Keymaster.cpp - SHIFTPHONES/android_system_vold - Gitiles

 /*
  * Copyright (C) 2016 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.h"

 #include <android-base/logging.h>
 #include <keymasterV4_0/authorization_set.h>
 #include <keymasterV4_0/keymaster_utils.h>

 namespace android {
 namespace vold {

 using ::android::hardware::hidl_string;
 using ::android::hardware::hidl_vec;
 using ::android::hardware::keymaster::V4_0::SecurityLevel;

 KeymasterOperation::~KeymasterOperation() {
     if (mDevice) mDevice->abort(mOpHandle);
 }

 bool KeymasterOperation::updateCompletely(const char* input, size_t inputLen,
                                           const std::function<void(const char*, size_t)> consumer) {
     uint32_t inputConsumed = 0;

     km::ErrorCode km_error;
     auto hidlCB = [&](km::ErrorCode ret, uint32_t inputConsumedDelta,
                       const hidl_vec<km::KeyParameter>& /*ignored*/,
                       const hidl_vec<uint8_t>& _output) {
         km_error = ret;
         if (km_error != km::ErrorCode::OK) return;
         inputConsumed += inputConsumedDelta;
         consumer(reinterpret_cast<const char*>(&_output[0]), _output.size());
     };

     while (inputConsumed != inputLen) {
         size_t toRead = static_cast<size_t>(inputLen - inputConsumed);
         auto inputBlob = km::support::blob2hidlVec(
             reinterpret_cast<const uint8_t*>(&input[inputConsumed]), toRead);
         // TODO(swillden): Need to handle getting a VerificationToken from the TEE if mDevice is
         // StrongBox, so we can provide it here.  The VerificationToken will need to be
         // requested/retrieved during Keymaster::begin().
         auto error = mDevice->update(mOpHandle, hidl_vec<km::KeyParameter>(), inputBlob,
                                      km::HardwareAuthToken(), km::VerificationToken(), hidlCB);
         if (!error.isOk()) {
             LOG(ERROR) << "update failed: " << error.description();
             mDevice = nullptr;
             return false;
         }
         if (km_error != km::ErrorCode::OK) {
             LOG(ERROR) << "update failed, code " << int32_t(km_error);
             mDevice = nullptr;
             return false;
         }
         if (inputConsumed > inputLen) {
             LOG(ERROR) << "update reported too much input consumed";
             mDevice = nullptr;
             return false;
         }
     }
     return true;
 }

 bool KeymasterOperation::finish(std::string* output) {
     km::ErrorCode km_error;
     auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<km::KeyParameter>& /*ignored*/,
                       const hidl_vec<uint8_t>& _output) {
         km_error = ret;
         if (km_error != km::ErrorCode::OK) return;
         if (output) output->assign(reinterpret_cast<const char*>(&_output[0]), _output.size());
     };
     auto error = mDevice->finish(mOpHandle, hidl_vec<km::KeyParameter>(), hidl_vec<uint8_t>(),
                                  hidl_vec<uint8_t>(), km::HardwareAuthToken(),
                                  km::VerificationToken(), hidlCb);
     mDevice = nullptr;
     if (!error.isOk()) {
         LOG(ERROR) << "finish failed: " << error.description();
         return false;
     }
     if (km_error != km::ErrorCode::OK) {
         LOG(ERROR) << "finish failed, code " << int32_t(km_error);
         return false;
     }
     return true;
 }

 Keymaster::Keymaster() {
     auto devices = KmDevice::enumerateAvailableDevices();
     for (auto& dev : devices) {
         // Explicitly avoid using STRONGBOX for now.
         // TODO: Re-enable STRONGBOX, since it's what we really want. b/77338527
         if (dev->halVersion().securityLevel != SecurityLevel::STRONGBOX) {
             mDevice = std::move(dev);
             break;
         }
     }
     if (!mDevice) return;
     auto& version = mDevice->halVersion();
     LOG(INFO) << "Using " << version.keymasterName << " from " << version.authorName
               << " for encryption.  Security level: " << toString(version.securityLevel)
               << ", HAL: " << mDevice->descriptor() << "/" << mDevice->instanceName();
 }

 bool Keymaster::generateKey(const km::AuthorizationSet& inParams, std::string* key) {
     km::ErrorCode km_error;
     auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<uint8_t>& keyBlob,
                       const km::KeyCharacteristics& /*ignored*/) {
         km_error = ret;
         if (km_error != km::ErrorCode::OK) return;
         if (key) key->assign(reinterpret_cast<const char*>(&keyBlob[0]), keyBlob.size());
     };

