TLS: add variables for the IETF standard name for the connection ciphersuite
[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 char * const exim_default_gnutls_priority = "NORMAL";
242
243 /* Guard library core initialisation */
244
245 static BOOL exim_gnutls_base_init_done = FALSE;
246
247 #ifndef DISABLE_OCSP
248 static BOOL gnutls_buggy_ocsp = FALSE;
249 #endif
250
251
252 /* ------------------------------------------------------------------------ */
253 /* macros */
254
255 #define MAX_HOST_LEN 255
256
257 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
258 the library logging; a value less than 0 disables the calls to set up logging
259 callbacks. Possibly GNuTLS also looks for an environment variable
260 "GNUTLS_DEBUG_LEVEL". */
261 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
262 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
263 #endif
264
265 #ifndef EXIM_CLIENT_DH_MIN_BITS
266 # define EXIM_CLIENT_DH_MIN_BITS 1024
267 #endif
268
269 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
270 can ask for a bit-strength. Without that, we stick to the constant we had
271 before, for now. */
272 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
273 # define EXIM_SERVER_DH_BITS_PRE2_12 1024
274 #endif
275
276 #define exim_gnutls_err_check(rc, Label) do { \
277 if ((rc) != GNUTLS_E_SUCCESS) \
278 return tls_error((Label), US gnutls_strerror(rc), host, errstr); \
279 } while (0)
280
281 #define expand_check_tlsvar(Varname, errstr) \
282 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
283
284 #if GNUTLS_VERSION_NUMBER >= 0x020c00
285 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
286 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
287 # define HAVE_GNUTLS_RND
288 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
289 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
290 * isn't available sometimes, so this needs to become a conditional
291 * compilation; the sanest way to deal with this being a problem on
292 * older OSes is to block it in the Local/Makefile with this compiler
293 * definition */
294 # ifndef AVOID_GNUTLS_PKCS11
295 # define HAVE_GNUTLS_PKCS11
296 # endif /* AVOID_GNUTLS_PKCS11 */
297 #endif
298
299
300
301
302 /* ------------------------------------------------------------------------ */
303 /* Callback declarations */
304
305 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
306 static void exim_gnutls_logger_cb(int level, const char *message);
307 #endif
308
309 static int exim_sni_handling_cb(gnutls_session_t session);
310
311 #ifndef DISABLE_OCSP
312 static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
313 gnutls_datum_t * ocsp_response);
314 #endif
315
316
317
318 /* ------------------------------------------------------------------------ */
319 /* Static functions */
320
321 /*************************************************
322 * Handle TLS error *
323 *************************************************/
324
325 /* Called from lots of places when errors occur before actually starting to do
326 the TLS handshake, that is, while the session is still in clear. Always returns
327 DEFER for a server and FAIL for a client so that most calls can use "return
328 tls_error(...)" to do this processing and then give an appropriate return. A
329 single function is used for both server and client, because it is called from
330 some shared functions.
331
332 Argument:
333 prefix text to include in the logged error
334 msg additional error string (may be NULL)
335 usually obtained from gnutls_strerror()
336 host NULL if setting up a server;
337 the connected host if setting up a client
338 errstr pointer to returned error string
339
340 Returns: OK/DEFER/FAIL
341 */
342
343 static int
344 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
345 uschar ** errstr)
346 {
347 if (errstr)
348 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
349 return host ? FAIL : DEFER;
350 }
351
352
353
354
355 /*************************************************
356 * Deal with logging errors during I/O *
357 *************************************************/
358
359 /* We have to get the identity of the peer from saved data.
360
361 Argument:
362 state the current GnuTLS exim state container
363 rc the GnuTLS error code, or 0 if it's a local error
364 when text identifying read or write
365 text local error text when ec is 0
366
367 Returns: nothing
368 */
369
370 static void
371 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
372 {
373 const uschar * msg;
374 uschar * errstr;
375
376 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
377 msg = string_sprintf("%s: %s", US gnutls_strerror(rc),
378 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
379 else
380 msg = US gnutls_strerror(rc);
381
382 (void) tls_error(when, msg, state->host, &errstr);
383
384 if (state->host)
385 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
386 state->host->name, state->host->address, errstr);
387 else
388 {
389 uschar * conn_info = smtp_get_connection_info();
390 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
391 /* I'd like to get separated H= here, but too hard for now */
392 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
393 }
394 }
395
396
397
398
399 /*************************************************
400 * Set various Exim expansion vars *
401 *************************************************/
402
403 #define exim_gnutls_cert_err(Label) \
404 do \
405 { \
406 if (rc != GNUTLS_E_SUCCESS) \
407 { \
408 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
409 (Label), gnutls_strerror(rc)); \
410 return rc; \
411 } \
412 } while (0)
413
414 static int
415 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
416 {
417 int rc;
418
419 rc = gnutls_x509_crt_init(crtp);
420 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
421
422 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
423 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
424
425 return rc;
426 }
427
428 #undef exim_gnutls_cert_err
429
430
431 /* We set various Exim global variables from the state, once a session has
432 been established. With TLS callouts, may need to change this to stack
433 variables, or just re-call it with the server state after client callout
434 has finished.
435
436 Make sure anything set here is unset in tls_getc().
437
438 Sets:
439 tls_active fd
440 tls_bits strength indicator
441 tls_certificate_verified bool indicator
442 tls_channelbinding_b64 for some SASL mechanisms
443 tls_cipher a string
444 tls_peercert pointer to library internal
445 tls_peerdn a string
446 tls_sni a (UTF-8) string
447 tls_ourcert pointer to library internal
448
449 Argument:
450 state the relevant exim_gnutls_state_st *
451 */
452
453 static void
454 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
455 {
456 gnutls_cipher_algorithm_t cipher;
457 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
458 int old_pool;
459 int rc;
460 gnutls_datum_t channel;
461 #endif
462 tls_support * tlsp = state->tlsp;
463
464 tlsp->active.sock = state->fd_out;
465 tlsp->active.tls_ctx = state;
466
467 cipher = gnutls_cipher_get(state->session);
468 /* returns size in "bytes" */
469 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
470
471 tlsp->cipher = state->ciphersuite;
472
473 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
474
475 tlsp->certificate_verified = state->peer_cert_verified;
476 #ifdef SUPPORT_DANE
477 tlsp->dane_verified = state->peer_dane_verified;
478 #endif
479
480 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
481 only available for use for authenticators while this TLS session is running. */
482
483 tls_channelbinding_b64 = NULL;
484 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
485 channel.data = NULL;
486 channel.size = 0;
487 if ((rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel)))
488 { DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); }
489 else
490 {
491 old_pool = store_pool;
492 store_pool = POOL_PERM;
493 tls_channelbinding_b64 = b64encode(CUS channel.data, (int)channel.size);
494 store_pool = old_pool;
495 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
496 }
497 #endif
498
499 /* peercert is set in peer_status() */
500 tlsp->peerdn = state->peerdn;
501 tlsp->sni = state->received_sni;
502
503 /* record our certificate */
504 {
505 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
506 gnutls_x509_crt_t crt;
507
508 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
509 }
510 }
511
512
513
514
515 /*************************************************
516 * Setup up DH parameters *
517 *************************************************/
518
519 /* Generating the D-H parameters may take a long time. They only need to
520 be re-generated every so often, depending on security policy. What we do is to
521 keep these parameters in a file in the spool directory. If the file does not
522 exist, we generate them. This means that it is easy to cause a regeneration.
523
524 The new file is written as a temporary file and renamed, so that an incomplete
525 file is never present. If two processes both compute some new parameters, you
526 waste a bit of effort, but it doesn't seem worth messing around with locking to
527 prevent this.
528
529 Returns: OK/DEFER/FAIL
530 */
531
532 static int
533 init_server_dh(uschar ** errstr)
534 {
535 int fd, rc;
536 unsigned int dh_bits;
537 gnutls_datum_t m;
538 uschar filename_buf[PATH_MAX];
539 uschar *filename = NULL;
540 size_t sz;
541 uschar *exp_tls_dhparam;
542 BOOL use_file_in_spool = FALSE;
543 BOOL use_fixed_file = FALSE;
544 host_item *host = NULL; /* dummy for macros */
545
546 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
547
548 rc = gnutls_dh_params_init(&dh_server_params);
549 exim_gnutls_err_check(rc, US"gnutls_dh_params_init");
550
551 m.data = NULL;
552 m.size = 0;
553
554 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
555 return DEFER;
556
557 if (!exp_tls_dhparam)
558 {
559 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
560 m.data = US std_dh_prime_default();
561 m.size = Ustrlen(m.data);
562 }
563 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
564 use_file_in_spool = TRUE;
565 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
566 {
567 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
568 return OK;
569 }
570 else if (exp_tls_dhparam[0] != '/')
571 {
572 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
573 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
574 m.size = Ustrlen(m.data);
575 }
576 else
577 {
578 use_fixed_file = TRUE;
579 filename = exp_tls_dhparam;
580 }
581
582 if (m.data)
583 {
584 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
585 exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
586 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
587 return OK;
588 }
589
590 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
591 /* If you change this constant, also change dh_param_fn_ext so that we can use a
592 different filename and ensure we have sufficient bits. */
593 dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL);
594 if (!dh_bits)
595 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
596 DEBUG(D_tls)
597 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
598 dh_bits);
599 #else
600 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
601 DEBUG(D_tls)
602 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
603 dh_bits);
604 #endif
605
606 /* Some clients have hard-coded limits. */
607 if (dh_bits > tls_dh_max_bits)
608 {
609 DEBUG(D_tls)
610 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
611 tls_dh_max_bits);
612 dh_bits = tls_dh_max_bits;
613 }
614
615 if (use_file_in_spool)
616 {
617 if (!string_format(filename_buf, sizeof(filename_buf),
618 "%s/gnutls-params-%d", spool_directory, dh_bits))
619 return tls_error(US"overlong filename", NULL, NULL, errstr);
620 filename = filename_buf;
621 }
622
623 /* Open the cache file for reading and if successful, read it and set up the
624 parameters. */
625
626 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
627 {
628 struct stat statbuf;
629 FILE *fp;
630 int saved_errno;
631
632 if (fstat(fd, &statbuf) < 0) /* EIO */
633 {
634 saved_errno = errno;
635 (void)close(fd);
636 return tls_error(US"TLS cache stat failed", US strerror(saved_errno), NULL, errstr);
637 }
638 if (!S_ISREG(statbuf.st_mode))
639 {
640 (void)close(fd);
641 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
642 }
643 if (!(fp = fdopen(fd, "rb")))
644 {
645 saved_errno = errno;
646 (void)close(fd);
647 return tls_error(US"fdopen(TLS cache stat fd) failed",
648 US strerror(saved_errno), NULL, errstr);
649 }
650
651 m.size = statbuf.st_size;
652 if (!(m.data = malloc(m.size)))
653 {
654 fclose(fp);
655 return tls_error(US"malloc failed", US strerror(errno), NULL, errstr);
656 }
657 if (!(sz = fread(m.data, m.size, 1, fp)))
658 {
659 saved_errno = errno;
660 fclose(fp);
661 free(m.data);
662 return tls_error(US"fread failed", US strerror(saved_errno), NULL, errstr);
663 }
664 fclose(fp);
665
666 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
667 free(m.data);
668 exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3");
669 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
670 }
671
672 /* If the file does not exist, fall through to compute new data and cache it.
