1 /* $NetBSD: tls_server.c,v 1.7 2013/09/25 19:12:35 tron Exp $ */ 2 3 /*++ 4 /* NAME 5 /* tls_server 3 6 /* SUMMARY 7 /* server-side TLS engine 8 /* SYNOPSIS 9 /* #include <tls.h> 10 /* 11 /* TLS_APPL_STATE *tls_server_init(props) 12 /* const TLS_SERVER_INIT_PROPS *props; 13 /* 14 /* TLS_SESS_STATE *tls_server_start(props) 15 /* const TLS_SERVER_START_PROPS *props; 16 /* 17 /* TLS_SESS_STATE *tls_server_post_accept(TLScontext) 18 /* TLS_SESS_STATE *TLScontext; 19 /* 20 /* void tls_server_stop(app_ctx, stream, failure, TLScontext) 21 /* TLS_APPL_STATE *app_ctx; 22 /* VSTREAM *stream; 23 /* int failure; 24 /* TLS_SESS_STATE *TLScontext; 25 /* DESCRIPTION 26 /* This module is the interface between Postfix TLS servers, 27 /* the OpenSSL library, and the TLS entropy and cache manager. 28 /* 29 /* See "EVENT_DRIVEN APPLICATIONS" below for using this code 30 /* in event-driven programs. 31 /* 32 /* tls_server_init() is called once when the SMTP server 33 /* initializes. 34 /* Certificate details are also decided during this phase, 35 /* so that peer-specific behavior is not possible. 36 /* 37 /* tls_server_start() activates the TLS feature for the VSTREAM 38 /* passed as argument. We assume that network buffers are flushed 39 /* and the TLS handshake can begin immediately. 40 /* 41 /* tls_server_stop() sends the "close notify" alert via 42 /* SSL_shutdown() to the peer and resets all connection specific 43 /* TLS data. As RFC2487 does not specify a separate shutdown, it 44 /* is assumed that the underlying TCP connection is shut down 45 /* immediately afterwards. Any further writes to the channel will 46 /* be discarded, and any further reads will report end-of-file. 47 /* If the failure flag is set, no SSL_shutdown() handshake is performed. 48 /* 49 /* Once the TLS connection is initiated, information about the TLS 50 /* state is available via the TLScontext structure: 51 /* .IP TLScontext->protocol 52 /* the protocol name (SSLv2, SSLv3, TLSv1), 53 /* .IP TLScontext->cipher_name 54 /* the cipher name (e.g. RC4/MD5), 55 /* .IP TLScontext->cipher_usebits 56 /* the number of bits actually used (e.g. 40), 57 /* .IP TLScontext->cipher_algbits 58 /* the number of bits the algorithm is based on (e.g. 128). 59 /* .PP 60 /* The last two values may differ from each other when export-strength 61 /* encryption is used. 62 /* 63 /* If the peer offered a certificate, part of the certificate data are 64 /* available as: 65 /* .IP TLScontext->peer_status 66 /* A bitmask field that records the status of the peer certificate 67 /* verification. One or more of TLS_CERT_FLAG_PRESENT and 68 /* TLS_CERT_FLAG_TRUSTED. 69 /* .IP TLScontext->peer_CN 70 /* Extracted CommonName of the peer, or zero-length string 71 /* when information could not be extracted. 72 /* .IP TLScontext->issuer_CN 73 /* Extracted CommonName of the issuer, or zero-length string 74 /* when information could not be extracted. 75 /* .IP TLScontext->peer_fingerprint 76 /* Fingerprint of the certificate, or zero-length string when no peer 77 /* certificate is available. 78 /* .PP 79 /* If no peer certificate is presented the peer_status is set to 0. 80 /* EVENT_DRIVEN APPLICATIONS 81 /* .ad 82 /* .fi 83 /* Event-driven programs manage multiple I/O channels. Such 84 /* programs cannot use the synchronous VSTREAM-over-TLS 85 /* implementation that the current TLS library provides, 86 /* including tls_server_stop() and the underlying tls_stream(3) 87 /* and tls_bio_ops(3) routines. 88 /* 89 /* With the current TLS library implementation, this means 90 /* that the application is responsible for calling and retrying 91 /* SSL_accept(), SSL_read(), SSL_write() and SSL_shutdown(). 92 /* 93 /* To maintain control over TLS I/O, an event-driven server 94 /* invokes tls_server_start() with a null VSTREAM argument and 95 /* with an fd argument that specifies the I/O file descriptor. 