crypto/lrw.c

   1 /* LRW: as defined by Cyril Guyot in
   2  *      http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
   3  *
   4  * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
   5  *
   6  * Based om ecb.c
   7  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU General Public License as published by the Free
  11  * Software Foundation; either version 2 of the License, or (at your option)
  12  * any later version.
  13  */
  14 /* This implementation is checked against the test vectors in the above
  15  * document and by a test vector provided by Ken Buchanan at
  16  * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
  17  *
  18  * The test vectors are included in the testing module tcrypt.[ch] */
  19 #include <crypto/algapi.h>
  20 #include <linux/err.h>
  21 #include <linux/init.h>
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/scatterlist.h>
  25 #include <linux/slab.h>
  26
  27 #include <crypto/b128ops.h>
  28 #include <crypto/gf128mul.h>
  29
  30 struct priv {
  31         struct crypto_cipher *child;
  32         /* optimizes multiplying a random (non incrementing, as at the
  33          * start of a new sector) value with key2, we could also have
  34          * used 4k optimization tables or no optimization at all. In the
  35          * latter case we would have to store key2 here */
  36         struct gf128mul_64k *table;
  37         /* stores:
  38          *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
  39          *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
  40          *  key2*{ 0,0,...1,1,1,1,1 }, etc
  41          * needed for optimized multiplication of incrementing values
  42          * with key2 */
  43         be128 mulinc[128];
  44 };
  45
  46 static inline void setbit128_bbe(void *b, int bit)
  47 {
  48         __set_bit(bit ^ 0x78, b);
  49 }
  50
  51 static int setkey(struct crypto_tfm *parent, const u8 *key,
  52                   unsigned int keylen)
  53 {
  54         struct priv *ctx = crypto_tfm_ctx(parent);
  55         struct crypto_cipher *child = ctx->child;
  56         int err, i;
  57         be128 tmp = { 0 };
  58         int bsize = crypto_cipher_blocksize(child);
  59
  60         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  61         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  62                                        CRYPTO_TFM_REQ_MASK);
  63         if ((err = crypto_cipher_setkey(child, key, keylen - bsize)))
  64                 return err;
  65         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  66                                      CRYPTO_TFM_RES_MASK);
  67
  68         if (ctx->table)
  69                 gf128mul_free_64k(ctx->table);
  70
  71         /* initialize multiplication table for Key2 */
  72         ctx->table = gf128mul_init_64k_bbe((be128 *)(key + keylen - bsize));
  73         if (!ctx->table)
  74                 return -ENOMEM;
  75
  76         /* initialize optimization table */
  77         for (i = 0; i < 128; i++) {
  78                 setbit128_bbe(&tmp, i);
  79                 ctx->mulinc[i] = tmp;
  80                 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
  81         }
  82
  83         return 0;
  84 }
  85
  86 struct sinfo {
  87         be128 t;
  88         struct crypto_tfm *tfm;
  89         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  90 };
  91
  92 static inline void inc(be128 *iv)
  93 {
  94         be64_add_cpu(&iv->b, 1);
  95         if (!iv->b)
  96                 be64_add_cpu(&iv->a, 1);
  97 }
  98
  99 static inline void lrw_round(struct sinfo *s, void *dst, const void *src)
 100 {
 101         be128_xor(dst, &s->t, src);             /* PP <- T xor P */
 102         s->fn(s->tfm, dst, dst);                /* CC <- E(Key2,PP) */
 103         be128_xor(dst, dst, &s->t);             /* C <- T xor CC */
 104 }
 105
 106 /* this returns the number of consequative 1 bits starting
 107  * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
 108 static inline int get_index128(be128 *block)
 109 {
 110         int x;
 111         __be32 *p = (__be32 *) block;
 112
 113         for (p += 3, x = 0; x < 128; p--, x += 32) {
 114                 u32 val = be32_to_cpup(p);
 115
 116                 if (!~val)
 117                         continue;
 118
 119                 return x + ffz(val);
 120         }
 121
 122         return x;
 123 }
 124
 125 static int crypt(struct blkcipher_desc *d,
 126                  struct blkcipher_walk *w, struct priv *ctx,
 127                  void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
 128 {
 129         int err;
 130         unsigned int avail;
 131         const int bs = crypto_cipher_blocksize(ctx->child);
 132         struct sinfo s = {
 133                 .tfm = crypto_cipher_tfm(ctx->child),
 134                 .fn = fn
 135         };
 136         be128 *iv;
 137         u8 *wsrc;
 138         u8 *wdst;
 139
 140         err = blkcipher_walk_virt(d, w);
 141         if (!(avail = w->nbytes))
 142                 return err;
 143
 144         wsrc = w->src.virt.addr;
 145         wdst = w->dst.virt.addr;
 146
 147         /* calculate first value of T */
