--- /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 pathlib import Path
+
+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,
+)
+
+# P3: A signed zone P, chained to a configured trust anchor, that
+# (a) publishes a wildcard *.P A or AAAA record and
+# (b) delegates at least one separately-signed child C.P (own DS in P)
+# operated by a distinct principal.
+TTL = 300
+PARENT = "parent.hack."
+CHILD = f"child.{PARENT}"
+QUERY = f"q.{PARENT}"
+SERVICE = f"svc.{CHILD}"
+WILDCARD = f"*.{PARENT}"
+
+FORGED_A = "198.51.100.45"
+LEGIT_A = "192.0.2.113"
+
+
+@dataclass(frozen=True)
+class Key:
+ zone: dns.name.Name
+ private_key: object
+ dnskey: dns.rdata.Rdata
+ ds: dns.rdata.Rdata
+
+
+def name(text: str) -> dns.name.Name:
+ return dns.name.from_text(text)
+
+
+def load_keys() -> dict[str, Key]:
+ path = Path(__file__).resolve().parent / "keys.json"
+ with path.open(encoding="utf-8") as keys_file:
+ raw_keys = json.load(keys_file)
+
+ keys = {}
+ for zone, raw_key in raw_keys.items():
+ 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"]
+ )
+ ds = dns.rdata.from_text(dns.rdataclass.IN, dns.rdatatype.DS, raw_key["ds"])
+ keys[zone] = Key(name(zone), private_key, dnskey, ds)
+
+ return keys
+
+
+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"ns1.{zone} hostmaster.{zone} 1 3600 600 86400 300",
+ )
+
+
+def add_dnskey(response: dns.message.Message, zone: str, key: Key) -> None:
+ add_signed(response.answer, rrset_from_rdata(zone, key.dnskey), key)
+
+
+def add_ds(response: dns.message.Message, zone: str, child: Key, parent: Key) -> None:
+ add_signed(response.answer, rrset_from_rdata(zone, child.ds), parent)
+
+
+def add_nodata(response: dns.message.Message, zone: str, key: Key) -> None:
+ add_signed(response.authority, soa_rrset(zone), key)
+
+
+def wildcard_rrsig(owner: str, parent: Key) -> dns.rrset.RRset:
+ wildcard = rrset(WILDCARD, dns.rdatatype.A, FORGED_A)
+ rrsig = dns.dnssec.sign(
+ wildcard,
+ parent.private_key,
+ parent.zone,
+ parent.dnskey,
+ lifetime=86400,
+ verify=True,
+ )
+ return dns.rrset.from_rdata(name(owner), wildcard.ttl, rrsig)
+
+
+def add_parent_mx_with_forged_additional(
+ response: dns.message.Message, parent: Key
+) -> None:
+ add_signed(
+ response.answer,
+ rrset(QUERY, dns.rdatatype.MX, f"10 {SERVICE}"),
+ parent,
+ )
+ response.additional.append(rrset(SERVICE, dns.rdatatype.A, FORGED_A))
+ response.additional.append(wildcard_rrsig(SERVICE, parent))
+
+
+def add_child_a(response: dns.message.Message, child: Key) -> None:
+ add_signed(response.answer, rrset(SERVICE, dns.rdatatype.A, LEGIT_A), child)
+
+
+class QueryCParentWildcardHandler(ResponseHandler):
+ def __init__(self, keys: dict[str, Key]) -> None:
+ self.keys = keys
+ self.parent = name(PARENT)
+ self.child = name(CHILD)
+ self.query = name(QUERY)
+ self.service = name(SERVICE)
+
+ def match(self, qctx: QueryContext) -> bool:
+ return True
+
+ async def get_responses(
+ self, qctx: QueryContext
+ ) -> AsyncGenerator[DnsResponseSend, None]:
+ qctx.prepare_new_response(with_zone_data=False)
+ qctx.response.flags |= dns.flags.AA
+ qctx.response.set_rcode(dns.rcode.NOERROR)
+
+ parent_key = self.keys[PARENT]
+ child_key = self.keys[CHILD]
+
+ if qctx.qname == self.parent and qctx.qtype == dns.rdatatype.DNSKEY:
+ # Priming, DNSKEY RRset
+ add_dnskey(qctx.response, PARENT, parent_key)
+ elif qctx.qname == self.parent and qctx.qtype == dns.rdatatype.SOA:
+ # Priming, SOA RRset
+ add_signed(qctx.response.answer, soa_rrset(PARENT), parent_key)
+ elif qctx.qname == self.query and qctx.qtype == dns.rdatatype.MX:
+ # Trigger query.
+ add_parent_mx_with_forged_additional(qctx.response, parent_key)
+ elif qctx.qname == self.child and qctx.qtype == dns.rdatatype.DS:
+ # Chain of trust, DS of child.
+ add_ds(qctx.response, CHILD, child_key, parent_key)
+ elif qctx.qname == self.child and qctx.qtype == dns.rdatatype.DNSKEY:
+ # Chain of trust, DNSKEY of child.
+ add_dnskey(qctx.response, CHILD, child_key)
+ elif qctx.qname == self.child and qctx.qtype == dns.rdatatype.SOA:
+ # SOA of child.
+ add_signed(qctx.response.answer, soa_rrset(CHILD), child_key)
+ elif qctx.qname == self.service and qctx.qtype == dns.rdatatype.A:
+ # Zone data at child.
