| 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 | # ifdef MACRO_PREDEF |
| 18 | # include "macro_predef.h" |
| 19 | |
| 20 | void |
| 21 | params_dkim(void) |
| 22 | { |
| 23 | builtin_macro_create_var(US"_DKIM_SIGN_HEADERS", US PDKIM_DEFAULT_SIGN_HEADERS); |
| 24 | } |
| 25 | # else /*!MACRO_PREDEF*/ |
| 26 | |
| 27 | |
| 28 | |
| 29 | |
| 30 | int dkim_verify_oldpool; |
| 31 | pdkim_ctx *dkim_verify_ctx = NULL; |
| 32 | pdkim_signature *dkim_signatures = NULL; |
| 33 | pdkim_signature *dkim_cur_sig = NULL; |
| 34 | static const uschar * dkim_collect_error = NULL; |
| 35 | |
| 36 | |
| 37 | |
| 38 | /*XXX the caller only uses the first record if we return multiple. |
| 39 | Could we hand back an allocated string? |
| 40 | */ |
| 41 | |
| 42 | static int |
| 43 | dkim_exim_query_dns_txt(char *name, char *answer) |
| 44 | { |
| 45 | dns_answer dnsa; |
| 46 | dns_scan dnss; |
| 47 | dns_record *rr; |
| 48 | |
| 49 | lookup_dnssec_authenticated = NULL; |
| 50 | if (dns_lookup(&dnsa, US name, T_TXT, NULL) != DNS_SUCCEED) |
| 51 | return PDKIM_FAIL; /*XXX better error detail? logging? */ |
| 52 | |
| 53 | /* Search for TXT record */ |
| 54 | |
| 55 | for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS); |
| 56 | rr; |
| 57 | rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT)) |
| 58 | if (rr->type == T_TXT) |
| 59 | { |
| 60 | int rr_offset = 0; |
| 61 | int answer_offset = 0; |
| 62 | |
| 63 | /* Copy record content to the answer buffer */ |
| 64 | |
| 65 | while (rr_offset < rr->size) |
| 66 | { |
| 67 | uschar len = rr->data[rr_offset++]; |
| 68 | snprintf(answer + answer_offset, |
| 69 | PDKIM_DNS_TXT_MAX_RECLEN - answer_offset, |
| 70 | "%.*s", (int)len, CS (rr->data + rr_offset)); |
| 71 | rr_offset += len; |
| 72 | answer_offset += len; |
| 73 | if (answer_offset >= PDKIM_DNS_TXT_MAX_RECLEN) |
| 74 | return PDKIM_FAIL; /*XXX better error detail? logging? */ |
| 75 | } |
| 76 | return PDKIM_OK; |
| 77 | } |
| 78 | |
| 79 | return PDKIM_FAIL; /*XXX better error detail? logging? */ |
| 80 | } |
| 81 | |
| 82 | |
| 83 | void |
| 84 | dkim_exim_init(void) |
| 85 | { |
| 86 | pdkim_init(); |
| 87 | } |
| 88 | |
| 89 | |
| 90 | |
| 91 | void |
| 92 | dkim_exim_verify_init(BOOL dot_stuffing) |
| 93 | { |
| 94 | /* There is a store-reset between header & body reception |
| 95 | so cannot use the main pool. Any allocs done by Exim |
| 96 | memory-handling must use the perm pool. */ |
| 97 | |
| 98 | dkim_verify_oldpool = store_pool; |
| 99 | store_pool = POOL_PERM; |
| 100 | |
| 101 | /* Free previous context if there is one */ |
| 102 | |
| 103 | if (dkim_verify_ctx) |
| 104 | pdkim_free_ctx(dkim_verify_ctx); |
| 105 | |
| 106 | /* Create new context */ |
| 107 | |
| 108 | dkim_verify_ctx = pdkim_init_verify(&dkim_exim_query_dns_txt, dot_stuffing); |
| 109 | dkim_collect_input = !!dkim_verify_ctx; |
| 110 | dkim_collect_error = NULL; |
| 111 | |
| 112 | /* Start feed up with any cached data */ |
| 113 | receive_get_cache(); |
| 114 | |
| 115 | store_pool = dkim_verify_oldpool; |
| 116 | } |
| 117 | |
| 118 | |
| 119 | void |
| 120 | dkim_exim_verify_feed(uschar * data, int len) |
| 121 | { |
| 122 | int rc; |
| 123 | |
