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/*
* Copyright (c) 2015 Google, Inc.
*/
#define TAG "ext4_utils"
#include "ext4_crypt_init_extensions.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 <cutils/klog.h>
#include "unencrypted_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
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
// ext4enc:TODO Get value from somewhere sensible
#define EXT4_IOC_SET_ENCRYPTION_POLICY \
_IOR('f', 19, struct ext4_encryption_policy)
/* Validate that all path items are available and accessible. */
static int is_path_valid(const char *path)
{
if (access(path, W_OK)) {
KLOG_ERROR(TAG, "Can't access %s: %s\n",strerror(errno), path);
return 0;
}
return 1;
}
static int is_dir_empty(const char *dirname)
{
int n = 0;
struct dirent *d;
DIR *dir;
dir = opendir(dirname);
while ((d = readdir(dir)) != NULL) {
if (strcmp(d->d_name, "lost+found") == 0) {
// Skip lost+found directory
} else if (++n > 2) {
break;
}
}
closedir(dir);
return n <= 2;
}
int do_policy_set(const char *directory, const char *policy, int policy_length)
{
struct stat st;
ssize_t ret;
if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) {
KLOG_ERROR("Policy wrong length\n");
return -EINVAL;
}
if (!is_path_valid(directory)) {
return -EINVAL;
}
stat(directory, &st);
if (!S_ISDIR(st.st_mode)) {
KLOG_ERROR(TAG, "Can only set policy on a directory (%s)\n", directory);
return -EINVAL;
}
if (!is_dir_empty(directory)) {
KLOG_ERROR(TAG, "Can only set policy on an empty directory (%s)\n",
directory);
return -EINVAL;
}
int fd = open(directory, O_DIRECTORY);
if (fd == -1) {
KLOG_ERROR(TAG, "Failed to open directory (%s)\n", directory);
return -EINVAL;
}
ext4_encryption_policy eep;
eep.version = 0;
eep.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
eep.filenames_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_CTS;
eep.flags = 0;
memcpy(eep.master_key_descriptor, policy, EXT4_KEY_DESCRIPTOR_SIZE);
ret = ioctl(fd, EXT4_IOC_SET_ENCRYPTION_POLICY, &eep);
auto preserve_errno = errno;
close(fd);
if (ret) {
KLOG_ERROR(TAG, "Failed to set encryption policy for %s: %s\n",
directory, strerror(preserve_errno));
return -EINVAL;
}
KLOG_INFO(TAG, "Encryption policy for %s is set to %02x%02x%02x%02x\n",
directory, policy[0], policy[1], policy[2], policy[3]);
return 0;
}
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