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Fix DNS not supporting wildcard matching #13158

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giograno merged 5 commits into from
Sep 24, 2025
Merged

Fix DNS not supporting wildcard matching #13158

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2cad473
refactor
skyrpex Sep 17, 2025
a5b2758
add alias wildcard resolution test
skyrpex Sep 17, 2025
76cfd4b
fix the issue
skyrpex Sep 17, 2025
b9257c2
add more assertions to the test
skyrpex Sep 17, 2025
17122ad
lint and format
skyrpex Sep 17, 2025
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15 changes: 12 additions & 3 deletions localstack-core/localstack/dns/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -445,13 +445,22 @@ def _skip_local_resolution(self, request) -> bool:
return True
return False

def _find_matching_aliases(self, question: DNSQuestion) -> list[AliasTarget] | None:
"""
Find aliases matching the question, supporting wildcards.
"""
qlabel = DNSLabel(to_bytes(question.qname))
qtype = RecordType[QTYPE[question.qtype]]
for (label, rtype), targets in self.aliases.items():
if rtype == qtype and qlabel.matchWildcard(label):
return targets
return None

def _resolve_alias(
self, request: DNSRecord, reply: DNSRecord, client_address: ClientAddress
) -> bool:
if request.q.qtype in (QTYPE.A, QTYPE.AAAA, QTYPE.CNAME):
key = (DNSLabel(to_bytes(request.q.qname)), RecordType[QTYPE[request.q.qtype]])
# check if we have aliases defined for our given qname/qtype pair
if aliases := self.aliases.get(key):
if aliases := self._find_matching_aliases(request.q):
for alias in aliases:
# if there is no health check, or the healthcheck is successful, we will consider this alias
# take the first alias passing this check
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18 changes: 18 additions & 0 deletions tests/unit/test_dns_server.py
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Expand Up @@ -137,6 +137,24 @@ def test_dns_server_add_multiple_hosts(self, dns_server, query_dns):
assert answer.answer
assert "123.123.123.123" in answer.to_text()

def test_dns_server_resolves_alias_wildcards(self, dns_server, query_dns):
"""Check if server resolves aliases with wildcards"""
dns_server.add_host("example.org", TargetRecord("1.1.1.1", RecordType.A))
answer = query_dns("subdomain1.example.org", "A")
assert len(answer.answer) == 0

dns_server.add_alias(
source_name="*.example.org",
record_type=RecordType.A,
target=AliasTarget(target="example.org"),
)
answer = query_dns("subdomain1.example.org", "A")
assert answer.answer
assert "1.1.1.1" in answer.to_text()
answer = query_dns("subdomain2.example.org", "A")
assert answer.answer
assert "1.1.1.1" in answer.to_text()

def test_overriding_with_dns_resolve_ip(self, dns_server, query_dns, monkeypatch):
monkeypatch.setattr(config, "DNS_RESOLVE_IP", "2.2.2.2")

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