feat: real DNS lookups, manual DKIM selectors, Cloudflare-ready DNS provider architecture

Agent-Logs-Url: https://github.com/christianlouis/dmarq/sessions/19d17518-732d-4644-889b-cc63256e19b1 Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
2026-03-29 18:53:35 +00:00
parent 4e4db14d36
commit 0d1a4fdac3
6 changed files with 1096 additions and 39 deletions
@@ -0,0 +1,269 @@
+"""
+Unit tests for app.services.dns_resolver.
+
+DNS network I/O is mocked at the ``lookup_txt`` level so no real DNS queries
+are made during testing.
+"""
+
+from unittest.mock import AsyncMock, patch
+
+import pytest
+
+from app.services.dns_resolver import (
+    BaseDNSProvider,
+    CloudflareDNSProvider,
+    DomainDNSResult,
+    SystemDNSProvider,
+    extract_dmarc_policy,
+    get_default_provider,
+)
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+class FakeDNSProvider(BaseDNSProvider):
+    """Concrete provider backed by a simple dict for deterministic tests."""
+
+    def __init__(self, records: dict):
+        self._records = records
+
+    async def lookup_txt(self, name: str):
+        if name in self._records:
+            return self._records[name]
+        raise LookupError(f"NXDOMAIN: {name}")
+
+
+# ---------------------------------------------------------------------------
+# extract_dmarc_policy
+# ---------------------------------------------------------------------------
+
+
+def test_extract_dmarc_policy_none():
+    record = "v=DMARC1; p=none; rua=mailto:dmarc@example.com"
+    assert extract_dmarc_policy(record) == "none"
+
+
+def test_extract_dmarc_policy_quarantine():
+    record = "v=DMARC1; p=quarantine; pct=100"
+    assert extract_dmarc_policy(record) == "quarantine"
+
+
+def test_extract_dmarc_policy_reject():
+    assert extract_dmarc_policy("v=DMARC1; p=reject") == "reject"
+
+
+def test_extract_dmarc_policy_missing_tag():
+    assert extract_dmarc_policy("v=DMARC1; rua=mailto:dmarc@example.com") is None
+
+
+def test_extract_dmarc_policy_none_input():
+    assert extract_dmarc_policy(None) is None
+
+
+# ---------------------------------------------------------------------------
+# BaseDNSProvider helpers via FakeDNSProvider
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_check_dmarc_found():
+    provider = FakeDNSProvider(
+        {"_dmarc.example.com": ["v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com"]}
+    )
+    found, record = await provider.check_dmarc("example.com")
+    assert found is True
+    assert record is not None
+    assert "p=quarantine" in record
+
+
+@pytest.mark.asyncio
+async def test_check_dmarc_not_found():
+    provider = FakeDNSProvider({})
+    found, record = await provider.check_dmarc("example.com")
+    assert found is False
+    assert record is None
+
+
+@pytest.mark.asyncio
+async def test_check_spf_found():
+    provider = FakeDNSProvider(
+        {"example.com": ["v=spf1 include:_spf.google.com ~all", "some-other-record"]}
+    )
+    found, record = await provider.check_spf("example.com")
+    assert found is True
+    assert record is not None
+    assert record.startswith("v=spf1")
+
+
+@pytest.mark.asyncio
+async def test_check_spf_not_found():
+    provider = FakeDNSProvider({"example.com": ["some-other-record"]})
+    found, record = await provider.check_spf("example.com")
+    assert found is False
+    assert record is None
+
+
+@pytest.mark.asyncio
+async def test_check_dkim_found_first_selector():
+    provider = FakeDNSProvider(
+        {"google._domainkey.example.com": ["v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3"]}
+    )
+    found, selector, record = await provider.check_dkim("example.com", ["google", "mail"])
+    assert found is True
+    assert selector == "google"
+    assert record is not None
+
+
+@pytest.mark.asyncio
+async def test_check_dkim_found_second_selector():
+    provider = FakeDNSProvider(
+        {"mail._domainkey.example.com": ["v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3"]}
+    )
+    found, selector, record = await provider.check_dkim("example.com", ["google", "mail"])
+    assert found is True
+    assert selector == "mail"
+
+
+@pytest.mark.asyncio
+async def test_check_dkim_not_found():
+    provider = FakeDNSProvider({})
+    found, selector, record = await provider.check_dkim("example.com", ["google", "mail"])
+    assert found is False
+    assert selector is None
+    assert record is None
+
+
+@pytest.mark.asyncio
+async def test_check_domain_all_present():
+    provider = FakeDNSProvider(
+        {
+            "_dmarc.example.com": ["v=DMARC1; p=none; rua=mailto:dmarc@example.com"],
+            "example.com": ["v=spf1 include:_spf.google.com ~all"],
+            "google._domainkey.example.com": ["v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3"],
+        }
+    )
+    result = await provider.check_domain("example.com", selectors=["google"])
+    assert isinstance(result, DomainDNSResult)
+    assert result.dmarc is True
+    assert result.spf is True
+    assert result.dkim is True
+    assert result.dkim_selector == "google"
+
+
+@pytest.mark.asyncio
+async def test_check_domain_none_present():
+    provider = FakeDNSProvider({})
+    result = await provider.check_domain("missing.example.com")
+    assert result.dmarc is False
+    assert result.spf is False
+    assert result.dkim is False
+
+
+@pytest.mark.asyncio
+async def test_check_domain_uses_common_selectors_as_fallback():
+    """When no selectors are passed, common selectors should be tried."""
