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_shash * tfm)201 static int cmac_init_tfm(struct crypto_shash *tfm) 202 { 203 struct shash_instance *inst = shash_alg_instance(tfm); 204 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm); 205 struct crypto_cipher_spawn *spawn; 206 struct crypto_cipher *cipher; 207 208 spawn = shash_instance_ctx(inst); 209 cipher = crypto_spawn_cipher(spawn); 210 if (IS_ERR(cipher)) 211 return PTR_ERR(cipher); 212 213 ctx->child = cipher; 214 215 return 0; 216 } 217 cmac_clone_tfm(struct crypto_shash * tfm,struct crypto_shash * otfm)218 static int cmac_clone_tfm(struct crypto_shash *tfm, struct crypto_shash *otfm) 219 { 220 struct cmac_tfm_ctx *octx = crypto_shash_ctx(otfm); 221 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm); 222 struct crypto_cipher *cipher; 223 224 cipher = crypto_clone_cipher(octx->child); 225 if (IS_ERR(cipher)) 226 return PTR_ERR(cipher); 227 228 ctx->child = cipher; 229 230 return 0; 231 } 232 cmac_exit_tfm(struct crypto_shash * tfm)233 static void cmac_exit_tfm(struct crypto_shash *tfm) 234 { 235 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm); 236 crypto_free_cipher(ctx->child); 237 } 238 cmac_create(struct crypto_template * tmpl,struct rtattr ** tb)239 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb) 240 { 241 struct shash_instance *inst; 242 struct crypto_cipher_spawn *spawn; 243 struct crypto_alg *alg; 244 unsigned long alignmask; 245 u32 mask; 246 int err; 247 248 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask); 249 if (err) 250 return err; 251 252 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL); 253 if (!inst) 254 return -ENOMEM; 255 spawn = shash_instance_ctx(inst); 256 257 err = crypto_grab_cipher(spawn, shash_crypto_instance(inst), 258 crypto_attr_alg_name(tb[1]), 0, mask); 259 if (err) 260 goto err_free_inst; 261 alg = crypto_spawn_cipher_alg(spawn); 262 263 switch (alg->cra_blocksize) { 264 case 16: 265 case 8: 266 break; 267 default: 268 err = -EINVAL; 269 goto err_free_inst; 270 } 271 272 err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg); 273 if (err) 274 goto err_free_inst; 275 276 alignmask = alg->cra_alignmask; 277 inst->alg.base.cra_alignmask = alignmask; 278 inst->alg.base.cra_priority = alg->cra_priority; 279 inst->alg.base.cra_blocksize = alg->cra_blocksize; 280 281 inst->alg.digestsize = alg->cra_blocksize; 282 inst->alg.descsize = 283 ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment()) 284 + (alignmask & ~(crypto_tfm_ctx_alignment() - 1)) 285 + alg->cra_blocksize * 2; 286 287 inst->alg.base.cra_ctxsize = 288 ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment()) 289 + ((alignmask | (__alignof__(__be64) - 1)) & 290 ~(crypto_tfm_ctx_alignment() - 1)) 291 + alg->cra_blocksize * 2; 292 293 inst->alg.init = crypto_cmac_digest_init; 294 inst->alg.update = crypto_cmac_digest_update; 295 inst->alg.final = crypto_cmac_digest_final; 296 inst->alg.setkey = crypto_cmac_digest_setkey; 297 inst->alg.init_tfm = cmac_init_tfm; 298 inst->alg.clone_tfm = cmac_clone_tfm; 299 inst->alg.exit_tfm = cmac_exit_tfm; 300 301 inst->free = shash_free_singlespawn_instance; 302 303 err = shash_register_instance(tmpl, inst); 304 if (err) { 305 err_free_inst: 306 shash_free_singlespawn_instance(inst); 307 } 308 return err; 309 } 310 311 static struct crypto_template crypto_cmac_tmpl = { 312 .name = "cmac", 313 .create = cmac_create, 314 .module = THIS_MODULE, 315 }; 316 crypto_cmac_module_init(void)317 static int __init crypto_cmac_module_init(void) 318 { 319 return crypto_register_template(&crypto_cmac_tmpl); 320 } 321 crypto_cmac_module_exit(void)322 static void __exit crypto_cmac_module_exit(void) 323 { 324 crypto_unregister_template(&crypto_cmac_tmpl); 325 } 326 327 subsys_initcall(crypto_cmac_module_init); 328 module_exit(crypto_cmac_module_exit); 329 330 MODULE_LICENSE("GPL"); 331 MODULE_DESCRIPTION("CMAC keyed hash algorithm"); 332 MODULE_ALIAS_CRYPTO("cmac"); 333 MODULE_IMPORT_NS(CRYPTO_INTERNAL); 334