ext4_utils/ext4_crypt.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 "ext4_utils/ext4_crypt.h"

 #include <array>

 #include <asm/ioctl.h>
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <string.h>
 #include <sys/syscall.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <cutils/properties.h>
 #include <logwrap/logwrap.h>
 #include <utils/misc.h>

 #define XATTR_NAME_ENCRYPTION_POLICY "encryption.policy"
 #define EXT4_KEYREF_DELIMITER ((char)'.')

 // ext4enc:TODO Include structure from somewhere sensible
 // MUST be in sync with ext4_crypto.c in kernel
 #define EXT4_KEY_DESCRIPTOR_SIZE 8
 #define EXT4_KEY_DESCRIPTOR_SIZE_HEX 17

 struct ext4_encryption_policy {
     uint8_t version;
     uint8_t contents_encryption_mode;
     uint8_t filenames_encryption_mode;
     uint8_t flags;
     uint8_t master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
 } __attribute__((__packed__));

 #define EXT4_ENCRYPTION_MODE_AES_256_XTS    1
 #define EXT4_ENCRYPTION_MODE_AES_256_CTS    4
 #define EXT4_ENCRYPTION_MODE_AES_256_HEH    126
 #define EXT4_ENCRYPTION_MODE_PRIVATE        127

 #define EXT4_POLICY_FLAGS_PAD_4         0x00
 #define EXT4_POLICY_FLAGS_PAD_8         0x01
 #define EXT4_POLICY_FLAGS_PAD_16        0x02
 #define EXT4_POLICY_FLAGS_PAD_32        0x03
 #define EXT4_POLICY_FLAGS_PAD_MASK      0x03
 #define EXT4_POLICY_FLAGS_VALID         0x03

 // ext4enc:TODO Get value from somewhere sensible
 #define EXT4_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct ext4_encryption_policy)
 #define EXT4_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct ext4_encryption_policy)

 #define HEX_LOOKUP "0123456789abcdef"

 bool e4crypt_is_native() {
     char value[PROPERTY_VALUE_MAX];
     property_get("ro.crypto.type", value, "none");
     return !strcmp(value, "file");
 }

 static void log_ls(const char* dirname) {
     std::array<const char*, 3> argv = {"ls", "-laZ", dirname};
     int status = 0;
     auto res =
         android_fork_execvp(argv.size(), const_cast<char**>(argv.data()), &status, false, true);
     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;
     }
 }

 static void policy_to_hex(const char* policy, char* hex) {
     for (size_t i = 0, j = 0; i < EXT4_KEY_DESCRIPTOR_SIZE; i++) {
         hex[j++] = HEX_LOOKUP[(policy[i] & 0xF0) >> 4];
         hex[j++] = HEX_LOOKUP[policy[i] & 0x0F];
     }
     hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX - 1] = '\0';
 }

 static bool is_dir_empty(const char *dirname, bool *is_empty)
 {
     int n = 0;
     auto dirp = std::unique_ptr<DIR, int (*)(DIR*)>(opendir(dirname), closedir);
     if (!dirp) {
         PLOG(ERROR) << "Unable to read directory: " << dirname;
         return false;
     }
     for (;;) {
         errno = 0;
         auto entry = readdir(dirp.get());
         if (!entry) {
             if (errno) {
                 PLOG(ERROR) << "Unable to read directory: " << dirname;
                 return false;
             }
             break;
         }
         if (strcmp(entry->d_name, "lost+found") != 0) { // Skip lost+found
             ++n;
             if (n > 2) {
                 *is_empty = false;
                 return true;
             }
         }
     }
     *is_empty = true;
     return true;
 }

