package discover
import (
"crypto/ecdsa"
"crypto/elliptic"
"encoding/hex"
"errors"
"fmt"
"io"
"math/big"
"math/rand"
"net"
"net/url"
"strconv"
"strings"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/crypto/secp256k1"
"github.com/ethereum/go-ethereum/rlp"
)
const nodeIDBits = 512
// Node represents a host on the network.
type Node struct {
ID NodeID
IP net.IP
DiscPort int // UDP listening port for discovery protocol
TCPPort int // TCP listening port for RLPx
}
func newNode(id NodeID, addr *net.UDPAddr) *Node {
return &Node{
ID: id,
IP: addr.IP,
DiscPort: addr.Port,
TCPPort: addr.Port,
}
}
func (n *Node) isValid() bool {
// TODO: don't accept localhost, LAN addresses from internet hosts
return !n.IP.IsMulticast() && !n.IP.IsUnspecified() && n.TCPPort != 0 && n.DiscPort != 0
}
func (n *Node) addr() *net.UDPAddr {
return &net.UDPAddr{IP: n.IP, Port: n.DiscPort}
}
// The string representation of a Node is a URL.
// Please see ParseNode for a description of the format.
func (n *Node) String() string {
addr := net.TCPAddr{IP: n.IP, Port: n.TCPPort}
u := url.URL{
Scheme: "enode",
User: url.User(fmt.Sprintf("%x", n.ID[:])),
Host: addr.String(),
}
if n.DiscPort != n.TCPPort {
u.RawQuery = "discport=" + strconv.Itoa(n.DiscPort)
}
return u.String()
}
// ParseNode parses a node URL.
//
// A node URL has scheme "enode".
//
// The hexadecimal node ID is encoded in the username portion of the
// URL, separated from the host by an @ sign. The hostname can only be
// given as an IP address, DNS domain names are not allowed. The port
// in the host name section is the TCP listening port. If the TCP and
// UDP (discovery) ports differ, the UDP port is specified as query
// parameter "discport".
//
// In the following example, the node URL describes
// a node with IP address 10.3.58.6, TCP listening port 30303
// and UDP discovery port 30301.
//
// enode://<hex node id>@10.3.58.6:30303?discport=30301
func ParseNode(rawurl string) (*Node, error) {
var n Node
u, err := url.Parse(rawurl)
if u.Scheme != "enode" {
return nil, errors.New("invalid URL scheme, want \"enode\"")
}
if u.User == nil {
return nil, errors.New("does not contain node ID")
}
if n.ID, err = HexID(u.User.String()); err != nil {
return nil, fmt.Errorf("invalid node ID (%v)", err)
}
ip, port, err := net.SplitHostPort(u.Host)
if err != nil {
return nil, fmt.Errorf("invalid host: %v", err)
}
if n.IP = net.ParseIP(ip); n.IP == nil {
return nil, errors.New("invalid IP address")
}
if n.TCPPort, err = strconv.Atoi(port); err != nil {
return nil, errors.New("invalid port")
}
qv := u.Query()
if qv.Get("discport") == "" {
n.DiscPort = n.TCPPort
} else {
if n.DiscPort, err = strconv.Atoi(qv.Get("discport")); err != nil {
return nil, errors.New("invalid discport in query")
}
}
return &n, nil
}
// MustParseNode parses a node URL. It panics if the URL is not valid.
func MustParseNode(rawurl string) *Node {
n, err := ParseNode(rawurl)
if err != nil {
panic("invalid node URL: " + err.Error())
}
return n
}
func (n Node) EncodeRLP(w io.Writer) error {
return rlp.Encode(w, rpcNode{IP: n.IP.String(), Port: uint16(n.TCPPort), ID: n.ID})
}
func (n *Node) DecodeRLP(s *rlp.Stream) (err error) {
var ext rpcNode
if err = s.Decode(&ext); err == nil {
n.TCPPort = int(ext.Port)
n.DiscPort = int(ext.Port)
n.ID = ext.ID
if n.IP = net.ParseIP(ext.IP); n.IP == nil {
return errors.New("invalid IP string")
}
}
return err
}
// NodeID is a unique identifier for each node.
