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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 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
  13 ;; by the Free Software Foundation; either version 3, or (at your
  14 ;; option) any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful, but
  17 ;; WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19 ;; 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; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  24 ;; Boston, MA 02110-1301, USA.
  25
  26 ;;; Commentary:
  27
  28 ;;; Code:
  29
  30 (eval-when-compile (require 'cl))
  31
  32 (require 'smime)
  33 (require 'mm-decode)
  34 (require 'mml-sec)
  35 (autoload 'message-narrow-to-headers "message")
  36 (autoload 'message-fetch-field "message")
  37
  38 (defvar mml-smime-use 'openssl)
  39
  40 (defvar mml-smime-function-alist
  41   '((openssl mml-smime-openssl-sign
  42              mml-smime-openssl-encrypt
  43              mml-smime-openssl-sign-query
  44              mml-smime-openssl-encrypt-query
  45              mml-smime-openssl-verify
  46              mml-smime-openssl-verify-test)
  47     (epg mml-smime-epg-sign
  48          mml-smime-epg-encrypt
  49          nil
  50          nil
  51          mml-smime-epg-verify
  52          mml-smime-epg-verify-test)))
  53
  54 (defcustom mml-smime-verbose mml-secure-verbose
  55   "If non-nil, ask the user about the current operation more verbosely."
  56   :group 'mime-security
  57   :type 'boolean)
  58
  59 (defcustom mml-smime-cache-passphrase mml-secure-cache-passphrase
  60   "If t, cache passphrase."
  61   :group 'mime-security
  62   :type 'boolean)
  63
  64 (defcustom mml-smime-passphrase-cache-expiry mml-secure-passphrase-cache-expiry
  65   "How many seconds the passphrase is cached.
  66 Whether the passphrase is cached at all is controlled by
  67 `mml-smime-cache-passphrase'."
  68   :group 'mime-security
  69   :type 'integer)
  70
  71 (defcustom mml-smime-signers nil
  72   "A list of your own key ID which will be used to sign a message."
  73   :group 'mime-security
  74   :type '(repeat (string :tag "Key ID")))
  75
  76 (defun mml-smime-sign (cont)
  77   (let ((func (nth 1 (assq mml-smime-use mml-smime-function-alist))))
  78     (if func
  79         (funcall func cont)
  80       (error "Cannot find sign function"))))
  81
  82 (defun mml-smime-encrypt (cont)
  83   (let ((func (nth 2 (assq mml-smime-use mml-smime-function-alist))))
  84     (if func
  85         (funcall func cont)
  86       (error "Cannot find encrypt function"))))
  87
  88 (defun mml-smime-sign-query ()
  89   (let ((func (nth 3 (assq mml-smime-use mml-smime-function-alist))))
  90     (if func
  91         (funcall func))))
  92
  93 (defun mml-smime-encrypt-query ()
  94   (let ((func (nth 4 (assq mml-smime-use mml-smime-function-alist))))
  95     (if func
  96         (funcall func))))
  97
  98 (defun mml-smime-verify (handle ctl)
  99   (let ((func (nth 5 (assq mml-smime-use mml-smime-function-alist))))
 100     (if func
 101         (funcall func handle ctl)
 102       handle)))
 103
 104 (defun mml-smime-verify-test (handle ctl)
 105   (let ((func (nth 6 (assq mml-smime-use mml-smime-function-alist))))
 106     (if func
 107         (funcall func handle ctl))))
 108
 109 (defun mml-smime-openssl-sign (cont)
 110   (when (null smime-keys)
 111     (customize-variable 'smime-keys)
 112     (error "No S/MIME keys configured, use customize to add your key"))
 113   (smime-sign-buffer (cdr (assq 'keyfile cont)))
 114   (goto-char (point-min))
 115   (while (search-forward "\r\n" nil t)
 116     (replace-match "\n" t t))
 117   (goto-char (point-max)))
 118
 119 (defun mml-smime-openssl-encrypt (cont)
 120   (let (certnames certfiles tmp file tmpfiles)
 121     ;; xxx tmp files are always an security issue
 122     (while (setq tmp (pop cont))
 123       (if (and (consp tmp) (eq (car tmp) 'certfile))
 124           (push (cdr tmp) certnames)))
 125     (while (setq tmp (pop certnames))
 126       (if (not (and (not (file-exists-p tmp))
 127                     (get-buffer tmp)))
 128           (push tmp certfiles)
 129         (setq file (mm-make-temp-file (expand-file-name "mml."
