/*
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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/contexts/soft_keymaster_context.h>
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#include <memory>
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#include <openssl/rand.h>
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#include <keymaster/android_keymaster_utils.h>
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#include <keymaster/key_blob_utils/auth_encrypted_key_blob.h>
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#include <keymaster/key_blob_utils/integrity_assured_key_blob.h>
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#include <keymaster/key_blob_utils/ocb_utils.h>
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#include <keymaster/key_blob_utils/software_keyblobs.h>
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#include <keymaster/km_openssl/aes_key.h>
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#include <keymaster/km_openssl/asymmetric_key.h>
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#include <keymaster/km_openssl/attestation_utils.h>
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#include <keymaster/km_openssl/hmac_key.h>
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#include <keymaster/km_openssl/openssl_err.h>
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#include <keymaster/km_openssl/triple_des_key.h>
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#include <keymaster/legacy_support/ec_keymaster0_key.h>
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#include <keymaster/legacy_support/ec_keymaster1_key.h>
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#include <keymaster/legacy_support/keymaster0_engine.h>
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#include <keymaster/legacy_support/rsa_keymaster0_key.h>
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#include <keymaster/legacy_support/rsa_keymaster1_key.h>
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#include <keymaster/logger.h>
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#include "soft_attestation_cert.h"
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using std::unique_ptr;
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namespace keymaster {
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namespace {
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KeymasterBlob string2Blob(const std::string& str) {
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return KeymasterBlob(reinterpret_cast<const uint8_t*>(str.data()), str.size());
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}
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} // anonymous namespace
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SoftKeymasterContext::SoftKeymasterContext(const std::string& root_of_trust)
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: rsa_factory_(new RsaKeyFactory(this)), ec_factory_(new EcKeyFactory(this)),
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aes_factory_(new AesKeyFactory(this, this)),
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tdes_factory_(new TripleDesKeyFactory(this, this)),
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hmac_factory_(new HmacKeyFactory(this, this)), km1_dev_(nullptr),
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root_of_trust_(string2Blob(root_of_trust)), os_version_(0), os_patchlevel_(0) {}
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SoftKeymasterContext::~SoftKeymasterContext() {}
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keymaster_error_t SoftKeymasterContext::SetHardwareDevice(keymaster0_device_t* keymaster0_device) {
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if (!keymaster0_device)
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return KM_ERROR_UNEXPECTED_NULL_POINTER;
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if ((keymaster0_device->flags & KEYMASTER_SOFTWARE_ONLY) != 0) {
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LOG_E("SoftKeymasterContext only wraps hardware keymaster0 devices", 0);
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return KM_ERROR_INVALID_ARGUMENT;
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}
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km0_engine_.reset(new Keymaster0Engine(keymaster0_device));
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rsa_factory_.reset(new RsaKeymaster0KeyFactory(this, km0_engine_.get()));
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ec_factory_.reset(new EcdsaKeymaster0KeyFactory(this, km0_engine_.get()));
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// Keep AES and HMAC factories.
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return KM_ERROR_OK;
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}
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keymaster_error_t SoftKeymasterContext::SetHardwareDevice(keymaster1_device_t* keymaster1_device) {
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if (!keymaster1_device)
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return KM_ERROR_UNEXPECTED_NULL_POINTER;
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km1_dev_ = keymaster1_device;
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km1_engine_.reset(new Keymaster1Engine(keymaster1_device));
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rsa_factory_.reset(new RsaKeymaster1KeyFactory(this, km1_engine_.get()));
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ec_factory_.reset(new EcdsaKeymaster1KeyFactory(this, km1_engine_.get()));
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// Use default HMAC and AES key factories. Higher layers will pass HMAC/AES keys/ops that are
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// supported by the hardware to it and other ones to the software-only factory.