673 If there was any other opening error, it is serious. */
674
675 else if (errno == ENOENT)
676 {
677 rc = -1;
678 DEBUG(D_tls)
679 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
680 }
681 else
682 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
683 NULL, NULL, errstr);
684
685 /* If ret < 0, either the cache file does not exist, or the data it contains
686 is not useful. One particular case of this is when upgrading from an older
687 release of Exim in which the data was stored in a different format. We don't
688 try to be clever and support both formats; we just regenerate new data in this
689 case. */
690
691 if (rc < 0)
692 {
693 uschar *temp_fn;
694 unsigned int dh_bits_gen = dh_bits;
695
696 if ((PATH_MAX - Ustrlen(filename)) < 10)
697 return tls_error(US"Filename too long to generate replacement",
698 filename, NULL, errstr);
699
700 temp_fn = string_copy(US"%s.XXXXXXX");
701 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
702 return tls_error(US"Unable to open temp file", US strerror(errno), NULL, errstr);
703 (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */
704
705 /* GnuTLS overshoots!
706 * If we ask for 2236, we might get 2237 or more.
707 * But there's no way to ask GnuTLS how many bits there really are.
708 * We can ask how many bits were used in a TLS session, but that's it!
709 * The prime itself is hidden behind too much abstraction.
710 * So we ask for less, and proceed on a wing and a prayer.
711 * First attempt, subtracted 3 for 2233 and got 2240.
712 */
713 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
714 {
715 dh_bits_gen = dh_bits - 10;
716 DEBUG(D_tls)
717 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
718 dh_bits_gen);
719 }
720
721 DEBUG(D_tls)
722 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
723 dh_bits_gen);
724 rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen);
725 exim_gnutls_err_check(rc, US"gnutls_dh_params_generate2");
726
727 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
728 and I confirmed that a NULL call to get the size first is how the GnuTLS
729 sample apps handle this. */
730
731 sz = 0;
732 m.data = NULL;
733 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
734 m.data, &sz);
735 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
736 exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3(NULL) sizing");
737 m.size = sz;
738 if (!(m.data = malloc(m.size)))
739 return tls_error(US"memory allocation failed", US strerror(errno), NULL, errstr);
740
741 /* this will return a size 1 less than the allocation size above */
742 rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
743 m.data, &sz);
744 if (rc != GNUTLS_E_SUCCESS)
745 {
746 free(m.data);
747 exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3() real");
748 }
749 m.size = sz; /* shrink by 1, probably */
750
751 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
752 {
753 free(m.data);
754 return tls_error(US"TLS cache write D-H params failed",
755 US strerror(errno), NULL, errstr);
756 }
757 free(m.data);
758 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
759 return tls_error(US"TLS cache write D-H params final newline failed",
760 US strerror(errno), NULL, errstr);
761
762 if ((rc = close(fd)))
763 return tls_error(US"TLS cache write close() failed", US strerror(errno), NULL, errstr);
764
765 if (Urename(temp_fn, filename) < 0)
766 return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"",
767 temp_fn, filename), US strerror(errno), NULL, errstr);
768
769 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
770 }
771
772 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
773 return OK;
774 }
775
776
777
778
779 /* Create and install a selfsigned certificate, for use in server mode */
780
781 static int
782 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
783 {
784 gnutls_x509_crt_t cert = NULL;
785 time_t now;
786 gnutls_x509_privkey_t pkey = NULL;
787 const uschar * where;
788 int rc;
789
790 where = US"initialising pkey";
791 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
792
793 where = US"initialising cert";
794 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
795
796 where = US"generating pkey";
797 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
798 #ifdef SUPPORT_PARAM_TO_PK_BITS
799 # ifndef GNUTLS_SEC_PARAM_MEDIUM
800 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
801 # endif
802 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
803 #else
804 2048,
805 #endif
806 0)))
807 goto err;
808
809 where = US"configuring cert";
810 now = 1;
811 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
812 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
813 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
814 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
815 || (rc = gnutls_x509_crt_set_key(cert, pkey))
816
817 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
818 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
819 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
820 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
821 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
822 GNUTLS_OID_X520_COMMON_NAME, 0,
823 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
824 )
825 goto err;
826
827 where = US"signing cert";
828 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
829
830 where = US"installing selfsign cert";
831 /* Since: 2.4.0 */
832 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
833 goto err;
834
835 rc = OK;
836
837 out:
838 if (cert) gnutls_x509_crt_deinit(cert);
839 if (pkey) gnutls_x509_privkey_deinit(pkey);
840 return rc;
841
842 err:
843 rc = tls_error(where, US gnutls_strerror(rc), NULL, errstr);
844 goto out;
845 }
846
847
848
849
850 /* Add certificate and key, from files.
851
852 Return:
853 Zero or negative: good. Negate value for certificate index if < 0.
854 Greater than zero: FAIL or DEFER code.
855 */
856
857 static int
858 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
859 uschar * certfile, uschar * keyfile, uschar ** errstr)
860 {
861 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
862 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
863 if (rc < 0)
864 return tls_error(
865 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
866 US gnutls_strerror(rc), host, errstr);
867 return -rc;
868 }
869
870
871 /*************************************************
872 * Variables re-expanded post-SNI *
873 *************************************************/
874
875 /* Called from both server and client code, via tls_init(), and also from
876 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
877
878 We can tell the two apart by state->received_sni being non-NULL in callback.
879
880 The callback should not call us unless state->trigger_sni_changes is true,
881 which we are responsible for setting on the first pass through.
882
883 Arguments:
884 state exim_gnutls_state_st *
885 errstr error string pointer
886
887 Returns: OK/DEFER/FAIL
888 */
889
890 static int
891 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
892 {
893 struct stat statbuf;
894 int rc;
895 const host_item *host = state->host; /* macro should be reconsidered? */
896 uschar *saved_tls_certificate = NULL;
897 uschar *saved_tls_privatekey = NULL;
898 uschar *saved_tls_verify_certificates = NULL;
899 uschar *saved_tls_crl = NULL;
900 int cert_count;
901
902 /* We check for tls_sni *before* expansion. */
903 if (!host) /* server */
904 if (!state->received_sni)
905 {
906 if ( state->tls_certificate
907 && ( Ustrstr(state->tls_certificate, US"tls_sni")
908 || Ustrstr(state->tls_certificate, US"tls_in_sni")
909 || Ustrstr(state->tls_certificate, US"tls_out_sni")
910 ) )
911 {
912 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
913 state->trigger_sni_changes = TRUE;
914 }
915 }
916 else
917 {
918 /* useful for debugging */
919 saved_tls_certificate = state->exp_tls_certificate;
920 saved_tls_privatekey = state->exp_tls_privatekey;
921 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
922 saved_tls_crl = state->exp_tls_crl;
923 }
924
925 rc = gnutls_certificate_allocate_credentials(&state->x509_cred);
926 exim_gnutls_err_check(rc, US"gnutls_certificate_allocate_credentials");
927
928 #ifdef SUPPORT_SRV_OCSP_STACK
929 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
930 #endif
931
932 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
933 state members, assuming consistent naming; and expand_check() returns
934 false if expansion failed, unless expansion was forced to fail. */
935
936 /* check if we at least have a certificate, before doing expensive
937 D-H generation. */
938
939 if (!expand_check_tlsvar(tls_certificate, errstr))
940 return DEFER;
941
942 /* certificate is mandatory in server, optional in client */
943
944 if ( !state->exp_tls_certificate
945 || !*state->exp_tls_certificate
946 )
947 if (!host)
948 return tls_install_selfsign(state, errstr);
949 else
950 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
951
952 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
953 return DEFER;
954
955 /* tls_privatekey is optional, defaulting to same file as certificate */
956
957 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
958 {
959 state->tls_privatekey = state->tls_certificate;
960 state->exp_tls_privatekey = state->exp_tls_certificate;
961 }
962
963
964 if (state->exp_tls_certificate && *state->exp_tls_certificate)
965 {
966 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
967 state->exp_tls_certificate, state->exp_tls_privatekey);
968
969 if (state->received_sni)
970 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
971 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
