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 /* Structure for collecting random data for seeding. */
40 typedef struct randstuff {
45 /* Local static variables */
47 static BOOL client_verify_callback_called = FALSE;
48 static BOOL server_verify_callback_called = FALSE;
49 static const uschar *sid_ctx = US"exim";
51 /* We have three different contexts to care about.
53 Simple case: client, `client_ctx`
54 As a client, we can be doing a callout or cut-through delivery while receiving
55 a message. So we have a client context, which should have options initialised
56 from the SMTP Transport.
59 There are two cases: with and without ServerNameIndication from the client.
60 Given TLS SNI, we can be using different keys, certs and various other
61 configuration settings, because they're re-expanded with $tls_sni set. This
62 allows vhosting with TLS. This SNI is sent in the handshake.
63 A client might not send SNI, so we need a fallback, and an initial setup too.
64 So as a server, we start out using `server_ctx`.
65 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
66 `server_sni` from `server_ctx` and then initialise settings by re-expanding
70 static SSL_CTX *client_ctx = NULL;
71 static SSL_CTX *server_ctx = NULL;
72 static SSL *client_ssl = NULL;
73 static SSL *server_ssl = NULL;
75 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
76 static SSL_CTX *server_sni = NULL;
79 static char ssl_errstring[256];
81 static int ssl_session_timeout = 200;
82 static BOOL client_verify_optional = FALSE;
83 static BOOL server_verify_optional = FALSE;
85 static BOOL reexpand_tls_files_for_sni = FALSE;
88 typedef struct tls_ext_ctx_cb {
96 uschar *file_expanded;
97 OCSP_RESPONSE *response;
100 X509_STORE *verify_store; /* non-null if status requested */
101 BOOL verify_required;
106 /* these are cached from first expand */
107 uschar *server_cipher_list;
108 /* only passed down to tls_error: */
111 #ifdef EXPERIMENTAL_CERTNAMES
112 uschar * verify_cert_hostnames;
116 /* should figure out a cleanup of API to handle state preserved per
117 implementation, for various reasons, which can be void * in the APIs.
118 For now, we hack around it. */
119 tls_ext_ctx_cb *client_static_cbinfo = NULL;
120 tls_ext_ctx_cb *server_static_cbinfo = NULL;
123 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
124 int (*cert_vfy_cb)(int, X509_STORE_CTX *) );
127 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
128 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
131 static int tls_server_stapling_cb(SSL *s, void *arg);
135 /*************************************************
137 *************************************************/
139 /* Called from lots of places when errors occur before actually starting to do
140 the TLS handshake, that is, while the session is still in clear. Always returns
141 DEFER for a server and FAIL for a client so that most calls can use "return
142 tls_error(...)" to do this processing and then give an appropriate return. A
143 single function is used for both server and client, because it is called from
144 some shared functions.
147 prefix text to include in the logged error
148 host NULL if setting up a server;
149 the connected host if setting up a client
150 msg error message or NULL if we should ask OpenSSL
152 Returns: OK/DEFER/FAIL
156 tls_error(uschar *prefix, host_item *host, uschar *msg)
160 ERR_error_string(ERR_get_error(), ssl_errstring);
161 msg = (uschar *)ssl_errstring;
166 uschar *conn_info = smtp_get_connection_info();
167 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
169 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
170 conn_info, prefix, msg);
175 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
176 host->name, host->address, prefix, msg);
183 /*************************************************
184 * Callback to generate RSA key *
185 *************************************************/
193 Returns: pointer to generated key
197 rsa_callback(SSL *s, int export, int keylength)
200 export = export; /* Shut picky compilers up */
201 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
202 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
205 ERR_error_string(ERR_get_error(), ssl_errstring);
206 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
218 x509_store_dump_cert_s_names(X509_STORE * store)
220 STACK_OF(X509_OBJECT) * roots= store->objs;
222 static uschar name[256];
224 for(i= 0; i<sk_X509_OBJECT_num(roots); i++)
226 X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i);
227 if(tmp_obj->type == X509_LU_X509)
229 X509 * current_cert= tmp_obj->data.x509;
230 X509_NAME_oneline(X509_get_subject_name(current_cert), CS name, sizeof(name));
231 debug_printf(" %s\n", name);
239 /*************************************************
240 * Callback for verification *
241 *************************************************/
243 /* The SSL library does certificate verification if set up to do so. This
244 callback has the current yes/no state is in "state". If verification succeeded,
245 we set up the tls_peerdn string. If verification failed, what happens depends
246 on whether the client is required to present a verifiable certificate or not.
248 If verification is optional, we change the state to yes, but still log the
249 verification error. For some reason (it really would help to have proper
250 documentation of OpenSSL), this callback function then gets called again, this
251 time with state = 1. In fact, that's useful, because we can set up the peerdn
252 value, but we must take care not to set the private verified flag on the second
255 Note: this function is not called if the client fails to present a certificate
256 when asked. We get here only if a certificate has been received. Handling of
257 optional verification for this case is done when requesting SSL to verify, by
258 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
261 state current yes/no state as 1/0
262 x509ctx certificate information.
