1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) University of Cambridge 1995 - 2012 */
6 /* See the file NOTICE for conditions of use and distribution. */
8 /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL
9 library. It is #included into the tls.c file when that library is used. The
10 code herein is based on a patch that was originally contributed by Steve
11 Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara.
13 No cryptographic code is included in Exim. All this module does is to call
14 functions from the OpenSSL library. */
19 #include <openssl/lhash.h>
20 #include <openssl/ssl.h>
21 #include <openssl/err.h>
22 #include <openssl/rand.h>
23 #ifdef EXPERIMENTAL_OCSP
24 #include <openssl/ocsp.h>
27 #ifdef EXPERIMENTAL_OCSP
28 #define EXIM_OCSP_SKEW_SECONDS (300L)
29 #define EXIM_OCSP_MAX_AGE (-1L)
32 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
33 #define EXIM_HAVE_OPENSSL_TLSEXT
36 /* Structure for collecting random data for seeding. */
38 typedef struct randstuff {
43 /* Local static variables */
45 static BOOL client_verify_callback_called = FALSE;
46 static BOOL server_verify_callback_called = FALSE;
47 static const uschar *sid_ctx = US"exim";
49 /* We have three different contexts to care about.
51 Simple case: client, `client_ctx`
52 As a client, we can be doing a callout or cut-through delivery while receiving
53 a message. So we have a client context, which should have options initialised
54 from the SMTP Transport.
57 There are two cases: with and without ServerNameIndication from the client.
58 Given TLS SNI, we can be using different keys, certs and various other
59 configuration settings, because they're re-expanded with $tls_sni set. This
60 allows vhosting with TLS. This SNI is sent in the handshake.
61 A client might not send SNI, so we need a fallback, and an initial setup too.
62 So as a server, we start out using `server_ctx`.
63 If SNI is sent by the client, then we as server, mid-negotiation, try to clone
64 `server_sni` from `server_ctx` and then initialise settings by re-expanding
68 static SSL_CTX *client_ctx = NULL;
69 static SSL_CTX *server_ctx = NULL;
70 static SSL *client_ssl = NULL;
71 static SSL *server_ssl = NULL;
73 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
74 static SSL_CTX *server_sni = NULL;
77 static char ssl_errstring[256];
79 static int ssl_session_timeout = 200;
80 static BOOL client_verify_optional = FALSE;
81 static BOOL server_verify_optional = FALSE;
83 static BOOL reexpand_tls_files_for_sni = FALSE;
86 typedef struct tls_ext_ctx_cb {
89 #ifdef EXPERIMENTAL_OCSP
91 uschar *ocsp_file_expanded;
92 OCSP_RESPONSE *ocsp_response;
95 /* these are cached from first expand */
96 uschar *server_cipher_list;
97 /* only passed down to tls_error: */
101 /* should figure out a cleanup of API to handle state preserved per
102 implementation, for various reasons, which can be void * in the APIs.
103 For now, we hack around it. */
104 tls_ext_ctx_cb *client_static_cbinfo = NULL;
105 tls_ext_ctx_cb *server_static_cbinfo = NULL;
108 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, BOOL client);
111 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
112 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
114 #ifdef EXPERIMENTAL_OCSP
115 static int tls_stapling_cb(SSL *s, void *arg);
119 /*************************************************
121 *************************************************/
123 /* Called from lots of places when errors occur before actually starting to do
124 the TLS handshake, that is, while the session is still in clear. Always returns
125 DEFER for a server and FAIL for a client so that most calls can use "return
126 tls_error(...)" to do this processing and then give an appropriate return. A
127 single function is used for both server and client, because it is called from
128 some shared functions.
131 prefix text to include in the logged error
132 host NULL if setting up a server;
133 the connected host if setting up a client
134 msg error message or NULL if we should ask OpenSSL
136 Returns: OK/DEFER/FAIL
140 tls_error(uschar *prefix, host_item *host, uschar *msg)
144 ERR_error_string(ERR_get_error(), ssl_errstring);
145 msg = (uschar *)ssl_errstring;
150 uschar *conn_info = smtp_get_connection_info();
151 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
153 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
154 conn_info, prefix, msg);
159 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
160 host->name, host->address, prefix, msg);
167 /*************************************************
168 * Callback to generate RSA key *
169 *************************************************/
177 Returns: pointer to generated key
181 rsa_callback(SSL *s, int export, int keylength)
184 export = export; /* Shut picky compilers up */
185 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
186 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
189 ERR_error_string(ERR_get_error(), ssl_errstring);
190 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
200 /*************************************************
201 * Callback for verification *
202 *************************************************/
204 /* The SSL library does certificate verification if set up to do so. This
205 callback has the current yes/no state is in "state". If verification succeeded,
206 we set up the tls_peerdn string. If verification failed, what happens depends
207 on whether the client is required to present a verifiable certificate or not.
