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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * CMAC: Cipher Block Mode for Authentication
4 *
5 * Copyright © 2013 Jussi Kivilinna <[email protected]>
6 *
7 * Based on work by:
8 * Copyright © 2013 Tom St Denis <[email protected]>
9 * Based on crypto/xcbc.c:
10 * Copyright © 2006 USAGI/WIDE Project,
11 * Author: Kazunori Miyazawa <[email protected]>
12 */
13
14#include <crypto/internal/cipher.h>
15#include <crypto/internal/hash.h>
16#include <crypto/utils.h>
17#include <linux/err.h>
18#include <linux/kernel.h>
19#include <linux/module.h>
20#include <linux/slab.h>
21#include <linux/string.h>
22
23/*
24 * +------------------------
25 * | <parent tfm>
26 * +------------------------
27 * | cmac_tfm_ctx
28 * +------------------------
29 * | consts (block size * 2)
30 * +------------------------
31 */
32struct cmac_tfm_ctx {
33 struct crypto_cipher *child;
34 __be64 consts[];
35};
36
37static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
38 const u8 *inkey, unsigned int keylen)
39{
40 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
41 unsigned int bs = crypto_shash_blocksize(parent);
42 __be64 *consts = ctx->consts;
43 u64 _const[2];
44 int i, err = 0;
45 u8 msb_mask, gfmask;
46
47 err = crypto_cipher_setkey(ctx->child, inkey, keylen);
48 if (err)
49 return err;
50
51 /* encrypt the zero block */
52 memset(consts, 0, bs);
53 crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
54
55 switch (bs) {
56 case 16:
57 gfmask = 0x87;
58 _const[0] = be64_to_cpu(consts[1]);
59 _const[1] = be64_to_cpu(consts[0]);
60
61 /* gf(2^128) multiply zero-ciphertext with u and u^2 */
62 for (i = 0; i < 4; i += 2) {
63 msb_mask = ((s64)_const[1] >> 63) & gfmask;
64 _const[1] = (_const[1] << 1) | (_const[0] >> 63);
65 _const[0] = (_const[0] << 1) ^ msb_mask;
66
67 consts[i + 0] = cpu_to_be64(_const[1]);
68 consts[i + 1] = cpu_to_be64(_const[0]);
69 }
70
71 break;
72 case 8:
73 gfmask = 0x1B;
74 _const[0] = be64_to_cpu(consts[0]);
75
76 /* gf(2^64) multiply zero-ciphertext with u and u^2 */
77 for (i = 0; i < 2; i++) {
78 msb_mask = ((s64)_const[0] >> 63) & gfmask;
79 _const[0] = (_const[0] << 1) ^ msb_mask;
80
81 consts[i] = cpu_to_be64(_const[0]);
82 }
83
84 break;
85 }
86
87 return 0;
88}
89
90static int crypto_cmac_digest_init(struct shash_desc *pdesc)
91{
92 int bs = crypto_shash_blocksize(pdesc->tfm);
93 u8 *prev = shash_desc_ctx(pdesc);
94
95 memset(prev, 0, bs);
96 return 0;
97}
98
99static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
100 unsigned int len)
101{
102 struct crypto_shash *parent = pdesc->tfm;
103 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
104 struct crypto_cipher *tfm = tctx->child;
105 int bs = crypto_shash_blocksize(parent);
106 u8 *prev = shash_desc_ctx(pdesc);
107
108 do {
109 crypto_xor(prev, p, bs);
110 crypto_cipher_encrypt_one(tfm, prev, prev);
111 p += bs;
112 len -= bs;
113 } while (len >= bs);
114 return len;
115}
116
117static int crypto_cmac_digest_finup(struct shash_desc *pdesc, const u8 *src,
118 unsigned int len, u8 *out)
119{
120 struct crypto_shash *parent = pdesc->tfm;
121 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
122 struct crypto_cipher *tfm = tctx->child;
123 int bs = crypto_shash_blocksize(parent);
