118 lines
3.8 KiB
Go
118 lines
3.8 KiB
Go
// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// +build nacl js nocgo
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package crypto
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import (
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"crypto/ecdsa"
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"crypto/elliptic"
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"errors"
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"fmt"
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"math/big"
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"github.com/btcsuite/btcd/btcec"
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)
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// Ecrecover returns the uncompressed public key that created the given signature.
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func Ecrecover(hash, sig []byte) ([]byte, error) {
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pub, err := SigToPub(hash, sig)
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if err != nil {
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return nil, err
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}
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bytes := (*btcec.PublicKey)(pub).SerializeUncompressed()
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return bytes, err
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}
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// SigToPub returns the public key that created the given signature.
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func SigToPub(hash, sig []byte) (*ecdsa.PublicKey, error) {
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// Convert to btcec input format with 'recovery id' v at the beginning.
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btcsig := make([]byte, 65)
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btcsig[0] = sig[64] + 27
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copy(btcsig[1:], sig)
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pub, _, err := btcec.RecoverCompact(btcec.S256(), btcsig, hash)
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return (*ecdsa.PublicKey)(pub), err
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}
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// Sign calculates an ECDSA signature.
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//
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// This function is susceptible to chosen plaintext attacks that can leak
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// information about the private key that is used for signing. Callers must
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// be aware that the given hash cannot be chosen by an adversery. Common
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// solution is to hash any input before calculating the signature.
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//
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// The produced signature is in the [R || S || V] format where V is 0 or 1.
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func Sign(hash []byte, prv *ecdsa.PrivateKey) ([]byte, error) {
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if len(hash) != 32 {
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return nil, fmt.Errorf("hash is required to be exactly 32 bytes (%d)", len(hash))
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}
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if prv.Curve != btcec.S256() {
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return nil, fmt.Errorf("private key curve is not secp256k1")
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}
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sig, err := btcec.SignCompact(btcec.S256(), (*btcec.PrivateKey)(prv), hash, false)
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if err != nil {
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return nil, err
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}
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// Convert to Ethereum signature format with 'recovery id' v at the end.
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v := sig[0] - 27
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copy(sig, sig[1:])
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sig[64] = v
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return sig, nil
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}
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// VerifySignature checks that the given public key created signature over hash.
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// The public key should be in compressed (33 bytes) or uncompressed (65 bytes) format.
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// The signature should have the 64 byte [R || S] format.
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func VerifySignature(pubkey, hash, signature []byte) bool {
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if len(signature) != 64 {
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return false
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}
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sig := &btcec.Signature{R: new(big.Int).SetBytes(signature[:32]), S: new(big.Int).SetBytes(signature[32:])}
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key, err := btcec.ParsePubKey(pubkey, btcec.S256())
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if err != nil {
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return false
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}
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// Reject malleable signatures. libsecp256k1 does this check but btcec doesn't.
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if sig.S.Cmp(secp256k1halfN) > 0 {
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return false
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}
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return sig.Verify(hash, key)
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}
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// DecompressPubkey parses a public key in the 33-byte compressed format.
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func DecompressPubkey(pubkey []byte) (*ecdsa.PublicKey, error) {
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if len(pubkey) != 33 {
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return nil, errors.New("invalid compressed public key length")
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}
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key, err := btcec.ParsePubKey(pubkey, btcec.S256())
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if err != nil {
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return nil, err
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}
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return key.ToECDSA(), nil
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}
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// CompressPubkey encodes a public key to the 33-byte compressed format.
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func CompressPubkey(pubkey *ecdsa.PublicKey) []byte {
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return (*btcec.PublicKey)(pubkey).SerializeCompressed()
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}
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// S256 returns an instance of the secp256k1 curve.
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func S256() elliptic.Curve {
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return btcec.S256()
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}
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