ad55f95cdae975fc8085b43e4b54fdff4265eab0
[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 expand_check_tlsvar(Varname, errstr) \
277 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
278
279 #if GNUTLS_VERSION_NUMBER >= 0x020c00
280 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
281 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
282 # define HAVE_GNUTLS_RND
283 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
284 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
285 * isn't available sometimes, so this needs to become a conditional
286 * compilation; the sanest way to deal with this being a problem on
287 * older OSes is to block it in the Local/Makefile with this compiler
288 * definition */
289 # ifndef AVOID_GNUTLS_PKCS11
290 # define HAVE_GNUTLS_PKCS11
291 # endif /* AVOID_GNUTLS_PKCS11 */
292 #endif
293
294
295
296
297 /* ------------------------------------------------------------------------ */
298 /* Callback declarations */
299
300 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
301 static void exim_gnutls_logger_cb(int level, const char *message);
302 #endif
303
304 static int exim_sni_handling_cb(gnutls_session_t session);
305
306 #ifndef DISABLE_OCSP
307 static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
308 gnutls_datum_t * ocsp_response);
309 #endif
310
311
312
313 /* ------------------------------------------------------------------------ */
314 /* Static functions */
315
316 /*************************************************
317 * Handle TLS error *
318 *************************************************/
319
320 /* Called from lots of places when errors occur before actually starting to do
321 the TLS handshake, that is, while the session is still in clear. Always returns
322 DEFER for a server and FAIL for a client so that most calls can use "return
323 tls_error(...)" to do this processing and then give an appropriate return. A
324 single function is used for both server and client, because it is called from
325 some shared functions.
326
327 Argument:
328 prefix text to include in the logged error
329 msg additional error string (may be NULL)
330 usually obtained from gnutls_strerror()
331 host NULL if setting up a server;
332 the connected host if setting up a client
333 errstr pointer to returned error string
334
335 Returns: OK/DEFER/FAIL
336 */
337
338 static int
339 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
340 uschar ** errstr)
341 {
342 if (errstr)
343 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
344 return host ? FAIL : DEFER;
345 }
346
347
348 static int
349 tls_error_gnu(const uschar *prefix, int err, const host_item *host,
350 uschar ** errstr)
351 {
352 return tls_error(prefix, US gnutls_strerror(err), host, errstr);
353 }
354
355 static int
356 tls_error_sys(const uschar *prefix, int err, const host_item *host,
357 uschar ** errstr)
358 {
359 return tls_error(prefix, US strerror(err), host, errstr);
360 }
361
362
363 /*************************************************
364 * Deal with logging errors during I/O *
365 *************************************************/
366
367 /* We have to get the identity of the peer from saved data.
368
369 Argument:
370 state the current GnuTLS exim state container
371 rc the GnuTLS error code, or 0 if it's a local error
372 when text identifying read or write
373 text local error text when rc is 0
374
375 Returns: nothing
376 */
377
378 static void
379 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
380 {
381 const uschar * msg;
382 uschar * errstr;
383
384 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
385 msg = string_sprintf("A TLS fatal alert has been received: %s",
386 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
387 else
388 msg = US gnutls_strerror(rc);
389
390 (void) tls_error(when, msg, state->host, &errstr);
391
392 if (state->host)
393 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
394 state->host->name, state->host->address, errstr);
395 else
396 {
397 uschar * conn_info = smtp_get_connection_info();
398 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
399 /* I'd like to get separated H= here, but too hard for now */
400 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
401 }
402 }
403
404
405
406
407 /*************************************************
408 * Set various Exim expansion vars *
409 *************************************************/
410
411 #define exim_gnutls_cert_err(Label) \
412 do \
413 { \
414 if (rc != GNUTLS_E_SUCCESS) \
415 { \
416 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
417 (Label), gnutls_strerror(rc)); \
418 return rc; \
419 } \
420 } while (0)
421
422 static int
423 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
424 {
425 int rc;
426
427 rc = gnutls_x509_crt_init(crtp);
428 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
429
430 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
431 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
432
433 return rc;
434 }
435
436 #undef exim_gnutls_cert_err
437
438
439 /* We set various Exim global variables from the state, once a session has
440 been established. With TLS callouts, may need to change this to stack
441 variables, or just re-call it with the server state after client callout
442 has finished.
443
444 Make sure anything set here is unset in tls_getc().
445
446 Sets:
447 tls_active fd
448 tls_bits strength indicator
449 tls_certificate_verified bool indicator
450 tls_channelbinding_b64 for some SASL mechanisms
451 tls_cipher a string
452 tls_peercert pointer to library internal
453 tls_peerdn a string
454 tls_sni a (UTF-8) string
455 tls_ourcert pointer to library internal
456
457 Argument:
458 state the relevant exim_gnutls_state_st *
459 */
460
461 static void
462 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
463 {
464 gnutls_cipher_algorithm_t cipher;
465 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
466 int old_pool;
467 int rc;
468 gnutls_datum_t channel;
469 #endif
470 tls_support * tlsp = state->tlsp;
471
472 tlsp->active.sock = state->fd_out;
473 tlsp->active.tls_ctx = state;
474
475 cipher = gnutls_cipher_get(state->session);
476 /* returns size in "bytes" */
477 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
478
479 tlsp->cipher = state->ciphersuite;
480
481 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
482
483 tlsp->certificate_verified = state->peer_cert_verified;
484 #ifdef SUPPORT_DANE
485 tlsp->dane_verified = state->peer_dane_verified;
486 #endif
487
488 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
489 only available for use for authenticators while this TLS session is running. */
490
491 tls_channelbinding_b64 = NULL;
492 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
493 channel.data = NULL;
494 channel.size = 0;
495 if ((rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel)))
496 { DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); }
497 else
498 {
499 old_pool = store_pool;
500 store_pool = POOL_PERM;
501 tls_channelbinding_b64 = b64encode(CUS channel.data, (int)channel.size);
502 store_pool = old_pool;
503 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
504 }
505 #endif
506
507 /* peercert is set in peer_status() */
508 tlsp->peerdn = state->peerdn;
509 tlsp->sni = state->received_sni;
510
511 /* record our certificate */
512 {
513 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
514 gnutls_x509_crt_t crt;
515
516 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
517 }
518 }
519
520
521
522
523 /*************************************************
524 * Setup up DH parameters *
525 *************************************************/
526
527 /* Generating the D-H parameters may take a long time. They only need to
528 be re-generated every so often, depending on security policy. What we do is to
529 keep these parameters in a file in the spool directory. If the file does not
530 exist, we generate them. This means that it is easy to cause a regeneration.
