TLS1.2 and TLS1.1 support with GnuTLS
[exim.git] / src / src / tls-gnu.c
CommitLineData
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1/*************************************************
2* Exim - an Internet mail transport agent *
3*************************************************/
4
0a49a7a4 5/* Copyright (c) University of Cambridge 1995 - 2009 */
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6/* See the file NOTICE for conditions of use and distribution. */
7
8/* This module provides TLS (aka SSL) support for Exim using the GnuTLS
9library. It is #included into tls.c when that library is used. The code herein
10is based on a patch that was contributed by Nikos Mavroyanopoulos.
11
12No cryptographic code is included in Exim. All this module does is to call
13functions from the GnuTLS library. */
14
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15/* Note: This appears to be using an old API from compat.h; it is likely that
16someone familiary with GnuTLS programming could rework a lot of this to a
17modern API and perhaps remove the explicit knowledge of crypto algorithms from
18Exim. Such a re-work would be most welcome and we'd sacrifice support for
19older GnuTLS releases without too many qualms -- maturity and experience
20in crypto libraries tends to improve their robustness against attack.
21Frankly, if you maintain it, you decide what's supported and what isn't. */
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22
23/* Heading stuff for GnuTLS */
24
25#include <gnutls/gnutls.h>
26#include <gnutls/x509.h>
27
28
29#define UNKNOWN_NAME "unknown"
87054a31 30#define DH_BITS 1024
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31#define PARAM_SIZE 2*1024
32
059ec3d9 33
7199e1ee 34/* Values for verify_requirment */
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35
36enum { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED };
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37
38/* Local static variables for GNUTLS */
39
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40static host_item *client_host;
41
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42static gnutls_dh_params dh_params = NULL;
43
44static gnutls_certificate_server_credentials x509_cred = NULL;
45static gnutls_session tls_session = NULL;
46
47static char ssl_errstring[256];
48
49static int ssl_session_timeout = 200;
50static int verify_requirement;
51
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52/* Priorities for TLS algorithms to use. In each case there's a default table,
53and space into which it can be copied and altered. */
059ec3d9 54
83da1223 55static const int default_proto_priority[16] = {
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56 /* These are gnutls_protocol_t enum values */
57#if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 7
58 GNUTLS_TLS1_2,
59#endif
60#if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 2
61 GNUTLS_TLS1_1,
62#endif
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63 GNUTLS_TLS1,
64 GNUTLS_SSL3,
65 0 };
66
67static int proto_priority[16];
059ec3d9 68
83da1223 69static const int default_kx_priority[16] = {
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70 GNUTLS_KX_RSA,
71 GNUTLS_KX_DHE_DSS,
72 GNUTLS_KX_DHE_RSA,
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73 0 };
74
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75static int kx_priority[16];
76
059ec3d9 77static int default_cipher_priority[16] = {
26dd5a95 78 GNUTLS_CIPHER_AES_256_CBC,
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79 GNUTLS_CIPHER_AES_128_CBC,
80 GNUTLS_CIPHER_3DES_CBC,
26dd5a95 81 GNUTLS_CIPHER_ARCFOUR_128,
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82 0 };
83
84static int cipher_priority[16];
85
83da1223 86static const int default_mac_priority[16] = {
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87 GNUTLS_MAC_SHA,
88 GNUTLS_MAC_MD5,
89 0 };
90
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91static int mac_priority[16];
92
93/* These two are currently not changeable. */
94
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95static const int comp_priority[16] = { GNUTLS_COMP_NULL, 0 };
96static const int cert_type_priority[16] = { GNUTLS_CRT_X509, 0 };
97
83da1223 98/* Tables of priority names and equivalent numbers */
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99
100typedef struct pri_item {
101 uschar *name;
102 int *values;
103} pri_item;
104
83da1223 105
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106#if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 7
107static int tls1_2_codes[] = { GNUTLS_TLS1_2, 0 };
108#endif
109#if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 2
110static int tls1_1_codes[] = { GNUTLS_TLS1_1, 0 };
111#endif
112/* more recent libraries define this as an equivalent value to the
113canonical GNUTLS_TLS1_0; since they're the same, we stick to the
114older name. */
115static int tls1_0_codes[] = { GNUTLS_TLS1, 0 };
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116static int ssl3_codes[] = { GNUTLS_SSL3, 0 };
117
118static pri_item proto_index[] = {
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119#if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 7
120 { US"TLS1.2", tls1_2_codes },
121#endif
122#if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 2
123 { US"TLS1.1", tls1_1_codes },
124#endif
125 { US"TLS1.0", tls1_0_codes },
126 { US"TLS1", tls1_0_codes },
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127 { US"SSL3", ssl3_codes }
128};
129
130
131static int kx_rsa_codes[] = { GNUTLS_KX_RSA,
132 GNUTLS_KX_DHE_RSA, 0 };
133static int kx_dhe_codes[] = { GNUTLS_KX_DHE_DSS,
134 GNUTLS_KX_DHE_RSA, 0 };
135static int kx_dhe_dss_codes[] = { GNUTLS_KX_DHE_DSS, 0 };
136static int kx_dhe_rsa_codes[] = { GNUTLS_KX_DHE_RSA, 0 };
137
138static pri_item kx_index[] = {
139 { US"DHE_DSS", kx_dhe_dss_codes },
140 { US"DHE_RSA", kx_dhe_rsa_codes },
141 { US"RSA", kx_rsa_codes },
142 { US"DHE", kx_dhe_codes }
143};
144
145
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146static int arcfour_128_codes[] = { GNUTLS_CIPHER_ARCFOUR_128, 0 };
147static int arcfour_40_codes[] = { GNUTLS_CIPHER_ARCFOUR_40, 0 };
148static int arcfour_codes[] = { GNUTLS_CIPHER_ARCFOUR_128,
149 GNUTLS_CIPHER_ARCFOUR_40, 0 };
150static int aes_256_codes[] = { GNUTLS_CIPHER_AES_256_CBC, 0 };
151static int aes_128_codes[] = { GNUTLS_CIPHER_AES_128_CBC, 0 };
152static int aes_codes[] = { GNUTLS_CIPHER_AES_256_CBC,
153 GNUTLS_CIPHER_AES_128_CBC, 0 };
154static int des3_codes[] = { GNUTLS_CIPHER_3DES_CBC, 0 };
155
156static pri_item cipher_index[] = {
157 { US"ARCFOUR_128", arcfour_128_codes },
158 { US"ARCFOUR_40", arcfour_40_codes },
159 { US"ARCFOUR", arcfour_codes },
160 { US"AES_256", aes_256_codes },
161 { US"AES_128", aes_128_codes },
162 { US"AES", aes_codes },
163 { US"3DES", des3_codes }
164};
165
166
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167static int mac_sha_codes[] = { GNUTLS_MAC_SHA, 0 };
168static int mac_md5_codes[] = { GNUTLS_MAC_MD5, 0 };
169
170static pri_item mac_index[] = {
171 { US"SHA", mac_sha_codes },
172 { US"SHA1", mac_sha_codes },
173 { US"MD5", mac_md5_codes }
174};
175
176
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177
178/*************************************************
179* Handle TLS error *
180*************************************************/
181
182/* Called from lots of places when errors occur before actually starting to do
183the TLS handshake, that is, while the session is still in clear. Always returns
184DEFER for a server and FAIL for a client so that most calls can use "return
185tls_error(...)" to do this processing and then give an appropriate return. A
186single function is used for both server and client, because it is called from
187some shared functions.
