src/src/tls.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2009 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* This module provides TLS (aka SSL) support for Exim. The code for OpenSSL is
   9 based on a patch that was originally contributed by Steve Haslam. It was
  10 adapted from stunnel, a GPL program by Michal Trojnara. The code for GNU TLS is
  11 based on a patch contributed by Nikos Mavroyanopoulos. Because these packages
  12 are so very different, the functions for each are kept in separate files. The
  13 relevant file is #included as required, after any any common functions.
  14
  15 No cryptographic code is included in Exim. All this module does is to call
  16 functions from the OpenSSL or GNU TLS libraries. */
  17
  18
  19 #include "exim.h"
  20
  21 /* This module is compiled only when it is specifically requested in the
  22 build-time configuration. However, some compilers don't like compiling empty
  23 modules, so keep them happy with a dummy when skipping the rest. Make it
  24 reference itself to stop picky compilers complaining that it is unused, and put
  25 in a dummy argument to stop even pickier compilers complaining about infinite
  26 loops. */
  27
  28 #ifndef SUPPORT_TLS
  29 static void dummy(int x) { dummy(x-1); }
  30 #else
  31
  32 /* Static variables that are used for buffering data by both sets of
  33 functions and the common functions below. */
  34
  35
  36 static uschar *ssl_xfer_buffer = NULL;
  37 static int ssl_xfer_buffer_size = 4096;
  38 static int ssl_xfer_buffer_lwm = 0;
  39 static int ssl_xfer_buffer_hwm = 0;
  40 static int ssl_xfer_eof = 0;
  41 static int ssl_xfer_error = 0;
  42
  43 uschar *tls_channelbinding_b64 = NULL;
  44
  45
  46 /*************************************************
  47 *       Expand string; give error on failure     *
  48 *************************************************/
  49
  50 /* If expansion is forced to fail, set the result NULL and return TRUE.
  51 Other failures return FALSE. For a server, an SMTP response is given.
  52
  53 Arguments:
  54   s         the string to expand; if NULL just return TRUE
  55   name      name of string being expanded (for error)
  56   result    where to put the result
  57
  58 Returns:    TRUE if OK; result may still be NULL after forced failure
  59 */
  60
  61 static BOOL
  62 expand_check(uschar *s, uschar *name, uschar **result)
  63 {
  64 if (s == NULL) *result = NULL; else
  65   {
  66   *result = expand_string(s);
  67   if (*result == NULL && !expand_string_forcedfail)
  68     {
  69     log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
  70       expand_string_message);
  71     return FALSE;
  72     }
  73   }
  74 return TRUE;
  75 }
  76
  77
  78 /*************************************************
  79 *        Many functions are package-specific     *
  80 *************************************************/
  81
  82 #ifdef USE_GNUTLS
  83 #include "tls-gnu.c"
  84 #else
  85 #include "tls-openssl.c"
  86 #endif
  87
  88
  89
  90 /*************************************************
  91 *           TLS version of ungetc                *
  92 *************************************************/
  93
  94 /* Puts a character back in the input buffer. Only ever
  95 called once.
  96
  97 Arguments:
  98   ch           the character
  99
 100 Returns:       the character
 101 */
 102
 103 int
 104 tls_ungetc(int ch)
 105 {
 106 ssl_xfer_buffer[--ssl_xfer_buffer_lwm] = ch;
 107 return ch;
 108 }
 109
 110
 111
 112 /*************************************************
 113 *           TLS version of feof                  *
 114 *************************************************/
 115
 116 /* Tests for a previous EOF
 117
 118 Arguments:     none
 119 Returns:       non-zero if the eof flag is set
 120 */
 121
 122 int
 123 tls_feof(void)
 124 {
 125 return ssl_xfer_eof;
 126 }
 127
 128
 129
 130 /*************************************************
 131 *              TLS version of ferror             *
 132 *************************************************/
 133
 134 /* Tests for a previous read error, and returns with errno
 135 restored to what it was when the error was detected.
 136
 137 >>>>> Hmm. Errno not handled yet. Where do we get it from?  >>>>>
 138
 139 Arguments:     none
 140 Returns:       non-zero if the error flag is set
 141 */
 142
 143 int
 144 tls_ferror(void)
 145 {
 146 return ssl_xfer_error;
 147 }
 148
 149
 150 /*************************************************
 151 *           TLS version of smtp_buffered         *
 152 *************************************************/
 153
 154 /* Tests for unused chars in the TLS input buffer.
 155
 156 Arguments:     none
 157 Returns:       TRUE/FALSE
 158 */
 159
 160 BOOL
 161 tls_smtp_buffered(void)
 162 {
 163 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm;
 164 }
 165
 166
 167 #endif  /* SUPPORT_TLS */
 168
 169 /* End of tls.c */