1 /* $NetBSD: tls_server.c,v 1.8 2014/07/06 19:45:50 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_cert_fprint 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 #define NOENGINE ((ENGINE *) 0) 282 #define TLS_TKT_NOKEYS -1 /* No keys for encryption */ 283 #define TLS_TKT_STALE 0 /* No matching keys for decryption */ 284 #define TLS_TKT_ACCEPT 1 /* Ticket decryptable and re-usable */ 285 #define TLS_TKT_REISSUE 2 /* Ticket decryptable, not re-usable */ 286 287 /* ticket_cb - configure tls session ticket encrypt/decrypt context */ 288 289 #if defined(SSL_OP_NO_TICKET) \ 290 && !defined(OPENSSL_NO_TLSEXT) \ 291 && OPENSSL_VERSION_NUMBER >= 0x0090808fL 292 293 static int ticket_cb(SSL *con, unsigned char name[], unsigned char iv[], 294 EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int create) 295 { 296 static const EVP_MD *sha256; 297 static const EVP_CIPHER *aes128; 298 TLS_TICKET_KEY *key; 299 TLS_SESS_STATE *TLScontext = SSL_get_ex_data(con, TLScontext_index); 300 int timeout = ((int) SSL_CTX_get_timeout(SSL_get_SSL_CTX(con))) / 2; 301 302 if ((!sha256 && (sha256 = EVP_sha256()) == 0) 303 || (!aes128 && (aes128 = EVP_aes_128_cbc()) == 0) 304 || (key = tls_mgr_key(create ? 0 : name, timeout)) == 0 305 || (create && RAND_bytes(iv, TLS_TICKET_IVLEN) <= 0)) 306 return (create ? TLS_TKT_NOKEYS : TLS_TKT_STALE); 307 308 HMAC_Init_ex(hctx, key->hmac, TLS_TICKET_MACLEN, sha256, NOENGINE); 309 310 if (create) { 311 EVP_EncryptInit_ex(ctx, aes128, NOENGINE, key->bits, iv); 312 memcpy((char *) name, (char *) key->name, TLS_TICKET_NAMELEN); 313 if (TLScontext->log_mask & TLS_LOG_CACHE) 314 msg_info("%s: Issuing session ticket, key expiration: %ld", 315 TLScontext->namaddr, (long) key->tout); 316 } else { 317 EVP_DecryptInit_ex(ctx, aes128, NOENGINE, key->bits, iv); 318 if (TLScontext->log_mask & TLS_LOG_CACHE) 319 msg_info("%s: Decrypting session ticket, key expiration: %ld", 320 TLScontext->namaddr, (long) key->tout); 321 } 322 TLScontext->ticketed = 1; 323 return (TLS_TKT_ACCEPT); 324 } 325 326 #endif 327 328 /* tls_server_init - initialize the server-side TLS engine */ 329 330 TLS_APPL_STATE *tls_server_init(const TLS_SERVER_INIT_PROPS *props) 331 { 332 SSL_CTX *server_ctx; 333 long off = 0; 334 int verify_flags = SSL_VERIFY_NONE; 335 int cachable; 336 int scache_timeout; 337 int ticketable = 0; 338 int protomask; 339 TLS_APPL_STATE *app_ctx; 340 int log_mask; 341 342 /* 343 * Convert user loglevel to internal logmask. 344 */ 345 log_mask = tls_log_mask(props->log_param, props->log_level); 346 347 if (log_mask & TLS_LOG_VERBOSE) 348 msg_info("initializing the server-side TLS engine"); 349 350 /* 351 * Load (mostly cipher related) TLS-library internal main.cf parameters. 352 */ 353 tls_param_init(); 354 355 /* 356 * Detect mismatch between compile-time headers and run-time library. 357 */ 358 tls_check_version(); 359 360 /* 361 * Initialize the OpenSSL library by the book! To start with, we must 362 * initialize the algorithms. We want cleartext error messages instead of 363 * just error codes, so we load the error_strings. 364 */ 365 SSL_load_error_strings(); 366 OpenSSL_add_ssl_algorithms(); 367 368 /* 369 * First validate the protocols. If these are invalid, we can't continue. 370 */ 371 protomask = tls_protocol_mask(props->protocols); 372 if (protomask == TLS_PROTOCOL_INVALID) { 373 /* tls_protocol_mask() logs no warning. */ 374 msg_warn("Invalid TLS protocol list \"%s\": disabling TLS support", 375 props->protocols); 376 return (0); 377 } 378 379 /* 380 * Create an application data index for SSL objects, so that we can 381 * attach TLScontext information; this information is needed inside 382 * tls_verify_certificate_callback(). 