209 If verification is optional, we change the state to yes, but still log the
210 verification error. For some reason (it really would help to have proper
211 documentation of OpenSSL), this callback function then gets called again, this
212 time with state = 1. In fact, that's useful, because we can set up the peerdn
213 value, but we must take care not to set the private verified flag on the second
216 Note: this function is not called if the client fails to present a certificate
217 when asked. We get here only if a certificate has been received. Handling of
218 optional verification for this case is done when requesting SSL to verify, by
219 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
222 state current yes/no state as 1/0
223 x509ctx certificate information.
224 client TRUE for client startup, FALSE for server startup
226 Returns: 1 if verified, 0 if not
230 verify_callback(int state, X509_STORE_CTX *x509ctx, BOOL client)
232 static uschar txt[256];
240 calledp= &client_verify_callback_called;
241 optionalp= &client_verify_optional;
246 calledp= &server_verify_callback_called;
247 optionalp= &server_verify_optional;
250 X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert),
251 CS txt, sizeof(txt));
255 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
256 x509ctx->error_depth,
257 X509_verify_cert_error_string(x509ctx->error),
259 tlsp->certificate_verified = FALSE;
261 if (!*optionalp) return 0; /* reject */
262 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
263 "tls_try_verify_hosts)\n");
264 return 1; /* accept */
267 if (x509ctx->error_depth != 0)
269 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n",
270 x509ctx->error_depth, txt);
274 DEBUG(D_tls) debug_printf("SSL%s peer: %s\n",
275 *calledp ? "" : " authenticated", txt);
279 if (!*calledp) tlsp->certificate_verified = TRUE;
282 return 1; /* accept */
286 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
288 return verify_callback(state, x509ctx, TRUE);
292 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
294 return verify_callback(state, x509ctx, FALSE);
299 /*************************************************
300 * Information callback *
301 *************************************************/
303 /* The SSL library functions call this from time to time to indicate what they
304 are doing. We copy the string to the debugging output when TLS debugging has
316 info_callback(SSL *s, int where, int ret)
320 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
325 /*************************************************
326 * Initialize for DH *
327 *************************************************/
329 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
332 dhparam DH parameter file or fixed parameter identity string
333 host connected host, if client; NULL if server
335 Returns: TRUE if OK (nothing to set up, or setup worked)
339 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
346 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
349 if (dhexpanded == NULL || *dhexpanded == '\0')
351 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
353 else if (dhexpanded[0] == '/')
355 bio = BIO_new_file(CS dhexpanded, "r");
358 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
359 host, US strerror(errno));
365 if (Ustrcmp(dhexpanded, "none") == 0)
367 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
371 pem = std_dh_prime_named(dhexpanded);
374 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
375 host, US strerror(errno));
378 bio = BIO_new_mem_buf(CS pem, -1);
381 dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
385 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
390 /* Even if it is larger, we silently return success rather than cause things
391 * to fail out, so that a too-large DH will not knock out all TLS; it's a
392 * debatable choice. */
393 if ((8*DH_size(dh)) > tls_dh_max_bits)
396 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
397 8*DH_size(dh), tls_dh_max_bits);
401 SSL_CTX_set_tmp_dh(sctx, dh);
403 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
404 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
416 #ifdef EXPERIMENTAL_OCSP
417 /*************************************************
418 * Load OCSP information into state *
419 *************************************************/
421 /* Called to load the OCSP response from the given file into memory, once
422 caller has determined this is needed. Checks validity. Debugs a message
425 ASSUMES: single response, for single cert.
428 sctx the SSL_CTX* to update
429 cbinfo various parts of session state
430 expanded the filename putatively holding an OCSP response
435 ocsp_load_response(SSL_CTX *sctx,
436 tls_ext_ctx_cb *cbinfo,
437 const uschar *expanded)
441 OCSP_BASICRESP *basic_response;
442 OCSP_SINGLERESP *single_response;
443 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
445 unsigned long verify_flags;
446 int status, reason, i;
448 cbinfo->ocsp_file_expanded = string_copy(expanded);
449 if (cbinfo->ocsp_response)
451 OCSP_RESPONSE_free(cbinfo->ocsp_response);
452 cbinfo->ocsp_response = NULL;
455 bio = BIO_new_file(CS cbinfo->ocsp_file_expanded, "rb");
458 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
459 cbinfo->ocsp_file_expanded);
463 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
467 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
471 status = OCSP_response_status(resp);
472 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
474 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
475 OCSP_response_status_str(status), status);
479 basic_response = OCSP_response_get1_basic(resp);
483 debug_printf("OCSP response parse error: unable to extract basic response.\n");
487 store = SSL_CTX_get_cert_store(sctx);
488 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
490 /* May need to expose ability to adjust those flags?
491 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
492 OCSP_TRUSTOTHER OCSP_NOINTERN */
494 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
498 ERR_error_string(ERR_get_error(), ssl_errstring);
499 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
504 /* Here's the simplifying assumption: there's only one response, for the
505 one certificate we use, and nothing for anything else in a chain. If this
506 proves false, we need to extract a cert id from our issued cert
507 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
508 right cert in the stack and then calls OCSP_single_get0_status()).
