| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2009 */ |
| 6 | /* See the file NOTICE for conditions of use and distribution. */ |
| 7 | |
| 8 | /* This module provides the TLS (aka SSL) support for Exim using the OpenSSL |
| 9 | library. It is #included into the tls.c file when that library is used. The |
| 10 | code herein is based on a patch that was originally contributed by Steve |
| 11 | Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara. |
| 12 | |
| 13 | No cryptographic code is included in Exim. All this module does is to call |
| 14 | functions from the OpenSSL library. */ |
| 15 | |
| 16 | |
| 17 | /* Heading stuff */ |
| 18 | |
| 19 | #include <openssl/lhash.h> |
| 20 | #include <openssl/ssl.h> |
| 21 | #include <openssl/err.h> |
| 22 | #include <openssl/rand.h> |
| 23 | |
| 24 | /* Structure for collecting random data for seeding. */ |
| 25 | |
| 26 | typedef struct randstuff { |
| 27 | struct timeval tv; |
| 28 | pid_t p; |
| 29 | } randstuff; |
| 30 | |
| 31 | /* Local static variables */ |
| 32 | |
| 33 | static BOOL verify_callback_called = FALSE; |
| 34 | static const uschar *sid_ctx = US"exim"; |
| 35 | |
| 36 | static SSL_CTX *ctx = NULL; |
| 37 | static SSL_CTX *ctx_sni = NULL; |
| 38 | static SSL *ssl = NULL; |
| 39 | |
| 40 | static char ssl_errstring[256]; |
| 41 | |
| 42 | static int ssl_session_timeout = 200; |
| 43 | static BOOL verify_optional = FALSE; |
| 44 | |
| 45 | static BOOL reexpand_tls_files_for_sni = FALSE; |
| 46 | |
| 47 | |
| 48 | typedef struct tls_ext_ctx_cb { |
| 49 | uschar *certificate; |
| 50 | uschar *privatekey; |
| 51 | uschar *dhparam; |
| 52 | /* these are cached from first expand */ |
| 53 | uschar *server_cipher_list; |
| 54 | /* only passed down to tls_error: */ |
| 55 | host_item *host; |
| 56 | } tls_ext_ctx_cb; |
| 57 | |
| 58 | /* should figure out a cleanup of API to handle state preserved per |
| 59 | implementation, for various reasons, which can be void * in the APIs. |
| 60 | For now, we hack around it. */ |
| 61 | tls_ext_ctx_cb *static_cbinfo = NULL; |
| 62 | |
| 63 | static int |
| 64 | setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional); |
| 65 | |
| 66 | |
| 67 | /************************************************* |
| 68 | * Handle TLS error * |
| 69 | *************************************************/ |
| 70 | |
| 71 | /* Called from lots of places when errors occur before actually starting to do |
| 72 | the TLS handshake, that is, while the session is still in clear. Always returns |
| 73 | DEFER for a server and FAIL for a client so that most calls can use "return |
| 74 | tls_error(...)" to do this processing and then give an appropriate return. A |
| 75 | single function is used for both server and client, because it is called from |
| 76 | some shared functions. |
| 77 | |
| 78 | Argument: |
| 79 | prefix text to include in the logged error |
| 80 | host NULL if setting up a server; |
| 81 | the connected host if setting up a client |
| 82 | msg error message or NULL if we should ask OpenSSL |
| 83 | |
| 84 | Returns: OK/DEFER/FAIL |
| 85 | */ |
| 86 | |
| 87 | static int |
| 88 | tls_error(uschar *prefix, host_item *host, uschar *msg) |
| 89 | { |
| 90 | if (msg == NULL) |
| 91 | { |
| 92 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 93 | msg = (uschar *)ssl_errstring; |
| 94 | } |
| 95 | |
| 96 | if (host == NULL) |
| 97 | { |
| 98 | uschar *conn_info = smtp_get_connection_info(); |
| 99 | if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) |
| 100 | conn_info += 5; |
| 101 | log_write(0, LOG_MAIN, "TLS error on %s (%s): %s", |
| 102 | conn_info, prefix, msg); |
| 103 | return DEFER; |
| 104 | } |
| 105 | else |
| 106 | { |
| 107 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s", |
| 108 | host->name, host->address, prefix, msg); |
| 109 | return FAIL; |
| 110 | } |
| 111 | } |
| 112 | |
| 113 | |
| 114 | |
| 115 | /************************************************* |
| 116 | * Callback to generate RSA key * |
| 117 | *************************************************/ |
| 118 | |
| 119 | /* |
| 120 | Arguments: |
| 121 | s SSL connection |
| 122 | export not used |
| 123 | keylength keylength |
| 124 | |
| 125 | Returns: pointer to generated key |
| 126 | */ |
| 127 | |
| 128 | static RSA * |
| 129 | rsa_callback(SSL *s, int export, int keylength) |
| 130 | { |
| 131 | RSA *rsa_key; |
| 132 | export = export; /* Shut picky compilers up */ |
| 133 | DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength); |
| 134 | rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL); |
| 135 | if (rsa_key == NULL) |
| 136 | { |
| 137 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 138 | log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s", |
| 139 | ssl_errstring); |
| 140 | return NULL; |
| 141 | } |
| 142 | return rsa_key; |
| 143 | } |
| 144 | |
| 145 | |
| 146 | |
| 147 | |
| 148 | /************************************************* |
| 149 | * Callback for verification * |
| 150 | *************************************************/ |
| 151 | |
| 152 | /* The SSL library does certificate verification if set up to do so. This |
| 153 | callback has the current yes/no state is in "state". If verification succeeded, |
| 154 | we set up the tls_peerdn string. If verification failed, what happens depends |
| 155 | on whether the client is required to present a verifiable certificate or not. |
| 156 | |
| 157 | If verification is optional, we change the state to yes, but still log the |
| 158 | verification error. For some reason (it really would help to have proper |
| 159 | documentation of OpenSSL), this callback function then gets called again, this |
| 160 | time with state = 1. In fact, that's useful, because we can set up the peerdn |
| 161 | value, but we must take care not to set the private verified flag on the second |
| 162 | time through. |
| 163 | |
| 164 | Note: this function is not called if the client fails to present a certificate |
| 165 | when asked. We get here only if a certificate has been received. Handling of |
| 166 | optional verification for this case is done when requesting SSL to verify, by |
| 167 | setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case. |
| 168 | |
| 169 | Arguments: |
| 170 | state current yes/no state as 1/0 |
| 171 | x509ctx certificate information. |
| 172 | |
| 173 | Returns: 1 if verified, 0 if not |
| 174 | */ |
| 175 | |
| 176 | static int |
| 177 | verify_callback(int state, X509_STORE_CTX *x509ctx) |
| 178 | { |
| 179 | static uschar txt[256]; |
| 180 | |
| 181 | X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert), |
| 182 | CS txt, sizeof(txt)); |
| 183 | |
| 184 | if (state == 0) |
| 185 | { |
| 186 | log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s", |
| 187 | x509ctx->error_depth, |
| 188 | X509_verify_cert_error_string(x509ctx->error), |
| 189 | txt); |
| 190 | tls_certificate_verified = FALSE; |
| 191 | verify_callback_called = TRUE; |
| 192 | if (!verify_optional) return 0; /* reject */ |
