km_openssl/block_cipher_operation.cpp - platform/system/keymaster - Git at Google

 /*
  * Copyright 2014 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 "block_cipher_operation.h"

 #include <stdio.h>

 #include <keymaster/new>

 #include <keymaster/UniquePtr.h>

 #include <openssl/aes.h>
 #include <openssl/err.h>
 #include <openssl/rand.h>

 #include <keymaster/logger.h>

 #include <keymaster/km_openssl/aes_key.h>
 #include <keymaster/km_openssl/openssl_err.h>
 #include <keymaster/km_openssl/openssl_utils.h>

 namespace keymaster {

 static const size_t GCM_NONCE_SIZE = 12;

 inline bool allows_padding(keymaster_block_mode_t block_mode) {
     switch (block_mode) {
     case KM_MODE_CTR:
     case KM_MODE_GCM:
         return false;
     case KM_MODE_ECB:
     case KM_MODE_CBC:
         return true;
     }
     assert(false /* Can't get here */);
     return false;
 }

 static keymaster_error_t GetAndValidateGcmTagLength(const AuthorizationSet& begin_params,
                                                     const AuthProxy& key_params,
                                                     size_t* tag_length) {
     uint32_t tag_length_bits;
     if (!begin_params.GetTagValue(TAG_MAC_LENGTH, &tag_length_bits)) {
         return KM_ERROR_MISSING_MAC_LENGTH;
     }

     uint32_t min_tag_length_bits;
     if (!key_params.GetTagValue(TAG_MIN_MAC_LENGTH, &min_tag_length_bits)) {
         LOG_E("AES GCM key must have KM_TAG_MIN_MAC_LENGTH", 0);
         return KM_ERROR_INVALID_KEY_BLOB;
     }

     if (tag_length_bits % 8 != 0 || tag_length_bits > kMaxGcmTagLength ||
         tag_length_bits < kMinGcmTagLength) {
         return KM_ERROR_UNSUPPORTED_MAC_LENGTH;
     }

     if (tag_length_bits < min_tag_length_bits) {
         return KM_ERROR_INVALID_MAC_LENGTH;
     }

     *tag_length = tag_length_bits / 8;
     return KM_ERROR_OK;
 }

 OperationPtr BlockCipherOperationFactory::CreateOperation(Key&& key,
                                                           const AuthorizationSet& begin_params,
                                                           keymaster_error_t* error) const {
     *error = KM_ERROR_OK;
     keymaster_block_mode_t block_mode;
     if (!begin_params.GetTagValue(TAG_BLOCK_MODE, &block_mode)) {
         LOG_E("%d block modes specified in begin params", begin_params.GetTagCount(TAG_BLOCK_MODE));
         *error = KM_ERROR_UNSUPPORTED_BLOCK_MODE;
         return nullptr;
     } else if (!supported(block_mode)) {
         LOG_E("Block mode %d not supported", block_mode);
         *error = KM_ERROR_UNSUPPORTED_BLOCK_MODE;
         return nullptr;
     } else if (!key.authorizations().Contains(TAG_BLOCK_MODE, block_mode)) {
         LOG_E("Block mode %d was specified, but not authorized by key", block_mode);
         *error = KM_ERROR_INCOMPATIBLE_BLOCK_MODE;
         return nullptr;
     }

     size_t tag_length = 0;
     if (block_mode == KM_MODE_GCM) {
         *error = GetAndValidateGcmTagLength(begin_params, key.authorizations(), &tag_length);
         if (*error != KM_ERROR_OK) {
             return nullptr;
         }
     }

     keymaster_padding_t padding;
     if (!GetAndValidatePadding(begin_params, key, &padding, error)) {
         return nullptr;
     }
     if (!allows_padding(block_mode) && padding != KM_PAD_NONE) {
         LOG_E("Mode does not support padding", 0);
         *error = KM_ERROR_INCOMPATIBLE_PADDING_MODE;
         return nullptr;
     }

     bool caller_nonce = key.authorizations().GetTagValue(TAG_CALLER_NONCE);

     OperationPtr op;
     switch (purpose_) {
     case KM_PURPOSE_ENCRYPT:
         op.reset(new (std::nothrow) BlockCipherEvpEncryptOperation(  //
             block_mode, padding, caller_nonce, tag_length, move(key), GetCipherDescription()));
         break;
     case KM_PURPOSE_DECRYPT:
         op.reset(new (std::nothrow) BlockCipherEvpDecryptOperation(
             block_mode, padding, tag_length, move(key), GetCipherDescription()));
         break;
     default:
         *error = KM_ERROR_UNSUPPORTED_PURPOSE;
         return nullptr;
     }

     if (!op) *error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
     return op;
 }

 static const keymaster_padding_t supported_padding_modes[] = {KM_PAD_NONE, KM_PAD_PKCS7};
 const keymaster_padding_t*
 BlockCipherOperationFactory::SupportedPaddingModes(size_t* padding_mode_count) const {
     *padding_mode_count = array_length(supported_padding_modes);
     return supported_padding_modes;
 }

