/*
* 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/wait.h>
#include <sys/stat.h>
#include <ctype.h>
#include <fcntl.h>
#include <inttypes.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 <errno.h>
#include <linux/kdev_t.h>
#include <time.h>
#include "cryptfs.h"
#include "cutils/properties.h"
#include "crypto_scrypt.h"
#include <hardware/keymaster.h>
#ifndef min /* already defined by windows.h */
#define min(a, b) ((a) < (b) ? (a) : (b))
#endif
#define UNUSED __attribute__((unused))
#define UNUSED __attribute__((unused))
#define DM_CRYPT_BUF_SIZE 4096
#define HASH_COUNT 2000
#define KEY_LEN_BYTES 16
#define IV_LEN_BYTES 16
#define KEY_IN_FOOTER "footer"
// "default_password" encoded into hex (d=0x64 etc)
#define DEFAULT_PASSWORD "64656661756c745f70617373776f7264"
#define EXT4_FS 1
#define F2FS_FS 2
#define TABLE_LOAD_RETRIES 10
#define RSA_KEY_SIZE 2048
#define RSA_KEY_SIZE_BYTES (RSA_KEY_SIZE / 8)
#define RSA_EXPONENT 0x10001
#define RETRY_MOUNT_ATTEMPTS 10
#define RETRY_MOUNT_DELAY_SECONDS 1
char *me = "cryptfs";
static unsigned char saved_master_key[KEY_LEN_BYTES];
static char *saved_mount_point;
static int master_key_saved = 0;
static struct crypt_persist_data *persist_data = NULL;
static char key_fname[PROPERTY_VALUE_MAX] = "";
static char real_blkdev[PROPERTY_VALUE_MAX] = "";
static char file_system[PROPERTY_VALUE_MAX] = "";
void set_partition_data(const char* block_device, const char* key_location, const char* fs)
{
strcpy(key_fname, key_location);
strcpy(real_blkdev, block_device);
strcpy(file_system, fs);
}
static int keymaster_init(keymaster_device_t **keymaster_dev)
{
int rc;
const hw_module_t* mod;
rc = hw_get_module_by_class(KEYSTORE_HARDWARE_MODULE_ID, NULL, &mod);
if (rc) {
printf("could not find any keystore module\n");
goto out;
}
rc = keymaster_open(mod, keymaster_dev);
if (rc) {
printf("could not open keymaster device in %s (%s)\n",
KEYSTORE_HARDWARE_MODULE_ID, strerror(-rc));
goto out;
}
return 0;
out:
*keymaster_dev = NULL;
return rc;
}
/* Should we use keymaster? */
static int keymaster_check_compatibility()
{
keymaster_device_t *keymaster_dev = 0;
int rc = 0;
if (keymaster_init(&keymaster_dev)) {
printf("Failed to init keymaster\n");
rc = -1;
goto out;
}
printf("keymaster version is %d\n", keymaster_dev->common.module->module_api_version);
if (keymaster_dev->common.module->module_api_version
< KEYMASTER_MODULE_API_VERSION_0_3) {
rc = 0;
goto out;
}
if (keymaster_dev->flags & KEYMASTER_BLOBS_ARE_STANDALONE) {
rc = 1;
}
out:
keymaster_close(keymaster_dev);
return rc;
}
/* Create a new keymaster key and store it in this footer */
static int keymaster_create_key(struct crypt_mnt_ftr *ftr)
{
uint8_t* key = 0;
keymaster_device_t *keymaster_dev = 0;
if (keymaster_init(&keymaster_dev)) {
printf("Failed to init keymaster\n");
return -1;
}
int rc = 0;
keymaster_rsa_keygen_params_t params;
memset(¶ms, '\0', sizeof(params));
params.public_exponent = RSA_EXPONENT;
params.modulus_size = RSA_KEY_SIZE;
size_t key_size;
if (keymaster_dev->generate_keypair(keymaster_dev, TYPE_RSA, ¶ms,
&key, &key_size)) {
printf("Failed to generate keypair\n");
rc = -1;
goto out;
}
if (key_size > KEYMASTER_BLOB_SIZE) {
printf("Keymaster key too large for crypto footer\n");
rc = -1;
goto out;
}
memcpy(ftr->keymaster_blob, key, key_size);
ftr->keymaster_blob_size = key_size;
out:
keymaster_close(keymaster_dev);
free(key);
return rc;
}
/* This signs the given object using the keymaster key. */
static int keymaster_sign_object(struct crypt_mnt_ftr *ftr,
const unsigned char *object,
const size_t object_size,
unsigned char **signature,
size_t *signature_size)
{
int rc = 0;
keymaster_device_t *keymaster_dev = 0;
if (keymaster_init(&keymaster_dev)) {
printf("Failed to init keymaster\n");
return -1;
}
/* We currently set the digest type to DIGEST_NONE because it's the
* only supported value for keymaster. A similar issue exists with
* PADDING_NONE. Long term both of these should likely change.
