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 /* Structure for collecting random data for seeding. */
99 typedef struct randstuff {
104 /* Local static variables */
106 static BOOL client_verify_callback_called = FALSE;
107 static BOOL server_verify_callback_called = FALSE;
108 static const uschar *sid_ctx = US"exim";
110 /* We have three different contexts to care about.
112 Simple case: client, `client_ctx`
113 As a client, we can be doing a callout or cut-through delivery while receiving
114 a message. So we have a client context, which should have options initialised
115 from the SMTP Transport.
118 There are two cases: with and without ServerNameIndication from the client.
119 Given TLS SNI, we can be using different keys, certs and various other
120 configuration settings, because they're re-expanded with $tls_sni set. This
121 allows vhosting with TLS. This SNI is sent in the handshake.
122 A client might not send SNI, so we need a fallback, and an initial setup too.
123 So as a server, we start out using `server_ctx`.
124 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
125 `server_sni` from `server_ctx` and then initialise settings by re-expanding
129 static SSL_CTX *client_ctx = NULL;
130 static SSL_CTX *server_ctx = NULL;
131 static SSL *client_ssl = NULL;
132 static SSL *server_ssl = NULL;
134 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
135 static SSL_CTX *server_sni = NULL;
138 static char ssl_errstring[256];
140 static int ssl_session_timeout = 200;
141 static BOOL client_verify_optional = FALSE;
142 static BOOL server_verify_optional = FALSE;
144 static BOOL reexpand_tls_files_for_sni = FALSE;
147 typedef struct tls_ext_ctx_cb {
152 STACK_OF(X509) *verify_stack; /* chain for verifying the proof */
156 uschar *file_expanded;
157 OCSP_RESPONSE *response;
160 X509_STORE *verify_store; /* non-null if status requested */
161 BOOL verify_required;
166 /* these are cached from first expand */
167 uschar *server_cipher_list;
168 /* only passed down to tls_error: */
170 const uschar * verify_cert_hostnames;
171 #ifndef DISABLE_EVENT
172 uschar * event_action;
176 /* should figure out a cleanup of API to handle state preserved per
177 implementation, for various reasons, which can be void * in the APIs.
178 For now, we hack around it. */
179 tls_ext_ctx_cb *client_static_cbinfo = NULL;
180 tls_ext_ctx_cb *server_static_cbinfo = NULL;
183 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
184 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr );
187 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
188 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
191 static int tls_server_stapling_cb(SSL *s, void *arg);
195 /*************************************************
197 *************************************************/
199 /* Called from lots of places when errors occur before actually starting to do
200 the TLS handshake, that is, while the session is still in clear. Always returns
201 DEFER for a server and FAIL for a client so that most calls can use "return
202 tls_error(...)" to do this processing and then give an appropriate return. A
203 single function is used for both server and client, because it is called from
204 some shared functions.
207 prefix text to include in the logged error
208 host NULL if setting up a server;
209 the connected host if setting up a client
210 msg error message or NULL if we should ask OpenSSL
211 errstr pointer to output error message
213 Returns: OK/DEFER/FAIL
217 tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr)
221 ERR_error_string(ERR_get_error(), ssl_errstring);
222 msg = US ssl_errstring;
225 if (errstr) *errstr = string_sprintf("(%s): %s", prefix, msg);
226 return host ? FAIL : DEFER;
231 /*************************************************
232 * Callback to generate RSA key *
233 *************************************************/
237 s SSL connection (not used)
241 Returns: pointer to generated key
245 rsa_callback(SSL *s, int export, int keylength)
248 #ifdef EXIM_HAVE_RSA_GENKEY_EX
249 BIGNUM *bn = BN_new();
252 export = export; /* Shut picky compilers up */
253 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
255 #ifdef EXIM_HAVE_RSA_GENKEY_EX
256 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
257 || !(rsa_key = RSA_new())
258 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
261 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
265 ERR_error_string(ERR_get_error(), ssl_errstring);
266 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
278 x509_store_dump_cert_s_names(X509_STORE * store)
280 STACK_OF(X509_OBJECT) * roots= store->objs;
282 static uschar name[256];
284 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
286 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
287 if(tmp_obj->type == X509_LU_X509)
289 X509 * current_cert= tmp_obj->data.x509;
290 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
291 name[sizeof(name)-1] = '\0';
292 debug_printf(" %s\n", name);
300 #ifndef DISABLE_EVENT
302 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
303 BOOL *calledp, const BOOL *optionalp, const uschar * what)
309 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
312 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
313 old_cert = tlsp->peercert;
314 tlsp->peercert = X509_dup(cert);
315 /* NB we do not bother setting peerdn */
316 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
318 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
319 "depth=%d cert=%s: %s",
320 tlsp == &tls_out ? deliver_host_address : sender_host_address,
321 what, depth, dn, yield);
325 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
326 return 1; /* reject (leaving peercert set) */
328 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
329 "(host in tls_try_verify_hosts)\n");
331 X509_free(tlsp->peercert);
332 tlsp->peercert = old_cert;
338 /*************************************************
339 * Callback for verification *
340 *************************************************/
342 /* The SSL library does certificate verification if set up to do so. This
343 callback has the current yes/no state is in "state". If verification succeeded,
344 we set the certificate-verified flag. If verification failed, what happens
345 depends on whether the client is required to present a verifiable certificate
348 If verification is optional, we change the state to yes, but still log the
349 verification error. For some reason (it really would help to have proper
350 documentation of OpenSSL), this callback function then gets called again, this
351 time with state = 1. We must take care not to set the private verified flag on
352 the second time through.
354 Note: this function is not called if the client fails to present a certificate
355 when asked. We get here only if a certificate has been received. Handling of
356 optional verification for this case is done when requesting SSL to verify, by
357 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
359 May be called multiple times for different issues with a certificate, even
360 for a given "depth" in the certificate chain.
363 preverify_ok current yes/no state as 1/0
364 x509ctx certificate information.
