Emit metrics on GitHub event_name claim

tests/unit/oidc/models/test_github.py

@@ -338,7 +338,7 @@ def test_github_publisher_missing_claims(self, monkeypatch, missing):
         ]
         assert scope.fingerprint == [missing]
 
-    def test_github_publisher_missing_optional_claims(self, monkeypatch):
+    def test_github_publisher_missing_optional_claims(self, metrics, monkeypatch):
         publisher = github.GitHubPublisher(
             repository_name="fakerepo",
             repository_owner="fakeowner",
@@ -352,6 +352,7 @@ def test_github_publisher_missing_optional_claims(self, monkeypatch):
 
         service_ = pretend.stub(
             jwt_identifier_exists=pretend.call_recorder(lambda s: False),
+            metrics=metrics,
         )
 
         signed_claims = {
@@ -433,6 +434,23 @@ def test_check_repository(self, truth, claim, valid):
         check = github.GitHubPublisher.__required_verifiable_claims__["repository"]
         assert check(truth, claim, pretend.stub()) == valid
 
+    def test_check_event_name_emits_metrics(self, metrics):
+        check = github.GitHubPublisher.__required_verifiable_claims__["event_name"]
+        publisher_service = pretend.stub(metrics=metrics)
+
+        assert check(
+            "throwaway",
+            "pull_request_target",
+            pretend.stub(),
+            publisher_service=publisher_service,
+        )
+        assert metrics.increment.calls == [
+            pretend.call(
+                "warehouse.oidc.claim",
+                tags=["publisher:GitHub", "event_name:pull_request_target"],
+            ),
+        ]
+
     @pytest.mark.parametrize(
         ("claim", "ref", "sha", "valid", "expected"),
         [

warehouse/oidc/models/github.py

@@ -28,6 +28,8 @@
 if typing.TYPE_CHECKING:
     from sqlalchemy.orm import Session
 
+    from warehouse.oidc.services import OIDCPublisherService
+
 GITHUB_OIDC_ISSUER_URL = "https://token.actions.githubusercontent.com"
 
 # This expression matches the workflow filename component of a GitHub
@@ -152,6 +154,18 @@ def _check_sub(
     return f"{org}:{repo}".lower() == ground_truth.lower()
 
 
+def _check_event_name(
+    ground_truth: str, signed_claim: str, _all_signed_claims: SignedClaims, **kwargs
+) -> bool:
+    # Log the event name
+    publisher_service: OIDCPublisherService = kwargs["publisher_service"]
+    publisher_service.metrics.increment(
+        "warehouse.oidc.claim", tags=["publisher:GitHub", f"event_name:{signed_claim}"]
+    )
+    # Always permit all event names for now
+    return True
+
+
 class GitHubPublisherMixin:
     """
     Common functionality for both pending and concrete GitHub OIDC publishers.
@@ -170,6 +184,7 @@ class GitHubPublisherMixin:
         "repository_owner_id": check_claim_binary(str.__eq__),
         "job_workflow_ref": _check_job_workflow_ref,
         "jti": check_existing_jti,
+        "event_name": _check_event_name,
     }
 
     __required_unverifiable_claims__: set[str] = {"ref", "sha"}
@@ -186,7 +201,6 @@ class GitHubPublisherMixin:
         "run_attempt",
         "head_ref",
         "base_ref",
-        "event_name",
         "ref_type",
         "repository_id",
         "workflow",
@@ -275,6 +289,11 @@ def jti(self) -> str:
         """Placeholder value for JTI."""
         return "placeholder"
 
+    @property
+    def event_name(self) -> str:
+        """Placeholder value for event_name (not used)"""
+        return "placeholder"
+
     def publisher_url(self, claims: SignedClaims | None = None) -> str:
         base = self.publisher_base_url
         sha = claims.get("sha") if claims else None