GnuTLS: Clarify the use of SSLKEYFILE
[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 >= 0x030300
74 # define GNUTLS_AUTO_GLOBAL_INIT
75 # define GNUTLS_AUTO_PKCS11_MANUAL
76 #endif
77 #if (GNUTLS_VERSION_NUMBER >= 0x030404) \
78 || (GNUTLS_VERSION_NUMBER >= 0x030311) && (GNUTLS_VERSION_NUMBER & 0xffff00 == 0x030300)
79 # ifndef DISABLE_OCSP
80 # define EXIM_HAVE_OCSP
81 # endif
82 #endif
83 #if GNUTLS_VERSION_NUMBER >= 0x030500
84 # define SUPPORT_GNUTLS_KEYLOG
85 #endif
86 #if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP)
87 # define SUPPORT_SRV_OCSP_STACK
88 #endif
89 #if GNUTLS_VERSION_NUMBER >= 0x030600
90 # define GNUTLS_AUTO_DHPARAMS
91 #endif
92 #if GNUTLS_VERSION_NUMBER >= 0x030603
93 # define EXIM_HAVE_TLS1_3
94 # define SUPPORT_GNUTLS_EXT_RAW_PARSE
95 # define GNUTLS_OCSP_STATUS_REQUEST_GET2
96 #endif
97
98 #ifdef SUPPORT_DANE
99 # if GNUTLS_VERSION_NUMBER >= 0x030000
100 # define DANESSL_USAGE_DANE_TA 2
101 # define DANESSL_USAGE_DANE_EE 3
102 # else
103 # error GnuTLS version too early for DANE
104 # endif
105 # if GNUTLS_VERSION_NUMBER < 0x999999
106 # define GNUTLS_BROKEN_DANE_VALIDATION
107 # endif
108 #endif
109
110 #ifdef EXPERIMENTAL_TLS_RESUME
111 # if GNUTLS_VERSION_NUMBER < 0x030603
112 # error GNUTLS version too early for session-resumption
113 # endif
114 #endif
115
116 #ifndef DISABLE_OCSP
117 # include <gnutls/ocsp.h>
118 #endif
119 #ifdef SUPPORT_DANE
120 # include <gnutls/dane.h>
121 #endif
122
123 #include "tls-cipher-stdname.c"
124
125
126 #ifdef MACRO_PREDEF
127 void
128 options_tls(void)
129 {
130 # ifdef EXPERIMENTAL_TLS_RESUME
131 builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING );
132 # endif
133 # ifdef EXIM_HAVE_TLS1_3
134 builtin_macro_create(US"_HAVE_TLS1_3");
135 # endif
136 # ifdef EXIM_HAVE_OCSP
137 builtin_macro_create(US"_HAVE_TLS_OCSP");
138 # endif
139 # ifdef SUPPORT_SRV_OCSP_STACK
140 builtin_macro_create(US"_HAVE_TLS_OCSP_LIST");
141 # endif
142 }
143 #else
144
145
146 /* GnuTLS 2 vs 3
147
148 GnuTLS 3 only:
149 gnutls_global_set_audit_log_function()
150
151 Changes:
152 gnutls_certificate_verify_peers2(): is new, drop the 2 for old version
153 */
154
155 /* Local static variables for GnuTLS */
156
157 /* Values for verify_requirement */
158
159 enum peer_verify_requirement
160 { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE };
161
162 /* This holds most state for server or client; with this, we can set up an
163 outbound TLS-enabled connection in an ACL callout, while not stomping all
164 over the TLS variables available for expansion.
165
166 Some of these correspond to variables in globals.c; those variables will
167 be set to point to content in one of these instances, as appropriate for
168 the stage of the process lifetime.
169
170 Not handled here: global tlsp->tls_channelbinding.
171 */
172
173 typedef struct exim_gnutls_state {
174 gnutls_session_t session;
175 gnutls_certificate_credentials_t x509_cred;
176 gnutls_priority_t priority_cache;
177 enum peer_verify_requirement verify_requirement;
178 int fd_in;
179 int fd_out;
180
181 BOOL peer_cert_verified:1;
182 BOOL peer_dane_verified:1;
183 BOOL trigger_sni_changes:1;
184 BOOL have_set_peerdn:1;
185 BOOL xfer_eof:1; /*XXX never gets set! */
186 BOOL xfer_error:1;
187 #ifdef SUPPORT_CORK
188 BOOL corked:1;
189 #endif
190
191 const struct host_item *host; /* NULL if server */
192 gnutls_x509_crt_t peercert;
193 uschar *peerdn;
194 uschar *ciphersuite;
195 uschar *received_sni;
196
197 const uschar *tls_certificate;
198 const uschar *tls_privatekey;
199 const uschar *tls_sni; /* client send only, not received */
200 const uschar *tls_verify_certificates;
201 const uschar *tls_crl;
202 const uschar *tls_require_ciphers;
203
204 uschar *exp_tls_certificate;
205 uschar *exp_tls_privatekey;
206 uschar *exp_tls_verify_certificates;
207 uschar *exp_tls_crl;
208 uschar *exp_tls_require_ciphers;
209 const uschar *exp_tls_verify_cert_hostnames;
210 #ifndef DISABLE_EVENT
211 uschar *event_action;
212 #endif
213 #ifdef SUPPORT_DANE
214 char * const * dane_data;
215 const int * dane_data_len;
216 #endif
217
218 tls_support *tlsp; /* set in tls_init() */
219
220 uschar *xfer_buffer;
221 int xfer_buffer_lwm;
222 int xfer_buffer_hwm;
223 } exim_gnutls_state_st;
224
225 static const exim_gnutls_state_st exim_gnutls_state_init = {
226 /* all elements not explicitly intialised here get 0/NULL/FALSE */
227 .fd_in = -1,
228 .fd_out = -1,
229 };
230
231 /* Not only do we have our own APIs which don't pass around state, assuming
232 it's held in globals, GnuTLS doesn't appear to let us register callback data
233 for callbacks, or as part of the session, so we have to keep a "this is the
234 context we're currently dealing with" pointer and rely upon being
235 single-threaded to keep from processing data on an inbound TLS connection while
236 talking to another TLS connection for an outbound check. This does mean that
237 there's no way for heart-beats to be responded to, for the duration of the
238 second connection.
239 XXX But see gnutls_session_get_ptr()
240 */
241
242 static exim_gnutls_state_st state_server;
243
244 #ifndef GNUTLS_AUTO_DHPARAMS
245 /* dh_params are initialised once within the lifetime of a process using TLS;
246 if we used TLS in a long-lived daemon, we'd have to reconsider this. But we
247 don't want to repeat this. */
248
249 static gnutls_dh_params_t dh_server_params = NULL;
250 #endif
251
252 static int ssl_session_timeout = 7200; /* Two hours */
253
254 static const uschar * const exim_default_gnutls_priority = US"NORMAL";
255
256 /* Guard library core initialisation */
257
258 static BOOL exim_gnutls_base_init_done = FALSE;
259
260 #ifndef DISABLE_OCSP
261 static BOOL gnutls_buggy_ocsp = FALSE;
262 static BOOL exim_testharness_disable_ocsp_validity_check = FALSE;
263 #endif
264
265 #ifdef EXPERIMENTAL_TLS_RESUME
266 static gnutls_datum_t server_sessticket_key;
267 #endif
268
269 /* ------------------------------------------------------------------------ */
270 /* macros */
271
272 #define MAX_HOST_LEN 255
273
274 /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup
275 the library logging; a value less than 0 disables the calls to set up logging
276 callbacks. GNuTLS also looks for an environment variable - except not for
277 setuid binaries, making it useless - "GNUTLS_DEBUG_LEVEL".
278 Allegedly the testscript line "GNUTLS_DEBUG_LEVEL=9 sudo exim ..." would work,
279 but the env var must be added to /etc/sudoers too. */
280 #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL
281 # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1
282 #endif
283
284 #ifndef EXIM_CLIENT_DH_MIN_BITS
285 # define EXIM_CLIENT_DH_MIN_BITS 1024
286 #endif
287
288 /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we
289 can ask for a bit-strength. Without that, we stick to the constant we had
290 before, for now. */
291 #ifndef EXIM_SERVER_DH_BITS_PRE2_12
292 # define EXIM_SERVER_DH_BITS_PRE2_12 1024
293 #endif
294
295 #define expand_check_tlsvar(Varname, errstr) \
296 expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr)
297
298 #if GNUTLS_VERSION_NUMBER >= 0x020c00
299 # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING
300 # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS
301 # define HAVE_GNUTLS_RND
302 /* The security fix we provide with the gnutls_allow_auto_pkcs11 option
303 * (4.82 PP/09) introduces a compatibility regression. The symbol simply
304 * isn't available sometimes, so this needs to become a conditional
305 * compilation; the sanest way to deal with this being a problem on
306 * older OSes is to block it in the Local/Makefile with this compiler
307 * definition */
308 # ifndef AVOID_GNUTLS_PKCS11
309 # define HAVE_GNUTLS_PKCS11
310 # endif /* AVOID_GNUTLS_PKCS11 */
311 #endif
312
313
314
315
316 /* ------------------------------------------------------------------------ */
317 /* Callback declarations */
318
319 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
320 static void exim_gnutls_logger_cb(int level, const char *message);
321 #endif
322
323 static int exim_sni_handling_cb(gnutls_session_t session);
324
325 #ifdef EXPERIMENTAL_TLS_RESUME
326 static int
327 tls_server_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
328 unsigned incoming, const gnutls_datum_t * msg);
329 #endif
330
331
332 /* Daemon one-time initialisation */
333 void
334 tls_daemon_init(void)
335 {
336 #ifdef EXPERIMENTAL_TLS_RESUME
337 /* We are dependent on the GnuTLS implementation of the Session Ticket
338 encryption; both the strength and the key rotation period. We hope that
339 the strength at least matches that of the ciphersuite (but GnuTLS does not
340 document this). */
341
342 static BOOL once = FALSE;
343 if (once) return;
344 once = TRUE;
345 gnutls_session_ticket_key_generate(&server_sessticket_key); /* >= 2.10.0 */
346 if (f.running_in_test_harness) ssl_session_timeout = 6;
347 #endif
348 }
349
350 /* ------------------------------------------------------------------------ */
351 /* Static functions */
352
353 /*************************************************
354 * Handle TLS error *
355 *************************************************/
356
357 /* Called from lots of places when errors occur before actually starting to do
358 the TLS handshake, that is, while the session is still in clear. Always returns
359 DEFER for a server and FAIL for a client so that most calls can use "return
360 tls_error(...)" to do this processing and then give an appropriate return. A
361 single function is used for both server and client, because it is called from
362 some shared functions.
363
364 Argument:
365 prefix text to include in the logged error
366 msg additional error string (may be NULL)
367 usually obtained from gnutls_strerror()
368 host NULL if setting up a server;
369 the connected host if setting up a client
370 errstr pointer to returned error string
371
372 Returns: OK/DEFER/FAIL
373 */
374
375 static int
376 tls_error(const uschar *prefix, const uschar *msg, const host_item *host,
377 uschar ** errstr)
378 {
379 if (errstr)
380 *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US"");
381 return host ? FAIL : DEFER;
382 }
383
384
385 static int
386 tls_error_gnu(const uschar *prefix, int err, const host_item *host,
387 uschar ** errstr)
388 {
389 return tls_error(prefix, US gnutls_strerror(err), host, errstr);
390 }
391
392 static int
393 tls_error_sys(const uschar *prefix, int err, const host_item *host,
394 uschar ** errstr)
395 {
396 return tls_error(prefix, US strerror(err), host, errstr);
397 }
398
399
400 /*************************************************
401 * Deal with logging errors during I/O *
402 *************************************************/
403
404 /* We have to get the identity of the peer from saved data.
405
406 Argument:
407 state the current GnuTLS exim state container
408 rc the GnuTLS error code, or 0 if it's a local error
409 when text identifying read or write
410 text local error text when rc is 0
411
412 Returns: nothing
413 */
414
415 static void
416 record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text)
417 {
418 const uschar * msg;
419 uschar * errstr;
420
421 if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED)
422 msg = string_sprintf("A TLS fatal alert has been received: %s",
423 US gnutls_alert_get_name(gnutls_alert_get(state->session)));
424 else
425 msg = US gnutls_strerror(rc);
426
427 (void) tls_error(when, msg, state->host, &errstr);
428
429 if (state->host)
430 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s",
431 state->host->name, state->host->address, errstr);
432 else
433 {
434 uschar * conn_info = smtp_get_connection_info();
435 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5;
436 /* I'd like to get separated H= here, but too hard for now */
437 log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr);
438 }
439 }
440
441
442
443
444 /*************************************************
445 * Set various Exim expansion vars *
446 *************************************************/
447
448 #define exim_gnutls_cert_err(Label) \
449 do \
450 { \
451 if (rc != GNUTLS_E_SUCCESS) \
452 { \
453 DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \
454 (Label), gnutls_strerror(rc)); \
455 return rc; \
456 } \
457 } while (0)
458
459 static int
460 import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp)
461 {
462 int rc;
463
464 rc = gnutls_x509_crt_init(crtp);
465 exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)");
466
467 rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER);
468 exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]");
469
470 return rc;
471 }
472
473 #undef exim_gnutls_cert_err
474
475
476 /* We set various Exim global variables from the state, once a session has
477 been established. With TLS callouts, may need to change this to stack
478 variables, or just re-call it with the server state after client callout
479 has finished.
