init/persistent_properties.cpp - third_party/android/platform/system/core - Git at Google

 /*
  * 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::ReadFdToString;
 using android::base::StartsWith;
 using android::base::WriteStringToFd;
 using android::base::unique_fd;

 namespace android {
 namespace init {

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

 namespace {

 constexpr const uint32_t kMagic = 0x8495E0B4;
 constexpr const char kLegacyPersistentPropertyDir[] = "/data/property";

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

     std::vector<std::pair<std::string, std::string>> 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));
         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)) {
             persistent_properties.emplace_back(entry->d_name, value);
         } 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);
     }
 }

 std::vector<std::pair<std::string, std::string>> LoadPersistentPropertiesFromMemory() {
     std::vector<std::pair<std::string, std::string>> 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<std::vector<std::pair<std::string, std::string>>*>(
                                 cookie);
                         properties->emplace_back(name, value);
                     }
                 },
                 cookie);
         },
         &properties);
     return properties;
 }

 class PersistentPropertyFileParser {
   public:
     PersistentPropertyFileParser(const std::string& contents) : contents_(contents), position_(0) {}
     Result<std::vector<std::pair<std::string, std::string>>> Parse();

   private:
     Result<std::string> ReadString();
     Result<uint32_t> ReadUint32();

     const std::string& contents_;
     size_t position_;
 };

 Result<std::vector<std::pair<std::string, std::string>>> PersistentPropertyFileParser::Parse() {
     std::vector<std::pair<std::string, std::string>> result;

     if (auto magic = ReadUint32(); magic) {
         if (*magic != kMagic) {
             return Error() << "Magic value '0x" << std::hex << *magic
                            << "' does not match expected value '0x" << kMagic << "'";
         }
     } else {
         return Error() << "Could not read magic value: " << magic.error();
     }

     if (auto version = ReadUint32(); version) {
         if (*version != 1) {
             return Error() << "Version '" << *version
                            << "' does not match any compatible version: (1)";
         }
     } else {
         return Error() << "Could not read version: " << version.error();
     }

     auto num_properties = ReadUint32();
     if (!num_properties) {
         return Error() << "Could not read num_properties: " << num_properties.error();
     }

     while (position_ < contents_.size()) {
         auto key = ReadString();
         if (!key) {
             return Error() << "Could not read key: " << key.error();
         }
         if (!StartsWith(*key, "persist.")) {
             return Error() << "Property '" << *key << "' does not starts with 'persist.'";
         }
         auto value = ReadString();
         if (!value) {
             return Error() << "Could not read value: " << value.error();
         }
         result.emplace_back(*key, *value);
     }

     if (result.size() != *num_properties) {
         return Error() << "Mismatch of number of persistent properties read, " << result.size()
                        << " and number of persistent properties expected, " << *num_properties;
     }

     return result;
 }

 Result<std::string> PersistentPropertyFileParser::ReadString() {
     auto string_length = ReadUint32();
     if (!string_length) {
         return Error() << "Could not read size for string";
     }

     if (position_ + *string_length > contents_.size()) {
         return Error() << "String size would cause it to overflow the input buffer";
     }
     auto result = std::string(contents_, position_, *string_length);
     position_ += *string_length;
     return result;
 }

 Result<uint32_t> PersistentPropertyFileParser::ReadUint32() {
     if (position_ + 3 > contents_.size()) {
         return Error() << "Input buffer not large enough to read uint32_t";
     }
     uint32_t result = *reinterpret_cast<const uint32_t*>(&contents_[position_]);
     position_ += sizeof(uint32_t);
     return result;
 }

 }  // namespace

 Result<std::vector<std::pair<std::string, std::string>>> LoadPersistentPropertyFile() {
     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();
     }
     auto parsed_contents = PersistentPropertyFileParser(*file_contents).Parse();
     if (!parsed_contents) {
         // If the file cannot be parsed, 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: " << parsed_contents.error();
     }
     return parsed_contents;
 }

 std::string GenerateFileContents(
     const std::vector<std::pair<std::string, std::string>>& persistent_properties) {
     std::string result;

     uint32_t magic = kMagic;
     result.append(reinterpret_cast<char*>(&magic), sizeof(uint32_t));

     uint32_t version = 1;
     result.append(reinterpret_cast<char*>(&version), sizeof(uint32_t));

     uint32_t num_properties = persistent_properties.size();
     result.append(reinterpret_cast<char*>(&num_properties), sizeof(uint32_t));

     for (const auto& [key, value] : persistent_properties) {
         uint32_t key_length = key.length();
         result.append(reinterpret_cast<char*>(&key_length), sizeof(uint32_t));
         result.append(key);
         uint32_t value_length = value.length();
         result.append(reinterpret_cast<char*>(&value_length), sizeof(uint32_t));
         result.append(value);
     }
     return result;
 }

 Result<Success> WritePersistentPropertyFile(
     const std::vector<std::pair<std::string, std::string>>& persistent_properties) {
     auto file_contents = GenerateFileContents(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";
     }
     if (!WriteStringToFd(file_contents, 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";
     }
     return Success();
 }

 // 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->begin(), persistent_properties->end(),
                            [&name](const auto& entry) { return entry.first == name; });
     if (it != persistent_properties->end()) {
         *it = {name, value};
     } else {
         persistent_properties->emplace_back(name, value);
     }

