init/persistent_properties.cpp - android_system_core - Gitiles

 /*
  * Copyright (C) 2017 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 "persistent_properties.h"

 #include <dirent.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/system_properties.h>
 #include <sys/types.h>

 #include <memory>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>

 #include "util.h"

 using android::base::Dirname;
 using android::base::ReadFdToString;
 using android::base::StartsWith;
 using android::base::unique_fd;
 using android::base::WriteStringToFd;

 namespace android {
 namespace init {

 std::string persistent_property_filename = "/data/property/persistent_properties";

 namespace {

 constexpr const char kLegacyPersistentPropertyDir[] = "/data/property";

 void AddPersistentProperty(const std::string& name, const std::string& value,
                            PersistentProperties* persistent_properties) {
     auto persistent_property_record = persistent_properties->add_properties();
     persistent_property_record->set_name(name);
     persistent_property_record->set_value(value);
 }

 Result<PersistentProperties> LoadLegacyPersistentProperties() {
     std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(kLegacyPersistentPropertyDir), closedir);
     if (!dir) {
         return ErrnoError() << "Unable to open persistent property directory \""
                             << kLegacyPersistentPropertyDir << "\"";
     }

     PersistentProperties persistent_properties;
     dirent* entry;
     while ((entry = readdir(dir.get())) != nullptr) {
         if (!StartsWith(entry->d_name, "persist.")) {
             continue;
         }
         if (entry->d_type != DT_REG) {
             continue;
         }

         unique_fd fd(openat(dirfd(dir.get()), entry->d_name, O_RDONLY | O_NOFOLLOW | O_CLOEXEC));
         if (fd == -1) {
             PLOG(ERROR) << "Unable to open persistent property file \"" << entry->d_name << "\"";
             continue;
         }

         struct stat sb;
         if (fstat(fd, &sb) == -1) {
             PLOG(ERROR) << "fstat on property file \"" << entry->d_name << "\" failed";
             continue;
         }

         // File must not be accessible to others, be owned by root/root, and
         // not be a hard link to any other file.
         if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0) || sb.st_uid != 0 || sb.st_gid != 0 ||
             sb.st_nlink != 1) {
             PLOG(ERROR) << "skipping insecure property file " << entry->d_name
                         << " (uid=" << sb.st_uid << " gid=" << sb.st_gid << " nlink=" << sb.st_nlink
                         << " mode=" << std::oct << sb.st_mode << ")";
             continue;
         }

         std::string value;
         if (ReadFdToString(fd, &value)) {
             AddPersistentProperty(entry->d_name, value, &persistent_properties);
         } else {
             PLOG(ERROR) << "Unable to read persistent property file " << entry->d_name;
         }
     }
     return persistent_properties;
 }

 void RemoveLegacyPersistentPropertyFiles() {
     std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(kLegacyPersistentPropertyDir), closedir);
     if (!dir) {
         PLOG(ERROR) << "Unable to open persistent property directory \""
                     << kLegacyPersistentPropertyDir << "\"";
         return;
     }

     dirent* entry;
     while ((entry = readdir(dir.get())) != nullptr) {
         if (!StartsWith(entry->d_name, "persist.")) {
             continue;
         }
         if (entry->d_type != DT_REG) {
             continue;
         }
         unlinkat(dirfd(dir.get()), entry->d_name, 0);
     }
 }

 PersistentProperties LoadPersistentPropertiesFromMemory() {
     PersistentProperties persistent_properties;
     __system_property_foreach(
         [](const prop_info* pi, void* cookie) {
             __system_property_read_callback(
                 pi,
                 [](void* cookie, const char* name, const char* value, unsigned serial) {
                     if (StartsWith(name, "persist.")) {
                         auto properties = reinterpret_cast<PersistentProperties*>(cookie);
                         AddPersistentProperty(name, value, properties);
                     }
                 },
                 cookie);
         },
         &persistent_properties);
     return persistent_properties;
 }

 Result<std::string> ReadPersistentPropertyFile() {
     const std::string temp_filename = persistent_property_filename + ".tmp";
     if (access(temp_filename.c_str(), F_OK) == 0) {
         LOG(INFO)
             << "Found temporary property file while attempting to persistent system properties"
                " a previous persistent property write may have failed";
         unlink(temp_filename.c_str());
     }
     auto file_contents = ReadFile(persistent_property_filename);
     if (!file_contents) {
         return Error() << "Unable to read persistent property file: " << file_contents.error();
     }
     return *file_contents;
 }