972 )
973 {
974 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
975 }
976 else
977 {
978 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
979 }
980
981 if (!host) /* server */
982 {
983 const uschar * clist = state->exp_tls_certificate;
984 const uschar * klist = state->exp_tls_privatekey;
985 const uschar * olist;
986 int csep = 0, ksep = 0, osep = 0, cnt = 0;
987 uschar * cfile, * kfile, * ofile;
988
989 #ifndef DISABLE_OCSP
990 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
991 return DEFER;
992 olist = ofile;
993 #endif
994
995 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
996
997 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
998 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
999 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
1000 return rc;
1001 else
1002 {
1003 int gnutls_cert_index = -rc;
1004 DEBUG(D_tls) debug_printf("TLS: cert/key %s registered\n", cfile);
1005
1006 /* Set the OCSP stapling server info */
1007
1008 #ifndef DISABLE_OCSP
1009 if (tls_ocsp_file)
1010 if (gnutls_buggy_ocsp)
1011 {
1012 DEBUG(D_tls)
1013 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1014 }
1015 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1016 {
1017 /* Use the full callback method for stapling just to get
1018 observability. More efficient would be to read the file once only,
1019 if it never changed (due to SNI). Would need restart on file update,
1020 or watch datestamp. */
1021
1022 # ifdef SUPPORT_SRV_OCSP_STACK
1023 rc = gnutls_certificate_set_ocsp_status_request_function2(
1024 state->x509_cred, gnutls_cert_index,
1025 server_ocsp_stapling_cb, ofile);
1026
1027 exim_gnutls_err_check(rc,
1028 US"gnutls_certificate_set_ocsp_status_request_function2");
1029 # else
1030 if (cnt++ > 0)
1031 {
1032 DEBUG(D_tls)
1033 debug_printf("oops; multiple OCSP files not supported\n");
1034 break;
1035 }
1036 gnutls_certificate_set_ocsp_status_request_function(
1037 state->x509_cred, server_ocsp_stapling_cb, ofile);
1038 # endif
1039
1040 DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile);
1041 }
1042 else
1043 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1044 #endif
1045 }
1046 }
1047 else
1048 {
1049 if (0 < (rc = tls_add_certfile(state, host,
1050 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1051 return rc;
1052 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1053 }
1054
1055 } /* tls_certificate */
1056
1057
1058 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1059 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1060 error message is provided. However, if we just refrain from setting anything up
1061 in that case, certificate verification fails, which seems to be the correct
1062 behaviour. */
1063
1064 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1065 {
1066 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1067 return DEFER;
1068 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1069 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1070 state->exp_tls_verify_certificates = NULL;
1071 #endif
1072 if (state->tls_crl && *state->tls_crl)
1073 if (!expand_check_tlsvar(tls_crl, errstr))
1074 return DEFER;
1075
1076 if (!(state->exp_tls_verify_certificates &&
1077 *state->exp_tls_verify_certificates))
1078 {
1079 DEBUG(D_tls)
1080 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1081 /* With no tls_verify_certificates, we ignore tls_crl too */
1082 return OK;
1083 }
1084 }
1085 else
1086 {
1087 DEBUG(D_tls)
1088 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1089 return OK;
1090 }
1091
1092 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1093 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1094 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1095 else
1096 #endif
1097 {
1098 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1099 {
1100 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
1101 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1102 strerror(errno));
1103 return DEFER;
1104 }
1105
1106 #ifndef SUPPORT_CA_DIR
1107 /* The test suite passes in /dev/null; we could check for that path explicitly,
1108 but who knows if someone has some weird FIFO which always dumps some certs, or
1109 other weirdness. The thing we really want to check is that it's not a
1110 directory, since while OpenSSL supports that, GnuTLS does not.
1111 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1112 if (S_ISDIR(statbuf.st_mode))
1113 {
1114 DEBUG(D_tls)
1115 debug_printf("verify certificates path is a dir: \"%s\"\n",
1116 state->exp_tls_verify_certificates);
1117 log_write(0, LOG_MAIN|LOG_PANIC,
1118 "tls_verify_certificates \"%s\" is a directory",
1119 state->exp_tls_verify_certificates);
1120 return DEFER;
1121 }
1122 #endif
1123
1124 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1125 state->exp_tls_verify_certificates, statbuf.st_size);
1126
1127 if (statbuf.st_size == 0)
1128 {
1129 DEBUG(D_tls)
1130 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1131 return OK;
1132 }
1133
1134 cert_count =
1135
1136 #ifdef SUPPORT_CA_DIR
1137 (statbuf.st_mode & S_IFMT) == S_IFDIR
1138 ?
1139 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1140 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1141 :
1142 #endif
1143 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1144 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1145 }
1146
1147 if (cert_count < 0)
1148 {
1149 rc = cert_count;
1150 exim_gnutls_err_check(rc, US"setting certificate trust");
1151 }
1152 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count);
1153
1154 if (state->tls_crl && *state->tls_crl &&
1155 state->exp_tls_crl && *state->exp_tls_crl)
1156 {
1157 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1158 cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1159 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM);
1160 if (cert_count < 0)
1161 {
1162 rc = cert_count;
1163 exim_gnutls_err_check(rc, US"gnutls_certificate_set_x509_crl_file");
1164 }
1165 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1166 }
1167
1168 return OK;
1169 }
1170
1171
1172
1173
1174 /*************************************************
1175 * Set X.509 state variables *
1176 *************************************************/
1177
1178 /* In GnuTLS, the registered cert/key are not replaced by a later
1179 set of a cert/key, so for SNI support we need a whole new x509_cred
1180 structure. Which means various other non-re-expanded pieces of state
1181 need to be re-set in the new struct, so the setting logic is pulled
1182 out to this.
1183
1184 Arguments:
1185 state exim_gnutls_state_st *
1186 errstr error string pointer
1187
1188 Returns: OK/DEFER/FAIL
1189 */
1190
1191 static int
1192 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1193 {
1194 int rc;
1195 const host_item *host = state->host; /* macro should be reconsidered? */
1196
1197 /* Create D-H parameters, or read them from the cache file. This function does
1198 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1199 client-side params. */
1200
1201 if (!state->host)
1202 {
1203 if (!dh_server_params)
1204 {
1205 rc = init_server_dh(errstr);
1206 if (rc != OK) return rc;
1207 }
1208 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1209 }
1210
1211 /* Link the credentials to the session. */
1212
1213 rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred);
1214 exim_gnutls_err_check(rc, US"gnutls_credentials_set");
1215
1216 return OK;
1217 }
1218
1219 /*************************************************
1220 * Initialize for GnuTLS *
1221 *************************************************/
1222
1223
1224 #ifndef DISABLE_OCSP
1225
1226 static BOOL
1227 tls_is_buggy_ocsp(void)
1228 {
1229 const uschar * s;
1230 uschar maj, mid, mic;
1231
1232 s = CUS gnutls_check_version(NULL);
1233 maj = atoi(CCS s);
1234 if (maj == 3)
1235 {
1236 while (*s && *s != '.') s++;
1237 mid = atoi(CCS ++s);
1238 if (mid <= 2)
1239 return TRUE;
1240 else if (mid >= 5)
1241 return FALSE;
1242 else
1243 {
1244 while (*s && *s != '.') s++;
1245 mic = atoi(CCS ++s);
1246 return mic <= (mid == 3 ? 16 : 3);
1247 }
1248 }
1249 return FALSE;
1250 }
1251
1252 #endif
1253
1254
1255 /* Called from both server and client code. In the case of a server, errors
1256 before actual TLS negotiation return DEFER.
1257
1258 Arguments:
1259 host connected host, if client; NULL if server
1260 certificate certificate file
1261 privatekey private key file
1262 sni TLS SNI to send, sometimes when client; else NULL
1263 cas CA certs file
1264 crl CRL file
1265 require_ciphers tls_require_ciphers setting
1266 caller_state returned state-info structure
1267 errstr error string pointer
1268
1269 Returns: OK/DEFER/FAIL
1270 */
1271
1272 static int
1273 tls_init(
1274 const host_item *host,
1275 const uschar *certificate,
1276 const uschar *privatekey,
1277 const uschar *sni,
1278 const uschar *cas,
1279 const uschar *crl,
1280 const uschar *require_ciphers,
1281 exim_gnutls_state_st **caller_state,
1282 tls_support * tlsp,
1283 uschar ** errstr)
1284 {
1285 exim_gnutls_state_st *state;
1286 int rc;
1287 size_t sz;
1288 const char *errpos;
1289 uschar *p;
1290 BOOL want_default_priorities;
1291
1292 if (!exim_gnutls_base_init_done)
1293 {
1294 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
1295
1296 #ifdef HAVE_GNUTLS_PKCS11
1297 /* By default, gnutls_global_init will init PKCS11 support in auto mode,
1298 which loads modules from a config file, which sounds good and may be wanted
1299 by some sysadmin, but also means in common configurations that GNOME keyring
1300 environment variables are used and so breaks for users calling mailq.
