Fix expansions for RFC 822 addresses having comments in local-part and/or domain...
[exim.git] / src / src / tls-gnu.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 /* Copyright (c) Phil Pennock 2012 */
9
10 /* This file provides TLS/SSL support for Exim using the GnuTLS library,
11 one of the available supported implementations. This file is #included into
12 tls.c when USE_GNUTLS has been set.
13
14 The code herein is a revamp of GnuTLS integration using the current APIs; the
15 original tls-gnu.c was based on a patch which was contributed by Nikos
16 Mavrogiannopoulos. The revamp is partially a rewrite, partially cut&paste as
17 appropriate.
18
19 APIs current as of GnuTLS 2.12.18; note that the GnuTLS manual is for GnuTLS 3,
20 which is not widely deployed by OS vendors. Will note issues below, which may
21 assist in updating the code in the future. Another sources of hints is
22 mod_gnutls for Apache (SNI callback registration and handling).
23
24 Keeping client and server variables more split than before and is currently
25 the norm, in anticipation of TLS in ACL callouts.
26
27 I wanted to switch to gnutls_certificate_set_verify_function() so that
28 certificate rejection could happen during handshake where it belongs, rather
29 than being dropped afterwards, but that was introduced in 2.10.0 and Debian
30 (6.0.5) is still on 2.8.6. So for now we have to stick with sub-par behaviour.
31
32 (I wasn't looking for libraries quite that old, when updating to get rid of
33 compiler warnings of deprecated APIs. If it turns out that a lot of the rest
34 require current GnuTLS, then we'll drop support for the ancient libraries).
35 */
36
37 #include <gnutls/gnutls.h>
38 /* needed for cert checks in verification and DN extraction: */
39 #include <gnutls/x509.h>
40 /* man-page is incorrect, gnutls_rnd() is not in gnutls.h: */
41 #include <gnutls/crypto.h>
42
43 /* needed to disable PKCS11 autoload unless requested */
44 #if GNUTLS_VERSION_NUMBER >= 0x020c00
45 # include <gnutls/pkcs11.h>
46 # define SUPPORT_PARAM_TO_PK_BITS
47 #endif
48 #if GNUTLS_VERSION_NUMBER < 0x030103 && !defined(DISABLE_OCSP)
49 # warning "GnuTLS library version too old; define DISABLE_OCSP in Makefile"
50 # define DISABLE_OCSP
51 #endif
52 #if GNUTLS_VERSION_NUMBER < 0x020a00 && !defined(DISABLE_EVENT)
53 # warning "GnuTLS library version too old; tls:cert event unsupported"
54 # define DISABLE_EVENT
55 #endif
56 #if GNUTLS_VERSION_NUMBER >= 0x030306
57 # define SUPPORT_CA_DIR
58 #else
59 # undef SUPPORT_CA_DIR
60 #endif
61 #if GNUTLS_VERSION_NUMBER >= 0x030014
62 # define SUPPORT_SYSDEFAULT_CABUNDLE
63 #endif
64 #if GNUTLS_VERSION_NUMBER >= 0x030104
65 # define GNUTLS_CERT_VFY_STATUS_PRINT
66 #endif
67 #if GNUTLS_VERSION_NUMBER >= 0x030109
68 # define SUPPORT_CORK
69 #endif
70 #if GNUTLS_VERSION_NUMBER >= 0x03010a
71 # define SUPPORT_GNUTLS_SESS_DESC
72 #endif
73 #if GNUTLS_VERSION_NUMBER >= 0x030500
74 # define SUPPORT_GNUTLS_KEYLOG
75 #endif
76 #if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP)
77 # define SUPPORT_SRV_OCSP_STACK
78 #endif
79
80 #ifdef SUPPORT_DANE
81 # if GNUTLS_VERSION_NUMBER >= 0x030000
82 # define DANESSL_USAGE_DANE_TA 2
83 # define DANESSL_USAGE_DANE_EE 3
84 # else
85 # error GnuTLS version too early for DANE
86 # endif
87 # if GNUTLS_VERSION_NUMBER < 0x999999
88 # define GNUTLS_BROKEN_DANE_VALIDATION
89 # endif
90 #endif
91
92 #ifndef DISABLE_OCSP
93 # include <gnutls/ocsp.h>
94 #endif
95 #ifdef SUPPORT_DANE
96 # include <gnutls/dane.h>
97 #endif
98
99 #include "tls-cipher-stdname.c"
100
101
102 /* GnuTLS 2 vs 3
103
104 GnuTLS 3 only:
105 gnutls_global_set_audit_log_function()
106
107 Changes:
108 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
109 */
110
111 /* Local static variables for GnuTLS */
112
113 /* Values for verify_requirement */
114
115 enum peer_verify_requirement
116 { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE };
117
118 /* This holds most state for server or client; with this, we can set up an
119 outbound TLS-enabled connection in an ACL callout, while not stomping all
120 over the TLS variables available for expansion.
121
122 Some of these correspond to variables in globals.c; those variables will
123 be set to point to content in one of these instances, as appropriate for
124 the stage of the process lifetime.
125
126 Not handled here: global tls_channelbinding_b64.
127 */
128
129 typedef struct exim_gnutls_state {
130 gnutls_session_t session;
131 gnutls_certificate_credentials_t x509_cred;
132 gnutls_priority_t priority_cache;
133 enum peer_verify_requirement verify_requirement;
134 int fd_in;
135 int fd_out;
136 BOOL peer_cert_verified;
137 BOOL peer_dane_verified;
138 BOOL trigger_sni_changes;
139 BOOL have_set_peerdn;
140 const struct host_item *host; /* NULL if server */
141 gnutls_x509_crt_t peercert;
142 uschar *peerdn;
143 uschar *ciphersuite;
144 uschar *received_sni;
145
146 const uschar *tls_certificate;
147 const uschar *tls_privatekey;
148 const uschar *tls_sni; /* client send only, not received */
149 const uschar *tls_verify_certificates;
150 const uschar *tls_crl;
151 const uschar *tls_require_ciphers;
152
153 uschar *exp_tls_certificate;
154 uschar *exp_tls_privatekey;
155 uschar *exp_tls_verify_certificates;
156 uschar *exp_tls_crl;
157 uschar *exp_tls_require_ciphers;
158 const uschar *exp_tls_verify_cert_hostnames;
159 #ifndef DISABLE_EVENT
160 uschar *event_action;
161 #endif
162 #ifdef SUPPORT_DANE
163 char * const * dane_data;
164 const int * dane_data_len;
165 #endif
166
167 tls_support *tlsp; /* set in tls_init() */
168
169 uschar *xfer_buffer;
170 int xfer_buffer_lwm;
171 int xfer_buffer_hwm;
172 BOOL xfer_eof; /*XXX never gets set! */
173 BOOL xfer_error;
174 } exim_gnutls_state_st;
175
176 static const exim_gnutls_state_st exim_gnutls_state_init = {
177 .session = NULL,
178 .x509_cred = NULL,
179 .priority_cache = NULL,
180 .verify_requirement = VERIFY_NONE,
181 .fd_in = -1,
182 .fd_out = -1,
183 .peer_cert_verified = FALSE,
184 .peer_dane_verified = FALSE,
185 .trigger_sni_changes =FALSE,
186 .have_set_peerdn = FALSE,
187 .host = NULL,
188 .peercert = NULL,
189 .peerdn = NULL,
190 .ciphersuite = NULL,
191 .received_sni = NULL,
192
193 .tls_certificate = NULL,
194 .tls_privatekey = NULL,
195 .tls_sni = NULL,
196 .tls_verify_certificates = NULL,
197 .tls_crl = NULL,
198 .tls_require_ciphers =NULL,
199
200 .exp_tls_certificate = NULL,
201 .exp_tls_privatekey = NULL,
202 .exp_tls_verify_certificates = NULL,
203 .exp_tls_crl = NULL,
204 .exp_tls_require_ciphers = NULL,
205 .exp_tls_verify_cert_hostnames = NULL,
206 #ifndef DISABLE_EVENT
207 .event_action = NULL,
208 #endif
209 .tlsp = NULL,
210
211 .xfer_buffer = NULL,
212 .xfer_buffer_lwm = 0,
213 .xfer_buffer_hwm = 0,
214 .xfer_eof = FALSE,
215 .xfer_error = FALSE,
216 };
217
218 /* Not only do we have our own APIs which don't pass around state, assuming
219 it's held in globals, GnuTLS doesn't appear to let us register callback data
220 for callbacks, or as part of the session, so we have to keep a "this is the
221 context we're currently dealing with" pointer and rely upon being
222 single-threaded to keep from processing data on an inbound TLS connection while
223 talking to another TLS connection for an outbound check. This does mean that
224 there's no way for heart-beats to be responded to, for the duration of the
225 second connection.
226 XXX But see gnutls_session_get_ptr()
227 */
228
229 static exim_gnutls_state_st state_server;
230
231 /* dh_params are initialised once within the lifetime of a process using TLS;
232 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
233 don't want to repeat this. */
234
235 static gnutls_dh_params_t dh_server_params = NULL;
236
237 /* No idea how this value was chosen; preserving it. Default is 3600. */
238
239 static const int ssl_session_timeout = 200;
240
241 static const uschar * const exim_default_gnutls_priority = US"NORMAL";
242
243 /* Guard library core initialisation */
244
245 static BOOL exim_gnutls_base_init_done = FALSE;
246
247 #ifndef DISABLE_OCSP
248 static BOOL gnutls_buggy_ocsp = FALSE;
249 #endif
250
251
252 /* ------------------------------------------------------------------------ */
253 /* macros */
254
255 #define MAX_HOST_LEN 255
256
257 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
258 the library logging; a value less than 0 disables the calls to set up logging
259 callbacks. Possibly GNuTLS also looks for an environment variable
260 "GNUTLS_DEBUG_LEVEL". */
261 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
262 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
263 #endif
264
265 #ifndef EXIM_CLIENT_DH_MIN_BITS
266 # define EXIM_CLIENT_DH_MIN_BITS 1024
267 #endif
268
269 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
270 can ask for a bit-strength. Without that, we stick to the constant we had
271 before, for now. */
272 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
273 # define EXIM_SERVER_DH_BITS_PRE2_12 1024
274 #endif
275
276 #define exim_gnutls_err_check(rc, Label) do { \
277 if ((rc) != GNUTLS_E_SUCCESS) \
278 return tls_error((Label), US gnutls_strerror(rc), host, errstr); \
279 } while (0)
280
281 #define expand_check_tlsvar(Varname, errstr) \
282 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
283
284 #if GNUTLS_VERSION_NUMBER >= 0x020c00
285 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
286 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
287 # define HAVE_GNUTLS_RND
288 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
289 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
290 * isn't available sometimes, so this needs to become a conditional
291 * compilation; the sanest way to deal with this being a problem on
292 * older OSes is to block it in the Local/Makefile with this compiler
293 * definition */
294 # ifndef AVOID_GNUTLS_PKCS11
295 # define HAVE_GNUTLS_PKCS11
296 # endif /* AVOID_GNUTLS_PKCS11 */
297 #endif
298
299
300
301
302 /* ------------------------------------------------------------------------ */
303 /* Callback declarations */
304
305 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
306 static void exim_gnutls_logger_cb(int level, const char *message);
307 #endif
308
309 static int exim_sni_handling_cb(gnutls_session_t session);
310
311 #ifndef DISABLE_OCSP
312 static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
313 gnutls_datum_t * ocsp_response);
314 #endif
315
316
317
318 /* ------------------------------------------------------------------------ */
319 /* Static functions */
320
321 /*************************************************
322 * Handle TLS error *
323 *************************************************/
324
325 /* Called from lots of places when errors occur before actually starting to do
326 the TLS handshake, that is, while the session is still in clear. Always returns
327 DEFER for a server and FAIL for a client so that most calls can use "return
328 tls_error(...)" to do this processing and then give an appropriate return. A
329 single function is used for both server and client, because it is called from
330 some shared functions.
