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 static SSL_CTX *client_ctx = NULL;
50 static SSL_CTX *server_ctx = NULL;
51 static SSL *client_ssl = NULL;
52 static SSL *server_ssl = NULL;
54 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
55 static SSL_CTX *client_sni = NULL;
56 static SSL_CTX *server_sni = NULL;
59 static char ssl_errstring[256];
61 static int ssl_session_timeout = 200;
62 static BOOL client_verify_optional = FALSE;
63 static BOOL server_verify_optional = FALSE;
65 static BOOL reexpand_tls_files_for_sni = FALSE;
68 typedef struct tls_ext_ctx_cb {
71 #ifdef EXPERIMENTAL_OCSP
73 uschar *ocsp_file_expanded;
74 OCSP_RESPONSE *ocsp_response;
77 /* these are cached from first expand */
78 uschar *server_cipher_list;
79 /* only passed down to tls_error: */
83 /* should figure out a cleanup of API to handle state preserved per
84 implementation, for various reasons, which can be void * in the APIs.
85 For now, we hack around it. */
86 tls_ext_ctx_cb *client_static_cbinfo = NULL;
87 tls_ext_ctx_cb *server_static_cbinfo = NULL;
90 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, BOOL client);
93 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
94 static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
96 #ifdef EXPERIMENTAL_OCSP
97 static int tls_stapling_cb(SSL *s, void *arg);
101 /*************************************************
103 *************************************************/
105 /* Called from lots of places when errors occur before actually starting to do
106 the TLS handshake, that is, while the session is still in clear. Always returns
107 DEFER for a server and FAIL for a client so that most calls can use "return
108 tls_error(...)" to do this processing and then give an appropriate return. A
109 single function is used for both server and client, because it is called from
110 some shared functions.
113 prefix text to include in the logged error
114 host NULL if setting up a server;
115 the connected host if setting up a client
116 msg error message or NULL if we should ask OpenSSL
118 Returns: OK/DEFER/FAIL
122 tls_error(uschar *prefix, host_item *host, uschar *msg)
126 ERR_error_string(ERR_get_error(), ssl_errstring);
127 msg = (uschar *)ssl_errstring;
132 uschar *conn_info = smtp_get_connection_info();
133 if (Ustrncmp(conn_info, US"SMTP ", 5) == 0)
135 log_write(0, LOG_MAIN, "TLS error on %s (%s): %s",
136 conn_info, prefix, msg);
141 log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s",
142 host->name, host->address, prefix, msg);
149 /*************************************************
150 * Callback to generate RSA key *
151 *************************************************/
159 Returns: pointer to generated key
163 rsa_callback(SSL *s, int export, int keylength)
166 export = export; /* Shut picky compilers up */
167 DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength);
168 rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL);
171 ERR_error_string(ERR_get_error(), ssl_errstring);
172 log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s",
182 /*************************************************
183 * Callback for verification *
184 *************************************************/
186 /* The SSL library does certificate verification if set up to do so. This
187 callback has the current yes/no state is in "state". If verification succeeded,
188 we set up the tls_peerdn string. If verification failed, what happens depends
189 on whether the client is required to present a verifiable certificate or not.
191 If verification is optional, we change the state to yes, but still log the
192 verification error. For some reason (it really would help to have proper
193 documentation of OpenSSL), this callback function then gets called again, this
194 time with state = 1. In fact, that's useful, because we can set up the peerdn
195 value, but we must take care not to set the private verified flag on the second
198 Note: this function is not called if the client fails to present a certificate
199 when asked. We get here only if a certificate has been received. Handling of
200 optional verification for this case is done when requesting SSL to verify, by
201 setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case.
204 state current yes/no state as 1/0
205 x509ctx certificate information.
206 client TRUE for client startup, FALSE for server startup
208 Returns: 1 if verified, 0 if not
212 verify_callback(int state, X509_STORE_CTX *x509ctx, BOOL client)
214 static uschar txt[256];
222 calledp= &client_verify_callback_called;
223 optionalp= &client_verify_optional;
228 calledp= &server_verify_callback_called;
229 optionalp= &server_verify_optional;
232 X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert),
233 CS txt, sizeof(txt));
237 log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s",
238 x509ctx->error_depth,
239 X509_verify_cert_error_string(x509ctx->error),
241 tlsp->certificate_verified = FALSE;
243 if (!*optionalp) return 0; /* reject */
244 DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in "
245 "tls_try_verify_hosts)\n");
246 return 1; /* accept */
249 if (x509ctx->error_depth != 0)
251 DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n",
252 x509ctx->error_depth, txt);
256 DEBUG(D_tls) debug_printf("SSL%s peer: %s\n",
257 *calledp ? "" : " authenticated", txt);
261 if (!*calledp) tlsp->certificate_verified = TRUE;
264 return 1; /* accept */
268 verify_callback_client(int state, X509_STORE_CTX *x509ctx)
270 return verify_callback(state, x509ctx, TRUE);
274 verify_callback_server(int state, X509_STORE_CTX *x509ctx)
276 return verify_callback(state, x509ctx, FALSE);
281 /*************************************************
282 * Information callback *
283 *************************************************/
285 /* The SSL library functions call this from time to time to indicate what they
286 are doing. We copy the string to the debugging output when TLS debugging has
298 info_callback(SSL *s, int where, int ret)
302 DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s));
307 /*************************************************
308 * Initialize for DH *
309 *************************************************/
311 /* If dhparam is set, expand it, and load up the parameters for DH encryption.
