| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2012 */ |
| 6 | /* See the file NOTICE for conditions of use and distribution. */ |
| 7 | |
| 8 | #include "../exim.h" |
| 9 | #include "lf_functions.h" |
| 10 | |
| 11 | |
| 12 | |
| 13 | /* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their |
| 14 | header files. */ |
| 15 | |
| 16 | #ifndef T_TXT |
| 17 | #define T_TXT 16 |
| 18 | #endif |
| 19 | |
| 20 | /* Many systems do not have T_SPF. */ |
| 21 | #ifndef T_SPF |
| 22 | #define T_SPF 99 |
| 23 | #endif |
| 24 | |
| 25 | /* Table of recognized DNS record types and their integer values. */ |
| 26 | |
| 27 | static const char *type_names[] = { |
| 28 | "a", |
| 29 | #if HAVE_IPV6 |
| 30 | "aaaa", |
| 31 | #ifdef SUPPORT_A6 |
| 32 | "a6", |
| 33 | #endif |
| 34 | #endif |
| 35 | "cname", |
| 36 | "csa", |
| 37 | "mx", |
| 38 | "mxh", |
| 39 | "ns", |
| 40 | "ptr", |
| 41 | "spf", |
| 42 | "srv", |
| 43 | "txt", |
| 44 | "zns" |
| 45 | }; |
| 46 | |
| 47 | static int type_values[] = { |
| 48 | T_A, |
| 49 | #if HAVE_IPV6 |
| 50 | T_AAAA, |
| 51 | #ifdef SUPPORT_A6 |
| 52 | T_A6, |
| 53 | #endif |
| 54 | #endif |
| 55 | T_CNAME, |
| 56 | T_CSA, /* Private type for "Client SMTP Authorization". */ |
| 57 | T_MX, |
| 58 | T_MXH, /* Private type for "MX hostnames" */ |
| 59 | T_NS, |
| 60 | T_PTR, |
| 61 | T_SPF, |
| 62 | T_SRV, |
| 63 | T_TXT, |
| 64 | T_ZNS /* Private type for "zone nameservers" */ |
| 65 | }; |
| 66 | |
| 67 | |
| 68 | /************************************************* |
| 69 | * Open entry point * |
| 70 | *************************************************/ |
| 71 | |
| 72 | /* See local README for interface description. */ |
| 73 | |
| 74 | static void * |
| 75 | dnsdb_open(uschar *filename, uschar **errmsg) |
| 76 | { |
| 77 | filename = filename; /* Keep picky compilers happy */ |
| 78 | errmsg = errmsg; /* Ditto */ |
| 79 | return (void *)(-1); /* Any non-0 value */ |
| 80 | } |
| 81 | |
| 82 | |
| 83 | |
| 84 | /************************************************* |
| 85 | * Find entry point for dnsdb * |
| 86 | *************************************************/ |
| 87 | |
| 88 | /* See local README for interface description. The query in the "keystring" may |
| 89 | consist of a number of parts. |
| 90 | |
| 91 | (a) If the first significant character is '>' then the next character is the |
| 92 | separator character that is used when multiple records are found. The default |
| 93 | separator is newline. |
| 94 | |
| 95 | (b) If the next character is ',' then the next character is the separator |
| 96 | character used for multiple items of text in "TXT" records. Alternatively, |
| 97 | if the next character is ';' then these multiple items are concatenated with |
| 98 | no separator. With neither of these options specified, only the first item |
| 99 | is output. |
| 100 | |
| 101 | (c) If the next sequence of characters is 'defer_FOO' followed by a comma, |
| 102 | the defer behaviour is set to FOO. The possible behaviours are: 'strict', where |
| 103 | any defer causes the whole lookup to defer; 'lax', where a defer causes the |
| 104 | whole lookup to defer only if none of the DNS queries succeeds; and 'never', |
| 105 | where all defers are as if the lookup failed. The default is 'lax'. |
| 106 | |
| 107 | (d) If the next sequence of characters is a sequence of letters and digits |
| 108 | followed by '=', it is interpreted as the name of the DNS record type. The |
| 109 | default is "TXT". |
| 110 | |
| 111 | (e) Then there follows list of domain names. This is a generalized Exim list, |
| 112 | which may start with '<' in order to set a specific separator. The default |
| 113 | separator, as always, is colon. */ |
| 114 | |
| 115 | static int |
| 116 | dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length, |
| 117 | uschar **result, uschar **errmsg, BOOL *do_cache) |
| 118 | { |
| 119 | int rc; |
| 120 | int size = 256; |
| 121 | int ptr = 0; |
| 122 | int sep = 0; |
| 123 | int defer_mode = PASS; |
| 124 | int type = T_TXT; |
| 125 | int failrc = FAIL; |
| 126 | uschar *outsep = US"\n"; |
| 127 | uschar *outsep2 = NULL; |