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

 std::vector<std::pair<std::string, std::string>> 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::ReadFdToString;
	using android::base::StartsWith;
	using android::base::WriteStringToFd;
	using android::base::unique_fd;

	namespace android {
	namespace init {

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

	namespace {

	constexpr const uint32_t kMagic = 0x8495E0B4;
	constexpr const char kLegacyPersistentPropertyDir[] = "/data/property";

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

	std::vector<std::pair<std::string, std::string>> 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));
	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)) {
	persistent_properties.emplace_back(entry->d_name, value);
	} 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);
	}
	}

	std::vector<std::pair<std::string, std::string>> LoadPersistentPropertiesFromMemory() {
	std::vector<std::pair<std::string, std::string>> 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<std::vector<std::pair<std::string, std::string>>*>(
	cookie);
	properties->emplace_back(name, value);
	}
	},
	cookie);
	},
	&properties);
	return properties;
	}

	class PersistentPropertyFileParser {
	public:
	PersistentPropertyFileParser(const std::string& contents) : contents_(contents), position_(0) {}
	Result<std::vector<std::pair<std::string, std::string>>> Parse();

	private:
	Result<std::string> ReadString();
	Result<uint32_t> ReadUint32();

	const std::string& contents_;
	size_t position_;
	};

	Result<std::vector<std::pair<std::string, std::string>>> PersistentPropertyFileParser::Parse() {
	std::vector<std::pair<std::string, std::string>> result;

	if (auto magic = ReadUint32(); magic) {
	if (*magic != kMagic) {
	return Error() << "Magic value '0x" << std::hex << *magic
	<< "' does not match expected value '0x" << kMagic << "'";
	}
	} else {
	return Error() << "Could not read magic value: " << magic.error();
	}

	if (auto version = ReadUint32(); version) {
	if (*version != 1) {
	return Error() << "Version '" << *version
	<< "' does not match any compatible version: (1)";
	}
	} else {
	return Error() << "Could not read version: " << version.error();
	}

	auto num_properties = ReadUint32();
	if (!num_properties) {
	return Error() << "Could not read num_properties: " << num_properties.error();
	}

	while (position_ < contents_.size()) {
	auto key = ReadString();
	if (!key) {
	return Error() << "Could not read key: " << key.error();
	}
	if (!StartsWith(*key, "persist.")) {
	return Error() << "Property '" << *key << "' does not starts with 'persist.'";
	}
	auto value = ReadString();
	if (!value) {
	return Error() << "Could not read value: " << value.error();
	}
	result.emplace_back(key, value);
	}

	if (result.size() != *num_properties) {
	return Error() << "Mismatch of number of persistent properties read, " << result.size()
	<< " and number of persistent properties expected, " << *num_properties;
	}

	return result;
	}

	Result<std::string> PersistentPropertyFileParser::ReadString() {
	auto string_length = ReadUint32();
	if (!string_length) {
	return Error() << "Could not read size for string";
	}

	if (position_ + *string_length > contents_.size()) {
	return Error() << "String size would cause it to overflow the input buffer";
	}
	auto result = std::string(contents_, position_, *string_length);
	position_ += *string_length;
	return result;
	}

	Result<uint32_t> PersistentPropertyFileParser::ReadUint32() {
	if (position_ + 3 > contents_.size()) {
	return Error() << "Input buffer not large enough to read uint32_t";
	}
	uint32_t result = reinterpret_cast<const uint32_t>(&contents_[position_]);
	position_ += sizeof(uint32_t);
	return result;
	}

	} // namespace

	Result<std::vector<std::pair<std::string, std::string>>> LoadPersistentPropertyFile() {
	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();
	}
	auto parsed_contents = PersistentPropertyFileParser(*file_contents).Parse();
	if (!parsed_contents) {
	// If the file cannot be parsed, 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: " << parsed_contents.error();
	}
	return parsed_contents;
	}

	std::string GenerateFileContents(
	const std::vector<std::pair<std::string, std::string>>& persistent_properties) {
	std::string result;

	uint32_t magic = kMagic;
	result.append(reinterpret_cast<char*>(&magic), sizeof(uint32_t));

	uint32_t version = 1;
	result.append(reinterpret_cast<char*>(&version), sizeof(uint32_t));

	uint32_t num_properties = persistent_properties.size();
	result.append(reinterpret_cast<char*>(&num_properties), sizeof(uint32_t));

	for (const auto& [key, value] : persistent_properties) {
	uint32_t key_length = key.length();
	result.append(reinterpret_cast<char*>(&key_length), sizeof(uint32_t));
	result.append(key);
	uint32_t value_length = value.length();
	result.append(reinterpret_cast<char*>(&value_length), sizeof(uint32_t));
	result.append(value);
	}
	return result;
	}

	Result<Success> WritePersistentPropertyFile(
	const std::vector<std::pair<std::string, std::string>>& persistent_properties) {
	auto file_contents = GenerateFileContents(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";
	}
	if (!WriteStringToFd(file_contents, 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";
	}
	return Success();
	}

	// 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->begin(), persistent_properties->end(),
	[&name](const auto& entry) { return entry.first == name; });
	if (it != persistent_properties->end()) {
	*it = {name, value};
	} else {
	persistent_properties->emplace_back(name, value);
	}

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

	std::vector<std::pair<std::string, std::string>> 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