TLS: variables $tls_(in,out)_tlsver
[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 # define OPENSSL_AUTO_SHA256
50 #else
51 # define EXIM_HAVE_EPHEM_RSA_KEX
52 # define EXIM_HAVE_RAND_PSEUDO
53 #endif
54 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
55 # define EXIM_HAVE_SHA256
56 #endif
57
58 /* X509_check_host provides sane certificate hostname checking, but was added
59 to OpenSSL late, after other projects forked off the code-base. So in
60 addition to guarding against the base version number, beware that LibreSSL
61 does not (at this time) support this function.
62
63 If LibreSSL gains a different API, perhaps via libtls, then we'll probably
64 opt to disentangle and ask a LibreSSL user to provide glue for a third
65 crypto provider for libtls instead of continuing to tie the OpenSSL glue
66 into even twistier knots. If LibreSSL gains the same API, we can just
67 change this guard and punt the issue for a while longer. */
68
69 #ifndef LIBRESSL_VERSION_NUMBER
70 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
71 # define EXIM_HAVE_OPENSSL_CHECKHOST
72 # define EXIM_HAVE_OPENSSL_DH_BITS
73 # define EXIM_HAVE_OPENSSL_TLS_METHOD
74 # define EXIM_HAVE_OPENSSL_KEYLOG
75 # define EXIM_HAVE_OPENSSL_CIPHER_GET_ID
76 # define EXIM_HAVE_SESSION_TICKET
77 # define EXIM_HAVE_OPESSL_TRACE
78 # define EXIM_HAVE_OPESSL_GET0_SERIAL
79 # else
80 # define EXIM_NEED_OPENSSL_INIT
81 # endif
82 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
83 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
84 # define EXIM_HAVE_OPENSSL_CHECKHOST
85 # endif
86 #endif
87
88 #if !defined(LIBRESSL_VERSION_NUMBER) \
89 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
90 # if !defined(OPENSSL_NO_ECDH)
91 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
92 # define EXIM_HAVE_ECDH
93 # endif
94 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
95 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
96 # endif
97 # endif
98 #endif
99
100 #ifndef LIBRESSL_VERSION_NUMBER
101 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
102 # define OPENSSL_HAVE_KEYLOG_CB
103 # define OPENSSL_HAVE_NUM_TICKETS
104 # define EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
105 # endif
106 #endif
107
108 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
109 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
110 # define DISABLE_OCSP
111 #endif
112
113 #ifdef EXPERIMENTAL_TLS_RESUME
114 # if OPENSSL_VERSION_NUMBER < 0x0101010L
115 # error OpenSSL version too old for session-resumption
116 # endif
117 #endif
118
119 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
120 # include <openssl/x509v3.h>
121 #endif
122
123 #ifndef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
124 # ifndef EXIM_HAVE_OPENSSL_CIPHER_GET_ID
125 # define SSL_CIPHER_get_id(c) (c->id)
126 # endif
127 # ifndef MACRO_PREDEF
128 # include "tls-cipher-stdname.c"
129 # endif
130 #endif
131
132 /*************************************************
133 * OpenSSL option parse *
134 *************************************************/
135
136 typedef struct exim_openssl_option {
137 uschar *name;
138 long value;
139 } exim_openssl_option;
140 /* We could use a macro to expand, but we need the ifdef and not all the
141 options document which version they were introduced in. Policylet: include
142 all options unless explicitly for DTLS, let the administrator choose which
143 to apply.
144
145 This list is current as of:
146 ==> 1.0.1b <==
147 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
148 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
149 */
150 static exim_openssl_option exim_openssl_options[] = {
151 /* KEEP SORTED ALPHABETICALLY! */
152 #ifdef SSL_OP_ALL
153 { US"all", (long) SSL_OP_ALL },
154 #endif
155 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
156 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
157 #endif
158 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
159 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
160 #endif
161 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
162 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
163 #endif
164 #ifdef SSL_OP_EPHEMERAL_RSA
165 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
166 #endif
167 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
168 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
169 #endif
170 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
171 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
172 #endif
173 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
174 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
175 #endif
176 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
177 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
178 #endif
179 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
180 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
181 #endif
182 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
183 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
184 #endif
185 #ifdef SSL_OP_NO_COMPRESSION
186 { US"no_compression", SSL_OP_NO_COMPRESSION },
187 #endif
188 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
189 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
190 #endif
191 #ifdef SSL_OP_NO_SSLv2
192 { US"no_sslv2", SSL_OP_NO_SSLv2 },
193 #endif
194 #ifdef SSL_OP_NO_SSLv3
195 { US"no_sslv3", SSL_OP_NO_SSLv3 },
196 #endif
197 #ifdef SSL_OP_NO_TICKET
198 { US"no_ticket", SSL_OP_NO_TICKET },
199 #endif
200 #ifdef SSL_OP_NO_TLSv1
201 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
202 #endif
203 #ifdef SSL_OP_NO_TLSv1_1
204 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
205 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
206 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
207 #else
208 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
209 #endif
210 #endif
211 #ifdef SSL_OP_NO_TLSv1_2
212 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
213 #endif
214 #ifdef SSL_OP_NO_TLSv1_3
215 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
216 #endif
217 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
218 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
219 #endif
220 #ifdef SSL_OP_SINGLE_DH_USE
221 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
222 #endif
223 #ifdef SSL_OP_SINGLE_ECDH_USE
224 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
225 #endif
226 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
227 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
228 #endif
229 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
230 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
231 #endif
232 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
233 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
234 #endif
235 #ifdef SSL_OP_TLS_D5_BUG
236 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
237 #endif
238 #ifdef SSL_OP_TLS_ROLLBACK_BUG
239 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
240 #endif
241 };
242
243 #ifndef MACRO_PREDEF
244 static int exim_openssl_options_size = nelem(exim_openssl_options);
245 #endif
246
247 #ifdef MACRO_PREDEF
248 void
249 options_tls(void)
250 {
251 uschar buf[64];
252
253 for (struct exim_openssl_option * o = exim_openssl_options;
254 o < exim_openssl_options + nelem(exim_openssl_options); o++)
255 {
256 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
257 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
258
259 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
260 builtin_macro_create(buf);
261 }
262
263 # ifdef EXPERIMENTAL_TLS_RESUME
264 builtin_macro_create_var(US"_RESUME_DECODE", RESUME_DECODE_STRING );
265 # endif
266 # ifdef SSL_OP_NO_TLSv1_3
267 builtin_macro_create(US"_HAVE_TLS1_3");
268 # endif
269 }
270 #else
271
272 /******************************************************************************/
273
274 /* Structure for collecting random data for seeding. */
275
276 typedef struct randstuff {
277 struct timeval tv;
278 pid_t p;
279 } randstuff;
280
281 /* Local static variables */
282
283 static BOOL client_verify_callback_called = FALSE;
284 static BOOL server_verify_callback_called = FALSE;
285 static const uschar *sid_ctx = US"exim";
286
287 /* We have three different contexts to care about.
288
289 Simple case: client, `client_ctx`
290 As a client, we can be doing a callout or cut-through delivery while receiving
291 a message. So we have a client context, which should have options initialised
292 from the SMTP Transport. We may also concurrently want to make TLS connections
293 to utility daemons, so client-contexts are allocated and passed around in call
294 args rather than using a gobal.
295
296 Server:
297 There are two cases: with and without ServerNameIndication from the client.
298 Given TLS SNI, we can be using different keys, certs and various other
299 configuration settings, because they're re-expanded with $tls_sni set. This
300 allows vhosting with TLS. This SNI is sent in the handshake.
301 A client might not send SNI, so we need a fallback, and an initial setup too.
302 So as a server, we start out using `server_ctx`.
303 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
304 `server_sni` from `server_ctx` and then initialise settings by re-expanding
305 configuration.
306 */
307
308 typedef struct {
309 SSL_CTX * ctx;
310 SSL * ssl;
311 gstring * corked;
312 } exim_openssl_client_tls_ctx;
313
314 static SSL_CTX *server_ctx = NULL;
315 static SSL *server_ssl = NULL;
316
317 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
318 static SSL_CTX *server_sni = NULL;
319 #endif
320
321 static char ssl_errstring[256];
322
323 static int ssl_session_timeout = 7200; /* Two hours */
324 static BOOL client_verify_optional = FALSE;
325 static BOOL server_verify_optional = FALSE;
326
327 static BOOL reexpand_tls_files_for_sni = FALSE;
328
329
330 typedef struct ocsp_resp {
331 struct ocsp_resp * next;
332 OCSP_RESPONSE * resp;
333 } ocsp_resplist;
334
335 typedef struct tls_ext_ctx_cb {
336 tls_support * tlsp;
337 uschar *certificate;
338 uschar *privatekey;
339 BOOL is_server;
340 #ifndef DISABLE_OCSP
341 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
342 union {
343 struct {
344 uschar *file;
345 const uschar *file_expanded;
346 ocsp_resplist *olist;
347 } server;
348 struct {
349 X509_STORE *verify_store; /* non-null if status requested */
350 BOOL verify_required;
351 } client;
352 } u_ocsp;
353 #endif
354 uschar *dhparam;
355 /* these are cached from first expand */
356 uschar *server_cipher_list;
357 /* only passed down to tls_error: */
358 host_item *host;
359 const uschar * verify_cert_hostnames;
360 #ifndef DISABLE_EVENT
361 uschar * event_action;
362 #endif
363 } tls_ext_ctx_cb;
364
365 /* should figure out a cleanup of API to handle state preserved per
366 implementation, for various reasons, which can be void * in the APIs.
367 For now, we hack around it. */
368 tls_ext_ctx_cb *client_static_cbinfo = NULL; /*XXX should not use static; multiple concurrent clients! */
369 tls_ext_ctx_cb *server_static_cbinfo = NULL;
370
371 static int
372 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
373 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
374
375 /* Callbacks */
376 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
377 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
378 #endif
379 #ifndef DISABLE_OCSP
380 static int tls_server_stapling_cb(SSL *s, void *arg);
381 #endif
382
383
384
385 /* Daemon-called, before every connection, key create/rotate */
386 #ifdef EXPERIMENTAL_TLS_RESUME
387 static void tk_init(void);
388 static int tls_exdata_idx = -1;
389 #endif
390
391 void
392 tls_daemon_init(void)
393 {
394 #ifdef EXPERIMENTAL_TLS_RESUME
395 tk_init();
396 #endif
397 return;
398 }
399
400
401 /*************************************************
402 * Handle TLS error *
403 *************************************************/
404
405 /* Called from lots of places when errors occur before actually starting to do
406 the TLS handshake, that is, while the session is still in clear. Always returns
407 DEFER for a server and FAIL for a client so that most calls can use "return
408 tls_error(...)" to do this processing and then give an appropriate return. A
409 single function is used for both server and client, because it is called from
410 some shared functions.
411
412 Argument:
413 prefix text to include in the logged error
414 host NULL if setting up a server;
415 the connected host if setting up a client
416 msg error message or NULL if we should ask OpenSSL
417 errstr pointer to output error message
418
419 Returns: OK/DEFER/FAIL
420 */
421
422 static int
423 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
424 {
425 if (!msg)
426 {
427 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
428 msg = US ssl_errstring;
429 }
430
431 msg = string_sprintf("(%s): %s", prefix, msg);
432 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
433 if (errstr) *errstr = msg;
434 return host ? FAIL : DEFER;
435 }
436
437
438
439 /*************************************************
440 * Callback to generate RSA key *
441 *************************************************/
442
443 /*
444 Arguments:
445 s SSL connection (not used)
446 export not used
447 keylength keylength
448
449 Returns: pointer to generated key
450 */
451
452 static RSA *
453 rsa_callback(SSL *s, int export, int keylength)
454 {
455 RSA *rsa_key;
456 #ifdef EXIM_HAVE_RSA_GENKEY_EX
457 BIGNUM *bn = BN_new();
458 #endif
459
460 export = export; /* Shut picky compilers up */
461 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
462
463 #ifdef EXIM_HAVE_RSA_GENKEY_EX
464 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
465 || !(rsa_key = RSA_new())
466 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
467 )
468 #else
469 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
470 #endif
471
472 {
473 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
474 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
475 ssl_errstring);
476 return NULL;
477 }
478 return rsa_key;
479 }
480
481
482
483 /* Extreme debug
484 #ifndef DISABLE_OCSP
485 void
486 x509_store_dump_cert_s_names(X509_STORE * store)
487 {
488 STACK_OF(X509_OBJECT) * roots= store->objs;
489 static uschar name[256];
490
491 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
492 {
493 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
494 if(tmp_obj->type == X509_LU_X509)
495 {
496 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
497 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
498 {
499 name[sizeof(name)-1] = '\0';
500 debug_printf(" %s\n", name);
501 }
502 }
503 }
504 }
505 #endif
506 */
507
508
509 #ifndef DISABLE_EVENT
510 static int
511 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
512 BOOL *calledp, const BOOL *optionalp, const uschar * what)
513 {
514 uschar * ev;
515 uschar * yield;
516 X509 * old_cert;
517
518 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
519 if (ev)
520 {
521 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
522 old_cert = tlsp->peercert;
523 tlsp->peercert = X509_dup(cert);
524 /* NB we do not bother setting peerdn */
525 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
526 {
527 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
528 "depth=%d cert=%s: %s",
529 tlsp == &tls_out ? deliver_host_address : sender_host_address,
530 what, depth, dn, yield);
531 *calledp = TRUE;
532 if (!*optionalp)
533 {
534 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
535 return 1; /* reject (leaving peercert set) */
536 }
537 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
538 "(host in tls_try_verify_hosts)\n");
539 tlsp->verify_override = TRUE;
540 }
541 X509_free(tlsp->peercert);
542 tlsp->peercert = old_cert;
543 }
544 return 0;
545 }
546 #endif
547
548 /*************************************************
549 * Callback for verification *
550 *************************************************/
551
552 /* The SSL library does certificate verification if set up to do so. This
553 callback has the current yes/no state is in "state". If verification succeeded,
554 we set the certificate-verified flag. If verification failed, what happens
555 depends on whether the client is required to present a verifiable certificate
556 or not.
