go-ethereum/p2p/discv5/udp.go
Felix Lange a98d1d67d6 p2p/discover, p2p/discv5: prevent relay of invalid IPs and low ports
The discovery DHT contains a number of hosts with LAN and loopback IPs.
These get relayed because some implementations do not perform any checks
on the IP.

go-ethereum already prevented relay in most cases because it verifies
that the host actually exists before adding it to the local table. But
this verification causes other issues. We have received several reports
where people's VPSs got shut down by hosting providers because sending
packets to random LAN hosts is indistinguishable from a slow port scan.

The new check prevents sending random packets to LAN by discarding LAN
IPs sent by Internet hosts (and loopback IPs from LAN and Internet
hosts). The new check also blacklists almost all currently registered
special-purpose networks assigned by IANA to avoid inciting random
responses from services in the LAN.

As another precaution against abuse of the DHT, ports below 1024 are now
considered invalid.
2016-11-22 22:21:18 +01:00

460 lines
13 KiB
Go

// Copyright 2016 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 discv5
import (
"bytes"
"crypto/ecdsa"
"errors"
"fmt"
"net"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
"github.com/ethereum/go-ethereum/p2p/nat"
"github.com/ethereum/go-ethereum/p2p/netutil"
"github.com/ethereum/go-ethereum/rlp"
)
const Version = 4
// Errors
var (
errPacketTooSmall = errors.New("too small")
errBadHash = errors.New("bad hash")
errExpired = errors.New("expired")
errUnsolicitedReply = errors.New("unsolicited reply")
errUnknownNode = errors.New("unknown node")
errTimeout = errors.New("RPC timeout")
errClockWarp = errors.New("reply deadline too far in the future")
errClosed = errors.New("socket closed")
)
// Timeouts
const (
respTimeout = 500 * time.Millisecond
sendTimeout = 500 * time.Millisecond
expiration = 20 * time.Second
ntpFailureThreshold = 32 // Continuous timeouts after which to check NTP
ntpWarningCooldown = 10 * time.Minute // Minimum amount of time to pass before repeating NTP warning
driftThreshold = 10 * time.Second // Allowed clock drift before warning user
)
// RPC request structures
type (
ping struct {
Version uint
From, To rpcEndpoint
Expiration uint64
// v5
Topics []Topic
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// pong is the reply to ping.
pong struct {
// This field should mirror the UDP envelope address
// of the ping packet, which provides a way to discover the
// the external address (after NAT).
To rpcEndpoint
ReplyTok []byte // This contains the hash of the ping packet.
Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
// v5
TopicHash common.Hash
TicketSerial uint32
WaitPeriods []uint32
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// findnode is a query for nodes close to the given target.
findnode struct {
Target NodeID // doesn't need to be an actual public key
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// findnode is a query for nodes close to the given target.
findnodeHash struct {
Target common.Hash
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// reply to findnode
neighbors struct {
Nodes []rpcNode
Expiration uint64
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
topicRegister struct {
Topics []Topic
Idx uint
Pong []byte
}
topicQuery struct {
Topic Topic
Expiration uint64
}
// reply to topicQuery
topicNodes struct {
Echo common.Hash
Nodes []rpcNode
}
rpcNode struct {
IP net.IP // len 4 for IPv4 or 16 for IPv6
UDP uint16 // for discovery protocol
TCP uint16 // for RLPx protocol
ID NodeID
}
rpcEndpoint struct {
IP net.IP // len 4 for IPv4 or 16 for IPv6
UDP uint16 // for discovery protocol
TCP uint16 // for RLPx protocol
}
)
const (
macSize = 256 / 8
sigSize = 520 / 8
headSize = macSize + sigSize // space of packet frame data
)
// Neighbors replies are sent across multiple packets to
// stay below the 1280 byte limit. We compute the maximum number
// of entries by stuffing a packet until it grows too large.
var maxNeighbors = func() int {
p := neighbors{Expiration: ^uint64(0)}
maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
for n := 0; ; n++ {
p.Nodes = append(p.Nodes, maxSizeNode)
size, _, err := rlp.EncodeToReader(p)
if err != nil {
// If this ever happens, it will be caught by the unit tests.
panic("cannot encode: " + err.Error())
}
if headSize+size+1 >= 1280 {
return n
}
}
}()
var maxTopicNodes = func() int {
p := topicNodes{}
maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
for n := 0; ; n++ {
p.Nodes = append(p.Nodes, maxSizeNode)
size, _, err := rlp.EncodeToReader(p)
if err != nil {
// If this ever happens, it will be caught by the unit tests.
panic("cannot encode: " + err.Error())
}
if headSize+size+1 >= 1280 {
return n
}
}
}()
func makeEndpoint(addr *net.UDPAddr, tcpPort uint16) rpcEndpoint {
ip := addr.IP.To4()
if ip == nil {
ip = addr.IP.To16()
}
return rpcEndpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
}
func (e1 rpcEndpoint) equal(e2 rpcEndpoint) bool {
return e1.UDP == e2.UDP && e1.TCP == e2.TCP && bytes.Equal(e1.IP, e2.IP)
}
func nodeFromRPC(sender *net.UDPAddr, rn rpcNode) (*Node, error) {
if err := netutil.CheckRelayIP(sender.IP, rn.IP); err != nil {
return nil, err
}
n := NewNode(rn.ID, rn.IP, rn.UDP, rn.TCP)
err := n.validateComplete()
return n, err
}
func nodeToRPC(n *Node) rpcNode {
return rpcNode{ID: n.ID, IP: n.IP, UDP: n.UDP, TCP: n.TCP}
}
type ingressPacket struct {
remoteID NodeID
remoteAddr *net.UDPAddr
ev nodeEvent
hash []byte
data interface{} // one of the RPC structs
rawData []byte
}
type conn interface {
ReadFromUDP(b []byte) (n int, addr *net.UDPAddr, err error)
WriteToUDP(b []byte, addr *net.UDPAddr) (n int, err error)
Close() error
LocalAddr() net.Addr
}
// udp implements the RPC protocol.
type udp struct {
conn conn
priv *ecdsa.PrivateKey
ourEndpoint rpcEndpoint
nat nat.Interface
net *Network
}
// ListenUDP returns a new table that listens for UDP packets on laddr.
func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBPath string) (*Network, error) {
transport, err := listenUDP(priv, laddr)
if err != nil {
return nil, err
}
net, err := newNetwork(transport, priv.PublicKey, natm, nodeDBPath)
if err != nil {
return nil, err
}
transport.net = net
go transport.readLoop()
return net, nil
}
func listenUDP(priv *ecdsa.PrivateKey, laddr string) (*udp, error) {
addr, err := net.ResolveUDPAddr("udp", laddr)
if err != nil {
return nil, err
}
conn, err := net.ListenUDP("udp", addr)
if err != nil {
return nil, err
}
return &udp{conn: conn, priv: priv, ourEndpoint: makeEndpoint(addr, uint16(addr.Port))}, nil
}
func (t *udp) localAddr() *net.UDPAddr {
return t.conn.LocalAddr().(*net.UDPAddr)
}
func (t *udp) Close() {
t.conn.Close()
}
func (t *udp) send(remote *Node, ptype nodeEvent, data interface{}) (hash []byte) {
hash, _ = t.sendPacket(remote.ID, remote.addr(), byte(ptype), data)
return hash
}
func (t *udp) sendPing(remote *Node, toaddr *net.UDPAddr, topics []Topic) (hash []byte) {
hash, _ = t.sendPacket(remote.ID, toaddr, byte(pingPacket), ping{
Version: Version,
From: t.ourEndpoint,
To: makeEndpoint(toaddr, uint16(toaddr.Port)), // TODO: maybe use known TCP port from DB
Expiration: uint64(time.Now().Add(expiration).Unix()),
Topics: topics,
})
return hash
}
func (t *udp) sendFindnode(remote *Node, target NodeID) {
t.sendPacket(remote.ID, remote.addr(), byte(findnodePacket), findnode{
Target: target,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
}
func (t *udp) sendNeighbours(remote *Node, results []*Node) {
// Send neighbors in chunks with at most maxNeighbors per packet
// to stay below the 1280 byte limit.
p := neighbors{Expiration: uint64(time.Now().Add(expiration).Unix())}
for i, result := range results {
p.Nodes = append(p.Nodes, nodeToRPC(result))
if len(p.Nodes) == maxNeighbors || i == len(results)-1 {
t.sendPacket(remote.ID, remote.addr(), byte(neighborsPacket), p)
p.Nodes = p.Nodes[:0]
}
}
}
func (t *udp) sendFindnodeHash(remote *Node, target common.Hash) {
t.sendPacket(remote.ID, remote.addr(), byte(findnodeHashPacket), findnodeHash{
Target: target,
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
