1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2014 */
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 #ifdef EXPERIMENTAL_OCSP
26 #include <openssl/ocsp.h>
29 #ifdef EXPERIMENTAL_OCSP
30 #define EXIM_OCSP_SKEW_SECONDS (300L)
31 #define EXIM_OCSP_MAX_AGE (-1L)
34 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
35 #define EXIM_HAVE_OPENSSL_TLSEXT
38 /* Structure for collecting random data for seeding. */
40 typedef struct randstuff {
45 /* Local static variables */
47 static BOOL client_verify_callback_called = FALSE;
48 static BOOL server_verify_callback_called = FALSE;
49 static const uschar *sid_ctx = US"exim";
51 /* We have three different contexts to care about.
53 Simple case: client, `client_ctx`
54 As a client, we can be doing a callout or cut-through delivery while receiving
55 a message. So we have a client context, which should have options initialised
56 from the SMTP Transport.
59 There are two cases: with and without ServerNameIndication from the client.
60 Given TLS SNI, we can be using different keys, certs and various other
61 configuration settings, because they're re-expanded with $tls_sni set. This
62 allows vhosting with TLS. This SNI is sent in the handshake.
63 A client might not send SNI, so we need a fallback, and an initial setup too.
64 So as a server, we start out using `server_ctx`.
65 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
66 `server_sni` from `server_ctx` and then initialise settings by re-expanding
70 static SSL_CTX *client_ctx = NULL;
71 static SSL_CTX *server_ctx = NULL;
72 static SSL *client_ssl = NULL;
73 static SSL *server_ssl = NULL;
75 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
76 static SSL_CTX *server_sni = NULL;
79 static char ssl_errstring[256];
81 static int ssl_session_timeout = 200;
82 static BOOL client_verify_optional = FALSE;
83 static BOOL server_verify_optional = FALSE;
85 static BOOL reexpand_tls_files_for_sni = FALSE;
88 typedef struct tls_ext_ctx_cb {
91 #ifdef EXPERIMENTAL_OCSP
96 uschar *file_expanded;
97 OCSP_RESPONSE *response;
100 X509_STORE *verify_store; /* non-null if status requested */
101 BOOL verify_required;
106 /* these are cached from first expand */
107 uschar *server_cipher_list;
108 /* only passed down to tls_error: */
112 /* should figure out a cleanup of API to handle state preserved per
113 implementation, for various reasons, which can be void * in the APIs.
114 For now, we hack around it. */
115 tls_ext_ctx_cb *client_static_cbinfo = NULL;
116 tls_ext_ctx_cb *server_static_cbinfo = NULL;
119 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
120 int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
123 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
124 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
126 #ifdef EXPERIMENTAL_OCSP
127 static int tls_server_stapling_cb(SSL *s, void *arg);
131 /*************************************************
133 *************************************************/
135 /* Called from lots of places when errors occur before actually starting to do
136 the TLS handshake, that is, while the session is still in clear. Always returns
137 DEFER for a server and FAIL for a client so that most calls can use "return
138 tls_error(...)" to do this processing and then give an appropriate return. A
139 single function is used for both server and client, because it is called from
140 some shared functions.
143 prefix text to include in the logged error
144 host NULL if setting up a server;
145 the connected host if setting up a client
146 msg error message or NULL if we should ask OpenSSL
148 Returns: OK/DEFER/FAIL
152 tls_error(uschar *prefix, host_item *host, uschar *msg)
156 ERR_error_string(ERR_get_error(), ssl_errstring);
157 msg = (uschar *)ssl_errstring;
162 uschar *conn_info = smtp_get_connection_info();
163 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
165 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
166 conn_info, prefix, msg);
171 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
172 host->name, host->address, prefix, msg);
179 /*************************************************
180 * Callback to generate RSA key *
181 *************************************************/
189 Returns: pointer to generated key
193 rsa_callback(SSL *s, int export, int keylength)
196 export = export; /* Shut picky compilers up */
197 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
198 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
201 ERR_error_string(ERR_get_error(), ssl_errstring);
202 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
212 #if defined(EXPERIMENTAL_OCSP)
214 x509_store_dump_cert_s_names(X509_STORE * store)
216 STACK_OF(X509_OBJECT) * roots= store->objs;
218 static uschar name[256];
220 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
222 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
223 if(tmp_obj->type == X509_LU_X509)
225 X509 * current_cert= tmp_obj->data.x509;
226 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
227 debug_printf(" %s\n", name);
235 /*************************************************
236 * Callback for verification *
237 *************************************************/
239 /* The SSL library does certificate verification if set up to do so. This
240 callback has the current yes/no state is in "state". If verification succeeded,
241 we set up the tls_peerdn string. If verification failed, what happens depends
242 on whether the client is required to present a verifiable certificate or not.
244 If verification is optional, we change the state to yes, but still log the
245 verification error. For some reason (it really would help to have proper
246 documentation of OpenSSL), this callback function then gets called again, this
247 time with state = 1. In fact, that's useful, because we can set up the peerdn
248 value, but we must take care not to set the private verified flag on the second
251 Note: this function is not called if the client fails to present a certificate
252 when asked. We get here only if a certificate has been received. Handling of
253 optional verification for this case is done when requesting SSL to verify, by
254 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
257 state current yes/no state as 1/0
258 x509ctx certificate information.