     auto error = mDevice->generateKey(inParams.hidl_data(), hidlCb);
     if (!error.isOk()) {
         LOG(ERROR) << "generate_key failed: " << error.description();
         return false;
     }
     if (km_error != km::ErrorCode::OK) {
         LOG(ERROR) << "generate_key failed, code " << int32_t(km_error);
         return false;
     }
     return true;
 }

 bool Keymaster::deleteKey(const std::string& key) {
     auto keyBlob = km::support::blob2hidlVec(key);
     auto error = mDevice->deleteKey(keyBlob);
     if (!error.isOk()) {
         LOG(ERROR) << "delete_key failed: " << error.description();
         return false;
     }
     if (error != km::ErrorCode::OK) {
         LOG(ERROR) << "delete_key failed, code " << int32_t(km::ErrorCode(error));
         return false;
     }
     return true;
 }

 bool Keymaster::upgradeKey(const std::string& oldKey, const km::AuthorizationSet& inParams,
                            std::string* newKey) {
     auto oldKeyBlob = km::support::blob2hidlVec(oldKey);
     km::ErrorCode km_error;
     auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<uint8_t>& upgradedKeyBlob) {
         km_error = ret;
         if (km_error != km::ErrorCode::OK) return;
         if (newKey)
             newKey->assign(reinterpret_cast<const char*>(&upgradedKeyBlob[0]),
                            upgradedKeyBlob.size());
     };
     auto error = mDevice->upgradeKey(oldKeyBlob, inParams.hidl_data(), hidlCb);
     if (!error.isOk()) {
         LOG(ERROR) << "upgrade_key failed: " << error.description();
         return false;
     }
     if (km_error != km::ErrorCode::OK) {
         LOG(ERROR) << "upgrade_key failed, code " << int32_t(km_error);
         return false;
     }
     return true;
 }

 KeymasterOperation Keymaster::begin(km::KeyPurpose purpose, const std::string& key,
                                     const km::AuthorizationSet& inParams,
                                     const km::HardwareAuthToken& authToken,
                                     km::AuthorizationSet* outParams) {
     auto keyBlob = km::support::blob2hidlVec(key);
     uint64_t mOpHandle;
     km::ErrorCode km_error;

     auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<km::KeyParameter>& _outParams,
                       uint64_t operationHandle) {
         km_error = ret;
         if (km_error != km::ErrorCode::OK) return;
         if (outParams) *outParams = _outParams;
         mOpHandle = operationHandle;
     };

     auto error = mDevice->begin(purpose, keyBlob, inParams.hidl_data(), authToken, hidlCb);
     if (!error.isOk()) {
         LOG(ERROR) << "begin failed: " << error.description();
         return KeymasterOperation(km::ErrorCode::UNKNOWN_ERROR);
     }
     if (km_error != km::ErrorCode::OK) {
         LOG(ERROR) << "begin failed, code " << int32_t(km_error);
         return KeymasterOperation(km_error);
     }
     return KeymasterOperation(mDevice.get(), mOpHandle);
 }

 bool Keymaster::isSecure() {
     return mDevice->halVersion().securityLevel != km::SecurityLevel::SOFTWARE;
 }

 }  // namespace vold
 }  // namespace android

 using namespace ::android::vold;

 int keymaster_compatibility_cryptfs_scrypt() {
     Keymaster dev;
     if (!dev) {
         LOG(ERROR) << "Failed to initiate keymaster session";
         return -1;
     }
     return dev.isSecure();
 }

 static bool write_string_to_buf(const std::string& towrite, uint8_t* buffer, uint32_t buffer_size,
                                 uint32_t* out_size) {
     if (!buffer || !out_size) {
         LOG(ERROR) << "Missing target pointers";
         return false;
     }
     *out_size = towrite.size();
     if (buffer_size < towrite.size()) {
         LOG(ERROR) << "Buffer too small " << buffer_size << " < " << towrite.size();
         return false;
     }
     memset(buffer, '\0', buffer_size);
     std::copy(towrite.begin(), towrite.end(), buffer);
     return true;
 }

 static km::AuthorizationSet keyParams(uint32_t rsa_key_size, uint64_t rsa_exponent,
                                       uint32_t ratelimit) {
     return km::AuthorizationSetBuilder()
         .RsaSigningKey(rsa_key_size, rsa_exponent)
         .NoDigestOrPadding()
         .Authorization(km::TAG_BLOB_USAGE_REQUIREMENTS, km::KeyBlobUsageRequirements::STANDALONE)
         .Authorization(km::TAG_NO_AUTH_REQUIRED)
         .Authorization(km::TAG_MIN_SECONDS_BETWEEN_OPS, ratelimit);
 }

