GnuTLS: Move to more-modern stapling API
[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 #ifdef EXPERIMENTAL_TLS_RESUME
93 # if GNUTLS_VERSION_NUMBER < 0x030603
94 # error GNUTLS version too early for session-resumption
95 # endif
96 #endif
97
98 #ifndef DISABLE_OCSP
99 # include <gnutls/ocsp.h>
100 #endif
101 #ifdef SUPPORT_DANE
102 # include <gnutls/dane.h>
103 #endif
104
105 #include "tls-cipher-stdname.c"
106
107
108 #ifdef MACRO_PREDEF
109 void
110 options_tls(void)
111 {
112 # ifdef EXPERIMENTAL_TLS_RESUME
113 builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING );
114 # endif
115 }
116 #else
117
118
119 /* GnuTLS 2 vs 3
120
121 GnuTLS 3 only:
122 gnutls_global_set_audit_log_function()
123
124 Changes:
125 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
126 */
127
128 /* Local static variables for GnuTLS */
129
130 /* Values for verify_requirement */
131
132 enum peer_verify_requirement
133 { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE };
134
135 /* This holds most state for server or client; with this, we can set up an
136 outbound TLS-enabled connection in an ACL callout, while not stomping all
137 over the TLS variables available for expansion.
138
139 Some of these correspond to variables in globals.c; those variables will
140 be set to point to content in one of these instances, as appropriate for
141 the stage of the process lifetime.
142
143 Not handled here: global tls_channelbinding_b64.
144 */
145
146 typedef struct exim_gnutls_state {
147 gnutls_session_t session;
148 gnutls_certificate_credentials_t x509_cred;
149 gnutls_priority_t priority_cache;
150 enum peer_verify_requirement verify_requirement;
151 int fd_in;
152 int fd_out;
153 BOOL peer_cert_verified;
154 BOOL peer_dane_verified;
155 BOOL trigger_sni_changes;
156 BOOL have_set_peerdn;
157 const struct host_item *host; /* NULL if server */
158 gnutls_x509_crt_t peercert;
159 uschar *peerdn;
160 uschar *ciphersuite;
161 uschar *received_sni;
162
163 const uschar *tls_certificate;
164 const uschar *tls_privatekey;
165 const uschar *tls_sni; /* client send only, not received */
166 const uschar *tls_verify_certificates;
167 const uschar *tls_crl;
168 const uschar *tls_require_ciphers;
169
170 uschar *exp_tls_certificate;
171 uschar *exp_tls_privatekey;
172 uschar *exp_tls_verify_certificates;
173 uschar *exp_tls_crl;
174 uschar *exp_tls_require_ciphers;
175 const uschar *exp_tls_verify_cert_hostnames;
176 #ifndef DISABLE_EVENT
177 uschar *event_action;
178 #endif
179 #ifdef SUPPORT_DANE
180 char * const * dane_data;
181 const int * dane_data_len;
182 #endif
183
184 tls_support *tlsp; /* set in tls_init() */
185
186 uschar *xfer_buffer;
187 int xfer_buffer_lwm;
188 int xfer_buffer_hwm;
189 BOOL xfer_eof; /*XXX never gets set! */
190 BOOL xfer_error;
191 } exim_gnutls_state_st;
192
193 static const exim_gnutls_state_st exim_gnutls_state_init = {
194 /* all elements not explicitly intialised here get 0/NULL/FALSE */
195 .fd_in = -1,
196 .fd_out = -1,
197 };
198
199 /* Not only do we have our own APIs which don't pass around state, assuming
200 it's held in globals, GnuTLS doesn't appear to let us register callback data
201 for callbacks, or as part of the session, so we have to keep a "this is the
202 context we're currently dealing with" pointer and rely upon being
203 single-threaded to keep from processing data on an inbound TLS connection while
204 talking to another TLS connection for an outbound check. This does mean that
205 there's no way for heart-beats to be responded to, for the duration of the
206 second connection.
207 XXX But see gnutls_session_get_ptr()
208 */
209
210 static exim_gnutls_state_st state_server;
211
212 /* dh_params are initialised once within the lifetime of a process using TLS;
213 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
214 don't want to repeat this. */
215
216 static gnutls_dh_params_t dh_server_params = NULL;
217
218 static int ssl_session_timeout = 7200; /* Two hours */
219
220 static const uschar * const exim_default_gnutls_priority = US"NORMAL";
221
222 /* Guard library core initialisation */
223
224 static BOOL exim_gnutls_base_init_done = FALSE;
225
226 #ifndef DISABLE_OCSP
227 static BOOL gnutls_buggy_ocsp = FALSE;
228 static BOOL exim_testharness_disable_ocsp_validity_check = FALSE;
229 #endif
230
231 #ifdef EXPERIMENTAL_TLS_RESUME
232 static gnutls_datum_t server_sessticket_key;
233 #endif
234
235 /* ------------------------------------------------------------------------ */
236 /* macros */
237
238 #define MAX_HOST_LEN 255
239
240 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
241 the library logging; a value less than 0 disables the calls to set up logging
242 callbacks. GNuTLS also looks for an environment variable - except not for
243 setuid binaries, making it useless - "GNUTLS_DEBUG_LEVEL".
244 Allegedly the testscript line "GNUTLS_DEBUG_LEVEL=9 sudo exim ..." would work,
245 but the env var must be added to /etc/sudoers too. */
246 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
247 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
248 #endif
249
250 #ifndef EXIM_CLIENT_DH_MIN_BITS
251 # define EXIM_CLIENT_DH_MIN_BITS 1024
252 #endif
253
254 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
255 can ask for a bit-strength. Without that, we stick to the constant we had
256 before, for now. */
257 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
258 # define EXIM_SERVER_DH_BITS_PRE2_12 1024
259 #endif
260
261 #define expand_check_tlsvar(Varname, errstr) \
262 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
263
264 #if GNUTLS_VERSION_NUMBER >= 0x020c00
265 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
266 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
267 # define HAVE_GNUTLS_RND
268 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
269 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
270 * isn't available sometimes, so this needs to become a conditional
271 * compilation; the sanest way to deal with this being a problem on
272 * older OSes is to block it in the Local/Makefile with this compiler
273 * definition */
274 # ifndef AVOID_GNUTLS_PKCS11
275 # define HAVE_GNUTLS_PKCS11
276 # endif /* AVOID_GNUTLS_PKCS11 */
277 #endif
278
279
280
281
282 /* ------------------------------------------------------------------------ */
283 /* Callback declarations */
284
285 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
286 static void exim_gnutls_logger_cb(int level, const char *message);
287 #endif
288
289 static int exim_sni_handling_cb(gnutls_session_t session);
290
291 #if !defined(DISABLE_OCSP)
292 static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
293 gnutls_datum_t * ocsp_response);
294 #endif
295
296 #ifdef EXPERIMENTAL_TLS_RESUME
297 static int
298 tls_server_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
299 unsigned incoming, const gnutls_datum_t * msg);
300 #endif
301
302
303 /* Daemon one-time initialisation */
304 void
305 tls_daemon_init(void)
306 {
307 #ifdef EXPERIMENTAL_TLS_RESUME
308 /* We are dependent on the GnuTLS implementation of the Session Ticket
309 encryption; both the strength and the key rotation period. We hope that
310 the strength at least matches that of the ciphersuite (but GnuTLS does not
311 document this). */
312
313 static BOOL once = FALSE;
314 if (once) return;
315 once = TRUE;
316 gnutls_session_ticket_key_generate(&server_sessticket_key); /* >= 2.10.0 */
317 if (f.running_in_test_harness) ssl_session_timeout = 6;
318 #endif
319 }
320
321 /* ------------------------------------------------------------------------ */
322 /* Static functions */
323
324 /*************************************************
325 * Handle TLS error *
326 *************************************************/
327
328 /* Called from lots of places when errors occur before actually starting to do
329 the TLS handshake, that is, while the session is still in clear. Always returns
330 DEFER for a server and FAIL for a client so that most calls can use "return
331 tls_error(...)" to do this processing and then give an appropriate return. A
332 single function is used for both server and client, because it is called from
333 some shared functions.
334
335 Argument:
336 prefix text to include in the logged error
337 msg additional error string (may be NULL)
338 usually obtained from gnutls_strerror()
339 host NULL if setting up a server;
340 the connected host if setting up a client
341 errstr pointer to returned error string
342
343 Returns: OK/DEFER/FAIL
344 */
345
346 static int
347 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
348 uschar ** errstr)
349 {
350 if (errstr)
351 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
352 return host ? FAIL : DEFER;
353 }
354
355
356 static int
357 tls_error_gnu(const uschar *prefix, int err, const host_item *host,
358 uschar ** errstr)
359 {
360 return tls_error(prefix, US gnutls_strerror(err), host, errstr);
361 }
362
363 static int
364 tls_error_sys(const uschar *prefix, int err, const host_item *host,
365 uschar ** errstr)
366 {
367 return tls_error(prefix, US strerror(err), host, errstr);
368 }
369
370
371 /*************************************************
372 * Deal with logging errors during I/O *
373 *************************************************/
374
375 /* We have to get the identity of the peer from saved data.
376
377 Argument:
378 state the current GnuTLS exim state container
379 rc the GnuTLS error code, or 0 if it's a local error
380 when text identifying read or write
381 text local error text when rc is 0
382
383 Returns: nothing
384 */
385
386 static void
387 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
388 {
389 const uschar * msg;
390 uschar * errstr;
391
392 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
393 msg = string_sprintf("A TLS fatal alert has been received: %s",
394 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
395 else
396 msg = US gnutls_strerror(rc);
397
398 (void) tls_error(when, msg, state->host, &errstr);
399
400 if (state->host)
401 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
402 state->host->name, state->host->address, errstr);
403 else
404 {
405 uschar * conn_info = smtp_get_connection_info();
406 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
407 /* I'd like to get separated H= here, but too hard for now */
408 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
409 }
410 }
411
412
413
414
415 /*************************************************
416 * Set various Exim expansion vars *
417 *************************************************/
418
419 #define exim_gnutls_cert_err(Label) \
420 do \
421 { \
422 if (rc != GNUTLS_E_SUCCESS) \
423 { \
424 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
425 (Label), gnutls_strerror(rc)); \
426 return rc; \
427 } \
428 } while (0)
429
430 static int
431 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
432 {
433 int rc;
434
435 rc = gnutls_x509_crt_init(crtp);
436 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
437
438 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
439 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
440
441 return rc;
442 }
443
444 #undef exim_gnutls_cert_err
445
446
447 /* We set various Exim global variables from the state, once a session has
448 been established. With TLS callouts, may need to change this to stack
449 variables, or just re-call it with the server state after client callout
450 has finished.
451
452 Make sure anything set here is unset in tls_getc().
453
454 Sets:
455 tls_active fd
456 tls_bits strength indicator
457 tls_certificate_verified bool indicator
458 tls_channelbinding_b64 for some SASL mechanisms
459 tls_cipher a string
460 tls_peercert pointer to library internal
461 tls_peerdn a string
462 tls_sni a (UTF-8) string
463 tls_ourcert pointer to library internal
464
465 Argument:
466 state the relevant exim_gnutls_state_st *
467 */
468
469 static void
470 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
471 {
472 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
473 int old_pool;
474 int rc;
475 gnutls_datum_t channel;
476 #endif
477 tls_support * tlsp = state->tlsp;
478
479 tlsp->active.sock = state->fd_out;
480 tlsp->active.tls_ctx = state;
481
482 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
483
484 tlsp->certificate_verified = state->peer_cert_verified;
485 #ifdef SUPPORT_DANE
486 tlsp->dane_verified = state->peer_dane_verified;
487 #endif
488
489 /* note that tls_channelbinding_b64 is not saved to the spool file, since it's
490 only available for use for authenticators while this TLS session is running. */
491
492 tls_channelbinding_b64 = NULL;
493 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
494 channel.data = NULL;
495 channel.size = 0;
496 if ((rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel)))
497 { DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); }
498 else
499 {
500 old_pool = store_pool;
501 store_pool = POOL_PERM;
502 tls_channelbinding_b64 = b64encode(CUS channel.data, (int)channel.size);
503 store_pool = old_pool;
504 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n");
505 }
506 #endif
507
508 /* peercert is set in peer_status() */
509 tlsp->peerdn = state->peerdn;
510 tlsp->sni = state->received_sni;
511
512 /* record our certificate */
513 {
514 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
515 gnutls_x509_crt_t crt;
516
517 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
518 }
519 }
520
521
522
523
524 /*************************************************
525 * Setup up DH parameters *
526 *************************************************/
527
528 /* Generating the D-H parameters may take a long time. They only need to
529 be re-generated every so often, depending on security policy. What we do is to
530 keep these parameters in a file in the spool directory. If the file does not
531 exist, we generate them. This means that it is easy to cause a regeneration.