| 128 | uschar *equals, *domain, *found; |
| 129 | uschar buffer[256]; |
| 130 | |
| 131 | /* Because we're the working in the search pool, we try to reclaim as much |
| 132 | store as possible later, so we preallocate the result here */ |
| 133 | |
| 134 | uschar *yield = store_get(size); |
| 135 | |
| 136 | dns_record *rr; |
| 137 | dns_answer dnsa; |
| 138 | dns_scan dnss; |
| 139 | |
| 140 | handle = handle; /* Keep picky compilers happy */ |
| 141 | filename = filename; |
| 142 | length = length; |
| 143 | do_cache = do_cache; |
| 144 | |
| 145 | /* If the string starts with '>' we change the output separator. |
| 146 | If it's followed by ';' or ',' we set the TXT output separator. */ |
| 147 | |
| 148 | while (isspace(*keystring)) keystring++; |
| 149 | if (*keystring == '>') |
| 150 | { |
| 151 | outsep = keystring + 1; |
| 152 | keystring += 2; |
| 153 | if (*keystring == ',') |
| 154 | { |
| 155 | outsep2 = keystring + 1; |
| 156 | keystring += 2; |
| 157 | } |
| 158 | else if (*keystring == ';') |
| 159 | { |
| 160 | outsep2 = US""; |
| 161 | keystring++; |
| 162 | } |
| 163 | while (isspace(*keystring)) keystring++; |
| 164 | } |
| 165 | |
| 166 | /* Check for a defer behaviour keyword. */ |
| 167 | |
| 168 | if (strncmpic(keystring, US"defer_", 6) == 0) |
| 169 | { |
| 170 | keystring += 6; |
| 171 | if (strncmpic(keystring, US"strict", 6) == 0) |
| 172 | { |
| 173 | defer_mode = DEFER; |
| 174 | keystring += 6; |
| 175 | } |
| 176 | else if (strncmpic(keystring, US"lax", 3) == 0) |
| 177 | { |
| 178 | defer_mode = PASS; |
| 179 | keystring += 3; |
| 180 | } |
| 181 | else if (strncmpic(keystring, US"never", 5) == 0) |
| 182 | { |
| 183 | defer_mode = OK; |
| 184 | keystring += 5; |
| 185 | } |
| 186 | else |
| 187 | { |
| 188 | *errmsg = US"unsupported dnsdb defer behaviour"; |
| 189 | return DEFER; |
| 190 | } |
| 191 | while (isspace(*keystring)) keystring++; |
| 192 | if (*keystring++ != ',') |
| 193 | { |
| 194 | *errmsg = US"dnsdb defer behaviour syntax error"; |
| 195 | return DEFER; |
| 196 | } |
| 197 | while (isspace(*keystring)) keystring++; |
| 198 | } |
| 199 | |
| 200 | /* If the keystring contains an = this must be preceded by a valid type name. */ |
| 201 | |
| 202 | if ((equals = Ustrchr(keystring, '=')) != NULL) |
| 203 | { |
| 204 | int i, len; |
| 205 | uschar *tend = equals; |
| 206 | |
| 207 | while (tend > keystring && isspace(tend[-1])) tend--; |
| 208 | len = tend - keystring; |
| 209 | |
| 210 | for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++) |
| 211 | { |
| 212 | if (len == Ustrlen(type_names[i]) && |
| 213 | strncmpic(keystring, US type_names[i], len) == 0) |
| 214 | { |
| 215 | type = type_values[i]; |
| 216 | break; |
| 217 | } |
| 218 | } |
| 219 | |
| 220 | if (i >= sizeof(type_names)/sizeof(uschar *)) |
| 221 | { |
| 222 | *errmsg = US"unsupported DNS record type"; |
| 223 | return DEFER; |
| 224 | } |
| 225 | |
| 226 | keystring = equals + 1; |
| 227 | while (isspace(*keystring)) keystring++; |
| 228 | } |
| 229 | |
| 230 | /* Initialize the resolver in case this is the first time it has been used. */ |
| 231 | |
| 232 | dns_init(FALSE, FALSE); |
| 233 | |
| 234 | /* The remainder of the string must be a list of domains. As long as the lookup |
| 235 | for at least one of them succeeds, we return success. Failure means that none |
| 236 | of them were found. |
| 237 | |
| 238 | The original implementation did not support a list of domains. Adding the list |
| 239 | feature is compatible, except in one case: when PTR records are being looked up |
| 240 | for a single IPv6 address. Fortunately, we can hack in a compatibility feature |
| 241 | here: If the type is PTR and no list separator is specified, and the entire |
| 242 | remaining string is valid as an IP address, set an impossible separator so that |
| 243 | it is treated as one item. */ |
| 244 | |
| 245 | if (type == T_PTR && keystring[0] != '<' && |
| 246 | string_is_ip_address(keystring, NULL) != 0) |
| 247 | sep = -1; |
| 248 | |
| 249 | /* Now scan the list and do a lookup for each item */ |
| 250 | |
