mirror of https://github.com/XTLS/Xray-core
81 lines
1.9 KiB
Go
81 lines
1.9 KiB
Go
package internal
|
|
|
|
//go:generate go run chacha_core_gen.go
|
|
|
|
import (
|
|
"encoding/binary"
|
|
)
|
|
|
|
const (
|
|
wordSize = 4 // the size of ChaCha20's words
|
|
stateSize = 16 // the size of ChaCha20's state, in words
|
|
blockSize = stateSize * wordSize // the size of ChaCha20's block, in bytes
|
|
)
|
|
|
|
type ChaCha20Stream struct {
|
|
state [stateSize]uint32 // the state as an array of 16 32-bit words
|
|
block [blockSize]byte // the keystream as an array of 64 bytes
|
|
offset int // the offset of used bytes in block
|
|
rounds int
|
|
}
|
|
|
|
func NewChaCha20Stream(key []byte, nonce []byte, rounds int) *ChaCha20Stream {
|
|
s := new(ChaCha20Stream)
|
|
// the magic constants for 256-bit keys
|
|
s.state[0] = 0x61707865
|
|
s.state[1] = 0x3320646e
|
|
s.state[2] = 0x79622d32
|
|
s.state[3] = 0x6b206574
|
|
|
|
for i := 0; i < 8; i++ {
|
|
s.state[i+4] = binary.LittleEndian.Uint32(key[i*4 : i*4+4])
|
|
}
|
|
|
|
switch len(nonce) {
|
|
case 8:
|
|
s.state[14] = binary.LittleEndian.Uint32(nonce[0:])
|
|
s.state[15] = binary.LittleEndian.Uint32(nonce[4:])
|
|
case 12:
|
|
s.state[13] = binary.LittleEndian.Uint32(nonce[0:4])
|
|
s.state[14] = binary.LittleEndian.Uint32(nonce[4:8])
|
|
s.state[15] = binary.LittleEndian.Uint32(nonce[8:12])
|
|
default:
|
|
panic("bad nonce length")
|
|
}
|
|
|
|
s.rounds = rounds
|
|
ChaCha20Block(&s.state, s.block[:], s.rounds)
|
|
return s
|
|
}
|
|
|
|
func (s *ChaCha20Stream) XORKeyStream(dst, src []byte) {
|
|
// Stride over the input in 64-byte blocks, minus the amount of keystream
|
|
// previously used. This will produce best results when processing blocks
|
|
// of a size evenly divisible by 64.
|
|
i := 0
|
|
max := len(src)
|
|
for i < max {
|
|
gap := blockSize - s.offset
|
|
|
|
limit := i + gap
|
|
if limit > max {
|
|
limit = max
|
|
}
|
|
|
|
o := s.offset
|
|
for j := i; j < limit; j++ {
|
|
dst[j] = src[j] ^ s.block[o]
|
|
o++
|
|
}
|
|
|
|
i += gap
|
|
s.offset = o
|
|
|
|
if o == blockSize {
|
|
s.offset = 0
|
|
s.state[12]++
|
|
ChaCha20Block(&s.state, s.block[:], s.rounds)
|
|
}
|
|
}
|
|
}
|