96 /* Then, tls_server_start() performs all the necessary 97 /* preparations before the TLS handshake and returns a partially 98 /* populated TLS context. The event-driven application is then 99 /* responsible for invoking SSL_accept(), and if successful, 100 /* for invoking tls_server_post_accept() to finish the work 101 /* that was started by tls_server_start(). In case of unrecoverable 102 /* failure, tls_server_post_accept() destroys the TLS context 103 /* and returns a null pointer value. 104 /* LICENSE 105 /* .ad 106 /* .fi 107 /* This software is free. You can do with it whatever you want. 108 /* The original author kindly requests that you acknowledge 109 /* the use of his software. 110 /* AUTHOR(S) 111 /* Originally written by: 112 /* Lutz Jaenicke 113 /* BTU Cottbus 114 /* Allgemeine Elektrotechnik 115 /* Universitaetsplatz 3-4 116 /* D-03044 Cottbus, Germany 117 /* 118 /* Updated by: 119 /* Wietse Venema 120 /* IBM T.J. Watson Research 121 /* P.O. Box 704 122 /* Yorktown Heights, NY 10598, USA 123 /* 124 /* Victor Duchovni 125 /* Morgan Stanley 126 /*--*/ 127 128 /* System library. */ 129 130 #include <sys_defs.h> 131 132 #ifdef USE_TLS 133 #include <unistd.h> 134 #include <string.h> 135 136 /* Utility library. */ 137 138 #include <mymalloc.h> 139 #include <vstring.h> 140 #include <vstream.h> 141 #include <dict.h> 142 #include <stringops.h> 143 #include <msg.h> 144 #include <hex_code.h> 145 #include <iostuff.h> /* non-blocking */ 146 147 /* Global library. */ 148 149 #include <mail_params.h> 150 151 /* TLS library. */ 152 153 #include <tls_mgr.h> 154 #define TLS_INTERNAL 155 #include <tls.h> 156 157 #define STR(x) vstring_str(x) 158 #define LEN(x) VSTRING_LEN(x) 159 160 /* Application-specific. */ 161 162 /* 163 * The session_id_context indentifies the service that created a session. 164 * This information is used to distinguish between multiple TLS-based 165 * servers running on the same server. We use the name of the mail system. 166 */ 167 static const char server_session_id_context[] = "Postfix/TLS"; 168 169 /* get_server_session_cb - callback to retrieve session from server cache */ 170 171 static SSL_SESSION *get_server_session_cb(SSL *ssl, unsigned char *session_id, 172 int session_id_length, 173 int *unused_copy) 174 { 175 const char *myname = "get_server_session_cb"; 176 TLS_SESS_STATE *TLScontext; 177 VSTRING *cache_id; 178 VSTRING *session_data = vstring_alloc(2048); 179 SSL_SESSION *session = 0; 180 181 if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0) 182 msg_panic("%s: null TLScontext in session lookup callback", myname); 183 184 #define GEN_CACHE_ID(buf, id, len, service) \ 185 do { \ 186 buf = vstring_alloc(2 * (len + strlen(service))); \ 187 hex_encode(buf, (char *) (id), (len)); \ 188 vstring_sprintf_append(buf, "&s=%s", (service)); \ 189 vstring_sprintf_append(buf, "&l=%ld", (long) SSLeay()); \ 190 } while (0) 191 192 193 GEN_CACHE_ID(cache_id, session_id, session_id_length, TLScontext->serverid); 194 195 if (TLScontext->log_mask & TLS_LOG_CACHE) 196 msg_info("%s: looking up session %s in %s cache", TLScontext->namaddr, 197 STR(cache_id), TLScontext->cache_type); 198 199 /* 200 * Load the session from cache and decode it. 201 */ 202 if (tls_mgr_lookup(TLScontext->cache_type, STR(cache_id), 203 session_data) == TLS_MGR_STAT_OK) { 204 session = tls_session_activate(STR(session_data), LEN(session_data)); 205 if (session && (TLScontext->log_mask & TLS_LOG_CACHE)) 206 msg_info("%s: reloaded session %s from %s cache", 207 TLScontext->namaddr, STR(cache_id), 208 TLScontext->cache_type); 209 } 210 211 /* 212 * Clean up. 213 */ 214 vstring_free(cache_id); 215 vstring_free(session_data); 216 217 return (session); 218 } 219 220 /* uncache_session - remove session from internal & external cache */ 221 222 static void uncache_session(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext) 223 { 224 VSTRING *cache_id; 225 SSL_SESSION *session = SSL_get_session(TLScontext->con); 226 227 SSL_CTX_remove_session(ctx, session); 228 229 if (TLScontext->cache_type == 0) 230 return; 231 232 GEN_CACHE_ID(cache_id, session->session_id, session->session_id_length, 233 TLScontext->serverid); 234 235 if (TLScontext->log_mask & TLS_LOG_CACHE) 236 msg_info("%s: remove session %s from %s cache", TLScontext->namaddr, 237 STR(cache_id), TLScontext->cache_type); 238 239 tls_mgr_delete(TLScontext->cache_type, STR(cache_id)); 240 vstring_free(cache_id); 241 } 242 243 /* new_server_session_cb - callback to save session to server cache */ 244 245 static int new_server_session_cb(SSL *ssl, SSL_SESSION *session) 246 { 247 const char *myname = "new_server_session_cb"; 248 VSTRING *cache_id; 249 TLS_SESS_STATE *TLScontext; 250 VSTRING *session_data; 251 252 if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0) 253 msg_panic("%s: null TLScontext in new session callback", myname); 254 255 GEN_CACHE_ID(cache_id, session->session_id, session->session_id_length, 256 TLScontext->serverid); 257 258 if (TLScontext->log_mask & TLS_LOG_CACHE) 259 msg_info("%s: save session %s to %s cache", TLScontext->namaddr, 260 STR(cache_id), TLScontext->cache_type); 261 262 /* 263 * Passivate and save the session state. 264 */ 265 session_data = tls_session_passivate(session); 266 if (session_data) 267 tls_mgr_update(TLScontext->cache_type, STR(cache_id), 268 STR(session_data), LEN(session_data)); 269 270 /* 271 * Clean up. 272 */ 273 if (session_data) 274 vstring_free(session_data); 275 vstring_free(cache_id); 276 SSL_SESSION_free(session); /* 200502 */ 277 278 return (1); 279 } 280 281 /* tls_server_init - initialize the server-side TLS engine */ 282 283 TLS_APPL_STATE *tls_server_init(const TLS_SERVER_INIT_PROPS *props) 284 { 285 SSL_CTX *server_ctx; 286 long off = 0; 287 int verify_flags = SSL_VERIFY_NONE; 288 int cachable; 289 int protomask; 290 TLS_APPL_STATE *app_ctx; 291 const EVP_MD *md_alg; 292 unsigned int md_len; 293 int log_mask; 294 295 /* 296 * Convert user loglevel to internal logmask. 297 */ 298 log_mask = tls_log_mask(props->log_param, props->log_level); 299 300 if (log_mask & TLS_LOG_VERBOSE) 301 msg_info("initializing the server-side TLS engine"); 302 303 /* 304 * Load (mostly cipher related) TLS-library internal main.cf parameters. 305 */ 306 tls_param_init(); 307 308 /* 309 * Detect mismatch between compile-time headers and run-time library. 310 */ 311 tls_check_version(); 312 313 /* 314 * Initialize the OpenSSL library by the book! To start with, we must 315 * initialize the algorithms. We want cleartext error messages instead of 316 * just error codes, so we load the error_strings. 317 */ 318 SSL_load_error_strings(); 319 OpenSSL_add_ssl_algorithms(); 320 321 /* 322 * First validate the protocols. If these are invalid, we can't continue. 323 */ 324 protomask = tls_protocol_mask(props->protocols); 325 if (protomask == TLS_PROTOCOL_INVALID) { 326 /* tls_protocol_mask() logs no warning. */ 327 msg_warn("Invalid TLS protocol list \"%s\": disabling TLS support", 328 props->protocols); 329 return (0); 330 } 331 332 /* 333 * Create an application data index for SSL objects, so that we can 334 * attach TLScontext information; this information is needed inside 335 * tls_verify_certificate_callback(). 336 */ 337 if (TLScontext_index < 0) { 338 if ((TLScontext_index = SSL_get_ex_new_index(0, 0, 0, 0, 0)) < 0) { 339 msg_warn("Cannot allocate SSL application data index: " 340 "disabling TLS support"); 341 return (0); 342 } 343 } 344 345 /* 346 * Register SHA-2 digests, if implemented and not already registered. 347 * Improves interoperability with clients and servers that prematurely 348 * deploy SHA-2 certificates. 