1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * CMAC: Cipher Block Mode for Authentication
4 *
5 * Copyright © 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi>
6 *
7 * Based on work by:
8 * Copyright © 2013 Tom St Denis <tstdenis@elliptictech.com>
9 * Based on crypto/xcbc.c:
10 * Copyright © 2006 USAGI/WIDE Project,
11 * Author: Kazunori Miyazawa <miyazawa@linux-ipv6.org>
12 */
13
14 #include <crypto/internal/cipher.h>
15 #include <crypto/internal/hash.h>
16 #include <linux/err.h>
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19
20 /*
21 * +------------------------
22 * | <parent tfm>
23 * +------------------------
24 * | cmac_tfm_ctx
25 * +------------------------
26 * | consts (block size * 2)
27 * +------------------------
28 */
29 struct cmac_tfm_ctx {
30 struct crypto_cipher *child;
31 __be64 consts[];
32 };
33
34 /*
35 * +------------------------
36 * | <shash desc>
37 * +------------------------
38 * | cmac_desc_ctx
39 * +------------------------
40 * | odds (block size)
41 * +------------------------
42 * | prev (block size)
43 * +------------------------
44 */
45 struct cmac_desc_ctx {
46 unsigned int len;
47 u8 odds[];
48 };
49
50 static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
51 const u8 *inkey, unsigned int keylen)
52 {
53 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
54 unsigned int bs = crypto_shash_blocksize(parent);
55 __be64 *consts = ctx->consts;
56 u64 _const[2];
57 int i, err = 0;
58 u8 msb_mask, gfmask;
59
60 err = crypto_cipher_setkey(ctx->child, inkey, keylen);
61 if (err)
62 return err;
63
64 /* encrypt the zero block */
65 memset(consts, 0, bs);
66 crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
67
68 switch (bs) {
69 case 16:
70 gfmask = 0x87;
71 _const[0] = be64_to_cpu(consts[1]);
72 _const[1] = be64_to_cpu(consts[0]);
73
74 /* gf(2^128) multiply zero-ciphertext with u and u^2 */
75 for (i = 0; i < 4; i += 2) {
76 msb_mask = ((s64)_const[1] >> 63) & gfmask;
77 _const[1] = (_const[1] << 1) | (_const[0] >> 63);
78 _const[0] = (_const[0] << 1) ^ msb_mask;
79
80 consts[i + 0] = cpu_to_be64(_const[1]);
81 consts[i + 1] = cpu_to_be64(_const[0]);
82 }
83
84 break;
85 case 8:
86 gfmask = 0x1B;
87 _const[0] = be64_to_cpu(consts[0]);
88
89 /* gf(2^64) multiply zero-ciphertext with u and u^2 */
90 for (i = 0; i < 2; i++) {
91 msb_mask = ((s64)_const[0] >> 63) & gfmask;
92 _const[0] = (_const[0] << 1) ^ msb_mask;
93
94 consts[i] = cpu_to_be64(_const[0]);
95 }
96
97 break;
98 }
99
100 return 0;
101 }
102
103 static int crypto_cmac_digest_init(struct shash_desc *pdesc)
104 {
105 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
106 int bs = crypto_shash_blocksize(pdesc->tfm);
107 u8 *prev = &ctx->odds[bs];
108
109 ctx->len = 0;
110 memset(prev, 0, bs);
111
112 return 0;
113 }
114
115 static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
116 unsigned int len)
117 {
118 struct crypto_shash *parent = pdesc->tfm;
119 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
120 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
121 struct crypto_cipher *tfm = tctx->child;
122 int bs = crypto_shash_blocksize(parent);
123 u8 *odds = ctx->odds;
124 u8 *prev = odds + bs;
125
126 /* checking the data can fill the block */
127 if ((ctx->len + len) <= bs) {
128 memcpy(odds + ctx->len, p, len);
129 ctx->len += len;
130 return 0;
131 }
132
133 /* filling odds with new data and encrypting it */
134 memcpy(odds + ctx->len, p, bs - ctx->len);
135 len -= bs - ctx->len;
136 p += bs - ctx->len;
137
138 crypto_xor(prev, odds, bs);
139 crypto_cipher_encrypt_one(tfm, prev, prev);
140
141 /* clearing the length */
142 ctx->len = 0;
143
144 /* encrypting the rest of data */
145 while (len > bs) {
146 crypto_xor(prev, p, bs);
147 crypto_cipher_encrypt_one(tfm, prev, prev);
148 p += bs;
149 len -= bs;
150 }
151
152 /* keeping the surplus of blocksize */
153 if (len) {
154 memcpy(odds, p, len);
155 ctx->len = len;
156 }
157
158 return 0;
159 }
160
161 static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out)
162 {
163 struct crypto_shash *parent = pdesc->tfm;
