lisp/net/tls.el

   1 ;;; tls.el --- TLS/SSL support via wrapper around GnuTLS
   2
   3 ;; Copyright (C) 1996, 1997, 1998, 1999, 2002, 2003, 2004, 2005, 2006,
   4 ;;   2007, 2008, 2009, 2010, 2011  Free Software Foundation, Inc.
   5
   6 ;; Author: Simon Josefsson <simon@josefsson.org>
   7 ;; Keywords: comm, tls, gnutls, ssl
   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 ;; This package implements a simple wrapper around "gnutls-cli" to
  27 ;; make Emacs support TLS/SSL.
  28 ;;
  29 ;; Usage is the same as `open-network-stream', i.e.:
  30 ;;
  31 ;; (setq tmp (open-tls-stream "test" (current-buffer) "news.mozilla.org" 563))
  32 ;; ...
  33 ;; #<process test>
  34 ;; (process-send-string tmp "mode reader\n")
  35 ;; 200 secnews.netscape.com Netscape-Collabra/3.52 03615 NNRP ready ...
  36 ;; nil
  37 ;; (process-send-string tmp "quit\n")
  38 ;; 205
  39 ;; nil
  40
  41 ;; To use this package as a replacement for ssl.el by William M. Perry
  42 ;; <wmperry@cs.indiana.edu>, you need to evaluate the following:
  43 ;;
  44 ;; (defalias 'open-ssl-stream 'open-tls-stream)
  45
  46 ;;; Code:
  47
  48 (autoload 'format-spec "format-spec")
  49 (autoload 'format-spec-make "format-spec")
  50
  51 (defgroup tls nil
  52   "Transport Layer Security (TLS) parameters."
  53   :group 'comm)
  54
  55 (defcustom tls-end-of-info
  56   (concat
  57    "\\("
  58    ;; `openssl s_client' regexp.  See ssl/ssl_txt.c lines 219-220.
  59    ;; According to apps/s_client.c line 1515 `---' is always the last
  60    ;; line that is printed by s_client before the real data.
  61    "^    Verify return code: .+\n---\n\\|"
  62    ;; `gnutls' regexp. See src/cli.c lines 721-.
  63    "^- Simple Client Mode:\n"
  64    "\\(\n\\|"                           ; ignore blank lines
  65    ;; According to GnuTLS v2.1.5 src/cli.c lines 640-650 and 705-715
  66    ;; in `main' the handshake will start after this message.  If the
  67    ;; handshake fails, the programs will abort.
  68    "^\\*\\*\\* Starting TLS handshake\n\\)*"
  69    "\\)")
  70   "Regexp matching end of TLS client informational messages.
  71 Client data stream begins after the last character matched by
  72 this.  The default matches `openssl s_client' (version 0.9.8c)
  73 and `gnutls-cli' (version 2.0.1) output."
  74   :version "22.2"
  75   :type 'regexp
  76   :group 'tls)
  77
  78 (defcustom tls-program '("gnutls-cli -p %p %h"
  79                          "gnutls-cli -p %p %h --protocols ssl3"
  80                          "openssl s_client -connect %h:%p -no_ssl2 -ign_eof")
  81   "List of strings containing commands to start TLS stream to a host.
  82 Each entry in the list is tried until a connection is successful.
  83 %h is replaced with server hostname, %p with port to connect to.
  84 The program should read input on stdin and write output to
  85 stdout.
  86
  87 See `tls-checktrust' on how to check trusted root certs.
  88
  89 Also see `tls-success' for what the program should output after
  90 successful negotiation."
  91   :type
  92   '(choice
  93     (list :tag "Choose commands"
  94           :value
  95           ("gnutls-cli -p %p %h"
  96            "gnutls-cli -p %p %h --protocols ssl3"
  97            "openssl s_client -connect %h:%p -no_ssl2 -ign_eof")
  98           (set :inline t
  99                ;; FIXME: add brief `:tag "..."' descriptions.
