| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2015 */ |
| 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 | Mavrogiannopoulos. 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 | # define SUPPORT_PARAM_TO_PK_BITS |
| 46 | #endif |
| 47 | #if GNUTLS_VERSION_NUMBER < 0x030103 && !defined(DISABLE_OCSP) |
| 48 | # warning "GnuTLS library version too old; define DISABLE_OCSP in Makefile" |
| 49 | # define DISABLE_OCSP |
| 50 | #endif |
| 51 | #if GNUTLS_VERSION_NUMBER < 0x020a00 && !defined(DISABLE_EVENT) |
| 52 | # warning "GnuTLS library version too old; tls:cert event unsupported" |
| 53 | # define DISABLE_EVENT |
| 54 | #endif |
| 55 | #if GNUTLS_VERSION_NUMBER >= 0x030306 |
| 56 | # define SUPPORT_CA_DIR |
| 57 | #else |
| 58 | # undef SUPPORT_CA_DIR |
| 59 | #endif |
| 60 | #if GNUTLS_VERSION_NUMBER >= 0x030014 |
| 61 | # define SUPPORT_SYSDEFAULT_CABUNDLE |
| 62 | #endif |
| 63 | |
| 64 | #ifndef DISABLE_OCSP |
| 65 | # include <gnutls/ocsp.h> |
| 66 | #endif |
| 67 | |
| 68 | /* GnuTLS 2 vs 3 |
| 69 | |
| 70 | GnuTLS 3 only: |
| 71 | gnutls_global_set_audit_log_function() |
| 72 | |
| 73 | Changes: |
| 74 | gnutls_certificate_verify_peers2(): is new, drop the 2 for old version |
| 75 | */ |
| 76 | |
| 77 | /* Local static variables for GnuTLS */ |
| 78 | |
| 79 | /* Values for verify_requirement */ |
| 80 | |
| 81 | enum peer_verify_requirement |
| 82 | { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED }; |
| 83 | |
| 84 | /* This holds most state for server or client; with this, we can set up an |
| 85 | outbound TLS-enabled connection in an ACL callout, while not stomping all |
| 86 | over the TLS variables available for expansion. |
| 87 | |
| 88 | Some of these correspond to variables in globals.c; those variables will |
| 89 | be set to point to content in one of these instances, as appropriate for |
| 90 | the stage of the process lifetime. |
| 91 | |
| 92 | Not handled here: global tls_channelbinding_b64. |
| 93 | */ |
| 94 | |
| 95 | typedef struct exim_gnutls_state { |
| 96 | gnutls_session_t session; |
| 97 | gnutls_certificate_credentials_t x509_cred; |
| 98 | gnutls_priority_t priority_cache; |
| 99 | enum peer_verify_requirement verify_requirement; |
| 100 | int fd_in; |
| 101 | int fd_out; |
| 102 | BOOL peer_cert_verified; |
| 103 | BOOL trigger_sni_changes; |
| 104 | BOOL have_set_peerdn; |
| 105 | const struct host_item *host; |
| 106 | gnutls_x509_crt_t peercert; |
| 107 | uschar *peerdn; |
| 108 | uschar *ciphersuite; |
| 109 | uschar *received_sni; |
| 110 | |
| 111 | const uschar *tls_certificate; |
| 112 | const uschar *tls_privatekey; |
| 113 | const uschar *tls_sni; /* client send only, not received */ |
| 114 | const uschar *tls_verify_certificates; |
| 115 | const uschar *tls_crl; |
| 116 | const uschar *tls_require_ciphers; |
| 117 | |
| 118 | uschar *exp_tls_certificate; |
| 119 | uschar *exp_tls_privatekey; |
| 120 | uschar *exp_tls_verify_certificates; |
| 121 | uschar *exp_tls_crl; |
| 122 | uschar *exp_tls_require_ciphers; |
| 123 | uschar *exp_tls_ocsp_file; |
| 124 | const uschar *exp_tls_verify_cert_hostnames; |
| 125 | #ifndef DISABLE_EVENT |
| 126 | uschar *event_action; |
| 127 | #endif |
| 128 | |
| 129 | tls_support *tlsp; /* set in tls_init() */ |
| 130 | |
| 131 | uschar *xfer_buffer; |
| 132 | int xfer_buffer_lwm; |
| 133 | int xfer_buffer_hwm; |
| 134 | int xfer_eof; |
| 135 | int xfer_error; |
| 136 | } exim_gnutls_state_st; |
| 137 | |
| 138 | static const exim_gnutls_state_st exim_gnutls_state_init = { |
| 139 | NULL, NULL, NULL, VERIFY_NONE, -1, -1, FALSE, FALSE, FALSE, |
| 140 | NULL, NULL, NULL, NULL, |
| 141 | NULL, NULL, NULL, NULL, NULL, NULL, |
| 142 | NULL, NULL, NULL, NULL, NULL, NULL, NULL, |
| 143 | NULL, |
| 144 | #ifndef DISABLE_EVENT |
| 145 | NULL, |
| 146 | #endif |
| 147 | NULL, |
| 148 | NULL, 0, 0, 0, 0, |
| 149 | }; |
| 150 | |
| 151 | /* Not only do we have our own APIs which don't pass around state, assuming |
| 152 | it's held in globals, GnuTLS doesn't appear to let us register callback data |
| 153 | for callbacks, or as part of the session, so we have to keep a "this is the |
| 154 | context we're currently dealing with" pointer and rely upon being |
| 155 | single-threaded to keep from processing data on an inbound TLS connection while |
| 156 | talking to another TLS connection for an outbound check. This does mean that |
| 157 | there's no way for heart-beats to be responded to, for the duration of the |
| 158 | second connection. |
| 159 | XXX But see gnutls_session_get_ptr() |
| 160 | */ |
| 161 | |
| 162 | static exim_gnutls_state_st state_server, state_client; |
| 163 | |
| 164 | /* dh_params are initialised once within the lifetime of a process using TLS; |
| 165 | if we used TLS in a long-lived daemon, we'd have to reconsider this. But we |
| 166 | don't want to repeat this. */ |
| 167 | |
| 168 | static gnutls_dh_params_t dh_server_params = NULL; |
| 169 | |
| 170 | /* No idea how this value was chosen; preserving it. Default is 3600. */ |
| 171 | |
| 172 | static const int ssl_session_timeout = 200; |
| 173 | |
| 174 | static const char * const exim_default_gnutls_priority = "NORMAL"; |
| 175 | |
| 176 | /* Guard library core initialisation */ |
| 177 | |
| 178 | static BOOL exim_gnutls_base_init_done = FALSE; |
| 179 | |
| 180 | #ifndef DISABLE_OCSP |
| 181 | static BOOL gnutls_buggy_ocsp = FALSE; |
| 182 | #endif |
| 183 | |
| 184 | |
| 185 | /* ------------------------------------------------------------------------ */ |
| 186 | /* macros */ |
| 187 | |
| 188 | #define MAX_HOST_LEN 255 |
| 189 | |
| 190 | /* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup |
| 191 | the library logging; a value less than 0 disables the calls to set up logging |
| 192 | callbacks. */ |
| 193 | #ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL |
| 194 | # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1 |
| 195 | #endif |
| 196 | |
| 197 | #ifndef EXIM_CLIENT_DH_MIN_BITS |
| 198 | # define EXIM_CLIENT_DH_MIN_BITS 1024 |
| 199 | #endif |
| 200 | |
| 201 | /* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we |
| 202 | can ask for a bit-strength. Without that, we stick to the constant we had |
| 203 | before, for now. */ |
| 204 | #ifndef EXIM_SERVER_DH_BITS_PRE2_12 |
| 205 | # define EXIM_SERVER_DH_BITS_PRE2_12 1024 |
| 206 | #endif |
| 207 | |
| 208 | #define exim_gnutls_err_check(Label) do { \ |
| 209 | if (rc != GNUTLS_E_SUCCESS) { return tls_error((Label), gnutls_strerror(rc), host); } } while (0) |
| 210 | |
| 211 | #define expand_check_tlsvar(Varname) expand_check(state->Varname, US #Varname, &state->exp_##Varname) |
| 212 | |
| 213 | #if GNUTLS_VERSION_NUMBER >= 0x020c00 |
| 214 | # define HAVE_GNUTLS_SESSION_CHANNEL_BINDING |
| 215 | # define HAVE_GNUTLS_SEC_PARAM_CONSTANTS |
| 216 | # define HAVE_GNUTLS_RND |
| 217 | /* The security fix we provide with the gnutls_allow_auto_pkcs11 option |
| 218 | * (4.82 PP/09) introduces a compatibility regression. The symbol simply |
| 219 | * isn't available sometimes, so this needs to become a conditional |
| 220 | * compilation; the sanest way to deal with this being a problem on |
| 221 | * older OSes is to block it in the Local/Makefile with this compiler |
| 222 | * definition */ |
| 223 | # ifndef AVOID_GNUTLS_PKCS11 |
| 224 | # define HAVE_GNUTLS_PKCS11 |
| 225 | # endif /* AVOID_GNUTLS_PKCS11 */ |
| 226 | #endif |
| 227 | |
| 228 | |
| 229 | |
| 230 | |
| 231 | /* ------------------------------------------------------------------------ */ |
| 232 | /* Callback declarations */ |
| 233 | |
| 234 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
| 235 | static void exim_gnutls_logger_cb(int level, const char *message); |
| 236 | #endif |
| 237 | |
| 238 | static int exim_sni_handling_cb(gnutls_session_t session); |
| 239 | |
| 240 | #ifndef DISABLE_OCSP |
| 241 | static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr, |
| 242 | gnutls_datum_t * ocsp_response); |
| 243 | #endif |
| 244 | |
| 245 | |
| 246 | |
| 247 | /* ------------------------------------------------------------------------ */ |
| 248 | /* Static functions */ |
| 249 | |
| 250 | /************************************************* |
| 251 | * Handle TLS error * |
| 252 | *************************************************/ |
| 253 | |
| 254 | /* Called from lots of places when errors occur before actually starting to do |
| 255 | the TLS handshake, that is, while the session is still in clear. Always returns |
| 256 | DEFER for a server and FAIL for a client so that most calls can use "return |
| 257 | tls_error(...)" to do this processing and then give an appropriate return. A |
| 258 | single function is used for both server and client, because it is called from |
| 259 | some shared functions. |
| 260 | |
| 261 | Argument: |
| 262 | prefix text to include in the logged error |
| 263 | msg additional error string (may be NULL) |
| 264 | usually obtained from gnutls_strerror() |
| 265 | host NULL if setting up a server; |
| 266 | the connected host if setting up a client |
| 267 | |
| 268 | Returns: OK/DEFER/FAIL |
| 269 | */ |
| 270 | |
| 271 | static int |
| 272 | tls_error(const uschar *prefix, const char *msg, const host_item *host) |
| 273 | { |
| 274 | if (host) |
| 275 | { |
| 276 | log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection (%s)%s%s", |
| 277 | host->name, host->address, prefix, msg ? ": " : "", msg ? msg : ""); |
| 278 | return FAIL; |
| 279 | } |
| 280 | else |
| 281 | { |
| 282 | uschar *conn_info = smtp_get_connection_info(); |
| 283 | if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) |
| 284 | conn_info += 5; |
| 285 | /* I'd like to get separated H= here, but too hard for now */ |
| 286 | log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s", |
| 287 | conn_info, prefix, msg ? ": " : "", msg ? msg : ""); |
| 288 | return DEFER; |
| 289 | } |
| 290 | } |
| 291 | |
| 292 | |
| 293 | |
| 294 | |
| 295 | /************************************************* |
| 296 | * Deal with logging errors during I/O * |
| 297 | *************************************************/ |
| 298 | |
| 299 | /* We have to get the identity of the peer from saved data. |
| 300 | |
| 301 | Argument: |
| 302 | state the current GnuTLS exim state container |
| 303 | rc the GnuTLS error code, or 0 if it's a local error |
| 304 | when text identifying read or write |
| 305 | text local error text when ec is 0 |
| 306 | |
| 307 | Returns: nothing |
| 308 | */ |
| 309 | |
| 310 | static void |
| 311 | record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text) |
| 312 | { |
| 313 | const char *msg; |
| 314 | |
| 315 | if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED) |
| 316 | msg = CS string_sprintf("%s: %s", US gnutls_strerror(rc), |
| 317 | US gnutls_alert_get_name(gnutls_alert_get(state->session))); |
| 318 | else |
| 319 | msg = gnutls_strerror(rc); |
| 320 | |
| 321 | tls_error(when, msg, state->host); |
| 322 | } |
| 323 | |
| 324 | |
| 325 | |
| 326 | |
| 327 | /************************************************* |
| 328 | * Set various Exim expansion vars * |
| 329 | *************************************************/ |
| 330 | |
| 331 | #define exim_gnutls_cert_err(Label) \ |
| 332 | do \ |
| 333 | { \ |
| 334 | if (rc != GNUTLS_E_SUCCESS) \ |
| 335 | { \ |
| 336 | DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \ |
| 337 | (Label), gnutls_strerror(rc)); \ |
| 338 | return rc; \ |
| 339 | } \ |
| 340 | } while (0) |
| 341 | |
| 342 | static int |
| 343 | import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp) |
| 344 | { |
| 345 | int rc; |
| 346 | |
| 347 | rc = gnutls_x509_crt_init(crtp); |
| 348 | exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)"); |
| 349 | |
| 350 | rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER); |
| 351 | exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]"); |
| 352 | |
| 353 | return rc; |
| 354 | } |
| 355 | |
| 356 | #undef exim_gnutls_cert_err |
| 357 | |
| 358 | |
| 359 | /* We set various Exim global variables from the state, once a session has |
| 360 | been established. With TLS callouts, may need to change this to stack |
| 361 | variables, or just re-call it with the server state after client callout |
| 362 | has finished. |
| 363 | |
| 364 | Make sure anything set here is unset in tls_getc(). |
| 365 | |
| 366 | Sets: |
| 367 | tls_active fd |
| 368 | tls_bits strength indicator |
| 369 | tls_certificate_verified bool indicator |
| 370 | tls_channelbinding_b64 for some SASL mechanisms |
| 371 | tls_cipher a string |
| 372 | tls_peercert pointer to library internal |
| 373 | tls_peerdn a string |
| 374 | tls_sni a (UTF-8) string |
| 375 | tls_ourcert pointer to library internal |
| 376 | |
| 377 | Argument: |
| 378 | state the relevant exim_gnutls_state_st * |
| 379 | */ |
| 380 | |
| 381 | static void |
| 382 | extract_exim_vars_from_tls_state(exim_gnutls_state_st * state) |
| 383 | { |
| 384 | gnutls_cipher_algorithm_t cipher; |
| 385 | #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING |
| 386 | int old_pool; |
| 387 | int rc; |
| 388 | gnutls_datum_t channel; |
| 389 | #endif |
| 390 | tls_support * tlsp = state->tlsp; |
| 391 | |
| 392 | tlsp->active = state->fd_out; |
| 393 | |
| 394 | cipher = gnutls_cipher_get(state->session); |
| 395 | /* returns size in "bytes" */ |
| 396 | tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8; |
| 397 | |
| 398 | tlsp->cipher = state->ciphersuite; |
| 399 | |
| 400 | DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite); |
| 401 | |
| 402 | tlsp->certificate_verified = state->peer_cert_verified; |
| 403 | |
| 404 | /* note that tls_channelbinding_b64 is not saved to the spool file, since it's |
| 405 | only available for use for authenticators while this TLS session is running. */ |
| 406 | |
| 407 | tls_channelbinding_b64 = NULL; |
| 408 | #ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING |
| 409 | channel.data = NULL; |
| 410 | channel.size = 0; |
| 411 | rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel); |
| 412 | if (rc) { |
| 413 | DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); |
| 414 | } else { |
| 415 | old_pool = store_pool; |
| 416 | store_pool = POOL_PERM; |
| 417 | tls_channelbinding_b64 = b64encode(channel.data, (int)channel.size); |
| 418 | store_pool = old_pool; |
| 419 | DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n"); |
| 420 | } |
| 421 | #endif |
| 422 | |
| 423 | /* peercert is set in peer_status() */ |
| 424 | tlsp->peerdn = state->peerdn; |
| 425 | tlsp->sni = state->received_sni; |
| 426 | |
| 427 | /* record our certificate */ |
| 428 | { |
| 429 | const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session); |
| 430 | gnutls_x509_crt_t crt; |
| 431 | |
| 432 | tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL; |
| 433 | } |
| 434 | } |
| 435 | |
| 436 | |
| 437 | |
| 438 | |
| 439 | /************************************************* |
| 440 | * Setup up DH parameters * |
| 441 | *************************************************/ |
| 442 | |
| 443 | /* Generating the D-H parameters may take a long time. They only need to |
| 444 | be re-generated every so often, depending on security policy. What we do is to |
| 445 | keep these parameters in a file in the spool directory. If the file does not |
| 446 | exist, we generate them. This means that it is easy to cause a regeneration. |
| 447 | |
| 448 | The new file is written as a temporary file and renamed, so that an incomplete |
| 449 | file is never present. If two processes both compute some new parameters, you |
| 450 | waste a bit of effort, but it doesn't seem worth messing around with locking to |
| 451 | prevent this. |
| 452 | |
| 453 | Returns: OK/DEFER/FAIL |
| 454 | */ |
| 455 | |
| 456 | static int |
| 457 | init_server_dh(void) |
| 458 | { |
| 459 | int fd, rc; |
| 460 | unsigned int dh_bits; |
| 461 | gnutls_datum_t m; |
| 462 | uschar filename_buf[PATH_MAX]; |
| 463 | uschar *filename = NULL; |
| 464 | size_t sz; |
| 465 | uschar *exp_tls_dhparam; |
| 466 | BOOL use_file_in_spool = FALSE; |
| 467 | BOOL use_fixed_file = FALSE; |
| 468 | host_item *host = NULL; /* dummy for macros */ |
| 469 | |
| 470 | DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n"); |
| 471 | |
| 472 | rc = gnutls_dh_params_init(&dh_server_params); |
| 473 | exim_gnutls_err_check(US"gnutls_dh_params_init"); |
| 474 | |
| 475 | m.data = NULL; |
| 476 | m.size = 0; |
| 477 | |
| 478 | if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam)) |
| 479 | return DEFER; |
| 480 | |
| 481 | if (!exp_tls_dhparam) |
| 482 | { |
| 483 | DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n"); |
| 484 | m.data = US std_dh_prime_default(); |
| 485 | m.size = Ustrlen(m.data); |
| 486 | } |
| 487 | else if (Ustrcmp(exp_tls_dhparam, "historic") == 0) |
| 488 | use_file_in_spool = TRUE; |
| 489 | else if (Ustrcmp(exp_tls_dhparam, "none") == 0) |
| 490 | { |
| 491 | DEBUG(D_tls) debug_printf("Requested no DH parameters.\n"); |
| 492 | return OK; |
| 493 | } |
| 494 | else if (exp_tls_dhparam[0] != '/') |
| 495 | { |
| 496 | if (!(m.data = US std_dh_prime_named(exp_tls_dhparam))) |
| 497 | return tls_error(US"No standard prime named", CS exp_tls_dhparam, NULL); |
| 498 | m.size = Ustrlen(m.data); |
| 499 | } |
| 500 | else |
| 501 | { |
| 502 | use_fixed_file = TRUE; |
| 503 | filename = exp_tls_dhparam; |
| 504 | } |
| 505 | |
| 506 | if (m.data) |
| 507 | { |
| 508 | rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); |
| 509 | exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3"); |
| 510 | DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n"); |
| 511 | return OK; |
| 512 | } |
| 513 | |
| 514 | #ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS |
| 515 | /* If you change this constant, also change dh_param_fn_ext so that we can use a |
| 516 | different filename and ensure we have sufficient bits. */ |
| 517 | dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL); |
| 518 | if (!dh_bits) |
| 519 | return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL); |
| 520 | DEBUG(D_tls) |
| 521 | debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n", |
| 522 | dh_bits); |
| 523 | #else |
| 524 | dh_bits = EXIM_SERVER_DH_BITS_PRE2_12; |
| 525 | DEBUG(D_tls) |
| 526 | debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n", |
| 527 | dh_bits); |
| 528 | #endif |
| 529 | |
| 530 | /* Some clients have hard-coded limits. */ |
| 531 | if (dh_bits > tls_dh_max_bits) |
| 532 | { |
| 533 | DEBUG(D_tls) |
| 534 | debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n", |
| 535 | tls_dh_max_bits); |
| 536 | dh_bits = tls_dh_max_bits; |
| 537 | } |
| 538 | |
| 539 | if (use_file_in_spool) |
| 540 | { |
| 541 | if (!string_format(filename_buf, sizeof(filename_buf), |
| 542 | "%s/gnutls-params-%d", spool_directory, dh_bits)) |
| 543 | return tls_error(US"overlong filename", NULL, NULL); |
| 544 | filename = filename_buf; |
| 545 | } |
| 546 | |
| 547 | /* Open the cache file for reading and if successful, read it and set up the |
| 548 | parameters. */ |
| 549 | |
| 550 | if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0) |
| 551 | { |
| 552 | struct stat statbuf; |
| 553 | FILE *fp; |
| 554 | int saved_errno; |
| 555 | |
| 556 | if (fstat(fd, &statbuf) < 0) /* EIO */ |
| 557 | { |
| 558 | saved_errno = errno; |
| 559 | (void)close(fd); |
| 560 | return tls_error(US"TLS cache stat failed", strerror(saved_errno), NULL); |
| 561 | } |
| 562 | if (!S_ISREG(statbuf.st_mode)) |
| 563 | { |
| 564 | (void)close(fd); |
| 565 | return tls_error(US"TLS cache not a file", NULL, NULL); |
| 566 | } |
| 567 | if (!(fp = fdopen(fd, "rb"))) |
| 568 | { |
| 569 | saved_errno = errno; |
| 570 | (void)close(fd); |
| 571 | return tls_error(US"fdopen(TLS cache stat fd) failed", |
| 572 | strerror(saved_errno), NULL); |
| 573 | } |
| 574 | |
| 575 | m.size = statbuf.st_size; |
| 576 | if (!(m.data = malloc(m.size))) |
| 577 | { |
| 578 | fclose(fp); |
| 579 | return tls_error(US"malloc failed", strerror(errno), NULL); |
| 580 | } |
| 581 | if (!(sz = fread(m.data, m.size, 1, fp))) |
| 582 | { |
| 583 | saved_errno = errno; |
| 584 | fclose(fp); |
| 585 | free(m.data); |
| 586 | return tls_error(US"fread failed", strerror(saved_errno), NULL); |
| 587 | } |
| 588 | fclose(fp); |
| 589 | |
| 590 | rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); |
| 591 | free(m.data); |
| 592 | exim_gnutls_err_check(US"gnutls_dh_params_import_pkcs3"); |
| 593 | DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename); |
| 594 | } |
| 595 | |
| 596 | /* If the file does not exist, fall through to compute new data and cache it. |
| 597 | If there was any other opening error, it is serious. */ |
| 598 | |
| 599 | else if (errno == ENOENT) |
| 600 | { |
| 601 | rc = -1; |
| 602 | DEBUG(D_tls) |
| 603 | debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename); |
| 604 | } |
| 605 | else |
| 606 | return tls_error(string_open_failed(errno, "\"%s\" for reading", filename), |
| 607 | NULL, NULL); |
| 608 | |
| 609 | /* If ret < 0, either the cache file does not exist, or the data it contains |
| 610 | is not useful. One particular case of this is when upgrading from an older |
| 611 | release of Exim in which the data was stored in a different format. We don't |
| 612 | try to be clever and support both formats; we just regenerate new data in this |
| 613 | case. */ |
| 614 | |
| 615 | if (rc < 0) |
| 616 | { |
| 617 | uschar *temp_fn; |
| 618 | unsigned int dh_bits_gen = dh_bits; |
| 619 | |
| 620 | if ((PATH_MAX - Ustrlen(filename)) < 10) |
| 621 | return tls_error(US"Filename too long to generate replacement", |
| 622 | CS filename, NULL); |
| 623 | |
| 624 | temp_fn = string_copy(US "%s.XXXXXXX"); |
| 625 | if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */ |
| 626 | return tls_error(US"Unable to open temp file", strerror(errno), NULL); |
| 627 | (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */ |
| 628 | |
| 629 | /* GnuTLS overshoots! |
| 630 | * If we ask for 2236, we might get 2237 or more. |
| 631 | * But there's no way to ask GnuTLS how many bits there really are. |
| 632 | * We can ask how many bits were used in a TLS session, but that's it! |
| 633 | * The prime itself is hidden behind too much abstraction. |
| 634 | * So we ask for less, and proceed on a wing and a prayer. |
| 635 | * First attempt, subtracted 3 for 2233 and got 2240. |
| 636 | */ |
| 637 | if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10) |
| 638 | { |
| 639 | dh_bits_gen = dh_bits - 10; |
| 640 | DEBUG(D_tls) |
| 641 | debug_printf("being paranoid about DH generation, make it '%d' bits'\n", |
| 642 | dh_bits_gen); |
| 643 | } |
