Root/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/uaccess.h>
31
32MODULE_LICENSE("GPL");
33MODULE_DESCRIPTION("loop blockdevice transferfunction adaptor / CryptoAPI");
34MODULE_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
39static int
40cryptoloop_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_blkcipher *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_blkcipher(cms, 0, CRYPTO_ALG_ASYNC);
86    if (IS_ERR(tfm))
87        return PTR_ERR(tfm);
88
89    err = crypto_blkcipher_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_blkcipher(tfm);
100
101 out:
102    return err;
103}
104
105
106typedef int (*encdec_cbc_t)(struct blkcipher_desc *desc,
107            struct scatterlist *sg_out,
108            struct scatterlist *sg_in,
109            unsigned int nsg);
110
111static int
112cryptoloop_transfer(struct loop_device *lo, int cmd,
113            struct page *raw_page, unsigned raw_off,
114            struct page *loop_page, unsigned loop_off,
115            int size, sector_t IV)
116{
117    struct crypto_blkcipher *tfm = lo->key_data;
118    struct blkcipher_desc desc = {
119        .tfm = tfm,
120        .flags = CRYPTO_TFM_REQ_MAY_SLEEP,
121    };
122    struct scatterlist sg_out;
123    struct scatterlist sg_in;
124
125    encdec_cbc_t encdecfunc;
126    struct page *in_page, *out_page;
127    unsigned in_offs, out_offs;
128    int err;
129
130    sg_init_table(&sg_out, 1);
131    sg_init_table(&sg_in, 1);
132
133    if (cmd == READ) {
134        in_page = raw_page;
135        in_offs = raw_off;
136        out_page = loop_page;
137        out_offs = loop_off;
138        encdecfunc = crypto_blkcipher_crt(tfm)->decrypt;
139    } else {
140        in_page = loop_page;
141        in_offs = loop_off;
142        out_page = raw_page;
143        out_offs = raw_off;
144        encdecfunc = crypto_blkcipher_crt(tfm)->encrypt;
145    }
146
147    while (size > 0) {
148        const int sz = min(size, LOOP_IV_SECTOR_SIZE);
149        u32 iv[4] = { 0, };
150        iv[0] = cpu_to_le32(IV & 0xffffffff);
151
152        sg_set_page(&sg_in, in_page, sz, in_offs);
153        sg_set_page(&sg_out, out_page, sz, out_offs);
154
155        desc.info = iv;
156        err = encdecfunc(&desc, &sg_out, &sg_in, sz);
157        if (err)
158            return err;
159
160        IV++;
161        size -= sz;
162        in_offs += sz;
163        out_offs += sz;
164    }
165
166    return 0;
167}
168
169static int
170cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
171{
172    return -EINVAL;
173}
174
175static int
176cryptoloop_release(struct loop_device *lo)
177{
178    struct crypto_blkcipher *tfm = lo->key_data;
179    if (tfm != NULL) {
180        crypto_free_blkcipher(tfm);
181        lo->key_data = NULL;
182        return 0;
183    }
184    printk(KERN_ERR "cryptoloop_release(): tfm == NULL?\n");
185    return -EINVAL;
186}
187
188static 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
197static int __init
198init_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
207static void __exit
208cleanup_cryptoloop(void)
209{
210    if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
211        printk(KERN_ERR
212            "cryptoloop: loop_unregister_transfer failed\n");
213}
214
215module_init(init_cryptoloop);
216module_exit(cleanup_cryptoloop);
217

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