de7af720d6
This a fix for an attack vector where the discovery protocol could be used to amplify traffic in a DDOS attack. A malicious actor would send a findnode request with the IP address and UDP port of the target as the source address. The recipient of the findnode packet would then send a neighbors packet (which is 16x the size of findnode) to the victim. Our solution is to require a 'bond' with the sender of findnode. If no bond exists, the findnode packet is not processed. A bond between nodes α and β is created when α replies to a ping from β. This (initial) version of the bonding implementation might still be vulnerable against replay attacks during the expiration time window. We will add stricter source address validation later.
346 lines
8.3 KiB
Go
346 lines
8.3 KiB
Go
package discover
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import (
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"crypto/ecdsa"
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"crypto/elliptic"
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"encoding/hex"
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"errors"
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"fmt"
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"io"
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"math/big"
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"math/rand"
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"net"
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"net/url"
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"strconv"
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"strings"
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"sync"
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"sync/atomic"
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"time"
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"github.com/ethereum/go-ethereum/crypto"
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"github.com/ethereum/go-ethereum/crypto/secp256k1"
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"github.com/ethereum/go-ethereum/rlp"
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)
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const nodeIDBits = 512
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// Node represents a host on the network.
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type Node struct {
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ID NodeID
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IP net.IP
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DiscPort int // UDP listening port for discovery protocol
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TCPPort int // TCP listening port for RLPx
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// this must be set/read using atomic load and store.
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activeStamp int64
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}
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func newNode(id NodeID, addr *net.UDPAddr) *Node {
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return &Node{
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ID: id,
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IP: addr.IP,
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DiscPort: addr.Port,
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TCPPort: addr.Port,
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}
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}
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func (n *Node) isValid() bool {
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// TODO: don't accept localhost, LAN addresses from internet hosts
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return !n.IP.IsMulticast() && !n.IP.IsUnspecified() && n.TCPPort != 0 && n.DiscPort != 0
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}
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func (n *Node) bumpActive() {
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stamp := time.Now().Unix()
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atomic.StoreInt64(&n.activeStamp, stamp)
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}
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func (n *Node) active() time.Time {
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stamp := atomic.LoadInt64(&n.activeStamp)
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return time.Unix(stamp, 0)
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}
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func (n *Node) addr() *net.UDPAddr {
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return &net.UDPAddr{IP: n.IP, Port: n.DiscPort}
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}
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// The string representation of a Node is a URL.
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// Please see ParseNode for a description of the format.
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func (n *Node) String() string {
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addr := net.TCPAddr{IP: n.IP, Port: n.TCPPort}
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u := url.URL{
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Scheme: "enode",
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User: url.User(fmt.Sprintf("%x", n.ID[:])),
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Host: addr.String(),
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}
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if n.DiscPort != n.TCPPort {
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u.RawQuery = "discport=" + strconv.Itoa(n.DiscPort)
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}
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return u.String()
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}
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// ParseNode parses a node URL.
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//
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// A node URL has scheme "enode".
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//
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// The hexadecimal node ID is encoded in the username portion of the
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// URL, separated from the host by an @ sign. The hostname can only be
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// given as an IP address, DNS domain names are not allowed. The port
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// in the host name section is the TCP listening port. If the TCP and
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// UDP (discovery) ports differ, the UDP port is specified as query
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// parameter "discport".
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//
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// In the following example, the node URL describes
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// a node with IP address 10.3.58.6, TCP listening port 30303
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// and UDP discovery port 30301.
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//
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// enode://<hex node id>@10.3.58.6:30303?discport=30301
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func ParseNode(rawurl string) (*Node, error) {
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var n Node
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u, err := url.Parse(rawurl)
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if u.Scheme != "enode" {
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return nil, errors.New("invalid URL scheme, want \"enode\"")
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}
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if u.User == nil {
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return nil, errors.New("does not contain node ID")
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}
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if n.ID, err = HexID(u.User.String()); err != nil {
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return nil, fmt.Errorf("invalid node ID (%v)", err)
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}
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ip, port, err := net.SplitHostPort(u.Host)
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if err != nil {
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return nil, fmt.Errorf("invalid host: %v", err)
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}
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if n.IP = net.ParseIP(ip); n.IP == nil {
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return nil, errors.New("invalid IP address")
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}
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if n.TCPPort, err = strconv.Atoi(port); err != nil {
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return nil, errors.New("invalid port")
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}
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qv := u.Query()
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if qv.Get("discport") == "" {
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n.DiscPort = n.TCPPort
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} else {
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if n.DiscPort, err = strconv.Atoi(qv.Get("discport")); err != nil {
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return nil, errors.New("invalid discport in query")
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}
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}
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return &n, nil
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}
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// MustParseNode parses a node URL. It panics if the URL is not valid.
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func MustParseNode(rawurl string) *Node {
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n, err := ParseNode(rawurl)
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if err != nil {
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panic("invalid node URL: " + err.Error())
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}
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return n
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}
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func (n Node) EncodeRLP(w io.Writer) error {
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return rlp.Encode(w, rpcNode{IP: n.IP.String(), Port: uint16(n.TCPPort), ID: n.ID})
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}
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func (n *Node) DecodeRLP(s *rlp.Stream) (err error) {
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var ext rpcNode
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if err = s.Decode(&ext); err == nil {
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n.TCPPort = int(ext.Port)
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n.DiscPort = int(ext.Port)
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n.ID = ext.ID
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if n.IP = net.ParseIP(ext.IP); n.IP == nil {
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return errors.New("invalid IP string")
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}
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}
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return err
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}
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// NodeID is a unique identifier for each node.
