| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2014 */ |
| 6 | /* See the file NOTICE for conditions of use and distribution. */ |
| 7 | |
| 8 | /* Copyright (c) Phil Pennock 2012 */ |
| 9 | |
| 10 | /* This file provides TLS/SSL support for Exim using the GnuTLS library, |
| 11 | one of the available supported implementations. This file is #included into |
| 12 | tls.c when USE_GNUTLS has been set. |
| 13 | |
| 14 | The code herein is a revamp of GnuTLS integration using the current APIs; the |
| 15 | original tls-gnu.c was based on a patch which was contributed by Nikos |
| 16 | Mavroyanopoulos. The revamp is partially a rewrite, partially cut&paste as |
| 17 | appropriate. |
| 18 | |
| 19 | APIs current as of GnuTLS 2.12.18; note that the GnuTLS manual is for GnuTLS 3, |
| 20 | which is not widely deployed by OS vendors. Will note issues below, which may |
| 21 | assist in updating the code in the future. Another sources of hints is |
| 22 | mod_gnutls for Apache (SNI callback registration and handling). |
| 23 | |
| 24 | Keeping client and server variables more split than before and is currently |
| 25 | the norm, in anticipation of TLS in ACL callouts. |
| 26 | |
| 27 | I wanted to switch to gnutls_certificate_set_verify_function() so that |
| 28 | certificate rejection could happen during handshake where it belongs, rather |
| 29 | than being dropped afterwards, but that was introduced in 2.10.0 and Debian |
| 30 | (6.0.5) is still on 2.8.6. So for now we have to stick with sub-par behaviour. |
| 31 | |
| 32 | (I wasn't looking for libraries quite that old, when updating to get rid of |
| 33 | compiler warnings of deprecated APIs. If it turns out that a lot of the rest |
| 34 | require current GnuTLS, then we'll drop support for the ancient libraries). |
| 35 | */ |
| 36 | |
| 37 | #include <gnutls/gnutls.h> |
| 38 | /* needed for cert checks in verification and DN extraction: */ |
| 39 | #include <gnutls/x509.h> |
| 40 | /* man-page is incorrect, gnutls_rnd() is not in gnutls.h: */ |
| 41 | #include <gnutls/crypto.h> |
| 42 | /* needed to disable PKCS11 autoload unless requested */ |
| 43 | #if GNUTLS_VERSION_NUMBER >= 0x020c00 |
| 44 | # include <gnutls/pkcs11.h> |
| 45 | #endif |
| 46 | |
| 47 | /* GnuTLS 2 vs 3 |
| 48 | |
| 49 | GnuTLS 3 only: |
| 50 | gnutls_global_set_audit_log_function() |
| 51 | |
| 52 | Changes: |
| 53 | gnutls_certificate_verify_peers2(): is new, drop the 2 for old version |
| 54 | */ |
| 55 | |
| 56 | /* Local static variables for GnuTLS */ |
| 57 | |
| 58 | /* Values for verify_requirement */ |
| 59 | |
| 60 | enum peer_verify_requirement { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED }; |
| 61 | |
| 62 | /* This holds most state for server or client; with this, we can set up an |
| 63 | outbound TLS-enabled connection in an ACL callout, while not stomping all |
| 64 | over the TLS variables available for expansion. |
| 65 | |
| 66 | Some of these correspond to variables in globals.c; those variables will |
| 67 | be set to point to content in one of these instances, as appropriate for |
| 68 | the stage of the process lifetime. |
| 69 | |
| 70 | Not handled here: global tls_channelbinding_b64. |
| 71 | */ |
| 72 | |
| 73 | typedef struct exim_gnutls_state { |
| 74 | gnutls_session_t session; |
| 75 | gnutls_certificate_credentials_t x509_cred; |
| 76 | gnutls_priority_t priority_cache; |
| 77 | enum peer_verify_requirement verify_requirement; |
| 78 | int fd_in; |
| 79 | int fd_out; |
| 80 | BOOL peer_cert_verified; |
| 81 | BOOL trigger_sni_changes; |
| 82 | BOOL have_set_peerdn; |
| 83 | const struct host_item *host; |
| 84 | uschar *peerdn; |
| 85 | uschar *ciphersuite; |
| 86 | uschar *received_sni; |
| 87 | |
| 88 | const uschar *tls_certificate; |
| 89 | const uschar *tls_privatekey; |
| 90 | const uschar *tls_sni; /* client send only, not received */ |
| 91 | const uschar *tls_verify_certificates; |
| 92 | const uschar *tls_crl; |
| 93 | const uschar *tls_require_ciphers; |
| 94 | uschar *exp_tls_certificate; |
| 95 | uschar *exp_tls_privatekey; |
| 96 | uschar *exp_tls_sni; |
| 97 | uschar *exp_tls_verify_certificates; |
| 98 | uschar *exp_tls_crl; |
| 99 | uschar *exp_tls_require_ciphers; |
| 100 | |
| 101 | tls_support *tlsp; /* set in tls_init() */ |
| 102 | |
| 103 | uschar *xfer_buffer; |
| 104 | int xfer_buffer_lwm; |
| 105 | int xfer_buffer_hwm; |
| 106 | int xfer_eof; |
| 107 | int xfer_error; |
| 108 | } exim_gnutls_state_st; |
| 109 | |
| 110 | static const exim_gnutls_state_st exim_gnutls_state_init = { |
| 111 | NULL, NULL, NULL, VERIFY_NONE, -1, -1, FALSE, FALSE, FALSE, |
| 112 | NULL, NULL, NULL, NULL, |
| 113 | NULL, NULL, NULL, NULL, NULL, NULL, |
| 114 | NULL, NULL, NULL, NULL, NULL, NULL, |
| 115 | NULL, |
| 116 | NULL, 0, 0, 0, 0, |
| 117 | }; |
| 118 | |
| 119 | /* Not only do we have our own APIs which don't pass around state, assuming |
| 120 | it's held in globals, GnuTLS doesn't appear to let us register callback data |
| 121 | for callbacks, or as part of the session, so we have to keep a "this is the |
| 122 | context we're currently dealing with" pointer and rely upon being |
| 123 | single-threaded to keep from processing data on an inbound TLS connection while |
| 124 | talking to another TLS connection for an outbound check. This does mean that |
| 125 | there's no way for heart-beats to be responded to, for the duration of the |
| 126 | second connection. */ |
| 127 | |
| 128 | static exim_gnutls_state_st state_server, state_client; |
| 129 | |
| 130 | /* dh_params are initialised once within the lifetime of a process using TLS; |
| 131 | if we used TLS in a long-lived daemon, we'd have to reconsider this. But we |
| 132 | don't want to repeat this. */ |
| 133 | |
| 134 | static gnutls_dh_params_t dh_server_params = NULL; |
| 135 | |
| 136 | /* No idea how this value was chosen; preserving it. Default is 3600. */ |
| 137 | |
| 138 | static const int ssl_session_timeout = 200; |
| 139 | |
| 140 | static const char * const exim_default_gnutls_priority = "NORMAL"; |
| 141 | |
| 142 | /* Guard library core initialisation */ |
| 143 | |
| 144 | static BOOL exim_gnutls_base_init_done = FALSE; |
| 145 | |
| 146 | |
| 147 | /* ------------------------------------------------------------------------ */ |
| 148 | /* macros */ |
| 149 | |
| 150 | #define MAX_HOST_LEN 255 |
| 151 | |
| 152 | /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup |
| 153 | the library logging; a value less than 0 disables the calls to set up logging |
| 154 | callbacks. */ |
| 155 | #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL |
| 156 | #define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1 |
| 157 | #endif |
| 158 | |
| 159 | #ifndef EXIM_CLIENT_DH_MIN_BITS |
| 160 | #define EXIM_CLIENT_DH_MIN_BITS 1024 |
| 161 | #endif |
| 162 | |
| 163 | /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we |
| 164 | can ask for a bit-strength. Without that, we stick to the constant we had |
| 165 | before, for now. */ |
| 166 | #ifndef EXIM_SERVER_DH_BITS_PRE2_12 |
| 167 | #define EXIM_SERVER_DH_BITS_PRE2_12 1024 |
| 168 | #endif |
| 169 | |
| 170 | #define exim_gnutls_err_check(Label) do { \ |
| 171 | if (rc != GNUTLS_E_SUCCESS) { return tls_error((Label), gnutls_strerror(rc), host); } } while (0) |
| 172 | |
| 173 | #define expand_check_tlsvar(Varname) expand_check(state->Varname, US #Varname, &state->exp_##Varname) |
| 174 | |
| 175 | #if GNUTLS_VERSION_NUMBER >= 0x020c00 |
| 176 | #define HAVE_GNUTLS_SESSION_CHANNEL_BINDING |
| 177 | #define HAVE_GNUTLS_SEC_PARAM_CONSTANTS |
| 178 | #define HAVE_GNUTLS_RND |
| 179 | /* The security fix we provide with the gnutls_allow_auto_pkcs11 option |
| 180 | * (4.82 PP/09) introduces a compatibility regression. The symbol simply |
| 181 | * isn't available sometimes, so this needs to become a conditional |
| 182 | * compilation; the sanest way to deal with this being a problem on |
| 183 | * older OSes is to block it in the Local/Makefile with this compiler |
| 184 | * definition */ |
| 185 | #ifndef AVOID_GNUTLS_PKCS11 |
| 186 | #define HAVE_GNUTLS_PKCS11 |
| 187 | #endif /* AVOID_GNUTLS_PKCS11 */ |
| 188 | #endif |
| 189 | |
| 190 | |
| 191 | |
| 192 | |
| 193 | /* ------------------------------------------------------------------------ */ |
| 194 | /* Callback declarations */ |
| 195 | |
| 196 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
| 197 | static void exim_gnutls_logger_cb(int level, const char *message); |
| 198 | #endif |
| 199 | |
| 200 | static int exim_sni_handling_cb(gnutls_session_t session); |
| 201 | |
| 202 | |
| 203 | |
| 204 | |
| 205 | /* ------------------------------------------------------------------------ */ |
| 206 | /* Static functions */ |
| 207 | |
| 208 | /************************************************* |
| 209 | * Handle TLS error * |
| 210 | *************************************************/ |
| 211 | |
| 212 | /* Called from lots of places when errors occur before actually starting to do |
| 213 | the TLS handshake, that is, while the session is still in clear. Always returns |
| 214 | DEFER for a server and FAIL for a client so that most calls can use "return |
| 215 | tls_error(...)" to do this processing and then give an appropriate return. A |
| 216 | single function is used for both server and client, because it is called from |
| 217 | some shared functions. |
| 218 | |
| 219 | Argument: |
| 220 | prefix text to include in the logged error |
| 221 | msg additional error string (may be NULL) |
| 222 | usually obtained from gnutls_strerror() |
| 223 | host NULL if setting up a server; |
| 224 | the connected host if setting up a client |
| 225 | |
