1 /* $NetBSD: tls_server.c,v 1.9 2017/02/14 01:16:48 christos 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 #if OPENSSL_VERSION_NUMBER >= 0x1000000fL 170 #define GET_SID(s, v, lptr) ((v) = SSL_SESSION_get_id((s), (lptr))) 171 172 #else /* Older OpenSSL releases */ 173 #define GET_SID(s, v, lptr) \ 174 do { (v) = (s)->session_id; *(lptr) = (s)->session_id_length; } while (0) 175 176 #endif /* OPENSSL_VERSION_NUMBER */ 177 178 /* OpenSSL 1.1.0 bitrot */ 179 #if OPENSSL_VERSION_NUMBER >= 0x10100000L 180 typedef const unsigned char *session_id_t; 181 182 #else 183 typedef unsigned char *session_id_t; 184 185 #endif 186 187 /* get_server_session_cb - callback to retrieve session from server cache */ 188 189 static SSL_SESSION *get_server_session_cb(SSL *ssl, session_id_t session_id, 190 int session_id_length, 191 int *unused_copy) 192 { 193 const char *myname = "get_server_session_cb"; 194 TLS_SESS_STATE *TLScontext; 195 VSTRING *cache_id; 196 VSTRING *session_data = vstring_alloc(2048); 197 SSL_SESSION *session = 0; 198 199 if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0) 200 msg_panic("%s: null TLScontext in session lookup callback", myname); 201 202 #define GEN_CACHE_ID(buf, id, len, service) \ 203 do { \ 204 buf = vstring_alloc(2 * (len + strlen(service))); \ 205 hex_encode(buf, (char *) (id), (len)); \ 206 vstring_sprintf_append(buf, "&s=%s", (service)); \ 207 vstring_sprintf_append(buf, "&l=%ld", (long) OpenSSL_version_num()); \ 208 } while (0) 209 210 211 GEN_CACHE_ID(cache_id, session_id, session_id_length, TLScontext->serverid); 212 213 if (TLScontext->log_mask & TLS_LOG_CACHE) 214 msg_info("%s: looking up session %s in %s cache", TLScontext->namaddr, 215 STR(cache_id), TLScontext->cache_type); 216 217 /* 218 * Load the session from cache and decode it. 219 */ 220 if (tls_mgr_lookup(TLScontext->cache_type, STR(cache_id), 221 session_data) == TLS_MGR_STAT_OK) { 222 session = tls_session_activate(STR(session_data), LEN(session_data)); 223 if (session && (TLScontext->log_mask & TLS_LOG_CACHE)) 224 msg_info("%s: reloaded session %s from %s cache", 225 TLScontext->namaddr, STR(cache_id), 226 TLScontext->cache_type); 227 } 228 229 /* 230 * Clean up. 231 */ 232 vstring_free(cache_id); 233 vstring_free(session_data); 234 235 return (session); 236 } 237 238 /* uncache_session - remove session from internal & external cache */ 239 240 static void uncache_session(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext) 241 { 242 VSTRING *cache_id; 243 SSL_SESSION *session = SSL_get_session(TLScontext->con); 244 const unsigned char *sid; 245 unsigned int sid_length; 246 247 SSL_CTX_remove_session(ctx, session); 248 249 if (TLScontext->cache_type == 0) 250 return; 251 252 GET_SID(session, sid, &sid_length); 253 GEN_CACHE_ID(cache_id, sid, sid_length, TLScontext->serverid); 254 255 if (TLScontext->log_mask & TLS_LOG_CACHE) 256 msg_info("%s: remove session %s from %s cache", TLScontext->namaddr, 257 STR(cache_id), TLScontext->cache_type); 258 259 tls_mgr_delete(TLScontext->cache_type, STR(cache_id)); 260 vstring_free(cache_id); 261 } 262 263 /* new_server_session_cb - callback to save session to server cache */ 264 265 static int new_server_session_cb(SSL *ssl, SSL_SESSION *session) 266 { 267 const char *myname = "new_server_session_cb"; 268 VSTRING *cache_id; 269 TLS_SESS_STATE *TLScontext; 270 VSTRING *session_data; 271 const unsigned char *sid; 272 unsigned int sid_length; 273 274 if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0) 275 msg_panic("%s: null TLScontext in new session callback", myname); 276 277 GET_SID(session, sid, &sid_length); 278 GEN_CACHE_ID(cache_id, sid, sid_length, TLScontext->serverid); 279 280 if (TLScontext->log_mask & TLS_LOG_CACHE) 281 msg_info("%s: save session %s to %s cache", TLScontext->namaddr, 282 STR(cache_id), TLScontext->cache_type); 283 284 /* 285 * Passivate and save the session state. 