int
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... */
for (i = 0; i < 10; i++)
{
uschar data[256];
dns_record *rr, cname_rr, type_rr;
dns_scan dnss;
int datalen, rc;
/* DNS lookup failures get passed straight back. */
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
name, but avoid scanning more than necessary. Note that we must copy the
contents of any rr blocks returned by dns_next_rr() as they use the same
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))
{
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;
}
/* 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)
{
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] != '*'
#ifdef EXPERIMENTAL_INTERNATIONAL
&& ( !string_is_utf8(*fully_qualified_name)
|| Ustrcmp(rr_name,
string_domain_utf8_to_alabel(*fully_qualified_name, NULL)) != 0
)
#endif
)
*fully_qualified_name = string_copy_dnsdomain(rr_name);
}
/* If any data records of the correct type were found, we are done. */
if (type_rr.data != NULL)
{
if (!secure_so_far) /* mark insecure if any element of CNAME chain was */
dns_set_insecure(dnsa);
return DNS_SUCCEED;
}
/* If there are no data records, we need to re-scan the DNS using the
domain given in the CNAME record, which should exist (otherwise we should
have had a failure from dns_lookup). However code against the possibility of
its not existing. */
if (cname_rr.data == NULL) return DNS_FAIL;
datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, sizeof(data));
if (datalen < 0) return DNS_FAIL;
name = data;
if (!dns_is_secure(dnsa))
secure_so_far = FALSE;
DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name);
} /* Loop back to do another lookup */
/*Control reaches here after 10 times round the CNAME loop. Something isn't
right... */
log_write(0, LOG_MAIN, "CNAME loop for %s encountered", orig_name);
return DNS_FAIL;
}
static int
dnsdb_find(void *handle, uschar *filename, const uschar *keystring, int length,
uschar **result, uschar **errmsg, uint *do_cache)
{
int rc;
int size = 256;
int ptr = 0;
int sep = 0;
int defer_mode = PASS;
int dnssec_mode = OK;
int save_retrans = dns_retrans;
int save_retry = dns_retry;
int type;
int failrc = FAIL;
const uschar *outsep = CUS"\n";
const uschar *outsep2 = NULL;
uschar *equals, *domain, *found;
/* 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.
If it's followed by ';' or ',' we set the TXT output separator. */
while (isspace(*keystring)) keystring++;
if (*keystring == '>')
{
outsep = keystring + 1;
keystring += 2;
if (*keystring == ',')
{
outsep2 = keystring + 1;
keystring += 2;
}
else if (*keystring == ';')
{
outsep2 = US"";
keystring++;
}
while (isspace(*keystring)) keystring++;
}
/* Check for a modifier keyword. */
for (;;)
{
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;
}
}
else if (strncmpic(keystring, US"dnssec_", 7) == 0)
{
keystring += 7;
if (strncmpic(keystring, US"strict", 6) == 0)
{ dnssec_mode = DEFER; keystring += 6; }
else if (strncmpic(keystring, US"lax", 3) == 0)
{ dnssec_mode = PASS; keystring += 3; }
else if (strncmpic(keystring, US"never", 5) == 0)
{ dnssec_mode = OK; keystring += 5; }
else
{
*errmsg = US"unsupported dnsdb dnssec behaviour";
return DEFER;
}
}
else if (strncmpic(keystring, US"retrans_", 8) == 0)
{
int timeout_sec;
if ((timeout_sec = readconf_readtime(keystring += 8, ',', FALSE)) <= 0)
{
*errmsg = US"unsupported dnsdb timeout value";
return DEFER;
}
dns_retrans = timeout_sec;
while (*keystring != ',') keystring++;
}
else if (strncmpic(keystring, US"retry_", 6) == 0)
{
int retries;
if ((retries = (int)strtol(CCS keystring + 6, CSS &keystring, 0)) < 0)
{
*errmsg = US"unsupported dnsdb retry count";
return DEFER;
}
dns_retry = retries;
}
else
break;
while (isspace(*keystring)) keystring++;
if (*keystring++ != ',')
{
*errmsg = US"dnsdb modifier syntax error";
return DEFER;
}
while (isspace(*keystring)) keystring++;
}
/* Figure out the "type" value if it is not T_TXT.
If the keystring contains an = this must be preceded by a valid type name. */
type = T_TXT;
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 < nelem(type_names); i++)
if (len == Ustrlen(type_names[i]) &&
strncmpic(keystring, US type_names[i], len) == 0)
{
type = type_values[i];
break;
}
if (i >= nelem(type_names))
{
*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, dnssec_mode != OK);
/* 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;
/* SPF strings should be concatenated without a separator, thus make
it the default if not defined (see RFC 4408 section 3.1.3).
Multiple SPF records are forbidden (section 3.1.2) but are currently
not handled specially, thus they are concatenated with \n by default.
MX priority and value are space-separated by default.
SRV and TLSA record parts are space-separated by default. */
if (!outsep2) switch(type)
{
case T_SPF: outsep2 = US""; break;
case T_SRV: case T_MX: case T_TLSA: outsep2 = US" "; break;
}
/* Now scan the list and do a lookup for each item */
while ((domain = string_nextinlist(&keystring, &sep, NULL, 0)))
{
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;
}
do
{
DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain);
/* Do the lookup and sort out the result. There are four special types that
are handled specially: T_CSA, T_ZNS, T_ADDRESSES and T_MXH.
