lisp/net/gnutls.el

   1 ;;; gnutls.el --- Support SSL/TLS connections through GnuTLS
   2
   3 ;; Copyright (C) 2010-2012 Free Software Foundation, Inc.
   4
   5 ;; Author: Ted Zlatanov <tzz@lifelogs.com>
   6 ;; Keywords: comm, tls, ssl, encryption
   7 ;; Originally-By: Simon Josefsson (See http://josefsson.org/emacs-security/)
   8 ;; Thanks-To: Lars Magne Ingebrigtsen <larsi@gnus.org>
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software: you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation, either version 3 of the License, or
  15 ;; (at your option) any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;; This package provides language bindings for the GnuTLS library
  28 ;; using the corresponding core functions in gnutls.c.  It should NOT
  29 ;; be used directly, only through open-protocol-stream.
  30
  31 ;; Simple test:
  32 ;;
  33 ;; (open-gnutls-stream "tls" "tls-buffer" "yourserver.com" "https")
  34 ;; (open-gnutls-stream "tls" "tls-buffer" "imap.gmail.com" "imaps")
  35
  36 ;;; Code:
  37
  38 (eval-when-compile (require 'cl))
  39
  40 (defgroup gnutls nil
  41   "Emacs interface to the GnuTLS library."
  42   :version "24.1"
  43   :prefix "gnutls-"
  44   :group 'net-utils)
  45
  46 (defcustom gnutls-algorithm-priority nil
  47   "If non-nil, this should be a TLS priority string.
  48 For instance, if you want to skip the \"dhe-rsa\" algorithm,
  49 set this variable to \"normal:-dhe-rsa\"."
  50   :group 'gnutls
  51   :type '(choice (const nil)
  52                  string))
  53
  54 (defcustom gnutls-trustfiles
  55   '(
  56     "/etc/ssl/certs/ca-certificates.crt" ; Debian, Ubuntu, Gentoo and Arch Linux
  57     "/etc/pki/tls/certs/ca-bundle.crt"   ; Fedora and RHEL
  58     "/etc/ssl/ca-bundle.pem"             ; Suse
  59     "/usr/ssl/cert/ca-bundle.crt"        ; Cygwin
  60     )
  61   "List of CA bundle location filenames or a function returning said list.
  62 The files may be in PEM or DER format, as per the GnuTLS documentation.
  63 The files may not exist, in which case they will be ignored."
  64   :group 'gnutls
  65   :type '(choice (function :tag "Function to produce list of bundle filenames")
  66                  (repeat (file :tag "Bundle filename"))))
  67
  68 ;;;###autoload
  69 (defcustom gnutls-min-prime-bits nil
  70   "The minimum number of bits to be used in Diffie-Hellman key exchange.
  71
  72 This sets the minimum accepted size of the key to be used in a
  73 client-server handshake.  If the server sends a prime with fewer than
  74 the specified number of bits the handshake will fail.
  75
  76 A value of nil says to use the default gnutls value."
  77   :type '(choice (const :tag "Use default value" nil)
  78                  (integer :tag "Number of bits" 512))
  79   :group 'gnutls)
  80
  81 (defun open-gnutls-stream (name buffer host service)
  82   "Open a SSL/TLS connection for a service to a host.
  83 Returns a subprocess-object to represent the connection.
  84 Input and output work as for subprocesses; `delete-process' closes it.
  85 Args are NAME BUFFER HOST SERVICE.
  86 NAME is name for process.  It is modified if necessary to make it unique.
  87 BUFFER is the buffer (or `buffer-name') to associate with the process.
  88  Process output goes at end of that buffer, unless you specify
  89  an output stream or filter function to handle the output.
  90  BUFFER may be also nil, meaning that this process is not associated
  91  with any buffer
  92 Third arg is name of the host to connect to, or its IP address.
  93 Fourth arg SERVICE is name of the service desired, or an integer
  94 specifying a port number to connect to.
  95
  96 Usage example:
  97
  98   \(with-temp-buffer
  99     \(open-gnutls-stream \"tls\"
 100                         \(current-buffer)
 101                         \"your server goes here\"
 102                         \"imaps\"))
 103
 104 This is a very simple wrapper around `gnutls-negotiate'.  See its
 105 documentation for the specific parameters you can use to open a
 106 GnuTLS connection, including specifying the credential type,
 107 trust and key files, and priority string."
 108   (gnutls-negotiate :process (open-network-stream name buffer host service)
 109                     :type 'gnutls-x509pki
 110                     :hostname host))
 111
 112 (put 'gnutls-error
 113      'error-conditions
 114      '(error gnutls-error))
 115 (put 'gnutls-error
 116      'error-message "GnuTLS error")
 117
 118 (declare-function gnutls-boot "gnutls.c" (proc type proplist))
 119 (declare-function gnutls-errorp "gnutls.c" (error))
 120
 121 (defun* gnutls-negotiate
 122     (&rest spec
 123            &key process type hostname priority-string
 124            trustfiles crlfiles keylist min-prime-bits
 125            verify-flags verify-error verify-hostname-error
 126            &allow-other-keys)
 127   "Negotiate a SSL/TLS connection.  Returns proc.  Signals gnutls-error.