314 dhparam DH parameter file or fixed parameter identity string
315 host connected host, if client; NULL if server
317 Returns: TRUE if OK (nothing to set up, or setup worked)
321 init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
328 if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
331 if (dhexpanded == NULL || *dhexpanded == '\0')
333 bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
335 else if (dhexpanded[0] == '/')
337 bio = BIO_new_file(CS dhexpanded, "r");
340 tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
341 host, US strerror(errno));
347 if (Ustrcmp(dhexpanded, "none") == 0)
349 DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
353 pem = std_dh_prime_named(dhexpanded);
356 tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
357 host, US strerror(errno));
360 bio = BIO_new_mem_buf(CS pem, -1);
363 dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
367 tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
372 /* Even if it is larger, we silently return success rather than cause things
373 * to fail out, so that a too-large DH will not knock out all TLS; it's a
374 * debatable choice. */
375 if ((8*DH_size(dh)) > tls_dh_max_bits)
378 debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
379 8*DH_size(dh), tls_dh_max_bits);
383 SSL_CTX_set_tmp_dh(sctx, dh);
385 debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
386 dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
398 #ifdef EXPERIMENTAL_OCSP
399 /*************************************************
400 * Load OCSP information into state *
401 *************************************************/
403 /* Called to load the OCSP response from the given file into memory, once
404 caller has determined this is needed. Checks validity. Debugs a message
407 ASSUMES: single response, for single cert.
410 sctx the SSL_CTX* to update
411 cbinfo various parts of session state
412 expanded the filename putatively holding an OCSP response
417 ocsp_load_response(SSL_CTX *sctx,
418 tls_ext_ctx_cb *cbinfo,
419 const uschar *expanded)
423 OCSP_BASICRESP *basic_response;
424 OCSP_SINGLERESP *single_response;
425 ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;
427 unsigned long verify_flags;
428 int status, reason, i;
430 cbinfo->ocsp_file_expanded = string_copy(expanded);
431 if (cbinfo->ocsp_response)
433 OCSP_RESPONSE_free(cbinfo->ocsp_response);
434 cbinfo->ocsp_response = NULL;
437 bio = BIO_new_file(CS cbinfo->ocsp_file_expanded, "rb");
440 DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n",
441 cbinfo->ocsp_file_expanded);
445 resp = d2i_OCSP_RESPONSE_bio(bio, NULL);
449 DEBUG(D_tls) debug_printf("Error reading OCSP response.\n");
453 status = OCSP_response_status(resp);
454 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
456 DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n",
457 OCSP_response_status_str(status), status);
461 basic_response = OCSP_response_get1_basic(resp);
465 debug_printf("OCSP response parse error: unable to extract basic response.\n");
469 store = SSL_CTX_get_cert_store(sctx);
470 verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */
472 /* May need to expose ability to adjust those flags?
473 OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT
474 OCSP_TRUSTOTHER OCSP_NOINTERN */
476 i = OCSP_basic_verify(basic_response, NULL, store, verify_flags);
480 ERR_error_string(ERR_get_error(), ssl_errstring);
481 debug_printf("OCSP response verify failure: %s\n", US ssl_errstring);
486 /* Here's the simplifying assumption: there's only one response, for the
487 one certificate we use, and nothing for anything else in a chain. If this
488 proves false, we need to extract a cert id from our issued cert
489 (tls_certificate) and use that for OCSP_resp_find_status() (which finds the
490 right cert in the stack and then calls OCSP_single_get0_status()).
492 I'm hoping to avoid reworking a bunch more of how we handle state here. */
493 single_response = OCSP_resp_get0(basic_response, 0);
494 if (!single_response)
497 debug_printf("Unable to get first response from OCSP basic response.\n");
501 status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd);
502 /* how does this status differ from the one above? */
503 if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL)
505 DEBUG(D_tls) debug_printf("OCSP response not valid (take 2): %s (%d)\n",
506 OCSP_response_status_str(status), status);
510 if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE))
512 DEBUG(D_tls) debug_printf("OCSP status invalid times.\n");
516 cbinfo->ocsp_response = resp;
523 /*************************************************
524 * Expand key and cert file specs *
525 *************************************************/
527 /* Called once during tls_init and possibly againt during TLS setup, for a
528 new context, if Server Name Indication was used and tls_sni was seen in
529 the certificate string.
532 sctx the SSL_CTX* to update
533 cbinfo various parts of session state
535 Returns: OK/DEFER/FAIL
539 tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo)
543 if (cbinfo->certificate == NULL)
546 if (Ustrstr(cbinfo->certificate, US"tls_sni") ||
547 Ustrstr(cbinfo->certificate, US"tls_in_sni") ||
548 Ustrstr(cbinfo->certificate, US"tls_out_sni")
550 reexpand_tls_files_for_sni = TRUE;
552 if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded))
555 if (expanded != NULL)
557 DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded);
558 if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded))
559 return tls_error(string_sprintf(
560 "SSL_CTX_use_certificate_chain_file file=%s", expanded),
564 if (cbinfo->privatekey != NULL &&
565 !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded))
568 /* If expansion was forced to fail, key_expanded will be NULL. If the result
569 of the expansion is an empty string, ignore it also, and assume the private
570 key is in the same file as the certificate. */
572 if (expanded != NULL && *expanded != 0)
574 DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded);
575 if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM))
576 return tls_error(string_sprintf(
577 "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL);
580 #ifdef EXPERIMENTAL_OCSP
581 if (cbinfo->ocsp_file != NULL)
583 if (!expand_check(cbinfo->ocsp_file, US"tls_ocsp_file", &expanded))
586 if (expanded != NULL && *expanded != 0)
588 DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded);
589 if (cbinfo->ocsp_file_expanded &&
590 (Ustrcmp(expanded, cbinfo->ocsp_file_expanded) == 0))
593 debug_printf("tls_ocsp_file value unchanged, using existing values.\n");
595 ocsp_load_response(sctx, cbinfo, expanded);
607 /*************************************************
608 * Callback to handle SNI *
609 *************************************************/
611 /* Called when acting as server during the TLS session setup if a Server Name
