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-rw-r--r--crypto/cts.c347
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diff --git a/crypto/cts.c b/crypto/cts.c
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1/*
2 * CTS: Cipher Text Stealing mode
3 *
4 * COPYRIGHT (c) 2008
5 * The Regents of the University of Michigan
6 * ALL RIGHTS RESERVED
7 *
8 * Permission is granted to use, copy, create derivative works
9 * and redistribute this software and such derivative works
10 * for any purpose, so long as the name of The University of
11 * Michigan is not used in any advertising or publicity
12 * pertaining to the use of distribution of this software
13 * without specific, written prior authorization. If the
14 * above copyright notice or any other identification of the
15 * University of Michigan is included in any copy of any
16 * portion of this software, then the disclaimer below must
17 * also be included.
18 *
19 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
20 * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
21 * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
22 * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
23 * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
24 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
25 * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
26 * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
27 * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
28 * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
29 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGES.
31 */
32
33/* Derived from various:
34 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
35 */
36
37/*
38 * This is the Cipher Text Stealing mode as described by
39 * Section 8 of rfc2040 and referenced by rfc3962.
40 * rfc3962 includes errata information in its Appendix A.
41 */
42
43#include <crypto/algapi.h>
44#include <linux/err.h>
45#include <linux/init.h>
46#include <linux/kernel.h>
47#include <linux/log2.h>
48#include <linux/module.h>
49#include <linux/scatterlist.h>
50#include <crypto/scatterwalk.h>
51#include <linux/slab.h>
52
53struct crypto_cts_ctx {
54 struct crypto_blkcipher *child;
55};
56
57static int crypto_cts_setkey(struct crypto_tfm *parent, const u8 *key,
58 unsigned int keylen)
59{
60 struct crypto_cts_ctx *ctx = crypto_tfm_ctx(parent);
61 struct crypto_blkcipher *child = ctx->child;
62 int err;
63
64 crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
65 crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
66 CRYPTO_TFM_REQ_MASK);
67 err = crypto_blkcipher_setkey(child, key, keylen);
68 crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
69 CRYPTO_TFM_RES_MASK);
70 return err;
71}
72
73static int cts_cbc_encrypt(struct crypto_cts_ctx *ctx,
74 struct blkcipher_desc *desc,
75 struct scatterlist *dst,
76 struct scatterlist *src,
77 unsigned int offset,
78 unsigned int nbytes)
79{
80 int bsize = crypto_blkcipher_blocksize(desc->tfm);
81 u8 tmp[bsize], tmp2[bsize];
82 struct blkcipher_desc lcldesc;
83 struct scatterlist sgsrc[1], sgdst[1];
84 int lastn = nbytes - bsize;
85 u8 iv[bsize];
86 u8 s[bsize * 2], d[bsize * 2];
87 int err;
88
89 if (lastn < 0)
90 return -EINVAL;
91
92 memset(s, 0, sizeof(s));
93 scatterwalk_map_and_copy(s, src, offset, nbytes, 0);
94
95 memcpy(iv, desc->info, bsize);
96
97 lcldesc.tfm = ctx->child;
98 lcldesc.info = iv;
99 lcldesc.flags = desc->flags;
100
101 sg_set_buf(&sgsrc[0], s, bsize);
102 sg_set_buf(&sgdst[0], tmp, bsize);
103 err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
104
105 memcpy(d + bsize, tmp, lastn);
106
107 lcldesc.info = tmp;
