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// Copyright 2017 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.
//go:build boringcrypto
package ecdsa
import (
"crypto/internal/boring"
"crypto/internal/boring/bbig"
"math/big"
"sync/atomic"
"unsafe"
)
// Cached conversions from Go PublicKey/PrivateKey to BoringCrypto.
//
// A new 'boring atomic.Value' field in both PublicKey and PrivateKey
// serves as a cache for the most recent conversion. The cache is an
// atomic.Value because code might reasonably set up a key and then
// (thinking it immutable) use it from multiple goroutines simultaneously.
// The first operation initializes the cache; if there are multiple simultaneous
// first operations, they will do redundant work but not step on each other.
//
// We could just assume that once used in a Sign or Verify operation,
// a particular key is never again modified, but that has not been a
// stated assumption before. Just in case there is any existing code that
// does modify the key between operations, we save the original values
// alongside the cached BoringCrypto key and check that the real key
// still matches before using the cached key. The theory is that the real
// operations are significantly more expensive than the comparison.
type boringPub struct {
key *boring.PublicKeyECDSA
orig PublicKey
}
func boringPublicKey(pub *PublicKey) (*boring.PublicKeyECDSA, error) {
b := (*boringPub)(atomic.LoadPointer(&pub.boring))
if b != nil && publicKeyEqual(&b.orig, pub) {
return b.key, nil
}
b = new(boringPub)
b.orig = copyPublicKey(pub)
key, err := boring.NewPublicKeyECDSA(b.orig.Curve.Params().Name, bbig.Enc(b.orig.X), bbig.Enc(b.orig.Y))
if err != nil {
return nil, err
}
b.key = key
atomic.StorePointer(&pub.boring, unsafe.Pointer(b))
return key, nil
}
type boringPriv struct {
key *boring.PrivateKeyECDSA
orig PrivateKey
}
func boringPrivateKey(priv *PrivateKey) (*boring.PrivateKeyECDSA, error) {
b := (*boringPriv)(atomic.LoadPointer(&priv.boring))
if b != nil && privateKeyEqual(&b.orig, priv) {
return b.key, nil
}
b = new(boringPriv)
b.orig = copyPrivateKey(priv)
key, err := boring.NewPrivateKeyECDSA(b.orig.Curve.Params().Name, bbig.Enc(b.orig.X), bbig.Enc(b.orig.Y), bbig.Enc(b.orig.D))
if err != nil {
return nil, err
}
b.key = key
atomic.StorePointer(&priv.boring, unsafe.Pointer(b))
return key, nil
}
func publicKeyEqual(k1, k2 *PublicKey) bool {
return k1.X != nil &&
k1.Curve.Params() == k2.Curve.Params() &&
k1.X.Cmp(k2.X) == 0 &&
k1.Y.Cmp(k2.Y) == 0
}
func privateKeyEqual(k1, k2 *PrivateKey) bool {
return publicKeyEqual(&k1.PublicKey, &k2.PublicKey) &&
k1.D.Cmp(k2.D) == 0
}
func copyPublicKey(k *PublicKey) PublicKey {
return PublicKey{
Curve: k.Curve,
X: new(big.Int).Set(k.X),
Y: new(big.Int).Set(k.Y),
}
}
func copyPrivateKey(k *PrivateKey) PrivateKey {
return PrivateKey{
PublicKey: copyPublicKey(&k.PublicKey),
D: new(big.Int).Set(k.D),
}
}
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