164 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
165 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
166 struct crypto_cipher *tfm = tctx->child;
167 int bs = crypto_shash_blocksize(parent);
168 u8 *odds = ctx->odds;
169 u8 *prev = odds + bs;
170 unsigned int offset = 0;
171
172 if (ctx->len != bs) {
173 unsigned int rlen;
174 u8 *p = odds + ctx->len;
175
176 *p = 0x80;
177 p++;
178
179 rlen = bs - ctx->len - 1;
180 if (rlen)
181 memset(p, 0, rlen);
182
183 offset += bs;
184 }
185
186 crypto_xor(prev, odds, bs);
187 crypto_xor(prev, (const u8 *)tctx->consts + offset, bs);
188
189 crypto_cipher_encrypt_one(tfm, out, prev);
190
191 return 0;
192 }
193
194 static int cmac_init_tfm(struct crypto_shash *tfm)
195 {
196 struct shash_instance *inst = shash_alg_instance(tfm);
197 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
198 struct crypto_cipher_spawn *spawn;
199 struct crypto_cipher *cipher;
200
201 spawn = shash_instance_ctx(inst);
202 cipher = crypto_spawn_cipher(spawn);
203 if (IS_ERR(cipher))
204 return PTR_ERR(cipher);
205
206 ctx->child = cipher;
207
208 return 0;
209 }
210
211 static int cmac_clone_tfm(struct crypto_shash *tfm, struct crypto_shash *otfm)
212 {
213 struct cmac_tfm_ctx *octx = crypto_shash_ctx(otfm);
214 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
215 struct crypto_cipher *cipher;
216
217 cipher = crypto_clone_cipher(octx->child);
218 if (IS_ERR(cipher))
219 return PTR_ERR(cipher);
220
221 ctx->child = cipher;
222
223 return 0;
224 }
225
226 static void cmac_exit_tfm(struct crypto_shash *tfm)
227 {
228 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
229 crypto_free_cipher(ctx->child);
230 }
231
232 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
233 {
234 struct shash_instance *inst;
235 struct crypto_cipher_spawn *spawn;
236 struct crypto_alg *alg;
237 u32 mask;
238 int err;
239
240 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
241 if (err)
242 return err;
243
244 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
245 if (!inst)
246 return -ENOMEM;
247 spawn = shash_instance_ctx(inst);
248
249 err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
250 crypto_attr_alg_name(tb[1]), 0, mask);
251 if (err)
252 goto err_free_inst;
253 alg = crypto_spawn_cipher_alg(spawn);
254
255 switch (alg->cra_blocksize) {
256 case 16:
257 case 8:
258 break;
259 default:
260 err = -EINVAL;
261 goto err_free_inst;
262 }
263
264 err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
265 if (err)
266 goto err_free_inst;
267
268 inst->alg.base.cra_priority = alg->cra_priority;
269 inst->alg.base.cra_blocksize = alg->cra_blocksize;
270 inst->alg.base.cra_ctxsize = sizeof(struct cmac_tfm_ctx) +
271 alg->cra_blocksize * 2;
272
273 inst->alg.digestsize = alg->cra_blocksize;
274 inst->alg.descsize = sizeof(struct cmac_desc_ctx) +
275 alg->cra_blocksize * 2;
276 inst->alg.init = crypto_cmac_digest_init;
277 inst->alg.update = crypto_cmac_digest_update;
278 inst->alg.final = crypto_cmac_digest_final;
279 inst->alg.setkey = crypto_cmac_digest_setkey;
280 inst->alg.init_tfm = cmac_init_tfm;
281 inst->alg.clone_tfm = cmac_clone_tfm;
282 inst->alg.exit_tfm = cmac_exit_tfm;
283
284 inst->free = shash_free_singlespawn_instance;
285
286 err = shash_register_instance(tmpl, inst);
287 if (err) {
288 err_free_inst:
289 shash_free_singlespawn_instance(inst);
290 }
291 return err;
292 }
293
294 static struct crypto_template crypto_cmac_tmpl = {
295 .name = "cmac",
296 .create = cmac_create,
297 .module = THIS_MODULE,
298 };
299
300 static int __init crypto_cmac_module_init(void)
301 {
302 return crypto_register_template(&crypto_cmac_tmpl);
303 }
304
305 static void __exit crypto_cmac_module_exit(void)
306 {
307 crypto_unregister_template(&crypto_cmac_tmpl);
308 }
309
310 subsys_initcall(crypto_cmac_module_init);
311 module_exit(crypto_cmac_module_exit);
312
313 MODULE_LICENSE("GPL");
314 MODULE_DESCRIPTION("CMAC keyed hash algorithm");
315 MODULE_ALIAS_CRYPTO("cmac");
316 MODULE_IMPORT_NS(CRYPTO_INTERNAL);
317
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