Fix expansions for RFC 822 addresses having comments in local-part and/or domain...
[exim.git] / src / src / tls-openssl.c
1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
6 /* See the file NOTICE for conditions of use and distribution. */
7
8 /* Portions Copyright (c) The OpenSSL Project 1999 */
9
10 /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL
11 library. It is #included into the tls.c file when that library is used. The
12 code herein is based on a patch that was originally contributed by Steve
13 Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara.
14
15 No cryptographic code is included in Exim. All this module does is to call
16 functions from the OpenSSL library. */
17
18
19 /* Heading stuff */
20
21 #include <openssl/lhash.h>
22 #include <openssl/ssl.h>
23 #include <openssl/err.h>
24 #include <openssl/rand.h>
25 #ifndef OPENSSL_NO_ECDH
26 # include <openssl/ec.h>
27 #endif
28 #ifndef DISABLE_OCSP
29 # include <openssl/ocsp.h>
30 #endif
31 #ifdef SUPPORT_DANE
32 # include "danessl.h"
33 #endif
34
35
36 #ifndef DISABLE_OCSP
37 # define EXIM_OCSP_SKEW_SECONDS (300L)
38 # define EXIM_OCSP_MAX_AGE (-1L)
39 #endif
40
41 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
42 # define EXIM_HAVE_OPENSSL_TLSEXT
43 #endif
44 #if OPENSSL_VERSION_NUMBER >= 0x00908000L
45 # define EXIM_HAVE_RSA_GENKEY_EX
46 #endif
47 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
48 # define EXIM_HAVE_OCSP_RESP_COUNT
49 #else
50 # define EXIM_HAVE_EPHEM_RSA_KEX
51 # define EXIM_HAVE_RAND_PSEUDO
52 #endif
53 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
54 # define EXIM_HAVE_SHA256
55 #endif
56
57 /* X509_check_host provides sane certificate hostname checking, but was added
58 to OpenSSL late, after other projects forked off the code-base. So in
59 addition to guarding against the base version number, beware that LibreSSL
60 does not (at this time) support this function.
61
62 If LibreSSL gains a different API, perhaps via libtls, then we'll probably
63 opt to disentangle and ask a LibreSSL user to provide glue for a third
64 crypto provider for libtls instead of continuing to tie the OpenSSL glue
65 into even twistier knots. If LibreSSL gains the same API, we can just
66 change this guard and punt the issue for a while longer. */
67
68 #ifndef LIBRESSL_VERSION_NUMBER
69 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
70 # define EXIM_HAVE_OPENSSL_CHECKHOST
71 # define EXIM_HAVE_OPENSSL_DH_BITS
72 # define EXIM_HAVE_OPENSSL_TLS_METHOD
73 # define EXIM_HAVE_OPENSSL_KEYLOG
74 # define EXIM_HAVE_OPENSSL_CIPHER_GET_ID
75 # else
76 # define EXIM_NEED_OPENSSL_INIT
77 # endif
78 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
79 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
80 # define EXIM_HAVE_OPENSSL_CHECKHOST
81 # endif
82 #endif
83
84 #if !defined(LIBRESSL_VERSION_NUMBER) \
85 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
86 # if !defined(OPENSSL_NO_ECDH)
87 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
88 # define EXIM_HAVE_ECDH
89 # endif
90 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
91 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
92 # endif
93 # endif
94 #endif
95
96 #ifndef LIBRESSL_VERSION_NUMBER
97 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
98 # define OPENSSL_HAVE_KEYLOG_CB
99 # define OPENSSL_HAVE_NUM_TICKETS
100 # define EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
101 # endif
102 #endif
103
104 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
105 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
106 # define DISABLE_OCSP
107 #endif
108
109 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
110 # include <openssl/x509v3.h>
111 #endif
112
113 #ifndef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
114 # ifndef EXIM_HAVE_OPENSSL_CIPHER_GET_ID
115 # define SSL_CIPHER_get_id(c) (c->id)
116 # endif
117 # include "tls-cipher-stdname.c"
118 #endif
119
120 /*************************************************
121 * OpenSSL option parse *
122 *************************************************/
123
124 typedef struct exim_openssl_option {
125 uschar *name;
126 long value;
127 } exim_openssl_option;
128 /* We could use a macro to expand, but we need the ifdef and not all the
129 options document which version they were introduced in. Policylet: include
130 all options unless explicitly for DTLS, let the administrator choose which
131 to apply.
132
133 This list is current as of:
134 ==> 1.0.1b <==
135 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
136 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
137 */
138 static exim_openssl_option exim_openssl_options[] = {
139 /* KEEP SORTED ALPHABETICALLY! */
140 #ifdef SSL_OP_ALL
141 { US"all", SSL_OP_ALL },
142 #endif
143 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
144 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
145 #endif
146 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
147 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
148 #endif
149 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
150 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
151 #endif
152 #ifdef SSL_OP_EPHEMERAL_RSA
153 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
154 #endif
155 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
156 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
157 #endif
158 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
159 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
160 #endif
161 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
162 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
163 #endif
164 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
165 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
166 #endif
167 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
168 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
169 #endif
170 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
171 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
172 #endif
173 #ifdef SSL_OP_NO_COMPRESSION
174 { US"no_compression", SSL_OP_NO_COMPRESSION },
175 #endif
176 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
177 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
178 #endif
179 #ifdef SSL_OP_NO_SSLv2
180 { US"no_sslv2", SSL_OP_NO_SSLv2 },
181 #endif
182 #ifdef SSL_OP_NO_SSLv3
183 { US"no_sslv3", SSL_OP_NO_SSLv3 },
184 #endif
185 #ifdef SSL_OP_NO_TICKET
186 { US"no_ticket", SSL_OP_NO_TICKET },
187 #endif
188 #ifdef SSL_OP_NO_TLSv1
189 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
190 #endif
191 #ifdef SSL_OP_NO_TLSv1_1
192 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
193 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
194 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
195 #else
196 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
197 #endif
198 #endif
199 #ifdef SSL_OP_NO_TLSv1_2
200 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
201 #endif
202 #ifdef SSL_OP_NO_TLSv1_3
203 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
204 #endif
205 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
206 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
207 #endif
208 #ifdef SSL_OP_SINGLE_DH_USE
209 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
210 #endif
211 #ifdef SSL_OP_SINGLE_ECDH_USE
212 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
213 #endif
214 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
215 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
216 #endif
217 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
218 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
219 #endif
220 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
221 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
222 #endif
223 #ifdef SSL_OP_TLS_D5_BUG
224 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
225 #endif
226 #ifdef SSL_OP_TLS_ROLLBACK_BUG
227 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
228 #endif
229 };
230
231 #ifndef MACRO_PREDEF
232 static int exim_openssl_options_size = nelem(exim_openssl_options);
233 #endif
234
235 #ifdef MACRO_PREDEF
236 void
237 options_tls(void)
238 {
239 uschar buf[64];
240
241 for (struct exim_openssl_option * o = exim_openssl_options;
242 o < exim_openssl_options + nelem(exim_openssl_options); o++)
243 {
244 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
245 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
246
247 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
248 builtin_macro_create(buf);
249 }
250 }
251 #else
252
253 /******************************************************************************/
254
255 /* Structure for collecting random data for seeding. */
256
257 typedef struct randstuff {
258 struct timeval tv;
259 pid_t p;
260 } randstuff;
261
262 /* Local static variables */
263
264 static BOOL client_verify_callback_called = FALSE;
265 static BOOL server_verify_callback_called = FALSE;
266 static const uschar *sid_ctx = US"exim";
267
268 /* We have three different contexts to care about.
269
270 Simple case: client, `client_ctx`
271 As a client, we can be doing a callout or cut-through delivery while receiving
272 a message. So we have a client context, which should have options initialised
273 from the SMTP Transport. We may also concurrently want to make TLS connections
274 to utility daemons, so client-contexts are allocated and passed around in call
275 args rather than using a gobal.
276
277 Server:
278 There are two cases: with and without ServerNameIndication from the client.
279 Given TLS SNI, we can be using different keys, certs and various other
280 configuration settings, because they're re-expanded with $tls_sni set. This
281 allows vhosting with TLS. This SNI is sent in the handshake.
282 A client might not send SNI, so we need a fallback, and an initial setup too.
283 So as a server, we start out using `server_ctx`.
284 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
285 `server_sni` from `server_ctx` and then initialise settings by re-expanding
286 configuration.
287 */
288
289 typedef struct {
290 SSL_CTX * ctx;
291 SSL * ssl;
292 } exim_openssl_client_tls_ctx;
293
294 static SSL_CTX *server_ctx = NULL;
295 static SSL *server_ssl = NULL;
296
297 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
298 static SSL_CTX *server_sni = NULL;
299 #endif
300
301 static char ssl_errstring[256];
302
303 static int ssl_session_timeout = 200;
304 static BOOL client_verify_optional = FALSE;
305 static BOOL server_verify_optional = FALSE;
306
307 static BOOL reexpand_tls_files_for_sni = FALSE;
308
309
310 typedef struct tls_ext_ctx_cb {
311 uschar *certificate;
312 uschar *privatekey;
313 BOOL is_server;
314 #ifndef DISABLE_OCSP
315 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
316 union {
317 struct {
318 uschar *file;
319 uschar *file_expanded;
320 OCSP_RESPONSE *response;
321 } server;
322 struct {
323 X509_STORE *verify_store; /* non-null if status requested */
324 BOOL verify_required;
325 } client;
326 } u_ocsp;
327 #endif
328 uschar *dhparam;
329 /* these are cached from first expand */
330 uschar *server_cipher_list;
331 /* only passed down to tls_error: */
332 host_item *host;
333 const uschar * verify_cert_hostnames;
334 #ifndef DISABLE_EVENT
335 uschar * event_action;
336 #endif
337 } tls_ext_ctx_cb;
338
339 /* should figure out a cleanup of API to handle state preserved per
340 implementation, for various reasons, which can be void * in the APIs.
341 For now, we hack around it. */
342 tls_ext_ctx_cb *client_static_cbinfo = NULL;
343 tls_ext_ctx_cb *server_static_cbinfo = NULL;
344
345 static int
346 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
347 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
348
349 /* Callbacks */
350 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
351 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
352 #endif
353 #ifndef DISABLE_OCSP
354 static int tls_server_stapling_cb(SSL *s, void *arg);
355 #endif
356
357
358 /*************************************************
359 * Handle TLS error *
360 *************************************************/
361
362 /* Called from lots of places when errors occur before actually starting to do
363 the TLS handshake, that is, while the session is still in clear. Always returns
364 DEFER for a server and FAIL for a client so that most calls can use "return
365 tls_error(...)" to do this processing and then give an appropriate return. A
366 single function is used for both server and client, because it is called from
367 some shared functions.
