split b58 checksum validation from address validation

address/base58/character.go

@@ -1,8 +1,8 @@
 package base58
 
 import (
-	"math/big"
 	"errors"
+	"math/big"
 )
 
 var b58_characters = [58]byte{0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x41, 0x42, 0x43, 0x44, 0x45,
@@ -11,7 +11,6 @@ var b58_characters = [58]byte {0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0
 	0x6a, 0x6b, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
 	0x79, 0x7a}
 
-
 func CharacterIndex(character byte) (*big.Int, error) {
 	for i := 0; i < 58; i++ {
 		if b58_characters[i] == character {

address/base58/checksum.go

@@ -0,0 +1,20 @@
+package base58
+
+import "crypto/sha256"
+
+const checksum_length = 4
+
+func VerifyBase58Checksum(v []byte) bool {
+	checksum := [checksum_length]byte{}
+	for i := range checksum {
+		checksum[i] = v[len(v)-checksum_length+i]
+	}
+	real_checksum := sha256.Sum256(v[:len(v)-checksum_length])
+	real_checksum = sha256.Sum256(real_checksum[:])
+	for i, c := range checksum {
+		if c != real_checksum[i] {
+			return false
+		}
+	}
+	return true
+}

address/base58/decode.go

@@ -1,8 +1,8 @@
 package base58
 
 import (
-	"math/big"
 	"errors"
+	"math/big"
 )
 
 func DecodeBase58(value string, size int64) ([]byte, error) {
@@ -32,5 +32,8 @@ func DecodeBase58(value string, size int64) ([]byte, error) {
 	if long_value.Int64() != 0 {
 		return result, errors.New("cannot decode to the given size")
 	}
+	if size != int64(len(result)) {
+		return result, errors.New("length mismatch")
+	}
 	return result, nil
 }

address/base58/encode.go

@@ -4,7 +4,7 @@ import (
 	"math/big"
 )
 
-func EncodeBase58(data []byte) (string) {
+func EncodeBase58(data []byte) string {
 	long_value := big.NewInt(0)
 	result := ""
 	for i := 0; i < len(data); i++ {

address/decode.go

@@ -14,5 +14,6 @@ func DecodeAddress(address string, blockchainName string) ([address_length]byte,
 	for i, b := range decoded {
 		buf[i] = b
 	}
+
 	return ValidateAddress(buf, blockchainName)
 }

address/validate.go

@@ -1,7 +1,7 @@
 package address
 
 import (
-	"crypto/sha256"
+	"./base58"
 	"errors"
 )
 
@@ -48,19 +48,8 @@ func PubKeyIsValid(address [address_length]byte) bool {
 	return true
 }
 
-func ChecksumIsValid(address [address_length]byte) bool {
-	checksum := [checksum_length]byte{}
-	for i := range checksum {
-		checksum[i] = address[prefix_length+pubkey_length+i]
-	}
-	real_checksum := sha256.Sum256(address[:prefix_length+pubkey_length])
-	real_checksum = sha256.Sum256(real_checksum[:])
-	for i, c := range checksum {
-		if c != real_checksum[i] {
-			return false
-		}
-	}
-	return true
+func AddressChecksumIsValid(address [address_length]byte) bool {
+	return base58.VerifyBase58Checksum(address[:])
 }
 
 func ValidateAddress(address [address_length]byte, blockchainName string) ([address_length]byte, error) {
@@ -73,7 +62,7 @@ func ValidateAddress(address [address_length]byte, blockchainName string) ([addr
 	if !PubKeyIsValid(address) {
 		return address, errors.New("invalid pubkey")
 	}
-	if !ChecksumIsValid(address) {
+	if !AddressChecksumIsValid(address) {
 		return address, errors.New("invalid address checksum")
 	}
 	return address, nil