| 251 | while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer))) |
| 252 | != NULL) |
| 253 | { |
| 254 | uschar rbuffer[256]; |
| 255 | int searchtype = (type == T_CSA)? T_SRV : /* record type we want */ |
| 256 | (type == T_MXH)? T_MX : |
| 257 | (type == T_ZNS)? T_NS : type; |
| 258 | |
| 259 | /* If the type is PTR or CSA, we have to construct the relevant magic lookup |
| 260 | key if the original is an IP address (some experimental protocols are using |
| 261 | PTR records for different purposes where the key string is a host name, and |
| 262 | Exim's extended CSA can be keyed by domains or IP addresses). This code for |
| 263 | doing the reversal is now in a separate function. */ |
| 264 | |
| 265 | if ((type == T_PTR || type == T_CSA) && |
| 266 | string_is_ip_address(domain, NULL) != 0) |
| 267 | { |
| 268 | dns_build_reverse(domain, rbuffer); |
| 269 | domain = rbuffer; |
| 270 | } |
| 271 | |
| 272 | DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain); |
| 273 | |
| 274 | /* Do the lookup and sort out the result. There are three special types that |
| 275 | are handled specially: T_CSA, T_ZNS and T_MXH. The former two are handled in |
| 276 | a special lookup function so that the facility could be used from other |
| 277 | parts of the Exim code. The latter affects only what happens later on in |
| 278 | this function, but for tidiness it is handled in a similar way. If the |
| 279 | lookup fails, continue with the next domain. In the case of DEFER, adjust |
| 280 | the final "nothing found" result, but carry on to the next domain. */ |
| 281 | |
| 282 | found = domain; |
| 283 | rc = dns_special_lookup(&dnsa, domain, type, &found); |
| 284 | |
| 285 | if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue; |
| 286 | if (rc != DNS_SUCCEED) |
| 287 | { |
| 288 | if (defer_mode == DEFER) return DEFER; /* always defer */ |
| 289 | else if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */ |
| 290 | continue; /* treat defer as fail */ |
| 291 | } |
| 292 | |
| 293 | /* Search the returned records */ |
| 294 | |
| 295 | for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS); |
| 296 | rr != NULL; |
| 297 | rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT)) |
| 298 | { |
| 299 | if (rr->type != searchtype) continue; |
| 300 | |
| 301 | /* There may be several addresses from an A6 record. Put the configured |
| 302 | separator between them, just as for between several records. However, A6 |
| 303 | support is not normally configured these days. */ |
| 304 | |
| 305 | if (type == T_A || |
| 306 | #ifdef SUPPORT_A6 |
| 307 | type == T_A6 || |
| 308 | #endif |
| 309 | type == T_AAAA) |
| 310 | { |
| 311 | dns_address *da; |
| 312 | for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next) |
| 313 | { |
| 314 | if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1); |
| 315 | yield = string_cat(yield, &size, &ptr, da->address, |
| 316 | Ustrlen(da->address)); |
| 317 | } |
| 318 | continue; |
| 319 | } |
| 320 | |
| 321 | /* Other kinds of record just have one piece of data each, but there may be |
| 322 | several of them, of course. */ |
| 323 | |
| 324 | if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1); |
| 325 | |
| 326 | if (type == T_TXT || type == T_SPF) |
| 327 | { |
| 328 | if (outsep2 == NULL) |
| 329 | { |
| 330 | /* output only the first item of data */ |
| 331 | yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1), |
| 332 | (rr->data)[0]); |
| 333 | } |
| 334 | else |
| 335 | { |
| 336 | /* output all items */ |
| 337 | int data_offset = 0; |
| 338 | while (data_offset < rr->size) |
| 339 | { |
| 340 | uschar chunk_len = (rr->data)[data_offset++]; |
| 341 | if (outsep2[0] != '\0' && data_offset != 1) |
| 342 | yield = string_cat(yield, &size, &ptr, outsep2, 1); |
| 343 | yield = string_cat(yield, &size, &ptr, |
| 344 | (uschar *)((rr->data)+data_offset), chunk_len); |
| 345 | data_offset += chunk_len; |
| 346 | } |
| 347 | } |
| 348 | } |
| 349 | else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SRV */ |
| 350 | { |
| 351 | int priority, weight, port; |
| 352 | uschar s[264]; |
| 353 | uschar *p = (uschar *)(rr->data); |
