OpenSSL: clearer log message for TCP conn close at SSL_accept
[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 # define EXIM_HAVE_OPESSL_GET0_SERIAL
78 # else
79 # define EXIM_NEED_OPENSSL_INIT
80 # endif
81 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
82 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
83 # define EXIM_HAVE_OPENSSL_CHECKHOST
84 # endif
85 #endif
86
87 #if !defined(LIBRESSL_VERSION_NUMBER) \
88 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
89 # if !defined(OPENSSL_NO_ECDH)
90 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
91 # define EXIM_HAVE_ECDH
92 # endif
93 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
94 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
95 # endif
96 # endif
97 #endif
98
99 #ifndef LIBRESSL_VERSION_NUMBER
100 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
101 # define OPENSSL_HAVE_KEYLOG_CB
102 # define OPENSSL_HAVE_NUM_TICKETS
103 # define EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
104 # endif
105 #endif
106
107 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
108 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
109 # define DISABLE_OCSP
110 #endif
111
112 #ifdef EXPERIMENTAL_TLS_RESUME
113 # if OPENSSL_VERSION_NUMBER < 0x0101010L
114 # error OpenSSL version too old for session-resumption
115 # endif
116 #endif
117
118 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
119 # include <openssl/x509v3.h>
120 #endif
121
122 #ifndef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
123 # ifndef EXIM_HAVE_OPENSSL_CIPHER_GET_ID
124 # define SSL_CIPHER_get_id(c) (c->id)
125 # endif
126 # ifndef MACRO_PREDEF
127 # include "tls-cipher-stdname.c"
128 # endif
129 #endif
130
131 /*************************************************
132 * OpenSSL option parse *
133 *************************************************/
134
135 typedef struct exim_openssl_option {
136 uschar *name;
137 long value;
138 } exim_openssl_option;
139 /* We could use a macro to expand, but we need the ifdef and not all the
140 options document which version they were introduced in. Policylet: include
141 all options unless explicitly for DTLS, let the administrator choose which
142 to apply.
143
144 This list is current as of:
145 ==> 1.0.1b <==
146 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
147 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
148 */
149 static exim_openssl_option exim_openssl_options[] = {
150 /* KEEP SORTED ALPHABETICALLY! */
151 #ifdef SSL_OP_ALL
152 { US"all", (long) SSL_OP_ALL },
153 #endif
154 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
155 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
156 #endif
157 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
158 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
159 #endif
160 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
161 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
162 #endif
163 #ifdef SSL_OP_EPHEMERAL_RSA
164 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
165 #endif
166 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
167 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
168 #endif
169 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
170 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
171 #endif
172 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
173 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
174 #endif
175 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
176 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
177 #endif
178 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
179 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
180 #endif
181 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
182 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
183 #endif
184 #ifdef SSL_OP_NO_COMPRESSION
185 { US"no_compression", SSL_OP_NO_COMPRESSION },
186 #endif
187 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
188 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
189 #endif
190 #ifdef SSL_OP_NO_SSLv2
191 { US"no_sslv2", SSL_OP_NO_SSLv2 },
192 #endif
193 #ifdef SSL_OP_NO_SSLv3
194 { US"no_sslv3", SSL_OP_NO_SSLv3 },
195 #endif
196 #ifdef SSL_OP_NO_TICKET
197 { US"no_ticket", SSL_OP_NO_TICKET },
198 #endif
199 #ifdef SSL_OP_NO_TLSv1
200 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
201 #endif
202 #ifdef SSL_OP_NO_TLSv1_1
203 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
204 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
205 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
206 #else
207 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
208 #endif
209 #endif
210 #ifdef SSL_OP_NO_TLSv1_2
211 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
212 #endif
213 #ifdef SSL_OP_NO_TLSv1_3
214 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
215 #endif
216 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
217 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
218 #endif
219 #ifdef SSL_OP_SINGLE_DH_USE
220 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
221 #endif
222 #ifdef SSL_OP_SINGLE_ECDH_USE
223 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
224 #endif
225 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
226 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
227 #endif
228 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
229 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
230 #endif
231 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
232 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
233 #endif
234 #ifdef SSL_OP_TLS_D5_BUG
235 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
236 #endif
237 #ifdef SSL_OP_TLS_ROLLBACK_BUG
238 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
239 #endif
240 };
241
242 #ifndef MACRO_PREDEF
243 static int exim_openssl_options_size = nelem(exim_openssl_options);
244 #endif
245
246 #ifdef MACRO_PREDEF
247 void
248 options_tls(void)
249 {
250 uschar buf[64];
251
252 for (struct exim_openssl_option * o = exim_openssl_options;
253 o < exim_openssl_options + nelem(exim_openssl_options); o++)
254 {
255 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
256 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
257
258 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
259 builtin_macro_create(buf);
260 }
261
262 # ifdef EXPERIMENTAL_TLS_RESUME
263 builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING );
264 # endif
265 # ifdef SSL_OP_NO_TLSv1_3
266 builtin_macro_create(US"_HAVE_TLS1_3");
267 # endif
268 }
269 #else
270
271 /******************************************************************************/
272
273 /* Structure for collecting random data for seeding. */
274
275 typedef struct randstuff {
276 struct timeval tv;
277 pid_t p;
278 } randstuff;
279
280 /* Local static variables */
281
282 static BOOL client_verify_callback_called = FALSE;
283 static BOOL server_verify_callback_called = FALSE;
284 static const uschar *sid_ctx = US"exim";
285
286 /* We have three different contexts to care about.
287
288 Simple case: client, `client_ctx`
289 As a client, we can be doing a callout or cut-through delivery while receiving
290 a message. So we have a client context, which should have options initialised
291 from the SMTP Transport. We may also concurrently want to make TLS connections
292 to utility daemons, so client-contexts are allocated and passed around in call
293 args rather than using a gobal.
294
295 Server:
296 There are two cases: with and without ServerNameIndication from the client.
297 Given TLS SNI, we can be using different keys, certs and various other
298 configuration settings, because they're re-expanded with $tls_sni set. This
299 allows vhosting with TLS. This SNI is sent in the handshake.
300 A client might not send SNI, so we need a fallback, and an initial setup too.
301 So as a server, we start out using `server_ctx`.
302 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
303 `server_sni` from `server_ctx` and then initialise settings by re-expanding
304 configuration.
305 */
306
307 typedef struct {
308 SSL_CTX * ctx;
309 SSL * ssl;
310 gstring * corked;
311 } exim_openssl_client_tls_ctx;
312
313 static SSL_CTX *server_ctx = NULL;
314 static SSL *server_ssl = NULL;
315
316 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
317 static SSL_CTX *server_sni = NULL;
318 #endif
319
320 static char ssl_errstring[256];
321
322 static int ssl_session_timeout = 7200; /* Two hours */
323 static BOOL client_verify_optional = FALSE;
324 static BOOL server_verify_optional = FALSE;
325
326 static BOOL reexpand_tls_files_for_sni = FALSE;
327
328
329 typedef struct ocsp_resp {
330 struct ocsp_resp * next;
331 OCSP_RESPONSE * resp;
332 } ocsp_resplist;
333
334 typedef struct tls_ext_ctx_cb {
335 tls_support * tlsp;
336 uschar *certificate;
337 uschar *privatekey;
338 BOOL is_server;
339 #ifndef DISABLE_OCSP
340 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
341 union {
342 struct {
343 uschar *file;
344 const uschar *file_expanded;
345 ocsp_resplist *olist;
346 } server;
347 struct {
348 X509_STORE *verify_store; /* non-null if status requested */
349 BOOL verify_required;
350 } client;
351 } u_ocsp;
352 #endif
353 uschar *dhparam;
354 /* these are cached from first expand */
355 uschar *server_cipher_list;
356 /* only passed down to tls_error: */
357 host_item *host;
358 const uschar * verify_cert_hostnames;
359 #ifndef DISABLE_EVENT
360 uschar * event_action;
361 #endif
362 } tls_ext_ctx_cb;
363
364 /* should figure out a cleanup of API to handle state preserved per
365 implementation, for various reasons, which can be void * in the APIs.
366 For now, we hack around it. */
367 tls_ext_ctx_cb *client_static_cbinfo = NULL; /*XXX should not use static; multiple concurrent clients! */
368 tls_ext_ctx_cb *server_static_cbinfo = NULL;
369
370 static int
371 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
372 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
373
374 /* Callbacks */
375 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
376 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
377 #endif
378 #ifndef DISABLE_OCSP
379 static int tls_server_stapling_cb(SSL *s, void *arg);
380 #endif
381
382
383
384 /* Daemon-called, before every connection, key create/rotate */
385 #ifdef EXPERIMENTAL_TLS_RESUME
386 static void tk_init(void);
387 static int tls_exdata_idx = -1;
388 #endif
389
390 void
391 tls_daemon_init(void)
392 {
393 #ifdef EXPERIMENTAL_TLS_RESUME
394 tk_init();
395 #endif
396 return;
397 }
398
399
400 /*************************************************
401 * Handle TLS error *
402 *************************************************/
403
404 /* Called from lots of places when errors occur before actually starting to do
405 the TLS handshake, that is, while the session is still in clear. Always returns
406 DEFER for a server and FAIL for a client so that most calls can use "return
407 tls_error(...)" to do this processing and then give an appropriate return. A
408 single function is used for both server and client, because it is called from
409 some shared functions.
410
411 Argument:
412 prefix text to include in the logged error
413 host NULL if setting up a server;
414 the connected host if setting up a client
415 msg error message or NULL if we should ask OpenSSL
416 errstr pointer to output error message
417
418 Returns: OK/DEFER/FAIL
419 */
420
421 static int
422 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
423 {
424 if (!msg)
425 {
426 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
427 msg = US ssl_errstring;
428 }
429
430 msg = string_sprintf("(%s): %s", prefix, msg);
431 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
432 if (errstr) *errstr = msg;
433 return host ? FAIL : DEFER;
434 }
435
436
437
438 /*************************************************
439 * Callback to generate RSA key *
440 *************************************************/
441
442 /*
443 Arguments:
444 s SSL connection (not used)
445 export not used
446 keylength keylength
447
448 Returns: pointer to generated key
449 */
450
451 static RSA *
452 rsa_callback(SSL *s, int export, int keylength)
453 {
454 RSA *rsa_key;
455 #ifdef EXIM_HAVE_RSA_GENKEY_EX
456 BIGNUM *bn = BN_new();
457 #endif
458
459 export = export; /* Shut picky compilers up */
460 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
461
462 #ifdef EXIM_HAVE_RSA_GENKEY_EX
463 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
464 || !(rsa_key = RSA_new())
465 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
466 )
467 #else
468 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
469 #endif
470
471 {
472 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
473 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
474 ssl_errstring);
475 return NULL;
476 }
477 return rsa_key;
478 }
479
480
481
482 /* Extreme debug
483 #ifndef DISABLE_OCSP
484 void
485 x509_store_dump_cert_s_names(X509_STORE * store)
486 {
487 STACK_OF(X509_OBJECT) * roots= store->objs;
488 static uschar name[256];
489
490 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
491 {
492 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
493 if(tmp_obj->type == X509_LU_X509)
494 {
495 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
496 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
497 {
498 name[sizeof(name)-1] = '\0';
499 debug_printf(" %s\n", name);
500 }
501 }
502 }
503 }
504 #endif
505 */
506
507
508 #ifndef DISABLE_EVENT
509 static int
510 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
511 BOOL *calledp, const BOOL *optionalp, const uschar * what)
512 {
513 uschar * ev;
514 uschar * yield;
515 X509 * old_cert;
516
517 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
518 if (ev)
519 {
520 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
521 old_cert = tlsp->peercert;
522 tlsp->peercert = X509_dup(cert);
523 /* NB we do not bother setting peerdn */
524 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
525 {
526 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
527 "depth=%d cert=%s: %s",
528 tlsp == &tls_out ? deliver_host_address : sender_host_address,
529 what, depth, dn, yield);
530 *calledp = TRUE;
531 if (!*optionalp)
532 {
533 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
534 return 1; /* reject (leaving peercert set) */
535 }
536 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
537 "(host in tls_try_verify_hosts)\n");
538 tlsp->verify_override = TRUE;
539 }
540 X509_free(tlsp->peercert);
541 tlsp->peercert = old_cert;
542 }
543 return 0;
544 }
545 #endif
546
547 /*************************************************
548 * Callback for verification *
549 *************************************************/
550
551 /* The SSL library does certificate verification if set up to do so. This
552 callback has the current yes/no state is in "state". If verification succeeded,
553 we set the certificate-verified flag. If verification failed, what happens
554 depends on whether the client is required to present a verifiable certificate
555 or not.
