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fix(decryption): eliminate data race in JPK decompression

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Package-level globals mShiftIndex and mFlag were shared across
concurrent goroutines calling UnpackSimple from quest handlers.
Replace with a local jpkState struct scoped to each decompression
call. Add concurrent safety test validated with -race.
This commit is contained in:
Houmgaor
2026-02-23 20:01:38 +01:00
parent f712e3c04d
commit 7af41a7796
2 changed files with 56 additions and 30 deletions
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43
common/decryption/jpk.go
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@@ -10,15 +10,16 @@ import (
"io"
)
var mShiftIndex = 0
var mFlag = byte(0)
// jpkState holds the mutable bit-reader state for a single JPK decompression.
// This is local to each call, making concurrent UnpackSimple calls safe.
type jpkState struct {
shiftIndex int
flag byte
}
// UnpackSimple decompresses a JPK type-3 compressed byte slice. If the data
// does not start with the JKR magic header it is returned unchanged.
func UnpackSimple(data []byte) []byte {
mShiftIndex = 0
mFlag = byte(0)
bf := byteframe.NewByteFrameFromBytes(data)
bf.SetLE()
header := bf.ReadUint32()
@@ -33,7 +34,8 @@ func UnpackSimple(data []byte) []byte {
outSize := bf.ReadInt32()
outBuffer := make([]byte, outSize)
_, _ = bf.Seek(int64(startOffset), io.SeekStart)
ProcessDecode(bf, outBuffer)
s := &jpkState{}
s.processDecode(bf, outBuffer)
return outBuffer
}
@@ -45,16 +47,21 @@ func UnpackSimple(data []byte) []byte {
// ProcessDecode runs the JPK LZ-style decompression loop, reading compressed
// tokens from data and writing decompressed bytes into outBuffer.
func ProcessDecode(data *byteframe.ByteFrame, outBuffer []byte) {
s := &jpkState{}
s.processDecode(data, outBuffer)
}
func (s *jpkState) processDecode(data *byteframe.ByteFrame, outBuffer []byte) {
outIndex := 0
for int(data.Index()) < len(data.Data()) && outIndex < len(outBuffer)-1 {
if JPKBitShift(data) == 0 {
if s.bitShift(data) == 0 {
outBuffer[outIndex] = ReadByte(data)
outIndex++
continue
} else {
if JPKBitShift(data) == 0 {
length := (JPKBitShift(data) << 1) | JPKBitShift(data)
if s.bitShift(data) == 0 {
length := (s.bitShift(data) << 1) | s.bitShift(data)
off := ReadByte(data)
JPKCopy(outBuffer, int(off), int(length)+3, &outIndex)
continue
@@ -67,8 +74,8 @@ func ProcessDecode(data *byteframe.ByteFrame, outBuffer []byte) {
JPKCopy(outBuffer, off, length+2, &outIndex)
continue
} else {
if JPKBitShift(data) == 0 {
length := (JPKBitShift(data) << 3) | (JPKBitShift(data) << 2) | (JPKBitShift(data) << 1) | JPKBitShift(data)
if s.bitShift(data) == 0 {
length := (s.bitShift(data) << 3) | (s.bitShift(data) << 2) | (s.bitShift(data) << 1) | s.bitShift(data)
JPKCopy(outBuffer, off, int(length)+2+8, &outIndex)
continue
} else {
@@ -89,17 +96,17 @@ func ProcessDecode(data *byteframe.ByteFrame, outBuffer []byte) {
}
}
// JPKBitShift reads one bit from the compressed stream's flag byte, refilling
// bitShift reads one bit from the compressed stream's flag byte, refilling
// the flag from the next byte in data when all 8 bits have been consumed.
func JPKBitShift(data *byteframe.ByteFrame) byte {
mShiftIndex--
func (s *jpkState) bitShift(data *byteframe.ByteFrame) byte {
s.shiftIndex--
if mShiftIndex < 0 {
mShiftIndex = 7
mFlag = ReadByte(data)
if s.shiftIndex < 0 {
s.shiftIndex = 7
s.flag = ReadByte(data)
}
return (byte)((mFlag >> mShiftIndex) & 1)
return (s.flag >> s.shiftIndex) & 1
}
// JPKCopy copies length bytes from a previous position in outBuffer (determined