223 lines
6.4 KiB
Go
223 lines
6.4 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// In Go 1.13, the ed25519 package was promoted to the standard library as
|
|
// crypto/ed25519, and this package became a wrapper for the standard library one.
|
|
//
|
|
// +build !go1.13
|
|
|
|
// Package ed25519 implements the Ed25519 signature algorithm. See
|
|
// https://ed25519.cr.yp.to/.
|
|
//
|
|
// These functions are also compatible with the “Ed25519” function defined in
|
|
// RFC 8032. However, unlike RFC 8032's formulation, this package's private key
|
|
// representation includes a public key suffix to make multiple signing
|
|
// operations with the same key more efficient. This package refers to the RFC
|
|
// 8032 private key as the “seed”.
|
|
package ed25519
|
|
|
|
// This code is a port of the public domain, “ref10” implementation of ed25519
|
|
// from SUPERCOP.
|
|
|
|
import (
|
|
"bytes"
|
|
"crypto"
|
|
cryptorand "crypto/rand"
|
|
"crypto/sha512"
|
|
"errors"
|
|
"io"
|
|
"strconv"
|
|
|
|
"golang.org/x/crypto/ed25519/internal/edwards25519"
|
|
)
|
|
|
|
const (
|
|
// PublicKeySize is the size, in bytes, of public keys as used in this package.
|
|
PublicKeySize = 32
|
|
// PrivateKeySize is the size, in bytes, of private keys as used in this package.
|
|
PrivateKeySize = 64
|
|
// SignatureSize is the size, in bytes, of signatures generated and verified by this package.
|
|
SignatureSize = 64
|
|
// SeedSize is the size, in bytes, of private key seeds. These are the private key representations used by RFC 8032.
|
|
SeedSize = 32
|
|
)
|
|
|
|
// PublicKey is the type of Ed25519 public keys.
|
|
type PublicKey []byte
|
|
|
|
// PrivateKey is the type of Ed25519 private keys. It implements crypto.Signer.
|
|
type PrivateKey []byte
|
|
|
|
// Public returns the PublicKey corresponding to priv.
|
|
func (priv PrivateKey) Public() crypto.PublicKey {
|
|
publicKey := make([]byte, PublicKeySize)
|
|
copy(publicKey, priv[32:])
|
|
return PublicKey(publicKey)
|
|
}
|
|
|
|
// Seed returns the private key seed corresponding to priv. It is provided for
|
|
// interoperability with RFC 8032. RFC 8032's private keys correspond to seeds
|
|
// in this package.
|
|
func (priv PrivateKey) Seed() []byte {
|
|
seed := make([]byte, SeedSize)
|
|
copy(seed, priv[:32])
|
|
return seed
|
|
}
|
|
|
|
// Sign signs the given message with priv.
|
|
// Ed25519 performs two passes over messages to be signed and therefore cannot
|
|
// handle pre-hashed messages. Thus opts.HashFunc() must return zero to
|
|
// indicate the message hasn't been hashed. This can be achieved by passing
|
|
// crypto.Hash(0) as the value for opts.
|
|
func (priv PrivateKey) Sign(rand io.Reader, message []byte, opts crypto.SignerOpts) (signature []byte, err error) {
|
|
if opts.HashFunc() != crypto.Hash(0) {
|
|
return nil, errors.New("ed25519: cannot sign hashed message")
|
|
}
|
|
|
|
return Sign(priv, message), nil
|
|
}
|
|
|
|
// GenerateKey generates a public/private key pair using entropy from rand.
|
|
// If rand is nil, crypto/rand.Reader will be used.
|
|
func GenerateKey(rand io.Reader) (PublicKey, PrivateKey, error) {
|
|
if rand == nil {
|
|
rand = cryptorand.Reader
|
|
}
|
|
|
|
seed := make([]byte, SeedSize)
|
|
if _, err := io.ReadFull(rand, seed); err != nil {
|
|
return nil, nil, err
|
|
}
|
|
|
|
privateKey := NewKeyFromSeed(seed)
|
|
publicKey := make([]byte, PublicKeySize)
|
|
copy(publicKey, privateKey[32:])
|
|
|
|
return publicKey, privateKey, nil
|
|
}
|
|
|
|
// NewKeyFromSeed calculates a private key from a seed. It will panic if
|
|
// len(seed) is not SeedSize. This function is provided for interoperability
|
|
// with RFC 8032. RFC 8032's private keys correspond to seeds in this
|
|
// package.
