/* $Cambridge: exim/src/src/lookups/dnsdb.c,v 1.19 2009/11/16 19:50:38 nm4 Exp $ */ /************************************************* * Exim - an Internet mail transport agent * *************************************************/ /* Copyright (c) University of Cambridge 1995 - 2009 */ /* See the file NOTICE for conditions of use and distribution. */ #include "../exim.h" #include "lf_functions.h" #include "dnsdb.h" /* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their header files. */ #ifndef T_TXT #define T_TXT 16 #endif /* Table of recognized DNS record types and their integer values. */ static char *type_names[] = { "a", #if HAVE_IPV6 "aaaa", #ifdef SUPPORT_A6 "a6", #endif #endif "cname", "csa", "mx", "mxh", "ns", "ptr", "srv", "txt", "zns" }; static int type_values[] = { T_A, #if HAVE_IPV6 T_AAAA, #ifdef SUPPORT_A6 T_A6, #endif #endif T_CNAME, T_CSA, /* Private type for "Client SMTP Authorization". */ T_MX, T_MXH, /* Private type for "MX hostnames" */ T_NS, T_PTR, T_SRV, T_TXT, T_ZNS /* Private type for "zone nameservers" */ }; /************************************************* * Open entry point * *************************************************/ /* See local README for interface description. */ void * dnsdb_open(uschar *filename, uschar **errmsg) { filename = filename; /* Keep picky compilers happy */ errmsg = errmsg; /* Ditto */ return (void *)(-1); /* Any non-0 value */ } /************************************************* * Find entry point for dnsdb * *************************************************/ /* See local README for interface description. The query in the "keystring" may consist of a number of parts. (a) If the first significant character is '>' then the next character is the separator character that is used when multiple records are found. The default separator is newline. (b) If the next sequence of characters is 'defer_FOO' followed by a comma, the defer behaviour is set to FOO. The possible behaviours are: 'strict', where any defer causes the whole lookup to defer; 'lax', where a defer causes the whole lookup to defer only if none of the DNS queries succeeds; and 'never', where all defers are as if the lookup failed. The default is 'lax'. (c) If the next sequence of characters is a sequence of letters and digits followed by '=', it is interpreted as the name of the DNS record type. The default is "TXT". (d) Then there follows list of domain names. This is a generalized Exim list, which may start with '<' in order to set a specific separator. The default separator, as always, is colon. */ int dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length, uschar **result, uschar **errmsg, BOOL *do_cache) { int rc; int size = 256; int ptr = 0; int sep = 0; int defer_mode = PASS; int type = T_TXT; int failrc = FAIL; uschar *outsep = US"\n"; uschar *equals, *domain, *found; uschar buffer[256]; /* Because we're the working in the search pool, we try to reclaim as much store as possible later, so we preallocate the result here */ uschar *yield = store_get(size); dns_record *rr; dns_answer dnsa; dns_scan dnss; handle = handle; /* Keep picky compilers happy */ filename = filename; length = length; do_cache = do_cache; /* If the string starts with '>' we change the output separator */ while (isspace(*keystring)) keystring++; if (*keystring == '>') { outsep = keystring + 1; keystring += 2; while (isspace(*keystring)) keystring++; } /* Check for a defer behaviour keyword. */ if (strncmpic(keystring, US"defer_", 6) == 0) { keystring += 6; if (strncmpic(keystring, US"strict", 6) == 0) { defer_mode = DEFER; keystring += 6; } else if (strncmpic(keystring, US"lax", 3) == 0) { defer_mode = PASS; keystring += 3; } else if (strncmpic(keystring, US"never", 5) == 0) { defer_mode = OK; keystring += 5; } else { *errmsg = US"unsupported dnsdb defer behaviour"; return DEFER; } while (isspace(*keystring)) keystring++; if (*keystring++ != ',') { *errmsg = US"dnsdb defer behaviour syntax error"; return DEFER; } while (isspace(*keystring)) keystring++; } /* If the keystring contains an = this must be preceded by a valid type name. */ if ((equals = Ustrchr(keystring, '=')) != NULL) { int i, len; uschar *tend = equals; while (tend > keystring && isspace(tend[-1])) tend--; len = tend - keystring; for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++) { if (len == Ustrlen(type_names[i]) && strncmpic(keystring, US type_names[i], len) == 0) { type = type_values[i]; break; } } if (i >= sizeof(type_names)/sizeof(uschar *)) { *errmsg = US"unsupported DNS record type"; return DEFER; } keystring = equals + 1; while (isspace(*keystring)) keystring++; } /* Initialize the resolver in case this is the first time it has been used. */ dns_init(FALSE, FALSE); /* The remainder of the string must be a list of domains. As long as the lookup for at least one of them succeeds, we return success. Failure means that none of them were found. The original implementation did not support a list of domains. Adding the list feature is compatible, except in one case: when PTR records are being looked up for a single IPv6 address. Fortunately, we can hack in a compatibility feature here: If the type is PTR and no