1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2017 */
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>
31 #ifdef EXPERIMENTAL_DANE
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
58 * X509_check_host provides sane certificate hostname checking, but was added
59 * to OpenSSL late, after other projects forked off the code-base. So in
60 * addition to guarding against the base version number, beware that LibreSSL
61 * does not (at this time) support this function.
63 * If LibreSSL gains a different API, perhaps via libtls, then we'll probably
64 * opt to disentangle and ask a LibreSSL user to provide glue for a third
65 * crypto provider for libtls instead of continuing to tie the OpenSSL glue
66 * into even twistier knots. If LibreSSL gains the same API, we can just
67 * change this guard and punt the issue for a while longer.
69 #ifndef LIBRESSL_VERSION_NUMBER
70 # if OPENSSL_VERSION_NUMBER >= 0x010100000L
71 # define EXIM_HAVE_OPENSSL_CHECKHOST
72 # define EXIM_HAVE_OPENSSL_DH_BITS
74 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
75 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
76 # define EXIM_HAVE_OPENSSL_CHECKHOST
80 #if !defined(LIBRESSL_VERSION_NUMBER) \
81 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
82 # if !defined(OPENSSL_NO_ECDH)
83 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
84 # define EXIM_HAVE_ECDH
86 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
87 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
92 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
93 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
97 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
98 # include <openssl/x509v3.h>
101 /* Structure for collecting random data for seeding. */
103 typedef struct randstuff {
108 /* Local static variables */
110 static BOOL client_verify_callback_called = FALSE;
111 static BOOL server_verify_callback_called = FALSE;
112 static const uschar *sid_ctx = US"exim";
114 /* We have three different contexts to care about.
116 Simple case: client, `client_ctx`
117 As a client, we can be doing a callout or cut-through delivery while receiving
118 a message. So we have a client context, which should have options initialised
119 from the SMTP Transport.
122 There are two cases: with and without ServerNameIndication from the client.
123 Given TLS SNI, we can be using different keys, certs and various other
124 configuration settings, because they're re-expanded with $tls_sni set. This
125 allows vhosting with TLS. This SNI is sent in the handshake.
126 A client might not send SNI, so we need a fallback, and an initial setup too.
127 So as a server, we start out using `server_ctx`.
128 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
129 `server_sni` from `server_ctx` and then initialise settings by re-expanding
133 static SSL_CTX *client_ctx = NULL;
134 static SSL_CTX *server_ctx = NULL;
135 static SSL *client_ssl = NULL;
136 static SSL *server_ssl = NULL;
138 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
139 static SSL_CTX *server_sni = NULL;
142 static char ssl_errstring[256];
144 static int ssl_session_timeout = 200;
145 static BOOL client_verify_optional = FALSE;
146 static BOOL server_verify_optional = FALSE;
148 static BOOL reexpand_tls_files_for_sni = FALSE;
151 typedef struct tls_ext_ctx_cb {
156 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
160 uschar *file_expanded;
161 OCSP_RESPONSE *response;
164 X509_STORE *verify_store; /* non-null if status requested */
165 BOOL verify_required;
170 /* these are cached from first expand */
171 uschar *server_cipher_list;
172 /* only passed down to tls_error: */
174 const uschar * verify_cert_hostnames;
175 #ifndef DISABLE_EVENT
176 uschar * event_action;
180 /* should figure out a cleanup of API to handle state preserved per
181 implementation, for various reasons, which can be void * in the APIs.
182 For now, we hack around it. */
183 tls_ext_ctx_cb *client_static_cbinfo = NULL;
184 tls_ext_ctx_cb *server_static_cbinfo = NULL;
187 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
188 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
191 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
192 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
195 static int tls_server_stapling_cb(SSL *s, void *arg);
199 /*************************************************
201 *************************************************/
203 /* Called from lots of places when errors occur before actually starting to do
204 the TLS handshake, that is, while the session is still in clear. Always returns
205 DEFER for a server and FAIL for a client so that most calls can use "return
206 tls_error(...)" to do this processing and then give an appropriate return. A
207 single function is used for both server and client, because it is called from
208 some shared functions.
211 prefix text to include in the logged error
212 host NULL if setting up a server;
213 the connected host if setting up a client
214 msg error message or NULL if we should ask OpenSSL
215 errstr pointer to output error message
217 Returns: OK/DEFER/FAIL
221 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
225 ERR_error_string(ERR_get_error(), ssl_errstring);
226 msg = US ssl_errstring;
229 if (errstr) *errstr = string_sprintf("(%s): %s", prefix, msg);
230 return host ? FAIL : DEFER;
235 /*************************************************
236 * Callback to generate RSA key *
237 *************************************************/
241 s SSL connection (not used)
245 Returns: pointer to generated key
249 rsa_callback(SSL *s, int export, int keylength)
252 #ifdef EXIM_HAVE_RSA_GENKEY_EX
253 BIGNUM *bn = BN_new();
256 export = export; /* Shut picky compilers up */
257 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
259 #ifdef EXIM_HAVE_RSA_GENKEY_EX
260 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
261 || !(rsa_key = RSA_new())
262 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
265 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
269 ERR_error_string(ERR_get_error(), ssl_errstring);
270 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
282 x509_store_dump_cert_s_names(X509_STORE * store)
284 STACK_OF(X509_OBJECT) * roots= store->objs;
286 static uschar name[256];
288 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
290 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
291 if(tmp_obj->type == X509_LU_X509)
293 X509 * current_cert= tmp_obj->data.x509;
294 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
295 name[sizeof(name)-1] = '\0';
296 debug_printf(" %s\n", name);
304 #ifndef DISABLE_EVENT
306 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
307 BOOL *calledp, const BOOL *optionalp, const uschar * what)
313 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
316 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
317 old_cert = tlsp->peercert;
318 tlsp->peercert = X509_dup(cert);
319 /* NB we do not bother setting peerdn */
320 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
322 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
323 "depth=%d cert=%s: %s",
324 tlsp == &tls_out ? deliver_host_address : sender_host_address,
325 what, depth, dn, yield);
329 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
330 return 1; /* reject (leaving peercert set) */
332 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
333 "(host in tls_try_verify_hosts)\n");
335 X509_free(tlsp->peercert);
336 tlsp->peercert = old_cert;
342 /*************************************************
343 * Callback for verification *
344 *************************************************/
346 /* The SSL library does certificate verification if set up to do so. This
347 callback has the current yes/no state is in "state". If verification succeeded,
348 we set the certificate-verified flag. If verification failed, what happens
349 depends on whether the client is required to present a verifiable certificate
352 If verification is optional, we change the state to yes, but still log the
353 verification error. For some reason (it really would help to have proper
354 documentation of OpenSSL), this callback function then gets called again, this
355 time with state = 1. We must take care not to set the private verified flag on
356 the second time through.
358 Note: this function is not called if the client fails to present a certificate
359 when asked. We get here only if a certificate has been received. Handling of
360 optional verification for this case is done when requesting SSL to verify, by
361 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
363 May be called multiple times for different issues with a certificate, even
364 for a given "depth" in the certificate chain.
367 preverify_ok current yes/no state as 1/0
368 x509ctx certificate information.
