libfscrypt/fscrypt.cpp - platform/system/extras - Git at Google

 /*
  * Copyright (C) 2015 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 "fscrypt/fscrypt.h"

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/properties.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 #include <asm/ioctl.h>
 #include <cutils/properties.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/fscrypt.h>
 #include <logwrap/logwrap.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 #include <utils/misc.h>

 #include <array>
 #include <string>
 #include <vector>

 using namespace std::string_literals;

 /* modes not supported by upstream kernel, so not in <linux/fscrypt.h> */
 #define FSCRYPT_MODE_AES_256_HEH 126
 #define FSCRYPT_MODE_PRIVATE 127

 #define HEX_LOOKUP "0123456789abcdef"

 struct ModeLookupEntry {
     std::string name;
     int id;
 };

 static const auto contents_modes = std::vector<ModeLookupEntry>{
         {"aes-256-xts"s, FSCRYPT_MODE_AES_256_XTS},
         {"software"s, FSCRYPT_MODE_AES_256_XTS},
         {"adiantum"s, FSCRYPT_MODE_ADIANTUM},
         {"ice"s, FSCRYPT_MODE_PRIVATE},
 };

 static const auto filenames_modes = std::vector<ModeLookupEntry>{
         {"aes-256-cts"s, FSCRYPT_MODE_AES_256_CTS},
         {"aes-256-heh"s, FSCRYPT_MODE_AES_256_HEH},
         {"adiantum"s, FSCRYPT_MODE_ADIANTUM},
         {"aes-256-hctr2"s, FSCRYPT_MODE_AES_256_HCTR2},
 };

 static bool LookupModeByName(const std::vector<struct ModeLookupEntry>& modes,
                              const std::string& name, int* result) {
     for (const auto& e : modes) {
         if (e.name == name) {
             *result = e.id;
             return true;
         }
     }
     return false;
 }

 static bool LookupModeById(const std::vector<struct ModeLookupEntry>& modes, int id,
                            std::string* result) {
     for (const auto& e : modes) {
         if (e.id == id) {
             *result = e.name;
             return true;
         }
     }
     return false;
 }

 // Returns true if FBE (File Based Encryption) is enabled.
 bool IsFbeEnabled() {
     char value[PROPERTY_VALUE_MAX];
     property_get("ro.crypto.type", value, "none");
     return !strcmp(value, "file");
 }

 namespace android {
 namespace fscrypt {

 static void log_ls(const char* dirname) {
     std::array<const char*, 3> argv = {"ls", "-laZ", dirname};
     int status = 0;
     auto res =
             logwrap_fork_execvp(argv.size(), argv.data(), &status, false, LOG_ALOG, false, nullptr);
     if (res != 0) {
         PLOG(ERROR) << argv[0] << " " << argv[1] << " " << argv[2] << "failed";
         return;
     }
     if (!WIFEXITED(status)) {
         LOG(ERROR) << argv[0] << " " << argv[1] << " " << argv[2]
                    << " did not exit normally, status: " << status;
         return;
     }
     if (WEXITSTATUS(status) != 0) {
         LOG(ERROR) << argv[0] << " " << argv[1] << " " << argv[2]
                    << " returned failure: " << WEXITSTATUS(status);
         return;
     }
 }

 void BytesToHex(const std::string& bytes, std::string* hex) {
     hex->clear();
     for (char c : bytes) {
         *hex += HEX_LOOKUP[(c & 0xF0) >> 4];
         *hex += HEX_LOOKUP[c & 0x0F];
     }
 }

 static bool fscrypt_is_encrypted(int fd) {
     fscrypt_policy_v1 policy;

     // success => encrypted with v1 policy
     // EINVAL => encrypted with v2 policy
     // ENODATA => not encrypted
     return ioctl(fd, FS_IOC_GET_ENCRYPTION_POLICY, &policy) == 0 || errno == EINVAL;
 }

 unsigned int GetFirstApiLevel() {
     return android::base::GetUintProperty<unsigned int>("ro.product.first_api_level", 0);
 }

 bool OptionsToString(const EncryptionOptions& options, std::string* options_string) {
     return OptionsToStringForApiLevel(GetFirstApiLevel(), options, options_string);
 }

 bool OptionsToStringForApiLevel(unsigned int first_api_level, const EncryptionOptions& options,
                                 std::string* options_string) {
     std::string contents_mode, filenames_mode;
     if (!LookupModeById(contents_modes, options.contents_mode, &contents_mode)) {
         return false;
     }
     if (!LookupModeById(filenames_modes, options.filenames_mode, &filenames_mode)) {
         return false;
     }
     *options_string = contents_mode + ":" + filenames_mode + ":v" + std::to_string(options.version);
     if ((options.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64)) {
         *options_string += "+inlinecrypt_optimized";
     }
     if ((options.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) {
         *options_string += "+emmc_optimized";
     }
     if (options.use_hw_wrapped_key) {
         *options_string += "+wrappedkey_v0";
     }