| 193 | DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in " |
| 194 | "tls_try_verify_hosts)\n"); |
| 195 | return 1; /* accept */ |
| 196 | } |
| 197 | |
| 198 | if (x509ctx->error_depth != 0) |
| 199 | { |
| 200 | DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n", |
| 201 | x509ctx->error_depth, txt); |
| 202 | } |
| 203 | else |
| 204 | { |
| 205 | DEBUG(D_tls) debug_printf("SSL%s peer: %s\n", |
| 206 | verify_callback_called? "" : " authenticated", txt); |
| 207 | tls_peerdn = txt; |
| 208 | } |
| 209 | |
| 210 | if (!verify_callback_called) tls_certificate_verified = TRUE; |
| 211 | verify_callback_called = TRUE; |
| 212 | |
| 213 | return 1; /* accept */ |
| 214 | } |
| 215 | |
| 216 | |
| 217 | |
| 218 | /************************************************* |
| 219 | * Information callback * |
| 220 | *************************************************/ |
| 221 | |
| 222 | /* The SSL library functions call this from time to time to indicate what they |
| 223 | are doing. We copy the string to the debugging output when TLS debugging has |
| 224 | been requested. |
| 225 | |
| 226 | Arguments: |
| 227 | s the SSL connection |
| 228 | where |
| 229 | ret |
| 230 | |
| 231 | Returns: nothing |
| 232 | */ |
| 233 | |
| 234 | static void |
| 235 | info_callback(SSL *s, int where, int ret) |
| 236 | { |
| 237 | where = where; |
| 238 | ret = ret; |
| 239 | DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s)); |
| 240 | } |
| 241 | |
| 242 | |
| 243 | |
| 244 | /************************************************* |
| 245 | * Initialize for DH * |
| 246 | *************************************************/ |
| 247 | |
| 248 | /* If dhparam is set, expand it, and load up the parameters for DH encryption. |
| 249 | |
| 250 | Arguments: |
| 251 | dhparam DH parameter file |
| 252 | host connected host, if client; NULL if server |
| 253 | |
| 254 | Returns: TRUE if OK (nothing to set up, or setup worked) |
| 255 | */ |
| 256 | |
| 257 | static BOOL |
| 258 | init_dh(uschar *dhparam, host_item *host) |
| 259 | { |
| 260 | BOOL yield = TRUE; |
| 261 | BIO *bio; |
| 262 | DH *dh; |
| 263 | uschar *dhexpanded; |
| 264 | |
| 265 | if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded)) |
| 266 | return FALSE; |
| 267 | |
| 268 | if (dhexpanded == NULL) return TRUE; |
| 269 | |
| 270 | if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL) |
| 271 | { |
| 272 | tls_error(string_sprintf("could not read dhparams file %s", dhexpanded), |
| 273 | host, (uschar *)strerror(errno)); |
| 274 | yield = FALSE; |
| 275 | } |
| 276 | else |
| 277 | { |
| 278 | if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL) |
| 279 | { |
| 280 | tls_error(string_sprintf("could not read dhparams file %s", dhexpanded), |
| 281 | host, NULL); |
| 282 | yield = FALSE; |
| 283 | } |
| 284 | else |
| 285 | { |
| 286 | SSL_CTX_set_tmp_dh(ctx, dh); |
| 287 | DEBUG(D_tls) |
| 288 | debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n", |
| 289 | dhexpanded, 8*DH_size(dh)); |
| 290 | DH_free(dh); |
| 291 | } |
| 292 | BIO_free(bio); |
| 293 | } |
| 294 | |
| 295 | return yield; |
| 296 | } |
| 297 | |
| 298 | |
| 299 | |
| 300 | |
| 301 | /************************************************* |
| 302 | * Expand key and cert file specs * |
| 303 | *************************************************/ |
| 304 | |
| 305 | /* Called once during tls_init and possibly againt during TLS setup, for a |
| 306 | new context, if Server Name Indication was used and tls_sni was seen in |
| 307 | the certificate string. |
| 308 | |
| 309 | Arguments: |
| 310 | sctx the SSL_CTX* to update |
| 311 | cbinfo various parts of session state |
| 312 | |
| 313 | Returns: OK/DEFER/FAIL |
| 314 | */ |
| 315 | |
| 316 | static int |
| 317 | tls_expand_session_files(SSL_CTX *sctx, const tls_ext_ctx_cb *cbinfo) |
| 318 | { |
| 319 | uschar *expanded; |
| 320 | |
| 321 | if (cbinfo->certificate == NULL) |
| 322 | return OK; |
| 323 | |
| 324 | if (Ustrstr(cbinfo->certificate, US"tls_sni")) |
| 325 | reexpand_tls_files_for_sni = TRUE; |
| 326 | |
| 327 | if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded)) |
| 328 | return DEFER; |
| 329 | |
| 330 | if (expanded != NULL) |
| 331 | { |
| 332 | DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded); |
| 333 | if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded)) |
| 334 | return tls_error(string_sprintf( |
| 335 | "SSL_CTX_use_certificate_chain_file file=%s", expanded), |
| 336 | cbinfo->host, NULL); |
| 337 | } |
| 338 | |
| 339 | if (cbinfo->privatekey != NULL && |
| 340 | !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded)) |
| 341 | return DEFER; |
| 342 | |
| 343 | /* If expansion was forced to fail, key_expanded will be NULL. If the result |
| 344 | of the expansion is an empty string, ignore it also, and assume the private |
| 345 | key is in the same file as the certificate. */ |
| 346 | |
| 347 | if (expanded != NULL && *expanded != 0) |
| 348 | { |
| 349 | DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded); |
| 350 | if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM)) |
| 351 | return tls_error(string_sprintf( |
| 352 | "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL); |
| 353 | } |
| 354 | |
| 355 | return OK; |
| 356 | } |
| 357 | |
| 358 | |
| 359 | |
| 360 | |
| 361 | /************************************************* |
| 362 | * Callback to handle SNI * |
| 363 | *************************************************/ |
| 364 | |
| 365 | /* Called when acting as server during the TLS session setup if a Server Name |
| 366 | Indication extension was sent by the client. |
| 367 | |
| 368 | API documentation is OpenSSL s_server.c implementation. |
| 369 | |
| 370 | Arguments: |
| 371 | s SSL* of the current session |
| 372 | ad unknown (part of OpenSSL API) (unused) |
| 373 | arg Callback of "our" registered data |
| 374 | |
| 375 | Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK} |
| 376 | */ |
| 377 | |
| 378 | static int |
| 379 | tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg); |
| 380 | /* pre-declared for SSL_CTX_set_tlsext_servername_callback call within func */ |
| 381 | |
| 382 | static int |
| 383 | tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg) |
| 384 | { |
| 385 | const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name); |
| 386 | const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg; |
| 387 | int rc; |
| 388 | int old_pool = store_pool; |
| 389 | |
| 390 | if (!servername) |
| 391 | return SSL_TLSEXT_ERR_OK; |
| 392 | |
| 393 | DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername, |
| 394 | reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)"); |
| 395 | |
| 396 | /* Make the extension value available for expansion */ |
| 397 | store_pool = POOL_PERM; |
| 398 | tls_sni = string_copy(US servername); |
| 399 | store_pool = old_pool; |
| 400 | |
| 401 | if (!reexpand_tls_files_for_sni) |
| 402 | return SSL_TLSEXT_ERR_OK; |
| 403 | |
