go: make LogID a struct type to match RFC

client/logclient.go

@@ -57,8 +57,8 @@ func (c *LogClient) addChainWithRetry(ctx context.Context, ctype ct.LogEntryType
 		return nil, err
 	}
 
-	var logID ct.SHA256Hash
-	copy(logID[:], resp.ID)
+	var logID ct.LogID
+	copy(logID.KeyID[:], resp.ID)
 	sct := &ct.SignedCertificateTimestamp{
 		SCTVersion: resp.SCTVersion,
 		LogID:      logID,
@@ -94,8 +94,8 @@ func (c *LogClient) AddJSON(ctx context.Context, data interface{}) (*ct.SignedCe
 	if err != nil {
 		return nil, err
 	}
-	var logID ct.SHA256Hash
-	copy(logID[:], resp.ID)
+	var logID ct.LogID
+	copy(logID.KeyID[:], resp.ID)
 	return &ct.SignedCertificateTimestamp{
 		SCTVersion: resp.SCTVersion,
 		LogID:      logID,

serialization.go

@@ -467,7 +467,7 @@ func serializeV1SCTHere(sct SignedCertificateTimestamp, here []byte) ([]byte, er
 	here[0] = byte(sct.SCTVersion)
 
 	// Write LogID
-	copy(here[1:33], sct.LogID[:])
+	copy(here[1:33], sct.LogID.KeyID[:])
 
 	// Write Timestamp
 	binary.BigEndian.PutUint64(here[33:41], sct.Timestamp)

serialization_test.go

@@ -249,9 +249,9 @@ const (
 	defaultSCTListHexString string = "0476007400380069616d617075626c69636b657973686174776f6669766573697864696765737400000000000004d20000040300097369676e617475726500380069616d617075626c69636b657973686174776f6669766573697864696765737400000000000004d20000040300097369676e6174757265"
 )
 
-func defaultSCTLogID() SHA256Hash {
-	var id SHA256Hash
-	copy(id[:], defaultSCTLogIDString)
+func defaultSCTLogID() LogID {
+	var id LogID
+	copy(id.KeyID[:], defaultSCTLogIDString)
 	return id
 }
 

signatures_test.go

@@ -143,8 +143,8 @@ func sigTestSCTWithSignature(t *testing.T, sig, keyID string) SignedCertificateT
 	if err != nil {
 		t.Fatalf("Failed to unmarshal sigTestCertSCTSignatureEC: %v", err)
 	}
-	var id SHA256Hash
-	copy(id[:], mustDehex(t, keyID))
+	var id LogID
+	copy(id.KeyID[:], mustDehex(t, keyID))
 	return SignedCertificateTimestamp{
 		SCTVersion: V1,
 		LogID:      id,

types.go

@@ -103,6 +103,11 @@ func (st SignatureType) String() string {
 // (section 3.1).
 type ASN1Cert []byte
 
+// LogID holds the hash of the Log's public key (section 3.2).
+type LogID struct {
+	KeyID [32]byte
+}
+
 // PreCert represents a Precertificate (section 3.2).
 type PreCert struct {
 	IssuerKeyHash  [issuerKeyHashLength]byte
@@ -237,15 +242,15 @@ type SignedTreeHead struct {
 // 3.2, 4.1 and 4.2.
 type SignedCertificateTimestamp struct {
 	SCTVersion Version         // The version of the protocol to which the SCT conforms
-	LogID      SHA256Hash      // The SHA-256 hash of the (DER-encoded) public key for the Log
+	LogID      LogID           // The SHA-256 hash of the (DER-encoded) public key for the Log
 	Timestamp  uint64          // Timestamp (in ms since unix epoch) at which the SCT was issued
 	Extensions CTExtensions    // For future extensions to the protocol
 	Signature  DigitallySigned // The Log's signature for this SCT
 }
 
 func (s SignedCertificateTimestamp) String() string {
 	return fmt.Sprintf("{Version:%d LogId:%s Timestamp:%d Extensions:'%s' Signature:%v}", s.SCTVersion,
-		base64.StdEncoding.EncodeToString(s.LogID[:]),
+		base64.StdEncoding.EncodeToString(s.LogID.KeyID[:]),
 		s.Timestamp,
 		s.Extensions,
 		s.Signature)