1/*++ 2/* NAME 3/* tls_server 3 4/* SUMMARY 5/* server-side TLS engine 6/* SYNOPSIS 7/* #include <tls.h> 8/* 9/* TLS_APPL_STATE *tls_server_init(props) 10/* const TLS_SERVER_INIT_PROPS *props; 11/* 12/* TLS_SESS_STATE *tls_server_start(props) 13/* const TLS_SERVER_START_PROPS *props; 14/* 15/* TLS_SESS_STATE *tls_server_post_accept(TLScontext) 16/* TLS_SESS_STATE *TLScontext; 17/* 18/* void tls_server_stop(app_ctx, stream, failure, TLScontext) 19/* TLS_APPL_STATE *app_ctx; 20/* VSTREAM *stream; 21/* int failure; 22/* TLS_SESS_STATE *TLScontext; 23/* DESCRIPTION 24/* This module is the interface between Postfix TLS servers, 25/* the OpenSSL library, and the TLS entropy and cache manager. 26/* 27/* See "EVENT_DRIVEN APPLICATIONS" below for using this code 28/* in event-driven programs. 29/* 30/* tls_server_init() is called once when the SMTP server 31/* initializes. 32/* Certificate details are also decided during this phase, 33/* so that peer-specific behavior is not possible. 34/* 35/* tls_server_start() activates the TLS feature for the VSTREAM 36/* passed as argument. We assume that network buffers are flushed 37/* and the TLS handshake can begin immediately. 38/* 39/* tls_server_stop() sends the "close notify" alert via 40/* SSL_shutdown() to the peer and resets all connection specific 41/* TLS data. As RFC2487 does not specify a separate shutdown, it 42/* is assumed that the underlying TCP connection is shut down 43/* immediately afterwards. Any further writes to the channel will 44/* be discarded, and any further reads will report end-of-file. 45/* If the failure flag is set, no SSL_shutdown() handshake is performed. 46/* 47/* Once the TLS connection is initiated, information about the TLS 48/* state is available via the TLScontext structure: 49/* .IP TLScontext->protocol 50/* the protocol name (SSLv2, SSLv3, TLSv1), 51/* .IP TLScontext->cipher_name 52/* the cipher name (e.g. RC4/MD5), 53/* .IP TLScontext->cipher_usebits 54/* the number of bits actually used (e.g. 40), 55/* .IP TLScontext->cipher_algbits 56/* the number of bits the algorithm is based on (e.g. 128). 57/* .PP 58/* The last two values may differ from each other when export-strength 59/* encryption is used. 60/* 61/* If the peer offered a certificate, part of the certificate data are 62/* available as: 63/* .IP TLScontext->peer_status 64/* A bitmask field that records the status of the peer certificate 65/* verification. One or more of TLS_CERT_FLAG_PRESENT and 66/* TLS_CERT_FLAG_TRUSTED. 67/* .IP TLScontext->peer_CN 68/* Extracted CommonName of the peer, or zero-length string 69/* when information could not be extracted. 70/* .IP TLScontext->issuer_CN 71/* Extracted CommonName of the issuer, or zero-length string 72/* when information could not be extracted. 73/* .IP TLScontext->peer_cert_fprint 74/* Fingerprint of the certificate, or zero-length string when no peer 75/* certificate is available. 76/* .PP 77/* If no peer certificate is presented the peer_status is set to 0. 78/* EVENT_DRIVEN APPLICATIONS 79/* .ad 80/* .fi 81/* Event-driven programs manage multiple I/O channels. Such 82/* programs cannot use the synchronous VSTREAM-over-TLS 83/* implementation that the current TLS library provides, 84/* including tls_server_stop() and the underlying tls_stream(3) 85/* and tls_bio_ops(3) routines. 86/* 87/* With the current TLS library implementation, this means 88/* that the application is responsible for calling and retrying 89/* SSL_accept(), SSL_read(), SSL_write() and SSL_shutdown(). 90/* 91/* To maintain control over TLS I/O, an event-driven server 92/* invokes tls_server_start() with a null VSTREAM argument and 93/* with an fd argument that specifies the I/O file descriptor. 94/* Then, tls_server_start() performs all the necessary 95/* preparations before the TLS handshake and returns a partially 96/* populated TLS context. The event-driven application is then 97/* responsible for invoking SSL_accept(), and if successful, 98/* for invoking tls_server_post_accept() to finish the work 99/* that was started by tls_server_start(). In case of unrecoverable 100/* failure, tls_server_post_accept() destroys the TLS context 101/* and returns a null pointer value. 