Create the "nsec_pending_cd" system test.
Co-Authored-By: Matthijs Mekking <matthijs@isc.org>
--- /dev/null
+#!/usr/bin/python3
+
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+from collections.abc import AsyncGenerator
+from dataclasses import dataclass
+from datetime import datetime, timedelta, timezone
+from pathlib import Path
+
+import base64
+import json
+
+from cryptography.hazmat.primitives import serialization
+
+import dns.dnssec
+import dns.flags
+import dns.message
+import dns.name
+import dns.rcode
+import dns.rdata
+import dns.rdataclass
+import dns.rdatatype
+import dns.rrset
+
+from isctest.asyncserver import (
+ AsyncDnsServer,
+ DnsResponseSend,
+ QueryContext,
+ ResponseHandler,
+)
+
+TTL = 300
+PARENT = "tld.test."
+ATTACKER = "attacker.tld.test."
+VICTIM = "victim.tld.test."
+VICTIM_A = "203.0.113.1"
+POISON_NEXT = f"b.{VICTIM}"
+
+
+@dataclass(frozen=True)
+class Key:
+ zone: dns.name.Name
+ private_key: object
+ dnskey: dns.rdata.Rdata
+
+
+def name(text: str) -> dns.name.Name:
+ return dns.name.from_text(text)
+
+
+def load_key() -> Key:
+ path = Path(__file__).resolve().parent / "keys.json"
+ with path.open(encoding="utf-8") as keys_file:
+ raw_key = json.load(keys_file)[PARENT]
+
+ private_key = serialization.load_pem_private_key(
+ raw_key["private_pem"].encode("ascii"),
+ password=None,
+ )
+ dnskey = dns.rdata.from_text(
+ dns.rdataclass.IN, dns.rdatatype.DNSKEY, raw_key["dnskey"]
+ )
+ return Key(name(PARENT), private_key, dnskey)
+
+
+def rrset(owner: str, rdtype: dns.rdatatype.RdataType, *rdatas: str) -> dns.rrset.RRset:
+ return dns.rrset.from_text(owner, TTL, dns.rdataclass.IN, rdtype, *rdatas)
+
+
+def rrset_from_rdata(owner: str, rdata: dns.rdata.Rdata) -> dns.rrset.RRset:
+ return dns.rrset.from_rdata(name(owner), TTL, rdata)
+
+
+def add_signed(
+ section: list[dns.rrset.RRset], covered: dns.rrset.RRset, signer: Key
+) -> None:
+ rrsig = dns.dnssec.sign(
+ covered,
+ signer.private_key,
+ signer.zone,
+ signer.dnskey,
+ lifetime=86400,
+ verify=True,
+ )
+ section.append(covered)
+ section.append(dns.rrset.from_rdata(covered.name, covered.ttl, rrsig))
+
+
+def soa_rrset(zone: str) -> dns.rrset.RRset:
+ return rrset(
+ zone,
+ dns.rdatatype.SOA,
+ f"ns.{zone} hostmaster.{zone} 1 3600 600 86400 300",
+ )
+
+
+def attacker_nsec_rrset() -> dns.rrset.RRset:
+ return rrset(
+ ATTACKER,
+ dns.rdatatype.NSEC,
+ f"{POISON_NEXT} NS SOA RRSIG NSEC DNSKEY",
+ )
+
+
+def garbage_rrsig(covered: dns.rrset.RRset, signer: Key) -> dns.rrset.RRset:
+ now = datetime.now(timezone.utc)
+ inception = (now - timedelta(hours=1)).strftime("%Y%m%d%H%M%S")
+ expiration = (now + timedelta(days=1)).strftime("%Y%m%d%H%M%S")
+ signature = base64.b64encode(bytes(64)).decode("ascii")
+ text = (
+ f"{dns.rdatatype.to_text(covered.rdtype)} "
+ f"{signer.dnskey.algorithm} 3 {covered.ttl} "
+ f"{expiration} {inception} 9999 {PARENT} {signature}"
+ )
