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/*

   Linux loop encryption enabling module

   Copyright (C)  2002 Herbert Valerio Riedel <hvr@gnu.org>

   Copyright (C)  2003 Fruhwirth Clemens <clemens@endorphin.org>

   This module is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 2 of the License, or

   (at your option) any later version.

   This module is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this module; if not, write to the Free Software

   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

#include <linux/module.h>

#include <linux/init.h>

#include <linux/string.h>

#include <linux/crypto.h>

#include <linux/blkdev.h>

#include <linux/loop.h>

#include <linux/scatterlist.h>

#include <asm/semaphore.h>

#include <asm/uaccess.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 *cipher;

        char *mode;

        char *cmsp = cms;                       /* c-m string pointer */

        struct crypto_blkcipher *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 = cmsp;

        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_blkcipher(cms, 0, CRYPTO_ALG_ASYNC);

        if (IS_ERR(tfm))

                return PTR_ERR(tfm);

        err = crypto_blkcipher_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_blkcipher(tfm);

 out:

        return err;

}

typedef int (*encdec_cbc_t)(struct blkcipher_desc *desc,

                        struct scatterlist *sg_out,

                        struct scatterlist *sg_in,

                        unsigned int nsg);

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_blkcipher *tfm = lo->key_data;

        struct blkcipher_desc desc = {

                .tfm = tfm,

                .flags = CRYPTO_TFM_REQ_MAY_SLEEP,

        };

        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;

        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_blkcipher_crt(tfm)->decrypt;

        } else {

                in_page = loop_page;

                in_offs = loop_off;

                out_page = raw_page;

                out_offs = raw_off;

                encdecfunc = crypto_blkcipher_crt(tfm)->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);

                desc.info = iv;

                err = encdecfunc(&desc, &sg_out, &sg_in, sz);

                if (err)

                        return err;

                IV++;

                size -= sz;

                in_offs += sz;

                out_offs += sz;

        }

        return 0;

}

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_blkcipher *tfm = lo->key_data;

        if (tfm != NULL) {

                crypto_free_blkcipher(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);