383 */ 384 if (TLScontext_index < 0) { 385 if ((TLScontext_index = SSL_get_ex_new_index(0, 0, 0, 0, 0)) < 0) { 386 msg_warn("Cannot allocate SSL application data index: " 387 "disabling TLS support"); 388 return (0); 389 } 390 } 391 392 /* 393 * If the administrator specifies an unsupported digest algorithm, fail 394 * now, rather than in the middle of a TLS handshake. 395 */ 396 if (!tls_validate_digest(props->mdalg)) { 397 msg_warn("disabling TLS support"); 398 return (0); 399 } 400 401 /* 402 * Initialize the PRNG (Pseudo Random Number Generator) with some seed 403 * from external and internal sources. Don't enable TLS without some real 404 * entropy. 405 */ 406 if (tls_ext_seed(var_tls_daemon_rand_bytes) < 0) { 407 msg_warn("no entropy for TLS key generation: disabling TLS support"); 408 return (0); 409 } 410 tls_int_seed(); 411 412 /* 413 * The SSL/TLS specifications require the client to send a message in the 414 * oldest specification it understands with the highest level it 415 * understands in the message. Netscape communicator can still 416 * communicate with SSLv2 servers, so it sends out a SSLv2 client hello. 417 * To deal with it, our server must be SSLv2 aware (even if we don't like 418 * SSLv2), so we need to have the SSLv23 server here. If we want to limit 419 * the protocol level, we can add an option to not use SSLv2/v3/TLSv1 420 * later. 421 */ 422 ERR_clear_error(); 423 if ((server_ctx = SSL_CTX_new(SSLv23_server_method())) == 0) { 424 msg_warn("cannot allocate server SSL_CTX: disabling TLS support"); 425 tls_print_errors(); 426 return (0); 427 } 428 429 /* 430 * See the verify callback in tls_verify.c 431 */ 432 SSL_CTX_set_verify_depth(server_ctx, props->verifydepth + 1); 433 434 /* 435 * The session cache is implemented by the tlsmgr(8) server. 436 * 437 * XXX 200502 Surprise: when OpenSSL purges an entry from the in-memory 438 * cache, it also attempts to purge the entry from the on-disk cache. 439 * This is undesirable, especially when we set the in-memory cache size 440 * to 1. For this reason we don't allow OpenSSL to purge on-disk cache 441 * entries, and leave it up to the tlsmgr process instead. Found by 442 * Victor Duchovni. 443 */ 444 if (tls_mgr_policy(props->cache_type, &cachable, 445 &scache_timeout) != TLS_MGR_STAT_OK) 446 scache_timeout = 0; 447 if (scache_timeout <= 0) 448 cachable = 0; 449 450 /* 451 * Protocol work-arounds, OpenSSL version dependent. 452 */ 453 off |= tls_bug_bits(); 454 455 /* 456 * Add SSL_OP_NO_TICKET when the timeout is zero or library support is 457 * incomplete. The SSL_CTX_set_tlsext_ticket_key_cb feature was added in 458 * OpenSSL 0.9.8h, while SSL_NO_TICKET was added in 0.9.8f. 459 */ 460 #ifdef SSL_OP_NO_TICKET 461 #if !defined(OPENSSL_NO_TLSEXT) && OPENSSL_VERSION_NUMBER >= 0x0090808fL 462 ticketable = (scache_timeout > 0 && !(off & SSL_OP_NO_TICKET)); 463 if (ticketable) 464 SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_cb); 465 #endif 466 if (!ticketable) 467 off |= SSL_OP_NO_TICKET; 468 #endif 469 470 SSL_CTX_set_options(server_ctx, off); 471 472 /* 473 * Global protocol selection. 474 */ 475 if (protomask != 0) 476 SSL_CTX_set_options(server_ctx, 477 ((protomask & TLS_PROTOCOL_TLSv1) ? SSL_OP_NO_TLSv1 : 0L) 478 | ((protomask & TLS_PROTOCOL_TLSv1_1) ? SSL_OP_NO_TLSv1_1 : 0L) 479 | ((protomask & TLS_PROTOCOL_TLSv1_2) ? SSL_OP_NO_TLSv1_2 : 0L) 480 | ((protomask & TLS_PROTOCOL_SSLv3) ? SSL_OP_NO_SSLv3 : 0L) 481 | ((protomask & TLS_PROTOCOL_SSLv2) ? SSL_OP_NO_SSLv2 : 0L)); 482 483 /* 484 * Some sites may want to give the client less rope. On the other hand, 485 * this could trigger inter-operability issues, the client should not 486 * offer ciphers it implements poorly, but this hasn't stopped some 487 * vendors from getting it wrong. 488 * 489 * XXX: Given OpenSSL's security history, nobody should still be using 490 * 0.9.7, let alone 0.9.6 or earlier. Warning added to TLS_README.html. 491 */ 492 if (var_tls_preempt_clist) 493 SSL_CTX_set_options(server_ctx, SSL_OP_CIPHER_SERVER_PREFERENCE); 494 495 /* 496 * Set the call-back routine to debug handshake progress. 