480
481 Make sure anything set here is unset in tls_getc().
482
483 Sets:
484 tls_active fd
485 tls_bits strength indicator
486 tls_certificate_verified bool indicator
487 tls_channelbinding for some SASL mechanisms
488 tls_ver a string
489 tls_cipher a string
490 tls_peercert pointer to library internal
491 tls_peerdn a string
492 tls_sni a (UTF-8) string
493 tls_ourcert pointer to library internal
494
495 Argument:
496 state the relevant exim_gnutls_state_st *
497 */
498
499 static void
500 extract_exim_vars_from_tls_state(exim_gnutls_state_st * state)
501 {
502 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
503 int old_pool;
504 int rc;
505 gnutls_datum_t channel;
506 #endif
507 tls_support * tlsp = state->tlsp;
508
509 tlsp->active.sock = state->fd_out;
510 tlsp->active.tls_ctx = state;
511
512 DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite);
513
514 tlsp->certificate_verified = state->peer_cert_verified;
515 #ifdef SUPPORT_DANE
516 tlsp->dane_verified = state->peer_dane_verified;
517 #endif
518
519 /* note that tls_channelbinding is not saved to the spool file, since it's
520 only available for use for authenticators while this TLS session is running. */
521
522 tlsp->channelbinding = NULL;
523 #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING
524 channel.data = NULL;
525 channel.size = 0;
526 if ((rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel)))
527 { DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); }
528 else
529 {
530 /* Declare the taintedness of the binding info. On server, untainted; on
531 client, tainted - being the Finish msg from the server. */
532
533 old_pool = store_pool;
534 store_pool = POOL_PERM;
535 tlsp->channelbinding = b64encode_taint(CUS channel.data, (int)channel.size,
536 !!state->host);
537 store_pool = old_pool;
538 DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage\n");
539 }
540 #endif
541
542 /* peercert is set in peer_status() */
543 tlsp->peerdn = state->peerdn;
544 tlsp->sni = state->received_sni;
545
546 /* record our certificate */
547 {
548 const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session);
549 gnutls_x509_crt_t crt;
550
551 tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL;
552 }
553 }
554
555
556
557
558 #ifndef GNUTLS_AUTO_DHPARAMS
559 /*************************************************
560 * Setup up DH parameters *
561 *************************************************/
562
563 /* Generating the D-H parameters may take a long time. They only need to
564 be re-generated every so often, depending on security policy. What we do is to
565 keep these parameters in a file in the spool directory. If the file does not
566 exist, we generate them. This means that it is easy to cause a regeneration.
567
568 The new file is written as a temporary file and renamed, so that an incomplete
569 file is never present. If two processes both compute some new parameters, you
570 waste a bit of effort, but it doesn't seem worth messing around with locking to
571 prevent this.
572
573 Returns: OK/DEFER/FAIL
574 */
575
576 static int
577 init_server_dh(uschar ** errstr)
578 {
579 int fd, rc;
580 unsigned int dh_bits;
581 gnutls_datum_t m = {.data = NULL, .size = 0};
582 uschar filename_buf[PATH_MAX];
583 uschar *filename = NULL;
584 size_t sz;
585 uschar *exp_tls_dhparam;
586 BOOL use_file_in_spool = FALSE;
587 host_item *host = NULL; /* dummy for macros */
588
589 DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n");
590
591 if ((rc = gnutls_dh_params_init(&dh_server_params)))
592 return tls_error_gnu(US"gnutls_dh_params_init", rc, host, errstr);
593
594 if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr))
595 return DEFER;
596
597 if (!exp_tls_dhparam)
598 {
599 DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n");
600 m.data = US std_dh_prime_default();
601 m.size = Ustrlen(m.data);
602 }
603 else if (Ustrcmp(exp_tls_dhparam, "historic") == 0)
604 use_file_in_spool = TRUE;
605 else if (Ustrcmp(exp_tls_dhparam, "none") == 0)
606 {
607 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
608 return OK;
609 }
610 else if (exp_tls_dhparam[0] != '/')
611 {
612 if (!(m.data = US std_dh_prime_named(exp_tls_dhparam)))
613 return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr);
614 m.size = Ustrlen(m.data);
615 }
616 else
617 filename = exp_tls_dhparam;
618
619 if (m.data)
620 {
621 if ((rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM)))
622 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
623 DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n");
624 return OK;
625 }
626
627 #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS
628 /* If you change this constant, also change dh_param_fn_ext so that we can use a
629 different filename and ensure we have sufficient bits. */
630
631 if (!(dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL)))
632 return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr);
633 DEBUG(D_tls)
634 debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n",
635 dh_bits);
636 #else
637 dh_bits = EXIM_SERVER_DH_BITS_PRE2_12;
638 DEBUG(D_tls)
639 debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n",
640 dh_bits);
641 #endif
642
643 /* Some clients have hard-coded limits. */
644 if (dh_bits > tls_dh_max_bits)
645 {
646 DEBUG(D_tls)
647 debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n",
648 tls_dh_max_bits);
649 dh_bits = tls_dh_max_bits;
650 }
651
652 if (use_file_in_spool)
653 {
654 if (!string_format(filename_buf, sizeof(filename_buf),
655 "%s/gnutls-params-%d", spool_directory, dh_bits))
656 return tls_error(US"overlong filename", NULL, NULL, errstr);
657 filename = filename_buf;
658 }
659
660 /* Open the cache file for reading and if successful, read it and set up the
661 parameters. */
662
663 if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0)
664 {
665 struct stat statbuf;
666 FILE *fp;
667 int saved_errno;
668
669 if (fstat(fd, &statbuf) < 0) /* EIO */
670 {
671 saved_errno = errno;
672 (void)close(fd);
673 return tls_error_sys(US"TLS cache stat failed", saved_errno, NULL, errstr);
674 }
675 if (!S_ISREG(statbuf.st_mode))
676 {
677 (void)close(fd);
678 return tls_error(US"TLS cache not a file", NULL, NULL, errstr);
679 }
680 if (!(fp = fdopen(fd, "rb")))
681 {
682 saved_errno = errno;
683 (void)close(fd);
684 return tls_error_sys(US"fdopen(TLS cache stat fd) failed",
685 saved_errno, NULL, errstr);
686 }
687
688 m.size = statbuf.st_size;
689 if (!(m.data = store_malloc(m.size)))
690 {
691 fclose(fp);
692 return tls_error_sys(US"malloc failed", errno, NULL, errstr);
693 }
694 if (!(sz = fread(m.data, m.size, 1, fp)))
695 {
696 saved_errno = errno;
697 fclose(fp);
698 store_free(m.data);
699 return tls_error_sys(US"fread failed", saved_errno, NULL, errstr);
700 }
701 fclose(fp);
702
703 rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM);
704 store_free(m.data);
705 if (rc)
706 return tls_error_gnu(US"gnutls_dh_params_import_pkcs3", rc, host, errstr);
707 DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename);
708 }
709
710 /* If the file does not exist, fall through to compute new data and cache it.
711 If there was any other opening error, it is serious. */
712
713 else if (errno == ENOENT)
714 {
715 rc = -1;
716 DEBUG(D_tls)
717 debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename);
718 }
719 else
720 return tls_error(string_open_failed(errno, "\"%s\" for reading", filename),
721 NULL, NULL, errstr);
722
723 /* If ret < 0, either the cache file does not exist, or the data it contains
724 is not useful. One particular case of this is when upgrading from an older
725 release of Exim in which the data was stored in a different format. We don't
726 try to be clever and support both formats; we just regenerate new data in this
727 case. */
728
729 if (rc < 0)
730 {
731 uschar *temp_fn;
732 unsigned int dh_bits_gen = dh_bits;
733
734 if ((PATH_MAX - Ustrlen(filename)) < 10)
735 return tls_error(US"Filename too long to generate replacement",
736 filename, NULL, errstr);
737
738 temp_fn = string_copy(US"%s.XXXXXXX");
739 if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */
740 return tls_error_sys(US"Unable to open temp file", errno, NULL, errstr);
741 (void)exim_chown(temp_fn, exim_uid, exim_gid); /* Probably not necessary */
742
743 /* GnuTLS overshoots! If we ask for 2236, we might get 2237 or more. But
744 there's no way to ask GnuTLS how many bits there really are. We can ask
745 how many bits were used in a TLS session, but that's it! The prime itself
746 is hidden behind too much abstraction. So we ask for less, and proceed on
747 a wing and a prayer. First attempt, subtracted 3 for 2233 and got 2240. */
748
749 if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10)
750 {
751 dh_bits_gen = dh_bits - 10;
752 DEBUG(D_tls)
753 debug_printf("being paranoid about DH generation, make it '%d' bits'\n",
754 dh_bits_gen);
755 }
756
757 DEBUG(D_tls)
758 debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n",
759 dh_bits_gen);
760 if ((rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen)))
761 return tls_error_gnu(US"gnutls_dh_params_generate2", rc, host, errstr);
762
763 /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time,
764 and I confirmed that a NULL call to get the size first is how the GnuTLS
765 sample apps handle this. */
766
767 sz = 0;
768 m.data = NULL;
769 if ( (rc = gnutls_dh_params_export_pkcs3(dh_server_params,
770 GNUTLS_X509_FMT_PEM, m.data, &sz))
771 && rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
772 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3(NULL) sizing",
773 rc, host, errstr);
774 m.size = sz;
775 if (!(m.data = store_malloc(m.size)))
776 return tls_error_sys(US"memory allocation failed", errno, NULL, errstr);
777
778 /* this will return a size 1 less than the allocation size above */
779 if ((rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM,
780 m.data, &sz)))
781 {
782 store_free(m.data);
783 return tls_error_gnu(US"gnutls_dh_params_export_pkcs3() real", rc, host, errstr);
784 }
785 m.size = sz; /* shrink by 1, probably */
786
787 if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size)
788 {
789 store_free(m.data);
790 return tls_error_sys(US"TLS cache write D-H params failed",
791 errno, NULL, errstr);
792 }
793 store_free(m.data);
794 if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1)
795 return tls_error_sys(US"TLS cache write D-H params final newline failed",
796 errno, NULL, errstr);
797
798 if ((rc = close(fd)))
799 return tls_error_sys(US"TLS cache write close() failed", errno, NULL, errstr);
800
801 if (Urename(temp_fn, filename) < 0)
802 return tls_error_sys(string_sprintf("failed to rename \"%s\" as \"%s\"",
803 temp_fn, filename), errno, NULL, errstr);
804
805 DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename);
806 }
807
808 DEBUG(D_tls) debug_printf("initialized server D-H parameters\n");
809 return OK;
810 }
811 #endif
812
813
814
815
816 /* Create and install a selfsigned certificate, for use in server mode */
817
818 static int
819 tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr)
820 {
821 gnutls_x509_crt_t cert = NULL;
822 time_t now;
823 gnutls_x509_privkey_t pkey = NULL;
824 const uschar * where;
825 int rc;
826
827 where = US"initialising pkey";
828 if ((rc = gnutls_x509_privkey_init(&pkey))) goto err;
829
830 where = US"initialising cert";
831 if ((rc = gnutls_x509_crt_init(&cert))) goto err;
832
833 where = US"generating pkey";
834 if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA,
835 #ifdef SUPPORT_PARAM_TO_PK_BITS
836 # ifndef GNUTLS_SEC_PARAM_MEDIUM
837 # define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH
838 # endif
839 gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM),
840 #else
841 2048,
842 #endif
843 0)))
844 goto err;
845
846 where = US"configuring cert";
847 now = 1;
848 if ( (rc = gnutls_x509_crt_set_version(cert, 3))
849 || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now)))
850 || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL)))
851 || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */
852 || (rc = gnutls_x509_crt_set_key(cert, pkey))
853
854 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
855 GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2))
856 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
857 GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15))
858 || (rc = gnutls_x509_crt_set_dn_by_oid(cert,
859 GNUTLS_OID_X520_COMMON_NAME, 0,
860 smtp_active_hostname, Ustrlen(smtp_active_hostname)))
861 )
862 goto err;
863
864 where = US"signing cert";
865 if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err;
866
867 where = US"installing selfsign cert";
868 /* Since: 2.4.0 */
869 if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey)))
870 goto err;
871
872 rc = OK;
873
874 out:
875 if (cert) gnutls_x509_crt_deinit(cert);
876 if (pkey) gnutls_x509_privkey_deinit(pkey);
877 return rc;
878
879 err:
880 rc = tls_error_gnu(where, rc, NULL, errstr);
881 goto out;
882 }
883
884
885
886
887 /* Add certificate and key, from files.
888
889 Return:
890 Zero or negative: good. Negate value for certificate index if < 0.
891 Greater than zero: FAIL or DEFER code.
892 */
893
894 static int
895 tls_add_certfile(exim_gnutls_state_st * state, const host_item * host,
896 uschar * certfile, uschar * keyfile, uschar ** errstr)
897 {
898 int rc = gnutls_certificate_set_x509_key_file(state->x509_cred,
899 CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM);
900 if (rc < 0)
901 return tls_error_gnu(
902 string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile),
903 rc, host, errstr);
904 return -rc;
905 }
906
907
908 #if !defined(DISABLE_OCSP) && !defined(SUPPORT_GNUTLS_EXT_RAW_PARSE)
909 /* Load an OCSP proof from file for sending by the server. Called
910 on getting a status-request handshake message, for earlier versions
911 of GnuTLS. */
912
913 static int
914 server_ocsp_stapling_cb(gnutls_session_t session, void * ptr,
915 gnutls_datum_t * ocsp_response)
916 {
917 int ret;
918 DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr);
919
920 if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0)
921 {
922 DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n",
923 CS ptr);
924 tls_in.ocsp = OCSP_NOT_RESP;
925 return GNUTLS_E_NO_CERTIFICATE_STATUS;
926 }
927
928 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
929 return 0;
930 }
931 #endif
932
933
934 #ifdef SUPPORT_GNUTLS_EXT_RAW_PARSE
935 /* Make a note that we saw a status-request */
936 static int
937 tls_server_clienthello_ext(void * ctx, unsigned tls_id,
938 const unsigned char *data, unsigned size)
939 {
940 /* https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml */
941 if (tls_id == 5) /* status_request */
942 {
943 DEBUG(D_tls) debug_printf("Seen status_request extension from client\n");
944 tls_in.ocsp = OCSP_NOT_RESP;
945 }
946 return 0;
947 }
948
949 /* Callback for client-hello, on server, if we think we might serve stapled-OCSP */
950 static int
951 tls_server_clienthello_cb(gnutls_session_t session, unsigned int htype,
952 unsigned when, unsigned int incoming, const gnutls_datum_t * msg)
953 {
954 /* Call fn for each extension seen. 3.6.3 onwards */
955 return gnutls_ext_raw_parse(NULL, tls_server_clienthello_ext, msg,
956 GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO);
957 }
958
959
960 /* Make a note that we saw a status-response */
961 static int
962 tls_server_servercerts_ext(void * ctx, unsigned tls_id,
963 const unsigned char *data, unsigned size)
964 {
965 /* debug_printf("%s %u\n", __FUNCTION__, tls_id); */
966 /* https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml */
967 if (FALSE && tls_id == 5) /* status_request */
968 {
969 DEBUG(D_tls) debug_printf("Seen status_request extension\n");
970 tls_in.ocsp = exim_testharness_disable_ocsp_validity_check
971 ? OCSP_VFY_NOT_TRIED : OCSP_VFIED; /* We know that GnuTLS verifies responses */
972 }
973 return 0;
974 }
975
976 /* Callback for certificates packet, on server, if we think we might serve stapled-OCSP */
977 static int
978 tls_server_servercerts_cb(gnutls_session_t session, unsigned int htype,
979 unsigned when, unsigned int incoming, const gnutls_datum_t * msg)
980 {
981 /* Call fn for each extension seen. 3.6.3 onwards */
982 #ifdef notdef
983 /*XXX crashes */
984 return gnutls_ext_raw_parse(NULL, tls_server_servercerts_ext, msg, 0);
985 #endif
986 }
987 #endif
988
989 /*XXX in tls1.3 the cert-status travel as an extension next to the cert, in the
990 "Handshake Protocol: Certificate" record.
