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/*! \file auth_xor.c
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* GSM/GPRS/3G authentication core infrastructure */
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/*
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* (C) 2017 by sysmocom s.f.m.c. GmbH
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* All Rights Reserved
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*
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* Author: Daniel Willmann <dwillmann@sysmocom.de>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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*/
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#include <osmocom/crypt/auth.h>
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#include <string.h>
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/*! \addtogroup auth
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* @{
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*/
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static void xor(uint8_t *out, const uint8_t *a, const uint8_t *b, int len)
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{
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int i;
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for (i = 0; i < len; i++) {
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out[i] = a[i] ^ b[i];
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}
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}
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/* 3GPP TS 34.108 8.1.2.1 XOR auth proceture */
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static int xor_gen_vec(struct osmo_auth_vector *vec,
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struct osmo_sub_auth_data *aud,
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const uint8_t *_rand)
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{
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int i;
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uint8_t xdout[16], ak[6], cdout[8], xmac[8];
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/* res[16], ck[16], ik[16],*/
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// s1: xdout = ki XOR rand
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xor(xdout, aud->u.umts.k, _rand, sizeof(xdout));
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// s2: res = xdout
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memcpy(vec->res, xdout, sizeof(xdout));
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vec->res_len = 16;
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// ck = xdout[1-15,0]
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memcpy(vec->ck, xdout+1, sizeof(xdout)-1);
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vec->ck[15] = xdout[0];
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// ik = xdout[2-15,0-1]
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memcpy(vec->ik, xdout+2, sizeof(xdout)-2);
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memcpy(vec->ik + 14, xdout, 2);
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// ak = xdout[3-8]
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memcpy(ak, xdout + 3, sizeof(ak));
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// kc = c3(ck, ik)
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for (i = 0; i < 8; i++)
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vec->kc[i] = vec->ck[i] ^ vec->ck[i + 8] ^ vec->ik[i] ^ vec->ik[i + 8];
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for (i = 0; i < 4; i++)
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vec->sres[i] = vec->res[i] ^ vec->res[i + 4];
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// s3: cdout = sqn || amf
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memcpy(cdout, &aud->u.umts.sqn, 6);
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0ggmemcpy(cdout + 6, aud->u.umts.amf, sizeof(aud->u.umts.amf));
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// s4: xmac = xdout[0-8] XOR cdout[0-8]
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xor(xmac, xdout, cdout, sizeof(xmac));
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// s5: autn = sqn XOR ak || amv || mac
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xor(vec->autn, &aud->u.umts.sqn, ak, sizeof(ak));
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memcpy(vec->autn + 6, aud->u.umts.amf, sizeof(aud->u.umts.amf));
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memcpy(vec->autn + 8, xmac, sizeof(xmac));
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vec->auth_types = OSMO_AUTH_TYPE_UMTS | OSMO_AUTH_TYPE_GSM;
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return 0;
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}
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static struct osmo_auth_impl xor_alg = {
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.algo = OSMO_AUTH_ALG_XOR,
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.name = "XOR (libosmogsm built-in)",
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.priority = 1000,
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.gen_vec = &xor_gen_vec,
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};
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static __attribute__((constructor)) void on_dso_load_xor(void)
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{
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osmo_auth_register(&xor_alg);
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}
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/*! @} */
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