1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2018 */
6 /* See the file NOTICE for conditions of use and distribution. */
8 /* Portions Copyright (c) The OpenSSL Project 1999 */
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.
15 No cryptographic code is included in Exim. All this module does is to call
16 functions from the OpenSSL library. */
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>
29 # include <openssl/ocsp.h>
37 # define EXIM_OCSP_SKEW_SECONDS (300L)
38 # define EXIM_OCSP_MAX_AGE (-1L)
41 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
42 # define EXIM_HAVE_OPENSSL_TLSEXT
44 #if OPENSSL_VERSION_NUMBER >= 0x00908000L
45 # define EXIM_HAVE_RSA_GENKEY_EX
47 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
48 # define EXIM_HAVE_OCSP_RESP_COUNT
50 # define EXIM_HAVE_EPHEM_RSA_KEX
51 # define EXIM_HAVE_RAND_PSEUDO
53 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
54 # define EXIM_HAVE_SHA256
57 /* X509_check_host provides sane certificate hostname checking, but was added
58 to OpenSSL late, after other projects forked off the code-base. So in
59 addition to guarding against the base version number, beware that LibreSSL
60 does not (at this time) support this function.
62 If LibreSSL gains a different API, perhaps via libtls, then we'll probably
63 opt to disentangle and ask a LibreSSL user to provide glue for a third
64 crypto provider for libtls instead of continuing to tie the OpenSSL glue
65 into even twistier knots. If LibreSSL gains the same API, we can just
66 change this guard and punt the issue for a while longer. */
68 #ifndef LIBRESSL_VERSION_NUMBER
69 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
70 # define EXIM_HAVE_OPENSSL_CHECKHOST
71 # define EXIM_HAVE_OPENSSL_DH_BITS
72 # define EXIM_HAVE_OPENSSL_TLS_METHOD
73 # define EXIM_HAVE_OPENSSL_KEYLOG
74 # define EXIM_HAVE_OPENSSL_CIPHER_GET_ID
76 # define EXIM_NEED_OPENSSL_INIT
78 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
79 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
80 # define EXIM_HAVE_OPENSSL_CHECKHOST
84 #if !defined(LIBRESSL_VERSION_NUMBER) \
85 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
86 # if !defined(OPENSSL_NO_ECDH)
87 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
88 # define EXIM_HAVE_ECDH
90 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
91 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
96 #ifndef LIBRESSL_VERSION_NUMBER
97 # if OPENSSL_VERSION_NUMBER >= 0x010101000L
98 # define OPENSSL_HAVE_KEYLOG_CB
99 # define OPENSSL_HAVE_NUM_TICKETS
100 # define EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
104 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
105 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
106 # define DISABLE_OCSP
109 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
110 # include <openssl/x509v3.h>
113 #ifndef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
114 # ifndef EXIM_HAVE_OPENSSL_CIPHER_GET_ID
115 # define SSL_CIPHER_get_id(c) (c->id)
117 # ifndef MACRO_PREDEF
118 # include "tls-cipher-stdname.c"
122 /*************************************************
123 * OpenSSL option parse *
124 *************************************************/
126 typedef struct exim_openssl_option {
129 } exim_openssl_option;
130 /* We could use a macro to expand, but we need the ifdef and not all the
131 options document which version they were introduced in. Policylet: include
132 all options unless explicitly for DTLS, let the administrator choose which
135 This list is current as of:
137 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
138 Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev
140 static exim_openssl_option exim_openssl_options[] = {
141 /* KEEP SORTED ALPHABETICALLY! */
143 { US"all", SSL_OP_ALL },
145 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
146 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
148 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
149 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
151 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
152 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
154 #ifdef SSL_OP_EPHEMERAL_RSA
155 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
157 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
158 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
160 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
161 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
163 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
164 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
166 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
167 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
169 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
170 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
172 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
173 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
175 #ifdef SSL_OP_NO_COMPRESSION
176 { US"no_compression", SSL_OP_NO_COMPRESSION },
178 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
179 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
181 #ifdef SSL_OP_NO_SSLv2
182 { US"no_sslv2", SSL_OP_NO_SSLv2 },
184 #ifdef SSL_OP_NO_SSLv3
185 { US"no_sslv3", SSL_OP_NO_SSLv3 },
187 #ifdef SSL_OP_NO_TICKET
188 { US"no_ticket", SSL_OP_NO_TICKET },
190 #ifdef SSL_OP_NO_TLSv1
191 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
193 #ifdef SSL_OP_NO_TLSv1_1
194 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
195 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
196 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
198 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
201 #ifdef SSL_OP_NO_TLSv1_2
202 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
204 #ifdef SSL_OP_NO_TLSv1_3
205 { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 },
207 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
208 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
210 #ifdef SSL_OP_SINGLE_DH_USE
211 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
213 #ifdef SSL_OP_SINGLE_ECDH_USE
214 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
216 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
217 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
219 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
220 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
222 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
223 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
225 #ifdef SSL_OP_TLS_D5_BUG
226 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
228 #ifdef SSL_OP_TLS_ROLLBACK_BUG
229 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
234 static int exim_openssl_options_size = nelem(exim_openssl_options);
243 for (struct exim_openssl_option * o = exim_openssl_options;
244 o < exim_openssl_options + nelem(exim_openssl_options); o++)
246 /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1
247 being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */
249 spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name);
250 builtin_macro_create(buf);
255 /******************************************************************************/
257 /* Structure for collecting random data for seeding. */
259 typedef struct randstuff {
264 /* Local static variables */
266 static BOOL client_verify_callback_called = FALSE;
267 static BOOL server_verify_callback_called = FALSE;
268 static const uschar *sid_ctx = US"exim";
270 /* We have three different contexts to care about.
272 Simple case: client, `client_ctx`
273 As a client, we can be doing a callout or cut-through delivery while receiving
274 a message. So we have a client context, which should have options initialised
275 from the SMTP Transport. We may also concurrently want to make TLS connections
276 to utility daemons, so client-contexts are allocated and passed around in call
277 args rather than using a gobal.
280 There are two cases: with and without ServerNameIndication from the client.
281 Given TLS SNI, we can be using different keys, certs and various other
282 configuration settings, because they're re-expanded with $tls_sni set. This
283 allows vhosting with TLS. This SNI is sent in the handshake.
284 A client might not send SNI, so we need a fallback, and an initial setup too.
285 So as a server, we start out using `server_ctx`.
286 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
287 `server_sni` from `server_ctx` and then initialise settings by re-expanding
295 } exim_openssl_client_tls_ctx;
297 static SSL_CTX *server_ctx = NULL;
298 static SSL *server_ssl = NULL;
300 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
301 static SSL_CTX *server_sni = NULL;
304 static char ssl_errstring[256];
306 static int ssl_session_timeout = 200;
307 static BOOL client_verify_optional = FALSE;
308 static BOOL server_verify_optional = FALSE;
310 static BOOL reexpand_tls_files_for_sni = FALSE;
313 typedef struct tls_ext_ctx_cb {
318 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
322 uschar *file_expanded;
323 OCSP_RESPONSE *response;
326 X509_STORE *verify_store; /* non-null if status requested */
327 BOOL verify_required;
332 /* these are cached from first expand */
333 uschar *server_cipher_list;
334 /* only passed down to tls_error: */
336 const uschar * verify_cert_hostnames;
337 #ifndef DISABLE_EVENT
338 uschar * event_action;
342 /* should figure out a cleanup of API to handle state preserved per
343 implementation, for various reasons, which can be void * in the APIs.
344 For now, we hack around it. */
345 tls_ext_ctx_cb *client_static_cbinfo = NULL;
346 tls_ext_ctx_cb *server_static_cbinfo = NULL;
349 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
350 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
353 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
354 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
357 static int tls_server_stapling_cb(SSL *s, void *arg);
361 /*************************************************
363 *************************************************/
365 /* Called from lots of places when errors occur before actually starting to do
366 the TLS handshake, that is, while the session is still in clear. Always returns
367 DEFER for a server and FAIL for a client so that most calls can use "return
368 tls_error(...)" to do this processing and then give an appropriate return. A
369 single function is used for both server and client, because it is called from
370 some shared functions.
373 prefix text to include in the logged error
374 host NULL if setting up a server;
375 the connected host if setting up a client
376 msg error message or NULL if we should ask OpenSSL
377 errstr pointer to output error message
379 Returns: OK/DEFER/FAIL
383 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
387 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
388 msg = US ssl_errstring;
391 msg = string_sprintf("(%s): %s", prefix, msg);
392 DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg);
393 if (errstr) *errstr = msg;
394 return host ? FAIL : DEFER;
399 /*************************************************
400 * Callback to generate RSA key *
401 *************************************************/
405 s SSL connection (not used)
409 Returns: pointer to generated key
413 rsa_callback(SSL *s, int export, int keylength)
416 #ifdef EXIM_HAVE_RSA_GENKEY_EX
417 BIGNUM *bn = BN_new();
420 export = export; /* Shut picky compilers up */
421 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
423 #ifdef EXIM_HAVE_RSA_GENKEY_EX
424 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
425 || !(rsa_key = RSA_new())
426 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
429 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
433 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
434 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
446 x509_store_dump_cert_s_names(X509_STORE * store)
448 STACK_OF(X509_OBJECT) * roots= store->objs;
449 static uschar name[256];
451 for (int i= 0; i < sk_X509_OBJECT_num(roots); i++)
453 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
454 if(tmp_obj->type == X509_LU_X509)
456 X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509);
457 if (X509_NAME_oneline(sn, CS name, sizeof(name)))
459 name[sizeof(name)-1] = '\0';
460 debug_printf(" %s\n", name);
469 #ifndef DISABLE_EVENT
471 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
472 BOOL *calledp, const BOOL *optionalp, const uschar * what)
478 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
481 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
482 old_cert = tlsp->peercert;
483 tlsp->peercert = X509_dup(cert);
484 /* NB we do not bother setting peerdn */
485 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
487 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
488 "depth=%d cert=%s: %s",
489 tlsp == &tls_out ? deliver_host_address : sender_host_address,
490 what, depth, dn, yield);
494 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
495 return 1; /* reject (leaving peercert set) */
497 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
498 "(host in tls_try_verify_hosts)\n");
500 X509_free(tlsp->peercert);
501 tlsp->peercert = old_cert;
507 /*************************************************
508 * Callback for verification *
509 *************************************************/
511 /* The SSL library does certificate verification if set up to do so. This
512 callback has the current yes/no state is in "state". If verification succeeded,
513 we set the certificate-verified flag. If verification failed, what happens
514 depends on whether the client is required to present a verifiable certificate
517 If verification is optional, we change the state to yes, but still log the
518 verification error. For some reason (it really would help to have proper
519 documentation of OpenSSL), this callback function then gets called again, this
520 time with state = 1. We must take care not to set the private verified flag on
521 the second time through.
523 Note: this function is not called if the client fails to present a certificate
524 when asked. We get here only if a certificate has been received. Handling of
525 optional verification for this case is done when requesting SSL to verify, by
526 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
528 May be called multiple times for different issues with a certificate, even
529 for a given "depth" in the certificate chain.
532 preverify_ok current yes/no state as 1/0
533 x509ctx certificate information.
534 tlsp per-direction (client vs. server) support data
535 calledp has-been-called flag
536 optionalp verification-is-optional flag
538 Returns: 0 if verification should fail, otherwise 1
542 verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx,
543 tls_support * tlsp, BOOL * calledp, BOOL * optionalp)
545 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
546 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
549 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
551 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
552 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
553 tlsp == &tls_out ? deliver_host_address : sender_host_address);
556 dn[sizeof(dn)-1] = '\0';
558 if (preverify_ok == 0)
560 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
561 *verify_mode, sender_host_address)
563 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
564 tlsp == &tls_out ? deliver_host_address : sender_host_address,
566 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
571 tlsp->peercert = X509_dup(cert); /* record failing cert */
572 return 0; /* reject */
574 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
575 "tls_try_verify_hosts)\n");
580 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
582 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
583 { /* client, wanting stapling */
584 /* Add the server cert's signing chain as the one
585 for the verification of the OCSP stapled information. */
587 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
590 sk_X509_push(client_static_cbinfo->verify_stack, cert);
593 #ifndef DISABLE_EVENT
594 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
595 return 0; /* reject, with peercert set */
600 const uschar * verify_cert_hostnames;
602 if ( tlsp == &tls_out
603 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
604 /* client, wanting hostname check */
607 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
608 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
609 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
611 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
612 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
615 const uschar * list = verify_cert_hostnames;
618 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
619 if ((rc = X509_check_host(cert, CCS name, 0,
620 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
621 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
626 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
627 tlsp == &tls_out ? deliver_host_address : sender_host_address);
634 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
637 uschar * extra = verify_mode
638 ? string_sprintf(" (during %c-verify for [%s])",
639 *verify_mode, sender_host_address)
641 log_write(0, LOG_MAIN,
642 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
643 tlsp == &tls_out ? deliver_host_address : sender_host_address,
644 extra, dn, verify_cert_hostnames);
649 tlsp->peercert = X509_dup(cert); /* record failing cert */
650 return 0; /* reject */
652 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
653 "tls_try_verify_hosts)\n");
657 #ifndef DISABLE_EVENT
658 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
659 return 0; /* reject, with peercert set */
662 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
663 *calledp ? "" : " authenticated", dn);
664 if (!*calledp) tlsp->certificate_verified = TRUE;
668 return 1; /* accept, at least for this level */
672 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
674 return verify_callback(preverify_ok, x509ctx, &tls_out,
675 &client_verify_callback_called, &client_verify_optional);
679 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
681 return verify_callback(preverify_ok, x509ctx, &tls_in,
682 &server_verify_callback_called, &server_verify_optional);
688 /* This gets called *by* the dane library verify callback, which interposes
692 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
694 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
696 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
697 #ifndef DISABLE_EVENT
698 BOOL dummy_called, optional = FALSE;
701 if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn)))
703 DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n");
704 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
705 deliver_host_address);
708 dn[sizeof(dn)-1] = '\0';
710 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
711 preverify_ok ? "ok":"BAD", depth, dn);
713 #ifndef DISABLE_EVENT
714 if (verify_event(&tls_out, cert, depth, dn,
715 &dummy_called, &optional, US"DANE"))
716 return 0; /* reject, with peercert set */
719 if (preverify_ok == 1)
721 tls_out.dane_verified = tls_out.certificate_verified = TRUE;
723 if (client_static_cbinfo->u_ocsp.client.verify_store)
724 { /* client, wanting stapling */
725 /* Add the server cert's signing chain as the one
726 for the verification of the OCSP stapled information. */
728 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
731 sk_X509_push(client_static_cbinfo->verify_stack, cert);
737 int err = X509_STORE_CTX_get_error(x509ctx);
739 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
740 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
746 #endif /*SUPPORT_DANE*/
749 /*************************************************
750 * Information callback *
751 *************************************************/
753 /* The SSL library functions call this from time to time to indicate what they
754 are doing. We copy the string to the debugging output when TLS debugging has
766 info_callback(SSL *s, int where, int ret)
772 if (where & SSL_ST_CONNECT)
773 str = US"SSL_connect";
774 else if (where & SSL_ST_ACCEPT)
775 str = US"SSL_accept";
777 str = US"SSL info (undefined)";
779 if (where & SSL_CB_LOOP)
780 debug_printf("%s: %s\n", str, SSL_state_string_long(s));
781 else if (where & SSL_CB_ALERT)
782 debug_printf("SSL3 alert %s:%s:%s\n",
783 str = where & SSL_CB_READ ? US"read" : US"write",
784 SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
785 else if (where & SSL_CB_EXIT)
787 debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s));
789 debug_printf("%s: error in %s\n", str, SSL_state_string_long(s));
790 else if (where & SSL_CB_HANDSHAKE_START)
791 debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s));
792 else if (where & SSL_CB_HANDSHAKE_DONE)
793 debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s));
797 #ifdef OPENSSL_HAVE_KEYLOG_CB
799 keylog_callback(const SSL *ssl, const char *line)
801 DEBUG(D_tls) debug_printf("%.200s\n", line);
807 /*************************************************
808 * Initialize for DH *
809 *************************************************/
811 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
814 sctx The current SSL CTX (inbound or outbound)
815 dhparam DH parameter file or fixed parameter identity string
816 host connected host, if client; NULL if server
817 errstr error string pointer
819 Returns: TRUE if OK (nothing to set up, or setup worked)
823 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
831 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
834 if (!dhexpanded || !*dhexpanded)
835 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
836 else if (dhexpanded[0] == '/')
838 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
840 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
841 host, US strerror(errno), errstr);
847 if (Ustrcmp(dhexpanded, "none") == 0)
849 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
853 if (!(pem = std_dh_prime_named(dhexpanded)))
855 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
856 host, US strerror(errno), errstr);
859 bio = BIO_new_mem_buf(CS pem, -1);
862 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
865 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
870 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
871 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
872 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
873 * If someone wants to dance at the edge, then they can raise the limit or use
874 * current libraries. */
875 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
876 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
877 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
878 dh_bitsize = DH_bits(dh);
880 dh_bitsize = 8 * DH_size(dh);
883 /* Even if it is larger, we silently return success rather than cause things
884 * to fail out, so that a too-large DH will not knock out all TLS; it's a
885 * debatable choice. */
886 if (dh_bitsize > tls_dh_max_bits)
889 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
890 dh_bitsize, tls_dh_max_bits);
894 SSL_CTX_set_tmp_dh(sctx, dh);
896 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
897 dhexpanded ? dhexpanded : US"default", dh_bitsize);
909 /*************************************************
910 * Initialize for ECDH *
911 *************************************************/
913 /* Load parameters for ECDH encryption.
