5ba51594c7
Message encoding functions have been renamed to catch any uses. The switch to the new encoder can cause subtle incompatibilities. If there are any users outside of our tree, they will at least be alerted that there was a change. NewMsg no longer exists. The replacements for EncodeMsg are called Send and SendItems.
433 lines
13 KiB
Go
433 lines
13 KiB
Go
package p2p
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import (
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rand"
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"errors"
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"fmt"
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"hash"
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"io"
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"net"
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"github.com/ethereum/go-ethereum/crypto"
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"github.com/ethereum/go-ethereum/crypto/ecies"
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"github.com/ethereum/go-ethereum/crypto/secp256k1"
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"github.com/ethereum/go-ethereum/crypto/sha3"
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"github.com/ethereum/go-ethereum/p2p/discover"
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"github.com/ethereum/go-ethereum/rlp"
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)
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const (
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sskLen = 16 // ecies.MaxSharedKeyLength(pubKey) / 2
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sigLen = 65 // elliptic S256
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pubLen = 64 // 512 bit pubkey in uncompressed representation without format byte
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shaLen = 32 // hash length (for nonce etc)
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authMsgLen = sigLen + shaLen + pubLen + shaLen + 1
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authRespLen = pubLen + shaLen + 1
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eciesBytes = 65 + 16 + 32
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encAuthMsgLen = authMsgLen + eciesBytes // size of the final ECIES payload sent as initiator's handshake
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encAuthRespLen = authRespLen + eciesBytes // size of the final ECIES payload sent as receiver's handshake
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)
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// conn represents a remote connection after encryption handshake
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// and protocol handshake have completed.
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//
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// The MsgReadWriter is usually layered as follows:
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//
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// netWrapper (I/O timeouts, thread-safe ReadMsg, WriteMsg)
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// rlpxFrameRW (message encoding, encryption, authentication)
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// bufio.ReadWriter (buffering)
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// net.Conn (network I/O)
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//
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type conn struct {
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MsgReadWriter
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*protoHandshake
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}
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// secrets represents the connection secrets
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// which are negotiated during the encryption handshake.
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type secrets struct {
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RemoteID discover.NodeID
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AES, MAC []byte
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EgressMAC, IngressMAC hash.Hash
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Token []byte
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}
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// protoHandshake is the RLP structure of the protocol handshake.
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type protoHandshake struct {
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Version uint64
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Name string
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Caps []Cap
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ListenPort uint64
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ID discover.NodeID
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}
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// setupConn starts a protocol session on the given connection.
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// It runs the encryption handshake and the protocol handshake.
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// If dial is non-nil, the connection the local node is the initiator.
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func setupConn(fd net.Conn, prv *ecdsa.PrivateKey, our *protoHandshake, dial *discover.Node) (*conn, error) {
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if dial == nil {
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return setupInboundConn(fd, prv, our)
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} else {
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return setupOutboundConn(fd, prv, our, dial)
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}
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}
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func setupInboundConn(fd net.Conn, prv *ecdsa.PrivateKey, our *protoHandshake) (*conn, error) {
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secrets, err := receiverEncHandshake(fd, prv, nil)
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if err != nil {
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return nil, fmt.Errorf("encryption handshake failed: %v", err)
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}
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// Run the protocol handshake using authenticated messages.
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rw := newRlpxFrameRW(fd, secrets)
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rhs, err := readProtocolHandshake(rw, our)
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if err != nil {
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return nil, err
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}
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if rhs.ID != secrets.RemoteID {
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return nil, errors.New("node ID in protocol handshake does not match encryption handshake")
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}
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// TODO: validate that handshake node ID matches
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if err := Send(rw, handshakeMsg, our); err != nil {
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return nil, fmt.Errorf("protocol write error: %v", err)
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}
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return &conn{rw, rhs}, nil
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}
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func setupOutboundConn(fd net.Conn, prv *ecdsa.PrivateKey, our *protoHandshake, dial *discover.Node) (*conn, error) {
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secrets, err := initiatorEncHandshake(fd, prv, dial.ID, nil)
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if err != nil {
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return nil, fmt.Errorf("encryption handshake failed: %v", err)
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}
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// Run the protocol handshake using authenticated messages.