259 client TRUE for client startup, FALSE for server startup
261 Returns: 1 if verified, 0 if not
265 verify_callback(int state, X509_STORE_CTX *x509ctx,
266 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
268 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
269 static uschar txt[256];
271 X509_NAME_oneline(X509_get_subject_name(cert),
272 CS txt, sizeof(txt));
276 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
277 X509_STORE_CTX_get_error_depth(x509ctx),
278 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
280 tlsp->certificate_verified = FALSE;
284 tlsp->peercert = X509_dup(cert);
285 return 0; /* reject */
287 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
288 "tls_try_verify_hosts)\n");
291 else if (X509_STORE_CTX_get_error_depth(x509ctx) != 0)
293 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n",
294 X509_STORE_CTX_get_error_depth(x509ctx), txt);
295 #ifdef EXPERIMENTAL_OCSP
296 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
297 { /* client, wanting stapling */
298 /* Add the server cert's signing chain as the one
299 for the verification of the OCSP stapled information. */
301 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
310 tlsp->peercert = X509_dup(cert);
311 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
312 *calledp ? "" : " authenticated", txt);
313 if (!*calledp) tlsp->certificate_verified = TRUE;
317 return 1; /* accept */
321 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
323 return verify_callback(state, x509ctx, &tls_out, &client_verify_callback_called, &client_verify_optional);
327 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
329 return verify_callback(state, x509ctx, &tls_in, &server_verify_callback_called, &server_verify_optional);
334 /*************************************************
335 * Information callback *
336 *************************************************/
338 /* The SSL library functions call this from time to time to indicate what they
339 are doing. We copy the string to the debugging output when TLS debugging has
351 info_callback(SSL *s, int where, int ret)
355 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
360 /*************************************************
361 * Initialize for DH *
362 *************************************************/
364 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
367 dhparam DH parameter file or fixed parameter identity string
368 host connected host, if client; NULL if server
370 Returns: TRUE if OK (nothing to set up, or setup worked)
374 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
381 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
384 if (dhexpanded == NULL || *dhexpanded == '\0')
386 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
388 else if (dhexpanded[0] == '/')
390 bio = BIO_new_file(CS dhexpanded, "r");
393 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
394 host, US strerror(errno));
400 if (Ustrcmp(dhexpanded, "none") == 0)
402 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
406 pem = std_dh_prime_named(dhexpanded);
409 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
410 host, US strerror(errno));
413 bio = BIO_new_mem_buf(CS pem, -1);
416 dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
420 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
425 /* Even if it is larger, we silently return success rather than cause things
426 * to fail out, so that a too-large DH will not knock out all TLS; it's a
427 * debatable choice. */
428 if ((8*DH_size(dh)) > tls_dh_max_bits)
431 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
432 8*DH_size(dh), tls_dh_max_bits);
436 SSL_CTX_set_tmp_dh(sctx, dh);
438 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
439 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
451 #ifdef EXPERIMENTAL_OCSP
452 /*************************************************
453 * Load OCSP information into state *
454 *************************************************/
456 /* Called to load the server OCSP response from the given file into memory, once
457 caller has determined this is needed. Checks validity. Debugs a message
460 ASSUMES: single response, for single cert.
463 sctx the SSL_CTX* to update
464 cbinfo various parts of session state
465 expanded the filename putatively holding an OCSP response
470 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
474 OCSP_BASICRESP *basic_response;
475 OCSP_SINGLERESP *single_response;
476 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
478 unsigned long verify_flags;
479 int status, reason, i;
481 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
482 if (cbinfo->u_ocsp.server.response)
484 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
485 cbinfo->u_ocsp.server.response = NULL;
488 bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb");
491 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
492 cbinfo->u_ocsp.server.file_expanded);
496 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
500 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
504 status = OCSP_response_status(resp);
505 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
507 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
508 OCSP_response_status_str(status), status);
512 basic_response = OCSP_response_get1_basic(resp);
516 debug_printf("OCSP response parse error: unable to extract basic response.\n");
520 store = SSL_CTX_get_cert_store(sctx);
521 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
523 /* May need to expose ability to adjust those flags?
524 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
525 OCSP_TRUSTOTHER OCSP_NOINTERN */
527 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
531 ERR_error_string(ERR_get_error(), ssl_errstring);
532 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
537 /* Here's the simplifying assumption: there's only one response, for the
538 one certificate we use, and nothing for anything else in a chain. If this
539 proves false, we need to extract a cert id from our issued cert
540 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
541 right cert in the stack and then calls OCSP_single_get0_status()).
543 I'm hoping to avoid reworking a bunch more of how we handle state here. */
544 single_response = OCSP_resp_get0(basic_response, 0);
545 if (!single_response)
548 debug_printf("Unable to get first response from OCSP basic response.\n");
552 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
553 if (status != V_OCSP_CERTSTATUS_GOOD)
555 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
556 OCSP_cert_status_str(status), status,
557 OCSP_crl_reason_str(reason), reason);
561 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
563 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
568 cbinfo->u_ocsp.server.response = resp;
572 if (running_in_test_harness)
574 extern char ** environ;
576 for (p = USS environ; *p != NULL; p++)
577 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
579 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
580 goto supply_response;
585 #endif /*EXPERIMENTAL_OCSP*/
590 /*************************************************
591 * Expand key and cert file specs *
592 *************************************************/
594 /* Called once during tls_init and possibly again during TLS setup, for a
595 new context, if Server Name Indication was used and tls_sni was seen in
596 the certificate string.
