feat(heuristics): add Fake Email analyzer to validate maintainer email domain

pyproject.toml

@@ -38,6 +38,7 @@ dependencies = [
     "problog >= 2.2.6,<3.0.0",
     "cryptography >=44.0.0,<45.0.0",
     "semgrep == 1.113.0",
+    "dnspython >=2.7.0,<3.0.0",
 ]
 keywords = []
 # https://pypi.org/classifiers/

src/macaron/malware_analyzer/pypi_heuristics/heuristics.py

@@ -43,6 +43,9 @@ class Heuristics(str, Enum):
     #: Indicates that the package source code contains suspicious code patterns.
     SUSPICIOUS_PATTERNS = "suspicious_patterns"
 
+    #: Indicates that the package maintainer's email address is suspicious or invalid.
+    FAKE_EMAIL = "fake_email"
+
 
 class HeuristicResult(str, Enum):
     """Result type indicating the outcome of a heuristic."""

src/macaron/malware_analyzer/pypi_heuristics/metadata/fake_email.py

@@ -0,0 +1,96 @@
+# Copyright (c) 2024 - 2025, Oracle and/or its affiliates. All rights reserved.
+# Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl/.
+
+"""The heuristic analyzer to check the email address of the package maintainers."""
+
+import logging
+import re
+
+import dns.resolver as dns_resolver
+
+from macaron.errors import HeuristicAnalyzerValueError
+from macaron.json_tools import JsonType
+from macaron.malware_analyzer.pypi_heuristics.base_analyzer import BaseHeuristicAnalyzer
+from macaron.malware_analyzer.pypi_heuristics.heuristics import HeuristicResult, Heuristics
+from macaron.slsa_analyzer.package_registry.pypi_registry import PyPIPackageJsonAsset
+
+logger: logging.Logger = logging.getLogger(__name__)
+
+
+class FakeEmailAnalyzer(BaseHeuristicAnalyzer):
+    """Analyze the email address of the package maintainers."""
+
+    def __init__(self) -> None:
+        super().__init__(
+            name="fake_email_analyzer",
+            heuristic=Heuristics.FAKE_EMAIL,
+            depends_on=None,
+        )
+
+    def is_valid_email(self, email: str) -> bool:
+        """Check if the email format is valid and the domain has MX records.
+
+        Parameters
+        ----------
+        email: str
+            The email address to check.
+
+        Returns
+        -------
+        bool:
+            ``True`` if the email address is valid, ``False`` otherwise.
+
+        Raises
+        ------
+        HeuristicAnalyzerValueError
+            if the failure is due to DNS resolution.
+        """
+        if not re.match(r"[^@]+@[^@]+\.[^@]+", email):
+            return False
+
+        domain = email.split("@")[1]
+        try:
+            records = dns_resolver.resolve(domain, "MX")
+            if not records:
+                return False
+        except Exception as err:
+            err_message = f"Failed to resolve domain {domain}: {err}"
+            raise HeuristicAnalyzerValueError(err_message) from err
+        return True
+
+    def analyze(self, pypi_package_json: PyPIPackageJsonAsset) -> tuple[HeuristicResult, dict[str, JsonType]]:
+        """Analyze the package.
+
+        Parameters
+        ----------
+        pypi_package_json: PyPIPackageJsonAsset
+            The PyPI package JSON asset object.
+
+        Returns
+        -------
+        tuple[HeuristicResult, dict[str, JsonType]]:
+            The result and related information collected during the analysis.
+
+        Raises
+        ------
+        HeuristicAnalyzerValueError
+            if the analysis fails.
+        """
+        response = pypi_package_json.download("")
+        if not response:
+            error_message = "Failed to download package JSON "
+            return HeuristicResult.FAIL, {"message": error_message}
+
+        data = pypi_package_json.package_json
+        author_email = data.get("info", {}).get("author_email", None)
+        maintainer_email = data.get("info", {}).get("maintainer_email", None)
+        if maintainer_email is None and author_email is None:
+            message = "No maintainers are available"
+            return HeuristicResult.SKIP, {"message": message}
+
+        if author_email is not None and not self.is_valid_email(author_email):
+            return HeuristicResult.FAIL, {"email": author_email}
+        if maintainer_email is not None and not self.is_valid_email(maintainer_email):
+            return HeuristicResult.FAIL, {"email": maintainer_email}
+
+        return HeuristicResult.PASS, {}

src/macaron/slsa_analyzer/checks/detect_malicious_metadata_check.py

@@ -20,6 +20,7 @@
 from macaron.malware_analyzer.pypi_heuristics.metadata.anomalous_version import AnomalousVersionAnalyzer
 from macaron.malware_analyzer.pypi_heuristics.metadata.closer_release_join_date import CloserReleaseJoinDateAnalyzer
 from macaron.malware_analyzer.pypi_heuristics.metadata.empty_project_link import EmptyProjectLinkAnalyzer
+from macaron.malware_analyzer.pypi_heuristics.metadata.fake_email import FakeEmailAnalyzer
 from macaron.malware_analyzer.pypi_heuristics.metadata.high_release_frequency import HighReleaseFrequencyAnalyzer
 from macaron.malware_analyzer.pypi_heuristics.metadata.one_release import OneReleaseAnalyzer
 from macaron.malware_analyzer.pypi_heuristics.metadata.source_code_repo import SourceCodeRepoAnalyzer
@@ -357,6 +358,7 @@ def run_check(self, ctx: AnalyzeContext) -> CheckResultData:
         WheelAbsenceAnalyzer,
         AnomalousVersionAnalyzer,
         TyposquattingPresenceAnalyzer,
+        FakeEmailAnalyzer,
     ]
 