991 So we need to spot the Certificate handshake message, parse it and spot any status_request extension(s)
992
993 This is different to tls1.2 - where it is a separate record (wireshake term) / handshake message (gnutls term).
994 */
995
996 #if defined(EXPERIMENTAL_TLS_RESUME) || defined(SUPPORT_GNUTLS_EXT_RAW_PARSE)
997 /* Callback for certificate-status, on server. We sent stapled OCSP. */
998 static int
999 tls_server_certstatus_cb(gnutls_session_t session, unsigned int htype,
1000 unsigned when, unsigned int incoming, const gnutls_datum_t * msg)
1001 {
1002 DEBUG(D_tls) debug_printf("Sending certificate-status\n"); /*XXX we get this for tls1.2 but not for 1.3 */
1003 #ifdef SUPPORT_SRV_OCSP_STACK
1004 tls_in.ocsp = exim_testharness_disable_ocsp_validity_check
1005 ? OCSP_VFY_NOT_TRIED : OCSP_VFIED; /* We know that GnuTLS verifies responses */
1006 #else
1007 tls_in.ocsp = OCSP_VFY_NOT_TRIED;
1008 #endif
1009 return 0;
1010 }
1011
1012 /* Callback for handshake messages, on server */
1013 static int
1014 tls_server_hook_cb(gnutls_session_t sess, u_int htype, unsigned when,
1015 unsigned incoming, const gnutls_datum_t * msg)
1016 {
1017 /* debug_printf("%s: htype %u\n", __FUNCTION__, htype); */
1018 switch (htype)
1019 {
1020 # ifdef SUPPORT_GNUTLS_EXT_RAW_PARSE
1021 case GNUTLS_HANDSHAKE_CLIENT_HELLO:
1022 return tls_server_clienthello_cb(sess, htype, when, incoming, msg);
1023 case GNUTLS_HANDSHAKE_CERTIFICATE_PKT:
1024 return tls_server_servercerts_cb(sess, htype, when, incoming, msg);
1025 # endif
1026 case GNUTLS_HANDSHAKE_CERTIFICATE_STATUS:
1027 return tls_server_certstatus_cb(sess, htype, when, incoming, msg);
1028 # ifdef EXPERIMENTAL_TLS_RESUME
1029 case GNUTLS_HANDSHAKE_NEW_SESSION_TICKET:
1030 return tls_server_ticket_cb(sess, htype, when, incoming, msg);
1031 # endif
1032 default:
1033 return 0;
1034 }
1035 }
1036 #endif
1037
1038
1039 #if !defined(DISABLE_OCSP) && defined(SUPPORT_GNUTLS_EXT_RAW_PARSE)
1040 static void
1041 tls_server_testharness_ocsp_fiddle(void)
1042 {
1043 extern char ** environ;
1044 if (environ) for (uschar ** p = USS environ; *p; p++)
1045 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1046 {
1047 DEBUG(D_tls) debug_printf("Permitting known bad OCSP response\n");
1048 exim_testharness_disable_ocsp_validity_check = TRUE;
1049 }
1050 }
1051 #endif
1052
1053 /*************************************************
1054 * Variables re-expanded post-SNI *
1055 *************************************************/
1056
1057 /* Called from both server and client code, via tls_init(), and also from
1058 the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni".
1059
1060 We can tell the two apart by state->received_sni being non-NULL in callback.
1061
1062 The callback should not call us unless state->trigger_sni_changes is true,
1063 which we are responsible for setting on the first pass through.
1064
1065 Arguments:
1066 state exim_gnutls_state_st *
1067 errstr error string pointer
1068
1069 Returns: OK/DEFER/FAIL
1070 */
1071
1072 static int
1073 tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr)
1074 {
1075 struct stat statbuf;
1076 int rc;
1077 const host_item *host = state->host; /* macro should be reconsidered? */
1078 uschar *saved_tls_certificate = NULL;
1079 uschar *saved_tls_privatekey = NULL;
1080 uschar *saved_tls_verify_certificates = NULL;
1081 uschar *saved_tls_crl = NULL;
1082 int cert_count;
1083
1084 /* We check for tls_sni *before* expansion. */
1085 if (!host) /* server */
1086 if (!state->received_sni)
1087 {
1088 if ( state->tls_certificate
1089 && ( Ustrstr(state->tls_certificate, US"tls_sni")
1090 || Ustrstr(state->tls_certificate, US"tls_in_sni")
1091 || Ustrstr(state->tls_certificate, US"tls_out_sni")
1092 ) )
1093 {
1094 DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n");
1095 state->trigger_sni_changes = TRUE;
1096 }
1097 }
1098 else
1099 {
1100 /* useful for debugging */
1101 saved_tls_certificate = state->exp_tls_certificate;
1102 saved_tls_privatekey = state->exp_tls_privatekey;
1103 saved_tls_verify_certificates = state->exp_tls_verify_certificates;
1104 saved_tls_crl = state->exp_tls_crl;
1105 }
1106
1107 if ((rc = gnutls_certificate_allocate_credentials(&state->x509_cred)))
1108 return tls_error_gnu(US"gnutls_certificate_allocate_credentials",
1109 rc, host, errstr);
1110
1111 #ifdef SUPPORT_SRV_OCSP_STACK
1112 gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2);
1113
1114 # if !defined(DISABLE_OCSP) && defined(SUPPORT_GNUTLS_EXT_RAW_PARSE)
1115 if (!host && tls_ocsp_file)
1116 {
1117 if (f.running_in_test_harness)
1118 tls_server_testharness_ocsp_fiddle();
1119
1120 if (exim_testharness_disable_ocsp_validity_check)
1121 gnutls_certificate_set_flags(state->x509_cred,
1122 GNUTLS_CERTIFICATE_API_V2 | GNUTLS_CERTIFICATE_SKIP_OCSP_RESPONSE_CHECK);
1123 }
1124 # endif
1125 #endif
1126
1127 /* remember: expand_check_tlsvar() is expand_check() but fiddling with
1128 state members, assuming consistent naming; and expand_check() returns
1129 false if expansion failed, unless expansion was forced to fail. */
1130
1131 /* check if we at least have a certificate, before doing expensive
1132 D-H generation. */
1133
1134 if (!expand_check_tlsvar(tls_certificate, errstr))
1135 return DEFER;
1136
1137 /* certificate is mandatory in server, optional in client */
1138
1139 if ( !state->exp_tls_certificate
1140 || !*state->exp_tls_certificate
1141 )
1142 if (!host)
1143 return tls_install_selfsign(state, errstr);
1144 else
1145 DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n");
1146
1147 if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr))
1148 return DEFER;
1149
1150 /* tls_privatekey is optional, defaulting to same file as certificate */
1151
1152 if (!state->tls_privatekey || !*state->tls_privatekey)
1153 {
1154 state->tls_privatekey = state->tls_certificate;
1155 state->exp_tls_privatekey = state->exp_tls_certificate;
1156 }
1157
1158
1159 if (state->exp_tls_certificate && *state->exp_tls_certificate)
1160 {
1161 DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n",
1162 state->exp_tls_certificate, state->exp_tls_privatekey);
1163
1164 if (state->received_sni)
1165 if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0
1166 && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0
1167 )
1168 {
1169 DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n");
1170 }
1171 else
1172 {
1173 DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n");
1174 }
1175
1176 if (!host) /* server */
1177 {
1178 const uschar * clist = state->exp_tls_certificate;
1179 const uschar * klist = state->exp_tls_privatekey;
1180 const uschar * olist;
1181 int csep = 0, ksep = 0, osep = 0, cnt = 0;
1182 uschar * cfile, * kfile, * ofile;
1183 #ifndef DISABLE_OCSP
1184 # ifdef SUPPORT_GNUTLS_EXT_RAW_PARSE
1185 gnutls_x509_crt_fmt_t ocsp_fmt = GNUTLS_X509_FMT_DER;
1186 # endif
1187
1188 if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr))
1189 return DEFER;
1190 olist = ofile;
1191 #endif
1192
1193 while (cfile = string_nextinlist(&clist, &csep, NULL, 0))
1194
1195 if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0)))
1196 return tls_error(US"cert/key setup: out of keys", NULL, host, errstr);
1197 else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr)))
1198 return rc;
1199 else
1200 {
1201 int gnutls_cert_index = -rc;
1202 DEBUG(D_tls) debug_printf("TLS: cert/key %d %s registered\n",
1203 gnutls_cert_index, cfile);
1204
1205 #ifndef DISABLE_OCSP
1206 if (tls_ocsp_file)
1207 {
1208 /* Set the OCSP stapling server info */
1209 if (gnutls_buggy_ocsp)
1210 {
1211 DEBUG(D_tls)
1212 debug_printf("GnuTLS library is buggy for OCSP; avoiding\n");
1213 }
1214 else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1215 {
1216 DEBUG(D_tls) debug_printf("OCSP response file %d = %s\n",
1217 gnutls_cert_index, ofile);
1218 # ifdef SUPPORT_GNUTLS_EXT_RAW_PARSE
1219 if (Ustrncmp(ofile, US"PEM ", 4) == 0)
1220 {
1221 ocsp_fmt = GNUTLS_X509_FMT_PEM;
1222 ofile += 4;
1223 }
1224 else if (Ustrncmp(ofile, US"DER ", 4) == 0)
1225 {
1226 ocsp_fmt = GNUTLS_X509_FMT_DER;
1227 ofile += 4;
1228 }
1229
1230 if ((rc = gnutls_certificate_set_ocsp_status_request_file2(
1231 state->x509_cred, CCS ofile, gnutls_cert_index,
1232 ocsp_fmt)) < 0)
1233 return tls_error_gnu(
1234 US"gnutls_certificate_set_ocsp_status_request_file2",
1235 rc, host, errstr);
1236 DEBUG(D_tls)
1237 debug_printf(" %d response%s loaded\n", rc, rc>1 ? "s":"");
1238
1239 /* Arrange callbacks for OCSP request observability */
1240
1241 gnutls_handshake_set_hook_function(state->session,
1242 GNUTLS_HANDSHAKE_ANY, GNUTLS_HOOK_POST, tls_server_hook_cb);
1243
1244 # else
1245 # if defined(SUPPORT_SRV_OCSP_STACK)
1246 if ((rc = gnutls_certificate_set_ocsp_status_request_function2(
1247 state->x509_cred, gnutls_cert_index,
1248 server_ocsp_stapling_cb, ofile)))
1249 return tls_error_gnu(
1250 US"gnutls_certificate_set_ocsp_status_request_function2",
1251 rc, host, errstr);
1252 else
1253 # endif
1254 {
1255 if (cnt++ > 0)
1256 {
1257 DEBUG(D_tls)
1258 debug_printf("oops; multiple OCSP files not supported\n");
1259 break;
1260 }
1261 gnutls_certificate_set_ocsp_status_request_function(
1262 state->x509_cred, server_ocsp_stapling_cb, ofile);
1263 }
1264 # endif /* SUPPORT_GNUTLS_EXT_RAW_PARSE */
1265 }
1266 else
1267 DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n");
1268 }
1269 #endif /* DISABLE_OCSP */
1270 }
1271 }
1272 else /* client */
1273 {
1274 if (0 < (rc = tls_add_certfile(state, host,
1275 state->exp_tls_certificate, state->exp_tls_privatekey, errstr)))
1276 return rc;
1277 DEBUG(D_tls) debug_printf("TLS: cert/key registered\n");
1278 }
1279
1280 } /* tls_certificate */
1281
1282
1283 /* Set the trusted CAs file if one is provided, and then add the CRL if one is
1284 provided. Experiment shows that, if the certificate file is empty, an unhelpful
1285 error message is provided. However, if we just refrain from setting anything up
1286 in that case, certificate verification fails, which seems to be the correct
1287 behaviour. */
1288
1289 if (state->tls_verify_certificates && *state->tls_verify_certificates)
1290 {
1291 if (!expand_check_tlsvar(tls_verify_certificates, errstr))
1292 return DEFER;
1293 #ifndef SUPPORT_SYSDEFAULT_CABUNDLE
1294 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1295 state->exp_tls_verify_certificates = NULL;
1296 #endif
1297 if (state->tls_crl && *state->tls_crl)
1298 if (!expand_check_tlsvar(tls_crl, errstr))
1299 return DEFER;
1300
1301 if (!(state->exp_tls_verify_certificates &&
1302 *state->exp_tls_verify_certificates))
1303 {
1304 DEBUG(D_tls)
1305 debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n");
1306 /* With no tls_verify_certificates, we ignore tls_crl too */
1307 return OK;
1308 }
1309 }
1310 else
1311 {
1312 DEBUG(D_tls)
1313 debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n");
1314 return OK;
1315 }
1316
1317 #ifdef SUPPORT_SYSDEFAULT_CABUNDLE
1318 if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0)
1319 cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred);
1320 else
1321 #endif
1322 {
1323 if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0)
1324 {
1325 log_write(0, LOG_MAIN|LOG_PANIC, "could not stat '%s' "
1326 "(tls_verify_certificates): %s", state->exp_tls_verify_certificates,
1327 strerror(errno));
1328 return DEFER;
1329 }
1330
1331 #ifndef SUPPORT_CA_DIR
1332 /* The test suite passes in /dev/null; we could check for that path explicitly,
1333 but who knows if someone has some weird FIFO which always dumps some certs, or
1334 other weirdness. The thing we really want to check is that it's not a
1335 directory, since while OpenSSL supports that, GnuTLS does not.