532
533 The new file is written as a temporary file and renamed, so that an incomplete
534 file is never present. If two processes both compute some new parameters, you
535 waste a bit of effort, but it doesn't seem worth messing around with locking to
536 prevent this.
537
538 Returns: OK/DEFER/FAIL
539 */
540
541 static int
542 init_server_dh(uschar ** errstr)
543 {
544 int fd, rc;
545 unsigned int dh_bits;
546 gnutls_datum_t m;
547 uschar filename_buf[PATH_MAX];
548 uschar *filename = NULL;
549 size_t sz;
550 uschar *exp_tls_dhparam;
551 BOOL use_file_in_spool = FALSE;
552 host_item *host = NULL; /* dummy for macros */
553
554 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
555
556 if ((rc = gnutls_dh_params_init(&dh_server_params)))
557 return tls_error_gnu(US"gnutls_dh_params_init", rc, host, errstr);
558
559 m.data = NULL;
560 m.size = 0;
561
562 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
563 return DEFER;
564
565 if (!exp_tls_dhparam)
566 {
567 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
568 m.data = US std_dh_prime_default();
569 m.size = Ustrlen(m.data);
570 }
571 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
572 use_file_in_spool = TRUE;
573 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
574 {
575 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
576 return OK;
577 }
578 else if (exp_tls_dhparam[0] != '/')
579 {
580 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
581 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
582 m.size = Ustrlen(m.data);
583 }
584 else
585 filename = exp_tls_dhparam;
586
587 if (m.data)
588 {
589 if ((rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM)))
590 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
591 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
592 return OK;
593 }
594
595 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
596 /* If you change this constant, also change dh_param_fn_ext so that we can use a
597 different filename and ensure we have sufficient bits. */
598
599 if (!(dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL)))
600 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
601 DEBUG(D_tls)
602 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
603 dh_bits);
604 #else
605 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
606 DEBUG(D_tls)
607 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
608 dh_bits);
609 #endif
610
611 /* Some clients have hard-coded limits. */
612 if (dh_bits > tls_dh_max_bits)
613 {
614 DEBUG(D_tls)
615 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
616 tls_dh_max_bits);
617 dh_bits = tls_dh_max_bits;
618 }
619
620 if (use_file_in_spool)
621 {
622 if (!string_format(filename_buf, sizeof(filename_buf),
623 "%s/gnutls-params-%d", spool_directory, dh_bits))
624 return tls_error(US"overlong filename", NULL, NULL, errstr);
625 filename = filename_buf;
626 }
627
628 /* Open the cache file for reading and if successful, read it and set up the
629 parameters. */
630
631 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
632 {
633 struct stat statbuf;
634 FILE *fp;
635 int saved_errno;
636
637 if (fstat(fd, &statbuf) < 0) /* EIO */
638 {
639 saved_errno = errno;
640 (void)close(fd);
641 return tls_error_sys(US"TLS cache stat failed", saved_errno, NULL, errstr);
642 }
643 if (!S_ISREG(statbuf.st_mode))
644 {
645 (void)close(fd);
646 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
647 }
648 if (!(fp = fdopen(fd, "rb")))
649 {
650 saved_errno = errno;
651 (void)close(fd);
652 return tls_error_sys(US"fdopen(TLS cache stat fd) failed",
653 saved_errno, NULL, errstr);
654 }
655
656 m.size = statbuf.st_size;
657 if (!(m.data = store_malloc(m.size)))
658 {
659 fclose(fp);
660 return tls_error_sys(US"malloc failed", errno, NULL, errstr);
661 }
662 if (!(sz = fread(m.data, m.size, 1, fp)))
663 {
664 saved_errno = errno;
665 fclose(fp);
666 store_free(m.data);
667 return tls_error_sys(US"fread failed", saved_errno, NULL, errstr);
668 }
669 fclose(fp);
670
671 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
672 store_free(m.data);
673 if (rc)
674 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
675 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
676 }
677
678 /* If the file does not exist, fall through to compute new data and cache it.
679 If there was any other opening error, it is serious. */
680
681 else if (errno == ENOENT)
682 {
683 rc = -1;
684 DEBUG(D_tls)
685 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
686 }
687 else
688 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
689 NULL, NULL, errstr);
690
691 /* If ret < 0, either the cache file does not exist, or the data it contains
692 is not useful. One particular case of this is when upgrading from an older
693 release of Exim in which the data was stored in a different format. We don't
694 try to be clever and support both formats; we just regenerate new data in this
695 case. */
696
697 if (rc < 0)
698 {
699 uschar *temp_fn;
700 unsigned int dh_bits_gen = dh_bits;
701
702 if ((PATH_MAX - Ustrlen(filename)) < 10)
703 return tls_error(US"Filename too long to generate replacement",
704 filename, NULL, errstr);
705
706 temp_fn = string_copy(US"%s.XXXXXXX");
707 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
708 return tls_error_sys(US"Unable to open temp file", errno, NULL, errstr);
709 (void)exim_chown(temp_fn, exim_uid, exim_gid); /* Probably not necessary */
710
711 /* GnuTLS overshoots!
712 * If we ask for 2236, we might get 2237 or more.
713 * But there's no way to ask GnuTLS how many bits there really are.
714 * We can ask how many bits were used in a TLS session, but that's it!
715 * The prime itself is hidden behind too much abstraction.
716 * So we ask for less, and proceed on a wing and a prayer.
717 * First attempt, subtracted 3 for 2233 and got 2240.
718 */
719 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
720 {
721 dh_bits_gen = dh_bits - 10;
722 DEBUG(D_tls)
723 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
724 dh_bits_gen);
725 }
726
727 DEBUG(D_tls)
728 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
729 dh_bits_gen);
730 if ((rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen)))
731 return tls_error_gnu(US"gnutls_dh_params_generate2", rc, host, errstr);
732
733 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
734 and I confirmed that a NULL call to get the size first is how the GnuTLS
735 sample apps handle this. */
736
737 sz = 0;
738 m.data = NULL;
739 if ( (rc = gnutls_dh_params_export_pkcs3(dh_server_params,
740 GNUTLS_X509_FMT_PEM, m.data, &sz))
741 && rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
742 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3(NULL) sizing",
743 rc, host, errstr);
744 m.size = sz;
745 if (!(m.data = store_malloc(m.size)))
746 return tls_error_sys(US"memory allocation failed", errno, NULL, errstr);
747
748 /* this will return a size 1 less than the allocation size above */
749 if ((rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
750 m.data, &sz)))
751 {
752 store_free(m.data);
753 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3() real", rc, host, errstr);
754 }
755 m.size = sz; /* shrink by 1, probably */
756
757 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
758 {
759 store_free(m.data);
760 return tls_error_sys(US"TLS cache write D-H params failed",
761 errno, NULL, errstr);
762 }
763 store_free(m.data);
764 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
765 return tls_error_sys(US"TLS cache write D-H params final newline failed",
766 errno, NULL, errstr);
767
768 if ((rc = close(fd)))
769 return tls_error_sys(US"TLS cache write close() failed", errno, NULL, errstr);
770
771 if (Urename(temp_fn, filename) < 0)
772 return tls_error_sys(string_sprintf("failed to rename \"%s\" as \"%s\"",
773 temp_fn, filename), errno, NULL, errstr);
774
775 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
776 }
777
778 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
779 return OK;
780 }
781
782
783
784
785 /* Create and install a selfsigned certificate, for use in server mode */
786
787 static int
788 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
789 {
790 gnutls_x509_crt_t cert = NULL;
791 time_t now;
792 gnutls_x509_privkey_t pkey = NULL;
793 const uschar * where;
794 int rc;
795
796 where = US"initialising pkey";
797 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
798
799 where = US"initialising cert";
800 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
801
802 where = US"generating pkey";
803 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
804 #ifdef SUPPORT_PARAM_TO_PK_BITS
805 # ifndef GNUTLS_SEC_PARAM_MEDIUM
806 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
807 # endif
808 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
809 #else
810 2048,
811 #endif
812 0)))
813 goto err;
814
815 where = US"configuring cert";
816 now = 1;
817 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
818 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
819 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
820 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
821 || (rc = gnutls_x509_crt_set_key(cert, pkey))
822
823 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
824 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
825 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
826 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
827 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
828 GNUTLS_OID_X520_COMMON_NAME, 0,
829 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
830 )
831 goto err;
832
833 where = US"signing cert";
834 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
835
836 where = US"installing selfsign cert";
837 /* Since: 2.4.0 */
838 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
839 goto err;
840
841 rc = OK;
842
843 out:
844 if (cert) gnutls_x509_crt_deinit(cert);
845 if (pkey) gnutls_x509_privkey_deinit(pkey);
846 return rc;
847
848 err:
849 rc = tls_error_gnu(where, rc, NULL, errstr);
850 goto out;
851 }
852
853
854
855
856 /* Add certificate and key, from files.
857
858 Return:
859 Zero or negative: good. Negate value for certificate index if < 0.
860 Greater than zero: FAIL or DEFER code.
861 */
862
863 static int
864 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
865 uschar * certfile, uschar * keyfile, uschar ** errstr)
866 {
867 /*XXX returns certs index for gnutls_certificate_set_x509_key_file(),
868 given suitable flags set */
869
870 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
871 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
872 if (rc < 0)
873 return tls_error_gnu(
874 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
875 rc, host, errstr);
876 return -rc;
877 }
878
879
880 /* Make a note that we saw a status-request */
881 static int
882 tls_server_clienthello_ext(void * ctx, unsigned tls_id,
883 const unsigned char *data, unsigned size)
884 {
885 /* https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml */
886 if (tls_id == 5) /* status_request */
887 {
888 DEBUG(D_tls) debug_printf("Seen status_request extension\n");
889 tls_in.ocsp = OCSP_NOT_RESP;
890 }
891 return 0;
892 }
893
894 /* Callback for client-hello, on server, if we think we might serve stapled-OCSP */
895 static int
896 tls_server_clienthello_cb(gnutls_session_t session, unsigned int htype,
897 unsigned when, unsigned int incoming, const gnutls_datum_t * msg)
898 {
899 /* Call fn for each extension seen. 3.6.3 onwards */
900 return gnutls_ext_raw_parse(NULL, tls_server_clienthello_ext, msg,
901 GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO);
902 }
903
904 /* Callback for certificate-status, on server. We sent stapled OCSP. */
905 static int
906 tls_server_certstatus_cb(gnutls_session_t session, unsigned int htype,
907 unsigned when, unsigned int incoming, const gnutls_datum_t * msg)
908 {
909 DEBUG(D_tls) debug_printf("Sending certificate-status\n");
910 #ifdef SUPPORT_SRV_OCSP_STACK
911 tls_in.ocsp = exim_testharness_disable_ocsp_validity_check
912 ? OCSP_VFY_NOT_TRIED : OCSP_VFIED; /* We know that GnuTLS verifies responses */
913 #else
914 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
915 #endif
916 return 0;
917 }
918
919 /* Callback for handshake messages, on server */
920 static int
921 tls_server_hook_cb(gnutls_session_t sess, u_int htype, unsigned when,
922 unsigned incoming, const gnutls_datum_t * msg)
923 {
924 switch (htype)
925 {
926 case GNUTLS_HANDSHAKE_CLIENT_HELLO:
927 return tls_server_clienthello_cb(sess, htype, when, incoming, msg);
928 case GNUTLS_HANDSHAKE_CERTIFICATE_STATUS:
929 return tls_server_certstatus_cb(sess, htype, when, incoming, msg);
930 #ifdef EXPERIMENTAL_TLS_RESUME
931 case GNUTLS_HANDSHAKE_NEW_SESSION_TICKET:
932 return tls_server_ticket_cb(sess, htype, when, incoming, msg);
933 #endif
934 default:
935 return 0;
936 }
937 }
938
939
940 static void
941 tls_server_testharness_ocsp_fiddle(void)
942 {
943 extern char ** environ;
944 if (environ) for (uschar ** p = USS environ; *p; p++)
945 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
946 {
947 DEBUG(D_tls) debug_printf("Permitting known bad OCSP response\n");
948 exim_testharness_disable_ocsp_validity_check = TRUE;
949 }
950 }
951
952 /*************************************************
953 * Variables re-expanded post-SNI *
954 *************************************************/
955
956 /* Called from both server and client code, via tls_init(), and also from
957 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
958
959 We can tell the two apart by state->received_sni being non-NULL in callback.
960
961 The callback should not call us unless state->trigger_sni_changes is true,
962 which we are responsible for setting on the first pass through.