510 I'm hoping to avoid reworking a bunch more of how we handle state here. */
511 single_response = OCSP_resp_get0(basic_response, 0);
512 if (!single_response)
515 debug_printf("Unable to get first response from OCSP basic response.\n");
519 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
520 /* how does this status differ from the one above? */
521 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
523 DEBUG(D_tls) debug_printf("OCSP response not valid (take 2): %s (%d)\n",
524 OCSP_response_status_str(status), status);
528 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
530 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
534 cbinfo->ocsp_response = resp;
541 /*************************************************
542 * Expand key and cert file specs *
543 *************************************************/
545 /* Called once during tls_init and possibly againt during TLS setup, for a
546 new context, if Server Name Indication was used and tls_sni was seen in
547 the certificate string.
550 sctx the SSL_CTX* to update
551 cbinfo various parts of session state
553 Returns: OK/DEFER/FAIL
557 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
561 if (cbinfo->certificate == NULL)
564 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
565 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
566 Ustrstr(cbinfo->certificate, US"tls_out_sni")
568 reexpand_tls_files_for_sni = TRUE;
570 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
573 if (expanded != NULL)
575 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
576 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
577 return tls_error(string_sprintf(
578 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
582 if (cbinfo->privatekey != NULL &&
583 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
586 /* If expansion was forced to fail, key_expanded will be NULL. If the result
587 of the expansion is an empty string, ignore it also, and assume the private
588 key is in the same file as the certificate. */
590 if (expanded != NULL && *expanded != 0)
592 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
593 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
594 return tls_error(string_sprintf(
595 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
598 #ifdef EXPERIMENTAL_OCSP
599 if (cbinfo->ocsp_file != NULL)
601 if (!expand_check(cbinfo->ocsp_file, US"tls_ocsp_file", &expanded))
604 if (expanded != NULL && *expanded != 0)
606 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
607 if (cbinfo->ocsp_file_expanded &&
608 (Ustrcmp(expanded, cbinfo->ocsp_file_expanded) == 0))
611 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
613 ocsp_load_response(sctx, cbinfo, expanded);
625 /*************************************************
626 * Callback to handle SNI *
627 *************************************************/
629 /* Called when acting as server during the TLS session setup if a Server Name
630 Indication extension was sent by the client.
632 API documentation is OpenSSL s_server.c implementation.
635 s SSL* of the current session
636 ad unknown (part of OpenSSL API) (unused)
637 arg Callback of "our" registered data
639 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
642 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
644 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
646 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
647 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
649 int old_pool = store_pool;
652 return SSL_TLSEXT_ERR_OK;
654 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
655 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
657 /* Make the extension value available for expansion */
658 store_pool = POOL_PERM;
659 tls_in.sni = string_copy(US servername);
660 store_pool = old_pool;
662 if (!reexpand_tls_files_for_sni)
663 return SSL_TLSEXT_ERR_OK;
665 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
666 not confident that memcpy wouldn't break some internal reference counting.
667 Especially since there's a references struct member, which would be off. */
669 server_sni = SSL_CTX_new(SSLv23_server_method());
672 ERR_error_string(ERR_get_error(), ssl_errstring);
673 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
674 return SSL_TLSEXT_ERR_NOACK;
677 /* Not sure how many of these are actually needed, since SSL object
678 already exists. Might even need this selfsame callback, for reneg? */
680 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
681 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
682 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
683 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
684 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
685 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
686 if (cbinfo->server_cipher_list)
687 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
688 #ifdef EXPERIMENTAL_OCSP
689 if (cbinfo->ocsp_file)
691 SSL_CTX_set_tlsext_status_cb(server_sni, tls_stapling_cb);
692 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
696 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, FALSE);
697 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
699 /* do this after setup_certs, because this can require the certs for verifying
701 rc = tls_expand_session_files(server_sni, cbinfo);
702 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
704 rc = init_dh(server_sni, cbinfo->dhparam, NULL);
705 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
707 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
708 SSL_set_SSL_CTX(s, server_sni);
710 return SSL_TLSEXT_ERR_OK;
712 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
717 #ifdef EXPERIMENTAL_OCSP
718 /*************************************************
719 * Callback to handle OCSP Stapling *
720 *************************************************/
722 /* Called when acting as server during the TLS session setup if the client
723 requests OCSP information with a Certificate Status Request.
