crypto/cmac.c

   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);