308 "S/MIME sign BUFFER with key in KEYFILE.
309 KEYFILE should contain a PEM encoded key and certificate."
311 (with-current-buffer (or buffer (current-buffer))
313 (point-min) (point-max)
316 (smime-get-key-with-certs-by-email
318 (concat "Sign using which key? "
319 (if smime-keys (concat "(default " (caar smime-keys) ") ")
321 smime-keys nil nil (car-safe (car-safe smime-keys))))))))
323 (defun smime-encrypt-buffer (&optional certfiles buffer)
324 "S/MIME encrypt BUFFER for recipients specified in CERTFILES.
325 CERTFILES is a list of filenames, each file is expected to consist of
326 a PEM encoded key and certificate. Uses current buffer if BUFFER is
329 (with-current-buffer (or buffer (current-buffer))
330 (smime-encrypt-region
331 (point-min) (point-max)
333 (list (read-file-name "Recipient's S/MIME certificate: "
334 smime-certificate-directory nil))))))
336 ;; Verify+decrypt region
338 (defun smime-verify-region (b e)
339 "Verify S/MIME message in region between B and E.
340 Returns non-nil on success.
341 Any details (stdout and stderr) are left in the buffer specified by
342 `smime-details-buffer'."
343 (smime-new-details-buffer)
344 (let ((CAs (append (if smime-CA-file
346 (expand-file-name smime-CA-file)))
347 (if smime-CA-directory
349 (expand-file-name smime-CA-directory))))))
351 (error "No CA configured"))
352 (if (apply 'smime-call-openssl-region b e (list smime-details-buffer t)
353 "smime" "-verify" "-out" "/dev/null" CAs)
355 (insert-buffer-substring smime-details-buffer)
358 (defun smime-noverify-region (b e)
359 "Verify integrity of S/MIME message in region between B and E.
360 Returns non-nil on success.
361 Any details (stdout and stderr) are left in the buffer specified by
362 `smime-details-buffer'."
363 (smime-new-details-buffer)
364 (if (apply 'smime-call-openssl-region b e (list smime-details-buffer t)
365 "smime" "-verify" "-noverify" "-out" '("/dev/null"))
367 (insert-buffer-substring smime-details-buffer)
373 (defun smime-decrypt-region (b e keyfile)
374 "Decrypt S/MIME message in region between B and E with key in KEYFILE.
375 On success, replaces region with decrypted data and return non-nil.
376 Any details (stderr on success, stdout and stderr on error) are left
377 in the buffer specified by `smime-details-buffer'."
378 (smime-new-details-buffer)
379 (let ((buffer (generate-new-buffer (generate-new-buffer-name " *smime*")))
380 CAs (passphrase (smime-ask-passphrase))
381 (tmpfile (smime-make-temp-file "smime")))
383 (setenv "GNUS_SMIME_PASSPHRASE" passphrase))
385 (apply 'smime-call-openssl-region b e
386 (list buffer tmpfile)
387 "smime" "-decrypt" "-recip" (expand-file-name keyfile)
389 (list "-passin" "env:GNUS_SMIME_PASSPHRASE")))
391 (setenv "GNUS_SMIME_PASSPHRASE" "" t))
392 (with-current-buffer smime-details-buffer
393 (insert-file-contents tmpfile)
394 (delete-file tmpfile)))
398 ;; `from' is dynamically bound in mm-dissect.
399 (insert "From: " from "\n"))
400 (insert-buffer-substring buffer)
403 (with-current-buffer smime-details-buffer
404 (insert-buffer-substring buffer))
407 (insert-buffer-substring smime-details-buffer)
410 ;; Verify+Decrypt buffer
412 (defun smime-verify-buffer (&optional buffer)
413 "Verify integrity of S/MIME message in BUFFER.
414 Uses current buffer if BUFFER is nil. Returns non-nil on success.
415 Any details (stdout and stderr) are left in the buffer specified by
416 `smime-details-buffer'."
418 (with-current-buffer (or buffer (current-buffer))
419 (smime-verify-region (point-min) (point-max))))
421 (defun smime-noverify-buffer (&optional buffer)
422 "Verify integrity of S/MIME message in BUFFER.
423 Does NOT verify validity of certificate (only message integrity).
424 Uses current buffer if BUFFER is nil. Returns non-nil on success.
425 Any details (stdout and stderr) are left in the buffer specified by
426 `smime-details-buffer'."
428 (with-current-buffer (or buffer (current-buffer))
429 (smime-noverify-region (point-min) (point-max))))
431 (defun smime-decrypt-buffer (&optional buffer keyfile)
432 "Decrypt S/MIME message in BUFFER using KEYFILE.
433 Uses current buffer if BUFFER is nil, and query user of KEYFILE if it's nil.
434 On success, replaces data in buffer and return non-nil.
435 Any details (stderr on success, stdout and stderr on error) are left
436 in the buffer specified by `smime-details-buffer'."