286 */ 287 session_data = tls_session_passivate(session); 288 if (session_data) 289 tls_mgr_update(TLScontext->cache_type, STR(cache_id), 290 STR(session_data), LEN(session_data)); 291 292 /* 293 * Clean up. 294 */ 295 if (session_data) 296 vstring_free(session_data); 297 vstring_free(cache_id); 298 SSL_SESSION_free(session); /* 200502 */ 299 300 return (1); 301 } 302 303 #define NOENGINE ((ENGINE *) 0) 304 #define TLS_TKT_NOKEYS -1 /* No keys for encryption */ 305 #define TLS_TKT_STALE 0 /* No matching keys for decryption */ 306 #define TLS_TKT_ACCEPT 1 /* Ticket decryptable and re-usable */ 307 #define TLS_TKT_REISSUE 2 /* Ticket decryptable, not re-usable */ 308 309 /* ticket_cb - configure tls session ticket encrypt/decrypt context */ 310 311 #if defined(SSL_OP_NO_TICKET) \ 312 && !defined(OPENSSL_NO_TLSEXT) \ 313 && OPENSSL_VERSION_NUMBER >= 0x0090808fL 314 315 static int ticket_cb(SSL *con, unsigned char name[], unsigned char iv[], 316 EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int create) 317 { 318 static const EVP_MD *sha256; 319 static const EVP_CIPHER *ciph; 320 TLS_TICKET_KEY *key; 321 TLS_SESS_STATE *TLScontext = SSL_get_ex_data(con, TLScontext_index); 322 int timeout = ((int) SSL_CTX_get_timeout(SSL_get_SSL_CTX(con))) / 2; 323 324 if ((!sha256 && (sha256 = EVP_sha256()) == 0) 325 || (!ciph && (ciph = EVP_get_cipherbyname(var_tls_tkt_cipher)) == 0) 326 || (key = tls_mgr_key(create ? 0 : name, timeout)) == 0 327 || (create && RAND_bytes(iv, TLS_TICKET_IVLEN) <= 0)) 328 return (create ? TLS_TKT_NOKEYS : TLS_TKT_STALE); 329 330 HMAC_Init_ex(hctx, key->hmac, TLS_TICKET_MACLEN, sha256, NOENGINE); 331 332 if (create) { 333 EVP_EncryptInit_ex(ctx, ciph, NOENGINE, key->bits, iv); 334 memcpy((void *) name, (void *) key->name, TLS_TICKET_NAMELEN); 335 if (TLScontext->log_mask & TLS_LOG_CACHE) 336 msg_info("%s: Issuing session ticket, key expiration: %ld", 337 TLScontext->namaddr, (long) key->tout); 338 } else { 339 EVP_DecryptInit_ex(ctx, ciph, NOENGINE, key->bits, iv); 340 if (TLScontext->log_mask & TLS_LOG_CACHE) 341 msg_info("%s: Decrypting session ticket, key expiration: %ld", 342 TLScontext->namaddr, (long) key->tout); 343 } 344 TLScontext->ticketed = 1; 345 return (TLS_TKT_ACCEPT); 346 } 347 348 #endif 349 350 /* tls_server_init - initialize the server-side TLS engine */ 351 352 TLS_APPL_STATE *tls_server_init(const TLS_SERVER_INIT_PROPS *props) 353 { 354 SSL_CTX *server_ctx; 355 long off = 0; 356 int verify_flags = SSL_VERIFY_NONE; 357 int cachable; 358 int scache_timeout; 359 int ticketable = 0; 360 int protomask; 361 TLS_APPL_STATE *app_ctx; 362 int log_mask; 363 364 /* 365 * Convert user loglevel to internal logmask. 366 */ 367 log_mask = tls_log_mask(props->log_param, props->log_level); 368 369 if (log_mask & TLS_LOG_VERBOSE) 370 msg_info("initializing the server-side TLS engine"); 371 372 /* 373 * Load (mostly cipher related) TLS-library internal main.cf parameters. 374 */ 375 tls_param_init(); 376 377 /* 378 * Detect mismatch between compile-time headers and run-time library. 379 */ 380 tls_check_version(); 381 382 #if OPENSSL_VERSION_NUMBER < 0x10100000L 383 384 /* 385 * Initialize the OpenSSL library by the book! To start with, we must 386 * initialize the algorithms. We want cleartext error messages instead of 387 * just error codes, so we load the error_strings. 