nas_stream_eea2.c

/*******************************************************************************
    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,
    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 OpenAirInterface.The full GNU General Public License is
   included in this distribution in the file called "COPYING". If not,
   see <http://www.gnu.org/licenses/>.

  Contact Information
  OpenAirInterface Admin: openair_admin@eurecom.fr
  OpenAirInterface Tech : openair_tech@eurecom.fr
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 *******************************************************************************/
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>

#include <nettle/nettle-meta.h>
#include <nettle/aes.h>
#include <nettle/ctr.h>

#include "assertions.h"
#include "conversions.h"
#include "secu_defs.h"

// #define SECU_DEBUG

int nas_stream_encrypt_eea2(nas_stream_cipher_t *stream_cipher, uint8_t *out)
{
    uint8_t m[16];
    uint32_t local_count;

    void *ctx;
    uint8_t *data;

    uint32_t zero_bit = 0;
    uint32_t byte_length;

    DevAssert(stream_cipher != NULL);
    DevAssert(out != NULL);

    zero_bit = stream_cipher->blength & 0x7;

    byte_length = stream_cipher->blength >> 3;
    if (zero_bit > 0)
        byte_length += 1;

    ctx = malloc(nettle_aes128.context_size);
    data = malloc(byte_length);

    local_count = hton_int32(stream_cipher->count);

    memset(m, 0, sizeof(m));
    memcpy(&m[0], &local_count, 4);
    m[4] = ((stream_cipher->bearer & 0x1F) << 3) |
              ((stream_cipher->direction & 0x01) << 2);
    /* Other bits are 0 */

#if defined(SECU_DEBUG)
    {
        int i;
        printf("Blength: %u, Zero bits: %u\n", stream_cipher->blength, zero_bit);
        for (i = 0; i < sizeof(m); i++)
            printf("0x%02x ", m[i]);
        printf("\n");
    }
#endif

    nettle_aes128.set_encrypt_key(ctx, stream_cipher->key_length,
                                  stream_cipher->key);

    nettle_ctr_crypt(ctx, nettle_aes128.encrypt,
                     nettle_aes128.block_size, m,
                     byte_length, data, stream_cipher->message);

    if (zero_bit > 0)
        data[byte_length - 1] = data[byte_length - 1] & (uint8_t)(0xFF << (8 - zero_bit));


    memcpy(out, data, byte_length);
    free(data);
    free(ctx);

    return 0;
}