/* * ChaCha20 256-bit cipher algorithm, RFC7539 * * Copyright (C) 2015 Martin Willi * * 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/algapi.h> #include <crypto/chacha20.h> #include <crypto/internal/skcipher.h> #include <linux/module.h> static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src, unsigned int bytes) { /* aligned to potentially speed up crypto_xor() */ u8 stream[CHACHA20_BLOCK_SIZE] __aligned(sizeof(long)); if (dst != src) memcpy(dst, src, bytes); while (bytes >= CHACHA20_BLOCK_SIZE) { chacha20_block(state, stream); crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE); bytes -= CHACHA20_BLOCK_SIZE; dst += CHACHA20_BLOCK_SIZE; } if (bytes) { chacha20_block(state, stream); crypto_xor(dst, stream, bytes); } } void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv) { state[0] = 0x61707865; /* "expa" */ state[1] = 0x3320646e; /* "nd 3" */ state[2] = 0x79622d32; /* "2-by" */ state[3] = 0x6b206574; /* "te k" */ state[4] = ctx->key[0]; state[5] = ctx->key[1]; state[6] = ctx->key[2]; state[7] = ctx->key[3]; state[8] = ctx->key[4]; state[9] = ctx->key[5]; state[10] = ctx->key[6]; state[11] = ctx->key[7]; state[12] = get_unaligned_le32(iv + 0); state[13] = get_unaligned_le32(iv + 4); state[14] = get_unaligned_le32(iv + 8); state[15] = get_unaligned_le32(iv + 12); } EXPORT_SYMBOL_GPL(crypto_chacha20_init); int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key, unsigned int keysize) { struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm); int i; if (keysize != CHACHA20_KEY_SIZE) return -EINVAL; for (i = 0; i < ARRAY_SIZE(ctx->key); i++) ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32)); return 0; } EXPORT_SYMBOL_GPL(crypto_chacha20_setkey); int crypto_chacha20_crypt(struct skcipher_request *req) { struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm); struct skcipher_walk walk; u32 state[16]; int err; err = skcipher_walk_virt(&walk, req, true); crypto_chacha20_init(state, ctx, walk.iv); while (walk.nbytes > 0) { unsigned int nbytes = walk.nbytes; if (nbytes < walk.total) nbytes = round_down(nbytes, walk.stride); chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr, nbytes); err = skcipher_walk_done(&walk, walk.nbytes - nbytes); } return err; } EXPORT_SYMBOL_GPL(crypto_chacha20_crypt); static struct skcipher_alg alg = { .base.cra_name = "chacha20", .base.cra_driver_name = "chacha20-generic", .base.cra_priority = 100, .base.cra_blocksize = 1, .base.cra_ctxsize = sizeof(struct chacha20_ctx), .base.cra_module = THIS_MODULE, .min_keysize = CHACHA20_KEY_SIZE, .max_keysize = CHACHA20_KEY_SIZE, .ivsize = CHACHA20_IV_SIZE, .chunksize = CHACHA20_BLOCK_SIZE, .setkey = crypto_chacha20_setkey, .encrypt = crypto_chacha20_crypt, .decrypt = crypto_chacha20_crypt, }; static int __init chacha20_generic_mod_init(void) { return crypto_register_skcipher(&alg); } static void __exit chacha20_generic_mod_fini(void) { crypto_unregister_skcipher(&alg); } module_init(chacha20_generic_mod_init); module_exit(chacha20_generic_mod_fini); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); MODULE_DESCRIPTION("chacha20 cipher algorithm"); MODULE_ALIAS_CRYPTO("chacha20"); MODULE_ALIAS_CRYPTO("chacha20-generic");