Actually make Padding work

crypto.go

@@ -43,7 +43,7 @@ func DecryptAndVerify(input []byte, key *rsa.PrivateKey, pub *rsa.PublicKey, sig
 	body := make([]byte, len(encBody))
 	dec := cipher2.NewCBCDecrypter(cipher, iv)
 	dec.CryptBlocks(body, encBody)
-	err = json.Unmarshal(unpad(body), v)
+	err = json.Unmarshal(Unpad(body), v)
 
 	if err != nil {
 		return err
@@ -112,16 +112,16 @@ func EncryptAndSign(v interface{}, key *rsa.PrivateKey, pub *rsa.PublicKey, sign
 	enc := cipher2.NewCBCEncrypter(cipher, iv)
 	enc.CryptBlocks(encBody, body)
 
-	copy(pad(encBody), encBody[len(encBody):])
+	copy(encBody[len(encBody):], Pad(encBody))
 	writer.Write([]byte(hex.EncodeToString(encBody)))
 
 	return nil
 }
 
-func pad(body []byte) []byte {
+func Pad(body []byte) []byte {
 	rest := len(body) % 8
 	if rest == 0 {
-		padLen := getPad(body)
+		padLen := GetPad(body)
 		if padLen != 0 {
 			return []byte{8, 8, 8, 8, 8, 8, 8, 8}
 		}
@@ -129,36 +129,37 @@ func pad(body []byte) []byte {
 		return []byte{}
 	}
 
-	pad := make([]byte, rest)
+	padLen := 8 - rest
+	pad := make([]byte, padLen)
 
-	for i := 0; i < rest; i++ {
-		pad[i] = byte(rest)
+	for i := 0; i < padLen; i++ {
+		pad[i] = byte(padLen)
 	}
 
 	return pad
 }
 
-func getPad(body []byte) int {
+func GetPad(body []byte) int {
 	lastIndex := len(body) - 1
-	padLen := body[lastIndex]
+	padLen := int(body[lastIndex])
 	if 1 < padLen && padLen < 9 {
 		isPadding := true
 
-		for i := byte(0); i < padLen; i++ {
-			if body[-i] != padLen {
+		for i := 0; i < padLen; i++ {
+			if body[lastIndex-i] != byte(padLen) {
 				isPadding = false
 				break
 			}
 		}
 
 		if isPadding {
-			return int(padLen)
+			return padLen
 		}
 	}
 
 	return 0
 }
 
-func unpad(body []byte) []byte {
-	return body[:len(body)-getPad(body)]
+func Unpad(body []byte) []byte {
+	return body[:len(body)-GetPad(body)]
 }

crypto_test.go

@@ -8,6 +8,22 @@ import (
 	"testing"
 )
 
+func TestPadding(t *testing.T) {
+	x := []byte{0, 0, 0}
+	x = append(x, service.Pad(x)...)
+
+	padLen := service.GetPad(x)
+
+	if padLen != 5 {
+		t.Errorf("Failed adding/measuring padding, Pad(%v, len=%d)", x, padLen)
+	}
+
+	y := service.Unpad(x)
+	if len(y) != 3 {
+		t.Errorf("Failed padding and unpadding, Pad(%v), Unpad(%v)", x, y)
+	}
+}
+
 func TestSingleRound(t *testing.T) {
 	keyA, _ := rsa.GenerateKey(rand.Reader, 4096)
 	keyB, _ := rsa.GenerateKey(rand.Reader, 4096)