| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge, 1995 - 2017 */ |
| 6 | /* See the file NOTICE for conditions of use and distribution. */ |
| 7 | |
| 8 | /* Code for DKIM support. Other DKIM relevant code is in |
| 9 | receive.c, transport.c and transports/smtp.c */ |
| 10 | |
| 11 | #include "exim.h" |
| 12 | |
| 13 | #ifndef DISABLE_DKIM |
| 14 | |
| 15 | #include "pdkim/pdkim.h" |
| 16 | |
| 17 | int dkim_verify_oldpool; |
| 18 | pdkim_ctx *dkim_verify_ctx = NULL; |
| 19 | pdkim_signature *dkim_signatures = NULL; |
| 20 | pdkim_signature *dkim_cur_sig = NULL; |
| 21 | static const uschar * dkim_collect_error = NULL; |
| 22 | |
| 23 | |
| 24 | |
| 25 | /*XXX the caller only uses the first record if we return multiple. |
| 26 | Could we hand back an allocated string? |
| 27 | */ |
| 28 | |
| 29 | static int |
| 30 | dkim_exim_query_dns_txt(char *name, char *answer) |
| 31 | { |
| 32 | dns_answer dnsa; |
| 33 | dns_scan dnss; |
| 34 | dns_record *rr; |
| 35 | |
| 36 | lookup_dnssec_authenticated = NULL; |
| 37 | if (dns_lookup(&dnsa, US name, T_TXT, NULL) != DNS_SUCCEED) |
| 38 | return PDKIM_FAIL; /*XXX better error detail? logging? */ |
| 39 | |
| 40 | /* Search for TXT record */ |
| 41 | |
| 42 | for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS); |
| 43 | rr; |
| 44 | rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT)) |
| 45 | if (rr->type == T_TXT) |
| 46 | { |
| 47 | int rr_offset = 0; |
| 48 | int answer_offset = 0; |
| 49 | |
| 50 | /* Copy record content to the answer buffer */ |
| 51 | |
| 52 | while (rr_offset < rr->size) |
| 53 | { |
| 54 | uschar len = rr->data[rr_offset++]; |
| 55 | snprintf(answer + answer_offset, |
| 56 | PDKIM_DNS_TXT_MAX_RECLEN - answer_offset, |
| 57 | "%.*s", (int)len, CS (rr->data + rr_offset)); |
| 58 | rr_offset += len; |
| 59 | answer_offset += len; |
| 60 | if (answer_offset >= PDKIM_DNS_TXT_MAX_RECLEN) |
| 61 | return PDKIM_FAIL; /*XXX better error detail? logging? */ |
| 62 | } |
| 63 | return PDKIM_OK; |
| 64 | } |
| 65 | |
| 66 | return PDKIM_FAIL; /*XXX better error detail? logging? */ |
| 67 | } |
| 68 | |
| 69 | |
| 70 | void |
| 71 | dkim_exim_init(void) |
| 72 | { |
| 73 | pdkim_init(); |
| 74 | } |
| 75 | |
| 76 | |
| 77 | |
| 78 | void |
| 79 | dkim_exim_verify_init(BOOL dot_stuffing) |
| 80 | { |
| 81 | /* There is a store-reset between header & body reception |
| 82 | so cannot use the main pool. Any allocs done by Exim |
| 83 | memory-handling must use the perm pool. */ |
| 84 | |
| 85 | dkim_verify_oldpool = store_pool; |
| 86 | store_pool = POOL_PERM; |
| 87 | |
| 88 | /* Free previous context if there is one */ |
| 89 | |
| 90 | if (dkim_verify_ctx) |
| 91 | pdkim_free_ctx(dkim_verify_ctx); |
| 92 | |
| 93 | /* Create new context */ |
| 94 | |
| 95 | dkim_verify_ctx = pdkim_init_verify(&dkim_exim_query_dns_txt, dot_stuffing); |
| 96 | dkim_collect_input = !!dkim_verify_ctx; |