 130                                                         mm-tmp-directory)))
 131         (with-current-buffer tmp
 132           (write-region (point-min) (point-max) file))
 133         (push file certfiles)
 134         (push file tmpfiles)))
 135     (if (smime-encrypt-buffer certfiles)
 136         (progn
 137           (while (setq tmp (pop tmpfiles))
 138             (delete-file tmp))
 139           t)
 140       (while (setq tmp (pop tmpfiles))
 141         (delete-file tmp))
 142       nil))
 143   (goto-char (point-max)))
 144
 145 (defvar gnus-extract-address-components)
 146
 147 (defun mml-smime-openssl-sign-query ()
 148   ;; query information (what certificate) from user when MML tag is
 149   ;; added, for use later by the signing process
 150   (when (null smime-keys)
 151     (customize-variable 'smime-keys)
 152     (error "No S/MIME keys configured, use customize to add your key"))
 153   (list 'keyfile
 154         (if (= (length smime-keys) 1)
 155             (cadar smime-keys)
 156           (or (let ((from (cadr (funcall (if (boundp
 157                                               'gnus-extract-address-components)
 158                                              gnus-extract-address-components
 159                                            'mail-extract-address-components)
 160                                          (or (save-excursion
 161                                                (save-restriction
 162                                                  (message-narrow-to-headers)
 163                                                  (message-fetch-field "from")))
 164                                              "")))))
 165                 (and from (smime-get-key-by-email from)))
 166               (smime-get-key-by-email
 167                (completing-read "Sign this part with what signature? "
 168                                 smime-keys nil nil
 169                                 (and (listp (car-safe smime-keys))
 170                                      (caar smime-keys))))))))
 171
 172 (defun mml-smime-get-file-cert ()
 173   (ignore-errors
 174     (list 'certfile (read-file-name
 175                      "File with recipient's S/MIME certificate: "
 176                      smime-certificate-directory nil t ""))))
 177
 178 (defun mml-smime-get-dns-cert ()
 179   ;; todo: deal with comma separated multiple recipients
 180   (let (result who bad cert)
 181     (condition-case ()
 182         (while (not result)
 183           (setq who (read-from-minibuffer
 184                      (format "%sLookup certificate for: " (or bad ""))
 185                      (cadr (funcall (if (boundp
 186                                          'gnus-extract-address-components)
 187                                         gnus-extract-address-components
 188                                       'mail-extract-address-components)
 189                                     (or (save-excursion
 190                                           (save-restriction
 191                                             (message-narrow-to-headers)
 192                                             (message-fetch-field "to")))
 193                                         "")))))
 194           (if (setq cert (smime-cert-by-dns who))
 195               (setq result (list 'certfile (buffer-name cert)))
 196             (setq bad (format "`%s' not found. " who))))
 197       (quit))
 198     result))
 199
 200 (defun mml-smime-get-ldap-cert ()
 201   ;; todo: deal with comma separated multiple recipients
 202   (let (result who bad cert)
 203     (condition-case ()
 204         (while (not result)
 205           (setq who (read-from-minibuffer
 206                      (format "%sLookup certificate for: " (or bad ""))
 207                      (cadr (funcall gnus-extract-address-components
 208                                     (or (save-excursion
 209                                           (save-restriction
 210                                             (message-narrow-to-headers)
 211                                             (message-fetch-field "to")))
 212                                         "")))))
 213           (if (setq cert (smime-cert-by-ldap who))
 214               (setq result (list 'certfile (buffer-name cert)))
 215             (setq bad (format "`%s' not found. " who))))
 216       (quit))
 217     result))
 218
 219 (defun mml-smime-openssl-encrypt-query ()
 220   ;; todo: try dns/ldap automatically first, before prompting user
 221   (let (certs done)
 222     (while (not done)
 223       (ecase (read (gnus-completing-read-with-default
 224                     "ldap" "Fetch certificate from"
 225                     '(("dns") ("ldap") ("file")) nil t))
 226         (dns (setq certs (append certs
 227                                  (mml-smime-get-dns-cert))))
 228         (ldap (setq certs (append certs
 229                                   (mml-smime-get-ldap-cert))))
 230         (file (setq certs (append certs
 231                                   (mml-smime-get-file-cert)))))
 232       (setq done (not (y-or-n-p "Add more recipients? "))))
 233     certs))
 234
 235 (defun mml-smime-openssl-verify (handle ctl)
 236   (with-temp-buffer
