| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge, 1995 - 2018 */ |
| 6 | /* Copyright (c) The Exim Maintainers 2020 */ |
| 7 | /* See the file NOTICE for conditions of use and distribution. */ |
| 8 | |
| 9 | /* Code for DKIM support. Other DKIM relevant code is in |
| 10 | receive.c, transport.c and transports/smtp.c */ |
| 11 | |
| 12 | #include "exim.h" |
| 13 | |
| 14 | #ifndef DISABLE_DKIM |
| 15 | |
| 16 | # include "pdkim/pdkim.h" |
| 17 | |
| 18 | # ifdef MACRO_PREDEF |
| 19 | # include "macro_predef.h" |
| 20 | |
| 21 | void |
| 22 | params_dkim(void) |
| 23 | { |
| 24 | builtin_macro_create_var(US"_DKIM_SIGN_HEADERS", US PDKIM_DEFAULT_SIGN_HEADERS); |
| 25 | builtin_macro_create_var(US"_DKIM_OVERSIGN_HEADERS", US PDKIM_OVERSIGN_HEADERS); |
| 26 | } |
| 27 | # else /*!MACRO_PREDEF*/ |
| 28 | |
| 29 | |
| 30 | |
| 31 | pdkim_ctx dkim_sign_ctx; |
| 32 | |
| 33 | int dkim_verify_oldpool; |
| 34 | pdkim_ctx *dkim_verify_ctx = NULL; |
| 35 | pdkim_signature *dkim_cur_sig = NULL; |
| 36 | static const uschar * dkim_collect_error = NULL; |
| 37 | |
| 38 | #define DKIM_MAX_SIGNATURES 20 |
| 39 | |
| 40 | |
| 41 | |
| 42 | /* Look up the DKIM record in DNS for the given hostname. |
| 43 | Will use the first found if there are multiple. |
| 44 | The return string is tainted, having come from off-site. |
| 45 | */ |
| 46 | |
| 47 | uschar * |
| 48 | dkim_exim_query_dns_txt(const uschar * name) |
| 49 | { |
| 50 | dns_answer * dnsa = store_get_dns_answer(); |
| 51 | dns_scan dnss; |
| 52 | rmark reset_point = store_mark(); |
| 53 | gstring * g = NULL; |
| 54 | |
| 55 | lookup_dnssec_authenticated = NULL; |
| 56 | if (dns_lookup(dnsa, name, T_TXT, NULL) != DNS_SUCCEED) |
| 57 | return NULL; /*XXX better error detail? logging? */ |
| 58 | |
| 59 | /* Search for TXT record */ |
| 60 | |
| 61 | for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); |
| 62 | rr; |
| 63 | rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) |
| 64 | if (rr->type == T_TXT) |
| 65 | { |
| 66 | int rr_offset = 0; |
| 67 | |
| 68 | /* Copy record content to the answer buffer */ |
| 69 | |
| 70 | while (rr_offset < rr->size) |
| 71 | { |
| 72 | uschar len = rr->data[rr_offset++]; |
| 73 | |
| 74 | g = string_catn(g, US(rr->data + rr_offset), len); |
| 75 | if (g->ptr >= PDKIM_DNS_TXT_MAX_RECLEN) |
| 76 | goto bad; |
| 77 | |
| 78 | rr_offset += len; |
| 79 | } |
| 80 | |
| 81 | /* check if this looks like a DKIM record */ |
| 82 | if (Ustrncmp(g->s, "v=", 2) != 0 || strncasecmp(CS g->s, "v=dkim", 6) == 0) |
| 83 | { |
| 84 | gstring_release_unused(g); |
| 85 | return string_from_gstring(g); |
| 86 | } |
| 87 | |
| 88 | if (g) g->ptr = 0; /* overwrite previous record */ |
| 89 | } |
| 90 | |
| 91 | bad: |
| 92 | store_reset(reset_point); |
| 93 | return NULL; /*XXX better error detail? logging? */ |
| 94 | } |
| 95 | |
| 96 | |
| 97 | void |
| 98 | dkim_exim_init(void) |
| 99 | { |
| 100 | if (f.dkim_init_done) return; |
| 101 | f.dkim_init_done = TRUE; |
| 102 | pdkim_init(); |
| 103 | } |
| 104 | |
| 105 | |
| 106 | |
| 107 | void |
| 108 | dkim_exim_verify_init(BOOL dot_stuffing) |
| 109 | { |
| 110 | dkim_exim_init(); |
| 111 | |
| 112 | /* There is a store-reset between header & body reception |
| 113 | so cannot use the main pool. Any allocs done by Exim |
| 114 | memory-handling must use the perm pool. */ |
| 115 | |
| 116 | dkim_verify_oldpool = store_pool; |
| 117 | store_pool = POOL_PERM; |
| 118 | |
| 119 | /* Free previous context if there is one */ |
| 120 | |
| 121 | if (dkim_verify_ctx) |
| 122 | pdkim_free_ctx(dkim_verify_ctx); |
| 123 | |
| 124 | /* Create new context */ |
| 125 | |
| 126 | dkim_verify_ctx = pdkim_init_verify(&dkim_exim_query_dns_txt, dot_stuffing); |
| 127 | dkim_collect_input = dkim_verify_ctx ? DKIM_MAX_SIGNATURES : 0; |
| 128 | dkim_collect_error = NULL; |
| 129 | |
| 130 | /* Start feed up with any cached data */ |
| 131 | receive_get_cache(); |
| 132 | |
| 133 | store_pool = dkim_verify_oldpool; |