|
|
func NewKeyFromSeed(seed []byte) PrivateKey {
|
|
if l := len(seed); l != SeedSize {
|
|
panic("ed25519: bad seed length: " + strconv.Itoa(l))
|
|
}
|
|
|
|
digest := sha512.Sum512(seed)
|
|
digest[0] &= 248
|
|
digest[31] &= 127
|
|
digest[31] |= 64
|
|
|
|
var A edwards25519.ExtendedGroupElement
|
|
var hBytes [32]byte
|
|
copy(hBytes[:], digest[:])
|
|
edwards25519.GeScalarMultBase(&A, &hBytes)
|
|
var publicKeyBytes [32]byte
|
|
A.ToBytes(&publicKeyBytes)
|
|
|
|
privateKey := make([]byte, PrivateKeySize)
|
|
copy(privateKey, seed)
|
|
copy(privateKey[32:], publicKeyBytes[:])
|
|
|
|
return privateKey
|
|
}
|
|
|
|
// Sign signs the message with privateKey and returns a signature. It will
|
|
// panic if len(privateKey) is not PrivateKeySize.
|
|
func Sign(privateKey PrivateKey, message []byte) []byte {
|
|
if l := len(privateKey); l != PrivateKeySize {
|
|
panic("ed25519: bad private key length: " + strconv.Itoa(l))
|
|
}
|
|
|
|
h := sha512.New()
|
|
h.Write(privateKey[:32])
|
|
|
|
var digest1, messageDigest, hramDigest [64]byte
|
|
var expandedSecretKey [32]byte
|
|
h.Sum(digest1[:0])
|
|
copy(expandedSecretKey[:], digest1[:])
|
|
expandedSecretKey[0] &= 248
|
|
expandedSecretKey[31] &= 63
|
|
expandedSecretKey[31] |= 64
|
|
|
|
h.Reset()
|
|
h.Write(digest1[32:])
|
|
h.Write(message)
|
|
h.Sum(messageDigest[:0])
|
|
|
|
var messageDigestReduced [32]byte
|
|
edwards25519.ScReduce(&messageDigestReduced, &messageDigest)
|
|
var R edwards25519.ExtendedGroupElement
|
|
edwards25519.GeScalarMultBase(&R, &messageDigestReduced)
|
|
|
|
var encodedR [32]byte
|
|
R.ToBytes(&encodedR)
|
|
|
|
h.Reset()
|
|
h.Write(encodedR[:])
|
|
h.Write(privateKey[32:])
|
|
h.Write(message)
|
|
h.Sum(hramDigest[:0])
|
|
var hramDigestReduced [32]byte
|
|
edwards25519.ScReduce(&hramDigestReduced, &hramDigest)
|
|
|
|
var s [32]byte
|
|
edwards25519.ScMulAdd(&s, &hramDigestReduced, &expandedSecretKey, &messageDigestReduced)
|
|
|
|
signature := make([]byte, SignatureSize)
|
|
copy(signature[:], encodedR[:])
|
|
copy(signature[32:], s[:])
|
|
|
|
return signature
|
|
}
|
|
|
|
// Verify reports whether sig is a valid signature of message by publicKey. It
|
|
// will panic if len(publicKey) is not PublicKeySize.
|
|
func Verify(publicKey PublicKey, message, sig []byte) bool {
|
|
if l := len(publicKey); l != PublicKeySize {
|
|
panic("ed25519: bad public key length: " + strconv.Itoa(l))
|
|
}
|
|
|
|
if len(sig) != SignatureSize || sig[63]&224 != 0 {
|
|
return false
|
|
}
|
|
|
|
var A edwards25519.ExtendedGroupElement
|
|
var publicKeyBytes [32]byte
|
|
copy(publicKeyBytes[:], publicKey)
|
|
if !A.FromBytes(&publicKeyBytes) {
|
|
return false
|
|
}
|
|
edwards25519.FeNeg(&A.X, &A.X)
|
|
edwards25519.FeNeg(&A.T, &A.T)
|
|
|
|
h := sha512.New()
|
|
h.Write(sig[:32])
|
|
h.Write(publicKey[:])
|
|
h.Write(message)
|
|
var digest [64]byte
|
|
h.Sum(digest[:0])
|
|
|
|
var hReduced [32]byte
|
|
edwards25519.ScReduce(&hReduced, &digest)
|
|
|
|
var R edwards25519.ProjectiveGroupElement
|
|
var s [32]byte
|
|
copy(s[:], sig[32:])
|
|
|
|
// https://tools.ietf.org/html/rfc8032#section-5.1.7 requires that s be in
|
|
// the range [0, order) in order to prevent signature malleability.
|
|
if !edwards25519.ScMinimal(&s) {
|
|
return false
|
|
}
|
|
|
|
edwards25519.GeDoubleScalarMultVartime(&R, &hReduced, &A, &s)
|
|
|
|
var checkR [32]byte
|
|
R.ToBytes(&checkR)
|
|
return bytes.Equal(sig[:32], checkR[:])
|
|
}
|