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p2p/discv5: use constant version prefix instead of hash

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This commit is contained in:
Zsolt Felfoldi 2018-01-04 22:28:45 +01:00
parent 313384f474
commit 2454a58cd3
1 changed files with 13 additions and 17 deletions
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28
p2p/discv5/udp.go
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@ -37,7 +37,7 @@ const Version = 4
// Errors // Errors
var ( var (
errPacketTooSmall = errors.New("too small") errPacketTooSmall = errors.New("too small")
errBadHash = errors.New("bad hash") errBadPrefix = errors.New("bad prefix")
errExpired = errors.New("expired") errExpired = errors.New("expired")
errUnsolicitedReply = errors.New("unsolicited reply") errUnsolicitedReply = errors.New("unsolicited reply")
errUnknownNode = errors.New("unknown node") errUnknownNode = errors.New("unknown node")
@ -145,10 +145,11 @@ type (
} }
) )
const ( var (
macSize = 256 / 8 versionPrefix = []byte("temporary discovery v5")
versionPrefixSize = len(versionPrefix)
sigSize = 520 / 8 sigSize = 520 / 8
headSize = macSize + sigSize // space of packet frame data headSize = versionPrefixSize + sigSize // space of packet frame data
) )
// Neighbors replies are sent across multiple packets to // Neighbors replies are sent across multiple packets to
@ -364,12 +365,9 @@ func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) (p, hash
log.Error(fmt.Sprint("could not sign packet:", err)) log.Error(fmt.Sprint("could not sign packet:", err))
return nil, nil, err return nil, nil, err
} }
copy(packet[macSize:], sig) copy(packet, versionPrefix)
// add the hash to the front. Note: this doesn't protect the copy(packet[versionPrefixSize:], sig)
// packet in any way. hash = crypto.Keccak256(packet[versionPrefixSize:])
hash = crypto.Keccak256(packet[macSize:])
hash[0]++ // guarantee incompatibility between v4 and temporary v5 packet formats
copy(packet, hash)
return packet, hash, nil return packet, hash, nil
} }
@ -413,18 +411,16 @@ func decodePacket(buffer []byte, pkt *ingressPacket) error {
} }
buf := make([]byte, len(buffer)) buf := make([]byte, len(buffer))
copy(buf, buffer) copy(buf, buffer)
hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:] prefix, sig, sigdata := buf[:versionPrefixSize], buf[versionPrefixSize:headSize], buf[headSize:]
shouldhash := crypto.Keccak256(buf[macSize:]) if !bytes.Equal(prefix, versionPrefix) {
shouldhash[0]++ // guarantee incompatibility between v4 and temporary v5 packet formats return errBadPrefix
if !bytes.Equal(hash, shouldhash) {
return errBadHash
} }
fromID, err := recoverNodeID(crypto.Keccak256(buf[headSize:]), sig) fromID, err := recoverNodeID(crypto.Keccak256(buf[headSize:]), sig)
if err != nil { if err != nil {
return err return err
} }
pkt.rawData = buf pkt.rawData = buf
pkt.hash = hash pkt.hash = crypto.Keccak256(buf[versionPrefixSize:])
pkt.remoteID = fromID pkt.remoteID = fromID
switch pkt.ev = nodeEvent(sigdata[0]); pkt.ev { switch pkt.ev = nodeEvent(sigdata[0]); pkt.ev {
case pingPacket: case pingPacket: