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