1 /* $NetBSD: tls_client.c,v 1.7 2013/08/21 20:12:31 tron Exp $ */ 2 3 /*++ 4 /* NAME 5 /* tls_client 6 /* SUMMARY 7 /* client-side TLS engine 8 /* SYNOPSIS 9 /* #include <tls.h> 10 /* 11 /* TLS_APPL_STATE *tls_client_init(init_props) 12 /* const TLS_CLIENT_INIT_PROPS *init_props; 13 /* 14 /* TLS_SESS_STATE *tls_client_start(start_props) 15 /* const TLS_CLIENT_START_PROPS *start_props; 16 /* 17 /* void tls_client_stop(app_ctx, stream, failure, TLScontext) 18 /* TLS_APPL_STATE *app_ctx; 19 /* VSTREAM *stream; 20 /* int failure; 21 /* TLS_SESS_STATE *TLScontext; 22 /* DESCRIPTION 23 /* This module is the interface between Postfix TLS clients, 24 /* the OpenSSL library and the TLS entropy and cache manager. 25 /* 26 /* The SMTP client will attempt to verify the server hostname 27 /* against the names listed in the server certificate. When 28 /* a hostname match is required, the verification fails 29 /* on certificate verification or hostname mis-match errors. 30 /* When no hostname match is required, hostname verification 31 /* failures are logged but they do not affect the TLS handshake 32 /* or the SMTP session. 33 /* 34 /* The rules for peer name wild-card matching differ between 35 /* RFC 2818 (HTTP over TLS) and RFC 2830 (LDAP over TLS), while 36 /* RFC RFC3207 (SMTP over TLS) does not specify a rule at all. 37 /* Postfix uses a restrictive match algorithm. One asterisk 38 /* ('*') is allowed as the left-most component of a wild-card 39 /* certificate name; it matches the left-most component of 40 /* the peer hostname. 41 /* 42 /* Another area where RFCs aren't always explicit is the 43 /* handling of dNSNames in peer certificates. RFC 3207 (SMTP 44 /* over TLS) does not mention dNSNames. Postfix follows the 45 /* strict rules in RFC 2818 (HTTP over TLS), section 3.1: The 46 /* Subject Alternative Name/dNSName has precedence over 47 /* CommonName. If at least one dNSName is provided, Postfix 48 /* verifies those against the peer hostname and ignores the 49 /* CommonName, otherwise Postfix verifies the CommonName 50 /* against the peer hostname. 51 /* 52 /* tls_client_init() is called once when the SMTP client 53 /* initializes. 54 /* Certificate details are also decided during this phase, 55 /* so peer-specific certificate selection is not possible. 56 /* 57 /* tls_client_start() activates the TLS session over an established 58 /* stream. We expect that network buffers are flushed and 59 /* the TLS handshake can begin immediately. 60 /* 61 /* tls_client_stop() sends the "close notify" alert via 62 /* SSL_shutdown() to the peer and resets all connection specific 63 /* TLS data. As RFC2487 does not specify a separate shutdown, it 64 /* is assumed that the underlying TCP connection is shut down 65 /* immediately afterwards. Any further writes to the channel will 66 /* be discarded, and any further reads will report end-of-file. 67 /* If the failure flag is set, no SSL_shutdown() handshake is performed. 68 /* 69 /* Once the TLS connection is initiated, information about the TLS 70 /* state is available via the TLScontext structure: 71 /* .IP TLScontext->protocol 72 /* the protocol name (SSLv2, SSLv3, TLSv1), 73 /* .IP TLScontext->cipher_name 74 /* the cipher name (e.g. RC4/MD5), 75 /* .IP TLScontext->cipher_usebits 76 /* the number of bits actually used (e.g. 40), 77 /* .IP TLScontext->cipher_algbits 78 /* the number of bits the algorithm is based on (e.g. 128). 79 /* .PP 80 /* The last two values may differ from each other when export-strength 81 /* encryption is used. 82 /* 83 /* If the peer offered a certificate, part of the certificate data are 84 /* available as: 85 /* .IP TLScontext->peer_status 86 /* A bitmask field that records the status of the peer certificate 87 /* verification. This consists of one or more of 88 /* TLS_CERT_FLAG_PRESENT, TLS_CERT_FLAG_ALTNAME, TLS_CERT_FLAG_TRUSTED 89 /* and TLS_CERT_FLAG_MATCHED. 90 /* .IP TLScontext->peer_CN 91 /* Extracted CommonName of the peer, or zero-length string if the 92 /* information could not be extracted. 93 /* .IP TLScontext->issuer_CN 94 /* Extracted CommonName of the issuer, or zero-length string if the 95 /* information could not be extracted. 96 /* .IP TLScontext->peer_fingerprint 97 /* At the fingerprint security level, if the peer presented a certificate 98 /* the fingerprint of the certificate. 99 /* .PP 100 /* If no peer certificate is presented the peer_status is set to 0. 101 /* LICENSE 102 /* .ad 103 /* .fi 104 /* This software is free. You can do with it whatever you want. 105 /* The original author kindly requests that you acknowledge 106 /* the use of his software. 