b5e5b3567c
Package crypto works with or without cgo, which is great. However, to make it work without cgo required setting the build tag `nocgo`. It's common to disable cgo by instead just setting the environment variable `CGO_ENABLED=0`. Setting this environment variable does _not_ implicitly set the build tag `nocgo`. So projects that try to build the crypto package with `CGO_ENABLED=0` will fail. I have done this myself several times. Until today, I had just assumed that this meant that this package requires cgo. But a small build tag change will make this case work. Instead of using `nocgo` and `!nocgo`, we can use `!cgo` and `cgo`, respectively. The `cgo` build tag is automatically set if cgo is enabled, and unset if it is disabled.
88 lines
3.1 KiB
Go
88 lines
3.1 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,cgo
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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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"fmt"
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"github.com/ethereum/go-ethereum/common/math"
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"github.com/ethereum/go-ethereum/crypto/secp256k1"
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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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return secp256k1.RecoverPubkey(hash, sig)
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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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s, err := Ecrecover(hash, sig)
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if err != nil {
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return nil, err
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}
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x, y := elliptic.Unmarshal(S256(), s)
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return &ecdsa.PublicKey{Curve: S256(), X: x, Y: y}, nil
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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) (sig []byte, err 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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seckey := math.PaddedBigBytes(prv.D, prv.Params().BitSize/8)
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defer zeroBytes(seckey)
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return secp256k1.Sign(hash, seckey)
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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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return secp256k1.VerifySignature(pubkey, hash, signature)
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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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x, y := secp256k1.DecompressPubkey(pubkey)
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if x == nil {
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return nil, fmt.Errorf("invalid public key")
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}
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return &ecdsa.PublicKey{X: x, Y: y, Curve: S256()}, 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 secp256k1.CompressPubkey(pubkey.X, pubkey.Y)
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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 secp256k1.S256()
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}
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