388 */ 389 SSL_load_error_strings(); 390 OpenSSL_add_ssl_algorithms(); 391 #endif 392 393 /* 394 * First validate the protocols. If these are invalid, we can't continue. 395 */ 396 protomask = tls_protocol_mask(props->protocols); 397 if (protomask == TLS_PROTOCOL_INVALID) { 398 /* tls_protocol_mask() logs no warning. */ 399 msg_warn("Invalid TLS protocol list \"%s\": disabling TLS support", 400 props->protocols); 401 return (0); 402 } 403 404 /* 405 * Create an application data index for SSL objects, so that we can 406 * attach TLScontext information; this information is needed inside 407 * tls_verify_certificate_callback(). 408 */ 409 if (TLScontext_index < 0) { 410 if ((TLScontext_index = SSL_get_ex_new_index(0, 0, 0, 0, 0)) < 0) { 411 msg_warn("Cannot allocate SSL application data index: " 412 "disabling TLS support"); 413 return (0); 414 } 415 } 416 417 /* 418 * If the administrator specifies an unsupported digest algorithm, fail 419 * now, rather than in the middle of a TLS handshake. 420 */ 421 if (!tls_validate_digest(props->mdalg)) { 422 msg_warn("disabling TLS support"); 423 return (0); 424 } 425 426 /* 427 * Initialize the PRNG (Pseudo Random Number Generator) with some seed 428 * from external and internal sources. Don't enable TLS without some real 429 * entropy. 430 */ 431 if (tls_ext_seed(var_tls_daemon_rand_bytes) < 0) { 432 msg_warn("no entropy for TLS key generation: disabling TLS support"); 433 return (0); 434 } 435 tls_int_seed(); 436 437 /* 438 * The SSL/TLS specifications require the client to send a message in the 439 * oldest specification it understands with the highest level it 440 * understands in the message. Netscape communicator can still 441 * communicate with SSLv2 servers, so it sends out a SSLv2 client hello. 442 * To deal with it, our server must be SSLv2 aware (even if we don't like 443 * SSLv2), so we need to have the SSLv23 server here. If we want to limit 444 * the protocol level, we can add an option to not use SSLv2/v3/TLSv1 445 * later. 446 * 447 * OpenSSL 1.1.0-dev deprecates SSLv23_server_method() in favour of 448 * TLS_client_method(), with the change in question signalled via a new 449 * TLS_ANY_VERSION macro. 450 */ 451 ERR_clear_error(); 452 #if OPENSSL_VERSION_NUMBER >= 0x10100000L && defined(TLS_ANY_VERSION) 453 server_ctx = SSL_CTX_new(TLS_server_method()); 454 #else 455 server_ctx = SSL_CTX_new(SSLv23_server_method()); 456 #endif 457 if (server_ctx == 0) { 458 msg_warn("cannot allocate server SSL_CTX: disabling TLS support"); 459 tls_print_errors(); 460 return (0); 461 } 462 #ifdef SSL_SECOP_PEER 463 /* Backwards compatible security as a base for opportunistic TLS. */ 464 SSL_CTX_set_security_level(server_ctx, 0); 465 #endif 466 467 /* 468 * See the verify callback in tls_verify.c 469 */ 470 SSL_CTX_set_verify_depth(server_ctx, props->verifydepth + 1); 471 472 /* 473 * The session cache is implemented by the tlsmgr(8) server. 474 * 475 * XXX 200502 Surprise: when OpenSSL purges an entry from the in-memory 476 * cache, it also attempts to purge the entry from the on-disk cache. 477 * This is undesirable, especially when we set the in-memory cache size 478 * to 1. For this reason we don't allow OpenSSL to purge on-disk cache 479 * entries, and leave it up to the tlsmgr process instead. Found by 480 * Victor Duchovni. 481 */ 482 if (tls_mgr_policy(props->cache_type, &cachable, 483 &scache_timeout) != TLS_MGR_STAT_OK) 484 scache_timeout = 0; 485 if (scache_timeout <= 0) 486 cachable = 0; 487 488 /* 489 * Protocol work-arounds, OpenSSL version dependent. 