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aka: EAP-AKA protocol implementation

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This commit is contained in:
James Prestwood 2017-08-21 14:09:06 -07:00 committed by Denis Kenzior
parent 7c61d0365e
commit 6aaa917dde
5 changed files with 719 additions and 1 deletions
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2
Makefile.am
View File

@ -86,7 +86,7 @@ src_iwd_SOURCES = src/main.c linux/nl80211.h \
src/rfkill.h src/rfkill.c \
src/watchlist.h src/watchlist.c \
src/ftutil.h src/ftutil.c \
src/iwd.h src/eap-sim.c \
src/iwd.h src/eap-sim.c src/eap-aka.c \
src/simutil.h src/simutil.c
src_iwd_LDADD = ell/libell-internal.la -ldl

561
src/eap-aka.c Normal file
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@ -0,0 +1,561 @@
/*
*
* Wireless daemon for Linux
*
* Copyright (C) 2017 Intel Corporation. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <ctype.h>
#include <stdio.h>
#include <errno.h>
#include <ell/ell.h>
#include "crypto.h"
#include "simutil.h"
/*
* EAP-AKA specific values
*/
#define EAP_AKA_KI_LEN 16
#define EAP_AKA_OPC_LEN 16
#define EAP_AKA_AMF_LEN 2
#define EAP_AKA_SQN_LEN 6
#define EAP_AKA_IK_LEN 16
#define EAP_AKA_CK_LEN 16
#define EAP_AKA_AUTN_LEN 16
#define EAP_AKA_RES_LEN 8
#define EAP_AKA_K_RE_LEN 32
#define EAP_AKA_ST_CHALLENGE 0x01
#define EAP_AKA_ST_AUTH_REJECT 0x02
#define EAP_AKA_ST_SYNC_FAILURE 0x04
#define EAP_AKA_ST_IDENTITY 0x05
#define EAP_AKA_ST_NOTIFICATION 0x0c
#define EAP_AKA_ST_CLIENT_ERROR 0x0e
/*
* Internal client state, tracked to ensure that we are receiving the right
* messages at the right time.
*/
enum eap_aka_state {
EAP_AKA_STATE_UNCONNECTED = 0,
EAP_AKA_STATE_IDENTITY,
EAP_AKA_STATE_CHALLENGE,
EAP_AKA_STATE_SUCCESS,
EAP_AKA_STATE_ERROR
};
struct eap_aka_handle {
enum eap_aka_state state;
/* Identity from SIM */
char *identity;
/* Derived master key */
uint8_t mk[EAP_SIM_MK_LEN];
/* Derived K_encr key from PRNG */
uint8_t k_encr[EAP_SIM_K_ENCR_LEN];
/* Derived K_aut key from PRNG */
uint8_t k_aut[EAP_SIM_K_AUT_LEN];
/* Derived MSK from PRNG */
uint8_t msk[EAP_SIM_MSK_LEN];
/* Derived EMSK from PRNG */
uint8_t emsk[EAP_SIM_EMSK_LEN];
/* Flag set if AT_ANY_ID_REQ was present */
bool any_id_req : 1;
/* Flag to indicate protected status indications */
bool protected : 1;
/* Subscriber key */
uint8_t ki[EAP_AKA_KI_LEN];
/* Key derived from OP and ki */
uint8_t opc[EAP_AKA_OPC_LEN];
/* Authentication management field */
uint8_t amf[EAP_AKA_AMF_LEN];
/* Sequence number */
uint8_t sqn[EAP_AKA_SQN_LEN];
/* Integrity key */
uint8_t ik[EAP_AKA_IK_LEN];
/* Signed response */
uint8_t res[EAP_AKA_RES_LEN];
/* Confidentiality key */