 static uint8_t e4crypt_get_policy_flags(int filenames_encryption_mode) {
     if (filenames_encryption_mode == EXT4_ENCRYPTION_MODE_AES_256_CTS) {
         // Use legacy padding with our original filenames encryption mode.
         return EXT4_POLICY_FLAGS_PAD_4;
     }
     // With a new mode we can use the better padding flag without breaking existing devices: pad
     // filenames with zeroes to the next 16-byte boundary.  This is more secure (helps hide the
     // length of filenames) and makes the inputs evenly divisible into blocks which is more
     // efficient for encryption and decryption.
     return EXT4_POLICY_FLAGS_PAD_16;
 }

 static bool e4crypt_policy_set(const char *directory, const char *policy,
                                size_t policy_length,
                                int contents_encryption_mode,
                                int filenames_encryption_mode) {
     if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
         LOG(ERROR) << "Policy wrong length: " << policy_length;
         return false;
     }
     char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];
     policy_to_hex(policy, policy_hex);

     int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
     if (fd == -1) {
         PLOG(ERROR) << "Failed to open directory " << directory;
         return false;
     }

     ext4_encryption_policy eep;
     eep.version = 0;
     eep.contents_encryption_mode = contents_encryption_mode;
     eep.filenames_encryption_mode = filenames_encryption_mode;
     eep.flags = e4crypt_get_policy_flags(filenames_encryption_mode);
     memcpy(eep.master_key_descriptor, policy, EXT4_KEY_DESCRIPTOR_SIZE);
     if (ioctl(fd, EXT4_IOC_SET_ENCRYPTION_POLICY, &eep)) {
         PLOG(ERROR) << "Failed to set encryption policy for " << directory  << " to " << policy_hex
             << " modes " << contents_encryption_mode << "/" << filenames_encryption_mode;
         close(fd);
         return false;
     }
     close(fd);

     LOG(INFO) << "Policy for " << directory << " set to " << policy_hex
         << " modes " << contents_encryption_mode << "/" << filenames_encryption_mode;
     return true;
 }

 static bool e4crypt_policy_get(const char *directory, char *policy,
                                size_t policy_length,
                                int contents_encryption_mode,
                                int filenames_encryption_mode) {
     if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
         LOG(ERROR) << "Policy wrong length: " << policy_length;
         return false;
     }

     int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
     if (fd == -1) {
         PLOG(ERROR) << "Failed to open directory " << directory;
         return false;
     }

     ext4_encryption_policy eep;
     memset(&eep, 0, sizeof(ext4_encryption_policy));
     if (ioctl(fd, EXT4_IOC_GET_ENCRYPTION_POLICY, &eep) != 0) {
         PLOG(ERROR) << "Failed to get encryption policy for " << directory;
         close(fd);
         log_ls(directory);
         return false;
     }
     close(fd);

     if ((eep.version != 0)
             || (eep.contents_encryption_mode != contents_encryption_mode)
             || (eep.filenames_encryption_mode != filenames_encryption_mode)
             || (eep.flags !=
                 e4crypt_get_policy_flags(filenames_encryption_mode))) {
         LOG(ERROR) << "Failed to find matching encryption policy for " << directory;
         return false;
     }
     memcpy(policy, eep.master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE);

     return true;
 }

 static bool e4crypt_policy_check(const char *directory, const char *policy,
                                  size_t policy_length,
                                  int contents_encryption_mode,
                                  int filenames_encryption_mode) {
     if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
         LOG(ERROR) << "Policy wrong length: " << policy_length;
         return false;
     }
     char existing_policy[EXT4_KEY_DESCRIPTOR_SIZE];
     if (!e4crypt_policy_get(directory, existing_policy, EXT4_KEY_DESCRIPTOR_SIZE,
                             contents_encryption_mode,
                             filenames_encryption_mode)) return false;
     char existing_policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];

     policy_to_hex(existing_policy, existing_policy_hex);