 BlockCipherEvpOperation::BlockCipherEvpOperation(keymaster_purpose_t purpose,
                                                  keymaster_block_mode_t block_mode,
                                                  keymaster_padding_t padding, bool caller_iv,
                                                  size_t tag_length, Key&& key,
                                                  const EvpCipherDescription& cipher_description)
     : Operation(purpose, key.hw_enforced_move(), key.sw_enforced_move()), block_mode_(block_mode),
       caller_iv_(caller_iv), tag_length_(tag_length), data_started_(false), padding_(padding),
       key_(key.key_material_move()), cipher_description_(cipher_description) {
     EVP_CIPHER_CTX_init(&ctx_);
 }

 BlockCipherEvpOperation::~BlockCipherEvpOperation() {
     EVP_CIPHER_CTX_cleanup(&ctx_);
 }

 keymaster_error_t BlockCipherEvpOperation::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 InitializeCipher(move(key_));
 }

 keymaster_error_t BlockCipherEvpOperation::Update(const AuthorizationSet& additional_params,
                                                   const Buffer& input,
                                                   AuthorizationSet* /* output_params */,
                                                   Buffer* output, size_t* input_consumed) {
     keymaster_error_t error;
     if (block_mode_ == KM_MODE_GCM && !HandleAad(additional_params, input, &error)) return error;
     if (!InternalUpdate(input.peek_read(), input.available_read(), output, &error)) return error;
     *input_consumed = input.available_read();

     return KM_ERROR_OK;
 }

 inline bool is_bad_decrypt(unsigned long error) {
     return (ERR_GET_LIB(error) == ERR_LIB_CIPHER &&  //
             ERR_GET_REASON(error) == CIPHER_R_BAD_DECRYPT);
 }

 keymaster_error_t BlockCipherEvpOperation::Finish(const AuthorizationSet& additional_params,
                                                   const Buffer& input,
                                                   const Buffer& /* signature */,
                                                   AuthorizationSet* output_params, Buffer* output) {
     keymaster_error_t error;
     if (!UpdateForFinish(additional_params, input, output_params, output, &error)) return error;
     if (!output->reserve(block_size_bytes())) return KM_ERROR_MEMORY_ALLOCATION_FAILED;

     if (block_mode_ == KM_MODE_GCM && aad_block_buf_len_ > 0 && !ProcessBufferedAadBlock(&error)) {
         return error;
     }

     int output_written = -1;
     if (!EVP_CipherFinal_ex(&ctx_, output->peek_write(), &output_written)) {
         if (tag_length_ > 0) return KM_ERROR_VERIFICATION_FAILED;
         LOG_E("Error encrypting final block: %s", ERR_error_string(ERR_peek_last_error(), nullptr));
         return TranslateLastOpenSslError();
     }

     assert(output_written >= 0);
     assert(static_cast<size_t>(output_written) <= block_size_bytes());
     if (!output->advance_write(output_written)) return KM_ERROR_UNKNOWN_ERROR;
     return KM_ERROR_OK;
 }

 bool BlockCipherEvpOperation::need_iv() const {
     switch (block_mode_) {
     case KM_MODE_CBC:
     case KM_MODE_CTR:
     case KM_MODE_GCM:
         return true;
     case KM_MODE_ECB:
         return false;
     default:
         // Shouldn't get here.
         assert(false);
         return false;
     }
 }

 keymaster_error_t BlockCipherEvpOperation::InitializeCipher(KeymasterKeyBlob key) {
     keymaster_error_t error;
     const EVP_CIPHER* cipher =
         cipher_description_.GetCipherInstance(key.key_material_size, block_mode_, &error);
     if (error) return error;

     if (!EVP_CipherInit_ex(&ctx_, cipher, nullptr /* engine */, key.key_material, iv_.data,
                            evp_encrypt_mode())) {
         return TranslateLastOpenSslError();
     }

     switch (padding_) {
     case KM_PAD_NONE:
         EVP_CIPHER_CTX_set_padding(&ctx_, 0 /* disable padding */);
         break;
     case KM_PAD_PKCS7:
         // This is the default for OpenSSL EVP cipher operations.
         break;
     default:
         return KM_ERROR_UNSUPPORTED_PADDING_MODE;
     }

     if (block_mode_ == KM_MODE_GCM) {
         aad_block_buf_.reset(new (std::nothrow) uint8_t[block_size_bytes()]);
         if (!aad_block_buf_) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
         aad_block_buf_len_ = 0;
     }

     return KM_ERROR_OK;
 }

 keymaster_error_t BlockCipherEvpOperation::GetIv(const AuthorizationSet& input_params) {
     keymaster_blob_t iv_blob;
     if (!input_params.GetTagValue(TAG_NONCE, &iv_blob)) {
         LOG_E("No IV provided", 0);
         return KM_ERROR_INVALID_ARGUMENT;
     }

     if (block_mode_ != KM_MODE_GCM && iv_blob.data_length != block_size_bytes()) {
         LOG_E("Expected %d-byte IV for operation, but got %d bytes", block_size_bytes(),
               iv_blob.data_length);
         return KM_ERROR_INVALID_NONCE;
     }

     if (block_mode_ == KM_MODE_GCM && iv_blob.data_length != GCM_NONCE_SIZE) {
         LOG_E("Expected %d-byte nonce for GCM operation, but got %d bytes", GCM_NONCE_SIZE,
               iv_blob.data_length);
         return KM_ERROR_INVALID_NONCE;
     }

     iv_ = KeymasterBlob(iv_blob.data, iv_blob.data_length);
     if (!iv_.data) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
     return KM_ERROR_OK;
 }