1301 To prevent this, we init PKCS11 first, which is the documented approach. */
1302 if (!gnutls_allow_auto_pkcs11)
1303 {
1304 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
1305 exim_gnutls_err_check(rc, US"gnutls_pkcs11_init");
1306 }
1307 #endif
1308
1309 rc = gnutls_global_init();
1310 exim_gnutls_err_check(rc, US"gnutls_global_init");
1311
1312 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1313 DEBUG(D_tls)
1314 {
1315 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1316 /* arbitrarily chosen level; bump upto 9 for more */
1317 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1318 }
1319 #endif
1320
1321 #ifndef DISABLE_OCSP
1322 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1323 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1324 #endif
1325
1326 exim_gnutls_base_init_done = TRUE;
1327 }
1328
1329 if (host)
1330 {
1331 /* For client-side sessions we allocate a context. This lets us run
1332 several in parallel. */
1333 int old_pool = store_pool;
1334 store_pool = POOL_PERM;
1335 state = store_get(sizeof(exim_gnutls_state_st));
1336 store_pool = old_pool;
1337
1338 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1339 state->tlsp = tlsp;
1340 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1341 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1342 }
1343 else
1344 {
1345 state = &state_server;
1346 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1347 state->tlsp = tlsp;
1348 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1349 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1350 }
1351 exim_gnutls_err_check(rc, US"gnutls_init");
1352
1353 state->host = host;
1354
1355 state->tls_certificate = certificate;
1356 state->tls_privatekey = privatekey;
1357 state->tls_require_ciphers = require_ciphers;
1358 state->tls_sni = sni;
1359 state->tls_verify_certificates = cas;
1360 state->tls_crl = crl;
1361
1362 /* This handles the variables that might get re-expanded after TLS SNI;
1363 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1364
1365 DEBUG(D_tls)
1366 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1367 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1368
1369 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1370 requires a new structure afterwards. */
1371
1372 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1373
1374 /* set SNI in client, only */
1375 if (host)
1376 {
1377 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1378 return DEFER;
1379 if (state->tlsp->sni && *state->tlsp->sni)
1380 {
1381 DEBUG(D_tls)
1382 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1383 sz = Ustrlen(state->tlsp->sni);
1384 rc = gnutls_server_name_set(state->session,
1385 GNUTLS_NAME_DNS, state->tlsp->sni, sz);
1386 exim_gnutls_err_check(rc, US"gnutls_server_name_set");
1387 }
1388 }
1389 else if (state->tls_sni)
1390 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1391 "have an SNI set for a server [%s]\n", state->tls_sni);
1392
1393 /* This is the priority string support,
1394 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1395 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1396 This was backwards incompatible, but means Exim no longer needs to track
1397 all algorithms and provide string forms for them. */
1398
1399 want_default_priorities = TRUE;
1400
1401 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1402 {
1403 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1404 return DEFER;
1405 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1406 {
1407 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n",
1408 state->exp_tls_require_ciphers);
1409
1410 rc = gnutls_priority_init(&state->priority_cache,
1411 CS state->exp_tls_require_ciphers, &errpos);
1412 want_default_priorities = FALSE;
1413 p = state->exp_tls_require_ciphers;
1414 }
1415 }
1416 if (want_default_priorities)
1417 {
1418 DEBUG(D_tls)
1419 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n",
1420 exim_default_gnutls_priority);
1421 rc = gnutls_priority_init(&state->priority_cache,
1422 exim_default_gnutls_priority, &errpos);
1423 p = US exim_default_gnutls_priority;
1424 }
1425
1426 exim_gnutls_err_check(rc, string_sprintf(
1427 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1428 p, errpos - CS p, errpos));
1429
1430 rc = gnutls_priority_set(state->session, state->priority_cache);
1431 exim_gnutls_err_check(rc, US"gnutls_priority_set");
1432
1433 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
1434
1435 /* Reduce security in favour of increased compatibility, if the admin
1436 decides to make that trade-off. */
1437 if (gnutls_compat_mode)
1438 {
1439 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
1440 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
1441 gnutls_session_enable_compatibility_mode(state->session);
1442 #else
1443 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
1444 #endif
1445 }
1446
1447 *caller_state = state;
1448 return OK;
1449 }
1450
1451
1452
1453 /*************************************************
1454 * Extract peer information *
1455 *************************************************/
1456
1457 static const uschar *
1458 cipher_stdname_kcm(gnutls_kx_algorithm_t kx, gnutls_cipher_algorithm_t cipher,
1459 gnutls_mac_algorithm_t mac)
1460 {
1461 uschar cs_id[2];
1462 gnutls_kx_algorithm_t kx_i;
1463 gnutls_cipher_algorithm_t cipher_i;
1464 gnutls_mac_algorithm_t mac_i;
1465
1466 for (size_t i = 0;
1467 gnutls_cipher_suite_info(i, cs_id, &kx_i, &cipher_i, &mac_i, NULL);
1468 i++)
1469 if (kx_i == kx && cipher_i == cipher && mac_i == mac)
1470 return cipher_stdname(cs_id[0], cs_id[1]);
1471 return NULL;
1472 }
1473
1474
1475
1476 /* Called from both server and client code.
1477 Only this is allowed to set state->peerdn and state->have_set_peerdn
1478 and we use that to detect double-calls.
1479
1480 NOTE: the state blocks last while the TLS connection is up, which is fine
1481 for logging in the server side, but for the client side, we log after teardown
1482 in src/deliver.c. While the session is up, we can twist about states and
1483 repoint tls_* globals, but those variables used for logging or other variable
1484 expansion that happens _after_ delivery need to have a longer life-time.
1485
1486 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1487 doing this more than once per generation of a state context. We set them in
1488 the state context, and repoint tls_* to them. After the state goes away, the
1489 tls_* copies of the pointers remain valid and client delivery logging is happy.
1490
1491 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1492 don't apply.
1493
1494 Arguments:
1495 state exim_gnutls_state_st *
1496 errstr pointer to error string
1497
1498 Returns: OK/DEFER/FAIL
1499 */
1500
1501 static int
1502 peer_status(exim_gnutls_state_st *state, uschar ** errstr)
1503 {
1504 const gnutls_datum_t *cert_list;
1505 int old_pool, rc;
1506 unsigned int cert_list_size = 0;
1507 gnutls_protocol_t protocol;
1508 gnutls_cipher_algorithm_t cipher;
1509 gnutls_kx_algorithm_t kx;
1510 gnutls_mac_algorithm_t mac;
1511 gnutls_certificate_type_t ct;
1512 gnutls_x509_crt_t crt;
1513 uschar *dn_buf;
1514 size_t sz;
1515
1516 if (state->have_set_peerdn)
1517 return OK;
1518 state->have_set_peerdn = TRUE;
1519
1520 state->peerdn = NULL;
1521
1522 /* tls_cipher */
1523 cipher = gnutls_cipher_get(state->session);
1524 protocol = gnutls_protocol_get_version(state->session);
1525 mac = gnutls_mac_get(state->session);
1526 kx = gnutls_kx_get(state->session);
1527
1528 old_pool = store_pool;
1529 {
1530 store_pool = POOL_PERM;
1531 state->ciphersuite = string_sprintf("%s:%s:%d",
1532 gnutls_protocol_get_name(protocol),
1533 gnutls_cipher_suite_get_name(kx, cipher, mac),
1534 (int) gnutls_cipher_get_key_size(cipher) * 8);
1535
1536 /* I don't see a way that spaces could occur, in the current GnuTLS
1537 code base, but it was a concern in the old code and perhaps older GnuTLS
1538 releases did return "TLS 1.0"; play it safe, just in case. */
1539
1540 for (uschar * p = state->ciphersuite; *p; p++) if (isspace(*p)) *p = '-';
1541 state->tlsp->cipher = state->ciphersuite;
1542
1543 state->tlsp->cipher_stdname = cipher_stdname_kcm(kx, cipher, mac);
1544 }
1545 store_pool = old_pool;
1546
1547 /* tls_peerdn */
1548 cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size);
1549
1550 if (!cert_list || cert_list_size == 0)
1551 {
1552 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1553 cert_list, cert_list_size);
1554 if (state->verify_requirement >= VERIFY_REQUIRED)
1555 return tls_error(US"certificate verification failed",
1556 US"no certificate received from peer", state->host, errstr);
1557 return OK;
1558 }
1559
1560 ct = gnutls_certificate_type_get(state->session);
1561 if (ct != GNUTLS_CRT_X509)
1562 {
1563 const uschar *ctn = US gnutls_certificate_type_get_name(ct);
1564 DEBUG(D_tls)
1565 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1566 if (state->verify_requirement >= VERIFY_REQUIRED)
1567 return tls_error(US"certificate verification not possible, unhandled type",
1568 ctn, state->host, errstr);
1569 return OK;
1570 }
1571
1572 #define exim_gnutls_peer_err(Label) \
1573 do { \
1574 if (rc != GNUTLS_E_SUCCESS) \
1575 { \
1576 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \
1577 (Label), gnutls_strerror(rc)); \
1578 if (state->verify_requirement >= VERIFY_REQUIRED) \
1579 return tls_error((Label), US gnutls_strerror(rc), state->host, errstr); \
1580 return OK; \
1581 } \
1582 } while (0)
1583
1584 rc = import_cert(&cert_list[0], &crt);
1585 exim_gnutls_peer_err(US"cert 0");
1586
1587 state->tlsp->peercert = state->peercert = crt;
1588
1589 sz = 0;
1590 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1591 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1592 {
1593 exim_gnutls_peer_err(US"getting size for cert DN failed");
1594 return FAIL; /* should not happen */
1595 }
1596 dn_buf = store_get_perm(sz);
1597 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1598 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1599
1600 state->peerdn = dn_buf;
1601
1602 return OK;
1603 #undef exim_gnutls_peer_err
1604 }
1605
1606
1607
1608
1609 /*************************************************
1610 * Verify peer certificate *
1611 *************************************************/
1612
1613 /* Called from both server and client code.
1614 *Should* be using a callback registered with
1615 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1616 the peer information, but that's too new for some OSes.
