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>
26 # include <openssl/ocsp.h>
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 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)
39 # warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile"
43 /* Structure for collecting random data for seeding. */
45 typedef struct randstuff {
50 /* Local static variables */
52 static BOOL client_verify_callback_called = FALSE;
53 static BOOL server_verify_callback_called = FALSE;
54 static const uschar *sid_ctx = US"exim";
56 /* We have three different contexts to care about.
58 Simple case: client, `client_ctx`
59 As a client, we can be doing a callout or cut-through delivery while receiving
60 a message. So we have a client context, which should have options initialised
61 from the SMTP Transport.
64 There are two cases: with and without ServerNameIndication from the client.
65 Given TLS SNI, we can be using different keys, certs and various other
66 configuration settings, because they're re-expanded with $tls_sni set. This
67 allows vhosting with TLS. This SNI is sent in the handshake.
68 A client might not send SNI, so we need a fallback, and an initial setup too.
69 So as a server, we start out using `server_ctx`.
70 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
71 `server_sni` from `server_ctx` and then initialise settings by re-expanding
75 static SSL_CTX *client_ctx = NULL;
76 static SSL_CTX *server_ctx = NULL;
77 static SSL *client_ssl = NULL;
78 static SSL *server_ssl = NULL;
80 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
81 static SSL_CTX *server_sni = NULL;
84 static char ssl_errstring[256];
86 static int ssl_session_timeout = 200;
87 static BOOL client_verify_optional = FALSE;
88 static BOOL server_verify_optional = FALSE;
90 static BOOL reexpand_tls_files_for_sni = FALSE;
93 typedef struct tls_ext_ctx_cb {
101 uschar *file_expanded;
102 OCSP_RESPONSE *response;
105 X509_STORE *verify_store; /* non-null if status requested */
106 BOOL verify_required;
111 /* these are cached from first expand */
112 uschar *server_cipher_list;
113 /* only passed down to tls_error: */
116 #ifdef EXPERIMENTAL_CERTNAMES
117 uschar * verify_cert_hostnames;
121 /* should figure out a cleanup of API to handle state preserved per
122 implementation, for various reasons, which can be void * in the APIs.
123 For now, we hack around it. */
124 tls_ext_ctx_cb *client_static_cbinfo = NULL;
125 tls_ext_ctx_cb *server_static_cbinfo = NULL;
128 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
129 int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
132 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
133 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
136 static int tls_server_stapling_cb(SSL *s, void *arg);
140 /*************************************************
142 *************************************************/
144 /* Called from lots of places when errors occur before actually starting to do
145 the TLS handshake, that is, while the session is still in clear. Always returns
146 DEFER for a server and FAIL for a client so that most calls can use "return
147 tls_error(...)" to do this processing and then give an appropriate return. A
148 single function is used for both server and client, because it is called from
149 some shared functions.
152 prefix text to include in the logged error
153 host NULL if setting up a server;
154 the connected host if setting up a client
155 msg error message or NULL if we should ask OpenSSL
157 Returns: OK/DEFER/FAIL
161 tls_error(uschar *prefix, host_item *host, uschar *msg)
165 ERR_error_string(ERR_get_error(), ssl_errstring);
166 msg = (uschar *)ssl_errstring;
171 uschar *conn_info = smtp_get_connection_info();
172 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
174 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
175 conn_info, prefix, msg);
180 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
181 host->name, host->address, prefix, msg);
188 /*************************************************
189 * Callback to generate RSA key *
190 *************************************************/
198 Returns: pointer to generated key
202 rsa_callback(SSL *s, int export, int keylength)
205 export = export; /* Shut picky compilers up */
206 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
207 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
210 ERR_error_string(ERR_get_error(), ssl_errstring);
211 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
223 x509_store_dump_cert_s_names(X509_STORE * store)
225 STACK_OF(X509_OBJECT) * roots= store->objs;
227 static uschar name[256];
229 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
231 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
232 if(tmp_obj->type == X509_LU_X509)
234 X509 * current_cert= tmp_obj->data.x509;
235 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
236 debug_printf(" %s\n", name);
244 /*************************************************
245 * Callback for verification *
246 *************************************************/
248 /* The SSL library does certificate verification if set up to do so. This
249 callback has the current yes/no state is in "state". If verification succeeded,
250 we set up the tls_peerdn string. If verification failed, what happens depends
251 on whether the client is required to present a verifiable certificate or not.
253 If verification is optional, we change the state to yes, but still log the
254 verification error. For some reason (it really would help to have proper
255 documentation of OpenSSL), this callback function then gets called again, this
256 time with state = 1. In fact, that's useful, because we can set up the peerdn
257 value, but we must take care not to set the private verified flag on the second
260 Note: this function is not called if the client fails to present a certificate
261 when asked. We get here only if a certificate has been received. Handling of
262 optional verification for this case is done when requesting SSL to verify, by
263 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
266 state current yes/no state as 1/0
267 x509ctx certificate information.