*/
keymaster_rsa_sign_params_t params;
params.digest_type = DIGEST_NONE;
params.padding_type = PADDING_NONE;
unsigned char to_sign[RSA_KEY_SIZE_BYTES];
size_t to_sign_size = sizeof(to_sign);
memset(to_sign, 0, RSA_KEY_SIZE_BYTES);
// To sign a message with RSA, the message must satisfy two
// constraints:
//
// 1. The message, when interpreted as a big-endian numeric value, must
// be strictly less than the public modulus of the RSA key. Note
// that because the most significant bit of the public modulus is
// guaranteed to be 1 (else it's an (n-1)-bit key, not an n-bit
// key), an n-bit message with most significant bit 0 always
// satisfies this requirement.
//
// 2. The message must have the same length in bits as the public
// modulus of the RSA key. This requirement isn't mathematically
// necessary, but is necessary to ensure consistency in
// implementations.
switch (ftr->kdf_type) {
case KDF_SCRYPT_KEYMASTER_UNPADDED:
// This is broken: It produces a message which is shorter than
// the public modulus, failing criterion 2.
memcpy(to_sign, object, object_size);
to_sign_size = object_size;
printf("Signing unpadded object\n");
break;
case KDF_SCRYPT_KEYMASTER_BADLY_PADDED:
// This is broken: Since the value of object is uniformly
// distributed, it produces a message that is larger than the
// public modulus with probability 0.25.
memcpy(to_sign, object, min(RSA_KEY_SIZE_BYTES, object_size));
printf("Signing end-padded object\n");
break;
case KDF_SCRYPT_KEYMASTER:
// This ensures the most significant byte of the signed message
// is zero. We could have zero-padded to the left instead, but
// this approach is slightly more robust against changes in
// object size. However, it's still broken (but not unusably
// so) because we really should be using a proper RSA padding
// function, such as OAEP.
//
// TODO(paullawrence): When keymaster 0.4 is available, change
// this to use the padding options it provides.
memcpy(to_sign + 1, object, min(RSA_KEY_SIZE_BYTES - 1, object_size));
printf("Signing safely-padded object\n");
break;
default:
printf("Unknown KDF type %d\n", ftr->kdf_type);
return -1;
}
rc = keymaster_dev->sign_data(keymaster_dev,
¶ms,
ftr->keymaster_blob,
ftr->keymaster_blob_size,
to_sign,
to_sign_size,
signature,
signature_size);
keymaster_close(keymaster_dev);
return rc;
}
/* Store password when userdata is successfully decrypted and mounted.
* Cleared by cryptfs_clear_password
*
* To avoid a double prompt at boot, we need to store the CryptKeeper
* password and pass it to KeyGuard, which uses it to unlock KeyStore.
* Since the entire framework is torn down and rebuilt after encryption,
* we have to use a daemon or similar to store the password. Since vold
* is secured against IPC except from system processes, it seems a reasonable
* place to store this.
*
* password should be cleared once it has been used.
*
* password is aged out after password_max_age_seconds seconds.
*/
static char* password = 0;
static int password_expiry_time = 0;
static const int password_max_age_seconds = 60;
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));
}
}
/**
* Gets the default device scrypt parameters for key derivation time tuning.
* The parameters should lead to about one second derivation time for the
* given device.
*/
static void get_device_scrypt_params(struct crypt_mnt_ftr *ftr) {
const int default_params[] = SCRYPT_DEFAULTS;
int params[] = SCRYPT_DEFAULTS;
char paramstr[PROPERTY_VALUE_MAX];
char *token;
char *saveptr;
int i;
property_get(SCRYPT_PROP, paramstr, "");
if (paramstr[0] != '\0') {
/*
* The token we're looking for should be three integers separated by
* colons (e.g., "12:8:1"). Scan the property to make sure it matches.
*/
for (i = 0, token = strtok_r(paramstr, ":", &saveptr);
token != NULL && i < 3;
i++, token = strtok_r(NULL, ":", &saveptr)) {
char *endptr;
params[i] = strtol(token, &endptr, 10);
/*
* Check that there was a valid number and it's 8-bit. If not,
* break out and the end check will take the default values.
*/
if ((*token == '\0') || (*endptr != '\0') || params[i] < 0 || params[i] > 255) {
break;
}
}
/*
* If there were not enough tokens or a token was malformed (not an
* integer), it will end up here and the default parameters can be
* taken.
*/
if ((i != 3) || (token != NULL)) {
printf("bad scrypt parameters '%s' should be like '12:8:1'; using defaults", paramstr);
memcpy(params, default_params, sizeof(params));
}
}
ftr->N_factor = params[0];
ftr->r_factor = params[1];
ftr->p_factor = params[2];
}
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;
}
static int get_crypt_ftr_info(char **metadata_fname, off64_t *off)
{
static int cached_data = 0;
static off64_t cached_off = 0;
static char cached_metadata_fname[PROPERTY_VALUE_MAX] = "";
int fd;
unsigned int nr_sec;
int rc = -1;
if (!cached_data) {
printf("get_crypt_ftr_info crypto key location: '%s'\n", key_fname);
if (!strcmp(key_fname, KEY_IN_FOOTER)) {
if ( (fd = open(real_blkdev, O_RDWR)) < 0) {
printf("Cannot open real block device %s\n", real_blkdev);
return -1;
}
if ((nr_sec = get_blkdev_size(fd))) {
/* 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.
