func (s *state) DecryptPacket(pkt *lob.Packet) (*lob.Packet, error) {
s.mtx.RLock()
defer s.mtx.RUnlock()
if !s.CanDecryptPacket() {
return nil, cipherset.ErrInvalidState
}
if pkt == nil {
return nil, nil
}
if !pkt.Header().IsZero() || pkt.BodyLen() < 16+4+4 {
return nil, cipherset.ErrInvalidPacket
}
var (
nonce [16]byte
bodyRaw []byte
innerRaw []byte
innerLen = pkt.BodyLen() - (16 + 4 + 4)
body = bufpool.New()
inner = bufpool.New().SetLen(innerLen)
)
pkt.Body(body.SetLen(pkt.BodyLen()).RawBytes()[:0])
bodyRaw = body.RawBytes()
innerRaw = inner.RawBytes()
// compare token
if !bytes.Equal(bodyRaw[:16], (*s.localToken)[:]) {
inner.Free()
body.Free()
return nil, cipherset.ErrInvalidPacket
}
// copy nonce
copy(nonce[:], bodyRaw[16:16+4])
{ // verify hmac
mac := bodyRaw[16+4+innerLen:]
macKey := append(s.lineDecryptionKey, nonce[:4]...)
h := hmac.New(sha256.New, macKey)
h.Write(bodyRaw[16+4 : 16+4+innerLen])
if subtle.ConstantTimeCompare(mac, fold(h.Sum(nil), 4)) != 1 {
inner.Free()
body.Free()
return nil, cipherset.ErrInvalidPacket
}
}
{ // decrypt inner
aesBlock, err := aes.NewCipher(s.lineDecryptionKey)
if err != nil {
inner.Free()
body.Free()
return nil, err
}
aes := Cipher.NewCTR(aesBlock, nonce[:])
if aes == nil {
inner.Free()
body.Free()
return nil, cipherset.ErrInvalidPacket
}
aes.XORKeyStream(innerRaw, bodyRaw[16+4:16+4+innerLen])
}
innerPkt, err := lob.Decode(inner)
if err != nil {
inner.Free()
body.Free()
return nil, err
}
inner.Free()
body.Free()
return innerPkt, nil
}
func (s *state) DecryptPacket(pkt *lob.Packet) (*lob.Packet, error) {
s.mtx.RLock()
defer s.mtx.RUnlock()
if !s.CanDecryptPacket() {
return nil, cipherset.ErrInvalidState
}
if pkt == nil {
return nil, nil
}
if !pkt.Header().IsZero() || pkt.BodyLen() < lenToken+lenNonce {
return nil, cipherset.ErrInvalidPacket
}
var (
nonce [lenNonce]byte
bodyRaw []byte
innerRaw []byte
innerPkt *lob.Packet
body = bufpool.New()
inner = bufpool.New()
ok bool
)
pkt.Body(body.SetLen(pkt.BodyLen()).RawBytes()[:0])
bodyRaw = body.RawBytes()
innerRaw = inner.RawBytes()
// compare token
if !bytes.Equal(bodyRaw[:lenToken], (*s.localToken)[:]) {
inner.Free()
body.Free()
return nil, cipherset.ErrInvalidPacket
}
// copy nonce
copy(nonce[:], bodyRaw[lenToken:lenToken+lenNonce])
// decrypt inner packet
innerRaw, ok = box.OpenAfterPrecomputation(
innerRaw[:0], bodyRaw[lenToken+lenNonce:], &nonce, s.lineDecryptionKey)
if !ok {
inner.Free()
body.Free()
return nil, cipherset.ErrInvalidPacket
}
inner.SetLen(len(innerRaw))
innerPkt, err := lob.Decode(inner)
if err != nil {
inner.Free()
body.Free()
return nil, err
}
inner.Free()
body.Free()
return innerPkt, nil
}
