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 u8 ctx[];
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 ctx[];
48 };
49
crypto_cmac_digest_setkey(struct crypto_shash * parent,const u8 * inkey,unsigned int keylen)50 static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
51 const u8 *inkey, unsigned int keylen)
52 {
53 unsigned long alignmask = crypto_shash_alignmask(parent);
54 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
55 unsigned int bs = crypto_shash_blocksize(parent);
56 __be64 *consts = PTR_ALIGN((void *)ctx->ctx,
57 (alignmask | (__alignof__(__be64) - 1)) + 1);
58 u64 _const[2];
59 int i, err = 0;
60 u8 msb_mask, gfmask;
61
62 err = crypto_cipher_setkey(ctx->child, inkey, keylen);
63 if (err)
64 return err;
65
66 /* encrypt the zero block */
67 memset(consts, 0, bs);
68 crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
69
70 switch (bs) {
71 case 16:
72 gfmask = 0x87;
73 _const[0] = be64_to_cpu(consts[1]);
74 _const[1] = be64_to_cpu(consts[0]);
75
76 /* gf(2^128) multiply zero-ciphertext with u and u^2 */
77 for (i = 0; i < 4; i += 2) {
78 msb_mask = ((s64)_const[1] >> 63) & gfmask;
79 _const[1] = (_const[1] << 1) | (_const[0] >> 63);
80 _const[0] = (_const[0] << 1) ^ msb_mask;
81
82 consts[i + 0] = cpu_to_be64(_const[1]);
83 consts[i + 1] = cpu_to_be64(_const[0]);
84 }
85
86 break;
87 case 8:
88 gfmask = 0x1B;
89 _const[0] = be64_to_cpu(consts[0]);
90
91 /* gf(2^64) multiply zero-ciphertext with u and u^2 */
92 for (i = 0; i < 2; i++) {
93 msb_mask = ((s64)_const[0] >> 63) & gfmask;
94 _const[0] = (_const[0] << 1) ^ msb_mask;
95
96 consts[i] = cpu_to_be64(_const[0]);
97 }
98
99 break;
100 }
101
102 return 0;
103 }
104
crypto_cmac_digest_init(struct shash_desc * pdesc)105 static int crypto_cmac_digest_init(struct shash_desc *pdesc)
106 {
107 unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm);
108 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
109 int bs = crypto_shash_blocksize(pdesc->tfm);
110 u8 *prev = PTR_ALIGN((void *)ctx->ctx, alignmask + 1) + bs;
111
112 ctx->len = 0;
113 memset(prev, 0, bs);
114
115 return 0;
116 }
117
crypto_cmac_digest_update(struct shash_desc * pdesc,const u8 * p,unsigned int len)118 static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
119 unsigned int len)
120 {
121 struct crypto_shash *parent = pdesc->tfm;
122 unsigned long alignmask = crypto_shash_alignmask(parent);
123 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
124 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
125 struct crypto_cipher *tfm = tctx->child;
126 int bs = crypto_shash_blocksize(parent);
127 u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
128 u8 *prev = odds + bs;
129
130 /* checking the data can fill the block */
131 if ((ctx->len + len) <= bs) {
132 memcpy(odds + ctx->len, p, len);
133 ctx->len += len;
134 return 0;
135 }
136
137 /* filling odds with new data and encrypting it */
138 memcpy(odds + ctx->len, p, bs - ctx->len);
139 len -= bs - ctx->len;
140 p += bs - ctx->len;
141
142 crypto_xor(prev, odds, bs);
143 crypto_cipher_encrypt_one(tfm, prev, prev);
144
145 /* clearing the length */
146 ctx->len = 0;
147
148 /* encrypting the rest of data */
149 while (len > bs) {
150 crypto_xor(prev, p, bs);
151 crypto_cipher_encrypt_one(tfm, prev, prev);
152 p += bs;
153 len -= bs;
154 }
155
156 /* keeping the surplus of blocksize */
157 if (len) {
158 memcpy(odds, p, len);
159 ctx->len = len;
160 }
161
162 return 0;
163 }
164
crypto_cmac_digest_final(struct shash_desc * pdesc,u8 * out)165 static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out)
166 {
167 struct crypto_shash *parent = pdesc->tfm;
168 unsigned long alignmask = crypto_shash_alignmask(parent);
169 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
170 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
171 struct crypto_cipher *tfm = tctx->child;
172 int bs = crypto_shash_blocksize(parent);
173 u8 *consts = PTR_ALIGN((void *)tctx->ctx,
174 (alignmask | (__alignof__(__be64) - 1)) + 1);
175 u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
176 u8 *prev = odds + bs;
177 unsigned int offset = 0;
178
179 if (ctx->len != bs) {
180 unsigned int rlen;
181 u8 *p = odds + ctx->len;
182
183 *p = 0x80;