*/
strlcpy(cached_metadata_fname, real_blkdev, sizeof(cached_metadata_fname));
cached_off = ((off64_t)nr_sec * 512) - CRYPT_FOOTER_OFFSET;
cached_data = 1;
} else {
printf("Cannot get size of block device %s\n", real_blkdev);
}
close(fd);
} else {
strlcpy(cached_metadata_fname, key_fname, sizeof(cached_metadata_fname));
cached_off = 0;
cached_data = 1;
}
}
if (cached_data) {
if (metadata_fname) {
*metadata_fname = cached_metadata_fname;
}
if (off) {
*off = cached_off;
}
rc = 0;
}
return rc;
}
static inline int unix_read(int fd, void* buff, int len)
{
return TEMP_FAILURE_RETRY(read(fd, buff, len));
}
static inline int unix_write(int fd, const void* buff, int len)
{
return TEMP_FAILURE_RETRY(write(fd, buff, len));
}
static void init_empty_persist_data(struct crypt_persist_data *pdata, int len)
{
memset(pdata, 0, len);
pdata->persist_magic = PERSIST_DATA_MAGIC;
pdata->persist_valid_entries = 0;
}
static int get_crypt_ftr_and_key(struct crypt_mnt_ftr *crypt_ftr)
{
int fd;
unsigned int nr_sec, cnt;
off64_t starting_off;
int rc = -1;
char *fname = NULL;
struct stat statbuf;
if (get_crypt_ftr_info(&fname, &starting_off)) {
printf("Unable to get crypt_ftr_info\n");
return -1;
}
if (fname[0] != '/') {
printf("Unexpected value for crypto key location\n");
return -1;
}
if ( (fd = open(fname, O_RDWR)) < 0) {
printf("Cannot open footer file %s for get\n", fname);
return -1;
}
/* Make sure it's 16 Kbytes in length */
fstat(fd, &statbuf);
if (S_ISREG(statbuf.st_mode) && (statbuf.st_size != 0x4000)) {
printf("footer file %s is not the expected size!\n", fname);
goto errout;
}
/* Seek to the start of the crypt footer */
if (lseek64(fd, starting_off, SEEK_SET) == -1) {
printf("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)) {
printf("Cannot read real block device footer\n");
goto errout;
}
if (crypt_ftr->magic != CRYPT_MNT_MAGIC) {
printf("Bad magic for real block device %s\n", fname);
goto errout;
}
if (crypt_ftr->major_version != CURRENT_MAJOR_VERSION) {
printf("Cannot understand major version %d real block device footer; expected %d\n",
crypt_ftr->major_version, CURRENT_MAJOR_VERSION);
goto errout;
}
if (crypt_ftr->minor_version > CURRENT_MINOR_VERSION) {
printf("Warning: crypto footer minor version %d, expected <= %d, continuing...\n",
crypt_ftr->minor_version, CURRENT_MINOR_VERSION);
}
/* If this is a verion 1.0 crypt_ftr, make it a 1.1 crypt footer, and update the
* copy on disk before returning.
*/
/*if (crypt_ftr->minor_version < CURRENT_MINOR_VERSION) {
upgrade_crypt_ftr(fd, crypt_ftr, starting_off);
}*/
/* Success! */
rc = 0;
errout:
close(fd);
return rc;
}
static int hexdigit (char c)
{
if (c >= '0' && c <= '9') return c - '0';
c = tolower(c);
if (c >= 'a' && c <= 'f') return c - 'a' + 10;
return -1;
}
static unsigned char* convert_hex_ascii_to_key(const char* master_key_ascii,
unsigned int* out_keysize)
{
unsigned int i;
*out_keysize = 0;
size_t size = strlen (master_key_ascii);
if (size % 2) {
printf("Trying to convert ascii string of odd length");
return NULL;
}
unsigned char* master_key = (unsigned char*) malloc(size / 2);
if (master_key == 0) {
printf("Cannot allocate");
return NULL;
}
for (i = 0; i < size; i += 2) {
int high_nibble = hexdigit (master_key_ascii[i]);
int low_nibble = hexdigit (master_key_ascii[i + 1]);
if(high_nibble < 0 || low_nibble < 0) {
printf("Invalid hex string");
free (master_key);
return NULL;
}
master_key[*out_keysize] = high_nibble * 16 + low_nibble;
(*out_keysize)++;
}
return master_key;
}
/* Convert a binary key of specified length into an ascii hex string equivalent,
* without the leading 0x and with null termination
*/
static 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 load_crypto_mapping_table(struct crypt_mnt_ftr *crypt_ftr, unsigned char *master_key,
char *real_blk_name, const char *name, int fd,
char *extra_params)
{
char buffer[DM_CRYPT_BUF_SIZE];
struct dm_ioctl *io;
struct dm_target_spec *tgt;
