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/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* CTraces
* =======
* Copyright 2022 The CTraces Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <ctraces/ctraces.h>
#if defined(unix) || defined (__unix) || defined(__unix__) || defined(__linux__) || \
defined(__APPLE__) || defined(__MACH__) || defined(__FreeBSD__) || defined(__ANDROID__)
#define ITS_A_UNIX_FRIEND
#endif
#ifdef CTR_HAVE_GETRANDOM
#include <sys/random.h>
#endif
#ifdef ITS_A_UNIX_FRIEND
#include <fcntl.h>
#include <unistd.h>
#else
// #define needed to link in RtlGenRandom(), a.k.a. SystemFunction036. See the
// "Community Additions" comment on MSDN here:
// http://msdn.microsoft.com/en-us/library/windows/desktop/aa387694.aspx
#define SystemFunction036 NTAPI SystemFunction036
#include <ntsecapi.h>
#undef SystemFunction036
#endif
#include <time.h>
ssize_t ctr_random_get(void *buf, size_t len)
{
int i;
ssize_t ret = 0;
unsigned int s;
char *tmp;
#ifdef CTR_HAVE_GETRANDOM
/*
* On Linux systems getrandom() is preferred, note that our use case it's pretty
* simple (no security stuff).
*/
ret = getrandom(buf, len, GRND_NONBLOCK);
return ret;
#endif
/* if getrandom() is not available and we are on Linux, macOS or BSD, try out /dev/urandom */
#ifdef ITS_A_UNIX_FRIEND
int fd;
fd = open("/dev/urandom", O_RDONLY);
if (fd > 0) {
ret = read(fd, buf, len);
close(fd);
return ret;
}
s = time(NULL);
/* fallback... a very slow way to compose a random buffer */
tmp = buf;
for (i = 0; i < len; i++) {
/* fixme: we need a good entropy here */
tmp[i] = rand_r(&s);
}
#else /* Windows ? */
ret = RtlGenRandom(buf, len);
#endif
return ret;
}
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