557
558 If verification is optional, we change the state to yes, but still log the
559 verification error. For some reason (it really would help to have proper
560 documentation of OpenSSL), this callback function then gets called again, this
561 time with state = 1. We must take care not to set the private verified flag on
562 the second time through.
563
564 Note: this function is not called if the client fails to present a certificate
565 when asked. We get here only if a certificate has been received. Handling of
566 optional verification for this case is done when requesting SSL to verify, by
567 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
568
569 May be called multiple times for different issues with a certificate, even
570 for a given "depth" in the certificate chain.
571
572 Arguments:
573 preverify_ok current yes/no state as 1/0
574 x509ctx certificate information.
575 tlsp per-direction (client vs. server) support data
576 calledp has-been-called flag
577 optionalp verification-is-optional flag
578
579 Returns: 0 if verification should fail, otherwise 1
580 */
581
582 static int
583 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
584 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
585 {
586 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
587 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
588 uschar dn[256];
589
590 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
591 {
592 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
593 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
594 tlsp == &tls_out ? deliver_host_address : sender_host_address);
595 return 0;
596 }
597 dn[sizeof(dn)-1] = '\0';
598
599 tlsp->verify_override = FALSE;
600 if (preverify_ok == 0)
601 {
602 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
603 *verify_mode, sender_host_address)
604 : US"";
605 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
606 tlsp == &tls_out ? deliver_host_address : sender_host_address,
607 extra, depth,
608 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
609 *calledp = TRUE;
610 if (!*optionalp)
611 {
612 if (!tlsp->peercert)
613 tlsp->peercert = X509_dup(cert); /* record failing cert */
614 return 0; /* reject */
615 }
616 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
617 "tls_try_verify_hosts)\n");
618 tlsp->verify_override = TRUE;
619 }
620
621 else if (depth != 0)
622 {
623 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
624 #ifndef DISABLE_OCSP
625 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
626 { /* client, wanting stapling */
627 /* Add the server cert's signing chain as the one
628 for the verification of the OCSP stapled information. */
629
630 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
631 cert))
632 ERR_clear_error();
633 sk_X509_push(client_static_cbinfo->verify_stack, cert);
634 }
635 #endif
636 #ifndef DISABLE_EVENT
637 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
638 return 0; /* reject, with peercert set */
639 #endif
640 }
641 else
642 {
643 const uschar * verify_cert_hostnames;
644
645 if ( tlsp == &tls_out
646 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
647 /* client, wanting hostname check */
648 {
649
650 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
651 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
652 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
653 # endif
654 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
655 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
656 # endif
657 int sep = 0;
658 const uschar * list = verify_cert_hostnames;
659 uschar * name;
660 int rc;
661 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
662 if ((rc = X509_check_host(cert, CCS name, 0,
663 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
664 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
665 NULL)))
666 {
667 if (rc < 0)
668 {
669 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
670 tlsp == &tls_out ? deliver_host_address : sender_host_address);
671 name = NULL;
672 }
673 break;
674 }
675 if (!name)
676 #else
677 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
678 #endif
679 {
680 uschar * extra = verify_mode
681 ? string_sprintf(" (during %c-verify for [%s])",
682 *verify_mode, sender_host_address)
683 : US"";
684 log_write(0, LOG_MAIN,
685 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
686 tlsp == &tls_out ? deliver_host_address : sender_host_address,
687 extra, dn, verify_cert_hostnames);
688 *calledp = TRUE;
689 if (!*optionalp)
690 {
691 if (!tlsp->peercert)
692 tlsp->peercert = X509_dup(cert); /* record failing cert */
693 return 0; /* reject */
694 }
695 DEBUG(D_tls) debug_printf("SSL verify name failure overridden (host in "
696 "tls_try_verify_hosts)\n");
697 tlsp->verify_override = TRUE;
698 }
699 }
700
701 #ifndef DISABLE_EVENT
702 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
703 return 0; /* reject, with peercert set */
704 #endif
705
706 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
707 *calledp ? "" : " authenticated", dn);
708 *calledp = TRUE;
709 }
710
711 return 1; /* accept, at least for this level */
712 }
713
714 static int
715 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
716 {
717 return verify_callback(preverify_ok, x509ctx, &tls_out,
718 &client_verify_callback_called, &client_verify_optional);
719 }
720
721 static int
722 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
723 {
724 return verify_callback(preverify_ok, x509ctx, &tls_in,
725 &server_verify_callback_called, &server_verify_optional);
726 }
727
728
729 #ifdef SUPPORT_DANE
730
731 /* This gets called *by* the dane library verify callback, which interposes
732 itself.
733 */
734 static int
735 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
736 {
737 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
738 uschar dn[256];
739 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
740 #ifndef DISABLE_EVENT
741 BOOL dummy_called, optional = FALSE;
742 #endif
743
744 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
745 {
746 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
747 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
748 deliver_host_address);
749 return 0;
750 }
751 dn[sizeof(dn)-1] = '\0';
752
753 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
754 preverify_ok ? "ok":"BAD", depth, dn);
755
756 #ifndef DISABLE_EVENT
757 if (verify_event(&tls_out, cert, depth, dn,
758 &dummy_called, &optional, US"DANE"))
759 return 0; /* reject, with peercert set */
760 #endif
761
762 if (preverify_ok == 1)
763 {
764 tls_out.dane_verified = TRUE;
765 #ifndef DISABLE_OCSP
766 if (client_static_cbinfo->u_ocsp.client.verify_store)
767 { /* client, wanting stapling */
768 /* Add the server cert's signing chain as the one
769 for the verification of the OCSP stapled information. */
770
771 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
772 cert))
773 ERR_clear_error();
774 sk_X509_push(client_static_cbinfo->verify_stack, cert);
775 }
776 #endif
777 }
778 else
779 {
780 int err = X509_STORE_CTX_get_error(x509ctx);
781 DEBUG(D_tls)
782 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
783 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
784 preverify_ok = 1;
785 }
786 return preverify_ok;
787 }
788
789 #endif /*SUPPORT_DANE*/
790
791
792 /*************************************************
793 * Information callback *
794 *************************************************/
795
796 /* The SSL library functions call this from time to time to indicate what they
797 are doing. We copy the string to the debugging output when TLS debugging has
798 been requested.
799
800 Arguments:
801 s the SSL connection
802 where
803 ret
804
805 Returns: nothing
806 */
807
808 static void
809 info_callback(SSL *s, int where, int ret)
810 {
811 DEBUG(D_tls)
812 {
813 const uschar * str;
814
815 if (where & SSL_ST_CONNECT)
816 str = US"SSL_connect";
817 else if (where & SSL_ST_ACCEPT)
818 str = US"SSL_accept";
819 else
820 str = US"SSL info (undefined)";
821
822 if (where & SSL_CB_LOOP)
823 debug_printf("%s: %s\n", str, SSL_state_string_long(s));
824 else if (where & SSL_CB_ALERT)
825 debug_printf("SSL3 alert %s:%s:%s\n",
826 str = where & SSL_CB_READ ? US"read" : US"write",
827 SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
828 else if (where & SSL_CB_EXIT)
829 if (ret == 0)
830 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
831 else if (ret < 0)
832 debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
833 else if (where & SSL_CB_HANDSHAKE_START)
834 debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
835 else if (where & SSL_CB_HANDSHAKE_DONE)
836 debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
837 }
838 }
839
840 #ifdef OPENSSL_HAVE_KEYLOG_CB
841 static void
842 keylog_callback(const SSL *ssl, const char *line)
843 {
844 DEBUG(D_tls) debug_printf("%.200s\n", line);
845 }
846 #endif
847
848
849 #ifdef EXPERIMENTAL_TLS_RESUME
850 /* Manage the keysets used for encrypting the session tickets, on the server. */
851
852 typedef struct { /* Session ticket encryption key */
853 uschar name[16];
854
855 const EVP_CIPHER * aes_cipher;
856 uschar aes_key[32]; /* size needed depends on cipher. aes_128 implies 128/8 = 16? */
857 const EVP_MD * hmac_hash;
858 uschar hmac_key[16];
859 time_t renew;
860 time_t expire;
861 } exim_stek;
862
863 static exim_stek exim_tk; /* current key */
864 static exim_stek exim_tk_old; /* previous key */
865
866 static void
867 tk_init(void)
868 {
869 time_t t = time(NULL);
870
871 if (exim_tk.name[0])
872 {
873 if (exim_tk.renew >= t) return;
874 exim_tk_old = exim_tk;
875 }
876
877 if (f.running_in_test_harness) ssl_session_timeout = 6;
878
879 DEBUG(D_tls) debug_printf("OpenSSL: %s STEK\n", exim_tk.name[0] ? "rotating" : "creating");
880 if (RAND_bytes(exim_tk.aes_key, sizeof(exim_tk.aes_key)) <= 0) return;
881 if (RAND_bytes(exim_tk.hmac_key, sizeof(exim_tk.hmac_key)) <= 0) return;
882 if (RAND_bytes(exim_tk.name+1, sizeof(exim_tk.name)-1) <= 0) return;
883
884 exim_tk.name[0] = 'E';
885 exim_tk.aes_cipher = EVP_aes_256_cbc();
886 exim_tk.hmac_hash = EVP_sha256();
887 exim_tk.expire = t + ssl_session_timeout;
888 exim_tk.renew = t + ssl_session_timeout/2;
889 }
890
891 static exim_stek *
892 tk_current(void)
893 {
894 if (!exim_tk.name[0]) return NULL;
895 return &exim_tk;
896 }
897
898 static exim_stek *
899 tk_find(const uschar * name)
900 {
901 return memcmp(name, exim_tk.name, sizeof(exim_tk.name)) == 0 ? &exim_tk
902 : memcmp(name, exim_tk_old.name, sizeof(exim_tk_old.name)) == 0 ? &exim_tk_old
903 : NULL;
904 }
905
906 /* Callback for session tickets, on server */
907 static int
908 ticket_key_callback(SSL * ssl, uschar key_name[16],
909 uschar * iv, EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int enc)
910 {
911 tls_support * tlsp = server_static_cbinfo->tlsp;
912 exim_stek * key;
913
914 if (enc)
915 {
916 DEBUG(D_tls) debug_printf("ticket_key_callback: create new session\n");
917 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
918
919 if (RAND_bytes(iv, EVP_MAX_IV_LENGTH) <= 0)
920 return -1; /* insufficient random */
921
922 if (!(key = tk_current())) /* current key doesn't exist or isn't valid */
923 return 0; /* key couldn't be created */
924 memcpy(key_name, key->name, 16);
925 DEBUG(D_tls) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - time(NULL));
926
927 /*XXX will want these dependent on the ssl session strength */
928 HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
929 key->hmac_hash, NULL);
930 EVP_EncryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv);
931
932 DEBUG(D_tls) debug_printf("ticket created\n");
933 return 1;
934 }
935 else
936 {
937 time_t now = time(NULL);
938