+ rdata = dns.rdata.from_text(dns.rdataclass.IN, dns.rdatatype.RRSIG, text)
+ return dns.rrset.from_rdata(covered.name, covered.ttl, rdata)
+
+
+def prepare_response(qctx: QueryContext) -> dns.message.Message:
+ qctx.prepare_new_response(with_zone_data=False)
+ qctx.response.flags |= dns.flags.AA
+ qctx.response.set_rcode(dns.rcode.NOERROR)
+ return qctx.response
+
+
+class PendingNsecHandler(ResponseHandler):
+ def __init__(self, key: Key) -> None:
+ self.key = key
+ self.parent = name(PARENT)
+ self.attacker = name(ATTACKER)
+ self.victim = name(VICTIM)
+
+ def match(self, qctx: QueryContext) -> bool:
+ return True
+
+ async def get_responses(
+ self, qctx: QueryContext
+ ) -> AsyncGenerator[DnsResponseSend, None]:
+ response = prepare_response(qctx)
+
+ if qctx.qname == self.parent and qctx.qtype == dns.rdatatype.DNSKEY:
+ add_signed(
+ response.answer,
+ rrset_from_rdata(PARENT, self.key.dnskey),
+ self.key,
+ )
+ elif qctx.qname == self.parent and qctx.qtype == dns.rdatatype.SOA:
+ add_signed(response.answer, soa_rrset(PARENT), self.key)
+ elif qctx.qname == self.attacker and qctx.qtype == dns.rdatatype.NSEC:
+ if qctx.query.flags & dns.flags.CD:
+ nsec = attacker_nsec_rrset()
+ response.answer.append(nsec)
+ response.answer.append(garbage_rrsig(nsec, self.key))
+ else:
+ response.set_rcode(dns.rcode.REFUSED)
+ elif qctx.qname == self.victim and qctx.qtype == dns.rdatatype.A:
+ add_signed(
+ response.answer,
+ rrset(VICTIM, dns.rdatatype.A, VICTIM_A),
+ self.key,
+ )
+ else:
+ response.set_rcode(dns.rcode.NXDOMAIN)
+ add_signed(response.authority, soa_rrset(PARENT), self.key)
+
+ yield DnsResponseSend(response, authoritative=True)
+
+
+def main() -> None:
+ server = AsyncDnsServer(default_aa=True)
+ server.install_response_handlers(PendingNsecHandler(load_key()))
+ server.run()
+
+
+if __name__ == "__main__":
+ main()
--- /dev/null
+// validating resolver
+
+options {
+ query-source address 10.53.0.2;
+ notify-source 10.53.0.2;
+ transfer-source 10.53.0.2;
+ port @PORT@;
+ pid-file "named.pid";
+ listen-on { 10.53.0.2; };
+ listen-on-v6 { none; };
+ recursion yes;
+ dnssec-validation yes;
+ synth-from-dnssec yes;
+};
+
+controls {
+ inet 10.53.0.2 port @CONTROLPORT@ allow { any; } keys { rndc_key; };
+};
+
+include "../../_common/rndc.key";
+
+zone "." {
+ type hint;
+ file "../../_common/root.hint";
+};
+
+zone "tld.test" {
+ type static-stub;
+ server-addresses { 10.53.0.1; };
+};
+
+trust-anchors {
+ tld.test. static-key 257 3 13 "@PARENT_DNSKEY@";
+};
--- /dev/null
+#!/usr/bin/python3
+
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+from pathlib import Path
+
+import json
+
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric import ec
+
+import dns.dnssec
+import dns.name
+import dns.rdataclass
+import dns.rdatatype
+import pytest
+
+import isctest
+
+PARENT = "tld.test"
+ATTACKER = "attacker.tld.test"
+VICTIM = "victim.tld.test"
+POISON_NEXT = f"b.{VICTIM}."