     EncryptionOptions options_check;
     if (!ParseOptionsForApiLevel(first_api_level, *options_string, &options_check)) {
         LOG(ERROR) << "Internal error serializing options as string: " << *options_string;
         return false;
     }
     if (options != options_check) {
         LOG(ERROR) << "Internal error serializing options as string, round trip failed: "
                    << *options_string;
         return false;
     }
     return true;
 }

 bool ParseOptions(const std::string& options_string, EncryptionOptions* options) {
     return ParseOptionsForApiLevel(GetFirstApiLevel(), options_string, options);
 }

 bool ParseOptionsForApiLevel(unsigned int first_api_level, const std::string& options_string,
                              EncryptionOptions* options) {
     auto parts = android::base::Split(options_string, ":");
     if (parts.size() > 3) {
         LOG(ERROR) << "Invalid encryption options: " << options;
         return false;
     }
     options->contents_mode = FSCRYPT_MODE_AES_256_XTS;
     if (parts.size() > 0 && !parts[0].empty()) {
         if (!LookupModeByName(contents_modes, parts[0], &options->contents_mode)) {
             LOG(ERROR) << "Invalid file contents encryption mode: " << parts[0];
             return false;
         }
     }
     if (options->contents_mode == FSCRYPT_MODE_ADIANTUM) {
         options->filenames_mode = FSCRYPT_MODE_ADIANTUM;
     } else {
         options->filenames_mode = FSCRYPT_MODE_AES_256_CTS;
     }
     if (parts.size() > 1 && !parts[1].empty()) {
         if (!LookupModeByName(filenames_modes, parts[1], &options->filenames_mode)) {
             LOG(ERROR) << "Invalid file names encryption mode: " << parts[1];
             return false;
         }
     }
     // Default to v2 after Q
     options->version = first_api_level > __ANDROID_API_Q__ ? 2 : 1;
     options->flags = 0;
     options->use_hw_wrapped_key = false;
     if (parts.size() > 2 && !parts[2].empty()) {
         auto flags = android::base::Split(parts[2], "+");
         for (const auto& flag : flags) {
             if (flag == "v1") {
                 options->version = 1;
             } else if (flag == "v2") {
                 options->version = 2;
             } else if (flag == "inlinecrypt_optimized") {
                 options->flags |= FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64;
             } else if (flag == "emmc_optimized") {
                 options->flags |= FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32;
             } else if (flag == "wrappedkey_v0") {
                 options->use_hw_wrapped_key = true;
             } else {
                 LOG(ERROR) << "Unknown flag: " << flag;
                 return false;
             }
         }
     }

     // In the original setting of v1 policies and AES-256-CTS we used 4-byte
     // padding of filenames, so retain that on old first_api_levels.
     //
     // For everything else, use 16-byte padding.  This is more secure (it helps
     // hide the length of filenames), and it makes the inputs evenly divisible
     // into cipher blocks which is more efficient for encryption and decryption.
     if (first_api_level <= __ANDROID_API_Q__ && options->version == 1 &&
         options->filenames_mode == FSCRYPT_MODE_AES_256_CTS) {
         options->flags |= FSCRYPT_POLICY_FLAGS_PAD_4;
     } else {
         options->flags |= FSCRYPT_POLICY_FLAGS_PAD_16;
     }

     // Use DIRECT_KEY for Adiantum, since it's much more efficient but just as
     // secure since Android doesn't reuse the same master key for multiple
     // encryption modes.
     if (options->contents_mode == FSCRYPT_MODE_ADIANTUM) {
         if (options->filenames_mode != FSCRYPT_MODE_ADIANTUM) {
             LOG(ERROR) << "Adiantum must be both contents and filenames mode or neither, invalid "
                           "options: "
                        << options_string;
             return false;
         }
         options->flags |= FSCRYPT_POLICY_FLAG_DIRECT_KEY;
     } else if (options->filenames_mode == FSCRYPT_MODE_ADIANTUM) {
         LOG(ERROR)
                 << "Adiantum must be both contents and filenames mode or neither, invalid options: "
                 << options_string;
         return false;
     }