939 DEBUG(D_tls) debug_printf("ticket_key_callback: retrieve session\n");
940 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
941
942 if (!(key = tk_find(key_name)) || key->expire < now)
943 {
944 DEBUG(D_tls)
945 {
946 debug_printf("ticket not usable (%s)\n", key ? "expired" : "not found");
947 if (key) debug_printf("STEK expire " TIME_T_FMT "\n", key->expire - now);
948 }
949 return 0;
950 }
951
952 HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
953 key->hmac_hash, NULL);
954 EVP_DecryptInit_ex(ctx, key->aes_cipher, NULL, key->aes_key, iv);
955
956 DEBUG(D_tls) debug_printf("ticket usable, STEK expire " TIME_T_FMT "\n", key->expire - now);
957
958 /* The ticket lifetime and renewal are the same as the STEK lifetime and
959 renewal, which is overenthusiastic. A factor of, say, 3x longer STEK would
960 be better. To do that we'd have to encode ticket lifetime in the name as
961 we don't yet see the restored session. Could check posthandshake for TLS1.3
962 and trigger a new ticket then, but cannot do that for TLS1.2 */
963 return key->renew < now ? 2 : 1;
964 }
965 }
966 #endif
967
968
969
970 /*************************************************
971 * Initialize for DH *
972 *************************************************/
973
974 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
975
976 Arguments:
977 sctx The current SSL CTX (inbound or outbound)
978 dhparam DH parameter file or fixed parameter identity string
979 host connected host, if client; NULL if server
980 errstr error string pointer
981
982 Returns: TRUE if OK (nothing to set up, or setup worked)
983 */
984
985 static BOOL
986 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
987 {
988 BIO *bio;
989 DH *dh;
990 uschar *dhexpanded;
991 const char *pem;
992 int dh_bitsize;
993
994 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
995 return FALSE;
996
997 if (!dhexpanded || !*dhexpanded)
998 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
999 else if (dhexpanded[0] == '/')
1000 {
1001 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
1002 {
1003 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
1004 host, US strerror(errno), errstr);
1005 return FALSE;
1006 }
1007 }
1008 else
1009 {
1010 if (Ustrcmp(dhexpanded, "none") == 0)
1011 {
1012 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
1013 return TRUE;
1014 }
1015
1016 if (!(pem = std_dh_prime_named(dhexpanded)))
1017 {
1018 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
1019 host, US strerror(errno), errstr);
1020 return FALSE;
1021 }
1022 bio = BIO_new_mem_buf(CS pem, -1);
1023 }
1024
1025 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
1026 {
1027 BIO_free(bio);
1028 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
1029 host, NULL, errstr);
1030 return FALSE;
1031 }
1032
1033 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
1034 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
1035 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
1036 * If someone wants to dance at the edge, then they can raise the limit or use
1037 * current libraries. */
1038 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
1039 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
1040 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
1041 dh_bitsize = DH_bits(dh);
1042 #else
1043 dh_bitsize = 8 * DH_size(dh);
1044 #endif
1045
1046 /* Even if it is larger, we silently return success rather than cause things
1047 * to fail out, so that a too-large DH will not knock out all TLS; it's a
1048 * debatable choice. */
1049 if (dh_bitsize > tls_dh_max_bits)
1050 {
1051 DEBUG(D_tls)
1052 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
1053 dh_bitsize, tls_dh_max_bits);
1054 }
1055 else
1056 {
1057 SSL_CTX_set_tmp_dh(sctx, dh);
1058 DEBUG(D_tls)
1059 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
1060 dhexpanded ? dhexpanded : US"default", dh_bitsize);
1061 }
1062
1063 DH_free(dh);
1064 BIO_free(bio);
1065
1066 return TRUE;
1067 }
1068
1069
1070
1071
1072 /*************************************************
1073 * Initialize for ECDH *
1074 *************************************************/
1075
1076 /* Load parameters for ECDH encryption.
1077
1078 For now, we stick to NIST P-256 because: it's simple and easy to configure;
1079 it avoids any patent issues that might bite redistributors; despite events in
1080 the news and concerns over curve choices, we're not cryptographers, we're not
1081 pretending to be, and this is "good enough" to be better than no support,
1082 protecting against most adversaries. Given another year or two, there might
1083 be sufficient clarity about a "right" way forward to let us make an informed
1084 decision, instead of a knee-jerk reaction.
1085
1086 Longer-term, we should look at supporting both various named curves and
1087 external files generated with "openssl ecparam", much as we do for init_dh().
1088 We should also support "none" as a value, to explicitly avoid initialisation.
1089
1090 Patches welcome.
1091
1092 Arguments:
1093 sctx The current SSL CTX (inbound or outbound)
1094 host connected host, if client; NULL if server
1095 errstr error string pointer
1096
1097 Returns: TRUE if OK (nothing to set up, or setup worked)
1098 */
1099
1100 static BOOL
1101 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
1102 {
1103 #ifdef OPENSSL_NO_ECDH
1104 return TRUE;
1105 #else
1106
1107 EC_KEY * ecdh;
1108 uschar * exp_curve;
1109 int nid;
1110 BOOL rv;
1111
1112 if (host) /* No ECDH setup for clients, only for servers */
1113 return TRUE;
1114
1115 # ifndef EXIM_HAVE_ECDH
1116 DEBUG(D_tls)
1117 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
1118 return TRUE;
1119 # else
1120
1121 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
1122 return FALSE;
1123 if (!exp_curve || !*exp_curve)
1124 return TRUE;
1125
1126 /* "auto" needs to be handled carefully.
1127 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
1128 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
1129 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
1130 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
1131 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
1132 */
1133 if (Ustrcmp(exp_curve, "auto") == 0)
1134 {
1135 #if OPENSSL_VERSION_NUMBER < 0x10002000L
1136 DEBUG(D_tls) debug_printf(
1137 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
1138 exp_curve = US"prime256v1";
1139 #else
1140 # if defined SSL_CTRL_SET_ECDH_AUTO
1141 DEBUG(D_tls) debug_printf(
1142 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
1143 SSL_CTX_set_ecdh_auto(sctx, 1);
1144 return TRUE;
1145 # else
1146 DEBUG(D_tls) debug_printf(
1147 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
1148 return TRUE;
1149 # endif
1150 #endif
1151 }
1152
1153 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
1154 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
1155 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
1156 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
1157 # endif
1158 )
1159 {
1160 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
1161 host, NULL, errstr);
1162 return FALSE;
1163 }
1164
1165 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
1166 {
1167 tls_error(US"Unable to create ec curve", host, NULL, errstr);
1168 return FALSE;
1169 }
1170
1171 /* The "tmp" in the name here refers to setting a temporary key
1172 not to the stability of the interface. */
1173
1174 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
1175 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
1176 else
1177 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1178
1179 EC_KEY_free(ecdh);
1180 return !rv;
1181
1182 # endif /*EXIM_HAVE_ECDH*/
1183 #endif /*OPENSSL_NO_ECDH*/
1184 }
1185
1186
1187
1188
1189 #ifndef DISABLE_OCSP
1190 /*************************************************
1191 * Load OCSP information into state *
1192 *************************************************/
1193 /* Called to load the server OCSP response from the given file into memory, once
1194 caller has determined this is needed. Checks validity. Debugs a message
1195 if invalid.
1196
1197 ASSUMES: single response, for single cert.
1198
1199 Arguments:
1200 sctx the SSL_CTX* to update
1201 cbinfo various parts of session state
1202 filename the filename putatively holding an OCSP response
1203
1204 */
1205
1206 static void
1207 ocsp_load_response(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo,
1208 const uschar * filename)
1209 {
1210 BIO * bio;
1211 OCSP_RESPONSE * resp;
1212 OCSP_BASICRESP * basic_response;
1213 OCSP_SINGLERESP * single_response;
1214 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1215 STACK_OF(X509) * sk;
1216 unsigned long verify_flags;
1217 int status, reason, i;
1218
1219 DEBUG(D_tls) debug_printf("tls_ocsp_file '%s'\n", filename);
1220
1221 if (!(bio = BIO_new_file(CS filename, "rb")))
1222 {
1223 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1224 filename);
1225 return;
1226 }
1227
1228 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1229 BIO_free(bio);
1230 if (!resp)
1231 {
1232 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1233 return;
1234 }
1235
1236 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1237 {
1238 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1239 OCSP_response_status_str(status), status);
1240 goto bad;
1241 }
1242
1243 #ifdef notdef
1244 {
1245 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1246 OCSP_RESPONSE_print(bp, resp, 0); /* extreme debug: stapling content */
1247 BIO_free(bp);
1248 }
1249 #endif
1250
1251 if (!(basic_response = OCSP_response_get1_basic(resp)))
1252 {
1253 DEBUG(D_tls)
1254 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1255 goto bad;
1256 }
1257
1258 sk = cbinfo->verify_stack;
1259 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1260
1261 /* May need to expose ability to adjust those flags?
1262 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1263 OCSP_TRUSTOTHER OCSP_NOINTERN */
1264
1265 /* This does a full verify on the OCSP proof before we load it for serving
1266 up; possibly overkill - just date-checks might be nice enough.
1267
1268 OCSP_basic_verify takes a "store" arg, but does not
1269 use it for the chain verification, which is all we do
1270 when OCSP_NOVERIFY is set. The content from the wire
1271 "basic_response" and a cert-stack "sk" are all that is used.
1272
1273 We have a stack, loaded in setup_certs() if tls_verify_certificates
1274 was a file (not a directory, or "system"). It is unfortunate we
1275 cannot used the connection context store, as that would neatly
1276 handle the "system" case too, but there seems to be no library
1277 function for getting a stack from a store.
1278 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
1279 We do not free the stack since it could be needed a second time for
1280 SNI handling.
1281
1282 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1283 be a public interface into the OpenSSL library (there's no manual entry) -
1284 But what with? We also use OCSP_basic_verify in the client stapling callback.
1285 And there we NEED it; we must verify that status... unless the
1286 library does it for us anyway? */
1287
1288 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1289 {
1290 DEBUG(D_tls)
1291 {
1292 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1293 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1294 }
1295 goto bad;
1296 }
1297
1298 /* Here's the simplifying assumption: there's only one response, for the
1299 one certificate we use, and nothing for anything else in a chain. If this
1300 proves false, we need to extract a cert id from our issued cert
1301 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1302 right cert in the stack and then calls OCSP_single_get0_status()).