349 */ 350 #if defined(LN_sha256) && defined(NID_sha256) && !defined(OPENSSL_NO_SHA256) 351 if (!EVP_get_digestbyname(LN_sha224)) 352 EVP_add_digest(EVP_sha224()); 353 if (!EVP_get_digestbyname(LN_sha256)) 354 EVP_add_digest(EVP_sha256()); 355 #endif 356 #if defined(LN_sha512) && defined(NID_sha512) && !defined(OPENSSL_NO_SHA512) 357 if (!EVP_get_digestbyname(LN_sha384)) 358 EVP_add_digest(EVP_sha384()); 359 if (!EVP_get_digestbyname(LN_sha512)) 360 EVP_add_digest(EVP_sha512()); 361 #endif 362 363 /* 364 * If the administrator specifies an unsupported digest algorithm, fail 365 * now, rather than in the middle of a TLS handshake. 366 */ 367 if ((md_alg = EVP_get_digestbyname(props->fpt_dgst)) == 0) { 368 msg_warn("Digest algorithm \"%s\" not found: disabling TLS support", 369 props->fpt_dgst); 370 return (0); 371 } 372 373 /* 374 * Sanity check: Newer shared libraries may use larger digests. 375 */ 376 if ((md_len = EVP_MD_size(md_alg)) > EVP_MAX_MD_SIZE) { 377 msg_warn("Digest algorithm \"%s\" output size %u too large:" 378 " disabling TLS support", props->fpt_dgst, md_len); 379 return (0); 380 } 381 382 /* 383 * Initialize the PRNG (Pseudo Random Number Generator) with some seed 384 * from external and internal sources. Don't enable TLS without some real 385 * entropy. 386 */ 387 if (tls_ext_seed(var_tls_daemon_rand_bytes) < 0) { 388 msg_warn("no entropy for TLS key generation: disabling TLS support"); 389 return (0); 390 } 391 tls_int_seed(); 392 393 /* 394 * The SSL/TLS specifications require the client to send a message in the 395 * oldest specification it understands with the highest level it 396 * understands in the message. Netscape communicator can still 397 * communicate with SSLv2 servers, so it sends out a SSLv2 client hello. 398 * To deal with it, our server must be SSLv2 aware (even if we don't like 399 * SSLv2), so we need to have the SSLv23 server here. If we want to limit 400 * the protocol level, we can add an option to not use SSLv2/v3/TLSv1 401 * later. 402 */ 403 ERR_clear_error(); 404 if ((server_ctx = SSL_CTX_new(SSLv23_server_method())) == 0) { 405 msg_warn("cannot allocate server SSL_CTX: disabling TLS support"); 406 tls_print_errors(); 407 return (0); 408 } 409 410 /* 411 * See the verify callback in tls_verify.c 412 */ 413 SSL_CTX_set_verify_depth(server_ctx, props->verifydepth + 1); 414 415 /* 416 * Protocol work-arounds, OpenSSL version dependent. 417 */ 418 #ifdef SSL_OP_NO_TICKET 419 off |= SSL_OP_NO_TICKET; 420 #endif 421 off |= tls_bug_bits(); 422 SSL_CTX_set_options(server_ctx, off); 423 424 /* 425 * Global protocol selection. 426 */ 427 if (protomask != 0) 428 SSL_CTX_set_options(server_ctx, 429 ((protomask & TLS_PROTOCOL_TLSv1) ? SSL_OP_NO_TLSv1 : 0L) 430 | ((protomask & TLS_PROTOCOL_TLSv1_1) ? SSL_OP_NO_TLSv1_1 : 0L) 431 | ((protomask & TLS_PROTOCOL_TLSv1_2) ? SSL_OP_NO_TLSv1_2 : 0L) 432 | ((protomask & TLS_PROTOCOL_SSLv3) ? SSL_OP_NO_SSLv3 : 0L) 433 | ((protomask & TLS_PROTOCOL_SSLv2) ? SSL_OP_NO_SSLv2 : 0L)); 434 435 #if OPENSSL_VERSION_NUMBER >= 0x0090700fL 436 437 /* 438 * Some sites may want to give the client less rope. On the other hand, 439 * this could trigger inter-operability issues, the client should not 440 * offer ciphers it implements poorly, but this hasn't stopped some 441 * vendors from getting it wrong. 442 * 443 * XXX: Given OpenSSL's security history, nobody should still be using 444 * 0.9.7, let alone 0.9.6 or earlier. Warning added to TLS_README.html. 445 */ 446 if (var_tls_preempt_clist) 447 SSL_CTX_set_options(server_ctx, SSL_OP_CIPHER_SERVER_PREFERENCE); 448 #endif 449 450 /* 451 * Set the call-back routine to debug handshake progress. 