612 Indication extension was sent by the client.
614 API documentation is OpenSSL s_server.c implementation.
617 s SSL* of the current session
618 ad unknown (part of OpenSSL API) (unused)
619 arg Callback of "our" registered data
621 Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
624 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
626 tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
628 const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
629 tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
631 int old_pool = store_pool;
634 return SSL_TLSEXT_ERR_OK;
636 DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername,
637 reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)");
639 /* Make the extension value available for expansion */
640 store_pool = POOL_PERM;
641 tls_in.sni = string_copy(US servername);
642 store_pool = old_pool;
644 if (!reexpand_tls_files_for_sni)
645 return SSL_TLSEXT_ERR_OK;
647 /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually;
648 not confident that memcpy wouldn't break some internal reference counting.
649 Especially since there's a references struct member, which would be off. */
651 server_sni = SSL_CTX_new(SSLv23_server_method());
654 ERR_error_string(ERR_get_error(), ssl_errstring);
655 DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring);
656 return SSL_TLSEXT_ERR_NOACK;
659 /* Not sure how many of these are actually needed, since SSL object
660 already exists. Might even need this selfsame callback, for reneg? */
662 SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx));
663 SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx));
664 SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx));
665 SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx));
666 SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb);
667 SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo);
668 if (cbinfo->server_cipher_list)
669 SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list);
670 #ifdef EXPERIMENTAL_OCSP
671 if (cbinfo->ocsp_file)
673 SSL_CTX_set_tlsext_status_cb(server_sni, tls_stapling_cb);
674 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
678 rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, FALSE);
679 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
681 /* do this after setup_certs, because this can require the certs for verifying
683 rc = tls_expand_session_files(server_sni, cbinfo);
684 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
686 rc = init_dh(server_sni, cbinfo->dhparam, NULL);
687 if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
689 DEBUG(D_tls) debug_printf("Switching SSL context.\n");
690 SSL_set_SSL_CTX(s, server_sni);
692 return SSL_TLSEXT_ERR_OK;
694 #endif /* EXIM_HAVE_OPENSSL_TLSEXT */
699 #ifdef EXPERIMENTAL_OCSP
700 /*************************************************
701 * Callback to handle OCSP Stapling *
702 *************************************************/
704 /* Called when acting as server during the TLS session setup if the client
705 requests OCSP information with a Certificate Status Request.
707 Documentation via openssl s_server.c and the Apache patch from the OpenSSL
713 tls_stapling_cb(SSL *s, void *arg)
715 const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg;
716 uschar *response_der;
717 int response_der_len;
719 DEBUG(D_tls) debug_printf("Received TLS status request (OCSP stapling); %s response.\n",
720 cbinfo->ocsp_response ? "have" : "lack");
721 if (!cbinfo->ocsp_response)
722 return SSL_TLSEXT_ERR_NOACK;
725 response_der_len = i2d_OCSP_RESPONSE(cbinfo->ocsp_response, &response_der);
726 if (response_der_len <= 0)
727 return SSL_TLSEXT_ERR_NOACK;
729 SSL_set_tlsext_status_ocsp_resp(ssl, response_der, response_der_len);
730 return SSL_TLSEXT_ERR_OK;
733 #endif /* EXPERIMENTAL_OCSP */
738 /*************************************************
739 * Initialize for TLS *
740 *************************************************/
742 /* Called from both server and client code, to do preliminary initialization of
746 host connected host, if client; NULL if server
747 dhparam DH parameter file
748 certificate certificate file
749 privatekey private key
750 addr address if client; NULL if server (for some randomness)
752 Returns: OK/DEFER/FAIL
756 tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate,
758 #ifdef EXPERIMENTAL_OCSP
761 address_item *addr, tls_ext_ctx_cb ** cbp)
766 tls_ext_ctx_cb *cbinfo;
768 cbinfo = store_malloc(sizeof(tls_ext_ctx_cb));
769 cbinfo->certificate = certificate;
770 cbinfo->privatekey = privatekey;
771 #ifdef EXPERIMENTAL_OCSP
772 cbinfo->ocsp_file = ocsp_file;
774 cbinfo->dhparam = dhparam;
777 SSL_load_error_strings(); /* basic set up */
778 OpenSSL_add_ssl_algorithms();
780 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
781 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
782 list of available digests. */
783 EVP_add_digest(EVP_sha256());
787 The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
788 negotiation in the different methods; as far as I can tell, the only
789 *_{server,client}_method which allows negotiation is SSLv23, which exists even
790 when OpenSSL is built without SSLv2 support.
