p2p: EIP-8 changes

4 files changed, 443 insertions, 149 deletions

diff --git a/p2p/message_test.go b/p2p/message_test.go
index 8599b7e87..013214e21 100644
--- a/p2p/message_test.go
+++ b/p2p/message_test.go
@@ -143,7 +143,8 @@ func TestEOFSignal(t *testing.T) {
 }
 
 func unhex(str string) []byte {
-	b, err := hex.DecodeString(strings.Replace(str, "\n", "", -1))
+	r := strings.NewReplacer("\t", "", " ", "", "\n", "")
+	b, err := hex.DecodeString(r.Replace(str))
 	if err != nil {
 		panic(fmt.Sprintf("invalid hex string: %q", str))
 	}
diff --git a/p2p/peer.go b/p2p/peer.go
index 72ed4069c..b9d6c099d 100644
--- a/p2p/peer.go
+++ b/p2p/peer.go
@@ -56,6 +56,9 @@ type protoHandshake struct {
 	Caps       []Cap
 	ListenPort uint64
 	ID         discover.NodeID
+
+	// Ignore additional fields (for forward compatibility).
+	Rest []rlp.RawValue `rlp:"tail"`
 }
 
 // Peer represents a connected remote node.
diff --git a/p2p/rlpx.go b/p2p/rlpx.go
index 8f429d6ec..9d6cba5b6 100644
--- a/p2p/rlpx.go
+++ b/p2p/rlpx.go
@@ -24,11 +24,14 @@ import (
 	"crypto/elliptic"
 	"crypto/hmac"
 	"crypto/rand"
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"hash"
 	"io"
+	mrand "math/rand"
 	"net"
+	"os"
 	"sync"
 	"time"
 
@@ -51,9 +54,10 @@ const (
 	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
+	eciesOverhead = 65 /* pubkey */ + 16 /* IV */ + 32 /* MAC */
+
+	encAuthMsgLen  = authMsgLen + eciesOverhead  // size of encrypted pre-EIP-8 initiator handshake
+	encAuthRespLen = authRespLen + eciesOverhead // size of encrypted pre-EIP-8 handshake reply
 
 	// total timeout for encryption handshake and protocol
 	// handshake in both directions.
@@ -151,10 +155,6 @@ func readProtocolHandshake(rw MsgReader, our *protoHandshake) (*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
 	}
@@ -200,6 +200,29 @@ type secrets struct {
 	Token                 []byte
 }
 
+// RLPx v4 handshake auth (defined in EIP-8).
+type authMsgV4 struct {
+	gotPlain bool // whether read packet had plain format.
+
+	Signature       [sigLen]byte
+	InitiatorPubkey [pubLen]byte
+	Nonce           [shaLen]byte
+	Version         uint
+
+	// Ignore additional fields (forward-compatibility)
+	Rest []rlp.RawValue `rlp:"tail"`
+}
+
+// RLPx v4 handshake response (defined in EIP-8).
+type authRespV4 struct {
+	RandomPubkey [pubLen]byte
+	Nonce        [shaLen]byte
+	Version      uint
+
+	// Ignore additional fields (forward-compatibility)
+	Rest []rlp.RawValue `rlp:"tail"`
+}
+
 // 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) {
@@ -215,7 +238,6 @@ func (h *encHandshake) secrets(auth, authResp []byte) (secrets, error) {
 		RemoteID: h.remoteID,
 		AES:      aesSecret,
 		MAC:      crypto.Sha3(ecdheSecret, aesSecret),
-		Token:    crypto.Sha3(sharedSecret),
 	}
 
 	// setup sha3 instances for the MACs
@@ -234,114 +256,89 @@ func (h *encHandshake) secrets(auth, authResp []byte) (secrets, error) {
 	return s, nil
 }
 
-func (h *encHandshake) ecdhShared(prv *ecdsa.PrivateKey) ([]byte, error) {
+// staticSharedSecret returns the static shared secret, the result
+// of key agreement between the local and remote static node key.
+func (h *encHandshake) staticSharedSecret(prv *ecdsa.PrivateKey) ([]byte, error) {
 	return ecies.ImportECDSA(prv).GenerateShared(h.remotePub, sskLen, sskLen)
 }
 