915 For now, we stick to NIST P-256 because: it's simple and easy to configure;
916 it avoids any patent issues that might bite redistributors; despite events in
917 the news and concerns over curve choices, we're not cryptographers, we're not
918 pretending to be, and this is "good enough" to be better than no support,
919 protecting against most adversaries. Given another year or two, there might
920 be sufficient clarity about a "right" way forward to let us make an informed
921 decision, instead of a knee-jerk reaction.
923 Longer-term, we should look at supporting both various named curves and
924 external files generated with "openssl ecparam", much as we do for init_dh().
925 We should also support "none" as a value, to explicitly avoid initialisation.
930 sctx The current SSL CTX (inbound or outbound)
931 host connected host, if client; NULL if server
932 errstr error string pointer
934 Returns: TRUE if OK (nothing to set up, or setup worked)
938 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
940 #ifdef OPENSSL_NO_ECDH
949 if (host) /* No ECDH setup for clients, only for servers */
952 # ifndef EXIM_HAVE_ECDH
954 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
958 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
960 if (!exp_curve || !*exp_curve)
963 /* "auto" needs to be handled carefully.
964 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
965 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
966 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
967 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
968 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
970 if (Ustrcmp(exp_curve, "auto") == 0)
972 #if OPENSSL_VERSION_NUMBER < 0x10002000L
973 DEBUG(D_tls) debug_printf(
974 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
975 exp_curve = US"prime256v1";
977 # if defined SSL_CTRL_SET_ECDH_AUTO
978 DEBUG(D_tls) debug_printf(
979 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
980 SSL_CTX_set_ecdh_auto(sctx, 1);
983 DEBUG(D_tls) debug_printf(
984 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
990 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
991 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
992 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
993 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
997 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
1002 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
1004 tls_error(US"Unable to create ec curve", host, NULL, errstr);
1008 /* The "tmp" in the name here refers to setting a temporary key
1009 not to the stability of the interface. */
1011 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
1012 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
1014 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
1019 # endif /*EXIM_HAVE_ECDH*/
1020 #endif /*OPENSSL_NO_ECDH*/
1026 #ifndef DISABLE_OCSP
1027 /*************************************************
1028 * Load OCSP information into state *
1029 *************************************************/
1030 /* Called to load the server OCSP response from the given file into memory, once
1031 caller has determined this is needed. Checks validity. Debugs a message
1034 ASSUMES: single response, for single cert.
1037 sctx the SSL_CTX* to update
1038 cbinfo various parts of session state
1039 expanded the filename putatively holding an OCSP response
1044 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
1047 OCSP_RESPONSE * resp;
1048 OCSP_BASICRESP * basic_response;
1049 OCSP_SINGLERESP * single_response;
1050 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
1051 STACK_OF(X509) * sk;
1052 unsigned long verify_flags;
1053 int status, reason, i;
1055 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
1056 if (cbinfo->u_ocsp.server.response)
1058 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
1059 cbinfo->u_ocsp.server.response = NULL;
1062 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
1064 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
1065 cbinfo->u_ocsp.server.file_expanded);
1069 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
1073 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
1077 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
1079 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
1080 OCSP_response_status_str(status), status);
1084 if (!(basic_response = OCSP_response_get1_basic(resp)))
1087 debug_printf("OCSP response parse error: unable to extract basic response.\n");
1091 sk = cbinfo->verify_stack;
1092 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
1094 /* May need to expose ability to adjust those flags?
1095 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
1096 OCSP_TRUSTOTHER OCSP_NOINTERN */
1098 /* This does a full verify on the OCSP proof before we load it for serving
1099 up; possibly overkill - just date-checks might be nice enough.
1101 OCSP_basic_verify takes a "store" arg, but does not
1102 use it for the chain verification, which is all we do
1103 when OCSP_NOVERIFY is set. The content from the wire
1104 "basic_response" and a cert-stack "sk" are all that is used.
1106 We have a stack, loaded in setup_certs() if tls_verify_certificates
1107 was a file (not a directory, or "system"). It is unfortunate we
1108 cannot used the connection context store, as that would neatly
1109 handle the "system" case too, but there seems to be no library
1110 function for getting a stack from a store.
1111 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
1112 We do not free the stack since it could be needed a second time for
1115 Separately we might try to replace using OCSP_basic_verify() - which seems to not
1116 be a public interface into the OpenSSL library (there's no manual entry) -
1117 But what with? We also use OCSP_basic_verify in the client stapling callback.
1118 And there we NEED it; we must verify that status... unless the
1119 library does it for us anyway? */
1121 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
1125 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1126 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
1131 /* Here's the simplifying assumption: there's only one response, for the
1132 one certificate we use, and nothing for anything else in a chain. If this
1133 proves false, we need to extract a cert id from our issued cert
1134 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
1135 right cert in the stack and then calls OCSP_single_get0_status()).
1137 I'm hoping to avoid reworking a bunch more of how we handle state here. */
1139 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
1142 debug_printf("Unable to get first response from OCSP basic response.\n");
1146 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
1147 if (status != V_OCSP_CERTSTATUS_GOOD)
1149 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
1150 OCSP_cert_status_str(status), status,
1151 OCSP_crl_reason_str(reason), reason);
1155 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1157 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
1162 cbinfo->u_ocsp.server.response = resp; /*XXX stack?*/
1166 if (f.running_in_test_harness)
1168 extern char ** environ;
1169 if (environ) for (uschar ** p = USS environ; *p; p++)
1170 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
1172 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
1173 goto supply_response;
1178 #endif /*!DISABLE_OCSP*/
1183 /* Create and install a selfsigned certificate, for use in server mode */
1186 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
1194 where = US"allocating pkey";
1195 if (!(pkey = EVP_PKEY_new()))
1198 where = US"allocating cert";
1199 if (!(x509 = X509_new()))
1202 where = US"generating pkey";
1203 if (!(rsa = rsa_callback(NULL, 0, 2048)))
1206 where = US"assigning pkey";
1207 if (!EVP_PKEY_assign_RSA(pkey, rsa))
1210 X509_set_version(x509, 2); /* N+1 - version 3 */
1211 ASN1_INTEGER_set(X509_get_serialNumber(x509), 1);
1212 X509_gmtime_adj(X509_get_notBefore(x509), 0);
1213 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
1214 X509_set_pubkey(x509, pkey);
1216 name = X509_get_subject_name(x509);
1217 X509_NAME_add_entry_by_txt(name, "C",
1218 MBSTRING_ASC, CUS "UK", -1, -1, 0);
1219 X509_NAME_add_entry_by_txt(name, "O",
1220 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1221 X509_NAME_add_entry_by_txt(name, "CN",
1222 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1223 X509_set_issuer_name(x509, name);
1225 where = US"signing cert";
1226 if (!X509_sign(x509, pkey, EVP_md5()))
1229 where = US"installing selfsign cert";
1230 if (!SSL_CTX_use_certificate(sctx, x509))
1233 where = US"installing selfsign key";
1234 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1240 (void) tls_error(where, NULL, NULL, errstr);
1241 if (x509) X509_free(x509);
1242 if (pkey) EVP_PKEY_free(pkey);
1250 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1253 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1254 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1255 return tls_error(string_sprintf(
1256 "SSL_CTX_use_certificate_chain_file file=%s", file),
1257 cbinfo->host, NULL, errstr);
1262 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1265 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1266 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1267 return tls_error(string_sprintf(
1268 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1273 /*************************************************
1274 * Expand key and cert file specs *
1275 *************************************************/
1277 /* Called once during tls_init and possibly again during TLS setup, for a
1278 new context, if Server Name Indication was used and tls_sni was seen in
1279 the certificate string.