368
369 Argument:
370 prefix text to include in the logged error
371 host NULL if setting up a server;
372 the connected host if setting up a client
373 msg error message or NULL if we should ask OpenSSL
374 errstr pointer to output error message
375
376 Returns: OK/DEFER/FAIL
377 */
378
379 static int
380 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
381 {
382 if (!msg)
383 {
384 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
385 msg = US ssl_errstring;
386 }
387
388 msg = string_sprintf("(%s): %s", prefix, msg);
389 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
390 if (errstr) *errstr = msg;
391 return host ? FAIL : DEFER;
392 }
393
394
395
396 /*************************************************
397 * Callback to generate RSA key *
398 *************************************************/
399
400 /*
401 Arguments:
402 s SSL connection (not used)
403 export not used
404 keylength keylength
405
406 Returns: pointer to generated key
407 */
408
409 static RSA *
410 rsa_callback(SSL *s, int export, int keylength)
411 {
412 RSA *rsa_key;
413 #ifdef EXIM_HAVE_RSA_GENKEY_EX
414 BIGNUM *bn = BN_new();
415 #endif
416
417 export = export; /* Shut picky compilers up */
418 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
419
420 #ifdef EXIM_HAVE_RSA_GENKEY_EX
421 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
422 || !(rsa_key = RSA_new())
423 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
424 )
425 #else
426 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
427 #endif
428
429 {
430 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
431 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
432 ssl_errstring);
433 return NULL;
434 }
435 return rsa_key;
436 }
437
438
439
440 /* Extreme debug
441 #ifndef DISABLE_OCSP
442 void
443 x509_store_dump_cert_s_names(X509_STORE * store)
444 {
445 STACK_OF(X509_OBJECT) * roots= store->objs;
446 static uschar name[256];
447
448 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
449 {
450 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
451 if(tmp_obj->type == X509_LU_X509)
452 {
453 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
454 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
455 {
456 name[sizeof(name)-1] = '\0';
457 debug_printf(" %s\n", name);
458 }
459 }
460 }
461 }
462 #endif
463 */
464
465
466 #ifndef DISABLE_EVENT
467 static int
468 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
469 BOOL *calledp, const BOOL *optionalp, const uschar * what)
470 {
471 uschar * ev;
472 uschar * yield;
473 X509 * old_cert;
474
475 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
476 if (ev)
477 {
478 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
479 old_cert = tlsp->peercert;
480 tlsp->peercert = X509_dup(cert);
481 /* NB we do not bother setting peerdn */
482 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
483 {
484 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
485 "depth=%d cert=%s: %s",
486 tlsp == &tls_out ? deliver_host_address : sender_host_address,
487 what, depth, dn, yield);
488 *calledp = TRUE;
489 if (!*optionalp)
490 {
491 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
492 return 1; /* reject (leaving peercert set) */
493 }
494 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
495 "(host in tls_try_verify_hosts)\n");
496 }
497 X509_free(tlsp->peercert);
498 tlsp->peercert = old_cert;
499 }
500 return 0;
501 }
502 #endif
503
504 /*************************************************
505 * Callback for verification *
506 *************************************************/
507
508 /* The SSL library does certificate verification if set up to do so. This
509 callback has the current yes/no state is in "state". If verification succeeded,
510 we set the certificate-verified flag. If verification failed, what happens
511 depends on whether the client is required to present a verifiable certificate
512 or not.
513
514 If verification is optional, we change the state to yes, but still log the
515 verification error. For some reason (it really would help to have proper
516 documentation of OpenSSL), this callback function then gets called again, this
517 time with state = 1. We must take care not to set the private verified flag on
518 the second time through.
519
520 Note: this function is not called if the client fails to present a certificate
521 when asked. We get here only if a certificate has been received. Handling of
522 optional verification for this case is done when requesting SSL to verify, by
523 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
524
525 May be called multiple times for different issues with a certificate, even
526 for a given "depth" in the certificate chain.
527
528 Arguments:
529 preverify_ok current yes/no state as 1/0
530 x509ctx certificate information.
531 tlsp per-direction (client vs. server) support data
532 calledp has-been-called flag
533 optionalp verification-is-optional flag
534
535 Returns: 0 if verification should fail, otherwise 1
536 */
537
538 static int
539 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
540 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
541 {
542 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
543 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
544 uschar dn[256];
545
546 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
547 {
548 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
549 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
550 tlsp == &tls_out ? deliver_host_address : sender_host_address);
551 return 0;
552 }
553 dn[sizeof(dn)-1] = '\0';
554
555 if (preverify_ok == 0)
556 {
557 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
558 *verify_mode, sender_host_address)
559 : US"";
560 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
561 tlsp == &tls_out ? deliver_host_address : sender_host_address,
562 extra, depth,
563 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
564 *calledp = TRUE;
565 if (!*optionalp)
566 {
567 if (!tlsp->peercert)
568 tlsp->peercert = X509_dup(cert); /* record failing cert */
569 return 0; /* reject */
570 }
571 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
572 "tls_try_verify_hosts)\n");
573 }
574
575 else if (depth != 0)
576 {
577 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
578 #ifndef DISABLE_OCSP
579 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
580 { /* client, wanting stapling */
581 /* Add the server cert's signing chain as the one
582 for the verification of the OCSP stapled information. */
583
584 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
585 cert))
586 ERR_clear_error();
587 sk_X509_push(client_static_cbinfo->verify_stack, cert);
588 }
589 #endif
590 #ifndef DISABLE_EVENT
591 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
592 return 0; /* reject, with peercert set */
593 #endif
594 }
595 else
596 {
597 const uschar * verify_cert_hostnames;
598
599 if ( tlsp == &tls_out
600 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
601 /* client, wanting hostname check */
602 {
603
604 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
605 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
606 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
607 # endif
608 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
609 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
610 # endif
611 int sep = 0;
612 const uschar * list = verify_cert_hostnames;
613 uschar * name;
614 int rc;
615 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
616 if ((rc = X509_check_host(cert, CCS name, 0,
617 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
618 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
619 NULL)))
620 {
621 if (rc < 0)
622 {
623 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
624 tlsp == &tls_out ? deliver_host_address : sender_host_address);
625 name = NULL;
626 }
627 break;
628 }
629 if (!name)
630 #else
631 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
632 #endif
633 {
634 uschar * extra = verify_mode
635 ? string_sprintf(" (during %c-verify for [%s])",
636 *verify_mode, sender_host_address)
637 : US"";
638 log_write(0, LOG_MAIN,
639 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
640 tlsp == &tls_out ? deliver_host_address : sender_host_address,
641 extra, dn, verify_cert_hostnames);
642 *calledp = TRUE;
643 if (!*optionalp)
644 {
645 if (!tlsp->peercert)
646 tlsp->peercert = X509_dup(cert); /* record failing cert */
647 return 0; /* reject */
648 }
649 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
650 "tls_try_verify_hosts)\n");
651 }
652 }
653
654 #ifndef DISABLE_EVENT
655 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
656 return 0; /* reject, with peercert set */
657 #endif
658
659 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
660 *calledp ? "" : " authenticated", dn);
661 if (!*calledp) tlsp->certificate_verified = TRUE;
662 *calledp = TRUE;
663 }
664
665 return 1; /* accept, at least for this level */
666 }
667
668 static int
669 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
670 {
671 return verify_callback(preverify_ok, x509ctx, &tls_out,
672 &client_verify_callback_called, &client_verify_optional);
673 }
674
675 static int
676 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
677 {
678 return verify_callback(preverify_ok, x509ctx, &tls_in,
679 &server_verify_callback_called, &server_verify_optional);
680 }
681
682
683 #ifdef SUPPORT_DANE
684
685 /* This gets called *by* the dane library verify callback, which interposes
686 itself.
687 */
688 static int
689 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
690 {
691 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
692 uschar dn[256];
693 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
694 #ifndef DISABLE_EVENT
695 BOOL dummy_called, optional = FALSE;
696 #endif
697
698 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
699 {
700 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
701 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
702 deliver_host_address);
703 return 0;
704 }
705 dn[sizeof(dn)-1] = '\0';
706
707 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
708 preverify_ok ? "ok":"BAD", depth, dn);
709
710 #ifndef DISABLE_EVENT
711 if (verify_event(&tls_out, cert, depth, dn,
712 &dummy_called, &optional, US"DANE"))
713 return 0; /* reject, with peercert set */
714 #endif
715
716 if (preverify_ok == 1)
717 {
718 tls_out.dane_verified = tls_out.certificate_verified = TRUE;
719 #ifndef DISABLE_OCSP
720 if (client_static_cbinfo->u_ocsp.client.verify_store)
721 { /* client, wanting stapling */
722 /* Add the server cert's signing chain as the one
723 for the verification of the OCSP stapled information. */
724
725 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
726 cert))
727 ERR_clear_error();
728 sk_X509_push(client_static_cbinfo->verify_stack, cert);
729 }
730 #endif
731 }
732 else
733 {
734 int err = X509_STORE_CTX_get_error(x509ctx);
735 DEBUG(D_tls)
736 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
737 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
738 preverify_ok = 1;
739 }
740 return preverify_ok;
741 }
742
743 #endif /*SUPPORT_DANE*/
744
745
746 /*************************************************
747 * Information callback *
748 *************************************************/
749
750 /* The SSL library functions call this from time to time to indicate what they
751 are doing. We copy the string to the debugging output when TLS debugging has
752 been requested.
753
754 Arguments:
755 s the SSL connection
756 where
757 ret
758
759 Returns: nothing
760 */
761
762 static void
763 info_callback(SSL *s, int where, int ret)
764 {
765 DEBUG(D_tls)
766 {
767 const uschar * str;
768
769 if (where & SSL_ST_CONNECT)
770 str = US"SSL_connect";
771 else if (where & SSL_ST_ACCEPT)
772 str = US"SSL_accept";
773 else
774 str = US"SSL info (undefined)";
775
776 if (where & SSL_CB_LOOP)
777 debug_printf("%s: %s\n", str, SSL_state_string_long(s));
778 else if (where & SSL_CB_ALERT)
779 debug_printf("SSL3 alert %s:%s:%s\n",
780 str = where & SSL_CB_READ ? US"read" : US"write",
781 SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
782 else if (where & SSL_CB_EXIT)
783 if (ret == 0)
784 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
785 else if (ret < 0)
786 debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
787 else if (where & SSL_CB_HANDSHAKE_START)
788 debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
789 else if (where & SSL_CB_HANDSHAKE_DONE)
790 debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
791 }
792 }
793
794 #ifdef OPENSSL_HAVE_KEYLOG_CB
795 static void
796 keylog_callback(const SSL *ssl, const char *line)
797 {
798 DEBUG(D_tls) debug_printf("%.200s\n", line);
799 }
800 #endif
801
802
803
804 /*************************************************
805 * Initialize for DH *
806 *************************************************/
807
808 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
809
810 Arguments:
811 sctx The current SSL CTX (inbound or outbound)
812 dhparam DH parameter file or fixed parameter identity string
813 host connected host, if client; NULL if server
814 errstr error string pointer
815
816 Returns: TRUE if OK (nothing to set up, or setup worked)
817 */
818
819 static BOOL
820 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
821 {
822 BIO *bio;
823 DH *dh;
824 uschar *dhexpanded;
825 const char *pem;
826 int dh_bitsize;
827
828 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
829 return FALSE;
830
831 if (!dhexpanded || !*dhexpanded)
832 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
833 else if (dhexpanded[0] == '/')
834 {
835 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
836 {
837 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
838 host, US strerror(errno), errstr);
839 return FALSE;
840 }
841 }
842 else
843 {
844 if (Ustrcmp(dhexpanded, "none") == 0)
845 {
846 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
847 return TRUE;
848 }
849
850 if (!(pem = std_dh_prime_named(dhexpanded)))
851 {
852 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
853 host, US strerror(errno), errstr);
854 return FALSE;
855 }
856 bio = BIO_new_mem_buf(CS pem, -1);
857 }
858
859 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
860 {
861 BIO_free(bio);
862 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
863 host, NULL, errstr);
864 return FALSE;
865 }
866
867 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
868 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
869 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
870 * If someone wants to dance at the edge, then they can raise the limit or use
871 * current libraries. */
872 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
873 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
874 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
875 dh_bitsize = DH_bits(dh);
876 #else
877 dh_bitsize = 8 * DH_size(dh);
878 #endif
879
880 /* Even if it is larger, we silently return success rather than cause things
881 * to fail out, so that a too-large DH will not knock out all TLS; it's a
882 * debatable choice. */
883 if (dh_bitsize > tls_dh_max_bits)
884 {
885 DEBUG(D_tls)
886 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
887 dh_bitsize, tls_dh_max_bits);
888 }
889 else
890 {
891 SSL_CTX_set_tmp_dh(sctx, dh);
892 DEBUG(D_tls)
893 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
894 dhexpanded ? dhexpanded : US"default", dh_bitsize);
895 }
896
897 DH_free(dh);
898 BIO_free(bio);
899
900 return TRUE;
901 }
902
903
904
905
906 /*************************************************
907 * Initialize for ECDH *
908 *************************************************/
909
910 /* Load parameters for ECDH encryption.