| 97 | dkim_collect_error = NULL; |
| 98 | |
| 99 | /* Start feed up with any cached data */ |
| 100 | receive_get_cache(); |
| 101 | |
| 102 | store_pool = dkim_verify_oldpool; |
| 103 | } |
| 104 | |
| 105 | |
| 106 | void |
| 107 | dkim_exim_verify_feed(uschar * data, int len) |
| 108 | { |
| 109 | int rc; |
| 110 | |
| 111 | store_pool = POOL_PERM; |
| 112 | if ( dkim_collect_input |
| 113 | && (rc = pdkim_feed(dkim_verify_ctx, data, len)) != PDKIM_OK) |
| 114 | { |
| 115 | dkim_collect_error = pdkim_errstr(rc); |
| 116 | log_write(0, LOG_MAIN, |
| 117 | "DKIM: validation error: %.100s", dkim_collect_error); |
| 118 | dkim_collect_input = FALSE; |
| 119 | } |
| 120 | store_pool = dkim_verify_oldpool; |
| 121 | } |
| 122 | |
| 123 | |
| 124 | void |
| 125 | dkim_exim_verify_finish(void) |
| 126 | { |
| 127 | pdkim_signature * sig = NULL; |
| 128 | int dkim_signers_size = 0, dkim_signers_ptr = 0, rc; |
| 129 | const uschar * errstr; |
| 130 | |
| 131 | store_pool = POOL_PERM; |
| 132 | |
| 133 | /* Delete eventual previous signature chain */ |
| 134 | |
| 135 | dkim_signers = NULL; |
| 136 | dkim_signatures = NULL; |
| 137 | |
| 138 | if (dkim_collect_error) |
| 139 | { |
| 140 | log_write(0, LOG_MAIN, |
| 141 | "DKIM: Error during validation, disabling signature verification: %.100s", |
| 142 | dkim_collect_error); |
| 143 | dkim_disable_verify = TRUE; |
| 144 | goto out; |
| 145 | } |
| 146 | |
| 147 | dkim_collect_input = FALSE; |
| 148 | |
| 149 | /* Finish DKIM operation and fetch link to signatures chain */ |
| 150 | |
| 151 | rc = pdkim_feed_finish(dkim_verify_ctx, &dkim_signatures, &errstr); |
| 152 | if (rc != PDKIM_OK) |
| 153 | { |
| 154 | log_write(0, LOG_MAIN, "DKIM: validation error: %.100s%s%s", pdkim_errstr(rc), |
| 155 | errstr ? ": " : "", errstr ? errstr : US""); |
| 156 | goto out; |
| 157 | } |
| 158 | |
| 159 | for (sig = dkim_signatures; sig; sig = sig->next) |
| 160 | { |
| 161 | int size = 0, ptr = 0; |
| 162 | uschar * logmsg = NULL, * s; |
| 163 | |
| 164 | /* Log a line for each signature */ |
| 165 | |
| 166 | if (!(s = sig->domain)) s = US"<UNSET>"; |
| 167 | logmsg = string_append(logmsg, &size, &ptr, 2, "d=", s); |
| 168 | if (!(s = sig->selector)) s = US"<UNSET>"; |
| 169 | logmsg = string_append(logmsg, &size, &ptr, 2, " s=", s); |
| 170 | logmsg = string_append(logmsg, &size, &ptr, 7, |
| 171 | " c=", sig->canon_headers == PDKIM_CANON_SIMPLE ? "simple" : "relaxed", |
| 172 | "/", sig->canon_body == PDKIM_CANON_SIMPLE ? "simple" : "relaxed", |
| 173 | " a=", dkim_sig_to_a_tag(sig), |
| 174 | string_sprintf(" b=%d", |
| 175 | (int)sig->sighash.len > -1 ? sig->sighash.len * 8 : 0)); |
| 176 | if ((s= sig->identity)) logmsg = string_append(logmsg, &size, &ptr, 2, " i=", s); |
| 177 | if (sig->created > 0) logmsg = string_append(logmsg, &size, &ptr, 1, |
| 178 | string_sprintf(" t=%lu", sig->created)); |
| 179 | if (sig->expires > 0) logmsg = string_append(logmsg, &size, &ptr, 1, |