1617
1618 Arguments:
1619 state exim_gnutls_state_st *
1620 errstr where to put an error message
1621
1622 Returns:
1623 FALSE if the session should be rejected
1624 TRUE if the cert is okay or we just don't care
1625 */
1626
1627 static BOOL
1628 verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
1629 {
1630 int rc;
1631 uint verify;
1632
1633 if (state->verify_requirement == VERIFY_NONE)
1634 return TRUE;
1635
1636 DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
1637 *errstr = NULL;
1638
1639 if ((rc = peer_status(state, errstr)) != OK)
1640 {
1641 verify = GNUTLS_CERT_INVALID;
1642 *errstr = US"certificate not supplied";
1643 }
1644 else
1645
1646 {
1647 #ifdef SUPPORT_DANE
1648 if (state->verify_requirement == VERIFY_DANE && state->host)
1649 {
1650 /* Using dane_verify_session_crt() would be easy, as it does it all for us
1651 including talking to a DNS resolver. But we want to do that bit ourselves
1652 as the testsuite intercepts and fakes its own DNS environment. */
1653
1654 dane_state_t s;
1655 dane_query_t r;
1656 uint lsize;
1657 const gnutls_datum_t * certlist =
1658 gnutls_certificate_get_peers(state->session, &lsize);
1659 int usage = tls_out.tlsa_usage;
1660
1661 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1662 /* Split the TLSA records into two sets, TA and EE selectors. Run the
1663 dane-verification separately so that we know which selector verified;
1664 then we know whether to do name-verification (needed for TA but not EE). */
1665
1666 if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
1667 { /* a mixed-usage bundle */
1668 int i, j, nrec;
1669 const char ** dd;
1670 int * ddl;
1671
1672 for(nrec = 0; state->dane_data_len[nrec]; ) nrec++;
1673 nrec++;
1674
1675 dd = store_get(nrec * sizeof(uschar *));
1676 ddl = store_get(nrec * sizeof(int));
1677 nrec--;
1678
1679 if ((rc = dane_state_init(&s, 0)))
1680 goto tlsa_prob;
1681
1682 for (usage = DANESSL_USAGE_DANE_EE;
1683 usage >= DANESSL_USAGE_DANE_TA; usage--)
1684 { /* take records with this usage */
1685 for (j = i = 0; i < nrec; i++)
1686 if (state->dane_data[i][0] == usage)
1687 {
1688 dd[j] = state->dane_data[i];
1689 ddl[j++] = state->dane_data_len[i];
1690 }
1691 if (j)
1692 {
1693 dd[j] = NULL;
1694 ddl[j] = 0;
1695
1696 if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
1697 goto tlsa_prob;
1698
1699 if ((rc = dane_verify_crt_raw(s, certlist, lsize,
1700 gnutls_certificate_type_get(state->session),
1701 r, 0,
1702 usage == DANESSL_USAGE_DANE_EE
1703 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1704 &verify)))
1705 {
1706 DEBUG(D_tls)
1707 debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
1708 }
1709 else if (verify == 0) /* verification passed */
1710 {
1711 usage = 1 << usage;
1712 break;
1713 }
1714 }
1715 }
1716
1717 if (rc) goto tlsa_prob;
1718 }
1719 else
1720 # endif
1721 {
1722 if ( (rc = dane_state_init(&s, 0))
1723 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
1724 1, 0))
1725 || (rc = dane_verify_crt_raw(s, certlist, lsize,
1726 gnutls_certificate_type_get(state->session),
1727 r, 0,
1728 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1729 usage == (1 << DANESSL_USAGE_DANE_EE)
1730 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1731 # else
1732 0,
1733 # endif
1734 &verify))
1735 )
1736 goto tlsa_prob;
1737 }
1738
1739 if (verify != 0) /* verification failed */
1740 {
1741 gnutls_datum_t str;
1742 (void) dane_verification_status_print(verify, &str, 0);
1743 *errstr = US str.data; /* don't bother to free */
1744 goto badcert;
1745 }
1746
1747 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1748 /* If a TA-mode TLSA record was used for verification we must additionally
1749 verify the cert name (but not the CA chain). For EE-mode, skip it. */
1750
1751 if (usage & (1 << DANESSL_USAGE_DANE_EE))
1752 # endif
1753 {
1754 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1755 goto goodcert;
1756 }
1757 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1758 /* Assume that the name on the A-record is the one that should be matching
1759 the cert. An alternate view is that the domain part of the email address
1760 is also permissible. */
1761
1762 if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1763 CS state->host->name))
1764 {
1765 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1766 goto goodcert;
1767 }
1768 # endif
1769 }
1770 #endif /*SUPPORT_DANE*/
1771
1772 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1773 }
1774
1775 /* Handle the result of verification. INVALID is set if any others are. */
1776
1777 if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
1778 {
1779 state->peer_cert_verified = FALSE;
1780 if (!*errstr)
1781 {
1782 #ifdef GNUTLS_CERT_VFY_STATUS_PRINT
1783 DEBUG(D_tls)
1784 {
1785 gnutls_datum_t txt;
1786
1787 if (gnutls_certificate_verification_status_print(verify,
1788 gnutls_certificate_type_get(state->session), &txt, 0)
1789 == GNUTLS_E_SUCCESS)
1790 {
1791 debug_printf("%s\n", txt.data);
1792 gnutls_free(txt.data);
1793 }
1794 }
1795 #endif
1796 *errstr = verify & GNUTLS_CERT_REVOKED
1797 ? US"certificate revoked" : US"certificate invalid";
1798 }
1799
1800 DEBUG(D_tls)
1801 debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
1802 *errstr, state->peerdn ? state->peerdn : US"<unset>");
1803
1804 if (state->verify_requirement >= VERIFY_REQUIRED)
1805 goto badcert;
1806 DEBUG(D_tls)
1807 debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
1808 }
1809
1810 else
1811 {
1812 /* Client side, check the server's certificate name versus the name on the
1813 A-record for the connection we made. What to do for server side - what name
1814 to use for client? We document that there is no such checking for server
1815 side. */
1816
1817 if ( state->exp_tls_verify_cert_hostnames
1818 && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1819 CS state->exp_tls_verify_cert_hostnames)
1820 )
1821 {
1822 DEBUG(D_tls)
1823 debug_printf("TLS certificate verification failed: cert name mismatch\n");
1824 if (state->verify_requirement >= VERIFY_REQUIRED)
1825 goto badcert;
1826 return TRUE;
1827 }
1828
1829 state->peer_cert_verified = TRUE;
1830 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
1831 state->peerdn ? state->peerdn : US"<unset>");
1832 }
1833
1834 goodcert:
1835 state->tlsp->peerdn = state->peerdn;
1836 return TRUE;
1837
1838 #ifdef SUPPORT_DANE
1839 tlsa_prob:
1840 *errstr = string_sprintf("TLSA record problem: %s",
1841 rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
1842 #endif
1843
1844 badcert:
1845 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1846 return FALSE;
1847 }
1848
1849
1850
1851
1852 /* ------------------------------------------------------------------------ */
1853 /* Callbacks */
1854
1855 /* Logging function which can be registered with
1856 * gnutls_global_set_log_function()
1857 * gnutls_global_set_log_level() 0..9
1858 */
1859 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1860 static void
1861 exim_gnutls_logger_cb(int level, const char *message)
1862 {
1863 size_t len = strlen(message);
1864 if (len < 1)
1865 {
1866 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1867 return;
1868 }
1869 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1870 message[len-1] == '\n' ? "" : "\n");
1871 }
1872 #endif
1873
1874
1875 /* Called after client hello, should handle SNI work.
1876 This will always set tls_sni (state->received_sni) if available,
1877 and may trigger presenting different certificates,
1878 if state->trigger_sni_changes is TRUE.
1879
1880 Should be registered with
1881 gnutls_handshake_set_post_client_hello_function()
1882
1883 "This callback must return 0 on success or a gnutls error code to terminate the
1884 handshake.".
1885
1886 For inability to get SNI information, we return 0.
1887 We only return non-zero if re-setup failed.
1888 Only used for server-side TLS.
1889 */
1890
1891 static int
1892 exim_sni_handling_cb(gnutls_session_t session)
1893 {
1894 char sni_name[MAX_HOST_LEN];
1895 size_t data_len = MAX_HOST_LEN;
1896 exim_gnutls_state_st *state = &state_server;
1897 unsigned int sni_type;
1898 int rc, old_pool;
1899 uschar * dummy_errstr;
1900
1901 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
1902 if (rc != GNUTLS_E_SUCCESS)
1903 {
1904 DEBUG(D_tls) {
1905 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
1906 debug_printf("TLS: no SNI presented in handshake.\n");
1907 else
1908 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
1909 gnutls_strerror(rc), rc);
1910 }
1911 return 0;
1912 }
1913
1914 if (sni_type != GNUTLS_NAME_DNS)
1915 {
1916 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
1917 return 0;
1918 }
1919
1920 /* We now have a UTF-8 string in sni_name */
1921 old_pool = store_pool;
1922 store_pool = POOL_PERM;
1923 state->received_sni = string_copyn(US sni_name, data_len);
1924 store_pool = old_pool;
1925
1926 /* We set this one now so that variable expansions below will work */
1927 state->tlsp->sni = state->received_sni;
1928
1929 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
1930 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
1931
1932 if (!state->trigger_sni_changes)
1933 return 0;
1934
1935 if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK)
1936 {
1937 /* If the setup of certs/etc failed before handshake, TLS would not have
1938 been offered. The best we can do now is abort. */
1939 return GNUTLS_E_APPLICATION_ERROR_MIN;
1940 }
1941
1942 rc = tls_set_remaining_x509(state, &dummy_errstr);
1943 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
1944
1945 return 0;
1946 }
1947
1948
1949
1950 #ifndef DISABLE_OCSP
1951
1952 static int
1953 server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
1954 gnutls_datum_t * ocsp_response)
1955 {
1956 int ret;
1957 DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
1958
1959 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
1960 {
1961 DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
1962 CS ptr);
1963 tls_in.ocsp = OCSP_NOT_RESP;
1964 return GNUTLS_E_NO_CERTIFICATE_STATUS;
1965 }
1966
1967 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
1968 return 0;
1969 }
1970
1971 #endif
1972
1973
1974 #ifndef DISABLE_EVENT
1975 /*
1976 We use this callback to get observability and detail-level control
1977 for an exim TLS connection (either direction), raising a tls:cert event
1978 for each cert in the chain presented by the peer. Any event
1979 can deny verification.
1980
1981 Return 0 for the handshake to continue or non-zero to terminate.
1982 */
1983
1984 static int
1985 verify_cb(gnutls_session_t session)
1986 {
1987 const gnutls_datum_t * cert_list;
1988 unsigned int cert_list_size = 0;
1989 gnutls_x509_crt_t crt;
1990 int rc;
1991 uschar * yield;
1992 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
1993
1994 if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
1995 while (cert_list_size--)
1996 {
1997 if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
1998 {
1999 DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
2000 cert_list_size, gnutls_strerror(rc));
2001 break;
2002 }
2003
2004 state->tlsp->peercert = crt;
2005 if ((yield = event_raise(state->event_action,
2006 US"tls:cert", string_sprintf("%d", cert_list_size))))
2007 {
2008 log_write(0, LOG_MAIN,
2009 "SSL verify denied by event-action: depth=%d: %s",
2010 cert_list_size, yield);
2011 return 1; /* reject */
2012 }
2013 state->tlsp->peercert = NULL;
2014 }
2015
2016 return 0;
2017 }
2018
2019 #endif
2020
2021
2022 static gstring *
2023 ddump(gnutls_datum_t * d)
2024 {
2025 gstring * g = string_get((d->size+1) * 2);
2026 uschar * s = d->data;
2027 for (unsigned i = d->size; i > 0; i--, s++)
2028 {
2029 g = string_catn(g, US "0123456789abcdef" + (*s >> 4), 1);
2030 g = string_catn(g, US "0123456789abcdef" + (*s & 0xf), 1);
2031 }
2032 return g;
2033 }
2034
2035 /* ------------------------------------------------------------------------ */
2036 /* Exported functions */
2037
2038
2039
2040
2041 /*************************************************
2042 * Start a TLS session in a server *
2043 *************************************************/
2044
2045 /* This is called when Exim is running as a server, after having received
2046 the STARTTLS command. It must respond to that command, and then negotiate
2047 a TLS session.