263 client TRUE for client startup, FALSE for server startup
265 Returns: 1 if verified, 0 if not
269 verify_callback(int state, X509_STORE_CTX *x509ctx,
270 tls_support *tlsp, BOOL *calledp, BOOL *optionalp)
272 X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx);
273 static uschar txt[256];
275 X509_NAME_oneline(X509_get_subject_name(cert), CS txt, sizeof(txt));
279 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
280 X509_STORE_CTX_get_error_depth(x509ctx),
281 X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)),
283 tlsp->certificate_verified = FALSE;
287 tlsp->peercert = X509_dup(cert);
288 return 0; /* reject */
290 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
291 "tls_try_verify_hosts)\n");
294 else if (X509_STORE_CTX_get_error_depth(x509ctx) != 0)
296 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n",
297 X509_STORE_CTX_get_error_depth(x509ctx), txt);
299 if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store)
300 { /* client, wanting stapling */
301 /* Add the server cert's signing chain as the one
302 for the verification of the OCSP stapled information. */
304 if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store,
312 #ifdef EXPERIMENTAL_CERTNAMES
313 uschar * verify_cert_hostnames;
317 tlsp->peercert = X509_dup(cert);
319 #ifdef EXPERIMENTAL_CERTNAMES
320 if ( tlsp == &tls_out
321 && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames)))
322 /* client, wanting hostname check */
324 # if OPENSSL_VERSION_NUMBER >= 0x010100000L || OPENSSL_VERSION_NUMBER >= 0x010002000L
327 uschar * list = verify_cert_hostnames;
329 while (name = string_nextinlist(&list, &sep, NULL, 0))
330 if (X509_check_host(cert, name, 0, 0))
334 log_write(0, LOG_MAIN,
335 "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
336 return 0; /* reject */
340 if (!tls_is_name_for_cert(verify_cert_hostnames, cert))
342 log_write(0, LOG_MAIN,
343 "SSL verify error: certificate name mismatch: \"%s\"\n", txt);
344 return 0; /* reject */
349 DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n",
350 *calledp ? "" : " authenticated", txt);
351 if (!*calledp) tlsp->certificate_verified = TRUE;
355 return 1; /* accept */
359 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
361 return verify_callback(state, x509ctx, &tls_out, &client_verify_callback_called, &client_verify_optional);
365 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
367 return verify_callback(state, x509ctx, &tls_in, &server_verify_callback_called, &server_verify_optional);
372 /*************************************************
373 * Information callback *
374 *************************************************/
376 /* The SSL library functions call this from time to time to indicate what they
377 are doing. We copy the string to the debugging output when TLS debugging has
389 info_callback(SSL *s, int where, int ret)
393 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
398 /*************************************************
399 * Initialize for DH *
400 *************************************************/
402 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
405 dhparam DH parameter file or fixed parameter identity string
406 host connected host, if client; NULL if server
408 Returns: TRUE if OK (nothing to set up, or setup worked)
412 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
419 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
422 if (dhexpanded == NULL || *dhexpanded == '\0')
424 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
426 else if (dhexpanded[0] == '/')
428 bio = BIO_new_file(CS dhexpanded, "r");
431 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
432 host, US strerror(errno));
438 if (Ustrcmp(dhexpanded, "none") == 0)
440 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
444 pem = std_dh_prime_named(dhexpanded);
447 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
448 host, US strerror(errno));
451 bio = BIO_new_mem_buf(CS pem, -1);
454 dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
458 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
463 /* Even if it is larger, we silently return success rather than cause things
464 * to fail out, so that a too-large DH will not knock out all TLS; it's a
465 * debatable choice. */
466 if ((8*DH_size(dh)) > tls_dh_max_bits)
469 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
470 8*DH_size(dh), tls_dh_max_bits);
474 SSL_CTX_set_tmp_dh(sctx, dh);
476 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
477 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
490 /*************************************************
491 * Load OCSP information into state *
492 *************************************************/
494 /* Called to load the server OCSP response from the given file into memory, once
495 caller has determined this is needed. Checks validity. Debugs a message
498 ASSUMES: single response, for single cert.
501 sctx the SSL_CTX* to update
502 cbinfo various parts of session state
503 expanded the filename putatively holding an OCSP response
508 ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded)
512 OCSP_BASICRESP *basic_response;
513 OCSP_SINGLERESP *single_response;
514 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
516 unsigned long verify_flags;
517 int status, reason, i;
519 cbinfo->u_ocsp.server.file_expanded = string_copy(expanded);
520 if (cbinfo->u_ocsp.server.response)
522 OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response);
523 cbinfo->u_ocsp.server.response = NULL;
526 bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb");
529 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
530 cbinfo->u_ocsp.server.file_expanded);
534 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
538 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
542 status = OCSP_response_status(resp);
543 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
545 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
546 OCSP_response_status_str(status), status);
550 basic_response = OCSP_response_get1_basic(resp);
554 debug_printf("OCSP response parse error: unable to extract basic response.\n");
558 store = SSL_CTX_get_cert_store(sctx);
559 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
561 /* May need to expose ability to adjust those flags?
562 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
563 OCSP_TRUSTOTHER OCSP_NOINTERN */
565 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
569 ERR_error_string(ERR_get_error(), ssl_errstring);
570 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
575 /* Here's the simplifying assumption: there's only one response, for the
576 one certificate we use, and nothing for anything else in a chain. If this
577 proves false, we need to extract a cert id from our issued cert
578 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
579 right cert in the stack and then calls OCSP_single_get0_status()).
581 I'm hoping to avoid reworking a bunch more of how we handle state here. */
582 single_response = OCSP_resp_get0(basic_response, 0);
583 if (!single_response)
586 debug_printf("Unable to get first response from OCSP basic response.\n");
590 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
591 if (status != V_OCSP_CERTSTATUS_GOOD)
593 DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n",
594 OCSP_cert_status_str(status), status,
595 OCSP_crl_reason_str(reason), reason);
599 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
601 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
606 cbinfo->u_ocsp.server.response = resp;
610 if (running_in_test_harness)
612 extern char ** environ;
614 for (p = USS environ; *p != NULL; p++)
615 if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0)
617 DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n");
618 goto supply_response;
623 #endif /*!DISABLE_OCSP*/
628 /*************************************************
629 * Expand key and cert file specs *
630 *************************************************/
632 /* Called once during tls_init and possibly again during TLS setup, for a
633 new context, if Server Name Indication was used and tls_sni was seen in
634 the certificate string.
