| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2009 */ |
| 6 | /* See the file NOTICE for conditions of use and distribution. */ |
| 7 | |
| 8 | /* This module provides TLS (aka SSL) support for Exim using the GnuTLS |
| 9 | library. It is #included into tls.c when that library is used. The code herein |
| 10 | is based on a patch that was contributed by Nikos Mavroyanopoulos. |
| 11 | |
| 12 | No cryptographic code is included in Exim. All this module does is to call |
| 13 | functions from the GnuTLS library. */ |
| 14 | |
| 15 | /* Note: This appears to be using an old API from compat.h; it is likely that |
| 16 | someone familiary with GnuTLS programming could rework a lot of this to a |
| 17 | modern API and perhaps remove the explicit knowledge of crypto algorithms from |
| 18 | Exim. Such a re-work would be most welcome and we'd sacrifice support for |
| 19 | older GnuTLS releases without too many qualms -- maturity and experience |
| 20 | in crypto libraries tends to improve their robustness against attack. |
| 21 | Frankly, if you maintain it, you decide what's supported and what isn't. */ |
| 22 | |
| 23 | /* Heading stuff for GnuTLS */ |
| 24 | |
| 25 | #include <gnutls/gnutls.h> |
| 26 | #include <gnutls/x509.h> |
| 27 | |
| 28 | |
| 29 | #define UNKNOWN_NAME "unknown" |
| 30 | #define DH_BITS 1024 |
| 31 | #define PARAM_SIZE 2*1024 |
| 32 | |
| 33 | |
| 34 | /* Values for verify_requirment */ |
| 35 | |
| 36 | enum { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED }; |
| 37 | |
| 38 | /* Local static variables for GNUTLS */ |
| 39 | |
| 40 | static host_item *client_host; |
| 41 | |
| 42 | static gnutls_dh_params dh_params = NULL; |
| 43 | |
| 44 | static gnutls_certificate_server_credentials x509_cred = NULL; |
| 45 | static gnutls_session tls_session = NULL; |
| 46 | |
| 47 | static char ssl_errstring[256]; |
| 48 | |
| 49 | static int ssl_session_timeout = 200; |
| 50 | static int verify_requirement; |
| 51 | |
| 52 | /* Priorities for TLS algorithms to use. In each case there's a default table, |
| 53 | and space into which it can be copied and altered. */ |
| 54 | |
| 55 | static const int default_proto_priority[16] = { |
| 56 | /* These are gnutls_protocol_t enum values */ |
| 57 | #if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 7 |
| 58 | GNUTLS_TLS1_2, |
| 59 | #endif |
| 60 | #if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 2 |
| 61 | GNUTLS_TLS1_1, |
| 62 | #endif |
| 63 | GNUTLS_TLS1, |
| 64 | GNUTLS_SSL3, |
| 65 | 0 }; |
| 66 | |
| 67 | static int proto_priority[16]; |
| 68 | |
| 69 | static const int default_kx_priority[16] = { |
| 70 | GNUTLS_KX_RSA, |
| 71 | GNUTLS_KX_DHE_DSS, |
| 72 | GNUTLS_KX_DHE_RSA, |
| 73 | 0 }; |
| 74 | |
| 75 | static int kx_priority[16]; |
| 76 | |
| 77 | static int default_cipher_priority[16] = { |
| 78 | GNUTLS_CIPHER_AES_256_CBC, |
| 79 | GNUTLS_CIPHER_AES_128_CBC, |
| 80 | GNUTLS_CIPHER_3DES_CBC, |
| 81 | GNUTLS_CIPHER_ARCFOUR_128, |
| 82 | 0 }; |
| 83 | |
| 84 | static int cipher_priority[16]; |
| 85 | |
| 86 | static const int default_mac_priority[16] = { |
| 87 | GNUTLS_MAC_SHA, |
| 88 | GNUTLS_MAC_MD5, |
| 89 | 0 }; |
| 90 | |
| 91 | static int mac_priority[16]; |
| 92 | |
| 93 | /* These two are currently not changeable. */ |
| 94 | |
| 95 | static const int comp_priority[16] = { GNUTLS_COMP_NULL, 0 }; |
| 96 | static const int cert_type_priority[16] = { GNUTLS_CRT_X509, 0 }; |
| 97 | |
| 98 | /* Tables of priority names and equivalent numbers */ |
| 99 | |
| 100 | typedef struct pri_item { |
| 101 | uschar *name; |
| 102 | int *values; |
| 103 | } pri_item; |
| 104 | |
| 105 | |
| 106 | #if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 7 |
| 107 | static int tls1_2_codes[] = { GNUTLS_TLS1_2, 0 }; |
| 108 | #endif |
| 109 | #if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 2 |
| 110 | static int tls1_1_codes[] = { GNUTLS_TLS1_1, 0 }; |
| 111 | #endif |
| 112 | /* more recent libraries define this as an equivalent value to the |
| 113 | canonical GNUTLS_TLS1_0; since they're the same, we stick to the |
| 114 | older name. */ |
| 115 | static int tls1_0_codes[] = { GNUTLS_TLS1, 0 }; |
| 116 | static int ssl3_codes[] = { GNUTLS_SSL3, 0 }; |
| 117 | |
| 118 | static pri_item proto_index[] = { |
| 119 | #if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 7 |
| 120 | { US"TLS1.2", tls1_2_codes }, |
| 121 | #endif |
| 122 | #if GNUTLS_VERSION_MAJOR > 1 || GNUTLS_VERSION_MINOR >= 2 |
| 123 | { US"TLS1.1", tls1_1_codes }, |
| 124 | #endif |
| 125 | { US"TLS1.0", tls1_0_codes }, |
| 126 | { US"TLS1", tls1_0_codes }, |
| 127 | { US"SSL3", ssl3_codes } |
| 128 | }; |
| 129 | |
| 130 | |
| 131 | static int kx_rsa_codes[] = { GNUTLS_KX_RSA, |
| 132 | GNUTLS_KX_DHE_RSA, 0 }; |
| 133 | static int kx_dhe_codes[] = { GNUTLS_KX_DHE_DSS, |
| 134 | GNUTLS_KX_DHE_RSA, 0 }; |
| 135 | static int kx_dhe_dss_codes[] = { GNUTLS_KX_DHE_DSS, 0 }; |
| 136 | static int kx_dhe_rsa_codes[] = { GNUTLS_KX_DHE_RSA, 0 }; |
| 137 | |
| 138 | static pri_item kx_index[] = { |
| 139 | { US"DHE_DSS", kx_dhe_dss_codes }, |
| 140 | { US"DHE_RSA", kx_dhe_rsa_codes }, |
| 141 | { US"RSA", kx_rsa_codes }, |
| 142 | { US"DHE", kx_dhe_codes } |
| 143 | }; |
| 144 | |
| 145 | |
| 146 | static int arcfour_128_codes[] = { GNUTLS_CIPHER_ARCFOUR_128, 0 }; |
| 147 | static int arcfour_40_codes[] = { GNUTLS_CIPHER_ARCFOUR_40, 0 }; |
| 148 | static int arcfour_codes[] = { GNUTLS_CIPHER_ARCFOUR_128, |
| 149 | GNUTLS_CIPHER_ARCFOUR_40, 0 }; |
| 150 | static int aes_256_codes[] = { GNUTLS_CIPHER_AES_256_CBC, 0 }; |
| 151 | static int aes_128_codes[] = { GNUTLS_CIPHER_AES_128_CBC, 0 }; |
| 152 | static int aes_codes[] = { GNUTLS_CIPHER_AES_256_CBC, |
| 153 | GNUTLS_CIPHER_AES_128_CBC, 0 }; |
| 154 | static int des3_codes[] = { GNUTLS_CIPHER_3DES_CBC, 0 }; |
| 155 | |
| 156 | static pri_item cipher_index[] = { |
| 157 | { US"ARCFOUR_128", arcfour_128_codes }, |
| 158 | { US"ARCFOUR_40", arcfour_40_codes }, |
| 159 | { US"ARCFOUR", arcfour_codes }, |
| 160 | { US"AES_256", aes_256_codes }, |
| 161 | { US"AES_128", aes_128_codes }, |
| 162 | { US"AES", aes_codes }, |
| 163 | { US"3DES", des3_codes } |
| 164 | }; |
| 165 | |