107 /* AUTHOR(S) 108 /* Originally written by: 109 /* Lutz Jaenicke 110 /* BTU Cottbus 111 /* Allgemeine Elektrotechnik 112 /* Universitaetsplatz 3-4 113 /* D-03044 Cottbus, Germany 114 /* 115 /* Updated by: 116 /* Wietse Venema 117 /* IBM T.J. Watson Research 118 /* P.O. Box 704 119 /* Yorktown Heights, NY 10598, USA 120 /* 121 /* Victor Duchovni 122 /* Morgan Stanley 123 /*--*/ 124 125 /* System library. */ 126 127 #include <sys_defs.h> 128 129 #ifdef USE_TLS 130 #include <string.h> 131 132 #ifdef STRCASECMP_IN_STRINGS_H 133 #include <strings.h> 134 #endif 135 136 /* Utility library. */ 137 138 #include <argv.h> 139 #include <mymalloc.h> 140 #include <vstring.h> 141 #include <vstream.h> 142 #include <stringops.h> 143 #include <msg.h> 144 #include <iostuff.h> /* non-blocking */ 145 146 /* Global library. */ 147 148 #include <mail_params.h> 149 150 /* TLS library. */ 151 152 #include <tls_mgr.h> 153 #define TLS_INTERNAL 154 #include <tls.h> 155 156 /* Application-specific. */ 157 158 #define STR vstring_str 159 #define LEN VSTRING_LEN 160 161 /* load_clnt_session - load session from client cache (non-callback) */ 162 163 static SSL_SESSION *load_clnt_session(TLS_SESS_STATE *TLScontext) 164 { 165 const char *myname = "load_clnt_session"; 166 SSL_SESSION *session = 0; 167 VSTRING *session_data = vstring_alloc(2048); 168 169 /* 170 * Prepare the query. 171 */ 172 if (TLScontext->log_mask & TLS_LOG_CACHE) 173 /* serverid already contains namaddrport information */ 174 msg_info("looking for session %s in %s cache", 175 TLScontext->serverid, TLScontext->cache_type); 176 177 /* 178 * We only get here if the cache_type is not empty. This code is not 179 * called unless caching is enabled and the cache_type is stored in the 180 * server SSL context. 181 */ 182 if (TLScontext->cache_type == 0) 183 msg_panic("%s: null client session cache type in session lookup", 184 myname); 185 186 /* 187 * Look up and activate the SSL_SESSION object. Errors are non-fatal, 188 * since caching is only an optimization. 189 */ 190 if (tls_mgr_lookup(TLScontext->cache_type, TLScontext->serverid, 191 session_data) == TLS_MGR_STAT_OK) { 192 session = tls_session_activate(STR(session_data), LEN(session_data)); 193 if (session) { 194 if (TLScontext->log_mask & TLS_LOG_CACHE) 195 /* serverid already contains namaddrport information */ 196 msg_info("reloaded session %s from %s cache", 197 TLScontext->serverid, TLScontext->cache_type); 198 } 199 } 200 201 /* 202 * Clean up. 203 */ 204 vstring_free(session_data); 205 206 return (session); 207 } 208 209 /* new_client_session_cb - name new session and save it to client cache */ 210 211 static int new_client_session_cb(SSL *ssl, SSL_SESSION *session) 212 { 213 const char *myname = "new_client_session_cb"; 214 TLS_SESS_STATE *TLScontext; 215 VSTRING *session_data; 216 217 /* 218 * The cache name (if caching is enabled in tlsmgr(8)) and the cache ID 219 * string for this session are stored in the TLScontext. It cannot be 220 * null at this point. 221 */ 222 if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0) 223 msg_panic("%s: null TLScontext in new session callback", myname); 224 225 /* 226 * We only get here if the cache_type is not empty. This callback is not 227 * set unless caching is enabled and the cache_type is stored in the 228 * server SSL context. 229 */ 230 if (TLScontext->cache_type == 0) 231 msg_panic("%s: null session cache type in new session callback", 232 myname); 233 234 if (TLScontext->log_mask & TLS_LOG_CACHE) 235 /* serverid already contains namaddrport information */ 236 msg_info("save session %s to %s cache", 237 TLScontext->serverid, TLScontext->cache_type); 238 239 #if (OPENSSL_VERSION_NUMBER < 0x00906011L) || (OPENSSL_VERSION_NUMBER == 0x00907000L) 240 241 /* 242 * Ugly Hack: OpenSSL before 0.9.6a does not store the verify result in 243 * sessions for the client side. We modify the session directly which is 244 * version specific, but this bug is version specific, too. 245 * 246 * READ: 0-09-06-01-1 = 0-9-6-a-beta1: all versions before beta1 have this 247 * bug, it has been fixed during development of 0.9.6a. The development 248 * version of 0.9.7 can have this bug, too. It has been fixed on 249 * 2000/11/29. 250 */ 251 session->verify_result = SSL_get_verify_result(TLScontext->con); 252 #endif 253 254 /* 255 * Passivate and save the session object. Errors are non-fatal, since 256 * caching is only an optimization. 