* Exim - an Internet mail transport agent *
*************************************************/
-/* Copyright (c) University of Cambridge 1995 - 2016 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */
/* See the file NOTICE for conditions of use and distribution. */
/* Functions for interfacing with the DNS. */
#include "exim.h"
-
/*************************************************
* Fake DNS resolver *
*************************************************/
{
int len = Ustrlen(domain);
int asize = size; /* Locally modified */
-uschar name[256];
+uschar * name;
uschar utilname[256];
uschar *aptr = answerptr; /* Locally modified */
struct stat statbuf;
/* Remove terminating dot. */
if (domain[len - 1] == '.') len--;
-Ustrncpy(name, domain, len);
-name[len] = 0;
+name = string_copyn(domain, len);
/* Look for the fakens utility, and if it exists, call it. */
if (Ustrchr(string, ':') == NULL)
#endif
{
- int i;
- for (i = 0; i < 4; i++)
+ for (int i = 0; i < 4; i++)
{
const uschar *ppp = p;
while (ppp > string && ppp[-1] != '.') ppp--;
*pp++ = '.';
p = ppp - 1;
}
- Ustrcpy(pp, "in-addr.arpa");
+ Ustrcpy(pp, US"in-addr.arpa");
}
/* Handle IPv6 address; convert to binary so as to fill out any
#if HAVE_IPV6
else
{
- int i;
int v6[4];
(void)host_aton(string, v6);
nibble, and look in the ip6.int domain. The domain was subsequently
changed to ip6.arpa. */
- for (i = 3; i >= 0; i--)
- {
- int j;
- for (j = 0; j < 32; j += 4)
- {
- sprintf(CS pp, "%x.", (v6[i] >> j) & 15);
- pp += 2;
- }
- }
- Ustrcpy(pp, "ip6.arpa.");
+ 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.");
/* Another way of doing IPv6 reverse lookups was proposed in conjunction
with A6 records. However, it fell out of favour when they did. The
Ustrcpy(pp, "\\[x");
pp += 3;
- for (i = 0; i < 4; i++)
+ for (int i = 0; i < 4; i++)
{
sprintf(pp, "%08X", v6[i]);
pp += 8;
}
- Ustrcpy(pp, "].ip6.arpa.");
+ Ustrcpy(pp, US"].ip6.arpa.");
**************************************************/
}
Return: TRUE for a bad result
*/
static BOOL
-dnss_inc(dns_answer * dnsa, dns_scan * dnss, unsigned delta)
+dnss_inc_aptr(const dns_answer * dnsa, dns_scan * dnss, unsigned delta)
{
return (dnss->aptr += delta) >= dnsa->answer + dnsa->answerlen;
}
Arguments:
dnsa pointer to dns answer block
dnss pointer to dns scan block
- reset option specifing what portion to scan, as described above
+ reset option specifying what portion to scan, as described above
Returns: next dns record, or NULL when no more
*/
dns_record *
-dns_next_rr(dns_answer *dnsa, dns_scan *dnss, int reset)
+dns_next_rr(const dns_answer *dnsa, dns_scan *dnss, int reset)
{
-HEADER *h = (HEADER *)dnsa->answer;
+const HEADER * h = (const HEADER *)dnsa->answer;
int namelen;
char * trace = NULL;
if (reset != RESET_NEXT)
{
- TRACE debug_printf("%s: reset\n", __FUNCTION__);
dnss->rrcount = ntohs(h->qdcount);
+ TRACE debug_printf("%s: reset (Q rrcount %d)\n", __FUNCTION__, dnss->rrcount);
dnss->aptr = dnsa->answer + sizeof(HEADER);
/* Skip over questions; failure to expand the name just gives up */
if (namelen < 0) goto null_return;
/* skip name & type & class */
TRACE trace = "Q-skip";
- if (dnss_inc(dnsa, dnss, namelen+4)) goto null_return;
+ if (dnss_inc_aptr(dnsa, dnss, namelen+4)) goto null_return;
}
/* Get the number of answer records. */
dnss->rrcount = ntohs(h->ancount);
+ TRACE debug_printf("%s: reset (A rrcount %d)\n", __FUNCTION__, dnss->rrcount);
/* Skip over answers if we want to look at the authority section. Also skip
the NS records (i.e. authority section) if wanting to look at the additional
{
TRACE debug_printf("%s: additional\n", __FUNCTION__);
dnss->rrcount += ntohs(h->nscount);
