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 cert 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 cert 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 if (log_extra_selector & LX_tls_cipher)
932 log_write(0, LOG_MAIN, "Received TLS cert status response, itself unverifiable");
933 BIO_printf(bp, "OCSP response verify failure\n");
934 ERR_print_errors(bp);
935 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
939 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
942 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
943 OCSP_SINGLERESP * single;
945 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
947 tls_out.ocsp = OCSP_FAILED;
948 log_write(0, LOG_MAIN, "OCSP stapling "
949 "with multiple responses not handled");
950 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
953 single = OCSP_resp_get0(bs, 0);
954 status = OCSP_single_get0_status(single, &reason, &rev,
958 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
959 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
960 if (!OCSP_check_validity(thisupd, nextupd,
961 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
963 tls_out.ocsp = OCSP_FAILED;
964 DEBUG(D_tls) ERR_print_errors(bp);
965 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
966 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
970 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
971 OCSP_cert_status_str(status));
974 case V_OCSP_CERTSTATUS_GOOD:
975 tls_out.ocsp = OCSP_VFIED;
978 case V_OCSP_CERTSTATUS_REVOKED:
979 tls_out.ocsp = OCSP_FAILED;
980 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
981 reason != -1 ? "; reason: " : "",
982 reason != -1 ? OCSP_crl_reason_str(reason) : "");
983 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
984 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
987 tls_out.ocsp = OCSP_FAILED;
988 log_write(0, LOG_MAIN,
989 "Server certificate status unknown, in OCSP stapling");
990 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
998 OCSP_RESPONSE_free(rsp);
1001 #endif /*!DISABLE_OCSP*/
1005 /*************************************************
1006 * Initialize for TLS *
1007 *************************************************/
1009 /* Called from both server and client code, to do preliminary initialization
1010 of the library. We allocate and return a context structure.
1013 host connected host, if client; NULL if server
1014 dhparam DH parameter file
1015 certificate certificate file
1016 privatekey private key
1017 ocsp_file file of stapling info (server); flag for require ocsp (client)
1018 addr address if client; NULL if server (for some randomness)
1019 cbp place to put allocated context
1021 Returns: OK/DEFER/FAIL
1025 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1027 #ifndef DISABLE_OCSP
1030 address_item *addr, tls_ext_ctx_cb ** cbp)
1035 tls_ext_ctx_cb *cbinfo;
1037 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1038 cbinfo->certificate = certificate;
1039 cbinfo->privatekey = privatekey;
1040 #ifndef DISABLE_OCSP
1041 if ((cbinfo->is_server = host==NULL))
1043 cbinfo->u_ocsp.server.file = ocsp_file;
1044 cbinfo->u_ocsp.server.file_expanded = NULL;
1045 cbinfo->u_ocsp.server.response = NULL;
1048 cbinfo->u_ocsp.client.verify_store = NULL;
1050 cbinfo->dhparam = dhparam;
1051 cbinfo->server_cipher_list = NULL;
1052 cbinfo->host = host;
1054 SSL_load_error_strings(); /* basic set up */
1055 OpenSSL_add_ssl_algorithms();
1057 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1058 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1059 list of available digests. */
1060 EVP_add_digest(EVP_sha256());
1063 /* Create a context.
1064 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1065 negotiation in the different methods; as far as I can tell, the only
1066 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1067 when OpenSSL is built without SSLv2 support.
1068 By disabling with openssl_options, we can let admins re-enable with the
1071 *ctxp = SSL_CTX_new((host == NULL)?
1072 SSLv23_server_method() : SSLv23_client_method());
1074 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
1076 /* It turns out that we need to seed the random number generator this early in
1077 order to get the full complement of ciphers to work. It took me roughly a day
1078 of work to discover this by experiment.
1080 On systems that have /dev/urandom, SSL may automatically seed itself from
1081 there. Otherwise, we have to make something up as best we can. Double check
1087 gettimeofday(&r.tv, NULL);
1090 RAND_seed((uschar *)(&r), sizeof(r));
1091 RAND_seed((uschar *)big_buffer, big_buffer_size);
1092 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1095 return tls_error(US"RAND_status", host,
1096 US"unable to seed random number generator");
1099 /* Set up the information callback, which outputs if debugging is at a suitable
1102 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1104 /* Automatically re-try reads/writes after renegotiation. */
1105 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1107 /* Apply administrator-supplied work-arounds.
