func (kx *KeyExchange) exchange1() error {
reply, err := kx.meetingPlace.Exchange(kx.Log, kx.meeting1[:], kx.message1[:], kx.ShutdownChan)
if err != nil {
return err
}
var peerDHPublic, encryptedPeerDHPublic [32]byte
if len(reply) < len(encryptedPeerDHPublic) {
return errors.New("panda: meeting point reply too small")
}
copy(encryptedPeerDHPublic[:], reply)
rijndael.NewCipher(&kx.key).Decrypt(&peerDHPublic, &encryptedPeerDHPublic)
curve25519.ScalarMult(&kx.sharedKey, &kx.dhPrivate, &peerDHPublic)
paddedLen := kx.meetingPlace.Padding()
padded := make([]byte, paddedLen-24 /* nonce */ -secretbox.Overhead)
binary.LittleEndian.PutUint32(padded, uint32(len(kx.kxBytes)))
copy(padded[4:], kx.kxBytes)
if _, err := io.ReadFull(kx.rand, padded[4+len(kx.kxBytes):]); err != nil {
return err
}
var nonce [24]byte
if _, err := io.ReadFull(kx.rand, nonce[:]); err != nil {
return err
}
kx.message2 = make([]byte, paddedLen)
copy(kx.message2, nonce[:])
secretbox.Seal(kx.message2[24:24], padded, &nonce, &kx.sharedKey)
return nil
}
func (kx *KeyExchange) derivePassword() error {
serialised, err := proto.Marshal(kx.sharedSecret.toProto())
if err != nil {
return err
}
if kx.Testing {
h := sha256.New()
h.Write([]byte{0})
h.Write(serialised)
h.Sum(kx.key[:0])
h.Reset()
h.Write([]byte{1})
h.Write(serialised)
h.Sum(kx.meeting1[:0])
h.Reset()
h.Write([]byte{2})
h.Write(serialised)
h.Sum(kx.meeting2[:0])
} else {
data, err := scrypt.Key(serialised, nil, 1<<17, 16, 4, 32*3)
if err != nil {
return err
}
copy(kx.key[:], data)
copy(kx.meeting1[:], data[32:])
copy(kx.meeting2[:], data[64:])
}
var encryptedDHPublic [32]byte
rijndael.NewCipher(&kx.key).Encrypt(&encryptedDHPublic, &kx.dhPublic)
l := len(encryptedDHPublic)
if padding := kx.meetingPlace.Padding(); l > padding {
return errors.New("panda: initial message too large for meeting place")
} else if l < padding {
l = padding
}
kx.message1 = make([]byte, l)
copy(kx.message1, encryptedDHPublic[:])
if _, err := io.ReadFull(kx.rand, kx.message1[len(encryptedDHPublic):]); err != nil {
return err
}
return nil
}
func (kx *KeyExchange) derivePassword() error {
serialised, err := proto.Marshal(kx.sharedSecret.toProto())
if err != nil {
return err
}
if kx.Testing {
h := sha256.New()
h.Write([]byte{0})
h.Write(serialised)
h.Sum(kx.key[:0])
h.Reset()
h.Write([]byte{1})
h.Write(serialised)
h.Sum(kx.meeting1[:0])
h.Reset()
h.Write([]byte{2})
h.Write(serialised)
h.Sum(kx.meeting2[:0])
} else {
var data []byte
if runtime.GOARCH == "386" && runtime.GOOS == "linux" {
// We're having GC problems on 32-bit systems with the
// scrypt allocation. In order to help the GC out, the
// scrypt computation is done in a subprocess.
cmd := exec.Command("/proc/self/exe", "--panda-scrypt")
var in, out bytes.Buffer
binary.Write(&in, binary.LittleEndian, uint32(len(serialised)))
in.Write(serialised)
cmd.Stdin = &in
cmd.Stdout = &out
cmd.Stderr = os.Stderr
if err := cmd.Run(); err != nil {
return err
}
data = out.Bytes()
if len(data) != 32*3 {
return errors.New("scrypt subprocess returned wrong number of bytes: " + strconv.Itoa(len(data)))
}
} else {
if data, err = scrypt.Key(serialised, nil, 1<<17, 16, 4, 32*3); err != nil {
return err
}
}
copy(kx.key[:], data)
copy(kx.meeting1[:], data[32:])
copy(kx.meeting2[:], data[64:])
}
var encryptedDHPublic [32]byte
rijndael.NewCipher(&kx.key).Encrypt(&encryptedDHPublic, &kx.dhPublic)
l := len(encryptedDHPublic)
if padding := kx.meetingPlace.Padding(); l > padding {
return errors.New("panda: initial message too large for meeting place")
} else if l < padding {
l = padding
}
kx.message1 = make([]byte, l)
copy(kx.message1, encryptedDHPublic[:])
if _, err := io.ReadFull(kx.rand, kx.message1[len(encryptedDHPublic):]); err != nil {
return err
}
return nil
}