| 166 | |
| 167 | static int mac_sha_codes[] = { GNUTLS_MAC_SHA, 0 }; |
| 168 | static int mac_md5_codes[] = { GNUTLS_MAC_MD5, 0 }; |
| 169 | |
| 170 | static pri_item mac_index[] = { |
| 171 | { US"SHA", mac_sha_codes }, |
| 172 | { US"SHA1", mac_sha_codes }, |
| 173 | { US"MD5", mac_md5_codes } |
| 174 | }; |
| 175 | |
| 176 | |
| 177 | |
| 178 | /************************************************* |
| 179 | * Handle TLS error * |
| 180 | *************************************************/ |
| 181 | |
| 182 | /* Called from lots of places when errors occur before actually starting to do |
| 183 | the TLS handshake, that is, while the session is still in clear. Always returns |
| 184 | DEFER for a server and FAIL for a client so that most calls can use "return |
| 185 | tls_error(...)" to do this processing and then give an appropriate return. A |
| 186 | single function is used for both server and client, because it is called from |
| 187 | some shared functions. |
| 188 | |
| 189 | Argument: |
| 190 | prefix text to include in the logged error |
| 191 | host NULL if setting up a server; |
| 192 | the connected host if setting up a client |
| 193 | msg additional error string (may be NULL) |
| 194 | usually obtained from gnutls_strerror() |
| 195 | |
| 196 | Returns: OK/DEFER/FAIL |
| 197 | */ |
| 198 | |
| 199 | static int |
| 200 | tls_error(uschar *prefix, host_item *host, const char *msg) |
| 201 | { |
| 202 | if (host == NULL) |
| 203 | { |
| 204 | uschar *conn_info = smtp_get_connection_info(); |
| 205 | if (strncmp(conn_info, "SMTP ", 5) == 0) |
| 206 | conn_info += 5; |
| 207 | log_write(0, LOG_MAIN, "TLS error on %s (%s)%s%s", |
| 208 | conn_info, prefix, msg ? ": " : "", msg ? msg : ""); |
| 209 | return DEFER; |
| 210 | } |
| 211 | else |
| 212 | { |
| 213 | log_write(0, LOG_MAIN, "TLS error on connection to %s [%s] (%s)%s%s", |
| 214 | host->name, host->address, prefix, msg ? ": " : "", msg ? msg : ""); |
| 215 | return FAIL; |
| 216 | } |
| 217 | } |
| 218 | |
| 219 | |
| 220 | |
| 221 | /************************************************* |
| 222 | * Verify certificate * |
| 223 | *************************************************/ |
| 224 | |
| 225 | /* Called after a successful handshake, when certificate verification is |
| 226 | required or optional, for both server and client. |
| 227 | |
| 228 | Arguments: |
| 229 | session GNUTLS session |
| 230 | error where to put text giving a reason for failure |
| 231 | |
| 232 | Returns: TRUE/FALSE |
| 233 | */ |
| 234 | |
| 235 | static BOOL |
| 236 | verify_certificate(gnutls_session session, const char **error) |
| 237 | { |
| 238 | int verify; |
| 239 | uschar *dn_string = US""; |
| 240 | const gnutls_datum *cert; |
| 241 | unsigned int cert_size = 0; |
| 242 | |
| 243 | *error = NULL; |
| 244 | |
| 245 | /* Get the peer's certificate. If it sent one, extract it's DN, and then |
| 246 | attempt to verify the certificate. If no certificate is supplied, verification |
| 247 | is forced to fail. */ |
| 248 | |
| 249 | cert = gnutls_certificate_get_peers(session, &cert_size); |
| 250 | if (cert != NULL) |
| 251 | { |
| 252 | uschar buff[1024]; |
| 253 | gnutls_x509_crt gcert; |
| 254 | |
| 255 | gnutls_x509_crt_init(&gcert); |
| 256 | dn_string = US"unknown"; |
| 257 | |
| 258 | if (gnutls_x509_crt_import(gcert, cert, GNUTLS_X509_FMT_DER) == 0) |
| 259 | { |
| 260 | size_t bufsize = sizeof(buff); |
| 261 | if (gnutls_x509_crt_get_dn(gcert, CS buff, &bufsize) >= 0) |
| 262 | dn_string = string_copy_malloc(buff); |
| 263 | } |
| 264 | |
| 265 | verify = gnutls_certificate_verify_peers(session); |
| 266 | } |
| 267 | else |
| 268 | { |
| 269 | DEBUG(D_tls) debug_printf("no peer certificate supplied\n"); |
| 270 | verify = GNUTLS_CERT_INVALID; |
| 271 | *error = "not supplied"; |
| 272 | } |
| 273 | |
| 274 | /* Handle the result of verification. INVALID seems to be set as well |
| 275 | as REVOKED, but leave the test for both. */ |
| 276 | |
| 277 | if ((verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) != 0) |
| 278 | { |
| 279 | tls_certificate_verified = FALSE; |
| 280 | if (*error == NULL) *error = ((verify & GNUTLS_CERT_REVOKED) != 0)? |
| 281 | "revoked" : "invalid"; |
| 282 | if (verify_requirement == VERIFY_REQUIRED) |
| 283 | { |
| 284 | DEBUG(D_tls) debug_printf("TLS certificate verification failed (%s): " |
| 285 | "peerdn=%s\n", *error, dn_string); |
| 286 | gnutls_alert_send(session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE); |
| 287 | return FALSE; /* reject */ |
| 288 | } |
| 289 | DEBUG(D_tls) debug_printf("TLS certificate verify failure (%s) overridden " |
| 290 | "(host in tls_try_verify_hosts): peerdn=%s\n", *error, dn_string); |
| 291 | } |
| 292 | else |
| 293 | { |
| 294 | tls_certificate_verified = TRUE; |
| 295 | DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=%s\n", |
| 296 | dn_string); |
| 297 | } |
| 298 | |
| 299 | tls_peerdn = dn_string; |
| 300 | return TRUE; /* accept */ |
| 301 | } |
| 302 | |
| 303 | |
| 304 | |
| 305 | /************************************************* |
| 306 | * Setup up DH parameters * |
| 307 | *************************************************/ |
| 308 | |
| 309 | /* Generating the D-H parameters may take a long time. They only need to |
| 310 | be re-generated every so often, depending on security policy. What we do is to |
| 311 | keep these parameters in a file in the spool directory. If the file does not |
| 312 | exist, we generate them. This means that it is easy to cause a regeneration. |
| 313 | |
| 314 | The new file is written as a temporary file and renamed, so that an incomplete |
| 315 | file is never present. If two processes both compute some new parameters, you |
| 316 | waste a bit of effort, but it doesn't seem worth messing around with locking to |
| 317 | prevent this. |
| 318 | |
| 319 | Argument: |
| 320 | host NULL for server, server for client (for error handling) |
| 321 | |
| 322 | Returns: OK/DEFER/FAIL |
| 323 | */ |
| 324 | |
| 325 | static int |
| 326 | init_dh(host_item *host) |
| 327 | { |
| 328 | int fd; |
| 329 | int ret; |
| 330 | gnutls_datum m; |
| 331 | uschar filename[200]; |
| 332 | |