531
532 The new file is written as a temporary file and renamed, so that an incomplete
533 file is never present. If two processes both compute some new parameters, you
534 waste a bit of effort, but it doesn't seem worth messing around with locking to
535 prevent this.
536
537 Returns: OK/DEFER/FAIL
538 */
539
540 static int
541 init_server_dh(uschar ** errstr)
542 {
543 int fd, rc;
544 unsigned int dh_bits;
545 gnutls_datum_t m;
546 uschar filename_buf[PATH_MAX];
547 uschar *filename = NULL;
548 size_t sz;
549 uschar *exp_tls_dhparam;
550 BOOL use_file_in_spool = FALSE;
551 host_item *host = NULL; /* dummy for macros */
552
553 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
554
555 if ((rc = gnutls_dh_params_init(&dh_server_params)))
556 return tls_error_gnu(US"gnutls_dh_params_init", rc, host, errstr);
557
558 m.data = NULL;
559 m.size = 0;
560
561 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
562 return DEFER;
563
564 if (!exp_tls_dhparam)
565 {
566 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
567 m.data = US std_dh_prime_default();
568 m.size = Ustrlen(m.data);
569 }
570 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
571 use_file_in_spool = TRUE;
572 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
573 {
574 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
575 return OK;
576 }
577 else if (exp_tls_dhparam[0] != '/')
578 {
579 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
580 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
581 m.size = Ustrlen(m.data);
582 }
583 else
584 filename = exp_tls_dhparam;
585
586 if (m.data)
587 {
588 if ((rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM)))
589 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
590 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
591 return OK;
592 }
593
594 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
595 /* If you change this constant, also change dh_param_fn_ext so that we can use a
596 different filename and ensure we have sufficient bits. */
597
598 if (!(dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL)))
599 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
600 DEBUG(D_tls)
601 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
602 dh_bits);
603 #else
604 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
605 DEBUG(D_tls)
606 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
607 dh_bits);
608 #endif
609
610 /* Some clients have hard-coded limits. */
611 if (dh_bits > tls_dh_max_bits)
612 {
613 DEBUG(D_tls)
614 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
615 tls_dh_max_bits);
616 dh_bits = tls_dh_max_bits;
617 }
618
619 if (use_file_in_spool)
620 {
621 if (!string_format(filename_buf, sizeof(filename_buf),
622 "%s/gnutls-params-%d", spool_directory, dh_bits))
623 return tls_error(US"overlong filename", NULL, NULL, errstr);
624 filename = filename_buf;
625 }
626
627 /* Open the cache file for reading and if successful, read it and set up the
628 parameters. */
629
630 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
631 {
632 struct stat statbuf;
633 FILE *fp;
634 int saved_errno;
635
636 if (fstat(fd, &statbuf) < 0) /* EIO */
637 {
638 saved_errno = errno;
639 (void)close(fd);
640 return tls_error_sys(US"TLS cache stat failed", saved_errno, NULL, errstr);
641 }
642 if (!S_ISREG(statbuf.st_mode))
643 {
644 (void)close(fd);
645 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
646 }
647 if (!(fp = fdopen(fd, "rb")))
648 {
649 saved_errno = errno;
650 (void)close(fd);
651 return tls_error_sys(US"fdopen(TLS cache stat fd) failed",
652 saved_errno, NULL, errstr);
653 }
654
655 m.size = statbuf.st_size;
656 if (!(m.data = malloc(m.size)))
657 {
658 fclose(fp);
659 return tls_error_sys(US"malloc failed", errno, NULL, errstr);
660 }
661 if (!(sz = fread(m.data, m.size, 1, fp)))
662 {
663 saved_errno = errno;
664 fclose(fp);
665 free(m.data);
666 return tls_error_sys(US"fread failed", saved_errno, NULL, errstr);
667 }
668 fclose(fp);
669
670 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
671 free(m.data);
672 if (rc)
673 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
674 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
675 }
676
677 /* If the file does not exist, fall through to compute new data and cache it.
678 If there was any other opening error, it is serious. */
679
680 else if (errno == ENOENT)
681 {
682 rc = -1;
683 DEBUG(D_tls)
684 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
685 }
686 else
687 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
688 NULL, NULL, errstr);
689
690 /* If ret < 0, either the cache file does not exist, or the data it contains
691 is not useful. One particular case of this is when upgrading from an older
692 release of Exim in which the data was stored in a different format. We don't
693 try to be clever and support both formats; we just regenerate new data in this
694 case. */
695
696 if (rc < 0)
697 {
698 uschar *temp_fn;
699 unsigned int dh_bits_gen = dh_bits;
700
701 if ((PATH_MAX - Ustrlen(filename)) < 10)
702 return tls_error(US"Filename too long to generate replacement",
703 filename, NULL, errstr);
704
705 temp_fn = string_copy(US"%s.XXXXXXX");
706 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
707 return tls_error_sys(US"Unable to open temp file", errno, NULL, errstr);
708 (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */
709
710 /* GnuTLS overshoots!
711 * If we ask for 2236, we might get 2237 or more.
712 * But there's no way to ask GnuTLS how many bits there really are.
713 * We can ask how many bits were used in a TLS session, but that's it!
714 * The prime itself is hidden behind too much abstraction.
715 * So we ask for less, and proceed on a wing and a prayer.
716 * First attempt, subtracted 3 for 2233 and got 2240.