     // IV generation methods are mutually exclusive
     int iv_methods = 0;
     iv_methods += !!(options->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64);
     iv_methods += !!(options->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32);
     iv_methods += !!(options->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY);
     if (iv_methods > 1) {
         LOG(ERROR) << "At most one IV generation method can be set, invalid options: "
                    << options_string;
         return false;
     }

     return true;
 }

 static std::string PolicyDebugString(const EncryptionPolicy& policy) {
     std::stringstream ss;
     std::string ref_hex;
     BytesToHex(policy.key_raw_ref, &ref_hex);
     ss << ref_hex;
     ss << " v" << policy.options.version;
     ss << " modes " << policy.options.contents_mode << "/" << policy.options.filenames_mode;
     ss << std::hex << " flags 0x" << policy.options.flags;
     return ss.str();
 }

 bool EnsurePolicy(const EncryptionPolicy& policy, const std::string& directory) {
     union {
         fscrypt_policy_v1 v1;
         fscrypt_policy_v2 v2;
     } kern_policy;
     memset(&kern_policy, 0, sizeof(kern_policy));

     switch (policy.options.version) {
         case 1:
             if (policy.key_raw_ref.size() != FSCRYPT_KEY_DESCRIPTOR_SIZE) {
                 LOG(ERROR) << "Invalid key descriptor length for v1 policy: "
                            << policy.key_raw_ref.size();
                 return false;
             }
             // Careful: FSCRYPT_POLICY_V1 is actually 0 in the API, so make sure
             // to use it here instead of a literal 1.
             kern_policy.v1.version = FSCRYPT_POLICY_V1;
             kern_policy.v1.contents_encryption_mode = policy.options.contents_mode;
             kern_policy.v1.filenames_encryption_mode = policy.options.filenames_mode;
             kern_policy.v1.flags = policy.options.flags;
             policy.key_raw_ref.copy(reinterpret_cast<char*>(kern_policy.v1.master_key_descriptor),
                                     FSCRYPT_KEY_DESCRIPTOR_SIZE);
             break;
         case 2:
             if (policy.key_raw_ref.size() != FSCRYPT_KEY_IDENTIFIER_SIZE) {
                 LOG(ERROR) << "Invalid key identifier length for v2 policy: "
                            << policy.key_raw_ref.size();
                 return false;
             }
             kern_policy.v2.version = FSCRYPT_POLICY_V2;
             kern_policy.v2.contents_encryption_mode = policy.options.contents_mode;
             kern_policy.v2.filenames_encryption_mode = policy.options.filenames_mode;
             kern_policy.v2.flags = policy.options.flags;
             policy.key_raw_ref.copy(reinterpret_cast<char*>(kern_policy.v2.master_key_identifier),
                                     FSCRYPT_KEY_IDENTIFIER_SIZE);
             break;
         default:
             LOG(ERROR) << "Invalid encryption policy version: " << policy.options.version;
             return false;
     }

     android::base::unique_fd fd(open(directory.c_str(), O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC));
     if (fd == -1) {
         PLOG(ERROR) << "Failed to open directory " << directory;
         return false;
     }

     bool already_encrypted = fscrypt_is_encrypted(fd);

     // FS_IOC_SET_ENCRYPTION_POLICY will set the policy if the directory is
     // unencrypted; otherwise it will verify that the existing policy matches.
     // Setting the policy will fail if the directory is already nonempty.
     if (ioctl(fd, FS_IOC_SET_ENCRYPTION_POLICY, &kern_policy) != 0) {
         std::string reason;
         switch (errno) {
             case EEXIST:
                 reason = "The directory already has a different encryption policy.";
                 break;
             default:
                 reason = strerror(errno);
                 break;
         }
         LOG(ERROR) << "Failed to set encryption policy of " << directory << " to "
                    << PolicyDebugString(policy) << ": " << reason;
         if (errno == ENOTEMPTY) {
             log_ls(directory.c_str());
         }
         return false;
     }

     if (already_encrypted) {
         LOG(INFO) << "Verified that " << directory << " has the encryption policy "
                   << PolicyDebugString(policy);
     } else {
         LOG(INFO) << "Encryption policy of " << directory << " set to "
                   << PolicyDebugString(policy);
     }
     return true;
 }

 }  // namespace fscrypt
 }  // namespace android
	/*
	* Copyright (C) 2015 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 "fscrypt/fscrypt.h"