637 sctx the SSL_CTX* to update
638 cbinfo various parts of session state
640 Returns: OK/DEFER/FAIL
644 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
648 if (cbinfo->certificate == NULL)
651 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
652 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
653 Ustrstr(cbinfo->certificate, US"tls_out_sni")
655 reexpand_tls_files_for_sni = TRUE;
657 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
660 if (expanded != NULL)
662 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
663 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
664 return tls_error(string_sprintf(
665 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
669 if (cbinfo->privatekey != NULL &&
670 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
673 /* If expansion was forced to fail, key_expanded will be NULL. If the result
674 of the expansion is an empty string, ignore it also, and assume the private
675 key is in the same file as the certificate. */
677 if (expanded != NULL && *expanded != 0)
679 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
680 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
681 return tls_error(string_sprintf(
682 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
686 if (cbinfo->is_server && cbinfo->u_ocsp.server.file != NULL)
688 if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded))
691 if (expanded != NULL && *expanded != 0)
693 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
694 if (cbinfo->u_ocsp.server.file_expanded &&
695 (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0))
698 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
700 ocsp_load_response(sctx, cbinfo, expanded);
712 /*************************************************
713 * Callback to handle SNI *
714 *************************************************/
716 /* Called when acting as server during the TLS session setup if a Server Name
717 Indication extension was sent by the client.
719 API documentation is OpenSSL s_server.c implementation.
722 s SSL* of the current session
723 ad unknown (part of OpenSSL API) (unused)
724 arg Callback of "our" registered data
726 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
729 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
731 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
733 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
734 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
736 int old_pool = store_pool;
739 return SSL_TLSEXT_ERR_OK;
741 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
742 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
744 /* Make the extension value available for expansion */
745 store_pool = POOL_PERM;
746 tls_in.sni = string_copy(US servername);
747 store_pool = old_pool;
749 if (!reexpand_tls_files_for_sni)
750 return SSL_TLSEXT_ERR_OK;
752 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
753 not confident that memcpy wouldn't break some internal reference counting.
754 Especially since there's a references struct member, which would be off. */
756 server_sni = SSL_CTX_new(SSLv23_server_method());
759 ERR_error_string(ERR_get_error(), ssl_errstring);
760 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
761 return SSL_TLSEXT_ERR_NOACK;
764 /* Not sure how many of these are actually needed, since SSL object
765 already exists. Might even need this selfsame callback, for reneg? */
767 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
768 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
769 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
770 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
771 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
772 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
773 if (cbinfo->server_cipher_list)
774 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
776 if (cbinfo->u_ocsp.server.file)
778 SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb);
779 SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo);
783 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, verify_callback_server);
784 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
786 /* do this after setup_certs, because this can require the certs for verifying
788 rc = tls_expand_session_files(server_sni, cbinfo);
789 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
791 rc = init_dh(server_sni, cbinfo->dhparam, NULL);
792 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
794 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
795 SSL_set_SSL_CTX(s, server_sni);
797 return SSL_TLSEXT_ERR_OK;
799 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
806 /*************************************************
807 * Callback to handle OCSP Stapling *
808 *************************************************/
810 /* Called when acting as server during the TLS session setup if the client
811 requests OCSP information with a Certificate Status Request.
813 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
819 tls_server_stapling_cb(SSL *s, void *arg)
821 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
822 uschar *response_der;
823 int response_der_len;
826 debug_printf("Received TLS status request (OCSP stapling); %s response.",
827 cbinfo->u_ocsp.server.response ? "have" : "lack");
829 tls_in.ocsp = OCSP_NOT_RESP;
830 if (!cbinfo->u_ocsp.server.response)
831 return SSL_TLSEXT_ERR_NOACK;
834 response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response,
836 if (response_der_len <= 0)
837 return SSL_TLSEXT_ERR_NOACK;
839 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
840 tls_in.ocsp = OCSP_VFIED;
841 return SSL_TLSEXT_ERR_OK;
846 time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time)
848 BIO_printf(bp, "\t%s: ", str);
849 ASN1_GENERALIZEDTIME_print(bp, time);
854 tls_client_stapling_cb(SSL *s, void *arg)
856 tls_ext_ctx_cb * cbinfo = arg;
857 const unsigned char * p;
863 DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):");
864 len = SSL_get_tlsext_status_ocsp_resp(s, &p);
867 /* Expect this when we requested ocsp but got none */
868 if ( cbinfo->u_ocsp.client.verify_required
869 && log_extra_selector & LX_tls_cipher)
870 log_write(0, LOG_MAIN, "Received TLS status callback, null content");
872 DEBUG(D_tls) debug_printf(" null\n");
873 return cbinfo->u_ocsp.client.verify_required ? 0 : 1;
876 if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len)))
878 tls_out.ocsp = OCSP_FAILED;
879 if (log_extra_selector & LX_tls_cipher)
880 log_write(0, LOG_MAIN, "Received TLS status response, parse error");
882 DEBUG(D_tls) debug_printf(" parse error\n");
886 if(!(bs = OCSP_response_get1_basic(rsp)))
888 tls_out.ocsp = OCSP_FAILED;
889 if (log_extra_selector & LX_tls_cipher)
890 log_write(0, LOG_MAIN, "Received TLS status response, error parsing response");
892 DEBUG(D_tls) debug_printf(" error parsing response\n");
893 OCSP_RESPONSE_free(rsp);
897 /* We'd check the nonce here if we'd put one in the request. */
898 /* However that would defeat cacheability on the server so we don't. */
900 /* This section of code reworked from OpenSSL apps source;