     if (memcmp(policy, existing_policy, EXT4_KEY_DESCRIPTOR_SIZE) != 0) {
         char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];
         policy_to_hex(policy, policy_hex);
         LOG(ERROR) << "Found policy " << existing_policy_hex << " at " << directory
                    << " which doesn't match expected value " << policy_hex;
         log_ls(directory);
         return false;
     }
     LOG(INFO) << "Found policy " << existing_policy_hex << " at " << directory
               << " which matches expected value";
     return true;
 }

 int e4crypt_policy_ensure(const char *directory, const char *policy,
                           size_t policy_length,
                           const char *contents_encryption_mode,
                           const char *filenames_encryption_mode) {
     int contents_mode = 0;
     int filenames_mode = 0;

     if (!strcmp(contents_encryption_mode, "software") ||
         !strcmp(contents_encryption_mode, "aes-256-xts")) {
         contents_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
     } else if (!strcmp(contents_encryption_mode, "ice")) {
         contents_mode = EXT4_ENCRYPTION_MODE_PRIVATE;
     } else {
         LOG(ERROR) << "Invalid file contents encryption mode: "
                    << contents_encryption_mode;
         return -1;
     }

     if (!strcmp(filenames_encryption_mode, "aes-256-cts")) {
         filenames_mode = EXT4_ENCRYPTION_MODE_AES_256_CTS;
     } else if (!strcmp(filenames_encryption_mode, "aes-256-heh")) {
         filenames_mode = EXT4_ENCRYPTION_MODE_AES_256_HEH;
     } else {
         LOG(ERROR) << "Invalid file names encryption mode: "
                    << filenames_encryption_mode;
         return -1;
     }

     bool is_empty;
     if (!is_dir_empty(directory, &is_empty)) return -1;
     if (is_empty) {
         if (!e4crypt_policy_set(directory, policy, policy_length,
                                 contents_mode, filenames_mode)) return -1;
     } else {
         if (!e4crypt_policy_check(directory, policy, policy_length,
                                   contents_mode, filenames_mode)) return -1;
     }
     return 0;
 }
	/*
	* 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 "ext4_utils/ext4_crypt.h"

	#include <array>

	#include <asm/ioctl.h>
	#include <dirent.h>
	#include <errno.h>
	#include <fcntl.h>
	#include <string.h>
	#include <sys/syscall.h>
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <unistd.h>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <cutils/properties.h>
	#include <logwrap/logwrap.h>
	#include <utils/misc.h>

	#define XATTR_NAME_ENCRYPTION_POLICY "encryption.policy"
	#define EXT4_KEYREF_DELIMITER ((char)'.')

	// ext4enc:TODO Include structure from somewhere sensible
	// MUST be in sync with ext4_crypto.c in kernel
	#define EXT4_KEY_DESCRIPTOR_SIZE 8
	#define EXT4_KEY_DESCRIPTOR_SIZE_HEX 17

	struct ext4_encryption_policy {
	uint8_t version;
	uint8_t contents_encryption_mode;
	uint8_t filenames_encryption_mode;
	uint8_t flags;
	uint8_t master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
	} __attribute__((__packed__));

	#define EXT4_ENCRYPTION_MODE_AES_256_XTS 1
	#define EXT4_ENCRYPTION_MODE_AES_256_CTS 4
	#define EXT4_ENCRYPTION_MODE_AES_256_HEH 126
	#define EXT4_ENCRYPTION_MODE_PRIVATE 127

	#define EXT4_POLICY_FLAGS_PAD_4 0x00
	#define EXT4_POLICY_FLAGS_PAD_8 0x01
	#define EXT4_POLICY_FLAGS_PAD_16 0x02
	#define EXT4_POLICY_FLAGS_PAD_32 0x03
	#define EXT4_POLICY_FLAGS_PAD_MASK 0x03
	#define EXT4_POLICY_FLAGS_VALID 0x03

	// ext4enc:TODO Get value from somewhere sensible
	#define EXT4_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct ext4_encryption_policy)
	#define EXT4_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct ext4_encryption_policy)

