/*      $OpenBSD: setresgid.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 <pwd.h>
#include <unistd.h>

#include "setuid_regress.h"

int
main(int argc, const char *argv[])
{
        struct kinfo_proc        kproc;
        struct passwd           *pw;
        gid_t                    gid;

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

        gid = getgid();

        if (setresgid(pw->pw_gid, -1, -1) == -1)
                err(1, "setgid 0");
        checkgids(pw->pw_gid, gid, gid, "0");

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

        /* we should be able to roll back our gids for now */
        if (setresgid(gid, -1, -1) == -1)
                err(1, "setgid 1");
        checkgids(gid, gid, gid, "1");

        if (setresgid(-1, pw->pw_gid, -1) == -1)
                err(1, "setgid 2");
        checkgids(gid, pw->pw_gid, gid, "2");

        /* we should be able to roll back our gids for now */
        if (setresgid(-1, gid, -1) == -1)
                err(1, "setgid 3");
        checkgids(gid, gid, gid, "3");

        /*
         * after changing our saved gid and dropping superuser privs,
         * we should be able to change our real and effective gids to
         * that of our saved gid, but not to anything else
         */

        if (setresgid(-1, -1, pw->pw_gid) == -1)
                err(1, "setgid 4");
        checkgids(gid, gid, pw->pw_gid, "4");

        if (setresuid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1)
                err(1, "setresuid 4");

        if (setresgid(pw->pw_gid, -1, -1) == -1)
                err(1, "setgid 5");
        checkgids(pw->pw_gid, gid, pw->pw_gid, "5");

        if (setresgid(-1, pw->pw_gid, -1) == -1)
                err(1, "setgid 6");
        checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "6");

        if (setresgid(gid, -1, -1) != -1)
                errx(1, "incorrectly capable of setting real gid");
        checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "7");

        if (setresgid(-1, gid, -1) != -1)
                errx(1, "incorrectly capable of setting effective gid");
        checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9");

        if (setresgid(-1, -1, gid) != -1)
                errx(1, "incorrectly capable of setting saved gid");
        checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9");

        /* sanity-check use of -1 as noop */
        if (setresgid(-1, -1, -1) == -1)
                errx(1, "-1 not properly recognized as noop");
        checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9");

        exit(0);
}