char *crypt_params;
char master_key_ascii[129]; /* Large enough to hold 512 bit key and null */
int i;
io = (struct dm_ioctl *) buffer;
/* Load the mapping table for this device */
tgt = (struct dm_target_spec *) &buffer[sizeof(struct dm_ioctl)];
ioctl_init(io, DM_CRYPT_BUF_SIZE, 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 %s", crypt_ftr->crypto_type_name,
master_key_ascii, real_blk_name, extra_params);
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;
for (i = 0; i < TABLE_LOAD_RETRIES; i++) {
if (! ioctl(fd, DM_TABLE_LOAD, io)) {
break;
}
usleep(500000);
}
if (i == TABLE_LOAD_RETRIES) {
/* We failed to load the table, return an error */
return -1;
} else {
return i + 1;
}
}
static int get_dm_crypt_version(int fd, const char *name, int *version)
{
char buffer[DM_CRYPT_BUF_SIZE];
struct dm_ioctl *io;
struct dm_target_versions *v;
int i;
io = (struct dm_ioctl *) buffer;
ioctl_init(io, DM_CRYPT_BUF_SIZE, name, 0);
if (ioctl(fd, DM_LIST_VERSIONS, io)) {
return -1;
}
/* Iterate over the returned versions, looking for name of "crypt".
* When found, get and return the version.
*/
v = (struct dm_target_versions *) &buffer[sizeof(struct dm_ioctl)];
while (v->next) {
if (! strcmp(v->name, "crypt")) {
/* We found the crypt driver, return the version, and get out */
version[0] = v->version[0];
version[1] = v->version[1];
version[2] = v->version[2];
return 0;
}
v = (struct dm_target_versions *)(((char *)v) + v->next);
}
return -1;
}
static int create_crypto_blk_dev(struct crypt_mnt_ftr *crypt_ftr, unsigned char *master_key,
char *real_blk_name, char *crypto_blk_name, const char *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 i;
int retval = -1;
int version[3];
char *extra_params;
int load_count;
if ((fd = open("/dev/device-mapper", O_RDWR)) < 0 ) {
printf("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)) {
printf("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)) {
printf("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);
extra_params = "";
if (! get_dm_crypt_version(fd, name, version)) {
/* Support for allow_discards was added in version 1.11.0 */
if ((version[0] >= 2) ||
((version[0] == 1) && (version[1] >= 11))) {
extra_params = "1 allow_discards";
printf("Enabling support for allow_discards in dmcrypt.\n");
}
}
load_count = load_crypto_mapping_table(crypt_ftr, master_key, real_blk_name, name,
fd, extra_params);
if (load_count < 0) {
printf("Cannot load dm-crypt mapping table.\n");
goto errout;
} else if (load_count > 1) {
printf("Took %d tries to load dmcrypt table.\n", load_count);
}
/* Resume this device to activate it */
ioctl_init(io, DM_CRYPT_BUF_SIZE, name, 0);
if (ioctl(fd, DM_DEV_SUSPEND, io)) {
printf("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 *name)
{
int fd;
char buffer[DM_CRYPT_BUF_SIZE];
struct dm_ioctl *io;
int retval = -1;
if ((fd = open("/dev/device-mapper", O_RDWR)) < 0 ) {
printf("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)) {
printf("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;
}
static int pbkdf2(const char *passwd, const unsigned char *salt,
unsigned char *ikey, void *params UNUSED)
{
printf("Using pbkdf2 for cryptfs KDF");
/* Turn the password into a key and IV that can decrypt the master key */
unsigned int keysize;
char* master_key = (char*)convert_hex_ascii_to_key(passwd, &keysize);
if (!master_key) return -1;
PKCS5_PBKDF2_HMAC_SHA1(master_key, keysize, salt, SALT_LEN,
HASH_COUNT, KEY_LEN_BYTES+IV_LEN_BYTES, ikey);
memset(master_key, 0, keysize);
free (master_key);
return 0;
}
static int scrypt(const char *passwd, const unsigned char *salt,
unsigned char *ikey, void *params)
{
printf("Using scrypt for cryptfs KDF\n");
struct crypt_mnt_ftr *ftr = (struct crypt_mnt_ftr *) params;
int N = 1 << ftr->N_factor;
int r = 1 << ftr->r_factor;
int p = 1 << ftr->p_factor;
/* Turn the password into a key and IV that can decrypt the master key */
