package p2p
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/hmac"
"crypto/rand"
"errors"
"fmt"
"hash"
"io"
"net"
"sync"
"time"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/crypto/ecies"
"github.com/ethereum/go-ethereum/crypto/secp256k1"
"github.com/ethereum/go-ethereum/crypto/sha3"
"github.com/ethereum/go-ethereum/p2p/discover"
"github.com/ethereum/go-ethereum/rlp"
)
const (
maxUint24 = ^uint32(0) >> 8
sskLen = 16 // ecies.MaxSharedKeyLength(pubKey) / 2
sigLen = 65 // elliptic S256
pubLen = 64 // 512 bit pubkey in uncompressed representation without format byte
shaLen = 32 // hash length (for nonce etc)
authMsgLen = sigLen + shaLen + pubLen + shaLen + 1
authRespLen = pubLen + shaLen + 1
eciesBytes = 65 + 16 + 32
encAuthMsgLen = authMsgLen + eciesBytes // size of the final ECIES payload sent as initiator's handshake
encAuthRespLen = authRespLen + eciesBytes // size of the final ECIES payload sent as receiver's handshake
// total timeout for encryption handshake and protocol
// handshake in both directions.
handshakeTimeout = 5 * time.Second
// This is the timeout for sending the disconnect reason.
// This is shorter than the usual timeout because we don't want
// to wait if the connection is known to be bad anyway.
discWriteTimeout = 1 * time.Second
)
// rlpx is the transport protocol used by actual (non-test) connections.
// It wraps the frame encoder with locks and read/write deadlines.
type rlpx struct {
fd net.Conn
rmu, wmu sync.Mutex
rw *rlpxFrameRW
}
func newRLPX(fd net.Conn) transport {
fd.SetDeadline(time.Now().Add(handshakeTimeout))
return &rlpx{fd: fd}
}
func (t *rlpx) ReadMsg() (Msg, error) {
t.rmu.Lock()
defer t.rmu.Unlock()
t.fd.SetReadDeadline(time.Now().Add(frameReadTimeout))
return t.rw.ReadMsg()
}
func (t *rlpx) WriteMsg(msg Msg) error {
t.wmu.Lock()
defer t.wmu.Unlock()
t.fd.SetWriteDeadline(time.Now().Add(frameWriteTimeout))
return t.rw.WriteMsg(msg)
}
func (t *rlpx) close(err error) {
t.wmu.Lock()
defer t.wmu.Unlock()
// Tell the remote end why we're disconnecting if possible.
if t.rw != nil {
if r, ok := err.(DiscReason); ok && r != DiscNetworkError {
t.fd.SetWriteDeadline(time.Now().Add(discWriteTimeout))
SendItems(t.rw, discMsg, r)
}
}
t.fd.Close()
}
// doEncHandshake runs the protocol handshake using authenticated
// messages. the protocol handshake is the first authenticated message
// and also verifies whether the encryption handshake 'worked' and the
// remote side actually provided the right public key.
func (t *rlpx) doProtoHandshake(our *protoHandshake) (their *protoHandshake, err error) {
// Writing our handshake happens concurrently, we prefer
// returning the handshake read error. If the remote side
// disconnects us early with a valid reason, we should return it
// as the error so it can be tracked elsewhere.
werr := make(chan error, 1)
go func() { werr <- Send(t.rw, handshakeMsg, our) }()
if their, err = readProtocolHandshake(t.rw, our); err != nil {
<-werr // make sure the write terminates too
return nil, err
}
if err := <-werr; err != nil {
return nil, fmt.Errorf("write error: %v", err)
}
return their, nil
}
func readProtocolHandshake(rw MsgReader, our *protoHandshake) (*protoHandshake, error) {
msg, err := rw.ReadMsg()
if err != nil {
return nil, err
}
if msg.Size > baseProtocolMaxMsgSize {
return nil, fmt.Errorf("message too big")
}
if msg.Code == discMsg {
// Disconnect before protocol handshake is valid according to the
// spec and we send it ourself if the posthanshake checks fail.