911
912 For now, we stick to NIST P-256 because: it's simple and easy to configure;
913 it avoids any patent issues that might bite redistributors; despite events in
914 the news and concerns over curve choices, we're not cryptographers, we're not
915 pretending to be, and this is "good enough" to be better than no support,
916 protecting against most adversaries. Given another year or two, there might
917 be sufficient clarity about a "right" way forward to let us make an informed
918 decision, instead of a knee-jerk reaction.
919
920 Longer-term, we should look at supporting both various named curves and
921 external files generated with "openssl ecparam", much as we do for init_dh().
922 We should also support "none" as a value, to explicitly avoid initialisation.
923
924 Patches welcome.
925
926 Arguments:
927 sctx The current SSL CTX (inbound or outbound)
928 host connected host, if client; NULL if server
929 errstr error string pointer
930
931 Returns: TRUE if OK (nothing to set up, or setup worked)
932 */
933
934 static BOOL
935 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
936 {
937 #ifdef OPENSSL_NO_ECDH
938 return TRUE;
939 #else
940
941 EC_KEY * ecdh;
942 uschar * exp_curve;
943 int nid;
944 BOOL rv;
945
946 if (host) /* No ECDH setup for clients, only for servers */
947 return TRUE;
948
949 # ifndef EXIM_HAVE_ECDH
950 DEBUG(D_tls)
951 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
952 return TRUE;
953 # else
954
955 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
956 return FALSE;
957 if (!exp_curve || !*exp_curve)
958 return TRUE;
959
960 /* "auto" needs to be handled carefully.
961 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
962 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
963 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
964 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
965 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
966 */
967 if (Ustrcmp(exp_curve, "auto") == 0)
968 {
969 #if OPENSSL_VERSION_NUMBER < 0x10002000L
970 DEBUG(D_tls) debug_printf(
971 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
972 exp_curve = US"prime256v1";
973 #else
974 # if defined SSL_CTRL_SET_ECDH_AUTO
975 DEBUG(D_tls) debug_printf(
976 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
977 SSL_CTX_set_ecdh_auto(sctx, 1);
978 return TRUE;
979 # else
980 DEBUG(D_tls) debug_printf(
981 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
982 return TRUE;
983 # endif
984 #endif
985 }
986
987 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
988 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
989 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
990 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
991 # endif
992 )
993 {
994 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
995 host, NULL, errstr);
996 return FALSE;
997 }
998
999 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
1000 {
1001 tls_error(US"Unable to create ec curve", host, NULL, errstr);
1002 return FALSE;
1003 }
1004
1005 /* The "tmp" in the name here refers to setting a temporary key
1006 not to the stability of the interface. */
1007
1008 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
1009 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
1010 else
1011 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1012
1013 EC_KEY_free(ecdh);
1014 return !rv;
1015
1016 # endif /*EXIM_HAVE_ECDH*/
1017 #endif /*OPENSSL_NO_ECDH*/
1018 }
1019
1020
1021
1022
1023 #ifndef DISABLE_OCSP
1024 /*************************************************
1025 * Load OCSP information into state *
1026 *************************************************/
1027 /* Called to load the server OCSP response from the given file into memory, once
1028 caller has determined this is needed. Checks validity. Debugs a message
1029 if invalid.
1030
1031 ASSUMES: single response, for single cert.
1032
1033 Arguments:
1034 sctx the SSL_CTX* to update
1035 cbinfo various parts of session state
1036 expanded the filename putatively holding an OCSP response
1037
1038 */
1039
1040 static void
1041 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
1042 {
1043 BIO * bio;
1044 OCSP_RESPONSE * resp;
1045 OCSP_BASICRESP * basic_response;
1046 OCSP_SINGLERESP * single_response;
1047 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1048 STACK_OF(X509) * sk;
1049 unsigned long verify_flags;
1050 int status, reason, i;
1051
1052 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
1053 if (cbinfo->u_ocsp.server.response)
1054 {
1055 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
1056 cbinfo->u_ocsp.server.response = NULL;
1057 }
1058
1059 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
1060 {
1061 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1062 cbinfo->u_ocsp.server.file_expanded);
1063 return;
1064 }
1065
1066 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1067 BIO_free(bio);
1068 if (!resp)
1069 {
1070 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1071 return;
1072 }
1073
1074 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1075 {
1076 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1077 OCSP_response_status_str(status), status);
1078 goto bad;
1079 }
1080
1081 if (!(basic_response = OCSP_response_get1_basic(resp)))
1082 {
1083 DEBUG(D_tls)
1084 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1085 goto bad;
1086 }
1087
1088 sk = cbinfo->verify_stack;
1089 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1090
1091 /* May need to expose ability to adjust those flags?
1092 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1093 OCSP_TRUSTOTHER OCSP_NOINTERN */
1094
1095 /* This does a full verify on the OCSP proof before we load it for serving
1096 up; possibly overkill - just date-checks might be nice enough.
1097
1098 OCSP_basic_verify takes a "store" arg, but does not
1099 use it for the chain verification, which is all we do
1100 when OCSP_NOVERIFY is set. The content from the wire
1101 "basic_response" and a cert-stack "sk" are all that is used.
1102
1103 We have a stack, loaded in setup_certs() if tls_verify_certificates
1104 was a file (not a directory, or "system"). It is unfortunate we
1105 cannot used the connection context store, as that would neatly
1106 handle the "system" case too, but there seems to be no library
1107 function for getting a stack from a store.
1108 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
1109 We do not free the stack since it could be needed a second time for
1110 SNI handling.
1111
1112 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1113 be a public interface into the OpenSSL library (there's no manual entry) -
1114 But what with? We also use OCSP_basic_verify in the client stapling callback.
1115 And there we NEED it; we must verify that status... unless the
1116 library does it for us anyway? */
1117
1118 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1119 {
1120 DEBUG(D_tls)
1121 {
1122 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1123 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1124 }
1125 goto bad;
1126 }
1127
1128 /* Here's the simplifying assumption: there's only one response, for the
1129 one certificate we use, and nothing for anything else in a chain. If this
1130 proves false, we need to extract a cert id from our issued cert
1131 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1132 right cert in the stack and then calls OCSP_single_get0_status()).
1133
1134 I'm hoping to avoid reworking a bunch more of how we handle state here. */
1135
1136 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1137 {
1138 DEBUG(D_tls)
1139 debug_printf("Unable to get first response from OCSP basic response.\n");
1140 goto bad;
1141 }
1142
1143 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1144 if (status != V_OCSP_CERTSTATUS_GOOD)
1145 {
1146 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1147 OCSP_cert_status_str(status), status,
1148 OCSP_crl_reason_str(reason), reason);
1149 goto bad;
1150 }
1151
1152 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1153 {
1154 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1155 goto bad;
1156 }
1157
1158 supply_response:
1159 cbinfo->u_ocsp.server.response = resp; /*XXX stack?*/
1160 return;
1161
1162 bad:
1163 if (f.running_in_test_harness)
1164 {
1165 extern char ** environ;
1166 if (environ) for (uschar ** p = USS environ; *p; p++)
1167 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1168 {
1169 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1170 goto supply_response;
1171 }
1172 }
1173 return;
1174 }
1175 #endif /*!DISABLE_OCSP*/
1176
1177
1178
1179
1180 /* Create and install a selfsigned certificate, for use in server mode */
1181
1182 static int
1183 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1184 {
1185 X509 * x509 = NULL;
1186 EVP_PKEY * pkey;
1187 RSA * rsa;
1188 X509_NAME * name;
1189 uschar * where;
1190
1191 where = US"allocating pkey";
1192 if (!(pkey = EVP_PKEY_new()))
1193 goto err;
1194
1195 where = US"allocating cert";
1196 if (!(x509 = X509_new()))
1197 goto err;
1198
1199 where = US"generating pkey";
1200 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1201 goto err;
1202
1203 where = US"assigning pkey";
1204 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1205 goto err;
1206
1207 X509_set_version(x509, 2); /* N+1 - version 3 */
1208 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1209 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1210 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
1211 X509_set_pubkey(x509, pkey);
1212
1213 name = X509_get_subject_name(x509);
1214 X509_NAME_add_entry_by_txt(name, "C",
1215 MBSTRING_ASC, CUS "UK", -1, -1, 0);
1216 X509_NAME_add_entry_by_txt(name, "O",
1217 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1218 X509_NAME_add_entry_by_txt(name, "CN",
1219 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1220 X509_set_issuer_name(x509, name);
1221
1222 where = US"signing cert";
1223 if (!X509_sign(x509, pkey, EVP_md5()))
1224 goto err;
1225
1226 where = US"installing selfsign cert";
1227 if (!SSL_CTX_use_certificate(sctx, x509))
1228 goto err;
1229
1230 where = US"installing selfsign key";
1231 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1232 goto err;
1233
1234 return OK;
1235
1236 err:
1237 (void) tls_error(where, NULL, NULL, errstr);
1238 if (x509) X509_free(x509);
1239 if (pkey) EVP_PKEY_free(pkey);
1240 return DEFER;
1241 }
1242
1243
1244
1245
1246 static int
1247 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1248 uschar ** errstr)
1249 {
1250 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1251 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1252 return tls_error(string_sprintf(
1253 "SSL_CTX_use_certificate_chain_file file=%s", file),
1254 cbinfo->host, NULL, errstr);
1255 return 0;
1256 }
1257
1258 static int
1259 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1260 uschar ** errstr)
1261 {
1262 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1263 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1264 return tls_error(string_sprintf(
1265 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1266 return 0;
1267 }
1268
1269
1270 /*************************************************
1271 * Expand key and cert file specs *
1272 *************************************************/
1273
1274 /* Called once during tls_init and possibly again during TLS setup, for a
1275 new context, if Server Name Indication was used and tls_sni was seen in
1276 the certificate string.
