/*******************************************************************************
    OpenAirInterface
    Copyright(c) 1999 - 2014 Eurecom

    OpenAirInterface 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 3 of the License, or
    (at your option) any later version.


    OpenAirInterface is distributed in the hope that it will be useful,
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    You should have received a copy of the GNU General Public License
    along with OpenAirInterface.The full GNU General Public License is
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   see <http://www.gnu.org/licenses/>.

  Contact Information
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  OpenAirInterface Tech : openair_tech@eurecom.fr
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  Address      : Eurecom, Compus SophiaTech 450, route des chappes, 06451 Biot, France.

 *******************************************************************************/
/*****************************************************************************
Source      SecurityModeControl.c

Version     0.1

Date        2013/04/22

Product     NAS stack

Subsystem   Template body file

Author      Frederic Maurel

Description Defines the security mode control EMM procedure executed by the
        Non-Access Stratum.

        The purpose of the NAS security mode control procedure is to
        take an EPS security context into use, and initialise and start
        NAS signalling security between the UE and the MME with the
        corresponding EPS NAS keys and EPS security algorithms.

        Furthermore, the network may also initiate a SECURITY MODE COM-
        MAND in order to change the NAS security algorithms for a cur-
        rent EPS security context already in use.

*****************************************************************************/

#include <stdlib.h> // malloc, free
#include <string.h> // memcpy
#include <inttypes.h>

#include "emm_proc.h"
#include "nas_log.h"
#include "nas_timer.h"

#include "emmData.h"

#include "emm_sap.h"
#include "emm_cause.h"

#include "UeSecurityCapability.h"

#if defined(ENABLE_ITTI)
# include "assertions.h"
#endif
#include "secu_defs.h"

/****************************************************************************/
/****************  E X T E R N A L    D E F I N I T I O N S  ****************/
/****************************************************************************/

/****************************************************************************/
/*******************  L O C A L    D E F I N I T I O N S  *******************/
/****************************************************************************/

/*
 * --------------------------------------------------------------------------
 *  Internal data handled by the security mode control procedure in the UE
 * --------------------------------------------------------------------------
 */
#ifdef NAS_UE
static int _security_kdf(const OctetString *kasme, OctetString *key,
                         UInt8_t algo_dist, UInt8_t algo_id);

static int _security_knas_enc(const OctetString *kasme, OctetString *knas_enc,
                              UInt8_t eia);
static int _security_knas_int(const OctetString *kasme, OctetString *knas_int,
                              UInt8_t eea);
static int _security_kenb(const OctetString *kasme, OctetString *kenb,
                          UInt32_t count);

/*
 * Internal data used for security mode control procedure
 */
static struct {
    OctetString kenb;           /* eNodeB security key      */
} _security_data;

static void _security_release(emm_security_context_t *ctx);
#endif  // NAS_UE

/*
 * --------------------------------------------------------------------------
 *  Internal data handled by the security mode control procedure in the MME
 * --------------------------------------------------------------------------
 */
#ifdef NAS_MME
/*
 * Timer handlers
 */
static void *_security_t3460_handler(void *);

/*
 * Function executed whenever the ongoing EMM procedure that initiated
 * the security mode control procedure is aborted or the maximum value of the
 * retransmission timer counter is exceed
 */
static int _security_abort(void *);
static int _security_select_algorithms(
    const int   ue_eiaP,
    const int   ue_eeaP,
    int * const mme_eiaP,
    int * const mme_eeaP);
/*
 * Internal data used for security mode control procedure
 */
typedef struct {
    unsigned int ueid;      /* UE identifier                       */
#define SECURITY_COUNTER_MAX    5
    unsigned int retransmission_count;  /* Retransmission counter   */
    int ksi;                /* NAS key set identifier               */
    int eea;                /* Replayed EPS encryption algorithms   */
    int eia;                /* Replayed EPS integrity algorithms    */
    int selected_eea;       /* Selected EPS encryption algorithms   */
    int selected_eia;       /* Selected EPS integrity algorithms    */
    int notify_failure;     /* Indicates whether the security mode control
                             * procedure failure shall be notified to the
                             * ongoing EMM procedure        */
} security_data_t;

static int _security_request(security_data_t *data, int is_new);
#endif // NAS_MME

/****************************************************************************/
/******************  E X P O R T E D    F U N C T I O N S  ******************/
/****************************************************************************/

