/*
* 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.
*/
/* TWRP NOTE: Kanged from system/extras/ext4_utils/ext4_crypt.cpp
* because policy_to_hex, e4crypt_policy_set, and e4crypt_policy_get
* are not exposed to be used. There was also a bug in e4crypt_policy_get
* that may or may not be fixed in the user's local repo:
* https://android.googlesource.com/platform/system/extras/+/30b93dd5715abcabd621235733733c0503f9c552
*/
#include "ext4_crypt.h"
#include <dirent.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <asm/ioctl.h>
#include <sys/syscall.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <cutils/properties.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 {
char version;
char contents_encryption_mode;
char filenames_encryption_mode;
char flags;
char 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_PRIVATE 127
static int encryption_mode = EXT4_ENCRYPTION_MODE_PRIVATE;
// 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"
extern "C" 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';
}
extern "C" bool e4crypt_policy_set(const char *directory, const char *policy,
size_t policy_length, int contents_encryption_mode) {
if (contents_encryption_mode == 0)
contents_encryption_mode = encryption_mode;
if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
printf("policy wrong length\n");
LOG(ERROR) << "Policy wrong length: " << policy_length;
return false;
}
int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
if (fd == -1) {
printf("failed to open %s\n", directory);
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 = EXT4_ENCRYPTION_MODE_AES_256_CTS;
eep.flags = 0;
memcpy(eep.master_key_descriptor, policy, EXT4_KEY_DESCRIPTOR_SIZE);
if (ioctl(fd, EXT4_IOC_SET_ENCRYPTION_POLICY, &eep)) {
printf("failed to set policy for '%s' '%s'\n", directory, policy);
PLOG(ERROR) << "Failed to set encryption policy for " << directory;
close(fd);
return false;
}
close(fd);
char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX];
policy_to_hex(policy, policy_hex);
LOG(INFO) << "Policy for " << directory << " set to " << policy_hex;
return true;
}
extern "C" bool e4crypt_policy_get(const char *directory, char *policy,
size_t policy_length, int contents_encryption_mode) {
if (contents_encryption_mode == 0)
contents_encryption_mode = 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);
return false;
}
close(fd);
if ((eep.version != 0)
|| (eep.contents_encryption_mode != contents_encryption_mode)
|| (eep.filenames_encryption_mode != EXT4_ENCRYPTION_MODE_AES_256_CTS)
|| (eep.flags != 0)) {
LOG(ERROR) << "Failed to find matching encryption policy for " << directory;
return false;
}
memcpy(policy, eep.master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE);
return true;
}
extern "C" bool e4crypt_set_mode() {
const char* mode_file = "/data/unencrypted/mode";
struct stat st;
if (stat(mode_file, &st) != 0 || st.st_size <= 0) {
printf("Invalid encryption mode file %s\n", mode_file);
return false;
}
size_t mode_size = st.st_size;
char contents_encryption_mode[mode_size + 1];
memset((void*)contents_encryption_mode, 0, mode_size + 1);
int fd = open(mode_file, O_RDONLY);
if (fd < 0) {
printf("error opening '%s': %s\n", mode_file, strerror(errno));
return false;
}
if (read(fd, contents_encryption_mode, mode_size) != mode_size) {
printf("read error on '%s': %s\n", mode_file, strerror(errno));
close(fd);
return false;
}
close(fd);
if (!strcmp(contents_encryption_mode, "software")) {
encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
} else if (!strcmp(contents_encryption_mode, "ice")) {
encryption_mode = EXT4_ENCRYPTION_MODE_PRIVATE;
} else {
printf("Invalid encryption mode '%s'\n", contents_encryption_mode);
return false;
}
printf("set encryption mode to %i\n", encryption_mode);
return true;
}
