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platform_system_vold/cryptfs.c
Ken Sumrall e874407036 Create and use a salt when calling pbkdf2 to encrypt/decrypt the master key. 
In order to prevent rainbow table attacks on decrypting the master key,
create a 16 byte "salt" by reading /dev/urandom.  This is done right after
reading urandom to get the master key for the filesystem.  The salt is
stored 32 bytes after the end of the key (a padding added to help prevent
accidental overwriting of the salt) and the salt is fixed at 16 bytes long.

This change will make existing encrypted filesystems unusable.

Change-Id: I420549d064c61d38aea78eef4d86c88acb265ca3
2011-01-18 22:01:55 -08:00

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/*
* Copyright (C) 2010 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.
*/
/* TO DO:
* 1. Perhaps keep several copies of the encrypted key, in case something
* goes horribly wrong?
*
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <linux/dm-ioctl.h>
#include <libgen.h>
#include <stdlib.h>
#include <sys/param.h>
#include <string.h>
#include <sys/mount.h>
#include <openssl/evp.h>
#include <openssl/sha.h>
#include <errno.h>
#include <sys/reboot.h>
#include "cryptfs.h"
#define LOG_TAG "Cryptfs"
#include "cutils/log.h"
#include "cutils/properties.h"
#define DM_CRYPT_BUF_SIZE 4096
#define DATA_MNT_POINT "/data"
char *me = "cryptfs";
static unsigned char saved_key_sha1[20] = { '\0' };
static int key_sha1_saved = 0;
static void ioctl_init(struct dm_ioctl *io, size_t dataSize, const char *name, unsigned flags)
{
memset(io, 0, dataSize);
io->data_size = dataSize;
io->data_start = sizeof(struct dm_ioctl);
io->version[0] = 4;
io->version[1] = 0;
io->version[2] = 0;
io->flags = flags;
if (name) {
strncpy(io->name, name, sizeof(io->name));
}
}
static unsigned int get_blkdev_size(int fd)
{
unsigned int nr_sec;
if ( (ioctl(fd, BLKGETSIZE, &nr_sec)) == -1) {
nr_sec = 0;
}
return nr_sec;
}
/* key or salt can be NULL, in which case just skip writing that value. Useful to
* update the failed mount count but not change the key.
*/
static int put_crypt_ftr_and_key(char *real_blk_name, struct crypt_mnt_ftr *crypt_ftr,
unsigned char *key, unsigned char *salt)
{
int fd;
unsigned int nr_sec, cnt;
off64_t off;
int rc = -1;
if ( (fd = open(real_blk_name, O_RDWR)) < 0) {
SLOGE("Cannot open real block device %s\n", real_blk_name);
return -1;
}
if ( (nr_sec = get_blkdev_size(fd)) == 0) {
SLOGE("Cannot get size of block device %s\n", real_blk_name);
goto errout;
}
/* If it's an encrypted Android partition, the last 16 Kbytes contain the
* encryption info footer and key, and plenty of bytes to spare for future
* growth.
*/
off = ((off64_t)nr_sec * 512) - CRYPT_FOOTER_OFFSET;
if (lseek64(fd, off, SEEK_SET) == -1) {
SLOGE("Cannot seek to real block device footer\n");
goto errout;
}
if ((cnt = write(fd, crypt_ftr, sizeof(struct crypt_mnt_ftr))) != sizeof(struct crypt_mnt_ftr)) {
SLOGE("Cannot write real block device footer\n");
goto errout;
}
if (key) {
if (crypt_ftr->keysize != 16) {
SLOGE("Keysize of %d bits not supported for real block device %s\n",
crypt_ftr->keysize * 8, real_blk_name);
goto errout;
}
if ( (cnt = write(fd, key, crypt_ftr->keysize)) != crypt_ftr->keysize) {
SLOGE("Cannot write key for real block device %s\n", real_blk_name);
goto errout;
}
}
if (salt) {
/* Compute the offset for start of the crypt footer */
off = ((off64_t)nr_sec * 512) - CRYPT_FOOTER_OFFSET;
/* Add in the length of the footer, key and padding */
off += sizeof(struct crypt_mnt_ftr) + crypt_ftr->keysize + KEY_TO_SALT_PADDING;
if (lseek64(fd, off, SEEK_SET) == -1) {
SLOGE("Cannot seek to real block device salt \n");
goto errout;
}
if ( (cnt = write(fd, salt, SALT_LEN)) != SALT_LEN) {
SLOGE("Cannot write salt for real block device %s\n", real_blk_name);
goto errout;
}
}
/* Success! */
rc = 0;
errout:
close(fd);
return rc;
}
static int get_crypt_ftr_and_key(char *real_blk_name, struct crypt_mnt_ftr *crypt_ftr,
unsigned char *key, unsigned char *salt)
{
int fd;
unsigned int nr_sec, cnt;
off64_t off;
int rc = -1;
if ( (fd = open(real_blk_name, O_RDWR)) < 0) {
SLOGE("Cannot open real block device %s\n", real_blk_name);
return -1;
}
if ( (nr_sec = get_blkdev_size(fd)) == 0) {
SLOGE("Cannot get size of block device %s\n", real_blk_name);
goto errout;
}
/* If it's an encrypted Android partition, the last 16 Kbytes contain the
* encryption info footer and key, and plenty of bytes to spare for future
* growth.