| 333 | /* Initialize the data structures for holding the parameters */ |
| 334 | |
| 335 | ret = gnutls_dh_params_init(&dh_params); |
| 336 | if (ret < 0) return tls_error(US"init dh_params", host, gnutls_strerror(ret)); |
| 337 | |
| 338 | /* Set up the name of the cache file */ |
| 339 | |
| 340 | if (!string_format(filename, sizeof(filename), "%s/gnutls-params", |
| 341 | spool_directory)) |
| 342 | return tls_error(US"overlong filename", host, NULL); |
| 343 | |
| 344 | /* Open the cache file for reading and if successful, read it and set up the |
| 345 | parameters. */ |
| 346 | |
| 347 | fd = Uopen(filename, O_RDONLY, 0); |
| 348 | if (fd >= 0) |
| 349 | { |
| 350 | struct stat statbuf; |
| 351 | if (fstat(fd, &statbuf) < 0) |
| 352 | { |
| 353 | (void)close(fd); |
| 354 | return tls_error(US"TLS cache stat failed", host, strerror(errno)); |
| 355 | } |
| 356 | |
| 357 | m.size = statbuf.st_size; |
| 358 | m.data = malloc(m.size); |
| 359 | if (m.data == NULL) |
| 360 | return tls_error(US"memory allocation failed", host, strerror(errno)); |
| 361 | errno = 0; |
| 362 | if (read(fd, m.data, m.size) != m.size) |
| 363 | return tls_error(US"TLS cache read failed", host, strerror(errno)); |
| 364 | (void)close(fd); |
| 365 | |
| 366 | ret = gnutls_dh_params_import_pkcs3(dh_params, &m, GNUTLS_X509_FMT_PEM); |
| 367 | if (ret < 0) |
| 368 | return tls_error(US"DH params import", host, gnutls_strerror(ret)); |
| 369 | DEBUG(D_tls) debug_printf("read D-H parameters from file\n"); |
| 370 | |
| 371 | free(m.data); |
| 372 | } |
| 373 | |
| 374 | /* If the file does not exist, fall through to compute new data and cache it. |
| 375 | If there was any other opening error, it is serious. */ |
| 376 | |
| 377 | else if (errno == ENOENT) |
| 378 | { |
| 379 | ret = -1; |
| 380 | DEBUG(D_tls) |
| 381 | debug_printf("parameter cache file %s does not exist\n", filename); |
| 382 | } |
| 383 | else |
| 384 | return tls_error(string_open_failed(errno, "%s for reading", filename), |
| 385 | host, NULL); |
| 386 | |
| 387 | /* If ret < 0, either the cache file does not exist, or the data it contains |
| 388 | is not useful. One particular case of this is when upgrading from an older |
| 389 | release of Exim in which the data was stored in a different format. We don't |
| 390 | try to be clever and support both formats; we just regenerate new data in this |
| 391 | case. */ |
| 392 | |
| 393 | if (ret < 0) |
| 394 | { |
| 395 | uschar tempfilename[sizeof(filename) + 10]; |
| 396 | |
| 397 | DEBUG(D_tls) debug_printf("generating %d bit Diffie-Hellman key...\n", |
| 398 | DH_BITS); |
| 399 | ret = gnutls_dh_params_generate2(dh_params, DH_BITS); |
| 400 | if (ret < 0) return tls_error(US"D-H key generation", host, gnutls_strerror(ret)); |
| 401 | |
| 402 | /* Write the parameters to a file in the spool directory so that we |
| 403 | can use them from other Exim processes. */ |
| 404 | |
| 405 | sprintf(CS tempfilename, "%s-%d", filename, (int)getpid()); |
| 406 | fd = Uopen(tempfilename, O_WRONLY|O_CREAT, 0400); |
| 407 | if (fd < 0) |
| 408 | return tls_error(string_open_failed(errno, "%s for writing", filename), |
| 409 | host, NULL); |
| 410 | (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */ |
| 411 | |
| 412 | /* export the parameters in a format that can be generated using GNUTLS' |
| 413 | * certtool or other programs. |
| 414 | * |
| 415 | * The commands for certtool are: |
| 416 | * $ certtool --generate-dh-params --bits 1024 > params |
| 417 | */ |
| 418 | |
| 419 | m.size = PARAM_SIZE; |
| 420 | m.data = malloc(m.size); |
| 421 | if (m.data == NULL) |
| 422 | return tls_error(US"memory allocation failed", host, strerror(errno)); |
| 423 | |
| 424 | m.size = PARAM_SIZE; |
| 425 | ret = gnutls_dh_params_export_pkcs3(dh_params, GNUTLS_X509_FMT_PEM, m.data, |
| 426 | &m.size); |
| 427 | if (ret < 0) |
| 428 | return tls_error(US"DH params export", host, gnutls_strerror(ret)); |
| 429 | |
| 430 | m.size = Ustrlen(m.data); |
| 431 | errno = 0; |
| 432 | if (write(fd, m.data, m.size) != m.size || write(fd, "\n", 1) != 1) |
| 433 | return tls_error(US"TLS cache write failed", host, strerror(errno)); |
| 434 | |
| 435 | free(m.data); |
| 436 | (void)close(fd); |
| 437 | |
| 438 | if (rename(CS tempfilename, CS filename) < 0) |
| 439 | return tls_error(string_sprintf("failed to rename %s as %s", |
| 440 | tempfilename, filename), host, strerror(errno)); |
| 441 | |
| 442 | DEBUG(D_tls) debug_printf("wrote D-H parameters to file %s\n", filename); |
| 443 | } |
| 444 | |
| 445 | DEBUG(D_tls) debug_printf("initialized D-H parameters\n"); |
| 446 | return OK; |
| 447 | } |
| 448 | |
| 449 | |
| 450 | |
| 451 | |
| 452 | /************************************************* |
| 453 | * Initialize for GnuTLS * |
| 454 | *************************************************/ |
| 455 | |
| 456 | /* Called from both server and client code. In the case of a server, errors |
| 457 | before actual TLS negotiation return DEFER. |
| 458 | |
| 459 | Arguments: |
| 460 | host connected host, if client; NULL if server |
| 461 | certificate certificate file |
| 462 | privatekey private key file |
| 463 | cas CA certs file |
| 464 | crl CRL file |
| 465 | |
| 466 | Returns: OK/DEFER/FAIL |
| 467 | */ |
| 468 | |
| 469 | static int |
| 470 | tls_init(host_item *host, uschar *certificate, uschar *privatekey, uschar *cas, |
| 471 | uschar *crl) |
| 472 | { |
| 473 | int rc; |
| 474 | uschar *cert_expanded, *key_expanded, *cas_expanded, *crl_expanded; |
| 475 | |
| 476 | client_host = host; |
| 477 | |
| 478 | rc = gnutls_global_init(); |
| 479 | if (rc < 0) return tls_error(US"tls-init", host, gnutls_strerror(rc)); |
| 480 | |
| 481 | /* Create D-H parameters, or read them from the cache file. This function does |
| 482 | its own SMTP error messaging. */ |
| 483 | |
| 484 | rc = init_dh(host); |
| 485 | if (rc != OK) return rc; |
| 486 | |
| 487 | /* Create the credentials structure */ |
| 488 | |
| 489 | rc = gnutls_certificate_allocate_credentials(&x509_cred); |
| 490 | if (rc < 0) |
| 491 | return tls_error(US"certificate_allocate_credentials", |
| 492 | host, gnutls_strerror(rc)); |
| 493 | |
