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csrand(): Use POSIX read(2) instead of the heavier stdio #1119

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merged 1 commit into from
Dec 2, 2024
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csrand(): Use POSIX read(2) instead of the heavier stdio #1119

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23 changes: 10 additions & 13 deletions lib/csrand.c
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Original file line number Diff line number Diff line change
@@ -1,21 +1,19 @@
/*
* SPDX-FileCopyrightText: Alejandro Colomar <alx@kernel.org>
*
* SPDX-License-Identifier: BSD-3-Clause
*/
// SPDX-FileCopyrightText: 2022-2024, Alejandro Colomar <alx@kernel.org>
// SPDX-License-Identifier: BSD-3-Clause

#include <config.h>

#ident "$Id$"

#include <fcntl.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#if HAVE_SYS_RANDOM_H
#include <sys/random.h>
#endif

#include "bit.h"
#include "defines.h"
#include "prototypes.h"
Expand All @@ -34,7 +32,7 @@ static unsigned long csrand_uniform_slow(unsigned long n);
unsigned long
csrand(void)
{
FILE *fp;
int fd;
unsigned long r;

#ifdef HAVE_GETENTROPY
Expand All @@ -56,17 +54,16 @@ csrand(void)
#endif

/* Use /dev/urandom as a last resort. */
fp = fopen("/dev/urandom", "r");
if (NULL == fp) {
fd = open("/dev/urandom", O_RDONLY);
if (fd == -1)
goto fail;
}

if (fread(&r, sizeof(r), 1, fp) != 1) {
fclose(fp);
if (read(fd, &r, sizeof(r)) != sizeof(r)) {
close(fd);
goto fail;
}

fclose(fp);
close(fd);
return r;

fail:
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