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/*
* Copyright (C) 2008 Martin Willi
* HSR 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.
*/
#include "padlock_rng.h"
typedef struct private_padlock_rng_t private_padlock_rng_t;
typedef enum padlock_quality_factor_t padlock_quality_factor_t;
/**
* Padlock RNG quality factors
*/
enum padlock_quality_factor_t {
/* Lowest quality: Reads 8 bytes */
PADLOCK_QF0 = 0x00,
/* Medium quality: Reads 4 bytes */
PADLOCK_QF1 = 0x01,
/* Better quality: Reads 2 bytes */
PADLOCK_QF2 = 0x10,
/* Highest quality: Reads 1 byte */
PADLOCK_QF3 = 0x11,
};
/**
* Private data of an padlock_rng_t object.
*/
struct private_padlock_rng_t {
/**
* Public padlock_rng_t interface.
*/
padlock_rng_t public;
/**
* Padlock quality factor
*/
padlock_quality_factor_t quality;
};
/**
* Get bytes from Padlock RNG. buf should have space for (len + 7)
*/
static void rng(char *buf, int len, int quality)
{
while (len > 0)
{
int status;
/* run XSTORE until we have all bytes needed. We do not use REP, as
* this should not be performance critical and it's easier this way. */
asm volatile (
".byte 0x0F,0xA7,0xC0 \n\t"
: "=D"(buf), "=a"(status)
: "d"(quality), "D"(buf));
/* bits[0..4] of status word contains the number of bytes read */
len -= status & 0x1F;
}
}
METHOD(rng_t, allocate_bytes, bool,
private_padlock_rng_t *this, size_t bytes, chunk_t *chunk)
{
chunk->len = bytes;
/* padlock requires some additional bytes */
chunk->ptr = malloc(bytes + 7);
rng(chunk->ptr, chunk->len, this->quality);
return TRUE;
}
METHOD(rng_t, get_bytes, bool,
private_padlock_rng_t *this, size_t bytes, uint8_t *buffer)
{
chunk_t chunk;
/* Padlock needs a larger buffer than "bytes", we need a new buffer */
allocate_bytes(this, bytes, &chunk);
memcpy(buffer, chunk.ptr, bytes);
chunk_clear(&chunk);
return TRUE;
}
METHOD(rng_t, destroy, void,
private_padlock_rng_t *this)
{
free(this);
}
/*
* Described in header.
*/
padlock_rng_t *padlock_rng_create(rng_quality_t quality)
{
private_padlock_rng_t *this;
INIT(this,
.public = {
.rng = {
.get_bytes = _get_bytes,
.allocate_bytes = _allocate_bytes,
.destroy = _destroy,
},
},
);
/* map RNG quality to Padlock quality factor */
switch (quality)
{
case RNG_WEAK:
this->quality = PADLOCK_QF0;
break;
case RNG_STRONG:
this->quality = PADLOCK_QF1;
break;
case RNG_TRUE:
this->quality = PADLOCK_QF3;
break;
default:
free(this);
return NULL;
}
return &this->public;
}
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