src/src/tls.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2012 */
   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 We're moving away from this; GnuTLS is already using a state, which
  36 can switch, so we can do TLS callouts during ACLs. */
  37
  38 static const int ssl_xfer_buffer_size = 4096;
  39 #ifndef USE_GNUTLS
  40 static uschar *ssl_xfer_buffer = NULL;
  41 static int ssl_xfer_buffer_lwm = 0;
  42 static int ssl_xfer_buffer_hwm = 0;
  43 static int ssl_xfer_eof = 0;
  44 static int ssl_xfer_error = 0;
  45 #endif
  46
  47 uschar *tls_channelbinding_b64 = NULL;
  48
  49
  50 /*************************************************
  51 *       Expand string; give error on failure     *
  52 *************************************************/
  53
  54 /* If expansion is forced to fail, set the result NULL and return TRUE.
  55 Other failures return FALSE. For a server, an SMTP response is given.
  56
  57 Arguments:
  58   s         the string to expand; if NULL just return TRUE
  59   name      name of string being expanded (for error)
  60   result    where to put the result
  61
  62 Returns:    TRUE if OK; result may still be NULL after forced failure
  63 */
  64
  65 static BOOL
  66 expand_check(const uschar *s, const uschar *name, uschar **result)
  67 {
  68 if (s == NULL) *result = NULL; else
  69   {
  70   *result = expand_string(US s); /* need to clean up const some more */
  71   if (*result == NULL && !expand_string_forcedfail)
  72     {
  73     log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
  74       expand_string_message);
  75     return FALSE;
  76     }
  77   }
  78 return TRUE;
  79 }
  80
  81
  82 /*************************************************
  83 *        Many functions are package-specific     *
  84 *************************************************/
  85
  86 #ifdef USE_GNUTLS
  87 #include "tls-gnu.c"
  88
  89 #define ssl_xfer_buffer (state_server.xfer_buffer)
  90 #define ssl_xfer_buffer_lwm (state_server.xfer_buffer_lwm)
  91 #define ssl_xfer_buffer_hwm (state_server.xfer_buffer_hwm)
  92 #define ssl_xfer_eof (state_server.xfer_eof)
  93 #define ssl_xfer_error (state_server.xfer_error)
  94
  95 #else
  96 #include "tls-openssl.c"
  97 #endif
  98
  99
 100
 101 /*************************************************
 102 *           TLS version of ungetc                *
 103 *************************************************/
 104
 105 /* Puts a character back in the input buffer. Only ever
 106 called once.
 107 Only used by the server-side TLS.
 108
 109 Arguments:
 110   ch           the character
 111
 112 Returns:       the character
 113 */
 114
 115 int
 116 tls_ungetc(int ch)
 117 {
 118 ssl_xfer_buffer[--ssl_xfer_buffer_lwm] = ch;
 119 return ch;
 120 }
 121
 122
 123
 124 /*************************************************
 125 *           TLS version of feof                  *
 126 *************************************************/
 127
 128 /* Tests for a previous EOF
 129 Only used by the server-side TLS.
 130
 131 Arguments:     none
 132 Returns:       non-zero if the eof flag is set
 133 */
 134
 135 int
 136 tls_feof(void)
 137 {
 138 return ssl_xfer_eof;
 139 }
 140
 141
 142
 143 /*************************************************
 144 *              TLS version of ferror             *
 145 *************************************************/
 146
 147 /* Tests for a previous read error, and returns with errno
 148 restored to what it was when the error was detected.
 149 Only used by the server-side TLS.
 150
 151 >>>>> Hmm. Errno not handled yet. Where do we get it from?  >>>>>
 152
 153 Arguments:     none
 154 Returns:       non-zero if the error flag is set
 155 */
 156
 157 int
 158 tls_ferror(void)
 159 {
 160 return ssl_xfer_error;
 161 }
 162
 163
 164 /*************************************************
 165 *           TLS version of smtp_buffered         *
 166 *************************************************/
 167
 168 /* Tests for unused chars in the TLS input buffer.
 169 Only used by the server-side TLS.
 170
 171 Arguments:     none
 172 Returns:       TRUE/FALSE
 173 */
 174
 175 BOOL
 176 tls_smtp_buffered(void)
 177 {
 178 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm;
 179 }
 180
 181
 182 #endif  /* SUPPORT_TLS */
 183
 184 /* End of tls.c */