}
func (t *udp) sendTopicRegister(remote *Node, topics []Topic, idx int, pong []byte) {
t.sendPacket(remote.ID, remote.addr(), byte(topicRegisterPacket), topicRegister{
Topics: topics,
Idx: uint(idx),
Pong: pong,
})
}
func (t *udp) sendTopicNodes(remote *Node, queryHash common.Hash, nodes []*Node) {
p := topicNodes{Echo: queryHash}
if len(nodes) == 0 {
t.sendPacket(remote.ID, remote.addr(), byte(topicNodesPacket), p)
return
}
for i, result := range nodes {
if netutil.CheckRelayIP(remote.IP, result.IP) != nil {
continue
}
p.Nodes = append(p.Nodes, nodeToRPC(result))
if len(p.Nodes) == maxTopicNodes || i == len(nodes)-1 {
t.sendPacket(remote.ID, remote.addr(), byte(topicNodesPacket), p)
p.Nodes = p.Nodes[:0]
}
}
}
func (t *udp) sendPacket(toid NodeID, toaddr *net.UDPAddr, ptype byte, req interface{}) (hash []byte, err error) {
//fmt.Println("sendPacket", nodeEvent(ptype), toaddr.String(), toid.String())
packet, hash, err := encodePacket(t.priv, ptype, req)
if err != nil {
//fmt.Println(err)
return hash, err
}
glog.V(logger.Detail).Infof(">>> %v to %x@%v\n", nodeEvent(ptype), toid[:8], toaddr)
if _, err = t.conn.WriteToUDP(packet, toaddr); err != nil {
glog.V(logger.Detail).Infoln("UDP send failed:", err)
}
//fmt.Println(err)
return hash, err
}
// zeroed padding space for encodePacket.
var headSpace = make([]byte, headSize)
func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) (p, hash []byte, err error) {
b := new(bytes.Buffer)
b.Write(headSpace)
b.WriteByte(ptype)
if err := rlp.Encode(b, req); err != nil {
glog.V(logger.Error).Infoln("error encoding packet:", err)
return nil, nil, err
}
packet := b.Bytes()
sig, err := crypto.Sign(crypto.Keccak256(packet[headSize:]), priv)
if err != nil {
glog.V(logger.Error).Infoln("could not sign packet:", err)
return nil, nil, err
}
copy(packet[macSize:], sig)
// add the hash to the front. Note: this doesn't protect the
// packet in any way.
hash = crypto.Keccak256(packet[macSize:])
copy(packet, hash)
return packet, hash, nil
}
// readLoop runs in its own goroutine. it injects ingress UDP packets
// into the network loop.
func (t *udp) readLoop() {
defer t.conn.Close()
// Discovery packets are defined to be no larger than 1280 bytes.
// Packets larger than this size will be cut at the end and treated
// as invalid because their hash won't match.
buf := make([]byte, 1280)
for {
nbytes, from, err := t.conn.ReadFromUDP(buf)
if netutil.IsTemporaryError(err) {
// Ignore temporary read errors.
glog.V(logger.Debug).Infof("Temporary read error: %v", err)
continue
} else if err != nil {
// Shut down the loop for permament errors.
glog.V(logger.Debug).Infof("Read error: %v", err)
return
}
t.handlePacket(from, buf[:nbytes])
}
}
func (t *udp) handlePacket(from *net.UDPAddr, buf []byte) error {
pkt := ingressPacket{remoteAddr: from}
if err := decodePacket(buf, &pkt); err != nil {
glog.V(logger.Debug).Infof("Bad packet from %v: %v\n", from, err)
//fmt.Println("bad packet", err)
return err
}
t.net.reqReadPacket(pkt)
return nil
}
func decodePacket(buffer []byte, pkt *ingressPacket) error {
if len(buffer) < headSize+1 {
return errPacketTooSmall
}
buf := make([]byte, len(buffer))
copy(buf, buffer)
hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
shouldhash := crypto.Keccak256(buf[macSize:])
if !bytes.Equal(hash, shouldhash) {
return errBadHash
}
fromID, err := recoverNodeID(crypto.Keccak256(buf[headSize:]), sig)
if err != nil {
return err
}
pkt.rawData = buf
pkt.hash = hash
pkt.remoteID = fromID
switch pkt.ev = nodeEvent(sigdata[0]); pkt.ev {
case pingPacket:
pkt.data = new(ping)
case pongPacket:
pkt.data = new(pong)
case findnodePacket:
pkt.data = new(findnode)
case neighborsPacket:
pkt.data = new(neighbors)
case findnodeHashPacket:
pkt.data = new(findnodeHash)
case topicRegisterPacket:
pkt.data = new(topicRegister)
case topicQueryPacket:
pkt.data = new(topicQuery)
case topicNodesPacket:
pkt.data = new(topicNodes)
default:
return fmt.Errorf("unknown packet type: %d", sigdata[0])
}
s := rlp.NewStream(bytes.NewReader(sigdata[1:]), 0)
err = s.Decode(pkt.data)
return err
}