452 */ 453 if (log_mask & TLS_LOG_DEBUG) 454 SSL_CTX_set_info_callback(server_ctx, tls_info_callback); 455 456 /* 457 * Load the CA public key certificates for both the server cert and for 458 * the verification of client certificates. As provided by OpenSSL we 459 * support two types of CA certificate handling: One possibility is to 460 * add all CA certificates to one large CAfile, the other possibility is 461 * a directory pointed to by CApath, containing separate files for each 462 * CA with softlinks named after the hash values of the certificate. The 463 * first alternative has the advantage that the file is opened and read 464 * at startup time, so that you don't have the hassle to maintain another 465 * copy of the CApath directory for chroot-jail. 466 */ 467 if (tls_set_ca_certificate_info(server_ctx, 468 props->CAfile, props->CApath) < 0) { 469 /* tls_set_ca_certificate_info() already logs a warning. */ 470 SSL_CTX_free(server_ctx); /* 200411 */ 471 return (0); 472 } 473 474 /* 475 * Load the server public key certificate and private key from file and 476 * check whether the cert matches the key. We can use RSA certificates 477 * ("cert") DSA certificates ("dcert") or ECDSA certificates ("eccert"). 478 * All three can be made available at the same time. The CA certificates 479 * for all three are handled in the same setup already finished. Which 480 * one is used depends on the cipher negotiated (that is: the first 481 * cipher listed by the client which does match the server). A client 482 * with RSA only (e.g. Netscape) will use the RSA certificate only. A 483 * client with openssl-library will use RSA first if not especially 484 * changed in the cipher setup. 485 */ 486 if (tls_set_my_certificate_key_info(server_ctx, 487 props->cert_file, 488 props->key_file, 489 props->dcert_file, 490 props->dkey_file, 491 props->eccert_file, 492 props->eckey_file) < 0) { 493 /* tls_set_my_certificate_key_info() already logs a warning. */ 494 SSL_CTX_free(server_ctx); /* 200411 */ 495 return (0); 496 } 497 498 /* 499 * According to OpenSSL documentation, a temporary RSA key is needed when 500 * export ciphers are in use, because the certified key cannot be 501 * directly used. 502 */ 503 SSL_CTX_set_tmp_rsa_callback(server_ctx, tls_tmp_rsa_cb); 504 505 /* 506 * Diffie-Hellman key generation parameters can either be loaded from 507 * files (preferred) or taken from compiled in values. First, set the 508 * callback that will select the values when requested, then load the 509 * (possibly) available DH parameters from files. We are generous with 510 * the error handling, since we do have default values compiled in, so we 511 * will not abort but just log the error message. 512 */ 513 SSL_CTX_set_tmp_dh_callback(server_ctx, tls_tmp_dh_cb); 514 if (*props->dh1024_param_file != 0) 515 tls_set_dh_from_file(props->dh1024_param_file, 1024); 516 if (*props->dh512_param_file != 0) 517 tls_set_dh_from_file(props->dh512_param_file, 512); 518 519 /* 520 * Enable EECDH if available, errors are not fatal, we just keep going 521 * with any remaining key-exchange algorithms. 522 */ 523 (void) tls_set_eecdh_curve(server_ctx, props->eecdh_grade); 524 525 /* 526 * If we want to check client certificates, we have to indicate it in 527 * advance. By now we only allow to decide on a global basis. If we want 528 * to allow certificate based relaying, we must ask the client to provide 529 * one with SSL_VERIFY_PEER. The client now can decide, whether it 530 * provides one or not. We can enforce a failure of the negotiation with 531 * SSL_VERIFY_FAIL_IF_NO_PEER_CERT, if we do not allow a connection 532 * without one. In the "server hello" following the initialization by the 533 * "client hello" the server must provide a list of CAs it is willing to 534 * accept. Some clever clients will then select one from the list of 535 * available certificates matching these CAs. Netscape Communicator will 536 * present the list of certificates for