drivers/block/cryptoloop.c

   1 /*
   2    Linux loop encryption enabling module
   3
   4    Copyright (C)  2002 Herbert Valerio Riedel <hvr@gnu.org>
   5    Copyright (C)  2003 Fruhwirth Clemens <clemens@endorphin.org>
   6
   7    This module is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This module is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this module; if not, write to the Free Software
  19    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include <linux/module.h>
  23
  24 #include <crypto/skcipher.h>
  25 #include <linux/init.h>
  26 #include <linux/string.h>
  27 #include <linux/blkdev.h>
  28 #include <linux/scatterlist.h>
  29 #include <linux/uaccess.h>
  30 #include "loop.h"
  31
  32 MODULE_LICENSE("GPL");
  33 MODULE_DESCRIPTION("loop blockdevice transferfunction adaptor / CryptoAPI");
  34 MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
  35
  36 #define LOOP_IV_SECTOR_BITS 9
  37 #define LOOP_IV_SECTOR_SIZE (1 << LOOP_IV_SECTOR_BITS)
  38
  39 static int
  40 cryptoloop_init(struct loop_device *lo, const struct loop_info64 *info)
  41 {
  42         int err = -EINVAL;
  43         int cipher_len;
  44         int mode_len;
  45         char cms[LO_NAME_SIZE];                 /* cipher-mode string */
  46         char *mode;
  47         char *cmsp = cms;                       /* c-m string pointer */
  48         struct crypto_skcipher *tfm;
  49
  50         /* encryption breaks for non sector aligned offsets */
  51
  52         if (info->lo_offset % LOOP_IV_SECTOR_SIZE)
  53                 goto out;
  54
  55         strncpy(cms, info->lo_crypt_name, LO_NAME_SIZE);
  56         cms[LO_NAME_SIZE - 1] = 0;
  57
  58         cipher_len = strcspn(cmsp, "-");
  59
  60         mode = cmsp + cipher_len;
  61         mode_len = 0;
  62         if (*mode) {
  63                 mode++;
  64                 mode_len = strcspn(mode, "-");
  65         }
  66
  67         if (!mode_len) {
  68                 mode = "cbc";
  69                 mode_len = 3;
  70         }
  71
  72         if (cipher_len + mode_len + 3 > LO_NAME_SIZE)
  73                 return -EINVAL;
  74
  75         memmove(cms, mode, mode_len);
  76         cmsp = cms + mode_len;
  77         *cmsp++ = '(';
  78         memcpy(cmsp, info->lo_crypt_name, cipher_len);
  79         cmsp += cipher_len;
  80         *cmsp++ = ')';
  81         *cmsp = 0;
  82
  83         tfm = crypto_alloc_skcipher(cms, 0, CRYPTO_ALG_ASYNC);
  84         if (IS_ERR(tfm))
  85                 return PTR_ERR(tfm);
  86
  87         err = crypto_skcipher_setkey(tfm, info->lo_encrypt_key,
  88                                      info->lo_encrypt_key_size);
  89
  90         if (err != 0)
  91                 goto out_free_tfm;
  92
  93         lo->key_data = tfm;
  94         return 0;
  95
  96  out_free_tfm:
  97         crypto_free_skcipher(tfm);
  98
  99  out:
 100         return err;
 101 }
 102
 103
 104 typedef int (*encdec_cbc_t)(struct skcipher_request *req);
 105
 106 static int
 107 cryptoloop_transfer(struct loop_device *lo, int cmd,
 108                     struct page *raw_page, unsigned raw_off,
 109                     struct page *loop_page, unsigned loop_off,
 110                     int size, sector_t IV)
 111 {
 112         struct crypto_skcipher *tfm = lo->key_data;
 113         SKCIPHER_REQUEST_ON_STACK(req, tfm);
 114         struct scatterlist sg_out;
 115         struct scatterlist sg_in;
 116
 117         encdec_cbc_t encdecfunc;
 118         struct page *in_page, *out_page;
 119         unsigned in_offs, out_offs;
 120         int err;
 121
 122         skcipher_request_set_tfm(req, tfm);
 123         skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
 124                                       NULL, NULL);
 125
 126         sg_init_table(&sg_out, 1);
 127         sg_init_table(&sg_in, 1);
 128
 129         if (cmd == READ) {
 130                 in_page = raw_page;
 131                 in_offs = raw_off;
 132                 out_page = loop_page;
 133                 out_offs = loop_off;
 134                 encdecfunc = crypto_skcipher_decrypt;
 135         } else {
 136                 in_page = loop_page;
 137                 in_offs = loop_off;
 138                 out_page = raw_page;
 139                 out_offs = raw_off;
 140                 encdecfunc = crypto_skcipher_encrypt;
 141         }
 142
 143         while (size > 0) {
 144                 const int sz = min(size, LOOP_IV_SECTOR_SIZE);
 145                 u32 iv[4] = { 0, };
 146                 iv[0] = cpu_to_le32(IV & 0xffffffff);
 147
 148                 sg_set_page(&sg_in, in_page, sz, in_offs);
 149                 sg_set_page(&sg_out, out_page, sz, out_offs);
 150
 151                 skcipher_request_set_crypt(req, &sg_in, &sg_out, sz, iv);
 152                 err = encdecfunc(req);
 153                 if (err)
 154                         goto out;
 155
 156                 IV++;
 157                 size -= sz;
 158                 in_offs += sz;
 159                 out_offs += sz;
 160         }
 161
 162         err = 0;
 163
 164 out:
 165         skcipher_request_zero(req);
 166         return err;
 167 }
 168
 169 static int
 170 cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
 171 {
 172         return -EINVAL;
 173 }
 174
 175 static int
 176 cryptoloop_release(struct loop_device *lo)
 177 {
 178         struct crypto_skcipher *tfm = lo->key_data;
 179         if (tfm != NULL) {
 180                 crypto_free_skcipher(tfm);
 181                 lo->key_data = NULL;
 182                 return 0;
 183         }
 184         printk(KERN_ERR "cryptoloop_release(): tfm == NULL?\n");
 185         return -EINVAL;
 186 }
 187
 188 static struct loop_func_table cryptoloop_funcs = {
 189         .number = LO_CRYPT_CRYPTOAPI,
 190         .init = cryptoloop_init,
 191         .ioctl = cryptoloop_ioctl,
 192         .transfer = cryptoloop_transfer,
 193         .release = cryptoloop_release,
 194         .owner = THIS_MODULE
 195 };
 196
 197 static int __init
 198 init_cryptoloop(void)
 199 {
 200         int rc = loop_register_transfer(&cryptoloop_funcs);
 201
 202         if (rc)
 203                 printk(KERN_ERR "cryptoloop: loop_register_transfer failed\n");
 204         return rc;
 205 }
 206
 207 static void __exit
 208 cleanup_cryptoloop(void)
 209 {
 210         if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
 211                 printk(KERN_ERR
 212                         "cryptoloop: loop_unregister_transfer failed\n");
 213 }
 214
 215 module_init(init_cryptoloop);
 216 module_exit(cleanup_cryptoloop);