257 */ 258 if ((session_data = tls_session_passivate(session)) != 0) { 259 tls_mgr_update(TLScontext->cache_type, TLScontext->serverid, 260 STR(session_data), LEN(session_data)); 261 vstring_free(session_data); 262 } 263 264 /* 265 * Clean up. 266 */ 267 SSL_SESSION_free(session); /* 200502 */ 268 269 return (1); 270 } 271 272 /* uncache_session - remove session from the external cache */ 273 274 static void uncache_session(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext) 275 { 276 SSL_SESSION *session = SSL_get_session(TLScontext->con); 277 278 SSL_CTX_remove_session(ctx, session); 279 if (TLScontext->cache_type == 0 || TLScontext->serverid == 0) 280 return; 281 282 if (TLScontext->log_mask & TLS_LOG_CACHE) 283 /* serverid already contains namaddrport information */ 284 msg_info("remove session %s from client cache", TLScontext->serverid); 285 286 tls_mgr_delete(TLScontext->cache_type, TLScontext->serverid); 287 } 288 289 /* tls_client_init - initialize client-side TLS engine */ 290 291 TLS_APPL_STATE *tls_client_init(const TLS_CLIENT_INIT_PROPS *props) 292 { 293 long off = 0; 294 int cachable; 295 SSL_CTX *client_ctx; 296 TLS_APPL_STATE *app_ctx; 297 const EVP_MD *md_alg; 298 unsigned int md_len; 299 int log_mask; 300 301 /* 302 * Convert user loglevel to internal logmask. 303 */ 304 log_mask = tls_log_mask(props->log_param, props->log_level); 305 306 if (log_mask & TLS_LOG_VERBOSE) 307 msg_info("initializing the client-side TLS engine"); 308 309 /* 310 * Load (mostly cipher related) TLS-library internal main.cf parameters. 311 */ 312 tls_param_init(); 313 314 /* 315 * Detect mismatch between compile-time headers and run-time library. 316 */ 317 tls_check_version(); 318 319 /* 320 * Initialize the OpenSSL library by the book! To start with, we must 321 * initialize the algorithms. We want cleartext error messages instead of 322 * just error codes, so we load the error_strings. 323 */ 324 SSL_load_error_strings(); 325 OpenSSL_add_ssl_algorithms(); 326 327 /* 328 * Create an application data index for SSL objects, so that we can 329 * attach TLScontext information; this information is needed inside 330 * tls_verify_certificate_callback(). 331 */ 332 if (TLScontext_index < 0) { 333 if ((TLScontext_index = SSL_get_ex_new_index(0, 0, 0, 0, 0)) < 0) { 334 msg_warn("Cannot allocate SSL application data index: " 335 "disabling TLS support"); 336 return (0); 337 } 338 } 339 340 /* 341 * If the administrator specifies an unsupported digest algorithm, fail 342 * now, rather than in the middle of a TLS handshake. 343 */ 344 if ((md_alg = EVP_get_digestbyname(props->fpt_dgst)) == 0) { 345 msg_warn("Digest algorithm \"%s\" not found: disabling TLS support", 346 props->fpt_dgst); 347 return (0); 348 } 349 350 /* 351 * Sanity check: Newer shared libraries may use larger digests. 352 */ 353 if ((md_len = EVP_MD_size(md_alg)) > EVP_MAX_MD_SIZE) { 354 msg_warn("Digest algorithm \"%s\" output size %u too large:" 355 " disabling TLS support", props->fpt_dgst, md_len); 356 return (0); 357 } 358 359 /* 360 * Initialize the PRNG (Pseudo Random Number Generator) with some seed 361 * from external and internal sources. Don't enable TLS without some real 362 * entropy. 363 */ 364 if (tls_ext_seed(var_tls_daemon_rand_bytes) < 0) { 365 msg_warn("no entropy for TLS key generation: disabling TLS support"); 366 return (0); 367 } 368 tls_int_seed(); 369 370 /* 371 * The SSL/TLS specifications require the client to send a message in the 372 * oldest specification it understands with the highest level it 373 * understands in the message. RFC2487 is only specified for TLSv1, but 374 * we want to be as compatible as possible, so we will start off with a 375 * SSLv2 greeting allowing the best we can offer: TLSv1. We can restrict 376 * this with the options setting later, anyhow. 377 */ 378 ERR_clear_error(); 379 if ((client_ctx = SSL_CTX_new(SSLv23_client_method())) == 0) { 380 msg_warn("cannot allocate client SSL_CTX: disabling TLS support"); 381 tls_print_errors(); 382 return (0); 383 } 384 385 /* 386 * See the verify callback in tls_verify.c 387 */ 388 SSL_CTX_set_verify_depth(client_ctx, props->verifydepth + 1); 389 390 /* 391 * Protocol selection is destination dependent, so we delay the protocol 392 * selection options to the per-session SSL object. 393 */ 394 off |= tls_bug_bits(); 395 SSL_CTX_set_options(client_ctx, off); 396 397 /* 398 * Set the call-back routine for verbose logging. 