selecting the one to be sent, or 537 * it will issue a warning, if there is no certificate matching the 538 * available CAs. 539 * 540 * With regard to the purpose of the certificate for relaying, we might like 541 * a later negotiation, maybe relaying would already be allowed for other 542 * reasons, but this would involve severe changes in the internal postfix 543 * logic, so we have to live with it the way it is. 544 */ 545 if (props->ask_ccert) 546 verify_flags = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE; 547 SSL_CTX_set_verify(server_ctx, verify_flags, 548 tls_verify_certificate_callback); 549 if (*props->CAfile) 550 SSL_CTX_set_client_CA_list(server_ctx, 551 SSL_load_client_CA_file(props->CAfile)); 552 553 /* 554 * Initialize our own TLS server handle, before diving into the details 555 * of TLS session cache management. 556 */ 557 app_ctx = tls_alloc_app_context(server_ctx, log_mask); 558 559 /* 560 * The session cache is implemented by the tlsmgr(8) server. 561 * 562 * XXX 200502 Surprise: when OpenSSL purges an entry from the in-memory 563 * cache, it also attempts to purge the entry from the on-disk cache. 564 * This is undesirable, especially when we set the in-memory cache size 565 * to 1. For this reason we don't allow OpenSSL to purge on-disk cache 566 * entries, and leave it up to the tlsmgr process instead. Found by 567 * Victor Duchovni. 568 */ 569 570 if (tls_mgr_policy(props->cache_type, &cachable) != TLS_MGR_STAT_OK) 571 cachable = 0; 572 573 if (cachable || props->set_sessid) { 574 575 /* 576 * Initialize the session cache. 577 * 578 * With a large number of concurrent smtpd(8) processes, it is not a 579 * good idea to cache multiple large session objects in each process. 580 * We set the internal cache size to 1, and don't register a 581 * "remove_cb" so as to avoid deleting good sessions from the 582 * external cache prematurely (when the internal cache is full, 583 * OpenSSL removes sessions from the external cache also)! 584 * 585 * This makes SSL_CTX_remove_session() not useful for flushing broken 586 * sessions from the external cache, so we must delete them directly 587 * (not via a callback). 588 * 589 * Set a session id context to identify to what type of server process 590 * created a session. In our case, the context is simply the name of 591 * the mail system: "Postfix/TLS". 592 */ 593 SSL_CTX_sess_set_cache_size(server_ctx, 1); 594 SSL_CTX_set_session_id_context(server_ctx, 595 (void *) &server_session_id_context, 596 sizeof(server_session_id_context)); 597 SSL_CTX_set_session_cache_mode(server_ctx, 598 SSL_SESS_CACHE_SERVER | 599 SSL_SESS_CACHE_NO_AUTO_CLEAR); 600 if (cachable) { 601 app_ctx->cache_type = mystrdup(props->cache_type); 602 603 SSL_CTX_sess_set_get_cb(server_ctx, get_server_session_cb); 604 SSL_CTX_sess_set_new_cb(server_ctx, new_server_session_cb); 605 } 606 607 /* 608 * OpenSSL ignores timed-out sessions. We need to set the internal 609 * cache timeout at least as high as the external cache timeout. This 610 * applies even if no internal cache is used. 611 */ 612 SSL_CTX_set_timeout(server_ctx, props->scache_timeout); 613 } else { 614 615 /* 616 * If we have no external cache, disable all caching. No use wasting 617 * server memory resources with sessions they are unlikely to be able 618 * to reuse. 619 */ 620 SSL_CTX_set_session_cache_mode(server_ctx, SSL_SESS_CACHE_OFF); 621 } 622 623 return (app_ctx); 624 } 625 626 /* 627 * This is the actual startup routine for a new connection. We expect that 628 * the SMTP buffers are flushed and the "220 Ready to start TLS" was sent to 629 * the client, so that we can immediately start the TLS handshake process. 