0c98aeba96c4d6cae0e071a5695243f9f2fb8b7d
[exim.git] / 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 (current_global_tls_state->xfer_buffer)
90 #define ssl_xfer_buffer_lwm (current_global_tls_state->xfer_buffer_lwm)
91 #define ssl_xfer_buffer_hwm (current_global_tls_state->xfer_buffer_hwm)
92 #define ssl_xfer_eof (current_global_tls_state->xfer_eof)
93 #define ssl_xfer_error (current_global_tls_state->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
108 Arguments:
109 ch the character
110
111 Returns: the character
112 */
113
114 int
115 tls_ungetc(int ch)
116 {
117 ssl_xfer_buffer[--ssl_xfer_buffer_lwm] = ch;
118 return ch;
119 }
120
121
122
123 /*************************************************
124 * TLS version of feof *
125 *************************************************/
126
127 /* Tests for a previous EOF
128
129 Arguments: none
130 Returns: non-zero if the eof flag is set
131 */
132
133 int
134 tls_feof(void)
135 {
136 return ssl_xfer_eof;
137 }
138
139
140
141 /*************************************************
142 * TLS version of ferror *
143 *************************************************/
144
145 /* Tests for a previous read error, and returns with errno
146 restored to what it was when the error was detected.
147
148 >>>>> Hmm. Errno not handled yet. Where do we get it from? >>>>>
149
150 Arguments: none
151 Returns: non-zero if the error flag is set
152 */
153
154 int
155 tls_ferror(void)
156 {
157 return ssl_xfer_error;
158 }
159
160
161 /*************************************************
162 * TLS version of smtp_buffered *
163 *************************************************/
164
165 /* Tests for unused chars in the TLS input buffer.
166
167 Arguments: none
168 Returns: TRUE/FALSE
169 */
170
171 BOOL
172 tls_smtp_buffered(void)
173 {
174 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm;
175 }
176
177
178 #endif /* SUPPORT_TLS */
179
180 /* End of tls.c */