1277
1278 Arguments:
1279 sctx the SSL_CTX* to update
1280 cbinfo various parts of session state
1281 errstr error string pointer
1282
1283 Returns: OK/DEFER/FAIL
1284 */
1285
1286 static int
1287 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1288 uschar ** errstr)
1289 {
1290 uschar *expanded;
1291
1292 if (!cbinfo->certificate)
1293 {
1294 if (!cbinfo->is_server) /* client */
1295 return OK;
1296 /* server */
1297 if (tls_install_selfsign(sctx, errstr) != OK)
1298 return DEFER;
1299 }
1300 else
1301 {
1302 int err;
1303
1304 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1305 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1306 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1307 )
1308 reexpand_tls_files_for_sni = TRUE;
1309
1310 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1311 return DEFER;
1312
1313 if (expanded)
1314 if (cbinfo->is_server)
1315 {
1316 const uschar * file_list = expanded;
1317 int sep = 0;
1318 uschar * file;
1319
1320 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1321 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1322 return err;
1323 }
1324 else /* would there ever be a need for multiple client certs? */
1325 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1326 return err;
1327
1328 if ( cbinfo->privatekey
1329 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1330 return DEFER;
1331
1332 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1333 of the expansion is an empty string, ignore it also, and assume the private
1334 key is in the same file as the certificate. */
1335
1336 if (expanded && *expanded)
1337 if (cbinfo->is_server)
1338 {
1339 const uschar * file_list = expanded;
1340 int sep = 0;
1341 uschar * file;
1342
1343 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1344 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1345 return err;
1346 }
1347 else /* would there ever be a need for multiple client certs? */
1348 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1349 return err;
1350 }
1351
1352 #ifndef DISABLE_OCSP
1353 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1354 {
1355 /*XXX stack*/
1356 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1357 return DEFER;
1358
1359 if (expanded && *expanded)
1360 {
1361 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1362 if ( cbinfo->u_ocsp.server.file_expanded
1363 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1364 {
1365 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1366 }
1367 else
1368 ocsp_load_response(sctx, cbinfo, expanded);
1369 }
1370 }
1371 #endif
1372
1373 return OK;
1374 }
1375
1376
1377
1378
1379 /*************************************************
1380 * Callback to handle SNI *
1381 *************************************************/
1382
1383 /* Called when acting as server during the TLS session setup if a Server Name
1384 Indication extension was sent by the client.
1385
1386 API documentation is OpenSSL s_server.c implementation.
1387
1388 Arguments:
1389 s SSL* of the current session
1390 ad unknown (part of OpenSSL API) (unused)
1391 arg Callback of "our" registered data
1392
1393 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1394 */
1395
1396 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1397 static int
1398 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1399 {
1400 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1401 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1402 int rc;
1403 int old_pool = store_pool;
1404 uschar * dummy_errstr;
1405
1406 if (!servername)
1407 return SSL_TLSEXT_ERR_OK;
1408
1409 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1410 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1411
1412 /* Make the extension value available for expansion */
1413 store_pool = POOL_PERM;
1414 tls_in.sni = string_copy(US servername);
1415 store_pool = old_pool;
1416
1417 if (!reexpand_tls_files_for_sni)
1418 return SSL_TLSEXT_ERR_OK;
1419
1420 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1421 not confident that memcpy wouldn't break some internal reference counting.
1422 Especially since there's a references struct member, which would be off. */
1423
1424 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1425 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1426 #else
1427 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1428 #endif
1429 {
1430 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1431 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1432 goto bad;
1433 }
1434
1435 /* Not sure how many of these are actually needed, since SSL object
1436 already exists. Might even need this selfsame callback, for reneg? */
1437
1438 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1439 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1440 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1441 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1442 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1443 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1444
1445 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1446 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1447 )
1448 goto bad;
1449
1450 if ( cbinfo->server_cipher_list
1451 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1452 goto bad;
1453
1454 #ifndef DISABLE_OCSP
1455 if (cbinfo->u_ocsp.server.file)
1456 {
1457 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1458 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1459 }
1460 #endif
1461
1462 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1463 verify_callback_server, &dummy_errstr)) != OK)
1464 goto bad;
1465
1466 /* do this after setup_certs, because this can require the certs for verifying
1467 OCSP information. */
1468 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1469 goto bad;
1470
1471 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1472 SSL_set_SSL_CTX(s, server_sni);
1473 return SSL_TLSEXT_ERR_OK;
1474
1475 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1476 }
1477 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1478
1479
1480
1481
1482 #ifndef DISABLE_OCSP
1483
1484 /*************************************************
1485 * Callback to handle OCSP Stapling *
1486 *************************************************/
1487
1488 /* Called when acting as server during the TLS session setup if the client
1489 requests OCSP information with a Certificate Status Request.
1490
1491 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1492 project.
1493
1494 */
1495
1496 static int
1497 tls_server_stapling_cb(SSL *s, void *arg)
1498 {
1499 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1500 uschar *response_der; /*XXX blob */
1501 int response_der_len;
1502
1503 /*XXX stack: use SSL_get_certificate() to see which cert; from that work
1504 out which ocsp blob to send. Unfortunately, SSL_get_certificate is known
1505 buggy in current OpenSSL; it returns the last cert loaded always rather than
1506 the one actually presented. So we can't support a stack of OCSP proofs at
1507 this time. */
1508
1509 DEBUG(D_tls)
1510 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1511 cbinfo->u_ocsp.server.response ? "have" : "lack");
1512
1513 tls_in.ocsp = OCSP_NOT_RESP;
1514 if (!cbinfo->u_ocsp.server.response)
1515 return SSL_TLSEXT_ERR_NOACK;
1516
1517 response_der = NULL;
1518 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response, /*XXX stack*/
1519 &response_der);
1520 if (response_der_len <= 0)
1521 return SSL_TLSEXT_ERR_NOACK;
1522
1523 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1524 tls_in.ocsp = OCSP_VFIED;
1525 return SSL_TLSEXT_ERR_OK;
1526 }
1527
1528
1529 static void
1530 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1531 {
1532 BIO_printf(bp, "\t%s: ", str);
1533 ASN1_GENERALIZEDTIME_print(bp, time);
1534 BIO_puts(bp, "\n");
1535 }
1536
1537 static int
1538 tls_client_stapling_cb(SSL *s, void *arg)
1539 {
1540 tls_ext_ctx_cb * cbinfo = arg;
1541 const unsigned char * p;
1542 int len;
1543 OCSP_RESPONSE * rsp;
1544 OCSP_BASICRESP * bs;
1545 int i;
1546
1547 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1548 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1549 if(!p)
1550 {
1551 /* Expect this when we requested ocsp but got none */
1552 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1553 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1554 else
1555 DEBUG(D_tls) debug_printf(" null\n");
1556 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1557 }
1558
1559 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1560 {
1561 tls_out.ocsp = OCSP_FAILED;
1562 if (LOGGING(tls_cipher))
1563 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1564 else
1565 DEBUG(D_tls) debug_printf(" parse error\n");
1566 return 0;
1567 }
1568
1569 if(!(bs = OCSP_response_get1_basic(rsp)))
1570 {
1571 tls_out.ocsp = OCSP_FAILED;
1572 if (LOGGING(tls_cipher))
1573 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1574 else
1575 DEBUG(D_tls) debug_printf(" error parsing response\n");
1576 OCSP_RESPONSE_free(rsp);
1577 return 0;
1578 }
1579
1580 /* We'd check the nonce here if we'd put one in the request. */
1581 /* However that would defeat cacheability on the server so we don't. */
1582
1583 /* This section of code reworked from OpenSSL apps source;
1584 The OpenSSL Project retains copyright:
1585 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1586 */
1587 {
1588 BIO * bp = NULL;
1589 int status, reason;
1590 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1591
1592 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1593
1594 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1595
1596 /* Use the chain that verified the server cert to verify the stapled info */
1597 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1598
1599 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1600 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1601 {
1602 tls_out.ocsp = OCSP_FAILED;
1603 if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1604 "Received TLS cert status response, itself unverifiable: %s",
1605 ERR_reason_error_string(ERR_peek_error()));
1606 BIO_printf(bp, "OCSP response verify failure\n");
1607 ERR_print_errors(bp);
1608 OCSP_RESPONSE_print(bp, rsp, 0);
1609 goto failed;
1610 }
1611
1612 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1613
1614 /*XXX So we have a good stapled OCSP status. How do we know
1615 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1616 OCSP_resp_find_status() which matches on a cert id, which presumably
1617 we should use. Making an id needs OCSP_cert_id_new(), which takes
1618 issuerName, issuerKey, serialNumber. Are they all in the cert?
1619
1620 For now, carry on blindly accepting the resp. */
1621
1622 {
1623 OCSP_SINGLERESP * single;
1624
1625 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1626 if (OCSP_resp_count(bs) != 1)
1627 #else
1628 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1629 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1630 #endif
1631 {
1632 tls_out.ocsp = OCSP_FAILED;
1633 log_write(0, LOG_MAIN, "OCSP stapling "
1634 "with multiple responses not handled");
1635 goto failed;
1636 }
1637 single = OCSP_resp_get0(bs, 0);
1638 status = OCSP_single_get0_status(single, &reason, &rev,
1639 &thisupd, &nextupd);
1640 }
1641
1642 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1643 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1644 if (!OCSP_check_validity(thisupd, nextupd,
1645 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1646 {
1647 tls_out.ocsp = OCSP_FAILED;
1648 DEBUG(D_tls) ERR_print_errors(bp);
1649 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1650 }
1651 else
1652 {
1653 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1654 OCSP_cert_status_str(status));
1655 switch(status)
1656 {
1657 case V_OCSP_CERTSTATUS_GOOD:
1658 tls_out.ocsp = OCSP_VFIED;
1659 i = 1;
1660 goto good;
1661 case V_OCSP_CERTSTATUS_REVOKED:
1662 tls_out.ocsp = OCSP_FAILED;
1663 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1664 reason != -1 ? "; reason: " : "",
1665 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1666 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1667 break;
1668 default:
1669 tls_out.ocsp = OCSP_FAILED;
1670 log_write(0, LOG_MAIN,
1671 "Server certificate status unknown, in OCSP stapling");
1672 break;
1673 }
1674 }
1675 failed:
1676 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1677 good:
1678 BIO_free(bp);
1679 }
1680
1681 OCSP_RESPONSE_free(rsp);
1682 return i;
1683 }
1684 #endif /*!DISABLE_OCSP*/
1685
1686
1687 /*************************************************
1688 * Initialize for TLS *
1689 *************************************************/
1690
1691 /* Called from both server and client code, to do preliminary initialization
1692 of the library. We allocate and return a context structure.
1693
1694 Arguments:
1695 ctxp returned SSL context
1696 host connected host, if client; NULL if server
1697 dhparam DH parameter file
1698 certificate certificate file
1699 privatekey private key
1700 ocsp_file file of stapling info (server); flag for require ocsp (client)
1701 addr address if client; NULL if server (for some randomness)
1702 cbp place to put allocated callback context
1703 errstr error string pointer
1704
1705 Returns: OK/DEFER/FAIL
1706 */
1707
1708 static int
1709 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1710 uschar *privatekey,
1711 #ifndef DISABLE_OCSP
1712 uschar *ocsp_file, /*XXX stack, in server*/
1713 #endif
1714 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1715 {
1716 SSL_CTX * ctx;
1717 long init_options;
1718 int rc;
1719 tls_ext_ctx_cb * cbinfo;
1720
1721 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1722 cbinfo->certificate = certificate;
1723 cbinfo->privatekey = privatekey;
1724 cbinfo->is_server = host==NULL;
1725 #ifndef DISABLE_OCSP
1726 cbinfo->verify_stack = NULL;
1727 if (!host)
1728 {
1729 cbinfo->u_ocsp.server.file = ocsp_file;
1730 cbinfo->u_ocsp.server.file_expanded = NULL;
1731 cbinfo->u_ocsp.server.response = NULL;
1732 }
1733 else
1734 cbinfo->u_ocsp.client.verify_store = NULL;
1735 #endif
1736 cbinfo->dhparam = dhparam;
1737 cbinfo->server_cipher_list = NULL;
1738 cbinfo->host = host;
1739 #ifndef DISABLE_EVENT
1740 cbinfo->event_action = NULL;
1741 #endif
1742
1743 #ifdef EXIM_NEED_OPENSSL_INIT
1744 SSL_load_error_strings(); /* basic set up */
1745 OpenSSL_add_ssl_algorithms();
1746 #endif
1747
1748 #ifdef EXIM_HAVE_SHA256
1749 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1750 list of available digests. */
1751 EVP_add_digest(EVP_sha256());
1752 #endif
1753
1754 /* Create a context.