 /*
  * Process Incoming Associated Authentication Data.
  *
  * This method is more complex than might be expected, because the underlying library silently does
  * the wrong thing when given partial AAD blocks, so we have to take care to process AAD in block
  * size increments, buffering (in aad_block_buf_) when given smaller amounts of data.
  */
 bool BlockCipherEvpOperation::HandleAad(const AuthorizationSet& input_params, const Buffer& input,
                                         keymaster_error_t* error) {
     assert(tag_length_ > 0);
     assert(error);

     keymaster_blob_t aad;
     if (input_params.GetTagValue(TAG_ASSOCIATED_DATA, &aad)) {
         if (data_started_) {
             *error = KM_ERROR_INVALID_TAG;
             return false;
         }

         if (aad_block_buf_len_ > 0) {
             FillBufferedAadBlock(&aad);
             if (aad_block_buf_len_ == block_size_bytes() && !ProcessBufferedAadBlock(error))
                 return false;
         }

         size_t block_size = block_size_bytes();
         size_t blocks_to_process = aad.data_length / block_size;
         if (blocks_to_process && !ProcessAadBlocks(aad.data, blocks_to_process, error))
             return false;
         aad.data += blocks_to_process * block_size;
         aad.data_length -= blocks_to_process * block_size;

         FillBufferedAadBlock(&aad);
         assert(aad.data_length == 0);
     }

     if (input.available_read()) {
         data_started_ = true;
         // Data has begun, no more AAD is allowed.  Process any buffered AAD.
         if (aad_block_buf_len_ > 0 && !ProcessBufferedAadBlock(error)) return false;
     }

     return true;
 }

 bool BlockCipherEvpOperation::ProcessBufferedAadBlock(keymaster_error_t* error) {
     int output_written;
     if (EVP_CipherUpdate(&ctx_, nullptr /* out */, &output_written, aad_block_buf_.get(),
                          aad_block_buf_len_)) {
         aad_block_buf_len_ = 0;
         return true;
     }
     *error = TranslateLastOpenSslError();
     return false;
 }

 bool BlockCipherEvpOperation::ProcessAadBlocks(const uint8_t* data, size_t blocks,
                                                keymaster_error_t* error) {
     int output_written;
     if (EVP_CipherUpdate(&ctx_, nullptr /* out */, &output_written, data,
                          blocks * block_size_bytes())) {
         return true;
     }
     *error = TranslateLastOpenSslError();
     return false;
 }

 inline size_t min(size_t a, size_t b) {
     return (a < b) ? a : b;
 }

 void BlockCipherEvpOperation::FillBufferedAadBlock(keymaster_blob_t* aad) {
     size_t to_buffer = min(block_size_bytes() - aad_block_buf_len_, aad->data_length);
     memcpy(aad_block_buf_.get() + aad_block_buf_len_, aad->data, to_buffer);
     aad->data += to_buffer;
     aad->data_length -= to_buffer;
     aad_block_buf_len_ += to_buffer;
 }

 bool BlockCipherEvpOperation::InternalUpdate(const uint8_t* input, size_t input_length,
                                              Buffer* output, keymaster_error_t* error) {
     assert(output);
     assert(error);

     if (!input_length) return true;

     if (!output->reserve(input_length + block_size_bytes())) {
         *error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
         return false;
     }

     int output_written = -1;
     if (!EVP_CipherUpdate(&ctx_, output->peek_write(), &output_written, input, input_length)) {
         *error = TranslateLastOpenSslError();
         return false;
     }
     return output->advance_write(output_written);
 }

 bool BlockCipherEvpOperation::UpdateForFinish(const AuthorizationSet& additional_params,
                                               const Buffer& input, AuthorizationSet* output_params,
                                               Buffer* output, keymaster_error_t* error) {
     if (input.available_read() || !additional_params.empty()) {
         size_t input_consumed;
         *error = Update(additional_params, input, output_params, output, &input_consumed);
         if (*error != KM_ERROR_OK) return false;
         if (input_consumed != input.available_read()) {
             *error = KM_ERROR_INVALID_INPUT_LENGTH;
             return false;
         }
     }

     return true;
 }

 keymaster_error_t BlockCipherEvpEncryptOperation::Begin(const AuthorizationSet& input_params,
                                                         AuthorizationSet* output_params) {
     if (!output_params) return KM_ERROR_OUTPUT_PARAMETER_NULL;

     if (need_iv()) {
         keymaster_error_t error = KM_ERROR_OK;
         if (input_params.find(TAG_NONCE) == -1) {
             error = GenerateIv();
         } else if (caller_iv_) {
             error = GetIv(input_params);
         } else {
             error = KM_ERROR_CALLER_NONCE_PROHIBITED;
         }

         if (error != KM_ERROR_OK) return error;
         output_params->push_back(TAG_NONCE, iv_.data, iv_.data_length);
     }

     return BlockCipherEvpOperation::Begin(input_params, output_params);
 }

 keymaster_error_t BlockCipherEvpEncryptOperation::Finish(const AuthorizationSet& additional_params,
                                                          const Buffer& input,
                                                          const Buffer& signature,
                                                          AuthorizationSet* output_params,
                                                          Buffer* output) {
     if (!output->reserve(input.available_read() + block_size_bytes() + tag_length_)) {
         return KM_ERROR_MEMORY_ALLOCATION_FAILED;
     }