556
557 If verification is optional, we change the state to yes, but still log the
558 verification error. For some reason (it really would help to have proper
559 documentation of OpenSSL), this callback function then gets called again, this
560 time with state = 1. We must take care not to set the private verified flag on
561 the second time through.
562
563 Note: this function is not called if the client fails to present a certificate
564 when asked. We get here only if a certificate has been received. Handling of
565 optional verification for this case is done when requesting SSL to verify, by
566 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
567
568 May be called multiple times for different issues with a certificate, even
569 for a given "depth" in the certificate chain.
570
571 Arguments:
572 preverify_ok current yes/no state as 1/0
573 x509ctx certificate information.
574 tlsp per-direction (client vs. server) support data
575 calledp has-been-called flag
576 optionalp verification-is-optional flag
577
578 Returns: 0 if verification should fail, otherwise 1
579 */
580
581 static int
582 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
583 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
584 {
585 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
586 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
587 uschar dn[256];
588
589 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
590 {
591 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
592 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
593 tlsp == &tls_out ? deliver_host_address : sender_host_address);
594 return 0;
595 }
596 dn[sizeof(dn)-1] = '\0';
597
598 tlsp->verify_override = FALSE;
599 if (preverify_ok == 0)
600 {
601 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
602 *verify_mode, sender_host_address)
603 : US"";
604 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
605 tlsp == &tls_out ? deliver_host_address : sender_host_address,
606 extra, depth,
607 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
608 *calledp = TRUE;
609 if (!*optionalp)
610 {
611 if (!tlsp->peercert)
612 tlsp->peercert = X509_dup(cert); /* record failing cert */
613 return 0; /* reject */
614 }
615 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
616 "tls_try_verify_hosts)\n");
617 tlsp->verify_override = TRUE;
618 }
619
620 else if (depth != 0)
621 {
622 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
623 #ifndef DISABLE_OCSP
624 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
625 { /* client, wanting stapling */
626 /* Add the server cert's signing chain as the one
627 for the verification of the OCSP stapled information. */
628
629 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
630 cert))
631 ERR_clear_error();
632 sk_X509_push(client_static_cbinfo->verify_stack, cert);
633 }
634 #endif
635 #ifndef DISABLE_EVENT
636 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
637 return 0; /* reject, with peercert set */
638 #endif
639 }
640 else
641 {
642 const uschar * verify_cert_hostnames;
643
644 if ( tlsp == &tls_out
645 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
646 /* client, wanting hostname check */
647 {
648
649 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
650 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
651 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
652 # endif
653 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
654 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
655 # endif
656 int sep = 0;
657 const uschar * list = verify_cert_hostnames;
658 uschar * name;
659 int rc;
660 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
661 if ((rc = X509_check_host(cert, CCS name, 0,
662 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
663 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
664 NULL)))
665 {
666 if (rc < 0)
667 {
668 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
669 tlsp == &tls_out ? deliver_host_address : sender_host_address);
670 name = NULL;
671 }
672 break;
673 }
674 if (!name)
675 #else
676 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
677 #endif
678 {
679 uschar * extra = verify_mode
680 ? string_sprintf(" (during %c-verify for [%s])",
681 *verify_mode, sender_host_address)
682 : US"";
683 log_write(0, LOG_MAIN,
684 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
685 tlsp == &tls_out ? deliver_host_address : sender_host_address,
686 extra, dn, verify_cert_hostnames);
687 *calledp = TRUE;
688 if (!*optionalp)
689 {
690 if (!tlsp->peercert)
691 tlsp->peercert = X509_dup(cert); /* record failing cert */
692 return 0; /* reject */
693 }
694 DEBUG(D_tls) debug_printf("SSL verify name failure overridden (host in "
695 "tls_try_verify_hosts)\n");
696 tlsp->verify_override = TRUE;
697 }
698 }
699
700 #ifndef DISABLE_EVENT
701 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
702 return 0; /* reject, with peercert set */
703 #endif
704
705 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
706 *calledp ? "" : " authenticated", dn);
707 *calledp = TRUE;
708 }
709
710 return 1; /* accept, at least for this level */
711 }
712
713 static int
714 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
715 {
716 return verify_callback(preverify_ok, x509ctx, &tls_out,
717 &client_verify_callback_called, &client_verify_optional);
718 }
719
720 static int
721 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
722 {
723 return verify_callback(preverify_ok, x509ctx, &tls_in,
724 &server_verify_callback_called, &server_verify_optional);
725 }
726
727
728 #ifdef SUPPORT_DANE
729
730 /* This gets called *by* the dane library verify callback, which interposes
731 itself.
732 */
733 static int
734 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
735 {
736 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
737 uschar dn[256];
738 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
739 #ifndef DISABLE_EVENT
740 BOOL dummy_called, optional = FALSE;
741 #endif
742
743 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
744 {
745 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
746 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
747 deliver_host_address);
748 return 0;
749 }
750 dn[sizeof(dn)-1] = '\0';
751
752 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
753 preverify_ok ? "ok":"BAD", depth, dn);
754
755 #ifndef DISABLE_EVENT
756 if (verify_event(&tls_out, cert, depth, dn,
757 &dummy_called, &optional, US"DANE"))
758 return 0; /* reject, with peercert set */
759 #endif
760
761 if (preverify_ok == 1)
762 {
763 tls_out.dane_verified = TRUE;
764 #ifndef DISABLE_OCSP
765 if (client_static_cbinfo->u_ocsp.client.verify_store)
766 { /* client, wanting stapling */
767 /* Add the server cert's signing chain as the one
768 for the verification of the OCSP stapled information. */
769
770 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
771 cert))
772 ERR_clear_error();
773 sk_X509_push(client_static_cbinfo->verify_stack, cert);
774 }
775 #endif
776 }
777 else
778 {
779 int err = X509_STORE_CTX_get_error(x509ctx);
780 DEBUG(D_tls)
781 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
782 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
783 preverify_ok = 1;
784 }
785 return preverify_ok;
786 }
787
788 #endif /*SUPPORT_DANE*/
789
790
791 /*************************************************
792 * Information callback *
793 *************************************************/
794
795 /* The SSL library functions call this from time to time to indicate what they
796 are doing. We copy the string to the debugging output when TLS debugging has
797 been requested.
798
799 Arguments:
800 s the SSL connection
801 where
802 ret
803
804 Returns: nothing
805 */
806
807 static void
808 info_callback(SSL *s, int where, int ret)
809 {
810 DEBUG(D_tls)
811 {
812 const uschar * str;
813
814 if (where & SSL_ST_CONNECT)
815 str = US"SSL_connect";
816 else if (where & SSL_ST_ACCEPT)
817 str = US"SSL_accept";
818 else
819 str = US"SSL info (undefined)";
820
821 if (where & SSL_CB_LOOP)
822 debug_printf("%s: %s\n", str, SSL_state_string_long(s));
823 else if (where & SSL_CB_ALERT)
824 debug_printf("SSL3 alert %s:%s:%s\n",
825 str = where & SSL_CB_READ ? US"read" : US"write",
826 SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
827 else if (where & SSL_CB_EXIT)
828 if (ret == 0)
829 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
830 else if (ret < 0)
831 debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
832 else if (where & SSL_CB_HANDSHAKE_START)
833 debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
834 else if (where & SSL_CB_HANDSHAKE_DONE)
835 debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
836 }
837 }
838
839 #ifdef OPENSSL_HAVE_KEYLOG_CB
840 static void
841 keylog_callback(const SSL *ssl, const char *line)
842 {
843 DEBUG(D_tls) debug_printf("%.200s\n", line);
844 }
845 #endif
846
847
848 #ifdef EXPERIMENTAL_TLS_RESUME
849 /* Manage the keysets used for encrypting the session tickets, on the server. */
850
851 typedef struct { /* Session ticket encryption key */
852 uschar name[16];
853
854 const EVP_CIPHER * aes_cipher;
855 uschar aes_key[32]; /* size needed depends on cipher. aes_128 implies 128/8 = 16? */
856 const EVP_MD * hmac_hash;
857 uschar hmac_key[16];
858 time_t renew;
859 time_t expire;
860 } exim_stek;
861
862 static exim_stek exim_tk; /* current key */
863 static exim_stek exim_tk_old; /* previous key */
864
865 static void
866 tk_init(void)
867 {
868 time_t t = time(NULL);
869
870 if (exim_tk.name[0])
871 {
872 if (exim_tk.renew >= t) return;
873 exim_tk_old = exim_tk;
874 }
875
876 if (f.running_in_test_harness) ssl_session_timeout = 6;
877
878 DEBUG(D_tls) debug_printf("OpenSSL: %s STEK\n", exim_tk.name[0] ? "rotating" : "creating");
879 if (RAND_bytes(exim_tk.aes_key, sizeof(exim_tk.aes_key)) <= 0) return;
880 if (RAND_bytes(exim_tk.hmac_key, sizeof(exim_tk.hmac_key)) <= 0) return;
881 if (RAND_bytes(exim_tk.name+1, sizeof(exim_tk.name)-1) <= 0) return;
882
883 exim_tk.name[0] = 'E';
884 exim_tk.aes_cipher = EVP_aes_256_cbc();
885 exim_tk.hmac_hash = EVP_sha256();
886 exim_tk.expire = t + ssl_session_timeout;
887 exim_tk.renew = t + ssl_session_timeout/2;
888 }
889
890 static exim_stek *
891 tk_current(void)
892 {
893 if (!exim_tk.name[0]) return NULL;
894 return &exim_tk;
895 }
896
897 static exim_stek *
898 tk_find(const uschar * name)
899 {
900 return memcmp(name, exim_tk.name, sizeof(exim_tk.name)) == 0 ? &exim_tk
901 : memcmp(name, exim_tk_old.name, sizeof(exim_tk_old.name)) == 0 ? &exim_tk_old
902 : NULL;
903 }
904
905 /* Callback for session tickets, on server */
906 static int
907 ticket_key_callback(SSL * ssl, uschar key_name[16],
908 uschar * iv, EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int enc)
909 {
910 tls_support * tlsp = server_static_cbinfo->tlsp;
911 exim_stek * key;
912
913 if (enc)
914 {
915 DEBUG(D_tls) debug_printf("ticket_key_callback: create new session\n");
916 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
917
918 if (RAND_bytes(iv, EVP_MAX_IV_LENGTH) <= 0)
919 return -1; /* insufficient random */
920
921 if (!(key = tk_current())) /* current key doesn't exist or isn't valid */
922 return 0; /* key couldn't be created */
923 memcpy(key_name, key->name, 16);
924 DEBUG(D_tls) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - time(NULL));
925
926 /*XXX will want these dependent on the ssl session strength */
927 HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
928 key->hmac_hash, NULL);
929 EVP_EncryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv);
930
931 DEBUG(D_tls) debug_printf("ticket created\n");
932 return 1;
933 }
934 else
935 {
936 time_t now = time(NULL);
937
938 DEBUG(D_tls) debug_printf("ticket_key_callback: retrieve session\n");
939 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
940
941 if (!(key = tk_find(key_name)) || key->expire < now)
942 {
943 DEBUG(D_tls)
944 {
945 debug_printf("ticket not usable (%s)\n", key ? "expired" : "not found");
946 if (key) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - now);
947 }
948 return 0;
949 }
950
951 HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
952 key->hmac_hash, NULL);
953 EVP_DecryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv);
954
955 DEBUG(D_tls) debug_printf("ticket usable, STEK expire " TIME_T_FMT "\n", key->expire - now);
956
957 /* The ticket lifetime and renewal are the same as the STEK lifetime and
958 renewal, which is overenthusiastic. A factor of, say, 3x longer STEK would
959 be better. To do that we'd have to encode ticket lifetime in the name as
960 we don't yet see the restored session. Could check posthandshake for TLS1.3
961 and trigger a new ticket then, but cannot do that for TLS1.2 */
962 return key->renew < now ? 2 : 1;
963 }
964 }
965 #endif
966
967
968
969 /*************************************************
970 * Initialize for DH *
971 *************************************************/
972
973 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
974
975 Arguments:
976 sctx The current SSL CTX (inbound or outbound)
977 dhparam DH parameter file or fixed parameter identity string
978 host connected host, if client; NULL if server
979 errstr error string pointer
980
981 Returns: TRUE if OK (nothing to set up, or setup worked)
982 */
983
984 static BOOL
985 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
986 {
987 BIO *bio;
988 DH *dh;
989 uschar *dhexpanded;
990 const char *pem;
991 int dh_bitsize;
992
993 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
994 return FALSE;
995
996 if (!dhexpanded || !*dhexpanded)
997 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
998 else if (dhexpanded[0] == '/')
999 {
1000 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
1001 {
1002 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
1003 host, US strerror(errno), errstr);
1004 return FALSE;
1005 }
1006 }
1007 else
1008 {
1009 if (Ustrcmp(dhexpanded, "none") == 0)
1010 {
1011 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
1012 return TRUE;
1013 }
1014
1015 if (!(pem = std_dh_prime_named(dhexpanded)))
1016 {
1017 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
1018 host, US strerror(errno), errstr);
1019 return FALSE;
1020 }
1021 bio = BIO_new_mem_buf(CS pem, -1);
1022 }
1023
1024 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
1025 {
1026 BIO_free(bio);
1027 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
1028 host, NULL, errstr);
1029 return FALSE;
1030 }
1031
1032 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
1033 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
1034 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
1035 * If someone wants to dance at the edge, then they can raise the limit or use
1036 * current libraries. */
1037 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
1038 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
1039 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
1040 dh_bitsize = DH_bits(dh);
1041 #else
1042 dh_bitsize = 8 * DH_size(dh);
1043 #endif
1044
1045 /* Even if it is larger, we silently return success rather than cause things
1046 * to fail out, so that a too-large DH will not knock out all TLS; it's a
1047 * debatable choice. */
1048 if (dh_bitsize > tls_dh_max_bits)
1049 {
1050 DEBUG(D_tls)
1051 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
1052 dh_bitsize, tls_dh_max_bits);
1053 }
1054 else
1055 {
1056 SSL_CTX_set_tmp_dh(sctx, dh);
1057 DEBUG(D_tls)
1058 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
1059 dhexpanded ? dhexpanded : US"default", dh_bitsize);
1060 }
1061
1062 DH_free(dh);
1063 BIO_free(bio);
1064
1065 return TRUE;
1066 }
1067
1068
1069
1070
1071 /*************************************************
1072 * Initialize for ECDH *
1073 *************************************************/
1074
1075 /* Load parameters for ECDH encryption.