1303
1304 I'm hoping to avoid reworking a bunch more of how we handle state here.
1305
1306 XXX that will change when we add support for (TLS1.3) whole-chain stapling
1307 */
1308
1309 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1310 {
1311 DEBUG(D_tls)
1312 debug_printf("Unable to get first response from OCSP basic response.\n");
1313 goto bad;
1314 }
1315
1316 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1317 if (status != V_OCSP_CERTSTATUS_GOOD)
1318 {
1319 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1320 OCSP_cert_status_str(status), status,
1321 OCSP_crl_reason_str(reason), reason);
1322 goto bad;
1323 }
1324
1325 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1326 {
1327 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1328 goto bad;
1329 }
1330
1331 supply_response:
1332 /* Add the resp to the list used by tls_server_stapling_cb() */
1333 {
1334 ocsp_resplist ** op = &cbinfo->u_ocsp.server.olist, * oentry;
1335 while (oentry = *op)
1336 op = &oentry->next;
1337 *op = oentry = store_get(sizeof(ocsp_resplist), FALSE);
1338 oentry->next = NULL;
1339 oentry->resp = resp;
1340 }
1341 return;
1342
1343 bad:
1344 if (f.running_in_test_harness)
1345 {
1346 extern char ** environ;
1347 if (environ) for (uschar ** p = USS environ; *p; p++)
1348 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1349 {
1350 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1351 goto supply_response;
1352 }
1353 }
1354 return;
1355 }
1356
1357
1358 static void
1359 ocsp_free_response_list(tls_ext_ctx_cb * cbinfo)
1360 {
1361 for (ocsp_resplist * olist = cbinfo->u_ocsp.server.olist; olist;
1362 olist = olist->next)
1363 OCSP_RESPONSE_free(olist->resp);
1364 cbinfo->u_ocsp.server.olist = NULL;
1365 }
1366 #endif /*!DISABLE_OCSP*/
1367
1368
1369
1370
1371 /* Create and install a selfsigned certificate, for use in server mode */
1372
1373 static int
1374 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1375 {
1376 X509 * x509 = NULL;
1377 EVP_PKEY * pkey;
1378 RSA * rsa;
1379 X509_NAME * name;
1380 uschar * where;
1381
1382 where = US"allocating pkey";
1383 if (!(pkey = EVP_PKEY_new()))
1384 goto err;
1385
1386 where = US"allocating cert";
1387 if (!(x509 = X509_new()))
1388 goto err;
1389
1390 where = US"generating pkey";
1391 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1392 goto err;
1393
1394 where = US"assigning pkey";
1395 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1396 goto err;
1397
1398 X509_set_version(x509, 2); /* N+1 - version 3 */
1399 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1400 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1401 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
1402 X509_set_pubkey(x509, pkey);
1403
1404 name = X509_get_subject_name(x509);
1405 X509_NAME_add_entry_by_txt(name, "C",
1406 MBSTRING_ASC, CUS "UK", -1, -1, 0);
1407 X509_NAME_add_entry_by_txt(name, "O",
1408 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1409 X509_NAME_add_entry_by_txt(name, "CN",
1410 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1411 X509_set_issuer_name(x509, name);
1412
1413 where = US"signing cert";
1414 if (!X509_sign(x509, pkey, EVP_md5()))
1415 goto err;
1416
1417 where = US"installing selfsign cert";
1418 if (!SSL_CTX_use_certificate(sctx, x509))
1419 goto err;
1420
1421 where = US"installing selfsign key";
1422 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1423 goto err;
1424
1425 return OK;
1426
1427 err:
1428 (void) tls_error(where, NULL, NULL, errstr);
1429 if (x509) X509_free(x509);
1430 if (pkey) EVP_PKEY_free(pkey);
1431 return DEFER;
1432 }
1433
1434
1435
1436
1437 static int
1438 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1439 uschar ** errstr)
1440 {
1441 DEBUG(D_tls) debug_printf("tls_certificate file '%s'\n", file);
1442 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1443 return tls_error(string_sprintf(
1444 "SSL_CTX_use_certificate_chain_file file=%s", file),
1445 cbinfo->host, NULL, errstr);
1446 return 0;
1447 }
1448
1449 static int
1450 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1451 uschar ** errstr)
1452 {
1453 DEBUG(D_tls) debug_printf("tls_privatekey file '%s'\n", file);
1454 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1455 return tls_error(string_sprintf(
1456 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1457 return 0;
1458 }
1459
1460
1461 /*************************************************
1462 * Expand key and cert file specs *
1463 *************************************************/
1464
1465 /* Called once during tls_init and possibly again during TLS setup, for a
1466 new context, if Server Name Indication was used and tls_sni was seen in
1467 the certificate string.
1468
1469 Arguments:
1470 sctx the SSL_CTX* to update
1471 cbinfo various parts of session state
1472 errstr error string pointer
1473
1474 Returns: OK/DEFER/FAIL
1475 */
1476
1477 static int
1478 tls_expand_session_files(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo,
1479 uschar ** errstr)
1480 {
1481 uschar * expanded;
1482
1483 if (!cbinfo->certificate)
1484 {
1485 if (!cbinfo->is_server) /* client */
1486 return OK;
1487 /* server */
1488 if (tls_install_selfsign(sctx, errstr) != OK)
1489 return DEFER;
1490 }
1491 else
1492 {
1493 int err;
1494
1495 if ( !reexpand_tls_files_for_sni
1496 && ( Ustrstr(cbinfo->certificate, US"tls_sni")
1497 || Ustrstr(cbinfo->certificate, US"tls_in_sni")
1498 || Ustrstr(cbinfo->certificate, US"tls_out_sni")
1499 ) )
1500 reexpand_tls_files_for_sni = TRUE;
1501
1502 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1503 return DEFER;
1504
1505 if (expanded)
1506 if (cbinfo->is_server)
1507 {
1508 const uschar * file_list = expanded;
1509 int sep = 0;
1510 uschar * file;
1511 #ifndef DISABLE_OCSP
1512 const uschar * olist = cbinfo->u_ocsp.server.file;
1513 int osep = 0;
1514 uschar * ofile;
1515
1516 if (olist)
1517 if (!expand_check(olist, US"tls_ocsp_file", USS &olist, errstr))
1518 return DEFER;
1519 if (olist && !*olist)
1520 olist = NULL;
1521
1522 if ( cbinfo->u_ocsp.server.file_expanded && olist
1523 && (Ustrcmp(olist, cbinfo->u_ocsp.server.file_expanded) == 0))
1524 {
1525 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1526 olist = NULL;
1527 }
1528 else
1529 {
1530 ocsp_free_response_list(cbinfo);
1531 cbinfo->u_ocsp.server.file_expanded = olist;
1532 }
1533 #endif
1534
1535 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1536 {
1537 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1538 return err;
1539
1540 #ifndef DISABLE_OCSP
1541 if (olist)
1542 if ((ofile = string_nextinlist(&olist, &osep, NULL, 0)))
1543 ocsp_load_response(sctx, cbinfo, ofile);
1544 else
1545 DEBUG(D_tls) debug_printf("ran out of ocsp file list\n");
1546 #endif
1547 }
1548 }
1549 else /* would there ever be a need for multiple client certs? */
1550 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1551 return err;
1552
1553 if ( cbinfo->privatekey
1554 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1555 return DEFER;
1556
1557 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1558 of the expansion is an empty string, ignore it also, and assume the private
1559 key is in the same file as the certificate. */
1560
1561 if (expanded && *expanded)
1562 if (cbinfo->is_server)
1563 {
1564 const uschar * file_list = expanded;
1565 int sep = 0;
1566 uschar * file;
1567
1568 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1569 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1570 return err;
1571 }
1572 else /* would there ever be a need for multiple client certs? */
1573 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1574 return err;
1575 }
1576
1577 return OK;
1578 }
1579
1580
1581
1582
1583 /*************************************************
1584 * Callback to handle SNI *
1585 *************************************************/
1586
1587 /* Called when acting as server during the TLS session setup if a Server Name
1588 Indication extension was sent by the client.
1589
1590 API documentation is OpenSSL s_server.c implementation.
1591
1592 Arguments:
1593 s SSL* of the current session
1594 ad unknown (part of OpenSSL API) (unused)
1595 arg Callback of "our" registered data
1596
1597 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1598
1599 XXX might need to change to using ClientHello callback,
1600 per https://www.openssl.org/docs/manmaster/man3/SSL_client_hello_cb_fn.html
1601 */
1602
1603 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1604 static int
1605 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1606 {
1607 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1608 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1609 int rc;
1610 int old_pool = store_pool;
1611 uschar * dummy_errstr;
1612
1613 if (!servername)
1614 return SSL_TLSEXT_ERR_OK;
1615
1616 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1617 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1618
1619 /* Make the extension value available for expansion */
1620 store_pool = POOL_PERM;
1621 tls_in.sni = string_copy_taint(US servername, TRUE);
1622 store_pool = old_pool;
1623
1624 if (!reexpand_tls_files_for_sni)
1625 return SSL_TLSEXT_ERR_OK;
1626
1627 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1628 not confident that memcpy wouldn't break some internal reference counting.
1629 Especially since there's a references struct member, which would be off. */
1630
1631 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1632 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1633 #else
1634 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1635 #endif
1636 {
1637 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1638 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1639 goto bad;
1640 }
1641
1642 /* Not sure how many of these are actually needed, since SSL object
1643 already exists. Might even need this selfsame callback, for reneg? */
1644
1645 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1646 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1647 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1648 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1649 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1650 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1651
1652 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1653 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1654 )
1655 goto bad;
1656
1657 if ( cbinfo->server_cipher_list
1658 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1659 goto bad;
1660
1661 #ifndef DISABLE_OCSP
1662 if (cbinfo->u_ocsp.server.file)
1663 {
1664 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1665 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1666 }
1667 #endif
1668
1669 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1670 verify_callback_server, &dummy_errstr)) != OK)
1671 goto bad;
1672
1673 /* do this after setup_certs, because this can require the certs for verifying
1674 OCSP information. */
1675 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1676 goto bad;
1677
1678 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1679 SSL_set_SSL_CTX(s, server_sni);
1680 return SSL_TLSEXT_ERR_OK;
1681
1682 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1683 }
1684 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1685
1686
1687
1688
1689 #ifndef DISABLE_OCSP
1690
1691 /*************************************************
1692 * Callback to handle OCSP Stapling *
1693 *************************************************/
1694
1695 /* Called when acting as server during the TLS session setup if the client
1696 requests OCSP information with a Certificate Status Request.
1697
1698 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1699 project.
1700
1701 */
1702
1703 static int
1704 tls_server_stapling_cb(SSL *s, void *arg)
1705 {
1706 const tls_ext_ctx_cb * cbinfo = (tls_ext_ctx_cb *) arg;
1707 ocsp_resplist * olist = cbinfo->u_ocsp.server.olist;
1708 uschar * response_der; /*XXX blob */
1709 int response_der_len;
1710
1711 DEBUG(D_tls)
1712 debug_printf("Received TLS status request (OCSP stapling); %s response list\n",
1713 olist ? "have" : "lack");
1714
1715 tls_in.ocsp = OCSP_NOT_RESP;
1716 if (!olist)
1717 return SSL_TLSEXT_ERR_NOACK;
1718
1719 #ifdef EXIM_HAVE_OPESSL_GET0_SERIAL
1720 {
1721 const X509 * cert_sent = SSL_get_certificate(s);
1722 const ASN1_INTEGER * cert_serial = X509_get0_serialNumber(cert_sent);
1723 const BIGNUM * cert_bn = ASN1_INTEGER_to_BN(cert_serial, NULL);
1724 const X509_NAME * cert_issuer = X509_get_issuer_name(cert_sent);
1725 uschar * chash;
1726 uint chash_len;
1727
1728 for (; olist; olist = olist->next)
1729 {
1730 OCSP_BASICRESP * bs = OCSP_response_get1_basic(olist->resp);
1731 const OCSP_SINGLERESP * single = OCSP_resp_get0(bs, 0);
1732 const OCSP_CERTID * cid = OCSP_SINGLERESP_get0_id(single);
1733 ASN1_INTEGER * res_cert_serial;
1734 const BIGNUM * resp_bn;
1735 ASN1_OCTET_STRING * res_cert_iNameHash;
1736
1737
1738 (void) OCSP_id_get0_info(&res_cert_iNameHash, NULL, NULL, &res_cert_serial,
1739 (OCSP_CERTID *) cid);
1740 resp_bn = ASN1_INTEGER_to_BN(res_cert_serial, NULL);
1741
1742 DEBUG(D_tls)
1743 {
1744 debug_printf("cert serial: %s\n", BN_bn2hex(cert_bn));
1745 debug_printf("resp serial: %s\n", BN_bn2hex(resp_bn));
1746 }
1747
1748 if (BN_cmp(cert_bn, resp_bn) == 0)
1749 {
1750 DEBUG(D_tls) debug_printf("matched serial for ocsp\n");
1751
1752 /*XXX TODO: check the rest of the list for duplicate matches.