| 180 | string_sprintf(" x=%lu", sig->expires)); |
| 181 | if (sig->bodylength > -1) logmsg = string_append(logmsg, &size, &ptr, 1, |
| 182 | string_sprintf(" l=%lu", sig->bodylength)); |
| 183 | |
| 184 | switch (sig->verify_status) |
| 185 | { |
| 186 | case PDKIM_VERIFY_NONE: |
| 187 | logmsg = string_append(logmsg, &size, &ptr, 1, " [not verified]"); |
| 188 | break; |
| 189 | |
| 190 | case PDKIM_VERIFY_INVALID: |
| 191 | logmsg = string_append(logmsg, &size, &ptr, 1, " [invalid - "); |
| 192 | switch (sig->verify_ext_status) |
| 193 | { |
| 194 | case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: |
| 195 | logmsg = string_append(logmsg, &size, &ptr, 1, |
| 196 | "public key record (currently?) unavailable]"); |
| 197 | break; |
| 198 | |
| 199 | case PDKIM_VERIFY_INVALID_BUFFER_SIZE: |
| 200 | logmsg = string_append(logmsg, &size, &ptr, 1, |
| 201 | "overlong public key record]"); |
| 202 | break; |
| 203 | |
| 204 | case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: |
| 205 | case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: |
| 206 | logmsg = string_append(logmsg, &size, &ptr, 1, |
| 207 | "syntax error in public key record]"); |
| 208 | break; |
| 209 | |
| 210 | case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: |
| 211 | logmsg = string_append(logmsg, &size, &ptr, 1, |
| 212 | "signature tag missing or invalid]"); |
| 213 | break; |
| 214 | |
| 215 | case PDKIM_VERIFY_INVALID_DKIM_VERSION: |
| 216 | logmsg = string_append(logmsg, &size, &ptr, 1, |
| 217 | "unsupported DKIM version]"); |
| 218 | break; |
| 219 | |
| 220 | default: |
| 221 | logmsg = string_append(logmsg, &size, &ptr, 1, |
| 222 | "unspecified problem]"); |
| 223 | } |
| 224 | break; |
| 225 | |
| 226 | case PDKIM_VERIFY_FAIL: |
| 227 | logmsg = |
| 228 | string_append(logmsg, &size, &ptr, 1, " [verification failed - "); |
| 229 | switch (sig->verify_ext_status) |
| 230 | { |
| 231 | case PDKIM_VERIFY_FAIL_BODY: |
| 232 | logmsg = string_append(logmsg, &size, &ptr, 1, |
| 233 | "body hash mismatch (body probably modified in transit)]"); |
| 234 | break; |
| 235 | |
| 236 | case PDKIM_VERIFY_FAIL_MESSAGE: |
| 237 | logmsg = string_append(logmsg, &size, &ptr, 1, |
| 238 | "signature did not verify (headers probably modified in transit)]"); |
| 239 | break; |
| 240 | |
| 241 | default: |
| 242 | logmsg = string_append(logmsg, &size, &ptr, 1, "unspecified reason]"); |
| 243 | } |
| 244 | break; |
| 245 | |
| 246 | case PDKIM_VERIFY_PASS: |
| 247 | logmsg = |
| 248 | string_append(logmsg, &size, &ptr, 1, " [verification succeeded]"); |
| 249 | break; |
| 250 | } |
| 251 | |
| 252 | logmsg[ptr] = '\0'; |
| 253 | log_write(0, LOG_MAIN, "DKIM: %s", logmsg); |
| 254 | |
| 255 | /* Build a colon-separated list of signing domains (and identities, if present) in dkim_signers */ |
| 256 | |
| 257 | if (sig->domain) |
| 258 | dkim_signers = string_append_listele(dkim_signers, &dkim_signers_size, |