 237     (insert-buffer-substring (mm-handle-multipart-original-buffer ctl))
 238     (goto-char (point-min))
 239     (insert (format "Content-Type: %s; " (mm-handle-media-type ctl)))
 240     (insert (format "protocol=\"%s\"; "
 241                     (mm-handle-multipart-ctl-parameter ctl 'protocol)))
 242     (insert (format "micalg=\"%s\"; "
 243                     (mm-handle-multipart-ctl-parameter ctl 'micalg)))
 244     (insert (format "boundary=\"%s\"\n\n"
 245                     (mm-handle-multipart-ctl-parameter ctl 'boundary)))
 246     (when (get-buffer smime-details-buffer)
 247       (kill-buffer smime-details-buffer))
 248     (let ((buf (current-buffer))
 249           (good-signature (smime-noverify-buffer))
 250           (good-certificate (and (or smime-CA-file smime-CA-directory)
 251                                  (smime-verify-buffer)))
 252           addresses openssl-output)
 253       (setq openssl-output (with-current-buffer smime-details-buffer
 254                              (buffer-string)))
 255       (if (not good-signature)
 256           (progn
 257             ;; we couldn't verify message, fail with openssl output as message
 258             (mm-set-handle-multipart-parameter
 259              mm-security-handle 'gnus-info "Failed")
 260             (mm-set-handle-multipart-parameter
 261              mm-security-handle 'gnus-details
 262              (concat "OpenSSL failed to verify message integrity:\n"
 263                      "-------------------------------------------\n"
 264                      openssl-output)))
 265         ;; verify mail addresses in mail against those in certificate
 266         (when (and (smime-pkcs7-region (point-min) (point-max))
 267                    (smime-pkcs7-certificates-region (point-min) (point-max)))
 268           (with-temp-buffer
 269             (insert-buffer-substring buf)
 270             (goto-char (point-min))
 271             (while (re-search-forward "-----END CERTIFICATE-----" nil t)
 272               (when (smime-pkcs7-email-region (point-min) (point))
 273                 (setq addresses (append (smime-buffer-as-string-region
 274                                          (point-min) (point)) addresses)))
 275               (delete-region (point-min) (point)))
 276             (setq addresses (mapcar 'downcase addresses))))
 277         (if (not (member (downcase (or (mm-handle-multipart-from ctl) "")) addresses))
 278             (mm-set-handle-multipart-parameter
 279              mm-security-handle 'gnus-info "Sender address forged")
 280           (if good-certificate
 281               (mm-set-handle-multipart-parameter
 282                mm-security-handle 'gnus-info "Ok (sender authenticated)")
 283             (mm-set-handle-multipart-parameter
 284              mm-security-handle 'gnus-info "Ok (sender not trusted)")))
 285         (mm-set-handle-multipart-parameter
 286          mm-security-handle 'gnus-details
 287          (concat "Sender claimed to be: " (mm-handle-multipart-from ctl) "\n"
 288                  (if addresses
 289                      (concat "Addresses in certificate: "
 290                              (mapconcat 'identity addresses ", "))
 291                    "No addresses found in certificate. (Requires OpenSSL 0.9.6 or later.)")
 292                  "\n" "\n"
 293                  "OpenSSL output:\n"
 294                  "---------------\n" openssl-output "\n"
 295                  "Certificate(s) inside S/MIME signature:\n"
 296                  "---------------------------------------\n"
 297                  (buffer-string) "\n")))))
 298   handle)
 299
 300 (defun mml-smime-openssl-verify-test (handle ctl)
 301   smime-openssl-program)
 302
 303 (defvar epg-user-id-alist)
 304 (defvar epg-digest-algorithm-alist)
 305 (defvar inhibit-redisplay)
 306 (defvar password-cache-expiry)
 307
 308 (eval-when-compile
 309   (autoload 'epg-make-context "epg")
 310   (autoload 'epg-context-set-armor "epg")
 311   (autoload 'epg-context-set-signers "epg")
 312   (autoload 'epg-context-result-for "epg")
 313   (autoload 'epg-new-signature-digest-algorithm "epg")
 314   (autoload 'epg-verify-result-to-string "epg")
 315   (autoload 'epg-list-keys "epg")
 316   (autoload 'epg-decrypt-string "epg")
 317   (autoload 'epg-verify-string "epg")
 318   (autoload 'epg-sign-string "epg")
 319   (autoload 'epg-encrypt-string "epg")
 320   (autoload 'epg-passphrase-callback-function "epg")
 321   (autoload 'epg-context-set-passphrase-callback "epg")
 322   (autoload 'epg-configuration "epg-config")
 323   (autoload 'epg-expand-group "epg-config")
 324   (autoload 'epa-select-keys "epa"))
 325
 326 (defvar mml-smime-epg-secret-key-id-list nil)
 327
 328 (defun mml-smime-epg-passphrase-callback (context key-id ignore)
 329   (if (eq key-id 'SYM)
 330       (epg-passphrase-callback-function context key-id nil)
 331     (let* (entry
 332            (passphrase
 333             (password-read
 334              (if (eq key-id 'PIN)
 335                  "Passphrase for PIN: "
 336                (if (setq entry (assoc key-id epg-user-id-alist))
 337                    (format "Passphrase for %s %s: " key-id (cdr entry))
 338                  (format "Passphrase for %s: " key-id)))
