golint tidy

crypto/rfc4757/checksum.go

@@ -7,6 +7,7 @@ import (
 	"io"
 )
 
+// Checksum returns a hash of the data in accordance with RFC 4757
 func Checksum(key []byte, usage uint32, data []byte) ([]byte, error) {
 	// Create hashing key
 	s := append([]byte(`signaturekey`), byte(0x00)) //includes zero octet at end
@@ -15,7 +16,7 @@ func Checksum(key []byte, usage uint32, data []byte) ([]byte, error) {
 	Ksign := mac.Sum(nil)
 
 	// Format data
-	tb := MessageTypeBytes(usage)
+	tb := UsageToMSMsgType(usage)
 	p := append(tb, data...)
 	h := md5.New()
 	rb := bytes.NewReader(p)
@@ -31,6 +32,7 @@ func Checksum(key []byte, usage uint32, data []byte) ([]byte, error) {
 	return mac.Sum(nil), nil
 }
 
+// HMAC returns a keyed MD5 checksum of the data
 func HMAC(key []byte, data []byte) []byte {
 	mac := hmac.New(md5.New, key)
 	mac.Write(data)

crypto/rfc4757/encryption.go

@@ -40,7 +40,7 @@ func EncryptMessage(key, data []byte, usage uint32, export bool, e etype.EType)
 		return []byte{}, fmt.Errorf("Error generating confounder: %v", err)
 	}
 	k1 := key
-	k2 := HMAC(k1, MessageTypeBytes(usage))
+	k2 := HMAC(k1, UsageToMSMsgType(usage))
 	toenc := append(confounder, data...)
 	chksum := HMAC(k2, toenc)
 	k3 := HMAC(k2, chksum)

crypto/rfc4757/keyDerivation.go

@@ -48,7 +48,7 @@ func deriveKeys(key, checksum []byte, usage uint32, export bool) (k1, k2, k3 []b
 	//k3 = HMAC(k1, checksum)
 	//return
 	k1 = key
-	k2 = HMAC(k1, MessageTypeBytes(usage))
+	k2 = HMAC(k1, UsageToMSMsgType(usage))
 	k3 = HMAC(k2, checksum)
 	return
 }

crypto/rfc4757/msgtype.go

@@ -2,18 +2,19 @@ package rfc4757
 
 import "encoding/binary"
 
-func MessageTypeBytes(T uint32) []byte {
+// UsageToMSMsgType converts Kerberos key usage numbers to Microsoft message type encoded as a little-endian four byte slice.
+func UsageToMSMsgType(usage uint32) []byte {
 	// Translate usage numbers to the Microsoft T numbers
-	switch T {
+	switch usage {
 	case 3:
-		T = 8
+		usage = 8
 	case 9:
-		T = 8
+		usage = 8
 	case 23:
-		T = 13
+		usage = 13
 	}
 	// Now convert to bytes
 	tb := make([]byte, 4) // We force an int32 input so we can't go over 4 bytes
-	binary.PutUvarint(tb, uint64(T))
+	binary.PutUvarint(tb, uint64(usage))
 	return tb
 }