#include "exim.h"
-
/*************************************************
* Fake DNS resolver *
*************************************************/
Arguments:
string the IP address as a string
- buffer a suitable buffer, long enough to hold the result
-Returns: nothing
+Returns: an allocated string
*/
-void
-dns_build_reverse(const uschar *string, uschar *buffer)
+uschar *
+dns_build_reverse(const uschar * string)
{
-const uschar *p = string + Ustrlen(string);
-uschar *pp = buffer;
+const uschar * p = string + Ustrlen(string);
+gstring * g = NULL;
/* Handle IPv4 address */
{
for (int i = 0; i < 4; i++)
{
- const uschar *ppp = p;
+ const uschar * ppp = p;
while (ppp > string && ppp[-1] != '.') ppp--;
- Ustrncpy(pp, ppp, p - ppp);
- pp += p - ppp;
- *pp++ = '.';
+ g = string_catn(g, ppp, p - ppp);
+ g = string_catn(g, US".", 1);
p = ppp - 1;
}
- Ustrcpy(pp, US"in-addr.arpa");
+ g = string_catn(g, US"in-addr.arpa", 12);
}
/* Handle IPv6 address; convert to binary so as to fill out any
else
{
int v6[4];
+
+ g = string_get_tainted(32, is_tainted(string));
(void)host_aton(string, v6);
/* The original specification for IPv6 reverse lookup was to invert each
for (int i = 3; i >= 0; i--)
for (int j = 0; j < 32; j += 4)
- pp += sprintf(CS pp, "%x.", (v6[i] >> j) & 15);
- Ustrcpy(pp, US"ip6.arpa.");
+ g = string_fmt_append(g, "%x.", (v6[i] >> j) & 15);
+ g = string_catn(g, US"ip6.arpa.", 9);
/* Another way of doing IPv6 reverse lookups was proposed in conjunction
with A6 records. However, it fell out of favour when they did. The
}
#endif
+return string_from_gstring(g);
}
const uschar * auth_name;
const uschar * trusted;
+if (dnsa->answerlen < 0) return FALSE;
if (h->ad) return TRUE;
-/* If the resolver we ask is authoritative for the domain in question, it
-* may not set the AD but the AA bit. If we explicitly trust
-* the resolver for that domain (via a domainlist in dns_trust_aa),
-* we return TRUE to indicate a secure answer.
-*/
+/* If the resolver we ask is authoritative for the domain in question, it may
+not set the AD but the AA bit. If we explicitly trust the resolver for that
+domain (via a domainlist in dns_trust_aa), we return TRUE to indicate a secure
+answer. */
if ( !h->aa
|| !dns_trust_aa
************************************************/
BOOL
-dns_is_aa(const dns_answer *dnsa)
+dns_is_aa(const dns_answer * dnsa)
{
#ifdef DISABLE_DNSSEC
return FALSE;
#else
-return ((const HEADER*)dnsa->answer)->aa;
+return dnsa->answerlen >= 0 && ((const HEADER *)dnsa->answer)->aa;
#endif
}
Returns: the return code
*/
-/*XXX the derivation of this value needs explaining */
+/* we need: 255 +1 + (max(typetext) == 5) +1 + max(chars_for_long-max) +1 */
#define DNS_FAILTAG_MAX 290
+#define DNS_FAILNODE_SIZE \
+ (sizeof(expiring_data) + sizeof(tree_node) + DNS_FAILTAG_MAX)
static int
dns_fail_return(const uschar * name, int type, time_t expiry, int rc)
e = previous->data.ptr;
else
{
- new = store_get_perm(
- sizeof(tree_node) + DNS_FAILTAG_MAX + sizeof(expiring_data), is_tainted(name));
-
+ e = store_get_perm(DNS_FAILNODE_SIZE, is_tainted(name));
+ new = (void *)(e+1);
dns_fail_tag(new->name, name, type);
- e = (expiring_data *)((char *)new + sizeof(tree_node) + DNS_FAILTAG_MAX);
new->data.ptr = e;
(void)tree_insertnode(&tree_dns_fails, new);
}
-/* Return the TTL suitable for an NXDOMAIN result, which is given
-in the SOA. We hope that one was returned in the lookup, and do not
-bother doing a separate lookup; if not found return a forever TTL.
-*/
-
-static time_t
-dns_expire_from_soa(dns_answer * dnsa)
-{
-const HEADER * h = (const HEADER *)dnsa->answer;
-dns_scan dnss;
-
/* This is really gross. The successful return value from res_search() is
the packet length, which is stored in dnsa->answerlen. If we get a
negative DNS reply then res_search() returns -1, which causes the bounds
success and packet length return values.) For added safety we only reset
the packet length if the packet header looks plausible. */
-if ( h->qr == 1 && h->opcode == QUERY && h->tc == 0
+static void
+fake_dnsa_len_for_fail(dns_answer * dnsa, int type)
+{
+const HEADER * h = (const HEADER *)dnsa->answer;
+
+if ( h->qr == 1 /* a response */
+ && h->opcode == QUERY
+ && h->tc == 0 /* nmessage not truncated */
&& (h->rcode == NOERROR || h->rcode == NXDOMAIN)
- && (ntohs(h->qdcount) == 1 || f.running_in_test_harness)
- && ntohs(h->ancount) == 0
- && ntohs(h->nscount) >= 1)
- dnsa->answerlen = sizeof(dnsa->answer);
+ && ( ntohs(h->qdcount) == 1 /* one question record */
+ || f.running_in_test_harness)
+ && ntohs(h->ancount) == 0 /* no answer records */
+ && ntohs(h->nscount) >= 1) /* authority records */
+ {
+ DEBUG(D_dns) debug_printf("faking res_search(%s) response length as %d\n",
+ dns_text_type(type), (int)sizeof(dnsa->answer));
+ dnsa->answerlen = sizeof(dnsa->answer);
+ }
+}
+
+
+/* Return the TTL suitable for an NXDOMAIN result, which is given
+in the SOA. We hope that one was returned in the lookup, and do not
+bother doing a separate lookup; if not found return a forever TTL.