| 259 | &dkim_signers_ptr, ':', sig->domain); |
| 260 | |
| 261 | if (sig->identity) |
| 262 | dkim_signers = string_append_listele(dkim_signers, &dkim_signers_size, |
| 263 | &dkim_signers_ptr, ':', sig->identity); |
| 264 | |
| 265 | /* Process next signature */ |
| 266 | } |
| 267 | |
| 268 | out: |
| 269 | store_pool = dkim_verify_oldpool; |
| 270 | } |
| 271 | |
| 272 | |
| 273 | void |
| 274 | dkim_exim_acl_setup(uschar * id) |
| 275 | { |
| 276 | pdkim_signature * sig; |
| 277 | uschar * cmp_val; |
| 278 | |
| 279 | dkim_cur_sig = NULL; |
| 280 | dkim_cur_signer = id; |
| 281 | |
| 282 | if (dkim_disable_verify || !id || !dkim_verify_ctx) |
| 283 | return; |
| 284 | |
| 285 | /* Find signature to run ACL on */ |
| 286 | |
| 287 | for (sig = dkim_signatures; sig; sig = sig->next) |
| 288 | if ( (cmp_val = Ustrchr(id, '@') != NULL ? US sig->identity : US sig->domain) |
| 289 | && strcmpic(cmp_val, id) == 0 |
| 290 | ) |
| 291 | { |
| 292 | dkim_cur_sig = sig; |
| 293 | |
| 294 | /* The "dkim_domain" and "dkim_selector" expansion variables have |
| 295 | related globals, since they are used in the signing code too. |
| 296 | Instead of inventing separate names for verification, we set |
| 297 | them here. This is easy since a domain and selector is guaranteed |
| 298 | to be in a signature. The other dkim_* expansion items are |
| 299 | dynamically fetched from dkim_cur_sig at expansion time (see |
| 300 | function below). */ |
| 301 | |
| 302 | dkim_signing_domain = US sig->domain; |
| 303 | dkim_signing_selector = US sig->selector; |
| 304 | dkim_key_length = sig->sighash.len * 8; |
| 305 | return; |
| 306 | } |
| 307 | } |
| 308 | |
| 309 | |
| 310 | static uschar * |
| 311 | dkim_exim_expand_defaults(int what) |
| 312 | { |
| 313 | switch (what) |
| 314 | { |
| 315 | case DKIM_ALGO: return US""; |
| 316 | case DKIM_BODYLENGTH: return US"9999999999999"; |
| 317 | case DKIM_CANON_BODY: return US""; |
| 318 | case DKIM_CANON_HEADERS: return US""; |
| 319 | case DKIM_COPIEDHEADERS: return US""; |
| 320 | case DKIM_CREATED: return US"0"; |
| 321 | case DKIM_EXPIRES: return US"9999999999999"; |
| 322 | case DKIM_HEADERNAMES: return US""; |
| 323 | case DKIM_IDENTITY: return US""; |
| 324 | case DKIM_KEY_GRANULARITY: return US"*"; |
| 325 | case DKIM_KEY_SRVTYPE: return US"*"; |
| 326 | case DKIM_KEY_NOTES: return US""; |
| 327 | case DKIM_KEY_TESTING: return US"0"; |
| 328 | case DKIM_NOSUBDOMAINS: return US"0"; |
| 329 | case DKIM_VERIFY_STATUS: return US"none"; |
| 330 | case DKIM_VERIFY_REASON: return US""; |
| 331 | default: return US""; |
| 332 | } |
| 333 | } |
| 334 | |
| 335 | |
| 336 | uschar * |
| 337 | dkim_exim_expand_query(int what) |
| 338 | { |
| 339 | if (!dkim_verify_ctx || dkim_disable_verify || !dkim_cur_sig) |
| 340 | return dkim_exim_expand_defaults(what); |
| 341 | |
| 342 | switch (what) |
| 343 | { |
