path: root/p2p/enr/idscheme.go

// Copyright 2018 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 enr

import (
    "crypto/ecdsa"
    "fmt"
    "sync"

    "github.com/ethereum/go-ethereum/common/math"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/crypto/sha3"
    "github.com/ethereum/go-ethereum/rlp"
)

// Registry of known identity schemes.
var schemes sync.Map

// An IdentityScheme is capable of verifying record signatures and
// deriving node addresses.
type IdentityScheme interface {
    Verify(r *Record, sig []byte) error
    NodeAddr(r *Record) []byte
}

// RegisterIdentityScheme adds an identity scheme to the global registry.
func RegisterIdentityScheme(name string, scheme IdentityScheme) {
    if _, loaded := schemes.LoadOrStore(name, scheme); loaded {
        panic("identity scheme " + name + " already registered")
    }
}

// FindIdentityScheme resolves name to an identity scheme in the global registry.
func FindIdentityScheme(name string) IdentityScheme {
    s, ok := schemes.Load(name)
    if !ok {
        return nil
    }
    return s.(IdentityScheme)
}

// v4ID is the "v4" identity scheme.
type v4ID struct{}

func init() {
    RegisterIdentityScheme("v4", v4ID{})
}

// SignV4 signs a record using the v4 scheme.
func SignV4(r *Record, privkey *ecdsa.PrivateKey) error {
    // Copy r to avoid modifying it if signing fails.
    cpy := *r
    cpy.Set(ID("v4"))
    cpy.Set(Secp256k1(privkey.PublicKey))

    h := sha3.NewKeccak256()
    rlp.Encode(h, cpy.AppendElements(nil))
    sig, err := crypto.Sign(h.Sum(nil), privkey)
    if err != nil {
        return err
    }
    sig = sig[:len(sig)-1] // remove v
    if err = cpy.SetSig("v4", sig); err == nil {
        *r = cpy
    }
    return err
}

// s256raw is an unparsed secp256k1 public key entry.
type s256raw []byte

func (s256raw) ENRKey() string { return "secp256k1" }

func (v4ID) Verify(r *Record, sig []byte) error {
    var entry s256raw
    if err := r.Load(&entry); err != nil {
        return err
    } else if len(entry) != 33 {
        return fmt.Errorf("invalid public key")
    }

    h := sha3.NewKeccak256()
    rlp.Encode(h, r.AppendElements(nil))
    if !crypto.VerifySignature(entry, h.Sum(nil), sig) {
        return errInvalidSig
    }
    return nil
}

func (v4ID) NodeAddr(r *Record) []byte {
    var pubkey Secp256k1
    err := r.Load(&pubkey)
    if err != nil {
        return nil
    }
    buf := make([]byte, 64)
    math.ReadBits(pubkey.X, buf[:32])
    math.ReadBits(pubkey.Y, buf[32:])
    return crypto.Keccak256(buf)
}