963
964 Arguments:
965 state exim_gnutls_state_st *
966 errstr error string pointer
967
968 Returns: OK/DEFER/FAIL
969 */
970
971 static int
972 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
973 {
974 struct stat statbuf;
975 int rc;
976 const host_item *host = state->host; /* macro should be reconsidered? */
977 uschar *saved_tls_certificate = NULL;
978 uschar *saved_tls_privatekey = NULL;
979 uschar *saved_tls_verify_certificates = NULL;
980 uschar *saved_tls_crl = NULL;
981 int cert_count;
982
983 /* We check for tls_sni *before* expansion. */
984 if (!host) /* server */
985 if (!state->received_sni)
986 {
987 if ( state->tls_certificate
988 && ( Ustrstr(state->tls_certificate, US"tls_sni")
989 || Ustrstr(state->tls_certificate, US"tls_in_sni")
990 || Ustrstr(state->tls_certificate, US"tls_out_sni")
991 ) )
992 {
993 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
994 state->trigger_sni_changes = TRUE;
995 }
996 }
997 else
998 {
999 /* useful for debugging */
1000 saved_tls_certificate = state->exp_tls_certificate;
1001 saved_tls_privatekey = state->exp_tls_privatekey;
1002 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
1003 saved_tls_crl = state->exp_tls_crl;
1004 }
1005
1006 if ((rc = gnutls_certificate_allocate_credentials(&state->x509_cred)))
1007 return tls_error_gnu(US"gnutls_certificate_allocate_credentials",
1008 rc, host, errstr);
1009
1010 #ifdef SUPPORT_SRV_OCSP_STACK
1011 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
1012 #endif
1013
1014 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
1015 state members, assuming consistent naming; and expand_check() returns
1016 false if expansion failed, unless expansion was forced to fail. */
1017
1018 /* check if we at least have a certificate, before doing expensive
1019 D-H generation. */
1020
1021 if (!expand_check_tlsvar(tls_certificate, errstr))
1022 return DEFER;
1023
1024 /* certificate is mandatory in server, optional in client */
1025
1026 if ( !state->exp_tls_certificate
1027 || !*state->exp_tls_certificate
1028 )
1029 if (!host)
1030 return tls_install_selfsign(state, errstr);
1031 else
1032 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
1033
1034 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
1035 return DEFER;
1036
1037 /* tls_privatekey is optional, defaulting to same file as certificate */
1038
1039 if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0')
1040 {
1041 state->tls_privatekey = state->tls_certificate;
1042 state->exp_tls_privatekey = state->exp_tls_certificate;
1043 }
1044
1045
1046 if (state->exp_tls_certificate && *state->exp_tls_certificate)
1047 {
1048 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
1049 state->exp_tls_certificate, state->exp_tls_privatekey);
1050
1051 if (state->received_sni)
1052 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
1053 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
1054 )
1055 {
1056 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
1057 }
1058 else
1059 {
1060 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
1061 }
1062
1063 if (!host) /* server */
1064 {
1065 const uschar * clist = state->exp_tls_certificate;
1066 const uschar * klist = state->exp_tls_privatekey;
1067 const uschar * olist;
1068 int csep = 0, ksep = 0, osep = 0, cnt = 0;
1069 uschar * cfile, * kfile, * ofile;
1070
1071 #ifndef DISABLE_OCSP
1072 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
1073 return DEFER;
1074 olist = ofile;
1075 #endif
1076
1077 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
1078
1079 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
1080 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
1081 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
1082 return rc;
1083 else
1084 {
1085 int gnutls_cert_index = -rc;
1086 DEBUG(D_tls) debug_printf("TLS: cert/key %d %s registered\n", gnutls_cert_index, cfile);
1087
1088 /* Set the OCSP stapling server info */
1089
1090 #ifndef DISABLE_OCSP
1091 if (tls_ocsp_file)
1092 {
1093 if (gnutls_buggy_ocsp)
1094 {
1095 DEBUG(D_tls)
1096 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1097 }
1098 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1099 {
1100 DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile);
1101
1102 # ifdef SUPPORT_SRV_OCSP_STACK
1103 if (f.running_in_test_harness) tls_server_testharness_ocsp_fiddle();
1104
1105 if (!exim_testharness_disable_ocsp_validity_check)
1106 {
1107 if ((rc = gnutls_certificate_set_ocsp_status_request_file2(
1108 state->x509_cred, CCS ofile, gnutls_cert_index,
1109 GNUTLS_X509_FMT_DER)) < 0)
1110 return tls_error_gnu(
1111 US"gnutls_certificate_set_ocsp_status_request_file2",
1112 rc, host, errstr);
1113
1114 /* Arrange callbacks for OCSP request observability */
1115
1116 gnutls_handshake_set_hook_function(state->session,
1117 GNUTLS_HANDSHAKE_ANY, GNUTLS_HOOK_POST, tls_server_hook_cb);
1118 }
1119 else
1120 # endif
1121 {
1122 if (cnt++ > 0)
1123 {
1124 DEBUG(D_tls)
1125 debug_printf("oops; multiple OCSP files not supported\n");
1126 break;
1127 }
1128 gnutls_certificate_set_ocsp_status_request_function(
1129 state->x509_cred, server_ocsp_stapling_cb, ofile);
1130 }
1131 }
1132 else
1133 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1134 #endif
1135 }
1136 }
1137 }
1138 else /* client */
1139 {
1140 if (0 < (rc = tls_add_certfile(state, host,
1141 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1142 return rc;
1143 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1144 }
1145
1146 } /* tls_certificate */
1147
1148
1149 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1150 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1151 error message is provided. However, if we just refrain from setting anything up
1152 in that case, certificate verification fails, which seems to be the correct
1153 behaviour. */
1154
1155 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1156 {
1157 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1158 return DEFER;
1159 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1160 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1161 state->exp_tls_verify_certificates = NULL;
1162 #endif
1163 if (state->tls_crl && *state->tls_crl)
1164 if (!expand_check_tlsvar(tls_crl, errstr))
1165 return DEFER;
1166
1167 if (!(state->exp_tls_verify_certificates &&
1168 *state->exp_tls_verify_certificates))
1169 {
1170 DEBUG(D_tls)
1171 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1172 /* With no tls_verify_certificates, we ignore tls_crl too */
1173 return OK;
1174 }
1175 }
1176 else
1177 {
1178 DEBUG(D_tls)
1179 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1180 return OK;
1181 }
1182
1183 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1184 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1185 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1186 else
1187 #endif
1188 {
1189 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1190 {
1191 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s "
1192 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1193 strerror(errno));
1194 return DEFER;
1195 }
1196
1197 #ifndef SUPPORT_CA_DIR
1198 /* The test suite passes in /dev/null; we could check for that path explicitly,
1199 but who knows if someone has some weird FIFO which always dumps some certs, or
1200 other weirdness. The thing we really want to check is that it's not a
1201 directory, since while OpenSSL supports that, GnuTLS does not.
1202 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1203 if (S_ISDIR(statbuf.st_mode))
1204 {
1205 DEBUG(D_tls)
1206 debug_printf("verify certificates path is a dir: \"%s\"\n",
1207 state->exp_tls_verify_certificates);
1208 log_write(0, LOG_MAIN|LOG_PANIC,
1209 "tls_verify_certificates \"%s\" is a directory",
1210 state->exp_tls_verify_certificates);
1211 return DEFER;
1212 }
1213 #endif
1214
1215 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1216 state->exp_tls_verify_certificates, statbuf.st_size);
1217
1218 if (statbuf.st_size == 0)
1219 {
1220 DEBUG(D_tls)
1221 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1222 return OK;
1223 }
1224
1225 cert_count =
1226
1227 #ifdef SUPPORT_CA_DIR
1228 (statbuf.st_mode & S_IFMT) == S_IFDIR
1229 ?
1230 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1231 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1232 :
1233 #endif
1234 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1235 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1236
1237 #ifdef SUPPORT_CA_DIR
1238 /* Mimic the behaviour with OpenSSL of not advertising a usable-cert list
1239 when using the directory-of-certs config model. */
1240
1241 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1242 gnutls_certificate_send_x509_rdn_sequence(state->session, 1);
1243 #endif
1244 }
1245
1246 if (cert_count < 0)
1247 return tls_error_gnu(US"setting certificate trust", cert_count, host, errstr);
1248 DEBUG(D_tls)
1249 debug_printf("Added %d certificate authorities.\n", cert_count);
1250
1251 if (state->tls_crl && *state->tls_crl &&
1252 state->exp_tls_crl && *state->exp_tls_crl)
1253 {
1254 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1255 if ((cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1256 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM)) < 0)
1257 return tls_error_gnu(US"gnutls_certificate_set_x509_crl_file",
1258 cert_count, host, errstr);
1259
1260 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1261 }
1262
1263 return OK;
1264 }
1265
1266
1267
1268
1269 /*************************************************
1270 * Set X.509 state variables *
1271 *************************************************/
1272
1273 /* In GnuTLS, the registered cert/key are not replaced by a later
1274 set of a cert/key, so for SNI support we need a whole new x509_cred
1275 structure. Which means various other non-re-expanded pieces of state
1276 need to be re-set in the new struct, so the setting logic is pulled
1277 out to this.
1278
1279 Arguments:
1280 state exim_gnutls_state_st *
1281 errstr error string pointer
1282
1283 Returns: OK/DEFER/FAIL
1284 */
1285
1286 static int
1287 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1288 {
1289 int rc;
1290 const host_item *host = state->host; /* macro should be reconsidered? */
1291
1292 /* Create D-H parameters, or read them from the cache file. This function does
1293 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1294 client-side params. */
1295
1296 if (!state->host)
1297 {
1298 if (!dh_server_params)
1299 if ((rc = init_server_dh(errstr)) != OK) return rc;
1300 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1301 }
1302
1303 /* Link the credentials to the session. */
1304
1305 if ((rc = gnutls_credentials_set(state->session,
1306 GNUTLS_CRD_CERTIFICATE, state->x509_cred)))
1307 return tls_error_gnu(US"gnutls_credentials_set", rc, host, errstr);
1308
1309 return OK;
1310 }
1311
1312 /*************************************************
1313 * Initialize for GnuTLS *
1314 *************************************************/
1315
1316
1317 #ifndef DISABLE_OCSP
1318
1319 static BOOL
1320 tls_is_buggy_ocsp(void)
1321 {
1322 const uschar * s;
1323 uschar maj, mid, mic;
1324
1325 s = CUS gnutls_check_version(NULL);
1326 maj = atoi(CCS s);
1327 if (maj == 3)
1328 {
1329 while (*s && *s != '.') s++;
1330 mid = atoi(CCS ++s);
1331 if (mid <= 2)
1332 return TRUE;
1333 else if (mid >= 5)
1334 return FALSE;
1335 else
1336 {
1337 while (*s && *s != '.') s++;
1338 mic = atoi(CCS ++s);
1339 return mic <= (mid == 3 ? 16 : 3);
1340 }
1341 }
1342 return FALSE;
1343 }
1344
1345 #endif
1346
1347
1348 /* Called from both server and client code. In the case of a server, errors
1349 before actual TLS negotiation return DEFER.
1350
1351 Arguments:
1352 host connected host, if client; NULL if server
1353 certificate certificate file
1354 privatekey private key file
1355 sni TLS SNI to send, sometimes when client; else NULL
1356 cas CA certs file
1357 crl CRL file
1358 require_ciphers tls_require_ciphers setting
1359 caller_state returned state-info structure
1360 errstr error string pointer
1361
1362 Returns: OK/DEFER/FAIL
1363 */
1364
1365 static int
1366 tls_init(
1367 const host_item *host,
1368 const uschar *certificate,
1369 const uschar *privatekey,
1370 const uschar *sni,
1371 const uschar *cas,
1372 const uschar *crl,
1373 const uschar *require_ciphers,
1374 exim_gnutls_state_st **caller_state,
1375 tls_support * tlsp,
1376 uschar ** errstr)
1377 {
1378 exim_gnutls_state_st * state;
1379 int rc;
1380 size_t sz;
1381 const char * errpos;
1382 const uschar * p;
1383
1384 if (!exim_gnutls_base_init_done)
1385 {
1386 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
1387
1388 #ifdef HAVE_GNUTLS_PKCS11
1389 /* By default, gnutls_global_init will init PKCS11 support in auto mode,
1390 which loads modules from a config file, which sounds good and may be wanted
1391 by some sysadmin, but also means in common configurations that GNOME keyring
1392 environment variables are used and so breaks for users calling mailq.