1336 So s/!S_ISREG/S_ISDIR/ and change some messaging ... */
1337 if (S_ISDIR(statbuf.st_mode))
1338 {
1339 DEBUG(D_tls)
1340 debug_printf("verify certificates path is a dir: \"%s\"\n",
1341 state->exp_tls_verify_certificates);
1342 log_write(0, LOG_MAIN|LOG_PANIC,
1343 "tls_verify_certificates \"%s\" is a directory",
1344 state->exp_tls_verify_certificates);
1345 return DEFER;
1346 }
1347 #endif
1348
1349 DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n",
1350 state->exp_tls_verify_certificates, statbuf.st_size);
1351
1352 if (statbuf.st_size == 0)
1353 {
1354 DEBUG(D_tls)
1355 debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n");
1356 return OK;
1357 }
1358
1359 cert_count =
1360
1361 #ifdef SUPPORT_CA_DIR
1362 (statbuf.st_mode & S_IFMT) == S_IFDIR
1363 ?
1364 gnutls_certificate_set_x509_trust_dir(state->x509_cred,
1365 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM)
1366 :
1367 #endif
1368 gnutls_certificate_set_x509_trust_file(state->x509_cred,
1369 CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM);
1370
1371 #ifdef SUPPORT_CA_DIR
1372 /* Mimic the behaviour with OpenSSL of not advertising a usable-cert list
1373 when using the directory-of-certs config model. */
1374
1375 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1376 gnutls_certificate_send_x509_rdn_sequence(state->session, 1);
1377 #endif
1378 }
1379
1380 if (cert_count < 0)
1381 return tls_error_gnu(US"setting certificate trust", cert_count, host, errstr);
1382 DEBUG(D_tls)
1383 debug_printf("Added %d certificate authorities.\n", cert_count);
1384
1385 if (state->tls_crl && *state->tls_crl &&
1386 state->exp_tls_crl && *state->exp_tls_crl)
1387 {
1388 DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl);
1389 if ((cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred,
1390 CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM)) < 0)
1391 return tls_error_gnu(US"gnutls_certificate_set_x509_crl_file",
1392 cert_count, host, errstr);
1393
1394 DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count);
1395 }
1396
1397 return OK;
1398 }
1399
1400
1401
1402
1403 /*************************************************
1404 * Set X.509 state variables *
1405 *************************************************/
1406
1407 /* In GnuTLS, the registered cert/key are not replaced by a later
1408 set of a cert/key, so for SNI support we need a whole new x509_cred
1409 structure. Which means various other non-re-expanded pieces of state
1410 need to be re-set in the new struct, so the setting logic is pulled
1411 out to this.
1412
1413 Arguments:
1414 state exim_gnutls_state_st *
1415 errstr error string pointer
1416
1417 Returns: OK/DEFER/FAIL
1418 */
1419
1420 static int
1421 tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr)
1422 {
1423 int rc;
1424 const host_item *host = state->host; /* macro should be reconsidered? */
1425
1426 #ifndef GNUTLS_AUTO_DHPARAMS
1427 /* Create D-H parameters, or read them from the cache file. This function does
1428 its own SMTP error messaging. This only happens for the server, TLS D-H ignores
1429 client-side params. */
1430
1431 if (!state->host)
1432 {
1433 if (!dh_server_params)
1434 if ((rc = init_server_dh(errstr)) != OK) return rc;
1435
1436 /* Unnecessary & discouraged with 3.6.0 or later */
1437 gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params);
1438 }
1439 #endif
1440
1441 /* Link the credentials to the session. */
1442
1443 if ((rc = gnutls_credentials_set(state->session,
1444 GNUTLS_CRD_CERTIFICATE, state->x509_cred)))
1445 return tls_error_gnu(US"gnutls_credentials_set", rc, host, errstr);
1446
1447 return OK;
1448 }
1449
1450 /*************************************************
1451 * Initialize for GnuTLS *
1452 *************************************************/
1453
1454
1455 #ifndef DISABLE_OCSP
1456
1457 static BOOL
1458 tls_is_buggy_ocsp(void)
1459 {
1460 const uschar * s;
1461 uschar maj, mid, mic;
1462
1463 s = CUS gnutls_check_version(NULL);
1464 maj = atoi(CCS s);
1465 if (maj == 3)
1466 {
1467 while (*s && *s != '.') s++;
1468 mid = atoi(CCS ++s);
1469 if (mid <= 2)
1470 return TRUE;
1471 else if (mid >= 5)
1472 return FALSE;
1473 else
1474 {
1475 while (*s && *s != '.') s++;
1476 mic = atoi(CCS ++s);
1477 return mic <= (mid == 3 ? 16 : 3);
1478 }
1479 }
1480 return FALSE;
1481 }
1482
1483 #endif
1484
1485
1486 /* Called from both server and client code. In the case of a server, errors
1487 before actual TLS negotiation return DEFER.
1488
1489 Arguments:
1490 host connected host, if client; NULL if server
1491 certificate certificate file
1492 privatekey private key file
1493 sni TLS SNI to send, sometimes when client; else NULL
1494 cas CA certs file
1495 crl CRL file
1496 require_ciphers tls_require_ciphers setting
1497 caller_state returned state-info structure
1498 errstr error string pointer
1499
1500 Returns: OK/DEFER/FAIL
1501 */
1502
1503 static int
1504 tls_init(
1505 const host_item *host,
1506 const uschar *certificate,
1507 const uschar *privatekey,
1508 const uschar *sni,
1509 const uschar *cas,
1510 const uschar *crl,
1511 const uschar *require_ciphers,
1512 exim_gnutls_state_st **caller_state,
1513 tls_support * tlsp,
1514 uschar ** errstr)
1515 {
1516 exim_gnutls_state_st * state;
1517 int rc;
1518 size_t sz;
1519 const char * errpos;
1520 const uschar * p;
1521
1522 if (!exim_gnutls_base_init_done)
1523 {
1524 DEBUG(D_tls) debug_printf("GnuTLS global init required.\n");
1525
1526 #if defined(HAVE_GNUTLS_PKCS11) && !defined(GNUTLS_AUTO_PKCS11_MANUAL)
1527 /* By default, gnutls_global_init will init PKCS11 support in auto mode,
1528 which loads modules from a config file, which sounds good and may be wanted
1529 by some sysadmin, but also means in common configurations that GNOME keyring
1530 environment variables are used and so breaks for users calling mailq.
1531 To prevent this, we init PKCS11 first, which is the documented approach. */
1532 if (!gnutls_allow_auto_pkcs11)
1533 if ((rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL)))
1534 return tls_error_gnu(US"gnutls_pkcs11_init", rc, host, errstr);
1535 #endif
1536
1537 #ifndef GNUTLS_AUTO_GLOBAL_INIT
1538 if ((rc = gnutls_global_init()))
1539 return tls_error_gnu(US"gnutls_global_init", rc, host, errstr);
1540 #endif
1541
1542 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
1543 DEBUG(D_tls)
1544 {
1545 gnutls_global_set_log_function(exim_gnutls_logger_cb);
1546 /* arbitrarily chosen level; bump up to 9 for more */
1547 gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
1548 }
1549 #endif
1550
1551 #ifndef DISABLE_OCSP
1552 if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp()))
1553 log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version");
1554 #endif
1555
1556 exim_gnutls_base_init_done = TRUE;
1557 }
1558
1559 if (host)
1560 {
1561 /* For client-side sessions we allocate a context. This lets us run
1562 several in parallel. */
1563 int old_pool = store_pool;
1564 store_pool = POOL_PERM;
1565 state = store_get(sizeof(exim_gnutls_state_st), FALSE);
1566 store_pool = old_pool;
1567
1568 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1569 state->tlsp = tlsp;
1570 DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n");
1571 rc = gnutls_init(&state->session, GNUTLS_CLIENT);
1572 }
1573 else
1574 {
1575 state = &state_server;
1576 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
1577 state->tlsp = tlsp;
1578 DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n");
1579 rc = gnutls_init(&state->session, GNUTLS_SERVER);
1580 }
1581 if (rc)
1582 return tls_error_gnu(US"gnutls_init", rc, host, errstr);
1583
1584 state->host = host;
1585
1586 state->tls_certificate = certificate;
1587 state->tls_privatekey = privatekey;
1588 state->tls_require_ciphers = require_ciphers;
1589 state->tls_sni = sni;
1590 state->tls_verify_certificates = cas;
1591 state->tls_crl = crl;
1592
1593 /* This handles the variables that might get re-expanded after TLS SNI;
1594 that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */
1595
1596 DEBUG(D_tls)
1597 debug_printf("Expanding various TLS configuration options for session credentials.\n");
1598 if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc;
1599
1600 /* These are all other parts of the x509_cred handling, since SNI in GnuTLS
1601 requires a new structure afterwards. */
1602
1603 if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc;
1604
1605 /* set SNI in client, only */
1606 if (host)
1607 {
1608 if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr))
1609 return DEFER;
1610 if (state->tlsp->sni && *state->tlsp->sni)
1611 {
1612 DEBUG(D_tls)
1613 debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni);
1614 sz = Ustrlen(state->tlsp->sni);
1615 if ((rc = gnutls_server_name_set(state->session,
1616 GNUTLS_NAME_DNS, state->tlsp->sni, sz)))
1617 return tls_error_gnu(US"gnutls_server_name_set", rc, host, errstr);
1618 }
1619 }
1620 else if (state->tls_sni)
1621 DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \
1622 "have an SNI set for a server [%s]\n", state->tls_sni);
1623
1624 /* This is the priority string support,
1625 http://www.gnutls.org/manual/html_node/Priority-Strings.html
1626 and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
1627 This was backwards incompatible, but means Exim no longer needs to track
1628 all algorithms and provide string forms for them. */
1629
1630 p = NULL;
1631 if (state->tls_require_ciphers && *state->tls_require_ciphers)
1632 {
1633 if (!expand_check_tlsvar(tls_require_ciphers, errstr))
1634 return DEFER;
1635 if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
1636 {
1637 p = state->exp_tls_require_ciphers;
1638 DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
1639 }
1640 }
1641 if (!p)
1642 {
1643 p = exim_default_gnutls_priority;
1644 DEBUG(D_tls)
1645 debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
1646 }
1647
1648 if ((rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos)))
1649 return tls_error_gnu(string_sprintf(
1650 "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
1651 p, errpos - CS p, errpos),
1652 rc, host, errstr);
1653
1654 if ((rc = gnutls_priority_set(state->session, state->priority_cache)))
1655 return tls_error_gnu(US"gnutls_priority_set", rc, host, errstr);
1656
1657 /* This also sets the server ticket expiration time to the same, and
1658 the STEK rotation time to 3x. */
1659
1660 gnutls_db_set_cache_expiration(state->session, ssl_session_timeout);
1661
1662 /* Reduce security in favour of increased compatibility, if the admin
1663 decides to make that trade-off. */
1664 if (gnutls_compat_mode)
1665 {
1666 #if LIBGNUTLS_VERSION_NUMBER >= 0x020104
1667 DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n");
1668 gnutls_session_enable_compatibility_mode(state->session);
1669 #else
1670 DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n");
1671 #endif
1672 }
1673
1674 *caller_state = state;
1675 return OK;
1676 }
1677
1678
1679
1680 /*************************************************
1681 * Extract peer information *
1682 *************************************************/
1683
1684 static const uschar *
1685 cipher_stdname_kcm(gnutls_kx_algorithm_t kx, gnutls_cipher_algorithm_t cipher,
1686 gnutls_mac_algorithm_t mac)
1687 {
1688 uschar cs_id[2];
1689 gnutls_kx_algorithm_t kx_i;
1690 gnutls_cipher_algorithm_t cipher_i;
1691 gnutls_mac_algorithm_t mac_i;
1692
1693 for (size_t i = 0;
1694 gnutls_cipher_suite_info(i, cs_id, &kx_i, &cipher_i, &mac_i, NULL);
1695 i++)
1696 if (kx_i == kx && cipher_i == cipher && mac_i == mac)
1697 return cipher_stdname(cs_id[0], cs_id[1]);
1698 return NULL;
1699 }
1700
1701
1702
1703 /* Called from both server and client code.
1704 Only this is allowed to set state->peerdn and state->have_set_peerdn
1705 and we use that to detect double-calls.
1706
1707 NOTE: the state blocks last while the TLS connection is up, which is fine
1708 for logging in the server side, but for the client side, we log after teardown
1709 in src/deliver.c. While the session is up, we can twist about states and
1710 repoint tls_* globals, but those variables used for logging or other variable
1711 expansion that happens _after_ delivery need to have a longer life-time.
1712
1713 So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from
1714 doing this more than once per generation of a state context. We set them in
1715 the state context, and repoint tls_* to them. After the state goes away, the
1716 tls_* copies of the pointers remain valid and client delivery logging is happy.
1717
1718 tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues
1719 don't apply.
