213 lines
6.0 KiB
C
213 lines
6.0 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 <crypto/algapi.h>
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#include <linux/crypto.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <crypto/chacha20.h>
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static inline u32 rotl32(u32 v, u8 n)
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{
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return (v << n) | (v >> (sizeof(v) * 8 - n));
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}
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static inline u32 le32_to_cpuvp(const void *p)
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{
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return le32_to_cpup(p);
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}
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static void chacha20_block(u32 *state, void *stream)
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{
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u32 x[16], *out = stream;
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int i;
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for (i = 0; i < ARRAY_SIZE(x); i++)
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x[i] = state[i];
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for (i = 0; i < 20; i += 2) {
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x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 16);
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x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 16);
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x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 16);
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x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 16);
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x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 12);
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x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 12);
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x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 12);
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x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 12);
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x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 8);
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x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 8);
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x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 8);
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x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 8);
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x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 7);
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x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 7);
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x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 7);
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x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 7);
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x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 16);
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x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 16);
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x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 16);
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x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 16);
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x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 12);
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x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 12);
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x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 12);
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x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 12);
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x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 8);
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x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 8);
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x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 8);
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x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 8);
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x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 7);
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x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 7);
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x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 7);
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x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 7);
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}
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for (i = 0; i < ARRAY_SIZE(x); i++)
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out[i] = cpu_to_le32(x[i] + state[i]);
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state[12]++;
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}
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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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u8 stream[CHACHA20_BLOCK_SIZE];
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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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static const char constant[16] = "expand 32-byte k";
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state[0] = le32_to_cpuvp(constant + 0);
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state[1] = le32_to_cpuvp(constant + 4);
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state[2] = le32_to_cpuvp(constant + 8);
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state[3] = le32_to_cpuvp(constant + 12);
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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] = le32_to_cpuvp(iv + 0);
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state[13] = le32_to_cpuvp(iv + 4);
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state[14] = le32_to_cpuvp(iv + 8);
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state[15] = le32_to_cpuvp(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_tfm *tfm, const u8 *key,
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unsigned int keysize)
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{
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struct chacha20_ctx *ctx = crypto_tfm_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] = le32_to_cpuvp(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 blkcipher_desc *desc, struct scatterlist *dst,
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struct scatterlist *src, unsigned int nbytes)
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{
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struct blkcipher_walk walk;
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u32 state[16];
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int err;
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blkcipher_walk_init(&walk, dst, src, nbytes);
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err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);
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crypto_chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);
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while (walk.nbytes >= CHACHA20_BLOCK_SIZE) {
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chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
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rounddown(walk.nbytes, CHACHA20_BLOCK_SIZE));
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err = blkcipher_walk_done(desc, &walk,
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walk.nbytes % CHACHA20_BLOCK_SIZE);
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}
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if (walk.nbytes) {
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chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
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walk.nbytes);
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err = blkcipher_walk_done(desc, &walk, 0);
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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 crypto_alg alg = {
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.cra_name = "chacha20",
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.cra_driver_name = "chacha20-generic",
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.cra_priority = 100,
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.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
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.cra_blocksize = 1,
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.cra_type = &crypto_blkcipher_type,
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.cra_ctxsize = sizeof(struct chacha20_ctx),
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.cra_alignmask = sizeof(u32) - 1,
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.cra_module = THIS_MODULE,
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.cra_u = {
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.blkcipher = {
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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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.geniv = "seqiv",
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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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},
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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_alg(&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_alg(&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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