901 The OpenSSL Project retains copyright:
902 Copyright (c) 1999 The OpenSSL Project. All rights reserved.
907 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
909 DEBUG(D_tls) bp = BIO_new_fp(stderr, BIO_NOCLOSE);
911 /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */
913 /* Use the chain that verified the server cert to verify the stapled info */
914 /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */
916 if ((i = OCSP_basic_verify(bs, NULL,
917 cbinfo->u_ocsp.client.verify_store, 0)) <= 0)
919 tls_out.ocsp = OCSP_FAILED;
920 BIO_printf(bp, "OCSP response verify failure\n");
921 ERR_print_errors(bp);
922 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
926 BIO_printf(bp, "OCSP response well-formed and signed OK\n");
929 STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses;
930 OCSP_SINGLERESP * single;
932 if (sk_OCSP_SINGLERESP_num(sresp) != 1)
934 tls_out.ocsp = OCSP_FAILED;
935 log_write(0, LOG_MAIN, "OCSP stapling "
936 "with multiple responses not handled");
937 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
940 single = OCSP_resp_get0(bs, 0);
941 status = OCSP_single_get0_status(single, &reason, &rev,
945 DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd);
946 DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd);
947 if (!OCSP_check_validity(thisupd, nextupd,
948 EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
950 tls_out.ocsp = OCSP_FAILED;
951 DEBUG(D_tls) ERR_print_errors(bp);
952 log_write(0, LOG_MAIN, "Server OSCP dates invalid");
953 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
957 DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n",
958 OCSP_cert_status_str(status));
961 case V_OCSP_CERTSTATUS_GOOD:
962 tls_out.ocsp = OCSP_VFIED;
965 case V_OCSP_CERTSTATUS_REVOKED:
966 tls_out.ocsp = OCSP_FAILED;
967 log_write(0, LOG_MAIN, "Server certificate revoked%s%s",
968 reason != -1 ? "; reason: " : "",
969 reason != -1 ? OCSP_crl_reason_str(reason) : "");
970 DEBUG(D_tls) time_print(bp, "Revocation Time", rev);
971 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
974 tls_out.ocsp = OCSP_FAILED;
975 log_write(0, LOG_MAIN,
976 "Server certificate status unknown, in OCSP stapling");
977 i = cbinfo->u_ocsp.client.verify_required ? 0 : 1;
985 OCSP_RESPONSE_free(rsp);
988 #endif /*!DISABLE_OCSP*/
992 /*************************************************
993 * Initialize for TLS *
994 *************************************************/
996 /* Called from both server and client code, to do preliminary initialization
997 of the library. We allocate and return a context structure.
1000 host connected host, if client; NULL if server
1001 dhparam DH parameter file
1002 certificate certificate file
1003 privatekey private key
1004 ocsp_file file of stapling info (server); flag for require ocsp (client)
1005 addr address if client; NULL if server (for some randomness)
1006 cbp place to put allocated context
1008 Returns: OK/DEFER/FAIL
1012 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
1014 #ifndef DISABLE_OCSP
1017 address_item *addr, tls_ext_ctx_cb ** cbp)
1022 tls_ext_ctx_cb *cbinfo;
1024 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
1025 cbinfo->certificate = certificate;
1026 cbinfo->privatekey = privatekey;
1027 #ifndef DISABLE_OCSP
1028 if ((cbinfo->is_server = host==NULL))
1030 cbinfo->u_ocsp.server.file = ocsp_file;
1031 cbinfo->u_ocsp.server.file_expanded = NULL;
1032 cbinfo->u_ocsp.server.response = NULL;
1035 cbinfo->u_ocsp.client.verify_store = NULL;
1037 cbinfo->dhparam = dhparam;
1038 cbinfo->host = host;
1040 SSL_load_error_strings(); /* basic set up */
1041 OpenSSL_add_ssl_algorithms();
1043 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1044 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1045 list of available digests. */
1046 EVP_add_digest(EVP_sha256());
1049 /* Create a context.
1050 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
1051 negotiation in the different methods; as far as I can tell, the only
1052 *_{server,client}_method which allows negotiation is SSLv23, which exists even
1053 when OpenSSL is built without SSLv2 support.
1054 By disabling with openssl_options, we can let admins re-enable with the
1057 *ctxp = SSL_CTX_new((host == NULL)?
1058 SSLv23_server_method() : SSLv23_client_method());
1060 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
1062 /* It turns out that we need to seed the random number generator this early in
1063 order to get the full complement of ciphers to work. It took me roughly a day
1064 of work to discover this by experiment.
1066 On systems that have /dev/urandom, SSL may automatically seed itself from
1067 there. Otherwise, we have to make something up as best we can. Double check
1073 gettimeofday(&r.tv, NULL);
1076 RAND_seed((uschar *)(&r), sizeof(r));
1077 RAND_seed((uschar *)big_buffer, big_buffer_size);
1078 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
1081 return tls_error(US"RAND_status", host,
1082 US"unable to seed random number generator");
1085 /* Set up the information callback, which outputs if debugging is at a suitable
1088 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
1090 /* Automatically re-try reads/writes after renegotiation. */
1091 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
1093 /* Apply administrator-supplied work-arounds.
1094 Historically we applied just one requested option,
1095 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
1096 moved to an administrator-controlled list of options to specify and
1097 grandfathered in the first one as the default value for "openssl_options".
