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/*
* 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 <stdio.h>
#include <UniquePtr.h>
#include <openssl/aes.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include <keymaster/logger.h>
#include "aes_key.h"
#include "aes_operation.h"
#include "openssl_err.h"
namespace keymaster {
static const size_t GCM_NONCE_SIZE = 12;
static const size_t GCM_MAX_TAG_LENGTH = 16;
static const size_t GCM_MIN_TAG_LENGTH = 12;
Operation* AesOperationFactory::CreateOperation(const Key& key,
const AuthorizationSet& begin_params,
keymaster_error_t* error) {
*error = KM_ERROR_OK;
const SymmetricKey* symmetric_key = static_cast<const SymmetricKey*>(&key);
switch (symmetric_key->key_data_size()) {
case 16:
case 24:
case 32:
break;
default:
*error = KM_ERROR_UNSUPPORTED_KEY_SIZE;
return nullptr;
}
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;
} else if (!supported(block_mode)) {
LOG_E("Block mode %d not supported", block_mode);
*error = KM_ERROR_UNSUPPORTED_BLOCK_MODE;
} 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;
}
size_t tag_length = 0;
if (block_mode == KM_MODE_GCM) {
uint32_t tag_length_bits;
if (!begin_params.GetTagValue(TAG_MAC_LENGTH, &tag_length_bits))
*error = KM_ERROR_MISSING_MAC_LENGTH;
tag_length = tag_length_bits / 8;
if (tag_length_bits % 8 != 0 || tag_length > GCM_MAX_TAG_LENGTH ||
tag_length < GCM_MIN_TAG_LENGTH)
*error = KM_ERROR_UNSUPPORTED_MAC_LENGTH;
}
keymaster_padding_t padding;
if (!begin_params.GetTagValue(TAG_PADDING, &padding)) {
LOG_E("%d padding modes specified in begin params", begin_params.GetTagCount(TAG_PADDING));
*error = KM_ERROR_UNSUPPORTED_PADDING_MODE;
} else if (!supported(padding)) {
LOG_E("Padding mode %d not supported", padding);
*error = KM_ERROR_UNSUPPORTED_PADDING_MODE;
} else if (block_mode == KM_MODE_CTR && padding != KM_PAD_NONE) {
LOG_E("CTR mode does not support padding", 0);
*error = KM_ERROR_INCOMPATIBLE_PADDING_MODE;
} else if (!key.authorizations().Contains(TAG_PADDING, padding)) {
LOG_E("Padding mode %d was specified, but not authorized by key", padding);
*error = KM_ERROR_INCOMPATIBLE_PADDING_MODE;
}
bool caller_nonce = key.authorizations().GetTagValue(TAG_CALLER_NONCE);
if (*error != KM_ERROR_OK)
return nullptr;
Operation* op = NULL;
switch (purpose()) {
case KM_PURPOSE_ENCRYPT:
op = new AesEvpEncryptOperation(block_mode, padding, caller_nonce, tag_length,
symmetric_key->key_data(), symmetric_key->key_data_size());
break;
case KM_PURPOSE_DECRYPT:
op = new AesEvpDecryptOperation(block_mode, padding, tag_length, symmetric_key->key_data(),
symmetric_key->key_data_size());
break;
default:
*error = KM_ERROR_UNSUPPORTED_PURPOSE;
return NULL;
}
if (!op)
*error = KM_ERROR_MEMORY_ALLOCATION_FAILED;
return op;
}
static const keymaster_block_mode_t supported_block_modes[] = {KM_MODE_ECB, KM_MODE_CBC,
KM_MODE_CTR, KM_MODE_GCM};
const keymaster_block_mode_t*
AesOperationFactory::SupportedBlockModes(size_t* block_mode_count) const {
*block_mode_count = array_length(supported_block_modes);
return supported_block_modes;
}
static const keymaster_padding_t supported_padding_modes[] = {KM_PAD_NONE, KM_PAD_PKCS7};
const keymaster_padding_t*
AesOperationFactory::SupportedPaddingModes(size_t* padding_mode_count) const {
*padding_mode_count = array_length(supported_padding_modes);
return supported_padding_modes;
}
AesEvpOperation::AesEvpOperation(keymaster_purpose_t purpose, keymaster_block_mode_t block_mode,