599 sctx the SSL_CTX* to update
600 cbinfo various parts of session state
602 Returns: OK/DEFER/FAIL
606 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
610 if (cbinfo->certificate == NULL)
613 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
614 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
615 Ustrstr(cbinfo->certificate, US"tls_out_sni")
617 reexpand_tls_files_for_sni = TRUE;
619 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
622 if (expanded != NULL)
624 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
625 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
626 return tls_error(string_sprintf(
627 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
631 if (cbinfo->privatekey != NULL &&
632 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
635 /* If expansion was forced to fail, key_expanded will be NULL. If the result
636 of the expansion is an empty string, ignore it also, and assume the private
637 key is in the same file as the certificate. */
639 if (expanded != NULL && *expanded != 0)
641 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
642 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
643 return tls_error(string_sprintf(
644 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
647 #ifdef EXPERIMENTAL_OCSP
648 if (cbinfo->is_server && cbinfo->u_ocsp.server.file != NULL)
650 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
653 if (expanded != NULL && *expanded != 0)
655 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
656 if (cbinfo->u_ocsp.server.file_expanded &&
657 (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
660 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
662 ocsp_load_response(sctx, cbinfo, expanded);
674 /*************************************************
675 * Callback to handle SNI *
676 *************************************************/
678 /* Called when acting as server during the TLS session setup if a Server Name
679 Indication extension was sent by the client.
681 API documentation is OpenSSL s_server.c implementation.
684 s SSL* of the current session
685 ad unknown (part of OpenSSL API) (unused)
686 arg Callback of "our" registered data
688 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
691 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
693 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
695 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
696 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
698 int old_pool = store_pool;
701 return SSL_TLSEXT_ERR_OK;
703 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
704 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
706 /* Make the extension value available for expansion */
707 store_pool = POOL_PERM;
708 tls_in.sni = string_copy(US servername);
709 store_pool = old_pool;
711 if (!reexpand_tls_files_for_sni)
712 return SSL_TLSEXT_ERR_OK;
714 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
715 not confident that memcpy wouldn't break some internal reference counting.
716 Especially since there's a references struct member, which would be off. */
718 server_sni = SSL_CTX_new(SSLv23_server_method());
721 ERR_error_string(ERR_get_error(), ssl_errstring);
722 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
723 return SSL_TLSEXT_ERR_NOACK;
726 /* Not sure how many of these are actually needed, since SSL object
727 already exists. Might even need this selfsame callback, for reneg? */
729 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
730 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
731 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
732 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
733 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
734 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
735 if (cbinfo->server_cipher_list)
736 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
737 #ifdef EXPERIMENTAL_OCSP
738 if (cbinfo->u_ocsp.server.file)
740 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
741 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
745 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server);
746 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
748 /* do this after setup_certs, because this can require the certs for verifying
750 rc = tls_expand_session_files(server_sni, cbinfo);
751 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
753 rc = init_dh(server_sni, cbinfo->dhparam, NULL);
754 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
756 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
757 SSL_set_SSL_CTX(s, server_sni);
759 return SSL_TLSEXT_ERR_OK;
761 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
766 #ifdef EXPERIMENTAL_OCSP
768 /*************************************************
769 * Callback to handle OCSP Stapling *
770 *************************************************/
772 /* Called when acting as server during the TLS session setup if the client
773 requests OCSP information with a Certificate Status Request.
775 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
781 tls_server_stapling_cb(SSL *s, void *arg)
783 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
784 uschar *response_der;
785 int response_der_len;
788 debug_printf("Received TLS status request (OCSP stapling); %s response.",
789 cbinfo->u_ocsp.server.response ? "have" : "lack");
791 tls_in.ocsp = OCSP_NOT_RESP;
792 if (!cbinfo->u_ocsp.server.response)
793 return SSL_TLSEXT_ERR_NOACK;
796 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
798 if (response_der_len <= 0)
799 return SSL_TLSEXT_ERR_NOACK;
801 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
802 tls_in.ocsp = OCSP_VFIED;
803 return SSL_TLSEXT_ERR_OK;
808 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
810 BIO_printf(bp, "\t%s: ", str);
811 ASN1_GENERALIZEDTIME_print(bp, time);
816 tls_client_stapling_cb(SSL *s, void *arg)
818 tls_ext_ctx_cb * cbinfo = arg;
819 const unsigned char * p;
825 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
826 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
829 /* Expect this when we requested ocsp but got none */
830 if ( cbinfo->u_ocsp.client.verify_required
831 && log_extra_selector & LX_tls_cipher)
832 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