717 */
718 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
719 {
720 dh_bits_gen = dh_bits - 10;
721 DEBUG(D_tls)
722 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
723 dh_bits_gen);
724 }
725
726 DEBUG(D_tls)
727 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
728 dh_bits_gen);
729 if ((rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen)))
730 return tls_error_gnu(US"gnutls_dh_params_generate2", rc, host, errstr);
731
732 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
733 and I confirmed that a NULL call to get the size first is how the GnuTLS
734 sample apps handle this. */
735
736 sz = 0;
737 m.data = NULL;
738 if ( (rc = gnutls_dh_params_export_pkcs3(dh_server_params,
739 GNUTLS_X509_FMT_PEM, m.data, &sz))
740 && rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
741 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3(NULL) sizing",
742 rc, host, errstr);
743 m.size = sz;
744 if (!(m.data = malloc(m.size)))
745 return tls_error_sys(US"memory allocation failed", errno, NULL, errstr);
746
747 /* this will return a size 1 less than the allocation size above */
748 if ((rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
749 m.data, &sz)))
750 {
751 free(m.data);
752 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3() real", rc, host, errstr);
753 }
754 m.size = sz; /* shrink by 1, probably */
755
756 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
757 {
758 free(m.data);
759 return tls_error_sys(US"TLS cache write D-H params failed",
760 errno, NULL, errstr);
761 }
762 free(m.data);
763 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
764 return tls_error_sys(US"TLS cache write D-H params final newline failed",
765 errno, NULL, errstr);
766
767 if ((rc = close(fd)))
768 return tls_error_sys(US"TLS cache write close() failed", errno, NULL, errstr);
769
770 if (Urename(temp_fn, filename) < 0)
771 return tls_error_sys(string_sprintf("failed to rename \"%s\" as \"%s\"",
772 temp_fn, filename), errno, NULL, errstr);
773
774 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
775 }
776
777 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
778 return OK;
779 }
780
781
782
783
784 /* Create and install a selfsigned certificate, for use in server mode */
785
786 static int
787 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
788 {
789 gnutls_x509_crt_t cert = NULL;
790 time_t now;
791 gnutls_x509_privkey_t pkey = NULL;
792 const uschar * where;
793 int rc;
794
795 where = US"initialising pkey";
796 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
797
798 where = US"initialising cert";
799 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
800
801 where = US"generating pkey";
802 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
803 #ifdef SUPPORT_PARAM_TO_PK_BITS
804 # ifndef GNUTLS_SEC_PARAM_MEDIUM
805 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
806 # endif
807 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
808 #else
809 2048,
810 #endif
811 0)))
812 goto err;
813
814 where = US"configuring cert";
815 now = 1;
816 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
817 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
818 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
819 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
820 || (rc = gnutls_x509_crt_set_key(cert, pkey))
821
822 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
823 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
824 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
825 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
826 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
827 GNUTLS_OID_X520_COMMON_NAME, 0,
828 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
829 )
830 goto err;
831
832 where = US"signing cert";
833 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
834
835 where = US"installing selfsign cert";
836 /* Since: 2.4.0 */
837 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
838 goto err;
839
840 rc = OK;
841
842 out:
843 if (cert) gnutls_x509_crt_deinit(cert);
844 if (pkey) gnutls_x509_privkey_deinit(pkey);
845 return rc;
846
847 err:
848 rc = tls_error_gnu(where, rc, NULL, errstr);
849 goto out;
850 }
851
852
853
854
855 /* Add certificate and key, from files.
856
857 Return:
858 Zero or negative: good. Negate value for certificate index if < 0.
859 Greater than zero: FAIL or DEFER code.
860 */
861
862 static int
863 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
864 uschar * certfile, uschar * keyfile, uschar ** errstr)
865 {
866 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
867 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
868 if (rc < 0)
869 return tls_error_gnu(
870 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
871 rc, host, errstr);
872 return -rc;
873 }
874
875
876 /*************************************************
877 * Variables re-expanded post-SNI *
878 *************************************************/
879
880 /* Called from both server and client code, via tls_init(), and also from
881 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
882
883 We can tell the two apart by state->received_sni being non-NULL in callback.
884
885 The callback should not call us unless state->trigger_sni_changes is true,
886 which we are responsible for setting on the first pass through.
887
888 Arguments:
889 state exim_gnutls_state_st *
890 errstr error string pointer
891
892 Returns: OK/DEFER/FAIL
893 */
894
895 static int
896 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
897 {
898 struct stat statbuf;
899 int rc;
900 const host_item *host = state->host; /* macro should be reconsidered? */
901 uschar *saved_tls_certificate = NULL;
902 uschar *saved_tls_privatekey = NULL;
903 uschar *saved_tls_verify_certificates = NULL;
904 uschar *saved_tls_crl = NULL;
905 int cert_count;
906
907 /* We check for tls_sni *before* expansion. */
908 if (!host) /* server */
909 if (!state->received_sni)
910 {
911 if ( state->tls_certificate
912 && ( Ustrstr(state->tls_certificate, US"tls_sni")
913 || Ustrstr(state->tls_certificate, US"tls_in_sni")
914 || Ustrstr(state->tls_certificate, US"tls_out_sni")
915 ) )
916 {
917 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
918 state->trigger_sni_changes = TRUE;
919 }
920 }
921 else
922 {
923 /* useful for debugging */
924 saved_tls_certificate = state->exp_tls_certificate;
925 saved_tls_privatekey = state->exp_tls_privatekey;
926 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
927 saved_tls_crl = state->exp_tls_crl;
928 }
929
930 if ((rc = gnutls_certificate_allocate_credentials(&state->x509_cred)))
931 return tls_error_gnu(US"gnutls_certificate_allocate_credentials",
932 rc, host, errstr);
933
934 #ifdef SUPPORT_SRV_OCSP_STACK
935 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
936 #endif
937
938 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
939 state members, assuming consistent naming; and expand_check() returns
940 false if expansion failed, unless expansion was forced to fail. */
941
942 /* check if we at least have a certificate, before doing expensive
943 D-H generation. */
944
945 if (!expand_check_tlsvar(tls_certificate, errstr))
946 return DEFER;
947
948 /* certificate is mandatory in server, optional in client */
949
950 if ( !state->exp_tls_certificate
951 || !*state->exp_tls_certificate
952 )
953 if (!host)
