| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2012 */ |
| 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 | #ifdef EXPERIMENTAL_OCSP |
| 24 | #include <openssl/ocsp.h> |
| 25 | #endif |
| 26 | |
| 27 | #ifdef EXPERIMENTAL_OCSP |
| 28 | #define EXIM_OCSP_SKEW_SECONDS (300L) |
| 29 | #define EXIM_OCSP_MAX_AGE (-1L) |
| 30 | #endif |
| 31 | |
| 32 | #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT) |
| 33 | #define EXIM_HAVE_OPENSSL_TLSEXT |
| 34 | #endif |
| 35 | |
| 36 | /* Structure for collecting random data for seeding. */ |
| 37 | |
| 38 | typedef struct randstuff { |
| 39 | struct timeval tv; |
| 40 | pid_t p; |
| 41 | } randstuff; |
| 42 | |
| 43 | /* Local static variables */ |
| 44 | |
| 45 | static BOOL client_verify_callback_called = FALSE; |
| 46 | static BOOL server_verify_callback_called = FALSE; |
| 47 | static const uschar *sid_ctx = US"exim"; |
| 48 | |
| 49 | /* We have three different contexts to care about. |
| 50 | |
| 51 | Simple case: client, `client_ctx` |
| 52 | As a client, we can be doing a callout or cut-through delivery while receiving |
| 53 | a message. So we have a client context, which should have options initialised |
| 54 | from the SMTP Transport. |
| 55 | |
| 56 | Server: |
| 57 | There are two cases: with and without ServerNameIndication from the client. |
| 58 | Given TLS SNI, we can be using different keys, certs and various other |
| 59 | configuration settings, because they're re-expanded with $tls_sni set. This |
| 60 | allows vhosting with TLS. This SNI is sent in the handshake. |
| 61 | A client might not send SNI, so we need a fallback, and an initial setup too. |
| 62 | So as a server, we start out using `server_ctx`. |
| 63 | If SNI is sent by the client, then we as server, mid-negotiation, try to clone |
| 64 | `server_sni` from `server_ctx` and then initialise settings by re-expanding |
| 65 | configuration. |
| 66 | */ |
| 67 | |
| 68 | static SSL_CTX *client_ctx = NULL; |
| 69 | static SSL_CTX *server_ctx = NULL; |
| 70 | static SSL *client_ssl = NULL; |
| 71 | static SSL *server_ssl = NULL; |
| 72 | |
| 73 | #ifdef EXIM_HAVE_OPENSSL_TLSEXT |
| 74 | static SSL_CTX *server_sni = NULL; |
| 75 | #endif |
| 76 | |
| 77 | static char ssl_errstring[256]; |
| 78 | |
| 79 | static int ssl_session_timeout = 200; |
| 80 | static BOOL client_verify_optional = FALSE; |
| 81 | static BOOL server_verify_optional = FALSE; |
| 82 | |
| 83 | static BOOL reexpand_tls_files_for_sni = FALSE; |
| 84 | |
| 85 | |
| 86 | typedef struct tls_ext_ctx_cb { |
| 87 | uschar *certificate; |
| 88 | uschar *privatekey; |
| 89 | #ifdef EXPERIMENTAL_OCSP |
| 90 | uschar *ocsp_file; |
| 91 | uschar *ocsp_file_expanded; |
| 92 | OCSP_RESPONSE *ocsp_response; |
| 93 | #endif |
| 94 | uschar *dhparam; |
| 95 | /* these are cached from first expand */ |
| 96 | uschar *server_cipher_list; |
| 97 | /* only passed down to tls_error: */ |
| 98 | host_item *host; |
| 99 | } tls_ext_ctx_cb; |
| 100 | |
| 101 | /* should figure out a cleanup of API to handle state preserved per |
| 102 | implementation, for various reasons, which can be void * in the APIs. |
| 103 | For now, we hack around it. */ |
| 104 | tls_ext_ctx_cb *client_static_cbinfo = NULL; |
| 105 | tls_ext_ctx_cb *server_static_cbinfo = NULL; |
| 106 | |
| 107 | static int |
| 108 | setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, BOOL client); |
| 109 | |
| 110 | /* Callbacks */ |
| 111 | #ifdef EXIM_HAVE_OPENSSL_TLSEXT |
| 112 | static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg); |
| 113 | #endif |
| 114 | #ifdef EXPERIMENTAL_OCSP |
| 115 | static int tls_stapling_cb(SSL *s, void *arg); |
| 116 | #endif |
| 117 | |
| 118 | |
| 119 | /************************************************* |
| 120 | * Handle TLS error * |
| 121 | *************************************************/ |
| 122 | |
| 123 | /* Called from lots of places when errors occur before actually starting to do |
| 124 | the TLS handshake, that is, while the session is still in clear. Always returns |
| 125 | DEFER for a server and FAIL for a client so that most calls can use "return |
| 126 | tls_error(...)" to do this processing and then give an appropriate return. A |
| 127 | single function is used for both server and client, because it is called from |
| 128 | some shared functions. |
| 129 | |
| 130 | Argument: |
| 131 | prefix text to include in the logged error |
| 132 | host NULL if setting up a server; |
| 133 | the connected host if setting up a client |
| 134 | msg error message or NULL if we should ask OpenSSL |
| 135 | |
| 136 | Returns: OK/DEFER/FAIL |
| 137 | */ |
| 138 | |
| 139 | static int |
| 140 | tls_error(uschar *prefix, host_item *host, uschar *msg) |
| 141 | { |
| 142 | if (msg == NULL) |
| 143 | { |
| 144 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 145 | msg = (uschar *)ssl_errstring; |
| 146 | } |
| 147 | |
| 148 | if (host == NULL) |
| 149 | { |
| 150 | uschar *conn_info = smtp_get_connection_info(); |
| 151 | if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) |
| 152 | conn_info += 5; |
| 153 | log_write(0, LOG_MAIN, "TLS error on %s (%s): %s", |
| 154 | conn_info, prefix, msg); |
| 155 | return DEFER; |
| 156 | } |
| 157 | else |
| 158 | { |
| 159 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s): %s", |
| 160 | host->name, host->address, prefix, msg); |
| 161 | return FAIL; |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | |
| 166 | |
| 167 | /************************************************* |
| 168 | * Callback to generate RSA key * |
| 169 | *************************************************/ |
| 170 | |
| 171 | /* |
| 172 | Arguments: |
| 173 | s SSL connection |
| 174 | export not used |
| 175 | keylength keylength |
| 176 | |
| 177 | Returns: pointer to generated key |
| 178 | */ |
| 179 | |
| 180 | static RSA * |
| 181 | rsa_callback(SSL *s, int export, int keylength) |
| 182 | { |
| 183 | RSA *rsa_key; |
| 184 | export = export; /* Shut picky compilers up */ |
| 185 | DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength); |
| 186 | rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL); |
| 187 | if (rsa_key == NULL) |
| 188 | { |
| 189 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 190 | log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s", |
| 191 | ssl_errstring); |
| 192 | return NULL; |
| 193 | } |
| 194 | return rsa_key; |
| 195 | } |
| 196 | |
| 197 | |
| 198 | |
| 199 | |
| 200 | /************************************************* |
| 201 | * Callback for verification * |
| 202 | *************************************************/ |
| 203 | |
| 204 | /* The SSL library does certificate verification if set up to do so. This |
| 205 | callback has the current yes/no state is in "state". If verification succeeded, |
| 206 | we set up the tls_peerdn string. If verification failed, what happens depends |
| 207 | on whether the client is required to present a verifiable certificate or not. |
| 208 | |
| 209 | If verification is optional, we change the state to yes, but still log the |
| 210 | verification error. For some reason (it really would help to have proper |
| 211 | documentation of OpenSSL), this callback function then gets called again, this |
| 212 | time with state = 1. In fact, that's useful, because we can set up the peerdn |
| 213 | value, but we must take care not to set the private verified flag on the second |
| 214 | time through. |
| 215 | |
| 216 | Note: this function is not called if the client fails to present a certificate |
| 217 | when asked. We get here only if a certificate has been received. Handling of |
| 218 | optional verification for this case is done when requesting SSL to verify, by |
| 219 | setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case. |
| 220 | |
| 221 | Arguments: |
| 222 | state current yes/no state as 1/0 |
| 223 | x509ctx certificate information. |
| 224 | client TRUE for client startup, FALSE for server startup |
| 225 | |
| 226 | Returns: 1 if verified, 0 if not |
| 227 | */ |
| 228 | |
| 229 | static int |
| 230 | verify_callback(int state, X509_STORE_CTX *x509ctx, BOOL client) |
| 231 | { |
| 232 | static uschar txt[256]; |
| 233 | tls_support * tlsp; |
| 234 | BOOL * calledp; |
| 235 | BOOL * optionalp; |
| 236 | |
| 237 | if (client) |
| 238 | { |
| 239 | tlsp= &tls_out; |
| 240 | calledp= &client_verify_callback_called; |
| 241 | optionalp= &client_verify_optional; |
| 242 | } |
| 243 | else |
| 244 | { |
| 245 | tlsp= &tls_in; |
| 246 | calledp= &server_verify_callback_called; |
| 247 | optionalp= &server_verify_optional; |
| 248 | } |
| 249 | |
| 250 | X509_NAME_oneline(X509_get_subject_name(x509ctx->current_cert), |
| 251 | CS txt, sizeof(txt)); |
| 252 | |
| 253 | if (state == 0) |
| 254 | { |
| 255 | log_write(0, LOG_MAIN, "SSL verify error: depth=%d error=%s cert=%s", |
| 256 | x509ctx->error_depth, |
| 257 | X509_verify_cert_error_string(x509ctx->error), |
| 258 | txt); |
| 259 | tlsp->certificate_verified = FALSE; |
| 260 | *calledp = TRUE; |
| 261 | if (!*optionalp) return 0; /* reject */ |