unsigned int keysize;
unsigned char* master_key = convert_hex_ascii_to_key(passwd, &keysize);
if (!master_key) return -1;
crypto_scrypt(master_key, keysize, salt, SALT_LEN, N, r, p, ikey,
KEY_LEN_BYTES + IV_LEN_BYTES);
memset(master_key, 0, keysize);
free (master_key);
return 0;
}
static int scrypt_keymaster(const char *passwd, const unsigned char *salt,
unsigned char *ikey, void *params)
{
printf("Using scrypt with keymaster for cryptfs KDF\n");
int rc;
unsigned int key_size;
size_t signature_size;
unsigned char* signature;
struct crypt_mnt_ftr *ftr = (struct crypt_mnt_ftr *) params;
int N = 1 << ftr->N_factor;
int r = 1 << ftr->r_factor;
int p = 1 << ftr->p_factor;
unsigned char* master_key = convert_hex_ascii_to_key(passwd, &key_size);
if (!master_key) {
printf("Failed to convert passwd from hex\n");
return -1;
}
rc = crypto_scrypt(master_key, key_size, salt, SALT_LEN,
N, r, p, ikey, KEY_LEN_BYTES + IV_LEN_BYTES);
memset(master_key, 0, key_size);
free(master_key);
if (rc) {
printf("scrypt failed\n");
return -1;
}
if (keymaster_sign_object(ftr, ikey, KEY_LEN_BYTES + IV_LEN_BYTES,
&signature, &signature_size)) {
printf("Signing failed\n");
return -1;
}
rc = crypto_scrypt(signature, signature_size, salt, SALT_LEN,
N, r, p, ikey, KEY_LEN_BYTES + IV_LEN_BYTES);
free(signature);
if (rc) {
printf("scrypt failed\n");
return -1;
}
return 0;
}
static int encrypt_master_key(const char *passwd, const unsigned char *salt,
const unsigned char *decrypted_master_key,
unsigned char *encrypted_master_key,
struct crypt_mnt_ftr *crypt_ftr)
{
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;
int rc = 0;
/* Turn the password into an intermediate key and IV that can decrypt the master key */
get_device_scrypt_params(crypt_ftr);
switch (crypt_ftr->kdf_type) {
case KDF_SCRYPT_KEYMASTER_UNPADDED:
case KDF_SCRYPT_KEYMASTER_BADLY_PADDED:
case KDF_SCRYPT_KEYMASTER:
if (keymaster_create_key(crypt_ftr)) {
printf("keymaster_create_key failed");
return -1;
}
if (scrypt_keymaster(passwd, salt, ikey, crypt_ftr)) {
printf("scrypt failed");
return -1;
}
break;
case KDF_SCRYPT:
if (scrypt(passwd, salt, ikey, crypt_ftr)) {
printf("scrypt failed");
return -1;
}
break;
default:
printf("Invalid kdf_type");
return -1;
}
/* Initialize the decryption engine */
if (! EVP_EncryptInit(&e_ctx, EVP_aes_128_cbc(), ikey, ikey+KEY_LEN_BYTES)) {
printf("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)) {
printf("EVP_EncryptUpdate failed\n");
return -1;
}
if (! EVP_EncryptFinal(&e_ctx, encrypted_master_key + encrypted_len, &final_len)) {
printf("EVP_EncryptFinal failed\n");
return -1;
}
if (encrypted_len + final_len != KEY_LEN_BYTES) {
printf("EVP_Encryption length check failed with %d, %d bytes\n", encrypted_len, final_len);
return -1;
}
/* Store the scrypt of the intermediate key, so we can validate if it's a
password error or mount error when things go wrong.
Note there's no need to check for errors, since if this is incorrect, we
simply won't wipe userdata, which is the correct default behavior
*/
int N = 1 << crypt_ftr->N_factor;
int r = 1 << crypt_ftr->r_factor;
int p = 1 << crypt_ftr->p_factor;
rc = crypto_scrypt(ikey, KEY_LEN_BYTES,
crypt_ftr->salt, sizeof(crypt_ftr->salt), N, r, p,
crypt_ftr->scrypted_intermediate_key,
sizeof(crypt_ftr->scrypted_intermediate_key));
if (rc) {
printf("encrypt_master_key: crypto_scrypt failed");
}
return 0;
}
static int decrypt_master_key_aux(char *passwd, unsigned char *salt,
unsigned char *encrypted_master_key,
unsigned char *decrypted_master_key,
kdf_func kdf, void *kdf_params,
unsigned char** intermediate_key,
size_t* intermediate_key_size)
{
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 an intermediate key and IV that can decrypt the
master key */
if (kdf(passwd, salt, ikey, kdf_params)) {
printf("kdf failed");
return -1;
}
/* 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;
}
/* Copy intermediate key if needed by params */
