1 /* 2 * CMAC: Cipher Block Mode for Authentication 3 * 4 * Copyright © 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi> 5 * 6 * Based on work by: 7 * Copyright © 2013 Tom St Denis <tstdenis@elliptictech.com> 8 * Based on crypto/xcbc.c: 9 * Copyright © 2006 USAGI/WIDE Project, 10 * Author: Kazunori Miyazawa <miyazawa@linux-ipv6.org> 11 * 12 * This program is free software; you can redistribute it and/or modify 13 * it under the terms of the GNU General Public License as published by 14 * the Free Software Foundation; either version 2 of the License, or 15 * (at your option) any later version. 16 * 17 */ 18 19 #include <crypto/internal/hash.h> 20 #include <linux/err.h> 21 #include <linux/kernel.h> 22 #include <linux/module.h> 23 24 /* 25 * +------------------------ 26 * | <parent tfm> 27 * +------------------------ 28 * | cmac_tfm_ctx 29 * +------------------------ 30 * | consts (block size * 2) 31 * +------------------------ 32 */ 33 struct cmac_tfm_ctx { 34 struct crypto_cipher *child; 35 u8 ctx[]; 36 }; 37 38 /* 39 * +------------------------ 40 * | <shash desc> 41 * +------------------------ 42 * | cmac_desc_ctx 43 * +------------------------ 44 * | odds (block size) 45 * +------------------------ 46 * | prev (block size) 47 * +------------------------ 48 */ 49 struct cmac_desc_ctx { 50 unsigned int len; 51 u8 ctx[]; 52 }; 53 54 static int crypto_cmac_digest_setkey(struct crypto_shash *parent, 55 const u8 *inkey, unsigned int keylen) 56 { 57 unsigned long alignmask = crypto_shash_alignmask(parent); 58 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent); 59 unsigned int bs = crypto_shash_blocksize(parent); 60 __be64 *consts = PTR_ALIGN((void *)ctx->ctx, alignmask + 1); 61 u64 _const[2]; 62 int i, err = 0; 63 u8 msb_mask, gfmask; 64 65 err = crypto_cipher_setkey(ctx->child, inkey, keylen); 66 if (err) 67 return err; 68 69 /* encrypt the zero block */ 70 memset(consts, 0, bs); 71 crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts); 72 73 switch (bs) { 74 case 16: 75 gfmask = 0x87; 76 _const[0] = be64_to_cpu(consts[1]); 77 _const[1] = be64_to_cpu(consts[0]); 78 79 /* gf(2^128) multiply zero-ciphertext with u and u^2 */ 80 for (i = 0; i < 4; i += 2) { 81 msb_mask = ((s64)_const[1] >> 63) & gfmask; 82 _const[1] = (_const[1] << 1) | (_const[0] >> 63); 83 _const[0] = (_const[0] << 1) ^ msb_mask; 84 85 consts[i + 0] = cpu_to_be64(_const[1]); 86 consts[i + 1] = cpu_to_be64(_const[0]); 87 } 88 89 break; 90 case 8: 91 gfmask = 0x1B; 92 _const[0] = be64_to_cpu(consts[0]); 93 94 /* gf(2^64) multiply zero-ciphertext with u and u^2 */ 95 for (i = 0; i < 2; i++) { 96 msb_mask = ((s64)_const[0] >> 63) & gfmask; 97 _const[0] = (_const[0] << 1) ^ msb_mask; 98 99 consts[i] = cpu_to_be64(_const[0]); 100 } 101 102 break; 103 } 104 105 return 0; 106 } 107 108 static int crypto_cmac_digest_init(struct shash_desc *pdesc) 109 { 110 unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm); 111 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc); 112 int bs = crypto_shash_blocksize(pdesc->tfm); 113 u8 *prev = PTR_ALIGN((void *)ctx->ctx, alignmask + 1) + bs; 114 115 ctx->len = 0; 116 memset(prev, 0, bs); 117 118 return 0; 119 } 120 121 static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p, 122 unsigned int len) 123 { 124 struct crypto_shash *parent = pdesc->tfm; 125 unsigned long alignmask = crypto_shash_alignmask(parent); 126 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent); 127 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc); 128 struct crypto_cipher *tfm = tctx->child; 129 int bs = crypto_shash_blocksize(parent); 130 u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1); 131 u8 *prev = odds + bs; 132 133 /* checking the data can