 }  // namespace

 Result<PersistentProperties> LoadPersistentPropertyFile() {
     auto file_contents = ReadPersistentPropertyFile();
     if (!file_contents) return file_contents.error();

     PersistentProperties persistent_properties;
     if (persistent_properties.ParseFromString(*file_contents)) return persistent_properties;

     // If the file cannot be parsed in either format, then we don't have any recovery
     // mechanisms, so we delete it to allow for future writes to take place successfully.
     unlink(persistent_property_filename.c_str());
     return Error() << "Unable to parse persistent property file: Could not parse protobuf";
 }

 Result<void> WritePersistentPropertyFile(const PersistentProperties& persistent_properties) {
     const std::string temp_filename = persistent_property_filename + ".tmp";
     unique_fd fd(TEMP_FAILURE_RETRY(
         open(temp_filename.c_str(), O_WRONLY | O_CREAT | O_NOFOLLOW | O_TRUNC | O_CLOEXEC, 0600)));
     if (fd == -1) {
         return ErrnoError() << "Could not open temporary properties file";
     }
     std::string serialized_string;
     if (!persistent_properties.SerializeToString(&serialized_string)) {
         return Error() << "Unable to serialize properties";
     }
     if (!WriteStringToFd(serialized_string, fd)) {
         return ErrnoError() << "Unable to write file contents";
     }
     fsync(fd);
     fd.reset();

     if (rename(temp_filename.c_str(), persistent_property_filename.c_str())) {
         int saved_errno = errno;
         unlink(temp_filename.c_str());
         return Error(saved_errno) << "Unable to rename persistent property file";
     }

     // rename() is atomic with regards to the kernel's filesystem buffers, but the parent
     // directories must be fsync()'ed otherwise, the rename is not necessarily written to storage.
     // Note in this case, that the source and destination directories are the same, so only one
     // fsync() is required.
     auto dir = Dirname(persistent_property_filename);
     auto dir_fd = unique_fd{open(dir.c_str(), O_DIRECTORY | O_RDONLY | O_CLOEXEC)};
     if (dir_fd < 0) {
         return ErrnoError() << "Unable to open persistent properties directory for fsync()";
     }
     fsync(dir_fd);

     return {};
 }

 // Persistent properties are not written often, so we rather not keep any data in memory and read
 // then rewrite the persistent property file for each update.
 void WritePersistentProperty(const std::string& name, const std::string& value) {
     auto persistent_properties = LoadPersistentPropertyFile();

     if (!persistent_properties) {
         LOG(ERROR) << "Recovering persistent properties from memory: "
                    << persistent_properties.error();
         persistent_properties = LoadPersistentPropertiesFromMemory();
     }
     auto it = std::find_if(persistent_properties->mutable_properties()->begin(),
                            persistent_properties->mutable_properties()->end(),
                            [&name](const auto& record) { return record.name() == name; });
     if (it != persistent_properties->mutable_properties()->end()) {
         it->set_name(name);
         it->set_value(value);
     } else {
         AddPersistentProperty(name, value, &persistent_properties.value());
     }

     if (auto result = WritePersistentPropertyFile(*persistent_properties); !result) {
         LOG(ERROR) << "Could not store persistent property: " << result.error();
     }
 }

 PersistentProperties LoadPersistentProperties() {
     auto persistent_properties = LoadPersistentPropertyFile();

     if (!persistent_properties) {
         LOG(ERROR) << "Could not load single persistent property file, trying legacy directory: "
                    << persistent_properties.error();
         persistent_properties = LoadLegacyPersistentProperties();
         if (!persistent_properties) {
             LOG(ERROR) << "Unable to load legacy persistent properties: "
                        << persistent_properties.error();
             return {};
         }
         if (auto result = WritePersistentPropertyFile(*persistent_properties); result) {
             RemoveLegacyPersistentPropertyFiles();
         } else {
             LOG(ERROR) << "Unable to write single persistent property file: " << result.error();
             // Fall through so that we still set the properties that we've read.
         }
     }

     return *persistent_properties;
 }

 }  // namespace init
 }  // namespace android
	/*
	* Copyright (C) 2017 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 "persistent_properties.h"