331
332 Argument:
333 prefix text to include in the logged error
334 msg additional error string (may be NULL)
335 usually obtained from gnutls_strerror()
336 host NULL if setting up a server;
337 the connected host if setting up a client
338 errstr pointer to returned error string
339
340 Returns: OK/DEFER/FAIL
341 */
342
343 static int
344 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
345 uschar ** errstr)
346 {
347 if (errstr)
348 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
349 return host ? FAIL : DEFER;
350 }
351
352
353
354
355 /*************************************************
356 * Deal with logging errors during I/O *
357 *************************************************/
358
359 /* We have to get the identity of the peer from saved data.
360
361 Argument:
362 state the current GnuTLS exim state container
363 rc the GnuTLS error code, or 0 if it's a local error
364 when text identifying read or write
365 text local error text when rc is 0
366
367 Returns: nothing
368 */
369
370 static void
371 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
372 {
373 const uschar * msg;
374 uschar * errstr;
375
376 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
377 msg = string_sprintf("A TLS fatal alert has been received: %s",
378 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
379 else
380 msg = US gnutls_strerror(rc);
381
382 (void) tls_error(when, msg, state->host, &errstr);
383
384 if (state->host)
385 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
386 state->host->name, state->host->address, errstr);
387 else
388 {
389 uschar * conn_info = smtp_get_connection_info();
390 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
391 /* I'd like to get separated H= here, but too hard for now */
392 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
393 }
394 }
395
396
397
398
399 /*************************************************
400 * Set various Exim expansion vars *
401 *************************************************/
402
403 #define exim_gnutls_cert_err(Label) \
404 do \
405 { \
406 if (rc != GNUTLS_E_SUCCESS) \
407 { \
408 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
409 (Label), gnutls_strerror(rc)); \
410 return rc; \
411 } \
412 } while (0)
413
414 static int
415 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
416 {
417 int rc;
418
419 rc = gnutls_x509_crt_init(crtp);
420 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
421
422 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
423 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
424
425 return rc;
426 }
427
428 #undef exim_gnutls_cert_err
429
430
431 /* We set various Exim global variables from the state, once a session has
432 been established. With TLS callouts, may need to change this to stack
433 variables, or just re-call it with the server state after client callout
434 has finished.
435
436 Make sure anything set here is unset in tls_getc().
437
438 Sets:
439 tls_active fd
440 tls_bits strength indicator
441 tls_certificate_verified bool indicator
442 tls_channelbinding_b64 for some SASL mechanisms
443 tls_cipher a string
444 tls_peercert pointer to library internal
445 tls_peerdn a string
446 tls_sni a (UTF-8) string
447 tls_ourcert pointer to library internal
448
449 Argument:
450 state the relevant exim_gnutls_state_st *
451 */
452
453 static void
454 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
455 {
456 gnutls_cipher_algorithm_t cipher;
457 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
458 int old_pool;
459 int rc;
460 gnutls_datum_t channel;
461 #endif
462 tls_support * tlsp = state->tlsp;
463
464 tlsp->active.sock = state->fd_out;
465 tlsp->active.tls_ctx = state;
466
467 cipher = gnutls_cipher_get(state->session);
468 /* returns size in "bytes" */
469 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
470
471 tlsp->cipher = state->ciphersuite;
472
473 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
474
475 tlsp->certificate_verified = state->peer_cert_verified;
476 #ifdef SUPPORT_DANE
477 tlsp->dane_verified = state->peer_dane_verified;
478 #endif
479
480 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
481 only available for use for authenticators while this TLS session is running. */
482
483 tls_channelbinding_b64 = NULL;
484 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
485 channel.data = NULL;
486 channel.size = 0;
487 if ((rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel)))
488 { DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); }
489 else
490 {
491 old_pool = store_pool;
492 store_pool = POOL_PERM;
493 tls_channelbinding_b64 = b64encode(CUS channel.data, (int)channel.size);
494 store_pool = old_pool;
495 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
496 }
497 #endif
498
499 /* peercert is set in peer_status() */
500 tlsp->peerdn = state->peerdn;
501 tlsp->sni = state->received_sni;
502
503 /* record our certificate */
504 {
505 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
506 gnutls_x509_crt_t crt;
507
508 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
509 }
510 }
511
512
513
514
515 /*************************************************
516 * Setup up DH parameters *
517 *************************************************/
518
519 /* Generating the D-H parameters may take a long time. They only need to
520 be re-generated every so often, depending on security policy. What we do is to
521 keep these parameters in a file in the spool directory. If the file does not
522 exist, we generate them. This means that it is easy to cause a regeneration.
523
524 The new file is written as a temporary file and renamed, so that an incomplete
525 file is never present. If two processes both compute some new parameters, you
526 waste a bit of effort, but it doesn't seem worth messing around with locking to
527 prevent this.
528
529 Returns: OK/DEFER/FAIL
530 */
531
532 static int
533 init_server_dh(uschar ** errstr)
534 {
535 int fd, rc;
536 unsigned int dh_bits;
537 gnutls_datum_t m;
538 uschar filename_buf[PATH_MAX];
539 uschar *filename = NULL;
540 size_t sz;
541 uschar *exp_tls_dhparam;
542 BOOL use_file_in_spool = FALSE;
543 BOOL use_fixed_file = FALSE;
544 host_item *host = NULL; /* dummy for macros */
545
546 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
547
548 rc = gnutls_dh_params_init(&dh_server_params);
549 exim_gnutls_err_check(rc, US"gnutls_dh_params_init");
550
551 m.data = NULL;
552 m.size = 0;
553
554 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
555 return DEFER;
556
557 if (!exp_tls_dhparam)
558 {
559 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
560 m.data = US std_dh_prime_default();
561 m.size = Ustrlen(m.data);
562 }
563 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
564 use_file_in_spool = TRUE;
565 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
566 {
567 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
568 return OK;
569 }
570 else if (exp_tls_dhparam[0] != '/')
571 {
572 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
573 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
574 m.size = Ustrlen(m.data);
575 }
576 else
577 {
578 use_fixed_file = TRUE;
579 filename = exp_tls_dhparam;
580 }
581
582 if (m.data)
583 {
584 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
585 exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
586 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
587 return OK;
588 }
589
590 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
591 /* If you change this constant, also change dh_param_fn_ext so that we can use a
592 different filename and ensure we have sufficient bits. */
593 dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL);
594 if (!dh_bits)
595 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
596 DEBUG(D_tls)
597 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
598 dh_bits);
599 #else
600 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
601 DEBUG(D_tls)
602 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
603 dh_bits);
604 #endif
605
606 /* Some clients have hard-coded limits. */
607 if (dh_bits > tls_dh_max_bits)
608 {
609 DEBUG(D_tls)
610 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
611 tls_dh_max_bits);
612 dh_bits = tls_dh_max_bits;
613 }
614
615 if (use_file_in_spool)
616 {
617 if (!string_format(filename_buf, sizeof(filename_buf),
618 "%s/gnutls-params-%d", spool_directory, dh_bits))
619 return tls_error(US"overlong filename", NULL, NULL, errstr);
620 filename = filename_buf;
621 }
622
623 /* Open the cache file for reading and if successful, read it and set up the
624 parameters. */
625
626 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
627 {
628 struct stat statbuf;
629 FILE *fp;
630 int saved_errno;
631
632 if (fstat(fd, &statbuf) < 0) /* EIO */
633 {
634 saved_errno = errno;
635 (void)close(fd);
636 return tls_error(US"TLS cache stat failed", US strerror(saved_errno), NULL, errstr);
637 }
638 if (!S_ISREG(statbuf.st_mode))
639 {
640 (void)close(fd);
641 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
642 }
643 if (!(fp = fdopen(fd, "rb")))
644 {
645 saved_errno = errno;
646 (void)close(fd);
647 return tls_error(US"fdopen(TLS cache stat fd) failed",
648 US strerror(saved_errno), NULL, errstr);
649 }
650
651 m.size = statbuf.st_size;
652 if (!(m.data = malloc(m.size)))
653 {
654 fclose(fp);
655 return tls_error(US"malloc failed", US strerror(errno), NULL, errstr);
656 }
657 if (!(sz = fread(m.data, m.size, 1, fp)))
658 {
659 saved_errno = errno;
660 fclose(fp);
661 free(m.data);
662 return tls_error(US"fread failed", US strerror(saved_errno), NULL, errstr);
663 }
664 fclose(fp);
665
666 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
667 free(m.data);
668 exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
669 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
670 }
671
672 /* If the file does not exist, fall through to compute new data and cache it.
673 If there was any other opening error, it is serious. */
674
675 else if (errno == ENOENT)
676 {
677 rc = -1;
678 DEBUG(D_tls)
679 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
680 }
681 else
682 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
683 NULL, NULL, errstr);
684
685 /* If ret < 0, either the cache file does not exist, or the data it contains
686 is not useful. One particular case of this is when upgrading from an older
687 release of Exim in which the data was stored in a different format. We don't
688 try to be clever and support both formats; we just regenerate new data in this
689 case. */
690
691 if (rc < 0)
692 {
693 uschar *temp_fn;
694 unsigned int dh_bits_gen = dh_bits;
695
696 if ((PATH_MAX - Ustrlen(filename)) < 10)
697 return tls_error(US"Filename too long to generate replacement",
698 filename, NULL, errstr);
699
700 temp_fn = string_copy(US"%s.XXXXXXX");
701 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
702 return tls_error(US"Unable to open temp file", US strerror(errno), NULL, errstr);
703 (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */
704
705 /* GnuTLS overshoots!
706 * If we ask for 2236, we might get 2237 or more.
707 * But there's no way to ask GnuTLS how many bits there really are.
708 * We can ask how many bits were used in a TLS session, but that's it!
709 * The prime itself is hidden behind too much abstraction.
710 * So we ask for less, and proceed on a wing and a prayer.
711 * First attempt, subtracted 3 for 2233 and got 2240.
