xref: /bionic/libc/upstream-openbsd/lib/libc/stdio/mktemp.c

/*	$OpenBSD: mktemp.c,v 1.33 2014/05/06 22:55:27 millert Exp $ */
/*
 * Copyright (c) 1996-1998, 2008 Theo de Raadt
 * Copyright (c) 1997, 2008-2009 Todd C. Miller
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>

#define MKTEMP_NAME	0
#define MKTEMP_FILE	1
#define MKTEMP_DIR	2

#define TEMPCHARS	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
#define NUM_CHARS	(sizeof(TEMPCHARS) - 1)
#define MIN_X		6

#ifndef nitems
#define nitems(_a)	(sizeof((_a)) / sizeof((_a)[0]))
#endif

static int
mktemp_internal(char *path, int slen, int mode)
{
	char *start, *cp, *ep;
	const char *tempchars = TEMPCHARS;
	unsigned int tries;
	struct stat sb;
	size_t len;
	int fd;

	len = strlen(path);
	if (len < MIN_X || slen < 0 || (size_t)slen > len - MIN_X) {
		errno = EINVAL;
		return(-1);
	}
	ep = path + len - slen;

	for (start = ep; start > path && start[-1] == 'X'; start--)
		;
	if (ep - start < MIN_X) {
		errno = EINVAL;
		return(-1);
	}

	tries = INT_MAX;
	do {
		cp = start;
		do {
			unsigned short rbuf[16];
			unsigned int i;

			/*
			 * Avoid lots of arc4random() calls by using
			 * a buffer sized for up to 16 Xs at a time.
			 */
			arc4random_buf(rbuf, sizeof(rbuf));
			for (i = 0; i < nitems(rbuf) && cp != ep; i++)
				*cp++ = tempchars[rbuf[i] % NUM_CHARS];
		} while (cp != ep);

		switch (mode) {
		case MKTEMP_NAME:
			if (lstat(path, &sb) != 0)
				return(errno == ENOENT ? 0 : -1);
			break;
		case MKTEMP_FILE:
			fd = open(path, O_CREAT|O_EXCL|O_RDWR, S_IRUSR|S_IWUSR);
			if (fd != -1 || errno != EEXIST)
				return(fd);
			break;
		case MKTEMP_DIR:
			if (mkdir(path, S_IRUSR|S_IWUSR|S_IXUSR) == 0)
				return(0);
			if (errno != EEXIST)
				return(-1);
			break;
		}
	} while (--tries);

	errno = EEXIST;
	return(-1);
}

char *_mktemp(char *);

char *
_mktemp(char *path)
{
	if (mktemp_internal(path, 0, MKTEMP_NAME) == -1)
		return(NULL);
	return(path);
}

__warn_references(mktemp,
    "warning: mktemp() possibly used unsafely; consider using mkstemp()");

char *
mktemp(char *path)
{
	return(_mktemp(path));
}

int
mkstemp(char *path)
{
	return(mktemp_internal(path, 0, MKTEMP_FILE));
}

int
mkstemps(char *path, int slen)
{
	return(mktemp_internal(path, slen, MKTEMP_FILE));
}

char *
mkdtemp(char *path)
{
	int error;

	error = mktemp_internal(path, 0, MKTEMP_DIR);
	return(error ? NULL : path);
}