1393 To prevent this, we init PKCS11 first, which is the documented approach. */
1394 if (!gnutls_allow_auto_pkcs11)
1395 if ((rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL)))
1396 return tls_error_gnu(US"gnutls_pkcs11_init", rc, host, errstr);
1397 #endif
1398
1399 if ((rc = gnutls_global_init()))
1400 return tls_error_gnu(US"gnutls_global_init", rc, host, errstr);
1401
1402 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1403 DEBUG(D_tls)
1404 {
1405 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1406 /* arbitrarily chosen level; bump up to 9 for more */
1407 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1408 }
1409 #endif
1410
1411 #ifndef DISABLE_OCSP
1412 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1413 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1414 #endif
1415
1416 exim_gnutls_base_init_done = TRUE;
1417 }
1418
1419 if (host)
1420 {
1421 /* For client-side sessions we allocate a context. This lets us run
1422 several in parallel. */
1423 int old_pool = store_pool;
1424 store_pool = POOL_PERM;
1425 state = store_get(sizeof(exim_gnutls_state_st), FALSE);
1426 store_pool = old_pool;
1427
1428 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1429 state->tlsp = tlsp;
1430 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1431 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1432 }
1433 else
1434 {
1435 state = &state_server;
1436 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1437 state->tlsp = tlsp;
1438 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1439 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1440 }
1441 if (rc)
1442 return tls_error_gnu(US"gnutls_init", rc, host, errstr);
1443
1444 state->host = host;
1445
1446 state->tls_certificate = certificate;
1447 state->tls_privatekey = privatekey;
1448 state->tls_require_ciphers = require_ciphers;
1449 state->tls_sni = sni;
1450 state->tls_verify_certificates = cas;
1451 state->tls_crl = crl;
1452
1453 /* This handles the variables that might get re-expanded after TLS SNI;
1454 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1455
1456 DEBUG(D_tls)
1457 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1458 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1459
1460 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1461 requires a new structure afterwards. */
1462
1463 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1464
1465 /* set SNI in client, only */
1466 if (host)
1467 {
1468 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1469 return DEFER;
1470 if (state->tlsp->sni && *state->tlsp->sni)
1471 {
1472 DEBUG(D_tls)
1473 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1474 sz = Ustrlen(state->tlsp->sni);
1475 if ((rc = gnutls_server_name_set(state->session,
1476 GNUTLS_NAME_DNS, state->tlsp->sni, sz)))
1477 return tls_error_gnu(US"gnutls_server_name_set", rc, host, errstr);
1478 }
1479 }
1480 else if (state->tls_sni)
1481 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1482 "have an SNI set for a server [%s]\n", state->tls_sni);
1483
1484 /* This is the priority string support,
1485 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1486 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1487 This was backwards incompatible, but means Exim no longer needs to track
1488 all algorithms and provide string forms for them. */
1489
1490 p = NULL;
1491 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1492 {
1493 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1494 return DEFER;
1495 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1496 {
1497 p = state->exp_tls_require_ciphers;
1498 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
1499 }
1500 }
1501 if (!p)
1502 {
1503 p = exim_default_gnutls_priority;
1504 DEBUG(D_tls)
1505 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
1506 }
1507
1508 if ((rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos)))
1509 return tls_error_gnu(string_sprintf(
1510 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1511 p, errpos - CS p, errpos),
1512 rc, host, errstr);
1513
1514 if ((rc = gnutls_priority_set(state->session, state->priority_cache)))
1515 return tls_error_gnu(US"gnutls_priority_set", rc, host, errstr);
1516
1517 /* This also sets the server ticket expiration time to the same, and
1518 the STEK rotation time to 3x. */
1519
1520 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
1521
1522 /* Reduce security in favour of increased compatibility, if the admin
1523 decides to make that trade-off. */
1524 if (gnutls_compat_mode)
1525 {
1526 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
1527 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
1528 gnutls_session_enable_compatibility_mode(state->session);
1529 #else
1530 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
1531 #endif
1532 }
1533
1534 *caller_state = state;
1535 return OK;
1536 }
1537
1538
1539
1540 /*************************************************
1541 * Extract peer information *
1542 *************************************************/
1543
1544 static const uschar *
1545 cipher_stdname_kcm(gnutls_kx_algorithm_t kx, gnutls_cipher_algorithm_t cipher,
1546 gnutls_mac_algorithm_t mac)
1547 {
1548 uschar cs_id[2];
1549 gnutls_kx_algorithm_t kx_i;
1550 gnutls_cipher_algorithm_t cipher_i;
1551 gnutls_mac_algorithm_t mac_i;
1552
1553 for (size_t i = 0;
1554 gnutls_cipher_suite_info(i, cs_id, &kx_i, &cipher_i, &mac_i, NULL);
1555 i++)
1556 if (kx_i == kx && cipher_i == cipher && mac_i == mac)
1557 return cipher_stdname(cs_id[0], cs_id[1]);
1558 return NULL;
1559 }
1560
1561
1562
1563 /* Called from both server and client code.
1564 Only this is allowed to set state->peerdn and state->have_set_peerdn
1565 and we use that to detect double-calls.
1566
1567 NOTE: the state blocks last while the TLS connection is up, which is fine
1568 for logging in the server side, but for the client side, we log after teardown
1569 in src/deliver.c. While the session is up, we can twist about states and
1570 repoint tls_* globals, but those variables used for logging or other variable
1571 expansion that happens _after_ delivery need to have a longer life-time.
1572
1573 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1574 doing this more than once per generation of a state context. We set them in
1575 the state context, and repoint tls_* to them. After the state goes away, the
1576 tls_* copies of the pointers remain valid and client delivery logging is happy.
1577
1578 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1579 don't apply.
1580
1581 Arguments:
1582 state exim_gnutls_state_st *
1583 errstr pointer to error string
1584
1585 Returns: OK/DEFER/FAIL
1586 */
1587
1588 static int
1589 peer_status(exim_gnutls_state_st * state, uschar ** errstr)
1590 {
1591 gnutls_session_t session = state->session;
1592 const gnutls_datum_t * cert_list;
1593 int old_pool, rc;
1594 unsigned int cert_list_size = 0;
1595 gnutls_protocol_t protocol;
1596 gnutls_cipher_algorithm_t cipher;
1597 gnutls_kx_algorithm_t kx;
1598 gnutls_mac_algorithm_t mac;
1599 gnutls_certificate_type_t ct;
1600 gnutls_x509_crt_t crt;
1601 uschar * dn_buf;
1602 size_t sz;
1603
1604 if (state->have_set_peerdn)
1605 return OK;
1606 state->have_set_peerdn = TRUE;
1607
1608 state->peerdn = NULL;
1609
1610 /* tls_cipher */
1611 cipher = gnutls_cipher_get(session);
1612 protocol = gnutls_protocol_get_version(session);
1613 mac = gnutls_mac_get(session);
1614 kx =
1615 #ifdef GNUTLS_TLS1_3
1616 protocol >= GNUTLS_TLS1_3 ? 0 :
1617 #endif
1618 gnutls_kx_get(session);
1619
1620 old_pool = store_pool;
1621 {
1622 tls_support * tlsp = state->tlsp;
1623 store_pool = POOL_PERM;
1624
1625 #ifdef SUPPORT_GNUTLS_SESS_DESC
1626 {
1627 gstring * g = NULL;
1628 uschar * s = US gnutls_session_get_desc(session), c;
1629
1630 /* Nikos M suggests we use this by preference. It returns like:
1631 (TLS1.3)-(ECDHE-SECP256R1)-(RSA-PSS-RSAE-SHA256)-(AES-256-GCM)
1632
1633 For partial back-compat, put a colon after the TLS version, replace the
1634 )-( grouping with __, replace in-group - with _ and append the :keysize. */
1635
1636 /* debug_printf("peer_status: gnutls_session_get_desc %s\n", s); */
1637
1638 for (s++; (c = *s) && c != ')'; s++) g = string_catn(g, s, 1);
1639 g = string_catn(g, US":", 1);
1640 if (*s) s++; /* now on _ between groups */
1641 while ((c = *s))
1642 {
1643 for (*++s && ++s; (c = *s) && c != ')'; s++) g = string_catn(g, c == '-' ? US"_" : s, 1);
1644 /* now on ) closing group */
1645 if ((c = *s) && *++s == '-') g = string_catn(g, US"__", 2);
1646 /* now on _ between groups */
1647 }
1648 g = string_catn(g, US":", 1);
1649 g = string_cat(g, string_sprintf("%d", (int) gnutls_cipher_get_key_size(cipher) * 8));
1650 state->ciphersuite = string_from_gstring(g);
1651 }
1652 #else
1653 state->ciphersuite = string_sprintf("%s:%s:%d",
1654 gnutls_protocol_get_name(protocol),
1655 gnutls_cipher_suite_get_name(kx, cipher, mac),
1656 (int) gnutls_cipher_get_key_size(cipher) * 8);
1657
1658 /* I don't see a way that spaces could occur, in the current GnuTLS
1659 code base, but it was a concern in the old code and perhaps older GnuTLS
1660 releases did return "TLS 1.0"; play it safe, just in case. */
1661
1662 for (uschar * p = state->ciphersuite; *p; p++) if (isspace(*p)) *p = '-';
1663 #endif
1664
1665 /* debug_printf("peer_status: ciphersuite %s\n", state->ciphersuite); */
1666
1667 tlsp->cipher = state->ciphersuite;
1668 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
1669
1670 tlsp->cipher_stdname = cipher_stdname_kcm(kx, cipher, mac);
1671 }
1672 store_pool = old_pool;
1673
1674 /* tls_peerdn */
1675 cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
1676
1677 if (!cert_list || cert_list_size == 0)
1678 {
1679 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1680 cert_list, cert_list_size);
1681 if (state->verify_requirement >= VERIFY_REQUIRED)
1682 return tls_error(US"certificate verification failed",
1683 US"no certificate received from peer", state->host, errstr);
1684 return OK;
1685 }
1686
1687 if ((ct = gnutls_certificate_type_get(session)) != GNUTLS_CRT_X509)
1688 {
1689 const uschar * ctn = US gnutls_certificate_type_get_name(ct);
1690 DEBUG(D_tls)
1691 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1692 if (state->verify_requirement >= VERIFY_REQUIRED)
1693 return tls_error(US"certificate verification not possible, unhandled type",
1694 ctn, state->host, errstr);
1695 return OK;
1696 }
1697
1698 #define exim_gnutls_peer_err(Label) \
1699 do { \
1700 if (rc != GNUTLS_E_SUCCESS) \
1701 { \
1702 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \
1703 (Label), gnutls_strerror(rc)); \
1704 if (state->verify_requirement >= VERIFY_REQUIRED) \
1705 return tls_error_gnu((Label), rc, state->host, errstr); \
1706 return OK; \
1707 } \
1708 } while (0)
1709
1710 rc = import_cert(&cert_list[0], &crt);
1711 exim_gnutls_peer_err(US"cert 0");
1712
1713 state->tlsp->peercert = state->peercert = crt;
1714
1715 sz = 0;
1716 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1717 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1718 {
1719 exim_gnutls_peer_err(US"getting size for cert DN failed");
1720 return FAIL; /* should not happen */
1721 }
1722 dn_buf = store_get_perm(sz, TRUE); /* tainted */
1723 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1724 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1725
1726 state->peerdn = dn_buf;
1727
1728 return OK;
1729 #undef exim_gnutls_peer_err
1730 }
1731
1732
1733
1734
1735 /*************************************************
1736 * Verify peer certificate *
1737 *************************************************/
1738
1739 /* Called from both server and client code.
1740 *Should* be using a callback registered with
1741 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1742 the peer information, but that's too new for some OSes.
