1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166
|
/* chacha-poly1305.c
AEAD mechanism based on chacha and poly1305.
Copyright (C) 2014, 2015 Niels Möller
This file is part of GNU Nettle.
GNU Nettle is free software: you can redistribute it and/or
modify it under the terms of either:
* the GNU Lesser General Public License as published by the Free
Software Foundation; either version 3 of the License, or (at your
option) any later version.
or
* 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.
or both in parallel, as here.
GNU Nettle is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received copies of the GNU General Public License and
the GNU Lesser General Public License along with this program. If
not, see http://www.gnu.org/licenses/.
*/
/* This implements chacha-poly1305 according to
draft-irtf-cfrg-chacha20-poly1305-08. The inputs to poly1305 are:
associated data
zero padding
ciphertext
zero padding
length of associated data (64-bit, little endian)
length of ciphertext (64-bit, little endian)
where the padding fields are 0-15 zero bytes, filling up to a
16-byte boundary.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include <string.h>
#include "chacha-poly1305.h"
#include "macros.h"
#define CHACHA_ROUNDS 20
/* FIXME: Also set nonce to zero, and implement nonce
auto-increment? */
void
chacha_poly1305_set_key (struct chacha_poly1305_ctx *ctx,
const uint8_t *key)
{
chacha_set_key (&ctx->chacha, key);
}
void
chacha_poly1305_set_nonce (struct chacha_poly1305_ctx *ctx,
const uint8_t *nonce)
{
union {
uint32_t x[_CHACHA_STATE_LENGTH];
uint8_t subkey[32];
} u;
chacha_set_nonce96 (&ctx->chacha, nonce);
/* Generate authentication key */
_chacha_core (u.x, ctx->chacha.state, CHACHA_ROUNDS);
poly1305_set_key (&ctx->poly1305, u.subkey);
/* For final poly1305 processing */
memcpy (ctx->s.b, u.subkey + 16, 16);
/* Increment block count */
ctx->chacha.state[12] = 1;
ctx->auth_size = ctx->data_size = ctx->index = 0;
}
/* FIXME: Duplicated in poly1305-aes128.c */
#define COMPRESS(ctx, data) _poly1305_block(&(ctx)->poly1305, (data), 1)
static void
poly1305_update (struct chacha_poly1305_ctx *ctx,
size_t length, const uint8_t *data)
{
MD_UPDATE (ctx, length, data, COMPRESS, (void) 0);
}
static void
poly1305_pad (struct chacha_poly1305_ctx *ctx)
{
if (ctx->index)
{
memset (ctx->block + ctx->index, 0,
POLY1305_BLOCK_SIZE - ctx->index);
_poly1305_block(&ctx->poly1305, ctx->block, 1);
ctx->index = 0;
}
}
void
chacha_poly1305_update (struct chacha_poly1305_ctx *ctx,
size_t length, const uint8_t *data)
{
assert (ctx->data_size == 0);
poly1305_update (ctx, length, data);
ctx->auth_size += length;
}
void
chacha_poly1305_encrypt (struct chacha_poly1305_ctx *ctx,
size_t length, uint8_t *dst, const uint8_t *src)
{
if (!length)
return;
assert (ctx->data_size % CHACHA_POLY1305_BLOCK_SIZE == 0);
poly1305_pad (ctx);
chacha_crypt (&ctx->chacha, length, dst, src);
poly1305_update (ctx, length, dst);
ctx->data_size += length;
}
void
chacha_poly1305_decrypt (struct chacha_poly1305_ctx *ctx,
size_t length, uint8_t *dst, const uint8_t *src)
{
if (!length)
return;
assert (ctx->data_size % CHACHA_POLY1305_BLOCK_SIZE == 0);
poly1305_pad (ctx);
poly1305_update (ctx, length, src);
chacha_crypt (&ctx->chacha, length, dst, src);
ctx->data_size += length;
}
void
chacha_poly1305_digest (struct chacha_poly1305_ctx *ctx,
size_t length, uint8_t *digest)
{
uint8_t buf[16];
poly1305_pad (ctx);
LE_WRITE_UINT64 (buf, ctx->auth_size);
LE_WRITE_UINT64 (buf + 8, ctx->data_size);
_poly1305_block (&ctx->poly1305, buf, 1);
poly1305_digest (&ctx->poly1305, &ctx->s);
memcpy (digest, &ctx->s.b, length);
}
|