| 124 | store_pool = POOL_PERM; |
| 125 | if ( dkim_collect_input |
| 126 | && (rc = pdkim_feed(dkim_verify_ctx, data, len)) != PDKIM_OK) |
| 127 | { |
| 128 | dkim_collect_error = pdkim_errstr(rc); |
| 129 | log_write(0, LOG_MAIN, |
| 130 | "DKIM: validation error: %.100s", dkim_collect_error); |
| 131 | dkim_collect_input = FALSE; |
| 132 | } |
| 133 | store_pool = dkim_verify_oldpool; |
| 134 | } |
| 135 | |
| 136 | |
| 137 | /* Log the result for the given signature */ |
| 138 | static void |
| 139 | dkim_exim_verify_log_sig(pdkim_signature * sig) |
| 140 | { |
| 141 | gstring * logmsg; |
| 142 | uschar * s; |
| 143 | |
| 144 | if (!sig) return; |
| 145 | |
| 146 | logmsg = string_catn(NULL, US"DKIM: ", 6); |
| 147 | if (!(s = sig->domain)) s = US"<UNSET>"; |
| 148 | logmsg = string_append(logmsg, 2, "d=", s); |
| 149 | if (!(s = sig->selector)) s = US"<UNSET>"; |
| 150 | logmsg = string_append(logmsg, 2, " s=", s); |
| 151 | logmsg = string_append(logmsg, 7, |
| 152 | " c=", sig->canon_headers == PDKIM_CANON_SIMPLE ? "simple" : "relaxed", |
| 153 | "/", sig->canon_body == PDKIM_CANON_SIMPLE ? "simple" : "relaxed", |
| 154 | " a=", dkim_sig_to_a_tag(sig), |
| 155 | string_sprintf(" b=" SIZE_T_FMT, |
| 156 | (int)sig->sighash.len > -1 ? sig->sighash.len * 8 : 0)); |
| 157 | if ((s= sig->identity)) logmsg = string_append(logmsg, 2, " i=", s); |
| 158 | if (sig->created > 0) logmsg = string_cat(logmsg, |
| 159 | string_sprintf(" t=%lu", sig->created)); |
| 160 | if (sig->expires > 0) logmsg = string_cat(logmsg, |
| 161 | string_sprintf(" x=%lu", sig->expires)); |
| 162 | if (sig->bodylength > -1) logmsg = string_cat(logmsg, |
| 163 | string_sprintf(" l=%lu", sig->bodylength)); |
| 164 | |
| 165 | if ( !dkim_verify_status |
| 166 | || ( dkim_verify_status == dkim_exim_expand_query(DKIM_VERIFY_STATUS) |
| 167 | && dkim_verify_reason == dkim_exim_expand_query(DKIM_VERIFY_REASON) |
| 168 | ) ) |
| 169 | switch (sig->verify_status) |
| 170 | { |
| 171 | case PDKIM_VERIFY_NONE: |
| 172 | logmsg = string_cat(logmsg, US" [not verified]"); |
| 173 | break; |
| 174 | |
| 175 | case PDKIM_VERIFY_INVALID: |
| 176 | logmsg = string_cat(logmsg, US" [invalid - "); |
| 177 | switch (sig->verify_ext_status) |
| 178 | { |
| 179 | case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: |
| 180 | logmsg = string_cat(logmsg, |
| 181 | US"public key record (currently?) unavailable]"); |
| 182 | break; |
| 183 | |
| 184 | case PDKIM_VERIFY_INVALID_BUFFER_SIZE: |
| 185 | logmsg = string_cat(logmsg, US"overlong public key record]"); |
| 186 | break; |
| 187 | |
| 188 | case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: |
| 189 | case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: |
| 190 | logmsg = string_cat(logmsg, US"syntax error in public key record]"); |
| 191 | break; |
| 192 | |
| 193 | case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: |
| 194 | logmsg = string_cat(logmsg, US"signature tag missing or invalid]"); |
| 195 | break; |
| 196 | |
| 197 | case PDKIM_VERIFY_INVALID_DKIM_VERSION: |
| 198 | logmsg = string_cat(logmsg, US"unsupported DKIM version]"); |
| 199 | break; |
| 200 | |
| 201 | default: |
| 202 | logmsg = string_cat(logmsg, US"unspecified problem]"); |