+var configSendEIP = os.Getenv("RLPX_EIP8") != ""
+
 // 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)
+	h := &encHandshake{initiator: true, remoteID: remoteID}
+	authMsg, err := h.makeAuthMsg(prv, token)
 	if err != nil {
 		return s, err
 	}
-	auth, err := h.authMsg(prv, token)
+	var authPacket []byte
+	if configSendEIP {
+		authPacket, err = sealEIP8(authMsg, h)
+	} else {
+		authPacket, err = authMsg.sealPlain(h)
+	}
 	if err != nil {
 		return s, err
 	}
-	if _, err = conn.Write(auth); err != nil {
+	if _, err = conn.Write(authPacket); err != nil {
 		return s, err
 	}
 
-	response := make([]byte, encAuthRespLen)
-	if _, err = io.ReadFull(conn, response); err != nil {
+	authRespMsg := new(authRespV4)
+	authRespPacket, err := readHandshakeMsg(authRespMsg, encAuthRespLen, prv, conn)
+	if err != nil {
 		return s, err
 	}
-	if err := h.decodeAuthResp(response, prv); err != nil {
+	if err := h.handleAuthResp(authRespMsg); err != nil {
 		return s, err
 	}
-	return h.secrets(auth, response)
+	return h.secrets(authPacket, authRespPacket)
 }
 
-func newInitiatorHandshake(remoteID discover.NodeID) (*encHandshake, error) {
-	rpub, err := remoteID.Pubkey()
+// makeAuthMsg creates the initiator handshake message.
+func (h *encHandshake) makeAuthMsg(prv *ecdsa.PrivateKey, token []byte) (*authMsgV4, error) {
+	rpub, err := h.remoteID.Pubkey()
 	if err != nil {
 		return nil, fmt.Errorf("bad remoteID: %v", err)
 	}
-	// generate random initiator nonce
-	n := make([]byte, shaLen)
-	if _, err := rand.Read(n); err != nil {
+	h.remotePub = ecies.ImportECDSAPublic(rpub)
+	// Generate random initiator nonce.
+	h.initNonce = make([]byte, shaLen)
+	if _, err := rand.Read(h.initNonce); err != nil {
 		return nil, err
 	}
-	// generate random keypair to use for signing
-	randpriv, err := ecies.GenerateKey(rand.Reader, secp256k1.S256(), nil)
+	// Generate random keypair to for ECDH.
+	h.randomPrivKey, err = ecies.GenerateKey(rand.Reader, secp256k1.S256(), nil)
 	if err != nil {
 		return nil, 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
+	// Sign known message: static-shared-secret ^ nonce
+	token, err = h.staticSharedSecret(prv)
+	if err != nil {
+		return nil, err
+	}
 	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)
+	msg := new(authMsgV4)
+	copy(msg.Signature[:], signature)
+	copy(msg.InitiatorPubkey[:], crypto.FromECDSAPub(&prv.PublicKey)[1:])
+	copy(msg.Nonce[:], h.initNonce)
+	msg.Version = 4
+	return msg, 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
+func (h *encHandshake) handleAuthResp(msg *authRespV4) (err error) {
+	h.respNonce = msg.Nonce[:]
+	h.remoteRandomPub, err = importPublicKey(msg.RandomPubkey[:])
+	return err
 }
 
 // receiverEncHandshake negotiates a session token on conn.
@@ -350,99 +347,165 @@ func (h *encHandshake) decodeAuthResp(auth []byte, prv *ecdsa.PrivateKey) error
 // 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 {
+	authMsg := new(authMsgV4)
+	authPacket, err := readHandshakeMsg(authMsg, encAuthMsgLen, prv, conn)
+	if err != nil {
 		return s, err
 	}
-	h, err := decodeAuthMsg(prv, token, auth)
-	if err != nil {
+	h := new(encHandshake)
+	if err := h.handleAuthMsg(authMsg, prv); err != nil {
 		return s, err
 	}
 
-	// send auth response
-	resp, err := h.authResp(prv, token)
+	authRespMsg, err := h.makeAuthResp()
 	if err != nil {
 		return s, err
 	}
-	if _, err = conn.Write(resp); err != nil {
-		return s, err
+	var authRespPacket []byte
+	if authMsg.gotPlain {
+		authRespPacket, err = authRespMsg.sealPlain(h)
+	} else {
+		authRespPacket, err = sealEIP8(authRespMsg, h)
 	}
-
-	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, secp256k1.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
+		return s, err
 	}
-
-	msg, err := crypto.Decrypt(prv, auth)
-	if err != nil {
-		return nil, fmt.Errorf("could not decrypt auth message (%v)", err)
+	if _, err = conn.Write(authRespPacket); err != nil {
+		return s, err
 	}
+	return h.secrets(authPacket, authRespPacket)
+}
 