490 */ 491 off |= tls_bug_bits(); 492 493 /* 494 * Add SSL_OP_NO_TICKET when the timeout is zero or library support is 495 * incomplete. The SSL_CTX_set_tlsext_ticket_key_cb feature was added in 496 * OpenSSL 0.9.8h, while SSL_NO_TICKET was added in 0.9.8f. 497 */ 498 #ifdef SSL_OP_NO_TICKET 499 #if !defined(OPENSSL_NO_TLSEXT) && OPENSSL_VERSION_NUMBER >= 0x0090808fL 500 ticketable = (*var_tls_tkt_cipher && scache_timeout > 0 501 && !(off & SSL_OP_NO_TICKET)); 502 if (ticketable) { 503 const EVP_CIPHER *ciph; 504 505 if ((ciph = EVP_get_cipherbyname(var_tls_tkt_cipher)) == 0 506 || EVP_CIPHER_mode(ciph) != EVP_CIPH_CBC_MODE 507 || EVP_CIPHER_iv_length(ciph) != TLS_TICKET_IVLEN 508 || EVP_CIPHER_key_length(ciph) < TLS_TICKET_IVLEN 509 || EVP_CIPHER_key_length(ciph) > TLS_TICKET_KEYLEN) { 510 msg_warn("%s: invalid value: %s; session tickets disabled", 511 VAR_TLS_TKT_CIPHER, var_tls_tkt_cipher); 512 ticketable = 0; 513 } 514 } 515 if (ticketable) 516 SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_cb); 517 #endif 518 if (!ticketable) 519 off |= SSL_OP_NO_TICKET; 520 #endif 521 522 SSL_CTX_set_options(server_ctx, off); 523 524 /* 525 * Global protocol selection. 526 */ 527 if (protomask != 0) 528 SSL_CTX_set_options(server_ctx, TLS_SSL_OP_PROTOMASK(protomask)); 529 530 /* 531 * Some sites may want to give the client less rope. On the other hand, 532 * this could trigger inter-operability issues, the client should not 533 * offer ciphers it implements poorly, but this hasn't stopped some 534 * vendors from getting it wrong. 535 * 536 * XXX: Given OpenSSL's security history, nobody should still be using 537 * 0.9.7, let alone 0.9.6 or earlier. Warning added to TLS_README.html. 538 */ 539 if (var_tls_preempt_clist) 540 SSL_CTX_set_options(server_ctx, SSL_OP_CIPHER_SERVER_PREFERENCE); 541 542 /* 543 * Set the call-back routine to debug handshake progress. 544 */ 545 if (log_mask & TLS_LOG_DEBUG) 546 SSL_CTX_set_info_callback(server_ctx, tls_info_callback); 547 548 /* 549 * Load the CA public key certificates for both the server cert and for 550 * the verification of client certificates. As provided by OpenSSL we 551 * support two types of CA certificate handling: One possibility is to 552 * add all CA certificates to one large CAfile, the other possibility is 553 * a directory pointed to by CApath, containing separate files for each 554 * CA with softlinks named after the hash values of the certificate. The 555 * first alternative has the advantage that the file is opened and read 556 * at startup time, so that you don't have the hassle to maintain another 557 * copy of the CApath directory for chroot-jail. 558 */ 559 if (tls_set_ca_certificate_info(server_ctx, 560 props->CAfile, props->CApath) < 0) { 561 /* tls_set_ca_certificate_info() already logs a warning. */ 562 SSL_CTX_free(server_ctx); /* 200411 */ 563 return (0); 564 } 565 566 /* 567 * Load the server public key certificate and private key from file and 568 * check whether the cert matches the key. We can use RSA certificates 569 * ("cert") DSA certificates ("dcert") or ECDSA certificates ("eccert"). 570 * All three can be made available at the same time. The CA certificates 571 * for all three are handled in the same setup already finished. Which 572 * one is used depends on the cipher negotiated (that is: the first 573 * cipher listed by the client which does match the server). A client 574 * with RSA only (e.g. Netscape) will use the RSA certificate only. A 575 * client with openssl-library will use RSA first if not especially 576 * changed in the cipher setup. 