| 203 | } |
| 204 | break; |
| 205 | |
| 206 | case PDKIM_VERIFY_FAIL: |
| 207 | logmsg = string_cat(logmsg, US" [verification failed - "); |
| 208 | switch (sig->verify_ext_status) |
| 209 | { |
| 210 | case PDKIM_VERIFY_FAIL_BODY: |
| 211 | logmsg = string_cat(logmsg, |
| 212 | US"body hash mismatch (body probably modified in transit)]"); |
| 213 | break; |
| 214 | |
| 215 | case PDKIM_VERIFY_FAIL_MESSAGE: |
| 216 | logmsg = string_cat(logmsg, |
| 217 | US"signature did not verify " |
| 218 | "(headers probably modified in transit)]"); |
| 219 | break; |
| 220 | |
| 221 | default: |
| 222 | logmsg = string_cat(logmsg, US"unspecified reason]"); |
| 223 | } |
| 224 | break; |
| 225 | |
| 226 | case PDKIM_VERIFY_PASS: |
| 227 | logmsg = string_cat(logmsg, US" [verification succeeded]"); |
| 228 | break; |
| 229 | } |
| 230 | else |
| 231 | logmsg = string_append(logmsg, 5, |
| 232 | US" [", dkim_verify_status, US" - ", dkim_verify_reason, US"]"); |
| 233 | |
| 234 | log_write(0, LOG_MAIN, "%s", string_from_gstring(logmsg)); |
| 235 | return; |
| 236 | } |
| 237 | |
| 238 | |
| 239 | /* Log a line for each signature */ |
| 240 | void |
| 241 | dkim_exim_verify_log_all(void) |
| 242 | { |
| 243 | pdkim_signature * sig; |
| 244 | for (sig = dkim_signatures; sig; sig = sig->next) dkim_exim_verify_log_sig(sig); |
| 245 | } |
| 246 | |
| 247 | |
| 248 | void |
| 249 | dkim_exim_verify_finish(void) |
| 250 | { |
| 251 | pdkim_signature * sig; |
| 252 | int rc; |
| 253 | gstring * g = NULL; |
| 254 | const uschar * errstr; |
| 255 | |
| 256 | store_pool = POOL_PERM; |
| 257 | |
| 258 | /* Delete eventual previous signature chain */ |
| 259 | |
| 260 | dkim_signers = NULL; |
| 261 | dkim_signatures = NULL; |
| 262 | |
| 263 | if (dkim_collect_error) |
| 264 | { |
| 265 | log_write(0, LOG_MAIN, |
| 266 | "DKIM: Error during validation, disabling signature verification: %.100s", |
| 267 | dkim_collect_error); |
| 268 | dkim_disable_verify = TRUE; |
| 269 | goto out; |
| 270 | } |
| 271 | |
| 272 | dkim_collect_input = FALSE; |
| 273 | |
| 274 | /* Finish DKIM operation and fetch link to signatures chain */ |
| 275 | |
| 276 | rc = pdkim_feed_finish(dkim_verify_ctx, &dkim_signatures, &errstr); |
| 277 | if (rc != PDKIM_OK) |
| 278 | { |
| 279 | log_write(0, LOG_MAIN, "DKIM: validation error: %.100s%s%s", pdkim_errstr(rc), |
| 280 | errstr ? ": " : "", errstr ? errstr : US""); |
| 281 | goto out; |
| 282 | } |
| 283 | |
| 284 | /* Build a colon-separated list of signing domains (and identities, if present) in dkim_signers */ |
| 285 | |
| 286 | for (sig = dkim_signatures; sig; sig = sig->next) |
| 287 | { |
| 288 | if (sig->domain) g = string_append_listele(g, ':', sig->domain); |
| 289 | if (sig->identity) g = string_append_listele(g, ':', sig->identity); |
| 290 | } |
| 291 | |
| 292 | if (g) dkim_signers = g->s; |
| 293 | |
| 294 | out: |
| 295 | store_pool = dkim_verify_oldpool; |
| 296 | } |
| 297 | |
| 298 | |
| 299 | |
| 300 | /* Args as per dkim_exim_acl_run() below */ |
| 301 | static int |
| 302 | dkim_acl_call(uschar * id, gstring ** res_ptr, |
| 303 | uschar ** user_msgptr, uschar ** log_msgptr) |
| 304 | { |