188
189Argument:
190 prefix text to include in the logged error
191 host NULL if setting up a server;
192 the connected host if setting up a client
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193 msg additional error string (may be NULL)
194 usually obtained from gnutls_strerror()
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195
196Returns: OK/DEFER/FAIL
197*/
198
199static int
7199e1ee 200tls_error(uschar *prefix, host_item *host, const char *msg)
059ec3d9 201{
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202if (host == NULL)
203 {
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204 uschar *conn_info = smtp_get_connection_info();
205 if (strncmp(conn_info, "SMTP ", 5) == 0)
206 conn_info += 5;
207 log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s",
208 conn_info, prefix, msg ? ": " : "", msg ? msg : "");
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209 return DEFER;
210 }
211else
212 {
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213 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s",
214 host->name, host->address, prefix, msg ? ": " : "", msg ? msg : "");
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215 return FAIL;
216 }
217}
218
219
220
221/*************************************************
222* Verify certificate *
223*************************************************/
224
225/* Called after a successful handshake, when certificate verification is
226required or optional, for both server and client.
227
228Arguments:
229 session GNUTLS session
230 error where to put text giving a reason for failure
231
232Returns: TRUE/FALSE
233*/
234
235static BOOL
7199e1ee 236verify_certificate(gnutls_session session, const char **error)
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237{
238int verify;
239uschar *dn_string = US"";
240const gnutls_datum *cert;
241unsigned int cert_size = 0;
242
243*error = NULL;
244
245/* Get the peer's certificate. If it sent one, extract it's DN, and then
246attempt to verify the certificate. If no certificate is supplied, verification
247is forced to fail. */
248
249cert = gnutls_certificate_get_peers(session, &cert_size);
250if (cert != NULL)
251 {
252 uschar buff[1024];
253 gnutls_x509_crt gcert;
254
255 gnutls_x509_crt_init(&gcert);
256 dn_string = US"unknown";
257
258 if (gnutls_x509_crt_import(gcert, cert, GNUTLS_X509_FMT_DER) == 0)
259 {
260 size_t bufsize = sizeof(buff);
261 if (gnutls_x509_crt_get_dn(gcert, CS buff, &bufsize) >= 0)
262 dn_string = string_copy_malloc(buff);
263 }
264
265 verify = gnutls_certificate_verify_peers(session);
266 }
267else
268 {
269 DEBUG(D_tls) debug_printf("no peer certificate supplied\n");
270 verify = GNUTLS_CERT_INVALID;
7199e1ee 271 *error = "not supplied";
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272 }
273
274/* Handle the result of verification. INVALID seems to be set as well
275as REVOKED, but leave the test for both. */
276
277if ((verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0)
278 {
279 tls_certificate_verified = FALSE;
280 if (*error == NULL) *error = ((verify & GNUTLS_CERT_REVOKED) != 0)?
7199e1ee 281 "revoked" : "invalid";
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282 if (verify_requirement == VERIFY_REQUIRED)
283 {
284 DEBUG(D_tls) debug_printf("TLS certificate verification failed (%s): "
285 "peerdn=%s\n", *error, dn_string);
286 gnutls_alert_send(session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
287 return FALSE; /* reject */
288 }
289 DEBUG(D_tls) debug_printf("TLS certificate verify failure (%s) overridden "
290 "(host in tls_try_verify_hosts): peerdn=%s\n", *error, dn_string);
291 }
292else
293 {
294 tls_certificate_verified = TRUE;
295 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n",
296 dn_string);
297 }
298
299tls_peerdn = dn_string;
300return TRUE; /* accept */
301}
302
303
304
059ec3d9 305/*************************************************
575643cd 306* Setup up DH parameters *
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307*************************************************/
308
575643cd 309/* Generating the D-H parameters may take a long time. They only need to
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310be re-generated every so often, depending on security policy. What we do is to
311keep these parameters in a file in the spool directory. If the file does not
312exist, we generate them. This means that it is easy to cause a regeneration.
313
314The new file is written as a temporary file and renamed, so that an incomplete
315file is never present. If two processes both compute some new parameters, you
316waste a bit of effort, but it doesn't seem worth messing around with locking to
317prevent this.