/*
 * --------------------------------------------------------------------------
 *      Security mode control procedure executed by the UE
 * --------------------------------------------------------------------------
 */
#ifdef NAS_UE
/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_security_mode_command()                              **
 **                                                                        **
 ** Description: Performs the MME requested security mode control proce-   **
 **      dure.                                                             **
 **                                                                        **
 **              3GPP TS 24.301, section 5.4.3.3                           **
 **      Upon receiving the SECURITY MODE COMMAND message, the UE          **
 **      shall check whether the message can be accepted or not.           **
 **      If accepted the UE shall send a SECURITY MODE COMPLETE            **
 **      message integrity protected with the selected NAS inte-           **
 **      grity algorithm and ciphered with the selected NAS ciphe-         **
 **      ring algorithm.                                                   **
 **                                                                        **
 ** Inputs:  native_ksi:    TRUE if the security context is of type        **
 **             native (for KSIASME)                                       **
 **      ksi:       The NAS ket sey identifier                             **
 **      seea:      Selected EPS cyphering algorithm                       **
 **      seia:      Selected EPS integrity algorithm                       **
 **      reea:      Replayed EPS cyphering algorithm                       **
 **      reia:      Replayed EPS integrity algorithm                       **
 **      Others:    None                                                   **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                                  **
 **      Others:    None                                                   **
 **                                                                        **
 ***************************************************************************/
int emm_proc_security_mode_command(int native_ksi, int ksi,
                                   int seea, int seia, int reea, int reia)
{
    LOG_FUNC_IN;

    int rc = RETURNerror;
    int emm_cause = EMM_CAUSE_SUCCESS;
    int security_context_is_new = FALSE;

    LOG_TRACE(INFO, "EMM-PROC  - Security mode control requested (ksi=%d)",
              ksi);

    /* Delete any previously stored RAND and RES and stop timer T3416 */
    (void) emm_proc_authentication_delete();

    /*
     * Check the replayed UE security capabilities
     */
    UInt8_t eea = (0x80 >> _emm_data.security->capability.encryption);
    UInt8_t eia = (0x80 >> _emm_data.security->capability.integrity);
    if ( (reea != eea) || (reia != eia) ) {
        LOG_TRACE(WARNING, "EMM-PROC  - Replayed UE security capabilities "
                  "rejected");
        emm_cause = EMM_CAUSE_UE_SECURITY_MISMATCH;

        /* XXX - For testing purpose UE always accepts EIA0
         * The UE shall accept "null integrity protection algorithm" EIA0 only
         * if a PDN connection for emergency bearer services is established or
         * the UE is establishing a PDN connection for emergency bearer services
         */
    }
    /*
     * Check the non-current EPS security context
     */
    else if (_emm_data.non_current == NULL) {
        LOG_TRACE(WARNING, "EMM-PROC  - Non-current EPS security context "
                  "is not valid");
        emm_cause = EMM_CAUSE_SECURITY_MODE_REJECTED;
    }
    /*
     * Update the non-current EPS security context
     */
    else {
        LOG_TRACE(INFO, "EMM-PROC  - Update the non-current EPS security context seea=%u seia=%u", seea, seia);
        /* Update selected cyphering and integrity algorithms */
        _emm_data.non_current->capability.encryption = seea;
        _emm_data.non_current->capability.integrity  = seia;

        /* Derive the NAS cyphering key */
        if (_emm_data.non_current->knas_enc.value == NULL) {
            _emm_data.non_current->knas_enc.value =
                (uint8_t *)calloc(1,AUTH_KNAS_ENC_SIZE);
            _emm_data.non_current->knas_enc.length = AUTH_KNAS_ENC_SIZE;
        }
        if (_emm_data.non_current->knas_enc.value != NULL) {
            LOG_TRACE(INFO, "EMM-PROC  - Update the non-current EPS security context knas_enc");
            rc = _security_knas_enc(&_emm_data.non_current->kasme,
                                    &_emm_data.non_current->knas_enc, seea);
        }
        /* Derive the NAS integrity key */
        if (_emm_data.non_current->knas_int.value == NULL) {
            _emm_data.non_current->knas_int.value =
                (uint8_t *)calloc(1,AUTH_KNAS_INT_SIZE);
            _emm_data.non_current->knas_int.length = AUTH_KNAS_INT_SIZE;
        }
        if (_emm_data.non_current->knas_int.value != NULL) {
            if (rc != RETURNerror) {
                LOG_TRACE(INFO, "EMM-PROC  - Update the non-current EPS security context knas_int");
                rc = _security_knas_int(&_emm_data.non_current->kasme,
                                        &_emm_data.non_current->knas_int, seia);
            }
        }
        /* Derive the eNodeB key */
        if (_security_data.kenb.value == NULL) {
            _security_data.kenb.value = (uint8_t *)calloc(1,AUTH_KENB_SIZE);
            _security_data.kenb.length = AUTH_KENB_SIZE;
        }
        if (_security_data.kenb.value != NULL) {
            if (rc != RETURNerror) {
                LOG_TRACE(INFO, "EMM-PROC  - Update the non-current EPS security context kenb");
                // LG COMMENT rc = _security_kenb(&_emm_data.security->kasme,
                rc = _security_kenb(&_emm_data.non_current->kasme,
                					&_security_data.kenb,
                                    *(UInt32_t *)(&_emm_data.non_current->ul_count));
            }
        }

