src/gsm/milenage/milenage.c

/*! \file milenage.c
 * 3GPP AKA - Milenage algorithm (3GPP TS 35.205, .206, .207, .208) */
/*
 * Copyright (c) 2006-2007 <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 *
 * SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 *
 * This file implements an example authentication algorithm defined for 3GPP
 * AKA. This can be used to implement a simple HLR/AuC into hlr_auc_gw to allow
 * EAP-AKA to be tested properly with real USIM cards.
 *
 * This implementations assumes that the r1..r5 and c1..c5 constants defined in
 * TS 35.206 are used, i.e., r1=64, r2=0, r3=32, r4=64, r5=96, c1=00..00,
 * c2=00..01, c3=00..02, c4=00..04, c5=00..08. The block cipher is assumed to
 * be AES (Rijndael).
 */

#include "includes.h"

#include "common.h"
#include "aes_wrap.h"
#include "milenage.h"
#include <osmocom/crypt/auth.h>

/**
 * milenage_f1 - Milenage f1 and f1* algorithms
 * @opc: OPc = 128-bit value derived from OP and K
 * @k: K = 128-bit subscriber key
 * @_rand: RAND = 128-bit random challenge
 * @sqn: SQN = 48-bit sequence number
 * @amf: AMF = 16-bit authentication management field
 * @mac_a: Buffer for MAC-A = 64-bit network authentication code, or %NULL
 * @mac_s: Buffer for MAC-S = 64-bit resync authentication code, or %NULL
 * Returns: 0 on success, -1 on failure
 */
int milenage_f1(const u8 *opc, const u8 *k, const u8 *_rand,
		const u8 *sqn, const u8 *amf, u8 *mac_a, u8 *mac_s)
{
	u8 tmp1[16], tmp2[16], tmp3[16];
	int i;

	/* tmp1 = TEMP = E_K(RAND XOR OP_C) */
	for (i = 0; i < 16; i++)
		tmp1[i] = _rand[i] ^ opc[i];
	if (aes_128_encrypt_block(k, tmp1, tmp1))
		return -1;

	/* tmp2 = IN1 = SQN || AMF || SQN || AMF */
	os_memcpy(tmp2, sqn, 6);
	os_memcpy(tmp2 + 6, amf, 2);
	os_memcpy(tmp2 + 8, tmp2, 8);

	/* OUT1 = E_K(TEMP XOR rot(IN1 XOR OP_C, r1) XOR c1) XOR OP_C */

	/* rotate (tmp2 XOR OP_C) by r1 (= 0x40 = 8 bytes) */
	for (i = 0; i < 16; i++)
		tmp3[(i + 8) % 16] = tmp2[i] ^ opc[i];
	/* XOR with TEMP = E_K(RAND XOR OP_C) */
	for (i = 0; i < 16; i++)
		tmp3[i] ^= tmp1[i];
	/* XOR with c1 (= ..00, i.e., NOP) */

	/* f1 || f1* = E_K(tmp3) XOR OP_c */
	if (aes_128_encrypt_block(k, tmp3, tmp1))
		return -1;
	for (i = 0; i < 16; i++)
		tmp1[i] ^= opc[i];
	if (mac_a)
		os_memcpy(mac_a, tmp1, 8); /* f1 */
	if (mac_s)
		os_memcpy(mac_s, tmp1 + 8, 8); /* f1* */
	return 0;
}


/**
 * milenage_f2345 - Milenage f2, f3, f4, f5, f5* algorithms
 * @opc: OPc = 128-bit value derived from OP and K
 * @k: K = 128-bit subscriber key
 * @_rand: RAND = 128-bit random challenge
 * @res: Buffer for RES = 64-bit signed response (f2), or %NULL
 * @ck: Buffer for CK = 128-bit confidentiality key (f3), or %NULL
 * @ik: Buffer for IK = 128-bit integrity key (f4), or %NULL
 * @ak: Buffer for AK = 48-bit anonymity key (f5), or %NULL
 * @akstar: Buffer for AK = 48-bit anonymity key (f5*), or %NULL
 * Returns: 0 on success, -1 on failure
 */
int milenage_f2345(const u8 *opc, const u8 *k, const u8 *_rand,
		   u8 *res, u8 *ck, u8 *ik, u8 *ak, u8 *akstar)
{
	u8 tmp1[16], tmp2[16], tmp3[16];
	int i;

	/* tmp2 = TEMP = E_K(RAND XOR OP_C) */
	for (i = 0; i < 16; i++)
		tmp1[i] = _rand[i] ^ opc[i];
	if (aes_128_encrypt_block(k, tmp1, tmp2))
		return -1;

	/* OUT2 = E_K(rot(TEMP XOR OP_C, r2) XOR c2) XOR OP_C */
	/* OUT3 = E_K(rot(TEMP XOR OP_C, r3) XOR c3) XOR OP_C */
	/* OUT4 = E_K(rot(TEMP XOR OP_C, r4) XOR c4) XOR OP_C */
	/* OUT5 = E_K(rot(TEMP XOR OP_C, r5) XOR c5) XOR OP_C */