369 tlsp per-direction (client vs. server) support data
370 calledp has-been-called flag
371 optionalp verification-is-optional flag
373 Returns: 0 if verification should fail, otherwise 1
377 verify_callback(int preverify_ok, X509_STORE_CTX *x509ctx,
378 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
380 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
381 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
384 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
385 dn[sizeof(dn)-1] = '\0';
387 if (preverify_ok == 0)
389 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
390 *verify_mode, sender_host_address)
392 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
393 tlsp == &tls_out ? deliver_host_address : sender_host_address,
395 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
400 tlsp->peercert = X509_dup(cert); /* record failing cert */
401 return 0; /* reject */
403 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
404 "tls_try_verify_hosts)\n");
409 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
411 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
412 { /* client, wanting stapling */
413 /* Add the server cert's signing chain as the one
414 for the verification of the OCSP stapled information. */
416 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
419 sk_X509_push(client_static_cbinfo->verify_stack, cert);
422 #ifndef DISABLE_EVENT
423 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
424 return 0; /* reject, with peercert set */
429 const uschar * verify_cert_hostnames;
431 if ( tlsp == &tls_out
432 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
433 /* client, wanting hostname check */
436 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
437 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
438 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
440 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
441 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
444 const uschar * list = verify_cert_hostnames;
447 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
448 if ((rc = X509_check_host(cert, CCS name, 0,
449 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
450 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
455 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
456 tlsp == &tls_out ? deliver_host_address : sender_host_address);
463 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
466 uschar * extra = verify_mode
467 ? string_sprintf(" (during %c-verify for [%s])",
468 *verify_mode, sender_host_address)
470 log_write(0, LOG_MAIN,
471 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
472 tlsp == &tls_out ? deliver_host_address : sender_host_address,
473 extra, dn, verify_cert_hostnames);
478 tlsp->peercert = X509_dup(cert); /* record failing cert */
479 return 0; /* reject */
481 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
482 "tls_try_verify_hosts)\n");
486 #ifndef DISABLE_EVENT
487 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
488 return 0; /* reject, with peercert set */
491 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
492 *calledp ? "" : " authenticated", dn);
493 if (!*calledp) tlsp->certificate_verified = TRUE;
497 return 1; /* accept, at least for this level */
501 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
503 return verify_callback(preverify_ok, x509ctx, &tls_out,
504 &client_verify_callback_called, &client_verify_optional);
508 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
510 return verify_callback(preverify_ok, x509ctx, &tls_in,
511 &server_verify_callback_called, &server_verify_optional);
515 #ifdef EXPERIMENTAL_DANE
517 /* This gets called *by* the dane library verify callback, which interposes
521 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
523 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
525 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
526 #ifndef DISABLE_EVENT
527 BOOL dummy_called, optional = FALSE;
530 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
531 dn[sizeof(dn)-1] = '\0';
533 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
534 preverify_ok ? "ok":"BAD", depth, dn);
536 #ifndef DISABLE_EVENT
537 if (verify_event(&tls_out, cert, depth, dn,
538 &dummy_called, &optional, US"DANE"))
539 return 0; /* reject, with peercert set */
542 if (preverify_ok == 1)
543 tls_out.dane_verified =
544 tls_out.certificate_verified = TRUE;
547 int err = X509_STORE_CTX_get_error(x509ctx);
549 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
550 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
556 #endif /*EXPERIMENTAL_DANE*/
559 /*************************************************
560 * Information callback *
561 *************************************************/
563 /* The SSL library functions call this from time to time to indicate what they
564 are doing. We copy the string to the debugging output when TLS debugging has
576 info_callback(SSL *s, int where, int ret)
580 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
585 /*************************************************
586 * Initialize for DH *
587 *************************************************/
589 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
592 sctx The current SSL CTX (inbound or outbound)
593 dhparam DH parameter file or fixed parameter identity string
594 host connected host, if client; NULL if server
595 errstr error string pointer
597 Returns: TRUE if OK (nothing to set up, or setup worked)
601 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
609 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
612 if (!dhexpanded || !*dhexpanded)
613 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
614 else if (dhexpanded[0] == '/')
616 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
618 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
619 host, US strerror(errno), errstr);
625 if (Ustrcmp(dhexpanded, "none") == 0)
627 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
631 if (!(pem = std_dh_prime_named(dhexpanded)))
633 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
634 host, US strerror(errno), errstr);
637 bio = BIO_new_mem_buf(CS pem, -1);
640 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
643 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
648 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
649 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
650 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
651 * If someone wants to dance at the edge, then they can raise the limit or use
652 * current libraries. */
653 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
654 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
655 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
656 dh_bitsize = DH_bits(dh);
658 dh_bitsize = 8 * DH_size(dh);
661 /* Even if it is larger, we silently return success rather than cause things
662 * to fail out, so that a too-large DH will not knock out all TLS; it's a
663 * debatable choice. */
664 if (dh_bitsize > tls_dh_max_bits)
667 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
668 dh_bitsize, tls_dh_max_bits);
672 SSL_CTX_set_tmp_dh(sctx, dh);
674 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
675 dhexpanded ? dhexpanded : US"default", dh_bitsize);
687 /*************************************************
688 * Initialize for ECDH *
689 *************************************************/
691 /* Load parameters for ECDH encryption.
693 For now, we stick to NIST P-256 because: it's simple and easy to configure;
694 it avoids any patent issues that might bite redistributors; despite events in
695 the news and concerns over curve choices, we're not cryptographers, we're not
696 pretending to be, and this is "good enough" to be better than no support,
697 protecting against most adversaries. Given another year or two, there might
698 be sufficient clarity about a "right" way forward to let us make an informed
699 decision, instead of a knee-jerk reaction.
701 Longer-term, we should look at supporting both various named curves and
702 external files generated with "openssl ecparam", much as we do for init_dh().
703 We should also support "none" as a value, to explicitly avoid initialisation.
708 sctx The current SSL CTX (inbound or outbound)
709 host connected host, if client; NULL if server
710 errstr error string pointer
712 Returns: TRUE if OK (nothing to set up, or setup worked)
716 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
718 #ifdef OPENSSL_NO_ECDH
727 if (host) /* No ECDH setup for clients, only for servers */
730 # ifndef EXIM_HAVE_ECDH
732 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
736 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
738 if (!exp_curve || !*exp_curve)
741 /* "auto" needs to be handled carefully.
742 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
743 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
744 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
745 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
746 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
748 if (Ustrcmp(exp_curve, "auto") == 0)
750 #if OPENSSL_VERSION_NUMBER < 0x10002000L
751 DEBUG(D_tls) debug_printf(
752 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
753 exp_curve = US"prime256v1";
755 # if defined SSL_CTRL_SET_ECDH_AUTO
756 DEBUG(D_tls) debug_printf(
757 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
758 SSL_CTX_set_ecdh_auto(sctx, 1);
761 DEBUG(D_tls) debug_printf(
762 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
768 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
769 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
770 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
771 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
775 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
780 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
782 tls_error(US"Unable to create ec curve", host, NULL, errstr);
786 /* The "tmp" in the name here refers to setting a temporary key
787 not to the stability of the interface. */
789 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
790 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
792 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
797 # endif /*EXIM_HAVE_ECDH*/
798 #endif /*OPENSSL_NO_ECDH*/
805 /*************************************************
806 * Load OCSP information into state *
807 *************************************************/
808 /* Called to load the server OCSP response from the given file into memory, once
809 caller has determined this is needed. Checks validity. Debugs a message
812 ASSUMES: single response, for single cert.
815 sctx the SSL_CTX* to update
816 cbinfo various parts of session state
817 expanded the filename putatively holding an OCSP response
822 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
825 OCSP_RESPONSE * resp;
826 OCSP_BASICRESP * basic_response;
827 OCSP_SINGLERESP * single_response;
828 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
830 unsigned long verify_flags;
831 int status, reason, i;
833 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
834 if (cbinfo->u_ocsp.server.response)
836 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
837 cbinfo->u_ocsp.server.response = NULL;
840 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
842 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
843 cbinfo->u_ocsp.server.file_expanded);
847 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
851 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
855 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
857 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
858 OCSP_response_status_str(status), status);
862 if (!(basic_response = OCSP_response_get1_basic(resp)))
865 debug_printf("OCSP response parse error: unable to extract basic response.\n");
869 sk = cbinfo->verify_stack;
870 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
872 /* May need to expose ability to adjust those flags?
