mirror of https://gerrit.osmocom.org/libosmocore
253 lines
7.4 KiB
C
253 lines
7.4 KiB
C
/* (C) 2010-2012 by Harald Welte <laforge@gnumonks.org>
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*
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* All Rights Reserved
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*
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* SPDX-License-Identifier: GPL-2.0+
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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 "config.h"
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#include <errno.h>
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#include <stdint.h>
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#include <string.h>
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#include <osmocom/core/utils.h>
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#include <osmocom/core/linuxlist.h>
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#include <osmocom/core/plugin.h>
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#include <osmocom/crypt/auth.h>
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/*! \addtogroup auth
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* @{
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* GSM/GPRS/3G authentication core infrastructure
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*
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* \file auth_core.c */
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static LLIST_HEAD(osmo_auths);
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static struct osmo_auth_impl *selected_auths[_OSMO_AUTH_ALG_NUM];
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/*! Register an authentication algorithm implementation with the core
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* \param[in] impl Structure describing implementation and it's callbacks
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* \returns 0 on success, or a negative error code on failure
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*
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* This function is called by an authentication implementation plugin to
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* register itself with the authentication core.
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*/
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int osmo_auth_register(struct osmo_auth_impl *impl)
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{
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if (impl->algo >= ARRAY_SIZE(selected_auths))
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return -ERANGE;
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llist_add_tail(&impl->list, &osmo_auths);
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/* check if we want to select this implementation over others */
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if (!selected_auths[impl->algo] ||
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(selected_auths[impl->algo]->priority > impl->priority))
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selected_auths[impl->algo] = impl;
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return 0;
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}
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/*! Load all available authentication plugins from the given path
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* \param[in] path Path name of the directory containing the plugins
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* \returns number of plugins loaded in case of success, negative in case of error
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*
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* This function will load all plugins contained in the specified path.
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*/
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int osmo_auth_load(const char *path)
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{
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/* load all plugins available from path */
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#if !defined(EMBEDDED)
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return osmo_plugin_load_all(path);
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#else
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return -1;
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#endif
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}
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/*! Determine if a given authentication algorithm is supported
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* \param[in] algo Algorithm which should be checked
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* \returns 1 if algo is supported, 0 if not, negative error on failure
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*
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* This function is used by an application to determine at runtime if a
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* given authentication algorithm is supported or not.
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*/
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int osmo_auth_supported(enum osmo_auth_algo algo)
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{
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if (algo >= ARRAY_SIZE(selected_auths))
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return -ERANGE;
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if (selected_auths[algo])
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return 1;
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return 0;
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}
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/* 3GPP TS 33.102 §6.8.2.3 C5 function to derive UMTS IK from GSM Kc */
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static inline void c5_function(uint8_t *ik, const uint8_t *kc)
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{
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unsigned int i;
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for (i = 0; i < 4; i++)
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ik[i] = kc[i] ^ kc[i+4];
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memcpy(ik+4, kc, 8);
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for (i = 12; i < 16; i++)
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ik[i] = ik[i-12];
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}
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/* 3GPP TS 33.102 §6.8.2.3 C4 function to derive UMTS CK from GSM Kc */
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void osmo_c4(uint8_t *ck, const uint8_t *kc)
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{
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memcpy(ck, kc, 8);
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memcpy(ck+8, kc, 8);
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}
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/*! Generate 3G CK + IK from 2G authentication vector
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* \param vec Authentication Vector to be modified
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* \returns 1 if the vector was changed, 0 otherwise
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*
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* This function performs the C5 and C4 functions to derive the UMTS key
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* material from the GSM key material in the supplied vector, _if_ the input
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* vector doesn't yet have UMTS authentication capability.
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*/
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int osmo_auth_3g_from_2g(struct osmo_auth_vector *vec)
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{
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if ((vec->auth_types & OSMO_AUTH_TYPE_GSM) &&
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!(vec->auth_types & OSMO_AUTH_TYPE_UMTS)) {
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c5_function(vec->ik, vec->kc);
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osmo_c4(vec->ck, vec->kc);
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/* We cannot actually set OSMO_AUTH_TYPE_UMTS as we have no
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* AUTN and no RES, and thus can only perform GSM
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* authentication with this tuple.