+*/
+
+time_t
+dns_expire_from_soa(dns_answer * dnsa, int type)
+{
+dns_scan dnss;
+
+fake_dnsa_len_for_fail(dnsa, type);
for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
/* Skip the SOA serial, refresh, retry & expire. Grab the TTL */
- if (p > dnsa->answer + dnsa->answerlen - 5 * NS_INT32SZ)
+ if (p > dnsa->answer + dnsa->answerlen - 5 * INT32SZ)
break;
- p += 4 * NS_INT32SZ;
+ p += 4 * INT32SZ;
GETLONG(ttl, p);
return time(NULL) + ttl;
*/
if ((rc = dns_fail_cache_hit(name, type)) > 0)
+ {
+ dnsa->answerlen = -1;
return rc;
+ }
#ifdef SUPPORT_I18N
/* Convert all names to a-label form before doing lookup */
This test is omitted for PTR records. These occur only in calls from the dnsdb
lookup, which constructs the names itself, so they should be OK. Besides,
-bitstring labels don't conform to normal name syntax. (But the aren't used any
-more.)
-
-For SRV records, we omit the initial _smtp._tcp. components at the start.
-The check has been seen to bite on the destination of a SRV lookup that
-initiall hit a CNAME, for which the next name had only two components.
-RFC2782 makes no mention of the possibiility of CNAMES, but the Wikipedia
-article on SRV says they are not a valid configuration. */
+bitstring labels don't conform to normal name syntax. (But they aren't used any
+more.) */
#ifndef STAND_ALONE /* Omit this for stand-alone tests */
if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT)
{
- const uschar *checkname = name;
int ovector[3*(EXPAND_MAXN+1)];
dns_pattern_init();
-
- /* For an SRV lookup, skip over the first two components (the service and
- protocol names, which both start with an underscore). */
-
- if (type == T_SRV || type == T_TLSA)
- {
- while (*checkname && *checkname++ != '.') ;
- while (*checkname && *checkname++ != '.') ;
- }
-
- if (pcre_exec(regex_check_dns_names, NULL, CCS checkname, Ustrlen(checkname),
+ if (pcre_exec(regex_check_dns_names, NULL, CCS name, Ustrlen(name),
0, PCRE_EOPT, ovector, nelem(ovector)) < 0)
{
DEBUG(D_dns)
(res_search), we call fakens_search(), which recognizes certain special
domains, and interfaces to a fake nameserver for certain special zones. */
+h_errno = 0;
dnsa->answerlen = f.running_in_test_harness
? fakens_search(name, type, dnsa->answer, sizeof(dnsa->answer))
: res_search(CCS name, C_IN, type, dnsa->answer, sizeof(dnsa->answer));
case HOST_NOT_FOUND:
DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n"
"returning DNS_NOMATCH\n", name, dns_text_type(type));
- return dns_fail_return(name, type, dns_expire_from_soa(dnsa), DNS_NOMATCH);
+ return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NOMATCH);
case TRY_AGAIN:
DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n",
}
DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning "
"DNS_NOMATCH\n", name);
- return dns_fail_return(name, type, dns_expire_from_soa(dnsa), DNS_NOMATCH);
+ return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NOMATCH);
#else /* For stand-alone tests */
return dns_fail_return(name, type, 0, DNS_AGAIN);
case NO_DATA:
DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n"
"returning DNS_NODATA\n", name, dns_text_type(type));
- return dns_fail_return(name, type, dns_expire_from_soa(dnsa), DNS_NODATA);
+ return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type), DNS_NODATA);
default:
DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n"
if (rc == DNS_NOMATCH)
{
- /* This is really gross. The successful return value from res_search() is
- the packet length, which is stored in dnsa->answerlen. If we get a
- negative DNS reply then res_search() returns -1, which causes the bounds
- checks for name decompression to fail when it is treated as a packet
- length, which in turn causes the authority search to fail. The correct
- packet length has been lost inside libresolv, so we have to guess a
- replacement value. (The only way to fix this properly would be to
- re-implement res_search() and res_query() so that they don't muddle their
- success and packet length return values.) For added safety we only reset
- the packet length if the packet header looks plausible. */
-
- const HEADER * h = (const HEADER *)dnsa->answer;
- if (h->qr == 1 && h->opcode == QUERY && h->tc == 0
- && (h->rcode == NOERROR || h->rcode == NXDOMAIN)
- && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0
- && ntohs(h->nscount) >= 1)
- dnsa->answerlen = sizeof(dnsa->answer);
+ fake_dnsa_len_for_fail(dnsa, T_CSA);
for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
git://git.exim.org / users / jgh / exim.git / blobdiff