268 client TRUE for client startup, FALSE for server startup
270 Returns: 1 if verified, 0 if not
274 verify_callback(int state, X509_STORE_CTX *x509ctx,
275 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
277 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
278 static uschar txt[256];
280 X509_NAME_oneline(X509_get_subject_name(cert), CS txt, sizeof(txt));
284 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
285 X509_STORE_CTX_get_error_depth(x509ctx),
286 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
288 tlsp->certificate_verified = FALSE;
292 tlsp->peercert = X509_dup(cert);
293 return 0; /* reject */
295 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
296 "tls_try_verify_hosts)\n");
299 else if (X509_STORE_CTX_get_error_depth(x509ctx) != 0)
301 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n",
302 X509_STORE_CTX_get_error_depth(x509ctx), txt);
304 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
305 { /* client, wanting stapling */
306 /* Add the server cert's signing chain as the one
307 for the verification of the OCSP stapled information. */
309 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
317 #ifdef EXPERIMENTAL_CERTNAMES
318 uschar * verify_cert_hostnames;
322 tlsp->peercert = X509_dup(cert);
324 #ifdef EXPERIMENTAL_CERTNAMES
325 if ( tlsp == &tls_out
326 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
327 /* client, wanting hostname check */
329 # if OPENSSL_VERSION_NUMBER >= 0x010100000L || OPENSSL_VERSION_NUMBER >= 0x010002000L
330 # ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
331 # define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0
335 uschar * list = verify_cert_hostnames;
338 while ((name = string_nextinlist(&list, &sep, NULL, 0)))
339 if ((rc = X509_check_host(cert, name, 0,
340 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS)))
344 log_write(0, LOG_MAIN, "SSL verify error: internal error\n");
351 log_write(0, LOG_MAIN,
352 "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
353 return 0; /* reject */
357 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
359 log_write(0, LOG_MAIN,
360 "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
361 return 0; /* reject */
366 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
367 *calledp ? "" : " authenticated", txt);
368 if (!*calledp) tlsp->certificate_verified = TRUE;
372 return 1; /* accept */
376 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
378 return verify_callback(state, x509ctx, &tls_out, &client_verify_callback_called, &client_verify_optional);
382 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
384 return verify_callback(state, x509ctx, &tls_in, &server_verify_callback_called, &server_verify_optional);
389 /*************************************************
390 * Information callback *
391 *************************************************/
393 /* The SSL library functions call this from time to time to indicate what they
394 are doing. We copy the string to the debugging output when TLS debugging has
406 info_callback(SSL *s, int where, int ret)
410 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
415 /*************************************************
416 * Initialize for DH *
417 *************************************************/
419 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
422 dhparam DH parameter file or fixed parameter identity string
423 host connected host, if client; NULL if server
425 Returns: TRUE if OK (nothing to set up, or setup worked)
429 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
436 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
439 if (!dhexpanded || !*dhexpanded)
440 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
441 else if (dhexpanded[0] == '/')
443 if (!(bio = BIO_new_file(CS dhexpanded, "r")))
445 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
446 host, US strerror(errno));
452 if (Ustrcmp(dhexpanded, "none") == 0)
454 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
458 if (!(pem = std_dh_prime_named(dhexpanded)))
460 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
461 host, US strerror(errno));
464 bio = BIO_new_mem_buf(CS pem, -1);
467 if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)))
470 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
475 /* Even if it is larger, we silently return success rather than cause things
476 * to fail out, so that a too-large DH will not knock out all TLS; it's a
477 * debatable choice. */
478 if ((8*DH_size(dh)) > tls_dh_max_bits)
481 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
482 8*DH_size(dh), tls_dh_max_bits);
486 SSL_CTX_set_tmp_dh(sctx, dh);
488 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
489 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
502 /*************************************************
503 * Load OCSP information into state *
504 *************************************************/
506 /* Called to load the server OCSP response from the given file into memory, once
507 caller has determined this is needed. Checks validity. Debugs a message
510 ASSUMES: single response, for single cert.
513 sctx the SSL_CTX* to update
514 cbinfo various parts of session state
515 expanded the filename putatively holding an OCSP response
520 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
524 OCSP_BASICRESP *basic_response;
525 OCSP_SINGLERESP *single_response;
526 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
528 unsigned long verify_flags;
529 int status, reason, i;
531 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
532 if (cbinfo->u_ocsp.server.response)
534 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
535 cbinfo->u_ocsp.server.response = NULL;
538 bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb");
541 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
542 cbinfo->u_ocsp.server.file_expanded);
546 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
550 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
554 status = OCSP_response_status(resp);
555 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
557 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
558 OCSP_response_status_str(status), status);
562 basic_response = OCSP_response_get1_basic(resp);
566 debug_printf("OCSP response parse error: unable to extract basic response.\n");
570 store = SSL_CTX_get_cert_store(sctx);
571 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
573 /* May need to expose ability to adjust those flags?
574 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
575 OCSP_TRUSTOTHER OCSP_NOINTERN */
577 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
581 ERR_error_string(ERR_get_error(), ssl_errstring);
582 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
587 /* Here's the simplifying assumption: there's only one response, for the
588 one certificate we use, and nothing for anything else in a chain. If this
589 proves false, we need to extract a cert id from our issued cert
590 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
591 right cert in the stack and then calls OCSP_single_get0_status()).
593 I'm hoping to avoid reworking a bunch more of how we handle state here. */
594 single_response = OCSP_resp_get0(basic_response, 0);
595 if (!single_response)
598 debug_printf("Unable to get first response from OCSP basic response.\n");
602 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
603 if (status != V_OCSP_CERTSTATUS_GOOD)
605 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
606 OCSP_cert_status_str(status), status,
607 OCSP_crl_reason_str(reason), reason);
611 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
613 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
618 cbinfo->u_ocsp.server.response = resp;
622 if (running_in_test_harness)
624 extern char ** environ;
626 for (p = USS environ; *p != NULL; p++)
627 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
629 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
630 goto supply_response;
635 #endif /*!DISABLE_OCSP*/
640 /*************************************************
641 * Expand key and cert file specs *
642 *************************************************/
644 /* Called once during tls_init and possibly again during TLS setup, for a
645 new context, if Server Name Indication was used and tls_sni was seen in
646 the certificate string.