 148         iv = (be128 *)w->iv;
 149         s.t = *iv;
 150
 151         /* T <- I*Key2 */
 152         gf128mul_64k_bbe(&s.t, ctx->table);
 153
 154         goto first;
 155
 156         for (;;) {
 157                 do {
 158                         /* T <- I*Key2, using the optimization
 159                          * discussed in the specification */
 160                         be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]);
 161                         inc(iv);
 162
 163 first:
 164                         lrw_round(&s, wdst, wsrc);
 165
 166                         wsrc += bs;
 167                         wdst += bs;
 168                 } while ((avail -= bs) >= bs);
 169
 170                 err = blkcipher_walk_done(d, w, avail);
 171                 if (!(avail = w->nbytes))
 172                         break;
 173
 174                 wsrc = w->src.virt.addr;
 175                 wdst = w->dst.virt.addr;
 176         }
 177
 178         return err;
 179 }
 180
 181 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 182                    struct scatterlist *src, unsigned int nbytes)
 183 {
 184         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 185         struct blkcipher_walk w;
 186
 187         blkcipher_walk_init(&w, dst, src, nbytes);
 188         return crypt(desc, &w, ctx,
 189                      crypto_cipher_alg(ctx->child)->cia_encrypt);
 190 }
 191
 192 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 193                    struct scatterlist *src, unsigned int nbytes)
 194 {
 195         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 196         struct blkcipher_walk w;
 197
 198         blkcipher_walk_init(&w, dst, src, nbytes);
 199         return crypt(desc, &w, ctx,
 200                      crypto_cipher_alg(ctx->child)->cia_decrypt);
 201 }
 202
 203 static int 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 priv *ctx = crypto_tfm_ctx(tfm);
 209         u32 *flags = &tfm->crt_flags;
 210
 211         cipher = crypto_spawn_cipher(spawn);
 212         if (IS_ERR(cipher))
 213                 return PTR_ERR(cipher);
 214
 215         if (crypto_cipher_blocksize(cipher) != 16) {
 216                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 217                 return -EINVAL;
 218         }
 219
 220         ctx->child = cipher;
 221         return 0;
 222 }
 223
 224 static void exit_tfm(struct crypto_tfm *tfm)
 225 {
 226         struct priv *ctx = crypto_tfm_ctx(tfm);
 227         if (ctx->table)
 228                 gf128mul_free_64k(ctx->table);
 229         crypto_free_cipher(ctx->child);
 230 }
 231
 232 static struct crypto_instance *alloc(struct rtattr **tb)
 233 {
 234         struct crypto_instance *inst;
 235         struct crypto_alg *alg;
 236         int err;
 237
 238         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 239         if (err)
 240                 return ERR_PTR(err);
 241
 242         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 243                                   CRYPTO_ALG_TYPE_MASK);
 244         if (IS_ERR(alg))
 245                 return ERR_CAST(alg);
 246
 247         inst = crypto_alloc_instance("lrw", alg);
 248         if (IS_ERR(inst))
 249                 goto out_put_alg;
 250
 251         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 252         inst->alg.cra_priority = alg->cra_priority;
 253         inst->alg.cra_blocksize = alg->cra_blocksize;
 254
 255         if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
 256         else inst->alg.cra_alignmask = alg->cra_alignmask;
 257         inst->alg.cra_type = &crypto_blkcipher_type;
 258
 259         if (!(alg->cra_blocksize % 4))
 260                 inst->alg.cra_alignmask |= 3;
 261         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 262         inst->alg.cra_blkcipher.min_keysize =
 263                 alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
 264         inst->alg.cra_blkcipher.max_keysize =
 265                 alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;
 266
 267         inst->alg.cra_ctxsize = sizeof(struct priv);
 268
 269         inst->alg.cra_init = init_tfm;
 270         inst->alg.cra_exit = exit_tfm;
 271
 272         inst->alg.cra_blkcipher.setkey = setkey;
 273         inst->alg.cra_blkcipher.encrypt = encrypt;
 274         inst->alg.cra_blkcipher.decrypt = decrypt;
 275
 276 out_put_alg:
 277         crypto_mod_put(alg);
 278         return inst;
 279 }
 280
 281 static void free(struct crypto_instance *inst)
 282 {
 283         crypto_drop_spawn(crypto_instance_ctx(inst));
 284         kfree(inst);
 285 }
 286
 287 static struct crypto_template crypto_tmpl = {
 288         .name = "lrw",
 289         .alloc = alloc,
 290         .free = free,
 291         .module = THIS_MODULE,
 292 };
 293
 294 static int __init crypto_module_init(void)
 295 {
 296         return crypto_register_template(&crypto_tmpl);
 297 }
 298
 299 static void __exit crypto_module_exit(void)
 300 {
 301         crypto_unregister_template(&crypto_tmpl);
 302 }
 303
 304 module_init(crypto_module_init);
 305 module_exit(crypto_module_exit);
 306
 307 MODULE_LICENSE("GPL");
 308 MODULE_DESCRIPTION("LRW block cipher mode");