// We can't return the reason directly, though, because it is echoed
// back otherwise. Wrap it in a string instead.
var reason [1]DiscReason
rlp.Decode(msg.Payload, &reason)
return nil, reason[0]
}
if msg.Code != handshakeMsg {
return nil, fmt.Errorf("expected handshake, got %x", msg.Code)
}
var hs protoHandshake
if err := msg.Decode(&hs); err != nil {
return nil, err
}
// validate handshake info
if hs.Version != our.Version {
return nil, DiscIncompatibleVersion
}
if (hs.ID == discover.NodeID{}) {
return nil, DiscInvalidIdentity
}
return &hs, nil
}
func (t *rlpx) doEncHandshake(prv *ecdsa.PrivateKey, dial *discover.Node) (discover.NodeID, error) {
var (
sec secrets
err error
)
if dial == nil {
sec, err = receiverEncHandshake(t.fd, prv, nil)
} else {
sec, err = initiatorEncHandshake(t.fd, prv, dial.ID, nil)
}
if err != nil {
return discover.NodeID{}, err
}
t.wmu.Lock()
t.rw = newRLPXFrameRW(t.fd, sec)
t.wmu.Unlock()
return sec.RemoteID, nil
}
// encHandshake contains the state of the encryption handshake.
type encHandshake struct {
initiator bool
remoteID discover.NodeID
remotePub *ecies.PublicKey // remote-pubk
initNonce, respNonce []byte // nonce
randomPrivKey *ecies.PrivateKey // ecdhe-random
remoteRandomPub *ecies.PublicKey // ecdhe-random-pubk
}
// secrets represents the connection secrets
// which are negotiated during the encryption handshake.
type secrets struct {
RemoteID discover.NodeID
AES, MAC []byte
EgressMAC, IngressMAC hash.Hash
Token []byte
}
// secrets is called after the handshake is completed.
// It extracts the connection secrets from the handshake values.
func (h *encHandshake) secrets(auth, authResp []byte) (secrets, error) {
ecdheSecret, err := h.randomPrivKey.GenerateShared(h.remoteRandomPub, sskLen, sskLen)
if err != nil {
return secrets{}, err
}
// derive base secrets from ephemeral key agreement
sharedSecret := crypto.Sha3(ecdheSecret, crypto.Sha3(h.respNonce, h.initNonce))
aesSecret := crypto.Sha3(ecdheSecret, sharedSecret)
s := secrets{
RemoteID: h.remoteID,
AES: aesSecret,
MAC: crypto.Sha3(ecdheSecret, aesSecret),
Token: crypto.Sha3(sharedSecret),
}
// setup sha3 instances for the MACs
mac1 := sha3.NewKeccak256()
mac1.Write(xor(s.MAC, h.respNonce))
mac1.Write(auth)
mac2 := sha3.NewKeccak256()
mac2.Write(xor(s.MAC, h.initNonce))
mac2.Write(authResp)
if h.initiator {
s.EgressMAC, s.IngressMAC = mac1, mac2
} else {
s.EgressMAC, s.IngressMAC = mac2, mac1
}
return s, nil
}
func (h *encHandshake) ecdhShared(prv *ecdsa.PrivateKey) ([]byte, error) {
return ecies.ImportECDSA(prv).GenerateShared(h.remotePub, sskLen, sskLen)
}
// initiatorEncHandshake negotiates a session token on conn.
// it should be called on the dialing side of the connection.
//
// prv is the local client's private key.
// token is the token from a previous session with this node.