| 134 | } |
| 135 | |
| 136 | |
| 137 | void |
| 138 | dkim_exim_verify_feed(uschar * data, int len) |
| 139 | { |
| 140 | int rc; |
| 141 | |
| 142 | store_pool = POOL_PERM; |
| 143 | if ( dkim_collect_input |
| 144 | && (rc = pdkim_feed(dkim_verify_ctx, data, len)) != PDKIM_OK) |
| 145 | { |
| 146 | dkim_collect_error = pdkim_errstr(rc); |
| 147 | log_write(0, LOG_MAIN, |
| 148 | "DKIM: validation error: %.100s", dkim_collect_error); |
| 149 | dkim_collect_input = 0; |
| 150 | } |
| 151 | store_pool = dkim_verify_oldpool; |
| 152 | } |
| 153 | |
| 154 | |
| 155 | /* Log the result for the given signature */ |
| 156 | static void |
| 157 | dkim_exim_verify_log_sig(pdkim_signature * sig) |
| 158 | { |
| 159 | gstring * logmsg; |
| 160 | uschar * s; |
| 161 | |
| 162 | if (!sig) return; |
| 163 | |
| 164 | /* Remember the domain for the first pass result */ |
| 165 | |
| 166 | if ( !dkim_verify_overall |
| 167 | && dkim_verify_status |
| 168 | ? Ustrcmp(dkim_verify_status, US"pass") == 0 |
| 169 | : sig->verify_status == PDKIM_VERIFY_PASS |
| 170 | ) |
| 171 | dkim_verify_overall = string_copy(sig->domain); |
| 172 | |
| 173 | /* Rewrite the sig result if the ACL overrode it. This is only |
| 174 | needed because the DMARC code (sigh) peeks at the dkim sigs. |
| 175 | Mark the sig for this having been done. */ |
| 176 | |
| 177 | if ( dkim_verify_status |
| 178 | && ( dkim_verify_status != dkim_exim_expand_query(DKIM_VERIFY_STATUS) |
| 179 | || dkim_verify_reason != dkim_exim_expand_query(DKIM_VERIFY_REASON) |
| 180 | ) ) |
| 181 | { /* overridden by ACL */ |
| 182 | sig->verify_ext_status = -1; |
| 183 | if (Ustrcmp(dkim_verify_status, US"fail") == 0) |
| 184 | sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_FAIL; |
| 185 | else if (Ustrcmp(dkim_verify_status, US"invalid") == 0) |
| 186 | sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_INVALID; |
| 187 | else if (Ustrcmp(dkim_verify_status, US"none") == 0) |
| 188 | sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_NONE; |
| 189 | else if (Ustrcmp(dkim_verify_status, US"pass") == 0) |
| 190 | sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_PASS; |
| 191 | else |
| 192 | sig->verify_status = -1; |
| 193 | } |
| 194 | |
| 195 | if (!LOGGING(dkim_verbose)) return; |
| 196 | |
| 197 | |
| 198 | logmsg = string_catn(NULL, US"DKIM: ", 6); |
| 199 | if (!(s = sig->domain)) s = US"<UNSET>"; |
| 200 | logmsg = string_append(logmsg, 2, "d=", s); |
| 201 | if (!(s = sig->selector)) s = US"<UNSET>"; |
| 202 | logmsg = string_append(logmsg, 2, " s=", s); |
| 203 | logmsg = string_fmt_append(logmsg, " c=%s/%s a=%s b=" SIZE_T_FMT, |
| 204 | sig->canon_headers == PDKIM_CANON_SIMPLE ? "simple" : "relaxed", |
| 205 | sig->canon_body == PDKIM_CANON_SIMPLE ? "simple" : "relaxed", |
| 206 | dkim_sig_to_a_tag(sig), |
| 207 | (int)sig->sighash.len > -1 ? sig->sighash.len * 8 : (size_t)0); |
| 208 | if ((s= sig->identity)) logmsg = string_append(logmsg, 2, " i=", s); |
| 209 | if (sig->created > 0) logmsg = string_fmt_append(logmsg, " t=%lu", |
| 210 | sig->created); |
| 211 | if (sig->expires > 0) logmsg = string_fmt_append(logmsg, " x=%lu", |
| 212 | sig->expires); |
| 213 | if (sig->bodylength > -1) logmsg = string_fmt_append(logmsg, " l=%lu", |
| 214 | sig->bodylength); |
| 215 | |
| 216 | if (sig->verify_status & PDKIM_VERIFY_POLICY) |
| 217 | logmsg = string_append(logmsg, 5, |
| 218 | US" [", dkim_verify_status, US" - ", dkim_verify_reason, US"]"); |
| 219 | else |
| 220 | switch (sig->verify_status) |
| 221 | { |
| 222 | case PDKIM_VERIFY_NONE: |
| 223 | logmsg = string_cat(logmsg, US" [not verified]"); |
| 224 | break; |
| 225 | |
| 226 | case PDKIM_VERIFY_INVALID: |
| 227 | logmsg = string_cat(logmsg, US" [invalid - "); |
| 228 | switch (sig->verify_ext_status) |
| 229 | { |
| 230 | case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: |
| 231 | logmsg = string_cat(logmsg, |
| 232 | US"public key record (currently?) unavailable]"); |
| 233 | break; |