| 494 | /* This stuff must be done for each session, because different certificates |
| 495 | may be required for different sessions. */ |
| 496 | |
| 497 | if (!expand_check(certificate, US"tls_certificate", &cert_expanded)) |
| 498 | return DEFER; |
| 499 | |
| 500 | key_expanded = NULL; |
| 501 | if (privatekey != NULL) |
| 502 | { |
| 503 | if (!expand_check(privatekey, US"tls_privatekey", &key_expanded)) |
| 504 | return DEFER; |
| 505 | } |
| 506 | |
| 507 | /* If expansion was forced to fail, key_expanded will be NULL. If the result of |
| 508 | the expansion is an empty string, ignore it also, and assume that the private |
| 509 | key is in the same file as the certificate. */ |
| 510 | |
| 511 | if (key_expanded == NULL || *key_expanded == 0) |
| 512 | key_expanded = cert_expanded; |
| 513 | |
| 514 | /* Set the certificate and private keys */ |
| 515 | |
| 516 | if (cert_expanded != NULL) |
| 517 | { |
| 518 | DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n", |
| 519 | cert_expanded, key_expanded); |
| 520 | rc = gnutls_certificate_set_x509_key_file(x509_cred, CS cert_expanded, |
| 521 | CS key_expanded, GNUTLS_X509_FMT_PEM); |
| 522 | if (rc < 0) |
| 523 | { |
| 524 | uschar *msg = string_sprintf("cert/key setup: cert=%s key=%s", |
| 525 | cert_expanded, key_expanded); |
| 526 | return tls_error(msg, host, gnutls_strerror(rc)); |
| 527 | } |
| 528 | } |
| 529 | |
| 530 | /* A certificate is mandatory in a server, but not in a client */ |
| 531 | |
| 532 | else |
| 533 | { |
| 534 | if (host == NULL) |
| 535 | return tls_error(US"no TLS server certificate is specified", NULL, NULL); |
| 536 | DEBUG(D_tls) debug_printf("no TLS client certificate is specified\n"); |
| 537 | } |
| 538 | |
| 539 | /* Set the trusted CAs file if one is provided, and then add the CRL if one is |
| 540 | provided. Experiment shows that, if the certificate file is empty, an unhelpful |
| 541 | error message is provided. However, if we just refrain from setting anything up |
| 542 | in that case, certificate verification fails, which seems to be the correct |
| 543 | behaviour. */ |
| 544 | |
| 545 | if (cas != NULL) |
| 546 | { |
| 547 | struct stat statbuf; |
| 548 | |
| 549 | if (!expand_check(cas, US"tls_verify_certificates", &cas_expanded)) |
| 550 | return DEFER; |
| 551 | |
| 552 | if (stat(CS cas_expanded, &statbuf) < 0) |
| 553 | { |
| 554 | log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s " |
| 555 | "(tls_verify_certificates): %s", cas_expanded, strerror(errno)); |
| 556 | return DEFER; |
| 557 | } |
| 558 | |
| 559 | DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n", |
| 560 | cas_expanded, statbuf.st_size); |
| 561 | |
| 562 | /* If the cert file is empty, there's no point in loading the CRL file. */ |
| 563 | |
| 564 | if (statbuf.st_size > 0) |
| 565 | { |
| 566 | rc = gnutls_certificate_set_x509_trust_file(x509_cred, CS cas_expanded, |
| 567 | GNUTLS_X509_FMT_PEM); |
| 568 | if (rc < 0) return tls_error(US"setup_certs", host, gnutls_strerror(rc)); |
| 569 | |
| 570 | if (crl != NULL && *crl != 0) |
| 571 | { |
| 572 | if (!expand_check(crl, US"tls_crl", &crl_expanded)) |
| 573 | return DEFER; |
| 574 | DEBUG(D_tls) debug_printf("loading CRL file = %s\n", crl_expanded); |
| 575 | rc = gnutls_certificate_set_x509_crl_file(x509_cred, CS crl_expanded, |
| 576 | GNUTLS_X509_FMT_PEM); |
| 577 | if (rc < 0) return tls_error(US"CRL setup", host, gnutls_strerror(rc)); |
| 578 | } |
| 579 | } |
| 580 | } |
| 581 | |
| 582 | /* Associate the parameters with the x509 credentials structure. */ |
| 583 | |
| 584 | gnutls_certificate_set_dh_params(x509_cred, dh_params); |
| 585 | |
| 586 | DEBUG(D_tls) debug_printf("initialized certificate stuff\n"); |
| 587 | return OK; |
| 588 | } |
| 589 | |
| 590 | |
| 591 | |
| 592 | |
| 593 | /************************************************* |
| 594 | * Remove from a priority list * |
| 595 | *************************************************/ |
| 596 | |
| 597 | /* Cautiously written so that it will remove duplicates if present. |
| 598 | |
| 599 | Arguments: |
| 600 | list a zero-terminated list |
| 601 | remove_list a zero-terminated list to be removed |
| 602 | |
| 603 | Returns: nothing |
| 604 | */ |
| 605 | |
| 606 | static void |
| 607 | remove_priority(int *list, int *remove_list) |
| 608 | { |
| 609 | for (; *remove_list != 0; remove_list++) |
| 610 | { |
| 611 | int *p = list; |
| 612 | while (*p != 0) |
| 613 | { |
| 614 | if (*p == *remove_list) |
| 615 | { |
| 616 | int *pp = p; |
| 617 | do { pp[0] = pp[1]; pp++; } while (*pp != 0); |
| 618 | } |
| 619 | else p++; |
| 620 | } |
| 621 | } |
| 622 | } |
| 623 | |
| 624 | |
| 625 | |
| 626 | /************************************************* |
| 627 | * Add to a priority list * |
| 628 | *************************************************/ |
| 629 | |
| 630 | /* Cautiously written to check the list size |
| 631 | |
| 632 | Arguments: |
| 633 | list a zero-terminated list |
| 634 | list_max maximum offset in the list |
| 635 | add_list a zero-terminated list to be added |
| 636 | |
| 637 | Returns: TRUE if OK; FALSE if list overflows |
| 638 | */ |
| 639 | |
| 640 | static BOOL |
| 641 | add_priority(int *list, int list_max, int *add_list) |
| 642 | { |
| 643 | int next = 0; |
| 644 | while (list[next] != 0) next++; |
| 645 | while (*add_list != 0) |
| 646 | { |
| 647 | if (next >= list_max) return FALSE; |
| 648 | list[next++] = *add_list++; |
| 649 | } |
| 650 | list[next] = 0; |
| 651 | return TRUE; |
| 652 | } |
| 653 | |
| 654 | |
| 655 | |
| 656 | /************************************************* |
| 657 | * Adjust a priority list * |
| 658 | *************************************************/ |
| 659 | |
| 660 | /* This function is called to adjust the lists of cipher algorithms, MAC |
| 661 | algorithms, key-exchange methods, and protocols. |
| 662 | |
| 663 | Arguments: |
| 664 | plist the appropriate priority list |
| 665 | psize the length of the list |
| 666 | s the configuation string |
| 667 | index the index of recognized strings |
| 668 | isize the length of the index |
| 669 | |
| 670 | |
| 671 | which text for an error message |
| 672 | |