873 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
874 OCSP_TRUSTOTHER OCSP_NOINTERN */
876 /* This does a full verify on the OCSP proof before we load it for serving
877 up; possibly overkill - just date-checks might be nice enough.
879 OCSP_basic_verify takes a "store" arg, but does not
880 use it for the chain verification, which is all we do
881 when OCSP_NOVERIFY is set. The content from the wire
882 "basic_response" and a cert-stack "sk" are all that is used.
884 We have a stack, loaded in setup_certs() if tls_verify_certificates
885 was a file (not a directory, or "system"). It is unfortunate we
886 cannot used the connection context store, as that would neatly
887 handle the "system" case too, but there seems to be no library
888 function for getting a stack from a store.
889 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
890 We do not free the stack since it could be needed a second time for
893 Separately we might try to replace using OCSP_basic_verify() - which seems to not
894 be a public interface into the OpenSSL library (there's no manual entry) -
895 But what with? We also use OCSP_basic_verify in the client stapling callback.
896 And there we NEED it; we must verify that status... unless the
897 library does it for us anyway? */
899 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
903 ERR_error_string(ERR_get_error(), ssl_errstring);
904 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
909 /* Here's the simplifying assumption: there's only one response, for the
910 one certificate we use, and nothing for anything else in a chain. If this
911 proves false, we need to extract a cert id from our issued cert
912 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
913 right cert in the stack and then calls OCSP_single_get0_status()).
915 I'm hoping to avoid reworking a bunch more of how we handle state here. */
917 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
920 debug_printf("Unable to get first response from OCSP basic response.\n");
924 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
925 if (status != V_OCSP_CERTSTATUS_GOOD)
927 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
928 OCSP_cert_status_str(status), status,
929 OCSP_crl_reason_str(reason), reason);
933 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
935 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
940 cbinfo->u_ocsp.server.response = resp;
944 if (running_in_test_harness)
946 extern char ** environ;
948 if (environ) for (p = USS environ; *p != NULL; p++)
949 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
951 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
952 goto supply_response;
957 #endif /*!DISABLE_OCSP*/
962 /* Create and install a selfsigned certificate, for use in server mode */
965 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
973 where = US"allocating pkey";
974 if (!(pkey = EVP_PKEY_new()))
977 where = US"allocating cert";
978 if (!(x509 = X509_new()))
981 where = US"generating pkey";
982 if (!(rsa = rsa_callback(NULL, 0, 1024)))
985 where = US"assigning pkey";
986 if (!EVP_PKEY_assign_RSA(pkey, rsa))
989 X509_set_version(x509, 2); /* N+1 - version 3 */
990 ASN1_INTEGER_set(X509_get_serialNumber(x509), 0);
991 X509_gmtime_adj(X509_get_notBefore(x509), 0);
992 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
993 X509_set_pubkey(x509, pkey);
995 name = X509_get_subject_name(x509);
996 X509_NAME_add_entry_by_txt(name, "C",
997 MBSTRING_ASC, CUS "UK", -1, -1, 0);
998 X509_NAME_add_entry_by_txt(name, "O",
999 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1000 X509_NAME_add_entry_by_txt(name, "CN",
1001 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1002 X509_set_issuer_name(x509, name);
1004 where = US"signing cert";
1005 if (!X509_sign(x509, pkey, EVP_md5()))
1008 where = US"installing selfsign cert";
1009 if (!SSL_CTX_use_certificate(sctx, x509))
1012 where = US"installing selfsign key";
1013 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1019 (void) tls_error(where, NULL, NULL, errstr);
1020 if (x509) X509_free(x509);
1021 if (pkey) EVP_PKEY_free(pkey);
1029 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1032 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1033 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1034 return tls_error(string_sprintf(
1035 "SSL_CTX_use_certificate_chain_file file=%s", file),
1036 cbinfo->host, NULL, errstr);
1041 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1044 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1045 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1046 return tls_error(string_sprintf(
1047 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1052 /*************************************************
1053 * Expand key and cert file specs *
1054 *************************************************/
1056 /* Called once during tls_init and possibly again during TLS setup, for a
1057 new context, if Server Name Indication was used and tls_sni was seen in
1058 the certificate string.
1061 sctx the SSL_CTX* to update
1062 cbinfo various parts of session state
1063 errstr error string pointer
1065 Returns: OK/DEFER/FAIL
1069 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1074 if (!cbinfo->certificate)
1076 if (!cbinfo->is_server) /* client */
1079 if (tls_install_selfsign(sctx, errstr) != OK)
1086 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1087 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1088 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1090 reexpand_tls_files_for_sni = TRUE;
1092 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1096 if (cbinfo->is_server)
1098 const uschar * file_list = expanded;
1102 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1103 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1106 else /* would there ever be a need for multiple client certs? */
1107 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1110 if (cbinfo->privatekey != NULL &&
1111 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1114 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1115 of the expansion is an empty string, ignore it also, and assume the private
1116 key is in the same file as the certificate. */
1118 if (expanded && *expanded)
1119 if (cbinfo->is_server)
1121 const uschar * file_list = expanded;
1125 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1126 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1129 else /* would there ever be a need for multiple client certs? */
1130 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1134 #ifndef DISABLE_OCSP
1135 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1137 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1140 if (expanded && *expanded)
1142 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1143 if ( cbinfo->u_ocsp.server.file_expanded
1144 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1146 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1149 ocsp_load_response(sctx, cbinfo, expanded);
1160 /*************************************************
1161 * Callback to handle SNI *
1162 *************************************************/
1164 /* Called when acting as server during the TLS session setup if a Server Name
1165 Indication extension was sent by the client.
1167 API documentation is OpenSSL s_server.c implementation.
1170 s SSL* of the current session
1171 ad unknown (part of OpenSSL API) (unused)
1172 arg Callback of "our" registered data
1174 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1177 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1179 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1181 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1182 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1184 int old_pool = store_pool;
1185 uschar * dummy_errstr;
1188 return SSL_TLSEXT_ERR_OK;
1190 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1191 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1193 /* Make the extension value available for expansion */
1194 store_pool = POOL_PERM;
1195 tls_in.sni = string_copy(US servername);
1196 store_pool = old_pool;
1198 if (!reexpand_tls_files_for_sni)
1199 return SSL_TLSEXT_ERR_OK;
1201 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1202 not confident that memcpy wouldn't break some internal reference counting.
1203 Especially since there's a references struct member, which would be off. */
1205 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1207 ERR_error_string(ERR_get_error(), ssl_errstring);
1208 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1209 return SSL_TLSEXT_ERR_NOACK;
1212 /* Not sure how many of these are actually needed, since SSL object
1213 already exists. Might even need this selfsame callback, for reneg? */
1215 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1216 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1217 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1218 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1219 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1220 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1222 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1223 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1225 return SSL_TLSEXT_ERR_NOACK;
1227 if (cbinfo->server_cipher_list)
1228 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
1229 #ifndef DISABLE_OCSP
1230 if (cbinfo->u_ocsp.server.file)
1232 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1233 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1237 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1238 verify_callback_server, &dummy_errstr)) != OK)
1239 return SSL_TLSEXT_ERR_NOACK;
1241 /* do this after setup_certs, because this can require the certs for verifying
1242 OCSP information. */
1243 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1244 return SSL_TLSEXT_ERR_NOACK;
1246 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1247 SSL_set_SSL_CTX(s, server_sni);
1249 return SSL_TLSEXT_ERR_OK;
1251 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1256 #ifndef DISABLE_OCSP
1258 /*************************************************
1259 * Callback to handle OCSP Stapling *
1260 *************************************************/
1262 /* Called when acting as server during the TLS session setup if the client
1263 requests OCSP information with a Certificate Status Request.