399 */ 400 if (log_mask & TLS_LOG_DEBUG) 401 SSL_CTX_set_info_callback(client_ctx, tls_info_callback); 402 403 /* 404 * Load the CA public key certificates for both the client cert and for 405 * the verification of server certificates. As provided by OpenSSL we 406 * support two types of CA certificate handling: One possibility is to 407 * add all CA certificates to one large CAfile, the other possibility is 408 * a directory pointed to by CApath, containing separate files for each 409 * CA with softlinks named after the hash values of the certificate. The 410 * first alternative has the advantage that the file is opened and read 411 * at startup time, so that you don't have the hassle to maintain another 412 * copy of the CApath directory for chroot-jail. 413 */ 414 if (tls_set_ca_certificate_info(client_ctx, 415 props->CAfile, props->CApath) < 0) { 416 /* tls_set_ca_certificate_info() already logs a warning. */ 417 SSL_CTX_free(client_ctx); /* 200411 */ 418 return (0); 419 } 420 421 /* 422 * We do not need a client certificate, so the certificates are only 423 * loaded (and checked) if supplied. A clever client would handle 424 * multiple client certificates and decide based on the list of 425 * acceptable CAs, sent by the server, which certificate to submit. 426 * OpenSSL does however not do this and also has no call-back hooks to 427 * easily implement it. 428 * 429 * Load the client public key certificate and private key from file and 430 * check whether the cert matches the key. We can use RSA certificates 431 * ("cert") DSA certificates ("dcert") or ECDSA certificates ("eccert"). 432 * All three can be made available at the same time. The CA certificates 433 * for all three are handled in the same setup already finished. Which 434 * one is used depends on the cipher negotiated (that is: the first 435 * cipher listed by the client which does match the server). The client 436 * certificate is presented after the server chooses the session cipher, 437 * so we will just present the right cert for the chosen cipher (if it 438 * uses certificates). 439 */ 440 if (tls_set_my_certificate_key_info(client_ctx, 441 props->cert_file, 442 props->key_file, 443 props->dcert_file, 444 props->dkey_file, 445 props->eccert_file, 446 props->eckey_file) < 0) { 447 /* tls_set_my_certificate_key_info() already logs a warning. */ 448 SSL_CTX_free(client_ctx); /* 200411 */ 449 return (0); 450 } 451 452 /* 453 * According to the OpenSSL documentation, temporary RSA key is needed 454 * export ciphers are in use. We have to provide one, so well, we just do 455 * it. 456 */ 457 SSL_CTX_set_tmp_rsa_callback(client_ctx, tls_tmp_rsa_cb); 458 459 /* 460 * Finally, the setup for the server certificate checking, done "by the 461 * book". 462 */ 463 SSL_CTX_set_verify(client_ctx, SSL_VERIFY_NONE, 464 tls_verify_certificate_callback); 465 466 /* 467 * Initialize the session cache. 468 * 469 * Since the client does not search an internal cache, we simply disable it. 470 * It is only useful for expiring old sessions, but we do that in the 471 * tlsmgr(8). 472 * 473 * This makes SSL_CTX_remove_session() not useful for flushing broken 474 * sessions from the external cache, so we must delete them directly (not 475 * via a callback). 476 */ 477 if (tls_mgr_policy(props->cache_type, &cachable) != TLS_MGR_STAT_OK) 478 cachable = 0; 479 480 /* 481 * Allocate an application context, and populate with mandatory protocol 482 * and cipher data. 483 */ 484 app_ctx = tls_alloc_app_context(client_ctx, log_mask); 485 486 /* 487 * The external session cache is implemented by the tlsmgr(8) process. 488 */ 489 if (cachable) { 490 491 app_ctx->cache_type = mystrdup(props->cache_type); 492 493 /* 494 * OpenSSL does not use callbacks to load sessions from a client 495 * cache, so we must invoke that function directly. Apparently, 496 * OpenSSL does not provide a way to pass session names from here to 497 * call-back routines that do session lookup. 498 * 499 * OpenSSL can, however, automatically save newly created sessions for 500 * us by callback (we create the session name in the call-back 501 * function). 502 * 503 * XXX gcc 2.95 can't compile #ifdef .. #endif in the expansion of 504 * SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_NO_INTERNAL_STORE | 505 * SSL_SESS_CACHE_NO_AUTO_CLEAR. 