791 By disabling with openssl_options, we can let admins re-enable with the
794 *ctxp = SSL_CTX_new((host == NULL)?
795 SSLv23_server_method() : SSLv23_client_method());
797 if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL);
799 /* It turns out that we need to seed the random number generator this early in
800 order to get the full complement of ciphers to work. It took me roughly a day
801 of work to discover this by experiment.
803 On systems that have /dev/urandom, SSL may automatically seed itself from
804 there. Otherwise, we have to make something up as best we can. Double check
810 gettimeofday(&r.tv, NULL);
813 RAND_seed((uschar *)(&r), sizeof(r));
814 RAND_seed((uschar *)big_buffer, big_buffer_size);
815 if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr));
818 return tls_error(US"RAND_status", host,
819 US"unable to seed random number generator");
822 /* Set up the information callback, which outputs if debugging is at a suitable
825 SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback);
827 /* Automatically re-try reads/writes after renegotiation. */
828 (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY);
830 /* Apply administrator-supplied work-arounds.
831 Historically we applied just one requested option,
832 SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we
833 moved to an administrator-controlled list of options to specify and
834 grandfathered in the first one as the default value for "openssl_options".
836 No OpenSSL version number checks: the options we accept depend upon the
837 availability of the option value macros from OpenSSL. */
839 okay = tls_openssl_options_parse(openssl_options, &init_options);
841 return tls_error(US"openssl_options parsing failed", host, NULL);
845 DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options);
846 if (!(SSL_CTX_set_options(*ctxp, init_options)))
847 return tls_error(string_sprintf(
848 "SSL_CTX_set_option(%#lx)", init_options), host, NULL);
851 DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
853 /* Initialize with DH parameters if supplied */
855 if (!init_dh(*ctxp, dhparam, host)) return DEFER;
857 /* Set up certificate and key (and perhaps OCSP info) */
859 rc = tls_expand_session_files(*ctxp, cbinfo);
860 if (rc != OK) return rc;
862 /* If we need to handle SNI, do so */
863 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
866 #ifdef EXPERIMENTAL_OCSP
867 /* We check ocsp_file, not ocsp_response, because we care about if
868 the option exists, not what the current expansion might be, as SNI might
869 change the certificate and OCSP file in use between now and the time the
870 callback is invoked. */
871 if (cbinfo->ocsp_file)
873 SSL_CTX_set_tlsext_status_cb(ctx, tls_stapling_cb);
874 SSL_CTX_set_tlsext_status_arg(ctx, cbinfo);
877 /* We always do this, so that $tls_sni is available even if not used in
879 SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb);
880 SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo);
884 /* Set up the RSA callback */
886 SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback);
888 /* Finally, set the timeout, and we are done */
890 SSL_CTX_set_timeout(*ctxp, ssl_session_timeout);
891 DEBUG(D_tls) debug_printf("Initialized TLS\n");
901 /*************************************************
902 * Get name of cipher in use *
903 *************************************************/
906 Argument: pointer to an SSL structure for the connection
907 buffer to use for answer
909 pointer to number of bits for cipher
914 construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits)
916 /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't
917 yet reflect that. It should be a safe change anyway, even 0.9.8 versions have
918 the accessor functions use const in the prototype. */
922 switch (ssl->session->ssl_version)
936 #ifdef TLS1_1_VERSION
942 #ifdef TLS1_2_VERSION
952 c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl);
953 SSL_CIPHER_get_bits(c, bits);
955 string_format(cipherbuf, bsize, "%s:%s:%u", ver,
956 SSL_CIPHER_get_name(c), *bits);
958 DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf);
965 /*************************************************
966 * Set up for verifying certificates *
967 *************************************************/
969 /* Called by both client and server startup
972 sctx SSL_CTX* to initialise
973 certs certs file or NULL
975 host NULL in a server; the remote host in a client
976 optional TRUE if called from a server for a host in tls_try_verify_hosts;
977 otherwise passed as FALSE
978 client TRUE if called for client startup, FALSE for server startup
980 Returns: OK/DEFER/FAIL
984 setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, BOOL client)
986 uschar *expcerts, *expcrl;
988 if (!expand_check(certs, US"tls_verify_certificates", &expcerts))
991 if (expcerts != NULL)
994 if (!SSL_CTX_set_default_verify_paths(sctx))
995 return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL);
997 if (Ustat(expcerts, &statbuf) < 0)
999 log_write(0, LOG_MAIN|LOG_PANIC,
1000 "failed to stat %s for certificates", expcerts);
1006 if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
1007 { file = NULL; dir = expcerts; }
1009 { file = expcerts; dir = NULL; }
1011 /* If a certificate file is empty, the next function fails with an
1012 unhelpful error message. If we skip it, we get the correct behaviour (no
1013 certificates are recognized, but the error message is still misleading (it
1014 says no certificate was supplied.) But this is better. */
1016 if ((file == NULL || statbuf.st_size > 0) &&
1017 !SSL_CTX_load_verify_locations(sctx, CS file, CS dir))
1018 return tls_error(US"SSL_CTX_load_verify_locations", host, NULL);
1022 SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file));
1026 /* Handle a certificate revocation list. */
1028 #if OPENSSL_VERSION_NUMBER > 0x00907000L
1030 /* This bit of code is now the version supplied by Lars Mainka. (I have
1031 * merely reformatted it into the Exim code style.)