1753 If any, need to also check the Issuer Name hash.
1754 Without this, we will provide the wrong status in the case of
1755 duplicate id. */
1756
1757 break;
1758 }
1759 DEBUG(D_tls) debug_printf("not match serial for ocsp\n");
1760 }
1761 if (!olist)
1762 {
1763 DEBUG(D_tls) debug_printf("failed to find match for ocsp\n");
1764 return SSL_TLSEXT_ERR_NOACK;
1765 }
1766 }
1767 #else
1768 if (olist->next)
1769 {
1770 DEBUG(D_tls) debug_printf("OpenSSL version too early to support multi-leaf OCSP\n");
1771 return SSL_TLSEXT_ERR_NOACK;
1772 }
1773 #endif
1774
1775 /*XXX could we do the i2d earlier, rather than during the callback? */
1776 response_der = NULL;
1777 response_der_len = i2d_OCSP_RESPONSE(olist->resp, &response_der);
1778 if (response_der_len <= 0)
1779 return SSL_TLSEXT_ERR_NOACK;
1780
1781 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1782 tls_in.ocsp = OCSP_VFIED;
1783 return SSL_TLSEXT_ERR_OK;
1784 }
1785
1786
1787 static void
1788 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1789 {
1790 BIO_printf(bp, "\t%s: ", str);
1791 ASN1_GENERALIZEDTIME_print(bp, time);
1792 BIO_puts(bp, "\n");
1793 }
1794
1795 static int
1796 tls_client_stapling_cb(SSL *s, void *arg)
1797 {
1798 tls_ext_ctx_cb * cbinfo = arg;
1799 const unsigned char * p;
1800 int len;
1801 OCSP_RESPONSE * rsp;
1802 OCSP_BASICRESP * bs;
1803 int i;
1804
1805 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1806 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1807 if(!p)
1808 {
1809 /* Expect this when we requested ocsp but got none */
1810 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1811 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1812 else
1813 DEBUG(D_tls) debug_printf(" null\n");
1814 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1815 }
1816
1817 if (!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1818 {
1819 tls_out.ocsp = OCSP_FAILED; /*XXX should use tlsp-> to permit concurrent outbound */
1820 if (LOGGING(tls_cipher))
1821 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1822 else
1823 DEBUG(D_tls) debug_printf(" parse error\n");
1824 return 0;
1825 }
1826
1827 if (!(bs = OCSP_response_get1_basic(rsp)))
1828 {
1829 tls_out.ocsp = OCSP_FAILED;
1830 if (LOGGING(tls_cipher))
1831 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1832 else
1833 DEBUG(D_tls) debug_printf(" error parsing response\n");
1834 OCSP_RESPONSE_free(rsp);
1835 return 0;
1836 }
1837
1838 /* We'd check the nonce here if we'd put one in the request. */
1839 /* However that would defeat cacheability on the server so we don't. */
1840
1841 /* This section of code reworked from OpenSSL apps source;
1842 The OpenSSL Project retains copyright:
1843 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1844 */
1845 {
1846 BIO * bp = NULL;
1847 int status, reason;
1848 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1849
1850 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1851
1852 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1853
1854 /* Use the chain that verified the server cert to verify the stapled info */
1855 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1856
1857 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1858 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1859 {
1860 tls_out.ocsp = OCSP_FAILED;
1861 if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1862 "Received TLS cert status response, itself unverifiable: %s",
1863 ERR_reason_error_string(ERR_peek_error()));
1864 BIO_printf(bp, "OCSP response verify failure\n");
1865 ERR_print_errors(bp);
1866 OCSP_RESPONSE_print(bp, rsp, 0);
1867 goto failed;
1868 }
1869
1870 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1871
1872 /*XXX So we have a good stapled OCSP status. How do we know
1873 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1874 OCSP_resp_find_status() which matches on a cert id, which presumably
1875 we should use. Making an id needs OCSP_cert_id_new(), which takes
1876 issuerName, issuerKey, serialNumber. Are they all in the cert?
1877
1878 For now, carry on blindly accepting the resp. */
1879
1880 {
1881 OCSP_SINGLERESP * single;
1882
1883 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1884 if (OCSP_resp_count(bs) != 1)
1885 #else
1886 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1887 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1888 #endif
1889 {
1890 tls_out.ocsp = OCSP_FAILED;
1891 log_write(0, LOG_MAIN, "OCSP stapling "
1892 "with multiple responses not handled");
1893 goto failed;
1894 }
1895 single = OCSP_resp_get0(bs, 0);
1896 status = OCSP_single_get0_status(single, &reason, &rev,
1897 &thisupd, &nextupd);
1898 }
1899
1900 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1901 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1902 if (!OCSP_check_validity(thisupd, nextupd,
1903 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1904 {
1905 tls_out.ocsp = OCSP_FAILED;
1906 DEBUG(D_tls) ERR_print_errors(bp);
1907 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1908 }
1909 else
1910 {
1911 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1912 OCSP_cert_status_str(status));
1913 switch(status)
1914 {
1915 case V_OCSP_CERTSTATUS_GOOD:
1916 tls_out.ocsp = OCSP_VFIED;
1917 i = 1;
1918 goto good;
1919 case V_OCSP_CERTSTATUS_REVOKED:
1920 tls_out.ocsp = OCSP_FAILED;
1921 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1922 reason != -1 ? "; reason: " : "",
1923 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1924 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1925 break;
1926 default:
1927 tls_out.ocsp = OCSP_FAILED;
1928 log_write(0, LOG_MAIN,
1929 "Server certificate status unknown, in OCSP stapling");
1930 break;
1931 }
1932 }
1933 failed:
1934 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1935 good:
1936 BIO_free(bp);
1937 }
1938
1939 OCSP_RESPONSE_free(rsp);
1940 return i;
1941 }
1942 #endif /*!DISABLE_OCSP*/
1943
1944
1945 /*************************************************
1946 * Initialize for TLS *
1947 *************************************************/
1948
1949 static void
1950 tls_openssl_init(void)
1951 {
1952 #ifdef EXIM_NEED_OPENSSL_INIT
1953 SSL_load_error_strings(); /* basic set up */
1954 OpenSSL_add_ssl_algorithms();
1955 #endif
1956
1957 #if defined(EXIM_HAVE_SHA256) && !defined(OPENSSL_AUTO_SHA256)
1958 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1959 list of available digests. */
1960 EVP_add_digest(EVP_sha256());
1961 #endif
1962 }
1963
1964
1965
1966 /* Called from both server and client code, to do preliminary initialization
1967 of the library. We allocate and return a context structure.
1968
1969 Arguments:
1970 ctxp returned SSL context
1971 host connected host, if client; NULL if server
1972 dhparam DH parameter file
1973 certificate certificate file
1974 privatekey private key
1975 ocsp_file file of stapling info (server); flag for require ocsp (client)
1976 addr address if client; NULL if server (for some randomness)
1977 cbp place to put allocated callback context
1978 errstr error string pointer
1979
1980 Returns: OK/DEFER/FAIL
1981 */
1982
1983 static int
1984 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1985 uschar *privatekey,
1986 #ifndef DISABLE_OCSP
1987 uschar *ocsp_file,
1988 #endif
1989 address_item *addr, tls_ext_ctx_cb ** cbp,
1990 tls_support * tlsp,
1991 uschar ** errstr)
1992 {
1993 SSL_CTX * ctx;
1994 long init_options;
1995 int rc;
1996 tls_ext_ctx_cb * cbinfo;
1997
1998 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1999 cbinfo->tlsp = tlsp;
2000 cbinfo->certificate = certificate;
2001 cbinfo->privatekey = privatekey;
2002 cbinfo->is_server = host==NULL;
2003 #ifndef DISABLE_OCSP
2004 cbinfo->verify_stack = NULL;
2005 if (!host)
2006 {
2007 cbinfo->u_ocsp.server.file = ocsp_file;
2008 cbinfo->u_ocsp.server.file_expanded = NULL;
2009 cbinfo->u_ocsp.server.olist = NULL;
2010 }
2011 else
2012 cbinfo->u_ocsp.client.verify_store = NULL;
2013 #endif
2014 cbinfo->dhparam = dhparam;
2015 cbinfo->server_cipher_list = NULL;
2016 cbinfo->host = host;
2017 #ifndef DISABLE_EVENT
2018 cbinfo->event_action = NULL;
2019 #endif
2020
2021 tls_openssl_init();
2022
2023 /* Create a context.
2024 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
2025 negotiation in the different methods; as far as I can tell, the only
2026 *_{server,client}_method which allows negotiation is SSLv23, which exists even
2027 when OpenSSL is built without SSLv2 support.
2028 By disabling with openssl_options, we can let admins re-enable with the
2029 existing knob. */
2030
2031 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
2032 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
2033 #else
2034 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
2035 #endif
2036 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
2037
2038 /* It turns out that we need to seed the random number generator this early in
2039 order to get the full complement of ciphers to work. It took me roughly a day
2040 of work to discover this by experiment.
2041
2042 On systems that have /dev/urandom, SSL may automatically seed itself from
2043 there. Otherwise, we have to make something up as best we can. Double check
2044 afterwards. */
2045
2046 if (!RAND_status())
2047 {
2048 randstuff r;
2049 gettimeofday(&r.tv, NULL);
2050 r.p = getpid();
2051
2052 RAND_seed(US (&r), sizeof(r));
2053 RAND_seed(US big_buffer, big_buffer_size);
2054 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
2055
2056 if (!RAND_status())
2057 return tls_error(US"RAND_status", host,
2058 US"unable to seed random number generator", errstr);
2059 }
2060
2061 /* Set up the information callback, which outputs if debugging is at a suitable
2062 level. */
2063
2064 DEBUG(D_tls)
2065 {
2066 SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
2067 #if defined(EXIM_HAVE_OPESSL_TRACE) && !defined(OPENSSL_NO_SSL_TRACE)
2068 /* this needs a debug build of OpenSSL */
2069 SSL_CTX_set_msg_callback(ctx, (void (*)())SSL_trace);
2070 #endif
2071 #ifdef OPENSSL_HAVE_KEYLOG_CB
2072 SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
2073 #endif
2074 }
2075
2076 /* Automatically re-try reads/writes after renegotiation. */
2077 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
2078
2079 /* Apply administrator-supplied work-arounds.
2080 Historically we applied just one requested option,
2081 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
2082 moved to an administrator-controlled list of options to specify and
2083 grandfathered in the first one as the default value for "openssl_options".
2084
2085 No OpenSSL version number checks: the options we accept depend upon the
2086 availability of the option value macros from OpenSSL. */
2087
2088 if (!tls_openssl_options_parse(openssl_options, &init_options))
2089 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
2090
2091 #ifdef EXPERIMENTAL_TLS_RESUME
2092 tlsp->resumption = RESUME_SUPPORTED;
2093 #endif
2094 if (init_options)
2095 {
2096 #ifdef EXPERIMENTAL_TLS_RESUME
2097 /* Should the server offer session resumption? */
2098 if (!host && verify_check_host(&tls_resumption_hosts) == OK)
2099 {
2100 DEBUG(D_tls) debug_printf("tls_resumption_hosts overrides openssl_options\n");
2101 init_options &= ~SSL_OP_NO_TICKET;
2102 tlsp->resumption |= RESUME_SERVER_TICKET; /* server will give ticket on request */
2103 tlsp->host_resumable = TRUE;
2104 }
2105 #endif
2106
2107 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
2108 if (!(SSL_CTX_set_options(ctx, init_options)))
2109 return tls_error(string_sprintf(
2110 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
2111 }
2112 else
2113 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
2114
2115 /* We'd like to disable session cache unconditionally, but foolish Outlook
2116 Express clients then give up the first TLS connection and make a second one
2117 (which works). Only when there is an IMAP service on the same machine.
2118 Presumably OE is trying to use the cache for A on B. Leave it enabled for
2119 now, until we work out a decent way of presenting control to the config. It
2120 will never be used because we use a new context every time. */
2121 #ifdef notdef
2122 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
2123 #endif
2124
2125 /* Initialize with DH parameters if supplied */
2126 /* Initialize ECDH temp key parameter selection */
2127
2128 if ( !init_dh(ctx, dhparam, host, errstr)
2129 || !init_ecdh(ctx, host, errstr)
2130 )
2131 return DEFER;
2132
2133 /* Set up certificate and key (and perhaps OCSP info) */
2134
2135 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
2136 return rc;
2137
2138 /* If we need to handle SNI or OCSP, do so */
2139
2140 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2141 # ifndef DISABLE_OCSP
2142 if (!(cbinfo->verify_stack = sk_X509_new_null()))
2143 {
2144 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
2145 return FAIL;
2146 }
2147 # endif
2148
2149 if (!host) /* server */
2150 {
2151 # ifndef DISABLE_OCSP
2152 /* We check u_ocsp.server.file, not server.olist, because we care about if
2153 the option exists, not what the current expansion might be, as SNI might
2154 change the certificate and OCSP file in use between now and the time the
2155 callback is invoked. */
2156 if (cbinfo->u_ocsp.server.file)
2157 {
2158 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
2159 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2160 }
2161 # endif
2162 /* We always do this, so that $tls_sni is available even if not used in
2163 tls_certificate */
2164 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
2165 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
2166 }
2167 # ifndef DISABLE_OCSP
2168 else /* client */
2169 if(ocsp_file) /* wanting stapling */
2170 {
2171 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
2172 {
2173 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
2174 return FAIL;
2175 }
2176 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
2177 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
2178 }
2179 # endif
2180 #endif
2181
2182 cbinfo->verify_cert_hostnames = NULL;
2183
2184 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
2185 /* Set up the RSA callback */
2186 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
2187 #endif
2188
2189 /* Finally, set the session cache timeout, and we are done.
