freebsd-skq/sys/crypto/chacha20/chacha20.c
des 4a175969bb Fix counter increment in Salsa and ChaCha.
In my eagerness to eliminate a branch which is taken once per 2^38
bytes of keystream, I forgot that the state words are in host order.
Thus, the counter increment code worked fine on little-endian
machines, but not on big-endian ones.  Switch to a simpler (branchful)
solution.
2017-04-22 01:06:23 +00:00

210 lines
5.7 KiB
C

/*-
* Copyright (c) 2017 Dag-Erling Smørgrav
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#ifdef _KERNEL
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/libkern.h>
#include <sys/module.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#else
#include <stdint.h>
#include <string.h>
#endif
#include <sys/endian.h>
#include <crypto/chacha20/chacha20.h>
#define rol32(x, n) \
((x) << ((n) & 0x1f) | (x) >> (-(n) & 0x1f))
#define CHACHA_QR(x, a, b, c, d) \
do { \
x[a] = x[a] + x[b]; x[d] = rol32(x[d] ^ x[a], 16); \
x[c] = x[c] + x[d]; x[b] = rol32(x[b] ^ x[c], 12); \
x[a] = x[a] + x[b]; x[d] = rol32(x[d] ^ x[a], 8); \
x[c] = x[c] + x[d]; x[b] = rol32(x[b] ^ x[c], 7); \
} while (0)
static const char magic128[] = "expand 16-byte k";
static const char magic256[] = "expand 32-byte k";
/*
* Fill the state array with 16 bytes of magic and 32 bytes of key,
* repeating the key if necessary. The 8-byte stream position and the
* 8-byte nonce are initialized to all-zeroes.
*/
void
chacha20_init(chacha20_ctx *ctx, const uint8_t *key, size_t keylen)
{
memset(ctx, 0, sizeof *ctx);
if (keylen == 32) {
/* magic */
ctx->state[ 0] = le32dec(magic256 + 0);
ctx->state[ 1] = le32dec(magic256 + 4);
ctx->state[ 2] = le32dec(magic256 + 8);
ctx->state[ 3] = le32dec(magic256 + 12);
/* first half of key */
ctx->state[ 4] = le32dec(key + 0);
ctx->state[ 5] = le32dec(key + 4);
ctx->state[ 6] = le32dec(key + 8);
ctx->state[ 7] = le32dec(key + 12);
/* second half of key */
ctx->state[ 8] = le32dec(key + 16);
ctx->state[ 9] = le32dec(key + 20);
ctx->state[10] = le32dec(key + 24);
ctx->state[11] = le32dec(key + 28);
} else {
/* magic */
ctx->state[ 0] = le32dec(magic128 + 0);
ctx->state[ 1] = le32dec(magic128 + 4);
ctx->state[ 2] = le32dec(magic128 + 8);
ctx->state[ 3] = le32dec(magic128 + 12);
/* first half of key */
ctx->state[ 4] = le32dec(key + 0);
ctx->state[ 5] = le32dec(key + 4);
ctx->state[ 6] = le32dec(key + 8);
ctx->state[ 7] = le32dec(key + 12);
/* repeat first half of key */
ctx->state[ 8] = le32dec(key + 0);
ctx->state[ 9] = le32dec(key + 4);
ctx->state[10] = le32dec(key + 8);
ctx->state[11] = le32dec(key + 12);
}
}
/*
* Reset the stream position and load a new nonce.
*/
void
chacha20_reset(chacha20_ctx *ctx, const uint8_t *nonce)
{
/* reset stream counter */
ctx->state[12] = 0;
ctx->state[13] = 0;
/* copy nonce */
ctx->state[14] = le32dec(nonce + 0);
ctx->state[15] = le32dec(nonce + 4);
}
/*
* Encryption: generate a block of keystream, xor it with the plaintext to
* produce the ciphertext, and increment the stream position. If vpt is
* NULL, simply copy the requested keystream to the output buffer.
*/
size_t
chacha20_encrypt(chacha20_ctx *ctx, const void *vpt, uint8_t *ct, size_t len)
{
const uint8_t *pt = vpt;
uint32_t mix[16];
uint8_t ks[64];
unsigned int b, i;
len -= len % sizeof ks;
for (b = 0; b < len; b += sizeof ks) {
memcpy(mix, ctx->state, sizeof mix);
for (i = 0; i < 20; i += 2) {
CHACHA_QR(mix, 0, 4, 8, 12);
CHACHA_QR(mix, 1, 5, 9, 13);
CHACHA_QR(mix, 2, 6, 10, 14);
CHACHA_QR(mix, 3, 7, 11, 15);
CHACHA_QR(mix, 0, 5, 10, 15);
CHACHA_QR(mix, 1, 6, 11, 12);
CHACHA_QR(mix, 2, 7, 8, 13);
CHACHA_QR(mix, 3, 4, 9, 14);
}
for (i = 0; i < 16; ++i)
le32enc(ks + i * 4, ctx->state[i] + mix[i]);
if (pt == NULL) {
memcpy(ct, ks, sizeof ks);
ct += sizeof ks;
} else {
for (i = 0; i < 64 && i < len; ++i)
*ct++ = *pt++ ^ ks[i];
}
if (++ctx->state[12] == 0)
++ctx->state[13];
}
return (len);
}
/*
* Decryption: identical to encryption.
*/
size_t
chacha20_decrypt(chacha20_ctx *ctx, const uint8_t *ct, void *vpt, size_t len)
{
return (chacha20_encrypt(ctx, ct, vpt, len));
}
/*
* Wipe our state.
*/
void
chacha20_finish(chacha20_ctx *ctx)
{
memset(ctx, 0, sizeof *ctx);
}
#ifdef _KERNEL
static int
chacha20_modevent(module_t mod, int evtype, void *unused)
{
switch (evtype) {
case MOD_LOAD:
return (0);
case MOD_UNLOAD:
return (0);
default:
return (EOPNOTSUPP);
}
}
static moduledata_t chacha20_mod = {
"chacha20",
chacha20_modevent,
0
};
DECLARE_MODULE(chacha20, chacha20_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST);
MODULE_VERSION(chacha20, 1);
#endif