1720
1721 Arguments:
1722 state exim_gnutls_state_st *
1723 errstr pointer to error string
1724
1725 Returns: OK/DEFER/FAIL
1726 */
1727
1728 static int
1729 peer_status(exim_gnutls_state_st * state, uschar ** errstr)
1730 {
1731 gnutls_session_t session = state->session;
1732 const gnutls_datum_t * cert_list;
1733 int old_pool, rc;
1734 unsigned int cert_list_size = 0;
1735 gnutls_protocol_t protocol;
1736 gnutls_cipher_algorithm_t cipher;
1737 gnutls_kx_algorithm_t kx;
1738 gnutls_mac_algorithm_t mac;
1739 gnutls_certificate_type_t ct;
1740 gnutls_x509_crt_t crt;
1741 uschar * dn_buf;
1742 size_t sz;
1743
1744 if (state->have_set_peerdn)
1745 return OK;
1746 state->have_set_peerdn = TRUE;
1747
1748 state->peerdn = NULL;
1749
1750 /* tls_cipher */
1751 cipher = gnutls_cipher_get(session);
1752 protocol = gnutls_protocol_get_version(session);
1753 mac = gnutls_mac_get(session);
1754 kx =
1755 #ifdef GNUTLS_TLS1_3
1756 protocol >= GNUTLS_TLS1_3 ? 0 :
1757 #endif
1758 gnutls_kx_get(session);
1759
1760 old_pool = store_pool;
1761 {
1762 tls_support * tlsp = state->tlsp;
1763 store_pool = POOL_PERM;
1764
1765 #ifdef SUPPORT_GNUTLS_SESS_DESC
1766 {
1767 gstring * g = NULL;
1768 uschar * s = US gnutls_session_get_desc(session), c;
1769
1770 /* Nikos M suggests we use this by preference. It returns like:
1771 (TLS1.3)-(ECDHE-SECP256R1)-(RSA-PSS-RSAE-SHA256)-(AES-256-GCM)
1772
1773 For partial back-compat, put a colon after the TLS version, replace the
1774 )-( grouping with __, replace in-group - with _ and append the :keysize. */
1775
1776 /* debug_printf("peer_status: gnutls_session_get_desc %s\n", s); */
1777
1778 for (s++; (c = *s) && c != ')'; s++) g = string_catn(g, s, 1);
1779
1780 tlsp->ver = string_copyn(g->s, g->ptr);
1781 for (uschar * p = US tlsp->ver; *p; p++)
1782 if (*p == '-') { *p = '\0'; break; } /* TLS1.0-PKIX -> TLS1.0 */
1783
1784 g = string_catn(g, US":", 1);
1785 if (*s) s++; /* now on _ between groups */
1786 while ((c = *s))
1787 {
1788 for (*++s && ++s; (c = *s) && c != ')'; s++)
1789 g = string_catn(g, c == '-' ? US"_" : s, 1);
1790 /* now on ) closing group */
1791 if ((c = *s) && *++s == '-') g = string_catn(g, US"__", 2);
1792 /* now on _ between groups */
1793 }
1794 g = string_catn(g, US":", 1);
1795 g = string_cat(g, string_sprintf("%d", (int) gnutls_cipher_get_key_size(cipher) * 8));
1796 state->ciphersuite = string_from_gstring(g);
1797 }
1798 #else
1799 state->ciphersuite = string_sprintf("%s:%s:%d",
1800 gnutls_protocol_get_name(protocol),
1801 gnutls_cipher_suite_get_name(kx, cipher, mac),
1802 (int) gnutls_cipher_get_key_size(cipher) * 8);
1803
1804 /* I don't see a way that spaces could occur, in the current GnuTLS
1805 code base, but it was a concern in the old code and perhaps older GnuTLS
1806 releases did return "TLS 1.0"; play it safe, just in case. */
1807
1808 for (uschar * p = state->ciphersuite; *p; p++) if (isspace(*p)) *p = '-';
1809 tlsp->ver = string_copyn(state->ciphersuite,
1810 Ustrchr(state->ciphersuite, ':') - state->ciphersuite);
1811 #endif
1812
1813 /* debug_printf("peer_status: ciphersuite %s\n", state->ciphersuite); */
1814
1815 tlsp->cipher = state->ciphersuite;
1816 tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8;
1817
1818 tlsp->cipher_stdname = cipher_stdname_kcm(kx, cipher, mac);
1819 }
1820 store_pool = old_pool;
1821
1822 /* tls_peerdn */
1823 cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
1824
1825 if (!cert_list || cert_list_size == 0)
1826 {
1827 DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n",
1828 cert_list, cert_list_size);
1829 if (state->verify_requirement >= VERIFY_REQUIRED)
1830 return tls_error(US"certificate verification failed",
1831 US"no certificate received from peer", state->host, errstr);
1832 return OK;
1833 }
1834
1835 if ((ct = gnutls_certificate_type_get(session)) != GNUTLS_CRT_X509)
1836 {
1837 const uschar * ctn = US gnutls_certificate_type_get_name(ct);
1838 DEBUG(D_tls)
1839 debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn);
1840 if (state->verify_requirement >= VERIFY_REQUIRED)
1841 return tls_error(US"certificate verification not possible, unhandled type",
1842 ctn, state->host, errstr);
1843 return OK;
1844 }
1845
1846 #define exim_gnutls_peer_err(Label) \
1847 do { \
1848 if (rc != GNUTLS_E_SUCCESS) \
1849 { \
1850 DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \
1851 (Label), gnutls_strerror(rc)); \
1852 if (state->verify_requirement >= VERIFY_REQUIRED) \
1853 return tls_error_gnu((Label), rc, state->host, errstr); \
1854 return OK; \
1855 } \
1856 } while (0)
1857
1858 rc = import_cert(&cert_list[0], &crt);
1859 exim_gnutls_peer_err(US"cert 0");
1860
1861 state->tlsp->peercert = state->peercert = crt;
1862
1863 sz = 0;
1864 rc = gnutls_x509_crt_get_dn(crt, NULL, &sz);
1865 if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER)
1866 {
1867 exim_gnutls_peer_err(US"getting size for cert DN failed");
1868 return FAIL; /* should not happen */
1869 }
1870 dn_buf = store_get_perm(sz, TRUE); /* tainted */
1871 rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz);
1872 exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]");
1873
1874 state->peerdn = dn_buf;
1875
1876 return OK;
1877 #undef exim_gnutls_peer_err
1878 }
1879
1880
1881
1882
1883 /*************************************************
1884 * Verify peer certificate *
1885 *************************************************/
1886
1887 /* Called from both server and client code.
1888 *Should* be using a callback registered with
1889 gnutls_certificate_set_verify_function() to fail the handshake if we dislike
1890 the peer information, but that's too new for some OSes.
1891
1892 Arguments:
1893 state exim_gnutls_state_st *
1894 errstr where to put an error message
1895
1896 Returns:
1897 FALSE if the session should be rejected
1898 TRUE if the cert is okay or we just don't care
1899 */
1900
1901 static BOOL
1902 verify_certificate(exim_gnutls_state_st * state, uschar ** errstr)
1903 {
1904 int rc;
1905 uint verify;
1906
1907 DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n");
1908 *errstr = NULL;
1909 rc = peer_status(state, errstr);
1910
1911 if (state->verify_requirement == VERIFY_NONE)
1912 return TRUE;
1913
1914 if (rc != OK || !state->peerdn)
1915 {
1916 verify = GNUTLS_CERT_INVALID;
1917 *errstr = US"certificate not supplied";
1918 }
1919 else
1920
1921 {
1922 #ifdef SUPPORT_DANE
1923 if (state->verify_requirement == VERIFY_DANE && state->host)
1924 {
1925 /* Using dane_verify_session_crt() would be easy, as it does it all for us
1926 including talking to a DNS resolver. But we want to do that bit ourselves
1927 as the testsuite intercepts and fakes its own DNS environment. */
1928
1929 dane_state_t s;
1930 dane_query_t r;
1931 uint lsize;
1932 const gnutls_datum_t * certlist =
1933 gnutls_certificate_get_peers(state->session, &lsize);
1934 int usage = tls_out.tlsa_usage;
1935
1936 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
1937 /* Split the TLSA records into two sets, TA and EE selectors. Run the
1938 dane-verification separately so that we know which selector verified;
1939 then we know whether to do name-verification (needed for TA but not EE). */
1940
1941 if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE)))
1942 { /* a mixed-usage bundle */
1943 int i, j, nrec;
1944 const char ** dd;
1945 int * ddl;
1946
1947 for (nrec = 0; state->dane_data_len[nrec]; ) nrec++;
1948 nrec++;
1949
1950 dd = store_get(nrec * sizeof(uschar *), FALSE);
1951 ddl = store_get(nrec * sizeof(int), FALSE);
1952 nrec--;
1953
1954 if ((rc = dane_state_init(&s, 0)))
1955 goto tlsa_prob;
1956
1957 for (usage = DANESSL_USAGE_DANE_EE;
1958 usage >= DANESSL_USAGE_DANE_TA; usage--)
1959 { /* take records with this usage */
1960 for (j = i = 0; i < nrec; i++)
1961 if (state->dane_data[i][0] == usage)
1962 {
1963 dd[j] = state->dane_data[i];
1964 ddl[j++] = state->dane_data_len[i];
1965 }
1966 if (j)
1967 {
1968 dd[j] = NULL;
1969 ddl[j] = 0;
1970
1971 if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0)))
1972 goto tlsa_prob;
1973
1974 if ((rc = dane_verify_crt_raw(s, certlist, lsize,
1975 gnutls_certificate_type_get(state->session),
1976 r, 0,
1977 usage == DANESSL_USAGE_DANE_EE
1978 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
1979 &verify)))
1980 {
1981 DEBUG(D_tls)
1982 debug_printf("TLSA record problem: %s\n", dane_strerror(rc));
1983 }
1984 else if (verify == 0) /* verification passed */
1985 {
1986 usage = 1 << usage;
1987 break;
1988 }
1989 }
1990 }
1991
1992 if (rc) goto tlsa_prob;
1993 }
1994 else
1995 # endif
1996 {
1997 if ( (rc = dane_state_init(&s, 0))
1998 || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len,
1999 1, 0))
2000 || (rc = dane_verify_crt_raw(s, certlist, lsize,
2001 gnutls_certificate_type_get(state->session),
2002 r, 0,
2003 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
2004 usage == (1 << DANESSL_USAGE_DANE_EE)
2005 ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0,
2006 # else
2007 0,
2008 # endif
2009 &verify))
2010 )
2011 goto tlsa_prob;
2012 }
2013
2014 if (verify != 0) /* verification failed */
2015 {
2016 gnutls_datum_t str;
2017 (void) dane_verification_status_print(verify, &str, 0);
2018 *errstr = US str.data; /* don't bother to free */
2019 goto badcert;
2020 }
2021
2022 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
2023 /* If a TA-mode TLSA record was used for verification we must additionally
2024 verify the cert name (but not the CA chain). For EE-mode, skip it. */
2025
2026 if (usage & (1 << DANESSL_USAGE_DANE_EE))
2027 # endif
2028 {
2029 state->peer_dane_verified = state->peer_cert_verified = TRUE;
2030 goto goodcert;
2031 }
2032 # ifdef GNUTLS_BROKEN_DANE_VALIDATION
2033 /* Assume that the name on the A-record is the one that should be matching
2034 the cert. An alternate view is that the domain part of the email address
2035 is also permissible. */
2036
2037 if (gnutls_x509_crt_check_hostname(state->tlsp->peercert,
2038 CS state->host->name))
2039 {
2040 state->peer_dane_verified = state->peer_cert_verified = TRUE;
2041 goto goodcert;
2042 }
2043 # endif
2044 }
2045 #endif /*SUPPORT_DANE*/
2046
2047 rc = gnutls_certificate_verify_peers2(state->session, &verify);
2048 }
2049
2050 /* Handle the result of verification. INVALID is set if any others are. */
2051
2052 if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED))
2053 {
2054 state->peer_cert_verified = FALSE;
2055 if (!*errstr)
2056 {
2057 #ifdef GNUTLS_CERT_VFY_STATUS_PRINT
2058 DEBUG(D_tls)
2059 {
2060 gnutls_datum_t txt;
2061
2062 if (gnutls_certificate_verification_status_print(verify,
2063 gnutls_certificate_type_get(state->session), &txt, 0)
2064 == GNUTLS_E_SUCCESS)
2065 {
2066 debug_printf("%s\n", txt.data);
2067 gnutls_free(txt.data);
2068 }
2069 }
2070 #endif
2071 *errstr = verify & GNUTLS_CERT_REVOKED
2072 ? US"certificate revoked" : US"certificate invalid";
2073 }
2074
2075 DEBUG(D_tls)
2076 debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n",
2077 *errstr, state->peerdn ? state->peerdn : US"<unset>");
2078
2079 if (state->verify_requirement >= VERIFY_REQUIRED)
2080 goto badcert;
2081 DEBUG(D_tls)
2082 debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n");
2083 }
2084
2085 else
2086 {
2087 /* Client side, check the server's certificate name versus the name on the
2088 A-record for the connection we made. What to do for server side - what name
2089 to use for client? We document that there is no such checking for server
2090 side. */
2091
2092 if ( state->exp_tls_verify_cert_hostnames
2093 && !gnutls_x509_crt_check_hostname(state->tlsp->peercert,
2094 CS state->exp_tls_verify_cert_hostnames)
2095 )
2096 {
2097 DEBUG(D_tls)
2098 debug_printf("TLS certificate verification failed: cert name mismatch\n");
2099 if (state->verify_requirement >= VERIFY_REQUIRED)
2100 goto badcert;
2101 return TRUE;
2102 }
2103
2104 state->peer_cert_verified = TRUE;
2105 DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n",
2106 state->peerdn ? state->peerdn : US"<unset>");
2107 }
2108
2109 goodcert:
2110 state->tlsp->peerdn = state->peerdn;
2111 return TRUE;
2112
2113 #ifdef SUPPORT_DANE
2114 tlsa_prob:
2115 *errstr = string_sprintf("TLSA record problem: %s",
2116 rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc));
2117 #endif
2118
2119 badcert:
2120 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE);
2121 return FALSE;
2122 }
2123
2124
2125
2126
2127 /* ------------------------------------------------------------------------ */
2128 /* Callbacks */
2129
2130 /* Logging function which can be registered with
2131 * gnutls_global_set_log_function()
2132 * gnutls_global_set_log_level() 0..9
2133 */
2134 #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
2135 static void
2136 exim_gnutls_logger_cb(int level, const char *message)
2137 {
2138 size_t len = strlen(message);
2139 if (len < 1)
2140 {
2141 DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
2142 return;
2143 }
2144 DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
2145 message[len-1] == '\n' ? "" : "\n");
2146 }
2147 #endif
2148
2149
2150 /* Called after client hello, should handle SNI work.
2151 This will always set tls_sni (state->received_sni) if available,
2152 and may trigger presenting different certificates,
2153 if state->trigger_sni_changes is TRUE.
2154
2155 Should be registered with
2156 gnutls_handshake_set_post_client_hello_function()
2157
2158 "This callback must return 0 on success or a gnutls error code to terminate the
2159 handshake.".