834 DEBUG(D_tls) debug_printf(" null\n");
835 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
838 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
840 tls_out.ocsp = OCSP_FAILED;
841 if (log_extra_selector & LX_tls_cipher)
842 log_write(0, LOG_MAIN, "Received TLS status response, parse error");
844 DEBUG(D_tls) debug_printf(" parse error\n");
848 if(!(bs = OCSP_response_get1_basic(rsp)))
850 tls_out.ocsp = OCSP_FAILED;
851 if (log_extra_selector & LX_tls_cipher)
852 log_write(0, LOG_MAIN, "Received TLS status response, error parsing response");
854 DEBUG(D_tls) debug_printf(" error parsing response\n");
855 OCSP_RESPONSE_free(rsp);
859 /* We'd check the nonce here if we'd put one in the request. */
860 /* However that would defeat cacheability on the server so we don't. */
862 /* This section of code reworked from OpenSSL apps source;
863 The OpenSSL Project retains copyright:
864 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
869 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
871 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
873 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
875 /* Use the chain that verified the server cert to verify the stapled info */
876 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
878 if ((i = OCSP_basic_verify(bs, NULL,
879 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
881 tls_out.ocsp = OCSP_FAILED;
882 BIO_printf(bp, "OCSP response verify failure\n");
883 ERR_print_errors(bp);
884 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
888 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
891 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
892 OCSP_SINGLERESP * single;
894 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
896 tls_out.ocsp = OCSP_FAILED;
897 log_write(0, LOG_MAIN, "OCSP stapling "
898 "with multiple responses not handled");
899 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
902 single = OCSP_resp_get0(bs, 0);
903 status = OCSP_single_get0_status(single, &reason, &rev,
907 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
908 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
909 if (!OCSP_check_validity(thisupd, nextupd,
910 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
912 tls_out.ocsp = OCSP_FAILED;
913 DEBUG(D_tls) ERR_print_errors(bp);
914 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
915 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
919 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
920 OCSP_cert_status_str(status));
923 case V_OCSP_CERTSTATUS_GOOD:
924 tls_out.ocsp = OCSP_VFIED;
927 case V_OCSP_CERTSTATUS_REVOKED:
928 tls_out.ocsp = OCSP_FAILED;
929 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
930 reason != -1 ? "; reason: " : "",
931 reason != -1 ? OCSP_crl_reason_str(reason) : "");
932 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
933 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
936 tls_out.ocsp = OCSP_FAILED;
937 log_write(0, LOG_MAIN,
938 "Server certificate status unknown, in OCSP stapling");
939 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
947 OCSP_RESPONSE_free(rsp);
950 #endif /*EXPERIMENTAL_OCSP*/
954 /*************************************************
955 * Initialize for TLS *
956 *************************************************/
958 /* Called from both server and client code, to do preliminary initialization of
962 host connected host, if client; NULL if server
963 dhparam DH parameter file
964 certificate certificate file
965 privatekey private key
966 ocsp_file file of stapling info (server); flag for require ocsp (client)
967 addr address if client; NULL if server (for some randomness)
969 Returns: OK/DEFER/FAIL
973 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
975 #ifdef EXPERIMENTAL_OCSP
978 address_item *addr, tls_ext_ctx_cb ** cbp)
983 tls_ext_ctx_cb *cbinfo;
985 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
986 cbinfo->certificate = certificate;
987 cbinfo->privatekey = privatekey;
988 #ifdef EXPERIMENTAL_OCSP
989 if ((cbinfo->is_server = host==NULL))
991 cbinfo->u_ocsp.server.file = ocsp_file;
992 cbinfo->u_ocsp.server.file_expanded = NULL;
993 cbinfo->u_ocsp.server.response = NULL;
996 cbinfo->u_ocsp.client.verify_store = NULL;
998 cbinfo->dhparam = dhparam;
1001 SSL_load_error_strings(); /* basic set up */
1002 OpenSSL_add_ssl_algorithms();
1004 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1005 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1006 list of available digests. */
1007 EVP_add_digest(EVP_sha256());
1010 /* Create a context.
1011 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1012 negotiation in the different methods; as far as I can tell, the only
1013 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1014 when OpenSSL is built without SSLv2 support.
1015 By disabling with openssl_options, we can let admins re-enable with the
1018 *ctxp = SSL_CTX_new((host == NULL)?
1019 SSLv23_server_method() : SSLv23_client_method());
1021 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
1023 /* It turns out that we need to seed the random number generator this early in
1024 order to get the full complement of ciphers to work. It took me roughly a day
1025 of work to discover this by experiment.
1027 On systems that have /dev/urandom, SSL may automatically seed itself from
1028 there. Otherwise, we have to make something up as best we can. Double check
1034 gettimeofday(&r.tv, NULL);
1037 RAND_seed((uschar *)(&r), sizeof(r));
1038 RAND_seed((uschar *)big_buffer, big_buffer_size);
1039 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1042 return tls_error(US"RAND_status", host,
1043 US"unable to seed random number generator");
1046 /* Set up the information callback, which outputs if debugging is at a suitable
1049 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1051 /* Automatically re-try reads/writes after renegotiation. */
1052 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1054 /* Apply administrator-supplied work-arounds.
1055 Historically we applied just one requested option,
1056 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1057 moved to an administrator-controlled list of options to specify and
1058 grandfathered in the first one as the default value for "openssl_options".
