1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2016 */
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
73 # if OPENSSL_VERSION_NUMBER >= 0x010000000L \
74 && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
75 # define EXIM_HAVE_OPENSSL_CHECKHOST
79 #if !defined(LIBRESSL_VERSION_NUMBER) \
80 || LIBRESSL_VERSION_NUMBER >= 0x20010000L
81 # if !defined(OPENSSL_NO_ECDH)
82 # if OPENSSL_VERSION_NUMBER >= 0x0090800fL
83 # define EXIM_HAVE_ECDH
85 # if OPENSSL_VERSION_NUMBER >= 0x10002000L
86 # if OPENSSL_VERSION_NUMBER < 0x10100000L
87 # define EXIM_HAVE_OPENSSL_ECDH_AUTO
89 # define EXIM_HAVE_OPENSSL_EC_NIST2NID
94 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
95 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
99 /* Structure for collecting random data for seeding. */
101 typedef struct randstuff {
106 /* Local static variables */
108 static BOOL client_verify_callback_called = FALSE;
109 static BOOL server_verify_callback_called = FALSE;
110 static const uschar *sid_ctx = US"exim";
112 /* We have three different contexts to care about.
114 Simple case: client, `client_ctx`
115 As a client, we can be doing a callout or cut-through delivery while receiving
116 a message. So we have a client context, which should have options initialised
117 from the SMTP Transport.
120 There are two cases: with and without ServerNameIndication from the client.
121 Given TLS SNI, we can be using different keys, certs and various other
122 configuration settings, because they're re-expanded with $tls_sni set. This
123 allows vhosting with TLS. This SNI is sent in the handshake.
124 A client might not send SNI, so we need a fallback, and an initial setup too.
125 So as a server, we start out using `server_ctx`.
126 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
127 `server_sni` from `server_ctx` and then initialise settings by re-expanding
131 static SSL_CTX *client_ctx = NULL;
132 static SSL_CTX *server_ctx = NULL;
133 static SSL *client_ssl = NULL;
134 static SSL *server_ssl = NULL;
136 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
137 static SSL_CTX *server_sni = NULL;
140 static char ssl_errstring[256];
142 static int ssl_session_timeout = 200;
143 static BOOL client_verify_optional = FALSE;
144 static BOOL server_verify_optional = FALSE;
146 static BOOL reexpand_tls_files_for_sni = FALSE;
149 typedef struct tls_ext_ctx_cb {
157 uschar *file_expanded;
158 OCSP_RESPONSE *response;
161 X509_STORE *verify_store; /* non-null if status requested */
162 STACK_OF(X509) *verify_stack;
163 BOOL verify_required;
168 /* these are cached from first expand */
169 uschar *server_cipher_list;
170 /* only passed down to tls_error: */
172 const uschar * verify_cert_hostnames;
173 #ifndef DISABLE_EVENT
174 uschar * event_action;
178 /* should figure out a cleanup of API to handle state preserved per
179 implementation, for various reasons, which can be void * in the APIs.
180 For now, we hack around it. */
181 tls_ext_ctx_cb *client_static_cbinfo = NULL;
182 tls_ext_ctx_cb *server_static_cbinfo = NULL;
185 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
186 int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
189 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
190 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
193 static int tls_server_stapling_cb(SSL *s, void *arg);
197 /*************************************************
199 *************************************************/
201 /* Called from lots of places when errors occur before actually starting to do
202 the TLS handshake, that is, while the session is still in clear. Always returns
203 DEFER for a server and FAIL for a client so that most calls can use "return
204 tls_error(...)" to do this processing and then give an appropriate return. A
205 single function is used for both server and client, because it is called from
206 some shared functions.
209 prefix text to include in the logged error
210 host NULL if setting up a server;
211 the connected host if setting up a client
212 msg error message or NULL if we should ask OpenSSL
214 Returns: OK/DEFER/FAIL
218 tls_error(uschar * prefix, const host_item * host, uschar * msg)
222 ERR_error_string(ERR_get_error(), ssl_errstring);
223 msg = (uschar *)ssl_errstring;
228 log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection (%s): %s",
229 host->name, host->address, prefix, msg);
234 uschar *conn_info = smtp_get_connection_info();
235 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
237 /* I'd like to get separated H= here, but too hard for now */
238 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
239 conn_info, prefix, msg);
246 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
247 /*************************************************
248 * Callback to generate RSA key *
249 *************************************************/
257 Returns: pointer to generated key
261 rsa_callback(SSL *s, int export, int keylength)
264 #ifdef EXIM_HAVE_RSA_GENKEY_EX
265 BIGNUM *bn = BN_new();
268 export = export; /* Shut picky compilers up */
269 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
271 #ifdef EXIM_HAVE_RSA_GENKEY_EX
272 if ( !BN_set_word(bn, (unsigned long)RSA_F4)
273 || !(rsa_key = RSA_new())
274 || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL)
277 if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL)))
281 ERR_error_string(ERR_get_error(), ssl_errstring);
282 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
295 x509_store_dump_cert_s_names(X509_STORE * store)
297 STACK_OF(X509_OBJECT) * roots= store->objs;
299 static uschar name[256];
301 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
303 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
304 if(tmp_obj->type == X509_LU_X509)
306 X509 * current_cert= tmp_obj->data.x509;
307 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
308 name[sizeof(name)-1] = '\0';
309 debug_printf(" %s\n", name);
317 #ifndef DISABLE_EVENT
319 verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn,
320 BOOL *calledp, const BOOL *optionalp, const uschar * what)
326 ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action;
329 DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth);
330 old_cert = tlsp->peercert;
331 tlsp->peercert = X509_dup(cert);
332 /* NB we do not bother setting peerdn */
333 if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth))))
335 log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: "
336 "depth=%d cert=%s: %s",
337 tlsp == &tls_out ? deliver_host_address : sender_host_address,
338 what, depth, dn, yield);
342 if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */
343 return 1; /* reject (leaving peercert set) */
345 DEBUG(D_tls) debug_printf("Event-action verify failure overridden "
346 "(host in tls_try_verify_hosts)\n");
348 X509_free(tlsp->peercert);
349 tlsp->peercert = old_cert;
355 /*************************************************
356 * Callback for verification *
357 *************************************************/
359 /* The SSL library does certificate verification if set up to do so. This
360 callback has the current yes/no state is in "state". If verification succeeded,
361 we set the certificate-verified flag. If verification failed, what happens
362 depends on whether the client is required to present a verifiable certificate
365 If verification is optional, we change the state to yes, but still log the
366 verification error. For some reason (it really would help to have proper
367 documentation of OpenSSL), this callback function then gets called again, this
368 time with state = 1. We must take care not to set the private verified flag on
369 the second time through.
371 Note: this function is not called if the client fails to present a certificate
372 when asked. We get here only if a certificate has been received. Handling of
373 optional verification for this case is done when requesting SSL to verify, by
374 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
376 May be called multiple times for different issues with a certificate, even
377 for a given "depth" in the certificate chain.
380 preverify_ok current yes/no state as 1/0
381 x509ctx certificate information.
