GnuTLS: Move to more-modern stapling API
[exim.git] / src / src / tls-openssl.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2019 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 /* Portions Copyright (c) The OpenSSL Project 1999 */
9
10 /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL
11 library. It is #included into the tls.c file when that library is used. The
12 code herein is based on a patch that was originally contributed by Steve
13 Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara.
14
15 No cryptographic code is included in Exim. All this module does is to call
16 functions from the OpenSSL library. */
17
18
19 /* Heading stuff */
20
21 #include <openssl/lhash.h>
22 #include <openssl/ssl.h>
23 #include <openssl/err.h>
24 #include <openssl/rand.h>
25 #ifndef OPENSSL_NO_ECDH
26 # include <openssl/ec.h>
27 #endif
28 #ifndef DISABLE_OCSP
29 # include <openssl/ocsp.h>
30 #endif
31 #ifdef SUPPORT_DANE
32 # include "danessl.h"
33 #endif
34
35
36 #ifndef DISABLE_OCSP
37 # define EXIM_OCSP_SKEW_SECONDS (300L)
38 # define EXIM_OCSP_MAX_AGE (-1L)
39 #endif
40
41 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
42 # define EXIM_HAVE_OPENSSL_TLSEXT
43 #endif
44 #if OPENSSL_VERSION_NUMBER >= 0x00908000L
45 # define EXIM_HAVE_RSA_GENKEY_EX
46 #endif
47 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
48 # define EXIM_HAVE_OCSP_RESP_COUNT
49 #else
50 # define EXIM_HAVE_EPHEM_RSA_KEX
51 # define EXIM_HAVE_RAND_PSEUDO
52 #endif
53 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
54 # define EXIM_HAVE_SHA256
55 #endif
56
57 /* X509_check_host provides sane certificate hostname checking, but was added
58 to OpenSSL late, after other projects forked off the code-base. So in
59 addition to guarding against the base version number, beware that LibreSSL
60 does not (at this time) support this function.
61
62 If LibreSSL gains a different API, perhaps via libtls, then we'll probably
63 opt to disentangle and ask a LibreSSL user to provide glue for a third
64 crypto provider for libtls instead of continuing to tie the OpenSSL glue
65 into even twistier knots. If LibreSSL gains the same API, we can just
66 change this guard and punt the issue for a while longer. */
67
68 #ifndef LIBRESSL_VERSION_NUMBER
69 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
70 # define EXIM_HAVE_OPENSSL_CHECKHOST
71 # define EXIM_HAVE_OPENSSL_DH_BITS
72 # define EXIM_HAVE_OPENSSL_TLS_METHOD
73 # define EXIM_HAVE_OPENSSL_KEYLOG
74 # define EXIM_HAVE_OPENSSL_CIPHER_GET_ID
75 # define EXIM_HAVE_SESSION_TICKET
76 # define EXIM_HAVE_OPESSL_TRACE
77 # else
78 # define EXIM_NEED_OPENSSL_INIT
79 # endif
80 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
81 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
82 # define EXIM_HAVE_OPENSSL_CHECKHOST
83 # endif
84 #endif
85
86 #if !defined(LIBRESSL_VERSION_NUMBER) \
87 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
88 # if !defined(OPENSSL_NO_ECDH)
89 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
90 # define EXIM_HAVE_ECDH
91 # endif
92 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
93 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
94 # endif
95 # endif
96 #endif
97
98 #ifndef LIBRESSL_VERSION_NUMBER
99 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
100 # define OPENSSL_HAVE_KEYLOG_CB
101 # define OPENSSL_HAVE_NUM_TICKETS
102 # define EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
103 # endif
104 #endif
105
106 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
107 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
108 # define DISABLE_OCSP
109 #endif
110
111 #ifdef EXPERIMENTAL_TLS_RESUME
112 # if OPENSSL_VERSION_NUMBER < 0x0101010L
113 # error OpenSSL version too old for session-resumption
114 # endif
115 #endif
116
117 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
118 # include <openssl/x509v3.h>
119 #endif
120
121 #ifndef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
122 # ifndef EXIM_HAVE_OPENSSL_CIPHER_GET_ID
123 # define SSL_CIPHER_get_id(c) (c->id)
124 # endif
125 # ifndef MACRO_PREDEF
126 # include "tls-cipher-stdname.c"
127 # endif
128 #endif
129
130 /*************************************************
131 * OpenSSL option parse *
132 *************************************************/
133
134 typedef struct exim_openssl_option {
135 uschar *name;
136 long value;
137 } exim_openssl_option;
138 /* We could use a macro to expand, but we need the ifdef and not all the
139 options document which version they were introduced in. Policylet: include
140 all options unless explicitly for DTLS, let the administrator choose which
141 to apply.
142
143 This list is current as of:
144 ==> 1.0.1b <==
145 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
146 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
147 */
148 static exim_openssl_option exim_openssl_options[] = {
149 /* KEEP SORTED ALPHABETICALLY! */
150 #ifdef SSL_OP_ALL
151 { US"all", (long) SSL_OP_ALL },
152 #endif
153 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
154 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
155 #endif
156 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
157 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
158 #endif
159 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
160 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
161 #endif
162 #ifdef SSL_OP_EPHEMERAL_RSA
163 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
164 #endif
165 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
166 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
167 #endif
168 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
169 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
170 #endif
171 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
172 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
173 #endif
174 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
175 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
176 #endif
177 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
178 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
179 #endif
180 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
181 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
182 #endif
183 #ifdef SSL_OP_NO_COMPRESSION
184 { US"no_compression", SSL_OP_NO_COMPRESSION },
185 #endif
186 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
187 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
188 #endif
189 #ifdef SSL_OP_NO_SSLv2
190 { US"no_sslv2", SSL_OP_NO_SSLv2 },
191 #endif
192 #ifdef SSL_OP_NO_SSLv3
193 { US"no_sslv3", SSL_OP_NO_SSLv3 },
194 #endif
195 #ifdef SSL_OP_NO_TICKET
196 { US"no_ticket", SSL_OP_NO_TICKET },
197 #endif
198 #ifdef SSL_OP_NO_TLSv1
199 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
200 #endif
201 #ifdef SSL_OP_NO_TLSv1_1
202 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
203 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
204 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
205 #else
206 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
207 #endif
208 #endif
209 #ifdef SSL_OP_NO_TLSv1_2
210 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
211 #endif
212 #ifdef SSL_OP_NO_TLSv1_3
213 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
214 #endif
215 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
216 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
217 #endif
218 #ifdef SSL_OP_SINGLE_DH_USE
219 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
220 #endif
221 #ifdef SSL_OP_SINGLE_ECDH_USE
222 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
223 #endif
224 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
225 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
226 #endif
227 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
228 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
229 #endif
230 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
231 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
232 #endif
233 #ifdef SSL_OP_TLS_D5_BUG
234 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
235 #endif
236 #ifdef SSL_OP_TLS_ROLLBACK_BUG
237 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
238 #endif
239 };
240
241 #ifndef MACRO_PREDEF
242 static int exim_openssl_options_size = nelem(exim_openssl_options);
243 #endif
244
245 #ifdef MACRO_PREDEF
246 void
247 options_tls(void)
248 {
249 uschar buf[64];
250
251 for (struct exim_openssl_option * o = exim_openssl_options;
252 o < exim_openssl_options + nelem(exim_openssl_options); o++)
253 {
254 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
255 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
256
257 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
258 builtin_macro_create(buf);
259 }
260
261 # ifdef EXPERIMENTAL_TLS_RESUME
262 builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING );
263 # endif
264 }
265 #else
266
267 /******************************************************************************/
268
269 /* Structure for collecting random data for seeding. */
270
271 typedef struct randstuff {
272 struct timeval tv;
273 pid_t p;
274 } randstuff;
275
276 /* Local static variables */
277
278 static BOOL client_verify_callback_called = FALSE;
279 static BOOL server_verify_callback_called = FALSE;
280 static const uschar *sid_ctx = US"exim";
281
282 /* We have three different contexts to care about.
283
284 Simple case: client, `client_ctx`
285 As a client, we can be doing a callout or cut-through delivery while receiving
286 a message. So we have a client context, which should have options initialised
287 from the SMTP Transport. We may also concurrently want to make TLS connections
288 to utility daemons, so client-contexts are allocated and passed around in call
289 args rather than using a gobal.
290
291 Server:
292 There are two cases: with and without ServerNameIndication from the client.
293 Given TLS SNI, we can be using different keys, certs and various other
294 configuration settings, because they're re-expanded with $tls_sni set. This
295 allows vhosting with TLS. This SNI is sent in the handshake.
296 A client might not send SNI, so we need a fallback, and an initial setup too.
297 So as a server, we start out using `server_ctx`.
298 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
299 `server_sni` from `server_ctx` and then initialise settings by re-expanding
300 configuration.
301 */
302
303 typedef struct {
304 SSL_CTX * ctx;
305 SSL * ssl;
306 gstring * corked;
307 } exim_openssl_client_tls_ctx;
308
309 static SSL_CTX *server_ctx = NULL;
310 static SSL *server_ssl = NULL;
311
312 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
313 static SSL_CTX *server_sni = NULL;
314 #endif
315
316 static char ssl_errstring[256];
317
318 static int ssl_session_timeout = 7200; /* Two hours */
319 static BOOL client_verify_optional = FALSE;
320 static BOOL server_verify_optional = FALSE;
321
322 static BOOL reexpand_tls_files_for_sni = FALSE;
323
324
325 typedef struct tls_ext_ctx_cb {
326 tls_support * tlsp;
327 uschar *certificate;
328 uschar *privatekey;
329 BOOL is_server;
330 #ifndef DISABLE_OCSP
331 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
332 union {
333 struct {
334 uschar *file;
335 uschar *file_expanded;
336 OCSP_RESPONSE *response;
337 } server;
338 struct {
339 X509_STORE *verify_store; /* non-null if status requested */
340 BOOL verify_required;
341 } client;
342 } u_ocsp;
343 #endif
344 uschar *dhparam;
345 /* these are cached from first expand */
346 uschar *server_cipher_list;
347 /* only passed down to tls_error: */
348 host_item *host;
349 const uschar * verify_cert_hostnames;
350 #ifndef DISABLE_EVENT
351 uschar * event_action;
352 #endif
353 } tls_ext_ctx_cb;
354
355 /* should figure out a cleanup of API to handle state preserved per
356 implementation, for various reasons, which can be void * in the APIs.
357 For now, we hack around it. */
358 tls_ext_ctx_cb *client_static_cbinfo = NULL; /*XXX should not use static; multiple concurrent clients! */
359 tls_ext_ctx_cb *server_static_cbinfo = NULL;
360
361 static int
362 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
363 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
364
365 /* Callbacks */
366 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
367 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
368 #endif
369 #ifndef DISABLE_OCSP
370 static int tls_server_stapling_cb(SSL *s, void *arg);
371 #endif
372
373
374
375 /* Daemon-called, before every connection, key create/rotate */
376 #ifdef EXPERIMENTAL_TLS_RESUME
377 static void tk_init(void);
378 static int tls_exdata_idx = -1;
379 #endif
380
381 void
382 tls_daemon_init(void)
383 {
384 #ifdef EXPERIMENTAL_TLS_RESUME
385 tk_init();
386 #endif
387 return;
388 }
389
390
391 /*************************************************
392 * Handle TLS error *
393 *************************************************/
394
395 /* Called from lots of places when errors occur before actually starting to do
396 the TLS handshake, that is, while the session is still in clear. Always returns
397 DEFER for a server and FAIL for a client so that most calls can use "return
398 tls_error(...)" to do this processing and then give an appropriate return. A
399 single function is used for both server and client, because it is called from
400 some shared functions.