365 tlsp per-direction (client vs. server) support data
366 calledp has-been-called flag
367 optionalp verification-is-optional flag
369 Returns: 0 if verification should fail, otherwise 1
373 verify_callback(int preverify_ok, X509_STORE_CTX *x509ctx,
374 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
376 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
377 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
380 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
381 dn[sizeof(dn)-1] = '\0';
383 if (preverify_ok == 0)
385 uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])",
386 *verify_mode, sender_host_address)
388 log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s",
389 tlsp == &tls_out ? deliver_host_address : sender_host_address,
391 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn);
396 tlsp->peercert = X509_dup(cert); /* record failing cert */
397 return 0; /* reject */
399 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
400 "tls_try_verify_hosts)\n");
405 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
407 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
408 { /* client, wanting stapling */
409 /* Add the server cert's signing chain as the one
410 for the verification of the OCSP stapled information. */
412 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
415 sk_X509_push(client_static_cbinfo->verify_stack, cert);
418 #ifndef DISABLE_EVENT
419 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
420 return 0; /* reject, with peercert set */
425 const uschar * verify_cert_hostnames;
427 if ( tlsp == &tls_out
428 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
429 /* client, wanting hostname check */
432 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
433 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
434 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
436 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
437 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
440 const uschar * list = verify_cert_hostnames;
443 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
444 if ((rc = X509_check_host(cert, CCS name, 0,
445 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
446 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
451 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
452 tlsp == &tls_out ? deliver_host_address : sender_host_address);
459 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
462 uschar * extra = verify_mode
463 ? string_sprintf(" (during %c-verify for [%s])",
464 *verify_mode, sender_host_address)
466 log_write(0, LOG_MAIN,
467 "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"",
468 tlsp == &tls_out ? deliver_host_address : sender_host_address,
469 extra, dn, verify_cert_hostnames);
474 tlsp->peercert = X509_dup(cert); /* record failing cert */
475 return 0; /* reject */
477 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
478 "tls_try_verify_hosts)\n");
482 #ifndef DISABLE_EVENT
483 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
484 return 0; /* reject, with peercert set */
487 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
488 *calledp ? "" : " authenticated", dn);
489 if (!*calledp) tlsp->certificate_verified = TRUE;
493 return 1; /* accept, at least for this level */
497 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
499 return verify_callback(preverify_ok, x509ctx, &tls_out,
500 &client_verify_callback_called, &client_verify_optional);
504 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
506 return verify_callback(preverify_ok, x509ctx, &tls_in,
507 &server_verify_callback_called, &server_verify_optional);
511 #ifdef EXPERIMENTAL_DANE
513 /* This gets called *by* the dane library verify callback, which interposes
517 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
519 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
521 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
522 #ifndef DISABLE_EVENT
523 BOOL dummy_called, optional = FALSE;
526 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
527 dn[sizeof(dn)-1] = '\0';
529 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
530 preverify_ok ? "ok":"BAD", depth, dn);
532 #ifndef DISABLE_EVENT
533 if (verify_event(&tls_out, cert, depth, dn,
534 &dummy_called, &optional, US"DANE"))
535 return 0; /* reject, with peercert set */
538 if (preverify_ok == 1)
539 tls_out.dane_verified =
540 tls_out.certificate_verified = TRUE;
543 int err = X509_STORE_CTX_get_error(x509ctx);
545 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
546 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
552 #endif /*EXPERIMENTAL_DANE*/
555 /*************************************************
556 * Information callback *
557 *************************************************/
559 /* The SSL library functions call this from time to time to indicate what they
560 are doing. We copy the string to the debugging output when TLS debugging has
572 info_callback(SSL *s, int where, int ret)
576 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
581 /*************************************************
582 * Initialize for DH *
583 *************************************************/
585 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
588 sctx The current SSL CTX (inbound or outbound)
589 dhparam DH parameter file or fixed parameter identity string
590 host connected host, if client; NULL if server
591 errstr error string pointer
593 Returns: TRUE if OK (nothing to set up, or setup worked)
597 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr)
605 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr))
608 if (!dhexpanded || !*dhexpanded)
609 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
610 else if (dhexpanded[0] == '/')
612 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
614 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
615 host, US strerror(errno), errstr);
621 if (Ustrcmp(dhexpanded, "none") == 0)
623 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
627 if (!(pem = std_dh_prime_named(dhexpanded)))
629 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
630 host, US strerror(errno), errstr);
633 bio = BIO_new_mem_buf(CS pem, -1);
636 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
639 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
644 /* note: our default limit of 2236 is not a multiple of 8; the limit comes from
645 * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with
646 * 2236. But older OpenSSL can only report in bytes (octets), not bits.
647 * If someone wants to dance at the edge, then they can raise the limit or use
648 * current libraries. */
649 #ifdef EXIM_HAVE_OPENSSL_DH_BITS
650 /* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022
651 * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */
652 dh_bitsize = DH_bits(dh);
654 dh_bitsize = 8 * DH_size(dh);
657 /* Even if it is larger, we silently return success rather than cause things
658 * to fail out, so that a too-large DH will not knock out all TLS; it's a
659 * debatable choice. */
660 if (dh_bitsize > tls_dh_max_bits)
663 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n",
664 dh_bitsize, tls_dh_max_bits);
668 SSL_CTX_set_tmp_dh(sctx, dh);
670 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
671 dhexpanded ? dhexpanded : US"default", dh_bitsize);
683 /*************************************************
684 * Initialize for ECDH *
685 *************************************************/
687 /* Load parameters for ECDH encryption.
689 For now, we stick to NIST P-256 because: it's simple and easy to configure;
690 it avoids any patent issues that might bite redistributors; despite events in
691 the news and concerns over curve choices, we're not cryptographers, we're not
692 pretending to be, and this is "good enough" to be better than no support,
693 protecting against most adversaries. Given another year or two, there might
694 be sufficient clarity about a "right" way forward to let us make an informed
695 decision, instead of a knee-jerk reaction.
697 Longer-term, we should look at supporting both various named curves and
698 external files generated with "openssl ecparam", much as we do for init_dh().
699 We should also support "none" as a value, to explicitly avoid initialisation.
704 sctx The current SSL CTX (inbound or outbound)
705 host connected host, if client; NULL if server
706 errstr error string pointer
708 Returns: TRUE if OK (nothing to set up, or setup worked)
712 init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr)
714 #ifdef OPENSSL_NO_ECDH
723 if (host) /* No ECDH setup for clients, only for servers */
726 # ifndef EXIM_HAVE_ECDH
728 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
732 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr))
734 if (!exp_curve || !*exp_curve)
737 /* "auto" needs to be handled carefully.
738 * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1
739 * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto
740 * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO)
741 * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection
742 * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b
744 if (Ustrcmp(exp_curve, "auto") == 0)
746 #if OPENSSL_VERSION_NUMBER < 0x10002000L
747 DEBUG(D_tls) debug_printf(
748 "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n");
749 exp_curve = US"prime256v1";
751 # if defined SSL_CTRL_SET_ECDH_AUTO
752 DEBUG(D_tls) debug_printf(
753 "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n");
754 SSL_CTX_set_ecdh_auto(sctx, 1);
757 DEBUG(D_tls) debug_printf(
758 "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n");
764 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
765 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
766 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
767 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
771 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve),
776 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
778 tls_error(US"Unable to create ec curve", host, NULL, errstr);
782 /* The "tmp" in the name here refers to setting a temporary key
783 not to the stability of the interface. */
785 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
786 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr);
788 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
793 # endif /*EXIM_HAVE_ECDH*/
794 #endif /*OPENSSL_NO_ECDH*/
801 /*************************************************
802 * Load OCSP information into state *
803 *************************************************/
804 /* Called to load the server OCSP response from the given file into memory, once
805 caller has determined this is needed. Checks validity. Debugs a message
808 ASSUMES: single response, for single cert.
811 sctx the SSL_CTX* to update
812 cbinfo various parts of session state
813 expanded the filename putatively holding an OCSP response
818 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
821 OCSP_RESPONSE * resp;
822 OCSP_BASICRESP * basic_response;
823 OCSP_SINGLERESP * single_response;
824 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
826 unsigned long verify_flags;
827 int status, reason, i;
829 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
830 if (cbinfo->u_ocsp.server.response)
832 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
833 cbinfo->u_ocsp.server.response = NULL;
836 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
838 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
839 cbinfo->u_ocsp.server.file_expanded);
843 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
847 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
851 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
853 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
854 OCSP_response_status_str(status), status);
858 if (!(basic_response = OCSP_response_get1_basic(resp)))
861 debug_printf("OCSP response parse error: unable to extract basic response.\n");
865 sk = cbinfo->verify_stack;
866 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
868 /* May need to expose ability to adjust those flags?
869 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
870 OCSP_TRUSTOTHER OCSP_NOINTERN */
872 /* This does a full verify on the OCSP proof before we load it for serving
873 up; possibly overkill - just date-checks might be nice enough.
875 OCSP_basic_verify takes a "store" arg, but does not
876 use it for the chain verification, which is all we do
877 when OCSP_NOVERIFY is set. The content from the wire
878 "basic_response" and a cert-stack "sk" are all that is used.
880 We have a stack, loaded in setup_certs() if tls_verify_certificates
881 was a file (not a directory, or "system"). It is unfortunate we
882 cannot used the connection context store, as that would neatly
883 handle the "system" case too, but there seems to be no library
884 function for getting a stack from a store.