| 644 | |
| 645 | DEBUG(D_tls) |
| 646 | debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n", |
| 647 | dh_bits_gen); |
| 648 | rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen); |
| 649 | exim_gnutls_err_check(US"gnutls_dh_params_generate2"); |
| 650 | |
| 651 | /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time, |
| 652 | and I confirmed that a NULL call to get the size first is how the GnuTLS |
| 653 | sample apps handle this. */ |
| 654 | |
| 655 | sz = 0; |
| 656 | m.data = NULL; |
| 657 | rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, |
| 658 | m.data, &sz); |
| 659 | if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) |
| 660 | exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3(NULL) sizing"); |
| 661 | m.size = sz; |
| 662 | if (!(m.data = malloc(m.size))) |
| 663 | return tls_error(US"memory allocation failed", strerror(errno), NULL); |
| 664 | |
| 665 | /* this will return a size 1 less than the allocation size above */ |
| 666 | rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, |
| 667 | m.data, &sz); |
| 668 | if (rc != GNUTLS_E_SUCCESS) |
| 669 | { |
| 670 | free(m.data); |
| 671 | exim_gnutls_err_check(US"gnutls_dh_params_export_pkcs3() real"); |
| 672 | } |
| 673 | m.size = sz; /* shrink by 1, probably */ |
| 674 | |
| 675 | if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size) |
| 676 | { |
| 677 | free(m.data); |
| 678 | return tls_error(US"TLS cache write D-H params failed", |
| 679 | strerror(errno), NULL); |
| 680 | } |
| 681 | free(m.data); |
| 682 | if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1) |
| 683 | return tls_error(US"TLS cache write D-H params final newline failed", |
| 684 | strerror(errno), NULL); |
| 685 | |
| 686 | if ((rc = close(fd))) |
| 687 | return tls_error(US"TLS cache write close() failed", strerror(errno), NULL); |
| 688 | |
| 689 | if (Urename(temp_fn, filename) < 0) |
| 690 | return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"", |
| 691 | temp_fn, filename), strerror(errno), NULL); |
| 692 | |
| 693 | DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename); |
| 694 | } |
| 695 | |
| 696 | DEBUG(D_tls) debug_printf("initialized server D-H parameters\n"); |
| 697 | return OK; |
| 698 | } |
| 699 | |
| 700 | |
| 701 | |
| 702 | |
| 703 | /* Create and install a selfsigned certificate, for use in server mode */ |
| 704 | |
| 705 | static int |
| 706 | tls_install_selfsign(exim_gnutls_state_st * state) |
| 707 | { |
| 708 | gnutls_x509_crt_t cert = NULL; |
| 709 | time_t now; |
| 710 | gnutls_x509_privkey_t pkey = NULL; |
| 711 | const uschar * where; |
| 712 | int rc; |
| 713 | |
| 714 | where = US"initialising pkey"; |
| 715 | if ((rc = gnutls_x509_privkey_init(&pkey))) goto err; |
| 716 | |
| 717 | where = US"initialising cert"; |
| 718 | if ((rc = gnutls_x509_crt_init(&cert))) goto err; |
| 719 | |
| 720 | where = US"generating pkey"; |
| 721 | if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA, |
| 722 | #ifdef SUPPORT_PARAM_TO_PK_BITS |
| 723 | gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_LOW), |
| 724 | #else |
| 725 | 1024, |
| 726 | #endif |
| 727 | 0))) |
| 728 | goto err; |
| 729 | |
| 730 | where = US"configuring cert"; |
| 731 | now = 0; |
| 732 | if ( (rc = gnutls_x509_crt_set_version(cert, 3)) |
| 733 | || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now))) |
| 734 | || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL))) |
| 735 | || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */ |
| 736 | || (rc = gnutls_x509_crt_set_key(cert, pkey)) |
| 737 | |
| 738 | || (rc = gnutls_x509_crt_set_dn_by_oid(cert, |
| 739 | GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2)) |
| 740 | || (rc = gnutls_x509_crt_set_dn_by_oid(cert, |
| 741 | GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15)) |
| 742 | || (rc = gnutls_x509_crt_set_dn_by_oid(cert, |
| 743 | GNUTLS_OID_X520_COMMON_NAME, 0, |
| 744 | smtp_active_hostname, Ustrlen(smtp_active_hostname))) |
| 745 | ) |
| 746 | goto err; |
| 747 | |
| 748 | where = US"signing cert"; |
| 749 | if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err; |
| 750 | |
| 751 | where = US"installing selfsign cert"; |
| 752 | /* Since: 2.4.0 */ |
| 753 | if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey))) |
| 754 | goto err; |
| 755 | |
| 756 | rc = OK; |
| 757 | |
| 758 | out: |
| 759 | if (cert) gnutls_x509_crt_deinit(cert); |
| 760 | if (pkey) gnutls_x509_privkey_deinit(pkey); |
| 761 | return rc; |
| 762 | |
| 763 | err: |
| 764 | rc = tls_error(where, gnutls_strerror(rc), NULL); |
| 765 | goto out; |
| 766 | } |
| 767 | |
| 768 | |
| 769 | |
| 770 | |
| 771 | /************************************************* |
| 772 | * Variables re-expanded post-SNI * |
| 773 | *************************************************/ |
| 774 | |
| 775 | /* Called from both server and client code, via tls_init(), and also from |
| 776 | the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni". |
| 777 | |
| 778 | We can tell the two apart by state->received_sni being non-NULL in callback. |
| 779 | |
| 780 | The callback should not call us unless state->trigger_sni_changes is true, |
| 781 | which we are responsible for setting on the first pass through. |
| 782 | |
| 783 | Arguments: |
| 784 | state exim_gnutls_state_st * |
| 785 | |
| 786 | Returns: OK/DEFER/FAIL |
| 787 | */ |
| 788 | |
| 789 | static int |
| 790 | tls_expand_session_files(exim_gnutls_state_st *state) |
| 791 | { |
| 792 | struct stat statbuf; |
| 793 | int rc; |
| 794 | const host_item *host = state->host; /* macro should be reconsidered? */ |
| 795 | uschar *saved_tls_certificate = NULL; |
| 796 | uschar *saved_tls_privatekey = NULL; |
| 797 | uschar *saved_tls_verify_certificates = NULL; |
| 798 | uschar *saved_tls_crl = NULL; |
| 799 | int cert_count; |
| 800 | |
| 801 | /* We check for tls_sni *before* expansion. */ |
| 802 | if (!host) /* server */ |
| 803 | if (!state->received_sni) |
| 804 | { |
| 805 | if (state->tls_certificate && |
| 806 | (Ustrstr(state->tls_certificate, US"tls_sni") || |
| 807 | Ustrstr(state->tls_certificate, US"tls_in_sni") || |
| 808 | Ustrstr(state->tls_certificate, US"tls_out_sni") |
| 809 | )) |
| 810 | { |
| 811 | DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n"); |
| 812 | state->trigger_sni_changes = TRUE; |
| 813 | } |
| 814 | } |
| 815 | else |
| 816 | { |
| 817 | /* useful for debugging */ |
| 818 | saved_tls_certificate = state->exp_tls_certificate; |
| 819 | saved_tls_privatekey = state->exp_tls_privatekey; |
| 820 | saved_tls_verify_certificates = state->exp_tls_verify_certificates; |
| 821 | saved_tls_crl = state->exp_tls_crl; |
| 822 | } |
| 823 | |
| 824 | rc = gnutls_certificate_allocate_credentials(&state->x509_cred); |
| 825 | exim_gnutls_err_check(US"gnutls_certificate_allocate_credentials"); |
| 826 | |
| 827 | /* remember: expand_check_tlsvar() is expand_check() but fiddling with |
| 828 | state members, assuming consistent naming; and expand_check() returns |
| 829 | false if expansion failed, unless expansion was forced to fail. */ |
| 830 | |
| 831 | /* check if we at least have a certificate, before doing expensive |
| 832 | D-H generation. */ |
| 833 | |
| 834 | if (!expand_check_tlsvar(tls_certificate)) |
| 835 | return DEFER; |
| 836 | |
| 837 | /* certificate is mandatory in server, optional in client */ |
| 838 | |
| 839 | if ( !state->exp_tls_certificate |
| 840 | || !*state->exp_tls_certificate |
| 841 | ) |
| 842 | if (!host) |
| 843 | return tls_install_selfsign(state); |
| 844 | else |
| 845 | DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n"); |
| 846 | |
| 847 | if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey)) |
| 848 | return DEFER; |
| 849 | |
| 850 | /* tls_privatekey is optional, defaulting to same file as certificate */ |
| 851 | |
| 852 | if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0') |
| 853 | { |
| 854 | state->tls_privatekey = state->tls_certificate; |
| 855 | state->exp_tls_privatekey = state->exp_tls_certificate; |
| 856 | } |
| 857 | |
| 858 | |
| 859 | if (state->exp_tls_certificate && *state->exp_tls_certificate) |
| 860 | { |
| 861 | DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n", |
| 862 | state->exp_tls_certificate, state->exp_tls_privatekey); |
| 863 | |
| 864 | if (state->received_sni) |
| 865 | if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0 |
| 866 | && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0 |
| 867 | ) |
| 868 | { |
| 869 | DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n"); |
| 870 | } |
| 871 | else |
| 872 | { |
| 873 | DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n"); |
| 874 | } |
| 875 | |
| 876 | rc = gnutls_certificate_set_x509_key_file(state->x509_cred, |
| 877 | CS state->exp_tls_certificate, CS state->exp_tls_privatekey, |
| 878 | GNUTLS_X509_FMT_PEM); |
| 879 | exim_gnutls_err_check( |
| 880 | string_sprintf("cert/key setup: cert=%s key=%s", |
| 881 | state->exp_tls_certificate, state->exp_tls_privatekey)); |
| 882 | DEBUG(D_tls) debug_printf("TLS: cert/key registered\n"); |
| 883 | } /* tls_certificate */ |
| 884 | |
| 885 | |
| 886 | /* Set the OCSP stapling server info */ |
| 887 | |
| 888 | #ifndef DISABLE_OCSP |
| 889 | if ( !host /* server */ |
| 890 | && tls_ocsp_file |
| 891 | ) |
| 892 | { |
| 893 | if (gnutls_buggy_ocsp) |
| 894 | { |
| 895 | DEBUG(D_tls) debug_printf("GnuTLS library is buggy for OCSP; avoiding\n"); |
| 896 | } |
| 897 | else |
| 898 | { |
| 899 | if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", |
| 900 | &state->exp_tls_ocsp_file)) |
| 901 | return DEFER; |
| 902 | |
| 903 | /* Use the full callback method for stapling just to get observability. |
| 904 | More efficient would be to read the file once only, if it never changed |
| 905 | (due to SNI). Would need restart on file update, or watch datestamp. */ |
| 906 | |
| 907 | gnutls_certificate_set_ocsp_status_request_function(state->x509_cred, |
| 908 | server_ocsp_stapling_cb, state->exp_tls_ocsp_file); |
| 909 | |
| 910 | DEBUG(D_tls) debug_printf("OCSP response file = %s\n", state->exp_tls_ocsp_file); |
| 911 | } |
| 912 | } |
| 913 | #endif |
| 914 | |
| 915 | |
| 916 | /* Set the trusted CAs file if one is provided, and then add the CRL if one is |
| 917 | provided. Experiment shows that, if the certificate file is empty, an unhelpful |
| 918 | error message is provided. However, if we just refrain from setting anything up |
| 919 | in that case, certificate verification fails, which seems to be the correct |
| 920 | behaviour. */ |
| 921 | |
| 922 | if (state->tls_verify_certificates && *state->tls_verify_certificates) |
| 923 | { |
| 924 | if (!expand_check_tlsvar(tls_verify_certificates)) |
| 925 | return DEFER; |
| 926 | #ifndef SUPPORT_SYSDEFAULT_CABUNDLE |
| 927 | if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0) |
| 928 | state->exp_tls_verify_certificates = NULL; |
| 929 | #endif |
| 930 | if (state->tls_crl && *state->tls_crl) |
| 931 | if (!expand_check_tlsvar(tls_crl)) |
| 932 | return DEFER; |
| 933 | |
| 934 | if (!(state->exp_tls_verify_certificates && |
| 935 | *state->exp_tls_verify_certificates)) |
| 936 | { |
| 937 | DEBUG(D_tls) |
| 938 | debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n"); |
| 939 | /* With no tls_verify_certificates, we ignore tls_crl too */ |
| 940 | return OK; |