1099 No OpenSSL version number checks: the options we accept depend upon the
1100 availability of the option value macros from OpenSSL. */
1102 okay = tls_openssl_options_parse(openssl_options, &init_options);
1104 return tls_error(US"openssl_options parsing failed", host, NULL);
1108 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
1109 if (!(SSL_CTX_set_options(*ctxp, init_options)))
1110 return tls_error(string_sprintf(
1111 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
1114 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
1116 /* Initialize with DH parameters if supplied */
1118 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
1120 /* Set up certificate and key (and perhaps OCSP info) */
1122 rc = tls_expand_session_files(*ctxp, cbinfo);
1123 if (rc != OK) return rc;
1125 /* If we need to handle SNI, do so */
1126 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1127 if (host == NULL) /* server */
1129 # ifndef DISABLE_OCSP
1130 /* We check u_ocsp.server.file, not server.response, because we care about if
1131 the option exists, not what the current expansion might be, as SNI might
1132 change the certificate and OCSP file in use between now and the time the
1133 callback is invoked. */
1134 if (cbinfo->u_ocsp.server.file)
1136 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_server_stapling_cb);
1137 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
1140 /* We always do this, so that $tls_sni is available even if not used in
1142 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
1143 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
1145 # ifndef DISABLE_OCSP
1147 if(ocsp_file) /* wanting stapling */
1149 if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new()))
1151 DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n");
1154 SSL_CTX_set_tlsext_status_cb(*ctxp, tls_client_stapling_cb);
1155 SSL_CTX_set_tlsext_status_arg(*ctxp, cbinfo);
1160 #ifdef EXPERIMENTAL_CERTNAMES
1161 cbinfo->verify_cert_hostnames = NULL;
1164 /* Set up the RSA callback */
1166 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
1168 /* Finally, set the timeout, and we are done */
1170 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
1171 DEBUG(D_tls) debug_printf("Initialized TLS\n");
1181 /*************************************************
1182 * Get name of cipher in use *
1183 *************************************************/
1186 Argument: pointer to an SSL structure for the connection
1187 buffer to use for answer
1189 pointer to number of bits for cipher
1194 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
1196 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
1197 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
1198 the accessor functions use const in the prototype. */
1199 const SSL_CIPHER *c;
1202 ver = (const uschar *)SSL_get_version(ssl);
1204 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
1205 SSL_CIPHER_get_bits(c, bits);
1207 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
1208 SSL_CIPHER_get_name(c), *bits);
1210 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
1217 /*************************************************
1218 * Set up for verifying certificates *
1219 *************************************************/
1221 /* Called by both client and server startup
1224 sctx SSL_CTX* to initialise
1225 certs certs file or NULL
1226 crl CRL file or NULL
1227 host NULL in a server; the remote host in a client
1228 optional TRUE if called from a server for a host in tls_try_verify_hosts;
1229 otherwise passed as FALSE
1230 cert_vfy_cb Callback function for certificate verification
1232 Returns: OK/DEFER/FAIL
1236 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional,
1237 int (*cert_vfy_cb)(int, X509_STORE_CTX *) )
1239 uschar *expcerts, *expcrl;
1241 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1244 if (expcerts != NULL && *expcerts != '\0')
1246 struct stat statbuf;
1247 if (!SSL_CTX_set_default_verify_paths(sctx))
1248 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1250 if (Ustat(expcerts, &statbuf) < 0)
1252 log_write(0, LOG_MAIN|LOG_PANIC,
1253 "failed to stat %s for certificates", expcerts);
1259 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1260 { file = NULL; dir = expcerts; }
1262 { file = expcerts; dir = NULL; }
1264 /* If a certificate file is empty, the next function fails with an
1265 unhelpful error message. If we skip it, we get the correct behaviour (no
1266 certificates are recognized, but the error message is still misleading (it
1267 says no certificate was supplied.) But this is better. */
1269 if ((file == NULL || statbuf.st_size > 0) &&
1270 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1271 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1275 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1279 /* Handle a certificate revocation list. */
1281 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1283 /* This bit of code is now the version supplied by Lars Mainka. (I have
1284 * merely reformatted it into the Exim code style.)
1286 * "From here I changed the code to add support for multiple crl's
1287 * in pem format in one file or to support hashed directory entries in
1288 * pem format instead of a file. This method now uses the library function
1289 * X509_STORE_load_locations to add the CRL location to the SSL context.
1290 * OpenSSL will then handle the verify against CA certs and CRLs by
1291 * itself in the verify callback." */
1293 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1294 if (expcrl != NULL && *expcrl != 0)
1296 struct stat statbufcrl;
1297 if (Ustat(expcrl, &statbufcrl) < 0)
1299 log_write(0, LOG_MAIN|LOG_PANIC,
1300 "failed to stat %s for certificates revocation lists", expcrl);
1305 /* is it a file or directory? */
1307 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1308 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1312 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1318 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1320 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1321 return tls_error(US"X509_STORE_load_locations", host, NULL);
1323 /* setting the flags to check against the complete crl chain */
1325 X509_STORE_set_flags(cvstore,
1326 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1330 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1332 /* If verification is optional, don't fail if no certificate */
1334 SSL_CTX_set_verify(sctx,
1335 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1344 /*************************************************
1345 * Start a TLS session in a server *
1346 *************************************************/
1348 /* This is called when Exim is running as a server, after having received
1349 the STARTTLS command. It must respond to that command, and then negotiate
1353 require_ciphers allowed ciphers
1355 Returns: OK on success
1356 DEFER for errors before the start of the negotiation
1357 FAIL for errors during the negotation; the server can't
1362 tls_server_start(const uschar *require_ciphers)
1366 tls_ext_ctx_cb *cbinfo;
1367 static uschar cipherbuf[256];
1369 /* Check for previous activation */
1371 if (tls_in.active >= 0)
1373 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1374 smtp_printf("554 Already in TLS\r\n");
1378 /* Initialize the SSL library. If it fails, it will already have logged
1381 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1382 #ifndef DISABLE_OCSP
1385 NULL, &server_static_cbinfo);
1386 if (rc != OK) return rc;
1387 cbinfo = server_static_cbinfo;
1389 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1392 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1393 were historically separated by underscores. So that I can use either form in my
1394 tests, and also for general convenience, we turn underscores into hyphens here.
1397 if (expciphers != NULL)
1399 uschar *s = expciphers;
1400 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1401 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1402 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1403 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1404 cbinfo->server_cipher_list = expciphers;
1407 /* If this is a host for which certificate verification is mandatory or
1408 optional, set up appropriately. */
1410 tls_in.certificate_verified = FALSE;
1411 server_verify_callback_called = FALSE;
1413 if (verify_check_host(&tls_verify_hosts) == OK)
1415 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1416 FALSE, verify_callback_server);
1417 if (rc != OK) return rc;
1418 server_verify_optional = FALSE;
1420 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1422 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL,
1423 TRUE, verify_callback_server);
1424 if (rc != OK) return rc;
1425 server_verify_optional = TRUE;
1428 /* Prepare for new connection */
1430 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1432 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1434 * With the SSL_clear(), we get strange interoperability bugs with
1435 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1436 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1438 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1439 * session shutdown. In this case, we have a brand new object and there's no
1440 * obvious reason to immediately clear it. I'm guessing that this was
1441 * originally added because of incomplete initialisation which the clear fixed,
1442 * in some historic release.