 128
 129 Note arguments are passed CL style, :type TYPE instead of just TYPE.
 130
 131 TYPE is `gnutls-x509pki' (default) or `gnutls-anon'.  Use nil for the default.
 132 PROCESS is a process returned by `open-network-stream'.
 133 HOSTNAME is the remote hostname.  It must be a valid string.
 134 PRIORITY-STRING is as per the GnuTLS docs, default is \"NORMAL\".
 135 TRUSTFILES is a list of CA bundles.  It defaults to `gnutls-trustfiles'.
 136 CRLFILES is a list of CRL files.
 137 KEYLIST is an alist of (client key file, client cert file) pairs.
 138 MIN-PRIME-BITS is the minimum acceptable size of Diffie-Hellman keys
 139 \(see `gnutls-min-prime-bits' for more information).  Use nil for the
 140 default.
 141
 142 When VERIFY-HOSTNAME-ERROR is not nil, an error will be raised
 143 when the hostname does not match the presented certificate's host
 144 name.  The exact verification algorithm is a basic implementation
 145 of the matching described in RFC2818 (HTTPS), which takes into
 146 account wildcards, and the DNSName/IPAddress subject alternative
 147 name PKIX extension.  See GnuTLS' gnutls_x509_crt_check_hostname
 148 for details.  When VERIFY-HOSTNAME-ERROR is nil, only a warning
 149 will be issued.
 150
 151 When VERIFY-ERROR is not nil, an error will be raised when the
 152 peer certificate verification fails as per GnuTLS'
 153 gnutls_certificate_verify_peers2.  Otherwise, only warnings will
 154 be shown about the verification failure.
 155
 156 VERIFY-FLAGS is a numeric OR of verification flags only for
 157 `gnutls-x509pki' connections.  See GnuTLS' x509.h for details;
 158 here's a recent version of the list.
 159
 160     GNUTLS_VERIFY_DISABLE_CA_SIGN = 1,
 161     GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT = 2,
 162     GNUTLS_VERIFY_DO_NOT_ALLOW_SAME = 4,
 163     GNUTLS_VERIFY_ALLOW_ANY_X509_V1_CA_CRT = 8,
 164     GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD2 = 16,
 165     GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5 = 32,
 166     GNUTLS_VERIFY_DISABLE_TIME_CHECKS = 64,
 167     GNUTLS_VERIFY_DISABLE_TRUSTED_TIME_CHECKS = 128,
 168     GNUTLS_VERIFY_DO_NOT_ALLOW_X509_V1_CA_CRT = 256
 169
 170 It must be omitted, a number, or nil; if omitted or nil it
 171 defaults to GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT."
 172   (let* ((type (or type 'gnutls-x509pki))
 173          (trustfiles (or trustfiles
 174                          (delq nil
 175                                (mapcar (lambda (f) (and f (file-exists-p f) f))
 176                                        (if (functionp gnutls-trustfiles)
 177                                            (funcall gnutls-trustfiles)
 178                                          gnutls-trustfiles)))))
 179          (priority-string (or priority-string
 180                               (cond
 181                                ((eq type 'gnutls-anon)
 182                                 "NORMAL:+ANON-DH:!ARCFOUR-128")
 183                                ((eq type 'gnutls-x509pki)
 184                                 (if gnutls-algorithm-priority
 185                                     (upcase gnutls-algorithm-priority)
 186                                   "NORMAL")))))
 187          (min-prime-bits (or min-prime-bits gnutls-min-prime-bits))
 188          (params `(:priority ,priority-string
 189                              :hostname ,hostname
 190                              :loglevel ,gnutls-log-level
 191                              :min-prime-bits ,min-prime-bits
 192                              :trustfiles ,trustfiles
 193                              :crlfiles ,crlfiles
 194                              :keylist ,keylist
 195                              :verify-flags ,verify-flags
 196                              :verify-error ,verify-error
 197                              :verify-hostname-error ,verify-hostname-error
 198                              :callbacks nil))
 199          ret)
 200
 201     (gnutls-message-maybe
 202      (setq ret (gnutls-boot process type params))
 203      "boot: %s" params)
 204
 205     (when (gnutls-errorp ret)
 206       ;; This is a error from the underlying C code.
 207       (signal 'gnutls-error (list process ret)))
 208
 209     process))
 210
 211 (declare-function gnutls-error-string "gnutls.c" (error))
 212
 213 (defun gnutls-message-maybe (doit format &rest params)
 214   "When DOIT, message with the caller name followed by FORMAT on PARAMS."
 215   ;; (apply 'debug format (or params '(nil)))
 216   (when (gnutls-errorp doit)
 217     (message "%s: (err=[%s] %s) %s"
 218              "gnutls.el"
 219              doit (gnutls-error-string doit)
 220              (apply 'format format (or params '(nil))))))
 221
 222 (provide 'gnutls)
 223
 224 ;;; gnutls.el ends here