1076
1077 For now, we stick to NIST P-256 because: it's simple and easy to configure;
1078 it avoids any patent issues that might bite redistributors; despite events in
1079 the news and concerns over curve choices, we're not cryptographers, we're not
1080 pretending to be, and this is "good enough" to be better than no support,
1081 protecting against most adversaries. Given another year or two, there might
1082 be sufficient clarity about a "right" way forward to let us make an informed
1083 decision, instead of a knee-jerk reaction.
1084
1085 Longer-term, we should look at supporting both various named curves and
1086 external files generated with "openssl ecparam", much as we do for init_dh().
1087 We should also support "none" as a value, to explicitly avoid initialisation.
1088
1089 Patches welcome.
1090
1091 Arguments:
1092 sctx The current SSL CTX (inbound or outbound)
1093 host connected host, if client; NULL if server
1094 errstr error string pointer
1095
1096 Returns: TRUE if OK (nothing to set up, or setup worked)
1097 */
1098
1099 static BOOL
1100 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
1101 {
1102 #ifdef OPENSSL_NO_ECDH
1103 return TRUE;
1104 #else
1105
1106 EC_KEY * ecdh;
1107 uschar * exp_curve;
1108 int nid;
1109 BOOL rv;
1110
1111 if (host) /* No ECDH setup for clients, only for servers */
1112 return TRUE;
1113
1114 # ifndef EXIM_HAVE_ECDH
1115 DEBUG(D_tls)
1116 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
1117 return TRUE;
1118 # else
1119
1120 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
1121 return FALSE;
1122 if (!exp_curve || !*exp_curve)
1123 return TRUE;
1124
1125 /* "auto" needs to be handled carefully.
1126 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
1127 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
1128 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
1129 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
1130 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
1131 */
1132 if (Ustrcmp(exp_curve, "auto") == 0)
1133 {
1134 #if OPENSSL_VERSION_NUMBER < 0x10002000L
1135 DEBUG(D_tls) debug_printf(
1136 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
1137 exp_curve = US"prime256v1";
1138 #else
1139 # if defined SSL_CTRL_SET_ECDH_AUTO
1140 DEBUG(D_tls) debug_printf(
1141 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
1142 SSL_CTX_set_ecdh_auto(sctx, 1);
1143 return TRUE;
1144 # else
1145 DEBUG(D_tls) debug_printf(
1146 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
1147 return TRUE;
1148 # endif
1149 #endif
1150 }
1151
1152 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
1153 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
1154 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
1155 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
1156 # endif
1157 )
1158 {
1159 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
1160 host, NULL, errstr);
1161 return FALSE;
1162 }
1163
1164 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
1165 {
1166 tls_error(US"Unable to create ec curve", host, NULL, errstr);
1167 return FALSE;
1168 }
1169
1170 /* The "tmp" in the name here refers to setting a temporary key
1171 not to the stability of the interface. */
1172
1173 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
1174 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
1175 else
1176 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1177
1178 EC_KEY_free(ecdh);
1179 return !rv;
1180
1181 # endif /*EXIM_HAVE_ECDH*/
1182 #endif /*OPENSSL_NO_ECDH*/
1183 }
1184
1185
1186
1187
1188 #ifndef DISABLE_OCSP
1189 /*************************************************
1190 * Load OCSP information into state *
1191 *************************************************/
1192 /* Called to load the server OCSP response from the given file into memory, once
1193 caller has determined this is needed. Checks validity. Debugs a message
1194 if invalid.
1195
1196 ASSUMES: single response, for single cert.
1197
1198 Arguments:
1199 sctx the SSL_CTX* to update
1200 cbinfo various parts of session state
1201 filename the filename putatively holding an OCSP response
1202
1203 */
1204
1205 static void
1206 ocsp_load_response(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo,
1207 const uschar * filename)
1208 {
1209 BIO * bio;
1210 OCSP_RESPONSE * resp;
1211 OCSP_BASICRESP * basic_response;
1212 OCSP_SINGLERESP * single_response;
1213 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1214 STACK_OF(X509) * sk;
1215 unsigned long verify_flags;
1216 int status, reason, i;
1217
1218 DEBUG(D_tls) debug_printf("tls_ocsp_file '%s'\n", filename);
1219
1220 if (!(bio = BIO_new_file(CS filename, "rb")))
1221 {
1222 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1223 filename);
1224 return;
1225 }
1226
1227 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1228 BIO_free(bio);
1229 if (!resp)
1230 {
1231 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1232 return;
1233 }
1234
1235 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1236 {
1237 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1238 OCSP_response_status_str(status), status);
1239 goto bad;
1240 }
1241
1242 #ifdef notdef
1243 {
1244 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1245 OCSP_RESPONSE_print(bp, resp, 0); /* extreme debug: stapling content */
1246 BIO_free(bp);
1247 }
1248 #endif
1249
1250 if (!(basic_response = OCSP_response_get1_basic(resp)))
1251 {
1252 DEBUG(D_tls)
1253 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1254 goto bad;
1255 }
1256
1257 sk = cbinfo->verify_stack;
1258 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1259
1260 /* May need to expose ability to adjust those flags?
1261 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1262 OCSP_TRUSTOTHER OCSP_NOINTERN */
1263
1264 /* This does a full verify on the OCSP proof before we load it for serving
1265 up; possibly overkill - just date-checks might be nice enough.
1266
1267 OCSP_basic_verify takes a "store" arg, but does not
1268 use it for the chain verification, which is all we do
1269 when OCSP_NOVERIFY is set. The content from the wire
1270 "basic_response" and a cert-stack "sk" are all that is used.
1271
1272 We have a stack, loaded in setup_certs() if tls_verify_certificates
1273 was a file (not a directory, or "system"). It is unfortunate we
1274 cannot used the connection context store, as that would neatly
1275 handle the "system" case too, but there seems to be no library
1276 function for getting a stack from a store.
1277 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
1278 We do not free the stack since it could be needed a second time for
1279 SNI handling.
1280
1281 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1282 be a public interface into the OpenSSL library (there's no manual entry) -
1283 But what with? We also use OCSP_basic_verify in the client stapling callback.
1284 And there we NEED it; we must verify that status... unless the
1285 library does it for us anyway? */
1286
1287 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1288 {
1289 DEBUG(D_tls)
1290 {
1291 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1292 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1293 }
1294 goto bad;
1295 }
1296
1297 /* Here's the simplifying assumption: there's only one response, for the
1298 one certificate we use, and nothing for anything else in a chain. If this
1299 proves false, we need to extract a cert id from our issued cert
1300 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1301 right cert in the stack and then calls OCSP_single_get0_status()).
1302
1303 I'm hoping to avoid reworking a bunch more of how we handle state here.
1304
1305 XXX that will change when we add support for (TLS1.3) whole-chain stapling
1306 */
1307
1308 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1309 {
1310 DEBUG(D_tls)
1311 debug_printf("Unable to get first response from OCSP basic response.\n");
1312 goto bad;
1313 }
1314
1315 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1316 if (status != V_OCSP_CERTSTATUS_GOOD)
1317 {
1318 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1319 OCSP_cert_status_str(status), status,
1320 OCSP_crl_reason_str(reason), reason);
1321 goto bad;
1322 }
1323
1324 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1325 {
1326 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1327 goto bad;
1328 }
1329
1330 supply_response:
1331 /* Add the resp to the list used by tls_server_stapling_cb() */
1332 {
1333 ocsp_resplist ** op = &cbinfo->u_ocsp.server.olist, * oentry;
1334 while (oentry = *op)
1335 op = &oentry->next;
1336 *op = oentry = store_get(sizeof(ocsp_resplist), FALSE);
1337 oentry->next = NULL;
1338 oentry->resp = resp;
1339 }
1340 return;
1341
1342 bad:
1343 if (f.running_in_test_harness)
1344 {
1345 extern char ** environ;
1346 if (environ) for (uschar ** p = USS environ; *p; p++)
1347 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1348 {
1349 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1350 goto supply_response;
1351 }
1352 }
1353 return;
1354 }
1355
1356
1357 static void
1358 ocsp_free_response_list(tls_ext_ctx_cb * cbinfo)
1359 {
1360 for (ocsp_resplist * olist = cbinfo->u_ocsp.server.olist; olist;
1361 olist = olist->next)
1362 OCSP_RESPONSE_free(olist->resp);
1363 cbinfo->u_ocsp.server.olist = NULL;
1364 }
1365 #endif /*!DISABLE_OCSP*/
1366
1367
1368
1369
1370 /* Create and install a selfsigned certificate, for use in server mode */
1371
1372 static int
1373 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1374 {
1375 X509 * x509 = NULL;
1376 EVP_PKEY * pkey;
1377 RSA * rsa;
1378 X509_NAME * name;
1379 uschar * where;
1380
1381 where = US"allocating pkey";
1382 if (!(pkey = EVP_PKEY_new()))
1383 goto err;
1384
1385 where = US"allocating cert";
1386 if (!(x509 = X509_new()))
1387 goto err;
1388
1389 where = US"generating pkey";
1390 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1391 goto err;
1392
1393 where = US"assigning pkey";
1394 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1395 goto err;
1396
1397 X509_set_version(x509, 2); /* N+1 - version 3 */
1398 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1399 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1400 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
1401 X509_set_pubkey(x509, pkey);
1402
1403 name = X509_get_subject_name(x509);
1404 X509_NAME_add_entry_by_txt(name, "C",
1405 MBSTRING_ASC, CUS "UK", -1, -1, 0);
1406 X509_NAME_add_entry_by_txt(name, "O",
1407 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1408 X509_NAME_add_entry_by_txt(name, "CN",
1409 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1410 X509_set_issuer_name(x509, name);
1411
1412 where = US"signing cert";
1413 if (!X509_sign(x509, pkey, EVP_md5()))
1414 goto err;
1415
1416 where = US"installing selfsign cert";
1417 if (!SSL_CTX_use_certificate(sctx, x509))
1418 goto err;
1419
1420 where = US"installing selfsign key";
1421 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1422 goto err;
1423
1424 return OK;
1425
1426 err:
1427 (void) tls_error(where, NULL, NULL, errstr);
1428 if (x509) X509_free(x509);
1429 if (pkey) EVP_PKEY_free(pkey);
1430 return DEFER;
1431 }
1432
1433
1434
1435
1436 static int
1437 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1438 uschar ** errstr)
1439 {
1440 DEBUG(D_tls) debug_printf("tls_certificate file '%s'\n", file);
1441 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1442 return tls_error(string_sprintf(
1443 "SSL_CTX_use_certificate_chain_file file=%s", file),
1444 cbinfo->host, NULL, errstr);
1445 return 0;
1446 }
1447
1448 static int
1449 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1450 uschar ** errstr)
1451 {
1452 DEBUG(D_tls) debug_printf("tls_privatekey file '%s'\n", file);
1453 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1454 return tls_error(string_sprintf(
1455 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1456 return 0;
1457 }
1458
1459
1460 /*************************************************
1461 * Expand key and cert file specs *
1462 *************************************************/
1463
1464 /* Called once during tls_init and possibly again during TLS setup, for a
1465 new context, if Server Name Indication was used and tls_sni was seen in
1466 the certificate string.