1060 No OpenSSL version number checks: the options we accept depend upon the
1061 availability of the option value macros from OpenSSL. */
1063 okay = tls_openssl_options_parse(openssl_options, &init_options);
1065 return tls_error(US"openssl_options parsing failed", host, NULL);
1069 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1070 if (!(SSL_CTX_set_options(*ctxp, init_options)))
1071 return tls_error(string_sprintf(
1072 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1075 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1077 /* Initialize with DH parameters if supplied */
1079 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
1081 /* Set up certificate and key (and perhaps OCSP info) */
1083 rc = tls_expand_session_files(*ctxp, cbinfo);
1084 if (rc != OK) return rc;
1086 /* If we need to handle SNI, do so */
1087 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1088 if (host == NULL) /* server */
1090 # ifdef EXPERIMENTAL_OCSP
1091 /* We check u_ocsp.server.file, not server.response, because we care about if
1092 the option exists, not what the current expansion might be, as SNI might
1093 change the certificate and OCSP file in use between now and the time the
1094 callback is invoked. */
1095 if (cbinfo->u_ocsp.server.file)
1097 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1098 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1101 /* We always do this, so that $tls_sni is available even if not used in
1103 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1104 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1106 # ifdef EXPERIMENTAL_OCSP
1108 if(ocsp_file) /* wanting stapling */
1110 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1112 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1115 SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1116 SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1121 /* Set up the RSA callback */
1123 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1125 /* Finally, set the timeout, and we are done */
1127 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1128 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1138 /*************************************************
1139 * Get name of cipher in use *
1140 *************************************************/
1143 Argument: pointer to an SSL structure for the connection
1144 buffer to use for answer
1146 pointer to number of bits for cipher
1151 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1153 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1154 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1155 the accessor functions use const in the prototype. */
1156 const SSL_CIPHER *c;
1159 ver = (const uschar *)SSL_get_version(ssl);
1161 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1162 SSL_CIPHER_get_bits(c, bits);
1164 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1165 SSL_CIPHER_get_name(c), *bits);
1167 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1174 /*************************************************
1175 * Set up for verifying certificates *
1176 *************************************************/
1178 /* Called by both client and server startup
1181 sctx SSL_CTX* to initialise
1182 certs certs file or NULL
1183 crl CRL file or NULL
1184 host NULL in a server; the remote host in a client
1185 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1186 otherwise passed as FALSE
1187 cert_vfy_cb Callback function for certificate verification
1189 Returns: OK/DEFER/FAIL
1193 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1194 int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1196 uschar *expcerts, *expcrl;
1198 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1201 if (expcerts != NULL && *expcerts != '\0')
1203 struct stat statbuf;
1204 if (!SSL_CTX_set_default_verify_paths(sctx))
1205 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1207 if (Ustat(expcerts, &statbuf) < 0)
1209 log_write(0, LOG_MAIN|LOG_PANIC,
1210 "failed to stat %s for certificates", expcerts);
1216 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1217 { file = NULL; dir = expcerts; }
1219 { file = expcerts; dir = NULL; }
1221 /* If a certificate file is empty, the next function fails with an
1222 unhelpful error message. If we skip it, we get the correct behaviour (no
1223 certificates are recognized, but the error message is still misleading (it
1224 says no certificate was supplied.) But this is better. */
1226 if ((file == NULL || statbuf.st_size > 0) &&
1227 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1228 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1232 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1236 /* Handle a certificate revocation list. */
1238 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1240 /* This bit of code is now the version supplied by Lars Mainka. (I have
1241 * merely reformatted it into the Exim code style.)
1243 * "From here I changed the code to add support for multiple crl's
1244 * in pem format in one file or to support hashed directory entries in
1245 * pem format instead of a file. This method now uses the library function
1246 * X509_STORE_load_locations to add the CRL location to the SSL context.
1247 * OpenSSL will then handle the verify against CA certs and CRLs by
1248 * itself in the verify callback." */
1250 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1251 if (expcrl != NULL && *expcrl != 0)
1253 struct stat statbufcrl;
1254 if (Ustat(expcrl, &statbufcrl) < 0)
1256 log_write(0, LOG_MAIN|LOG_PANIC,
1257 "failed to stat %s for certificates revocation lists", expcrl);
1262 /* is it a file or directory? */
1264 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1265 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1269 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1275 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1277 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1278 return tls_error(US"X509_STORE_load_locations", host, NULL);
1280 /* setting the flags to check against the complete crl chain */
1282 X509_STORE_set_flags(cvstore,
1283 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1287 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1289 /* If verification is optional, don't fail if no certificate */
1291 SSL_CTX_set_verify(sctx,
1292 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1301 /*************************************************
1302 * Start a TLS session in a server *
1303 *************************************************/
1305 /* This is called when Exim is running as a server, after having received
1306 the STARTTLS command. It must respond to that command, and then negotiate
1310 require_ciphers allowed ciphers
1312 Returns: OK on success
1313 DEFER for errors before the start of the negotiation
1314 FAIL for errors during the negotation; the server can't
1319 tls_server_start(const uschar *require_ciphers)
1323 tls_ext_ctx_cb *cbinfo;
1324 static uschar cipherbuf[256];
1326 /* Check for previous activation */
1328 if (tls_in.active >= 0)
1330 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1331 smtp_printf("554 Already in TLS\r\n");
1335 /* Initialize the SSL library. If it fails, it will already have logged
1338 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1339 #ifdef EXPERIMENTAL_OCSP
1342 NULL, &server_static_cbinfo);
1343 if (rc != OK) return rc;
1344 cbinfo = server_static_cbinfo;
1346 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1349 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1350 were historically separated by underscores. So that I can use either form in my
1351 tests, and also for general convenience, we turn underscores into hyphens here.
1354 if (expciphers != NULL)
1356 uschar *s = expciphers;
1357 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1358 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1359 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1360 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1361 cbinfo->server_cipher_list = expciphers;
1364 /* If this is a host for which certificate verification is mandatory or
1365 optional, set up appropriately. */
1367 tls_in.certificate_verified = FALSE;
1368 server_verify_callback_called = FALSE;
1370 if (verify_check_host(&tls_verify_hosts) == OK)
1372 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1373 FALSE, verify_callback_server);
1374 if (rc != OK) return rc;
1375 server_verify_optional = FALSE;
1377 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1379 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1380 TRUE, verify_callback_server);
1381 if (rc != OK) return rc;
1382 server_verify_optional = TRUE;
1385 /* Prepare for new connection */
1387 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1389 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1391 * With the SSL_clear(), we get strange interoperability bugs with
1392 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1393 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1395 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1396 * session shutdown. In this case, we have a brand new object and there's no
1397 * obvious reason to immediately clear it. I'm guessing that this was
1398 * originally added because of incomplete initialisation which the clear fixed,
1399 * in some historic release.