1033 * "From here I changed the code to add support for multiple crl's
1034 * in pem format in one file or to support hashed directory entries in
1035 * pem format instead of a file. This method now uses the library function
1036 * X509_STORE_load_locations to add the CRL location to the SSL context.
1037 * OpenSSL will then handle the verify against CA certs and CRLs by
1038 * itself in the verify callback." */
1040 if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER;
1041 if (expcrl != NULL && *expcrl != 0)
1043 struct stat statbufcrl;
1044 if (Ustat(expcrl, &statbufcrl) < 0)
1046 log_write(0, LOG_MAIN|LOG_PANIC,
1047 "failed to stat %s for certificates revocation lists", expcrl);
1052 /* is it a file or directory? */
1054 X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx);
1055 if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR)
1059 DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir);
1065 DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file);
1067 if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0)
1068 return tls_error(US"X509_STORE_load_locations", host, NULL);
1070 /* setting the flags to check against the complete crl chain */
1072 X509_STORE_set_flags(cvstore,
1073 X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
1077 #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */
1079 /* If verification is optional, don't fail if no certificate */
1081 SSL_CTX_set_verify(sctx,
1082 SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT),
1083 client ? verify_callback_client : verify_callback_server);
1091 /*************************************************
1092 * Start a TLS session in a server *
1093 *************************************************/
1095 /* This is called when Exim is running as a server, after having received
1096 the STARTTLS command. It must respond to that command, and then negotiate
1100 require_ciphers allowed ciphers
1102 Returns: OK on success
1103 DEFER for errors before the start of the negotiation
1104 FAIL for errors during the negotation; the server can't
1109 tls_server_start(const uschar *require_ciphers)
1113 tls_ext_ctx_cb *cbinfo;
1114 static uschar cipherbuf[256];
1116 /* Check for previous activation */
1118 if (tls_in.active >= 0)
1120 tls_error(US"STARTTLS received after TLS started", NULL, US"");
1121 smtp_printf("554 Already in TLS\r\n");
1125 /* Initialize the SSL library. If it fails, it will already have logged
1128 rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey,
1129 #ifdef EXPERIMENTAL_OCSP
1132 NULL, &server_static_cbinfo);
1133 if (rc != OK) return rc;
1134 cbinfo = server_static_cbinfo;
1136 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1139 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1140 were historically separated by underscores. So that I can use either form in my
1141 tests, and also for general convenience, we turn underscores into hyphens here.
1144 if (expciphers != NULL)
1146 uschar *s = expciphers;
1147 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1148 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1149 if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers))
1150 return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL);
1151 cbinfo->server_cipher_list = expciphers;
1154 /* If this is a host for which certificate verification is mandatory or
1155 optional, set up appropriately. */
1157 tls_in.certificate_verified = FALSE;
1158 server_verify_callback_called = FALSE;
1160 if (verify_check_host(&tls_verify_hosts) == OK)
1162 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, FALSE, FALSE);
1163 if (rc != OK) return rc;
1164 server_verify_optional = FALSE;
1166 else if (verify_check_host(&tls_try_verify_hosts) == OK)
1168 rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, TRUE, FALSE);
1169 if (rc != OK) return rc;
1170 server_verify_optional = TRUE;
1173 /* Prepare for new connection */
1175 if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL);
1177 /* Warning: we used to SSL_clear(ssl) here, it was removed.
1179 * With the SSL_clear(), we get strange interoperability bugs with
1180 * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in
1181 * OpenSSL itself, as a clear should not lead to inability to follow protocols.
1183 * The SSL_clear() call is to let an existing SSL* be reused, typically after
1184 * session shutdown. In this case, we have a brand new object and there's no
1185 * obvious reason to immediately clear it. I'm guessing that this was
1186 * originally added because of incomplete initialisation which the clear fixed,
1187 * in some historic release.
1190 /* Set context and tell client to go ahead, except in the case of TLS startup
1191 on connection, where outputting anything now upsets the clients and tends to
1192 make them disconnect. We need to have an explicit fflush() here, to force out
1193 the response. Other smtp_printf() calls do not need it, because in non-TLS
1194 mode, the fflush() happens when smtp_getc() is called. */
1196 SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx));
1197 if (!tls_in.on_connect)
1199 smtp_printf("220 TLS go ahead\r\n");
1203 /* Now negotiate the TLS session. We put our own timer on it, since it seems
1204 that the OpenSSL library doesn't. */
1206 SSL_set_wfd(server_ssl, fileno(smtp_out));
1207 SSL_set_rfd(server_ssl, fileno(smtp_in));
1208 SSL_set_accept_state(server_ssl);
1210 DEBUG(D_tls) debug_printf("Calling SSL_accept\n");
1212 sigalrm_seen = FALSE;
1213 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1214 rc = SSL_accept(server_ssl);
1219 tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL);
1220 if (ERR_get_error() == 0)
1221 log_write(0, LOG_MAIN,
1222 "TLS client disconnected cleanly (rejected our certificate?)");
1226 DEBUG(D_tls) debug_printf("SSL_accept was successful\n");
1228 /* TLS has been set up. Adjust the input functions to read via TLS,
1229 and initialize things. */
1231 construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits);
1232 tls_in.cipher = cipherbuf;
1237 if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL)
1238 debug_printf("Shared ciphers: %s\n", buf);
1242 /* Only used by the server-side tls (tls_in), including tls_getc.