| 262 | DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in " |
| 263 | "tls_try_verify_hosts)\n"); |
| 264 | return 1; /* accept */ |
| 265 | } |
| 266 | |
| 267 | if (x509ctx->error_depth != 0) |
| 268 | { |
| 269 | DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d cert=%s\n", |
| 270 | x509ctx->error_depth, txt); |
| 271 | } |
| 272 | else |
| 273 | { |
| 274 | DEBUG(D_tls) debug_printf("SSL%s peer: %s\n", |
| 275 | *calledp ? "" : " authenticated", txt); |
| 276 | tlsp->peerdn = txt; |
| 277 | } |
| 278 | |
| 279 | if (!*calledp) tlsp->certificate_verified = TRUE; |
| 280 | *calledp = TRUE; |
| 281 | |
| 282 | return 1; /* accept */ |
| 283 | } |
| 284 | |
| 285 | static int |
| 286 | verify_callback_client(int state, X509_STORE_CTX *x509ctx) |
| 287 | { |
| 288 | return verify_callback(state, x509ctx, TRUE); |
| 289 | } |
| 290 | |
| 291 | static int |
| 292 | verify_callback_server(int state, X509_STORE_CTX *x509ctx) |
| 293 | { |
| 294 | return verify_callback(state, x509ctx, FALSE); |
| 295 | } |
| 296 | |
| 297 | |
| 298 | |
| 299 | /************************************************* |
| 300 | * Information callback * |
| 301 | *************************************************/ |
| 302 | |
| 303 | /* The SSL library functions call this from time to time to indicate what they |
| 304 | are doing. We copy the string to the debugging output when TLS debugging has |
| 305 | been requested. |
| 306 | |
| 307 | Arguments: |
| 308 | s the SSL connection |
| 309 | where |
| 310 | ret |
| 311 | |
| 312 | Returns: nothing |
| 313 | */ |
| 314 | |
| 315 | static void |
| 316 | info_callback(SSL *s, int where, int ret) |
| 317 | { |
| 318 | where = where; |
| 319 | ret = ret; |
| 320 | DEBUG(D_tls) debug_printf("SSL info: %s\n", SSL_state_string_long(s)); |
| 321 | } |
| 322 | |
| 323 | |
| 324 | |
| 325 | /************************************************* |
| 326 | * Initialize for DH * |
| 327 | *************************************************/ |
| 328 | |
| 329 | /* If dhparam is set, expand it, and load up the parameters for DH encryption. |
| 330 | |
| 331 | Arguments: |
| 332 | dhparam DH parameter file or fixed parameter identity string |
| 333 | host connected host, if client; NULL if server |
| 334 | |
| 335 | Returns: TRUE if OK (nothing to set up, or setup worked) |
| 336 | */ |
| 337 | |
| 338 | static BOOL |
| 339 | init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host) |
| 340 | { |
| 341 | BIO *bio; |
| 342 | DH *dh; |
| 343 | uschar *dhexpanded; |
| 344 | const char *pem; |
| 345 | |
| 346 | if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded)) |
| 347 | return FALSE; |
| 348 | |
| 349 | if (dhexpanded == NULL || *dhexpanded == '\0') |
| 350 | { |
| 351 | bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1); |
| 352 | } |
| 353 | else if (dhexpanded[0] == '/') |
| 354 | { |
| 355 | bio = BIO_new_file(CS dhexpanded, "r"); |
| 356 | if (bio == NULL) |
| 357 | { |
| 358 | tls_error(string_sprintf("could not read dhparams file %s", dhexpanded), |
| 359 | host, US strerror(errno)); |
| 360 | return FALSE; |
| 361 | } |
| 362 | } |
| 363 | else |
| 364 | { |
| 365 | if (Ustrcmp(dhexpanded, "none") == 0) |
| 366 | { |
| 367 | DEBUG(D_tls) debug_printf("Requested no DH parameters.\n"); |
| 368 | return TRUE; |
| 369 | } |
| 370 | |
| 371 | pem = std_dh_prime_named(dhexpanded); |
| 372 | if (!pem) |
| 373 | { |
| 374 | tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded), |
| 375 | host, US strerror(errno)); |
| 376 | return FALSE; |
| 377 | } |
| 378 | bio = BIO_new_mem_buf(CS pem, -1); |
| 379 | } |
| 380 | |
| 381 | dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL); |
| 382 | if (dh == NULL) |
| 383 | { |
| 384 | BIO_free(bio); |
| 385 | tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded), |
| 386 | host, NULL); |
| 387 | return FALSE; |
| 388 | } |
| 389 | |
| 390 | /* Even if it is larger, we silently return success rather than cause things |
| 391 | * to fail out, so that a too-large DH will not knock out all TLS; it's a |
| 392 | * debatable choice. */ |
| 393 | if ((8*DH_size(dh)) > tls_dh_max_bits) |
| 394 | { |
| 395 | DEBUG(D_tls) |
| 396 | debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d", |
| 397 | 8*DH_size(dh), tls_dh_max_bits); |
| 398 | } |
| 399 | else |
| 400 | { |
| 401 | SSL_CTX_set_tmp_dh(sctx, dh); |
| 402 | DEBUG(D_tls) |
| 403 | debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n", |
| 404 | dhexpanded ? dhexpanded : US"default", 8*DH_size(dh)); |
| 405 | } |
| 406 | |
| 407 | DH_free(dh); |
| 408 | BIO_free(bio); |
| 409 | |
| 410 | return TRUE; |
| 411 | } |
| 412 | |
| 413 | |
| 414 | |
| 415 | |
| 416 | #ifdef EXPERIMENTAL_OCSP |
| 417 | /************************************************* |
| 418 | * Load OCSP information into state * |
| 419 | *************************************************/ |
| 420 | |
| 421 | /* Called to load the OCSP response from the given file into memory, once |
| 422 | caller has determined this is needed. Checks validity. Debugs a message |
| 423 | if invalid. |
| 424 | |
| 425 | ASSUMES: single response, for single cert. |
| 426 | |
| 427 | Arguments: |
| 428 | sctx the SSL_CTX* to update |
| 429 | cbinfo various parts of session state |
| 430 | expanded the filename putatively holding an OCSP response |
| 431 | |
| 432 | */ |
| 433 | |
| 434 | static void |
| 435 | ocsp_load_response(SSL_CTX *sctx, |
| 436 | tls_ext_ctx_cb *cbinfo, |
| 437 | const uschar *expanded) |
| 438 | { |
| 439 | BIO *bio; |
| 440 | OCSP_RESPONSE *resp; |
| 441 | OCSP_BASICRESP *basic_response; |
| 442 | OCSP_SINGLERESP *single_response; |
| 443 | ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd; |
| 444 | X509_STORE *store; |
| 445 | unsigned long verify_flags; |
| 446 | int status, reason, i; |
| 447 | |
| 448 | cbinfo->ocsp_file_expanded = string_copy(expanded); |
| 449 | if (cbinfo->ocsp_response) |
| 450 | { |
| 451 | OCSP_RESPONSE_free(cbinfo->ocsp_response); |
| 452 | cbinfo->ocsp_response = NULL; |
| 453 | } |
| 454 | |
| 455 | bio = BIO_new_file(CS cbinfo->ocsp_file_expanded, "rb"); |
| 456 | if (!bio) |
| 457 | { |
| 458 | DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n", |
| 459 | cbinfo->ocsp_file_expanded); |
| 460 | return; |
| 461 | } |
| 462 | |
| 463 | resp = d2i_OCSP_RESPONSE_bio(bio, NULL); |
| 464 | BIO_free(bio); |
| 465 | if (!resp) |
| 466 | { |
| 467 | DEBUG(D_tls) debug_printf("Error reading OCSP response.\n"); |
| 468 | return; |
| 469 | } |
| 470 | |
| 471 | status = OCSP_response_status(resp); |
| 472 | if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL) |
| 473 | { |
| 474 | DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n", |
| 475 | OCSP_response_status_str(status), status); |
| 476 | return; |
| 477 | } |
| 478 | |
| 479 | basic_response = OCSP_response_get1_basic(resp); |
| 480 | if (!basic_response) |
| 481 | { |
| 482 | DEBUG(D_tls) |
| 483 | debug_printf("OCSP response parse error: unable to extract basic response.\n"); |
| 484 | return; |
| 485 | } |
| 486 | |
| 487 | store = SSL_CTX_get_cert_store(sctx); |
| 488 | verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */ |
| 489 | |
| 490 | /* May need to expose ability to adjust those flags? |
| 491 | OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT |
| 492 | OCSP_TRUSTOTHER OCSP_NOINTERN */ |
| 493 | |
| 494 | i = OCSP_basic_verify(basic_response, NULL, store, verify_flags); |
| 495 | if (i <= 0) |
| 496 | { |
| 497 | DEBUG(D_tls) { |
| 498 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 499 | debug_printf("OCSP response verify failure: %s\n", US ssl_errstring); |
| 500 | } |
| 501 | return; |
| 502 | } |
| 503 | |
| 504 | /* Here's the simplifying assumption: there's only one response, for the |
| 505 | one certificate we use, and nothing for anything else in a chain. If this |
| 506 | proves false, we need to extract a cert id from our issued cert |
| 507 | (tls_certificate) and use that for OCSP_resp_find_status() (which finds the |
| 508 | right cert in the stack and then calls OCSP_single_get0_status()). |
| 509 | |
| 510 | I'm hoping to avoid reworking a bunch more of how we handle state here. */ |
| 511 | single_response = OCSP_resp_get0(basic_response, 0); |
| 512 | if (!single_response) |
| 513 | { |
| 514 | DEBUG(D_tls) |
| 515 | debug_printf("Unable to get first response from OCSP basic response.\n"); |
| 516 | return; |
| 517 | } |
| 518 | |
| 519 | status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd); |
| 520 | /* how does this status differ from the one above? */ |
| 521 | if (status != OCSP_RESPONSE_STATUS_SUCCESSFUL) |
| 522 | { |
| 523 | DEBUG(D_tls) debug_printf("OCSP response not valid (take 2): %s (%d)\n", |
| 524 | OCSP_response_status_str(status), status); |
| 525 | return; |
| 526 | } |
| 527 | |
| 528 | if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE)) |
| 529 | { |
| 530 | DEBUG(D_tls) debug_printf("OCSP status invalid times.\n"); |
| 531 | return; |
| 532 | } |
| 533 | |
| 534 | cbinfo->ocsp_response = resp; |
| 535 | } |
| 536 | #endif |
| 537 | |
| 538 | |
| 539 | |
| 540 | |
