/*      $OpenBSD: setresuid_effective_exec.c,v 1.3 2021/12/15 18:42:38 anton Exp $      */
/*
 *      Written by Bret Stephen Lambert <blambert@openbsd.org> 2014
 *      Public Domain.
 */

#include <sys/types.h>
#include <sys/signal.h>
#include <sys/proc.h>
#include <sys/sysctl.h>
#include <sys/wait.h>

#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pwd.h>
#include <unistd.h>

#include "setuid_regress.h"

int
main(int argc, char *argv[])
{
        struct kinfo_proc        kproc;
        struct passwd           *pw;
        char                    *toexec = NULL;
        uid_t                    uid;

        if (argc > 1) {
                argv ++;
                if ((toexec = strdup(argv[0])) == NULL)
                        err(1, "strdup");
        }

        if ((pw = getpwnam(_SETUID_REGRESS_USER)) == NULL)
                err(1, "unknown user \"%s\"", _SETUID_REGRESS_USER);

        uid = getuid();

        if (setresuid(-1, pw->pw_uid, -1) == -1)
                err(1, "setuid");
        checkuids(uid, pw->pw_uid, uid, "setuid");

        /* should only respond to setuid upon exec */
        if (issetugid())
                errx(1, "process incorrectly as issetugid()");

        if (read_kproc_pid(&kproc, getpid()) == -1)
                err(1, "kproc read failed");

        if (!(kproc.p_psflags & PS_SUGID))
                errx(1, "PS_SUGID not set");
        if (kproc.p_psflags & PS_SUGIDEXEC)
                errx(1, "PS_SUGIDEXEC incorrectly set");

        if (toexec != NULL)
                if (execv(toexec, argv) == -1)
                        err(1, "exec of %s failed", toexec);
        free(toexec);

        exit(0);
}