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 on 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
  20#include <crypto/algapi.h>
  21#include <linux/err.h>
  22#include <linux/init.h>
  23#include <linux/kernel.h>
  24#include <linux/module.h>
  25#include <linux/scatterlist.h>
  26#include <linux/slab.h>
  27
  28#include <crypto/b128ops.h>
  29#include <crypto/gf128mul.h>
  30#include <crypto/lrw.h>
  31
  32struct priv {
  33        struct crypto_cipher *child;
  34        struct lrw_table_ctx table;
  35};
  36
  37static inline void setbit128_bbe(void *b, int bit)
  38{
  39        __set_bit(bit ^ (0x80 -
  40#ifdef __BIG_ENDIAN
  41                         BITS_PER_LONG
  42#else
  43                         BITS_PER_BYTE
  44#endif
  45                        ), b);
  46}
  47
  48int lrw_init_table(struct lrw_table_ctx *ctx, const u8 *tweak)
  49{
  50        be128 tmp = { 0 };
  51        int i;
  52
  53        if (ctx->table)
  54                gf128mul_free_64k(ctx->table);
  55
  56        /* initialize multiplication table for Key2 */
  57        ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
  58        if (!ctx->table)
  59                return -ENOMEM;
  60
  61        /* initialize optimization table */
  62        for (i = 0; i < 128; i++) {
  63                setbit128_bbe(&tmp, i);
  64                ctx->mulinc[i] = tmp;
  65                gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
  66        }
  67
  68        return 0;
  69}
  70EXPORT_SYMBOL_GPL(lrw_init_table);
  71
  72void lrw_free_table(struct lrw_table_ctx *ctx)
  73{
  74        if (ctx->table)
  75                gf128mul_free_64k(ctx->table);
  76}
  77EXPORT_SYMBOL_GPL(lrw_free_table);
  78
  79static int setkey(struct crypto_tfm *parent, const u8 *key,
  80                  unsigned int keylen)
  81{
  82        struct priv *ctx = crypto_tfm_ctx(parent);
  83        struct crypto_cipher *child = ctx->child;
  84        int err, bsize = LRW_BLOCK_SIZE;
  85        const u8 *tweak = key + keylen - bsize;
  86
  87        crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  88        crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  89                                       CRYPTO_TFM_REQ_MASK);
  90        err = crypto_cipher_setkey(child, key, keylen - bsize);
  91        if (err)
  92                return err;
  93        crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  94                                     CRYPTO_TFM_RES_MASK);
  95
  96        return lrw_init_table(&ctx->table, tweak);
  97}
  98
  99struct sinfo {
 100        be128 t;
 101        struct crypto_tfm *tfm;
 102        void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
 103};
 104
 105static inline void inc(be128 *iv)
 106{
 107        be64_add_cpu(&iv->b, 1);
 108        if (!iv->b)
 109                be64_add_cpu(&iv->a, 1);
 110}
 111
 112static inline void lrw_round(struct sinfo *s, void *dst, const void *src)
 113{
 114        be128_xor(dst, &s->t, src);             /* PP <- T xor P */
 115        s->fn(s->tfm, dst, dst);                /* CC <- E(Key2,PP) */
 116        be128_xor(dst, dst, &s->t);             /* C <- T xor CC */
 117}
 118
 119/* this returns the number of consequative 1 bits starting
 120 * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
 121static inline int get_index128(be128 *block)
 122{
 123        int x;
 124        __be32 *p = (__be32 *) block;
 125
 126        for (p += 3, x = 0; x < 128; p--, x += 32) {
 127                u32 val = be32_to_cpup(p);
 128
 129                if (!~val)
 130                        continue;
 131
 132                return x + ffz(val);
 133        }
 134
 135        return x;
 136}
 137
 138static int crypt(struct blkcipher_desc *d,
 139                 struct blkcipher_walk *w, struct priv *ctx,
 140                 void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
 141{
 142        int err;
 143        unsigned int avail;
 144        const int bs = LRW_BLOCK_SIZE;
 145        struct sinfo s = {
 146                .tfm = crypto_cipher_tfm(ctx->child),
 147                .fn = fn
 148        };
 149        be128 *iv;
 150        u8 *wsrc;
 151        u8 *wdst;
 152
 153        err = blkcipher_walk_virt(d, w);
 154        if (!(avail = w->nbytes))