The first two are handled in a special lookup function so that the facility
could be used from other parts of the Exim code. T_ADDRESSES is handled by looping
over the types of A lookup. T_MXH affects only what happens later on in
this function, but for tidiness it is handled by the "special". 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;
#if HAVE_IPV6
if (type == T_ADDRESSES) /* NB cannot happen unless HAVE_IPV6 */
{
if (searchtype == T_ADDRESSES) searchtype = T_AAAA;
else if (searchtype == T_AAAA) searchtype = T_A;
rc = dns_special_lookup(&dnsa, domain, searchtype, CUSS &found);
}
else
#endif
rc = dns_special_lookup(&dnsa, domain, type, CUSS &found);
lookup_dnssec_authenticated = dnssec_mode==OK ? NULL
: dns_is_secure(&dnsa) ? US"yes" : US"no";
if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
if ( rc != DNS_SUCCEED
|| (dnssec_mode == DEFER && !dns_is_secure(&dnsa))
)
{
if (defer_mode == DEFER)
{
dns_retrans = save_retrans;
dns_retry = save_retry;
dns_init(FALSE, FALSE, FALSE); /* clr dnssec bit */
return DEFER; /* always defer */
}
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;
if (*do_cache > rr->ttl)
*do_cache = rr->ttl;
if (type == T_A || type == T_AAAA || type == T_ADDRESSES)
{
dns_address *da;
for (da = dns_address_from_rr(&dnsa, rr); da; da = da->next)
{
if (ptr != 0) yield = string_catn(yield, &size, &ptr, outsep, 1);
yield = string_cat(yield, &size, &ptr, 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_catn(yield, &size, &ptr, outsep, 1);
if (type == T_TXT || type == T_SPF)
{
if (outsep2 == NULL)
{
/* output only the first item of data */
yield = string_catn(yield, &size, &ptr, (uschar *)(rr->data+1),
(rr->data)[0]);
}
else
{
/* output all items */
int data_offset = 0;
while (data_offset < rr->size)
{
uschar chunk_len = (rr->data)[data_offset++];
if (outsep2[0] != '\0' && data_offset != 1)
yield = string_catn(yield, &size, &ptr, outsep2, 1);
yield = string_catn(yield, &size, &ptr,
US ((rr->data)+data_offset), chunk_len);
data_offset += chunk_len;
}
}
}
else if (type == T_TLSA)
{
uint8_t usage, selector, matching_type;
uint16_t i, payload_length;
uschar s[MAX_TLSA_EXPANDED_SIZE];
uschar * sp = s;
uschar * p = US rr->data;
usage = *p++;
selector = *p++;
matching_type = *p++;
/* What's left after removing the first 3 bytes above */
payload_length = rr->size - 3;
sp += sprintf(CS s, "%d%c%d%c%d%c", usage, *outsep2,
selector, *outsep2, matching_type, *outsep2);
/* Now append the cert/identifier, one hex char at a time */
for (i=0;
i < payload_length && sp-s < (MAX_TLSA_EXPANDED_SIZE - 4);
i++)
sp += sprintf(CS sp, "%02x", (unsigned char)p[i]);
yield = string_cat(yield, &size, &ptr, s);
}
else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SOA, T_SRV */
{
int priority, weight, port;
uschar s[264];
uschar * p = US rr->data;
switch (type)
{
case T_MXH:
/* mxh ignores the priority number and includes only the hostnames */
GETSHORT(priority, p);
break;
case T_MX:
GETSHORT(priority, p);
sprintf(CS s, "%d%c", priority, *outsep2);
yield = string_cat(yield, &size, &ptr, s);
break;
case T_SRV:
GETSHORT(priority, p);
GETSHORT(weight, p);
GETSHORT(port, p);
sprintf(CS s, "%d%c%d%c%d%c", priority, *outsep2,
weight, *outsep2, port, *outsep2);
yield = string_cat(yield, &size, &ptr, s);
break;
case 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 (Ustrcmp(found, domain) != 0)
{
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_catn(yield, &size, &ptr, s, 2);
break;
default:
break;
}
/* 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);
if (type == T_SOA && outsep2 != NULL)
{
unsigned long serial, refresh, retry, expire, minimum;
p += rc;
yield = string_catn(yield, &size, &ptr, outsep2, 1);
rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
(DN_EXPAND_ARG4_TYPE)s, sizeof(s));
if (rc < 0)
{
log_write(0, LOG_MAIN, "responsible-mailbox truncated: type=%s "
"domain=%s", dns_text_type(type), domain);
break;
}
else yield = string_cat(yield, &size, &ptr, s);
p += rc;
GETLONG(serial, p); GETLONG(refresh, p);
GETLONG(retry, p); GETLONG(expire, p); GETLONG(minimum, p);
sprintf(CS s, "%c%lu%c%lu%c%lu%c%lu%c%lu",
*outsep2, serial, *outsep2, refresh,
*outsep2, retry, *outsep2, expire, *outsep2, minimum);
yield = string_cat(yield, &size, &ptr, s);
}
}
} /* Loop for list of returned records */
/* Loop for set of A-lookup types */
} while (type == T_ADDRESSES && searchtype != T_A);
} /* 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. */
dns_retrans = save_retrans;
dns_retry = save_retry;
dns_init(FALSE, FALSE, FALSE); /* clear the dnssec bit for getaddrbyname */
if (ptr == 0) return failrc;
yield[ptr] = 0;
*result = yield;
return OK;
}