382 tlsp per-direction (client vs. server) support data
383 calledp has-been-called flag
384 optionalp verification-is-optional flag
386 Returns: 0 if verification should fail, otherwise 1
390 verify_callback(int preverify_ok, X509_STORE_CTX *x509ctx,
391 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
393 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
394 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
397 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
398 dn[sizeof(dn)-1] = '\0';
400 if (preverify_ok == 0)
402 log_write(0, LOG_MAIN, "[%s] SSL verify error: depth=%d error=%s cert=%s",
403 tlsp == &tls_out ? deliver_host_address : sender_host_address,
405 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
411 tlsp->peercert = X509_dup(cert); /* record failing cert */
412 return 0; /* reject */
414 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
415 "tls_try_verify_hosts)\n");
420 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn);
422 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
423 { /* client, wanting stapling */
424 /* Add the server cert's signing chain as the one
425 for the verification of the OCSP stapled information. */
427 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
430 sk_X509_push(client_static_cbinfo->u_ocsp.client.verify_stack, cert);
433 #ifndef DISABLE_EVENT
434 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
435 return 0; /* reject, with peercert set */
440 const uschar * verify_cert_hostnames;
442 if ( tlsp == &tls_out
443 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
444 /* client, wanting hostname check */
447 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
448 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
449 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
451 # ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
452 # define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0
455 const uschar * list = verify_cert_hostnames;
458 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
459 if ((rc = X509_check_host(cert, CCS name, 0,
460 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
461 | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS,
466 log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error",
467 tlsp == &tls_out ? deliver_host_address : sender_host_address);
474 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
477 log_write(0, LOG_MAIN,
478 "[%s] SSL verify error: certificate name mismatch: \"%s\"",
479 tlsp == &tls_out ? deliver_host_address : sender_host_address,
485 tlsp->peercert = X509_dup(cert); /* record failing cert */
486 return 0; /* reject */
488 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
489 "tls_try_verify_hosts)\n");
493 #ifndef DISABLE_EVENT
494 if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL"))
495 return 0; /* reject, with peercert set */
498 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
499 *calledp ? "" : " authenticated", dn);
500 if (!*calledp) tlsp->certificate_verified = TRUE;
504 return 1; /* accept, at least for this level */
508 verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx)
510 return verify_callback(preverify_ok, x509ctx, &tls_out,
511 &client_verify_callback_called, &client_verify_optional);
515 verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx)
517 return verify_callback(preverify_ok, x509ctx, &tls_in,
518 &server_verify_callback_called, &server_verify_optional);
522 #ifdef EXPERIMENTAL_DANE
524 /* This gets called *by* the dane library verify callback, which interposes
528 verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx)
530 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
532 #ifndef DISABLE_EVENT
533 int depth = X509_STORE_CTX_get_error_depth(x509ctx);
534 BOOL dummy_called, optional = FALSE;
537 X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn));
538 dn[sizeof(dn)-1] = '\0';
540 DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n",
541 preverify_ok ? "ok":"BAD", depth, dn);
543 #ifndef DISABLE_EVENT
544 if (verify_event(&tls_out, cert, depth, dn,
545 &dummy_called, &optional, US"DANE"))
546 return 0; /* reject, with peercert set */
549 if (preverify_ok == 1)
550 tls_out.dane_verified =
551 tls_out.certificate_verified = TRUE;
554 int err = X509_STORE_CTX_get_error(x509ctx);
556 debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err));
557 if (err == X509_V_ERR_APPLICATION_VERIFICATION)
563 #endif /*EXPERIMENTAL_DANE*/
566 /*************************************************
567 * Information callback *
568 *************************************************/
570 /* The SSL library functions call this from time to time to indicate what they
571 are doing. We copy the string to the debugging output when TLS debugging has
583 info_callback(SSL *s, int where, int ret)
587 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
592 /*************************************************
593 * Initialize for DH *
594 *************************************************/
596 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
599 sctx The current SSL CTX (inbound or outbound)
600 dhparam DH parameter file or fixed parameter identity string
601 host connected host, if client; NULL if server
603 Returns: TRUE if OK (nothing to set up, or setup worked)
607 init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host)
614 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
617 if (!dhexpanded || !*dhexpanded)
618 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
619 else if (dhexpanded[0] == '/')
621 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
623 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
624 host, US strerror(errno));
630 if (Ustrcmp(dhexpanded, "none") == 0)
632 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
636 if (!(pem = std_dh_prime_named(dhexpanded)))
638 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
639 host, US strerror(errno));
642 bio = BIO_new_mem_buf(CS pem, -1);
645 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
648 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
653 /* Even if it is larger, we silently return success rather than cause things
654 * to fail out, so that a too-large DH will not knock out all TLS; it's a
655 * debatable choice. */
656 if ((8*DH_size(dh)) > tls_dh_max_bits)
659 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
660 8*DH_size(dh), tls_dh_max_bits);
664 SSL_CTX_set_tmp_dh(sctx, dh);
666 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
667 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
679 /*************************************************
680 * Initialize for ECDH *
681 *************************************************/
683 /* Load parameters for ECDH encryption.
685 For now, we stick to NIST P-256 because: it's simple and easy to configure;
686 it avoids any patent issues that might bite redistributors; despite events in
687 the news and concerns over curve choices, we're not cryptographers, we're not
688 pretending to be, and this is "good enough" to be better than no support,
689 protecting against most adversaries. Given another year or two, there might
690 be sufficient clarity about a "right" way forward to let us make an informed
691 decision, instead of a knee-jerk reaction.
693 Longer-term, we should look at supporting both various named curves and
694 external files generated with "openssl ecparam", much as we do for init_dh().
695 We should also support "none" as a value, to explicitly avoid initialisation.
700 sctx The current SSL CTX (inbound or outbound)
701 host connected host, if client; NULL if server
703 Returns: TRUE if OK (nothing to set up, or setup worked)
707 init_ecdh(SSL_CTX * sctx, host_item * host)
709 #ifdef OPENSSL_NO_ECDH
718 if (host) /* No ECDH setup for clients, only for servers */
721 # ifndef EXIM_HAVE_ECDH
723 debug_printf("No OpenSSL API to define ECDH parameters, skipping\n");
727 if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve))
729 if (!exp_curve || !*exp_curve)
732 # ifdef EXIM_HAVE_OPENSSL_ECDH_AUTO
733 /* check if new enough library to support auto ECDH temp key parameter selection */
734 if (Ustrcmp(exp_curve, "auto") == 0)
736 DEBUG(D_tls) debug_printf(
737 "ECDH temp key parameter settings: OpenSSL 1.2+ autoselection\n");
738 SSL_CTX_set_ecdh_auto(sctx, 1);
743 DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve);
744 if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef
745 # ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID
746 && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef
750 tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'",
756 if (!(ecdh = EC_KEY_new_by_curve_name(nid)))
758 tls_error(US"Unable to create ec curve", host, NULL);
762 /* The "tmp" in the name here refers to setting a temporary key
763 not to the stability of the interface. */
765 if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0))
766 tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL);
768 DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve);
773 # endif /*EXIM_HAVE_ECDH*/
774 #endif /*OPENSSL_NO_ECDH*/
781 /*************************************************
782 * Load OCSP information into state *
783 *************************************************/
785 static STACK_OF(X509) *
786 cert_stack_from_store(X509_STORE * store)
788 STACK_OF(X509_OBJECT) * roots= store->objs;
789 STACK_OF(X509) * sk = sk_X509_new_null();
792 for(i = sk_X509_OBJECT_num(roots) - 1; i >= 0; i--)
794 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
795 if(tmp_obj->type == X509_LU_X509)
797 X509 * x = tmp_obj->data.x509;
805 cert_stack_free(STACK_OF(X509) * sk)
807 while (sk_X509_num(sk) > 0) (void) sk_X509_pop(sk);
813 /* Called to load the server OCSP response from the given file into memory, once