318
319Argument:
320 host NULL for server, server for client (for error handling)
321
322Returns: OK/DEFER/FAIL
323*/
324
325static int
575643cd 326init_dh(host_item *host)
059ec3d9 327{
b5aea5e1 328int fd;
182ad5cf 329int ret;
b5aea5e1 330gnutls_datum m;
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331uschar filename[200];
332
333/* Initialize the data structures for holding the parameters */
334
059ec3d9 335ret = gnutls_dh_params_init(&dh_params);
7199e1ee 336if (ret < 0) return tls_error(US"init dh_params", host, gnutls_strerror(ret));
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337
338/* Set up the name of the cache file */
339
340if (!string_format(filename, sizeof(filename), "%s/gnutls-params",
341 spool_directory))
7199e1ee 342 return tls_error(US"overlong filename", host, NULL);
059ec3d9 343
b5aea5e1 344/* Open the cache file for reading and if successful, read it and set up the
575643cd 345parameters. */
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346
347fd = Uopen(filename, O_RDONLY, 0);
b5aea5e1 348if (fd >= 0)
059ec3d9 349 {
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350 struct stat statbuf;
351 if (fstat(fd, &statbuf) < 0)
352 {
353 (void)close(fd);
7199e1ee 354 return tls_error(US"TLS cache stat failed", host, strerror(errno));
b5aea5e1 355 }
059ec3d9 356
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357 m.size = statbuf.st_size;
358 m.data = malloc(m.size);
359 if (m.data == NULL)
7199e1ee
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360 return tls_error(US"memory allocation failed", host, strerror(errno));
361 errno = 0;
b5aea5e1 362 if (read(fd, m.data, m.size) != m.size)
7199e1ee 363 return tls_error(US"TLS cache read failed", host, strerror(errno));
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364 (void)close(fd);
365
411ef850 366 ret = gnutls_dh_params_import_pkcs3(dh_params, &m, GNUTLS_X509_FMT_PEM);
7199e1ee
TF
367 if (ret < 0)
368 return tls_error(US"DH params import", host, gnutls_strerror(ret));
575643cd 369 DEBUG(D_tls) debug_printf("read D-H parameters from file\n");
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370
371 free(m.data);
372 }
373
374/* If the file does not exist, fall through to compute new data and cache it.
375If there was any other opening error, it is serious. */
376
182ad5cf
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377else if (errno == ENOENT)
378 {
379 ret = -1;
380 DEBUG(D_tls)
381 debug_printf("parameter cache file %s does not exist\n", filename);
382 }
383else
b5aea5e1 384 return tls_error(string_open_failed(errno, "%s for reading", filename),
7199e1ee 385 host, NULL);
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386
387/* If ret < 0, either the cache file does not exist, or the data it contains
388is not useful. One particular case of this is when upgrading from an older
389release of Exim in which the data was stored in a different format. We don't
390try to be clever and support both formats; we just regenerate new data in this
391case. */
392
393if (ret < 0)
394 {
395 uschar tempfilename[sizeof(filename) + 10];
059ec3d9 396
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397 DEBUG(D_tls) debug_printf("generating %d bit Diffie-Hellman key...\n",
398 DH_BITS);
399 ret = gnutls_dh_params_generate2(dh_params, DH_BITS);
7199e1ee 400 if (ret < 0) return tls_error(US"D-H key generation", host, gnutls_strerror(ret));
059ec3d9
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401
402 /* Write the parameters to a file in the spool directory so that we
403 can use them from other Exim processes. */
404
405 sprintf(CS tempfilename, "%s-%d", filename, (int)getpid());
406 fd = Uopen(tempfilename, O_WRONLY|O_CREAT, 0400);
407 if (fd < 0)
408 return tls_error(string_open_failed(errno, "%s for writing", filename),
7199e1ee 409 host, NULL);
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410 (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */
411
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412 /* export the parameters in a format that can be generated using GNUTLS'
413 * certtool or other programs.
414 *
415 * The commands for certtool are:
411ef850 416 * $ certtool --generate-dh-params --bits 1024 > params
b5aea5e1
PH
417 */
418
419 m.size = PARAM_SIZE;
420 m.data = malloc(m.size);
421 if (m.data == NULL)
7199e1ee 422 return tls_error(US"memory allocation failed", host, strerror(errno));
b5aea5e1 423
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424 m.size = PARAM_SIZE;
425 ret = gnutls_dh_params_export_pkcs3(dh_params, GNUTLS_X509_FMT_PEM, m.data,
426 &m.size);
7199e1ee
TF
427 if (ret < 0)
428 return tls_error(US"DH params export", host, gnutls_strerror(ret));
059ec3d9 429
b5aea5e1 430 m.size = Ustrlen(m.data);
7199e1ee 431 errno = 0;
b5aea5e1 432 if (write(fd, m.data, m.size) != m.size || write(fd, "\n", 1) != 1)
7199e1ee 433 return tls_error(US"TLS cache write failed", host, strerror(errno));
059ec3d9 434
b5aea5e1 435 free(m.data);
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436 (void)close(fd);
437
438 if (rename(CS tempfilename, CS filename) < 0)
7199e1ee
TF
439 return tls_error(string_sprintf("failed to rename %s as %s",
440 tempfilename, filename), host, strerror(errno));
059ec3d9 441
411ef850 442 DEBUG(D_tls) debug_printf("wrote D-H parameters to file %s\n", filename);
059ec3d9
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443 }
444
411ef850 445DEBUG(D_tls) debug_printf("initialized D-H parameters\n");
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446return OK;
447}
448
449
450
451
452/*************************************************
453* Initialize for GnuTLS *
454*************************************************/
455
456/* Called from both server and client code. In the case of a server, errors
457before actual TLS negotiation return DEFER.
