iam: GetUserPolicy returns NoSuchEntity for a policy name the user does not have (#11944)

* iam: GetUserPolicy returns NoSuchEntity for a policy name the user does not have

When the user has stored inline policies, an unknown name fell through to the
policy rebuilt from the user's actions, so a deleted policy still read back.
The standalone IAM server already returns NoSuchEntity here.

* iam: return service failure when listing inline policies fails

A ListUserInlinePolicies error in GetUserPolicy fell through to
action-based reconstruction, masking a store failure as a policy
document. Propagate it as ServiceFailureException instead, matching
the standalone iam server and the other callers in this file.

* iam: return service failure when the inline policy store read fails

---------

Co-authored-by: chrislusf <chrislusf@users.noreply.github.com>
Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

weed/s3api/s3api_embedded_iam.go

@@ -1291,9 +1291,9 @@ func (e *EmbeddedIamApi) GetUserPolicy(s3cfg *iam_pb.S3ApiConfiguration, values
 			ctx := context.Background()
 			storedDoc, storeErr := e.credentialManager.GetUserInlinePolicy(ctx, userName, policyName)
 			if storeErr != nil {
-				glog.Warningf("GetUserPolicy: failed to read stored inline policy %q for user %s: %v; falling back to reconstruction", policyName, userName, storeErr)
+				return resp, &iamError{Code: iam.ErrCodeServiceFailureException, Error: fmt.Errorf("get inline policy %s for %s: %w", policyName, userName, storeErr)}
 			}
-			if storeErr == nil && storedDoc != nil {
+			if storedDoc != nil {
 				policyDocumentJSON, err := json.Marshal(storedDoc)
 				if err != nil {
 					return resp, &iamError{Code: iam.ErrCodeServiceFailureException, Error: err}
@@ -1301,6 +1301,14 @@ func (e *EmbeddedIamApi) GetUserPolicy(s3cfg *iam_pb.S3ApiConfiguration, values
 				resp.GetUserPolicyResult.PolicyDocument = string(policyDocumentJSON)
 				return resp, nil
 			}
+			// The user has stored inline policies, but none by this name
+			policyNames, err := e.credentialManager.ListUserInlinePolicies(ctx, userName)
+			if err != nil {
+				return resp, &iamError{Code: iam.ErrCodeServiceFailureException, Error: fmt.Errorf("list inline policies for %s: %w", userName, err)}
+			}
+			if len(policyNames) > 0 {
+				return resp, &iamError{Code: iam.ErrCodeNoSuchEntityException, Error: fmt.Errorf("the user policy with name %s cannot be found", policyName)}
+			}
 		}
 
 		// Fallback: reconstruct from ident.Actions (lossy - fine-grained actions

weed/s3api/s3api_embedded_iam_test.go

@@ -1979,6 +1979,56 @@ func TestEmbeddedIamGetUserPolicyFallback(t *testing.T) {
 	assert.ElementsMatch(t, []string{"arn:aws:s3:::b-le*", "arn:aws:s3:::b-le*/*"}, stmt.Resource.Strings())
 }
 
+// TestEmbeddedIamGetUserPolicyMissingName checks that a policy name the user does not have
+// is NoSuchEntity, not a policy rebuilt from the user's other inline policies.
+func TestEmbeddedIamGetUserPolicyMissingName(t *testing.T) {
+	api := NewEmbeddedIamApiForTest()
+	s3cfg := &iam_pb.S3ApiConfiguration{
+		Identities: []*iam_pb.Identity{{Name: "steward"}},
+	}
+	api.mockConfig = s3cfg
+
+	_, iamErr := api.PutUserPolicy(s3cfg, url.Values{
+		"UserName":       []string{"steward"},
+		"PolicyName":     []string{"read"},
+		"PolicyDocument": []string{`{"Version":"2012-10-17","Statement":[{"Effect":"Allow","Action":"s3:GetObject","Resource":"arn:aws:s3:::b/*"}]}`},
+	})
+	require.Nil(t, iamErr)
+
+	_, iamErr = api.GetUserPolicy(s3cfg, url.Values{
+		"UserName":   []string{"steward"},
+		"PolicyName": []string{"write"},
+	})
+	require.NotNil(t, iamErr)
+	assert.Equal(t, iam.ErrCodeNoSuchEntityException, iamErr.Code)
+}
+
+// TestEmbeddedIamGetUserPolicyStoreError checks that a store failure surfaces as
+// ServiceFailure instead of rebuilding a policy from the identity's actions.
+func TestEmbeddedIamGetUserPolicyStoreError(t *testing.T) {
+	api := NewEmbeddedIamApiForTest()
+	s3cfg := &iam_pb.S3ApiConfiguration{
+		Identities: []*iam_pb.Identity{{Name: "steward"}},
+	}
+	api.mockConfig = s3cfg
+
+	_, iamErr := api.PutUserPolicy(s3cfg, url.Values{
+		"UserName":       []string{"steward"},
+		"PolicyName":     []string{"read"},
+		"PolicyDocument": []string{`{"Version":"2012-10-17","Statement":[{"Effect":"Allow","Action":"s3:GetObject","Resource":"arn:aws:s3:::b/*"}]}`},
+	})
+	require.Nil(t, iamErr)
+
+	api.credentialManager = &credential.CredentialManager{Store: &memory.MemoryStore{}}
+
+	_, iamErr = api.GetUserPolicy(s3cfg, url.Values{
+		"UserName":   []string{"steward"},
+		"PolicyName": []string{"read"},
+	})
+	require.NotNil(t, iamErr)
+	assert.Equal(t, iam.ErrCodeServiceFailureException, iamErr.Code)
+}
+
 // TestEmbeddedIamGetUserPolicyUserNotFound tests GetUserPolicy with non-existent user
 func TestEmbeddedIamGetUserPolicyUserNotFound(t *testing.T) {
 	api := NewEmbeddedIamApiForTest()