| 344 | case DKIM_ALGO: |
| 345 | return dkim_sig_to_a_tag(dkim_cur_sig); |
| 346 | |
| 347 | case DKIM_BODYLENGTH: |
| 348 | return dkim_cur_sig->bodylength >= 0 |
| 349 | ? string_sprintf(OFF_T_FMT, (LONGLONG_T) dkim_cur_sig->bodylength) |
| 350 | : dkim_exim_expand_defaults(what); |
| 351 | |
| 352 | case DKIM_CANON_BODY: |
| 353 | switch (dkim_cur_sig->canon_body) |
| 354 | { |
| 355 | case PDKIM_CANON_RELAXED: return US"relaxed"; |
| 356 | case PDKIM_CANON_SIMPLE: |
| 357 | default: return US"simple"; |
| 358 | } |
| 359 | |
| 360 | case DKIM_CANON_HEADERS: |
| 361 | switch (dkim_cur_sig->canon_headers) |
| 362 | { |
| 363 | case PDKIM_CANON_RELAXED: return US"relaxed"; |
| 364 | case PDKIM_CANON_SIMPLE: |
| 365 | default: return US"simple"; |
| 366 | } |
| 367 | |
| 368 | case DKIM_COPIEDHEADERS: |
| 369 | return dkim_cur_sig->copiedheaders |
| 370 | ? US dkim_cur_sig->copiedheaders : dkim_exim_expand_defaults(what); |
| 371 | |
| 372 | case DKIM_CREATED: |
| 373 | return dkim_cur_sig->created > 0 |
| 374 | ? string_sprintf("%llu", dkim_cur_sig->created) |
| 375 | : dkim_exim_expand_defaults(what); |
| 376 | |
| 377 | case DKIM_EXPIRES: |
| 378 | return dkim_cur_sig->expires > 0 |
| 379 | ? string_sprintf("%llu", dkim_cur_sig->expires) |
| 380 | : dkim_exim_expand_defaults(what); |
| 381 | |
| 382 | case DKIM_HEADERNAMES: |
| 383 | return dkim_cur_sig->headernames |
| 384 | ? dkim_cur_sig->headernames : dkim_exim_expand_defaults(what); |
| 385 | |
| 386 | case DKIM_IDENTITY: |
| 387 | return dkim_cur_sig->identity |
| 388 | ? US dkim_cur_sig->identity : dkim_exim_expand_defaults(what); |
| 389 | |
| 390 | case DKIM_KEY_GRANULARITY: |
| 391 | return dkim_cur_sig->pubkey |
| 392 | ? dkim_cur_sig->pubkey->granularity |
| 393 | ? US dkim_cur_sig->pubkey->granularity |
| 394 | : dkim_exim_expand_defaults(what) |
| 395 | : dkim_exim_expand_defaults(what); |
| 396 | |
| 397 | case DKIM_KEY_SRVTYPE: |
| 398 | return dkim_cur_sig->pubkey |
| 399 | ? dkim_cur_sig->pubkey->srvtype |
| 400 | ? US dkim_cur_sig->pubkey->srvtype |
| 401 | : dkim_exim_expand_defaults(what) |
| 402 | : dkim_exim_expand_defaults(what); |
| 403 | |
| 404 | case DKIM_KEY_NOTES: |
| 405 | return dkim_cur_sig->pubkey |
| 406 | ? dkim_cur_sig->pubkey->notes |
| 407 | ? US dkim_cur_sig->pubkey->notes |
| 408 | : dkim_exim_expand_defaults(what) |
| 409 | : dkim_exim_expand_defaults(what); |
| 410 | |
| 411 | case DKIM_KEY_TESTING: |
| 412 | return dkim_cur_sig->pubkey |
| 413 | ? dkim_cur_sig->pubkey->testing |
| 414 | ? US"1" |
| 415 | : dkim_exim_expand_defaults(what) |
| 416 | : dkim_exim_expand_defaults(what); |
| 417 | |
| 418 | case DKIM_NOSUBDOMAINS: |
| 419 | return dkim_cur_sig->pubkey |
| 420 | ? dkim_cur_sig->pubkey->no_subdomaining |
| 421 | ? US"1" |
| 422 | : dkim_exim_expand_defaults(what) |
| 423 | : dkim_exim_expand_defaults(what); |
| 424 | |
| 425 | case DKIM_VERIFY_STATUS: |
| 426 | switch (dkim_cur_sig->verify_status) |