954 return tls_install_selfsign(state, errstr);
955 else
956 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
957
958 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
959 return DEFER;
960
961 /* tls_privatekey is optional, defaulting to same file as certificate */
962
963 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
964 {
965 state->tls_privatekey = state->tls_certificate;
966 state->exp_tls_privatekey = state->exp_tls_certificate;
967 }
968
969
970 if (state->exp_tls_certificate && *state->exp_tls_certificate)
971 {
972 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
973 state->exp_tls_certificate, state->exp_tls_privatekey);
974
975 if (state->received_sni)
976 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
977 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
978 )
979 {
980 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
981 }
982 else
983 {
984 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
985 }
986
987 if (!host) /* server */
988 {
989 const uschar * clist = state->exp_tls_certificate;
990 const uschar * klist = state->exp_tls_privatekey;
991 const uschar * olist;
992 int csep = 0, ksep = 0, osep = 0, cnt = 0;
993 uschar * cfile, * kfile, * ofile;
994
995 #ifndef DISABLE_OCSP
996 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
997 return DEFER;
998 olist = ofile;
999 #endif
1000
1001 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
1002
1003 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
1004 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
1005 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
1006 return rc;
1007 else
1008 {
1009 int gnutls_cert_index = -rc;
1010 DEBUG(D_tls) debug_printf("TLS: cert/key %s registered\n", cfile);
1011
1012 /* Set the OCSP stapling server info */
1013
1014 #ifndef DISABLE_OCSP
1015 if (tls_ocsp_file)
1016 if (gnutls_buggy_ocsp)
1017 {
1018 DEBUG(D_tls)
1019 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1020 }
1021 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1022 {
1023 /* Use the full callback method for stapling just to get
1024 observability. More efficient would be to read the file once only,
1025 if it never changed (due to SNI). Would need restart on file update,
1026 or watch datestamp. */
1027
1028 # ifdef SUPPORT_SRV_OCSP_STACK
1029 if ((rc = gnutls_certificate_set_ocsp_status_request_function2(
1030 state->x509_cred, gnutls_cert_index,
1031 server_ocsp_stapling_cb, ofile)))
1032 return tls_error_gnu(
1033 US"gnutls_certificate_set_ocsp_status_request_function2",
1034 rc, host, errstr);
1035 # else
1036 if (cnt++ > 0)
1037 {
1038 DEBUG(D_tls)
1039 debug_printf("oops; multiple OCSP files not supported\n");
1040 break;
1041 }
1042 gnutls_certificate_set_ocsp_status_request_function(
1043 state->x509_cred, server_ocsp_stapling_cb, ofile);
1044 # endif
1045
1046 DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile);
1047 }
1048 else
1049 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1050 #endif
1051 }
1052 }
1053 else
1054 {
1055 if (0 < (rc = tls_add_certfile(state, host,
1056 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1057 return rc;
1058 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1059 }
1060
1061 } /* tls_certificate */
1062
1063
1064 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1065 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1066 error message is provided. However, if we just refrain from setting anything up
1067 in that case, certificate verification fails, which seems to be the correct
1068 behaviour. */
1069
1070 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1071 {
1072 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1073 return DEFER;
1074 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1075 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1076 state->exp_tls_verify_certificates = NULL;
1077 #endif
1078 if (state->tls_crl && *state->tls_crl)
1079 if (!expand_check_tlsvar(tls_crl, errstr))
1080 return DEFER;
1081
1082 if (!(state->exp_tls_verify_certificates &&
1083 *state->exp_tls_verify_certificates))
1084 {
1085 DEBUG(D_tls)
1086 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1087 /* With no tls_verify_certificates, we ignore tls_crl too */
1088 return OK;
1089 }
1090 }
1091 else
1092 {
1093 DEBUG(D_tls)
1094 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1095 return OK;
1096 }
1097
1098 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1099 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1100 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1101 else
1102 #endif
1103 {
1104 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1105 {
1106 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
1107 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1108 strerror(errno));
1109 return DEFER;
1110 }
1111
1112 #ifndef SUPPORT_CA_DIR
1113 /* The test suite passes in /dev/null; we could check for that path explicitly,
1114 but who knows if someone has some weird FIFO which always dumps some certs, or
1115 other weirdness. The thing we really want to check is that it's not a
1116 directory, since while OpenSSL supports that, GnuTLS does not.
1117 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1118 if (S_ISDIR(statbuf.st_mode))
1119 {
1120 DEBUG(D_tls)
1121 debug_printf("verify certificates path is a dir: \"%s\"\n",
1122 state->exp_tls_verify_certificates);
1123 log_write(0, LOG_MAIN|LOG_PANIC,
1124 "tls_verify_certificates \"%s\" is a directory",
1125 state->exp_tls_verify_certificates);
1126 return DEFER;
1127 }
1128 #endif
1129
1130 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1131 state->exp_tls_verify_certificates, statbuf.st_size);
1132
1133 if (statbuf.st_size == 0)
1134 {
1135 DEBUG(D_tls)
1136 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1137 return OK;
1138 }
1139
1140 cert_count =
1141
1142 #ifdef SUPPORT_CA_DIR
1143 (statbuf.st_mode & S_IFMT) == S_IFDIR
1144 ?
1145 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1146 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1147 :
1148 #endif
1149 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1150 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1151 }
1152
1153 if (cert_count < 0)
1154 return tls_error_gnu(US"setting certificate trust", cert_count, host, errstr);
1155 DEBUG(D_tls)
1156 debug_printf("Added %d certificate authorities.\n", cert_count);
1157
1158 if (state->tls_crl && *state->tls_crl &&
1159 state->exp_tls_crl && *state->exp_tls_crl)
1160 {
1161 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1162 if ((cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1163 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM)) < 0)
1164 return tls_error_gnu(US"gnutls_certificate_set_x509_crl_file",
1165 cert_count, host, errstr);
1166
1167 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1168 }
1169
1170 return OK;
1171 }
1172
1173
1174
1175
1176 /*************************************************
1177 * Set X.509 state variables *
1178 *************************************************/
1179
1180 /* In GnuTLS, the registered cert/key are not replaced by a later
1181 set of a cert/key, so for SNI support we need a whole new x509_cred
1182 structure. Which means various other non-re-expanded pieces of state
1183 need to be re-set in the new struct, so the setting logic is pulled
1184 out to this.
