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/*
* 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 <nvram/core/storage.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/unique_fd.h>
#include <nvram/core/logger.h>
// An NVRAM storage layer implementation backed by the file system.
//
// NOTE: This does not meet the tamper evidence requirements for
// access-controlled NVRAM implementations, since the file system can't provide
// sufficient protection against tampering by attackers.
namespace {
// Name of the storage object holding the header.
const char kHeaderFileName[] = "header";
// Pattern for space data storage object names.
const char kSpaceDataFileNamePattern[] = "space_%08x";
// Temporary file name used in write-rename atomic write operations.
const char kTempFileName[] = "temp";
// Maximum size of objects we're willing to read and write.
const off_t kMaxFileSize = 2048;
// Buffer size for formatting names.
using NameBuffer = char[16];
// Global data directory descriptor.
int g_data_dir_fd = -1;
// Formats the storage object name for the given space index.
bool FormatSpaceFileName(NameBuffer name, uint32_t index) {
int ret =
snprintf(name, sizeof(NameBuffer), kSpaceDataFileNamePattern, index);
return ret >= 0 && ret < static_cast<int>(sizeof(NameBuffer));
};
nvram::storage::Status DeleteFile(const char* name) {
if (TEMP_FAILURE_RETRY(unlinkat(g_data_dir_fd, name, 0))) {
if (errno == ENOENT) {
return nvram::storage::Status::kNotFound;
}
PLOG(ERROR) << "Failed to remove " << name;
return nvram::storage::Status::kStorageError;
}
return nvram::storage::Status::kSuccess;
}
// Loads the storage object identified by |name|.
nvram::storage::Status LoadFile(const char* name, nvram::Blob* blob) {
android::base::unique_fd data_file_fd(
TEMP_FAILURE_RETRY(openat(g_data_dir_fd, name, O_RDONLY)));
if (data_file_fd.get() < 0) {
if (errno == ENOENT) {
return nvram::storage::Status::kNotFound;
}
PLOG(ERROR) << "Failed to open " << name;
return nvram::storage::Status::kStorageError;
}
struct stat data_file_stat;
if (TEMP_FAILURE_RETRY(fstat(data_file_fd.get(), &data_file_stat))) {
PLOG(ERROR) << "Failed to stat " << name;
return nvram::storage::Status::kStorageError;
}
if (data_file_stat.st_size > kMaxFileSize) {
LOG(ERROR) << "Bad size for " << name << ":" << data_file_stat.st_size;
return nvram::storage::Status::kStorageError;
}
if (!blob->Resize(data_file_stat.st_size)) {
LOG(ERROR) << "Failed to allocate read buffer for " << name;
return nvram::storage::Status::kStorageError;
}
if (!android::base::ReadFully(data_file_fd.get(), blob->data(),
blob->size())) {
PLOG(ERROR) << "Failed to read " << name;
return nvram::storage::Status::kStorageError;
}
return nvram::storage::Status::kSuccess;
}
// Writes blob to the storage object indicated by |name|.
nvram::storage::Status StoreFile(const char* name, const nvram::Blob& blob) {
android::base::unique_fd data_file_fd(TEMP_FAILURE_RETRY(
openat(g_data_dir_fd, kTempFileName, O_WRONLY | O_CREAT | O_TRUNC,
S_IRUSR | S_IWUSR)));
if (data_file_fd.get() < 0) {
if (errno == ENOENT) {
return nvram::storage::Status::kNotFound;
}
PLOG(ERROR) << "Failed to open " << kTempFileName;
return nvram::storage::Status::kStorageError;
}
if (!android::base::WriteFully(data_file_fd.get(), blob.data(),
blob.size())) {
PLOG(ERROR) << "Failed to write " << kTempFileName;
DeleteFile(kTempFileName);
return nvram::storage::Status::kStorageError;
}
// Force the file contents to be written to disk.
if (TEMP_FAILURE_RETRY(fdatasync(data_file_fd.get()))) {
PLOG(ERROR) << "Failed to sync " << kTempFileName;
DeleteFile(kTempFileName);
return nvram::storage::Status::kStorageError;
}
data_file_fd.reset();
// Move the file into place.
if (TEMP_FAILURE_RETRY(
renameat(g_data_dir_fd, kTempFileName, g_data_dir_fd, name))) {
PLOG(ERROR) << "Failed to move " << kTempFileName << " to " << name;
DeleteFile(kTempFileName);
return nvram::storage::Status::kStorageError;
}
// Force the directory meta data to be written to disk.
if (TEMP_FAILURE_RETRY(fsync(g_data_dir_fd))) {
PLOG(ERROR) << "Failed to sync data directory";
return nvram::storage::Status::kStorageError;
}
return nvram::storage::Status::kSuccess;
}
} // namespace
// Initializes the storage layer with the provided data directory descriptor.
void InitStorage(int data_dir_fd) {
g_data_dir_fd = data_dir_fd;
}
namespace nvram {
namespace storage {
Status LoadHeader(Blob* blob) {
return LoadFile(kHeaderFileName, blob);
}
Status StoreHeader(const Blob& blob) {
return StoreFile(kHeaderFileName, blob);
}
Status LoadSpace(uint32_t index, Blob* blob) {
NameBuffer name;
if (!FormatSpaceFileName(name, index)) {
return Status::kStorageError;
}
return LoadFile(name, blob);
}
Status StoreSpace(uint32_t index, const Blob& blob) {
NameBuffer name;
if (!FormatSpaceFileName(name, index)) {
return Status::kStorageError;
}
return StoreFile(name, blob);
}
Status DeleteSpace(uint32_t index) {
NameBuffer name;
if (!FormatSpaceFileName(name, index)) {
return Status::kStorageError;
}
return DeleteFile(name);
}
} // namespace storage
} // namespace nvram
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