630 */ 631 TLS_SESS_STATE *tls_server_start(const TLS_SERVER_START_PROPS *props) 632 { 633 int sts; 634 TLS_SESS_STATE *TLScontext; 635 const char *cipher_list; 636 TLS_APPL_STATE *app_ctx = props->ctx; 637 int log_mask = app_ctx->log_mask; 638 639 /* 640 * Implicitly enable logging of trust chain errors when verified certs 641 * are required. 642 */ 643 if (props->requirecert) 644 log_mask |= TLS_LOG_UNTRUSTED; 645 646 if (log_mask & TLS_LOG_VERBOSE) 647 msg_info("setting up TLS connection from %s", props->namaddr); 648 649 cipher_list = tls_set_ciphers(app_ctx, "TLS", props->cipher_grade, 650 props->cipher_exclusions); 651 if (cipher_list == 0) { 652 msg_warn("%s: %s: aborting TLS session", props->namaddr, 653 vstring_str(app_ctx->why)); 654 return (0); 655 } 656 if (log_mask & TLS_LOG_VERBOSE) 657 msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list); 658 659 /* 660 * Allocate a new TLScontext for the new connection and get an SSL 661 * structure. Add the location of TLScontext to the SSL to later retrieve 662 * the information inside the tls_verify_certificate_callback(). 663 */ 664 TLScontext = tls_alloc_sess_context(log_mask, props->namaddr); 665 TLScontext->cache_type = app_ctx->cache_type; 666 667 TLScontext->serverid = mystrdup(props->serverid); 668 TLScontext->am_server = 1; 669 670 TLScontext->fpt_dgst = mystrdup(props->fpt_dgst); 671 TLScontext->stream = props->stream; 672 673 ERR_clear_error(); 674 if ((TLScontext->con = (SSL *) SSL_new(app_ctx->ssl_ctx)) == 0) { 675 msg_warn("Could not allocate 'TLScontext->con' with SSL_new()"); 676 tls_print_errors(); 677 tls_free_context(TLScontext); 678 return (0); 679 } 680 if (!SSL_set_ex_data(TLScontext->con, TLScontext_index, TLScontext)) { 681 msg_warn("Could not set application data for 'TLScontext->con'"); 682 tls_print_errors(); 683 tls_free_context(TLScontext); 684 return (0); 685 } 686 687 /* 688 * Before really starting anything, try to seed the PRNG a little bit 689 * more. 690 */ 691 tls_int_seed(); 692 (void) tls_ext_seed(var_tls_daemon_rand_bytes); 693 694 /* 695 * Initialize the SSL connection to accept state. This should not be 696 * necessary anymore since 0.9.3, but the call is still in the library 697 * and maintaining compatibility never hurts. 698 */ 699 SSL_set_accept_state(TLScontext->con); 700 701 /* 702 * Connect the SSL connection with the network socket. 703 */ 704 if (SSL_set_fd(TLScontext->con, props->stream == 0 ? props->fd : 705 vstream_fileno(props->stream)) != 1) { 706 msg_info("SSL_set_fd error to %s", props->namaddr); 707 tls_print_errors(); 708 uncache_session(app_ctx->ssl_ctx, TLScontext); 709 tls_free_context(TLScontext); 710 return (0); 711 } 712 713 /* 714 * If the debug level selected is high enough, all of the data is dumped: 715 * TLS_LOG_TLSPKTS will dump the SSL negotiation, TLS_LOG_ALLPKTS will 716 * dump everything. 717 * 718 * We do have an SSL_set_fd() and now suddenly a BIO_ routine is called? 719 * Well there is a BIO below the SSL routines that is automatically 720 * created for us, so we can use it for debugging purposes. 721 */ 722 if (log_mask & TLS_LOG_TLSPKTS) 723 BIO_set_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb); 724 725 /* 726 * If we don't trigger the handshake in the library, leave control over 727 * SSL_accept/read/write/etc with the application. 728 */ 729 if (props->stream == 0) 730 return (TLScontext); 731 732 /* 733 * Turn on non-blocking I/O so that we can enforce timeouts on network 734 * I/O. 735 */ 736 non_blocking(vstream_fileno(props->stream), NON_BLOCKING); 737 738 /* 739 * Start TLS negotiations. This process is a black box that invokes our 740 * call-backs for session caching and certificate verification. 741 * 742 * Error handling: If the SSL handhake fails, we print out an error message 743 * and remove all TLS state concerning this session. 