506 */ 507 #ifndef SSL_SESS_CACHE_NO_INTERNAL_STORE 508 #define SSL_SESS_CACHE_NO_INTERNAL_STORE 0 509 #endif 510 511 SSL_CTX_set_session_cache_mode(client_ctx, 512 SSL_SESS_CACHE_CLIENT | 513 SSL_SESS_CACHE_NO_INTERNAL_STORE | 514 SSL_SESS_CACHE_NO_AUTO_CLEAR); 515 SSL_CTX_sess_set_new_cb(client_ctx, new_client_session_cb); 516 } 517 return (app_ctx); 518 } 519 520 /* match_hostname - match hostname against pattern */ 521 522 static int match_hostname(const char *peerid, 523 const TLS_CLIENT_START_PROPS *props) 524 { 525 const ARGV *cmatch_argv; 526 const char *nexthop = props->nexthop; 527 const char *hname = props->host; 528 const char *pattern; 529 const char *pattern_left; 530 int sub; 531 int i; 532 int idlen; 533 int patlen; 534 535 if ((cmatch_argv = props->matchargv) == 0) 536 return 0; 537 538 /* 539 * Match the peerid against each pattern until we find a match. 540 */ 541 for (i = 0; i < cmatch_argv->argc; ++i) { 542 sub = 0; 543 if (!strcasecmp(cmatch_argv->argv[i], "nexthop")) 544 pattern = nexthop; 545 else if (!strcasecmp(cmatch_argv->argv[i], "hostname")) 546 pattern = hname; 547 else if (!strcasecmp(cmatch_argv->argv[i], "dot-nexthop")) { 548 pattern = nexthop; 549 sub = 1; 550 } else { 551 pattern = cmatch_argv->argv[i]; 552 if (*pattern == '.' && pattern[1] != '\0') { 553 ++pattern; 554 sub = 1; 555 } 556 } 557 558 /* 559 * Sub-domain match: peerid is any sub-domain of pattern. 560 */ 561 if (sub) { 562 if ((idlen = strlen(peerid)) > (patlen = strlen(pattern)) + 1 563 && peerid[idlen - patlen - 1] == '.' 564 && !strcasecmp(peerid + (idlen - patlen), pattern)) 565 return (1); 566 else 567 continue; 568 } 569 570 /* 571 * Exact match and initial "*" match. The initial "*" in a peerid 572 * matches exactly one hostname component, under the condition that 573 * the peerid contains multiple hostname components. 574 */ 575 if (!strcasecmp(peerid, pattern) 576 || (peerid[0] == '*' && peerid[1] == '.' && peerid[2] != 0 577 && (pattern_left = strchr(pattern, '.')) != 0 578 && strcasecmp(pattern_left + 1, peerid + 2) == 0)) 579 return (1); 580 } 581 return (0); 582 } 583 584 /* verify_extract_name - verify peer name and extract peer information */ 585 586 static void verify_extract_name(TLS_SESS_STATE *TLScontext, X509 *peercert, 587 const TLS_CLIENT_START_PROPS *props) 588 { 589 int i; 590 int r; 591 int matched = 0; 592 int dnsname_match; 593 int verify_peername = 0; 594 int log_certmatch; 595 int verbose; 596 const char *dnsname; 597 const GENERAL_NAME *gn; 598 599 STACK_OF(GENERAL_NAME) * gens; 600 601 /* 602 * On exit both peer_CN and issuer_CN should be set. 603 */ 604 TLScontext->issuer_CN = tls_issuer_CN(peercert, TLScontext); 605 606 /* 607 * Is the certificate trust chain valid and trusted? 608 */ 609 if (SSL_get_verify_result(TLScontext->con) == X509_V_OK) 610 TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED; 611 612 if (TLS_CERT_IS_TRUSTED(TLScontext) && props->tls_level >= TLS_LEV_VERIFY) 613 verify_peername = 1; 614 615 /* Force cert processing so we can log the data? */ 616 log_certmatch = TLScontext->log_mask & TLS_LOG_CERTMATCH; 617 618 /* Log cert details when processing? */ 619 verbose = log_certmatch || (TLScontext->log_mask & TLS_LOG_VERBOSE); 620 621 if (verify_peername || log_certmatch) { 622 623 /* 624 * Verify the dNSName(s) in the peer certificate against the nexthop 625 * and hostname. 626 * 627 * If DNS names are present, we use the first matching (or else simply 628 * the first) DNS name as the subject CN. The CommonName in the 629 * issuer DN is obsolete when SubjectAltName is available. This 630 * yields much less surprising logs, because we log the name we 631 * verified or a name we checked and failed to match. 632 * 633 * XXX: The nexthop and host name may both be the same network address 634 * rather than a DNS name. In this case we really should be looking 635 * for GEN_IPADD entries, not GEN_DNS entries. 636 * 637 * XXX: In ideal world the caller who used the address to build the 638 * connection would tell us that the nexthop is the connection 639 * address, but if that is not practical, we can parse the nexthop 640 * again here. 641 */ 642 gens = X509_get_ext_d2i(peercert, NID_subject_alt_name, 0, 0); 643 if (gens) { 644 r = sk_GENERAL_NAME_num(gens); 645 for (i = 0; i < r; ++i) { 646 gn = sk_GENERAL_NAME_value(gens, i); 647 if (gn->type != GEN_DNS) 648 continue; 649 650 /* 651 * Even if we have an invalid DNS name, we still ultimately 652 * ignore the CommonName, because subjectAltName:DNS is 653 * present (though malformed). Replace any previous peer_CN 654 * if empty or we get a match. 655 * 656 * We always set at least an empty peer_CN if the ALTNAME cert 657 * flag is set. If not, we set peer_CN from the cert 658 * CommonName below, so peer_CN is always non-null on return. 