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/*
* Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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 any later version.
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* You can also choose to distribute this program under the terms of
* the Unmodified Binary Distribution Licence (as given in the file
* COPYING.UBDL), provided that you have satisfied its requirements.
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
/** @file
*
* Linux entropy source
*
*/
#include <stdint.h>
#include <errno.h>
#include <ipxe/linux_api.h>
#include <ipxe/entropy.h>
struct entropy_source linux_entropy __entropy_source ( ENTROPY_NORMAL );
/** Entropy source filename */
static const char entropy_filename[] = "/dev/random";
/** Entropy source file handle */
static int entropy_fd;
/**
* Enable entropy gathering
*
* @ret rc Return status code
*/
static int linux_entropy_enable ( void ) {
/* Open entropy source */
entropy_fd = linux_open ( entropy_filename, O_RDONLY );
if ( entropy_fd < 0 ) {
DBGC ( &entropy_fd, "ENTROPY could not open %s: %s\n",
entropy_filename, linux_strerror ( linux_errno ) );
return entropy_fd;
}
/* linux_get_noise() reads a single byte from /dev/random,
* which is supposed to block until a sufficient amount of
* entropy is available. We therefore assume that each sample
* contains exactly 8 bits of entropy.
*/
entropy_init ( &linux_entropy, MIN_ENTROPY ( 8.0 ) );
return 0;
}
/**
* Disable entropy gathering
*
*/
static void linux_entropy_disable ( void ) {
/* Close entropy source */
linux_close ( entropy_fd );
}
/**
* Get noise sample
*
* @ret noise Noise sample
* @ret rc Return status code
*/
static int linux_get_noise ( noise_sample_t *noise ) {
uint8_t byte;
ssize_t len;
/* Read a single byte from entropy source */
len = linux_read ( entropy_fd, &byte, sizeof ( byte ) );
if ( len < 0 ) {
DBGC ( &entropy_fd, "ENTROPY could not read from %s: %s\n",
entropy_filename, linux_strerror ( linux_errno ) );
return len;
}
if ( len == 0 ) {
DBGC ( &entropy_fd, "ENTROPY EOF on reading from %s: %s\n",
entropy_filename, linux_strerror ( linux_errno ) );
return -EPIPE;
}
*noise = byte;
return 0;
}
/** Linux entropy source */
struct entropy_source linux_entropy __entropy_source ( ENTROPY_NORMAL ) = {
.name = "linux",
.enable = linux_entropy_enable,
.disable = linux_entropy_disable,
.get_noise = linux_get_noise,
};
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