| 305 | int rc; |
| 306 | DEBUG(D_receive) |
| 307 | debug_printf("calling acl_smtp_dkim for dkim_cur_signer='%s'\n", id); |
| 308 | |
| 309 | rc = acl_check(ACL_WHERE_DKIM, NULL, acl_smtp_dkim, user_msgptr, log_msgptr); |
| 310 | dkim_exim_verify_log_sig(dkim_cur_sig); |
| 311 | *res_ptr = string_append_listele(*res_ptr, ':', dkim_verify_status); |
| 312 | return rc; |
| 313 | } |
| 314 | |
| 315 | |
| 316 | |
| 317 | /* For the given identity, run the DKIM ACL once for each matching signature. |
| 318 | |
| 319 | Arguments |
| 320 | id Identity to look for in dkim signatures |
| 321 | res_ptr ptr to growable string-list of status results, |
| 322 | appended to per ACL run |
| 323 | user_msgptr where to put a user error (for SMTP response) |
| 324 | log_msgptr where to put a logging message (not for SMTP response) |
| 325 | |
| 326 | Returns: OK access is granted by an ACCEPT verb |
| 327 | DISCARD access is granted by a DISCARD verb |
| 328 | FAIL access is denied |
| 329 | FAIL_DROP access is denied; drop the connection |
| 330 | DEFER can't tell at the moment |
| 331 | ERROR disaster |
| 332 | */ |
| 333 | |
| 334 | int |
| 335 | dkim_exim_acl_run(uschar * id, gstring ** res_ptr, |
| 336 | uschar ** user_msgptr, uschar ** log_msgptr) |
| 337 | { |
| 338 | pdkim_signature * sig; |
| 339 | uschar * cmp_val; |
| 340 | int rc = -1; |
| 341 | |
| 342 | dkim_verify_status = US"none"; |
| 343 | dkim_verify_reason = US""; |
| 344 | dkim_cur_signer = id; |
| 345 | |
| 346 | if (dkim_disable_verify || !id || !dkim_verify_ctx) |
| 347 | return OK; |
| 348 | |
| 349 | /* Find signatures to run ACL on */ |
| 350 | |
| 351 | for (sig = dkim_signatures; sig; sig = sig->next) |
| 352 | if ( (cmp_val = Ustrchr(id, '@') != NULL ? US sig->identity : US sig->domain) |
| 353 | && strcmpic(cmp_val, id) == 0 |
| 354 | ) |
| 355 | { |
| 356 | /* The "dkim_domain" and "dkim_selector" expansion variables have |
| 357 | related globals, since they are used in the signing code too. |
| 358 | Instead of inventing separate names for verification, we set |
| 359 | them here. This is easy since a domain and selector is guaranteed |
| 360 | to be in a signature. The other dkim_* expansion items are |
| 361 | dynamically fetched from dkim_cur_sig at expansion time (see |
| 362 | function below). */ |
| 363 | |
| 364 | dkim_cur_sig = sig; |
| 365 | dkim_signing_domain = US sig->domain; |
| 366 | dkim_signing_selector = US sig->selector; |
| 367 | dkim_key_length = sig->sighash.len * 8; |
| 368 | |
| 369 | /* These two return static strings, so we can compare the addr |
| 370 | later to see if the ACL overwrote them. Check that when logging */ |
| 371 | |
| 372 | dkim_verify_status = dkim_exim_expand_query(DKIM_VERIFY_STATUS); |
| 373 | dkim_verify_reason = dkim_exim_expand_query(DKIM_VERIFY_REASON); |
| 374 | |
| 375 | if ((rc = dkim_acl_call(id, res_ptr, user_msgptr, log_msgptr)) != OK) |
| 376 | return rc; |
| 377 | } |
| 378 | |
| 379 | if (rc != -1) |
| 380 | return rc; |
| 381 | |
| 382 | /* No matching sig found. Call ACL once anyway. */ |
| 383 | |
| 384 | dkim_cur_sig = NULL; |
| 385 | return dkim_acl_call(id, res_ptr, user_msgptr, log_msgptr); |
| 386 | } |