725 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
731 tls_stapling_cb(SSL *s, void *arg)
733 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
734 uschar *response_der;
735 int response_der_len;
737 DEBUG(D_tls) debug_printf("Received TLS status request (OCSP stapling); %s response.\n",
738 cbinfo->ocsp_response ? "have" : "lack");
739 if (!cbinfo->ocsp_response)
740 return SSL_TLSEXT_ERR_NOACK;
743 response_der_len = i2d_OCSP_RESPONSE(cbinfo->ocsp_response, &response_der);
744 if (response_der_len <= 0)
745 return SSL_TLSEXT_ERR_NOACK;
747 SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len);
748 return SSL_TLSEXT_ERR_OK;
751 #endif /* EXPERIMENTAL_OCSP */
756 /*************************************************
757 * Initialize for TLS *
758 *************************************************/
760 /* Called from both server and client code, to do preliminary initialization of
764 host connected host, if client; NULL if server
765 dhparam DH parameter file
766 certificate certificate file
767 privatekey private key
768 addr address if client; NULL if server (for some randomness)
770 Returns: OK/DEFER/FAIL
774 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
776 #ifdef EXPERIMENTAL_OCSP
779 address_item *addr, tls_ext_ctx_cb ** cbp)
784 tls_ext_ctx_cb *cbinfo;
786 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
787 cbinfo->certificate = certificate;
788 cbinfo->privatekey = privatekey;
789 #ifdef EXPERIMENTAL_OCSP
790 cbinfo->ocsp_file = ocsp_file;
792 cbinfo->dhparam = dhparam;
795 SSL_load_error_strings(); /* basic set up */
796 OpenSSL_add_ssl_algorithms();
798 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
799 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
800 list of available digests. */
801 EVP_add_digest(EVP_sha256());
805 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
806 negotiation in the different methods; as far as I can tell, the only
807 *_{server,client}_method which allows negotiation is SSLv23, which exists even
808 when OpenSSL is built without SSLv2 support.
809 By disabling with openssl_options, we can let admins re-enable with the
812 *ctxp = SSL_CTX_new((host == NULL)?
813 SSLv23_server_method() : SSLv23_client_method());
815 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
817 /* It turns out that we need to seed the random number generator this early in
818 order to get the full complement of ciphers to work. It took me roughly a day
819 of work to discover this by experiment.
821 On systems that have /dev/urandom, SSL may automatically seed itself from
822 there. Otherwise, we have to make something up as best we can. Double check
828 gettimeofday(&r.tv, NULL);
831 RAND_seed((uschar *)(&r), sizeof(r));
832 RAND_seed((uschar *)big_buffer, big_buffer_size);
833 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
836 return tls_error(US"RAND_status", host,
837 US"unable to seed random number generator");
840 /* Set up the information callback, which outputs if debugging is at a suitable
843 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
845 /* Automatically re-try reads/writes after renegotiation. */
846 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
848 /* Apply administrator-supplied work-arounds.
849 Historically we applied just one requested option,
850 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
851 moved to an administrator-controlled list of options to specify and
852 grandfathered in the first one as the default value for "openssl_options".
854 No OpenSSL version number checks: the options we accept depend upon the
855 availability of the option value macros from OpenSSL. */
857 okay = tls_openssl_options_parse(openssl_options, &init_options);
859 return tls_error(US"openssl_options parsing failed", host, NULL);
863 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
864 if (!(SSL_CTX_set_options(*ctxp, init_options)))
865 return tls_error(string_sprintf(
866 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
869 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
871 /* Initialize with DH parameters if supplied */
873 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
875 /* Set up certificate and key (and perhaps OCSP info) */
877 rc = tls_expand_session_files(*ctxp, cbinfo);
878 if (rc != OK) return rc;
880 /* If we need to handle SNI, do so */
881 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
884 #ifdef EXPERIMENTAL_OCSP
885 /* We check ocsp_file, not ocsp_response, because we care about if
886 the option exists, not what the current expansion might be, as SNI might
887 change the certificate and OCSP file in use between now and the time the
888 callback is invoked. */
889 if (cbinfo->ocsp_file)
891 SSL_CTX_set_tlsext_status_cb(server_ctx, tls_stapling_cb);
892 SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo);
895 /* We always do this, so that $tls_sni is available even if not used in
897 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
898 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
902 /* Set up the RSA callback */
904 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
906 /* Finally, set the timeout, and we are done */
908 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
909 DEBUG(D_tls) debug_printf("Initialized TLS\n");
919 /*************************************************
920 * Get name of cipher in use *
921 *************************************************/
924 Argument: pointer to an SSL structure for the connection
925 buffer to use for answer
927 pointer to number of bits for cipher
932 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
934 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
935 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
936 the accessor functions use const in the prototype. */
940 switch (ssl->session->ssl_version)
954 #ifdef TLS1_1_VERSION
960 #ifdef TLS1_2_VERSION
970 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
971 SSL_CIPHER_get_bits(c, bits);
973 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
974 SSL_CIPHER_get_name(c), *bits);
976 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
983 /*************************************************
984 * Set up for verifying certificates *
985 *************************************************/
987 /* Called by both client and server startup
990 sctx SSL_CTX* to initialise
991 certs certs file or NULL
993 host NULL in a server; the remote host in a client
994 optional TRUE if called from a server for a host in tls_try_verify_hosts;
995 otherwise passed as FALSE
996 client TRUE if called for client startup, FALSE for server startup
998 Returns: OK/DEFER/FAIL
1002 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, BOOL client)
1004 uschar *expcerts, *expcrl;
1006 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
1009 if (expcerts != NULL)
1011 struct stat statbuf;
1012 if (!SSL_CTX_set_default_verify_paths(sctx))
1013 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
1015 if (Ustat(expcerts, &statbuf) < 0)
1017 log_write(0, LOG_MAIN|LOG_PANIC,
1018 "failed to stat %s for certificates", expcerts);
1024 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1025 { file = NULL; dir = expcerts; }
1027 { file = expcerts; dir = NULL; }
1029 /* If a certificate file is empty, the next function fails with an
1030 unhelpful error message. If we skip it, we get the correct behaviour (no
1031 certificates are recognized, but the error message is still misleading (it
1032 says no certificate was supplied.) But this is better. */
1034 if ((file == NULL || statbuf.st_size > 0) &&
1035 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1036 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1040 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1044 /* Handle a certificate revocation list. */
1046 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1048 /* This bit of code is now the version supplied by Lars Mainka. (I have
1049 * merely reformatted it into the Exim code style.)