 int keymaster_create_key_for_cryptfs_scrypt(uint32_t rsa_key_size, uint64_t rsa_exponent,
                                             uint32_t ratelimit, uint8_t* key_buffer,
                                             uint32_t key_buffer_size, uint32_t* key_out_size) {
     if (key_out_size) {
         *key_out_size = 0;
     }
     Keymaster dev;
     if (!dev) {
         LOG(ERROR) << "Failed to initiate keymaster session";
         return -1;
     }
     std::string key;
     if (!dev.generateKey(keyParams(rsa_key_size, rsa_exponent, ratelimit), &key)) return -1;
     if (!write_string_to_buf(key, key_buffer, key_buffer_size, key_out_size)) return -1;
     return 0;
 }

 int keymaster_upgrade_key_for_cryptfs_scrypt(uint32_t rsa_key_size, uint64_t rsa_exponent,
                                              uint32_t ratelimit, const uint8_t* key_blob,
                                              size_t key_blob_size, uint8_t* key_buffer,
                                              uint32_t key_buffer_size, uint32_t* key_out_size) {
     if (key_out_size) {
         *key_out_size = 0;
     }
     Keymaster dev;
     if (!dev) {
         LOG(ERROR) << "Failed to initiate keymaster session";
         return -1;
     }
     std::string old_key(reinterpret_cast<const char*>(key_blob), key_blob_size);
     std::string new_key;
     if (!dev.upgradeKey(old_key, keyParams(rsa_key_size, rsa_exponent, ratelimit), &new_key))
         return -1;
     if (!write_string_to_buf(new_key, key_buffer, key_buffer_size, key_out_size)) return -1;
     return 0;
 }

 KeymasterSignResult keymaster_sign_object_for_cryptfs_scrypt(
     const uint8_t* key_blob, size_t key_blob_size, uint32_t ratelimit, const uint8_t* object,
     const size_t object_size, uint8_t** signature_buffer, size_t* signature_buffer_size) {
     Keymaster dev;
     if (!dev) {
         LOG(ERROR) << "Failed to initiate keymaster session";
         return KeymasterSignResult::error;
     }
     if (!key_blob || !object || !signature_buffer || !signature_buffer_size) {
         LOG(ERROR) << __FILE__ << ":" << __LINE__ << ":Invalid argument";
         return KeymasterSignResult::error;
     }

     km::AuthorizationSet outParams;
     std::string key(reinterpret_cast<const char*>(key_blob), key_blob_size);
     std::string input(reinterpret_cast<const char*>(object), object_size);
     std::string output;
     KeymasterOperation op;

     auto paramBuilder = km::AuthorizationSetBuilder().NoDigestOrPadding();
     while (true) {
         op = dev.begin(km::KeyPurpose::SIGN, key, paramBuilder, km::HardwareAuthToken(), &outParams);
         if (op.errorCode() == km::ErrorCode::KEY_RATE_LIMIT_EXCEEDED) {
             sleep(ratelimit);
             continue;
         } else
             break;
     }

     if (op.errorCode() == km::ErrorCode::KEY_REQUIRES_UPGRADE) {
         LOG(ERROR) << "Keymaster key requires upgrade";
         return KeymasterSignResult::upgrade;
     }

     if (op.errorCode() != km::ErrorCode::OK) {
         LOG(ERROR) << "Error starting keymaster signature transaction: " << int32_t(op.errorCode());
         return KeymasterSignResult::error;
     }

     if (!op.updateCompletely(input, &output)) {
         LOG(ERROR) << "Error sending data to keymaster signature transaction: "
                    << uint32_t(op.errorCode());
         return KeymasterSignResult::error;
     }

     if (!op.finish(&output)) {
         LOG(ERROR) << "Error finalizing keymaster signature transaction: "
                    << int32_t(op.errorCode());
         return KeymasterSignResult::error;
     }

     *signature_buffer = reinterpret_cast<uint8_t*>(malloc(output.size()));
     if (*signature_buffer == nullptr) {
         LOG(ERROR) << "Error allocation buffer for keymaster signature";
         return KeymasterSignResult::error;
     }
     *signature_buffer_size = output.size();
     std::copy(output.data(), output.data() + output.size(), *signature_buffer);
     return KeymasterSignResult::ok;
 }
	/*
	* Copyright (C) 2016 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.h"