458
459Arguments:
460 host connected host, if client; NULL if server
461 certificate certificate file
462 privatekey private key file
463 cas CA certs file
464 crl CRL file
465
466Returns: OK/DEFER/FAIL
467*/
468
469static int
470tls_init(host_item *host, uschar *certificate, uschar *privatekey, uschar *cas,
471 uschar *crl)
472{
473int rc;
474uschar *cert_expanded, *key_expanded, *cas_expanded, *crl_expanded;
475
7199e1ee 476client_host = host;
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477
478rc = gnutls_global_init();
7199e1ee 479if (rc < 0) return tls_error(US"tls-init", host, gnutls_strerror(rc));
059ec3d9 480
575643cd
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481/* Create D-H parameters, or read them from the cache file. This function does
482its own SMTP error messaging. */
059ec3d9 483
575643cd 484rc = init_dh(host);
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485if (rc != OK) return rc;
486
487/* Create the credentials structure */
488
489rc = gnutls_certificate_allocate_credentials(&x509_cred);
7199e1ee
TF
490if (rc < 0)
491 return tls_error(US"certificate_allocate_credentials",
492 host, gnutls_strerror(rc));
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493
494/* This stuff must be done for each session, because different certificates
495may be required for different sessions. */
496
497if (!expand_check(certificate, US"tls_certificate", &cert_expanded))
498 return DEFER;
499
c91535f3 500key_expanded = NULL;
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501if (privatekey != NULL)
502 {
503 if (!expand_check(privatekey, US"tls_privatekey", &key_expanded))
504 return DEFER;
505 }
c91535f3
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506
507/* If expansion was forced to fail, key_expanded will be NULL. If the result of
508the expansion is an empty string, ignore it also, and assume that the private
509key is in the same file as the certificate. */
510
511if (key_expanded == NULL || *key_expanded == 0)
512 key_expanded = cert_expanded;
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513
514/* Set the certificate and private keys */
515
516if (cert_expanded != NULL)
517 {
518 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
519 cert_expanded, key_expanded);
520 rc = gnutls_certificate_set_x509_key_file(x509_cred, CS cert_expanded,
521 CS key_expanded, GNUTLS_X509_FMT_PEM);
8e669ac1 522 if (rc < 0)
de365ded
PH
523 {
524 uschar *msg = string_sprintf("cert/key setup: cert=%s key=%s",
8e669ac1 525 cert_expanded, key_expanded);
7199e1ee 526 return tls_error(msg, host, gnutls_strerror(rc));
8e669ac1 527 }
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528 }
529
530/* A certificate is mandatory in a server, but not in a client */
531
532else
533 {
534 if (host == NULL)
7199e1ee 535 return tls_error(US"no TLS server certificate is specified", NULL, NULL);
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536 DEBUG(D_tls) debug_printf("no TLS client certificate is specified\n");
537 }
538
539/* Set the trusted CAs file if one is provided, and then add the CRL if one is
540provided. Experiment shows that, if the certificate file is empty, an unhelpful
541error message is provided. However, if we just refrain from setting anything up
542in that case, certificate verification fails, which seems to be the correct
543behaviour. */
544
545if (cas != NULL)
546 {
547 struct stat statbuf;
548
549 if (!expand_check(cas, US"tls_verify_certificates", &cas_expanded))
550 return DEFER;
551
552 if (stat(CS cas_expanded, &statbuf) < 0)
553 {
554 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
555 "(tls_verify_certificates): %s", cas_expanded, strerror(errno));
556 return DEFER;
557 }
558
b1c749bb
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559 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
560 cas_expanded, statbuf.st_size);
059ec3d9
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561
562 /* If the cert file is empty, there's no point in loading the CRL file. */
563
564 if (statbuf.st_size > 0)
565 {
566 rc = gnutls_certificate_set_x509_trust_file(x509_cred, CS cas_expanded,
567 GNUTLS_X509_FMT_PEM);
7199e1ee 568 if (rc < 0) return tls_error(US"setup_certs", host, gnutls_strerror(rc));
059ec3d9
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569
570 if (crl != NULL && *crl != 0)
571 {
572 if (!expand_check(crl, US"tls_crl", &crl_expanded))
573 return DEFER;
574 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", crl_expanded);
575 rc = gnutls_certificate_set_x509_crl_file(x509_cred, CS crl_expanded,
576 GNUTLS_X509_FMT_PEM);
7199e1ee 577 if (rc < 0) return tls_error(US"CRL setup", host, gnutls_strerror(rc));
059ec3d9
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578 }
579 }
580 }
581
582/* Associate the parameters with the x509 credentials structure. */
583
584gnutls_certificate_set_dh_params(x509_cred, dh_params);
059ec3d9
PH
585
586DEBUG(D_tls) debug_printf("initialized certificate stuff\n");
587return OK;
588}
589
590
591
592
593/*************************************************
83da1223 594* Remove from a priority list *
059ec3d9
PH
595*************************************************/
596
597/* Cautiously written so that it will remove duplicates if present.
598
599Arguments:
600 list a zero-terminated list
601 remove_list a zero-terminated list to be removed
602
603Returns: nothing
604*/
605
606static void
83da1223 607remove_priority(int *list, int *remove_list)
059ec3d9
PH
608{
609for (; *remove_list != 0; remove_list++)
610 {
611 int *p = list;
612 while (*p != 0)
613 {
614 if (*p == *remove_list)
615 {
616 int *pp = p;
617 do { pp[0] = pp[1]; pp++; } while (*pp != 0);
618 }
619 else p++;
620 }
621 }
622}
623
624
625
626/*************************************************
83da1223 627* Add to a priority list *
059ec3d9
PH
628*************************************************/
629
630/* Cautiously written to check the list size
631
632Arguments:
633 list a zero-terminated list
634 list_max maximum offset in the list
635 add_list a zero-terminated list to be added
636
637Returns: TRUE if OK; FALSE if list overflows
638*/
639
640static BOOL
83da1223 641add_priority(int *list, int list_max, int *add_list)
059ec3d9
PH
642{
643int next = 0;
644while (list[next] != 0) next++;
645while (*add_list != 0)
646 {
647 if (next >= list_max) return FALSE;
648 list[next++] = *add_list++;
649 }
650list[next] = 0;
651return TRUE;
652}
653
654
655
656/*************************************************
83da1223
PH
657* Adjust a priority list *
658*************************************************/
659
660/* This function is called to adjust the lists of cipher algorithms, MAC
661algorithms, key-exchange methods, and protocols.