108
109 sg_set_buf(&sgsrc[0], s + bsize, bsize);
110 sg_set_buf(&sgdst[0], tmp2, bsize);
111 err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
112
113 memcpy(d, tmp2, bsize);
114
115 scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);
116
117 memcpy(desc->info, tmp2, bsize);
118
119 return err;
120}
121
122static int crypto_cts_encrypt(struct blkcipher_desc *desc,
123 struct scatterlist *dst, struct scatterlist *src,
124 unsigned int nbytes)
125{
126 struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
127 int bsize = crypto_blkcipher_blocksize(desc->tfm);
128 int tot_blocks = (nbytes + bsize - 1) / bsize;
129 int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
130 struct blkcipher_desc lcldesc;
131 int err;
132
133 lcldesc.tfm = ctx->child;
134 lcldesc.info = desc->info;
135 lcldesc.flags = desc->flags;
136
137 if (tot_blocks == 1) {
138 err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src, bsize);
139 } else if (nbytes <= bsize * 2) {
140 err = cts_cbc_encrypt(ctx, desc, dst, src, 0, nbytes);
141 } else {
142 /* do normal function for tot_blocks - 2 */
143 err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src,
144 cbc_blocks * bsize);
145 if (err == 0) {
146 /* do cts for final two blocks */
147 err = cts_cbc_encrypt(ctx, desc, dst, src,
148 cbc_blocks * bsize,
149 nbytes - (cbc_blocks * bsize));
150 }
151 }
152
153 return err;
154}
155
156static int cts_cbc_decrypt(struct crypto_cts_ctx *ctx,
157 struct blkcipher_desc *desc,
158 struct scatterlist *dst,
159 struct scatterlist *src,
160 unsigned int offset,
161 unsigned int nbytes)
162{
163 int bsize = crypto_blkcipher_blocksize(desc->tfm);
164 u8 tmp[bsize];
165 struct blkcipher_desc lcldesc;
166 struct scatterlist sgsrc[1], sgdst[1];
167 int lastn = nbytes - bsize;
168 u8 iv[bsize];
169 u8 s[bsize * 2], d[bsize * 2];
170 int err;
171
172 if (lastn < 0)
173 return -EINVAL;
174
175 scatterwalk_map_and_copy(s, src, offset, nbytes, 0);
176
177 lcldesc.tfm = ctx->child;
178 lcldesc.info = iv;
179 lcldesc.flags = desc->flags;
180
181 /* 1. Decrypt Cn-1 (s) to create Dn (tmp)*/
182 memset(iv, 0, sizeof(iv));
183 sg_set_buf(&sgsrc[0], s, bsize);
184 sg_set_buf(&sgdst[0], tmp, bsize);
185 err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
186 if (err)
187 return err;
188 /* 2. Pad Cn with zeros at the end to create C of length BB */
189 memset(iv, 0, sizeof(iv));
190 memcpy(iv, s + bsize, lastn);
191 /* 3. Exclusive-or Dn (tmp) with C (iv) to create Xn (tmp) */
192 crypto_xor(tmp, iv, bsize);
193 /* 4. Select the first Ln bytes of Xn (tmp) to create Pn */
194 memcpy(d + bsize, tmp, lastn);
195
196 /* 5. Append the tail (BB - Ln) bytes of Xn (tmp) to Cn to create En */
197 memcpy(s + bsize + lastn, tmp + lastn, bsize - lastn);
198 /* 6. Decrypt En to create Pn-1 */
199 memset(iv, 0, sizeof(iv));
200 sg_set_buf(&sgsrc[0], s + bsize, bsize);
201 sg_set_buf(&sgdst[0], d, bsize);
202 err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
203
204 /* XOR with previous block */
205 crypto_xor(d, desc->info, bsize);
206
207 scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);
208
209 memcpy(desc->info, s, bsize);
210 return err;
211}
212
213static int crypto_cts_decrypt(struct blkcipher_desc *desc,
214 struct scatterlist *dst, struct scatterlist *src,
215 unsigned int nbytes)
216{
217 struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
218 int bsize = crypto_blkcipher_blocksize(desc->tfm);
219 int tot_blocks = (nbytes + bsize - 1) / bsize;
220 int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
221 struct blkcipher_desc lcldesc;
222 int err;
223
224 lcldesc.tfm = ctx->child;
