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 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 } 103 104 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 } 116 117 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 } 163 164 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 } 199 200 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 }; 215 216 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 } 221 222 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 int err; 229 230 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH); 231 if (err) 232 return err; 233 234 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL); 235 if (!inst) 236 return -ENOMEM; 237 spawn = shash_instance_ctx(inst); 238 239 err = crypto_grab_cipher(spawn, shash_crypto_instance(inst), 240 crypto_attr_alg_name(tb[1]), 0, 0); 241 if (err) 242 goto err_free_inst; 243 alg = crypto_spawn_cipher_alg(spawn); 244 245 switch (alg->cra_blocksize) { 246 case 16: 247 case 8: 248 break; 249 default: 250 err = -EINVAL; 251 goto err_free_inst; 252 } 253 254 err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg); 255 if (err) 256 goto err_free_inst; 257 258 alignmask = alg->cra_alignmask; 259 inst->alg.base.cra_alignmask = alignmask; 260 inst->alg.base.cra_priority = alg->cra_priority; 261 inst->alg.base.cra_blocksize = alg->cra_blocksize; 262 263 inst->alg.digestsize = alg->cra_blocksize; 264 inst->alg.descsize = 265 ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment()) 266 + (alignmask & ~(crypto_tfm_ctx_alignment() - 1)) 267 + alg->cra_blocksize * 2; 268 269 inst->alg.base.cra_ctxsize = 270 ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment()) 271 + ((alignmask | (__alignof__(__be64) - 1)) & 272 ~(crypto_tfm_ctx_alignment() - 1)) 273 + alg->cra_blocksize * 2; 274 275 inst->alg.base.cra_init = cmac_init_tfm; 276 inst->alg.base.cra_exit = cmac_exit_tfm; 277 278 inst->alg.init = crypto_cmac_digest_init; 279 inst->alg.update = crypto_cmac_digest_update; 280 inst->alg.final = crypto_cmac_digest_final; 281 inst->alg.setkey = crypto_cmac_digest_setkey; 282 283 inst->free = shash_free_singlespawn_instance; 284 285 err = shash_register_instance(tmpl, inst); 286 if (err) { 287 err_free_inst: 288 shash_free_singlespawn_instance(inst); 289 } 290 return err; 291 } 292 293 static struct crypto_template crypto_cmac_tmpl = { 294 .name = "cmac", 295 .create = cmac_create, 296 .module = THIS_MODULE, 297 }; 298 299 static int __init crypto_cmac_module_init(void) 300 { 301 return crypto_register_template(&crypto_cmac_tmpl); 302 } 303 304 static void __exit crypto_cmac_module_exit(void) 305 { 306 crypto_unregister_template(&crypto_cmac_tmpl); 307 } 308 309 subsys_initcall(crypto_cmac_module_init); 310 module_exit(crypto_cmac_module_exit); 311 312 MODULE_LICENSE("GPL"); 313 MODULE_DESCRIPTION("CMAC keyed hash algorithm"); 314 MODULE_ALIAS_CRYPTO("cmac"); 315