1265 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1271 tls_server_stapling_cb(SSL *s, void *arg)
1273 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1274 uschar *response_der;
1275 int response_der_len;
1278 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1279 cbinfo->u_ocsp.server.response ? "have" : "lack");
1281 tls_in.ocsp = OCSP_NOT_RESP;
1282 if (!cbinfo->u_ocsp.server.response)
1283 return SSL_TLSEXT_ERR_NOACK;
1285 response_der = NULL;
1286 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
1288 if (response_der_len <= 0)
1289 return SSL_TLSEXT_ERR_NOACK;
1291 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1292 tls_in.ocsp = OCSP_VFIED;
1293 return SSL_TLSEXT_ERR_OK;
1298 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1300 BIO_printf(bp, "\t%s: ", str);
1301 ASN1_GENERALIZEDTIME_print(bp, time);
1306 tls_client_stapling_cb(SSL *s, void *arg)
1308 tls_ext_ctx_cb * cbinfo = arg;
1309 const unsigned char * p;
1311 OCSP_RESPONSE * rsp;
1312 OCSP_BASICRESP * bs;
1315 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1316 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1319 /* Expect this when we requested ocsp but got none */
1320 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1321 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1323 DEBUG(D_tls) debug_printf(" null\n");
1324 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1327 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1329 tls_out.ocsp = OCSP_FAILED;
1330 if (LOGGING(tls_cipher))
1331 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1333 DEBUG(D_tls) debug_printf(" parse error\n");
1337 if(!(bs = OCSP_response_get1_basic(rsp)))
1339 tls_out.ocsp = OCSP_FAILED;
1340 if (LOGGING(tls_cipher))
1341 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1343 DEBUG(D_tls) debug_printf(" error parsing response\n");
1344 OCSP_RESPONSE_free(rsp);
1348 /* We'd check the nonce here if we'd put one in the request. */
1349 /* However that would defeat cacheability on the server so we don't. */
1351 /* This section of code reworked from OpenSSL apps source;
1352 The OpenSSL Project retains copyright:
1353 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1358 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1360 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
1362 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1364 /* Use the chain that verified the server cert to verify the stapled info */
1365 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1367 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1368 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1370 tls_out.ocsp = OCSP_FAILED;
1371 if (LOGGING(tls_cipher))
1372 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
1373 BIO_printf(bp, "OCSP response verify failure\n");
1374 ERR_print_errors(bp);
1378 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1380 /*XXX So we have a good stapled OCSP status. How do we know
1381 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1382 OCSP_resp_find_status() which matches on a cert id, which presumably
1383 we should use. Making an id needs OCSP_cert_id_new(), which takes
1384 issuerName, issuerKey, serialNumber. Are they all in the cert?
1386 For now, carry on blindly accepting the resp. */
1389 OCSP_SINGLERESP * single;
1391 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1392 if (OCSP_resp_count(bs) != 1)
1394 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1395 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1398 tls_out.ocsp = OCSP_FAILED;
1399 log_write(0, LOG_MAIN, "OCSP stapling "
1400 "with multiple responses not handled");
1403 single = OCSP_resp_get0(bs, 0);
1404 status = OCSP_single_get0_status(single, &reason, &rev,
1405 &thisupd, &nextupd);
1408 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1409 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1410 if (!OCSP_check_validity(thisupd, nextupd,
1411 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1413 tls_out.ocsp = OCSP_FAILED;
1414 DEBUG(D_tls) ERR_print_errors(bp);
1415 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1419 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1420 OCSP_cert_status_str(status));
1423 case V_OCSP_CERTSTATUS_GOOD:
1424 tls_out.ocsp = OCSP_VFIED;
1427 case V_OCSP_CERTSTATUS_REVOKED:
1428 tls_out.ocsp = OCSP_FAILED;
1429 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1430 reason != -1 ? "; reason: " : "",
1431 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1432 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1435 tls_out.ocsp = OCSP_FAILED;
1436 log_write(0, LOG_MAIN,
1437 "Server certificate status unknown, in OCSP stapling");
1442 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1447 OCSP_RESPONSE_free(rsp);
1450 #endif /*!DISABLE_OCSP*/
1453 /*************************************************
1454 * Initialize for TLS *
1455 *************************************************/
1457 /* Called from both server and client code, to do preliminary initialization
1458 of the library. We allocate and return a context structure.
1461 ctxp returned SSL context
1462 host connected host, if client; NULL if server
1463 dhparam DH parameter file
1464 certificate certificate file
1465 privatekey private key
1466 ocsp_file file of stapling info (server); flag for require ocsp (client)
1467 addr address if client; NULL if server (for some randomness)
1468 cbp place to put allocated callback context
1469 errstr error string pointer
1471 Returns: OK/DEFER/FAIL
1475 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1477 #ifndef DISABLE_OCSP
1480 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1485 tls_ext_ctx_cb * cbinfo;
1487 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1488 cbinfo->certificate = certificate;
1489 cbinfo->privatekey = privatekey;
1490 cbinfo->is_server = host==NULL;
1491 #ifndef DISABLE_OCSP
1492 cbinfo->verify_stack = NULL;
1495 cbinfo->u_ocsp.server.file = ocsp_file;
1496 cbinfo->u_ocsp.server.file_expanded = NULL;
1497 cbinfo->u_ocsp.server.response = NULL;
1500 cbinfo->u_ocsp.client.verify_store = NULL;
1502 cbinfo->dhparam = dhparam;
1503 cbinfo->server_cipher_list = NULL;
1504 cbinfo->host = host;
1505 #ifndef DISABLE_EVENT
1506 cbinfo->event_action = NULL;
1509 SSL_load_error_strings(); /* basic set up */
1510 OpenSSL_add_ssl_algorithms();
1512 #ifdef EXIM_HAVE_SHA256
1513 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1514 list of available digests. */
1515 EVP_add_digest(EVP_sha256());
1518 /* Create a context.
1519 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1520 negotiation in the different methods; as far as I can tell, the only
1521 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1522 when OpenSSL is built without SSLv2 support.
1523 By disabling with openssl_options, we can let admins re-enable with the
1526 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1527 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1529 /* It turns out that we need to seed the random number generator this early in
1530 order to get the full complement of ciphers to work. It took me roughly a day
1531 of work to discover this by experiment.
1533 On systems that have /dev/urandom, SSL may automatically seed itself from
1534 there. Otherwise, we have to make something up as best we can. Double check
1540 gettimeofday(&r.tv, NULL);
1543 RAND_seed(US (&r), sizeof(r));
1544 RAND_seed(US big_buffer, big_buffer_size);
1545 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1548 return tls_error(US"RAND_status", host,
1549 US"unable to seed random number generator", errstr);
1552 /* Set up the information callback, which outputs if debugging is at a suitable
1555 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1557 /* Automatically re-try reads/writes after renegotiation. */
1558 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1560 /* Apply administrator-supplied work-arounds.
