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/hash.h>
15 #include <linux/err.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18
19 /*
20 * +------------------------
21 * | <parent tfm>
22 * +------------------------
23 * | cmac_tfm_ctx
24 * +------------------------
25 * | consts (block size * 2)
26 * +------------------------
27 */
28 struct cmac_tfm_ctx {
29 struct crypto_cipher *child;
30 u8 ctx[];
31 };
32
33 /*
34 * +------------------------
35 * | <shash desc>
36 * +------------------------
37 * | cmac_desc_ctx
38 * +------------------------
39 * | odds (block size)
40 * +------------------------
41 * | prev (block size)
42 * +------------------------
43 */
44 struct cmac_desc_ctx {
45 unsigned int len;
46 u8 ctx[];
47 };
48
crypto_cmac_digest_setkey(struct crypto_shash * parent,const u8 * inkey,unsigned int keylen)49 static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
50 const u8 *inkey, unsigned int keylen)
51 {
52 unsigned long alignmask = crypto_shash_alignmask(parent);
53 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
54 unsigned int bs = crypto_shash_blocksize(parent);
55 __be64 *consts = PTR_ALIGN((void *)ctx->ctx,
56 (alignmask | (__alignof__(__be64) - 1)) + 1);
57 u64 _const[2];
58 int i, err = 0;
59 u8 msb_mask, gfmask;
60
61 err = crypto_cipher_setkey(ctx->child, inkey, keylen);
62 if (err)
63 return err;
64
65 /* encrypt the zero block */
66 memset(consts, 0, bs);
67 crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
68
69 switch (bs) {
70 case 16:
71 gfmask = 0x87;
72 _const[0] = be64_to_cpu(consts[1]);
73 _const[1] = be64_to_cpu(consts[0]);
74
75 /* gf(2^128) multiply zero-ciphertext with u and u^2 */
76 for (i = 0; i < 4; i += 2) {
77 msb_mask = ((s64)_const[1] >> 63) & gfmask;
78 _const[1] = (_const[1] << 1) | (_const[0] >> 63);
79 _const[0] = (_const[0] << 1) ^ msb_mask;
80
81 consts[i + 0] = cpu_to_be64(_const[1]);
82 consts[i + 1] = cpu_to_be64(_const[0]);
83 }
84
85 break;
86 case 8:
87 gfmask = 0x1B;
88 _const[0] = be64_to_cpu(consts[0]);
89
90 /* gf(2^64) multiply zero-ciphertext with u and u^2 */
91 for (i = 0; i < 2; i++) {
92 msb_mask = ((s64)_const[0] >> 63) & gfmask;
93 _const[0] = (_const[0] << 1) ^ msb_mask;
94
95 consts[i] = cpu_to_be64(_const[0]);
96 }
97
98 break;
99 }
100
101 return 0;
102 }
103
crypto_cmac_digest_init(struct shash_desc * pdesc)104 static int crypto_cmac_digest_init(struct shash_desc *pdesc)
105 {
106 unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm);
107 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
108 int bs = crypto_shash_blocksize(pdesc->tfm);
109 u8 *prev = PTR_ALIGN((void *)ctx->ctx, alignmask + 1) + bs;
110
111 ctx->len = 0;
112 memset(prev, 0, bs);
113
114 return 0;
115 }
116
crypto_cmac_digest_update(struct shash_desc * pdesc,const u8 * p,unsigned int len)117 static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
118 unsigned int len)
119 {
120 struct crypto_shash *parent = pdesc->tfm;
121 unsigned long alignmask = crypto_shash_alignmask(parent);
122 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
123 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
124 struct crypto_cipher *tfm = tctx->child;
125 int bs = crypto_shash_blocksize(parent);
126 u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
127 u8 *prev = odds + bs;
128
129 /* checking the data can fill the block */
130 if ((ctx->len + len) <= bs) {
131 memcpy(odds + ctx->len, p, len);
132 ctx->len += len;
133 return 0;
134 }
135
136 /* filling odds with new data and encrypting it */
137 memcpy(odds + ctx->len, p, bs - ctx->len);
138 len -= bs - ctx->len;
139 p += bs - ctx->len;
140
141 crypto_xor(prev, odds, bs);
142 crypto_cipher_encrypt_one(tfm, prev, prev);
143
144 /* clearing the length */
145 ctx->len = 0;
146
147 /* encrypting the rest of data */
148 while (len > bs) {
149 crypto_xor(prev, p, bs);
150 crypto_cipher_encrypt_one(tfm, prev, prev);
151 p += bs;
152 len -= bs;
153 }
154
155 /* keeping the surplus of blocksize */