2160
2161 For inability to get SNI information, we return 0.
2162 We only return non-zero if re-setup failed.
2163 Only used for server-side TLS.
2164 */
2165
2166 static int
2167 exim_sni_handling_cb(gnutls_session_t session)
2168 {
2169 char sni_name[MAX_HOST_LEN];
2170 size_t data_len = MAX_HOST_LEN;
2171 exim_gnutls_state_st *state = &state_server;
2172 unsigned int sni_type;
2173 int rc, old_pool;
2174 uschar * dummy_errstr;
2175
2176 rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0);
2177 if (rc != GNUTLS_E_SUCCESS)
2178 {
2179 DEBUG(D_tls)
2180 if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE)
2181 debug_printf("TLS: no SNI presented in handshake.\n");
2182 else
2183 debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n",
2184 gnutls_strerror(rc), rc);
2185 return 0;
2186 }
2187
2188 if (sni_type != GNUTLS_NAME_DNS)
2189 {
2190 DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type);
2191 return 0;
2192 }
2193
2194 /* We now have a UTF-8 string in sni_name */
2195 old_pool = store_pool;
2196 store_pool = POOL_PERM;
2197 state->received_sni = string_copy_taint(US sni_name, TRUE);
2198 store_pool = old_pool;
2199
2200 /* We set this one now so that variable expansions below will work */
2201 state->tlsp->sni = state->received_sni;
2202
2203 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name,
2204 state->trigger_sni_changes ? "" : " (unused for certificate selection)");
2205
2206 if (!state->trigger_sni_changes)
2207 return 0;
2208
2209 if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK)
2210 {
2211 /* If the setup of certs/etc failed before handshake, TLS would not have
2212 been offered. The best we can do now is abort. */
2213 return GNUTLS_E_APPLICATION_ERROR_MIN;
2214 }
2215
2216 rc = tls_set_remaining_x509(state, &dummy_errstr);
2217 if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN;
2218
2219 return 0;
2220 }
2221
2222
2223
2224 #ifndef DISABLE_EVENT
2225 /*
2226 We use this callback to get observability and detail-level control
2227 for an exim TLS connection (either direction), raising a tls:cert event
2228 for each cert in the chain presented by the peer. Any event
2229 can deny verification.
2230
2231 Return 0 for the handshake to continue or non-zero to terminate.
2232 */
2233
2234 static int
2235 verify_cb(gnutls_session_t session)
2236 {
2237 const gnutls_datum_t * cert_list;
2238 unsigned int cert_list_size = 0;
2239 gnutls_x509_crt_t crt;
2240 int rc;
2241 uschar * yield;
2242 exim_gnutls_state_st * state = gnutls_session_get_ptr(session);
2243
2244 if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size)))
2245 while (cert_list_size--)
2246 {
2247 if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS)
2248 {
2249 DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n",
2250 cert_list_size, gnutls_strerror(rc));
2251 break;
2252 }
2253
2254 state->tlsp->peercert = crt;
2255 if ((yield = event_raise(state->event_action,
2256 US"tls:cert", string_sprintf("%d", cert_list_size))))
2257 {
2258 log_write(0, LOG_MAIN,
2259 "SSL verify denied by event-action: depth=%d: %s",
2260 cert_list_size, yield);
2261 return 1; /* reject */
2262 }
2263 state->tlsp->peercert = NULL;
2264 }
2265
2266 return 0;
2267 }
2268
2269 #endif
2270
2271
2272 static gstring *
2273 ddump(gnutls_datum_t * d)
2274 {
2275 gstring * g = string_get((d->size+1) * 2);
2276 uschar * s = d->data;
2277 for (unsigned i = d->size; i > 0; i--, s++)
2278 {
2279 g = string_catn(g, US "0123456789abcdef" + (*s >> 4), 1);
2280 g = string_catn(g, US "0123456789abcdef" + (*s & 0xf), 1);
2281 }
2282 return g;
2283 }
2284
2285 static void
2286 post_handshake_debug(exim_gnutls_state_st * state)
2287 {
2288 #ifdef SUPPORT_GNUTLS_SESS_DESC
2289 debug_printf("%s\n", gnutls_session_get_desc(state->session));
2290 #endif
2291
2292 #ifdef SUPPORT_GNUTLS_KEYLOG
2293 # ifdef EXIM_HAVE_TLS1_3
2294 if (gnutls_protocol_get_version(state->session) < GNUTLS_TLS1_3)
2295 # else
2296 if (TRUE)
2297 # endif
2298 {
2299 gnutls_datum_t c, s;
2300 gstring * gc, * gs;
2301 /* For TLS1.2 we only want the client random and the master secret */
2302 gnutls_session_get_random(state->session, &c, &s);
2303 gnutls_session_get_master_secret(state->session, &s);
2304 gc = ddump(&c);
2305 gs = ddump(&s);
2306 debug_printf("CLIENT_RANDOM %.*s %.*s\n", (int)gc->ptr, gc->s, (int)gs->ptr, gs->s);
2307 }
2308 else
2309 debug_printf("To get keying info for TLS1.3 is hard:\n"
2310 " Set environment variable SSLKEYLOGFILE to a filename relative to the spool directory,\n"
2311 " and make sure it is writable by the Exim runtime user.\n"
2312 " Add SSLKEYLOGFILE to keep_environment in the exim config.\n"
2313 " Start Exim as root.\n"
2314 " If using sudo, add SSLKEYLOGFILE to env_keep in /etc/sudoers\n"
2315 " (works for TLS1.2 also, and saves cut-paste into file).\n"
2316 " Trying to use add_environment for this will not work\n");
2317 #endif
2318 }
2319
2320
2321 #ifdef EXPERIMENTAL_TLS_RESUME
2322 static int
2323 tls_server_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
2324 unsigned incoming, const gnutls_datum_t * msg)
2325 {
2326 DEBUG(D_tls) debug_printf("newticket cb\n");
2327 tls_in.resumption |= RESUME_CLIENT_REQUESTED;
2328 return 0;
2329 }
2330
2331 static void
2332 tls_server_resume_prehandshake(exim_gnutls_state_st * state)
2333 {
2334 /* Should the server offer session resumption? */
2335 tls_in.resumption = RESUME_SUPPORTED;
2336 if (verify_check_host(&tls_resumption_hosts) == OK)
2337 {
2338 int rc;
2339 /* GnuTLS appears to not do ticket overlap, but does emit a fresh ticket when
2340 an offered resumption is unacceptable. We lose one resumption per ticket
2341 lifetime, and sessions cannot be indefinitely re-used. There seems to be no
2342 way (3.6.7) of changing the default number of 2 TLS1.3 tickets issued, but at
2343 least they go out in a single packet. */
2344
2345 if (!(rc = gnutls_session_ticket_enable_server(state->session,
2346 &server_sessticket_key)))
2347 tls_in.resumption |= RESUME_SERVER_TICKET;
2348 else
2349 DEBUG(D_tls)
2350 debug_printf("enabling session tickets: %s\n", US gnutls_strerror(rc));
2351
2352 /* Try to tell if we see a ticket request */
2353 gnutls_handshake_set_hook_function(state->session,
2354 GNUTLS_HANDSHAKE_ANY, GNUTLS_HOOK_POST, tls_server_hook_cb);
2355 }
2356 }
2357
2358 static void
2359 tls_server_resume_posthandshake(exim_gnutls_state_st * state)
2360 {
2361 if (gnutls_session_resumption_requested(state->session))
2362 {
2363 /* This tells us the client sent a full ticket. We use a
2364 callback on session-ticket request, elsewhere, to tell
2365 if a client asked for a ticket. */
2366
2367 tls_in.resumption |= RESUME_CLIENT_SUGGESTED;
2368 DEBUG(D_tls) debug_printf("client requested resumption\n");
2369 }
2370 if (gnutls_session_is_resumed(state->session))
2371 {
2372 tls_in.resumption |= RESUME_USED;
2373 DEBUG(D_tls) debug_printf("Session resumed\n");
2374 }
2375 }
2376 #endif
2377 /* ------------------------------------------------------------------------ */
2378 /* Exported functions */
2379
2380
2381
2382
2383 /*************************************************
2384 * Start a TLS session in a server *
2385 *************************************************/
2386
2387 /* This is called when Exim is running as a server, after having received
2388 the STARTTLS command. It must respond to that command, and then negotiate
2389 a TLS session.
2390
2391 Arguments:
2392 require_ciphers list of allowed ciphers or NULL
2393 errstr pointer to error string
2394
2395 Returns: OK on success
2396 DEFER for errors before the start of the negotiation
2397 FAIL for errors during the negotiation; the server can't
2398 continue running.
2399 */
2400
2401 int
2402 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2403 {
2404 int rc;
2405 exim_gnutls_state_st * state = NULL;
2406
2407 /* Check for previous activation */
2408 if (tls_in.active.sock >= 0)
2409 {
2410 tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr);
2411 smtp_printf("554 Already in TLS\r\n", FALSE);
2412 return FAIL;
2413 }
2414
2415 /* Initialize the library. If it fails, it will already have logged the error
2416 and sent an SMTP response. */
2417
2418 DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n");
2419
2420 {
2421 #ifdef MEASURE_TIMING
2422 struct timeval t0;
2423 gettimeofday(&t0, NULL);
2424 #endif
2425
2426 if ((rc = tls_init(NULL, tls_certificate, tls_privatekey,
2427 NULL, tls_verify_certificates, tls_crl,
2428 require_ciphers, &state, &tls_in, errstr)) != OK) return rc;
2429
2430 #ifdef MEASURE_TIMING
2431 report_time_since(&t0, US"server tls_init (delta)");
2432 #endif
2433 }
2434
2435 #ifdef EXPERIMENTAL_TLS_RESUME
2436 tls_server_resume_prehandshake(state);
2437 #endif
2438
2439 /* If this is a host for which certificate verification is mandatory or
2440 optional, set up appropriately. */
2441
2442 if (verify_check_host(&tls_verify_hosts) == OK)
2443 {
2444 DEBUG(D_tls)
2445 debug_printf("TLS: a client certificate will be required.\n");
2446 state->verify_requirement = VERIFY_REQUIRED;
2447 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2448 }
2449 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2450 {
2451 DEBUG(D_tls)
2452 debug_printf("TLS: a client certificate will be requested but not required.\n");
2453 state->verify_requirement = VERIFY_OPTIONAL;
2454 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2455 }
2456 else
2457 {
2458 DEBUG(D_tls)
2459 debug_printf("TLS: a client certificate will not be requested.\n");
2460 state->verify_requirement = VERIFY_NONE;
2461 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2462 }
2463
2464 #ifndef DISABLE_EVENT
2465 if (event_action)
2466 {
2467 state->event_action = event_action;
2468 gnutls_session_set_ptr(state->session, state);
2469 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2470 }
2471 #endif
2472
2473 /* Register SNI handling; always, even if not in tls_certificate, so that the
2474 expansion variable $tls_sni is always available. */
2475
2476 gnutls_handshake_set_post_client_hello_function(state->session,
2477 exim_sni_handling_cb);
2478
2479 /* Set context and tell client to go ahead, except in the case of TLS startup
2480 on connection, where outputting anything now upsets the clients and tends to
2481 make them disconnect. We need to have an explicit fflush() here, to force out
2482 the response. Other smtp_printf() calls do not need it, because in non-TLS
2483 mode, the fflush() happens when smtp_getc() is called. */
2484
2485 if (!state->tlsp->on_connect)
2486 {
2487 smtp_printf("220 TLS go ahead\r\n", FALSE);
2488 fflush(smtp_out);
2489 }
2490
2491 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2492 that the GnuTLS library doesn't.
2493 From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you
2494 to set (and clear down afterwards) up a pull-timeout callback function that does
2495 a select, so we're no better off unless avoiding signals becomes an issue. */
2496
2497 gnutls_transport_set_ptr2(state->session,
2498 (gnutls_transport_ptr_t)(long) fileno(smtp_in),
2499 (gnutls_transport_ptr_t)(long) fileno(smtp_out));
2500 state->fd_in = fileno(smtp_in);
2501 state->fd_out = fileno(smtp_out);
2502
2503 sigalrm_seen = FALSE;
2504 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2505 do
2506 rc = gnutls_handshake(state->session);
2507 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2508 ALARM_CLR(0);
2509
2510 if (rc != GNUTLS_E_SUCCESS)
2511 {
2512 /* It seems that, except in the case of a timeout, we have to close the
2513 connection right here; otherwise if the other end is running OpenSSL it hangs
2514 until the server times out. */
2515
2516 if (sigalrm_seen)
2517 {
2518 tls_error(US"gnutls_handshake", US"timed out", NULL, errstr);
2519 gnutls_db_remove_session(state->session);
2520 }
2521 else
2522 {
2523 tls_error_gnu(US"gnutls_handshake", rc, NULL, errstr);
2524 (void) gnutls_alert_send_appropriate(state->session, rc);
2525 gnutls_deinit(state->session);
2526 gnutls_certificate_free_credentials(state->x509_cred);
2527 millisleep(500);
2528 shutdown(state->fd_out, SHUT_WR);
2529 for (int i = 1024; fgetc(smtp_in) != EOF && i > 0; ) i--; /* drain skt */
2530 (void)fclose(smtp_out);
2531 (void)fclose(smtp_in);
2532 smtp_out = smtp_in = NULL;
2533 }
2534
2535 return FAIL;
2536 }
2537
2538 #ifdef GNUTLS_SFLAGS_EXT_MASTER_SECRET
2539 if (gnutls_session_get_flags(state->session) & GNUTLS_SFLAGS_EXT_MASTER_SECRET)
2540 tls_in.ext_master_secret = TRUE;
2541 #endif
2542
2543 #ifdef EXPERIMENTAL_TLS_RESUME
2544 tls_server_resume_posthandshake(state);
2545 #endif
2546
2547 DEBUG(D_tls) post_handshake_debug(state);
2548
2549 /* Verify after the fact */
2550
2551 if (!verify_certificate(state, errstr))
2552 {
2553 if (state->verify_requirement != VERIFY_OPTIONAL)
2554 {
2555 (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr);
2556 return FAIL;
2557 }
2558 DEBUG(D_tls)
2559 debug_printf("TLS: continuing on only because verification was optional, after: %s\n",
2560 *errstr);
2561 }
2562
2563 /* Sets various Exim expansion variables; always safe within server */
2564
2565 extract_exim_vars_from_tls_state(state);
2566
2567 /* TLS has been set up. Adjust the input functions to read via TLS,
2568 and initialize appropriately. */
2569
2570 state->xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2571
2572 receive_getc = tls_getc;
2573 receive_getbuf = tls_getbuf;
2574 receive_get_cache = tls_get_cache;
2575 receive_ungetc = tls_ungetc;
2576 receive_feof = tls_feof;
2577 receive_ferror = tls_ferror;
2578 receive_smtp_buffered = tls_smtp_buffered;
2579
2580 return OK;
2581 }
2582
2583
2584
2585
2586 static void
2587 tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state,
2588 smtp_transport_options_block * ob)
2589 {
2590 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2591 {
2592 state->exp_tls_verify_cert_hostnames =
2593 #ifdef SUPPORT_I18N
2594 string_domain_utf8_to_alabel(host->name, NULL);
2595 #else
2596 host->name;
2597 #endif
2598 DEBUG(D_tls)
2599 debug_printf("TLS: server cert verification includes hostname: \"%s\".\n",
2600 state->exp_tls_verify_cert_hostnames);
2601 }
2602 }
2603
2604
2605
2606
2607 #ifdef SUPPORT_DANE
2608 /* Given our list of RRs from the TLSA lookup, build a lookup block in
2609 GnuTLS-DANE's preferred format. Hang it on the state str for later
2610 use in DANE verification.