649 sctx the SSL_CTX* to update
650 cbinfo various parts of session state
652 Returns: OK/DEFER/FAIL
656 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
660 if (cbinfo->certificate == NULL)
663 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
664 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
665 Ustrstr(cbinfo->certificate, US"tls_out_sni")
667 reexpand_tls_files_for_sni = TRUE;
669 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
672 if (expanded != NULL)
674 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
675 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
676 return tls_error(string_sprintf(
677 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
681 if (cbinfo->privatekey != NULL &&
682 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
685 /* If expansion was forced to fail, key_expanded will be NULL. If the result
686 of the expansion is an empty string, ignore it also, and assume the private
687 key is in the same file as the certificate. */
689 if (expanded != NULL && *expanded != 0)
691 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
692 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
693 return tls_error(string_sprintf(
694 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
698 if (cbinfo->is_server && cbinfo->u_ocsp.server.file != NULL)
700 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
703 if (expanded != NULL && *expanded != 0)
705 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
706 if (cbinfo->u_ocsp.server.file_expanded &&
707 (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
710 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
712 ocsp_load_response(sctx, cbinfo, expanded);
724 /*************************************************
725 * Callback to handle SNI *
726 *************************************************/
728 /* Called when acting as server during the TLS session setup if a Server Name
729 Indication extension was sent by the client.
731 API documentation is OpenSSL s_server.c implementation.
734 s SSL* of the current session
735 ad unknown (part of OpenSSL API) (unused)
736 arg Callback of "our" registered data
738 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
741 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
743 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
745 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
746 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
748 int old_pool = store_pool;
751 return SSL_TLSEXT_ERR_OK;
753 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
754 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
756 /* Make the extension value available for expansion */
757 store_pool = POOL_PERM;
758 tls_in.sni = string_copy(US servername);
759 store_pool = old_pool;
761 if (!reexpand_tls_files_for_sni)
762 return SSL_TLSEXT_ERR_OK;
764 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
765 not confident that memcpy wouldn't break some internal reference counting.
766 Especially since there's a references struct member, which would be off. */
768 if (!(server_sni = SSL_CTX_new(SSLv23_server_method())))
770 ERR_error_string(ERR_get_error(), ssl_errstring);
771 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
772 return SSL_TLSEXT_ERR_NOACK;
775 /* Not sure how many of these are actually needed, since SSL object
776 already exists. Might even need this selfsame callback, for reneg? */
778 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
779 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
780 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
781 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
782 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
783 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
784 if (cbinfo->server_cipher_list)
785 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
787 if (cbinfo->u_ocsp.server.file)
789 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
790 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
794 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server);
795 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
797 /* do this after setup_certs, because this can require the certs for verifying
799 rc = tls_expand_session_files(server_sni, cbinfo);
800 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
802 if (!init_dh(server_sni, cbinfo->dhparam, NULL))
803 return SSL_TLSEXT_ERR_NOACK;
805 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
806 SSL_set_SSL_CTX(s, server_sni);
808 return SSL_TLSEXT_ERR_OK;
810 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
817 /*************************************************
818 * Callback to handle OCSP Stapling *
819 *************************************************/
821 /* Called when acting as server during the TLS session setup if the client
822 requests OCSP information with a Certificate Status Request.
824 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
830 tls_server_stapling_cb(SSL *s, void *arg)
832 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
833 uschar *response_der;
834 int response_der_len;
837 debug_printf("Received TLS status request (OCSP stapling); %s response.",
838 cbinfo->u_ocsp.server.response ? "have" : "lack");
840 tls_in.ocsp = OCSP_NOT_RESP;
841 if (!cbinfo->u_ocsp.server.response)
842 return SSL_TLSEXT_ERR_NOACK;
845 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
847 if (response_der_len <= 0)
848 return SSL_TLSEXT_ERR_NOACK;
850 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
851 tls_in.ocsp = OCSP_VFIED;
852 return SSL_TLSEXT_ERR_OK;
857 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
859 BIO_printf(bp, "\t%s: ", str);
860 ASN1_GENERALIZEDTIME_print(bp, time);
865 tls_client_stapling_cb(SSL *s, void *arg)
867 tls_ext_ctx_cb * cbinfo = arg;
868 const unsigned char * p;
874 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
875 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
878 /* Expect this when we requested ocsp but got none */
879 if ( cbinfo->u_ocsp.client.verify_required
880 && log_extra_selector & LX_tls_cipher)
881 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
883 DEBUG(D_tls) debug_printf(" null\n");
884 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
887 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
889 tls_out.ocsp = OCSP_FAILED;
890 if (log_extra_selector & LX_tls_cipher)
891 log_write(0, LOG_MAIN, "Received TLS status response, parse error");
893 DEBUG(D_tls) debug_printf(" parse error\n");
897 if(!(bs = OCSP_response_get1_basic(rsp)))
899 tls_out.ocsp = OCSP_FAILED;
900 if (log_extra_selector & LX_tls_cipher)
901 log_write(0, LOG_MAIN, "Received TLS status response, error parsing response");
903 DEBUG(D_tls) debug_printf(" error parsing response\n");
904 OCSP_RESPONSE_free(rsp);
908 /* We'd check the nonce here if we'd put one in the request. */
909 /* However that would defeat cacheability on the server so we don't. */
911 /* This section of code reworked from OpenSSL apps source;
912 The OpenSSL Project retains copyright:
913 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
918 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
920 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
922 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
924 /* Use the chain that verified the server cert to verify the stapled info */
925 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
927 if ((i = OCSP_basic_verify(bs, NULL,
928 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
930 tls_out.ocsp = OCSP_FAILED;
931 BIO_printf(bp, "OCSP response verify failure\n");
932 ERR_print_errors(bp);
933 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
937 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
940 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
941 OCSP_SINGLERESP * single;
943 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
945 tls_out.ocsp = OCSP_FAILED;
946 log_write(0, LOG_MAIN, "OCSP stapling "
947 "with multiple responses not handled");
948 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
951 single = OCSP_resp_get0(bs, 0);
952 status = OCSP_single_get0_status(single, &reason, &rev,
956 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
957 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
958 if (!OCSP_check_validity(thisupd, nextupd,
959 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
961 tls_out.ocsp = OCSP_FAILED;
962 DEBUG(D_tls) ERR_print_errors(bp);
963 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
964 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
968 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
969 OCSP_cert_status_str(status));
972 case V_OCSP_CERTSTATUS_GOOD:
973 tls_out.ocsp = OCSP_VFIED;
976 case V_OCSP_CERTSTATUS_REVOKED:
977 tls_out.ocsp = OCSP_FAILED;
978 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
979 reason != -1 ? "; reason: " : "",
980 reason != -1 ? OCSP_crl_reason_str(reason) : "");
981 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
982 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
985 tls_out.ocsp = OCSP_FAILED;
986 log_write(0, LOG_MAIN,
987 "Server certificate status unknown, in OCSP stapling");
988 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
996 OCSP_RESPONSE_free(rsp);
999 #endif /*!DISABLE_OCSP*/
1003 /*************************************************
1004 * Initialize for TLS *
1005 *************************************************/
1007 /* Called from both server and client code, to do preliminary initialization
1008 of the library. We allocate and return a context structure.