1755 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1756 negotiation in the different methods; as far as I can tell, the only
1757 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1758 when OpenSSL is built without SSLv2 support.
1759 By disabling with openssl_options, we can let admins re-enable with the
1760 existing knob. */
1761
1762 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1763 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
1764 #else
1765 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1766 #endif
1767 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1768
1769 /* It turns out that we need to seed the random number generator this early in
1770 order to get the full complement of ciphers to work. It took me roughly a day
1771 of work to discover this by experiment.
1772
1773 On systems that have /dev/urandom, SSL may automatically seed itself from
1774 there. Otherwise, we have to make something up as best we can. Double check
1775 afterwards. */
1776
1777 if (!RAND_status())
1778 {
1779 randstuff r;
1780 gettimeofday(&r.tv, NULL);
1781 r.p = getpid();
1782
1783 RAND_seed(US (&r), sizeof(r));
1784 RAND_seed(US big_buffer, big_buffer_size);
1785 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1786
1787 if (!RAND_status())
1788 return tls_error(US"RAND_status", host,
1789 US"unable to seed random number generator", errstr);
1790 }
1791
1792 /* Set up the information callback, which outputs if debugging is at a suitable
1793 level. */
1794
1795 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1796 #ifdef OPENSSL_HAVE_KEYLOG_CB
1797 DEBUG(D_tls) SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
1798 #endif
1799
1800 /* Automatically re-try reads/writes after renegotiation. */
1801 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1802
1803 /* Apply administrator-supplied work-arounds.
1804 Historically we applied just one requested option,
1805 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1806 moved to an administrator-controlled list of options to specify and
1807 grandfathered in the first one as the default value for "openssl_options".
1808
1809 No OpenSSL version number checks: the options we accept depend upon the
1810 availability of the option value macros from OpenSSL. */
1811
1812 if (!tls_openssl_options_parse(openssl_options, &init_options))
1813 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1814
1815 if (init_options)
1816 {
1817 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1818 if (!(SSL_CTX_set_options(ctx, init_options)))
1819 return tls_error(string_sprintf(
1820 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1821 }
1822 else
1823 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1824
1825 #ifdef OPENSSL_HAVE_NUM_TICKETS
1826 SSL_CTX_set_num_tickets(ctx, 0); /* send no TLS1.3 stateful-tickets */
1827 #endif
1828
1829 /* We'd like to disable session cache unconditionally, but foolish Outlook
1830 Express clients then give up the first TLS connection and make a second one
1831 (which works). Only when there is an IMAP service on the same machine.
1832 Presumably OE is trying to use the cache for A on B. Leave it enabled for
1833 now, until we work out a decent way of presenting control to the config. It
1834 will never be used because we use a new context every time. */
1835 #ifdef notdef
1836 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1837 #endif
1838
1839 /* Initialize with DH parameters if supplied */
1840 /* Initialize ECDH temp key parameter selection */
1841
1842 if ( !init_dh(ctx, dhparam, host, errstr)
1843 || !init_ecdh(ctx, host, errstr)
1844 )
1845 return DEFER;
1846
1847 /* Set up certificate and key (and perhaps OCSP info) */
1848
1849 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1850 return rc;
1851
1852 /* If we need to handle SNI or OCSP, do so */
1853
1854 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1855 # ifndef DISABLE_OCSP
1856 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1857 {
1858 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1859 return FAIL;
1860 }
1861 # endif
1862
1863 if (!host) /* server */
1864 {
1865 # ifndef DISABLE_OCSP
1866 /* We check u_ocsp.server.file, not server.response, because we care about if
1867 the option exists, not what the current expansion might be, as SNI might
1868 change the certificate and OCSP file in use between now and the time the
1869 callback is invoked. */
1870 if (cbinfo->u_ocsp.server.file)
1871 {
1872 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1873 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1874 }
1875 # endif
1876 /* We always do this, so that $tls_sni is available even if not used in
1877 tls_certificate */
1878 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1879 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1880 }
1881 # ifndef DISABLE_OCSP
1882 else /* client */
1883 if(ocsp_file) /* wanting stapling */
1884 {
1885 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1886 {
1887 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1888 return FAIL;
1889 }
1890 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1891 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1892 }
1893 # endif
1894 #endif
1895
1896 cbinfo->verify_cert_hostnames = NULL;
1897
1898 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1899 /* Set up the RSA callback */
1900 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1901 #endif
1902
1903 /* Finally, set the timeout, and we are done */
1904
1905 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1906 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1907
1908 *cbp = cbinfo;
1909 *ctxp = ctx;
1910
1911 return OK;
1912 }
1913
1914
1915
1916
1917 /*************************************************
1918 * Get name of cipher in use *
1919 *************************************************/
1920
1921 /*
1922 Argument: pointer to an SSL structure for the connection
1923 pointer to number of bits for cipher
1924 Returns: pointer to allocated string in perm-pool
1925 */
1926
1927 static uschar *
1928 construct_cipher_name(SSL * ssl, int * bits)
1929 {
1930 int pool = store_pool;
1931 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
1932 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1933 the accessor functions use const in the prototype. */
1934
1935 const uschar * ver = CUS SSL_get_version(ssl);
1936 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1937 uschar * s;
1938
1939 SSL_CIPHER_get_bits(c, bits);
1940
1941 store_pool = POOL_PERM;
1942 s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits);
1943 store_pool = pool;
1944 DEBUG(D_tls) debug_printf("Cipher: %s\n", s);
1945 return s;
1946 }
1947
1948
1949 /* Get IETF-standard name for ciphersuite.
1950 Argument: pointer to an SSL structure for the connection
1951 Returns: pointer to string
1952 */
1953
1954 static const uschar *
1955 cipher_stdname_ssl(SSL * ssl)
1956 {
1957 #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
1958 return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl));
1959 #else
1960 ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl));
1961 return cipher_stdname(id >> 8, id & 0xff);
1962 #endif
1963 }
1964
1965
1966 static void
1967 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
1968 {
1969 /*XXX we might consider a list-of-certs variable for the cert chain.
1970 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1971 in list-handling functions, also consider the difference between the entire
1972 chain and the elements sent by the peer. */
1973
1974 tlsp->peerdn = NULL;
1975
1976 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1977 if (!tlsp->peercert)
1978 tlsp->peercert = SSL_get_peer_certificate(ssl);
1979 /* Beware anonymous ciphers which lead to server_cert being NULL */
1980 if (tlsp->peercert)
1981 if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
1982 { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
1983 else
1984 {
1985 peerdn[siz-1] = '\0';
1986 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1987 }
1988 }
1989
1990
1991
1992
1993
1994 /*************************************************
1995 * Set up for verifying certificates *
1996 *************************************************/
1997
1998 #ifndef DISABLE_OCSP
1999 /* Load certs from file, return TRUE on success */
2000
2001 static BOOL
2002 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
2003 {
2004 BIO * bp;
2005 X509 * x;
2006
2007 while (sk_X509_num(verify_stack) > 0)
2008 X509_free(sk_X509_pop(verify_stack));
2009
2010 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
2011 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
2012 sk_X509_push(verify_stack, x);
2013 BIO_free(bp);
2014 return TRUE;
2015 }
2016 #endif
2017
2018
2019
2020 /* Called by both client and server startup; on the server possibly
2021 repeated after a Server Name Indication.
2022
2023 Arguments:
2024 sctx SSL_CTX* to initialise
2025 certs certs file or NULL
2026 crl CRL file or NULL
2027 host NULL in a server; the remote host in a client
2028 optional TRUE if called from a server for a host in tls_try_verify_hosts;
2029 otherwise passed as FALSE
2030 cert_vfy_cb Callback function for certificate verification
2031 errstr error string pointer
2032
2033 Returns: OK/DEFER/FAIL
2034 */
2035
2036 static int
2037 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2038 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2039 {
2040 uschar *expcerts, *expcrl;
2041
2042 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2043 return DEFER;
2044 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2045
2046 if (expcerts && *expcerts)
2047 {
2048 /* Tell the library to use its compiled-in location for the system default
2049 CA bundle. Then add the ones specified in the config, if any. */
2050
2051 if (!SSL_CTX_set_default_verify_paths(sctx))
2052 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2053
2054 if (Ustrcmp(expcerts, "system") != 0)
2055 {
2056 struct stat statbuf;
2057
2058 if (Ustat(expcerts, &statbuf) < 0)
2059 {
2060 log_write(0, LOG_MAIN|LOG_PANIC,
2061 "failed to stat %s for certificates", expcerts);
2062 return DEFER;
2063 }
2064 else
2065 {
2066 uschar *file, *dir;
2067 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2068 { file = NULL; dir = expcerts; }
2069 else
2070 {
2071 file = expcerts; dir = NULL;
2072 #ifndef DISABLE_OCSP
2073 /* In the server if we will be offering an OCSP proof, load chain from
2074 file for verifying the OCSP proof at load time. */
2075
2076 if ( !host
2077 && statbuf.st_size > 0
2078 && server_static_cbinfo->u_ocsp.server.file
2079 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2080 )
2081 {
2082 log_write(0, LOG_MAIN|LOG_PANIC,
2083 "failed to load cert chain from %s", file);
2084 return DEFER;
2085 }
2086 #endif
2087 }
2088
2089 /* If a certificate file is empty, the next function fails with an
2090 unhelpful error message. If we skip it, we get the correct behaviour (no
2091 certificates are recognized, but the error message is still misleading (it
2092 says no certificate was supplied). But this is better. */
2093
2094 if ( (!file || statbuf.st_size > 0)
2095 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2096 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2097
2098 /* Load the list of CAs for which we will accept certs, for sending
2099 to the client. This is only for the one-file tls_verify_certificates
2100 variant.
2101 If a list isn't loaded into the server, but some verify locations are set,
2102 the server end appears to make a wildcard request for client certs.
2103 Meanwhile, the client library as default behaviour *ignores* the list
2104 we send over the wire - see man SSL_CTX_set_client_cert_cb.
2105 Because of this, and that the dir variant is likely only used for
2106 the public-CA bundle (not for a private CA), not worth fixing. */
2107
2108 if (file)
2109 {
2110 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2111
2112 SSL_CTX_set_client_CA_list(sctx, names);
2113 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2114 sk_X509_NAME_num(names));
2115 }
2116 }
2117 }
2118
2119 /* Handle a certificate revocation list. */
2120
2121 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2122
2123 /* This bit of code is now the version supplied by Lars Mainka. (I have
2124 merely reformatted it into the Exim code style.)
2125
2126 "From here I changed the code to add support for multiple crl's
2127 in pem format in one file or to support hashed directory entries in
2128 pem format instead of a file. This method now uses the library function
2129 X509_STORE_load_locations to add the CRL location to the SSL context.
2130 OpenSSL will then handle the verify against CA certs and CRLs by
2131 itself in the verify callback." */
2132
2133 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2134 if (expcrl && *expcrl)
2135 {
2136 struct stat statbufcrl;
2137 if (Ustat(expcrl, &statbufcrl) < 0)
2138 {
2139 log_write(0, LOG_MAIN|LOG_PANIC,
2140 "failed to stat %s for certificates revocation lists", expcrl);
2141 return DEFER;
2142 }
2143 else
2144 {
2145 /* is it a file or directory? */
2146 uschar *file, *dir;
2147 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2148 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2149 {
2150 file = NULL;
2151 dir = expcrl;
2152 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2153 }
2154 else
2155 {
2156 file = expcrl;
2157 dir = NULL;
2158 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2159 }
2160 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2161 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2162
2163 /* setting the flags to check against the complete crl chain */
2164
2165 X509_STORE_set_flags(cvstore,
2166 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2167 }
2168 }
2169
2170 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2171
2172 /* If verification is optional, don't fail if no certificate */
2173
2174 SSL_CTX_set_verify(sctx,
2175 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2176 cert_vfy_cb);
2177 }
2178
2179 return OK;
2180 }
2181
2182
2183
2184 /*************************************************
2185 * Start a TLS session in a server *
2186 *************************************************/
2187
2188 /* This is called when Exim is running as a server, after having received
2189 the STARTTLS command. It must respond to that command, and then negotiate
2190 a TLS session.