	#include <dirent.h>
	#include <fcntl.h>
	#include <sys/stat.h>
	#include <sys/system_properties.h>
	#include <sys/types.h>

	#include <memory>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/strings.h>
	#include <android-base/unique_fd.h>

	#include "util.h"

	using android::base::Dirname;
	using android::base::ReadFdToString;
	using android::base::StartsWith;
	using android::base::unique_fd;
	using android::base::WriteStringToFd;

	namespace android {
	namespace init {

	std::string persistent_property_filename = "/data/property/persistent_properties";

	namespace {

	constexpr const char kLegacyPersistentPropertyDir[] = "/data/property";

	void AddPersistentProperty(const std::string& name, const std::string& value,
	PersistentProperties* persistent_properties) {
	auto persistent_property_record = persistent_properties->add_properties();
	persistent_property_record->set_name(name);
	persistent_property_record->set_value(value);
	}

	Result<PersistentProperties> LoadLegacyPersistentProperties() {
	std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(kLegacyPersistentPropertyDir), closedir);
	if (!dir) {
	return ErrnoError() << "Unable to open persistent property directory \""
	<< kLegacyPersistentPropertyDir << "\"";
	}

	PersistentProperties persistent_properties;
	dirent* entry;
	while ((entry = readdir(dir.get())) != nullptr) {
	if (!StartsWith(entry->d_name, "persist.")) {
	continue;
	}
	if (entry->d_type != DT_REG) {
	continue;
	}

	unique_fd fd(openat(dirfd(dir.get()), entry->d_name, O_RDONLY \| O_NOFOLLOW \| O_CLOEXEC));
	if (fd == -1) {
	PLOG(ERROR) << "Unable to open persistent property file \"" << entry->d_name << "\"";
	continue;
	}

	struct stat sb;
	if (fstat(fd, &sb) == -1) {
	PLOG(ERROR) << "fstat on property file \"" << entry->d_name << "\" failed";
	continue;
	}

	// File must not be accessible to others, be owned by root/root, and
	// not be a hard link to any other file.
	if (((sb.st_mode & (S_IRWXG \| S_IRWXO)) != 0) \|\| sb.st_uid != 0 \|\| sb.st_gid != 0 \|\|
	sb.st_nlink != 1) {
	PLOG(ERROR) << "skipping insecure property file " << entry->d_name
	<< " (uid=" << sb.st_uid << " gid=" << sb.st_gid << " nlink=" << sb.st_nlink
	<< " mode=" << std::oct << sb.st_mode << ")";
	continue;
	}

	std::string value;
	if (ReadFdToString(fd, &value)) {
	AddPersistentProperty(entry->d_name, value, &persistent_properties);
	} else {
	PLOG(ERROR) << "Unable to read persistent property file " << entry->d_name;
	}
	}
	return persistent_properties;
	}

	void RemoveLegacyPersistentPropertyFiles() {
	std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(kLegacyPersistentPropertyDir), closedir);
	if (!dir) {
	PLOG(ERROR) << "Unable to open persistent property directory \""
	<< kLegacyPersistentPropertyDir << "\"";
	return;
	}

	dirent* entry;
	while ((entry = readdir(dir.get())) != nullptr) {
	if (!StartsWith(entry->d_name, "persist.")) {
	continue;
	}
	if (entry->d_type != DT_REG) {
	continue;
	}
	unlinkat(dirfd(dir.get()), entry->d_name, 0);
	}
	}

	PersistentProperties LoadPersistentPropertiesFromMemory() {
	PersistentProperties persistent_properties;
	__system_property_foreach(
	[](const prop_info* pi, void* cookie) {
	__system_property_read_callback(
	pi,
	[](void* cookie, const char* name, const char* value, unsigned serial) {
	if (StartsWith(name, "persist.")) {
	auto properties = reinterpret_cast<PersistentProperties*>(cookie);
	AddPersistentProperty(name, value, properties);
	}
	},
	cookie);
	},
	&persistent_properties);
	return persistent_properties;
	}

	Result<std::string> ReadPersistentPropertyFile() {
	const std::string temp_filename = persistent_property_filename + ".tmp";
	if (access(temp_filename.c_str(), F_OK) == 0) {
	LOG(INFO)
	<< "Found temporary property file while attempting to persistent system properties"
	" a previous persistent property write may have failed";
	unlink(temp_filename.c_str());
	}
	auto file_contents = ReadFile(persistent_property_filename);
	if (!file_contents) {
	return Error() << "Unable to read persistent property file: " << file_contents.error();
	}
	return *file_contents;
	}