        /*
         * NAS security mode command accepted by the UE
         */
        if (rc != RETURNerror) {
            LOG_TRACE(INFO, "EMM-PROC  - NAS security mode command accepted by the UE");
            /* Update the current EPS security context */
            if ( native_ksi && (_emm_data.security->type != EMM_KSI_NATIVE) ) {
                /* The type of security context flag included in the SECURITY
                 * MODE COMMAND message is set to "native security context" and
                 * the UE has a mapped EPS security context as the current EPS
                 * security context */
                if ( (_emm_data.non_current->type == EMM_KSI_NATIVE) &&
                        (_emm_data.non_current->eksi == ksi) ) {
                    /* The KSI matches the non-current native EPS security
                     * context; the UE shall take the non-current native EPS
                     * security context into use which then becomes the
                     * current native EPS security context and delete the
                     * mapped EPS security context */
                    LOG_TRACE(INFO,
                              "EMM-PROC  - Update Current security context");
                    /* Release non-current security context */
                    _security_release(_emm_data.security);
                    _emm_data.security = _emm_data.non_current;
                    /* Reset the uplink NAS COUNT counter */
                    _emm_data.security->ul_count.overflow = 0;
                    _emm_data.security->ul_count.seq_num = 0;
                    /* Set new security context indicator */
                    security_context_is_new = TRUE;
                }
            }

            if ( !native_ksi && (_emm_data.security->type != EMM_KSI_NATIVE) ) {
                /* The type of security context flag included in the SECURITY
                 * MODE COMMAND message is set to "mapped security context" and
                 * the UE has a mapped EPS security context as the current EPS
                 * security context */
                if (ksi != _emm_data.security->eksi) {
                    /* The KSI does not match the current EPS security context;
                     * the UE shall reset the uplink NAS COUNT counter */
                    LOG_TRACE(INFO,
                              "EMM-PROC  - Reset uplink NAS COUNT counter");
                    _emm_data.security->ul_count.overflow = 0;
                    _emm_data.security->ul_count.seq_num = 0;
                }
            }

            _emm_data.security->selected_algorithms.encryption = seea;
            _emm_data.security->selected_algorithms.integrity  = seia;

        }
        /*
         * NAS security mode command not accepted by the UE
         */
        else {
            /* Setup EMM cause code */
            emm_cause = EMM_CAUSE_SECURITY_MODE_REJECTED;
            /* Release security mode control internal data */
            if (_security_data.kenb.value) {
                free(_security_data.kenb.value);
                _security_data.kenb.value = NULL;
                _security_data.kenb.length = 0;
            }
        }
    }

    /* Setup EMM procedure handler to be executed upon receiving
     * lower layer notification */
    rc = emm_proc_lowerlayer_initialize(NULL, NULL, NULL, NULL);
    if (rc != RETURNok) {
        LOG_TRACE(WARNING,
                  "EMM-PROC  - Failed to initialize EMM procedure handler");
        LOG_FUNC_RETURN (RETURNerror);
    }

    /*
     * Notify EMM-AS SAP that Security Mode response message has to be sent
     * to the network
     */
    emm_sap_t emm_sap;
    emm_sap.primitive = EMMAS_SECURITY_RES;
    emm_sap.u.emm_as.u.security.guti = _emm_data.guti;
    emm_sap.u.emm_as.u.security.ueid = 0;
    emm_sap.u.emm_as.u.security.msgType = EMM_AS_MSG_TYPE_SMC;
    emm_sap.u.emm_as.u.security.emm_cause = emm_cause;
    /* Setup EPS NAS security data */
    emm_as_set_security_data(&emm_sap.u.emm_as.u.security.sctx,
                             _emm_data.security, security_context_is_new, TRUE);
    rc = emm_sap_send(&emm_sap);

    LOG_FUNC_RETURN (rc);
}
#endif // NAS_UE

/*
 * --------------------------------------------------------------------------
 *      Security mode control procedure executed by the MME
 * --------------------------------------------------------------------------
 */
#ifdef NAS_MME


/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_security_mode_control()                          **
 **                                                                        **
 ** Description: Initiates the security mode control procedure.            **
 **                                                                        **
 **              3GPP TS 24.301, section 5.4.3.2                           **
 **      The MME initiates the NAS security mode control procedure **
 **      by sending a SECURITY MODE COMMAND message to the UE and  **
 **      starting timer T3460. The message shall be sent unciphe-  **
 **      red but shall be integrity protected using the NAS inte-  **
 **      grity key based on KASME.                                 **
 **                                                                        **
 ** Inputs:  ueid:      UE lower layer identifier                  **
 **      ksi:       NAS key set identifier                     **
 **      eea:       Replayed EPS encryption algorithms         **
 **      eia:       Replayed EPS integrity algorithms          **
 **      success:   Callback function executed when the secu-  **
 **             rity mode control procedure successfully   **
 **             completes                                  **
 **      reject:    Callback function executed when the secu-  **
 **             rity mode control procedure fails or is    **
 **             rejected                                   **
 **      failure:   Callback function executed whener a lower  **
 **             layer failure occured before the security  **
 **             mode control procedure comnpletes          **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
int emm_proc_security_mode_control(unsigned int ueid, int ksi, int eea, int eia,
                                   emm_common_success_callback_t success,
                                   emm_common_reject_callback_t reject,
                                   emm_common_failure_callback_t failure)
{
    int rc = RETURNerror;
    int security_context_is_new = FALSE;
    int mme_eea                 = NAS_SECURITY_ALGORITHMS_EEA0;
    int mme_eia                 = NAS_SECURITY_ALGORITHMS_EIA0;
    /* Get the UE context */
    emm_data_context_t *emm_ctx = NULL;

