-/*************************************************
-* Perform a single dnsbl lookup *
-*************************************************/
-
-/* This function is called from verify_check_dnsbl() below. It is also called
-recursively from within itself when domain and domain_txt are different
-pointers, in order to get the TXT record from the alternate domain.
-
-Arguments:
- domain the outer dnsbl domain
- domain_txt alternate domain to lookup TXT record on success; when the
- same domain is to be used, domain_txt == domain (that is,
- the pointers must be identical, not just the text)
- keydomain the current keydomain (for debug message)
- prepend subdomain to lookup (like keydomain, but
- reversed if IP address)
- iplist the list of matching IP addresses, or NULL for "any"
- bitmask true if bitmask matching is wanted
- match_type condition for 'succeed' result
- 0 => Any RR in iplist (=)
- 1 => No RR in iplist (!=)
- 2 => All RRs in iplist (==)
- 3 => Some RRs not in iplist (!==)
- the two bits are defined as MT_NOT and MT_ALL
- defer_return what to return for a defer
-
-Returns: OK if lookup succeeded
- FAIL if not
-*/
-
-static int
-one_check_dnsbl(uschar *domain, uschar *domain_txt, uschar *keydomain,
- uschar *prepend, uschar *iplist, BOOL bitmask, int match_type,
- int defer_return)
-{
-dns_answer * dnsa = store_get_dns_answer();
-dns_scan dnss;
-tree_node *t;
-dnsbl_cache_block *cb;
-int old_pool = store_pool;
-uschar * query;
-int qlen;
-
-/* Construct the specific query domainname */
-
-query = string_sprintf("%s.%s", prepend, domain);
-if ((qlen = Ustrlen(query)) >= 256)
- {
- log_write(0, LOG_MAIN|LOG_PANIC, "dnslist query is too long "
- "(ignored): %s...", query);
- return FAIL;
- }
-
-/* Look for this query in the cache. */
-
-if ( (t = tree_search(dnsbl_cache, query))
- && (cb = t->data.ptr)->expiry > time(NULL)
- )
-
-/* Previous lookup was cached */
-
- {
- HDEBUG(D_dnsbl) debug_printf("dnslists: using result of previous lookup\n");
- }
-
-/* If not cached from a previous lookup, we must do a DNS lookup, and
-cache the result in permanent memory. */
-
-else
- {
- uint ttl = 3600; /* max TTL for positive cache entries */
-
- store_pool = POOL_PERM;
-
- if (t)
- {
- HDEBUG(D_dnsbl) debug_printf("cached data found but past valid time; ");
- }
-
- else
- { /* Set up a tree entry to cache the lookup */
- t = store_get(sizeof(tree_node) + qlen + 1 + 1, is_tainted(query));
- Ustrcpy(t->name, query);
- t->data.ptr = cb = store_get(sizeof(dnsbl_cache_block), FALSE);
- (void)tree_insertnode(&dnsbl_cache, t);
- }
-
- /* Do the DNS lookup . */
-
- HDEBUG(D_dnsbl) debug_printf("new DNS lookup for %s\n", query);
- cb->rc = dns_basic_lookup(dnsa, query, T_A);
- cb->text_set = FALSE;
- cb->text = NULL;
- cb->rhs = NULL;
-
- /* If the lookup succeeded, cache the RHS address. The code allows for
- more than one address - this was for complete generality and the possible
- use of A6 records. However, A6 records are no longer supported. Leave the code
- here, just in case.
-
- Quite apart from one A6 RR generating multiple addresses, there are DNS
- lists that return more than one A record, so we must handle multiple
- addresses generated in that way as well.
