/*      $NetBSD: gettemp.c,v 1.25 2025/12/18 17:45:29 christos Exp $    */

/*
 * Copyright (c) 1987, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "gettemp.h"

#if !HAVE_NBTOOL_CONFIG_H || !HAVE_MKSTEMP || !HAVE_MKDTEMP

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)mktemp.c    8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: gettemp.c,v 1.25 2025/12/18 17:45:29 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

static const unsigned char padchar[] =
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

#ifndef O_DIRECT
#define O_DIRECT 0
#endif
#ifndef O_CLOFORK
#define O_CLOFORK 0
#endif

#if HAVE_NBTOOL_CONFIG_H
static uint32_t
arc4random_uniform(uint32_t upper_bound)
{
        if (upper_bound == 0)
                return 0;

        uint32_t r;
        uint32_t limit = RAND_MAX - (RAND_MAX % upper_bound);

        do
                r = (uint32_t)rand();
        while (r >= limit);

        return r % upper_bound;
}
#endif

int
GETTEMP(char *path, int *doopen, int domkdir, int slen, int oflags)
{
        char *start, *trv, *suffp, *carryp;
        const char *pad;
        struct stat sbuf;
        int rval;
        uint32_t r;
        char carrybuf[MAXPATHLEN];

        _DIAGASSERT(path != NULL);
        /* doopen may be NULL */
        if ((doopen != NULL && domkdir) || slen < 0 ||
            (oflags & ~(O_APPEND | O_DIRECT | O_SHLOCK | O_EXLOCK | O_SYNC |
            O_CLOEXEC | O_CLOFORK)) != 0) {
                errno = EINVAL;
                return 0;
        }

        for (trv = path; *trv != '\0'; ++trv)
                continue;

        if (trv - path >= MAXPATHLEN) {
                errno = ENAMETOOLONG;
                return 0;
        }
        trv -= slen;
        suffp = trv;
        --trv;
        if (trv < path || NULL != strchr(suffp, '/')) {
                errno = EINVAL;
                return 0;
        }

        /* Fill space with random characters */
        while (trv >= path && *trv == 'X') {
                r = arc4random_uniform((unsigned int)(sizeof(padchar) - 1));
                *trv-- = padchar[r];
        }
        start = trv + 1;

        /* save first combination of random characters */
        memcpy(carrybuf, start, (size_t)(suffp - start));

        /*
         * check the target directory.
         */
        if (doopen != NULL || domkdir) {
                for (; trv > path; --trv) {
                        if (*trv == '/') {
                                *trv = '\0';
                                rval = stat(path, &sbuf);
                                *trv = '/';
                                if (rval != 0)
                                        return 0;
                                if (!S_ISDIR(sbuf.st_mode)) {
                                        errno = ENOTDIR;
                                        return 0;
                                }
                                break;
                        }
                }
        }

        for (;;) {
                if (doopen) {
                        if ((*doopen = open(path, O_CREAT|O_EXCL|O_RDWR|oflags,
                            0600)) != -1)
                                return 1;
                        if (errno != EEXIST)
                                return 0;
                } else if (domkdir) {
                        if (mkdir(path, 0700) != -1)
                                return 1;
                        if (errno != EEXIST)
                                return 0;
                } else if (lstat(path, &sbuf))
                        return errno == ENOENT;

                /*
                 * If we have a collision,
                 * cycle through the space of filenames
                 */
                for (trv = start, carryp = carrybuf;;) {
                        /* have we tried all possible permutations? */
                        if (trv == suffp)
                                return 0; /* yes - exit with EEXIST */
                        pad = strchr((const char *)padchar, *trv);
                        if (pad == NULL) {
                                /* this should never happen */
                                errno = EIO;
                                return 0;
                        }
                        /* increment character */
                        *trv = (*++pad == '\0') ? padchar[0] : *pad;
                        /* carry to next position? */
                        if (*trv == *carryp) {
                                /* increment position and loop */
                                ++trv;
                                ++carryp;
                        } else {
                                /* try with new name */
                                break;
                        }
                }
        }
        /*NOTREACHED*/
}

#endif /* !HAVE_NBTOOL_CONFIG_H || !HAVE_MKSTEMP || !HAVE_MKDTEMP */