659 */ 660 TLScontext->peer_status |= TLS_CERT_FLAG_ALTNAME; 661 dnsname = tls_dns_name(gn, TLScontext); 662 if (dnsname && *dnsname) { 663 if ((dnsname_match = match_hostname(dnsname, props)) != 0) 664 matched++; 665 /* Keep the first matched name. */ 666 if (TLScontext->peer_CN 667 && ((dnsname_match && matched == 1) 668 || *TLScontext->peer_CN == 0)) { 669 myfree(TLScontext->peer_CN); 670 TLScontext->peer_CN = 0; 671 } 672 if (verbose) 673 msg_info("%s: %ssubjectAltName: %s", props->namaddr, 674 dnsname_match ? "Matched " : "", dnsname); 675 } 676 if (TLScontext->peer_CN == 0) 677 TLScontext->peer_CN = mystrdup(dnsname ? dnsname : ""); 678 if (matched && !log_certmatch) 679 break; 680 } 681 if (verify_peername && matched) 682 TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED; 683 684 /* 685 * (Sam Rushing, Ironport) Free stack *and* member GENERAL_NAME 686 * objects 687 */ 688 sk_GENERAL_NAME_pop_free(gens, GENERAL_NAME_free); 689 } 690 691 /* 692 * No subjectAltNames, peer_CN is taken from CommonName. 693 */ 694 if (TLScontext->peer_CN == 0) { 695 TLScontext->peer_CN = tls_peer_CN(peercert, TLScontext); 696 if (*TLScontext->peer_CN) 697 matched = match_hostname(TLScontext->peer_CN, props); 698 if (verify_peername && matched) 699 TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED; 700 if (verbose) 701 msg_info("%s %sCommonName %s", props->namaddr, 702 matched ? "Matched " : "", TLScontext->peer_CN); 703 } else if (verbose) { 704 char *tmpcn = tls_peer_CN(peercert, TLScontext); 705 706 /* 707 * Though the CommonName was superceded by a subjectAltName, log 708 * it when certificate match debugging was requested. 709 */ 710 msg_info("%s CommonName %s", TLScontext->namaddr, tmpcn); 711 myfree(tmpcn); 712 } 713 } else 714 TLScontext->peer_CN = tls_peer_CN(peercert, TLScontext); 715 716 /* 717 * Give them a clue. Problems with trust chain verification were logged 718 * when the session was first negotiated, before the session was stored 719 * into the cache. We don't want mystery failures, so log the fact the 720 * real problem is to be found in the past. 721 */ 722 if (TLScontext->session_reused 723 && !TLS_CERT_IS_TRUSTED(TLScontext) 724 && (TLScontext->log_mask & TLS_LOG_UNTRUSTED)) 725 msg_info("%s: re-using session with untrusted certificate, " 726 "look for details earlier in the log", props->namaddr); 727 } 728 729 /* verify_extract_print - extract and verify peer fingerprint */ 730 731 static void verify_extract_print(TLS_SESS_STATE *TLScontext, X509 *peercert, 732 const TLS_CLIENT_START_PROPS *props) 733 { 734 char **cpp; 735 736 /* Non-null by contract */ 737 TLScontext->peer_fingerprint = tls_fingerprint(peercert, props->fpt_dgst); 738 TLScontext->peer_pkey_fprint = tls_pkey_fprint(peercert, props->fpt_dgst); 739 740 /* 741 * Compare the fingerprint against each acceptable value, ignoring 742 * upper/lower case differences. 743 */ 744 if (props->tls_level == TLS_LEV_FPRINT) { 745 for (cpp = props->matchargv->argv; *cpp; ++cpp) { 746 if (strcasecmp(TLScontext->peer_fingerprint, *cpp) == 0 747 || strcasecmp(TLScontext->peer_pkey_fprint, *cpp) == 0) { 748 TLScontext->peer_status |= TLS_CERT_FLAG_MATCHED; 749 break; 750 } 751 } 752 } 753 } 754 755 /* 756 * This is the actual startup routine for the connection. We expect that the 757 * buffers are flushed and the "220 Ready to start TLS" was received by us, 758 * so that we can immediately start the TLS handshake process. 759 */ 760 TLS_SESS_STATE *tls_client_start(const TLS_CLIENT_START_PROPS *props) 761 { 762 int sts; 763 int protomask; 764 const char *cipher_list; 765 SSL_SESSION *session; 766 const SSL_CIPHER *cipher; 767 X509 *peercert; 768 TLS_SESS_STATE *TLScontext; 769 TLS_APPL_STATE *app_ctx = props->ctx; 770 VSTRING *myserverid; 771 int log_mask = app_ctx->log_mask; 772 773 /* 774 * When certificate verification is required, log trust chain validation 775 * errors even when disabled by default for opportunistic sessions. 776 */ 777 if (props->tls_level >= TLS_LEV_VERIFY) 778 log_mask |= TLS_LOG_UNTRUSTED; 779 780 if (log_mask & TLS_LOG_VERBOSE) 781 msg_info("setting up TLS connection to %s", props->namaddr); 782 783 /* 784 * First make sure we have valid protocol and cipher parameters 785 * 786 * The cipherlist will be applied to the global SSL context, where it can be 787 * repeatedly reset if necessary, but the protocol restrictions will be 788 * is applied to the SSL connection, because protocol restrictions in the 789 * global context cannot be cleared. 790 */ 791 792 /* 793 * OpenSSL will ignore cached sessions that use the wrong protocol. So we 794 * do not need to filter out cached sessions with the "wrong" protocol, 795 * rather OpenSSL will simply negotiate a new session. 