-	// 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])
+func (h *encHandshake) handleAuthMsg(msg *authMsgV4, prv *ecdsa.PrivateKey) error {
+	// Import the remote identity.
+	h.initNonce = msg.Nonce[:]
+	h.remoteID = msg.InitiatorPubkey
 	rpub, err := h.remoteID.Pubkey()
 	if err != nil {
-		return nil, fmt.Errorf("bad remoteID: %#v", err)
+		return 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
+	// Generate random keypair for ECDH.
+	// If a private key is already set, use it instead of generating one (for testing).
+	if h.randomPrivKey == nil {
+		h.randomPrivKey, err = ecies.GenerateKey(rand.Reader, secp256k1.S256(), nil)
+		if err != nil {
+			return err
 		}
 	}
+
+	// Check the signature.
+	token, err := h.staticSharedSecret(prv)
+	if err != nil {
+		return err
+	}
 	signedMsg := xor(token, h.initNonce)
-	remoteRandomPub, err := secp256k1.RecoverPubkey(signedMsg, msg[:sigLen])
+	remoteRandomPub, err := secp256k1.RecoverPubkey(signedMsg, msg.Signature[:])
 	if err != nil {
+		return err
+	}
+	h.remoteRandomPub, _ = importPublicKey(remoteRandomPub)
+	return nil
+}
+
+func (h *encHandshake) makeAuthResp() (msg *authRespV4, err error) {
+	// Generate random nonce.
+	h.respNonce = make([]byte, shaLen)
+	if _, err = rand.Read(h.respNonce); err != nil {
 		return nil, err
 	}
 
-	// validate the sha3 of recovered pubkey
-	remoteRandomPubMAC := msg[sigLen : sigLen+shaLen]
-	shaRemoteRandomPub := crypto.Sha3(remoteRandomPub[1:])
-	if !bytes.Equal(remoteRandomPubMAC, shaRemoteRandomPub) {
-		return nil, fmt.Errorf("sha3 of recovered ephemeral pubkey does not match checksum in auth message")
+	msg = new(authRespV4)
+	copy(msg.Nonce[:], h.respNonce)
+	copy(msg.RandomPubkey[:], exportPubkey(&h.randomPrivKey.PublicKey))
+	msg.Version = 4
+	return msg, nil
+}
+
+func (msg *authMsgV4) sealPlain(h *encHandshake) ([]byte, error) {
+	buf := make([]byte, authMsgLen)
+	n := copy(buf, msg.Signature[:])
+	n += copy(buf[n:], crypto.Sha3(exportPubkey(&h.randomPrivKey.PublicKey)))
+	n += copy(buf[n:], msg.InitiatorPubkey[:])
+	n += copy(buf[n:], msg.Nonce[:])
+	buf[n] = 0 // token-flag
+	return ecies.Encrypt(rand.Reader, h.remotePub, buf, nil, nil)
+}
+
+func (msg *authMsgV4) decodePlain(input []byte) {
+	n := copy(msg.Signature[:], input)
+	n += shaLen // skip sha3(initiator-ephemeral-pubk)
+	n += copy(msg.InitiatorPubkey[:], input[n:])
+	n += copy(msg.Nonce[:], input[n:])
+	msg.Version = 4
+	msg.gotPlain = true
+}
+
+func (msg *authRespV4) sealPlain(hs *encHandshake) ([]byte, error) {
+	buf := make([]byte, authRespLen)
+	n := copy(buf, msg.RandomPubkey[:])
+	n += copy(buf[n:], msg.Nonce[:])
+	return ecies.Encrypt(rand.Reader, hs.remotePub, buf, nil, nil)
+}
+
+func (msg *authRespV4) decodePlain(input []byte) {
+	n := copy(msg.RandomPubkey[:], input)
+	n += copy(msg.Nonce[:], input[n:])
+	msg.Version = 4
+}
+
+var padSpace = make([]byte, 300)
+
+func sealEIP8(msg interface{}, h *encHandshake) ([]byte, error) {
+	buf := new(bytes.Buffer)
+	if err := rlp.Encode(buf, msg); err != nil {
+		return nil, err
 	}
+	// pad with random amount of data. the amount needs to be at least 100 bytes to make
+	// the message distinguishable from pre-EIP-8 handshakes.
+	pad := padSpace[:mrand.Intn(len(padSpace)-100)+100]
+	buf.Write(pad)
+	prefix := make([]byte, 2)
+	binary.BigEndian.PutUint16(prefix, uint16(buf.Len()+eciesOverhead))
 