1051 * "From here I changed the code to add support for multiple crl's
1052 * in pem format in one file or to support hashed directory entries in
1053 * pem format instead of a file. This method now uses the library function
1054 * X509_STORE_load_locations to add the CRL location to the SSL context.
1055 * OpenSSL will then handle the verify against CA certs and CRLs by
1056 * itself in the verify callback." */
1058 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1059 if (expcrl != NULL && *expcrl != 0)
1061 struct stat statbufcrl;
1062 if (Ustat(expcrl, &statbufcrl) < 0)
1064 log_write(0, LOG_MAIN|LOG_PANIC,
1065 "failed to stat %s for certificates revocation lists", expcrl);
1070 /* is it a file or directory? */
1072 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1073 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1077 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1083 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1085 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1086 return tls_error(US"X509_STORE_load_locations", host, NULL);
1088 /* setting the flags to check against the complete crl chain */
1090 X509_STORE_set_flags(cvstore,
1091 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1095 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1097 /* If verification is optional, don't fail if no certificate */
1099 SSL_CTX_set_verify(sctx,
1100 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1101 client ? verify_callback_client : verify_callback_server);
1109 /*************************************************
1110 * Start a TLS session in a server *
1111 *************************************************/
1113 /* This is called when Exim is running as a server, after having received
1114 the STARTTLS command. It must respond to that command, and then negotiate
1118 require_ciphers allowed ciphers
1120 Returns: OK on success
1121 DEFER for errors before the start of the negotiation
1122 FAIL for errors during the negotation; the server can't
1127 tls_server_start(const uschar *require_ciphers)
1131 tls_ext_ctx_cb *cbinfo;
1132 static uschar cipherbuf[256];
1134 /* Check for previous activation */
1136 if (tls_in.active >= 0)
1138 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1139 smtp_printf("554 Already in TLS\r\n");
1143 /* Initialize the SSL library. If it fails, it will already have logged
1146 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1147 #ifdef EXPERIMENTAL_OCSP
1150 NULL, &server_static_cbinfo);
1151 if (rc != OK) return rc;
1152 cbinfo = server_static_cbinfo;
1154 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1157 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1158 were historically separated by underscores. So that I can use either form in my
1159 tests, and also for general convenience, we turn underscores into hyphens here.
1162 if (expciphers != NULL)
1164 uschar *s = expciphers;
1165 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1166 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1167 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1168 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1169 cbinfo->server_cipher_list = expciphers;
1172 /* If this is a host for which certificate verification is mandatory or
1173 optional, set up appropriately. */
1175 tls_in.certificate_verified = FALSE;
1176 server_verify_callback_called = FALSE;
1178 if (verify_check_host(&tls_verify_hosts) == OK)
1180 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, FALSE, FALSE);
1181 if (rc != OK) return rc;
1182 server_verify_optional = FALSE;
1184 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1186 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, TRUE, FALSE);
1187 if (rc != OK) return rc;
1188 server_verify_optional = TRUE;
1191 /* Prepare for new connection */
1193 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1195 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1197 * With the SSL_clear(), we get strange interoperability bugs with
1198 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1199 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1201 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1202 * session shutdown. In this case, we have a brand new object and there's no
1203 * obvious reason to immediately clear it. I'm guessing that this was
1204 * originally added because of incomplete initialisation which the clear fixed,
1205 * in some historic release.