1467
1468 Arguments:
1469 sctx the SSL_CTX* to update
1470 cbinfo various parts of session state
1471 errstr error string pointer
1472
1473 Returns: OK/DEFER/FAIL
1474 */
1475
1476 static int
1477 tls_expand_session_files(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo,
1478 uschar ** errstr)
1479 {
1480 uschar * expanded;
1481
1482 if (!cbinfo->certificate)
1483 {
1484 if (!cbinfo->is_server) /* client */
1485 return OK;
1486 /* server */
1487 if (tls_install_selfsign(sctx, errstr) != OK)
1488 return DEFER;
1489 }
1490 else
1491 {
1492 int err;
1493
1494 if ( !reexpand_tls_files_for_sni
1495 && ( Ustrstr(cbinfo->certificate, US"tls_sni")
1496 || Ustrstr(cbinfo->certificate, US"tls_in_sni")
1497 || Ustrstr(cbinfo->certificate, US"tls_out_sni")
1498 ) )
1499 reexpand_tls_files_for_sni = TRUE;
1500
1501 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1502 return DEFER;
1503
1504 if (expanded)
1505 if (cbinfo->is_server)
1506 {
1507 const uschar * file_list = expanded;
1508 int sep = 0;
1509 uschar * file;
1510 #ifndef DISABLE_OCSP
1511 const uschar * olist = cbinfo->u_ocsp.server.file;
1512 int osep = 0;
1513 uschar * ofile;
1514
1515 if (olist)
1516 if (!expand_check(olist, US"tls_ocsp_file", USS &olist, errstr))
1517 return DEFER;
1518 if (olist && !*olist)
1519 olist = NULL;
1520
1521 if ( cbinfo->u_ocsp.server.file_expanded && olist
1522 && (Ustrcmp(olist, cbinfo->u_ocsp.server.file_expanded) == 0))
1523 {
1524 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1525 olist = NULL;
1526 }
1527 else
1528 {
1529 ocsp_free_response_list(cbinfo);
1530 cbinfo->u_ocsp.server.file_expanded = olist;
1531 }
1532 #endif
1533
1534 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1535 {
1536 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1537 return err;
1538
1539 #ifndef DISABLE_OCSP
1540 if (olist)
1541 if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1542 ocsp_load_response(sctx, cbinfo, ofile);
1543 else
1544 DEBUG(D_tls) debug_printf("ran out of ocsp file list\n");
1545 #endif
1546 }
1547 }
1548 else /* would there ever be a need for multiple client certs? */
1549 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1550 return err;
1551
1552 if ( cbinfo->privatekey
1553 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1554 return DEFER;
1555
1556 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1557 of the expansion is an empty string, ignore it also, and assume the private
1558 key is in the same file as the certificate. */
1559
1560 if (expanded && *expanded)
1561 if (cbinfo->is_server)
1562 {
1563 const uschar * file_list = expanded;
1564 int sep = 0;
1565 uschar * file;
1566
1567 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1568 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1569 return err;
1570 }
1571 else /* would there ever be a need for multiple client certs? */
1572 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1573 return err;
1574 }
1575
1576 return OK;
1577 }
1578
1579
1580
1581
1582 /*************************************************
1583 * Callback to handle SNI *
1584 *************************************************/
1585
1586 /* Called when acting as server during the TLS session setup if a Server Name
1587 Indication extension was sent by the client.
1588
1589 API documentation is OpenSSL s_server.c implementation.
1590
1591 Arguments:
1592 s SSL* of the current session
1593 ad unknown (part of OpenSSL API) (unused)
1594 arg Callback of "our" registered data
1595
1596 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1597
1598 XXX might need to change to using ClientHello callback,
1599 per https://www.openssl.org/docs/manmaster/man3/SSL_client_hello_cb_fn.html
1600 */
1601
1602 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1603 static int
1604 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1605 {
1606 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1607 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1608 int rc;
1609 int old_pool = store_pool;
1610 uschar * dummy_errstr;
1611
1612 if (!servername)
1613 return SSL_TLSEXT_ERR_OK;
1614
1615 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1616 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1617
1618 /* Make the extension value available for expansion */
1619 store_pool = POOL_PERM;
1620 tls_in.sni = string_copy_taint(US servername, TRUE);
1621 store_pool = old_pool;
1622
1623 if (!reexpand_tls_files_for_sni)
1624 return SSL_TLSEXT_ERR_OK;
1625
1626 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1627 not confident that memcpy wouldn't break some internal reference counting.
1628 Especially since there's a references struct member, which would be off. */
1629
1630 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1631 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1632 #else
1633 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1634 #endif
1635 {
1636 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1637 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1638 goto bad;
1639 }
1640
1641 /* Not sure how many of these are actually needed, since SSL object
1642 already exists. Might even need this selfsame callback, for reneg? */
1643
1644 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1645 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1646 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1647 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1648 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1649 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1650
1651 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1652 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1653 )
1654 goto bad;
1655
1656 if ( cbinfo->server_cipher_list
1657 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1658 goto bad;
1659
1660 #ifndef DISABLE_OCSP
1661 if (cbinfo->u_ocsp.server.file)
1662 {
1663 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1664 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1665 }
1666 #endif
1667
1668 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1669 verify_callback_server, &dummy_errstr)) != OK)
1670 goto bad;
1671
1672 /* do this after setup_certs, because this can require the certs for verifying
1673 OCSP information. */
1674 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1675 goto bad;
1676
1677 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1678 SSL_set_SSL_CTX(s, server_sni);
1679 return SSL_TLSEXT_ERR_OK;
1680
1681 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1682 }
1683 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1684
1685
1686
1687
1688 #ifndef DISABLE_OCSP
1689
1690 /*************************************************
1691 * Callback to handle OCSP Stapling *
1692 *************************************************/
1693
1694 /* Called when acting as server during the TLS session setup if the client
1695 requests OCSP information with a Certificate Status Request.
1696
1697 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1698 project.
1699
1700 */
1701
1702 static int
1703 tls_server_stapling_cb(SSL *s, void *arg)
1704 {
1705 const tls_ext_ctx_cb * cbinfo = (tls_ext_ctx_cb *) arg;
1706 ocsp_resplist * olist = cbinfo->u_ocsp.server.olist;
1707 uschar * response_der; /*XXX blob */
1708 int response_der_len;
1709
1710 DEBUG(D_tls)
1711 debug_printf("Received TLS status request (OCSP stapling); %s response list\n",
1712 olist ? "have" : "lack");
1713
1714 tls_in.ocsp = OCSP_NOT_RESP;
1715 if (!olist)
1716 return SSL_TLSEXT_ERR_NOACK;
1717
1718 #ifdef EXIM_HAVE_OPESSL_GET0_SERIAL
1719 {
1720 const X509 * cert_sent = SSL_get_certificate(s);
1721 const ASN1_INTEGER * cert_serial = X509_get0_serialNumber(cert_sent);
1722 const BIGNUM * cert_bn = ASN1_INTEGER_to_BN(cert_serial, NULL);
1723 const X509_NAME * cert_issuer = X509_get_issuer_name(cert_sent);
1724 uschar * chash;
1725 uint chash_len;
1726
1727 for (; olist; olist = olist->next)
1728 {
1729 OCSP_BASICRESP * bs = OCSP_response_get1_basic(olist->resp);
1730 const OCSP_SINGLERESP * single = OCSP_resp_get0(bs, 0);
1731 const OCSP_CERTID * cid = OCSP_SINGLERESP_get0_id(single);
1732 ASN1_INTEGER * res_cert_serial;
1733 const BIGNUM * resp_bn;
1734 ASN1_OCTET_STRING * res_cert_iNameHash;
1735
1736
1737 (void) OCSP_id_get0_info(&res_cert_iNameHash, NULL, NULL, &res_cert_serial,
1738 (OCSP_CERTID *) cid);
1739 resp_bn = ASN1_INTEGER_to_BN(res_cert_serial, NULL);
1740
1741 DEBUG(D_tls)
1742 {
1743 debug_printf("cert serial: %s\n", BN_bn2hex(cert_bn));
1744 debug_printf("resp serial: %s\n", BN_bn2hex(resp_bn));
1745 }
1746
1747 if (BN_cmp(cert_bn, resp_bn) == 0)
1748 {
1749 DEBUG(D_tls) debug_printf("matched serial for ocsp\n");
1750
1751 /*XXX TODO: check the rest of the list for duplicate matches.
1752 If any, need to also check the Issuer Name hash.
1753 Without this, we will provide the wrong status in the case of
1754 duplicate id. */
1755
1756 break;
1757 }
1758 DEBUG(D_tls) debug_printf("not match serial for ocsp\n");
1759 }
1760 if (!olist)
1761 {
1762 DEBUG(D_tls) debug_printf("failed to find match for ocsp\n");
1763 return SSL_TLSEXT_ERR_NOACK;
1764 }
1765 }
1766 #else
1767 if (olist->next)
1768 {
1769 DEBUG(D_tls) debug_printf("OpenSSL version too early to support multi-leaf OCSP\n");
1770 return SSL_TLSEXT_ERR_NOACK;
1771 }
1772 #endif
1773
1774 /*XXX could we do the i2d earlier, rather than during the callback? */
1775 response_der = NULL;
1776 response_der_len = i2d_OCSP_RESPONSE(olist->resp, &response_der);
1777 if (response_der_len <= 0)
1778 return SSL_TLSEXT_ERR_NOACK;
1779
1780 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1781 tls_in.ocsp = OCSP_VFIED;
1782 return SSL_TLSEXT_ERR_OK;
1783 }
1784
1785
1786 static void
1787 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1788 {
1789 BIO_printf(bp, "\t%s: ", str);
1790 ASN1_GENERALIZEDTIME_print(bp, time);
1791 BIO_puts(bp, "\n");
1792 }
1793
1794 static int
1795 tls_client_stapling_cb(SSL *s, void *arg)
1796 {
1797 tls_ext_ctx_cb * cbinfo = arg;
1798 const unsigned char * p;
1799 int len;
1800 OCSP_RESPONSE * rsp;
1801 OCSP_BASICRESP * bs;
1802 int i;
1803
1804 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1805 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1806 if(!p)
1807 {
1808 /* Expect this when we requested ocsp but got none */
1809 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1810 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1811 else
1812 DEBUG(D_tls) debug_printf(" null\n");
1813 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1814 }
1815
1816 if (!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1817 {
1818 tls_out.ocsp = OCSP_FAILED; /*XXX should use tlsp-> to permit concurrent outbound */
1819 if (LOGGING(tls_cipher))
1820 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1821 else
1822 DEBUG(D_tls) debug_printf(" parse error\n");
1823 return 0;
1824 }
1825
1826 if (!(bs = OCSP_response_get1_basic(rsp)))
1827 {
1828 tls_out.ocsp = OCSP_FAILED;
1829 if (LOGGING(tls_cipher))
1830 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1831 else
1832 DEBUG(D_tls) debug_printf(" error parsing response\n");
1833 OCSP_RESPONSE_free(rsp);
1834 return 0;
1835 }
1836
1837 /* We'd check the nonce here if we'd put one in the request. */
1838 /* However that would defeat cacheability on the server so we don't. */
1839
1840 /* This section of code reworked from OpenSSL apps source;
1841 The OpenSSL Project retains copyright:
1842 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1843 */
1844 {
1845 BIO * bp = NULL;
1846 int status, reason;
1847 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1848
1849 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1850
1851 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1852
1853 /* Use the chain that verified the server cert to verify the stapled info */
1854 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1855
1856 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1857 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1858 {
1859 tls_out.ocsp = OCSP_FAILED;
1860 if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1861 "Received TLS cert status response, itself unverifiable: %s",
1862 ERR_reason_error_string(ERR_peek_error()));
1863 BIO_printf(bp, "OCSP response verify failure\n");
1864 ERR_print_errors(bp);
1865 OCSP_RESPONSE_print(bp, rsp, 0);
1866 goto failed;
1867 }
1868
1869 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1870
1871 /*XXX So we have a good stapled OCSP status. How do we know
1872 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1873 OCSP_resp_find_status() which matches on a cert id, which presumably
1874 we should use. Making an id needs OCSP_cert_id_new(), which takes
1875 issuerName, issuerKey, serialNumber. Are they all in the cert?
