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/*! \file oap.c
* Osmocom Authentication Protocol message encoder/decoder */
/*
* (C) 2015-2016 by sysmocom s.f.m.c. GmbH
* All Rights Reserved
*
* Author: Neels Hofmeyr
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <osmocom/core/utils.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/msgb.h>
#include <osmocom/gsm/tlv.h>
#include <osmocom/gsm/oap.h>
#include <stdint.h>
/*! \addtogroup oap
* @{
* Osmocom Authentication Protocol
*/
/*! Decode OAP message data.
* \param[out] oap_msg Parsed data is written to this instance.
* \param[in] data Pointer to the data buffer containing the OAP message.
* \param[in] data_len Length of the OAP message data.
* \returns 0 on success, a negative cause value on failure.
*/
int osmo_oap_decode(struct osmo_oap_message *oap_msg,
const uint8_t *const_data, size_t data_len)
{
int rc;
uint8_t tag;
/* the shift/match functions expect non-const pointers, but we'll
* either copy the data or cast pointers back to const before returning
* them
*/
uint8_t *data = (uint8_t *)const_data;
uint8_t *value;
size_t value_len;
memset(oap_msg, 0, sizeof(*oap_msg));
/* message type */
rc = osmo_shift_v_fixed(&data, &data_len, 1, &value);
if (rc < 0)
return -GMM_CAUSE_INV_MAND_INFO;
oap_msg->message_type = osmo_decode_big_endian(value, 1);
/* specific parts */
while (data_len > 0) {
enum osmo_oap_iei iei;
rc = osmo_shift_tlv(&data, &data_len, &tag, &value, &value_len);
if (rc < 0)
return -GMM_CAUSE_PROTO_ERR_UNSPEC;
iei = tag;
switch (iei) {
case OAP_CLIENT_ID_IE:
if (value_len != 2) {
LOGP(DLOAP, LOGL_NOTICE,
"OAP IE type client ID (%d) should be 2 octets, but has %d\n",
(int)iei, (int)value_len);
return -GMM_CAUSE_PROTO_ERR_UNSPEC;
}
oap_msg->client_id = osmo_decode_big_endian(value, value_len);
if (oap_msg->client_id == 0) {
LOGP(DLOAP, LOGL_NOTICE,
"OAP IE type client ID (%d): client ID must be nonzero.\n",
(int)iei);
return -GMM_CAUSE_PROTO_ERR_UNSPEC;
}
break;
case OAP_AUTN_IE:
if (value_len != sizeof(oap_msg->autn)) {
LOGP(DLOAP, LOGL_NOTICE,
"OAP IE type AUTN (%d) should be %d octets, but has %d\n",
(int)iei, (int)sizeof(oap_msg->autn), (int)value_len);
return -GMM_CAUSE_PROTO_ERR_UNSPEC;
}
memcpy(oap_msg->autn, value, value_len);
oap_msg->autn_present = value_len ? 1 : 0;
break;
case OAP_RAND_IE:
if (value_len != sizeof(oap_msg->rand)) {
LOGP(DLOAP, LOGL_NOTICE,
"OAP IE type RAND (%d) should be %d octets, but has %d\n",
(int)iei, (int)sizeof(oap_msg->rand), (int)value_len);
return -GMM_CAUSE_PROTO_ERR_UNSPEC;
}
memcpy(oap_msg->rand, value, value_len);
oap_msg->rand_present = value_len ? 1 : 0;
break;
case OAP_XRES_IE:
if (value_len != sizeof(oap_msg->xres)) {
LOGP(DLOAP, LOGL_NOTICE,
"OAP IE type XRES (%d) should be %d octets, but has %d\n",
(int)iei, (int)sizeof(oap_msg->xres), (int)value_len);
return -GMM_CAUSE_PROTO_ERR_UNSPEC;
}
memcpy(oap_msg->xres, value, value_len);
oap_msg->xres_present = value_len ? 1 : 0;
break;
case OAP_AUTS_IE:
if (value_len != sizeof(oap_msg->auts)) {
LOGP(DLOAP, LOGL_NOTICE,
"OAP IE type AUTS (%d) should be %d octets, but has %d\n",
(int)iei, (int)sizeof(oap_msg->auts), (int)value_len);
return -GMM_CAUSE_PROTO_ERR_UNSPEC;
}
memcpy(oap_msg->auts, value, value_len);
oap_msg->auts_present = value_len ? 1 : 0;
break;
case OAP_CAUSE_IE:
if (value_len > 1) {
LOGP(DLOAP, LOGL_ERROR,
"OAP cause may not exceed one octet, is %d", (int)value_len);
return -GMM_CAUSE_PROTO_ERR_UNSPEC;
}
oap_msg->cause = *value;
break;
default:
LOGP(DLOAP, LOGL_NOTICE,
"OAP IE type %d unknown\n", iei);
continue;
}
}
return 0;
}
/*! Compose OAP message data.
* \param[out] msg OAP message data is appended to this message buffer.
* \param[in] oap_msg Elements to encode in the message data.
*/
void osmo_oap_encode(struct msgb *msg, const struct osmo_oap_message *oap_msg)
{
uint8_t u8;
/* generic part */
OSMO_ASSERT(oap_msg->message_type);
msgb_v_put(msg, (uint8_t)oap_msg->message_type);
/* specific parts */
if ((u8 = oap_msg->cause))
msgb_tlv_put(msg, OAP_CAUSE_IE, sizeof(u8), &u8);
if (oap_msg->client_id > 0)
msgb_tlv_put(msg, OAP_CLIENT_ID_IE, sizeof(oap_msg->client_id),
osmo_encode_big_endian(oap_msg->client_id,
sizeof(oap_msg->client_id)));
if (oap_msg->rand_present)
msgb_tlv_put(msg, OAP_RAND_IE, sizeof(oap_msg->rand), oap_msg->rand);
if (oap_msg->autn_present)
msgb_tlv_put(msg, OAP_AUTN_IE, sizeof(oap_msg->autn), oap_msg->autn);
if (oap_msg->auts_present)
msgb_tlv_put(msg, OAP_AUTS_IE, sizeof(oap_msg->auts), oap_msg->auts);
if (oap_msg->xres_present)
msgb_tlv_put(msg, OAP_XRES_IE, sizeof(oap_msg->xres), oap_msg->xres);
msg->l2h = msg->data;
}
/*! @} */
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