662
663Arguments:
664 plist the appropriate priority list
665 psize the length of the list
666 s the configuation string
667 index the index of recognized strings
668 isize the length of the index
669
670
671 which text for an error message
672
673Returns: FALSE if the table overflows, else TRUE
674*/
675
676static BOOL
677set_priority(int *plist, int psize, uschar *s, pri_item *index, int isize,
678 uschar *which)
679{
680int sep = 0;
681BOOL first = TRUE;
682uschar *t;
683
684while ((t = string_nextinlist(&s, &sep, big_buffer, big_buffer_size)) != NULL)
685 {
686 int i;
687 BOOL exclude = t[0] == '!';
688 if (first && !exclude) plist[0] = 0;
689 first = FALSE;
690 for (i = 0; i < isize; i++)
691 {
692 uschar *ss = strstric(t, index[i].name, FALSE);
693 if (ss != NULL)
694 {
695 uschar *endss = ss + Ustrlen(index[i].name);
696 if ((ss == t || !isalnum(ss[-1])) && !isalnum(*endss))
697 {
698 if (exclude)
699 remove_priority(plist, index[i].values);
700 else
701 {
702 if (!add_priority(plist, psize, index[i].values))
703 {
704 log_write(0, LOG_MAIN|LOG_PANIC, "GnuTLS init failed: %s "
705 "priority table overflow", which);
706 return FALSE;
707 }
708 }
709 }
710 }
711 }
712 }
713
714DEBUG(D_tls)
715 {
716 int *ptr = plist;
717 debug_printf("adjusted %s priorities:", which);
718 while (*ptr != 0) debug_printf(" %d", *ptr++);
719 debug_printf("\n");
720 }
721
722return TRUE;
723}
724
725
726
727
728/*************************************************
059ec3d9
PH
729* Initialize a single GNUTLS session *
730*************************************************/
731
732/* Set the algorithm, the db backend, whether to request certificates etc.
733
734TLS in Exim was first implemented using OpenSSL. This has a function to which
735you pass a list of cipher suites that are permitted/not permitted. GnuTLS works
736differently. It operates using priority lists for the different components of
737cipher suites.
738
739For compatibility of configuration, we scan a list of cipher suites and set
740priorities therefrom. However, at the moment, we pay attention only to the bulk
741cipher.
742
743Arguments:
744 side one of GNUTLS_SERVER, GNUTLS_CLIENT
83da1223
PH
745 expciphers expanded ciphers list or NULL
746 expmac expanded MAC list or NULL
747 expkx expanded key-exchange list or NULL
748 expproto expanded protocol list or NULL
059ec3d9
PH
749
750Returns: a gnutls_session, or NULL if there is a problem
751*/
752
753static gnutls_session
83da1223
PH
754tls_session_init(int side, uschar *expciphers, uschar *expmac, uschar *expkx,
755 uschar *expproto)
059ec3d9
PH
756{
757gnutls_session session;
758
759gnutls_init(&session, side);
760
83da1223
PH
761/* Initialize the lists of permitted protocols, key-exchange methods, ciphers,
762and MACs. */
059ec3d9
PH
763
764memcpy(cipher_priority, default_cipher_priority, sizeof(cipher_priority));
83da1223
PH
765memcpy(mac_priority, default_mac_priority, sizeof(mac_priority));
766memcpy(kx_priority, default_kx_priority, sizeof(kx_priority));
767memcpy(proto_priority, default_proto_priority, sizeof(proto_priority));
768
769/* The names OpenSSL uses in tls_require_ciphers are of the form DES-CBC3-SHA,
770using hyphen separators. GnuTLS uses underscore separators. So that I can use
771either form for tls_require_ciphers in my tests, and also for general
772convenience, we turn hyphens into underscores before scanning the list. */
059ec3d9
PH
773
774if (expciphers != NULL)
775 {
059ec3d9
PH
776 uschar *s = expciphers;
777 while (*s != 0) { if (*s == '-') *s = '_'; s++; }
83da1223 778 }
059ec3d9 779
83da1223
PH
780if ((expciphers != NULL &&
781 !set_priority(cipher_priority, sizeof(cipher_priority)/sizeof(int),
782 expciphers, cipher_index, sizeof(cipher_index)/sizeof(pri_item),
783 US"cipher")) ||
784 (expmac != NULL &&
785 !set_priority(mac_priority, sizeof(mac_priority)/sizeof(int),
786 expmac, mac_index, sizeof(mac_index)/sizeof(pri_item),
787 US"MAC")) ||
788 (expkx != NULL &&
789 !set_priority(kx_priority, sizeof(kx_priority)/sizeof(int),
790 expkx, kx_index, sizeof(kx_index)/sizeof(pri_item),
791 US"key-exchange")) ||
792 (expproto != NULL &&
793 !set_priority(proto_priority, sizeof(proto_priority)/sizeof(int),
794 expproto, proto_index, sizeof(proto_index)/sizeof(pri_item),
795 US"protocol")))
796 {
797 gnutls_deinit(session);
798 return NULL;
059ec3d9
PH
799 }
800
801/* Define the various priorities */
802
803gnutls_cipher_set_priority(session, cipher_priority);
804gnutls_compression_set_priority(session, comp_priority);
805gnutls_kx_set_priority(session, kx_priority);
83da1223 806gnutls_protocol_set_priority(session, proto_priority);
059ec3d9
PH
807gnutls_mac_set_priority(session, mac_priority);
808
809gnutls_cred_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred);
810
811gnutls_dh_set_prime_bits(session, DH_BITS);
812
813/* Request or demand a certificate of the peer, as configured. This will
814happen only in a server. */
815
816if (verify_requirement != VERIFY_NONE)
817 gnutls_certificate_server_set_request(session,
818 (verify_requirement == VERIFY_OPTIONAL)?