1011 host connected host, if client; NULL if server
1012 dhparam DH parameter file
1013 certificate certificate file
1014 privatekey private key
1015 ocsp_file file of stapling info (server); flag for require ocsp (client)
1016 addr address if client; NULL if server (for some randomness)
1017 cbp place to put allocated context
1019 Returns: OK/DEFER/FAIL
1023 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1025 #ifndef DISABLE_OCSP
1028 address_item *addr, tls_ext_ctx_cb ** cbp)
1033 tls_ext_ctx_cb *cbinfo;
1035 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1036 cbinfo->certificate = certificate;
1037 cbinfo->privatekey = privatekey;
1038 #ifndef DISABLE_OCSP
1039 if ((cbinfo->is_server = host==NULL))
1041 cbinfo->u_ocsp.server.file = ocsp_file;
1042 cbinfo->u_ocsp.server.file_expanded = NULL;
1043 cbinfo->u_ocsp.server.response = NULL;
1046 cbinfo->u_ocsp.client.verify_store = NULL;
1048 cbinfo->dhparam = dhparam;
1049 cbinfo->server_cipher_list = NULL;
1050 cbinfo->host = host;
1052 SSL_load_error_strings(); /* basic set up */
1053 OpenSSL_add_ssl_algorithms();
1055 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1056 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1057 list of available digests. */
1058 EVP_add_digest(EVP_sha256());
1061 /* Create a context.
1062 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1063 negotiation in the different methods; as far as I can tell, the only
1064 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1065 when OpenSSL is built without SSLv2 support.
1066 By disabling with openssl_options, we can let admins re-enable with the
1069 *ctxp = SSL_CTX_new((host == NULL)?
1070 SSLv23_server_method() : SSLv23_client_method());
1072 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
1074 /* It turns out that we need to seed the random number generator this early in
1075 order to get the full complement of ciphers to work. It took me roughly a day
1076 of work to discover this by experiment.
1078 On systems that have /dev/urandom, SSL may automatically seed itself from
1079 there. Otherwise, we have to make something up as best we can. Double check
1085 gettimeofday(&r.tv, NULL);
1088 RAND_seed((uschar *)(&r), sizeof(r));
1089 RAND_seed((uschar *)big_buffer, big_buffer_size);
1090 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1093 return tls_error(US"RAND_status", host,
1094 US"unable to seed random number generator");
1097 /* Set up the information callback, which outputs if debugging is at a suitable
1100 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1102 /* Automatically re-try reads/writes after renegotiation. */
1103 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1105 /* Apply administrator-supplied work-arounds.
1106 Historically we applied just one requested option,
1107 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1108 moved to an administrator-controlled list of options to specify and
1109 grandfathered in the first one as the default value for "openssl_options".