uint8_t ck[EAP_AKA_CK_LEN];
/* Authentication value from AuC */
uint8_t autn[EAP_AKA_AUTN_LEN];
};
static int eap_aka_probe(struct eap_state *eap, const char *name)
{
struct eap_aka_handle *aka;
if (strcasecmp(name, "AKA"))
return -ENOTSUP;
aka = l_new(struct eap_aka_handle, 1);
eap_set_data(eap, aka);
return 0;
}
static void eap_aka_remove(struct eap_state *eap)
{
struct eap_aka_handle *aka = eap_get_data(eap);
l_free(aka->identity);
l_free(aka);
eap_set_data(eap, NULL);
}
static bool derive_aka_mk(const char *identity, uint8_t *ik, uint8_t *ck,
uint8_t *mk)
{
int ret;
struct iovec iov[5];
struct l_checksum *checksum = l_checksum_new(L_CHECKSUM_SHA1);
if (!checksum) {
l_error("could not create SHA1 checksum");
return false;
}
iov[0].iov_base = (void *)identity;
iov[0].iov_len = strlen(identity);
iov[1].iov_base = (void *)ik;
iov[1].iov_len = EAP_AKA_IK_LEN;
iov[2].iov_base = (void *)ck;
iov[2].iov_len = EAP_AKA_CK_LEN;
if (!l_checksum_updatev(checksum, iov, 3))
goto mk_error;
ret = l_checksum_get_digest(checksum, mk, EAP_SIM_MK_LEN);
l_checksum_free(checksum);
return (ret == EAP_SIM_MK_LEN);
mk_error:
l_checksum_free(checksum);
l_error("error deriving master key");
return false;
}
/*
* Handles EAP-AKA Challenge subtype
*/
static void handle_challenge(struct eap_state *eap, const uint8_t *pkt,
size_t len)
{
struct eap_aka_handle *aka = eap_get_data(eap);
struct eap_sim_tlv_iter iter;
uint8_t prng_buf[160];
size_t resp_len = 40;
uint8_t response[resp_len + 4];
uint8_t *pos = response;
const uint8_t *rand = NULL;
const uint8_t *autn = NULL;
if (len < 3) {
l_error("packet is too small");
goto chal_error;
}
if (aka->state != EAP_AKA_STATE_IDENTITY) {
l_error("invalid packet for EAP-AKA state");
goto chal_error;
}
eap_sim_tlv_iter_init(&iter, pkt + 3, len - 3);
while (eap_sim_tlv_iter_next(&iter)) {
const uint8_t *contents = eap_sim_tlv_iter_get_data(&iter);
uint16_t length = eap_sim_tlv_iter_get_length(&iter);
switch (eap_sim_tlv_iter_get_type(&iter)) {
case EAP_SIM_AT_AUTN:
if (length < EAP_AKA_AUTN_LEN + 2) {
l_error("malformed AT_AUTN");
goto chal_error;
}
autn = contents + 2;
break;
case EAP_SIM_AT_RAND:
if (length < EAP_SIM_RAND_LEN + 2) {
l_error("malformed AT_RAND");
goto chal_error;
}
rand = contents + 2;
break;
case EAP_SIM_AT_RESULT_IND:
if (length < 2) {
l_error("malformed AT_RESULT_IND");
goto chal_error;
}
aka->protected = 1;
resp_len += 4;
break;
case EAP_SIM_AT_NEXT_PSEUDONYM:
case EAP_SIM_AT_NEXT_REAUTH_ID:
case EAP_SIM_AT_IV:
case EAP_SIM_AT_ENCR_DATA:
case EAP_SIM_AT_PADDING:
case EAP_SIM_AT_CHECKCODE:
case EAP_SIM_AT_MAC:
/*
* AT_BIDDING is defined in RFC 5448 (AKA'). It is used to
* communicate support for AKA', if supported.