2611
2612 We point at the dnsa data not copy it, so it must remain valid until
2613 after verification is done.*/
2614
2615 static BOOL
2616 dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa)
2617 {
2618 dns_scan dnss;
2619 int i;
2620 const char ** dane_data;
2621 int * dane_data_len;
2622
2623 i = 1;
2624 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2625 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2626 ) if (rr->type == T_TLSA) i++;
2627
2628 dane_data = store_get(i * sizeof(uschar *), FALSE);
2629 dane_data_len = store_get(i * sizeof(int), FALSE);
2630
2631 i = 0;
2632 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2633 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2634 ) if (rr->type == T_TLSA && rr->size > 3)
2635 {
2636 const uschar * p = rr->data;
2637 /*XXX need somehow to mark rr and its data as tainted. Doues this mean copying it? */
2638 uint8_t usage = p[0], sel = p[1], type = p[2];
2639
2640 DEBUG(D_tls)
2641 debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size);
2642
2643 if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE)
2644 || (sel != 0 && sel != 1)
2645 )
2646 continue;
2647 switch(type)
2648 {
2649 case 0: /* Full: cannot check at present */
2650 break;
2651 case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */
2652 break;
2653 case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */
2654 break;
2655 default: continue;
2656 }
2657
2658 tls_out.tlsa_usage |= 1<<usage;
2659 dane_data[i] = CS p;
2660 dane_data_len[i++] = rr->size;
2661 }
2662
2663 if (!i) return FALSE;
2664
2665 dane_data[i] = NULL;
2666 dane_data_len[i] = 0;
2667
2668 state->dane_data = (char * const *)dane_data;
2669 state->dane_data_len = dane_data_len;
2670 return TRUE;
2671 }
2672 #endif
2673
2674
2675
2676 #ifdef EXPERIMENTAL_TLS_RESUME
2677 /* On the client, get any stashed session for the given IP from hints db
2678 and apply it to the ssl-connection for attempted resumption. Although
2679 there is a gnutls_session_ticket_enable_client() interface it is
2680 documented as unnecessary (as of 3.6.7) as "session tickets are emabled
2681 by deafult". There seems to be no way to disable them, so even hosts not
2682 enabled by the transport option will be sent a ticket request. We will
2683 however avoid storing and retrieving session information. */
2684
2685 static void
2686 tls_retrieve_session(tls_support * tlsp, gnutls_session_t session,
2687 host_item * host, smtp_transport_options_block * ob)
2688 {
2689 tlsp->resumption = RESUME_SUPPORTED;
2690 if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK)
2691 {
2692 dbdata_tls_session * dt;
2693 int len, rc;
2694 open_db dbblock, * dbm_file;
2695
2696 DEBUG(D_tls)
2697 debug_printf("check for resumable session for %s\n", host->address);
2698 tlsp->host_resumable = TRUE;
2699 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
2700 if ((dbm_file = dbfn_open(US"tls", O_RDONLY, &dbblock, FALSE, FALSE)))
2701 {
2702 /* Key for the db is the IP. We'd like to filter the retrieved session
2703 for ticket advisory expiry, but 3.6.1 seems to give no access to that */
2704
2705 if ((dt = dbfn_read_with_length(dbm_file, host->address, &len)))
2706 if (!(rc = gnutls_session_set_data(session,
2707 CUS dt->session, (size_t)len - sizeof(dbdata_tls_session))))
2708 {
2709 DEBUG(D_tls) debug_printf("good session\n");
2710 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
2711 }
2712 else DEBUG(D_tls) debug_printf("setting session resumption data: %s\n",
2713 US gnutls_strerror(rc));
2714 dbfn_close(dbm_file);
2715 }
2716 }
2717 }
2718
2719
2720 static void
2721 tls_save_session(tls_support * tlsp, gnutls_session_t session, const host_item * host)
2722 {
2723 /* TLS 1.2 - we get both the callback and the direct posthandshake call,
2724 but this flag is not set until the second. TLS 1.3 it's the other way about.
2725 Keep both calls as the session data cannot be extracted before handshake
2726 completes. */
2727
2728 if (gnutls_session_get_flags(session) & GNUTLS_SFLAGS_SESSION_TICKET)
2729 {
2730 gnutls_datum_t tkt;
2731 int rc;
2732
2733 DEBUG(D_tls) debug_printf("server offered session ticket\n");
2734 tlsp->ticket_received = TRUE;
2735 tlsp->resumption |= RESUME_SERVER_TICKET;
2736
2737 if (tlsp->host_resumable)
2738 if (!(rc = gnutls_session_get_data2(session, &tkt)))
2739 {
2740 open_db dbblock, * dbm_file;
2741 int dlen = sizeof(dbdata_tls_session) + tkt.size;
2742 dbdata_tls_session * dt = store_get(dlen, TRUE);
2743
2744 DEBUG(D_tls) debug_printf("session data size %u\n", (unsigned)tkt.size);
2745 memcpy(dt->session, tkt.data, tkt.size);
2746 gnutls_free(tkt.data);
2747
2748 if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE)))
2749 {
2750 /* key for the db is the IP */
2751 dbfn_delete(dbm_file, host->address);
2752 dbfn_write(dbm_file, host->address, dt, dlen);
2753 dbfn_close(dbm_file);
2754
2755 DEBUG(D_tls)
2756 debug_printf("wrote session db (len %u)\n", (unsigned)dlen);
2757 }
2758 }
2759 else DEBUG(D_tls)
2760 debug_printf("extract session data: %s\n", US gnutls_strerror(rc));
2761 }
2762 }
2763
2764
2765 /* With a TLS1.3 session, the ticket(s) are not seen until
2766 the first data read is attempted. And there's often two of them.
2767 Pick them up with this callback. We are also called for 1.2
2768 but we do nothing.
2769 */
2770 static int
2771 tls_client_ticket_cb(gnutls_session_t sess, u_int htype, unsigned when,
2772 unsigned incoming, const gnutls_datum_t * msg)
2773 {
2774 exim_gnutls_state_st * state = gnutls_session_get_ptr(sess);
2775 tls_support * tlsp = state->tlsp;
2776
2777 DEBUG(D_tls) debug_printf("newticket cb\n");
2778
2779 if (!tlsp->ticket_received)
2780 tls_save_session(tlsp, sess, state->host);
2781 return 0;
2782 }
2783
2784
2785 static void
2786 tls_client_resume_prehandshake(exim_gnutls_state_st * state,
2787 tls_support * tlsp, host_item * host,
2788 smtp_transport_options_block * ob)
2789 {
2790 gnutls_session_set_ptr(state->session, state);
2791 gnutls_handshake_set_hook_function(state->session,
2792 GNUTLS_HANDSHAKE_NEW_SESSION_TICKET, GNUTLS_HOOK_POST, tls_client_ticket_cb);
2793
2794 tls_retrieve_session(tlsp, state->session, host, ob);
2795 }
2796
2797 static void
2798 tls_client_resume_posthandshake(exim_gnutls_state_st * state,
2799 tls_support * tlsp, host_item * host)
2800 {
2801 if (gnutls_session_is_resumed(state->session))
2802 {
2803 DEBUG(D_tls) debug_printf("Session resumed\n");
2804 tlsp->resumption |= RESUME_USED;
2805 }
2806
2807 tls_save_session(tlsp, state->session, host);
2808 }
2809 #endif /* EXPERIMENTAL_TLS_RESUME */
2810
2811
2812 /*************************************************
2813 * Start a TLS session in a client *
2814 *************************************************/
2815
2816 /* Called from the smtp transport after STARTTLS has been accepted.
2817
2818 Arguments:
2819 cctx connection context
2820 conn_args connection details
2821 cookie datum for randomness (not used)
2822 tlsp record details of channel configuration here; must be non-NULL
2823 errstr error string pointer
2824
2825 Returns: TRUE for success with TLS session context set in smtp context,
2826 FALSE on error
2827 */
2828
2829 BOOL
2830 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
2831 void * cookie ARG_UNUSED,
2832 tls_support * tlsp, uschar ** errstr)
2833 {
2834 host_item * host = conn_args->host; /* for msgs and option-tests */
2835 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
2836 smtp_transport_options_block * ob = tb
2837 ? (smtp_transport_options_block *)tb->options_block
2838 : &smtp_transport_option_defaults;
2839 int rc;
2840 exim_gnutls_state_st * state = NULL;
2841 uschar * cipher_list = NULL;
2842
2843 #ifndef DISABLE_OCSP
2844 BOOL require_ocsp =
2845 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2846 BOOL request_ocsp = require_ocsp ? TRUE
2847 : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2848 #endif
2849
2850 DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", cctx->sock);
2851
2852 #ifdef SUPPORT_DANE
2853 /* If dane is flagged, have either request or require dane for this host, and
2854 a TLSA record found. Therefore, dane verify required. Which implies cert must
2855 be requested and supplied, dane verify must pass, and cert verify irrelevant
2856 (incl. hostnames), and (caller handled) require_tls */
2857
2858 if (conn_args->dane && ob->dane_require_tls_ciphers)
2859 {
2860 /* not using expand_check_tlsvar because not yet in state */
2861 if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2862 &cipher_list, errstr))
2863 return FALSE;
2864 cipher_list = cipher_list && *cipher_list
2865 ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers;
2866 }
2867 #endif
2868
2869 if (!cipher_list)
2870 cipher_list = ob->tls_require_ciphers;
2871
2872 {
2873 #ifdef MEASURE_TIMING
2874 struct timeval t0;
2875 gettimeofday(&t0, NULL);
2876 #endif
2877
2878 if (tls_init(host, ob->tls_certificate, ob->tls_privatekey,
2879 ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl,
2880 cipher_list, &state, tlsp, errstr) != OK)
2881 return FALSE;
2882
2883 #ifdef MEASURE_TIMING
2884 report_time_since(&t0, US"client tls_init (delta)");
2885 #endif
2886 }
2887
2888 {
2889 int dh_min_bits = ob->tls_dh_min_bits;
2890 if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS)
2891 {
2892 DEBUG(D_tls)
2893 debug_printf("WARNING: tls_dh_min_bits far too low,"
2894 " clamping %d up to %d\n",
2895 dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS);
2896 dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS;
2897 }
2898
2899 DEBUG(D_tls) debug_printf("Setting D-H prime minimum"
2900 " acceptable bits to %d\n",
2901 dh_min_bits);
2902 gnutls_dh_set_prime_bits(state->session, dh_min_bits);
2903 }
2904
2905 /* Stick to the old behaviour for compatibility if tls_verify_certificates is
2906 set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only
2907 the specified host patterns if one of them is defined */
2908
2909 #ifdef SUPPORT_DANE
2910 if (conn_args->dane && dane_tlsa_load(state, &conn_args->tlsa_dnsa))
2911 {
2912 DEBUG(D_tls)
2913 debug_printf("TLS: server certificate DANE required.\n");
2914 state->verify_requirement = VERIFY_DANE;
2915 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2916 }
2917 else
2918 #endif
2919 if ( ( state->exp_tls_verify_certificates
2920 && !ob->tls_verify_hosts
2921 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2922 )
2923 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2924 )
2925 {
2926 tls_client_setup_hostname_checks(host, state, ob);
2927 DEBUG(D_tls)
2928 debug_printf("TLS: server certificate verification required.\n");
2929 state->verify_requirement = VERIFY_REQUIRED;
2930 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE);
2931 }
2932 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2933 {
2934 tls_client_setup_hostname_checks(host, state, ob);
2935 DEBUG(D_tls)
2936 debug_printf("TLS: server certificate verification optional.\n");
2937 state->verify_requirement = VERIFY_OPTIONAL;
2938 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST);
2939 }
2940 else
2941 {
2942 DEBUG(D_tls)
2943 debug_printf("TLS: server certificate verification not required.\n");
2944 state->verify_requirement = VERIFY_NONE;
2945 gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE);
2946 }
2947
2948 #ifndef DISABLE_OCSP
2949 /* supported since GnuTLS 3.1.3 */
2950 if (request_ocsp)
2951 {
2952 DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n");
2953 if ((rc = gnutls_ocsp_status_request_enable_client(state->session,
2954 NULL, 0, NULL)) != OK)
2955 {
2956 tls_error_gnu(US"cert-status-req", rc, state->host, errstr);
2957 return FALSE;
2958 }
2959 tlsp->ocsp = OCSP_NOT_RESP;
2960 }
2961 #endif
2962
2963 #ifdef EXPERIMENTAL_TLS_RESUME
2964 tls_client_resume_prehandshake(state, tlsp, host, ob);
2965 #endif
2966
2967 #ifndef DISABLE_EVENT
2968 if (tb && tb->event_action)
2969 {
2970 state->event_action = tb->event_action;
2971 gnutls_session_set_ptr(state->session, state);
2972 gnutls_certificate_set_verify_function(state->x509_cred, verify_cb);
2973 }
2974 #endif
2975
2976 gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) cctx->sock);
2977 state->fd_in = cctx->sock;
2978 state->fd_out = cctx->sock;
2979
2980 DEBUG(D_tls) debug_printf("about to gnutls_handshake\n");
2981 /* There doesn't seem to be a built-in timeout on connection. */
2982
2983 sigalrm_seen = FALSE;
2984 ALARM(ob->command_timeout);
2985 do
2986 rc = gnutls_handshake(state->session);
2987 while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen);
2988 ALARM_CLR(0);
2989
2990 if (rc != GNUTLS_E_SUCCESS)
2991 {
2992 if (sigalrm_seen)
2993 {
2994 gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED);
2995 tls_error(US"gnutls_handshake", US"timed out", state->host, errstr);
2996 }
2997 else
2998 tls_error_gnu(US"gnutls_handshake", rc, state->host, errstr);
2999 return FALSE;
3000 }
3001
3002 DEBUG(D_tls) post_handshake_debug(state);
3003
3004 /* Verify late */
3005
3006 if (!verify_certificate(state, errstr))
3007 {
3008 tls_error(US"certificate verification failed", *errstr, state->host, errstr);
3009 return FALSE;
3010 }
3011
3012 #ifdef GNUTLS_SFLAGS_EXT_MASTER_SECRET
3013 if (gnutls_session_get_flags(state->session) & GNUTLS_SFLAGS_EXT_MASTER_SECRET)
3014 tlsp->ext_master_secret = TRUE;
3015 #endif
3016
3017 #ifndef DISABLE_OCSP
3018 if (request_ocsp)
3019 {
3020 DEBUG(D_tls)
3021 {
3022 gnutls_datum_t stapling;
3023 gnutls_ocsp_resp_t resp;
3024 gnutls_datum_t printed;
3025 unsigned idx = 0;
3026
3027 for (;
3028 # ifdef GNUTLS_OCSP_STATUS_REQUEST_GET2
3029 (rc = gnutls_ocsp_status_request_get2(state->session, idx, &stapling)) == 0;
3030 #else
3031 (rc = gnutls_ocsp_status_request_get(state->session, &stapling)) == 0;
3032 #endif
3033 idx++)
3034 if ( (rc= gnutls_ocsp_resp_init(&resp)) == 0
3035 && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0
3036 && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_COMPACT, &printed)) == 0
3037 )
3038 {
3039 debug_printf("%.4096s", printed.data);
3040 gnutls_free(printed.data);
3041 }
3042 else
3043 (void) tls_error_gnu(US"ocsp decode", rc, state->host, errstr);
3044 if (idx == 0 && rc)
3045 (void) tls_error_gnu(US"ocsp decode", rc, state->host, errstr);
3046 }
3047
3048 if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0)
3049 {
3050 tlsp->ocsp = OCSP_FAILED;
3051 tls_error(US"certificate status check failed", NULL, state->host, errstr);
3052 if (require_ocsp)
3053 return FALSE;
3054 }
3055 else
3056 {
3057 DEBUG(D_tls) debug_printf("Passed OCSP checking\n");
3058 tlsp->ocsp = OCSP_VFIED;
3059 }
3060 }
3061 #endif
3062
3063 #ifdef EXPERIMENTAL_TLS_RESUME
3064 tls_client_resume_posthandshake(state, tlsp, host);
3065 #endif
3066
3067 /* Sets various Exim expansion variables; may need to adjust for ACL callouts */
3068
3069 extract_exim_vars_from_tls_state(state);
3070
3071 cctx->tls_ctx = state;
3072 return TRUE;
3073 }
3074
3075
3076
3077
3078 /*************************************************
3079 * Close down a TLS session *
3080 *************************************************/
3081
3082 /* This is also called from within a delivery subprocess forked from the
3083 daemon, to shut down the TLS library, without actually doing a shutdown (which
3084 would tamper with the TLS session in the parent process).