1185
1186 Arguments:
1187 state exim_gnutls_state_st *
1188 errstr error string pointer
1189
1190 Returns: OK/DEFER/FAIL
1191 */
1192
1193 static int
1194 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1195 {
1196 int rc;
1197 const host_item *host = state->host; /* macro should be reconsidered? */
1198
1199 /* Create D-H parameters, or read them from the cache file. This function does
1200 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1201 client-side params. */
1202
1203 if (!state->host)
1204 {
1205 if (!dh_server_params)
1206 if ((rc = init_server_dh(errstr)) != OK) return rc;
1207 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1208 }
1209
1210 /* Link the credentials to the session. */
1211
1212 if ((rc = gnutls_credentials_set(state->session,
1213 GNUTLS_CRD_CERTIFICATE, state->x509_cred)))
1214 return tls_error_gnu(US"gnutls_credentials_set", rc, host, errstr);
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 const 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 if ((rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL)))
1303 return tls_error_gnu(US"gnutls_pkcs11_init", rc, host, errstr);
1304 #endif
1305
1306 if ((rc = gnutls_global_init()))
1307 return tls_error_gnu(US"gnutls_global_init", rc, host, errstr);
1308
1309 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1310 DEBUG(D_tls)
1311 {
1312 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1313 /* arbitrarily chosen level; bump up to 9 for more */
1314 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1315 }
1316 #endif
1317
1318 #ifndef DISABLE_OCSP
1319 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1320 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1321 #endif
1322
1323 exim_gnutls_base_init_done = TRUE;
1324 }
1325
1326 if (host)
1327 {
1328 /* For client-side sessions we allocate a context. This lets us run
1329 several in parallel. */
1330 int old_pool = store_pool;
1331 store_pool = POOL_PERM;
1332 state = store_get(sizeof(exim_gnutls_state_st));
1333 store_pool = old_pool;
1334
1335 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1336 state->tlsp = tlsp;
1337 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1338 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1339 }
1340 else
1341 {
1342 state = &state_server;
1343 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1344 state->tlsp = tlsp;
1345 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1346 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1347 }
1348 if (rc)
1349 return tls_error_gnu(US"gnutls_init", rc, host, errstr);
1350
1351 state->host = host;
1352
1353 state->tls_certificate = certificate;
1354 state->tls_privatekey = privatekey;
1355 state->tls_require_ciphers = require_ciphers;
1356 state->tls_sni = sni;
1357 state->tls_verify_certificates = cas;
1358 state->tls_crl = crl;
1359
1360 /* This handles the variables that might get re-expanded after TLS SNI;
1361 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1362
1363 DEBUG(D_tls)
1364 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1365 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1366
1367 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1368 requires a new structure afterwards. */
1369
1370 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1371
1372 /* set SNI in client, only */
1373 if (host)
1374 {
1375 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1376 return DEFER;
1377 if (state->tlsp->sni && *state->tlsp->sni)
1378 {
1379 DEBUG(D_tls)
1380 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1381 sz = Ustrlen(state->tlsp->sni);
1382 if ((rc = gnutls_server_name_set(state->session,
1383 GNUTLS_NAME_DNS, state->tlsp->sni, sz)))
1384 return tls_error_gnu(US"gnutls_server_name_set", rc, host, errstr);
1385 }
1386 }
1387 else if (state->tls_sni)
1388 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1389 "have an SNI set for a server [%s]\n", state->tls_sni);
1390
1391 /* This is the priority string support,
1392 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1393 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1394 This was backwards incompatible, but means Exim no longer needs to track
1395 all algorithms and provide string forms for them. */
1396
1397 p = NULL;
1398 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1399 {
1400 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1401 return DEFER;
1402 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1403 {
1404 p = state->exp_tls_require_ciphers;
1405 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
1406 }
1407 }
1408 if (!p)
1409 {
1410 p = exim_default_gnutls_priority;
1411 DEBUG(D_tls)
1412 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
1413 }
1414
1415 if ((rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos)))
1416 return tls_error_gnu(string_sprintf(
1417 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1418 p, errpos - CS p, errpos),
1419 rc, host, errstr);
1420
1421 if ((rc = gnutls_priority_set(state->session, state->priority_cache)))
1422 return tls_error_gnu(US"gnutls_priority_set", rc, host, errstr);
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_gnu((Label), 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_gnu(US"gnutls_handshake", 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 cctx connection context
2328 conn_args connection details
2329 cookie datum for randomness (not used)
2330 tlsp record details of channel configuration here; must be non-NULL
2331 errstr error string pointer
2332
2333 Returns: TRUE for success with TLS session context set in smtp context,
2334 FALSE on error
2335 */
2336
2337 BOOL
2338 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
2339 void * cookie ARG_UNUSED,
2340 tls_support * tlsp, uschar ** errstr)
2341 {
2342 host_item * host = conn_args->host; /* for msgs and option-tests */
2343 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
2344 smtp_transport_options_block * ob = tb
2345 ? (smtp_transport_options_block *)tb->options_block
2346 : &smtp_transport_option_defaults;
2347 int rc;
2348 exim_gnutls_state_st * state = NULL;
2349 uschar * cipher_list = NULL;
2350
2351 #ifndef DISABLE_OCSP
2352 BOOL require_ocsp =
2353 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2354 BOOL request_ocsp = require_ocsp ? TRUE
2355 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2356 #endif
2357
2358 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", cctx->sock);
2359
2360 #ifdef SUPPORT_DANE
2361 /* If dane is flagged, have either request or require dane for this host, and