1445 /* Set context and tell client to go ahead, except in the case of TLS startup
1446 on connection, where outputting anything now upsets the clients and tends to
1447 make them disconnect. We need to have an explicit fflush() here, to force out
1448 the response. Other smtp_printf() calls do not need it, because in non-TLS
1449 mode, the fflush() happens when smtp_getc() is called. */
1451 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1452 if (!tls_in.on_connect)
1454 smtp_printf("220 TLS go ahead\r\n");
1458 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1459 that the OpenSSL library doesn't. */
1461 SSL_set_wfd(server_ssl, fileno(smtp_out));
1462 SSL_set_rfd(server_ssl, fileno(smtp_in));
1463 SSL_set_accept_state(server_ssl);
1465 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1467 sigalrm_seen = FALSE;
1468 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1469 rc = SSL_accept(server_ssl);
1474 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1475 if (ERR_get_error() == 0)
1476 log_write(0, LOG_MAIN,
1477 "TLS client disconnected cleanly (rejected our certificate?)");
1481 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1483 /* TLS has been set up. Adjust the input functions to read via TLS,
1484 and initialize things. */
1486 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1487 tls_in.cipher = cipherbuf;
1492 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1493 debug_printf("Shared ciphers: %s\n", buf);
1496 /* Record the certificate we presented */
1498 X509 * crt = SSL_get_certificate(server_ssl);
1499 tls_in.ourcert = crt ? X509_dup(crt) : NULL;
1502 /* Only used by the server-side tls (tls_in), including tls_getc.
1503 Client-side (tls_out) reads (seem to?) go via
1504 smtp_read_response()/ip_recv().
1505 Hence no need to duplicate for _in and _out.
1507 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1508 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1509 ssl_xfer_eof = ssl_xfer_error = 0;
1511 receive_getc = tls_getc;
1512 receive_ungetc = tls_ungetc;
1513 receive_feof = tls_feof;
1514 receive_ferror = tls_ferror;
1515 receive_smtp_buffered = tls_smtp_buffered;
1517 tls_in.active = fileno(smtp_out);
1525 /*************************************************
1526 * Start a TLS session in a client *
1527 *************************************************/
1529 /* Called from the smtp transport after STARTTLS has been accepted.
1532 fd the fd of the connection
1533 host connected host (for messages)
1534 addr the first address
1535 ob smtp transport options
1537 Returns: OK on success
1538 FAIL otherwise - note that tls_error() will not give DEFER
1539 because this is not a server
1543 tls_client_start(int fd, host_item *host, address_item *addr,
1546 smtp_transport_options_block * ob = v_ob;
1547 static uschar txt[256];
1551 static uschar cipherbuf[256];
1552 #ifndef DISABLE_OCSP
1553 BOOL require_ocsp = verify_check_this_host(&ob->hosts_require_ocsp,
1554 NULL, host->name, host->address, NULL) == OK;
1555 BOOL request_ocsp = require_ocsp ? TRUE
1556 : verify_check_this_host(&ob->hosts_request_ocsp,
1557 NULL, host->name, host->address, NULL) == OK;
1560 rc = tls_init(&client_ctx, host, NULL,
1561 ob->tls_certificate, ob->tls_privatekey,
1562 #ifndef DISABLE_OCSP
1563 (void *)(long)request_ocsp,
1565 addr, &client_static_cbinfo);
1566 if (rc != OK) return rc;
1568 tls_out.certificate_verified = FALSE;
1569 client_verify_callback_called = FALSE;
1571 if (!expand_check(ob->tls_require_ciphers, US"tls_require_ciphers",
1575 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1576 are separated by underscores. So that I can use either form in my tests, and
1577 also for general convenience, we turn underscores into hyphens here. */
1579 if (expciphers != NULL)
1581 uschar *s = expciphers;
1582 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1583 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1584 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1585 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1588 /* stick to the old behaviour for compatibility if tls_verify_certificates is
1589 set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only
1590 the specified host patterns if one of them is defined */
1592 if ((!ob->tls_verify_hosts && !ob->tls_try_verify_hosts) ||
1593 (verify_check_host(&ob->tls_verify_hosts) == OK))
1595 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1596 ob->tls_crl, host, FALSE, verify_callback_client)) != OK)
1598 client_verify_optional = FALSE;
1600 #ifdef EXPERIMENTAL_CERTNAMES
1601 if (ob->tls_verify_cert_hostnames)
1603 if (!expand_check(ob->tls_verify_cert_hostnames,
1604 US"tls_verify_cert_hostnames",
1605 &client_static_cbinfo->verify_cert_hostnames))
1607 if (client_static_cbinfo->verify_cert_hostnames)
1608 DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n",
1609 client_static_cbinfo->verify_cert_hostnames);
1613 else if (verify_check_host(&ob->tls_try_verify_hosts) == OK)
1615 if ((rc = setup_certs(client_ctx, ob->tls_verify_certificates,
1616 ob->tls_crl, host, TRUE, verify_callback_client)) != OK)
1618 client_verify_optional = TRUE;
1621 if ((client_ssl = SSL_new(client_ctx)) == NULL)
1622 return tls_error(US"SSL_new", host, NULL);
1623 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1624 SSL_set_fd(client_ssl, fd);
1625 SSL_set_connect_state(client_ssl);
1629 if (!expand_check(ob->tls_sni, US"tls_sni", &tls_out.sni))
1631 if (tls_out.sni == NULL)
1633 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1635 else if (!Ustrlen(tls_out.sni))
1639 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1640 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1641 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1644 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1650 #ifndef DISABLE_OCSP
1651 /* Request certificate status at connection-time. If the server
1652 does OCSP stapling we will get the callback (set in tls_init()) */
1655 SSL_set_tlsext_status_type(client_ssl, TLSEXT_STATUSTYPE_ocsp);
1656 client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp;
1657 tls_out.ocsp = OCSP_NOT_RESP;
1661 /* There doesn't seem to be a built-in timeout on connection. */
1663 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1664 sigalrm_seen = FALSE;
1665 alarm(ob->command_timeout);
1666 rc = SSL_connect(client_ssl);
1670 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1672 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1674 /* Beware anonymous ciphers which lead to server_cert being NULL */
1675 /*XXX server_cert is never freed... use X509_free() */
1676 server_cert = SSL_get_peer_certificate (client_ssl);
1679 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1680 CS txt, sizeof(txt));
1681 tls_out.peerdn = txt; /*XXX a static buffer... */
1684 tls_out.peerdn = NULL;
1686 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1687 tls_out.cipher = cipherbuf;
1689 /* Record the certificate we presented */
1691 X509 * crt = SSL_get_certificate(client_ssl);
1692 tls_out.ourcert = crt ? X509_dup(crt) : NULL;
1695 tls_out.active = fd;
1703 /*************************************************
1704 * TLS version of getc *
1705 *************************************************/
1707 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1708 it refills the buffer via the SSL reading function.