1876
1877 For now, carry on blindly accepting the resp. */
1878
1879 {
1880 OCSP_SINGLERESP * single;
1881
1882 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1883 if (OCSP_resp_count(bs) != 1)
1884 #else
1885 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1886 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1887 #endif
1888 {
1889 tls_out.ocsp = OCSP_FAILED;
1890 log_write(0, LOG_MAIN, "OCSP stapling "
1891 "with multiple responses not handled");
1892 goto failed;
1893 }
1894 single = OCSP_resp_get0(bs, 0);
1895 status = OCSP_single_get0_status(single, &reason, &rev,
1896 &thisupd, &nextupd);
1897 }
1898
1899 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1900 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1901 if (!OCSP_check_validity(thisupd, nextupd,
1902 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1903 {
1904 tls_out.ocsp = OCSP_FAILED;
1905 DEBUG(D_tls) ERR_print_errors(bp);
1906 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1907 }
1908 else
1909 {
1910 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1911 OCSP_cert_status_str(status));
1912 switch(status)
1913 {
1914 case V_OCSP_CERTSTATUS_GOOD:
1915 tls_out.ocsp = OCSP_VFIED;
1916 i = 1;
1917 goto good;
1918 case V_OCSP_CERTSTATUS_REVOKED:
1919 tls_out.ocsp = OCSP_FAILED;
1920 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1921 reason != -1 ? "; reason: " : "",
1922 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1923 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1924 break;
1925 default:
1926 tls_out.ocsp = OCSP_FAILED;
1927 log_write(0, LOG_MAIN,
1928 "Server certificate status unknown, in OCSP stapling");
1929 break;
1930 }
1931 }
1932 failed:
1933 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1934 good:
1935 BIO_free(bp);
1936 }
1937
1938 OCSP_RESPONSE_free(rsp);
1939 return i;
1940 }
1941 #endif /*!DISABLE_OCSP*/
1942
1943
1944 /*************************************************
1945 * Initialize for TLS *
1946 *************************************************/
1947
1948 /* Called from both server and client code, to do preliminary initialization
1949 of the library. We allocate and return a context structure.
1950
1951 Arguments:
1952 ctxp returned SSL context
1953 host connected host, if client; NULL if server
1954 dhparam DH parameter file
1955 certificate certificate file
1956 privatekey private key
1957 ocsp_file file of stapling info (server); flag for require ocsp (client)
1958 addr address if client; NULL if server (for some randomness)
1959 cbp place to put allocated callback context
1960 errstr error string pointer
1961
1962 Returns: OK/DEFER/FAIL
1963 */
1964
1965 static int
1966 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1967 uschar *privatekey,
1968 #ifndef DISABLE_OCSP
1969 uschar *ocsp_file,
1970 #endif
1971 address_item *addr, tls_ext_ctx_cb ** cbp,
1972 tls_support * tlsp,
1973 uschar ** errstr)
1974 {
1975 SSL_CTX * ctx;
1976 long init_options;
1977 int rc;
1978 tls_ext_ctx_cb * cbinfo;
1979
1980 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1981 cbinfo->tlsp = tlsp;
1982 cbinfo->certificate = certificate;
1983 cbinfo->privatekey = privatekey;
1984 cbinfo->is_server = host==NULL;
1985 #ifndef DISABLE_OCSP
1986 cbinfo->verify_stack = NULL;
1987 if (!host)
1988 {
1989 cbinfo->u_ocsp.server.file = ocsp_file;
1990 cbinfo->u_ocsp.server.file_expanded = NULL;
1991 cbinfo->u_ocsp.server.olist = NULL;
1992 }
1993 else
1994 cbinfo->u_ocsp.client.verify_store = NULL;
1995 #endif
1996 cbinfo->dhparam = dhparam;
1997 cbinfo->server_cipher_list = NULL;
1998 cbinfo->host = host;
1999 #ifndef DISABLE_EVENT
2000 cbinfo->event_action = NULL;
2001 #endif
2002
2003 #ifdef EXIM_NEED_OPENSSL_INIT
2004 SSL_load_error_strings(); /* basic set up */
2005 OpenSSL_add_ssl_algorithms();
2006 #endif
2007
2008 #ifdef EXIM_HAVE_SHA256
2009 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2010 list of available digests. */
2011 EVP_add_digest(EVP_sha256());
2012 #endif
2013
2014 /* Create a context.
2015 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
2016 negotiation in the different methods; as far as I can tell, the only
2017 *_{server,client}_method which allows negotiation is SSLv23, which exists even
2018 when OpenSSL is built without SSLv2 support.
2019 By disabling with openssl_options, we can let admins re-enable with the
2020 existing knob. */
2021
2022 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
2023 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
2024 #else
2025 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
2026 #endif
2027 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
2028
2029 /* It turns out that we need to seed the random number generator this early in
2030 order to get the full complement of ciphers to work. It took me roughly a day
2031 of work to discover this by experiment.
2032
2033 On systems that have /dev/urandom, SSL may automatically seed itself from
2034 there. Otherwise, we have to make something up as best we can. Double check
2035 afterwards. */
2036
2037 if (!RAND_status())
2038 {
2039 randstuff r;
2040 gettimeofday(&r.tv, NULL);
2041 r.p = getpid();
2042
2043 RAND_seed(US (&r), sizeof(r));
2044 RAND_seed(US big_buffer, big_buffer_size);
2045 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
2046
2047 if (!RAND_status())
2048 return tls_error(US"RAND_status", host,
2049 US"unable to seed random number generator", errstr);
2050 }
2051
2052 /* Set up the information callback, which outputs if debugging is at a suitable
2053 level. */
2054
2055 DEBUG(D_tls)
2056 {
2057 SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
2058 #if defined(EXIM_HAVE_OPESSL_TRACE) && !defined(OPENSSL_NO_SSL_TRACE)
2059 /* this needs a debug build of OpenSSL */
2060 SSL_CTX_set_msg_callback(ctx, (void (*)())SSL_trace);
2061 #endif
2062 #ifdef OPENSSL_HAVE_KEYLOG_CB
2063 SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
2064 #endif
2065 }
2066
2067 /* Automatically re-try reads/writes after renegotiation. */
2068 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
2069
2070 /* Apply administrator-supplied work-arounds.
2071 Historically we applied just one requested option,
2072 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
2073 moved to an administrator-controlled list of options to specify and
2074 grandfathered in the first one as the default value for "openssl_options".
2075
2076 No OpenSSL version number checks: the options we accept depend upon the
2077 availability of the option value macros from OpenSSL. */
2078
2079 if (!tls_openssl_options_parse(openssl_options, &init_options))
2080 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
2081
2082 #ifdef EXPERIMENTAL_TLS_RESUME
2083 tlsp->resumption = RESUME_SUPPORTED;
2084 #endif
2085 if (init_options)
2086 {
2087 #ifdef EXPERIMENTAL_TLS_RESUME
2088 /* Should the server offer session resumption? */
2089 if (!host && verify_check_host(&tls_resumption_hosts) == OK)
2090 {
2091 DEBUG(D_tls) debug_printf("tls_resumption_hosts overrides openssl_options\n");
2092 init_options &= ~SSL_OP_NO_TICKET;
2093 tlsp->resumption |= RESUME_SERVER_TICKET; /* server will give ticket on request */
2094 tlsp->host_resumable = TRUE;
2095 }
2096 #endif
2097
2098 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
2099 if (!(SSL_CTX_set_options(ctx, init_options)))
2100 return tls_error(string_sprintf(
2101 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
2102 }
2103 else
2104 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
2105
2106 /* We'd like to disable session cache unconditionally, but foolish Outlook
2107 Express clients then give up the first TLS connection and make a second one
2108 (which works). Only when there is an IMAP service on the same machine.
2109 Presumably OE is trying to use the cache for A on B. Leave it enabled for
2110 now, until we work out a decent way of presenting control to the config. It
2111 will never be used because we use a new context every time. */
2112 #ifdef notdef
2113 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
2114 #endif
2115
2116 /* Initialize with DH parameters if supplied */
2117 /* Initialize ECDH temp key parameter selection */
2118
2119 if ( !init_dh(ctx, dhparam, host, errstr)
2120 || !init_ecdh(ctx, host, errstr)
2121 )
2122 return DEFER;
2123
2124 /* Set up certificate and key (and perhaps OCSP info) */
2125
2126 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
2127 return rc;
2128
2129 /* If we need to handle SNI or OCSP, do so */
2130
2131 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2132 # ifndef DISABLE_OCSP
2133 if (!(cbinfo->verify_stack = sk_X509_new_null()))
2134 {
2135 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
2136 return FAIL;
2137 }
2138 # endif
2139
2140 if (!host) /* server */
2141 {
2142 # ifndef DISABLE_OCSP
2143 /* We check u_ocsp.server.file, not server.olist, because we care about if
2144 the option exists, not what the current expansion might be, as SNI might
2145 change the certificate and OCSP file in use between now and the time the
2146 callback is invoked. */
2147 if (cbinfo->u_ocsp.server.file)
2148 {
2149 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
2150 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2151 }
2152 # endif
2153 /* We always do this, so that $tls_sni is available even if not used in
2154 tls_certificate */
2155 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
2156 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
2157 }
2158 # ifndef DISABLE_OCSP
2159 else /* client */
2160 if(ocsp_file) /* wanting stapling */
2161 {
2162 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
2163 {
2164 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
2165 return FAIL;
2166 }
2167 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
2168 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2169 }
2170 # endif
2171 #endif
2172
2173 cbinfo->verify_cert_hostnames = NULL;
2174
2175 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
2176 /* Set up the RSA callback */
2177 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
2178 #endif
2179
2180 /* Finally, set the session cache timeout, and we are done.
2181 The period appears to be also used for (server-generated) session tickets */
2182
2183 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
2184 DEBUG(D_tls) debug_printf("Initialized TLS\n");
2185
2186 *cbp = cbinfo;
2187 *ctxp = ctx;
2188
2189 return OK;
2190 }
2191
2192
2193
2194
2195 /*************************************************
2196 * Get name of cipher in use *
2197 *************************************************/
2198
2199 /*
2200 Argument: pointer to an SSL structure for the connection
2201 pointer to number of bits for cipher
2202 Returns: pointer to allocated string in perm-pool
2203 */
2204
2205 static uschar *
2206 construct_cipher_name(SSL * ssl, int * bits)
2207 {
2208 int pool = store_pool;
2209 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
2210 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
2211 the accessor functions use const in the prototype. */
2212
2213 const uschar * ver = CUS SSL_get_version(ssl);
2214 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
2215 uschar * s;
2216
2217 SSL_CIPHER_get_bits(c, bits);
2218
2219 store_pool = POOL_PERM;
2220 s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits);
2221 store_pool = pool;
2222 DEBUG(D_tls) debug_printf("Cipher: %s\n", s);
2223 return s;
2224 }
2225
2226
2227 /* Get IETF-standard name for ciphersuite.