2048
2049 Arguments:
2050 require_ciphers list of allowed ciphers or NULL
2051 errstr pointer to error string
2052
2053 Returns: OK on success
2054 DEFER for errors before the start of the negotiation
2055 FAIL for errors during the negotiation; the server can't
2056 continue running.
2057 */
2058
2059 int
2060 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2061 {
2062 int rc;
2063 exim_gnutls_state_st * state = NULL;
2064
2065 /* Check for previous activation */
2066 if (tls_in.active.sock >= 0)
2067 {
2068 tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
2069 smtp_printf("554 Already in TLS\r\n", FALSE);
2070 return FAIL;
2071 }
2072
2073 /* Initialize the library. If it fails, it will already have logged the error
2074 and sent an SMTP response. */
2075
2076 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
2077
2078 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
2079 NULL, tls_verify_certificates, tls_crl,
2080 require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
2081
2082 /* If this is a host for which certificate verification is mandatory or
2083 optional, set up appropriately. */
2084
2085 if (verify_check_host(&tls_verify_hosts) == OK)
2086 {
2087 DEBUG(D_tls)
2088 debug_printf("TLS: a client certificate will be required.\n");
2089 state->verify_requirement = VERIFY_REQUIRED;
2090 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2091 }
2092 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2093 {
2094 DEBUG(D_tls)
2095 debug_printf("TLS: a client certificate will be requested but not required.\n");
2096 state->verify_requirement = VERIFY_OPTIONAL;
2097 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2098 }
2099 else
2100 {
2101 DEBUG(D_tls)
2102 debug_printf("TLS: a client certificate will not be requested.\n");
2103 state->verify_requirement = VERIFY_NONE;
2104 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2105 }
2106
2107 #ifndef DISABLE_EVENT
2108 if (event_action)
2109 {
2110 state->event_action = event_action;
2111 gnutls_session_set_ptr(state->session, state);
2112 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2113 }
2114 #endif
2115
2116 /* Register SNI handling; always, even if not in tls_certificate, so that the
2117 expansion variable $tls_sni is always available. */
2118
2119 gnutls_handshake_set_post_client_hello_function(state->session,
2120 exim_sni_handling_cb);
2121
2122 /* Set context and tell client to go ahead, except in the case of TLS startup
2123 on connection, where outputting anything now upsets the clients and tends to
2124 make them disconnect. We need to have an explicit fflush() here, to force out
2125 the response. Other smtp_printf() calls do not need it, because in non-TLS
2126 mode, the fflush() happens when smtp_getc() is called. */
2127
2128 if (!state->tlsp->on_connect)
2129 {
2130 smtp_printf("220 TLS go ahead\r\n", FALSE);
2131 fflush(smtp_out);
2132 }
2133
2134 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2135 that the GnuTLS library doesn't.
2136 From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
2137 to set (and clear down afterwards) up a pull-timeout callback function that does
2138 a select, so we're no better off unless avoiding signals becomes an issue. */
2139
2140 gnutls_transport_set_ptr2(state->session,
2141 (gnutls_transport_ptr_t)(long) fileno(smtp_in),
2142 (gnutls_transport_ptr_t)(long) fileno(smtp_out));
2143 state->fd_in = fileno(smtp_in);
2144 state->fd_out = fileno(smtp_out);
2145
2146 sigalrm_seen = FALSE;
2147 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2148 do
2149 rc = gnutls_handshake(state->session);
2150 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2151 ALARM_CLR(0);
2152
2153 if (rc != GNUTLS_E_SUCCESS)
2154 {
2155 /* It seems that, except in the case of a timeout, we have to close the
2156 connection right here; otherwise if the other end is running OpenSSL it hangs
2157 until the server times out. */
2158
2159 if (sigalrm_seen)
2160 {
2161 tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
2162 gnutls_db_remove_session(state->session);
2163 }
2164 else
2165 {
2166 tls_error(US"gnutls_handshake", US gnutls_strerror(rc), NULL, errstr);
2167 (void) gnutls_alert_send_appropriate(state->session, rc);
2168 gnutls_deinit(state->session);
2169 gnutls_certificate_free_credentials(state->x509_cred);
2170 millisleep(500);
2171 shutdown(state->fd_out, SHUT_WR);
2172 for (int i = 1024; fgetc(smtp_in) != EOF && i > 0; ) i--; /* drain skt */
2173 (void)fclose(smtp_out);
2174 (void)fclose(smtp_in);
2175 smtp_out = smtp_in = NULL;
2176 }
2177
2178 return FAIL;
2179 }
2180
2181 DEBUG(D_tls)
2182 {
2183 debug_printf("gnutls_handshake was successful\n");
2184 #ifdef SUPPORT_GNUTLS_SESS_DESC
2185 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2186 #endif
2187 #ifdef SUPPORT_GNUTLS_KEYLOG
2188 {
2189 gnutls_datum_t c, s;
2190 gstring * gc, * gs;
2191 gnutls_session_get_random(state->session, &c, &s);
2192 gnutls_session_get_master_secret(state->session, &s);
2193 gc = ddump(&c);
2194 gs = ddump(&s);
2195 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2196 }
2197 #endif
2198 }
2199
2200 /* Verify after the fact */
2201
2202 if (!verify_certificate(state, errstr))
2203 {
2204 if (state->verify_requirement != VERIFY_OPTIONAL)
2205 {
2206 (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr);
2207 return FAIL;
2208 }
2209 DEBUG(D_tls)
2210 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
2211 *errstr);
2212 }
2213
2214 /* Figure out peer DN, and if authenticated, etc. */
2215
2216 if ((rc = peer_status(state, NULL)) != OK) return rc;
2217
2218 /* Sets various Exim expansion variables; always safe within server */
2219
2220 extract_exim_vars_from_tls_state(state);
2221
2222 /* TLS has been set up. Adjust the input functions to read via TLS,
2223 and initialize appropriately. */
2224
2225 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2226
2227 receive_getc = tls_getc;
2228 receive_getbuf = tls_getbuf;
2229 receive_get_cache = tls_get_cache;
2230 receive_ungetc = tls_ungetc;
2231 receive_feof = tls_feof;
2232 receive_ferror = tls_ferror;
2233 receive_smtp_buffered = tls_smtp_buffered;
2234
2235 return OK;
2236 }
2237
2238
2239
2240
2241 static void
2242 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
2243 smtp_transport_options_block * ob)
2244 {
2245 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2246 {
2247 state->exp_tls_verify_cert_hostnames =
2248 #ifdef SUPPORT_I18N
2249 string_domain_utf8_to_alabel(host->name, NULL);
2250 #else
2251 host->name;
2252 #endif
2253 DEBUG(D_tls)
2254 debug_printf("TLS: server cert verification includes hostname: \"%s\".\n",
2255 state->exp_tls_verify_cert_hostnames);
2256 }
2257 }
2258
2259
2260
2261
2262 #ifdef SUPPORT_DANE
2263 /* Given our list of RRs from the TLSA lookup, build a lookup block in
2264 GnuTLS-DANE's preferred format. Hang it on the state str for later
2265 use in DANE verification.
2266
2267 We point at the dnsa data not copy it, so it must remain valid until
2268 after verification is done.*/
2269
2270 static BOOL
2271 dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
2272 {
2273 dns_scan dnss;
2274 int i;
2275 const char ** dane_data;
2276 int * dane_data_len;
2277
2278 i = 1;
2279 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2280 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2281 ) if (rr->type == T_TLSA) i++;
2282
2283 dane_data = store_get(i * sizeof(uschar *));
2284 dane_data_len = store_get(i * sizeof(int));
2285
2286 i = 0;
2287 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2288 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2289 ) if (rr->type == T_TLSA && rr->size > 3)
2290 {
2291 const uschar * p = rr->data;
2292 uint8_t usage = p[0], sel = p[1], type = p[2];
2293
2294 DEBUG(D_tls)
2295 debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
2296
2297 if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
2298 || (sel != 0 && sel != 1)
2299 )
2300 continue;
2301 switch(type)
2302 {
2303 case 0: /* Full: cannot check at present */
2304 break;
2305 case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */
2306 break;
2307 case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */
2308 break;
2309 default: continue;
2310 }
2311
2312 tls_out.tlsa_usage |= 1<<usage;
2313 dane_data[i] = CS p;
2314 dane_data_len[i++] = rr->size;
2315 }
2316
2317 if (!i) return FALSE;
2318
2319 dane_data[i] = NULL;
2320 dane_data_len[i] = 0;
2321
2322 state->dane_data = (char * const *)dane_data;
2323 state->dane_data_len = dane_data_len;
2324 return TRUE;
2325 }
2326 #endif
2327
2328
2329
2330 /*************************************************
2331 * Start a TLS session in a client *
2332 *************************************************/
2333
2334 /* Called from the smtp transport after STARTTLS has been accepted.
2335
2336 Arguments:
2337 fd the fd of the connection
2338 host connected host (for messages and option-tests)
2339 addr the first address (not used)
2340 tb transport (always smtp)
2341 tlsa_dnsa non-NULL, either request or require dane for this host, and
2342 a TLSA record found. Therefore, dane verify required.
2343 Which implies cert must be requested and supplied, dane
2344 verify must pass, and cert verify irrelevant (incl.
