253 lines
6.7 KiB
C
253 lines
6.7 KiB
C
/*
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* Salsa20: Salsa20 stream cipher algorithm
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*
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* Copyright (c) 2007 Tan Swee Heng <thesweeheng@gmail.com>
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*
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* Derived from:
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* - salsa20.c: Public domain C code by Daniel J. Bernstein <djb@cr.yp.to>
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*
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* Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream
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* Cipher Project. It is designed by Daniel J. Bernstein <djb@cr.yp.to>.
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* More information about eSTREAM and Salsa20 can be found here:
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* http://www.ecrypt.eu.org/stream/
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* http://cr.yp.to/snuffle.html
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/errno.h>
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#include <linux/crypto.h>
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#include <linux/types.h>
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#include <linux/bitops.h>
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#include <crypto/algapi.h>
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#include <asm/byteorder.h>
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#define SALSA20_IV_SIZE 8U
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#define SALSA20_MIN_KEY_SIZE 16U
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#define SALSA20_MAX_KEY_SIZE 32U
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/*
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* Start of code taken from D. J. Bernstein's reference implementation.
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* With some modifications and optimizations made to suit our needs.
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*/
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/*
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salsa20-ref.c version 20051118
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D. J. Bernstein
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Public domain.
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*/
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#define U32TO8_LITTLE(p, v) \
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{ (p)[0] = (v >> 0) & 0xff; (p)[1] = (v >> 8) & 0xff; \
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(p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; }
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#define U8TO32_LITTLE(p) \
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(((u32)((p)[0]) ) | ((u32)((p)[1]) << 8) | \
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((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24) )
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struct salsa20_ctx
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{
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u32 input[16];
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};
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static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
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{
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u32 x[16];
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int i;
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memcpy(x, input, sizeof(x));
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for (i = 20; i > 0; i -= 2) {
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x[ 4] ^= rol32((x[ 0] + x[12]), 7);
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x[ 8] ^= rol32((x[ 4] + x[ 0]), 9);
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x[12] ^= rol32((x[ 8] + x[ 4]), 13);
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x[ 0] ^= rol32((x[12] + x[ 8]), 18);
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x[ 9] ^= rol32((x[ 5] + x[ 1]), 7);
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x[13] ^= rol32((x[ 9] + x[ 5]), 9);
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x[ 1] ^= rol32((x[13] + x[ 9]), 13);
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x[ 5] ^= rol32((x[ 1] + x[13]), 18);
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x[14] ^= rol32((x[10] + x[ 6]), 7);
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x[ 2] ^= rol32((x[14] + x[10]), 9);
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x[ 6] ^= rol32((x[ 2] + x[14]), 13);
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x[10] ^= rol32((x[ 6] + x[ 2]), 18);
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x[ 3] ^= rol32((x[15] + x[11]), 7);
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x[ 7] ^= rol32((x[ 3] + x[15]), 9);
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x[11] ^= rol32((x[ 7] + x[ 3]), 13);
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x[15] ^= rol32((x[11] + x[ 7]), 18);
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x[ 1] ^= rol32((x[ 0] + x[ 3]), 7);
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x[ 2] ^= rol32((x[ 1] + x[ 0]), 9);
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x[ 3] ^= rol32((x[ 2] + x[ 1]), 13);
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x[ 0] ^= rol32((x[ 3] + x[ 2]), 18);
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x[ 6] ^= rol32((x[ 5] + x[ 4]), 7);
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x[ 7] ^= rol32((x[ 6] + x[ 5]), 9);
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x[ 4] ^= rol32((x[ 7] + x[ 6]), 13);
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x[ 5] ^= rol32((x[ 4] + x[ 7]), 18);
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x[11] ^= rol32((x[10] + x[ 9]), 7);
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x[ 8] ^= rol32((x[11] + x[10]), 9);
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x[ 9] ^= rol32((x[ 8] + x[11]), 13);
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x[10] ^= rol32((x[ 9] + x[ 8]), 18);
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x[12] ^= rol32((x[15] + x[14]), 7);
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x[13] ^= rol32((x[12] + x[15]), 9);
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x[14] ^= rol32((x[13] + x[12]), 13);
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x[15] ^= rol32((x[14] + x[13]), 18);
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}
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for (i = 0; i < 16; ++i)
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x[i] += input[i];
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for (i = 0; i < 16; ++i)
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U32TO8_LITTLE(output + 4 * i,x[i]);
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}
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static const char sigma[16] = "expand 32-byte k";
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static const char tau[16] = "expand 16-byte k";
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static void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k, u32 kbytes)
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{
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const char *constants;
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ctx->input[1] = U8TO32_LITTLE(k + 0);
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ctx->input[2] = U8TO32_LITTLE(k + 4);
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ctx->input[3] = U8TO32_LITTLE(k + 8);
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ctx->input[4] = U8TO32_LITTLE(k + 12);
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if (kbytes == 32) { /* recommended */
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k += 16;
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constants = sigma;
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} else { /* kbytes == 16 */
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constants = tau;
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}
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ctx->input[11] = U8TO32_LITTLE(k + 0);
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ctx->input[12] = U8TO32_LITTLE(k + 4);