-	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
+	enc, err := ecies.Encrypt(rand.Reader, h.remotePub, buf.Bytes(), nil, prefix)
+	return append(prefix, enc...), err
+}
+
+type plainDecoder interface {
+	decodePlain([]byte)
+}
+
+func readHandshakeMsg(msg plainDecoder, plainSize int, prv *ecdsa.PrivateKey, r io.Reader) ([]byte, error) {
+	buf := make([]byte, plainSize)
+	if _, err := io.ReadFull(r, buf); err != nil {
+		return buf, err
+	}
+	// Attempt decoding pre-EIP-8 "plain" format.
+	key := ecies.ImportECDSA(prv)
+	if dec, err := key.Decrypt(rand.Reader, buf, nil, nil); err == nil {
+		msg.decodePlain(dec)
+		return buf, nil
 	}
-	// encrypt using remote-pubk
-	return ecies.Encrypt(rand.Reader, h.remotePub, resp, nil, nil)
+	// Could be EIP-8 format, try that.
+	prefix := buf[:2]
+	size := binary.BigEndian.Uint16(prefix)
+	if size < uint16(plainSize) {
+		return buf, fmt.Errorf("size underflow, need at least %d bytes", plainSize)
+	}
+	buf = append(buf, make([]byte, size-uint16(plainSize)+2)...)
+	if _, err := io.ReadFull(r, buf[plainSize:]); err != nil {
+		return buf, err
+	}
+	dec, err := key.Decrypt(rand.Reader, buf[2:], nil, prefix)
+	if err != nil {
+		return buf, err
+	}
+	// Can't use rlp.DecodeBytes here because it rejects
+	// trailing data (forward-compatibility).
+	s := rlp.NewStream(bytes.NewReader(dec), 0)
+	return buf, s.Decode(msg)
 }
 
 // importPublicKey unmarshals 512 bit public keys.
@@ -458,7 +521,11 @@ func importPublicKey(pubKey []byte) (*ecies.PublicKey, error) {
 		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
+	pub := crypto.ToECDSAPub(pubKey65)
+	if pub.X == nil {
+		return nil, fmt.Errorf("invalid public key")
+	}
+	return ecies.ImportECDSAPublic(pub), nil
 }
 
 func exportPubkey(pub *ecies.PublicKey) []byte {
diff --git a/p2p/rlpx_test.go b/p2p/rlpx_test.go
index 7cc7548e2..f9583e224 100644
--- a/p2p/rlpx_test.go
+++ b/p2p/rlpx_test.go
@@ -21,6 +21,7 @@ import (
 	"crypto/rand"
 	"errors"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net"
 	"reflect"
@@ -162,6 +163,7 @@ func TestProtocolHandshake(t *testing.T) {
 	wg.Add(2)
 	go func() {
 		defer wg.Done()
+		defer fd1.Close()
 		rlpx := newRLPX(fd0)
 		remid, err := rlpx.doEncHandshake(prv0, node1)
 		if err != nil {
@@ -178,6 +180,7 @@ func TestProtocolHandshake(t *testing.T) {
 			t.Errorf("dial side proto handshake error: %v", err)
 			return
 		}
+		phs.Rest = nil
 		if !reflect.DeepEqual(phs, hs1) {
 			t.Errorf("dial side proto handshake mismatch:\ngot: %s\nwant: %s\n", spew.Sdump(phs), spew.Sdump(hs1))
 			return
@@ -186,6 +189,7 @@ func TestProtocolHandshake(t *testing.T) {
 	}()
 	go func() {
 		defer wg.Done()
+		defer fd1.Close()
 		rlpx := newRLPX(fd1)
 		remid, err := rlpx.doEncHandshake(prv1, nil)
 		if err != nil {
@@ -202,6 +206,7 @@ func TestProtocolHandshake(t *testing.T) {
 			t.Errorf("listen side proto handshake error: %v", err)
 			return
 		}
+		phs.Rest = nil
 		if !reflect.DeepEqual(phs, hs0) {
 			t.Errorf("listen side proto handshake mismatch:\ngot: %s\nwant: %s\n", spew.Sdump(phs), spew.Sdump(hs0))
 			return
@@ -216,7 +221,6 @@ func TestProtocolHandshake(t *testing.T) {
 