1561 Historically we applied just one requested option,
1562 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1563 moved to an administrator-controlled list of options to specify and
1564 grandfathered in the first one as the default value for "openssl_options".
1566 No OpenSSL version number checks: the options we accept depend upon the
1567 availability of the option value macros from OpenSSL. */
1569 if (!tls_openssl_options_parse(openssl_options, &init_options))
1570 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1574 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1575 if (!(SSL_CTX_set_options(ctx, init_options)))
1576 return tls_error(string_sprintf(
1577 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1580 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1582 /* Disable session cache unconditionally */
1584 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1586 /* Initialize with DH parameters if supplied */
1587 /* Initialize ECDH temp key parameter selection */
1589 if ( !init_dh(ctx, dhparam, host, errstr)
1590 || !init_ecdh(ctx, host, errstr)
1594 /* Set up certificate and key (and perhaps OCSP info) */
1596 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1599 /* If we need to handle SNI or OCSP, do so */
1601 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1602 # ifndef DISABLE_OCSP
1603 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1605 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1610 if (host == NULL) /* server */
1612 # ifndef DISABLE_OCSP
1613 /* We check u_ocsp.server.file, not server.response, because we care about if
1614 the option exists, not what the current expansion might be, as SNI might
1615 change the certificate and OCSP file in use between now and the time the
1616 callback is invoked. */
1617 if (cbinfo->u_ocsp.server.file)
1619 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1620 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1623 /* We always do this, so that $tls_sni is available even if not used in
1625 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1626 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1628 # ifndef DISABLE_OCSP
1630 if(ocsp_file) /* wanting stapling */
1632 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1634 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1637 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1638 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1643 cbinfo->verify_cert_hostnames = NULL;
1645 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1646 /* Set up the RSA callback */
1647 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1650 /* Finally, set the timeout, and we are done */
1652 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1653 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1664 /*************************************************
1665 * Get name of cipher in use *
1666 *************************************************/
1669 Argument: pointer to an SSL structure for the connection
1670 buffer to use for answer
1672 pointer to number of bits for cipher
1677 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1679 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1680 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1681 the accessor functions use const in the prototype. */
1682 const SSL_CIPHER *c;
1685 ver = (const uschar *)SSL_get_version(ssl);
1687 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1688 SSL_CIPHER_get_bits(c, bits);
1690 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1691 SSL_CIPHER_get_name(c), *bits);
1693 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1698 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned bsize)
1700 /*XXX we might consider a list-of-certs variable for the cert chain.
1701 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1702 in list-handling functions, also consider the difference between the entire
1703 chain and the elements sent by the peer. */
1705 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1706 if (!tlsp->peercert)
1707 tlsp->peercert = SSL_get_peer_certificate(ssl);
1708 /* Beware anonymous ciphers which lead to server_cert being NULL */
1711 X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, bsize);
1712 peerdn[bsize-1] = '\0';
1713 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1716 tlsp->peerdn = NULL;
1723 /*************************************************
1724 * Set up for verifying certificates *
1725 *************************************************/
1727 /* Load certs from file, return TRUE on success */
1730 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
1735 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
1736 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
1737 sk_X509_push(verify_stack, x);
1744 /* Called by both client and server startup
1747 sctx SSL_CTX* to initialise
1748 certs certs file or NULL
1749 crl CRL file or NULL
1750 host NULL in a server; the remote host in a client
1751 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1752 otherwise passed as FALSE
1753 cert_vfy_cb Callback function for certificate verification
1754 errstr error string pointer
1756 Returns: OK/DEFER/FAIL
1760 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1761 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
1763 uschar *expcerts, *expcrl;
1765 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
1767 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
1769 if (expcerts && *expcerts)
1771 /* Tell the library to use its compiled-in location for the system default
1772 CA bundle. Then add the ones specified in the config, if any. */
1774 if (!SSL_CTX_set_default_verify_paths(sctx))
1775 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
1777 if (Ustrcmp(expcerts, "system") != 0)
1779 struct stat statbuf;
1781 if (Ustat(expcerts, &statbuf) < 0)
1783 log_write(0, LOG_MAIN|LOG_PANIC,
1784 "failed to stat %s for certificates", expcerts);
1790 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1791 { file = NULL; dir = expcerts; }
1794 file = expcerts; dir = NULL;
1795 #ifndef DISABLE_OCSP
1796 /* In the server if we will be offering an OCSP proof, load chain from
1797 file for verifying the OCSP proof at load time. */
1800 && statbuf.st_size > 0
1801 && server_static_cbinfo->u_ocsp.server.file
1802 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
1805 log_write(0, LOG_MAIN|LOG_PANIC,
1806 "failed to load cert hain from %s", file);
1812 /* If a certificate file is empty, the next function fails with an
1813 unhelpful error message. If we skip it, we get the correct behaviour (no
1814 certificates are recognized, but the error message is still misleading (it
1815 says no certificate was supplied). But this is better. */
1817 if ( (!file || statbuf.st_size > 0)
1818 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1819 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
1821 /* Load the list of CAs for which we will accept certs, for sending
1822 to the client. This is only for the one-file tls_verify_certificates
1824 If a list isn't loaded into the server, but
1825 some verify locations are set, the server end appears to make
1826 a wildcard request for client certs.
1827 Meanwhile, the client library as default behaviour *ignores* the list
1828 we send over the wire - see man SSL_CTX_set_client_cert_cb.
1829 Because of this, and that the dir variant is likely only used for
1830 the public-CA bundle (not for a private CA), not worth fixing.
1834 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
1836 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
1837 sk_X509_NAME_num(names));
1838 SSL_CTX_set_client_CA_list(sctx, names);
1843 /* Handle a certificate revocation list. */
1845 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1847 /* This bit of code is now the version supplied by Lars Mainka. (I have
1848 merely reformatted it into the Exim code style.)
1850 "From here I changed the code to add support for multiple crl's
1851 in pem format in one file or to support hashed directory entries in
1852 pem format instead of a file. This method now uses the library function
1853 X509_STORE_load_locations to add the CRL location to the SSL context.
1854 OpenSSL will then handle the verify against CA certs and CRLs by
1855 itself in the verify callback." */
1857 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
1858 if (expcrl && *expcrl)
1860 struct stat statbufcrl;
1861 if (Ustat(expcrl, &statbufcrl) < 0)
1863 log_write(0, LOG_MAIN|LOG_PANIC,
1864 "failed to stat %s for certificates revocation lists", expcrl);
1869 /* is it a file or directory? */
1871 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1872 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1876 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1882 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1884 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1885 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
1887 /* setting the flags to check against the complete crl chain */
1889 X509_STORE_set_flags(cvstore,
1890 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1894 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1896 /* If verification is optional, don't fail if no certificate */
1898 SSL_CTX_set_verify(sctx,
1899 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1908 /*************************************************
1909 * Start a TLS session in a server *
1910 *************************************************/
1912 /* This is called when Exim is running as a server, after having received
1913 the STARTTLS command. It must respond to that command, and then negotiate
1917 require_ciphers allowed ciphers
1918 errstr pointer to error message
1920 Returns: OK on success
1921 DEFER for errors before the start of the negotiation
1922 FAIL for errors during the negotiation; the server can't
1927 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
1930 uschar * expciphers;
1931 tls_ext_ctx_cb * cbinfo;
1932 static uschar peerdn[256];
1933 static uschar cipherbuf[256];
1935 /* Check for previous activation */
1937 if (tls_in.active >= 0)
1939 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
1940 smtp_printf("554 Already in TLS\r\n", FALSE);
1944 /* Initialize the SSL library. If it fails, it will already have logged
1947 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1948 #ifndef DISABLE_OCSP
1951 NULL, &server_static_cbinfo, errstr);
1952 if (rc != OK) return rc;
1953 cbinfo = server_static_cbinfo;
1955 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
1958 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1959 were historically separated by underscores. So that I can use either form in my
1960 tests, and also for general convenience, we turn underscores into hyphens here.