| 427 | { |
| 428 | case PDKIM_VERIFY_INVALID: return US"invalid"; |
| 429 | case PDKIM_VERIFY_FAIL: return US"fail"; |
| 430 | case PDKIM_VERIFY_PASS: return US"pass"; |
| 431 | case PDKIM_VERIFY_NONE: |
| 432 | default: return US"none"; |
| 433 | } |
| 434 | |
| 435 | case DKIM_VERIFY_REASON: |
| 436 | switch (dkim_cur_sig->verify_ext_status) |
| 437 | { |
| 438 | case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: |
| 439 | return US"pubkey_unavailable"; |
| 440 | case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:return US"pubkey_dns_syntax"; |
| 441 | case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: return US"pubkey_der_syntax"; |
| 442 | case PDKIM_VERIFY_FAIL_BODY: return US"bodyhash_mismatch"; |
| 443 | case PDKIM_VERIFY_FAIL_MESSAGE: return US"signature_incorrect"; |
| 444 | } |
| 445 | |
| 446 | default: |
| 447 | return US""; |
| 448 | } |
| 449 | } |
| 450 | |
| 451 | |
| 452 | /* Generate signatures for the given file, returning a string. |
| 453 | If a prefix is given, prepend it to the file for the calculations. |
| 454 | */ |
| 455 | |
| 456 | uschar * |
| 457 | dkim_exim_sign(int fd, off_t off, uschar * prefix, |
| 458 | struct ob_dkim * dkim, const uschar ** errstr) |
| 459 | { |
| 460 | const uschar * dkim_domain; |
| 461 | int sep = 0; |
| 462 | uschar *seen_items = NULL; |
| 463 | int seen_items_size = 0; |
| 464 | int seen_items_offset = 0; |
| 465 | uschar *dkim_canon_expanded; |
| 466 | uschar *dkim_sign_headers_expanded; |
| 467 | uschar *dkim_private_key_expanded; |
| 468 | uschar *dkim_hash_expanded; |
| 469 | pdkim_ctx *ctx = NULL; |
| 470 | uschar *rc = NULL; |
| 471 | uschar *sigbuf = NULL; |
| 472 | int sigsize = 0; |
| 473 | int sigptr = 0; |
| 474 | pdkim_signature *signature; |
| 475 | int pdkim_canon; |
| 476 | int pdkim_rc; |
| 477 | int sread; |
| 478 | uschar buf[4096]; |
| 479 | int save_errno = 0; |
| 480 | int old_pool = store_pool; |
| 481 | |
| 482 | store_pool = POOL_MAIN; |
| 483 | |
| 484 | if (!(dkim_domain = expand_cstring(dkim->dkim_domain))) |
| 485 | { |
| 486 | /* expansion error, do not send message. */ |
| 487 | log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand " |
| 488 | "dkim_domain: %s", expand_string_message); |
| 489 | goto bad; |
| 490 | } |
| 491 | |
| 492 | /* Set $dkim_domain expansion variable to each unique domain in list. */ |
| 493 | |
| 494 | while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep, NULL, 0))) |
| 495 | { |
| 496 | if (dkim_signing_domain[0] == '\0') |
| 497 | continue; |
| 498 | |
| 499 | /* Only sign once for each domain, no matter how often it |
| 500 | appears in the expanded list. */ |
| 501 | |
| 502 | if (seen_items) |
| 503 | { |
| 504 | const uschar *seen_items_list = seen_items; |
| 505 | if (match_isinlist(dkim_signing_domain, |
| 506 | &seen_items_list, 0, NULL, NULL, MCL_STRING, TRUE, |
| 507 | NULL) == OK) |
| 508 | continue; |