 func TestProtocolHandshakeErrors(t *testing.T) {
 	our := &protoHandshake{Version: 3, Caps: []Cap{{"foo", 2}, {"bar", 3}}, Name: "quux"}
-	id := randomID()
 	tests := []struct {
 		code uint64
 		msg  interface{}
@@ -244,11 +248,6 @@ func TestProtocolHandshakeErrors(t *testing.T) {
 		},
 		{
 			code: handshakeMsg,
-			msg:  &protoHandshake{Version: 9944, ID: id},
-			err:  DiscIncompatibleVersion,
-		},
-		{
-			code: handshakeMsg,
 			msg:  &protoHandshake{Version: 3},
 			err:  DiscInvalidIdentity,
 		},
@@ -374,3 +373,227 @@ func TestRLPXFrameRW(t *testing.T) {
 		}
 	}
 }
+
+type handshakeAuthTest struct {
+	input       string
+	isPlain     bool
+	wantVersion uint
+	wantRest    []rlp.RawValue
+}
+
+var eip8HandshakeAuthTests = []handshakeAuthTest{
+	// (Auth₁) RLPx v4 plain encoding
+	{
+		input: `
+			048ca79ad18e4b0659fab4853fe5bc58eb83992980f4c9cc147d2aa31532efd29a3d3dc6a3d89eaf
+			913150cfc777ce0ce4af2758bf4810235f6e6ceccfee1acc6b22c005e9e3a49d6448610a58e98744
+			ba3ac0399e82692d67c1f58849050b3024e21a52c9d3b01d871ff5f210817912773e610443a9ef14
+			2e91cdba0bd77b5fdf0769b05671fc35f83d83e4d3b0b000c6b2a1b1bba89e0fc51bf4e460df3105
+			c444f14be226458940d6061c296350937ffd5e3acaceeaaefd3c6f74be8e23e0f45163cc7ebd7622
+			0f0128410fd05250273156d548a414444ae2f7dea4dfca2d43c057adb701a715bf59f6fb66b2d1d2
+			0f2c703f851cbf5ac47396d9ca65b6260bd141ac4d53e2de585a73d1750780db4c9ee4cd4d225173
+			a4592ee77e2bd94d0be3691f3b406f9bba9b591fc63facc016bfa8
+		`,
+		isPlain:     true,
+		wantVersion: 4,
+	},
+	// (Auth₂) EIP-8 encoding
+	{
+		input: `
+			01b304ab7578555167be8154d5cc456f567d5ba302662433674222360f08d5f1534499d3678b513b
+			0fca474f3a514b18e75683032eb63fccb16c156dc6eb2c0b1593f0d84ac74f6e475f1b8d56116b84
+			9634a8c458705bf83a626ea0384d4d7341aae591fae42ce6bd5c850bfe0b999a694a49bbbaf3ef6c
+			da61110601d3b4c02ab6c30437257a6e0117792631a4b47c1d52fc0f8f89caadeb7d02770bf999cc
+			147d2df3b62e1ffb2c9d8c125a3984865356266bca11ce7d3a688663a51d82defaa8aad69da39ab6
+			d5470e81ec5f2a7a47fb865ff7cca21516f9299a07b1bc63ba56c7a1a892112841ca44b6e0034dee
+			70c9adabc15d76a54f443593fafdc3b27af8059703f88928e199cb122362a4b35f62386da7caad09
+			c001edaeb5f8a06d2b26fb6cb93c52a9fca51853b68193916982358fe1e5369e249875bb8d0d0ec3
+			6f917bc5e1eafd5896d46bd61ff23f1a863a8a8dcd54c7b109b771c8e61ec9c8908c733c0263440e
+			2aa067241aaa433f0bb053c7b31a838504b148f570c0ad62837129e547678c5190341e4f1693956c
+			3bf7678318e2d5b5340c9e488eefea198576344afbdf66db5f51204a6961a63ce072c8926c
+		`,
+		wantVersion: 4,
+		wantRest:    []rlp.RawValue{},
+	},
+	// (Auth₃) RLPx v4 EIP-8 encoding with version 56, additional list elements
+	{
+		input: `
+			01b8044c6c312173685d1edd268aa95e1d495474c6959bcdd10067ba4c9013df9e40ff45f5bfd6f7
