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 ^ (0x80 -
  49 #ifdef __BIG_ENDIAN
  50                          BITS_PER_LONG
  51 #else
  52                          BITS_PER_BYTE
  53 #endif
  54                         ), b);
  55 }
  56
  57 static int setkey(struct crypto_tfm *parent, const u8 *key,
  58                   unsigned int keylen)
  59 {
  60         struct priv *ctx = crypto_tfm_ctx(parent);
  61         struct crypto_cipher *child = ctx->child;
  62         int err, i;
  63         be128 tmp = { 0 };
  64         int bsize = crypto_cipher_blocksize(child);
  65
  66         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  67         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  68                                        CRYPTO_TFM_REQ_MASK);
  69         if ((err = crypto_cipher_setkey(child, key, keylen - bsize)))
  70                 return err;
  71         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  72                                      CRYPTO_TFM_RES_MASK);
  73
  74         if (ctx->table)
  75                 gf128mul_free_64k(ctx->table);
  76
  77         /* initialize multiplication table for Key2 */
  78         ctx->table = gf128mul_init_64k_bbe((be128 *)(key + keylen - bsize));
  79         if (!ctx->table)
  80                 return -ENOMEM;
  81
  82         /* initialize optimization table */
  83         for (i = 0; i < 128; i++) {
  84                 setbit128_bbe(&tmp, i);
  85                 ctx->mulinc[i] = tmp;
  86                 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
  87         }
  88
  89         return 0;
  90 }
  91
  92 struct sinfo {
  93         be128 t;
  94         struct crypto_tfm *tfm;
  95         void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  96 };
  97
  98 static inline void inc(be128 *iv)
  99 {
 100         be64_add_cpu(&iv->b, 1);
 101         if (!iv->b)
 102                 be64_add_cpu(&iv->a, 1);
 103 }
 104
 105 static inline void lrw_round(struct sinfo *s, void *dst, const void *src)
 106 {
 107         be128_xor(dst, &s->t, src);             /* PP <- T xor P */
 108         s->fn(s->tfm, dst, dst);                /* CC <- E(Key2,PP) */
 109         be128_xor(dst, dst, &s->t);             /* C <- T xor CC */
 110 }
 111
 112 /* this returns the number of consequative 1 bits starting
 113  * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
 114 static inline int get_index128(be128 *block)
 115 {
 116         int x;
 117         __be32 *p = (__be32 *) block;
 118
 119         for (p += 3, x = 0; x < 128; p--, x += 32) {
 120                 u32 val = be32_to_cpup(p);
 121
 122                 if (!~val)
 123                         continue;
 124
 125                 return x + ffz(val);
 126         }
 127
 128         return x;
 129 }
 130
 131 static int crypt(struct blkcipher_desc *d,
 132                  struct blkcipher_walk *w, struct priv *ctx,
 133                  void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
 134 {
 135         int err;
 136         unsigned int avail;
 137         const int bs = crypto_cipher_blocksize(ctx->child);
 138         struct sinfo s = {
 139                 .tfm = crypto_cipher_tfm(ctx->child),
 140                 .fn = fn
 141         };
 142         be128 *iv;
 143         u8 *wsrc;
 144         u8 *wdst;
 145
 146         err = blkcipher_walk_virt(d, w);
 147         if (!(avail = w->nbytes))
 148                 return err;
 149
 150         wsrc = w->src.virt.addr;
 151         wdst = w->dst.virt.addr;
 152
 153         /* calculate first value of T */
 154         iv = (be128 *)w->iv;
 155         s.t = *iv;
 156
 157         /* T <- I*Key2 */
 158         gf128mul_64k_bbe(&s.t, ctx->table);
 159
 160         goto first;
 161
 162         for (;;) {
 163                 do {
 164                         /* T <- I*Key2, using the optimization
 165                          * discussed in the specification */
 166                         be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]);
 167                         inc(iv);
 168
 169 first:
 170                         lrw_round(&s, wdst, wsrc);
 171
 172                         wsrc += bs;
 173                         wdst += bs;
 174                 } while ((avail -= bs) >= bs);
 175
 176                 err = blkcipher_walk_done(d, w, avail);
 177                 if (!(avail = w->nbytes))
 178                         break;
 179
 180                 wsrc = w->src.virt.addr;
 181                 wdst = w->dst.virt.addr;