102/* LICENSE 103/* .ad 104/* .fi 105/* This software is free. You can do with it whatever you want. 106/* The original author kindly requests that you acknowledge 107/* the use of his software. 108/* AUTHOR(S) 109/* Originally written by: 110/* Lutz Jaenicke 111/* BTU Cottbus 112/* Allgemeine Elektrotechnik 113/* Universitaetsplatz 3-4 114/* D-03044 Cottbus, Germany 115/* 116/* Updated by: 117/* Wietse Venema 118/* IBM T.J. Watson Research 119/* P.O. Box 704 120/* Yorktown Heights, NY 10598, USA 121/* 122/* Victor Duchovni 123/* Morgan Stanley 124/*--*/ 125 126/* System library. */ 127 128#include <sys_defs.h> 129 130#ifdef USE_TLS 131#include <unistd.h> 132#include <string.h> 133 134/* Utility library. */ 135 136#include <mymalloc.h> 137#include <vstring.h> 138#include <vstream.h> 139#include <dict.h> 140#include <stringops.h> 141#include <msg.h> 142#include <hex_code.h> 143#include <iostuff.h> /* non-blocking */ 144 145/* Global library. */ 146 147#include <mail_params.h> 148 149/* TLS library. */ 150 151#include <tls_mgr.h> 152#define TLS_INTERNAL 153#include <tls.h> 154 155#define STR(x) vstring_str(x) 156#define LEN(x) VSTRING_LEN(x) 157 158/* Application-specific. */ 159 160 /* 161 * The session_id_context indentifies the service that created a session. 162 * This information is used to distinguish between multiple TLS-based 163 * servers running on the same server. We use the name of the mail system. 164 */ 165static const char server_session_id_context[] = "Postfix/TLS"; 166 167/* get_server_session_cb - callback to retrieve session from server cache */ 168 169static SSL_SESSION *get_server_session_cb(SSL *ssl, unsigned char *session_id, 170 int session_id_length, 171 int *unused_copy) 172{ 173 const char *myname = "get_server_session_cb"; 174 TLS_SESS_STATE *TLScontext; 175 VSTRING *cache_id; 176 VSTRING *session_data = vstring_alloc(2048); 177 SSL_SESSION *session = 0; 178 179 if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0) 180 msg_panic("%s: null TLScontext in session lookup callback", myname); 181 182#define GEN_CACHE_ID(buf, id, len, service) \ 183 do { \ 184 buf = vstring_alloc(2 * (len + strlen(service))); \ 185 hex_encode(buf, (char *) (id), (len)); \ 186 vstring_sprintf_append(buf, "&s=%s", (service)); \ 187 vstring_sprintf_append(buf, "&l=%ld", (long) SSLeay()); \ 188 } while (0) 189 190 191 GEN_CACHE_ID(cache_id, session_id, session_id_length, TLScontext->serverid); 192 193 if (TLScontext->log_mask & TLS_LOG_CACHE) 194 msg_info("%s: looking up session %s in %s cache", TLScontext->namaddr, 195 STR(cache_id), TLScontext->cache_type); 196 197 /* 198 * Load the session from cache and decode it. 199 */ 200 if (tls_mgr_lookup(TLScontext->cache_type, STR(cache_id), 201 session_data) == TLS_MGR_STAT_OK) { 202 session = tls_session_activate(STR(session_data), LEN(session_data)); 203 if (session && (TLScontext->log_mask & TLS_LOG_CACHE)) 204 msg_info("%s: reloaded session %s from %s cache", 205 TLScontext->namaddr, STR(cache_id), 206 TLScontext->cache_type); 207 } 208 209 /* 210 * Clean up. 211 */ 212 vstring_free(cache_id); 213 vstring_free(session_data); 214 215 return (session); 216} 217 218/* uncache_session - remove session from internal & external cache */ 219 220static void uncache_session(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext) 221{ 222 VSTRING *cache_id; 223 SSL_SESSION *session = SSL_get_session(TLScontext->con); 224 225 SSL_CTX_remove_session(ctx, session); 226 227 if (TLScontext->cache_type == 0) 228 return; 229 230 GEN_CACHE_ID(cache_id, session->session_id, session->session_id_length, 231 TLScontext->serverid); 232 233 if (TLScontext->log_mask & TLS_LOG_CACHE) 234 msg_info("%s: remove session %s from %s cache", TLScontext->namaddr, 235 STR(cache_id), TLScontext->cache_type); 236 237 tls_mgr_delete(TLScontext->cache_type, STR(cache_id)); 