3085
3086 Arguments:
3087 ct_ctx client context pointer, or NULL for the one global server context
3088 shutdown 1 if TLS close-alert is to be sent,
3089 2 if also response to be waited for
3090
3091 Returns: nothing
3092 */
3093
3094 void
3095 tls_close(void * ct_ctx, int shutdown)
3096 {
3097 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
3098 tls_support * tlsp = state->tlsp;
3099
3100 if (!tlsp || tlsp->active.sock < 0) return; /* TLS was not active */
3101
3102 if (shutdown)
3103 {
3104 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3105 shutdown > 1 ? " (with response-wait)" : "");
3106
3107 ALARM(2);
3108 gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
3109 ALARM_CLR(0);
3110 }
3111
3112 if (!ct_ctx) /* server */
3113 {
3114 receive_getc = smtp_getc;
3115 receive_getbuf = smtp_getbuf;
3116 receive_get_cache = smtp_get_cache;
3117 receive_ungetc = smtp_ungetc;
3118 receive_feof = smtp_feof;
3119 receive_ferror = smtp_ferror;
3120 receive_smtp_buffered = smtp_buffered;
3121 }
3122
3123 gnutls_deinit(state->session);
3124 gnutls_certificate_free_credentials(state->x509_cred);
3125
3126 tlsp->active.sock = -1;
3127 tlsp->active.tls_ctx = NULL;
3128 /* Leave bits, peercert, cipher, peerdn, certificate_verified set, for logging */
3129 tlsp->channelbinding = NULL;
3130
3131
3132 if (state->xfer_buffer) store_free(state->xfer_buffer);
3133 memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init));
3134 }
3135
3136
3137
3138
3139 static BOOL
3140 tls_refill(unsigned lim)
3141 {
3142 exim_gnutls_state_st * state = &state_server;
3143 ssize_t inbytes;
3144
3145 DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n",
3146 state->session, state->xfer_buffer, ssl_xfer_buffer_size);
3147
3148 sigalrm_seen = FALSE;
3149 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
3150
3151 do
3152 inbytes = gnutls_record_recv(state->session, state->xfer_buffer,
3153 MIN(ssl_xfer_buffer_size, lim));
3154 while (inbytes == GNUTLS_E_AGAIN);
3155
3156 if (smtp_receive_timeout > 0) ALARM_CLR(0);
3157
3158 if (had_command_timeout) /* set by signal handler */
3159 smtp_command_timeout_exit(); /* does not return */
3160 if (had_command_sigterm)
3161 smtp_command_sigterm_exit();
3162 if (had_data_timeout)
3163 smtp_data_timeout_exit();
3164 if (had_data_sigint)
3165 smtp_data_sigint_exit();
3166
3167 /* Timeouts do not get this far. A zero-byte return appears to mean that the
3168 TLS session has been closed down, not that the socket itself has been closed
3169 down. Revert to non-TLS handling. */
3170
3171 if (sigalrm_seen)
3172 {
3173 DEBUG(D_tls) debug_printf("Got tls read timeout\n");
3174 state->xfer_error = TRUE;
3175 return FALSE;
3176 }
3177
3178 else if (inbytes == 0)
3179 {
3180 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
3181 tls_close(NULL, TLS_NO_SHUTDOWN);
3182 return FALSE;
3183 }
3184
3185 /* Handle genuine errors */
3186
3187 else if (inbytes < 0)
3188 {
3189 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
3190 record_io_error(state, (int) inbytes, US"recv", NULL);
3191 state->xfer_error = TRUE;
3192 return FALSE;
3193 }
3194 #ifndef DISABLE_DKIM
3195 dkim_exim_verify_feed(state->xfer_buffer, inbytes);
3196 #endif
3197 state->xfer_buffer_hwm = (int) inbytes;
3198 state->xfer_buffer_lwm = 0;
3199 return TRUE;
3200 }
3201
3202 /*************************************************
3203 * TLS version of getc *
3204 *************************************************/
3205
3206 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
3207 it refills the buffer via the GnuTLS reading function.
3208 Only used by the server-side TLS.
3209
3210 This feeds DKIM and should be used for all message-body reads.
3211
3212 Arguments: lim Maximum amount to read/buffer
3213 Returns: the next character or EOF
3214 */
3215
3216 int
3217 tls_getc(unsigned lim)
3218 {
3219 exim_gnutls_state_st * state = &state_server;
3220
3221 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
3222 if (!tls_refill(lim))
3223 return state->xfer_error ? EOF : smtp_getc(lim);
3224
3225 /* Something in the buffer; return next uschar */
3226
3227 return state->xfer_buffer[state->xfer_buffer_lwm++];
3228 }
3229
3230 uschar *
3231 tls_getbuf(unsigned * len)
3232 {
3233 exim_gnutls_state_st * state = &state_server;
3234 unsigned size;
3235 uschar * buf;
3236
3237 if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm)
3238 if (!tls_refill(*len))
3239 {
3240 if (!state->xfer_error) return smtp_getbuf(len);
3241 *len = 0;
3242 return NULL;
3243 }
3244
3245 if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len)
3246 size = *len;
3247 buf = &state->xfer_buffer[state->xfer_buffer_lwm];
3248 state->xfer_buffer_lwm += size;
3249 *len = size;
3250 return buf;
3251 }
3252
3253
3254 void
3255 tls_get_cache()
3256 {
3257 #ifndef DISABLE_DKIM
3258 exim_gnutls_state_st * state = &state_server;
3259 int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm;
3260 if (n > 0)
3261 dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n);
3262 #endif
3263 }
3264
3265
3266 BOOL
3267 tls_could_read(void)
3268 {
3269 return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm
3270 || gnutls_record_check_pending(state_server.session) > 0;
3271 }
3272
3273
3274
3275
3276 /*************************************************
3277 * Read bytes from TLS channel *
3278 *************************************************/
3279
3280 /* This does not feed DKIM, so if the caller uses this for reading message body,
3281 then the caller must feed DKIM.
3282
3283 Arguments:
3284 ct_ctx client context pointer, or NULL for the one global server context
3285 buff buffer of data
3286 len size of buffer
3287
3288 Returns: the number of bytes read
3289 -1 after a failed read, including EOF
3290 */
3291
3292 int
3293 tls_read(void * ct_ctx, uschar *buff, size_t len)
3294 {
3295 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
3296 ssize_t inbytes;
3297
3298 if (len > INT_MAX)
3299 len = INT_MAX;
3300
3301 if (state->xfer_buffer_lwm < state->xfer_buffer_hwm)
3302 DEBUG(D_tls)
3303 debug_printf("*** PROBABLY A BUG *** " \
3304 "tls_read() called with data in the tls_getc() buffer, %d ignored\n",
3305 state->xfer_buffer_hwm - state->xfer_buffer_lwm);
3306
3307 DEBUG(D_tls)
3308 debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n",
3309 state->session, buff, len);
3310
3311 do
3312 inbytes = gnutls_record_recv(state->session, buff, len);
3313 while (inbytes == GNUTLS_E_AGAIN);
3314
3315 if (inbytes > 0) return inbytes;
3316 if (inbytes == 0)
3317 {
3318 DEBUG(D_tls) debug_printf("Got TLS_EOF\n");
3319 }
3320 else
3321 {
3322 DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv\n", __FUNCTION__);
3323 record_io_error(state, (int)inbytes, US"recv", NULL);
3324 }
3325
3326 return -1;
3327 }
3328
3329
3330
3331
3332 /*************************************************
3333 * Write bytes down TLS channel *
3334 *************************************************/
3335
3336 /*
3337 Arguments:
3338 ct_ctx client context pointer, or NULL for the one global server context
3339 buff buffer of data
3340 len number of bytes
3341 more more data expected soon
3342
3343 Calling with len zero and more unset will flush buffered writes. The buff
3344 argument can be null for that case.
3345
3346 Returns: the number of bytes after a successful write,
3347 -1 after a failed write
3348 */
3349
3350 int
3351 tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more)
3352 {
3353 ssize_t outbytes;
3354 size_t left = len;
3355 exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server;
3356 #ifdef SUPPORT_CORK
3357
3358 if (more && !state->corked) gnutls_record_cork(state->session);
3359 #endif
3360
3361 DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__,
3362 buff, left, more ? ", more" : "");
3363
3364 while (left > 0)
3365 {
3366 DEBUG(D_tls) debug_printf("gnutls_record_send(%p, %p, " SIZE_T_FMT ")\n",
3367 state->session, buff, left);
3368
3369 do
3370 outbytes = gnutls_record_send(state->session, buff, left);
3371 while (outbytes == GNUTLS_E_AGAIN);
3372
3373 DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes);
3374 if (outbytes < 0)
3375 {
3376 DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__);
3377 record_io_error(state, outbytes, US"send", NULL);
3378 return -1;
3379 }
3380 if (outbytes == 0)
3381 {
3382 record_io_error(state, 0, US"send", US"TLS channel closed on write");
3383 return -1;
3384 }
3385
3386 left -= outbytes;
3387 buff += outbytes;
3388 }
3389
3390 if (len > INT_MAX)
3391 {
3392 DEBUG(D_tls)
3393 debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n",
3394 len);
3395 len = INT_MAX;
3396 }
3397
3398 #ifdef SUPPORT_CORK
3399 if (more != state->corked)
3400 {
3401 if (!more) (void) gnutls_record_uncork(state->session, 0);
3402 state->corked = more;
3403 }
3404 #endif
3405
3406 return (int) len;
3407 }
3408
3409
3410
3411
3412 /*************************************************
3413 * Random number generation *
3414 *************************************************/
3415
3416 /* Pseudo-random number generation. The result is not expected to be
3417 cryptographically strong but not so weak that someone will shoot themselves
3418 in the foot using it as a nonce in input in some email header scheme or
3419 whatever weirdness they'll twist this into. The result should handle fork()
3420 and avoid repeating sequences. OpenSSL handles that for us.
3421
3422 Arguments:
3423 max range maximum
3424 Returns a random number in range [0, max-1]
3425 */
3426
3427 #ifdef HAVE_GNUTLS_RND
3428 int
3429 vaguely_random_number(int max)
3430 {
3431 unsigned int r;
3432 int i, needed_len;
3433 uschar smallbuf[sizeof(r)];
3434
3435 if (max <= 1)
3436 return 0;
3437
3438 needed_len = sizeof(r);
3439 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3440 asked for a number less than 10. */
3441
3442 for (r = max, i = 0; r; ++i)
3443 r >>= 1;
3444 i = (i + 7) / 8;
3445 if (i < needed_len)
3446 needed_len = i;
3447
3448 i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len);
3449 if (i < 0)
3450 {
3451 DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n");
3452 return vaguely_random_number_fallback(max);
3453 }
3454 r = 0;
3455 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3456 r = r * 256 + *p;
3457
3458 /* We don't particularly care about weighted results; if someone wants
3459 * smooth distribution and cares enough then they should submit a patch then. */
3460 return r % max;
3461 }
3462 #else /* HAVE_GNUTLS_RND */