	/* f2 and f5 */
	/* rotate by r2 (= 0, i.e., NOP) */
	for (i = 0; i < 16; i++)
		tmp1[i] = tmp2[i] ^ opc[i];
	tmp1[15] ^= 1; /* XOR c2 (= ..01) */
	/* f5 || f2 = E_K(tmp1) XOR OP_c */
	if (aes_128_encrypt_block(k, tmp1, tmp3))
		return -1;
	for (i = 0; i < 16; i++)
		tmp3[i] ^= opc[i];
	if (res)
		os_memcpy(res, tmp3 + 8, 8); /* f2 */
	if (ak)
		os_memcpy(ak, tmp3, 6); /* f5 */

	/* f3 */
	if (ck) {
		/* rotate by r3 = 0x20 = 4 bytes */
		for (i = 0; i < 16; i++)
			tmp1[(i + 12) % 16] = tmp2[i] ^ opc[i];
		tmp1[15] ^= 2; /* XOR c3 (= ..02) */
		if (aes_128_encrypt_block(k, tmp1, ck))
			return -1;
		for (i = 0; i < 16; i++)
			ck[i] ^= opc[i];
	}

	/* f4 */
	if (ik) {
		/* rotate by r4 = 0x40 = 8 bytes */
		for (i = 0; i < 16; i++)
			tmp1[(i + 8) % 16] = tmp2[i] ^ opc[i];
		tmp1[15] ^= 4; /* XOR c4 (= ..04) */
		if (aes_128_encrypt_block(k, tmp1, ik))
			return -1;
		for (i = 0; i < 16; i++)
			ik[i] ^= opc[i];
	}

	/* f5* */
	if (akstar) {
		/* rotate by r5 = 0x60 = 12 bytes */
		for (i = 0; i < 16; i++)
			tmp1[(i + 4) % 16] = tmp2[i] ^ opc[i];
		tmp1[15] ^= 8; /* XOR c5 (= ..08) */
		if (aes_128_encrypt_block(k, tmp1, tmp1))
			return -1;
		for (i = 0; i < 6; i++)
			akstar[i] = tmp1[i] ^ opc[i];
	}

	return 0;
}


/**
 * milenage_generate - Generate AKA AUTN,IK,CK,RES
 * @opc: OPc = 128-bit operator variant algorithm configuration field (encr.)
 * @amf: AMF = 16-bit authentication management field
 * @k: K = 128-bit subscriber key
 * @sqn: SQN = 48-bit sequence number
 * @_rand: RAND = 128-bit random challenge
 * @autn: Buffer for AUTN = 128-bit authentication token
 * @ik: Buffer for IK = 128-bit integrity key (f4), or %NULL
 * @ck: Buffer for CK = 128-bit confidentiality key (f3), or %NULL
 * @res: Buffer for RES = 64-bit signed response (f2), or %NULL
 * @res_len: Max length for res; set to used length or 0 on failure
 */
void milenage_generate(const u8 *opc, const u8 *amf, const u8 *k,
		       const u8 *sqn, const u8 *_rand, u8 *autn, u8 *ik,
		       u8 *ck, u8 *res, size_t *res_len)
{
	int i;
	u8 mac_a[8], ak[6];

	if (*res_len < 8) {
		*res_len = 0;
		return;
	}
	if (milenage_f1(opc, k, _rand, sqn, amf, mac_a, NULL) ||
	    milenage_f2345(opc, k, _rand, res, ck, ik, ak, NULL)) {
		*res_len = 0;
		return;
	}
	*res_len = 8;

	/* AUTN = (SQN ^ AK) || AMF || MAC */
	for (i = 0; i < 6; i++)
		autn[i] = sqn[i] ^ ak[i];
	os_memcpy(autn + 6, amf, 2);
	os_memcpy(autn + 8, mac_a, 8);
}


/**
 * milenage_auts - Milenage AUTS validation
 * @opc: OPc = 128-bit operator variant algorithm configuration field (encr.)
 * @k: K = 128-bit subscriber key
 * @_rand: RAND = 128-bit random challenge
 * @auts: AUTS = 112-bit authentication token from client
 * @sqn: Buffer for SQN = 48-bit sequence number
 * Returns: 0 = success (sqn filled), -1 on failure
 */
int milenage_auts(const u8 *opc, const u8 *k, const u8 *_rand, const u8 *auts,
		  u8 *sqn)
{
	u8 amf[2] = { 0x00, 0x00 }; /* TS 33.102 v7.0.0, 6.3.3 */
	u8 ak[6], mac_s[8];
	int i;

	if (milenage_f2345(opc, k, _rand, NULL, NULL, NULL, NULL, ak))
		return -1;
	for (i = 0; i < 6; i++)
		sqn[i] = auts[i] ^ ak[i];
	if (milenage_f1(opc, k, _rand, sqn, amf, NULL, mac_s) ||
	    memcmp(mac_s, auts + 6, 8) != 0)
		return -1;
	return 0;
}