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rw := newRlpxFrameRW(fd, secrets)
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if err := Send(rw, handshakeMsg, our); err != nil {
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return nil, fmt.Errorf("protocol write error: %v", err)
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}
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rhs, err := readProtocolHandshake(rw, our)
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if err != nil {
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return nil, fmt.Errorf("protocol handshake read error: %v", err)
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}
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if rhs.ID != dial.ID {
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return nil, errors.New("dialed node id mismatch")
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}
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return &conn{rw, rhs}, nil
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}
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// encHandshake contains the state of the encryption handshake.
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type encHandshake struct {
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initiator bool
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remoteID discover.NodeID
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remotePub *ecies.PublicKey // remote-pubk
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initNonce, respNonce []byte // nonce
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randomPrivKey *ecies.PrivateKey // ecdhe-random
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remoteRandomPub *ecies.PublicKey // ecdhe-random-pubk
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}
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// secrets is called after the handshake is completed.
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// It extracts the connection secrets from the handshake values.
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func (h *encHandshake) secrets(auth, authResp []byte) (secrets, error) {
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ecdheSecret, err := h.randomPrivKey.GenerateShared(h.remoteRandomPub, sskLen, sskLen)
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if err != nil {
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return secrets{}, err
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}
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// derive base secrets from ephemeral key agreement
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sharedSecret := crypto.Sha3(ecdheSecret, crypto.Sha3(h.respNonce, h.initNonce))
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aesSecret := crypto.Sha3(ecdheSecret, sharedSecret)
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s := secrets{
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RemoteID: h.remoteID,
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AES: aesSecret,
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MAC: crypto.Sha3(ecdheSecret, aesSecret),
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Token: crypto.Sha3(sharedSecret),
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}
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// setup sha3 instances for the MACs
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mac1 := sha3.NewKeccak256()
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mac1.Write(xor(s.MAC, h.respNonce))
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mac1.Write(auth)
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mac2 := sha3.NewKeccak256()
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mac2.Write(xor(s.MAC, h.initNonce))
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mac2.Write(authResp)
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if h.initiator {
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s.EgressMAC, s.IngressMAC = mac1, mac2
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} else {
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s.EgressMAC, s.IngressMAC = mac2, mac1
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}
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return s, nil
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}
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func (h *encHandshake) ecdhShared(prv *ecdsa.PrivateKey) ([]byte, error) {
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return ecies.ImportECDSA(prv).GenerateShared(h.remotePub, sskLen, sskLen)
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}
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// initiatorEncHandshake negotiates a session token on conn.
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// it should be called on the dialing side of the connection.
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//
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// prv is the local client's private key.
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// token is the token from a previous session with this node.
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func initiatorEncHandshake(conn io.ReadWriter, prv *ecdsa.PrivateKey, remoteID discover.NodeID, token []byte) (s secrets, err error) {
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h, err := newInitiatorHandshake(remoteID)
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if err != nil {
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return s, err
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}
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auth, err := h.authMsg(prv, token)
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if err != nil {
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return s, err
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}
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if _, err = conn.Write(auth); err != nil {
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return s, err
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}
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response := make([]byte, encAuthRespLen)
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if _, err = io.ReadFull(conn, response); err != nil {
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return s, err
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}
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if err := h.decodeAuthResp(response, prv); err != nil {
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return s, err
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}
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return h.secrets(auth, response)
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}
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func newInitiatorHandshake(remoteID discover.NodeID) (*encHandshake, error) {
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// generate random initiator nonce
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n := make([]byte, shaLen)
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if _, err := rand.Read(n); err != nil {
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return nil, err
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}
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// generate random keypair to use for signing
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randpriv, err := ecies.GenerateKey(rand.Reader, crypto.S256(), nil)
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if err != nil {
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return nil, err
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}
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rpub, err := remoteID.Pubkey()
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if err != nil {
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return nil, fmt.Errorf("bad remoteID: %v", err)
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}
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h := &encHandshake{
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initiator: true,
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remoteID: remoteID,
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remotePub: ecies.ImportECDSAPublic(rpub),
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initNonce: n,
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randomPrivKey: randpriv,
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}
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return h, nil
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}
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// authMsg creates an encrypted initiator handshake message.