| 941 | } |
| 942 | } |
| 943 | else |
| 944 | { |
| 945 | DEBUG(D_tls) |
| 946 | debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n"); |
| 947 | return OK; |
| 948 | } |
| 949 | |
| 950 | #ifdef SUPPORT_SYSDEFAULT_CABUNDLE |
| 951 | if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0) |
| 952 | cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred); |
| 953 | else |
| 954 | #endif |
| 955 | { |
| 956 | if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0) |
| 957 | { |
| 958 | log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s " |
| 959 | "(tls_verify_certificates): %s", state->exp_tls_verify_certificates, |
| 960 | strerror(errno)); |
| 961 | return DEFER; |
| 962 | } |
| 963 | |
| 964 | #ifndef SUPPORT_CA_DIR |
| 965 | /* The test suite passes in /dev/null; we could check for that path explicitly, |
| 966 | but who knows if someone has some weird FIFO which always dumps some certs, or |
| 967 | other weirdness. The thing we really want to check is that it's not a |
| 968 | directory, since while OpenSSL supports that, GnuTLS does not. |
| 969 | So s/!S_ISREG/S_ISDIR/ and change some messaging ... */ |
| 970 | if (S_ISDIR(statbuf.st_mode)) |
| 971 | { |
| 972 | DEBUG(D_tls) |
| 973 | debug_printf("verify certificates path is a dir: \"%s\"\n", |
| 974 | state->exp_tls_verify_certificates); |
| 975 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 976 | "tls_verify_certificates \"%s\" is a directory", |
| 977 | state->exp_tls_verify_certificates); |
| 978 | return DEFER; |
| 979 | } |
| 980 | #endif |
| 981 | |
| 982 | DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n", |
| 983 | state->exp_tls_verify_certificates, statbuf.st_size); |
| 984 | |
| 985 | if (statbuf.st_size == 0) |
| 986 | { |
| 987 | DEBUG(D_tls) |
| 988 | debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n"); |
| 989 | return OK; |
| 990 | } |
| 991 | |
| 992 | cert_count = |
| 993 | |
| 994 | #ifdef SUPPORT_CA_DIR |
| 995 | (statbuf.st_mode & S_IFMT) == S_IFDIR |
| 996 | ? |
| 997 | gnutls_certificate_set_x509_trust_dir(state->x509_cred, |
| 998 | CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM) |
| 999 | : |
| 1000 | #endif |
| 1001 | gnutls_certificate_set_x509_trust_file(state->x509_cred, |
| 1002 | CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM); |
| 1003 | } |
| 1004 | |
| 1005 | if (cert_count < 0) |
| 1006 | { |
| 1007 | rc = cert_count; |
| 1008 | exim_gnutls_err_check(US"setting certificate trust"); |
| 1009 | } |
| 1010 | DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count); |
| 1011 | |
| 1012 | if (state->tls_crl && *state->tls_crl && |
| 1013 | state->exp_tls_crl && *state->exp_tls_crl) |
| 1014 | { |
| 1015 | DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl); |
| 1016 | cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred, |
| 1017 | CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM); |
| 1018 | if (cert_count < 0) |
| 1019 | { |
| 1020 | rc = cert_count; |
| 1021 | exim_gnutls_err_check(US"gnutls_certificate_set_x509_crl_file"); |
| 1022 | } |
| 1023 | DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count); |
| 1024 | } |
| 1025 | |
| 1026 | return OK; |
| 1027 | } |
| 1028 | |
| 1029 | |
| 1030 | |
| 1031 | |
| 1032 | /************************************************* |
| 1033 | * Set X.509 state variables * |
| 1034 | *************************************************/ |
| 1035 | |
| 1036 | /* In GnuTLS, the registered cert/key are not replaced by a later |
| 1037 | set of a cert/key, so for SNI support we need a whole new x509_cred |
| 1038 | structure. Which means various other non-re-expanded pieces of state |
| 1039 | need to be re-set in the new struct, so the setting logic is pulled |
| 1040 | out to this. |
| 1041 | |
| 1042 | Arguments: |
| 1043 | state exim_gnutls_state_st * |
| 1044 | |
| 1045 | Returns: OK/DEFER/FAIL |
| 1046 | */ |
| 1047 | |
| 1048 | static int |
| 1049 | tls_set_remaining_x509(exim_gnutls_state_st *state) |
| 1050 | { |
| 1051 | int rc; |
| 1052 | const host_item *host = state->host; /* macro should be reconsidered? */ |
| 1053 | |
| 1054 | /* Create D-H parameters, or read them from the cache file. This function does |
| 1055 | its own SMTP error messaging. This only happens for the server, TLS D-H ignores |
| 1056 | client-side params. */ |
| 1057 | |
| 1058 | if (!state->host) |
| 1059 | { |
| 1060 | if (!dh_server_params) |
| 1061 | { |
| 1062 | rc = init_server_dh(); |
| 1063 | if (rc != OK) return rc; |
| 1064 | } |
| 1065 | gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params); |
| 1066 | } |
| 1067 | |
| 1068 | /* Link the credentials to the session. */ |
| 1069 | |
| 1070 | rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred); |
| 1071 | exim_gnutls_err_check(US"gnutls_credentials_set"); |
| 1072 | |
| 1073 | return OK; |
| 1074 | } |
| 1075 | |
| 1076 | /************************************************* |
| 1077 | * Initialize for GnuTLS * |
| 1078 | *************************************************/ |
| 1079 | |
| 1080 | |
| 1081 | #ifndef DISABLE_OCSP |
| 1082 | |
| 1083 | static BOOL |
| 1084 | tls_is_buggy_ocsp(void) |
| 1085 | { |
| 1086 | const uschar * s; |
| 1087 | uschar maj, mid, mic; |
| 1088 | |
| 1089 | s = CUS gnutls_check_version(NULL); |
| 1090 | maj = atoi(CCS s); |
| 1091 | if (maj == 3) |
| 1092 | { |
| 1093 | while (*s && *s != '.') s++; |
| 1094 | mid = atoi(CCS ++s); |
| 1095 | if (mid <= 2) |
| 1096 | return TRUE; |
| 1097 | else if (mid >= 5) |
| 1098 | return FALSE; |
| 1099 | else |
| 1100 | { |
| 1101 | while (*s && *s != '.') s++; |
| 1102 | mic = atoi(CCS ++s); |
| 1103 | return mic <= (mid == 3 ? 16 : 3); |
| 1104 | } |
| 1105 | } |
| 1106 | return FALSE; |
| 1107 | } |
| 1108 | |
| 1109 | #endif |
| 1110 | |
| 1111 | |
| 1112 | /* Called from both server and client code. In the case of a server, errors |
| 1113 | before actual TLS negotiation return DEFER. |
| 1114 | |
| 1115 | Arguments: |
| 1116 | host connected host, if client; NULL if server |
| 1117 | certificate certificate file |
| 1118 | privatekey private key file |
| 1119 | sni TLS SNI to send, sometimes when client; else NULL |
| 1120 | cas CA certs file |
| 1121 | crl CRL file |
| 1122 | require_ciphers tls_require_ciphers setting |
| 1123 | caller_state returned state-info structure |
| 1124 | |
| 1125 | Returns: OK/DEFER/FAIL |
| 1126 | */ |
| 1127 | |
| 1128 | static int |
| 1129 | tls_init( |
| 1130 | const host_item *host, |
| 1131 | const uschar *certificate, |
| 1132 | const uschar *privatekey, |
| 1133 | const uschar *sni, |
| 1134 | const uschar *cas, |
| 1135 | const uschar *crl, |
| 1136 | const uschar *require_ciphers, |
| 1137 | exim_gnutls_state_st **caller_state) |
| 1138 | { |
| 1139 | exim_gnutls_state_st *state; |
| 1140 | int rc; |
| 1141 | size_t sz; |
| 1142 | const char *errpos; |
| 1143 | uschar *p; |
| 1144 | BOOL want_default_priorities; |
| 1145 | |
| 1146 | if (!exim_gnutls_base_init_done) |
| 1147 | { |
| 1148 | DEBUG(D_tls) debug_printf("GnuTLS global init required.\n"); |
| 1149 | |
| 1150 | #ifdef HAVE_GNUTLS_PKCS11 |
| 1151 | /* By default, gnutls_global_init will init PKCS11 support in auto mode, |
| 1152 | which loads modules from a config file, which sounds good and may be wanted |
| 1153 | by some sysadmin, but also means in common configurations that GNOME keyring |
| 1154 | environment variables are used and so breaks for users calling mailq. |
| 1155 | To prevent this, we init PKCS11 first, which is the documented approach. */ |
| 1156 | if (!gnutls_allow_auto_pkcs11) |
| 1157 | { |
| 1158 | rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL); |
| 1159 | exim_gnutls_err_check(US"gnutls_pkcs11_init"); |
| 1160 | } |
| 1161 | #endif |
| 1162 | |
| 1163 | rc = gnutls_global_init(); |
| 1164 | exim_gnutls_err_check(US"gnutls_global_init"); |
| 1165 | |
| 1166 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
| 1167 | DEBUG(D_tls) |
| 1168 | { |
| 1169 | gnutls_global_set_log_function(exim_gnutls_logger_cb); |
| 1170 | /* arbitrarily chosen level; bump upto 9 for more */ |
| 1171 | gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); |
| 1172 | } |
| 1173 | #endif |
| 1174 | |
| 1175 | #ifndef DISABLE_OCSP |
| 1176 | if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp())) |
| 1177 | log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version"); |
| 1178 | #endif |
| 1179 | |
| 1180 | exim_gnutls_base_init_done = TRUE; |
| 1181 | } |
| 1182 | |
| 1183 | if (host) |
| 1184 | { |
| 1185 | state = &state_client; |
| 1186 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); |
| 1187 | state->tlsp = &tls_out; |
| 1188 | DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n"); |
| 1189 | rc = gnutls_init(&state->session, GNUTLS_CLIENT); |
| 1190 | } |
| 1191 | else |
| 1192 | { |
| 1193 | state = &state_server; |
| 1194 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); |
| 1195 | state->tlsp = &tls_in; |
| 1196 | DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n"); |
| 1197 | rc = gnutls_init(&state->session, GNUTLS_SERVER); |
| 1198 | } |
| 1199 | exim_gnutls_err_check(US"gnutls_init"); |
| 1200 | |
| 1201 | state->host = host; |
| 1202 | |
| 1203 | state->tls_certificate = certificate; |
| 1204 | state->tls_privatekey = privatekey; |
| 1205 | state->tls_require_ciphers = require_ciphers; |
| 1206 | state->tls_sni = sni; |
| 1207 | state->tls_verify_certificates = cas; |
| 1208 | state->tls_crl = crl; |
| 1209 | |
| 1210 | /* This handles the variables that might get re-expanded after TLS SNI; |
| 1211 | that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */ |
| 1212 | |
| 1213 | DEBUG(D_tls) |
| 1214 | debug_printf("Expanding various TLS configuration options for session credentials.\n"); |
| 1215 | rc = tls_expand_session_files(state); |
| 1216 | if (rc != OK) return rc; |
| 1217 | |
| 1218 | /* These are all other parts of the x509_cred handling, since SNI in GnuTLS |
| 1219 | requires a new structure afterwards. */ |
| 1220 | |
| 1221 | rc = tls_set_remaining_x509(state); |
| 1222 | if (rc != OK) return rc; |
| 1223 | |
| 1224 | /* set SNI in client, only */ |
| 1225 | if (host) |
| 1226 | { |
| 1227 | if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni)) |
| 1228 | return DEFER; |
| 1229 | if (state->tlsp->sni && *state->tlsp->sni) |
| 1230 | { |
| 1231 | DEBUG(D_tls) |
| 1232 | debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni); |
| 1233 | sz = Ustrlen(state->tlsp->sni); |
| 1234 | rc = gnutls_server_name_set(state->session, |
| 1235 | GNUTLS_NAME_DNS, state->tlsp->sni, sz); |
| 1236 | exim_gnutls_err_check(US"gnutls_server_name_set"); |
| 1237 | } |
| 1238 | } |
| 1239 | else if (state->tls_sni) |
| 1240 | DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \ |
| 1241 | "have an SNI set for a client [%s]\n", state->tls_sni); |
| 1242 | |
| 1243 | /* This is the priority string support, |
| 1244 | http://www.gnutls.org/manual/html_node/Priority-Strings.html |
| 1245 | and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols. |
| 1246 | This was backwards incompatible, but means Exim no longer needs to track |
| 1247 | all algorithms and provide string forms for them. */ |
| 1248 | |
| 1249 | want_default_priorities = TRUE; |
| 1250 | |
| 1251 | if (state->tls_require_ciphers && *state->tls_require_ciphers) |
| 1252 | { |