| 509 | |
| 510 | seen_items = |
| 511 | string_append(seen_items, &seen_items_size, &seen_items_offset, 1, ":"); |
| 512 | } |
| 513 | |
| 514 | seen_items = |
| 515 | string_append(seen_items, &seen_items_size, &seen_items_offset, 1, |
| 516 | dkim_signing_domain); |
| 517 | seen_items[seen_items_offset] = '\0'; |
| 518 | |
| 519 | /* Set up $dkim_selector expansion variable. */ |
| 520 | |
| 521 | if (!(dkim_signing_selector = expand_string(dkim->dkim_selector))) |
| 522 | { |
| 523 | log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand " |
| 524 | "dkim_selector: %s", expand_string_message); |
| 525 | goto bad; |
| 526 | } |
| 527 | |
| 528 | /* Get canonicalization to use */ |
| 529 | |
| 530 | dkim_canon_expanded = dkim->dkim_canon |
| 531 | ? expand_string(dkim->dkim_canon) : US"relaxed"; |
| 532 | if (!dkim_canon_expanded) |
| 533 | { |
| 534 | /* expansion error, do not send message. */ |
| 535 | log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand " |
| 536 | "dkim_canon: %s", expand_string_message); |
| 537 | goto bad; |
| 538 | } |
| 539 | |
| 540 | if (Ustrcmp(dkim_canon_expanded, "relaxed") == 0) |
| 541 | pdkim_canon = PDKIM_CANON_RELAXED; |
| 542 | else if (Ustrcmp(dkim_canon_expanded, "simple") == 0) |
| 543 | pdkim_canon = PDKIM_CANON_SIMPLE; |
| 544 | else |
| 545 | { |
| 546 | log_write(0, LOG_MAIN, |
| 547 | "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n", |
| 548 | dkim_canon_expanded); |
| 549 | pdkim_canon = PDKIM_CANON_RELAXED; |
| 550 | } |
| 551 | |
| 552 | dkim_sign_headers_expanded = NULL; |
| 553 | if (dkim->dkim_sign_headers) |
| 554 | if (!(dkim_sign_headers_expanded = expand_string(dkim->dkim_sign_headers))) |
| 555 | { |
| 556 | log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand " |
| 557 | "dkim_sign_headers: %s", expand_string_message); |
| 558 | goto bad; |
| 559 | } |
| 560 | /* else pass NULL, which means default header list */ |
| 561 | |
| 562 | /* Get private key to use. */ |
| 563 | |
| 564 | if (!(dkim_private_key_expanded = expand_string(dkim->dkim_private_key))) |
| 565 | { |
| 566 | log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand " |
| 567 | "dkim_private_key: %s", expand_string_message); |
| 568 | goto bad; |
| 569 | } |
| 570 | |
| 571 | if ( Ustrlen(dkim_private_key_expanded) == 0 |
| 572 | || Ustrcmp(dkim_private_key_expanded, "0") == 0 |
| 573 | || Ustrcmp(dkim_private_key_expanded, "false") == 0 |
| 574 | ) |
| 575 | continue; /* don't sign, but no error */ |
| 576 | |
| 577 | if (dkim_private_key_expanded[0] == '/') |
| 578 | { |
| 579 | int privkey_fd, off = 0, len; |
| 580 | |
| 581 | /* Looks like a filename, load the private key. */ |
| 582 | |
| 583 | memset(big_buffer, 0, big_buffer_size); |
| 584 | |
| 585 | if ((privkey_fd = open(CS dkim_private_key_expanded, O_RDONLY)) < 0) |
| 586 | { |
| 587 | log_write(0, LOG_MAIN | LOG_PANIC, "unable to open " |