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return KM_ERROR_OK;
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}
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keymaster_error_t SoftKeymasterContext::SetSystemVersion(uint32_t os_version,
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uint32_t os_patchlevel) {
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os_version_ = os_version;
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os_patchlevel_ = os_patchlevel;
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return KM_ERROR_OK;
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}
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void SoftKeymasterContext::GetSystemVersion(uint32_t* os_version, uint32_t* os_patchlevel) const {
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*os_version = os_version_;
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*os_patchlevel = os_patchlevel_;
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}
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KeyFactory* SoftKeymasterContext::GetKeyFactory(keymaster_algorithm_t algorithm) const {
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switch (algorithm) {
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case KM_ALGORITHM_RSA:
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return rsa_factory_.get();
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case KM_ALGORITHM_EC:
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return ec_factory_.get();
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case KM_ALGORITHM_AES:
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return aes_factory_.get();
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case KM_ALGORITHM_TRIPLE_DES:
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return tdes_factory_.get();
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case KM_ALGORITHM_HMAC:
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return hmac_factory_.get();
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default:
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return nullptr;
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}
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}
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static keymaster_algorithm_t supported_algorithms[] = {KM_ALGORITHM_RSA, KM_ALGORITHM_EC,
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KM_ALGORITHM_AES, KM_ALGORITHM_HMAC};
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keymaster_algorithm_t*
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SoftKeymasterContext::GetSupportedAlgorithms(size_t* algorithms_count) const {
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*algorithms_count = array_length(supported_algorithms);
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return supported_algorithms;
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}
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OperationFactory* SoftKeymasterContext::GetOperationFactory(keymaster_algorithm_t algorithm,
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keymaster_purpose_t purpose) const {
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KeyFactory* key_factory = GetKeyFactory(algorithm);
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if (!key_factory)
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return nullptr;
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return key_factory->GetOperationFactory(purpose);
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}
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static keymaster_error_t TranslateAuthorizationSetError(AuthorizationSet::Error err) {
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switch (err) {
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case AuthorizationSet::OK:
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return KM_ERROR_OK;
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case AuthorizationSet::ALLOCATION_FAILURE:
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return KM_ERROR_MEMORY_ALLOCATION_FAILED;
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case AuthorizationSet::MALFORMED_DATA:
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return KM_ERROR_UNKNOWN_ERROR;
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}
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return KM_ERROR_OK;
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}
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static keymaster_error_t SetAuthorizations(const AuthorizationSet& key_description,
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keymaster_key_origin_t origin, uint32_t os_version,
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uint32_t os_patchlevel, AuthorizationSet* hw_enforced,
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AuthorizationSet* sw_enforced) {
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sw_enforced->Clear();
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for (auto& entry : key_description) {
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switch (entry.tag) {
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// These cannot be specified by the client.
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case KM_TAG_ROOT_OF_TRUST:
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case KM_TAG_ORIGIN:
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LOG_E("Root of trust and origin tags may not be specified", 0);
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return KM_ERROR_INVALID_TAG;
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// These don't work.
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case KM_TAG_ROLLBACK_RESISTANT:
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LOG_E("KM_TAG_ROLLBACK_RESISTANT not supported", 0);
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return KM_ERROR_UNSUPPORTED_TAG;
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// These are hidden.
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case KM_TAG_APPLICATION_ID:
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case KM_TAG_APPLICATION_DATA:
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break;
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// Everything else we just copy into sw_enforced, unless the KeyFactory has placed it in
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// hw_enforced, in which case we defer to its decision.
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default:
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if (hw_enforced->GetTagCount(entry.tag) == 0)
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sw_enforced->push_back(entry);
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break;
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}
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}
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sw_enforced->push_back(TAG_CREATION_DATETIME, java_time(time(nullptr)));
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sw_enforced->push_back(TAG_ORIGIN, origin);
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sw_enforced->push_back(TAG_OS_VERSION, os_version);
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sw_enforced->push_back(TAG_OS_PATCHLEVEL, os_patchlevel);
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return TranslateAuthorizationSetError(sw_enforced->is_valid());
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}
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keymaster_error_t SoftKeymasterContext::CreateKeyBlob(const AuthorizationSet& key_description,
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const keymaster_key_origin_t origin,
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const KeymasterKeyBlob& key_material,
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KeymasterKeyBlob* blob,
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AuthorizationSet* hw_enforced,
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AuthorizationSet* sw_enforced) const {
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keymaster_error_t error = SetAuthorizations(key_description, origin, os_version_,
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os_patchlevel_, hw_enforced, sw_enforced);
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if (error != KM_ERROR_OK)
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return error;
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AuthorizationSet hidden;
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error = BuildHiddenAuthorizations(key_description, &hidden, root_of_trust_);
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if (error != KM_ERROR_OK)
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return error;
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return SerializeIntegrityAssuredBlob(key_material, hidden, *hw_enforced, *sw_enforced, blob);
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}
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keymaster_error_t SoftKeymasterContext::UpgradeKeyBlob(const KeymasterKeyBlob& key_to_upgrade,
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const AuthorizationSet& upgrade_params,
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KeymasterKeyBlob* upgraded_key) const {
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UniquePtr<Key> key;
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keymaster_error_t error = ParseKeyBlob(key_to_upgrade, upgrade_params, &key);
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if (error != KM_ERROR_OK)
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return error;
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// Three cases here:
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//
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// 1. Software key blob. Version info, if present, is in sw_enforced. If not present, we
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// should add it.