| 1253 | if (!expand_check_tlsvar(tls_require_ciphers)) |
| 1254 | return DEFER; |
| 1255 | if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers) |
| 1256 | { |
| 1257 | DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", |
| 1258 | state->exp_tls_require_ciphers); |
| 1259 | |
| 1260 | rc = gnutls_priority_init(&state->priority_cache, |
| 1261 | CS state->exp_tls_require_ciphers, &errpos); |
| 1262 | want_default_priorities = FALSE; |
| 1263 | p = state->exp_tls_require_ciphers; |
| 1264 | } |
| 1265 | } |
| 1266 | if (want_default_priorities) |
| 1267 | { |
| 1268 | DEBUG(D_tls) |
| 1269 | debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", |
| 1270 | exim_default_gnutls_priority); |
| 1271 | rc = gnutls_priority_init(&state->priority_cache, |
| 1272 | exim_default_gnutls_priority, &errpos); |
| 1273 | p = US exim_default_gnutls_priority; |
| 1274 | } |
| 1275 | |
| 1276 | exim_gnutls_err_check(string_sprintf( |
| 1277 | "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"", |
| 1278 | p, errpos - CS p, errpos)); |
| 1279 | |
| 1280 | rc = gnutls_priority_set(state->session, state->priority_cache); |
| 1281 | exim_gnutls_err_check(US"gnutls_priority_set"); |
| 1282 | |
| 1283 | gnutls_db_set_cache_expiration(state->session, ssl_session_timeout); |
| 1284 | |
| 1285 | /* Reduce security in favour of increased compatibility, if the admin |
| 1286 | decides to make that trade-off. */ |
| 1287 | if (gnutls_compat_mode) |
| 1288 | { |
| 1289 | #if LIBGNUTLS_VERSION_NUMBER >= 0x020104 |
| 1290 | DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n"); |
| 1291 | gnutls_session_enable_compatibility_mode(state->session); |
| 1292 | #else |
| 1293 | DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n"); |
| 1294 | #endif |
| 1295 | } |
| 1296 | |
| 1297 | *caller_state = state; |
| 1298 | return OK; |
| 1299 | } |
| 1300 | |
| 1301 | |
| 1302 | |
| 1303 | /************************************************* |
| 1304 | * Extract peer information * |
| 1305 | *************************************************/ |
| 1306 | |
| 1307 | /* Called from both server and client code. |
| 1308 | Only this is allowed to set state->peerdn and state->have_set_peerdn |
| 1309 | and we use that to detect double-calls. |
| 1310 | |
| 1311 | NOTE: the state blocks last while the TLS connection is up, which is fine |
| 1312 | for logging in the server side, but for the client side, we log after teardown |
| 1313 | in src/deliver.c. While the session is up, we can twist about states and |
| 1314 | repoint tls_* globals, but those variables used for logging or other variable |
| 1315 | expansion that happens _after_ delivery need to have a longer life-time. |
| 1316 | |
| 1317 | So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from |
| 1318 | doing this more than once per generation of a state context. We set them in |
| 1319 | the state context, and repoint tls_* to them. After the state goes away, the |
| 1320 | tls_* copies of the pointers remain valid and client delivery logging is happy. |
| 1321 | |
| 1322 | tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues |
| 1323 | don't apply. |
| 1324 | |
| 1325 | Arguments: |
| 1326 | state exim_gnutls_state_st * |
| 1327 | |
| 1328 | Returns: OK/DEFER/FAIL |
| 1329 | */ |
| 1330 | |
| 1331 | static int |
| 1332 | peer_status(exim_gnutls_state_st *state) |
| 1333 | { |
| 1334 | uschar cipherbuf[256]; |
| 1335 | const gnutls_datum_t *cert_list; |
| 1336 | int old_pool, rc; |
| 1337 | unsigned int cert_list_size = 0; |
| 1338 | gnutls_protocol_t protocol; |
| 1339 | gnutls_cipher_algorithm_t cipher; |
| 1340 | gnutls_kx_algorithm_t kx; |
| 1341 | gnutls_mac_algorithm_t mac; |
| 1342 | gnutls_certificate_type_t ct; |
| 1343 | gnutls_x509_crt_t crt; |
| 1344 | uschar *p, *dn_buf; |
| 1345 | size_t sz; |
| 1346 | |
| 1347 | if (state->have_set_peerdn) |
| 1348 | return OK; |
| 1349 | state->have_set_peerdn = TRUE; |
| 1350 | |
| 1351 | state->peerdn = NULL; |
| 1352 | |
| 1353 | /* tls_cipher */ |
| 1354 | cipher = gnutls_cipher_get(state->session); |
| 1355 | protocol = gnutls_protocol_get_version(state->session); |
| 1356 | mac = gnutls_mac_get(state->session); |
| 1357 | kx = gnutls_kx_get(state->session); |
| 1358 | |
| 1359 | string_format(cipherbuf, sizeof(cipherbuf), |
| 1360 | "%s:%s:%d", |
| 1361 | gnutls_protocol_get_name(protocol), |
| 1362 | gnutls_cipher_suite_get_name(kx, cipher, mac), |
| 1363 | (int) gnutls_cipher_get_key_size(cipher) * 8); |
| 1364 | |
| 1365 | /* I don't see a way that spaces could occur, in the current GnuTLS |
| 1366 | code base, but it was a concern in the old code and perhaps older GnuTLS |
| 1367 | releases did return "TLS 1.0"; play it safe, just in case. */ |
| 1368 | for (p = cipherbuf; *p != '\0'; ++p) |
| 1369 | if (isspace(*p)) |
| 1370 | *p = '-'; |
| 1371 | old_pool = store_pool; |
| 1372 | store_pool = POOL_PERM; |
| 1373 | state->ciphersuite = string_copy(cipherbuf); |
| 1374 | store_pool = old_pool; |
| 1375 | state->tlsp->cipher = state->ciphersuite; |
| 1376 | |
| 1377 | /* tls_peerdn */ |
| 1378 | cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size); |
| 1379 | |
| 1380 | if (cert_list == NULL || cert_list_size == 0) |
| 1381 | { |
| 1382 | DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n", |
| 1383 | cert_list, cert_list_size); |
| 1384 | if (state->verify_requirement >= VERIFY_REQUIRED) |
| 1385 | return tls_error(US"certificate verification failed", |
| 1386 | "no certificate received from peer", state->host); |
| 1387 | return OK; |
| 1388 | } |
| 1389 | |
| 1390 | ct = gnutls_certificate_type_get(state->session); |
| 1391 | if (ct != GNUTLS_CRT_X509) |
| 1392 | { |
| 1393 | const char *ctn = gnutls_certificate_type_get_name(ct); |
| 1394 | DEBUG(D_tls) |
| 1395 | debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn); |
| 1396 | if (state->verify_requirement >= VERIFY_REQUIRED) |
| 1397 | return tls_error(US"certificate verification not possible, unhandled type", |
| 1398 | ctn, state->host); |
| 1399 | return OK; |
| 1400 | } |
| 1401 | |
| 1402 | #define exim_gnutls_peer_err(Label) \ |
| 1403 | do { \ |
| 1404 | if (rc != GNUTLS_E_SUCCESS) \ |
| 1405 | { \ |
| 1406 | DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \ |
| 1407 | (Label), gnutls_strerror(rc)); \ |
| 1408 | if (state->verify_requirement >= VERIFY_REQUIRED) \ |
| 1409 | return tls_error((Label), gnutls_strerror(rc), state->host); \ |
| 1410 | return OK; \ |
| 1411 | } \ |
| 1412 | } while (0) |
| 1413 | |
| 1414 | rc = import_cert(&cert_list[0], &crt); |
| 1415 | exim_gnutls_peer_err(US"cert 0"); |
| 1416 | |
| 1417 | state->tlsp->peercert = state->peercert = crt; |
| 1418 | |
| 1419 | sz = 0; |
| 1420 | rc = gnutls_x509_crt_get_dn(crt, NULL, &sz); |
| 1421 | if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) |
| 1422 | { |
| 1423 | exim_gnutls_peer_err(US"getting size for cert DN failed"); |
| 1424 | return FAIL; /* should not happen */ |
| 1425 | } |
| 1426 | dn_buf = store_get_perm(sz); |
| 1427 | rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz); |
| 1428 | exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]"); |
| 1429 | |
| 1430 | state->peerdn = dn_buf; |
| 1431 | |
| 1432 | return OK; |
| 1433 | #undef exim_gnutls_peer_err |
| 1434 | } |
| 1435 | |
| 1436 | |
| 1437 | |
| 1438 | |
| 1439 | /************************************************* |
| 1440 | * Verify peer certificate * |
| 1441 | *************************************************/ |
| 1442 | |
| 1443 | /* Called from both server and client code. |
| 1444 | *Should* be using a callback registered with |
| 1445 | gnutls_certificate_set_verify_function() to fail the handshake if we dislike |
| 1446 | the peer information, but that's too new for some OSes. |
| 1447 | |
| 1448 | Arguments: |
| 1449 | state exim_gnutls_state_st * |
| 1450 | error where to put an error message |
| 1451 | |
| 1452 | Returns: |
| 1453 | FALSE if the session should be rejected |
| 1454 | TRUE if the cert is okay or we just don't care |
| 1455 | */ |
| 1456 | |
| 1457 | static BOOL |
| 1458 | verify_certificate(exim_gnutls_state_st *state, const char **error) |
| 1459 | { |
| 1460 | int rc; |
| 1461 | unsigned int verify; |
| 1462 | |
| 1463 | *error = NULL; |
| 1464 | |
| 1465 | if ((rc = peer_status(state)) != OK) |
| 1466 | { |
| 1467 | verify = GNUTLS_CERT_INVALID; |
| 1468 | *error = "certificate not supplied"; |
| 1469 | } |
| 1470 | else |
| 1471 | rc = gnutls_certificate_verify_peers2(state->session, &verify); |
| 1472 | |
| 1473 | /* Handle the result of verification. INVALID seems to be set as well |
| 1474 | as REVOKED, but leave the test for both. */ |
| 1475 | |
| 1476 | if (rc < 0 || |
| 1477 | verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED) |
| 1478 | ) |
| 1479 | { |
| 1480 | state->peer_cert_verified = FALSE; |
| 1481 | if (!*error) |
| 1482 | *error = verify & GNUTLS_CERT_REVOKED |
| 1483 | ? "certificate revoked" : "certificate invalid"; |
| 1484 | |
| 1485 | DEBUG(D_tls) |
| 1486 | debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n", |
| 1487 | *error, state->peerdn ? state->peerdn : US"<unset>"); |
| 1488 | |
| 1489 | if (state->verify_requirement >= VERIFY_REQUIRED) |
| 1490 | { |
| 1491 | gnutls_alert_send(state->session, |
| 1492 | GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE); |
| 1493 | return FALSE; |
| 1494 | } |
| 1495 | DEBUG(D_tls) |
| 1496 | debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n"); |
| 1497 | } |
| 1498 | |
| 1499 | else |
| 1500 | { |
| 1501 | if (state->exp_tls_verify_cert_hostnames) |
| 1502 | { |
| 1503 | int sep = 0; |
| 1504 | const uschar * list = state->exp_tls_verify_cert_hostnames; |
| 1505 | uschar * name; |
| 1506 | while ((name = string_nextinlist(&list, &sep, NULL, 0))) |
| 1507 | if (gnutls_x509_crt_check_hostname(state->tlsp->peercert, CS name)) |
| 1508 | break; |
| 1509 | if (!name) |
| 1510 | { |
| 1511 | DEBUG(D_tls) |
| 1512 | debug_printf("TLS certificate verification failed: cert name mismatch\n"); |
| 1513 | if (state->verify_requirement >= VERIFY_REQUIRED) |
| 1514 | { |
| 1515 | gnutls_alert_send(state->session, |
| 1516 | GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE); |
| 1517 | return FALSE; |
| 1518 | } |
| 1519 | return TRUE; |
| 1520 | } |
| 1521 | } |
| 1522 | state->peer_cert_verified = TRUE; |
| 1523 | DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n", |
| 1524 | state->peerdn ? state->peerdn : US"<unset>"); |
| 1525 | } |
| 1526 | |
| 1527 | state->tlsp->peerdn = state->peerdn; |
| 1528 | |
| 1529 | return TRUE; |
| 1530 | } |
| 1531 | |
| 1532 | |
| 1533 | |
| 1534 | |
| 1535 | /* ------------------------------------------------------------------------ */ |
| 1536 | /* Callbacks */ |
| 1537 | |
| 1538 | /* Logging function which can be registered with |
| 1539 | * gnutls_global_set_log_function() |
| 1540 | * gnutls_global_set_log_level() 0..9 |
| 1541 | */ |
| 1542 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
| 1543 | static void |
| 1544 | exim_gnutls_logger_cb(int level, const char *message) |
| 1545 | { |
| 1546 | size_t len = strlen(message); |
| 1547 | if (len < 1) |
| 1548 | { |
| 1549 | DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level); |
| 1550 | return; |
| 1551 | } |
| 1552 | DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message, |
