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