1111 No OpenSSL version number checks: the options we accept depend upon the
1112 availability of the option value macros from OpenSSL. */
1114 okay = tls_openssl_options_parse(openssl_options, &init_options);
1116 return tls_error(US"openssl_options parsing failed", host, NULL);
1120 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1121 if (!(SSL_CTX_set_options(*ctxp, init_options)))
1122 return tls_error(string_sprintf(
1123 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1126 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1128 /* Initialize with DH parameters if supplied */
1130 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
1132 /* Set up certificate and key (and perhaps OCSP info) */
1134 rc = tls_expand_session_files(*ctxp, cbinfo);
1135 if (rc != OK) return rc;
1137 /* If we need to handle SNI, do so */
1138 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1139 if (host == NULL) /* server */
1141 # ifndef DISABLE_OCSP
1142 /* We check u_ocsp.server.file, not server.response, because we care about if
1143 the option exists, not what the current expansion might be, as SNI might
1144 change the certificate and OCSP file in use between now and the time the
1145 callback is invoked. */
1146 if (cbinfo->u_ocsp.server.file)
1148 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1149 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1152 /* We always do this, so that $tls_sni is available even if not used in
1154 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1155 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1157 # ifndef DISABLE_OCSP
1159 if(ocsp_file) /* wanting stapling */
1161 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1163 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1166 SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1167 SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1172 #ifdef EXPERIMENTAL_CERTNAMES
1173 cbinfo->verify_cert_hostnames = NULL;
1176 /* Set up the RSA callback */
1178 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1180 /* Finally, set the timeout, and we are done */
1182 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1183 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1193 /*************************************************
1194 * Get name of cipher in use *
1195 *************************************************/
1198 Argument: pointer to an SSL structure for the connection
1199 buffer to use for answer
1201 pointer to number of bits for cipher
1206 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1208 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1209 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1210 the accessor functions use const in the prototype. */
1211 const SSL_CIPHER *c;
1214 ver = (const uschar *)SSL_get_version(ssl);
1216 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1217 SSL_CIPHER_get_bits(c, bits);
1219 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1220 SSL_CIPHER_get_name(c), *bits);
1222 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1229 /*************************************************
1230 * Set up for verifying certificates *
1231 *************************************************/
1233 /* Called by both client and server startup
1236 sctx SSL_CTX* to initialise
1237 certs certs file or NULL
1238 crl CRL file or NULL
1239 host NULL in a server; the remote host in a client
1240 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1241 otherwise passed as FALSE
1242 cert_vfy_cb Callback function for certificate verification
1244 Returns: OK/DEFER/FAIL
1248 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1249 int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1251 uschar *expcerts, *expcrl;
1253 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1256 if (expcerts != NULL && *expcerts != '\0')
1258 struct stat statbuf;
1259 if (!SSL_CTX_set_default_verify_paths(sctx))
1260 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1262 if (Ustat(expcerts, &statbuf) < 0)
1264 log_write(0, LOG_MAIN|LOG_PANIC,
1265 "failed to stat %s for certificates", expcerts);
1271 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1272 { file = NULL; dir = expcerts; }
1274 { file = expcerts; dir = NULL; }
1276 /* If a certificate file is empty, the next function fails with an
1277 unhelpful error message. If we skip it, we get the correct behaviour (no
1278 certificates are recognized, but the error message is still misleading (it
1279 says no certificate was supplied.) But this is better. */
1281 if ((file == NULL || statbuf.st_size > 0) &&
1282 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1283 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1287 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1291 /* Handle a certificate revocation list. */
1293 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1295 /* This bit of code is now the version supplied by Lars Mainka. (I have
1296 * merely reformatted it into the Exim code style.)
1298 * "From here I changed the code to add support for multiple crl's
1299 * in pem format in one file or to support hashed directory entries in
1300 * pem format instead of a file. This method now uses the library function
1301 * X509_STORE_load_locations to add the CRL location to the SSL context.
1302 * OpenSSL will then handle the verify against CA certs and CRLs by
1303 * itself in the verify callback." */
1305 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1306 if (expcrl != NULL && *expcrl != 0)
1308 struct stat statbufcrl;
1309 if (Ustat(expcrl, &statbufcrl) < 0)
1311 log_write(0, LOG_MAIN|LOG_PANIC,
1312 "failed to stat %s for certificates revocation lists", expcrl);
1317 /* is it a file or directory? */
1319 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1320 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1324 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1330 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1332 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1333 return tls_error(US"X509_STORE_load_locations", host, NULL);
1335 /* setting the flags to check against the complete crl chain */
1337 X509_STORE_set_flags(cvstore,
1338 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1342 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1344 /* If verification is optional, don't fail if no certificate */
1346 SSL_CTX_set_verify(sctx,
1347 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1356 /*************************************************
1357 * Start a TLS session in a server *
1358 *************************************************/
1360 /* This is called when Exim is running as a server, after having received
1361 the STARTTLS command. It must respond to that command, and then negotiate
1365 require_ciphers allowed ciphers
1367 Returns: OK on success
1368 DEFER for errors before the start of the negotiation
1369 FAIL for errors during the negotation; the server can't
1374 tls_server_start(const uschar *require_ciphers)
1378 tls_ext_ctx_cb *cbinfo;
1379 static uschar cipherbuf[256];
1381 /* Check for previous activation */
1383 if (tls_in.active >= 0)
1385 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1386 smtp_printf("554 Already in TLS\r\n");
1390 /* Initialize the SSL library. If it fails, it will already have logged
1393 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1394 #ifndef DISABLE_OCSP
1397 NULL, &server_static_cbinfo);
1398 if (rc != OK) return rc;
1399 cbinfo = server_static_cbinfo;
1401 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1404 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1405 were historically separated by underscores. So that I can use either form in my
1406 tests, and also for general convenience, we turn underscores into hyphens here.
1409 if (expciphers != NULL)
1411 uschar *s = expciphers;
1412 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1413 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1414 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1415 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1416 cbinfo->server_cipher_list = expciphers;
1419 /* If this is a host for which certificate verification is mandatory or
1420 optional, set up appropriately. */
1422 tls_in.certificate_verified = FALSE;
1423 server_verify_callback_called = FALSE;
1425 if (verify_check_host(&tls_verify_hosts) == OK)
1427 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1428 FALSE, verify_callback_server);
1429 if (rc != OK) return rc;
1430 server_verify_optional = FALSE;
1432 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1434 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1435 TRUE, verify_callback_server);
1436 if (rc != OK) return rc;
1437 server_verify_optional = TRUE;
1440 /* Prepare for new connection */
1442 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1444 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1446 * With the SSL_clear(), we get strange interoperability bugs with
1447 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1448 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1450 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1451 * session shutdown. In this case, we have a brand new object and there's no
1452 * obvious reason to immediately clear it. I'm guessing that this was
1453 * originally added because of incomplete initialisation which the clear fixed,
1454 * in some historic release.