| 226 | Returns: OK/DEFER/FAIL |
| 227 | */ |
| 228 | |
| 229 | static int |
| 230 | tls_error(const uschar *prefix, const char *msg, const host_item *host) |
| 231 | { |
| 232 | if (host) |
| 233 | { |
| 234 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s", |
| 235 | host->name, host->address, prefix, msg ? ": " : "", msg ? msg : ""); |
| 236 | return FAIL; |
| 237 | } |
| 238 | else |
| 239 | { |
| 240 | uschar *conn_info = smtp_get_connection_info(); |
| 241 | if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) |
| 242 | conn_info += 5; |
| 243 | log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s", |
| 244 | conn_info, prefix, msg ? ": " : "", msg ? msg : ""); |
| 245 | return DEFER; |
| 246 | } |
| 247 | } |
| 248 | |
| 249 | |
| 250 | |
| 251 | |
| 252 | /************************************************* |
| 253 | * Deal with logging errors during I/O * |
| 254 | *************************************************/ |
| 255 | |
| 256 | /* We have to get the identity of the peer from saved data. |
| 257 | |
| 258 | Argument: |
| 259 | state the current GnuTLS exim state container |
| 260 | rc the GnuTLS error code, or 0 if it's a local error |
| 261 | when text identifying read or write |
| 262 | text local error text when ec is 0 |
| 263 | |
| 264 | Returns: nothing |
| 265 | */ |
| 266 | |
| 267 | static void |
| 268 | record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text) |
| 269 | { |
| 270 | const char *msg; |
| 271 | |
| 272 | if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED) |
| 273 | msg = CS string_sprintf("%s: %s", US gnutls_strerror(rc), |
| 274 | US gnutls_alert_get_name(gnutls_alert_get(state->session))); |
| 275 | else |
| 276 | msg = gnutls_strerror(rc); |
| 277 | |
| 278 | tls_error(when, msg, state->host); |
| 279 | } |
| 280 | |
| 281 | |
| 282 | |
| 283 | |
| 284 | /************************************************* |
| 285 | * Set various Exim expansion vars * |
| 286 | *************************************************/ |
| 287 | |
| 288 | /* We set various Exim global variables from the state, once a session has |
| 289 | been established. With TLS callouts, may need to change this to stack |
| 290 | variables, or just re-call it with the server state after client callout |
| 291 | has finished. |
| 292 | |
| 293 | Make sure anything set here is inset in tls_getc(). |
| 294 | |
| 295 | Sets: |
| 296 | tls_active fd |
| 297 | tls_bits strength indicator |
| 298 | tls_certificate_verified bool indicator |
| 299 | tls_channelbinding_b64 for some SASL mechanisms |
| 300 | tls_cipher a string |
| 301 | tls_peerdn a string |
| 302 | tls_sni a (UTF-8) string |
| 303 | |
| 304 | Argument: |
| 305 | state the relevant exim_gnutls_state_st * |
| 306 | */ |
| 307 | |
| 308 | static void |
| 309 | extract_exim_vars_from_tls_state(exim_gnutls_state_st *state, BOOL is_server) |
| 310 | { |
| 311 | gnutls_cipher_algorithm_t cipher; |
| 312 | #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING |
| 313 | int old_pool; |
| 314 | int rc; |
| 315 | gnutls_datum_t channel; |
| 316 | #endif |
| 317 | |
| 318 | state->tlsp->active = state->fd_out; |
| 319 | |
| 320 | cipher = gnutls_cipher_get(state->session); |
| 321 | /* returns size in "bytes" */ |
| 322 | state->tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8; |
| 323 | |
| 324 | state->tlsp->cipher = state->ciphersuite; |
| 325 | |
| 326 | DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite); |
| 327 | |
| 328 | state->tlsp->certificate_verified = state->peer_cert_verified; |
| 329 | |
| 330 | /* note that tls_channelbinding_b64 is not saved to the spool file, since it's |
| 331 | only available for use for authenticators while this TLS session is running. */ |
| 332 | |
| 333 | tls_channelbinding_b64 = NULL; |
| 334 | #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING |
| 335 | channel.data = NULL; |
| 336 | channel.size = 0; |
| 337 | rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel); |
| 338 | if (rc) { |
| 339 | DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); |
| 340 | } else { |
| 341 | old_pool = store_pool; |
| 342 | store_pool = POOL_PERM; |
| 343 | tls_channelbinding_b64 = auth_b64encode(channel.data, (int)channel.size); |
| 344 | store_pool = old_pool; |
| 345 | DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n"); |
| 346 | } |
| 347 | #endif |
| 348 | |
| 349 | state->tlsp->peerdn = state->peerdn; |
| 350 | state->tlsp->sni = state->received_sni; |
| 351 | } |
| 352 | |
| 353 | |
| 354 | |
| 355 | |
| 356 | /************************************************* |
| 357 | * Setup up DH parameters * |
| 358 | *************************************************/ |
| 359 | |
| 360 | /* Generating the D-H parameters may take a long time. They only need to |
| 361 | be re-generated every so often, depending on security policy. What we do is to |
| 362 | keep these parameters in a file in the spool directory. If the file does not |
| 363 | exist, we generate them. This means that it is easy to cause a regeneration. |
| 364 | |
| 365 | The new file is written as a temporary file and renamed, so that an incomplete |
| 366 | file is never present. If two processes both compute some new parameters, you |
| 367 | waste a bit of effort, but it doesn't seem worth messing around with locking to |
| 368 | prevent this. |
| 369 | |
| 370 | Returns: OK/DEFER/FAIL |
| 371 | */ |
| 372 | |
| 373 | static int |
| 374 | init_server_dh(void) |
| 375 | { |
| 376 | int fd, rc; |
| 377 | unsigned int dh_bits; |
| 378 | gnutls_datum m; |
| 379 | uschar filename_buf[PATH_MAX]; |
| 380 | uschar *filename = NULL; |
| 381 | size_t sz; |
| 382 | uschar *exp_tls_dhparam; |
| 383 | BOOL use_file_in_spool = FALSE; |
| 384 | BOOL use_fixed_file = FALSE; |
| 385 | host_item *host = NULL; /* dummy for macros */ |
| 386 | |
| 387 | DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n"); |
| 388 | |
| 389 | rc = gnutls_dh_params_init(&dh_server_params); |
| 390 | exim_gnutls_err_check(US"gnutls_dh_params_init"); |
| 391 | |
| 392 | m.data = NULL; |
| 393 | m.size = 0; |
| 394 | |
| 395 | if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam)) |
| 396 | return DEFER; |
| 397 | |
| 398 | if (!exp_tls_dhparam) |
| 399 | { |
| 400 | DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n"); |
| 401 | m.data = US std_dh_prime_default(); |
| 402 | m.size = Ustrlen(m.data); |
| 403 | } |
| 404 | else if (Ustrcmp(exp_tls_dhparam, "historic") == 0) |
| 405 | use_file_in_spool = TRUE; |
| 406 | else if (Ustrcmp(exp_tls_dhparam, "none") == 0) |
| 407 | { |
| 408 | DEBUG(D_tls) debug_printf("Requested no DH parameters.\n"); |
| 409 | return OK; |
| 410 | } |
| 411 | else if (exp_tls_dhparam[0] != '/') |
| 412 | { |
| 413 | m.data = US std_dh_prime_named(exp_tls_dhparam); |
| 414 | if (m.data == NULL) |
| 415 | return tls_error(US"No standard prime named", CS exp_tls_dhparam, NULL); |
| 416 | m.size = Ustrlen(m.data); |
| 417 | } |
| 418 | else |
| 419 | { |
| 420 | use_fixed_file = TRUE; |
| 421 | filename = exp_tls_dhparam; |
| 422 | } |
| 423 | |
| 424 | if (m.data) |
| 425 | { |
| 426 | rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); |
| 427 | exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3"); |
| 428 | DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n"); |
| 429 | return OK; |
| 430 | } |
| 431 | |
| 432 | #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS |
| 433 | /* If you change this constant, also change dh_param_fn_ext so that we can use a |
| 434 | different filename and ensure we have sufficient bits. */ |
| 435 | dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL); |
| 436 | if (!dh_bits) |
| 437 | return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL); |
| 438 | DEBUG(D_tls) |
| 439 | debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n", |
| 440 | dh_bits); |
| 441 | #else |
| 442 | dh_bits = EXIM_SERVER_DH_BITS_PRE2_12; |
| 443 | DEBUG(D_tls) |
| 444 | debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n", |
| 445 | dh_bits); |
| 446 | #endif |
| 447 | |
| 448 | /* Some clients have hard-coded limits. */ |
| 449 | if (dh_bits > tls_dh_max_bits) |
| 450 | { |
| 451 | DEBUG(D_tls) |
| 452 | debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n", |
| 453 | tls_dh_max_bits); |
| 454 | dh_bits = tls_dh_max_bits; |
| 455 | } |
| 456 | |
| 457 | if (use_file_in_spool) |
| 458 | { |
| 459 | if (!string_format(filename_buf, sizeof(filename_buf), |
| 460 | "%s/gnutls-params-%d", spool_directory, dh_bits)) |
| 461 | return tls_error(US"overlong filename", NULL, NULL); |
| 462 | filename = filename_buf; |
| 463 | } |
| 464 | |
| 465 | /* Open the cache file for reading and if successful, read it and set up the |
| 466 | parameters. */ |
| 467 | |
| 468 | fd = Uopen(filename, O_RDONLY, 0); |
| 469 | if (fd >= 0) |
| 470 | { |
| 471 | struct stat statbuf; |
| 472 | FILE *fp; |
| 473 | int saved_errno; |
| 474 | |
| 475 | if (fstat(fd, &statbuf) < 0) /* EIO */ |
| 476 | { |
| 477 | saved_errno = errno; |
| 478 | (void)close(fd); |
| 479 | return tls_error(US"TLS cache stat failed", strerror(saved_errno), NULL); |
| 480 | } |
| 481 | if (!S_ISREG(statbuf.st_mode)) |
| 482 | { |
| 483 | (void)close(fd); |
| 484 | return tls_error(US"TLS cache not a file", NULL, NULL); |
| 485 | } |
| 486 | fp = fdopen(fd, "rb"); |
| 487 | if (!fp) |
| 488 | { |
| 489 | saved_errno = errno; |
| 490 | (void)close(fd); |
| 491 | return tls_error(US"fdopen(TLS cache stat fd) failed", |
| 492 | strerror(saved_errno), NULL); |
| 493 | } |
| 494 | |
| 495 | m.size = statbuf.st_size; |
| 496 | m.data = malloc(m.size); |
| 497 | if (m.data == NULL) |
| 498 | { |
| 499 | fclose(fp); |