func initiatorEncHandshake(conn io.ReadWriter, prv *ecdsa.PrivateKey, remoteID discover.NodeID, token []byte) (s secrets, err error) {
h, err := newInitiatorHandshake(remoteID)
if err != nil {
return s, err
}
auth, err := h.authMsg(prv, token)
if err != nil {
return s, err
}
if _, err = conn.Write(auth); err != nil {
return s, err
}
response := make([]byte, encAuthRespLen)
if _, err = io.ReadFull(conn, response); err != nil {
return s, err
}
if err := h.decodeAuthResp(response, prv); err != nil {
return s, err
}
return h.secrets(auth, response)
}
func newInitiatorHandshake(remoteID discover.NodeID) (*encHandshake, error) {
// generate random initiator nonce
n := make([]byte, shaLen)
if _, err := rand.Read(n); err != nil {
return nil, err
}
// generate random keypair to use for signing
randpriv, err := ecies.GenerateKey(rand.Reader, crypto.S256(), nil)
if err != nil {
return nil, err
}
rpub, err := remoteID.Pubkey()
if err != nil {
return nil, fmt.Errorf("bad remoteID: %v", err)
}
h := &encHandshake{
initiator: true,
remoteID: remoteID,
remotePub: ecies.ImportECDSAPublic(rpub),
initNonce: n,
randomPrivKey: randpriv,
}
return h, nil
}
// authMsg creates an encrypted initiator handshake message.
func (h *encHandshake) authMsg(prv *ecdsa.PrivateKey, token []byte) ([]byte, error) {
var tokenFlag byte
if token == nil {
// no session token found means we need to generate shared secret.
// ecies shared secret is used as initial session token for new peers
// generate shared key from prv and remote pubkey
var err error
if token, err = h.ecdhShared(prv); err != nil {
return nil, err
}
} else {
// for known peers, we use stored token from the previous session
tokenFlag = 0x01
}
// sign known message:
// ecdh-shared-secret^nonce for new peers
// token^nonce for old peers
signed := xor(token, h.initNonce)
signature, err := crypto.Sign(signed, h.randomPrivKey.ExportECDSA())
if err != nil {
return nil, err
}
// encode auth message
// signature || sha3(ecdhe-random-pubk) || pubk || nonce || token-flag
msg := make([]byte, authMsgLen)
n := copy(msg, signature)
n += copy(msg[n:], crypto.Sha3(exportPubkey(&h.randomPrivKey.PublicKey)))
n += copy(msg[n:], crypto.FromECDSAPub(&prv.PublicKey)[1:])
n += copy(msg[n:], h.initNonce)
msg[n] = tokenFlag
// encrypt auth message using remote-pubk
return ecies.Encrypt(rand.Reader, h.remotePub, msg, nil, nil)
}
// decodeAuthResp decode an encrypted authentication response message.
func (h *encHandshake) decodeAuthResp(auth []byte, prv *ecdsa.PrivateKey) error {
msg, err := crypto.Decrypt(prv, auth)
if err != nil {
return fmt.Errorf("could not decrypt auth response (%v)", err)
}
h.respNonce = msg[pubLen : pubLen+shaLen]
h.remoteRandomPub, err = importPublicKey(msg[:pubLen])
if err != nil {
return err
}
// ignore token flag for now
return nil
}
// receiverEncHandshake negotiates a session token on conn.
// it should be called on the listening side of the connection.
//
// prv is the local client's private key.
// token is the token from a previous session with this node.
func receiverEncHandshake(conn io.ReadWriter, prv *ecdsa.PrivateKey, token []byte) (s secrets, err error) {
// read remote auth sent by initiator.
auth := make([]byte, encAuthMsgLen)
if _, err := io.ReadFull(conn, auth); err != nil {
return s, err
}
h, err := decodeAuthMsg(prv, token, auth)
if err != nil {
return s, err
}
// send auth response
resp, err := h.authResp(prv, token)
if err != nil {
return s, err
}
if _, err = conn.Write(resp); err != nil {
return s, err
}
return h.secrets(auth, resp)
}
func decodeAuthMsg(prv *ecdsa.PrivateKey, token []byte, auth []byte) (*encHandshake, error) {
var err error
h := new(encHandshake)
// generate random keypair for session
h.randomPrivKey, err = ecies.GenerateKey(rand.Reader, crypto.S256(), nil)
if err != nil {
return nil, err
}
// generate random nonce
h.respNonce = make([]byte, shaLen)
if _, err = rand.Read(h.respNonce); err != nil {
return nil, err
}
msg, err := crypto.Decrypt(prv, auth)
if err != nil {
return nil, fmt.Errorf("could not decrypt auth message (%v)", err)
}
// decode message parameters
// signature || sha3(ecdhe-random-pubk) || pubk || nonce || token-flag
h.initNonce = msg[authMsgLen-shaLen-1 : authMsgLen-1]
copy(h.remoteID[:], msg[sigLen+shaLen:sigLen+shaLen+pubLen])
rpub, err := h.remoteID.Pubkey()
if err != nil {
return nil, fmt.Errorf("bad remoteID: %#v", err)
}
h.remotePub = ecies.ImportECDSAPublic(rpub)
// recover remote random pubkey from signed message.
if token == nil {
// TODO: it is an error if the initiator has a token and we don't. check that.