796 * 797 * Still, we salt the session lookup key with the protocol list, so that 798 * sessions found in the cache are always acceptable. 799 */ 800 protomask = tls_protocol_mask(props->protocols); 801 if (protomask == TLS_PROTOCOL_INVALID) { 802 /* tls_protocol_mask() logs no warning. */ 803 msg_warn("%s: Invalid TLS protocol list \"%s\": aborting TLS session", 804 props->namaddr, props->protocols); 805 return (0); 806 } 807 myserverid = vstring_alloc(100); 808 vstring_sprintf_append(myserverid, "%s&p=%d", props->serverid, protomask); 809 810 /* 811 * Per session cipher selection for sessions with mandatory encryption 812 * 813 * By the time a TLS client is negotiating ciphers it has already offered to 814 * re-use a session, it is too late to renege on the offer. So we must 815 * not attempt to re-use sessions whose ciphers are too weak. We salt the 816 * session lookup key with the cipher list, so that sessions found in the 817 * cache are always acceptable. 818 */ 819 cipher_list = tls_set_ciphers(app_ctx, "TLS", props->cipher_grade, 820 props->cipher_exclusions); 821 if (cipher_list == 0) { 822 msg_warn("%s: %s: aborting TLS session", 823 props->namaddr, vstring_str(app_ctx->why)); 824 vstring_free(myserverid); 825 return (0); 826 } 827 if (log_mask & TLS_LOG_VERBOSE) 828 msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list); 829 vstring_sprintf_append(myserverid, "&c=%s", cipher_list); 830 831 /* 832 * Finally, salt the session key with the OpenSSL library version, 833 * (run-time, rather than compile-time, just in case that matters). 834 */ 835 vstring_sprintf_append(myserverid, "&l=%ld", (long) SSLeay()); 836 837 /* 838 * Allocate a new TLScontext for the new connection and get an SSL 839 * structure. Add the location of TLScontext to the SSL to later retrieve 840 * the information inside the tls_verify_certificate_callback(). 841 * 842 * If session caching was enabled when TLS was initialized, the cache type 843 * is stored in the client SSL context. 844 */ 845 TLScontext = tls_alloc_sess_context(log_mask, props->namaddr); 846 TLScontext->cache_type = app_ctx->cache_type; 847 848 TLScontext->serverid = vstring_export(myserverid); 849 TLScontext->stream = props->stream; 850 851 if ((TLScontext->con = SSL_new(app_ctx->ssl_ctx)) == NULL) { 852 msg_warn("Could not allocate 'TLScontext->con' with SSL_new()"); 853 tls_print_errors(); 854 tls_free_context(TLScontext); 855 return (0); 856 } 857 if (!SSL_set_ex_data(TLScontext->con, TLScontext_index, TLScontext)) { 858 msg_warn("Could not set application data for 'TLScontext->con'"); 859 tls_print_errors(); 860 tls_free_context(TLScontext); 861 return (0); 862 } 863 864 /* 865 * Apply session protocol restrictions. 866 */ 867 if (protomask != 0) 868 SSL_set_options(TLScontext->con, 869 ((protomask & TLS_PROTOCOL_TLSv1) ? SSL_OP_NO_TLSv1 : 0L) 870 | ((protomask & TLS_PROTOCOL_TLSv1_1) ? SSL_OP_NO_TLSv1_1 : 0L) 871 | ((protomask & TLS_PROTOCOL_TLSv1_2) ? SSL_OP_NO_TLSv1_2 : 0L) 872 | ((protomask & TLS_PROTOCOL_SSLv3) ? SSL_OP_NO_SSLv3 : 0L) 873 | ((protomask & TLS_PROTOCOL_SSLv2) ? SSL_OP_NO_SSLv2 : 0L)); 874 875 /* 876 * XXX To avoid memory leaks we must always call SSL_SESSION_free() after 877 * calling SSL_set_session(), regardless of whether or not the session 878 * will be reused. 879 */ 880 if (TLScontext->cache_type) { 881 session = load_clnt_session(TLScontext); 882 if (session) { 883 SSL_set_session(TLScontext->con, session); 884 SSL_SESSION_free(session); /* 200411 */ 885 #if (OPENSSL_VERSION_NUMBER < 0x00906011L) || (OPENSSL_VERSION_NUMBER == 0x00907000L) 886 887 /* 888 * Ugly Hack: OpenSSL before 0.9.6a does not store the verify 889 * result in sessions for the client side. We modify the session 890 * directly which is version specific, but this bug is version 891 * specific, too. 892 * 893 * READ: 0-09-06-01-1 = 0-9-6-a-beta1: all versions before beta1 894 * have this bug, it has been fixed during development of 0.9.6a. 895 * The development version of 0.9.7 can have this bug, too. It 896 * has been fixed on 2000/11/29. 897 */ 898 SSL_set_verify_result(TLScontext->con, session->verify_result); 899 #endif 900 901 } 902 } 903 904 /* 905 * Before really starting anything, try to seed the PRNG a little bit 906 * more. 907 */ 908 tls_int_seed(); 909 (void) tls_ext_seed(var_tls_daemon_rand_bytes); 910 911 /* 912 * Initialize the SSL connection to connect state. This should not be 913 * necessary anymore since 0.9.3, but the call is still in the library 914 * and maintaining compatibility never hurts. 