1965 uschar * s = expciphers;
1966 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1967 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1968 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1969 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
1970 cbinfo->server_cipher_list = expciphers;
1973 /* If this is a host for which certificate verification is mandatory or
1974 optional, set up appropriately. */
1976 tls_in.certificate_verified = FALSE;
1977 #ifdef EXPERIMENTAL_DANE
1978 tls_in.dane_verified = FALSE;
1980 server_verify_callback_called = FALSE;
1982 if (verify_check_host(&tls_verify_hosts) == OK)
1984 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1985 FALSE, verify_callback_server, errstr);
1986 if (rc != OK) return rc;
1987 server_verify_optional = FALSE;
1989 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1991 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1992 TRUE, verify_callback_server, errstr);
1993 if (rc != OK) return rc;
1994 server_verify_optional = TRUE;
1997 /* Prepare for new connection */
1999 if (!(server_ssl = SSL_new(server_ctx)))
2000 return tls_error(US"SSL_new", NULL, NULL, errstr);
2002 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2004 * With the SSL_clear(), we get strange interoperability bugs with
2005 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2006 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2008 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2009 * session shutdown. In this case, we have a brand new object and there's no
2010 * obvious reason to immediately clear it. I'm guessing that this was
2011 * originally added because of incomplete initialisation which the clear fixed,
2012 * in some historic release.
2015 /* Set context and tell client to go ahead, except in the case of TLS startup
2016 on connection, where outputting anything now upsets the clients and tends to
2017 make them disconnect. We need to have an explicit fflush() here, to force out
2018 the response. Other smtp_printf() calls do not need it, because in non-TLS
2019 mode, the fflush() happens when smtp_getc() is called. */
2021 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2022 if (!tls_in.on_connect)
2024 smtp_printf("220 TLS go ahead\r\n", FALSE);
2028 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2029 that the OpenSSL library doesn't. */
2031 SSL_set_wfd(server_ssl, fileno(smtp_out));
2032 SSL_set_rfd(server_ssl, fileno(smtp_in));
2033 SSL_set_accept_state(server_ssl);
2035 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2037 sigalrm_seen = FALSE;
2038 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2039 rc = SSL_accept(server_ssl);
2044 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2048 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2050 /* TLS has been set up. Adjust the input functions to read via TLS,
2051 and initialize things. */
2053 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2055 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
2056 tls_in.cipher = cipherbuf;
2061 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
2062 debug_printf("Shared ciphers: %s\n", buf);
2065 /* Record the certificate we presented */
2067 X509 * crt = SSL_get_certificate(server_ssl);
2068 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2071 /* Only used by the server-side tls (tls_in), including tls_getc.
2072 Client-side (tls_out) reads (seem to?) go via
2073 smtp_read_response()/ip_recv().
2074 Hence no need to duplicate for _in and _out.
2076 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2077 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2078 ssl_xfer_eof = ssl_xfer_error = 0;
2080 receive_getc = tls_getc;
2081 receive_getbuf = tls_getbuf;
2082 receive_get_cache = tls_get_cache;
2083 receive_ungetc = tls_ungetc;
2084 receive_feof = tls_feof;
2085 receive_ferror = tls_ferror;
2086 receive_smtp_buffered = tls_smtp_buffered;
2088 tls_in.active = fileno(smtp_out);
2096 tls_client_basic_ctx_init(SSL_CTX * ctx,
2097 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2101 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2102 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2103 the specified host patterns if one of them is defined */
2105 if ( ( !ob->tls_verify_hosts
2106 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2108 || (verify_check_given_host(&ob->tls_verify_hosts, host) == OK)
2110 client_verify_optional = FALSE;
2111 else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
2112 client_verify_optional = TRUE;
2116 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2117 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2121 if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
2123 cbinfo->verify_cert_hostnames =
2125 string_domain_utf8_to_alabel(host->name, NULL);
2129 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2130 cbinfo->verify_cert_hostnames);
2136 #ifdef EXPERIMENTAL_DANE
2138 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2142 const char * hostnames[2] = { CS host->name, NULL };
2145 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2146 return tls_error(US"hostnames load", host, NULL, errstr);
2148 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
2150 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2151 ) if (rr->type == T_TLSA)
2153 const uschar * p = rr->data;
2154 uint8_t usage, selector, mtype;
2155 const char * mdname;
2159 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2160 if (usage != 2 && usage != 3) continue;
2167 default: continue; /* Only match-types 0, 1, 2 are supported */
2168 case 0: mdname = NULL; break;
2169 case 1: mdname = "sha256"; break;
2170 case 2: mdname = "sha512"; break;
2174 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2177 return tls_error(US"tlsa load", host, NULL, errstr);
2178 case 0: /* action not taken */
2182 tls_out.tlsa_usage |= 1<<usage;
2188 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2191 #endif /*EXPERIMENTAL_DANE*/
2195 /*************************************************
2196 * Start a TLS session in a client *
2197 *************************************************/
2199 /* Called from the smtp transport after STARTTLS has been accepted.
