2015-01-18 09:46:08 +00:00
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package p2p
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import (
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2015-01-29 03:16:10 +00:00
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// "binary"
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2015-01-18 09:46:08 +00:00
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"crypto/ecdsa"
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"crypto/rand"
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"fmt"
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2015-01-19 23:42:13 +00:00
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"io"
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2015-01-18 09:46:08 +00:00
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"github.com/ethereum/go-ethereum/crypto"
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2015-02-13 23:25:47 +00:00
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"github.com/ethereum/go-ethereum/crypto/ecies"
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2015-01-26 14:50:12 +00:00
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"github.com/ethereum/go-ethereum/crypto/secp256k1"
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ethlogger "github.com/ethereum/go-ethereum/logger"
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"github.com/ethereum/go-ethereum/p2p/discover"
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2015-01-18 09:46:08 +00:00
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)
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2015-01-21 14:45:53 +00:00
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var clogger = ethlogger.NewLogger("CRYPTOID")
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2015-01-26 14:50:12 +00:00
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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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2015-01-18 09:46:08 +00:00
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2015-02-05 02:07:58 +00:00
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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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2015-01-18 09:46:08 +00:00
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2015-01-21 14:45:53 +00:00
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type hexkey []byte
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func (self hexkey) String() string {
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return fmt.Sprintf("(%d) %x", len(self), []byte(self))
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}
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2015-02-05 02:07:58 +00:00
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func encHandshake(conn io.ReadWriter, prv *ecdsa.PrivateKey, dial *discover.Node) (
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remoteID discover.NodeID,
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sessionToken []byte,
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err error,
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) {
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if dial == nil {
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var remotePubkey []byte
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sessionToken, remotePubkey, err = inboundEncHandshake(conn, prv, nil)
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copy(remoteID[:], remotePubkey)
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} else {
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remoteID = dial.ID
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sessionToken, err = outboundEncHandshake(conn, prv, remoteID[:], nil)
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}
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return remoteID, sessionToken, err
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2015-01-29 03:16:10 +00:00
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}
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2015-02-05 02:07:58 +00:00
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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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2015-01-29 03:16:10 +00:00
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if err != nil {
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return nil, err
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2015-01-29 03:16:10 +00:00
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}
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if sessionToken != nil {
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clogger.Debugf("session-token: %v", hexkey(sessionToken))
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2015-01-19 11:21:13 +00:00
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}
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2015-02-05 02:07:58 +00:00
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clogger.Debugf("initiator-nonce: %v", hexkey(initNonce))
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clogger.Debugf("initiator-random-private-key: %v", hexkey(crypto.FromECDSA(randomPrivKey)))
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randomPublicKeyS, _ := exportPublicKey(&randomPrivKey.PublicKey)
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clogger.Debugf("initiator-random-public-key: %v", hexkey(randomPublicKeyS))
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if _, err = conn.Write(auth); err != nil {
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return nil, err
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2015-01-20 16:47:46 +00:00
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}
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2015-02-05 02:07:58 +00:00
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clogger.Debugf("initiator handshake: %v", hexkey(auth))
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2015-01-20 16:47:46 +00:00
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2015-02-05 02:07:58 +00:00
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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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2015-01-20 16:47:46 +00:00
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}