// The node identifier is a marshaled elliptic curve public key.
type NodeID [nodeIDBits / 8]byte
// NodeID prints as a long hexadecimal number.
func (n NodeID) String() string {
return fmt.Sprintf("%x", n[:])
}
// The Go syntax representation of a NodeID is a call to HexID.
func (n NodeID) GoString() string {
return fmt.Sprintf("discover.HexID(\"%x\")", n[:])
}
// HexID converts a hex string to a NodeID.
// The string may be prefixed with 0x.
func HexID(in string) (NodeID, error) {
if strings.HasPrefix(in, "0x") {
in = in[2:]
}
var id NodeID
b, err := hex.DecodeString(in)
if err != nil {
return id, err
} else if len(b) != len(id) {
return id, fmt.Errorf("wrong length, need %d hex bytes", len(id))
}
copy(id[:], b)
return id, nil
}
// MustHexID converts a hex string to a NodeID.
// It panics if the string is not a valid NodeID.
func MustHexID(in string) NodeID {
id, err := HexID(in)
if err != nil {
panic(err)
}
return id
}
// PubkeyID returns a marshaled representation of the given public key.
func PubkeyID(pub *ecdsa.PublicKey) NodeID {
var id NodeID
pbytes := elliptic.Marshal(pub.Curve, pub.X, pub.Y)
if len(pbytes)-1 != len(id) {
panic(fmt.Errorf("need %d bit pubkey, got %d bits", (len(id)+1)*8, len(pbytes)))
}
copy(id[:], pbytes[1:])
return id
}
// Pubkey returns the public key represented by the node ID.
// It returns an error if the ID is not a point on the curve.
func (id NodeID) Pubkey() (*ecdsa.PublicKey, error) {
p := &ecdsa.PublicKey{Curve: crypto.S256(), X: new(big.Int), Y: new(big.Int)}
half := len(id) / 2
p.X.SetBytes(id[:half])
p.Y.SetBytes(id[half:])
if !p.Curve.IsOnCurve(p.X, p.Y) {
return nil, errors.New("not a point on the S256 curve")
}
return p, nil
}
// recoverNodeID computes the public key used to sign the
// given hash from the signature.
func recoverNodeID(hash, sig []byte) (id NodeID, err error) {
pubkey, err := secp256k1.RecoverPubkey(hash, sig)
if err != nil {
return id, err
}
if len(pubkey)-1 != len(id) {
return id, fmt.Errorf("recovered pubkey has %d bits, want %d bits", len(pubkey)*8, (len(id)+1)*8)
}
for i := range id {
id[i] = pubkey[i+1]
}
return id, nil
}
// distcmp compares the distances a->target and b->target.
// Returns -1 if a is closer to target, 1 if b is closer to target
// and 0 if they are equal.
func distcmp(target, a, b NodeID) int {
for i := range target {
da := a[i] ^ target[i]
db := b[i] ^ target[i]
if da > db {
return 1
} else if da < db {
return -1
}
}
return 0
}
// table of leading zero counts for bytes [0..255]
var lzcount = [256]int{
8, 7, 6, 6, 5, 5, 5, 5,
4, 4, 4, 4, 4, 4, 4, 4,
3, 3, 3, 3, 3, 3, 3, 3,
3, 3, 3, 3, 3, 3, 3, 3,
2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 2, 2, 2, 2, 2,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
}
// logdist returns the logarithmic distance between a and b, log2(a ^ b).
func logdist(a, b NodeID) int {
lz := 0
for i := range a {
x := a[i] ^ b[i]
if x == 0 {
lz += 8
} else {
lz += lzcount[x]
break
}
}
return len(a)*8 - lz
}
// randomID returns a random NodeID such that logdist(a, b) == n
func randomID(a NodeID, n int) (b NodeID) {
if n == 0 {
return a
}
// flip bit at position n, fill the rest with random bits
b = a
pos := len(a) - n/8 - 1
bit := byte(0x01) << (byte(n%8) - 1)
if bit == 0 {
pos++
bit = 0x80
}
b[pos] = a[pos]&^bit | ^a[pos]&bit // TODO: randomize end bits
for i := pos + 1; i < len(a); i++ {
b[i] = byte(rand.Intn(255))
}
return b
}