2362 a TLSA record found. Therefore, dane verify required. Which implies cert must
2363 be requested and supplied, dane verify must pass, and cert verify irrelevant
2364 (incl. hostnames), and (caller handled) require_tls */
2365
2366 if (conn_args->dane && ob->dane_require_tls_ciphers)
2367 {
2368 /* not using expand_check_tlsvar because not yet in state */
2369 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2370 &cipher_list, errstr))
2371 return FALSE;
2372 cipher_list = cipher_list && *cipher_list
2373 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2374 }
2375 #endif
2376
2377 if (!cipher_list)
2378 cipher_list = ob->tls_require_ciphers;
2379
2380 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2381 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2382 cipher_list, &state, tlsp, errstr) != OK)
2383 return FALSE;
2384
2385 {
2386 int dh_min_bits = ob->tls_dh_min_bits;
2387 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2388 {
2389 DEBUG(D_tls)
2390 debug_printf("WARNING: tls_dh_min_bits far too low,"
2391 " clamping %d up to %d\n",
2392 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2393 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2394 }
2395
2396 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2397 " acceptable bits to %d\n",
2398 dh_min_bits);
2399 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2400 }
2401
2402 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2403 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2404 the specified host patterns if one of them is defined */
2405
2406 #ifdef SUPPORT_DANE
2407 if (conn_args->dane && dane_tlsa_load(state, &conn_args->tlsa_dnsa))
2408 {
2409 DEBUG(D_tls)
2410 debug_printf("TLS: server certificate DANE required.\n");
2411 state->verify_requirement = VERIFY_DANE;
2412 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2413 }
2414 else
2415 #endif
2416 if ( ( state->exp_tls_verify_certificates
2417 && !ob->tls_verify_hosts
2418 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2419 )
2420 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2421 )
2422 {
2423 tls_client_setup_hostname_checks(host, state, ob);
2424 DEBUG(D_tls)
2425 debug_printf("TLS: server certificate verification required.\n");
2426 state->verify_requirement = VERIFY_REQUIRED;
2427 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2428 }
2429 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2430 {
2431 tls_client_setup_hostname_checks(host, state, ob);
2432 DEBUG(D_tls)
2433 debug_printf("TLS: server certificate verification optional.\n");
2434 state->verify_requirement = VERIFY_OPTIONAL;
2435 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2436 }
2437 else
2438 {
2439 DEBUG(D_tls)
2440 debug_printf("TLS: server certificate verification not required.\n");
2441 state->verify_requirement = VERIFY_NONE;
2442 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2443 }
2444
2445 #ifndef DISABLE_OCSP
2446 /* supported since GnuTLS 3.1.3 */
2447 if (request_ocsp)
2448 {
2449 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2450 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2451 NULL, 0, NULL)) != OK)
2452 {
2453 tls_error_gnu(US"cert-status-req", rc, state->host, errstr);
2454 return FALSE;
2455 }
2456 tlsp->ocsp = OCSP_NOT_RESP;
2457 }
2458 #endif
2459
2460 #ifndef DISABLE_EVENT
2461 if (tb && tb->event_action)
2462 {
2463 state->event_action = tb->event_action;
2464 gnutls_session_set_ptr(state->session, state);
2465 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2466 }
2467 #endif
2468
2469 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) cctx->sock);
2470 state->fd_in = cctx->sock;
2471 state->fd_out = cctx->sock;
2472
2473 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2474 /* There doesn't seem to be a built-in timeout on connection. */
2475
2476 sigalrm_seen = FALSE;
2477 ALARM(ob->command_timeout);
2478 do
2479 rc = gnutls_handshake(state->session);
2480 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2481 ALARM_CLR(0);
2482
2483 if (rc != GNUTLS_E_SUCCESS)
2484 {
2485 if (sigalrm_seen)
2486 {
2487 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2488 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2489 }
2490 else
2491 tls_error_gnu(US"gnutls_handshake", rc, state->host, errstr);
2492 return FALSE;
2493 }
2494
2495 DEBUG(D_tls)
2496 {
2497 debug_printf("gnutls_handshake was successful\n");
2498 #ifdef SUPPORT_GNUTLS_SESS_DESC
2499 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2500 #endif
2501 #ifdef SUPPORT_GNUTLS_KEYLOG
2502 {
2503 gnutls_datum_t c, s;
2504 gstring * gc, * gs;
2505 gnutls_session_get_random(state->session, &c, &s);
2506 gnutls_session_get_master_secret(state->session, &s);
2507 gc = ddump(&c);
2508 gs = ddump(&s);
2509 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2510 }
2511 #endif
2512 }
2513
2514 /* Verify late */
2515
2516 if (!verify_certificate(state, errstr))
2517 {
2518 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
2519 return FALSE;
2520 }
2521
2522 #ifndef DISABLE_OCSP
2523 if (require_ocsp)
2524 {
2525 DEBUG(D_tls)
2526 {
2527 gnutls_datum_t stapling;
2528 gnutls_ocsp_resp_t resp;
2529 gnutls_datum_t printed;
2530 if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0
2531 && (rc= gnutls_ocsp_resp_init(&resp)) == 0
2532 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
2533 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0
2534 )
2535 {
2536 debug_printf("%.4096s", printed.data);
2537 gnutls_free(printed.data);
2538 }
2539 else
2540 (void) tls_error_gnu(US"ocsp decode", rc, state->host, errstr);
2541 }
2542
2543 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
2544 {
2545 tlsp->ocsp = OCSP_FAILED;
2546 tls_error(US"certificate status check failed", NULL, state->host, errstr);
2547 return FALSE;
2548 }
2549 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
2550 tlsp->ocsp = OCSP_VFIED;
2551 }
2552 #endif
2553
2554 /* Figure out peer DN, and if authenticated, etc. */
2555
2556 if (peer_status(state, errstr) != OK)
2557 return FALSE;
2558
2559 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
2560
2561 extract_exim_vars_from_tls_state(state);
2562
2563 cctx->tls_ctx = state;
2564 return TRUE;
2565 }
2566
2567
2568
2569
2570 /*************************************************
2571 * Close down a TLS session *
2572 *************************************************/
2573
2574 /* This is also called from within a delivery subprocess forked from the
2575 daemon, to shut down the TLS library, without actually doing a shutdown (which
2576 would tamper with the TLS session in the parent process).