// no session token means we need to generate shared secret.
// ecies shared secret is used as initial session token for new peers.
// generate shared key from prv and remote pubkey.
if token, err = h.ecdhShared(prv); err != nil {
return nil, err
}
}
signedMsg := xor(token, h.initNonce)
remoteRandomPub, err := secp256k1.RecoverPubkey(signedMsg, msg[:sigLen])
if err != nil {
return nil, err
}
h.remoteRandomPub, _ = importPublicKey(remoteRandomPub)
return h, nil
}
// authResp generates the encrypted authentication response message.
func (h *encHandshake) authResp(prv *ecdsa.PrivateKey, token []byte) ([]byte, error) {
// responder auth message
// E(remote-pubk, ecdhe-random-pubk || nonce || 0x0)
resp := make([]byte, authRespLen)
n := copy(resp, exportPubkey(&h.randomPrivKey.PublicKey))
n += copy(resp[n:], h.respNonce)
if token == nil {
resp[n] = 0
} else {
resp[n] = 1
}
// encrypt using remote-pubk
return ecies.Encrypt(rand.Reader, h.remotePub, resp, nil, nil)
}
// importPublicKey unmarshals 512 bit public keys.
func importPublicKey(pubKey []byte) (*ecies.PublicKey, error) {
var pubKey65 []byte
switch len(pubKey) {
case 64:
// add 'uncompressed key' flag
pubKey65 = append([]byte{0x04}, pubKey...)
case 65:
pubKey65 = pubKey
default:
return nil, fmt.Errorf("invalid public key length %v (expect 64/65)", len(pubKey))
}
// TODO: fewer pointless conversions
return ecies.ImportECDSAPublic(crypto.ToECDSAPub(pubKey65)), nil
}
func exportPubkey(pub *ecies.PublicKey) []byte {
if pub == nil {
panic("nil pubkey")
}
return elliptic.Marshal(pub.Curve, pub.X, pub.Y)[1:]
}
func xor(one, other []byte) (xor []byte) {
xor = make([]byte, len(one))
for i := 0; i < len(one); i++ {
xor[i] = one[i] ^ other[i]
}
return xor
}
var (
// this is used in place of actual frame header data.
// TODO: replace this when Msg contains the protocol type code.
zeroHeader = []byte{0xC2, 0x80, 0x80}
// sixteen zero bytes
zero16 = make([]byte, 16)
)
// rlpxFrameRW implements a simplified version of RLPx framing.
// chunked messages are not supported and all headers are equal to
// zeroHeader.
//
// rlpxFrameRW is not safe for concurrent use from multiple goroutines.
type rlpxFrameRW struct {
conn io.ReadWriter
enc cipher.Stream
dec cipher.Stream
macCipher cipher.Block
egressMAC hash.Hash
ingressMAC hash.Hash
}
func newRLPXFrameRW(conn io.ReadWriter, s secrets) *rlpxFrameRW {
macc, err := aes.NewCipher(s.MAC)
if err != nil {
panic("invalid MAC secret: " + err.Error())
}
encc, err := aes.NewCipher(s.AES)
if err != nil {
panic("invalid AES secret: " + err.Error())
}
// we use an all-zeroes IV for AES because the key used
// for encryption is ephemeral.