keymaster_padding_t padding, bool caller_iv, size_t tag_length,
const uint8_t* key, size_t key_size)
: Operation(purpose), block_mode_(block_mode), caller_iv_(caller_iv), tag_length_(tag_length),
data_started_(false), key_size_(key_size), padding_(padding) {
memcpy(key_, key, key_size_);
EVP_CIPHER_CTX_init(&ctx_);
}
AesEvpOperation::~AesEvpOperation() {
EVP_CIPHER_CTX_cleanup(&ctx_);
memset_s(aad_block_buf_.get(), AES_BLOCK_SIZE, 0);
}
keymaster_error_t AesEvpOperation::Begin(const AuthorizationSet& /* input_params */,
AuthorizationSet* /* output_params */) {
if (block_mode_ == KM_MODE_GCM) {
aad_block_buf_length_ = 0;
aad_block_buf_.reset(new uint8_t[AES_BLOCK_SIZE]);
if (!aad_block_buf_.get())
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
return InitializeCipher();
}
keymaster_error_t AesEvpOperation::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)
if (!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 AesEvpOperation::Finish(const AuthorizationSet& /* additional_params */,
const Buffer& /* signature */,
AuthorizationSet* /* output_params */, Buffer* output) {
if (!output->reserve(AES_BLOCK_SIZE))
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
keymaster_error_t error;
if (block_mode_ == KM_MODE_GCM && aad_block_buf_length_ > 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(), NULL));
return TranslateLastOpenSslError();
}
assert(output_written <= AES_BLOCK_SIZE);
output->advance_write(output_written);
return KM_ERROR_OK;
}
bool AesEvpOperation::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 AesEvpOperation::InitializeCipher() {
const EVP_CIPHER* cipher;
switch (block_mode_) {
case KM_MODE_ECB:
switch (key_size_) {
case 16:
cipher = EVP_aes_128_ecb();
break;
case 24:
cipher = EVP_aes_192_ecb();
break;
case 32:
cipher = EVP_aes_256_ecb();
break;
default:
return KM_ERROR_UNSUPPORTED_KEY_SIZE;
}
break;
case KM_MODE_CBC:
switch (key_size_) {
case 16:
cipher = EVP_aes_128_cbc();
break;
case 24:
cipher = EVP_aes_192_cbc();
break;
case 32:
cipher = EVP_aes_256_cbc();
break;
default:
return KM_ERROR_UNSUPPORTED_KEY_SIZE;
}
break;
case KM_MODE_CTR:
switch (key_size_) {
case 16:
cipher = EVP_aes_128_ctr();
break;
case 24:
cipher = EVP_aes_192_ctr();
break;
case 32:
cipher = EVP_aes_256_ctr();
break;
default:
return KM_ERROR_UNSUPPORTED_KEY_SIZE;
}
break;
case KM_MODE_GCM:
switch (key_size_) {
case 16:
cipher = EVP_aes_128_gcm();
break;
case 24:
cipher = EVP_aes_192_gcm();
break;
case 32:
cipher = EVP_aes_256_gcm();
break;
default:
return KM_ERROR_UNSUPPORTED_KEY_SIZE;
}
break;
default:
return KM_ERROR_UNSUPPORTED_BLOCK_MODE;
}
if (!EVP_CipherInit_ex(&ctx_, cipher, NULL /* engine */, key_, iv_.get(), 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_length_ = 0;
aad_block_buf_.reset(new uint8_t[AES_BLOCK_SIZE]);
if (!aad_block_buf_.get())
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
return KM_ERROR_OK;
}
keymaster_error_t AesEvpOperation::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 != AES_BLOCK_SIZE) {
LOG_E("Expected %d-byte IV for AES operation, but got %d bytes", AES_BLOCK_SIZE,
iv_blob.data_length);
return KM_ERROR_INVALID_NONCE;
}
iv_.reset(dup_array(iv_blob.data, iv_blob.data_length));
if (!iv_.get())
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
iv_length_ = iv_blob.data_length;
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
* AES_BLOCK_SIZE increments, buffering (in aad_block_buf_) when given smaller amounts of data.
