p2p/discover: implement v5.1 wire protocol (#21647)

This change implements the Discovery v5.1 wire protocol and
also adds an interactive test suite for this protocol.

p2p/discover/v5wire/session.go

@@ -0,0 +1,142 @@
+// Copyright 2020 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package v5wire
+
+import (
+	"crypto/ecdsa"
+	crand "crypto/rand"
+	"encoding/binary"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/hashicorp/golang-lru/simplelru"
+)
+
+const handshakeTimeout = time.Second
+
+// The SessionCache keeps negotiated encryption keys and
+// state for in-progress handshakes in the Discovery v5 wire protocol.
+type SessionCache struct {
+	sessions   *simplelru.LRU
+	handshakes map[sessionID]*Whoareyou
+	clock      mclock.Clock
+
+	// hooks for overriding randomness.
+	nonceGen        func(uint32) (Nonce, error)
+	maskingIVGen    func([]byte) error
+	ephemeralKeyGen func() (*ecdsa.PrivateKey, error)
+}
+
+// sessionID identifies a session or handshake.
+type sessionID struct {
+	id   enode.ID
+	addr string
+}
+
+// session contains session information
+type session struct {
+	writeKey     []byte
+	readKey      []byte
+	nonceCounter uint32
+}
+
+// keysFlipped returns a copy of s with the read and write keys flipped.
+func (s *session) keysFlipped() *session {
+	return &session{s.readKey, s.writeKey, s.nonceCounter}
+}
+
+func NewSessionCache(maxItems int, clock mclock.Clock) *SessionCache {
+	cache, err := simplelru.NewLRU(maxItems, nil)
+	if err != nil {
+		panic("can't create session cache")
+	}
+	return &SessionCache{
+		sessions:        cache,
+		handshakes:      make(map[sessionID]*Whoareyou),
+		clock:           clock,
+		nonceGen:        generateNonce,
+		maskingIVGen:    generateMaskingIV,
+		ephemeralKeyGen: crypto.GenerateKey,
+	}
+}
+
+func generateNonce(counter uint32) (n Nonce, err error) {
+	binary.BigEndian.PutUint32(n[:4], counter)
+	_, err = crand.Read(n[4:])
+	return n, err
+}
+
+func generateMaskingIV(buf []byte) error {
+	_, err := crand.Read(buf)
+	return err
+}
+
+// nextNonce creates a nonce for encrypting a message to the given session.
+func (sc *SessionCache) nextNonce(s *session) (Nonce, error) {
+	s.nonceCounter++
+	return sc.nonceGen(s.nonceCounter)
+}
+
+// session returns the current session for the given node, if any.
+func (sc *SessionCache) session(id enode.ID, addr string) *session {
+	item, ok := sc.sessions.Get(sessionID{id, addr})
+	if !ok {
+		return nil
+	}
+	return item.(*session)
+}
+
+// readKey returns the current read key for the given node.
+func (sc *SessionCache) readKey(id enode.ID, addr string) []byte {
+	if s := sc.session(id, addr); s != nil {
+		return s.readKey
+	}
+	return nil
+}
+
+// storeNewSession stores new encryption keys in the cache.
+func (sc *SessionCache) storeNewSession(id enode.ID, addr string, s *session) {
+	sc.sessions.Add(sessionID{id, addr}, s)
+}
+
+// getHandshake gets the handshake challenge we previously sent to the given remote node.
+func (sc *SessionCache) getHandshake(id enode.ID, addr string) *Whoareyou {
+	return sc.handshakes[sessionID{id, addr}]
+}
+
+// storeSentHandshake stores the handshake challenge sent to the given remote node.
+func (sc *SessionCache) storeSentHandshake(id enode.ID, addr string, challenge *Whoareyou) {
+	challenge.sent = sc.clock.Now()
+	sc.handshakes[sessionID{id, addr}] = challenge
+}
+
+// deleteHandshake deletes handshake data for the given node.
+func (sc *SessionCache) deleteHandshake(id enode.ID, addr string) {
+	delete(sc.handshakes, sessionID{id, addr})
+}
+
+// handshakeGC deletes timed-out handshakes.
+func (sc *SessionCache) handshakeGC() {
+	deadline := sc.clock.Now().Add(-handshakeTimeout)
+	for key, challenge := range sc.handshakes {
+		if challenge.sent < deadline {
+			delete(sc.handshakes, key)
+		}
+	}
+}