/*
 * Copyright (c) 2010  Philip Guenther <guenther@openbsd.org>
 *
 * Public domain.
 *
 * Verify that mkstemp() and mkstemps() doesn't overrun or underrun
 * the template buffer and that it can generate names that don't
 * contain any X's
 */

#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <unistd.h>

#define MAX_TEMPLATE_LEN        10
#define MAX_TRIES               100
#define MIN_Xs                  6

#define SUFFIX  ".suff"
#define SLEN    (sizeof SUFFIX - 1)

long pg;

/*
 * verify that a path generated by mkstemp() or mkstemp() looks like a
 * reasonable expansion of the template and matches the fd.  Returns true
 * if all the X's were replaced with non-X's
 */
int
check(int fd, char const *path, char const *prefix, size_t plen,
    char const *suffix, size_t slen, int tlen)
{
        struct stat sb, fsb;
        char const *p;

        if (tlen < MIN_Xs) {
                if (fd >= 0)
                        errx(1, "mkstemp(%s) succeed with too few Xs", path);
                if (errno != EINVAL)
                        err(1, "mkstemp(%s) failed with wrong errno", path);
                return 1;
        }
        if (fd < 0)
                err(1, "mkstemp(%s)", path);
        if (stat(path, &sb))
                err(1, "stat(%s)", path);
        if (fstat(fd, &fsb))
                err(1, "fstat(%d==%s)", fd, path);
        if (sb.st_dev != fsb.st_dev || sb.st_ino != fsb.st_ino)
                errx(1, "stat mismatch");
        close(fd);
        if (memcmp(path, prefix, plen) != 0)
                errx(1, "prefix changed!  %s vs %s", prefix, path);
        if (memcmp(path + plen + tlen, suffix, slen + 1) != 0)
                errx(1, "suffix changed!  %s vs %s", suffix, path);
        for (p = path + plen; p < path + plen + tlen; p++)
                if (*p == '\0')
                        errx(1, "unexpected truncation");
                else if (*p == 'X')
                        return 0;
        return 1;
}


void
try_mkstemp(char *p, char const *prefix, int len)
{
        char *q;
        size_t plen = strlen(prefix);
        int tries, fd;

        for (tries = 0; tries < MAX_TRIES; tries++) {
                memcpy(p, prefix, plen);
                memset(p + plen, 'X', len);
                p[plen + len] = '\0';
                fd = mkstemp(p);
                if (check(fd, p, prefix, plen, "", 0, len))
                        return;
        }
        errx(1, "exceeded MAX_TRIES");
}

void
try_mkstemps(char *p, char const *prefix, int len, char const *suffix)
{
        char *q;
        size_t plen = strlen(prefix);
        size_t slen = strlen(suffix);
        int tries, fd;

        for (tries = 0; tries < MAX_TRIES; tries++) {
                memcpy(p, prefix, plen);
                memset(p + plen, 'X', len);
                memcpy(p + plen + len, suffix, slen + 1);
                fd = mkstemps(p, slen);
                if (check(fd, p, prefix, plen, suffix, slen, len))
                        return;
        }
        errx(1, "exceeded MAX_TRIES");
}

int
main(void)
{
        struct stat sb, fsb;
        char cwd[PATH_MAX + 1];
        char *p;
        size_t clen;
        int i;

        pg = sysconf(_SC_PAGESIZE);
        if (getcwd(cwd, sizeof cwd - 1) == NULL)
                err(1, "getcwd");
        clen = strlen(cwd);
        cwd[clen++] = '/';
        cwd[clen] = '\0';
        p = mmap(NULL, pg * 3, PROT_READ | PROT_WRITE, MAP_ANON, -1, 0);
        if (p == MAP_FAILED)
                err(1, "mmap");
        if (mprotect(p, pg, PROT_NONE) || mprotect(p + pg * 2, pg, PROT_NONE))
                err(1, "mprotect");
        p += pg;

        i = MAX_TEMPLATE_LEN + 1;
        while (i-- > 0) {
                /* try first at the start of a page, no prefix */
                try_mkstemp(p, "", i);
                /* now at the end of the page, no prefix */
                try_mkstemp(p + pg - i - 1, "", i);
                /* start of the page, prefixed with the cwd */
                try_mkstemp(p, cwd, i);
                /* how about at the end of the page, prefixed with cwd? */
                try_mkstemp(p + pg - clen - i - 1, cwd, i);

                /* again, with mkstemps() and an empty suffix */
                /* try first at the start of a page, no prefix */
                try_mkstemps(p, "", i, "");
                /* now at the end of the page, no prefix */
                try_mkstemps(p + pg - i - 1, "", i, "");
                /* start of the page, prefixed with the cwd */
                try_mkstemps(p, cwd, i, "");
                /* how about at the end of the page, prefixed with cwd? */
                try_mkstemps(p + pg - clen - i - 1, cwd, i, "");

                /* mkstemps() and a non-empty suffix */
                /* try first at the start of a page, no prefix */
                try_mkstemps(p, "", i, SUFFIX);
                /* now at the end of the page, no prefix */
                try_mkstemps(p + pg - i - SLEN - 1, "", i, SUFFIX);
                /* start of the page, prefixed with the cwd */
                try_mkstemps(p, cwd, i, SUFFIX);
                /* how about at the end of the page, prefixed with cwd? */
                try_mkstemps(p + pg - clen - i - SLEN - 1, cwd, i, SUFFIX);

        }

        return 0;
}