238 vstring_free(cache_id); 239} 240 241/* new_server_session_cb - callback to save session to server cache */ 242 243static int new_server_session_cb(SSL *ssl, SSL_SESSION *session) 244{ 245 const char *myname = "new_server_session_cb"; 246 VSTRING *cache_id; 247 TLS_SESS_STATE *TLScontext; 248 VSTRING *session_data; 249 250 if ((TLScontext = SSL_get_ex_data(ssl, TLScontext_index)) == 0) 251 msg_panic("%s: null TLScontext in new session callback", myname); 252 253 GEN_CACHE_ID(cache_id, session->session_id, session->session_id_length, 254 TLScontext->serverid); 255 256 if (TLScontext->log_mask & TLS_LOG_CACHE) 257 msg_info("%s: save session %s to %s cache", TLScontext->namaddr, 258 STR(cache_id), TLScontext->cache_type); 259 260 /* 261 * Passivate and save the session state. 262 */ 263 session_data = tls_session_passivate(session); 264 if (session_data) 265 tls_mgr_update(TLScontext->cache_type, STR(cache_id), 266 STR(session_data), LEN(session_data)); 267 268 /* 269 * Clean up. 270 */ 271 if (session_data) 272 vstring_free(session_data); 273 vstring_free(cache_id); 274 SSL_SESSION_free(session); /* 200502 */ 275 276 return (1); 277} 278 279#define NOENGINE ((ENGINE *) 0) 280#define TLS_TKT_NOKEYS -1 /* No keys for encryption */ 281#define TLS_TKT_STALE 0 /* No matching keys for decryption */ 282#define TLS_TKT_ACCEPT 1 /* Ticket decryptable and re-usable */ 283#define TLS_TKT_REISSUE 2 /* Ticket decryptable, not re-usable */ 284 285/* ticket_cb - configure tls session ticket encrypt/decrypt context */ 286 287#if defined(SSL_OP_NO_TICKET) \ 288 && !defined(OPENSSL_NO_TLSEXT) \ 289 && OPENSSL_VERSION_NUMBER >= 0x0090808fL 290 291static int ticket_cb(SSL *con, unsigned char name[], unsigned char iv[], 292 EVP_CIPHER_CTX * ctx, HMAC_CTX * hctx, int create) 293{ 294 static const EVP_MD *sha256; 295 static const EVP_CIPHER *aes128; 296 TLS_TICKET_KEY *key; 297 TLS_SESS_STATE *TLScontext = SSL_get_ex_data(con, TLScontext_index); 298 int timeout = ((int) SSL_CTX_get_timeout(SSL_get_SSL_CTX(con))) / 2; 299 300 if ((!sha256 && (sha256 = EVP_sha256()) == 0) 301 || (!aes128 && (aes128 = EVP_aes_128_cbc()) == 0) 302 || (key = tls_mgr_key(create ? 0 : name, timeout)) == 0 303 || (create && RAND_bytes(iv, TLS_TICKET_IVLEN) <= 0)) 304 return (create ? TLS_TKT_NOKEYS : TLS_TKT_STALE); 305 306 HMAC_Init_ex(hctx, key->hmac, TLS_TICKET_MACLEN, sha256, NOENGINE); 307 308 if (create) { 309 EVP_EncryptInit_ex(ctx, aes128, NOENGINE, key->bits, iv); 310 memcpy((char *) name, (char *) key->name, TLS_TICKET_NAMELEN); 311 if (TLScontext->log_mask & TLS_LOG_CACHE) 312 msg_info("%s: Issuing session ticket, key expiration: %ld", 313 TLScontext->namaddr, (long) key->tout); 314 } else { 315 EVP_DecryptInit_ex(ctx, aes128, NOENGINE, key->bits, iv); 316 if (TLScontext->log_mask & TLS_LOG_CACHE) 317 msg_info("%s: Decrypting session ticket, key expiration: %ld", 318 TLScontext->namaddr, (long) key->tout); 319 } 320 TLScontext->ticketed = 1; 321 return (TLS_TKT_ACCEPT); 322} 323 324#endif 325 326/* tls_server_init - initialize the server-side TLS engine */ 327 328TLS_APPL_STATE *tls_server_init(const TLS_SERVER_INIT_PROPS *props) 329{ 330 SSL_CTX *server_ctx; 331 long off = 0; 332 int verify_flags = SSL_VERIFY_NONE; 333 int cachable; 334 int scache_timeout; 335 int ticketable = 0; 336 int protomask; 337 TLS_APPL_STATE *app_ctx; 338 int log_mask; 339 340 /* 341 * Convert user loglevel to internal logmask. 342 */ 343 log_mask = tls_log_mask(props->log_param, props->log_level); 344 345 if (log_mask & TLS_LOG_VERBOSE) 346 msg_info("initializing the server-side TLS engine"); 347 348 /* 349 * Load (mostly cipher related) TLS-library internal main.cf parameters. 350 */ 351 tls_param_init(); 352 353 /* 354 * Detect mismatch between compile-time headers and run-time library. 355 */ 356 tls_check_version(); 357 358 /* 359 * Initialize the OpenSSL library by the book! To start with, we must 360 * initialize the algorithms. We want cleartext error messages instead of 361 * just error codes, so we load the error_strings. 