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ctx->input[13] = U8TO32_LITTLE(k + 8);
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ctx->input[14] = U8TO32_LITTLE(k + 12);
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ctx->input[0] = U8TO32_LITTLE(constants + 0);
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ctx->input[5] = U8TO32_LITTLE(constants + 4);
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ctx->input[10] = U8TO32_LITTLE(constants + 8);
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ctx->input[15] = U8TO32_LITTLE(constants + 12);
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}
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static void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv)
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{
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ctx->input[6] = U8TO32_LITTLE(iv + 0);
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ctx->input[7] = U8TO32_LITTLE(iv + 4);
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ctx->input[8] = 0;
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ctx->input[9] = 0;
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}
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static void salsa20_encrypt_bytes(struct salsa20_ctx *ctx, u8 *dst,
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const u8 *src, unsigned int bytes)
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{
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u8 buf[64];
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if (dst != src)
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memcpy(dst, src, bytes);
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while (bytes) {
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salsa20_wordtobyte(buf, ctx->input);
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ctx->input[8]++;
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if (!ctx->input[8])
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ctx->input[9]++;
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if (bytes <= 64) {
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crypto_xor(dst, buf, bytes);
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return;
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}
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crypto_xor(dst, buf, 64);
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bytes -= 64;
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dst += 64;
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}
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}
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/*
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* End of code taken from D. J. Bernstein's reference implementation.
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*/
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static int setkey(struct crypto_tfm *tfm, const u8 *key,
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unsigned int keysize)
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{
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struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
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salsa20_keysetup(ctx, key, keysize);
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return 0;
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}
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static int encrypt(struct blkcipher_desc *desc,
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struct scatterlist *dst, struct scatterlist *src,
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unsigned int nbytes)
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{
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struct blkcipher_walk walk;
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struct crypto_blkcipher *tfm = desc->tfm;
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struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
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int err;
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blkcipher_walk_init(&walk, dst, src, nbytes);
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err = blkcipher_walk_virt_block(desc, &walk, 64);
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salsa20_ivsetup(ctx, walk.iv);
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if (likely(walk.nbytes == nbytes))
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{
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salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
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walk.src.virt.addr, nbytes);
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return blkcipher_walk_done(desc, &walk, 0);
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}
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while (walk.nbytes >= 64) {
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salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
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walk.src.virt.addr,
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walk.nbytes - (walk.nbytes % 64));
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err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
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}
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if (walk.nbytes) {
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salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
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walk.src.virt.addr, walk.nbytes);
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err = blkcipher_walk_done(desc, &walk, 0);
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}
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return err;
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}
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static struct crypto_alg alg = {
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.cra_name = "salsa20",
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.cra_driver_name = "salsa20-generic",
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.cra_priority = 100,
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.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
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.cra_type = &crypto_blkcipher_type,
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.cra_blocksize = 1,
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.cra_ctxsize = sizeof(struct salsa20_ctx),
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.cra_alignmask = 3,
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.cra_module = THIS_MODULE,
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.cra_list = LIST_HEAD_INIT(alg.cra_list),
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.cra_u = {
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.blkcipher = {
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.setkey = setkey,
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.encrypt = encrypt,
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.decrypt = encrypt,
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.min_keysize = SALSA20_MIN_KEY_SIZE,
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.max_keysize = SALSA20_MAX_KEY_SIZE,
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.ivsize = SALSA20_IV_SIZE,
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}
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}
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};
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static int __init salsa20_generic_mod_init(void)
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{
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return crypto_register_alg(&alg);
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}
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static void __exit salsa20_generic_mod_fini(void)
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{
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crypto_unregister_alg(&alg);
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}
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module_init(salsa20_generic_mod_init);
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module_exit(salsa20_generic_mod_fini);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
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MODULE_ALIAS("salsa20");
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