| 673 | Returns: FALSE if the table overflows, else TRUE |
| 674 | */ |
| 675 | |
| 676 | static BOOL |
| 677 | set_priority(int *plist, int psize, uschar *s, pri_item *index, int isize, |
| 678 | uschar *which) |
| 679 | { |
| 680 | int sep = 0; |
| 681 | BOOL first = TRUE; |
| 682 | uschar *t; |
| 683 | |
| 684 | while ((t = string_nextinlist(&s, &sep, big_buffer, big_buffer_size)) != NULL) |
| 685 | { |
| 686 | int i; |
| 687 | BOOL exclude = t[0] == '!'; |
| 688 | if (first && !exclude) plist[0] = 0; |
| 689 | first = FALSE; |
| 690 | for (i = 0; i < isize; i++) |
| 691 | { |
| 692 | uschar *ss = strstric(t, index[i].name, FALSE); |
| 693 | if (ss != NULL) |
| 694 | { |
| 695 | uschar *endss = ss + Ustrlen(index[i].name); |
| 696 | if ((ss == t || !isalnum(ss[-1])) && !isalnum(*endss)) |
| 697 | { |
| 698 | if (exclude) |
| 699 | remove_priority(plist, index[i].values); |
| 700 | else |
| 701 | { |
| 702 | if (!add_priority(plist, psize, index[i].values)) |
| 703 | { |
| 704 | log_write(0, LOG_MAIN|LOG_PANIC, "GnuTLS init failed: %s " |
| 705 | "priority table overflow", which); |
| 706 | return FALSE; |
| 707 | } |
| 708 | } |
| 709 | } |
| 710 | } |
| 711 | } |
| 712 | } |
| 713 | |
| 714 | DEBUG(D_tls) |
| 715 | { |
| 716 | int *ptr = plist; |
| 717 | debug_printf("adjusted %s priorities:", which); |
| 718 | while (*ptr != 0) debug_printf(" %d", *ptr++); |
| 719 | debug_printf("\n"); |
| 720 | } |
| 721 | |
| 722 | return TRUE; |
| 723 | } |
| 724 | |
| 725 | |
| 726 | |
| 727 | |
| 728 | /************************************************* |
| 729 | * Initialize a single GNUTLS session * |
| 730 | *************************************************/ |
| 731 | |
| 732 | /* Set the algorithm, the db backend, whether to request certificates etc. |
| 733 | |
| 734 | TLS in Exim was first implemented using OpenSSL. This has a function to which |
| 735 | you pass a list of cipher suites that are permitted/not permitted. GnuTLS works |
| 736 | differently. It operates using priority lists for the different components of |
| 737 | cipher suites. |
| 738 | |
| 739 | For compatibility of configuration, we scan a list of cipher suites and set |
| 740 | priorities therefrom. However, at the moment, we pay attention only to the bulk |
| 741 | cipher. |
| 742 | |
| 743 | Arguments: |
| 744 | side one of GNUTLS_SERVER, GNUTLS_CLIENT |
| 745 | expciphers expanded ciphers list or NULL |
| 746 | expmac expanded MAC list or NULL |
| 747 | expkx expanded key-exchange list or NULL |
| 748 | expproto expanded protocol list or NULL |
| 749 | |
| 750 | Returns: a gnutls_session, or NULL if there is a problem |
| 751 | */ |
| 752 | |
| 753 | static gnutls_session |
| 754 | tls_session_init(int side, uschar *expciphers, uschar *expmac, uschar *expkx, |
| 755 | uschar *expproto) |
| 756 | { |
| 757 | gnutls_session session; |
| 758 | |
| 759 | gnutls_init(&session, side); |
| 760 | |
| 761 | /* Initialize the lists of permitted protocols, key-exchange methods, ciphers, |
| 762 | and MACs. */ |
| 763 | |
| 764 | memcpy(cipher_priority, default_cipher_priority, sizeof(cipher_priority)); |
| 765 | memcpy(mac_priority, default_mac_priority, sizeof(mac_priority)); |
| 766 | memcpy(kx_priority, default_kx_priority, sizeof(kx_priority)); |
| 767 | memcpy(proto_priority, default_proto_priority, sizeof(proto_priority)); |
| 768 | |
| 769 | /* The names OpenSSL uses in tls_require_ciphers are of the form DES-CBC3-SHA, |
| 770 | using hyphen separators. GnuTLS uses underscore separators. So that I can use |
| 771 | either form for tls_require_ciphers in my tests, and also for general |
| 772 | convenience, we turn hyphens into underscores before scanning the list. */ |
| 773 | |
| 774 | if (expciphers != NULL) |
| 775 | { |
| 776 | uschar *s = expciphers; |
| 777 | while (*s != 0) { if (*s == '-') *s = '_'; s++; } |
| 778 | } |
| 779 | |
| 780 | if ((expciphers != NULL && |
| 781 | !set_priority(cipher_priority, sizeof(cipher_priority)/sizeof(int), |
| 782 | expciphers, cipher_index, sizeof(cipher_index)/sizeof(pri_item), |
| 783 | US"cipher")) || |
| 784 | (expmac != NULL && |
| 785 | !set_priority(mac_priority, sizeof(mac_priority)/sizeof(int), |
| 786 | expmac, mac_index, sizeof(mac_index)/sizeof(pri_item), |
| 787 | US"MAC")) || |
| 788 | (expkx != NULL && |
| 789 | !set_priority(kx_priority, sizeof(kx_priority)/sizeof(int), |
| 790 | expkx, kx_index, sizeof(kx_index)/sizeof(pri_item), |
| 791 | US"key-exchange")) || |
| 792 | (expproto != NULL && |
| 793 | !set_priority(proto_priority, sizeof(proto_priority)/sizeof(int), |
| 794 | expproto, proto_index, sizeof(proto_index)/sizeof(pri_item), |
| 795 | US"protocol"))) |
| 796 | { |
| 797 | gnutls_deinit(session); |
| 798 | return NULL; |
| 799 | } |
| 800 | |
| 801 | /* Define the various priorities */ |
| 802 | |
| 803 | gnutls_cipher_set_priority(session, cipher_priority); |
| 804 | gnutls_compression_set_priority(session, comp_priority); |
| 805 | gnutls_kx_set_priority(session, kx_priority); |
| 806 | gnutls_protocol_set_priority(session, proto_priority); |
| 807 | gnutls_mac_set_priority(session, mac_priority); |
| 808 | |
| 809 | gnutls_cred_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred); |
| 810 | |
| 811 | gnutls_dh_set_prime_bits(session, DH_BITS); |
| 812 | |
| 813 | /* Request or demand a certificate of the peer, as configured. This will |
| 814 | happen only in a server. */ |
| 815 | |
| 816 | if (verify_requirement != VERIFY_NONE) |
| 817 | gnutls_certificate_server_set_request(session, |
| 818 | (verify_requirement == VERIFY_OPTIONAL)? |
| 819 | GNUTLS_CERT_REQUEST : GNUTLS_CERT_REQUIRE); |
| 820 | |
| 821 | gnutls_db_set_cache_expiration(session, ssl_session_timeout); |
| 822 | |
| 823 | /* Reduce security in favour of increased compatibility, if the admin |
| 824 | decides to make that trade-off. */ |
| 825 | if (gnutls_compat_mode) |
| 826 | { |
| 827 | #if LIBGNUTLS_VERSION_NUMBER >= 0x020104 |
| 828 | DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n"); |
| 829 | gnutls_session_enable_compatibility_mode(session); |
| 830 | #else |
| 831 | DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n"); |
| 832 | #endif |
| 833 | } |