-
- Mark the cache entry with the "now" plus the minimum of the address TTLs,
- or the RFC 2308 negative-cache value from the SOA if none were found. */
-
- switch (cb->rc)
- {
- case DNS_SUCCEED:
- {
- dns_address ** addrp = &cb->rhs;
- dns_address * da;
- for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
- rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
- if (rr->type == T_A && (da = dns_address_from_rr(dnsa, rr)))
- {
- *addrp = da;
- while (da->next) da = da->next;
- addrp = &da->next;
- if (ttl > rr->ttl) ttl = rr->ttl;
- }
-
- if (cb->rhs)
- {
- cb->expiry = time(NULL) + ttl;
- break;
- }
-
- /* If we didn't find any A records, change the return code. This can
- happen when there is a CNAME record but there are no A records for what
- it points to. */
-
- cb->rc = DNS_NODATA;
- }
- /*FALLTHROUGH*/
-
- case DNS_NOMATCH:
- case DNS_NODATA:
- {
- /* Although there already is a neg-cache layer maintained by
- dns_basic_lookup(), we have a dnslist cache entry allocated and
- tree-inserted. So we may as well use it. */
-
- time_t soa_negttl = dns_expire_from_soa(dnsa, T_A);
- cb->expiry = soa_negttl ? soa_negttl : time(NULL) + ttl;
- break;
- }
-
- default:
- cb->expiry = time(NULL) + ttl;
- break;
- }
-
- store_pool = old_pool;
- HDEBUG(D_dnsbl) debug_printf("dnslists: wrote cache entry, ttl=%d\n",
- (int)(cb->expiry - time(NULL)));
- }
-
-/* We now have the result of the DNS lookup, either newly done, or cached
-from a previous call. If the lookup succeeded, check against the address
-list if there is one. This may be a positive equality list (introduced by
-"="), a negative equality list (introduced by "!="), a positive bitmask
-list (introduced by "&"), or a negative bitmask list (introduced by "!&").*/
-
-if (cb->rc == DNS_SUCCEED)
- {
- dns_address * da = NULL;
- uschar *addlist = cb->rhs->address;
-
- /* For A and AAAA records, there may be multiple addresses from multiple
- records. For A6 records (currently not expected to be used) there may be
- multiple addresses from a single record. */
-
- for (da = cb->rhs->next; da; da = da->next)
- addlist = string_sprintf("%s, %s", addlist, da->address);
-
- HDEBUG(D_dnsbl) debug_printf("DNS lookup for %s succeeded (yielding %s)\n",
- query, addlist);
-
- /* Address list check; this can be either for equality, or via a bitmask.
- In the latter case, all the bits must match. */
-
- if (iplist)
- {
- for (da = cb->rhs; da; da = da->next)
- {
- int ipsep = ',';
- const uschar *ptr = iplist;
- uschar *res;
-
- /* Handle exact matching */
-
- if (!bitmask)
- {
- while ((res = string_nextinlist(&ptr, &ipsep, NULL, 0)))
- if (Ustrcmp(CS da->address, res) == 0)
- break;
- }
-
- /* Handle bitmask matching */
-
- else
- {
- int address[4];
- int mask = 0;
-
- /* At present, all known DNS blocking lists use A records, with
- IPv4 addresses on the RHS encoding the information they return. I
- wonder if this will linger on as the last vestige of IPv4 when IPv6
- is ubiquitous? Anyway, for now we use paranoia code to completely
- ignore IPv6 addresses. The default mask is 0, which always matches.
- We change this only for IPv4 addresses in the list. */
-
- if (host_aton(da->address, address) == 1) mask = address[0];
-
- /* Scan the returned addresses, skipping any that are IPv6 */
-
- while ((res = string_nextinlist(&ptr, &ipsep, NULL, 0)))
- {
- if (host_aton(res, address) != 1) continue;
- if ((address[0] & mask) == address[0]) break;
- }
- }
-
- /* If either
-
- (a) An IP address in an any ('=') list matched, or
- (b) No IP address in an all ('==') list matched
-
- then we're done searching. */
-
- if (((match_type & MT_ALL) != 0) == (res == NULL)) break;
- }
-
- /* If da == NULL, either
-
- (a) No IP address in an any ('=') list matched, or
- (b) An IP address in an all ('==') list didn't match
-
- so behave as if the DNSBL lookup had not succeeded, i.e. the host is not on
- the list. */
-
- if ((match_type == MT_NOT || match_type == MT_ALL) != (da == NULL))
- {
- HDEBUG(D_dnsbl)
- {
- uschar *res = NULL;
- switch(match_type)
- {
- case 0:
- res = US"was no match"; break;
- case MT_NOT:
- res = US"was an exclude match"; break;
- case MT_ALL:
- res = US"was an IP address that did not match"; break;
- case MT_NOT|MT_ALL:
- res = US"were no IP addresses that did not match"; break;
- }
- debug_printf("=> but we are not accepting this block class because\n");
- debug_printf("=> there %s for %s%c%s\n",
- res,
- ((match_type & MT_ALL) == 0)? "" : "=",
- bitmask? '&' : '=', iplist);
- }
- return FAIL;
- }
- }
-
- /* Either there was no IP list, or the record matched, implying that the