1457 /* Set context and tell client to go ahead, except in the case of TLS startup
1458 on connection, where outputting anything now upsets the clients and tends to
1459 make them disconnect. We need to have an explicit fflush() here, to force out
1460 the response. Other smtp_printf() calls do not need it, because in non-TLS
1461 mode, the fflush() happens when smtp_getc() is called. */
1463 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1464 if (!tls_in.on_connect)
1466 smtp_printf("220 TLS go ahead\r\n");
1470 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1471 that the OpenSSL library doesn't. */
1473 SSL_set_wfd(server_ssl, fileno(smtp_out));
1474 SSL_set_rfd(server_ssl, fileno(smtp_in));
1475 SSL_set_accept_state(server_ssl);
1477 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1479 sigalrm_seen = FALSE;
1480 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1481 rc = SSL_accept(server_ssl);
1486 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1487 if (ERR_get_error() == 0)
1488 log_write(0, LOG_MAIN,
1489 "TLS client disconnected cleanly (rejected our certificate?)");
1493 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1495 /* TLS has been set up. Adjust the input functions to read via TLS,
1496 and initialize things. */
1498 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1499 tls_in.cipher = cipherbuf;
1504 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1505 debug_printf("Shared ciphers: %s\n", buf);
1508 /* Record the certificate we presented */
1510 X509 * crt = SSL_get_certificate(server_ssl);
1511 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1514 /* Only used by the server-side tls (tls_in), including tls_getc.
1515 Client-side (tls_out) reads (seem to?) go via
1516 smtp_read_response()/ip_recv().
1517 Hence no need to duplicate for _in and _out.
1519 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1520 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1521 ssl_xfer_eof = ssl_xfer_error = 0;
1523 receive_getc = tls_getc;
1524 receive_ungetc = tls_ungetc;
1525 receive_feof = tls_feof;
1526 receive_ferror = tls_ferror;
1527 receive_smtp_buffered = tls_smtp_buffered;
1529 tls_in.active = fileno(smtp_out);
1537 /*************************************************
1538 * Start a TLS session in a client *
1539 *************************************************/
1541 /* Called from the smtp transport after STARTTLS has been accepted.
1544 fd the fd of the connection
1545 host connected host (for messages)
1546 addr the first address
1547 ob smtp transport options
1549 Returns: OK on success
1550 FAIL otherwise - note that tls_error() will not give DEFER
1551 because this is not a server
1555 tls_client_start(int fd, host_item *host, address_item *addr,
1558 smtp_transport_options_block * ob = v_ob;
1559 static uschar txt[256];
1563 static uschar cipherbuf[256];
1564 #ifndef DISABLE_OCSP
1565 BOOL require_ocsp = verify_check_this_host(&ob->hosts_require_ocsp,
1566 NULL, host->name, host->address, NULL) == OK;
1567 BOOL request_ocsp = require_ocsp ? TRUE
1568 : verify_check_this_host(&ob->hosts_request_ocsp,
1569 NULL, host->name, host->address, NULL) == OK;
1572 rc = tls_init(&client_ctx, host, NULL,
1573 ob->tls_certificate, ob->tls_privatekey,
1574 #ifndef DISABLE_OCSP
1575 (void *)(long)request_ocsp,
1577 addr, &client_static_cbinfo);
1578 if (rc != OK) return rc;
1580 tls_out.certificate_verified = FALSE;
1581 client_verify_callback_called = FALSE;
1583 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
1587 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1588 are separated by underscores. So that I can use either form in my tests, and
1589 also for general convenience, we turn underscores into hyphens here. */
1591 if (expciphers != NULL)
1593 uschar *s = expciphers;
1594 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1595 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1596 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1597 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1600 /* stick to the old behaviour for compatibility if tls_verify_certificates is
1601 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
1602 the specified host patterns if one of them is defined */
1604 if ((!ob->tls_verify_hosts && !ob->tls_try_verify_hosts) ||
1605 (verify_check_host(&ob->tls_verify_hosts) == OK))
1607 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1608 ob->tls_crl, host, FALSE, verify_callback_client)) != OK)
1610 client_verify_optional = FALSE;
1612 #ifdef EXPERIMENTAL_CERTNAMES
1613 if (ob->tls_verify_cert_hostnames)
1615 if (!expand_check(ob->tls_verify_cert_hostnames,
1616 US"tls_verify_cert_hostnames",
1617 &client_static_cbinfo->verify_cert_hostnames))
1619 if (client_static_cbinfo->verify_cert_hostnames)
1620 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
1621 client_static_cbinfo->verify_cert_hostnames);
1625 else if (verify_check_host(&ob->tls_try_verify_hosts) == OK)
1627 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1628 ob->tls_crl, host, TRUE, verify_callback_client)) != OK)
1630 client_verify_optional = TRUE;
1633 if ((client_ssl = SSL_new(client_ctx)) == NULL)
1634 return tls_error(US"SSL_new", host, NULL);
1635 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1636 SSL_set_fd(client_ssl, fd);
1637 SSL_set_connect_state(client_ssl);
1641 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
1643 if (tls_out.sni == NULL)
1645 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1647 else if (!Ustrlen(tls_out.sni))
1651 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1652 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1653 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1656 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1662 #ifndef DISABLE_OCSP
1663 /* Request certificate status at connection-time. If the server
1664 does OCSP stapling we will get the callback (set in tls_init()) */
1667 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
1668 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
1669 tls_out.ocsp = OCSP_NOT_RESP;
1673 /* There doesn't seem to be a built-in timeout on connection. */
1675 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1676 sigalrm_seen = FALSE;
1677 alarm(ob->command_timeout);
1678 rc = SSL_connect(client_ssl);
1682 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1684 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1686 /* Beware anonymous ciphers which lead to server_cert being NULL */
1687 /*XXX server_cert is never freed... use X509_free() */
1688 server_cert = SSL_get_peer_certificate (client_ssl);
1691 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1692 CS txt, sizeof(txt));
1693 tls_out.peerdn = txt; /*XXX a static buffer... */
1696 tls_out.peerdn = NULL;
1698 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1699 tls_out.cipher = cipherbuf;
1701 /* Record the certificate we presented */
1703 X509 * crt = SSL_get_certificate(client_ssl);
1704 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
1707 tls_out.active = fd;
1715 /*************************************************
1716 * TLS version of getc *
1717 *************************************************/
1719 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1720 it refills the buffer via the SSL reading function.