1243 Client-side (tls_out) reads (seem to?) go via
1244 smtp_read_response()/ip_recv().
1245 Hence no need to duplicate for _in and _out.
1247 ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size);
1248 ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0;
1249 ssl_xfer_eof = ssl_xfer_error = 0;
1251 receive_getc = tls_getc;
1252 receive_ungetc = tls_ungetc;
1253 receive_feof = tls_feof;
1254 receive_ferror = tls_ferror;
1255 receive_smtp_buffered = tls_smtp_buffered;
1257 tls_in.active = fileno(smtp_out);
1265 /*************************************************
1266 * Start a TLS session in a client *
1267 *************************************************/
1269 /* Called from the smtp transport after STARTTLS has been accepted.
1272 fd the fd of the connection
1273 host connected host (for messages)
1274 addr the first address
1275 dhparam DH parameter file
1276 certificate certificate file
1277 privatekey private key file
1278 sni TLS SNI to send to remote host
1279 verify_certs file for certificate verify
1280 crl file containing CRL
1281 require_ciphers list of allowed ciphers
1282 dh_min_bits minimum number of bits acceptable in server's DH prime
1284 timeout startup timeout
1286 Returns: OK on success
1287 FAIL otherwise - note that tls_error() will not give DEFER
1288 because this is not a server
1292 tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam,
1293 uschar *certificate, uschar *privatekey, uschar *sni,
1294 uschar *verify_certs, uschar *crl,
1295 uschar *require_ciphers, int dh_min_bits ARG_UNUSED, int timeout)
1297 static uschar txt[256];
1301 static uschar cipherbuf[256];
1303 rc = tls_init(&client_ctx, host, dhparam, certificate, privatekey,
1304 #ifdef EXPERIMENTAL_OCSP
1307 addr, &client_static_cbinfo);
1308 if (rc != OK) return rc;
1310 tls_out.certificate_verified = FALSE;
1311 client_verify_callback_called = FALSE;
1313 if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers))
1316 /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they
1317 are separated by underscores. So that I can use either form in my tests, and
1318 also for general convenience, we turn underscores into hyphens here. */
1320 if (expciphers != NULL)
1322 uschar *s = expciphers;
1323 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1324 DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers);
1325 if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers))
1326 return tls_error(US"SSL_CTX_set_cipher_list", host, NULL);
1329 rc = setup_certs(client_ctx, verify_certs, crl, host, FALSE, TRUE);
1330 if (rc != OK) return rc;
1332 if ((client_ssl = SSL_new(client_ctx)) == NULL) return tls_error(US"SSL_new", host, NULL);
1333 SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx));
1334 SSL_set_fd(client_ssl, fd);
1335 SSL_set_connect_state(client_ssl);
1339 if (!expand_check(sni, US"tls_sni", &tls_out.sni))
1341 if (tls_out.sni == NULL)
1343 DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n");
1345 else if (!Ustrlen(tls_out.sni))
1349 #ifdef EXIM_HAVE_OPENSSL_TLSEXT
1350 DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni);
1351 SSL_set_tlsext_host_name(client_ssl, tls_out.sni);
1354 debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
1360 /* There doesn't seem to be a built-in timeout on connection. */
1362 DEBUG(D_tls) debug_printf("Calling SSL_connect\n");
1363 sigalrm_seen = FALSE;
1365 rc = SSL_connect(client_ssl);
1369 return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL);
1371 DEBUG(D_tls) debug_printf("SSL_connect succeeded\n");
1373 /* Beware anonymous ciphers which lead to server_cert being NULL */
1374 server_cert = SSL_get_peer_certificate (client_ssl);
1377 tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert),
1378 CS txt, sizeof(txt));
1379 tls_out.peerdn = txt;
1382 tls_out.peerdn = NULL;
1384 construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits);
1385 tls_out.cipher = cipherbuf;
1387 tls_out.active = fd;
1395 /*************************************************
1396 * TLS version of getc *
1397 *************************************************/
1399 /* This gets the next byte from the TLS input buffer. If the buffer is empty,
1400 it refills the buffer via the SSL reading function.
1403 Returns: the next character or EOF
1405 Only used by the server-side TLS.
1411 if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm)
1416 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl,
1417 ssl_xfer_buffer, ssl_xfer_buffer_size);
1419 if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout);
1420 inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size);
1421 error = SSL_get_error(server_ssl, inbytes);
1424 /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been
1425 closed down, not that the socket itself has been closed down. Revert to
1426 non-SSL handling. */
1428 if (error == SSL_ERROR_ZERO_RETURN)
1430 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1432 receive_getc = smtp_getc;
1433 receive_ungetc = smtp_ungetc;
1434 receive_feof = smtp_feof;
1435 receive_ferror = smtp_ferror;
1436 receive_smtp_buffered = smtp_buffered;
1438 SSL_free(server_ssl);
1442 tls_in.cipher = NULL;
1443 tls_in.peerdn = NULL;
1449 /* Handle genuine errors */
1451 else if (error == SSL_ERROR_SSL)
1453 ERR_error_string(ERR_get_error(), ssl_errstring);
1454 log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring);
1459 else if (error != SSL_ERROR_NONE)
1461 DEBUG(D_tls) debug_printf("Got SSL error %d\n", error);
1466 #ifndef DISABLE_DKIM
1467 dkim_exim_verify_feed(ssl_xfer_buffer, inbytes);
1469 ssl_xfer_buffer_hwm = inbytes;
1470 ssl_xfer_buffer_lwm = 0;
1473 /* Something in the buffer; return next uschar */
1475 return ssl_xfer_buffer[ssl_xfer_buffer_lwm++];