401
402 Argument:
403 prefix text to include in the logged error
404 host NULL if setting up a server;
405 the connected host if setting up a client
406 msg error message or NULL if we should ask OpenSSL
407 errstr pointer to output error message
408
409 Returns: OK/DEFER/FAIL
410 */
411
412 static int
413 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
414 {
415 if (!msg)
416 {
417 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
418 msg = US ssl_errstring;
419 }
420
421 msg = string_sprintf("(%s): %s", prefix, msg);
422 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
423 if (errstr) *errstr = msg;
424 return host ? FAIL : DEFER;
425 }
426
427
428
429 /*************************************************
430 * Callback to generate RSA key *
431 *************************************************/
432
433 /*
434 Arguments:
435 s SSL connection (not used)
436 export not used
437 keylength keylength
438
439 Returns: pointer to generated key
440 */
441
442 static RSA *
443 rsa_callback(SSL *s, int export, int keylength)
444 {
445 RSA *rsa_key;
446 #ifdef EXIM_HAVE_RSA_GENKEY_EX
447 BIGNUM *bn = BN_new();
448 #endif
449
450 export = export; /* Shut picky compilers up */
451 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
452
453 #ifdef EXIM_HAVE_RSA_GENKEY_EX
454 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
455 || !(rsa_key = RSA_new())
456 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
457 )
458 #else
459 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
460 #endif
461
462 {
463 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
464 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
465 ssl_errstring);
466 return NULL;
467 }
468 return rsa_key;
469 }
470
471
472
473 /* Extreme debug
474 #ifndef DISABLE_OCSP
475 void
476 x509_store_dump_cert_s_names(X509_STORE * store)
477 {
478 STACK_OF(X509_OBJECT) * roots= store->objs;
479 static uschar name[256];
480
481 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
482 {
483 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
484 if(tmp_obj->type == X509_LU_X509)
485 {
486 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
487 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
488 {
489 name[sizeof(name)-1] = '\0';
490 debug_printf(" %s\n", name);
491 }
492 }
493 }
494 }
495 #endif
496 */
497
498
499 #ifndef DISABLE_EVENT
500 static int
501 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
502 BOOL *calledp, const BOOL *optionalp, const uschar * what)
503 {
504 uschar * ev;
505 uschar * yield;
506 X509 * old_cert;
507
508 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
509 if (ev)
510 {
511 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
512 old_cert = tlsp->peercert;
513 tlsp->peercert = X509_dup(cert);
514 /* NB we do not bother setting peerdn */
515 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
516 {
517 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
518 "depth=%d cert=%s: %s",
519 tlsp == &tls_out ? deliver_host_address : sender_host_address,
520 what, depth, dn, yield);
521 *calledp = TRUE;
522 if (!*optionalp)
523 {
524 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
525 return 1; /* reject (leaving peercert set) */
526 }
527 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
528 "(host in tls_try_verify_hosts)\n");
529 tlsp->verify_override = TRUE;
530 }
531 X509_free(tlsp->peercert);
532 tlsp->peercert = old_cert;
533 }
534 return 0;
535 }
536 #endif
537
538 /*************************************************
539 * Callback for verification *
540 *************************************************/
541
542 /* The SSL library does certificate verification if set up to do so. This
543 callback has the current yes/no state is in "state". If verification succeeded,
544 we set the certificate-verified flag. If verification failed, what happens
545 depends on whether the client is required to present a verifiable certificate
546 or not.
547
548 If verification is optional, we change the state to yes, but still log the
549 verification error. For some reason (it really would help to have proper
550 documentation of OpenSSL), this callback function then gets called again, this
551 time with state = 1. We must take care not to set the private verified flag on
552 the second time through.
553
554 Note: this function is not called if the client fails to present a certificate
555 when asked. We get here only if a certificate has been received. Handling of
556 optional verification for this case is done when requesting SSL to verify, by
557 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
558
559 May be called multiple times for different issues with a certificate, even
560 for a given "depth" in the certificate chain.
561
562 Arguments:
563 preverify_ok current yes/no state as 1/0
564 x509ctx certificate information.
565 tlsp per-direction (client vs. server) support data
566 calledp has-been-called flag
567 optionalp verification-is-optional flag
568
569 Returns: 0 if verification should fail, otherwise 1
570 */
571
572 static int
573 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
574 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
575 {
576 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
577 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
578 uschar dn[256];
579
580 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
581 {
582 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
583 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
584 tlsp == &tls_out ? deliver_host_address : sender_host_address);
585 return 0;
586 }
587 dn[sizeof(dn)-1] = '\0';
588
589 tlsp->verify_override = FALSE;
590 if (preverify_ok == 0)
591 {
592 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
593 *verify_mode, sender_host_address)
594 : US"";
595 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
596 tlsp == &tls_out ? deliver_host_address : sender_host_address,
597 extra, depth,
598 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
599 *calledp = TRUE;
600 if (!*optionalp)
601 {
602 if (!tlsp->peercert)
603 tlsp->peercert = X509_dup(cert); /* record failing cert */
604 return 0; /* reject */
605 }
606 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
607 "tls_try_verify_hosts)\n");
608 tlsp->verify_override = TRUE;
609 }
610
611 else if (depth != 0)
612 {
613 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
614 #ifndef DISABLE_OCSP
615 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
616 { /* client, wanting stapling */
617 /* Add the server cert's signing chain as the one
618 for the verification of the OCSP stapled information. */
619
620 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
621 cert))
622 ERR_clear_error();
623 sk_X509_push(client_static_cbinfo->verify_stack, cert);
624 }
625 #endif
626 #ifndef DISABLE_EVENT
627 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
628 return 0; /* reject, with peercert set */
629 #endif
630 }
631 else
632 {
633 const uschar * verify_cert_hostnames;
634
635 if ( tlsp == &tls_out
636 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
637 /* client, wanting hostname check */
638 {
639
640 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
641 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
642 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
643 # endif
644 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
645 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
646 # endif
647 int sep = 0;
648 const uschar * list = verify_cert_hostnames;
649 uschar * name;
650 int rc;
651 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
652 if ((rc = X509_check_host(cert, CCS name, 0,
653 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
654 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
655 NULL)))
656 {
657 if (rc < 0)
658 {
659 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
660 tlsp == &tls_out ? deliver_host_address : sender_host_address);
661 name = NULL;
662 }
663 break;
664 }
665 if (!name)
666 #else
667 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
668 #endif
669 {
670 uschar * extra = verify_mode
671 ? string_sprintf(" (during %c-verify for [%s])",
672 *verify_mode, sender_host_address)
673 : US"";
674 log_write(0, LOG_MAIN,
675 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
676 tlsp == &tls_out ? deliver_host_address : sender_host_address,
677 extra, dn, verify_cert_hostnames);
678 *calledp = TRUE;
679 if (!*optionalp)
680 {
681 if (!tlsp->peercert)
682 tlsp->peercert = X509_dup(cert); /* record failing cert */
683 return 0; /* reject */
684 }
685 DEBUG(D_tls) debug_printf("SSL verify name failure overridden (host in "
686 "tls_try_verify_hosts)\n");
687 tlsp->verify_override = TRUE;
688 }
689 }
690
691 #ifndef DISABLE_EVENT
692 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
693 return 0; /* reject, with peercert set */
694 #endif
695
696 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
697 *calledp ? "" : " authenticated", dn);
698 *calledp = TRUE;
699 }
700
701 return 1; /* accept, at least for this level */
702 }
703
704 static int
705 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
706 {
707 return verify_callback(preverify_ok, x509ctx, &tls_out,
708 &client_verify_callback_called, &client_verify_optional);
709 }
710
711 static int
712 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
713 {
714 return verify_callback(preverify_ok, x509ctx, &tls_in,
715 &server_verify_callback_called, &server_verify_optional);
716 }
717
718
719 #ifdef SUPPORT_DANE
720
721 /* This gets called *by* the dane library verify callback, which interposes
722 itself.
723 */
724 static int
725 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
726 {
727 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
728 uschar dn[256];
729 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
730 #ifndef DISABLE_EVENT
731 BOOL dummy_called, optional = FALSE;
732 #endif
733
734 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
735 {
736 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
737 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
738 deliver_host_address);
739 return 0;
740 }
741 dn[sizeof(dn)-1] = '\0';
742
743 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
744 preverify_ok ? "ok":"BAD", depth, dn);
745
746 #ifndef DISABLE_EVENT
747 if (verify_event(&tls_out, cert, depth, dn,
748 &dummy_called, &optional, US"DANE"))
749 return 0; /* reject, with peercert set */
750 #endif
751
752 if (preverify_ok == 1)
753 {
754 tls_out.dane_verified = TRUE;
755 #ifndef DISABLE_OCSP
756 if (client_static_cbinfo->u_ocsp.client.verify_store)
757 { /* client, wanting stapling */
758 /* Add the server cert's signing chain as the one
759 for the verification of the OCSP stapled information. */
760
761 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
762 cert))
763 ERR_clear_error();
764 sk_X509_push(client_static_cbinfo->verify_stack, cert);
765 }
766 #endif
767 }
768 else
769 {
770 int err = X509_STORE_CTX_get_error(x509ctx);
771 DEBUG(D_tls)
772 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
773 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
774 preverify_ok = 1;
775 }
776 return preverify_ok;
777 }
778
779 #endif /*SUPPORT_DANE*/
780
781
782 /*************************************************
783 * Information callback *
784 *************************************************/
785
786 /* The SSL library functions call this from time to time to indicate what they
787 are doing. We copy the string to the debugging output when TLS debugging has
788 been requested.
