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/*
* (C) 2021 by sysmocom s.f.m.c. GmbH
*
* Author: Eric Wild <ewild@sysmocom.de>
*
* All Rights Reserved
*
* SPDX-License-Identifier: GPL-2.0+
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of 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.
*
* This program 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.
*
*/
#include <stdint.h>
#include <string.h>
#include "config.h"
#if (USE_GNUTLS)
#include <gnutls/gnutls.h>
#include <gnutls/crypto.h>
#define HMAC_FUNC(k,lk,s,sl,out) gnutls_hmac_fast(GNUTLS_MAC_SHA256,k,lk,s,sl,out)
#else
#include <osmocom/crypt/kdf.h>
#define HMAC_FUNC(k,lk,s,sl,out) hmac_sha256(k,lk,s,sl,out)
#endif
#include <osmocom/core/bit32gen.h>
#include <osmocom/crypt/kdf.h>
#include "kdf/common.h"
#include "kdf/sha256.h"
#if (USE_GNUTLS)
/* gnutls < 3.3.0 requires global init.
* gnutls >= 3.3.0 does it automatic.
* It doesn't hurt calling it twice,
* as long it's not done at the same time (threads).
*/
__attribute__((constructor))
static void on_dso_load_gnutls(void)
{
if (!gnutls_check_version("3.3.0"))
gnutls_global_init();
}
__attribute__((destructor))
static void on_dso_unload_gnutls(void)
{
if (!gnutls_check_version("3.3.0"))
gnutls_global_deinit();
}
#endif
/*
* This file uses the generic key derivation function defined in 3GPP TS 33.220 Annex B
*
* The S parameter always consists of concatenated values FC | P0 | L0 | Pi | Li | ...
* with Pi = Parameter number i and Li = Length of Pi (two octets)
*
* FC is either a single octet or two octets 0xff | FC
* FC values ranges depend on the specification parts that use the KDF,
* they are defined in 3GPP TS 33.220 Annex B.2.2
*
*/
/*! \addtogroup kdf
* @{
* key derivation functions
*
* \file kdf.c */
/* 3GPP TS 33.102 B.5 */
void osmo_kdf_kc128(const uint8_t* ck, const uint8_t* ik, uint8_t* kc128) {
uint8_t k[16*2];
uint8_t s[1];
uint8_t out_tmp256[32];
memcpy (&k[0], ck, 16);
memcpy (&k[16], ik, 16);
s[0] = 0x32; // yeah, really just one FC byte..
HMAC_FUNC(k, 32, s, 1, out_tmp256);
memcpy(kc128, out_tmp256, 16);
}
/* 3GPP TS 33.401 A.2 */
void osmo_kdf_kasme(const uint8_t *ck, const uint8_t *ik, const uint8_t* plmn_id,
const uint8_t *sqn, const uint8_t *ak, uint8_t *kasme)
{
uint8_t s[14];
uint8_t k[16*2];
int i;
memcpy(&k[0], ck, 16);
memcpy(&k[16], ik, 16);
s[0] = 0x10;
memcpy(&s[1], plmn_id, 3);
s[4] = 0x00;
s[5] = 0x03;
for (i = 0; i < 6; i++)
s[6+i] = sqn[i] ^ ak[i];
s[12] = 0x00;
s[13] = 0x06;
HMAC_FUNC(k, 32, s, 14, kasme);
}
/* 3GPP TS 33.401 A.3 */
void osmo_kdf_enb(const uint8_t *kasme, uint32_t ul_count, uint8_t *kenb)
{
uint8_t s[7];
s[0] = 0x11;
osmo_store32be(ul_count, &s[1]);
s[5] = 0x00;
s[6] = 0x04;
HMAC_FUNC(kasme, 32, s, 7, kenb);
}
/* 3GPP TS 33.401 A.4 */
void osmo_kdf_nh(const uint8_t *kasme, const uint8_t *sync_input, uint8_t *nh)
{
uint8_t s[35];
s[0] = 0x12;
memcpy(s+1, sync_input, 32);
s[33] = 0x00;
s[34] = 0x20;
HMAC_FUNC(kasme, 32, s, 35, nh);
}
/* 3GPP TS 33.401 A.7 */
void osmo_kdf_nas(uint8_t algo_type, uint8_t algo_id, const uint8_t *kasme, uint8_t *knas)
{
uint8_t s[7];
uint8_t out[32];
s[0] = 0x15;
s[1] = algo_type;
s[2] = 0x00;
s[3] = 0x01;
s[4] = algo_id;
s[5] = 0x00;
s[6] = 0x01;
HMAC_FUNC(kasme, 32, s, 7, out);
memcpy(knas, out+16, 16);
}
/*! @} */
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