| 834 | |
| 835 | DEBUG(D_tls) debug_printf("initialized GnuTLS session\n"); |
| 836 | return session; |
| 837 | } |
| 838 | |
| 839 | |
| 840 | |
| 841 | /************************************************* |
| 842 | * Get name of cipher in use * |
| 843 | *************************************************/ |
| 844 | |
| 845 | /* The answer is left in a static buffer, and tls_cipher is set to point |
| 846 | to it. |
| 847 | |
| 848 | Argument: pointer to a GnuTLS session |
| 849 | Returns: nothing |
| 850 | */ |
| 851 | |
| 852 | static void |
| 853 | construct_cipher_name(gnutls_session session) |
| 854 | { |
| 855 | static uschar cipherbuf[256]; |
| 856 | uschar *ver; |
| 857 | int bits, c, kx, mac; |
| 858 | |
| 859 | ver = string_copy( |
| 860 | US gnutls_protocol_get_name(gnutls_protocol_get_version(session))); |
| 861 | if (Ustrncmp(ver, "TLS ", 4) == 0) ver[3] = '-'; /* Don't want space */ |
| 862 | |
| 863 | c = gnutls_cipher_get(session); |
| 864 | bits = gnutls_cipher_get_key_size(c); |
| 865 | |
| 866 | mac = gnutls_mac_get(session); |
| 867 | kx = gnutls_kx_get(session); |
| 868 | |
| 869 | string_format(cipherbuf, sizeof(cipherbuf), "%s:%s:%u", ver, |
| 870 | gnutls_cipher_suite_get_name(kx, c, mac), bits); |
| 871 | tls_cipher = cipherbuf; |
| 872 | |
| 873 | DEBUG(D_tls) debug_printf("cipher: %s\n", cipherbuf); |
| 874 | } |
| 875 | |
| 876 | |
| 877 | |
| 878 | /************************************************* |
| 879 | * Start a TLS session in a server * |
| 880 | *************************************************/ |
| 881 | |
| 882 | /* This is called when Exim is running as a server, after having received |
| 883 | the STARTTLS command. It must respond to that command, and then negotiate |
| 884 | a TLS session. |
| 885 | |
| 886 | Arguments: |
| 887 | require_ciphers list of allowed ciphers or NULL |
| 888 | require_mac list of allowed MACs or NULL |
| 889 | require_kx list of allowed key_exchange methods or NULL |
| 890 | require_proto list of allowed protocols or NULL |
| 891 | |
| 892 | Returns: OK on success |
| 893 | DEFER for errors before the start of the negotiation |
| 894 | FAIL for errors during the negotation; the server can't |
| 895 | continue running. |
| 896 | */ |
| 897 | |
| 898 | int |
| 899 | tls_server_start(uschar *require_ciphers, uschar *require_mac, |
| 900 | uschar *require_kx, uschar *require_proto) |
| 901 | { |
| 902 | int rc; |
| 903 | const char *error; |
| 904 | uschar *expciphers = NULL; |
| 905 | uschar *expmac = NULL; |
| 906 | uschar *expkx = NULL; |
| 907 | uschar *expproto = NULL; |
| 908 | |
| 909 | /* Check for previous activation */ |
| 910 | |
| 911 | if (tls_active >= 0) |
| 912 | { |
| 913 | tls_error("STARTTLS received after TLS started", NULL, ""); |
| 914 | smtp_printf("554 Already in TLS\r\n"); |
| 915 | return FAIL; |
| 916 | } |
| 917 | |
| 918 | /* Initialize the library. If it fails, it will already have logged the error |
| 919 | and sent an SMTP response. */ |
| 920 | |
| 921 | DEBUG(D_tls) debug_printf("initializing GnuTLS as a server\n"); |
| 922 | |
| 923 | rc = tls_init(NULL, tls_certificate, tls_privatekey, tls_verify_certificates, |
| 924 | tls_crl); |
| 925 | if (rc != OK) return rc; |
| 926 | |
| 927 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers) || |
| 928 | !expand_check(require_mac, US"gnutls_require_mac", &expmac) || |
| 929 | !expand_check(require_kx, US"gnutls_require_kx", &expkx) || |
| 930 | !expand_check(require_proto, US"gnutls_require_proto", &expproto)) |
| 931 | return FAIL; |
| 932 | |
| 933 | /* If this is a host for which certificate verification is mandatory or |
| 934 | optional, set up appropriately. */ |
| 935 | |
| 936 | tls_certificate_verified = FALSE; |
| 937 | verify_requirement = VERIFY_NONE; |
| 938 | |
| 939 | if (verify_check_host(&tls_verify_hosts) == OK) |
| 940 | verify_requirement = VERIFY_REQUIRED; |
| 941 | else if (verify_check_host(&tls_try_verify_hosts) == OK) |
| 942 | verify_requirement = VERIFY_OPTIONAL; |
| 943 | |
| 944 | /* Prepare for new connection */ |
| 945 | |
| 946 | tls_session = tls_session_init(GNUTLS_SERVER, expciphers, expmac, expkx, |
| 947 | expproto); |
| 948 | if (tls_session == NULL) |
| 949 | return tls_error(US"tls_session_init", NULL, |
| 950 | gnutls_strerror(GNUTLS_E_MEMORY_ERROR)); |
| 951 | |
| 952 | /* Set context and tell client to go ahead, except in the case of TLS startup |
| 953 | on connection, where outputting anything now upsets the clients and tends to |
| 954 | make them disconnect. We need to have an explicit fflush() here, to force out |
| 955 | the response. Other smtp_printf() calls do not need it, because in non-TLS |
| 956 | mode, the fflush() happens when smtp_getc() is called. */ |
| 957 | |
| 958 | if (!tls_on_connect) |
| 959 | { |
| 960 | smtp_printf("220 TLS go ahead\r\n"); |
| 961 | fflush(smtp_out); |
| 962 | } |
| 963 | |
| 964 | /* Now negotiate the TLS session. We put our own timer on it, since it seems |
| 965 | that the GnuTLS library doesn't. */ |
| 966 | |
| 967 | gnutls_transport_set_ptr2(tls_session, (gnutls_transport_ptr)fileno(smtp_in), |
| 968 | (gnutls_transport_ptr)fileno(smtp_out)); |
| 969 | |
| 970 | sigalrm_seen = FALSE; |
| 971 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 972 | rc = gnutls_handshake(tls_session); |
| 973 | alarm(0); |
| 974 | |
| 975 | if (rc < 0) |
| 976 | { |
| 977 | tls_error(US"gnutls_handshake", NULL, |
| 978 | sigalrm_seen ? "timed out" : gnutls_strerror(rc)); |
| 979 | |
| 980 | /* It seems that, except in the case of a timeout, we have to close the |
| 981 | connection right here; otherwise if the other end is running OpenSSL it hangs |
| 982 | until the server times out. */ |
| 983 | |
| 984 | if (!sigalrm_seen) |
| 985 | { |
| 986 | (void)fclose(smtp_out); |
| 987 | (void)fclose(smtp_in); |
| 988 | } |
| 989 | |
| 990 | return FAIL; |
| 991 | } |
| 992 | |
| 993 | DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); |
| 994 | |
| 995 | if (verify_requirement != VERIFY_NONE && |
| 996 | !verify_certificate(tls_session, &error)) |
| 997 | { |
| 998 | tls_error(US"certificate verification failed", NULL, error); |
| 999 | return FAIL; |