712 */
713 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
714 {
715 dh_bits_gen = dh_bits - 10;
716 DEBUG(D_tls)
717 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
718 dh_bits_gen);
719 }
720
721 DEBUG(D_tls)
722 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
723 dh_bits_gen);
724 rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen);
725 exim_gnutls_err_check(rc, US"gnutls_dh_params_generate2");
726
727 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
728 and I confirmed that a NULL call to get the size first is how the GnuTLS
729 sample apps handle this. */
730
731 sz = 0;
732 m.data = NULL;
733 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
734 m.data, &sz);
735 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
736 exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3(NULL) sizing");
737 m.size = sz;
738 if (!(m.data = malloc(m.size)))
739 return tls_error(US"memory allocation failed", US strerror(errno), NULL, errstr);
740
741 /* this will return a size 1 less than the allocation size above */
742 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
743 m.data, &sz);
744 if (rc != GNUTLS_E_SUCCESS)
745 {
746 free(m.data);
747 exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3() real");
748 }
749 m.size = sz; /* shrink by 1, probably */
750
751 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
752 {
753 free(m.data);
754 return tls_error(US"TLS cache write D-H params failed",
755 US strerror(errno), NULL, errstr);
756 }
757 free(m.data);
758 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
759 return tls_error(US"TLS cache write D-H params final newline failed",
760 US strerror(errno), NULL, errstr);
761
762 if ((rc = close(fd)))
763 return tls_error(US"TLS cache write close() failed", US strerror(errno), NULL, errstr);
764
765 if (Urename(temp_fn, filename) < 0)
766 return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
767 temp_fn, filename), US strerror(errno), NULL, errstr);
768
769 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
770 }
771
772 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
773 return OK;
774 }
775
776
777
778
779 /* Create and install a selfsigned certificate, for use in server mode */
780
781 static int
782 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
783 {
784 gnutls_x509_crt_t cert = NULL;
785 time_t now;
786 gnutls_x509_privkey_t pkey = NULL;
787 const uschar * where;
788 int rc;
789
790 where = US"initialising pkey";
791 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
792
793 where = US"initialising cert";
794 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
795
796 where = US"generating pkey";
797 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
798 #ifdef SUPPORT_PARAM_TO_PK_BITS
799 # ifndef GNUTLS_SEC_PARAM_MEDIUM
800 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
801 # endif
802 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
803 #else
804 2048,
805 #endif
806 0)))
807 goto err;
808
809 where = US"configuring cert";
810 now = 1;
811 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
812 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
813 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
814 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
815 || (rc = gnutls_x509_crt_set_key(cert, pkey))
816
817 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
818 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
819 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
820 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
821 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
822 GNUTLS_OID_X520_COMMON_NAME, 0,
823 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
824 )
825 goto err;
826
827 where = US"signing cert";
828 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
829
830 where = US"installing selfsign cert";
831 /* Since: 2.4.0 */
832 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
833 goto err;
834
835 rc = OK;
836
837 out:
838 if (cert) gnutls_x509_crt_deinit(cert);
839 if (pkey) gnutls_x509_privkey_deinit(pkey);
840 return rc;
841
842 err:
843 rc = tls_error(where, US gnutls_strerror(rc), NULL, errstr);
844 goto out;
845 }
846
847
848
849
850 /* Add certificate and key, from files.
851
852 Return:
853 Zero or negative: good. Negate value for certificate index if < 0.
854 Greater than zero: FAIL or DEFER code.
855 */
856
857 static int
858 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
859 uschar * certfile, uschar * keyfile, uschar ** errstr)
860 {
861 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
862 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
863 if (rc < 0)
864 return tls_error(
865 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
866 US gnutls_strerror(rc), host, errstr);
867 return -rc;
868 }
869
870
871 /*************************************************
872 * Variables re-expanded post-SNI *
873 *************************************************/
874
875 /* Called from both server and client code, via tls_init(), and also from
876 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
877
878 We can tell the two apart by state->received_sni being non-NULL in callback.
879
880 The callback should not call us unless state->trigger_sni_changes is true,
881 which we are responsible for setting on the first pass through.
882
883 Arguments:
884 state exim_gnutls_state_st *
885 errstr error string pointer
886
887 Returns: OK/DEFER/FAIL
888 */
889
890 static int
891 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
892 {
893 struct stat statbuf;
894 int rc;
895 const host_item *host = state->host; /* macro should be reconsidered? */
896 uschar *saved_tls_certificate = NULL;
897 uschar *saved_tls_privatekey = NULL;
898 uschar *saved_tls_verify_certificates = NULL;
899 uschar *saved_tls_crl = NULL;
900 int cert_count;
901
902 /* We check for tls_sni *before* expansion. */
903 if (!host) /* server */
904 if (!state->received_sni)
905 {
906 if ( state->tls_certificate
907 && ( Ustrstr(state->tls_certificate, US"tls_sni")
908 || Ustrstr(state->tls_certificate, US"tls_in_sni")
909 || Ustrstr(state->tls_certificate, US"tls_out_sni")
910 ) )
911 {
912 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
913 state->trigger_sni_changes = TRUE;
914 }
915 }
916 else
917 {
918 /* useful for debugging */
919 saved_tls_certificate = state->exp_tls_certificate;
920 saved_tls_privatekey = state->exp_tls_privatekey;
921 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
922 saved_tls_crl = state->exp_tls_crl;
923 }
924
925 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
926 exim_gnutls_err_check(rc, US"gnutls_certificate_allocate_credentials");
927
928 #ifdef SUPPORT_SRV_OCSP_STACK
929 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
930 #endif
931
932 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
933 state members, assuming consistent naming; and expand_check() returns
934 false if expansion failed, unless expansion was forced to fail. */
935
936 /* check if we at least have a certificate, before doing expensive
937 D-H generation. */
938
939 if (!expand_check_tlsvar(tls_certificate, errstr))
940 return DEFER;
941
942 /* certificate is mandatory in server, optional in client */
943
944 if ( !state->exp_tls_certificate
945 || !*state->exp_tls_certificate
946 )
947 if (!host)
948 return tls_install_selfsign(state, errstr);
949 else
950 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
951
952 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
953 return DEFER;
954
955 /* tls_privatekey is optional, defaulting to same file as certificate */
956
957 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
958 {
959 state->tls_privatekey = state->tls_certificate;
960 state->exp_tls_privatekey = state->exp_tls_certificate;
961 }
962
963
964 if (state->exp_tls_certificate && *state->exp_tls_certificate)
965 {
966 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
967 state->exp_tls_certificate, state->exp_tls_privatekey);
968
969 if (state->received_sni)
970 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
971 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
972 )
973 {
974 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
975 }
976 else
977 {
978 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
979 }
980
981 if (!host) /* server */
982 {
983 const uschar * clist = state->exp_tls_certificate;
984 const uschar * klist = state->exp_tls_privatekey;
985 const uschar * olist;
986 int csep = 0, ksep = 0, osep = 0, cnt = 0;
987 uschar * cfile, * kfile, * ofile;
988
989 #ifndef DISABLE_OCSP
990 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
991 return DEFER;
992 olist = ofile;
993 #endif
994
995 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
996
997 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
998 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
999 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
1000 return rc;
1001 else
1002 {
1003 int gnutls_cert_index = -rc;
1004 DEBUG(D_tls) debug_printf("TLS: cert/key %s registered\n", cfile);
1005
1006 /* Set the OCSP stapling server info */
1007
1008 #ifndef DISABLE_OCSP
1009 if (tls_ocsp_file)
1010 if (gnutls_buggy_ocsp)
1011 {
1012 DEBUG(D_tls)
1013 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1014 }
1015 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1016 {
1017 /* Use the full callback method for stapling just to get
1018 observability. More efficient would be to read the file once only,
1019 if it never changed (due to SNI). Would need restart on file update,
1020 or watch datestamp. */
1021
1022 # ifdef SUPPORT_SRV_OCSP_STACK
1023 rc = gnutls_certificate_set_ocsp_status_request_function2(
1024 state->x509_cred, gnutls_cert_index,
1025 server_ocsp_stapling_cb, ofile);
1026
1027 exim_gnutls_err_check(rc,
1028 US"gnutls_certificate_set_ocsp_status_request_function2");
1029 # else
1030 if (cnt++ > 0)
1031 {
1032 DEBUG(D_tls)
1033 debug_printf("oops; multiple OCSP files not supported\n");
1034 break;
1035 }
1036 gnutls_certificate_set_ocsp_status_request_function(
1037 state->x509_cred, server_ocsp_stapling_cb, ofile);
1038 # endif
1039
1040 DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile);
1041 }
1042 else
1043 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1044 #endif
1045 }
1046 }
1047 else
1048 {
1049 if (0 < (rc = tls_add_certfile(state, host,
1050 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1051 return rc;
1052 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1053 }
1054
1055 } /* tls_certificate */
1056
1057
1058 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1059 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1060 error message is provided. However, if we just refrain from setting anything up
1061 in that case, certificate verification fails, which seems to be the correct
1062 behaviour. */
1063
1064 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1065 {
1066 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1067 return DEFER;
1068 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1069 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1070 state->exp_tls_verify_certificates = NULL;
1071 #endif
1072 if (state->tls_crl && *state->tls_crl)
1073 if (!expand_check_tlsvar(tls_crl, errstr))
1074 return DEFER;
1075
1076 if (!(state->exp_tls_verify_certificates &&
1077 *state->exp_tls_verify_certificates))
1078 {
1079 DEBUG(D_tls)
1080 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1081 /* With no tls_verify_certificates, we ignore tls_crl too */
1082 return OK;
1083 }
1084 }
1085 else
1086 {
1087 DEBUG(D_tls)
1088 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1089 return OK;
1090 }
1091
1092 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1093 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1094 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1095 else
1096 #endif
1097 {
1098 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1099 {
1100 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
1101 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1102 strerror(errno));
1103 return DEFER;
1104 }
1105
1106 #ifndef SUPPORT_CA_DIR
1107 /* The test suite passes in /dev/null; we could check for that path explicitly,
1108 but who knows if someone has some weird FIFO which always dumps some certs, or
1109 other weirdness. The thing we really want to check is that it's not a
1110 directory, since while OpenSSL supports that, GnuTLS does not.
1111 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1112 if (S_ISDIR(statbuf.st_mode))
1113 {
1114 DEBUG(D_tls)
1115 debug_printf("verify certificates path is a dir: \"%s\"\n",
1116 state->exp_tls_verify_certificates);
1117 log_write(0, LOG_MAIN|LOG_PANIC,
1118 "tls_verify_certificates \"%s\" is a directory",
1119 state->exp_tls_verify_certificates);
1120 return DEFER;
1121 }
1122 #endif
1123
1124 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1125 state->exp_tls_verify_certificates, statbuf.st_size);
1126
1127 if (statbuf.st_size == 0)
1128 {
1129 DEBUG(D_tls)
1130 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1131 return OK;
1132 }
1133
1134 cert_count =
1135
1136 #ifdef SUPPORT_CA_DIR
1137 (statbuf.st_mode & S_IFMT) == S_IFDIR
1138 ?