814 caller has determined this is needed. Checks validity. Debugs a message
817 ASSUMES: single response, for single cert.
820 sctx the SSL_CTX* to update
821 cbinfo various parts of session state
822 expanded the filename putatively holding an OCSP response
827 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
830 OCSP_RESPONSE * resp;
831 OCSP_BASICRESP * basic_response;
832 OCSP_SINGLERESP * single_response;
833 ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd;
836 unsigned long verify_flags;
837 int status, reason, i;
839 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
840 if (cbinfo->u_ocsp.server.response)
842 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
843 cbinfo->u_ocsp.server.response = NULL;
846 if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb")))
848 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
849 cbinfo->u_ocsp.server.file_expanded);
853 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
857 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
861 if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL)
863 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
864 OCSP_response_status_str(status), status);
868 if (!(basic_response = OCSP_response_get1_basic(resp)))
871 debug_printf("OCSP response parse error: unable to extract basic response.\n");
875 store = SSL_CTX_get_cert_store(sctx);
876 sk = cert_stack_from_store(store);
877 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
879 /* May need to expose ability to adjust those flags?
880 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
881 OCSP_TRUSTOTHER OCSP_NOINTERN */
883 /* This does a full verify on the OCSP proof before we load it for serviing
884 up; possibly overkill - just date-checks might be nice enough.
886 OCSP_basic_verify takes a "store" arg, but does not
887 use it for the chain verification, which is all we do
888 when OCSP_NOVERIFY is set. The content from the wire
889 "basic_response" and a cert-stack "sk" are all that is used.
891 Seperately we might try to replace using OCSP_basic_verify() - which seems to not
892 be a public interface into the OpenSSL library (there's no manual entry) -
893 But what with? We also use OCSP_basic_verify in the client stapling callback.
894 And there we NEED it; we miust verify that status... unless the
895 library does it for us anyway? */
897 if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0)
901 ERR_error_string(ERR_get_error(), ssl_errstring);
902 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)
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 /* deprecated, use RSA_generate_key_ex() */
983 if (!(rsa = RSA_generate_key(1024, RSA_F4, NULL, NULL)))
986 where = US"assiging pkey";
987 if (!EVP_PKEY_assign_RSA(pkey, rsa))
990 X509_set_version(x509, 2); /* N+1 - version 3 */
991 ASN1_INTEGER_set(X509_get_serialNumber(x509), 0);
992 X509_gmtime_adj(X509_get_notBefore(x509), 0);
993 X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */
994 X509_set_pubkey(x509, pkey);
996 name = X509_get_subject_name(x509);
997 X509_NAME_add_entry_by_txt(name, "C",
998 MBSTRING_ASC, CUS "UK", -1, -1, 0);
999 X509_NAME_add_entry_by_txt(name, "O",
1000 MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0);
1001 X509_NAME_add_entry_by_txt(name, "CN",
1002 MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0);
1003 X509_set_issuer_name(x509, name);
1005 where = US"signing cert";
1006 if (!X509_sign(x509, pkey, EVP_md5()))
1009 where = US"installing selfsign cert";
1010 if (!SSL_CTX_use_certificate(sctx, x509))
1013 where = US"installing selfsign key";
1014 if (!SSL_CTX_use_PrivateKey(sctx, pkey))
1020 (void) tls_error(where, NULL, NULL);
1021 if (x509) X509_free(x509);
1022 if (pkey) EVP_PKEY_free(pkey);
1029 /*************************************************
1030 * Expand key and cert file specs *
1031 *************************************************/
1033 /* Called once during tls_init and possibly again during TLS setup, for a
1034 new context, if Server Name Indication was used and tls_sni was seen in
1035 the certificate string.
1038 sctx the SSL_CTX* to update
1039 cbinfo various parts of session state
1041 Returns: OK/DEFER/FAIL
1045 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
1049 if (!cbinfo->certificate)
1051 if (cbinfo->host) /* client */
1054 if (tls_install_selfsign(sctx) != OK)
1059 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
1060 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
1061 Ustrstr(cbinfo->certificate, US"tls_out_sni")
1063 reexpand_tls_files_for_sni = TRUE;
1065 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
1068 if (expanded != NULL)
1070 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
1071 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
1072 return tls_error(string_sprintf(
1073 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
1074 cbinfo->host, NULL);
1077 if (cbinfo->privatekey != NULL &&
1078 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
1081 /* If expansion was forced to fail, key_expanded will be NULL. If the result
1082 of the expansion is an empty string, ignore it also, and assume the private
1083 key is in the same file as the certificate. */
1085 if (expanded && *expanded)
1087 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
1088 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
1089 return tls_error(string_sprintf(
1090 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
1094 #ifndef DISABLE_OCSP
1095 if (cbinfo->is_server && cbinfo->u_ocsp.server.file)
1097 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
1100 if (expanded && *expanded)
1102 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
1103 if ( cbinfo->u_ocsp.server.file_expanded
1104 && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
1106 DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n");
1110 ocsp_load_response(sctx, cbinfo, expanded);
1122 /*************************************************
1123 * Callback to handle SNI *
1124 *************************************************/
1126 /* Called when acting as server during the TLS session setup if a Server Name
1127 Indication extension was sent by the client.
1129 API documentation is OpenSSL s_server.c implementation.
1132 s SSL* of the current session
1133 ad unknown (part of OpenSSL API) (unused)
1134 arg Callback of "our" registered data
1136 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
1139 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1141 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
1143 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
1144 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1146 int old_pool = store_pool;
1149 return SSL_TLSEXT_ERR_OK;
1151 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
1152 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
1154 /* Make the extension value available for expansion */
1155 store_pool = POOL_PERM;
1156 tls_in.sni = string_copy(US servername);
1157 store_pool = old_pool;
1159 if (!reexpand_tls_files_for_sni)
1160 return SSL_TLSEXT_ERR_OK;
1162 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
1163 not confident that memcpy wouldn't break some internal reference counting.
1164 Especially since there's a references struct member, which would be off. */
1166 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
1168 ERR_error_string(ERR_get_error(), ssl_errstring);
1169 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
1170 return SSL_TLSEXT_ERR_NOACK;
1173 /* Not sure how many of these are actually needed, since SSL object
1174 already exists. Might even need this selfsame callback, for reneg? */
1176 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
1177 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
1178 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
1179 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
1180 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
1181 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
1183 if ( !init_dh(server_sni, cbinfo->dhparam, NULL)
1184 || !init_ecdh(server_sni, NULL)
1186 return SSL_TLSEXT_ERR_NOACK;
1188 if (cbinfo->server_cipher_list)
1189 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
1190 #ifndef DISABLE_OCSP
1191 if (cbinfo->u_ocsp.server.file)
1193 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
1194 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
1198 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server);
1199 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
1201 /* do this after setup_certs, because this can require the certs for verifying
1202 OCSP information. */
1203 if ((rc = tls_expand_session_files(server_sni, cbinfo)) != OK)
1204 return SSL_TLSEXT_ERR_NOACK;
1206 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
1207 SSL_set_SSL_CTX(s, server_sni);
1209 return SSL_TLSEXT_ERR_OK;
1211 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
1216 #ifndef DISABLE_OCSP
1218 /*************************************************
1219 * Callback to handle OCSP Stapling *
1220 *************************************************/
1222 /* Called when acting as server during the TLS session setup if the client
1223 requests OCSP information with a Certificate Status Request.