362 */ 363 SSL_load_error_strings(); 364 OpenSSL_add_ssl_algorithms(); 365 366 /* 367 * First validate the protocols. If these are invalid, we can't continue. 368 */ 369 protomask = tls_protocol_mask(props->protocols); 370 if (protomask == TLS_PROTOCOL_INVALID) { 371 /* tls_protocol_mask() logs no warning. */ 372 msg_warn("Invalid TLS protocol list \"%s\": disabling TLS support", 373 props->protocols); 374 return (0); 375 } 376 377 /* 378 * Create an application data index for SSL objects, so that we can 379 * attach TLScontext information; this information is needed inside 380 * tls_verify_certificate_callback(). 381 */ 382 if (TLScontext_index < 0) { 383 if ((TLScontext_index = SSL_get_ex_new_index(0, 0, 0, 0, 0)) < 0) { 384 msg_warn("Cannot allocate SSL application data index: " 385 "disabling TLS support"); 386 return (0); 387 } 388 } 389 390 /* 391 * If the administrator specifies an unsupported digest algorithm, fail 392 * now, rather than in the middle of a TLS handshake. 393 */ 394 if (!tls_validate_digest(props->mdalg)) { 395 msg_warn("disabling TLS support"); 396 return (0); 397 } 398 399 /* 400 * Initialize the PRNG (Pseudo Random Number Generator) with some seed 401 * from external and internal sources. Don't enable TLS without some real 402 * entropy. 403 */ 404 if (tls_ext_seed(var_tls_daemon_rand_bytes) < 0) { 405 msg_warn("no entropy for TLS key generation: disabling TLS support"); 406 return (0); 407 } 408 tls_int_seed(); 409 410 /* 411 * The SSL/TLS specifications require the client to send a message in the 412 * oldest specification it understands with the highest level it 413 * understands in the message. Netscape communicator can still 414 * communicate with SSLv2 servers, so it sends out a SSLv2 client hello. 415 * To deal with it, our server must be SSLv2 aware (even if we don't like 416 * SSLv2), so we need to have the SSLv23 server here. If we want to limit 417 * the protocol level, we can add an option to not use SSLv2/v3/TLSv1 418 * later. 419 */ 420 ERR_clear_error(); 421 if ((server_ctx = SSL_CTX_new(SSLv23_server_method())) == 0) { 422 msg_warn("cannot allocate server SSL_CTX: disabling TLS support"); 423 tls_print_errors(); 424 return (0); 425 } 426 427 /* 428 * See the verify callback in tls_verify.c 429 */ 430 SSL_CTX_set_verify_depth(server_ctx, props->verifydepth + 1); 431 432 /* 433 * The session cache is implemented by the tlsmgr(8) server. 434 * 435 * XXX 200502 Surprise: when OpenSSL purges an entry from the in-memory 436 * cache, it also attempts to purge the entry from the on-disk cache. 437 * This is undesirable, especially when we set the in-memory cache size 438 * to 1. For this reason we don't allow OpenSSL to purge on-disk cache 439 * entries, and leave it up to the tlsmgr process instead. Found by 440 * Victor Duchovni. 441 */ 442 if (tls_mgr_policy(props->cache_type, &cachable, 443 &scache_timeout) != TLS_MGR_STAT_OK) 444 scache_timeout = 0; 445 if (scache_timeout <= 0) 446 cachable = 0; 447 448 /* 449 * Protocol work-arounds, OpenSSL version dependent. 450 */ 451 off |= tls_bug_bits(); 452 453 /* 454 * Add SSL_OP_NO_TICKET when the timeout is zero or library support is 455 * incomplete. The SSL_CTX_set_tlsext_ticket_key_cb feature was added in 456 * OpenSSL 0.9.8h, while SSL_NO_TICKET was added in 0.9.8f. 457 */ 458#ifdef SSL_OP_NO_TICKET 459#if !defined(OPENSSL_NO_TLSEXT) && OPENSSL_VERSION_NUMBER >= 0x0090808fL 460 ticketable = (scache_timeout > 0 && !(off & SSL_OP_NO_TICKET)); 461 if (ticketable) 462 SSL_CTX_set_tlsext_ticket_key_cb(server_ctx, ticket_cb); 463#endif 464 if (!ticketable) 465 off |= SSL_OP_NO_TICKET; 466#endif 467 468 SSL_CTX_set_options(server_ctx, off); 469 470 /* 471 * Global protocol selection. 