    LOG_FUNC_IN;

    LOG_TRACE(INFO, "EMM-PROC  - Initiate security mode control procedure "
              "KSI = %d EEA = %d EIA = %d",
              ksi, eea, eia);

#if defined(EPC_BUILD)
    if (ueid > 0) {
        emm_ctx = emm_data_context_get(&_emm_data, ueid);
    }
#else
    if (ueid < EMM_DATA_NB_UE_MAX) {
        emm_ctx = _emm_data.ctx[ueid];
    }
#endif

    if (emm_ctx && emm_ctx->security) {
        if (emm_ctx->security->type == EMM_KSI_NOT_AVAILABLE) {
            /* The security mode control procedure is initiated to take into use
             * the EPS security context created after a successful execution of
             * the EPS authentication procedure */
            emm_ctx->security->type = EMM_KSI_NATIVE;
            emm_ctx->security->eksi = ksi;
            emm_ctx->security->dl_count.overflow = 0;
            emm_ctx->security->dl_count.seq_num = 0;

            /* TODO !!! Compute Kasme, and NAS cyphering and integrity keys */
            // LG: Kasme should have been received from authentication
            //     information request (S6A)
            // Kasme is located in emm_ctx->vector.kasme
            FREE_OCTET_STRING(emm_ctx->security->kasme);

            emm_ctx->security->kasme.value = malloc(32);
            memcpy(emm_ctx->security->kasme.value,
            	emm_ctx->vector.kasme,
            	32);
            emm_ctx->security->kasme.length = 32;

            rc = _security_select_algorithms(
                eia,
                eea,
                &mme_eia,
                &mme_eea);

            emm_ctx->security->selected_algorithms.encryption = mme_eea;
            emm_ctx->security->selected_algorithms.integrity  = mme_eia;

            if (rc == RETURNerror) {
                LOG_TRACE(WARNING,
                    "EMM-PROC  - Failed to select security algorithms");
                LOG_FUNC_RETURN (RETURNerror);
            }

            if ( ! emm_ctx->security->knas_int.value) {
                emm_ctx->security->knas_int.value = malloc(AUTH_KNAS_INT_SIZE);
            } else {
            	LOG_TRACE(ERROR,
                    " TODO realloc emm_ctx->security->knas_int OctetString");
                LOG_FUNC_RETURN (RETURNerror);
            }
            emm_ctx->security->knas_int.length = AUTH_KNAS_INT_SIZE;
            derive_key_nas(
                NAS_INT_ALG,
                emm_ctx->security->selected_algorithms.integrity,
                emm_ctx->vector.kasme,
                emm_ctx->security->knas_int.value);

            if ( ! emm_ctx->security->knas_enc.value) {
                emm_ctx->security->knas_enc.value = malloc(AUTH_KNAS_ENC_SIZE);
            } else {
            	LOG_TRACE(ERROR,
                    " TODO realloc emm_ctx->security->knas_enc OctetString");
                LOG_FUNC_RETURN (RETURNerror);
            }
            emm_ctx->security->knas_enc.length = AUTH_KNAS_ENC_SIZE;
            derive_key_nas(
                NAS_ENC_ALG,
                emm_ctx->security->selected_algorithms.encryption,
                emm_ctx->vector.kasme,
                emm_ctx->security->knas_enc.value);

            /* Set new security context indicator */
            security_context_is_new = TRUE;
        }
    } else {
        LOG_TRACE(WARNING, "EMM-PROC  - No EPS security context exists");
        LOG_FUNC_RETURN (RETURNerror);
    }

    /* Allocate parameters of the retransmission timer callback */
    security_data_t *data =
        (security_data_t *)malloc(sizeof(security_data_t));

    if (data != NULL) {
        /* Setup ongoing EMM procedure callback functions */
        rc = emm_proc_common_initialize(ueid, success, reject, failure,
                                        _security_abort, data);
        if (rc != RETURNok) {
            LOG_TRACE(WARNING, "Failed to initialize EMM callback functions");
            free(data);
            LOG_FUNC_RETURN (RETURNerror);
        }
        /* Set the UE identifier */
        data->ueid = ueid;
        /* Reset the retransmission counter */
        data->retransmission_count = 0;
        /* Set the key set identifier */
        data->ksi = ksi;
        /* Set the EPS encryption algorithms to be replayed to the UE */
        data->eea = eea;
        /* Set the EPS integrity algorithms to be replayed to the UE */
        data->eia = eia;
        /* Set the EPS encryption algorithms to be replayed to the UE */
        data->selected_eea = emm_ctx->security->selected_algorithms.encryption;
        /* Set the EPS integrity algorithms to be replayed to the UE */
        data->selected_eia = emm_ctx->security->selected_algorithms.integrity;
        /* Set the failure notification indicator */
        data->notify_failure = FALSE;
        /* Send security mode command message to the UE */
        rc = _security_request(data, security_context_is_new);
        if (rc != RETURNerror) {
            /*
             * Notify EMM that common procedure has been initiated
             */
            emm_sap_t emm_sap;
            emm_sap.primitive = EMMREG_COMMON_PROC_REQ;
            emm_sap.u.emm_reg.ueid = ueid;
            emm_sap.u.emm_reg.ctx  = emm_ctx;
            rc = emm_sap_send(&emm_sap);
        }
    }