1282 sctx the SSL_CTX* to update
1283 cbinfo various parts of session state
1284 errstr error string pointer
1286 Returns: OK/DEFER/FAIL
1290 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1295 if (!cbinfo->certificate)
1297 if (!cbinfo->is_server) /* client */
1300 if (tls_install_selfsign(sctx, errstr) != OK)
1307 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1308 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1309 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1311 reexpand_tls_files_for_sni = TRUE;
1313 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1317 if (cbinfo->is_server)
1319 const uschar * file_list = expanded;
1323 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1324 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1327 else /* would there ever be a need for multiple client certs? */
1328 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1331 if ( cbinfo->privatekey
1332 && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1335 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1336 of the expansion is an empty string, ignore it also, and assume the private
1337 key is in the same file as the certificate. */
1339 if (expanded && *expanded)
1340 if (cbinfo->is_server)
1342 const uschar * file_list = expanded;
1346 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1347 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1350 else /* would there ever be a need for multiple client certs? */
1351 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1355 #ifndef DISABLE_OCSP
1356 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1359 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1362 if (expanded && *expanded)
1364 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1365 if ( cbinfo->u_ocsp.server.file_expanded
1366 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1368 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1371 ocsp_load_response(sctx, cbinfo, expanded);
1382 /*************************************************
1383 * Callback to handle SNI *
1384 *************************************************/
1386 /* Called when acting as server during the TLS session setup if a Server Name
1387 Indication extension was sent by the client.
1389 API documentation is OpenSSL s_server.c implementation.
1392 s SSL* of the current session
1393 ad unknown (part of OpenSSL API) (unused)
1394 arg Callback of "our" registered data
1396 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1399 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1401 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1403 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1404 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1406 int old_pool = store_pool;
1407 uschar * dummy_errstr;
1410 return SSL_TLSEXT_ERR_OK;
1412 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1413 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1415 /* Make the extension value available for expansion */
1416 store_pool = POOL_PERM;
1417 tls_in.sni = string_copy(US servername);
1418 store_pool = old_pool;
1420 if (!reexpand_tls_files_for_sni)
1421 return SSL_TLSEXT_ERR_OK;
1423 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1424 not confident that memcpy wouldn't break some internal reference counting.
1425 Especially since there's a references struct member, which would be off. */
1427 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1428 if (!(server_sni = SSL_CTX_new(TLS_server_method())))
1430 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1433 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
1434 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1438 /* Not sure how many of these are actually needed, since SSL object
1439 already exists. Might even need this selfsame callback, for reneg? */
1441 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1442 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1443 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1444 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1445 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1446 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1448 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1449 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1453 if ( cbinfo->server_cipher_list
1454 && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list))
1457 #ifndef DISABLE_OCSP
1458 if (cbinfo->u_ocsp.server.file)
1460 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1461 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1465 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1466 verify_callback_server, &dummy_errstr)) != OK)
1469 /* do this after setup_certs, because this can require the certs for verifying
1470 OCSP information. */
1471 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1474 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1475 SSL_set_SSL_CTX(s, server_sni);
1476 return SSL_TLSEXT_ERR_OK;
1478 bad: return SSL_TLSEXT_ERR_ALERT_FATAL;
1480 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1485 #ifndef DISABLE_OCSP
1487 /*************************************************
1488 * Callback to handle OCSP Stapling *
1489 *************************************************/
1491 /* Called when acting as server during the TLS session setup if the client
1492 requests OCSP information with a Certificate Status Request.
1494 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1500 tls_server_stapling_cb(SSL *s, void *arg)
1502 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1503 uschar *response_der; /*XXX blob */
1504 int response_der_len;
1506 /*XXX stack: use SSL_get_certificate() to see which cert; from that work
1507 out which ocsp blob to send. Unfortunately, SSL_get_certificate is known
1508 buggy in current OpenSSL; it returns the last cert loaded always rather than
1509 the one actually presented. So we can't support a stack of OCSP proofs at
1513 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1514 cbinfo->u_ocsp.server.response ? "have" : "lack");
1516 tls_in.ocsp = OCSP_NOT_RESP;
1517 if (!cbinfo->u_ocsp.server.response)
1518 return SSL_TLSEXT_ERR_NOACK;
1520 response_der = NULL;
1521 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response, /*XXX stack*/
1523 if (response_der_len <= 0)
1524 return SSL_TLSEXT_ERR_NOACK;
1526 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1527 tls_in.ocsp = OCSP_VFIED;
1528 return SSL_TLSEXT_ERR_OK;
1533 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1535 BIO_printf(bp, "\t%s: ", str);
1536 ASN1_GENERALIZEDTIME_print(bp, time);
1541 tls_client_stapling_cb(SSL *s, void *arg)
1543 tls_ext_ctx_cb * cbinfo = arg;
1544 const unsigned char * p;
1546 OCSP_RESPONSE * rsp;
1547 OCSP_BASICRESP * bs;
1550 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1551 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1554 /* Expect this when we requested ocsp but got none */
1555 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1556 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1558 DEBUG(D_tls) debug_printf(" null\n");
1559 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1562 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1564 tls_out.ocsp = OCSP_FAILED;
1565 if (LOGGING(tls_cipher))
1566 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1568 DEBUG(D_tls) debug_printf(" parse error\n");
1572 if(!(bs = OCSP_response_get1_basic(rsp)))
1574 tls_out.ocsp = OCSP_FAILED;
1575 if (LOGGING(tls_cipher))
1576 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1578 DEBUG(D_tls) debug_printf(" error parsing response\n");
1579 OCSP_RESPONSE_free(rsp);
1583 /* We'd check the nonce here if we'd put one in the request. */
1584 /* However that would defeat cacheability on the server so we don't. */
1586 /* This section of code reworked from OpenSSL apps source;
1587 The OpenSSL Project retains copyright:
1588 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1593 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1595 DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
1597 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1599 /* Use the chain that verified the server cert to verify the stapled info */
1600 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1602 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1603 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1605 tls_out.ocsp = OCSP_FAILED;
1606 if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN,
1607 "Received TLS cert status response, itself unverifiable: %s",
1608 ERR_reason_error_string(ERR_peek_error()));
1609 BIO_printf(bp, "OCSP response verify failure\n");
1610 ERR_print_errors(bp);
1611 OCSP_RESPONSE_print(bp, rsp, 0);
1615 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1617 /*XXX So we have a good stapled OCSP status. How do we know
1618 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1619 OCSP_resp_find_status() which matches on a cert id, which presumably
1620 we should use. Making an id needs OCSP_cert_id_new(), which takes
1621 issuerName, issuerKey, serialNumber. Are they all in the cert?
1623 For now, carry on blindly accepting the resp. */
1626 OCSP_SINGLERESP * single;
1628 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1629 if (OCSP_resp_count(bs) != 1)
1631 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1632 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1635 tls_out.ocsp = OCSP_FAILED;
1636 log_write(0, LOG_MAIN, "OCSP stapling "
1637 "with multiple responses not handled");
1640 single = OCSP_resp_get0(bs, 0);
1641 status = OCSP_single_get0_status(single, &reason, &rev,
1642 &thisupd, &nextupd);
1645 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1646 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1647 if (!OCSP_check_validity(thisupd, nextupd,
1648 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1650 tls_out.ocsp = OCSP_FAILED;
1651 DEBUG(D_tls) ERR_print_errors(bp);
1652 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1656 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1657 OCSP_cert_status_str(status));
1660 case V_OCSP_CERTSTATUS_GOOD:
1661 tls_out.ocsp = OCSP_VFIED;
1664 case V_OCSP_CERTSTATUS_REVOKED:
1665 tls_out.ocsp = OCSP_FAILED;
1666 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1667 reason != -1 ? "; reason: " : "",
1668 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1669 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1672 tls_out.ocsp = OCSP_FAILED;
1673 log_write(0, LOG_MAIN,
1674 "Server certificate status unknown, in OCSP stapling");
1679 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1684 OCSP_RESPONSE_free(rsp);
1687 #endif /*!DISABLE_OCSP*/
1690 /*************************************************
1691 * Initialize for TLS *
1692 *************************************************/
1694 /* Called from both server and client code, to do preliminary initialization
1695 of the library. We allocate and return a context structure.
1698 ctxp returned SSL context
1699 host connected host, if client; NULL if server
1700 dhparam DH parameter file
1701 certificate certificate file
1702 privatekey private key
1703 ocsp_file file of stapling info (server); flag for require ocsp (client)
1704 addr address if client; NULL if server (for some randomness)
1705 cbp place to put allocated callback context
1706 errstr error string pointer
1708 Returns: OK/DEFER/FAIL
1712 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1714 #ifndef DISABLE_OCSP
1715 uschar *ocsp_file, /*XXX stack, in server*/
1717 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1722 tls_ext_ctx_cb * cbinfo;
1724 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1725 cbinfo->certificate = certificate;
1726 cbinfo->privatekey = privatekey;
1727 cbinfo->is_server = host==NULL;
1728 #ifndef DISABLE_OCSP
1729 cbinfo->verify_stack = NULL;
1732 cbinfo->u_ocsp.server.file = ocsp_file;
1733 cbinfo->u_ocsp.server.file_expanded = NULL;
1734 cbinfo->u_ocsp.server.response = NULL;
1737 cbinfo->u_ocsp.client.verify_store = NULL;
1739 cbinfo->dhparam = dhparam;
1740 cbinfo->server_cipher_list = NULL;
1741 cbinfo->host = host;
1742 #ifndef DISABLE_EVENT
1743 cbinfo->event_action = NULL;
1746 #ifdef EXIM_NEED_OPENSSL_INIT
1747 SSL_load_error_strings(); /* basic set up */
1748 OpenSSL_add_ssl_algorithms();
1751 #ifdef EXIM_HAVE_SHA256
1752 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1753 list of available digests. */
1754 EVP_add_digest(EVP_sha256());
1757 /* Create a context.
