1 files changed, 363 insertions, 0 deletions
diff --git a/p2p/crypto.go b/p2p/crypto.go
new file mode 100644
index 000000000..2692d708c
--- /dev/null
+++ b/p2p/crypto.go
@@ -0,0 +1,363 @@
+package p2p
+
+import (
+	// "binary"
+	"crypto/ecdsa"
+	"crypto/rand"
+	"fmt"
+	"io"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/crypto/secp256k1"
+	ethlogger "github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/p2p/discover"
+	"github.com/obscuren/ecies"
+)
+
+var clogger = ethlogger.NewLogger("CRYPTOID")
+
+const (
+	sskLen = 16 // ecies.MaxSharedKeyLength(pubKey) / 2
+	sigLen = 65 // elliptic S256
+	pubLen = 64 // 512 bit pubkey in uncompressed representation without format byte
+	shaLen = 32 // hash length (for nonce etc)
+
+	authMsgLen  = sigLen + shaLen + pubLen + shaLen + 1
+	authRespLen = pubLen + shaLen + 1
+
+	eciesBytes = 65 + 16 + 32
+	iHSLen     = authMsgLen + eciesBytes  // size of the final ECIES payload sent as initiator's handshake
+	rHSLen     = authRespLen + eciesBytes // size of the final ECIES payload sent as receiver's handshake
+)
+
+type hexkey []byte
+
+func (self hexkey) String() string {
+	return fmt.Sprintf("(%d) %x", len(self), []byte(self))
+}
+
+func encHandshake(conn io.ReadWriter, prv *ecdsa.PrivateKey, dial *discover.Node) (
+	remoteID discover.NodeID,
+	sessionToken []byte,
+	err error,
+) {
+	if dial == nil {
+		var remotePubkey []byte
+		sessionToken, remotePubkey, err = inboundEncHandshake(conn, prv, nil)
+		copy(remoteID[:], remotePubkey)
+	} else {
+		remoteID = dial.ID
+		sessionToken, err = outboundEncHandshake(conn, prv, remoteID[:], nil)
+	}
+	return remoteID, sessionToken, err
+}
+
+// outboundEncHandshake negotiates a session token on conn.
+// it should be called on the dialing side of the connection.
+//
+// privateKey is the local client's private key
+// remotePublicKey is the remote peer's node ID
+// sessionToken is the token from a previous session with this node.
+func outboundEncHandshake(conn io.ReadWriter, prvKey *ecdsa.PrivateKey, remotePublicKey []byte, sessionToken []byte) (
+	newSessionToken []byte,
+	err error,
+) {
+	auth, initNonce, randomPrivKey, err := authMsg(prvKey, remotePublicKey, sessionToken)
+	if err != nil {
+		return nil, err
+	}
+	if sessionToken != nil {
+		clogger.Debugf("session-token: %v", hexkey(sessionToken))
+	}
+
+	clogger.Debugf("initiator-nonce: %v", hexkey(initNonce))
+	clogger.Debugf("initiator-random-private-key: %v", hexkey(crypto.FromECDSA(randomPrivKey)))
+	randomPublicKeyS, _ := exportPublicKey(&randomPrivKey.PublicKey)
+	clogger.Debugf("initiator-random-public-key: %v", hexkey(randomPublicKeyS))
+	if _, err = conn.Write(auth); err != nil {
+		return nil, err
+	}
+	clogger.Debugf("initiator handshake: %v", hexkey(auth))
+
+	response := make([]byte, rHSLen)
+	if _, err = io.ReadFull(conn, response); err != nil {
+		return nil, err
+	}
+	recNonce, remoteRandomPubKey, _, err := completeHandshake(response, prvKey)
+	if err != nil {
+		return nil, err
+	}
+
+	clogger.Debugf("receiver-nonce: %v", hexkey(recNonce))
+	remoteRandomPubKeyS, _ := exportPublicKey(remoteRandomPubKey)
+	clogger.Debugf("receiver-random-public-key: %v", hexkey(remoteRandomPubKeyS))
+	return newSession(initNonce, recNonce, randomPrivKey, remoteRandomPubKey)
+}
+
+// authMsg creates the initiator handshake.