1108 Historically we applied just one requested option,
1109 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1110 moved to an administrator-controlled list of options to specify and
1111 grandfathered in the first one as the default value for "openssl_options".
1113 No OpenSSL version number checks: the options we accept depend upon the
1114 availability of the option value macros from OpenSSL. */
1116 okay = tls_openssl_options_parse(openssl_options, &init_options);
1118 return tls_error(US"openssl_options parsing failed", host, NULL);
1122 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1123 if (!(SSL_CTX_set_options(*ctxp, init_options)))
1124 return tls_error(string_sprintf(
1125 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1128 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1130 /* Initialize with DH parameters if supplied */
1132 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
1134 /* Set up certificate and key (and perhaps OCSP info) */
1136 rc = tls_expand_session_files(*ctxp, cbinfo);
1137 if (rc != OK) return rc;
1139 /* If we need to handle SNI, do so */
1140 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1141 if (host == NULL) /* server */
1143 # ifndef DISABLE_OCSP
1144 /* We check u_ocsp.server.file, not server.response, because we care about if
1145 the option exists, not what the current expansion might be, as SNI might
1146 change the certificate and OCSP file in use between now and the time the
1147 callback is invoked. */
1148 if (cbinfo->u_ocsp.server.file)
1150 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1151 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1154 /* We always do this, so that $tls_sni is available even if not used in
1156 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1157 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1159 # ifndef DISABLE_OCSP
1161 if(ocsp_file) /* wanting stapling */
1163 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1165 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1168 SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1169 SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1174 #ifdef EXPERIMENTAL_CERTNAMES
1175 cbinfo->verify_cert_hostnames = NULL;
1178 /* Set up the RSA callback */
1180 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1182 /* Finally, set the timeout, and we are done */
1184 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1185 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1195 /*************************************************
1196 * Get name of cipher in use *
1197 *************************************************/
1200 Argument: pointer to an SSL structure for the connection
1201 buffer to use for answer
1203 pointer to number of bits for cipher
1208 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1210 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1211 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1212 the accessor functions use const in the prototype. */
1213 const SSL_CIPHER *c;
1216 ver = (const uschar *)SSL_get_version(ssl);
1218 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1219 SSL_CIPHER_get_bits(c, bits);
1221 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1222 SSL_CIPHER_get_name(c), *bits);
1224 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1231 /*************************************************
1232 * Set up for verifying certificates *
1233 *************************************************/
1235 /* Called by both client and server startup
1238 sctx SSL_CTX* to initialise
1239 certs certs file or NULL
1240 crl CRL file or NULL
1241 host NULL in a server; the remote host in a client
1242 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1243 otherwise passed as FALSE
1244 cert_vfy_cb Callback function for certificate verification
1246 Returns: OK/DEFER/FAIL
1250 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1251 int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1253 uschar *expcerts, *expcrl;
1255 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1258 if (expcerts != NULL && *expcerts != '\0')
1260 struct stat statbuf;
1261 if (!SSL_CTX_set_default_verify_paths(sctx))
1262 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1264 if (Ustat(expcerts, &statbuf) < 0)
1266 log_write(0, LOG_MAIN|LOG_PANIC,
1267 "failed to stat %s for certificates", expcerts);
1273 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1274 { file = NULL; dir = expcerts; }
1276 { file = expcerts; dir = NULL; }
1278 /* If a certificate file is empty, the next function fails with an
1279 unhelpful error message. If we skip it, we get the correct behaviour (no
1280 certificates are recognized, but the error message is still misleading (it
1281 says no certificate was supplied.) But this is better. */
1283 if ((file == NULL || statbuf.st_size > 0) &&
1284 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1285 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1289 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1293 /* Handle a certificate revocation list. */
1295 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1297 /* This bit of code is now the version supplied by Lars Mainka. (I have
1298 * merely reformatted it into the Exim code style.)