1402 /* Set context and tell client to go ahead, except in the case of TLS startup
1403 on connection, where outputting anything now upsets the clients and tends to
1404 make them disconnect. We need to have an explicit fflush() here, to force out
1405 the response. Other smtp_printf() calls do not need it, because in non-TLS
1406 mode, the fflush() happens when smtp_getc() is called. */
1408 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1409 if (!tls_in.on_connect)
1411 smtp_printf("220 TLS go ahead\r\n");
1415 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1416 that the OpenSSL library doesn't. */
1418 SSL_set_wfd(server_ssl, fileno(smtp_out));
1419 SSL_set_rfd(server_ssl, fileno(smtp_in));
1420 SSL_set_accept_state(server_ssl);
1422 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1424 sigalrm_seen = FALSE;
1425 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1426 rc = SSL_accept(server_ssl);
1431 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1432 if (ERR_get_error() == 0)
1433 log_write(0, LOG_MAIN,
1434 "TLS client disconnected cleanly (rejected our certificate?)");
1438 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1440 /* TLS has been set up. Adjust the input functions to read via TLS,
1441 and initialize things. */
1443 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1444 tls_in.cipher = cipherbuf;
1449 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1450 debug_printf("Shared ciphers: %s\n", buf);
1453 /* Record the certificate we presented */
1455 X509 * crt = SSL_get_certificate(server_ssl);
1456 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1459 /* Only used by the server-side tls (tls_in), including tls_getc.
1460 Client-side (tls_out) reads (seem to?) go via
1461 smtp_read_response()/ip_recv().
1462 Hence no need to duplicate for _in and _out.
1464 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1465 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1466 ssl_xfer_eof = ssl_xfer_error = 0;
1468 receive_getc = tls_getc;
1469 receive_ungetc = tls_ungetc;
1470 receive_feof = tls_feof;
1471 receive_ferror = tls_ferror;
1472 receive_smtp_buffered = tls_smtp_buffered;
1474 tls_in.active = fileno(smtp_out);
1482 /*************************************************
1483 * Start a TLS session in a client *
1484 *************************************************/
1486 /* Called from the smtp transport after STARTTLS has been accepted.
1489 fd the fd of the connection
1490 host connected host (for messages)
1491 addr the first address
1492 ob smtp transport options
1494 Returns: OK on success
1495 FAIL otherwise - note that tls_error() will not give DEFER
1496 because this is not a server
1500 tls_client_start(int fd, host_item *host, address_item *addr,
1503 smtp_transport_options_block * ob = v_ob;
1504 static uschar txt[256];
1508 static uschar cipherbuf[256];
1509 #ifdef EXPERIMENTAL_OCSP
1510 BOOL require_ocsp = verify_check_this_host(&ob->hosts_require_ocsp,
1511 NULL, host->name, host->address, NULL) == OK;
1512 BOOL request_ocsp = require_ocsp ? TRUE
1513 : verify_check_this_host(&ob->hosts_request_ocsp,
1514 NULL, host->name, host->address, NULL) == OK;
1517 rc = tls_init(&client_ctx, host, NULL,
1518 ob->tls_certificate, ob->tls_privatekey,
1519 #ifdef EXPERIMENTAL_OCSP
1520 (void *)(long)request_ocsp,
1522 addr, &client_static_cbinfo);
1523 if (rc != OK) return rc;
1525 tls_out.certificate_verified = FALSE;
1526 client_verify_callback_called = FALSE;
1528 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
1532 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1533 are separated by underscores. So that I can use either form in my tests, and
1534 also for general convenience, we turn underscores into hyphens here. */
1536 if (expciphers != NULL)
1538 uschar *s = expciphers;
1539 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1540 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1541 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1542 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1545 /* stick to the old behaviour for compatibility if tls_verify_certificates is
1546 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
1547 the specified host patterns if one of them is defined */
1548 if ((!ob->tls_verify_hosts && !ob->tls_try_verify_hosts) ||
1549 (verify_check_host(&ob->tls_verify_hosts) == OK))
1551 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1552 ob->tls_crl, host, FALSE, verify_callback_client)) != OK)
1554 client_verify_optional = FALSE;
1556 else if (verify_check_host(&ob->tls_try_verify_hosts) == OK)
1558 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1559 ob->tls_crl, host, TRUE, verify_callback_client)) != OK)
1561 client_verify_optional = TRUE;
1564 if ((client_ssl = SSL_new(client_ctx)) == NULL)
1565 return tls_error(US"SSL_new", host, NULL);
1566 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1567 SSL_set_fd(client_ssl, fd);
1568 SSL_set_connect_state(client_ssl);
1572 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
1574 if (tls_out.sni == NULL)
1576 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1578 else if (!Ustrlen(tls_out.sni))
1582 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1583 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1584 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1587 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1593 #ifdef EXPERIMENTAL_OCSP
1594 /* Request certificate status at connection-time. If the server
1595 does OCSP stapling we will get the callback (set in tls_init()) */
1598 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
1599 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
1600 tls_out.ocsp = OCSP_NOT_RESP;
1604 /* There doesn't seem to be a built-in timeout on connection. */
1606 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1607 sigalrm_seen = FALSE;
1608 alarm(ob->command_timeout);
1609 rc = SSL_connect(client_ssl);
1613 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1615 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1617 /* Beware anonymous ciphers which lead to server_cert being NULL */
1618 /*XXX server_cert is never freed... use X509_free() */
1619 server_cert = SSL_get_peer_certificate (client_ssl);
1622 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1623 CS txt, sizeof(txt));
1624 tls_out.peerdn = txt; /*XXX a static buffer... */
1627 tls_out.peerdn = NULL;
1629 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1630 tls_out.cipher = cipherbuf;
1632 /* Record the certificate we presented */
1634 X509 * crt = SSL_get_certificate(client_ssl);
1635 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
1638 tls_out.active = fd;
1646 /*************************************************
1647 * TLS version of getc *
1648 *************************************************/
1650 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1651 it refills the buffer via the SSL reading function.