2190 The period appears to be also used for (server-generated) session tickets */
2191
2192 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
2193 DEBUG(D_tls) debug_printf("Initialized TLS\n");
2194
2195 *cbp = cbinfo;
2196 *ctxp = ctx;
2197
2198 return OK;
2199 }
2200
2201
2202
2203
2204 /*************************************************
2205 * Get name of cipher in use *
2206 *************************************************/
2207
2208 /*
2209 Argument: pointer to an SSL structure for the connection
2210 pointer to number of bits for cipher
2211 Returns: pointer to allocated string in perm-pool
2212 */
2213
2214 static uschar *
2215 construct_cipher_name(SSL * ssl, const uschar * ver, int * bits)
2216 {
2217 int pool = store_pool;
2218 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
2219 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
2220 the accessor functions use const in the prototype. */
2221
2222 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
2223 uschar * s;
2224
2225 SSL_CIPHER_get_bits(c, bits);
2226
2227 store_pool = POOL_PERM;
2228 s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits);
2229 store_pool = pool;
2230 DEBUG(D_tls) debug_printf("Cipher: %s\n", s);
2231 return s;
2232 }
2233
2234
2235 /* Get IETF-standard name for ciphersuite.
2236 Argument: pointer to an SSL structure for the connection
2237 Returns: pointer to string
2238 */
2239
2240 static const uschar *
2241 cipher_stdname_ssl(SSL * ssl)
2242 {
2243 #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
2244 return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl));
2245 #else
2246 ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl));
2247 return cipher_stdname(id >> 8, id & 0xff);
2248 #endif
2249 }
2250
2251
2252 static const uschar *
2253 tlsver_name(SSL * ssl)
2254 {
2255 uschar * s, * p;
2256 int pool = store_pool;
2257
2258 store_pool = POOL_PERM;
2259 s = string_copy(US SSL_get_version(ssl));
2260 store_pool = pool;
2261 if ((p = Ustrchr(s, 'v'))) /* TLSv1.2 -> TLS1.2 */
2262 for (;; p++) if (!(*p = p[1])) break;
2263 return CUS s;
2264 }
2265
2266
2267 static void
2268 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
2269 {
2270 /*XXX we might consider a list-of-certs variable for the cert chain.
2271 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
2272 in list-handling functions, also consider the difference between the entire
2273 chain and the elements sent by the peer. */
2274
2275 tlsp->peerdn = NULL;
2276
2277 /* Will have already noted peercert on a verify fail; possibly not the leaf */
2278 if (!tlsp->peercert)
2279 tlsp->peercert = SSL_get_peer_certificate(ssl);
2280 /* Beware anonymous ciphers which lead to server_cert being NULL */
2281 if (tlsp->peercert)
2282 if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
2283 { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
2284 else
2285 {
2286 int oldpool = store_pool;
2287
2288 peerdn[siz-1] = '\0'; /* paranoia */
2289 store_pool = POOL_PERM;
2290 tlsp->peerdn = string_copy(peerdn);
2291 store_pool = oldpool;
2292
2293 /* We used to set CV in the cert-verify callbacks (either plain or dane)
2294 but they don't get called on session-resumption. So use the official
2295 interface, which uses the resumed value. Unfortunately this claims verified
2296 when it actually failed but we're in try-verify mode, due to us wanting the
2297 knowlege that it failed so needing to have the callback and forcing a
2298 permissive return. If we don't force it, the TLS startup is failed.
2299 The extra bit of information is set in verify_override in the cb, stashed
2300 for resumption next to the TLS session, and used here. */
2301
2302 if (!tlsp->verify_override)
2303 tlsp->certificate_verified = SSL_get_verify_result(ssl) == X509_V_OK;
2304 }
2305 }
2306
2307
2308
2309
2310
2311 /*************************************************
2312 * Set up for verifying certificates *
2313 *************************************************/
2314
2315 #ifndef DISABLE_OCSP
2316 /* Load certs from file, return TRUE on success */
2317
2318 static BOOL
2319 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
2320 {
2321 BIO * bp;
2322 X509 * x;
2323
2324 while (sk_X509_num(verify_stack) > 0)
2325 X509_free(sk_X509_pop(verify_stack));
2326
2327 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
2328 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
2329 sk_X509_push(verify_stack, x);
2330 BIO_free(bp);
2331 return TRUE;
2332 }
2333 #endif
2334
2335
2336
2337 /* Called by both client and server startup; on the server possibly
2338 repeated after a Server Name Indication.
2339
2340 Arguments:
2341 sctx SSL_CTX* to initialise
2342 certs certs file or NULL
2343 crl CRL file or NULL
2344 host NULL in a server; the remote host in a client
2345 optional TRUE if called from a server for a host in tls_try_verify_hosts;
2346 otherwise passed as FALSE
2347 cert_vfy_cb Callback function for certificate verification
2348 errstr error string pointer
2349
2350 Returns: OK/DEFER/FAIL
2351 */
2352
2353 static int
2354 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2355 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2356 {
2357 uschar *expcerts, *expcrl;
2358
2359 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2360 return DEFER;
2361 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2362
2363 if (expcerts && *expcerts)
2364 {
2365 /* Tell the library to use its compiled-in location for the system default
2366 CA bundle. Then add the ones specified in the config, if any. */
2367
2368 if (!SSL_CTX_set_default_verify_paths(sctx))
2369 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2370
2371 if (Ustrcmp(expcerts, "system") != 0)
2372 {
2373 struct stat statbuf;
2374
2375 if (Ustat(expcerts, &statbuf) < 0)
2376 {
2377 log_write(0, LOG_MAIN|LOG_PANIC,
2378 "failed to stat %s for certificates", expcerts);
2379 return DEFER;
2380 }
2381 else
2382 {
2383 uschar *file, *dir;
2384 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2385 { file = NULL; dir = expcerts; }
2386 else
2387 {
2388 file = expcerts; dir = NULL;
2389 #ifndef DISABLE_OCSP
2390 /* In the server if we will be offering an OCSP proof, load chain from
2391 file for verifying the OCSP proof at load time. */
2392
2393 /*XXX Glitch! The file here is tls_verify_certs: the chain for verifying the client cert.
2394 This is inconsistent with the need to verify the OCSP proof of the server cert.
2395 */
2396
2397 if ( !host
2398 && statbuf.st_size > 0
2399 && server_static_cbinfo->u_ocsp.server.file
2400 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2401 )
2402 {
2403 log_write(0, LOG_MAIN|LOG_PANIC,
2404 "failed to load cert chain from %s", file);
2405 return DEFER;
2406 }
2407 #endif
2408 }
2409
2410 /* If a certificate file is empty, the next function fails with an
2411 unhelpful error message. If we skip it, we get the correct behaviour (no
2412 certificates are recognized, but the error message is still misleading (it
2413 says no certificate was supplied). But this is better. */
2414
2415 if ( (!file || statbuf.st_size > 0)
2416 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2417 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2418
2419 /* Load the list of CAs for which we will accept certs, for sending
2420 to the client. This is only for the one-file tls_verify_certificates
2421 variant.
2422 If a list isn't loaded into the server, but some verify locations are set,
2423 the server end appears to make a wildcard request for client certs.
2424 Meanwhile, the client library as default behaviour *ignores* the list
2425 we send over the wire - see man SSL_CTX_set_client_cert_cb.
2426 Because of this, and that the dir variant is likely only used for
2427 the public-CA bundle (not for a private CA), not worth fixing. */
2428
2429 if (file)
2430 {
2431 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2432
2433 SSL_CTX_set_client_CA_list(sctx, names);
2434 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2435 sk_X509_NAME_num(names));
2436 }
2437 }
2438 }
2439
2440 /* Handle a certificate revocation list. */
2441
2442 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2443
2444 /* This bit of code is now the version supplied by Lars Mainka. (I have
2445 merely reformatted it into the Exim code style.)
2446
2447 "From here I changed the code to add support for multiple crl's
2448 in pem format in one file or to support hashed directory entries in
2449 pem format instead of a file. This method now uses the library function
2450 X509_STORE_load_locations to add the CRL location to the SSL context.
2451 OpenSSL will then handle the verify against CA certs and CRLs by
2452 itself in the verify callback." */
2453
2454 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2455 if (expcrl && *expcrl)
2456 {
2457 struct stat statbufcrl;
2458 if (Ustat(expcrl, &statbufcrl) < 0)
2459 {
2460 log_write(0, LOG_MAIN|LOG_PANIC,
2461 "failed to stat %s for certificates revocation lists", expcrl);
2462 return DEFER;
2463 }
2464 else
2465 {
2466 /* is it a file or directory? */
2467 uschar *file, *dir;
2468 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2469 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2470 {
2471 file = NULL;
2472 dir = expcrl;
2473 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2474 }
2475 else
2476 {
2477 file = expcrl;
2478 dir = NULL;
2479 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2480 }
2481 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2482 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2483
2484 /* setting the flags to check against the complete crl chain */
2485
2486 X509_STORE_set_flags(cvstore,
2487 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2488 }
2489 }
2490
2491 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2492
2493 /* If verification is optional, don't fail if no certificate */
2494
2495 SSL_CTX_set_verify(sctx,
2496 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2497 cert_vfy_cb);
2498 }
2499
2500 return OK;
2501 }
2502
2503
2504
2505 /*************************************************
2506 * Start a TLS session in a server *
2507 *************************************************/
2508
2509 /* This is called when Exim is running as a server, after having received
2510 the STARTTLS command. It must respond to that command, and then negotiate
2511 a TLS session.
2512
2513 Arguments:
2514 require_ciphers allowed ciphers
2515 errstr pointer to error message
2516
2517 Returns: OK on success
2518 DEFER for errors before the start of the negotiation
2519 FAIL for errors during the negotiation; the server can't
2520 continue running.
2521 */
2522
2523 int
2524 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2525 {
2526 int rc;
2527 uschar * expciphers;
2528 tls_ext_ctx_cb * cbinfo;
2529 static uschar peerdn[256];
2530
2531 /* Check for previous activation */
2532
2533 if (tls_in.active.sock >= 0)
2534 {
2535 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2536 smtp_printf("554 Already in TLS\r\n", FALSE);
2537 return FAIL;
2538 }
2539
2540 /* Initialize the SSL library. If it fails, it will already have logged
2541 the error. */
2542
2543 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2544 #ifndef DISABLE_OCSP
2545 tls_ocsp_file,
2546 #endif
2547 NULL, &server_static_cbinfo, &tls_in, errstr);
2548 if (rc != OK) return rc;
2549 cbinfo = server_static_cbinfo;
2550
2551 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2552 return FAIL;
2553
2554 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2555 were historically separated by underscores. So that I can use either form in my
2556 tests, and also for general convenience, we turn underscores into hyphens here.
2557
2558 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2559 for TLS 1.3 . Since we do not call it at present we get the default list:
2560 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2561 */
2562
2563 if (expciphers)
2564 {
2565 for (uschar * s = expciphers; *s; s++ ) if (*s == '_') *s = '-';
2566 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2567 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2568 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2569 cbinfo->server_cipher_list = expciphers;
2570 }
2571
2572 /* If this is a host for which certificate verification is mandatory or
2573 optional, set up appropriately. */
2574
2575 tls_in.certificate_verified = FALSE;
2576 #ifdef SUPPORT_DANE
2577 tls_in.dane_verified = FALSE;
2578 #endif
2579 server_verify_callback_called = FALSE;
2580
2581 if (verify_check_host(&tls_verify_hosts) == OK)
2582 {
2583 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2584 FALSE, verify_callback_server, errstr);
2585 if (rc != OK) return rc;
2586 server_verify_optional = FALSE;
2587 }
2588 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2589 {
2590 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2591 TRUE, verify_callback_server, errstr);
2592 if (rc != OK) return rc;
2593 server_verify_optional = TRUE;
2594 }
2595
2596 #ifdef EXPERIMENTAL_TLS_RESUME
2597 SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_key_callback);
2598 /* despite working, appears to always return failure, so ignoring */
2599 #endif
2600 #ifdef OPENSSL_HAVE_NUM_TICKETS
2601 # ifdef EXPERIMENTAL_TLS_RESUME
2602 SSL_CTX_set_num_tickets(server_ctx, tls_in.host_resumable ? 1 : 0);
2603 # else
2604 SSL_CTX_set_num_tickets(server_ctx, 0); /* send no TLS1.3 stateful-tickets */
2605 # endif
2606 #endif
2607
2608
2609 /* Prepare for new connection */
2610
2611 if (!(server_ssl = SSL_new(server_ctx)))
2612 return tls_error(US"SSL_new", NULL, NULL, errstr);
2613
2614 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2615 *
2616 * With the SSL_clear(), we get strange interoperability bugs with
2617 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2618 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2619 *
2620 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2621 * session shutdown. In this case, we have a brand new object and there's no
2622 * obvious reason to immediately clear it. I'm guessing that this was
2623 * originally added because of incomplete initialisation which the clear fixed,
2624 * in some historic release.