2577
2578 Arguments:
2579 ct_ctx client context pointer, or NULL for the one global server context
2580 shutdown 1 if TLS close-alert is to be sent,
2581 2 if also response to be waited for
2582
2583 Returns: nothing
2584 */
2585
2586 void
2587 tls_close(void * ct_ctx, int shutdown)
2588 {
2589 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2590
2591 if (!state->tlsp || state->tlsp->active.sock < 0) return; /* TLS was not active */
2592
2593 if (shutdown)
2594 {
2595 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
2596 shutdown > 1 ? " (with response-wait)" : "");
2597
2598 ALARM(2);
2599 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
2600 ALARM_CLR(0);
2601 }
2602
2603 gnutls_deinit(state->session);
2604 gnutls_certificate_free_credentials(state->x509_cred);
2605
2606
2607 state->tlsp->active.sock = -1;
2608 state->tlsp->active.tls_ctx = NULL;
2609 if (state->xfer_buffer) store_free(state->xfer_buffer);
2610 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
2611 }
2612
2613
2614
2615
2616 static BOOL
2617 tls_refill(unsigned lim)
2618 {
2619 exim_gnutls_state_st * state = &state_server;
2620 ssize_t inbytes;
2621
2622 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
2623 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
2624
2625 sigalrm_seen = FALSE;
2626 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2627
2628 do
2629 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
2630 MIN(ssl_xfer_buffer_size, lim));
2631 while (inbytes == GNUTLS_E_AGAIN);
2632
2633 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2634
2635 if (had_command_timeout) /* set by signal handler */
2636 smtp_command_timeout_exit(); /* does not return */
2637 if (had_command_sigterm)
2638 smtp_command_sigterm_exit();
2639 if (had_data_timeout)
2640 smtp_data_timeout_exit();
2641 if (had_data_sigint)
2642 smtp_data_sigint_exit();
2643
2644 /* Timeouts do not get this far. A zero-byte return appears to mean that the
2645 TLS session has been closed down, not that the socket itself has been closed
2646 down. Revert to non-TLS handling. */
2647
2648 if (sigalrm_seen)
2649 {
2650 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
2651 state->xfer_error = TRUE;
2652 return FALSE;
2653 }
2654
2655 else if (inbytes == 0)
2656 {
2657 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2658
2659 receive_getc = smtp_getc;
2660 receive_getbuf = smtp_getbuf;
2661 receive_get_cache = smtp_get_cache;
2662 receive_ungetc = smtp_ungetc;
2663 receive_feof = smtp_feof;
2664 receive_ferror = smtp_ferror;
2665 receive_smtp_buffered = smtp_buffered;
2666
2667 gnutls_deinit(state->session);
2668 gnutls_certificate_free_credentials(state->x509_cred);
2669
2670 state->session = NULL;
2671 state->tlsp->active.sock = -1;
2672 state->tlsp->active.tls_ctx = NULL;
2673 state->tlsp->bits = 0;
2674 state->tlsp->certificate_verified = FALSE;
2675 tls_channelbinding_b64 = NULL;
2676 state->tlsp->cipher = NULL;
2677 state->tlsp->peercert = NULL;
2678 state->tlsp->peerdn = NULL;
2679
2680 return FALSE;
2681 }
2682
2683 /* Handle genuine errors */
2684
2685 else if (inbytes < 0)
2686 {
2687 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
2688 record_io_error(state, (int) inbytes, US"recv", NULL);
2689 state->xfer_error = TRUE;
2690 return FALSE;
2691 }
2692 #ifndef DISABLE_DKIM
2693 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
2694 #endif
2695 state->xfer_buffer_hwm = (int) inbytes;
2696 state->xfer_buffer_lwm = 0;
2697 return TRUE;
2698 }
2699
2700 /*************************************************
2701 * TLS version of getc *
2702 *************************************************/
2703
2704 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2705 it refills the buffer via the GnuTLS reading function.
2706 Only used by the server-side TLS.
2707
2708 This feeds DKIM and should be used for all message-body reads.
2709
2710 Arguments: lim Maximum amount to read/buffer
2711 Returns: the next character or EOF
2712 */
2713
2714 int
2715 tls_getc(unsigned lim)
2716 {
2717 exim_gnutls_state_st * state = &state_server;
2718
2719 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2720 if (!tls_refill(lim))
2721 return state->xfer_error ? EOF : smtp_getc(lim);
2722
2723 /* Something in the buffer; return next uschar */
2724
2725 return state->xfer_buffer[state->xfer_buffer_lwm++];
2726 }
2727
2728 uschar *
2729 tls_getbuf(unsigned * len)
2730 {
2731 exim_gnutls_state_st * state = &state_server;
2732 unsigned size;
2733 uschar * buf;
2734
2735 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2736 if (!tls_refill(*len))
2737 {
2738 if (!state->xfer_error) return smtp_getbuf(len);
2739 *len = 0;
2740 return NULL;
2741 }
2742
2743 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
2744 size = *len;
2745 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
2746 state->xfer_buffer_lwm += size;
2747 *len = size;
2748 return buf;
2749 }
2750
2751
2752 void
2753 tls_get_cache()
2754 {
2755 #ifndef DISABLE_DKIM
2756 exim_gnutls_state_st * state = &state_server;
2757 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
2758 if (n > 0)
2759 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
2760 #endif
2761 }
2762
2763
2764 BOOL
2765 tls_could_read(void)
2766 {
2767 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
2768 || gnutls_record_check_pending(state_server.session) > 0;
2769 }
2770
2771
2772
2773
2774 /*************************************************
2775 * Read bytes from TLS channel *
2776 *************************************************/
2777
2778 /* This does not feed DKIM, so if the caller uses this for reading message body,
2779 then the caller must feed DKIM.