*/
case EAP_SIM_AT_BIDDING:
/* RFC 4187, Section 10.1 */
break;
default:
l_error("attribute %u was found in Challenge",
eap_sim_tlv_iter_get_type(&iter));
goto chal_error;
}
}
eap_aka_get_milenage(aka->opc, aka->ki, rand, aka->sqn, aka->amf,
aka->autn, aka->ck, aka->ik, aka->res);
if (memcmp(autn, aka->autn, EAP_AKA_AUTN_LEN)) {
l_error("EAP_SIM_AT_AUTN is not valid");
goto chal_error;
}
if (!derive_aka_mk(aka->identity, aka->ik, aka->ck, aka->mk)) {
l_error("error deriving MK");
goto chal_fatal;
}
eap_sim_fips_prf(aka->mk, 20, prng_buf, 160);
if (!eap_sim_get_encryption_keys(prng_buf, aka->k_encr, aka->k_aut,
aka->msk, aka->emsk)) {
l_error("could not derive encryption keys");
goto chal_fatal;
}
if (!eap_sim_verify_mac(eap, EAP_TYPE_AKA, pkt, len, aka->k_aut, NULL,
0)) {
l_error("MAC was not valid");
goto chal_error;
}
aka->state = EAP_AKA_STATE_CHALLENGE;
pos += eap_sim_build_header(eap, EAP_TYPE_AKA, EAP_AKA_ST_CHALLENGE,
pos, resp_len);
pos += eap_sim_add_attribute(pos, EAP_SIM_AT_RES,
EAP_SIM_PAD_LENGTH_BITS, aka->res, EAP_AKA_RES_LEN);
if (aka->protected)
pos += eap_sim_add_attribute(pos, EAP_SIM_AT_RESULT_IND,
EAP_SIM_PAD_NONE, NULL, 2);
pos += eap_sim_add_attribute(pos, EAP_SIM_AT_MAC, EAP_SIM_PAD_NONE,
NULL, EAP_SIM_MAC_LEN);
if (!eap_sim_derive_mac(response, resp_len, aka->k_aut,
pos - EAP_SIM_MAC_LEN)) {
l_error("error deriving MAC");
goto chal_fatal;
}
eap_send_response(eap, EAP_TYPE_AKA, response, resp_len);
if (!aka->protected) {
eap_method_success(eap);
eap_set_key_material(eap, aka->msk, 32, NULL, 0, NULL, 0);
aka->state = EAP_AKA_STATE_SUCCESS;
}
return;
chal_fatal:
eap_method_error(eap);
aka->state = EAP_AKA_STATE_ERROR;
return;
chal_error:
eap_sim_client_error(eap, EAP_TYPE_AKA, EAP_SIM_ERROR_PROCESS);
}
/*
* Handles Notification subtype
*/
static void handle_notification(struct eap_state *eap, const uint8_t *pkt,
size_t len)
{
struct eap_aka_handle *aka = eap_get_data(eap);
struct eap_sim_tlv_iter iter;
int32_t value = -1;
if (len < 3) {
l_error("packet is too small");
goto notif_error;
}
eap_sim_tlv_iter_init(&iter, pkt + 3, len - 3);
while (eap_sim_tlv_iter_next(&iter)) {
const uint8_t *contents = eap_sim_tlv_iter_get_data(&iter);
uint16_t length = eap_sim_tlv_iter_get_length(&iter);
switch (eap_sim_tlv_iter_get_type(&iter)) {
case EAP_SIM_AT_NOTIFICATION:
if (length < 2) {
l_error("malformed AT_NOTIFICATION");
goto notif_error;
}
value = l_get_be16(contents);
break;
case EAP_SIM_AT_IV:
case EAP_SIM_AT_ENCR_DATA:
case EAP_SIM_AT_PADDING:
case EAP_SIM_AT_MAC:
/* RFC 4186, Section 10.1 */
break;
default:
l_error("attribute type %u not allowed in Notification",
eap_sim_tlv_iter_get_type(&iter));
goto notif_error;
}
}
if (value == EAP_SIM_SUCCESS && aka->protected &&
aka->state == EAP_AKA_STATE_CHALLENGE) {
/* header + MAC + MAC header */
uint8_t response[8 + EAP_SIM_MAC_LEN + 4];
uint8_t *pos = response;
/*
* Server sent successful result indication
*/
eap_method_success(eap);
eap_set_key_material(eap, aka->msk, 32, NULL, 0, NULL, 0);
/*
* Build response packet
*/
pos += eap_sim_build_header(eap, EAP_TYPE_AKA,
EAP_AKA_ST_NOTIFICATION, pos, 20);
pos += eap_sim_add_attribute(pos, EAP_SIM_AT_MAC,
EAP_SIM_PAD_NONE, NULL, EAP_SIM_MAC_LEN);
if (!eap_sim_derive_mac(response, pos - response, aka->k_aut,
response + 12)) {
l_error("could not derive MAC");
eap_method_error(eap);
aka->state = EAP_AKA_STATE_ERROR;
return;
}
eap_send_response(eap, EAP_TYPE_AKA, response, pos - response);
aka->state = EAP_AKA_STATE_SUCCESS;
return;
} else if (value == EAP_SIM_SUCCESS) {
/*
* Unexpected success notification, what should
* be done here?