| 387 | |
| 388 | |
| 389 | static uschar * |
| 390 | dkim_exim_expand_defaults(int what) |
| 391 | { |
| 392 | switch (what) |
| 393 | { |
| 394 | case DKIM_ALGO: return US""; |
| 395 | case DKIM_BODYLENGTH: return US"9999999999999"; |
| 396 | case DKIM_CANON_BODY: return US""; |
| 397 | case DKIM_CANON_HEADERS: return US""; |
| 398 | case DKIM_COPIEDHEADERS: return US""; |
| 399 | case DKIM_CREATED: return US"0"; |
| 400 | case DKIM_EXPIRES: return US"9999999999999"; |
| 401 | case DKIM_HEADERNAMES: return US""; |
| 402 | case DKIM_IDENTITY: return US""; |
| 403 | case DKIM_KEY_GRANULARITY: return US"*"; |
| 404 | case DKIM_KEY_SRVTYPE: return US"*"; |
| 405 | case DKIM_KEY_NOTES: return US""; |
| 406 | case DKIM_KEY_TESTING: return US"0"; |
| 407 | case DKIM_NOSUBDOMAINS: return US"0"; |
| 408 | case DKIM_VERIFY_STATUS: return US"none"; |
| 409 | case DKIM_VERIFY_REASON: return US""; |
| 410 | default: return US""; |
| 411 | } |
| 412 | } |
| 413 | |
| 414 | |
| 415 | uschar * |
| 416 | dkim_exim_expand_query(int what) |
| 417 | { |
| 418 | if (!dkim_verify_ctx || dkim_disable_verify || !dkim_cur_sig) |
| 419 | return dkim_exim_expand_defaults(what); |
| 420 | |
| 421 | switch (what) |
| 422 | { |
| 423 | case DKIM_ALGO: |
| 424 | return dkim_sig_to_a_tag(dkim_cur_sig); |
| 425 | |
| 426 | case DKIM_BODYLENGTH: |
| 427 | return dkim_cur_sig->bodylength >= 0 |
| 428 | ? string_sprintf("%ld", dkim_cur_sig->bodylength) |
| 429 | : dkim_exim_expand_defaults(what); |
| 430 | |
| 431 | case DKIM_CANON_BODY: |
| 432 | switch (dkim_cur_sig->canon_body) |
| 433 | { |
| 434 | case PDKIM_CANON_RELAXED: return US"relaxed"; |
| 435 | case PDKIM_CANON_SIMPLE: |
| 436 | default: return US"simple"; |
| 437 | } |
| 438 | |
| 439 | case DKIM_CANON_HEADERS: |
| 440 | switch (dkim_cur_sig->canon_headers) |
| 441 | { |
| 442 | case PDKIM_CANON_RELAXED: return US"relaxed"; |
| 443 | case PDKIM_CANON_SIMPLE: |
| 444 | default: return US"simple"; |
| 445 | } |
| 446 | |
| 447 | case DKIM_COPIEDHEADERS: |
| 448 | return dkim_cur_sig->copiedheaders |
| 449 | ? US dkim_cur_sig->copiedheaders : dkim_exim_expand_defaults(what); |
| 450 | |
| 451 | case DKIM_CREATED: |
| 452 | return dkim_cur_sig->created > 0 |
| 453 | ? string_sprintf("%lu", dkim_cur_sig->created) |
| 454 | : dkim_exim_expand_defaults(what); |
| 455 | |
| 456 | case DKIM_EXPIRES: |
| 457 | return dkim_cur_sig->expires > 0 |
| 458 | ? string_sprintf("%lu", dkim_cur_sig->expires) |
| 459 | : dkim_exim_expand_defaults(what); |
| 460 | |
| 461 | case DKIM_HEADERNAMES: |
| 462 | return dkim_cur_sig->headernames |
| 463 | ? dkim_cur_sig->headernames : dkim_exim_expand_defaults(what); |
| 464 | |
| 465 | case DKIM_IDENTITY: |
| 466 | return dkim_cur_sig->identity |
| 467 | ? US dkim_cur_sig->identity : dkim_exim_expand_defaults(what); |
| 468 | |
| 469 | case DKIM_KEY_GRANULARITY: |
| 470 | return dkim_cur_sig->pubkey |
| 471 | ? dkim_cur_sig->pubkey->granularity |
| 472 | ? US dkim_cur_sig->pubkey->granularity |
| 473 | : dkim_exim_expand_defaults(what) |
| 474 | : dkim_exim_expand_defaults(what); |
| 475 | |
| 476 | case DKIM_KEY_SRVTYPE: |
| 477 | return dkim_cur_sig->pubkey |
| 478 | ? dkim_cur_sig->pubkey->srvtype |