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2015-01-21 10:22:07 +00:00
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2015-02-05 02:07:58 +00:00
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clogger.Debugf("receiver-nonce: %v", hexkey(recNonce))
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remoteRandomPubKeyS, _ := exportPublicKey(remoteRandomPubKey)
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clogger.Debugf("receiver-random-public-key: %v", hexkey(remoteRandomPubKeyS))
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return newSession(initNonce, recNonce, randomPrivKey, remoteRandomPubKey)
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}
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2015-01-21 10:22:07 +00:00
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2015-02-05 02:07:58 +00:00
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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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2015-01-18 09:46:08 +00:00
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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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2015-01-18 23:53:45 +00:00
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2015-01-26 14:50:12 +00:00
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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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2015-01-26 16:16:23 +00:00
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if sessionToken, err = ecies.ImportECDSA(prvKey).GenerateShared(ecies.ImportECDSAPublic(remotePubKey), sskLen, sskLen); err != nil {
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2015-01-18 23:53:45 +00:00
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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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2015-01-18 23:53:45 +00:00
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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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2015-02-05 02:07:58 +00:00
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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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2015-01-18 23:53:45 +00:00
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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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2015-02-05 02:07:58 +00:00
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if randomPrvKey, err = crypto.GenerateKey(); err != nil {
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2015-01-18 09:46:08 +00:00
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return
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}
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2015-01-18 23:53:45 +00:00
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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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2015-01-18 23:53:45 +00:00
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// signature = sign(ecdhe-random, shared-secret)
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2015-01-18 09:46:08 +00:00
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// uses secp256k1.Sign
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2015-01-19 04:53:48 +00:00
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if signature, err = crypto.Sign(sharedSecret, randomPrvKey); err != nil {
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2015-01-18 09:46:08 +00:00
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return
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}
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2015-01-18 23:53:45 +00:00
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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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2015-01-20 16:47:46 +00:00
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var randomPubKey64 []byte
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2015-02-05 02:07:58 +00:00
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if randomPubKey64, err = exportPublicKey(&randomPrvKey.PublicKey); err != nil {
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2015-01-20 16:47:46 +00:00
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return
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}
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2015-01-26 16:16:23 +00:00
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var pubKey64 []byte
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2015-02-05 02:07:58 +00:00
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if pubKey64, err = exportPublicKey(&prvKey.PublicKey); err != nil {
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2015-01-26 16:16:23 +00:00
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return
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}
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2015-01-26 14:50:12 +00:00
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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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2015-01-18 23:53:45 +00:00
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// nonce is already in the slice
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// stick tokenFlag byte to the end
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2015-02-05 02:07:58 +00:00
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msg[authMsgLen-1] = tokenFlag
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2015-01-18 23:53:45 +00:00
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// encrypt using remote-pubk
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2015-01-18 09:46:08 +00:00
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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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2015-02-05 02:07:58 +00:00
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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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2015-01-18 09:46:08 +00:00
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var msg []byte
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2015-02-05 02:07:58 +00:00