497 */ 498 if (log_mask & TLS_LOG_DEBUG) 499 SSL_CTX_set_info_callback(server_ctx, tls_info_callback); 500 501 /* 502 * Load the CA public key certificates for both the server cert and for 503 * the verification of client certificates. As provided by OpenSSL we 504 * support two types of CA certificate handling: One possibility is to 505 * add all CA certificates to one large CAfile, the other possibility is 506 * a directory pointed to by CApath, containing separate files for each 507 * CA with softlinks named after the hash values of the certificate. The 508 * first alternative has the advantage that the file is opened and read 509 * at startup time, so that you don't have the hassle to maintain another 510 * copy of the CApath directory for chroot-jail. 511 */ 512 if (tls_set_ca_certificate_info(server_ctx, 513 props->CAfile, props->CApath) < 0) { 514 /* tls_set_ca_certificate_info() already logs a warning. */ 515 SSL_CTX_free(server_ctx); /* 200411 */ 516 return (0); 517 } 518 519 /* 520 * Load the server public key certificate and private key from file and 521 * check whether the cert matches the key. We can use RSA certificates 522 * ("cert") DSA certificates ("dcert") or ECDSA certificates ("eccert"). 523 * All three can be made available at the same time. The CA certificates 524 * for all three are handled in the same setup already finished. Which 525 * one is used depends on the cipher negotiated (that is: the first 526 * cipher listed by the client which does match the server). A client 527 * with RSA only (e.g. Netscape) will use the RSA certificate only. A 528 * client with openssl-library will use RSA first if not especially 529 * changed in the cipher setup. 530 */ 531 if (tls_set_my_certificate_key_info(server_ctx, 532 props->cert_file, 533 props->key_file, 534 props->dcert_file, 535 props->dkey_file, 536 props->eccert_file, 537 props->eckey_file) < 0) { 538 /* tls_set_my_certificate_key_info() already logs a warning. */ 539 SSL_CTX_free(server_ctx); /* 200411 */ 540 return (0); 541 } 542 543 /* 544 * According to OpenSSL documentation, a temporary RSA key is needed when 545 * export ciphers are in use, because the certified key cannot be 546 * directly used. 547 */ 548 SSL_CTX_set_tmp_rsa_callback(server_ctx, tls_tmp_rsa_cb); 549 550 /* 551 * Diffie-Hellman key generation parameters can either be loaded from 552 * files (preferred) or taken from compiled in values. First, set the 553 * callback that will select the values when requested, then load the 554 * (possibly) available DH parameters from files. We are generous with 555 * the error handling, since we do have default values compiled in, so we 556 * will not abort but just log the error message. 557 */ 558 SSL_CTX_set_tmp_dh_callback(server_ctx, tls_tmp_dh_cb); 559 if (*props->dh1024_param_file != 0) 560 tls_set_dh_from_file(props->dh1024_param_file, 1024); 561 if (*props->dh512_param_file != 0) 562 tls_set_dh_from_file(props->dh512_param_file, 512); 563 564 /* 565 * Enable EECDH if available, errors are not fatal, we just keep going 566 * with any remaining key-exchange algorithms. 567 */ 568 (void) tls_set_eecdh_curve(server_ctx, props->eecdh_grade); 569 570 /* 571 * If we want to check client certificates, we have to indicate it in 572 * advance. By now we only allow to decide on a global basis. If we want 573 * to allow certificate based relaying, we must ask the client to provide 574 * one with SSL_VERIFY_PEER. The client now can decide, whether it 575 * provides one or not. We can enforce a failure of the negotiation with 576 * SSL_VERIFY_FAIL_IF_NO_PEER_CERT, if we do not allow a connection 577 * without one. In the "server hello" following the initialization by the 578 * "client hello" the server must provide a list of CAs it is