789
790 Arguments:
791 s the SSL connection
792 where
793 ret
794
795 Returns: nothing
796 */
797
798 static void
799 info_callback(SSL *s, int where, int ret)
800 {
801 DEBUG(D_tls)
802 {
803 const uschar * str;
804
805 if (where & SSL_ST_CONNECT)
806 str = US"SSL_connect";
807 else if (where & SSL_ST_ACCEPT)
808 str = US"SSL_accept";
809 else
810 str = US"SSL info (undefined)";
811
812 if (where & SSL_CB_LOOP)
813 debug_printf("%s: %s\n", str, SSL_state_string_long(s));
814 else if (where & SSL_CB_ALERT)
815 debug_printf("SSL3 alert %s:%s:%s\n",
816 str = where & SSL_CB_READ ? US"read" : US"write",
817 SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
818 else if (where & SSL_CB_EXIT)
819 if (ret == 0)
820 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
821 else if (ret < 0)
822 debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
823 else if (where & SSL_CB_HANDSHAKE_START)
824 debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
825 else if (where & SSL_CB_HANDSHAKE_DONE)
826 debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
827 }
828 }
829
830 #ifdef OPENSSL_HAVE_KEYLOG_CB
831 static void
832 keylog_callback(const SSL *ssl, const char *line)
833 {
834 DEBUG(D_tls) debug_printf("%.200s\n", line);
835 }
836 #endif
837
838
839 #ifdef EXPERIMENTAL_TLS_RESUME
840 /* Manage the keysets used for encrypting the session tickets, on the server. */
841
842 typedef struct { /* Session ticket encryption key */
843 uschar name[16];
844
845 const EVP_CIPHER * aes_cipher;
846 uschar aes_key[32]; /* size needed depends on cipher. aes_128 implies 128/8 = 16? */
847 const EVP_MD * hmac_hash;
848 uschar hmac_key[16];
849 time_t renew;
850 time_t expire;
851 } exim_stek;
852
853 static exim_stek exim_tk; /* current key */
854 static exim_stek exim_tk_old; /* previous key */
855
856 static void
857 tk_init(void)
858 {
859 time_t t = time(NULL);
860
861 if (exim_tk.name[0])
862 {
863 if (exim_tk.renew >= t) return;
864 exim_tk_old = exim_tk;
865 }
866
867 if (f.running_in_test_harness) ssl_session_timeout = 6;
868
869 DEBUG(D_tls) debug_printf("OpenSSL: %s STEK\n", exim_tk.name[0] ? "rotating" : "creating");
870 if (RAND_bytes(exim_tk.aes_key, sizeof(exim_tk.aes_key)) <= 0) return;
871 if (RAND_bytes(exim_tk.hmac_key, sizeof(exim_tk.hmac_key)) <= 0) return;
872 if (RAND_bytes(exim_tk.name+1, sizeof(exim_tk.name)-1) <= 0) return;
873
874 exim_tk.name[0] = 'E';
875 exim_tk.aes_cipher = EVP_aes_256_cbc();
876 exim_tk.hmac_hash = EVP_sha256();
877 exim_tk.expire = t + ssl_session_timeout;
878 exim_tk.renew = t + ssl_session_timeout/2;
879 }
880
881 static exim_stek *
882 tk_current(void)
883 {
884 if (!exim_tk.name[0]) return NULL;
885 return &exim_tk;
886 }
887
888 static exim_stek *
889 tk_find(const uschar * name)
890 {
891 return memcmp(name, exim_tk.name, sizeof(exim_tk.name)) == 0 ? &exim_tk
892 : memcmp(name, exim_tk_old.name, sizeof(exim_tk_old.name)) == 0 ? &exim_tk_old
893 : NULL;
894 }
895
896 /* Callback for session tickets, on server */
897 static int
898 ticket_key_callback(SSL * ssl, uschar key_name[16],
899 uschar * iv, EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int enc)
900 {
901 tls_support * tlsp = server_static_cbinfo->tlsp;
902 exim_stek * key;
903
904 if (enc)
905 {
906 DEBUG(D_tls) debug_printf("ticket_key_callback: create new session\n");
907 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
908
909 if (RAND_bytes(iv, EVP_MAX_IV_LENGTH) <= 0)
910 return -1; /* insufficient random */
911
912 if (!(key = tk_current())) /* current key doesn't exist or isn't valid */
913 return 0; /* key couldn't be created */
914 memcpy(key_name, key->name, 16);
915 DEBUG(D_tls) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - time(NULL));
916
917 /*XXX will want these dependent on the ssl session strength */
918 HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
919 key->hmac_hash, NULL);
920 EVP_EncryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv);
921
922 DEBUG(D_tls) debug_printf("ticket created\n");
923 return 1;
924 }
925 else
926 {
927 time_t now = time(NULL);
928
929 DEBUG(D_tls) debug_printf("ticket_key_callback: retrieve session\n");
930 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
931
932 if (!(key = tk_find(key_name)) || key->expire < now)
933 {
934 DEBUG(D_tls)
935 {
936 debug_printf("ticket not usable (%s)\n", key ? "expired" : "not found");
937 if (key) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - now);
938 }
939 return 0;
940 }
941
942 HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
943 key->hmac_hash, NULL);
944 EVP_DecryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv);
945
946 DEBUG(D_tls) debug_printf("ticket usable, STEK expire " TIME_T_FMT "\n", key->expire - now);
947
948 /* The ticket lifetime and renewal are the same as the STEK lifetime and
949 renewal, which is overenthusiastic. A factor of, say, 3x longer STEK would
950 be better. To do that we'd have to encode ticket lifetime in the name as
951 we don't yet see the restored session. Could check posthandshake for TLS1.3
952 and trigger a new ticket then, but cannot do that for TLS1.2 */
953 return key->renew < now ? 2 : 1;
954 }
955 }
956 #endif
957
958
959
960 /*************************************************
961 * Initialize for DH *
962 *************************************************/
963
964 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
965
966 Arguments:
967 sctx The current SSL CTX (inbound or outbound)
968 dhparam DH parameter file or fixed parameter identity string
969 host connected host, if client; NULL if server
970 errstr error string pointer
971
972 Returns: TRUE if OK (nothing to set up, or setup worked)
973 */
974
975 static BOOL
976 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
977 {
978 BIO *bio;
979 DH *dh;
980 uschar *dhexpanded;
981 const char *pem;
982 int dh_bitsize;
983
984 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
985 return FALSE;
986
987 if (!dhexpanded || !*dhexpanded)
988 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
989 else if (dhexpanded[0] == '/')
990 {
991 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
992 {
993 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
994 host, US strerror(errno), errstr);
995 return FALSE;
996 }
997 }
998 else
999 {
1000 if (Ustrcmp(dhexpanded, "none") == 0)
1001 {
1002 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
1003 return TRUE;
1004 }
1005
1006 if (!(pem = std_dh_prime_named(dhexpanded)))
1007 {
1008 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
1009 host, US strerror(errno), errstr);
1010 return FALSE;
1011 }
1012 bio = BIO_new_mem_buf(CS pem, -1);
1013 }
1014
1015 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
1016 {
1017 BIO_free(bio);
1018 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
1019 host, NULL, errstr);
1020 return FALSE;
1021 }
1022
1023 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
1024 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
1025 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
1026 * If someone wants to dance at the edge, then they can raise the limit or use
1027 * current libraries. */
1028 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
1029 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
1030 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
1031 dh_bitsize = DH_bits(dh);
1032 #else
1033 dh_bitsize = 8 * DH_size(dh);
1034 #endif
1035
1036 /* Even if it is larger, we silently return success rather than cause things
1037 * to fail out, so that a too-large DH will not knock out all TLS; it's a
1038 * debatable choice. */
1039 if (dh_bitsize > tls_dh_max_bits)
1040 {
1041 DEBUG(D_tls)
1042 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
1043 dh_bitsize, tls_dh_max_bits);
1044 }
1045 else
1046 {
1047 SSL_CTX_set_tmp_dh(sctx, dh);
1048 DEBUG(D_tls)
1049 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
1050 dhexpanded ? dhexpanded : US"default", dh_bitsize);
1051 }
1052
1053 DH_free(dh);
1054 BIO_free(bio);
1055
1056 return TRUE;
1057 }
1058
1059
1060
1061
1062 /*************************************************
1063 * Initialize for ECDH *
1064 *************************************************/
1065
1066 /* Load parameters for ECDH encryption.
1067
1068 For now, we stick to NIST P-256 because: it's simple and easy to configure;
1069 it avoids any patent issues that might bite redistributors; despite events in
1070 the news and concerns over curve choices, we're not cryptographers, we're not
1071 pretending to be, and this is "good enough" to be better than no support,
1072 protecting against most adversaries. Given another year or two, there might
1073 be sufficient clarity about a "right" way forward to let us make an informed
1074 decision, instead of a knee-jerk reaction.
1075
1076 Longer-term, we should look at supporting both various named curves and
1077 external files generated with "openssl ecparam", much as we do for init_dh().
1078 We should also support "none" as a value, to explicitly avoid initialisation.
1079
1080 Patches welcome.
1081
1082 Arguments:
1083 sctx The current SSL CTX (inbound or outbound)
1084 host connected host, if client; NULL if server
1085 errstr error string pointer
1086
1087 Returns: TRUE if OK (nothing to set up, or setup worked)
1088 */
1089
1090 static BOOL
1091 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
1092 {
1093 #ifdef OPENSSL_NO_ECDH
1094 return TRUE;
1095 #else
1096
1097 EC_KEY * ecdh;
1098 uschar * exp_curve;
1099 int nid;
1100 BOOL rv;
1101
1102 if (host) /* No ECDH setup for clients, only for servers */
1103 return TRUE;
1104
1105 # ifndef EXIM_HAVE_ECDH
1106 DEBUG(D_tls)
1107 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
1108 return TRUE;
1109 # else
1110
1111 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
1112 return FALSE;
1113 if (!exp_curve || !*exp_curve)
1114 return TRUE;
1115
1116 /* "auto" needs to be handled carefully.
1117 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
1118 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
1119 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
1120 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
1121 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
1122 */
1123 if (Ustrcmp(exp_curve, "auto") == 0)
1124 {
1125 #if OPENSSL_VERSION_NUMBER < 0x10002000L
1126 DEBUG(D_tls) debug_printf(
1127 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
1128 exp_curve = US"prime256v1";
1129 #else
1130 # if defined SSL_CTRL_SET_ECDH_AUTO
1131 DEBUG(D_tls) debug_printf(
1132 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
1133 SSL_CTX_set_ecdh_auto(sctx, 1);
1134 return TRUE;
1135 # else
1136 DEBUG(D_tls) debug_printf(
1137 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
1138 return TRUE;
1139 # endif
1140 #endif
1141 }
1142
1143 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
1144 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
1145 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
1146 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
1147 # endif
1148 )
1149 {
1150 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
1151 host, NULL, errstr);
1152 return FALSE;
1153 }
1154
1155 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
1156 {
1157 tls_error(US"Unable to create ec curve", host, NULL, errstr);
1158 return FALSE;
1159 }
1160
1161 /* The "tmp" in the name here refers to setting a temporary key
1162 not to the stability of the interface. */
1163
1164 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
1165 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
1166 else
1167 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1168
1169 EC_KEY_free(ecdh);
1170 return !rv;
1171
1172 # endif /*EXIM_HAVE_ECDH*/
1173 #endif /*OPENSSL_NO_ECDH*/
1174 }
1175
1176
1177
1178
1179 #ifndef DISABLE_OCSP
1180 /*************************************************
1181 * Load OCSP information into state *
1182 *************************************************/
1183 /* Called to load the server OCSP response from the given file into memory, once
1184 caller has determined this is needed. Checks validity. Debugs a message
1185 if invalid.
1186
1187 ASSUMES: single response, for single cert.
1188
1189 Arguments:
1190 sctx the SSL_CTX* to update
1191 cbinfo various parts of session state
1192 expanded the filename putatively holding an OCSP response
1193
1194 */
1195
1196 static void
1197 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
1198 {
1199 BIO * bio;
1200 OCSP_RESPONSE * resp;
1201 OCSP_BASICRESP * basic_response;
1202 OCSP_SINGLERESP * single_response;
1203 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1204 STACK_OF(X509) * sk;
1205 unsigned long verify_flags;
1206 int status, reason, i;
1207
1208 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
1209 if (cbinfo->u_ocsp.server.response)
1210 {
1211 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
1212 cbinfo->u_ocsp.server.response = NULL;
1213 }
1214
1215 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
1216 {
1217 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1218 cbinfo->u_ocsp.server.file_expanded);
1219 return;
1220 }
1221
1222 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1223 BIO_free(bio);
1224 if (!resp)
1225 {
1226 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1227 return;
1228 }
1229
1230 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1231 {
1232 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1233 OCSP_response_status_str(status), status);
1234 goto bad;
1235 }
1236
1237 if (!(basic_response = OCSP_response_get1_basic(resp)))
1238 {
1239 DEBUG(D_tls)
1240 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1241 goto bad;
1242 }
1243
1244 sk = cbinfo->verify_stack;
1245 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1246
1247 /* May need to expose ability to adjust those flags?
1248 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1249 OCSP_TRUSTOTHER OCSP_NOINTERN */
1250
1251 /* This does a full verify on the OCSP proof before we load it for serving
1252 up; possibly overkill - just date-checks might be nice enough.
1253
1254 OCSP_basic_verify takes a "store" arg, but does not
1255 use it for the chain verification, which is all we do
1256 when OCSP_NOVERIFY is set. The content from the wire
1257 "basic_response" and a cert-stack "sk" are all that is used.
1258
1259 We have a stack, loaded in setup_certs() if tls_verify_certificates
1260 was a file (not a directory, or "system"). It is unfortunate we
1261 cannot used the connection context store, as that would neatly
1262 handle the "system" case too, but there seems to be no library
1263 function for getting a stack from a store.
1264 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
1265 We do not free the stack since it could be needed a second time for
1266 SNI handling.
1267
1268 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1269 be a public interface into the OpenSSL library (there's no manual entry) -
1270 But what with? We also use OCSP_basic_verify in the client stapling callback.
1271 And there we NEED it; we must verify that status... unless the
1272 library does it for us anyway? */
1273
1274 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1275 {
1276 DEBUG(D_tls)
1277 {
1278 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1279 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1280 }
1281 goto bad;
1282 }
1283
1284 /* Here's the simplifying assumption: there's only one response, for the
1285 one certificate we use, and nothing for anything else in a chain. If this
1286 proves false, we need to extract a cert id from our issued cert
1287 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1288 right cert in the stack and then calls OCSP_single_get0_status()).