1208 /* Set context and tell client to go ahead, except in the case of TLS startup
1209 on connection, where outputting anything now upsets the clients and tends to
1210 make them disconnect. We need to have an explicit fflush() here, to force out
1211 the response. Other smtp_printf() calls do not need it, because in non-TLS
1212 mode, the fflush() happens when smtp_getc() is called. */
1214 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1215 if (!tls_in.on_connect)
1217 smtp_printf("220 TLS go ahead\r\n");
1221 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1222 that the OpenSSL library doesn't. */
1224 SSL_set_wfd(server_ssl, fileno(smtp_out));
1225 SSL_set_rfd(server_ssl, fileno(smtp_in));
1226 SSL_set_accept_state(server_ssl);
1228 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1230 sigalrm_seen = FALSE;
1231 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1232 rc = SSL_accept(server_ssl);
1237 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1238 if (ERR_get_error() == 0)
1239 log_write(0, LOG_MAIN,
1240 "TLS client disconnected cleanly (rejected our certificate?)");
1244 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1246 /* TLS has been set up. Adjust the input functions to read via TLS,
1247 and initialize things. */
1249 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1250 tls_in.cipher = cipherbuf;
1255 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1256 debug_printf("Shared ciphers: %s\n", buf);
1260 /* Only used by the server-side tls (tls_in), including tls_getc.
1261 Client-side (tls_out) reads (seem to?) go via
1262 smtp_read_response()/ip_recv().
1263 Hence no need to duplicate for _in and _out.
1265 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1266 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1267 ssl_xfer_eof = ssl_xfer_error = 0;
1269 receive_getc = tls_getc;
1270 receive_ungetc = tls_ungetc;
1271 receive_feof = tls_feof;
1272 receive_ferror = tls_ferror;
1273 receive_smtp_buffered = tls_smtp_buffered;
1275 tls_in.active = fileno(smtp_out);
1283 /*************************************************
1284 * Start a TLS session in a client *
1285 *************************************************/
1287 /* Called from the smtp transport after STARTTLS has been accepted.
1290 fd the fd of the connection
1291 host connected host (for messages)
1292 addr the first address
1293 dhparam DH parameter file
1294 certificate certificate file
1295 privatekey private key file
1296 sni TLS SNI to send to remote host
1297 verify_certs file for certificate verify
1298 crl file containing CRL
1299 require_ciphers list of allowed ciphers
1300 dh_min_bits minimum number of bits acceptable in server's DH prime
1302 timeout startup timeout
1304 Returns: OK on success
1305 FAIL otherwise - note that tls_error() will not give DEFER
1306 because this is not a server
1310 tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
1311 uschar *certificate, uschar *privatekey, uschar *sni,
1312 uschar *verify_certs, uschar *crl,
1313 uschar *require_ciphers, int dh_min_bits ARG_UNUSED, int timeout)
1315 static uschar txt[256];
1319 static uschar cipherbuf[256];
1321 rc = tls_init(&client_ctx, host, dhparam, certificate, privatekey,
1322 #ifdef EXPERIMENTAL_OCSP
1325 addr, &client_static_cbinfo);
1326 if (rc != OK) return rc;
1328 tls_out.certificate_verified = FALSE;
1329 client_verify_callback_called = FALSE;
1331 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1334 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1335 are separated by underscores. So that I can use either form in my tests, and
1336 also for general convenience, we turn underscores into hyphens here. */
1338 if (expciphers != NULL)
1340 uschar *s = expciphers;
1341 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1342 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1343 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1344 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1347 rc = setup_certs(client_ctx, verify_certs, crl, host, FALSE, TRUE);
1348 if (rc != OK) return rc;
1350 if ((client_ssl = SSL_new(client_ctx)) == NULL) return tls_error(US"SSL_new", host, NULL);
1351 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1352 SSL_set_fd(client_ssl, fd);
1353 SSL_set_connect_state(client_ssl);
1357 if (!expand_check(sni, US"tls_sni", &tls_out.sni))
1359 if (tls_out.sni == NULL)
1361 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1363 else if (!Ustrlen(tls_out.sni))
1367 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1368 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1369 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1372 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1378 /* There doesn't seem to be a built-in timeout on connection. */
1380 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1381 sigalrm_seen = FALSE;
1383 rc = SSL_connect(client_ssl);
1387 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1389 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1391 /* Beware anonymous ciphers which lead to server_cert being NULL */
1392 server_cert = SSL_get_peer_certificate (client_ssl);
1395 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1396 CS txt, sizeof(txt));
1397 tls_out.peerdn = txt;
1400 tls_out.peerdn = NULL;
1402 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1403 tls_out.cipher = cipherbuf;
1405 tls_out.active = fd;
1413 /*************************************************
1414 * TLS version of getc *
1415 *************************************************/
1417 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1418 it refills the buffer via the SSL reading function.
