blob: 9ca3ed4fd06921149815444f3e402e82e2f18715 [file] [log] [blame]
/*
* 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 <array>
#include <asm/ioctl.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/fs.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/syscall.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>
#include <fscrypt/fscrypt.h>
#include "fscrypt_policy.h"
static int encryption_mode = FS_ENCRYPTION_MODE_PRIVATE;
bool fscrypt_is_native() {
LOG(ERROR) << "fscrypt_is_native::ro.crypto.type";
char value[PROPERTY_VALUE_MAX];
property_get("ro.crypto.type", value, "none");
return !strcmp(value, "file");
}
extern "C" void bytes_to_hex(const uint8_t *bytes, size_t num_bytes, char *hex) {
for (size_t i = 0; i < num_bytes; i++) {
sprintf(&hex[2 * i], "%02x", bytes[i]);
}
}
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 fscrypt_get_policy_flags(int filenames_encryption_mode) {
if (filenames_encryption_mode == FS_ENCRYPTION_MODE_AES_256_CTS) {
// Use legacy padding with our original filenames encryption mode.
return FS_POLICY_FLAGS_PAD_4;
} else if (filenames_encryption_mode == FS_ENCRYPTION_MODE_ADIANTUM) {
// 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
return (FS_POLICY_FLAGS_PAD_16 | FS_POLICY_FLAG_DIRECT_KEY);
}
// 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 FS_POLICY_FLAGS_PAD_16;
}
extern "C" bool fscrypt_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);
std::string contents_encryption_mode_string = std::string(contents_encryption_mode);
int pos = contents_encryption_mode_string.find(":");
LOG(INFO) << "contents_encryption_mode_string: " << contents_encryption_mode_string.substr(0, pos);
if (contents_encryption_mode_string.substr(0, pos) == "software") {
encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
} else if (contents_encryption_mode_string.substr(0, pos) == "ice") {
encryption_mode = FS_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;
}
#ifdef USE_FSCRYPT_POLICY_V1
extern "C" bool fscrypt_policy_set_struct(const char *directory, const struct fscrypt_policy_v1 *fep) {
#else
extern "C" bool fscrypt_policy_set_struct(const char *directory, const struct fscrypt_policy_v2 *fep) {
#endif
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;
}
if (ioctl(fd, FS_IOC_SET_ENCRYPTION_POLICY, fep)) {
PLOG(ERROR) << "Failed to set encryption policy for " << directory;
close(fd);
return false;
}
close(fd);
return true;
}
#ifdef USE_FSCRYPT_POLICY_V1
extern "C" bool fscrypt_policy_get_struct(const char *directory, struct fscrypt_policy_v1 *fep) {
#else
extern "C" bool fscrypt_policy_get_struct(const char *directory, struct fscrypt_policy_v2 *fep) {
#endif
int fd = open(directory, O_DIRECTORY | O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
if (fd == -1) {
PLOG(ERROR) << "Failed to open directory " << directory;
return false;
}
#ifdef USE_FSCRYPT_POLICY_V1
memset(fep, 0, sizeof(fscrypt_policy_v1));
#else
memset(fep, 0, sizeof(fscrypt_policy_v2));
#endif
struct fscrypt_get_policy_ex_arg ex_policy = {0};
ex_policy.policy_size = sizeof(ex_policy.policy);
if (ioctl(fd, FS_IOC_GET_ENCRYPTION_POLICY_EX, &ex_policy) != 0) {
PLOG(ERROR) << "Failed to get encryption policy for " << directory;
close(fd);
return false;
}
#ifdef USE_FSCRYPT_POLICY_V1
memcpy(fep, &ex_policy.policy.v1, sizeof(ex_policy.policy.v1));
#else
memcpy(fep, &ex_policy.policy.v2, sizeof(ex_policy.policy.v2));
#endif
close(fd);
return true;
}