if (intermediate_key && intermediate_key_size) {
*intermediate_key = (unsigned char*) malloc(KEY_LEN_BYTES);
if (intermediate_key) {
memcpy(*intermediate_key, ikey, KEY_LEN_BYTES);
*intermediate_key_size = KEY_LEN_BYTES;
}
}
return 0;
}
static void get_kdf_func(struct crypt_mnt_ftr *ftr, kdf_func *kdf, void** kdf_params)
{
if (ftr->kdf_type == KDF_SCRYPT_KEYMASTER_UNPADDED ||
ftr->kdf_type == KDF_SCRYPT_KEYMASTER_BADLY_PADDED ||
ftr->kdf_type == KDF_SCRYPT_KEYMASTER) {
*kdf = scrypt_keymaster;
*kdf_params = ftr;
} else if (ftr->kdf_type == KDF_SCRYPT) {
*kdf = scrypt;
*kdf_params = ftr;
} else {
*kdf = pbkdf2;
*kdf_params = NULL;
}
}
static int decrypt_master_key(char *passwd, unsigned char *decrypted_master_key,
struct crypt_mnt_ftr *crypt_ftr,
unsigned char** intermediate_key,
size_t* intermediate_key_size)
{
kdf_func kdf;
void *kdf_params;
int ret;
get_kdf_func(crypt_ftr, &kdf, &kdf_params);
ret = decrypt_master_key_aux(passwd, crypt_ftr->salt, crypt_ftr->master_key,
decrypted_master_key, kdf, kdf_params,
intermediate_key, intermediate_key_size);
if (ret != 0) {
printf("failure decrypting master key");
}
return ret;
}
static int test_mount_encrypted_fs(struct crypt_mnt_ftr* crypt_ftr,
char *passwd, char *mount_point, char *label)
{
/* Allocate enough space for a 256 bit key, but we may use less */
unsigned char decrypted_master_key[32];
char crypto_blkdev[MAXPATHLEN];
char tmp_mount_point[64];
unsigned int orig_failed_decrypt_count;
int rc;
kdf_func kdf;
void *kdf_params;
int use_keymaster = 0;
int upgrade = 0;
unsigned char* intermediate_key = 0;
size_t intermediate_key_size = 0;
printf("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) ) {
if (decrypt_master_key(passwd, decrypted_master_key, crypt_ftr,
&intermediate_key, &intermediate_key_size)) {
printf("Failed to decrypt master key\n");
rc = -1;
goto errout;
}
}
// Create crypto block device - all (non fatal) code paths
// need it
if (create_crypto_blk_dev(crypt_ftr, decrypted_master_key,
real_blkdev, crypto_blkdev, label)) {
printf("Error creating decrypted block device\n");
rc = -1;
goto errout;
}
/* Work out if the problem is the password or the data */
unsigned char scrypted_intermediate_key[sizeof(crypt_ftr->
scrypted_intermediate_key)];
int N = 1 << crypt_ftr->N_factor;
int r = 1 << crypt_ftr->r_factor;
int p = 1 << crypt_ftr->p_factor;
rc = crypto_scrypt(intermediate_key, intermediate_key_size,
crypt_ftr->salt, sizeof(crypt_ftr->salt),
N, r, p, scrypted_intermediate_key,
sizeof(scrypted_intermediate_key));
// Does the key match the crypto footer?
if (rc == 0 && memcmp(scrypted_intermediate_key,
crypt_ftr->scrypted_intermediate_key,
sizeof(scrypted_intermediate_key)) == 0) {
printf("Password matches\n");
rc = 0;
} else {
/* Try mounting the file system anyway, just in case the problem's with
* the footer, not the key. */
sprintf(tmp_mount_point, "%s/tmp_mnt", mount_point);
mkdir(tmp_mount_point, 0755);
if (mount(crypto_blkdev, tmp_mount_point, file_system, NULL, NULL) != 0) {
printf("Error temp mounting decrypted block device '%s'\n", crypto_blkdev);
delete_crypto_blk_dev(label);
rc = ++crypt_ftr->failed_decrypt_count;
//put_crypt_ftr_and_key(crypt_ftr); // Do not penalize for attempting to decrypt in recovery
} else {
/* Success! */
printf("Password did not match but decrypted drive mounted - continue\n");
umount(tmp_mount_point);
rc = 0;
}
}
if (rc == 0) {
/*crypt_ftr->failed_decrypt_count = 0;
if (orig_failed_decrypt_count != 0) {
put_crypt_ftr_and_key(crypt_ftr);
}*/
/* 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 the master key so we can reencrypted the key
* the key when we want to change the password on it. */
/*memcpy(saved_master_key, decrypted_master_key, KEY_LEN_BYTES);
saved_mount_point = strdup(mount_point);
master_key_saved = 1;
printf("%s(): Master key saved\n", __FUNCTION__);*/
rc = 0;
// Upgrade if we're not using the latest KDF.
