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crypt.go
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crypt.go
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package maplepacket
import (
"crypto/aes"
"crypto/cipher"
)
// GetPacketLength -
func GetPacketLength(encryptedHeader []byte) int {
return int((uint16(encryptedHeader[0]) + uint16(encryptedHeader[1])*0x100) ^
(uint16(encryptedHeader[2]) + uint16(encryptedHeader[3])*0x100))
}
func GenerateNewIV(oldIv []byte) []byte {
var ivShiftKey = [...]byte{
0xEC, 0x3F, 0x77, 0xA4, 0x45, 0xD0, 0x71, 0xBF, 0xB7, 0x98, 0x20, 0xFC, 0x4B, 0xE9, 0xB3, 0xE1,
0x5C, 0x22, 0xF7, 0x0C, 0x44, 0x1B, 0x81, 0xBD, 0x63, 0x8D, 0xD4, 0xC3, 0xF2, 0x10, 0x19, 0xE0,
0xFB, 0xA1, 0x6E, 0x66, 0xEA, 0xAE, 0xD6, 0xCE, 0x06, 0x18, 0x4E, 0xEB, 0x78, 0x95, 0xDB, 0xBA,
0xB6, 0x42, 0x7A, 0x2A, 0x83, 0x0B, 0x54, 0x67, 0x6D, 0xE8, 0x65, 0xE7, 0x2F, 0x07, 0xF3, 0xAA,
0x27, 0x7B, 0x85, 0xB0, 0x26, 0xFD, 0x8B, 0xA9, 0xFA, 0xBE, 0xA8, 0xD7, 0xCB, 0xCC, 0x92, 0xDA,
0xF9, 0x93, 0x60, 0x2D, 0xDD, 0xD2, 0xA2, 0x9B, 0x39, 0x5F, 0x82, 0x21, 0x4C, 0x69, 0xF8, 0x31,
0x87, 0xEE, 0x8E, 0xAD, 0x8C, 0x6A, 0xBC, 0xB5, 0x6B, 0x59, 0x13, 0xF1, 0x04, 0x00, 0xF6, 0x5A,
0x35, 0x79, 0x48, 0x8F, 0x15, 0xCD, 0x97, 0x57, 0x12, 0x3E, 0x37, 0xFF, 0x9D, 0x4F, 0x51, 0xF5,
0xA3, 0x70, 0xBB, 0x14, 0x75, 0xC2, 0xB8, 0x72, 0xC0, 0xED, 0x7D, 0x68, 0xC9, 0x2E, 0x0D, 0x62,
0x46, 0x17, 0x11, 0x4D, 0x6C, 0xC4, 0x7E, 0x53, 0xC1, 0x25, 0xC7, 0x9A, 0x1C, 0x88, 0x58, 0x2C,
0x89, 0xDC, 0x02, 0x64, 0x40, 0x01, 0x5D, 0x38, 0xA5, 0xE2, 0xAF, 0x55, 0xD5, 0xEF, 0x1A, 0x7C,
0xA7, 0x5B, 0xA6, 0x6F, 0x86, 0x9F, 0x73, 0xE6, 0x0A, 0xDE, 0x2B, 0x99, 0x4A, 0x47, 0x9C, 0xDF,
0x09, 0x76, 0x9E, 0x30, 0x0E, 0xE4, 0xB2, 0x94, 0xA0, 0x3B, 0x34, 0x1D, 0x28, 0x0F, 0x36, 0xE3,
0x23, 0xB4, 0x03, 0xD8, 0x90, 0xC8, 0x3C, 0xFE, 0x5E, 0x32, 0x24, 0x50, 0x1F, 0x3A, 0x43, 0x8A,
0x96, 0x41, 0x74, 0xAC, 0x52, 0x33, 0xF0, 0xD9, 0x29, 0x80, 0xB1, 0x16, 0xD3, 0xAB, 0x91, 0xB9,
0x84, 0x7F, 0x61, 0x1E, 0xCF, 0xC5, 0xD1, 0x56, 0x3D, 0xCA, 0xF4, 0x05, 0xC6, 0xE5, 0x08, 0x49}
newIV := []byte{0xF2, 0x53, 0x50, 0xC6}
for i := 0; i < 4; i++ {
input := oldIv[i]
shiftVal := ivShiftKey[input]
newIV[0] += ivShiftKey[newIV[1]] - input
newIV[1] -= newIV[2] ^ shiftVal
newIV[2] ^= ivShiftKey[newIV[3]] + input
newIV[3] -= newIV[0] - shiftVal
val := uint32(newIV[3])<<24 | uint32(newIV[2])<<16 | uint32(newIV[1])<<8 | uint32(newIV[0])
shift := val>>0x1D | val<<0x03
newIV[0] = byte(shift & uint32(0xFF))
newIV[1] = byte(shift >> 8 & uint32(0xFF))
newIV[2] = byte(shift >> 16 & uint32(0xFF))
newIV[3] = byte(shift >> 24 & uint32(0xFF))
}
return newIV
}