     keymaster_error_t error =
         BlockCipherEvpOperation::Finish(additional_params, input, signature, output_params, output);
     if (error != KM_ERROR_OK) return error;

     if (tag_length_ > 0) {
         if (!output->reserve(tag_length_)) return KM_ERROR_MEMORY_ALLOCATION_FAILED;

         if (!EVP_CIPHER_CTX_ctrl(&ctx_, EVP_CTRL_GCM_GET_TAG, tag_length_, output->peek_write()))
             return TranslateLastOpenSslError();
         if (!output->advance_write(tag_length_)) return KM_ERROR_UNKNOWN_ERROR;
     }

     return KM_ERROR_OK;
 }

 keymaster_error_t BlockCipherEvpEncryptOperation::GenerateIv() {
     iv_.Reset((block_mode_ == KM_MODE_GCM) ? GCM_NONCE_SIZE : block_size_bytes());
     if (!iv_.data) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
     if (RAND_bytes(iv_.writable_data(), iv_.data_length) != 1) return TranslateLastOpenSslError();
     return KM_ERROR_OK;
 }

 keymaster_error_t BlockCipherEvpDecryptOperation::Begin(const AuthorizationSet& input_params,
                                                         AuthorizationSet* output_params) {
     if (need_iv()) {
         keymaster_error_t error = GetIv(input_params);
         if (error != KM_ERROR_OK) return error;
     }

     if (tag_length_ > 0) {
         tag_buf_.reset(new (std::nothrow) uint8_t[tag_length_]);
         if (!tag_buf_) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
         tag_buf_len_ = 0;
     }

     return BlockCipherEvpOperation::Begin(input_params, output_params);
 }

 keymaster_error_t BlockCipherEvpDecryptOperation::Update(const AuthorizationSet& additional_params,
                                                          const Buffer& input,
                                                          AuthorizationSet* /* output_params */,
                                                          Buffer* output, size_t* input_consumed) {
     if (!output || !input_consumed) return KM_ERROR_OUTPUT_PARAMETER_NULL;

     // Barring error, we'll consume it all.
     *input_consumed = input.available_read();

     keymaster_error_t error;
     if (block_mode_ == KM_MODE_GCM) {
         if (!HandleAad(additional_params, input, &error)) return error;
         return ProcessAllButTagLengthBytes(input, output);
     }

     if (!InternalUpdate(input.peek_read(), input.available_read(), output, &error)) return error;
     return KM_ERROR_OK;
 }

 keymaster_error_t BlockCipherEvpDecryptOperation::ProcessAllButTagLengthBytes(const Buffer& input,
                                                                               Buffer* output) {
     if (input.available_read() <= tag_buf_unused()) {
         BufferCandidateTagData(input.peek_read(), input.available_read());
         return KM_ERROR_OK;
     }

     const size_t data_available = tag_buf_len_ + input.available_read();

     const size_t to_process = data_available - tag_length_;
     const size_t to_process_from_tag_buf = min(to_process, tag_buf_len_);
     const size_t to_process_from_input = to_process - to_process_from_tag_buf;

     if (!output->reserve(to_process + block_size_bytes())) return KM_ERROR_MEMORY_ALLOCATION_FAILED;

     keymaster_error_t error;
     if (!ProcessTagBufContentsAsData(to_process_from_tag_buf, output, &error)) return error;

     if (!InternalUpdate(input.peek_read(), to_process_from_input, output, &error)) return error;

     BufferCandidateTagData(input.peek_read() + to_process_from_input,
                            input.available_read() - to_process_from_input);
     assert(tag_buf_unused() == 0);

     return KM_ERROR_OK;
 }

 bool BlockCipherEvpDecryptOperation::ProcessTagBufContentsAsData(size_t to_process, Buffer* output,
                                                                  keymaster_error_t* error) {
     assert(to_process <= tag_buf_len_);
     if (!InternalUpdate(tag_buf_.get(), to_process, output, error)) return false;
     if (to_process < tag_buf_len_) {
         memmove(tag_buf_.get(), tag_buf_.get() + to_process, tag_buf_len_ - to_process);
     }
     tag_buf_len_ -= to_process;
     return true;
 }

 void BlockCipherEvpDecryptOperation::BufferCandidateTagData(const uint8_t* data,
                                                             size_t data_length) {
     assert(data_length <= tag_length_ - tag_buf_len_);
     memcpy(tag_buf_.get() + tag_buf_len_, data, data_length);
     tag_buf_len_ += data_length;
 }

 keymaster_error_t BlockCipherEvpDecryptOperation::Finish(const AuthorizationSet& additional_params,
                                                          const Buffer& input,
                                                          const Buffer& signature,
                                                          AuthorizationSet* output_params,
                                                          Buffer* output) {
     keymaster_error_t error;
     if (!UpdateForFinish(additional_params, input, output_params, output, &error)) return error;

     if (tag_buf_len_ < tag_length_) {
         return KM_ERROR_INVALID_INPUT_LENGTH;
     } else if (tag_length_ > 0 &&
                !EVP_CIPHER_CTX_ctrl(&ctx_, EVP_CTRL_GCM_SET_TAG, tag_length_, tag_buf_.get())) {
         return TranslateLastOpenSslError();
     }