+func authMsg(prvKey *ecdsa.PrivateKey, remotePubKeyS, sessionToken []byte) (
+	auth, initNonce []byte,
+	randomPrvKey *ecdsa.PrivateKey,
+	err error,
+) {
+	// session init, common to both parties
+	remotePubKey, err := importPublicKey(remotePubKeyS)
+	if err != nil {
+		return
+	}
+
+	var tokenFlag byte // = 0x00
+	if sessionToken == 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
+		if sessionToken, err = ecies.ImportECDSA(prvKey).GenerateShared(ecies.ImportECDSAPublic(remotePubKey), sskLen, sskLen); err != nil {
+			return
+		}
+		// tokenFlag = 0x00 // redundant
+	} else {
+		// for known peers, we use stored token from the previous session
+		tokenFlag = 0x01
+	}
+
+	//E(remote-pubk, S(ecdhe-random, ecdh-shared-secret^nonce) || H(ecdhe-random-pubk) || pubk || nonce || 0x0)
+	// E(remote-pubk, S(ecdhe-random, token^nonce) || H(ecdhe-random-pubk) || pubk || nonce || 0x1)
+	// allocate msgLen long message,
+	var msg []byte = make([]byte, authMsgLen)
+	initNonce = msg[authMsgLen-shaLen-1 : authMsgLen-1]
+	if _, err = rand.Read(initNonce); err != nil {
+		return
+	}
+	// create known message
+	// ecdh-shared-secret^nonce for new peers
+	// token^nonce for old peers
+	var sharedSecret = xor(sessionToken, initNonce)
+
+	// generate random keypair to use for signing
+	if randomPrvKey, err = crypto.GenerateKey(); err != nil {
+		return
+	}
+	// sign shared secret (message known to both parties): shared-secret
+	var signature []byte
+	// signature = sign(ecdhe-random, shared-secret)
+	// uses secp256k1.Sign
+	if signature, err = crypto.Sign(sharedSecret, randomPrvKey); err != nil {
+		return
+	}
+
+	// message
+	// signed-shared-secret || H(ecdhe-random-pubk) || pubk || nonce || 0x0
+	copy(msg, signature) // copy signed-shared-secret
+	// H(ecdhe-random-pubk)
+	var randomPubKey64 []byte
+	if randomPubKey64, err = exportPublicKey(&randomPrvKey.PublicKey); err != nil {
+		return
+	}
+	var pubKey64 []byte
+	if pubKey64, err = exportPublicKey(&prvKey.PublicKey); err != nil {
+		return
+	}
+	copy(msg[sigLen:sigLen+shaLen], crypto.Sha3(randomPubKey64))
+	// pubkey copied to the correct segment.
+	copy(msg[sigLen+shaLen:sigLen+shaLen+pubLen], pubKey64)
+	// nonce is already in the slice
+	// stick tokenFlag byte to the end
+	msg[authMsgLen-1] = tokenFlag
+
+	// encrypt using remote-pubk
+	// auth = eciesEncrypt(remote-pubk, msg)
+	if auth, err = crypto.Encrypt(remotePubKey, msg); err != nil {
+		return
+	}
+	return
+}
+
+// completeHandshake is called when the initiator receives an
+// authentication response (aka receiver handshake). It completes the
+// handshake by reading off parameters the remote peer provides needed
+// to set up the secure session.
+func completeHandshake(auth []byte, prvKey *ecdsa.PrivateKey) (
+	respNonce []byte,
+	remoteRandomPubKey *ecdsa.PublicKey,
+	tokenFlag bool,
+	err error,
+) {
+	var msg []byte
+	// they prove that msg is meant for me,
+	// I prove I possess private key if i can read it
+	if msg, err = crypto.Decrypt(prvKey, auth); err != nil {
+		return
+	}
+
+	respNonce = msg[pubLen : pubLen+shaLen]
+	var remoteRandomPubKeyS = msg[:pubLen]
+	if remoteRandomPubKey, err = importPublicKey(remoteRandomPubKeyS); err != nil {
+		return
+	}
+	if msg[authRespLen-1] == 0x01 {
+		tokenFlag = true
+	}
+	return
+}
+
+// inboundEncHandshake negotiates a session token on conn.
+// it should be called on the listening side of the connection.
+//
+// privateKey is the local client's private key
+// sessionToken is the token from a previous session with this node.
+func inboundEncHandshake(conn io.ReadWriter, prvKey *ecdsa.PrivateKey, sessionToken []byte) (
+	token, remotePubKey []byte,
+	err error,
+) {
+	// we are listening connection. we are responders in the
+	// handshake. Extract info from the authentication. The initiator
+	// starts by sending us a handshake that we need to respond to. so
+	// we read auth message first, then respond.
+	auth := make([]byte, iHSLen)
+	if _, err := io.ReadFull(conn, auth); err != nil {
+		return nil, nil, err
+	}
+	response, recNonce, initNonce, remotePubKey, randomPrivKey, remoteRandomPubKey, err := authResp(auth, sessionToken, prvKey)
+	if err != nil {
+		return nil, nil, err
+	}
+	clogger.Debugf("receiver-nonce: %v", hexkey(recNonce))
+	clogger.Debugf("receiver-random-priv-key: %v", hexkey(crypto.FromECDSA(randomPrivKey)))
+	if _, err = conn.Write(response); err != nil {
+		return nil, nil, err
+	}
+	clogger.Debugf("receiver handshake:\n%v", hexkey(response))
+	token, err = newSession(initNonce, recNonce, randomPrivKey, remoteRandomPubKey)
+	return token, remotePubKey, err
+}
+
+// authResp is called by peer if it accepted (but not
+// initiated) the connection from the remote. It is passed the initiator
+// handshake received and the session token belonging to the
+// remote initiator.
+//
+// The first return value is the authentication response (aka receiver
+// handshake) that is to be sent to the remote initiator.