func GenerateHeader(dataLength int, iv []byte, mapleVersion int) []byte {
a := (int(iv[3]) << 8) | int(iv[2])
header := make([]byte, 4)
a ^= -(mapleVersion + 1)
b := a ^ dataLength
header[0] = byte(a % 0x100)
header[1] = byte((a - int(header[0])) / 0x100)
header[2] = byte(b ^ 0x100)
header[3] = byte((b - int(header[2])) / 0x100)
return header
}
// ror - Taken from Kagami
func ror(val byte, num int) byte {
for i := 0; i < num; i++ {
var lowbit int
if val&1 > 0 {
lowbit = 1
} else {
lowbit = 0
}
val >>= 1
val |= byte(lowbit << 7)
}
return val
}
// rol - Taken from Kagami
func rol(val byte, num int) byte {
var highbit int
for i := 0; i < num; i++ {
if val&0x80 > 0 {
highbit = 1
} else {
highbit = 0
}
val <<= 1
val |= byte(highbit)
}
return val
}
// Decrypt - Taken from Kagami
func Decrypt(buf []byte) {
var j int32
var a, b, c byte
for i := byte(0); i < 3; i++ {
a = 0
b = 0
for j = int32(len(buf)); j > 0; j-- {
c = buf[j-1]
c = rol(c, 3)
c ^= 0x13
a = c
c ^= b
c = byte(int32(c) - j)
c = ror(c, 4)
b = a
buf[j-1] = c
}
a = 0
b = 0
for j = int32(len(buf)); j > 0; j-- {
c = buf[int32(len(buf))-j]
c -= 0x48
c ^= 0xFF
c = rol(c, int(j))
a = c
c ^= b
c = byte(int32(c) - j)
c = ror(c, 3)
b = a
buf[int32(len(buf))-j] = c
}
}
}
// Encrypt - Taken from Kagami
func Encrypt(buf []byte) {
var j int32
var a, c byte
for i := byte(0); i < 3; i++ {
a = 0
for j = int32(len(buf)); j > 0; j-- {
c = buf[int32(len(buf))-j]
c = rol(c, 3)
c = byte(int32(c) + j)
c ^= a
a = c
c = ror(a, int(j))
c ^= 0xFF
c += 0x48
buf[int32(len(buf))-j] = c
}
a = 0
for j = int32(len(buf)); j > 0; j-- {
c = buf[j-1]
c = rol(c, 4)
c = byte(int32(c) + j)
c ^= a
a = c
c ^= 0x13
c = ror(c, 3)
buf[j-1] = c
}
}
}
const blocksize = 1460
var aeskey = [32]byte{
0x13, 0x00, 0x00, 0x00,
0x08, 0x00, 0x00, 0x00,
0x06, 0x00, 0x00, 0x00,
0xB4, 0x00, 0x00, 0x00,
0x1B, 0x00, 0x00, 0x00,
0x0F, 0x00, 0x00, 0x00,
0x33, 0x00, 0x00, 0x00,
0x52, 0x00, 0x00, 0x00}
// Encrypt and Decrypt - Taken from kagami
func AesCrypt(buf []byte, key [16]byte) {
var pos, tpos, cbwrite, cb int32 = 0, 0, 0, int32(len(buf))
var first byte = 1
cb = int32(len(buf))
// I'm not 100% sure what this exactly does but apparently maple
// decrypts packets in blocks of 1460 bytes to work around
// packet limitations or something
for cb > pos {
tpos = blocksize - int32(first*4)
if cb > pos+tpos {
cbwrite = tpos
} else {
cbwrite = cb - pos
}
block, err := aes.NewCipher(aeskey[:])
if err != nil {
panic(err) // cbf to handle this unlikely error
}
stream := cipher.NewOFB(block, key[:])
stream.XORKeyStream(buf[pos:pos+cbwrite], buf[pos:pos+cbwrite])
pos += tpos
if first == 1 {
first = 0
}
}
}