819 GNUTLS_CERT_REQUEST : GNUTLS_CERT_REQUIRE);
820
821gnutls_db_set_cache_expiration(session, ssl_session_timeout);
822
e6060e2c
NM
823/* Reduce security in favour of increased compatibility, if the admin
824decides to make that trade-off. */
825if (gnutls_compat_mode)
826 {
827#if LIBGNUTLS_VERSION_NUMBER >= 0x020104
828 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
829 gnutls_session_enable_compatibility_mode(session);
830#else
831 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
832#endif
833 }
834
059ec3d9
PH
835DEBUG(D_tls) debug_printf("initialized GnuTLS session\n");
836return session;
837}
838
839
840
841/*************************************************
842* Get name of cipher in use *
843*************************************************/
844
845/* The answer is left in a static buffer, and tls_cipher is set to point
846to it.
847
848Argument: pointer to a GnuTLS session
849Returns: nothing
850*/
851
852static void
853construct_cipher_name(gnutls_session session)
854{
855static uschar cipherbuf[256];
856uschar *ver;
857int bits, c, kx, mac;
858
859ver = string_copy(
860 US gnutls_protocol_get_name(gnutls_protocol_get_version(session)));
861if (Ustrncmp(ver, "TLS ", 4) == 0) ver[3] = '-'; /* Don't want space */
862
863c = gnutls_cipher_get(session);
864bits = gnutls_cipher_get_key_size(c);
865
866mac = gnutls_mac_get(session);
867kx = gnutls_kx_get(session);
868
869string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver,
870 gnutls_cipher_suite_get_name(kx, c, mac), bits);
871tls_cipher = cipherbuf;
872
873DEBUG(D_tls) debug_printf("cipher: %s\n", cipherbuf);
874}
875
876
877
878/*************************************************
879* Start a TLS session in a server *
880*************************************************/
881
882/* This is called when Exim is running as a server, after having received
883the STARTTLS command. It must respond to that command, and then negotiate
884a TLS session.
885
886Arguments:
83da1223
PH
887 require_ciphers list of allowed ciphers or NULL
888 require_mac list of allowed MACs or NULL
889 require_kx list of allowed key_exchange methods or NULL
890 require_proto list of allowed protocols or NULL
059ec3d9
PH
891
892Returns: OK on success
893 DEFER for errors before the start of the negotiation
894 FAIL for errors during the negotation; the server can't
895 continue running.
896*/
897
898int
83da1223
PH
899tls_server_start(uschar *require_ciphers, uschar *require_mac,
900 uschar *require_kx, uschar *require_proto)
059ec3d9
PH
901{
902int rc;
7199e1ee 903const char *error;
059ec3d9 904uschar *expciphers = NULL;
83da1223
PH
905uschar *expmac = NULL;
906uschar *expkx = NULL;
907uschar *expproto = NULL;
059ec3d9
PH
908
909/* Check for previous activation */
910
911if (tls_active >= 0)
912 {
7199e1ee 913 tls_error("STARTTLS received after TLS started", NULL, "");
059ec3d9
PH
914 smtp_printf("554 Already in TLS\r\n");
915 return FAIL;
916 }
917
918/* Initialize the library. If it fails, it will already have logged the error
919and sent an SMTP response. */
920
921DEBUG(D_tls) debug_printf("initializing GnuTLS as a server\n");
922
923rc = tls_init(NULL, tls_certificate, tls_privatekey, tls_verify_certificates,
924 tls_crl);
925if (rc != OK) return rc;
926
83da1223
PH
927if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers) ||
928 !expand_check(require_mac, US"gnutls_require_mac", &expmac) ||
929 !expand_check(require_kx, US"gnutls_require_kx", &expkx) ||
930 !expand_check(require_proto, US"gnutls_require_proto", &expproto))
059ec3d9
PH
931 return FAIL;
932
933/* If this is a host for which certificate verification is mandatory or
934optional, set up appropriately. */
935
936tls_certificate_verified = FALSE;
937verify_requirement = VERIFY_NONE;
938
939if (verify_check_host(&tls_verify_hosts) == OK)
940 verify_requirement = VERIFY_REQUIRED;
941else if (verify_check_host(&tls_try_verify_hosts) == OK)
942 verify_requirement = VERIFY_OPTIONAL;
943
944/* Prepare for new connection */
945
83da1223
PH
946tls_session = tls_session_init(GNUTLS_SERVER, expciphers, expmac, expkx,
947 expproto);
059ec3d9 948if (tls_session == NULL)
7199e1ee
TF
949 return tls_error(US"tls_session_init", NULL,
950 gnutls_strerror(GNUTLS_E_MEMORY_ERROR));
059ec3d9
PH
951
952/* Set context and tell client to go ahead, except in the case of TLS startup
953on connection, where outputting anything now upsets the clients and tends to
954make them disconnect. We need to have an explicit fflush() here, to force out
955the response. Other smtp_printf() calls do not need it, because in non-TLS
956mode, the fflush() happens when smtp_getc() is called. */
957
958if (!tls_on_connect)
959 {
960 smtp_printf("220 TLS go ahead\r\n");
961 fflush(smtp_out);
962 }
963
964/* Now negotiate the TLS session. We put our own timer on it, since it seems
965that the GnuTLS library doesn't. */
966
56f5d9bd
PH
967gnutls_transport_set_ptr2(tls_session, (gnutls_transport_ptr)fileno(smtp_in),
968 (gnutls_transport_ptr)fileno(smtp_out));
059ec3d9
PH
969
970sigalrm_seen = FALSE;
971if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
972rc = gnutls_handshake(tls_session);
973alarm(0);
974
975if (rc < 0)
976 {
7199e1ee
TF
977 tls_error(US"gnutls_handshake", NULL,
978 sigalrm_seen ? "timed out" : gnutls_strerror(rc));
059ec3d9
PH
979
980 /* It seems that, except in the case of a timeout, we have to close the
981 connection right here; otherwise if the other end is running OpenSSL it hangs
982 until the server times out. */
983
984 if (!sigalrm_seen)
985 {
f1e894f3
PH
986 (void)fclose(smtp_out);
987 (void)fclose(smtp_in);
059ec3d9
PH
988 }
989
990 return FAIL;
991 }
992
993DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n");
994
995if (verify_requirement != VERIFY_NONE &&
996 !verify_certificate(tls_session, &error))
997 {
7199e1ee 998 tls_error(US"certificate verification failed", NULL, error);
059ec3d9
PH
999 return FAIL;
1000 }
1001
1002construct_cipher_name(tls_session);
1003
1004/* TLS has been set up. Adjust the input functions to read via TLS,
1005and initialize appropriately. */
1006
1007ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1008ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1009ssl_xfer_eof = ssl_xfer_error = 0;
1010
1011receive_getc = tls_getc;
1012receive_ungetc = tls_ungetc;
1013receive_feof = tls_feof;
1014receive_ferror = tls_ferror;
58eb016e 1015receive_smtp_buffered = tls_smtp_buffered;
059ec3d9
PH
1016
1017tls_active = fileno(smtp_out);
1018
1019return OK;
1020}
1021
1022
1023
1024
1025/*************************************************
1026* Start a TLS session in a client *
1027*************************************************/
1028
1029/* Called from the smtp transport after STARTTLS has been accepted.