1139 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1140 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1141 :
1142 #endif
1143 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1144 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1145 }
1146
1147 if (cert_count < 0)
1148 {
1149 rc = cert_count;
1150 exim_gnutls_err_check(rc, US"setting certificate trust");
1151 }
1152 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
1153
1154 if (state->tls_crl && *state->tls_crl &&
1155 state->exp_tls_crl && *state->exp_tls_crl)
1156 {
1157 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1158 cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1159 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
1160 if (cert_count < 0)
1161 {
1162 rc = cert_count;
1163 exim_gnutls_err_check(rc, US"gnutls_certificate_set_x509_crl_file");
1164 }
1165 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1166 }
1167
1168 return OK;
1169 }
1170
1171
1172
1173
1174 /*************************************************
1175 * Set X.509 state variables *
1176 *************************************************/
1177
1178 /* In GnuTLS, the registered cert/key are not replaced by a later
1179 set of a cert/key, so for SNI support we need a whole new x509_cred
1180 structure. Which means various other non-re-expanded pieces of state
1181 need to be re-set in the new struct, so the setting logic is pulled
1182 out to this.
1183
1184 Arguments:
1185 state exim_gnutls_state_st *
1186 errstr error string pointer
1187
1188 Returns: OK/DEFER/FAIL
1189 */
1190
1191 static int
1192 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1193 {
1194 int rc;
1195 const host_item *host = state->host; /* macro should be reconsidered? */
1196
1197 /* Create D-H parameters, or read them from the cache file. This function does
1198 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1199 client-side params. */
1200
1201 if (!state->host)
1202 {
1203 if (!dh_server_params)
1204 {
1205 rc = init_server_dh(errstr);
1206 if (rc != OK) return rc;
1207 }
1208 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1209 }
1210
1211 /* Link the credentials to the session. */
1212
1213 rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
1214 exim_gnutls_err_check(rc, US"gnutls_credentials_set");
1215
1216 return OK;
1217 }
1218
1219 /*************************************************
1220 * Initialize for GnuTLS *
1221 *************************************************/
1222
1223
1224 #ifndef DISABLE_OCSP
1225
1226 static BOOL
1227 tls_is_buggy_ocsp(void)
1228 {
1229 const uschar * s;
1230 uschar maj, mid, mic;
1231
1232 s = CUS gnutls_check_version(NULL);
1233 maj = atoi(CCS s);
1234 if (maj == 3)
1235 {
1236 while (*s && *s != '.') s++;
1237 mid = atoi(CCS ++s);
1238 if (mid <= 2)
1239 return TRUE;
1240 else if (mid >= 5)
1241 return FALSE;
1242 else
1243 {
1244 while (*s && *s != '.') s++;
1245 mic = atoi(CCS ++s);
1246 return mic <= (mid == 3 ? 16 : 3);
1247 }
1248 }
1249 return FALSE;
1250 }
1251
1252 #endif
1253
1254
1255 /* Called from both server and client code. In the case of a server, errors
1256 before actual TLS negotiation return DEFER.
1257
1258 Arguments:
1259 host connected host, if client; NULL if server
1260 certificate certificate file
1261 privatekey private key file
1262 sni TLS SNI to send, sometimes when client; else NULL
1263 cas CA certs file
1264 crl CRL file
1265 require_ciphers tls_require_ciphers setting
1266 caller_state returned state-info structure
1267 errstr error string pointer
1268
1269 Returns: OK/DEFER/FAIL
1270 */
1271
1272 static int
1273 tls_init(
1274 const host_item *host,
1275 const uschar *certificate,
1276 const uschar *privatekey,
1277 const uschar *sni,
1278 const uschar *cas,
1279 const uschar *crl,
1280 const uschar *require_ciphers,
1281 exim_gnutls_state_st **caller_state,
1282 tls_support * tlsp,
1283 uschar ** errstr)
1284 {
1285 exim_gnutls_state_st *state;
1286 int rc;
1287 size_t sz;
1288 const char *errpos;
1289 uschar *p;
1290
1291 if (!exim_gnutls_base_init_done)
1292 {
1293 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
1294
1295 #ifdef HAVE_GNUTLS_PKCS11
1296 /* By default, gnutls_global_init will init PKCS11 support in auto mode,
1297 which loads modules from a config file, which sounds good and may be wanted
1298 by some sysadmin, but also means in common configurations that GNOME keyring
1299 environment variables are used and so breaks for users calling mailq.
1300 To prevent this, we init PKCS11 first, which is the documented approach. */
1301 if (!gnutls_allow_auto_pkcs11)
1302 {
1303 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
1304 exim_gnutls_err_check(rc, US"gnutls_pkcs11_init");
1305 }
1306 #endif
1307
1308 rc = gnutls_global_init();
1309 exim_gnutls_err_check(rc, US"gnutls_global_init");
1310
1311 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1312 DEBUG(D_tls)
1313 {
1314 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1315 /* arbitrarily chosen level; bump up to 9 for more */
1316 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1317 }
1318 #endif
1319
1320 #ifndef DISABLE_OCSP
1321 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1322 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1323 #endif
1324
1325 exim_gnutls_base_init_done = TRUE;
1326 }
1327
1328 if (host)
1329 {
1330 /* For client-side sessions we allocate a context. This lets us run
1331 several in parallel. */
1332 int old_pool = store_pool;
1333 store_pool = POOL_PERM;
1334 state = store_get(sizeof(exim_gnutls_state_st));
1335 store_pool = old_pool;
1336
1337 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1338 state->tlsp = tlsp;
1339 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1340 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1341 }
1342 else
1343 {
1344 state = &state_server;
1345 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1346 state->tlsp = tlsp;
1347 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1348 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1349 }
1350 exim_gnutls_err_check(rc, US"gnutls_init");
1351
1352 state->host = host;
1353
1354 state->tls_certificate = certificate;
1355 state->tls_privatekey = privatekey;
1356 state->tls_require_ciphers = require_ciphers;
1357 state->tls_sni = sni;
1358 state->tls_verify_certificates = cas;
1359 state->tls_crl = crl;
1360
1361 /* This handles the variables that might get re-expanded after TLS SNI;
1362 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1363
1364 DEBUG(D_tls)
1365 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1366 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1367
1368 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1369 requires a new structure afterwards. */
1370
1371 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1372
1373 /* set SNI in client, only */
1374 if (host)
1375 {
1376 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1377 return DEFER;
1378 if (state->tlsp->sni && *state->tlsp->sni)
1379 {
1380 DEBUG(D_tls)
1381 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1382 sz = Ustrlen(state->tlsp->sni);
1383 rc = gnutls_server_name_set(state->session,
1384 GNUTLS_NAME_DNS, state->tlsp->sni, sz);
1385 exim_gnutls_err_check(rc, US"gnutls_server_name_set");
1386 }
1387 }
1388 else if (state->tls_sni)
1389 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1390 "have an SNI set for a server [%s]\n", state->tls_sni);
1391
1392 /* This is the priority string support,
1393 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1394 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1395 This was backwards incompatible, but means Exim no longer needs to track
1396 all algorithms and provide string forms for them. */
1397
1398 p = NULL;
1399 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1400 {
1401 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1402 return DEFER;
1403 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1404 {
1405 p = state->exp_tls_require_ciphers;
1406 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
1407 }
1408 }
1409 if (!p)
1410 {
1411 p = exim_default_gnutls_priority;
1412 DEBUG(D_tls)
1413 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
1414 }
1415 rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos);
1416
1417 exim_gnutls_err_check(rc, string_sprintf(
1418 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1419 p, errpos - CS p, errpos));
1420
1421 rc = gnutls_priority_set(state->session, state->priority_cache);
1422 exim_gnutls_err_check(rc, US"gnutls_priority_set");
1423
1424 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
1425
1426 /* Reduce security in favour of increased compatibility, if the admin
1427 decides to make that trade-off. */
1428 if (gnutls_compat_mode)
1429 {
1430 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
1431 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
1432 gnutls_session_enable_compatibility_mode(state->session);
1433 #else
1434 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
1435 #endif
1436 }
1437
1438 *caller_state = state;
1439 return OK;
1440 }
1441
1442
1443
1444 /*************************************************
1445 * Extract peer information *
1446 *************************************************/
1447
1448 static const uschar *
1449 cipher_stdname_kcm(gnutls_kx_algorithm_t kx, gnutls_cipher_algorithm_t cipher,
1450 gnutls_mac_algorithm_t mac)
1451 {
1452 uschar cs_id[2];
1453 gnutls_kx_algorithm_t kx_i;
1454 gnutls_cipher_algorithm_t cipher_i;
1455 gnutls_mac_algorithm_t mac_i;
1456
1457 for (size_t i = 0;
1458 gnutls_cipher_suite_info(i, cs_id, &kx_i, &cipher_i, &mac_i, NULL);
1459 i++)
1460 if (kx_i == kx && cipher_i == cipher && mac_i == mac)
1461 return cipher_stdname(cs_id[0], cs_id[1]);
1462 return NULL;
1463 }
1464
1465
1466
1467 /* Called from both server and client code.
1468 Only this is allowed to set state->peerdn and state->have_set_peerdn
1469 and we use that to detect double-calls.
1470
1471 NOTE: the state blocks last while the TLS connection is up, which is fine
1472 for logging in the server side, but for the client side, we log after teardown
1473 in src/deliver.c. While the session is up, we can twist about states and
1474 repoint tls_* globals, but those variables used for logging or other variable
1475 expansion that happens _after_ delivery need to have a longer life-time.
1476
1477 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1478 doing this more than once per generation of a state context. We set them in
1479 the state context, and repoint tls_* to them. After the state goes away, the
1480 tls_* copies of the pointers remain valid and client delivery logging is happy.
1481
1482 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1483 don't apply.