1289
1290 I'm hoping to avoid reworking a bunch more of how we handle state here. */
1291
1292 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1293 {
1294 DEBUG(D_tls)
1295 debug_printf("Unable to get first response from OCSP basic response.\n");
1296 goto bad;
1297 }
1298
1299 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1300 if (status != V_OCSP_CERTSTATUS_GOOD)
1301 {
1302 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1303 OCSP_cert_status_str(status), status,
1304 OCSP_crl_reason_str(reason), reason);
1305 goto bad;
1306 }
1307
1308 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1309 {
1310 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1311 goto bad;
1312 }
1313
1314 supply_response:
1315 /*XXX stack? (these tag points are for multiple leaf-cert support for ocsp */
1316 cbinfo->u_ocsp.server.response = resp;
1317 return;
1318
1319 bad:
1320 if (f.running_in_test_harness)
1321 {
1322 extern char ** environ;
1323 if (environ) for (uschar ** p = USS environ; *p; p++)
1324 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1325 {
1326 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1327 goto supply_response;
1328 }
1329 }
1330 return;
1331 }
1332 #endif /*!DISABLE_OCSP*/
1333
1334
1335
1336
1337 /* Create and install a selfsigned certificate, for use in server mode */
1338
1339 static int
1340 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1341 {
1342 X509 * x509 = NULL;
1343 EVP_PKEY * pkey;
1344 RSA * rsa;
1345 X509_NAME * name;
1346 uschar * where;
1347
1348 where = US"allocating pkey";
1349 if (!(pkey = EVP_PKEY_new()))
1350 goto err;
1351
1352 where = US"allocating cert";
1353 if (!(x509 = X509_new()))
1354 goto err;
1355
1356 where = US"generating pkey";
1357 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1358 goto err;
1359
1360 where = US"assigning pkey";
1361 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1362 goto err;
1363
1364 X509_set_version(x509, 2); /* N+1 - version 3 */
1365 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1366 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1367 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
1368 X509_set_pubkey(x509, pkey);
1369
1370 name = X509_get_subject_name(x509);
1371 X509_NAME_add_entry_by_txt(name, "C",
1372 MBSTRING_ASC, CUS "UK", -1, -1, 0);
1373 X509_NAME_add_entry_by_txt(name, "O",
1374 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1375 X509_NAME_add_entry_by_txt(name, "CN",
1376 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1377 X509_set_issuer_name(x509, name);
1378
1379 where = US"signing cert";
1380 if (!X509_sign(x509, pkey, EVP_md5()))
1381 goto err;
1382
1383 where = US"installing selfsign cert";
1384 if (!SSL_CTX_use_certificate(sctx, x509))
1385 goto err;
1386
1387 where = US"installing selfsign key";
1388 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1389 goto err;
1390
1391 return OK;
1392
1393 err:
1394 (void) tls_error(where, NULL, NULL, errstr);
1395 if (x509) X509_free(x509);
1396 if (pkey) EVP_PKEY_free(pkey);
1397 return DEFER;
1398 }
1399
1400
1401
1402
1403 static int
1404 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1405 uschar ** errstr)
1406 {
1407 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1408 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1409 return tls_error(string_sprintf(
1410 "SSL_CTX_use_certificate_chain_file file=%s", file),
1411 cbinfo->host, NULL, errstr);
1412 return 0;
1413 }
1414
1415 static int
1416 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1417 uschar ** errstr)
1418 {
1419 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1420 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1421 return tls_error(string_sprintf(
1422 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1423 return 0;
1424 }
1425
1426
1427 /*************************************************
1428 * Expand key and cert file specs *
1429 *************************************************/
1430
1431 /* Called once during tls_init and possibly again during TLS setup, for a
1432 new context, if Server Name Indication was used and tls_sni was seen in
1433 the certificate string.
1434
1435 Arguments:
1436 sctx the SSL_CTX* to update
1437 cbinfo various parts of session state
1438 errstr error string pointer
1439
1440 Returns: OK/DEFER/FAIL
1441 */
1442
1443 static int
1444 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1445 uschar ** errstr)
1446 {
1447 uschar *expanded;
1448
1449 if (!cbinfo->certificate)
1450 {
1451 if (!cbinfo->is_server) /* client */
1452 return OK;
1453 /* server */
1454 if (tls_install_selfsign(sctx, errstr) != OK)
1455 return DEFER;
1456 }
1457 else
1458 {
1459 int err;
1460
1461 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1462 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1463 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1464 )
1465 reexpand_tls_files_for_sni = TRUE;
1466
1467 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1468 return DEFER;
1469
1470 if (expanded)
1471 if (cbinfo->is_server)
1472 {
1473 const uschar * file_list = expanded;
1474 int sep = 0;
1475 uschar * file;
1476
1477 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1478 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1479 return err;
1480 }
1481 else /* would there ever be a need for multiple client certs? */
1482 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1483 return err;
1484
1485 if ( cbinfo->privatekey
1486 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1487 return DEFER;
1488
1489 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1490 of the expansion is an empty string, ignore it also, and assume the private
1491 key is in the same file as the certificate. */
1492
1493 if (expanded && *expanded)
1494 if (cbinfo->is_server)
1495 {
1496 const uschar * file_list = expanded;
1497 int sep = 0;
1498 uschar * file;
1499
1500 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1501 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1502 return err;
1503 }
1504 else /* would there ever be a need for multiple client certs? */
1505 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1506 return err;
1507 }
1508
1509 #ifndef DISABLE_OCSP
1510 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1511 {
1512 /*XXX stack*/
1513 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1514 return DEFER;
1515
1516 if (expanded && *expanded)
1517 {
1518 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1519 if ( cbinfo->u_ocsp.server.file_expanded
1520 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1521 {
1522 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1523 }
1524 else
1525 ocsp_load_response(sctx, cbinfo, expanded);
1526 }
1527 }
1528 #endif
1529
1530 return OK;
1531 }
1532
1533
1534
1535
1536 /*************************************************
1537 * Callback to handle SNI *
1538 *************************************************/
1539
1540 /* Called when acting as server during the TLS session setup if a Server Name
1541 Indication extension was sent by the client.
1542
1543 API documentation is OpenSSL s_server.c implementation.
1544
1545 Arguments:
1546 s SSL* of the current session
1547 ad unknown (part of OpenSSL API) (unused)
1548 arg Callback of "our" registered data
1549
1550 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1551
1552 XXX might need to change to using ClientHello callback,
1553 per https://www.openssl.org/docs/manmaster/man3/SSL_client_hello_cb_fn.html
1554 */
1555
1556 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1557 static int
1558 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1559 {
1560 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1561 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1562 int rc;
1563 int old_pool = store_pool;
1564 uschar * dummy_errstr;
1565
1566 if (!servername)
1567 return SSL_TLSEXT_ERR_OK;
1568
1569 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1570 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1571
1572 /* Make the extension value available for expansion */
1573 store_pool = POOL_PERM;
1574 tls_in.sni = string_copy_taint(US servername, TRUE);
1575 store_pool = old_pool;
1576
1577 if (!reexpand_tls_files_for_sni)
1578 return SSL_TLSEXT_ERR_OK;
1579
1580 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1581 not confident that memcpy wouldn't break some internal reference counting.
1582 Especially since there's a references struct member, which would be off. */
1583
1584 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1585 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1586 #else
1587 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1588 #endif
1589 {
1590 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1591 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1592 goto bad;
1593 }
1594
1595 /* Not sure how many of these are actually needed, since SSL object
1596 already exists. Might even need this selfsame callback, for reneg? */
1597
1598 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1599 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1600 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1601 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1602 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1603 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1604
1605 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1606 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1607 )
1608 goto bad;
1609
1610 if ( cbinfo->server_cipher_list
1611 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1612 goto bad;
1613
1614 #ifndef DISABLE_OCSP
1615 if (cbinfo->u_ocsp.server.file)
1616 {
1617 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1618 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1619 }
1620 #endif
1621
1622 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1623 verify_callback_server, &dummy_errstr)) != OK)
1624 goto bad;
1625
1626 /* do this after setup_certs, because this can require the certs for verifying
1627 OCSP information. */
1628 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1629 goto bad;
1630
1631 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1632 SSL_set_SSL_CTX(s, server_sni);
1633 return SSL_TLSEXT_ERR_OK;
1634
1635 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1636 }
1637 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1638
1639
1640
1641
1642 #ifndef DISABLE_OCSP
1643
1644 /*************************************************
1645 * Callback to handle OCSP Stapling *
1646 *************************************************/
1647
1648 /* Called when acting as server during the TLS session setup if the client
1649 requests OCSP information with a Certificate Status Request.
1650
1651 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1652 project.
1653
1654 */
1655
1656 static int
1657 tls_server_stapling_cb(SSL *s, void *arg)
1658 {
1659 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1660 uschar *response_der; /*XXX blob */
1661 int response_der_len;
1662
1663 /*XXX stack: use SSL_get_certificate() to see which cert; from that work
1664 out which ocsp blob to send. Unfortunately, SSL_get_certificate is known
1665 buggy in current OpenSSL; it returns the last cert loaded always rather than
1666 the one actually presented. So we can't support a stack of OCSP proofs at
1667 this time. */
1668
1669 DEBUG(D_tls)
1670 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1671 cbinfo->u_ocsp.server.response ? "have" : "lack");
1672
1673 tls_in.ocsp = OCSP_NOT_RESP;
1674 if (!cbinfo->u_ocsp.server.response)
1675 return SSL_TLSEXT_ERR_NOACK;
1676
1677 response_der = NULL;
1678 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response, /*XXX stack*/
1679 &response_der);
1680 if (response_der_len <= 0)
1681 return SSL_TLSEXT_ERR_NOACK;
1682
1683 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1684 tls_in.ocsp = OCSP_VFIED;
1685 return SSL_TLSEXT_ERR_OK;
1686 }
1687
1688
1689 static void
1690 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1691 {
1692 BIO_printf(bp, "\t%s: ", str);
1693 ASN1_GENERALIZEDTIME_print(bp, time);
1694 BIO_puts(bp, "\n");
1695 }
1696
1697 static int
1698 tls_client_stapling_cb(SSL *s, void *arg)
1699 {
1700 tls_ext_ctx_cb * cbinfo = arg;
1701 const unsigned char * p;
1702 int len;
1703 OCSP_RESPONSE * rsp;
1704 OCSP_BASICRESP * bs;
1705 int i;
1706
1707 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1708 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1709 if(!p)
1710 {
1711 /* Expect this when we requested ocsp but got none */
1712 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1713 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1714 else
1715 DEBUG(D_tls) debug_printf(" null\n");
1716 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1717 }
1718
1719 if (!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1720 {
1721 tls_out.ocsp = OCSP_FAILED; /*XXX should use tlsp-> to permit concurrent outbound */
1722 if (LOGGING(tls_cipher))
1723 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1724 else
1725 DEBUG(D_tls) debug_printf(" parse error\n");
1726 return 0;
1727 }
1728
1729 if (!(bs = OCSP_response_get1_basic(rsp)))
1730 {
1731 tls_out.ocsp = OCSP_FAILED;
1732 if (LOGGING(tls_cipher))
1733 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1734 else
1735 DEBUG(D_tls) debug_printf(" error parsing response\n");
1736 OCSP_RESPONSE_free(rsp);
1737 return 0;
1738 }
1739
1740 /* We'd check the nonce here if we'd put one in the request. */
1741 /* However that would defeat cacheability on the server so we don't. */
1742
1743 /* This section of code reworked from OpenSSL apps source;
1744 The OpenSSL Project retains copyright:
1745 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1746 */
1747 {
1748 BIO * bp = NULL;
1749 int status, reason;
1750 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1751
1752 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1753
1754 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1755
1756 /* Use the chain that verified the server cert to verify the stapled info */
1757 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1758
1759 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1760 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1761 {
1762 tls_out.ocsp = OCSP_FAILED;
1763 if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1764 "Received TLS cert status response, itself unverifiable: %s",
1765 ERR_reason_error_string(ERR_peek_error()));
1766 BIO_printf(bp, "OCSP response verify failure\n");
1767 ERR_print_errors(bp);
1768 OCSP_RESPONSE_print(bp, rsp, 0);
1769 goto failed;
1770 }
1771
1772 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1773
1774 /*XXX So we have a good stapled OCSP status. How do we know
1775 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1776 OCSP_resp_find_status() which matches on a cert id, which presumably
1777 we should use. Making an id needs OCSP_cert_id_new(), which takes
1778 issuerName, issuerKey, serialNumber. Are they all in the cert?