1711 Returns: the next character or EOF
1713 Only used by the server-side TLS.
1719 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1724 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1725 ssl_xfer_buffer, ssl_xfer_buffer_size);
1727 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1728 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1729 error = SSL_get_error(server_ssl, inbytes);
1732 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1733 closed down, not that the socket itself has been closed down. Revert to
1734 non-SSL handling. */
1736 if (error == SSL_ERROR_ZERO_RETURN)
1738 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1740 receive_getc = smtp_getc;
1741 receive_ungetc = smtp_ungetc;
1742 receive_feof = smtp_feof;
1743 receive_ferror = smtp_ferror;
1744 receive_smtp_buffered = smtp_buffered;
1746 SSL_free(server_ssl);
1750 tls_in.cipher = NULL;
1751 tls_in.peerdn = NULL;
1757 /* Handle genuine errors */
1759 else if (error == SSL_ERROR_SSL)
1761 ERR_error_string(ERR_get_error(), ssl_errstring);
1762 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1767 else if (error != SSL_ERROR_NONE)
1769 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1774 #ifndef DISABLE_DKIM
1775 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1777 ssl_xfer_buffer_hwm = inbytes;
1778 ssl_xfer_buffer_lwm = 0;
1781 /* Something in the buffer; return next uschar */
1783 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1788 /*************************************************
1789 * Read bytes from TLS channel *
1790 *************************************************/
1797 Returns: the number of bytes read
1798 -1 after a failed read
1800 Only used by the client-side TLS.
1804 tls_read(BOOL is_server, uschar *buff, size_t len)
1806 SSL *ssl = is_server ? server_ssl : client_ssl;
1810 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1811 buff, (unsigned int)len);
1813 inbytes = SSL_read(ssl, CS buff, len);
1814 error = SSL_get_error(ssl, inbytes);
1816 if (error == SSL_ERROR_ZERO_RETURN)
1818 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1821 else if (error != SSL_ERROR_NONE)
1833 /*************************************************
1834 * Write bytes down TLS channel *
1835 *************************************************/
1839 is_server channel specifier
1843 Returns: the number of bytes after a successful write,
1844 -1 after a failed write
1846 Used by both server-side and client-side TLS.
1850 tls_write(BOOL is_server, const uschar *buff, size_t len)
1855 SSL *ssl = is_server ? server_ssl : client_ssl;
1857 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1860 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1861 outbytes = SSL_write(ssl, CS buff, left);
1862 error = SSL_get_error(ssl, outbytes);
1863 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1867 ERR_error_string(ERR_get_error(), ssl_errstring);
1868 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1871 case SSL_ERROR_NONE:
1876 case SSL_ERROR_ZERO_RETURN:
1877 log_write(0, LOG_MAIN, "SSL channel closed on write");
1880 case SSL_ERROR_SYSCALL:
1881 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1882 sender_fullhost ? sender_fullhost : US"<unknown>",
1886 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1895 /*************************************************
1896 * Close down a TLS session *
1897 *************************************************/
1899 /* This is also called from within a delivery subprocess forked from the
1900 daemon, to shut down the TLS library, without actually doing a shutdown (which
1901 would tamper with the SSL session in the parent process).
1903 Arguments: TRUE if SSL_shutdown is to be called
1906 Used by both server-side and client-side TLS.
1910 tls_close(BOOL is_server, BOOL shutdown)
1912 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1913 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1915 if (*fdp < 0) return; /* TLS was not active */
1919 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1920 SSL_shutdown(*sslp);
1932 /*************************************************
1933 * Let tls_require_ciphers be checked at startup *
1934 *************************************************/
1936 /* The tls_require_ciphers option, if set, must be something which the
1939 Returns: NULL on success, or error message
1943 tls_validate_require_cipher(void)
1946 uschar *s, *expciphers, *err;
1948 /* this duplicates from tls_init(), we need a better "init just global
1949 state, for no specific purpose" singleton function of our own */
1951 SSL_load_error_strings();
1952 OpenSSL_add_ssl_algorithms();
1953 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1954 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1955 list of available digests. */
1956 EVP_add_digest(EVP_sha256());
1959 if (!(tls_require_ciphers && *tls_require_ciphers))
1962 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1963 return US"failed to expand tls_require_ciphers";
1965 if (!(expciphers && *expciphers))
1968 /* normalisation ripped from above */
1970 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1974 ctx = SSL_CTX_new(SSLv23_server_method());
1977 ERR_error_string(ERR_get_error(), ssl_errstring);
1978 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1982 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1984 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1986 ERR_error_string(ERR_get_error(), ssl_errstring);
1987 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
1998 /*************************************************
1999 * Report the library versions. *
2000 *************************************************/
2002 /* There have historically been some issues with binary compatibility in
2003 OpenSSL libraries; if Exim (like many other applications) is built against
2004 one version of OpenSSL but the run-time linker picks up another version,
2005 it can result in serious failures, including crashing with a SIGSEGV. So
2006 report the version found by the compiler and the run-time version.
2008 Note: some OS vendors backport security fixes without changing the version
2009 number/string, and the version date remains unchanged. The _build_ date
2010 will change, so we can more usefully assist with version diagnosis by also
2011 reporting the build date.