+func authResp(auth, sessionToken []byte, prvKey *ecdsa.PrivateKey) (
+	authResp, respNonce, initNonce, remotePubKeyS []byte,
+	randomPrivKey *ecdsa.PrivateKey,
+	remoteRandomPubKey *ecdsa.PublicKey,
+	err error,
+) {
+	// they prove that msg is meant for me,
+	// I prove I possess private key if i can read it
+	msg, err := crypto.Decrypt(prvKey, auth)
+	if err != nil {
+		return
+	}
+
+	remotePubKeyS = msg[sigLen+shaLen : sigLen+shaLen+pubLen]
+	remotePubKey, _ := importPublicKey(remotePubKeyS)
+
+	var tokenFlag byte
+	if sessionToken == 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
+		if sessionToken, err = ecies.ImportECDSA(prvKey).GenerateShared(ecies.ImportECDSAPublic(remotePubKey), sskLen, sskLen); err != nil {
+			return
+		}
+		// tokenFlag = 0x00 // redundant
+	} else {
+		// for known peers, we use stored token from the previous session
+		tokenFlag = 0x01
+	}
+
+	// the initiator nonce is read off the end of the message
+	initNonce = msg[authMsgLen-shaLen-1 : authMsgLen-1]
+	// I prove that i own prv key (to derive shared secret, and read
+	// nonce off encrypted msg) and that I own shared secret they
+	// prove they own the private key belonging to ecdhe-random-pubk
+	// we can now reconstruct the signed message and recover the peers
+	// pubkey
+	var signedMsg = xor(sessionToken, initNonce)
+	var remoteRandomPubKeyS []byte
+	if remoteRandomPubKeyS, err = secp256k1.RecoverPubkey(signedMsg, msg[:sigLen]); err != nil {
+		return
+	}
+	// convert to ECDSA standard
+	if remoteRandomPubKey, err = importPublicKey(remoteRandomPubKeyS); err != nil {
+		return
+	}
+
+	// now we find ourselves a long task too, fill it random
+	var resp = make([]byte, authRespLen)
+	// generate shaLen long nonce
+	respNonce = resp[pubLen : pubLen+shaLen]
+	if _, err = rand.Read(respNonce); err != nil {
+		return
+	}
+	// generate random keypair for session
+	if randomPrivKey, err = crypto.GenerateKey(); err != nil {
+		return
+	}
+	// responder auth message
+	// E(remote-pubk, ecdhe-random-pubk || nonce || 0x0)
+	var randomPubKeyS []byte
+	if randomPubKeyS, err = exportPublicKey(&randomPrivKey.PublicKey); err != nil {
+		return
+	}
+	copy(resp[:pubLen], randomPubKeyS)
+	// nonce is already in the slice
+	resp[authRespLen-1] = tokenFlag
+
+	// encrypt using remote-pubk
+	// auth = eciesEncrypt(remote-pubk, msg)
+	// why not encrypt with ecdhe-random-remote
+	if authResp, err = crypto.Encrypt(remotePubKey, resp); err != nil {
+		return
+	}
+	return
+}
+
+// newSession is called after the handshake is completed. The
+// arguments are values negotiated in the handshake. The return value
+// is a new session Token to be remembered for the next time we
+// connect with this peer.
+func newSession(initNonce, respNonce []byte, privKey *ecdsa.PrivateKey, remoteRandomPubKey *ecdsa.PublicKey) ([]byte, error) {
+	// 3) Now we can trust ecdhe-random-pubk to derive new keys
+	//ecdhe-shared-secret = ecdh.agree(ecdhe-random, remote-ecdhe-random-pubk)
+	pubKey := ecies.ImportECDSAPublic(remoteRandomPubKey)
+	dhSharedSecret, err := ecies.ImportECDSA(privKey).GenerateShared(pubKey, sskLen, sskLen)
+	if err != nil {
+		return nil, err
+	}
+	sharedSecret := crypto.Sha3(dhSharedSecret, crypto.Sha3(respNonce, initNonce))
+	sessionToken := crypto.Sha3(sharedSecret)
+	return sessionToken, nil
+}
+
+// importPublicKey unmarshals 512 bit public keys.
+func importPublicKey(pubKey []byte) (pubKeyEC *ecdsa.PublicKey, err error) {
+	var pubKey65 []byte
+	switch len(pubKey) {
+	case 64:
+		// add 'uncompressed key' flag
+		pubKey65 = append([]byte{0x04}, pubKey...)
+	case 65:
+		pubKey65 = pubKey
+	default:
+		return nil, fmt.Errorf("invalid public key length %v (expect 64/65)", len(pubKey))
+	}
+	return crypto.ToECDSAPub(pubKey65), nil
+}
+
+func exportPublicKey(pubKeyEC *ecdsa.PublicKey) (pubKey []byte, err error) {
+	if pubKeyEC == nil {
+		return nil, fmt.Errorf("no ECDSA public key given")
+	}
+	return crypto.FromECDSAPub(pubKeyEC)[1:], nil
+}
+
+func xor(one, other []byte) (xor []byte) {
+	xor = make([]byte, len(one))
+	for i := 0; i < len(one); i++ {
+		xor[i] = one[i] ^ other[i]
+	}
+	return xor
+}