/*
  Copyright (c) 2009 by Jeff Weisberg
  Author: Jeff Weisberg <jaw @ tcp4me.com>
  Created: 2009-Feb-21 11:42 (EST)
  Function: become root
 
  $Id: suex.c,v 1.1 2009/02/21 16:43:46 jaw Exp $

  portions adapted from BSD su
  
*/

#include <stdio.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/time.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <grp.h>
#include <pwd.h>

#define SUPER_GROUP_NAME	"super-users"

char *mytty(void);

main(int argc, char **argv){
		
	int retcode;
	char cmdline[1024];
	int gids[NGROUPS_MAX],gidval;
	int i=0,uid, super_gid;
	int arg, nuid = 0, ngid = 0;
	struct passwd *pwd;
	struct group *grp;
	char *username;

	if ((pwd=getpwuid(uid = getuid()))==NULL){
		/* you have no entry in pw file */
		fprintf(stderr, "suex: who are you\n");
		exit(-1);
	}

	if ( (grp=getgrnam(SUPER_GROUP_NAME))==NULL){
		/* no super user group in group file */
		fprintf(stderr, "suex: super user group non-existant\n");
		exit(-1);
	}
	
	username = strdup(pwd->pw_name);
	openlog("suex:", LOG_PID|LOG_CONS, LOG_AUTH);	/* tell syslog all about it */


	gidval = getgroups(NGROUPS_MAX, gids); /* check if in group super-user */
	while ( (i<=gidval)&&(gids[i] != grp->gr_gid) ) i++;
	if ( gids[i] != grp->gr_gid ){
		syslog(LOG_AUTH|LOG_NOTICE, "suex failed for %s (%d) on %s", username, uid, mytty());
		fprintf(stderr,"You are not authorized to use this command\nSorry!\n");
		exit(-1);
	}

	/* parse cmd line */
	/* -u user */
	for(arg=1; arg<argc; arg++){
	    
	    if( !strcmp(argv[arg], "-u") ){
		pwd = getpwnam( argv[arg+1] );
		if( !pwd ){
		    fprintf(stderr, "no such user %s\n", argv[arg+1]);
		    exit(-1);
		}
		nuid = pwd->pw_uid;
		arg ++;
		continue;
	    }
	    
	    break;
	}

	/* cmdline for logging */
	cmdline[0] = 0;
	for(i=arg; i<argc; i++){
	    if(cmdline[0]) strncat(cmdline, " ", sizeof(cmdline));
	    strncat(cmdline, argv[i], sizeof(cmdline));
	}
	
	setuid( nuid );		/* become root */
	setgid( ngid ); 	/* become daemon group */
	syslog(LOG_AUTH|LOG_INFO, "suex succeded for %s(%d)=>%d on %s [%s]", username, uid, nuid, mytty(), cmdline);
	
	if (argc > arg ){
	    execvp( argv[arg], &argv[arg] );
	}else{
	    char *shell = getenv("SHELL");
	    if( !shell || !*shell ) shell = "sh";
	    execlp( shell, shell, 0 );
	}
	fprintf(stderr, "%s: %s failed\n",argv[0],argv[1]);
	exit(-1);
}

char *mytty(void){
	char *p;
	return((p=ttyname(STDERR_FILENO))?p:"Unknown tty");
}