+ TRACE debug_printf("%s: reset (NS rrcount %d)\n", __FUNCTION__, dnss->rrcount);
}
if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL)
if (namelen < 0) goto null_return;
/* skip name, type, class & TTL */
TRACE trace = "A-hdr";
- if (dnss_inc(dnsa, dnss, namelen+8)) goto null_return;
+ if (dnss_inc_aptr(dnsa, dnss, namelen+8)) goto null_return;
GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */
/* skip over it */
TRACE trace = "A-skip";
- if (dnss_inc(dnsa, dnss, dnss->srr.size)) goto null_return;
+ if (dnss_inc_aptr(dnsa, dnss, dnss->srr.size)) goto null_return;
}
dnss->rrcount = reset == RESET_AUTHORITY
? ntohs(h->nscount) : ntohs(h->arcount);
+ TRACE debug_printf("%s: reset (%s rrcount %d)\n", __FUNCTION__,
+ reset == RESET_AUTHORITY ? "NS" : "AR", dnss->rrcount);
}
TRACE debug_printf("%s: %d RRs to read\n", __FUNCTION__, dnss->rrcount);
}
from the following bytes. */
TRACE trace = "R-name";
-if (dnss_inc(dnsa, dnss, namelen)) goto null_return;
+if (dnss_inc_aptr(dnsa, dnss, namelen)) goto null_return;
GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */
TRACE trace = "R-class";
-if (dnss_inc(dnsa, dnss, 2)) goto null_return; /* Don't want class */
+if (dnss_inc_aptr(dnsa, dnss, 2)) goto null_return; /* Don't want class */
GETLONG(dnss->srr.ttl, dnss->aptr); /* TTL */
GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */
dnss->srr.data = dnss->aptr; /* The record's data follows */
/* Return a pointer to the dns_record structure within the dns_answer. This is
for convenience so that the scans can use nice-looking for loops. */
+TRACE debug_printf("%s: return %s\n", __FUNCTION__, dns_text_type(dnss->srr.type));
return &dnss->srr;
null_return:
- TRACE debug_printf("%s: terminate (%d RRs left). Last op: %s\n",
- __FUNCTION__, dnss->rrcount, trace);
+ TRACE debug_printf("%s: terminate (%d RRs left). Last op: %s; errno %d %s\n",
+ __FUNCTION__, dnss->rrcount, trace, errno, strerror(errno));
dnss->rrcount = 0;
return NULL;
}
-/* Extract the AUTHORITY information from the answer. If the
-answer isn't authoritive (AA not set), we do not extract anything.
+/* Extract the AUTHORITY information from the answer. If the answer isn't
+authoritative (AA not set), we do not extract anything.
+
+The AUTHORITY section contains NS records if the name in question was found,
+it contains a SOA record otherwise. (This is just from experience and some
+tests, is there some spec?)
-The AUTHORITIVE section contains NS records if
-the name in question was found, it contains a SOA record
-otherwise. (This is just from experience and some tests, is there
-some spec?)
+Scan the whole AUTHORITY section, since it may contain other records
+(e.g. NSEC3) too.
-We've cycle through the AUTHORITY section, since it may contain
-other records (e.g. NSEC3) too. */
+Return: name for the authority, in an allocated string, or NULL if none found */
static const uschar *
dns_extract_auth_name(const dns_answer * dnsa) /* FIXME: const dns_answer */
{
dns_scan dnss;
-dns_record * rr;
-HEADER * h = (HEADER *) dnsa->answer;
-
-if (!h->nscount || !h->aa) return NULL;
-for (rr = dns_next_rr((dns_answer*) dnsa, &dnss, RESET_AUTHORITY);
- rr;
- rr = dns_next_rr((dns_answer*) dnsa, &dnss, RESET_NEXT))
- if (rr->type == (h->ancount ? T_NS : T_SOA)) return rr->name;
+const HEADER * h = (const HEADER *) dnsa->answer;
+
+if (h->nscount && h->aa)
+ for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
+ rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
+ if (rr->type == (h->ancount ? T_NS : T_SOA))
+ return string_copy(rr->name);
return NULL;
}
/* We do not perform DNSSEC work ourselves; if the administrator has installed
a verifying resolver which sets AD as appropriate, though, we'll use that.