885 [ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ]
886 We do not free the stack since it could be needed a second time for
889 Separately we might try to replace using OCSP_basic_verify() - which seems to not
890 be a public interface into the OpenSSL library (there's no manual entry) -
891 But what with? We also use OCSP_basic_verify in the client stapling callback.
892 And there we NEED it; we must verify that status... unless the
893 library does it for us anyway? */
895 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
899 ERR_error_string(ERR_get_error(), ssl_errstring);
900 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
905 /* Here's the simplifying assumption: there's only one response, for the
906 one certificate we use, and nothing for anything else in a chain. If this
907 proves false, we need to extract a cert id from our issued cert
908 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
909 right cert in the stack and then calls OCSP_single_get0_status()).
911 I'm hoping to avoid reworking a bunch more of how we handle state here. */
913 if (!(single_response = OCSP_resp_get0(basic_response, 0)))
916 debug_printf("Unable to get first response from OCSP basic response.\n");
920 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
921 if (status != V_OCSP_CERTSTATUS_GOOD)
923 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
924 OCSP_cert_status_str(status), status,
925 OCSP_crl_reason_str(reason), reason);
929 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
931 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
936 cbinfo->u_ocsp.server.response = resp; /*XXX stack?*/
940 if (running_in_test_harness)
942 extern char ** environ;
944 if (environ) for (p = USS environ; *p; p++)
945 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
947 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
948 goto supply_response;
953 #endif /*!DISABLE_OCSP*/
958 /* Create and install a selfsigned certificate, for use in server mode */
961 tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr)
969 where = US"allocating pkey";
970 if (!(pkey = EVP_PKEY_new()))
973 where = US"allocating cert";
974 if (!(x509 = X509_new()))
977 where = US"generating pkey";
978 if (!(rsa = rsa_callback(NULL, 0, 1024)))
981 where = US"assigning pkey";
982 if (!EVP_PKEY_assign_RSA(pkey, rsa))
985 X509_set_version(x509, 2); /* N+1 - version 3 */
986 ASN1_INTEGER_set(X509_get_serialNumber(x509), 0);
987 X509_gmtime_adj(X509_get_notBefore(x509), 0);
988 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
989 X509_set_pubkey(x509, pkey);
991 name = X509_get_subject_name(x509);
992 X509_NAME_add_entry_by_txt(name, "C",
993 MBSTRING_ASC, CUS "UK", -1, -1, 0);
994 X509_NAME_add_entry_by_txt(name, "O",
995 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
996 X509_NAME_add_entry_by_txt(name, "CN",
997 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
998 X509_set_issuer_name(x509, name);
1000 where = US"signing cert";
1001 if (!X509_sign(x509, pkey, EVP_md5()))
1004 where = US"installing selfsign cert";
1005 if (!SSL_CTX_use_certificate(sctx, x509))
1008 where = US"installing selfsign key";
1009 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1015 (void) tls_error(where, NULL, NULL, errstr);
1016 if (x509) X509_free(x509);
1017 if (pkey) EVP_PKEY_free(pkey);
1025 tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1028 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file);
1029 if (!SSL_CTX_use_certificate_chain_file(sctx, CS file))
1030 return tls_error(string_sprintf(
1031 "SSL_CTX_use_certificate_chain_file file=%s", file),
1032 cbinfo->host, NULL, errstr);
1037 tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file,
1040 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file);
1041 if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM))
1042 return tls_error(string_sprintf(
1043 "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr);
1048 /*************************************************
1049 * Expand key and cert file specs *
1050 *************************************************/
1052 /* Called once during tls_init and possibly again during TLS setup, for a
1053 new context, if Server Name Indication was used and tls_sni was seen in
1054 the certificate string.
1057 sctx the SSL_CTX* to update
1058 cbinfo various parts of session state
1059 errstr error string pointer
1061 Returns: OK/DEFER/FAIL
1065 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo,
1070 if (!cbinfo->certificate)
1072 if (!cbinfo->is_server) /* client */
1075 if (tls_install_selfsign(sctx, errstr) != OK)
1082 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1083 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1084 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1086 reexpand_tls_files_for_sni = TRUE;
1088 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr))
1092 if (cbinfo->is_server)
1094 const uschar * file_list = expanded;
1098 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1099 if ((err = tls_add_certfile(sctx, cbinfo, file, errstr)))
1102 else /* would there ever be a need for multiple client certs? */
1103 if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr)))
1106 if (cbinfo->privatekey != NULL &&
1107 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr))
1110 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1111 of the expansion is an empty string, ignore it also, and assume the private
1112 key is in the same file as the certificate. */
1114 if (expanded && *expanded)
1115 if (cbinfo->is_server)
1117 const uschar * file_list = expanded;
1121 while (file = string_nextinlist(&file_list, &sep, NULL, 0))
1122 if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr)))
1125 else /* would there ever be a need for multiple client certs? */
1126 if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr)))
1130 #ifndef DISABLE_OCSP
1131 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1134 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr))
1137 if (expanded && *expanded)
1139 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1140 if ( cbinfo->u_ocsp.server.file_expanded
1141 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1143 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1146 ocsp_load_response(sctx, cbinfo, expanded);
1157 /*************************************************
1158 * Callback to handle SNI *
1159 *************************************************/
1161 /* Called when acting as server during the TLS session setup if a Server Name
1162 Indication extension was sent by the client.
1164 API documentation is OpenSSL s_server.c implementation.
1167 s SSL* of the current session
1168 ad unknown (part of OpenSSL API) (unused)
1169 arg Callback of "our" registered data
1171 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1174 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1176 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1178 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1179 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1181 int old_pool = store_pool;
1182 uschar * dummy_errstr;
1185 return SSL_TLSEXT_ERR_OK;
1187 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1188 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1190 /* Make the extension value available for expansion */
1191 store_pool = POOL_PERM;
1192 tls_in.sni = string_copy(US servername);
1193 store_pool = old_pool;
1195 if (!reexpand_tls_files_for_sni)
1196 return SSL_TLSEXT_ERR_OK;
1198 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1199 not confident that memcpy wouldn't break some internal reference counting.
1200 Especially since there's a references struct member, which would be off. */
1202 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1204 ERR_error_string(ERR_get_error(), ssl_errstring);
1205 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1206 return SSL_TLSEXT_ERR_NOACK;
1209 /* Not sure how many of these are actually needed, since SSL object
1210 already exists. Might even need this selfsame callback, for reneg? */
1212 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1213 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1214 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1215 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1216 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1217 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1219 if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr)
1220 || !init_ecdh(server_sni, NULL, &dummy_errstr)
1222 return SSL_TLSEXT_ERR_NOACK;
1224 if (cbinfo->server_cipher_list)
1225 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
1226 #ifndef DISABLE_OCSP
1227 if (cbinfo->u_ocsp.server.file)
1229 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1230 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1234 if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE,
1235 verify_callback_server, &dummy_errstr)) != OK)
1236 return SSL_TLSEXT_ERR_NOACK;
1238 /* do this after setup_certs, because this can require the certs for verifying
1239 OCSP information. */
1240 if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK)
1241 return SSL_TLSEXT_ERR_NOACK;
1243 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1244 SSL_set_SSL_CTX(s, server_sni);
1246 return SSL_TLSEXT_ERR_OK;
1248 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1253 #ifndef DISABLE_OCSP
1255 /*************************************************
1256 * Callback to handle OCSP Stapling *
1257 *************************************************/
1259 /* Called when acting as server during the TLS session setup if the client
1260 requests OCSP information with a Certificate Status Request.