| 541 | /************************************************* |
| 542 | * Expand key and cert file specs * |
| 543 | *************************************************/ |
| 544 | |
| 545 | /* Called once during tls_init and possibly againt during TLS setup, for a |
| 546 | new context, if Server Name Indication was used and tls_sni was seen in |
| 547 | the certificate string. |
| 548 | |
| 549 | Arguments: |
| 550 | sctx the SSL_CTX* to update |
| 551 | cbinfo various parts of session state |
| 552 | |
| 553 | Returns: OK/DEFER/FAIL |
| 554 | */ |
| 555 | |
| 556 | static int |
| 557 | tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo) |
| 558 | { |
| 559 | uschar *expanded; |
| 560 | |
| 561 | if (cbinfo->certificate == NULL) |
| 562 | return OK; |
| 563 | |
| 564 | if (Ustrstr(cbinfo->certificate, US"tls_sni") || |
| 565 | Ustrstr(cbinfo->certificate, US"tls_in_sni") || |
| 566 | Ustrstr(cbinfo->certificate, US"tls_out_sni") |
| 567 | ) |
| 568 | reexpand_tls_files_for_sni = TRUE; |
| 569 | |
| 570 | if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded)) |
| 571 | return DEFER; |
| 572 | |
| 573 | if (expanded != NULL) |
| 574 | { |
| 575 | DEBUG(D_tls) debug_printf("tls_certificate file %s\n", expanded); |
| 576 | if (!SSL_CTX_use_certificate_chain_file(sctx, CS expanded)) |
| 577 | return tls_error(string_sprintf( |
| 578 | "SSL_CTX_use_certificate_chain_file file=%s", expanded), |
| 579 | cbinfo->host, NULL); |
| 580 | } |
| 581 | |
| 582 | if (cbinfo->privatekey != NULL && |
| 583 | !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded)) |
| 584 | return DEFER; |
| 585 | |
| 586 | /* If expansion was forced to fail, key_expanded will be NULL. If the result |
| 587 | of the expansion is an empty string, ignore it also, and assume the private |
| 588 | key is in the same file as the certificate. */ |
| 589 | |
| 590 | if (expanded != NULL && *expanded != 0) |
| 591 | { |
| 592 | DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", expanded); |
| 593 | if (!SSL_CTX_use_PrivateKey_file(sctx, CS expanded, SSL_FILETYPE_PEM)) |
| 594 | return tls_error(string_sprintf( |
| 595 | "SSL_CTX_use_PrivateKey_file file=%s", expanded), cbinfo->host, NULL); |
| 596 | } |
| 597 | |
| 598 | #ifdef EXPERIMENTAL_OCSP |
| 599 | if (cbinfo->ocsp_file != NULL) |
| 600 | { |
| 601 | if (!expand_check(cbinfo->ocsp_file, US"tls_ocsp_file", &expanded)) |
| 602 | return DEFER; |
| 603 | |
| 604 | if (expanded != NULL && *expanded != 0) |
| 605 | { |
| 606 | DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded); |
| 607 | if (cbinfo->ocsp_file_expanded && |
| 608 | (Ustrcmp(expanded, cbinfo->ocsp_file_expanded) == 0)) |
| 609 | { |
| 610 | DEBUG(D_tls) |
| 611 | debug_printf("tls_ocsp_file value unchanged, using existing values.\n"); |
| 612 | } else { |
| 613 | ocsp_load_response(sctx, cbinfo, expanded); |
| 614 | } |
| 615 | } |
| 616 | } |
| 617 | #endif |
| 618 | |
| 619 | return OK; |
| 620 | } |
| 621 | |
| 622 | |
| 623 | |
| 624 | |
| 625 | /************************************************* |
| 626 | * Callback to handle SNI * |
| 627 | *************************************************/ |
| 628 | |
| 629 | /* Called when acting as server during the TLS session setup if a Server Name |
| 630 | Indication extension was sent by the client. |
| 631 | |
| 632 | API documentation is OpenSSL s_server.c implementation. |
| 633 | |
| 634 | Arguments: |
| 635 | s SSL* of the current session |
| 636 | ad unknown (part of OpenSSL API) (unused) |
| 637 | arg Callback of "our" registered data |
| 638 | |
| 639 | Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK} |
| 640 | */ |
| 641 | |
| 642 | #ifdef EXIM_HAVE_OPENSSL_TLSEXT |
| 643 | static int |
| 644 | tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg) |
| 645 | { |
| 646 | const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name); |
| 647 | tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg; |
| 648 | int rc; |
| 649 | int old_pool = store_pool; |
| 650 | |
| 651 | if (!servername) |
| 652 | return SSL_TLSEXT_ERR_OK; |
| 653 | |
| 654 | DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername, |
| 655 | reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)"); |
| 656 | |
| 657 | /* Make the extension value available for expansion */ |
| 658 | store_pool = POOL_PERM; |
| 659 | tls_in.sni = string_copy(US servername); |
| 660 | store_pool = old_pool; |
| 661 | |
| 662 | if (!reexpand_tls_files_for_sni) |
| 663 | return SSL_TLSEXT_ERR_OK; |
| 664 | |
| 665 | /* Can't find an SSL_CTX_clone() or equivalent, so we do it manually; |
| 666 | not confident that memcpy wouldn't break some internal reference counting. |
| 667 | Especially since there's a references struct member, which would be off. */ |
| 668 | |
| 669 | server_sni = SSL_CTX_new(SSLv23_server_method()); |
| 670 | if (!server_sni) |
| 671 | { |
| 672 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 673 | DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring); |
| 674 | return SSL_TLSEXT_ERR_NOACK; |
| 675 | } |
| 676 | |
| 677 | /* Not sure how many of these are actually needed, since SSL object |
| 678 | already exists. Might even need this selfsame callback, for reneg? */ |
| 679 | |
| 680 | SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx)); |
| 681 | SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx)); |
| 682 | SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx)); |
| 683 | SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx)); |
| 684 | SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb); |
| 685 | SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo); |
| 686 | if (cbinfo->server_cipher_list) |
| 687 | SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list); |
| 688 | #ifdef EXPERIMENTAL_OCSP |
| 689 | if (cbinfo->ocsp_file) |
| 690 | { |
| 691 | SSL_CTX_set_tlsext_status_cb(server_sni, tls_stapling_cb); |
| 692 | SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo); |
| 693 | } |
| 694 | #endif |
| 695 | |
| 696 | rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, FALSE); |
| 697 | if (rc != OK) return SSL_TLSEXT_ERR_NOACK; |
| 698 | |
| 699 | /* do this after setup_certs, because this can require the certs for verifying |
| 700 | OCSP information. */ |
| 701 | rc = tls_expand_session_files(server_sni, cbinfo); |
| 702 | if (rc != OK) return SSL_TLSEXT_ERR_NOACK; |
| 703 | |
| 704 | rc = init_dh(server_sni, cbinfo->dhparam, NULL); |
| 705 | if (rc != OK) return SSL_TLSEXT_ERR_NOACK; |
| 706 | |
| 707 | DEBUG(D_tls) debug_printf("Switching SSL context.\n"); |
| 708 | SSL_set_SSL_CTX(s, server_sni); |
| 709 | |
| 710 | return SSL_TLSEXT_ERR_OK; |
| 711 | } |
| 712 | #endif /* EXIM_HAVE_OPENSSL_TLSEXT */ |
| 713 | |
| 714 | |
| 715 | |
| 716 | |
| 717 | #ifdef EXPERIMENTAL_OCSP |
| 718 | /************************************************* |
| 719 | * Callback to handle OCSP Stapling * |
| 720 | *************************************************/ |
| 721 | |
| 722 | /* Called when acting as server during the TLS session setup if the client |
| 723 | requests OCSP information with a Certificate Status Request. |
| 724 | |
| 725 | Documentation via openssl s_server.c and the Apache patch from the OpenSSL |
| 726 | project. |
| 727 | |
| 728 | */ |
| 729 | |
| 730 | static int |
| 731 | tls_stapling_cb(SSL *s, void *arg) |
| 732 | { |
| 733 | const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg; |
| 734 | uschar *response_der; |
| 735 | int response_der_len; |
| 736 | |
| 737 | DEBUG(D_tls) debug_printf("Received TLS status request (OCSP stapling); %s response.\n", |
| 738 | cbinfo->ocsp_response ? "have" : "lack"); |
| 739 | if (!cbinfo->ocsp_response) |
| 740 | return SSL_TLSEXT_ERR_NOACK; |
| 741 | |
| 742 | response_der = NULL; |
| 743 | response_der_len = i2d_OCSP_RESPONSE(cbinfo->ocsp_response, &response_der); |
| 744 | if (response_der_len <= 0) |
| 745 | return SSL_TLSEXT_ERR_NOACK; |
| 746 | |
| 747 | SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len); |
| 748 | return SSL_TLSEXT_ERR_OK; |
| 749 | } |
| 750 | |
| 751 | #endif /* EXPERIMENTAL_OCSP */ |
| 752 | |
| 753 | |
| 754 | |
| 755 | |
| 756 | /************************************************* |
| 757 | * Initialize for TLS * |
| 758 | *************************************************/ |
| 759 | |
| 760 | /* Called from both server and client code, to do preliminary initialization of |
| 761 | the library. |
| 762 | |
| 763 | Arguments: |
| 764 | host connected host, if client; NULL if server |
| 765 | dhparam DH parameter file |
| 766 | certificate certificate file |
| 767 | privatekey private key |
| 768 | addr address if client; NULL if server (for some randomness) |
| 769 | |
| 770 | Returns: OK/DEFER/FAIL |
| 771 | */ |
| 772 | |
| 773 | static int |
| 774 | tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate, |
| 775 | uschar *privatekey, |
| 776 | #ifdef EXPERIMENTAL_OCSP |
| 777 | uschar *ocsp_file, |
| 778 | #endif |
| 779 | address_item *addr, tls_ext_ctx_cb ** cbp) |
| 780 | { |
| 781 | long init_options; |
| 782 | int rc; |
| 783 | BOOL okay; |
| 784 | tls_ext_ctx_cb *cbinfo; |
| 785 | |