225 lcldesc.info = desc->info;
226 lcldesc.flags = desc->flags;
227
228 if (tot_blocks == 1) {
229 err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src, bsize);
230 } else if (nbytes <= bsize * 2) {
231 err = cts_cbc_decrypt(ctx, desc, dst, src, 0, nbytes);
232 } else {
233 /* do normal function for tot_blocks - 2 */
234 err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src,
235 cbc_blocks * bsize);
236 if (err == 0) {
237 /* do cts for final two blocks */
238 err = cts_cbc_decrypt(ctx, desc, dst, src,
239 cbc_blocks * bsize,
240 nbytes - (cbc_blocks * bsize));
241 }
242 }
243 return err;
244}
245
246static int crypto_cts_init_tfm(struct crypto_tfm *tfm)
247{
248 struct crypto_instance *inst = (void *)tfm->__crt_alg;
249 struct crypto_spawn *spawn = crypto_instance_ctx(inst);
250 struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
251 struct crypto_blkcipher *cipher;
252
253 cipher = crypto_spawn_blkcipher(spawn);
254 if (IS_ERR(cipher))
255 return PTR_ERR(cipher);
256
257 ctx->child = cipher;
258 return 0;
259}
260
261static void crypto_cts_exit_tfm(struct crypto_tfm *tfm)
262{
263 struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
264 crypto_free_blkcipher(ctx->child);
265}
266
267static struct crypto_instance *crypto_cts_alloc(struct rtattr **tb)
268{
269 struct crypto_instance *inst;
270 struct crypto_alg *alg;
271 int err;
272
273 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
274 if (err)
275 return ERR_PTR(err);
276
277 alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
278 CRYPTO_ALG_TYPE_MASK);
279 err = PTR_ERR(alg);
280 if (IS_ERR(alg))
281 return ERR_PTR(err);
282
283 inst = ERR_PTR(-EINVAL);
284 if (!is_power_of_2(alg->cra_blocksize))
285 goto out_put_alg;
286
287 inst = crypto_alloc_instance("cts", alg);
288 if (IS_ERR(inst))
289 goto out_put_alg;
290
291 inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
292 inst->alg.cra_priority = alg->cra_priority;
293 inst->alg.cra_blocksize = alg->cra_blocksize;
294 inst->alg.cra_alignmask = alg->cra_alignmask;
295 inst->alg.cra_type = &crypto_blkcipher_type;
296
297 /* We access the data as u32s when xoring. */
298 inst->alg.cra_alignmask |= __alignof__(u32) - 1;
299
300 inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
301 inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize;
302 inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize;
303
304 inst->alg.cra_blkcipher.geniv = "seqiv";
305
306 inst->alg.cra_ctxsize = sizeof(struct crypto_cts_ctx);
307
308 inst->alg.cra_init = crypto_cts_init_tfm;
309 inst->alg.cra_exit = crypto_cts_exit_tfm;
310
311 inst->alg.cra_blkcipher.setkey = crypto_cts_setkey;
312 inst->alg.cra_blkcipher.encrypt = crypto_cts_encrypt;
313 inst->alg.cra_blkcipher.decrypt = crypto_cts_decrypt;
314
315out_put_alg:
316 crypto_mod_put(alg);
317 return inst;
318}
319
320static void crypto_cts_free(struct crypto_instance *inst)
321{
322 crypto_drop_spawn(crypto_instance_ctx(inst));
323 kfree(inst);
324}
325
326static struct crypto_template crypto_cts_tmpl = {
327 .name = "cts",
328 .alloc = crypto_cts_alloc,
329 .free = crypto_cts_free,
330 .module = THIS_MODULE,
331};
332
333static int __init crypto_cts_module_init(void)
334{
335 return crypto_register_template(&crypto_cts_tmpl);
336}
337
338static void __exit crypto_cts_module_exit(void)
339{
340 crypto_unregister_template(&crypto_cts_tmpl);
341}
342
343module_init(crypto_cts_module_init);
344module_exit(crypto_cts_module_exit);
345
346MODULE_LICENSE("Dual BSD/GPL");
347MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
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