/
keys.go
129 lines (108 loc) · 3.07 KB
/
keys.go
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package spotcontrol
import (
"crypto/hmac"
"crypto/rand"
"crypto/sha1"
"encoding/base64"
"log"
"math/big"
)
type privateKeys struct {
privateKey *big.Int
publicKey *big.Int
generator *big.Int
prime *big.Int
clientNonce []byte
}
type sharedKeys struct {
challenge []byte
sendKey []byte
recvKey []byte
}
func randomVec(count int) []byte {
c := count
b := make([]byte, c)
_, err := rand.Read(b)
if err != nil {
log.Fatal("error:", err)
}
return b
}
func powm(base, exp, modulus *big.Int) *big.Int {
exp2 := big.NewInt(0).SetBytes(exp.Bytes())
base2 := big.NewInt(0).SetBytes(base.Bytes())
modulus2 := big.NewInt(0).SetBytes(modulus.Bytes())
zero := big.NewInt(0)
result := big.NewInt(1)
temp := new(big.Int)
for zero.Cmp(exp2) != 0 {
if temp.Rem(exp2, big.NewInt(2)).Cmp(zero) != 0 {
result = result.Mul(result, base2)
result = result.Rem(result, modulus2)
}
exp2 = exp2.Rsh(exp2, 1)
base2 = base2.Mul(base2, base2)
base2 = base2.Rem(base2, modulus2)
}
return result
}
func generateKeys() privateKeys {
private := new(big.Int)
private.SetBytes(randomVec(95))
nonce := randomVec(0x10)
return generateKeysFromPrivate(private, nonce)
}
func generateKeysFromPrivate(private *big.Int, nonce []byte) privateKeys {
DH_GENERATOR := big.NewInt(0x2)
DH_PRIME := new(big.Int)
DH_PRIME.SetBytes([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xc9,
0x0f, 0xda, 0xa2, 0x21, 0x68, 0xc2, 0x34, 0xc4, 0xc6,
0x62, 0x8b, 0x80, 0xdc, 0x1c, 0xd1, 0x29, 0x02, 0x4e,
0x08, 0x8a, 0x67, 0xcc, 0x74, 0x02, 0x0b, 0xbe, 0xa6,
0x3b, 0x13, 0x9b, 0x22, 0x51, 0x4a, 0x08, 0x79, 0x8e,
0x34, 0x04, 0xdd, 0xef, 0x95, 0x19, 0xb3, 0xcd, 0x3a,
0x43, 0x1b, 0x30, 0x2b, 0x0a, 0x6d, 0xf2, 0x5f, 0x14,
0x37, 0x4f, 0xe1, 0x35, 0x6d, 0x6d, 0x51, 0xc2, 0x45,
0xe4, 0x85, 0xb5, 0x76, 0x62, 0x5e, 0x7e, 0xc6, 0xf4,
0x4c, 0x42, 0xe9, 0xa6, 0x3a, 0x36, 0x20, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff})
return privateKeys{
privateKey: private,
publicKey: powm(DH_GENERATOR, private, DH_PRIME),
generator: DH_GENERATOR,
prime: DH_PRIME,
clientNonce: nonce,
}
}
func (p *privateKeys) addRemoteKey(remote []byte, clientPacket []byte, serverPacket []byte) sharedKeys {
remote_be := new(big.Int)
remote_be.SetBytes(remote)
shared_key := powm(remote_be, p.privateKey, p.prime)
data := make([]byte, 0, 100)
mac := hmac.New(sha1.New, shared_key.Bytes())
for i := 1; i < 6; i++ {
mac.Write(clientPacket)
mac.Write(serverPacket)
mac.Write([]byte{uint8(i)})
data = append(data, mac.Sum(nil)...)
mac.Reset()
}
mac = hmac.New(sha1.New, data[0:0x14])
mac.Write(clientPacket)
mac.Write(serverPacket)
return sharedKeys{
challenge: mac.Sum(nil),
sendKey: data[0x14:0x34],
recvKey: data[0x34:0x54],
}
}
func (p *privateKeys) SharedKey(publicKey string) []byte {
publicKeyBytes, _ := base64.StdEncoding.DecodeString(publicKey)
publicBig := new(big.Int)
publicBig.SetBytes(publicKeyBytes)
sharedKey := powm(publicBig, p.privateKey, p.prime)
return sharedKey.Bytes()
}
func (p *privateKeys) pubKey() []byte {
return p.publicKey.Bytes()
}