1743
1744 Arguments:
1745 state exim_gnutls_state_st *
1746 errstr where to put an error message
1747
1748 Returns:
1749 FALSE if the session should be rejected
1750 TRUE if the cert is okay or we just don't care
1751 */
1752
1753 static BOOL
1754 verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
1755 {
1756 int rc;
1757 uint verify;
1758
1759 DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
1760 *errstr = NULL;
1761 rc = peer_status(state, errstr);
1762
1763 if (state->verify_requirement == VERIFY_NONE)
1764 return TRUE;
1765
1766 if (rc != OK || !state->peerdn)
1767 {
1768 verify = GNUTLS_CERT_INVALID;
1769 *errstr = US"certificate not supplied";
1770 }
1771 else
1772
1773 {
1774 #ifdef SUPPORT_DANE
1775 if (state->verify_requirement == VERIFY_DANE && state->host)
1776 {
1777 /* Using dane_verify_session_crt() would be easy, as it does it all for us
1778 including talking to a DNS resolver. But we want to do that bit ourselves
1779 as the testsuite intercepts and fakes its own DNS environment. */
1780
1781 dane_state_t s;
1782 dane_query_t r;
1783 uint lsize;
1784 const gnutls_datum_t * certlist =
1785 gnutls_certificate_get_peers(state->session, &lsize);
1786 int usage = tls_out.tlsa_usage;
1787
1788 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1789 /* Split the TLSA records into two sets, TA and EE selectors. Run the
1790 dane-verification separately so that we know which selector verified;
1791 then we know whether to do name-verification (needed for TA but not EE). */
1792
1793 if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
1794 { /* a mixed-usage bundle */
1795 int i, j, nrec;
1796 const char ** dd;
1797 int * ddl;
1798
1799 for(nrec = 0; state->dane_data_len[nrec]; ) nrec++;
1800 nrec++;
1801
1802 dd = store_get(nrec * sizeof(uschar *), FALSE);
1803 ddl = store_get(nrec * sizeof(int), FALSE);
1804 nrec--;
1805
1806 if ((rc = dane_state_init(&s, 0)))
1807 goto tlsa_prob;
1808
1809 for (usage = DANESSL_USAGE_DANE_EE;
1810 usage >= DANESSL_USAGE_DANE_TA; usage--)
1811 { /* take records with this usage */
1812 for (j = i = 0; i < nrec; i++)
1813 if (state->dane_data[i][0] == usage)
1814 {
1815 dd[j] = state->dane_data[i];
1816 ddl[j++] = state->dane_data_len[i];
1817 }
1818 if (j)
1819 {
1820 dd[j] = NULL;
1821 ddl[j] = 0;
1822
1823 if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
1824 goto tlsa_prob;
1825
1826 if ((rc = dane_verify_crt_raw(s, certlist, lsize,
1827 gnutls_certificate_type_get(state->session),
1828 r, 0,
1829 usage == DANESSL_USAGE_DANE_EE
1830 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1831 &verify)))
1832 {
1833 DEBUG(D_tls)
1834 debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
1835 }
1836 else if (verify == 0) /* verification passed */
1837 {
1838 usage = 1 << usage;
1839 break;
1840 }
1841 }
1842 }
1843
1844 if (rc) goto tlsa_prob;
1845 }
1846 else
1847 # endif
1848 {
1849 if ( (rc = dane_state_init(&s, 0))
1850 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
1851 1, 0))
1852 || (rc = dane_verify_crt_raw(s, certlist, lsize,
1853 gnutls_certificate_type_get(state->session),
1854 r, 0,
1855 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1856 usage == (1 << DANESSL_USAGE_DANE_EE)
1857 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1858 # else
1859 0,
1860 # endif
1861 &verify))
1862 )
1863 goto tlsa_prob;
1864 }
1865
1866 if (verify != 0) /* verification failed */
1867 {
1868 gnutls_datum_t str;
1869 (void) dane_verification_status_print(verify, &str, 0);
1870 *errstr = US str.data; /* don't bother to free */
1871 goto badcert;
1872 }
1873
1874 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1875 /* If a TA-mode TLSA record was used for verification we must additionally
1876 verify the cert name (but not the CA chain). For EE-mode, skip it. */
1877
1878 if (usage & (1 << DANESSL_USAGE_DANE_EE))
1879 # endif
1880 {
1881 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1882 goto goodcert;
1883 }
1884 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1885 /* Assume that the name on the A-record is the one that should be matching
1886 the cert. An alternate view is that the domain part of the email address
1887 is also permissible. */
1888
1889 if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1890 CS state->host->name))
1891 {
1892 state->peer_dane_verified = state->peer_cert_verified = TRUE;
1893 goto goodcert;
1894 }
1895 # endif
1896 }
1897 #endif /*SUPPORT_DANE*/
1898
1899 rc = gnutls_certificate_verify_peers2(state->session, &verify);
1900 }
1901
1902 /* Handle the result of verification. INVALID is set if any others are. */
1903
1904 if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
1905 {
1906 state->peer_cert_verified = FALSE;
1907 if (!*errstr)
1908 {
1909 #ifdef GNUTLS_CERT_VFY_STATUS_PRINT
1910 DEBUG(D_tls)
1911 {
1912 gnutls_datum_t txt;
1913
1914 if (gnutls_certificate_verification_status_print(verify,
1915 gnutls_certificate_type_get(state->session), &txt, 0)
1916 == GNUTLS_E_SUCCESS)
1917 {
1918 debug_printf("%s\n", txt.data);
1919 gnutls_free(txt.data);
1920 }
1921 }
1922 #endif
1923 *errstr = verify & GNUTLS_CERT_REVOKED
1924 ? US"certificate revoked" : US"certificate invalid";
1925 }
1926
1927 DEBUG(D_tls)
1928 debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
1929 *errstr, state->peerdn ? state->peerdn : US"<unset>");
1930
1931 if (state->verify_requirement >= VERIFY_REQUIRED)
1932 goto badcert;
1933 DEBUG(D_tls)
1934 debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
1935 }
1936
1937 else
1938 {
1939 /* Client side, check the server's certificate name versus the name on the
1940 A-record for the connection we made. What to do for server side - what name
1941 to use for client? We document that there is no such checking for server
1942 side. */
1943
1944 if ( state->exp_tls_verify_cert_hostnames
1945 && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
1946 CS state->exp_tls_verify_cert_hostnames)
1947 )
1948 {
1949 DEBUG(D_tls)
1950 debug_printf("TLS certificate verification failed: cert name mismatch\n");
1951 if (state->verify_requirement >= VERIFY_REQUIRED)
1952 goto badcert;
1953 return TRUE;
1954 }
1955
1956 state->peer_cert_verified = TRUE;
1957 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
1958 state->peerdn ? state->peerdn : US"<unset>");
1959 }
1960
1961 goodcert:
1962 state->tlsp->peerdn = state->peerdn;
1963 return TRUE;
1964
1965 #ifdef SUPPORT_DANE
1966 tlsa_prob:
1967 *errstr = string_sprintf("TLSA record problem: %s",
1968 rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
1969 #endif
1970
1971 badcert:
1972 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
1973 return FALSE;
1974 }
1975
1976
1977
1978
1979 /* ------------------------------------------------------------------------ */
1980 /* Callbacks */
1981
1982 /* Logging function which can be registered with
1983 * gnutls_global_set_log_function()
1984 * gnutls_global_set_log_level() 0..9
1985 */
1986 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1987 static void
1988 exim_gnutls_logger_cb(int level, const char *message)
1989 {
1990 size_t len = strlen(message);
1991 if (len < 1)
1992 {
1993 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
1994 return;
1995 }
1996 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
1997 message[len-1] == '\n' ? "" : "\n");
1998 }
1999 #endif
2000
2001
2002 /* Called after client hello, should handle SNI work.
2003 This will always set tls_sni (state->received_sni) if available,
2004 and may trigger presenting different certificates,
2005 if state->trigger_sni_changes is TRUE.
2006
2007 Should be registered with
2008 gnutls_handshake_set_post_client_hello_function()
2009
2010 "This callback must return 0 on success or a gnutls error code to terminate the
2011 handshake.".
2012
2013 For inability to get SNI information, we return 0.
2014 We only return non-zero if re-setup failed.
2015 Only used for server-side TLS.
2016 */
2017
2018 static int
2019 exim_sni_handling_cb(gnutls_session_t session)
2020 {
2021 char sni_name[MAX_HOST_LEN];
2022 size_t data_len = MAX_HOST_LEN;
2023 exim_gnutls_state_st *state = &state_server;
2024 unsigned int sni_type;
2025 int rc, old_pool;
2026 uschar * dummy_errstr;
2027
2028 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
2029 if (rc != GNUTLS_E_SUCCESS)
2030 {
2031 DEBUG(D_tls)
2032 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
2033 debug_printf("TLS: no SNI presented in handshake.\n");
2034 else
2035 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
2036 gnutls_strerror(rc), rc);
2037 return 0;
2038 }
2039
2040 if (sni_type != GNUTLS_NAME_DNS)
2041 {
2042 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
2043 return 0;
2044 }
2045
2046 /* We now have a UTF-8 string in sni_name */
2047 old_pool = store_pool;
2048 store_pool = POOL_PERM;
2049 state->received_sni = string_copy_taint(US sni_name, TRUE);
2050 store_pool = old_pool;
2051
2052 /* We set this one now so that variable expansions below will work */
2053 state->tlsp->sni = state->received_sni;
2054
2055 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
2056 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
2057
2058 if (!state->trigger_sni_changes)
2059 return 0;
2060
2061 if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK)
2062 {
2063 /* If the setup of certs/etc failed before handshake, TLS would not have
2064 been offered. The best we can do now is abort. */
2065 return GNUTLS_E_APPLICATION_ERROR_MIN;
2066 }
2067
2068 rc = tls_set_remaining_x509(state, &dummy_errstr);
2069 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
2070
2071 return 0;
2072 }
2073
2074
2075
2076 #if !defined(DISABLE_OCSP)
2077
2078 static int
2079 server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
2080 gnutls_datum_t * ocsp_response)
2081 {
2082 int ret;
2083 DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
2084
2085 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
2086 {
2087 DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
2088 CS ptr);
2089 tls_in.ocsp = OCSP_NOT_RESP;
2090 return GNUTLS_E_NO_CERTIFICATE_STATUS;
2091 }
2092
2093 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
2094 return 0;
2095 }
2096
2097 #endif
2098
2099
2100 #ifndef DISABLE_EVENT
2101 /*
2102 We use this callback to get observability and detail-level control
2103 for an exim TLS connection (either direction), raising a tls:cert event
2104 for each cert in the chain presented by the peer. Any event
2105 can deny verification.