1758 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1759 negotiation in the different methods; as far as I can tell, the only
1760 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1761 when OpenSSL is built without SSLv2 support.
1762 By disabling with openssl_options, we can let admins re-enable with the
1765 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
1766 if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method())))
1768 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1770 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1772 /* It turns out that we need to seed the random number generator this early in
1773 order to get the full complement of ciphers to work. It took me roughly a day
1774 of work to discover this by experiment.
1776 On systems that have /dev/urandom, SSL may automatically seed itself from
1777 there. Otherwise, we have to make something up as best we can. Double check
1783 gettimeofday(&r.tv, NULL);
1786 RAND_seed(US (&r), sizeof(r));
1787 RAND_seed(US big_buffer, big_buffer_size);
1788 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1791 return tls_error(US"RAND_status", host,
1792 US"unable to seed random number generator", errstr);
1795 /* Set up the information callback, which outputs if debugging is at a suitable
1798 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1799 #ifdef OPENSSL_HAVE_KEYLOG_CB
1800 DEBUG(D_tls) SSL_CTX_set_keylog_callback(ctx, (void (*)())keylog_callback);
1803 /* Automatically re-try reads/writes after renegotiation. */
1804 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1806 /* Apply administrator-supplied work-arounds.
1807 Historically we applied just one requested option,
1808 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1809 moved to an administrator-controlled list of options to specify and
1810 grandfathered in the first one as the default value for "openssl_options".
1812 No OpenSSL version number checks: the options we accept depend upon the
1813 availability of the option value macros from OpenSSL. */
1815 if (!tls_openssl_options_parse(openssl_options, &init_options))
1816 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1820 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1821 if (!(SSL_CTX_set_options(ctx, init_options)))
1822 return tls_error(string_sprintf(
1823 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1826 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1828 #ifdef OPENSSL_HAVE_NUM_TICKETS
1829 SSL_CTX_set_num_tickets(ctx, 0); /* send no TLS1.3 stateful-tickets */
1832 /* We'd like to disable session cache unconditionally, but foolish Outlook
1833 Express clients then give up the first TLS connection and make a second one
1834 (which works). Only when there is an IMAP service on the same machine.
1835 Presumably OE is trying to use the cache for A on B. Leave it enabled for
1836 now, until we work out a decent way of presenting control to the config. It
1837 will never be used because we use a new context every time. */
1839 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1842 /* Initialize with DH parameters if supplied */
1843 /* Initialize ECDH temp key parameter selection */
1845 if ( !init_dh(ctx, dhparam, host, errstr)
1846 || !init_ecdh(ctx, host, errstr)
1850 /* Set up certificate and key (and perhaps OCSP info) */
1852 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1855 /* If we need to handle SNI or OCSP, do so */
1857 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1858 # ifndef DISABLE_OCSP
1859 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1861 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1866 if (!host) /* server */
1868 # ifndef DISABLE_OCSP
1869 /* We check u_ocsp.server.file, not server.response, because we care about if
1870 the option exists, not what the current expansion might be, as SNI might
1871 change the certificate and OCSP file in use between now and the time the
1872 callback is invoked. */
1873 if (cbinfo->u_ocsp.server.file)
1875 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1876 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1879 /* We always do this, so that $tls_sni is available even if not used in
1881 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1882 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1884 # ifndef DISABLE_OCSP
1886 if(ocsp_file) /* wanting stapling */
1888 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1890 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1893 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1894 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1899 cbinfo->verify_cert_hostnames = NULL;
1901 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1902 /* Set up the RSA callback */
1903 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1906 /* Finally, set the timeout, and we are done */
1908 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1909 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1920 /*************************************************
1921 * Get name of cipher in use *
1922 *************************************************/
1925 Argument: pointer to an SSL structure for the connection
1926 pointer to number of bits for cipher
1927 Returns: pointer to allocated string in perm-pool
1931 construct_cipher_name(SSL * ssl, int * bits)
1933 int pool = store_pool;
1934 /* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't
1935 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1936 the accessor functions use const in the prototype. */
1938 const uschar * ver = CUS SSL_get_version(ssl);
1939 const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1942 SSL_CIPHER_get_bits(c, bits);
1944 store_pool = POOL_PERM;
1945 s = string_sprintf("%s:%s:%u", ver, SSL_CIPHER_get_name(c), *bits);
1947 DEBUG(D_tls) debug_printf("Cipher: %s\n", s);
1952 /* Get IETF-standard name for ciphersuite.
1953 Argument: pointer to an SSL structure for the connection
1954 Returns: pointer to string
1957 static const uschar *
1958 cipher_stdname_ssl(SSL * ssl)
1960 #ifdef EXIM_HAVE_OPENSSL_CIPHER_STD_NAME
1961 return CUS SSL_CIPHER_standard_name(SSL_get_current_cipher(ssl));
1963 ushort id = 0xffff & SSL_CIPHER_get_id(SSL_get_current_cipher(ssl));
1964 return cipher_stdname(id >> 8, id & 0xff);
1970 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz)
1972 /*XXX we might consider a list-of-certs variable for the cert chain.
1973 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1974 in list-handling functions, also consider the difference between the entire
1975 chain and the elements sent by the peer. */
1977 tlsp->peerdn = NULL;
1979 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1980 if (!tlsp->peercert)
1981 tlsp->peercert = SSL_get_peer_certificate(ssl);
1982 /* Beware anonymous ciphers which lead to server_cert being NULL */
1984 if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz))
1985 { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); }
1988 peerdn[siz-1] = '\0';
1989 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1997 /*************************************************
1998 * Set up for verifying certificates *
1999 *************************************************/
2001 #ifndef DISABLE_OCSP
2002 /* Load certs from file, return TRUE on success */
2005 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
2010 while (sk_X509_num(verify_stack) > 0)
2011 X509_free(sk_X509_pop(verify_stack));
2013 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
2014 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
2015 sk_X509_push(verify_stack, x);
2023 /* Called by both client and server startup; on the server possibly
2024 repeated after a Server Name Indication.
2027 sctx SSL_CTX* to initialise
2028 certs certs file or NULL
2029 crl CRL file or NULL
2030 host NULL in a server; the remote host in a client
2031 optional TRUE if called from a server for a host in tls_try_verify_hosts;
2032 otherwise passed as FALSE
2033 cert_vfy_cb Callback function for certificate verification
2034 errstr error string pointer
2036 Returns: OK/DEFER/FAIL
2040 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
2041 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
2043 uschar *expcerts, *expcrl;
2045 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
2047 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
2049 if (expcerts && *expcerts)
2051 /* Tell the library to use its compiled-in location for the system default
2052 CA bundle. Then add the ones specified in the config, if any. */
2054 if (!SSL_CTX_set_default_verify_paths(sctx))
2055 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
2057 if (Ustrcmp(expcerts, "system") != 0)
2059 struct stat statbuf;
2061 if (Ustat(expcerts, &statbuf) < 0)
2063 log_write(0, LOG_MAIN|LOG_PANIC,
2064 "failed to stat %s for certificates", expcerts);
2070 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
2071 { file = NULL; dir = expcerts; }
2074 file = expcerts; dir = NULL;
2075 #ifndef DISABLE_OCSP
2076 /* In the server if we will be offering an OCSP proof, load chain from
2077 file for verifying the OCSP proof at load time. */
2080 && statbuf.st_size > 0
2081 && server_static_cbinfo->u_ocsp.server.file
2082 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
2085 log_write(0, LOG_MAIN|LOG_PANIC,
2086 "failed to load cert chain from %s", file);
2092 /* If a certificate file is empty, the next function fails with an
2093 unhelpful error message. If we skip it, we get the correct behaviour (no
2094 certificates are recognized, but the error message is still misleading (it
2095 says no certificate was supplied). But this is better. */
2097 if ( (!file || statbuf.st_size > 0)
2098 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
2099 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
2101 /* Load the list of CAs for which we will accept certs, for sending
2102 to the client. This is only for the one-file tls_verify_certificates
2104 If a list isn't loaded into the server, but some verify locations are set,
2105 the server end appears to make a wildcard request for client certs.
2106 Meanwhile, the client library as default behaviour *ignores* the list
2107 we send over the wire - see man SSL_CTX_set_client_cert_cb.
2108 Because of this, and that the dir variant is likely only used for
2109 the public-CA bundle (not for a private CA), not worth fixing. */
2113 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
2115 SSL_CTX_set_client_CA_list(sctx, names);
2116 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
2117 sk_X509_NAME_num(names));
2122 /* Handle a certificate revocation list. */
2124 #if OPENSSL_VERSION_NUMBER > 0x00907000L
2126 /* This bit of code is now the version supplied by Lars Mainka. (I have
2127 merely reformatted it into the Exim code style.)
