Package: release.debian.org
Severity: normal
Tags: bullseye
User: release.debian@packages.debian.org
Usertags: pu
X-Debbugs-Cc: jakub.ruzi...@nic.cz
[ Reason ]
Fixing bug #991463 (CVE-2021-40083) - potential DoS.
[ Impact ]
Vulnerability to DoS attack.
[ Tests ]
I've tested the fix manually by running the deckard (DNS test harness)
test sets/resolver/val_iter_high.rpl supplied with the upstream fix.
It's not trivial to setup system for deckard so I've used upstream
Debian bullseye docker image from Knot CI:
docker run -it --privileged
registry.nic.cz/knot/knot-resolver/ci/debian-11:knot-3.0
With current knot-resolver-5.3.1-1 the test failed.
With suggested knot-resolver-5.3.1-1+deb11u1 the test passed.
[ Risks ]
This is a simple backport of upstream fix.
Upstream tests run during package build so chances of something
breaking are small.
[ Checklist ]
[*] *all* changes are documented in the d/changelog
[*] I reviewed all changes and I approve them
[*] attach debdiff against the package in (old)stable
[*] the issue is verified as fixed in unstable
[ Changes ]
Backport of upstream fix for #991463:
https://gitlab.nic.cz/knot/knot-resolver/-/merge_requests/1169/diffs#c22c39e3a02cdfb0d3d47b16ff46e65d196df19d
diff -Nru knot-resolver-5.3.1/debian/changelog
knot-resolver-5.3.1/debian/changelog
--- knot-resolver-5.3.1/debian/changelog2021-04-12 05:59:28.0
+
+++ knot-resolver-5.3.1/debian/changelog2021-08-31 16:20:00.0
+
@@ -1,3 +1,10 @@
+knot-resolver (5.3.1-1+deb11u1) bullseye; urgency=medium
+
+ * Fix possible assertion failure in NSEC3 edge-case (CVE-2021-40083)
+(Closes: #991463)
+
+ -- Jakub Ružička Tue, 31 Aug 2021 16:20:00 +
+
knot-resolver (5.3.1-1) unstable; urgency=medium
[ Jakub Ružička ]
diff -Nru knot-resolver-5.3.1/debian/gbp.conf
knot-resolver-5.3.1/debian/gbp.conf
--- knot-resolver-5.3.1/debian/gbp.conf 2021-04-12 05:59:28.0 +
+++ knot-resolver-5.3.1/debian/gbp.conf 2021-08-31 16:20:00.0 +
@@ -1,5 +1,5 @@
[DEFAULT]
-debian-branch = debian/master
+debian-branch = debian/bullseye
debian-tag = debian/%(version)s
upstream-branch = upstream
upstream-tag = upstream/%(version)s
diff -Nru
knot-resolver-5.3.1/debian/patches/0002-validator-avoid-assertion-in-an-edge-case.patch
knot-resolver-5.3.1/debian/patches/0002-validator-avoid-assertion-in-an-edge-case.patch
---
knot-resolver-5.3.1/debian/patches/0002-validator-avoid-assertion-in-an-edge-case.patch
1970-01-01 00:00:00.0 +
+++
knot-resolver-5.3.1/debian/patches/0002-validator-avoid-assertion-in-an-edge-case.patch
2021-08-31 16:20:00.0 +
@@ -0,0 +1,58 @@
+From: =?utf-8?b?VmxhZGltw61yIMSMdW7DoXQ=?=
+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(, 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