1300 * "From here I changed the code to add support for multiple crl's
1301 * in pem format in one file or to support hashed directory entries in
1302 * pem format instead of a file. This method now uses the library function
1303 * X509_STORE_load_locations to add the CRL location to the SSL context.
1304 * OpenSSL will then handle the verify against CA certs and CRLs by
1305 * itself in the verify callback." */
1307 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1308 if (expcrl != NULL && *expcrl != 0)
1310 struct stat statbufcrl;
1311 if (Ustat(expcrl, &statbufcrl) < 0)
1313 log_write(0, LOG_MAIN|LOG_PANIC,
1314 "failed to stat %s for certificates revocation lists", expcrl);
1319 /* is it a file or directory? */
1321 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1322 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1326 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1332 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1334 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1335 return tls_error(US"X509_STORE_load_locations", host, NULL);
1337 /* setting the flags to check against the complete crl chain */
1339 X509_STORE_set_flags(cvstore,
1340 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1344 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1346 /* If verification is optional, don't fail if no certificate */
1348 SSL_CTX_set_verify(sctx,
1349 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1358 /*************************************************
1359 * Start a TLS session in a server *
1360 *************************************************/
1362 /* This is called when Exim is running as a server, after having received
1363 the STARTTLS command. It must respond to that command, and then negotiate
1367 require_ciphers allowed ciphers
1369 Returns: OK on success
1370 DEFER for errors before the start of the negotiation
1371 FAIL for errors during the negotation; the server can't
1376 tls_server_start(const uschar *require_ciphers)
1380 tls_ext_ctx_cb *cbinfo;
1381 static uschar cipherbuf[256];
1383 /* Check for previous activation */
1385 if (tls_in.active >= 0)
1387 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1388 smtp_printf("554 Already in TLS\r\n");
1392 /* Initialize the SSL library. If it fails, it will already have logged
1395 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1396 #ifndef DISABLE_OCSP
1399 NULL, &server_static_cbinfo);
1400 if (rc != OK) return rc;
1401 cbinfo = server_static_cbinfo;
1403 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1406 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1407 were historically separated by underscores. So that I can use either form in my
1408 tests, and also for general convenience, we turn underscores into hyphens here.
1411 if (expciphers != NULL)
1413 uschar *s = expciphers;
1414 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1415 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1416 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1417 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1418 cbinfo->server_cipher_list = expciphers;
1421 /* If this is a host for which certificate verification is mandatory or
1422 optional, set up appropriately. */
1424 tls_in.certificate_verified = FALSE;
1425 server_verify_callback_called = FALSE;
1427 if (verify_check_host(&tls_verify_hosts) == OK)
1429 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1430 FALSE, verify_callback_server);
1431 if (rc != OK) return rc;
1432 server_verify_optional = FALSE;
1434 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1436 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1437 TRUE, verify_callback_server);
1438 if (rc != OK) return rc;
1439 server_verify_optional = TRUE;
1442 /* Prepare for new connection */
1444 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1446 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1448 * With the SSL_clear(), we get strange interoperability bugs with
1449 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1450 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1452 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1453 * session shutdown. In this case, we have a brand new object and there's no
1454 * obvious reason to immediately clear it. I'm guessing that this was
1455 * originally added because of incomplete initialisation which the clear fixed,
1456 * in some historic release.
1459 /* Set context and tell client to go ahead, except in the case of TLS startup
1460 on connection, where outputting anything now upsets the clients and tends to
1461 make them disconnect. We need to have an explicit fflush() here, to force out
1462 the response. Other smtp_printf() calls do not need it, because in non-TLS
1463 mode, the fflush() happens when smtp_getc() is called. */
1465 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1466 if (!tls_in.on_connect)
1468 smtp_printf("220 TLS go ahead\r\n");
1472 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1473 that the OpenSSL library doesn't. */
1475 SSL_set_wfd(server_ssl, fileno(smtp_out));
1476 SSL_set_rfd(server_ssl, fileno(smtp_in));
1477 SSL_set_accept_state(server_ssl);
1479 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1481 sigalrm_seen = FALSE;
1482 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1483 rc = SSL_accept(server_ssl);
1488 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1489 if (ERR_get_error() == 0)
1490 log_write(0, LOG_MAIN,
1491 "TLS client disconnected cleanly (rejected our certificate?)");
1495 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1497 /* TLS has been set up. Adjust the input functions to read via TLS,
1498 and initialize things. */
1500 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1501 tls_in.cipher = cipherbuf;
1506 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1507 debug_printf("Shared ciphers: %s\n", buf);
1510 /* Record the certificate we presented */
1512 X509 * crt = SSL_get_certificate(server_ssl);
1513 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1516 /* Only used by the server-side tls (tls_in), including tls_getc.