| 479 | ? US dkim_cur_sig->pubkey->srvtype |
| 480 | : dkim_exim_expand_defaults(what) |
| 481 | : dkim_exim_expand_defaults(what); |
| 482 | |
| 483 | case DKIM_KEY_NOTES: |
| 484 | return dkim_cur_sig->pubkey |
| 485 | ? dkim_cur_sig->pubkey->notes |
| 486 | ? US dkim_cur_sig->pubkey->notes |
| 487 | : dkim_exim_expand_defaults(what) |
| 488 | : dkim_exim_expand_defaults(what); |
| 489 | |
| 490 | case DKIM_KEY_TESTING: |
| 491 | return dkim_cur_sig->pubkey |
| 492 | ? dkim_cur_sig->pubkey->testing |
| 493 | ? US"1" |
| 494 | : dkim_exim_expand_defaults(what) |
| 495 | : dkim_exim_expand_defaults(what); |
| 496 | |
| 497 | case DKIM_NOSUBDOMAINS: |
| 498 | return dkim_cur_sig->pubkey |
| 499 | ? dkim_cur_sig->pubkey->no_subdomaining |
| 500 | ? US"1" |
| 501 | : dkim_exim_expand_defaults(what) |
| 502 | : dkim_exim_expand_defaults(what); |
| 503 | |
| 504 | case DKIM_VERIFY_STATUS: |
| 505 | switch (dkim_cur_sig->verify_status) |
| 506 | { |
| 507 | case PDKIM_VERIFY_INVALID: return US"invalid"; |
| 508 | case PDKIM_VERIFY_FAIL: return US"fail"; |
| 509 | case PDKIM_VERIFY_PASS: return US"pass"; |
| 510 | case PDKIM_VERIFY_NONE: |
| 511 | default: return US"none"; |
| 512 | } |
| 513 | |
| 514 | case DKIM_VERIFY_REASON: |
| 515 | switch (dkim_cur_sig->verify_ext_status) |
| 516 | { |
| 517 | case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: |
| 518 | return US"pubkey_unavailable"; |
| 519 | case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:return US"pubkey_dns_syntax"; |
| 520 | case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: return US"pubkey_der_syntax"; |
| 521 | case PDKIM_VERIFY_FAIL_BODY: return US"bodyhash_mismatch"; |
| 522 | case PDKIM_VERIFY_FAIL_MESSAGE: return US"signature_incorrect"; |
| 523 | } |
| 524 | |
| 525 | default: |
| 526 | return US""; |
| 527 | } |
| 528 | } |
| 529 | |
| 530 | |
| 531 | /* Generate signatures for the given file, returning a string. |
| 532 | If a prefix is given, prepend it to the file for the calculations. |
| 533 | */ |
| 534 | |
| 535 | gstring * |
| 536 | dkim_exim_sign(int fd, off_t off, uschar * prefix, |
| 537 | struct ob_dkim * dkim, const uschar ** errstr) |
| 538 | { |
| 539 | const uschar * dkim_domain; |
| 540 | int sep = 0; |
| 541 | gstring * seen_doms = NULL; |
| 542 | pdkim_ctx ctx; |
| 543 | pdkim_signature * sig; |
| 544 | gstring * sigbuf; |
| 545 | int pdkim_rc; |
| 546 | int sread; |
| 547 | uschar buf[4096]; |
| 548 | int save_errno = 0; |
| 549 | int old_pool = store_pool; |
| 550 | uschar * errwhen; |
| 551 | |
| 552 | store_pool = POOL_MAIN; |
| 553 | |
| 554 | pdkim_init_context(&ctx, dkim->dot_stuffed, &dkim_exim_query_dns_txt); |
| 555 | |
| 556 | if (!(dkim_domain = expand_cstring(dkim->dkim_domain))) |
| 557 | /* expansion error, do not send message. */ |
| 558 | { errwhen = US"dkim_domain"; goto expand_bad; } |
| 559 | |
| 560 | /* Set $dkim_domain expansion variable to each unique domain in list. */ |
| 561 | |
| 562 | while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep, NULL, 0))) |
| 563 | { |
| 564 | const uschar * dkim_sel; |
| 565 | int sel_sep = 0; |
| 566 | |
| 567 | if (dkim_signing_domain[0] == '\0') |
