From afb8154eab2961996b321ac3fe5a21602e3b1aff Mon Sep 17 00:00:00 2001
From: Steven Roose <stevenroose@gmail.com>
Date: Mon, 4 Dec 2017 19:34:15 +0100
Subject: [PATCH] common: improve IsHexAddress and add tests (#15551)

Also unexport isHex, hasHexPrefix because IsHexAddress is the only caller.

Fixes #15550
---
 common/bytes.go      | 26 +++++++++++++++++---------
 common/bytes_test.go | 34 +++++++++++++++++++++-------------
 common/types.go      |  9 +++------
 common/types_test.go | 24 ++++++++++++++++++++++++
 4 files changed, 65 insertions(+), 28 deletions(-)

diff --git a/common/bytes.go b/common/bytes.go
index bb40ac1d70..ba00e8a4b2 100644
--- a/common/bytes.go
+++ b/common/bytes.go
@@ -17,9 +17,7 @@
 // Package common contains various helper functions.
 package common
 
-import (
-	"encoding/hex"
-)
+import "encoding/hex"
 
 func ToHex(b []byte) string {
 	hex := Bytes2Hex(b)
@@ -55,14 +53,24 @@ func CopyBytes(b []byte) (copiedBytes []byte) {
 	return
 }
 
-func HasHexPrefix(str string) bool {
-	l := len(str)
-	return l >= 2 && str[0:2] == "0x"
+func hasHexPrefix(str string) bool {
+	return len(str) >= 2 && str[0] == '0' && (str[1] == 'x' || str[1] == 'X')
 }
 
-func IsHex(str string) bool {
-	l := len(str)
-	return l >= 4 && l%2 == 0 && str[0:2] == "0x"
+func isHexCharacter(c byte) bool {
+	return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F')
+}
+
+func isHex(str string) bool {
+	if len(str)%2 != 0 {
+		return false
+	}
+	for _, c := range []byte(str) {
+		if !isHexCharacter(c) {
+			return false
+		}
+	}
+	return true
 }
 
 func Bytes2Hex(d []byte) string {
diff --git a/common/bytes_test.go b/common/bytes_test.go
index 71631e6dd7..97dd34d159 100644
--- a/common/bytes_test.go
+++ b/common/bytes_test.go
@@ -34,19 +34,6 @@ func (s *BytesSuite) TestCopyBytes(c *checker.C) {
 	c.Assert(res1, checker.DeepEquals, exp1)
 }
 
-func (s *BytesSuite) TestIsHex(c *checker.C) {
-	data1 := "a9e67e"
-	exp1 := false
-	res1 := IsHex(data1)
-	c.Assert(res1, checker.DeepEquals, exp1)
-
-	data2 := "0xa9e67e00"
-	exp2 := true
-	res2 := IsHex(data2)
-	c.Assert(res2, checker.DeepEquals, exp2)
-
-}
-
 func (s *BytesSuite) TestLeftPadBytes(c *checker.C) {
 	val1 := []byte{1, 2, 3, 4}
 	exp1 := []byte{0, 0, 0, 0, 1, 2, 3, 4}
@@ -78,6 +65,27 @@ func TestFromHex(t *testing.T) {
 	}
 }
 
+func TestIsHex(t *testing.T) {
+	tests := []struct {
+		input string
+		ok    bool
+	}{
+		{"", true},
+		{"0", false},
+		{"00", true},
+		{"a9e67e", true},
+		{"A9E67E", true},
+		{"0xa9e67e", false},
+		{"a9e67e001", false},
+		{"0xHELLO_MY_NAME_IS_STEVEN_@#$^&*", false},
+	}
+	for _, test := range tests {
+		if ok := isHex(test.input); ok != test.ok {
+			t.Errorf("isHex(%q) = %v, want %v", test.input, ok, test.ok)
+		}
+	}
+}
+
 func TestFromHexOddLength(t *testing.T) {
 	input := "0x1"
 	expected := []byte{1}
diff --git a/common/types.go b/common/types.go
index d31bbf741b..fdc67480c2 100644
--- a/common/types.go
+++ b/common/types.go
@@ -150,13 +150,10 @@ func HexToAddress(s string) Address    { return BytesToAddress(FromHex(s)) }
 // IsHexAddress verifies whether a string can represent a valid hex-encoded
 // Ethereum address or not.
 func IsHexAddress(s string) bool {
-	if len(s) == 2+2*AddressLength && IsHex(s) {
-		return true
+	if hasHexPrefix(s) {
+		s = s[2:]
 	}
-	if len(s) == 2*AddressLength && IsHex("0x"+s) {
-		return true
-	}
-	return false
+	return len(s) == 2*AddressLength && isHex(s)
 }
 
 // Get the string representation of the underlying address
diff --git a/common/types_test.go b/common/types_test.go
index 6f3b315761..db636812ce 100644
--- a/common/types_test.go
+++ b/common/types_test.go
@@ -35,6 +35,30 @@ func TestBytesConversion(t *testing.T) {
 	}
 }
 
+func TestIsHexAddress(t *testing.T) {
+	tests := []struct {
+		str string
+		exp bool
+	}{
+		{"0x5aaeb6053f3e94c9b9a09f33669435e7ef1beaed", true},
+		{"5aaeb6053f3e94c9b9a09f33669435e7ef1beaed", true},
+		{"0X5aaeb6053f3e94c9b9a09f33669435e7ef1beaed", true},
+		{"0XAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA", true},
+		{"0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA", true},
+		{"0x5aaeb6053f3e94c9b9a09f33669435e7ef1beaed1", false},
+		{"0x5aaeb6053f3e94c9b9a09f33669435e7ef1beae", false},
+		{"5aaeb6053f3e94c9b9a09f33669435e7ef1beaed11", false},
+		{"0xxaaeb6053f3e94c9b9a09f33669435e7ef1beaed", false},
+	}
+
+	for _, test := range tests {
+		if result := IsHexAddress(test.str); result != test.exp {
+			t.Errorf("IsHexAddress(%s) == %v; expected %v",
+				test.str, result, test.exp)
+		}
+	}
+}
+
 func TestHashJsonValidation(t *testing.T) {
 	var tests = []struct {
 		Prefix string