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/properties.h>
	#include <android-base/strings.h>
	#include <android-base/unique_fd.h>
	#include <asm/ioctl.h>
	#include <cutils/properties.h>
	#include <errno.h>
	#include <fcntl.h>
	#include <linux/fscrypt.h>
	#include <logwrap/logwrap.h>
	#include <string.h>
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <unistd.h>
	#include <utils/misc.h>

	#include <array>
	#include <string>
	#include <vector>

	using namespace std::string_literals;

	/* modes not supported by upstream kernel, so not in <linux/fscrypt.h> */
	#define FSCRYPT_MODE_AES_256_HEH 126
	#define FSCRYPT_MODE_PRIVATE 127

	#define HEX_LOOKUP "0123456789abcdef"

	struct ModeLookupEntry {
	std::string name;
	int id;
	};

	static const auto contents_modes = std::vector<ModeLookupEntry>{
	{"aes-256-xts"s, FSCRYPT_MODE_AES_256_XTS},
	{"software"s, FSCRYPT_MODE_AES_256_XTS},
	{"adiantum"s, FSCRYPT_MODE_ADIANTUM},
	{"ice"s, FSCRYPT_MODE_PRIVATE},
	};

	static const auto filenames_modes = std::vector<ModeLookupEntry>{
	{"aes-256-cts"s, FSCRYPT_MODE_AES_256_CTS},
	{"aes-256-heh"s, FSCRYPT_MODE_AES_256_HEH},
	{"adiantum"s, FSCRYPT_MODE_ADIANTUM},
	{"aes-256-hctr2"s, FSCRYPT_MODE_AES_256_HCTR2},
	};

	static bool LookupModeByName(const std::vector<struct ModeLookupEntry>& modes,
	const std::string& name, int* result) {
	for (const auto& e : modes) {
	if (e.name == name) {
	*result = e.id;
	return true;
	}
	}
	return false;
	}

	static bool LookupModeById(const std::vector<struct ModeLookupEntry>& modes, int id,
	std::string* result) {
	for (const auto& e : modes) {
	if (e.id == id) {
	*result = e.name;
	return true;
	}
	}
	return false;
	}

	// Returns true if FBE (File Based Encryption) is enabled.
	bool IsFbeEnabled() {
	char value[PROPERTY_VALUE_MAX];
	property_get("ro.crypto.type", value, "none");
	return !strcmp(value, "file");
	}

	namespace android {
	namespace fscrypt {

	static void log_ls(const char* dirname) {
	std::array<const char*, 3> argv = {"ls", "-laZ", dirname};
	int status = 0;
	auto res =
	logwrap_fork_execvp(argv.size(), argv.data(), &status, false, LOG_ALOG, false, nullptr);
	if (res != 0) {
	PLOG(ERROR) << argv[0] << " " << argv[1] << " " << argv[2] << "failed";
	return;
	}
	if (!WIFEXITED(status)) {
	LOG(ERROR) << argv[0] << " " << argv[1] << " " << argv[2]
	<< " did not exit normally, status: " << status;
	return;
	}
	if (WEXITSTATUS(status) != 0) {
	LOG(ERROR) << argv[0] << " " << argv[1] << " " << argv[2]
	<< " returned failure: " << WEXITSTATUS(status);
	return;
	}
	}

	void BytesToHex(const std::string& bytes, std::string* hex) {
	hex->clear();
	for (char c : bytes) {
	*hex += HEX_LOOKUP[(c & 0xF0) >> 4];
	*hex += HEX_LOOKUP[c & 0x0F];
	}
	}

	static bool fscrypt_is_encrypted(int fd) {
	fscrypt_policy_v1 policy;

	// success => encrypted with v1 policy
	// EINVAL => encrypted with v2 policy
	// ENODATA => not encrypted
	return ioctl(fd, FS_IOC_GET_ENCRYPTION_POLICY, &policy) == 0 \|\| errno == EINVAL;
	}

	unsigned int GetFirstApiLevel() {
	return android::base::GetUintProperty<unsigned int>("ro.product.first_api_level", 0);
	}

	bool OptionsToString(const EncryptionOptions& options, std::string* options_string) {
	return OptionsToStringForApiLevel(GetFirstApiLevel(), options, options_string);
	}

	bool OptionsToStringForApiLevel(unsigned int first_api_level, const EncryptionOptions& options,
	std::string* options_string) {
	std::string contents_mode, filenames_mode;
	if (!LookupModeById(contents_modes, options.contents_mode, &contents_mode)) {
	return false;
	}
	if (!LookupModeById(filenames_modes, options.filenames_mode, &filenames_mode)) {
	return false;
	}
	*options_string = contents_mode + ":" + filenames_mode + ":v" + std::to_string(options.version);
	if ((options.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64)) {
	*options_string += "+inlinecrypt_optimized";
	}
	if ((options.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) {
	*options_string += "+emmc_optimized";
	}
	if (options.use_hw_wrapped_key) {
	*options_string += "+wrappedkey_v0";
	}