1225 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
1231 tls_server_stapling_cb(SSL *s, void *arg)
1233 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
1234 uschar *response_der;
1235 int response_der_len;
1238 debug_printf("Received TLS status request (OCSP stapling); %s response\n",
1239 cbinfo->u_ocsp.server.response ? "have" : "lack");
1241 tls_in.ocsp = OCSP_NOT_RESP;
1242 if (!cbinfo->u_ocsp.server.response)
1243 return SSL_TLSEXT_ERR_NOACK;
1245 response_der = NULL;
1246 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
1248 if (response_der_len <= 0)
1249 return SSL_TLSEXT_ERR_NOACK;
1251 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
1252 tls_in.ocsp = OCSP_VFIED;
1253 return SSL_TLSEXT_ERR_OK;
1258 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
1260 BIO_printf(bp, "\t%s: ", str);
1261 ASN1_GENERALIZEDTIME_print(bp, time);
1266 tls_client_stapling_cb(SSL *s, void *arg)
1268 tls_ext_ctx_cb * cbinfo = arg;
1269 const unsigned char * p;
1271 OCSP_RESPONSE * rsp;
1272 OCSP_BASICRESP * bs;
1275 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
1276 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
1279 /* Expect this when we requested ocsp but got none */
1280 if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher))
1281 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
1283 DEBUG(D_tls) debug_printf(" null\n");
1284 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1287 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
1289 tls_out.ocsp = OCSP_FAILED;
1290 if (LOGGING(tls_cipher))
1291 log_write(0, LOG_MAIN, "Received TLS cert status response, parse error");
1293 DEBUG(D_tls) debug_printf(" parse error\n");
1297 if(!(bs = OCSP_response_get1_basic(rsp)))
1299 tls_out.ocsp = OCSP_FAILED;
1300 if (LOGGING(tls_cipher))
1301 log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response");
1303 DEBUG(D_tls) debug_printf(" error parsing response\n");
1304 OCSP_RESPONSE_free(rsp);
1308 /* We'd check the nonce here if we'd put one in the request. */
1309 /* However that would defeat cacheability on the server so we don't. */
1311 /* This section of code reworked from OpenSSL apps source;
1312 The OpenSSL Project retains copyright:
1313 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
1318 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
1320 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
1322 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
1324 /* Use the chain that verified the server cert to verify the stapled info */
1325 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
1327 if ((i = OCSP_basic_verify(bs, cbinfo->u_ocsp.client.verify_stack,
1328 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
1330 tls_out.ocsp = OCSP_FAILED;
1331 if (LOGGING(tls_cipher))
1332 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
1333 BIO_printf(bp, "OCSP response verify failure\n");
1334 ERR_print_errors(bp);
1338 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
1340 /*XXX So we have a good stapled OCSP status. How do we know
1341 it is for the cert of interest? OpenSSL 1.1.0 has a routine
1342 OCSP_resp_find_status() which matches on a cert id, which presumably
1343 we should use. Making an id needs OCSP_cert_id_new(), which takes
1344 issuerName, issuerKey, serialNumber. Are they all in the cert?
1346 For now, carry on blindly accepting the resp. */
1349 OCSP_SINGLERESP * single;
1351 #ifdef EXIM_HAVE_OCSP_RESP_COUNT
1352 if (OCSP_resp_count(bs) != 1)
1354 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
1355 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
1358 tls_out.ocsp = OCSP_FAILED;
1359 log_write(0, LOG_MAIN, "OCSP stapling "
1360 "with multiple responses not handled");
1363 single = OCSP_resp_get0(bs, 0);
1364 status = OCSP_single_get0_status(single, &reason, &rev,
1365 &thisupd, &nextupd);
1368 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
1369 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
1370 if (!OCSP_check_validity(thisupd, nextupd,
1371 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
1373 tls_out.ocsp = OCSP_FAILED;
1374 DEBUG(D_tls) ERR_print_errors(bp);
1375 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
1379 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
1380 OCSP_cert_status_str(status));
1383 case V_OCSP_CERTSTATUS_GOOD:
1384 tls_out.ocsp = OCSP_VFIED;
1387 case V_OCSP_CERTSTATUS_REVOKED:
1388 tls_out.ocsp = OCSP_FAILED;
1389 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
1390 reason != -1 ? "; reason: " : "",
1391 reason != -1 ? OCSP_crl_reason_str(reason) : "");
1392 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
1395 tls_out.ocsp = OCSP_FAILED;
1396 log_write(0, LOG_MAIN,
1397 "Server certificate status unknown, in OCSP stapling");
1402 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
1407 OCSP_RESPONSE_free(rsp);
1410 #endif /*!DISABLE_OCSP*/
1413 /*************************************************
1414 * Initialize for TLS *
1415 *************************************************/
1417 /* Called from both server and client code, to do preliminary initialization
1418 of the library. We allocate and return a context structure.
1421 ctxp returned SSL context
1422 host connected host, if client; NULL if server
1423 dhparam DH parameter file
1424 certificate certificate file
1425 privatekey private key
1426 ocsp_file file of stapling info (server); flag for require ocsp (client)
1427 addr address if client; NULL if server (for some randomness)
1428 cbp place to put allocated callback context
1430 Returns: OK/DEFER/FAIL
1434 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1436 #ifndef DISABLE_OCSP
1439 address_item *addr, tls_ext_ctx_cb ** cbp)
1444 tls_ext_ctx_cb * cbinfo;
1446 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1447 cbinfo->certificate = certificate;
1448 cbinfo->privatekey = privatekey;
1449 #ifndef DISABLE_OCSP
1450 if ((cbinfo->is_server = host==NULL))
1452 cbinfo->u_ocsp.server.file = ocsp_file;
1453 cbinfo->u_ocsp.server.file_expanded = NULL;
1454 cbinfo->u_ocsp.server.response = NULL;
1458 cbinfo->u_ocsp.client.verify_store = NULL;
1459 cbinfo->u_ocsp.client.verify_stack = NULL;
1462 cbinfo->dhparam = dhparam;
1463 cbinfo->server_cipher_list = NULL;
1464 cbinfo->host = host;
1465 #ifndef DISABLE_EVENT
1466 cbinfo->event_action = NULL;
1469 SSL_load_error_strings(); /* basic set up */
1470 OpenSSL_add_ssl_algorithms();
1472 #ifdef EXIM_HAVE_SHA256
1473 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1474 list of available digests. */
1475 EVP_add_digest(EVP_sha256());
1478 /* Create a context.
1479 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1480 negotiation in the different methods; as far as I can tell, the only
1481 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1482 when OpenSSL is built without SSLv2 support.
1483 By disabling with openssl_options, we can let admins re-enable with the
1486 *ctxp = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method());
1488 if (!*ctxp) return tls_error(US"SSL_CTX_new", host, NULL);
1490 /* It turns out that we need to seed the random number generator this early in
1491 order to get the full complement of ciphers to work. It took me roughly a day
1492 of work to discover this by experiment.
1494 On systems that have /dev/urandom, SSL may automatically seed itself from
1495 there. Otherwise, we have to make something up as best we can. Double check
1501 gettimeofday(&r.tv, NULL);
1504 RAND_seed((uschar *)(&r), sizeof(r));
1505 RAND_seed((uschar *)big_buffer, big_buffer_size);
1506 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1509 return tls_error(US"RAND_status", host,
1510 US"unable to seed random number generator");
1513 /* Set up the information callback, which outputs if debugging is at a suitable
1516 DEBUG(D_tls) SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1518 /* Automatically re-try reads/writes after renegotiation. */
1519 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1521 /* Apply administrator-supplied work-arounds.
