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package main
import (
"crypto/cipher"
"errors"
"github.com/aead/chacha20poly1305" // Needed for XChaCha20Poly1305, TODO:
"golang.org/x/crypto/blake2s"
"sync"
"time"
)
type MACStatePeer struct {
mutex sync.RWMutex
cookieSet time.Time
cookie [blake2s.Size128]byte
lastMAC1 [blake2s.Size128]byte
keyMAC1 [blake2s.Size]byte
keyMAC2 [blake2s.Size]byte
xaead cipher.AEAD
}
func (state *MACStatePeer) Init(pk NoisePublicKey) {
state.mutex.Lock()
defer state.mutex.Unlock()
func() {
hsh, _ := blake2s.New256(nil)
hsh.Write([]byte(WGLabelMAC1))
hsh.Write(pk[:])
hsh.Sum(state.keyMAC1[:0])
}()
func() {
hsh, _ := blake2s.New256(nil)
hsh.Write([]byte(WGLabelCookie))
hsh.Write(pk[:])
hsh.Sum(state.keyMAC2[:0])
}()
state.xaead, _ = chacha20poly1305.NewXCipher(state.keyMAC2[:])
state.cookieSet = time.Time{} // never
}
func (state *MACStatePeer) AddMacs(msg []byte) {
size := len(msg)
if size < blake2s.Size128*2 {
panic(errors.New("bug: message too short"))
}
startMac1 := size - (blake2s.Size128 * 2)
startMac2 := size - blake2s.Size128
mac1 := msg[startMac1 : startMac1+blake2s.Size128]
mac2 := msg[startMac2 : startMac2+blake2s.Size128]
state.mutex.Lock()
defer state.mutex.Unlock()
// set mac1
func() {
mac, _ := blake2s.New128(state.keyMAC1[:])
mac.Write(msg[:startMac1])
mac.Sum(state.lastMAC1[:0])
}()
copy(mac1, state.lastMAC1[:])
// set mac2
if state.cookieSet.IsZero() {
return
}
if time.Now().Sub(state.cookieSet) > CookieRefreshTime {
state.cookieSet = time.Time{}
return
}
func() {
mac, _ := blake2s.New128(state.cookie[:])
mac.Write(msg[:startMac2])
mac.Sum(mac2[:0])
}()
}
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