list separator is specified, and the entire remaining string is valid as an IP address, set an impossible separator so that it is treated as one item. */ if (type == T_PTR && keystring[0] != '<' && string_is_ip_address(keystring, NULL) != 0) sep = -1; /* Now scan the list and do a lookup for each item */ while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer))) != NULL) { uschar rbuffer[256]; int searchtype = (type == T_CSA)? T_SRV : /* record type we want */ (type == T_MXH)? T_MX : (type == T_ZNS)? T_NS : type; /* If the type is PTR or CSA, we have to construct the relevant magic lookup key if the original is an IP address (some experimental protocols are using PTR records for different purposes where the key string is a host name, and Exim's extended CSA can be keyed by domains or IP addresses). This code for doing the reversal is now in a separate function. */ if ((type == T_PTR || type == T_CSA) && string_is_ip_address(domain, NULL) != 0) { dns_build_reverse(domain, rbuffer); domain = rbuffer; } DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain); /* Do the lookup and sort out the result. There are three special types that are handled specially: T_CSA, T_ZNS and T_MXH. The former two are handled in a special lookup function so that the facility could be used from other parts of the Exim code. The latter affects only what happens later on in this function, but for tidiness it is handled in a similar way. If the lookup fails, continue with the next domain. In the case of DEFER, adjust the final "nothing found" result, but carry on to the next domain. */ found = domain; rc = dns_special_lookup(&dnsa, domain, type, &found); if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue; if (rc != DNS_SUCCEED) { if (defer_mode == DEFER) return DEFER; /* always defer */ else if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */ continue; /* treat defer as fail */ } /* Search the returned records */ for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS); rr != NULL; rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT)) { if (rr->type != searchtype) continue; /* There may be several addresses from an A6 record. Put the configured separator between them, just as for between several records. However, A6 support is not normally configured these days. */ if (type == T_A || #ifdef SUPPORT_A6 type == T_A6 || #endif type == T_AAAA) { dns_address *da; for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next) { if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1); yield = string_cat(yield, &size, &ptr, da->address, Ustrlen(da->address)); } continue; } /* Other kinds of record just have one piece of data each, but there may be several of them, of course. */ if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1); if (type == T_TXT) { int data_offset = 0; while (data_offset < rr->size) { uschar chunk_len = (rr->data)[data_offset++]; yield = string_cat(yield, &size, &ptr, (uschar *)((rr->data)+data_offset), chunk_len); data_offset += chunk_len; } } else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SRV */ { int priority, weight, port; uschar s[264]; uschar *p = (uschar *)(rr->data); if (type == T_MXH) { /* mxh ignores the priority number and includes only the hostnames */ GETSHORT(priority, p); } else if (type == T_MX) { GETSHORT(priority, p); sprintf(CS s, "%d ", priority); yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); } else if (type == T_SRV) { GETSHORT(priority, p); GETSHORT(weight, p); GETSHORT(port, p); sprintf(CS s, "%d %d %d ", priority, weight, port); yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); } else if (type == T_CSA) { /* See acl_verify_csa() for more comments about CSA. */ GETSHORT(priority, p); GETSHORT(weight, p); GETSHORT(port, p); if (priority != 1) continue; /* CSA version must be 1 */ /* If the CSA record we found is not the one we asked for, analyse the subdomain assertions in the port field, else analyse the direct authorization status in the weight field. */ if (found != domain) { if (port & 1) *s = 'X'; /* explicit authorization required */ else *s = '?'; /* no subdomain assertions here */ } else { if (weight < 2) *s = 'N'; /* not authorized */ else if (weight == 2) *s = 'Y'; /* authorized */ else if (weight == 3) *s = '?'; /* unauthorizable */ else continue; /* invalid */ } s[1] = ' '; yield = string_cat(yield, &size, &ptr, s, 2); } /* GETSHORT() has advanced the pointer to the target domain. */ rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p, (DN_EXPAND_ARG4_TYPE)(s), sizeof(s)); /* If an overlong response was received, the data will have been truncated and dn_expand may fail. */ if (rc < 0) { log_write(0, LOG_MAIN, "host name alias list truncated: type=%s " "domain=%s", dns_text_type(type), domain); break; } else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); } } /* Loop for list of returned records */ } /* Loop for list of domains */ /* Reclaim unused memory */ store_reset(yield + ptr + 1); /* If ptr == 0 we have not found anything. Otherwise, insert the terminating zero and return the result. */ if (ptr == 0) return failrc; yield[ptr] = 0; *result = yield; return OK; } /* End of lookups/dnsdb.c */