| 354 | |
| 355 | if (type == T_MXH) |
| 356 | { |
| 357 | /* mxh ignores the priority number and includes only the hostnames */ |
| 358 | GETSHORT(priority, p); |
| 359 | } |
| 360 | else if (type == T_MX) |
| 361 | { |
| 362 | GETSHORT(priority, p); |
| 363 | sprintf(CS s, "%d ", priority); |
| 364 | yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); |
| 365 | } |
| 366 | else if (type == T_SRV) |
| 367 | { |
| 368 | GETSHORT(priority, p); |
| 369 | GETSHORT(weight, p); |
| 370 | GETSHORT(port, p); |
| 371 | sprintf(CS s, "%d %d %d ", priority, weight, port); |
| 372 | yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); |
| 373 | } |
| 374 | else if (type == T_CSA) |
| 375 | { |
| 376 | /* See acl_verify_csa() for more comments about CSA. */ |
| 377 | |
| 378 | GETSHORT(priority, p); |
| 379 | GETSHORT(weight, p); |
| 380 | GETSHORT(port, p); |
| 381 | |
| 382 | if (priority != 1) continue; /* CSA version must be 1 */ |
| 383 | |
| 384 | /* If the CSA record we found is not the one we asked for, analyse |
| 385 | the subdomain assertions in the port field, else analyse the direct |
| 386 | authorization status in the weight field. */ |
| 387 | |
| 388 | if (found != domain) |
| 389 | { |
| 390 | if (port & 1) *s = 'X'; /* explicit authorization required */ |
| 391 | else *s = '?'; /* no subdomain assertions here */ |
| 392 | } |
| 393 | else |
| 394 | { |
| 395 | if (weight < 2) *s = 'N'; /* not authorized */ |
| 396 | else if (weight == 2) *s = 'Y'; /* authorized */ |
| 397 | else if (weight == 3) *s = '?'; /* unauthorizable */ |
| 398 | else continue; /* invalid */ |
| 399 | } |
| 400 | |
| 401 | s[1] = ' '; |
| 402 | yield = string_cat(yield, &size, &ptr, s, 2); |
| 403 | } |
| 404 | |
| 405 | /* GETSHORT() has advanced the pointer to the target domain. */ |
| 406 | |
| 407 | rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p, |
| 408 | (DN_EXPAND_ARG4_TYPE)(s), sizeof(s)); |
| 409 | |
| 410 | /* If an overlong response was received, the data will have been |
| 411 | truncated and dn_expand may fail. */ |
| 412 | |
| 413 | if (rc < 0) |
| 414 | { |
| 415 | log_write(0, LOG_MAIN, "host name alias list truncated: type=%s " |
| 416 | "domain=%s", dns_text_type(type), domain); |
| 417 | break; |
| 418 | } |
| 419 | else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); |
| 420 | } |
| 421 | } /* Loop for list of returned records */ |
| 422 | } /* Loop for list of domains */ |
| 423 | |
| 424 | /* Reclaim unused memory */ |
| 425 | |
| 426 | store_reset(yield + ptr + 1); |
| 427 | |
| 428 | /* If ptr == 0 we have not found anything. Otherwise, insert the terminating |
| 429 | zero and return the result. */ |
| 430 | |
| 431 | if (ptr == 0) return failrc; |
| 432 | yield[ptr] = 0; |
| 433 | *result = yield; |
| 434 | return OK; |
| 435 | } |
| 436 | |
| 437 | |
| 438 | |
| 439 | /************************************************* |
| 440 | * Version reporting entry point * |
| 441 | *************************************************/ |
| 442 | |
| 443 | /* See local README for interface description. */ |
| 444 | |
| 445 | #include "../version.h" |
| 446 | |
| 447 | void |
| 448 | dnsdb_version_report(FILE *f) |
| 449 | { |
| 450 | #ifdef DYNLOOKUP |
| 451 | fprintf(f, "Library version: DNSDB: Exim version %s\n", EXIM_VERSION_STR); |
| 452 | #endif |
| 453 | } |
| 454 | |
| 455 | |
| 456 | static lookup_info _lookup_info = { |
| 457 | US"dnsdb", /* lookup name */ |
| 458 | lookup_querystyle, /* query style */ |
| 459 | dnsdb_open, /* open function */ |
| 460 | NULL, /* check function */ |
| 461 | dnsdb_find, /* find function */ |
| 462 | NULL, /* no close function */ |
| 463 | NULL, /* no tidy function */ |
| 464 | NULL, /* no quoting function */ |
| 465 | dnsdb_version_report /* version reporting */ |
| 466 | }; |
| 467 | |
| 468 | #ifdef DYNLOOKUP |
| 469 | #define dnsdb_lookup_module_info _lookup_module_info |
| 470 | #endif |
| 471 | |
| 472 | static lookup_info *_lookup_list[] = { &_lookup_info }; |
| 473 | lookup_module_info dnsdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 }; |
| 474 | |
| 475 | /* End of lookups/dnsdb.c */ |