| 786 | cbinfo = store_malloc(sizeof(tls_ext_ctx_cb)); |
| 787 | cbinfo->certificate = certificate; |
| 788 | cbinfo->privatekey = privatekey; |
| 789 | #ifdef EXPERIMENTAL_OCSP |
| 790 | cbinfo->ocsp_file = ocsp_file; |
| 791 | cbinfo->ocsp_file_expanded = NULL; |
| 792 | cbinfo->ocsp_response = NULL; |
| 793 | #endif |
| 794 | cbinfo->dhparam = dhparam; |
| 795 | cbinfo->host = host; |
| 796 | |
| 797 | SSL_load_error_strings(); /* basic set up */ |
| 798 | OpenSSL_add_ssl_algorithms(); |
| 799 | |
| 800 | #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256) |
| 801 | /* SHA256 is becoming ever more popular. This makes sure it gets added to the |
| 802 | list of available digests. */ |
| 803 | EVP_add_digest(EVP_sha256()); |
| 804 | #endif |
| 805 | |
| 806 | /* Create a context. |
| 807 | The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant |
| 808 | negotiation in the different methods; as far as I can tell, the only |
| 809 | *_{server,client}_method which allows negotiation is SSLv23, which exists even |
| 810 | when OpenSSL is built without SSLv2 support. |
| 811 | By disabling with openssl_options, we can let admins re-enable with the |
| 812 | existing knob. */ |
| 813 | |
| 814 | *ctxp = SSL_CTX_new((host == NULL)? |
| 815 | SSLv23_server_method() : SSLv23_client_method()); |
| 816 | |
| 817 | if (*ctxp == NULL) return tls_error(US"SSL_CTX_new", host, NULL); |
| 818 | |
| 819 | /* It turns out that we need to seed the random number generator this early in |
| 820 | order to get the full complement of ciphers to work. It took me roughly a day |
| 821 | of work to discover this by experiment. |
| 822 | |
| 823 | On systems that have /dev/urandom, SSL may automatically seed itself from |
| 824 | there. Otherwise, we have to make something up as best we can. Double check |
| 825 | afterwards. */ |
| 826 | |
| 827 | if (!RAND_status()) |
| 828 | { |
| 829 | randstuff r; |
| 830 | gettimeofday(&r.tv, NULL); |
| 831 | r.p = getpid(); |
| 832 | |
| 833 | RAND_seed((uschar *)(&r), sizeof(r)); |
| 834 | RAND_seed((uschar *)big_buffer, big_buffer_size); |
| 835 | if (addr != NULL) RAND_seed((uschar *)addr, sizeof(addr)); |
| 836 | |
| 837 | if (!RAND_status()) |
| 838 | return tls_error(US"RAND_status", host, |
| 839 | US"unable to seed random number generator"); |
| 840 | } |
| 841 | |
| 842 | /* Set up the information callback, which outputs if debugging is at a suitable |
| 843 | level. */ |
| 844 | |
| 845 | SSL_CTX_set_info_callback(*ctxp, (void (*)())info_callback); |
| 846 | |
| 847 | /* Automatically re-try reads/writes after renegotiation. */ |
| 848 | (void) SSL_CTX_set_mode(*ctxp, SSL_MODE_AUTO_RETRY); |
| 849 | |
| 850 | /* Apply administrator-supplied work-arounds. |
| 851 | Historically we applied just one requested option, |
| 852 | SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we |
| 853 | moved to an administrator-controlled list of options to specify and |
| 854 | grandfathered in the first one as the default value for "openssl_options". |
| 855 | |
| 856 | No OpenSSL version number checks: the options we accept depend upon the |
| 857 | availability of the option value macros from OpenSSL. */ |
| 858 | |
| 859 | okay = tls_openssl_options_parse(openssl_options, &init_options); |
| 860 | if (!okay) |
| 861 | return tls_error(US"openssl_options parsing failed", host, NULL); |
| 862 | |
| 863 | if (init_options) |
| 864 | { |
| 865 | DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options); |
| 866 | if (!(SSL_CTX_set_options(*ctxp, init_options))) |
| 867 | return tls_error(string_sprintf( |
| 868 | "SSL_CTX_set_option(%#lx)", init_options), host, NULL); |
| 869 | } |
| 870 | else |
| 871 | DEBUG(D_tls) debug_printf("no SSL CTX options to set\n"); |
| 872 | |
| 873 | /* Initialize with DH parameters if supplied */ |
| 874 | |
| 875 | if (!init_dh(*ctxp, dhparam, host)) return DEFER; |
| 876 | |
| 877 | /* Set up certificate and key (and perhaps OCSP info) */ |
| 878 | |
| 879 | rc = tls_expand_session_files(*ctxp, cbinfo); |
| 880 | if (rc != OK) return rc; |
| 881 | |
| 882 | /* If we need to handle SNI, do so */ |
| 883 | #ifdef EXIM_HAVE_OPENSSL_TLSEXT |
| 884 | if (host == NULL) |
| 885 | { |
| 886 | #ifdef EXPERIMENTAL_OCSP |
| 887 | /* We check ocsp_file, not ocsp_response, because we care about if |
| 888 | the option exists, not what the current expansion might be, as SNI might |
| 889 | change the certificate and OCSP file in use between now and the time the |
| 890 | callback is invoked. */ |
| 891 | if (cbinfo->ocsp_file) |
| 892 | { |
| 893 | SSL_CTX_set_tlsext_status_cb(server_ctx, tls_stapling_cb); |
| 894 | SSL_CTX_set_tlsext_status_arg(server_ctx, cbinfo); |
| 895 | } |
| 896 | #endif |
| 897 | /* We always do this, so that $tls_sni is available even if not used in |
| 898 | tls_certificate */ |
| 899 | SSL_CTX_set_tlsext_servername_callback(*ctxp, tls_servername_cb); |
| 900 | SSL_CTX_set_tlsext_servername_arg(*ctxp, cbinfo); |
| 901 | } |
| 902 | #endif |
| 903 | |
| 904 | /* Set up the RSA callback */ |
| 905 | |
| 906 | SSL_CTX_set_tmp_rsa_callback(*ctxp, rsa_callback); |
| 907 | |
| 908 | /* Finally, set the timeout, and we are done */ |
| 909 | |
| 910 | SSL_CTX_set_timeout(*ctxp, ssl_session_timeout); |
| 911 | DEBUG(D_tls) debug_printf("Initialized TLS\n"); |
| 912 | |
| 913 | *cbp = cbinfo; |
| 914 | |
| 915 | return OK; |
| 916 | } |
| 917 | |
| 918 | |
| 919 | |
| 920 | |
| 921 | /************************************************* |
| 922 | * Get name of cipher in use * |
| 923 | *************************************************/ |
| 924 | |
| 925 | /* |
| 926 | Argument: pointer to an SSL structure for the connection |
| 927 | buffer to use for answer |
| 928 | size of buffer |
| 929 | pointer to number of bits for cipher |
| 930 | Returns: nothing |
| 931 | */ |
| 932 | |
| 933 | static void |
| 934 | construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits) |
| 935 | { |
| 936 | /* With OpenSSL 1.0.0a, this needs to be const but the documentation doesn't |
| 937 | yet reflect that. It should be a safe change anyway, even 0.9.8 versions have |
| 938 | the accessor functions use const in the prototype. */ |
| 939 | const SSL_CIPHER *c; |
| 940 | uschar *ver; |
| 941 | |
| 942 | switch (ssl->session->ssl_version) |
| 943 | { |
| 944 | case SSL2_VERSION: |
| 945 | ver = US"SSLv2"; |
| 946 | break; |
| 947 | |
| 948 | case SSL3_VERSION: |
| 949 | ver = US"SSLv3"; |
| 950 | break; |
| 951 | |
| 952 | case TLS1_VERSION: |
| 953 | ver = US"TLSv1"; |
| 954 | break; |
| 955 | |
| 956 | #ifdef TLS1_1_VERSION |
| 957 | case TLS1_1_VERSION: |
| 958 | ver = US"TLSv1.1"; |
| 959 | break; |
| 960 | #endif |
| 961 | |
| 962 | #ifdef TLS1_2_VERSION |
| 963 | case TLS1_2_VERSION: |
| 964 | ver = US"TLSv1.2"; |
| 965 | break; |
| 966 | #endif |
| 967 | |
| 968 | default: |
| 969 | ver = US"UNKNOWN"; |
| 970 | } |
| 971 | |
| 972 | c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl); |
| 973 | SSL_CIPHER_get_bits(c, bits); |
| 974 | |
| 975 | string_format(cipherbuf, bsize, "%s:%s:%u", ver, |
| 976 | SSL_CIPHER_get_name(c), *bits); |
| 977 | |
| 978 | DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf); |
| 979 | } |
| 980 | |
| 981 | |
| 982 | |
| 983 | |
| 984 | |
| 985 | /************************************************* |
| 986 | * Set up for verifying certificates * |
| 987 | *************************************************/ |
| 988 | |
| 989 | /* Called by both client and server startup |
| 990 | |
| 991 | Arguments: |
| 992 | sctx SSL_CTX* to initialise |
| 993 | certs certs file or NULL |
| 994 | crl CRL file or NULL |
| 995 | host NULL in a server; the remote host in a client |
| 996 | optional TRUE if called from a server for a host in tls_try_verify_hosts; |
| 997 | otherwise passed as FALSE |
| 998 | client TRUE if called for client startup, FALSE for server startup |
| 999 | |
| 1000 | Returns: OK/DEFER/FAIL |
| 1001 | */ |
| 1002 | |
| 1003 | static int |
| 1004 | setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, BOOL client) |
| 1005 | { |
| 1006 | uschar *expcerts, *expcrl; |
| 1007 | |
| 1008 | if (!expand_check(certs, US"tls_verify_certificates", &expcerts)) |
| 1009 | return DEFER; |
| 1010 | |
| 1011 | if (expcerts != NULL && *expcerts != '\0') |
| 1012 | { |
| 1013 | struct stat statbuf; |
| 1014 | if (!SSL_CTX_set_default_verify_paths(sctx)) |
| 1015 | return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL); |
| 1016 | |
| 1017 | if (Ustat(expcerts, &statbuf) < 0) |
| 1018 | { |
| 1019 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 1020 | "failed to stat %s for certificates", expcerts); |
| 1021 | return DEFER; |
| 1022 | } |
| 1023 | else |
| 1024 | { |
| 1025 | uschar *file, *dir; |
| 1026 | if ((statbuf.st_mode & S_IFMT) == S_IFDIR) |
| 1027 | { file = NULL; dir = expcerts; } |
| 1028 | else |
| 1029 | { file = expcerts; dir = NULL; } |
| 1030 | |
| 1031 | /* If a certificate file is empty, the next function fails with an |
| 1032 | unhelpful error message. If we skip it, we get the correct behaviour (no |