2228 Argument: pointer to an SSL structure for the connection
2229 Returns: pointer to string
2230 */
2231
2232 static const uschar *
2233 cipher_stdname_ssl(SSL * ssl)
2234 {
2235 #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
2236 return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl));
2237 #else
2238 ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl));
2239 return cipher_stdname(id >> 8, id & 0xff);
2240 #endif
2241 }
2242
2243
2244 static void
2245 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
2246 {
2247 /*XXX we might consider a list-of-certs variable for the cert chain.
2248 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
2249 in list-handling functions, also consider the difference between the entire
2250 chain and the elements sent by the peer. */
2251
2252 tlsp->peerdn = NULL;
2253
2254 /* Will have already noted peercert on a verify fail; possibly not the leaf */
2255 if (!tlsp->peercert)
2256 tlsp->peercert = SSL_get_peer_certificate(ssl);
2257 /* Beware anonymous ciphers which lead to server_cert being NULL */
2258 if (tlsp->peercert)
2259 if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
2260 { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
2261 else
2262 {
2263 int oldpool = store_pool;
2264
2265 peerdn[siz-1] = '\0'; /* paranoia */
2266 store_pool = POOL_PERM;
2267 tlsp->peerdn = string_copy(peerdn);
2268 store_pool = oldpool;
2269
2270 /* We used to set CV in the cert-verify callbacks (either plain or dane)
2271 but they don't get called on session-resumption. So use the official
2272 interface, which uses the resumed value. Unfortunately this claims verified
2273 when it actually failed but we're in try-verify mode, due to us wanting the
2274 knowlege that it failed so needing to have the callback and forcing a
2275 permissive return. If we don't force it, the TLS startup is failed.
2276 The extra bit of information is set in verify_override in the cb, stashed
2277 for resumption next to the TLS session, and used here. */
2278
2279 if (!tlsp->verify_override)
2280 tlsp->certificate_verified = SSL_get_verify_result(ssl) == X509_V_OK;
2281 }
2282 }
2283
2284
2285
2286
2287
2288 /*************************************************
2289 * Set up for verifying certificates *
2290 *************************************************/
2291
2292 #ifndef DISABLE_OCSP
2293 /* Load certs from file, return TRUE on success */
2294
2295 static BOOL
2296 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
2297 {
2298 BIO * bp;
2299 X509 * x;
2300
2301 while (sk_X509_num(verify_stack) > 0)
2302 X509_free(sk_X509_pop(verify_stack));
2303
2304 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
2305 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
2306 sk_X509_push(verify_stack, x);
2307 BIO_free(bp);
2308 return TRUE;
2309 }
2310 #endif
2311
2312
2313
2314 /* Called by both client and server startup; on the server possibly
2315 repeated after a Server Name Indication.
2316
2317 Arguments:
2318 sctx SSL_CTX* to initialise
2319 certs certs file or NULL
2320 crl CRL file or NULL
2321 host NULL in a server; the remote host in a client
2322 optional TRUE if called from a server for a host in tls_try_verify_hosts;
2323 otherwise passed as FALSE
2324 cert_vfy_cb Callback function for certificate verification
2325 errstr error string pointer
2326
2327 Returns: OK/DEFER/FAIL
2328 */
2329
2330 static int
2331 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2332 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2333 {
2334 uschar *expcerts, *expcrl;
2335
2336 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2337 return DEFER;
2338 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2339
2340 if (expcerts && *expcerts)
2341 {
2342 /* Tell the library to use its compiled-in location for the system default
2343 CA bundle. Then add the ones specified in the config, if any. */
2344
2345 if (!SSL_CTX_set_default_verify_paths(sctx))
2346 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2347
2348 if (Ustrcmp(expcerts, "system") != 0)
2349 {
2350 struct stat statbuf;
2351
2352 if (Ustat(expcerts, &statbuf) < 0)
2353 {
2354 log_write(0, LOG_MAIN|LOG_PANIC,
2355 "failed to stat %s for certificates", expcerts);
2356 return DEFER;
2357 }
2358 else
2359 {
2360 uschar *file, *dir;
2361 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2362 { file = NULL; dir = expcerts; }
2363 else
2364 {
2365 file = expcerts; dir = NULL;
2366 #ifndef DISABLE_OCSP
2367 /* In the server if we will be offering an OCSP proof, load chain from
2368 file for verifying the OCSP proof at load time. */
2369
2370 /*XXX Glitch! The file here is tls_verify_certs: the chain for verifying the client cert.
2371 This is inconsistent with the need to verify the OCSP proof of the server cert.
2372 */
2373
2374 if ( !host
2375 && statbuf.st_size > 0
2376 && server_static_cbinfo->u_ocsp.server.file
2377 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2378 )
2379 {
2380 log_write(0, LOG_MAIN|LOG_PANIC,
2381 "failed to load cert chain from %s", file);
2382 return DEFER;
2383 }
2384 #endif
2385 }
2386
2387 /* If a certificate file is empty, the next function fails with an
2388 unhelpful error message. If we skip it, we get the correct behaviour (no
2389 certificates are recognized, but the error message is still misleading (it
2390 says no certificate was supplied). But this is better. */
2391
2392 if ( (!file || statbuf.st_size > 0)
2393 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2394 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2395
2396 /* Load the list of CAs for which we will accept certs, for sending
2397 to the client. This is only for the one-file tls_verify_certificates
2398 variant.
2399 If a list isn't loaded into the server, but some verify locations are set,
2400 the server end appears to make a wildcard request for client certs.
2401 Meanwhile, the client library as default behaviour *ignores* the list
2402 we send over the wire - see man SSL_CTX_set_client_cert_cb.
2403 Because of this, and that the dir variant is likely only used for
2404 the public-CA bundle (not for a private CA), not worth fixing. */
2405
2406 if (file)
2407 {
2408 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2409
2410 SSL_CTX_set_client_CA_list(sctx, names);
2411 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2412 sk_X509_NAME_num(names));
2413 }
2414 }
2415 }
2416
2417 /* Handle a certificate revocation list. */
2418
2419 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2420
2421 /* This bit of code is now the version supplied by Lars Mainka. (I have
2422 merely reformatted it into the Exim code style.)
2423
2424 "From here I changed the code to add support for multiple crl's
2425 in pem format in one file or to support hashed directory entries in
2426 pem format instead of a file. This method now uses the library function
2427 X509_STORE_load_locations to add the CRL location to the SSL context.
2428 OpenSSL will then handle the verify against CA certs and CRLs by
2429 itself in the verify callback." */
2430
2431 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2432 if (expcrl && *expcrl)
2433 {
2434 struct stat statbufcrl;
2435 if (Ustat(expcrl, &statbufcrl) < 0)
2436 {
2437 log_write(0, LOG_MAIN|LOG_PANIC,
2438 "failed to stat %s for certificates revocation lists", expcrl);
2439 return DEFER;
2440 }
2441 else
2442 {
2443 /* is it a file or directory? */
2444 uschar *file, *dir;
2445 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2446 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2447 {
2448 file = NULL;
2449 dir = expcrl;
2450 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2451 }
2452 else
2453 {
2454 file = expcrl;
2455 dir = NULL;
2456 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2457 }
2458 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2459 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2460
2461 /* setting the flags to check against the complete crl chain */
2462
2463 X509_STORE_set_flags(cvstore,
2464 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2465 }
2466 }
2467
2468 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2469
2470 /* If verification is optional, don't fail if no certificate */
2471
2472 SSL_CTX_set_verify(sctx,
2473 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2474 cert_vfy_cb);
2475 }
2476
2477 return OK;
2478 }
2479
2480
2481
2482 /*************************************************
2483 * Start a TLS session in a server *
2484 *************************************************/
2485
2486 /* This is called when Exim is running as a server, after having received
2487 the STARTTLS command. It must respond to that command, and then negotiate
2488 a TLS session.
2489
2490 Arguments:
2491 require_ciphers allowed ciphers
2492 errstr pointer to error message
2493
2494 Returns: OK on success
2495 DEFER for errors before the start of the negotiation
2496 FAIL for errors during the negotiation; the server can't
2497 continue running.
2498 */
2499
2500 int
2501 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2502 {
2503 int rc;
2504 uschar * expciphers;
2505 tls_ext_ctx_cb * cbinfo;
2506 static uschar peerdn[256];
2507
2508 /* Check for previous activation */
2509
2510 if (tls_in.active.sock >= 0)
2511 {
2512 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2513 smtp_printf("554 Already in TLS\r\n", FALSE);
2514 return FAIL;
2515 }
2516
2517 /* Initialize the SSL library. If it fails, it will already have logged
2518 the error. */
2519
2520 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2521 #ifndef DISABLE_OCSP
2522 tls_ocsp_file,
2523 #endif
2524 NULL, &server_static_cbinfo, &tls_in, errstr);
2525 if (rc != OK) return rc;
2526 cbinfo = server_static_cbinfo;
2527
2528 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2529 return FAIL;
2530
2531 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2532 were historically separated by underscores. So that I can use either form in my
2533 tests, and also for general convenience, we turn underscores into hyphens here.
2534
2535 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2536 for TLS 1.3 . Since we do not call it at present we get the default list:
2537 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2538 */
2539
2540 if (expciphers)
2541 {
2542 for (uschar * s = expciphers; *s; s++ ) if (*s == '_') *s = '-';
2543 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2544 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2545 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2546 cbinfo->server_cipher_list = expciphers;
2547 }
2548
2549 /* If this is a host for which certificate verification is mandatory or
2550 optional, set up appropriately. */
2551
2552 tls_in.certificate_verified = FALSE;
2553 #ifdef SUPPORT_DANE
2554 tls_in.dane_verified = FALSE;
2555 #endif
2556 server_verify_callback_called = FALSE;
2557
2558 if (verify_check_host(&tls_verify_hosts) == OK)
2559 {
2560 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2561 FALSE, verify_callback_server, errstr);
2562 if (rc != OK) return rc;
2563 server_verify_optional = FALSE;
2564 }
2565 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2566 {
2567 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2568 TRUE, verify_callback_server, errstr);
2569 if (rc != OK) return rc;
2570 server_verify_optional = TRUE;
2571 }
2572
2573 #ifdef EXPERIMENTAL_TLS_RESUME
2574 SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_key_callback);
2575 /* despite working, appears to always return failure, so ignoring */
2576 #endif
2577 #ifdef OPENSSL_HAVE_NUM_TICKETS
2578 # ifdef EXPERIMENTAL_TLS_RESUME
2579 SSL_CTX_set_num_tickets(server_ctx, tls_in.host_resumable ? 1 : 0);
2580 # else
2581 SSL_CTX_set_num_tickets(server_ctx, 0); /* send no TLS1.3 stateful-tickets */
2582 # endif
2583 #endif
2584
2585
2586 /* Prepare for new connection */
2587
2588 if (!(server_ssl = SSL_new(server_ctx)))
2589 return tls_error(US"SSL_new", NULL, NULL, errstr);
2590
2591 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2592 *
2593 * With the SSL_clear(), we get strange interoperability bugs with
2594 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2595 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2596 *
2597 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2598 * session shutdown. In this case, we have a brand new object and there's no
2599 * obvious reason to immediately clear it. I'm guessing that this was
2600 * originally added because of incomplete initialisation which the clear fixed,
2601 * in some historic release.