 155                return err;
 156
 157        wsrc = w->src.virt.addr;
 158        wdst = w->dst.virt.addr;
 159
 160        /* calculate first value of T */
 161        iv = (be128 *)w->iv;
 162        s.t = *iv;
 163
 164        /* T <- I*Key2 */
 165        gf128mul_64k_bbe(&s.t, ctx->table.table);
 166
 167        goto first;
 168
 169        for (;;) {
 170                do {
 171                        /* T <- I*Key2, using the optimization
 172                         * discussed in the specification */
 173                        be128_xor(&s.t, &s.t,
 174                                  &ctx->table.mulinc[get_index128(iv)]);
 175                        inc(iv);
 176
 177first:
 178                        lrw_round(&s, wdst, wsrc);
 179
 180                        wsrc += bs;
 181                        wdst += bs;
 182                } while ((avail -= bs) >= bs);
 183
 184                err = blkcipher_walk_done(d, w, avail);
 185                if (!(avail = w->nbytes))
 186                        break;
 187
 188                wsrc = w->src.virt.addr;
 189                wdst = w->dst.virt.addr;
 190        }
 191
 192        return err;
 193}
 194
 195static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 196                   struct scatterlist *src, unsigned int nbytes)
 197{
 198        struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 199        struct blkcipher_walk w;
 200
 201        blkcipher_walk_init(&w, dst, src, nbytes);
 202        return crypt(desc, &w, ctx,
 203                     crypto_cipher_alg(ctx->child)->cia_encrypt);
 204}
 205
 206static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 207                   struct scatterlist *src, unsigned int nbytes)
 208{
 209        struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
 210        struct blkcipher_walk w;
 211
 212        blkcipher_walk_init(&w, dst, src, nbytes);
 213        return crypt(desc, &w, ctx,
 214                     crypto_cipher_alg(ctx->child)->cia_decrypt);
 215}
 216
 217int lrw_crypt(struct blkcipher_desc *desc, struct scatterlist *sdst,
 218              struct scatterlist *ssrc, unsigned int nbytes,
 219              struct lrw_crypt_req *req)
 220{
 221        const unsigned int bsize = LRW_BLOCK_SIZE;
 222        const unsigned int max_blks = req->tbuflen / bsize;
 223        struct lrw_table_ctx *ctx = req->table_ctx;
 224        struct blkcipher_walk walk;
 225        unsigned int nblocks;
 226        be128 *iv, *src, *dst, *t;
 227        be128 *t_buf = req->tbuf;
 228        int err, i;
 229
 230        BUG_ON(max_blks < 1);
 231
 232        blkcipher_walk_init(&walk, sdst, ssrc, nbytes);
 233
 234        err = blkcipher_walk_virt(desc, &walk);
 235        nbytes = walk.nbytes;
 236        if (!nbytes)
 237                return err;
 238
 239        nblocks = min(walk.nbytes / bsize, max_blks);
 240        src = (be128 *)walk.src.virt.addr;
 241        dst = (be128 *)walk.dst.virt.addr;
 242
 243        /* calculate first value of T */
 244        iv = (be128 *)walk.iv;
 245        t_buf[0] = *iv;
 246
 247        /* T <- I*Key2 */
 248        gf128mul_64k_bbe(&t_buf[0], ctx->table);
 249
 250        i = 0;
 251        goto first;
 252
 253        for (;;) {
 254                do {
 255                        for (i = 0; i < nblocks; i++) {
 256                                /* T <- I*Key2, using the optimization
 257                                 * discussed in the specification */
 258                                be128_xor(&t_buf[i], t,
 259                                                &ctx->mulinc[get_index128(iv)]);
 260                                inc(iv);
 261first:
 262                                t = &t_buf[i];
 263
 264                                /* PP <- T xor P */
 265                                be128_xor(dst + i, t, src + i);
 266                        }
 267
 268                        /* CC <- E(Key2,PP) */
 269                        req->crypt_fn(req->crypt_ctx, (u8 *)dst,
 270                                      nblocks * bsize);
 271
 272                        /* C <- T xor CC */
 273                        for (i = 0; i < nblocks; i++)
 274                                be128_xor(dst + i, dst + i, &t_buf[i]);
 275
