Differential D14785 Diff 40575 head/lib/libc/gen/getentropy.c

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head/lib/libc/gen/getentropy.c

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	#include <sys/param.h>			#include <sys/param.h>
	#include <sys/random.h>			#include <sys/random.h>

	#include <errno.h>			#include <errno.h>
	#include <stdlib.h>			#include <stdlib.h>

	#include "libc_private.h"			#include "libc_private.h"

				/*
				* If a newer libc is accidentally installed on an older kernel, provide high
				* quality random data anyway. The sysctl interface is not as fast and does
				* not block by itself, but is provided by even very old kernels.
				*/
				static int
				getentropy_fallback(void *buf, size_t buflen)
				{
				/*
				* oldp (buf) == NULL has a special meaning for sysctl that results in
				* no EFAULT. For compatibility with the kernel getrandom(2), detect
				* this case and return the appropriate error.
				*/
				if (buf == NULL && buflen > 0) {
				errno = EFAULT;
				return (-1);
				}
				if (__arc4_sysctl(buf, buflen) != buflen) {
				if (errno == EFAULT)
				return (-1);
				/*
				* This cannot happen. _arc4_sysctl() spins until the random
				* device is seeded and then repeatedly reads until the full
				* request is satisfied. The only way for this to return a zero
				* byte or short read is if sysctl(2) on the kern.arandom MIB
				* fails. In this case, exceping the user-provided-a-bogus-
				* buffer EFAULT, give up (like for arc4random(3)'s arc4_stir).
				*/
				abort();
				}
				return (0);
				}

	int			int
	getentropy(void *buf, size_t buflen)			getentropy(void *buf, size_t buflen)
	{			{
	ssize_t rd;			ssize_t rd;

	if (buflen > 256) {			if (buflen > 256) {
	errno = EIO;			errno = EIO;
	return (-1);			return (-1);
	}			}

	while (buflen > 0) {			while (buflen > 0) {
	rd = getrandom(buf, buflen, 0);			rd = getrandom(buf, buflen, 0);
	if (rd == -1) {			if (rd == -1) {
	if (errno == EINTR)			if (errno == EINTR)
	continue;			continue;
	else if (errno == ENOSYS)			else if (errno == ENOSYS)
	abort();			return (getentropy_fallback(buf, buflen));
	else			else
	return (-1);			return (-1);
	}			}

	/* This cannot happen. */			/* This cannot happen. */
	if (rd == 0)			if (rd == 0)
	abort();			abort();

	buf = (char *)buf + rd;			buf = (char *)buf + rd;
	buflen -= rd;			buflen -= rd;
	}			}

	return (0);			return (0);
	}			}