1723 Returns: the next character or EOF
1725 Only used by the server-side TLS.
1731 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1736 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1737 ssl_xfer_buffer, ssl_xfer_buffer_size);
1739 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1740 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1741 error = SSL_get_error(server_ssl, inbytes);
1744 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1745 closed down, not that the socket itself has been closed down. Revert to
1746 non-SSL handling. */
1748 if (error == SSL_ERROR_ZERO_RETURN)
1750 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1752 receive_getc = smtp_getc;
1753 receive_ungetc = smtp_ungetc;
1754 receive_feof = smtp_feof;
1755 receive_ferror = smtp_ferror;
1756 receive_smtp_buffered = smtp_buffered;
1758 SSL_free(server_ssl);
1762 tls_in.cipher = NULL;
1763 tls_in.peerdn = NULL;
1769 /* Handle genuine errors */
1771 else if (error == SSL_ERROR_SSL)
1773 ERR_error_string(ERR_get_error(), ssl_errstring);
1774 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1779 else if (error != SSL_ERROR_NONE)
1781 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1786 #ifndef DISABLE_DKIM
1787 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1789 ssl_xfer_buffer_hwm = inbytes;
1790 ssl_xfer_buffer_lwm = 0;
1793 /* Something in the buffer; return next uschar */
1795 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1800 /*************************************************
1801 * Read bytes from TLS channel *
1802 *************************************************/
1809 Returns: the number of bytes read
1810 -1 after a failed read
1812 Only used by the client-side TLS.
1816 tls_read(BOOL is_server, uschar *buff, size_t len)
1818 SSL *ssl = is_server ? server_ssl : client_ssl;
1822 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1823 buff, (unsigned int)len);
1825 inbytes = SSL_read(ssl, CS buff, len);
1826 error = SSL_get_error(ssl, inbytes);
1828 if (error == SSL_ERROR_ZERO_RETURN)
1830 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1833 else if (error != SSL_ERROR_NONE)
1845 /*************************************************
1846 * Write bytes down TLS channel *
1847 *************************************************/
1851 is_server channel specifier
1855 Returns: the number of bytes after a successful write,
1856 -1 after a failed write
1858 Used by both server-side and client-side TLS.
1862 tls_write(BOOL is_server, const uschar *buff, size_t len)
1867 SSL *ssl = is_server ? server_ssl : client_ssl;
1869 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1872 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1873 outbytes = SSL_write(ssl, CS buff, left);
1874 error = SSL_get_error(ssl, outbytes);
1875 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1879 ERR_error_string(ERR_get_error(), ssl_errstring);
1880 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1883 case SSL_ERROR_NONE:
1888 case SSL_ERROR_ZERO_RETURN:
1889 log_write(0, LOG_MAIN, "SSL channel closed on write");
1892 case SSL_ERROR_SYSCALL:
1893 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1894 sender_fullhost ? sender_fullhost : US"<unknown>",
1898 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1907 /*************************************************
1908 * Close down a TLS session *
1909 *************************************************/
1911 /* This is also called from within a delivery subprocess forked from the
1912 daemon, to shut down the TLS library, without actually doing a shutdown (which
1913 would tamper with the SSL session in the parent process).
1915 Arguments: TRUE if SSL_shutdown is to be called
1918 Used by both server-side and client-side TLS.
1922 tls_close(BOOL is_server, BOOL shutdown)
1924 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1925 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1927 if (*fdp < 0) return; /* TLS was not active */
1931 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1932 SSL_shutdown(*sslp);
1944 /*************************************************
1945 * Let tls_require_ciphers be checked at startup *
1946 *************************************************/
1948 /* The tls_require_ciphers option, if set, must be something which the
1951 Returns: NULL on success, or error message
1955 tls_validate_require_cipher(void)
1958 uschar *s, *expciphers, *err;
1960 /* this duplicates from tls_init(), we need a better "init just global
1961 state, for no specific purpose" singleton function of our own */
1963 SSL_load_error_strings();
1964 OpenSSL_add_ssl_algorithms();
1965 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1966 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1967 list of available digests. */
1968 EVP_add_digest(EVP_sha256());
1971 if (!(tls_require_ciphers && *tls_require_ciphers))
1974 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1975 return US"failed to expand tls_require_ciphers";
1977 if (!(expciphers && *expciphers))
1980 /* normalisation ripped from above */
1982 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1986 ctx = SSL_CTX_new(SSLv23_server_method());
1989 ERR_error_string(ERR_get_error(), ssl_errstring);
1990 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1994 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1996 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1998 ERR_error_string(ERR_get_error(), ssl_errstring);
1999 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2010 /*************************************************
2011 * Report the library versions. *
2012 *************************************************/
2014 /* There have historically been some issues with binary compatibility in
2015 OpenSSL libraries; if Exim (like many other applications) is built against
2016 one version of OpenSSL but the run-time linker picks up another version,
2017 it can result in serious failures, including crashing with a SIGSEGV. So
2018 report the version found by the compiler and the run-time version.
2020 Note: some OS vendors backport security fixes without changing the version
2021 number/string, and the version date remains unchanged. The _build_ date
2022 will change, so we can more usefully assist with version diagnosis by also
2023 reporting the build date.