| 500 | return tls_error(US"malloc failed", strerror(errno), NULL); |
| 501 | } |
| 502 | sz = fread(m.data, m.size, 1, fp); |
| 503 | if (!sz) |
| 504 | { |
| 505 | saved_errno = errno; |
| 506 | fclose(fp); |
| 507 | free(m.data); |
| 508 | return tls_error(US"fread failed", strerror(saved_errno), NULL); |
| 509 | } |
| 510 | fclose(fp); |
| 511 | |
| 512 | rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); |
| 513 | free(m.data); |
| 514 | exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3"); |
| 515 | DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename); |
| 516 | } |
| 517 | |
| 518 | /* If the file does not exist, fall through to compute new data and cache it. |
| 519 | If there was any other opening error, it is serious. */ |
| 520 | |
| 521 | else if (errno == ENOENT) |
| 522 | { |
| 523 | rc = -1; |
| 524 | DEBUG(D_tls) |
| 525 | debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename); |
| 526 | } |
| 527 | else |
| 528 | return tls_error(string_open_failed(errno, "\"%s\" for reading", filename), |
| 529 | NULL, NULL); |
| 530 | |
| 531 | /* If ret < 0, either the cache file does not exist, or the data it contains |
| 532 | is not useful. One particular case of this is when upgrading from an older |
| 533 | release of Exim in which the data was stored in a different format. We don't |
| 534 | try to be clever and support both formats; we just regenerate new data in this |
| 535 | case. */ |
| 536 | |
| 537 | if (rc < 0) |
| 538 | { |
| 539 | uschar *temp_fn; |
| 540 | unsigned int dh_bits_gen = dh_bits; |
| 541 | |
| 542 | if ((PATH_MAX - Ustrlen(filename)) < 10) |
| 543 | return tls_error(US"Filename too long to generate replacement", |
| 544 | CS filename, NULL); |
| 545 | |
| 546 | temp_fn = string_copy(US "%s.XXXXXXX"); |
| 547 | fd = mkstemp(CS temp_fn); /* modifies temp_fn */ |
| 548 | if (fd < 0) |
| 549 | return tls_error(US"Unable to open temp file", strerror(errno), NULL); |
| 550 | (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */ |
| 551 | |
| 552 | /* GnuTLS overshoots! |
| 553 | * If we ask for 2236, we might get 2237 or more. |
| 554 | * But there's no way to ask GnuTLS how many bits there really are. |
| 555 | * We can ask how many bits were used in a TLS session, but that's it! |
| 556 | * The prime itself is hidden behind too much abstraction. |
| 557 | * So we ask for less, and proceed on a wing and a prayer. |
| 558 | * First attempt, subtracted 3 for 2233 and got 2240. |
| 559 | */ |
| 560 | if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10) |
| 561 | { |
| 562 | dh_bits_gen = dh_bits - 10; |
| 563 | DEBUG(D_tls) |
| 564 | debug_printf("being paranoid about DH generation, make it '%d' bits'\n", |
| 565 | dh_bits_gen); |
| 566 | } |
| 567 | |
| 568 | DEBUG(D_tls) |
| 569 | debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n", |
| 570 | dh_bits_gen); |
| 571 | rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen); |
| 572 | exim_gnutls_err_check(US"gnutls_dh_params_generate2"); |
| 573 | |
| 574 | /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time, |
| 575 | and I confirmed that a NULL call to get the size first is how the GnuTLS |
| 576 | sample apps handle this. */ |
| 577 | |
| 578 | sz = 0; |
| 579 | m.data = NULL; |
| 580 | rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, |
| 581 | m.data, &sz); |
| 582 | if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) |
| 583 | exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3(NULL) sizing"); |
| 584 | m.size = sz; |
| 585 | m.data = malloc(m.size); |
| 586 | if (m.data == NULL) |
| 587 | return tls_error(US"memory allocation failed", strerror(errno), NULL); |
| 588 | /* this will return a size 1 less than the allocation size above */ |
| 589 | rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, |
| 590 | m.data, &sz); |
| 591 | if (rc != GNUTLS_E_SUCCESS) |
| 592 | { |
| 593 | free(m.data); |
| 594 | exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real"); |
| 595 | } |
| 596 | m.size = sz; /* shrink by 1, probably */ |
| 597 | |
| 598 | sz = write_to_fd_buf(fd, m.data, (size_t) m.size); |
| 599 | if (sz != m.size) |
| 600 | { |
| 601 | free(m.data); |
| 602 | return tls_error(US"TLS cache write D-H params failed", |
| 603 | strerror(errno), NULL); |
| 604 | } |
| 605 | free(m.data); |
| 606 | sz = write_to_fd_buf(fd, US"\n", 1); |
| 607 | if (sz != 1) |
| 608 | return tls_error(US"TLS cache write D-H params final newline failed", |
| 609 | strerror(errno), NULL); |
| 610 | |
| 611 | rc = close(fd); |
| 612 | if (rc) |
| 613 | return tls_error(US"TLS cache write close() failed", |
| 614 | strerror(errno), NULL); |
| 615 | |
| 616 | if (Urename(temp_fn, filename) < 0) |
| 617 | return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"", |
| 618 | temp_fn, filename), strerror(errno), NULL); |
| 619 | |
| 620 | DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename); |
| 621 | } |
| 622 | |
| 623 | DEBUG(D_tls) debug_printf("initialized server D-H parameters\n"); |
| 624 | return OK; |
| 625 | } |
| 626 | |
| 627 | |
| 628 | |
| 629 | |
| 630 | /************************************************* |
| 631 | * Variables re-expanded post-SNI * |
| 632 | *************************************************/ |
| 633 | |
| 634 | /* Called from both server and client code, via tls_init(), and also from |
| 635 | the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni". |
| 636 | |
| 637 | We can tell the two apart by state->received_sni being non-NULL in callback. |
| 638 | |
| 639 | The callback should not call us unless state->trigger_sni_changes is true, |
| 640 | which we are responsible for setting on the first pass through. |
| 641 | |
| 642 | Arguments: |
| 643 | state exim_gnutls_state_st * |
| 644 | |
| 645 | Returns: OK/DEFER/FAIL |
| 646 | */ |
| 647 | |
| 648 | static int |
| 649 | tls_expand_session_files(exim_gnutls_state_st *state) |
| 650 | { |
| 651 | struct stat statbuf; |
| 652 | int rc; |
| 653 | const host_item *host = state->host; /* macro should be reconsidered? */ |
| 654 | uschar *saved_tls_certificate = NULL; |
| 655 | uschar *saved_tls_privatekey = NULL; |
| 656 | uschar *saved_tls_verify_certificates = NULL; |
| 657 | uschar *saved_tls_crl = NULL; |
| 658 | int cert_count; |
| 659 | |
| 660 | /* We check for tls_sni *before* expansion. */ |
| 661 | if (!state->host) |
| 662 | { |
| 663 | if (!state->received_sni) |
| 664 | { |
| 665 | if (state->tls_certificate && |
| 666 | (Ustrstr(state->tls_certificate, US"tls_sni") || |
| 667 | Ustrstr(state->tls_certificate, US"tls_in_sni") || |
| 668 | Ustrstr(state->tls_certificate, US"tls_out_sni") |
| 669 | )) |
| 670 | { |
| 671 | DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n"); |
| 672 | state->trigger_sni_changes = TRUE; |
| 673 | } |
| 674 | } |
| 675 | else |
| 676 | { |
| 677 | /* useful for debugging */ |
| 678 | saved_tls_certificate = state->exp_tls_certificate; |
| 679 | saved_tls_privatekey = state->exp_tls_privatekey; |
| 680 | saved_tls_verify_certificates = state->exp_tls_verify_certificates; |
| 681 | saved_tls_crl = state->exp_tls_crl; |
| 682 | } |
| 683 | } |
| 684 | |
| 685 | rc = gnutls_certificate_allocate_credentials(&state->x509_cred); |
| 686 | exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials"); |
| 687 | |
| 688 | /* remember: expand_check_tlsvar() is expand_check() but fiddling with |
| 689 | state members, assuming consistent naming; and expand_check() returns |
| 690 | false if expansion failed, unless expansion was forced to fail. */ |
| 691 | |
| 692 | /* check if we at least have a certificate, before doing expensive |
| 693 | D-H generation. */ |
| 694 | |
| 695 | if (!expand_check_tlsvar(tls_certificate)) |
| 696 | return DEFER; |
| 697 | |
| 698 | /* certificate is mandatory in server, optional in client */ |
| 699 | |
| 700 | if ((state->exp_tls_certificate == NULL) || |
| 701 | (*state->exp_tls_certificate == '\0')) |
| 702 | { |
| 703 | if (state->host == NULL) |
| 704 | return tls_error(US"no TLS server certificate is specified", NULL, NULL); |
| 705 | else |
| 706 | DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n"); |
| 707 | } |
| 708 | |
| 709 | if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey)) |
| 710 | return DEFER; |
| 711 | |
| 712 | /* tls_privatekey is optional, defaulting to same file as certificate */ |
| 713 | |
| 714 | if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0') |
| 715 | { |
| 716 | state->tls_privatekey = state->tls_certificate; |
| 717 | state->exp_tls_privatekey = state->exp_tls_certificate; |
| 718 | } |
| 719 | |
| 720 | |
| 721 | if (state->exp_tls_certificate && *state->exp_tls_certificate) |
| 722 | { |
| 723 | DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n", |
| 724 | state->exp_tls_certificate, state->exp_tls_privatekey); |
| 725 | |
| 726 | if (state->received_sni) |
| 727 | { |
| 728 | if ((Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0) && |
| 729 | (Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0)) |
| 730 | { |
| 731 | DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n"); |
| 732 | } |
| 733 | else |
| 734 | { |
| 735 | DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n"); |
| 736 | } |
| 737 | } |
| 738 | |
| 739 | rc = gnutls_certificate_set_x509_key_file(state->x509_cred, |
| 740 | CS state->exp_tls_certificate, CS state->exp_tls_privatekey, |
| 741 | GNUTLS_X509_FMT_PEM); |
| 742 | exim_gnutls_err_check( |
| 743 | string_sprintf("cert/key setup: cert=%s key=%s", |
| 744 | state->exp_tls_certificate, state->exp_tls_privatekey)); |
| 745 | DEBUG(D_tls) debug_printf("TLS: cert/key registered\n"); |
| 746 | } /* tls_certificate */ |