2345 hostnames), and (caller handled) require_tls
2346 tlsp record details of channel configuration
2347 errstr error string pointer
2348
2349 Returns: Pointer to TLS session context, or NULL on error
2350 */
2351
2352 void *
2353 tls_client_start(int fd, host_item *host,
2354 address_item *addr ARG_UNUSED,
2355 transport_instance * tb,
2356 #ifdef SUPPORT_DANE
2357 dns_answer * tlsa_dnsa,
2358 #endif
2359 tls_support * tlsp, uschar ** errstr)
2360 {
2361 smtp_transport_options_block *ob = tb
2362 ? (smtp_transport_options_block *)tb->options_block
2363 : &smtp_transport_option_defaults;
2364 int rc;
2365 exim_gnutls_state_st * state = NULL;
2366 uschar *cipher_list = NULL;
2367
2368 #ifndef DISABLE_OCSP
2369 BOOL require_ocsp =
2370 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2371 BOOL request_ocsp = require_ocsp ? TRUE
2372 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2373 #endif
2374
2375 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd);
2376
2377 #ifdef SUPPORT_DANE
2378 if (tlsa_dnsa && ob->dane_require_tls_ciphers)
2379 {
2380 /* not using expand_check_tlsvar because not yet in state */
2381 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2382 &cipher_list, errstr))
2383 return NULL;
2384 cipher_list = cipher_list && *cipher_list
2385 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2386 }
2387 #endif
2388
2389 if (!cipher_list)
2390 cipher_list = ob->tls_require_ciphers;
2391
2392 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2393 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2394 cipher_list, &state, tlsp, errstr) != OK)
2395 return NULL;
2396
2397 {
2398 int dh_min_bits = ob->tls_dh_min_bits;
2399 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2400 {
2401 DEBUG(D_tls)
2402 debug_printf("WARNING: tls_dh_min_bits far too low,"
2403 " clamping %d up to %d\n",
2404 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2405 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2406 }
2407
2408 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2409 " acceptable bits to %d\n",
2410 dh_min_bits);
2411 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2412 }
2413
2414 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2415 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2416 the specified host patterns if one of them is defined */
2417
2418 #ifdef SUPPORT_DANE
2419 if (tlsa_dnsa && dane_tlsa_load(state, tlsa_dnsa))
2420 {
2421 DEBUG(D_tls)
2422 debug_printf("TLS: server certificate DANE required.\n");
2423 state->verify_requirement = VERIFY_DANE;
2424 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2425 }
2426 else
2427 #endif
2428 if ( ( state->exp_tls_verify_certificates
2429 && !ob->tls_verify_hosts
2430 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2431 )
2432 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2433 )
2434 {
2435 tls_client_setup_hostname_checks(host, state, ob);
2436 DEBUG(D_tls)
2437 debug_printf("TLS: server certificate verification required.\n");
2438 state->verify_requirement = VERIFY_REQUIRED;
2439 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2440 }
2441 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2442 {
2443 tls_client_setup_hostname_checks(host, state, ob);
2444 DEBUG(D_tls)
2445 debug_printf("TLS: server certificate verification optional.\n");
2446 state->verify_requirement = VERIFY_OPTIONAL;
2447 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2448 }
2449 else
2450 {
2451 DEBUG(D_tls)
2452 debug_printf("TLS: server certificate verification not required.\n");
2453 state->verify_requirement = VERIFY_NONE;
2454 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2455 }
2456
2457 #ifndef DISABLE_OCSP
2458 /* supported since GnuTLS 3.1.3 */
2459 if (request_ocsp)
2460 {
2461 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2462 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2463 NULL, 0, NULL)) != OK)
2464 {
2465 tls_error(US"cert-status-req", US gnutls_strerror(rc), state->host, errstr);
2466 return NULL;
2467 }
2468 tlsp->ocsp = OCSP_NOT_RESP;
2469 }
2470 #endif
2471
2472 #ifndef DISABLE_EVENT
2473 if (tb && tb->event_action)
2474 {
2475 state->event_action = tb->event_action;
2476 gnutls_session_set_ptr(state->session, state);
2477 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2478 }
2479 #endif
2480
2481 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) fd);
2482 state->fd_in = fd;
2483 state->fd_out = fd;
2484
2485 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2486 /* There doesn't seem to be a built-in timeout on connection. */
2487
2488 sigalrm_seen = FALSE;
2489 ALARM(ob->command_timeout);
2490 do
2491 rc = gnutls_handshake(state->session);
2492 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2493 ALARM_CLR(0);
2494
2495 if (rc != GNUTLS_E_SUCCESS)
2496 {
2497 if (sigalrm_seen)
2498 {
2499 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2500 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2501 }
2502 else
2503 tls_error(US"gnutls_handshake", US gnutls_strerror(rc), state->host, errstr);
2504 return NULL;
2505 }
2506
2507 DEBUG(D_tls)
2508 {
2509 debug_printf("gnutls_handshake was successful\n");
2510 #ifdef SUPPORT_GNUTLS_SESS_DESC
2511 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2512 #endif
2513 #ifdef SUPPORT_GNUTLS_KEYLOG
2514 {
2515 gnutls_datum_t c, s;
2516 gstring * gc, * gs;
2517 gnutls_session_get_random(state->session, &c, &s);
2518 gnutls_session_get_master_secret(state->session, &s);
2519 gc = ddump(&c);
2520 gs = ddump(&s);
2521 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2522 }
2523 #endif
2524 }
2525
2526 /* Verify late */
2527
2528 if (!verify_certificate(state, errstr))
2529 {
2530 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
2531 return NULL;
2532 }
2533
2534 #ifndef DISABLE_OCSP
2535 if (require_ocsp)
2536 {
2537 DEBUG(D_tls)
2538 {
2539 gnutls_datum_t stapling;
2540 gnutls_ocsp_resp_t resp;
2541 gnutls_datum_t printed;
2542 if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0
2543 && (rc= gnutls_ocsp_resp_init(&resp)) == 0
2544 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
2545 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0
2546 )
2547 {
2548 debug_printf("%.4096s", printed.data);
2549 gnutls_free(printed.data);
2550 }
2551 else
2552 (void) tls_error(US"ocsp decode", US gnutls_strerror(rc), state->host, errstr);
2553 }
2554
2555 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
2556 {
2557 tlsp->ocsp = OCSP_FAILED;
2558 tls_error(US"certificate status check failed", NULL, state->host, errstr);
2559 return NULL;
2560 }
2561 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
2562 tlsp->ocsp = OCSP_VFIED;
2563 }
2564 #endif
2565
2566 /* Figure out peer DN, and if authenticated, etc. */
2567
2568 if (peer_status(state, errstr) != OK)
2569 return NULL;
2570
2571 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
2572
2573 extract_exim_vars_from_tls_state(state);
2574
2575 return state;
2576 }
2577
2578
2579
2580
2581 /*************************************************
2582 * Close down a TLS session *
2583 *************************************************/
2584
2585 /* This is also called from within a delivery subprocess forked from the
2586 daemon, to shut down the TLS library, without actually doing a shutdown (which
2587 would tamper with the TLS session in the parent process).
2588
2589 Arguments:
2590 ct_ctx client context pointer, or NULL for the one global server context
2591 shutdown 1 if TLS close-alert is to be sent,
2592 2 if also response to be waited for
2593
2594 Returns: nothing
2595 */
2596
2597 void
2598 tls_close(void * ct_ctx, int shutdown)
2599 {
2600 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2601
2602 if (!state->tlsp || state->tlsp->active.sock < 0) return; /* TLS was not active */
2603
2604 if (shutdown)
2605 {
2606 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
2607 shutdown > 1 ? " (with response-wait)" : "");
2608
2609 ALARM(2);
2610 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
2611 ALARM_CLR(0);
2612 }
2613
2614 gnutls_deinit(state->session);
2615 gnutls_certificate_free_credentials(state->x509_cred);
2616
2617
2618 state->tlsp->active.sock = -1;
2619 state->tlsp->active.tls_ctx = NULL;
2620 if (state->xfer_buffer) store_free(state->xfer_buffer);
2621 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
2622 }
2623
2624
2625
2626
2627 static BOOL
2628 tls_refill(unsigned lim)
2629 {
2630 exim_gnutls_state_st * state = &state_server;
2631 ssize_t inbytes;
2632
2633 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
2634 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
2635
2636 sigalrm_seen = FALSE;
2637 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2638
2639 do
2640 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
2641 MIN(ssl_xfer_buffer_size, lim));
2642 while (inbytes == GNUTLS_E_AGAIN);
2643
2644 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2645
2646 if (had_command_timeout) /* set by signal handler */
2647 smtp_command_timeout_exit(); /* does not return */
2648 if (had_command_sigterm)
2649 smtp_command_sigterm_exit();
2650 if (had_data_timeout)
2651 smtp_data_timeout_exit();
2652 if (had_data_sigint)
2653 smtp_data_sigint_exit();
2654
2655 /* Timeouts do not get this far. A zero-byte return appears to mean that the
2656 TLS session has been closed down, not that the socket itself has been closed
2657 down. Revert to non-TLS handling. */
2658
2659 if (sigalrm_seen)
2660 {
2661 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
2662 state->xfer_error = TRUE;
2663 return FALSE;
2664 }
2665
2666 else if (inbytes == 0)
2667 {
2668 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2669
2670 receive_getc = smtp_getc;
2671 receive_getbuf = smtp_getbuf;
2672 receive_get_cache = smtp_get_cache;
2673 receive_ungetc = smtp_ungetc;
2674 receive_feof = smtp_feof;
2675 receive_ferror = smtp_ferror;
2676 receive_smtp_buffered = smtp_buffered;
2677
2678 gnutls_deinit(state->session);
2679 gnutls_certificate_free_credentials(state->x509_cred);
2680
2681 state->session = NULL;
2682 state->tlsp->active.sock = -1;
2683 state->tlsp->active.tls_ctx = NULL;
2684 state->tlsp->bits = 0;
2685 state->tlsp->certificate_verified = FALSE;
2686 tls_channelbinding_b64 = NULL;
2687 state->tlsp->cipher = NULL;
2688 state->tlsp->peercert = NULL;
2689 state->tlsp->peerdn = NULL;
2690
2691 return FALSE;
2692 }
2693
2694 /* Handle genuine errors */
2695
2696 else if (inbytes < 0)
2697 {
2698 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__);
2699 record_io_error(state, (int) inbytes, US"recv", NULL);
2700 state->xfer_error = TRUE;
2701 return FALSE;
2702 }
2703 #ifndef DISABLE_DKIM
2704 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
2705 #endif
2706 state->xfer_buffer_hwm = (int) inbytes;
2707 state->xfer_buffer_lwm = 0;
2708 return TRUE;
2709 }
2710
2711 /*************************************************
2712 * TLS version of getc *
2713 *************************************************/
2714
2715 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2716 it refills the buffer via the GnuTLS reading function.