1779
1780 For now, carry on blindly accepting the resp. */
1781
1782 {
1783 OCSP_SINGLERESP * single;
1784
1785 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1786 if (OCSP_resp_count(bs) != 1)
1787 #else
1788 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1789 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1790 #endif
1791 {
1792 tls_out.ocsp = OCSP_FAILED;
1793 log_write(0, LOG_MAIN, "OCSP stapling "
1794 "with multiple responses not handled");
1795 goto failed;
1796 }
1797 single = OCSP_resp_get0(bs, 0);
1798 status = OCSP_single_get0_status(single, &reason, &rev,
1799 &thisupd, &nextupd);
1800 }
1801
1802 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1803 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1804 if (!OCSP_check_validity(thisupd, nextupd,
1805 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1806 {
1807 tls_out.ocsp = OCSP_FAILED;
1808 DEBUG(D_tls) ERR_print_errors(bp);
1809 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1810 }
1811 else
1812 {
1813 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1814 OCSP_cert_status_str(status));
1815 switch(status)
1816 {
1817 case V_OCSP_CERTSTATUS_GOOD:
1818 tls_out.ocsp = OCSP_VFIED;
1819 i = 1;
1820 goto good;
1821 case V_OCSP_CERTSTATUS_REVOKED:
1822 tls_out.ocsp = OCSP_FAILED;
1823 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1824 reason != -1 ? "; reason: " : "",
1825 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1826 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1827 break;
1828 default:
1829 tls_out.ocsp = OCSP_FAILED;
1830 log_write(0, LOG_MAIN,
1831 "Server certificate status unknown, in OCSP stapling");
1832 break;
1833 }
1834 }
1835 failed:
1836 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1837 good:
1838 BIO_free(bp);
1839 }
1840
1841 OCSP_RESPONSE_free(rsp);
1842 return i;
1843 }
1844 #endif /*!DISABLE_OCSP*/
1845
1846
1847 /*************************************************
1848 * Initialize for TLS *
1849 *************************************************/
1850
1851 /* Called from both server and client code, to do preliminary initialization
1852 of the library. We allocate and return a context structure.
1853
1854 Arguments:
1855 ctxp returned SSL context
1856 host connected host, if client; NULL if server
1857 dhparam DH parameter file
1858 certificate certificate file
1859 privatekey private key
1860 ocsp_file file of stapling info (server); flag for require ocsp (client)
1861 addr address if client; NULL if server (for some randomness)
1862 cbp place to put allocated callback context
1863 errstr error string pointer
1864
1865 Returns: OK/DEFER/FAIL
1866 */
1867
1868 static int
1869 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1870 uschar *privatekey,
1871 #ifndef DISABLE_OCSP
1872 uschar *ocsp_file, /*XXX stack, in server*/
1873 #endif
1874 address_item *addr, tls_ext_ctx_cb ** cbp,
1875 tls_support * tlsp,
1876 uschar ** errstr)
1877 {
1878 SSL_CTX * ctx;
1879 long init_options;
1880 int rc;
1881 tls_ext_ctx_cb * cbinfo;
1882
1883 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1884 cbinfo->tlsp = tlsp;
1885 cbinfo->certificate = certificate;
1886 cbinfo->privatekey = privatekey;
1887 cbinfo->is_server = host==NULL;
1888 #ifndef DISABLE_OCSP
1889 cbinfo->verify_stack = NULL;
1890 if (!host)
1891 {
1892 cbinfo->u_ocsp.server.file = ocsp_file;
1893 cbinfo->u_ocsp.server.file_expanded = NULL;
1894 cbinfo->u_ocsp.server.response = NULL;
1895 }
1896 else
1897 cbinfo->u_ocsp.client.verify_store = NULL;
1898 #endif
1899 cbinfo->dhparam = dhparam;
1900 cbinfo->server_cipher_list = NULL;
1901 cbinfo->host = host;
1902 #ifndef DISABLE_EVENT
1903 cbinfo->event_action = NULL;
1904 #endif
1905
1906 #ifdef EXIM_NEED_OPENSSL_INIT
1907 SSL_load_error_strings(); /* basic set up */
1908 OpenSSL_add_ssl_algorithms();
1909 #endif
1910
1911 #ifdef EXIM_HAVE_SHA256
1912 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1913 list of available digests. */
1914 EVP_add_digest(EVP_sha256());
1915 #endif
1916
1917 /* Create a context.
1918 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1919 negotiation in the different methods; as far as I can tell, the only
1920 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1921 when OpenSSL is built without SSLv2 support.
1922 By disabling with openssl_options, we can let admins re-enable with the
1923 existing knob. */
1924
1925 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1926 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
1927 #else
1928 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1929 #endif
1930 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1931
1932 /* It turns out that we need to seed the random number generator this early in
1933 order to get the full complement of ciphers to work. It took me roughly a day
1934 of work to discover this by experiment.
1935
1936 On systems that have /dev/urandom, SSL may automatically seed itself from
1937 there. Otherwise, we have to make something up as best we can. Double check
1938 afterwards. */
1939
1940 if (!RAND_status())
1941 {
1942 randstuff r;
1943 gettimeofday(&r.tv, NULL);
1944 r.p = getpid();
1945
1946 RAND_seed(US (&r), sizeof(r));
1947 RAND_seed(US big_buffer, big_buffer_size);
1948 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1949
1950 if (!RAND_status())
1951 return tls_error(US"RAND_status", host,
1952 US"unable to seed random number generator", errstr);
1953 }
1954
1955 /* Set up the information callback, which outputs if debugging is at a suitable
1956 level. */
1957
1958 DEBUG(D_tls)
1959 {
1960 SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1961 #if defined(EXIM_HAVE_OPESSL_TRACE) && !defined(OPENSSL_NO_SSL_TRACE)
1962 /* this needs a debug build of OpenSSL */
1963 SSL_CTX_set_msg_callback(ctx, (void (*)())SSL_trace);
1964 #endif
1965 #ifdef OPENSSL_HAVE_KEYLOG_CB
1966 SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
1967 #endif
1968 }
1969
1970 /* Automatically re-try reads/writes after renegotiation. */
1971 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1972
1973 /* Apply administrator-supplied work-arounds.
1974 Historically we applied just one requested option,
1975 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1976 moved to an administrator-controlled list of options to specify and
1977 grandfathered in the first one as the default value for "openssl_options".
1978
1979 No OpenSSL version number checks: the options we accept depend upon the
1980 availability of the option value macros from OpenSSL. */
1981
1982 if (!tls_openssl_options_parse(openssl_options, &init_options))
1983 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1984
1985 #ifdef EXPERIMENTAL_TLS_RESUME
1986 tlsp->resumption = RESUME_SUPPORTED;
1987 #endif
1988 if (init_options)
1989 {
1990 #ifdef EXPERIMENTAL_TLS_RESUME
1991 /* Should the server offer session resumption? */
1992 if (!host && verify_check_host(&tls_resumption_hosts) == OK)
1993 {
1994 DEBUG(D_tls) debug_printf("tls_resumption_hosts overrides openssl_options\n");
1995 init_options &= ~SSL_OP_NO_TICKET;
1996 tlsp->resumption |= RESUME_SERVER_TICKET; /* server will give ticket on request */
1997 tlsp->host_resumable = TRUE;
1998 }
1999 #endif
2000
2001 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
2002 if (!(SSL_CTX_set_options(ctx, init_options)))
2003 return tls_error(string_sprintf(
2004 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
2005 }
2006 else
2007 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
2008
2009 /* We'd like to disable session cache unconditionally, but foolish Outlook
2010 Express clients then give up the first TLS connection and make a second one
2011 (which works). Only when there is an IMAP service on the same machine.
2012 Presumably OE is trying to use the cache for A on B. Leave it enabled for
2013 now, until we work out a decent way of presenting control to the config. It
2014 will never be used because we use a new context every time. */
2015 #ifdef notdef
2016 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
2017 #endif
2018
2019 /* Initialize with DH parameters if supplied */
2020 /* Initialize ECDH temp key parameter selection */
2021
2022 if ( !init_dh(ctx, dhparam, host, errstr)
2023 || !init_ecdh(ctx, host, errstr)
2024 )
2025 return DEFER;
2026
2027 /* Set up certificate and key (and perhaps OCSP info) */
2028
2029 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
2030 return rc;
2031
2032 /* If we need to handle SNI or OCSP, do so */
2033
2034 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2035 # ifndef DISABLE_OCSP
2036 if (!(cbinfo->verify_stack = sk_X509_new_null()))
2037 {
2038 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
2039 return FAIL;
2040 }
2041 # endif
2042
2043 if (!host) /* server */
2044 {
2045 # ifndef DISABLE_OCSP
2046 /* We check u_ocsp.server.file, not server.response, because we care about if
2047 the option exists, not what the current expansion might be, as SNI might
2048 change the certificate and OCSP file in use between now and the time the
2049 callback is invoked. */
2050 if (cbinfo->u_ocsp.server.file)
2051 {
2052 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
2053 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2054 }
2055 # endif
2056 /* We always do this, so that $tls_sni is available even if not used in
2057 tls_certificate */
2058 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
2059 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
2060 }
2061 # ifndef DISABLE_OCSP
2062 else /* client */
2063 if(ocsp_file) /* wanting stapling */
2064 {
2065 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
2066 {
2067 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
2068 return FAIL;
2069 }
2070 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
2071 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2072 }
2073 # endif
2074 #endif
2075
2076 cbinfo->verify_cert_hostnames = NULL;
2077
2078 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
2079 /* Set up the RSA callback */
2080 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
2081 #endif
2082
2083 /* Finally, set the session cache timeout, and we are done.
2084 The period appears to be also used for (server-generated) session tickets */
2085
2086 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
2087 DEBUG(D_tls) debug_printf("Initialized TLS\n");
2088
2089 *cbp = cbinfo;
2090 *ctxp = ctx;
2091
2092 return OK;
2093 }
2094
2095
2096
2097
2098 /*************************************************
2099 * Get name of cipher in use *
2100 *************************************************/
2101
2102 /*
2103 Argument: pointer to an SSL structure for the connection
2104 pointer to number of bits for cipher
2105 Returns: pointer to allocated string in perm-pool
2106 */
2107
2108 static uschar *
2109 construct_cipher_name(SSL * ssl, int * bits)
2110 {
2111 int pool = store_pool;
2112 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
2113 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
2114 the accessor functions use const in the prototype. */
2115
2116 const uschar * ver = CUS SSL_get_version(ssl);
2117 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
2118 uschar * s;
2119
2120 SSL_CIPHER_get_bits(c, bits);
2121
2122 store_pool = POOL_PERM;
2123 s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits);
2124 store_pool = pool;
2125 DEBUG(D_tls) debug_printf("Cipher: %s\n", s);
2126 return s;
2127 }
2128
2129
2130 /* Get IETF-standard name for ciphersuite.
2131 Argument: pointer to an SSL structure for the connection
2132 Returns: pointer to string
2133 */
2134
2135 static const uschar *
2136 cipher_stdname_ssl(SSL * ssl)
2137 {
2138 #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
2139 return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl));
2140 #else
2141 ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl));
2142 return cipher_stdname(id >> 8, id & 0xff);
2143 #endif
2144 }
2145
2146
2147 static void
2148 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
2149 {
2150 /*XXX we might consider a list-of-certs variable for the cert chain.
2151 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
2152 in list-handling functions, also consider the difference between the entire
2153 chain and the elements sent by the peer. */
2154
2155 tlsp->peerdn = NULL;
2156
2157 /* Will have already noted peercert on a verify fail; possibly not the leaf */
2158 if (!tlsp->peercert)
2159 tlsp->peercert = SSL_get_peer_certificate(ssl);
2160 /* Beware anonymous ciphers which lead to server_cert being NULL */
2161 if (tlsp->peercert)
2162 if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
2163 { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
2164 else
2165 {
2166 int oldpool = store_pool;
2167
2168 peerdn[siz-1] = '\0'; /* paranoia */
2169 store_pool = POOL_PERM;
2170 tlsp->peerdn = string_copy(peerdn);
2171 store_pool = oldpool;
2172
2173 /* We used to set CV in the cert-verify callbacks (either plain or dane)
2174 but they don't get called on session-resumption. So use the official
2175 interface, which uses the resumed value. Unfortunately this claims verified
2176 when it actually failed but we're in try-verify mode, due to us wanting the
2177 knowlege that it failed so needing to have the callback and forcing a
2178 permissive return. If we don't force it, the TLS startup is failed.