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//
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// 2. Keymaster0 hardware key blob. Version info, if present, is in sw_enforced. If not
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// present we should add it.
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//
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// 3. Keymaster1 hardware key blob. Version info is not present and we shouldn't have been
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// asked to upgrade.
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// Handle case 3.
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if (km1_dev_ && key->hw_enforced().Contains(TAG_PURPOSE) &&
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!key->hw_enforced().Contains(TAG_OS_PATCHLEVEL))
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return KM_ERROR_INVALID_ARGUMENT;
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// Handle case 1 and 2
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return UpgradeSoftKeyBlob(key, os_version_, os_patchlevel_, upgrade_params, upgraded_key);
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}
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keymaster_error_t SoftKeymasterContext::ParseKeyBlob(const KeymasterKeyBlob& blob,
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const AuthorizationSet& additional_params,
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UniquePtr<Key>* key) const {
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// This is a little bit complicated.
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//
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// The SoftKeymasterContext has to handle a lot of different kinds of key blobs.
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//
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// 1. New keymaster1 software key blobs. These are integrity-assured but not encrypted. The
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// raw key material and auth sets should be extracted and returned. This is the kind
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// produced by this context when the KeyFactory doesn't use keymaster0 to back the keys.
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//
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// 2. Old keymaster1 software key blobs. These are OCB-encrypted with an all-zero master key.
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// They should be decrypted and the key material and auth sets extracted and returned.
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//
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// 3. Old keymaster0 software key blobs. These are raw key material with a small header tacked
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// on the front. They don't have auth sets, so reasonable defaults are generated and
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// returned along with the raw key material.
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//
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// 4. New keymaster0 hardware key blobs. These are integrity-assured but not encrypted (though
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// they're protected by the keymaster0 hardware implementation). The keymaster0 key blob
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// and auth sets should be extracted and returned.
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//
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// 5. Keymaster1 hardware key blobs. These are raw hardware key blobs. They contain auth
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// sets, which we retrieve from the hardware module.
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//
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// 6. Old keymaster0 hardware key blobs. These are raw hardware key blobs. They don't have
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// auth sets so reasonable defaults are generated and returned along with the key blob.
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//
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// Determining what kind of blob has arrived is somewhat tricky. What helps is that
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// integrity-assured and OCB-encrypted blobs are self-consistent and effectively impossible to
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// parse as anything else. Old keymaster0 software key blobs have a header. It's reasonably
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// unlikely that hardware keys would have the same header. So anything that is neither
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// integrity-assured nor OCB-encrypted and lacks the old software key header is assumed to be
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// keymaster0 hardware.
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AuthorizationSet hw_enforced;
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AuthorizationSet sw_enforced;
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KeymasterKeyBlob key_material;
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AuthorizationSet hidden;
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keymaster_error_t error;
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auto constructKey = [&, this] () mutable -> keymaster_error_t {
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// GetKeyFactory
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if (error != KM_ERROR_OK) return error;
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keymaster_algorithm_t algorithm;
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if (!hw_enforced.GetTagValue(TAG_ALGORITHM, &algorithm) &&
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!sw_enforced.GetTagValue(TAG_ALGORITHM, &algorithm)) {
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return KM_ERROR_INVALID_ARGUMENT;
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}
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auto factory = GetKeyFactory(algorithm);
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return factory->LoadKey(move(key_material), additional_params, move(hw_enforced),
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move(sw_enforced), key);
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};
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error = BuildHiddenAuthorizations(additional_params, &hidden, root_of_trust_);
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if (error != KM_ERROR_OK)
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return error;
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// Assume it's an integrity-assured blob (new software-only blob, or new keymaster0-backed
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// blob).
