drivers/block/cryptoloop.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3    Linux loop encryption enabling module
   4
   5    Copyright (C)  2002 Herbert Valerio Riedel <hvr@gnu.org>
   6    Copyright (C)  2003 Fruhwirth Clemens <clemens@endorphin.org>
   7
   8  */
   9
  10 #include <linux/module.h>
  11
  12 #include <crypto/skcipher.h>
  13 #include <linux/init.h>
  14 #include <linux/string.h>
  15 #include <linux/blkdev.h>
  16 #include <linux/scatterlist.h>
  17 #include <linux/uaccess.h>
  18 #include "loop.h"
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_DESCRIPTION("loop blockdevice transferfunction adaptor / CryptoAPI");
  22 MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
  23
  24 #define LOOP_IV_SECTOR_BITS 9
  25 #define LOOP_IV_SECTOR_SIZE (1 << LOOP_IV_SECTOR_BITS)
  26
  27 static int
  28 cryptoloop_init(struct loop_device *lo, const struct loop_info64 *info)
  29 {
  30         int err = -EINVAL;
  31         int cipher_len;
  32         int mode_len;
  33         char cms[LO_NAME_SIZE];                 /* cipher-mode string */
  34         char *mode;
  35         char *cmsp = cms;                       /* c-m string pointer */
  36         struct crypto_sync_skcipher *tfm;
  37
  38         /* encryption breaks for non sector aligned offsets */
  39
  40         if (info->lo_offset % LOOP_IV_SECTOR_SIZE)
  41                 goto out;
  42
  43         strncpy(cms, info->lo_crypt_name, LO_NAME_SIZE);
  44         cms[LO_NAME_SIZE - 1] = 0;
  45
  46         cipher_len = strcspn(cmsp, "-");
  47
  48         mode = cmsp + cipher_len;
  49         mode_len = 0;
  50         if (*mode) {
  51                 mode++;
  52                 mode_len = strcspn(mode, "-");
  53         }
  54
  55         if (!mode_len) {
  56                 mode = "cbc";
  57                 mode_len = 3;
  58         }
  59
  60         if (cipher_len + mode_len + 3 > LO_NAME_SIZE)
  61                 return -EINVAL;
  62
  63         memmove(cms, mode, mode_len);
  64         cmsp = cms + mode_len;
  65         *cmsp++ = '(';
  66         memcpy(cmsp, info->lo_crypt_name, cipher_len);
  67         cmsp += cipher_len;
  68         *cmsp++ = ')';
  69         *cmsp = 0;
  70
  71         tfm = crypto_alloc_sync_skcipher(cms, 0, 0);
  72         if (IS_ERR(tfm))
  73                 return PTR_ERR(tfm);
  74
  75         err = crypto_sync_skcipher_setkey(tfm, info->lo_encrypt_key,
  76                                           info->lo_encrypt_key_size);
  77
  78         if (err != 0)
  79                 goto out_free_tfm;
  80
  81         lo->key_data = tfm;
  82         return 0;
  83
  84  out_free_tfm:
  85         crypto_free_sync_skcipher(tfm);
  86
  87  out:
  88         return err;
  89 }
  90
  91
  92 typedef int (*encdec_cbc_t)(struct skcipher_request *req);
  93
  94 static int
  95 cryptoloop_transfer(struct loop_device *lo, int cmd,
  96                     struct page *raw_page, unsigned raw_off,
  97                     struct page *loop_page, unsigned loop_off,
  98                     int size, sector_t IV)
  99 {
 100         struct crypto_sync_skcipher *tfm = lo->key_data;
 101         SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
 102         struct scatterlist sg_out;
 103         struct scatterlist sg_in;
 104
 105         encdec_cbc_t encdecfunc;
 106         struct page *in_page, *out_page;
 107         unsigned in_offs, out_offs;
 108         int err;
 109
 110         skcipher_request_set_sync_tfm(req, tfm);
 111         skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
 112                                       NULL, NULL);
 113
 114         sg_init_table(&sg_out, 1);
 115         sg_init_table(&sg_in, 1);
 116
 117         if (cmd == READ) {
 118                 in_page = raw_page;
 119                 in_offs = raw_off;
 120                 out_page = loop_page;
 121                 out_offs = loop_off;
 122                 encdecfunc = crypto_skcipher_decrypt;
 123         } else {
 124                 in_page = loop_page;
 125                 in_offs = loop_off;
 126                 out_page = raw_page;
 127                 out_offs = raw_off;
 128                 encdecfunc = crypto_skcipher_encrypt;
 129         }
 130
 131         while (size > 0) {
 132                 const int sz = min(size, LOOP_IV_SECTOR_SIZE);
 133                 u32 iv[4] = { 0, };
 134                 iv[0] = cpu_to_le32(IV & 0xffffffff);
 135
 136                 sg_set_page(&sg_in, in_page, sz, in_offs);
 137                 sg_set_page(&sg_out, out_page, sz, out_offs);
 138
 139                 skcipher_request_set_crypt(req, &sg_in, &sg_out, sz, iv);
 140                 err = encdecfunc(req);
 141                 if (err)
 142                         goto out;
 143
 144                 IV++;
 145                 size -= sz;
 146                 in_offs += sz;
 147                 out_offs += sz;
 148         }
 149
 150         err = 0;
 151
 152 out:
 153         skcipher_request_zero(req);
 154         return err;
 155 }
 156
 157 static int
 158 cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
 159 {
 160         return -EINVAL;
 161 }
 162
 163 static int
 164 cryptoloop_release(struct loop_device *lo)
 165 {
 166         struct crypto_sync_skcipher *tfm = lo->key_data;
 167         if (tfm != NULL) {
 168                 crypto_free_sync_skcipher(tfm);
 169                 lo->key_data = NULL;
 170                 return 0;
 171         }
 172         printk(KERN_ERR "cryptoloop_release(): tfm == NULL?\n");
 173         return -EINVAL;
 174 }
 175
 176 static struct loop_func_table cryptoloop_funcs = {
 177         .number = LO_CRYPT_CRYPTOAPI,
 178         .init = cryptoloop_init,
 179         .ioctl = cryptoloop_ioctl,
 180         .transfer = cryptoloop_transfer,
 181         .release = cryptoloop_release,
 182         .owner = THIS_MODULE
 183 };
 184
 185 static int __init
 186 init_cryptoloop(void)
 187 {
 188         int rc = loop_register_transfer(&cryptoloop_funcs);
 189
 190         if (rc)
 191                 printk(KERN_ERR "cryptoloop: loop_register_transfer failed\n");
 192         return rc;
 193 }
 194
 195 static void __exit
 196 cleanup_cryptoloop(void)
 197 {
 198         if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
 199                 printk(KERN_ERR
 200                         "cryptoloop: loop_unregister_transfer failed\n");
 201 }
 202
 203 module_init(init_cryptoloop);
 204 module_exit(cleanup_cryptoloop);