| 234 | |
| 235 | case PDKIM_VERIFY_INVALID_BUFFER_SIZE: |
| 236 | logmsg = string_cat(logmsg, US"overlong public key record]"); |
| 237 | break; |
| 238 | |
| 239 | case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: |
| 240 | case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: |
| 241 | logmsg = string_cat(logmsg, US"syntax error in public key record]"); |
| 242 | break; |
| 243 | |
| 244 | case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: |
| 245 | logmsg = string_cat(logmsg, US"signature tag missing or invalid]"); |
| 246 | break; |
| 247 | |
| 248 | case PDKIM_VERIFY_INVALID_DKIM_VERSION: |
| 249 | logmsg = string_cat(logmsg, US"unsupported DKIM version]"); |
| 250 | break; |
| 251 | |
| 252 | default: |
| 253 | logmsg = string_cat(logmsg, US"unspecified problem]"); |
| 254 | } |
| 255 | break; |
| 256 | |
| 257 | case PDKIM_VERIFY_FAIL: |
| 258 | logmsg = string_cat(logmsg, US" [verification failed - "); |
| 259 | switch (sig->verify_ext_status) |
| 260 | { |
| 261 | case PDKIM_VERIFY_FAIL_BODY: |
| 262 | logmsg = string_cat(logmsg, |
| 263 | US"body hash mismatch (body probably modified in transit)]"); |
| 264 | break; |
| 265 | |
| 266 | case PDKIM_VERIFY_FAIL_MESSAGE: |
| 267 | logmsg = string_cat(logmsg, |
| 268 | US"signature did not verify " |
| 269 | "(headers probably modified in transit)]"); |
| 270 | break; |
| 271 | |
| 272 | case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE: |
| 273 | logmsg = string_cat(logmsg, |
| 274 | US"signature invalid (key too short)]"); |
| 275 | break; |
| 276 | |
| 277 | default: |
| 278 | logmsg = string_cat(logmsg, US"unspecified reason]"); |
| 279 | } |
| 280 | break; |
| 281 | |
| 282 | case PDKIM_VERIFY_PASS: |
| 283 | logmsg = string_cat(logmsg, US" [verification succeeded]"); |
| 284 | break; |
| 285 | } |
| 286 | |
| 287 | log_write(0, LOG_MAIN, "%s", string_from_gstring(logmsg)); |
| 288 | return; |
| 289 | } |
| 290 | |
| 291 | |
| 292 | /* Log a line for each signature */ |
| 293 | void |
| 294 | dkim_exim_verify_log_all(void) |
| 295 | { |
| 296 | for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next) |
| 297 | dkim_exim_verify_log_sig(sig); |
| 298 | } |
| 299 | |
| 300 | |
| 301 | void |
| 302 | dkim_exim_verify_finish(void) |
| 303 | { |
| 304 | int rc; |
| 305 | gstring * g = NULL; |
| 306 | const uschar * errstr = NULL; |
| 307 | |
| 308 | store_pool = POOL_PERM; |
| 309 | |
| 310 | /* Delete eventual previous signature chain */ |
| 311 | |
| 312 | dkim_signers = NULL; |
| 313 | dkim_signatures = NULL; |
| 314 | |
| 315 | if (dkim_collect_error) |
| 316 | { |
| 317 | log_write(0, LOG_MAIN, |
| 318 | "DKIM: Error during validation, disabling signature verification: %.100s", |
| 319 | dkim_collect_error); |
| 320 | f.dkim_disable_verify = TRUE; |
| 321 | goto out; |
| 322 | } |
| 323 | |
| 324 | dkim_collect_input = 0; |
| 325 | |
| 326 | /* Finish DKIM operation and fetch link to signatures chain */ |
| 327 | |
| 328 | rc = pdkim_feed_finish(dkim_verify_ctx, (pdkim_signature **)&dkim_signatures, |
| 329 | &errstr); |
| 330 | if (rc != PDKIM_OK && errstr) |
| 331 | log_write(0, LOG_MAIN, "DKIM: validation error: %s", errstr); |
| 332 | |
| 333 | /* Build a colon-separated list of signing domains (and identities, if present) in dkim_signers */ |
| 334 | |
| 335 | for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next) |
| 336 | { |
| 337 | if (sig->domain) g = string_append_listele(g, ':', sig->domain); |
| 338 | if (sig->identity) g = string_append_listele(g, ':', sig->identity); |
| 339 | } |
| 340 | |
| 341 | if (g) dkim_signers = g->s; |
| 342 | |
| 343 | out: |
| 344 | store_pool = dkim_verify_oldpool; |
| 345 | } |
| 346 | |
| 347 | |
| 348 | |
| 349 | /* Args as per dkim_exim_acl_run() below */ |
| 350 | static int |
| 351 | dkim_acl_call(uschar * id, gstring ** res_ptr, |
| 352 | uschar ** user_msgptr, uschar ** log_msgptr) |
| 353 | { |
| 354 | int rc; |
| 355 | DEBUG(D_receive) |