 100                ;; (repeat :inline t :tag "Other" (string))
 101                ;; See `tls-checktrust':
 102                (const "gnutls-cli --x509cafile /etc/ssl/certs/ca-certificates.crt -p %p %h")
 103                (const "gnutls-cli --x509cafile /etc/ssl/certs/ca-certificates.crt -p %p %h --protocols ssl3")
 104                (const "openssl s_client -connect %h:%p -CAfile /etc/ssl/certs/ca-certificates.crt -no_ssl2 -ign_eof")
 105                ;; No trust check:
 106                (const "gnutls-cli -p %p %h")
 107                (const "gnutls-cli -p %p %h --protocols ssl3")
 108                (const "openssl s_client -connect %h:%p -no_ssl2 -ign_eof"))
 109           (repeat :inline t :tag "Other" (string)))
 110     (const :tag "Default list of commands"
 111            ("gnutls-cli -p %p %h"
 112             "gnutls-cli -p %p %h --protocols ssl3"
 113             "openssl s_client -connect %h:%p -no_ssl2 -ign_eof"))
 114     (list :tag "List of commands"
 115           (repeat :tag "Command" (string))))
 116   :version "22.1"
 117   :group 'tls)
 118
 119 (defcustom tls-process-connection-type nil
 120   "Value for `process-connection-type' to use when starting TLS process."
 121   :version "22.1"
 122   :type 'boolean
 123   :group 'tls)
 124
 125 (defcustom tls-success "- Handshake was completed\\|SSL handshake has read "
 126   "Regular expression indicating completed TLS handshakes.
 127 The default is what GNUTLS's \"gnutls-cli\" or OpenSSL's
 128 \"openssl s_client\" outputs."
 129   :version "22.1"
 130   :type 'regexp
 131   :group 'tls)
 132
 133 (defcustom tls-checktrust nil
 134   "Indicate if certificates should be checked against trusted root certs.
 135 If this is `ask', the user can decide whether to accept an
 136 untrusted certificate.  You may have to adapt `tls-program' in
 137 order to make this feature work properly, i.e., to ensure that
 138 the external program knows about the root certificates you
 139 consider trustworthy, e.g.:
 140
 141 \(setq tls-program
 142       '(\"gnutls-cli --x509cafile /etc/ssl/certs/ca-certificates.crt -p %p %h\"
 143         \"gnutls-cli --x509cafile /etc/ssl/certs/ca-certificates.crt -p %p %h --protocols ssl3\"
 144         \"openssl s_client -connect %h:%p -CAfile /etc/ssl/certs/ca-certificates.crt -no_ssl2 -ign_eof\"))"
 145   :type '(choice (const :tag "Always" t)
 146                  (const :tag "Never" nil)
 147                  (const :tag "Ask" ask))
 148   :version "23.1" ;; No Gnus
 149   :group 'tls)
 150
 151 (defcustom tls-untrusted
 152   "- Peer's certificate is NOT trusted\\|Verify return code: \\([^0] \\|.[^ ]\\)"
 153   "Regular expression indicating failure of TLS certificate verification.
 154 The default is what GNUTLS's \"gnutls-cli\" or OpenSSL's
 155 \"openssl s_client\" return in the event of unsuccessful
 156 verification."
 157   :type 'regexp
 158   :version "23.1" ;; No Gnus
 159   :group 'tls)
 160
 161 (defcustom tls-hostmismatch
 162   "# The hostname in the certificate does NOT match"
 163   "Regular expression indicating a host name mismatch in certificate.
 164 When the host name specified in the certificate doesn't match the
 165 name of the host you are connecting to, gnutls-cli issues a
 166 warning to this effect.  There is no such feature in openssl.  Set
 167 this to nil if you want to ignore host name mismatches."
 168   :type 'regexp
 169   :version "23.1" ;; No Gnus
 170   :group 'tls)
 171
 172 (defcustom tls-certtool-program (executable-find "certtool")
 173   "Name of  GnuTLS certtool.
 174 Used by `tls-certificate-information'."
 175   :version "22.1"
 176   :type 'string
 177   :group 'tls)
 178
 179 (defun tls-certificate-information (der)
 180   "Parse X.509 certificate in DER format into an assoc list."
 181   (let ((certificate (concat "-----BEGIN CERTIFICATE-----\n"
 182                              (base64-encode-string der)
 183                              "\n-----END CERTIFICATE-----\n"))
 184         (exit-code 0))
 185     (with-current-buffer (get-buffer-create " *certtool*")
 186       (erase-buffer)
 187       (insert certificate)
 188       (setq exit-code (condition-case ()
 189                           (call-process-region (point-min) (point-max)
 190                                                tls-certtool-program
 191                                                t (list (current-buffer) nil) t
 192                                                "--certificate-info")
 193                         (error -1)))
 194       (if (/= exit-code 0)
 195           nil
 196         (let ((vals nil))
 197           (goto-char (point-min))
 198           (while (re-search-forward "^\\([^:]+\\): \\(.*\\)" nil t)
 199             (push (cons (match-string 1) (match-string 2)) vals))
 200           (nreverse vals))))))
 201
 202 (defun open-tls-stream (name buffer host port)
 203   "Open a TLS connection for a port to a host.
