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/*
* Copyright (C) 2005-2006 Martin Willi
* Copyright (C) 2005 Jan Hutter
* Hochschule fuer Technik Rapperswil
*
* 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. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* 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.
*
* $Id: prf_plus.c 4524 2008-10-29 14:12:54Z martin $
*/
#include <string.h>
#include "prf_plus.h"
typedef struct private_prf_plus_t private_prf_plus_t;
/**
* Private data of an prf_plus_t object.
*
*/
struct private_prf_plus_t {
/**
* Public interface of prf_plus_t.
*/
prf_plus_t public;
/**
* PRF to use.
*/
prf_t *prf;
/**
* Initial seed.
*/
chunk_t seed;
/**
* Buffer to store current PRF result.
*/
chunk_t buffer;
/**
* Already given out bytes in current buffer.
*/
size_t given_out;
/**
* Octet which will be appended to the seed.
*/
u_int8_t appending_octet;
};
/**
* Implementation of prf_plus_t.get_bytes.
*/
static void get_bytes(private_prf_plus_t *this, size_t length, u_int8_t *buffer)
{
chunk_t appending_chunk;
size_t bytes_in_round;
size_t total_bytes_written = 0;
appending_chunk.ptr = &(this->appending_octet);
appending_chunk.len = 1;
while (length > 0)
{ /* still more to do... */
if (this->buffer.len == this->given_out)
{ /* no bytes left in buffer, get next*/
this->prf->get_bytes(this->prf, this->buffer, NULL);
this->prf->get_bytes(this->prf, this->seed, NULL);
this->prf->get_bytes(this->prf, appending_chunk, this->buffer.ptr);
this->given_out = 0;
this->appending_octet++;
}
/* how many bytes can we write in this round ? */
bytes_in_round = min(length, this->buffer.len - this->given_out);
/* copy bytes from buffer with offset */
memcpy(buffer + total_bytes_written, this->buffer.ptr + this->given_out, bytes_in_round);
length -= bytes_in_round;
this->given_out += bytes_in_round;
total_bytes_written += bytes_in_round;
}
}
/**
* Implementation of prf_plus_t.allocate_bytes.
*/
static void allocate_bytes(private_prf_plus_t *this, size_t length, chunk_t *chunk)
{
if (length)
{
chunk->ptr = malloc(length);
chunk->len = length;
get_bytes(this, length, chunk->ptr);
}
else
{
*chunk = chunk_empty;
}
}
/**
* Implementation of prf_plus_t.destroy.
*/
static void destroy(private_prf_plus_t *this)
{
free(this->buffer.ptr);
free(this->seed.ptr);
free(this);
}
/*
* Description in header.
*/
prf_plus_t *prf_plus_create(prf_t *prf, chunk_t seed)
{
private_prf_plus_t *this;
chunk_t appending_chunk;
this = malloc_thing(private_prf_plus_t);
/* set public methods */
this->public.get_bytes = (void (*)(prf_plus_t *,size_t,u_int8_t*))get_bytes;
this->public.allocate_bytes = (void (*)(prf_plus_t *,size_t,chunk_t*))allocate_bytes;
this->public.destroy = (void (*)(prf_plus_t *))destroy;
/* take over prf */
this->prf = prf;
/* allocate buffer for prf output */
this->buffer.len = prf->get_block_size(prf);
this->buffer.ptr = malloc(this->buffer.len);
this->appending_octet = 0x01;
/* clone seed */
this->seed.ptr = clalloc(seed.ptr, seed.len);
this->seed.len = seed.len;
/* do the first run */
appending_chunk.ptr = &(this->appending_octet);
appending_chunk.len = 1;
this->prf->get_bytes(this->prf, this->seed, NULL);
this->prf->get_bytes(this->prf, appending_chunk, this->buffer.ptr);
this->given_out = 0;
this->appending_octet++;
return &(this->public);
}
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