	#include <android-base/logging.h>
	#include <keymasterV4_0/authorization_set.h>
	#include <keymasterV4_0/keymaster_utils.h>

	namespace android {
	namespace vold {

	using ::android::hardware::hidl_string;
	using ::android::hardware::hidl_vec;
	using ::android::hardware::keymaster::V4_0::SecurityLevel;

	KeymasterOperation::~KeymasterOperation() {
	if (mDevice) mDevice->abort(mOpHandle);
	}

	bool KeymasterOperation::updateCompletely(const char* input, size_t inputLen,
	const std::function<void(const char*, size_t)> consumer) {
	uint32_t inputConsumed = 0;

	km::ErrorCode km_error;
	auto hidlCB = [&](km::ErrorCode ret, uint32_t inputConsumedDelta,
	const hidl_vec<km::KeyParameter>& /ignored/,
	const hidl_vec<uint8_t>& _output) {
	km_error = ret;
	if (km_error != km::ErrorCode::OK) return;
	inputConsumed += inputConsumedDelta;
	consumer(reinterpret_cast<const char*>(&_output[0]), _output.size());
	};

	while (inputConsumed != inputLen) {
	size_t toRead = static_cast<size_t>(inputLen - inputConsumed);
	auto inputBlob = km::support::blob2hidlVec(
	reinterpret_cast<const uint8_t*>(&input[inputConsumed]), toRead);
	// TODO(swillden): Need to handle getting a VerificationToken from the TEE if mDevice is
	// StrongBox, so we can provide it here. The VerificationToken will need to be
	// requested/retrieved during Keymaster::begin().
	auto error = mDevice->update(mOpHandle, hidl_vec<km::KeyParameter>(), inputBlob,
	km::HardwareAuthToken(), km::VerificationToken(), hidlCB);
	if (!error.isOk()) {
	LOG(ERROR) << "update failed: " << error.description();
	mDevice = nullptr;
	return false;
	}
	if (km_error != km::ErrorCode::OK) {
	LOG(ERROR) << "update failed, code " << int32_t(km_error);
	mDevice = nullptr;
	return false;
	}
	if (inputConsumed > inputLen) {
	LOG(ERROR) << "update reported too much input consumed";
	mDevice = nullptr;
	return false;
	}
	}
	return true;
	}

	bool KeymasterOperation::finish(std::string* output) {
	km::ErrorCode km_error;
	auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<km::KeyParameter>& /ignored/,
	const hidl_vec<uint8_t>& _output) {
	km_error = ret;
	if (km_error != km::ErrorCode::OK) return;
	if (output) output->assign(reinterpret_cast<const char*>(&_output[0]), _output.size());
	};
	auto error = mDevice->finish(mOpHandle, hidl_vec<km::KeyParameter>(), hidl_vec<uint8_t>(),
	hidl_vec<uint8_t>(), km::HardwareAuthToken(),
	km::VerificationToken(), hidlCb);
	mDevice = nullptr;
	if (!error.isOk()) {
	LOG(ERROR) << "finish failed: " << error.description();
	return false;
	}
	if (km_error != km::ErrorCode::OK) {
	LOG(ERROR) << "finish failed, code " << int32_t(km_error);
	return false;
	}
	return true;
	}

	Keymaster::Keymaster() {
	auto devices = KmDevice::enumerateAvailableDevices();
	for (auto& dev : devices) {
	// Explicitly avoid using STRONGBOX for now.
	// TODO: Re-enable STRONGBOX, since it's what we really want. b/77338527
	if (dev->halVersion().securityLevel != SecurityLevel::STRONGBOX) {
	mDevice = std::move(dev);
	break;
	}
	}
	if (!mDevice) return;
	auto& version = mDevice->halVersion();
	LOG(INFO) << "Using " << version.keymasterName << " from " << version.authorName
	<< " for encryption. Security level: " << toString(version.securityLevel)
	<< ", HAL: " << mDevice->descriptor() << "/" << mDevice->instanceName();
	}

	bool Keymaster::generateKey(const km::AuthorizationSet& inParams, std::string* key) {
	km::ErrorCode km_error;
	auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<uint8_t>& keyBlob,
	const km::KeyCharacteristics& /ignored/) {
	km_error = ret;
	if (km_error != km::ErrorCode::OK) return;
	if (key) key->assign(reinterpret_cast<const char*>(&keyBlob[0]), keyBlob.size());
	};

