coredns/plugin/cache/dnssec.go
Miek Gieben 35b40a84f2
plugin/cache: Fix filtering (#4148)
The filtering of DNSSEC records in the cache plugin was not done
correctly. Also the change to introduced this bug didn't take into
account that the cache - by virtue of differentiating between DNSSEC and
no-DNSSEC - relied on not copying the data from the cache.

This change copies and then filters the data and factors the filtering
into a function that is used in two places (albeit with on ugly boolean
parameters to prevent copying things twice).

Add tests, do_test.go is moved to test/cache_test.go because the OPT
handing is done outside of the cache plugin. The core server re-attaches
the correct OPT when replying, so that makes for a better e2e test.

Added small unit test for filterRRslice and an explicit test that asks
for DNSSEC first and then plain, and vice versa to test cache behavior.

Fixes: #4146

Signed-off-by: Miek Gieben <miek@miek.nl>
2020-09-28 07:53:00 -07:00

43 lines
981 B
Go

package cache
import "github.com/miekg/dns"
// isDNSSEC returns true if r is a DNSSEC record. NSEC,NSEC3,DS and RRSIG/SIG
// are DNSSEC records. DNSKEYs is not in this list on the assumption that the
// client explictly asked for it.
func isDNSSEC(r dns.RR) bool {
switch r.Header().Rrtype {
case dns.TypeNSEC:
return true
case dns.TypeNSEC3:
return true
case dns.TypeDS:
return true
case dns.TypeRRSIG:
return true
case dns.TypeSIG:
return true
}
return false
}
// filterRRSlice filters rrs and removes DNSSEC RRs when do is false. In the returned slice
// the TTLs are set to ttl. If dup is true the RRs in rrs are _copied_ into the slice that is
// returned.
func filterRRSlice(rrs []dns.RR, ttl uint32, do, dup bool) []dns.RR {
j := 0
rs := make([]dns.RR, len(rrs), len(rrs))
for _, r := range rrs {
if !do && isDNSSEC(r) {
continue
}
r.Header().Ttl = ttl
if dup {
rs[j] = dns.Copy(r)
} else {
rs[j] = r
}
j++
}
return rs[:j]
}