184 p++;
185
186 rlen = bs - ctx->len - 1;
187 if (rlen)
188 memset(p, 0, rlen);
189
190 offset += bs;
191 }
192
193 crypto_xor(prev, odds, bs);
194 crypto_xor(prev, consts + offset, bs);
195
196 crypto_cipher_encrypt_one(tfm, out, prev);
197
198 return 0;
199 }
200
cmac_init_tfm(struct crypto_shash * tfm)201 static int cmac_init_tfm(struct crypto_shash *tfm)
202 {
203 struct shash_instance *inst = shash_alg_instance(tfm);
204 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
205 struct crypto_cipher_spawn *spawn;
206 struct crypto_cipher *cipher;
207
208 spawn = shash_instance_ctx(inst);
209 cipher = crypto_spawn_cipher(spawn);
210 if (IS_ERR(cipher))
211 return PTR_ERR(cipher);
212
213 ctx->child = cipher;
214
215 return 0;
216 }
217
cmac_clone_tfm(struct crypto_shash * tfm,struct crypto_shash * otfm)218 static int cmac_clone_tfm(struct crypto_shash *tfm, struct crypto_shash *otfm)
219 {
220 struct cmac_tfm_ctx *octx = crypto_shash_ctx(otfm);
221 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
222 struct crypto_cipher *cipher;
223
224 cipher = crypto_clone_cipher(octx->child);
225 if (IS_ERR(cipher))
226 return PTR_ERR(cipher);
227
228 ctx->child = cipher;
229
230 return 0;
231 }
232
cmac_exit_tfm(struct crypto_shash * tfm)233 static void cmac_exit_tfm(struct crypto_shash *tfm)
234 {
235 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
236 crypto_free_cipher(ctx->child);
237 }
238
cmac_create(struct crypto_template * tmpl,struct rtattr ** tb)239 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
240 {
241 struct shash_instance *inst;
242 struct crypto_cipher_spawn *spawn;
243 struct crypto_alg *alg;
244 unsigned long alignmask;
245 u32 mask;
246 int err;
247
248 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
249 if (err)
250 return err;
251
252 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
253 if (!inst)
254 return -ENOMEM;
255 spawn = shash_instance_ctx(inst);
256
257 err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
258 crypto_attr_alg_name(tb[1]), 0, mask);
259 if (err)
260 goto err_free_inst;
261 alg = crypto_spawn_cipher_alg(spawn);
262
263 switch (alg->cra_blocksize) {
264 case 16:
265 case 8:
266 break;
267 default:
268 err = -EINVAL;
269 goto err_free_inst;
270 }
271
272 err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
273 if (err)
274 goto err_free_inst;
275
276 alignmask = alg->cra_alignmask;
277 inst->alg.base.cra_alignmask = alignmask;
278 inst->alg.base.cra_priority = alg->cra_priority;
279 inst->alg.base.cra_blocksize = alg->cra_blocksize;
280
281 inst->alg.digestsize = alg->cra_blocksize;
282 inst->alg.descsize =
283 ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment())
284 + (alignmask & ~(crypto_tfm_ctx_alignment() - 1))
285 + alg->cra_blocksize * 2;
286
287 inst->alg.base.cra_ctxsize =
288 ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment())
289 + ((alignmask | (__alignof__(__be64) - 1)) &
290 ~(crypto_tfm_ctx_alignment() - 1))
291 + alg->cra_blocksize * 2;
292
293 inst->alg.init = crypto_cmac_digest_init;
294 inst->alg.update = crypto_cmac_digest_update;
295 inst->alg.final = crypto_cmac_digest_final;
296 inst->alg.setkey = crypto_cmac_digest_setkey;
297 inst->alg.init_tfm = cmac_init_tfm;
298 inst->alg.clone_tfm = cmac_clone_tfm;
299 inst->alg.exit_tfm = cmac_exit_tfm;
300
301 inst->free = shash_free_singlespawn_instance;
302
303 err = shash_register_instance(tmpl, inst);
304 if (err) {
305 err_free_inst:
306 shash_free_singlespawn_instance(inst);
307 }
308 return err;
309 }
310
311 static struct crypto_template crypto_cmac_tmpl = {
312 .name = "cmac",
313 .create = cmac_create,
314 .module = THIS_MODULE,
315 };
316
crypto_cmac_module_init(void)317 static int __init crypto_cmac_module_init(void)
318 {
319 return crypto_register_template(&crypto_cmac_tmpl);
320 }
321
crypto_cmac_module_exit(void)322 static void __exit crypto_cmac_module_exit(void)
323 {
324 crypto_unregister_template(&crypto_cmac_tmpl);
325 }
326
327 subsys_initcall(crypto_cmac_module_init);
328 module_exit(crypto_cmac_module_exit);
329
330 MODULE_LICENSE("GPL");
331 MODULE_DESCRIPTION("CMAC keyed hash algorithm");
332 MODULE_ALIAS_CRYPTO("cmac");
333 MODULE_IMPORT_NS(CRYPTO_INTERNAL);
334