2191
2192 Arguments:
2193 require_ciphers allowed ciphers
2194 errstr pointer to error message
2195
2196 Returns: OK on success
2197 DEFER for errors before the start of the negotiation
2198 FAIL for errors during the negotiation; the server can't
2199 continue running.
2200 */
2201
2202 int
2203 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2204 {
2205 int rc;
2206 uschar * expciphers;
2207 tls_ext_ctx_cb * cbinfo;
2208 static uschar peerdn[256];
2209
2210 /* Check for previous activation */
2211
2212 if (tls_in.active.sock >= 0)
2213 {
2214 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2215 smtp_printf("554 Already in TLS\r\n", FALSE);
2216 return FAIL;
2217 }
2218
2219 /* Initialize the SSL library. If it fails, it will already have logged
2220 the error. */
2221
2222 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2223 #ifndef DISABLE_OCSP
2224 tls_ocsp_file, /*XXX stack*/
2225 #endif
2226 NULL, &server_static_cbinfo, errstr);
2227 if (rc != OK) return rc;
2228 cbinfo = server_static_cbinfo;
2229
2230 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2231 return FAIL;
2232
2233 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2234 were historically separated by underscores. So that I can use either form in my
2235 tests, and also for general convenience, we turn underscores into hyphens here.
2236
2237 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2238 for TLS 1.3 . Since we do not call it at present we get the default list:
2239 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2240 */
2241
2242 if (expciphers)
2243 {
2244 uschar * s = expciphers;
2245 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2246 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2247 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2248 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2249 cbinfo->server_cipher_list = expciphers;
2250 }
2251
2252 /* If this is a host for which certificate verification is mandatory or
2253 optional, set up appropriately. */
2254
2255 tls_in.certificate_verified = FALSE;
2256 #ifdef SUPPORT_DANE
2257 tls_in.dane_verified = FALSE;
2258 #endif
2259 server_verify_callback_called = FALSE;
2260
2261 if (verify_check_host(&tls_verify_hosts) == OK)
2262 {
2263 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2264 FALSE, verify_callback_server, errstr);
2265 if (rc != OK) return rc;
2266 server_verify_optional = FALSE;
2267 }
2268 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2269 {
2270 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2271 TRUE, verify_callback_server, errstr);
2272 if (rc != OK) return rc;
2273 server_verify_optional = TRUE;
2274 }
2275
2276 /* Prepare for new connection */
2277
2278 if (!(server_ssl = SSL_new(server_ctx)))
2279 return tls_error(US"SSL_new", NULL, NULL, errstr);
2280
2281 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2282 *
2283 * With the SSL_clear(), we get strange interoperability bugs with
2284 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2285 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2286 *
2287 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2288 * session shutdown. In this case, we have a brand new object and there's no
2289 * obvious reason to immediately clear it. I'm guessing that this was
2290 * originally added because of incomplete initialisation which the clear fixed,
2291 * in some historic release.
2292 */
2293
2294 /* Set context and tell client to go ahead, except in the case of TLS startup
2295 on connection, where outputting anything now upsets the clients and tends to
2296 make them disconnect. We need to have an explicit fflush() here, to force out
2297 the response. Other smtp_printf() calls do not need it, because in non-TLS
2298 mode, the fflush() happens when smtp_getc() is called. */
2299
2300 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2301 if (!tls_in.on_connect)
2302 {
2303 smtp_printf("220 TLS go ahead\r\n", FALSE);
2304 fflush(smtp_out);
2305 }
2306
2307 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2308 that the OpenSSL library doesn't. */
2309
2310 SSL_set_wfd(server_ssl, fileno(smtp_out));
2311 SSL_set_rfd(server_ssl, fileno(smtp_in));
2312 SSL_set_accept_state(server_ssl);
2313
2314 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2315
2316 sigalrm_seen = FALSE;
2317 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2318 rc = SSL_accept(server_ssl);
2319 ALARM_CLR(0);
2320
2321 if (rc <= 0)
2322 {
2323 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2324 return FAIL;
2325 }
2326
2327 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2328 ERR_clear_error(); /* Even success can leave errors in the stack. Seen with
2329 anon-authentication ciphersuite negociated. */
2330
2331 /* TLS has been set up. Adjust the input functions to read via TLS,
2332 and initialize things. */
2333
2334 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2335
2336 tls_in.cipher = construct_cipher_name(server_ssl, &tls_in.bits);
2337 tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl);
2338
2339 DEBUG(D_tls)
2340 {
2341 uschar buf[2048];
2342 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)))
2343 debug_printf("Shared ciphers: %s\n", buf);
2344
2345 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2346 {
2347 BIO * bp = BIO_new(BIO_s_mem());
2348 uschar * s;
2349 int len;
2350 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2351 len = (int) BIO_get_mem_data(bp, CSS &s);
2352 debug_printf("%.*s", len, s);
2353 BIO_free(bp);
2354 }
2355 #endif
2356 }
2357
2358 /* Record the certificate we presented */
2359 {
2360 X509 * crt = SSL_get_certificate(server_ssl);
2361 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2362 }
2363
2364 /* Only used by the server-side tls (tls_in), including tls_getc.
2365 Client-side (tls_out) reads (seem to?) go via
2366 smtp_read_response()/ip_recv().
2367 Hence no need to duplicate for _in and _out.
2368 */
2369 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2370 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2371 ssl_xfer_eof = ssl_xfer_error = FALSE;
2372
2373 receive_getc = tls_getc;
2374 receive_getbuf = tls_getbuf;
2375 receive_get_cache = tls_get_cache;
2376 receive_ungetc = tls_ungetc;
2377 receive_feof = tls_feof;
2378 receive_ferror = tls_ferror;
2379 receive_smtp_buffered = tls_smtp_buffered;
2380
2381 tls_in.active.sock = fileno(smtp_out);
2382 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2383 return OK;
2384 }
2385
2386
2387
2388
2389 static int
2390 tls_client_basic_ctx_init(SSL_CTX * ctx,
2391 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2392 uschar ** errstr)
2393 {
2394 int rc;
2395 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2396 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2397 the specified host patterns if one of them is defined */
2398
2399 if ( ( !ob->tls_verify_hosts
2400 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2401 )
2402 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2403 )
2404 client_verify_optional = FALSE;
2405 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2406 client_verify_optional = TRUE;
2407 else
2408 return OK;
2409
2410 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2411 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2412 errstr)) != OK)
2413 return rc;
2414
2415 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2416 {
2417 cbinfo->verify_cert_hostnames =
2418 #ifdef SUPPORT_I18N
2419 string_domain_utf8_to_alabel(host->name, NULL);
2420 #else
2421 host->name;
2422 #endif
2423 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2424 cbinfo->verify_cert_hostnames);
2425 }
2426 return OK;
2427 }
2428
2429
2430 #ifdef SUPPORT_DANE
2431 static int
2432 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2433 {
2434 dns_scan dnss;
2435 const char * hostnames[2] = { CS host->name, NULL };
2436 int found = 0;
2437
2438 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2439 return tls_error(US"hostnames load", host, NULL, errstr);
2440
2441 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2442 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2443 ) if (rr->type == T_TLSA && rr->size > 3)
2444 {
2445 const uschar * p = rr->data;
2446 uint8_t usage, selector, mtype;
2447 const char * mdname;
2448
2449 usage = *p++;
2450
2451 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2452 if (usage != 2 && usage != 3) continue;
2453
2454 selector = *p++;
2455 mtype = *p++;
2456
2457 switch (mtype)
2458 {
2459 default: continue; /* Only match-types 0, 1, 2 are supported */
2460 case 0: mdname = NULL; break;
2461 case 1: mdname = "sha256"; break;
2462 case 2: mdname = "sha512"; break;
2463 }
2464
2465 found++;
2466 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2467 {
2468 default:
2469 return tls_error(US"tlsa load", host, NULL, errstr);
2470 case 0: /* action not taken */
2471 case 1: break;
2472 }
2473
2474 tls_out.tlsa_usage |= 1<<usage;
2475 }
2476
2477 if (found)
2478 return OK;
2479
2480 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2481 return DEFER;
2482 }
2483 #endif /*SUPPORT_DANE*/
2484
2485
2486
2487 /*************************************************
2488 * Start a TLS session in a client *
2489 *************************************************/
2490
2491 /* Called from the smtp transport after STARTTLS has been accepted.