	#define HEX_LOOKUP "0123456789abcdef"

	bool e4crypt_is_native() {
	char value[PROPERTY_VALUE_MAX];
	property_get("ro.crypto.type", value, "none");
	return !strcmp(value, "file");
	}

	static void log_ls(const char* dirname) {
	std::array<const char*, 3> argv = {"ls", "-laZ", dirname};
	int status = 0;
	auto res =
	android_fork_execvp(argv.size(), const_cast<char**>(argv.data()), &status, false, true);
	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;
	}
	}

	static void policy_to_hex(const char* policy, char* hex) {
	for (size_t i = 0, j = 0; i < EXT4_KEY_DESCRIPTOR_SIZE; i++) {
	hex[j++] = HEX_LOOKUP[(policy[i] & 0xF0) >> 4];
	hex[j++] = HEX_LOOKUP[policy[i] & 0x0F];
	}
	hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX - 1] = '\0';
	}

	static bool is_dir_empty(const char dirname, bool is_empty)
	{
	int n = 0;
	auto dirp = std::unique_ptr<DIR, int ()(DIR)>(opendir(dirname), closedir);
	if (!dirp) {
	PLOG(ERROR) << "Unable to read directory: " << dirname;
	return false;
	}
	for (;;) {
	errno = 0;
	auto entry = readdir(dirp.get());
	if (!entry) {
	if (errno) {
	PLOG(ERROR) << "Unable to read directory: " << dirname;
	return false;
	}
	break;
	}
	if (strcmp(entry->d_name, "lost+found") != 0) { // Skip lost+found
	++n;
	if (n > 2) {
	*is_empty = false;
	return true;
	}
	}
	}
	*is_empty = true;
	return true;
	}

	static uint8_t e4crypt_get_policy_flags(int filenames_encryption_mode) {
	if (filenames_encryption_mode == EXT4_ENCRYPTION_MODE_AES_256_CTS) {
	// Use legacy padding with our original filenames encryption mode.
	return EXT4_POLICY_FLAGS_PAD_4;
	}
	// With a new mode we can use the better padding flag without breaking existing devices: pad
	// filenames with zeroes to the next 16-byte boundary. This is more secure (helps hide the
	// length of filenames) and makes the inputs evenly divisible into blocks which is more
	// efficient for encryption and decryption.
	return EXT4_POLICY_FLAGS_PAD_16;
	}

	static bool e4crypt_policy_set(const char directory, const char policy,
	size_t policy_length,
	int contents_encryption_mode,
	int filenames_encryption_mode) {
	if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
	LOG(ERROR) << "Policy wrong length: " << policy_length;
	return false;
	}
	char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];
	policy_to_hex(policy, policy_hex);

	int fd = open(directory, O_DIRECTORY \| O_NOFOLLOW \| O_CLOEXEC);
	if (fd == -1) {
	PLOG(ERROR) << "Failed to open directory " << directory;
	return false;
	}

	ext4_encryption_policy eep;
	eep.version = 0;
	eep.contents_encryption_mode = contents_encryption_mode;
	eep.filenames_encryption_mode = filenames_encryption_mode;
	eep.flags = e4crypt_get_policy_flags(filenames_encryption_mode);
	memcpy(eep.master_key_descriptor, policy, EXT4_KEY_DESCRIPTOR_SIZE);
	if (ioctl(fd, EXT4_IOC_SET_ENCRYPTION_POLICY, &eep)) {
	PLOG(ERROR) << "Failed to set encryption policy for " << directory << " to " << policy_hex
	<< " modes " << contents_encryption_mode << "/" << filenames_encryption_mode;
	close(fd);
	return false;
	}
	close(fd);