438 (with-current-buffer (or buffer (current-buffer))
439 (smime-decrypt-region
440 (point-min) (point-max)
443 (smime-get-key-by-email
445 (concat "Decipher using which key? "
446 (if smime-keys (concat "(default " (caar smime-keys) ") ")
448 smime-keys nil nil (car-safe (car-safe smime-keys)))))))))
450 ;; Various operations
452 (defun smime-new-details-buffer ()
453 (with-current-buffer (get-buffer-create smime-details-buffer)
456 (defun smime-pkcs7-region (b e)
457 "Convert S/MIME message between points B and E into a PKCS7 message."
458 (smime-new-details-buffer)
459 (when (smime-call-openssl-region b e smime-details-buffer "smime" "-pk7out")
461 (insert-buffer-substring smime-details-buffer)
464 (defun smime-pkcs7-certificates-region (b e)
465 "Extract any certificates enclosed in PKCS7 message between points B and E."
466 (smime-new-details-buffer)
467 (when (smime-call-openssl-region
468 b e smime-details-buffer "pkcs7" "-print_certs" "-text")
470 (insert-buffer-substring smime-details-buffer)
473 (defun smime-pkcs7-email-region (b e)
474 "Get email addresses contained in certificate between points B and E.
475 A string or a list of strings is returned."
476 (smime-new-details-buffer)
477 (when (smime-call-openssl-region
478 b e smime-details-buffer "x509" "-email" "-noout")
480 (insert-buffer-substring smime-details-buffer)
485 (defun smime-get-certfiles (keyfile keys)
487 (let ((curkey (car keys))
488 (otherkeys (cdr keys)))
489 (if (string= keyfile (cadr curkey))
491 (smime-get-certfiles keyfile otherkeys)))))
495 (defalias 'smime-point-at-eol
496 (if (fboundp 'point-at-eol)
498 'line-end-position)))
500 (defun smime-buffer-as-string-region (b e)
501 "Return each line in region between B and E as a list of strings."
506 (let ((str (buffer-substring (point) (smime-point-at-eol))))
507 (unless (string= "" str)
514 (defun smime-mail-to-domain (mailaddr)
515 (if (string-match "@" mailaddr)
516 (replace-match "." 'fixedcase 'literal mailaddr)
519 (defun smime-cert-by-dns (mail)
520 (let* ((dig-dns-server smime-dns-server)
521 (digbuf (dig-invoke (smime-mail-to-domain mail) "cert" nil nil "+vc"))
522 (retbuf (generate-new-buffer (format "*certificate for %s*" mail)))
523 (certrr (with-current-buffer digbuf
524 (dig-extract-rr (smime-mail-to-domain mail) "cert")))
525 (cert (and certrr (dig-rr-get-pkix-cert certrr))))
527 (with-current-buffer retbuf
528 (insert "-----BEGIN CERTIFICATE-----\n")
529 (let ((i 0) (len (length cert)))
530 (while (> (- len 64) i)
531 (insert (substring cert i (+ i 64)) "\n")
533 (insert (substring cert i len) "\n"))
534 (insert "-----END CERTIFICATE-----\n"))
542 (defvar smime-buffer "*SMIME*")
544 (defvar smime-mode-map nil)
545 (put 'smime-mode 'mode-class 'special)
547 (unless smime-mode-map
548 (setq smime-mode-map (make-sparse-keymap))
549 (suppress-keymap smime-mode-map)
551 (define-key smime-mode-map "q" 'smime-exit)
552 (define-key smime-mode-map "f" 'smime-certificate-info))
555 "Major mode for browsing, viewing and fetching certificates.
557 All normal editing commands are switched off.
560 The following commands are available:
564 (kill-all-local-variables)
565 (setq major-mode 'smime-mode)
566 (setq mode-name "SMIME")
567 (setq mode-line-process nil)
568 (use-local-map smime-mode-map)
569 (buffer-disable-undo)
570 (setq truncate-lines t)
571 (setq buffer-read-only t))
573 (defun smime-certificate-info (certfile)
574 (interactive "fCertificate file: ")
575 (let ((buffer (get-buffer-create (format "*certificate %s*" certfile))))
576 (switch-to-buffer buffer)
578 (call-process smime-openssl-program nil buffer 'display
579 "x509" "-in" (expand-file-name certfile) "-text")
581 (set-buffer-modified-p nil)
583 (goto-char (point-min))))
585 (defun smime-draw-buffer ()
586 (with-current-buffer smime-buffer
587 (let (buffer-read-only)
589 (insert "\nYour keys:\n")
590 (dolist (key smime-keys)
592 (format "\t\t%s: %s\n" (car key) (cadr key))))
593 (insert "\nTrusted Certificate Authoritys:\n")
594 (insert "\nKnown Certificates:\n"))))
597 "Go to the SMIME buffer."
599 (unless (get-buffer smime-buffer)
601 (set-buffer (get-buffer-create smime-buffer))
604 (switch-to-buffer smime-buffer))
607 "Quit the S/MIME buffer."
609 (kill-buffer (current-buffer)))
613 (defun smime-get-key-by-email (email)
614 (cadr (assoc email smime-keys)))
616 (defun smime-get-key-with-certs-by-email (email)
617 (cdr (assoc email smime-keys)))
621 ;;; smime.el ends here