p2p: disable encryption handshake
The diff is a bit bigger than expected because the protocol handshake logic has moved out of Peer. This is necessary because the protocol handshake will have custom framing in the final protocol.
This commit is contained in:
Felix Lange
434
p2p/handshake.go
Normal file
434
p2p/handshake.go
Normal file
@ -0,0 +1,434 @@
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package p2p
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import (
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"crypto/ecdsa"
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"crypto/rand"
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"errors"
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"fmt"
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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/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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iHSLen = authMsgLen + eciesBytes // size of the final ECIES payload sent as initiator's handshake
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rHSLen = authRespLen + eciesBytes // size of the final ECIES payload sent as receiver's handshake
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)
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type conn struct {
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*frameRW
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*protoHandshake
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}
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func newConn(fd net.Conn, hs *protoHandshake) *conn {
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return &conn{newFrameRW(fd, msgWriteTimeout), hs}
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}
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// encHandshake represents information about the remote end
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// of a connection that is negotiated during the encryption handshake.
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type encHandshake struct {
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ID discover.NodeID
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IngressMAC []byte
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EgressMAC []byte
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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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// var remotePubkey []byte
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// sessionToken, remotePubkey, err = inboundEncHandshake(fd, prv, nil)
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// copy(remoteID[:], remotePubkey)
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rw := newFrameRW(fd, msgWriteTimeout)
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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 err := writeProtocolHandshake(rw, 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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// remoteID = dial.ID
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// sessionToken, err = outboundEncHandshake(fd, prv, remoteID[:], nil)
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rw := newFrameRW(fd, msgWriteTimeout)
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if err := writeProtocolHandshake(rw, 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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// outboundEncHandshake 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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// privateKey is the local client's private key
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// remotePublicKey is the remote peer's node ID
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// sessionToken is the token from a previous session with this node.
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func outboundEncHandshake(conn io.ReadWriter, prvKey *ecdsa.PrivateKey, remotePublicKey []byte, sessionToken []byte) (
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newSessionToken []byte,
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err error,
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) {
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auth, initNonce, randomPrivKey, err := authMsg(prvKey, remotePublicKey, sessionToken)
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if err != nil {
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return nil, err
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}
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if _, err = conn.Write(auth); err != nil {
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return nil, err
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}
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response := make([]byte, rHSLen)
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if _, err = io.ReadFull(conn, response); err != nil {
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return nil, err
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}
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recNonce, remoteRandomPubKey, _, err := completeHandshake(response, prvKey)
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if err != nil {
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return nil, err
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}
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return newSession(initNonce, recNonce, randomPrivKey, remoteRandomPubKey)
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}
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// authMsg creates the initiator handshake.
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func authMsg(prvKey *ecdsa.PrivateKey, remotePubKeyS, sessionToken []byte) (
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auth, initNonce []byte,
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randomPrvKey *ecdsa.PrivateKey,
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err error,
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) {
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// session init, common to both parties
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remotePubKey, err := importPublicKey(remotePubKeyS)
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if err != nil {
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return
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}
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var tokenFlag byte // = 0x00
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if sessionToken == 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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if sessionToken, err = ecies.ImportECDSA(prvKey).GenerateShared(ecies.ImportECDSAPublic(remotePubKey), sskLen, sskLen); err != nil {
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return
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}
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// tokenFlag = 0x00 // redundant
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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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//E(remote-pubk, S(ecdhe-random, ecdh-shared-secret^nonce) || H(ecdhe-random-pubk) || pubk || nonce || 0x0)
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// E(remote-pubk, S(ecdhe-random, token^nonce) || H(ecdhe-random-pubk) || pubk || nonce || 0x1)
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// allocate msgLen long message,
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var msg []byte = make([]byte, authMsgLen)
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initNonce = msg[authMsgLen-shaLen-1 : authMsgLen-1]
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if _, err = rand.Read(initNonce); err != nil {
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return
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}
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// create 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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var sharedSecret = xor(sessionToken, initNonce)
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// generate random keypair to use for signing
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if randomPrvKey, err = crypto.GenerateKey(); err != nil {
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return
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}
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// sign shared secret (message known to both parties): shared-secret
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var signature []byte
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// signature = sign(ecdhe-random, shared-secret)
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// uses secp256k1.Sign
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if signature, err = crypto.Sign(sharedSecret, randomPrvKey); err != nil {
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return
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}
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// message
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// signed-shared-secret || H(ecdhe-random-pubk) || pubk || nonce || 0x0
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copy(msg, signature) // copy signed-shared-secret
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// H(ecdhe-random-pubk)
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var randomPubKey64 []byte
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if randomPubKey64, err = exportPublicKey(&randomPrvKey.PublicKey); err != nil {
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return
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}
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var pubKey64 []byte
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if pubKey64, err = exportPublicKey(&prvKey.PublicKey); err != nil {
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return
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}
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copy(msg[sigLen:sigLen+shaLen], crypto.Sha3(randomPubKey64))
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// pubkey copied to the correct segment.
