Better API for ValidatedProvenance

experimental/auth-logic/wrappers/provenance_build_wrapper.go

@@ -45,17 +45,15 @@ func (pbw ProvenanceBuildWrapper) EmitStatement() (UnattributedStatement, error)
 		return UnattributedStatement{}, fmt.Errorf("provenance build wrapper couldn't parse provenance file: %v", err)
 	}
 
-	provenance := validatedProvenance.GetProvenance()
-
 	// TODO(#69): Set the verifier as a field in pbw, and use that here.
 	verifier := verify.AmberProvenanceMetadataVerifier{}
 	if err := verifier.Verify(pbw.ProvenanceFilePath); err != nil {
 		return UnattributedStatement{}, fmt.Errorf("verification of the provenance file failed: %v", err)
 	}
 
 	simpleProv := simplifiedProvenance{
-		AppName:        SanitizeName(provenance.Subject[0].Name),
-		MeasuredSha256: provenance.Subject[0].Digest["sha256"],
+		AppName:        SanitizeName(validatedProvenance.GetBinaryName()),
+		MeasuredSha256: validatedProvenance.GetBinarySHA256Hash(),
 	}
 
 	policyTemplate, err := template.ParseFiles(provenanceBuilderTemplate)

experimental/auth-logic/wrappers/provenance_wrapper.go

@@ -37,14 +37,10 @@ func (p ProvenanceWrapper) EmitStatement() (UnattributedStatement, error) {
 		return UnattributedStatement{}, fmt.Errorf("provenance wrapper couldn't prase provenance file: %v", err)
 	}
 
-	provenance := validatedProvenance.GetProvenance()
-	sanitizedAppName := SanitizeName(provenance.Subject[0].Name)
-	expectedHash, hashOk := provenance.Subject[0].Digest["sha256"]
-
-	if !hashOk {
-		return UnattributedStatement{}, fmt.Errorf("provenance file did not give an expected hash")
-	}
+	sanitizedAppName := SanitizeName(validatedProvenance.GetBinaryName())
+	expectedHash := validatedProvenance.GetBinarySHA256Hash()
 
+	provenance := validatedProvenance.GetProvenance()
 	predicate := provenance.Predicate.(slsa.ProvenancePredicate)
 	builderName := predicate.Builder.ID
 
@@ -66,5 +62,5 @@ func GetAppNameFromProvenance(provenanceFilePath string) (string, error) {
 		return "", fmt.Errorf("provenance wrapper couldn't prase provenance file: %v", err)
 	}
 
-	return validatedProvenance.GetProvenance().Subject[0].Name, nil
+	return validatedProvenance.GetBinaryName(), nil
 }

internal/verifier/verifier.go

@@ -43,6 +43,7 @@ type ReproducibleProvenanceVerifier struct {
 // it and verifying that the resulting binary has a hash equal to the one
 // specified in the subject of the given provenance file. If the hashes are
 // different returns an error, otherwise returns nil.
+// TODO(#126): Refactor and separate verification logic from the logic for reading the file.
 func (verifier *ReproducibleProvenanceVerifier) Verify(provenanceFilePath string) error {
 	provenance, err := amber.ParseProvenanceFile(provenanceFilePath)
 	if err != nil {
@@ -68,7 +69,7 @@ func (verifier *ReproducibleProvenanceVerifier) Verify(provenanceFilePath string
 	}
 
 	// The provenance is valid, therefore `expectedBinaryHash` is guaranteed to be non-empty.
-	expectedBinaryHash := provenance.GetProvenance().Subject[0].Digest["sha256"]
+	expectedBinaryHash := provenance.GetBinarySHA256Hash()
 
 	if err := buildConfig.VerifyBinarySha256Hash(expectedBinaryHash); err != nil {
 		return fmt.Errorf("failed to verify the hash of the built binary: %v", err)

internal/verifier/verifier_test.go

@@ -56,8 +56,8 @@ func TestReproducibleProvenanceVerifier_invalidHash(t *testing.T) {
 
 	want := "failed to verify the hash of the built binary"
 
-	if err := verifier.Verify(invalidHashProvenancePath); !strings.Contains(err.Error(), want) {
-		t.Fatalf("want error containing message %q, got %v", want, err)
+	if got := verifier.Verify(invalidHashProvenancePath); !strings.Contains(got.Error(), want) {
+		t.Fatalf("got %v, want error message containing %q,", got, want)
 	}
 }
 
@@ -75,8 +75,8 @@ func TestReproducibleProvenanceVerifier_badCommand(t *testing.T) {
 
 	want := "couldn't build the binary"
 
-	if err := verifier.Verify(badCommandProvenancePath); !strings.Contains(err.Error(), want) {
-		t.Fatalf("want error containing message %q, got %v", want, err)
+	if got := verifier.Verify(badCommandProvenancePath); !strings.Contains(got.Error(), want) {
+		t.Fatalf("got %v, want error message containing %q,", got, want)
 	}
 }
 

pkg/amber/provenance.go

@@ -72,6 +72,16 @@ func (p *ValidatedProvenance) GetProvenance() intoto.Statement {
 	}
 }
 
+// GetBinarySHA256Hash returns the SHA256 hash of the subject.
+func (p *ValidatedProvenance) GetBinarySHA256Hash() string {
+	return p.provenance.Subject[0].Digest["sha256"]
+}
+
+// GetBinaryName returns the name of the subject.
+func (p *ValidatedProvenance) GetBinaryName() string {
+	return p.provenance.Subject[0].Name
+}
+
 func validateSLSAProvenanceJSON(provenanceFile []byte) error {
 	schemaFile, err := os.ReadFile(SchemaPath)
 	if err != nil {

pkg/amber/provenance_test.go

@@ -54,7 +54,7 @@ func TestExampleProvenance(t *testing.T) {
 	testutil.AssertEq(t, "commitHash length", len(predicate.Materials[1].Digest["sha1"]), wantSHA1HexDigitLength)
 	testutil.AssertEq(t, "builderImageID length", len(predicate.Materials[0].Digest["sha256"]), wantSHA256HexDigitLength)
 	testutil.AssertEq(t, "builderImageURI", predicate.Materials[0].URI, fmt.Sprintf("gcr.io/oak-ci/oak@sha256:%s", predicate.Materials[0].Digest["sha256"]))
-	testutil.AssertEq(t, "subjectName", provenance.Subject[0].Name, "oak_functions_loader")
+	testutil.AssertEq(t, "subjectName", validatedProvenance.GetBinaryName(), "oak_functions_loader")
 	testutil.AssertNonEmpty(t, "command[0]", buildConfig.Command[0])
 	testutil.AssertNonEmpty(t, "command[1]", buildConfig.Command[1])
 	testutil.AssertNonEmpty(t, "builderId", predicate.Builder.ID)