	LOG(INFO) << "Policy for " << directory << " set to " << policy_hex
	<< " modes " << contents_encryption_mode << "/" << filenames_encryption_mode;
	return true;
	}

	static bool e4crypt_policy_get(const char directory, char policy,
	size_t policy_length,
	int contents_encryption_mode,
	int filenames_encryption_mode) {
	if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
	LOG(ERROR) << "Policy wrong length: " << policy_length;
	return false;
	}

	int fd = open(directory, O_DIRECTORY \| O_NOFOLLOW \| O_CLOEXEC);
	if (fd == -1) {
	PLOG(ERROR) << "Failed to open directory " << directory;
	return false;
	}

	ext4_encryption_policy eep;
	memset(&eep, 0, sizeof(ext4_encryption_policy));
	if (ioctl(fd, EXT4_IOC_GET_ENCRYPTION_POLICY, &eep) != 0) {
	PLOG(ERROR) << "Failed to get encryption policy for " << directory;
	close(fd);
	log_ls(directory);
	return false;
	}
	close(fd);

	if ((eep.version != 0)
	\|\| (eep.contents_encryption_mode != contents_encryption_mode)
	\|\| (eep.filenames_encryption_mode != filenames_encryption_mode)
	\|\| (eep.flags !=
	e4crypt_get_policy_flags(filenames_encryption_mode))) {
	LOG(ERROR) << "Failed to find matching encryption policy for " << directory;
	return false;
	}
	memcpy(policy, eep.master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE);

	return true;
	}

	static bool e4crypt_policy_check(const char directory, const char policy,
	size_t policy_length,
	int contents_encryption_mode,
	int filenames_encryption_mode) {
	if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
	LOG(ERROR) << "Policy wrong length: " << policy_length;
	return false;
	}
	char existing_policy[EXT4_KEY_DESCRIPTOR_SIZE];
	if (!e4crypt_policy_get(directory, existing_policy, EXT4_KEY_DESCRIPTOR_SIZE,
	contents_encryption_mode,
	filenames_encryption_mode)) return false;
	char existing_policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];

	policy_to_hex(existing_policy, existing_policy_hex);

	if (memcmp(policy, existing_policy, EXT4_KEY_DESCRIPTOR_SIZE) != 0) {
	char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];
	policy_to_hex(policy, policy_hex);
	LOG(ERROR) << "Found policy " << existing_policy_hex << " at " << directory
	<< " which doesn't match expected value " << policy_hex;
	log_ls(directory);
	return false;
	}
	LOG(INFO) << "Found policy " << existing_policy_hex << " at " << directory
	<< " which matches expected value";
	return true;
	}

	int e4crypt_policy_ensure(const char directory, const char policy,
	size_t policy_length,
	const char *contents_encryption_mode,
	const char *filenames_encryption_mode) {
	int contents_mode = 0;
	int filenames_mode = 0;

	if (!strcmp(contents_encryption_mode, "software") \|\|
	!strcmp(contents_encryption_mode, "aes-256-xts")) {
	contents_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
	} else if (!strcmp(contents_encryption_mode, "ice")) {
	contents_mode = EXT4_ENCRYPTION_MODE_PRIVATE;
	} else {
	LOG(ERROR) << "Invalid file contents encryption mode: "
	<< contents_encryption_mode;
	return -1;
	}

	if (!strcmp(filenames_encryption_mode, "aes-256-cts")) {
	filenames_mode = EXT4_ENCRYPTION_MODE_AES_256_CTS;
	} else if (!strcmp(filenames_encryption_mode, "aes-256-heh")) {
	filenames_mode = EXT4_ENCRYPTION_MODE_AES_256_HEH;
	} else {
	LOG(ERROR) << "Invalid file names encryption mode: "
	<< filenames_encryption_mode;
	return -1;
	}

	bool is_empty;
	if (!is_dir_empty(directory, &is_empty)) return -1;
	if (is_empty) {
	if (!e4crypt_policy_set(directory, policy, policy_length,
	contents_mode, filenames_mode)) return -1;
	} else {
	if (!e4crypt_policy_check(directory, policy, policy_length,
	contents_mode, filenames_mode)) return -1;
	}
	return 0;
	}