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copy(msg[sigLen+shaLen:sigLen+shaLen+pubLen], pubKey64)
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// nonce is already in the slice
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// stick tokenFlag byte to the end
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msg[authMsgLen-1] = tokenFlag
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// encrypt using remote-pubk
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// auth = eciesEncrypt(remote-pubk, msg)
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if auth, err = crypto.Encrypt(remotePubKey, msg); err != nil {
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return
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}
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return
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}
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// completeHandshake is called when the initiator receives an
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// authentication response (aka receiver handshake). It completes the
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// handshake by reading off parameters the remote peer provides needed
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// to set up the secure session.
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func completeHandshake(auth []byte, prvKey *ecdsa.PrivateKey) (
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respNonce []byte,
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remoteRandomPubKey *ecdsa.PublicKey,
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tokenFlag bool,
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err error,
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) {
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var msg []byte
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// they prove that msg is meant for me,
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// I prove I possess private key if i can read it
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if msg, err = crypto.Decrypt(prvKey, auth); err != nil {
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return
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}
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respNonce = msg[pubLen : pubLen+shaLen]
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var remoteRandomPubKeyS = msg[:pubLen]
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if remoteRandomPubKey, err = importPublicKey(remoteRandomPubKeyS); err != nil {
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return
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}
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if msg[authRespLen-1] == 0x01 {
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tokenFlag = true
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}
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return
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}
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// inboundEncHandshake 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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// privateKey is the local client's private key
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// sessionToken is the token from a previous session with this node.
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func inboundEncHandshake(conn io.ReadWriter, prvKey *ecdsa.PrivateKey, sessionToken []byte) (
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token, remotePubKey []byte,
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err error,
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) {
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// we are listening connection. we are responders in the
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// handshake. Extract info from the authentication. The initiator
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// starts by sending us a handshake that we need to respond to. so
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// we read auth message first, then respond.
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auth := make([]byte, iHSLen)
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if _, err := io.ReadFull(conn, auth); err != nil {
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return nil, nil, err
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}
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response, recNonce, initNonce, remotePubKey, randomPrivKey, remoteRandomPubKey, err := authResp(auth, sessionToken, prvKey)
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if err != nil {
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return nil, nil, err
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}
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if _, err = conn.Write(response); err != nil {
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return nil, nil, err
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}
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token, err = newSession(initNonce, recNonce, randomPrivKey, remoteRandomPubKey)
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return token, remotePubKey, err
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}
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// authResp is called by peer if it accepted (but not
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// initiated) the connection from the remote. It is passed the initiator
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// handshake received and the session token belonging to the
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// remote initiator.
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//
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// The first return value is the authentication response (aka receiver
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// handshake) that is to be sent to the remote initiator.