2625 */
2626
2627 /* Set context and tell client to go ahead, except in the case of TLS startup
2628 on connection, where outputting anything now upsets the clients and tends to
2629 make them disconnect. We need to have an explicit fflush() here, to force out
2630 the response. Other smtp_printf() calls do not need it, because in non-TLS
2631 mode, the fflush() happens when smtp_getc() is called. */
2632
2633 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2634 if (!tls_in.on_connect)
2635 {
2636 smtp_printf("220 TLS go ahead\r\n", FALSE);
2637 fflush(smtp_out);
2638 }
2639
2640 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2641 that the OpenSSL library doesn't. */
2642
2643 SSL_set_wfd(server_ssl, fileno(smtp_out));
2644 SSL_set_rfd(server_ssl, fileno(smtp_in));
2645 SSL_set_accept_state(server_ssl);
2646
2647 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2648
2649 sigalrm_seen = FALSE;
2650 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2651 rc = SSL_accept(server_ssl);
2652 ALARM_CLR(0);
2653
2654 if (rc <= 0)
2655 {
2656 int error = SSL_get_error(server_ssl, rc);
2657 switch(error)
2658 {
2659 case SSL_ERROR_NONE:
2660 break;
2661
2662 case SSL_ERROR_ZERO_RETURN:
2663 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2664 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2665
2666 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2667 SSL_shutdown(server_ssl);
2668
2669 tls_close(NULL, TLS_NO_SHUTDOWN);
2670 return FAIL;
2671
2672 /* Handle genuine errors */
2673 case SSL_ERROR_SSL:
2674 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2675 return FAIL;
2676
2677 default:
2678 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2679 if (error == SSL_ERROR_SYSCALL)
2680 {
2681 if (!errno)
2682 {
2683 *errstr = US"SSL_accept: TCP connection closed by peer";
2684 return FAIL;
2685 }
2686 DEBUG(D_tls) debug_printf(" - syscall %s\n", strerror(errno));
2687 }
2688 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2689 return FAIL;
2690 }
2691 }
2692
2693 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2694 ERR_clear_error(); /* Even success can leave errors in the stack. Seen with
2695 anon-authentication ciphersuite negotiated. */
2696
2697 #ifdef EXPERIMENTAL_TLS_RESUME
2698 if (SSL_session_reused(server_ssl))
2699 {
2700 tls_in.resumption |= RESUME_USED;
2701 DEBUG(D_tls) debug_printf("Session reused\n");
2702 }
2703 #endif
2704
2705 /* TLS has been set up. Record data for the connection,
2706 adjust the input functions to read via TLS, and initialize things. */
2707
2708 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2709
2710 tls_in.ver = tlsver_name(server_ssl);
2711 tls_in.cipher = construct_cipher_name(server_ssl, tls_in.ver, &tls_in.bits);
2712 tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl);
2713
2714 DEBUG(D_tls)
2715 {
2716 uschar buf[2048];
2717 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)))
2718 debug_printf("Shared ciphers: %s\n", buf);
2719
2720 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2721 {
2722 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2723 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2724 BIO_free(bp);
2725 }
2726 #endif
2727
2728 #ifdef EXIM_HAVE_SESSION_TICKET
2729 {
2730 SSL_SESSION * ss = SSL_get_session(server_ssl);
2731 if (SSL_SESSION_has_ticket(ss)) /* 1.1.0 */
2732 debug_printf("The session has a ticket, life %lu seconds\n",
2733 SSL_SESSION_get_ticket_lifetime_hint(ss));
2734 }
2735 #endif
2736 }
2737
2738 /* Record the certificate we presented */
2739 {
2740 X509 * crt = SSL_get_certificate(server_ssl);
2741 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2742 }
2743
2744 /* Only used by the server-side tls (tls_in), including tls_getc.
2745 Client-side (tls_out) reads (seem to?) go via
2746 smtp_read_response()/ip_recv().
2747 Hence no need to duplicate for _in and _out.
2748 */
2749 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2750 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2751 ssl_xfer_eof = ssl_xfer_error = FALSE;
2752
2753 receive_getc = tls_getc;
2754 receive_getbuf = tls_getbuf;
2755 receive_get_cache = tls_get_cache;
2756 receive_ungetc = tls_ungetc;
2757 receive_feof = tls_feof;
2758 receive_ferror = tls_ferror;
2759 receive_smtp_buffered = tls_smtp_buffered;
2760
2761 tls_in.active.sock = fileno(smtp_out);
2762 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2763 return OK;
2764 }
2765
2766
2767
2768
2769 static int
2770 tls_client_basic_ctx_init(SSL_CTX * ctx,
2771 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2772 uschar ** errstr)
2773 {
2774 int rc;
2775 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2776 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2777 the specified host patterns if one of them is defined */
2778
2779 if ( ( !ob->tls_verify_hosts
2780 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2781 )
2782 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2783 )
2784 client_verify_optional = FALSE;
2785 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2786 client_verify_optional = TRUE;
2787 else
2788 return OK;
2789
2790 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2791 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2792 errstr)) != OK)
2793 return rc;
2794
2795 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2796 {
2797 cbinfo->verify_cert_hostnames =
2798 #ifdef SUPPORT_I18N
2799 string_domain_utf8_to_alabel(host->name, NULL);
2800 #else
2801 host->name;
2802 #endif
2803 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2804 cbinfo->verify_cert_hostnames);
2805 }
2806 return OK;
2807 }
2808
2809
2810 #ifdef SUPPORT_DANE
2811 static int
2812 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2813 {
2814 dns_scan dnss;
2815 const char * hostnames[2] = { CS host->name, NULL };
2816 int found = 0;
2817
2818 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2819 return tls_error(US"hostnames load", host, NULL, errstr);
2820
2821 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2822 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2823 ) if (rr->type == T_TLSA && rr->size > 3)
2824 {
2825 const uschar * p = rr->data;
2826 uint8_t usage, selector, mtype;
2827 const char * mdname;
2828
2829 usage = *p++;
2830
2831 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2832 if (usage != 2 && usage != 3) continue;
2833
2834 selector = *p++;
2835 mtype = *p++;
2836
2837 switch (mtype)
2838 {
2839 default: continue; /* Only match-types 0, 1, 2 are supported */
2840 case 0: mdname = NULL; break;
2841 case 1: mdname = "sha256"; break;
2842 case 2: mdname = "sha512"; break;
2843 }
2844
2845 found++;
2846 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2847 {
2848 default:
2849 return tls_error(US"tlsa load", host, NULL, errstr);
2850 case 0: /* action not taken */
2851 case 1: break;
2852 }
2853
2854 tls_out.tlsa_usage |= 1<<usage;
2855 }
2856
2857 if (found)
2858 return OK;
2859
2860 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2861 return DEFER;
2862 }
2863 #endif /*SUPPORT_DANE*/
2864
2865
2866
2867 #ifdef EXPERIMENTAL_TLS_RESUME
2868 /* On the client, get any stashed session for the given IP from hints db
2869 and apply it to the ssl-connection for attempted resumption. */
2870
2871 static void
2872 tls_retrieve_session(tls_support * tlsp, SSL * ssl, const uschar * key)
2873 {
2874 tlsp->resumption |= RESUME_SUPPORTED;
2875 if (tlsp->host_resumable)
2876 {
2877 dbdata_tls_session * dt;
2878 int len;
2879 open_db dbblock, * dbm_file;
2880
2881 tlsp->resumption |= RESUME_CLIENT_REQUESTED;
2882 DEBUG(D_tls) debug_printf("checking for resumable session for %s\n", key);
2883 if ((dbm_file = dbfn_open(US"tls", O_RDONLY, &dbblock, FALSE, FALSE)))
2884 {
2885 /* key for the db is the IP */
2886 if ((dt = dbfn_read_with_length(dbm_file, key, &len)))
2887 {
2888 SSL_SESSION * ss = NULL;
2889 const uschar * sess_asn1 = dt->session;
2890
2891 len -= sizeof(dbdata_tls_session);
2892 if (!(d2i_SSL_SESSION(&ss, &sess_asn1, (long)len)))
2893 {
2894 DEBUG(D_tls)
2895 {
2896 ERR_error_string_n(ERR_get_error(),
2897 ssl_errstring, sizeof(ssl_errstring));
2898 debug_printf("decoding session: %s\n", ssl_errstring);
2899 }
2900 }
2901 #ifdef EXIM_HAVE_SESSION_TICKET
2902 else if ( SSL_SESSION_get_ticket_lifetime_hint(ss) + dt->time_stamp
2903 < time(NULL))
2904 {
2905 DEBUG(D_tls) debug_printf("session expired\n");
2906 dbfn_delete(dbm_file, key);
2907 }
2908 #endif
2909 else if (!SSL_set_session(ssl, ss))
2910 {
2911 DEBUG(D_tls)
2912 {
2913 ERR_error_string_n(ERR_get_error(),
2914 ssl_errstring, sizeof(ssl_errstring));
2915 debug_printf("applying session to ssl: %s\n", ssl_errstring);
2916 }
2917 }
2918 else
2919 {
2920 DEBUG(D_tls) debug_printf("good session\n");
2921 tlsp->resumption |= RESUME_CLIENT_SUGGESTED;
2922 tlsp->verify_override = dt->verify_override;
2923 tlsp->ocsp = dt->ocsp;
2924 }
2925 }
2926 else
2927 DEBUG(D_tls) debug_printf("no session record\n");
2928 dbfn_close(dbm_file);
2929 }
2930 }
2931 }
2932
2933
2934 /* On the client, save the session for later resumption */
2935
2936 static int
2937 tls_save_session_cb(SSL * ssl, SSL_SESSION * ss)
2938 {
2939 tls_ext_ctx_cb * cbinfo = SSL_get_ex_data(ssl, tls_exdata_idx);
2940 tls_support * tlsp;
2941
2942 DEBUG(D_tls) debug_printf("tls_save_session_cb\n");
2943
2944 if (!cbinfo || !(tlsp = cbinfo->tlsp)->host_resumable) return 0;
2945
2946 # ifdef OPENSSL_HAVE_NUM_TICKETS
2947 if (SSL_SESSION_is_resumable(ss)) /* 1.1.1 */
2948 # endif
2949 {
2950 int len = i2d_SSL_SESSION(ss, NULL);
2951 int dlen = sizeof(dbdata_tls_session) + len;
2952 dbdata_tls_session * dt = store_get(dlen, TRUE);
2953 uschar * s = dt->session;
2954 open_db dbblock, * dbm_file;
2955
2956 DEBUG(D_tls) debug_printf("session is resumable\n");
2957 tlsp->resumption |= RESUME_SERVER_TICKET; /* server gave us a ticket */
2958
2959 dt->verify_override = tlsp->verify_override;
2960 dt->ocsp = tlsp->ocsp;
2961 (void) i2d_SSL_SESSION(ss, &s); /* s gets bumped to end */
2962
2963 if ((dbm_file = dbfn_open(US"tls", O_RDWR, &dbblock, FALSE, FALSE)))
2964 {
2965 const uschar * key = cbinfo->host->address;
2966 dbfn_delete(dbm_file, key);
2967 dbfn_write(dbm_file, key, dt, dlen);
2968 dbfn_close(dbm_file);
2969 DEBUG(D_tls) debug_printf("wrote session (len %u) to db\n",
2970 (unsigned)dlen);
2971 }
2972 }
2973 return 1;
2974 }
2975
2976
2977 static void
2978 tls_client_ctx_resume_prehandshake(
2979 exim_openssl_client_tls_ctx * exim_client_ctx, tls_support * tlsp,
2980 smtp_transport_options_block * ob, host_item * host)
2981 {
2982 /* Should the client request a session resumption ticket? */
2983 if (verify_check_given_host(CUSS &ob->tls_resumption_hosts, host) == OK)
2984 {
2985 tlsp->host_resumable = TRUE;
2986
2987 SSL_CTX_set_session_cache_mode(exim_client_ctx->ctx,
2988 SSL_SESS_CACHE_CLIENT
2989 | SSL_SESS_CACHE_NO_INTERNAL | SSL_SESS_CACHE_NO_AUTO_CLEAR);
2990 SSL_CTX_sess_set_new_cb(exim_client_ctx->ctx, tls_save_session_cb);
2991 }
2992 }
2993
2994 static BOOL
2995 tls_client_ssl_resume_prehandshake(SSL * ssl, tls_support * tlsp,
2996 host_item * host, uschar ** errstr)
2997 {
2998 if (tlsp->host_resumable)
2999 {
3000 DEBUG(D_tls)
3001 debug_printf("tls_resumption_hosts overrides openssl_options, enabling tickets\n");
3002 SSL_clear_options(ssl, SSL_OP_NO_TICKET);
3003
3004 tls_exdata_idx = SSL_get_ex_new_index(0, 0, 0, 0, 0);
3005 if (!SSL_set_ex_data(ssl, tls_exdata_idx, client_static_cbinfo))
3006 {
3007 tls_error(US"set ex_data", host, NULL, errstr);
3008 return FALSE;
3009 }
3010 debug_printf("tls_exdata_idx %d cbinfo %p\n", tls_exdata_idx, client_static_cbinfo);
3011 }
3012
3013 tlsp->resumption = RESUME_SUPPORTED;
3014 /* Pick up a previous session, saved on an old ticket */
3015 tls_retrieve_session(tlsp, ssl, host->address);
3016 return TRUE;
3017 }
3018
3019 static void
3020 tls_client_resume_posthandshake(exim_openssl_client_tls_ctx * exim_client_ctx,
3021 tls_support * tlsp)
3022 {
3023 if (SSL_session_reused(exim_client_ctx->ssl))
3024 {
3025 DEBUG(D_tls) debug_printf("The session was reused\n");
3026 tlsp->resumption |= RESUME_USED;
3027 }
3028 }
3029 #endif /* EXPERIMENTAL_TLS_RESUME */
3030
3031
3032 /*************************************************
3033 * Start a TLS session in a client *
3034 *************************************************/
3035
3036 /* Called from the smtp transport after STARTTLS has been accepted.
