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/*
* Copyright 2021 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/ecdh_operation.h>
#include <utility>
#include <vector>
#include <keymaster/km_openssl/ec_key.h>
#include <keymaster/km_openssl/openssl_err.h>
#include <keymaster/km_openssl/openssl_utils.h>
#include <keymaster/logger.h>
#include <openssl/curve25519.h>
#include <openssl/err.h>
namespace keymaster {
keymaster_error_t EcdhOperation::Begin(const AuthorizationSet& /*input_params*/,
AuthorizationSet* /*output_params*/) {
auto rc = GenerateRandom(reinterpret_cast<uint8_t*>(&operation_handle_),
(size_t)sizeof(operation_handle_));
if (rc != KM_ERROR_OK) {
return rc;
}
return KM_ERROR_OK;
}
keymaster_error_t EcdhOperation::Update(const AuthorizationSet& /*additional_params*/,
const Buffer& /*input*/,
AuthorizationSet* /*output_params*/, Buffer* /*output*/,
size_t* /*input_consumed*/) {
return KM_ERROR_OK;
}
keymaster_error_t EcdhOperation::Finish(const AuthorizationSet& /*additional_params*/,
const Buffer& input, const Buffer& /*signature*/,
AuthorizationSet* /*output_params*/, Buffer* output) {
const unsigned char* encodedPublicKey = input.begin();
EVP_PKEY* pkeyRaw = d2i_PUBKEY(nullptr, &encodedPublicKey, input.available_read());
if (pkeyRaw == nullptr) {
LOG_E("Error decoding key", 0);
return KM_ERROR_INVALID_ARGUMENT;
}
auto pkey = EVP_PKEY_Ptr(pkeyRaw);
auto ctx = EVP_PKEY_CTX_Ptr(EVP_PKEY_CTX_new(ecdh_key_.get(), nullptr));
if (ctx.get() == nullptr) {
LOG_E("Memory allocation failed", 0);
return TranslateLastOpenSslError();
}
if (EVP_PKEY_derive_init(ctx.get()) != 1) {
LOG_E("Context initialization failed", 0);
return TranslateLastOpenSslError();
}
if (EVP_PKEY_derive_set_peer(ctx.get(), pkey.get()) != 1) {
LOG_E("Error setting peer key", 0);
return KM_ERROR_INVALID_ARGUMENT;
}
size_t sharedSecretLen = 0;
if (EVP_PKEY_derive(ctx.get(), nullptr, &sharedSecretLen) != 1) {
LOG_E("Error deriving key", 0);
return TranslateLastOpenSslError();
}
if (!output->reserve(sharedSecretLen)) {
LOG_E("Error reserving data in output buffer", 0);
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
if (EVP_PKEY_derive(ctx.get(), output->peek_write(), &sharedSecretLen) != 1) {
LOG_E("Error deriving key", 0);
return TranslateLastOpenSslError();
}
output->advance_write(sharedSecretLen);
return KM_ERROR_OK;
}
keymaster_error_t X25519Operation::Finish(const AuthorizationSet& /*additional_params*/,
const Buffer& input, const Buffer& /*signature*/,
AuthorizationSet* /*output_params*/, Buffer* output) {
// Retrieve the peer X25519 key from within the ASN.1 SubjectPublicKeyInfo.
const unsigned char* encodedPublicKey = input.begin();
EVP_PKEY* pkeyRaw = d2i_PUBKEY(nullptr, &encodedPublicKey, input.available_read());
if (pkeyRaw == nullptr) {
LOG_E("Error decoding key", 0);
return KM_ERROR_INVALID_ARGUMENT;
}
auto pkey = EVP_PKEY_Ptr(pkeyRaw);
int pkey_type = EVP_PKEY_id(pkey.get());
if (pkey_type != EVP_PKEY_X25519) {
LOG_E("Unexpected peer public key type %d", pkey_type);
return KM_ERROR_INVALID_ARGUMENT;
}
size_t pub_key_len = X25519_PUBLIC_VALUE_LEN;
uint8_t pub_key[X25519_PUBLIC_VALUE_LEN];
if (EVP_PKEY_get_raw_public_key(pkey.get(), pub_key, &pub_key_len) == 0) {
LOG_E("Error extracting key", 0);
return KM_ERROR_INVALID_ARGUMENT;
}
if (pub_key_len != X25519_PUBLIC_VALUE_LEN) {
LOG_E("Invalid length %d of peer key", pub_key_len);
return KM_ERROR_INVALID_ARGUMENT;
}
size_t key_len = X25519_PRIVATE_KEY_LEN;
uint8_t priv_key[X25519_PRIVATE_KEY_LEN];
if (EVP_PKEY_get_raw_private_key(ecdh_key_.get(), priv_key, &key_len) == 0) {
return TranslateLastOpenSslError();
}
if (key_len != X25519_PRIVATE_KEY_LEN) {
return KM_ERROR_UNKNOWN_ERROR;
}
if (!output->reserve(X25519_SHARED_KEY_LEN)) {
LOG_E("Error reserving data in output buffer", 0);
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
if (X25519(output->peek_write(), priv_key, pub_key) != 1) {
LOG_E("Error deriving key", 0);
return TranslateLastOpenSslError();
}
output->advance_write(X25519_SHARED_KEY_LEN);
return KM_ERROR_OK;
}
OperationPtr EcdhOperationFactory::CreateOperation(Key&& key,
const AuthorizationSet& /*begin_params*/,
keymaster_error_t* error) {
const AsymmetricKey& ecdh_key = static_cast<AsymmetricKey&>(key);
EVP_PKEY_Ptr pkey(ecdh_key.InternalToEvp());
if (pkey.get() == nullptr) {
*error = KM_ERROR_UNKNOWN_ERROR;
return nullptr;
}
*error = KM_ERROR_OK;
EcdhOperation* op = nullptr;
switch (EVP_PKEY_id(pkey.get())) {
case EVP_PKEY_X25519:
op = new (std::nothrow) X25519Operation(std::move(key.hw_enforced_move()),
std::move(key.sw_enforced_move()), pkey.release());
break;
case EVP_PKEY_EC:
op = new (std::nothrow) EcdhOperation(std::move(key.hw_enforced_move()),
std::move(key.sw_enforced_move()), pkey.release());
break;
default:
*error = KM_ERROR_UNKNOWN_ERROR;
return nullptr;
}
if (!op) {
*error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
return nullptr;
}
return OperationPtr(op);
}
} // namespace keymaster
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