1654 Returns: the next character or EOF
1656 Only used by the server-side TLS.
1662 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1667 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1668 ssl_xfer_buffer, ssl_xfer_buffer_size);
1670 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1671 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1672 error = SSL_get_error(server_ssl, inbytes);
1675 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1676 closed down, not that the socket itself has been closed down. Revert to
1677 non-SSL handling. */
1679 if (error == SSL_ERROR_ZERO_RETURN)
1681 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1683 receive_getc = smtp_getc;
1684 receive_ungetc = smtp_ungetc;
1685 receive_feof = smtp_feof;
1686 receive_ferror = smtp_ferror;
1687 receive_smtp_buffered = smtp_buffered;
1689 SSL_free(server_ssl);
1693 tls_in.cipher = NULL;
1694 tls_in.peerdn = NULL;
1700 /* Handle genuine errors */
1702 else if (error == SSL_ERROR_SSL)
1704 ERR_error_string(ERR_get_error(), ssl_errstring);
1705 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1710 else if (error != SSL_ERROR_NONE)
1712 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1717 #ifndef DISABLE_DKIM
1718 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1720 ssl_xfer_buffer_hwm = inbytes;
1721 ssl_xfer_buffer_lwm = 0;
1724 /* Something in the buffer; return next uschar */
1726 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1731 /*************************************************
1732 * Read bytes from TLS channel *
1733 *************************************************/
1740 Returns: the number of bytes read
1741 -1 after a failed read
1743 Only used by the client-side TLS.
1747 tls_read(BOOL is_server, uschar *buff, size_t len)
1749 SSL *ssl = is_server ? server_ssl : client_ssl;
1753 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1754 buff, (unsigned int)len);
1756 inbytes = SSL_read(ssl, CS buff, len);
1757 error = SSL_get_error(ssl, inbytes);
1759 if (error == SSL_ERROR_ZERO_RETURN)
1761 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1764 else if (error != SSL_ERROR_NONE)
1776 /*************************************************
1777 * Write bytes down TLS channel *
1778 *************************************************/
1782 is_server channel specifier
1786 Returns: the number of bytes after a successful write,
1787 -1 after a failed write
1789 Used by both server-side and client-side TLS.
1793 tls_write(BOOL is_server, const uschar *buff, size_t len)
1798 SSL *ssl = is_server ? server_ssl : client_ssl;
1800 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1803 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1804 outbytes = SSL_write(ssl, CS buff, left);
1805 error = SSL_get_error(ssl, outbytes);
1806 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1810 ERR_error_string(ERR_get_error(), ssl_errstring);
1811 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1814 case SSL_ERROR_NONE:
1819 case SSL_ERROR_ZERO_RETURN:
1820 log_write(0, LOG_MAIN, "SSL channel closed on write");
1823 case SSL_ERROR_SYSCALL:
1824 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1825 sender_fullhost ? sender_fullhost : US"<unknown>",
1829 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1838 /*************************************************
1839 * Close down a TLS session *
1840 *************************************************/
1842 /* This is also called from within a delivery subprocess forked from the
1843 daemon, to shut down the TLS library, without actually doing a shutdown (which
1844 would tamper with the SSL session in the parent process).
1846 Arguments: TRUE if SSL_shutdown is to be called
1849 Used by both server-side and client-side TLS.
1853 tls_close(BOOL is_server, BOOL shutdown)
1855 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1856 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1858 if (*fdp < 0) return; /* TLS was not active */
1862 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1863 SSL_shutdown(*sslp);
1875 /*************************************************
1876 * Let tls_require_ciphers be checked at startup *
1877 *************************************************/
1879 /* The tls_require_ciphers option, if set, must be something which the
1882 Returns: NULL on success, or error message
1886 tls_validate_require_cipher(void)
1889 uschar *s, *expciphers, *err;
1891 /* this duplicates from tls_init(), we need a better "init just global
1892 state, for no specific purpose" singleton function of our own */
1894 SSL_load_error_strings();
1895 OpenSSL_add_ssl_algorithms();
1896 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1897 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1898 list of available digests. */
1899 EVP_add_digest(EVP_sha256());
1902 if (!(tls_require_ciphers && *tls_require_ciphers))
1905 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1906 return US"failed to expand tls_require_ciphers";
1908 if (!(expciphers && *expciphers))
1911 /* normalisation ripped from above */
1913 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1917 ctx = SSL_CTX_new(SSLv23_server_method());
1920 ERR_error_string(ERR_get_error(), ssl_errstring);
1921 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1925 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1927 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1929 ERR_error_string(ERR_get_error(), ssl_errstring);
1930 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
1941 /*************************************************
1942 * Report the library versions. *
1943 *************************************************/
1945 /* There have historically been some issues with binary compatibility in
1946 OpenSSL libraries; if Exim (like many other applications) is built against
1947 one version of OpenSSL but the run-time linker picks up another version,
1948 it can result in serious failures, including crashing with a SIGSEGV. So
1949 report the version found by the compiler and the run-time version.
1951 Note: some OS vendors backport security fixes without changing the version
1952 number/string, and the version date remains unchanged. The _build_ date
1953 will change, so we can more usefully assist with version diagnosis by also
1954 reporting the build date.
