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