| 1033 | certificates are recognized, but the error message is still misleading (it |
| 1034 | says no certificate was supplied.) But this is better. */ |
| 1035 | |
| 1036 | if ((file == NULL || statbuf.st_size > 0) && |
| 1037 | !SSL_CTX_load_verify_locations(sctx, CS file, CS dir)) |
| 1038 | return tls_error(US"SSL_CTX_load_verify_locations", host, NULL); |
| 1039 | |
| 1040 | if (file != NULL) |
| 1041 | { |
| 1042 | SSL_CTX_set_client_CA_list(sctx, SSL_load_client_CA_file(CS file)); |
| 1043 | } |
| 1044 | } |
| 1045 | |
| 1046 | /* Handle a certificate revocation list. */ |
| 1047 | |
| 1048 | #if OPENSSL_VERSION_NUMBER > 0x00907000L |
| 1049 | |
| 1050 | /* This bit of code is now the version supplied by Lars Mainka. (I have |
| 1051 | * merely reformatted it into the Exim code style.) |
| 1052 | |
| 1053 | * "From here I changed the code to add support for multiple crl's |
| 1054 | * in pem format in one file or to support hashed directory entries in |
| 1055 | * pem format instead of a file. This method now uses the library function |
| 1056 | * X509_STORE_load_locations to add the CRL location to the SSL context. |
| 1057 | * OpenSSL will then handle the verify against CA certs and CRLs by |
| 1058 | * itself in the verify callback." */ |
| 1059 | |
| 1060 | if (!expand_check(crl, US"tls_crl", &expcrl)) return DEFER; |
| 1061 | if (expcrl != NULL && *expcrl != 0) |
| 1062 | { |
| 1063 | struct stat statbufcrl; |
| 1064 | if (Ustat(expcrl, &statbufcrl) < 0) |
| 1065 | { |
| 1066 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 1067 | "failed to stat %s for certificates revocation lists", expcrl); |
| 1068 | return DEFER; |
| 1069 | } |
| 1070 | else |
| 1071 | { |
| 1072 | /* is it a file or directory? */ |
| 1073 | uschar *file, *dir; |
| 1074 | X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx); |
| 1075 | if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR) |
| 1076 | { |
| 1077 | file = NULL; |
| 1078 | dir = expcrl; |
| 1079 | DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir); |
| 1080 | } |
| 1081 | else |
| 1082 | { |
| 1083 | file = expcrl; |
| 1084 | dir = NULL; |
| 1085 | DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file); |
| 1086 | } |
| 1087 | if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0) |
| 1088 | return tls_error(US"X509_STORE_load_locations", host, NULL); |
| 1089 | |
| 1090 | /* setting the flags to check against the complete crl chain */ |
| 1091 | |
| 1092 | X509_STORE_set_flags(cvstore, |
| 1093 | X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL); |
| 1094 | } |
| 1095 | } |
| 1096 | |
| 1097 | #endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */ |
| 1098 | |
| 1099 | /* If verification is optional, don't fail if no certificate */ |
| 1100 | |
| 1101 | SSL_CTX_set_verify(sctx, |
| 1102 | SSL_VERIFY_PEER | (optional? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT), |
| 1103 | client ? verify_callback_client : verify_callback_server); |
| 1104 | } |
| 1105 | |
| 1106 | return OK; |
| 1107 | } |
| 1108 | |
| 1109 | |
| 1110 | |
| 1111 | /************************************************* |
| 1112 | * Start a TLS session in a server * |
| 1113 | *************************************************/ |
| 1114 | |
| 1115 | /* This is called when Exim is running as a server, after having received |
| 1116 | the STARTTLS command. It must respond to that command, and then negotiate |
| 1117 | a TLS session. |
| 1118 | |
| 1119 | Arguments: |
| 1120 | require_ciphers allowed ciphers |
| 1121 | |
| 1122 | Returns: OK on success |
| 1123 | DEFER for errors before the start of the negotiation |
| 1124 | FAIL for errors during the negotation; the server can't |
| 1125 | continue running. |
| 1126 | */ |
| 1127 | |
| 1128 | int |
| 1129 | tls_server_start(const uschar *require_ciphers) |
| 1130 | { |
| 1131 | int rc; |
| 1132 | uschar *expciphers; |
| 1133 | tls_ext_ctx_cb *cbinfo; |
| 1134 | static uschar cipherbuf[256]; |
| 1135 | |
| 1136 | /* Check for previous activation */ |
| 1137 | |
| 1138 | if (tls_in.active >= 0) |
| 1139 | { |
| 1140 | tls_error(US"STARTTLS received after TLS started", NULL, US""); |
| 1141 | smtp_printf("554 Already in TLS\r\n"); |
| 1142 | return FAIL; |
| 1143 | } |
| 1144 | |
| 1145 | /* Initialize the SSL library. If it fails, it will already have logged |
| 1146 | the error. */ |
| 1147 | |
| 1148 | rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey, |
| 1149 | #ifdef EXPERIMENTAL_OCSP |
| 1150 | tls_ocsp_file, |
| 1151 | #endif |
| 1152 | NULL, &server_static_cbinfo); |
| 1153 | if (rc != OK) return rc; |
| 1154 | cbinfo = server_static_cbinfo; |
| 1155 | |
| 1156 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) |
| 1157 | return FAIL; |
| 1158 | |
| 1159 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they |
| 1160 | were historically separated by underscores. So that I can use either form in my |
| 1161 | tests, and also for general convenience, we turn underscores into hyphens here. |
| 1162 | */ |
| 1163 | |
| 1164 | if (expciphers != NULL) |
| 1165 | { |
| 1166 | uschar *s = expciphers; |
| 1167 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } |
| 1168 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); |
| 1169 | if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers)) |
| 1170 | return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL); |
| 1171 | cbinfo->server_cipher_list = expciphers; |
| 1172 | } |
| 1173 | |
| 1174 | /* If this is a host for which certificate verification is mandatory or |
| 1175 | optional, set up appropriately. */ |
| 1176 | |
| 1177 | tls_in.certificate_verified = FALSE; |
| 1178 | server_verify_callback_called = FALSE; |
| 1179 | |
| 1180 | if (verify_check_host(&tls_verify_hosts) == OK) |
| 1181 | { |
| 1182 | rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, FALSE, FALSE); |
| 1183 | if (rc != OK) return rc; |
| 1184 | server_verify_optional = FALSE; |
| 1185 | } |
| 1186 | else if (verify_check_host(&tls_try_verify_hosts) == OK) |
| 1187 | { |
| 1188 | rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, TRUE, FALSE); |
| 1189 | if (rc != OK) return rc; |
| 1190 | server_verify_optional = TRUE; |
| 1191 | } |
| 1192 | |
| 1193 | /* Prepare for new connection */ |
| 1194 | |
| 1195 | if ((server_ssl = SSL_new(server_ctx)) == NULL) return tls_error(US"SSL_new", NULL, NULL); |
| 1196 | |
| 1197 | /* Warning: we used to SSL_clear(ssl) here, it was removed. |
| 1198 | * |
| 1199 | * With the SSL_clear(), we get strange interoperability bugs with |
| 1200 | * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in |
| 1201 | * OpenSSL itself, as a clear should not lead to inability to follow protocols. |
| 1202 | * |
| 1203 | * The SSL_clear() call is to let an existing SSL* be reused, typically after |
| 1204 | * session shutdown. In this case, we have a brand new object and there's no |
| 1205 | * obvious reason to immediately clear it. I'm guessing that this was |
| 1206 | * originally added because of incomplete initialisation which the clear fixed, |
| 1207 | * in some historic release. |
| 1208 | */ |
| 1209 | |
| 1210 | /* Set context and tell client to go ahead, except in the case of TLS startup |
| 1211 | on connection, where outputting anything now upsets the clients and tends to |
| 1212 | make them disconnect. We need to have an explicit fflush() here, to force out |
| 1213 | the response. Other smtp_printf() calls do not need it, because in non-TLS |
| 1214 | mode, the fflush() happens when smtp_getc() is called. */ |
| 1215 | |
| 1216 | SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx)); |
| 1217 | if (!tls_in.on_connect) |
| 1218 | { |
| 1219 | smtp_printf("220 TLS go ahead\r\n"); |
| 1220 | fflush(smtp_out); |
| 1221 | } |
| 1222 | |
| 1223 | /* Now negotiate the TLS session. We put our own timer on it, since it seems |
| 1224 | that the OpenSSL library doesn't. */ |
| 1225 | |
| 1226 | SSL_set_wfd(server_ssl, fileno(smtp_out)); |
| 1227 | SSL_set_rfd(server_ssl, fileno(smtp_in)); |
| 1228 | SSL_set_accept_state(server_ssl); |
| 1229 | |
| 1230 | DEBUG(D_tls) debug_printf("Calling SSL_accept\n"); |
| 1231 | |
| 1232 | sigalrm_seen = FALSE; |
| 1233 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 1234 | rc = SSL_accept(server_ssl); |
| 1235 | alarm(0); |
| 1236 | |
| 1237 | if (rc <= 0) |
| 1238 | { |
| 1239 | tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL); |
| 1240 | if (ERR_get_error() == 0) |
| 1241 | log_write(0, LOG_MAIN, |
| 1242 | "TLS client disconnected cleanly (rejected our certificate?)"); |
| 1243 | return FAIL; |
| 1244 | } |
| 1245 | |
| 1246 | DEBUG(D_tls) debug_printf("SSL_accept was successful\n"); |
| 1247 | |
| 1248 | /* TLS has been set up. Adjust the input functions to read via TLS, |
| 1249 | and initialize things. */ |
| 1250 | |
| 1251 | construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits); |
| 1252 | tls_in.cipher = cipherbuf; |
| 1253 | |
| 1254 | DEBUG(D_tls) |
| 1255 | { |
| 1256 | uschar buf[2048]; |
| 1257 | if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL) |
| 1258 | debug_printf("Shared ciphers: %s\n", buf); |