| 588 | "private key file for reading: %s", |
| 589 | dkim_private_key_expanded); |
| 590 | goto bad; |
| 591 | } |
| 592 | |
| 593 | do |
| 594 | { |
| 595 | if ((len = read(privkey_fd, big_buffer + off, big_buffer_size - 2 - off)) < 0) |
| 596 | { |
| 597 | (void) close(privkey_fd); |
| 598 | log_write(0, LOG_MAIN|LOG_PANIC, "unable to read private key file: %s", |
| 599 | dkim_private_key_expanded); |
| 600 | goto bad; |
| 601 | } |
| 602 | off += len; |
| 603 | } |
| 604 | while (len > 0); |
| 605 | |
| 606 | (void) close(privkey_fd); |
| 607 | big_buffer[off] = '\0'; |
| 608 | dkim_private_key_expanded = big_buffer; |
| 609 | } |
| 610 | |
| 611 | if (!(dkim_hash_expanded = expand_string(dkim->dkim_hash))) |
| 612 | { |
| 613 | log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand " |
| 614 | "dkim_hash: %s", expand_string_message); |
| 615 | goto bad; |
| 616 | } |
| 617 | |
| 618 | /*XXX so we currently nail signing to RSA + given hash. |
| 619 | Need to extract algo from privkey and check for disallowed combos. */ |
| 620 | |
| 621 | if (!(ctx = pdkim_init_sign(dkim_signing_domain, |
| 622 | dkim_signing_selector, |
| 623 | dkim_private_key_expanded, |
| 624 | dkim_hash_expanded, |
| 625 | dkim->dot_stuffed, |
| 626 | &dkim_exim_query_dns_txt, |
| 627 | errstr |
| 628 | ))) |
| 629 | goto bad; |
| 630 | dkim_private_key_expanded[0] = '\0'; |
| 631 | pdkim_set_optional(ctx, |
| 632 | CS dkim_sign_headers_expanded, |
| 633 | NULL, |
| 634 | pdkim_canon, |
| 635 | pdkim_canon, -1, 0, 0); |
| 636 | |
| 637 | if (prefix) |
| 638 | pdkim_feed(ctx, prefix, Ustrlen(prefix)); |
| 639 | |
| 640 | if (lseek(fd, off, SEEK_SET) < 0) |
| 641 | sread = -1; |
| 642 | else |
| 643 | while ((sread = read(fd, &buf, sizeof(buf))) > 0) |
| 644 | if ((pdkim_rc = pdkim_feed(ctx, buf, sread)) != PDKIM_OK) |
| 645 | goto pk_bad; |
| 646 | |
| 647 | /* Handle failed read above. */ |
| 648 | if (sread == -1) |
| 649 | { |
| 650 | debug_printf("DKIM: Error reading -K file.\n"); |
| 651 | save_errno = errno; |
| 652 | goto bad; |
| 653 | } |
| 654 | |
| 655 | if ((pdkim_rc = pdkim_feed_finish(ctx, &signature, errstr)) != PDKIM_OK) |
| 656 | goto pk_bad; |
| 657 | |
| 658 | sigbuf = string_append(sigbuf, &sigsize, &sigptr, 2, |
| 659 | US signature->signature_header, US"\r\n"); |
| 660 | |
| 661 | pdkim_free_ctx(ctx); |
| 662 | ctx = NULL; |
| 663 | } |
| 664 | |
| 665 | if (sigbuf) |
| 666 | { |
| 667 | sigbuf[sigptr] = '\0'; |
| 668 | rc = sigbuf; |
| 669 | } |
| 670 | else |
| 671 | rc = US""; |
| 672 | |
| 673 | CLEANUP: |
| 674 | if (ctx) |
| 675 | pdkim_free_ctx(ctx); |
| 676 | store_pool = old_pool; |
| 677 | errno = save_errno; |
| 678 | return rc; |
| 679 | |
| 680 | pk_bad: |
| 681 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 682 | "DKIM: signing failed: %.100s", pdkim_errstr(pdkim_rc)); |
| 683 | bad: |
| 684 | rc = NULL; |
| 685 | goto CLEANUP; |
| 686 | } |
| 687 | |
| 688 | #endif |