2179 The extra bit of information is set in verify_override in the cb, stashed
2180 for resumption next to the TLS session, and used here. */
2181
2182 if (!tlsp->verify_override)
2183 tlsp->certificate_verified = SSL_get_verify_result(ssl) == X509_V_OK;
2184 }
2185 }
2186
2187
2188
2189
2190
2191 /*************************************************
2192 * Set up for verifying certificates *
2193 *************************************************/
2194
2195 #ifndef DISABLE_OCSP
2196 /* Load certs from file, return TRUE on success */
2197
2198 static BOOL
2199 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
2200 {
2201 BIO * bp;
2202 X509 * x;
2203
2204 while (sk_X509_num(verify_stack) > 0)
2205 X509_free(sk_X509_pop(verify_stack));
2206
2207 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
2208 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
2209 sk_X509_push(verify_stack, x);
2210 BIO_free(bp);
2211 return TRUE;
2212 }
2213 #endif
2214
2215
2216
2217 /* Called by both client and server startup; on the server possibly
2218 repeated after a Server Name Indication.
2219
2220 Arguments:
2221 sctx SSL_CTX* to initialise
2222 certs certs file or NULL
2223 crl CRL file or NULL
2224 host NULL in a server; the remote host in a client
2225 optional TRUE if called from a server for a host in tls_try_verify_hosts;
2226 otherwise passed as FALSE
2227 cert_vfy_cb Callback function for certificate verification
2228 errstr error string pointer
2229
2230 Returns: OK/DEFER/FAIL
2231 */
2232
2233 static int
2234 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2235 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2236 {
2237 uschar *expcerts, *expcrl;
2238
2239 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2240 return DEFER;
2241 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2242
2243 if (expcerts && *expcerts)
2244 {
2245 /* Tell the library to use its compiled-in location for the system default
2246 CA bundle. Then add the ones specified in the config, if any. */
2247
2248 if (!SSL_CTX_set_default_verify_paths(sctx))
2249 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2250
2251 if (Ustrcmp(expcerts, "system") != 0)
2252 {
2253 struct stat statbuf;
2254
2255 if (Ustat(expcerts, &statbuf) < 0)
2256 {
2257 log_write(0, LOG_MAIN|LOG_PANIC,
2258 "failed to stat %s for certificates", expcerts);
2259 return DEFER;
2260 }
2261 else
2262 {
2263 uschar *file, *dir;
2264 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2265 { file = NULL; dir = expcerts; }
2266 else
2267 {
2268 file = expcerts; dir = NULL;
2269 #ifndef DISABLE_OCSP
2270 /* In the server if we will be offering an OCSP proof, load chain from
2271 file for verifying the OCSP proof at load time. */
2272
2273 if ( !host
2274 && statbuf.st_size > 0
2275 && server_static_cbinfo->u_ocsp.server.file
2276 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2277 )
2278 {
2279 log_write(0, LOG_MAIN|LOG_PANIC,
2280 "failed to load cert chain from %s", file);
2281 return DEFER;
2282 }
2283 #endif
2284 }
2285
2286 /* If a certificate file is empty, the next function fails with an
2287 unhelpful error message. If we skip it, we get the correct behaviour (no
2288 certificates are recognized, but the error message is still misleading (it
2289 says no certificate was supplied). But this is better. */
2290
2291 if ( (!file || statbuf.st_size > 0)
2292 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2293 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2294
2295 /* Load the list of CAs for which we will accept certs, for sending
2296 to the client. This is only for the one-file tls_verify_certificates
2297 variant.
2298 If a list isn't loaded into the server, but some verify locations are set,
2299 the server end appears to make a wildcard request for client certs.
2300 Meanwhile, the client library as default behaviour *ignores* the list
2301 we send over the wire - see man SSL_CTX_set_client_cert_cb.
2302 Because of this, and that the dir variant is likely only used for
2303 the public-CA bundle (not for a private CA), not worth fixing. */
2304
2305 if (file)
2306 {
2307 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2308
2309 SSL_CTX_set_client_CA_list(sctx, names);
2310 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2311 sk_X509_NAME_num(names));
2312 }
2313 }
2314 }
2315
2316 /* Handle a certificate revocation list. */
2317
2318 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2319
2320 /* This bit of code is now the version supplied by Lars Mainka. (I have
2321 merely reformatted it into the Exim code style.)
2322
2323 "From here I changed the code to add support for multiple crl's
2324 in pem format in one file or to support hashed directory entries in
2325 pem format instead of a file. This method now uses the library function
2326 X509_STORE_load_locations to add the CRL location to the SSL context.
2327 OpenSSL will then handle the verify against CA certs and CRLs by
2328 itself in the verify callback." */
2329
2330 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2331 if (expcrl && *expcrl)
2332 {
2333 struct stat statbufcrl;
2334 if (Ustat(expcrl, &statbufcrl) < 0)
2335 {
2336 log_write(0, LOG_MAIN|LOG_PANIC,
2337 "failed to stat %s for certificates revocation lists", expcrl);
2338 return DEFER;
2339 }
2340 else
2341 {
2342 /* is it a file or directory? */
2343 uschar *file, *dir;
2344 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2345 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2346 {
2347 file = NULL;
2348 dir = expcrl;
2349 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2350 }
2351 else
2352 {
2353 file = expcrl;
2354 dir = NULL;
2355 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2356 }
2357 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2358 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2359
2360 /* setting the flags to check against the complete crl chain */
2361
2362 X509_STORE_set_flags(cvstore,
2363 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2364 }
2365 }
2366
2367 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2368
2369 /* If verification is optional, don't fail if no certificate */
2370
2371 SSL_CTX_set_verify(sctx,
2372 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2373 cert_vfy_cb);
2374 }
2375
2376 return OK;
2377 }
2378
2379
2380
2381 /*************************************************
2382 * Start a TLS session in a server *
2383 *************************************************/
2384
2385 /* This is called when Exim is running as a server, after having received
2386 the STARTTLS command. It must respond to that command, and then negotiate
2387 a TLS session.
2388
2389 Arguments:
2390 require_ciphers allowed ciphers
2391 errstr pointer to error message
2392
2393 Returns: OK on success
2394 DEFER for errors before the start of the negotiation
2395 FAIL for errors during the negotiation; the server can't
2396 continue running.
2397 */
2398
2399 int
2400 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2401 {
2402 int rc;
2403 uschar * expciphers;
2404 tls_ext_ctx_cb * cbinfo;
2405 static uschar peerdn[256];
2406
2407 /* Check for previous activation */
2408
2409 if (tls_in.active.sock >= 0)
2410 {
2411 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2412 smtp_printf("554 Already in TLS\r\n", FALSE);
2413 return FAIL;
2414 }
2415
2416 /* Initialize the SSL library. If it fails, it will already have logged
2417 the error. */
2418
2419 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2420 #ifndef DISABLE_OCSP
2421 tls_ocsp_file, /*XXX stack*/
2422 #endif
2423 NULL, &server_static_cbinfo, &tls_in, errstr);
2424 if (rc != OK) return rc;
2425 cbinfo = server_static_cbinfo;
2426
2427 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2428 return FAIL;
2429
2430 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2431 were historically separated by underscores. So that I can use either form in my
2432 tests, and also for general convenience, we turn underscores into hyphens here.
2433
2434 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2435 for TLS 1.3 . Since we do not call it at present we get the default list:
2436 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2437 */
2438
2439 if (expciphers)
2440 {
2441 for (uschar * s = expciphers; *s; s++ ) if (*s == '_') *s = '-';
2442 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2443 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2444 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2445 cbinfo->server_cipher_list = expciphers;
2446 }
2447
2448 /* If this is a host for which certificate verification is mandatory or
2449 optional, set up appropriately. */
2450
2451 tls_in.certificate_verified = FALSE;
2452 #ifdef SUPPORT_DANE
2453 tls_in.dane_verified = FALSE;
2454 #endif
2455 server_verify_callback_called = FALSE;
2456
2457 if (verify_check_host(&tls_verify_hosts) == OK)
2458 {
2459 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2460 FALSE, verify_callback_server, errstr);
2461 if (rc != OK) return rc;
2462 server_verify_optional = FALSE;
2463 }
2464 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2465 {
2466 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2467 TRUE, verify_callback_server, errstr);
2468 if (rc != OK) return rc;
2469 server_verify_optional = TRUE;
2470 }
2471
2472 #ifdef EXPERIMENTAL_TLS_RESUME
2473 SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_key_callback);
2474 /* despite working, appears to always return failure, so ignoring */
2475 #endif
2476 #ifdef OPENSSL_HAVE_NUM_TICKETS
2477 # ifdef EXPERIMENTAL_TLS_RESUME
2478 SSL_CTX_set_num_tickets(server_ctx, tls_in.host_resumable ? 1 : 0);
2479 # else
2480 SSL_CTX_set_num_tickets(server_ctx, 0); /* send no TLS1.3 stateful-tickets */
2481 # endif
2482 #endif
2483
2484
2485 /* Prepare for new connection */
2486
2487 if (!(server_ssl = SSL_new(server_ctx)))
2488 return tls_error(US"SSL_new", NULL, NULL, errstr);
2489
2490 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2491 *
2492 * With the SSL_clear(), we get strange interoperability bugs with
2493 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2494 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2495 *
2496 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2497 * session shutdown. In this case, we have a brand new object and there's no
2498 * obvious reason to immediately clear it. I'm guessing that this was
2499 * originally added because of incomplete initialisation which the clear fixed,
2500 * in some historic release.
2501 */
2502
2503 /* Set context and tell client to go ahead, except in the case of TLS startup
2504 on connection, where outputting anything now upsets the clients and tends to
2505 make them disconnect. We need to have an explicit fflush() here, to force out
2506 the response. Other smtp_printf() calls do not need it, because in non-TLS
2507 mode, the fflush() happens when smtp_getc() is called. */
2508
2509 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2510 if (!tls_in.on_connect)
2511 {
2512 smtp_printf("220 TLS go ahead\r\n", FALSE);
2513 fflush(smtp_out);
2514 }
2515
2516 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2517 that the OpenSSL library doesn't. */
2518
2519 SSL_set_wfd(server_ssl, fileno(smtp_out));
2520 SSL_set_rfd(server_ssl, fileno(smtp_in));
2521 SSL_set_accept_state(server_ssl);
2522
2523 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2524
2525 sigalrm_seen = FALSE;
2526 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2527 rc = SSL_accept(server_ssl);
2528 ALARM_CLR(0);
2529
2530 if (rc <= 0)
2531 {
2532 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2533 return FAIL;
2534 }
2535
2536 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2537 ERR_clear_error(); /* Even success can leave errors in the stack. Seen with
2538 anon-authentication ciphersuite negotiated. */
2539
2540 #ifdef EXPERIMENTAL_TLS_RESUME
2541 if (SSL_session_reused(server_ssl))
2542 {
2543 tls_in.resumption |= RESUME_USED;
2544 DEBUG(D_tls) debug_printf("Session reused\n");
2545 }
2546 #endif
2547
2548 /* TLS has been set up. Adjust the input functions to read via TLS,
2549 and initialize things. */
2550
2551 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2552
2553 tls_in.cipher = construct_cipher_name(server_ssl, &tls_in.bits);
2554 tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl);
2555
2556 DEBUG(D_tls)
2557 {
2558 uschar buf[2048];
2559 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)))
2560 debug_printf("Shared ciphers: %s\n", buf);
2561
2562 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2563 {
2564 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2565 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2566 BIO_free(bp);
2567 }
2568 #endif
2569
2570 #ifdef EXIM_HAVE_SESSION_TICKET
2571 {
2572 SSL_SESSION * ss = SSL_get_session(server_ssl);
2573 if (SSL_SESSION_has_ticket(ss)) /* 1.1.0 */
2574 debug_printf("The session has a ticket, life %lu seconds\n",
2575 SSL_SESSION_get_ticket_lifetime_hint(ss));
2576 }
2577 #endif
2578 }
2579
2580 /* Record the certificate we presented */
2581 {
2582 X509 * crt = SSL_get_certificate(server_ssl);
2583 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2584 }
2585
2586 /* Only used by the server-side tls (tls_in), including tls_getc.
2587 Client-side (tls_out) reads (seem to?) go via
2588 smtp_read_response()/ip_recv().