| 1259 | } |
| 1260 | |
| 1261 | |
| 1262 | /* Only used by the server-side tls (tls_in), including tls_getc. |
| 1263 | Client-side (tls_out) reads (seem to?) go via |
| 1264 | smtp_read_response()/ip_recv(). |
| 1265 | Hence no need to duplicate for _in and _out. |
| 1266 | */ |
| 1267 | ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); |
| 1268 | ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; |
| 1269 | ssl_xfer_eof = ssl_xfer_error = 0; |
| 1270 | |
| 1271 | receive_getc = tls_getc; |
| 1272 | receive_ungetc = tls_ungetc; |
| 1273 | receive_feof = tls_feof; |
| 1274 | receive_ferror = tls_ferror; |
| 1275 | receive_smtp_buffered = tls_smtp_buffered; |
| 1276 | |
| 1277 | tls_in.active = fileno(smtp_out); |
| 1278 | return OK; |
| 1279 | } |
| 1280 | |
| 1281 | |
| 1282 | |
| 1283 | |
| 1284 | |
| 1285 | /************************************************* |
| 1286 | * Start a TLS session in a client * |
| 1287 | *************************************************/ |
| 1288 | |
| 1289 | /* Called from the smtp transport after STARTTLS has been accepted. |
| 1290 | |
| 1291 | Argument: |
| 1292 | fd the fd of the connection |
| 1293 | host connected host (for messages) |
| 1294 | addr the first address |
| 1295 | dhparam DH parameter file |
| 1296 | certificate certificate file |
| 1297 | privatekey private key file |
| 1298 | sni TLS SNI to send to remote host |
| 1299 | verify_certs file for certificate verify |
| 1300 | crl file containing CRL |
| 1301 | require_ciphers list of allowed ciphers |
| 1302 | dh_min_bits minimum number of bits acceptable in server's DH prime |
| 1303 | (unused in OpenSSL) |
| 1304 | timeout startup timeout |
| 1305 | |
| 1306 | Returns: OK on success |
| 1307 | FAIL otherwise - note that tls_error() will not give DEFER |
| 1308 | because this is not a server |
| 1309 | */ |
| 1310 | |
| 1311 | int |
| 1312 | tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam, |
| 1313 | uschar *certificate, uschar *privatekey, uschar *sni, |
| 1314 | uschar *verify_certs, uschar *crl, |
| 1315 | uschar *require_ciphers, int dh_min_bits ARG_UNUSED, int timeout) |
| 1316 | { |
| 1317 | static uschar txt[256]; |
| 1318 | uschar *expciphers; |
| 1319 | X509* server_cert; |
| 1320 | int rc; |
| 1321 | static uschar cipherbuf[256]; |
| 1322 | |
| 1323 | rc = tls_init(&client_ctx, host, dhparam, certificate, privatekey, |
| 1324 | #ifdef EXPERIMENTAL_OCSP |
| 1325 | NULL, |
| 1326 | #endif |
| 1327 | addr, &client_static_cbinfo); |
| 1328 | if (rc != OK) return rc; |
| 1329 | |
| 1330 | tls_out.certificate_verified = FALSE; |
| 1331 | client_verify_callback_called = FALSE; |
| 1332 | |
| 1333 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers)) |
| 1334 | return FAIL; |
| 1335 | |
| 1336 | /* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they |
| 1337 | are separated by underscores. So that I can use either form in my tests, and |
| 1338 | also for general convenience, we turn underscores into hyphens here. */ |
| 1339 | |
| 1340 | if (expciphers != NULL) |
| 1341 | { |
| 1342 | uschar *s = expciphers; |
| 1343 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } |
| 1344 | DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); |
| 1345 | if (!SSL_CTX_set_cipher_list(client_ctx, CS expciphers)) |
| 1346 | return tls_error(US"SSL_CTX_set_cipher_list", host, NULL); |
| 1347 | } |
| 1348 | |
| 1349 | rc = setup_certs(client_ctx, verify_certs, crl, host, FALSE, TRUE); |
| 1350 | if (rc != OK) return rc; |
| 1351 | |
| 1352 | if ((client_ssl = SSL_new(client_ctx)) == NULL) return tls_error(US"SSL_new", host, NULL); |
| 1353 | SSL_set_session_id_context(client_ssl, sid_ctx, Ustrlen(sid_ctx)); |
| 1354 | SSL_set_fd(client_ssl, fd); |
| 1355 | SSL_set_connect_state(client_ssl); |
| 1356 | |
| 1357 | if (sni) |
| 1358 | { |
| 1359 | if (!expand_check(sni, US"tls_sni", &tls_out.sni)) |
| 1360 | return FAIL; |
| 1361 | if (tls_out.sni == NULL) |
| 1362 | { |
| 1363 | DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n"); |
| 1364 | } |
| 1365 | else if (!Ustrlen(tls_out.sni)) |
| 1366 | tls_out.sni = NULL; |
| 1367 | else |
| 1368 | { |
| 1369 | #ifdef EXIM_HAVE_OPENSSL_TLSEXT |
| 1370 | DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_out.sni); |
| 1371 | SSL_set_tlsext_host_name(client_ssl, tls_out.sni); |
| 1372 | #else |
| 1373 | DEBUG(D_tls) |
| 1374 | debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n", |
| 1375 | tls_out.sni); |
| 1376 | #endif |
| 1377 | } |
| 1378 | } |
| 1379 | |
| 1380 | /* There doesn't seem to be a built-in timeout on connection. */ |
| 1381 | |
| 1382 | DEBUG(D_tls) debug_printf("Calling SSL_connect\n"); |
| 1383 | sigalrm_seen = FALSE; |
| 1384 | alarm(timeout); |
| 1385 | rc = SSL_connect(client_ssl); |
| 1386 | alarm(0); |
| 1387 | |
| 1388 | if (rc <= 0) |
| 1389 | return tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL); |
| 1390 | |
| 1391 | DEBUG(D_tls) debug_printf("SSL_connect succeeded\n"); |
| 1392 | |
| 1393 | /* Beware anonymous ciphers which lead to server_cert being NULL */ |
| 1394 | server_cert = SSL_get_peer_certificate (client_ssl); |
| 1395 | if (server_cert) |
| 1396 | { |
| 1397 | tls_out.peerdn = US X509_NAME_oneline(X509_get_subject_name(server_cert), |
| 1398 | CS txt, sizeof(txt)); |
| 1399 | tls_out.peerdn = txt; |
| 1400 | } |
| 1401 | else |
| 1402 | tls_out.peerdn = NULL; |
| 1403 | |
| 1404 | construct_cipher_name(client_ssl, cipherbuf, sizeof(cipherbuf), &tls_out.bits); |
| 1405 | tls_out.cipher = cipherbuf; |
| 1406 | |
| 1407 | tls_out.active = fd; |
| 1408 | return OK; |
| 1409 | } |
| 1410 | |
| 1411 | |
| 1412 | |
| 1413 | |
| 1414 | |
| 1415 | /************************************************* |
| 1416 | * TLS version of getc * |
| 1417 | *************************************************/ |
| 1418 | |
| 1419 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, |
| 1420 | it refills the buffer via the SSL reading function. |
| 1421 | |
| 1422 | Arguments: none |
| 1423 | Returns: the next character or EOF |
| 1424 | |
| 1425 | Only used by the server-side TLS. |
| 1426 | */ |
| 1427 | |
| 1428 | int |
| 1429 | tls_getc(void) |
| 1430 | { |
| 1431 | if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) |
| 1432 | { |
| 1433 | int error; |
| 1434 | int inbytes; |
| 1435 | |
| 1436 | DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl, |
| 1437 | ssl_xfer_buffer, ssl_xfer_buffer_size); |
| 1438 | |
| 1439 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 1440 | inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, ssl_xfer_buffer_size); |
| 1441 | error = SSL_get_error(server_ssl, inbytes); |
| 1442 | alarm(0); |
| 1443 | |
| 1444 | /* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been |
| 1445 | closed down, not that the socket itself has been closed down. Revert to |
| 1446 | non-SSL handling. */ |
| 1447 | |
| 1448 | if (error == SSL_ERROR_ZERO_RETURN) |
| 1449 | { |
| 1450 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); |
| 1451 | |
| 1452 | receive_getc = smtp_getc; |
| 1453 | receive_ungetc = smtp_ungetc; |
| 1454 | receive_feof = smtp_feof; |
| 1455 | receive_ferror = smtp_ferror; |
| 1456 | receive_smtp_buffered = smtp_buffered; |
| 1457 | |
| 1458 | SSL_free(server_ssl); |
| 1459 | server_ssl = NULL; |
| 1460 | tls_in.active = -1; |
| 1461 | tls_in.bits = 0; |
| 1462 | tls_in.cipher = NULL; |
| 1463 | tls_in.peerdn = NULL; |
| 1464 | tls_in.sni = NULL; |
| 1465 | |
| 1466 | return smtp_getc(); |
| 1467 | } |
| 1468 | |
| 1469 | /* Handle genuine errors */ |
| 1470 | |
| 1471 | else if (error == SSL_ERROR_SSL) |
| 1472 | { |
| 1473 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 1474 | log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring); |
| 1475 | ssl_xfer_error = 1; |
| 1476 | return EOF; |
| 1477 | } |
| 1478 | |
| 1479 | else if (error != SSL_ERROR_NONE) |
| 1480 | { |
| 1481 | DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); |
| 1482 | ssl_xfer_error = 1; |
| 1483 | return EOF; |
| 1484 | } |
| 1485 | |
| 1486 | #ifndef DISABLE_DKIM |
| 1487 | dkim_exim_verify_feed(ssl_xfer_buffer, inbytes); |
| 1488 | #endif |
| 1489 | ssl_xfer_buffer_hwm = inbytes; |
| 1490 | ssl_xfer_buffer_lwm = 0; |
| 1491 | } |
| 1492 | |
| 1493 | /* Something in the buffer; return next uschar */ |
| 1494 | |
| 1495 | return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; |
| 1496 | } |
| 1497 | |
| 1498 | |
| 1499 | |
| 1500 | /************************************************* |
| 1501 | * Read bytes from TLS channel * |
| 1502 | *************************************************/ |
| 1503 | |
| 1504 | /* |
| 1505 | Arguments: |
| 1506 | buff buffer of data |
| 1507 | len size of buffer |
| 1508 | |
| 1509 | Returns: the number of bytes read |
| 1510 | -1 after a failed read |
| 1511 | |
| 1512 | Only used by the client-side TLS. |
| 1513 | */ |
| 1514 | |
| 1515 | int |
| 1516 | tls_read(BOOL is_server, uschar *buff, size_t len) |
| 1517 | { |
| 1518 | SSL *ssl = is_server ? server_ssl : client_ssl; |
| 1519 | int inbytes; |
| 1520 | int error; |
| 1521 | |