2602 */
2603
2604 /* Set context and tell client to go ahead, except in the case of TLS startup
2605 on connection, where outputting anything now upsets the clients and tends to
2606 make them disconnect. We need to have an explicit fflush() here, to force out
2607 the response. Other smtp_printf() calls do not need it, because in non-TLS
2608 mode, the fflush() happens when smtp_getc() is called. */
2609
2610 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2611 if (!tls_in.on_connect)
2612 {
2613 smtp_printf("220 TLS go ahead\r\n", FALSE);
2614 fflush(smtp_out);
2615 }
2616
2617 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2618 that the OpenSSL library doesn't. */
2619
2620 SSL_set_wfd(server_ssl, fileno(smtp_out));
2621 SSL_set_rfd(server_ssl, fileno(smtp_in));
2622 SSL_set_accept_state(server_ssl);
2623
2624 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2625
2626 sigalrm_seen = FALSE;
2627 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2628 rc = SSL_accept(server_ssl);
2629 ALARM_CLR(0);
2630
2631 if (rc <= 0)
2632 {
2633 int error = SSL_get_error(server_ssl, rc);
2634 switch(error)
2635 {
2636 case SSL_ERROR_NONE:
2637 break;
2638
2639 case SSL_ERROR_ZERO_RETURN:
2640 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2641 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2642
2643 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2644 SSL_shutdown(server_ssl);
2645
2646 tls_close(NULL, TLS_NO_SHUTDOWN);
2647 return FAIL;
2648
2649 /* Handle genuine errors */
2650 case SSL_ERROR_SSL:
2651 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2652 return FAIL;
2653
2654 default:
2655 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2656 if (error == SSL_ERROR_SYSCALL)
2657 {
2658 if (!errno)
2659 {
2660 *errstr = US"SSL_accept: TCP connection closed by peer";
2661 return FAIL;
2662 }
2663 DEBUG(D_tls) debug_printf(" - syscall %s\n", strerror(errno));
2664 }
2665 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2666 return FAIL;
2667 }
2668 }
2669
2670 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2671 ERR_clear_error(); /* Even success can leave errors in the stack. Seen with
2672 anon-authentication ciphersuite negotiated. */
2673
2674 #ifdef EXPERIMENTAL_TLS_RESUME
2675 if (SSL_session_reused(server_ssl))
2676 {
2677 tls_in.resumption |= RESUME_USED;
2678 DEBUG(D_tls) debug_printf("Session reused\n");
2679 }
2680 #endif
2681
2682 /* TLS has been set up. Adjust the input functions to read via TLS,
2683 and initialize things. */
2684
2685 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2686
2687 tls_in.cipher = construct_cipher_name(server_ssl, &tls_in.bits);
2688 tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl);
2689
2690 DEBUG(D_tls)
2691 {
2692 uschar buf[2048];
2693 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)))
2694 debug_printf("Shared ciphers: %s\n", buf);
2695
2696 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2697 {
2698 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2699 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2700 BIO_free(bp);
2701 }
2702 #endif
2703
2704 #ifdef EXIM_HAVE_SESSION_TICKET
2705 {
2706 SSL_SESSION * ss = SSL_get_session(server_ssl);
2707 if (SSL_SESSION_has_ticket(ss)) /* 1.1.0 */
2708 debug_printf("The session has a ticket, life %lu seconds\n",
2709 SSL_SESSION_get_ticket_lifetime_hint(ss));
2710 }
2711 #endif
2712 }
2713
2714 /* Record the certificate we presented */
2715 {
2716 X509 * crt = SSL_get_certificate(server_ssl);
2717 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2718 }
2719
2720 /* Only used by the server-side tls (tls_in), including tls_getc.
2721 Client-side (tls_out) reads (seem to?) go via
2722 smtp_read_response()/ip_recv().
2723 Hence no need to duplicate for _in and _out.
2724 */
2725 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2726 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2727 ssl_xfer_eof = ssl_xfer_error = FALSE;
2728
2729 receive_getc = tls_getc;
2730 receive_getbuf = tls_getbuf;
2731 receive_get_cache = tls_get_cache;
2732 receive_ungetc = tls_ungetc;
2733 receive_feof = tls_feof;
2734 receive_ferror = tls_ferror;
2735 receive_smtp_buffered = tls_smtp_buffered;
2736
2737 tls_in.active.sock = fileno(smtp_out);
2738 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2739 return OK;
2740 }
2741
2742
2743
2744
2745 static int
2746 tls_client_basic_ctx_init(SSL_CTX * ctx,
2747 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2748 uschar ** errstr)
2749 {
2750 int rc;
2751 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2752 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2753 the specified host patterns if one of them is defined */
2754
2755 if ( ( !ob->tls_verify_hosts
2756 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2757 )
2758 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2759 )
2760 client_verify_optional = FALSE;
2761 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2762 client_verify_optional = TRUE;
2763 else
2764 return OK;
2765
2766 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2767 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2768 errstr)) != OK)
2769 return rc;
2770
2771 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2772 {
2773 cbinfo->verify_cert_hostnames =
2774 #ifdef SUPPORT_I18N
2775 string_domain_utf8_to_alabel(host->name, NULL);
2776 #else
2777 host->name;
2778 #endif
2779 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2780 cbinfo->verify_cert_hostnames);
2781 }
2782 return OK;
2783 }
2784
2785
2786 #ifdef SUPPORT_DANE
2787 static int
2788 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2789 {
2790 dns_scan dnss;
2791 const char * hostnames[2] = { CS host->name, NULL };
2792 int found = 0;
2793
2794 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2795 return tls_error(US"hostnames load", host, NULL, errstr);
2796
2797 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2798 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2799 ) if (rr->type == T_TLSA && rr->size > 3)
2800 {
2801 const uschar * p = rr->data;
2802 uint8_t usage, selector, mtype;
2803 const char * mdname;
2804
2805 usage = *p++;
2806
2807 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2808 if (usage != 2 && usage != 3) continue;
2809
2810 selector = *p++;
2811 mtype = *p++;
2812
2813 switch (mtype)
2814 {
2815 default: continue; /* Only match-types 0, 1, 2 are supported */
2816 case 0: mdname = NULL; break;
2817 case 1: mdname = "sha256"; break;
2818 case 2: mdname = "sha512"; break;
2819 }
2820
2821 found++;
2822 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2823 {
2824 default:
2825 return tls_error(US"tlsa load", host, NULL, errstr);
2826 case 0: /* action not taken */
2827 case 1: break;
2828 }
2829
2830 tls_out.tlsa_usage |= 1<<usage;
2831 }
2832
2833 if (found)
2834 return OK;
2835
2836 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2837 return DEFER;
2838 }
2839 #endif /*SUPPORT_DANE*/
2840
2841
2842
2843 #ifdef EXPERIMENTAL_TLS_RESUME
2844 /* On the client, get any stashed session for the given IP from hints db
2845 and apply it to the ssl-connection for attempted resumption. */
2846
2847 static void
2848 tls_retrieve_session(tls_support * tlsp, SSL * ssl, const uschar * key)
2849 {
2850 tlsp->resumption |= RESUME_SUPPORTED;
2851 if (tlsp->host_resumable)
2852 {
2853 dbdata_tls_session * dt;
2854 int len;
2855 open_db dbblock, * dbm_file;
2856
2857 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
2858 DEBUG(D_tls) debug_printf("checking for resumable session for %s\n", key);
2859 if ((dbm_file = dbfn_open(US"tls", O_RDONLY, &dbblock, FALSE, FALSE)))
2860 {
2861 /* key for the db is the IP */
2862 if ((dt = dbfn_read_with_length(dbm_file, key, &len)))
2863 {
2864 SSL_SESSION * ss = NULL;
2865 const uschar * sess_asn1 = dt->session;
2866
2867 len -= sizeof(dbdata_tls_session);
2868 if (!(d2i_SSL_SESSION(&ss, &sess_asn1, (long)len)))
2869 {
2870 DEBUG(D_tls)
2871 {
2872 ERR_error_string_n(ERR_get_error(),
2873 ssl_errstring, sizeof(ssl_errstring));
2874 debug_printf("decoding session: %s\n", ssl_errstring);
2875 }
2876 }
2877 #ifdef EXIM_HAVE_SESSION_TICKET
2878 else if ( SSL_SESSION_get_ticket_lifetime_hint(ss) + dt->time_stamp
2879 < time(NULL))
2880 {
2881 DEBUG(D_tls) debug_printf("session expired\n");
2882 dbfn_delete(dbm_file, key);
2883 }
2884 #endif
2885 else if (!SSL_set_session(ssl, ss))
2886 {
2887 DEBUG(D_tls)
2888 {
2889 ERR_error_string_n(ERR_get_error(),
2890 ssl_errstring, sizeof(ssl_errstring));
2891 debug_printf("applying session to ssl: %s\n", ssl_errstring);
2892 }
2893 }
2894 else
2895 {
2896 DEBUG(D_tls) debug_printf("good session\n");
2897 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
2898 tlsp->verify_override = dt->verify_override;
2899 tlsp->ocsp = dt->ocsp;
2900 }
2901 }
2902 else
2903 DEBUG(D_tls) debug_printf("no session record\n");
2904 dbfn_close(dbm_file);
2905 }
2906 }
2907 }
2908
2909
2910 /* On the client, save the session for later resumption */
2911
2912 static int
2913 tls_save_session_cb(SSL * ssl, SSL_SESSION * ss)
2914 {
2915 tls_ext_ctx_cb * cbinfo = SSL_get_ex_data(ssl, tls_exdata_idx);
2916 tls_support * tlsp;
2917
2918 DEBUG(D_tls) debug_printf("tls_save_session_cb\n");
2919
2920 if (!cbinfo || !(tlsp = cbinfo->tlsp)->host_resumable) return 0;
2921
2922 # ifdef OPENSSL_HAVE_NUM_TICKETS
2923 if (SSL_SESSION_is_resumable(ss)) /* 1.1.1 */
2924 # endif
2925 {
2926 int len = i2d_SSL_SESSION(ss, NULL);
2927 int dlen = sizeof(dbdata_tls_session) + len;
2928 dbdata_tls_session * dt = store_get(dlen, TRUE);
2929 uschar * s = dt->session;
2930 open_db dbblock, * dbm_file;
2931
2932 DEBUG(D_tls) debug_printf("session is resumable\n");
2933 tlsp->resumption |= RESUME_SERVER_TICKET; /* server gave us a ticket */
2934
2935 dt->verify_override = tlsp->verify_override;
2936 dt->ocsp = tlsp->ocsp;
2937 (void) i2d_SSL_SESSION(ss, &s); /* s gets bumped to end */
2938
2939 if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE)))
2940 {
2941 const uschar * key = cbinfo->host->address;
2942 dbfn_delete(dbm_file, key);
2943 dbfn_write(dbm_file, key, dt, dlen);
2944 dbfn_close(dbm_file);
2945 DEBUG(D_tls) debug_printf("wrote session (len %u) to db\n",
2946 (unsigned)dlen);
2947 }
2948 }
2949 return 1;
2950 }
2951
2952
2953 static void
2954 tls_client_ctx_resume_prehandshake(
2955 exim_openssl_client_tls_ctx * exim_client_ctx, tls_support * tlsp,
2956 smtp_transport_options_block * ob, host_item * host)
2957 {
2958 /* Should the client request a session resumption ticket? */
2959 if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK)
2960 {
2961 tlsp->host_resumable = TRUE;
2962
2963 SSL_CTX_set_session_cache_mode(exim_client_ctx->ctx,
2964 SSL_SESS_CACHE_CLIENT
2965 | SSL_SESS_CACHE_NO_INTERNAL | SSL_SESS_CACHE_NO_AUTO_CLEAR);
2966 SSL_CTX_sess_set_new_cb(exim_client_ctx->ctx, tls_save_session_cb);
2967 }
2968 }
2969
2970 static BOOL
2971 tls_client_ssl_resume_prehandshake(SSL * ssl, tls_support * tlsp,
2972 host_item * host, uschar ** errstr)
2973 {
2974 if (tlsp->host_resumable)
2975 {
2976 DEBUG(D_tls)
2977 debug_printf("tls_resumption_hosts overrides openssl_options, enabling tickets\n");
2978 SSL_clear_options(ssl, SSL_OP_NO_TICKET);
2979
2980 tls_exdata_idx = SSL_get_ex_new_index(0, 0, 0, 0, 0);
2981 if (!SSL_set_ex_data(ssl, tls_exdata_idx, client_static_cbinfo))
2982 {
2983 tls_error(US"set ex_data", host, NULL, errstr);
2984 return FALSE;
2985 }
2986 debug_printf("tls_exdata_idx %d cbinfo %p\n", tls_exdata_idx, client_static_cbinfo);
2987 }
2988
2989 tlsp->resumption = RESUME_SUPPORTED;
2990 /* Pick up a previous session, saved on an old ticket */
2991 tls_retrieve_session(tlsp, ssl, host->address);
2992 return TRUE;
2993 }
2994
2995 static void
2996 tls_client_resume_posthandshake(exim_openssl_client_tls_ctx * exim_client_ctx,
2997 tls_support * tlsp)
2998 {
2999 if (SSL_session_reused(exim_client_ctx->ssl))
3000 {
3001 DEBUG(D_tls) debug_printf("The session was reused\n");
3002 tlsp->resumption |= RESUME_USED;
3003 }
3004 }
3005 #endif /* EXPERIMENTAL_TLS_RESUME */
3006
3007
3008 /*************************************************
3009 * Start a TLS session in a client *
3010 *************************************************/
3011
3012 /* Called from the smtp transport after STARTTLS has been accepted.