1480 /*************************************************
1481 * Read bytes from TLS channel *
1482 *************************************************/
1489 Returns: the number of bytes read
1490 -1 after a failed read
1492 Only used by the client-side TLS.
1496 tls_read(BOOL is_server, uschar *buff, size_t len)
1498 SSL *ssl = is_server ? server_ssl : client_ssl;
1502 DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl,
1503 buff, (unsigned int)len);
1505 inbytes = SSL_read(ssl, CS buff, len);
1506 error = SSL_get_error(ssl, inbytes);
1508 if (error == SSL_ERROR_ZERO_RETURN)
1510 DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n");
1513 else if (error != SSL_ERROR_NONE)
1525 /*************************************************
1526 * Write bytes down TLS channel *
1527 *************************************************/
1531 is_server channel specifier
1535 Returns: the number of bytes after a successful write,
1536 -1 after a failed write
1538 Used by both server-side and client-side TLS.
1542 tls_write(BOOL is_server, const uschar *buff, size_t len)
1547 SSL *ssl = is_server ? server_ssl : client_ssl;
1549 DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left);
1552 DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left);
1553 outbytes = SSL_write(ssl, CS buff, left);
1554 error = SSL_get_error(ssl, outbytes);
1555 DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
1559 ERR_error_string(ERR_get_error(), ssl_errstring);
1560 log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
1563 case SSL_ERROR_NONE:
1568 case SSL_ERROR_ZERO_RETURN:
1569 log_write(0, LOG_MAIN, "SSL channel closed on write");
1572 case SSL_ERROR_SYSCALL:
1573 log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
1574 sender_fullhost ? sender_fullhost : US"<unknown>",
1578 log_write(0, LOG_MAIN, "SSL_write error %d", error);
1587 /*************************************************
1588 * Close down a TLS session *
1589 *************************************************/
1591 /* This is also called from within a delivery subprocess forked from the
1592 daemon, to shut down the TLS library, without actually doing a shutdown (which
1593 would tamper with the SSL session in the parent process).
1595 Arguments: TRUE if SSL_shutdown is to be called
1598 Used by both server-side and client-side TLS.
1602 tls_close(BOOL is_server, BOOL shutdown)
1604 SSL **sslp = is_server ? &server_ssl : &client_ssl;
1605 int *fdp = is_server ? &tls_in.active : &tls_out.active;
1607 if (*fdp < 0) return; /* TLS was not active */
1611 DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n");
1612 SSL_shutdown(*sslp);
1624 /*************************************************
1625 * Let tls_require_ciphers be checked at startup *
1626 *************************************************/
1628 /* The tls_require_ciphers option, if set, must be something which the
1631 Returns: NULL on success, or error message
1635 tls_validate_require_cipher(void)
1638 uschar *s, *expciphers, *err;
1640 /* this duplicates from tls_init(), we need a better "init just global
1641 state, for no specific purpose" singleton function of our own */
1643 SSL_load_error_strings();
1644 OpenSSL_add_ssl_algorithms();
1645 #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
1646 /* SHA256 is becoming ever more popular. This makes sure it gets added to the
1647 list of available digests. */
1648 EVP_add_digest(EVP_sha256());
1651 if (!(tls_require_ciphers && *tls_require_ciphers))
1654 if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
1655 return US"failed to expand tls_require_ciphers";
1657 if (!(expciphers && *expciphers))
1660 /* normalisation ripped from above */
1662 while (*s != 0) { if (*s == '_') *s = '-'; s++; }
1666 ctx = SSL_CTX_new(SSLv23_server_method());
1669 ERR_error_string(ERR_get_error(), ssl_errstring);
1670 return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
1674 debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
1676 if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
1678 ERR_error_string(ERR_get_error(), ssl_errstring);
1679 err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
1690 /*************************************************
1691 * Report the library versions. *
1692 *************************************************/
1694 /* There have historically been some issues with binary compatibility in
1695 OpenSSL libraries; if Exim (like many other applications) is built against
1696 one version of OpenSSL but the run-time linker picks up another version,
1697 it can result in serious failures, including crashing with a SIGSEGV. So
1698 report the version found by the compiler and the run-time version.
1700 Arguments: a FILE* to print the results to
1705 tls_version_report(FILE *f)
1707 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
1709 OPENSSL_VERSION_TEXT,
1710 SSLeay_version(SSLEAY_VERSION));
1716 /*************************************************
1717 * Random number generation *
1718 *************************************************/
1720 /* Pseudo-random number generation. The result is not expected to be
1721 cryptographically strong but not so weak that someone will shoot themselves
1722 in the foot using it as a nonce in input in some email header scheme or
1723 whatever weirdness they'll twist this into. The result should handle fork()
1724 and avoid repeating sequences. OpenSSL handles that for us.
