feat: add support for Google Cloud-based Trusted Publishers (#114)

Author: woodruffw

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- The `GooglePublisher` type has been added to support
+  Google Cloud-based Trusted Publishers
+  ([#114](https://github.com/trailofbits/pypi-attestations/pull/114))
+
 ## [0.0.23]
 
 ### Added

README.md

@@ -141,6 +141,11 @@ pypi-attestations verify attestation  \
 ```
 
 ### Verifying a PyPI package
+
+> [!IMPORTANT]
+> This subcommand supports publish attestations from GitHub and GitLab.
+> It **does not currently support** Google Cloud-based publish attestations.
+
 > [!NOTE]
 > The package to verify can be passed either as a path to a local file, a
 > `pypi:` prefixed filename (e.g: 'pypi:sampleproject-1.0.0-py3-none-any.whl'),
@@ -161,8 +166,8 @@ pypi-attestations verify pypi --repository https://github.com/sigstore/sigstore-
   ~/Downloads/sigstore-3.6.1-py3-none-any.whl
 ```
 
-This command downloads the artifact and its provenance from PyPI. The artifact 
-is then verified against the provenance, while also checking that the provenance's 
+This command downloads the artifact and its provenance from PyPI. The artifact
+is then verified against the provenance, while also checking that the provenance's
 signing identity matches the repository specified by the user.
 
 ### Converting a Sigstore bundle into a PEP 740 Attestation

src/pypi_attestations/_cli.py

@@ -31,8 +31,9 @@
     ConversionError,
     Distribution,
     GitHubPublisher,
+    GitLabPublisher,
+    GooglePublisher,
     Provenance,
-    Publisher,
 )
 
 if typing.TYPE_CHECKING:  # pragma: no cover
@@ -382,7 +383,9 @@ def _get_provenance_from_pypi(dist: Distribution) -> Provenance:
         _die(f"Invalid provenance: {validation_error}")
 
 
-def _check_repository_identity(expected_repository_url: str, publisher: Publisher) -> None:
+def _check_repository_identity(
+    expected_repository_url: str, publisher: GitHubPublisher | GitLabPublisher
+) -> None:
     """Check that a repository url matches the given publisher's identity."""
     validator = (
         validators.Validator()
@@ -566,6 +569,8 @@ def _verify_pypi(args: argparse.Namespace) -> None:
     try:
         for attestation_bundle in provenance.attestation_bundles:
             publisher = attestation_bundle.publisher
+            if isinstance(publisher, GooglePublisher):  # pragma: no cover
+                _die("This CLI doesn't support Google Cloud-based publisher verification")
             _check_repository_identity(expected_repository_url=args.repository, publisher=publisher)
             policy = publisher._as_policy()  # noqa: SLF001
             for attestation in attestation_bundle.attestations:

src/pypi_attestations/_impl.py

@@ -648,7 +648,22 @@ def _as_policy(self) -> VerificationPolicy:
         return _GitLabTrustedPublisherPolicy(self.repository, self.workflow_filepath)
 
 
-_Publisher = Union[GitHubPublisher, GitLabPublisher]
+class GooglePublisher(_PublisherBase):
+    """A Google Cloud-based Trusted Publisher."""
+
+    kind: Literal["Google"] = "Google"
+
+    email: str
+    """
+    The email address of the Google Cloud service account that performed
+    the publishing action.
+    """
+
+    def _as_policy(self) -> VerificationPolicy:
+        return policy.Identity(identity=self.email, issuer="https://accounts.google.com")
+
+
+_Publisher = Union[GitHubPublisher, GitLabPublisher, GooglePublisher]
 Publisher = Annotated[_Publisher, Field(discriminator="kind")]
 
 

test/assets/200170367.pem

@@ -0,0 +1,20 @@
+See: https://search.sigstore.dev/?logIndex=200170367
+
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

test/test_impl.py

@@ -668,7 +668,7 @@ def test_encoding(self) -> None:
         assert "\\n" not in model.model_dump_json()
 
 
-class TestGitHubublisher:
+class TestGitHubPublisher:
     def test_verifies_cert_with_missing_ref(self) -> None:
         cert_path = _ASSETS / "no-source-repository-ref-extension.pem"
         cert = x509.load_pem_x509_certificate(cert_path.read_bytes())
@@ -717,3 +717,14 @@ def test_fails_cert_with_no_digest_or_ref(self) -> None:
             ),
         ):
             publisher._as_policy().verify(cert)
+
+
+class TestGooglePublisher:
+    def test_verifies(self) -> None:
+        cert_path = _ASSETS / "200170367.pem"
+        cert = x509.load_pem_x509_certificate(cert_path.read_bytes())
+
+        publisher = impl.GooglePublisher(
+            email="919436158236-compute@developer.gserviceaccount.com",
+        )
+        publisher._as_policy().verify(cert)