- domain is on the list. We now want to find a corresponding TXT record. If an
- alternate domain is specified for the TXT record, call this function
- recursively to look that up; this has the side effect of re-checking that
- there is indeed an A record at the alternate domain. */
-
- if (domain_txt != domain)
- return one_check_dnsbl(domain_txt, domain_txt, keydomain, prepend, NULL,
- FALSE, match_type, defer_return);
-
- /* If there is no alternate domain, look up a TXT record in the main domain
- if it has not previously been cached. */
-
- if (!cb->text_set)
- {
- cb->text_set = TRUE;
- if (dns_basic_lookup(dnsa, query, T_TXT) == DNS_SUCCEED)
- for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
- rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
- if (rr->type == T_TXT)
- {
- int len = (rr->data)[0];
- if (len > 511) len = 127;
- store_pool = POOL_PERM;
- cb->text = string_sprintf("%.*s", len, CUS (rr->data+1));
- store_pool = old_pool;
- break;
- }
- }
-
- dnslist_value = addlist;
- dnslist_text = cb->text;
- return OK;
- }
-
-/* There was a problem with the DNS lookup */
-
-if (cb->rc != DNS_NOMATCH && cb->rc != DNS_NODATA)
- {
- log_write(L_dnslist_defer, LOG_MAIN,
- "DNS list lookup defer (probably timeout) for %s: %s", query,
- (defer_return == OK)? US"assumed in list" :
- (defer_return == FAIL)? US"assumed not in list" :
- US"returned DEFER");
- return defer_return;
- }
-
-/* No entry was found in the DNS; continue for next domain */
-
-HDEBUG(D_dnsbl)
- {
- debug_printf("DNS lookup for %s failed\n", query);
- debug_printf("=> that means %s is not listed at %s\n",
- keydomain, domain);
- }
-
-return FAIL;
-}
-
-
-
-
-/*************************************************
-* Check host against DNS black lists *
-*************************************************/
-
-/* This function runs checks against a list of DNS black lists, until one
-matches. Each item on the list can be of the form
-
- domain=ip-address/key
-
-The domain is the right-most domain that is used for the query, for example,
-blackholes.mail-abuse.org. If the IP address is present, there is a match only
-if the DNS lookup returns a matching IP address. Several addresses may be
-given, comma-separated, for example: x.y.z=127.0.0.1,127.0.0.2.
-
-If no key is given, what is looked up in the domain is the inverted IP address
-of the current client host. If a key is given, it is used to construct the
-domain for the lookup. For example:
-
- dsn.rfc-ignorant.org/$sender_address_domain
-
-After finding a match in the DNS, the domain is placed in $dnslist_domain, and
-then we check for a TXT record for an error message, and if found, save its
-value in $dnslist_text. We also cache everything in a tree, to optimize
-multiple lookups.
-
-The TXT record is normally looked up in the same domain as the A record, but
-when many lists are combined in a single DNS domain, this will not be a very
-specific message. It is possible to specify a different domain for looking up
-TXT records; this is given before the main domain, comma-separated. For
-example:
-
- dnslists = http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
- socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3
-
-The caching ensures that only one lookup in dnsbl.sorbs.net is done.
-
-Note: an address for testing RBL is 192.203.178.39
-Note: an address for testing DUL is 192.203.178.4
-Note: a domain for testing RFCI is example.tld.dsn.rfc-ignorant.org
-
-Arguments:
- where the acl type
- listptr the domain/address/data list
- log_msgptr log message on error
-
-Returns: OK successful lookup (i.e. the address is on the list), or
- lookup deferred after +include_unknown
- FAIL name not found, or no data found for the given type, or
- lookup deferred after +exclude_unknown (default)
- DEFER lookup failure, if +defer_unknown was set
-*/
-
-int
-verify_check_dnsbl(int where, const uschar ** listptr, uschar ** log_msgptr)
-{
-int sep = 0;
-int defer_return = FAIL;
-const uschar *list = *listptr;
-uschar *domain;
-uschar revadd[128]; /* Long enough for IPv6 address */
-
-/* Indicate that the inverted IP address is not yet set up */
-
-revadd[0] = 0;
-
-/* In case this is the first time the DNS resolver is being used. */
-
-dns_init(FALSE, FALSE, FALSE); /*XXX dnssec? */
-
-/* Loop through all the domains supplied, until something matches */
-
-while ((domain = string_nextinlist(&list, &sep, NULL, 0)))
- {
- int rc;
- BOOL bitmask = FALSE;
- int match_type = 0;
- uschar *domain_txt;
- uschar *comma;
- uschar *iplist;
- uschar *key;
-