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error = DeserializeIntegrityAssuredBlob(blob, hidden, &key_material, &hw_enforced, &sw_enforced);
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if (error != KM_ERROR_INVALID_KEY_BLOB)
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return constructKey();
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// Wasn't an integrity-assured blob. Maybe it's an OCB-encrypted blob.
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error = ParseOcbAuthEncryptedBlob(blob, hidden, &key_material, &hw_enforced, &sw_enforced);
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if (error == KM_ERROR_OK)
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LOG_D("Parsed an old keymaster1 software key", 0);
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if (error != KM_ERROR_INVALID_KEY_BLOB)
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return constructKey();
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// Wasn't an OCB-encrypted blob. Maybe it's an old softkeymaster blob.
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error = ParseOldSoftkeymasterBlob(blob, &key_material, &hw_enforced, &sw_enforced);
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if (error == KM_ERROR_OK)
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LOG_D("Parsed an old sofkeymaster key", 0);
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if (error != KM_ERROR_INVALID_KEY_BLOB)
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return constructKey();
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if (km1_dev_) {
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error = ParseKeymaster1HwBlob(blob, additional_params, &key_material, &hw_enforced,
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&sw_enforced);
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} else if (km0_engine_) {
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error = ParseKeymaster0HwBlob(blob, &key_material, &hw_enforced, &sw_enforced);
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} else {
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return KM_ERROR_INVALID_KEY_BLOB;
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}
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return constructKey();
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}
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keymaster_error_t SoftKeymasterContext::DeleteKey(const KeymasterKeyBlob& blob) const {
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if (km1_engine_) {
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// HACK. Due to a bug with Qualcomm's Keymaster implementation, which causes the device to
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// reboot if we pass it a key blob it doesn't understand, we need to check for software
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// keys. If it looks like a software key there's nothing to do so we just return.
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KeymasterKeyBlob key_material;
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AuthorizationSet hw_enforced, sw_enforced;
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keymaster_error_t error = DeserializeIntegrityAssuredBlob_NoHmacCheck(
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blob, &key_material, &hw_enforced, &sw_enforced);
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if (error == KM_ERROR_OK) {
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return KM_ERROR_OK;
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}
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return km1_engine_->DeleteKey(blob);
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}
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if (km0_engine_) {
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// This could be a keymaster0 hardware key, and it could be either raw or encapsulated in an
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// integrity-assured blob. If it's integrity-assured, we can't validate it strongly,
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// because we don't have the necessary additional_params data. However, the probability
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// that anything other than an integrity-assured blob would have all of the structure
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// required to decode as a valid blob is low -- unless it's maliciously-constructed, but the
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// deserializer should be proof against bad data, as should the keymaster0 hardware.
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//
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// Thus, we first try to parse it as integrity-assured. If that works, we pass the result
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// to the underlying hardware. If not, we pass blob unmodified to the underlying hardware.
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KeymasterKeyBlob key_material;
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AuthorizationSet hw_enforced, sw_enforced;
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keymaster_error_t error = DeserializeIntegrityAssuredBlob_NoHmacCheck(
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blob, &key_material, &hw_enforced, &sw_enforced);
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if (error == KM_ERROR_OK && km0_engine_->DeleteKey(key_material))
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return KM_ERROR_OK;
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km0_engine_->DeleteKey(blob);
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// We succeed unconditionally at this point, even if delete failed. Failure indicates that
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// either the blob is a software blob (which we can't distinguish with certainty without
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// additional_params) or because it is a hardware blob and the hardware failed. In the
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// first case, there is no error. In the second case, the client can't do anything to fix
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// it anyway, so it's not too harmful to simply swallow the error. This is not ideal, but
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// it's the least-bad alternative.
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return KM_ERROR_OK;
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}
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// Nothing to do for software-only contexts.