*/
l_error("Unexpected success notification");
} else {
/*
* All other values are error conditions.
* Nothing unique can be done for any error so
* print the code and signal EAP failure.
*/
l_error("Error authenticating: code=%u", value);
}
notif_error:
eap_sim_client_error(eap, EAP_TYPE_AKA, EAP_SIM_ERROR_PROCESS);
}
static void handle_identity(struct eap_state *eap, const uint8_t *pkt,
size_t len)
{
struct eap_aka_handle *aka = eap_get_data(eap);
uint8_t response[8 + strlen(aka->identity) + 4];
uint8_t *pos = response;
if (aka->state != EAP_AKA_STATE_UNCONNECTED) {
l_error("invalid packet for EAP-AKA state");
eap_sim_client_error(eap, EAP_TYPE_AKA, EAP_SIM_ERROR_PROCESS);
return;
}
aka->state = EAP_AKA_STATE_IDENTITY;
/*
* Build response packet
*/
pos += eap_sim_build_header(eap, EAP_TYPE_AKA, EAP_AKA_ST_IDENTITY, pos,
20);
pos += eap_sim_add_attribute(pos, EAP_SIM_AT_IDENTITY,
EAP_SIM_PAD_LENGTH, (uint8_t *)aka->identity,
strlen(aka->identity));
eap_send_response(eap, EAP_TYPE_AKA, response, pos - response);
}
static void eap_aka_handle_request(struct eap_state *eap,
const uint8_t *pkt, size_t len)
{
if (len < 1) {
l_error("packet is too small");
goto req_error;
}
switch (pkt[0]) {
case EAP_AKA_ST_IDENTITY:
handle_identity(eap, pkt, len);
break;
case EAP_AKA_ST_CHALLENGE:
handle_challenge(eap, pkt, len);
break;
case EAP_AKA_ST_NOTIFICATION:
handle_notification(eap, pkt, len);
break;
default:
l_error("unknown EAP-SIM subtype: %u", pkt[0]);
goto req_error;
}
return;
req_error:
eap_sim_client_error(eap, EAP_TYPE_AKA, EAP_SIM_ERROR_PROCESS);
}
static bool eap_aka_load_settings(struct eap_state *eap,
struct l_settings *settings,
const char *prefix)
{
struct eap_aka_handle *aka = eap_get_data(eap);
char setting[64];
const char *imsi;
const char *ki;
const char *opc;
const char *amf;
const char *sqn;
size_t len;
snprintf(setting, sizeof(setting), "%sAKA-IMSI", prefix);
imsi = l_settings_get_value(settings, "Security", setting);
if (imsi)
aka->identity = l_strdup(imsi);
snprintf(setting, sizeof(setting), "%sAKA-KI", prefix);
ki = l_settings_get_value(settings, "Security", setting);
if (ki) {
uint8_t *val = l_util_from_hexstring(ki, &len);
memcpy(aka->ki, val, len);
l_free(val);
}
snprintf(setting, sizeof(setting), "%sAKA-OPC", prefix);
opc = l_settings_get_value(settings, "Security", setting);
if (opc) {
uint8_t *val = l_util_from_hexstring(opc, &len);
memcpy(aka->opc, val, len);
l_free(val);
}
snprintf(setting, sizeof(setting), "%sAKA-AMF", prefix);