*/
off = ((off64_t)nr_sec * 512) - CRYPT_FOOTER_OFFSET;
if (lseek64(fd, off, SEEK_SET) == -1) {
SLOGE("Cannot seek to real block device footer\n");
goto errout;
}
if ( (cnt = read(fd, crypt_ftr, sizeof(struct crypt_mnt_ftr))) != sizeof(struct crypt_mnt_ftr)) {
SLOGE("Cannot read real block device footer\n");
goto errout;
}
if (crypt_ftr->magic != CRYPT_MNT_MAGIC) {
SLOGE("Bad magic for real block device %s\n", real_blk_name);
goto errout;
}
if (crypt_ftr->major_version != 1) {
SLOGE("Cannot understand major version %d real block device footer\n",
crypt_ftr->major_version);
goto errout;
}
if (crypt_ftr->minor_version != 0) {
SLOGW("Warning: crypto footer minor version %d, expected 0, continuing...\n",
crypt_ftr->minor_version);
}
if (crypt_ftr->ftr_size > sizeof(struct crypt_mnt_ftr)) {
/* the footer size is bigger than we expected.
* Skip to it's stated end so we can read the key.
*/
if (lseek(fd, crypt_ftr->ftr_size - sizeof(struct crypt_mnt_ftr), SEEK_CUR) == -1) {
SLOGE("Cannot seek to start of key\n");
goto errout;
}
}
if (crypt_ftr->keysize != 16) {
SLOGE("Keysize of %d bits not supported for real block device %s\n",
crypt_ftr->keysize * 8, real_blk_name);
goto errout;
}
if ( (cnt = read(fd, key, crypt_ftr->keysize)) != crypt_ftr->keysize) {
SLOGE("Cannot read key for real block device %s\n", real_blk_name);
goto errout;
}
if (lseek64(fd, KEY_TO_SALT_PADDING, SEEK_CUR) == -1) {
SLOGE("Cannot seek to real block device salt\n");
goto errout;
}
if ( (cnt = read(fd, salt, SALT_LEN)) != SALT_LEN) {
SLOGE("Cannot read salt for real block device %s\n", real_blk_name);
goto errout;
}
/* Success! */
rc = 0;
errout:
close(fd);
return rc;
}
/* Convert a binary key of specified length into an ascii hex string equivalent,
* without the leading 0x and with null termination
*/
void convert_key_to_hex_ascii(unsigned char *master_key, unsigned int keysize,
char *master_key_ascii)
{
unsigned int i, a;
unsigned char nibble;
for (i=0, a=0; i<keysize; i++, a+=2) {
/* For each byte, write out two ascii hex digits */
nibble = (master_key[i] >> 4) & 0xf;
master_key_ascii[a] = nibble + (nibble > 9 ? 0x37 : 0x30);
nibble = master_key[i] & 0xf;
master_key_ascii[a+1] = nibble + (nibble > 9 ? 0x37 : 0x30);
}
/* Add the null termination */
master_key_ascii[a] = '\0';
}
static int create_crypto_blk_dev(struct crypt_mnt_ftr *crypt_ftr, unsigned char *master_key,
char *real_blk_name, char *crypto_blk_name)
{
char buffer[DM_CRYPT_BUF_SIZE];
char master_key_ascii[129]; /* Large enough to hold 512 bit key and null */
char *crypt_params;
struct dm_ioctl *io;
struct dm_target_spec *tgt;
unsigned int minor;
int fd;
int retval = -1;
char *name ="datadev"; /* FIX ME: Make me a parameter */
if ((fd = open("/dev/device-mapper", O_RDWR)) < 0 ) {
SLOGE("Cannot open device-mapper\n");
goto errout;
}
io = (struct dm_ioctl *) buffer;
ioctl_init(io, DM_CRYPT_BUF_SIZE, name, 0);
if (ioctl(fd, DM_DEV_CREATE, io)) {
SLOGE("Cannot create dm-crypt device\n");
goto errout;
}
/* Get the device status, in particular, the name of it's device file */
ioctl_init(io, DM_CRYPT_BUF_SIZE, name, 0);
if (ioctl(fd, DM_DEV_STATUS, io)) {
SLOGE("Cannot retrieve dm-crypt device status\n");
goto errout;
}
minor = (io->dev & 0xff) | ((io->dev >> 12) & 0xfff00);
snprintf(crypto_blk_name, MAXPATHLEN, "/dev/block/dm-%u", minor);
/* Load the mapping table for this device */
tgt = (struct dm_target_spec *) &buffer[sizeof(struct dm_ioctl)];
