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/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_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_alg *alg;
 226         unsigned long alignmask;
 227         int err;
 228
 229         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
 230         if (err)
 231                 return err;
 232
 233         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 234                                   CRYPTO_ALG_TYPE_MASK);
 235         if (IS_ERR(alg))
 236                 return PTR_ERR(alg);
 237
 238         switch (alg->cra_blocksize) {
 239         case 16:
 240         case 8:
 241                 break;
 242         default:
 243                 err = -EINVAL;
 244                 goto out_put_alg;
 245         }
 246
 247         inst = shash_alloc_instance("cmac", alg);
 248         err = PTR_ERR(inst);
 249         if (IS_ERR(inst))
 250                 goto out_put_alg;
 251
 252         err = crypto_init_spawn(shash_instance_ctx(inst), alg,
 253                                 shash_crypto_instance(inst),
 254                                 CRYPTO_ALG_TYPE_MASK);
 255         if (err)
 256                 goto out_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         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 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");