1522 Historically we applied just one requested option,
1523 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1524 moved to an administrator-controlled list of options to specify and
1525 grandfathered in the first one as the default value for "openssl_options".
1527 No OpenSSL version number checks: the options we accept depend upon the
1528 availability of the option value macros from OpenSSL. */
1530 okay = tls_openssl_options_parse(openssl_options, &init_options);
1532 return tls_error(US"openssl_options parsing failed", host, NULL);
1536 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1537 if (!(SSL_CTX_set_options(*ctxp, init_options)))
1538 return tls_error(string_sprintf(
1539 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1542 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1544 /* Initialize with DH parameters if supplied */
1545 /* Initialize ECDH temp key parameter selection */
1547 if ( !init_dh(*ctxp, dhparam, host)
1548 || !init_ecdh(*ctxp, host)
1552 /* Set up certificate and key (and perhaps OCSP info) */
1554 if ((rc = tls_expand_session_files(*ctxp, cbinfo)) != OK)
1557 /* If we need to handle SNI, do so */
1558 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1559 if (host == NULL) /* server */
1561 # ifndef DISABLE_OCSP
1562 /* We check u_ocsp.server.file, not server.response, because we care about if
1563 the option exists, not what the current expansion might be, as SNI might
1564 change the certificate and OCSP file in use between now and the time the
1565 callback is invoked. */
1566 if (cbinfo->u_ocsp.server.file)
1568 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1569 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1572 /* We always do this, so that $tls_sni is available even if not used in
1574 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1575 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1577 # ifndef DISABLE_OCSP
1579 if(ocsp_file) /* wanting stapling */
1581 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1583 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1586 if (!(cbinfo->u_ocsp.client.verify_stack = sk_X509_new_null()))
1588 DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n");
1591 SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1592 SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1597 cbinfo->verify_cert_hostnames = NULL;
1599 #ifdef EXIM_HAVE_EPHEM_RSA_KEX
1600 /* Set up the RSA callback */
1601 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1604 /* Finally, set the timeout, and we are done */
1606 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1607 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1617 /*************************************************
1618 * Get name of cipher in use *
1619 *************************************************/
1622 Argument: pointer to an SSL structure for the connection
1623 buffer to use for answer
1625 pointer to number of bits for cipher
1630 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1632 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1633 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1634 the accessor functions use const in the prototype. */
1635 const SSL_CIPHER *c;
1638 ver = (const uschar *)SSL_get_version(ssl);
1640 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1641 SSL_CIPHER_get_bits(c, bits);
1643 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1644 SSL_CIPHER_get_name(c), *bits);
1646 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1651 peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned bsize)
1653 /*XXX we might consider a list-of-certs variable for the cert chain.
1654 SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support
1655 in list-handling functions, also consider the difference between the entire
1656 chain and the elements sent by the peer. */
1658 /* Will have already noted peercert on a verify fail; possibly not the leaf */
1659 if (!tlsp->peercert)
1660 tlsp->peercert = SSL_get_peer_certificate(ssl);
1661 /* Beware anonymous ciphers which lead to server_cert being NULL */
1664 X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, bsize);
1665 peerdn[bsize-1] = '\0';
1666 tlsp->peerdn = peerdn; /*XXX a static buffer... */
1669 tlsp->peerdn = NULL;
1676 /*************************************************
1677 * Set up for verifying certificates *
1678 *************************************************/
1680 /* Called by both client and server startup
1683 sctx SSL_CTX* to initialise
1684 certs certs file or NULL
1685 crl CRL file or NULL
1686 host NULL in a server; the remote host in a client
1687 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1688 otherwise passed as FALSE
1689 cert_vfy_cb Callback function for certificate verification
1691 Returns: OK/DEFER/FAIL
1695 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1696 int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1698 uschar *expcerts, *expcrl;
1700 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1703 if (expcerts && *expcerts)
1705 /* Tell the library to use its compiled-in location for the system default
1706 CA bundle. Then add the ones specified in the config, if any. */
1708 if (!SSL_CTX_set_default_verify_paths(sctx))
1709 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1711 if (Ustrcmp(expcerts, "system") != 0)
1713 struct stat statbuf;
1715 if (Ustat(expcerts, &statbuf) < 0)
1717 log_write(0, LOG_MAIN|LOG_PANIC,
1718 "failed to stat %s for certificates", expcerts);
1724 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1725 { file = NULL; dir = expcerts; }
1727 { file = expcerts; dir = NULL; }
1729 /* If a certificate file is empty, the next function fails with an
1730 unhelpful error message. If we skip it, we get the correct behaviour (no
1731 certificates are recognized, but the error message is still misleading (it
1732 says no certificate was supplied.) But this is better. */
1734 if ( (!file || statbuf.st_size > 0)
1735 && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1736 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1738 /* Load the list of CAs for which we will accept certs, for sending
1739 to the client. This is only for the one-file tls_verify_certificates
1741 If a list isn't loaded into the server, but
1742 some verify locations are set, the server end appears to make
1743 a wildcard reqest for client certs.
1744 Meanwhile, the client library as default behaviour *ignores* the list
1745 we send over the wire - see man SSL_CTX_set_client_cert_cb.
1746 Because of this, and that the dir variant is likely only used for
1747 the public-CA bundle (not for a private CA), not worth fixing.
1751 STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file);
1753 DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n",
1754 sk_X509_NAME_num(names));
1755 SSL_CTX_set_client_CA_list(sctx, names);
1760 /* Handle a certificate revocation list. */
1762 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1764 /* This bit of code is now the version supplied by Lars Mainka. (I have
1765 merely reformatted it into the Exim code style.)
1767 "From here I changed the code to add support for multiple crl's
1768 in pem format in one file or to support hashed directory entries in
1769 pem format instead of a file. This method now uses the library function
1770 X509_STORE_load_locations to add the CRL location to the SSL context.
1771 OpenSSL will then handle the verify against CA certs and CRLs by
1772 itself in the verify callback." */
1774 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1775 if (expcrl && *expcrl)
1777 struct stat statbufcrl;
1778 if (Ustat(expcrl, &statbufcrl) < 0)
1780 log_write(0, LOG_MAIN|LOG_PANIC,
1781 "failed to stat %s for certificates revocation lists", expcrl);
1786 /* is it a file or directory? */
1788 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1789 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1793 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1799 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1801 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1802 return tls_error(US"X509_STORE_load_locations", host, NULL);
1804 /* setting the flags to check against the complete crl chain */
1806 X509_STORE_set_flags(cvstore,
1807 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1811 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1813 /* If verification is optional, don't fail if no certificate */
1815 SSL_CTX_set_verify(sctx,
1816 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1825 /*************************************************
1826 * Start a TLS session in a server *
1827 *************************************************/
1829 /* This is called when Exim is running as a server, after having received
1830 the STARTTLS command. It must respond to that command, and then negotiate
1834 require_ciphers allowed ciphers
1836 Returns: OK on success
1837 DEFER for errors before the start of the negotiation
1838 FAIL for errors during the negotation; the server can't
1843 tls_server_start(const uschar *require_ciphers)
1847 tls_ext_ctx_cb *cbinfo;
1848 static uschar peerdn[256];
1849 static uschar cipherbuf[256];
1851 /* Check for previous activation */
1853 if (tls_in.active >= 0)
1855 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1856 smtp_printf("554 Already in TLS\r\n");
1860 /* Initialize the SSL library. If it fails, it will already have logged
1863 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1864 #ifndef DISABLE_OCSP
1867 NULL, &server_static_cbinfo);
1868 if (rc != OK) return rc;
1869 cbinfo = server_static_cbinfo;
1871 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1874 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1875 were historically separated by underscores. So that I can use either form in my
1876 tests, and also for general convenience, we turn underscores into hyphens here.