| 356 | debug_printf("calling acl_smtp_dkim for dkim_cur_signer='%s'\n", id); |
| 357 | |
| 358 | rc = acl_check(ACL_WHERE_DKIM, NULL, acl_smtp_dkim, user_msgptr, log_msgptr); |
| 359 | dkim_exim_verify_log_sig(dkim_cur_sig); |
| 360 | *res_ptr = string_append_listele(*res_ptr, ':', dkim_verify_status); |
| 361 | return rc; |
| 362 | } |
| 363 | |
| 364 | |
| 365 | |
| 366 | /* For the given identity, run the DKIM ACL once for each matching signature. |
| 367 | |
| 368 | Arguments |
| 369 | id Identity to look for in dkim signatures |
| 370 | res_ptr ptr to growable string-list of status results, |
| 371 | appended to per ACL run |
| 372 | user_msgptr where to put a user error (for SMTP response) |
| 373 | log_msgptr where to put a logging message (not for SMTP response) |
| 374 | |
| 375 | Returns: OK access is granted by an ACCEPT verb |
| 376 | DISCARD access is granted by a DISCARD verb |
| 377 | FAIL access is denied |
| 378 | FAIL_DROP access is denied; drop the connection |
| 379 | DEFER can't tell at the moment |
| 380 | ERROR disaster |
| 381 | */ |
| 382 | |
| 383 | int |
| 384 | dkim_exim_acl_run(uschar * id, gstring ** res_ptr, |
| 385 | uschar ** user_msgptr, uschar ** log_msgptr) |
| 386 | { |
| 387 | uschar * cmp_val; |
| 388 | int rc = -1; |
| 389 | |
| 390 | dkim_verify_status = US"none"; |
| 391 | dkim_verify_reason = US""; |
| 392 | dkim_cur_signer = id; |
| 393 | |
| 394 | if (f.dkim_disable_verify || !id || !dkim_verify_ctx) |
| 395 | return OK; |
| 396 | |
| 397 | /* Find signatures to run ACL on */ |
| 398 | |
| 399 | for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next) |
| 400 | if ( (cmp_val = Ustrchr(id, '@') != NULL ? US sig->identity : US sig->domain) |
| 401 | && strcmpic(cmp_val, id) == 0 |
| 402 | ) |
| 403 | { |
| 404 | /* The "dkim_domain" and "dkim_selector" expansion variables have |
| 405 | related globals, since they are used in the signing code too. |
| 406 | Instead of inventing separate names for verification, we set |
| 407 | them here. This is easy since a domain and selector is guaranteed |
| 408 | to be in a signature. The other dkim_* expansion items are |
| 409 | dynamically fetched from dkim_cur_sig at expansion time (see |
| 410 | dkim_exim_expand_query() below). */ |
| 411 | |
| 412 | dkim_cur_sig = sig; |
| 413 | dkim_signing_domain = US sig->domain; |
| 414 | dkim_signing_selector = US sig->selector; |
| 415 | dkim_key_length = sig->keybits; |
| 416 | |
| 417 | /* These two return static strings, so we can compare the addr |
| 418 | later to see if the ACL overwrote them. Check that when logging */ |
| 419 | |
| 420 | dkim_verify_status = dkim_exim_expand_query(DKIM_VERIFY_STATUS); |
| 421 | dkim_verify_reason = dkim_exim_expand_query(DKIM_VERIFY_REASON); |
| 422 | |
| 423 | if ((rc = dkim_acl_call(id, res_ptr, user_msgptr, log_msgptr)) != OK) |
| 424 | return rc; |
| 425 | } |
| 426 | |
| 427 | if (rc != -1) |
| 428 | return rc; |
| 429 | |
| 430 | /* No matching sig found. Call ACL once anyway. */ |
| 431 | |
| 432 | dkim_cur_sig = NULL; |
| 433 | return dkim_acl_call(id, res_ptr, user_msgptr, log_msgptr); |
| 434 | } |
| 435 | |
| 436 | |
| 437 | static uschar * |
| 438 | dkim_exim_expand_defaults(int what) |
| 439 | { |
| 440 | switch (what) |
| 441 | { |
| 442 | case DKIM_ALGO: return US""; |
| 443 | case DKIM_BODYLENGTH: return US"9999999999999"; |
| 444 | case DKIM_CANON_BODY: return US""; |
| 445 | case DKIM_CANON_HEADERS: return US""; |
| 446 | case DKIM_COPIEDHEADERS: return US""; |
| 447 | case DKIM_CREATED: return US"0"; |
| 448 | case DKIM_EXPIRES: return US"9999999999999"; |
| 449 | case DKIM_HEADERNAMES: return US""; |
| 450 | case DKIM_IDENTITY: return US""; |
| 451 | case DKIM_KEY_GRANULARITY: return US"*"; |
| 452 | case DKIM_KEY_SRVTYPE: return US"*"; |
| 453 | case DKIM_KEY_NOTES: return US""; |
| 454 | case DKIM_KEY_TESTING: return US"0"; |
| 455 | case DKIM_NOSUBDOMAINS: return US"0"; |
| 456 | case DKIM_VERIFY_STATUS: return US"none"; |
| 457 | case DKIM_VERIFY_REASON: return US""; |