| 404 | /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually; |
| 405 | not confident that memcpy wouldn't break some internal reference counting. |
| 406 | Especially since there's a references struct member, which would be off. */ |
| 407 | |
| 408 | ctx_sni = SSL_CTX_new(SSLv23_server_method()); |
| 409 | if (!ctx_sni) |
| 410 | { |
| 411 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 412 | DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring); |
| 413 | return SSL_TLSEXT_ERR_NOACK; |
| 414 | } |
| 415 | |
| 416 | /* Not sure how many of these are actually needed, since SSL object |
| 417 | already exists. Might even need this selfsame callback, for reneg? */ |
| 418 | |
| 419 | SSL_CTX_set_info_callback(ctx_sni, SSL_CTX_get_info_callback(ctx)); |
| 420 | SSL_CTX_set_mode(ctx_sni, SSL_CTX_get_mode(ctx)); |
| 421 | SSL_CTX_set_options(ctx_sni, SSL_CTX_get_options(ctx)); |
| 422 | SSL_CTX_set_timeout(ctx_sni, SSL_CTX_get_timeout(ctx)); |
| 423 | SSL_CTX_set_tlsext_servername_callback(ctx_sni, tls_servername_cb); |
| 424 | SSL_CTX_set_tlsext_servername_arg(ctx_sni, cbinfo); |
| 425 | if (cbinfo->server_cipher_list) |
| 426 | SSL_CTX_set_cipher_list(ctx_sni, CS cbinfo->server_cipher_list); |
| 427 | |
| 428 | rc = tls_expand_session_files(ctx_sni, cbinfo); |
| 429 | if (rc != OK) return SSL_TLSEXT_ERR_NOACK; |
| 430 | |
| 431 | rc = setup_certs(ctx_sni, tls_verify_certificates, tls_crl, NULL, FALSE); |
| 432 | if (rc != OK) return SSL_TLSEXT_ERR_NOACK; |
| 433 | |
| 434 | DEBUG(D_tls) debug_printf("Switching SSL context.\n"); |
| 435 | SSL_set_SSL_CTX(s, ctx_sni); |
| 436 | |
| 437 | return SSL_TLSEXT_ERR_OK; |
| 438 | } |
| 439 | |
| 440 | |
| 441 | |
| 442 | |
| 443 | /************************************************* |
| 444 | * Initialize for TLS * |
| 445 | *************************************************/ |
| 446 | |
| 447 | /* Called from both server and client code, to do preliminary initialization of |
| 448 | the library. |
| 449 | |
| 450 | Arguments: |
| 451 | host connected host, if client; NULL if server |
| 452 | dhparam DH parameter file |
| 453 | certificate certificate file |
| 454 | privatekey private key |
| 455 | addr address if client; NULL if server (for some randomness) |
| 456 | |
| 457 | Returns: OK/DEFER/FAIL |
| 458 | */ |
| 459 | |
| 460 | static int |
| 461 | tls_init(host_item *host, uschar *dhparam, uschar *certificate, |
| 462 | uschar *privatekey, address_item *addr) |
| 463 | { |
| 464 | long init_options; |
| 465 | int rc; |
| 466 | BOOL okay; |
| 467 | tls_ext_ctx_cb *cbinfo; |
| 468 | |
| 469 | cbinfo = store_malloc(sizeof(tls_ext_ctx_cb)); |
| 470 | cbinfo->certificate = certificate; |
| 471 | cbinfo->privatekey = privatekey; |
| 472 | cbinfo->dhparam = dhparam; |
| 473 | cbinfo->host = host; |
| 474 | |
| 475 | SSL_load_error_strings(); /* basic set up */ |
| 476 | OpenSSL_add_ssl_algorithms(); |
| 477 | |
| 478 | #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256) |
| 479 | /* SHA256 is becoming ever more popular. This makes sure it gets added to the |
| 480 | list of available digests. */ |
| 481 | EVP_add_digest(EVP_sha256()); |
| 482 | #endif |
| 483 | |
| 484 | /* Create a context */ |
| 485 | |
| 486 | ctx = SSL_CTX_new((host == NULL)? |
| 487 | SSLv23_server_method() : SSLv23_client_method()); |
| 488 | |
| 489 | if (ctx == NULL) return tls_error(US"SSL_CTX_new", host, NULL); |
| 490 | |
| 491 | /* It turns out that we need to seed the random number generator this early in |
| 492 | order to get the full complement of ciphers to work. It took me roughly a day |
| 493 | of work to discover this by experiment. |
| 494 | |
| 495 | On systems that have /dev/urandom, SSL may automatically seed itself from |
| 496 | there. Otherwise, we have to make something up as best we can. Double check |
| 497 | afterwards. */ |
| 498 | |
| 499 | if (!RAND_status()) |
| 500 | { |
| 501 | randstuff r; |
| 502 | gettimeofday(&r.tv, NULL); |
| 503 | r.p = getpid(); |
| 504 | |
| 505 | RAND_seed((uschar *)(&r), sizeof(r)); |
| 506 | RAND_seed((uschar *)big_buffer, big_buffer_size); |
| 507 | if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr)); |
| 508 | |
| 509 | if (!RAND_status()) |
| 510 | return tls_error(US"RAND_status", host, |
| 511 | US"unable to seed random number generator"); |
| 512 | } |
| 513 | |
| 514 | /* Set up the information callback, which outputs if debugging is at a suitable |
| 515 | level. */ |
| 516 | |
| 517 | SSL_CTX_set_info_callback(ctx, (void (*)())info_callback); |
| 518 | |
| 519 | /* Automatically re-try reads/writes after renegotiation. */ |
| 520 | (void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY); |
| 521 | |
| 522 | /* Apply administrator-supplied work-arounds. |
| 523 | Historically we applied just one requested option, |
| 524 | SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we |
| 525 | moved to an administrator-controlled list of options to specify and |
| 526 | grandfathered in the first one as the default value for "openssl_options". |
| 527 | |
| 528 | No OpenSSL version number checks: the options we accept depend upon the |
| 529 | availability of the option value macros from OpenSSL. */ |
| 530 | |
| 531 | okay = tls_openssl_options_parse(openssl_options, &init_options); |
| 532 | if (!okay) |
| 533 | return tls_error(US"openssl_options parsing failed", host, NULL); |
| 534 | |
| 535 | if (init_options) |
| 536 | { |
| 537 | DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options); |
| 538 | if (!(SSL_CTX_set_options(ctx, init_options))) |
| 539 | return tls_error(string_sprintf( |
| 540 | "SSL_CTX_set_option(%#lx)", init_options), host, NULL); |
| 541 | } |
| 542 | else |
| 543 | DEBUG(D_tls) debug_printf("no SSL CTX options to set\n"); |
| 544 | |
| 545 | /* Initialize with DH parameters if supplied */ |
| 546 | |
| 547 | if (!init_dh(dhparam, host)) return DEFER; |
| 548 | |
| 549 | /* Set up certificate and key */ |
| 550 | |
| 551 | rc = tls_expand_session_files(ctx, cbinfo); |
| 552 | if (rc != OK) return rc; |
| 553 | |
| 554 | /* If we need to handle SNI, do so */ |
| 555 | #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT) |
| 556 | if (host == NULL) |
| 557 | { |
| 558 | /* We always do this, so that $tls_sni is available even if not used in |
| 559 | tls_certificate */ |
| 560 | SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb); |
| 561 | SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo); |
| 562 | } |
| 563 | #endif |
| 564 | |
| 565 | /* Set up the RSA callback */ |
| 566 | |
| 567 | SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback); |
| 568 | |
| 569 | /* Finally, set the timeout, and we are done */ |
| 570 | |
| 571 | SSL_CTX_set_timeout(ctx, ssl_session_timeout); |
| 572 | DEBUG(D_tls) debug_printf("Initialized TLS\n"); |
| 573 | |
| 574 | static_cbinfo = cbinfo; |
| 575 | |
| 576 | return OK; |
| 577 | } |
| 578 | |
| 579 | |
| 580 | |
| 581 | |
| 582 | /************************************************* |
