lisp/net/tls.el

   1 ;;; tls.el --- TLS/SSL support via wrapper around GnuTLS
   2
   3 ;; Copyright (C) 1996-1999, 2002-2017 Free Software Foundation, Inc.
   4
   5 ;; Author: Simon Josefsson <simon@josefsson.org>
   6 ;; Keywords: comm, tls, gnutls, ssl
   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 ;; This package implements a simple wrapper around "gnutls-cli" to
  26 ;; make Emacs support TLS/SSL.
  27 ;;
  28 ;; Usage is the same as `open-network-stream', i.e.:
  29 ;;
  30 ;; (setq tmp (open-tls-stream "test" (current-buffer) "news.mozilla.org" 563))
  31 ;; ...
  32 ;; #<process test>
  33 ;; (process-send-string tmp "mode reader\n")
  34 ;; 200 secnews.netscape.com Netscape-Collabra/3.52 03615 NNRP ready ...
  35 ;; nil
  36 ;; (process-send-string tmp "quit\n")
  37 ;; 205
  38 ;; nil
  39
  40 ;; To use this package as a replacement for ssl.el by William M. Perry
  41 ;; <wmperry@cs.indiana.edu>, you need to evaluate the following:
  42 ;;
  43 ;; (defalias 'open-ssl-stream 'open-tls-stream)
  44
  45 ;;; Code:
  46
  47 (require 'gnutls)
  48
  49 (autoload 'format-spec "format-spec")
  50 (autoload 'format-spec-make "format-spec")
  51
  52 (defgroup tls nil
  53   "Transport Layer Security (TLS) parameters."
  54   :group 'comm)
  55
  56 (defcustom tls-end-of-info
  57   (concat
  58    "\\("
  59    ;; `openssl s_client' regexp.  See ssl/ssl_txt.c lines 219-220.
  60    ;; According to apps/s_client.c line 1515 `---' is always the last
  61    ;; line that is printed by s_client before the real data.
  62    "^    Verify return code: .+\n---\n\\|"
  63    ;; `gnutls' regexp. See src/cli.c lines 721-.
  64    "^- Simple Client Mode:\n"
  65    "\\(\n\\|"                           ; ignore blank lines
  66    ;; According to GnuTLS v2.1.5 src/cli.c lines 640-650 and 705-715
  67    ;; in `main' the handshake will start after this message.  If the
  68    ;; handshake fails, the programs will abort.
  69    "^\\*\\*\\* Starting TLS handshake\n\\)*"
  70    "\\)")
  71   "Regexp matching end of TLS client informational messages.
  72 Client data stream begins after the last character matched by
  73 this.  The default matches `openssl s_client' (version 0.9.8c)
  74 and `gnutls-cli' (version 2.0.1) output."
  75   :version "22.2"
  76   :type 'regexp
  77   :group 'tls)
  78
  79 (defcustom tls-program
  80   '("gnutls-cli --x509cafile %t -p %p %h"
  81     "gnutls-cli --x509cafile %t -p %p %h --protocols ssl3"
  82     "openssl s_client -connect %h:%p -no_ssl2 -ign_eof")
  83   "List of strings containing commands to start TLS stream to a host.
  84 Each entry in the list is tried until a connection is successful.
  85 %h is replaced with the server hostname, %p with the port to
  86 connect to, and %t with a file name containing trusted certificates.
  87 The program should read input on stdin and write output to stdout.
  88
  89 See `tls-checktrust' on how to check trusted root certs.
  90
  91 Also see `tls-success' for what the program should output after
  92 successful negotiation."
  93   :type
  94   '(choice
  95     (const :tag "Default list of commands"
  96            ("gnutls-cli --x509cafile %t -p %p %h"
  97             "gnutls-cli --x509cafile %t -p %p %h --protocols ssl3"
  98             "openssl s_client -CAfile %t -connect %h:%p -no_ssl2 -ign_eof"))
  99     (list :tag "Choose commands"
 100           :value
 101           ("gnutls-cli --x509cafile %t -p %p %h"
 102            "gnutls-cli --x509cafile %t -p %p %h --protocols ssl3"
 103            "openssl s_client -connect %h:%p -no_ssl2 -ign_eof")
 104           (set :inline t
 105                ;; FIXME: add brief `:tag "..."' descriptions.