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func (h *encHandshake) authMsg(prv *ecdsa.PrivateKey, token []byte) ([]byte, error) {
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var tokenFlag byte
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if token == nil {
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// no session token found means we need to generate shared secret.
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// ecies shared secret is used as initial session token for new peers
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// generate shared key from prv and remote pubkey
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var err error
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if token, err = h.ecdhShared(prv); err != nil {
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return nil, err
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}
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} else {
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// for known peers, we use stored token from the previous session
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tokenFlag = 0x01
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}
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// sign known message:
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// ecdh-shared-secret^nonce for new peers
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// token^nonce for old peers
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signed := xor(token, h.initNonce)
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signature, err := crypto.Sign(signed, h.randomPrivKey.ExportECDSA())
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if err != nil {
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return nil, err
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}
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// encode auth message
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// signature || sha3(ecdhe-random-pubk) || pubk || nonce || token-flag
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msg := make([]byte, authMsgLen)
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n := copy(msg, signature)
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n += copy(msg[n:], crypto.Sha3(exportPubkey(&h.randomPrivKey.PublicKey)))
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n += copy(msg[n:], crypto.FromECDSAPub(&prv.PublicKey)[1:])
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n += copy(msg[n:], h.initNonce)
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msg[n] = tokenFlag
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// encrypt auth message using remote-pubk
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return ecies.Encrypt(rand.Reader, h.remotePub, msg, nil, nil)
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}
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// decodeAuthResp decode an encrypted authentication response message.
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func (h *encHandshake) decodeAuthResp(auth []byte, prv *ecdsa.PrivateKey) error {
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msg, err := crypto.Decrypt(prv, auth)
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if err != nil {
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return fmt.Errorf("could not decrypt auth response (%v)", err)
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}
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h.respNonce = msg[pubLen : pubLen+shaLen]
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h.remoteRandomPub, err = importPublicKey(msg[:pubLen])
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if err != nil {
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return err
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}
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// ignore token flag for now
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return nil
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}
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// receiverEncHandshake negotiates a session token on conn.
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// it should be called on the listening side of the connection.
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//
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// prv is the local client's private key.
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// token is the token from a previous session with this node.
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func receiverEncHandshake(conn io.ReadWriter, prv *ecdsa.PrivateKey, token []byte) (s secrets, err error) {
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// read remote auth sent by initiator.
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auth := make([]byte, encAuthMsgLen)
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if _, err := io.ReadFull(conn, auth); err != nil {
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return s, err
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}
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h, err := decodeAuthMsg(prv, token, auth)
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if err != nil {
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return s, err
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}
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// send auth response
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resp, err := h.authResp(prv, token)
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if err != nil {
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return s, err
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}
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if _, err = conn.Write(resp); err != nil {
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return s, err
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}
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return h.secrets(auth, resp)
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}
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func decodeAuthMsg(prv *ecdsa.PrivateKey, token []byte, auth []byte) (*encHandshake, error) {
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var err error
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h := new(encHandshake)
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// generate random keypair for session
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h.randomPrivKey, err = ecies.GenerateKey(rand.Reader, crypto.S256(), nil)
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if err != nil {
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return nil, err
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}
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// generate random nonce
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h.respNonce = make([]byte, shaLen)
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if _, err = rand.Read(h.respNonce); err != nil {
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return nil, err
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}
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msg, err := crypto.Decrypt(prv, auth)
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if err != nil {
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return nil, fmt.Errorf("could not decrypt auth message (%v)", err)
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}
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// decode message parameters
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// signature || sha3(ecdhe-random-pubk) || pubk || nonce || token-flag
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h.initNonce = msg[authMsgLen-shaLen-1 : authMsgLen-1]
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copy(h.remoteID[:], msg[sigLen+shaLen:sigLen+shaLen+pubLen])
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rpub, err := h.remoteID.Pubkey()
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if err != nil {
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return nil, fmt.Errorf("bad remoteID: %#v", err)
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}
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h.remotePub = ecies.ImportECDSAPublic(rpub)
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// recover remote random pubkey from signed message.