/*use_keymaster = keymaster_check_compatibility();
if (crypt_ftr->kdf_type == KDF_SCRYPT_KEYMASTER) {
// Don't allow downgrade
} else if (use_keymaster == 1 && crypt_ftr->kdf_type != KDF_SCRYPT_KEYMASTER) {
crypt_ftr->kdf_type = KDF_SCRYPT_KEYMASTER;
upgrade = 1;
} else if (use_keymaster == 0 && crypt_ftr->kdf_type != KDF_SCRYPT) {
crypt_ftr->kdf_type = KDF_SCRYPT;
upgrade = 1;
}
if (upgrade) {
rc = encrypt_master_key(passwd, crypt_ftr->salt, saved_master_key,
crypt_ftr->master_key, crypt_ftr);
if (!rc) {
rc = put_crypt_ftr_and_key(crypt_ftr);
}
printf("Key Derivation Function upgrade: rc=%d\n", rc);
// Do not fail even if upgrade failed - machine is bootable
// Note that if this code is ever hit, there is a *serious* problem
// since KDFs should never fail. You *must* fix the kdf before
// proceeding!
if (rc) {
printf("Upgrade failed with error %d,"
" but continuing with previous state\n",
rc);
rc = 0;
}
}*/
}
errout:
if (intermediate_key) {
memset(intermediate_key, 0, intermediate_key_size);
free(intermediate_key);
}
return rc;
}
/* Called by vold when it wants to undo the crypto mapping of a volume it
* manages. This is usually in response to a factory reset, when we want
* to undo the crypto mapping so the volume is formatted in the clear.
*/
int cryptfs_revert_volume(const char *label)
{
return delete_crypto_blk_dev((char *)label);
}
int check_unmounted_and_get_ftr(struct crypt_mnt_ftr* crypt_ftr)
{
char encrypted_state[PROPERTY_VALUE_MAX];
property_get("ro.crypto.state", encrypted_state, "");
if ( master_key_saved || strcmp(encrypted_state, "encrypted") ) {
printf("encrypted fs already validated or not running with encryption,"
" aborting\n");
//return -1;
}
if (get_crypt_ftr_and_key(crypt_ftr)) {
printf("Error getting crypt footer and key\n");
return -1;
}
return 0;
}
/*
* TODO - transition patterns to new format in calling code
* and remove this vile hack, and the use of hex in
* the password passing code.
*
* Patterns are passed in zero based (i.e. the top left dot
* is represented by zero, the top middle one etc), but we want
* to store them '1' based.
* This is to allow us to migrate the calling code to use this
* convention. It also solves a nasty problem whereby scrypt ignores
* trailing zeros, so patterns ending at the top left could be
* truncated, and similarly, you could add the top left to any
* pattern and still match.
* adjust_passwd is a hack function that returns the alternate representation
* if the password appears to be a pattern (hex numbers all less than 09)
* If it succeeds we need to try both, and in particular try the alternate
* first. If the original matches, then we need to update the footer
* with the alternate.
* All code that accepts passwords must adjust them first. Since
* cryptfs_check_passwd is always the first function called after a migration
* (and indeed on any boot) we only need to do the double try in this
* function.
*/
char* adjust_passwd(const char* passwd)
{
size_t index, length;
if (!passwd) {
return 0;
}
// Check even length. Hex encoded passwords are always
// an even length, since each character encodes to two characters.
length = strlen(passwd);
if (length % 2) {
printf("Password not correctly hex encoded.");
return 0;
}
// Check password is old-style pattern - a collection of hex
// encoded bytes less than 9 (00 through 08)
for (index = 0; index < length; index +=2) {
if (passwd[index] != '0'
|| passwd[index + 1] < '0' || passwd[index + 1] > '8') {
return 0;
}
}
// Allocate room for adjusted passwd and null terminate
char* adjusted = malloc(length + 1);
adjusted[length] = 0;
// Add 0x31 ('1') to each character
for (index = 0; index < length; index += 2) {
// output is 31 through 39 so set first byte to three, second to src + 1
adjusted[index] = '3';
adjusted[index + 1] = passwd[index + 1] + 1;
}
return adjusted;
}
/*
* Passwords in L get passed from Android to cryptfs in hex, so a '1'
* gets converted to '31' where 31 is 0x31 which is the ascii character
* code in hex of the character '1'. This function will convert the
* regular character codes to their hexadecimal representation to make
* decrypt work properly with Android 5.0 lollipop decryption.
*/
char* hexadj_passwd(const char* passwd)
{
size_t index, length;
char* ptr = passwd;
if (!passwd) {
return 0;
}
length = strlen(passwd);
// Allocate room for hex passwd and null terminate
char* hex = malloc((length * 2) + 1);
hex[length * 2] = 0;
// Convert to hex
for (index = 0; index < length; index++) {
sprintf(hex + (index * 2), "%02X", *ptr);
ptr++;
}
return hex;
}
int cryptfs_check_footer()
{
int rc = -1;
struct crypt_mnt_ftr crypt_ftr;
rc = get_crypt_ftr_and_key(&crypt_ftr);
return rc;
}
int cryptfs_check_passwd(char *passwd)
{
struct crypt_mnt_ftr crypt_ftr;
int rc;
rc = check_unmounted_and_get_ftr(&crypt_ftr);
if (rc)
return rc;
char* adjusted_passwd = adjust_passwd(passwd);
char* hex_passwd = hexadj_passwd(passwd);
if (adjusted_passwd) {
int failed_decrypt_count = crypt_ftr.failed_decrypt_count;
rc = test_mount_encrypted_fs(&crypt_ftr, adjusted_passwd,
DATA_MNT_POINT, "userdata");
// Maybe the original one still works?