ioctl_init(io, 4096, name, 0);
io->target_count = 1;
tgt->status = 0;
tgt->sector_start = 0;
tgt->length = crypt_ftr->fs_size;
strcpy(tgt->target_type, "crypt");
crypt_params = buffer + sizeof(struct dm_ioctl) + sizeof(struct dm_target_spec);
convert_key_to_hex_ascii(master_key, crypt_ftr->keysize, master_key_ascii);
sprintf(crypt_params, "%s %s 0 %s 0", crypt_ftr->crypto_type_name,
master_key_ascii, real_blk_name);
crypt_params += strlen(crypt_params) + 1;
crypt_params = (char *) (((unsigned long)crypt_params + 7) & ~8); /* Align to an 8 byte boundary */
tgt->next = crypt_params - buffer;
if (ioctl(fd, DM_TABLE_LOAD, io)) {
SLOGE("Cannot load dm-crypt mapping table.\n");
goto errout;
}
/* Resume this device to activate it */
ioctl_init(io, 4096, name, 0);
if (ioctl(fd, DM_DEV_SUSPEND, io)) {
SLOGE("Cannot resume the dm-crypt device\n");
goto errout;
}
/* We made it here with no errors. Woot! */
retval = 0;
errout:
close(fd); /* If fd is <0 from a failed open call, it's safe to just ignore the close error */
return retval;
}
static int delete_crypto_blk_dev(char *crypto_blkdev)
{
int fd;
char buffer[DM_CRYPT_BUF_SIZE];
struct dm_ioctl *io;
char *name ="datadev"; /* FIX ME: Make me a paraameter */
int retval = -1;
if ((fd = open("/dev/device-mapper", O_RDWR)) < 0 ) {
SLOGE("Cannot open device-mapper\n");
goto errout;
}
io = (struct dm_ioctl *) buffer;
ioctl_init(io, DM_CRYPT_BUF_SIZE, name, 0);
if (ioctl(fd, DM_DEV_REMOVE, io)) {
SLOGE("Cannot remove dm-crypt device\n");
goto errout;
}
/* We made it here with no errors. Woot! */
retval = 0;
errout:
close(fd); /* If fd is <0 from a failed open call, it's safe to just ignore the close error */
return retval;
}
#define HASH_COUNT 2000
#define KEY_LEN_BYTES 16
#define IV_LEN_BYTES 16
static void pbkdf2(char *passwd, unsigned char *salt, unsigned char *ikey)
{
/* Turn the password into a key and IV that can decrypt the master key */
PKCS5_PBKDF2_HMAC_SHA1(passwd, strlen(passwd), salt, SALT_LEN,
HASH_COUNT, KEY_LEN_BYTES+IV_LEN_BYTES, ikey);
}
static int encrypt_master_key(char *passwd, unsigned char *salt,
unsigned char *decrypted_master_key,
unsigned char *encrypted_master_key)
{
unsigned char ikey[32+32] = { 0 }; /* Big enough to hold a 256 bit key and 256 bit IV */
EVP_CIPHER_CTX e_ctx;
int encrypted_len, final_len;
/* Turn the password into a key and IV that can decrypt the master key */
pbkdf2(passwd, salt, ikey);
/* Initialize the decryption engine */
if (! EVP_EncryptInit(&e_ctx, EVP_aes_128_cbc(), ikey, ikey+KEY_LEN_BYTES)) {
SLOGE("EVP_EncryptInit failed\n");
return -1;
}
EVP_CIPHER_CTX_set_padding(&e_ctx, 0); /* Turn off padding as our data is block aligned */
/* Encrypt the master key */
if (! EVP_EncryptUpdate(&e_ctx, encrypted_master_key, &encrypted_len,
decrypted_master_key, KEY_LEN_BYTES)) {
SLOGE("EVP_EncryptUpdate failed\n");
return -1;
}
if (! EVP_EncryptFinal(&e_ctx, encrypted_master_key + encrypted_len, &final_len)) {
SLOGE("EVP_EncryptFinal failed\n");
return -1;
}
if (encrypted_len + final_len != KEY_LEN_BYTES) {
SLOGE("EVP_Encryption length check failed with %d, %d bytes\n", encrypted_len, final_len);
return -1;
} else {
return 0;
}
}
static int decrypt_master_key(char *passwd, unsigned char *salt,
unsigned char *encrypted_master_key,
unsigned char *decrypted_master_key)
{
unsigned char ikey[32+32] = { 0 }; /* Big enough to hold a 256 bit key and 256 bit IV */