     # name used to query the result of all problog rules, so it can be accessed outside the model.
@@ -424,13 +426,18 @@ def run_check(self, ctx: AnalyzeContext) -> CheckResultData:
         failed({Heuristics.ONE_RELEASE.value}),
         failed({Heuristics.ANOMALOUS_VERSION.value}).
 
+    % Package released recently with the a maintainer email address that is not valid.
+    {Confidence.MEDIUM.value}::trigger(malware_medium_confidence_3) :-
+        quickUndetailed,
+        failed({Heuristics.FAKE_EMAIL.value}).
     % ----- Evaluation -----
 
     % Aggregate result
     {problog_result_access} :- trigger(malware_high_confidence_1).
     {problog_result_access} :- trigger(malware_high_confidence_2).
     {problog_result_access} :- trigger(malware_high_confidence_3).
     {problog_result_access} :- trigger(malware_high_confidence_4).
+    {problog_result_access} :- trigger(malware_medium_confidence_3).
     {problog_result_access} :- trigger(malware_medium_confidence_2).
     {problog_result_access} :- trigger(malware_medium_confidence_1).
     query({problog_result_access}).

tests/malware_analyzer/pypi/test_fake_email.py

@@ -0,0 +1,166 @@
+# Copyright (c) 2024 - 2025, Oracle and/or its affiliates. All rights reserved.
+# Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl/.
+
+"""Tests for the FakeEmailAnalyzer heuristic."""
+
+
+from collections.abc import Generator
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from macaron.malware_analyzer.pypi_heuristics.heuristics import HeuristicResult
+from macaron.malware_analyzer.pypi_heuristics.metadata.fake_email import FakeEmailAnalyzer
+from macaron.slsa_analyzer.package_registry.pypi_registry import PyPIPackageJsonAsset
+
+
+@pytest.fixture(name="analyzer")
+def analyzer_fixture() -> FakeEmailAnalyzer:
+    """Pytest fixture to create a FakeEmailAnalyzer instance."""
+    return FakeEmailAnalyzer()
+
+
+@pytest.fixture(name="pypi_package_json_asset_mock")
+def pypi_package_json_asset_mock_fixture() -> MagicMock:
+    """Pytest fixture for a mock PyPIPackageJsonAsset."""
+    mock_asset = MagicMock(spec=PyPIPackageJsonAsset)
+    # Default to successful download, tests can override
+    mock_asset.download = MagicMock(return_value=True)
+    # package_json should be set by each test to simulate different PyPI responses
+    mock_asset.package_json = {}
+    return mock_asset
+
+
+@pytest.fixture(name="mock_dns_resolve")
+def mock_dns_resolve_fixture() -> Generator[MagicMock]:
+    """General purpose mock for dns.resolver.resolve.
+
+    Patches where dns_resolver is imported in the module under test.
+    """
+    with patch("macaron.malware_analyzer.pypi_heuristics.metadata.fake_email.dns_resolver.resolve") as mock_resolve:
+        # Default behavior: simulate successful MX record lookup.
+        mock_mx_record = MagicMock()
+        mock_mx_record.exchange = "mail.default-domain.com"
+        mock_resolve.return_value = [mock_mx_record]
+        yield mock_resolve
+
+
+# Tests for the analyze method
+def test_analyze_download_failure(analyzer: FakeEmailAnalyzer, pypi_package_json_asset_mock: MagicMock) -> None:
+    """Test the analyzer fails if downloading package JSON fails."""
+    pypi_package_json_asset_mock.download.return_value = False
+    result, info = analyzer.analyze(pypi_package_json_asset_mock)
+    assert result == HeuristicResult.FAIL
+    assert "message" in info
+    assert isinstance(info["message"], str)
+    assert "Failed to download package JSON" in info["message"]
+    pypi_package_json_asset_mock.download.assert_called_once_with("")
+
+
+def test_analyze_skip_no_emails_present(analyzer: FakeEmailAnalyzer, pypi_package_json_asset_mock: MagicMock) -> None:
+    """Test the analyzer skips if no author_email or maintainer_email is present."""
+    pypi_package_json_asset_mock.package_json = {"info": {"author_email": None, "maintainer_email": None}}
+    result, info = analyzer.analyze(pypi_package_json_asset_mock)
+    assert result == HeuristicResult.SKIP
+    assert info["message"] == "No maintainers are available"
+
+
+def test_analyze_skip_no_info_key(analyzer: FakeEmailAnalyzer, pypi_package_json_asset_mock: MagicMock) -> None:
+    """Test the analyzer skips if 'info' key is missing in PyPI data."""
+    pypi_package_json_asset_mock.package_json = {}  # No 'info' key
+    result, info = analyzer.analyze(pypi_package_json_asset_mock)
+    assert result == HeuristicResult.SKIP
