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Handle SERVFAIL responses to DS queries better.

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On 15/5/2023 8.8.8.8 was returning SERVFAIL for a query on ec.europa.eu

ec.europa.eu is not a domain cut, that happens at jrc.ec.europa.eu. which
does return a signed proof of non-existance for a DS record.
Abandoning the search for a DS or proof of non existence at ec.europa.eu
renders everything within that domain BOGUS, since nothing is signed.

This code changes behaviour on a SERVFAIL to continue looking
deeper for a DS or proof of its nonexistence.
This commit is contained in:
Simon Kelley
2023-05-15 18:11:06 +01:00
parent 1d6fe0ea84
commit 31c91b40bd
2 changed files with 37 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

63
src/dnssec.c
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@@ -921,7 +921,7 @@ int dnssec_validate_by_ds(time_t now, struct dns_header *header, size_t plen, ch
int dnssec_validate_ds(time_t now, struct dns_header *header, size_t plen, char *name, char *keyname, int class)
{
unsigned char *p = (unsigned char *)(header+1);
int qtype, qclass, rc, i, neganswer, nons, neg_ttl = 0, found_supported = 0;
int qtype, qclass, rc, i, neganswer = 0, nons = 0, servfail = 0, neg_ttl = 0, found_supported = 0;
int aclass, atype, rdlen, flags;
unsigned long ttl;
union all_addr a;
@@ -934,35 +934,43 @@ int dnssec_validate_ds(time_t now, struct dns_header *header, size_t plen, char
GETSHORT(qclass, p);
if (qtype != T_DS || qclass != class)
rc = STAT_BOGUS;
else
rc = dnssec_validate_reply(now, header, plen, name, keyname, NULL, 0, &neganswer, &nons, &neg_ttl);
if (STAT_ISEQUAL(rc, STAT_INSECURE))
{
my_syslog(LOG_WARNING, _("Insecure DS reply received for %s, check domain configuration and upstream DNS server DNSSEC support"), name);
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL, "BOGUS DS - not secure", 0);
return STAT_BOGUS | DNSSEC_FAIL_INDET;
}
p = (unsigned char *)(header+1);
if (!extract_name(header, plen, &p, name, 1, 4))
return STAT_BOGUS;
return STAT_BOGUS;
p += 4; /* qtype, qclass */
/* If the key needed to validate the DS is on the same domain as the DS, we'll
loop getting nowhere. Stop that now. This can happen of the DS answer comes
from the DS's zone, and not the parent zone. */
if (STAT_ISEQUAL(rc, STAT_NEED_KEY) && hostname_isequal(name, keyname))
/* A SERVFAIL answer has been seen to a DS query not at start of authority,
so treat it as such and continue to search for a DS or proof of no existence
further down the tree. */
if (RCODE(header) == SERVFAIL)
servfail = neganswer = nons = 1;
else
{
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL, "BOGUS DS", 0);
return STAT_BOGUS;
rc = dnssec_validate_reply(now, header, plen, name, keyname, NULL, 0, &neganswer, &nons, &neg_ttl);
if (STAT_ISEQUAL(rc, STAT_INSECURE))
{
my_syslog(LOG_WARNING, _("Insecure DS reply received for %s, check domain configuration and upstream DNS server DNSSEC support"), name);
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL, "BOGUS DS - not secure", 0);
return STAT_BOGUS | DNSSEC_FAIL_INDET;
}
p = (unsigned char *)(header+1);
if (!extract_name(header, plen, &p, name, 1, 4))
return STAT_BOGUS;
p += 4; /* qtype, qclass */
/* If the key needed to validate the DS is on the same domain as the DS, we'll
loop getting nowhere. Stop that now. This can happen of the DS answer comes
from the DS's zone, and not the parent zone. */
if (STAT_ISEQUAL(rc, STAT_NEED_KEY) && hostname_isequal(name, keyname))
{
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL, "BOGUS DS", 0);
return STAT_BOGUS;
}
if (!STAT_ISEQUAL(rc, STAT_SECURE))
return rc;
}
if (!STAT_ISEQUAL(rc, STAT_SECURE))
return rc;
if (!neganswer)
{
cache_start_insert();
@@ -1060,7 +1068,8 @@ int dnssec_validate_ds(time_t now, struct dns_header *header, size_t plen, char
cache_end_insert();
if (neganswer)
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL, nons ? "no DS/cut" : "no DS", 0);
log_query(F_NOEXTRA | F_UPSTREAM, name, NULL,
servfail ? "SERVFAIL" : (nons ? "no DS/cut" : "no DS"), 0);
return STAT_OK;
}