1517 Client-side (tls_out) reads (seem to?) go via
1518 smtp_read_response()/ip_recv().
1519 Hence no need to duplicate for _in and _out.
1521 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1522 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1523 ssl_xfer_eof = ssl_xfer_error = 0;
1525 receive_getc = tls_getc;
1526 receive_ungetc = tls_ungetc;
1527 receive_feof = tls_feof;
1528 receive_ferror = tls_ferror;
1529 receive_smtp_buffered = tls_smtp_buffered;
1531 tls_in.active = fileno(smtp_out);
1539 /*************************************************
1540 * Start a TLS session in a client *
1541 *************************************************/
1543 /* Called from the smtp transport after STARTTLS has been accepted.
1546 fd the fd of the connection
1547 host connected host (for messages)
1548 addr the first address
1549 ob smtp transport options
1551 Returns: OK on success
1552 FAIL otherwise - note that tls_error() will not give DEFER
1553 because this is not a server
1557 tls_client_start(int fd, host_item *host, address_item *addr,
1560 smtp_transport_options_block * ob = v_ob;
1561 static uschar txt[256];
1565 static uschar cipherbuf[256];
1566 #ifndef DISABLE_OCSP
1567 BOOL require_ocsp = verify_check_this_host(&ob->hosts_require_ocsp,
1568 NULL, host->name, host->address, NULL) == OK;
1569 BOOL request_ocsp = require_ocsp ? TRUE
1570 : verify_check_this_host(&ob->hosts_request_ocsp,
1571 NULL, host->name, host->address, NULL) == OK;
1574 rc = tls_init(&client_ctx, host, NULL,
1575 ob->tls_certificate, ob->tls_privatekey,
1576 #ifndef DISABLE_OCSP
1577 (void *)(long)request_ocsp,
1579 addr, &client_static_cbinfo);
1580 if (rc != OK) return rc;
1582 tls_out.certificate_verified = FALSE;
1583 client_verify_callback_called = FALSE;
1585 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
1589 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1590 are separated by underscores. So that I can use either form in my tests, and
1591 also for general convenience, we turn underscores into hyphens here. */
1593 if (expciphers != NULL)
1595 uschar *s = expciphers;
1596 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1597 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1598 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1599 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1602 /* stick to the old behaviour for compatibility if tls_verify_certificates is
1603 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
1604 the specified host patterns if one of them is defined */
1606 if ((!ob->tls_verify_hosts && !ob->tls_try_verify_hosts) ||
1607 (verify_check_host(&ob->tls_verify_hosts) == OK))
1609 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1610 ob->tls_crl, host, FALSE, verify_callback_client)) != OK)
1612 client_verify_optional = FALSE;
1614 #ifdef EXPERIMENTAL_CERTNAMES
1615 if (ob->tls_verify_cert_hostnames)
1617 if (!expand_check(ob->tls_verify_cert_hostnames,
1618 US"tls_verify_cert_hostnames",
1619 &client_static_cbinfo->verify_cert_hostnames))
1621 if (client_static_cbinfo->verify_cert_hostnames)
1622 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
1623 client_static_cbinfo->verify_cert_hostnames);
1627 else if (verify_check_host(&ob->tls_try_verify_hosts) == OK)
1629 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1630 ob->tls_crl, host, TRUE, verify_callback_client)) != OK)
1632 client_verify_optional = TRUE;
1635 if ((client_ssl = SSL_new(client_ctx)) == NULL)
1636 return tls_error(US"SSL_new", host, NULL);
1637 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1638 SSL_set_fd(client_ssl, fd);
1639 SSL_set_connect_state(client_ssl);
1643 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
1645 if (tls_out.sni == NULL)
1647 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1649 else if (!Ustrlen(tls_out.sni))
1653 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1654 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1655 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1658 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1664 #ifndef DISABLE_OCSP
1665 /* Request certificate status at connection-time. If the server
1666 does OCSP stapling we will get the callback (set in tls_init()) */
1669 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
1670 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
1671 tls_out.ocsp = OCSP_NOT_RESP;
1675 /* There doesn't seem to be a built-in timeout on connection. */
1677 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1678 sigalrm_seen = FALSE;
1679 alarm(ob->command_timeout);
1680 rc = SSL_connect(client_ssl);