if (rc) {
// Don't double count this failure
crypt_ftr.failed_decrypt_count = failed_decrypt_count;
rc = test_mount_encrypted_fs(&crypt_ftr, passwd,
DATA_MNT_POINT, "userdata");
if (!rc) {
// cryptfs_changepw also adjusts so pass original
// Note that adjust_passwd only recognises patterns
// so we can safely use CRYPT_TYPE_PATTERN
printf("TWRP NOT Updating pattern to new format");
//cryptfs_changepw(CRYPT_TYPE_PATTERN, passwd);
} else if (hex_passwd) {
rc = test_mount_encrypted_fs(&crypt_ftr, hex_passwd,
DATA_MNT_POINT, "userdata");
}
}
free(adjusted_passwd);
} else {
rc = test_mount_encrypted_fs(&crypt_ftr, passwd,
DATA_MNT_POINT, "userdata");
if (rc && hex_passwd) {
rc = test_mount_encrypted_fs(&crypt_ftr, hex_passwd,
DATA_MNT_POINT, "userdata");
}
}
if (hex_passwd)
free(hex_passwd);
/*if (rc == 0 && crypt_ftr.crypt_type != CRYPT_TYPE_DEFAULT) {
printf("cryptfs_check_passwd update expiry time?\n");
cryptfs_clear_password();
password = strdup(passwd);
struct timespec now;
clock_gettime(CLOCK_BOOTTIME, &now);
password_expiry_time = now.tv_sec + password_max_age_seconds;
}*/
return rc;
}
int cryptfs_verify_passwd(char *passwd)
{
struct crypt_mnt_ftr crypt_ftr;
/* Allocate enough space for a 256 bit key, but we may use less */
unsigned char decrypted_master_key[32];
char encrypted_state[PROPERTY_VALUE_MAX];
int rc;
property_get("ro.crypto.state", encrypted_state, "");
if (strcmp(encrypted_state, "encrypted") ) {
printf("device not encrypted, aborting");
return -2;
}
if (!master_key_saved) {
printf("encrypted fs not yet mounted, aborting");
return -1;
}
if (!saved_mount_point) {
printf("encrypted fs failed to save mount point, aborting");
return -1;
}
if (get_crypt_ftr_and_key(&crypt_ftr)) {
printf("Error getting crypt footer and key\n");
return -1;
}
if (crypt_ftr.flags & CRYPT_MNT_KEY_UNENCRYPTED) {
/* If the device has no password, then just say the password is valid */
rc = 0;
} else {
char* adjusted_passwd = adjust_passwd(passwd);
if (adjusted_passwd) {
passwd = adjusted_passwd;
}
decrypt_master_key(passwd, decrypted_master_key, &crypt_ftr, 0, 0);
if (!memcmp(decrypted_master_key, saved_master_key, crypt_ftr.keysize)) {
/* They match, the password is correct */
rc = 0;
} else {
/* If incorrect, sleep for a bit to prevent dictionary attacks */
sleep(1);
rc = 1;
}
free(adjusted_passwd);
}
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 int cryptfs_init_crypt_mnt_ftr(struct crypt_mnt_ftr *ftr)
{
off64_t off;
memset(ftr, 0, sizeof(struct crypt_mnt_ftr));
ftr->magic = CRYPT_MNT_MAGIC;
ftr->major_version = CURRENT_MAJOR_VERSION;
ftr->minor_version = CURRENT_MINOR_VERSION;
ftr->ftr_size = sizeof(struct crypt_mnt_ftr);
ftr->keysize = KEY_LEN_BYTES;
switch (keymaster_check_compatibility()) {
case 1:
ftr->kdf_type = KDF_SCRYPT_KEYMASTER;
break;
case 0:
ftr->kdf_type = KDF_SCRYPT;
break;
default:
printf("keymaster_check_compatibility failed");
return -1;
}
get_device_scrypt_params(ftr);
ftr->persist_data_size = CRYPT_PERSIST_DATA_SIZE;
if (get_crypt_ftr_info(NULL, &off) == 0) {
ftr->persist_data_offset[0] = off + CRYPT_FOOTER_TO_PERSIST_OFFSET;
ftr->persist_data_offset[1] = off + CRYPT_FOOTER_TO_PERSIST_OFFSET +
ftr->persist_data_size;
}
return 0;
}
/* Returns type of the password, default, pattern, pin or password.
*/
int cryptfs_get_password_type(void)
{
struct crypt_mnt_ftr crypt_ftr;
if (get_crypt_ftr_and_key(&crypt_ftr)) {
printf("Error getting crypt footer and key\n");
return -1;
}
if (crypt_ftr.flags & CRYPT_INCONSISTENT_STATE) {
return -1;
}
return crypt_ftr.crypt_type;
}