1030
1031Arguments:
1032 fd the fd of the connection
1033 host connected host (for messages)
83da1223 1034 addr the first address (not used)
059ec3d9
PH
1035 dhparam DH parameter file
1036 certificate certificate file
1037 privatekey private key file
1038 verify_certs file for certificate verify
1039 verify_crl CRL for verify
83da1223
PH
1040 require_ciphers list of allowed ciphers or NULL
1041 require_mac list of allowed MACs or NULL
1042 require_kx list of allowed key_exchange methods or NULL
1043 require_proto list of allowed protocols or NULL
059ec3d9
PH
1044 timeout startup timeout
1045
1046Returns: OK/DEFER/FAIL (because using common functions),
1047 but for a client, DEFER and FAIL have the same meaning
1048*/
1049
1050int
1051tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
1052 uschar *certificate, uschar *privatekey, uschar *verify_certs,
83da1223
PH
1053 uschar *verify_crl, uschar *require_ciphers, uschar *require_mac,
1054 uschar *require_kx, uschar *require_proto, int timeout)
059ec3d9
PH
1055{
1056const gnutls_datum *server_certs;
1057uschar *expciphers = NULL;
83da1223
PH
1058uschar *expmac = NULL;
1059uschar *expkx = NULL;
1060uschar *expproto = NULL;
7199e1ee 1061const char *error;
059ec3d9
PH
1062unsigned int server_certs_size;
1063int rc;
1064
1065DEBUG(D_tls) debug_printf("initializing GnuTLS as a client\n");
1066
059ec3d9
PH
1067verify_requirement = (verify_certs == NULL)? VERIFY_NONE : VERIFY_REQUIRED;
1068rc = tls_init(host, certificate, privatekey, verify_certs, verify_crl);
1069if (rc != OK) return rc;
1070
83da1223
PH
1071if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers) ||
1072 !expand_check(require_mac, US"gnutls_require_mac", &expmac) ||
1073 !expand_check(require_kx, US"gnutls_require_kx", &expkx) ||
1074 !expand_check(require_proto, US"gnutls_require_proto", &expproto))
059ec3d9
PH
1075 return FAIL;
1076
83da1223
PH
1077tls_session = tls_session_init(GNUTLS_CLIENT, expciphers, expmac, expkx,
1078 expproto);
1079
059ec3d9 1080if (tls_session == NULL)
7199e1ee
TF
1081 return tls_error(US "tls_session_init", host,
1082 gnutls_strerror(GNUTLS_E_MEMORY_ERROR));
059ec3d9
PH
1083
1084gnutls_transport_set_ptr(tls_session, (gnutls_transport_ptr)fd);
1085
1086/* There doesn't seem to be a built-in timeout on connection. */
1087
1088sigalrm_seen = FALSE;
1089alarm(timeout);
1090rc = gnutls_handshake(tls_session);
1091alarm(0);
1092
1093if (rc < 0)
7199e1ee
TF
1094 return tls_error(US "gnutls_handshake", host,
1095 sigalrm_seen ? "timed out" : gnutls_strerror(rc));
059ec3d9
PH
1096
1097server_certs = gnutls_certificate_get_peers(tls_session, &server_certs_size);
1098
1099if (server_certs != NULL)
1100 {
1101 uschar buff[1024];
1102 gnutls_x509_crt gcert;
1103
1104 gnutls_x509_crt_init(&gcert);
1105 tls_peerdn = US"unknown";
1106
1107 if (gnutls_x509_crt_import(gcert, server_certs, GNUTLS_X509_FMT_DER) == 0)
1108 {
1109 size_t bufsize = sizeof(buff);
1110 if (gnutls_x509_crt_get_dn(gcert, CS buff, &bufsize) >= 0)
1111 tls_peerdn = string_copy_malloc(buff);
1112 }
1113 }
1114
1115/* Should we also verify the hostname here? */
1116
1117if (verify_requirement != VERIFY_NONE &&
1118 !verify_certificate(tls_session, &error))
7199e1ee 1119 return tls_error(US"certificate verification failed", host, error);
059ec3d9
PH
1120
1121construct_cipher_name(tls_session); /* Sets tls_cipher */
1122tls_active = fd;
1123return OK;
1124}
1125
1126
1127
1128/*************************************************
1129* Deal with logging errors during I/O *
1130*************************************************/
1131
1132/* We have to get the identity of the peer from saved data.
