src/src/tls.c

   1 /* $Cambridge: exim/src/src/tls.c,v 1.6 2009/11/16 19:50:37 nm4 Exp $ */
   2
   3 /*************************************************
   4 *     Exim - an Internet mail transport agent    *
   5 *************************************************/
   6
   7 /* Copyright (c) University of Cambridge 1995 - 2009 */
   8 /* See the file NOTICE for conditions of use and distribution. */
   9
  10 /* This module provides TLS (aka SSL) support for Exim. The code for OpenSSL is
  11 based on a patch that was originally contributed by Steve Haslam. It was
  12 adapted from stunnel, a GPL program by Michal Trojnara. The code for GNU TLS is
  13 based on a patch contributed by Nikos Mavroyanopoulos. Because these packages
  14 are so very different, the functions for each are kept in separate files. The
  15 relevant file is #included as required, after any any common functions.
  16
  17 No cryptographic code is included in Exim. All this module does is to call
  18 functions from the OpenSSL or GNU TLS libraries. */
  19
  20
  21 #include "exim.h"
  22
  23 /* This module is compiled only when it is specifically requested in the
  24 build-time configuration. However, some compilers don't like compiling empty
  25 modules, so keep them happy with a dummy when skipping the rest. Make it
  26 reference itself to stop picky compilers complaining that it is unused, and put
  27 in a dummy argument to stop even pickier compilers complaining about infinite
  28 loops. */
  29
  30 #ifndef SUPPORT_TLS
  31 static void dummy(int x) { dummy(x-1); }
  32 #else
  33
  34 /* Static variables that are used for buffering data by both sets of
  35 functions and the common functions below. */
  36
  37
  38 static uschar *ssl_xfer_buffer = NULL;
  39 static int ssl_xfer_buffer_size = 4096;
  40 static int ssl_xfer_buffer_lwm = 0;
  41 static int ssl_xfer_buffer_hwm = 0;
  42 static int ssl_xfer_eof = 0;
  43 static int ssl_xfer_error = 0;
  44
  45
  46
  47 /*************************************************
  48 *       Expand string; give error on failure     *
  49 *************************************************/
  50
  51 /* If expansion is forced to fail, set the result NULL and return TRUE.
  52 Other failures return FALSE. For a server, an SMTP response is given.
  53
  54 Arguments:
  55   s         the string to expand; if NULL just return TRUE
  56   name      name of string being expanded (for error)
  57   result    where to put the result
  58
  59 Returns:    TRUE if OK; result may still be NULL after forced failure
  60 */
  61
  62 static BOOL
  63 expand_check(uschar *s, uschar *name, uschar **result)
  64 {
  65 if (s == NULL) *result = NULL; else
  66   {
  67   *result = expand_string(s);
  68   if (*result == NULL && !expand_string_forcedfail)
  69     {
  70     log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
  71       expand_string_message);
  72     return FALSE;
  73     }
  74   }
  75 return TRUE;
  76 }
  77
  78
  79 /*************************************************
  80 *        Many functions are package-specific     *
  81 *************************************************/
  82
  83 #ifdef USE_GNUTLS
  84 #include "tls-gnu.c"
  85 #else
  86 #include "tls-openssl.c"
  87 #endif
  88
  89
  90
  91 /*************************************************
  92 *           TLS version of ungetc                *
  93 *************************************************/
  94
  95 /* Puts a character back in the input buffer. Only ever
  96 called once.
  97
  98 Arguments:
  99   ch           the character
 100
 101 Returns:       the character
 102 */
 103
 104 int
 105 tls_ungetc(int ch)
 106 {
 107 ssl_xfer_buffer[--ssl_xfer_buffer_lwm] = ch;
 108 return ch;
 109 }
 110
 111
 112
 113 /*************************************************
 114 *           TLS version of feof                  *
 115 *************************************************/
 116
 117 /* Tests for a previous EOF
 118
 119 Arguments:     none
 120 Returns:       non-zero if the eof flag is set
 121 */
 122
 123 int
 124 tls_feof(void)
 125 {
 126 return ssl_xfer_eof;
 127 }
 128
 129
 130
 131 /*************************************************
 132 *              TLS version of ferror             *
 133 *************************************************/
 134
 135 /* Tests for a previous read error, and returns with errno
 136 restored to what it was when the error was detected.
 137
 138 >>>>> Hmm. Errno not handled yet. Where do we get it from?  >>>>>
 139
 140 Arguments:     none
 141 Returns:       non-zero if the error flag is set
 142 */
 143
 144 int
 145 tls_ferror(void)
 146 {
 147 return ssl_xfer_error;
 148 }
 149
 150
 151 /*************************************************
 152 *           TLS version of smtp_buffered         *
 153 *************************************************/
 154
 155 /* Tests for unused chars in the TLS input buffer.
 156
 157 Arguments:     none
 158 Returns:       TRUE/FALSE
 159 */
 160
 161 BOOL
 162 tls_smtp_buffered(void)
 163 {
 164 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm;
 165 }
 166
 167
 168 #endif  /* SUPPORT_TLS */
 169
 170 /* End of tls.c */