744 */ 745 sts = tls_bio_accept(vstream_fileno(props->stream), props->timeout, 746 TLScontext); 747 if (sts <= 0) { 748 if (ERR_peek_error() != 0) { 749 msg_info("SSL_accept error from %s: %d", props->namaddr, sts); 750 tls_print_errors(); 751 } else if (errno != 0) { 752 msg_info("SSL_accept error from %s: %m", props->namaddr); 753 } else { 754 msg_info("SSL_accept error from %s: lost connection", 755 props->namaddr); 756 } 757 tls_free_context(TLScontext); 758 return (0); 759 } 760 return (tls_server_post_accept(TLScontext)); 761 } 762 763 /* tls_server_post_accept - post-handshake processing */ 764 765 TLS_SESS_STATE *tls_server_post_accept(TLS_SESS_STATE *TLScontext) 766 { 767 const SSL_CIPHER *cipher; 768 X509 *peer; 769 char buf[CCERT_BUFSIZ]; 770 771 /* Turn off packet dump if only dumping the handshake */ 772 if ((TLScontext->log_mask & TLS_LOG_ALLPKTS) == 0) 773 BIO_set_callback(SSL_get_rbio(TLScontext->con), 0); 774 775 /* 776 * The caller may want to know if this session was reused or if a new 777 * session was negotiated. 778 */ 779 TLScontext->session_reused = SSL_session_reused(TLScontext->con); 780 if ((TLScontext->log_mask & TLS_LOG_CACHE) && TLScontext->session_reused) 781 msg_info("%s: Reusing old session", TLScontext->namaddr); 782 783 /* 784 * Let's see whether a peer certificate is available and what is the 785 * actual information. We want to save it for later use. 786 */ 787 peer = SSL_get_peer_certificate(TLScontext->con); 788 if (peer != NULL) { 789 TLScontext->peer_status |= TLS_CERT_FLAG_PRESENT; 790 if (SSL_get_verify_result(TLScontext->con) == X509_V_OK) 791 TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED; 792 793 if (TLScontext->log_mask & TLS_LOG_VERBOSE) { 794 X509_NAME_oneline(X509_get_subject_name(peer), 795 buf, sizeof(buf)); 796 msg_info("subject=%s", buf); 797 X509_NAME_oneline(X509_get_issuer_name(peer), 798 buf, sizeof(buf)); 799 msg_info("issuer=%s", buf); 800 } 801 TLScontext->peer_CN = tls_peer_CN(peer, TLScontext); 802 TLScontext->issuer_CN = tls_issuer_CN(peer, TLScontext); 803 TLScontext->peer_fingerprint = 804 tls_fingerprint(peer, TLScontext->fpt_dgst); 805 TLScontext->peer_pkey_fprint = 806 tls_pkey_fprint(peer, TLScontext->fpt_dgst); 807 808 if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_PEERCERT)) { 809 msg_info("%s: subject_CN=%s, issuer=%s, fingerprint=%s" 810 ", pkey_fingerprint=%s", 811 TLScontext->namaddr, 812 TLScontext->peer_CN, TLScontext->issuer_CN, 813 TLScontext->peer_fingerprint, 814 TLScontext->peer_pkey_fprint); 815 } 816 X509_free(peer); 817 } else { 818 TLScontext->peer_CN = mystrdup(""); 819 TLScontext->issuer_CN = mystrdup(""); 820 TLScontext->peer_fingerprint = mystrdup(""); 821 } 822 823 /* 824 * Finally, collect information about protocol and cipher for logging 825 */ 826 TLScontext->protocol = SSL_get_version(TLScontext->con); 827 cipher = SSL_get_current_cipher(TLScontext->con); 828 TLScontext->cipher_name = SSL_CIPHER_get_name(cipher); 829 TLScontext->cipher_usebits = SSL_CIPHER_get_bits(cipher, 830 &(TLScontext->cipher_algbits)); 831 832 /* 833 * If the library triggered the SSL handshake, switch to the 834 * tls_timed_read/write() functions and make the TLScontext available to 835 * those functions. Otherwise, leave control over SSL_read/write/etc. 836 * with the application. 837 */ 838 if (TLScontext->stream != 0) 839 tls_stream_start(TLScontext->stream, TLScontext); 840 841 /* 842 * All the key facts in a single log entry. 843 */ 844 if (TLScontext->log_mask & TLS_LOG_SUMMARY) 845 msg_info("%s TLS connection established from %s: %s with cipher %s " 846 "(%d/%d bits)", !TLS_CERT_IS_PRESENT(TLScontext) ? "Anonymous" 847 : TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted", 848 TLScontext->namaddr, TLScontext->protocol, TLScontext->cipher_name, 849 TLScontext->cipher_usebits, TLScontext->cipher_algbits); 850 851 tls_int_seed(); 852 853 return (TLScontext); 854 } 855 856 #endif /* USE_TLS */ 857