3037
3038 Arguments:
3039 cctx connection context
3040 conn_args connection details
3041 cookie datum for randomness; can be NULL
3042 tlsp record details of TLS channel configuration here; must be non-NULL
3043 errstr error string pointer
3044
3045 Returns: TRUE for success with TLS session context set in connection context,
3046 FALSE on error
3047 */
3048
3049 BOOL
3050 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
3051 void * cookie, tls_support * tlsp, uschar ** errstr)
3052 {
3053 host_item * host = conn_args->host; /* for msgs and option-tests */
3054 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
3055 smtp_transport_options_block * ob = tb
3056 ? (smtp_transport_options_block *)tb->options_block
3057 : &smtp_transport_option_defaults;
3058 exim_openssl_client_tls_ctx * exim_client_ctx;
3059 uschar * expciphers;
3060 int rc;
3061 static uschar peerdn[256];
3062
3063 #ifndef DISABLE_OCSP
3064 BOOL request_ocsp = FALSE;
3065 BOOL require_ocsp = FALSE;
3066 #endif
3067
3068 rc = store_pool;
3069 store_pool = POOL_PERM;
3070 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx), FALSE);
3071 exim_client_ctx->corked = NULL;
3072 store_pool = rc;
3073
3074 #ifdef SUPPORT_DANE
3075 tlsp->tlsa_usage = 0;
3076 #endif
3077
3078 #ifndef DISABLE_OCSP
3079 {
3080 # ifdef SUPPORT_DANE
3081 if ( conn_args->dane
3082 && ob->hosts_request_ocsp[0] == '*'
3083 && ob->hosts_request_ocsp[1] == '\0'
3084 )
3085 {
3086 /* Unchanged from default. Use a safer one under DANE */
3087 request_ocsp = TRUE;
3088 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
3089 " {= {4}{$tls_out_tlsa_usage}} } "
3090 " {*}{}}";
3091 }
3092 # endif
3093
3094 if ((require_ocsp =
3095 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
3096 request_ocsp = TRUE;
3097 else
3098 # ifdef SUPPORT_DANE
3099 if (!request_ocsp)
3100 # endif
3101 request_ocsp =
3102 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
3103 }
3104 #endif
3105
3106 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
3107 ob->tls_certificate, ob->tls_privatekey,
3108 #ifndef DISABLE_OCSP
3109 (void *)(long)request_ocsp,
3110 #endif
3111 cookie, &client_static_cbinfo, tlsp, errstr);
3112 if (rc != OK) return FALSE;
3113
3114 tlsp->certificate_verified = FALSE;
3115 client_verify_callback_called = FALSE;
3116
3117 expciphers = NULL;
3118 #ifdef SUPPORT_DANE
3119 if (conn_args->dane)
3120 {
3121 /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
3122 other failures should be treated as problems. */
3123 if (ob->dane_require_tls_ciphers &&
3124 !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
3125 &expciphers, errstr))
3126 return FALSE;
3127 if (expciphers && *expciphers == '\0')
3128 expciphers = NULL;
3129 }
3130 #endif
3131 if (!expciphers &&
3132 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
3133 &expciphers, errstr))
3134 return FALSE;
3135
3136 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
3137 are separated by underscores. So that I can use either form in my tests, and
3138 also for general convenience, we turn underscores into hyphens here. */
3139
3140 if (expciphers)
3141 {
3142 uschar *s = expciphers;
3143 while (*s) { if (*s == '_') *s = '-'; s++; }
3144 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
3145 if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
3146 {
3147 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
3148 return FALSE;
3149 }
3150 }
3151
3152 #ifdef SUPPORT_DANE
3153 if (conn_args->dane)
3154 {
3155 SSL_CTX_set_verify(exim_client_ctx->ctx,
3156 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
3157 verify_callback_client_dane);
3158
3159 if (!DANESSL_library_init())
3160 {
3161 tls_error(US"library init", host, NULL, errstr);
3162 return FALSE;
3163 }
3164 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
3165 {
3166 tls_error(US"context init", host, NULL, errstr);
3167 return FALSE;
3168 }
3169 }
3170 else
3171
3172 #endif
3173
3174 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
3175 client_static_cbinfo, errstr) != OK)
3176 return FALSE;
3177
3178 #ifdef EXPERIMENTAL_TLS_RESUME
3179 tls_client_ctx_resume_prehandshake(exim_client_ctx, tlsp, ob, host);
3180 #endif
3181
3182
3183 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
3184 {
3185 tls_error(US"SSL_new", host, NULL, errstr);
3186 return FALSE;
3187 }
3188 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
3189
3190 SSL_set_fd(exim_client_ctx->ssl, cctx->sock);
3191 SSL_set_connect_state(exim_client_ctx->ssl);
3192
3193 if (ob->tls_sni)
3194 {
3195 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
3196 return FALSE;
3197 if (!tlsp->sni)
3198 {
3199 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
3200 }
3201 else if (!Ustrlen(tlsp->sni))
3202 tlsp->sni = NULL;
3203 else
3204 {
3205 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
3206 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
3207 SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
3208 #else
3209 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
3210 tlsp->sni);
3211 #endif
3212 }
3213 }
3214
3215 #ifdef SUPPORT_DANE
3216 if (conn_args->dane)
3217 if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK)
3218 return FALSE;
3219 #endif
3220
3221 #ifndef DISABLE_OCSP
3222 /* Request certificate status at connection-time. If the server
3223 does OCSP stapling we will get the callback (set in tls_init()) */
3224 # ifdef SUPPORT_DANE
3225 if (request_ocsp)
3226 {
3227 const uschar * s;
3228 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
3229 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
3230 )
3231 { /* Re-eval now $tls_out_tlsa_usage is populated. If
3232 this means we avoid the OCSP request, we wasted the setup
3233 cost in tls_init(). */
3234 require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
3235 request_ocsp = require_ocsp
3236 || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
3237 }
3238 }
3239 # endif
3240
3241 if (request_ocsp)
3242 {
3243 SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
3244 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
3245 tlsp->ocsp = OCSP_NOT_RESP;
3246 }
3247 #endif
3248
3249 #ifdef EXPERIMENTAL_TLS_RESUME
3250 if (!tls_client_ssl_resume_prehandshake(exim_client_ctx->ssl, tlsp, host,
3251 errstr))
3252 return FALSE;
3253 #endif
3254
3255 #ifndef DISABLE_EVENT
3256 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
3257 #endif
3258
3259 /* There doesn't seem to be a built-in timeout on connection. */
3260
3261 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
3262 sigalrm_seen = FALSE;
3263 ALARM(ob->command_timeout);
3264 rc = SSL_connect(exim_client_ctx->ssl);
3265 ALARM_CLR(0);
3266
3267 #ifdef SUPPORT_DANE
3268 if (conn_args->dane)
3269 DANESSL_cleanup(exim_client_ctx->ssl);
3270 #endif
3271
3272 if (rc <= 0)
3273 {
3274 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
3275 return FALSE;
3276 }
3277
3278 DEBUG(D_tls)
3279 {
3280 debug_printf("SSL_connect succeeded\n");
3281 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
3282 {
3283 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
3284 SSL_SESSION_print_keylog(bp, SSL_get_session(exim_client_ctx->ssl));
3285 BIO_free(bp);
3286 }
3287 #endif
3288 }
3289
3290 #ifdef EXPERIMENTAL_TLS_RESUME
3291 tls_client_resume_posthandshake(exim_client_ctx, tlsp);
3292 #endif
3293
3294 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
3295
3296 tlsp->ver = tlsver_name(exim_client_ctx->ssl);
3297 tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, tlsp->ver, &tlsp->bits);
3298 tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl);
3299
3300 /* Record the certificate we presented */
3301 {
3302 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
3303 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
3304 }
3305
3306 tlsp->active.sock = cctx->sock;
3307 tlsp->active.tls_ctx = exim_client_ctx;
3308 cctx->tls_ctx = exim_client_ctx;
3309 return TRUE;
3310 }
3311
3312
3313
3314
3315
3316 static BOOL
3317 tls_refill(unsigned lim)
3318 {
3319 int error;
3320 int inbytes;
3321
3322 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
3323 ssl_xfer_buffer, ssl_xfer_buffer_size);
3324
3325 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
3326 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
3327 MIN(ssl_xfer_buffer_size, lim));
3328 error = SSL_get_error(server_ssl, inbytes);
3329 if (smtp_receive_timeout > 0) ALARM_CLR(0);
3330
3331 if (had_command_timeout) /* set by signal handler */
3332 smtp_command_timeout_exit(); /* does not return */
3333 if (had_command_sigterm)
3334 smtp_command_sigterm_exit();
3335 if (had_data_timeout)
3336 smtp_data_timeout_exit();
3337 if (had_data_sigint)
3338 smtp_data_sigint_exit();
3339
3340 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
3341 closed down, not that the socket itself has been closed down. Revert to
3342 non-SSL handling. */
3343
3344 switch(error)
3345 {
3346 case SSL_ERROR_NONE:
3347 break;
3348
3349 case SSL_ERROR_ZERO_RETURN:
3350 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
3351
3352 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
3353 SSL_shutdown(server_ssl);
3354
3355 tls_close(NULL, TLS_NO_SHUTDOWN);
3356 return FALSE;
3357
3358 /* Handle genuine errors */
3359 case SSL_ERROR_SSL:
3360 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3361 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
3362 ssl_xfer_error = TRUE;
3363 return FALSE;
3364
3365 default:
3366 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
3367 DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
3368 debug_printf(" - syscall %s\n", strerror(errno));
3369 ssl_xfer_error = TRUE;
3370 return FALSE;
3371 }
3372
3373 #ifndef DISABLE_DKIM
3374 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
3375 #endif
3376 ssl_xfer_buffer_hwm = inbytes;
3377 ssl_xfer_buffer_lwm = 0;
3378 return TRUE;
3379 }
3380
3381
3382 /*************************************************
3383 * TLS version of getc *
3384 *************************************************/
3385
3386 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
3387 it refills the buffer via the SSL reading function.
3388
3389 Arguments: lim Maximum amount to read/buffer
3390 Returns: the next character or EOF
3391
3392 Only used by the server-side TLS.
3393 */
3394
3395 int
3396 tls_getc(unsigned lim)
3397 {
3398 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3399 if (!tls_refill(lim))
3400 return ssl_xfer_error ? EOF : smtp_getc(lim);
3401
3402 /* Something in the buffer; return next uschar */
3403
3404 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
3405 }
3406
3407 uschar *
3408 tls_getbuf(unsigned * len)
3409 {
3410 unsigned size;
3411 uschar * buf;
3412
3413 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
3414 if (!tls_refill(*len))
3415 {
3416 if (!ssl_xfer_error) return smtp_getbuf(len);
3417 *len = 0;
3418 return NULL;
3419 }
3420
3421 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)