+			2471f93a91b493f8e00abc4b80f682973de715d77ba3a005a242eb859f9a211d93a347fa64b597bf
+			280a6b88e26299cf263b01b8dfdb712278464fd1c25840b995e84d367d743f66c0e54a586725b7bb
+			f12acca27170ae3283c1073adda4b6d79f27656993aefccf16e0d0409fe07db2dc398a1b7e8ee93b
+			cd181485fd332f381d6a050fba4c7641a5112ac1b0b61168d20f01b479e19adf7fdbfa0905f63352
+			bfc7e23cf3357657455119d879c78d3cf8c8c06375f3f7d4861aa02a122467e069acaf513025ff19
+			6641f6d2810ce493f51bee9c966b15c5043505350392b57645385a18c78f14669cc4d960446c1757
+			1b7c5d725021babbcd786957f3d17089c084907bda22c2b2675b4378b114c601d858802a55345a15
+			116bc61da4193996187ed70d16730e9ae6b3bb8787ebcaea1871d850997ddc08b4f4ea668fbf3740
+			7ac044b55be0908ecb94d4ed172ece66fd31bfdadf2b97a8bc690163ee11f5b575a4b44e36e2bfb2
+			f0fce91676fd64c7773bac6a003f481fddd0bae0a1f31aa27504e2a533af4cef3b623f4791b2cca6
+			d490
+		`,
+		wantVersion: 56,
+		wantRest:    []rlp.RawValue{{0x01}, {0x02}, {0xC2, 0x04, 0x05}},
+	},
+}
+
+type handshakeAckTest struct {
+	input       string
+	wantVersion uint
+	wantRest    []rlp.RawValue
+}
+
+var eip8HandshakeRespTests = []handshakeAckTest{
+	// (Ack₁) RLPx v4 plain encoding
+	{
+		input: `
+			049f8abcfa9c0dc65b982e98af921bc0ba6e4243169348a236abe9df5f93aa69d99cadddaa387662
+			b0ff2c08e9006d5a11a278b1b3331e5aaabf0a32f01281b6f4ede0e09a2d5f585b26513cb794d963
+			5a57563921c04a9090b4f14ee42be1a5461049af4ea7a7f49bf4c97a352d39c8d02ee4acc416388c
+			1c66cec761d2bc1c72da6ba143477f049c9d2dde846c252c111b904f630ac98e51609b3b1f58168d
+			dca6505b7196532e5f85b259a20c45e1979491683fee108e9660edbf38f3add489ae73e3dda2c71b
+			d1497113d5c755e942d1
+		`,
+		wantVersion: 4,
+	},
+	// (Ack₂) EIP-8 encoding
+	{
+		input: `
+			01ea0451958701280a56482929d3b0757da8f7fbe5286784beead59d95089c217c9b917788989470
+			b0e330cc6e4fb383c0340ed85fab836ec9fb8a49672712aeabbdfd1e837c1ff4cace34311cd7f4de
+			05d59279e3524ab26ef753a0095637ac88f2b499b9914b5f64e143eae548a1066e14cd2f4bd7f814
+			c4652f11b254f8a2d0191e2f5546fae6055694aed14d906df79ad3b407d94692694e259191cde171
+			ad542fc588fa2b7333313d82a9f887332f1dfc36cea03f831cb9a23fea05b33deb999e85489e645f
+			6aab1872475d488d7bd6c7c120caf28dbfc5d6833888155ed69d34dbdc39c1f299be1057810f34fb
+			e754d021bfca14dc989753d61c413d261934e1a9c67ee060a25eefb54e81a4d14baff922180c395d
+			3f998d70f46f6b58306f969627ae364497e73fc27f6d17ae45a413d322cb8814276be6ddd13b885b
+			201b943213656cde498fa0e9ddc8e0b8f8a53824fbd82254f3e2c17e8eaea009c38b4aa0a3f306e8
+			797db43c25d68e86f262e564086f59a2fc60511c42abfb3057c247a8a8fe4fb3ccbadde17514b7ac
+			8000cdb6a912778426260c47f38919a91f25f4b5ffb455d6aaaf150f7e5529c100ce62d6d92826a7
+			1778d809bdf60232ae21ce8a437eca8223f45ac37f6487452ce626f549b3b5fdee26afd2072e4bc7
+			5833c2464c805246155289f4
+		`,
+		wantVersion: 4,