 106                ;; (repeat :inline t :tag "Other" (string))
 107                ;; No trust check:
 108                (const "gnutls-cli --insecure -p %p %h")
 109                (const "gnutls-cli --insecure -p %p %h --protocols ssl3")
 110                (const "openssl s_client -connect %h:%p -no_ssl2 -ign_eof"))
 111           (repeat :inline t :tag "Other" (string)))
 112     (list :tag "List of commands"
 113           (repeat :tag "Command" (string))))
 114   :version "22.1"
 115   :group 'tls)
 116
 117 (defcustom tls-process-connection-type nil
 118   "Value for `process-connection-type' to use when starting TLS process."
 119   :version "22.1"
 120   :type 'boolean
 121   :group 'tls)
 122
 123 (defcustom tls-success "- Handshake was completed\\|SSL handshake has read "
 124   "Regular expression indicating completed TLS handshakes.
 125 The default is what GnuTLS's \"gnutls-cli\" or OpenSSL's
 126 \"openssl s_client\" outputs."
 127   :version "22.1"
 128   :type 'regexp
 129   :group 'tls)
 130
 131 (defcustom tls-checktrust nil
 132   "Indicate if certificates should be checked against trusted root certs.
 133 If this is `ask', the user can decide whether to accept an
 134 untrusted certificate.  You may have to adapt `tls-program' in
 135 order to make this feature work properly, i.e., to ensure that
 136 the external program knows about the root certificates you
 137 consider trustworthy, e.g.:
 138
 139 \(setq tls-program
 140       \\='(\"gnutls-cli --x509cafile /etc/ssl/certs/ca-certificates.crt -p %p %h\"
 141         \"gnutls-cli --x509cafile /etc/ssl/certs/ca-certificates.crt -p %p %h --protocols ssl3\"
 142         \"openssl s_client -connect %h:%p -CAfile /etc/ssl/certs/ca-certificates.crt -no_ssl2 -ign_eof\"))"
 143   :type '(choice (const :tag "Always" t)
 144                  (const :tag "Never" nil)
 145                  (const :tag "Ask" ask))
 146   :version "23.1" ;; No Gnus
 147   :group 'tls)
 148
 149 (defcustom tls-untrusted
 150   "- Peer's certificate is NOT trusted\\|Verify return code: \\([^0] \\|.[^ ]\\)"
 151   "Regular expression indicating failure of TLS certificate verification.
 152 The default is what GnuTLS's \"gnutls-cli\" or OpenSSL's
 153 \"openssl s_client\" return in the event of unsuccessful
 154 verification."
 155   :type 'regexp
 156   :version "23.1" ;; No Gnus
 157   :group 'tls)
 158
 159 (defcustom tls-hostmismatch
 160   "# The hostname in the certificate does NOT match"
 161   "Regular expression indicating a host name mismatch in certificate.
 162 When the host name specified in the certificate doesn't match the
 163 name of the host you are connecting to, gnutls-cli issues a
 164 warning to this effect.  There is no such feature in openssl.  Set
 165 this to nil if you want to ignore host name mismatches."
 166   :type 'regexp
 167   :version "23.1" ;; No Gnus
 168   :group 'tls)
 169
 170 (defcustom tls-certtool-program "certtool"
 171   "Name of GnuTLS certtool.
 172 Used by `tls-certificate-information'."
 173   :version "22.1"
 174   :type 'string
 175   :group 'tls)
 176
 177 (defalias 'tls-format-message
 178   (if (fboundp 'format-message) 'format-message
 179     ;; for Emacs < 25, and XEmacs, don't worry about quote translation.
 180     'format))
 181
 182 (defun tls-certificate-information (der)
 183   "Parse X.509 certificate in DER format into an assoc list."
 184   (let ((certificate (concat "-----BEGIN CERTIFICATE-----\n"
 185                              (base64-encode-string der)
 186                              "\n-----END CERTIFICATE-----\n"))
 187         (exit-code 0))
 188     (with-current-buffer (get-buffer-create " *certtool*")
 189       (erase-buffer)
 190       (insert certificate)
 191       (setq exit-code (condition-case ()
 192                           (call-process-region (point-min) (point-max)
 193                                                tls-certtool-program
 194                                                t (list (current-buffer) nil) t
 195                                                "--certificate-info")
 196                         (error -1)))
 197       (if (/= exit-code 0)
 198           nil
 199         (let ((vals nil))
 200           (goto-char (point-min))
 201           (while (re-search-forward "^\\([^:]+\\): \\(.*\\)" nil t)
 202             (push (cons (match-string 1) (match-string 2)) vals))
 203           (nreverse vals))))))
 204
 205 (defun open-tls-stream (name buffer host port)
 206   "Open a TLS connection for a port to a host.