2780
2781 Arguments:
2782 ct_ctx client context pointer, or NULL for the one global server context
2783 buff buffer of data
2784 len size of buffer
2785
2786 Returns: the number of bytes read
2787 -1 after a failed read, including EOF
2788 */
2789
2790 int
2791 tls_read(void * ct_ctx, uschar *buff, size_t len)
2792 {
2793 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2794 ssize_t inbytes;
2795
2796 if (len > INT_MAX)
2797 len = INT_MAX;
2798
2799 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
2800 DEBUG(D_tls)
2801 debug_printf("*** PROBABLY A BUG *** " \
2802 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
2803 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
2804
2805 DEBUG(D_tls)
2806 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
2807 state->session, buff, len);
2808
2809 do
2810 inbytes = gnutls_record_recv(state->session, buff, len);
2811 while (inbytes == GNUTLS_E_AGAIN);
2812
2813 if (inbytes > 0) return inbytes;
2814 if (inbytes == 0)
2815 {
2816 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2817 }
2818 else
2819 {
2820 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
2821 record_io_error(state, (int)inbytes, US"recv", NULL);
2822 }
2823
2824 return -1;
2825 }
2826
2827
2828
2829
2830 /*************************************************
2831 * Write bytes down TLS channel *
2832 *************************************************/
2833
2834 /*
2835 Arguments:
2836 ct_ctx client context pointer, or NULL for the one global server context
2837 buff buffer of data
2838 len number of bytes
2839 more more data expected soon
2840
2841 Returns: the number of bytes after a successful write,
2842 -1 after a failed write
2843 */
2844
2845 int
2846 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
2847 {
2848 ssize_t outbytes;
2849 size_t left = len;
2850 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2851 #ifdef SUPPORT_CORK
2852 static BOOL corked = FALSE;
2853
2854 if (more && !corked) gnutls_record_cork(state->session);
2855 #endif
2856
2857 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
2858 buff, left, more ? ", more" : "");
2859
2860 while (left > 0)
2861 {
2862 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
2863 buff, left);
2864
2865 do
2866 outbytes = gnutls_record_send(state->session, buff, left);
2867 while (outbytes == GNUTLS_E_AGAIN);
2868
2869 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
2870 if (outbytes < 0)
2871 {
2872 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
2873 record_io_error(state, outbytes, US"send", NULL);
2874 return -1;
2875 }
2876 if (outbytes == 0)
2877 {
2878 record_io_error(state, 0, US"send", US"TLS channel closed on write");
2879 return -1;
2880 }
2881
2882 left -= outbytes;
2883 buff += outbytes;
2884 }
2885
2886 if (len > INT_MAX)
2887 {
2888 DEBUG(D_tls)
2889 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
2890 len);
2891 len = INT_MAX;
2892 }
2893
2894 #ifdef SUPPORT_CORK
2895 if (more != corked)
2896 {
2897 if (!more) (void) gnutls_record_uncork(state->session, 0);
2898 corked = more;
2899 }
2900 #endif
2901
2902 return (int) len;
2903 }
2904
2905
2906
2907
2908 /*************************************************
2909 * Random number generation *
2910 *************************************************/
2911
2912 /* Pseudo-random number generation. The result is not expected to be
2913 cryptographically strong but not so weak that someone will shoot themselves
2914 in the foot using it as a nonce in input in some email header scheme or
2915 whatever weirdness they'll twist this into. The result should handle fork()
2916 and avoid repeating sequences. OpenSSL handles that for us.
2917
2918 Arguments:
2919 max range maximum
2920 Returns a random number in range [0, max-1]
2921 */
2922
2923 #ifdef HAVE_GNUTLS_RND
2924 int
2925 vaguely_random_number(int max)
2926 {
2927 unsigned int r;
2928 int i, needed_len;
2929 uschar smallbuf[sizeof(r)];
2930
2931 if (max <= 1)
2932 return 0;
2933
2934 needed_len = sizeof(r);
2935 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2936 asked for a number less than 10. */
2937
2938 for (r = max, i = 0; r; ++i)
2939 r >>= 1;
2940 i = (i + 7) / 8;
2941 if (i < needed_len)
2942 needed_len = i;
2943
2944 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
2945 if (i < 0)
2946 {
2947 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
2948 return vaguely_random_number_fallback(max);
2949 }
2950 r = 0;
2951 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
2952 r = r * 256 + *p;
2953
2954 /* We don't particularly care about weighted results; if someone wants
2955 * smooth distribution and cares enough then they should submit a patch then. */
2956 return r % max;
2957 }
2958 #else /* HAVE_GNUTLS_RND */
2959 int
2960 vaguely_random_number(int max)
2961 {
2962 return vaguely_random_number_fallback(max);
2963 }
2964 #endif /* HAVE_GNUTLS_RND */
2965
2966
2967
2968
2969 /*************************************************
2970 * Let tls_require_ciphers be checked at startup *
2971 *************************************************/
2972
2973 /* The tls_require_ciphers option, if set, must be something which the
2974 library can parse.
2975
2976 Returns: NULL on success, or error message
2977 */
2978
2979 uschar *
2980 tls_validate_require_cipher(void)
2981 {
2982 int rc;
2983 uschar *expciphers = NULL;
2984 gnutls_priority_t priority_cache;
2985 const char *errpos;
2986 uschar * dummy_errstr;
2987
2988 #define validate_check_rc(Label) do { \
2989 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
2990 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
2991 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
2992
2993 if (exim_gnutls_base_init_done)
2994 log_write(0, LOG_MAIN|LOG_PANIC,
2995 "already initialised GnuTLS, Exim developer bug");
2996
2997 #ifdef HAVE_GNUTLS_PKCS11
2998 if (!gnutls_allow_auto_pkcs11)
2999 {
3000 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
3001 validate_check_rc(US"gnutls_pkcs11_init");
3002 }
3003 #endif
3004 rc = gnutls_global_init();
3005 validate_check_rc(US"gnutls_global_init()");
3006 exim_gnutls_base_init_done = TRUE;
3007
3008 if (!(tls_require_ciphers && *tls_require_ciphers))
3009 return_deinit(NULL);
3010
3011 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3012 &dummy_errstr))
3013 return_deinit(US"failed to expand tls_require_ciphers");
3014
3015 if (!(expciphers && *expciphers))
3016 return_deinit(NULL);
3017
3018 DEBUG(D_tls)
3019 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3020
3021 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
3022 validate_check_rc(string_sprintf(
3023 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
3024 expciphers, errpos - CS expciphers, errpos));
3025
3026 #undef return_deinit
3027 #undef validate_check_rc
3028 gnutls_global_deinit();
3029
3030 return NULL;
3031 }
3032
3033
3034
3035
3036 /*************************************************
3037 * Report the library versions. *
3038 *************************************************/
3039
3040 /* See a description in tls-openssl.c for an explanation of why this exists.
3041
3042 Arguments: a FILE* to print the results to
3043 Returns: nothing
3044 */
3045
3046 void
3047 tls_version_report(FILE *f)
3048 {
3049 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
3050 " Runtime: %s\n",
3051 LIBGNUTLS_VERSION,
3052 gnutls_check_version(NULL));
3053 }
3054
3055 /* vi: aw ai sw=2
3056 */
3057 /* End of tls-gnu.c */