2717 Only used by the server-side TLS.
2718
2719 This feeds DKIM and should be used for all message-body reads.
2720
2721 Arguments: lim Maximum amount to read/bufffer
2722 Returns: the next character or EOF
2723 */
2724
2725 int
2726 tls_getc(unsigned lim)
2727 {
2728 exim_gnutls_state_st * state = &state_server;
2729
2730 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2731 if (!tls_refill(lim))
2732 return state->xfer_error ? EOF : smtp_getc(lim);
2733
2734 /* Something in the buffer; return next uschar */
2735
2736 return state->xfer_buffer[state->xfer_buffer_lwm++];
2737 }
2738
2739 uschar *
2740 tls_getbuf(unsigned * len)
2741 {
2742 exim_gnutls_state_st * state = &state_server;
2743 unsigned size;
2744 uschar * buf;
2745
2746 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
2747 if (!tls_refill(*len))
2748 {
2749 if (!state->xfer_error) return smtp_getbuf(len);
2750 *len = 0;
2751 return NULL;
2752 }
2753
2754 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
2755 size = *len;
2756 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
2757 state->xfer_buffer_lwm += size;
2758 *len = size;
2759 return buf;
2760 }
2761
2762
2763 void
2764 tls_get_cache()
2765 {
2766 #ifndef DISABLE_DKIM
2767 exim_gnutls_state_st * state = &state_server;
2768 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
2769 if (n > 0)
2770 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
2771 #endif
2772 }
2773
2774
2775 BOOL
2776 tls_could_read(void)
2777 {
2778 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
2779 || gnutls_record_check_pending(state_server.session) > 0;
2780 }
2781
2782
2783
2784
2785 /*************************************************
2786 * Read bytes from TLS channel *
2787 *************************************************/
2788
2789 /* This does not feed DKIM, so if the caller uses this for reading message body,
2790 then the caller must feed DKIM.
2791
2792 Arguments:
2793 ct_ctx client context pointer, or NULL for the one global server context
2794 buff buffer of data
2795 len size of buffer
2796
2797 Returns: the number of bytes read
2798 -1 after a failed read, including EOF
2799 */
2800
2801 int
2802 tls_read(void * ct_ctx, uschar *buff, size_t len)
2803 {
2804 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2805 ssize_t inbytes;
2806
2807 if (len > INT_MAX)
2808 len = INT_MAX;
2809
2810 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
2811 DEBUG(D_tls)
2812 debug_printf("*** PROBABLY A BUG *** " \
2813 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
2814 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
2815
2816 DEBUG(D_tls)
2817 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
2818 state->session, buff, len);
2819
2820 do
2821 inbytes = gnutls_record_recv(state->session, buff, len);
2822 while (inbytes == GNUTLS_E_AGAIN);
2823
2824 if (inbytes > 0) return inbytes;
2825 if (inbytes == 0)
2826 {
2827 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
2828 }
2829 else
2830 {
2831 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__);
2832 record_io_error(state, (int)inbytes, US"recv", NULL);
2833 }
2834
2835 return -1;
2836 }
2837
2838
2839
2840
2841 /*************************************************
2842 * Write bytes down TLS channel *
2843 *************************************************/
2844
2845 /*
2846 Arguments:
2847 ct_ctx client context pointer, or NULL for the one global server context
2848 buff buffer of data
2849 len number of bytes
2850 more more data expected soon
2851
2852 Returns: the number of bytes after a successful write,
2853 -1 after a failed write
2854 */
2855
2856 int
2857 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
2858 {
2859 ssize_t outbytes;
2860 size_t left = len;
2861 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2862 #ifdef SUPPORT_CORK
2863 static BOOL corked = FALSE;
2864
2865 if (more && !corked) gnutls_record_cork(state->session);
2866 #endif
2867
2868 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
2869 buff, left, more ? ", more" : "");
2870
2871 while (left > 0)
2872 {
2873 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
2874 buff, left);
2875
2876 do
2877 outbytes = gnutls_record_send(state->session, buff, left);
2878 while (outbytes == GNUTLS_E_AGAIN);
2879
2880 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
2881 if (outbytes < 0)
2882 {
2883 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
2884 record_io_error(state, outbytes, US"send", NULL);
2885 return -1;
2886 }
2887 if (outbytes == 0)
2888 {
2889 record_io_error(state, 0, US"send", US"TLS channel closed on write");
2890 return -1;
2891 }
2892
2893 left -= outbytes;
2894 buff += outbytes;
2895 }
2896
2897 if (len > INT_MAX)
2898 {
2899 DEBUG(D_tls)
2900 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
2901 len);
2902 len = INT_MAX;
2903 }
2904
2905 #ifdef SUPPORT_CORK
2906 if (more != corked)
2907 {
2908 if (!more) (void) gnutls_record_uncork(state->session, 0);
2909 corked = more;
2910 }
2911 #endif
2912
2913 return (int) len;
2914 }
2915
2916
2917
2918
2919 /*************************************************
2920 * Random number generation *
2921 *************************************************/
2922
2923 /* Pseudo-random number generation. The result is not expected to be
2924 cryptographically strong but not so weak that someone will shoot themselves
2925 in the foot using it as a nonce in input in some email header scheme or
2926 whatever weirdness they'll twist this into. The result should handle fork()
2927 and avoid repeating sequences. OpenSSL handles that for us.
2928
2929 Arguments:
2930 max range maximum
2931 Returns a random number in range [0, max-1]
2932 */
2933
2934 #ifdef HAVE_GNUTLS_RND
2935 int
2936 vaguely_random_number(int max)
2937 {
2938 unsigned int r;
2939 int i, needed_len;
2940 uschar smallbuf[sizeof(r)];
2941
2942 if (max <= 1)
2943 return 0;
2944
2945 needed_len = sizeof(r);
2946 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2947 asked for a number less than 10. */
2948
2949 for (r = max, i = 0; r; ++i)
2950 r >>= 1;
2951 i = (i + 7) / 8;
2952 if (i < needed_len)
2953 needed_len = i;
2954
2955 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
2956 if (i < 0)
2957 {
2958 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
2959 return vaguely_random_number_fallback(max);
2960 }
2961 r = 0;
2962 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
2963 r = r * 256 + *p;
2964
2965 /* We don't particularly care about weighted results; if someone wants
2966 * smooth distribution and cares enough then they should submit a patch then. */
2967 return r % max;
2968 }
2969 #else /* HAVE_GNUTLS_RND */
2970 int
2971 vaguely_random_number(int max)
2972 {
2973 return vaguely_random_number_fallback(max);
2974 }
2975 #endif /* HAVE_GNUTLS_RND */
2976
2977
2978
2979
2980 /*************************************************
2981 * Let tls_require_ciphers be checked at startup *
2982 *************************************************/
2983
2984 /* The tls_require_ciphers option, if set, must be something which the
2985 library can parse.
2986
2987 Returns: NULL on success, or error message
2988 */
2989
2990 uschar *
2991 tls_validate_require_cipher(void)
2992 {
2993 int rc;
2994 uschar *expciphers = NULL;
2995 gnutls_priority_t priority_cache;
2996 const char *errpos;
2997 uschar * dummy_errstr;
2998
2999 #define validate_check_rc(Label) do { \
3000 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
3001 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
3002 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
3003
3004 if (exim_gnutls_base_init_done)
3005 log_write(0, LOG_MAIN|LOG_PANIC,
3006 "already initialised GnuTLS, Exim developer bug");
3007
3008 #ifdef HAVE_GNUTLS_PKCS11
3009 if (!gnutls_allow_auto_pkcs11)
3010 {
3011 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
3012 validate_check_rc(US"gnutls_pkcs11_init");
3013 }
3014 #endif
3015 rc = gnutls_global_init();
3016 validate_check_rc(US"gnutls_global_init()");
3017 exim_gnutls_base_init_done = TRUE;
3018
3019 if (!(tls_require_ciphers && *tls_require_ciphers))
3020 return_deinit(NULL);
3021
3022 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3023 &dummy_errstr))
3024 return_deinit(US"failed to expand tls_require_ciphers");
3025
3026 if (!(expciphers && *expciphers))
3027 return_deinit(NULL);
3028
3029 DEBUG(D_tls)
3030 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3031
3032 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
3033 validate_check_rc(string_sprintf(
3034 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
3035 expciphers, errpos - CS expciphers, errpos));
3036
3037 #undef return_deinit
3038 #undef validate_check_rc
3039 gnutls_global_deinit();
3040
3041 return NULL;
3042 }
3043
3044
3045
3046
3047 /*************************************************
3048 * Report the library versions. *
3049 *************************************************/
3050
3051 /* See a description in tls-openssl.c for an explanation of why this exists.
3052
3053 Arguments: a FILE* to print the results to
3054 Returns: nothing
3055 */
3056
3057 void
3058 tls_version_report(FILE *f)
3059 {
3060 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
3061 " Runtime: %s\n",
3062 LIBGNUTLS_VERSION,
3063 gnutls_check_version(NULL));
3064 }
3065
3066 /* vi: aw ai sw=2
3067 */
3068 /* End of tls-gnu.c */