| 747 | |
| 748 | /* Set the trusted CAs file if one is provided, and then add the CRL if one is |
| 749 | provided. Experiment shows that, if the certificate file is empty, an unhelpful |
| 750 | error message is provided. However, if we just refrain from setting anything up |
| 751 | in that case, certificate verification fails, which seems to be the correct |
| 752 | behaviour. */ |
| 753 | |
| 754 | if (state->tls_verify_certificates && *state->tls_verify_certificates) |
| 755 | { |
| 756 | if (!expand_check_tlsvar(tls_verify_certificates)) |
| 757 | return DEFER; |
| 758 | if (state->tls_crl && *state->tls_crl) |
| 759 | if (!expand_check_tlsvar(tls_crl)) |
| 760 | return DEFER; |
| 761 | |
| 762 | if (!(state->exp_tls_verify_certificates && |
| 763 | *state->exp_tls_verify_certificates)) |
| 764 | { |
| 765 | DEBUG(D_tls) |
| 766 | debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n"); |
| 767 | /* With no tls_verify_certificates, we ignore tls_crl too */ |
| 768 | return OK; |
| 769 | } |
| 770 | } |
| 771 | else |
| 772 | { |
| 773 | DEBUG(D_tls) |
| 774 | debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n"); |
| 775 | return OK; |
| 776 | } |
| 777 | |
| 778 | if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0) |
| 779 | { |
| 780 | log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s " |
| 781 | "(tls_verify_certificates): %s", state->exp_tls_verify_certificates, |
| 782 | strerror(errno)); |
| 783 | return DEFER; |
| 784 | } |
| 785 | |
| 786 | /* The test suite passes in /dev/null; we could check for that path explicitly, |
| 787 | but who knows if someone has some weird FIFO which always dumps some certs, or |
| 788 | other weirdness. The thing we really want to check is that it's not a |
| 789 | directory, since while OpenSSL supports that, GnuTLS does not. |
| 790 | So s/!S_ISREG/S_ISDIR/ and change some messsaging ... */ |
| 791 | if (S_ISDIR(statbuf.st_mode)) |
| 792 | { |
| 793 | DEBUG(D_tls) |
| 794 | debug_printf("verify certificates path is a dir: \"%s\"\n", |
| 795 | state->exp_tls_verify_certificates); |
| 796 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 797 | "tls_verify_certificates \"%s\" is a directory", |
| 798 | state->exp_tls_verify_certificates); |
| 799 | return DEFER; |
| 800 | } |
| 801 | |
| 802 | DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n", |
| 803 | state->exp_tls_verify_certificates, statbuf.st_size); |
| 804 | |
| 805 | if (statbuf.st_size == 0) |
| 806 | { |
| 807 | DEBUG(D_tls) |
| 808 | debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n"); |
| 809 | return OK; |
| 810 | } |
| 811 | |
| 812 | cert_count = gnutls_certificate_set_x509_trust_file(state->x509_cred, |
| 813 | CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM); |
| 814 | if (cert_count < 0) |
| 815 | { |
| 816 | rc = cert_count; |
| 817 | exim_gnutls_err_check(US"gnutls_certificate_set_x509_trust_file"); |
| 818 | } |
| 819 | DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count); |
| 820 | |
| 821 | if (state->tls_crl && *state->tls_crl && |
| 822 | state->exp_tls_crl && *state->exp_tls_crl) |
| 823 | { |
| 824 | DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl); |
| 825 | cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred, |
| 826 | CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM); |
| 827 | if (cert_count < 0) |
| 828 | { |
| 829 | rc = cert_count; |
| 830 | exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file"); |
| 831 | } |
| 832 | DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count); |
| 833 | } |
| 834 | |
| 835 | return OK; |
| 836 | } |
| 837 | |
| 838 | |
| 839 | |
| 840 | |
| 841 | /************************************************* |
| 842 | * Set X.509 state variables * |
| 843 | *************************************************/ |
| 844 | |
| 845 | /* In GnuTLS, the registered cert/key are not replaced by a later |
| 846 | set of a cert/key, so for SNI support we need a whole new x509_cred |
| 847 | structure. Which means various other non-re-expanded pieces of state |
| 848 | need to be re-set in the new struct, so the setting logic is pulled |
| 849 | out to this. |
| 850 | |
| 851 | Arguments: |
| 852 | state exim_gnutls_state_st * |
| 853 | |
| 854 | Returns: OK/DEFER/FAIL |
| 855 | */ |
| 856 | |
| 857 | static int |
| 858 | tls_set_remaining_x509(exim_gnutls_state_st *state) |
| 859 | { |
| 860 | int rc; |
| 861 | const host_item *host = state->host; /* macro should be reconsidered? */ |
| 862 | |
| 863 | /* Create D-H parameters, or read them from the cache file. This function does |
| 864 | its own SMTP error messaging. This only happens for the server, TLS D-H ignores |
| 865 | client-side params. */ |
| 866 | |
| 867 | if (!state->host) |
| 868 | { |
| 869 | if (!dh_server_params) |
| 870 | { |
| 871 | rc = init_server_dh(); |
| 872 | if (rc != OK) return rc; |
| 873 | } |
| 874 | gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params); |
| 875 | } |
| 876 | |
| 877 | /* Link the credentials to the session. */ |
| 878 | |
| 879 | rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred); |
| 880 | exim_gnutls_err_check(US"gnutls_credentials_set"); |
| 881 | |
| 882 | return OK; |
| 883 | } |
| 884 | |
| 885 | /************************************************* |
| 886 | * Initialize for GnuTLS * |
| 887 | *************************************************/ |
| 888 | |
| 889 | /* Called from both server and client code. In the case of a server, errors |
| 890 | before actual TLS negotiation return DEFER. |
| 891 | |
| 892 | Arguments: |
| 893 | host connected host, if client; NULL if server |
| 894 | certificate certificate file |
| 895 | privatekey private key file |
| 896 | sni TLS SNI to send, sometimes when client; else NULL |
| 897 | cas CA certs file |
| 898 | crl CRL file |
| 899 | require_ciphers tls_require_ciphers setting |
| 900 | caller_state returned state-info structure |
| 901 | |
| 902 | Returns: OK/DEFER/FAIL |
| 903 | */ |
| 904 | |
| 905 | static int |
| 906 | tls_init( |
| 907 | const host_item *host, |
| 908 | const uschar *certificate, |
| 909 | const uschar *privatekey, |
| 910 | const uschar *sni, |
| 911 | const uschar *cas, |
| 912 | const uschar *crl, |
| 913 | const uschar *require_ciphers, |
| 914 | exim_gnutls_state_st **caller_state) |
| 915 | { |
| 916 | exim_gnutls_state_st *state; |
| 917 | int rc; |
| 918 | size_t sz; |
| 919 | const char *errpos; |
| 920 | uschar *p; |
| 921 | BOOL want_default_priorities; |
| 922 | |
| 923 | if (!exim_gnutls_base_init_done) |
| 924 | { |
| 925 | DEBUG(D_tls) debug_printf("GnuTLS global init required.\n"); |
| 926 | |
| 927 | #ifdef HAVE_GNUTLS_PKCS11 |
| 928 | /* By default, gnutls_global_init will init PKCS11 support in auto mode, |
| 929 | which loads modules from a config file, which sounds good and may be wanted |
| 930 | by some sysadmin, but also means in common configurations that GNOME keyring |
| 931 | environment variables are used and so breaks for users calling mailq. |
| 932 | To prevent this, we init PKCS11 first, which is the documented approach. */ |
| 933 | if (!gnutls_allow_auto_pkcs11) |
| 934 | { |
| 935 | rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL); |
| 936 | exim_gnutls_err_check(US"gnutls_pkcs11_init"); |
| 937 | } |
| 938 | #endif |
| 939 | |
| 940 | rc = gnutls_global_init(); |
| 941 | exim_gnutls_err_check(US"gnutls_global_init"); |
| 942 | |
| 943 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
| 944 | DEBUG(D_tls) |
| 945 | { |
| 946 | gnutls_global_set_log_function(exim_gnutls_logger_cb); |
| 947 | /* arbitrarily chosen level; bump upto 9 for more */ |
| 948 | gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); |
| 949 | } |
| 950 | #endif |
| 951 | |
| 952 | exim_gnutls_base_init_done = TRUE; |
| 953 | } |
| 954 | |
| 955 | if (host) |
| 956 | { |
| 957 | state = &state_client; |
| 958 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); |
| 959 | state->tlsp = &tls_out; |
| 960 | DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n"); |
| 961 | rc = gnutls_init(&state->session, GNUTLS_CLIENT); |
| 962 | } |
| 963 | else |
| 964 | { |
| 965 | state = &state_server; |
| 966 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); |
| 967 | state->tlsp = &tls_in; |
| 968 | DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n"); |
| 969 | rc = gnutls_init(&state->session, GNUTLS_SERVER); |
| 970 | } |
| 971 | exim_gnutls_err_check(US"gnutls_init"); |
| 972 | |
| 973 | state->host = host; |
| 974 | |
| 975 | state->tls_certificate = certificate; |
| 976 | state->tls_privatekey = privatekey; |
| 977 | state->tls_require_ciphers = require_ciphers; |
| 978 | state->tls_sni = sni; |
| 979 | state->tls_verify_certificates = cas; |
| 980 | state->tls_crl = crl; |
| 981 | |
| 982 | /* This handles the variables that might get re-expanded after TLS SNI; |
| 983 | that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */ |
| 984 | |
| 985 | DEBUG(D_tls) |
| 986 | debug_printf("Expanding various TLS configuration options for session credentials.\n"); |
| 987 | rc = tls_expand_session_files(state); |
| 988 | if (rc != OK) return rc; |
| 989 | |
| 990 | /* These are all other parts of the x509_cred handling, since SNI in GnuTLS |
| 991 | requires a new structure afterwards. */ |
| 992 | |
| 993 | rc = tls_set_remaining_x509(state); |
| 994 | if (rc != OK) return rc; |
| 995 | |
| 996 | /* set SNI in client, only */ |
| 997 | if (host) |
| 998 | { |
| 999 | if (!expand_check(state->tlsp->sni, US"tls_out_sni", &state->exp_tls_sni)) |
| 1000 | return DEFER; |
| 1001 | if (state->exp_tls_sni && *state->exp_tls_sni) |
| 1002 | { |
| 1003 | DEBUG(D_tls) |