1728 Returns a random number in range [0, max-1]
1732 vaguely_random_number(int max)
1737 uschar smallbuf[sizeof(r)];
1742 /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */
1746 gettimeofday(&r.tv, NULL);
1749 RAND_seed((uschar *)(&r), sizeof(r));
1751 /* We're after pseudo-random, not random; if we still don't have enough data
1752 in the internal PRNG then our options are limited. We could sleep and hope
1753 for entropy to come along (prayer technique) but if the system is so depleted
1754 in the first place then something is likely to just keep taking it. Instead,
1755 we'll just take whatever little bit of pseudo-random we can still manage to
1758 needed_len = sizeof(r);
1759 /* Don't take 8 times more entropy than needed if int is 8 octets and we were
1760 asked for a number less than 10. */
1761 for (r = max, i = 0; r; ++i)
1767 /* We do not care if crypto-strong */
1768 i = RAND_pseudo_bytes(smallbuf, needed_len);
1772 debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n");
1773 return vaguely_random_number_fallback(max);
1777 for (p = smallbuf; needed_len; --needed_len, ++p)
1783 /* We don't particularly care about weighted results; if someone wants
1784 smooth distribution and cares enough then they should submit a patch then. */
1791 /*************************************************
1792 * OpenSSL option parse *
1793 *************************************************/
1795 /* Parse one option for tls_openssl_options_parse below
1798 name one option name
1799 value place to store a value for it
1800 Returns success or failure in parsing
1803 struct exim_openssl_option {
1807 /* We could use a macro to expand, but we need the ifdef and not all the
1808 options document which version they were introduced in. Policylet: include
1809 all options unless explicitly for DTLS, let the administrator choose which
1812 This list is current as of:
1814 static struct exim_openssl_option exim_openssl_options[] = {
1815 /* KEEP SORTED ALPHABETICALLY! */
1817 { US"all", SSL_OP_ALL },
1819 #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
1820 { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION },
1822 #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
1823 { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE },
1825 #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
1826 { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS },
1828 #ifdef SSL_OP_EPHEMERAL_RSA
1829 { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA },
1831 #ifdef SSL_OP_LEGACY_SERVER_CONNECT
1832 { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT },
1834 #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER
1835 { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER },
1837 #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG
1838 { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG },
1840 #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING
1841 { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING },
1843 #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG
1844 { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG },
1846 #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
1847 { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG },
1849 #ifdef SSL_OP_NO_COMPRESSION
1850 { US"no_compression", SSL_OP_NO_COMPRESSION },
1852 #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
1853 { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION },
1855 #ifdef SSL_OP_NO_SSLv2
1856 { US"no_sslv2", SSL_OP_NO_SSLv2 },
1858 #ifdef SSL_OP_NO_SSLv3
1859 { US"no_sslv3", SSL_OP_NO_SSLv3 },
1861 #ifdef SSL_OP_NO_TICKET
1862 { US"no_ticket", SSL_OP_NO_TICKET },
1864 #ifdef SSL_OP_NO_TLSv1
1865 { US"no_tlsv1", SSL_OP_NO_TLSv1 },
1867 #ifdef SSL_OP_NO_TLSv1_1
1868 #if SSL_OP_NO_TLSv1_1 == 0x00000400L
1869 /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */
1870 #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring
1872 { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 },
1875 #ifdef SSL_OP_NO_TLSv1_2
1876 { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 },
1878 #ifdef SSL_OP_SINGLE_DH_USE
1879 { US"single_dh_use", SSL_OP_SINGLE_DH_USE },
1881 #ifdef SSL_OP_SINGLE_ECDH_USE
1882 { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE },
1884 #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG
1885 { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG },
1887 #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG
1888 { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG },
1890 #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG
1891 { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG },
1893 #ifdef SSL_OP_TLS_D5_BUG
1894 { US"tls_d5_bug", SSL_OP_TLS_D5_BUG },
1896 #ifdef SSL_OP_TLS_ROLLBACK_BUG
1897 { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG },
1900 static int exim_openssl_options_size =
1901 sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option);
1905 tls_openssl_one_option_parse(uschar *name, long *value)
1908 int last = exim_openssl_options_size;
1909 while (last > first)
1911 int middle = (first + last)/2;
1912 int c = Ustrcmp(name, exim_openssl_options[middle].name);
1915 *value = exim_openssl_options[middle].value;
1929 /*************************************************
1930 * OpenSSL option parsing logic *
1931 *************************************************/
1933 /* OpenSSL has a number of compatibility options which an administrator might
1934 reasonably wish to set. Interpret a list similarly to decode_bits(), so that
1935 we look like log_selector.
1938 option_spec the administrator-supplied string of options
1939 results ptr to long storage for the options bitmap
1940 Returns success or failure
1944 tls_openssl_options_parse(uschar *option_spec, long *results)
1949 BOOL adding, item_parsed;
1952 /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
1953 * from default because it increases BEAST susceptibility. */
1954 #ifdef SSL_OP_NO_SSLv2
1955 result |= SSL_OP_NO_SSLv2;
1958 if (option_spec == NULL)
1964 for (s=option_spec; *s != '\0'; /**/)
1966 while (isspace(*s)) ++s;
1969 if (*s != '+' && *s != '-')
1971 DEBUG(D_tls) debug_printf("malformed openssl option setting: "
1972 "+ or - expected but found \"%s\"\n", s);
1975 adding = *s++ == '+';
1976 for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ;
1979 item_parsed = tls_openssl_one_option_parse(s, &item);
1982 DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s);
1985 DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n",
1986 adding ? "adding" : "removing", result, item, s);
1999 /* End of tls-openssl.c */