1484
1485 Arguments:
1486 state exim_gnutls_state_st *
1487 errstr pointer to error string
1488
1489 Returns: OK/DEFER/FAIL
1490 */
1491
1492 static int
1493 peer_status(exim_gnutls_state_st *state, uschar ** errstr)
1494 {
1495 const gnutls_datum_t *cert_list;
1496 int old_pool, rc;
1497 unsigned int cert_list_size = 0;
1498 gnutls_protocol_t protocol;
1499 gnutls_cipher_algorithm_t cipher;
1500 gnutls_kx_algorithm_t kx;
1501 gnutls_mac_algorithm_t mac;
1502 gnutls_certificate_type_t ct;
1503 gnutls_x509_crt_t crt;
1504 uschar *dn_buf;
1505 size_t sz;
1506
1507 if (state->have_set_peerdn)
1508 return OK;
1509 state->have_set_peerdn = TRUE;
1510
1511 state->peerdn = NULL;
1512
1513 /* tls_cipher */
1514 cipher = gnutls_cipher_get(state->session);
1515 protocol = gnutls_protocol_get_version(state->session);
1516 mac = gnutls_mac_get(state->session);
1517 kx = gnutls_kx_get(state->session);
1518
1519 old_pool = store_pool;
1520 {
1521 store_pool = POOL_PERM;
1522 state->ciphersuite = string_sprintf("%s:%s:%d",
1523 gnutls_protocol_get_name(protocol),
1524 gnutls_cipher_suite_get_name(kx, cipher, mac),
1525 (int) gnutls_cipher_get_key_size(cipher) * 8);
1526
1527 /* I don't see a way that spaces could occur, in the current GnuTLS
1528 code base, but it was a concern in the old code and perhaps older GnuTLS
1529 releases did return "TLS 1.0"; play it safe, just in case. */
1530
1531 for (uschar * p = state->ciphersuite; *p; p++) if (isspace(*p)) *p = '-';
1532 state->tlsp->cipher = state->ciphersuite;
1533
1534 state->tlsp->cipher_stdname = cipher_stdname_kcm(kx, cipher, mac);
1535 }
1536 store_pool = old_pool;
1537
1538 /* tls_peerdn */
1539 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1540
1541 if (!cert_list || cert_list_size == 0)
1542 {
1543 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1544 cert_list, cert_list_size);
1545 if (state->verify_requirement >= VERIFY_REQUIRED)
1546 return tls_error(US"certificate verification failed",
1547 US"no certificate received from peer", state->host, errstr);
1548 return OK;
1549 }
1550
1551 if ((ct = gnutls_certificate_type_get(state->session)) != GNUTLS_CRT_X509)
1552 {
1553 const uschar * ctn = US gnutls_certificate_type_get_name(ct);
1554 DEBUG(D_tls)
1555 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1556 if (state->verify_requirement >= VERIFY_REQUIRED)
1557 return tls_error(US"certificate verification not possible, unhandled type",
1558 ctn, state->host, errstr);
1559 return OK;
1560 }
1561
1562 #define exim_gnutls_peer_err(Label) \
1563 do { \
1564 if (rc != GNUTLS_E_SUCCESS) \
1565 { \
1566 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \
1567 (Label), gnutls_strerror(rc)); \
1568 if (state->verify_requirement >= VERIFY_REQUIRED) \
1569 return tls_error((Label), US gnutls_strerror(rc), state->host, errstr); \
1570 return OK; \
1571 } \
1572 } while (0)
1573
1574 rc = import_cert(&cert_list[0], &crt);
1575 exim_gnutls_peer_err(US"cert 0");
1576
1577 state->tlsp->peercert = state->peercert = crt;
1578
1579 sz = 0;
1580 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1581 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1582 {
1583 exim_gnutls_peer_err(US"getting size for cert DN failed");
1584 return FAIL; /* should not happen */
1585 }
1586 dn_buf = store_get_perm(sz);
1587 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1588 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1589
1590 state->peerdn = dn_buf;
1591
1592 return OK;
1593 #undef exim_gnutls_peer_err
1594 }
1595
1596
1597
1598
1599 /*************************************************
1600 * Verify peer certificate *
1601 *************************************************/
1602
1603 /* Called from both server and client code.
1604 *Should* be using a callback registered with
1605 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1606 the peer information, but that's too new for some OSes.
1607
1608 Arguments:
1609 state exim_gnutls_state_st *
1610 errstr where to put an error message
1611
1612 Returns:
1613 FALSE if the session should be rejected
1614 TRUE if the cert is okay or we just don't care
1615 */
1616
1617 static BOOL
1618 verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
1619 {
1620 int rc;
1621 uint verify;
1622
1623 if (state->verify_requirement == VERIFY_NONE)
1624 return TRUE;
1625
1626 DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
1627 *errstr = NULL;
1628
1629 if ((rc = peer_status(state, errstr)) != OK || !state->peerdn)
1630 {
1631 verify = GNUTLS_CERT_INVALID;
1632 *errstr = US"certificate not supplied";
1633 }
1634 else
1635
1636 {
1637 #ifdef SUPPORT_DANE
1638 if (state->verify_requirement == VERIFY_DANE && state->host)
1639 {
1640 /* Using dane_verify_session_crt() would be easy, as it does it all for us
1641 including talking to a DNS resolver. But we want to do that bit ourselves
1642 as the testsuite intercepts and fakes its own DNS environment. */
1643
1644 dane_state_t s;
1645 dane_query_t r;
1646 uint lsize;
1647 const gnutls_datum_t * certlist =
1648 gnutls_certificate_get_peers(state->session, &lsize);
1649 int usage = tls_out.tlsa_usage;
1650
1651 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1652 /* Split the TLSA records into two sets, TA and EE selectors. Run the
1653 dane-verification separately so that we know which selector verified;
1654 then we know whether to do name-verification (needed for TA but not EE). */
1655
1656 if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
1657 { /* a mixed-usage bundle */
1658 int i, j, nrec;
1659 const char ** dd;
1660 int * ddl;
1661
1662 for(nrec = 0; state->dane_data_len[nrec]; ) nrec++;
1663 nrec++;
1664
1665 dd = store_get(nrec * sizeof(uschar *));
1666 ddl = store_get(nrec * sizeof(int));
1667 nrec--;
1668
1669 if ((rc = dane_state_init(&s, 0)))
1670 goto tlsa_prob;
1671
1672 for (usage = DANESSL_USAGE_DANE_EE;
1673 usage >= DANESSL_USAGE_DANE_TA; usage--)
1674 { /* take records with this usage */
1675 for (j = i = 0; i < nrec; i++)
1676 if (state->dane_data[i][0] == usage)
1677 {
1678 dd[j] = state->dane_data[i];
1679 ddl[j++] = state->dane_data_len[i];
1680 }
1681 if (j)
1682 {
1683 dd[j] = NULL;
1684 ddl[j] = 0;
1685
1686 if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
1687 goto tlsa_prob;
1688
1689 if ((rc = dane_verify_crt_raw(s, certlist, lsize,
1690 gnutls_certificate_type_get(state->session),
1691 r, 0,
1692 usage == DANESSL_USAGE_DANE_EE
1693 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1694 &verify)))
1695 {
1696 DEBUG(D_tls)
1697 debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
1698 }
1699 else if (verify == 0) /* verification passed */
1700 {
1701 usage = 1 << usage;
1702 break;
1703 }
1704 }
1705 }
1706
1707 if (rc) goto tlsa_prob;
1708 }
1709 else
1710 # endif
1711 {
1712 if ( (rc = dane_state_init(&s, 0))
1713 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
1714 1, 0))
1715 || (rc = dane_verify_crt_raw(s, certlist, lsize,
1716 gnutls_certificate_type_get(state->session),
1717 r, 0,
1718 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1719 usage == (1 << DANESSL_USAGE_DANE_EE)
1720 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1721 # else
1722 0,
1723 # endif
1724 &verify))
1725 )
1726 goto tlsa_prob;
1727 }
1728
1729 if (verify != 0) /* verification failed */
1730 {
1731 gnutls_datum_t str;
1732 (void) dane_verification_status_print(verify, &str, 0);
1733 *errstr = US str.data; /* don't bother to free */
1734 goto badcert;
1735 }
1736
1737 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1738 /* If a TA-mode TLSA record was used for verification we must additionally
1739 verify the cert name (but not the CA chain). For EE-mode, skip it. */
1740
1741 if (usage & (1 << DANESSL_USAGE_DANE_EE))
1742 # endif
1743 {
1744 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1745 goto goodcert;
1746 }
1747 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1748 /* Assume that the name on the A-record is the one that should be matching
1749 the cert. An alternate view is that the domain part of the email address
1750 is also permissible. */
1751
1752 if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1753 CS state->host->name))
1754 {
1755 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1756 goto goodcert;
1757 }
1758 # endif
1759 }
1760 #endif /*SUPPORT_DANE*/
1761
1762 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1763 }
1764
1765 /* Handle the result of verification. INVALID is set if any others are. */
1766
1767 if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
1768 {
1769 state->peer_cert_verified = FALSE;
1770 if (!*errstr)
1771 {
1772 #ifdef GNUTLS_CERT_VFY_STATUS_PRINT
1773 DEBUG(D_tls)
1774 {
1775 gnutls_datum_t txt;
1776
1777 if (gnutls_certificate_verification_status_print(verify,
1778 gnutls_certificate_type_get(state->session), &txt, 0)
1779 == GNUTLS_E_SUCCESS)
1780 {
1781 debug_printf("%s\n", txt.data);
1782 gnutls_free(txt.data);
1783 }
1784 }
1785 #endif
1786 *errstr = verify & GNUTLS_CERT_REVOKED
1787 ? US"certificate revoked" : US"certificate invalid";
1788 }
1789
1790 DEBUG(D_tls)
1791 debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
1792 *errstr, state->peerdn ? state->peerdn : US"<unset>");
1793
1794 if (state->verify_requirement >= VERIFY_REQUIRED)
1795 goto badcert;
1796 DEBUG(D_tls)
1797 debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
1798 }
1799
1800 else
1801 {
1802 /* Client side, check the server's certificate name versus the name on the
1803 A-record for the connection we made. What to do for server side - what name
1804 to use for client? We document that there is no such checking for server
1805 side. */
1806
1807 if ( state->exp_tls_verify_cert_hostnames
1808 && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1809 CS state->exp_tls_verify_cert_hostnames)
1810 )
1811 {
1812 DEBUG(D_tls)
1813 debug_printf("TLS certificate verification failed: cert name mismatch\n");
1814 if (state->verify_requirement >= VERIFY_REQUIRED)
1815 goto badcert;
1816 return TRUE;
1817 }
1818
1819 state->peer_cert_verified = TRUE;
1820 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
1821 state->peerdn ? state->peerdn : US"<unset>");
1822 }
1823
1824 goodcert:
1825 state->tlsp->peerdn = state->peerdn;
1826 return TRUE;
1827
1828 #ifdef SUPPORT_DANE
1829 tlsa_prob:
1830 *errstr = string_sprintf("TLSA record problem: %s",
1831 rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
1832 #endif
1833
1834 badcert:
1835 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1836 return FALSE;
1837 }
1838
1839
1840
1841
1842 /* ------------------------------------------------------------------------ */
1843 /* Callbacks */
1844
1845 /* Logging function which can be registered with
1846 * gnutls_global_set_log_function()
1847 * gnutls_global_set_log_level() 0..9
1848 */
1849 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1850 static void
1851 exim_gnutls_logger_cb(int level, const char *message)
1852 {
1853 size_t len = strlen(message);
1854 if (len < 1)
1855 {
1856 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1857 return;
1858 }
1859 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1860 message[len-1] == '\n' ? "" : "\n");
1861 }
1862 #endif
1863
1864
1865 /* Called after client hello, should handle SNI work.
1866 This will always set tls_sni (state->received_sni) if available,
1867 and may trigger presenting different certificates,
1868 if state->trigger_sni_changes is TRUE.
1869
1870 Should be registered with
1871 gnutls_handshake_set_post_client_hello_function()
1872
1873 "This callback must return 0 on success or a gnutls error code to terminate the
1874 handshake.".
