aboutsummaryrefslogtreecommitdiffstats
path: root/p2p/discover/node.go
blob: a14f294249717ab381144f5281a7cbc7d9dc1b81 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
// Copyright 2015 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 discover

import (
    "crypto/ecdsa"
    "crypto/elliptic"
    "encoding/hex"
    "errors"
    "fmt"
    "math/big"
    "math/rand"
    "net"
    "net/url"
    "strconv"
    "strings"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/crypto/secp256k1"
)

const nodeIDBits = 512

// Node represents a host on the network.
type Node struct {
    IP       net.IP // len 4 for IPv4 or 16 for IPv6
    UDP, TCP uint16 // port numbers
    ID       NodeID // the node's public key

    // This is a cached copy of sha3(ID) which is used for node
    // distance calculations. This is part of Node in order to make it
    // possible to write tests that need a node at a certain distance.
    // In those tests, the content of sha will not actually correspond
    // with ID.
    sha common.Hash

    // whether this node is currently being pinged in order to replace
    // it in a bucket
    contested bool
}

func newNode(id NodeID, ip net.IP, udpPort, tcpPort uint16) *Node {
    if ipv4 := ip.To4(); ipv4 != nil {
        ip = ipv4
    }
    return &Node{
        IP:  ip,
        UDP: udpPort,
        TCP: tcpPort,
        ID:  id,
        sha: crypto.Sha3Hash(id[:]),
    }
}

func (n *Node) addr() *net.UDPAddr {
    return &net.UDPAddr{IP: n.IP, Port: int(n.UDP)}
}

// 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: int(n.TCP)}
    u := url.URL{
        Scheme: "enode",
        User:   url.User(fmt.Sprintf("%x", n.ID[:])),
        Host:   addr.String(),
    }
    if n.UDP != n.TCP {
        u.RawQuery = "discport=" + strconv.Itoa(int(n.UDP))
    }
    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 (
        id               NodeID
        ip               net.IP
        tcpPort, udpPort uint64
    )
    u, err := url.Parse(rawurl)
    if u.Scheme != "enode" {
        return nil, errors.New("invalid URL scheme, want \"enode\"")
    }
    // Parse the Node ID from the user portion.
    if u.User == nil {
        return nil, errors.New("does not contain node ID")
    }
    if id, err = HexID(u.User.String()); err != nil {
        return nil, fmt.Errorf("invalid node ID (%v)", err)
    }
    // Parse the IP address.
    host, port, err := net.SplitHostPort(u.Host)
    if err != nil {
        return nil, fmt.Errorf("invalid host: %v", err)
    }
    if ip = net.ParseIP(host); ip == nil {
        return nil, errors.New("invalid IP address")
    }
    // Ensure the IP is 4 bytes long for IPv4 addresses.
    if ipv4 := ip.To4(); ipv4 != nil {
        ip = ipv4
    }
    // Parse the port numbers.
    if tcpPort, err = strconv.ParseUint(port, 10, 16); err != nil {
        return nil, errors.New("invalid port")
    }
    udpPort = tcpPort
    qv := u.Query()
    if qv.Get("discport") != "" {
        udpPort, err = strconv.ParseUint(qv.Get("discport"), 10, 16)
        if err != nil {
            return nil, errors.New("invalid discport in query")
        }
    }
    return newNode(id, ip, uint16(udpPort), uint16(tcpPort)), 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
}

// 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 common.Hash) 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 common.Hash) 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
}

// hashAtDistance returns a random hash such that logdist(a, b) == n
func hashAtDistance(a common.Hash, n int) (b common.Hash) {
    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
}