| 583 | * Get name of cipher in use * |
| 584 | *************************************************/ |
| 585 | |
| 586 | /* The answer is left in a static buffer, and tls_cipher is set to point |
| 587 | to it. |
| 588 | |
| 589 | Argument: pointer to an SSL structure for the connection |
| 590 | Returns: nothing |
| 591 | */ |
| 592 | |
| 593 | static void |
| 594 | construct_cipher_name(SSL *ssl) |
| 595 | { |
| 596 | static uschar cipherbuf[256]; |
| 597 | /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't |
| 598 | yet reflect that. It should be a safe change anyway, even 0.9.8 versions have |
| 599 | the accessor functions use const in the prototype. */ |
| 600 | const SSL_CIPHER *c; |
| 601 | uschar *ver; |
| 602 | |
| 603 | switch (ssl->session->ssl_version) |
| 604 | { |
| 605 | case SSL2_VERSION: |
| 606 | ver = US"SSLv2"; |
| 607 | break; |
| 608 | |
| 609 | case SSL3_VERSION: |
| 610 | ver = US"SSLv3"; |
| 611 | break; |
| 612 | |
| 613 | case TLS1_VERSION: |
| 614 | ver = US"TLSv1"; |
| 615 | break; |
| 616 | |
| 617 | #ifdef TLS1_1_VERSION |
| 618 | case TLS1_1_VERSION: |
| 619 | ver = US"TLSv1.1"; |
| 620 | break; |
| 621 | #endif |
| 622 | |
| 623 | #ifdef TLS1_2_VERSION |
| 624 | case TLS1_2_VERSION: |
| 625 | ver = US"TLSv1.2"; |
| 626 | break; |
| 627 | #endif |
| 628 | |
| 629 | default: |
| 630 | ver = US"UNKNOWN"; |
| 631 | } |
| 632 | |
| 633 | c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl); |
| 634 | SSL_CIPHER_get_bits(c, &tls_bits); |
| 635 | |
| 636 | string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver, |
| 637 | SSL_CIPHER_get_name(c), tls_bits); |
| 638 | tls_cipher = cipherbuf; |
| 639 | |
| 640 | DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf); |
| 641 | } |
| 642 | |
| 643 | |
| 644 | |
| 645 | |
| 646 | |
| 647 | /************************************************* |
| 648 | * Set up for verifying certificates * |
| 649 | *************************************************/ |
| 650 | |
| 651 | /* Called by both client and server startup |
| 652 | |
| 653 | Arguments: |
| 654 | sctx SSL_CTX* to initialise |
| 655 | certs certs file or NULL |
| 656 | crl CRL file or NULL |
| 657 | host NULL in a server; the remote host in a client |
| 658 | optional TRUE if called from a server for a host in tls_try_verify_hosts; |
| 659 | otherwise passed as FALSE |
| 660 | |
| 661 | Returns: OK/DEFER/FAIL |
| 662 | */ |
| 663 | |
| 664 | static int |
| 665 | setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional) |
| 666 | { |
| 667 | uschar *expcerts, *expcrl; |
| 668 | |
| 669 | if (!expand_check(certs, US"tls_verify_certificates", &expcerts)) |
| 670 | return DEFER; |
| 671 | |
| 672 | if (expcerts != NULL) |
| 673 | { |
| 674 | struct stat statbuf; |
| 675 | if (!SSL_CTX_set_default_verify_paths(sctx)) |
| 676 | return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL); |
| 677 | |
| 678 | if (Ustat(expcerts, &statbuf) < 0) |
| 679 | { |
| 680 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 681 | "failed to stat %s for certificates", expcerts); |
| 682 | return DEFER; |
| 683 | } |
| 684 | else |
| 685 | { |
| 686 | uschar *file, *dir; |
| 687 | if ((statbuf.st_mode & S_IFMT) == S_IFDIR) |
| 688 | { file = NULL; dir = expcerts; } |
| 689 | else |
| 690 | { file = expcerts; dir = NULL; } |
| 691 | |
| 692 | /* If a certificate file is empty, the next function fails with an |
| 693 | unhelpful error message. If we skip it, we get the correct behaviour (no |
| 694 | certificates are recognized, but the error message is still misleading (it |
| 695 | says no certificate was supplied.) But this is better. */ |
| 696 | |
| 697 | if ((file == NULL || statbuf.st_size > 0) && |
| 698 | !SSL_CTX_load_verify_locations(sctx, CS file, CS dir)) |
| 699 | return tls_error(US"SSL_CTX_load_verify_locations", host, NULL); |
| 700 | |
| 701 | if (file != NULL) |
| 702 | { |
| 703 | SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file)); |
| 704 | } |
| 705 | } |
| 706 | |
| 707 | /* Handle a certificate revocation list. */ |
| 708 | |
| 709 | #if OPENSSL_VERSION_NUMBER > 0x00907000L |
| 710 | |
| 711 | /* This bit of code is now the version supplied by Lars Mainka. (I have |
| 712 | * merely reformatted it into the Exim code style.) |
| 713 | |
| 714 | * "From here I changed the code to add support for multiple crl's |
| 715 | * in pem format in one file or to support hashed directory entries in |
| 716 | * pem format instead of a file. This method now uses the library function |
| 717 | * X509_STORE_load_locations to add the CRL location to the SSL context. |
| 718 | * OpenSSL will then handle the verify against CA certs and CRLs by |
| 719 | * itself in the verify callback." */ |
| 720 | |
| 721 | if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER; |
| 722 | if (expcrl != NULL && *expcrl != 0) |
| 723 | { |
| 724 | struct stat statbufcrl; |
| 725 | if (Ustat(expcrl, &statbufcrl) < 0) |
| 726 | { |
| 727 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 728 | "failed to stat %s for certificates revocation lists", expcrl); |
| 729 | return DEFER; |
| 730 | } |
| 731 | else |
| 732 | { |
| 733 | /* is it a file or directory? */ |
| 734 | uschar *file, *dir; |
| 735 | X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx); |
| 736 | if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR) |
| 737 | { |
| 738 | file = NULL; |
| 739 | dir = expcrl; |
| 740 | DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir); |
| 741 | } |
| 742 | else |
| 743 | { |
| 744 | file = expcrl; |
| 745 | dir = NULL; |
| 746 | DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file); |
| 747 | } |
| 748 | if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0) |
| 749 | return tls_error(US"X509_STORE_load_locations", host, NULL); |
| 750 | |
| 751 | /* setting the flags to check against the complete crl chain */ |
| 752 | |
| 753 | X509_STORE_set_flags(cvstore, |
| 754 | X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL); |
| 755 | } |
| 756 | } |
| 757 | |
| 758 | #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */ |
| 759 | |
| 760 | /* If verification is optional, don't fail if no certificate */ |
| 761 | |
| 762 | SSL_CTX_set_verify(sctx, |
| 763 | SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT), |
| 764 | verify_callback); |
| 765 | } |
| 766 | |
| 767 | return OK; |
| 768 | } |
| 769 | |
| 770 | |
| 771 | |
| 772 | /************************************************* |
| 773 | * Start a TLS session in a server * |
| 774 | *************************************************/ |
| 775 | |
| 776 | /* This is called when Exim is running as a server, after having received |
| 777 | the STARTTLS command. It must respond to that command, and then negotiate |
| 778 | a TLS session. |
| 779 | |
| 780 | Arguments: |
| 781 | require_ciphers allowed ciphers |
| 782 | ------------------------------------------------------ |
| 783 | require_mac list of allowed MACs ) Not used |
| 784 | require_kx list of allowed key_exchange methods ) for |