     AuthorizationSet empty_params;
     Buffer empty_input;
     return BlockCipherEvpOperation::Finish(empty_params, empty_input, signature, output_params,
                                            output);
 }

 keymaster_error_t BlockCipherEvpOperation::Abort() {
     return KM_ERROR_OK;
 }

 }  // namespace keymaster
	/*
	* Copyright 2014 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 "block_cipher_operation.h"

	#include <stdio.h>

	#include <keymaster/new>

	#include <keymaster/UniquePtr.h>

	#include <openssl/aes.h>
	#include <openssl/err.h>
	#include <openssl/rand.h>

	#include <keymaster/logger.h>

	#include <keymaster/km_openssl/aes_key.h>
	#include <keymaster/km_openssl/openssl_err.h>
	#include <keymaster/km_openssl/openssl_utils.h>

	namespace keymaster {

	static const size_t GCM_NONCE_SIZE = 12;

	inline bool allows_padding(keymaster_block_mode_t block_mode) {
	switch (block_mode) {
	case KM_MODE_CTR:
	case KM_MODE_GCM:
	return false;
	case KM_MODE_ECB:
	case KM_MODE_CBC:
	return true;
	}
	assert(false /* Can't get here */);
	return false;
	}

	static keymaster_error_t GetAndValidateGcmTagLength(const AuthorizationSet& begin_params,
	const AuthProxy& key_params,
	size_t* tag_length) {
	uint32_t tag_length_bits;
	if (!begin_params.GetTagValue(TAG_MAC_LENGTH, &tag_length_bits)) {
	return KM_ERROR_MISSING_MAC_LENGTH;
	}

	uint32_t min_tag_length_bits;
	if (!key_params.GetTagValue(TAG_MIN_MAC_LENGTH, &min_tag_length_bits)) {
	LOG_E("AES GCM key must have KM_TAG_MIN_MAC_LENGTH", 0);
	return KM_ERROR_INVALID_KEY_BLOB;
	}

	if (tag_length_bits % 8 != 0 \|\| tag_length_bits > kMaxGcmTagLength \|\|
	tag_length_bits < kMinGcmTagLength) {
	return KM_ERROR_UNSUPPORTED_MAC_LENGTH;
	}

	if (tag_length_bits < min_tag_length_bits) {
	return KM_ERROR_INVALID_MAC_LENGTH;
	}

	*tag_length = tag_length_bits / 8;
	return KM_ERROR_OK;
	}

	OperationPtr BlockCipherOperationFactory::CreateOperation(Key&& key,
	const AuthorizationSet& begin_params,
	keymaster_error_t* error) const {
	*error = KM_ERROR_OK;
	keymaster_block_mode_t block_mode;
	if (!begin_params.GetTagValue(TAG_BLOCK_MODE, &block_mode)) {
	LOG_E("%d block modes specified in begin params", begin_params.GetTagCount(TAG_BLOCK_MODE));
	*error = KM_ERROR_UNSUPPORTED_BLOCK_MODE;
	return nullptr;
	} else if (!supported(block_mode)) {
	LOG_E("Block mode %d not supported", block_mode);
	*error = KM_ERROR_UNSUPPORTED_BLOCK_MODE;
	return nullptr;
	} else if (!key.authorizations().Contains(TAG_BLOCK_MODE, block_mode)) {
	LOG_E("Block mode %d was specified, but not authorized by key", block_mode);
	*error = KM_ERROR_INCOMPATIBLE_BLOCK_MODE;
	return nullptr;
	}

	size_t tag_length = 0;
	if (block_mode == KM_MODE_GCM) {
	*error = GetAndValidateGcmTagLength(begin_params, key.authorizations(), &tag_length);
	if (*error != KM_ERROR_OK) {
	return nullptr;
	}
	}

	keymaster_padding_t padding;
	if (!GetAndValidatePadding(begin_params, key, &padding, error)) {
	return nullptr;
	}
	if (!allows_padding(block_mode) && padding != KM_PAD_NONE) {
	LOG_E("Mode does not support padding", 0);
	*error = KM_ERROR_INCOMPATIBLE_PADDING_MODE;
	return nullptr;
	}

	bool caller_nonce = key.authorizations().GetTagValue(TAG_CALLER_NONCE);

	OperationPtr op;
	switch (purpose_) {
	case KM_PURPOSE_ENCRYPT:
	op.reset(new (std::nothrow) BlockCipherEvpEncryptOperation( //
	block_mode, padding, caller_nonce, tag_length, move(key), GetCipherDescription()));
	break;
	case KM_PURPOSE_DECRYPT:
	op.reset(new (std::nothrow) BlockCipherEvpDecryptOperation(
	block_mode, padding, tag_length, move(key), GetCipherDescription()));
	break;
	default:
	*error = KM_ERROR_UNSUPPORTED_PURPOSE;
	return nullptr;
	}

	if (!op) *error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
	return op;
	}

	static const keymaster_padding_t supported_padding_modes[] = {KM_PAD_NONE, KM_PAD_PKCS7};
	const keymaster_padding_t*
	BlockCipherOperationFactory::SupportedPaddingModes(size_t* padding_mode_count) const {
	*padding_mode_count = array_length(supported_padding_modes);
	return supported_padding_modes;
	}

