tests/src/random.c

/**
 * \file random.c
 *
 * \brief   This file contains the helper functions to generate random numbers
 *          for the purpose of testing.
 */

/*  Copyright (C) 2020, ARM Limited, All Rights Reserved
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  This file is part of mbed TLS (https://tls.mbed.org)
 */

#include <test/macros.h>
#include <test/random.h>
#include <string.h>

int rnd_std_rand( void *rng_state, unsigned char *output, size_t len )
{
#if !defined(__OpenBSD__)
    size_t i;

    if( rng_state != NULL )
        rng_state  = NULL;

    for( i = 0; i < len; ++i )
        output[i] = rand();
#else
    if( rng_state != NULL )
        rng_state = NULL;

    arc4random_buf( output, len );
#endif /* !OpenBSD */

    return( 0 );
}

int rnd_zero_rand( void *rng_state, unsigned char *output, size_t len )
{
    if( rng_state != NULL )
        rng_state  = NULL;

    memset( output, 0, len );

    return( 0 );
}

int rnd_buffer_rand( void *rng_state, unsigned char *output, size_t len )
{
    rnd_buf_info *info = (rnd_buf_info *) rng_state;
    size_t use_len;

    if( rng_state == NULL )
        return( rnd_std_rand( NULL, output, len ) );

    use_len = len;
    if( len > info->length )
        use_len = info->length;

    if( use_len )
    {
        memcpy( output, info->buf, use_len );
        info->buf += use_len;
        info->length -= use_len;
    }

    if( len - use_len > 0 )
        return( rnd_std_rand( NULL, output + use_len, len - use_len ) );

    return( 0 );
}

int rnd_pseudo_rand( void *rng_state, unsigned char *output, size_t len )
{
    rnd_pseudo_info *info = (rnd_pseudo_info *) rng_state;
    uint32_t i, *k, sum, delta=0x9E3779B9;
    unsigned char result[4], *out = output;

    if( rng_state == NULL )
        return( rnd_std_rand( NULL, output, len ) );

    k = info->key;

    while( len > 0 )
    {
        size_t use_len = ( len > 4 ) ? 4 : len;
        sum = 0;

        for( i = 0; i < 32; i++ )
        {
            info->v0 += ( ( ( info->v1 << 4 ) ^ ( info->v1 >> 5 ) )
                            + info->v1 ) ^ ( sum + k[sum & 3] );
            sum += delta;
            info->v1 += ( ( ( info->v0 << 4 ) ^ ( info->v0 >> 5 ) )
                            + info->v0 ) ^ ( sum + k[( sum>>11 ) & 3] );
        }

        PUT_UINT32_BE( info->v0, result, 0 );
        memcpy( out, result, use_len );
        len -= use_len;
        out += 4;
    }

    return( 0 );
}