| 458 | default: return US""; |
| 459 | } |
| 460 | } |
| 461 | |
| 462 | |
| 463 | uschar * |
| 464 | dkim_exim_expand_query(int what) |
| 465 | { |
| 466 | if (!dkim_verify_ctx || f.dkim_disable_verify || !dkim_cur_sig) |
| 467 | return dkim_exim_expand_defaults(what); |
| 468 | |
| 469 | switch (what) |
| 470 | { |
| 471 | case DKIM_ALGO: |
| 472 | return dkim_sig_to_a_tag(dkim_cur_sig); |
| 473 | |
| 474 | case DKIM_BODYLENGTH: |
| 475 | return dkim_cur_sig->bodylength >= 0 |
| 476 | ? string_sprintf("%ld", dkim_cur_sig->bodylength) |
| 477 | : dkim_exim_expand_defaults(what); |
| 478 | |
| 479 | case DKIM_CANON_BODY: |
| 480 | switch (dkim_cur_sig->canon_body) |
| 481 | { |
| 482 | case PDKIM_CANON_RELAXED: return US"relaxed"; |
| 483 | case PDKIM_CANON_SIMPLE: |
| 484 | default: return US"simple"; |
| 485 | } |
| 486 | |
| 487 | case DKIM_CANON_HEADERS: |
| 488 | switch (dkim_cur_sig->canon_headers) |
| 489 | { |
| 490 | case PDKIM_CANON_RELAXED: return US"relaxed"; |
| 491 | case PDKIM_CANON_SIMPLE: |
| 492 | default: return US"simple"; |
| 493 | } |
| 494 | |
| 495 | case DKIM_COPIEDHEADERS: |
| 496 | return dkim_cur_sig->copiedheaders |
| 497 | ? US dkim_cur_sig->copiedheaders : dkim_exim_expand_defaults(what); |
| 498 | |
| 499 | case DKIM_CREATED: |
| 500 | return dkim_cur_sig->created > 0 |
| 501 | ? string_sprintf("%lu", dkim_cur_sig->created) |
| 502 | : dkim_exim_expand_defaults(what); |
| 503 | |
| 504 | case DKIM_EXPIRES: |
| 505 | return dkim_cur_sig->expires > 0 |
| 506 | ? string_sprintf("%lu", dkim_cur_sig->expires) |
| 507 | : dkim_exim_expand_defaults(what); |
| 508 | |
| 509 | case DKIM_HEADERNAMES: |
| 510 | return dkim_cur_sig->headernames |
| 511 | ? dkim_cur_sig->headernames : dkim_exim_expand_defaults(what); |
| 512 | |
| 513 | case DKIM_IDENTITY: |
| 514 | return dkim_cur_sig->identity |
| 515 | ? US dkim_cur_sig->identity : dkim_exim_expand_defaults(what); |
| 516 | |
| 517 | case DKIM_KEY_GRANULARITY: |
| 518 | return dkim_cur_sig->pubkey |
| 519 | ? dkim_cur_sig->pubkey->granularity |
| 520 | ? US dkim_cur_sig->pubkey->granularity |
| 521 | : dkim_exim_expand_defaults(what) |
| 522 | : dkim_exim_expand_defaults(what); |
| 523 | |
| 524 | case DKIM_KEY_SRVTYPE: |
| 525 | return dkim_cur_sig->pubkey |
| 526 | ? dkim_cur_sig->pubkey->srvtype |
| 527 | ? US dkim_cur_sig->pubkey->srvtype |
| 528 | : dkim_exim_expand_defaults(what) |
| 529 | : dkim_exim_expand_defaults(what); |
| 530 | |
| 531 | case DKIM_KEY_NOTES: |
| 532 | return dkim_cur_sig->pubkey |
| 533 | ? dkim_cur_sig->pubkey->notes |
| 534 | ? US dkim_cur_sig->pubkey->notes |
| 535 | : dkim_exim_expand_defaults(what) |
| 536 | : dkim_exim_expand_defaults(what); |
| 537 | |
| 538 | case DKIM_KEY_TESTING: |
| 539 | return dkim_cur_sig->pubkey |
| 540 | ? dkim_cur_sig->pubkey->testing |
| 541 | ? US"1" |
| 542 | : dkim_exim_expand_defaults(what) |
| 543 | : dkim_exim_expand_defaults(what); |
| 544 | |
| 545 | case DKIM_NOSUBDOMAINS: |
| 546 | return dkim_cur_sig->pubkey |
| 547 | ? dkim_cur_sig->pubkey->no_subdomaining |
| 548 | ? US"1" |
| 549 | : dkim_exim_expand_defaults(what) |
| 550 | : dkim_exim_expand_defaults(what); |
| 551 | |
| 552 | case DKIM_VERIFY_STATUS: |
| 553 | switch (dkim_cur_sig->verify_status) |
| 554 | { |
| 555 | case PDKIM_VERIFY_INVALID: return US"invalid"; |
| 556 | case PDKIM_VERIFY_FAIL: return US"fail"; |
| 557 | case PDKIM_VERIFY_PASS: return US"pass"; |
| 558 | case PDKIM_VERIFY_NONE: |
| 559 | default: return US"none"; |
| 560 | } |
| 561 | |
| 562 | case DKIM_VERIFY_REASON: |
| 563 | switch (dkim_cur_sig->verify_ext_status) |
| 564 | { |
| 565 | case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: |
| 566 | return US"pubkey_unavailable"; |
| 567 | case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:return US"pubkey_dns_syntax"; |
| 568 | case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: return US"pubkey_der_syntax"; |
