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Diffstat (limited to 'crypto/salsa20_generic.c')
| -rw-r--r-- | crypto/salsa20_generic.c | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/crypto/salsa20_generic.c b/crypto/salsa20_generic.c new file mode 100644 index 000000000..3418869da --- /dev/null +++ b/crypto/salsa20_generic.c @@ -0,0 +1,212 @@ +/* + * 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: + * https://www.ecrypt.eu.org/stream/ + * https://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 <asm/unaligned.h> +#include <crypto/internal/skcipher.h> +#include <linux/module.h> + +#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"); |