1262 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1268 tls_server_stapling_cb(SSL *s, void *arg)
1270 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1271 uschar *response_der; /*XXX blob */
1272 int response_der_len;
1274 /*XXX stack: use SSL_get_certificate() to see which cert; from that work
1275 out which ocsp blob to send. Unfortunately, SSL_get_certificate is known
1276 buggy in current OpenSSL; it returns the last cert loaded always rather than
1277 the one actually presented. So we can't support a stack of OCSP proofs at
1281 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1282 cbinfo->u_ocsp.server.response ? "have" : "lack");
1284 tls_in.ocsp = OCSP_NOT_RESP;
1285 if (!cbinfo->u_ocsp.server.response)
1286 return SSL_TLSEXT_ERR_NOACK;
1288 response_der = NULL;
1289 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response, /*XXX stack*/
1291 if (response_der_len <= 0)
1292 return SSL_TLSEXT_ERR_NOACK;
1294 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1295 tls_in.ocsp = OCSP_VFIED;
1296 return SSL_TLSEXT_ERR_OK;
1301 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1303 BIO_printf(bp, "\t%s: ", str);
1304 ASN1_GENERALIZEDTIME_print(bp, time);
1309 tls_client_stapling_cb(SSL *s, void *arg)
1311 tls_ext_ctx_cb * cbinfo = arg;
1312 const unsigned char * p;
1314 OCSP_RESPONSE * rsp;
1315 OCSP_BASICRESP * bs;
1318 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1319 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1322 /* Expect this when we requested ocsp but got none */
1323 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1324 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1326 DEBUG(D_tls) debug_printf(" null\n");
1327 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1330 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1332 tls_out.ocsp = OCSP_FAILED;
1333 if (LOGGING(tls_cipher))
1334 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1336 DEBUG(D_tls) debug_printf(" parse error\n");
1340 if(!(bs = OCSP_response_get1_basic(rsp)))
1342 tls_out.ocsp = OCSP_FAILED;
1343 if (LOGGING(tls_cipher))
1344 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1346 DEBUG(D_tls) debug_printf(" error parsing response\n");
1347 OCSP_RESPONSE_free(rsp);
1351 /* We'd check the nonce here if we'd put one in the request. */
1352 /* However that would defeat cacheability on the server so we don't. */
1354 /* This section of code reworked from OpenSSL apps source;
1355 The OpenSSL Project retains copyright:
1356 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1361 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1363 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
1365 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1367 /* Use the chain that verified the server cert to verify the stapled info */
1368 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1370 if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack,
1371 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1373 tls_out.ocsp = OCSP_FAILED;
1374 if (LOGGING(tls_cipher))
1375 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
1376 BIO_printf(bp, "OCSP response verify failure\n");
1377 ERR_print_errors(bp);
1381 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1383 /*XXX So we have a good stapled OCSP status. How do we know
1384 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1385 OCSP_resp_find_status() which matches on a cert id, which presumably
1386 we should use. Making an id needs OCSP_cert_id_new(), which takes
1387 issuerName, issuerKey, serialNumber. Are they all in the cert?
1389 For now, carry on blindly accepting the resp. */
1392 OCSP_SINGLERESP * single;
1394 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1395 if (OCSP_resp_count(bs) != 1)
1397 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1398 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1401 tls_out.ocsp = OCSP_FAILED;
1402 log_write(0, LOG_MAIN, "OCSP stapling "
1403 "with multiple responses not handled");
1406 single = OCSP_resp_get0(bs, 0);
1407 status = OCSP_single_get0_status(single, &reason, &rev,
1408 &thisupd, &nextupd);
1411 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1412 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1413 if (!OCSP_check_validity(thisupd, nextupd,
1414 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1416 tls_out.ocsp = OCSP_FAILED;
1417 DEBUG(D_tls) ERR_print_errors(bp);
1418 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1422 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1423 OCSP_cert_status_str(status));
1426 case V_OCSP_CERTSTATUS_GOOD:
1427 tls_out.ocsp = OCSP_VFIED;
1430 case V_OCSP_CERTSTATUS_REVOKED:
1431 tls_out.ocsp = OCSP_FAILED;
1432 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1433 reason != -1 ? "; reason: " : "",
1434 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1435 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1438 tls_out.ocsp = OCSP_FAILED;
1439 log_write(0, LOG_MAIN,
1440 "Server certificate status unknown, in OCSP stapling");
1445 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1450 OCSP_RESPONSE_free(rsp);
1453 #endif /*!DISABLE_OCSP*/
1456 /*************************************************
1457 * Initialize for TLS *
1458 *************************************************/
1460 /* Called from both server and client code, to do preliminary initialization
1461 of the library. We allocate and return a context structure.
1464 ctxp returned SSL context
1465 host connected host, if client; NULL if server
1466 dhparam DH parameter file
1467 certificate certificate file
1468 privatekey private key
1469 ocsp_file file of stapling info (server); flag for require ocsp (client)
1470 addr address if client; NULL if server (for some randomness)
1471 cbp place to put allocated callback context
1472 errstr error string pointer
1474 Returns: OK/DEFER/FAIL
1478 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1480 #ifndef DISABLE_OCSP
1481 uschar *ocsp_file, /*XXX stack, in server*/
1483 address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr)
1488 tls_ext_ctx_cb * cbinfo;
1490 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1491 cbinfo->certificate = certificate;
1492 cbinfo->privatekey = privatekey;
1493 #ifndef DISABLE_OCSP
1494 cbinfo->verify_stack = NULL;
1495 if ((cbinfo->is_server = host==NULL))
1497 cbinfo->u_ocsp.server.file = ocsp_file;
1498 cbinfo->u_ocsp.server.file_expanded = NULL;
1499 cbinfo->u_ocsp.server.response = NULL;
1502 cbinfo->u_ocsp.client.verify_store = NULL;
1504 cbinfo->dhparam = dhparam;
1505 cbinfo->server_cipher_list = NULL;
1506 cbinfo->host = host;
1507 #ifndef DISABLE_EVENT
1508 cbinfo->event_action = NULL;
1511 SSL_load_error_strings(); /* basic set up */
1512 OpenSSL_add_ssl_algorithms();
1514 #ifdef EXIM_HAVE_SHA256
1515 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1516 list of available digests. */
1517 EVP_add_digest(EVP_sha256());
1520 /* Create a context.
1521 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1522 negotiation in the different methods; as far as I can tell, the only
1523 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1524 when OpenSSL is built without SSLv2 support.
1525 By disabling with openssl_options, we can let admins re-enable with the
1528 if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method())))
1529 return tls_error(US"SSL_CTX_new", host, NULL, errstr);
1531 /* It turns out that we need to seed the random number generator this early in
1532 order to get the full complement of ciphers to work. It took me roughly a day
1533 of work to discover this by experiment.
1535 On systems that have /dev/urandom, SSL may automatically seed itself from
1536 there. Otherwise, we have to make something up as best we can. Double check
1542 gettimeofday(&r.tv, NULL);
1545 RAND_seed(US (&r), sizeof(r));
1546 RAND_seed(US big_buffer, big_buffer_size);
1547 if (addr != NULL) RAND_seed(US addr, sizeof(addr));
1550 return tls_error(US"RAND_status", host,
1551 US"unable to seed random number generator", errstr);
1554 /* Set up the information callback, which outputs if debugging is at a suitable
1557 DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback);
1559 /* Automatically re-try reads/writes after renegotiation. */
1560 (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);
1562 /* Apply administrator-supplied work-arounds.
1563 Historically we applied just one requested option,
1564 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1565 moved to an administrator-controlled list of options to specify and
1566 grandfathered in the first one as the default value for "openssl_options".