1879 if (expciphers != NULL)
1881 uschar *s = expciphers;
1882 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1883 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1884 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1885 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1886 cbinfo->server_cipher_list = expciphers;
1889 /* If this is a host for which certificate verification is mandatory or
1890 optional, set up appropriately. */
1892 tls_in.certificate_verified = FALSE;
1893 #ifdef EXPERIMENTAL_DANE
1894 tls_in.dane_verified = FALSE;
1896 server_verify_callback_called = FALSE;
1898 if (verify_check_host(&tls_verify_hosts) == OK)
1900 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1901 FALSE, verify_callback_server);
1902 if (rc != OK) return rc;
1903 server_verify_optional = FALSE;
1905 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1907 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1908 TRUE, verify_callback_server);
1909 if (rc != OK) return rc;
1910 server_verify_optional = TRUE;
1913 /* Prepare for new connection */
1915 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1917 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1919 * With the SSL_clear(), we get strange interoperability bugs with
1920 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1921 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1923 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1924 * session shutdown. In this case, we have a brand new object and there's no
1925 * obvious reason to immediately clear it. I'm guessing that this was
1926 * originally added because of incomplete initialisation which the clear fixed,
1927 * in some historic release.
1930 /* Set context and tell client to go ahead, except in the case of TLS startup
1931 on connection, where outputting anything now upsets the clients and tends to
1932 make them disconnect. We need to have an explicit fflush() here, to force out
1933 the response. Other smtp_printf() calls do not need it, because in non-TLS
1934 mode, the fflush() happens when smtp_getc() is called. */
1936 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1937 if (!tls_in.on_connect)
1939 smtp_printf("220 TLS go ahead\r\n");
1943 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1944 that the OpenSSL library doesn't. */
1946 SSL_set_wfd(server_ssl, fileno(smtp_out));
1947 SSL_set_rfd(server_ssl, fileno(smtp_in));
1948 SSL_set_accept_state(server_ssl);
1950 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1952 sigalrm_seen = FALSE;
1953 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1954 rc = SSL_accept(server_ssl);
1959 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1960 if (ERR_get_error() == 0)
1961 log_write(0, LOG_MAIN,
1962 "TLS client disconnected cleanly (rejected our certificate?)");
1966 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1968 /* TLS has been set up. Adjust the input functions to read via TLS,
1969 and initialize things. */
1971 peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn));
1973 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1974 tls_in.cipher = cipherbuf;
1979 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1980 debug_printf("Shared ciphers: %s\n", buf);
1983 /* Record the certificate we presented */
1985 X509 * crt = SSL_get_certificate(server_ssl);
1986 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1989 /* Only used by the server-side tls (tls_in), including tls_getc.
1990 Client-side (tls_out) reads (seem to?) go via
1991 smtp_read_response()/ip_recv().
1992 Hence no need to duplicate for _in and _out.
1994 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1995 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1996 ssl_xfer_eof = ssl_xfer_error = 0;
1998 receive_getc = tls_getc;
1999 receive_get_cache = tls_get_cache;
2000 receive_ungetc = tls_ungetc;
2001 receive_feof = tls_feof;
2002 receive_ferror = tls_ferror;
2003 receive_smtp_buffered = tls_smtp_buffered;
2005 tls_in.active = fileno(smtp_out);
2013 tls_client_basic_ctx_init(SSL_CTX * ctx,
2014 host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo
2018 /* stick to the old behaviour for compatibility if tls_verify_certificates is
2019 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
2020 the specified host patterns if one of them is defined */
2022 if ( ( !ob->tls_verify_hosts
2023 && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts)
2025 || (verify_check_given_host(&ob->tls_verify_hosts, host) == OK)
2027 client_verify_optional = FALSE;
2028 else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK)
2029 client_verify_optional = TRUE;
2033 if ((rc = setup_certs(ctx, ob->tls_verify_certificates,
2034 ob->tls_crl, host, client_verify_optional, verify_callback_client)) != OK)
2037 if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK)
2039 cbinfo->verify_cert_hostnames =
2041 string_domain_utf8_to_alabel(host->name, NULL);
2045 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
2046 cbinfo->verify_cert_hostnames);
2052 #ifdef EXPERIMENTAL_DANE
2054 dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa)
2058 const char * hostnames[2] = { CS host->name, NULL };
2061 if (DANESSL_init(ssl, NULL, hostnames) != 1)
2062 return tls_error(US"hostnames load", host, NULL);
2064 for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
2066 rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
2067 ) if (rr->type == T_TLSA)
2069 uschar * p = rr->data;
2070 uint8_t usage, selector, mtype;
2071 const char * mdname;
2075 /* Only DANE-TA(2) and DANE-EE(3) are supported */
2076 if (usage != 2 && usage != 3) continue;
2083 default: continue; /* Only match-types 0, 1, 2 are supported */
2084 case 0: mdname = NULL; break;
2085 case 1: mdname = "sha256"; break;
2086 case 2: mdname = "sha512"; break;
2090 switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3))
2093 return tls_error(US"tlsa load", host, NULL);
2094 case 0: /* action not taken */
2098 tls_out.tlsa_usage |= 1<<usage;
2104 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
2107 #endif /*EXPERIMENTAL_DANE*/
2111 /*************************************************
2112 * Start a TLS session in a client *
2113 *************************************************/
2115 /* Called from the smtp transport after STARTTLS has been accepted.