| 569 | case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE: return US"pubkey_too_short"; |
| 570 | case PDKIM_VERIFY_FAIL_BODY: return US"bodyhash_mismatch"; |
| 571 | case PDKIM_VERIFY_FAIL_MESSAGE: return US"signature_incorrect"; |
| 572 | } |
| 573 | |
| 574 | default: |
| 575 | return US""; |
| 576 | } |
| 577 | } |
| 578 | |
| 579 | |
| 580 | void |
| 581 | dkim_exim_sign_init(void) |
| 582 | { |
| 583 | int old_pool = store_pool; |
| 584 | |
| 585 | dkim_exim_init(); |
| 586 | store_pool = POOL_MAIN; |
| 587 | pdkim_init_context(&dkim_sign_ctx, FALSE, &dkim_exim_query_dns_txt); |
| 588 | store_pool = old_pool; |
| 589 | } |
| 590 | |
| 591 | |
| 592 | /* Generate signatures for the given file. |
| 593 | If a prefix is given, prepend it to the file for the calculations. |
| 594 | |
| 595 | Return: |
| 596 | NULL: error; error string written |
| 597 | string: signature header(s), or a zero-length string (not an error) |
| 598 | */ |
| 599 | |
| 600 | gstring * |
| 601 | dkim_exim_sign(int fd, off_t off, uschar * prefix, |
| 602 | struct ob_dkim * dkim, const uschar ** errstr) |
| 603 | { |
| 604 | const uschar * dkim_domain = NULL; |
| 605 | int sep = 0; |
| 606 | gstring * seen_doms = NULL; |
| 607 | pdkim_signature * sig; |
| 608 | gstring * sigbuf; |
| 609 | int pdkim_rc; |
| 610 | int sread; |
| 611 | uschar buf[4096]; |
| 612 | int save_errno = 0; |
| 613 | int old_pool = store_pool; |
| 614 | uschar * errwhen; |
| 615 | const uschar * s; |
| 616 | |
| 617 | if (dkim->dot_stuffed) |
| 618 | dkim_sign_ctx.flags |= PDKIM_DOT_TERM; |
| 619 | |
| 620 | store_pool = POOL_MAIN; |
| 621 | |
| 622 | if ((s = dkim->dkim_domain) && !(dkim_domain = expand_cstring(s))) |
| 623 | /* expansion error, do not send message. */ |
| 624 | { errwhen = US"dkim_domain"; goto expand_bad; } |
| 625 | |
| 626 | /* Set $dkim_domain expansion variable to each unique domain in list. */ |
| 627 | |
| 628 | if (dkim_domain) |
| 629 | while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep, NULL, 0))) |
| 630 | { |
| 631 | const uschar * dkim_sel; |
| 632 | int sel_sep = 0; |
| 633 | |
| 634 | if (dkim_signing_domain[0] == '\0') |
| 635 | continue; |
| 636 | |
| 637 | /* Only sign once for each domain, no matter how often it |
| 638 | appears in the expanded list. */ |
| 639 | |
| 640 | dkim_signing_domain = string_copylc(dkim_signing_domain); |
| 641 | if (match_isinlist(dkim_signing_domain, CUSS &seen_doms, |
| 642 | 0, NULL, NULL, MCL_STRING, TRUE, NULL) == OK) |
| 643 | continue; |
| 644 | |
| 645 | seen_doms = string_append_listele(seen_doms, ':', dkim_signing_domain); |
| 646 | |
| 647 | /* Set $dkim_selector expansion variable to each selector in list, |
| 648 | for this domain. */ |
| 649 | |
| 650 | if (!(dkim_sel = expand_string(dkim->dkim_selector))) |
| 651 | { errwhen = US"dkim_selector"; goto expand_bad; } |
| 652 | |
| 653 | while ((dkim_signing_selector = string_nextinlist(&dkim_sel, &sel_sep, |
| 654 | NULL, 0))) |
| 655 | { |
| 656 | uschar * dkim_canon_expanded; |
| 657 | int pdkim_canon; |
| 658 | uschar * dkim_sign_headers_expanded = NULL; |
| 659 | uschar * dkim_private_key_expanded; |
| 660 | uschar * dkim_hash_expanded; |
| 661 | uschar * dkim_identity_expanded = NULL; |
| 662 | uschar * dkim_timestamps_expanded = NULL; |
| 663 | unsigned long tval = 0, xval = 0; |
| 664 | |
| 665 | /* Get canonicalization to use */ |
| 666 | |
| 667 | dkim_canon_expanded = dkim->dkim_canon |
| 668 | ? expand_string(dkim->dkim_canon) : US"relaxed"; |
| 669 | if (!dkim_canon_expanded) /* expansion error, do not send message. */ |
| 670 | { errwhen = US"dkim_canon"; goto expand_bad; } |
| 671 | |
| 672 | if (Ustrcmp(dkim_canon_expanded, "relaxed") == 0) |
| 673 | pdkim_canon = PDKIM_CANON_RELAXED; |
| 674 | else if (Ustrcmp(dkim_canon_expanded, "simple") == 0) |
| 675 | pdkim_canon = PDKIM_CANON_SIMPLE; |
| 676 | else |
| 677 | { |
| 678 | log_write(0, LOG_MAIN, |
| 679 | "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n", |
| 680 | dkim_canon_expanded); |