| 785 | require_proto list of allowed protocols ) OpenSSL |
| 786 | ------------------------------------------------------ |
| 787 | |
| 788 | Returns: OK on success |
| 789 | DEFER for errors before the start of the negotiation |
| 790 | FAIL for errors during the negotation; the server can't |
| 791 | continue running. |
| 792 | */ |
| 793 | |
| 794 | int |
| 795 | tls_server_start(uschar *require_ciphers, uschar *require_mac, |
| 796 | uschar *require_kx, uschar *require_proto) |
| 797 | { |
| 798 | int rc; |
| 799 | uschar *expciphers; |
| 800 | tls_ext_ctx_cb *cbinfo; |
| 801 | |
| 802 | /* Check for previous activation */ |
| 803 | |
| 804 | if (tls_active >= 0) |
| 805 | { |
| 806 | tls_error(US"STARTTLS received after TLS started", NULL, US""); |
| 807 | smtp_printf("554 Already in TLS\r\n"); |
| 808 | return FAIL; |
| 809 | } |
| 810 | |
| 811 | /* Initialize the SSL library. If it fails, it will already have logged |
| 812 | the error. */ |
| 813 | |
| 814 | rc = tls_init(NULL, tls_dhparam, tls_certificate, tls_privatekey, NULL); |
| 815 | if (rc != OK) return rc; |
| 816 | cbinfo = static_cbinfo; |
| 817 | |
| 818 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) |
| 819 | return FAIL; |
| 820 | |
| 821 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they |
| 822 | are separated by underscores. So that I can use either form in my tests, and |
| 823 | also for general convenience, we turn underscores into hyphens here. */ |
| 824 | |
| 825 | if (expciphers != NULL) |
| 826 | { |
| 827 | uschar *s = expciphers; |
| 828 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } |
| 829 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); |
| 830 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) |
| 831 | return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL); |
| 832 | cbinfo->server_cipher_list = expciphers; |
| 833 | } |
| 834 | |
| 835 | /* If this is a host for which certificate verification is mandatory or |
| 836 | optional, set up appropriately. */ |
| 837 | |
| 838 | tls_certificate_verified = FALSE; |
| 839 | verify_callback_called = FALSE; |
| 840 | |
| 841 | if (verify_check_host(&tls_verify_hosts) == OK) |
| 842 | { |
| 843 | rc = setup_certs(ctx, tls_verify_certificates, tls_crl, NULL, FALSE); |
| 844 | if (rc != OK) return rc; |
| 845 | verify_optional = FALSE; |
| 846 | } |
| 847 | else if (verify_check_host(&tls_try_verify_hosts) == OK) |
| 848 | { |
| 849 | rc = setup_certs(ctx, tls_verify_certificates, tls_crl, NULL, TRUE); |
| 850 | if (rc != OK) return rc; |
| 851 | verify_optional = TRUE; |
| 852 | } |
| 853 | |
| 854 | /* Prepare for new connection */ |
| 855 | |
| 856 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL); |
| 857 | |
| 858 | /* Warning: we used to SSL_clear(ssl) here, it was removed. |
| 859 | * |
| 860 | * With the SSL_clear(), we get strange interoperability bugs with |
| 861 | * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in |
| 862 | * OpenSSL itself, as a clear should not lead to inability to follow protocols. |
| 863 | * |
| 864 | * The SSL_clear() call is to let an existing SSL* be reused, typically after |
| 865 | * session shutdown. In this case, we have a brand new object and there's no |
| 866 | * obvious reason to immediately clear it. I'm guessing that this was |
| 867 | * originally added because of incomplete initialisation which the clear fixed, |
| 868 | * in some historic release. |
| 869 | */ |
| 870 | |
| 871 | /* Set context and tell client to go ahead, except in the case of TLS startup |
| 872 | on connection, where outputting anything now upsets the clients and tends to |
| 873 | make them disconnect. We need to have an explicit fflush() here, to force out |
| 874 | the response. Other smtp_printf() calls do not need it, because in non-TLS |
| 875 | mode, the fflush() happens when smtp_getc() is called. */ |
| 876 | |
| 877 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); |
| 878 | if (!tls_on_connect) |
| 879 | { |
| 880 | smtp_printf("220 TLS go ahead\r\n"); |
| 881 | fflush(smtp_out); |
| 882 | } |
| 883 | |
| 884 | /* Now negotiate the TLS session. We put our own timer on it, since it seems |
| 885 | that the OpenSSL library doesn't. */ |
| 886 | |
| 887 | SSL_set_wfd(ssl, fileno(smtp_out)); |
| 888 | SSL_set_rfd(ssl, fileno(smtp_in)); |
| 889 | SSL_set_accept_state(ssl); |
| 890 | |
| 891 | DEBUG(D_tls) debug_printf("Calling SSL_accept\n"); |
| 892 | |
| 893 | sigalrm_seen = FALSE; |
| 894 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 895 | rc = SSL_accept(ssl); |
| 896 | alarm(0); |
| 897 | |
| 898 | if (rc <= 0) |
| 899 | { |
| 900 | tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL); |
| 901 | if (ERR_get_error() == 0) |
| 902 | log_write(0, LOG_MAIN, |
| 903 | "TLS client disconnected cleanly (rejected our certificate?)"); |
| 904 | return FAIL; |
| 905 | } |
| 906 | |
| 907 | DEBUG(D_tls) debug_printf("SSL_accept was successful\n"); |
| 908 | |
| 909 | /* TLS has been set up. Adjust the input functions to read via TLS, |
| 910 | and initialize things. */ |
| 911 | |
| 912 | construct_cipher_name(ssl); |
| 913 | |
| 914 | DEBUG(D_tls) |
| 915 | { |
| 916 | uschar buf[2048]; |
| 917 | if (SSL_get_shared_ciphers(ssl, CS buf, sizeof(buf)) != NULL) |
| 918 | debug_printf("Shared ciphers: %s\n", buf); |
| 919 | } |
| 920 | |
| 921 | |
| 922 | ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); |
| 923 | ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; |
| 924 | ssl_xfer_eof = ssl_xfer_error = 0; |
| 925 | |
| 926 | receive_getc = tls_getc; |
| 927 | receive_ungetc = tls_ungetc; |
| 928 | receive_feof = tls_feof; |
| 929 | receive_ferror = tls_ferror; |
| 930 | receive_smtp_buffered = tls_smtp_buffered; |
| 931 | |
| 932 | tls_active = fileno(smtp_out); |
| 933 | return OK; |
| 934 | } |
| 935 | |
| 936 | |
| 937 | |
| 938 | |
| 939 | |
| 940 | /************************************************* |
| 941 | * Start a TLS session in a client * |
| 942 | *************************************************/ |
| 943 | |
| 944 | /* Called from the smtp transport after STARTTLS has been accepted. |
| 945 | |
| 946 | Argument: |
| 947 | fd the fd of the connection |
| 948 | host connected host (for messages) |
| 949 | addr the first address |
| 950 | dhparam DH parameter file |
| 951 | certificate certificate file |
| 952 | privatekey private key file |
| 953 | sni TLS SNI to send to remote host |
| 954 | verify_certs file for certificate verify |
| 955 | crl file containing CRL |
| 956 | require_ciphers list of allowed ciphers |
| 957 | ------------------------------------------------------ |
| 958 | require_mac list of allowed MACs ) Not used |
| 959 | require_kx list of allowed key_exchange methods ) for |
| 960 | require_proto list of allowed protocols ) OpenSSL |
| 961 | ------------------------------------------------------ |
| 962 | timeout startup timeout |
| 963 | |
| 964 | Returns: OK on success |
