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 <linux/init.h>
  25 #include <linux/string.h>
  26 #include <linux/crypto.h>
  27 #include <linux/blkdev.h>
  28 #include <linux/loop.h>
  29 #include <linux/scatterlist.h>
  30 #include <asm/semaphore.h>
  31 #include <asm/uaccess.h>
  32
  33 MODULE_LICENSE("GPL");
  34 MODULE_DESCRIPTION("loop blockdevice transferfunction adaptor / CryptoAPI");
  35 MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
  36
  37 #define LOOP_IV_SECTOR_BITS 9
  38 #define LOOP_IV_SECTOR_SIZE (1 << LOOP_IV_SECTOR_BITS)
  39
  40 static int
  41 cryptoloop_init(struct loop_device *lo, const struct loop_info64 *info)
  42 {
  43         int err = -EINVAL;
  44         int cipher_len;
  45         int mode_len;
  46         char cms[LO_NAME_SIZE];                 /* cipher-mode string */
  47         char *cipher;
  48         char *mode;
  49         char *cmsp = cms;                       /* c-m string pointer */
  50         struct crypto_blkcipher *tfm;
  51
  52         /* encryption breaks for non sector aligned offsets */
  53
  54         if (info->lo_offset % LOOP_IV_SECTOR_SIZE)
  55                 goto out;
  56
  57         strncpy(cms, info->lo_crypt_name, LO_NAME_SIZE);
  58         cms[LO_NAME_SIZE - 1] = 0;
  59
  60         cipher = cmsp;
  61         cipher_len = strcspn(cmsp, "-");
  62
  63         mode = cmsp + cipher_len;
  64         mode_len = 0;
  65         if (*mode) {
  66                 mode++;
  67                 mode_len = strcspn(mode, "-");
  68         }
  69
  70         if (!mode_len) {
  71                 mode = "cbc";
  72                 mode_len = 3;
  73         }
  74
  75         if (cipher_len + mode_len + 3 > LO_NAME_SIZE)
  76                 return -EINVAL;
  77
  78         memmove(cms, mode, mode_len);
  79         cmsp = cms + mode_len;
  80         *cmsp++ = '(';
  81         memcpy(cmsp, info->lo_crypt_name, cipher_len);
  82         cmsp += cipher_len;
  83         *cmsp++ = ')';
  84         *cmsp = 0;
  85
  86         tfm = crypto_alloc_blkcipher(cms, 0, CRYPTO_ALG_ASYNC);
  87         if (IS_ERR(tfm))
  88                 return PTR_ERR(tfm);
  89
  90         err = crypto_blkcipher_setkey(tfm, info->lo_encrypt_key,
  91                                       info->lo_encrypt_key_size);
  92
  93         if (err != 0)
  94                 goto out_free_tfm;
  95
  96         lo->key_data = tfm;
  97         return 0;
  98
  99  out_free_tfm:
 100         crypto_free_blkcipher(tfm);
 101
 102  out:
 103         return err;
 104 }
 105
 106
 107 typedef int (*encdec_cbc_t)(struct blkcipher_desc *desc,
 108                         struct scatterlist *sg_out,
 109                         struct scatterlist *sg_in,
 110                         unsigned int nsg);
 111
 112 static int
 113 cryptoloop_transfer(struct loop_device *lo, int cmd,
 114                     struct page *raw_page, unsigned raw_off,
 115                     struct page *loop_page, unsigned loop_off,
 116                     int size, sector_t IV)
 117 {
 118         struct crypto_blkcipher *tfm = lo->key_data;
 119         struct blkcipher_desc desc = {
 120                 .tfm = tfm,
 121                 .flags = CRYPTO_TFM_REQ_MAY_SLEEP,
 122         };
 123         struct scatterlist sg_out;
 124         struct scatterlist sg_in;
 125
 126         encdec_cbc_t encdecfunc;
 127         struct page *in_page, *out_page;
 128         unsigned in_offs, out_offs;
 129         int err;
 130
 131         sg_init_table(&sg_out, 1);
 132         sg_init_table(&sg_in, 1);
 133
 134         if (cmd == READ) {
 135                 in_page = raw_page;
 136                 in_offs = raw_off;
 137                 out_page = loop_page;
 138                 out_offs = loop_off;
 139                 encdecfunc = crypto_blkcipher_crt(tfm)->decrypt;
 140         } else {
 141                 in_page = loop_page;
 142                 in_offs = loop_off;
 143                 out_page = raw_page;
 144                 out_offs = raw_off;
 145                 encdecfunc = crypto_blkcipher_crt(tfm)->encrypt;
 146         }
 147
 148         while (size > 0) {
 149                 const int sz = min(size, LOOP_IV_SECTOR_SIZE);
 150                 u32 iv[4] = { 0, };
 151                 iv[0] = cpu_to_le32(IV & 0xffffffff);
 152
 153                 sg_set_page(&sg_in, in_page);
 154                 sg_in.offset = in_offs;
 155                 sg_in.length = sz;
 156
 157                 sg_set_page(&sg_out, out_page);
 158                 sg_out.offset = out_offs;
 159                 sg_out.length = sz;
 160
 161                 desc.info = iv;
 162                 err = encdecfunc(&desc, &sg_out, &sg_in, sz);
 163                 if (err)
 164                         return err;
 165
 166                 IV++;
 167                 size -= sz;
 168                 in_offs += sz;
 169                 out_offs += sz;
 170         }
 171
 172         return 0;
 173 }
 174
 175 static int
 176 cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
 177 {
 178         return -EINVAL;
 179 }
 180
 181 static int
 182 cryptoloop_release(struct loop_device *lo)
 183 {
 184         struct crypto_blkcipher *tfm = lo->key_data;
 185         if (tfm != NULL) {
 186                 crypto_free_blkcipher(tfm);
 187                 lo->key_data = NULL;
 188                 return 0;
 189         }
 190         printk(KERN_ERR "cryptoloop_release(): tfm == NULL?\n");
 191         return -EINVAL;
 192 }
 193
 194 static struct loop_func_table cryptoloop_funcs = {
 195         .number = LO_CRYPT_CRYPTOAPI,
 196         .init = cryptoloop_init,
 197         .ioctl = cryptoloop_ioctl,
 198         .transfer = cryptoloop_transfer,
 199         .release = cryptoloop_release,
 200         .owner = THIS_MODULE
 201 };
 202
 203 static int __init
 204 init_cryptoloop(void)
 205 {
 206         int rc = loop_register_transfer(&cryptoloop_funcs);
 207
 208         if (rc)
 209                 printk(KERN_ERR "cryptoloop: loop_register_transfer failed\n");
 210         return rc;
 211 }
 212
 213 static void __exit
 214 cleanup_cryptoloop(void)
 215 {
 216         if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
 217                 printk(KERN_ERR
 218                         "cryptoloop: loop_unregister_transfer failed\n");
 219 }
 220
 221 module_init(init_cryptoloop);
 222 module_exit(cleanup_cryptoloop);