472 */ 473 if (protomask != 0) 474 SSL_CTX_set_options(server_ctx, 475 ((protomask & TLS_PROTOCOL_TLSv1) ? SSL_OP_NO_TLSv1 : 0L) 476 | ((protomask & TLS_PROTOCOL_TLSv1_1) ? SSL_OP_NO_TLSv1_1 : 0L) 477 | ((protomask & TLS_PROTOCOL_TLSv1_2) ? SSL_OP_NO_TLSv1_2 : 0L) 478 | ((protomask & TLS_PROTOCOL_SSLv3) ? SSL_OP_NO_SSLv3 : 0L) 479 | ((protomask & TLS_PROTOCOL_SSLv2) ? SSL_OP_NO_SSLv2 : 0L)); 480 481 /* 482 * Some sites may want to give the client less rope. On the other hand, 483 * this could trigger inter-operability issues, the client should not 484 * offer ciphers it implements poorly, but this hasn't stopped some 485 * vendors from getting it wrong. 486 * 487 * XXX: Given OpenSSL's security history, nobody should still be using 488 * 0.9.7, let alone 0.9.6 or earlier. Warning added to TLS_README.html. 489 */ 490 if (var_tls_preempt_clist) 491 SSL_CTX_set_options(server_ctx, SSL_OP_CIPHER_SERVER_PREFERENCE); 492 493 /* 494 * Set the call-back routine to debug handshake progress. 495 */ 496 if (log_mask & TLS_LOG_DEBUG) 497 SSL_CTX_set_info_callback(server_ctx, tls_info_callback); 498 499 /* 500 * Load the CA public key certificates for both the server cert and for 501 * the verification of client certificates. As provided by OpenSSL we 502 * support two types of CA certificate handling: One possibility is to 503 * add all CA certificates to one large CAfile, the other possibility is 504 * a directory pointed to by CApath, containing separate files for each 505 * CA with softlinks named after the hash values of the certificate. The 506 * first alternative has the advantage that the file is opened and read 507 * at startup time, so that you don't have the hassle to maintain another 508 * copy of the CApath directory for chroot-jail. 509 */ 510 if (tls_set_ca_certificate_info(server_ctx, 511 props->CAfile, props->CApath) < 0) { 512 /* tls_set_ca_certificate_info() already logs a warning. */ 513 SSL_CTX_free(server_ctx); /* 200411 */ 514 return (0); 515 } 516 517 /* 518 * Load the server public key certificate and private key from file and 519 * check whether the cert matches the key. We can use RSA certificates 520 * ("cert") DSA certificates ("dcert") or ECDSA certificates ("eccert"). 521 * All three can be made available at the same time. The CA certificates 522 * for all three are handled in the same setup already finished. Which 523 * one is used depends on the cipher negotiated (that is: the first 524 * cipher listed by the client which does match the server). A client 525 * with RSA only (e.g. Netscape) will use the RSA certificate only. A 526 * client with openssl-library will use RSA first if not especially 527 * changed in the cipher setup. 528 */ 529 if (tls_set_my_certificate_key_info(server_ctx, 530 props->cert_file, 531 props->key_file, 532 props->dcert_file, 533 props->dkey_file, 534 props->eccert_file, 535 props->eckey_file) < 0) { 536 /* tls_set_my_certificate_key_info() already logs a warning. */ 537 SSL_CTX_free(server_ctx); /* 200411 */ 538 return (0); 539 } 540 541 /* 542 * According to OpenSSL documentation, a temporary RSA key is needed when 543 * export ciphers are in use, because the certified key cannot be 544 * directly used. 545 */ 546 SSL_CTX_set_tmp_rsa_callback(server_ctx, tls_tmp_rsa_cb); 547 548 /* 549 * Diffie-Hellman key generation parameters can either be loaded from 550 * files (preferred) or taken from compiled in values. First, set the 551 * callback that will select the values when requested, then load the 552 * (possibly) available DH parameters from files. We are generous with 553 * the error handling, since we do have default values compiled in, so we 554 * will not abort but just log the error message. 555 */ 556 SSL_CTX_set_tmp_dh_callback(server_ctx, tls_tmp_dh_cb); 557 if (*props->dh1024_param_file != 0) 558 tls_set_dh_from_file(props->dh1024_param_file, 1024); 559 if (*props->dh512_param_file != 0) 560 tls_set_dh_from_file(props->dh512_param_file, 512); 561 562 /* 563 * Enable EECDH if available, errors are not fatal, we just keep going 564 * with any remaining key-exchange algorithms. 