915 */ 916 SSL_set_connect_state(TLScontext->con); 917 918 /* 919 * Connect the SSL connection with the network socket. 920 */ 921 if (SSL_set_fd(TLScontext->con, vstream_fileno(props->stream)) != 1) { 922 msg_info("SSL_set_fd error to %s", props->namaddr); 923 tls_print_errors(); 924 uncache_session(app_ctx->ssl_ctx, TLScontext); 925 tls_free_context(TLScontext); 926 return (0); 927 } 928 929 /* 930 * Turn on non-blocking I/O so that we can enforce timeouts on network 931 * I/O. 932 */ 933 non_blocking(vstream_fileno(props->stream), NON_BLOCKING); 934 935 /* 936 * If the debug level selected is high enough, all of the data is dumped: 937 * TLS_LOG_TLSPKTS will dump the SSL negotiation, TLS_LOG_ALLPKTS will 938 * dump everything. 939 * 940 * We do have an SSL_set_fd() and now suddenly a BIO_ routine is called? 941 * Well there is a BIO below the SSL routines that is automatically 942 * created for us, so we can use it for debugging purposes. 943 */ 944 if (log_mask & TLS_LOG_TLSPKTS) 945 BIO_set_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb); 946 947 /* 948 * Start TLS negotiations. This process is a black box that invokes our 949 * call-backs for certificate verification. 950 * 951 * Error handling: If the SSL handhake fails, we print out an error message 952 * and remove all TLS state concerning this session. 953 */ 954 sts = tls_bio_connect(vstream_fileno(props->stream), props->timeout, 955 TLScontext); 956 if (sts <= 0) { 957 if (ERR_peek_error() != 0) { 958 msg_info("SSL_connect error to %s: %d", props->namaddr, sts); 959 tls_print_errors(); 960 } else if (errno != 0) { 961 msg_info("SSL_connect error to %s: %m", props->namaddr); 962 } else { 963 msg_info("SSL_connect error to %s: lost connection", 964 props->namaddr); 965 } 966 uncache_session(app_ctx->ssl_ctx, TLScontext); 967 tls_free_context(TLScontext); 968 return (0); 969 } 970 /* Turn off packet dump if only dumping the handshake */ 971 if ((log_mask & TLS_LOG_ALLPKTS) == 0) 972 BIO_set_callback(SSL_get_rbio(TLScontext->con), 0); 973 974 /* 975 * The caller may want to know if this session was reused or if a new 976 * session was negotiated. 977 */ 978 TLScontext->session_reused = SSL_session_reused(TLScontext->con); 979 if ((log_mask & TLS_LOG_CACHE) && TLScontext->session_reused) 980 msg_info("%s: Reusing old session", TLScontext->namaddr); 981 982 /* 983 * Do peername verification if requested and extract useful information 984 * from the certificate for later use. 985 */ 986 if ((peercert = SSL_get_peer_certificate(TLScontext->con)) != 0) { 987 TLScontext->peer_status |= TLS_CERT_FLAG_PRESENT; 988 989 /* 990 * Peer name or fingerprint verification as requested. 991 * Unconditionally set peer_CN, issuer_CN and peer_fingerprint. 992 */ 993 verify_extract_name(TLScontext, peercert, props); 994 verify_extract_print(TLScontext, peercert, props); 995 996 if (TLScontext->log_mask & 997 (TLS_LOG_CERTMATCH | TLS_LOG_VERBOSE | TLS_LOG_PEERCERT)) 998 msg_info("%s: subject_CN=%s, issuer_CN=%s, " 999 "fingerprint=%s, pkey_fingerprint=%s", props->namaddr, 1000 TLScontext->peer_CN, TLScontext->issuer_CN, 1001 TLScontext->peer_fingerprint, 1002 TLScontext->peer_pkey_fprint); 1003 X509_free(peercert); 1004 } else { 1005 TLScontext->issuer_CN = mystrdup(""); 1006 TLScontext->peer_CN = mystrdup(""); 1007 TLScontext->peer_fingerprint = mystrdup(""); 1008 TLScontext->peer_pkey_fprint = mystrdup(""); 1009 } 1010 1011 /* 1012 * Finally, collect information about protocol and cipher for logging 1013 */ 1014 TLScontext->protocol = SSL_get_version(TLScontext->con); 1015 cipher = SSL_get_current_cipher(TLScontext->con); 1016 TLScontext->cipher_name = SSL_CIPHER_get_name(cipher); 1017 TLScontext->cipher_usebits = SSL_CIPHER_get_bits(cipher, 1018 &(TLScontext->cipher_algbits)); 1019 1020 /* 1021 * The TLS engine is active. Switch to the tls_timed_read/write() 1022 * functions and make the TLScontext available to those functions. 1023 */ 1024 tls_stream_start(props->stream, TLScontext); 1025 1026 /* 1027 * All the key facts in a single log entry. 1028 */ 1029 if (log_mask & TLS_LOG_SUMMARY) 1030 msg_info("%s TLS connection established to %s: %s with cipher %s " 1031 "(%d/%d bits)", TLS_CERT_IS_MATCHED(TLScontext) ? "Verified" : 1032 TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted", 1033 props->namaddr, TLScontext->protocol, TLScontext->cipher_name, 1034 TLScontext->cipher_usebits, TLScontext->cipher_algbits); 1035 1036 tls_int_seed(); 1037 1038 return (TLScontext); 1039 } 1040 1041 #endif /* USE_TLS */ 1042