+    assert info["message"] == "No maintainers are available"
+
+
+def test_analyze_fail_empty_author_email(analyzer: FakeEmailAnalyzer, pypi_package_json_asset_mock: MagicMock) -> None:
+    """Test analyzer fails for empty author_email string (maintainer_email is None)."""
+    pypi_package_json_asset_mock.package_json = {"info": {"author_email": "", "maintainer_email": None}}
+    result, info = analyzer.analyze(pypi_package_json_asset_mock)
+    assert result == HeuristicResult.FAIL
+    assert info["email"] == ""
+
+
+def test_analyze_pass_only_maintainer_email_valid(
+    analyzer: FakeEmailAnalyzer, pypi_package_json_asset_mock: MagicMock, mock_dns_resolve: MagicMock
+) -> None:
+    """Test analyzer passes when only maintainer_email is present and valid."""
+    mock_mx_record = MagicMock()
+    mock_mx_record.exchange = "mail.example.net"
+    mock_dns_resolve.return_value = [mock_mx_record]
+
+    pypi_package_json_asset_mock.package_json = {
+        "info": {"author_email": None, "maintainer_email": "[email protected]"}
+    }
+    result, info = analyzer.analyze(pypi_package_json_asset_mock)
+    assert result == HeuristicResult.PASS
+    assert info == {}
+    mock_dns_resolve.assert_called_once_with("example.net", "MX")
+
+
+def test_analyze_pass_both_emails_valid(
+    analyzer: FakeEmailAnalyzer, pypi_package_json_asset_mock: MagicMock, mock_dns_resolve: MagicMock
+) -> None:
+    """Test the analyzer passes when both emails are present and valid."""
+
+    def side_effect_dns_resolve(domain: str, record_type: str = "MX") -> list[MagicMock]:
+        mock_mx = MagicMock()
+        domains = {
+            "MX": {"example.com", "example.net"},
+        }
+        if domain not in domains.get(record_type, set()):
+            pytest.fail(f"Unexpected domain for DNS resolve: {domain}")
+        mock_mx.exchange = f"mail.{domain}"
+        return [mock_mx]
+
+    mock_dns_resolve.side_effect = side_effect_dns_resolve
+
+    pypi_package_json_asset_mock.package_json = {
+        "info": {"author_email": "[email protected]", "maintainer_email": "[email protected]"}
+    }
+    result, info = analyzer.analyze(pypi_package_json_asset_mock)
+    assert result == HeuristicResult.PASS
+    assert info == {}
+    assert mock_dns_resolve.call_count == 2
+    mock_dns_resolve.assert_any_call("example.com", "MX")
+    mock_dns_resolve.assert_any_call("example.net", "MX")
+
+
+def test_analyze_fail_author_email_invalid_format(
+    analyzer: FakeEmailAnalyzer, pypi_package_json_asset_mock: MagicMock, mock_dns_resolve: MagicMock
+) -> None:
+    """Test analyzer fails when author_email has an invalid format."""
+    pypi_package_json_asset_mock.package_json = {
+        "info": {"author_email": "bad_email_format", "maintainer_email": "[email protected]"}
+    }
+    result, info = analyzer.analyze(pypi_package_json_asset_mock)
+    assert result == HeuristicResult.FAIL
+    assert info["email"] == "bad_email_format"
+    mock_dns_resolve.assert_not_called()  # Regex check fails before DNS lookup
+
+
+# Tests for the is_valid_email method
+def test_is_valid_email_valid_email_with_mx(analyzer: FakeEmailAnalyzer, mock_dns_resolve: MagicMock) -> None:
+    """Test is_valid_email returns True for a valid email with MX records."""
+    mock_mx_record = MagicMock()
+    mock_mx_record.exchange = "mail.example.com"
+    mock_dns_resolve.return_value = [mock_mx_record]
+    assert analyzer.is_valid_email("[email protected]") is True
+    mock_dns_resolve.assert_called_once_with("example.com", "MX")
+
+
+def test_is_valid_email_invalid_format(analyzer: FakeEmailAnalyzer, mock_dns_resolve: MagicMock) -> None:
+    """Test is_valid_email method with various invalid email formats."""
+    assert not analyzer.is_valid_email("not_an_email")
+    assert not analyzer.is_valid_email("test@")
+    assert not analyzer.is_valid_email("@example.com")
+    assert not analyzer.is_valid_email("test@example")
+    assert not analyzer.is_valid_email("")
+    mock_dns_resolve.assert_not_called()
+
+
+def test_is_valid_email_no_mx_records_returned(analyzer: FakeEmailAnalyzer, mock_dns_resolve: MagicMock) -> None:
+    """Test is_valid_email returns False if DNS resolve returns no MX records."""
+    mock_dns_resolve.return_value = []  # Simulate no MX records found
+    assert analyzer.is_valid_email("[email protected]") is False
+    mock_dns_resolve.assert_called_once_with("no-mx-domain.com", "MX")