1875
1876 For inability to get SNI information, we return 0.
1877 We only return non-zero if re-setup failed.
1878 Only used for server-side TLS.
1879 */
1880
1881 static int
1882 exim_sni_handling_cb(gnutls_session_t session)
1883 {
1884 char sni_name[MAX_HOST_LEN];
1885 size_t data_len = MAX_HOST_LEN;
1886 exim_gnutls_state_st *state = &state_server;
1887 unsigned int sni_type;
1888 int rc, old_pool;
1889 uschar * dummy_errstr;
1890
1891 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1892 if (rc != GNUTLS_E_SUCCESS)
1893 {
1894 DEBUG(D_tls) {
1895 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1896 debug_printf("TLS: no SNI presented in handshake.\n");
1897 else
1898 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1899 gnutls_strerror(rc), rc);
1900 }
1901 return 0;
1902 }
1903
1904 if (sni_type != GNUTLS_NAME_DNS)
1905 {
1906 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1907 return 0;
1908 }
1909
1910 /* We now have a UTF-8 string in sni_name */
1911 old_pool = store_pool;
1912 store_pool = POOL_PERM;
1913 state->received_sni = string_copyn(US sni_name, data_len);
1914 store_pool = old_pool;
1915
1916 /* We set this one now so that variable expansions below will work */
1917 state->tlsp->sni = state->received_sni;
1918
1919 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1920 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1921
1922 if (!state->trigger_sni_changes)
1923 return 0;
1924
1925 if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK)
1926 {
1927 /* If the setup of certs/etc failed before handshake, TLS would not have
1928 been offered. The best we can do now is abort. */
1929 return GNUTLS_E_APPLICATION_ERROR_MIN;
1930 }
1931
1932 rc = tls_set_remaining_x509(state, &dummy_errstr);
1933 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1934
1935 return 0;
1936 }
1937
1938
1939
1940 #ifndef DISABLE_OCSP
1941
1942 static int
1943 server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
1944 gnutls_datum_t * ocsp_response)
1945 {
1946 int ret;
1947 DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
1948
1949 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
1950 {
1951 DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
1952 CS ptr);
1953 tls_in.ocsp = OCSP_NOT_RESP;
1954 return GNUTLS_E_NO_CERTIFICATE_STATUS;
1955 }
1956
1957 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
1958 return 0;
1959 }
1960
1961 #endif
1962
1963
1964 #ifndef DISABLE_EVENT
1965 /*
1966 We use this callback to get observability and detail-level control
1967 for an exim TLS connection (either direction), raising a tls:cert event
1968 for each cert in the chain presented by the peer. Any event
1969 can deny verification.
1970
1971 Return 0 for the handshake to continue or non-zero to terminate.
1972 */
1973
1974 static int
1975 verify_cb(gnutls_session_t session)
1976 {
1977 const gnutls_datum_t * cert_list;
1978 unsigned int cert_list_size = 0;
1979 gnutls_x509_crt_t crt;
1980 int rc;
1981 uschar * yield;
1982 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
1983
1984 if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
1985 while (cert_list_size--)
1986 {
1987 if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
1988 {
1989 DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
1990 cert_list_size, gnutls_strerror(rc));
1991 break;
1992 }
1993
1994 state->tlsp->peercert = crt;
1995 if ((yield = event_raise(state->event_action,
1996 US"tls:cert", string_sprintf("%d", cert_list_size))))
1997 {
1998 log_write(0, LOG_MAIN,
1999 "SSL verify denied by event-action: depth=%d: %s",
2000 cert_list_size, yield);
2001 return 1; /* reject */
2002 }
2003 state->tlsp->peercert = NULL;
2004 }
2005
2006 return 0;
2007 }
2008
2009 #endif
2010
2011
2012 static gstring *
2013 ddump(gnutls_datum_t * d)
2014 {
2015 gstring * g = string_get((d->size+1) * 2);
2016 uschar * s = d->data;
2017 for (unsigned i = d->size; i > 0; i--, s++)
2018 {
2019 g = string_catn(g, US "0123456789abcdef" + (*s >> 4), 1);
2020 g = string_catn(g, US "0123456789abcdef" + (*s & 0xf), 1);
2021 }
2022 return g;
2023 }
2024
2025 /* ------------------------------------------------------------------------ */
2026 /* Exported functions */
2027
2028
2029
2030
2031 /*************************************************
2032 * Start a TLS session in a server *
2033 *************************************************/
2034
2035 /* This is called when Exim is running as a server, after having received
2036 the STARTTLS command. It must respond to that command, and then negotiate
2037 a TLS session.
2038
2039 Arguments:
2040 require_ciphers list of allowed ciphers or NULL
2041 errstr pointer to error string
2042
2043 Returns: OK on success
2044 DEFER for errors before the start of the negotiation
2045 FAIL for errors during the negotiation; the server can't
2046 continue running.
2047 */
2048
2049 int
2050 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2051 {
2052 int rc;
2053 exim_gnutls_state_st * state = NULL;
2054
2055 /* Check for previous activation */
2056 if (tls_in.active.sock >= 0)
2057 {
2058 tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
2059 smtp_printf("554 Already in TLS\r\n", FALSE);
2060 return FAIL;
2061 }
2062
2063 /* Initialize the library. If it fails, it will already have logged the error
2064 and sent an SMTP response. */
2065
2066 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
2067
2068 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
2069 NULL, tls_verify_certificates, tls_crl,
2070 require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
2071
2072 /* If this is a host for which certificate verification is mandatory or
2073 optional, set up appropriately. */
2074
2075 if (verify_check_host(&tls_verify_hosts) == OK)
2076 {
2077 DEBUG(D_tls)
2078 debug_printf("TLS: a client certificate will be required.\n");
2079 state->verify_requirement = VERIFY_REQUIRED;
2080 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2081 }
2082 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2083 {
2084 DEBUG(D_tls)
2085 debug_printf("TLS: a client certificate will be requested but not required.\n");
2086 state->verify_requirement = VERIFY_OPTIONAL;
2087 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2088 }
2089 else
2090 {
2091 DEBUG(D_tls)
2092 debug_printf("TLS: a client certificate will not be requested.\n");
2093 state->verify_requirement = VERIFY_NONE;
2094 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2095 }
2096
2097 #ifndef DISABLE_EVENT
2098 if (event_action)
2099 {
2100 state->event_action = event_action;
2101 gnutls_session_set_ptr(state->session, state);
2102 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2103 }
2104 #endif
2105
2106 /* Register SNI handling; always, even if not in tls_certificate, so that the
2107 expansion variable $tls_sni is always available. */
2108
2109 gnutls_handshake_set_post_client_hello_function(state->session,
2110 exim_sni_handling_cb);
2111
2112 /* Set context and tell client to go ahead, except in the case of TLS startup
2113 on connection, where outputting anything now upsets the clients and tends to
2114 make them disconnect. We need to have an explicit fflush() here, to force out
2115 the response. Other smtp_printf() calls do not need it, because in non-TLS
2116 mode, the fflush() happens when smtp_getc() is called. */
2117
2118 if (!state->tlsp->on_connect)
2119 {
2120 smtp_printf("220 TLS go ahead\r\n", FALSE);
2121 fflush(smtp_out);
2122 }
2123
2124 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2125 that the GnuTLS library doesn't.
2126 From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
2127 to set (and clear down afterwards) up a pull-timeout callback function that does
2128 a select, so we're no better off unless avoiding signals becomes an issue. */
2129
2130 gnutls_transport_set_ptr2(state->session,
2131 (gnutls_transport_ptr_t)(long) fileno(smtp_in),
2132 (gnutls_transport_ptr_t)(long) fileno(smtp_out));
2133 state->fd_in = fileno(smtp_in);
2134 state->fd_out = fileno(smtp_out);
2135
2136 sigalrm_seen = FALSE;
2137 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2138 do
2139 rc = gnutls_handshake(state->session);
2140 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2141 ALARM_CLR(0);
2142
2143 if (rc != GNUTLS_E_SUCCESS)
2144 {
2145 /* It seems that, except in the case of a timeout, we have to close the
2146 connection right here; otherwise if the other end is running OpenSSL it hangs
2147 until the server times out. */
2148
2149 if (sigalrm_seen)
2150 {
2151 tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
2152 gnutls_db_remove_session(state->session);
2153 }
2154 else
2155 {
2156 tls_error(US"gnutls_handshake", US gnutls_strerror(rc), NULL, errstr);
2157 (void) gnutls_alert_send_appropriate(state->session, rc);
2158 gnutls_deinit(state->session);
2159 gnutls_certificate_free_credentials(state->x509_cred);
2160 millisleep(500);
2161 shutdown(state->fd_out, SHUT_WR);
2162 for (int i = 1024; fgetc(smtp_in) != EOF && i > 0; ) i--; /* drain skt */
2163 (void)fclose(smtp_out);
2164 (void)fclose(smtp_in);
2165 smtp_out = smtp_in = NULL;
2166 }
2167
2168 return FAIL;
2169 }
2170
2171 DEBUG(D_tls)
2172 {
2173 debug_printf("gnutls_handshake was successful\n");
2174 #ifdef SUPPORT_GNUTLS_SESS_DESC
2175 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2176 #endif
2177 #ifdef SUPPORT_GNUTLS_KEYLOG
2178 {
2179 gnutls_datum_t c, s;
2180 gstring * gc, * gs;
2181 gnutls_session_get_random(state->session, &c, &s);
2182 gnutls_session_get_master_secret(state->session, &s);
2183 gc = ddump(&c);
2184 gs = ddump(&s);
2185 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2186 }
2187 #endif
2188 }
2189
2190 /* Verify after the fact */
2191
2192 if (!verify_certificate(state, errstr))
2193 {
2194 if (state->verify_requirement != VERIFY_OPTIONAL)
2195 {
2196 (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr);
2197 return FAIL;
2198 }
2199 DEBUG(D_tls)
2200 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
2201 *errstr);
2202 }
2203
2204 /* Figure out peer DN, and if authenticated, etc. */
2205
2206 if ((rc = peer_status(state, NULL)) != OK) return rc;
2207
2208 /* Sets various Exim expansion variables; always safe within server */
2209
2210 extract_exim_vars_from_tls_state(state);
2211
2212 /* TLS has been set up. Adjust the input functions to read via TLS,
2213 and initialize appropriately. */
2214
2215 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2216
2217 receive_getc = tls_getc;
2218 receive_getbuf = tls_getbuf;
2219 receive_get_cache = tls_get_cache;
2220 receive_ungetc = tls_ungetc;
2221 receive_feof = tls_feof;
2222 receive_ferror = tls_ferror;
2223 receive_smtp_buffered = tls_smtp_buffered;
2224
2225 return OK;
2226 }
2227
2228
2229
2230
2231 static void
2232 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
2233 smtp_transport_options_block * ob)
2234 {
2235 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2236 {
2237 state->exp_tls_verify_cert_hostnames =
2238 #ifdef SUPPORT_I18N
2239 string_domain_utf8_to_alabel(host->name, NULL);
2240 #else
2241 host->name;
2242 #endif
2243 DEBUG(D_tls)
2244 debug_printf("TLS: server cert verification includes hostname: \"%s\".\n",
2245 state->exp_tls_verify_cert_hostnames);
2246 }
2247 }
2248
2249
2250
2251
2252 #ifdef SUPPORT_DANE
2253 /* Given our list of RRs from the TLSA lookup, build a lookup block in
2254 GnuTLS-DANE's preferred format. Hang it on the state str for later
2255 use in DANE verification.
