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cryptoloop.c

/*
   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);

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