3013
3014 Arguments:
3015 cctx connection context
3016 conn_args connection details
3017 cookie datum for randomness; can be NULL
3018 tlsp record details of TLS channel configuration here; must be non-NULL
3019 errstr error string pointer
3020
3021 Returns: TRUE for success with TLS session context set in connection context,
3022 FALSE on error
3023 */
3024
3025 BOOL
3026 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
3027 void * cookie, tls_support * tlsp, uschar ** errstr)
3028 {
3029 host_item * host = conn_args->host; /* for msgs and option-tests */
3030 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
3031 smtp_transport_options_block * ob = tb
3032 ? (smtp_transport_options_block *)tb->options_block
3033 : &smtp_transport_option_defaults;
3034 exim_openssl_client_tls_ctx * exim_client_ctx;
3035 uschar * expciphers;
3036 int rc;
3037 static uschar peerdn[256];
3038
3039 #ifndef DISABLE_OCSP
3040 BOOL request_ocsp = FALSE;
3041 BOOL require_ocsp = FALSE;
3042 #endif
3043
3044 rc = store_pool;
3045 store_pool = POOL_PERM;
3046 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx), FALSE);
3047 exim_client_ctx->corked = NULL;
3048 store_pool = rc;
3049
3050 #ifdef SUPPORT_DANE
3051 tlsp->tlsa_usage = 0;
3052 #endif
3053
3054 #ifndef DISABLE_OCSP
3055 {
3056 # ifdef SUPPORT_DANE
3057 if ( conn_args->dane
3058 && ob->hosts_request_ocsp[0] == '*'
3059 && ob->hosts_request_ocsp[1] == '\0'
3060 )
3061 {
3062 /* Unchanged from default. Use a safer one under DANE */
3063 request_ocsp = TRUE;
3064 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
3065 " {= {4}{$tls_out_tlsa_usage}} } "
3066 " {*}{}}";
3067 }
3068 # endif
3069
3070 if ((require_ocsp =
3071 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
3072 request_ocsp = TRUE;
3073 else
3074 # ifdef SUPPORT_DANE
3075 if (!request_ocsp)
3076 # endif
3077 request_ocsp =
3078 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
3079 }
3080 #endif
3081
3082 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
3083 ob->tls_certificate, ob->tls_privatekey,
3084 #ifndef DISABLE_OCSP
3085 (void *)(long)request_ocsp,
3086 #endif
3087 cookie, &client_static_cbinfo, tlsp, errstr);
3088 if (rc != OK) return FALSE;
3089
3090 tlsp->certificate_verified = FALSE;
3091 client_verify_callback_called = FALSE;
3092
3093 expciphers = NULL;
3094 #ifdef SUPPORT_DANE
3095 if (conn_args->dane)
3096 {
3097 /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
3098 other failures should be treated as problems. */
3099 if (ob->dane_require_tls_ciphers &&
3100 !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
3101 &expciphers, errstr))
3102 return FALSE;
3103 if (expciphers && *expciphers == '\0')
3104 expciphers = NULL;
3105 }
3106 #endif
3107 if (!expciphers &&
3108 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
3109 &expciphers, errstr))
3110 return FALSE;
3111
3112 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
3113 are separated by underscores. So that I can use either form in my tests, and
3114 also for general convenience, we turn underscores into hyphens here. */
3115
3116 if (expciphers)
3117 {
3118 uschar *s = expciphers;
3119 while (*s) { if (*s == '_') *s = '-'; s++; }
3120 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
3121 if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
3122 {
3123 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
3124 return FALSE;
3125 }
3126 }
3127
3128 #ifdef SUPPORT_DANE
3129 if (conn_args->dane)
3130 {
3131 SSL_CTX_set_verify(exim_client_ctx->ctx,
3132 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
3133 verify_callback_client_dane);
3134
3135 if (!DANESSL_library_init())
3136 {
3137 tls_error(US"library init", host, NULL, errstr);
3138 return FALSE;
3139 }
3140 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
3141 {
3142 tls_error(US"context init", host, NULL, errstr);
3143 return FALSE;
3144 }
3145 }
3146 else
3147
3148 #endif
3149
3150 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
3151 client_static_cbinfo, errstr) != OK)
3152 return FALSE;
3153
3154 #ifdef EXPERIMENTAL_TLS_RESUME
3155 tls_client_ctx_resume_prehandshake(exim_client_ctx, tlsp, ob, host);
3156 #endif
3157
3158
3159 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
3160 {
3161 tls_error(US"SSL_new", host, NULL, errstr);
3162 return FALSE;
3163 }
3164 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
3165
3166 SSL_set_fd(exim_client_ctx->ssl, cctx->sock);
3167 SSL_set_connect_state(exim_client_ctx->ssl);
3168
3169 if (ob->tls_sni)
3170 {
3171 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
3172 return FALSE;
3173 if (!tlsp->sni)
3174 {
3175 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
3176 }
3177 else if (!Ustrlen(tlsp->sni))
3178 tlsp->sni = NULL;
3179 else
3180 {
3181 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
3182 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
3183 SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
3184 #else
3185 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
3186 tlsp->sni);
3187 #endif
3188 }
3189 }
3190
3191 #ifdef SUPPORT_DANE
3192 if (conn_args->dane)
3193 if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK)
3194 return FALSE;
3195 #endif
3196
3197 #ifndef DISABLE_OCSP
3198 /* Request certificate status at connection-time. If the server
3199 does OCSP stapling we will get the callback (set in tls_init()) */
3200 # ifdef SUPPORT_DANE
3201 if (request_ocsp)
3202 {
3203 const uschar * s;
3204 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
3205 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
3206 )
3207 { /* Re-eval now $tls_out_tlsa_usage is populated. If
3208 this means we avoid the OCSP request, we wasted the setup
3209 cost in tls_init(). */
3210 require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
3211 request_ocsp = require_ocsp
3212 || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
3213 }
3214 }
3215 # endif
3216
3217 if (request_ocsp)
3218 {
3219 SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
3220 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
3221 tlsp->ocsp = OCSP_NOT_RESP;
3222 }
3223 #endif
3224
3225 #ifdef EXPERIMENTAL_TLS_RESUME
3226 if (!tls_client_ssl_resume_prehandshake(exim_client_ctx->ssl, tlsp, host,
3227 errstr))
3228 return FALSE;
3229 #endif
3230
3231 #ifndef DISABLE_EVENT
3232 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
3233 #endif
3234
3235 /* There doesn't seem to be a built-in timeout on connection. */
3236
3237 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
3238 sigalrm_seen = FALSE;
3239 ALARM(ob->command_timeout);
3240 rc = SSL_connect(exim_client_ctx->ssl);
3241 ALARM_CLR(0);
3242
3243 #ifdef SUPPORT_DANE
3244 if (conn_args->dane)
3245 DANESSL_cleanup(exim_client_ctx->ssl);
3246 #endif
3247
3248 if (rc <= 0)
3249 {
3250 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
3251 return FALSE;
3252 }
3253
3254 DEBUG(D_tls)
3255 {
3256 debug_printf("SSL_connect succeeded\n");
3257 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
3258 {
3259 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
3260 SSL_SESSION_print_keylog(bp, SSL_get_session(exim_client_ctx->ssl));
3261 BIO_free(bp);
3262 }
3263 #endif
3264 }
3265
3266 #ifdef EXPERIMENTAL_TLS_RESUME
3267 tls_client_resume_posthandshake(exim_client_ctx, tlsp);
3268 #endif
3269
3270 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
3271
3272 tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, &tlsp->bits);
3273 tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl);
3274
3275 /* Record the certificate we presented */
3276 {
3277 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
3278 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
3279 }
3280
3281 tlsp->active.sock = cctx->sock;
3282 tlsp->active.tls_ctx = exim_client_ctx;
3283 cctx->tls_ctx = exim_client_ctx;
3284 return TRUE;
3285 }
3286
3287
3288
3289
3290
3291 static BOOL
3292 tls_refill(unsigned lim)
3293 {
3294 int error;
3295 int inbytes;
3296
3297 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
3298 ssl_xfer_buffer, ssl_xfer_buffer_size);
3299
3300 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
3301 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
3302 MIN(ssl_xfer_buffer_size, lim));
3303 error = SSL_get_error(server_ssl, inbytes);
3304 if (smtp_receive_timeout > 0) ALARM_CLR(0);
3305
3306 if (had_command_timeout) /* set by signal handler */
3307 smtp_command_timeout_exit(); /* does not return */
3308 if (had_command_sigterm)
3309 smtp_command_sigterm_exit();
3310 if (had_data_timeout)
3311 smtp_data_timeout_exit();
3312 if (had_data_sigint)
3313 smtp_data_sigint_exit();
3314
3315 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
3316 closed down, not that the socket itself has been closed down. Revert to
3317 non-SSL handling. */
3318
3319 switch(error)
3320 {
3321 case SSL_ERROR_NONE:
3322 break;
3323
3324 case SSL_ERROR_ZERO_RETURN:
3325 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
3326
3327 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
3328 SSL_shutdown(server_ssl);
3329
3330 tls_close(NULL, TLS_NO_SHUTDOWN);
3331 return FALSE;
3332
3333 /* Handle genuine errors */
3334 case SSL_ERROR_SSL:
3335 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3336 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
3337 ssl_xfer_error = TRUE;
3338 return FALSE;
3339
3340 default:
3341 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
3342 DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
3343 debug_printf(" - syscall %s\n", strerror(errno));
3344 ssl_xfer_error = TRUE;
3345 return FALSE;
3346 }
3347
3348 #ifndef DISABLE_DKIM
3349 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
3350 #endif
3351 ssl_xfer_buffer_hwm = inbytes;
3352 ssl_xfer_buffer_lwm = 0;
3353 return TRUE;
3354 }
3355
3356
3357 /*************************************************
3358 * TLS version of getc *
3359 *************************************************/
3360
3361 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
3362 it refills the buffer via the SSL reading function.
3363
3364 Arguments: lim Maximum amount to read/buffer
3365 Returns: the next character or EOF
3366
3367 Only used by the server-side TLS.
3368 */
3369
3370 int
3371 tls_getc(unsigned lim)
3372 {
3373 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3374 if (!tls_refill(lim))
3375 return ssl_xfer_error ? EOF : smtp_getc(lim);
3376
3377 /* Something in the buffer; return next uschar */
3378
3379 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
3380 }
3381
3382 uschar *
3383 tls_getbuf(unsigned * len)
3384 {
3385 unsigned size;
3386 uschar * buf;
3387
3388 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3389 if (!tls_refill(*len))
3390 {
3391 if (!ssl_xfer_error) return smtp_getbuf(len);
3392 *len = 0;
3393 return NULL;
3394 }
3395
3396 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
3397 size = *len;
3398 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
3399 ssl_xfer_buffer_lwm += size;
3400 *len = size;
3401 return buf;
3402 }
3403
3404
3405 void
3406 tls_get_cache()
3407 {
3408 #ifndef DISABLE_DKIM
3409 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
3410 if (n > 0)
3411 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
3412 #endif
3413 }
3414
3415
3416 BOOL
3417 tls_could_read(void)
3418 {
3419 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
3420 }
3421
3422
3423 /*************************************************