2589 Hence no need to duplicate for _in and _out.
2590 */
2591 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2592 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2593 ssl_xfer_eof = ssl_xfer_error = FALSE;
2594
2595 receive_getc = tls_getc;
2596 receive_getbuf = tls_getbuf;
2597 receive_get_cache = tls_get_cache;
2598 receive_ungetc = tls_ungetc;
2599 receive_feof = tls_feof;
2600 receive_ferror = tls_ferror;
2601 receive_smtp_buffered = tls_smtp_buffered;
2602
2603 tls_in.active.sock = fileno(smtp_out);
2604 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2605 return OK;
2606 }
2607
2608
2609
2610
2611 static int
2612 tls_client_basic_ctx_init(SSL_CTX * ctx,
2613 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2614 uschar ** errstr)
2615 {
2616 int rc;
2617 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2618 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2619 the specified host patterns if one of them is defined */
2620
2621 if ( ( !ob->tls_verify_hosts
2622 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2623 )
2624 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2625 )
2626 client_verify_optional = FALSE;
2627 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2628 client_verify_optional = TRUE;
2629 else
2630 return OK;
2631
2632 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2633 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2634 errstr)) != OK)
2635 return rc;
2636
2637 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2638 {
2639 cbinfo->verify_cert_hostnames =
2640 #ifdef SUPPORT_I18N
2641 string_domain_utf8_to_alabel(host->name, NULL);
2642 #else
2643 host->name;
2644 #endif
2645 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2646 cbinfo->verify_cert_hostnames);
2647 }
2648 return OK;
2649 }
2650
2651
2652 #ifdef SUPPORT_DANE
2653 static int
2654 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2655 {
2656 dns_scan dnss;
2657 const char * hostnames[2] = { CS host->name, NULL };
2658 int found = 0;
2659
2660 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2661 return tls_error(US"hostnames load", host, NULL, errstr);
2662
2663 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2664 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2665 ) if (rr->type == T_TLSA && rr->size > 3)
2666 {
2667 const uschar * p = rr->data;
2668 uint8_t usage, selector, mtype;
2669 const char * mdname;
2670
2671 usage = *p++;
2672
2673 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2674 if (usage != 2 && usage != 3) continue;
2675
2676 selector = *p++;
2677 mtype = *p++;
2678
2679 switch (mtype)
2680 {
2681 default: continue; /* Only match-types 0, 1, 2 are supported */
2682 case 0: mdname = NULL; break;
2683 case 1: mdname = "sha256"; break;
2684 case 2: mdname = "sha512"; break;
2685 }
2686
2687 found++;
2688 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2689 {
2690 default:
2691 return tls_error(US"tlsa load", host, NULL, errstr);
2692 case 0: /* action not taken */
2693 case 1: break;
2694 }
2695
2696 tls_out.tlsa_usage |= 1<<usage;
2697 }
2698
2699 if (found)
2700 return OK;
2701
2702 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2703 return DEFER;
2704 }
2705 #endif /*SUPPORT_DANE*/
2706
2707
2708
2709 #ifdef EXPERIMENTAL_TLS_RESUME
2710 /* On the client, get any stashed session for the given IP from hints db
2711 and apply it to the ssl-connection for attempted resumption. */
2712
2713 static void
2714 tls_retrieve_session(tls_support * tlsp, SSL * ssl, const uschar * key)
2715 {
2716 tlsp->resumption |= RESUME_SUPPORTED;
2717 if (tlsp->host_resumable)
2718 {
2719 dbdata_tls_session * dt;
2720 int len;
2721 open_db dbblock, * dbm_file;
2722
2723 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
2724 DEBUG(D_tls) debug_printf("checking for resumable session for %s\n", key);
2725 if ((dbm_file = dbfn_open(US"tls", O_RDONLY, &dbblock, FALSE, FALSE)))
2726 {
2727 /* key for the db is the IP */
2728 if ((dt = dbfn_read_with_length(dbm_file, key, &len)))
2729 {
2730 SSL_SESSION * ss = NULL;
2731 const uschar * sess_asn1 = dt->session;
2732
2733 len -= sizeof(dbdata_tls_session);
2734 if (!(d2i_SSL_SESSION(&ss, &sess_asn1, (long)len)))
2735 {
2736 DEBUG(D_tls)
2737 {
2738 ERR_error_string_n(ERR_get_error(),
2739 ssl_errstring, sizeof(ssl_errstring));
2740 debug_printf("decoding session: %s\n", ssl_errstring);
2741 }
2742 }
2743 #ifdef EXIM_HAVE_SESSION_TICKET
2744 else if ( SSL_SESSION_get_ticket_lifetime_hint(ss) + dt->time_stamp
2745 < time(NULL))
2746 {
2747 DEBUG(D_tls) debug_printf("session expired\n");
2748 dbfn_delete(dbm_file, key);
2749 }
2750 #endif
2751 else if (!SSL_set_session(ssl, ss))
2752 {
2753 DEBUG(D_tls)
2754 {
2755 ERR_error_string_n(ERR_get_error(),
2756 ssl_errstring, sizeof(ssl_errstring));
2757 debug_printf("applying session to ssl: %s\n", ssl_errstring);
2758 }
2759 }
2760 else
2761 {
2762 DEBUG(D_tls) debug_printf("good session\n");
2763 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
2764 tlsp->verify_override = dt->verify_override;
2765 tlsp->ocsp = dt->ocsp;
2766 }
2767 }
2768 else
2769 DEBUG(D_tls) debug_printf("no session record\n");
2770 dbfn_close(dbm_file);
2771 }
2772 }
2773 }
2774
2775
2776 /* On the client, save the session for later resumption */
2777
2778 static int
2779 tls_save_session_cb(SSL * ssl, SSL_SESSION * ss)
2780 {
2781 tls_ext_ctx_cb * cbinfo = SSL_get_ex_data(ssl, tls_exdata_idx);
2782 tls_support * tlsp;
2783
2784 DEBUG(D_tls) debug_printf("tls_save_session_cb\n");
2785
2786 if (!cbinfo || !(tlsp = cbinfo->tlsp)->host_resumable) return 0;
2787
2788 # ifdef OPENSSL_HAVE_NUM_TICKETS
2789 if (SSL_SESSION_is_resumable(ss)) /* 1.1.1 */
2790 # endif
2791 {
2792 int len = i2d_SSL_SESSION(ss, NULL);
2793 int dlen = sizeof(dbdata_tls_session) + len;
2794 dbdata_tls_session * dt = store_get(dlen, TRUE);
2795 uschar * s = dt->session;
2796 open_db dbblock, * dbm_file;
2797
2798 DEBUG(D_tls) debug_printf("session is resumable\n");
2799 tlsp->resumption |= RESUME_SERVER_TICKET; /* server gave us a ticket */
2800
2801 dt->verify_override = tlsp->verify_override;
2802 dt->ocsp = tlsp->ocsp;
2803 (void) i2d_SSL_SESSION(ss, &s); /* s gets bumped to end */
2804
2805 if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE)))
2806 {
2807 const uschar * key = cbinfo->host->address;
2808 dbfn_delete(dbm_file, key);
2809 dbfn_write(dbm_file, key, dt, dlen);
2810 dbfn_close(dbm_file);
2811 DEBUG(D_tls) debug_printf("wrote session (len %u) to db\n",
2812 (unsigned)dlen);
2813 }
2814 }
2815 return 1;
2816 }
2817
2818
2819 static void
2820 tls_client_ctx_resume_prehandshake(
2821 exim_openssl_client_tls_ctx * exim_client_ctx, tls_support * tlsp,
2822 smtp_transport_options_block * ob, host_item * host)
2823 {
2824 /* Should the client request a session resumption ticket? */
2825 if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK)
2826 {
2827 tlsp->host_resumable = TRUE;
2828
2829 SSL_CTX_set_session_cache_mode(exim_client_ctx->ctx,
2830 SSL_SESS_CACHE_CLIENT
2831 | SSL_SESS_CACHE_NO_INTERNAL | SSL_SESS_CACHE_NO_AUTO_CLEAR);
2832 SSL_CTX_sess_set_new_cb(exim_client_ctx->ctx, tls_save_session_cb);
2833 }
2834 }
2835
2836 static BOOL
2837 tls_client_ssl_resume_prehandshake(SSL * ssl, tls_support * tlsp,
2838 host_item * host, uschar ** errstr)
2839 {
2840 if (tlsp->host_resumable)
2841 {
2842 DEBUG(D_tls)
2843 debug_printf("tls_resumption_hosts overrides openssl_options, enabling tickets\n");
2844 SSL_clear_options(ssl, SSL_OP_NO_TICKET);
2845
2846 tls_exdata_idx = SSL_get_ex_new_index(0, 0, 0, 0, 0);
2847 if (!SSL_set_ex_data(ssl, tls_exdata_idx, client_static_cbinfo))
2848 {
2849 tls_error(US"set ex_data", host, NULL, errstr);
2850 return FALSE;
2851 }
2852 debug_printf("tls_exdata_idx %d cbinfo %p\n", tls_exdata_idx, client_static_cbinfo);
2853 }
2854
2855 tlsp->resumption = RESUME_SUPPORTED;
2856 /* Pick up a previous session, saved on an old ticket */
2857 tls_retrieve_session(tlsp, ssl, host->address);
2858 return TRUE;
2859 }
2860
2861 static void
2862 tls_client_resume_posthandshake(exim_openssl_client_tls_ctx * exim_client_ctx,
2863 tls_support * tlsp)
2864 {
2865 if (SSL_session_reused(exim_client_ctx->ssl))
2866 {
2867 DEBUG(D_tls) debug_printf("The session was reused\n");
2868 tlsp->resumption |= RESUME_USED;
2869 }
2870 }
2871 #endif /* EXPERIMENTAL_TLS_RESUME */
2872
2873
2874 /*************************************************
2875 * Start a TLS session in a client *
2876 *************************************************/
2877
2878 /* Called from the smtp transport after STARTTLS has been accepted.
