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From: =?utf-8?b?VmxhZGltw61yIMSMdW7DoXQ=?= <vladimir.cunat@nic.cz>
Date: Mon, 12 Apr 2021 15:23:02 +0200
Subject: [PATCH] validator: avoid assertion in an edge-case
Case: NSEC3 with too many iterations used for a positive wildcard proof.
To really fix the answers, this also needed fixing the `any_rank` part
which I somehow forgot in commit 7107faebc :-(
---
lib/dnssec/nsec3.c | 7 +++++++
lib/dnssec/nsec3.h | 1 +
lib/layer/validate.c | 3 ++-
3 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/lib/dnssec/nsec3.c b/lib/dnssec/nsec3.c
index e9e536a..f3a48c0 100644
--- a/lib/dnssec/nsec3.c
+++ b/lib/dnssec/nsec3.c
@@ -596,6 +596,13 @@ int kr_nsec3_wildcard_answer_response_check(const knot_pkt_t *pkt, knot_section_
if (rrset->type != KNOT_RRTYPE_NSEC3) {
continue;
}
+ if (knot_nsec3_iters(rrset->rrs.rdata) > KR_NSEC3_MAX_ITERATIONS) {
+ /* Avoid hashing with too many iterations.
+ * If we get here, the `sname` wildcard probably ends up bogus,
+ * but it gets downgraded to KR_RANK_INSECURE when validator
+ * gets to verifying one of these over-limit NSEC3 RRs. */
+ continue;
+ }
int ret = covers_name(&flags, rrset, sname);
if (ret != 0) {
return ret;
diff --git a/lib/dnssec/nsec3.h b/lib/dnssec/nsec3.h
index 1e316f5..0fdbfce 100644
--- a/lib/dnssec/nsec3.h
+++ b/lib/dnssec/nsec3.h
@@ -39,6 +39,7 @@ int kr_nsec3_name_error_response_check(const knot_pkt_t *pkt, knot_section_t sec
* KNOT_ERANGE - NSEC3 RR that covers a wildcard
* has been found, but has opt-out flag set;
* otherwise - error.
+ * Records over KR_NSEC3_MAX_ITERATIONS are skipped, so you probably get kr_error(ENOENT).
*/
int kr_nsec3_wildcard_answer_response_check(const knot_pkt_t *pkt, knot_section_t section_id,
const knot_dname_t *sname, int trim_to_next);
diff --git a/lib/layer/validate.c b/lib/layer/validate.c
index cf5dda2..cf5c88a 100644
--- a/lib/layer/validate.c
+++ b/lib/layer/validate.c
@@ -894,7 +894,8 @@ static void rank_records(struct kr_query *qry, bool any_rank, enum kr_rank rank_
bailiwick) < 0) {
continue;
}
- if (kr_rank_test(entry->rank, KR_RANK_INITIAL)
+ if (any_rank
+ || kr_rank_test(entry->rank, KR_RANK_INITIAL)
|| kr_rank_test(entry->rank, KR_RANK_TRY)
|| kr_rank_test(entry->rank, KR_RANK_MISSING)) {
kr_rank_set(&entry->rank, rank_to_set);
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