package tools
import (
"encoding/binary"
"encoding/hex"
"regexp"
)
func PatchBinary(input []byte) []byte {
if input == nil {
return nil
}
stringCode := hex.EncodeToString(input)
stringCode = Patch(stringCode)
result, _ := hex.DecodeString(stringCode)
return result
}
func patchPattern1(input string) string {
// Case 1
// PUSH1 v1 DUP1 PUSH1 v2 PUSH1 v3 CODECOPY
// we have to set v1 = v1 + 1
r, _ := regexp.Compile("60..8060..60..39")
loc := r.FindStringIndex(input)
if len(loc) > 0 {
valLoc := loc[0]/2 + 1
bString, _ := hex.DecodeString(input)
bString[valLoc]++
input = hex.EncodeToString(bString)
}
return input
}
func patchPattern2(input string) string {
// Case 2
// PUSH2 v1 v2 DUP1 PUSH2 v3 PUSH1 v4 CODECOPY
// we have to set BigEndian(v1,v2)++
r, _ := regexp.Compile("61....8061....60..39")
loc := r.FindStringIndex(input)
if len(loc) > 0 {
valLoc := loc[0]/2 + 1
bString, _ := hex.DecodeString(input)
val := binary.BigEndian.Uint16(bString[valLoc : valLoc+2])
val++
binary.BigEndian.PutUint16(bString[valLoc:], val)
input = hex.EncodeToString(bString)
}
return input
}
func patchPattern3(input string) string {
// Case 3
// PUSH1 v1 DUP1 PUSH3 v2 v3 v4 DUP4 CODECOPY
// we have to set BigEndian(v2,v3,v4)++
r, _ := regexp.Compile("60..8062......8339")
loc := r.FindStringIndex(input)
if len(loc) > 0 {
valLoc := loc[0]/2 + 4
bString, _ := hex.DecodeString(input)
toConvert := append([]byte{0}, bString[valLoc:valLoc+3]...)
tmpBinary := make([]byte, 4)
val := binary.BigEndian.Uint32(toConvert)
val--
binary.BigEndian.PutUint32(tmpBinary, val)
bString[valLoc] = tmpBinary[1]
bString[valLoc+1] = tmpBinary[2]
bString[valLoc+2] = tmpBinary[3]
input = hex.EncodeToString(bString)
}
return input
}
func patchPattern4(input string) string {
// Case 4
// PUSH2 v1 v2 DUP1 PUSH2 v3 DUP4 CODECOPY
// we have to set BigEndian(v1,v2)+2
r, _ := regexp.Compile("61....8061....8339")
loc := r.FindStringIndex(input)
if len(loc) > 0 {
valLoc := loc[0]/2 + 1
bString, _ := hex.DecodeString(input)
val := binary.BigEndian.Uint16(bString[valLoc : valLoc+2])
val = val + 2
binary.BigEndian.PutUint16(bString[valLoc:], val)
input = hex.EncodeToString(bString)
}
return input
}
func patchPattern5(input string) string {
// Case 5
// PUSH1 v1 DUP1 PUSH2 v2 v3 DUP4 CODECOPY
// we have to set BigEndian(v2,v3)++
r, _ := regexp.Compile("60..8061....8339")
loc := r.FindStringIndex(input)
if len(loc) > 0 {
valLoc := loc[0]/2 + 4
bString, _ := hex.DecodeString(input)
val := binary.BigEndian.Uint16(bString[valLoc : valLoc+2])
val = val + 1
binary.BigEndian.PutUint16(bString[valLoc:], val)
input = hex.EncodeToString(bString)
}
return input
}
func patchPattern6(input string) string {
// Case 6
// SUB DUP1 PUSH2 v2 v3 DUP4 CODECOPY
// we have to set BigEndian(v2,v3)++
r, _ := regexp.Compile("038061....8339")
loc := r.FindStringIndex(input)
if len(loc) > 0 {
valLoc := loc[0]/2 + 3
bString, _ := hex.DecodeString(input)
val := binary.BigEndian.Uint16(bString[valLoc : valLoc+2])
val = val + 1
binary.BigEndian.PutUint16(bString[valLoc:], val)
input = hex.EncodeToString(bString)
}
return input
}
func addPrefix(input string) string {
r, _ := regexp.Compile("6060604052")
loc := r.FindAllStringIndex(input, -1)
if len(loc) > 0 {
for i, offset := range loc {
insertLoc := offset[0] + i*2
if !isDelegateCall(input, insertLoc) {
input = input[:insertLoc] + "00" + input[insertLoc:]
}
}
if input[0:2] != "00" {
input = "00" + input
}
}
return input
}
func isDelegateCall(input string, codeStartAt int) bool {
delegateCallPrefix := "6504032353da7150"
prefixLen := len(delegateCallPrefix)
newStartAt := codeStartAt - prefixLen
if newStartAt >= 0 {
if input[newStartAt:newStartAt+prefixLen] == delegateCallPrefix {
return true
}
}
return false
}
// Patch patch lagacy bytecode(hex string) to new vm interface compatible bytecode
func Patch(input string) string {
if len(input) == 0 {
return input
}
input = patchPattern1(input)
input = patchPattern2(input)
input = patchPattern3(input)
input = patchPattern4(input)
input = patchPattern5(input)
input = patchPattern6(input)
result := addPrefix(input)
return result
}