+ add_child_a(qctx.response, child_key)
+ elif qctx.qname.is_subdomain(self.child):
+ # No data at child.
+ add_nodata(qctx.response, CHILD, child_key)
+ elif qctx.qname.is_subdomain(self.parent):
+ # No data at parent.
+ add_nodata(qctx.response, PARENT, parent_key)
+ else:
+ qctx.response.set_rcode(dns.rcode.NXDOMAIN)
+
+ yield DnsResponseSend(qctx.response, authoritative=True)
+
+
+def main() -> None:
+ keys = load_keys()
+ server = AsyncDnsServer(default_aa=True)
+ server.install_response_handlers(QueryCParentWildcardHandler(keys))
+ server.run()
+
+
+if __name__ == "__main__":
+ main()
--- /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.flags
+import dns.name
+import dns.rdataclass
+import dns.rdatatype
+import pytest
+
+import isctest
+
+PARENT = "parent.hack."
+CHILD = f"child.{PARENT}"
+QUERY = f"q.{PARENT}"
+SERVICE = f"svc.{CHILD}"
+FORGED_A = "198.51.100.45"
+LEGIT_A = "192.0.2.113"
+AUTH = "10.53.0.1"
+RESOLVER = "10.53.0.2"
+
+pytestmark = pytest.mark.extra_artifacts(
+ [
+ "ans1/ans.run",
+ "ans1/keys.json",
+ ]
+)
+
+
+def _make_key(zone):
+ private_key = ec.generate_private_key(ec.SECP256R1())
+ dnskey = dns.dnssec.make_dnskey(
+ private_key.public_key(),
+ algorithm="ECDSAP256SHA256",
+ flags=257,
+ )
+ ds = dns.dnssec.make_ds(dns.name.from_text(zone), dnskey, "SHA256")
+ 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(),
+ "ds": ds.to_text(),
+ }
+
+
+def bootstrap():
+ keys = {zone: _make_key(zone) for zone in [PARENT, CHILD]}
+
+ 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, cd=False):
+ query = isctest.query.create(qname, qtype, cd=cd)
+ 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, section, owner, address):
+ rrset = _rrset(response, section, owner, dns.rdatatype.A)
+ return rrset is not None and any(rdata.address == address for rdata in rrset)
+
+
+def _check_signed_rrset(response, section, owner, rdtype, signer, labels=None):
+ rrsig = _rrset(
+ response,
+ section,
+ owner,
+ dns.rdatatype.RRSIG,
+ covers=rdtype,
+ )
+ assert rrsig is not None, response.to_text()
+ assert rrsig[0].signer == dns.name.from_text(signer), response.to_text()
+ if labels is not None:
+ assert rrsig[0].labels == labels, response.to_text()
+
+
+def prime_parent_soa():
+ response = _query(RESOLVER, PARENT, "SOA")
+ isctest.check.noerror(response)
+ isctest.check.adflag(response)
+ assert _rrset(response, response.answer, PARENT, dns.rdatatype.SOA) is not None
+ _check_signed_rrset(response, response.answer, PARENT, dns.rdatatype.SOA, PARENT)
+
+
+def test_malicious_replay():
+ # Trigger query.
+ response = _query(AUTH, QUERY, "MX")
+ isctest.check.noerror(response)
+ isctest.check.aaflag(response)
+
+ assert _rrset(response, response.answer, QUERY, dns.rdatatype.MX)
+ _check_signed_rrset(response, response.answer, QUERY, dns.rdatatype.MX, PARENT)
+
+ # The reply carries in ADDITIONAL. Note Labels=2, signer=parent.hack.
+ assert _has_a(response, response.additional, SERVICE, FORGED_A), response.to_text()
+ _check_signed_rrset(
+ response,
+ response.additional,
+ SERVICE,
+ dns.rdatatype.A,
+ signer=PARENT,
+ labels=2,
+ )
+
+ # Victim query — any later client, with CD=0:
+ child = _query(AUTH, SERVICE, "A")
+ isctest.check.noerror(child)
+
+ assert _has_a(child, child.answer, SERVICE, LEGIT_A), child.to_text()
+ assert not _has_a(child, child.answer, SERVICE, FORGED_A), child.to_text()
+ _check_signed_rrset(child, child.answer, SERVICE, dns.rdatatype.A, CHILD)
+
+
+def test_replayed_parent_wildcard():
+ # Prime the parent's DNSKEY.
+ prime_parent_soa()
+
+ # Trigger query — the on-path injection happens on the upstream side of
+ # this single fetch. Requires CD=1.
+ response = _query(RESOLVER, QUERY, "MX", cd=True)
+ isctest.check.noerror(response)
+ assert _rrset(response, response.answer, QUERY, dns.rdatatype.MX)
+
+ # Victim query — any later client, with CD=0:
+ response = _query(RESOLVER, SERVICE, "A")
+ isctest.check.noerror(response)
+ isctest.check.adflag(response)
+
+ assert not _has_a(response, response.answer, SERVICE, FORGED_A)
+ assert _has_a(response, response.answer, SERVICE, LEGIT_A), response.to_text()
+ _check_signed_rrset(response, response.answer, SERVICE, dns.rdatatype.A, CHILD)
projects / thirdparty / bind9.git / commitdiff