 276                        src += nblocks;
 277                        dst += nblocks;
 278                        nbytes -= nblocks * bsize;
 279                        nblocks = min(nbytes / bsize, max_blks);
 280                } while (nblocks > 0);
 281
 282                err = blkcipher_walk_done(desc, &walk, nbytes);
 283                nbytes = walk.nbytes;
 284                if (!nbytes)
 285                        break;
 286
 287                nblocks = min(nbytes / bsize, max_blks);
 288                src = (be128 *)walk.src.virt.addr;
 289                dst = (be128 *)walk.dst.virt.addr;
 290        }
 291
 292        return err;
 293}
 294EXPORT_SYMBOL_GPL(lrw_crypt);
 295
 296static int init_tfm(struct crypto_tfm *tfm)
 297{
 298        struct crypto_cipher *cipher;
 299        struct crypto_instance *inst = (void *)tfm->__crt_alg;
 300        struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 301        struct priv *ctx = crypto_tfm_ctx(tfm);
 302        u32 *flags = &tfm->crt_flags;
 303
 304        cipher = crypto_spawn_cipher(spawn);
 305        if (IS_ERR(cipher))
 306                return PTR_ERR(cipher);
 307
 308        if (crypto_cipher_blocksize(cipher) != LRW_BLOCK_SIZE) {
 309                *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 310                crypto_free_cipher(cipher);
 311                return -EINVAL;
 312        }
 313
 314        ctx->child = cipher;
 315        return 0;
 316}
 317
 318static void exit_tfm(struct crypto_tfm *tfm)
 319{
 320        struct priv *ctx = crypto_tfm_ctx(tfm);
 321
 322        lrw_free_table(&ctx->table);
 323        crypto_free_cipher(ctx->child);
 324}
 325
 326static struct crypto_instance *alloc(struct rtattr **tb)
 327{
 328        struct crypto_instance *inst;
 329        struct crypto_alg *alg;
 330        int err;
 331
 332        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
 333        if (err)
 334                return ERR_PTR(err);
 335
 336        alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 337                                  CRYPTO_ALG_TYPE_MASK);
 338        if (IS_ERR(alg))
 339                return ERR_CAST(alg);
 340
 341        inst = crypto_alloc_instance("lrw", alg);
 342        if (IS_ERR(inst))
 343                goto out_put_alg;
 344
 345        inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
 346        inst->alg.cra_priority = alg->cra_priority;
 347        inst->alg.cra_blocksize = alg->cra_blocksize;
 348
 349        if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
 350        else inst->alg.cra_alignmask = alg->cra_alignmask;
 351        inst->alg.cra_type = &crypto_blkcipher_type;
 352
 353        if (!(alg->cra_blocksize % 4))
 354                inst->alg.cra_alignmask |= 3;
 355        inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
 356        inst->alg.cra_blkcipher.min_keysize =
 357                alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
 358        inst->alg.cra_blkcipher.max_keysize =
 359                alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;
 360
 361        inst->alg.cra_ctxsize = sizeof(struct priv);
 362
 363        inst->alg.cra_init = init_tfm;
 364        inst->alg.cra_exit = exit_tfm;
 365
 366        inst->alg.cra_blkcipher.setkey = setkey;
 367        inst->alg.cra_blkcipher.encrypt = encrypt;
 368        inst->alg.cra_blkcipher.decrypt = decrypt;
 369
 370out_put_alg:
 371        crypto_mod_put(alg);
 372        return inst;
 373}
 374
 375static void free(struct crypto_instance *inst)
 376{
 377        crypto_drop_spawn(crypto_instance_ctx(inst));
 378        kfree(inst);
 379}
 380
 381static struct crypto_template crypto_tmpl = {
 382        .name = "lrw",
 383        .alloc = alloc,
 384        .free = free,
 385        .module = THIS_MODULE,
 386};
 387
 388static int __init crypto_module_init(void)
 389{
 390        return crypto_register_template(&crypto_tmpl);
 391}
 392
 393static void __exit crypto_module_exit(void)
 394{
 395        crypto_unregister_template(&crypto_tmpl);
 396}
 397
 398module_init(crypto_module_init);
 399module_exit(crypto_module_exit);
 400
 401MODULE_LICENSE("GPL");
 402MODULE_DESCRIPTION("LRW block cipher mode");
 403
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