156 if (len) {
157 memcpy(odds, p, len);
158 ctx->len = len;
159 }
160
161 return 0;
162 }
163
crypto_cmac_digest_final(struct shash_desc * pdesc,u8 * out)164 static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out)
165 {
166 struct crypto_shash *parent = pdesc->tfm;
167 unsigned long alignmask = crypto_shash_alignmask(parent);
168 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
169 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
170 struct crypto_cipher *tfm = tctx->child;
171 int bs = crypto_shash_blocksize(parent);
172 u8 *consts = PTR_ALIGN((void *)tctx->ctx,
173 (alignmask | (__alignof__(__be64) - 1)) + 1);
174 u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
175 u8 *prev = odds + bs;
176 unsigned int offset = 0;
177
178 if (ctx->len != bs) {
179 unsigned int rlen;
180 u8 *p = odds + ctx->len;
181
182 *p = 0x80;
183 p++;
184
185 rlen = bs - ctx->len - 1;
186 if (rlen)
187 memset(p, 0, rlen);
188
189 offset += bs;
190 }
191
192 crypto_xor(prev, odds, bs);
193 crypto_xor(prev, consts + offset, bs);
194
195 crypto_cipher_encrypt_one(tfm, out, prev);
196
197 return 0;
198 }
199
cmac_init_tfm(struct crypto_tfm * tfm)200 static int cmac_init_tfm(struct crypto_tfm *tfm)
201 {
202 struct crypto_cipher *cipher;
203 struct crypto_instance *inst = (void *)tfm->__crt_alg;
204 struct crypto_cipher_spawn *spawn = crypto_instance_ctx(inst);
205 struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
206
207 cipher = crypto_spawn_cipher(spawn);
208 if (IS_ERR(cipher))
209 return PTR_ERR(cipher);
210
211 ctx->child = cipher;
212
213 return 0;
214 };
215
cmac_exit_tfm(struct crypto_tfm * tfm)216 static void cmac_exit_tfm(struct crypto_tfm *tfm)
217 {
218 struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
219 crypto_free_cipher(ctx->child);
220 }
221
cmac_create(struct crypto_template * tmpl,struct rtattr ** tb)222 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
223 {
224 struct shash_instance *inst;
225 struct crypto_cipher_spawn *spawn;
226 struct crypto_alg *alg;
227 unsigned long alignmask;
228 u32 mask;
229 int err;
230
231 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
232 if (err)
233 return err;
234
235 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
236 if (!inst)
237 return -ENOMEM;
238 spawn = shash_instance_ctx(inst);
239
240 err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
241 crypto_attr_alg_name(tb[1]), 0, mask);
242 if (err)
243 goto err_free_inst;
244 alg = crypto_spawn_cipher_alg(spawn);
245
246 switch (alg->cra_blocksize) {
247 case 16:
248 case 8:
249 break;
250 default:
251 err = -EINVAL;
252 goto err_free_inst;
253 }
254
255 err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
256 if (err)
257 goto err_free_inst;
258
259 alignmask = alg->cra_alignmask;
260 inst->alg.base.cra_alignmask = alignmask;
261 inst->alg.base.cra_priority = alg->cra_priority;
262 inst->alg.base.cra_blocksize = alg->cra_blocksize;
263
264 inst->alg.digestsize = alg->cra_blocksize;
265 inst->alg.descsize =
266 ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment())
267 + (alignmask & ~(crypto_tfm_ctx_alignment() - 1))
268 + alg->cra_blocksize * 2;
269
270 inst->alg.base.cra_ctxsize =
271 ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment())
272 + ((alignmask | (__alignof__(__be64) - 1)) &
273 ~(crypto_tfm_ctx_alignment() - 1))
274 + alg->cra_blocksize * 2;
275
276 inst->alg.base.cra_init = cmac_init_tfm;
277 inst->alg.base.cra_exit = cmac_exit_tfm;
278
279 inst->alg.init = crypto_cmac_digest_init;
280 inst->alg.update = crypto_cmac_digest_update;
281 inst->alg.final = crypto_cmac_digest_final;
282 inst->alg.setkey = crypto_cmac_digest_setkey;
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
crypto_cmac_module_init(void)300 static int __init crypto_cmac_module_init(void)
301 {
302 return crypto_register_template(&crypto_cmac_tmpl);
303 }
304
crypto_cmac_module_exit(void)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