- HDEBUG(D_dnsbl) debug_printf("dnslists check: %s\n", domain);
-
- /* Deal with special values that change the behaviour on defer */
-
- if (domain[0] == '+')
- {
- if (strcmpic(domain, US"+include_unknown") == 0) defer_return = OK;
- else if (strcmpic(domain, US"+exclude_unknown") == 0) defer_return = FAIL;
- else if (strcmpic(domain, US"+defer_unknown") == 0) defer_return = DEFER;
- else
- log_write(0, LOG_MAIN|LOG_PANIC, "unknown item in dnslist (ignored): %s",
- domain);
- continue;
- }
-
- /* See if there's explicit data to be looked up */
-
- if ((key = Ustrchr(domain, '/'))) *key++ = 0;
-
- /* See if there's a list of addresses supplied after the domain name. This is
- introduced by an = or a & character; if preceded by = we require all matches
- and if preceded by ! we invert the result. */
-
- if (!(iplist = Ustrchr(domain, '=')))
- {
- bitmask = TRUE;
- iplist = Ustrchr(domain, '&');
- }
-
- if (iplist) /* Found either = or & */
- {
- if (iplist > domain && iplist[-1] == '!') /* Handle preceding ! */
- {
- match_type |= MT_NOT;
- iplist[-1] = 0;
- }
-
- *iplist++ = 0; /* Terminate domain, move on */
-
- /* If we found = (bitmask == FALSE), check for == or =& */
-
- if (!bitmask && (*iplist == '=' || *iplist == '&'))
- {
- bitmask = *iplist++ == '&';
- match_type |= MT_ALL;
- }
- }
-
-
- /* If there is a comma in the domain, it indicates that a second domain for
- looking up TXT records is provided, before the main domain. Otherwise we must
- set domain_txt == domain. */
-
- domain_txt = domain;
- if ((comma = Ustrchr(domain, ',')))
- {
- *comma++ = 0;
- domain = comma;
- }
-
- /* Check that what we have left is a sensible domain name. There is no reason
- why these domains should in fact use the same syntax as hosts and email
- domains, but in practice they seem to. However, there is little point in
- actually causing an error here, because that would no doubt hold up incoming
- mail. Instead, I'll just log it. */
-
- for (uschar * s = domain; *s; s++)
- if (!isalnum(*s) && *s != '-' && *s != '.' && *s != '_')
- {
- log_write(0, LOG_MAIN, "dnslists domain \"%s\" contains "
- "strange characters - is this right?", domain);
- break;
- }
-
- /* Check the alternate domain if present */
-
- if (domain_txt != domain) for (uschar * s = domain_txt; *s; s++)
- if (!isalnum(*s) && *s != '-' && *s != '.' && *s != '_')
- {
- log_write(0, LOG_MAIN, "dnslists domain \"%s\" contains "
- "strange characters - is this right?", domain_txt);
- break;
- }
-
- /* If there is no key string, construct the query by adding the domain name
- onto the inverted host address, and perform a single DNS lookup. */
-
- if (!key)
- {
- if (where == ACL_WHERE_NOTSMTP_START || where == ACL_WHERE_NOTSMTP)
- {
- *log_msgptr = string_sprintf
- ("cannot test auto-keyed dnslists condition in %s ACL",
- acl_wherenames[where]);
- return ERROR;
- }
- if (!sender_host_address) return FAIL; /* can never match */
- if (revadd[0] == 0) invert_address(revadd, sender_host_address);
- rc = one_check_dnsbl(domain, domain_txt, sender_host_address, revadd,
- iplist, bitmask, match_type, defer_return);
- if (rc == OK)
- {
- dnslist_domain = string_copy(domain_txt);
- dnslist_matched = string_copy(sender_host_address);
- HDEBUG(D_dnsbl) debug_printf("=> that means %s is listed at %s\n",
- sender_host_address, dnslist_domain);
- }
- if (rc != FAIL) return rc; /* OK or DEFER */
- }
-
- /* If there is a key string, it can be a list of domains or IP addresses to
- be concatenated with the main domain. */
-
- else
- {
- int keysep = 0;
- BOOL defer = FALSE;
- uschar *keydomain;
- uschar keyrevadd[128];
-
- while ((keydomain = string_nextinlist(CUSS &key, &keysep, NULL, 0)))
- {
- uschar *prepend = keydomain;
-
- if (string_is_ip_address(keydomain, NULL) != 0)
- {
- invert_address(keyrevadd, keydomain);
- prepend = keyrevadd;
- }
-
- rc = one_check_dnsbl(domain, domain_txt, keydomain, prepend, iplist,
- bitmask, match_type, defer_return);
- if (rc == OK)
- {
- dnslist_domain = string_copy(domain_txt);
- dnslist_matched = string_copy(keydomain);
- HDEBUG(D_dnsbl) debug_printf("=> that means %s is listed at %s\n",
- keydomain, dnslist_domain);
- return OK;
- }
-
- /* If the lookup deferred, remember this fact. We keep trying the rest
- of the list to see if we get a useful result, and if we don't, we return
- DEFER at the end. */
-
- if (rc == DEFER) defer = TRUE;
- } /* continue with next keystring domain/address */
-
- if (defer) return DEFER;
- }
- } /* continue with next dnsdb outer domain */
-
-return FAIL;
-}
-
-
-
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