fill the block */ 134 if ((ctx->len + len) <= bs) { 135 memcpy(odds + ctx->len, p, len); 136 ctx->len += len; 137 return 0; 138 } 139 140 /* filling odds with new data and encrypting it */ 141 memcpy(odds + ctx->len, p, bs - ctx->len); 142 len -= bs - ctx->len; 143 p += bs - ctx->len; 144 145 crypto_xor(prev, odds, bs); 146 crypto_cipher_encrypt_one(tfm, prev, prev); 147 148 /* clearing the length */ 149 ctx->len = 0; 150 151 /* encrypting the rest of data */ 152 while (len > bs) { 153 crypto_xor(prev, p, bs); 154 crypto_cipher_encrypt_one(tfm, prev, prev); 155 p += bs; 156 len -= bs; 157 } 158 159 /* keeping the surplus of blocksize */ 160 if (len) { 161 memcpy(odds, p, len); 162 ctx->len = len; 163 } 164 165 return 0; 166 } 167 168 static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out) 169 { 170 struct crypto_shash *parent = pdesc->tfm; 171 unsigned long alignmask = crypto_shash_alignmask(parent); 172 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent); 173 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc); 174 struct crypto_cipher *tfm = tctx->child; 175 int bs = crypto_shash_blocksize(parent); 176 u8 *consts = PTR_ALIGN((void *)tctx->ctx, alignmask + 1); 177 u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1); 178 u8 *prev = odds + bs; 179 unsigned int offset = 0; 180 181 if (ctx->len != bs) { 182 unsigned int rlen; 183 u8 *p = odds + ctx->len; 184 185 *p = 0x80; 186 p++; 187 188 rlen = bs - ctx->len - 1; 189 if (rlen) 190 memset(p, 0, rlen); 191 192 offset += bs; 193 } 194 195 crypto_xor(prev, odds, bs); 196 crypto_xor(prev, consts + offset, bs); 197 198 crypto_cipher_encrypt_one(tfm, out, prev); 199 200 return 0; 201 } 202 203 static int cmac_init_tfm(struct crypto_tfm *tfm) 204 { 205 struct crypto_cipher *cipher; 206 struct crypto_instance *inst = (void *)tfm->__crt_alg; 207 struct crypto_spawn *spawn = crypto_instance_ctx(inst); 208 struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm); 209 210 cipher = crypto_spawn_cipher(spawn); 211 if (IS_ERR(cipher)) 212 return PTR_ERR(cipher); 213 214 ctx->child = cipher; 215 216 return 0; 217 }; 218 219 static void cmac_exit_tfm(struct crypto_tfm *tfm) 220 { 221 struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm); 222 crypto_free_cipher(ctx->child); 223 } 224 225 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb) 226 { 227 struct shash_instance *inst; 228 struct crypto_alg *alg; 229 unsigned long alignmask; 230 int err; 231 232 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH); 233 if (err) 234 return err; 235 236 alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, 237 CRYPTO_ALG_TYPE_MASK); 238 if (IS_ERR(alg)) 239 return PTR_ERR(alg); 240 241 switch (alg->cra_blocksize) { 242 case 16: 243 case 8: 244 break; 245 default: 246 goto out_put_alg; 247 } 248 249 inst = shash_alloc_instance("cmac", alg); 250 err = PTR_ERR(inst); 251 if (IS_ERR(inst)) 252 goto out_put_alg; 253 254 err = crypto_init_spawn(shash_instance_ctx(inst), alg, 255 shash_crypto_instance(inst), 256 CRYPTO_ALG_TYPE_MASK); 257 if (err) 258 goto out_free_inst; 259 260 alignmask = alg->cra_alignmask | (sizeof(long) - 1); 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), alignmask + 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 err = shash_register_instance(tmpl, inst); 284 if (err) { 285 out_free_inst: 286 shash_free_instance(shash_crypto_instance(inst)); 287 } 288 289 out_put_alg: 290 crypto_mod_put(alg); 291 return err; 292 } 293 294 static struct crypto_template crypto_cmac_tmpl = { 295 .name = "cmac", 296 .create = cmac_create, 297 .free = shash_free_instance, 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 module_init(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