    LOG_FUNC_RETURN (rc);
}

/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_security_mode_complete()                         **
 **                                                                        **
 ** Description: Performs the security mode control completion procedure   **
 **      executed by the network.                                  **
 **                                                                        **
 **              3GPP TS 24.301, section 5.4.3.4                           **
 **      Upon receiving the SECURITY MODE COMPLETE message, the    **
 **      MME shall stop timer T3460.                               **
 **      From this time onward the MME shall integrity protect and **
 **      encipher all signalling messages with the selected NAS    **
 **      integrity and ciphering algorithms.                       **
 **                                                                        **
 ** Inputs:  ueid:      UE lower layer identifier                  **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
int emm_proc_security_mode_complete(unsigned int ueid)
{
    emm_data_context_t *emm_ctx = NULL;

    int rc = RETURNerror;
    emm_sap_t emm_sap;

    LOG_FUNC_IN;

    LOG_TRACE(INFO, "EMM-PROC  - Security mode complete (ueid=%u)", ueid);

    /* Stop timer T3460 */
    LOG_TRACE(INFO, "EMM-PROC  - Stop timer T3460 (%d)", T3460.id);
    T3460.id = nas_timer_stop(T3460.id);

    /* Release retransmission timer paramaters */
    security_data_t *data = (security_data_t *)(emm_proc_common_get_args(ueid));
    if (data) {
        free(data);
    }

    /* Get the UE context */
#if defined(EPC_BUILD)
    if (ueid > 0) {
        emm_ctx = emm_data_context_get(&_emm_data, ueid);
    }
#else
    if (ueid < EMM_DATA_NB_UE_MAX) {
        emm_ctx = _emm_data.ctx[ueid];
    }
#endif

    if (emm_ctx && emm_ctx->security) {
        /*
         * Notify EMM that the authentication procedure successfully completed
         */
        emm_sap.primitive = EMMREG_COMMON_PROC_CNF;
        emm_sap.u.emm_reg.ueid = ueid;
        emm_sap.u.emm_reg.ctx  = emm_ctx;
        emm_sap.u.emm_reg.u.common.is_attached = emm_ctx->is_attached;
    } else {
        LOG_TRACE(ERROR, "EMM-PROC  - No EPS security context exists");
        /*
         * Notify EMM that the authentication procedure failed
         */
        emm_sap.primitive = EMMREG_COMMON_PROC_REJ;
        emm_sap.u.emm_reg.ueid = ueid;
        emm_sap.u.emm_reg.ctx  = emm_ctx;
    }

    rc = emm_sap_send(&emm_sap);

    LOG_FUNC_RETURN (rc);
}

/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_security_mode_reject()                           **
 **                                                                        **
 ** Description: Performs the security mode control not accepted by the UE **
 **                                                                        **
 **              3GPP TS 24.301, section 5.4.3.5                           **
 **      Upon receiving the SECURITY MODE REJECT message, the MME  **
 **      shall stop timer T3460 and abort the ongoing procedure    **
 **      that triggered the initiation of the NAS security mode    **
 **      control procedure.                                        **
 **      The MME shall apply the EPS security context in use befo- **
 **      re the initiation of the security mode control procedure, **
 **      if any, to protect any subsequent messages.               **
 **                                                                        **
 **                                                                        **
 ** Inputs:  ueid:      UE lower layer identifier                  **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
int emm_proc_security_mode_reject(unsigned int ueid)
{
    emm_data_context_t *emm_ctx = NULL;
    int rc = RETURNerror;

    LOG_FUNC_IN;

    LOG_TRACE(WARNING, "EMM-PROC  - Security mode command not accepted by the UE"
              "(ueid=0x%08x)", ueid);

    /* Stop timer T3460 */
    LOG_TRACE(INFO, "EMM-PROC  - Stop timer T3460 (%d)", T3460.id);
    T3460.id = nas_timer_stop(T3460.id);

    /* Release retransmission timer paramaters */
    security_data_t *data = (security_data_t *)(emm_proc_common_get_args(ueid));
    if (data) {
        free(data);
    }

    /* Get the UE context */
#if defined(EPC_BUILD)
    if (ueid > 0) {
        emm_ctx = emm_data_context_get(&_emm_data, ueid);
        DevAssert(emm_ctx != NULL);
    }
#else
    if (ueid < EMM_DATA_NB_UE_MAX) {
        emm_ctx = _emm_data.ctx[ueid];
    }
#endif
    /* Set the key set identifier to its previous value */
    if (emm_ctx && emm_ctx->security) {
        /* XXX - Usually, the MME should be able to maintain a current and
         * a non-current EPS security context simultaneously as the UE do.
         * This implementation choose to have only one security context by UE
         * in the MME, thus security mode control procedure is only performed
         * to take into use the first EPS security context created after a
         * successful execution of the EPS authentication procedure */
        emm_ctx->security->type = EMM_KSI_NOT_AVAILABLE;
    }