-(AD = Authentic Data, AA = Authoritive Answer)
+(AD = Authentic Data, AA = Authoritative Answer)
Argument: pointer to dns answer block
Returns: bool indicating presence of AD bit
debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n");
return FALSE;
#else
-HEADER * h = (HEADER *) dnsa->answer;
+const HEADER * h = (const HEADER *) dnsa->answer;
const uschar * auth_name;
const uschar * trusted;
if (h->ad) return TRUE;
-/* If the resolver we ask is authoritive for the domain in question, it
+/* 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.
{
#ifndef DISABLE_DNSSEC
HEADER * h = (HEADER *)dnsa->answer;
-h->ad = 0;
+h->aa = h->ad = 0;
#endif
}
/************************************************
* Check whether the AA bit is set *
* We need this to warn if we requested AD *
- * from an authoritive server *
+ * from an authoritative server *
************************************************/
BOOL
#ifdef DISABLE_DNSSEC
return FALSE;
#else
-return ((HEADER*)dnsa->answer)->aa;
+return ((const HEADER*)dnsa->answer)->aa;
#endif
}
* Cache a failed DNS lookup result *
*************************************************/
+static void
+dns_fail_tag(uschar * buf, const uschar * name, int dns_type)
+{
+res_state resp = os_get_dns_resolver_res();
+
+/*XX buf needs to be 255 +1 + (max(typetext) == 5) +1 + max(chars_for_long-max) +1
+We truncate the name here for safety... could use a dynamic string. */
+
+sprintf(CS buf, "%.255s-%s-%lx", name, dns_text_type(dns_type),
+ (unsigned long) resp->options);
+}
+
+
/* We cache failed lookup results so as not to experience timeouts many
times for the same domain. We need to retain the resolver options because they
may change. For successful lookups, we rely on resolver and/or name server
Arguments:
name the domain name
type the lookup type
+ expiry time TTL expires, or zero for unlimited
rc the return code
Returns: the return code
*/
+/* 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_return(const uschar * name, int type, int rc)
+dns_fail_return(const uschar * name, int type, time_t expiry, int rc)
{
-res_state resp = os_get_dns_resolver_res();
-tree_node *node = store_get_perm(sizeof(tree_node) + 290);
-sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type),
- (unsigned long) resp->options);
-node->data.val = rc;
-(void)tree_insertnode(&tree_dns_fails, node);
+uschar node_name[DNS_FAILTAG_MAX];
+tree_node * previous, * new;
+expiring_data * e;
+
+dns_fail_tag(node_name, name, type);
+if ((previous = tree_search(tree_dns_fails, node_name)))
+ e = previous->data.ptr;
+else
+ {
+ e = store_get_perm(DNS_FAILNODE_SIZE, is_tainted(name));
+ new = (void *)(e+1);
+ dns_fail_tag(new->name, name, type);
+ new->data.ptr = e;
+ (void)tree_insertnode(&tree_dns_fails, new);
+ }
+
+DEBUG(D_dns) debug_printf(" %s neg-cache entry for %s, ttl %d\n",
+ previous ? "update" : "writing",
+ node_name, expiry ? (int)(expiry - time(NULL)) : -1);
+e->expiry = expiry;
+e->data.val = rc;
return rc;
}
+
+/* Return the cached result of a known-bad lookup, or -1.