 207 Returns a subprocess-object to represent the connection.
 208 Input and output work as for subprocesses; `delete-process' closes it.
 209 Args are NAME BUFFER HOST PORT.
 210 NAME is name for process.  It is modified if necessary to make it unique.
 211 BUFFER is the buffer (or buffer name) to associate with the process.
 212  Process output goes at end of that buffer, unless you specify
 213  an output stream or filter function to handle the output.
 214  BUFFER may be also nil, meaning that this process is not associated
 215  with any buffer
 216 Third arg is name of the host to connect to, or its IP address.
 217 Fourth arg PORT is an integer specifying a port to connect to."
 218   (let ((cmds tls-program)
 219         (use-temp-buffer (null buffer))
 220         process cmd done)
 221     (if use-temp-buffer
 222         (setq buffer (generate-new-buffer " TLS"))
 223       ;; BUFFER is a string but does not exist as a buffer object.
 224       (unless (and (get-buffer buffer)
 225                    (buffer-name (get-buffer buffer)))
 226         (generate-new-buffer buffer)))
 227     (with-current-buffer buffer
 228       (message "Opening TLS connection to `%s'..." host)
 229       (while (and (not done) (setq cmd (pop cmds)))
 230         (let ((process-connection-type tls-process-connection-type)
 231               (formatted-cmd
 232                (format-spec
 233                 cmd
 234                 (format-spec-make
 235                  ?t (car (gnutls-trustfiles))
 236                  ?h host
 237                  ?p (if (integerp port)
 238                         (int-to-string port)
 239                       port)))))
 240           (message "Opening TLS connection with `%s'..." formatted-cmd)
 241           (setq process (start-process
 242                          name buffer shell-file-name shell-command-switch
 243                          formatted-cmd))
 244           (while (and process
 245                       (memq (process-status process) '(open run))
 246                       (progn
 247                         (goto-char (point-min))
 248                         (not (setq done (re-search-forward
 249                                          tls-success nil t)))))
 250             (unless (accept-process-output process 1)
 251               (sit-for 1)))
 252           (message "Opening TLS connection with `%s'...%s" formatted-cmd
 253                    (if done "done" "failed"))
 254           (if (not done)
 255               (delete-process process)
 256             ;; advance point to after all informational messages that
 257             ;; `openssl s_client' and `gnutls' print
 258             (let ((start-of-data nil))
 259               (while
 260                   (not (setq start-of-data
 261                              ;; the string matching `tls-end-of-info'
 262                              ;; might come in separate chunks from
 263                              ;; `accept-process-output', so start the
 264                              ;; search where `tls-success' ended
 265                              (save-excursion
 266                                (if (re-search-forward tls-end-of-info nil t)
 267                                    (match-end 0)))))
 268                 (accept-process-output process 1))
 269               (if start-of-data
 270                   ;; move point to start of client data
 271                   (goto-char start-of-data)))
 272             (setq done process))))
 273       (when (and done
 274                  (or
 275                   (and tls-checktrust
 276                        (save-excursion
 277                          (goto-char (point-min))
 278                          (re-search-forward tls-untrusted nil t))
 279                        (or
 280                         (and (not (eq tls-checktrust 'ask))
 281                              (message "The certificate presented by `%s' is \
 282 NOT trusted." host))
 283                         (not (yes-or-no-p
 284                               (tls-format-message "\
 285 The certificate presented by `%s' is NOT trusted. Accept anyway? " host)))))
 286                   (and tls-hostmismatch
 287                        (save-excursion
 288                          (goto-char (point-min))
 289                          (re-search-forward tls-hostmismatch nil t))
 290                        (not (yes-or-no-p
 291                              (format "Host name in certificate doesn't \
 292 match `%s'. Connect anyway? " host))))))
 293         (setq done nil)
 294         (delete-process process))
 295       ;; Delete all the informational messages that could confuse
 296       ;; future uses of `buffer'.
 297       (delete-region (point-min) (point)))
 298     (message "Opening TLS connection to `%s'...%s"
 299              host (if done "done" "failed"))
 300     (when use-temp-buffer
 301       (if done (set-process-buffer process nil))
 302       (kill-buffer buffer))
 303     done))
 304
 305 (provide 'tls)
 306
 307 ;;; tls.el ends here