2879
2880 Arguments:
2881 cctx connection context
2882 conn_args connection details
2883 cookie datum for randomness; can be NULL
2884 tlsp record details of TLS channel configuration here; must be non-NULL
2885 errstr error string pointer
2886
2887 Returns: TRUE for success with TLS session context set in connection context,
2888 FALSE on error
2889 */
2890
2891 BOOL
2892 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
2893 void * cookie, tls_support * tlsp, uschar ** errstr)
2894 {
2895 host_item * host = conn_args->host; /* for msgs and option-tests */
2896 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
2897 smtp_transport_options_block * ob = tb
2898 ? (smtp_transport_options_block *)tb->options_block
2899 : &smtp_transport_option_defaults;
2900 exim_openssl_client_tls_ctx * exim_client_ctx;
2901 uschar * expciphers;
2902 int rc;
2903 static uschar peerdn[256];
2904
2905 #ifndef DISABLE_OCSP
2906 BOOL request_ocsp = FALSE;
2907 BOOL require_ocsp = FALSE;
2908 #endif
2909
2910 rc = store_pool;
2911 store_pool = POOL_PERM;
2912 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx), FALSE);
2913 exim_client_ctx->corked = NULL;
2914 store_pool = rc;
2915
2916 #ifdef SUPPORT_DANE
2917 tlsp->tlsa_usage = 0;
2918 #endif
2919
2920 #ifndef DISABLE_OCSP
2921 {
2922 # ifdef SUPPORT_DANE
2923 if ( conn_args->dane
2924 && ob->hosts_request_ocsp[0] == '*'
2925 && ob->hosts_request_ocsp[1] == '\0'
2926 )
2927 {
2928 /* Unchanged from default. Use a safer one under DANE */
2929 request_ocsp = TRUE;
2930 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2931 " {= {4}{$tls_out_tlsa_usage}} } "
2932 " {*}{}}";
2933 }
2934 # endif
2935
2936 if ((require_ocsp =
2937 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
2938 request_ocsp = TRUE;
2939 else
2940 # ifdef SUPPORT_DANE
2941 if (!request_ocsp)
2942 # endif
2943 request_ocsp =
2944 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2945 }
2946 #endif
2947
2948 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
2949 ob->tls_certificate, ob->tls_privatekey,
2950 #ifndef DISABLE_OCSP
2951 (void *)(long)request_ocsp,
2952 #endif
2953 cookie, &client_static_cbinfo, tlsp, errstr);
2954 if (rc != OK) return FALSE;
2955
2956 tlsp->certificate_verified = FALSE;
2957 client_verify_callback_called = FALSE;
2958
2959 expciphers = NULL;
2960 #ifdef SUPPORT_DANE
2961 if (conn_args->dane)
2962 {
2963 /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
2964 other failures should be treated as problems. */
2965 if (ob->dane_require_tls_ciphers &&
2966 !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2967 &expciphers, errstr))
2968 return FALSE;
2969 if (expciphers && *expciphers == '\0')
2970 expciphers = NULL;
2971 }
2972 #endif
2973 if (!expciphers &&
2974 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2975 &expciphers, errstr))
2976 return FALSE;
2977
2978 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2979 are separated by underscores. So that I can use either form in my tests, and
2980 also for general convenience, we turn underscores into hyphens here. */
2981
2982 if (expciphers)
2983 {
2984 uschar *s = expciphers;
2985 while (*s) { if (*s == '_') *s = '-'; s++; }
2986 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2987 if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
2988 {
2989 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2990 return FALSE;
2991 }
2992 }
2993
2994 #ifdef SUPPORT_DANE
2995 if (conn_args->dane)
2996 {
2997 SSL_CTX_set_verify(exim_client_ctx->ctx,
2998 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2999 verify_callback_client_dane);
3000
3001 if (!DANESSL_library_init())
3002 {
3003 tls_error(US"library init", host, NULL, errstr);
3004 return FALSE;
3005 }
3006 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
3007 {
3008 tls_error(US"context init", host, NULL, errstr);
3009 return FALSE;
3010 }
3011 }
3012 else
3013
3014 #endif
3015
3016 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
3017 client_static_cbinfo, errstr) != OK)
3018 return FALSE;
3019
3020 #ifdef EXPERIMENTAL_TLS_RESUME
3021 tls_client_ctx_resume_prehandshake(exim_client_ctx, tlsp, ob, host);
3022 #endif
3023
3024
3025 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
3026 {
3027 tls_error(US"SSL_new", host, NULL, errstr);
3028 return FALSE;
3029 }
3030 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
3031
3032 SSL_set_fd(exim_client_ctx->ssl, cctx->sock);
3033 SSL_set_connect_state(exim_client_ctx->ssl);
3034
3035 if (ob->tls_sni)
3036 {
3037 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
3038 return FALSE;
3039 if (!tlsp->sni)
3040 {
3041 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
3042 }
3043 else if (!Ustrlen(tlsp->sni))
3044 tlsp->sni = NULL;
3045 else
3046 {
3047 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
3048 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
3049 SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
3050 #else
3051 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
3052 tlsp->sni);
3053 #endif
3054 }
3055 }
3056
3057 #ifdef SUPPORT_DANE
3058 if (conn_args->dane)
3059 if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK)
3060 return FALSE;
3061 #endif
3062
3063 #ifndef DISABLE_OCSP
3064 /* Request certificate status at connection-time. If the server
3065 does OCSP stapling we will get the callback (set in tls_init()) */
3066 # ifdef SUPPORT_DANE
3067 if (request_ocsp)
3068 {
3069 const uschar * s;
3070 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
3071 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
3072 )
3073 { /* Re-eval now $tls_out_tlsa_usage is populated. If
3074 this means we avoid the OCSP request, we wasted the setup
3075 cost in tls_init(). */
3076 require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
3077 request_ocsp = require_ocsp
3078 || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
3079 }
3080 }
3081 # endif
3082
3083 if (request_ocsp)
3084 {
3085 SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
3086 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
3087 tlsp->ocsp = OCSP_NOT_RESP;
3088 }
3089 #endif
3090
3091 #ifdef EXPERIMENTAL_TLS_RESUME
3092 if (!tls_client_ssl_resume_prehandshake(exim_client_ctx->ssl, tlsp, host,
3093 errstr))
3094 return FALSE;
3095 #endif
3096
3097 #ifndef DISABLE_EVENT
3098 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
3099 #endif
3100
3101 /* There doesn't seem to be a built-in timeout on connection. */
3102
3103 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
3104 sigalrm_seen = FALSE;
3105 ALARM(ob->command_timeout);
3106 rc = SSL_connect(exim_client_ctx->ssl);
3107 ALARM_CLR(0);
3108
3109 #ifdef SUPPORT_DANE
3110 if (conn_args->dane)
3111 DANESSL_cleanup(exim_client_ctx->ssl);
3112 #endif
3113
3114 if (rc <= 0)
3115 {
3116 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
3117 return FALSE;
3118 }
3119
3120 DEBUG(D_tls)
3121 {
3122 debug_printf("SSL_connect succeeded\n");
3123 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
3124 {
3125 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
3126 SSL_SESSION_print_keylog(bp, SSL_get_session(exim_client_ctx->ssl));
3127 BIO_free(bp);
3128 }
3129 #endif
3130 }
3131
3132 #ifdef EXPERIMENTAL_TLS_RESUME
3133 tls_client_resume_posthandshake(exim_client_ctx, tlsp);
3134 #endif
3135
3136 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
3137
3138 tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, &tlsp->bits);
3139 tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl);
3140
3141 /* Record the certificate we presented */
3142 {
3143 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
3144 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
3145 }
3146
3147 tlsp->active.sock = cctx->sock;
3148 tlsp->active.tls_ctx = exim_client_ctx;
3149 cctx->tls_ctx = exim_client_ctx;
3150 return TRUE;
3151 }
3152
3153
3154
3155
3156
3157 static BOOL
3158 tls_refill(unsigned lim)
3159 {
3160 int error;
3161 int inbytes;
3162
3163 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
3164 ssl_xfer_buffer, ssl_xfer_buffer_size);
3165
3166 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
3167 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
3168 MIN(ssl_xfer_buffer_size, lim));
3169 error = SSL_get_error(server_ssl, inbytes);
3170 if (smtp_receive_timeout > 0) ALARM_CLR(0);
3171
3172 if (had_command_timeout) /* set by signal handler */
3173 smtp_command_timeout_exit(); /* does not return */
3174 if (had_command_sigterm)
3175 smtp_command_sigterm_exit();
3176 if (had_data_timeout)
3177 smtp_data_timeout_exit();
3178 if (had_data_sigint)
3179 smtp_data_sigint_exit();
3180
3181 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
3182 closed down, not that the socket itself has been closed down. Revert to
3183 non-SSL handling. */
3184
3185 switch(error)
3186 {
3187 case SSL_ERROR_NONE:
3188 break;
3189
3190 case SSL_ERROR_ZERO_RETURN:
3191 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
3192
3193 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
3194 SSL_shutdown(server_ssl);
3195
3196 tls_close(NULL, TLS_NO_SHUTDOWN);
3197 return FALSE;
3198
3199 /* Handle genuine errors */
3200 case SSL_ERROR_SSL:
3201 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3202 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
3203 ssl_xfer_error = TRUE;
3204 return FALSE;
3205
3206 default:
3207 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
3208 DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
3209 debug_printf(" - syscall %s\n", strerror(errno));
3210 ssl_xfer_error = TRUE;
3211 return FALSE;
3212 }
3213
3214 #ifndef DISABLE_DKIM
3215 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
3216 #endif
3217 ssl_xfer_buffer_hwm = inbytes;
3218 ssl_xfer_buffer_lwm = 0;
3219 return TRUE;
3220 }
3221
3222
3223 /*************************************************
3224 * TLS version of getc *
3225 *************************************************/
3226
3227 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
3228 it refills the buffer via the SSL reading function.
3229
3230 Arguments: lim Maximum amount to read/buffer
3231 Returns: the next character or EOF
3232
3233 Only used by the server-side TLS.
3234 */
3235
3236 int
3237 tls_getc(unsigned lim)
3238 {
3239 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3240 if (!tls_refill(lim))
3241 return ssl_xfer_error ? EOF : smtp_getc(lim);
3242
3243 /* Something in the buffer; return next uschar */
3244
3245 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
3246 }
3247
3248 uschar *
3249 tls_getbuf(unsigned * len)
3250 {
3251 unsigned size;
3252 uschar * buf;
3253
3254 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3255 if (!tls_refill(*len))
3256 {
3257 if (!ssl_xfer_error) return smtp_getbuf(len);
3258 *len = 0;
3259 return NULL;
3260 }
3261
3262 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
3263 size = *len;
3264 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
3265 ssl_xfer_buffer_lwm += size;
3266 *len = size;
3267 return buf;
3268 }
3269
3270
3271 void
3272 tls_get_cache()
3273 {
3274 #ifndef DISABLE_DKIM
3275 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
3276 if (n > 0)
3277 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
3278 #endif
3279 }
3280
3281
3282 BOOL
3283 tls_could_read(void)
3284 {
3285 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
3286 }
3287
3288
3289 /*************************************************
3290 * Read bytes from TLS channel *
3291 *************************************************/
3292
3293 /*
3294 Arguments:
3295 ct_ctx client context pointer, or NULL for the one global server context
3296 buff buffer of data
3297 len size of buffer
3298
3299 Returns: the number of bytes read
3300 -1 after a failed read, including EOF
3301
3302 Only used by the client-side TLS.
3303 */
3304
3305 int
3306 tls_read(void * ct_ctx, uschar *buff, size_t len)
3307 {
3308 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
3309 int inbytes;
3310 int error;
3311
3312 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
3313 buff, (unsigned int)len);
3314
3315 inbytes = SSL_read(ssl, CS buff, len);
3316 error = SSL_get_error(ssl, inbytes);
3317
3318 if (error == SSL_ERROR_ZERO_RETURN)
3319 {
3320 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
3321 return -1;
3322 }
3323 else if (error != SSL_ERROR_NONE)
3324 return -1;
3325
3326 return inbytes;
3327 }
3328
3329
3330
3331
3332
3333 /*************************************************
3334 * Write bytes down TLS channel *
3335 *************************************************/
3336
3337 /*
3338 Arguments:
3339 ct_ctx client context pointer, or NULL for the one global server context
3340 buff buffer of data
3341 len number of bytes
3342 more further data expected soon
3343
3344 Returns: the number of bytes after a successful write,
3345 -1 after a failed write
3346
3347 Used by both server-side and client-side TLS.
3348 */
3349
3350 int
3351 tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
3352 {
3353 size_t olen = len;
3354 int outbytes, error;
3355 SSL * ssl = ct_ctx
3356 ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
3357 static gstring * server_corked = NULL;
3358 gstring ** corkedp = ct_ctx
3359 ? &((exim_openssl_client_tls_ctx *)ct_ctx)->corked : &server_corked;
3360 gstring * corked = *corkedp;
3361
3362 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
3363 buff, (unsigned long)len, more ? ", more" : "");
3364
3365 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
3366 "more" is notified. This hack is only ok if small amounts are involved AND only
3367 one stream does it, in one context (i.e. no store reset). Currently it is used
3368 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only.
3369 We support callouts done by the server process by using a separate client
3370 context for the stashed information. */
3371 /* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's
3372 a store reset there, so use POOL_PERM. */
3373 /* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */
3374
3375 if ((more || corked))
3376 {
3377 #ifdef SUPPORT_PIPE_CONNECT
3378 int save_pool = store_pool;
3379 store_pool = POOL_PERM;
3380 #endif
3381
3382 corked = string_catn(corked, buff, len);
3383
3384 #ifdef SUPPORT_PIPE_CONNECT
3385 store_pool = save_pool;
3386 #endif
3387
3388 if (more)
3389 {
3390 *corkedp = corked;
3391 return len;
3392 }
3393 buff = CUS corked->s;
3394 len = corked->ptr;
3395 *corkedp = NULL;
3396 }
3397
3398 for (int left = len; left > 0;)
3399 {
3400 DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left);
3401 outbytes = SSL_write(ssl, CS buff, left);
3402 error = SSL_get_error(ssl, outbytes);
3403 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
3404 switch (error)
3405 {
3406 case SSL_ERROR_SSL:
3407 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3408 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
3409 return -1;
3410
3411 case SSL_ERROR_NONE:
3412 left -= outbytes;
3413 buff += outbytes;
3414 break;
3415
3416 case SSL_ERROR_ZERO_RETURN:
3417 log_write(0, LOG_MAIN, "SSL channel closed on write");
3418 return -1;
3419
3420 case SSL_ERROR_SYSCALL:
3421 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
3422 sender_fullhost ? sender_fullhost : US"<unknown>",
3423 strerror(errno));
3424 return -1;
3425
3426 default:
3427 log_write(0, LOG_MAIN, "SSL_write error %d", error);
3428 return -1;
3429 }