577 */ 578 if (tls_set_my_certificate_key_info(server_ctx, 579 props->cert_file, 580 props->key_file, 581 props->dcert_file, 582 props->dkey_file, 583 props->eccert_file, 584 props->eckey_file) < 0) { 585 /* tls_set_my_certificate_key_info() already logs a warning. */ 586 SSL_CTX_free(server_ctx); /* 200411 */ 587 return (0); 588 } 589 590 /* 591 * 2015-12-05: Ephemeral RSA removed from OpenSSL 1.1.0-dev 592 */ 593 #if OPENSSL_VERSION_NUMBER < 0x10100000L 594 595 /* 596 * According to OpenSSL documentation, a temporary RSA key is needed when 597 * export ciphers are in use, because the certified key cannot be 598 * directly used. 599 */ 600 SSL_CTX_set_tmp_rsa_callback(server_ctx, tls_tmp_rsa_cb); 601 #endif 602 603 /* 604 * Diffie-Hellman key generation parameters can either be loaded from 605 * files (preferred) or taken from compiled in values. First, set the 606 * callback that will select the values when requested, then load the 607 * (possibly) available DH parameters from files. We are generous with 608 * the error handling, since we do have default values compiled in, so we 609 * will not abort but just log the error message. 610 */ 611 SSL_CTX_set_tmp_dh_callback(server_ctx, tls_tmp_dh_cb); 612 if (*props->dh1024_param_file != 0) 613 tls_set_dh_from_file(props->dh1024_param_file, 1024); 614 if (*props->dh512_param_file != 0) 615 tls_set_dh_from_file(props->dh512_param_file, 512); 616 617 /* 618 * Enable EECDH if available, errors are not fatal, we just keep going 619 * with any remaining key-exchange algorithms. 620 */ 621 (void) tls_set_eecdh_curve(server_ctx, props->eecdh_grade); 622 623 /* 624 * If we want to check client certificates, we have to indicate it in 625 * advance. By now we only allow to decide on a global basis. If we want 626 * to allow certificate based relaying, we must ask the client to provide 627 * one with SSL_VERIFY_PEER. The client now can decide, whether it 628 * provides one or not. We can enforce a failure of the negotiation with 629 * SSL_VERIFY_FAIL_IF_NO_PEER_CERT, if we do not allow a connection 630 * without one. In the "server hello" following the initialization by the 631 * "client hello" the server must provide a list of CAs it is willing to 632 * accept. Some clever clients will then select one from the list of 633 * available certificates matching these CAs. Netscape Communicator will 634 * present the list of certificates for selecting the one to be sent, or 635 * it will issue a warning, if there is no certificate matching the 636 * available CAs. 637 * 638 * With regard to the purpose of the certificate for relaying, we might like 639 * a later negotiation, maybe relaying would already be allowed for other 640 * reasons, but this would involve severe changes in the internal postfix 641 * logic, so we have to live with it the way it is. 642 */ 643 if (props->ask_ccert) 644 verify_flags = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE; 645 SSL_CTX_set_verify(server_ctx, verify_flags, 646 tls_verify_certificate_callback); 647 if (*props->CAfile) 648 SSL_CTX_set_client_CA_list(server_ctx, 649 SSL_load_client_CA_file(props->CAfile)); 650 651 /* 652 * Initialize our own TLS server handle, before diving into the details 653 * of TLS session cache management. 654 */ 655 app_ctx = tls_alloc_app_context(server_ctx, log_mask); 656 657 if (cachable || ticketable || props->set_sessid) { 658 659 /* 660 * Initialize the session cache. 661 * 662 * With a large number of concurrent smtpd(8) processes, it is not a 663 * good idea to cache multiple large session objects in each process. 664 * We set the internal cache size to 1, and don't register a 665 * "remove_cb" so as to avoid deleting good sessions from the 666 * external cache prematurely (when the internal cache is full, 667 * OpenSSL removes sessions from the external cache also)! 