willing to 579 * accept. Some clever clients will then select one from the list of 580 * available certificates matching these CAs. Netscape Communicator will 581 * present the list of certificates for selecting the one to be sent, or 582 * it will issue a warning, if there is no certificate matching the 583 * available CAs. 584 * 585 * With regard to the purpose of the certificate for relaying, we might like 586 * a later negotiation, maybe relaying would already be allowed for other 587 * reasons, but this would involve severe changes in the internal postfix 588 * logic, so we have to live with it the way it is. 589 */ 590 if (props->ask_ccert) 591 verify_flags = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE; 592 SSL_CTX_set_verify(server_ctx, verify_flags, 593 tls_verify_certificate_callback); 594 if (*props->CAfile) 595 SSL_CTX_set_client_CA_list(server_ctx, 596 SSL_load_client_CA_file(props->CAfile)); 597 598 /* 599 * Initialize our own TLS server handle, before diving into the details 600 * of TLS session cache management. 601 */ 602 app_ctx = tls_alloc_app_context(server_ctx, log_mask); 603 604 if (cachable || ticketable || props->set_sessid) { 605 606 /* 607 * Initialize the session cache. 608 * 609 * With a large number of concurrent smtpd(8) processes, it is not a 610 * good idea to cache multiple large session objects in each process. 611 * We set the internal cache size to 1, and don't register a 612 * "remove_cb" so as to avoid deleting good sessions from the 613 * external cache prematurely (when the internal cache is full, 614 * OpenSSL removes sessions from the external cache also)! 615 * 616 * This makes SSL_CTX_remove_session() not useful for flushing broken 617 * sessions from the external cache, so we must delete them directly 618 * (not via a callback). 619 * 620 * Set a session id context to identify to what type of server process 621 * created a session. In our case, the context is simply the name of 622 * the mail system: "Postfix/TLS". 623 */ 624 SSL_CTX_sess_set_cache_size(server_ctx, 1); 625 SSL_CTX_set_session_id_context(server_ctx, 626 (void *) &server_session_id_context, 627 sizeof(server_session_id_context)); 628 SSL_CTX_set_session_cache_mode(server_ctx, 629 SSL_SESS_CACHE_SERVER | 630 SSL_SESS_CACHE_NO_AUTO_CLEAR); 631 if (cachable) { 632 app_ctx->cache_type = mystrdup(props->cache_type); 633 634 SSL_CTX_sess_set_get_cb(server_ctx, get_server_session_cb); 635 SSL_CTX_sess_set_new_cb(server_ctx, new_server_session_cb); 636 } 637 638 /* 639 * OpenSSL ignores timed-out sessions. We need to set the internal 640 * cache timeout at least as high as the external cache timeout. This 641 * applies even if no internal cache is used. We set the session 642 * lifetime to twice the cache lifetime, which is also the issuing 643 * and retired key validation lifetime of session tickets keys. This 644 * way a session always lasts longer than the server's ability to 645 * decrypt its session ticket. Otherwise, a bug in OpenSSL may fail 646 * to re-issue tickets when sessions decrypt, but are expired. 647 */ 648 SSL_CTX_set_timeout(server_ctx, 2 * scache_timeout); 649 } else { 650 651 /* 652 * If we have no external cache, disable all caching. No use wasting 653 * server memory resources with sessions they are unlikely to be able 654 * to reuse. 655 */ 656 SSL_CTX_set_session_cache_mode(server_ctx, SSL_SESS_CACHE_OFF); 657 } 658 659 return (app_ctx); 660 } 661 662 /* 663 * This is the actual startup routine for a new connection. We expect that 664 * the SMTP buffers are flushed and the "220 Ready to start TLS" was sent to 665 * the client, so that we can immediately start the TLS handshake process. 666 */ 667 TLS_SESS_STATE *tls_server_start(const TLS_SERVER_START_PROPS *props) 668 { 669 int sts; 670 TLS_SESS_STATE *TLScontext; 671 const char *cipher_list; 672 TLS_APPL_STATE *app_ctx = props->ctx; 673 int log_mask = app_ctx->log_mask; 674 675 /* 676 * Implicitly enable logging of trust chain errors when verified certs 677 * are required. 