+		wantRest:    []rlp.RawValue{},
+	},
+	// (Ack₃) EIP-8 encoding with version 57, additional list elements
+	{
+		input: `
+			01f004076e58aae772bb101ab1a8e64e01ee96e64857ce82b1113817c6cdd52c09d26f7b90981cd7
+			ae835aeac72e1573b8a0225dd56d157a010846d888dac7464baf53f2ad4e3d584531fa203658fab0
+			3a06c9fd5e35737e417bc28c1cbf5e5dfc666de7090f69c3b29754725f84f75382891c561040ea1d
+			dc0d8f381ed1b9d0d4ad2a0ec021421d847820d6fa0ba66eaf58175f1b235e851c7e2124069fbc20
+			2888ddb3ac4d56bcbd1b9b7eab59e78f2e2d400905050f4a92dec1c4bdf797b3fc9b2f8e84a482f3
+			d800386186712dae00d5c386ec9387a5e9c9a1aca5a573ca91082c7d68421f388e79127a5177d4f8
+			590237364fd348c9611fa39f78dcdceee3f390f07991b7b47e1daa3ebcb6ccc9607811cb17ce51f1
+			c8c2c5098dbdd28fca547b3f58c01a424ac05f869f49c6a34672ea2cbbc558428aa1fe48bbfd6115
+			8b1b735a65d99f21e70dbc020bfdface9f724a0d1fb5895db971cc81aa7608baa0920abb0a565c9c
+			436e2fd13323428296c86385f2384e408a31e104670df0791d93e743a3a5194ee6b076fb6323ca59
+			3011b7348c16cf58f66b9633906ba54a2ee803187344b394f75dd2e663a57b956cb830dd7a908d4f
+			39a2336a61ef9fda549180d4ccde21514d117b6c6fd07a9102b5efe710a32af4eeacae2cb3b1dec0
+			35b9593b48b9d3ca4c13d245d5f04169b0b1
+		`,
+		wantVersion: 57,
+		wantRest:    []rlp.RawValue{{0x06}, {0xC2, 0x07, 0x08}, {0x81, 0xFA}},
+	},
+}
+
+func TestHandshakeForwardCompatibility(t *testing.T) {
+	var (
+		keyA, _       = crypto.HexToECDSA("49a7b37aa6f6645917e7b807e9d1c00d4fa71f18343b0d4122a4d2df64dd6fee")
+		keyB, _       = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		pubA          = crypto.FromECDSAPub(&keyA.PublicKey)[1:]
+		pubB          = crypto.FromECDSAPub(&keyB.PublicKey)[1:]
+		ephA, _       = crypto.HexToECDSA("869d6ecf5211f1cc60418a13b9d870b22959d0c16f02bec714c960dd2298a32d")
+		ephB, _       = crypto.HexToECDSA("e238eb8e04fee6511ab04c6dd3c89ce097b11f25d584863ac2b6d5b35b1847e4")
+		ephPubA       = crypto.FromECDSAPub(&ephA.PublicKey)[1:]
+		ephPubB       = crypto.FromECDSAPub(&ephB.PublicKey)[1:]
+		nonceA        = unhex("7e968bba13b6c50e2c4cd7f241cc0d64d1ac25c7f5952df231ac6a2bda8ee5d6")
+		nonceB        = unhex("559aead08264d5795d3909718cdd05abd49572e84fe55590eef31a88a08fdffd")
+		_, _, _, _    = pubA, pubB, ephPubA, ephPubB
+		authSignature = unhex("299ca6acfd35e3d72d8ba3d1e2b60b5561d5af5218eb5bc182045769eb4226910a301acae3b369fffc4a4899d6b02531e89fd4fe36a2cf0d93607ba470b50f7800")
+		_             = authSignature
+	)
+	makeAuth := func(test handshakeAuthTest) *authMsgV4 {
+		msg := &authMsgV4{Version: test.wantVersion, Rest: test.wantRest, gotPlain: test.isPlain}
+		copy(msg.Signature[:], authSignature)
+		copy(msg.InitiatorPubkey[:], pubA)
+		copy(msg.Nonce[:], nonceA)
+		return msg
+	}
+	makeAck := func(test handshakeAckTest) *authRespV4 {
