Merge pull request #658 from HuKeping/error-types

Error types

tuf/data/errors.go

@@ -20,3 +20,21 @@ type ErrMissingMeta struct {
 func (e ErrMissingMeta) Error() string {
 	return fmt.Sprintf("tuf: sha256 checksum required for %s", e.Role)
 }
+
+// ErrInvalidChecksum is the error to be returned when checksum is invalid
+type ErrInvalidChecksum struct {
+	alg string
+}
+
+func (e ErrInvalidChecksum) Error() string {
+	return fmt.Sprintf("%s checksum invalid", e.alg)
+}
+
+// ErrMismatchedChecksum is the error to be returned when checksum is mismatched
+type ErrMismatchedChecksum struct {
+	alg string
+}
+
+func (e ErrMismatchedChecksum) Error() string {
+	return fmt.Sprintf("%s checksum mismatched", e.alg)
+}

tuf/data/types.go

@@ -141,13 +141,13 @@ func CheckHashes(payload []byte, hashes Hashes) error {
 		case notary.SHA256:
 			checksum := sha256.Sum256(payload)
 			if subtle.ConstantTimeCompare(checksum[:], v) == 0 {
-				return fmt.Errorf("%s checksum mismatched", k)
+				return ErrMismatchedChecksum{alg: notary.SHA256}
 			}
 			cnt++
 		case notary.SHA512:
 			checksum := sha512.Sum512(payload)
 			if subtle.ConstantTimeCompare(checksum[:], v) == 0 {
-				return fmt.Errorf("%s checksum mismatched", k)
+				return ErrMismatchedChecksum{alg: notary.SHA512}
 			}
 			cnt++
 		}
@@ -169,12 +169,12 @@ func CheckValidHashStructures(hashes Hashes) error {
 		switch k {
 		case notary.SHA256:
 			if len(v) != sha256.Size {
-				return fmt.Errorf("invalid %s checksum", notary.SHA256)
+				return ErrInvalidChecksum{alg: notary.SHA256}
 			}
 			cnt++
 		case notary.SHA512:
 			if len(v) != sha512.Size {
-				return fmt.Errorf("invalid %s checksum", notary.SHA512)
+				return ErrInvalidChecksum{alg: notary.SHA512}
 			}
 			cnt++
 		}

tuf/data/types_test.go

@@ -102,15 +102,13 @@ func TestCheckHashes(t *testing.T) {
 	malicious256 := make(Hashes)
 	malicious256["sha256"] = []byte("malicious data")
 	err = CheckHashes(raw, malicious256)
-	require.Error(t, err)
-	require.Contains(t, err.Error(), "checksum mismatched")
+	require.IsType(t, ErrMismatchedChecksum{}, err)
 
 	// Expected to fail due to the failure of sha512
 	malicious512 := make(Hashes)
 	malicious512["sha512"] = []byte("malicious data")
 	err = CheckHashes(raw, malicious512)
-	require.Error(t, err)
-	require.Contains(t, err.Error(), "checksum mismatched")
+	require.IsType(t, ErrMismatchedChecksum{}, err)
 
 	// Expected to fail because of the failure of sha512
 	// even though the sha256 is OK.
@@ -120,8 +118,7 @@ func TestCheckHashes(t *testing.T) {
 	doubleFace["sha512"], err = hex.DecodeString("d13e2b60d74c2e6f4f449b5e536814edf9a4827f5a9f4f957fc92e77609b9c92")
 	require.NoError(t, err)
 	err = CheckHashes(raw, doubleFace)
-	require.Error(t, err)
-	require.Contains(t, err.Error(), "checksum mismatched")
+	require.IsType(t, ErrMismatchedChecksum{}, err)
 }
 
 func TestCheckValidHashStructures(t *testing.T) {
@@ -158,6 +155,5 @@ func TestCheckValidHashStructures(t *testing.T) {
 	// Should failed since the first '0' is missing.
 	hashes["sha256"], err = hex.DecodeString("1234567890a4f2307e49160fa242db6fb95f071ad81a198eeb7d770e61cd6d8")
 	err = CheckValidHashStructures(hashes)
-	require.Error(t, err)
-	require.Contains(t, err.Error(), "invalid")
+	require.IsType(t, ErrInvalidChecksum{}, err)
 }