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/* $OpenBSD: chachapoly.c,v 1.6 2020/07/22 13:54:30 tobhe Exp $ */
/*
* Copyright (c) 2015 Mike Belopuhov
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <lib/libkern/libkern.h>
#include <crypto/chacha_private.h>
#include <crypto/poly1305.h>
#include <crypto/chachapoly.h>
int
chacha20_setkey(void *sched, u_int8_t *key, int len)
{
struct chacha20_ctx *ctx = (struct chacha20_ctx *)sched;
if (len != CHACHA20_KEYSIZE + CHACHA20_SALT)
return (-1);
/* initial counter is 1 */
ctx->nonce[0] = 1;
memcpy(ctx->nonce + CHACHA20_CTR, key + CHACHA20_KEYSIZE,
CHACHA20_SALT);
chacha_keysetup((chacha_ctx *)&ctx->block, key, CHACHA20_KEYSIZE * 8);
return (0);
}
void
chacha20_reinit(caddr_t key, u_int8_t *iv)
{
struct chacha20_ctx *ctx = (struct chacha20_ctx *)key;
chacha_ivsetup((chacha_ctx *)ctx->block, iv, ctx->nonce);
}
void
chacha20_crypt(caddr_t key, u_int8_t *data)
{
struct chacha20_ctx *ctx = (struct chacha20_ctx *)key;
chacha_encrypt_bytes((chacha_ctx *)ctx->block, data, data,
CHACHA20_BLOCK_LEN);
}
void
Chacha20_Poly1305_Init(void *xctx)
{
CHACHA20_POLY1305_CTX *ctx = xctx;
memset(ctx, 0, sizeof(*ctx));
}
void
Chacha20_Poly1305_Setkey(void *xctx, const uint8_t *key, uint16_t klen)
{
CHACHA20_POLY1305_CTX *ctx = xctx;
/* salt is provided with the key material */
memcpy(ctx->nonce + CHACHA20_CTR, key + CHACHA20_KEYSIZE,
CHACHA20_SALT);
chacha_keysetup((chacha_ctx *)&ctx->chacha, key, CHACHA20_KEYSIZE * 8);
}
void
Chacha20_Poly1305_Reinit(void *xctx, const uint8_t *iv, uint16_t ivlen)
{
CHACHA20_POLY1305_CTX *ctx = xctx;
/* initial counter is 0 */
chacha_ivsetup((chacha_ctx *)&ctx->chacha, iv, ctx->nonce);
chacha_encrypt_bytes((chacha_ctx *)&ctx->chacha, ctx->key, ctx->key,
POLY1305_KEYLEN);
poly1305_init((poly1305_state *)&ctx->poly, ctx->key);
}
int
Chacha20_Poly1305_Update(void *xctx, const uint8_t *data, uint16_t len)
{
static const char zeroes[POLY1305_BLOCK_LEN];
CHACHA20_POLY1305_CTX *ctx = xctx;
size_t rem;
poly1305_update((poly1305_state *)&ctx->poly, data, len);
/* number of bytes in the last 16 byte block */
rem = (len + POLY1305_BLOCK_LEN) & (POLY1305_BLOCK_LEN - 1);
if (rem > 0)
poly1305_update((poly1305_state *)&ctx->poly, zeroes,
POLY1305_BLOCK_LEN - rem);
return (0);
}
void
Chacha20_Poly1305_Final(uint8_t tag[POLY1305_TAGLEN], void *xctx)
{
CHACHA20_POLY1305_CTX *ctx = xctx;
poly1305_finish((poly1305_state *)&ctx->poly, tag);
explicit_bzero(ctx, sizeof(*ctx));
}
static const uint8_t pad0[16] = { 0 };
void
chacha20poly1305_encrypt(
uint8_t *dst,
const uint8_t *src,
const size_t src_len,
const uint8_t *ad,
const size_t ad_len,
const uint64_t nonce,
const uint8_t key[CHACHA20POLY1305_KEY_SIZE]
) {
poly1305_state poly1305_ctx;
chacha_ctx chacha_ctx;
union {
uint8_t b0[CHACHA20POLY1305_KEY_SIZE];
uint64_t lens[2];
} b = { { 0 } };
uint64_t le_nonce = htole64(nonce);
chacha_keysetup(&chacha_ctx, key, CHACHA20POLY1305_KEY_SIZE * 8);
chacha_ivsetup(&chacha_ctx, (uint8_t *) &le_nonce, NULL);
chacha_encrypt_bytes(&chacha_ctx, b.b0, b.b0, sizeof(b.b0));
poly1305_init(&poly1305_ctx, b.b0);
poly1305_update(&poly1305_ctx, ad, ad_len);
poly1305_update(&poly1305_ctx, pad0, (0x10 - ad_len) & 0xf);
chacha_encrypt_bytes(&chacha_ctx, (uint8_t *) src, dst, src_len);