	auto error = mDevice->generateKey(inParams.hidl_data(), hidlCb);
	if (!error.isOk()) {
	LOG(ERROR) << "generate_key failed: " << error.description();
	return false;
	}
	if (km_error != km::ErrorCode::OK) {
	LOG(ERROR) << "generate_key failed, code " << int32_t(km_error);
	return false;
	}
	return true;
	}

	bool Keymaster::deleteKey(const std::string& key) {
	auto keyBlob = km::support::blob2hidlVec(key);
	auto error = mDevice->deleteKey(keyBlob);
	if (!error.isOk()) {
	LOG(ERROR) << "delete_key failed: " << error.description();
	return false;
	}
	if (error != km::ErrorCode::OK) {
	LOG(ERROR) << "delete_key failed, code " << int32_t(km::ErrorCode(error));
	return false;
	}
	return true;
	}

	bool Keymaster::upgradeKey(const std::string& oldKey, const km::AuthorizationSet& inParams,
	std::string* newKey) {
	auto oldKeyBlob = km::support::blob2hidlVec(oldKey);
	km::ErrorCode km_error;
	auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<uint8_t>& upgradedKeyBlob) {
	km_error = ret;
	if (km_error != km::ErrorCode::OK) return;
	if (newKey)
	newKey->assign(reinterpret_cast<const char*>(&upgradedKeyBlob[0]),
	upgradedKeyBlob.size());
	};
	auto error = mDevice->upgradeKey(oldKeyBlob, inParams.hidl_data(), hidlCb);
	if (!error.isOk()) {
	LOG(ERROR) << "upgrade_key failed: " << error.description();
	return false;
	}
	if (km_error != km::ErrorCode::OK) {
	LOG(ERROR) << "upgrade_key failed, code " << int32_t(km_error);
	return false;
	}
	return true;
	}

	KeymasterOperation Keymaster::begin(km::KeyPurpose purpose, const std::string& key,
	const km::AuthorizationSet& inParams,
	const km::HardwareAuthToken& authToken,
	km::AuthorizationSet* outParams) {
	auto keyBlob = km::support::blob2hidlVec(key);
	uint64_t mOpHandle;
	km::ErrorCode km_error;

	auto hidlCb = [&](km::ErrorCode ret, const hidl_vec<km::KeyParameter>& _outParams,
	uint64_t operationHandle) {
	km_error = ret;
	if (km_error != km::ErrorCode::OK) return;
	if (outParams) *outParams = _outParams;
	mOpHandle = operationHandle;
	};

	auto error = mDevice->begin(purpose, keyBlob, inParams.hidl_data(), authToken, hidlCb);
	if (!error.isOk()) {
	LOG(ERROR) << "begin failed: " << error.description();
	return KeymasterOperation(km::ErrorCode::UNKNOWN_ERROR);
	}
	if (km_error != km::ErrorCode::OK) {
	LOG(ERROR) << "begin failed, code " << int32_t(km_error);
	return KeymasterOperation(km_error);
	}
	return KeymasterOperation(mDevice.get(), mOpHandle);
	}

	bool Keymaster::isSecure() {
	return mDevice->halVersion().securityLevel != km::SecurityLevel::SOFTWARE;
	}

	} // namespace vold
	} // namespace android

	using namespace ::android::vold;

	int keymaster_compatibility_cryptfs_scrypt() {
	Keymaster dev;
	if (!dev) {
	LOG(ERROR) << "Failed to initiate keymaster session";
	return -1;
	}
	return dev.isSecure();
	}

	static bool write_string_to_buf(const std::string& towrite, uint8_t* buffer, uint32_t buffer_size,
	uint32_t* out_size) {
	if (!buffer \|\| !out_size) {
	LOG(ERROR) << "Missing target pointers";
	return false;
	}
	*out_size = towrite.size();
	if (buffer_size < towrite.size()) {
	LOG(ERROR) << "Buffer too small " << buffer_size << " < " << towrite.size();
	return false;
	}
	memset(buffer, '\0', buffer_size);
	std::copy(towrite.begin(), towrite.end(), buffer);
	return true;
	}

	static km::AuthorizationSet keyParams(uint32_t rsa_key_size, uint64_t rsa_exponent,
	uint32_t ratelimit) {
	return km::AuthorizationSetBuilder()
	.RsaSigningKey(rsa_key_size, rsa_exponent)
	.NoDigestOrPadding()
	.Authorization(km::TAG_BLOB_USAGE_REQUIREMENTS, km::KeyBlobUsageRequirements::STANDALONE)
	.Authorization(km::TAG_NO_AUTH_REQUIRED)
	.Authorization(km::TAG_MIN_SECONDS_BETWEEN_OPS, ratelimit);
	}