1684 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1686 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1688 /* Beware anonymous ciphers which lead to server_cert being NULL */
1689 /*XXX server_cert is never freed... use X509_free() */
1690 server_cert = SSL_get_peer_certificate (client_ssl);
1693 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1694 CS txt, sizeof(txt));
1695 tls_out.peerdn = txt; /*XXX a static buffer... */
1698 tls_out.peerdn = NULL;
1700 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1701 tls_out.cipher = cipherbuf;
1703 /* Record the certificate we presented */
1705 X509 * crt = SSL_get_certificate(client_ssl);
1706 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
1709 tls_out.active = fd;
1717 /*************************************************
1718 * TLS version of getc *
1719 *************************************************/
1721 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1722 it refills the buffer via the SSL reading function.
1725 Returns: the next character or EOF
1727 Only used by the server-side TLS.
1733 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1738 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1739 ssl_xfer_buffer, ssl_xfer_buffer_size);
1741 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1742 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1743 error = SSL_get_error(server_ssl, inbytes);
1746 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1747 closed down, not that the socket itself has been closed down. Revert to
1748 non-SSL handling. */
1750 if (error == SSL_ERROR_ZERO_RETURN)
1752 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1754 receive_getc = smtp_getc;
1755 receive_ungetc = smtp_ungetc;
1756 receive_feof = smtp_feof;
1757 receive_ferror = smtp_ferror;
1758 receive_smtp_buffered = smtp_buffered;
1760 SSL_free(server_ssl);
1764 tls_in.cipher = NULL;
1765 tls_in.peerdn = NULL;
1771 /* Handle genuine errors */
1773 else if (error == SSL_ERROR_SSL)
1775 ERR_error_string(ERR_get_error(), ssl_errstring);
1776 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1781 else if (error != SSL_ERROR_NONE)
1783 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1788 #ifndef DISABLE_DKIM
1789 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1791 ssl_xfer_buffer_hwm = inbytes;
1792 ssl_xfer_buffer_lwm = 0;
1795 /* Something in the buffer; return next uschar */
1797 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1802 /*************************************************
1803 * Read bytes from TLS channel *
1804 *************************************************/
1811 Returns: the number of bytes read
1812 -1 after a failed read
1814 Only used by the client-side TLS.
1818 tls_read(BOOL is_server, uschar *buff, size_t len)
1820 SSL *ssl = is_server ? server_ssl : client_ssl;
1824 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1825 buff, (unsigned int)len);
1827 inbytes = SSL_read(ssl, CS buff, len);
1828 error = SSL_get_error(ssl, inbytes);
1830 if (error == SSL_ERROR_ZERO_RETURN)
1832 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1835 else if (error != SSL_ERROR_NONE)
1847 /*************************************************
1848 * Write bytes down TLS channel *
1849 *************************************************/
1853 is_server channel specifier
1857 Returns: the number of bytes after a successful write,
1858 -1 after a failed write
1860 Used by both server-side and client-side TLS.
1864 tls_write(BOOL is_server, const uschar *buff, size_t len)
1869 SSL *ssl = is_server ? server_ssl : client_ssl;
1871 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1874 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1875 outbytes = SSL_write(ssl, CS buff, left);
1876 error = SSL_get_error(ssl, outbytes);
1877 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1881 ERR_error_string(ERR_get_error(), ssl_errstring);
1882 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1885 case SSL_ERROR_NONE:
1890 case SSL_ERROR_ZERO_RETURN:
1891 log_write(0, LOG_MAIN, "SSL channel closed on write");
1894 case SSL_ERROR_SYSCALL:
1895 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1896 sender_fullhost ? sender_fullhost : US"<unknown>",
1900 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1909 /*************************************************
1910 * Close down a TLS session *
1911 *************************************************/
1913 /* This is also called from within a delivery subprocess forked from the
1914 daemon, to shut down the TLS library, without actually doing a shutdown (which
1915 would tamper with the SSL session in the parent process).