/**
 * gsm_milenage - Generate GSM-Milenage (3GPP TS 55.205) authentication triplet
 * @opc: OPc = 128-bit operator variant algorithm configuration field (encr.)
 * @k: K = 128-bit subscriber key
 * @_rand: RAND = 128-bit random challenge
 * @sres: Buffer for SRES = 32-bit SRES
 * @kc: Buffer for Kc = 64-bit Kc
 * Returns: 0 on success, -1 on failure
 */
int gsm_milenage(const u8 *opc, const u8 *k, const u8 *_rand, u8 *sres, u8 *kc)
{
	u8 res[8], ck[16], ik[16];

	if (milenage_f2345(opc, k, _rand, res, ck, ik, NULL, NULL))
		return -1;

	osmo_auth_c3(kc, ck, ik);
	osmo_auth_c2(sres, res, sizeof(res), 1);

	return 0;
}


/**
 * milenage_generate - Generate AKA AUTN,IK,CK,RES
 * @opc: OPc = 128-bit operator variant algorithm configuration field (encr.)
 * @k: K = 128-bit subscriber key
 * @sqn: SQN = 48-bit sequence number
 * @_rand: RAND = 128-bit random challenge
 * @autn: AUTN = 128-bit authentication token
 * @ik: Buffer for IK = 128-bit integrity key (f4), or %NULL
 * @ck: Buffer for CK = 128-bit confidentiality key (f3), or %NULL
 * @res: Buffer for RES = 64-bit signed response (f2), or %NULL
 * @res_len: Variable that will be set to RES length
 * @auts: 112-bit buffer for AUTS
 * Returns: 0 on success, -1 on failure, or -2 on synchronization failure
 */
int milenage_check(const u8 *opc, const u8 *k, const u8 *sqn, const u8 *_rand,
		   const u8 *autn, u8 *ik, u8 *ck, u8 *res, size_t *res_len,
		   u8 *auts)
{
	int i;
	u8 mac_a[8], ak[6], rx_sqn[6];
	const u8 *amf;

	wpa_hexdump(MSG_DEBUG, "Milenage: AUTN", autn, 16);
	wpa_hexdump(MSG_DEBUG, "Milenage: RAND", _rand, 16);

	if (milenage_f2345(opc, k, _rand, res, ck, ik, ak, NULL))
		return -1;

	*res_len = 8;
	wpa_hexdump_key(MSG_DEBUG, "Milenage: RES", res, *res_len);
	wpa_hexdump_key(MSG_DEBUG, "Milenage: CK", ck, 16);
	wpa_hexdump_key(MSG_DEBUG, "Milenage: IK", ik, 16);
	wpa_hexdump_key(MSG_DEBUG, "Milenage: AK", ak, 6);

	/* AUTN = (SQN ^ AK) || AMF || MAC */
	for (i = 0; i < 6; i++)
		rx_sqn[i] = autn[i] ^ ak[i];
	wpa_hexdump(MSG_DEBUG, "Milenage: SQN", rx_sqn, 6);

	if (os_memcmp(rx_sqn, sqn, 6) <= 0) {
		u8 auts_amf[2] = { 0x00, 0x00 }; /* TS 33.102 v7.0.0, 6.3.3 */
		if (milenage_f2345(opc, k, _rand, NULL, NULL, NULL, NULL, ak))
			return -1;
		wpa_hexdump_key(MSG_DEBUG, "Milenage: AK*", ak, 6);
		for (i = 0; i < 6; i++)
			auts[i] = sqn[i] ^ ak[i];
		if (milenage_f1(opc, k, _rand, sqn, auts_amf, NULL, auts + 6))
			return -1;
		wpa_hexdump(MSG_DEBUG, "Milenage: AUTS", auts, 14);
		return -2;
	}

	amf = autn + 6;
	wpa_hexdump(MSG_DEBUG, "Milenage: AMF", amf, 2);
	if (milenage_f1(opc, k, _rand, rx_sqn, amf, mac_a, NULL))
		return -1;

	wpa_hexdump(MSG_DEBUG, "Milenage: MAC_A", mac_a, 8);

	if (os_memcmp(mac_a, autn + 8, 8) != 0) {
		wpa_printf(MSG_DEBUG, "Milenage: MAC mismatch");
		wpa_hexdump(MSG_DEBUG, "Milenage: Received MAC_A",
			    autn + 8, 8);
		return -1;
	}

	return 0;
}

int milenage_opc_gen(u8 *opc, const u8 *k, const u8 *op)
{
	int i;

	/* Encrypt OP using K */
	if (aes_128_encrypt_block(k, op, opc))
		return -1;

	/* XOR the resulting Ek(OP) with OP */
	for (i = 0; i < 16; i++)
		opc[i] = opc[i] ^ op[i];

	return 0;
}