 204 Returns a subprocess-object to represent the connection.
 205 Input and output work as for subprocesses; `delete-process' closes it.
 206 Args are NAME BUFFER HOST PORT.
 207 NAME is name for process.  It is modified if necessary to make it unique.
 208 BUFFER is the buffer (or buffer name) to associate with the process.
 209  Process output goes at end of that buffer, unless you specify
 210  an output stream or filter function to handle the output.
 211  BUFFER may be also nil, meaning that this process is not associated
 212  with any buffer
 213 Third arg is name of the host to connect to, or its IP address.
 214 Fourth arg PORT is an integer specifying a port to connect to."
 215   (let ((cmds tls-program)
 216         (use-temp-buffer (null buffer))
 217         process cmd done)
 218     (if use-temp-buffer
 219         (setq buffer (generate-new-buffer " TLS"))
 220       ;; BUFFER is a string but does not exist as a buffer object.
 221       (unless (and (get-buffer buffer)
 222                    (buffer-name (get-buffer buffer)))
 223         (generate-new-buffer buffer)))
 224     (with-current-buffer buffer
 225       (message "Opening TLS connection to `%s'..." host)
 226       (while (and (not done) (setq cmd (pop cmds)))
 227         (let ((process-connection-type tls-process-connection-type)
 228               (formatted-cmd
 229                (format-spec
 230                 cmd
 231                 (format-spec-make
 232                  ?h host
 233                  ?p (if (integerp port)
 234                         (int-to-string port)
 235                       port))))
 236               response)
 237           (message "Opening TLS connection with `%s'..." formatted-cmd)
 238           (setq process (start-process
 239                          name buffer shell-file-name shell-command-switch
 240                          formatted-cmd))
 241           (while (and process
 242                       (memq (process-status process) '(open run))
 243                       (progn
 244                         (goto-char (point-min))
 245                         (not (setq done (re-search-forward
 246                                          tls-success nil t)))))
 247             (unless (accept-process-output process 1)
 248               (sit-for 1)))
 249           (message "Opening TLS connection with `%s'...%s" formatted-cmd
 250                    (if done "done" "failed"))
 251           (if (not done)
 252               (delete-process process)
 253             ;; advance point to after all informational messages that
 254             ;; `openssl s_client' and `gnutls' print
 255             (let ((start-of-data nil))
 256               (while
 257                   (not (setq start-of-data
 258                              ;; the string matching `tls-end-of-info'
 259                              ;; might come in separate chunks from
 260                              ;; `accept-process-output', so start the
 261                              ;; search where `tls-success' ended
 262                              (save-excursion
 263                                (if (re-search-forward tls-end-of-info nil t)
 264                                    (match-end 0)))))
 265                 (accept-process-output process 1))
 266               (if start-of-data
 267                   ;; move point to start of client data
 268                   (goto-char start-of-data)))
 269             (setq done process))))
 270       (when (and done
 271                  (or
 272                   (and tls-checktrust
 273                        (save-excursion
 274                          (goto-char (point-min))
 275                          (re-search-forward tls-untrusted nil t))
 276                        (or
 277                         (and (not (eq tls-checktrust 'ask))
 278                              (message "The certificate presented by `%s' is \
 279 NOT trusted." host))
 280                         (not (yes-or-no-p
 281                               (format "The certificate presented by `%s' is \
 282 NOT trusted. Accept anyway? " host)))))
 283                   (and tls-hostmismatch
 284                        (save-excursion
 285                          (goto-char (point-min))
 286                          (re-search-forward tls-hostmismatch nil t))
 287                        (not (yes-or-no-p
 288                              (format "Host name in certificate doesn't \
 289 match `%s'. Connect anyway? " host))))))
 290         (setq done nil)
 291         (delete-process process)))
 292     (message "Opening TLS connection to `%s'...%s"
 293              host (if done "done" "failed"))
 294     (when use-temp-buffer
 295       (if done (set-process-buffer process nil))
 296       (kill-buffer buffer))
 297     done))
 298
 299 (provide 'tls)
 300
 301 ;; arch-tag: 5596d1c4-facc-4bc4-94a9-9863b928d7ac
 302 ;;; tls.el ends here