 339              (if (eq key-id 'PIN)
 340                  "PIN"
 341                key-id))))
 342       (when passphrase
 343         (let ((password-cache-expiry mml-smime-passphrase-cache-expiry))
 344           (password-cache-add key-id passphrase))
 345         (setq mml-smime-epg-secret-key-id-list
 346               (cons key-id mml-smime-epg-secret-key-id-list))
 347         (copy-sequence passphrase)))))
 348
 349 (defun mml-smime-epg-find-usable-key (keys usage)
 350   (catch 'found
 351     (while keys
 352       (let ((pointer (epg-key-sub-key-list (car keys))))
 353         (while pointer
 354           (if (and (memq usage (epg-sub-key-capability (car pointer)))
 355                    (not (memq (epg-sub-key-validity (car pointer))
 356                               '(revoked expired))))
 357               (throw 'found (car keys)))
 358           (setq pointer (cdr pointer))))
 359       (setq keys (cdr keys)))))
 360
 361 (defun mml-smime-epg-sign (cont)
 362   (let* ((inhibit-redisplay t)
 363          (context (epg-make-context 'CMS))
 364          (boundary (mml-compute-boundary cont))
 365          signer-key
 366          (signers
 367           (or (message-options-get 'mml-smime-epg-signers)
 368               (message-options-set
 369               'mml-smime-epg-signers
 370               (if mml-smime-verbose
 371                   (epa-select-keys context "\
 372 Select keys for signing.
 373 If no one is selected, default secret key is used.  "
 374                                    mml-smime-signers t)
 375                 (if mml-smime-signers
 376                     (mapcar
 377                      (lambda (signer)
 378                        (setq signer-key (mml-smime-epg-find-usable-key
 379                                          (epg-list-keys context signer t)
 380                                          'sign))
 381                        (unless (or signer-key
 382                                    (y-or-n-p
 383                                     (format "No secret key for %s; skip it? "
 384                                             signer)))
 385                          (error "No secret key for %s" signer))
 386                        signer-key)
 387                      mml-smime-signers))))))
 388          signature micalg)
 389     (epg-context-set-signers context signers)
 390     (if mml-smime-cache-passphrase
 391         (epg-context-set-passphrase-callback
 392          context
 393          #'mml-smime-epg-passphrase-callback))
 394     (condition-case error
 395         (setq signature (epg-sign-string context
 396                                          (mm-replace-in-string (buffer-string)
 397                                                                "\n" "\r\n")
 398                                          t)
 399               mml-smime-epg-secret-key-id-list nil)
 400       (error
 401        (while mml-smime-epg-secret-key-id-list
 402          (password-cache-remove (car mml-smime-epg-secret-key-id-list))
 403          (setq mml-smime-epg-secret-key-id-list
 404                (cdr mml-smime-epg-secret-key-id-list)))
 405        (signal (car error) (cdr error))))
 406     (if (epg-context-result-for context 'sign)
 407         (setq micalg (epg-new-signature-digest-algorithm
 408                       (car (epg-context-result-for context 'sign)))))
 409     (goto-char (point-min))
 410     (insert (format "Content-Type: multipart/signed; boundary=\"%s\";\n"
 411                     boundary))
 412     (if micalg
 413         (insert (format "\tmicalg=%s; "
 414                         (downcase
 415                          (cdr (assq micalg
 416                                     epg-digest-algorithm-alist))))))
 417     (insert "protocol=\"application/pkcs7-signature\"\n")
 418     (insert (format "\n--%s\n" boundary))
 419     (goto-char (point-max))
 420     (insert (format "\n--%s\n" boundary))
 421     (insert "Content-Type: application/pkcs7-signature; name=smime.p7s
 422 Content-Transfer-Encoding: base64
 423 Content-Disposition: attachment; filename=smime.p7s
 424
 425 ")
 426     (insert (base64-encode-string signature) "\n")
 427     (goto-char (point-max))
 428     (insert (format "--%s--\n" boundary))
 429     (goto-char (point-max))))
 430
 431 (defun mml-smime-epg-encrypt (cont)
 432   (let ((inhibit-redisplay t)
 433         (context (epg-make-context 'CMS))
 434         (config (epg-configuration))
 435         (recipients (message-options-get 'mml-smime-epg-recipients))
 436         cipher signers
 437         (boundary (mml-compute-boundary cont))
 438         recipient-key)
 439     (unless recipients
 440       (setq recipients
 441             (apply #'nconc
 442                    (mapcar
 443                     (lambda (recipient)
 444                       (or (epg-expand-group config recipient)
 445                           (list recipient)))
 446                     (split-string
 447                      (or (message-options-get 'message-recipients)
 448                          (message-options-set 'message-recipients
 449                                               (read-string "Recipients: ")))
 450                      "[ \f\t\n\r\v,]+"))))