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*/
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return 1;
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}
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return 0;
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}
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/*! Generate authentication vector
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* \param[out] vec Generated authentication vector
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* \param[in] aud Subscriber-specific key material
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* \param[in] _rand Random challenge to be used
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* \returns 0 on success, negative error on failure
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*
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* This function performs the core cryptographic function of the AUC,
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* computing authentication triples/quintuples based on the permanent
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* subscriber data and a random value. The result is what is forwarded
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* by the AUC via HLR and VLR to the MSC which will then be able to
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* invoke authentication with the MS
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*/
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int osmo_auth_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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struct osmo_auth_impl *impl = selected_auths[aud->algo];
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int rc;
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if (!impl)
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return -ENOENT;
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rc = impl->gen_vec(vec, aud, _rand);
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if (rc < 0)
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return rc;
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memcpy(vec->rand, _rand, sizeof(vec->rand));
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return 0;
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}
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/*! Generate authentication vector and re-sync sequence
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* \param[out] vec Generated authentication vector
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* \param[in] aud Subscriber-specific key material
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* \param[in] auts AUTS value sent by the SIM/MS
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* \param[in] rand_auts RAND value sent by the SIM/MS
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* \param[in] _rand Random challenge to be used to generate vector
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* \returns 0 on success, negative error on failure
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*
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* This function performs a special variant of the core cryptographic
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* function of the AUC: computing authentication triples/quintuples
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* based on the permanent subscriber data, a random value as well as the
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* AUTS and RAND values returned by the SIM/MS. This special variant is
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* needed if the sequence numbers between MS and AUC have for some
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* reason become different.
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*/
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int osmo_auth_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, const uint8_t *rand_auts,
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const uint8_t *_rand)
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{
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struct osmo_auth_impl *impl = selected_auths[aud->algo];
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int rc;
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if (!impl || !impl->gen_vec_auts)
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return -ENOENT;
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rc = impl->gen_vec_auts(vec, aud, auts, rand_auts, _rand);
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if (rc < 0)
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return rc;
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memcpy(vec->rand, _rand, sizeof(vec->rand));
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return 0;
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}
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static const struct value_string auth_alg_vals[] = {
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{ OSMO_AUTH_ALG_NONE, "None" },
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{ OSMO_AUTH_ALG_COMP128v1, "COMP128v1" },
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{ OSMO_AUTH_ALG_COMP128v2, "COMP128v2" },
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{ OSMO_AUTH_ALG_COMP128v3, "COMP128v3" },
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{ OSMO_AUTH_ALG_XOR, "XOR" },
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{ OSMO_AUTH_ALG_MILENAGE, "MILENAGE" },
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{ 0, NULL }
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};
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/*! Get human-readable name of authentication algorithm */
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const char *osmo_auth_alg_name(enum osmo_auth_algo alg)
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{
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return get_value_string(auth_alg_vals, alg);
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}
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/*! Parse human-readable name of authentication algorithm */
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enum osmo_auth_algo osmo_auth_alg_parse(const char *name)
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{
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return get_string_value(auth_alg_vals, name);
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}
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const struct value_string osmo_sub_auth_type_names[] = {
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{ OSMO_AUTH_TYPE_NONE, "None" },
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{ OSMO_AUTH_TYPE_GSM, "GSM" },
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{ OSMO_AUTH_TYPE_UMTS, "UMTS" },
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{ 0, NULL }
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};
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/* Derive GSM AKA ciphering key Kc from UMTS AKA CK and IK (auth function c3 from 3GPP TS 33.103 §
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* 4.6.1).
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* \param[out] kc GSM AKA Kc, 8 byte target buffer.
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* \param[in] ck UMTS AKA CK, 16 byte input buffer.
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* \param[in] ik UMTS AKA IK, 16 byte input buffer.
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*/
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void osmo_auth_c3(uint8_t kc[], const uint8_t ck[], const uint8_t ik[])
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{
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int i;
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for (i = 0; i < 8; i++)
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kc[i] = ck[i] ^ ck[i + 8] ^ ik[i] ^ ik[i + 8];
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}
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/*! @} */
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