1421 Returns: the next character or EOF
1423 Only used by the server-side TLS.
1429 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1434 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1435 ssl_xfer_buffer, ssl_xfer_buffer_size);
1437 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1438 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1439 error = SSL_get_error(server_ssl, inbytes);
1442 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1443 closed down, not that the socket itself has been closed down. Revert to
1444 non-SSL handling. */
1446 if (error == SSL_ERROR_ZERO_RETURN)
1448 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1450 receive_getc = smtp_getc;
1451 receive_ungetc = smtp_ungetc;
1452 receive_feof = smtp_feof;
1453 receive_ferror = smtp_ferror;
1454 receive_smtp_buffered = smtp_buffered;
1456 SSL_free(server_ssl);
1460 tls_in.cipher = NULL;
1461 tls_in.peerdn = NULL;
1467 /* Handle genuine errors */
1469 else if (error == SSL_ERROR_SSL)
1471 ERR_error_string(ERR_get_error(), ssl_errstring);
1472 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1477 else if (error != SSL_ERROR_NONE)
1479 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1484 #ifndef DISABLE_DKIM
1485 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1487 ssl_xfer_buffer_hwm = inbytes;
1488 ssl_xfer_buffer_lwm = 0;
1491 /* Something in the buffer; return next uschar */
1493 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1498 /*************************************************
1499 * Read bytes from TLS channel *
1500 *************************************************/
1507 Returns: the number of bytes read
1508 -1 after a failed read
1510 Only used by the client-side TLS.
1514 tls_read(BOOL is_server, uschar *buff, size_t len)
1516 SSL *ssl = is_server ? server_ssl : client_ssl;
1520 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1521 buff, (unsigned int)len);
1523 inbytes = SSL_read(ssl, CS buff, len);
1524 error = SSL_get_error(ssl, inbytes);
1526 if (error == SSL_ERROR_ZERO_RETURN)
1528 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1531 else if (error != SSL_ERROR_NONE)
1543 /*************************************************
1544 * Write bytes down TLS channel *
1545 *************************************************/
1549 is_server channel specifier
1553 Returns: the number of bytes after a successful write,
1554 -1 after a failed write
1556 Used by both server-side and client-side TLS.
1560 tls_write(BOOL is_server, const uschar *buff, size_t len)
1565 SSL *ssl = is_server ? server_ssl : client_ssl;
1567 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1570 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1571 outbytes = SSL_write(ssl, CS buff, left);
1572 error = SSL_get_error(ssl, outbytes);
1573 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1577 ERR_error_string(ERR_get_error(), ssl_errstring);
1578 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1581 case SSL_ERROR_NONE:
1586 case SSL_ERROR_ZERO_RETURN:
1587 log_write(0, LOG_MAIN, "SSL channel closed on write");
1590 case SSL_ERROR_SYSCALL:
1591 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1592 sender_fullhost ? sender_fullhost : US"<unknown>",
1596 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1605 /*************************************************
1606 * Close down a TLS session *
1607 *************************************************/
1609 /* This is also called from within a delivery subprocess forked from the
1610 daemon, to shut down the TLS library, without actually doing a shutdown (which
1611 would tamper with the SSL session in the parent process).
1613 Arguments: TRUE if SSL_shutdown is to be called
1616 Used by both server-side and client-side TLS.
1620 tls_close(BOOL is_server, BOOL shutdown)
1622 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1623 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1625 if (*fdp < 0) return; /* TLS was not active */
1629 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1630 SSL_shutdown(*sslp);
1642 /*************************************************
1643 * Let tls_require_ciphers be checked at startup *
1644 *************************************************/
1646 /* The tls_require_ciphers option, if set, must be something which the
1649 Returns: NULL on success, or error message
1653 tls_validate_require_cipher(void)
1656 uschar *s, *expciphers, *err;
1658 /* this duplicates from tls_init(), we need a better "init just global
1659 state, for no specific purpose" singleton function of our own */
1661 SSL_load_error_strings();
1662 OpenSSL_add_ssl_algorithms();
1663 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1664 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1665 list of available digests. */
1666 EVP_add_digest(EVP_sha256());
1669 if (!(tls_require_ciphers && *tls_require_ciphers))
1672 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1673 return US"failed to expand tls_require_ciphers";
1675 if (!(expciphers && *expciphers))
1678 /* normalisation ripped from above */
1680 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1684 ctx = SSL_CTX_new(SSLv23_server_method());
1687 ERR_error_string(ERR_get_error(), ssl_errstring);
1688 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1692 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1694 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1696 ERR_error_string(ERR_get_error(), ssl_errstring);
1697 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
1708 /*************************************************
1709 * Report the library versions. *
1710 *************************************************/
1712 /* There have historically been some issues with binary compatibility in
1713 OpenSSL libraries; if Exim (like many other applications) is built against
1714 one version of OpenSSL but the run-time linker picks up another version,
1715 it can result in serious failures, including crashing with a SIGSEGV. So
1716 report the version found by the compiler and the run-time version.
1718 Arguments: a FILE* to print the results to
1723 tls_version_report(FILE *f)
1725 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
1727 OPENSSL_VERSION_TEXT,
1728 SSLeay_version(SSLEAY_VERSION));
1734 /*************************************************
1735 * Random number generation *
1736 *************************************************/
1738 /* Pseudo-random number generation. The result is not expected to be
1739 cryptographically strong but not so weak that someone will shoot themselves
1740 in the foot using it as a nonce in input in some email header scheme or
1741 whatever weirdness they'll twist this into. The result should handle fork()
1742 and avoid repeating sequences. OpenSSL handles that for us.