    /*
     * Notify EMM that the authentication procedure failed
     */
    emm_sap_t emm_sap;
    emm_sap.primitive = EMMREG_COMMON_PROC_REJ;
    emm_sap.u.emm_reg.ueid = ueid;
    emm_sap.u.emm_reg.ctx  = emm_ctx;
    rc = emm_sap_send(&emm_sap);

    LOG_FUNC_RETURN (rc);
}
#endif // NAS_MME

/****************************************************************************/
/*********************  L O C A L    F U N C T I O N S  *********************/
/****************************************************************************/

#ifdef NAS_UE
/*
 * --------------------------------------------------------------------------
 *              UE specific local functions
 * --------------------------------------------------------------------------
 */

/****************************************************************************
 **                                                                        **
 ** Name:    _security_release()                                       **
 **                                                                        **
 ** Description: Releases the given EPS NAS security context               **
 **                                                                        **
 ** Inputs:  ctx:       The EPS NAS security context to release    **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    None                                       **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
static void _security_release(emm_security_context_t *ctx)
{
    LOG_FUNC_IN;

    if (ctx) {
        /* Release Kasme security key */
        if (ctx->kasme.value) {
            free(ctx->kasme.value);
            ctx->kasme.value  = NULL;
            ctx->kasme.length = 0;
        }
        /* Release NAS cyphering key */
        if (ctx->knas_enc.value) {
            free(ctx->knas_enc.value);
            ctx->knas_enc.value  = NULL;
            ctx->knas_enc.length = 0;
        }
        /* Release NAS integrity key */
        if (ctx->knas_int.value) {
            free(ctx->knas_int.value);
            ctx->knas_int.value  = NULL;
            ctx->knas_int.length = 0;
        }
        /* Release the NAS security context */
        free(ctx);
    }

    LOG_FUNC_OUT;
}

/****************************************************************************
 **                                                                        **
 ** Name:    _security_knas_enc()                                      **
 **                                                                        **
 ** Description: Algorithm Key generation function used for the derivation **
 **      of NAS encryption key Knas-enc from the Kasme.            **
 **                                                                        **
 **              3GPP TS 33.401, Annex A.7                                 **
 **                                                                        **
 ** Inputs:  kasme:     Key Access Security Management Entity      **
 **      eea:       Cyphering algorithm identity               **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     knas_enc:  Derived key for NAS cyphering algorithm    **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
static int _security_knas_enc(const OctetString *kasme, OctetString *knas_enc,
                              UInt8_t eea)
{
    LOG_FUNC_IN;
    LOG_TRACE(INFO, "%s  with algo dist %d algo id %d", __FUNCTION__,0x01, eea);
    LOG_FUNC_RETURN (_security_kdf(kasme, knas_enc, 0x01, eea));
}

/****************************************************************************
 **                                                                        **
 ** Name:    _security_knas_int()                                      **
 **                                                                        **
 ** Description: Algorithm Key generation function used for the derivation **
 **      of NAS integrity key Knas-int from the Kasme.             **
 **                                                                        **
 **              3GPP TS 33.401, Annex A.7                                 **
 **                                                                        **
 ** Inputs:  kasme:     Key Access Security Management Entity      **
 **      eia:       Integrity algorithm identity               **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     knas_int:  Derived key for NAS integrity algorithm    **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
static int _security_knas_int(const OctetString *kasme, OctetString *knas_int,
                              UInt8_t eia)
{
    LOG_FUNC_IN;
    LOG_TRACE(INFO, "%s  with algo dist %d algo id %d", __FUNCTION__,0x02, eia);
    LOG_FUNC_RETURN (_security_kdf(kasme, knas_int, 0x02, eia));
}

/****************************************************************************
 **                                                                        **
 ** Name:    _security_kenb()                                          **
 **                                                                        **
 ** Description: Computes the eNodeB key from Kasme and the given value of **
 **      uplink NAS counter.                                       **
 **                                                                        **
 **              3GPP TS 33.401, Annex A.3                                 **
 **                                                                        **
 ** Inputs:  kasme:     Key Access Security Management Entity      **
 **      count:     Uplink NAS counter value                   **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     kenb:      eNodeB security key                        **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
static int _security_kenb(const OctetString *kasme, OctetString *kenb,
                          UInt32_t count)
{
    /* Compute the KDF input parameter
     * S = FC(0x11) || UL NAS Count || 0x00 0x04
     */
    UInt8_t  input[32];
    UInt16_t length    = 4;
    int      offset    = 0;

    LOG_TRACE(INFO, "%s  with count= %d", __FUNCTION__, count);
    memset(input, 0, 32);
    input[0] = 0x11;
    // P0
    input[1] = count >> 24;
    input[2] = (UInt8_t)(count >> 16);
    input[3] = (UInt8_t)(count >> 8);
    input[4] = (UInt8_t)count;
    // L0
    input[5] = 0;
    input[6] = 4;

    kdf(kasme->value, 32, input, 7, kenb->value, 32);
    kenb->length = 32;
    return (RETURNok);
}

