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
cryptoloop_init(struct loop_device * lo,const struct loop_info64 * info)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
cryptoloop_transfer(struct loop_device * lo,int cmd,struct page * raw_page,unsigned raw_off,struct page * loop_page,unsigned loop_off,int size,sector_t IV)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
cryptoloop_ioctl(struct loop_device * lo,int cmd,unsigned long arg)170 cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
171 {
172 return -EINVAL;
173 }
174
175 static int
cryptoloop_release(struct loop_device * lo)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
init_cryptoloop(void)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
cleanup_cryptoloop(void)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);
217