668 * 669 * This makes SSL_CTX_remove_session() not useful for flushing broken 670 * sessions from the external cache, so we must delete them directly 671 * (not via a callback). 672 * 673 * Set a session id context to identify to what type of server process 674 * created a session. In our case, the context is simply the name of 675 * the mail system: "Postfix/TLS". 676 */ 677 SSL_CTX_sess_set_cache_size(server_ctx, 1); 678 SSL_CTX_set_session_id_context(server_ctx, 679 (void *) &server_session_id_context, 680 sizeof(server_session_id_context)); 681 SSL_CTX_set_session_cache_mode(server_ctx, 682 SSL_SESS_CACHE_SERVER | 683 SSL_SESS_CACHE_NO_AUTO_CLEAR); 684 if (cachable) { 685 app_ctx->cache_type = mystrdup(props->cache_type); 686 687 SSL_CTX_sess_set_get_cb(server_ctx, get_server_session_cb); 688 SSL_CTX_sess_set_new_cb(server_ctx, new_server_session_cb); 689 } 690 691 /* 692 * OpenSSL ignores timed-out sessions. We need to set the internal 693 * cache timeout at least as high as the external cache timeout. This 694 * applies even if no internal cache is used. We set the session 695 * lifetime to twice the cache lifetime, which is also the issuing 696 * and retired key validation lifetime of session tickets keys. This 697 * way a session always lasts longer than the server's ability to 698 * decrypt its session ticket. Otherwise, a bug in OpenSSL may fail 699 * to re-issue tickets when sessions decrypt, but are expired. 700 */ 701 SSL_CTX_set_timeout(server_ctx, 2 * scache_timeout); 702 } else { 703 704 /* 705 * If we have no external cache, disable all caching. No use wasting 706 * server memory resources with sessions they are unlikely to be able 707 * to reuse. 708 */ 709 SSL_CTX_set_session_cache_mode(server_ctx, SSL_SESS_CACHE_OFF); 710 } 711 712 return (app_ctx); 713 } 714 715 /* 716 * This is the actual startup routine for a new connection. We expect that 717 * the SMTP buffers are flushed and the "220 Ready to start TLS" was sent to 718 * the client, so that we can immediately start the TLS handshake process. 719 */ 720 TLS_SESS_STATE *tls_server_start(const TLS_SERVER_START_PROPS *props) 721 { 722 int sts; 723 TLS_SESS_STATE *TLScontext; 724 const char *cipher_list; 725 TLS_APPL_STATE *app_ctx = props->ctx; 726 int log_mask = app_ctx->log_mask; 727 728 /* 729 * Implicitly enable logging of trust chain errors when verified certs 730 * are required. 731 */ 732 if (props->requirecert) 733 log_mask |= TLS_LOG_UNTRUSTED; 734 735 if (log_mask & TLS_LOG_VERBOSE) 736 msg_info("setting up TLS connection from %s", props->namaddr); 737 738 cipher_list = tls_set_ciphers(app_ctx, "TLS", props->cipher_grade, 739 props->cipher_exclusions); 740 if (cipher_list == 0) { 741 msg_warn("%s: %s: aborting TLS session", props->namaddr, 742 vstring_str(app_ctx->why)); 743 return (0); 744 } 745 if (log_mask & TLS_LOG_VERBOSE) 746 msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list); 747 748 /* 749 * Allocate a new TLScontext for the new connection and get an SSL 750 * structure. Add the location of TLScontext to the SSL to later retrieve 751 * the information inside the tls_verify_certificate_callback(). 