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// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/quic/crypto/curve25519_key_exchange.h"
#include "base/basictypes.h"
#include "base/logging.h"
#include "crypto/curve25519.h"
#include "net/quic/crypto/quic_random.h"
using base::StringPiece;
using std::string;
namespace net {
Curve25519KeyExchange::Curve25519KeyExchange() {}
Curve25519KeyExchange::~Curve25519KeyExchange() {}
// static
Curve25519KeyExchange* Curve25519KeyExchange::New(
const StringPiece& private_key) {
Curve25519KeyExchange* ka;
// We don't want to #include the NaCl headers in the public header file, so
// we use literals for the sizes of private_key_ and public_key_. Here we
// assert that those values are equal to the values from the NaCl header.
static_assert(sizeof(ka->private_key_) == crypto::curve25519::kScalarBytes,
"header out of sync");
static_assert(sizeof(ka->public_key_) == crypto::curve25519::kBytes,
"header out of sync");
if (private_key.size() != crypto::curve25519::kScalarBytes) {
return nullptr;
}
ka = new Curve25519KeyExchange();
memcpy(ka->private_key_, private_key.data(),
crypto::curve25519::kScalarBytes);
crypto::curve25519::ScalarBaseMult(ka->private_key_, ka->public_key_);
return ka;
}
// static
string Curve25519KeyExchange::NewPrivateKey(QuicRandom* rand) {
uint8 private_key[crypto::curve25519::kScalarBytes];
rand->RandBytes(private_key, sizeof(private_key));
// This makes |private_key| a valid scalar, as specified on
// http://cr.yp.to/ecdh.html
private_key[0] &= 248;
private_key[31] &= 127;
private_key[31] |= 64;
return string(reinterpret_cast<char*>(private_key), sizeof(private_key));
}
KeyExchange* Curve25519KeyExchange::NewKeyPair(QuicRandom* rand) const {
const string private_value = NewPrivateKey(rand);
return Curve25519KeyExchange::New(private_value);
}
bool Curve25519KeyExchange::CalculateSharedKey(
const StringPiece& peer_public_value,
string* out_result) const {
if (peer_public_value.size() != crypto::curve25519::kBytes) {
return false;
}
uint8 result[crypto::curve25519::kBytes];
crypto::curve25519::ScalarMult(
private_key_,
reinterpret_cast<const uint8*>(peer_public_value.data()),
result);
out_result->assign(reinterpret_cast<char*>(result), sizeof(result));
return true;
}
StringPiece Curve25519KeyExchange::public_value() const {
return StringPiece(reinterpret_cast<const char*>(public_key_),
sizeof(public_key_));
}
QuicTag Curve25519KeyExchange::tag() const { return kC255; }
} // namespace net
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