EVP_CIPHER_CTX d_ctx;
int decrypted_len, final_len;
/* Turn the password into a key and IV that can decrypt the master key */
pbkdf2(passwd, salt, ikey);
/* Initialize the decryption engine */
if (! EVP_DecryptInit(&d_ctx, EVP_aes_128_cbc(), ikey, ikey+KEY_LEN_BYTES)) {
return -1;
}
EVP_CIPHER_CTX_set_padding(&d_ctx, 0); /* Turn off padding as our data is block aligned */
/* Decrypt the master key */
if (! EVP_DecryptUpdate(&d_ctx, decrypted_master_key, &decrypted_len,
encrypted_master_key, KEY_LEN_BYTES)) {
return -1;
}
if (! EVP_DecryptFinal(&d_ctx, decrypted_master_key + decrypted_len, &final_len)) {
return -1;
}
if (decrypted_len + final_len != KEY_LEN_BYTES) {
return -1;
} else {
return 0;
}
}
static int create_encrypted_random_key(char *passwd, unsigned char *master_key, unsigned char *salt)
{
int fd;
unsigned char key_buf[KEY_LEN_BYTES];
EVP_CIPHER_CTX e_ctx;
int encrypted_len, final_len;
/* Get some random bits for a key */
fd = open("/dev/urandom", O_RDONLY);
read(fd, key_buf, sizeof(key_buf));
read(fd, salt, SALT_LEN);
close(fd);
/* Now encrypt it with the password */
return encrypt_master_key(passwd, salt, key_buf, master_key);
}
static int get_orig_mount_parms(char *mount_point, char *fs_type, char *real_blkdev,
unsigned long *mnt_flags, char *fs_options)
{
char mount_point2[32];
char fs_flags[32];
property_get("ro.crypto.fs_type", fs_type, "");
property_get("ro.crypto.fs_real_blkdev", real_blkdev, "");
property_get("ro.crypto.fs_mnt_point", mount_point2, "");
property_get("ro.crypto.fs_options", fs_options, "");
property_get("ro.crypto.fs_flags", fs_flags, "");
*mnt_flags = strtol(fs_flags, 0, 0);
if (strcmp(mount_point, mount_point2)) {
/* Consistency check. These should match. If not, something odd happened. */
return -1;
}
return 0;
}
static int wait_and_unmount(char *mountpoint)
{
int i, rc;
#define WAIT_UNMOUNT_COUNT 20
/* Now umount the tmpfs filesystem */
for (i=0; i<WAIT_UNMOUNT_COUNT; i++) {
if (umount(mountpoint)) {
sleep(1);
i++;
} else {
break;
}
}
if (i < WAIT_UNMOUNT_COUNT) {
SLOGD("unmounting %s succeeded\n", mountpoint);
rc = 0;
} else {
SLOGE("unmounting %s failed\n", mountpoint);
rc = -1;
}
return rc;
}
#define DATA_PREP_TIMEOUT 100
static int prep_data_fs(void)
{
int i;
/* Do the prep of the /data filesystem */
property_set("vold.post_fs_data_done", "0");
property_set("vold.decrypt", "trigger_post_fs_data");
SLOGD("Just triggered post_fs_data\n");
/* Wait a max of 25 seconds, hopefully it takes much less */
for (i=0; i<DATA_PREP_TIMEOUT; i++) {
char p[16];;
property_get("vold.post_fs_data_done", p, "0");
if (*p == '1') {
break;
} else {
usleep(250000);
}
}
if (i == DATA_PREP_TIMEOUT) {
/* Ugh, we failed to prep /data in time. Bail. */
return -1;
} else {
SLOGD("post_fs_data done\n");
return 0;
}
}
int cryptfs_restart(void)
{
char fs_type[32];
char real_blkdev[MAXPATHLEN];
char crypto_blkdev[MAXPATHLEN];
char fs_options[256];
unsigned long mnt_flags;
struct stat statbuf;
int rc = -1, i;
static int restart_successful = 0;
/* Validate that it's OK to call this routine */
if (! key_sha1_saved) {
SLOGE("Encrypted filesystem not validated, aborting");
return -1;
}
if (restart_successful) {
SLOGE("System already restarted with encrypted disk, aborting");
return -1;
}
/* Here is where we shut down the framework. The init scripts
* start all services in one of three classes: core, main or late_start.