| 1004 | debug_printf("Setting TLS client SNI to \"%s\"\n", state->exp_tls_sni); |
| 1005 | sz = Ustrlen(state->exp_tls_sni); |
| 1006 | rc = gnutls_server_name_set(state->session, |
| 1007 | GNUTLS_NAME_DNS, state->exp_tls_sni, sz); |
| 1008 | exim_gnutls_err_check(US"gnutls_server_name_set"); |
| 1009 | } |
| 1010 | } |
| 1011 | else if (state->tls_sni) |
| 1012 | DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \ |
| 1013 | "have an SNI set for a client [%s]\n", state->tls_sni); |
| 1014 | |
| 1015 | /* This is the priority string support, |
| 1016 | http://www.gnutls.org/manual/html_node/Priority-Strings.html |
| 1017 | and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols. |
| 1018 | This was backwards incompatible, but means Exim no longer needs to track |
| 1019 | all algorithms and provide string forms for them. */ |
| 1020 | |
| 1021 | want_default_priorities = TRUE; |
| 1022 | |
| 1023 | if (state->tls_require_ciphers && *state->tls_require_ciphers) |
| 1024 | { |
| 1025 | if (!expand_check_tlsvar(tls_require_ciphers)) |
| 1026 | return DEFER; |
| 1027 | if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers) |
| 1028 | { |
| 1029 | DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", |
| 1030 | state->exp_tls_require_ciphers); |
| 1031 | |
| 1032 | rc = gnutls_priority_init(&state->priority_cache, |
| 1033 | CS state->exp_tls_require_ciphers, &errpos); |
| 1034 | want_default_priorities = FALSE; |
| 1035 | p = state->exp_tls_require_ciphers; |
| 1036 | } |
| 1037 | } |
| 1038 | if (want_default_priorities) |
| 1039 | { |
| 1040 | DEBUG(D_tls) |
| 1041 | debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", |
| 1042 | exim_default_gnutls_priority); |
| 1043 | rc = gnutls_priority_init(&state->priority_cache, |
| 1044 | exim_default_gnutls_priority, &errpos); |
| 1045 | p = US exim_default_gnutls_priority; |
| 1046 | } |
| 1047 | |
| 1048 | exim_gnutls_err_check(string_sprintf( |
| 1049 | "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"", |
| 1050 | p, errpos - CS p, errpos)); |
| 1051 | |
| 1052 | rc = gnutls_priority_set(state->session, state->priority_cache); |
| 1053 | exim_gnutls_err_check(US"gnutls_priority_set"); |
| 1054 | |
| 1055 | gnutls_db_set_cache_expiration(state->session, ssl_session_timeout); |
| 1056 | |
| 1057 | /* Reduce security in favour of increased compatibility, if the admin |
| 1058 | decides to make that trade-off. */ |
| 1059 | if (gnutls_compat_mode) |
| 1060 | { |
| 1061 | #if LIBGNUTLS_VERSION_NUMBER >= 0x020104 |
| 1062 | DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n"); |
| 1063 | gnutls_session_enable_compatibility_mode(state->session); |
| 1064 | #else |
| 1065 | DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n"); |
| 1066 | #endif |
| 1067 | } |
| 1068 | |
| 1069 | *caller_state = state; |
| 1070 | return OK; |
| 1071 | } |
| 1072 | |
| 1073 | |
| 1074 | |
| 1075 | |
| 1076 | /************************************************* |
| 1077 | * Extract peer information * |
| 1078 | *************************************************/ |
| 1079 | |
| 1080 | /* Called from both server and client code. |
| 1081 | Only this is allowed to set state->peerdn and state->have_set_peerdn |
| 1082 | and we use that to detect double-calls. |
| 1083 | |
| 1084 | NOTE: the state blocks last while the TLS connection is up, which is fine |
| 1085 | for logging in the server side, but for the client side, we log after teardown |
| 1086 | in src/deliver.c. While the session is up, we can twist about states and |
| 1087 | repoint tls_* globals, but those variables used for logging or other variable |
| 1088 | expansion that happens _after_ delivery need to have a longer life-time. |
| 1089 | |
| 1090 | So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from |
| 1091 | doing this more than once per generation of a state context. We set them in |
| 1092 | the state context, and repoint tls_* to them. After the state goes away, the |
| 1093 | tls_* copies of the pointers remain valid and client delivery logging is happy. |
| 1094 | |
| 1095 | tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues |
| 1096 | don't apply. |
| 1097 | |
| 1098 | Arguments: |
| 1099 | state exim_gnutls_state_st * |
| 1100 | |
| 1101 | Returns: OK/DEFER/FAIL |
| 1102 | */ |
| 1103 | |
| 1104 | static int |
| 1105 | peer_status(exim_gnutls_state_st *state) |
| 1106 | { |
| 1107 | uschar cipherbuf[256]; |
| 1108 | const gnutls_datum *cert_list; |
| 1109 | int old_pool, rc; |
| 1110 | unsigned int cert_list_size = 0; |
| 1111 | gnutls_protocol_t protocol; |
| 1112 | gnutls_cipher_algorithm_t cipher; |
| 1113 | gnutls_kx_algorithm_t kx; |
| 1114 | gnutls_mac_algorithm_t mac; |
| 1115 | gnutls_certificate_type_t ct; |
| 1116 | gnutls_x509_crt_t crt; |
| 1117 | uschar *p, *dn_buf; |
| 1118 | size_t sz; |
| 1119 | |
| 1120 | if (state->have_set_peerdn) |
| 1121 | return OK; |
| 1122 | state->have_set_peerdn = TRUE; |
| 1123 | |
| 1124 | state->peerdn = NULL; |
| 1125 | |
| 1126 | /* tls_cipher */ |
| 1127 | cipher = gnutls_cipher_get(state->session); |
| 1128 | protocol = gnutls_protocol_get_version(state->session); |
| 1129 | mac = gnutls_mac_get(state->session); |
| 1130 | kx = gnutls_kx_get(state->session); |
| 1131 | |
| 1132 | string_format(cipherbuf, sizeof(cipherbuf), |
| 1133 | "%s:%s:%d", |
| 1134 | gnutls_protocol_get_name(protocol), |
| 1135 | gnutls_cipher_suite_get_name(kx, cipher, mac), |
| 1136 | (int) gnutls_cipher_get_key_size(cipher) * 8); |
| 1137 | |
| 1138 | /* I don't see a way that spaces could occur, in the current GnuTLS |
| 1139 | code base, but it was a concern in the old code and perhaps older GnuTLS |
| 1140 | releases did return "TLS 1.0"; play it safe, just in case. */ |
| 1141 | for (p = cipherbuf; *p != '\0'; ++p) |
| 1142 | if (isspace(*p)) |
| 1143 | *p = '-'; |
| 1144 | old_pool = store_pool; |
| 1145 | store_pool = POOL_PERM; |
| 1146 | state->ciphersuite = string_copy(cipherbuf); |
| 1147 | store_pool = old_pool; |
| 1148 | state->tlsp->cipher = state->ciphersuite; |
| 1149 | |
| 1150 | /* tls_peerdn */ |
| 1151 | cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size); |
| 1152 | |
| 1153 | if (cert_list == NULL || cert_list_size == 0) |
| 1154 | { |
| 1155 | DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n", |
| 1156 | cert_list, cert_list_size); |
| 1157 | if (state->verify_requirement == VERIFY_REQUIRED) |
| 1158 | return tls_error(US"certificate verification failed", |
| 1159 | "no certificate received from peer", state->host); |
| 1160 | return OK; |
| 1161 | } |
| 1162 | |
| 1163 | ct = gnutls_certificate_type_get(state->session); |
| 1164 | if (ct != GNUTLS_CRT_X509) |
| 1165 | { |
| 1166 | const char *ctn = gnutls_certificate_type_get_name(ct); |
| 1167 | DEBUG(D_tls) |
| 1168 | debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn); |
| 1169 | if (state->verify_requirement == VERIFY_REQUIRED) |
| 1170 | return tls_error(US"certificate verification not possible, unhandled type", |
| 1171 | ctn, state->host); |
| 1172 | return OK; |
| 1173 | } |
| 1174 | |
| 1175 | #define exim_gnutls_peer_err(Label) do { \ |
| 1176 | if (rc != GNUTLS_E_SUCCESS) { \ |
| 1177 | DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", (Label), gnutls_strerror(rc)); \ |
| 1178 | if (state->verify_requirement == VERIFY_REQUIRED) { return tls_error((Label), gnutls_strerror(rc), state->host); } \ |
| 1179 | return OK; } } while (0) |
| 1180 | |
| 1181 | rc = gnutls_x509_crt_init(&crt); |
| 1182 | exim_gnutls_peer_err(US"gnutls_x509_crt_init (crt)"); |
| 1183 | |
| 1184 | rc = gnutls_x509_crt_import(crt, &cert_list[0], GNUTLS_X509_FMT_DER); |
| 1185 | exim_gnutls_peer_err(US"failed to import certificate [gnutls_x509_crt_import(cert 0)]"); |
| 1186 | sz = 0; |
| 1187 | rc = gnutls_x509_crt_get_dn(crt, NULL, &sz); |
| 1188 | if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) |
| 1189 | { |
| 1190 | exim_gnutls_peer_err(US"getting size for cert DN failed"); |
| 1191 | return FAIL; /* should not happen */ |
| 1192 | } |
| 1193 | dn_buf = store_get_perm(sz); |
| 1194 | rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz); |
| 1195 | exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]"); |
| 1196 | state->peerdn = dn_buf; |
| 1197 | |
| 1198 | return OK; |
| 1199 | #undef exim_gnutls_peer_err |
| 1200 | } |
| 1201 | |
| 1202 | |
| 1203 | |
| 1204 | |
| 1205 | /************************************************* |
| 1206 | * Verify peer certificate * |
| 1207 | *************************************************/ |
| 1208 | |
| 1209 | /* Called from both server and client code. |
| 1210 | *Should* be using a callback registered with |
| 1211 | gnutls_certificate_set_verify_function() to fail the handshake if we dislike |
| 1212 | the peer information, but that's too new for some OSes. |
| 1213 | |
| 1214 | Arguments: |
| 1215 | state exim_gnutls_state_st * |
| 1216 | error where to put an error message |
| 1217 | |
| 1218 | Returns: |
| 1219 | FALSE if the session should be rejected |
| 1220 | TRUE if the cert is okay or we just don't care |
| 1221 | */ |
| 1222 | |
| 1223 | static BOOL |
| 1224 | verify_certificate(exim_gnutls_state_st *state, const char **error) |
| 1225 | { |
| 1226 | int rc; |
| 1227 | unsigned int verify; |
| 1228 | |
| 1229 | *error = NULL; |
| 1230 | |
| 1231 | rc = peer_status(state); |
| 1232 | if (rc != OK) |
| 1233 | { |
| 1234 | verify = GNUTLS_CERT_INVALID; |
| 1235 | *error = "not supplied"; |
| 1236 | } |
| 1237 | else |
| 1238 | { |
| 1239 | rc = gnutls_certificate_verify_peers2(state->session, &verify); |
| 1240 | } |
| 1241 | |
| 1242 | /* Handle the result of verification. INVALID seems to be set as well |