| 965 | FAIL otherwise - note that tls_error() will not give DEFER |
| 966 | because this is not a server |
| 967 | */ |
| 968 | |
| 969 | int |
| 970 | tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam, |
| 971 | uschar *certificate, uschar *privatekey, uschar *sni, |
| 972 | uschar *verify_certs, uschar *crl, |
| 973 | uschar *require_ciphers, uschar *require_mac, uschar *require_kx, |
| 974 | uschar *require_proto, int timeout) |
| 975 | { |
| 976 | static uschar txt[256]; |
| 977 | uschar *expciphers; |
| 978 | X509* server_cert; |
| 979 | int rc; |
| 980 | |
| 981 | rc = tls_init(host, dhparam, certificate, privatekey, addr); |
| 982 | if (rc != OK) return rc; |
| 983 | |
| 984 | tls_certificate_verified = FALSE; |
| 985 | verify_callback_called = FALSE; |
| 986 | |
| 987 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) |
| 988 | return FAIL; |
| 989 | |
| 990 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they |
| 991 | are separated by underscores. So that I can use either form in my tests, and |
| 992 | also for general convenience, we turn underscores into hyphens here. */ |
| 993 | |
| 994 | if (expciphers != NULL) |
| 995 | { |
| 996 | uschar *s = expciphers; |
| 997 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } |
| 998 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); |
| 999 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) |
| 1000 | return tls_error(US"SSL_CTX_set_cipher_list", host, NULL); |
| 1001 | } |
| 1002 | |
| 1003 | rc = setup_certs(ctx, verify_certs, crl, host, FALSE); |
| 1004 | if (rc != OK) return rc; |
| 1005 | |
| 1006 | if ((ssl = SSL_new(ctx)) == NULL) return tls_error(US"SSL_new", host, NULL); |
| 1007 | SSL_set_session_id_context(ssl, sid_ctx, Ustrlen(sid_ctx)); |
| 1008 | SSL_set_fd(ssl, fd); |
| 1009 | SSL_set_connect_state(ssl); |
| 1010 | |
| 1011 | if (sni) |
| 1012 | { |
| 1013 | if (!expand_check(sni, US"tls_sni", &tls_sni)) |
| 1014 | return FAIL; |
| 1015 | if (!Ustrlen(tls_sni)) |
| 1016 | tls_sni = NULL; |
| 1017 | else |
| 1018 | { |
| 1019 | DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_sni); |
| 1020 | SSL_set_tlsext_host_name(ssl, tls_sni); |
| 1021 | } |
| 1022 | } |
| 1023 | |
| 1024 | /* There doesn't seem to be a built-in timeout on connection. */ |
| 1025 | |
| 1026 | DEBUG(D_tls) debug_printf("Calling SSL_connect\n"); |
| 1027 | sigalrm_seen = FALSE; |
| 1028 | alarm(timeout); |
| 1029 | rc = SSL_connect(ssl); |
| 1030 | alarm(0); |
| 1031 | |
| 1032 | if (rc <= 0) |
| 1033 | return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL); |
| 1034 | |
| 1035 | DEBUG(D_tls) debug_printf("SSL_connect succeeded\n"); |
| 1036 | |
| 1037 | /* Beware anonymous ciphers which lead to server_cert being NULL */ |
| 1038 | server_cert = SSL_get_peer_certificate (ssl); |
| 1039 | if (server_cert) |
| 1040 | { |
| 1041 | tls_peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert), |
| 1042 | CS txt, sizeof(txt)); |
| 1043 | tls_peerdn = txt; |
| 1044 | } |
| 1045 | else |
| 1046 | tls_peerdn = NULL; |
| 1047 | |
| 1048 | construct_cipher_name(ssl); /* Sets tls_cipher */ |
| 1049 | |
| 1050 | tls_active = fd; |
| 1051 | return OK; |
| 1052 | } |
| 1053 | |
| 1054 | |
| 1055 | |
| 1056 | |
| 1057 | |
| 1058 | /************************************************* |
| 1059 | * TLS version of getc * |
| 1060 | *************************************************/ |
| 1061 | |
| 1062 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, |
| 1063 | it refills the buffer via the SSL reading function. |
| 1064 | |
| 1065 | Arguments: none |
| 1066 | Returns: the next character or EOF |
| 1067 | */ |
| 1068 | |
| 1069 | int |
| 1070 | tls_getc(void) |
| 1071 | { |
| 1072 | if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) |
| 1073 | { |
| 1074 | int error; |
| 1075 | int inbytes; |
| 1076 | |
| 1077 | DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl, |
| 1078 | ssl_xfer_buffer, ssl_xfer_buffer_size); |
| 1079 | |
| 1080 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 1081 | inbytes = SSL_read(ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size); |
| 1082 | error = SSL_get_error(ssl, inbytes); |
| 1083 | alarm(0); |
| 1084 | |
| 1085 | /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been |
| 1086 | closed down, not that the socket itself has been closed down. Revert to |
| 1087 | non-SSL handling. */ |
| 1088 | |
| 1089 | if (error == SSL_ERROR_ZERO_RETURN) |
| 1090 | { |
| 1091 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); |
| 1092 | |
| 1093 | receive_getc = smtp_getc; |
| 1094 | receive_ungetc = smtp_ungetc; |
| 1095 | receive_feof = smtp_feof; |
| 1096 | receive_ferror = smtp_ferror; |
| 1097 | receive_smtp_buffered = smtp_buffered; |
| 1098 | |
| 1099 | SSL_free(ssl); |
| 1100 | ssl = NULL; |
| 1101 | tls_active = -1; |
| 1102 | tls_bits = 0; |
| 1103 | tls_cipher = NULL; |
| 1104 | tls_peerdn = NULL; |
| 1105 | tls_sni = NULL; |
| 1106 | |
| 1107 | return smtp_getc(); |
| 1108 | } |
| 1109 | |
| 1110 | /* Handle genuine errors */ |
| 1111 | |
| 1112 | else if (error == SSL_ERROR_SSL) |
| 1113 | { |
| 1114 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 1115 | log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring); |
| 1116 | ssl_xfer_error = 1; |
| 1117 | return EOF; |
| 1118 | } |
| 1119 | |
| 1120 | else if (error != SSL_ERROR_NONE) |
| 1121 | { |
| 1122 | DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); |
| 1123 | ssl_xfer_error = 1; |
| 1124 | return EOF; |
| 1125 | } |
| 1126 | |
| 1127 | #ifndef DISABLE_DKIM |
| 1128 | dkim_exim_verify_feed(ssl_xfer_buffer, inbytes); |
| 1129 | #endif |
| 1130 | ssl_xfer_buffer_hwm = inbytes; |
| 1131 | ssl_xfer_buffer_lwm = 0; |
| 1132 | } |
| 1133 | |
| 1134 | /* Something in the buffer; return next uschar */ |
| 1135 | |
| 1136 | return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; |
| 1137 | } |
| 1138 | |
| 1139 | |
| 1140 | |
| 1141 | /************************************************* |
| 1142 | * Read bytes from TLS channel * |
| 1143 | *************************************************/ |
| 1144 | |
| 1145 | /* |
| 1146 | Arguments: |
| 1147 | buff buffer of data |
| 1148 | len size of buffer |
| 1149 | |
| 1150 | Returns: the number of bytes read |
| 1151 | -1 after a failed read |
| 1152 | */ |
| 1153 | |
| 1154 | int |
| 1155 | tls_read(uschar *buff, size_t len) |
| 1156 | { |
| 1157 | int inbytes; |
| 1158 | int error; |
| 1159 | |
| 1160 | DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl, |
| 1161 | buff, (unsigned int)len); |
| 1162 | |
| 1163 | inbytes = SSL_read(ssl, CS buff, len); |
| 1164 | error = SSL_get_error(ssl, inbytes); |
| 1165 | |
| 1166 | if (error == SSL_ERROR_ZERO_RETURN) |
| 1167 | { |
| 1168 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); |
| 1169 | return -1; |
| 1170 | } |
| 1171 | else if (error != SSL_ERROR_NONE) |
| 1172 | { |
| 1173 | return -1; |
| 1174 | } |
| 1175 | |
| 1176 | return inbytes; |
| 1177 | } |
| 1178 | |
| 1179 | |
| 1180 | |
| 1181 | |