565 */ 566 (void) tls_set_eecdh_curve(server_ctx, props->eecdh_grade); 567 568 /* 569 * If we want to check client certificates, we have to indicate it in 570 * advance. By now we only allow to decide on a global basis. If we want 571 * to allow certificate based relaying, we must ask the client to provide 572 * one with SSL_VERIFY_PEER. The client now can decide, whether it 573 * provides one or not. We can enforce a failure of the negotiation with 574 * SSL_VERIFY_FAIL_IF_NO_PEER_CERT, if we do not allow a connection 575 * without one. In the "server hello" following the initialization by the 576 * "client hello" the server must provide a list of CAs it is willing to 577 * accept. Some clever clients will then select one from the list of 578 * available certificates matching these CAs. Netscape Communicator will 579 * present the list of certificates for selecting the one to be sent, or 580 * it will issue a warning, if there is no certificate matching the 581 * available CAs. 582 * 583 * With regard to the purpose of the certificate for relaying, we might like 584 * a later negotiation, maybe relaying would already be allowed for other 585 * reasons, but this would involve severe changes in the internal postfix 586 * logic, so we have to live with it the way it is. 587 */ 588 if (props->ask_ccert) 589 verify_flags = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE; 590 SSL_CTX_set_verify(server_ctx, verify_flags, 591 tls_verify_certificate_callback); 592 if (*props->CAfile) 593 SSL_CTX_set_client_CA_list(server_ctx, 594 SSL_load_client_CA_file(props->CAfile)); 595 596 /* 597 * Initialize our own TLS server handle, before diving into the details 598 * of TLS session cache management. 599 */ 600 app_ctx = tls_alloc_app_context(server_ctx, log_mask); 601 602 if (cachable || ticketable || props->set_sessid) { 603 604 /* 605 * Initialize the session cache. 606 * 607 * With a large number of concurrent smtpd(8) processes, it is not a 608 * good idea to cache multiple large session objects in each process. 609 * We set the internal cache size to 1, and don't register a 610 * "remove_cb" so as to avoid deleting good sessions from the 611 * external cache prematurely (when the internal cache is full, 612 * OpenSSL removes sessions from the external cache also)! 613 * 614 * This makes SSL_CTX_remove_session() not useful for flushing broken 615 * sessions from the external cache, so we must delete them directly 616 * (not via a callback). 617 * 618 * Set a session id context to identify to what type of server process 619 * created a session. In our case, the context is simply the name of 620 * the mail system: "Postfix/TLS". 621 */ 622 SSL_CTX_sess_set_cache_size(server_ctx, 1); 623 SSL_CTX_set_session_id_context(server_ctx, 624 (void *) &server_session_id_context, 625 sizeof(server_session_id_context)); 626 SSL_CTX_set_session_cache_mode(server_ctx, 627 SSL_SESS_CACHE_SERVER | 628 SSL_SESS_CACHE_NO_AUTO_CLEAR); 629 if (cachable) { 630 app_ctx->cache_type = mystrdup(props->cache_type); 631 632 SSL_CTX_sess_set_get_cb(server_ctx, get_server_session_cb); 633 SSL_CTX_sess_set_new_cb(server_ctx, new_server_session_cb); 634 } 635 636 /* 637 * OpenSSL ignores timed-out sessions. We need to set the internal 638 * cache timeout at least as high as the external cache timeout. This 639 * applies even if no internal cache is used. We set the session 640 * lifetime to twice the cache lifetime, which is also the issuing 641 * and retired key validation lifetime of session tickets keys. This 642 * way a session always lasts longer than the server's ability to 643 * decrypt its session ticket. Otherwise, a bug in OpenSSL may fail 644 * to re-issue tickets when sessions decrypt, but are expired. 645 */ 646 SSL_CTX_set_timeout(server_ctx, 2 * scache_timeout); 647 } else { 648 649 /* 650 * If we have no external cache, disable all caching. No use wasting 651 * server memory resources with sessions they are unlikely to be able 652 * to reuse. 653 */ 654 SSL_CTX_set_session_cache_mode(server_ctx, SSL_SESS_CACHE_OFF); 655 } 656 657 return (app_ctx); 658} 659 660 /* 661 * This is the actual startup routine for a new connection. We expect that 662 * the SMTP buffers are flushed and the "220 Ready to start TLS" was sent to 663 * the client, so that we can immediately start the TLS handshake process. 