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
20MODULE_LICENSE("GPL");
21MODULE_DESCRIPTION("loop blockdevice transferfunction adaptor / CryptoAPI");
22MODULE_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
27static int
28cryptoloop_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
92typedef int (*encdec_cbc_t)(struct skcipher_request *req);
93
94static int
95cryptoloop_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
152out:
153	skcipher_request_zero(req);
154	return err;
155}
156
157static int
158cryptoloop_ioctl(struct loop_device *lo, int cmd, unsigned long arg)
159{
160	return -EINVAL;
161}
162
163static int
164cryptoloop_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
176static 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
185static int __init
186init_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	else
193		pr_warn("the cryptoloop driver has been deprecated and will be removed in in Linux 5.16\n");
194	return rc;
195}
196
197static void __exit
198cleanup_cryptoloop(void)
199{
200	if (loop_unregister_transfer(LO_CRYPT_CRYPTOAPI))
201		printk(KERN_ERR
202			"cryptoloop: loop_unregister_transfer failed\n");
203}
204
205module_init(init_cryptoloop);
206module_exit(cleanup_cryptoloop);
207