752 */ 753 TLScontext = tls_alloc_sess_context(log_mask, props->namaddr); 754 TLScontext->cache_type = app_ctx->cache_type; 755 756 TLScontext->serverid = mystrdup(props->serverid); 757 TLScontext->am_server = 1; 758 TLScontext->stream = props->stream; 759 TLScontext->mdalg = props->mdalg; 760 761 ERR_clear_error(); 762 if ((TLScontext->con = (SSL *) SSL_new(app_ctx->ssl_ctx)) == 0) { 763 msg_warn("Could not allocate 'TLScontext->con' with SSL_new()"); 764 tls_print_errors(); 765 tls_free_context(TLScontext); 766 return (0); 767 } 768 if (!SSL_set_ex_data(TLScontext->con, TLScontext_index, TLScontext)) { 769 msg_warn("Could not set application data for 'TLScontext->con'"); 770 tls_print_errors(); 771 tls_free_context(TLScontext); 772 return (0); 773 } 774 #ifdef SSL_SECOP_PEER 775 /* When authenticating the peer, use 80-bit plus OpenSSL security level */ 776 if (props->requirecert) 777 SSL_set_security_level(TLScontext->con, 1); 778 #endif 779 780 /* 781 * Before really starting anything, try to seed the PRNG a little bit 782 * more. 783 */ 784 tls_int_seed(); 785 (void) tls_ext_seed(var_tls_daemon_rand_bytes); 786 787 /* 788 * Initialize the SSL connection to accept state. This should not be 789 * necessary anymore since 0.9.3, but the call is still in the library 790 * and maintaining compatibility never hurts. 791 */ 792 SSL_set_accept_state(TLScontext->con); 793 794 /* 795 * Connect the SSL connection with the network socket. 796 */ 797 if (SSL_set_fd(TLScontext->con, props->stream == 0 ? props->fd : 798 vstream_fileno(props->stream)) != 1) { 799 msg_info("SSL_set_fd error to %s", props->namaddr); 800 tls_print_errors(); 801 uncache_session(app_ctx->ssl_ctx, TLScontext); 802 tls_free_context(TLScontext); 803 return (0); 804 } 805 806 /* 807 * If the debug level selected is high enough, all of the data is dumped: 808 * TLS_LOG_TLSPKTS will dump the SSL negotiation, TLS_LOG_ALLPKTS will 809 * dump everything. 810 * 811 * We do have an SSL_set_fd() and now suddenly a BIO_ routine is called? 812 * Well there is a BIO below the SSL routines that is automatically 813 * created for us, so we can use it for debugging purposes. 814 */ 815 if (log_mask & TLS_LOG_TLSPKTS) 816 BIO_set_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb); 817 818 /* 819 * If we don't trigger the handshake in the library, leave control over 820 * SSL_accept/read/write/etc with the application. 821 */ 822 if (props->stream == 0) 823 return (TLScontext); 824 825 /* 826 * Turn on non-blocking I/O so that we can enforce timeouts on network 827 * I/O. 828 */ 829 non_blocking(vstream_fileno(props->stream), NON_BLOCKING); 830 831 /* 832 * Start TLS negotiations. This process is a black box that invokes our 833 * call-backs for session caching and certificate verification. 834 * 835 * Error handling: If the SSL handhake fails, we print out an error message 836 * and remove all TLS state concerning this session. 837 */ 838 sts = tls_bio_accept(vstream_fileno(props->stream), props->timeout, 839 TLScontext); 840 if (sts <= 0) { 841 if (ERR_peek_error() != 0) { 842 msg_info("SSL_accept error from %s: %d", props->namaddr, sts); 843 tls_print_errors(); 844 } else if (errno != 0) { 845 msg_info("SSL_accept error from %s: %m", props->namaddr); 846 } else { 847 msg_info("SSL_accept error from %s: lost connection", 848 props->namaddr); 849 } 850 tls_free_context(TLScontext); 851 return (0); 852 } 853 return (tls_server_post_accept(TLScontext)); 854 } 855 856 /* tls_server_post_accept - post-handshake processing */ 857 858 TLS_SESS_STATE *tls_server_post_accept(TLS_SESS_STATE *TLScontext) 859 { 860 SSL_CIPHER_const SSL_CIPHER *cipher; 861 X509 *peer; 862 char buf[CCERT_BUFSIZ]; 863 864 /* Turn off packet dump if only dumping the handshake */ 865 if ((TLScontext->log_mask & TLS_LOG_ALLPKTS) == 0) 866 BIO_set_callback(SSL_get_rbio(TLScontext->con), 0); 867 868 /* 869 * The caller may want to know if this session was reused or if a new 870 * session was negotiated. 