1568 No OpenSSL version number checks: the options we accept depend upon the
1569 availability of the option value macros from OpenSSL. */
1571 if (!tls_openssl_options_parse(openssl_options, &init_options))
1572 return tls_error(US"openssl_options parsing failed", host, NULL, errstr);
1576 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1577 if (!(SSL_CTX_set_options(ctx, init_options)))
1578 return tls_error(string_sprintf(
1579 "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr);
1582 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1584 /* Disable session cache unconditionally */
1586 (void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
1588 /* Initialize with DH parameters if supplied */
1589 /* Initialize ECDH temp key parameter selection */
1591 if ( !init_dh(ctx, dhparam, host, errstr)
1592 || !init_ecdh(ctx, host, errstr)
1596 /* Set up certificate and key (and perhaps OCSP info) */
1598 if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK)
1601 /* If we need to handle SNI or OCSP, do so */
1603 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1604 # ifndef DISABLE_OCSP
1605 if (!(cbinfo->verify_stack = sk_X509_new_null()))
1607 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1612 if (host == NULL) /* server */
1614 # ifndef DISABLE_OCSP
1615 /* We check u_ocsp.server.file, not server.response, because we care about if
1616 the option exists, not what the current expansion might be, as SNI might
1617 change the certificate and OCSP file in use between now and the time the
1618 callback is invoked. */
1619 if (cbinfo->u_ocsp.server.file)
1621 SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb);
1622 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1625 /* We always do this, so that $tls_sni is available even if not used in
1627 SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb);
1628 SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo);
1630 # ifndef DISABLE_OCSP
1632 if(ocsp_file) /* wanting stapling */
1634 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1636 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1639 SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb);
1640 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
1645 cbinfo->verify_cert_hostnames = NULL;
1647 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1648 /* Set up the RSA callback */
1649 SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback);
1652 /* Finally, set the timeout, and we are done */
1654 SSL_CTX_set_timeout(ctx, ssl_session_timeout);
1655 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1666 /*************************************************
1667 * Get name of cipher in use *
1668 *************************************************/
1671 Argument: pointer to an SSL structure for the connection
1672 buffer to use for answer
1674 pointer to number of bits for cipher
1679 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1681 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1682 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1683 the accessor functions use const in the prototype. */
1684 const SSL_CIPHER *c;
1687 ver = (const uschar *)SSL_get_version(ssl);
1689 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1690 SSL_CIPHER_get_bits(c, bits);
1692 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1693 SSL_CIPHER_get_name(c), *bits);
1695 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1700 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned bsize)
1702 /*XXX we might consider a list-of-certs variable for the cert chain.
1703 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1704 in list-handling functions, also consider the difference between the entire
1705 chain and the elements sent by the peer. */
1707 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1708 if (!tlsp->peercert)
1709 tlsp->peercert = SSL_get_peer_certificate(ssl);
1710 /* Beware anonymous ciphers which lead to server_cert being NULL */
1713 X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, bsize);
1714 peerdn[bsize-1] = '\0';
1715 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1718 tlsp->peerdn = NULL;
1725 /*************************************************
1726 * Set up for verifying certificates *
1727 *************************************************/
1729 /* Load certs from file, return TRUE on success */
1732 chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack)
1737 if (!(bp = BIO_new_file(CS file, "r"))) return FALSE;
1738 while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL)))
1739 sk_X509_push(verify_stack, x);
1746 /* Called by both client and server startup
1749 sctx SSL_CTX* to initialise
1750 certs certs file or NULL
1751 crl CRL file or NULL
1752 host NULL in a server; the remote host in a client
1753 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1754 otherwise passed as FALSE
1755 cert_vfy_cb Callback function for certificate verification
1756 errstr error string pointer
1758 Returns: OK/DEFER/FAIL
1762 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1763 int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr)
1765 uschar *expcerts, *expcrl;
1767 if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr))
1769 DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts);
1771 if (expcerts && *expcerts)
1773 /* Tell the library to use its compiled-in location for the system default
1774 CA bundle. Then add the ones specified in the config, if any. */
1776 if (!SSL_CTX_set_default_verify_paths(sctx))
1777 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr);
1779 if (Ustrcmp(expcerts, "system") != 0)
1781 struct stat statbuf;
1783 if (Ustat(expcerts, &statbuf) < 0)
1785 log_write(0, LOG_MAIN|LOG_PANIC,
1786 "failed to stat %s for certificates", expcerts);
1792 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1793 { file = NULL; dir = expcerts; }
1796 file = expcerts; dir = NULL;
1797 #ifndef DISABLE_OCSP
1798 /* In the server if we will be offering an OCSP proof, load chain from
1799 file for verifying the OCSP proof at load time. */
1802 && statbuf.st_size > 0
1803 && server_static_cbinfo->u_ocsp.server.file
1804 && !chain_from_pem_file(file, server_static_cbinfo->verify_stack)
1807 log_write(0, LOG_MAIN|LOG_PANIC,
1808 "failed to load cert hain from %s", file);
1814 /* If a certificate file is empty, the next function fails with an
1815 unhelpful error message. If we skip it, we get the correct behaviour (no
1816 certificates are recognized, but the error message is still misleading (it
1817 says no certificate was supplied). But this is better. */
1819 if ( (!file || statbuf.st_size > 0)
1820 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1821 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr);
1823 /* Load the list of CAs for which we will accept certs, for sending
1824 to the client. This is only for the one-file tls_verify_certificates
1826 If a list isn't loaded into the server, but
1827 some verify locations are set, the server end appears to make
1828 a wildcard request for client certs.
1829 Meanwhile, the client library as default behaviour *ignores* the list
1830 we send over the wire - see man SSL_CTX_set_client_cert_cb.
1831 Because of this, and that the dir variant is likely only used for
1832 the public-CA bundle (not for a private CA), not worth fixing.
1836 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
1838 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
1839 sk_X509_NAME_num(names));
1840 SSL_CTX_set_client_CA_list(sctx, names);
1845 /* Handle a certificate revocation list. */
1847 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1849 /* This bit of code is now the version supplied by Lars Mainka. (I have
1850 merely reformatted it into the Exim code style.)
1852 "From here I changed the code to add support for multiple crl's
1853 in pem format in one file or to support hashed directory entries in
1854 pem format instead of a file. This method now uses the library function
1855 X509_STORE_load_locations to add the CRL location to the SSL context.
1856 OpenSSL will then handle the verify against CA certs and CRLs by
1857 itself in the verify callback." */
1859 if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER;
1860 if (expcrl && *expcrl)
1862 struct stat statbufcrl;
1863 if (Ustat(expcrl, &statbufcrl) < 0)
1865 log_write(0, LOG_MAIN|LOG_PANIC,
1866 "failed to stat %s for certificates revocation lists", expcrl);
1871 /* is it a file or directory? */
1873 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1874 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1878 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1884 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1886 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1887 return tls_error(US"X509_STORE_load_locations", host, NULL, errstr);
1889 /* setting the flags to check against the complete crl chain */
1891 X509_STORE_set_flags(cvstore,
1892 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1896 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1898 /* If verification is optional, don't fail if no certificate */
1900 SSL_CTX_set_verify(sctx,
1901 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1910 /*************************************************
1911 * Start a TLS session in a server *
1912 *************************************************/
1914 /* This is called when Exim is running as a server, after having received
1915 the STARTTLS command. It must respond to that command, and then negotiate
1919 require_ciphers allowed ciphers
1920 errstr pointer to error message
1922 Returns: OK on success
1923 DEFER for errors before the start of the negotiation
1924 FAIL for errors during the negotiation; the server can't
1929 tls_server_start(const uschar * require_ciphers, uschar ** errstr)
1932 uschar * expciphers;
1933 tls_ext_ctx_cb * cbinfo;
1934 static uschar peerdn[256];
1935 static uschar cipherbuf[256];
1937 /* Check for previous activation */
1939 if (tls_in.active >= 0)
1941 tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr);
1942 smtp_printf("554 Already in TLS\r\n", FALSE);
1946 /* Initialize the SSL library. If it fails, it will already have logged
1949 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1950 #ifndef DISABLE_OCSP
1951 tls_ocsp_file, /*XXX stack*/
1953 NULL, &server_static_cbinfo, errstr);
1954 if (rc != OK) return rc;
1955 cbinfo = server_static_cbinfo;
1957 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr))
1960 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1961 were historically separated by underscores. So that I can use either form in my
1962 tests, and also for general convenience, we turn underscores into hyphens here.