2013 Arguments: a FILE* to print the results to
2018 tls_version_report(FILE *f)
2020 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
2023 OPENSSL_VERSION_TEXT,
2024 SSLeay_version(SSLEAY_VERSION),
2025 SSLeay_version(SSLEAY_BUILT_ON));
2026 /* third line is 38 characters for the %s and the line is 73 chars long;
2027 the OpenSSL output includes a "built on: " prefix already. */
2033 /*************************************************
2034 * Random number generation *
2035 *************************************************/
2037 /* Pseudo-random number generation. The result is not expected to be
2038 cryptographically strong but not so weak that someone will shoot themselves
2039 in the foot using it as a nonce in input in some email header scheme or
2040 whatever weirdness they'll twist this into. The result should handle fork()
2041 and avoid repeating sequences. OpenSSL handles that for us.
2045 Returns a random number in range [0, max-1]
2049 vaguely_random_number(int max)
2053 static pid_t pidlast = 0;
2056 uschar smallbuf[sizeof(r)];
2062 if (pidnow != pidlast)
2064 /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state
2065 is unique for each thread", this doesn't apparently apply across processes,
2066 so our own warning from vaguely_random_number_fallback() applies here too.
2067 Fix per PostgreSQL. */
2073 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
2077 gettimeofday(&r.tv, NULL);
2080 RAND_seed((uschar *)(&r), sizeof(r));
2082 /* We're after pseudo-random, not random; if we still don't have enough data
2083 in the internal PRNG then our options are limited. We could sleep and hope
2084 for entropy to come along (prayer technique) but if the system is so depleted
2085 in the first place then something is likely to just keep taking it. Instead,
2086 we'll just take whatever little bit of pseudo-random we can still manage to
2089 needed_len = sizeof(r);
2090 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
2091 asked for a number less than 10. */
2092 for (r = max, i = 0; r; ++i)
2098 /* We do not care if crypto-strong */
2099 i = RAND_pseudo_bytes(smallbuf, needed_len);
2103 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
2104 return vaguely_random_number_fallback(max);
2108 for (p = smallbuf; needed_len; --needed_len, ++p)
2114 /* We don't particularly care about weighted results; if someone wants
2115 smooth distribution and cares enough then they should submit a patch then. */
2122 /*************************************************
2123 * OpenSSL option parse *
2124 *************************************************/
2126 /* Parse one option for tls_openssl_options_parse below
2129 name one option name
2130 value place to store a value for it
2131 Returns success or failure in parsing
2134 struct exim_openssl_option {
2138 /* We could use a macro to expand, but we need the ifdef and not all the
2139 options document which version they were introduced in. Policylet: include
2140 all options unless explicitly for DTLS, let the administrator choose which
2143 This list is current as of:
2145 Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev
2147 static struct exim_openssl_option exim_openssl_options[] = {
2148 /* KEEP SORTED ALPHABETICALLY! */
2150 { US"all", SSL_OP_ALL },
2152 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
2153 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
2155 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
2156 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
2158 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
2159 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
2161 #ifdef SSL_OP_EPHEMERAL_RSA
2162 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
2164 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
2165 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
2167 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
2168 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
2170 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
2171 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
2173 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
2174 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
2176 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
2177 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
2179 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
2180 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
2182 #ifdef SSL_OP_NO_COMPRESSION
2183 { US"no_compression", SSL_OP_NO_COMPRESSION },
2185 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
2186 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
2188 #ifdef SSL_OP_NO_SSLv2
2189 { US"no_sslv2", SSL_OP_NO_SSLv2 },
2191 #ifdef SSL_OP_NO_SSLv3
2192 { US"no_sslv3", SSL_OP_NO_SSLv3 },
2194 #ifdef SSL_OP_NO_TICKET
2195 { US"no_ticket", SSL_OP_NO_TICKET },
2197 #ifdef SSL_OP_NO_TLSv1
2198 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
2200 #ifdef SSL_OP_NO_TLSv1_1
2201 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
2202 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
2203 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
2205 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
2208 #ifdef SSL_OP_NO_TLSv1_2
2209 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
2211 #ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG
2212 { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG },
2214 #ifdef SSL_OP_SINGLE_DH_USE
2215 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
2217 #ifdef SSL_OP_SINGLE_ECDH_USE
2218 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
2220 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
2221 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
2223 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
2224 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
2226 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
2227 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
2229 #ifdef SSL_OP_TLS_D5_BUG
2230 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
2232 #ifdef SSL_OP_TLS_ROLLBACK_BUG
2233 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
2236 static int exim_openssl_options_size =
2237 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
2241 tls_openssl_one_option_parse(uschar *name, long *value)
2244 int last = exim_openssl_options_size;
2245 while (last > first)
2247 int middle = (first + last)/2;
2248 int c = Ustrcmp(name, exim_openssl_options[middle].name);
2251 *value = exim_openssl_options[middle].value;
2265 /*************************************************
2266 * OpenSSL option parsing logic *
2267 *************************************************/
2269 /* OpenSSL has a number of compatibility options which an administrator might
2270 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
2271 we look like log_selector.
2274 option_spec the administrator-supplied string of options
2275 results ptr to long storage for the options bitmap
2276 Returns success or failure
2280 tls_openssl_options_parse(uschar *option_spec, long *results)
2285 BOOL adding, item_parsed;
2288 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
2289 * from default because it increases BEAST susceptibility. */
2290 #ifdef SSL_OP_NO_SSLv2
2291 result |= SSL_OP_NO_SSLv2;
2294 if (option_spec == NULL)
2300 for (s=option_spec; *s != '\0'; /**/)
2302 while (isspace(*s)) ++s;
2305 if (*s != '+' && *s != '-')
2307 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
2308 "+ or - expected but found \"%s\"\n", s);
2311 adding = *s++ == '+';
2312 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
2315 item_parsed = tls_openssl_one_option_parse(s, &item);
2318 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2321 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2322 adding ? "adding" : "removing", result, item, s);
2337 /* End of tls-openssl.c */