+*/
+static int
+dns_fail_cache_hit(const uschar * name, int type)
+{
+uschar node_name[DNS_FAILTAG_MAX];
+tree_node * previous;
+expiring_data * e;
+int val, rc;
+
+dns_fail_tag(node_name, name, type);
+if (!(previous = tree_search(tree_dns_fails, node_name)))
+ return -1;
+
+e = previous->data.ptr;
+val = e->data.val;
+rc = e->expiry && e->expiry <= time(NULL) ? -1 : val;
+
+DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: %scached value %s%s\n",
+ name, dns_text_type(type),
+ rc == -1 ? "" : "using ",
+ val == DNS_NOMATCH ? "DNS_NOMATCH" :
+ val == DNS_NODATA ? "DNS_NODATA" :
+ val == DNS_AGAIN ? "DNS_AGAIN" :
+ val == DNS_FAIL ? "DNS_FAIL" : "??",
+ rc == -1 ? " past valid time" : "");
+
+return rc;
+}
+
+
+
+/* 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)
+{
+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
+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. */
+
+if ( h->qr == 1 && h->opcode == QUERY && h->tc == 0
+ && (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);
+
+for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
+ rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
+ ) if (rr->type == T_SOA)
+ {
+ const uschar * p = rr->data;
+ uschar discard_buf[256];
+ int len;
+ unsigned long ttl;
+
+ /* Skip the mname & rname strings */
+
+ if ((len = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
+ p, (DN_EXPAND_ARG4_TYPE)discard_buf, 256)) < 0)
+ break;
+ p += len;
+ if ((len = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
+ p, (DN_EXPAND_ARG4_TYPE)discard_buf, 256)) < 0)
+ break;
+ p += len;
+
+ /* Skip the SOA serial, refresh, retry & expire. Grab the TTL */
+
+ if (p > dnsa->answer + dnsa->answerlen - 5 * INT32SZ)
+ break;
+ p += 4 * INT32SZ;
+ GETLONG(ttl, p);
+
+ return time(NULL) + ttl;
+ }
+DEBUG(D_dns) debug_printf("DNS: no SOA record found for neg-TTL\n");
+return 0;
+}
+
+
/*************************************************
* Do basic DNS lookup *
*************************************************/
/* Call the resolver to look up the given domain name, using the given type,
and check the result. The error code TRY_AGAIN is documented as meaning "non-
-Authoritive Host not found, or SERVERFAIL". Sometimes there are badly set
+Authoritative Host not found, or SERVERFAIL". Sometimes there are badly set
up nameservers that produce this error continually, so there is the option of
providing a list of domains for which this is treated as a non-existent
host.
+The dns_answer structure is pretty big; enough to hold a max-sized DNS message
+- so best allocated from fast-release memory. As of writing, all our callers
+use a stack-auto variable.
+
Arguments:
dnsa pointer to dns_answer structure
name name to look up
*/
int
-dns_basic_lookup(dns_answer *dnsa, const uschar *name, int type)
+dns_basic_lookup(dns_answer * dnsa, const uschar * name, int type)
{
+int rc;
#ifndef STAND_ALONE
-int rc = -1;
-const uschar *save_domain;
+const uschar * save_domain;
#endif
-res_state resp = os_get_dns_resolver_res();
-
-tree_node *previous;
-uschar node_name[290];
/* DNS lookup failures of any kind are cached in a tree. This is mainly so that
a timeout on one domain doesn't happen time and time again for messages that
have many addresses in the same domain. We rely on the resolver and name server
-caching for successful lookups. */
+caching for successful lookups.
+*/
-sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type),
- (unsigned long) resp->options);
-previous = tree_search(tree_dns_fails, node_name);
-if (previous != NULL)
- {
- DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n",
- name, dns_text_type(type),
- (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" :
- (previous->data.val == DNS_NODATA)? "DNS_NODATA" :
- (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" :
- (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??");
- return previous->data.val;
- }
+if ((rc = dns_fail_cache_hit(name, type)) > 0)
+ return rc;
#ifdef SUPPORT_I18N
/* Convert all names to a-label form before doing lookup */
DEBUG(D_dns)
debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name,
errstr);
- host_find_failed_syntax = TRUE;
+ f.host_find_failed_syntax = TRUE;
return DNS_NOMATCH;
}
name = alabel;
}
#endif
-/* If configured, check the hygene of the name passed to lookup. Otherwise,
+/* If configured, check the hygiene of the name passed to lookup. Otherwise,
although DNS lookups may give REFUSED at the lower level, some resolvers
turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such
domains cannot be in the DNS. The check is now done by a regular expression;
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. */
+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. */
#ifndef STAND_ALONE /* Omit this for stand-alone tests */
if (type == T_SRV || type == T_TLSA)
{
- while (*checkname++ != '.');
- while (*checkname++ != '.');
+ while (*checkname && *checkname++ != '.') ;
+ while (*checkname && *checkname++ != '.') ;
}
if (pcre_exec(regex_check_dns_names, NULL, CCS checkname, Ustrlen(checkname),
- 0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0)
+ 0, PCRE_EOPT, ovector, nelem(ovector)) < 0)
{
DEBUG(D_dns)
debug_printf("DNS name syntax check failed: %s (%s)\n", name,
dns_text_type(type));
- host_find_failed_syntax = TRUE;
+ f.host_find_failed_syntax = TRUE;
return DNS_NOMATCH;
}
}
(res_search), we call fakens_search(), which recognizes certain special
domains, and interfaces to a fake nameserver for certain special zones. */
-dnsa->answerlen = running_in_test_harness
- ? fakens_search(name, type, dnsa->answer, MAXPACKET)
- : res_search(CCS name, C_IN, type, dnsa->answer, MAXPACKET);
+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));
-if (dnsa->answerlen > MAXPACKET)
+if (dnsa->answerlen > (int) sizeof(dnsa->answer))
{
- DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet (size %d), truncating to %d.\n",
- name, dns_text_type(type), dnsa->answerlen, MAXPACKET);
- dnsa->answerlen = MAXPACKET;
+ DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet"
+ " (size %d), truncating to %u.\n",
+ name, dns_text_type(type), dnsa->answerlen, (unsigned int) sizeof(dnsa->answer));
+ dnsa->answerlen = sizeof(dnsa->answer);
}
if (dnsa->answerlen < 0) switch (h_errno)
{
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_return(name, type, DNS_NOMATCH);
+ 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);
case TRY_AGAIN:
- DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n",
- name, dns_text_type(type));
+ DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n",
+ name, dns_text_type(type));
- /* Cut this out for various test programs */
+ /* Cut this out for various test programs */
#ifndef STAND_ALONE
- save_domain = deliver_domain;
- deliver_domain = string_copy(name); /* set $domain */
- rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL,
- MCL_DOMAIN, TRUE, NULL);
- deliver_domain = save_domain;
- if (rc != OK)
- {
- DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
- return dns_return(name, type, DNS_AGAIN);
- }
- DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning "
- "DNS_NOMATCH\n", name);
- return dns_return(name, type, DNS_NOMATCH);
+ save_domain = deliver_domain;
+ deliver_domain = string_copy(name); /* set $domain */
+ rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL,
+ MCL_DOMAIN, TRUE, NULL);
+ deliver_domain = save_domain;
+ if (rc != OK)
+ {
+ DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
+ return dns_fail_return(name, type, 0, DNS_AGAIN);
+ }
+ 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);
#else /* For stand-alone tests */
- return dns_return(name, type, DNS_AGAIN);
+ return dns_fail_return(name, type, 0, DNS_AGAIN);
#endif
case NO_RECOVERY:
- DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n"
- "returning DNS_FAIL\n", name, dns_text_type(type));
- return dns_return(name, type, DNS_FAIL);
+ DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n"
+ "returning DNS_FAIL\n", name, dns_text_type(type));
+ return dns_fail_return(name, type, 0, DNS_FAIL);
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_return(name, type, DNS_NODATA);
+ 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);
default:
- DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n"
- "returning DNS_FAIL\n", name, dns_text_type(type), h_errno);
- return dns_return(name, type, DNS_FAIL);
+ DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n"
+ "returning DNS_FAIL\n", name, dns_text_type(type), h_errno);
+ return dns_fail_return(name, type, 0, DNS_FAIL);
}
DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n",
/* Look up the given domain name, using the given type. Follow CNAMEs if
necessary, but only so many times. There aren't supposed to be CNAME chains in
the DNS, but you are supposed to cope with them if you find them.
+By default, follow one CNAME since a resolver has been seen, faced with
+an MX request and a CNAME (to an A) but no MX present, returning the CNAME.