2129 "From here I changed the code to add support for multiple crl's
2130 in pem format in one file or to support hashed directory entries in
2131 pem format instead of a file. This method now uses the library function
2132 X509_STORE_load_locations to add the CRL location to the SSL context.
2133 OpenSSL will then handle the verify against CA certs and CRLs by
2134 itself in the verify callback." */
2136 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
2137 if (expcrl && *expcrl)
2139 struct stat statbufcrl;
2140 if (Ustat(expcrl, &statbufcrl) < 0)
2142 log_write(0, LOG_MAIN|LOG_PANIC,
2143 "failed to stat %s for certificates revocation lists", expcrl);
2148 /* is it a file or directory? */
2150 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
2151 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
2155 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
2161 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
2163 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
2164 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
2166 /* setting the flags to check against the complete crl chain */
2168 X509_STORE_set_flags(cvstore,
2169 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
2173 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
2175 /* If verification is optional, don't fail if no certificate */
2177 SSL_CTX_set_verify(sctx,
2178 SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
2187 /*************************************************
2188 * Start a TLS session in a server *
2189 *************************************************/
2191 /* This is called when Exim is running as a server, after having received
2192 the STARTTLS command. It must respond to that command, and then negotiate
2196 require_ciphers allowed ciphers
2197 errstr pointer to error message
2199 Returns: OK on success
2200 DEFER for errors before the start of the negotiation
2201 FAIL for errors during the negotiation; the server can't
2206 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
2209 uschar * expciphers;
2210 tls_ext_ctx_cb * cbinfo;
2211 static uschar peerdn[256];
2213 /* Check for previous activation */
2215 if (tls_in.active.sock >= 0)
2217 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
2218 smtp_printf("554 Already in TLS\r\n", FALSE);
2222 /* Initialize the SSL library. If it fails, it will already have logged
2225 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
2226 #ifndef DISABLE_OCSP
2227 tls_ocsp_file, /*XXX stack*/
2229 NULL, &server_static_cbinfo, errstr);
2230 if (rc != OK) return rc;
2231 cbinfo = server_static_cbinfo;
2233 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
2236 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2237 were historically separated by underscores. So that I can use either form in my
2238 tests, and also for general convenience, we turn underscores into hyphens here.
2240 XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites()
2241 for TLS 1.3 . Since we do not call it at present we get the default list:
2242 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
2247 uschar * s = expciphers;
2248 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2249 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2250 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
2251 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
2252 cbinfo->server_cipher_list = expciphers;
2255 /* If this is a host for which certificate verification is mandatory or
2256 optional, set up appropriately. */
2258 tls_in.certificate_verified = FALSE;
2260 tls_in.dane_verified = FALSE;
2262 server_verify_callback_called = FALSE;
2264 if (verify_check_host(&tls_verify_hosts) == OK)
2266 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2267 FALSE, verify_callback_server, errstr);
2268 if (rc != OK) return rc;
2269 server_verify_optional = FALSE;
2271 else if (verify_check_host(&tls_try_verify_hosts) == OK)
2273 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
2274 TRUE, verify_callback_server, errstr);
2275 if (rc != OK) return rc;
2276 server_verify_optional = TRUE;
2279 /* Prepare for new connection */
2281 if (!(server_ssl = SSL_new(server_ctx)))
2282 return tls_error(US"SSL_new", NULL, NULL, errstr);
2284 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2286 * With the SSL_clear(), we get strange interoperability bugs with
2287 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2288 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2290 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2291 * session shutdown. In this case, we have a brand new object and there's no
2292 * obvious reason to immediately clear it. I'm guessing that this was
2293 * originally added because of incomplete initialisation which the clear fixed,
2294 * in some historic release.
2297 /* Set context and tell client to go ahead, except in the case of TLS startup
2298 on connection, where outputting anything now upsets the clients and tends to
2299 make them disconnect. We need to have an explicit fflush() here, to force out
2300 the response. Other smtp_printf() calls do not need it, because in non-TLS
2301 mode, the fflush() happens when smtp_getc() is called. */
2303 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2304 if (!tls_in.on_connect)
2306 smtp_printf("220 TLS go ahead\r\n", FALSE);
2310 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2311 that the OpenSSL library doesn't. */
2313 SSL_set_wfd(server_ssl, fileno(smtp_out));
2314 SSL_set_rfd(server_ssl, fileno(smtp_in));
2315 SSL_set_accept_state(server_ssl);
2317 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2319 sigalrm_seen = FALSE;
2320 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2321 rc = SSL_accept(server_ssl);
2326 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2330 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2331 ERR_clear_error(); /* Even success can leave errors in the stack. Seen with
2332 anon-authentication ciphersuite negociated. */
2334 /* TLS has been set up. Adjust the input functions to read via TLS,
2335 and initialize things. */
2337 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2339 tls_in.cipher = construct_cipher_name(server_ssl, &tls_in.bits);
2340 tls_in.cipher_stdname = cipher_stdname_ssl(server_ssl);
2345 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)))
2346 debug_printf("Shared ciphers: %s\n", buf);
2348 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2350 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2351 SSL_SESSION_print_keylog(bp, SSL_get_session(server_ssl));
2357 /* Record the certificate we presented */
2359 X509 * crt = SSL_get_certificate(server_ssl);
2360 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2363 /* Only used by the server-side tls (tls_in), including tls_getc.
2364 Client-side (tls_out) reads (seem to?) go via
2365 smtp_read_response()/ip_recv().
2366 Hence no need to duplicate for _in and _out.
2368 if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2369 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2370 ssl_xfer_eof = ssl_xfer_error = FALSE;
2372 receive_getc = tls_getc;
2373 receive_getbuf = tls_getbuf;
2374 receive_get_cache = tls_get_cache;
2375 receive_ungetc = tls_ungetc;
2376 receive_feof = tls_feof;
2377 receive_ferror = tls_ferror;
2378 receive_smtp_buffered = tls_smtp_buffered;
2380 tls_in.active.sock = fileno(smtp_out);
2381 tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */
2389 tls_client_basic_ctx_init(SSL_CTX * ctx,
2390 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2394 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2395 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2396 the specified host patterns if one of them is defined */
2398 if ( ( !ob->tls_verify_hosts
2399 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2401 || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK
2403 client_verify_optional = FALSE;
2404 else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK)
2405 client_verify_optional = TRUE;
2409 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2410 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2414 if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK)
2416 cbinfo->verify_cert_hostnames =
2418 string_domain_utf8_to_alabel(host->name, NULL);
2422 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2423 cbinfo->verify_cert_hostnames);
2431 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2434 const char * hostnames[2] = { CS host->name, NULL };
2437 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2438 return tls_error(US"hostnames load", host, NULL, errstr);
2440 for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
2441 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2442 ) if (rr->type == T_TLSA && rr->size > 3)
2444 const uschar * p = rr->data;
2445 uint8_t usage, selector, mtype;
2446 const char * mdname;
2450 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2451 if (usage != 2 && usage != 3) continue;
2458 default: continue; /* Only match-types 0, 1, 2 are supported */
2459 case 0: mdname = NULL; break;
2460 case 1: mdname = "sha256"; break;
2461 case 2: mdname = "sha512"; break;
2465 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2468 return tls_error(US"tlsa load", host, NULL, errstr);
2469 case 0: /* action not taken */
2473 tls_out.tlsa_usage |= 1<<usage;
2479 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2482 #endif /*SUPPORT_DANE*/
2486 /*************************************************
2487 * Start a TLS session in a client *
2488 *************************************************/
2490 /* Called from the smtp transport after STARTTLS has been accepted.