* On boot, we start core and main. Now, we stop main, but not core,
* as core includes vold and a few other really important things that
* we need to keep running. Once main has stopped, we should be able
* to umount the tmpfs /data, then mount the encrypted /data.
* We then restart the class main, and also the class late_start.
* At the moment, I've only put a few things in late_start that I know
* are not needed to bring up the framework, and that also cause problems
* with unmounting the tmpfs /data, but I hope to add add more services
* to the late_start class as we optimize this to decrease the delay
* till the user is asked for the password to the filesystem.
*/
/* The init files are setup to stop the class main when vold.decrypt is
* set to trigger_reset_main.
*/
property_set("vold.decrypt", "trigger_reset_main");
SLOGD("Just asked init to shut down class main\n");
/* Now that the framework is shutdown, we should be able to umount()
* the tmpfs filesystem, and mount the real one.
*/
property_get("ro.crypto.fs_crypto_blkdev", crypto_blkdev, "");
if (strlen(crypto_blkdev) == 0) {
SLOGE("fs_crypto_blkdev not set\n");
return -1;
}
if (! get_orig_mount_parms(DATA_MNT_POINT, fs_type, real_blkdev, &mnt_flags, fs_options)) {
SLOGD("Just got orig mount parms\n");
if (! (rc = wait_and_unmount(DATA_MNT_POINT)) ) {
/* If that succeeded, then mount the decrypted filesystem */
mount(crypto_blkdev, DATA_MNT_POINT, fs_type, mnt_flags, fs_options);
/* Create necessary paths on /data */
if (prep_data_fs()) {
return -1;
}
/* startup service classes main and late_start */
property_set("vold.decrypt", "trigger_restart_framework");
SLOGD("Just triggered restart_framework\n");
/* Give it a few moments to get started */
sleep(1);
}
}
if (rc == 0) {
restart_successful = 1;
}
return rc;
}
static int test_mount_encrypted_fs(char *passwd, char *mount_point)
{
struct crypt_mnt_ftr crypt_ftr;
/* Allocate enough space for a 256 bit key, but we may use less */
unsigned char encrypted_master_key[32], decrypted_master_key[32];
unsigned char salt[SALT_LEN];
char crypto_blkdev[MAXPATHLEN];
char real_blkdev[MAXPATHLEN];
char fs_type[32];
char fs_options[256];
char tmp_mount_point[64];
unsigned long mnt_flags;
unsigned int orig_failed_decrypt_count;
char encrypted_state[32];
int rc;
property_get("ro.crypto.state", encrypted_state, "");
if ( key_sha1_saved || strcmp(encrypted_state, "encrypted") ) {
SLOGE("encrypted fs already validated or not running with encryption, aborting");
return -1;
}
if (get_orig_mount_parms(mount_point, fs_type, real_blkdev, &mnt_flags, fs_options)) {
SLOGE("Error reading original mount parms for mount point %s\n", mount_point);
return -1;
}
if (get_crypt_ftr_and_key(real_blkdev, &crypt_ftr, encrypted_master_key, salt)) {
SLOGE("Error getting crypt footer and key\n");
return -1;
}
SLOGD("crypt_ftr->fs_size = %lld\n", crypt_ftr.fs_size);
orig_failed_decrypt_count = crypt_ftr.failed_decrypt_count;
if (! (crypt_ftr.flags & CRYPT_MNT_KEY_UNENCRYPTED) ) {
decrypt_master_key(passwd, salt, encrypted_master_key, decrypted_master_key);
}
if (create_crypto_blk_dev(&crypt_ftr, decrypted_master_key,
real_blkdev, crypto_blkdev)) {
SLOGE("Error creating decrypted block device\n");
return -1;
}
/* If init detects an encrypted filesystme, it writes a file for each such
* encrypted fs into the tmpfs /data filesystem, and then the framework finds those
* files and passes that data to me */
/* Create a tmp mount point to try mounting the decryptd fs
* Since we're here, the mount_point should be a tmpfs filesystem, so make
* a directory in it to test mount the decrypted filesystem.
