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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/crypto/krb/prng/fortuna/prng_os.c - OS-native PRNG implementation */
/*
* Copyright (C) 2011 by the Massachusetts Institute of Technology.
* All rights reserved.
*
*
* Export of this software from the United States of America may require
* a specific license from the United States Government. It is the
* responsibility of any person or organization contemplating export to
* obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. Furthermore if you modify this software you must label
* your software as modified software and not distribute it in such a
* fashion that it might be confused with the original M.I.T. software.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
/*
* This file implements a PRNG module which relies on the system's /dev/urandom
* device. An OS packager can select this module given sufficient confidence
* in the operating system's native PRNG quality.
*/
#include "crypto_int.h"
#define DEVICE "/dev/urandom"
static int fd = -1;
int
k5_prng_init(void)
{
/* Try to open the random device read-write; if that fails, read-only is
* okay. */
fd = open(DEVICE, O_RDWR, 0);
if (fd == -1)
fd = open(DEVICE, O_RDONLY, 0);
if (fd == -1)
return errno;
return 0;
}
void
k5_prng_cleanup(void)
{
close(fd);
fd = -1;
}
krb5_error_code KRB5_CALLCONV
krb5_c_random_add_entropy(krb5_context context, unsigned int randsource,
const krb5_data *indata)
{
krb5_error_code ret;
ret = krb5int_crypto_init();
if (ret)
return ret;
/* Some random devices let user-space processes contribute entropy. Don't
* worry if this fails. */
(void)write(fd, indata->data, indata->length);
return 0;
}
krb5_error_code KRB5_CALLCONV
krb5_c_random_make_octets(krb5_context context, krb5_data *outdata)
{
char *buf = outdata->data;
size_t len = outdata->length;
ssize_t count;
while (len > 0) {
count = read(fd, buf, len);
if (count == 0) /* Not expected from a random device. */
return KRB5_CRYPTO_INTERNAL;
if (count == -1)
return errno;
buf += count;
len -= count;
}
return 0;
}
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