| 1243 | as REVOKED, but leave the test for both. */ |
| 1244 | |
| 1245 | if ((rc < 0) || (verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0) |
| 1246 | { |
| 1247 | state->peer_cert_verified = FALSE; |
| 1248 | if (*error == NULL) |
| 1249 | *error = ((verify & GNUTLS_CERT_REVOKED) != 0) ? "revoked" : "invalid"; |
| 1250 | |
| 1251 | DEBUG(D_tls) |
| 1252 | debug_printf("TLS certificate verification failed (%s): peerdn=%s\n", |
| 1253 | *error, state->peerdn ? state->peerdn : US"<unset>"); |
| 1254 | |
| 1255 | if (state->verify_requirement == VERIFY_REQUIRED) |
| 1256 | { |
| 1257 | gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE); |
| 1258 | return FALSE; |
| 1259 | } |
| 1260 | DEBUG(D_tls) |
| 1261 | debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n"); |
| 1262 | } |
| 1263 | else |
| 1264 | { |
| 1265 | state->peer_cert_verified = TRUE; |
| 1266 | DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n", |
| 1267 | state->peerdn ? state->peerdn : US"<unset>"); |
| 1268 | } |
| 1269 | |
| 1270 | state->tlsp->peerdn = state->peerdn; |
| 1271 | |
| 1272 | return TRUE; |
| 1273 | } |
| 1274 | |
| 1275 | |
| 1276 | |
| 1277 | |
| 1278 | /* ------------------------------------------------------------------------ */ |
| 1279 | /* Callbacks */ |
| 1280 | |
| 1281 | /* Logging function which can be registered with |
| 1282 | * gnutls_global_set_log_function() |
| 1283 | * gnutls_global_set_log_level() 0..9 |
| 1284 | */ |
| 1285 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
| 1286 | static void |
| 1287 | exim_gnutls_logger_cb(int level, const char *message) |
| 1288 | { |
| 1289 | size_t len = strlen(message); |
| 1290 | if (len < 1) |
| 1291 | { |
| 1292 | DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level); |
| 1293 | return; |
| 1294 | } |
| 1295 | DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message, |
| 1296 | message[len-1] == '\n' ? "" : "\n"); |
| 1297 | } |
| 1298 | #endif |
| 1299 | |
| 1300 | |
| 1301 | /* Called after client hello, should handle SNI work. |
| 1302 | This will always set tls_sni (state->received_sni) if available, |
| 1303 | and may trigger presenting different certificates, |
| 1304 | if state->trigger_sni_changes is TRUE. |
| 1305 | |
| 1306 | Should be registered with |
| 1307 | gnutls_handshake_set_post_client_hello_function() |
| 1308 | |
| 1309 | "This callback must return 0 on success or a gnutls error code to terminate the |
| 1310 | handshake.". |
| 1311 | |
| 1312 | For inability to get SNI information, we return 0. |
| 1313 | We only return non-zero if re-setup failed. |
| 1314 | Only used for server-side TLS. |
| 1315 | */ |
| 1316 | |
| 1317 | static int |
| 1318 | exim_sni_handling_cb(gnutls_session_t session) |
| 1319 | { |
| 1320 | char sni_name[MAX_HOST_LEN]; |
| 1321 | size_t data_len = MAX_HOST_LEN; |
| 1322 | exim_gnutls_state_st *state = &state_server; |
| 1323 | unsigned int sni_type; |
| 1324 | int rc, old_pool; |
| 1325 | |
| 1326 | rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0); |
| 1327 | if (rc != GNUTLS_E_SUCCESS) |
| 1328 | { |
| 1329 | DEBUG(D_tls) { |
| 1330 | if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) |
| 1331 | debug_printf("TLS: no SNI presented in handshake.\n"); |
| 1332 | else |
| 1333 | debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n", |
| 1334 | gnutls_strerror(rc), rc); |
| 1335 | }; |
| 1336 | return 0; |
| 1337 | } |
| 1338 | |
| 1339 | if (sni_type != GNUTLS_NAME_DNS) |
| 1340 | { |
| 1341 | DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type); |
| 1342 | return 0; |
| 1343 | } |
| 1344 | |
| 1345 | /* We now have a UTF-8 string in sni_name */ |
| 1346 | old_pool = store_pool; |
| 1347 | store_pool = POOL_PERM; |
| 1348 | state->received_sni = string_copyn(US sni_name, data_len); |
| 1349 | store_pool = old_pool; |
| 1350 | |
| 1351 | /* We set this one now so that variable expansions below will work */ |
| 1352 | state->tlsp->sni = state->received_sni; |
| 1353 | |
| 1354 | DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name, |
| 1355 | state->trigger_sni_changes ? "" : " (unused for certificate selection)"); |
| 1356 | |
| 1357 | if (!state->trigger_sni_changes) |
| 1358 | return 0; |
| 1359 | |
| 1360 | rc = tls_expand_session_files(state); |
| 1361 | if (rc != OK) |
| 1362 | { |
| 1363 | /* If the setup of certs/etc failed before handshake, TLS would not have |
| 1364 | been offered. The best we can do now is abort. */ |
| 1365 | return GNUTLS_E_APPLICATION_ERROR_MIN; |
| 1366 | } |
| 1367 | |
| 1368 | rc = tls_set_remaining_x509(state); |
| 1369 | if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN; |
| 1370 | |
| 1371 | return 0; |
| 1372 | } |
| 1373 | |
| 1374 | |
| 1375 | |
| 1376 | |
| 1377 | /* ------------------------------------------------------------------------ */ |
| 1378 | /* Exported functions */ |
| 1379 | |
| 1380 | |
| 1381 | |
| 1382 | |
| 1383 | /************************************************* |
| 1384 | * Start a TLS session in a server * |
| 1385 | *************************************************/ |
| 1386 | |
| 1387 | /* This is called when Exim is running as a server, after having received |
| 1388 | the STARTTLS command. It must respond to that command, and then negotiate |
| 1389 | a TLS session. |
| 1390 | |
| 1391 | Arguments: |
| 1392 | require_ciphers list of allowed ciphers or NULL |
| 1393 | |
| 1394 | Returns: OK on success |
| 1395 | DEFER for errors before the start of the negotiation |
| 1396 | FAIL for errors during the negotation; the server can't |
| 1397 | continue running. |
| 1398 | */ |
| 1399 | |
| 1400 | int |
| 1401 | tls_server_start(const uschar *require_ciphers) |
| 1402 | { |
| 1403 | int rc; |
| 1404 | const char *error; |
| 1405 | exim_gnutls_state_st *state = NULL; |
| 1406 | |
| 1407 | /* Check for previous activation */ |
| 1408 | if (tls_in.active >= 0) |
| 1409 | { |
| 1410 | tls_error(US"STARTTLS received after TLS started", "", NULL); |
| 1411 | smtp_printf("554 Already in TLS\r\n"); |
| 1412 | return FAIL; |
| 1413 | } |
| 1414 | |
| 1415 | /* Initialize the library. If it fails, it will already have logged the error |
| 1416 | and sent an SMTP response. */ |
| 1417 | |
| 1418 | DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n"); |
| 1419 | |
| 1420 | rc = tls_init(NULL, tls_certificate, tls_privatekey, |
| 1421 | NULL, tls_verify_certificates, tls_crl, |
| 1422 | require_ciphers, &state); |
| 1423 | if (rc != OK) return rc; |
| 1424 | |
| 1425 | /* If this is a host for which certificate verification is mandatory or |
| 1426 | optional, set up appropriately. */ |
| 1427 | |
| 1428 | if (verify_check_host(&tls_verify_hosts) == OK) |
| 1429 | { |
| 1430 | DEBUG(D_tls) debug_printf("TLS: a client certificate will be required.\n"); |
| 1431 | state->verify_requirement = VERIFY_REQUIRED; |
| 1432 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); |
| 1433 | } |
| 1434 | else if (verify_check_host(&tls_try_verify_hosts) == OK) |
| 1435 | { |
| 1436 | DEBUG(D_tls) debug_printf("TLS: a client certificate will be requested but not required.\n"); |
| 1437 | state->verify_requirement = VERIFY_OPTIONAL; |
| 1438 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); |
| 1439 | } |
| 1440 | else |
| 1441 | { |
| 1442 | DEBUG(D_tls) debug_printf("TLS: a client certificate will not be requested.\n"); |
| 1443 | state->verify_requirement = VERIFY_NONE; |
| 1444 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); |
| 1445 | } |
| 1446 | |
| 1447 | /* Register SNI handling; always, even if not in tls_certificate, so that the |
| 1448 | expansion variable $tls_sni is always available. */ |
| 1449 | |
| 1450 | gnutls_handshake_set_post_client_hello_function(state->session, |
| 1451 | exim_sni_handling_cb); |
| 1452 | |
| 1453 | /* Set context and tell client to go ahead, except in the case of TLS startup |
| 1454 | on connection, where outputting anything now upsets the clients and tends to |
| 1455 | make them disconnect. We need to have an explicit fflush() here, to force out |
| 1456 | the response. Other smtp_printf() calls do not need it, because in non-TLS |
| 1457 | mode, the fflush() happens when smtp_getc() is called. */ |
| 1458 | |
| 1459 | if (!state->tlsp->on_connect) |
| 1460 | { |
| 1461 | smtp_printf("220 TLS go ahead\r\n"); |
| 1462 | fflush(smtp_out); /*XXX JGH */ |
| 1463 | } |
| 1464 | |
| 1465 | /* Now negotiate the TLS session. We put our own timer on it, since it seems |
| 1466 | that the GnuTLS library doesn't. */ |
| 1467 | |
| 1468 | gnutls_transport_set_ptr2(state->session, |
| 1469 | (gnutls_transport_ptr)fileno(smtp_in), |
| 1470 | (gnutls_transport_ptr)fileno(smtp_out)); |
| 1471 | state->fd_in = fileno(smtp_in); |
| 1472 | state->fd_out = fileno(smtp_out); |
| 1473 | |
| 1474 | sigalrm_seen = FALSE; |
| 1475 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 1476 | do |
| 1477 | { |
| 1478 | rc = gnutls_handshake(state->session); |
| 1479 | } while ((rc == GNUTLS_E_AGAIN) || |
| 1480 | (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen)); |
| 1481 | alarm(0); |
| 1482 | |
| 1483 | if (rc != GNUTLS_E_SUCCESS) |
| 1484 | { |
| 1485 | tls_error(US"gnutls_handshake", |
| 1486 | sigalrm_seen ? "timed out" : gnutls_strerror(rc), NULL); |
| 1487 | /* It seems that, except in the case of a timeout, we have to close the |
| 1488 | connection right here; otherwise if the other end is running OpenSSL it hangs |
| 1489 | until the server times out. */ |
| 1490 | |
| 1491 | if (!sigalrm_seen) |
| 1492 | { |
| 1493 | (void)fclose(smtp_out); |
| 1494 | (void)fclose(smtp_in); |
| 1495 | } |
| 1496 | |
| 1497 | return FAIL; |
| 1498 | } |