amf = l_settings_get_value(settings, "Security", setting);
if (amf) {
uint8_t *val = l_util_from_hexstring(amf, &len);
memcpy(aka->amf, val, len);
l_free(val);
}
snprintf(setting, sizeof(setting), "%sAKA-SQN", prefix);
sqn = l_settings_get_value(settings, "Security", setting);
if (sqn) {
uint8_t *val = l_util_from_hexstring(sqn, &len);
memcpy(aka->sqn, val, len);
l_free(val);
}
return true;
}
static struct eap_method eap_aka = {
.request_type = EAP_TYPE_AKA,
.exports_msk = true,
.name = "AKA",
.probe = eap_aka_probe,
.remove = eap_aka_remove,
.handle_request = eap_aka_handle_request,
.load_settings = eap_aka_load_settings,
};
static int eap_aka_init(void)
{
l_debug("");
return eap_register_method(&eap_aka);
}
static void eap_aka_exit(void)
{
l_debug("");
eap_unregister_method(&eap_aka);
}
EAP_METHOD_BUILTIN(eap_aka, eap_aka_init, eap_aka_exit)

1
src/eap.h
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@ -73,6 +73,7 @@ enum eap_type {
EAP_TYPE_TLS_EAP = 13,
EAP_TYPE_SIM = 18,
EAP_TYPE_TTLS = 21,
EAP_TYPE_AKA = 23,
EAP_TYPE_MSCHAPV2 = 26,
EAP_TYPE_EXPANDED = 254,
};

127
src/simutil.c
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@ -143,6 +143,133 @@ static void G(uint32_t *out, uint8_t *block)
memcpy(out, H, sizeof(H));
}
/*
* Helper to XOR an array
* to - result of XOR array
* a - array 1
* b - array 2
* len - size of aray
*/
#define XOR(to, a, b, len) \
for (i = 0; i < len; i++) { \
to[i] = a[i] ^ b[i]; \
}
bool eap_aka_get_milenage(const uint8_t *opc, const uint8_t *k,
const uint8_t *rand, const uint8_t *sqn, const uint8_t *amf,
uint8_t *autn, uint8_t *ck, uint8_t *ik, uint8_t *res)
{
/* algorithm variables: TEMP, IN1, OUT1, OUT2, OUT5 (OUT3/4 == IK/CK) */
uint8_t temp[16];
uint8_t in1[16];
uint8_t out1[16], out2[16], out5[16];
/* other variables */
struct l_cipher *aes;
int i;
uint8_t tmp1[16];
uint8_t tmp2[16];
aes = l_cipher_new(L_CIPHER_AES, k, 16);
/* temp = TEMP = E[RAND ^ OPc]k */
XOR(tmp1, rand, opc, 16);
l_cipher_encrypt(aes, tmp1, temp, 16);
/* IN1[0-47] = SQN[0-47] */
memcpy(in1, sqn, 6);
/* IN1[48-63] = AMF[0-15] */
memcpy(in1 + 6, amf, 2);
/* IN1[64-111] = SQN[0-47] */
memcpy(in1 + 8, sqn, 6);
/* IN1[112-127] = AMF[0-15] */
memcpy(in1 + 14, amf, 2);
/*
* f1 and f1* output OUT1
*/
/*
* tmp1 = rot(IN1 ^ OPc)r1
* r1 = 64 bits = 8 bytes
*/
for (i = 0; i < 16; i++)
tmp1[(i + 8) % 16] = in1[i] ^ opc[i];
/* tmp2 = TEMP ^ tmp1 */
XOR(tmp2, temp, tmp1, 16);
/* tmp2 = E[tmp2]k */
l_cipher_encrypt(aes, tmp2, tmp1, 16);