664 */ 665TLS_SESS_STATE *tls_server_start(const TLS_SERVER_START_PROPS *props) 666{ 667 int sts; 668 TLS_SESS_STATE *TLScontext; 669 const char *cipher_list; 670 TLS_APPL_STATE *app_ctx = props->ctx; 671 int log_mask = app_ctx->log_mask; 672 673 /* 674 * Implicitly enable logging of trust chain errors when verified certs 675 * are required. 676 */ 677 if (props->requirecert) 678 log_mask |= TLS_LOG_UNTRUSTED; 679 680 if (log_mask & TLS_LOG_VERBOSE) 681 msg_info("setting up TLS connection from %s", props->namaddr); 682 683 cipher_list = tls_set_ciphers(app_ctx, "TLS", props->cipher_grade, 684 props->cipher_exclusions); 685 if (cipher_list == 0) { 686 msg_warn("%s: %s: aborting TLS session", props->namaddr, 687 vstring_str(app_ctx->why)); 688 return (0); 689 } 690 if (log_mask & TLS_LOG_VERBOSE) 691 msg_info("%s: TLS cipher list \"%s\"", props->namaddr, cipher_list); 692 693 /* 694 * Allocate a new TLScontext for the new connection and get an SSL 695 * structure. Add the location of TLScontext to the SSL to later retrieve 696 * the information inside the tls_verify_certificate_callback(). 697 */ 698 TLScontext = tls_alloc_sess_context(log_mask, props->namaddr); 699 TLScontext->cache_type = app_ctx->cache_type; 700 701 TLScontext->serverid = mystrdup(props->serverid); 702 TLScontext->am_server = 1; 703 TLScontext->stream = props->stream; 704 TLScontext->mdalg = props->mdalg; 705 706 ERR_clear_error(); 707 if ((TLScontext->con = (SSL *) SSL_new(app_ctx->ssl_ctx)) == 0) { 708 msg_warn("Could not allocate 'TLScontext->con' with SSL_new()"); 709 tls_print_errors(); 710 tls_free_context(TLScontext); 711 return (0); 712 } 713 if (!SSL_set_ex_data(TLScontext->con, TLScontext_index, TLScontext)) { 714 msg_warn("Could not set application data for 'TLScontext->con'"); 715 tls_print_errors(); 716 tls_free_context(TLScontext); 717 return (0); 718 } 719 720 /* 721 * Before really starting anything, try to seed the PRNG a little bit 722 * more. 723 */ 724 tls_int_seed(); 725 (void) tls_ext_seed(var_tls_daemon_rand_bytes); 726 727 /* 728 * Initialize the SSL connection to accept state. This should not be 729 * necessary anymore since 0.9.3, but the call is still in the library 730 * and maintaining compatibility never hurts. 731 */ 732 SSL_set_accept_state(TLScontext->con); 733 734 /* 735 * Connect the SSL connection with the network socket. 736 */ 737 if (SSL_set_fd(TLScontext->con, props->stream == 0 ? props->fd : 738 vstream_fileno(props->stream)) != 1) { 739 msg_info("SSL_set_fd error to %s", props->namaddr); 740 tls_print_errors(); 741 uncache_session(app_ctx->ssl_ctx, TLScontext); 742 tls_free_context(TLScontext); 743 return (0); 744 } 745 746 /* 747 * If the debug level selected is high enough, all of the data is dumped: 748 * TLS_LOG_TLSPKTS will dump the SSL negotiation, TLS_LOG_ALLPKTS will 749 * dump everything. 750 * 751 * We do have an SSL_set_fd() and now suddenly a BIO_ routine is called? 752 * Well there is a BIO below the SSL routines that is automatically 753 * created for us, so we can use it for debugging purposes. 754 */ 755 if (log_mask & TLS_LOG_TLSPKTS) 756 BIO_set_callback(SSL_get_rbio(TLScontext->con), tls_bio_dump_cb); 757 758 /* 759 * If we don't trigger the handshake in the library, leave control over 760 * SSL_accept/read/write/etc with the application. 761 */ 762 if (props->stream == 0) 763 return (TLScontext); 764 765 /* 766 * Turn on non-blocking I/O so that we can enforce timeouts on network 767 * I/O. 768 */ 769 non_blocking(vstream_fileno(props->stream), NON_BLOCKING); 770 771 /* 772 * Start TLS negotiations. This process is a black box that invokes our 773 * call-backs for session caching and certificate verification. 774 * 775 * Error handling: If the SSL handhake fails, we print out an error message 776 * and remove all TLS state concerning this session. 