	int keymaster_create_key_for_cryptfs_scrypt(uint32_t rsa_key_size, uint64_t rsa_exponent,
	uint32_t ratelimit, uint8_t* key_buffer,
	uint32_t key_buffer_size, uint32_t* key_out_size) {
	if (key_out_size) {
	*key_out_size = 0;
	}
	Keymaster dev;
	if (!dev) {
	LOG(ERROR) << "Failed to initiate keymaster session";
	return -1;
	}
	std::string key;
	if (!dev.generateKey(keyParams(rsa_key_size, rsa_exponent, ratelimit), &key)) return -1;
	if (!write_string_to_buf(key, key_buffer, key_buffer_size, key_out_size)) return -1;
	return 0;
	}

	int keymaster_upgrade_key_for_cryptfs_scrypt(uint32_t rsa_key_size, uint64_t rsa_exponent,
	uint32_t ratelimit, const uint8_t* key_blob,
	size_t key_blob_size, uint8_t* key_buffer,
	uint32_t key_buffer_size, uint32_t* key_out_size) {
	if (key_out_size) {
	*key_out_size = 0;
	}
	Keymaster dev;
	if (!dev) {
	LOG(ERROR) << "Failed to initiate keymaster session";
	return -1;
	}
	std::string old_key(reinterpret_cast<const char*>(key_blob), key_blob_size);
	std::string new_key;
	if (!dev.upgradeKey(old_key, keyParams(rsa_key_size, rsa_exponent, ratelimit), &new_key))
	return -1;
	if (!write_string_to_buf(new_key, key_buffer, key_buffer_size, key_out_size)) return -1;
	return 0;
	}

	KeymasterSignResult keymaster_sign_object_for_cryptfs_scrypt(
	const uint8_t* key_blob, size_t key_blob_size, uint32_t ratelimit, const uint8_t* object,
	const size_t object_size, uint8_t** signature_buffer, size_t* signature_buffer_size) {
	Keymaster dev;
	if (!dev) {
	LOG(ERROR) << "Failed to initiate keymaster session";
	return KeymasterSignResult::error;
	}
	if (!key_blob \|\| !object \|\| !signature_buffer \|\| !signature_buffer_size) {
	LOG(ERROR) << __FILE__ << ":" << __LINE__ << ":Invalid argument";
	return KeymasterSignResult::error;
	}

	km::AuthorizationSet outParams;
	std::string key(reinterpret_cast<const char*>(key_blob), key_blob_size);
	std::string input(reinterpret_cast<const char*>(object), object_size);
	std::string output;
	KeymasterOperation op;

	auto paramBuilder = km::AuthorizationSetBuilder().NoDigestOrPadding();
	while (true) {
	op = dev.begin(km::KeyPurpose::SIGN, key, paramBuilder, km::HardwareAuthToken(), &outParams);
	if (op.errorCode() == km::ErrorCode::KEY_RATE_LIMIT_EXCEEDED) {
	sleep(ratelimit);
	continue;
	} else
	break;
	}

	if (op.errorCode() == km::ErrorCode::KEY_REQUIRES_UPGRADE) {
	LOG(ERROR) << "Keymaster key requires upgrade";
	return KeymasterSignResult::upgrade;
	}

	if (op.errorCode() != km::ErrorCode::OK) {
	LOG(ERROR) << "Error starting keymaster signature transaction: " << int32_t(op.errorCode());
	return KeymasterSignResult::error;
	}

	if (!op.updateCompletely(input, &output)) {
	LOG(ERROR) << "Error sending data to keymaster signature transaction: "
	<< uint32_t(op.errorCode());
	return KeymasterSignResult::error;
	}

	if (!op.finish(&output)) {
	LOG(ERROR) << "Error finalizing keymaster signature transaction: "
	<< int32_t(op.errorCode());
	return KeymasterSignResult::error;
	}

	signature_buffer = reinterpret_cast<uint8_t>(malloc(output.size()));
	if (*signature_buffer == nullptr) {
	LOG(ERROR) << "Error allocation buffer for keymaster signature";
	return KeymasterSignResult::error;
	}
	*signature_buffer_size = output.size();
	std::copy(output.data(), output.data() + output.size(), *signature_buffer);
	return KeymasterSignResult::ok;
	}