*/
bool AesEvpOperation::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_length_ > 0) {
FillBufferedAadBlock(&aad);
if (aad_block_buf_length_ == AES_BLOCK_SIZE && !ProcessBufferedAadBlock(error))
return false;
}
size_t blocks_to_process = aad.data_length / AES_BLOCK_SIZE;
if (blocks_to_process && !ProcessAadBlocks(aad.data, blocks_to_process, error))
return false;
aad.data += blocks_to_process * AES_BLOCK_SIZE;
aad.data_length -= blocks_to_process * AES_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_length_ > 0 && !ProcessBufferedAadBlock(error))
return false;
}
return true;
}
bool AesEvpOperation::ProcessBufferedAadBlock(keymaster_error_t* error) {
int output_written;
if (EVP_CipherUpdate(&ctx_, nullptr /* out */, &output_written, aad_block_buf_.get(),
aad_block_buf_length_)) {
aad_block_buf_length_ = 0;
return true;
}
*error = TranslateLastOpenSslError();
return false;
}
bool AesEvpOperation::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 * AES_BLOCK_SIZE))
return true;
*error = TranslateLastOpenSslError();
return false;
}
inline size_t min(size_t a, size_t b) {
return (a < b) ? a : b;
}
void AesEvpOperation::FillBufferedAadBlock(keymaster_blob_t* aad) {
size_t to_buffer = min(AES_BLOCK_SIZE - aad_block_buf_length_, aad->data_length);
memcpy(aad_block_buf_.get() + aad_block_buf_length_, aad->data, to_buffer);
aad->data += to_buffer;
aad->data_length -= to_buffer;
aad_block_buf_length_ += to_buffer;
}
bool AesEvpOperation::InternalUpdate(const uint8_t* input, size_t input_length, Buffer* output,
keymaster_error_t* error) {
assert(output);
assert(error);
if (!output->reserve(input_length + AES_BLOCK_SIZE)) {
*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;
}
output->advance_write(output_written);
return true;
}
keymaster_error_t AesEvpEncryptOperation::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)
output_params->push_back(TAG_NONCE, iv_.get(), iv_length_);
else
return error;
}
return AesEvpOperation::Begin(input_params, output_params);
}
keymaster_error_t AesEvpEncryptOperation::Finish(const AuthorizationSet& additional_params,
const Buffer& signature,
AuthorizationSet* output_params, Buffer* output) {
if (!output->reserve(AES_BLOCK_SIZE + tag_length_))
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
keymaster_error_t error =
AesEvpOperation::Finish(additional_params, signature, output_params, output);
if (error != KM_ERROR_OK)
return error;
if (tag_length_ > 0) {
if (!output->reserve(output->available_read() + 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();
output->advance_write(tag_length_);
}
return KM_ERROR_OK;
}
keymaster_error_t AesEvpEncryptOperation::GenerateIv() {
iv_length_ = (block_mode_ == KM_MODE_GCM) ? GCM_NONCE_SIZE : AES_BLOCK_SIZE;
iv_.reset(new uint8_t[iv_length_]);
if (!iv_.get())
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
if (RAND_bytes(iv_.get(), iv_length_) != 1)
return TranslateLastOpenSslError();
return KM_ERROR_OK;
}
keymaster_error_t AesEvpDecryptOperation::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_length_ = 0;
tag_buf_.reset(new uint8_t[tag_length_]);
if (!tag_buf_.get())
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
return AesEvpOperation::Begin(input_params, output_params);
}
keymaster_error_t AesEvpDecryptOperation::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 AesEvpDecryptOperation::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_length_ + 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_length_);
const size_t to_process_from_input = to_process - to_process_from_tag_buf;
if (!output->reserve(to_process + AES_BLOCK_SIZE))
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 AesEvpDecryptOperation::ProcessTagBufContentsAsData(size_t to_process, Buffer* output,
keymaster_error_t* error) {
assert(to_process <= tag_buf_length_);
if (!InternalUpdate(tag_buf_.get(), to_process, output, error))
return false;
if (to_process < tag_buf_length_)
memmove(tag_buf_.get(), tag_buf_.get() + to_process, tag_buf_length_ - to_process);
tag_buf_length_ -= to_process;
return true;
}
void AesEvpDecryptOperation::BufferCandidateTagData(const uint8_t* data, size_t data_length) {
assert(data_length <= tag_length_ - tag_buf_length_);
memcpy(tag_buf_.get() + tag_buf_length_, data, data_length);
tag_buf_length_ += data_length;
}
keymaster_error_t AesEvpDecryptOperation::Finish(const AuthorizationSet& additional_params,
const Buffer& signature,
AuthorizationSet* output_params, Buffer* output) {
if (tag_buf_length_ < 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();
return AesEvpOperation::Finish(additional_params, signature, output_params, output);
}
keymaster_error_t AesEvpOperation::Abort() {
return KM_ERROR_OK;
}
} // namespace keymaster