1917 Arguments: TRUE if SSL_shutdown is to be called
1920 Used by both server-side and client-side TLS.
1924 tls_close(BOOL is_server, BOOL shutdown)
1926 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1927 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1929 if (*fdp < 0) return; /* TLS was not active */
1933 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1934 SSL_shutdown(*sslp);
1946 /*************************************************
1947 * Let tls_require_ciphers be checked at startup *
1948 *************************************************/
1950 /* The tls_require_ciphers option, if set, must be something which the
1953 Returns: NULL on success, or error message
1957 tls_validate_require_cipher(void)
1960 uschar *s, *expciphers, *err;
1962 /* this duplicates from tls_init(), we need a better "init just global
1963 state, for no specific purpose" singleton function of our own */
1965 SSL_load_error_strings();
1966 OpenSSL_add_ssl_algorithms();
1967 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1968 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1969 list of available digests. */
1970 EVP_add_digest(EVP_sha256());
1973 if (!(tls_require_ciphers && *tls_require_ciphers))
1976 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1977 return US"failed to expand tls_require_ciphers";
1979 if (!(expciphers && *expciphers))
1982 /* normalisation ripped from above */
1984 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1988 ctx = SSL_CTX_new(SSLv23_server_method());
1991 ERR_error_string(ERR_get_error(), ssl_errstring);
1992 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1996 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1998 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
2000 ERR_error_string(ERR_get_error(), ssl_errstring);
2001 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
2012 /*************************************************
2013 * Report the library versions. *
2014 *************************************************/
2016 /* There have historically been some issues with binary compatibility in
2017 OpenSSL libraries; if Exim (like many other applications) is built against
2018 one version of OpenSSL but the run-time linker picks up another version,
2019 it can result in serious failures, including crashing with a SIGSEGV. So
2020 report the version found by the compiler and the run-time version.
2022 Note: some OS vendors backport security fixes without changing the version
2023 number/string, and the version date remains unchanged. The _build_ date
2024 will change, so we can more usefully assist with version diagnosis by also
2025 reporting the build date.
2027 Arguments: a FILE* to print the results to
2032 tls_version_report(FILE *f)
2034 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2037 OPENSSL_VERSION_TEXT,
2038 SSLeay_version(SSLEAY_VERSION),
2039 SSLeay_version(SSLEAY_BUILT_ON));
2040 /* third line is 38 characters for the %s and the line is 73 chars long;
2041 the OpenSSL output includes a "built on: " prefix already. */
2047 /*************************************************
2048 * Random number generation *
2049 *************************************************/
2051 /* Pseudo-random number generation. The result is not expected to be
2052 cryptographically strong but not so weak that someone will shoot themselves
2053 in the foot using it as a nonce in input in some email header scheme or
2054 whatever weirdness they'll twist this into. The result should handle fork()
2055 and avoid repeating sequences. OpenSSL handles that for us.
2059 Returns a random number in range [0, max-1]
2063 vaguely_random_number(int max)
2067 static pid_t pidlast = 0;
2070 uschar smallbuf[sizeof(r)];
2076 if (pidnow != pidlast)
2078 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2079 is unique for each thread", this doesn't apparently apply across processes,
2080 so our own warning from vaguely_random_number_fallback() applies here too.