| 1000 | } |
| 1001 | |
| 1002 | construct_cipher_name(tls_session); |
| 1003 | |
| 1004 | /* TLS has been set up. Adjust the input functions to read via TLS, |
| 1005 | and initialize appropriately. */ |
| 1006 | |
| 1007 | ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); |
| 1008 | ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; |
| 1009 | ssl_xfer_eof = ssl_xfer_error = 0; |
| 1010 | |
| 1011 | receive_getc = tls_getc; |
| 1012 | receive_ungetc = tls_ungetc; |
| 1013 | receive_feof = tls_feof; |
| 1014 | receive_ferror = tls_ferror; |
| 1015 | receive_smtp_buffered = tls_smtp_buffered; |
| 1016 | |
| 1017 | tls_active = fileno(smtp_out); |
| 1018 | |
| 1019 | return OK; |
| 1020 | } |
| 1021 | |
| 1022 | |
| 1023 | |
| 1024 | |
| 1025 | /************************************************* |
| 1026 | * Start a TLS session in a client * |
| 1027 | *************************************************/ |
| 1028 | |
| 1029 | /* Called from the smtp transport after STARTTLS has been accepted. |
| 1030 | |
| 1031 | Arguments: |
| 1032 | fd the fd of the connection |
| 1033 | host connected host (for messages) |
| 1034 | addr the first address (not used) |
| 1035 | dhparam DH parameter file |
| 1036 | certificate certificate file |
| 1037 | privatekey private key file |
| 1038 | verify_certs file for certificate verify |
| 1039 | verify_crl CRL for verify |
| 1040 | require_ciphers list of allowed ciphers or NULL |
| 1041 | require_mac list of allowed MACs or NULL |
| 1042 | require_kx list of allowed key_exchange methods or NULL |
| 1043 | require_proto list of allowed protocols or NULL |
| 1044 | timeout startup timeout |
| 1045 | |
| 1046 | Returns: OK/DEFER/FAIL (because using common functions), |
| 1047 | but for a client, DEFER and FAIL have the same meaning |
| 1048 | */ |
| 1049 | |
| 1050 | int |
| 1051 | tls_client_start(int fd, host_item *host, address_item *addr, uschar *dhparam, |
| 1052 | uschar *certificate, uschar *privatekey, uschar *verify_certs, |
| 1053 | uschar *verify_crl, uschar *require_ciphers, uschar *require_mac, |
| 1054 | uschar *require_kx, uschar *require_proto, int timeout) |
| 1055 | { |
| 1056 | const gnutls_datum *server_certs; |
| 1057 | uschar *expciphers = NULL; |
| 1058 | uschar *expmac = NULL; |
| 1059 | uschar *expkx = NULL; |
| 1060 | uschar *expproto = NULL; |
| 1061 | const char *error; |
| 1062 | unsigned int server_certs_size; |
| 1063 | int rc; |
| 1064 | |
| 1065 | DEBUG(D_tls) debug_printf("initializing GnuTLS as a client\n"); |
| 1066 | |
| 1067 | verify_requirement = (verify_certs == NULL)? VERIFY_NONE : VERIFY_REQUIRED; |
| 1068 | rc = tls_init(host, certificate, privatekey, verify_certs, verify_crl); |
| 1069 | if (rc != OK) return rc; |
| 1070 | |
| 1071 | if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers) || |
| 1072 | !expand_check(require_mac, US"gnutls_require_mac", &expmac) || |
| 1073 | !expand_check(require_kx, US"gnutls_require_kx", &expkx) || |
| 1074 | !expand_check(require_proto, US"gnutls_require_proto", &expproto)) |
| 1075 | return FAIL; |
| 1076 | |
| 1077 | tls_session = tls_session_init(GNUTLS_CLIENT, expciphers, expmac, expkx, |
| 1078 | expproto); |
| 1079 | |
| 1080 | if (tls_session == NULL) |
| 1081 | return tls_error(US "tls_session_init", host, |
| 1082 | gnutls_strerror(GNUTLS_E_MEMORY_ERROR)); |
| 1083 | |
| 1084 | gnutls_transport_set_ptr(tls_session, (gnutls_transport_ptr)fd); |
| 1085 | |
| 1086 | /* There doesn't seem to be a built-in timeout on connection. */ |
| 1087 | |
| 1088 | sigalrm_seen = FALSE; |
| 1089 | alarm(timeout); |
| 1090 | rc = gnutls_handshake(tls_session); |
| 1091 | alarm(0); |
| 1092 | |
| 1093 | if (rc < 0) |
| 1094 | return tls_error(US "gnutls_handshake", host, |
| 1095 | sigalrm_seen ? "timed out" : gnutls_strerror(rc)); |
| 1096 | |
| 1097 | server_certs = gnutls_certificate_get_peers(tls_session, &server_certs_size); |
| 1098 | |
| 1099 | if (server_certs != NULL) |
| 1100 | { |
| 1101 | uschar buff[1024]; |
| 1102 | gnutls_x509_crt gcert; |
| 1103 | |
| 1104 | gnutls_x509_crt_init(&gcert); |
| 1105 | tls_peerdn = US"unknown"; |
| 1106 | |
| 1107 | if (gnutls_x509_crt_import(gcert, server_certs, GNUTLS_X509_FMT_DER) == 0) |
| 1108 | { |
| 1109 | size_t bufsize = sizeof(buff); |
| 1110 | if (gnutls_x509_crt_get_dn(gcert, CS buff, &bufsize) >= 0) |
| 1111 | tls_peerdn = string_copy_malloc(buff); |
| 1112 | } |
| 1113 | } |
| 1114 | |
| 1115 | /* Should we also verify the hostname here? */ |
| 1116 | |
| 1117 | if (verify_requirement != VERIFY_NONE && |
| 1118 | !verify_certificate(tls_session, &error)) |
| 1119 | return tls_error(US"certificate verification failed", host, error); |
| 1120 | |
| 1121 | construct_cipher_name(tls_session); /* Sets tls_cipher */ |
| 1122 | tls_active = fd; |
| 1123 | return OK; |
| 1124 | } |
| 1125 | |
| 1126 | |
| 1127 | |
| 1128 | /************************************************* |
| 1129 | * Deal with logging errors during I/O * |
| 1130 | *************************************************/ |
| 1131 | |
| 1132 | /* We have to get the identity of the peer from saved data. |
| 1133 | |
| 1134 | Argument: |
| 1135 | ec the GnuTLS error code, or 0 if it's a local error |
| 1136 | when text identifying read or write |
| 1137 | text local error text when ec is 0 |
| 1138 | |
| 1139 | Returns: nothing |
| 1140 | */ |
| 1141 | |
| 1142 | static void |
| 1143 | record_io_error(int ec, uschar *when, uschar *text) |
| 1144 | { |
| 1145 | const char *msg; |
| 1146 | |
| 1147 | if (ec == GNUTLS_E_FATAL_ALERT_RECEIVED) |
| 1148 | msg = string_sprintf("%s: %s", gnutls_strerror(ec), |
| 1149 | gnutls_alert_get_name(gnutls_alert_get(tls_session))); |
| 1150 | else |
| 1151 | msg = gnutls_strerror(ec); |
| 1152 | |
| 1153 | tls_error(when, client_host, msg); |
| 1154 | } |
| 1155 | |
| 1156 | |
| 1157 | |
| 1158 | /************************************************* |
| 1159 | * TLS version of getc * |
| 1160 | *************************************************/ |
| 1161 | |
| 1162 | /* This gets the next byte from the TLS input buffer. If the buffer is empty, |
| 1163 | it refills the buffer via the GnuTLS reading function. |
| 1164 | |