	BlockCipherEvpOperation::BlockCipherEvpOperation(keymaster_purpose_t purpose,
	keymaster_block_mode_t block_mode,
	keymaster_padding_t padding, bool caller_iv,
	size_t tag_length, Key&& key,
	const EvpCipherDescription& cipher_description)
	: Operation(purpose, key.hw_enforced_move(), key.sw_enforced_move()), block_mode_(block_mode),
	caller_iv_(caller_iv), tag_length_(tag_length), data_started_(false), padding_(padding),
	key_(key.key_material_move()), cipher_description_(cipher_description) {
	EVP_CIPHER_CTX_init(&ctx_);
	}

	BlockCipherEvpOperation::~BlockCipherEvpOperation() {
	EVP_CIPHER_CTX_cleanup(&ctx_);
	}

	keymaster_error_t BlockCipherEvpOperation::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 InitializeCipher(move(key_));
	}

	keymaster_error_t BlockCipherEvpOperation::Update(const AuthorizationSet& additional_params,
	const Buffer& input,
	AuthorizationSet* /* output_params */,
	Buffer* output, size_t* input_consumed) {
	keymaster_error_t error;
	if (block_mode_ == KM_MODE_GCM && !HandleAad(additional_params, input, &error)) return error;
	if (!InternalUpdate(input.peek_read(), input.available_read(), output, &error)) return error;
	*input_consumed = input.available_read();

	return KM_ERROR_OK;
	}

	inline bool is_bad_decrypt(unsigned long error) {
	return (ERR_GET_LIB(error) == ERR_LIB_CIPHER && //
	ERR_GET_REASON(error) == CIPHER_R_BAD_DECRYPT);
	}

	keymaster_error_t BlockCipherEvpOperation::Finish(const AuthorizationSet& additional_params,
	const Buffer& input,
	const Buffer& /* signature */,
	AuthorizationSet* output_params, Buffer* output) {
	keymaster_error_t error;
	if (!UpdateForFinish(additional_params, input, output_params, output, &error)) return error;
	if (!output->reserve(block_size_bytes())) return KM_ERROR_MEMORY_ALLOCATION_FAILED;

	if (block_mode_ == KM_MODE_GCM && aad_block_buf_len_ > 0 && !ProcessBufferedAadBlock(&error)) {
	return error;
	}

	int output_written = -1;
	if (!EVP_CipherFinal_ex(&ctx_, output->peek_write(), &output_written)) {
	if (tag_length_ > 0) return KM_ERROR_VERIFICATION_FAILED;
	LOG_E("Error encrypting final block: %s", ERR_error_string(ERR_peek_last_error(), nullptr));
	return TranslateLastOpenSslError();
	}

	assert(output_written >= 0);
	assert(static_cast<size_t>(output_written) <= block_size_bytes());
	if (!output->advance_write(output_written)) return KM_ERROR_UNKNOWN_ERROR;
	return KM_ERROR_OK;
	}

	bool BlockCipherEvpOperation::need_iv() const {
	switch (block_mode_) {
	case KM_MODE_CBC:
	case KM_MODE_CTR:
	case KM_MODE_GCM:
	return true;
	case KM_MODE_ECB:
	return false;
	default:
	// Shouldn't get here.
	assert(false);
	return false;
	}
	}

	keymaster_error_t BlockCipherEvpOperation::InitializeCipher(KeymasterKeyBlob key) {
	keymaster_error_t error;
	const EVP_CIPHER* cipher =
	cipher_description_.GetCipherInstance(key.key_material_size, block_mode_, &error);
	if (error) return error;

	if (!EVP_CipherInit_ex(&ctx_, cipher, nullptr /* engine */, key.key_material, iv_.data,
	evp_encrypt_mode())) {
	return TranslateLastOpenSslError();
	}

	switch (padding_) {
	case KM_PAD_NONE:
	EVP_CIPHER_CTX_set_padding(&ctx_, 0 /* disable padding */);
	break;
	case KM_PAD_PKCS7:
	// This is the default for OpenSSL EVP cipher operations.
	break;
	default:
	return KM_ERROR_UNSUPPORTED_PADDING_MODE;
	}

	if (block_mode_ == KM_MODE_GCM) {
	aad_block_buf_.reset(new (std::nothrow) uint8_t[block_size_bytes()]);
	if (!aad_block_buf_) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
	aad_block_buf_len_ = 0;
	}

	return KM_ERROR_OK;
	}

	keymaster_error_t BlockCipherEvpOperation::GetIv(const AuthorizationSet& input_params) {
	keymaster_blob_t iv_blob;
	if (!input_params.GetTagValue(TAG_NONCE, &iv_blob)) {
	LOG_E("No IV provided", 0);
	return KM_ERROR_INVALID_ARGUMENT;
	}

	if (block_mode_ != KM_MODE_GCM && iv_blob.data_length != block_size_bytes()) {
	LOG_E("Expected %d-byte IV for operation, but got %d bytes", block_size_bytes(),
	iv_blob.data_length);
	return KM_ERROR_INVALID_NONCE;
	}

	if (block_mode_ == KM_MODE_GCM && iv_blob.data_length != GCM_NONCE_SIZE) {
	LOG_E("Expected %d-byte nonce for GCM operation, but got %d bytes", GCM_NONCE_SIZE,
	iv_blob.data_length);
	return KM_ERROR_INVALID_NONCE;
	}

	iv_ = KeymasterBlob(iv_blob.data, iv_blob.data_length);
	if (!iv_.data) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
	return KM_ERROR_OK;
	}