1967 uschar * s = expciphers;
1968 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1969 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1970 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1971 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr);
1972 cbinfo->server_cipher_list = expciphers;
1975 /* If this is a host for which certificate verification is mandatory or
1976 optional, set up appropriately. */
1978 tls_in.certificate_verified = FALSE;
1979 #ifdef EXPERIMENTAL_DANE
1980 tls_in.dane_verified = FALSE;
1982 server_verify_callback_called = FALSE;
1984 if (verify_check_host(&tls_verify_hosts) == OK)
1986 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1987 FALSE, verify_callback_server, errstr);
1988 if (rc != OK) return rc;
1989 server_verify_optional = FALSE;
1991 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1993 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1994 TRUE, verify_callback_server, errstr);
1995 if (rc != OK) return rc;
1996 server_verify_optional = TRUE;
1999 /* Prepare for new connection */
2001 if (!(server_ssl = SSL_new(server_ctx)))
2002 return tls_error(US"SSL_new", NULL, NULL, errstr);
2004 /* Warning: we used to SSL_clear(ssl) here, it was removed.
2006 * With the SSL_clear(), we get strange interoperability bugs with
2007 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
2008 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
2010 * The SSL_clear() call is to let an existing SSL* be reused, typically after
2011 * session shutdown. In this case, we have a brand new object and there's no
2012 * obvious reason to immediately clear it. I'm guessing that this was
2013 * originally added because of incomplete initialisation which the clear fixed,
2014 * in some historic release.
2017 /* Set context and tell client to go ahead, except in the case of TLS startup
2018 on connection, where outputting anything now upsets the clients and tends to
2019 make them disconnect. We need to have an explicit fflush() here, to force out
2020 the response. Other smtp_printf() calls do not need it, because in non-TLS
2021 mode, the fflush() happens when smtp_getc() is called. */
2023 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
2024 if (!tls_in.on_connect)
2026 smtp_printf("220 TLS go ahead\r\n", FALSE);
2030 /* Now negotiate the TLS session. We put our own timer on it, since it seems
2031 that the OpenSSL library doesn't. */
2033 SSL_set_wfd(server_ssl, fileno(smtp_out));
2034 SSL_set_rfd(server_ssl, fileno(smtp_in));
2035 SSL_set_accept_state(server_ssl);
2037 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
2039 sigalrm_seen = FALSE;
2040 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2041 rc = SSL_accept(server_ssl);
2046 (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr);
2050 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
2052 /* TLS has been set up. Adjust the input functions to read via TLS,
2053 and initialize things. */
2055 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
2057 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
2058 tls_in.cipher = cipherbuf;
2063 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
2064 debug_printf("Shared ciphers: %s\n", buf);
2067 /* Record the certificate we presented */
2069 X509 * crt = SSL_get_certificate(server_ssl);
2070 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
2073 /* Only used by the server-side tls (tls_in), including tls_getc.
2074 Client-side (tls_out) reads (seem to?) go via
2075 smtp_read_response()/ip_recv().
2076 Hence no need to duplicate for _in and _out.
2078 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
2079 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
2080 ssl_xfer_eof = ssl_xfer_error = 0;
2082 receive_getc = tls_getc;
2083 receive_getbuf = tls_getbuf;
2084 receive_get_cache = tls_get_cache;
2085 receive_ungetc = tls_ungetc;
2086 receive_feof = tls_feof;
2087 receive_ferror = tls_ferror;
2088 receive_smtp_buffered = tls_smtp_buffered;
2090 tls_in.active = fileno(smtp_out);
2098 tls_client_basic_ctx_init(SSL_CTX * ctx,
2099 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo,
2103 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2104 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2105 the specified host patterns if one of them is defined */
2107 if ( ( !ob->tls_verify_hosts
2108 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2110 || (verify_check_given_host(&ob->tls_verify_hosts, host) == OK)
2112 client_verify_optional = FALSE;
2113 else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
2114 client_verify_optional = TRUE;
2118 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2119 ob->tls_crl, host, client_verify_optional, verify_callback_client,
2123 if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
2125 cbinfo->verify_cert_hostnames =
2127 string_domain_utf8_to_alabel(host->name, NULL);
2131 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2132 cbinfo->verify_cert_hostnames);
2138 #ifdef EXPERIMENTAL_DANE
2140 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr)
2144 const char * hostnames[2] = { CS host->name, NULL };
2147 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2148 return tls_error(US"hostnames load", host, NULL, errstr);
2150 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
2152 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2153 ) if (rr->type == T_TLSA)
2155 const uschar * p = rr->data;
2156 uint8_t usage, selector, mtype;
2157 const char * mdname;
2161 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2162 if (usage != 2 && usage != 3) continue;
2169 default: continue; /* Only match-types 0, 1, 2 are supported */
2170 case 0: mdname = NULL; break;
2171 case 1: mdname = "sha256"; break;
2172 case 2: mdname = "sha512"; break;
2176 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2179 return tls_error(US"tlsa load", host, NULL, errstr);
2180 case 0: /* action not taken */
2184 tls_out.tlsa_usage |= 1<<usage;
2190 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2193 #endif /*EXPERIMENTAL_DANE*/
2197 /*************************************************
2198 * Start a TLS session in a client *
2199 *************************************************/
2201 /* Called from the smtp transport after STARTTLS has been accepted.