| 1522 | DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl, |
| 1523 | buff, (unsigned int)len); |
| 1524 | |
| 1525 | inbytes = SSL_read(ssl, CS buff, len); |
| 1526 | error = SSL_get_error(ssl, inbytes); |
| 1527 | |
| 1528 | if (error == SSL_ERROR_ZERO_RETURN) |
| 1529 | { |
| 1530 | DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); |
| 1531 | return -1; |
| 1532 | } |
| 1533 | else if (error != SSL_ERROR_NONE) |
| 1534 | { |
| 1535 | return -1; |
| 1536 | } |
| 1537 | |
| 1538 | return inbytes; |
| 1539 | } |
| 1540 | |
| 1541 | |
| 1542 | |
| 1543 | |
| 1544 | |
| 1545 | /************************************************* |
| 1546 | * Write bytes down TLS channel * |
| 1547 | *************************************************/ |
| 1548 | |
| 1549 | /* |
| 1550 | Arguments: |
| 1551 | is_server channel specifier |
| 1552 | buff buffer of data |
| 1553 | len number of bytes |
| 1554 | |
| 1555 | Returns: the number of bytes after a successful write, |
| 1556 | -1 after a failed write |
| 1557 | |
| 1558 | Used by both server-side and client-side TLS. |
| 1559 | */ |
| 1560 | |
| 1561 | int |
| 1562 | tls_write(BOOL is_server, const uschar *buff, size_t len) |
| 1563 | { |
| 1564 | int outbytes; |
| 1565 | int error; |
| 1566 | int left = len; |
| 1567 | SSL *ssl = is_server ? server_ssl : client_ssl; |
| 1568 | |
| 1569 | DEBUG(D_tls) debug_printf("tls_do_write(%p, %d)\n", buff, left); |
| 1570 | while (left > 0) |
| 1571 | { |
| 1572 | DEBUG(D_tls) debug_printf("SSL_write(SSL, %p, %d)\n", buff, left); |
| 1573 | outbytes = SSL_write(ssl, CS buff, left); |
| 1574 | error = SSL_get_error(ssl, outbytes); |
| 1575 | DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error); |
| 1576 | switch (error) |
| 1577 | { |
| 1578 | case SSL_ERROR_SSL: |
| 1579 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 1580 | log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring); |
| 1581 | return -1; |
| 1582 | |
| 1583 | case SSL_ERROR_NONE: |
| 1584 | left -= outbytes; |
| 1585 | buff += outbytes; |
| 1586 | break; |
| 1587 | |
| 1588 | case SSL_ERROR_ZERO_RETURN: |
| 1589 | log_write(0, LOG_MAIN, "SSL channel closed on write"); |
| 1590 | return -1; |
| 1591 | |
| 1592 | case SSL_ERROR_SYSCALL: |
| 1593 | log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s", |
| 1594 | sender_fullhost ? sender_fullhost : US"<unknown>", |
| 1595 | strerror(errno)); |
| 1596 | |
| 1597 | default: |
| 1598 | log_write(0, LOG_MAIN, "SSL_write error %d", error); |
| 1599 | return -1; |
| 1600 | } |
| 1601 | } |
| 1602 | return len; |
| 1603 | } |
| 1604 | |
| 1605 | |
| 1606 | |
| 1607 | /************************************************* |
| 1608 | * Close down a TLS session * |
| 1609 | *************************************************/ |
| 1610 | |
| 1611 | /* This is also called from within a delivery subprocess forked from the |
| 1612 | daemon, to shut down the TLS library, without actually doing a shutdown (which |
| 1613 | would tamper with the SSL session in the parent process). |
| 1614 | |
| 1615 | Arguments: TRUE if SSL_shutdown is to be called |
| 1616 | Returns: nothing |
| 1617 | |
| 1618 | Used by both server-side and client-side TLS. |
| 1619 | */ |
| 1620 | |
| 1621 | void |
| 1622 | tls_close(BOOL is_server, BOOL shutdown) |
| 1623 | { |
| 1624 | SSL **sslp = is_server ? &server_ssl : &client_ssl; |
| 1625 | int *fdp = is_server ? &tls_in.active : &tls_out.active; |
| 1626 | |
| 1627 | if (*fdp < 0) return; /* TLS was not active */ |
| 1628 | |
| 1629 | if (shutdown) |
| 1630 | { |
| 1631 | DEBUG(D_tls) debug_printf("tls_close(): shutting down SSL\n"); |
| 1632 | SSL_shutdown(*sslp); |
| 1633 | } |
| 1634 | |
| 1635 | SSL_free(*sslp); |
| 1636 | *sslp = NULL; |
| 1637 | |
| 1638 | *fdp = -1; |
| 1639 | } |
| 1640 | |
| 1641 | |
| 1642 | |
| 1643 | |
| 1644 | /************************************************* |
| 1645 | * Let tls_require_ciphers be checked at startup * |
| 1646 | *************************************************/ |
| 1647 | |
| 1648 | /* The tls_require_ciphers option, if set, must be something which the |
| 1649 | library can parse. |
| 1650 | |
| 1651 | Returns: NULL on success, or error message |
| 1652 | */ |
| 1653 | |
| 1654 | uschar * |
| 1655 | tls_validate_require_cipher(void) |
| 1656 | { |
| 1657 | SSL_CTX *ctx; |
| 1658 | uschar *s, *expciphers, *err; |
| 1659 | |
| 1660 | /* this duplicates from tls_init(), we need a better "init just global |
| 1661 | state, for no specific purpose" singleton function of our own */ |
| 1662 | |
| 1663 | SSL_load_error_strings(); |
| 1664 | OpenSSL_add_ssl_algorithms(); |
| 1665 | #if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256) |
| 1666 | /* SHA256 is becoming ever more popular. This makes sure it gets added to the |
| 1667 | list of available digests. */ |
| 1668 | EVP_add_digest(EVP_sha256()); |
| 1669 | #endif |
| 1670 | |
| 1671 | if (!(tls_require_ciphers && *tls_require_ciphers)) |
| 1672 | return NULL; |
| 1673 | |
| 1674 | if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers)) |
| 1675 | return US"failed to expand tls_require_ciphers"; |
| 1676 | |
| 1677 | if (!(expciphers && *expciphers)) |
| 1678 | return NULL; |
| 1679 | |
| 1680 | /* normalisation ripped from above */ |
| 1681 | s = expciphers; |
| 1682 | while (*s != 0) { if (*s == '_') *s = '-'; s++; } |
| 1683 | |
| 1684 | err = NULL; |
| 1685 | |
| 1686 | ctx = SSL_CTX_new(SSLv23_server_method()); |
| 1687 | if (!ctx) |
| 1688 | { |
| 1689 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 1690 | return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring); |
| 1691 | } |
| 1692 | |
| 1693 | DEBUG(D_tls) |
| 1694 | debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers); |
| 1695 | |
| 1696 | if (!SSL_CTX_set_cipher_list(ctx, CS expciphers)) |
| 1697 | { |
| 1698 | ERR_error_string(ERR_get_error(), ssl_errstring); |
| 1699 | err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers); |
| 1700 | } |
| 1701 | |
| 1702 | SSL_CTX_free(ctx); |
| 1703 | |
| 1704 | return err; |
| 1705 | } |
| 1706 | |
| 1707 | |
| 1708 | |
| 1709 | |
| 1710 | /************************************************* |
| 1711 | * Report the library versions. * |
| 1712 | *************************************************/ |
| 1713 | |
| 1714 | /* There have historically been some issues with binary compatibility in |
| 1715 | OpenSSL libraries; if Exim (like many other applications) is built against |
| 1716 | one version of OpenSSL but the run-time linker picks up another version, |
| 1717 | it can result in serious failures, including crashing with a SIGSEGV. So |
| 1718 | report the version found by the compiler and the run-time version. |
| 1719 | |
| 1720 | Arguments: a FILE* to print the results to |
| 1721 | Returns: nothing |
| 1722 | */ |
| 1723 | |
| 1724 | void |
| 1725 | tls_version_report(FILE *f) |
| 1726 | { |
| 1727 | fprintf(f, "Library version: OpenSSL: Compile: %s\n" |
| 1728 | " Runtime: %s\n", |
| 1729 | OPENSSL_VERSION_TEXT, |
| 1730 | SSLeay_version(SSLEAY_VERSION)); |
| 1731 | } |
| 1732 | |
| 1733 | |
| 1734 | |
| 1735 | |
| 1736 | /************************************************* |
| 1737 | * Random number generation * |
| 1738 | *************************************************/ |
| 1739 | |
| 1740 | /* Pseudo-random number generation. The result is not expected to be |
| 1741 | cryptographically strong but not so weak that someone will shoot themselves |
| 1742 | in the foot using it as a nonce in input in some email header scheme or |
| 1743 | whatever weirdness they'll twist this into. The result should handle fork() |
| 1744 | and avoid repeating sequences. OpenSSL handles that for us. |
| 1745 | |
| 1746 | Arguments: |
| 1747 | max range maximum |
| 1748 | Returns a random number in range [0, max-1] |
| 1749 | */ |
| 1750 | |
| 1751 | int |
| 1752 | vaguely_random_number(int max) |
| 1753 | { |
| 1754 | unsigned int r; |
| 1755 | int i, needed_len; |
| 1756 | static pid_t pidlast = 0; |
| 1757 | pid_t pidnow; |
| 1758 | uschar *p; |
| 1759 | uschar smallbuf[sizeof(r)]; |
| 1760 | |
| 1761 | if (max <= 1) |
| 1762 | return 0; |
| 1763 | |
| 1764 | pidnow = getpid(); |
| 1765 | if (pidnow != pidlast) |
| 1766 | { |
| 1767 | /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state |
| 1768 | is unique for each thread", this doesn't apparently apply across processes, |
| 1769 | so our own warning from vaguely_random_number_fallback() applies here too. |
| 1770 | Fix per PostgreSQL. */ |
| 1771 | if (pidlast != 0) |
| 1772 | RAND_cleanup(); |
| 1773 | pidlast = pidnow; |
| 1774 | } |
| 1775 | |
| 1776 | /* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */ |
| 1777 | if (!RAND_status()) |
| 1778 | { |
| 1779 | randstuff r; |
| 1780 | gettimeofday(&r.tv, NULL); |
| 1781 | r.p = getpid(); |
| 1782 | |
| 1783 | RAND_seed((uschar *)(&r), sizeof(r)); |
| 1784 | } |
| 1785 | /* We're after pseudo-random, not random; if we still don't have enough data |
| 1786 | in the internal PRNG then our options are limited. We could sleep and hope |
| 1787 | for entropy to come along (prayer technique) but if the system is so depleted |