1746 Returns a random number in range [0, max-1]
1750 vaguely_random_number(int max)
1755 uschar smallbuf[sizeof(r)];
1760 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
1764 gettimeofday(&r.tv, NULL);
1767 RAND_seed((uschar *)(&r), sizeof(r));
1769 /* We're after pseudo-random, not random; if we still don't have enough data
1770 in the internal PRNG then our options are limited. We could sleep and hope
1771 for entropy to come along (prayer technique) but if the system is so depleted
1772 in the first place then something is likely to just keep taking it. Instead,
1773 we'll just take whatever little bit of pseudo-random we can still manage to
1776 needed_len = sizeof(r);
1777 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1778 asked for a number less than 10. */
1779 for (r = max, i = 0; r; ++i)
1785 /* We do not care if crypto-strong */
1786 i = RAND_pseudo_bytes(smallbuf, needed_len);
1790 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
1791 return vaguely_random_number_fallback(max);
1795 for (p = smallbuf; needed_len; --needed_len, ++p)
1801 /* We don't particularly care about weighted results; if someone wants
1802 smooth distribution and cares enough then they should submit a patch then. */
1809 /*************************************************
1810 * OpenSSL option parse *
1811 *************************************************/
1813 /* Parse one option for tls_openssl_options_parse below
1816 name one option name
1817 value place to store a value for it
1818 Returns success or failure in parsing
1821 struct exim_openssl_option {
1825 /* We could use a macro to expand, but we need the ifdef and not all the
1826 options document which version they were introduced in. Policylet: include
1827 all options unless explicitly for DTLS, let the administrator choose which
1830 This list is current as of:
1832 static struct exim_openssl_option exim_openssl_options[] = {
1833 /* KEEP SORTED ALPHABETICALLY! */
1835 { US"all", SSL_OP_ALL },
1837 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
1838 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
1840 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
1841 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
1843 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
1844 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
1846 #ifdef SSL_OP_EPHEMERAL_RSA
1847 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
1849 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
1850 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
1852 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
1853 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
1855 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
1856 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
1858 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
1859 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
1861 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
1862 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
1864 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
1865 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
1867 #ifdef SSL_OP_NO_COMPRESSION
1868 { US"no_compression", SSL_OP_NO_COMPRESSION },
1870 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
1871 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
1873 #ifdef SSL_OP_NO_SSLv2
1874 { US"no_sslv2", SSL_OP_NO_SSLv2 },
1876 #ifdef SSL_OP_NO_SSLv3
1877 { US"no_sslv3", SSL_OP_NO_SSLv3 },
1879 #ifdef SSL_OP_NO_TICKET
1880 { US"no_ticket", SSL_OP_NO_TICKET },
1882 #ifdef SSL_OP_NO_TLSv1
1883 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
1885 #ifdef SSL_OP_NO_TLSv1_1
1886 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
1887 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
1888 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
1890 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
1893 #ifdef SSL_OP_NO_TLSv1_2
1894 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
1896 #ifdef SSL_OP_SINGLE_DH_USE
1897 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
1899 #ifdef SSL_OP_SINGLE_ECDH_USE
1900 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
1902 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
1903 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
1905 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
1906 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
1908 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
1909 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
1911 #ifdef SSL_OP_TLS_D5_BUG
1912 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
1914 #ifdef SSL_OP_TLS_ROLLBACK_BUG
1915 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
1918 static int exim_openssl_options_size =
1919 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
1923 tls_openssl_one_option_parse(uschar *name, long *value)
1926 int last = exim_openssl_options_size;
1927 while (last > first)
1929 int middle = (first + last)/2;
1930 int c = Ustrcmp(name, exim_openssl_options[middle].name);
1933 *value = exim_openssl_options[middle].value;
1947 /*************************************************
1948 * OpenSSL option parsing logic *
1949 *************************************************/
1951 /* OpenSSL has a number of compatibility options which an administrator might
1952 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
1953 we look like log_selector.
1956 option_spec the administrator-supplied string of options
1957 results ptr to long storage for the options bitmap
1958 Returns success or failure
1962 tls_openssl_options_parse(uschar *option_spec, long *results)
1967 BOOL adding, item_parsed;
1970 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
1971 * from default because it increases BEAST susceptibility. */
1972 #ifdef SSL_OP_NO_SSLv2
1973 result |= SSL_OP_NO_SSLv2;
1976 if (option_spec == NULL)
1982 for (s=option_spec; *s != '\0'; /**/)
1984 while (isspace(*s)) ++s;
1987 if (*s != '+' && *s != '-')
1989 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
1990 "+ or - expected but found \"%s\"\n", s);
1993 adding = *s++ == '+';
1994 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
1997 item_parsed = tls_openssl_one_option_parse(s, &item);
2000 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
2003 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
2004 adding ? "adding" : "removing", result, item, s);
2017 /* End of tls-openssl.c */