The assumption is made that if the resolver gives back records of the
requested type *and* a CNAME, we don't need to make another call to look up
dns_lookup(dns_answer *dnsa, const uschar *name, int type,
const uschar **fully_qualified_name)
{
-int i;
const uschar *orig_name = name;
BOOL secure_so_far = TRUE;
-/* Loop to follow CNAME chains so far, but no further... */
+/* By default, assume the resolver follows CNAME chains (and returns NODATA for
+an unterminated one). If it also does that for a CNAME loop, fine; if it returns
+a CNAME (maybe the last?) whine about it. However, retain the coding for dumb
+resolvers hiding behind a config variable. Loop to follow CNAME chains so far,
+but no further... The testsuite tests the latter case, mostly assuming that the
+former will work. */
-for (i = 0; i < 10; i++)
+for (int i = 0; i <= dns_cname_loops; i++)
{
uschar * data;
- dns_record *rr, cname_rr, type_rr;
+ dns_record cname_rr, type_rr;
dns_scan dnss;
- int datalen, rc;
+ int rc;
/* DNS lookup failures get passed straight back. */
- if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) return rc;
+ if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED)
+ return rc;
/* We should have either records of the required type, or a CNAME record,
or both. We need to know whether both exist for getting the fully qualified
area in the dnsa block. */
cname_rr.data = type_rr.data = NULL;
- for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
- rr;
- rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
- {
+ for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
+ rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
if (rr->type == type)
{
if (type_rr.data == NULL) type_rr = *rr;
if (cname_rr.data != NULL) break;
}
- else if (rr->type == T_CNAME) cname_rr = *rr;
- }
+ else if (rr->type == T_CNAME)
+ cname_rr = *rr;
/* For the first time round this loop, if a CNAME was found, take the fully
qualified name from it; otherwise from the first data record, if present. */
- if (i == 0 && fully_qualified_name != NULL)
+ if (i == 0 && fully_qualified_name)
{
- uschar * rr_name = cname_rr.data ? cname_rr.name
- : type_rr.data ? type_rr.name : NULL;
+ uschar * rr_name = cname_rr.data
+ ? cname_rr.name : type_rr.data ? type_rr.name : NULL;
if ( rr_name
&& Ustrcmp(rr_name, *fully_qualified_name) != 0
&& rr_name[0] != '*'
if (!cname_rr.data)
return DNS_FAIL;
- data = store_get(256);
- datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
- cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256);
- if (datalen < 0)
+ /* DNS data comes from the outside, hence tainted */
+ data = store_get(256, TRUE);
+ if (dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
+ cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256) < 0)
return DNS_FAIL;
name = data;
assertion field. */
case T_CSA:
{
- uschar *srvname, *namesuff, *tld, *p;
+ uschar *srvname, *namesuff, *tld;
int priority, weight, port;
int limit, rc, i;
BOOL ipv6;
success and packet length return values.) For added safety we only reset
the packet length if the packet header looks plausible. */
- HEADER *h = (HEADER *)dnsa->answer;
+ 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 = MAXPACKET;
+ dnsa->answerlen = sizeof(dnsa->answer);
for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
- rr;
- rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
+ rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
)
if (rr->type != T_SOA) continue;
else if (strcmpic(rr->name, US"") == 0 ||
might make stricter assertions than its parent domain. */
for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
- rr;
- rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
+ rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) if (rr->type == T_SRV)
{
- if (rr->type != T_SRV) continue;
+ const uschar * p = rr->data;
/* Extract the numerical SRV fields (p is incremented) */
- p = rr->data;
GETSHORT(priority, p);
GETSHORT(weight, p); weight = weight; /* compiler quietening */
GETSHORT(port, p);
uschar *p = US rr->data;
if (p + 4 <= dnsa_lim)
{
- yield = store_get(sizeof(dns_address) + 20);
+ /* the IP is not regarded as tainted */
+ yield = store_get(sizeof(dns_address) + 20, FALSE);
(void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
yield->next = NULL;
}
if (rr->data + 16 <= dnsa_lim)
{
struct in6_addr in6;
- int i;
- for (i = 0; i < 16; i++) in6.s6_addr[i] = rr->data[i];
- yield = store_get(sizeof(dns_address) + 50);
+ for (int i = 0; i < 16; i++) in6.s6_addr[i] = rr->data[i];
+ yield = store_get(sizeof(dns_address) + 50, FALSE);
inet_ntop(AF_INET6, &in6, CS yield->address, 50);
yield->next = NULL;
}
projects / exim.git / blobdiff