	} // namespace

	Result<PersistentProperties> LoadPersistentPropertyFile() {
	auto file_contents = ReadPersistentPropertyFile();
	if (!file_contents) return file_contents.error();

	PersistentProperties persistent_properties;
	if (persistent_properties.ParseFromString(*file_contents)) return persistent_properties;

	// If the file cannot be parsed in either format, then we don't have any recovery
	// mechanisms, so we delete it to allow for future writes to take place successfully.
	unlink(persistent_property_filename.c_str());
	return Error() << "Unable to parse persistent property file: Could not parse protobuf";
	}

	Result<void> WritePersistentPropertyFile(const PersistentProperties& persistent_properties) {
	const std::string temp_filename = persistent_property_filename + ".tmp";
	unique_fd fd(TEMP_FAILURE_RETRY(
	open(temp_filename.c_str(), O_WRONLY \| O_CREAT \| O_NOFOLLOW \| O_TRUNC \| O_CLOEXEC, 0600)));
	if (fd == -1) {
	return ErrnoError() << "Could not open temporary properties file";
	}
	std::string serialized_string;
	if (!persistent_properties.SerializeToString(&serialized_string)) {
	return Error() << "Unable to serialize properties";
	}
	if (!WriteStringToFd(serialized_string, fd)) {
	return ErrnoError() << "Unable to write file contents";
	}
	fsync(fd);
	fd.reset();

	if (rename(temp_filename.c_str(), persistent_property_filename.c_str())) {
	int saved_errno = errno;
	unlink(temp_filename.c_str());
	return Error(saved_errno) << "Unable to rename persistent property file";
	}

	// rename() is atomic with regards to the kernel's filesystem buffers, but the parent
	// directories must be fsync()'ed otherwise, the rename is not necessarily written to storage.
	// Note in this case, that the source and destination directories are the same, so only one
	// fsync() is required.
	auto dir = Dirname(persistent_property_filename);
	auto dir_fd = unique_fd{open(dir.c_str(), O_DIRECTORY \| O_RDONLY \| O_CLOEXEC)};
	if (dir_fd < 0) {
	return ErrnoError() << "Unable to open persistent properties directory for fsync()";
	}
	fsync(dir_fd);

	return {};
	}

	// Persistent properties are not written often, so we rather not keep any data in memory and read
	// then rewrite the persistent property file for each update.
	void WritePersistentProperty(const std::string& name, const std::string& value) {
	auto persistent_properties = LoadPersistentPropertyFile();

	if (!persistent_properties) {
	LOG(ERROR) << "Recovering persistent properties from memory: "
	<< persistent_properties.error();
	persistent_properties = LoadPersistentPropertiesFromMemory();
	}
	auto it = std::find_if(persistent_properties->mutable_properties()->begin(),
	persistent_properties->mutable_properties()->end(),
	[&name](const auto& record) { return record.name() == name; });
	if (it != persistent_properties->mutable_properties()->end()) {
	it->set_name(name);
	it->set_value(value);
	} else {
	AddPersistentProperty(name, value, &persistent_properties.value());
	}

	if (auto result = WritePersistentPropertyFile(*persistent_properties); !result) {
	LOG(ERROR) << "Could not store persistent property: " << result.error();
	}
	}

	PersistentProperties LoadPersistentProperties() {
	auto persistent_properties = LoadPersistentPropertyFile();

	if (!persistent_properties) {
	LOG(ERROR) << "Could not load single persistent property file, trying legacy directory: "
	<< persistent_properties.error();
	persistent_properties = LoadLegacyPersistentProperties();
	if (!persistent_properties) {
	LOG(ERROR) << "Unable to load legacy persistent properties: "
	<< persistent_properties.error();
	return {};
	}
	if (auto result = WritePersistentPropertyFile(*persistent_properties); result) {
	RemoveLegacyPersistentPropertyFiles();
	} else {
	LOG(ERROR) << "Unable to write single persistent property file: " << result.error();
	// Fall through so that we still set the properties that we've read.
	}
	}

	return *persistent_properties;
	}

	} // namespace init
	} // namespace android