2202 fd the fd of the connection
2203 host connected host (for messages)
2204 addr the first address
2205 tb transport (always smtp)
2206 tlsa_dnsa tlsa lookup, if DANE, else null
2207 errstr error string pointer
2209 Returns: OK on success
2210 FAIL otherwise - note that tls_error() will not give DEFER
2211 because this is not a server
2215 tls_client_start(int fd, host_item *host, address_item *addr,
2216 transport_instance * tb,
2217 #ifdef EXPERIMENTAL_DANE
2218 dns_answer * tlsa_dnsa,
2222 smtp_transport_options_block * ob =
2223 (smtp_transport_options_block *)tb->options_block;
2224 static uschar peerdn[256];
2225 uschar * expciphers;
2227 static uschar cipherbuf[256];
2229 #ifndef DISABLE_OCSP
2230 BOOL request_ocsp = FALSE;
2231 BOOL require_ocsp = FALSE;
2234 #ifdef EXPERIMENTAL_DANE
2235 tls_out.tlsa_usage = 0;
2238 #ifndef DISABLE_OCSP
2240 # ifdef EXPERIMENTAL_DANE
2242 && ob->hosts_request_ocsp[0] == '*'
2243 && ob->hosts_request_ocsp[1] == '\0'
2246 /* Unchanged from default. Use a safer one under DANE */
2247 request_ocsp = TRUE;
2248 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2249 " {= {4}{$tls_out_tlsa_usage}} } "
2255 verify_check_given_host(&ob->hosts_require_ocsp, host) == OK))
2256 request_ocsp = TRUE;
2258 # ifdef EXPERIMENTAL_DANE
2262 verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2266 rc = tls_init(&client_ctx, host, NULL,
2267 ob->tls_certificate, ob->tls_privatekey,
2268 #ifndef DISABLE_OCSP
2269 (void *)(long)request_ocsp,
2271 addr, &client_static_cbinfo, errstr);
2272 if (rc != OK) return rc;
2274 tls_out.certificate_verified = FALSE;
2275 client_verify_callback_called = FALSE;
2277 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2278 &expciphers, errstr))
2281 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2282 are separated by underscores. So that I can use either form in my tests, and
2283 also for general convenience, we turn underscores into hyphens here. */
2287 uschar *s = expciphers;
2288 while (*s) { if (*s == '_') *s = '-'; s++; }
2289 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2290 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
2291 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2294 #ifdef EXPERIMENTAL_DANE
2297 SSL_CTX_set_verify(client_ctx,
2298 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2299 verify_callback_client_dane);
2301 if (!DANESSL_library_init())
2302 return tls_error(US"library init", host, NULL, errstr);
2303 if (DANESSL_CTX_init(client_ctx) <= 0)
2304 return tls_error(US"context init", host, NULL, errstr);
2310 if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob,
2311 client_static_cbinfo, errstr)) != OK)
2314 if ((client_ssl = SSL_new(client_ctx)) == NULL)
2315 return tls_error(US"SSL_new", host, NULL, errstr);
2316 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
2317 SSL_set_fd(client_ssl, fd);
2318 SSL_set_connect_state(client_ssl);
2322 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni, errstr))
2326 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2328 else if (!Ustrlen(tls_out.sni))
2332 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2333 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
2334 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
2336 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2342 #ifdef EXPERIMENTAL_DANE
2344 if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa, errstr)) != OK)
2348 #ifndef DISABLE_OCSP
2349 /* Request certificate status at connection-time. If the server
2350 does OCSP stapling we will get the callback (set in tls_init()) */
2351 # ifdef EXPERIMENTAL_DANE
2355 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2356 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2358 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2359 this means we avoid the OCSP request, we wasted the setup
2360 cost in tls_init(). */
2361 require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
2362 request_ocsp = require_ocsp
2363 || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2370 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
2371 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2372 tls_out.ocsp = OCSP_NOT_RESP;
2376 #ifndef DISABLE_EVENT
2377 client_static_cbinfo->event_action = tb->event_action;
2380 /* There doesn't seem to be a built-in timeout on connection. */
2382 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2383 sigalrm_seen = FALSE;
2384 alarm(ob->command_timeout);
2385 rc = SSL_connect(client_ssl);
2388 #ifdef EXPERIMENTAL_DANE
2390 DANESSL_cleanup(client_ssl);
2394 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL,
2397 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
2399 peer_cert(client_ssl, &tls_out, peerdn, sizeof(peerdn));
2401 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
2402 tls_out.cipher = cipherbuf;
2404 /* Record the certificate we presented */
2406 X509 * crt = SSL_get_certificate(client_ssl);
2407 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
2410 tls_out.active = fd;
2419 tls_refill(unsigned lim)
2424 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2425 ssl_xfer_buffer, ssl_xfer_buffer_size);
2427 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2428 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2429 MIN(ssl_xfer_buffer_size, lim));
2430 error = SSL_get_error(server_ssl, inbytes);
2433 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2434 closed down, not that the socket itself has been closed down. Revert to
2435 non-SSL handling. */
2437 if (error == SSL_ERROR_ZERO_RETURN)
2439 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2441 receive_getc = smtp_getc;
2442 receive_getbuf = smtp_getbuf;
2443 receive_get_cache = smtp_get_cache;
2444 receive_ungetc = smtp_ungetc;
2445 receive_feof = smtp_feof;
2446 receive_ferror = smtp_ferror;
2447 receive_smtp_buffered = smtp_buffered;
2449 SSL_free(server_ssl);
2453 tls_in.cipher = NULL;
2454 tls_in.peerdn = NULL;
2460 /* Handle genuine errors */
2462 else if (error == SSL_ERROR_SSL)
2464 ERR_error_string(ERR_get_error(), ssl_errstring);
2465 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2470 else if (error != SSL_ERROR_NONE)
2472 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2477 #ifndef DISABLE_DKIM
2478 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2480 ssl_xfer_buffer_hwm = inbytes;
2481 ssl_xfer_buffer_lwm = 0;
2486 /*************************************************
2487 * TLS version of getc *
2488 *************************************************/
2490 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2491 it refills the buffer via the SSL reading function.
2493 Arguments: lim Maximum amount to read/buffer
2494 Returns: the next character or EOF
2496 Only used by the server-side TLS.
2500 tls_getc(unsigned lim)
2502 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2503 if (!tls_refill(lim))
2504 return ssl_xfer_error ? EOF : smtp_getc(lim);
2506 /* Something in the buffer; return next uschar */
2508 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2512 tls_getbuf(unsigned * len)
2517 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2518 if (!tls_refill(*len))
2520 if (!ssl_xfer_error) return smtp_getbuf(len);
2525 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2527 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2528 ssl_xfer_buffer_lwm += size;
2537 #ifndef DISABLE_DKIM
2538 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2540 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2546 tls_could_read(void)
2548 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2552 /*************************************************
2553 * Read bytes from TLS channel *
2554 *************************************************/
2561 Returns: the number of bytes read
2562 -1 after a failed read
2564 Only used by the client-side TLS.
2568 tls_read(BOOL is_server, uschar *buff, size_t len)
2570 SSL *ssl = is_server ? server_ssl : client_ssl;
2574 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2575 buff, (unsigned int)len);
2577 inbytes = SSL_read(ssl, CS buff, len);
2578 error = SSL_get_error(ssl, inbytes);
2580 if (error == SSL_ERROR_ZERO_RETURN)
2582 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2585 else if (error != SSL_ERROR_NONE)
2595 /*************************************************
2596 * Write bytes down TLS channel *
2597 *************************************************/
2601 is_server channel specifier
2604 more further data expected soon
2606 Returns: the number of bytes after a successful write,
2607 -1 after a failed write
2609 Used by both server-side and client-side TLS.
2613 tls_write(BOOL is_server, const uschar *buff, size_t len, BOOL more)
2615 int outbytes, error, left;
2616 SSL *ssl = is_server ? server_ssl : client_ssl;
2617 static gstring * corked = NULL;
2619 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2620 buff, (unsigned long)len, more ? ", more" : "");
2622 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2623 "more" is notified. This hack is only ok if small amounts are involved AND only
2624 one stream does it, in one context (i.e. no store reset). Currently it is used
2625 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */
2627 if (is_server && (more || corked))
2629 corked = string_catn(corked, buff, len);
2632 buff = CUS corked->s;
2637 for (left = len; left > 0;)
2639 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2640 outbytes = SSL_write(ssl, CS buff, left);
2641 error = SSL_get_error(ssl, outbytes);
2642 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2646 ERR_error_string(ERR_get_error(), ssl_errstring);
2647 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2650 case SSL_ERROR_NONE:
2655 case SSL_ERROR_ZERO_RETURN:
2656 log_write(0, LOG_MAIN, "SSL channel closed on write");
2659 case SSL_ERROR_SYSCALL:
2660 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2661 sender_fullhost ? sender_fullhost : US"<unknown>",
2666 log_write(0, LOG_MAIN, "SSL_write error %d", error);
2675 /*************************************************
2676 * Close down a TLS session *
2677 *************************************************/
2679 /* This is also called from within a delivery subprocess forked from the
2680 daemon, to shut down the TLS library, without actually doing a shutdown (which
2681 would tamper with the SSL session in the parent process).