iv := make([]byte, encc.BlockSize())
return &rlpxFrameRW{
conn: conn,
enc: cipher.NewCTR(encc, iv),
dec: cipher.NewCTR(encc, iv),
macCipher: macc,
egressMAC: s.EgressMAC,
ingressMAC: s.IngressMAC,
}
}
func (rw *rlpxFrameRW) WriteMsg(msg Msg) error {
ptype, _ := rlp.EncodeToBytes(msg.Code)
// write header
headbuf := make([]byte, 32)
fsize := uint32(len(ptype)) + msg.Size
if fsize > maxUint24 {
return errors.New("message size overflows uint24")
}
putInt24(fsize, headbuf) // TODO: check overflow
copy(headbuf[3:], zeroHeader)
rw.enc.XORKeyStream(headbuf[:16], headbuf[:16]) // first half is now encrypted
// write header MAC
copy(headbuf[16:], updateMAC(rw.egressMAC, rw.macCipher, headbuf[:16]))
if _, err := rw.conn.Write(headbuf); err != nil {
return err
}
// write encrypted frame, updating the egress MAC hash with
// the data written to conn.
tee := cipher.StreamWriter{S: rw.enc, W: io.MultiWriter(rw.conn, rw.egressMAC)}
if _, err := tee.Write(ptype); err != nil {
return err
}
if _, err := io.Copy(tee, msg.Payload); err != nil {
return err
}
if padding := fsize % 16; padding > 0 {
if _, err := tee.Write(zero16[:16-padding]); err != nil {
return err
}
}
// write frame MAC. egress MAC hash is up to date because
// frame content was written to it as well.
fmacseed := rw.egressMAC.Sum(nil)
mac := updateMAC(rw.egressMAC, rw.macCipher, fmacseed)
_, err := rw.conn.Write(mac)
return err
}
func (rw *rlpxFrameRW) ReadMsg() (msg Msg, err error) {
// read the header
headbuf := make([]byte, 32)
if _, err := io.ReadFull(rw.conn, headbuf); err != nil {
return msg, err
}
// verify header mac
shouldMAC := updateMAC(rw.ingressMAC, rw.macCipher, headbuf[:16])
if !hmac.Equal(shouldMAC, headbuf[16:]) {
return msg, errors.New("bad header MAC")
}
rw.dec.XORKeyStream(headbuf[:16], headbuf[:16]) // first half is now decrypted
fsize := readInt24(headbuf)
// ignore protocol type for now
// read the frame content
var rsize = fsize // frame size rounded up to 16 byte boundary
if padding := fsize % 16; padding > 0 {
rsize += 16 - padding
}
framebuf := make([]byte, rsize)
if _, err := io.ReadFull(rw.conn, framebuf); err != nil {
return msg, err
}
// read and validate frame MAC. we can re-use headbuf for that.
rw.ingressMAC.Write(framebuf)
fmacseed := rw.ingressMAC.Sum(nil)
if _, err := io.ReadFull(rw.conn, headbuf[:16]); err != nil {
return msg, err
}
shouldMAC = updateMAC(rw.ingressMAC, rw.macCipher, fmacseed)
if !hmac.Equal(shouldMAC, headbuf[:16]) {
return msg, errors.New("bad frame MAC")
}
// decrypt frame content
rw.dec.XORKeyStream(framebuf, framebuf)
// decode message code
content := bytes.NewReader(framebuf[:fsize])
if err := rlp.Decode(content, &msg.Code); err != nil {
return msg, err
}
msg.Size = uint32(content.Len())
msg.Payload = content
return msg, nil
}
// updateMAC reseeds the given hash with encrypted seed.
// it returns the first 16 bytes of the hash sum after seeding.
func updateMAC(mac hash.Hash, block cipher.Block, seed []byte) []byte {
aesbuf := make([]byte, aes.BlockSize)
block.Encrypt(aesbuf, mac.Sum(nil))
for i := range aesbuf {
aesbuf[i] ^= seed[i]
}
mac.Write(aesbuf)
return mac.Sum(nil)[:16]
}
func readInt24(b []byte) uint32 {
return uint32(b[2]) | uint32(b[1])<<8 | uint32(b[0])<<16
}
func putInt24(v uint32, b []byte) {
b[0] = byte(v >> 16)
b[1] = byte(v >> 8)
b[2] = byte(v)
}