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// The node identifier is a marshaled elliptic curve public key.
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type NodeID [nodeIDBits / 8]byte
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// NodeID prints as a long hexadecimal number.
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func (n NodeID) String() string {
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return fmt.Sprintf("%x", n[:])
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}
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// The Go syntax representation of a NodeID is a call to HexID.
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func (n NodeID) GoString() string {
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return fmt.Sprintf("discover.HexID(\"%x\")", n[:])
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}
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// HexID converts a hex string to a NodeID.
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// The string may be prefixed with 0x.
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func HexID(in string) (NodeID, error) {
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if strings.HasPrefix(in, "0x") {
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in = in[2:]
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}
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var id NodeID
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b, err := hex.DecodeString(in)
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if err != nil {
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return id, err
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} else if len(b) != len(id) {
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return id, fmt.Errorf("wrong length, need %d hex bytes", len(id))
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}
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copy(id[:], b)
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return id, nil
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}
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// MustHexID converts a hex string to a NodeID.
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// It panics if the string is not a valid NodeID.
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func MustHexID(in string) NodeID {
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id, err := HexID(in)
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if err != nil {
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panic(err)
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}
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return id
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}
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// PubkeyID returns a marshaled representation of the given public key.
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func PubkeyID(pub *ecdsa.PublicKey) NodeID {
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var id NodeID
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pbytes := elliptic.Marshal(pub.Curve, pub.X, pub.Y)
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if len(pbytes)-1 != len(id) {
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panic(fmt.Errorf("need %d bit pubkey, got %d bits", (len(id)+1)*8, len(pbytes)))
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}
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copy(id[:], pbytes[1:])
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return id
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}
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// Pubkey returns the public key represented by the node ID.
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// It returns an error if the ID is not a point on the curve.
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func (id NodeID) Pubkey() (*ecdsa.PublicKey, error) {
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p := &ecdsa.PublicKey{Curve: crypto.S256(), X: new(big.Int), Y: new(big.Int)}
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half := len(id) / 2
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p.X.SetBytes(id[:half])
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p.Y.SetBytes(id[half:])
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if !p.Curve.IsOnCurve(p.X, p.Y) {
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return nil, errors.New("not a point on the S256 curve")
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}
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return p, nil
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}
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// recoverNodeID computes the public key used to sign the
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// given hash from the signature.
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func recoverNodeID(hash, sig []byte) (id NodeID, err error) {
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pubkey, err := secp256k1.RecoverPubkey(hash, sig)
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if err != nil {
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return id, err
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}
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if len(pubkey)-1 != len(id) {
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return id, fmt.Errorf("recovered pubkey has %d bits, want %d bits", len(pubkey)*8, (len(id)+1)*8)
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}
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for i := range id {
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id[i] = pubkey[i+1]
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}
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return id, nil
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}
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// distcmp compares the distances a->target and b->target.
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// Returns -1 if a is closer to target, 1 if b is closer to target
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// and 0 if they are equal.
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func distcmp(target, a, b NodeID) int {
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for i := range target {
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da := a[i] ^ target[i]
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db := b[i] ^ target[i]
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if da > db {
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return 1
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} else if da < db {
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return -1
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}
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}
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return 0
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}
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// table of leading zero counts for bytes [0..255]
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var lzcount = [256]int{
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8, 7, 6, 6, 5, 5, 5, 5,
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4, 4, 4, 4, 4, 4, 4, 4,
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3, 3, 3, 3, 3, 3, 3, 3,
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3, 3, 3, 3, 3, 3, 3, 3,
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2, 2, 2, 2, 2, 2, 2, 2,
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2, 2, 2, 2, 2, 2, 2, 2,
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2, 2, 2, 2, 2, 2, 2, 2,
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2, 2, 2, 2, 2, 2, 2, 2,
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1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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}
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// logdist returns the logarithmic distance between a and b, log2(a ^ b).
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func logdist(a, b NodeID) int {
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lz := 0
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for i := range a {
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x := a[i] ^ b[i]
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if x == 0 {
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lz += 8
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} else {
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lz += lzcount[x]
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break
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}
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}
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return len(a)*8 - lz
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}
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// randomID returns a random NodeID such that logdist(a, b) == n
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func randomID(a NodeID, n int) (b NodeID) {
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if n == 0 {
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return a
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}
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// flip bit at position n, fill the rest with random bits
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b = a
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pos := len(a) - n/8 - 1
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bit := byte(0x01) << (byte(n%8) - 1)
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if bit == 0 {
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pos++
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bit = 0x80
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}
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b[pos] = a[pos]&^bit | ^a[pos]&bit // TODO: randomize end bits
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for i := pos + 1; i < len(a); i++ {
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b[i] = byte(rand.Intn(255))
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}
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return b
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}
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// nodeDB stores all nodes we know about.
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type nodeDB struct {
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mu sync.RWMutex
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byID map[NodeID]*Node
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}
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func (db *nodeDB) get(id NodeID) *Node {
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db.mu.RLock()
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defer db.mu.RUnlock()
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return db.byID[id]
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}
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func (db *nodeDB) add(id NodeID, addr *net.UDPAddr, tcpPort uint16) *Node {
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db.mu.Lock()
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defer db.mu.Unlock()
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if db.byID == nil {
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db.byID = make(map[NodeID]*Node)
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}
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n := &Node{ID: id, IP: addr.IP, DiscPort: addr.Port, TCPPort: int(tcpPort)}
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db.byID[n.ID] = n
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return n
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}
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