2492
2493 Argument:
2494 fd the fd of the connection
2495 host connected host (for messages and option-tests)
2496 addr the first address (for some randomness; can be NULL)
2497 tb transport (always smtp)
2498 tlsa_dnsa tlsa lookup, if DANE, else null
2499 tlsp record details of channel configuration here; must be non-NULL
2500 errstr error string pointer
2501
2502 Returns: Pointer to TLS session context, or NULL on error
2503 */
2504
2505 void *
2506 tls_client_start(int fd, host_item *host, address_item *addr,
2507 transport_instance * tb,
2508 #ifdef SUPPORT_DANE
2509 dns_answer * tlsa_dnsa,
2510 #endif
2511 tls_support * tlsp, uschar ** errstr)
2512 {
2513 smtp_transport_options_block * ob = tb
2514 ? (smtp_transport_options_block *)tb->options_block
2515 : &smtp_transport_option_defaults;
2516 exim_openssl_client_tls_ctx * exim_client_ctx;
2517 static uschar peerdn[256];
2518 uschar * expciphers;
2519 int rc;
2520
2521 #ifndef DISABLE_OCSP
2522 BOOL request_ocsp = FALSE;
2523 BOOL require_ocsp = FALSE;
2524 #endif
2525
2526 rc = store_pool;
2527 store_pool = POOL_PERM;
2528 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx));
2529 store_pool = rc;
2530
2531 #ifdef SUPPORT_DANE
2532 tlsp->tlsa_usage = 0;
2533 #endif
2534
2535 #ifndef DISABLE_OCSP
2536 {
2537 # ifdef SUPPORT_DANE
2538 if ( tlsa_dnsa
2539 && ob->hosts_request_ocsp[0] == '*'
2540 && ob->hosts_request_ocsp[1] == '\0'
2541 )
2542 {
2543 /* Unchanged from default. Use a safer one under DANE */
2544 request_ocsp = TRUE;
2545 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2546 " {= {4}{$tls_out_tlsa_usage}} } "
2547 " {*}{}}";
2548 }
2549 # endif
2550
2551 if ((require_ocsp =
2552 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
2553 request_ocsp = TRUE;
2554 else
2555 # ifdef SUPPORT_DANE
2556 if (!request_ocsp)
2557 # endif
2558 request_ocsp =
2559 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2560 }
2561 #endif
2562
2563 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
2564 ob->tls_certificate, ob->tls_privatekey,
2565 #ifndef DISABLE_OCSP
2566 (void *)(long)request_ocsp,
2567 #endif
2568 addr, &client_static_cbinfo, errstr);
2569 if (rc != OK) return NULL;
2570
2571 tlsp->certificate_verified = FALSE;
2572 client_verify_callback_called = FALSE;
2573
2574 expciphers = NULL;
2575 #ifdef SUPPORT_DANE
2576 if (tlsa_dnsa)
2577 {
2578 /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
2579 other failures should be treated as problems. */
2580 if (ob->dane_require_tls_ciphers &&
2581 !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2582 &expciphers, errstr))
2583 return NULL;
2584 if (expciphers && *expciphers == '\0')
2585 expciphers = NULL;
2586 }
2587 #endif
2588 if (!expciphers &&
2589 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2590 &expciphers, errstr))
2591 return NULL;
2592
2593 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2594 are separated by underscores. So that I can use either form in my tests, and
2595 also for general convenience, we turn underscores into hyphens here. */
2596
2597 if (expciphers)
2598 {
2599 uschar *s = expciphers;
2600 while (*s) { if (*s == '_') *s = '-'; s++; }
2601 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2602 if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
2603 {
2604 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2605 return NULL;
2606 }
2607 }
2608
2609 #ifdef SUPPORT_DANE
2610 if (tlsa_dnsa)
2611 {
2612 SSL_CTX_set_verify(exim_client_ctx->ctx,
2613 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2614 verify_callback_client_dane);
2615
2616 if (!DANESSL_library_init())
2617 {
2618 tls_error(US"library init", host, NULL, errstr);
2619 return NULL;
2620 }
2621 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
2622 {
2623 tls_error(US"context init", host, NULL, errstr);
2624 return NULL;
2625 }
2626 }
2627 else
2628
2629 #endif
2630
2631 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
2632 client_static_cbinfo, errstr) != OK)
2633 return NULL;
2634
2635 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
2636 {
2637 tls_error(US"SSL_new", host, NULL, errstr);
2638 return NULL;
2639 }
2640 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
2641 SSL_set_fd(exim_client_ctx->ssl, fd);
2642 SSL_set_connect_state(exim_client_ctx->ssl);
2643
2644 if (ob->tls_sni)
2645 {
2646 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
2647 return NULL;
2648 if (!tlsp->sni)
2649 {
2650 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2651 }
2652 else if (!Ustrlen(tlsp->sni))
2653 tlsp->sni = NULL;
2654 else
2655 {
2656 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2657 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
2658 SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
2659 #else
2660 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2661 tlsp->sni);
2662 #endif
2663 }
2664 }
2665
2666 #ifdef SUPPORT_DANE
2667 if (tlsa_dnsa)
2668 if (dane_tlsa_load(exim_client_ctx->ssl, host, tlsa_dnsa, errstr) != OK)
2669 return NULL;
2670 #endif
2671
2672 #ifndef DISABLE_OCSP
2673 /* Request certificate status at connection-time. If the server
2674 does OCSP stapling we will get the callback (set in tls_init()) */
2675 # ifdef SUPPORT_DANE
2676 if (request_ocsp)
2677 {
2678 const uschar * s;
2679 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2680 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2681 )
2682 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2683 this means we avoid the OCSP request, we wasted the setup
2684 cost in tls_init(). */
2685 require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2686 request_ocsp = require_ocsp
2687 || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2688 }
2689 }
2690 # endif
2691
2692 if (request_ocsp)
2693 {
2694 SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
2695 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2696 tlsp->ocsp = OCSP_NOT_RESP;
2697 }
2698 #endif
2699
2700 #ifndef DISABLE_EVENT
2701 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
2702 #endif
2703
2704 /* There doesn't seem to be a built-in timeout on connection. */
2705
2706 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2707 sigalrm_seen = FALSE;
2708 ALARM(ob->command_timeout);
2709 rc = SSL_connect(exim_client_ctx->ssl);
2710 ALARM_CLR(0);
2711
2712 #ifdef SUPPORT_DANE
2713 if (tlsa_dnsa)
2714 DANESSL_cleanup(exim_client_ctx->ssl);
2715 #endif
2716
2717 if (rc <= 0)
2718 {
2719 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
2720 return NULL;
2721 }
2722
2723 DEBUG(D_tls)
2724 {
2725 debug_printf("SSL_connect succeeded\n");
2726 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2727 {
2728 BIO * bp = BIO_new(BIO_s_mem());
2729 uschar * s;
2730 int len;
2731 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2732 len = (int) BIO_get_mem_data(bp, CSS &s);
2733 debug_printf("%.*s", len, s);
2734 BIO_free(bp);
2735 }
2736 #endif
2737 }
2738
2739 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
2740
2741 tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, &tlsp->bits);
2742 tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl);
2743
2744 /* Record the certificate we presented */
2745 {
2746 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
2747 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
2748 }
2749
2750 tlsp->active.sock = fd;
2751 tlsp->active.tls_ctx = exim_client_ctx;
2752 return exim_client_ctx;
2753 }
2754
2755
2756
2757
2758
2759 static BOOL
2760 tls_refill(unsigned lim)
2761 {
2762 int error;
2763 int inbytes;
2764
2765 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2766 ssl_xfer_buffer, ssl_xfer_buffer_size);
2767
2768 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2769 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2770 MIN(ssl_xfer_buffer_size, lim));
2771 error = SSL_get_error(server_ssl, inbytes);
2772 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2773
2774 if (had_command_timeout) /* set by signal handler */
2775 smtp_command_timeout_exit(); /* does not return */
2776 if (had_command_sigterm)
2777 smtp_command_sigterm_exit();
2778 if (had_data_timeout)
2779 smtp_data_timeout_exit();
2780 if (had_data_sigint)
2781 smtp_data_sigint_exit();
2782
2783 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2784 closed down, not that the socket itself has been closed down. Revert to
2785 non-SSL handling. */
2786
2787 switch(error)
2788 {
2789 case SSL_ERROR_NONE:
2790 break;
2791
2792 case SSL_ERROR_ZERO_RETURN:
2793 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2794
2795 receive_getc = smtp_getc;
2796 receive_getbuf = smtp_getbuf;
2797 receive_get_cache = smtp_get_cache;
2798 receive_ungetc = smtp_ungetc;
2799 receive_feof = smtp_feof;
2800 receive_ferror = smtp_ferror;
2801 receive_smtp_buffered = smtp_buffered;
2802
2803 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2804 SSL_shutdown(server_ssl);
2805
2806 #ifndef DISABLE_OCSP
2807 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
2808 server_static_cbinfo->verify_stack = NULL;
2809 #endif
2810 SSL_free(server_ssl);
2811 SSL_CTX_free(server_ctx);
2812 server_ctx = NULL;
2813 server_ssl = NULL;
2814 tls_in.active.sock = -1;
2815 tls_in.active.tls_ctx = NULL;
2816 tls_in.bits = 0;
2817 tls_in.cipher = NULL;
2818 tls_in.peerdn = NULL;
2819 tls_in.sni = NULL;
2820
2821 return FALSE;
2822
2823 /* Handle genuine errors */
2824 case SSL_ERROR_SSL:
2825 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
2826 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2827 ssl_xfer_error = TRUE;
2828 return FALSE;
2829
2830 default:
2831 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2832 DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
2833 debug_printf(" - syscall %s\n", strerror(errno));
2834 ssl_xfer_error = TRUE;
2835 return FALSE;
2836 }
2837
2838 #ifndef DISABLE_DKIM
2839 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2840 #endif
2841 ssl_xfer_buffer_hwm = inbytes;
2842 ssl_xfer_buffer_lwm = 0;
2843 return TRUE;
2844 }
2845
2846
2847 /*************************************************
2848 * TLS version of getc *
2849 *************************************************/
2850
2851 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2852 it refills the buffer via the SSL reading function.
2853
2854 Arguments: lim Maximum amount to read/buffer
2855 Returns: the next character or EOF
2856
2857 Only used by the server-side TLS.
2858 */
2859
2860 int
2861 tls_getc(unsigned lim)
2862 {
2863 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2864 if (!tls_refill(lim))
2865 return ssl_xfer_error ? EOF : smtp_getc(lim);
2866
2867 /* Something in the buffer; return next uschar */
2868
2869 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2870 }
2871
2872 uschar *
2873 tls_getbuf(unsigned * len)
2874 {
2875 unsigned size;
2876 uschar * buf;
2877
2878 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2879 if (!tls_refill(*len))
2880 {
2881 if (!ssl_xfer_error) return smtp_getbuf(len);
2882 *len = 0;
2883 return NULL;
2884 }
2885
2886 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2887 size = *len;
2888 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2889 ssl_xfer_buffer_lwm += size;
2890 *len = size;
2891 return buf;
2892 }
2893
2894
2895 void
2896 tls_get_cache()
2897 {
2898 #ifndef DISABLE_DKIM
2899 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2900 if (n > 0)
2901 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2902 #endif
2903 }
2904
2905
2906 BOOL
2907 tls_could_read(void)
2908 {
2909 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2910 }
2911
2912
2913 /*************************************************
2914 * Read bytes from TLS channel *
2915 *************************************************/
2916
2917 /*
2918 Arguments:
2919 ct_ctx client context pointer, or NULL for the one global server context
2920 buff buffer of data
2921 len size of buffer
2922
2923 Returns: the number of bytes read
2924 -1 after a failed read, including EOF
2925
2926 Only used by the client-side TLS.
2927 */
2928
2929 int
2930 tls_read(void * ct_ctx, uschar *buff, size_t len)
2931 {
2932 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2933 int inbytes;
2934 int error;
2935
2936 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2937 buff, (unsigned int)len);
2938
2939 inbytes = SSL_read(ssl, CS buff, len);
2940 error = SSL_get_error(ssl, inbytes);
2941
2942 if (error == SSL_ERROR_ZERO_RETURN)
2943 {
2944 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2945 return -1;
2946 }
2947 else if (error != SSL_ERROR_NONE)
2948 return -1;
2949
2950 return inbytes;
2951 }
2952
2953
2954
2955
2956
2957 /*************************************************
2958 * Write bytes down TLS channel *
2959 *************************************************/
2960
2961 /*
2962 Arguments:
2963 ct_ctx client context pointer, or NULL for the one global server context
2964 buff buffer of data
2965 len number of bytes
2966 more further data expected soon
2967
2968 Returns: the number of bytes after a successful write,
2969 -1 after a failed write
2970
2971 Used by both server-side and client-side TLS.
2972 */
2973
2974 int
2975 tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
2976 {
2977 size_t olen = len;
2978 int outbytes, error;
2979 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2980 static gstring * corked = NULL;
2981
2982 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2983 buff, (unsigned long)len, more ? ", more" : "");
2984
2985 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2986 "more" is notified. This hack is only ok if small amounts are involved AND only
2987 one stream does it, in one context (i.e. no store reset). Currently it is used
2988 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */
2989 /* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's
2990 a store reset there, so use POOL_PERM. */
2991 /* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */
2992
2993 if ((more || corked))
2994 {
2995 #ifdef EXPERIMENTAL_PIPE_CONNECT
2996 int save_pool = store_pool;
2997 store_pool = POOL_PERM;
2998 #endif
2999
3000 corked = string_catn(corked, buff, len);
3001
3002 #ifdef EXPERIMENTAL_PIPE_CONNECT
3003 store_pool = save_pool;
3004 #endif
3005
3006 if (more)
3007 return len;
3008 buff = CUS corked->s;
3009 len = corked->ptr;
3010 corked = NULL;
3011 }
3012
3013 for (int left = len; left > 0;)
3014 {
3015 DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left);
3016 outbytes = SSL_write(ssl, CS buff, left);
3017 error = SSL_get_error(ssl, outbytes);
3018 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
3019 switch (error)
3020 {
3021 case SSL_ERROR_SSL:
3022 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3023 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
3024 return -1;
3025
3026 case SSL_ERROR_NONE:
3027 left -= outbytes;
3028 buff += outbytes;
3029 break;
3030
3031 case SSL_ERROR_ZERO_RETURN:
3032 log_write(0, LOG_MAIN, "SSL channel closed on write");
3033 return -1;
3034
3035 case SSL_ERROR_SYSCALL:
3036 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
3037 sender_fullhost ? sender_fullhost : US"<unknown>",
3038 strerror(errno));
3039 return -1;
3040
3041 default:
3042 log_write(0, LOG_MAIN, "SSL_write error %d", error);
3043 return -1;
3044 }
3045 }
3046 return olen;
3047 }
3048
3049
3050
3051 /*************************************************
3052 * Close down a TLS session *
3053 *************************************************/
3054
3055 /* This is also called from within a delivery subprocess forked from the
3056 daemon, to shut down the TLS library, without actually doing a shutdown (which
3057 would tamper with the SSL session in the parent process).