2256
2257 We point at the dnsa data not copy it, so it must remain valid until
2258 after verification is done.*/
2259
2260 static BOOL
2261 dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
2262 {
2263 dns_scan dnss;
2264 int i;
2265 const char ** dane_data;
2266 int * dane_data_len;
2267
2268 i = 1;
2269 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2270 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2271 ) if (rr->type == T_TLSA) i++;
2272
2273 dane_data = store_get(i * sizeof(uschar *));
2274 dane_data_len = store_get(i * sizeof(int));
2275
2276 i = 0;
2277 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2278 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2279 ) if (rr->type == T_TLSA && rr->size > 3)
2280 {
2281 const uschar * p = rr->data;
2282 uint8_t usage = p[0], sel = p[1], type = p[2];
2283
2284 DEBUG(D_tls)
2285 debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
2286
2287 if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
2288 || (sel != 0 && sel != 1)
2289 )
2290 continue;
2291 switch(type)
2292 {
2293 case 0: /* Full: cannot check at present */
2294 break;
2295 case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */
2296 break;
2297 case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */
2298 break;
2299 default: continue;
2300 }
2301
2302 tls_out.tlsa_usage |= 1<<usage;
2303 dane_data[i] = CS p;
2304 dane_data_len[i++] = rr->size;
2305 }
2306
2307 if (!i) return FALSE;
2308
2309 dane_data[i] = NULL;
2310 dane_data_len[i] = 0;
2311
2312 state->dane_data = (char * const *)dane_data;
2313 state->dane_data_len = dane_data_len;
2314 return TRUE;
2315 }
2316 #endif
2317
2318
2319
2320 /*************************************************
2321 * Start a TLS session in a client *
2322 *************************************************/
2323
2324 /* Called from the smtp transport after STARTTLS has been accepted.
2325
2326 Arguments:
2327 fd the fd of the connection
2328 host connected host (for messages and option-tests)
2329 addr the first address (not used)
2330 tb transport (always smtp)
2331 tlsa_dnsa non-NULL, either request or require dane for this host, and
2332 a TLSA record found. Therefore, dane verify required.
2333 Which implies cert must be requested and supplied, dane
2334 verify must pass, and cert verify irrelevant (incl.
2335 hostnames), and (caller handled) require_tls
2336 tlsp record details of channel configuration
2337 errstr error string pointer
2338
2339 Returns: Pointer to TLS session context, or NULL on error
2340 */
2341
2342 void *
2343 tls_client_start(int fd, host_item *host,
2344 address_item *addr ARG_UNUSED,
2345 transport_instance * tb,
2346 #ifdef SUPPORT_DANE
2347 dns_answer * tlsa_dnsa,
2348 #endif
2349 tls_support * tlsp, uschar ** errstr)
2350 {
2351 smtp_transport_options_block *ob = tb
2352 ? (smtp_transport_options_block *)tb->options_block
2353 : &smtp_transport_option_defaults;
2354 int rc;
2355 exim_gnutls_state_st * state = NULL;
2356 uschar *cipher_list = NULL;
2357
2358 #ifndef DISABLE_OCSP
2359 BOOL require_ocsp =
2360 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2361 BOOL request_ocsp = require_ocsp ? TRUE
2362 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2363 #endif
2364
2365 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
2366
2367 #ifdef SUPPORT_DANE
2368 if (tlsa_dnsa && ob->dane_require_tls_ciphers)
2369 {
2370 /* not using expand_check_tlsvar because not yet in state */
2371 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2372 &cipher_list, errstr))
2373 return NULL;
2374 cipher_list = cipher_list && *cipher_list
2375 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2376 }
2377 #endif
2378
2379 if (!cipher_list)
2380 cipher_list = ob->tls_require_ciphers;
2381
2382 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2383 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2384 cipher_list, &state, tlsp, errstr) != OK)
2385 return NULL;
2386
2387 {
2388 int dh_min_bits = ob->tls_dh_min_bits;
2389 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2390 {
2391 DEBUG(D_tls)
2392 debug_printf("WARNING: tls_dh_min_bits far too low,"
2393 " clamping %d up to %d\n",
2394 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2395 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2396 }
2397
2398 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2399 " acceptable bits to %d\n",
2400 dh_min_bits);
2401 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2402 }
2403
2404 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2405 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2406 the specified host patterns if one of them is defined */
2407
2408 #ifdef SUPPORT_DANE
2409 if (tlsa_dnsa && dane_tlsa_load(state, tlsa_dnsa))
2410 {
2411 DEBUG(D_tls)
2412 debug_printf("TLS: server certificate DANE required.\n");
2413 state->verify_requirement = VERIFY_DANE;
2414 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2415 }
2416 else
2417 #endif
2418 if ( ( state->exp_tls_verify_certificates
2419 && !ob->tls_verify_hosts
2420 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2421 )
2422 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2423 )
2424 {
2425 tls_client_setup_hostname_checks(host, state, ob);
2426 DEBUG(D_tls)
2427 debug_printf("TLS: server certificate verification required.\n");
2428 state->verify_requirement = VERIFY_REQUIRED;
2429 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2430 }
2431 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2432 {
2433 tls_client_setup_hostname_checks(host, state, ob);
2434 DEBUG(D_tls)
2435 debug_printf("TLS: server certificate verification optional.\n");
2436 state->verify_requirement = VERIFY_OPTIONAL;
2437 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2438 }
2439 else
2440 {
2441 DEBUG(D_tls)
2442 debug_printf("TLS: server certificate verification not required.\n");
2443 state->verify_requirement = VERIFY_NONE;
2444 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2445 }
2446
2447 #ifndef DISABLE_OCSP
2448 /* supported since GnuTLS 3.1.3 */
2449 if (request_ocsp)
2450 {
2451 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2452 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2453 NULL, 0, NULL)) != OK)
2454 {
2455 tls_error(US"cert-status-req", US gnutls_strerror(rc), state->host, errstr);
2456 return NULL;
2457 }
2458 tlsp->ocsp = OCSP_NOT_RESP;
2459 }
2460 #endif
2461
2462 #ifndef DISABLE_EVENT
2463 if (tb && tb->event_action)
2464 {
2465 state->event_action = tb->event_action;
2466 gnutls_session_set_ptr(state->session, state);
2467 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2468 }
2469 #endif
2470
2471 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) fd);
2472 state->fd_in = fd;
2473 state->fd_out = fd;
2474
2475 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2476 /* There doesn't seem to be a built-in timeout on connection. */
2477
2478 sigalrm_seen = FALSE;
2479 ALARM(ob->command_timeout);
2480 do
2481 rc = gnutls_handshake(state->session);
2482 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2483 ALARM_CLR(0);
2484
2485 if (rc != GNUTLS_E_SUCCESS)
2486 {
2487 if (sigalrm_seen)
2488 {
2489 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2490 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2491 }
2492 else
2493 tls_error(US"gnutls_handshake", US gnutls_strerror(rc), state->host, errstr);
2494 return NULL;
2495 }
2496
2497 DEBUG(D_tls)
2498 {
2499 debug_printf("gnutls_handshake was successful\n");
2500 #ifdef SUPPORT_GNUTLS_SESS_DESC
2501 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2502 #endif
2503 #ifdef SUPPORT_GNUTLS_KEYLOG
2504 {
2505 gnutls_datum_t c, s;
2506 gstring * gc, * gs;
2507 gnutls_session_get_random(state->session, &c, &s);
2508 gnutls_session_get_master_secret(state->session, &s);
2509 gc = ddump(&c);
2510 gs = ddump(&s);
2511 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2512 }
2513 #endif
2514 }
2515
2516 /* Verify late */
2517
2518 if (!verify_certificate(state, errstr))
2519 {
2520 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
2521 return NULL;
2522 }
2523
2524 #ifndef DISABLE_OCSP
2525 if (require_ocsp)
2526 {
2527 DEBUG(D_tls)
2528 {
2529 gnutls_datum_t stapling;
2530 gnutls_ocsp_resp_t resp;
2531 gnutls_datum_t printed;
2532 if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0
2533 && (rc= gnutls_ocsp_resp_init(&resp)) == 0
2534 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
2535 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0
2536 )
2537 {
2538 debug_printf("%.4096s", printed.data);
2539 gnutls_free(printed.data);
2540 }
2541 else
2542 (void) tls_error(US"ocsp decode", US gnutls_strerror(rc), state->host, errstr);
2543 }
2544
2545 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
2546 {
2547 tlsp->ocsp = OCSP_FAILED;
2548 tls_error(US"certificate status check failed", NULL, state->host, errstr);
2549 return NULL;
2550 }
2551 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
2552 tlsp->ocsp = OCSP_VFIED;
2553 }
2554 #endif
2555
2556 /* Figure out peer DN, and if authenticated, etc. */
2557
2558 if (peer_status(state, errstr) != OK)
2559 return NULL;
2560
2561 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
2562
2563 extract_exim_vars_from_tls_state(state);
2564
2565 return state;
2566 }
2567
2568
2569
2570
2571 /*************************************************
2572 * Close down a TLS session *
2573 *************************************************/
2574
2575 /* This is also called from within a delivery subprocess forked from the
2576 daemon, to shut down the TLS library, without actually doing a shutdown (which
2577 would tamper with the TLS session in the parent process).