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if token == nil {
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// TODO: it is an error if the initiator has a token and we don't. check that.
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// no session token means we need to generate shared secret.
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// ecies shared secret is used as initial session token for new peers.
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// generate shared key from prv and remote pubkey.
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if token, err = h.ecdhShared(prv); err != nil {
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return nil, err
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}
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}
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signedMsg := xor(token, h.initNonce)
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remoteRandomPub, err := secp256k1.RecoverPubkey(signedMsg, msg[:sigLen])
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if err != nil {
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return nil, err
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}
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h.remoteRandomPub, _ = importPublicKey(remoteRandomPub)
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return h, nil
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}
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// authResp generates the encrypted authentication response message.
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func (h *encHandshake) authResp(prv *ecdsa.PrivateKey, token []byte) ([]byte, error) {
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// responder auth message
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// E(remote-pubk, ecdhe-random-pubk || nonce || 0x0)
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resp := make([]byte, authRespLen)
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n := copy(resp, exportPubkey(&h.randomPrivKey.PublicKey))
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n += copy(resp[n:], h.respNonce)
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if token == nil {
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resp[n] = 0
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} else {
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resp[n] = 1
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}
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// encrypt using remote-pubk
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return ecies.Encrypt(rand.Reader, h.remotePub, resp, nil, nil)
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}
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// importPublicKey unmarshals 512 bit public keys.
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func importPublicKey(pubKey []byte) (*ecies.PublicKey, error) {
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var pubKey65 []byte
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switch len(pubKey) {
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case 64:
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// add 'uncompressed key' flag
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pubKey65 = append([]byte{0x04}, pubKey...)
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case 65:
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pubKey65 = pubKey
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default:
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return nil, fmt.Errorf("invalid public key length %v (expect 64/65)", len(pubKey))
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}
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// TODO: fewer pointless conversions
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return ecies.ImportECDSAPublic(crypto.ToECDSAPub(pubKey65)), nil
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}
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func exportPubkey(pub *ecies.PublicKey) []byte {
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if pub == nil {
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panic("nil pubkey")
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}
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return elliptic.Marshal(pub.Curve, pub.X, pub.Y)[1:]
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}
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func xor(one, other []byte) (xor []byte) {
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xor = make([]byte, len(one))
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for i := 0; i < len(one); i++ {
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xor[i] = one[i] ^ other[i]
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}
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return xor
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}
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func readProtocolHandshake(r MsgReader, our *protoHandshake) (*protoHandshake, error) {
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// read and handle remote handshake
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msg, err := r.ReadMsg()
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if err != nil {
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return nil, err
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}
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if msg.Code == discMsg {
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// disconnect before protocol handshake is valid according to the
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// spec and we send it ourself if Server.addPeer fails.
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var reason DiscReason
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rlp.Decode(msg.Payload, &reason)
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return nil, discRequestedError(reason)
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}
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if msg.Code != handshakeMsg {
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return nil, fmt.Errorf("expected handshake, got %x", msg.Code)
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}
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if msg.Size > baseProtocolMaxMsgSize {
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return nil, fmt.Errorf("message too big (%d > %d)", msg.Size, baseProtocolMaxMsgSize)
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}
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var hs protoHandshake
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if err := msg.Decode(&hs); err != nil {
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return nil, err
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}
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// validate handshake info
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if hs.Version != our.Version {
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return nil, newPeerError(errP2PVersionMismatch, "required version %d, received %d\n", baseProtocolVersion, hs.Version)
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}
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if (hs.ID == discover.NodeID{}) {
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return nil, newPeerError(errPubkeyInvalid, "missing")
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}
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return &hs, nil
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}
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