| 681 | pdkim_canon = PDKIM_CANON_RELAXED; |
| 682 | } |
| 683 | |
| 684 | if ( dkim->dkim_sign_headers |
| 685 | && !(dkim_sign_headers_expanded = expand_string(dkim->dkim_sign_headers))) |
| 686 | { errwhen = US"dkim_sign_header"; goto expand_bad; } |
| 687 | /* else pass NULL, which means default header list */ |
| 688 | |
| 689 | /* Get private key to use. */ |
| 690 | |
| 691 | if (!(dkim_private_key_expanded = expand_string(dkim->dkim_private_key))) |
| 692 | { errwhen = US"dkim_private_key"; goto expand_bad; } |
| 693 | |
| 694 | if ( Ustrlen(dkim_private_key_expanded) == 0 |
| 695 | || Ustrcmp(dkim_private_key_expanded, "0") == 0 |
| 696 | || Ustrcmp(dkim_private_key_expanded, "false") == 0 |
| 697 | ) |
| 698 | continue; /* don't sign, but no error */ |
| 699 | |
| 700 | if ( dkim_private_key_expanded[0] == '/' |
| 701 | && !(dkim_private_key_expanded = |
| 702 | expand_file_big_buffer(dkim_private_key_expanded))) |
| 703 | goto bad; |
| 704 | |
| 705 | if (!(dkim_hash_expanded = expand_string(dkim->dkim_hash))) |
| 706 | { errwhen = US"dkim_hash"; goto expand_bad; } |
| 707 | |
| 708 | if (dkim->dkim_identity) |
| 709 | if (!(dkim_identity_expanded = expand_string(dkim->dkim_identity))) |
| 710 | { errwhen = US"dkim_identity"; goto expand_bad; } |
| 711 | else if (!*dkim_identity_expanded) |
| 712 | dkim_identity_expanded = NULL; |
| 713 | |
| 714 | if (dkim->dkim_timestamps) |
| 715 | if (!(dkim_timestamps_expanded = expand_string(dkim->dkim_timestamps))) |
| 716 | { errwhen = US"dkim_timestamps"; goto expand_bad; } |
| 717 | else |
| 718 | xval = (tval = (unsigned long) time(NULL)) |
| 719 | + strtoul(CCS dkim_timestamps_expanded, NULL, 10); |
| 720 | |
| 721 | if (!(sig = pdkim_init_sign(&dkim_sign_ctx, dkim_signing_domain, |
| 722 | dkim_signing_selector, |
| 723 | dkim_private_key_expanded, |
| 724 | dkim_hash_expanded, |
| 725 | errstr |
| 726 | ))) |
| 727 | goto bad; |
| 728 | dkim_private_key_expanded[0] = '\0'; |
| 729 | |
| 730 | pdkim_set_optional(sig, |
| 731 | CS dkim_sign_headers_expanded, |
| 732 | CS dkim_identity_expanded, |
| 733 | pdkim_canon, |
| 734 | pdkim_canon, -1, tval, xval); |
| 735 | |
| 736 | if (!pdkim_set_sig_bodyhash(&dkim_sign_ctx, sig)) |
| 737 | goto bad; |
| 738 | |
| 739 | if (!dkim_sign_ctx.sig) /* link sig to context chain */ |
| 740 | dkim_sign_ctx.sig = sig; |
| 741 | else |
| 742 | { |
| 743 | pdkim_signature * n = dkim_sign_ctx.sig; |
| 744 | while (n->next) n = n->next; |
| 745 | n->next = sig; |
| 746 | } |
| 747 | } |
| 748 | } |
| 749 | |
| 750 | /* We may need to carry on with the data-feed even if there are no DKIM sigs to |
| 751 | produce, if some other package (eg. ARC) is signing. */ |
| 752 | |
| 753 | if (!dkim_sign_ctx.sig && !dkim->force_bodyhash) |
| 754 | { |
| 755 | DEBUG(D_transport) debug_printf("DKIM: no viable signatures to use\n"); |
| 756 | sigbuf = string_get(1); /* return a zero-len string */ |
| 757 | } |
| 758 | else |
| 759 | { |
| 760 | if (prefix && (pdkim_rc = pdkim_feed(&dkim_sign_ctx, prefix, Ustrlen(prefix))) != PDKIM_OK) |
| 761 | goto pk_bad; |
| 762 | |
| 763 | if (lseek(fd, off, SEEK_SET) < 0) |
| 764 | sread = -1; |
| 765 | else |
| 766 | while ((sread = read(fd, &buf, sizeof(buf))) > 0) |
| 767 | if ((pdkim_rc = pdkim_feed(&dkim_sign_ctx, buf, sread)) != PDKIM_OK) |
| 768 | goto pk_bad; |
| 769 | |
| 770 | /* Handle failed read above. */ |
| 771 | if (sread == -1) |
| 772 | { |
| 773 | debug_printf("DKIM: Error reading -K file.\n"); |
| 774 | save_errno = errno; |
| 775 | goto bad; |
| 776 | } |
| 777 | |
| 778 | /* Build string of headers, one per signature */ |
| 779 | |
| 780 | if ((pdkim_rc = pdkim_feed_finish(&dkim_sign_ctx, &sig, errstr)) != PDKIM_OK) |
| 781 | goto pk_bad; |
| 782 | |
| 783 | if (!sig) |
| 784 | { |
| 785 | DEBUG(D_transport) debug_printf("DKIM: no signatures to use\n"); |
| 786 | sigbuf = string_get(1); /* return a zero-len string */ |
| 787 | } |
| 788 | else for (sigbuf = NULL; sig; sig = sig->next) |
