salsa20_glue.c

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/*
 * Glue code for optimized assembly version of  Salsa20.
 *
 * Copyright (c) 2007 Tan Swee Heng <[email protected]>
 *
 * The assembly codes are public domain assembly codes written by Daniel. J.
 * Bernstein <[email protected]>. The codes are modified to include indentation
 * and to remove extraneous comments and functions that are not needed.
 * - i586 version, renamed as salsa20-i586-asm_32.S
 *   available from <http://cr.yp.to/snuffle/salsa20/x86-pm/salsa20.s>
 * - x86-64 version, renamed as salsa20-x86_64-asm_64.S
 *   available from <http://cr.yp.to/snuffle/salsa20/amd64-3/salsa20.s>
 *
 * 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.
 *
 */

#include <crypto/algapi.h>
#include <linux/module.h>
#include <linux/crypto.h>

#define SALSA20_IV_SIZE        8U
#define SALSA20_MIN_KEY_SIZE  16U
#define SALSA20_MAX_KEY_SIZE  32U

// use the ECRYPT_* function names
#define salsa20_keysetup        ECRYPT_keysetup
#define salsa20_ivsetup         ECRYPT_ivsetup
#define salsa20_encrypt_bytes   ECRYPT_encrypt_bytes

struct salsa20_ctx
{
    u32 input[16];
};

asmlinkage void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k,
                 u32 keysize, u32 ivsize);
asmlinkage void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv);
asmlinkage void salsa20_encrypt_bytes(struct salsa20_ctx *ctx,
                      const u8 *src, u8 *dst, u32 bytes);

static int setkey(struct crypto_tfm *tfm, const u8 *key,
          unsigned int keysize)
{
    struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
    salsa20_keysetup(ctx, key, keysize*8, SALSA20_IV_SIZE*8);
    return 0;
}

static int encrypt(struct blkcipher_desc *desc,
           struct scatterlist *dst, struct scatterlist *src,
           unsigned int nbytes)
{
    struct blkcipher_walk walk;
    struct crypto_blkcipher *tfm = desc->tfm;
    struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
    int err;

    blkcipher_walk_init(&walk, dst, src, nbytes);
    err = blkcipher_walk_virt_block(desc, &walk, 64);

    salsa20_ivsetup(ctx, walk.iv);

    if (likely(walk.nbytes == nbytes))
    {
        salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
                      walk.dst.virt.addr, nbytes);
        return blkcipher_walk_done(desc, &walk, 0);
    }

    while (walk.nbytes >= 64) {
        salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
                      walk.dst.virt.addr,
                      walk.nbytes - (walk.nbytes % 64));
        err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
    }

    if (walk.nbytes) {
        salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
                      walk.dst.virt.addr, walk.nbytes);
        err = blkcipher_walk_done(desc, &walk, 0);
    }

    return err;
}

static struct crypto_alg alg = {
    .cra_name           =   "salsa20",
    .cra_driver_name    =   "salsa20-asm",
    .cra_priority       =   200,
    .cra_flags          =   CRYPTO_ALG_TYPE_BLKCIPHER,
    .cra_type           =   &crypto_blkcipher_type,
    .cra_blocksize      =   1,
    .cra_ctxsize        =   sizeof(struct salsa20_ctx),
    .cra_alignmask      =   3,
    .cra_module         =   THIS_MODULE,
    .cra_u              =   {
        .blkcipher = {
            .setkey         =   setkey,
            .encrypt        =   encrypt,
            .decrypt        =   encrypt,
            .min_keysize    =   SALSA20_MIN_KEY_SIZE,
            .max_keysize    =   SALSA20_MAX_KEY_SIZE,
            .ivsize         =   SALSA20_IV_SIZE,
        }
    }
};

static int __init init(void)
{
    return crypto_register_alg(&alg);
}

static void __exit fini(void)
{
    crypto_unregister_alg(&alg);
}

module_init(init);
module_exit(fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm (optimized assembly version)");
MODULE_ALIAS("salsa20");
MODULE_ALIAS("salsa20-asm");