2081 Fix per PostgreSQL. */
2087 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2091 gettimeofday(&r.tv, NULL);
2094 RAND_seed((uschar *)(&r), sizeof(r));
2096 /* We're after pseudo-random, not random; if we still don't have enough data
2097 in the internal PRNG then our options are limited. We could sleep and hope
2098 for entropy to come along (prayer technique) but if the system is so depleted
2099 in the first place then something is likely to just keep taking it. Instead,
2100 we'll just take whatever little bit of pseudo-random we can still manage to
2103 needed_len = sizeof(r);
2104 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2105 asked for a number less than 10. */
2106 for (r = max, i = 0; r; ++i)
2112 /* We do not care if crypto-strong */
2113 i = RAND_pseudo_bytes(smallbuf, needed_len);
2117 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2118 return vaguely_random_number_fallback(max);
2122 for (p = smallbuf; needed_len; --needed_len, ++p)
2128 /* We don't particularly care about weighted results; if someone wants
2129 smooth distribution and cares enough then they should submit a patch then. */
2136 /*************************************************
2137 * OpenSSL option parse *
2138 *************************************************/
2140 /* Parse one option for tls_openssl_options_parse below
2143 name one option name
2144 value place to store a value for it
2145 Returns success or failure in parsing
2148 struct exim_openssl_option {
2152 /* We could use a macro to expand, but we need the ifdef and not all the
2153 options document which version they were introduced in. Policylet: include
2154 all options unless explicitly for DTLS, let the administrator choose which
2157 This list is current as of:
2159 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2161 static struct exim_openssl_option exim_openssl_options[] = {
2162 /* KEEP SORTED ALPHABETICALLY! */
2164 { US"all", SSL_OP_ALL },
2166 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2167 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2169 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2170 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2172 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2173 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2175 #ifdef SSL_OP_EPHEMERAL_RSA
2176 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2178 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2179 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2181 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2182 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2184 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2185 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2187 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2188 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2190 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2191 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2193 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2194 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2196 #ifdef SSL_OP_NO_COMPRESSION
2197 { US"no_compression", SSL_OP_NO_COMPRESSION },
2199 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2200 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2202 #ifdef SSL_OP_NO_SSLv2
2203 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2205 #ifdef SSL_OP_NO_SSLv3
2206 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2208 #ifdef SSL_OP_NO_TICKET
2209 { US"no_ticket", SSL_OP_NO_TICKET },
2211 #ifdef SSL_OP_NO_TLSv1
2212 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2214 #ifdef SSL_OP_NO_TLSv1_1
2215 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2216 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2217 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2219 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2222 #ifdef SSL_OP_NO_TLSv1_2
2223 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2225 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2226 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2228 #ifdef SSL_OP_SINGLE_DH_USE
2229 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2231 #ifdef SSL_OP_SINGLE_ECDH_USE
2232 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2234 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2235 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2237 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2238 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2240 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2241 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2243 #ifdef SSL_OP_TLS_D5_BUG
2244 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2246 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2247 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2250 static int exim_openssl_options_size =
2251 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2255 tls_openssl_one_option_parse(uschar *name, long *value)
2258 int last = exim_openssl_options_size;
2259 while (last > first)
2261 int middle = (first + last)/2;
2262 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2265 *value = exim_openssl_options[middle].value;
2279 /*************************************************
2280 * OpenSSL option parsing logic *
2281 *************************************************/
2283 /* OpenSSL has a number of compatibility options which an administrator might
2284 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
2285 we look like log_selector.
2288 option_spec the administrator-supplied string of options
2289 results ptr to long storage for the options bitmap
2290 Returns success or failure
2294 tls_openssl_options_parse(uschar *option_spec, long *results)
2299 BOOL adding, item_parsed;
2302 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2303 * from default because it increases BEAST susceptibility. */
2304 #ifdef SSL_OP_NO_SSLv2
2305 result |= SSL_OP_NO_SSLv2;
2308 if (option_spec == NULL)
2314 for (s=option_spec; *s != '\0'; /**/)
2316 while (isspace(*s)) ++s;
2319 if (*s != '+' && *s != '-')
2321 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2322 "+ or - expected but found \"%s\"\n", s);
2325 adding = *s++ == '+';
2326 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2329 item_parsed = tls_openssl_one_option_parse(s, &item);
2332 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2335 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2336 adding ? "adding" : "removing", result, item, s);
2351 /* End of tls-openssl.c */