| 1553 | message[len-1] == '\n' ? "" : "\n"); |
| 1554 | } |
| 1555 | #endif |
| 1556 | |
| 1557 | |
| 1558 | /* Called after client hello, should handle SNI work. |
| 1559 | This will always set tls_sni (state->received_sni) if available, |
| 1560 | and may trigger presenting different certificates, |
| 1561 | if state->trigger_sni_changes is TRUE. |
| 1562 | |
| 1563 | Should be registered with |
| 1564 | gnutls_handshake_set_post_client_hello_function() |
| 1565 | |
| 1566 | "This callback must return 0 on success or a gnutls error code to terminate the |
| 1567 | handshake.". |
| 1568 | |
| 1569 | For inability to get SNI information, we return 0. |
| 1570 | We only return non-zero if re-setup failed. |
| 1571 | Only used for server-side TLS. |
| 1572 | */ |
| 1573 | |
| 1574 | static int |
| 1575 | exim_sni_handling_cb(gnutls_session_t session) |
| 1576 | { |
| 1577 | char sni_name[MAX_HOST_LEN]; |
| 1578 | size_t data_len = MAX_HOST_LEN; |
| 1579 | exim_gnutls_state_st *state = &state_server; |
| 1580 | unsigned int sni_type; |
| 1581 | int rc, old_pool; |
| 1582 | |
| 1583 | rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0); |
| 1584 | if (rc != GNUTLS_E_SUCCESS) |
| 1585 | { |
| 1586 | DEBUG(D_tls) { |
| 1587 | if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) |
| 1588 | debug_printf("TLS: no SNI presented in handshake.\n"); |
| 1589 | else |
| 1590 | debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n", |
| 1591 | gnutls_strerror(rc), rc); |
| 1592 | }; |
| 1593 | return 0; |
| 1594 | } |
| 1595 | |
| 1596 | if (sni_type != GNUTLS_NAME_DNS) |
| 1597 | { |
| 1598 | DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type); |
| 1599 | return 0; |
| 1600 | } |
| 1601 | |
| 1602 | /* We now have a UTF-8 string in sni_name */ |
| 1603 | old_pool = store_pool; |
| 1604 | store_pool = POOL_PERM; |
| 1605 | state->received_sni = string_copyn(US sni_name, data_len); |
| 1606 | store_pool = old_pool; |
| 1607 | |
| 1608 | /* We set this one now so that variable expansions below will work */ |
| 1609 | state->tlsp->sni = state->received_sni; |
| 1610 | |
| 1611 | DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name, |
| 1612 | state->trigger_sni_changes ? "" : " (unused for certificate selection)"); |
| 1613 | |
| 1614 | if (!state->trigger_sni_changes) |
| 1615 | return 0; |
| 1616 | |
| 1617 | rc = tls_expand_session_files(state); |
| 1618 | if (rc != OK) |
| 1619 | { |
| 1620 | /* If the setup of certs/etc failed before handshake, TLS would not have |
| 1621 | been offered. The best we can do now is abort. */ |
| 1622 | return GNUTLS_E_APPLICATION_ERROR_MIN; |
| 1623 | } |
| 1624 | |
| 1625 | rc = tls_set_remaining_x509(state); |
| 1626 | if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN; |
| 1627 | |
| 1628 | return 0; |
| 1629 | } |
| 1630 | |
| 1631 | |
| 1632 | |
| 1633 | #ifndef DISABLE_OCSP |
| 1634 | |
| 1635 | static int |
| 1636 | server_ocsp_stapling_cb(gnutls_session_t session, void * ptr, |
| 1637 | gnutls_datum_t * ocsp_response) |
| 1638 | { |
| 1639 | int ret; |
| 1640 | |
| 1641 | if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0) |
| 1642 | { |
| 1643 | DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n", |
| 1644 | (char *)ptr); |
| 1645 | tls_in.ocsp = OCSP_NOT_RESP; |
| 1646 | return GNUTLS_E_NO_CERTIFICATE_STATUS; |
| 1647 | } |
| 1648 | |
| 1649 | tls_in.ocsp = OCSP_VFY_NOT_TRIED; |
| 1650 | return 0; |
| 1651 | } |
| 1652 | |
| 1653 | #endif |
| 1654 | |
| 1655 | |
| 1656 | #ifndef DISABLE_EVENT |
| 1657 | /* |
| 1658 | We use this callback to get observability and detail-level control |
| 1659 | for an exim TLS connection (either direction), raising a tls:cert event |
| 1660 | for each cert in the chain presented by the peer. Any event |
| 1661 | can deny verification. |
| 1662 | |
| 1663 | Return 0 for the handshake to continue or non-zero to terminate. |
| 1664 | */ |
| 1665 | |
| 1666 | static int |
| 1667 | verify_cb(gnutls_session_t session) |
| 1668 | { |
| 1669 | const gnutls_datum_t * cert_list; |
| 1670 | unsigned int cert_list_size = 0; |
| 1671 | gnutls_x509_crt_t crt; |
| 1672 | int rc; |
| 1673 | uschar * yield; |
| 1674 | exim_gnutls_state_st * state = gnutls_session_get_ptr(session); |
| 1675 | |
| 1676 | cert_list = gnutls_certificate_get_peers(session, &cert_list_size); |
| 1677 | if (cert_list) |
| 1678 | while (cert_list_size--) |
| 1679 | { |
| 1680 | rc = import_cert(&cert_list[cert_list_size], &crt); |
| 1681 | if (rc != GNUTLS_E_SUCCESS) |
| 1682 | { |
| 1683 | DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n", |
| 1684 | cert_list_size, gnutls_strerror(rc)); |
| 1685 | break; |
| 1686 | } |
| 1687 | |
| 1688 | state->tlsp->peercert = crt; |
| 1689 | if ((yield = event_raise(state->event_action, |
| 1690 | US"tls:cert", string_sprintf("%d", cert_list_size)))) |
| 1691 | { |
| 1692 | log_write(0, LOG_MAIN, |
| 1693 | "SSL verify denied by event-action: depth=%d: %s", |
| 1694 | cert_list_size, yield); |
| 1695 | return 1; /* reject */ |
| 1696 | } |
| 1697 | state->tlsp->peercert = NULL; |
| 1698 | } |
| 1699 | |
| 1700 | return 0; |
| 1701 | } |
| 1702 | |
| 1703 | #endif |
| 1704 | |
| 1705 | |
| 1706 | |
| 1707 | /* ------------------------------------------------------------------------ */ |
| 1708 | /* Exported functions */ |
| 1709 | |
| 1710 | |
| 1711 | |
| 1712 | |
| 1713 | /************************************************* |
| 1714 | * Start a TLS session in a server * |
| 1715 | *************************************************/ |
| 1716 | |
| 1717 | /* This is called when Exim is running as a server, after having received |
| 1718 | the STARTTLS command. It must respond to that command, and then negotiate |
| 1719 | a TLS session. |
| 1720 | |
| 1721 | Arguments: |
| 1722 | require_ciphers list of allowed ciphers or NULL |
| 1723 | |
| 1724 | Returns: OK on success |
| 1725 | DEFER for errors before the start of the negotiation |
| 1726 | FAIL for errors during the negotiation; the server can't |
| 1727 | continue running. |
| 1728 | */ |
| 1729 | |
| 1730 | int |
| 1731 | tls_server_start(const uschar *require_ciphers) |
| 1732 | { |
| 1733 | int rc; |
| 1734 | const char *error; |
| 1735 | exim_gnutls_state_st *state = NULL; |
| 1736 | |
| 1737 | /* Check for previous activation */ |
| 1738 | if (tls_in.active >= 0) |
| 1739 | { |
| 1740 | tls_error(US"STARTTLS received after TLS started", "", NULL); |
| 1741 | smtp_printf("554 Already in TLS\r\n"); |
| 1742 | return FAIL; |
| 1743 | } |
| 1744 | |
| 1745 | /* Initialize the library. If it fails, it will already have logged the error |
| 1746 | and sent an SMTP response. */ |
| 1747 | |
| 1748 | DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n"); |
| 1749 | |
| 1750 | rc = tls_init(NULL, tls_certificate, tls_privatekey, |
| 1751 | NULL, tls_verify_certificates, tls_crl, |
| 1752 | require_ciphers, &state); |
| 1753 | if (rc != OK) return rc; |
| 1754 | |
| 1755 | /* If this is a host for which certificate verification is mandatory or |
| 1756 | optional, set up appropriately. */ |
| 1757 | |
| 1758 | if (verify_check_host(&tls_verify_hosts) == OK) |
| 1759 | { |
| 1760 | DEBUG(D_tls) |
| 1761 | debug_printf("TLS: a client certificate will be required.\n"); |
| 1762 | state->verify_requirement = VERIFY_REQUIRED; |
| 1763 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); |
| 1764 | } |
| 1765 | else if (verify_check_host(&tls_try_verify_hosts) == OK) |
| 1766 | { |
| 1767 | DEBUG(D_tls) |
| 1768 | debug_printf("TLS: a client certificate will be requested but not required.\n"); |
| 1769 | state->verify_requirement = VERIFY_OPTIONAL; |
| 1770 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); |
| 1771 | } |
| 1772 | else |
| 1773 | { |
| 1774 | DEBUG(D_tls) |
| 1775 | debug_printf("TLS: a client certificate will not be requested.\n"); |
| 1776 | state->verify_requirement = VERIFY_NONE; |
| 1777 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); |
| 1778 | } |
| 1779 | |
| 1780 | #ifndef DISABLE_EVENT |
| 1781 | if (event_action) |
| 1782 | { |
| 1783 | state->event_action = event_action; |
| 1784 | gnutls_session_set_ptr(state->session, state); |
| 1785 | gnutls_certificate_set_verify_function(state->x509_cred, verify_cb); |
| 1786 | } |
| 1787 | #endif |
| 1788 | |
| 1789 | /* Register SNI handling; always, even if not in tls_certificate, so that the |
| 1790 | expansion variable $tls_sni is always available. */ |
| 1791 | |
| 1792 | gnutls_handshake_set_post_client_hello_function(state->session, |
| 1793 | exim_sni_handling_cb); |
| 1794 | |
| 1795 | /* Set context and tell client to go ahead, except in the case of TLS startup |
| 1796 | on connection, where outputting anything now upsets the clients and tends to |
| 1797 | make them disconnect. We need to have an explicit fflush() here, to force out |
| 1798 | the response. Other smtp_printf() calls do not need it, because in non-TLS |
| 1799 | mode, the fflush() happens when smtp_getc() is called. */ |
| 1800 | |
| 1801 | if (!state->tlsp->on_connect) |
| 1802 | { |
| 1803 | smtp_printf("220 TLS go ahead\r\n"); |
| 1804 | fflush(smtp_out); |
| 1805 | } |
| 1806 | |
| 1807 | /* Now negotiate the TLS session. We put our own timer on it, since it seems |
| 1808 | that the GnuTLS library doesn't. */ |
| 1809 | |
| 1810 | gnutls_transport_set_ptr2(state->session, |
| 1811 | (gnutls_transport_ptr_t)(long) fileno(smtp_in), |
| 1812 | (gnutls_transport_ptr_t)(long) fileno(smtp_out)); |
| 1813 | state->fd_in = fileno(smtp_in); |
| 1814 | state->fd_out = fileno(smtp_out); |
| 1815 | |
| 1816 | sigalrm_seen = FALSE; |
| 1817 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 1818 | do |
| 1819 | rc = gnutls_handshake(state->session); |
| 1820 | while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen); |
| 1821 | alarm(0); |
| 1822 | |
| 1823 | if (rc != GNUTLS_E_SUCCESS) |
| 1824 | { |
| 1825 | /* It seems that, except in the case of a timeout, we have to close the |
| 1826 | connection right here; otherwise if the other end is running OpenSSL it hangs |
| 1827 | until the server times out. */ |
| 1828 | |
| 1829 | if (sigalrm_seen) |
| 1830 | { |
| 1831 | tls_error(US"gnutls_handshake", "timed out", NULL); |
| 1832 | gnutls_db_remove_session(state->session); |
| 1833 | } |
| 1834 | else |
| 1835 | { |
| 1836 | tls_error(US"gnutls_handshake", gnutls_strerror(rc), NULL); |
| 1837 | (void) gnutls_alert_send_appropriate(state->session, rc); |
| 1838 | gnutls_deinit(state->session); |
| 1839 | gnutls_certificate_free_credentials(state->x509_cred); |
| 1840 | millisleep(500); |
| 1841 | shutdown(state->fd_out, SHUT_WR); |
| 1842 | for (rc = 1024; fgetc(smtp_in) != EOF && rc > 0; ) rc--; /* drain skt */ |
| 1843 | (void)fclose(smtp_out); |
| 1844 | (void)fclose(smtp_in); |
| 1845 | smtp_out = smtp_in = NULL; |
| 1846 | } |
| 1847 | |
| 1848 | return FAIL; |
| 1849 | } |
| 1850 | |
| 1851 | DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); |
| 1852 | |
| 1853 | /* Verify after the fact */ |
| 1854 | |
| 1855 | if ( state->verify_requirement != VERIFY_NONE |
| 1856 | && !verify_certificate(state, &error)) |
| 1857 | { |
| 1858 | if (state->verify_requirement != VERIFY_OPTIONAL) |
| 1859 | { |
| 1860 | tls_error(US"certificate verification failed", error, NULL); |
| 1861 | return FAIL; |
| 1862 | } |
| 1863 | DEBUG(D_tls) |
