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 *cipher;
  47         char *mode;
  48         char *cmsp = cms;                       /* c-m string pointer */
  49         struct crypto_skcipher *tfm;
  50
  51         /* encryption breaks for non sector aligned offsets */
  52
  53         if (info->lo_offset % LOOP_IV_SECTOR_SIZE)
  54                 goto out;
  55
  56         strncpy(cms, info->lo_crypt_name, LO_NAME_SIZE);
  57         cms[LO_NAME_SIZE - 1] = 0;
  58
  59         cipher = cmsp;
  60         cipher_len = strcspn(cmsp, "-");
  61
  62         mode = cmsp + cipher_len;
  63         mode_len = 0;
  64         if (*mode) {
  65                 mode++;
  66                 mode_len = strcspn(mode, "-");
  67         }
  68
  69         if (!mode_len) {
  70                 mode = "cbc";
  71                 mode_len = 3;
  72         }
  73
  74         if (cipher_len + mode_len + 3 > LO_NAME_SIZE)
  75                 return -EINVAL;
  76
  77         memmove(cms, mode, mode_len);
  78         cmsp = cms + mode_len;
  79         *cmsp++ = '(';
  80         memcpy(cmsp, info->lo_crypt_name, cipher_len);
  81         cmsp += cipher_len;
  82         *cmsp++ = ')';
  83         *cmsp = 0;
  84
  85         tfm = crypto_alloc_skcipher(cms, 0, CRYPTO_ALG_ASYNC);
  86         if (IS_ERR(tfm))
  87                 return PTR_ERR(tfm);
  88
  89         err = crypto_skcipher_setkey(tfm, info->lo_encrypt_key,
  90                                      info->lo_encrypt_key_size);
  91
  92         if (err != 0)
  93                 goto out_free_tfm;
  94
  95         lo->key_data = tfm;
  96         return 0;
  97
  98  out_free_tfm:
  99         crypto_free_skcipher(tfm);
 100
 101  out:
 102         return err;
 103 }
 104
 105
 106 typedef int (*encdec_cbc_t)(struct skcipher_request *req);
 107
 108 static int
 109 cryptoloop_transfer(struct loop_device *lo, int cmd,
 110                     struct page *raw_page, unsigned raw_off,
 111                     struct page *loop_page, unsigned loop_off,
 112                     int size, sector_t IV)
 113 {
 114         struct crypto_skcipher *tfm = lo->key_data;
 115         SKCIPHER_REQUEST_ON_STACK(req, tfm);
 116         struct scatterlist sg_out;
 117         struct scatterlist sg_in;
 118
 119         encdec_cbc_t encdecfunc;
 120         struct page *in_page, *out_page;
 121         unsigned in_offs, out_offs;
 122         int err;
 123
 124         skcipher_request_set_tfm(req, tfm);
 125         skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
 126                                       NULL, NULL);
 127
 128         sg_init_table(&sg_out, 1);
 129         sg_init_table(&sg_in, 1);
 130
 131         if (cmd == READ) {
 132                 in_page = raw_page;
 133                 in_offs = raw_off;
 134                 out_page = loop_page;
 135                 out_offs = loop_off;
 136                 encdecfunc = crypto_skcipher_decrypt;
 137         } else {
 138                 in_page = loop_page;
 139                 in_offs = loop_off;
 140                 out_page = raw_page;
 141                 out_offs = raw_off;
 142                 encdecfunc = crypto_skcipher_encrypt;
 143         }
 144
 145         while (size > 0) {
 146                 const int sz = min(size, LOOP_IV_SECTOR_SIZE);
 147                 u32 iv[4] = { 0, };
 148                 iv[0] = cpu_to_le32(IV & 0xffffffff);
 149
 150                 sg_set_page(&sg_in, in_page, sz, in_offs);
 151                 sg_set_page(&sg_out, out_page, sz, out_offs);
 152
 153                 skcipher_request_set_crypt(req, &sg_in, &sg_out, sz, iv);
 154                 err = encdecfunc(req);
 155                 if (err)
 156                         goto out;
 157
 158                 IV++;
 159                 size -= sz;
 160                 in_offs += sz;
 161                 out_offs += sz;
 162         }
 163
 164         err = 0;
 165
 166 out:
 167         skcipher_request_zero(req);
 168         return err;
 169 }
 170
 171 static int
 172 cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
 173 {
 174         return -EINVAL;
 175 }
 176
 177 static int
 178 cryptoloop_release(struct loop_device *lo)
 179 {
 180         struct crypto_skcipher *tfm = lo->key_data;
 181         if (tfm != NULL) {
 182                 crypto_free_skcipher(tfm);
 183                 lo->key_data = NULL;
 184                 return 0;
 185         }
 186         printk(KERN_ERR "cryptoloop_release(): tfm == NULL?\n");
 187         return -EINVAL;
 188 }
 189
 190 static struct loop_func_table cryptoloop_funcs = {
 191         .number = LO_CRYPT_CRYPTOAPI,
 192         .init = cryptoloop_init,
 193         .ioctl = cryptoloop_ioctl,
 194         .transfer = cryptoloop_transfer,
 195         .release = cryptoloop_release,
 196         .owner = THIS_MODULE
 197 };
 198
 199 static int __init
 200 init_cryptoloop(void)
 201 {
 202         int rc = loop_register_transfer(&cryptoloop_funcs);
 203
 204         if (rc)
 205                 printk(KERN_ERR "cryptoloop: loop_register_transfer failed\n");
 206         return rc;
 207 }
 208
 209 static void __exit
 210 cleanup_cryptoloop(void)
 211 {
 212         if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
 213                 printk(KERN_ERR
 214                         "cryptoloop: loop_unregister_transfer failed\n");
 215 }
 216
 217 module_init(init_cryptoloop);
 218 module_exit(cleanup_cryptoloop);