| 1499 | |
| 1500 | DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); |
| 1501 | |
| 1502 | /* Verify after the fact */ |
| 1503 | |
| 1504 | if (state->verify_requirement != VERIFY_NONE) |
| 1505 | { |
| 1506 | if (!verify_certificate(state, &error)) |
| 1507 | { |
| 1508 | if (state->verify_requirement == VERIFY_OPTIONAL) |
| 1509 | { |
| 1510 | DEBUG(D_tls) |
| 1511 | debug_printf("TLS: continuing on only because verification was optional, after: %s\n", |
| 1512 | error); |
| 1513 | } |
| 1514 | else |
| 1515 | { |
| 1516 | tls_error(US"certificate verification failed", error, NULL); |
| 1517 | return FAIL; |
| 1518 | } |
| 1519 | } |
| 1520 | } |
| 1521 | |
| 1522 | /* Figure out peer DN, and if authenticated, etc. */ |
| 1523 | |
| 1524 | rc = peer_status(state); |
| 1525 | if (rc != OK) return rc; |
| 1526 | |
| 1527 | /* Sets various Exim expansion variables; always safe within server */ |
| 1528 | |
| 1529 | extract_exim_vars_from_tls_state(state, TRUE); |
| 1530 | |
| 1531 | /* TLS has been set up. Adjust the input functions to read via TLS, |
| 1532 | and initialize appropriately. */ |
| 1533 | |
| 1534 | state->xfer_buffer = store_malloc(ssl_xfer_buffer_size); |
| 1535 | |
| 1536 | receive_getc = tls_getc; |
| 1537 | receive_ungetc = tls_ungetc; |
| 1538 | receive_feof = tls_feof; |
| 1539 | receive_ferror = tls_ferror; |
| 1540 | receive_smtp_buffered = tls_smtp_buffered; |
| 1541 | |
| 1542 | return OK; |
| 1543 | } |
| 1544 | |
| 1545 | |
| 1546 | |
| 1547 | |
| 1548 | /************************************************* |
| 1549 | * Start a TLS session in a client * |
| 1550 | *************************************************/ |
| 1551 | |
| 1552 | /* Called from the smtp transport after STARTTLS has been accepted. |
| 1553 | |
| 1554 | Arguments: |
| 1555 | fd the fd of the connection |
| 1556 | host connected host (for messages) |
| 1557 | addr the first address (not used) |
| 1558 | certificate certificate file |
| 1559 | privatekey private key file |
| 1560 | sni TLS SNI to send to remote host |
| 1561 | verify_certs file for certificate verify |
| 1562 | verify_crl CRL for verify |
| 1563 | require_ciphers list of allowed ciphers or NULL |
| 1564 | dh_min_bits minimum number of bits acceptable in server's DH prime |
| 1565 | timeout startup timeout |
| 1566 | verify_hosts mandatory client verification |
| 1567 | try_verify_hosts optional client verification |
| 1568 | |
| 1569 | Returns: OK/DEFER/FAIL (because using common functions), |
| 1570 | but for a client, DEFER and FAIL have the same meaning |
| 1571 | */ |
| 1572 | |
| 1573 | int |
| 1574 | tls_client_start(int fd, host_item *host, |
| 1575 | address_item *addr ARG_UNUSED, |
| 1576 | uschar *certificate, uschar *privatekey, uschar *sni, |
| 1577 | uschar *verify_certs, uschar *verify_crl, |
| 1578 | uschar *require_ciphers, |
| 1579 | #ifdef EXPERIMENTAL_OCSP |
| 1580 | uschar *require_ocsp ARG_UNUSED, |
| 1581 | #endif |
| 1582 | int dh_min_bits, int timeout, |
| 1583 | uschar *verify_hosts, uschar *try_verify_hosts) |
| 1584 | { |
| 1585 | int rc; |
| 1586 | const char *error; |
| 1587 | exim_gnutls_state_st *state = NULL; |
| 1588 | |
| 1589 | DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd); |
| 1590 | |
| 1591 | rc = tls_init(host, certificate, privatekey, |
| 1592 | sni, verify_certs, verify_crl, require_ciphers, &state); |
| 1593 | if (rc != OK) return rc; |
| 1594 | |
| 1595 | if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS) |
| 1596 | { |
| 1597 | DEBUG(D_tls) |
| 1598 | debug_printf("WARNING: tls_dh_min_bits far too low, clamping %d up to %d\n", |
| 1599 | dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS); |
| 1600 | dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS; |
| 1601 | } |
| 1602 | |
| 1603 | DEBUG(D_tls) debug_printf("Setting D-H prime minimum acceptable bits to %d\n", |
| 1604 | dh_min_bits); |
| 1605 | gnutls_dh_set_prime_bits(state->session, dh_min_bits); |
| 1606 | |
| 1607 | /* stick to the old behaviour for compatibility if tls_verify_certificates is |
| 1608 | set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only |
| 1609 | the specified host patterns if one of them is defined */ |
| 1610 | if (((state->exp_tls_verify_certificates != NULL) && (verify_hosts == NULL) && (try_verify_hosts == NULL)) || |
| 1611 | (verify_check_host(&verify_hosts) == OK)) |
| 1612 | { |
| 1613 | DEBUG(D_tls) debug_printf("TLS: server certificate verification required.\n"); |
| 1614 | state->verify_requirement = VERIFY_REQUIRED; |
| 1615 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); |
| 1616 | } |
| 1617 | else if (verify_check_host(&try_verify_hosts) == OK) |
| 1618 | { |
| 1619 | DEBUG(D_tls) debug_printf("TLS: server certificate verification optional.\n"); |
| 1620 | state->verify_requirement = VERIFY_OPTIONAL; |
| 1621 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); |
| 1622 | } |
| 1623 | else |
| 1624 | { |
| 1625 | DEBUG(D_tls) debug_printf("TLS: server certificate verification not required.\n"); |
| 1626 | state->verify_requirement = VERIFY_NONE; |
| 1627 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); |
| 1628 | } |
| 1629 | |
| 1630 | gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr)fd); |
| 1631 | state->fd_in = fd; |
| 1632 | state->fd_out = fd; |
| 1633 | |
| 1634 | /* There doesn't seem to be a built-in timeout on connection. */ |
| 1635 | |
| 1636 | sigalrm_seen = FALSE; |
| 1637 | alarm(timeout); |
| 1638 | do |
| 1639 | { |
| 1640 | rc = gnutls_handshake(state->session); |
| 1641 | } while ((rc == GNUTLS_E_AGAIN) || |
| 1642 | (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen)); |
| 1643 | alarm(0); |
| 1644 | |
| 1645 | if (rc != GNUTLS_E_SUCCESS) |
| 1646 | return tls_error(US"gnutls_handshake", |
| 1647 | sigalrm_seen ? "timed out" : gnutls_strerror(rc), state->host); |
| 1648 | |
| 1649 | DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); |
| 1650 | |
| 1651 | /* Verify late */ |
| 1652 | |
| 1653 | if (state->verify_requirement != VERIFY_NONE && |
| 1654 | !verify_certificate(state, &error)) |
| 1655 | return tls_error(US"certificate verification failed", error, state->host); |
| 1656 | |
| 1657 | /* Figure out peer DN, and if authenticated, etc. */ |
| 1658 | |
| 1659 | rc = peer_status(state); |
| 1660 | if (rc != OK) return rc; |
| 1661 | |
| 1662 | /* Sets various Exim expansion variables; may need to adjust for ACL callouts */ |
| 1663 | |
| 1664 | extract_exim_vars_from_tls_state(state, FALSE); |
| 1665 | |
| 1666 | return OK; |
| 1667 | } |
| 1668 | |
| 1669 | |
| 1670 | |
| 1671 | |
| 1672 | /************************************************* |
| 1673 | * Close down a TLS session * |
| 1674 | *************************************************/ |
| 1675 | |
| 1676 | /* This is also called from within a delivery subprocess forked from the |
| 1677 | daemon, to shut down the TLS library, without actually doing a shutdown (which |
| 1678 | would tamper with the TLS session in the parent process). |
| 1679 | |
| 1680 | Arguments: TRUE if gnutls_bye is to be called |
| 1681 | Returns: nothing |
| 1682 | */ |
| 1683 | |
| 1684 | void |
| 1685 | tls_close(BOOL is_server, BOOL shutdown) |
| 1686 | { |
| 1687 | exim_gnutls_state_st *state = is_server ? &state_server : &state_client; |
| 1688 | |
| 1689 | if (!state->tlsp || state->tlsp->active < 0) return; /* TLS was not active */ |
| 1690 | |
| 1691 | if (shutdown) |
| 1692 | { |
| 1693 | DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n"); |
| 1694 | gnutls_bye(state->session, GNUTLS_SHUT_WR); |
| 1695 | } |
| 1696 | |
| 1697 | gnutls_deinit(state->session); |
| 1698 | |
| 1699 | state->tlsp->active = -1; |
| 1700 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); |
| 1701 | |
| 1702 | if ((state_server.session == NULL) && (state_client.session == NULL)) |
| 1703 | { |
| 1704 | gnutls_global_deinit(); |
| 1705 | exim_gnutls_base_init_done = FALSE; |
| 1706 | } |
| 1707 | |
| 1708 | } |
| 1709 | |
| 1710 | |
| 1711 | |
| 1712 | |
| 1713 | /************************************************* |
| 1714 | * TLS version of getc * |
| 1715 | *************************************************/ |
| 1716 | |
| 1717 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, |
| 1718 | it refills the buffer via the GnuTLS reading function. |
| 1719 | Only used by the server-side TLS. |
| 1720 | |
| 1721 | This feeds DKIM and should be used for all message-body reads. |
| 1722 | |
| 1723 | Arguments: none |
| 1724 | Returns: the next character or EOF |
| 1725 | */ |
| 1726 | |
| 1727 | int |
| 1728 | tls_getc(void) |
| 1729 | { |
| 1730 | exim_gnutls_state_st *state = &state_server; |
| 1731 | if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm) |
| 1732 | { |
| 1733 | ssize_t inbytes; |
| 1734 | |
| 1735 | DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n", |
| 1736 | state->session, state->xfer_buffer, ssl_xfer_buffer_size); |
| 1737 | |
| 1738 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 1739 | inbytes = gnutls_record_recv(state->session, state->xfer_buffer, |
| 1740 | ssl_xfer_buffer_size); |
| 1741 | alarm(0); |
| 1742 | |
| 1743 | /* A zero-byte return appears to mean that the TLS session has been |
| 1744 | closed down, not that the socket itself has been closed down. Revert to |
| 1745 | non-TLS handling. */ |
| 1746 | |
| 1747 | if (inbytes == 0) |
| 1748 | { |
| 1749 | DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); |
| 1750 | |
| 1751 | receive_getc = smtp_getc; |
| 1752 | receive_ungetc = smtp_ungetc; |
| 1753 | receive_feof = smtp_feof; |
| 1754 | receive_ferror = smtp_ferror; |
| 1755 | receive_smtp_buffered = smtp_buffered; |
