/*
|
* Copyright 2015 The Android Open Source Project
|
*
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
* you may not use this file except in compliance with the License.
|
* You may obtain a copy of the License at
|
*
|
* http://www.apache.org/licenses/LICENSE-2.0
|
*
|
* Unless required by applicable law or agreed to in writing, software
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
* See the License for the specific language governing permissions and
|
* limitations under the License.
|
*/
|
|
#include <keymaster/km_openssl/nist_curve_key_exchange.h>
|
|
#include <openssl/ec.h>
|
#include <openssl/ecdh.h>
|
#include <openssl/err.h>
|
#include <openssl/evp.h>
|
|
#include <keymaster/km_openssl/openssl_err.h>
|
|
namespace keymaster {
|
|
NistCurveKeyExchange::NistCurveKeyExchange(EC_KEY* private_key, keymaster_error_t* error)
|
: private_key_(private_key) {
|
if (!private_key_.get() || !EC_KEY_check_key(private_key_.get())) {
|
*error = KM_ERROR_INVALID_ARGUMENT;
|
return;
|
}
|
*error = ExtractPublicKey();
|
}
|
|
/* static */
|
NistCurveKeyExchange* NistCurveKeyExchange::GenerateKeyExchange(keymaster_ec_curve_t curve) {
|
int curve_name;
|
switch (curve) {
|
case KM_EC_CURVE_P_224:
|
curve_name = NID_secp224r1;
|
break;
|
case KM_EC_CURVE_P_256:
|
curve_name = NID_X9_62_prime256v1;
|
break;
|
case KM_EC_CURVE_P_384:
|
curve_name = NID_secp384r1;
|
break;
|
case KM_EC_CURVE_P_521:
|
curve_name = NID_secp521r1;
|
break;
|
default:
|
LOG_E("Not a NIST curve: %d", curve);
|
return nullptr;
|
}
|
|
UniquePtr<EC_KEY, EC_KEY_Delete> key(EC_KEY_new_by_curve_name(curve_name));
|
if (!key.get() || !EC_KEY_generate_key(key.get())) {
|
return nullptr;
|
}
|
keymaster_error_t error;
|
UniquePtr<NistCurveKeyExchange> key_exchange(new (std::nothrow)
|
NistCurveKeyExchange(key.get(), &error));
|
if (!key_exchange.get()) error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
|
if (error != KM_ERROR_OK) return nullptr;
|
(void)key.release();
|
|
return key_exchange.release();
|
}
|
|
keymaster_error_t NistCurveKeyExchange::ExtractPublicKey() {
|
const EC_GROUP* group = EC_KEY_get0_group(private_key_.get());
|
size_t field_len_bits;
|
keymaster_error_t error = ec_get_group_size(group, &field_len_bits);
|
if (error != KM_ERROR_OK) return error;
|
|
shared_secret_len_ = (field_len_bits + 7) / 8;
|
public_key_len_ = 1 + 2 * shared_secret_len_;
|
public_key_.reset(new (std::nothrow) uint8_t[public_key_len_]);
|
if (!public_key_.get()) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
|
if (EC_POINT_point2oct(group, EC_KEY_get0_public_key(private_key_.get()),
|
POINT_CONVERSION_UNCOMPRESSED, public_key_.get(), public_key_len_,
|
nullptr /* ctx */) != public_key_len_) {
|
return TranslateLastOpenSslError();
|
}
|
return KM_ERROR_OK;
|
}
|
|
bool NistCurveKeyExchange::CalculateSharedKey(const Buffer& peer_public_value,
|
Buffer* out_result) const {
|
|
return CalculateSharedKey(peer_public_value.peek_read(), peer_public_value.available_read(),
|
out_result);
|
}
|
|
bool NistCurveKeyExchange::CalculateSharedKey(const uint8_t* peer_public_value,
|
size_t peer_public_value_len,
|
Buffer* out_result) const {
|
const EC_GROUP* group = EC_KEY_get0_group(private_key_.get());
|
UniquePtr<EC_POINT, EC_POINT_Delete> point(EC_POINT_new(group));
|
if (!point.get() ||
|
!EC_POINT_oct2point(/* also test if point is on curve */
|
group, point.get(), peer_public_value, peer_public_value_len,
|
nullptr /* ctx */) ||
|
!EC_POINT_is_on_curve(group, point.get(), nullptr /* ctx */)) {
|
LOG_E("Can't convert peer public value to point: %d", TranslateLastOpenSslError());
|
return false;
|
}
|
|
UniquePtr<uint8_t[]> result(new (std::nothrow) uint8_t[shared_secret_len_]);
|
if (!result.get()) return false;
|
if (ECDH_compute_key(result.get(), shared_secret_len_, point.get(), private_key_.get(),
|
nullptr /* kdf */) != static_cast<int>(shared_secret_len_)) {
|
LOG_E("Can't compute ECDH shared key: %d", TranslateLastOpenSslError());
|
return false;
|
}
|
|
out_result->Reinitialize(result.get(), shared_secret_len_);
|
return true;
|
}
|
|
bool NistCurveKeyExchange::public_value(Buffer* public_value) const {
|
if (public_key_.get() != nullptr && public_key_len_ != 0) {
|
return public_value->Reinitialize(public_key_.get(), public_key_len_);
|
}
|
return false;
|
}
|
|
} // namespace keymaster
|