1956 Arguments: a FILE* to print the results to
1961 tls_version_report(FILE *f)
1963 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
1966 OPENSSL_VERSION_TEXT,
1967 SSLeay_version(SSLEAY_VERSION),
1968 SSLeay_version(SSLEAY_BUILT_ON));
1969 /* third line is 38 characters for the %s and the line is 73 chars long;
1970 the OpenSSL output includes a "built on: " prefix already. */
1976 /*************************************************
1977 * Random number generation *
1978 *************************************************/
1980 /* Pseudo-random number generation. The result is not expected to be
1981 cryptographically strong but not so weak that someone will shoot themselves
1982 in the foot using it as a nonce in input in some email header scheme or
1983 whatever weirdness they'll twist this into. The result should handle fork()
1984 and avoid repeating sequences. OpenSSL handles that for us.
1988 Returns a random number in range [0, max-1]
1992 vaguely_random_number(int max)
1996 static pid_t pidlast = 0;
1999 uschar smallbuf[sizeof(r)];
2005 if (pidnow != pidlast)
2007 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2008 is unique for each thread", this doesn't apparently apply across processes,
2009 so our own warning from vaguely_random_number_fallback() applies here too.
2010 Fix per PostgreSQL. */
2016 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2020 gettimeofday(&r.tv, NULL);
2023 RAND_seed((uschar *)(&r), sizeof(r));
2025 /* We're after pseudo-random, not random; if we still don't have enough data
2026 in the internal PRNG then our options are limited. We could sleep and hope
2027 for entropy to come along (prayer technique) but if the system is so depleted
2028 in the first place then something is likely to just keep taking it. Instead,
2029 we'll just take whatever little bit of pseudo-random we can still manage to
2032 needed_len = sizeof(r);
2033 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2034 asked for a number less than 10. */
2035 for (r = max, i = 0; r; ++i)
2041 /* We do not care if crypto-strong */
2042 i = RAND_pseudo_bytes(smallbuf, needed_len);
2046 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2047 return vaguely_random_number_fallback(max);
2051 for (p = smallbuf; needed_len; --needed_len, ++p)
2057 /* We don't particularly care about weighted results; if someone wants
2058 smooth distribution and cares enough then they should submit a patch then. */
2065 /*************************************************
2066 * OpenSSL option parse *
2067 *************************************************/
2069 /* Parse one option for tls_openssl_options_parse below
2072 name one option name
2073 value place to store a value for it
2074 Returns success or failure in parsing
2077 struct exim_openssl_option {
2081 /* We could use a macro to expand, but we need the ifdef and not all the
2082 options document which version they were introduced in. Policylet: include
2083 all options unless explicitly for DTLS, let the administrator choose which
2086 This list is current as of:
2088 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2090 static struct exim_openssl_option exim_openssl_options[] = {
2091 /* KEEP SORTED ALPHABETICALLY! */
2093 { US"all", SSL_OP_ALL },
2095 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2096 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2098 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2099 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2101 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2102 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2104 #ifdef SSL_OP_EPHEMERAL_RSA
2105 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2107 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2108 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2110 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2111 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2113 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2114 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2116 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2117 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2119 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2120 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2122 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2123 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2125 #ifdef SSL_OP_NO_COMPRESSION
2126 { US"no_compression", SSL_OP_NO_COMPRESSION },
2128 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2129 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2131 #ifdef SSL_OP_NO_SSLv2
2132 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2134 #ifdef SSL_OP_NO_SSLv3
2135 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2137 #ifdef SSL_OP_NO_TICKET
2138 { US"no_ticket", SSL_OP_NO_TICKET },
2140 #ifdef SSL_OP_NO_TLSv1
2141 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2143 #ifdef SSL_OP_NO_TLSv1_1
2144 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2145 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2146 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2148 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2151 #ifdef SSL_OP_NO_TLSv1_2
2152 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2154 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2155 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2157 #ifdef SSL_OP_SINGLE_DH_USE
2158 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2160 #ifdef SSL_OP_SINGLE_ECDH_USE
2161 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2163 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2164 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2166 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2167 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2169 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2170 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2172 #ifdef SSL_OP_TLS_D5_BUG
2173 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2175 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2176 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2179 static int exim_openssl_options_size =
2180 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2184 tls_openssl_one_option_parse(uschar *name, long *value)
2187 int last = exim_openssl_options_size;
2188 while (last > first)
2190 int middle = (first + last)/2;
2191 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2194 *value = exim_openssl_options[middle].value;
2208 /*************************************************
2209 * OpenSSL option parsing logic *
2210 *************************************************/
2212 /* OpenSSL has a number of compatibility options which an administrator might
2213 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
2214 we look like log_selector.
2217 option_spec the administrator-supplied string of options
2218 results ptr to long storage for the options bitmap
2219 Returns success or failure
2223 tls_openssl_options_parse(uschar *option_spec, long *results)
2228 BOOL adding, item_parsed;
2231 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2232 * from default because it increases BEAST susceptibility. */
2233 #ifdef SSL_OP_NO_SSLv2
2234 result |= SSL_OP_NO_SSLv2;
2237 if (option_spec == NULL)
2243 for (s=option_spec; *s != '\0'; /**/)
2245 while (isspace(*s)) ++s;
2248 if (*s != '+' && *s != '-')
2250 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2251 "+ or - expected but found \"%s\"\n", s);
2254 adding = *s++ == '+';
2255 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2258 item_parsed = tls_openssl_one_option_parse(s, &item);
2261 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2264 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2265 adding ? "adding" : "removing", result, item, s);
2280 /* End of tls-openssl.c */