/* * Salsa20: Salsa20 stream cipher algorithm * * Copyright (c) 2007 Tan Swee Heng <thesweeheng@gmail.com> * * Derived from: * - salsa20.c: Public domain C code by Daniel J. Bernstein <djb@cr.yp.to> * * Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream * Cipher Project. It is designed by Daniel J. Bernstein <djb@cr.yp.to>. * More information about eSTREAM and Salsa20 can be found here: * http://www.ecrypt.eu.org/stream/ * http://cr.yp.to/snuffle.html * * 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 <linux/init.h> #include <linux/module.h> #include <linux/errno.h> #include <linux/crypto.h> #include <linux/types.h> #include <linux/bitops.h> #include <crypto/algapi.h> #include <asm/byteorder.h> #define SALSA20_IV_SIZE 8U #define SALSA20_MIN_KEY_SIZE 16U #define SALSA20_MAX_KEY_SIZE 32U /* * Start of code taken from D. J. Bernstein's reference implementation. * With some modifications and optimizations made to suit our needs. */ /* salsa20-ref.c version 20051118 D. J. Bernstein Public domain. */ #define U32TO8_LITTLE(p, v) \ { (p)[0] = (v >> 0) & 0xff; (p)[1] = (v >> 8) & 0xff; \ (p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; } #define U8TO32_LITTLE(p) \ (((u32)((p)[0]) ) | ((u32)((p)[1]) << 8) | \ ((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24) ) struct salsa20_ctx { u32 input[16]; }; static void salsa20_wordtobyte(u8 output[64], const u32 input[16]) { u32 x[16]; int i; memcpy(x, input, sizeof(x)); for (i = 20; i > 0; i -= 2) { x[ 4] ^= rol32((x[ 0] + x[12]), 7); x[ 8] ^= rol32((x[ 4] + x[ 0]), 9); x[12] ^= rol32((x[ 8] + x[ 4]), 13); x[ 0] ^= rol32((x[12] + x[ 8]), 18); x[ 9] ^= rol32((x[ 5] + x[ 1]), 7); x[13] ^= rol32((x[ 9] + x[ 5]), 9); x[ 1] ^= rol32((x[13] + x[ 9]), 13); x[ 5] ^= rol32((x[ 1] + x[13]), 18); x[14] ^= rol32((x[10] + x[ 6]), 7); x[ 2] ^= rol32((x[14] + x[10]), 9); x[ 6] ^= rol32((x[ 2] + x[14]), 13); x[10] ^= rol32((x[ 6] + x[ 2]), 18); x[ 3] ^= rol32((x[15] + x[11]), 7); x[ 7] ^= rol32((x[ 3] + x[15]), 9); x[11] ^= rol32((x[ 7] + x[ 3]), 13); x[15] ^= rol32((x[11] + x[ 7]), 18); x[ 1] ^= rol32((x[ 0] + x[ 3]), 7); x[ 2] ^= rol32((x[ 1] + x[ 0]), 9); x[ 3] ^= rol32((x[ 2] + x[ 1]), 13); x[ 0] ^= rol32((x[ 3] + x[ 2]), 18); x[ 6] ^= rol32((x[ 5] + x[ 4]), 7); x[ 7] ^= rol32((x[ 6] + x[ 5]), 9); x[ 4] ^= rol32((x[ 7] + x[ 6]), 13); x[ 5] ^= rol32((x[ 4] + x[ 7]), 18); x[11] ^= rol32((x[10] + x[ 9]), 7); x[ 8] ^= rol32((x[11] + x[10]), 9); x[ 9] ^= rol32((x[ 8] + x[11]), 13); x[10] ^= rol32((x[ 9] + x[ 8]), 18); x[12] ^= rol32((x[15] + x[14]), 7); x[13] ^= rol32((x[12] + x[15]), 9); x[14] ^= rol32((x[13] + x[12]), 13); x[15] ^= rol32((x[14] + x[13]), 18); } for (i = 0; i < 16; ++i) x[i] += input[i]; for (i = 0; i < 16; ++i) U32TO8_LITTLE(output + 4 * i,x[i]); } static const char sigma[16] = "expand 32-byte k"; static const char tau[16] = "expand 16-byte k"; static void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k, u32 kbytes) { const char *constants; ctx->input[1] = U8TO32_LITTLE(k + 0); ctx->input[2] = U8TO32_LITTLE(k + 4); ctx->input[3] = U8TO32_LITTLE(k + 8); ctx->input[4] = U8TO32_LITTLE(k + 12); if (kbytes == 32) { /* recommended */ k += 16; constants = sigma; } else { /* kbytes == 16 */ constants = tau; } ctx->input[11] = U8TO32_LITTLE(k + 0); ctx->input[12] = U8TO32_LITTLE(k + 4); ctx->input[13] = U8TO32_LITTLE(k + 8); ctx->input[14] = U8TO32_LITTLE(k + 12); ctx->input[0] = U8TO32_LITTLE(constants + 0); ctx->input[5] = U8TO32_LITTLE(constants + 4); ctx->input[10] = U8TO32_LITTLE(constants + 8); ctx->input[15] = U8TO32_LITTLE(constants + 12); } static void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv) { ctx->input[6] = U8TO32_LITTLE(iv + 0); ctx->input[7] = U8TO32_LITTLE(iv + 4); ctx->input[8] = 0; ctx->input[9] = 0; } static void salsa20_encrypt_bytes(struct salsa20_ctx *ctx, u8 *dst, const u8 *src, unsigned int bytes) { u8 buf[64]; if (dst != src) memcpy(dst, src, bytes); while (bytes) { salsa20_wordtobyte(buf, ctx->input); ctx->input[8]++; if (!ctx->input[8]) ctx->input[9]++; if (bytes <= 64) { crypto_xor(dst, buf, bytes); return; } crypto_xor(dst, buf, 64); bytes -= 64; dst += 64; } } /* * End of code taken from D. J. Bernstein's reference implementation. */ 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); 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.dst.virt.addr, walk.src.virt.addr, nbytes); return blkcipher_walk_done(desc, &walk, 0); } while (walk.nbytes >= 64) { salsa20_encrypt_bytes(ctx, walk.dst.virt.addr, walk.src.virt.addr, walk.nbytes - (walk.nbytes % 64)); err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64); } if (walk.nbytes) { salsa20_encrypt_bytes(ctx, walk.dst.virt.addr, walk.src.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-generic", .cra_priority = 100, .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 salsa20_generic_mod_init(void) { return crypto_register_alg(&alg); } static void __exit salsa20_generic_mod_fini(void) { crypto_unregister_alg(&alg); } module_init(salsa20_generic_mod_init); module_exit(salsa20_generic_mod_fini); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm"); MODULE_ALIAS_CRYPTO("salsa20");