| 1788 | in the first place then something is likely to just keep taking it. Instead, |
| 1789 | we'll just take whatever little bit of pseudo-random we can still manage to |
| 1790 | get. */ |
| 1791 | |
| 1792 | needed_len = sizeof(r); |
| 1793 | /* Don't take 8 times more entropy than needed if int is 8 octets and we were |
| 1794 | asked for a number less than 10. */ |
| 1795 | for (r = max, i = 0; r; ++i) |
| 1796 | r >>= 1; |
| 1797 | i = (i + 7) / 8; |
| 1798 | if (i < needed_len) |
| 1799 | needed_len = i; |
| 1800 | |
| 1801 | /* We do not care if crypto-strong */ |
| 1802 | i = RAND_pseudo_bytes(smallbuf, needed_len); |
| 1803 | if (i < 0) |
| 1804 | { |
| 1805 | DEBUG(D_all) |
| 1806 | debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n"); |
| 1807 | return vaguely_random_number_fallback(max); |
| 1808 | } |
| 1809 | |
| 1810 | r = 0; |
| 1811 | for (p = smallbuf; needed_len; --needed_len, ++p) |
| 1812 | { |
| 1813 | r *= 256; |
| 1814 | r += *p; |
| 1815 | } |
| 1816 | |
| 1817 | /* We don't particularly care about weighted results; if someone wants |
| 1818 | smooth distribution and cares enough then they should submit a patch then. */ |
| 1819 | return r % max; |
| 1820 | } |
| 1821 | |
| 1822 | |
| 1823 | |
| 1824 | |
| 1825 | /************************************************* |
| 1826 | * OpenSSL option parse * |
| 1827 | *************************************************/ |
| 1828 | |
| 1829 | /* Parse one option for tls_openssl_options_parse below |
| 1830 | |
| 1831 | Arguments: |
| 1832 | name one option name |
| 1833 | value place to store a value for it |
| 1834 | Returns success or failure in parsing |
| 1835 | */ |
| 1836 | |
| 1837 | struct exim_openssl_option { |
| 1838 | uschar *name; |
| 1839 | long value; |
| 1840 | }; |
| 1841 | /* We could use a macro to expand, but we need the ifdef and not all the |
| 1842 | options document which version they were introduced in. Policylet: include |
| 1843 | all options unless explicitly for DTLS, let the administrator choose which |
| 1844 | to apply. |
| 1845 | |
| 1846 | This list is current as of: |
| 1847 | ==> 1.0.1b <== */ |
| 1848 | static struct exim_openssl_option exim_openssl_options[] = { |
| 1849 | /* KEEP SORTED ALPHABETICALLY! */ |
| 1850 | #ifdef SSL_OP_ALL |
| 1851 | { US"all", SSL_OP_ALL }, |
| 1852 | #endif |
| 1853 | #ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION |
| 1854 | { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION }, |
| 1855 | #endif |
| 1856 | #ifdef SSL_OP_CIPHER_SERVER_PREFERENCE |
| 1857 | { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE }, |
| 1858 | #endif |
| 1859 | #ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS |
| 1860 | { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS }, |
| 1861 | #endif |
| 1862 | #ifdef SSL_OP_EPHEMERAL_RSA |
| 1863 | { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA }, |
| 1864 | #endif |
| 1865 | #ifdef SSL_OP_LEGACY_SERVER_CONNECT |
| 1866 | { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT }, |
| 1867 | #endif |
| 1868 | #ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER |
| 1869 | { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER }, |
| 1870 | #endif |
| 1871 | #ifdef SSL_OP_MICROSOFT_SESS_ID_BUG |
| 1872 | { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG }, |
| 1873 | #endif |
| 1874 | #ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING |
| 1875 | { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING }, |
| 1876 | #endif |
| 1877 | #ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG |
| 1878 | { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG }, |
| 1879 | #endif |
| 1880 | #ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG |
| 1881 | { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG }, |
| 1882 | #endif |
| 1883 | #ifdef SSL_OP_NO_COMPRESSION |
| 1884 | { US"no_compression", SSL_OP_NO_COMPRESSION }, |
| 1885 | #endif |
| 1886 | #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION |
| 1887 | { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION }, |
| 1888 | #endif |
| 1889 | #ifdef SSL_OP_NO_SSLv2 |
| 1890 | { US"no_sslv2", SSL_OP_NO_SSLv2 }, |
| 1891 | #endif |
| 1892 | #ifdef SSL_OP_NO_SSLv3 |
| 1893 | { US"no_sslv3", SSL_OP_NO_SSLv3 }, |
| 1894 | #endif |
| 1895 | #ifdef SSL_OP_NO_TICKET |
| 1896 | { US"no_ticket", SSL_OP_NO_TICKET }, |
| 1897 | #endif |
| 1898 | #ifdef SSL_OP_NO_TLSv1 |
| 1899 | { US"no_tlsv1", SSL_OP_NO_TLSv1 }, |
| 1900 | #endif |
| 1901 | #ifdef SSL_OP_NO_TLSv1_1 |
| 1902 | #if SSL_OP_NO_TLSv1_1 == 0x00000400L |
| 1903 | /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */ |
| 1904 | #warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring |
| 1905 | #else |
| 1906 | { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 }, |
| 1907 | #endif |
| 1908 | #endif |
| 1909 | #ifdef SSL_OP_NO_TLSv1_2 |
| 1910 | { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 }, |
| 1911 | #endif |
| 1912 | #ifdef SSL_OP_SINGLE_DH_USE |
| 1913 | { US"single_dh_use", SSL_OP_SINGLE_DH_USE }, |
| 1914 | #endif |
| 1915 | #ifdef SSL_OP_SINGLE_ECDH_USE |
| 1916 | { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE }, |
| 1917 | #endif |
| 1918 | #ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG |
| 1919 | { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG }, |
| 1920 | #endif |
| 1921 | #ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG |
| 1922 | { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG }, |
| 1923 | #endif |
| 1924 | #ifdef SSL_OP_TLS_BLOCK_PADDING_BUG |
| 1925 | { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG }, |
| 1926 | #endif |
| 1927 | #ifdef SSL_OP_TLS_D5_BUG |
| 1928 | { US"tls_d5_bug", SSL_OP_TLS_D5_BUG }, |
| 1929 | #endif |
| 1930 | #ifdef SSL_OP_TLS_ROLLBACK_BUG |
| 1931 | { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG }, |
| 1932 | #endif |
| 1933 | }; |
| 1934 | static int exim_openssl_options_size = |
| 1935 | sizeof(exim_openssl_options)/sizeof(struct exim_openssl_option); |
| 1936 | |
| 1937 | |
| 1938 | static BOOL |
| 1939 | tls_openssl_one_option_parse(uschar *name, long *value) |
| 1940 | { |
| 1941 | int first = 0; |
| 1942 | int last = exim_openssl_options_size; |
| 1943 | while (last > first) |
| 1944 | { |
| 1945 | int middle = (first + last)/2; |
| 1946 | int c = Ustrcmp(name, exim_openssl_options[middle].name); |
| 1947 | if (c == 0) |
| 1948 | { |
| 1949 | *value = exim_openssl_options[middle].value; |
| 1950 | return TRUE; |
| 1951 | } |
| 1952 | else if (c > 0) |
| 1953 | first = middle + 1; |
| 1954 | else |
| 1955 | last = middle; |
| 1956 | } |
| 1957 | return FALSE; |
| 1958 | } |
| 1959 | |
| 1960 | |
| 1961 | |
| 1962 | |
| 1963 | /************************************************* |
| 1964 | * OpenSSL option parsing logic * |
| 1965 | *************************************************/ |
| 1966 | |
| 1967 | /* OpenSSL has a number of compatibility options which an administrator might |
| 1968 | reasonably wish to set. Interpret a list similarly to decode_bits(), so that |
| 1969 | we look like log_selector. |
| 1970 | |
| 1971 | Arguments: |
| 1972 | option_spec the administrator-supplied string of options |
| 1973 | results ptr to long storage for the options bitmap |
| 1974 | Returns success or failure |
| 1975 | */ |
| 1976 | |
| 1977 | BOOL |
| 1978 | tls_openssl_options_parse(uschar *option_spec, long *results) |
| 1979 | { |
| 1980 | long result, item; |
| 1981 | uschar *s, *end; |
| 1982 | uschar keep_c; |
| 1983 | BOOL adding, item_parsed; |
| 1984 | |
| 1985 | result = 0L; |
| 1986 | /* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed |
| 1987 | * from default because it increases BEAST susceptibility. */ |
| 1988 | #ifdef SSL_OP_NO_SSLv2 |
| 1989 | result |= SSL_OP_NO_SSLv2; |
| 1990 | #endif |
| 1991 | |
| 1992 | if (option_spec == NULL) |
| 1993 | { |
| 1994 | *results = result; |
| 1995 | return TRUE; |
| 1996 | } |
| 1997 | |
| 1998 | for (s=option_spec; *s != '\0'; /**/) |
| 1999 | { |
| 2000 | while (isspace(*s)) ++s; |
| 2001 | if (*s == '\0') |
| 2002 | break; |
| 2003 | if (*s != '+' && *s != '-') |
| 2004 | { |
| 2005 | DEBUG(D_tls) debug_printf("malformed openssl option setting: " |
| 2006 | "+ or - expected but found \"%s\"\n", s); |
| 2007 | return FALSE; |
| 2008 | } |
| 2009 | adding = *s++ == '+'; |
| 2010 | for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ; |
| 2011 | keep_c = *end; |
| 2012 | *end = '\0'; |
| 2013 | item_parsed = tls_openssl_one_option_parse(s, &item); |
| 2014 | if (!item_parsed) |
| 2015 | { |
| 2016 | DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s); |
| 2017 | return FALSE; |
| 2018 | } |
| 2019 | DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n", |
| 2020 | adding ? "adding" : "removing", result, item, s); |
| 2021 | if (adding) |
| 2022 | result |= item; |
| 2023 | else |
| 2024 | result &= ~item; |
| 2025 | *end = keep_c; |
| 2026 | s = end; |
| 2027 | } |
| 2028 | |
| 2029 | *results = result; |
| 2030 | return TRUE; |
| 2031 | } |
| 2032 | |
| 2033 | /* End of tls-openssl.c */ |