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_tfm * tfm)201 static int cmac_init_tfm(struct crypto_tfm *tfm)
202 {
203 	struct crypto_cipher *cipher;
204 	struct crypto_instance *inst = (void *)tfm->__crt_alg;
205 	struct crypto_cipher_spawn *spawn = crypto_instance_ctx(inst);
206 	struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
207 
208 	cipher = crypto_spawn_cipher(spawn);
209 	if (IS_ERR(cipher))
210 		return PTR_ERR(cipher);
211 
212 	ctx->child = cipher;
213 
214 	return 0;
215 };
216 
cmac_exit_tfm(struct crypto_tfm * tfm)217 static void cmac_exit_tfm(struct crypto_tfm *tfm)
218 {
219 	struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
220 	crypto_free_cipher(ctx->child);
221 }
222 
cmac_create(struct crypto_template * tmpl,struct rtattr ** tb)223 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
224 {
225 	struct shash_instance *inst;
226 	struct crypto_cipher_spawn *spawn;
227 	struct crypto_alg *alg;
228 	unsigned long alignmask;
229 	u32 mask;
230 	int err;
231 
232 	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
233 	if (err)
234 		return err;
235 
236 	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
237 	if (!inst)
238 		return -ENOMEM;
239 	spawn = shash_instance_ctx(inst);
240 
241 	err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
242 				 crypto_attr_alg_name(tb[1]), 0, mask);
243 	if (err)
244 		goto err_free_inst;
245 	alg = crypto_spawn_cipher_alg(spawn);
246 
247 	switch (alg->cra_blocksize) {
248 	case 16:
249 	case 8:
250 		break;
251 	default:
252 		err = -EINVAL;
253 		goto err_free_inst;
254 	}
255 
256 	err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
257 	if (err)
258 		goto err_free_inst;
259 
260 	alignmask = alg->cra_alignmask;
261 	inst->alg.base.cra_alignmask = alignmask;
262 	inst->alg.base.cra_priority = alg->cra_priority;
263 	inst->alg.base.cra_blocksize = alg->cra_blocksize;
264 
265 	inst->alg.digestsize = alg->cra_blocksize;
266 	inst->alg.descsize =
267 		ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment())
268 		+ (alignmask & ~(crypto_tfm_ctx_alignment() - 1))
269 		+ alg->cra_blocksize * 2;
270 
271 	inst->alg.base.cra_ctxsize =
272 		ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment())
273 		+ ((alignmask | (__alignof__(__be64) - 1)) &
274 		   ~(crypto_tfm_ctx_alignment() - 1))
275 		+ alg->cra_blocksize * 2;
276 
277 	inst->alg.base.cra_init = cmac_init_tfm;
278 	inst->alg.base.cra_exit = cmac_exit_tfm;
279 
280 	inst->alg.init = crypto_cmac_digest_init;
281 	inst->alg.update = crypto_cmac_digest_update;
282 	inst->alg.final = crypto_cmac_digest_final;
283 	inst->alg.setkey = crypto_cmac_digest_setkey;
284 
285 	inst->free = shash_free_singlespawn_instance;
286 
287 	err = shash_register_instance(tmpl, inst);
288 	if (err) {
289 err_free_inst:
290 		shash_free_singlespawn_instance(inst);
291 	}
292 	return err;
293 }
294 
295 static struct crypto_template crypto_cmac_tmpl = {
296 	.name = "cmac",
297 	.create = cmac_create,
298 	.module = THIS_MODULE,
299 };
300 
crypto_cmac_module_init(void)301 static int __init crypto_cmac_module_init(void)
302 {
303 	return crypto_register_template(&crypto_cmac_tmpl);
304 }
305 
crypto_cmac_module_exit(void)306 static void __exit crypto_cmac_module_exit(void)
307 {
308 	crypto_unregister_template(&crypto_cmac_tmpl);
309 }
310 
311 subsys_initcall(crypto_cmac_module_init);
312 module_exit(crypto_cmac_module_exit);
313 
314 MODULE_LICENSE("GPL");
315 MODULE_DESCRIPTION("CMAC keyed hash algorithm");
316 MODULE_ALIAS_CRYPTO("cmac");
317 MODULE_IMPORT_NS(CRYPTO_INTERNAL);
318