mirror of https://gerrit.osmocom.org/libosmocore
188 lines
4.8 KiB
C
188 lines
4.8 KiB
C
/*! \file auth_xor.c
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* GSM/GPRS/3G authentication core infrastructure */
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/*
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* (C) 2018 by Harald Welte <laforge@gnumonks.org>
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* (C) 2017 by sysmocom s.f.m.c. GmbH
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*
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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 <string.h>
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#include <stdint.h>
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#include <errno.h>
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#include <osmocom/core/bit64gen.h>
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#include <osmocom/crypt/auth.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, size_t len)
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{
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size_t 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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/* 3GPP TS 34.108, section 8.1.2.1 */
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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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uint8_t xdout[16], cdout[8];
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uint8_t ak[6], xmac[8];
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int i;
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/* Step 1: xdout = (ki or k) ^ rand */
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if (aud->type == OSMO_AUTH_TYPE_GSM)
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xor(xdout, aud->u.gsm.ki, _rand, sizeof(xdout));
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else if (aud->type == OSMO_AUTH_TYPE_UMTS)
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xor(xdout, aud->u.umts.k, _rand, sizeof(xdout));
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else
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return -ENOTSUP;
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/**
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* Step 2: res = xdout
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*
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* Suggested length for res is 128 bits, i.e. 16 bytes,
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* but also can be in range: 30 < n < 128 bits.
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*/
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memcpy(vec->res, xdout, sizeof(xdout));
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vec->res_len = sizeof(xdout);
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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 + sizeof(xdout) - 2, xdout, 2);
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/* ak = xdout[3-8] */
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memcpy(ak, xdout + 3, sizeof(ak));
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/**
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* 3GPP TS 33.102, clause 6.8.1.2, b
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* sres = c2(res) = res[0-3] ^ res[4-7] ^ res[8-11] ^ res[12-15]
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*/
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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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vec->sres[i] ^= vec->res[i + 8] ^ vec->res[i + 12];
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}
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/**
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* 3GPP TS 33.102, clause 6.8.1.2, c
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* kc = c3(ck, ik) = ck[0-7] ^ ck[8-15] ^ ik[0-7] ^ ik[8-15]
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* FIXME: do we really have CK/IK for GSM?
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*/
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osmo_auth_c3(vec->kc, vec->ck, vec->ik);
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/* The further part is UMTS specific */
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if (aud->type != OSMO_AUTH_TYPE_UMTS) {
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vec->auth_types = OSMO_AUTH_TYPE_GSM;
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return 0;
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}
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/**
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* Step 3: cdout = sqn[0-5] || amf[0-1]
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* NOTE (for USIM): sqn[0-5] = autn[0-5] ^ ak[0-5]
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*/
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osmo_store64be_ext(aud->u.umts.sqn, cdout, 6);
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memcpy(cdout + 6, aud->u.umts.amf, 2);
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/* Step 4: xmac = xdout[0-8] ^ cdout[0-8] */
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xor(xmac, xdout, cdout, sizeof(xmac));
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/**
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* Step 5: autn = sqn ^ ak || amf || mac
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* NOTE: cdout still contains SQN from step 3
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*/
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xor(vec->autn, cdout, ak, sizeof(ak));
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memcpy(vec->autn + 6, aud->u.umts.amf, 2);
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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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/* 3GPP TS 34.108, section 8.1.2.2 */
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static int xor_gen_vec_auts(struct osmo_auth_vector *vec,
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struct osmo_sub_auth_data *aud,
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const uint8_t *auts,
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const uint8_t *rand_auts,
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const uint8_t *_rand)
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{
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uint8_t xdout[16], cdout[8];
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uint8_t ak[6], xmac[8];
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uint8_t sqnms[6];
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/* Step 1: xdout = (ki or k) ^ rand */
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if (aud->type == OSMO_AUTH_TYPE_GSM)
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xor(xdout, aud->u.gsm.ki, _rand, sizeof(xdout));
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else if (aud->type == OSMO_AUTH_TYPE_UMTS)
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xor(xdout, aud->u.umts.k, _rand, sizeof(xdout));
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else
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return -ENOTSUP;
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/* Step 2: ak = xdout[2-8] */
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memcpy(ak, xdout + 3, 6);
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/* sqnms = auts[0-5] ^ ak[0-5] */
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xor(sqnms, auts, ak, sizeof(ak));
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/* cdout = sqnms || amf* (dummy) */
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memcpy(cdout, sqnms, 6);
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memset(cdout + 6, 0x00, 2);
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/* xmac = xdout[0-7] ^ cdout[0-7] */
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xor(xmac, xdout, cdout, 8);
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/* Compare the last 64 bits of received AUTS with the locally-generated MAC-S */
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if (memcmp(auts + 6, xmac, 8))
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return -1;
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/* Update the "largest used SQN" from the USIM,
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* milenage_gen_vec() will increment it. */
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aud->u.umts.sqn_ms = osmo_load64be_ext(sqnms, 6) >> 16;
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aud->u.umts.sqn = aud->u.umts.sqn_ms;
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return xor_gen_vec(vec, aud, _rand);
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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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.gen_vec_auts = &xor_gen_vec_auts,
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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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