/****************************************************************************
 **                                                                        **
 ** Name:    _security_kdf()                                           **
 **                                                                        **
 ** Description: Algorithm Key generation function used for the derivation **
 **      of keys for NAS integrity and NAS encryption algorithms   **
 **      from Kasme, algorithm types and algorithm identities.     **
 **                                                                        **
 **              3GPP TS 33.401, Annex A.7                                 **
 **                                                                        **
 ** Inputs:  kasme:     Key Access Security Management Entity      **
 **      algo_dist: Algorithm type distinguisher               **
 **      algo_id:   Algorithm identity                         **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     key:       Derived key for NAS security protection    **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
static int _security_kdf(const OctetString *kasme, OctetString *key,
                         UInt8_t algo_dist, UInt8_t algo_id)
{
    /* Compute the KDF input parameter
     * S = FC(0x15) || Algorithm distinguisher || 0x00 0x01
            || Algorithm identity || 0x00 0x01
    */
    UInt8_t input[32];
    UInt8_t output[32];
    LOG_TRACE(DEBUG, "%s:%u output key mem %p lenth %u",
    		__FUNCTION__, __LINE__,
    		key->value,
    		key->length);
    memset(input, 0, 32);
    // FC
    input[0] = 0x15;
    // P0 = Algorithm distinguisher
    input[1] = algo_dist;
    // L0 = 0x00 01
    input[2] = 0x00;
    input[3] = 0x01;
    // P1 = Algorithm identity
    input[4] = algo_id;
    // L1 = length of Algorithm identity 0x00 0x01
    input[5] = 0x00;
    input[6] = 0x01;

    /* Compute the derived key */
    kdf(kasme->value, kasme->length, input, 7, output, 32);
    memcpy(key->value, &output[31 - key->length + 1], key->length);
    return (RETURNok);
}
#endif // NAS_UE

#ifdef NAS_MME
/*
 * --------------------------------------------------------------------------
 *              Timer handlers
 * --------------------------------------------------------------------------
 */

/****************************************************************************
 **                                                                        **
 ** Name:    _security_t3460_handler()                                 **
 **                                                                        **
 ** Description: T3460 timeout handler                                     **
 **      Upon T3460 timer expiration, the security mode command    **
 **      message is retransmitted and the timer restarted. When    **
 **      retransmission counter is exceed, the MME shall abort the **
 **      security mode control procedure.                          **
 **                                                                        **
 **              3GPP TS 24.301, section 5.4.3.7, case b                   **
 **                                                                        **
 ** Inputs:  args:      handler parameters                         **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    None                                       **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
static void *_security_t3460_handler(void *args)
{
    LOG_FUNC_IN;

    int rc;

    security_data_t *data = (security_data_t *)(args);

    /* Increment the retransmission counter */
    data->retransmission_count += 1;

    LOG_TRACE(WARNING, "EMM-PROC  - T3460 timer expired, retransmission "
              "counter = %d", data->retransmission_count);

    if (data->retransmission_count < SECURITY_COUNTER_MAX) {
        /* Send security mode command message to the UE */
        rc = _security_request(data, FALSE);
    } else {
        /* Set the failure notification indicator */
        data->notify_failure = TRUE;
        /* Abort the security mode control procedure */
        rc = _security_abort(data);
    }

    LOG_FUNC_RETURN (NULL);
}

/*
 * --------------------------------------------------------------------------
 *              MME specific local functions
 * --------------------------------------------------------------------------
 */

/****************************************************************************
 **                                                                        **
 ** Name:    _security_request()                                       **
 **                                                                        **
 ** Description: Sends SECURITY MODE COMMAND message and start timer T3460 **
 **                                                                        **
 ** Inputs:  data:      Security mode control internal data        **
 **      is_new:    Indicates whether a new security context   **
 **             has just been taken into use               **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    T3460                                      **
 **                                                                        **
 ***************************************************************************/
int _security_request(security_data_t *data, int is_new)
{
    struct emm_data_context_s *emm_ctx = NULL;

    emm_sap_t emm_sap;
    int rc;

    LOG_FUNC_IN;

    /*
     * Notify EMM-AS SAP that Security Mode Command message has to be sent
     * to the UE
     */
    emm_sap.primitive = EMMAS_SECURITY_REQ;
    emm_sap.u.emm_as.u.security.guti         = NULL;
    emm_sap.u.emm_as.u.security.ueid         = data->ueid;
    emm_sap.u.emm_as.u.security.msgType      = EMM_AS_MSG_TYPE_SMC;
    emm_sap.u.emm_as.u.security.ksi          = data->ksi;
    emm_sap.u.emm_as.u.security.eea          = data->eea;
    emm_sap.u.emm_as.u.security.eia          = data->eia;
    emm_sap.u.emm_as.u.security.selected_eea = data->selected_eea;
    emm_sap.u.emm_as.u.security.selected_eia = data->selected_eia;