| 789 | sigbuf = string_append(sigbuf, 2, US sig->signature_header, US"\r\n"); |
| 790 | } |
| 791 | |
| 792 | CLEANUP: |
| 793 | (void) string_from_gstring(sigbuf); |
| 794 | store_pool = old_pool; |
| 795 | errno = save_errno; |
| 796 | return sigbuf; |
| 797 | |
| 798 | pk_bad: |
| 799 | log_write(0, LOG_MAIN|LOG_PANIC, |
| 800 | "DKIM: signing failed: %.100s", pdkim_errstr(pdkim_rc)); |
| 801 | bad: |
| 802 | sigbuf = NULL; |
| 803 | goto CLEANUP; |
| 804 | |
| 805 | expand_bad: |
| 806 | *errstr = string_sprintf("failed to expand %s: %s", |
| 807 | errwhen, expand_string_message); |
| 808 | log_write(0, LOG_MAIN | LOG_PANIC, "%s", *errstr); |
| 809 | goto bad; |
| 810 | } |
| 811 | |
| 812 | |
| 813 | |
| 814 | |
| 815 | gstring * |
| 816 | authres_dkim(gstring * g) |
| 817 | { |
| 818 | int start = 0; /* compiler quietening */ |
| 819 | |
| 820 | DEBUG(D_acl) start = g->ptr; |
| 821 | |
| 822 | for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next) |
| 823 | { |
| 824 | g = string_catn(g, US";\n\tdkim=", 8); |
| 825 | |
| 826 | if (sig->verify_status & PDKIM_VERIFY_POLICY) |
| 827 | g = string_append(g, 5, |
| 828 | US"policy (", dkim_verify_status, US" - ", dkim_verify_reason, US")"); |
| 829 | else switch(sig->verify_status) |
| 830 | { |
| 831 | case PDKIM_VERIFY_NONE: g = string_cat(g, US"none"); break; |
| 832 | case PDKIM_VERIFY_INVALID: |
| 833 | switch (sig->verify_ext_status) |
| 834 | { |
| 835 | case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: |
| 836 | g = string_cat(g, US"tmperror (pubkey unavailable)\n\t\t"); break; |
| 837 | case PDKIM_VERIFY_INVALID_BUFFER_SIZE: |
| 838 | g = string_cat(g, US"permerror (overlong public key record)\n\t\t"); break; |
| 839 | case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: |
| 840 | case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: |
| 841 | g = string_cat(g, US"neutral (public key record import problem)\n\t\t"); |
| 842 | break; |
| 843 | case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: |
| 844 | g = string_cat(g, US"neutral (signature tag missing or invalid)\n\t\t"); |
| 845 | break; |
| 846 | case PDKIM_VERIFY_INVALID_DKIM_VERSION: |
| 847 | g = string_cat(g, US"neutral (unsupported DKIM version)\n\t\t"); |
| 848 | break; |
| 849 | default: |
| 850 | g = string_cat(g, US"permerror (unspecified problem)\n\t\t"); break; |
| 851 | } |
| 852 | break; |
| 853 | case PDKIM_VERIFY_FAIL: |
| 854 | switch (sig->verify_ext_status) |
| 855 | { |
| 856 | case PDKIM_VERIFY_FAIL_BODY: |
| 857 | g = string_cat(g, |
| 858 | US"fail (body hash mismatch; body probably modified in transit)\n\t\t"); |
| 859 | break; |
| 860 | case PDKIM_VERIFY_FAIL_MESSAGE: |
| 861 | g = string_cat(g, |
| 862 | US"fail (signature did not verify; headers probably modified in transit)\n\t\t"); |
| 863 | break; |
| 864 | case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE: /* should this really be "polcy"? */ |
| 865 | g = string_fmt_append(g, "fail (public key too short: %u bits)\n\t\t", sig->keybits); |
| 866 | break; |
| 867 | default: |
| 868 | g = string_cat(g, US"fail (unspecified reason)\n\t\t"); |
| 869 | break; |
| 870 | } |
| 871 | break; |
| 872 | case PDKIM_VERIFY_PASS: g = string_cat(g, US"pass"); break; |
| 873 | default: g = string_cat(g, US"permerror"); break; |
| 874 | } |
| 875 | if (sig->domain) g = string_append(g, 2, US" header.d=", sig->domain); |
| 876 | if (sig->identity) g = string_append(g, 2, US" header.i=", sig->identity); |
| 877 | if (sig->selector) g = string_append(g, 2, US" header.s=", sig->selector); |
| 878 | g = string_append(g, 2, US" header.a=", dkim_sig_to_a_tag(sig)); |
| 879 | } |
| 880 | |
| 881 | DEBUG(D_acl) |
| 882 | if (g->ptr == start) |
| 883 | debug_printf("DKIM: no authres\n"); |
| 884 | else |
| 885 | debug_printf("DKIM: authres '%.*s'\n", g->ptr - start - 3, g->s + start + 3); |
| 886 | return g; |
| 887 | } |
| 888 | |
| 889 | |
| 890 | # endif /*!MACRO_PREDEF*/ |
| 891 | #endif /*!DISABLE_DKIM*/ |