/*
 * assume uid/gid combos for testing
 *
 * Copyright (C) 2006 Herbert Poetzl <herbert@13thfloor.at>
 *
 * This program is free software; you can redistribute it and/or modify 
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation; either version 2 of the License, or 
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of 
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License 
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * V0.01 initial implementation
 * V0.02 minor cleanup regarding return code
 *
 */

#include <stdlib.h>
#include <stdio.h>
#include <getopt.h>

#include <sys/types.h>
#include <sys/fsuid.h>
#include <unistd.h>

#define VERSION		"V0.02"

#define SHORT_OPTS	":heu:g:U:G:"

#define USAGE	    "Usage: %s <opts>* -- <program> <args>*\n"

#define OPTIONS	    "Options are:\n" \
                    "  -h,--help         print this help message\n" \
 		    "  -e,--effective    use effective uid/gid\n" \
 		    "  -u,--uid <num>    user id to assume\n" \
 		    "  -g,--gid <num>    group id to assume\n" \
 		    "  -U,--fsuid <num>  filesystem user id\n" \
 		    "  -G,--fsgid <num>  filesystem group id\n"

static const
struct option LONG_OPTS[] = {
	{ "help",	no_argument,       0, 'h' },
	{ "effective",	no_argument,       0, 'e' },
	{ "uid",	required_argument, 0, 'u' },
	{ "gid",	required_argument, 0, 'g' },
	{ "fsuid",	required_argument, 0, 'U' },
	{ "fsgid",	required_argument, 0, 'G' },
	{ 0,0,0,0 }
};

static  char 	*cmd_name = NULL;

static int	opt_uid = 0;
static int 	opt_gid = 0;

static int	opt_fsuid = 0;
static int 	opt_fsgid = 0;

static int  	opt_effective = 0;

static uid_t	uid[2] = {0,0};
static gid_t 	gid[2] = {0,0};


#define check(n,a) do {		\
    	    if  (n(a))		\
	    	perror(#n);	\
    	} while (0)


int	main(int argc, char *argv[])
{
        extern int optind;
        extern char *optarg;

        char c, errflg = 0;

        cmd_name = argv[0];
        while ((c = getopt_long(argc, argv, SHORT_OPTS, LONG_OPTS, 0)) != EOF) {
            switch (c) {
            case 'h':
                fprintf(stderr,
                    "This is %s version " VERSION "\n" 
		    USAGE "\n" OPTIONS "\n"
                    ,cmd_name, cmd_name);
                exit(0);
                break;
		
	    case 'e':
		opt_effective = 1;
	        break;
	    case 'u':
		uid[0] = atoi(optarg);
		opt_uid = 1;
	        break;
	    case 'g':
		gid[0] = atoi(optarg);
		opt_gid = 1;
	        break;
	    case 'U':
		uid[1] = atoi(optarg);
		opt_fsuid = 1;
	        break;
	    case 'G':
		gid[1] = atoi(optarg);
		opt_fsgid = 1;
	        break;
				
            case '?':
            default:
                errflg++;
                break;
            }
        }
        if (errflg) {
            fprintf(stderr, USAGE "%s -h or --help for help.\n",
                cmd_name, cmd_name);
            exit(2);
        }
	
	if (opt_gid) {
    	    if (opt_effective)
	    	check(setegid, gid[0]);
	    else
	    	check(setgid, gid[0]);
	}
	if (opt_uid) {
    	    if (opt_effective)
	    	check(seteuid ,uid[0]);
	    else
	    	check(setuid, uid[0]);
	}
	
	if (opt_fsgid)
	    setfsgid(gid[1]);
	if (opt_fsuid)
	    setfsuid(uid[1]);
	
	if (argc > optind)
	    execvp(argv[optind], argv+optind);
	exit(0);
}