From: Alessio Podda Date: Thu, 4 Jun 2026 14:30:35 +0000 (+0200) Subject: Reproducer for #5887 out of zone NSEC-next syntheisis X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=454bb99da49b66187423d0ff93bea9ad13252991;p=thirdparty%2Fbind9.git Reproducer for #5887 out of zone NSEC-next syntheisis Create the "nsec_child_next" system test. Co-Authored-By: Evan Hunt --- diff --git a/bin/tests/system/nsec_child_next/ans1/ans.py b/bin/tests/system/nsec_child_next/ans1/ans.py new file mode 100644 index 00000000000..31b5770c0fe --- /dev/null +++ b/bin/tests/system/nsec_child_next/ans1/ans.py @@ -0,0 +1,197 @@ +#!/usr/bin/python3 + +# Copyright (C) Internet Systems Consortium, Inc. ("ISC") +# +# SPDX-License-Identifier: MPL-2.0 + +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.rdata +import dns.rdataclass +import dns.rcode +import dns.rdatatype +import dns.rrset + +from isctest.asyncserver import ( + AsyncDnsServer, + DnsResponseSend, + QueryContext, + ResponseHandler, +) + +TTL = 300 +PARENT = "p.test." +EVIL = "evil.p.test." +POISON = f"0.{EVIL}" +POISON_NEXT = "zzz.p.test." +TARGET = f"target.{PARENT}" +TARGET_A = "192.0.2.77" + + +@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 nsec_rrset(owner: str, next_name: str, *types: str) -> dns.rrset.RRset: + return rrset(owner, dns.rdatatype.NSEC, f"{next_name} {' '.join(types)}") + + +def parent_apex_nsec() -> dns.rrset.RRset: + return nsec_rrset(PARENT, EVIL, "NS", "SOA", "RRSIG", "NSEC", "DNSKEY") + + +def evil_delegation_nsec() -> dns.rrset.RRset: + return nsec_rrset(EVIL, f"ns.{PARENT}", "NS", "RRSIG", "NSEC") + + +def malicious_nsec() -> dns.rrset.RRset: + return nsec_rrset(POISON, POISON_NEXT, "A", "RRSIG", "NSEC") + + +def garbage_rrsig(covered: dns.rrset.RRset) -> 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") + labels = len(covered.name.labels) - 1 + text = ( + f"{dns.rdatatype.to_text(covered.rdtype)} " + f"13 {labels} {covered.ttl} {expiration} {inception} " + f"12345 {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 + + +def add_parent_denial( + response: dns.message.Message, signer: Key, nsec: dns.rrset.RRset +) -> None: + add_signed(response.authority, soa_rrset(PARENT), signer) + add_signed(response.authority, nsec, signer) + + +class InsecureNsecNextHandler(ResponseHandler): + def __init__(self, key: Key) -> None: + self.key = key + self.parent = name(PARENT) + self.evil = name(EVIL) + self.poison = name(POISON) + self.target = name(TARGET) + + def match(self, qctx: QueryContext) -> bool: + return qctx.qname.is_subdomain(self.parent) + + 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.parent and qctx.qtype == dns.rdatatype.NSEC: + add_signed(response.answer, parent_apex_nsec(), self.key) + elif qctx.qname == self.evil and qctx.qtype == dns.rdatatype.DS: + add_parent_denial(response, self.key, evil_delegation_nsec()) + elif qctx.qname == self.poison and qctx.qtype == dns.rdatatype.NSEC: + nsec = malicious_nsec() + response.answer.append(nsec) + response.answer.append(garbage_rrsig(nsec)) + elif qctx.qname == self.target and qctx.qtype == dns.rdatatype.A: + add_signed( + response.answer, + rrset(TARGET, dns.rdatatype.A, TARGET_A), + self.key, + ) + else: + response.set_rcode(dns.rcode.NXDOMAIN) + add_parent_denial(response, self.key, parent_apex_nsec()) + + yield DnsResponseSend(response, authoritative=True) + + +def main() -> None: + server = AsyncDnsServer(default_aa=True) + server.install_response_handlers(InsecureNsecNextHandler(load_key())) + server.run() + + +if __name__ == "__main__": + main() diff --git a/bin/tests/system/nsec_child_next/ns2/named.conf.j2 b/bin/tests/system/nsec_child_next/ns2/named.conf.j2 new file mode 100644 index 00000000000..bf8edefea68 --- /dev/null +++ b/bin/tests/system/nsec_child_next/ns2/named.conf.j2 @@ -0,0 +1,34 @@ +// 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; + qname-minimization off; +}; + +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 "p.test" { + type static-stub; + server-addresses { 10.53.0.1; }; +}; + +trust-anchors { + p.test. static-key 257 3 13 "@PARENT_DNSKEY@"; +}; diff --git a/bin/tests/system/nsec_child_next/tests_nsec_child_next.py b/bin/tests/system/nsec_child_next/tests_nsec_child_next.py new file mode 100644 index 00000000000..760d81831fd --- /dev/null +++ b/bin/tests/system/nsec_child_next/tests_nsec_child_next.py @@ -0,0 +1,138 @@ +#!/usr/bin/python3 + +# Copyright (C) Internet Systems Consortium, Inc. ("ISC") +# +# SPDX-License-Identifier: MPL-2.0 + +from pathlib import Path + +import json + +from cryptography.hazmat.primitives import serialization +from cryptography.hazmat.primitives.asymmetric import ec + +import dns.dnssec +import dns.flags +import dns.name +import dns.rdataclass +import dns.rdatatype +import pytest + +import isctest + +PARENT = "p.test." +EVIL = "evil.p.test." +POISON = f"0.{EVIL}" +POISON_NEXT = "zzz.p.test." +TARGET = f"target.{PARENT}" +TARGET_A = "192.0.2.77" +AUTH = "10.53.0.1" +RESOLVER = "10.53.0.2" + +pytestmark = pytest.mark.extra_artifacts( + [ + "ans*/ans.run", + "ans*/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(): + keys = {PARENT: _make_key()} + Path("ans1/keys.json").write_text(json.dumps(keys, indent=2), encoding="ascii") + parent_dnskey = "".join(keys[PARENT]["dnskey"].split()[3:]) + return {"PARENT_DNSKEY": parent_dnskey} + + +def _query(server, qname, qtype): + query = isctest.query.create(qname, qtype) + 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_malicious_nsec(response, section): + nsec = _rrset(response, section, POISON, 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, + POISON, + dns.rdatatype.RRSIG, + covers=dns.rdatatype.NSEC, + ) + assert rrsig is not None, response.to_text() + assert rrsig[0].signer == dns.name.from_text(PARENT), response.to_text() + assert rrsig[0].key_tag == 12345, response.to_text() + + +def _prime_parent_for_aggressive_nsec(): + soa = _query(RESOLVER, PARENT, "SOA") + isctest.check.noerror(soa) + isctest.check.adflag(soa) + + nsec = _query(RESOLVER, PARENT, "NSEC") + isctest.check.noerror(nsec) + isctest.check.adflag(nsec) + + +def test_direct_insecure_child_nsec_next_fixture(): + poison = _query(AUTH, POISON, "NSEC") + isctest.check.noerror(poison) + assert poison.flags & dns.flags.AA + _check_malicious_nsec(poison, poison.answer) + + +def test_resolver_does_not_synth_from_insecure_child_nsec(): + _prime_parent_for_aggressive_nsec() + + poison = _query(RESOLVER, POISON, "NSEC") + isctest.check.noerror(poison) + isctest.check.noadflag(poison) + _check_malicious_nsec(poison, poison.answer) + + response = _query(RESOLVER, TARGET, "A") + isctest.check.noerror(response) + assert _has_a(response, TARGET, TARGET_A), response.to_text() + isctest.check.adflag(response) + assert _rrset(response, response.authority, POISON, dns.rdatatype.NSEC) is None