2683 Arguments: TRUE if SSL_shutdown is to be called
2686 Used by both server-side and client-side TLS.
2690 tls_close(BOOL is_server, BOOL shutdown)
2692 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2693 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2695 if (*fdp < 0) return; /* TLS was not active */
2699 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2700 SSL_shutdown(*sslp);
2712 /*************************************************
2713 * Let tls_require_ciphers be checked at startup *
2714 *************************************************/
2716 /* The tls_require_ciphers option, if set, must be something which the
2719 Returns: NULL on success, or error message
2723 tls_validate_require_cipher(void)
2726 uschar *s, *expciphers, *err;
2728 /* this duplicates from tls_init(), we need a better "init just global
2729 state, for no specific purpose" singleton function of our own */
2731 SSL_load_error_strings();
2732 OpenSSL_add_ssl_algorithms();
2733 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2734 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2735 list of available digests. */
2736 EVP_add_digest(EVP_sha256());
2739 if (!(tls_require_ciphers && *tls_require_ciphers))
2742 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
2744 return US"failed to expand tls_require_ciphers";
2746 if (!(expciphers && *expciphers))
2749 /* normalisation ripped from above */
2751 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2755 ctx = SSL_CTX_new(SSLv23_server_method());
2758 ERR_error_string(ERR_get_error(), ssl_errstring);
2759 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2763 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2765 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2767 ERR_error_string(ERR_get_error(), ssl_errstring);
2768 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
2769 expciphers, ssl_errstring);
2780 /*************************************************
2781 * Report the library versions. *
2782 *************************************************/
2784 /* There have historically been some issues with binary compatibility in
2785 OpenSSL libraries; if Exim (like many other applications) is built against
2786 one version of OpenSSL but the run-time linker picks up another version,
2787 it can result in serious failures, including crashing with a SIGSEGV. So
2788 report the version found by the compiler and the run-time version.
2790 Note: some OS vendors backport security fixes without changing the version
2791 number/string, and the version date remains unchanged. The _build_ date
2792 will change, so we can more usefully assist with version diagnosis by also
2793 reporting the build date.
2795 Arguments: a FILE* to print the results to
2800 tls_version_report(FILE *f)
2802 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2805 OPENSSL_VERSION_TEXT,
2806 SSLeay_version(SSLEAY_VERSION),
2807 SSLeay_version(SSLEAY_BUILT_ON));
2808 /* third line is 38 characters for the %s and the line is 73 chars long;
2809 the OpenSSL output includes a "built on: " prefix already. */
2815 /*************************************************
2816 * Random number generation *
2817 *************************************************/
2819 /* Pseudo-random number generation. The result is not expected to be
2820 cryptographically strong but not so weak that someone will shoot themselves
2821 in the foot using it as a nonce in input in some email header scheme or
2822 whatever weirdness they'll twist this into. The result should handle fork()
2823 and avoid repeating sequences. OpenSSL handles that for us.
2827 Returns a random number in range [0, max-1]
2831 vaguely_random_number(int max)
2835 static pid_t pidlast = 0;
2838 uschar smallbuf[sizeof(r)];
2844 if (pidnow != pidlast)
2846 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2847 is unique for each thread", this doesn't apparently apply across processes,
2848 so our own warning from vaguely_random_number_fallback() applies here too.
2849 Fix per PostgreSQL. */
2855 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2859 gettimeofday(&r.tv, NULL);
2862 RAND_seed(US (&r), sizeof(r));
2864 /* We're after pseudo-random, not random; if we still don't have enough data
2865 in the internal PRNG then our options are limited. We could sleep and hope
2866 for entropy to come along (prayer technique) but if the system is so depleted
2867 in the first place then something is likely to just keep taking it. Instead,
2868 we'll just take whatever little bit of pseudo-random we can still manage to
2871 needed_len = sizeof(r);
2872 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2873 asked for a number less than 10. */
2874 for (r = max, i = 0; r; ++i)
2880 #ifdef EXIM_HAVE_RAND_PSEUDO
2881 /* We do not care if crypto-strong */
2882 i = RAND_pseudo_bytes(smallbuf, needed_len);
2884 i = RAND_bytes(smallbuf, needed_len);
2890 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2891 return vaguely_random_number_fallback(max);
2895 for (p = smallbuf; needed_len; --needed_len, ++p)
2901 /* We don't particularly care about weighted results; if someone wants
2902 smooth distribution and cares enough then they should submit a patch then. */
2909 /*************************************************
2910 * OpenSSL option parse *
2911 *************************************************/
2913 /* Parse one option for tls_openssl_options_parse below
2916 name one option name
2917 value place to store a value for it
2918 Returns success or failure in parsing
2921 struct exim_openssl_option {
2925 /* We could use a macro to expand, but we need the ifdef and not all the
2926 options document which version they were introduced in. Policylet: include
2927 all options unless explicitly for DTLS, let the administrator choose which
2930 This list is current as of:
2932 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2934 static struct exim_openssl_option exim_openssl_options[] = {
2935 /* KEEP SORTED ALPHABETICALLY! */
2937 { US"all", SSL_OP_ALL },
2939 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2940 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2942 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2943 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2945 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2946 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2948 #ifdef SSL_OP_EPHEMERAL_RSA
2949 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2951 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2952 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2954 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2955 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2957 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2958 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2960 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2961 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2963 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2964 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2966 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2967 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2969 #ifdef SSL_OP_NO_COMPRESSION
2970 { US"no_compression", SSL_OP_NO_COMPRESSION },
2972 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2973 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2975 #ifdef SSL_OP_NO_SSLv2
2976 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2978 #ifdef SSL_OP_NO_SSLv3
2979 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2981 #ifdef SSL_OP_NO_TICKET
2982 { US"no_ticket", SSL_OP_NO_TICKET },
2984 #ifdef SSL_OP_NO_TLSv1
2985 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2987 #ifdef SSL_OP_NO_TLSv1_1
2988 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2989 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2990 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2992 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2995 #ifdef SSL_OP_NO_TLSv1_2
2996 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2998 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2999 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
3001 #ifdef SSL_OP_SINGLE_DH_USE
3002 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
3004 #ifdef SSL_OP_SINGLE_ECDH_USE
3005 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
3007 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
3008 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
3010 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
3011 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
3013 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
3014 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
3016 #ifdef SSL_OP_TLS_D5_BUG
3017 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
3019 #ifdef SSL_OP_TLS_ROLLBACK_BUG
3020 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
3023 static int exim_openssl_options_size =
3024 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
3028 tls_openssl_one_option_parse(uschar *name, long *value)
3031 int last = exim_openssl_options_size;
3032 while (last > first)
3034 int middle = (first + last)/2;
3035 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3038 *value = exim_openssl_options[middle].value;
3052 /*************************************************
3053 * OpenSSL option parsing logic *
3054 *************************************************/
3056 /* OpenSSL has a number of compatibility options which an administrator might
3057 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3058 we look like log_selector.
3061 option_spec the administrator-supplied string of options
3062 results ptr to long storage for the options bitmap
3063 Returns success or failure
3067 tls_openssl_options_parse(uschar *option_spec, long *results)
3072 BOOL adding, item_parsed;
3074 result = SSL_OP_NO_TICKET;
3075 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3076 * from default because it increases BEAST susceptibility. */
3077 #ifdef SSL_OP_NO_SSLv2
3078 result |= SSL_OP_NO_SSLv2;
3080 #ifdef SSL_OP_SINGLE_DH_USE
3081 result |= SSL_OP_SINGLE_DH_USE;
3090 for (s=option_spec; *s != '\0'; /**/)
3092 while (isspace(*s)) ++s;
3095 if (*s != '+' && *s != '-')
3097 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3098 "+ or - expected but found \"%s\"\n", s);
3101 adding = *s++ == '+';
3102 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3105 item_parsed = tls_openssl_one_option_parse(s, &item);
3109 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3112 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
3113 adding ? "adding" : "removing", result, item, s);
3127 /* End of tls-openssl.c */