2204 fd the fd of the connection
2205 host connected host (for messages)
2206 addr the first address
2207 tb transport (always smtp)
2208 tlsa_dnsa tlsa lookup, if DANE, else null
2209 errstr error string pointer
2211 Returns: OK on success
2212 FAIL otherwise - note that tls_error() will not give DEFER
2213 because this is not a server
2217 tls_client_start(int fd, host_item *host, address_item *addr,
2218 transport_instance * tb,
2219 #ifdef EXPERIMENTAL_DANE
2220 dns_answer * tlsa_dnsa,
2224 smtp_transport_options_block * ob =
2225 (smtp_transport_options_block *)tb->options_block;
2226 static uschar peerdn[256];
2227 uschar * expciphers;
2229 static uschar cipherbuf[256];
2231 #ifndef DISABLE_OCSP
2232 BOOL request_ocsp = FALSE;
2233 BOOL require_ocsp = FALSE;
2236 #ifdef EXPERIMENTAL_DANE
2237 tls_out.tlsa_usage = 0;
2240 #ifndef DISABLE_OCSP
2242 # ifdef EXPERIMENTAL_DANE
2244 && ob->hosts_request_ocsp[0] == '*'
2245 && ob->hosts_request_ocsp[1] == '\0'
2248 /* Unchanged from default. Use a safer one under DANE */
2249 request_ocsp = TRUE;
2250 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2251 " {= {4}{$tls_out_tlsa_usage}} } "
2257 verify_check_given_host(&ob->hosts_require_ocsp, host) == OK))
2258 request_ocsp = TRUE;
2260 # ifdef EXPERIMENTAL_DANE
2264 verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2268 rc = tls_init(&client_ctx, host, NULL,
2269 ob->tls_certificate, ob->tls_privatekey,
2270 #ifndef DISABLE_OCSP
2271 (void *)(long)request_ocsp,
2273 addr, &client_static_cbinfo, errstr);
2274 if (rc != OK) return rc;
2276 tls_out.certificate_verified = FALSE;
2277 client_verify_callback_called = FALSE;
2279 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2280 &expciphers, errstr))
2283 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2284 are separated by underscores. So that I can use either form in my tests, and
2285 also for general convenience, we turn underscores into hyphens here. */
2289 uschar *s = expciphers;
2290 while (*s) { if (*s == '_') *s = '-'; s++; }
2291 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2292 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
2293 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr);
2296 #ifdef EXPERIMENTAL_DANE
2299 SSL_CTX_set_verify(client_ctx,
2300 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2301 verify_callback_client_dane);
2303 if (!DANESSL_library_init())
2304 return tls_error(US"library init", host, NULL, errstr);
2305 if (DANESSL_CTX_init(client_ctx) <= 0)
2306 return tls_error(US"context init", host, NULL, errstr);
2312 if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob,
2313 client_static_cbinfo, errstr)) != OK)
2316 if ((client_ssl = SSL_new(client_ctx)) == NULL)
2317 return tls_error(US"SSL_new", host, NULL, errstr);
2318 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
2319 SSL_set_fd(client_ssl, fd);
2320 SSL_set_connect_state(client_ssl);
2324 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni, errstr))
2328 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2330 else if (!Ustrlen(tls_out.sni))
2334 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2335 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
2336 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
2338 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2344 #ifdef EXPERIMENTAL_DANE
2346 if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa, errstr)) != OK)
2350 #ifndef DISABLE_OCSP
2351 /* Request certificate status at connection-time. If the server
2352 does OCSP stapling we will get the callback (set in tls_init()) */
2353 # ifdef EXPERIMENTAL_DANE
2357 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2358 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2360 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2361 this means we avoid the OCSP request, we wasted the setup
2362 cost in tls_init(). */
2363 require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
2364 request_ocsp = require_ocsp
2365 || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2372 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
2373 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2374 tls_out.ocsp = OCSP_NOT_RESP;
2378 #ifndef DISABLE_EVENT
2379 client_static_cbinfo->event_action = tb->event_action;
2382 /* There doesn't seem to be a built-in timeout on connection. */
2384 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2385 sigalrm_seen = FALSE;
2386 alarm(ob->command_timeout);
2387 rc = SSL_connect(client_ssl);
2390 #ifdef EXPERIMENTAL_DANE
2392 DANESSL_cleanup(client_ssl);
2396 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL,
2399 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
2401 peer_cert(client_ssl, &tls_out, peerdn, sizeof(peerdn));
2403 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
2404 tls_out.cipher = cipherbuf;
2406 /* Record the certificate we presented */
2408 X509 * crt = SSL_get_certificate(client_ssl);
2409 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
2412 tls_out.active = fd;
2421 tls_refill(unsigned lim)
2426 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2427 ssl_xfer_buffer, ssl_xfer_buffer_size);
2429 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2430 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer,
2431 MIN(ssl_xfer_buffer_size, lim));
2432 error = SSL_get_error(server_ssl, inbytes);
2435 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2436 closed down, not that the socket itself has been closed down. Revert to
2437 non-SSL handling. */
2439 if (error == SSL_ERROR_ZERO_RETURN)
2441 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2443 receive_getc = smtp_getc;
2444 receive_getbuf = smtp_getbuf;
2445 receive_get_cache = smtp_get_cache;
2446 receive_ungetc = smtp_ungetc;
2447 receive_feof = smtp_feof;
2448 receive_ferror = smtp_ferror;
2449 receive_smtp_buffered = smtp_buffered;
2451 SSL_free(server_ssl);
2455 tls_in.cipher = NULL;
2456 tls_in.peerdn = NULL;
2462 /* Handle genuine errors */
2464 else if (error == SSL_ERROR_SSL)
2466 ERR_error_string(ERR_get_error(), ssl_errstring);
2467 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2472 else if (error != SSL_ERROR_NONE)
2474 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2479 #ifndef DISABLE_DKIM
2480 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2482 ssl_xfer_buffer_hwm = inbytes;
2483 ssl_xfer_buffer_lwm = 0;
2488 /*************************************************
2489 * TLS version of getc *
2490 *************************************************/
2492 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2493 it refills the buffer via the SSL reading function.
2495 Arguments: lim Maximum amount to read/buffer
2496 Returns: the next character or EOF
2498 Only used by the server-side TLS.
2502 tls_getc(unsigned lim)
2504 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2505 if (!tls_refill(lim))
2506 return ssl_xfer_error ? EOF : smtp_getc(lim);
2508 /* Something in the buffer; return next uschar */
2510 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2514 tls_getbuf(unsigned * len)
2519 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2520 if (!tls_refill(*len))
2522 if (!ssl_xfer_error) return smtp_getbuf(len);
2527 if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len)
2529 buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm];
2530 ssl_xfer_buffer_lwm += size;
2539 #ifndef DISABLE_DKIM
2540 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2542 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2548 tls_could_read(void)
2550 return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0;
2554 /*************************************************
2555 * Read bytes from TLS channel *
2556 *************************************************/
2563 Returns: the number of bytes read
2564 -1 after a failed read
2566 Only used by the client-side TLS.
2570 tls_read(BOOL is_server, uschar *buff, size_t len)
2572 SSL *ssl = is_server ? server_ssl : client_ssl;
2576 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2577 buff, (unsigned int)len);
2579 inbytes = SSL_read(ssl, CS buff, len);
2580 error = SSL_get_error(ssl, inbytes);
2582 if (error == SSL_ERROR_ZERO_RETURN)
2584 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2587 else if (error != SSL_ERROR_NONE)
2597 /*************************************************
2598 * Write bytes down TLS channel *
2599 *************************************************/
2603 is_server channel specifier
2606 more further data expected soon
2608 Returns: the number of bytes after a successful write,
2609 -1 after a failed write
2611 Used by both server-side and client-side TLS.
2615 tls_write(BOOL is_server, const uschar *buff, size_t len, BOOL more)
2617 int outbytes, error, left;
2618 SSL *ssl = is_server ? server_ssl : client_ssl;
2619 static gstring * corked = NULL;
2621 DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
2622 buff, (unsigned long)len, more ? ", more" : "");
2624 /* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
2625 "more" is notified. This hack is only ok if small amounts are involved AND only
2626 one stream does it, in one context (i.e. no store reset). Currently it is used
2627 for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */
2629 if (is_server && (more || corked))
2631 corked = string_catn(corked, buff, len);
2634 buff = CUS corked->s;
2639 for (left = len; left > 0;)
2641 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2642 outbytes = SSL_write(ssl, CS buff, left);
2643 error = SSL_get_error(ssl, outbytes);
2644 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2648 ERR_error_string(ERR_get_error(), ssl_errstring);
2649 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2652 case SSL_ERROR_NONE:
2657 case SSL_ERROR_ZERO_RETURN:
2658 log_write(0, LOG_MAIN, "SSL channel closed on write");
2661 case SSL_ERROR_SYSCALL:
2662 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2663 sender_fullhost ? sender_fullhost : US"<unknown>",
2668 log_write(0, LOG_MAIN, "SSL_write error %d", error);
2677 /*************************************************
2678 * Close down a TLS session *
2679 *************************************************/
2681 /* This is also called from within a delivery subprocess forked from the
2682 daemon, to shut down the TLS library, without actually doing a shutdown (which
2683 would tamper with the SSL session in the parent process).