+    # Use 'default' which is in COMMON_DKIM_SELECTORS
+    provider = FakeDNSProvider({"default._domainkey.example.com": ["v=DKIM1; k=rsa; p=ABC"]})
+    result = await provider.check_domain("example.com", selectors=[])
+    assert result.dkim is True
+    assert result.dkim_selector == "default"
+
+
+@pytest.mark.asyncio
+async def test_check_domain_manual_selectors_take_priority():
+    """Manually supplied selectors must be checked before common ones."""
+    # Only the manual selector 'custom' has a record
+    provider = FakeDNSProvider({"custom._domainkey.example.com": ["v=DKIM1; k=rsa; p=XYZ"]})
+    result = await provider.check_domain("example.com", selectors=["custom"])
+    assert result.dkim is True
+    assert result.dkim_selector == "custom"
+
+
+# ---------------------------------------------------------------------------
+# SystemDNSProvider
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_system_provider_returns_txt_records():
+    """SystemDNSProvider.lookup_txt should decode dnspython rdata correctly."""
+    mock_string = b"v=DMARC1; p=none"
+
+    class FakeRdata:
+        strings = [mock_string]
+
+    class FakeAnswers:
+        def __iter__(self):
+            return iter([FakeRdata()])
+
+    with patch("dns.asyncresolver.resolve", new=AsyncMock(return_value=FakeAnswers())):
+        provider = SystemDNSProvider()
+        records = await provider.lookup_txt("_dmarc.example.com")
+
+    assert records == ["v=DMARC1; p=none"]
+
+
+@pytest.mark.asyncio
+async def test_system_provider_raises_lookup_error_on_dns_exception():
+    import dns.exception  # type: ignore[import]
+
+    with patch(
+        "dns.asyncresolver.resolve",
+        new=AsyncMock(side_effect=dns.exception.DNSException("NXDOMAIN")),
+    ):
+        provider = SystemDNSProvider()
+        with pytest.raises(LookupError):
+            await provider.lookup_txt("nonexistent.example.com")
+
+
+# ---------------------------------------------------------------------------
+# CloudflareDNSProvider
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_cloudflare_provider_parses_doh_response():
+    """CloudflareDNSProvider should parse the Cloudflare DoH JSON response."""
+    from unittest.mock import MagicMock
+
+    fake_response_data = {
+        "Answer": [
+            {"type": 16, "data": '"v=DMARC1; p=reject"'},
+            {"type": 1, "data": "93.184.216.34"},  # A record — should be ignored
+        ]
+    }
+
+    mock_response = AsyncMock()
+    mock_response.raise_for_status = MagicMock()  # raise_for_status is synchronous in httpx
+    mock_response.json = lambda: fake_response_data
+
+    with patch("httpx.AsyncClient.get", new=AsyncMock(return_value=mock_response)):
+        provider = CloudflareDNSProvider()
+        records = await provider.lookup_txt("_dmarc.example.com")
+
+    assert records == ["v=DMARC1; p=reject"]
+
+
+@pytest.mark.asyncio
+async def test_cloudflare_provider_raises_on_http_error():
+    import httpx
+
+    with patch(
+        "httpx.AsyncClient.get",
+        new=AsyncMock(side_effect=httpx.RequestError("connection refused")),
+    ):
+        provider = CloudflareDNSProvider()
+        with pytest.raises(LookupError):
+            await provider.lookup_txt("_dmarc.example.com")
+
+
+# ---------------------------------------------------------------------------
+# get_default_provider
+# ---------------------------------------------------------------------------
+
+
+def test_get_default_provider_returns_system():
+    provider = get_default_provider()
+    assert isinstance(provider, SystemDNSProvider)