	EncryptionOptions options_check;
	if (!ParseOptionsForApiLevel(first_api_level, *options_string, &options_check)) {
	LOG(ERROR) << "Internal error serializing options as string: " << *options_string;
	return false;
	}
	if (options != options_check) {
	LOG(ERROR) << "Internal error serializing options as string, round trip failed: "
	<< *options_string;
	return false;
	}
	return true;
	}

	bool ParseOptions(const std::string& options_string, EncryptionOptions* options) {
	return ParseOptionsForApiLevel(GetFirstApiLevel(), options_string, options);
	}

	bool ParseOptionsForApiLevel(unsigned int first_api_level, const std::string& options_string,
	EncryptionOptions* options) {
	auto parts = android::base::Split(options_string, ":");
	if (parts.size() > 3) {
	LOG(ERROR) << "Invalid encryption options: " << options;
	return false;
	}
	options->contents_mode = FSCRYPT_MODE_AES_256_XTS;
	if (parts.size() > 0 && !parts[0].empty()) {
	if (!LookupModeByName(contents_modes, parts[0], &options->contents_mode)) {
	LOG(ERROR) << "Invalid file contents encryption mode: " << parts[0];
	return false;
	}
	}
	if (options->contents_mode == FSCRYPT_MODE_ADIANTUM) {
	options->filenames_mode = FSCRYPT_MODE_ADIANTUM;
	} else {
	options->filenames_mode = FSCRYPT_MODE_AES_256_CTS;
	}
	if (parts.size() > 1 && !parts[1].empty()) {
	if (!LookupModeByName(filenames_modes, parts[1], &options->filenames_mode)) {
	LOG(ERROR) << "Invalid file names encryption mode: " << parts[1];
	return false;
	}
	}
	// Default to v2 after Q
	options->version = first_api_level > __ANDROID_API_Q__ ? 2 : 1;
	options->flags = 0;
	options->use_hw_wrapped_key = false;
	if (parts.size() > 2 && !parts[2].empty()) {
	auto flags = android::base::Split(parts[2], "+");
	for (const auto& flag : flags) {
	if (flag == "v1") {
	options->version = 1;
	} else if (flag == "v2") {
	options->version = 2;
	} else if (flag == "inlinecrypt_optimized") {
	options->flags \|= FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64;
	} else if (flag == "emmc_optimized") {
	options->flags \|= FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32;
	} else if (flag == "wrappedkey_v0") {
	options->use_hw_wrapped_key = true;
	} else {
	LOG(ERROR) << "Unknown flag: " << flag;
	return false;
	}
	}
	}

	// In the original setting of v1 policies and AES-256-CTS we used 4-byte
	// padding of filenames, so retain that on old first_api_levels.
	//
	// For everything else, use 16-byte padding. This is more secure (it helps
	// hide the length of filenames), and it makes the inputs evenly divisible
	// into cipher blocks which is more efficient for encryption and decryption.
	if (first_api_level <= __ANDROID_API_Q__ && options->version == 1 &&
	options->filenames_mode == FSCRYPT_MODE_AES_256_CTS) {
	options->flags \|= FSCRYPT_POLICY_FLAGS_PAD_4;
	} else {
	options->flags \|= FSCRYPT_POLICY_FLAGS_PAD_16;
	}

	// Use DIRECT_KEY for Adiantum, since it's much more efficient but just as
	// secure since Android doesn't reuse the same master key for multiple
	// encryption modes.
	if (options->contents_mode == FSCRYPT_MODE_ADIANTUM) {
	if (options->filenames_mode != FSCRYPT_MODE_ADIANTUM) {
	LOG(ERROR) << "Adiantum must be both contents and filenames mode or neither, invalid "
	"options: "
	<< options_string;
	return false;
	}
	options->flags \|= FSCRYPT_POLICY_FLAG_DIRECT_KEY;
	} else if (options->filenames_mode == FSCRYPT_MODE_ADIANTUM) {
	LOG(ERROR)
	<< "Adiantum must be both contents and filenames mode or neither, invalid options: "
	<< options_string;
	return false;
	}