/* out1 = OUT1 = tmp1 ^ opc */
XOR(out1, tmp1, opc, 16);
/*
* f2 outputs OUT2 (RES | AK)
*
* r2 = 0 == no rotation
*/
/* tmp1 = rot(TEMP ^ OPc)r2 */
XOR(tmp1, temp, opc, 16);
/* tmp1 ^ c2. c2 at bit 127 == 1 */
tmp1[15] ^= 1;
l_cipher_encrypt(aes, tmp1, out2, 16);
/* get RES from OUT2 */
XOR(out2, out2, opc, 16);
memcpy(res, out2 + 8, 8);
/* AUTN = (SQN ^ AK) | AMF | MAC_A */
XOR(autn, sqn, out2, 6);
memcpy(autn + 6, amf, 2);
memcpy(autn + 8, out1, 8);
/*
* f3 outputs CK (OUT3)
*
* tmp1 = rot(TEMP ^ OPc)r3
*
* r3 = 32 bits = 4 bytes
*/
for (i = 0; i < 16; i++)
tmp1[(i + 12) % 16] = temp[i] ^ opc[i];
/* tmp1 ^ c3. c3 at bit 126 == 1 */
tmp1[15] ^= 1 << 1;
l_cipher_encrypt(aes, tmp1, ck, 16);
/* ck ^ opc */
XOR(ck, ck, opc, 16);
/*
* f4 outputs IK (OUT4)
*
* tmp1 = rot(TEMP ^ OPc)r4
*
* r4 = 64 bits = 8 bytes
*/
for (i = 0; i < 16; i++)
tmp1[(i + 8) % 16] = temp[i] ^ opc[i];
/* tmp1 ^ c4. c4 at bit 125 == 1 */
tmp1[15] ^= 1 << 2;
l_cipher_encrypt(aes, tmp1, ik, 16);
/* ik ^ opc */
XOR(ik, ik, opc, 16);
/*
* f5* outputs AK' (OUT5)
*/
for (i = 0; i < 16; i++)
tmp1[(i + 4) % 16] = temp[i] ^ opc[i];
/* tmp1 ^ c5. c5 at bit 124 == 1 */
tmp1[15] ^= 1 << 3;
l_cipher_encrypt(aes, tmp1, out5, 16);
/* out5 ^ opc */
XOR(out5, out5, opc, 16);
l_cipher_free(aes);
return true;
}
void eap_sim_fips_prf(const void *seed, size_t slen, uint8_t *out, size_t olen)
{
uint8_t xkey[64];

29
src/simutil.h
View File

@ -122,6 +122,35 @@ enum eap_sim_fail {
*/
void eap_sim_fips_prf(const void *seed, size_t slen, uint8_t *out, size_t olen);
/*
* 3GPP TS 35.206
*
* Algorithm for generating milenage parameters.
*
* opc - Input: OPc value
* k - Input: K key value
* rand - Input: Rand from server
* sqn - Input: Sequence number
* amf - Input: AMF value
*
* autn - Output: AUTN computed
* ck - Output: CK computed
* ik - Output: IK computed
* res - Output: RES computed
*
* Internal Functions used:
* f1 and f1* output MAC-A and MAC-S. MAC-A along with SQN/AK/AMF make AUTN
* f2 outputs RES where RES == OUT2[8-16]
* f3 outputs CK where CK == OUT3[0-16]
* f4 outputs IK where IK == OUT4[0-16]
* f5 outputs AK where AK == OUT2[0-6]
*
* f5* outputs AK', not used with EAP-AKA
*/
bool eap_aka_get_milenage(const uint8_t *opc, const uint8_t *k,
const uint8_t *rand, const uint8_t *sqn, const uint8_t *amf,
uint8_t *autn, uint8_t *ck, uint8_t *ik, uint8_t *res);
/*
* Separate PRNG data into encryption keys. k_encr and k_aut may be NULL in the
* case of fast re-authentication.