	/*
	* Process Incoming Associated Authentication Data.
	*
	* This method is more complex than might be expected, because the underlying library silently does
	* the wrong thing when given partial AAD blocks, so we have to take care to process AAD in block
	* size increments, buffering (in aad_block_buf_) when given smaller amounts of data.
	*/
	bool BlockCipherEvpOperation::HandleAad(const AuthorizationSet& input_params, const Buffer& input,
	keymaster_error_t* error) {
	assert(tag_length_ > 0);
	assert(error);

	keymaster_blob_t aad;
	if (input_params.GetTagValue(TAG_ASSOCIATED_DATA, &aad)) {
	if (data_started_) {
	*error = KM_ERROR_INVALID_TAG;
	return false;
	}

	if (aad_block_buf_len_ > 0) {
	FillBufferedAadBlock(&aad);
	if (aad_block_buf_len_ == block_size_bytes() && !ProcessBufferedAadBlock(error))
	return false;
	}

	size_t block_size = block_size_bytes();
	size_t blocks_to_process = aad.data_length / block_size;
	if (blocks_to_process && !ProcessAadBlocks(aad.data, blocks_to_process, error))
	return false;
	aad.data += blocks_to_process * block_size;
	aad.data_length -= blocks_to_process * block_size;

	FillBufferedAadBlock(&aad);
	assert(aad.data_length == 0);
	}

	if (input.available_read()) {
	data_started_ = true;
	// Data has begun, no more AAD is allowed. Process any buffered AAD.
	if (aad_block_buf_len_ > 0 && !ProcessBufferedAadBlock(error)) return false;
	}

	return true;
	}

	bool BlockCipherEvpOperation::ProcessBufferedAadBlock(keymaster_error_t* error) {
	int output_written;
	if (EVP_CipherUpdate(&ctx_, nullptr /* out */, &output_written, aad_block_buf_.get(),
	aad_block_buf_len_)) {
	aad_block_buf_len_ = 0;
	return true;
	}
	*error = TranslateLastOpenSslError();
	return false;
	}

	bool BlockCipherEvpOperation::ProcessAadBlocks(const uint8_t* data, size_t blocks,
	keymaster_error_t* error) {
	int output_written;
	if (EVP_CipherUpdate(&ctx_, nullptr /* out */, &output_written, data,
	blocks * block_size_bytes())) {
	return true;
	}
	*error = TranslateLastOpenSslError();
	return false;
	}

	inline size_t min(size_t a, size_t b) {
	return (a < b) ? a : b;
	}

	void BlockCipherEvpOperation::FillBufferedAadBlock(keymaster_blob_t* aad) {
	size_t to_buffer = min(block_size_bytes() - aad_block_buf_len_, aad->data_length);
	memcpy(aad_block_buf_.get() + aad_block_buf_len_, aad->data, to_buffer);
	aad->data += to_buffer;
	aad->data_length -= to_buffer;
	aad_block_buf_len_ += to_buffer;
	}

	bool BlockCipherEvpOperation::InternalUpdate(const uint8_t* input, size_t input_length,
	Buffer* output, keymaster_error_t* error) {
	assert(output);
	assert(error);

	if (!input_length) return true;

	if (!output->reserve(input_length + block_size_bytes())) {
	*error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
	return false;
	}

	int output_written = -1;
	if (!EVP_CipherUpdate(&ctx_, output->peek_write(), &output_written, input, input_length)) {
	*error = TranslateLastOpenSslError();
	return false;
	}
	return output->advance_write(output_written);
	}

	bool BlockCipherEvpOperation::UpdateForFinish(const AuthorizationSet& additional_params,
	const Buffer& input, AuthorizationSet* output_params,
	Buffer* output, keymaster_error_t* error) {
	if (input.available_read() \|\| !additional_params.empty()) {
	size_t input_consumed;
	*error = Update(additional_params, input, output_params, output, &input_consumed);
	if (*error != KM_ERROR_OK) return false;
	if (input_consumed != input.available_read()) {
	*error = KM_ERROR_INVALID_INPUT_LENGTH;
	return false;
	}
	}

	return true;
	}

	keymaster_error_t BlockCipherEvpEncryptOperation::Begin(const AuthorizationSet& input_params,
	AuthorizationSet* output_params) {
	if (!output_params) return KM_ERROR_OUTPUT_PARAMETER_NULL;

	if (need_iv()) {
	keymaster_error_t error = KM_ERROR_OK;
	if (input_params.find(TAG_NONCE) == -1) {
	error = GenerateIv();
	} else if (caller_iv_) {
	error = GetIv(input_params);
	} else {
	error = KM_ERROR_CALLER_NONCE_PROHIBITED;
	}

	if (error != KM_ERROR_OK) return error;
	output_params->push_back(TAG_NONCE, iv_.data, iv_.data_length);
	}

	return BlockCipherEvpOperation::Begin(input_params, output_params);
	}

	keymaster_error_t BlockCipherEvpEncryptOperation::Finish(const AuthorizationSet& additional_params,
	const Buffer& input,
	const Buffer& signature,
	AuthorizationSet* output_params,
	Buffer* output) {
	if (!output->reserve(input.available_read() + block_size_bytes() + tag_length_)) {
	return KM_ERROR_MEMORY_ALLOCATION_FAILED;
	}

	keymaster_error_t error =
	BlockCipherEvpOperation::Finish(additional_params, input, signature, output_params, output);
	if (error != KM_ERROR_OK) return error;