 182         }
 183
 184         return err;
 185 }
 186
 187 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 188                    struct scatterlist *src, unsigned int nbytes)
 189 {
 190         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 191         struct blkcipher_walk w;
 192
 193         blkcipher_walk_init(&w, dst, src, nbytes);
 194         return crypt(desc, &w, ctx,
 195                      crypto_cipher_alg(ctx->child)->cia_encrypt);
 196 }
 197
 198 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 199                    struct scatterlist *src, unsigned int nbytes)
 200 {
 201         struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 202         struct blkcipher_walk w;
 203
 204         blkcipher_walk_init(&w, dst, src, nbytes);
 205         return crypt(desc, &w, ctx,
 206                      crypto_cipher_alg(ctx->child)->cia_decrypt);
 207 }
 208
 209 static int init_tfm(struct crypto_tfm *tfm)
 210 {
 211         struct crypto_cipher *cipher;
 212         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 213         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 214         struct priv *ctx = crypto_tfm_ctx(tfm);
 215         u32 *flags = &tfm->crt_flags;
 216
 217         cipher = crypto_spawn_cipher(spawn);
 218         if (IS_ERR(cipher))
 219                 return PTR_ERR(cipher);
 220
 221         if (crypto_cipher_blocksize(cipher) != 16) {
 222                 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 223                 return -EINVAL;
 224         }
 225
 226         ctx->child = cipher;
 227         return 0;
 228 }
 229
 230 static void exit_tfm(struct crypto_tfm *tfm)
 231 {
 232         struct priv *ctx = crypto_tfm_ctx(tfm);
 233         if (ctx->table)
 234                 gf128mul_free_64k(ctx->table);
 235         crypto_free_cipher(ctx->child);
 236 }
 237
 238 static struct crypto_instance *alloc(struct rtattr **tb)
 239 {
 240         struct crypto_instance *inst;
 241         struct crypto_alg *alg;
 242         int err;
 243
 244         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 245         if (err)
 246                 return ERR_PTR(err);
 247
 248         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 249                                   CRYPTO_ALG_TYPE_MASK);
 250         if (IS_ERR(alg))
 251                 return ERR_CAST(alg);
 252
 253         inst = crypto_alloc_instance("lrw", alg);
 254         if (IS_ERR(inst))
 255                 goto out_put_alg;
 256
 257         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 258         inst->alg.cra_priority = alg->cra_priority;
 259         inst->alg.cra_blocksize = alg->cra_blocksize;
 260
 261         if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
 262         else inst->alg.cra_alignmask = alg->cra_alignmask;
 263         inst->alg.cra_type = &crypto_blkcipher_type;
 264
 265         if (!(alg->cra_blocksize % 4))
 266                 inst->alg.cra_alignmask |= 3;
 267         inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 268         inst->alg.cra_blkcipher.min_keysize =
 269                 alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
 270         inst->alg.cra_blkcipher.max_keysize =
 271                 alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;
 272
 273         inst->alg.cra_ctxsize = sizeof(struct priv);
 274
 275         inst->alg.cra_init = init_tfm;
 276         inst->alg.cra_exit = exit_tfm;
 277
 278         inst->alg.cra_blkcipher.setkey = setkey;
 279         inst->alg.cra_blkcipher.encrypt = encrypt;
 280         inst->alg.cra_blkcipher.decrypt = decrypt;
 281
 282 out_put_alg:
 283         crypto_mod_put(alg);
 284         return inst;
 285 }
 286
 287 static void free(struct crypto_instance *inst)
 288 {
 289         crypto_drop_spawn(crypto_instance_ctx(inst));
 290         kfree(inst);
 291 }
 292
 293 static struct crypto_template crypto_tmpl = {
 294         .name = "lrw",
 295         .alloc = alloc,
 296         .free = free,
 297         .module = THIS_MODULE,
 298 };
 299
 300 static int __init crypto_module_init(void)
 301 {
 302         return crypto_register_template(&crypto_tmpl);
 303 }
 304
 305 static void __exit crypto_module_exit(void)
 306 {
 307         crypto_unregister_template(&crypto_tmpl);
 308 }
 309
 310 module_init(crypto_module_init);
 311 module_exit(crypto_module_exit);
 312
 313 MODULE_LICENSE("GPL");
 314 MODULE_DESCRIPTION("LRW block cipher mode");
 315 MODULE_ALIAS_CRYPTO("lrw");