2025 Arguments: a FILE* to print the results to
2030 tls_version_report(FILE *f)
2032 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2035 OPENSSL_VERSION_TEXT,
2036 SSLeay_version(SSLEAY_VERSION),
2037 SSLeay_version(SSLEAY_BUILT_ON));
2038 /* third line is 38 characters for the %s and the line is 73 chars long;
2039 the OpenSSL output includes a "built on: " prefix already. */
2045 /*************************************************
2046 * Random number generation *
2047 *************************************************/
2049 /* Pseudo-random number generation. The result is not expected to be
2050 cryptographically strong but not so weak that someone will shoot themselves
2051 in the foot using it as a nonce in input in some email header scheme or
2052 whatever weirdness they'll twist this into. The result should handle fork()
2053 and avoid repeating sequences. OpenSSL handles that for us.
2057 Returns a random number in range [0, max-1]
2061 vaguely_random_number(int max)
2065 static pid_t pidlast = 0;
2068 uschar smallbuf[sizeof(r)];
2074 if (pidnow != pidlast)
2076 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2077 is unique for each thread", this doesn't apparently apply across processes,
2078 so our own warning from vaguely_random_number_fallback() applies here too.
2079 Fix per PostgreSQL. */
2085 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2089 gettimeofday(&r.tv, NULL);
2092 RAND_seed((uschar *)(&r), sizeof(r));
2094 /* We're after pseudo-random, not random; if we still don't have enough data
2095 in the internal PRNG then our options are limited. We could sleep and hope
2096 for entropy to come along (prayer technique) but if the system is so depleted
2097 in the first place then something is likely to just keep taking it. Instead,
2098 we'll just take whatever little bit of pseudo-random we can still manage to
2101 needed_len = sizeof(r);
2102 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2103 asked for a number less than 10. */
2104 for (r = max, i = 0; r; ++i)
2110 /* We do not care if crypto-strong */
2111 i = RAND_pseudo_bytes(smallbuf, needed_len);
2115 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2116 return vaguely_random_number_fallback(max);
2120 for (p = smallbuf; needed_len; --needed_len, ++p)
2126 /* We don't particularly care about weighted results; if someone wants
2127 smooth distribution and cares enough then they should submit a patch then. */
2134 /*************************************************
2135 * OpenSSL option parse *
2136 *************************************************/
2138 /* Parse one option for tls_openssl_options_parse below
2141 name one option name
2142 value place to store a value for it
2143 Returns success or failure in parsing
2146 struct exim_openssl_option {
2150 /* We could use a macro to expand, but we need the ifdef and not all the
2151 options document which version they were introduced in. Policylet: include
2152 all options unless explicitly for DTLS, let the administrator choose which
2155 This list is current as of:
2157 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2159 static struct exim_openssl_option exim_openssl_options[] = {
2160 /* KEEP SORTED ALPHABETICALLY! */
2162 { US"all", SSL_OP_ALL },
2164 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2165 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2167 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2168 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2170 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2171 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2173 #ifdef SSL_OP_EPHEMERAL_RSA
2174 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2176 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2177 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2179 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2180 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2182 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2183 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2185 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2186 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2188 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2189 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2191 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2192 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2194 #ifdef SSL_OP_NO_COMPRESSION
2195 { US"no_compression", SSL_OP_NO_COMPRESSION },
2197 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2198 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2200 #ifdef SSL_OP_NO_SSLv2
2201 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2203 #ifdef SSL_OP_NO_SSLv3
2204 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2206 #ifdef SSL_OP_NO_TICKET
2207 { US"no_ticket", SSL_OP_NO_TICKET },
2209 #ifdef SSL_OP_NO_TLSv1
2210 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2212 #ifdef SSL_OP_NO_TLSv1_1
2213 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2214 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2215 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2217 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2220 #ifdef SSL_OP_NO_TLSv1_2
2221 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2223 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2224 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2226 #ifdef SSL_OP_SINGLE_DH_USE
2227 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2229 #ifdef SSL_OP_SINGLE_ECDH_USE
2230 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2232 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2233 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2235 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2236 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2238 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2239 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2241 #ifdef SSL_OP_TLS_D5_BUG
2242 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2244 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2245 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2248 static int exim_openssl_options_size =
2249 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2253 tls_openssl_one_option_parse(uschar *name, long *value)
2256 int last = exim_openssl_options_size;
2257 while (last > first)
2259 int middle = (first + last)/2;
2260 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2263 *value = exim_openssl_options[middle].value;
2277 /*************************************************
2278 * OpenSSL option parsing logic *
2279 *************************************************/
2281 /* OpenSSL has a number of compatibility options which an administrator might
2282 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
2283 we look like log_selector.
2286 option_spec the administrator-supplied string of options
2287 results ptr to long storage for the options bitmap
2288 Returns success or failure
2292 tls_openssl_options_parse(uschar *option_spec, long *results)
2297 BOOL adding, item_parsed;
2300 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2301 * from default because it increases BEAST susceptibility. */
2302 #ifdef SSL_OP_NO_SSLv2
2303 result |= SSL_OP_NO_SSLv2;
2306 if (option_spec == NULL)
2312 for (s=option_spec; *s != '\0'; /**/)
2314 while (isspace(*s)) ++s;
2317 if (*s != '+' && *s != '-')
2319 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2320 "+ or - expected but found \"%s\"\n", s);
2323 adding = *s++ == '+';
2324 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2327 item_parsed = tls_openssl_one_option_parse(s, &item);
2330 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2333 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2334 adding ? "adding" : "removing", result, item, s);
2349 /* End of tls-openssl.c */