871 */ 872 TLScontext->session_reused = SSL_session_reused(TLScontext->con); 873 if ((TLScontext->log_mask & TLS_LOG_CACHE) && TLScontext->session_reused) 874 msg_info("%s: Reusing old session%s", TLScontext->namaddr, 875 TLScontext->ticketed ? " (RFC 5077 session ticket)" : ""); 876 877 /* 878 * Let's see whether a peer certificate is available and what is the 879 * actual information. We want to save it for later use. 880 */ 881 peer = SSL_get_peer_certificate(TLScontext->con); 882 if (peer != NULL) { 883 TLScontext->peer_status |= TLS_CERT_FLAG_PRESENT; 884 if (SSL_get_verify_result(TLScontext->con) == X509_V_OK) 885 TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED; 886 887 if (TLScontext->log_mask & TLS_LOG_VERBOSE) { 888 X509_NAME_oneline(X509_get_subject_name(peer), 889 buf, sizeof(buf)); 890 msg_info("subject=%s", printable(buf, '?')); 891 X509_NAME_oneline(X509_get_issuer_name(peer), 892 buf, sizeof(buf)); 893 msg_info("issuer=%s", printable(buf, '?')); 894 } 895 TLScontext->peer_CN = tls_peer_CN(peer, TLScontext); 896 TLScontext->issuer_CN = tls_issuer_CN(peer, TLScontext); 897 TLScontext->peer_cert_fprint = tls_cert_fprint(peer, TLScontext->mdalg); 898 TLScontext->peer_pkey_fprint = tls_pkey_fprint(peer, TLScontext->mdalg); 899 900 if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_PEERCERT)) { 901 msg_info("%s: subject_CN=%s, issuer=%s, fingerprint=%s" 902 ", pkey_fingerprint=%s", 903 TLScontext->namaddr, 904 TLScontext->peer_CN, TLScontext->issuer_CN, 905 TLScontext->peer_cert_fprint, 906 TLScontext->peer_pkey_fprint); 907 } 908 X509_free(peer); 909 910 /* 911 * Give them a clue. Problems with trust chain verification are 912 * logged when the session is first negotiated, before the session is 913 * stored into the cache. We don't want mystery failures, so log the 914 * fact the real problem is to be found in the past. 915 */ 916 if (!TLS_CERT_IS_TRUSTED(TLScontext) 917 && (TLScontext->log_mask & TLS_LOG_UNTRUSTED)) { 918 if (TLScontext->session_reused == 0) 919 tls_log_verify_error(TLScontext); 920 else 921 msg_info("%s: re-using session with untrusted certificate, " 922 "look for details earlier in the log", 923 TLScontext->namaddr); 924 } 925 } else { 926 TLScontext->peer_CN = mystrdup(""); 927 TLScontext->issuer_CN = mystrdup(""); 928 TLScontext->peer_cert_fprint = mystrdup(""); 929 TLScontext->peer_pkey_fprint = mystrdup(""); 930 } 931 932 /* 933 * Finally, collect information about protocol and cipher for logging 934 */ 935 TLScontext->protocol = SSL_get_version(TLScontext->con); 936 cipher = SSL_get_current_cipher(TLScontext->con); 937 TLScontext->cipher_name = SSL_CIPHER_get_name(cipher); 938 TLScontext->cipher_usebits = SSL_CIPHER_get_bits(cipher, 939 &(TLScontext->cipher_algbits)); 940 941 /* 942 * If the library triggered the SSL handshake, switch to the 943 * tls_timed_read/write() functions and make the TLScontext available to 944 * those functions. Otherwise, leave control over SSL_read/write/etc. 945 * with the application. 946 */ 947 if (TLScontext->stream != 0) 948 tls_stream_start(TLScontext->stream, TLScontext); 949 950 /* 951 * All the key facts in a single log entry. 952 */ 953 if (TLScontext->log_mask & TLS_LOG_SUMMARY) 954 msg_info("%s TLS connection established from %s: %s with cipher %s " 955 "(%d/%d bits)", !TLS_CERT_IS_PRESENT(TLScontext) ? "Anonymous" 956 : TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted", 957 TLScontext->namaddr, TLScontext->protocol, TLScontext->cipher_name, 958 TLScontext->cipher_usebits, TLScontext->cipher_algbits); 959 960 tls_int_seed(); 961 962 return (TLScontext); 963 } 964 965 #endif /* USE_TLS */ 966