2106
2107 Return 0 for the handshake to continue or non-zero to terminate.
2108 */
2109
2110 static int
2111 verify_cb(gnutls_session_t session)
2112 {
2113 const gnutls_datum_t * cert_list;
2114 unsigned int cert_list_size = 0;
2115 gnutls_x509_crt_t crt;
2116 int rc;
2117 uschar * yield;
2118 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
2119
2120 if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
2121 while (cert_list_size--)
2122 {
2123 if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
2124 {
2125 DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
2126 cert_list_size, gnutls_strerror(rc));
2127 break;
2128 }
2129
2130 state->tlsp->peercert = crt;
2131 if ((yield = event_raise(state->event_action,
2132 US"tls:cert", string_sprintf("%d", cert_list_size))))
2133 {
2134 log_write(0, LOG_MAIN,
2135 "SSL verify denied by event-action: depth=%d: %s",
2136 cert_list_size, yield);
2137 return 1; /* reject */
2138 }
2139 state->tlsp->peercert = NULL;
2140 }
2141
2142 return 0;
2143 }
2144
2145 #endif
2146
2147
2148 static gstring *
2149 ddump(gnutls_datum_t * d)
2150 {
2151 gstring * g = string_get((d->size+1) * 2);
2152 uschar * s = d->data;
2153 for (unsigned i = d->size; i > 0; i--, s++)
2154 {
2155 g = string_catn(g, US "0123456789abcdef" + (*s >> 4), 1);
2156 g = string_catn(g, US "0123456789abcdef" + (*s & 0xf), 1);
2157 }
2158 return g;
2159 }
2160
2161 static void
2162 post_handshake_debug(exim_gnutls_state_st * state)
2163 {
2164 #ifdef SUPPORT_GNUTLS_SESS_DESC
2165 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2166 #endif
2167 #ifdef SUPPORT_GNUTLS_KEYLOG
2168 # ifdef GNUTLS_TLS1_3
2169 if (gnutls_protocol_get_version(state->session) < GNUTLS_TLS1_3)
2170 #else
2171 if (TRUE)
2172 #endif
2173 {
2174 gnutls_datum_t c, s;
2175 gstring * gc, * gs;
2176 /* we only want the client random and the master secret */
2177 gnutls_session_get_random(state->session, &c, &s);
2178 gnutls_session_get_master_secret(state->session, &s);
2179 gc = ddump(&c);
2180 gs = ddump(&s);
2181 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2182 }
2183 else
2184 debug_printf("To get keying info for TLS1.3 is hard:\n"
2185 " set environment variable SSLKEYLOGFILE to a filename writable by uid exim\n"
2186 " add SSLKEYLOGFILE to keep_environment in the exim config\n"
2187 " run exim as root\n"
2188 " if using sudo, add SSLKEYLOGFILE to env_keep in /etc/sudoers\n");
2189 #endif
2190 }
2191
2192
2193 #ifdef EXPERIMENTAL_TLS_RESUME
2194 static int
2195 tls_server_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
2196 unsigned incoming, const gnutls_datum_t * msg)
2197 {
2198 DEBUG(D_tls) debug_printf("newticket cb\n");
2199 tls_in.resumption |= RESUME_CLIENT_REQUESTED;
2200 return 0;
2201 }
2202
2203 static void
2204 tls_server_resume_prehandshake(exim_gnutls_state_st * state)
2205 {
2206 /* Should the server offer session resumption? */
2207 tls_in.resumption = RESUME_SUPPORTED;
2208 if (verify_check_host(&tls_resumption_hosts) == OK)
2209 {
2210 int rc;
2211 /* GnuTLS appears to not do ticket overlap, but does emit a fresh ticket when
2212 an offered resumption is unacceptable. We lose one resumption per ticket
2213 lifetime, and sessions cannot be indefinitely re-used. There seems to be no
2214 way (3.6.7) of changing the default number of 2 TLS1.3 tickets issued, but at
2215 least they go out in a single packet. */
2216
2217 if (!(rc = gnutls_session_ticket_enable_server(state->session,
2218 &server_sessticket_key)))
2219 tls_in.resumption |= RESUME_SERVER_TICKET;
2220 else
2221 DEBUG(D_tls)
2222 debug_printf("enabling session tickets: %s\n", US gnutls_strerror(rc));
2223
2224 /* Try to tell if we see a ticket request */
2225 gnutls_handshake_set_hook_function(state->session,
2226 GNUTLS_HANDSHAKE_ANY, GNUTLS_HOOK_POST, tls_server_hook_cb);
2227 }
2228 }
2229
2230 static void
2231 tls_server_resume_posthandshake(exim_gnutls_state_st * state)
2232 {
2233 if (gnutls_session_resumption_requested(state->session))
2234 {
2235 /* This tells us the client sent a full ticket. We use a
2236 callback on session-ticket request, elsewhere, to tell
2237 if a client asked for a ticket. */
2238
2239 tls_in.resumption |= RESUME_CLIENT_SUGGESTED;
2240 DEBUG(D_tls) debug_printf("client requested resumption\n");
2241 }
2242 if (gnutls_session_is_resumed(state->session))
2243 {
2244 tls_in.resumption |= RESUME_USED;
2245 DEBUG(D_tls) debug_printf("Session resumed\n");
2246 }
2247 }
2248 #endif
2249 /* ------------------------------------------------------------------------ */
2250 /* Exported functions */
2251
2252
2253
2254
2255 /*************************************************
2256 * Start a TLS session in a server *
2257 *************************************************/
2258
2259 /* This is called when Exim is running as a server, after having received
2260 the STARTTLS command. It must respond to that command, and then negotiate
2261 a TLS session.
2262
2263 Arguments:
2264 require_ciphers list of allowed ciphers or NULL
2265 errstr pointer to error string
2266
2267 Returns: OK on success
2268 DEFER for errors before the start of the negotiation
2269 FAIL for errors during the negotiation; the server can't
2270 continue running.
2271 */
2272
2273 int
2274 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2275 {
2276 int rc;
2277 exim_gnutls_state_st * state = NULL;
2278
2279 /* Check for previous activation */
2280 if (tls_in.active.sock >= 0)
2281 {
2282 tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
2283 smtp_printf("554 Already in TLS\r\n", FALSE);
2284 return FAIL;
2285 }
2286
2287 /* Initialize the library. If it fails, it will already have logged the error
2288 and sent an SMTP response. */
2289
2290 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
2291
2292 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
2293 NULL, tls_verify_certificates, tls_crl,
2294 require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
2295
2296 #ifdef EXPERIMENTAL_TLS_RESUME
2297 tls_server_resume_prehandshake(state);
2298 #endif
2299
2300 /* If this is a host for which certificate verification is mandatory or
2301 optional, set up appropriately. */
2302
2303 if (verify_check_host(&tls_verify_hosts) == OK)
2304 {
2305 DEBUG(D_tls)
2306 debug_printf("TLS: a client certificate will be required.\n");
2307 state->verify_requirement = VERIFY_REQUIRED;
2308 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2309 }
2310 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2311 {
2312 DEBUG(D_tls)
2313 debug_printf("TLS: a client certificate will be requested but not required.\n");
2314 state->verify_requirement = VERIFY_OPTIONAL;
2315 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2316 }
2317 else
2318 {
2319 DEBUG(D_tls)
2320 debug_printf("TLS: a client certificate will not be requested.\n");
2321 state->verify_requirement = VERIFY_NONE;
2322 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2323 }
2324
2325 #ifndef DISABLE_EVENT
2326 if (event_action)
2327 {
2328 state->event_action = event_action;
2329 gnutls_session_set_ptr(state->session, state);
2330 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2331 }
2332 #endif
2333
2334 /* Register SNI handling; always, even if not in tls_certificate, so that the
2335 expansion variable $tls_sni is always available. */
2336
2337 gnutls_handshake_set_post_client_hello_function(state->session,
2338 exim_sni_handling_cb);
2339
2340 /* Set context and tell client to go ahead, except in the case of TLS startup
2341 on connection, where outputting anything now upsets the clients and tends to
2342 make them disconnect. We need to have an explicit fflush() here, to force out
2343 the response. Other smtp_printf() calls do not need it, because in non-TLS
2344 mode, the fflush() happens when smtp_getc() is called. */
2345
2346 if (!state->tlsp->on_connect)
2347 {
2348 smtp_printf("220 TLS go ahead\r\n", FALSE);
2349 fflush(smtp_out);
2350 }
2351
2352 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2353 that the GnuTLS library doesn't.
2354 From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
2355 to set (and clear down afterwards) up a pull-timeout callback function that does
2356 a select, so we're no better off unless avoiding signals becomes an issue. */
2357
2358 gnutls_transport_set_ptr2(state->session,
2359 (gnutls_transport_ptr_t)(long) fileno(smtp_in),
2360 (gnutls_transport_ptr_t)(long) fileno(smtp_out));
2361 state->fd_in = fileno(smtp_in);
2362 state->fd_out = fileno(smtp_out);
2363
2364 sigalrm_seen = FALSE;
2365 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2366 do
2367 rc = gnutls_handshake(state->session);
2368 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2369 ALARM_CLR(0);
2370
2371 if (rc != GNUTLS_E_SUCCESS)
2372 {
2373 /* It seems that, except in the case of a timeout, we have to close the
2374 connection right here; otherwise if the other end is running OpenSSL it hangs
2375 until the server times out. */
2376
2377 if (sigalrm_seen)
2378 {
2379 tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
2380 gnutls_db_remove_session(state->session);
2381 }
2382 else
2383 {
2384 tls_error_gnu(US"gnutls_handshake", rc, NULL, errstr);
2385 (void) gnutls_alert_send_appropriate(state->session, rc);
2386 gnutls_deinit(state->session);
2387 gnutls_certificate_free_credentials(state->x509_cred);
2388 millisleep(500);
2389 shutdown(state->fd_out, SHUT_WR);
2390 for (int i = 1024; fgetc(smtp_in) != EOF && i > 0; ) i--; /* drain skt */
2391 (void)fclose(smtp_out);
2392 (void)fclose(smtp_in);
2393 smtp_out = smtp_in = NULL;
2394 }
2395
2396 return FAIL;
2397 }
2398
2399 #ifdef EXPERIMENTAL_TLS_RESUME
2400 tls_server_resume_posthandshake(state);
2401 #endif
2402
2403 DEBUG(D_tls) post_handshake_debug(state);
2404
2405 /* Verify after the fact */
2406
2407 if (!verify_certificate(state, errstr))
2408 {
2409 if (state->verify_requirement != VERIFY_OPTIONAL)
2410 {
2411 (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr);
2412 return FAIL;
2413 }
2414 DEBUG(D_tls)
2415 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
2416 *errstr);
2417 }
2418
2419 /* Sets various Exim expansion variables; always safe within server */
2420
2421 extract_exim_vars_from_tls_state(state);
2422
2423 /* TLS has been set up. Adjust the input functions to read via TLS,
2424 and initialize appropriately. */
2425
2426 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2427
2428 receive_getc = tls_getc;
2429 receive_getbuf = tls_getbuf;
2430 receive_get_cache = tls_get_cache;
2431 receive_ungetc = tls_ungetc;
2432 receive_feof = tls_feof;
2433 receive_ferror = tls_ferror;
2434 receive_smtp_buffered = tls_smtp_buffered;
2435
2436 return OK;
2437 }
2438
2439
2440
2441
2442 static void
2443 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
2444 smtp_transport_options_block * ob)
2445 {
2446 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2447 {
2448 state->exp_tls_verify_cert_hostnames =
2449 #ifdef SUPPORT_I18N
2450 string_domain_utf8_to_alabel(host->name, NULL);
2451 #else
2452 host->name;
2453 #endif
2454 DEBUG(D_tls)
2455 debug_printf("TLS: server cert verification includes hostname: \"%s\".\n",
2456 state->exp_tls_verify_cert_hostnames);
2457 }
2458 }
2459
2460
2461
2462
2463 #ifdef SUPPORT_DANE
2464 /* Given our list of RRs from the TLSA lookup, build a lookup block in
2465 GnuTLS-DANE's preferred format. Hang it on the state str for later
2466 use in DANE verification.
2467
2468 We point at the dnsa data not copy it, so it must remain valid until
2469 after verification is done.*/
2470
2471 static BOOL
2472 dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
2473 {
2474 dns_scan dnss;
2475 int i;
2476 const char ** dane_data;
2477 int * dane_data_len;
2478
2479 i = 1;
2480 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2481 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2482 ) if (rr->type == T_TLSA) i++;
2483
2484 dane_data = store_get(i * sizeof(uschar *), FALSE);
2485 dane_data_len = store_get(i * sizeof(int), FALSE);
2486
2487 i = 0;
2488 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2489 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2490 ) if (rr->type == T_TLSA && rr->size > 3)
2491 {
2492 const uschar * p = rr->data;
2493 /*XXX need somehow to mark rr and its data as tainted. Doues this mean copying it? */
2494 uint8_t usage = p[0], sel = p[1], type = p[2];
2495
2496 DEBUG(D_tls)
2497 debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
2498
2499 if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
2500 || (sel != 0 && sel != 1)
2501 )
2502 continue;
2503 switch(type)
2504 {
2505 case 0: /* Full: cannot check at present */
2506 break;
2507 case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */
2508 break;
2509 case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */
2510 break;
2511 default: continue;
2512 }
2513
2514 tls_out.tlsa_usage |= 1<<usage;
2515 dane_data[i] = CS p;
2516 dane_data_len[i++] = rr->size;
2517 }
2518
2519 if (!i) return FALSE;
2520
2521 dane_data[i] = NULL;
2522 dane_data_len[i] = 0;
2523
2524 state->dane_data = (char * const *)dane_data;
2525 state->dane_data_len = dane_data_len;
2526 return TRUE;
2527 }
2528 #endif
2529
2530
2531
2532 #ifdef EXPERIMENTAL_TLS_RESUME
2533 /* On the client, get any stashed session for the given IP from hints db
2534 and apply it to the ssl-connection for attempted resumption. Although
2535 there is a gnutls_session_ticket_enable_client() interface it is
2536 documented as unnecessary (as of 3.6.7) as "session tickets are emabled
2537 by deafult". There seems to be no way to disable them, so even hosts not
2538 enabled by the transport option will be sent a ticket request. We will
2539 however avoid storing and retrieving session information. */
2540
2541 static void
2542 tls_retrieve_session(tls_support * tlsp, gnutls_session_t session,
2543 host_item * host, smtp_transport_options_block * ob)
2544 {
2545 tlsp->resumption = RESUME_SUPPORTED;
2546 if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK)
2547 {
2548 dbdata_tls_session * dt;
2549 int len, rc;
2550 open_db dbblock, * dbm_file;
2551
2552 DEBUG(D_tls)
2553 debug_printf("check for resumable session for %s\n", host->address);
2554 tlsp->host_resumable = TRUE;
2555 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
2556 if ((dbm_file = dbfn_open(US"tls", O_RDONLY, &dbblock, FALSE, FALSE)))
2557 {
2558 /* Key for the db is the IP. We'd like to filter the retrieved session
2559 for ticket advisory expiry, but 3.6.1 seems to give no access to that */
2560
2561 if ((dt = dbfn_read_with_length(dbm_file, host->address, &len)))
2562 if (!(rc = gnutls_session_set_data(session,
2563 CUS dt->session, (size_t)len - sizeof(dbdata_tls_session))))
2564 {
2565 DEBUG(D_tls) debug_printf("good session\n");
2566 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
2567 }
2568 else DEBUG(D_tls) debug_printf("setting session resumption data: %s\n",
2569 US gnutls_strerror(rc));
2570 dbfn_close(dbm_file);
2571 }
2572 }
2573 }
2574
2575
2576 static void
2577 tls_save_session(tls_support * tlsp, gnutls_session_t session, const host_item * host)
2578 {
2579 /* TLS 1.2 - we get both the callback and the direct posthandshake call,
2580 but this flag is not set until the second. TLS 1.3 it's the other way about.