+VICTIM_A = "203.0.113.1"
+AUTH = "10.53.0.1"
+RESOLVER = "10.53.0.2"
+
+pytestmark = pytest.mark.extra_artifacts(
+ [
+ "ans1/ans.run",
+ "ans1/keys.json",
+ ]
+)
+
+
+def _make_key():
+ private_key = ec.generate_private_key(ec.SECP256R1())
+ dnskey = dns.dnssec.make_dnskey(
+ private_key.public_key(),
+ algorithm="ECDSAP256SHA256",
+ flags=257,
+ )
+ private_pem = private_key.private_bytes(
+ encoding=serialization.Encoding.PEM,
+ format=serialization.PrivateFormat.PKCS8,
+ encryption_algorithm=serialization.NoEncryption(),
+ ).decode("ascii")
+ return {
+ "private_pem": private_pem,
+ "dnskey": dnskey.to_text(),
+ }
+
+
+def bootstrap():
+ # Step 0: Setup Attacker Zone
+ keys = {f"{PARENT}.": _make_key()}
+
+ Path("ans1/keys.json").write_text(json.dumps(keys, indent=2), encoding="ascii")
+
+ parent_dnskey = "".join(keys[f"{PARENT}."]["dnskey"].split()[3:])
+ return {"PARENT_DNSKEY": parent_dnskey}
+
+
+def _query(server, qname, qtype, cd=False, dnssec=True):
+ query = isctest.query.create(qname, qtype, cd=cd, dnssec=dnssec)
+ return isctest.query.tcp(query, server)
+
+
+def _rrset(response, section, owner, rdtype, covers=None):
+ if covers is None:
+ return response.get_rrset(
+ section,
+ dns.name.from_text(owner),
+ dns.rdataclass.IN,
+ rdtype,
+ )
+ return response.get_rrset(
+ section,
+ dns.name.from_text(owner),
+ dns.rdataclass.IN,
+ rdtype,
+ covers=covers,
+ )
+
+
+def _has_a(response, owner, address):
+ rrset = _rrset(response, response.answer, owner, dns.rdatatype.A)
+ return rrset is not None and any(rdata.address == address for rdata in rrset)
+
+
+def _check_attacker_nsec(response, section):
+ nsec = _rrset(response, section, f"{ATTACKER}.", dns.rdatatype.NSEC)
+ assert nsec is not None, response.to_text()
+ assert nsec[0].next == dns.name.from_text(POISON_NEXT), response.to_text()
+
+ rrsig = _rrset(
+ response,
+ section,
+ f"{ATTACKER}.",
+ dns.rdatatype.RRSIG,
+ covers=dns.rdatatype.NSEC,
+ )
+ assert rrsig is not None, response.to_text()
+ assert rrsig[0].signer == dns.name.from_text(f"{PARENT}."), response.to_text()
+ assert rrsig[0].key_tag == 9999, response.to_text()
+
+
+def test_pending_trust_nsec_cd_cache_poisoning():
+ """
+ Reproducer for #5872:
+ F-004 Cache Poisoning via Pending-Trust NSEC in Aggressive Cache
+ """
+ # Step 1: Prime SOA parent (and DNSKEY as subquery)
+ soa = _query(RESOLVER, PARENT, "SOA")
+ isctest.check.noerror(soa)
+ isctest.check.adflag(soa)
+
+ # Step 2: Inject Forged NSEC via CD=1 Query
+ poison = _query(RESOLVER, ATTACKER, "NSEC", cd=True)
+ isctest.check.noerror(poison)
+ isctest.check.noadflag(poison)
+ _check_attacker_nsec(poison, poison.answer)
+
+ # Step 3: Exploit Against Victim Domain
+ response = _query(RESOLVER, VICTIM, "A")
+ isctest.check.noerror(response)
+ assert _has_a(response, VICTIM, VICTIM_A), response.to_text()
+ isctest.check.adflag(response)
+ assert _rrset(response, response.authority, ATTACKER, dns.rdatatype.NSEC) is None
+
+ # Step 4: Exploit Against Stub Client
+ response = _query(RESOLVER, VICTIM, "A", dnssec=False)
+ isctest.check.noerror(response)
+ assert _has_a(response, VICTIM, VICTIM_A), response.to_text()
+ isctest.check.adflag(response)
+ assert _rrset(response, response.authority, ATTACKER, dns.rdatatype.NSEC) is None
+
+ # Step 5: Verify Upstream Queries
+ with open("ans1/ans.run", "r", encoding="utf-8") as file:
+ assert f"Received {VICTIM}" in file.read()
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