124 u8 *prev = shash_desc_ctx(pdesc);
125 unsigned int offset = 0;
126
127 crypto_xor(prev, src, len);
128 if (len != bs) {
129 prev[len] ^= 0x80;
130 offset += bs;
131 }
132 crypto_xor(prev, (const u8 *)tctx->consts + offset, bs);
133 crypto_cipher_encrypt_one(tfm, out, prev);
134 return 0;
135}
136
137static int cmac_init_tfm(struct crypto_shash *tfm)
138{
139 struct shash_instance *inst = shash_alg_instance(tfm);
140 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
141 struct crypto_cipher_spawn *spawn;
142 struct crypto_cipher *cipher;
143
144 spawn = shash_instance_ctx(inst);
145 cipher = crypto_spawn_cipher(spawn);
146 if (IS_ERR(cipher))
147 return PTR_ERR(cipher);
148
149 ctx->child = cipher;
150
151 return 0;
152}
153
154static void cmac_exit_tfm(struct crypto_shash *tfm)
155{
156 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
157 crypto_free_cipher(ctx->child);
158}
159
160static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
161{
162 struct shash_instance *inst;
163 struct crypto_cipher_spawn *spawn;
164 struct crypto_alg *alg;
165 u32 mask;
166 int err;
167
168 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
169 if (err)
170 return err;
171
172 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
173 if (!inst)
174 return -ENOMEM;
175 spawn = shash_instance_ctx(inst);
176
177 err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
178 crypto_attr_alg_name(tb[1]), 0, mask);
179 if (err)
180 goto err_free_inst;
181 alg = crypto_spawn_cipher_alg(spawn);
182
183 switch (alg->cra_blocksize) {
184 case 16:
185 case 8:
186 break;
187 default:
188 err = -EINVAL;
189 goto err_free_inst;
190 }
191
192 err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
193 if (err)
194 goto err_free_inst;
195
196 inst->alg.base.cra_priority = alg->cra_priority;
197 inst->alg.base.cra_blocksize = alg->cra_blocksize;
198 inst->alg.base.cra_ctxsize = sizeof(struct cmac_tfm_ctx) +
199 alg->cra_blocksize * 2;
200 inst->alg.base.cra_flags = CRYPTO_AHASH_ALG_BLOCK_ONLY |
201 CRYPTO_AHASH_ALG_FINAL_NONZERO;
202
203 inst->alg.digestsize = alg->cra_blocksize;
204 inst->alg.descsize = alg->cra_blocksize;
205 inst->alg.init = crypto_cmac_digest_init;
206 inst->alg.update = crypto_cmac_digest_update;
207 inst->alg.finup = crypto_cmac_digest_finup;
208 inst->alg.setkey = crypto_cmac_digest_setkey;
209 inst->alg.init_tfm = cmac_init_tfm;
210 inst->alg.exit_tfm = cmac_exit_tfm;
211
212 inst->free = shash_free_singlespawn_instance;
213
214 err = shash_register_instance(tmpl, inst);
215 if (err) {
216err_free_inst:
217 shash_free_singlespawn_instance(inst);
218 }
219 return err;
220}
221
222static struct crypto_template crypto_cmac_tmpl = {
223 .name = "cmac",
224 .create = cmac_create,
225 .module = THIS_MODULE,
226};
227
228static int __init crypto_cmac_module_init(void)
229{
230 return crypto_register_template(&crypto_cmac_tmpl);
231}
232
233static void __exit crypto_cmac_module_exit(void)
234{
235 crypto_unregister_template(&crypto_cmac_tmpl);
236}
237
238module_init(crypto_cmac_module_init);
239module_exit(crypto_cmac_module_exit);
240
241MODULE_LICENSE("GPL");
242MODULE_DESCRIPTION("CMAC keyed hash algorithm");
243MODULE_ALIAS_CRYPTO("cmac");
244MODULE_IMPORT_NS("CRYPTO_INTERNAL");