/* * Salsa20: Salsa20 stream cipher algorithm * * Copyright (c) 2007 Tan Swee Heng * * Derived from: * - salsa20.c: Public domain C code by Daniel J. Bernstein * * Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream * Cipher Project. It is designed by Daniel J. Bernstein . * 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 #include #include #define SALSA20_IV_SIZE 8 #define SALSA20_MIN_KEY_SIZE 16 #define SALSA20_MAX_KEY_SIZE 32 #define SALSA20_BLOCK_SIZE 64 struct salsa20_ctx { u32 initial_state[16]; }; static void salsa20_block(u32 *state, __le32 *stream) { u32 x[16]; int i; memcpy(x, state, sizeof(x)); for (i = 0; i < 20; 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++) stream[i] = cpu_to_le32(x[i] + state[i]); if (++state[8] == 0) state[9]++; } static void salsa20_docrypt(u32 *state, u8 *dst, const u8 *src, unsigned int bytes) { __le32 stream[SALSA20_BLOCK_SIZE / sizeof(__le32)]; while (bytes >= SALSA20_BLOCK_SIZE) { salsa20_block(state, stream); crypto_xor_cpy(dst, src, (const u8 *)stream, SALSA20_BLOCK_SIZE); bytes -= SALSA20_BLOCK_SIZE; dst += SALSA20_BLOCK_SIZE; src += SALSA20_BLOCK_SIZE; } if (bytes) { salsa20_block(state, stream); crypto_xor_cpy(dst, src, (const u8 *)stream, bytes); } } static void salsa20_init(u32 *state, const struct salsa20_ctx *ctx, const u8 *iv) { memcpy(state, ctx->initial_state, sizeof(ctx->initial_state)); state[6] = get_unaligned_le32(iv + 0); state[7] = get_unaligned_le32(iv + 4); } static int salsa20_setkey(struct crypto_skcipher *tfm, const u8 *key, unsigned int keysize) { static const char sigma[16] = "expand 32-byte k"; static const char tau[16] = "expand 16-byte k"; struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm); const char *constants; if (keysize != SALSA20_MIN_KEY_SIZE && keysize != SALSA20_MAX_KEY_SIZE) return -EINVAL; ctx->initial_state[1] = get_unaligned_le32(key + 0); ctx->initial_state[2] = get_unaligned_le32(key + 4); ctx->initial_state[3] = get_unaligned_le32(key + 8); ctx->initial_state[4] = get_unaligned_le32(key + 12); if (keysize == 32) { /* recommended */ key += 16; constants = sigma; } else { /* keysize == 16 */ constants = tau; } ctx->initial_state[11] = get_unaligned_le32(key + 0); ctx->initial_state[12] = get_unaligned_le32(key + 4); ctx->initial_state[13] = get_unaligned_le32(key + 8); ctx->initial_state[14] = get_unaligned_le32(key + 12); ctx->initial_state[0] = get_unaligned_le32(constants + 0); ctx->initial_state[5] = get_unaligned_le32(constants + 4); ctx->initial_state[10] = get_unaligned_le32(constants + 8); ctx->initial_state[15] = get_unaligned_le32(constants + 12); /* space for the nonce; it will be overridden for each request */ ctx->initial_state[6] = 0; ctx->initial_state[7] = 0; /* initial block number */ ctx->initial_state[8] = 0; ctx->initial_state[9] = 0; return 0; } static int salsa20_crypt(struct skcipher_request *req) { struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); const struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm); struct skcipher_walk walk; u32 state[16]; int err; err = skcipher_walk_virt(&walk, req, false); salsa20_init(state, ctx, req->iv); while (walk.nbytes > 0) { unsigned int nbytes = walk.nbytes; if (nbytes < walk.total) nbytes = round_down(nbytes, walk.stride); salsa20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr, nbytes); err = skcipher_walk_done(&walk, walk.nbytes - nbytes); } return err; } static struct skcipher_alg alg = { .base.cra_name = "salsa20", .base.cra_driver_name = "salsa20-generic", .base.cra_priority = 100, .base.cra_blocksize = 1, .base.cra_ctxsize = sizeof(struct salsa20_ctx), .base.cra_module = THIS_MODULE, .min_keysize = SALSA20_MIN_KEY_SIZE, .max_keysize = SALSA20_MAX_KEY_SIZE, .ivsize = SALSA20_IV_SIZE, .chunksize = SALSA20_BLOCK_SIZE, .setkey = salsa20_setkey, .encrypt = salsa20_crypt, .decrypt = salsa20_crypt, }; static int __init salsa20_generic_mod_init(void) { return crypto_register_skcipher(&alg); } static void __exit salsa20_generic_mod_fini(void) { crypto_unregister_skcipher(&alg); } subsys_initcall(salsa20_generic_mod_init); module_exit(salsa20_generic_mod_fini); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm"); MODULE_ALIAS_CRYPTO("salsa20"); MODULE_ALIAS_CRYPTO("salsa20-generic");