*/
sprintf(tmp_mount_point, "%s/tmp_mnt", mount_point);
mkdir(tmp_mount_point, 0755);
if ( mount(crypto_blkdev, tmp_mount_point, "ext4", MS_RDONLY, "") ) {
SLOGE("Error temp mounting decrypted block device\n");
delete_crypto_blk_dev(crypto_blkdev);
crypt_ftr.failed_decrypt_count++;
} else {
/* Success, so just umount and we'll mount it properly when we restart
* the framework.
*/
umount(tmp_mount_point);
crypt_ftr.failed_decrypt_count = 0;
}
if (orig_failed_decrypt_count != crypt_ftr.failed_decrypt_count) {
put_crypt_ftr_and_key(real_blkdev, &crypt_ftr, 0, 0);
}
if (crypt_ftr.failed_decrypt_count) {
/* We failed to mount the device, so return an error */
rc = crypt_ftr.failed_decrypt_count;
} else {
/* Woot! Success! Save the name of the crypto block device
* so we can mount it when restarting the framework.
*/
property_set("ro.crypto.fs_crypto_blkdev", crypto_blkdev);
/* Also save a SHA1 of the master key so we can know if we
* successfully decrypted the key when we want to change the
* password on it.
*/
SHA1(decrypted_master_key, KEY_LEN_BYTES, saved_key_sha1);
key_sha1_saved = 1;
rc = 0;
}
return rc;
}
int cryptfs_check_passwd(char *passwd)
{
int rc = -1;
rc = test_mount_encrypted_fs(passwd, DATA_MNT_POINT);
return rc;
}
/* Initialize a crypt_mnt_ftr structure. The keysize is
* defaulted to 16 bytes, and the filesystem size to 0.
* Presumably, at a minimum, the caller will update the
* filesystem size and crypto_type_name after calling this function.
*/
static void cryptfs_init_crypt_mnt_ftr(struct crypt_mnt_ftr *ftr)
{
ftr->magic = CRYPT_MNT_MAGIC;
ftr->major_version = 1;
ftr->minor_version = 0;
ftr->ftr_size = sizeof(struct crypt_mnt_ftr);
ftr->flags = 0;
ftr->keysize = 16;
ftr->spare1 = 0;
ftr->fs_size = 0;
ftr->failed_decrypt_count = 0;
ftr->crypto_type_name[0] = '\0';
}
static int cryptfs_enable_wipe(char *crypto_blkdev, off64_t size)
{
char cmdline[256];
int rc = -1;
snprintf(cmdline, sizeof(cmdline), "/system/bin/make_ext4fs -a /data -l %lld %s",
size * 512, crypto_blkdev);
SLOGI("Making empty filesystem with command %s\n", cmdline);
if (system(cmdline)) {
SLOGE("Error creating empty filesystem on %s\n", crypto_blkdev);
} else {
SLOGD("Successfully created empty filesystem on %s\n", crypto_blkdev);
rc = 0;
}
return rc;
}
static inline int unix_read(int fd, void* buff, int len)
{
int ret;
do { ret = read(fd, buff, len); } while (ret < 0 && errno == EINTR);
return ret;
}
static inline int unix_write(int fd, const void* buff, int len)
{
int ret;
do { ret = write(fd, buff, len); } while (ret < 0 && errno == EINTR);
return ret;
}
#define CRYPT_INPLACE_BUFSIZE 4096
#define CRYPT_SECTORS_PER_BUFSIZE (CRYPT_INPLACE_BUFSIZE / 512)
static int cryptfs_enable_inplace(char *crypto_blkdev, char *real_blkdev, off64_t size)
{
int realfd, cryptofd;
char *buf[CRYPT_INPLACE_BUFSIZE];
int rc = -1;
off64_t numblocks, i, remainder;
off64_t one_pct, cur_pct, new_pct;
if ( (realfd = open(real_blkdev, O_RDONLY)) < 0) {
SLOGE("Error opening real_blkdev %s for inplace encrypt\n", real_blkdev);
return -1;
}
if ( (cryptofd = open(crypto_blkdev, O_WRONLY)) < 0) {
SLOGE("Error opening crypto_blkdev %s for inplace encrypt\n", crypto_blkdev);
close(realfd);
return -1;
}
/* This is pretty much a simple loop of reading 4K, and writing 4K.