2581 Keep both calls as the session data cannot be extracted before handshake
2582 completes. */
2583
2584 if (gnutls_session_get_flags(session) & GNUTLS_SFLAGS_SESSION_TICKET)
2585 {
2586 gnutls_datum_t tkt;
2587 int rc;
2588
2589 DEBUG(D_tls) debug_printf("server offered session ticket\n");
2590 tlsp->ticket_received = TRUE;
2591 tlsp->resumption |= RESUME_SERVER_TICKET;
2592
2593 if (tlsp->host_resumable)
2594 if (!(rc = gnutls_session_get_data2(session, &tkt)))
2595 {
2596 open_db dbblock, * dbm_file;
2597 int dlen = sizeof(dbdata_tls_session) + tkt.size;
2598 dbdata_tls_session * dt = store_get(dlen, TRUE);
2599
2600 DEBUG(D_tls) debug_printf("session data size %u\n", (unsigned)tkt.size);
2601 memcpy(dt->session, tkt.data, tkt.size);
2602 gnutls_free(tkt.data);
2603
2604 if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE)))
2605 {
2606 /* key for the db is the IP */
2607 dbfn_delete(dbm_file, host->address);
2608 dbfn_write(dbm_file, host->address, dt, dlen);
2609 dbfn_close(dbm_file);
2610
2611 DEBUG(D_tls)
2612 debug_printf("wrote session db (len %u)\n", (unsigned)dlen);
2613 }
2614 }
2615 else DEBUG(D_tls)
2616 debug_printf("extract session data: %s\n", US gnutls_strerror(rc));
2617 }
2618 }
2619
2620
2621 /* With a TLS1.3 session, the ticket(s) are not seen until
2622 the first data read is attempted. And there's often two of them.
2623 Pick them up with this callback. We are also called for 1.2
2624 but we do nothing.
2625 */
2626 static int
2627 tls_client_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
2628 unsigned incoming, const gnutls_datum_t * msg)
2629 {
2630 exim_gnutls_state_st * state = gnutls_session_get_ptr(sess);
2631 tls_support * tlsp = state->tlsp;
2632
2633 DEBUG(D_tls) debug_printf("newticket cb\n");
2634
2635 if (!tlsp->ticket_received)
2636 tls_save_session(tlsp, sess, state->host);
2637 return 0;
2638 }
2639
2640
2641 static void
2642 tls_client_resume_prehandshake(exim_gnutls_state_st * state,
2643 tls_support * tlsp, host_item * host,
2644 smtp_transport_options_block * ob)
2645 {
2646 gnutls_session_set_ptr(state->session, state);
2647 gnutls_handshake_set_hook_function(state->session,
2648 GNUTLS_HANDSHAKE_NEW_SESSION_TICKET, GNUTLS_HOOK_POST, tls_client_ticket_cb);
2649
2650 tls_retrieve_session(tlsp, state->session, host, ob);
2651 }
2652
2653 static void
2654 tls_client_resume_posthandshake(exim_gnutls_state_st * state,
2655 tls_support * tlsp, host_item * host)
2656 {
2657 if (gnutls_session_is_resumed(state->session))
2658 {
2659 DEBUG(D_tls) debug_printf("Session resumed\n");
2660 tlsp->resumption |= RESUME_USED;
2661 }
2662
2663 tls_save_session(tlsp, state->session, host);
2664 }
2665 #endif /* EXPERIMENTAL_TLS_RESUME */
2666
2667
2668 /*************************************************
2669 * Start a TLS session in a client *
2670 *************************************************/
2671
2672 /* Called from the smtp transport after STARTTLS has been accepted.
2673
2674 Arguments:
2675 cctx connection context
2676 conn_args connection details
2677 cookie datum for randomness (not used)
2678 tlsp record details of channel configuration here; must be non-NULL
2679 errstr error string pointer
2680
2681 Returns: TRUE for success with TLS session context set in smtp context,
2682 FALSE on error
2683 */
2684
2685 BOOL
2686 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
2687 void * cookie ARG_UNUSED,
2688 tls_support * tlsp, uschar ** errstr)
2689 {
2690 host_item * host = conn_args->host; /* for msgs and option-tests */
2691 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
2692 smtp_transport_options_block * ob = tb
2693 ? (smtp_transport_options_block *)tb->options_block
2694 : &smtp_transport_option_defaults;
2695 int rc;
2696 exim_gnutls_state_st * state = NULL;
2697 uschar * cipher_list = NULL;
2698
2699 #ifndef DISABLE_OCSP
2700 BOOL require_ocsp =
2701 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2702 BOOL request_ocsp = require_ocsp ? TRUE
2703 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2704 #endif
2705
2706 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", cctx->sock);
2707
2708 #ifdef SUPPORT_DANE
2709 /* If dane is flagged, have either request or require dane for this host, and
2710 a TLSA record found. Therefore, dane verify required. Which implies cert must
2711 be requested and supplied, dane verify must pass, and cert verify irrelevant
2712 (incl. hostnames), and (caller handled) require_tls */
2713
2714 if (conn_args->dane && ob->dane_require_tls_ciphers)
2715 {
2716 /* not using expand_check_tlsvar because not yet in state */
2717 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2718 &cipher_list, errstr))
2719 return FALSE;
2720 cipher_list = cipher_list && *cipher_list
2721 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2722 }
2723 #endif
2724
2725 if (!cipher_list)
2726 cipher_list = ob->tls_require_ciphers;
2727
2728 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2729 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2730 cipher_list, &state, tlsp, errstr) != OK)
2731 return FALSE;
2732
2733 {
2734 int dh_min_bits = ob->tls_dh_min_bits;
2735 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2736 {
2737 DEBUG(D_tls)
2738 debug_printf("WARNING: tls_dh_min_bits far too low,"
2739 " clamping %d up to %d\n",
2740 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2741 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2742 }
2743
2744 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2745 " acceptable bits to %d\n",
2746 dh_min_bits);
2747 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2748 }
2749
2750 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2751 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2752 the specified host patterns if one of them is defined */
2753
2754 #ifdef SUPPORT_DANE
2755 if (conn_args->dane && dane_tlsa_load(state, &conn_args->tlsa_dnsa))
2756 {
2757 DEBUG(D_tls)
2758 debug_printf("TLS: server certificate DANE required.\n");
2759 state->verify_requirement = VERIFY_DANE;
2760 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2761 }
2762 else
2763 #endif
2764 if ( ( state->exp_tls_verify_certificates
2765 && !ob->tls_verify_hosts
2766 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2767 )
2768 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2769 )
2770 {
2771 tls_client_setup_hostname_checks(host, state, ob);
2772 DEBUG(D_tls)
2773 debug_printf("TLS: server certificate verification required.\n");
2774 state->verify_requirement = VERIFY_REQUIRED;
2775 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2776 }
2777 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2778 {
2779 tls_client_setup_hostname_checks(host, state, ob);
2780 DEBUG(D_tls)
2781 debug_printf("TLS: server certificate verification optional.\n");
2782 state->verify_requirement = VERIFY_OPTIONAL;
2783 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2784 }
2785 else
2786 {
2787 DEBUG(D_tls)
2788 debug_printf("TLS: server certificate verification not required.\n");
2789 state->verify_requirement = VERIFY_NONE;
2790 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2791 }
2792
2793 #ifndef DISABLE_OCSP
2794 /* supported since GnuTLS 3.1.3 */
2795 if (request_ocsp)
2796 {
2797 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2798 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2799 NULL, 0, NULL)) != OK)
2800 {
2801 tls_error_gnu(US"cert-status-req", rc, state->host, errstr);
2802 return FALSE;
2803 }
2804 tlsp->ocsp = OCSP_NOT_RESP;
2805 }
2806 #endif
2807
2808 #ifdef EXPERIMENTAL_TLS_RESUME
2809 tls_client_resume_prehandshake(state, tlsp, host, ob);
2810 #endif
2811
2812 #ifndef DISABLE_EVENT
2813 if (tb && tb->event_action)
2814 {
2815 state->event_action = tb->event_action;
2816 gnutls_session_set_ptr(state->session, state);
2817 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2818 }
2819 #endif
2820
2821 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) cctx->sock);
2822 state->fd_in = cctx->sock;
2823 state->fd_out = cctx->sock;
2824
2825 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2826 /* There doesn't seem to be a built-in timeout on connection. */
2827
2828 sigalrm_seen = FALSE;
2829 ALARM(ob->command_timeout);
2830 do
2831 rc = gnutls_handshake(state->session);
2832 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2833 ALARM_CLR(0);
2834
2835 if (rc != GNUTLS_E_SUCCESS)
2836 {
2837 if (sigalrm_seen)
2838 {
2839 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2840 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2841 }
2842 else
2843 tls_error_gnu(US"gnutls_handshake", rc, state->host, errstr);
2844 return FALSE;
2845 }
2846
2847 DEBUG(D_tls) post_handshake_debug(state);
2848
2849 /* Verify late */
2850
2851 if (!verify_certificate(state, errstr))
2852 {
2853 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
2854 return FALSE;
2855 }
2856
2857 #ifndef DISABLE_OCSP
2858 if (request_ocsp)
2859 {
2860 DEBUG(D_tls)
2861 {
2862 gnutls_datum_t stapling;
2863 gnutls_ocsp_resp_t resp;
2864 gnutls_datum_t printed;
2865 if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0
2866 && (rc= gnutls_ocsp_resp_init(&resp)) == 0
2867 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
2868 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0
2869 )
2870 {
2871 debug_printf("%.4096s", printed.data);
2872 gnutls_free(printed.data);
2873 }
2874 else
2875 (void) tls_error_gnu(US"ocsp decode", rc, state->host, errstr);
2876 }
2877
2878 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
2879 {
2880 tlsp->ocsp = OCSP_FAILED;
2881 tls_error(US"certificate status check failed", NULL, state->host, errstr);
2882 if (require_ocsp)
2883 return FALSE;
2884 }
2885 else
2886 {
2887 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
2888 tlsp->ocsp = OCSP_VFIED;
2889 }
2890 }
2891 #endif
2892
2893 #ifdef EXPERIMENTAL_TLS_RESUME
2894 tls_client_resume_posthandshake(state, tlsp, host);
2895 #endif
2896
2897 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
2898
2899 extract_exim_vars_from_tls_state(state);
2900
2901 cctx->tls_ctx = state;
2902 return TRUE;
2903 }
2904
2905
2906
2907
2908 /*************************************************
2909 * Close down a TLS session *
2910 *************************************************/
2911
2912 /* This is also called from within a delivery subprocess forked from the
2913 daemon, to shut down the TLS library, without actually doing a shutdown (which
2914 would tamper with the TLS session in the parent process).