	// IV generation methods are mutually exclusive
	int iv_methods = 0;
	iv_methods += !!(options->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64);
	iv_methods += !!(options->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32);
	iv_methods += !!(options->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY);
	if (iv_methods > 1) {
	LOG(ERROR) << "At most one IV generation method can be set, invalid options: "
	<< options_string;
	return false;
	}

	return true;
	}

	static std::string PolicyDebugString(const EncryptionPolicy& policy) {
	std::stringstream ss;
	std::string ref_hex;
	BytesToHex(policy.key_raw_ref, &ref_hex);
	ss << ref_hex;
	ss << " v" << policy.options.version;
	ss << " modes " << policy.options.contents_mode << "/" << policy.options.filenames_mode;
	ss << std::hex << " flags 0x" << policy.options.flags;
	return ss.str();
	}

	bool EnsurePolicy(const EncryptionPolicy& policy, const std::string& directory) {
	union {
	fscrypt_policy_v1 v1;
	fscrypt_policy_v2 v2;
	} kern_policy;
	memset(&kern_policy, 0, sizeof(kern_policy));

	switch (policy.options.version) {
	case 1:
	if (policy.key_raw_ref.size() != FSCRYPT_KEY_DESCRIPTOR_SIZE) {
	LOG(ERROR) << "Invalid key descriptor length for v1 policy: "
	<< policy.key_raw_ref.size();
	return false;
	}
	// Careful: FSCRYPT_POLICY_V1 is actually 0 in the API, so make sure
	// to use it here instead of a literal 1.
	kern_policy.v1.version = FSCRYPT_POLICY_V1;
	kern_policy.v1.contents_encryption_mode = policy.options.contents_mode;
	kern_policy.v1.filenames_encryption_mode = policy.options.filenames_mode;
	kern_policy.v1.flags = policy.options.flags;
	policy.key_raw_ref.copy(reinterpret_cast<char*>(kern_policy.v1.master_key_descriptor),
	FSCRYPT_KEY_DESCRIPTOR_SIZE);
	break;
	case 2:
	if (policy.key_raw_ref.size() != FSCRYPT_KEY_IDENTIFIER_SIZE) {
	LOG(ERROR) << "Invalid key identifier length for v2 policy: "
	<< policy.key_raw_ref.size();
	return false;
	}
	kern_policy.v2.version = FSCRYPT_POLICY_V2;
	kern_policy.v2.contents_encryption_mode = policy.options.contents_mode;
	kern_policy.v2.filenames_encryption_mode = policy.options.filenames_mode;
	kern_policy.v2.flags = policy.options.flags;
	policy.key_raw_ref.copy(reinterpret_cast<char*>(kern_policy.v2.master_key_identifier),
	FSCRYPT_KEY_IDENTIFIER_SIZE);
	break;
	default:
	LOG(ERROR) << "Invalid encryption policy version: " << policy.options.version;
	return false;
	}

	android::base::unique_fd fd(open(directory.c_str(), O_DIRECTORY \| O_NOFOLLOW \| O_CLOEXEC));
	if (fd == -1) {
	PLOG(ERROR) << "Failed to open directory " << directory;
	return false;
	}

	bool already_encrypted = fscrypt_is_encrypted(fd);

	// FS_IOC_SET_ENCRYPTION_POLICY will set the policy if the directory is
	// unencrypted; otherwise it will verify that the existing policy matches.
	// Setting the policy will fail if the directory is already nonempty.
	if (ioctl(fd, FS_IOC_SET_ENCRYPTION_POLICY, &kern_policy) != 0) {
	std::string reason;
	switch (errno) {
	case EEXIST:
	reason = "The directory already has a different encryption policy.";
	break;
	default:
	reason = strerror(errno);
	break;
	}
	LOG(ERROR) << "Failed to set encryption policy of " << directory << " to "
	<< PolicyDebugString(policy) << ": " << reason;
	if (errno == ENOTEMPTY) {
	log_ls(directory.c_str());
	}
	return false;
	}

	if (already_encrypted) {
	LOG(INFO) << "Verified that " << directory << " has the encryption policy "
	<< PolicyDebugString(policy);
	} else {
	LOG(INFO) << "Encryption policy of " << directory << " set to "
	<< PolicyDebugString(policy);
	}
	return true;
	}

	} // namespace fscrypt
	} // namespace android