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return KM_ERROR_OK;
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}
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keymaster_error_t SoftKeymasterContext::DeleteAllKeys() const {
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if (km1_engine_)
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return km1_engine_->DeleteAllKeys();
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if (km0_engine_ && !km0_engine_->DeleteAllKeys())
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return KM_ERROR_UNKNOWN_ERROR;
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return KM_ERROR_OK;
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}
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keymaster_error_t SoftKeymasterContext::AddRngEntropy(const uint8_t* buf, size_t length) const {
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RAND_add(buf, length, 0 /* Don't assume any entropy is added to the pool. */);
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return KM_ERROR_OK;
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}
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keymaster_error_t SoftKeymasterContext::ParseKeymaster1HwBlob(
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const KeymasterKeyBlob& blob, const AuthorizationSet& additional_params,
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KeymasterKeyBlob* key_material, AuthorizationSet* hw_enforced,
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AuthorizationSet* sw_enforced) const {
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assert(km1_dev_);
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keymaster_blob_t client_id = {nullptr, 0};
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keymaster_blob_t app_data = {nullptr, 0};
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keymaster_blob_t* client_id_ptr = nullptr;
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keymaster_blob_t* app_data_ptr = nullptr;
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if (additional_params.GetTagValue(TAG_APPLICATION_ID, &client_id))
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client_id_ptr = &client_id;
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if (additional_params.GetTagValue(TAG_APPLICATION_DATA, &app_data))
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app_data_ptr = &app_data;
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// Get key characteristics, which incidentally verifies that the HW recognizes the key.
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keymaster_key_characteristics_t* characteristics;
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keymaster_error_t error = km1_dev_->get_key_characteristics(km1_dev_, &blob, client_id_ptr,
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app_data_ptr, &characteristics);
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if (error != KM_ERROR_OK)
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return error;
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unique_ptr<keymaster_key_characteristics_t, Characteristics_Delete> characteristics_deleter(
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characteristics);
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LOG_D("Module \"%s\" accepted key", km1_dev_->common.module->name);
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hw_enforced->Reinitialize(characteristics->hw_enforced);
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sw_enforced->Reinitialize(characteristics->sw_enforced);
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*key_material = blob;
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return KM_ERROR_OK;
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}
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keymaster_error_t SoftKeymasterContext::ParseKeymaster0HwBlob(const KeymasterKeyBlob& blob,
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KeymasterKeyBlob* key_material,
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AuthorizationSet* hw_enforced,
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AuthorizationSet* sw_enforced) const {
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assert(km0_engine_);
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unique_ptr<EVP_PKEY, EVP_PKEY_Delete> tmp_key(km0_engine_->GetKeymaster0PublicKey(blob));
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if (!tmp_key)
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return KM_ERROR_INVALID_KEY_BLOB;
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LOG_D("Module \"%s\" accepted key", km0_engine_->device()->common.module->name);
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keymaster_error_t error = FakeKeyAuthorizations(tmp_key.get(), hw_enforced, sw_enforced);
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if (error == KM_ERROR_OK)
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*key_material = blob;
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return error;
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}
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keymaster_error_t SoftKeymasterContext::GenerateAttestation(const Key& key,
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const AuthorizationSet& attest_params, CertChainPtr* cert_chain) const {
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keymaster_error_t error = KM_ERROR_OK;
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keymaster_algorithm_t key_algorithm;
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if (!key.authorizations().GetTagValue(TAG_ALGORITHM, &key_algorithm)) {
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return KM_ERROR_UNKNOWN_ERROR;
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}
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if ((key_algorithm != KM_ALGORITHM_RSA && key_algorithm != KM_ALGORITHM_EC))
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return KM_ERROR_INCOMPATIBLE_ALGORITHM;
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// We have established that the given key has the correct algorithm, and because this is the
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// SoftKeymasterContext we can assume that the Key is an AsymmetricKey. So we can downcast.
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const AsymmetricKey& asymmetric_key = static_cast<const AsymmetricKey&>(key);
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auto attestation_chain = getAttestationChain(key_algorithm, &error);
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if (error != KM_ERROR_OK) return error;
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auto attestation_key = getAttestationKey(key_algorithm, &error);
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if (error != KM_ERROR_OK) return error;
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return generate_attestation(asymmetric_key, attest_params,
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*attestation_chain, *attestation_key, *this, cert_chain);
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}
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keymaster_error_t SoftKeymasterContext::UnwrapKey(const KeymasterKeyBlob&, const KeymasterKeyBlob&,
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const AuthorizationSet&, const KeymasterKeyBlob&,
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AuthorizationSet*, keymaster_key_format_t*,
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KeymasterKeyBlob*) const {
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return KM_ERROR_UNIMPLEMENTED;
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}
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} // namespace keymaster
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