2493 cctx connection context
2494 conn_args connection details
2495 cookie datum for randomness; can be NULL
2496 tlsp record details of TLS channel configuration here; must be non-NULL
2497 errstr error string pointer
2499 Returns: TRUE for success with TLS session context set in connection context,
2504 tls_client_start(client_conn_ctx * cctx, smtp_connect_args * conn_args,
2505 void * cookie, tls_support * tlsp, uschar ** errstr)
2507 host_item * host = conn_args->host; /* for msgs and option-tests */
2508 transport_instance * tb = conn_args->tblock; /* always smtp or NULL */
2509 smtp_transport_options_block * ob = tb
2510 ? (smtp_transport_options_block *)tb->options_block
2511 : &smtp_transport_option_defaults;
2512 exim_openssl_client_tls_ctx * exim_client_ctx;
2513 uschar * expciphers;
2515 static uschar peerdn[256];
2517 #ifndef DISABLE_OCSP
2518 BOOL request_ocsp = FALSE;
2519 BOOL require_ocsp = FALSE;
2523 store_pool = POOL_PERM;
2524 exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx));
2525 exim_client_ctx->corked = NULL;
2529 tlsp->tlsa_usage = 0;
2532 #ifndef DISABLE_OCSP
2534 # ifdef SUPPORT_DANE
2535 if ( conn_args->dane
2536 && ob->hosts_request_ocsp[0] == '*'
2537 && ob->hosts_request_ocsp[1] == '\0'
2540 /* Unchanged from default. Use a safer one under DANE */
2541 request_ocsp = TRUE;
2542 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2543 " {= {4}{$tls_out_tlsa_usage}} } "
2549 verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK))
2550 request_ocsp = TRUE;
2552 # ifdef SUPPORT_DANE
2556 verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2560 rc = tls_init(&exim_client_ctx->ctx, host, NULL,
2561 ob->tls_certificate, ob->tls_privatekey,
2562 #ifndef DISABLE_OCSP
2563 (void *)(long)request_ocsp,
2565 cookie, &client_static_cbinfo, errstr);
2566 if (rc != OK) return FALSE;
2568 tlsp->certificate_verified = FALSE;
2569 client_verify_callback_called = FALSE;
2573 if (conn_args->dane)
2575 /* We fall back to tls_require_ciphers if unset, empty or forced failure, but
2576 other failures should be treated as problems. */
2577 if (ob->dane_require_tls_ciphers &&
2578 !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers",
2579 &expciphers, errstr))
2581 if (expciphers && *expciphers == '\0')
2586 !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2587 &expciphers, errstr))
2590 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2591 are separated by underscores. So that I can use either form in my tests, and
2592 also for general convenience, we turn underscores into hyphens here. */
2596 uschar *s = expciphers;
2597 while (*s) { if (*s == '_') *s = '-'; s++; }
2598 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2599 if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers))
2601 tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2607 if (conn_args->dane)
2609 SSL_CTX_set_verify(exim_client_ctx->ctx,
2610 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2611 verify_callback_client_dane);
2613 if (!DANESSL_library_init())
2615 tls_error(US"library init", host, NULL, errstr);
2618 if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0)
2620 tls_error(US"context init", host, NULL, errstr);
2628 if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob,
2629 client_static_cbinfo, errstr) != OK)
2632 if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx)))
2634 tls_error(US"SSL_new", host, NULL, errstr);
2637 SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx));
2638 SSL_set_fd(exim_client_ctx->ssl, cctx->sock);
2639 SSL_set_connect_state(exim_client_ctx->ssl);
2643 if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr))
2647 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2649 else if (!Ustrlen(tlsp->sni))
2653 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2654 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni);
2655 SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni);
2657 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2664 if (conn_args->dane)
2665 if (dane_tlsa_load(exim_client_ctx->ssl, host, &conn_args->tlsa_dnsa, errstr) != OK)
2669 #ifndef DISABLE_OCSP
2670 /* Request certificate status at connection-time. If the server
2671 does OCSP stapling we will get the callback (set in tls_init()) */
2672 # ifdef SUPPORT_DANE
2676 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2677 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2679 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2680 this means we avoid the OCSP request, we wasted the setup
2681 cost in tls_init(). */
2682 require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK;
2683 request_ocsp = require_ocsp
2684 || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK;
2691 SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp);
2692 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2693 tlsp->ocsp = OCSP_NOT_RESP;
2697 #ifndef DISABLE_EVENT
2698 client_static_cbinfo->event_action = tb ? tb->event_action : NULL;
2701 /* There doesn't seem to be a built-in timeout on connection. */
2703 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2704 sigalrm_seen = FALSE;
2705 ALARM(ob->command_timeout);
2706 rc = SSL_connect(exim_client_ctx->ssl);
2710 if (conn_args->dane)
2711 DANESSL_cleanup(exim_client_ctx->ssl);
2716 tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr);
2722 debug_printf("SSL_connect succeeded\n");
2723 #ifdef EXIM_HAVE_OPENSSL_KEYLOG
2725 BIO * bp = BIO_new_fp(debug_file, BIO_NOCLOSE);
2726 SSL_SESSION_print_keylog(bp, SSL_get_session(exim_client_ctx->ssl));
2732 peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn));
2734 tlsp->cipher = construct_cipher_name(exim_client_ctx->ssl, &tlsp->bits);
2735 tlsp->cipher_stdname = cipher_stdname_ssl(exim_client_ctx->ssl);
2737 /* Record the certificate we presented */
2739 X509 * crt = SSL_get_certificate(exim_client_ctx->ssl);
2740 tlsp->ourcert = crt ? X509_dup(crt) : NULL;
2743 tlsp->active.sock = cctx->sock;
2744 tlsp->active.tls_ctx = exim_client_ctx;
2745 cctx->tls_ctx = exim_client_ctx;
2754 tls_refill(unsigned lim)
2759 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2760 ssl_xfer_buffer, ssl_xfer_buffer_size);
2762 if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout);
2763 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2764 MIN(ssl_xfer_buffer_size, lim));
2765 error = SSL_get_error(server_ssl, inbytes);
2766 if (smtp_receive_timeout > 0) ALARM_CLR(0);
2768 if (had_command_timeout) /* set by signal handler */
2769 smtp_command_timeout_exit(); /* does not return */
2770 if (had_command_sigterm)
2771 smtp_command_sigterm_exit();
2772 if (had_data_timeout)
2773 smtp_data_timeout_exit();
2774 if (had_data_sigint)
2775 smtp_data_sigint_exit();
2777 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2778 closed down, not that the socket itself has been closed down. Revert to
2779 non-SSL handling. */
2783 case SSL_ERROR_NONE:
2786 case SSL_ERROR_ZERO_RETURN:
2787 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2789 receive_getc = smtp_getc;
2790 receive_getbuf = smtp_getbuf;
2791 receive_get_cache = smtp_get_cache;
2792 receive_ungetc = smtp_ungetc;
2793 receive_feof = smtp_feof;
2794 receive_ferror = smtp_ferror;
2795 receive_smtp_buffered = smtp_buffered;
2797 if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN)
2798 SSL_shutdown(server_ssl);
2800 #ifndef DISABLE_OCSP
2801 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
2802 server_static_cbinfo->verify_stack = NULL;
2804 SSL_free(server_ssl);
2805 SSL_CTX_free(server_ctx);
2808 tls_in.active.sock = -1;
2809 tls_in.active.tls_ctx = NULL;
2811 tls_in.cipher = NULL;
2812 tls_in.peerdn = NULL;
2817 /* Handle genuine errors */
2819 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
2820 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2821 ssl_xfer_error = TRUE;
2825 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2826 DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL)
2827 debug_printf(" - syscall %s\n", strerror(errno));
2828 ssl_xfer_error = TRUE;
2832 #ifndef DISABLE_DKIM
2833 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2835 ssl_xfer_buffer_hwm = inbytes;
2836 ssl_xfer_buffer_lwm = 0;
2841 /*************************************************
2842 * TLS version of getc *
2843 *************************************************/
2845 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2846 it refills the buffer via the SSL reading function.
2848 Arguments: lim Maximum amount to read/buffer
2849 Returns: the next character or EOF
2851 Only used by the server-side TLS.
2855 tls_getc(unsigned lim)
2857 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2858 if (!tls_refill(lim))
2859 return ssl_xfer_error ? EOF : smtp_getc(lim);
2861 /* Something in the buffer; return next uschar */
2863 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2867 tls_getbuf(unsigned * len)
2872 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2873 if (!tls_refill(*len))
2875 if (!ssl_xfer_error) return smtp_getbuf(len);
2880 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2882 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2883 ssl_xfer_buffer_lwm += size;
2892 #ifndef DISABLE_DKIM
2893 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2895 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2901 tls_could_read(void)
2903 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2907 /*************************************************
2908 * Read bytes from TLS channel *
2909 *************************************************/
2913 ct_ctx client context pointer, or NULL for the one global server context
2917 Returns: the number of bytes read
2918 -1 after a failed read, including EOF
2920 Only used by the client-side TLS.
2924 tls_read(void * ct_ctx, uschar *buff, size_t len)
2926 SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2930 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2931 buff, (unsigned int)len);
2933 inbytes = SSL_read(ssl, CS buff, len);
2934 error = SSL_get_error(ssl, inbytes);
2936 if (error == SSL_ERROR_ZERO_RETURN)
2938 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2941 else if (error != SSL_ERROR_NONE)
2951 /*************************************************
2952 * Write bytes down TLS channel *
2953 *************************************************/
2957 ct_ctx client context pointer, or NULL for the one global server context
2960 more further data expected soon
2962 Returns: the number of bytes after a successful write,
2963 -1 after a failed write
2965 Used by both server-side and client-side TLS.
2969 tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
2972 int outbytes, error;
2974 ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
2975 static gstring * server_corked = NULL;
2976 gstring ** corkedp = ct_ctx
2977 ? &((exim_openssl_client_tls_ctx *)ct_ctx)->corked : &server_corked;
2978 gstring * corked = *corkedp;
2980 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2981 buff, (unsigned long)len, more ? ", more" : "");
2983 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2984 "more" is notified. This hack is only ok if small amounts are involved AND only
2985 one stream does it, in one context (i.e. no store reset). Currently it is used
2986 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only.