| 1756 | |
| 1757 | gnutls_deinit(state->session); |
| 1758 | state->session = NULL; |
| 1759 | state->tlsp->active = -1; |
| 1760 | state->tlsp->bits = 0; |
| 1761 | state->tlsp->certificate_verified = FALSE; |
| 1762 | tls_channelbinding_b64 = NULL; /*XXX JGH */ |
| 1763 | state->tlsp->cipher = NULL; |
| 1764 | state->tlsp->peerdn = NULL; |
| 1765 | |
| 1766 | return smtp_getc(); |
| 1767 | } |
| 1768 | |
| 1769 | /* Handle genuine errors */ |
| 1770 | |
| 1771 | else if (inbytes < 0) |
| 1772 | { |
| 1773 | record_io_error(state, (int) inbytes, US"recv", NULL); |
| 1774 | state->xfer_error = 1; |
| 1775 | return EOF; |
| 1776 | } |
| 1777 | #ifndef DISABLE_DKIM |
| 1778 | dkim_exim_verify_feed(state->xfer_buffer, inbytes); |
| 1779 | #endif |
| 1780 | state->xfer_buffer_hwm = (int) inbytes; |
| 1781 | state->xfer_buffer_lwm = 0; |
| 1782 | } |
| 1783 | |
| 1784 | /* Something in the buffer; return next uschar */ |
| 1785 | |
| 1786 | return state->xfer_buffer[state->xfer_buffer_lwm++]; |
| 1787 | } |
| 1788 | |
| 1789 | |
| 1790 | |
| 1791 | |
| 1792 | /************************************************* |
| 1793 | * Read bytes from TLS channel * |
| 1794 | *************************************************/ |
| 1795 | |
| 1796 | /* This does not feed DKIM, so if the caller uses this for reading message body, |
| 1797 | then the caller must feed DKIM. |
| 1798 | |
| 1799 | Arguments: |
| 1800 | buff buffer of data |
| 1801 | len size of buffer |
| 1802 | |
| 1803 | Returns: the number of bytes read |
| 1804 | -1 after a failed read |
| 1805 | */ |
| 1806 | |
| 1807 | int |
| 1808 | tls_read(BOOL is_server, uschar *buff, size_t len) |
| 1809 | { |
| 1810 | exim_gnutls_state_st *state = is_server ? &state_server : &state_client; |
| 1811 | ssize_t inbytes; |
| 1812 | |
| 1813 | if (len > INT_MAX) |
| 1814 | len = INT_MAX; |
| 1815 | |
| 1816 | if (state->xfer_buffer_lwm < state->xfer_buffer_hwm) |
| 1817 | DEBUG(D_tls) |
| 1818 | debug_printf("*** PROBABLY A BUG *** " \ |
| 1819 | "tls_read() called with data in the tls_getc() buffer, %d ignored\n", |
| 1820 | state->xfer_buffer_hwm - state->xfer_buffer_lwm); |
| 1821 | |
| 1822 | DEBUG(D_tls) |
| 1823 | debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n", |
| 1824 | state->session, buff, len); |
| 1825 | |
| 1826 | inbytes = gnutls_record_recv(state->session, buff, len); |
| 1827 | if (inbytes > 0) return inbytes; |
| 1828 | if (inbytes == 0) |
| 1829 | { |
| 1830 | DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); |
| 1831 | } |
| 1832 | else record_io_error(state, (int)inbytes, US"recv", NULL); |
| 1833 | |
| 1834 | return -1; |
| 1835 | } |
| 1836 | |
| 1837 | |
| 1838 | |
| 1839 | |
| 1840 | /************************************************* |
| 1841 | * Write bytes down TLS channel * |
| 1842 | *************************************************/ |
| 1843 | |
| 1844 | /* |
| 1845 | Arguments: |
| 1846 | is_server channel specifier |
| 1847 | buff buffer of data |
| 1848 | len number of bytes |
| 1849 | |
| 1850 | Returns: the number of bytes after a successful write, |
| 1851 | -1 after a failed write |
| 1852 | */ |
| 1853 | |
| 1854 | int |
| 1855 | tls_write(BOOL is_server, const uschar *buff, size_t len) |
| 1856 | { |
| 1857 | ssize_t outbytes; |
| 1858 | size_t left = len; |
| 1859 | exim_gnutls_state_st *state = is_server ? &state_server : &state_client; |
| 1860 | |
| 1861 | DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left); |
| 1862 | while (left > 0) |
| 1863 | { |
| 1864 | DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n", |
| 1865 | buff, left); |
| 1866 | outbytes = gnutls_record_send(state->session, buff, left); |
| 1867 | |
| 1868 | DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes); |
| 1869 | if (outbytes < 0) |
| 1870 | { |
| 1871 | record_io_error(state, outbytes, US"send", NULL); |
| 1872 | return -1; |
| 1873 | } |
| 1874 | if (outbytes == 0) |
| 1875 | { |
| 1876 | record_io_error(state, 0, US"send", US"TLS channel closed on write"); |
| 1877 | return -1; |
| 1878 | } |
| 1879 | |
| 1880 | left -= outbytes; |
| 1881 | buff += outbytes; |
| 1882 | } |
| 1883 | |
| 1884 | if (len > INT_MAX) |
| 1885 | { |
| 1886 | DEBUG(D_tls) |
| 1887 | debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n", |
| 1888 | len); |
| 1889 | len = INT_MAX; |
| 1890 | } |
| 1891 | |
| 1892 | return (int) len; |
| 1893 | } |
| 1894 | |
| 1895 | |
| 1896 | |
| 1897 | |
| 1898 | /************************************************* |
| 1899 | * Random number generation * |
| 1900 | *************************************************/ |
| 1901 | |
| 1902 | /* Pseudo-random number generation. The result is not expected to be |
| 1903 | cryptographically strong but not so weak that someone will shoot themselves |
| 1904 | in the foot using it as a nonce in input in some email header scheme or |
| 1905 | whatever weirdness they'll twist this into. The result should handle fork() |
| 1906 | and avoid repeating sequences. OpenSSL handles that for us. |
| 1907 | |
| 1908 | Arguments: |
| 1909 | max range maximum |
| 1910 | Returns a random number in range [0, max-1] |
| 1911 | */ |
| 1912 | |
| 1913 | #ifdef HAVE_GNUTLS_RND |
| 1914 | int |
| 1915 | vaguely_random_number(int max) |
| 1916 | { |
| 1917 | unsigned int r; |
| 1918 | int i, needed_len; |
| 1919 | uschar *p; |
| 1920 | uschar smallbuf[sizeof(r)]; |
| 1921 | |
| 1922 | if (max <= 1) |
| 1923 | return 0; |
| 1924 | |
| 1925 | needed_len = sizeof(r); |
| 1926 | /* Don't take 8 times more entropy than needed if int is 8 octets and we were |
| 1927 | * asked for a number less than 10. */ |
| 1928 | for (r = max, i = 0; r; ++i) |
| 1929 | r >>= 1; |
| 1930 | i = (i + 7) / 8; |
| 1931 | if (i < needed_len) |
| 1932 | needed_len = i; |
| 1933 | |
| 1934 | i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len); |
| 1935 | if (i < 0) |
| 1936 | { |
| 1937 | DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n"); |
| 1938 | return vaguely_random_number_fallback(max); |
| 1939 | } |
| 1940 | r = 0; |
| 1941 | for (p = smallbuf; needed_len; --needed_len, ++p) |
| 1942 | { |
| 1943 | r *= 256; |
| 1944 | r += *p; |
| 1945 | } |
| 1946 | |
| 1947 | /* We don't particularly care about weighted results; if someone wants |
| 1948 | * smooth distribution and cares enough then they should submit a patch then. */ |
| 1949 | return r % max; |
| 1950 | } |
| 1951 | #else /* HAVE_GNUTLS_RND */ |
| 1952 | int |
| 1953 | vaguely_random_number(int max) |
| 1954 | { |
| 1955 | return vaguely_random_number_fallback(max); |
| 1956 | } |
| 1957 | #endif /* HAVE_GNUTLS_RND */ |
| 1958 | |
| 1959 | |
| 1960 | |
| 1961 | |
| 1962 | /************************************************* |
| 1963 | * Let tls_require_ciphers be checked at startup * |
| 1964 | *************************************************/ |
| 1965 | |
| 1966 | /* The tls_require_ciphers option, if set, must be something which the |
| 1967 | library can parse. |
| 1968 | |
| 1969 | Returns: NULL on success, or error message |
| 1970 | */ |
| 1971 | |
| 1972 | uschar * |
| 1973 | tls_validate_require_cipher(void) |
| 1974 | { |
| 1975 | int rc; |
| 1976 | uschar *expciphers = NULL; |
| 1977 | gnutls_priority_t priority_cache; |
| 1978 | const char *errpos; |
| 1979 | |
| 1980 | #define validate_check_rc(Label) do { \ |
| 1981 | if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \ |
| 1982 | return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0) |
| 1983 | #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0) |
| 1984 | |
| 1985 | if (exim_gnutls_base_init_done) |
| 1986 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 1987 | "already initialised GnuTLS, Exim developer bug"); |
| 1988 | |
| 1989 | #ifdef HAVE_GNUTLS_PKCS11 |
| 1990 | if (!gnutls_allow_auto_pkcs11) |
| 1991 | { |
| 1992 | rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL); |
| 1993 | validate_check_rc(US"gnutls_pkcs11_init"); |
| 1994 | } |
| 1995 | #endif |
| 1996 | rc = gnutls_global_init(); |
| 1997 | validate_check_rc(US"gnutls_global_init()"); |
| 1998 | exim_gnutls_base_init_done = TRUE; |
| 1999 | |
| 2000 | if (!(tls_require_ciphers && *tls_require_ciphers)) |
| 2001 | return_deinit(NULL); |
| 2002 | |
| 2003 | if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers)) |
| 2004 | return_deinit(US"failed to expand tls_require_ciphers"); |
| 2005 | |
| 2006 | if (!(expciphers && *expciphers)) |
| 2007 | return_deinit(NULL); |
| 2008 | |
| 2009 | DEBUG(D_tls) |
| 2010 | debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers); |
| 2011 | |
| 2012 | rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos); |
| 2013 | validate_check_rc(string_sprintf( |
| 2014 | "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"", |
| 2015 | expciphers, errpos - CS expciphers, errpos)); |
| 2016 | |
| 2017 | #undef return_deinit |
| 2018 | #undef validate_check_rc |
| 2019 | gnutls_global_deinit(); |
| 2020 | |
| 2021 | return NULL; |
| 2022 | } |
| 2023 | |
| 2024 | |
| 2025 | |
| 2026 | |
| 2027 | /************************************************* |
| 2028 | * Report the library versions. * |
| 2029 | *************************************************/ |
| 2030 | |
| 2031 | /* See a description in tls-openssl.c for an explanation of why this exists. |
| 2032 | |
| 2033 | Arguments: a FILE* to print the results to |
| 2034 | Returns: nothing |
| 2035 | */ |
| 2036 | |
| 2037 | void |
| 2038 | tls_version_report(FILE *f) |
| 2039 | { |
| 2040 | fprintf(f, "Library version: GnuTLS: Compile: %s\n" |
| 2041 | " Runtime: %s\n", |
| 2042 | LIBGNUTLS_VERSION, |
| 2043 | gnutls_check_version(NULL)); |
| 2044 | } |
| 2045 | |
| 2046 | /* End of tls-gnu.c */ |