linux/crypto/lrw.c
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   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
  30struct 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
  46static 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
  57static 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
  92struct sinfo {
  93        be128 t;
  94        struct crypto_tfm *tfm;
  95        void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  96};
  97
  98static 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
 105static 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 */
 114static 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
 131static 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
 169first:
 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
 187static 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
 198static 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
 209static 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
 230static 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
 238static 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
 282out_put_alg:
 283        crypto_mod_put(alg);
 284        return inst;
 285}
 286
 287static void free(struct crypto_instance *inst)
 288{
 289        crypto_drop_spawn(crypto_instance_ctx(inst));
 290        kfree(inst);
 291}
 292
 293static struct crypto_template crypto_tmpl = {
 294        .name = "lrw",
 295        .alloc = alloc,
 296        .free = free,
 297        .module = THIS_MODULE,
 298};
 299
 300static int __init crypto_module_init(void)
 301{
 302        return crypto_register_template(&crypto_tmpl);
 303}
 304
 305static void __exit crypto_module_exit(void)
 306{
 307        crypto_unregister_template(&crypto_tmpl);
 308}
 309
 310module_init(crypto_module_init);
 311module_exit(crypto_module_exit);
 312
 313MODULE_LICENSE("GPL");
 314MODULE_DESCRIPTION("LRW block cipher mode");
 315
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