| 568 | continue; |
| 569 | |
| 570 | /* Only sign once for each domain, no matter how often it |
| 571 | appears in the expanded list. */ |
| 572 | |
| 573 | if (match_isinlist(dkim_signing_domain, CUSS &seen_doms, |
| 574 | 0, NULL, NULL, MCL_STRING, TRUE, NULL) == OK) |
| 575 | continue; |
| 576 | |
| 577 | seen_doms = string_append_listele(seen_doms, ':', dkim_signing_domain); |
| 578 | |
| 579 | /* Set $dkim_selector expansion variable to each selector in list, |
| 580 | for this domain. */ |
| 581 | |
| 582 | if (!(dkim_sel = expand_string(dkim->dkim_selector))) |
| 583 | if (!(dkim_signing_selector = expand_string(dkim->dkim_selector))) |
| 584 | { errwhen = US"dkim_selector"; goto expand_bad; } |
| 585 | |
| 586 | while ((dkim_signing_selector = string_nextinlist(&dkim_sel, &sel_sep, |
| 587 | NULL, 0))) |
| 588 | { |
| 589 | uschar * dkim_canon_expanded; |
| 590 | int pdkim_canon; |
| 591 | uschar * dkim_sign_headers_expanded = NULL; |
| 592 | uschar * dkim_private_key_expanded; |
| 593 | uschar * dkim_hash_expanded; |
| 594 | uschar * dkim_identity_expanded = NULL; |
| 595 | |
| 596 | /* Get canonicalization to use */ |
| 597 | |
| 598 | dkim_canon_expanded = dkim->dkim_canon |
| 599 | ? expand_string(dkim->dkim_canon) : US"relaxed"; |
| 600 | if (!dkim_canon_expanded) /* expansion error, do not send message. */ |
| 601 | { errwhen = US"dkim_canon"; goto expand_bad; } |
| 602 | |
| 603 | if (Ustrcmp(dkim_canon_expanded, "relaxed") == 0) |
| 604 | pdkim_canon = PDKIM_CANON_RELAXED; |
| 605 | else if (Ustrcmp(dkim_canon_expanded, "simple") == 0) |
| 606 | pdkim_canon = PDKIM_CANON_SIMPLE; |
| 607 | else |
| 608 | { |
| 609 | log_write(0, LOG_MAIN, |
| 610 | "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n", |
| 611 | dkim_canon_expanded); |
| 612 | pdkim_canon = PDKIM_CANON_RELAXED; |
| 613 | } |
| 614 | |
| 615 | if ( dkim->dkim_sign_headers |
| 616 | && !(dkim_sign_headers_expanded = expand_string(dkim->dkim_sign_headers))) |
| 617 | { errwhen = US"dkim_sign_header"; goto expand_bad; } |
| 618 | /* else pass NULL, which means default header list */ |
| 619 | |
| 620 | /* Get private key to use. */ |
| 621 | |
| 622 | if (!(dkim_private_key_expanded = expand_string(dkim->dkim_private_key))) |
| 623 | { errwhen = US"dkim_private_key"; goto expand_bad; } |
| 624 | |
| 625 | if ( Ustrlen(dkim_private_key_expanded) == 0 |
| 626 | || Ustrcmp(dkim_private_key_expanded, "0") == 0 |
| 627 | || Ustrcmp(dkim_private_key_expanded, "false") == 0 |
| 628 | ) |
| 629 | continue; /* don't sign, but no error */ |
| 630 | |
| 631 | if (dkim_private_key_expanded[0] == '/') |
| 632 | { |
| 633 | int privkey_fd, off = 0, len; |
| 634 | |
| 635 | /* Looks like a filename, load the private key. */ |
| 636 | |
| 637 | memset(big_buffer, 0, big_buffer_size); |
| 638 | |
| 639 | if ((privkey_fd = open(CS dkim_private_key_expanded, O_RDONLY)) < 0) |
| 640 | { |
| 641 | log_write(0, LOG_MAIN | LOG_PANIC, "unable to open " |
| 642 | "private key file for reading: %s", |
| 643 | dkim_private_key_expanded); |
| 644 | goto bad; |
| 645 | } |
| 646 | |
| 647 | do |
| 648 | { |
| 649 | if ((len = read(privkey_fd, big_buffer + off, big_buffer_size - 2 - off)) < 0) |