+		msg := &authRespV4{Version: test.wantVersion, Rest: test.wantRest}
+		copy(msg.RandomPubkey[:], ephPubB)
+		copy(msg.Nonce[:], nonceB)
+		return msg
+	}
+
+	// check auth msg parsing
+	for _, test := range eip8HandshakeAuthTests {
+		r := bytes.NewReader(unhex(test.input))
+		msg := new(authMsgV4)
+		ciphertext, err := readHandshakeMsg(msg, encAuthMsgLen, keyB, r)
+		if err != nil {
+			t.Errorf("error for input %x:\n  %v", unhex(test.input), err)
+			continue
+		}
+		if !bytes.Equal(ciphertext, unhex(test.input)) {
+			t.Errorf("wrong ciphertext for input %x:\n  %x", unhex(test.input), ciphertext)
+		}
+		want := makeAuth(test)
+		if !reflect.DeepEqual(msg, want) {
+			t.Errorf("wrong msg for input %x:\ngot %s\nwant %s", unhex(test.input), spew.Sdump(msg), spew.Sdump(want))
+		}
+	}
+
+	// check auth resp parsing
+	for _, test := range eip8HandshakeRespTests {
+		input := unhex(test.input)
+		r := bytes.NewReader(input)
+		msg := new(authRespV4)
+		ciphertext, err := readHandshakeMsg(msg, encAuthRespLen, keyA, r)
+		if err != nil {
+			t.Errorf("error for input %x:\n  %v", input, err)
+			continue
+		}
+		if !bytes.Equal(ciphertext, input) {
+			t.Errorf("wrong ciphertext for input %x:\n  %x", input, err)
+		}
+		want := makeAck(test)
+		if !reflect.DeepEqual(msg, want) {
+			t.Errorf("wrong msg for input %x:\ngot %s\nwant %s", input, spew.Sdump(msg), spew.Sdump(want))
+		}
+	}
+
+	// check derivation for (Auth₂, Ack₂) on recipient side
+	var (
+		hs = &encHandshake{
+			initiator:     false,
+			respNonce:     nonceB,
+			randomPrivKey: ecies.ImportECDSA(ephB),
+		}
+		authCiphertext     = unhex(eip8HandshakeAuthTests[1].input)
+		authRespCiphertext = unhex(eip8HandshakeRespTests[1].input)
+		authMsg            = makeAuth(eip8HandshakeAuthTests[1])
+		wantAES            = unhex("80e8632c05fed6fc2a13b0f8d31a3cf645366239170ea067065aba8e28bac487")
+		wantMAC            = unhex("2ea74ec5dae199227dff1af715362700e989d889d7a493cb0639691efb8e5f98")
+		wantFooIngressHash = unhex("0c7ec6340062cc46f5e9f1e3cf86f8c8c403c5a0964f5df0ebd34a75ddc86db5")
+	)
+	if err := hs.handleAuthMsg(authMsg, keyB); err != nil {
+		t.Fatalf("handleAuthMsg: %v", err)
+	}
+	derived, err := hs.secrets(authCiphertext, authRespCiphertext)
+	if err != nil {
+		t.Fatalf("secrets: %v", err)
+	}
+	if !bytes.Equal(derived.AES, wantAES) {
+		t.Errorf("aes-secret mismatch:\ngot %x\nwant %x", derived.AES, wantAES)
+	}
+	if !bytes.Equal(derived.MAC, wantMAC) {
+		t.Errorf("mac-secret mismatch:\ngot %x\nwant %x", derived.MAC, wantMAC)
+	}
+	io.WriteString(derived.IngressMAC, "foo")
+	fooIngressHash := derived.IngressMAC.Sum(nil)
+	if !bytes.Equal(fooIngressHash, wantFooIngressHash) {
+		t.Errorf("ingress-mac('foo') mismatch:\ngot %x\nwant %x", fooIngressHash, wantFooIngressHash)
+	}
+}