| 1864 | debug_printf("TLS: continuing on only because verification was optional, after: %s\n", |
| 1865 | error); |
| 1866 | } |
| 1867 | |
| 1868 | /* Figure out peer DN, and if authenticated, etc. */ |
| 1869 | |
| 1870 | if ((rc = peer_status(state)) != OK) return rc; |
| 1871 | |
| 1872 | /* Sets various Exim expansion variables; always safe within server */ |
| 1873 | |
| 1874 | extract_exim_vars_from_tls_state(state); |
| 1875 | |
| 1876 | /* TLS has been set up. Adjust the input functions to read via TLS, |
| 1877 | and initialize appropriately. */ |
| 1878 | |
| 1879 | state->xfer_buffer = store_malloc(ssl_xfer_buffer_size); |
| 1880 | |
| 1881 | receive_getc = tls_getc; |
| 1882 | receive_get_cache = tls_get_cache; |
| 1883 | receive_ungetc = tls_ungetc; |
| 1884 | receive_feof = tls_feof; |
| 1885 | receive_ferror = tls_ferror; |
| 1886 | receive_smtp_buffered = tls_smtp_buffered; |
| 1887 | |
| 1888 | return OK; |
| 1889 | } |
| 1890 | |
| 1891 | |
| 1892 | |
| 1893 | |
| 1894 | static void |
| 1895 | tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state, |
| 1896 | smtp_transport_options_block * ob) |
| 1897 | { |
| 1898 | if (verify_check_given_host(&ob->tls_verify_cert_hostnames, host) == OK) |
| 1899 | { |
| 1900 | state->exp_tls_verify_cert_hostnames = |
| 1901 | #ifdef SUPPORT_I18N |
| 1902 | string_domain_utf8_to_alabel(host->name, NULL); |
| 1903 | #else |
| 1904 | host->name; |
| 1905 | #endif |
| 1906 | DEBUG(D_tls) |
| 1907 | debug_printf("TLS: server cert verification includes hostname: \"%s\".\n", |
| 1908 | state->exp_tls_verify_cert_hostnames); |
| 1909 | } |
| 1910 | } |
| 1911 | |
| 1912 | |
| 1913 | /************************************************* |
| 1914 | * Start a TLS session in a client * |
| 1915 | *************************************************/ |
| 1916 | |
| 1917 | /* Called from the smtp transport after STARTTLS has been accepted. |
| 1918 | |
| 1919 | Arguments: |
| 1920 | fd the fd of the connection |
| 1921 | host connected host (for messages) |
| 1922 | addr the first address (not used) |
| 1923 | tb transport (always smtp) |
| 1924 | |
| 1925 | Returns: OK/DEFER/FAIL (because using common functions), |
| 1926 | but for a client, DEFER and FAIL have the same meaning |
| 1927 | */ |
| 1928 | |
| 1929 | int |
| 1930 | tls_client_start(int fd, host_item *host, |
| 1931 | address_item *addr ARG_UNUSED, |
| 1932 | transport_instance *tb |
| 1933 | #ifdef EXPERIMENTAL_DANE |
| 1934 | , dns_answer * unused_tlsa_dnsa |
| 1935 | #endif |
| 1936 | ) |
| 1937 | { |
| 1938 | smtp_transport_options_block *ob = |
| 1939 | (smtp_transport_options_block *)tb->options_block; |
| 1940 | int rc; |
| 1941 | const char *error; |
| 1942 | exim_gnutls_state_st *state = NULL; |
| 1943 | #ifndef DISABLE_OCSP |
| 1944 | BOOL require_ocsp = |
| 1945 | verify_check_given_host(&ob->hosts_require_ocsp, host) == OK; |
| 1946 | BOOL request_ocsp = require_ocsp ? TRUE |
| 1947 | : verify_check_given_host(&ob->hosts_request_ocsp, host) == OK; |
| 1948 | #endif |
| 1949 | |
| 1950 | DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd); |
| 1951 | |
| 1952 | if ((rc = tls_init(host, ob->tls_certificate, ob->tls_privatekey, |
| 1953 | ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl, |
| 1954 | ob->tls_require_ciphers, &state)) != OK) |
| 1955 | return rc; |
| 1956 | |
| 1957 | { |
| 1958 | int dh_min_bits = ob->tls_dh_min_bits; |
| 1959 | if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS) |
| 1960 | { |
| 1961 | DEBUG(D_tls) |
| 1962 | debug_printf("WARNING: tls_dh_min_bits far too low," |
| 1963 | " clamping %d up to %d\n", |
| 1964 | dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS); |
| 1965 | dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS; |
| 1966 | } |
| 1967 | |
| 1968 | DEBUG(D_tls) debug_printf("Setting D-H prime minimum" |
| 1969 | " acceptable bits to %d\n", |
| 1970 | dh_min_bits); |
| 1971 | gnutls_dh_set_prime_bits(state->session, dh_min_bits); |
| 1972 | } |
| 1973 | |
| 1974 | /* Stick to the old behaviour for compatibility if tls_verify_certificates is |
| 1975 | set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only |
| 1976 | the specified host patterns if one of them is defined */ |
| 1977 | |
| 1978 | if ( ( state->exp_tls_verify_certificates |
| 1979 | && !ob->tls_verify_hosts |
| 1980 | && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts) |
| 1981 | ) |
| 1982 | || verify_check_given_host(&ob->tls_verify_hosts, host) == OK |
| 1983 | ) |
| 1984 | { |
| 1985 | tls_client_setup_hostname_checks(host, state, ob); |
| 1986 | DEBUG(D_tls) |
| 1987 | debug_printf("TLS: server certificate verification required.\n"); |
| 1988 | state->verify_requirement = VERIFY_REQUIRED; |
| 1989 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); |
| 1990 | } |
| 1991 | else if (verify_check_given_host(&ob->tls_try_verify_hosts, host) == OK) |
| 1992 | { |
| 1993 | tls_client_setup_hostname_checks(host, state, ob); |
| 1994 | DEBUG(D_tls) |
| 1995 | debug_printf("TLS: server certificate verification optional.\n"); |
| 1996 | state->verify_requirement = VERIFY_OPTIONAL; |
| 1997 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); |
| 1998 | } |
| 1999 | else |
| 2000 | { |
| 2001 | DEBUG(D_tls) |
| 2002 | debug_printf("TLS: server certificate verification not required.\n"); |
| 2003 | state->verify_requirement = VERIFY_NONE; |
| 2004 | gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); |
| 2005 | } |
| 2006 | |
| 2007 | #ifndef DISABLE_OCSP |
| 2008 | /* supported since GnuTLS 3.1.3 */ |
| 2009 | if (request_ocsp) |
| 2010 | { |
| 2011 | DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n"); |
| 2012 | if ((rc = gnutls_ocsp_status_request_enable_client(state->session, |
| 2013 | NULL, 0, NULL)) != OK) |
| 2014 | return tls_error(US"cert-status-req", |
| 2015 | gnutls_strerror(rc), state->host); |
| 2016 | tls_out.ocsp = OCSP_NOT_RESP; |
| 2017 | } |
| 2018 | #endif |
| 2019 | |
| 2020 | #ifndef DISABLE_EVENT |
| 2021 | if (tb->event_action) |
| 2022 | { |
| 2023 | state->event_action = tb->event_action; |
| 2024 | gnutls_session_set_ptr(state->session, state); |
| 2025 | gnutls_certificate_set_verify_function(state->x509_cred, verify_cb); |
| 2026 | } |
| 2027 | #endif |
| 2028 | |
| 2029 | gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) fd); |
| 2030 | state->fd_in = fd; |
| 2031 | state->fd_out = fd; |
| 2032 | |
| 2033 | DEBUG(D_tls) debug_printf("about to gnutls_handshake\n"); |
| 2034 | /* There doesn't seem to be a built-in timeout on connection. */ |
| 2035 | |
| 2036 | sigalrm_seen = FALSE; |
| 2037 | alarm(ob->command_timeout); |
| 2038 | do |
| 2039 | { |
| 2040 | rc = gnutls_handshake(state->session); |
| 2041 | } while ((rc == GNUTLS_E_AGAIN) || |
| 2042 | (rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen)); |
| 2043 | alarm(0); |
| 2044 | |
| 2045 | if (rc != GNUTLS_E_SUCCESS) |
| 2046 | if (sigalrm_seen) |
| 2047 | { |
| 2048 | gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED); |
| 2049 | return tls_error(US"gnutls_handshake", "timed out", state->host); |
| 2050 | } |
| 2051 | else |
| 2052 | return tls_error(US"gnutls_handshake", gnutls_strerror(rc), state->host); |
| 2053 | |
| 2054 | DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); |
| 2055 | |
| 2056 | /* Verify late */ |
| 2057 | |
| 2058 | if (state->verify_requirement != VERIFY_NONE && |
| 2059 | !verify_certificate(state, &error)) |
| 2060 | return tls_error(US"certificate verification failed", error, state->host); |
| 2061 | |
| 2062 | #ifndef DISABLE_OCSP |
| 2063 | if (require_ocsp) |
| 2064 | { |
| 2065 | DEBUG(D_tls) |
| 2066 | { |
| 2067 | gnutls_datum_t stapling; |
| 2068 | gnutls_ocsp_resp_t resp; |
| 2069 | gnutls_datum_t printed; |
| 2070 | if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0 |
| 2071 | && (rc= gnutls_ocsp_resp_init(&resp)) == 0 |
| 2072 | && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0 |
| 2073 | && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0 |
| 2074 | ) |
| 2075 | { |
| 2076 | debug_printf("%.4096s", printed.data); |
| 2077 | gnutls_free(printed.data); |
| 2078 | } |
| 2079 | else |
| 2080 | (void) tls_error(US"ocsp decode", gnutls_strerror(rc), state->host); |
| 2081 | } |
| 2082 | |
| 2083 | if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0) |
| 2084 | { |
| 2085 | tls_out.ocsp = OCSP_FAILED; |
| 2086 | return tls_error(US"certificate status check failed", NULL, state->host); |
| 2087 | } |
| 2088 | DEBUG(D_tls) debug_printf("Passed OCSP checking\n"); |
| 2089 | tls_out.ocsp = OCSP_VFIED; |
| 2090 | } |
| 2091 | #endif |
| 2092 | |
| 2093 | /* Figure out peer DN, and if authenticated, etc. */ |
| 2094 | |
| 2095 | if ((rc = peer_status(state)) != OK) |
| 2096 | return rc; |
| 2097 | |
| 2098 | /* Sets various Exim expansion variables; may need to adjust for ACL callouts */ |
| 2099 | |
| 2100 | extract_exim_vars_from_tls_state(state); |
| 2101 | |
| 2102 | return OK; |
| 2103 | } |
| 2104 | |
| 2105 | |
| 2106 | |
| 2107 | |
| 2108 | /************************************************* |
| 2109 | * Close down a TLS session * |
| 2110 | *************************************************/ |
| 2111 | |
| 2112 | /* This is also called from within a delivery subprocess forked from the |
| 2113 | daemon, to shut down the TLS library, without actually doing a shutdown (which |
| 2114 | would tamper with the TLS session in the parent process). |
| 2115 | |
| 2116 | Arguments: TRUE if gnutls_bye is to be called |
| 2117 | Returns: nothing |
| 2118 | */ |
| 2119 | |
| 2120 | void |
| 2121 | tls_close(BOOL is_server, BOOL shutdown) |
| 2122 | { |
| 2123 | exim_gnutls_state_st *state = is_server ? &state_server : &state_client; |
| 2124 | |
| 2125 | if (!state->tlsp || state->tlsp->active < 0) return; /* TLS was not active */ |
| 2126 | |
| 2127 | if (shutdown) |
| 2128 | { |
| 2129 | DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n"); |
| 2130 | gnutls_bye(state->session, GNUTLS_SHUT_WR); |
| 2131 | } |
| 2132 | |
| 2133 | gnutls_deinit(state->session); |
| 2134 | gnutls_certificate_free_credentials(state->x509_cred); |
| 2135 | |
| 2136 | |
| 2137 | state->tlsp->active = -1; |
| 2138 | memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); |
| 2139 | |
| 2140 | if ((state_server.session == NULL) && (state_client.session == NULL)) |
| 2141 | { |
| 2142 | gnutls_global_deinit(); |
| 2143 | exim_gnutls_base_init_done = FALSE; |
| 2144 | } |
| 2145 | |
| 2146 | } |
| 2147 | |
| 2148 | |
| 2149 | |
| 2150 | |
| 2151 | /************************************************* |
| 2152 | * TLS version of getc * |
| 2153 | *************************************************/ |
| 2154 | |
| 2155 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, |
| 2156 | it refills the buffer via the GnuTLS reading function. |
| 2157 | Only used by the server-side TLS. |
| 2158 | |
| 2159 | This feeds DKIM and should be used for all message-body reads. |
| 2160 | |
| 2161 | Arguments: lim Maximum amount to read/bufffer |
| 2162 | Returns: the next character or EOF |
| 2163 | */ |
| 2164 | |
| 2165 | int |
| 2166 | tls_getc(unsigned lim) |
| 2167 | { |
| 2168 | exim_gnutls_state_st *state = &state_server; |
| 2169 | if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm) |
| 2170 | { |
| 2171 | ssize_t inbytes; |
| 2172 | |
| 2173 | DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n", |
