xref: /xsrc/external/mit/xdm/dist/xdmshell/xdmshell.c

/*
 * xdmshell - simple program for running xdm from login
 *
 *
Copyright 1988, 1998  The Open Group

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documentation for any purpose is hereby granted without fee, provided that
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in this Software without prior written authorization from The Open Group.
 * *
 * Author:  Jim Fulton, MIT X Consortium
 *
 * This program should probably be setuid to root.
 *
 * WARNING:  Make sure that you tailor your Xresources file to have a
 * way of invoking the abort-display() action.  Otherwise, you won't be able
 * bring down X when you are finished.
 */


#include <stdio.h>
#include "dm.h"
#include <errno.h>
#include <unistd.h>

#ifndef BINDIR
# define BINDIR "/usr/bin/X11"
#endif

/*
 * HP-UX does have vfork, but A/UX doesn't
 */
#ifdef HAVE_WORKING_VFORK /* autoconf's preferred name */
# define HAS_VFORK
#endif

#ifndef HAS_VFORK
# define vfork() fork()
#endif

static char *ProgramName;

static int exec_args (
    char *filename,
    char **args)
{
    pid_t pid;
    waitType status;

    if (!filename) return -1;

    if (filename[0] != '/') {
	fprintf (stderr,
	       "%s:  attempt to execute program with relative pathname:  %s\n",
		 ProgramName, filename);
	return -1;
    }

    if (access (filename, X_OK) != 0) return -1;

    switch (pid = vfork ()) {
      case -1:						/* error */
	return -1;
      case 0:    					/* child */
	execv (filename, args);
	_exit (1);
	/* NOTREACHED */
      default:						/* parent */
	while (wait (&status) != pid) ;
    }
    return waitCode (status);
}

#if defined(sun)
static int exec_one_arg (
    char    *filename,
    char    *arg)
{
    char    *argv[3];

    argv[0] = filename;
    argv[1] = arg;
    argv[2] = NULL;
    return exec_args (filename, argv);
}
#endif

int
main (
    int argc,
    char *argv[])
{
    int ttyfd;
    char cmdbuf[256];
    char *args[10];

    ProgramName = argv[0];

    if (argc > 1) {
	fprintf (stderr, "usage:  %s\r\n", ProgramName);
	exit (1);
    }

    ttyfd = open ("/dev/tty", O_RDWR, 0);
    if (ttyfd < 3) {			/* stdin = 0, stdout = 1, stderr = 2 */
	fprintf (stderr,
		 "%s:  must be run directly from the console.\r\n",
		 ProgramName);
	exit (1);
    }
    (void) close (ttyfd);

    /* make xdm run in a non-setuid environment */
    if (setuid (geteuid()) == -1) {
	fprintf(stderr, "%s: cannot setuid (error %d, %s)\r\n",
		ProgramName, errno, strerror(errno));
	exit(1);
    }

    /*
     * exec /usr/bin/X11/xdm -nodaemon -udpPort 0
     */
    strcpy (cmdbuf, BINDIR);
    strcat (cmdbuf, "/xdm");
    args[0] = cmdbuf;
    args[1] = "-nodaemon";
    args[2] = "-udpPort";
    args[3] = "0";
    args[4] = NULL;
    if (exec_args (cmdbuf, args) == -1) {
	fprintf (stderr, "%s:  unable to execute %s (error %d, %s)\r\n",
		 ProgramName, cmdbuf, errno, strerror(errno));
	exit (1);
    }

#ifdef sun
    strcpy (cmdbuf, BINDIR);
    strcat (cmdbuf, "/kbd_mode");
    (void) exec_one_arg (cmdbuf, "-a");
#endif

    exit (0);
    /*NOTREACHED*/
}