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// SPDX-License-Identifier: GPL-2.0-or-later
/*
Linux loop encryption enabling module
Copyright (C) 2002 Herbert Valerio Riedel <hvr@gnu.org>
Copyright (C) 2003 Fruhwirth Clemens <clemens@endorphin.org>
*/
#include <linux/module.h>
#include <crypto/skcipher.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/blkdev.h>
#include <linux/scatterlist.h>
#include <linux/uaccess.h>
#include "loop.h"
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("loop blockdevice transferfunction adaptor / CryptoAPI");
MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
#define LOOP_IV_SECTOR_BITS 9
#define LOOP_IV_SECTOR_SIZE (1 << LOOP_IV_SECTOR_BITS)
static int
cryptoloop_init(struct loop_device *lo, const struct loop_info64 *info)
{
int err = -EINVAL;
int cipher_len;
int mode_len;
char cms[LO_NAME_SIZE]; /* cipher-mode string */
char *mode;
char *cmsp = cms; /* c-m string pointer */
struct crypto_sync_skcipher *tfm;
/* encryption breaks for non sector aligned offsets */
if (info->lo_offset % LOOP_IV_SECTOR_SIZE)
goto out;
strncpy(cms, info->lo_crypt_name, LO_NAME_SIZE);
cms[LO_NAME_SIZE - 1] = 0;
cipher_len = strcspn(cmsp, "-");
mode = cmsp + cipher_len;
mode_len = 0;
if (*mode) {
mode++;
mode_len = strcspn(mode, "-");
}
if (!mode_len) {
mode = "cbc";
mode_len = 3;
}
if (cipher_len + mode_len + 3 > LO_NAME_SIZE)
return -EINVAL;
memmove(cms, mode, mode_len);
cmsp = cms + mode_len;
*cmsp++ = '(';
memcpy(cmsp, info->lo_crypt_name, cipher_len);
cmsp += cipher_len;
*cmsp++ = ')';
*cmsp = 0;
tfm = crypto_alloc_sync_skcipher(cms, 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
err = crypto_sync_skcipher_setkey(tfm, info->lo_encrypt_key,
info->lo_encrypt_key_size);
if (err != 0)
goto out_free_tfm;
lo->key_data = tfm;
return 0;
out_free_tfm:
crypto_free_sync_skcipher(tfm);
out:
return err;
}
typedef int (*encdec_cbc_t)(struct skcipher_request *req);
static int
cryptoloop_transfer(struct loop_device *lo, int cmd,
struct page *raw_page, unsigned raw_off,
struct page *loop_page, unsigned loop_off,
int size, sector_t IV)
{
struct crypto_sync_skcipher *tfm = lo->key_data;
SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
struct scatterlist sg_out;
struct scatterlist sg_in;
encdec_cbc_t encdecfunc;
struct page *in_page, *out_page;
unsigned in_offs, out_offs;
int err;
skcipher_request_set_sync_tfm(req, tfm);
skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
NULL, NULL);
sg_init_table(&sg_out, 1);
sg_init_table(&sg_in, 1);
if (cmd == READ) {
in_page = raw_page;
in_offs = raw_off;
out_page = loop_page;
out_offs = loop_off;
encdecfunc = crypto_skcipher_decrypt;
} else {
in_page = loop_page;
in_offs = loop_off;
out_page = raw_page;
out_offs = raw_off;
encdecfunc = crypto_skcipher_encrypt;
}
while (size > 0) {
const int sz = min(size, LOOP_IV_SECTOR_SIZE);
u32 iv[4] = { 0, };
iv[0] = cpu_to_le32(IV & 0xffffffff);
sg_set_page(&sg_in, in_page, sz, in_offs);
sg_set_page(&sg_out, out_page, sz, out_offs);
skcipher_request_set_crypt(req, &sg_in, &sg_out, sz, iv);
err = encdecfunc(req);
if (err)
goto out;
IV++;
size -= sz;
in_offs += sz;
out_offs += sz;
}
err = 0;
out:
skcipher_request_zero(req);
return err;
}
static int
cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
{
return -EINVAL;
}
static int
cryptoloop_release(struct loop_device *lo)
{
struct crypto_sync_skcipher *tfm = lo->key_data;
if (tfm != NULL) {
crypto_free_sync_skcipher(tfm);
lo->key_data = NULL;
return 0;
}
printk(KERN_ERR "cryptoloop_release(): tfm == NULL?\n");
return -EINVAL;
}
static struct loop_func_table cryptoloop_funcs = {
.number = LO_CRYPT_CRYPTOAPI,
.init = cryptoloop_init,
.ioctl = cryptoloop_ioctl,
.transfer = cryptoloop_transfer,
.release = cryptoloop_release,
.owner = THIS_MODULE
};
static int __init
init_cryptoloop(void)
{
int rc = loop_register_transfer(&cryptoloop_funcs);
if (rc)
printk(KERN_ERR "cryptoloop: loop_register_transfer failed\n");
return rc;
}
static void __exit
cleanup_cryptoloop(void)
{
if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
printk(KERN_ERR
"cryptoloop: loop_unregister_transfer failed\n");
}
module_init(init_cryptoloop);
module_exit(cleanup_cryptoloop);
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