678 */ 679 if (props->requirecert) 680 log_mask |= TLS_LOG_UNTRUSTED; 681 682 if (log_mask & TLS_LOG_VERBOSE) 683 msg_info("setting up TLS connection from %s", props->namaddr); 684 685 cipher_list = tls_set_ciphers(app_ctx, "TLS", props->cipher_grade, 686 props->cipher_exclusions); 687 if (cipher_list == 0) { 688 msg_warn("%s: %s: aborting TLS session", props->namaddr, 689 vstring_str(app_ctx->why)); 690 return (0); 691 } 692 if (log_mask & TLS_LOG_VERBOSE) 693 msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list); 694 695 /* 696 * Allocate a new TLScontext for the new connection and get an SSL 697 * structure. Add the location of TLScontext to the SSL to later retrieve 698 * the information inside the tls_verify_certificate_callback(). 699 */ 700 TLScontext = tls_alloc_sess_context(log_mask, props->namaddr); 701 TLScontext->cache_type = app_ctx->cache_type; 702 703 TLScontext->serverid = mystrdup(props->serverid); 704 TLScontext->am_server = 1; 705 TLScontext->stream = props->stream; 706 TLScontext->mdalg = props->mdalg; 707 708 ERR_clear_error(); 709 if ((TLScontext->con = (SSL *) SSL_new(app_ctx->ssl_ctx)) == 0) { 710 msg_warn("Could not allocate 'TLScontext->con' with SSL_new()"); 711 tls_print_errors(); 712 tls_free_context(TLScontext); 713 return (0); 714 } 715 if (!SSL_set_ex_data(TLScontext->con, TLScontext_index, TLScontext)) { 716 msg_warn("Could not set application data for 'TLScontext->con'"); 717 tls_print_errors(); 718 tls_free_context(TLScontext); 719 return (0); 720 } 721 722 /* 723 * Before really starting anything, try to seed the PRNG a little bit 724 * more. 725 */ 726 tls_int_seed(); 727 (void) tls_ext_seed(var_tls_daemon_rand_bytes); 728 729 /* 730 * Initialize the SSL connection to accept state. This should not be 731 * necessary anymore since 0.9.3, but the call is still in the library 732 * and maintaining compatibility never hurts. 733 */ 734 SSL_set_accept_state(TLScontext->con); 735 736 /* 737 * Connect the SSL connection with the network socket. 738 */ 739 if (SSL_set_fd(TLScontext->con, props->stream == 0 ? props->fd : 740 vstream_fileno(props->stream)) != 1) { 741 msg_info("SSL_set_fd error to %s", props->namaddr); 742 tls_print_errors(); 743 uncache_session(app_ctx->ssl_ctx, TLScontext); 744 tls_free_context(TLScontext); 745 return (0); 746 } 747 748 /* 749 * If the debug level selected is high enough, all of the data is dumped: 750 * TLS_LOG_TLSPKTS will dump the SSL negotiation, TLS_LOG_ALLPKTS will 751 * dump everything. 752 * 753 * We do have an SSL_set_fd() and now suddenly a BIO_ routine is called? 754 * Well there is a BIO below the SSL routines that is automatically 755 * created for us, so we can use it for debugging purposes. 756 */ 757 if (log_mask & TLS_LOG_TLSPKTS) 758 BIO_set_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb); 759 760 /* 761 * If we don't trigger the handshake in the library, leave control over 762 * SSL_accept/read/write/etc with the application. 763 */ 764 if (props->stream == 0) 765 return (TLScontext); 766 767 /* 768 * Turn on non-blocking I/O so that we can enforce timeouts on network 769 * I/O. 770 */ 771 non_blocking(vstream_fileno(props->stream), NON_BLOCKING); 772 773 /* 774 * Start TLS negotiations. This process is a black box that invokes our 775 * call-backs for session caching and certificate verification. 776 * 777 * Error handling: If the SSL handhake fails, we print out an error message 778 * and remove all TLS state concerning this session. 