| 1165 | Arguments: none |
| 1166 | Returns: the next character or EOF |
| 1167 | */ |
| 1168 | |
| 1169 | int |
| 1170 | tls_getc(void) |
| 1171 | { |
| 1172 | if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) |
| 1173 | { |
| 1174 | int inbytes; |
| 1175 | |
| 1176 | DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%lx, %lx, %u)\n", |
| 1177 | (long) tls_session, (long) ssl_xfer_buffer, ssl_xfer_buffer_size); |
| 1178 | |
| 1179 | if (smtp_receive_timeout > 0) alarm(smtp_receive_timeout); |
| 1180 | inbytes = gnutls_record_recv(tls_session, CS ssl_xfer_buffer, |
| 1181 | ssl_xfer_buffer_size); |
| 1182 | alarm(0); |
| 1183 | |
| 1184 | /* A zero-byte return appears to mean that the TLS session has been |
| 1185 | closed down, not that the socket itself has been closed down. Revert to |
| 1186 | non-TLS handling. */ |
| 1187 | |
| 1188 | if (inbytes == 0) |
| 1189 | { |
| 1190 | DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); |
| 1191 | |
| 1192 | receive_getc = smtp_getc; |
| 1193 | receive_ungetc = smtp_ungetc; |
| 1194 | receive_feof = smtp_feof; |
| 1195 | receive_ferror = smtp_ferror; |
| 1196 | receive_smtp_buffered = smtp_buffered; |
| 1197 | |
| 1198 | gnutls_deinit(tls_session); |
| 1199 | tls_session = NULL; |
| 1200 | tls_active = -1; |
| 1201 | tls_cipher = NULL; |
| 1202 | tls_peerdn = NULL; |
| 1203 | |
| 1204 | return smtp_getc(); |
| 1205 | } |
| 1206 | |
| 1207 | /* Handle genuine errors */ |
| 1208 | |
| 1209 | else if (inbytes < 0) |
| 1210 | { |
| 1211 | record_io_error(inbytes, US"recv", NULL); |
| 1212 | ssl_xfer_error = 1; |
| 1213 | return EOF; |
| 1214 | } |
| 1215 | #ifndef DISABLE_DKIM |
| 1216 | dkim_exim_verify_feed(ssl_xfer_buffer, inbytes); |
| 1217 | #endif |
| 1218 | ssl_xfer_buffer_hwm = inbytes; |
| 1219 | ssl_xfer_buffer_lwm = 0; |
| 1220 | } |
| 1221 | |
| 1222 | |
| 1223 | /* Something in the buffer; return next uschar */ |
| 1224 | |
| 1225 | return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; |
| 1226 | } |
| 1227 | |
| 1228 | |
| 1229 | |
| 1230 | /************************************************* |
| 1231 | * Read bytes from TLS channel * |
| 1232 | *************************************************/ |
| 1233 | |
| 1234 | /* |
| 1235 | Arguments: |
| 1236 | buff buffer of data |
| 1237 | len size of buffer |
| 1238 | |
| 1239 | Returns: the number of bytes read |
| 1240 | -1 after a failed read |
| 1241 | */ |
| 1242 | |
| 1243 | int |
| 1244 | tls_read(uschar *buff, size_t len) |
| 1245 | { |
| 1246 | int inbytes; |
| 1247 | |
| 1248 | DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%lx, %lx, %u)\n", |
| 1249 | (long) tls_session, (long) buff, len); |
| 1250 | |
| 1251 | inbytes = gnutls_record_recv(tls_session, CS buff, len); |
| 1252 | if (inbytes > 0) return inbytes; |
| 1253 | if (inbytes == 0) |
| 1254 | { |
| 1255 | DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); |
| 1256 | } |
| 1257 | else record_io_error(inbytes, US"recv", NULL); |
| 1258 | |
| 1259 | return -1; |
| 1260 | } |
| 1261 | |
| 1262 | |
| 1263 | |
| 1264 | /************************************************* |
| 1265 | * Write bytes down TLS channel * |
| 1266 | *************************************************/ |
| 1267 | |
| 1268 | /* |
| 1269 | Arguments: |
| 1270 | buff buffer of data |
| 1271 | len number of bytes |
| 1272 | |
| 1273 | Returns: the number of bytes after a successful write, |
| 1274 | -1 after a failed write |
| 1275 | */ |
| 1276 | |
| 1277 | int |
| 1278 | tls_write(const uschar *buff, size_t len) |
| 1279 | { |
| 1280 | int outbytes; |
| 1281 | int left = len; |
| 1282 | |
| 1283 | DEBUG(D_tls) debug_printf("tls_do_write(%lx, %d)\n", (long) buff, left); |
| 1284 | while (left > 0) |
| 1285 | { |
| 1286 | DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %lx, %d)\n", (long)buff, |
| 1287 | left); |
| 1288 | outbytes = gnutls_record_send(tls_session, CS buff, left); |
| 1289 | |
| 1290 | DEBUG(D_tls) debug_printf("outbytes=%d\n", outbytes); |
| 1291 | if (outbytes < 0) |
| 1292 | { |
| 1293 | record_io_error(outbytes, US"send", NULL); |
| 1294 | return -1; |
| 1295 | } |
| 1296 | if (outbytes == 0) |
| 1297 | { |
| 1298 | record_io_error(0, US"send", US"TLS channel closed on write"); |
| 1299 | return -1; |
| 1300 | } |
| 1301 | |
| 1302 | left -= outbytes; |
| 1303 | buff += outbytes; |
| 1304 | } |
| 1305 | |
| 1306 | return len; |
| 1307 | } |
| 1308 | |
| 1309 | |
| 1310 | |
| 1311 | /************************************************* |
| 1312 | * Close down a TLS session * |
| 1313 | *************************************************/ |
| 1314 | |
| 1315 | /* This is also called from within a delivery subprocess forked from the |
| 1316 | daemon, to shut down the TLS library, without actually doing a shutdown (which |
| 1317 | would tamper with the TLS session in the parent process). |
| 1318 | |
| 1319 | Arguments: TRUE if gnutls_bye is to be called |
| 1320 | Returns: nothing |
| 1321 | */ |
| 1322 | |
| 1323 | void |
| 1324 | tls_close(BOOL shutdown) |
| 1325 | { |
| 1326 | if (tls_active < 0) return; /* TLS was not active */ |
| 1327 | |
| 1328 | if (shutdown) |
| 1329 | { |
| 1330 | DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS\n"); |
| 1331 | gnutls_bye(tls_session, GNUTLS_SHUT_WR); |
| 1332 | } |
| 1333 | |
| 1334 | gnutls_deinit(tls_session); |
| 1335 | tls_session = NULL; |
| 1336 | gnutls_global_deinit(); |
| 1337 | |
| 1338 | tls_active = -1; |
| 1339 | } |
| 1340 | |
| 1341 | |
| 1342 | |
| 1343 | |
| 1344 | /************************************************* |
| 1345 | * Report the library versions. * |
| 1346 | *************************************************/ |
| 1347 | |
| 1348 | /* See a description in tls-openssl.c for an explanation of why this exists. |
| 1349 | |
| 1350 | Arguments: a FILE* to print the results to |
| 1351 | Returns: nothing |
| 1352 | */ |
| 1353 | |
| 1354 | void |
| 1355 | tls_version_report(FILE *f) |
| 1356 | { |
| 1357 | fprintf(f, "Library version: GnuTLS: Compile: %s\n" |
| 1358 | " Runtime: %s\n", |
| 1359 | LIBGNUTLS_VERSION, |
| 1360 | gnutls_check_version(NULL)); |
| 1361 | } |
| 1362 | |
| 1363 | /* End of tls-gnu.c */ |