2987 We support callouts done by the server process by using a separate client
2988 context for the stashed information. */
2989 /* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's
2990 a store reset there, so use POOL_PERM. */
2991 /* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */
2993 if ((more || corked))
2995 #ifdef EXPERIMENTAL_PIPE_CONNECT
2996 int save_pool = store_pool;
2997 store_pool = POOL_PERM;
3000 corked = string_catn(corked, buff, len);
3002 #ifdef EXPERIMENTAL_PIPE_CONNECT
3003 store_pool = save_pool;
3011 buff = CUS corked->s;
3016 for (int left = len; left > 0;)
3018 DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left);
3019 outbytes = SSL_write(ssl, CS buff, left);
3020 error = SSL_get_error(ssl, outbytes);
3021 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
3025 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3026 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
3029 case SSL_ERROR_NONE:
3034 case SSL_ERROR_ZERO_RETURN:
3035 log_write(0, LOG_MAIN, "SSL channel closed on write");
3038 case SSL_ERROR_SYSCALL:
3039 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
3040 sender_fullhost ? sender_fullhost : US"<unknown>",
3045 log_write(0, LOG_MAIN, "SSL_write error %d", error);
3054 /*************************************************
3055 * Close down a TLS session *
3056 *************************************************/
3058 /* This is also called from within a delivery subprocess forked from the
3059 daemon, to shut down the TLS library, without actually doing a shutdown (which
3060 would tamper with the SSL session in the parent process).
3063 ct_ctx client TLS context pointer, or NULL for the one global server context
3064 shutdown 1 if TLS close-alert is to be sent,
3065 2 if also response to be waited for
3069 Used by both server-side and client-side TLS.
3073 tls_close(void * ct_ctx, int shutdown)
3075 exim_openssl_client_tls_ctx * o_ctx = ct_ctx;
3076 SSL_CTX **ctxp = o_ctx ? &o_ctx->ctx : &server_ctx;
3077 SSL **sslp = o_ctx ? &o_ctx->ssl : &server_ssl;
3078 int *fdp = o_ctx ? &tls_out.active.sock : &tls_in.active.sock;
3080 if (*fdp < 0) return; /* TLS was not active */
3085 DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n",
3086 shutdown > 1 ? " (with response-wait)" : "");
3088 if ( (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */
3092 rc = SSL_shutdown(*sslp); /* wait for response */
3096 if (rc < 0) DEBUG(D_tls)
3098 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3099 debug_printf("SSL_shutdown: %s\n", ssl_errstring);
3103 #ifndef DISABLE_OCSP
3104 if (!o_ctx) /* server side */
3106 sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free);
3107 server_static_cbinfo->verify_stack = NULL;
3111 SSL_CTX_free(*ctxp);
3121 /*************************************************
3122 * Let tls_require_ciphers be checked at startup *
3123 *************************************************/
3125 /* The tls_require_ciphers option, if set, must be something which the
3128 Returns: NULL on success, or error message
3132 tls_validate_require_cipher(void)
3135 uschar *s, *expciphers, *err;
3137 /* this duplicates from tls_init(), we need a better "init just global
3138 state, for no specific purpose" singleton function of our own */
3140 #ifdef EXIM_NEED_OPENSSL_INIT
3141 SSL_load_error_strings();
3142 OpenSSL_add_ssl_algorithms();
3144 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
3145 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
3146 list of available digests. */
3147 EVP_add_digest(EVP_sha256());
3150 if (!(tls_require_ciphers && *tls_require_ciphers))
3153 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
3155 return US"failed to expand tls_require_ciphers";
3157 if (!(expciphers && *expciphers))
3160 /* normalisation ripped from above */
3162 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
3166 #ifdef EXIM_HAVE_OPENSSL_TLS_METHOD
3167 if (!(ctx = SSL_CTX_new(TLS_server_method())))
3169 if (!(ctx = SSL_CTX_new(SSLv23_server_method())))
3172 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3173 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
3177 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
3179 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
3181 ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
3182 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
3183 expciphers, ssl_errstring);
3194 /*************************************************
3195 * Report the library versions. *
3196 *************************************************/
3198 /* There have historically been some issues with binary compatibility in
3199 OpenSSL libraries; if Exim (like many other applications) is built against
3200 one version of OpenSSL but the run-time linker picks up another version,
3201 it can result in serious failures, including crashing with a SIGSEGV. So
3202 report the version found by the compiler and the run-time version.
3204 Note: some OS vendors backport security fixes without changing the version
3205 number/string, and the version date remains unchanged. The _build_ date
3206 will change, so we can more usefully assist with version diagnosis by also
3207 reporting the build date.
3209 Arguments: a FILE* to print the results to
3214 tls_version_report(FILE *f)
3216 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
3219 OPENSSL_VERSION_TEXT,
3220 SSLeay_version(SSLEAY_VERSION),
3221 SSLeay_version(SSLEAY_BUILT_ON));
3222 /* third line is 38 characters for the %s and the line is 73 chars long;
3223 the OpenSSL output includes a "built on: " prefix already. */
3229 /*************************************************
3230 * Random number generation *
3231 *************************************************/
3233 /* Pseudo-random number generation. The result is not expected to be
3234 cryptographically strong but not so weak that someone will shoot themselves
3235 in the foot using it as a nonce in input in some email header scheme or
3236 whatever weirdness they'll twist this into. The result should handle fork()
3237 and avoid repeating sequences. OpenSSL handles that for us.
3241 Returns a random number in range [0, max-1]
3245 vaguely_random_number(int max)
3249 static pid_t pidlast = 0;
3251 uschar smallbuf[sizeof(r)];
3257 if (pidnow != pidlast)
3259 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
3260 is unique for each thread", this doesn't apparently apply across processes,
3261 so our own warning from vaguely_random_number_fallback() applies here too.
3262 Fix per PostgreSQL. */
3268 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
3272 gettimeofday(&r.tv, NULL);
3275 RAND_seed(US (&r), sizeof(r));
3277 /* We're after pseudo-random, not random; if we still don't have enough data
3278 in the internal PRNG then our options are limited. We could sleep and hope
3279 for entropy to come along (prayer technique) but if the system is so depleted
3280 in the first place then something is likely to just keep taking it. Instead,
3281 we'll just take whatever little bit of pseudo-random we can still manage to
3284 needed_len = sizeof(r);
3285 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
3286 asked for a number less than 10. */
3287 for (r = max, i = 0; r; ++i)
3293 #ifdef EXIM_HAVE_RAND_PSEUDO
3294 /* We do not care if crypto-strong */
3295 i = RAND_pseudo_bytes(smallbuf, needed_len);
3297 i = RAND_bytes(smallbuf, needed_len);
3303 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
3304 return vaguely_random_number_fallback(max);
3308 for (uschar * p = smallbuf; needed_len; --needed_len, ++p)
3311 /* We don't particularly care about weighted results; if someone wants
3312 smooth distribution and cares enough then they should submit a patch then. */
3319 /*************************************************
3320 * OpenSSL option parse *
3321 *************************************************/
3323 /* Parse one option for tls_openssl_options_parse below
3326 name one option name
3327 value place to store a value for it
3328 Returns success or failure in parsing
3334 tls_openssl_one_option_parse(uschar *name, long *value)
3337 int last = exim_openssl_options_size;
3338 while (last > first)
3340 int middle = (first + last)/2;
3341 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3344 *value = exim_openssl_options[middle].value;
3358 /*************************************************
3359 * OpenSSL option parsing logic *
3360 *************************************************/
3362 /* OpenSSL has a number of compatibility options which an administrator might
3363 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3364 we look like log_selector.
3367 option_spec the administrator-supplied string of options
3368 results ptr to long storage for the options bitmap
3369 Returns success or failure
3373 tls_openssl_options_parse(uschar *option_spec, long *results)
3378 BOOL adding, item_parsed;
3380 result = SSL_OP_NO_TICKET;
3381 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3382 * from default because it increases BEAST susceptibility. */
3383 #ifdef SSL_OP_NO_SSLv2
3384 result |= SSL_OP_NO_SSLv2;
3386 #ifdef SSL_OP_SINGLE_DH_USE
3387 result |= SSL_OP_SINGLE_DH_USE;
3396 for (uschar * s = option_spec; *s != '\0'; /**/)
3398 while (isspace(*s)) ++s;
3401 if (*s != '+' && *s != '-')
3403 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3404 "+ or - expected but found \"%s\"\n", s);
3407 adding = *s++ == '+';
3408 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3411 item_parsed = tls_openssl_one_option_parse(s, &item);
3415 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3418 DEBUG(D_tls) debug_printf("openssl option, %s %8lx: %lx (%s)\n",
3419 adding ? "adding to " : "removing from", result, item, s);
3431 #endif /*!MACRO_PREDEF*/
3434 /* End of tls-openssl.c */