3058
3059 Arguments:
3060 ct_ctx client TLS context pointer, or NULL for the one global server context
3061 shutdown 1 if TLS close-alert is to be sent,
3062 2 if also response to be waited for
3063
3064 Returns: nothing
3065
3066 Used by both server-side and client-side TLS.
3067 */
3068
3069 void
3070 tls_close(void * ct_ctx, int shutdown)
3071 {
3072 exim_openssl_client_tls_ctx * o_ctx = ct_ctx;
3073 SSL_CTX **ctxp = o_ctx ? &o_ctx->ctx : &server_ctx;
3074 SSL **sslp = o_ctx ? &o_ctx->ssl : &server_ssl;
3075 int *fdp = o_ctx ? &tls_out.active.sock : &tls_in.active.sock;
3076
3077 if (*fdp < 0) return; /* TLS was not active */
3078
3079 if (shutdown)
3080 {
3081 int rc;
3082 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3083 shutdown > 1 ? " (with response-wait)" : "");
3084
3085 if ( (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */
3086 && shutdown > 1)
3087 {
3088 ALARM(2);
3089 rc = SSL_shutdown(*sslp); /* wait for response */
3090 ALARM_CLR(0);
3091 }
3092
3093 if (rc < 0) DEBUG(D_tls)
3094 {
3095 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3096 debug_printf("SSL_shutdown: %s\n", ssl_errstring);
3097 }
3098 }
3099
3100 #ifndef DISABLE_OCSP
3101 if (!o_ctx) /* server side */
3102 {
3103 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
3104 server_static_cbinfo->verify_stack = NULL;
3105 }
3106 #endif
3107
3108 SSL_CTX_free(*ctxp);
3109 SSL_free(*sslp);
3110 *ctxp = NULL;
3111 *sslp = NULL;
3112 *fdp = -1;
3113 }
3114
3115
3116
3117
3118 /*************************************************
3119 * Let tls_require_ciphers be checked at startup *
3120 *************************************************/
3121
3122 /* The tls_require_ciphers option, if set, must be something which the
3123 library can parse.
3124
3125 Returns: NULL on success, or error message
3126 */
3127
3128 uschar *
3129 tls_validate_require_cipher(void)
3130 {
3131 SSL_CTX *ctx;
3132 uschar *s, *expciphers, *err;
3133
3134 /* this duplicates from tls_init(), we need a better "init just global
3135 state, for no specific purpose" singleton function of our own */
3136
3137 #ifdef EXIM_NEED_OPENSSL_INIT
3138 SSL_load_error_strings();
3139 OpenSSL_add_ssl_algorithms();
3140 #endif
3141 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
3142 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
3143 list of available digests. */
3144 EVP_add_digest(EVP_sha256());
3145 #endif
3146
3147 if (!(tls_require_ciphers && *tls_require_ciphers))
3148 return NULL;
3149
3150 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3151 &err))
3152 return US"failed to expand tls_require_ciphers";
3153
3154 if (!(expciphers && *expciphers))
3155 return NULL;
3156
3157 /* normalisation ripped from above */
3158 s = expciphers;
3159 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
3160
3161 err = NULL;
3162
3163 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
3164 if (!(ctx = SSL_CTX_new(TLS_server_method())))
3165 #else
3166 if (!(ctx = SSL_CTX_new(SSLv23_server_method())))
3167 #endif
3168 {
3169 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3170 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
3171 }
3172
3173 DEBUG(D_tls)
3174 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3175
3176 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
3177 {
3178 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3179 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
3180 expciphers, ssl_errstring);
3181 }
3182
3183 SSL_CTX_free(ctx);
3184
3185 return err;
3186 }
3187
3188
3189
3190
3191 /*************************************************
3192 * Report the library versions. *
3193 *************************************************/
3194
3195 /* There have historically been some issues with binary compatibility in
3196 OpenSSL libraries; if Exim (like many other applications) is built against
3197 one version of OpenSSL but the run-time linker picks up another version,
3198 it can result in serious failures, including crashing with a SIGSEGV. So
3199 report the version found by the compiler and the run-time version.
3200
3201 Note: some OS vendors backport security fixes without changing the version
3202 number/string, and the version date remains unchanged. The _build_ date
3203 will change, so we can more usefully assist with version diagnosis by also
3204 reporting the build date.
3205
3206 Arguments: a FILE* to print the results to
3207 Returns: nothing
3208 */
3209
3210 void
3211 tls_version_report(FILE *f)
3212 {
3213 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
3214 " Runtime: %s\n"
3215 " : %s\n",
3216 OPENSSL_VERSION_TEXT,
3217 SSLeay_version(SSLEAY_VERSION),
3218 SSLeay_version(SSLEAY_BUILT_ON));
3219 /* third line is 38 characters for the %s and the line is 73 chars long;
3220 the OpenSSL output includes a "built on: " prefix already. */
3221 }
3222
3223
3224
3225
3226 /*************************************************
3227 * Random number generation *
3228 *************************************************/
3229
3230 /* Pseudo-random number generation. The result is not expected to be
3231 cryptographically strong but not so weak that someone will shoot themselves
3232 in the foot using it as a nonce in input in some email header scheme or
3233 whatever weirdness they'll twist this into. The result should handle fork()
3234 and avoid repeating sequences. OpenSSL handles that for us.
3235
3236 Arguments:
3237 max range maximum
3238 Returns a random number in range [0, max-1]
3239 */
3240
3241 int
3242 vaguely_random_number(int max)
3243 {
3244 unsigned int r;
3245 int i, needed_len;
3246 static pid_t pidlast = 0;
3247 pid_t pidnow;
3248 uschar smallbuf[sizeof(r)];
3249
3250 if (max <= 1)
3251 return 0;
3252
3253 pidnow = getpid();
3254 if (pidnow != pidlast)
3255 {
3256 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
3257 is unique for each thread", this doesn't apparently apply across processes,
3258 so our own warning from vaguely_random_number_fallback() applies here too.
3259 Fix per PostgreSQL. */
3260 if (pidlast != 0)
3261 RAND_cleanup();
3262 pidlast = pidnow;
3263 }
3264
3265 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
3266 if (!RAND_status())
3267 {
3268 randstuff r;
3269 gettimeofday(&r.tv, NULL);
3270 r.p = getpid();
3271
3272 RAND_seed(US (&r), sizeof(r));
3273 }
3274 /* We're after pseudo-random, not random; if we still don't have enough data
3275 in the internal PRNG then our options are limited. We could sleep and hope
3276 for entropy to come along (prayer technique) but if the system is so depleted
3277 in the first place then something is likely to just keep taking it. Instead,
3278 we'll just take whatever little bit of pseudo-random we can still manage to
3279 get. */
3280
3281 needed_len = sizeof(r);
3282 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3283 asked for a number less than 10. */
3284 for (r = max, i = 0; r; ++i)
3285 r >>= 1;
3286 i = (i + 7) / 8;
3287 if (i < needed_len)
3288 needed_len = i;
3289
3290 #ifdef EXIM_HAVE_RAND_PSEUDO
3291 /* We do not care if crypto-strong */
3292 i = RAND_pseudo_bytes(smallbuf, needed_len);
3293 #else
3294 i = RAND_bytes(smallbuf, needed_len);
3295 #endif
3296
3297 if (i < 0)
3298 {
3299 DEBUG(D_all)
3300 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
3301 return vaguely_random_number_fallback(max);
3302 }
3303
3304 r = 0;
3305 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3306 r = 256 * r + *p;
3307
3308 /* We don't particularly care about weighted results; if someone wants
3309 smooth distribution and cares enough then they should submit a patch then. */
3310 return r % max;
3311 }
3312
3313
3314
3315
3316 /*************************************************
3317 * OpenSSL option parse *
3318 *************************************************/
3319
3320 /* Parse one option for tls_openssl_options_parse below
3321
3322 Arguments:
3323 name one option name
3324 value place to store a value for it
3325 Returns success or failure in parsing
3326 */
3327
3328
3329
3330 static BOOL
3331 tls_openssl_one_option_parse(uschar *name, long *value)
3332 {
3333 int first = 0;
3334 int last = exim_openssl_options_size;
3335 while (last > first)
3336 {
3337 int middle = (first + last)/2;
3338 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3339 if (c == 0)
3340 {
3341 *value = exim_openssl_options[middle].value;
3342 return TRUE;
3343 }
3344 else if (c > 0)
3345 first = middle + 1;
3346 else
3347 last = middle;
3348 }
3349 return FALSE;
3350 }
3351
3352
3353
3354
3355 /*************************************************
3356 * OpenSSL option parsing logic *
3357 *************************************************/
3358
3359 /* OpenSSL has a number of compatibility options which an administrator might
3360 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3361 we look like log_selector.
3362
3363 Arguments:
3364 option_spec the administrator-supplied string of options
3365 results ptr to long storage for the options bitmap
3366 Returns success or failure
3367 */
3368
3369 BOOL
3370 tls_openssl_options_parse(uschar *option_spec, long *results)
3371 {
3372 long result, item;
3373 uschar *end;
3374 uschar keep_c;
3375 BOOL adding, item_parsed;
3376
3377 result = SSL_OP_NO_TICKET;
3378 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3379 * from default because it increases BEAST susceptibility. */
3380 #ifdef SSL_OP_NO_SSLv2
3381 result |= SSL_OP_NO_SSLv2;
3382 #endif
3383 #ifdef SSL_OP_SINGLE_DH_USE
3384 result |= SSL_OP_SINGLE_DH_USE;
3385 #endif
3386
3387 if (!option_spec)
3388 {
3389 *results = result;
3390 return TRUE;
3391 }
3392
3393 for (uschar * s = option_spec; *s != '\0'; /**/)
3394 {
3395 while (isspace(*s)) ++s;
3396 if (*s == '\0')
3397 break;
3398 if (*s != '+' && *s != '-')
3399 {
3400 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3401 "+ or - expected but found \"%s\"\n", s);
3402 return FALSE;
3403 }
3404 adding = *s++ == '+';
3405 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3406 keep_c = *end;
3407 *end = '\0';
3408 item_parsed = tls_openssl_one_option_parse(s, &item);
3409 *end = keep_c;
3410 if (!item_parsed)
3411 {
3412 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3413 return FALSE;
3414 }
3415 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
3416 adding ? "adding" : "removing", result, item, s);
3417 if (adding)
3418 result |= item;
3419 else
3420 result &= ~item;
3421 s = end;
3422 }
3423
3424 *results = result;
3425 return TRUE;
3426 }
3427
3428 #endif /*!MACRO_PREDEF*/
3429 /* vi: aw ai sw=2
3430 */
3431 /* End of tls-openssl.c */