2578
2579 Arguments:
2580 ct_ctx client context pointer, or NULL for the one global server context
2581 shutdown 1 if TLS close-alert is to be sent,
2582 2 if also response to be waited for
2583
2584 Returns: nothing
2585 */
2586
2587 void
2588 tls_close(void * ct_ctx, int shutdown)
2589 {
2590 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2591
2592 if (!state->tlsp || state->tlsp->active.sock < 0) return; /* TLS was not active */
2593
2594 if (shutdown)
2595 {
2596 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
2597 shutdown > 1 ? " (with response-wait)" : "");
2598
2599 ALARM(2);
2600 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
2601 ALARM_CLR(0);
2602 }
2603
2604 gnutls_deinit(state->session);
2605 gnutls_certificate_free_credentials(state->x509_cred);
2606
2607
2608 state->tlsp->active.sock = -1;
2609 state->tlsp->active.tls_ctx = NULL;
2610 if (state->xfer_buffer) store_free(state->xfer_buffer);
2611 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
2612 }
2613
2614
2615
2616
2617 static BOOL
2618 tls_refill(unsigned lim)
2619 {
2620 exim_gnutls_state_st * state = &state_server;
2621 ssize_t inbytes;
2622
2623 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
2624 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
2625
2626 sigalrm_seen = FALSE;
2627 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2628
2629 do
2630 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
2631 MIN(ssl_xfer_buffer_size, lim));
2632 while (inbytes == GNUTLS_E_AGAIN);
2633
2634 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2635
2636 if (had_command_timeout) /* set by signal handler */
2637 smtp_command_timeout_exit(); /* does not return */
2638 if (had_command_sigterm)
2639 smtp_command_sigterm_exit();
2640 if (had_data_timeout)
2641 smtp_data_timeout_exit();
2642 if (had_data_sigint)
2643 smtp_data_sigint_exit();
2644
2645 /* Timeouts do not get this far. A zero-byte return appears to mean that the
2646 TLS session has been closed down, not that the socket itself has been closed
2647 down. Revert to non-TLS handling. */
2648
2649 if (sigalrm_seen)
2650 {
2651 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
2652 state->xfer_error = TRUE;
2653 return FALSE;
2654 }
2655
2656 else if (inbytes == 0)
2657 {
2658 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2659
2660 receive_getc = smtp_getc;
2661 receive_getbuf = smtp_getbuf;
2662 receive_get_cache = smtp_get_cache;
2663 receive_ungetc = smtp_ungetc;
2664 receive_feof = smtp_feof;
2665 receive_ferror = smtp_ferror;
2666 receive_smtp_buffered = smtp_buffered;
2667
2668 gnutls_deinit(state->session);
2669 gnutls_certificate_free_credentials(state->x509_cred);
2670
2671 state->session = NULL;
2672 state->tlsp->active.sock = -1;
2673 state->tlsp->active.tls_ctx = NULL;
2674 state->tlsp->bits = 0;
2675 state->tlsp->certificate_verified = FALSE;
2676 tls_channelbinding_b64 = NULL;
2677 state->tlsp->cipher = NULL;
2678 state->tlsp->peercert = NULL;
2679 state->tlsp->peerdn = NULL;
2680
2681 return FALSE;
2682 }
2683
2684 /* Handle genuine errors */
2685
2686 else if (inbytes < 0)
2687 {
2688 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
2689 record_io_error(state, (int) inbytes, US"recv", NULL);
2690 state->xfer_error = TRUE;
2691 return FALSE;
2692 }
2693 #ifndef DISABLE_DKIM
2694 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
2695 #endif
2696 state->xfer_buffer_hwm = (int) inbytes;
2697 state->xfer_buffer_lwm = 0;
2698 return TRUE;
2699 }
2700
2701 /*************************************************
2702 * TLS version of getc *
2703 *************************************************/
2704
2705 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2706 it refills the buffer via the GnuTLS reading function.
2707 Only used by the server-side TLS.
2708
2709 This feeds DKIM and should be used for all message-body reads.
2710
2711 Arguments: lim Maximum amount to read/buffer
2712 Returns: the next character or EOF
2713 */
2714
2715 int
2716 tls_getc(unsigned lim)
2717 {
2718 exim_gnutls_state_st * state = &state_server;
2719
2720 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2721 if (!tls_refill(lim))
2722 return state->xfer_error ? EOF : smtp_getc(lim);
2723
2724 /* Something in the buffer; return next uschar */
2725
2726 return state->xfer_buffer[state->xfer_buffer_lwm++];
2727 }
2728
2729 uschar *
2730 tls_getbuf(unsigned * len)
2731 {
2732 exim_gnutls_state_st * state = &state_server;
2733 unsigned size;
2734 uschar * buf;
2735
2736 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2737 if (!tls_refill(*len))
2738 {
2739 if (!state->xfer_error) return smtp_getbuf(len);
2740 *len = 0;
2741 return NULL;
2742 }
2743
2744 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
2745 size = *len;
2746 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
2747 state->xfer_buffer_lwm += size;
2748 *len = size;
2749 return buf;
2750 }
2751
2752
2753 void
2754 tls_get_cache()
2755 {
2756 #ifndef DISABLE_DKIM
2757 exim_gnutls_state_st * state = &state_server;
2758 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
2759 if (n > 0)
2760 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
2761 #endif
2762 }
2763
2764
2765 BOOL
2766 tls_could_read(void)
2767 {
2768 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
2769 || gnutls_record_check_pending(state_server.session) > 0;
2770 }
2771
2772
2773
2774
2775 /*************************************************
2776 * Read bytes from TLS channel *
2777 *************************************************/
2778
2779 /* This does not feed DKIM, so if the caller uses this for reading message body,
2780 then the caller must feed DKIM.
2781
2782 Arguments:
2783 ct_ctx client context pointer, or NULL for the one global server context
2784 buff buffer of data
2785 len size of buffer
2786
2787 Returns: the number of bytes read
2788 -1 after a failed read, including EOF
2789 */
2790
2791 int
2792 tls_read(void * ct_ctx, uschar *buff, size_t len)
2793 {
2794 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2795 ssize_t inbytes;
2796
2797 if (len > INT_MAX)
2798 len = INT_MAX;
2799
2800 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
2801 DEBUG(D_tls)
2802 debug_printf("*** PROBABLY A BUG *** " \
2803 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
2804 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
2805
2806 DEBUG(D_tls)
2807 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
2808 state->session, buff, len);
2809
2810 do
2811 inbytes = gnutls_record_recv(state->session, buff, len);
2812 while (inbytes == GNUTLS_E_AGAIN);
2813
2814 if (inbytes > 0) return inbytes;
2815 if (inbytes == 0)
2816 {
2817 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2818 }
2819 else
2820 {
2821 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
2822 record_io_error(state, (int)inbytes, US"recv", NULL);
2823 }
2824
2825 return -1;
2826 }
2827
2828
2829
2830
2831 /*************************************************
2832 * Write bytes down TLS channel *
2833 *************************************************/
2834
2835 /*
2836 Arguments:
2837 ct_ctx client context pointer, or NULL for the one global server context
2838 buff buffer of data
2839 len number of bytes
2840 more more data expected soon
2841
2842 Returns: the number of bytes after a successful write,
2843 -1 after a failed write
2844 */
2845
2846 int
2847 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
2848 {
2849 ssize_t outbytes;
2850 size_t left = len;
2851 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2852 #ifdef SUPPORT_CORK
2853 static BOOL corked = FALSE;
2854
2855 if (more && !corked) gnutls_record_cork(state->session);
2856 #endif
2857
2858 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
2859 buff, left, more ? ", more" : "");
2860
2861 while (left > 0)
2862 {
2863 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
2864 buff, left);
2865
2866 do
2867 outbytes = gnutls_record_send(state->session, buff, left);
2868 while (outbytes == GNUTLS_E_AGAIN);
2869
2870 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
2871 if (outbytes < 0)
2872 {
2873 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
2874 record_io_error(state, outbytes, US"send", NULL);
2875 return -1;
2876 }
2877 if (outbytes == 0)
2878 {
2879 record_io_error(state, 0, US"send", US"TLS channel closed on write");
2880 return -1;
2881 }
2882
2883 left -= outbytes;
2884 buff += outbytes;
2885 }
2886
2887 if (len > INT_MAX)
2888 {
2889 DEBUG(D_tls)
2890 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
2891 len);
2892 len = INT_MAX;
2893 }
2894
2895 #ifdef SUPPORT_CORK
2896 if (more != corked)
2897 {
2898 if (!more) (void) gnutls_record_uncork(state->session, 0);
2899 corked = more;
2900 }
2901 #endif
2902
2903 return (int) len;
2904 }
2905
2906
2907
2908
2909 /*************************************************
2910 * Random number generation *
2911 *************************************************/
2912
2913 /* Pseudo-random number generation. The result is not expected to be
2914 cryptographically strong but not so weak that someone will shoot themselves
2915 in the foot using it as a nonce in input in some email header scheme or
2916 whatever weirdness they'll twist this into. The result should handle fork()
2917 and avoid repeating sequences. OpenSSL handles that for us.
2918
2919 Arguments:
2920 max range maximum
2921 Returns a random number in range [0, max-1]
2922 */
2923
2924 #ifdef HAVE_GNUTLS_RND
2925 int
2926 vaguely_random_number(int max)
2927 {
2928 unsigned int r;
2929 int i, needed_len;
2930 uschar smallbuf[sizeof(r)];
2931
2932 if (max <= 1)
2933 return 0;
2934
2935 needed_len = sizeof(r);
2936 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2937 asked for a number less than 10. */
2938
2939 for (r = max, i = 0; r; ++i)
2940 r >>= 1;
2941 i = (i + 7) / 8;
2942 if (i < needed_len)
2943 needed_len = i;
2944
2945 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
2946 if (i < 0)
2947 {
2948 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
2949 return vaguely_random_number_fallback(max);
2950 }
2951 r = 0;
2952 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
2953 r = r * 256 + *p;
2954
2955 /* We don't particularly care about weighted results; if someone wants
2956 * smooth distribution and cares enough then they should submit a patch then. */
2957 return r % max;
2958 }
2959 #else /* HAVE_GNUTLS_RND */
2960 int
2961 vaguely_random_number(int max)
2962 {
2963 return vaguely_random_number_fallback(max);
2964 }
2965 #endif /* HAVE_GNUTLS_RND */
2966
2967
2968
2969
2970 /*************************************************
2971 * Let tls_require_ciphers be checked at startup *
2972 *************************************************/
2973
2974 /* The tls_require_ciphers option, if set, must be something which the
2975 library can parse.
2976
2977 Returns: NULL on success, or error message
2978 */
2979
2980 uschar *
2981 tls_validate_require_cipher(void)
2982 {
2983 int rc;
2984 uschar *expciphers = NULL;
2985 gnutls_priority_t priority_cache;
2986 const char *errpos;
2987 uschar * dummy_errstr;
2988
2989 #define validate_check_rc(Label) do { \
2990 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
2991 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
2992 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
2993
2994 if (exim_gnutls_base_init_done)
2995 log_write(0, LOG_MAIN|LOG_PANIC,
2996 "already initialised GnuTLS, Exim developer bug");
2997
2998 #ifdef HAVE_GNUTLS_PKCS11
2999 if (!gnutls_allow_auto_pkcs11)
3000 {
3001 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
3002 validate_check_rc(US"gnutls_pkcs11_init");
3003 }
3004 #endif
3005 rc = gnutls_global_init();
3006 validate_check_rc(US"gnutls_global_init()");
3007 exim_gnutls_base_init_done = TRUE;
3008
3009 if (!(tls_require_ciphers && *tls_require_ciphers))
3010 return_deinit(NULL);
3011
3012 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3013 &dummy_errstr))
3014 return_deinit(US"failed to expand tls_require_ciphers");
3015
3016 if (!(expciphers && *expciphers))
3017 return_deinit(NULL);
3018
3019 DEBUG(D_tls)
3020 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3021
3022 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
3023 validate_check_rc(string_sprintf(
3024 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
3025 expciphers, errpos - CS expciphers, errpos));
3026
3027 #undef return_deinit
3028 #undef validate_check_rc
3029 gnutls_global_deinit();
3030
3031 return NULL;
3032 }
3033
3034
3035
3036
3037 /*************************************************
3038 * Report the library versions. *
3039 *************************************************/
3040
3041 /* See a description in tls-openssl.c for an explanation of why this exists.
3042
3043 Arguments: a FILE* to print the results to
3044 Returns: nothing
3045 */
3046
3047 void
3048 tls_version_report(FILE *f)
3049 {
3050 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
3051 " Runtime: %s\n",
3052 LIBGNUTLS_VERSION,
3053 gnutls_check_version(NULL));
3054 }
3055
3056 /* vi: aw ai sw=2
3057 */
3058 /* End of tls-gnu.c */