| 1182 | |
| 1183 | /************************************************* |
| 1184 | * Write bytes down TLS channel * |
| 1185 | *************************************************/ |
| 1186 | |
| 1187 | /* |
| 1188 | Arguments: |
| 1189 | buff buffer of data |
| 1190 | len number of bytes |
| 1191 | |
| 1192 | Returns: the number of bytes after a successful write, |
| 1193 | -1 after a failed write |
| 1194 | */ |
| 1195 | |
| 1196 | int |
| 1197 | tls_write(const uschar *buff, size_t len) |
| 1198 | { |
| 1199 | int outbytes; |
| 1200 | int error; |
| 1201 | int left = len; |
| 1202 | |
| 1203 | DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left); |
| 1204 | while (left > 0) |
| 1205 | { |
| 1206 | DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left); |
| 1207 | outbytes = SSL_write(ssl, CS buff, left); |
| 1208 | error = SSL_get_error(ssl, outbytes); |
| 1209 | DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error); |
| 1210 | switch (error) |
| 1211 | { |
| 1212 | case SSL_ERROR_SSL: |
| 1213 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 1214 | log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring); |
| 1215 | return -1; |
| 1216 | |
| 1217 | case SSL_ERROR_NONE: |
| 1218 | left -= outbytes; |
| 1219 | buff += outbytes; |
| 1220 | break; |
| 1221 | |
| 1222 | case SSL_ERROR_ZERO_RETURN: |
| 1223 | log_write(0, LOG_MAIN, "SSL channel closed on write"); |
| 1224 | return -1; |
| 1225 | |
| 1226 | default: |
| 1227 | log_write(0, LOG_MAIN, "SSL_write error %d", error); |
| 1228 | return -1; |
| 1229 | } |
| 1230 | } |
| 1231 | return len; |
| 1232 | } |
| 1233 | |
| 1234 | |
| 1235 | |
| 1236 | /************************************************* |
| 1237 | * Close down a TLS session * |
| 1238 | *************************************************/ |
| 1239 | |
| 1240 | /* This is also called from within a delivery subprocess forked from the |
| 1241 | daemon, to shut down the TLS library, without actually doing a shutdown (which |
| 1242 | would tamper with the SSL session in the parent process). |
| 1243 | |
| 1244 | Arguments: TRUE if SSL_shutdown is to be called |
| 1245 | Returns: nothing |
| 1246 | */ |
| 1247 | |
| 1248 | void |
| 1249 | tls_close(BOOL shutdown) |
| 1250 | { |
| 1251 | if (tls_active < 0) return; /* TLS was not active */ |
| 1252 | |
| 1253 | if (shutdown) |
| 1254 | { |
| 1255 | DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n"); |
| 1256 | SSL_shutdown(ssl); |
| 1257 | } |
| 1258 | |
| 1259 | SSL_free(ssl); |
| 1260 | ssl = NULL; |
| 1261 | |
| 1262 | tls_active = -1; |
| 1263 | } |
| 1264 | |
| 1265 | |
| 1266 | |
| 1267 | |
| 1268 | /************************************************* |
| 1269 | * Report the library versions. * |
| 1270 | *************************************************/ |
| 1271 | |
| 1272 | /* There have historically been some issues with binary compatibility in |
| 1273 | OpenSSL libraries; if Exim (like many other applications) is built against |
| 1274 | one version of OpenSSL but the run-time linker picks up another version, |
| 1275 | it can result in serious failures, including crashing with a SIGSEGV. So |
| 1276 | report the version found by the compiler and the run-time version. |
| 1277 | |
| 1278 | Arguments: a FILE* to print the results to |
| 1279 | Returns: nothing |
| 1280 | */ |
| 1281 | |
| 1282 | void |
| 1283 | tls_version_report(FILE *f) |
| 1284 | { |
| 1285 | fprintf(f, "Library version: OpenSSL: Compile: %s\n" |
| 1286 | " Runtime: %s\n", |
| 1287 | OPENSSL_VERSION_TEXT, |
| 1288 | SSLeay_version(SSLEAY_VERSION)); |
| 1289 | } |
| 1290 | |
| 1291 | |
| 1292 | |
| 1293 | |
| 1294 | /************************************************* |
| 1295 | * Pseudo-random number generation * |
| 1296 | *************************************************/ |
| 1297 | |
| 1298 | /* Pseudo-random number generation. The result is not expected to be |
| 1299 | cryptographically strong but not so weak that someone will shoot themselves |
| 1300 | in the foot using it as a nonce in input in some email header scheme or |
| 1301 | whatever weirdness they'll twist this into. The result should handle fork() |
| 1302 | and avoid repeating sequences. OpenSSL handles that for us. |
| 1303 | |
| 1304 | Arguments: |
| 1305 | max range maximum |
| 1306 | Returns a random number in range [0, max-1] |
| 1307 | */ |
| 1308 | |
| 1309 | int |
| 1310 | pseudo_random_number(int max) |
| 1311 | { |
| 1312 | unsigned int r; |
| 1313 | int i, needed_len; |
| 1314 | uschar *p; |
| 1315 | uschar smallbuf[sizeof(r)]; |
| 1316 | |
| 1317 | if (max <= 1) |
| 1318 | return 0; |
| 1319 | |
| 1320 | /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */ |
| 1321 | if (!RAND_status()) |
| 1322 | { |
| 1323 | randstuff r; |
| 1324 | gettimeofday(&r.tv, NULL); |
| 1325 | r.p = getpid(); |
| 1326 | |
| 1327 | RAND_seed((uschar *)(&r), sizeof(r)); |
| 1328 | } |
| 1329 | /* We're after pseudo-random, not random; if we still don't have enough data |
| 1330 | in the internal PRNG then our options are limited. We could sleep and hope |
| 1331 | for entropy to come along (prayer technique) but if the system is so depleted |
| 1332 | in the first place then something is likely to just keep taking it. Instead, |
| 1333 | we'll just take whatever little bit of pseudo-random we can still manage to |
| 1334 | get. */ |
| 1335 | |
| 1336 | needed_len = sizeof(r); |
| 1337 | /* Don't take 8 times more entropy than needed if int is 8 octets and we were |
| 1338 | asked for a number less than 10. */ |
| 1339 | for (r = max, i = 0; r; ++i) |
| 1340 | r >>= 1; |
| 1341 | i = (i + 7) / 8; |
| 1342 | if (i < needed_len) |
| 1343 | needed_len = i; |
| 1344 | |
| 1345 | /* We do not care if crypto-strong */ |
| 1346 | (void) RAND_pseudo_bytes(smallbuf, needed_len); |
| 1347 | r = 0; |
| 1348 | for (p = smallbuf; needed_len; --needed_len, ++p) |
| 1349 | { |
| 1350 | r *= 256; |
| 1351 | r += *p; |
| 1352 | } |
| 1353 | |
| 1354 | /* We don't particularly care about weighted results; if someone wants |
| 1355 | smooth distribution and cares enough then they should submit a patch then. */ |
| 1356 | return r % max; |
| 1357 | } |
| 1358 | |
| 1359 | |
| 1360 | |
| 1361 | |
| 1362 | /************************************************* |
| 1363 | * OpenSSL option parse * |
| 1364 | *************************************************/ |
| 1365 | |
| 1366 | /* Parse one option for tls_openssl_options_parse below |
| 1367 | |
| 1368 | Arguments: |
| 1369 | name one option name |
| 1370 | value place to store a value for it |
| 1371 | Returns success or failure in parsing |
| 1372 | */ |
| 1373 | |
| 1374 | struct exim_openssl_option { |
| 1375 | uschar *name; |
| 1376 | long value; |
| 1377 | }; |
| 1378 | /* We could use a macro to expand, but we need the ifdef and not all the |
| 1379 | options document which version they were introduced in. Policylet: include |
| 1380 | all options unless explicitly for DTLS, let the administrator choose which |
