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         if (!(iv->b = cpu_to_be64(be64_to_cpu(iv->b) + 1)))
  95                 iv->a = cpu_to_be64(be64_to_cpu(iv->a) + 1);
  96 }
  97
  98 static inline void lrw_round(struct sinfo *s, void *dst, const void *src)
  99 {
 100         be128_xor(dst, &s->t, src);             /* PP <- T xor P */
 101         s->fn(s->tfm, dst, dst);                /* CC <- E(Key2,PP) */
 102         be128_xor(dst, dst, &s->t);             /* C <- T xor CC */
 103 }
 104
 105 /* this returns the number of consequative 1 bits starting
 106  * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
 107 static inline int get_index128(be128 *block)
 108 {
 109         int x;
 110         __be32 *p = (__be32 *) block;
 111
 112         for (p += 3, x = 0; x < 128; p--, x += 32) {
 113                 u32 val = be32_to_cpup(p);
 114
 115                 if (!~val)
 116                         continue;
 117
 118                 return x + ffz(val);
 119         }
 120
 121         return x;
 122 }
 123
 124 static int crypt(struct blkcipher_desc *d,
 125                  struct blkcipher_walk *w, struct priv *ctx,
 126                  void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
 127 {
 128         int err;
 129         unsigned int avail;
 130         const int bs = crypto_cipher_blocksize(ctx->child);
 131         struct sinfo s = {
 132                 .tfm = crypto_cipher_tfm(ctx->child),
 133                 .fn = fn
 134         };
 135         be128 *iv;
 136         u8 *wsrc;
 137         u8 *wdst;
 138
 139         err = blkcipher_walk_virt(d, w);
 140         if (!(avail = w->nbytes))
 141                 return err;
 142
 143         wsrc = w->src.virt.addr;
 144         wdst = w->dst.virt.addr;
 145
 146         /* calculate first value of T */
 147         iv = (be128 *)w->iv;
 148         s.t = *iv;
 149
 150         /* T <- I*Key2 */
 151         gf128mul_64k_bbe(&s.t, ctx->table);
 152
 153         goto first;
 154
 155         for (;;) {
 156                 do {
 157                         /* T <- I*Key2, using the optimization
 158                          * discussed in the specification */
 159                         be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]);
 160                         inc(iv);
 161
 162 first:
 163                         lrw_round(&s, wdst, wsrc);
 164
 165                         wsrc += bs;
 166                         wdst += bs;
 167                 } while ((avail -= bs) >= bs);
 168
 169                 err = blkcipher_walk_done(d, w, avail);
 170                 if (!(avail = w->nbytes))
 171                         break;
 172
 173                 wsrc = w->src.virt.addr;
 174                 wdst = w->dst.virt.addr;
 175         }
 176
 177         return err;
 178 }
 179
 180 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 181                    struct scatterlist *src, unsigned int nbytes)
 182 {
 183         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 184         struct blkcipher_walk w;
 185
 186         blkcipher_walk_init(&w, dst, src, nbytes);
 187         return crypt(desc, &w, ctx,
 188                      crypto_cipher_alg(ctx->child)->cia_encrypt);
 189 }
 190
 191 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 192                    struct scatterlist *src, unsigned int nbytes)
 193 {
 194         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 195         struct blkcipher_walk w;
 196
 197         blkcipher_walk_init(&w, dst, src, nbytes);
 198         return crypt(desc, &w, ctx,
 199                      crypto_cipher_alg(ctx->child)->cia_decrypt);
 200 }
 201
 202 static int init_tfm(struct crypto_tfm *tfm)
 203 {
 204         struct crypto_cipher *cipher;
 205         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 206         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 207         struct priv *ctx = crypto_tfm_ctx(tfm);
 208         u32 *flags = &tfm->crt_flags;
 209
 210         cipher = crypto_spawn_cipher(spawn);
 211         if (IS_ERR(cipher))
 212                 return PTR_ERR(cipher);
 213
 214         if (crypto_cipher_blocksize(cipher) != 16) {
 215                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 216                 return -EINVAL;
 217         }
 218
 219         ctx->child = cipher;
 220         return 0;
 221 }
 222
 223 static void exit_tfm(struct crypto_tfm *tfm)
 224 {
 225         struct priv *ctx = crypto_tfm_ctx(tfm);
 226         if (ctx->table)
 227                 gf128mul_free_64k(ctx->table);
 228         crypto_free_cipher(ctx->child);
 229 }
 230
 231 static struct crypto_instance *alloc(struct rtattr **tb)
 232 {
 233         struct crypto_instance *inst;
 234         struct crypto_alg *alg;
 235         int err;
 236
 237         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 238         if (err)
 239                 return ERR_PTR(err);
 240
 241         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 242                                   CRYPTO_ALG_TYPE_MASK);
 243         if (IS_ERR(alg))
 244                 return ERR_PTR(PTR_ERR(alg));
 245
 246         inst = crypto_alloc_instance("lrw", alg);
 247         if (IS_ERR(inst))
 248                 goto out_put_alg;
 249
 250         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 251         inst->alg.cra_priority = alg->cra_priority;
 252         inst->alg.cra_blocksize = alg->cra_blocksize;
 253
 254         if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
 255         else inst->alg.cra_alignmask = alg->cra_alignmask;
 256         inst->alg.cra_type = &crypto_blkcipher_type;
 257
 258         if (!(alg->cra_blocksize % 4))
 259                 inst->alg.cra_alignmask |= 3;
 260         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 261         inst->alg.cra_blkcipher.min_keysize =
 262                 alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
 263         inst->alg.cra_blkcipher.max_keysize =
 264                 alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;
 265
 266         inst->alg.cra_ctxsize = sizeof(struct priv);
 267
 268         inst->alg.cra_init = init_tfm;
 269         inst->alg.cra_exit = exit_tfm;
 270
 271         inst->alg.cra_blkcipher.setkey = setkey;
 272         inst->alg.cra_blkcipher.encrypt = encrypt;
 273         inst->alg.cra_blkcipher.decrypt = decrypt;
 274
 275 out_put_alg:
 276         crypto_mod_put(alg);
 277         return inst;
 278 }
 279
 280 static void free(struct crypto_instance *inst)
 281 {
 282         crypto_drop_spawn(crypto_instance_ctx(inst));
 283         kfree(inst);
 284 }
 285
 286 static struct crypto_template crypto_tmpl = {
 287         .name = "lrw",
 288         .alloc = alloc,
 289         .free = free,
 290         .module = THIS_MODULE,
 291 };
 292
 293 static int __init crypto_module_init(void)
 294 {
 295         return crypto_register_template(&crypto_tmpl);
 296 }
 297
 298 static void __exit crypto_module_exit(void)
 299 {
 300         crypto_unregister_template(&crypto_tmpl);
 301 }
 302
 303 module_init(crypto_module_init);
 304 module_exit(crypto_module_exit);
 305
 306 MODULE_LICENSE("GPL");
 307 MODULE_DESCRIPTION("LRW block cipher mode");