* The size passed in is the number of 512 byte sectors in the filesystem.
* So compute the number of whole 4K blocks we should read/write,
* and the remainder.
*/
numblocks = size / CRYPT_SECTORS_PER_BUFSIZE;
remainder = size % CRYPT_SECTORS_PER_BUFSIZE;
SLOGE("Encrypting filesystem in place...");
one_pct = numblocks / 100;
cur_pct = 0;
/* process the majority of the filesystem in blocks */
for (i=0; i<numblocks; i++) {
new_pct = i / one_pct;
if (new_pct > cur_pct) {
char buf[8];
cur_pct = new_pct;
snprintf(buf, sizeof(buf), "%lld", cur_pct);
property_set("vold.encrypt_progress", buf);
}
if (unix_read(realfd, buf, CRYPT_INPLACE_BUFSIZE) <= 0) {
SLOGE("Error reading real_blkdev %s for inplace encrypt\n", crypto_blkdev);
goto errout;
}
if (unix_write(cryptofd, buf, CRYPT_INPLACE_BUFSIZE) <= 0) {
SLOGE("Error writing crypto_blkdev %s for inplace encrypt\n", crypto_blkdev);
goto errout;
}
}
/* Do any remaining sectors */
for (i=0; i<remainder; i++) {
if (unix_read(realfd, buf, 512) <= 0) {
SLOGE("Error reading rival sectors from real_blkdev %s for inplace encrypt\n", crypto_blkdev);
goto errout;
}
if (unix_write(cryptofd, buf, 512) <= 0) {
SLOGE("Error writing final sectors to crypto_blkdev %s for inplace encrypt\n", crypto_blkdev);
goto errout;
}
}
property_set("vold.encrypt_progress", "100");
rc = 0;
errout:
close(realfd);
close(cryptofd);
return rc;
}
#define CRYPTO_ENABLE_WIPE 1
#define CRYPTO_ENABLE_INPLACE 2
#define FRAMEWORK_BOOT_WAIT 60
int cryptfs_enable(char *howarg, char *passwd)
{
int how = 0;
char crypto_blkdev[MAXPATHLEN], real_blkdev[MAXPATHLEN];
char fs_type[32], fs_options[256], mount_point[32];
unsigned long mnt_flags, nr_sec;
unsigned char master_key[16], decrypted_master_key[16];
unsigned char salt[SALT_LEN];
int rc=-1, fd, i;
struct crypt_mnt_ftr crypt_ftr;
char tmpfs_options[80];
char encrypted_state[32];
property_get("ro.crypto.state", encrypted_state, "");
if (strcmp(encrypted_state, "unencrypted")) {
SLOGE("Device is already running encrypted, aborting");
return -1;
}
if (!strcmp(howarg, "wipe")) {
how = CRYPTO_ENABLE_WIPE;
} else if (! strcmp(howarg, "inplace")) {
how = CRYPTO_ENABLE_INPLACE;
} else {
/* Shouldn't happen, as CommandListener vets the args */
return -1;
}
get_orig_mount_parms(mount_point, fs_type, real_blkdev, &mnt_flags, fs_options);
/* The init files are setup to stop the class main and late start when
* vold sets trigger_shutdown_framework.
*/
property_set("vold.decrypt", "trigger_shutdown_framework");
SLOGD("Just asked init to shut down class main\n");
if (wait_and_unmount("/mnt/sdcard")) {
return -1;
}
/* Now unmount the /data partition. */
if (wait_and_unmount(DATA_MNT_POINT)) {
return -1;
}
/* Do extra work for a better UX when doing the long inplace encryption */
if (how == CRYPTO_ENABLE_INPLACE) {
/* Now that /data is unmounted, we need to mount a tmpfs
* /data, set a property saying we're doing inplace encryption,
* and restart the framework.