| 1381 | to apply. |
| 1382 | |
| 1383 | This list is current as of: |
| 1384 | ==> 1.0.1b <== */ |
| 1385 | static struct exim_openssl_option exim_openssl_options[] = { |
| 1386 | /* KEEP SORTED ALPHABETICALLY! */ |
| 1387 | #ifdef SSL_OP_ALL |
| 1388 | { US"all", SSL_OP_ALL }, |
| 1389 | #endif |
| 1390 | #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION |
| 1391 | { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION }, |
| 1392 | #endif |
| 1393 | #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE |
| 1394 | { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE }, |
| 1395 | #endif |
| 1396 | #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS |
| 1397 | { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS }, |
| 1398 | #endif |
| 1399 | #ifdef SSL_OP_EPHEMERAL_RSA |
| 1400 | { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA }, |
| 1401 | #endif |
| 1402 | #ifdef SSL_OP_LEGACY_SERVER_CONNECT |
| 1403 | { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT }, |
| 1404 | #endif |
| 1405 | #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER |
| 1406 | { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER }, |
| 1407 | #endif |
| 1408 | #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG |
| 1409 | { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG }, |
| 1410 | #endif |
| 1411 | #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING |
| 1412 | { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING }, |
| 1413 | #endif |
| 1414 | #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG |
| 1415 | { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG }, |
| 1416 | #endif |
| 1417 | #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG |
| 1418 | { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG }, |
| 1419 | #endif |
| 1420 | #ifdef SSL_OP_NO_COMPRESSION |
| 1421 | { US"no_compression", SSL_OP_NO_COMPRESSION }, |
| 1422 | #endif |
| 1423 | #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION |
| 1424 | { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION }, |
| 1425 | #endif |
| 1426 | #ifdef SSL_OP_NO_SSLv2 |
| 1427 | { US"no_sslv2", SSL_OP_NO_SSLv2 }, |
| 1428 | #endif |
| 1429 | #ifdef SSL_OP_NO_SSLv3 |
| 1430 | { US"no_sslv3", SSL_OP_NO_SSLv3 }, |
| 1431 | #endif |
| 1432 | #ifdef SSL_OP_NO_TICKET |
| 1433 | { US"no_ticket", SSL_OP_NO_TICKET }, |
| 1434 | #endif |
| 1435 | #ifdef SSL_OP_NO_TLSv1 |
| 1436 | { US"no_tlsv1", SSL_OP_NO_TLSv1 }, |
| 1437 | #endif |
| 1438 | #ifdef SSL_OP_NO_TLSv1_1 |
| 1439 | #if SSL_OP_NO_TLSv1_1 == 0x00000400L |
| 1440 | /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */ |
| 1441 | #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring |
| 1442 | #else |
| 1443 | { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 }, |
| 1444 | #endif |
| 1445 | #endif |
| 1446 | #ifdef SSL_OP_NO_TLSv1_2 |
| 1447 | { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 }, |
| 1448 | #endif |
| 1449 | #ifdef SSL_OP_SINGLE_DH_USE |
| 1450 | { US"single_dh_use", SSL_OP_SINGLE_DH_USE }, |
| 1451 | #endif |
| 1452 | #ifdef SSL_OP_SINGLE_ECDH_USE |
| 1453 | { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE }, |
| 1454 | #endif |
| 1455 | #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG |
| 1456 | { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG }, |
| 1457 | #endif |
| 1458 | #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG |
| 1459 | { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG }, |
| 1460 | #endif |
| 1461 | #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG |
| 1462 | { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG }, |
| 1463 | #endif |
| 1464 | #ifdef SSL_OP_TLS_D5_BUG |
| 1465 | { US"tls_d5_bug", SSL_OP_TLS_D5_BUG }, |
| 1466 | #endif |
| 1467 | #ifdef SSL_OP_TLS_ROLLBACK_BUG |
| 1468 | { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG }, |
| 1469 | #endif |
| 1470 | }; |
| 1471 | static int exim_openssl_options_size = |
| 1472 | sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option); |
| 1473 | |
| 1474 | |
| 1475 | static BOOL |
| 1476 | tls_openssl_one_option_parse(uschar *name, long *value) |
| 1477 | { |
| 1478 | int first = 0; |
| 1479 | int last = exim_openssl_options_size; |
| 1480 | while (last > first) |
| 1481 | { |
| 1482 | int middle = (first + last)/2; |
| 1483 | int c = Ustrcmp(name, exim_openssl_options[middle].name); |
| 1484 | if (c == 0) |
| 1485 | { |
| 1486 | *value = exim_openssl_options[middle].value; |
| 1487 | return TRUE; |
| 1488 | } |
| 1489 | else if (c > 0) |
| 1490 | first = middle + 1; |
| 1491 | else |
| 1492 | last = middle; |
| 1493 | } |
| 1494 | return FALSE; |
| 1495 | } |
| 1496 | |
| 1497 | |
| 1498 | |
| 1499 | |
| 1500 | /************************************************* |
| 1501 | * OpenSSL option parsing logic * |
| 1502 | *************************************************/ |
| 1503 | |
| 1504 | /* OpenSSL has a number of compatibility options which an administrator might |
| 1505 | reasonably wish to set. Interpret a list similarly to decode_bits(), so that |
| 1506 | we look like log_selector. |
| 1507 | |
| 1508 | Arguments: |
| 1509 | option_spec the administrator-supplied string of options |
| 1510 | results ptr to long storage for the options bitmap |
| 1511 | Returns success or failure |
| 1512 | */ |
| 1513 | |
| 1514 | BOOL |
| 1515 | tls_openssl_options_parse(uschar *option_spec, long *results) |
| 1516 | { |
| 1517 | long result, item; |
| 1518 | uschar *s, *end; |
| 1519 | uschar keep_c; |
| 1520 | BOOL adding, item_parsed; |
| 1521 | |
| 1522 | result = 0L; |
| 1523 | /* Prior to 4.78 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed |
| 1524 | * from default because it increases BEAST susceptibility. */ |
| 1525 | |
| 1526 | if (option_spec == NULL) |
| 1527 | { |
| 1528 | *results = result; |
| 1529 | return TRUE; |
| 1530 | } |
| 1531 | |
| 1532 | for (s=option_spec; *s != '\0'; /**/) |
| 1533 | { |
| 1534 | while (isspace(*s)) ++s; |
| 1535 | if (*s == '\0') |
| 1536 | break; |
| 1537 | if (*s != '+' && *s != '-') |
| 1538 | { |
| 1539 | DEBUG(D_tls) debug_printf("malformed openssl option setting: " |
| 1540 | "+ or - expected but found \"%s\"\n", s); |
| 1541 | return FALSE; |
| 1542 | } |
| 1543 | adding = *s++ == '+'; |
| 1544 | for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ; |
| 1545 | keep_c = *end; |
| 1546 | *end = '\0'; |
| 1547 | item_parsed = tls_openssl_one_option_parse(s, &item); |
| 1548 | if (!item_parsed) |
| 1549 | { |
| 1550 | DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s); |
| 1551 | return FALSE; |
| 1552 | } |
| 1553 | DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n", |
| 1554 | adding ? "adding" : "removing", result, item, s); |
| 1555 | if (adding) |
| 1556 | result |= item; |
| 1557 | else |
| 1558 | result &= ~item; |
| 1559 | *end = keep_c; |
| 1560 | s = end; |
| 1561 | } |
| 1562 | |
| 1563 | *results = result; |
| 1564 | return TRUE; |
| 1565 | } |
| 1566 | |
| 1567 | /* End of tls-openssl.c */ |