777 */ 778 sts = tls_bio_accept(vstream_fileno(props->stream), props->timeout, 779 TLScontext); 780 if (sts <= 0) { 781 if (ERR_peek_error() != 0) { 782 msg_info("SSL_accept error from %s: %d", props->namaddr, sts); 783 tls_print_errors(); 784 } else if (errno != 0) { 785 msg_info("SSL_accept error from %s: %m", props->namaddr); 786 } else { 787 msg_info("SSL_accept error from %s: lost connection", 788 props->namaddr); 789 } 790 tls_free_context(TLScontext); 791 return (0); 792 } 793 return (tls_server_post_accept(TLScontext)); 794} 795 796/* tls_server_post_accept - post-handshake processing */ 797 798TLS_SESS_STATE *tls_server_post_accept(TLS_SESS_STATE *TLScontext) 799{ 800 SSL_CIPHER_const SSL_CIPHER *cipher; 801 X509 *peer; 802 char buf[CCERT_BUFSIZ]; 803 804 /* Turn off packet dump if only dumping the handshake */ 805 if ((TLScontext->log_mask & TLS_LOG_ALLPKTS) == 0) 806 BIO_set_callback(SSL_get_rbio(TLScontext->con), 0); 807 808 /* 809 * The caller may want to know if this session was reused or if a new 810 * session was negotiated. 811 */ 812 TLScontext->session_reused = SSL_session_reused(TLScontext->con); 813 if ((TLScontext->log_mask & TLS_LOG_CACHE) && TLScontext->session_reused) 814 msg_info("%s: Reusing old session%s", TLScontext->namaddr, 815 TLScontext->ticketed ? " (RFC 5077 session ticket)" : ""); 816 817 /* 818 * Let's see whether a peer certificate is available and what is the 819 * actual information. We want to save it for later use. 820 */ 821 peer = SSL_get_peer_certificate(TLScontext->con); 822 if (peer != NULL) { 823 TLScontext->peer_status |= TLS_CERT_FLAG_PRESENT; 824 if (SSL_get_verify_result(TLScontext->con) == X509_V_OK) 825 TLScontext->peer_status |= TLS_CERT_FLAG_TRUSTED; 826 827 if (TLScontext->log_mask & TLS_LOG_VERBOSE) { 828 X509_NAME_oneline(X509_get_subject_name(peer), 829 buf, sizeof(buf)); 830 msg_info("subject=%s", buf); 831 X509_NAME_oneline(X509_get_issuer_name(peer), 832 buf, sizeof(buf)); 833 msg_info("issuer=%s", buf); 834 } 835 TLScontext->peer_CN = tls_peer_CN(peer, TLScontext); 836 TLScontext->issuer_CN = tls_issuer_CN(peer, TLScontext); 837 TLScontext->peer_cert_fprint = tls_cert_fprint(peer, TLScontext->mdalg); 838 TLScontext->peer_pkey_fprint = tls_pkey_fprint(peer, TLScontext->mdalg); 839 840 if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_PEERCERT)) { 841 msg_info("%s: subject_CN=%s, issuer=%s, fingerprint=%s" 842 ", pkey_fingerprint=%s", 843 TLScontext->namaddr, 844 TLScontext->peer_CN, TLScontext->issuer_CN, 845 TLScontext->peer_cert_fprint, 846 TLScontext->peer_pkey_fprint); 847 } 848 X509_free(peer); 849 } else { 850 TLScontext->peer_CN = mystrdup(""); 851 TLScontext->issuer_CN = mystrdup(""); 852 TLScontext->peer_cert_fprint = mystrdup(""); 853 TLScontext->peer_pkey_fprint = mystrdup(""); 854 } 855 856 /* 857 * Finally, collect information about protocol and cipher for logging 858 */ 859 TLScontext->protocol = SSL_get_version(TLScontext->con); 860 cipher = SSL_get_current_cipher(TLScontext->con); 861 TLScontext->cipher_name = SSL_CIPHER_get_name(cipher); 862 TLScontext->cipher_usebits = SSL_CIPHER_get_bits(cipher, 863 &(TLScontext->cipher_algbits)); 864 865 /* 866 * If the library triggered the SSL handshake, switch to the 867 * tls_timed_read/write() functions and make the TLScontext available to 868 * those functions. Otherwise, leave control over SSL_read/write/etc. 869 * with the application. 870 */ 871 if (TLScontext->stream != 0) 872 tls_stream_start(TLScontext->stream, TLScontext); 873 874 /* 875 * All the key facts in a single log entry. 876 */ 877 if (TLScontext->log_mask & TLS_LOG_SUMMARY) 878 msg_info("%s TLS connection established from %s: %s with cipher %s " 879 "(%d/%d bits)", !TLS_CERT_IS_PRESENT(TLScontext) ? "Anonymous" 880 : TLS_CERT_IS_TRUSTED(TLScontext) ? "Trusted" : "Untrusted", 881 TLScontext->namaddr, TLScontext->protocol, TLScontext->cipher_name, 882 TLScontext->cipher_usebits, TLScontext->cipher_algbits); 883 884 tls_int_seed(); 885 886 return (TLScontext); 887} 888 889#endif /* USE_TLS */ 890