1133
1134Argument:
1135 ec the GnuTLS error code, or 0 if it's a local error
1136 when text identifying read or write
1137 text local error text when ec is 0
1138
1139Returns: nothing
1140*/
1141
1142static void
1143record_io_error(int ec, uschar *when, uschar *text)
1144{
7199e1ee 1145const char *msg;
059ec3d9
PH
1146
1147if (ec == GNUTLS_E_FATAL_ALERT_RECEIVED)
7199e1ee 1148 msg = string_sprintf("%s: %s", gnutls_strerror(ec),
059ec3d9 1149 gnutls_alert_get_name(gnutls_alert_get(tls_session)));
059ec3d9 1150else
7199e1ee
TF
1151 msg = gnutls_strerror(ec);
1152
1153tls_error(when, client_host, msg);
059ec3d9
PH
1154}
1155
1156
1157
1158/*************************************************
1159* TLS version of getc *
1160*************************************************/
1161
1162/* This gets the next byte from the TLS input buffer. If the buffer is empty,
1163it refills the buffer via the GnuTLS reading function.
1164
1165Arguments: none
1166Returns: the next character or EOF
1167*/
1168
1169int
1170tls_getc(void)
1171{
1172if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1173 {
1174 int inbytes;
1175
1176 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%lx, %lx, %u)\n",
1177 (long) tls_session, (long) ssl_xfer_buffer, ssl_xfer_buffer_size);
1178
1179 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1180 inbytes = gnutls_record_recv(tls_session, CS ssl_xfer_buffer,
1181 ssl_xfer_buffer_size);
1182 alarm(0);
1183
1184 /* A zero-byte return appears to mean that the TLS session has been
1185 closed down, not that the socket itself has been closed down. Revert to
1186 non-TLS handling. */
1187
1188 if (inbytes == 0)
1189 {
1190 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1191
1192 receive_getc = smtp_getc;
1193 receive_ungetc = smtp_ungetc;
1194 receive_feof = smtp_feof;
1195 receive_ferror = smtp_ferror;
58eb016e 1196 receive_smtp_buffered = smtp_buffered;
059ec3d9
PH
1197
1198 gnutls_deinit(tls_session);
1199 tls_session = NULL;
1200 tls_active = -1;
1201 tls_cipher = NULL;
1202 tls_peerdn = NULL;
1203
1204 return smtp_getc();
1205 }
1206
1207 /* Handle genuine errors */
1208
1209 else if (inbytes < 0)
1210 {
1211 record_io_error(inbytes, US"recv", NULL);
1212 ssl_xfer_error = 1;
1213 return EOF;
1214 }
80a47a2c
TK
1215#ifndef DISABLE_DKIM
1216 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1217#endif
059ec3d9
PH
1218 ssl_xfer_buffer_hwm = inbytes;
1219 ssl_xfer_buffer_lwm = 0;
1220 }
1221
1222
1223/* Something in the buffer; return next uschar */
1224
1225return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1226}
1227
1228
1229
1230/*************************************************
1231* Read bytes from TLS channel *
1232*************************************************/
1233
1234/*
1235Arguments:
1236 buff buffer of data
1237 len size of buffer
1238
1239Returns: the number of bytes read
1240 -1 after a failed read
1241*/
1242
1243int
1244tls_read(uschar *buff, size_t len)
1245{
1246int inbytes;
1247
1248DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%lx, %lx, %u)\n",
1249 (long) tls_session, (long) buff, len);
1250
1251inbytes = gnutls_record_recv(tls_session, CS buff, len);
1252if (inbytes > 0) return inbytes;
1253if (inbytes == 0)
1254 {
1255 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
1256 }
1257else record_io_error(inbytes, US"recv", NULL);
1258
1259return -1;
1260}
1261
1262
1263
1264/*************************************************
1265* Write bytes down TLS channel *
1266*************************************************/
1267
1268/*
1269Arguments:
1270 buff buffer of data
1271 len number of bytes
1272
1273Returns: the number of bytes after a successful write,
1274 -1 after a failed write
1275*/
1276
1277int
1278tls_write(const uschar *buff, size_t len)
1279{
1280int outbytes;
1281int left = len;
1282
1283DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long) buff, left);
1284while (left > 0)
1285 {
1286 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %lx, %d)\n", (long)buff,
1287 left);
1288 outbytes = gnutls_record_send(tls_session, CS buff, left);
1289
1290 DEBUG(D_tls) debug_printf("outbytes=%d\n", outbytes);
1291 if (outbytes < 0)
1292 {
1293 record_io_error(outbytes, US"send", NULL);
1294 return -1;
1295 }
1296 if (outbytes == 0)
1297 {
1298 record_io_error(0, US"send", US"TLS channel closed on write");
1299 return -1;
1300 }
1301
1302 left -= outbytes;
1303 buff += outbytes;
1304 }
1305
1306return len;
1307}
1308
1309
1310
1311/*************************************************
1312* Close down a TLS session *
1313*************************************************/
1314
1315/* This is also called from within a delivery subprocess forked from the
1316daemon, to shut down the TLS library, without actually doing a shutdown (which
1317would tamper with the TLS session in the parent process).
1318
1319Arguments: TRUE if gnutls_bye is to be called
1320Returns: nothing
1321*/
1322
1323void
1324tls_close(BOOL shutdown)
1325{
1326if (tls_active < 0) return; /* TLS was not active */
1327
1328if (shutdown)
1329 {
1330 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n");
1331 gnutls_bye(tls_session, GNUTLS_SHUT_WR);
1332 }
1333
1334gnutls_deinit(tls_session);
1335tls_session = NULL;
1336gnutls_global_deinit();
1337
1338tls_active = -1;
1339}
1340
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1341
1342
1343
1344/*************************************************
1345* Report the library versions. *
1346*************************************************/
1347
1348/* See a description in tls-openssl.c for an explanation of why this exists.
1349
1350Arguments: a FILE* to print the results to
1351Returns: nothing
1352*/
1353
1354void
1355tls_version_report(FILE *f)
1356{
754a0503
PP
1357fprintf(f, "Library version: GnuTLS: Compile: %s\n"
1358 " Runtime: %s\n",
1359 LIBGNUTLS_VERSION,
1360 gnutls_check_version(NULL));
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1361}
1362
059ec3d9 1363/* End of tls-gnu.c */