#if defined(EPC_BUILD)
    if (data->ueid > 0) {
        emm_ctx = emm_data_context_get(&_emm_data, data->ueid);
    }
#else
    if (data->ueid < EMM_DATA_NB_UE_MAX) {
        emm_ctx = _emm_data.ctx[data->ueid];
    }
#endif

    /* Setup EPS NAS security data */
    emm_as_set_security_data(&emm_sap.u.emm_as.u.security.sctx,
                             emm_ctx->security, is_new, FALSE);
    rc = emm_sap_send(&emm_sap);

    if (rc != RETURNerror) {
        if (T3460.id != NAS_TIMER_INACTIVE_ID) {
            /* Re-start T3460 timer */
            T3460.id = nas_timer_restart(T3460.id);
        } else {
            /* Start T3460 timer */
            T3460.id = nas_timer_start(T3460.sec, _security_t3460_handler, data);
        }
        LOG_TRACE(INFO,"EMM-PROC  - Timer T3460 (%d) expires in %ld seconds",
                  T3460.id, T3460.sec);
    }

    LOG_FUNC_RETURN (rc);
}

/****************************************************************************
 **                                                                        **
 ** Name:    _security_abort()                                         **
 **                                                                        **
 ** Description: Aborts the security mode control procedure currently in   **
 **      progress                                                  **
 **                                                                        **
 ** Inputs:  args:      Security mode control data to be released  **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    T3460                                      **
 **                                                                        **
 ***************************************************************************/
static int _security_abort(void *args)
{
    LOG_FUNC_IN;

    int rc = RETURNerror;

    security_data_t *data = (security_data_t *)(args);

    if (data) {
        unsigned int ueid = data->ueid;
        int notify_failure = data->notify_failure;

        LOG_TRACE(WARNING, "EMM-PROC  - Abort security mode control procedure "
                  "(ueid=%u)", ueid);

        /* Stop timer T3460 */
        if (T3460.id != NAS_TIMER_INACTIVE_ID) {
            LOG_TRACE(INFO, "EMM-PROC  - Stop timer T3460 (%d)", T3460.id);
            T3460.id = nas_timer_stop(T3460.id);
        }
        /* Release retransmission timer paramaters */
        free(data);

        /*
         * Notify EMM that the security mode control procedure failed
         */
        if (notify_failure) {
            emm_sap_t emm_sap;
            emm_sap.primitive = EMMREG_COMMON_PROC_REJ;
            emm_sap.u.emm_reg.ueid = ueid;
            rc = emm_sap_send(&emm_sap);
        } else {
            rc = RETURNok;
        }
    }

    LOG_FUNC_RETURN (rc);
}


/****************************************************************************
 **                                                                        **
 ** Name:    _security_select_algorithms()                                 **
 **                                                                        **
 ** Description: Select int and enc algorithms based on UE capabilities and**
 **      MME capabilities and MME preferences                              **
 **                                                                        **
 ** Inputs:  ue_eia:      integrity algorithms supported by UE             **
 **          ue_eea:      ciphering algorithms supported by UE             **
 **                                                                        **
 ** Outputs: mme_eia:     integrity algorithms supported by MME            **
 **          mme_eea:     ciphering algorithms supported by MME            **
 **                                                                        **
 **      Return:    RETURNok, RETURNerror                                  **
 **      Others:    None                                                   **
 **                                                                        **
 ***************************************************************************/
static int _security_select_algorithms(
    const int   ue_eiaP,
    const int   ue_eeaP,
    int * const mme_eiaP,
    int * const mme_eeaP)
{
    LOG_FUNC_IN;

    int rc                = RETURNerror;
    int preference_index;

    *mme_eiaP = NAS_SECURITY_ALGORITHMS_EIA0;
    *mme_eeaP = NAS_SECURITY_ALGORITHMS_EEA0;

    for (preference_index = 0; preference_index < 8; preference_index++) {
        if (ue_eiaP & (0x80 >> _emm_data.conf.prefered_integrity_algorithm[preference_index])) {
            LOG_TRACE(DEBUG,
                    "Selected  NAS_SECURITY_ALGORITHMS_EIA%d (choice num %d)",
                    _emm_data.conf.prefered_integrity_algorithm[preference_index],
                    preference_index);
            *mme_eiaP = _emm_data.conf.prefered_integrity_algorithm[preference_index];
            break;
        }
    }

    for (preference_index = 0; preference_index < 8; preference_index++) {
        if (ue_eeaP & (0x80 >> _emm_data.conf.prefered_ciphering_algorithm[preference_index])) {
            LOG_TRACE(DEBUG,
                    "Selected  NAS_SECURITY_ALGORITHMS_EEA%d (choice num %d)",
                    _emm_data.conf.prefered_ciphering_algorithm[preference_index],
                    preference_index);
            *mme_eeaP = _emm_data.conf.prefered_ciphering_algorithm[preference_index];
            break;
        }
    }
    LOG_FUNC_RETURN (RETURNok);
}

#endif // NAS_MME