 451       (if mml-smime-verbose
 452           (setq recipients
 453                 (epa-select-keys context "\
 454 Select recipients for encryption.
 455 If no one is selected, symmetric encryption will be performed.  "
 456                                  recipients))
 457         (setq recipients
 458               (mapcar
 459                (lambda (recipient)
 460                  (setq recipient-key (mml-smime-epg-find-usable-key
 461                                       (epg-list-keys context recipient)
 462                                       'encrypt))
 463                  (unless (or recipient-key
 464                              (y-or-n-p
 465                               (format "No public key for %s; skip it? "
 466                                       recipient)))
 467                    (error "No public key for %s" recipient))
 468                  recipient-key)
 469                recipients))
 470         (unless recipients
 471           (error "No recipient specified")))
 472       (message-options-set 'mml-smime-epg-recipients recipients))
 473     (if mml-smime-cache-passphrase
 474         (epg-context-set-passphrase-callback
 475          context
 476          #'mml-smime-epg-passphrase-callback))
 477     (condition-case error
 478         (setq cipher
 479               (epg-encrypt-string context (buffer-string) recipients)
 480               mml-smime-epg-secret-key-id-list nil)
 481       (error
 482        (while mml-smime-epg-secret-key-id-list
 483          (password-cache-remove (car mml-smime-epg-secret-key-id-list))
 484          (setq mml-smime-epg-secret-key-id-list
 485                (cdr mml-smime-epg-secret-key-id-list)))
 486        (signal (car error) (cdr error))))
 487     (delete-region (point-min) (point-max))
 488     (goto-char (point-min))
 489     (insert "\
 490 Content-Type: application/pkcs7-mime;
 491  smime-type=enveloped-data;
 492  name=smime.p7m
 493 Content-Transfer-Encoding: base64
 494 Content-Disposition: attachment; filename=smime.p7m
 495
 496 ")
 497     (insert (base64-encode-string cipher))
 498     (goto-char (point-max))))
 499
 500 (defun mml-smime-epg-verify (handle ctl)
 501   (catch 'error
 502     (let ((inhibit-redisplay t)
 503           context plain signature-file part signature)
 504       (when (or (null (setq part (mm-find-raw-part-by-type
 505                                   ctl (or (mm-handle-multipart-ctl-parameter
 506                                            ctl 'protocol)
 507                                           "application/pkcs7-signature")
 508                                   t)))
 509                 (null (setq signature (mm-find-part-by-type
 510                                        (cdr handle)
 511                                        "application/pkcs7-signature"
 512                                        nil t))))
 513         (mm-set-handle-multipart-parameter
 514          mm-security-handle 'gnus-info "Corrupted")
 515         (throw 'error handle))
 516       (setq part (mm-replace-in-string part "\n" "\r\n" t)
 517             context (epg-make-context 'CMS))
 518       (condition-case error
 519           (setq plain (epg-verify-string context (mm-get-part signature) part))
 520         (error
 521          (mm-set-handle-multipart-parameter
 522           mm-security-handle 'gnus-info "Failed")
 523          (if (eq (car error) 'quit)
 524              (mm-set-handle-multipart-parameter
 525               mm-security-handle 'gnus-details "Quit.")
 526            (mm-set-handle-multipart-parameter
 527             mm-security-handle 'gnus-details (format "%S" error)))
 528          (throw 'error handle)))
 529       (mm-set-handle-multipart-parameter
 530        mm-security-handle 'gnus-info
 531        (epg-verify-result-to-string (epg-context-result-for context 'verify)))
 532       handle)))
 533
 534 (defun mml-smime-epg-verify-test (handle ctl)
 535   t)
 536
 537 (provide 'mml-smime)
 538
 539 ;;; arch-tag: f1bf94d4-f2cd-4c6f-b059-ad69492817e2
 540 ;;; mml-smime.el ends here