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/* SPDX-License-Identifier: GPL-3.0-or-later
* Copyright © 2019-2021 The TokTok team.
*/
#include "timed_auth.h"
#include <string.h>
#include "attributes.h"
#include "ccompat.h"
#include "crypto_core.h"
#include "mono_time.h"
non_null(1, 6) nullable(4)
static void create_timed_auth_to_hash(const Mono_Time *mono_time, uint16_t timeout, bool previous, const uint8_t *data,
uint16_t length, uint8_t *to_hash)
{
const uint64_t t = (mono_time_get(mono_time) / timeout) - (previous ? 1 : 0);
memcpy(to_hash, &t, sizeof(t));
if (data != nullptr) {
memcpy(to_hash + sizeof(t), data, length);
}
}
void generate_timed_auth(const Mono_Time *mono_time, uint16_t timeout, const uint8_t *key,
const uint8_t *data, uint16_t length, uint8_t *timed_auth)
{
const uint16_t to_hash_size = sizeof(uint64_t) + length;
VLA(uint8_t, to_hash, to_hash_size);
create_timed_auth_to_hash(mono_time, timeout, false, data, length, to_hash);
crypto_hmac(timed_auth, key, to_hash, to_hash_size);
}
bool check_timed_auth(const Mono_Time *mono_time, uint16_t timeout, const uint8_t *key, const uint8_t *data,
uint16_t length, const uint8_t *timed_auth)
{
const uint16_t to_hash_size = sizeof(uint64_t) + length;
VLA(uint8_t, to_hash, to_hash_size);
for (uint8_t i = 0; i < 2; ++i) {
create_timed_auth_to_hash(mono_time, timeout, i != 0, data, length, to_hash);
if (crypto_hmac_verify(timed_auth, key, to_hash, to_hash_size)) {
return true;
}
}
return false;
}
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