779 */ 780 sts = tls_bio_accept(vstream_fileno(props->stream), props->timeout, 781 TLScontext); 782 if (sts <= 0) { 783 if (ERR_peek_error() != 0) { 784 msg_info("SSL_accept error from %s: %d", props->namaddr, sts); 785 tls_print_errors(); 786 } else if (errno != 0) { 787 msg_info("SSL_accept error from %s: %m", props->namaddr); 788 } else { 789 msg_info("SSL_accept error from %s: lost connection", 790 props->namaddr); 791 } 792 tls_free_context(TLScontext); 793 return (0); 794 } 795 return (tls_server_post_accept(TLScontext)); 796 } 797 798 /* tls_server_post_accept - post-handshake processing */ 799 800 TLS_SESS_STATE *tls_server_post_accept(TLS_SESS_STATE *TLScontext) 801 { 802 SSL_CIPHER_const SSL_CIPHER *cipher; 803 X509 *peer; 804 char buf[CCERT_BUFSIZ]; 805 806 /* Turn off packet dump if only dumping the handshake */ 807 if ((TLScontext->log_mask & TLS_LOG_ALLPKTS) == 0) 808 BIO_set_callback(SSL_get_rbio(TLScontext->con), 0); 809 810 /* 811 * The caller may want to know if this session was reused or if a new 812 * session was negotiated. 813 */ 814 TLScontext->session_reused = SSL_session_reused(TLScontext->con); 815 if ((TLScontext->log_mask & TLS_LOG_CACHE) && TLScontext->session_reused) 816 msg_info("%s: Reusing old session%s", TLScontext->namaddr, 817 TLScontext->ticketed ? " (RFC 5077 session ticket)" : ""); 818 819 /* 820 * Let's see whether a peer certificate is available and what is the 821 * actual information. We want to save it for later use. 822 */ 823 peer = SSL_get_peer_certificate(TLScontext->con); 824 if (peer != NULL) { 825 TLScontext->peer_status |= TLS_CERT_FLAG_PRESENT; 826 if (SSL_get_verify_result(TLScontext->con) == X509_V_OK) 827 TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED; 828 829 if (TLScontext->log_mask & TLS_LOG_VERBOSE) { 830 X509_NAME_oneline(X509_get_subject_name(peer), 831 buf, sizeof(buf)); 832 msg_info("subject=%s", buf); 833 X509_NAME_oneline(X509_get_issuer_name(peer), 834 buf, sizeof(buf)); 835 msg_info("issuer=%s", buf); 836 } 837 TLScontext->peer_CN = tls_peer_CN(peer, TLScontext); 838 TLScontext->issuer_CN = tls_issuer_CN(peer, TLScontext); 839 TLScontext->peer_cert_fprint = tls_cert_fprint(peer, TLScontext->mdalg); 840 TLScontext->peer_pkey_fprint = tls_pkey_fprint(peer, TLScontext->mdalg); 841 842 if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_PEERCERT)) { 843 msg_info("%s: subject_CN=%s, issuer=%s, fingerprint=%s" 844 ", pkey_fingerprint=%s", 845 TLScontext->namaddr, 846 TLScontext->peer_CN, TLScontext->issuer_CN, 847 TLScontext->peer_cert_fprint, 848 TLScontext->peer_pkey_fprint); 849 } 850 X509_free(peer); 851 } else { 852 TLScontext->peer_CN = mystrdup(""); 853 TLScontext->issuer_CN = mystrdup(""); 854 TLScontext->peer_cert_fprint = mystrdup(""); 855 TLScontext->peer_pkey_fprint = mystrdup(""); 856 } 857 858 /* 859 * Finally, collect information about protocol and cipher for logging 860 */ 861 TLScontext->protocol = SSL_get_version(TLScontext->con); 862 cipher = SSL_get_current_cipher(TLScontext->con); 863 TLScontext->cipher_name = SSL_CIPHER_get_name(cipher); 864 TLScontext->cipher_usebits = SSL_CIPHER_get_bits(cipher, 865 &(TLScontext->cipher_algbits)); 866 867 /* 868 * If the library triggered the SSL handshake, switch to the 869 * tls_timed_read/write() functions and make the TLScontext available to 870 * those functions. Otherwise, leave control over SSL_read/write/etc. 871 * with the application. 872 */ 873 if (TLScontext->stream != 0) 874 tls_stream_start(TLScontext->stream, TLScontext); 875 876 /* 877 * All the key facts in a single log entry. 878 */ 879 if (TLScontext->log_mask & TLS_LOG_SUMMARY) 880 msg_info("%s TLS connection established from %s: %s with cipher %s " 881 "(%d/%d bits)", !TLS_CERT_IS_PRESENT(TLScontext) ? "Anonymous" 882 : TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted", 883 TLScontext->namaddr, TLScontext->protocol, TLScontext->cipher_name, 884 TLScontext->cipher_usebits, TLScontext->cipher_algbits); 885 886 tls_int_seed(); 887 888 return (TLScontext); 889 } 890 891 #endif /* USE_TLS */ 892