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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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2015-01-19 23:42:13 +00:00
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return
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}
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2015-02-05 02:07:58 +00:00
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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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clogger.Debugf("receiver-nonce: %v", hexkey(recNonce))
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clogger.Debugf("receiver-random-priv-key: %v", hexkey(crypto.FromECDSA(randomPrivKey)))
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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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clogger.Debugf("receiver handshake:\n%v", hexkey(response))
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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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2015-01-18 09:46:08 +00:00
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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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2015-02-05 02:07:58 +00:00
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msg, err := crypto.Decrypt(prvKey, auth)
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if err != nil {
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2015-01-18 09:46:08 +00:00
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return
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}
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2015-02-05 02:07:58 +00:00
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remotePubKeyS = msg[sigLen+shaLen : sigLen+shaLen+pubLen]
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remotePubKey, _ := importPublicKey(remotePubKeyS)
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2015-01-19 00:55:24 +00:00
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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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2015-01-26 16:16:23 +00:00
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if sessionToken, err = ecies.ImportECDSA(prvKey).GenerateShared(ecies.ImportECDSAPublic(remotePubKey), sskLen, sskLen); err != nil {
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2015-01-19 00:55:24 +00:00
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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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2015-02-05 02:07:58 +00:00
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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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2015-01-20 16:47:46 +00:00
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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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2015-01-18 09:46:08 +00:00
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return
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}
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2015-01-19 00:55:24 +00:00
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// convert to ECDSA standard
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2015-02-05 02:07:58 +00:00
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if remoteRandomPubKey, err = importPublicKey(remoteRandomPubKeyS); err != nil {
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2015-01-18 09:46:08 +00:00
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return
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|
}
|
2015-01-18 23:53:45 +00:00
|
|
|
|
2015-01-19 00:55:24 +00:00
|
|
|
// now we find ourselves a long task too, fill it random
|
2015-02-05 02:07:58 +00:00
|
|
|
var resp = make([]byte, authRespLen)
|
2015-01-26 14:50:12 +00:00
|
|
|
// generate shaLen long nonce
|
|
|
|
respNonce = resp[pubLen : pubLen+shaLen]
|
2015-02-05 02:07:58 +00:00
|
|
|
if _, err = rand.Read(respNonce); err != nil {
|
2015-01-18 23:53:45 +00:00
|
|
|
return
|
|
|
|
}
|
2015-01-19 00:55:24 +00:00
|
|
|
// generate random keypair for session
|
2015-02-05 02:07:58 +00:00
|
|
|
if randomPrivKey, err = crypto.GenerateKey(); err != nil {
|
2015-01-18 23:53:45 +00:00
|
|
|
return
|
|
|
|
}
|
2015-01-19 00:55:24 +00:00
|
|
|
// responder auth message
|
2015-01-18 23:53:45 +00:00
|
|
|
// E(remote-pubk, ecdhe-random-pubk || nonce || 0x0)
|
2015-01-20 16:47:46 +00:00
|
|
|
var randomPubKeyS []byte
|
2015-02-05 02:07:58 +00:00
|
|
|
if randomPubKeyS, err = exportPublicKey(&randomPrivKey.PublicKey); err != nil {
|
2015-01-20 16:47:46 +00:00
|
|
|
return
|
|
|
|
}
|
|
|
|
copy(resp[:pubLen], randomPubKeyS)
|
2015-01-18 23:53:45 +00:00
|
|
|
// nonce is already in the slice
|
2015-02-05 02:07:58 +00:00
|
|
|
resp[authRespLen-1] = tokenFlag
|
2015-01-18 23:53:45 +00:00
|
|
|
|
|
|
|
// 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
|
|
|
|
}
|
|
|
|
|
2015-02-05 02:07:58 +00:00
|
|
|
// 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
|
2015-01-18 23:53:45 +00:00
|
|
|
}
|
2015-02-05 02:07:58 +00:00
|
|
|
sharedSecret := crypto.Sha3(dhSharedSecret, crypto.Sha3(respNonce, initNonce))
|
|
|
|
sessionToken := crypto.Sha3(sharedSecret)
|
|
|
|
return sessionToken, nil
|
|
|
|
}
|
2015-01-18 23:53:45 +00:00
|
|
|
|
2015-02-05 02:07:58 +00:00
|
|
|
// 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))
|
2015-01-18 23:53:45 +00:00
|
|
|
}
|
2015-02-05 02:07:58 +00:00
|
|
|
return crypto.ToECDSAPub(pubKey65), nil
|
2015-01-18 23:53:45 +00:00
|
|
|
}
|
|
|
|
|
2015-02-05 02:07:58 +00:00
|
|
|
func exportPublicKey(pubKeyEC *ecdsa.PublicKey) (pubKey []byte, err error) {
|
|
|
|
if pubKeyEC == nil {
|
|
|
|
return nil, fmt.Errorf("no ECDSA public key given")
|
2015-01-18 09:46:08 +00:00
|
|
|
}
|
2015-02-05 02:07:58 +00:00
|
|
|
return crypto.FromECDSAPub(pubKeyEC)[1:], nil
|
2015-01-18 09:46:08 +00:00
|
|
|
}
|
|
|
|
|
2015-02-05 02:07:58 +00:00
|
|
|
func xor(one, other []byte) (xor []byte) {
|
2015-01-18 23:53:45 +00:00
|
|
|
xor = make([]byte, len(one))
|
2015-01-18 09:46:08 +00:00
|
|
|
for i := 0; i < len(one); i++ {
|
|
|
|
xor[i] = one[i] ^ other[i]
|
|
|
|
}
|
2015-02-05 02:07:58 +00:00
|
|
|
return xor
|
2015-01-18 09:46:08 +00:00
|
|
|
}
|