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/*! \file auth_xor.c
* GSM XOR-2G algorithm as specified in Annex 4 (A.4.1.2) of 3GPP TS 51.010-1.
* This is implemented by typical GSM MS tester */
/*
* (C) 2023 by Harald Welte <laforge@gnumonks.org>
*
* All Rights Reserved
*
* Author: Daniel Willmann <dwillmann@sysmocom.de>
*
* All Rights Reserved
*
* 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 <string.h>
#include <stdint.h>
#include <errno.h>
#include <osmocom/crypt/auth.h>
/*! \addtogroup auth
* @{
*/
static void xor(uint8_t *out, const uint8_t *a, const uint8_t *b, size_t len)
{
size_t i;
for (i = 0; i < len; i++)
out[i] = a[i] ^ b[i];
}
/* GSM XOR-2G algorithm as specified in Annex 4 (A.4.1.2) of 3GPP TS 51.010-1. */
static int xor2g_gen_vec(struct osmo_auth_vector *vec,
struct osmo_sub_auth_data2 *aud,
const uint8_t *_rand)
{
uint8_t res1[16];
OSMO_ASSERT(aud->algo == OSMO_AUTH_ALG_XOR_2G);
if (aud->type != OSMO_AUTH_TYPE_GSM)
return -ENOTSUP;
/* Step 1: XOR to the challenge RAND, a predefined number Ki, having the same bit length (128 bits) as
* RAND. */
xor(res1, aud->u.gsm.ki, _rand, sizeof(res1));
/* Step 2: The most significant 32 bits of RES1 form SRES. */
memcpy(vec->sres, res1, 4);
/* The next 64 bits of RES1 form Kc */
memcpy(vec->kc, res1+4, 8);
vec->auth_types = OSMO_AUTH_TYPE_GSM;
return 0;
}
static struct osmo_auth_impl xor2g_alg = {
.algo = OSMO_AUTH_ALG_XOR_2G,
.name = "XOR-2G (libosmogsm built-in)",
.priority = 1000,
.gen_vec = &xor2g_gen_vec,
};
static __attribute__((constructor)) void on_dso_load_xor(void)
{
osmo_auth_register(&xor2g_alg);
}
/*! @} */
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