poly1305_update(&poly1305_ctx, dst, src_len);
poly1305_update(&poly1305_ctx, pad0, (0x10 - src_len) & 0xf);
b.lens[0] = htole64(ad_len);
b.lens[1] = htole64(src_len);
poly1305_update(&poly1305_ctx, (uint8_t *)b.lens, sizeof(b.lens));
poly1305_finish(&poly1305_ctx, dst + src_len);
explicit_bzero(&chacha_ctx, sizeof(chacha_ctx));
explicit_bzero(&b, sizeof(b));
}
int
chacha20poly1305_decrypt(
uint8_t *dst,
const uint8_t *src,
const size_t src_len,
const uint8_t *ad,
const size_t ad_len,
const uint64_t nonce,
const uint8_t key[CHACHA20POLY1305_KEY_SIZE]
) {
poly1305_state poly1305_ctx;
chacha_ctx chacha_ctx;
int ret;
size_t dst_len;
union {
uint8_t b0[CHACHA20POLY1305_KEY_SIZE];
uint8_t mac[CHACHA20POLY1305_AUTHTAG_SIZE];
uint64_t lens[2];
} b = { { 0 } };
uint64_t le_nonce = htole64(nonce);
if (src_len < CHACHA20POLY1305_AUTHTAG_SIZE)
return 0;
chacha_keysetup(&chacha_ctx, key, CHACHA20POLY1305_KEY_SIZE * 8);
chacha_ivsetup(&chacha_ctx, (uint8_t *) &le_nonce, NULL);
chacha_encrypt_bytes(&chacha_ctx, b.b0, b.b0, sizeof(b.b0));
poly1305_init(&poly1305_ctx, b.b0);
poly1305_update(&poly1305_ctx, ad, ad_len);
poly1305_update(&poly1305_ctx, pad0, (0x10 - ad_len) & 0xf);
dst_len = src_len - CHACHA20POLY1305_AUTHTAG_SIZE;
poly1305_update(&poly1305_ctx, src, dst_len);
poly1305_update(&poly1305_ctx, pad0, (0x10 - dst_len) & 0xf);
b.lens[0] = htole64(ad_len);
b.lens[1] = htole64(dst_len);
poly1305_update(&poly1305_ctx, (uint8_t *)b.lens, sizeof(b.lens));
poly1305_finish(&poly1305_ctx, b.mac);
ret = timingsafe_bcmp(b.mac, src + dst_len, CHACHA20POLY1305_AUTHTAG_SIZE);
if (!ret)
chacha_encrypt_bytes(&chacha_ctx, (uint8_t *) src, dst, dst_len);
explicit_bzero(&chacha_ctx, sizeof(chacha_ctx));
explicit_bzero(&b, sizeof(b));
return !ret;
}
void
xchacha20poly1305_encrypt(
uint8_t *dst,
const uint8_t *src,
const size_t src_len,
const uint8_t *ad,
const size_t ad_len,
const uint8_t nonce[XCHACHA20POLY1305_NONCE_SIZE],
const uint8_t key[CHACHA20POLY1305_KEY_SIZE]
) {
int i;
uint32_t derived_key[CHACHA20POLY1305_KEY_SIZE / sizeof(uint32_t)];
uint64_t h_nonce;
memcpy(&h_nonce, nonce + 16, sizeof(h_nonce));
h_nonce = le64toh(h_nonce);
hchacha20(derived_key, nonce, key);
for(i = 0; i < (sizeof(derived_key)/sizeof(derived_key[0])); i++)
(derived_key[i]) = htole32((derived_key[i]));
chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len,
h_nonce, (uint8_t *)derived_key);
explicit_bzero(derived_key, CHACHA20POLY1305_KEY_SIZE);
}
int
xchacha20poly1305_decrypt(
uint8_t *dst,
const uint8_t *src,
const size_t src_len,
const uint8_t *ad,
const size_t ad_len,
const uint8_t nonce[XCHACHA20POLY1305_NONCE_SIZE],
const uint8_t key[CHACHA20POLY1305_KEY_SIZE]
) {
int ret, i;
uint32_t derived_key[CHACHA20POLY1305_KEY_SIZE / sizeof(uint32_t)];
uint64_t h_nonce;
memcpy(&h_nonce, nonce + 16, sizeof(h_nonce));
h_nonce = le64toh(h_nonce);
hchacha20(derived_key, nonce, key);
for(i = 0; i < (sizeof(derived_key)/sizeof(derived_key[0])); i++)
(derived_key[i]) = htole32((derived_key[i]));
ret = chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len,
h_nonce, (uint8_t *)derived_key);
explicit_bzero(derived_key, CHACHA20POLY1305_KEY_SIZE);
return ret;
}
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