| 2174 | state->session, state->xfer_buffer, ssl_xfer_buffer_size); |
| 2175 | |
| 2176 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 2177 | inbytes = gnutls_record_recv(state->session, state->xfer_buffer, |
| 2178 | MIN(ssl_xfer_buffer_size, lim)); |
| 2179 | alarm(0); |
| 2180 | |
| 2181 | /* Timeouts do not get this far; see command_timeout_handler(). |
| 2182 | A zero-byte return appears to mean that the TLS session has been |
| 2183 | closed down, not that the socket itself has been closed down. Revert to |
| 2184 | non-TLS handling. */ |
| 2185 | |
| 2186 | if (sigalrm_seen) |
| 2187 | { |
| 2188 | DEBUG(D_tls) debug_printf("Got tls read timeout\n"); |
| 2189 | state->xfer_error = 1; |
| 2190 | return EOF; |
| 2191 | } |
| 2192 | |
| 2193 | else if (inbytes == 0) |
| 2194 | { |
| 2195 | DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); |
| 2196 | |
| 2197 | receive_getc = smtp_getc; |
| 2198 | receive_get_cache = smtp_get_cache; |
| 2199 | receive_ungetc = smtp_ungetc; |
| 2200 | receive_feof = smtp_feof; |
| 2201 | receive_ferror = smtp_ferror; |
| 2202 | receive_smtp_buffered = smtp_buffered; |
| 2203 | |
| 2204 | gnutls_deinit(state->session); |
| 2205 | gnutls_certificate_free_credentials(state->x509_cred); |
| 2206 | |
| 2207 | state->session = NULL; |
| 2208 | state->tlsp->active = -1; |
| 2209 | state->tlsp->bits = 0; |
| 2210 | state->tlsp->certificate_verified = FALSE; |
| 2211 | tls_channelbinding_b64 = NULL; |
| 2212 | state->tlsp->cipher = NULL; |
| 2213 | state->tlsp->peercert = NULL; |
| 2214 | state->tlsp->peerdn = NULL; |
| 2215 | |
| 2216 | return smtp_getc(lim); |
| 2217 | } |
| 2218 | |
| 2219 | /* Handle genuine errors */ |
| 2220 | |
| 2221 | else if (inbytes < 0) |
| 2222 | { |
| 2223 | record_io_error(state, (int) inbytes, US"recv", NULL); |
| 2224 | state->xfer_error = 1; |
| 2225 | return EOF; |
| 2226 | } |
| 2227 | #ifndef DISABLE_DKIM |
| 2228 | dkim_exim_verify_feed(state->xfer_buffer, inbytes); |
| 2229 | #endif |
| 2230 | state->xfer_buffer_hwm = (int) inbytes; |
| 2231 | state->xfer_buffer_lwm = 0; |
| 2232 | } |
| 2233 | |
| 2234 | /* Something in the buffer; return next uschar */ |
| 2235 | |
| 2236 | return state->xfer_buffer[state->xfer_buffer_lwm++]; |
| 2237 | } |
| 2238 | |
| 2239 | void |
| 2240 | tls_get_cache() |
| 2241 | { |
| 2242 | #ifndef DISABLE_DKIM |
| 2243 | exim_gnutls_state_st * state = &state_server; |
| 2244 | int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm; |
| 2245 | if (n > 0) |
| 2246 | dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n); |
| 2247 | #endif |
| 2248 | } |
| 2249 | |
| 2250 | |
| 2251 | |
| 2252 | |
| 2253 | /************************************************* |
| 2254 | * Read bytes from TLS channel * |
| 2255 | *************************************************/ |
| 2256 | |
| 2257 | /* This does not feed DKIM, so if the caller uses this for reading message body, |
| 2258 | then the caller must feed DKIM. |
| 2259 | |
| 2260 | Arguments: |
| 2261 | buff buffer of data |
| 2262 | len size of buffer |
| 2263 | |
| 2264 | Returns: the number of bytes read |
| 2265 | -1 after a failed read |
| 2266 | */ |
| 2267 | |
| 2268 | int |
| 2269 | tls_read(BOOL is_server, uschar *buff, size_t len) |
| 2270 | { |
| 2271 | exim_gnutls_state_st *state = is_server ? &state_server : &state_client; |
| 2272 | ssize_t inbytes; |
| 2273 | |
| 2274 | if (len > INT_MAX) |
| 2275 | len = INT_MAX; |
| 2276 | |
| 2277 | if (state->xfer_buffer_lwm < state->xfer_buffer_hwm) |
| 2278 | DEBUG(D_tls) |
| 2279 | debug_printf("*** PROBABLY A BUG *** " \ |
| 2280 | "tls_read() called with data in the tls_getc() buffer, %d ignored\n", |
| 2281 | state->xfer_buffer_hwm - state->xfer_buffer_lwm); |
| 2282 | |
| 2283 | DEBUG(D_tls) |
| 2284 | debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n", |
| 2285 | state->session, buff, len); |
| 2286 | |
| 2287 | inbytes = gnutls_record_recv(state->session, buff, len); |
| 2288 | if (inbytes > 0) return inbytes; |
| 2289 | if (inbytes == 0) |
| 2290 | { |
| 2291 | DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); |
| 2292 | } |
| 2293 | else record_io_error(state, (int)inbytes, US"recv", NULL); |
| 2294 | |
| 2295 | return -1; |
| 2296 | } |
| 2297 | |
| 2298 | |
| 2299 | |
| 2300 | |
| 2301 | /************************************************* |
| 2302 | * Write bytes down TLS channel * |
| 2303 | *************************************************/ |
| 2304 | |
| 2305 | /* |
| 2306 | Arguments: |
| 2307 | is_server channel specifier |
| 2308 | buff buffer of data |
| 2309 | len number of bytes |
| 2310 | |
| 2311 | Returns: the number of bytes after a successful write, |
| 2312 | -1 after a failed write |
| 2313 | */ |
| 2314 | |
| 2315 | int |
| 2316 | tls_write(BOOL is_server, const uschar *buff, size_t len) |
| 2317 | { |
| 2318 | ssize_t outbytes; |
| 2319 | size_t left = len; |
| 2320 | exim_gnutls_state_st *state = is_server ? &state_server : &state_client; |
| 2321 | |
| 2322 | DEBUG(D_tls) debug_printf("tls_do_write(%p, " SIZE_T_FMT ")\n", buff, left); |
| 2323 | while (left > 0) |
| 2324 | { |
| 2325 | DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n", |
| 2326 | buff, left); |
| 2327 | outbytes = gnutls_record_send(state->session, buff, left); |
| 2328 | |
| 2329 | DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes); |
| 2330 | if (outbytes < 0) |
| 2331 | { |
| 2332 | record_io_error(state, outbytes, US"send", NULL); |
| 2333 | return -1; |
| 2334 | } |
| 2335 | if (outbytes == 0) |
| 2336 | { |
| 2337 | record_io_error(state, 0, US"send", US"TLS channel closed on write"); |
| 2338 | return -1; |
| 2339 | } |
| 2340 | |
| 2341 | left -= outbytes; |
| 2342 | buff += outbytes; |
| 2343 | } |
| 2344 | |
| 2345 | if (len > INT_MAX) |
| 2346 | { |
| 2347 | DEBUG(D_tls) |
| 2348 | debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n", |
| 2349 | len); |
| 2350 | len = INT_MAX; |
| 2351 | } |
| 2352 | |
| 2353 | return (int) len; |
| 2354 | } |
| 2355 | |
| 2356 | |
| 2357 | |
| 2358 | |
| 2359 | /************************************************* |
| 2360 | * Random number generation * |
| 2361 | *************************************************/ |
| 2362 | |
| 2363 | /* Pseudo-random number generation. The result is not expected to be |
| 2364 | cryptographically strong but not so weak that someone will shoot themselves |
| 2365 | in the foot using it as a nonce in input in some email header scheme or |
| 2366 | whatever weirdness they'll twist this into. The result should handle fork() |
| 2367 | and avoid repeating sequences. OpenSSL handles that for us. |
| 2368 | |
| 2369 | Arguments: |
| 2370 | max range maximum |
| 2371 | Returns a random number in range [0, max-1] |
| 2372 | */ |
| 2373 | |
| 2374 | #ifdef HAVE_GNUTLS_RND |
| 2375 | int |
| 2376 | vaguely_random_number(int max) |
| 2377 | { |
| 2378 | unsigned int r; |
| 2379 | int i, needed_len; |
| 2380 | uschar *p; |
| 2381 | uschar smallbuf[sizeof(r)]; |
| 2382 | |
| 2383 | if (max <= 1) |
| 2384 | return 0; |
| 2385 | |
| 2386 | needed_len = sizeof(r); |
| 2387 | /* Don't take 8 times more entropy than needed if int is 8 octets and we were |
| 2388 | * asked for a number less than 10. */ |
| 2389 | for (r = max, i = 0; r; ++i) |
| 2390 | r >>= 1; |
| 2391 | i = (i + 7) / 8; |
| 2392 | if (i < needed_len) |
| 2393 | needed_len = i; |
| 2394 | |
| 2395 | i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len); |
| 2396 | if (i < 0) |
| 2397 | { |
| 2398 | DEBUG(D_all) debug_printf("gnutls_rnd() failed, using fallback.\n"); |
| 2399 | return vaguely_random_number_fallback(max); |
| 2400 | } |
| 2401 | r = 0; |
| 2402 | for (p = smallbuf; needed_len; --needed_len, ++p) |
| 2403 | { |
| 2404 | r *= 256; |
| 2405 | r += *p; |
| 2406 | } |
| 2407 | |
| 2408 | /* We don't particularly care about weighted results; if someone wants |
| 2409 | * smooth distribution and cares enough then they should submit a patch then. */ |
| 2410 | return r % max; |
| 2411 | } |
| 2412 | #else /* HAVE_GNUTLS_RND */ |
| 2413 | int |
| 2414 | vaguely_random_number(int max) |
| 2415 | { |
| 2416 | return vaguely_random_number_fallback(max); |
| 2417 | } |
| 2418 | #endif /* HAVE_GNUTLS_RND */ |
| 2419 | |
| 2420 | |
| 2421 | |
| 2422 | |
| 2423 | /************************************************* |
| 2424 | * Let tls_require_ciphers be checked at startup * |
| 2425 | *************************************************/ |
| 2426 | |
| 2427 | /* The tls_require_ciphers option, if set, must be something which the |
| 2428 | library can parse. |
| 2429 | |
| 2430 | Returns: NULL on success, or error message |
| 2431 | */ |
| 2432 | |
| 2433 | uschar * |
| 2434 | tls_validate_require_cipher(void) |
| 2435 | { |
| 2436 | int rc; |
| 2437 | uschar *expciphers = NULL; |
| 2438 | gnutls_priority_t priority_cache; |
| 2439 | const char *errpos; |
| 2440 | |
| 2441 | #define validate_check_rc(Label) do { \ |
| 2442 | if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \ |
| 2443 | return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0) |
| 2444 | #define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0) |
| 2445 | |
| 2446 | if (exim_gnutls_base_init_done) |
| 2447 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 2448 | "already initialised GnuTLS, Exim developer bug"); |
| 2449 | |
| 2450 | #ifdef HAVE_GNUTLS_PKCS11 |
| 2451 | if (!gnutls_allow_auto_pkcs11) |
| 2452 | { |
| 2453 | rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL); |
| 2454 | validate_check_rc(US"gnutls_pkcs11_init"); |
| 2455 | } |
| 2456 | #endif |
| 2457 | rc = gnutls_global_init(); |
| 2458 | validate_check_rc(US"gnutls_global_init()"); |
| 2459 | exim_gnutls_base_init_done = TRUE; |
| 2460 | |
| 2461 | if (!(tls_require_ciphers && *tls_require_ciphers)) |
| 2462 | return_deinit(NULL); |
| 2463 | |
| 2464 | if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers)) |
| 2465 | return_deinit(US"failed to expand tls_require_ciphers"); |
| 2466 | |
| 2467 | if (!(expciphers && *expciphers)) |
| 2468 | return_deinit(NULL); |
| 2469 | |
| 2470 | DEBUG(D_tls) |
| 2471 | debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers); |
| 2472 | |
| 2473 | rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos); |
| 2474 | validate_check_rc(string_sprintf( |
| 2475 | "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"", |
| 2476 | expciphers, errpos - CS expciphers, errpos)); |
| 2477 | |
| 2478 | #undef return_deinit |
| 2479 | #undef validate_check_rc |
| 2480 | gnutls_global_deinit(); |
| 2481 | |
| 2482 | return NULL; |
| 2483 | } |
| 2484 | |
| 2485 | |
| 2486 | |
| 2487 | |
| 2488 | /************************************************* |
| 2489 | * Report the library versions. * |
| 2490 | *************************************************/ |
| 2491 | |
| 2492 | /* See a description in tls-openssl.c for an explanation of why this exists. |
| 2493 | |
| 2494 | Arguments: a FILE* to print the results to |
| 2495 | Returns: nothing |
| 2496 | */ |
| 2497 | |
| 2498 | void |
| 2499 | tls_version_report(FILE *f) |
| 2500 | { |
| 2501 | fprintf(f, "Library version: GnuTLS: Compile: %s\n" |
| 2502 | " Runtime: %s\n", |
| 2503 | LIBGNUTLS_VERSION, |
| 2504 | gnutls_check_version(NULL)); |
| 2505 | } |
| 2506 | |
| 2507 | /* vi: aw ai sw=2 |
| 2508 | */ |
| 2509 | /* End of tls-gnu.c */ |