xref: /openbmc/linux/crypto/cmac.c (revision 1cb8f3e2d8fe7533c26df9925a83bd3d185b312e)
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  
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  
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  
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  
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  
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  
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  
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  
301  static int __init crypto_cmac_module_init(void)
302  {
303  	return crypto_register_template(&crypto_cmac_tmpl);
304  }
305  
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