*/
property_get("ro.crypto.tmpfs_options", tmpfs_options, "");
if (mount("tmpfs", DATA_MNT_POINT, "tmpfs", MS_NOATIME | MS_NOSUID | MS_NODEV,
tmpfs_options) < 0) {
return -1;
}
/* Tells the framework that inplace encryption is starting */
property_set("vold.encrypt_progress", "0");
/* restart the framework. */
/* Create necessary paths on /data */
if (prep_data_fs()) {
return -1;
}
/* startup service classes main and late_start */
property_set("vold.decrypt", "trigger_restart_min_framework");
SLOGD("Just triggered restart_min_framework\n");
/* OK, the framework is restarted and will soon be showing a
* progress bar. Time to setup an encrypted mapping, and
* either write a new filesystem, or encrypt in place updating
* the progress bar as we work.
*/
}
/* Start the actual work of making an encrypted filesystem */
fd = open(real_blkdev, O_RDONLY);
if ( (nr_sec = get_blkdev_size(fd)) == 0) {
SLOGE("Cannot get size of block device %s\n", real_blkdev);
return -1;
}
close(fd);
/* Initialize a crypt_mnt_ftr for the partition */
cryptfs_init_crypt_mnt_ftr(&crypt_ftr);
crypt_ftr.fs_size = nr_sec - (CRYPT_FOOTER_OFFSET / 512);
strcpy((char *)crypt_ftr.crypto_type_name, "aes-cbc-essiv:sha256");
/* Make an encrypted master key */
if (create_encrypted_random_key(passwd, master_key, salt)) {
SLOGE("Cannot create encrypted master key\n");
return -1;
}
/* Write the key to the end of the partition */
put_crypt_ftr_and_key(real_blkdev, &crypt_ftr, master_key, salt);
decrypt_master_key(passwd, salt, master_key, decrypted_master_key);
create_crypto_blk_dev(&crypt_ftr, decrypted_master_key, real_blkdev, crypto_blkdev);
if (how == CRYPTO_ENABLE_WIPE) {
rc = cryptfs_enable_wipe(crypto_blkdev, crypt_ftr.fs_size);
} else if (how == CRYPTO_ENABLE_INPLACE) {
rc = cryptfs_enable_inplace(crypto_blkdev, real_blkdev, crypt_ftr.fs_size);
} else {
/* Shouldn't happen */
SLOGE("cryptfs_enable: internal error, unknown option\n");
return -1;
}
/* Undo the dm-crypt mapping whether we succeed or not */
delete_crypto_blk_dev(crypto_blkdev);
if (! rc) {
/* Success */
sleep(2); /* Give the UI a change to show 100% progress */
sync();
reboot(LINUX_REBOOT_CMD_RESTART);
}
/* Only returns on error */
return rc;
}
int cryptfs_changepw(char *oldpw, char *newpw)
{
struct crypt_mnt_ftr crypt_ftr;
unsigned char encrypted_master_key[32], decrypted_master_key[32];
unsigned char salt[SALT_LEN];
unsigned char new_key_sha1[20];
char real_blkdev[MAXPATHLEN];
/* This is only allowed after we've successfully decrypted the master key */
if (! key_sha1_saved) {
SLOGE("Key not saved, aborting");
return -1;
}
property_get("ro.crypto.fs_real_blkdev", real_blkdev, "");
if (strlen(real_blkdev) == 0) {
SLOGE("Can't find real blkdev");
return -1;
}
/* get key */
if (get_crypt_ftr_and_key(real_blkdev, &crypt_ftr, encrypted_master_key, salt)) {
SLOGE("Error getting crypt footer and key");
return -1;
}
/* decrypt key with old passwd */
decrypt_master_key(oldpw, salt, encrypted_master_key, decrypted_master_key);
/* compute sha1 of decrypted key */
SHA1(decrypted_master_key, KEY_LEN_BYTES, new_key_sha1);
/* If computed sha1 and saved sha1 match, encrypt key with new passwd */
if (! memcmp(saved_key_sha1, new_key_sha1, sizeof(saved_key_sha1))) {
/* they match, it's safe to re-encrypt the key */
encrypt_master_key(newpw, salt, decrypted_master_key, encrypted_master_key);
/* save the key */
put_crypt_ftr_and_key(real_blkdev, &crypt_ftr, encrypted_master_key, 0);
} else {
SLOGE("SHA1 mismatch");
return -1;
}
return 0;
}
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