2118 fd the fd of the connection
2119 host connected host (for messages)
2120 addr the first address
2121 tb transport (always smtp)
2122 tlsa_dnsa tlsa lookup, if DANE, else null
2124 Returns: OK on success
2125 FAIL otherwise - note that tls_error() will not give DEFER
2126 because this is not a server
2130 tls_client_start(int fd, host_item *host, address_item *addr,
2131 transport_instance *tb
2132 #ifdef EXPERIMENTAL_DANE
2133 , dns_answer * tlsa_dnsa
2137 smtp_transport_options_block * ob =
2138 (smtp_transport_options_block *)tb->options_block;
2139 static uschar peerdn[256];
2140 uschar * expciphers;
2142 static uschar cipherbuf[256];
2144 #ifndef DISABLE_OCSP
2145 BOOL request_ocsp = FALSE;
2146 BOOL require_ocsp = FALSE;
2149 #ifdef EXPERIMENTAL_DANE
2150 tls_out.tlsa_usage = 0;
2153 #ifndef DISABLE_OCSP
2155 # ifdef EXPERIMENTAL_DANE
2157 && ob->hosts_request_ocsp[0] == '*'
2158 && ob->hosts_request_ocsp[1] == '\0'
2161 /* Unchanged from default. Use a safer one under DANE */
2162 request_ocsp = TRUE;
2163 ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} "
2164 " {= {4}{$tls_out_tlsa_usage}} } "
2170 verify_check_given_host(&ob->hosts_require_ocsp, host) == OK))
2171 request_ocsp = TRUE;
2173 # ifdef EXPERIMENTAL_DANE
2177 verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2181 rc = tls_init(&client_ctx, host, NULL,
2182 ob->tls_certificate, ob->tls_privatekey,
2183 #ifndef DISABLE_OCSP
2184 (void *)(long)request_ocsp,
2186 addr, &client_static_cbinfo);
2187 if (rc != OK) return rc;
2189 tls_out.certificate_verified = FALSE;
2190 client_verify_callback_called = FALSE;
2192 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
2196 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
2197 are separated by underscores. So that I can use either form in my tests, and
2198 also for general convenience, we turn underscores into hyphens here. */
2200 if (expciphers != NULL)
2202 uschar *s = expciphers;
2203 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2204 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
2205 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
2206 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
2209 #ifdef EXPERIMENTAL_DANE
2212 SSL_CTX_set_verify(client_ctx,
2213 SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
2214 verify_callback_client_dane);
2216 if (!DANESSL_library_init())
2217 return tls_error(US"library init", host, NULL);
2218 if (DANESSL_CTX_init(client_ctx) <= 0)
2219 return tls_error(US"context init", host, NULL);
2225 if ((rc = tls_client_basic_ctx_init(client_ctx, host, ob, client_static_cbinfo))
2229 if ((client_ssl = SSL_new(client_ctx)) == NULL)
2230 return tls_error(US"SSL_new", host, NULL);
2231 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
2232 SSL_set_fd(client_ssl, fd);
2233 SSL_set_connect_state(client_ssl);
2237 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
2239 if (tls_out.sni == NULL)
2241 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
2243 else if (!Ustrlen(tls_out.sni))
2247 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
2248 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
2249 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
2251 log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n",
2257 #ifdef EXPERIMENTAL_DANE
2259 if ((rc = dane_tlsa_load(client_ssl, host, tlsa_dnsa)) != OK)
2263 #ifndef DISABLE_OCSP
2264 /* Request certificate status at connection-time. If the server
2265 does OCSP stapling we will get the callback (set in tls_init()) */
2266 # ifdef EXPERIMENTAL_DANE
2270 if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2271 || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage"))
2273 { /* Re-eval now $tls_out_tlsa_usage is populated. If
2274 this means we avoid the OCSP request, we wasted the setup
2275 cost in tls_init(). */
2276 require_ocsp = verify_check_given_host(&ob->hosts_require_ocsp, host) == OK;
2277 request_ocsp = require_ocsp
2278 || verify_check_given_host(&ob->hosts_request_ocsp, host) == OK;
2285 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
2286 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
2287 tls_out.ocsp = OCSP_NOT_RESP;
2291 #ifndef DISABLE_EVENT
2292 client_static_cbinfo->event_action = tb->event_action;
2295 /* There doesn't seem to be a built-in timeout on connection. */
2297 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
2298 sigalrm_seen = FALSE;
2299 alarm(ob->command_timeout);
2300 rc = SSL_connect(client_ssl);
2303 #ifdef EXPERIMENTAL_DANE
2305 DANESSL_cleanup(client_ssl);
2309 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
2311 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
2313 peer_cert(client_ssl, &tls_out, peerdn, sizeof(peerdn));
2315 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
2316 tls_out.cipher = cipherbuf;
2318 /* Record the certificate we presented */
2320 X509 * crt = SSL_get_certificate(client_ssl);
2321 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
2324 tls_out.active = fd;
2332 /*************************************************
2333 * TLS version of getc *
2334 *************************************************/
2336 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
2337 it refills the buffer via the SSL reading function.
2340 Returns: the next character or EOF
2342 Only used by the server-side TLS.
2348 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
2353 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
2354 ssl_xfer_buffer, ssl_xfer_buffer_size);
2356 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
2357 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
2358 error = SSL_get_error(server_ssl, inbytes);
2361 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
2362 closed down, not that the socket itself has been closed down. Revert to
2363 non-SSL handling. */
2365 if (error == SSL_ERROR_ZERO_RETURN)
2367 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2369 receive_getc = smtp_getc;
2370 receive_get_cache = smtp_get_cache;
2371 receive_ungetc = smtp_ungetc;
2372 receive_feof = smtp_feof;
2373 receive_ferror = smtp_ferror;
2374 receive_smtp_buffered = smtp_buffered;
2376 SSL_free(server_ssl);
2380 tls_in.cipher = NULL;
2381 tls_in.peerdn = NULL;
2387 /* Handle genuine errors */
2389 else if (error == SSL_ERROR_SSL)
2391 ERR_error_string(ERR_get_error(), ssl_errstring);
2392 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
2397 else if (error != SSL_ERROR_NONE)
2399 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
2404 #ifndef DISABLE_DKIM
2405 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
2407 ssl_xfer_buffer_hwm = inbytes;
2408 ssl_xfer_buffer_lwm = 0;
2411 /* Something in the buffer; return next uschar */
2413 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
2419 #ifndef DISABLE_DKIM
2420 int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm;
2422 dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n);
2428 /*************************************************
2429 * Read bytes from TLS channel *
2430 *************************************************/
2437 Returns: the number of bytes read
2438 -1 after a failed read
2440 Only used by the client-side TLS.
2444 tls_read(BOOL is_server, uschar *buff, size_t len)
2446 SSL *ssl = is_server ? server_ssl : client_ssl;
2450 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
2451 buff, (unsigned int)len);
2453 inbytes = SSL_read(ssl, CS buff, len);
2454 error = SSL_get_error(ssl, inbytes);
2456 if (error == SSL_ERROR_ZERO_RETURN)
2458 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
2461 else if (error != SSL_ERROR_NONE)
2473 /*************************************************
2474 * Write bytes down TLS channel *
2475 *************************************************/
2479 is_server channel specifier
2483 Returns: the number of bytes after a successful write,
2484 -1 after a failed write
2486 Used by both server-side and client-side TLS.
2490 tls_write(BOOL is_server, const uschar *buff, size_t len)
2495 SSL *ssl = is_server ? server_ssl : client_ssl;
2497 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
2500 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
2501 outbytes = SSL_write(ssl, CS buff, left);
2502 error = SSL_get_error(ssl, outbytes);
2503 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
2507 ERR_error_string(ERR_get_error(), ssl_errstring);
2508 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
2511 case SSL_ERROR_NONE:
2516 case SSL_ERROR_ZERO_RETURN:
2517 log_write(0, LOG_MAIN, "SSL channel closed on write");
2520 case SSL_ERROR_SYSCALL:
2521 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
2522 sender_fullhost ? sender_fullhost : US"<unknown>",
2527 log_write(0, LOG_MAIN, "SSL_write error %d", error);
2536 /*************************************************
2537 * Close down a TLS session *
2538 *************************************************/
2540 /* This is also called from within a delivery subprocess forked from the
2541 daemon, to shut down the TLS library, without actually doing a shutdown (which
2542 would tamper with the SSL session in the parent process).