| 650 | { |
| 651 | (void) close(privkey_fd); |
| 652 | log_write(0, LOG_MAIN|LOG_PANIC, "unable to read private key file: %s", |
| 653 | dkim_private_key_expanded); |
| 654 | goto bad; |
| 655 | } |
| 656 | off += len; |
| 657 | } |
| 658 | while (len > 0); |
| 659 | |
| 660 | (void) close(privkey_fd); |
| 661 | big_buffer[off] = '\0'; |
| 662 | dkim_private_key_expanded = big_buffer; |
| 663 | } |
| 664 | |
| 665 | if (!(dkim_hash_expanded = expand_string(dkim->dkim_hash))) |
| 666 | { errwhen = US"dkim_hash"; goto expand_bad; } |
| 667 | |
| 668 | if (dkim->dkim_identity) |
| 669 | if (!(dkim_identity_expanded = expand_string(dkim->dkim_identity))) |
| 670 | { errwhen = US"dkim_identity"; goto expand_bad; } |
| 671 | else if (!*dkim_identity_expanded) |
| 672 | dkim_identity_expanded = NULL; |
| 673 | |
| 674 | /*XXX so we currently nail signing to RSA + this hash. |
| 675 | Need to extract algo from privkey and check for disallowed combos. */ |
| 676 | |
| 677 | if (!(sig = pdkim_init_sign(&ctx, dkim_signing_domain, |
| 678 | dkim_signing_selector, |
| 679 | dkim_private_key_expanded, |
| 680 | dkim_hash_expanded, |
| 681 | errstr |
| 682 | ))) |
| 683 | goto bad; |
| 684 | dkim_private_key_expanded[0] = '\0'; |
| 685 | |
| 686 | pdkim_set_optional(sig, |
| 687 | CS dkim_sign_headers_expanded, |
| 688 | dkim_identity_expanded, |
| 689 | pdkim_canon, |
| 690 | pdkim_canon, -1, 0, 0); |
| 691 | |
| 692 | if (!ctx.sig) /* link sig to context chain */ |
| 693 | ctx.sig = sig; |
| 694 | else |
| 695 | { |
| 696 | pdkim_signature * n = ctx.sig; |
| 697 | while (n->next) n = n->next; |
| 698 | n->next = sig; |
| 699 | } |
| 700 | } |
| 701 | } |
| 702 | |
| 703 | if (prefix) |
| 704 | pdkim_feed(&ctx, prefix, Ustrlen(prefix)); |
| 705 | |
| 706 | if (lseek(fd, off, SEEK_SET) < 0) |
| 707 | sread = -1; |
| 708 | else |
| 709 | while ((sread = read(fd, &buf, sizeof(buf))) > 0) |
| 710 | if ((pdkim_rc = pdkim_feed(&ctx, buf, sread)) != PDKIM_OK) |
| 711 | goto pk_bad; |
| 712 | |
| 713 | /* Handle failed read above. */ |
| 714 | if (sread == -1) |
| 715 | { |
| 716 | debug_printf("DKIM: Error reading -K file.\n"); |
| 717 | save_errno = errno; |
| 718 | goto bad; |
| 719 | } |
| 720 | |
| 721 | /* Build string of headers, one per signature */ |
| 722 | |
| 723 | if ((pdkim_rc = pdkim_feed_finish(&ctx, &sig, errstr)) != PDKIM_OK) |
| 724 | goto pk_bad; |
| 725 | |
| 726 | for (sigbuf = NULL; sig; sig = sig->next) |
| 727 | sigbuf = string_append(sigbuf, 2, US sig->signature_header, US"\r\n"); |
| 728 | |
| 729 | (void) string_from_gstring(sigbuf); |
| 730 | |
| 731 | CLEANUP: |
| 732 | store_pool = old_pool; |
| 733 | errno = save_errno; |
| 734 | return sigbuf; |
| 735 | |
| 736 | pk_bad: |
| 737 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 738 | "DKIM: signing failed: %.100s", pdkim_errstr(pdkim_rc)); |
| 739 | bad: |
| 740 | sigbuf = NULL; |
| 741 | goto CLEANUP; |
| 742 | |
| 743 | expand_bad: |
| 744 | log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand %s: %s", |
| 745 | errwhen, expand_string_message); |
| 746 | goto bad; |
| 747 | } |
| 748 | |
| 749 | # endif /*!MACRO_PREDEF*/ |
| 750 | #endif /*!DISABLE_DKIM*/ |