	if (tag_length_ > 0) {
	if (!output->reserve(tag_length_)) return KM_ERROR_MEMORY_ALLOCATION_FAILED;

	if (!EVP_CIPHER_CTX_ctrl(&ctx_, EVP_CTRL_GCM_GET_TAG, tag_length_, output->peek_write()))
	return TranslateLastOpenSslError();
	if (!output->advance_write(tag_length_)) return KM_ERROR_UNKNOWN_ERROR;
	}

	return KM_ERROR_OK;
	}

	keymaster_error_t BlockCipherEvpEncryptOperation::GenerateIv() {
	iv_.Reset((block_mode_ == KM_MODE_GCM) ? GCM_NONCE_SIZE : block_size_bytes());
	if (!iv_.data) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
	if (RAND_bytes(iv_.writable_data(), iv_.data_length) != 1) return TranslateLastOpenSslError();
	return KM_ERROR_OK;
	}

	keymaster_error_t BlockCipherEvpDecryptOperation::Begin(const AuthorizationSet& input_params,
	AuthorizationSet* output_params) {
	if (need_iv()) {
	keymaster_error_t error = GetIv(input_params);
	if (error != KM_ERROR_OK) return error;
	}

	if (tag_length_ > 0) {
	tag_buf_.reset(new (std::nothrow) uint8_t[tag_length_]);
	if (!tag_buf_) return KM_ERROR_MEMORY_ALLOCATION_FAILED;
	tag_buf_len_ = 0;
	}

	return BlockCipherEvpOperation::Begin(input_params, output_params);
	}

	keymaster_error_t BlockCipherEvpDecryptOperation::Update(const AuthorizationSet& additional_params,
	const Buffer& input,
	AuthorizationSet* /* output_params */,
	Buffer* output, size_t* input_consumed) {
	if (!output \|\| !input_consumed) return KM_ERROR_OUTPUT_PARAMETER_NULL;

	// Barring error, we'll consume it all.
	*input_consumed = input.available_read();

	keymaster_error_t error;
	if (block_mode_ == KM_MODE_GCM) {
	if (!HandleAad(additional_params, input, &error)) return error;
	return ProcessAllButTagLengthBytes(input, output);
	}

	if (!InternalUpdate(input.peek_read(), input.available_read(), output, &error)) return error;
	return KM_ERROR_OK;
	}

	keymaster_error_t BlockCipherEvpDecryptOperation::ProcessAllButTagLengthBytes(const Buffer& input,
	Buffer* output) {
	if (input.available_read() <= tag_buf_unused()) {
	BufferCandidateTagData(input.peek_read(), input.available_read());
	return KM_ERROR_OK;
	}

	const size_t data_available = tag_buf_len_ + input.available_read();

	const size_t to_process = data_available - tag_length_;
	const size_t to_process_from_tag_buf = min(to_process, tag_buf_len_);
	const size_t to_process_from_input = to_process - to_process_from_tag_buf;

	if (!output->reserve(to_process + block_size_bytes())) return KM_ERROR_MEMORY_ALLOCATION_FAILED;

	keymaster_error_t error;
	if (!ProcessTagBufContentsAsData(to_process_from_tag_buf, output, &error)) return error;

	if (!InternalUpdate(input.peek_read(), to_process_from_input, output, &error)) return error;

	BufferCandidateTagData(input.peek_read() + to_process_from_input,
	input.available_read() - to_process_from_input);
	assert(tag_buf_unused() == 0);

	return KM_ERROR_OK;
	}

	bool BlockCipherEvpDecryptOperation::ProcessTagBufContentsAsData(size_t to_process, Buffer* output,
	keymaster_error_t* error) {
	assert(to_process <= tag_buf_len_);
	if (!InternalUpdate(tag_buf_.get(), to_process, output, error)) return false;
	if (to_process < tag_buf_len_) {
	memmove(tag_buf_.get(), tag_buf_.get() + to_process, tag_buf_len_ - to_process);
	}
	tag_buf_len_ -= to_process;
	return true;
	}

	void BlockCipherEvpDecryptOperation::BufferCandidateTagData(const uint8_t* data,
	size_t data_length) {
	assert(data_length <= tag_length_ - tag_buf_len_);
	memcpy(tag_buf_.get() + tag_buf_len_, data, data_length);
	tag_buf_len_ += data_length;
	}

	keymaster_error_t BlockCipherEvpDecryptOperation::Finish(const AuthorizationSet& additional_params,
	const Buffer& input,
	const Buffer& signature,
	AuthorizationSet* output_params,
	Buffer* output) {
	keymaster_error_t error;
	if (!UpdateForFinish(additional_params, input, output_params, output, &error)) return error;

	if (tag_buf_len_ < tag_length_) {
	return KM_ERROR_INVALID_INPUT_LENGTH;
	} else if (tag_length_ > 0 &&
	!EVP_CIPHER_CTX_ctrl(&ctx_, EVP_CTRL_GCM_SET_TAG, tag_length_, tag_buf_.get())) {
	return TranslateLastOpenSslError();
	}

	AuthorizationSet empty_params;
	Buffer empty_input;
	return BlockCipherEvpOperation::Finish(empty_params, empty_input, signature, output_params,
	output);
	}

	keymaster_error_t BlockCipherEvpOperation::Abort() {
	return KM_ERROR_OK;
	}

	} // namespace keymaster