2544 Arguments: TRUE if SSL_shutdown is to be called
2547 Used by both server-side and client-side TLS.
2551 tls_close(BOOL is_server, BOOL shutdown)
2553 SSL **sslp = is_server ? &server_ssl : &client_ssl;
2554 int *fdp = is_server ? &tls_in.active : &tls_out.active;
2556 if (*fdp < 0) return; /* TLS was not active */
2560 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
2561 SSL_shutdown(*sslp);
2573 /*************************************************
2574 * Let tls_require_ciphers be checked at startup *
2575 *************************************************/
2577 /* The tls_require_ciphers option, if set, must be something which the
2580 Returns: NULL on success, or error message
2584 tls_validate_require_cipher(void)
2587 uschar *s, *expciphers, *err;
2589 /* this duplicates from tls_init(), we need a better "init just global
2590 state, for no specific purpose" singleton function of our own */
2592 SSL_load_error_strings();
2593 OpenSSL_add_ssl_algorithms();
2594 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
2595 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
2596 list of available digests. */
2597 EVP_add_digest(EVP_sha256());
2600 if (!(tls_require_ciphers && *tls_require_ciphers))
2603 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
2604 return US"failed to expand tls_require_ciphers";
2606 if (!(expciphers && *expciphers))
2609 /* normalisation ripped from above */
2611 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
2615 ctx = SSL_CTX_new(SSLv23_server_method());
2618 ERR_error_string(ERR_get_error(), ssl_errstring);
2619 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
2623 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
2625 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2627 ERR_error_string(ERR_get_error(), ssl_errstring);
2628 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2639 /*************************************************
2640 * Report the library versions. *
2641 *************************************************/
2643 /* There have historically been some issues with binary compatibility in
2644 OpenSSL libraries; if Exim (like many other applications) is built against
2645 one version of OpenSSL but the run-time linker picks up another version,
2646 it can result in serious failures, including crashing with a SIGSEGV. So
2647 report the version found by the compiler and the run-time version.
2649 Note: some OS vendors backport security fixes without changing the version
2650 number/string, and the version date remains unchanged. The _build_ date
2651 will change, so we can more usefully assist with version diagnosis by also
2652 reporting the build date.
2654 Arguments: a FILE* to print the results to
2659 tls_version_report(FILE *f)
2661 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2664 OPENSSL_VERSION_TEXT,
2665 SSLeay_version(SSLEAY_VERSION),
2666 SSLeay_version(SSLEAY_BUILT_ON));
2667 /* third line is 38 characters for the %s and the line is 73 chars long;
2668 the OpenSSL output includes a "built on: " prefix already. */
2674 /*************************************************
2675 * Random number generation *
2676 *************************************************/
2678 /* Pseudo-random number generation. The result is not expected to be
2679 cryptographically strong but not so weak that someone will shoot themselves
2680 in the foot using it as a nonce in input in some email header scheme or
2681 whatever weirdness they'll twist this into. The result should handle fork()
2682 and avoid repeating sequences. OpenSSL handles that for us.
2686 Returns a random number in range [0, max-1]
2690 vaguely_random_number(int max)
2694 static pid_t pidlast = 0;
2697 uschar smallbuf[sizeof(r)];
2703 if (pidnow != pidlast)
2705 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2706 is unique for each thread", this doesn't apparently apply across processes,
2707 so our own warning from vaguely_random_number_fallback() applies here too.
2708 Fix per PostgreSQL. */
2714 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2718 gettimeofday(&r.tv, NULL);
2721 RAND_seed((uschar *)(&r), sizeof(r));
2723 /* We're after pseudo-random, not random; if we still don't have enough data
2724 in the internal PRNG then our options are limited. We could sleep and hope
2725 for entropy to come along (prayer technique) but if the system is so depleted
2726 in the first place then something is likely to just keep taking it. Instead,
2727 we'll just take whatever little bit of pseudo-random we can still manage to
2730 needed_len = sizeof(r);
2731 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2732 asked for a number less than 10. */
2733 for (r = max, i = 0; r; ++i)
2739 #ifdef EXIM_HAVE_RAND_PSEUDO
2740 /* We do not care if crypto-strong */
2741 i = RAND_pseudo_bytes(smallbuf, needed_len);
2743 i = RAND_bytes(smallbuf, needed_len);
2749 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2750 return vaguely_random_number_fallback(max);
2754 for (p = smallbuf; needed_len; --needed_len, ++p)
2760 /* We don't particularly care about weighted results; if someone wants
2761 smooth distribution and cares enough then they should submit a patch then. */
2768 /*************************************************
2769 * OpenSSL option parse *
2770 *************************************************/
2772 /* Parse one option for tls_openssl_options_parse below
2775 name one option name
2776 value place to store a value for it
2777 Returns success or failure in parsing
2780 struct exim_openssl_option {
2784 /* We could use a macro to expand, but we need the ifdef and not all the
2785 options document which version they were introduced in. Policylet: include
2786 all options unless explicitly for DTLS, let the administrator choose which
2789 This list is current as of:
2791 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2793 static struct exim_openssl_option exim_openssl_options[] = {
2794 /* KEEP SORTED ALPHABETICALLY! */
2796 { US"all", SSL_OP_ALL },
2798 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2799 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2801 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2802 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2804 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2805 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2807 #ifdef SSL_OP_EPHEMERAL_RSA
2808 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2810 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2811 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2813 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2814 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2816 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2817 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2819 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2820 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2822 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2823 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2825 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2826 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2828 #ifdef SSL_OP_NO_COMPRESSION
2829 { US"no_compression", SSL_OP_NO_COMPRESSION },
2831 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2832 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2834 #ifdef SSL_OP_NO_SSLv2
2835 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2837 #ifdef SSL_OP_NO_SSLv3
2838 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2840 #ifdef SSL_OP_NO_TICKET
2841 { US"no_ticket", SSL_OP_NO_TICKET },
2843 #ifdef SSL_OP_NO_TLSv1
2844 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2846 #ifdef SSL_OP_NO_TLSv1_1
2847 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2848 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2849 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2851 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2854 #ifdef SSL_OP_NO_TLSv1_2
2855 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2857 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2858 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2860 #ifdef SSL_OP_SINGLE_DH_USE
2861 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2863 #ifdef SSL_OP_SINGLE_ECDH_USE
2864 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2866 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2867 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2869 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2870 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2872 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2873 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2875 #ifdef SSL_OP_TLS_D5_BUG
2876 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2878 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2879 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2882 static int exim_openssl_options_size =
2883 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2887 tls_openssl_one_option_parse(uschar *name, long *value)
2890 int last = exim_openssl_options_size;
2891 while (last > first)
2893 int middle = (first + last)/2;
2894 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2897 *value = exim_openssl_options[middle].value;
2911 /*************************************************
2912 * OpenSSL option parsing logic *
2913 *************************************************/
2915 /* OpenSSL has a number of compatibility options which an administrator might
2916 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
2917 we look like log_selector.
2920 option_spec the administrator-supplied string of options
2921 results ptr to long storage for the options bitmap
2922 Returns success or failure
2926 tls_openssl_options_parse(uschar *option_spec, long *results)
2931 BOOL adding, item_parsed;
2934 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2935 * from default because it increases BEAST susceptibility. */
2936 #ifdef SSL_OP_NO_SSLv2
2937 result |= SSL_OP_NO_SSLv2;
2939 #ifdef SSL_OP_SINGLE_DH_USE
2940 result |= SSL_OP_SINGLE_DH_USE;
2943 if (option_spec == NULL)
2949 for (s=option_spec; *s != '\0'; /**/)
2951 while (isspace(*s)) ++s;
2954 if (*s != '+' && *s != '-')
2956 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2957 "+ or - expected but found \"%s\"\n", s);
2960 adding = *s++ == '+';
2961 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2964 item_parsed = tls_openssl_one_option_parse(s, &item);
2968 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2971 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2972 adding ? "adding" : "removing", result, item, s);
2986 /* End of tls-openssl.c */