2685 Arguments: TRUE if SSL_shutdown is to be called
2688 Used by both server-side and client-side TLS.
2692 tls_close(BOOL is_server, BOOL shutdown)
2694 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2695 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2697 if (*fdp < 0) return; /* TLS was not active */
2701 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2702 SSL_shutdown(*sslp);
2714 /*************************************************
2715 * Let tls_require_ciphers be checked at startup *
2716 *************************************************/
2718 /* The tls_require_ciphers option, if set, must be something which the
2721 Returns: NULL on success, or error message
2725 tls_validate_require_cipher(void)
2728 uschar *s, *expciphers, *err;
2730 /* this duplicates from tls_init(), we need a better "init just global
2731 state, for no specific purpose" singleton function of our own */
2733 SSL_load_error_strings();
2734 OpenSSL_add_ssl_algorithms();
2735 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2736 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2737 list of available digests. */
2738 EVP_add_digest(EVP_sha256());
2741 if (!(tls_require_ciphers && *tls_require_ciphers))
2744 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers,
2746 return US"failed to expand tls_require_ciphers";
2748 if (!(expciphers && *expciphers))
2751 /* normalisation ripped from above */
2753 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2757 ctx = SSL_CTX_new(SSLv23_server_method());
2760 ERR_error_string(ERR_get_error(), ssl_errstring);
2761 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2765 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2767 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2769 ERR_error_string(ERR_get_error(), ssl_errstring);
2770 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s",
2771 expciphers, ssl_errstring);
2782 /*************************************************
2783 * Report the library versions. *
2784 *************************************************/
2786 /* There have historically been some issues with binary compatibility in
2787 OpenSSL libraries; if Exim (like many other applications) is built against
2788 one version of OpenSSL but the run-time linker picks up another version,
2789 it can result in serious failures, including crashing with a SIGSEGV. So
2790 report the version found by the compiler and the run-time version.
2792 Note: some OS vendors backport security fixes without changing the version
2793 number/string, and the version date remains unchanged. The _build_ date
2794 will change, so we can more usefully assist with version diagnosis by also
2795 reporting the build date.
2797 Arguments: a FILE* to print the results to
2802 tls_version_report(FILE *f)
2804 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2807 OPENSSL_VERSION_TEXT,
2808 SSLeay_version(SSLEAY_VERSION),
2809 SSLeay_version(SSLEAY_BUILT_ON));
2810 /* third line is 38 characters for the %s and the line is 73 chars long;
2811 the OpenSSL output includes a "built on: " prefix already. */
2817 /*************************************************
2818 * Random number generation *
2819 *************************************************/
2821 /* Pseudo-random number generation. The result is not expected to be
2822 cryptographically strong but not so weak that someone will shoot themselves
2823 in the foot using it as a nonce in input in some email header scheme or
2824 whatever weirdness they'll twist this into. The result should handle fork()
2825 and avoid repeating sequences. OpenSSL handles that for us.
2829 Returns a random number in range [0, max-1]
2833 vaguely_random_number(int max)
2837 static pid_t pidlast = 0;
2840 uschar smallbuf[sizeof(r)];
2846 if (pidnow != pidlast)
2848 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2849 is unique for each thread", this doesn't apparently apply across processes,
2850 so our own warning from vaguely_random_number_fallback() applies here too.
2851 Fix per PostgreSQL. */
2857 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2861 gettimeofday(&r.tv, NULL);
2864 RAND_seed(US (&r), sizeof(r));
2866 /* We're after pseudo-random, not random; if we still don't have enough data
2867 in the internal PRNG then our options are limited. We could sleep and hope
2868 for entropy to come along (prayer technique) but if the system is so depleted
2869 in the first place then something is likely to just keep taking it. Instead,
2870 we'll just take whatever little bit of pseudo-random we can still manage to
2873 needed_len = sizeof(r);
2874 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2875 asked for a number less than 10. */
2876 for (r = max, i = 0; r; ++i)
2882 #ifdef EXIM_HAVE_RAND_PSEUDO
2883 /* We do not care if crypto-strong */
2884 i = RAND_pseudo_bytes(smallbuf, needed_len);
2886 i = RAND_bytes(smallbuf, needed_len);
2892 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2893 return vaguely_random_number_fallback(max);
2897 for (p = smallbuf; needed_len; --needed_len, ++p)
2903 /* We don't particularly care about weighted results; if someone wants
2904 smooth distribution and cares enough then they should submit a patch then. */
2911 /*************************************************
2912 * OpenSSL option parse *
2913 *************************************************/
2915 /* Parse one option for tls_openssl_options_parse below
2918 name one option name
2919 value place to store a value for it
2920 Returns success or failure in parsing
2923 struct exim_openssl_option {
2927 /* We could use a macro to expand, but we need the ifdef and not all the
2928 options document which version they were introduced in. Policylet: include
2929 all options unless explicitly for DTLS, let the administrator choose which
2932 This list is current as of:
2934 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2936 static struct exim_openssl_option exim_openssl_options[] = {
2937 /* KEEP SORTED ALPHABETICALLY! */
2939 { US"all", SSL_OP_ALL },
2941 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2942 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2944 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2945 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2947 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2948 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2950 #ifdef SSL_OP_EPHEMERAL_RSA
2951 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2953 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2954 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2956 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2957 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2959 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2960 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2962 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2963 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2965 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2966 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2968 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2969 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2971 #ifdef SSL_OP_NO_COMPRESSION
2972 { US"no_compression", SSL_OP_NO_COMPRESSION },
2974 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2975 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2977 #ifdef SSL_OP_NO_SSLv2
2978 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2980 #ifdef SSL_OP_NO_SSLv3
2981 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2983 #ifdef SSL_OP_NO_TICKET
2984 { US"no_ticket", SSL_OP_NO_TICKET },
2986 #ifdef SSL_OP_NO_TLSv1
2987 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2989 #ifdef SSL_OP_NO_TLSv1_1
2990 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2991 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2992 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2994 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2997 #ifdef SSL_OP_NO_TLSv1_2
2998 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
3000 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
3001 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
3003 #ifdef SSL_OP_SINGLE_DH_USE
3004 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
3006 #ifdef SSL_OP_SINGLE_ECDH_USE
3007 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
3009 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
3010 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
3012 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
3013 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
3015 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
3016 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
3018 #ifdef SSL_OP_TLS_D5_BUG
3019 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
3021 #ifdef SSL_OP_TLS_ROLLBACK_BUG
3022 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
3025 static int exim_openssl_options_size =
3026 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
3030 tls_openssl_one_option_parse(uschar *name, long *value)
3033 int last = exim_openssl_options_size;
3034 while (last > first)
3036 int middle = (first + last)/2;
3037 int c = Ustrcmp(name, exim_openssl_options[middle].name);
3040 *value = exim_openssl_options[middle].value;
3054 /*************************************************
3055 * OpenSSL option parsing logic *
3056 *************************************************/
3058 /* OpenSSL has a number of compatibility options which an administrator might
3059 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
3060 we look like log_selector.
3063 option_spec the administrator-supplied string of options
3064 results ptr to long storage for the options bitmap
3065 Returns success or failure
3069 tls_openssl_options_parse(uschar *option_spec, long *results)
3074 BOOL adding, item_parsed;
3076 result = SSL_OP_NO_TICKET;
3077 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
3078 * from default because it increases BEAST susceptibility. */
3079 #ifdef SSL_OP_NO_SSLv2
3080 result |= SSL_OP_NO_SSLv2;
3082 #ifdef SSL_OP_SINGLE_DH_USE
3083 result |= SSL_OP_SINGLE_DH_USE;
3092 for (s=option_spec; *s != '\0'; /**/)
3094 while (isspace(*s)) ++s;
3097 if (*s != '+' && *s != '-')
3099 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
3100 "+ or - expected but found \"%s\"\n", s);
3103 adding = *s++ == '+';
3104 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
3107 item_parsed = tls_openssl_one_option_parse(s, &item);
3111 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
3114 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
3115 adding ? "adding" : "removing", result, item, s);
3129 /* End of tls-openssl.c */