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func authResp(auth, sessionToken []byte, prvKey *ecdsa.PrivateKey) (
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authResp, respNonce, initNonce, remotePubKeyS []byte,
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randomPrivKey *ecdsa.PrivateKey,
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remoteRandomPubKey *ecdsa.PublicKey,
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err error,
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) {
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// they prove that msg is meant for me,
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// I prove I possess private key if i can read it
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msg, err := crypto.Decrypt(prvKey, auth)
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if err != nil {
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return
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}
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remotePubKeyS = msg[sigLen+shaLen : sigLen+shaLen+pubLen]
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remotePubKey, _ := importPublicKey(remotePubKeyS)
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var tokenFlag byte
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if sessionToken == 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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if sessionToken, err = ecies.ImportECDSA(prvKey).GenerateShared(ecies.ImportECDSAPublic(remotePubKey), sskLen, sskLen); err != nil {
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return
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}
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// tokenFlag = 0x00 // redundant
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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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// the initiator nonce is read off the end of the message
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initNonce = msg[authMsgLen-shaLen-1 : authMsgLen-1]
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// I prove that i own prv key (to derive shared secret, and read
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// nonce off encrypted msg) and that I own shared secret they
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// prove they own the private key belonging to ecdhe-random-pubk
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// we can now reconstruct the signed message and recover the peers
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// pubkey
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var signedMsg = xor(sessionToken, initNonce)
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var remoteRandomPubKeyS []byte
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if remoteRandomPubKeyS, err = secp256k1.RecoverPubkey(signedMsg, msg[:sigLen]); err != nil {
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return
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}
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// convert to ECDSA standard
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if remoteRandomPubKey, err = importPublicKey(remoteRandomPubKeyS); err != nil {
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return
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}
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// now we find ourselves a long task too, fill it random
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var resp = make([]byte, authRespLen)
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// generate shaLen long nonce
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respNonce = resp[pubLen : pubLen+shaLen]
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if _, err = rand.Read(respNonce); err != nil {
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return
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}
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// generate random keypair for session
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if randomPrivKey, err = crypto.GenerateKey(); err != nil {
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return
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}
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// responder auth message
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// E(remote-pubk, ecdhe-random-pubk || nonce || 0x0)
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var randomPubKeyS []byte
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if randomPubKeyS, err = exportPublicKey(&randomPrivKey.PublicKey); err != nil {
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return
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}
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copy(resp[:pubLen], randomPubKeyS)
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// nonce is already in the slice
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resp[authRespLen-1] = tokenFlag
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// encrypt using remote-pubk
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// auth = eciesEncrypt(remote-pubk, msg)
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// why not encrypt with ecdhe-random-remote
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if authResp, err = crypto.Encrypt(remotePubKey, resp); err != nil {
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return
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}
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return
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}
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// newSession is called after the handshake is completed. The
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// arguments are values negotiated in the handshake. The return value
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// is a new session Token to be remembered for the next time we
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// connect with this peer.
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func newSession(initNonce, respNonce []byte, privKey *ecdsa.PrivateKey, remoteRandomPubKey *ecdsa.PublicKey) ([]byte, error) {
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// 3) Now we can trust ecdhe-random-pubk to derive new keys
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//ecdhe-shared-secret = ecdh.agree(ecdhe-random, remote-ecdhe-random-pubk)
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pubKey := ecies.ImportECDSAPublic(remoteRandomPubKey)
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dhSharedSecret, err := ecies.ImportECDSA(privKey).GenerateShared(pubKey, sskLen, sskLen)
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if err != nil {
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return nil, err
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}
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sharedSecret := crypto.Sha3(dhSharedSecret, crypto.Sha3(respNonce, initNonce))
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sessionToken := crypto.Sha3(sharedSecret)
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return sessionToken, nil
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}
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// importPublicKey unmarshals 512 bit public keys.
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func importPublicKey(pubKey []byte) (pubKeyEC *ecdsa.PublicKey, err 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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return crypto.ToECDSAPub(pubKey65), nil
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}
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func exportPublicKey(pubKeyEC *ecdsa.PublicKey) (pubKey []byte, err error) {
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if pubKeyEC == nil {
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return nil, fmt.Errorf("no ECDSA public key given")
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}
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return crypto.FromECDSAPub(pubKeyEC)[1:], nil
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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 writeProtocolHandshake(w MsgWriter, our *protoHandshake) error {
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return EncodeMsg(w, handshakeMsg, our.Version, our.Name, our.Caps, our.ListenPort, our.ID[:])
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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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