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/* LRW: as defined by Cyril Guyot in
* http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
*
* Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
*
* Based om ecb.c
* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*/
/* This implementation is checked against the test vectors in the above
* document and by a test vector provided by Ken Buchanan at
* http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
*
* The test vectors are included in the testing module tcrypt.[ch] */
#include <crypto/algapi.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <crypto/b128ops.h>
#include <crypto/gf128mul.h>
struct priv {
struct crypto_cipher *child;
/* optimizes multiplying a random (non incrementing, as at the
* start of a new sector) value with key2, we could also have
* used 4k optimization tables or no optimization at all. In the
* latter case we would have to store key2 here */
struct gf128mul_64k *table;
/* stores:
* key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
* key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
* key2*{ 0,0,...1,1,1,1,1 }, etc
* needed for optimized multiplication of incrementing values
* with key2 */
be128 mulinc[128];
};
static inline void setbit128_bbe(void *b, int bit)
{
__set_bit(bit ^ 0x78, b);
}
static int setkey(struct crypto_tfm *parent, const u8 *key,
unsigned int keylen)
{
struct priv *ctx = crypto_tfm_ctx(parent);
struct crypto_cipher *child = ctx->child;
int err, i;
be128 tmp = { 0 };
int bsize = crypto_cipher_blocksize(child);
crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
CRYPTO_TFM_REQ_MASK);
if ((err = crypto_cipher_setkey(child, key, keylen - bsize)))
return err;
crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
CRYPTO_TFM_RES_MASK);
if (ctx->table)
gf128mul_free_64k(ctx->table);
/* initialize multiplication table for Key2 */
ctx->table = gf128mul_init_64k_bbe((be128 *)(key + keylen - bsize));
if (!ctx->table)
return -ENOMEM;
/* initialize optimization table */
for (i = 0; i < 128; i++) {
setbit128_bbe(&tmp, i);
ctx->mulinc[i] = tmp;
gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
}
return 0;
}
struct sinfo {
be128 t;
struct crypto_tfm *tfm;
void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
};
static inline void inc(be128 *iv)
{
if (!(iv->b = cpu_to_be64(be64_to_cpu(iv->b) + 1)))
iv->a = cpu_to_be64(be64_to_cpu(iv->a) + 1);
}
static inline void lrw_round(struct sinfo *s, void *dst, const void *src)
{
be128_xor(dst, &s->t, src); /* PP <- T xor P */
s->fn(s->tfm, dst, dst); /* CC <- E(Key2,PP) */
be128_xor(dst, dst, &s->t); /* C <- T xor CC */
}
/* this returns the number of consequative 1 bits starting
* from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
static inline int get_index128(be128 *block)
{
int x;
__be32 *p = (__be32 *) block;
for (p += 3, x = 0; x < 128; p--, x += 32) {
u32 val = be32_to_cpup(p);
if (!~val)
continue;
return x + ffz(val);
}
return x;
}
static int crypt(struct blkcipher_desc *d,
struct blkcipher_walk *w, struct priv *ctx,
void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
{
int err;
unsigned int avail;
const int bs = crypto_cipher_blocksize(ctx->child);
struct sinfo s = {
.tfm = crypto_cipher_tfm(ctx->child),
.fn = fn
};
be128 *iv;
u8 *wsrc;
u8 *wdst;
err = blkcipher_walk_virt(d, w);
if (!(avail = w->nbytes))
return err;
wsrc = w->src.virt.addr;
wdst = w->dst.virt.addr;
/* calculate first value of T */
iv = (be128 *)w->iv;
s.t = *iv;
/* T <- I*Key2 */
gf128mul_64k_bbe(&s.t, ctx->table);
goto first;
for (;;) {
do {
/* T <- I*Key2, using the optimization
* discussed in the specification */
be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]);
inc(iv);
first:
lrw_round(&s, wdst, wsrc);
wsrc += bs;
wdst += bs;
} while ((avail -= bs) >= bs);
err = blkcipher_walk_done(d, w, avail);
if (!(avail = w->nbytes))
break;
wsrc = w->src.virt.addr;
wdst = w->dst.virt.addr;
}
return err;
}
static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
struct scatterlist *src, unsigned int nbytes)
{
struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
struct blkcipher_walk w;
blkcipher_walk_init(&w, dst, src, nbytes);
return crypt(desc, &w, ctx,
crypto_cipher_alg(ctx->child)->cia_encrypt);
}
static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
struct scatterlist *src, unsigned int nbytes)
{
struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
struct blkcipher_walk w;
blkcipher_walk_init(&w, dst, src, nbytes);
return crypt(desc, &w, ctx,
crypto_cipher_alg(ctx->child)->cia_decrypt);
}
static int init_tfm(struct crypto_tfm *tfm)
{
struct crypto_cipher *cipher;
struct crypto_instance *inst = (void *)tfm->__crt_alg;
struct crypto_spawn *spawn = crypto_instance_ctx(inst);
struct priv *ctx = crypto_tfm_ctx(tfm);
u32 *flags = &tfm->crt_flags;
cipher = crypto_spawn_cipher(spawn);
if (IS_ERR(cipher))
return PTR_ERR(cipher);
if (crypto_cipher_blocksize(cipher) != 16) {
*flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
return -EINVAL;
}
ctx->child = cipher;
return 0;
}
static void exit_tfm(struct crypto_tfm *tfm)
{
struct priv *ctx = crypto_tfm_ctx(tfm);
if (ctx->table)
gf128mul_free_64k(ctx->table);
crypto_free_cipher(ctx->child);
}
static struct crypto_instance *alloc(struct rtattr **tb)
{
struct crypto_instance *inst;
struct crypto_alg *alg;
int err;
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
if (err)
return ERR_PTR(err);
alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
CRYPTO_ALG_TYPE_MASK);
if (IS_ERR(alg))
return ERR_CAST(alg);
inst = crypto_alloc_instance("lrw", alg);
if (IS_ERR(inst))
goto out_put_alg;
inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
inst->alg.cra_priority = alg->cra_priority;
inst->alg.cra_blocksize = alg->cra_blocksize;
if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
else inst->alg.cra_alignmask = alg->cra_alignmask;
inst->alg.cra_type = &crypto_blkcipher_type;
if (!(alg->cra_blocksize % 4))
inst->alg.cra_alignmask |= 3;
inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
inst->alg.cra_blkcipher.min_keysize =
alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
inst->alg.cra_blkcipher.max_keysize =
alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;
inst->alg.cra_ctxsize = sizeof(struct priv);
inst->alg.cra_init = init_tfm;
inst->alg.cra_exit = exit_tfm;
inst->alg.cra_blkcipher.setkey = setkey;
inst->alg.cra_blkcipher.encrypt = encrypt;
inst->alg.cra_blkcipher.decrypt = decrypt;
out_put_alg:
crypto_mod_put(alg);
return inst;
}
static void free(struct crypto_instance *inst)
{
crypto_drop_spawn(crypto_instance_ctx(inst));
kfree(inst);
}
static struct crypto_template crypto_tmpl = {
.name = "lrw",
.alloc = alloc,
.free = free,
.module = THIS_MODULE,
};
static int __init crypto_module_init(void)
{
return crypto_register_template(&crypto_tmpl);
}
static void __exit crypto_module_exit(void)
{
crypto_unregister_template(&crypto_tmpl);
}
module_init(crypto_module_init);
module_exit(crypto_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("LRW block cipher mode");
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