2adcc31bb4
The previous metric was pubkey1^pubkey2, as specified in the Kademlia paper. We missed that EC public keys are not uniformly distributed. Using the hash of the public keys addresses that. It also makes it a bit harder to generate node IDs that are close to a particular node.
305 lines
7.6 KiB
Go
305 lines
7.6 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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"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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"github.com/ethereum/go-ethereum/common"
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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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)
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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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IP net.IP // len 4 for IPv4 or 16 for IPv6
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UDP, TCP uint16 // port numbers
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ID NodeID // the node's public key
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// This is a cached copy of sha3(ID) which is used for node
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// distance calculations. This is part of Node in order to make it
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// possible to write tests that need a node at a certain distance.
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// In those tests, the content of sha will not actually correspond
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// with ID.
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sha common.Hash
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}
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func newNode(id NodeID, ip net.IP, udpPort, tcpPort uint16) *Node {
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if ipv4 := ip.To4(); ipv4 != nil {
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ip = ipv4
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}
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return &Node{
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IP: ip,
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UDP: udpPort,
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TCP: tcpPort,
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ID: id,
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sha: crypto.Sha3Hash(id[:]),
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}
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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: int(n.UDP)}
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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: int(n.TCP)}
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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.UDP != n.TCP {
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u.RawQuery = "discport=" + strconv.Itoa(int(n.UDP))
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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 (
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id NodeID
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ip net.IP
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tcpPort, udpPort uint64
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)
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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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// Parse the Node ID from the user portion.
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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 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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// Parse the IP address.
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host, 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 ip = net.ParseIP(host); ip == nil {
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return nil, errors.New("invalid IP address")
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}
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// Ensure the IP is 4 bytes long for IPv4 addresses.
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if ipv4 := ip.To4(); ipv4 != nil {
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ip = ipv4
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}
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// Parse the port numbers.
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if tcpPort, err = strconv.ParseUint(port, 10, 16); err != nil {
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return nil, errors.New("invalid port")
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}
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udpPort = tcpPort
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qv := u.Query()
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if qv.Get("discport") != "" {
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udpPort, err = strconv.ParseUint(qv.Get("discport"), 10, 16)
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if 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 newNode(id, ip, uint16(udpPort), uint16(tcpPort)), 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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// 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 common.Hash) 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 common.Hash) 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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// hashAtDistance returns a random hash such that logdist(a, b) == n
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func hashAtDistance(a common.Hash, n int) (b common.Hash) {
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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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