2915
2916 Arguments:
2917 ct_ctx client context pointer, or NULL for the one global server context
2918 shutdown 1 if TLS close-alert is to be sent,
2919 2 if also response to be waited for
2920
2921 Returns: nothing
2922 */
2923
2924 void
2925 tls_close(void * ct_ctx, int shutdown)
2926 {
2927 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
2928 tls_support * tlsp = state->tlsp;
2929
2930 if (!tlsp || tlsp->active.sock < 0) return; /* TLS was not active */
2931
2932 if (shutdown)
2933 {
2934 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
2935 shutdown > 1 ? " (with response-wait)" : "");
2936
2937 ALARM(2);
2938 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
2939 ALARM_CLR(0);
2940 }
2941
2942 if (!ct_ctx) /* server */
2943 {
2944 receive_getc = smtp_getc;
2945 receive_getbuf = smtp_getbuf;
2946 receive_get_cache = smtp_get_cache;
2947 receive_ungetc = smtp_ungetc;
2948 receive_feof = smtp_feof;
2949 receive_ferror = smtp_ferror;
2950 receive_smtp_buffered = smtp_buffered;
2951 }
2952
2953 gnutls_deinit(state->session);
2954 gnutls_certificate_free_credentials(state->x509_cred);
2955
2956 tlsp->active.sock = -1;
2957 tlsp->active.tls_ctx = NULL;
2958 /* Leave bits, peercert, cipher, peerdn, certificate_verified set, for logging */
2959 tls_channelbinding_b64 = NULL;
2960
2961
2962 if (state->xfer_buffer) store_free(state->xfer_buffer);
2963 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
2964 }
2965
2966
2967
2968
2969 static BOOL
2970 tls_refill(unsigned lim)
2971 {
2972 exim_gnutls_state_st * state = &state_server;
2973 ssize_t inbytes;
2974
2975 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
2976 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
2977
2978 sigalrm_seen = FALSE;
2979 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2980
2981 do
2982 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
2983 MIN(ssl_xfer_buffer_size, lim));
2984 while (inbytes == GNUTLS_E_AGAIN);
2985
2986 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2987
2988 if (had_command_timeout) /* set by signal handler */
2989 smtp_command_timeout_exit(); /* does not return */
2990 if (had_command_sigterm)
2991 smtp_command_sigterm_exit();
2992 if (had_data_timeout)
2993 smtp_data_timeout_exit();
2994 if (had_data_sigint)
2995 smtp_data_sigint_exit();
2996
2997 /* Timeouts do not get this far. A zero-byte return appears to mean that the
2998 TLS session has been closed down, not that the socket itself has been closed
2999 down. Revert to non-TLS handling. */
3000
3001 if (sigalrm_seen)
3002 {
3003 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
3004 state->xfer_error = TRUE;
3005 return FALSE;
3006 }
3007
3008 else if (inbytes == 0)
3009 {
3010 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
3011 tls_close(NULL, TLS_NO_SHUTDOWN);
3012 return FALSE;
3013 }
3014
3015 /* Handle genuine errors */
3016
3017 else if (inbytes < 0)
3018 {
3019 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
3020 record_io_error(state, (int) inbytes, US"recv", NULL);
3021 state->xfer_error = TRUE;
3022 return FALSE;
3023 }
3024 #ifndef DISABLE_DKIM
3025 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
3026 #endif
3027 state->xfer_buffer_hwm = (int) inbytes;
3028 state->xfer_buffer_lwm = 0;
3029 return TRUE;
3030 }
3031
3032 /*************************************************
3033 * TLS version of getc *
3034 *************************************************/
3035
3036 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
3037 it refills the buffer via the GnuTLS reading function.
3038 Only used by the server-side TLS.
3039
3040 This feeds DKIM and should be used for all message-body reads.
3041
3042 Arguments: lim Maximum amount to read/buffer
3043 Returns: the next character or EOF
3044 */
3045
3046 int
3047 tls_getc(unsigned lim)
3048 {
3049 exim_gnutls_state_st * state = &state_server;
3050
3051 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
3052 if (!tls_refill(lim))
3053 return state->xfer_error ? EOF : smtp_getc(lim);
3054
3055 /* Something in the buffer; return next uschar */
3056
3057 return state->xfer_buffer[state->xfer_buffer_lwm++];
3058 }
3059
3060 uschar *
3061 tls_getbuf(unsigned * len)
3062 {
3063 exim_gnutls_state_st * state = &state_server;
3064 unsigned size;
3065 uschar * buf;
3066
3067 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
3068 if (!tls_refill(*len))
3069 {
3070 if (!state->xfer_error) return smtp_getbuf(len);
3071 *len = 0;
3072 return NULL;
3073 }
3074
3075 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
3076 size = *len;
3077 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
3078 state->xfer_buffer_lwm += size;
3079 *len = size;
3080 return buf;
3081 }
3082
3083
3084 void
3085 tls_get_cache()
3086 {
3087 #ifndef DISABLE_DKIM
3088 exim_gnutls_state_st * state = &state_server;
3089 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
3090 if (n > 0)
3091 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
3092 #endif
3093 }
3094
3095
3096 BOOL
3097 tls_could_read(void)
3098 {
3099 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
3100 || gnutls_record_check_pending(state_server.session) > 0;
3101 }
3102
3103
3104
3105
3106 /*************************************************
3107 * Read bytes from TLS channel *
3108 *************************************************/
3109
3110 /* This does not feed DKIM, so if the caller uses this for reading message body,
3111 then the caller must feed DKIM.
3112
3113 Arguments:
3114 ct_ctx client context pointer, or NULL for the one global server context
3115 buff buffer of data
3116 len size of buffer
3117
3118 Returns: the number of bytes read
3119 -1 after a failed read, including EOF
3120 */
3121
3122 int
3123 tls_read(void * ct_ctx, uschar *buff, size_t len)
3124 {
3125 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
3126 ssize_t inbytes;
3127
3128 if (len > INT_MAX)
3129 len = INT_MAX;
3130
3131 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
3132 DEBUG(D_tls)
3133 debug_printf("*** PROBABLY A BUG *** " \
3134 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
3135 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
3136
3137 DEBUG(D_tls)
3138 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
3139 state->session, buff, len);
3140
3141 do
3142 inbytes = gnutls_record_recv(state->session, buff, len);
3143 while (inbytes == GNUTLS_E_AGAIN);
3144
3145 if (inbytes > 0) return inbytes;
3146 if (inbytes == 0)
3147 {
3148 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
3149 }
3150 else
3151 {
3152 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
3153 record_io_error(state, (int)inbytes, US"recv", NULL);
3154 }
3155
3156 return -1;
3157 }
3158
3159
3160
3161
3162 /*************************************************
3163 * Write bytes down TLS channel *
3164 *************************************************/
3165
3166 /*
3167 Arguments:
3168 ct_ctx client context pointer, or NULL for the one global server context
3169 buff buffer of data
3170 len number of bytes
3171 more more data expected soon
3172
3173 Returns: the number of bytes after a successful write,
3174 -1 after a failed write
3175 */
3176
3177 int
3178 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
3179 {
3180 ssize_t outbytes;
3181 size_t left = len;
3182 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
3183 #ifdef SUPPORT_CORK
3184 static BOOL corked = FALSE;
3185
3186 if (more && !corked) gnutls_record_cork(state->session);
3187 #endif
3188
3189 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
3190 buff, left, more ? ", more" : "");
3191
3192 while (left > 0)
3193 {
3194 DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n",
3195 buff, left);
3196
3197 do
3198 outbytes = gnutls_record_send(state->session, buff, left);
3199 while (outbytes == GNUTLS_E_AGAIN);
3200
3201 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
3202 if (outbytes < 0)
3203 {
3204 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
3205 record_io_error(state, outbytes, US"send", NULL);
3206 return -1;
3207 }
3208 if (outbytes == 0)
3209 {
3210 record_io_error(state, 0, US"send", US"TLS channel closed on write");
3211 return -1;
3212 }
3213
3214 left -= outbytes;
3215 buff += outbytes;
3216 }
3217
3218 if (len > INT_MAX)
3219 {
3220 DEBUG(D_tls)
3221 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
3222 len);
3223 len = INT_MAX;
3224 }
3225
3226 #ifdef SUPPORT_CORK
3227 if (more != corked)
3228 {
3229 if (!more) (void) gnutls_record_uncork(state->session, 0);
3230 corked = more;
3231 }
3232 #endif
3233
3234 return (int) len;
3235 }
3236
3237
3238
3239
3240 /*************************************************
3241 * Random number generation *
3242 *************************************************/
3243
3244 /* Pseudo-random number generation. The result is not expected to be
3245 cryptographically strong but not so weak that someone will shoot themselves
3246 in the foot using it as a nonce in input in some email header scheme or
3247 whatever weirdness they'll twist this into. The result should handle fork()
3248 and avoid repeating sequences. OpenSSL handles that for us.
3249
3250 Arguments:
3251 max range maximum
3252 Returns a random number in range [0, max-1]
3253 */
3254
3255 #ifdef HAVE_GNUTLS_RND
3256 int
3257 vaguely_random_number(int max)
3258 {
3259 unsigned int r;
3260 int i, needed_len;
3261 uschar smallbuf[sizeof(r)];
3262
3263 if (max <= 1)
3264 return 0;
3265
3266 needed_len = sizeof(r);
3267 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3268 asked for a number less than 10. */
3269
3270 for (r = max, i = 0; r; ++i)
3271 r >>= 1;
3272 i = (i + 7) / 8;
3273 if (i < needed_len)
3274 needed_len = i;
3275
3276 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
3277 if (i < 0)
3278 {
3279 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
3280 return vaguely_random_number_fallback(max);
3281 }
3282 r = 0;
3283 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3284 r = r * 256 + *p;
3285
3286 /* We don't particularly care about weighted results; if someone wants
3287 * smooth distribution and cares enough then they should submit a patch then. */
3288 return r % max;
3289 }
3290 #else /* HAVE_GNUTLS_RND */
3291 int
3292 vaguely_random_number(int max)
3293 {
3294 return vaguely_random_number_fallback(max);
3295 }
3296 #endif /* HAVE_GNUTLS_RND */
3297
3298
3299
3300
3301 /*************************************************
3302 * Let tls_require_ciphers be checked at startup *
3303 *************************************************/
3304
3305 /* The tls_require_ciphers option, if set, must be something which the
3306 library can parse.
3307
3308 Returns: NULL on success, or error message
3309 */
3310
3311 uschar *
3312 tls_validate_require_cipher(void)
3313 {
3314 int rc;
3315 uschar *expciphers = NULL;
3316 gnutls_priority_t priority_cache;
3317 const char *errpos;
3318 uschar * dummy_errstr;
3319
3320 #define validate_check_rc(Label) do { \
3321 if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \
3322 return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0)
3323 #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0)
3324
3325 if (exim_gnutls_base_init_done)
3326 log_write(0, LOG_MAIN|LOG_PANIC,
3327 "already initialised GnuTLS, Exim developer bug");
3328
3329 #ifdef HAVE_GNUTLS_PKCS11
3330 if (!gnutls_allow_auto_pkcs11)
3331 {
3332 rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL);
3333 validate_check_rc(US"gnutls_pkcs11_init");
3334 }
3335 #endif
3336 rc = gnutls_global_init();
3337 validate_check_rc(US"gnutls_global_init()");
3338 exim_gnutls_base_init_done = TRUE;
3339
3340 if (!(tls_require_ciphers && *tls_require_ciphers))
3341 return_deinit(NULL);
3342
3343 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3344 &dummy_errstr))
3345 return_deinit(US"failed to expand tls_require_ciphers");
3346
3347 if (!(expciphers && *expciphers))
3348 return_deinit(NULL);
3349
3350 DEBUG(D_tls)
3351 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3352
3353 rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos);
3354 validate_check_rc(string_sprintf(
3355 "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"",
3356 expciphers, errpos - CS expciphers, errpos));
3357
3358 #undef return_deinit
3359 #undef validate_check_rc
3360 gnutls_global_deinit();
3361
3362 return NULL;
3363 }
3364
3365
3366
3367
3368 /*************************************************
3369 * Report the library versions. *
3370 *************************************************/
3371
3372 /* See a description in tls-openssl.c for an explanation of why this exists.
3373
3374 Arguments: a FILE* to print the results to
3375 Returns: nothing
3376 */
3377
3378 void
3379 tls_version_report(FILE *f)
3380 {
3381 fprintf(f, "Library version: GnuTLS: Compile: %s\n"
3382 " Runtime: %s\n",
3383 LIBGNUTLS_VERSION,
3384 gnutls_check_version(NULL));
3385 }
3386
3387 #endif /*!MACRO_PREDEF*/
3388 /* vi: aw ai sw=2
3389 */
3390 /* End of tls-gnu.c */