path: root/src/cerberus.c

/**
 * cerberus – Minimal login program
 * 
 * Copyright © 2013  Mattias Andrée (maandree@member.fsf.org)
 * 
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */
#include <stdio.h>
#include <termios.h>
#include <unistd.h>


/**
 * Mane method
 * 
 * @param   argc  The number of command line arguments
 * @param   argv  The command line arguments
 * @return        Return code
 */
int main(int argc, char** argv)
{
  char* username = NULL;
  char* hostname = NULL;
  char preserve_env = 0;
  struct termios saved_stty;
  struct termios stty;
  int i;
  
  /* Disable echoing */
  tcgetattr(STDIN_FILENO, &saved_stty);
  stty = saved_stty;
  stty.c_lflag &= ~ECHO;
  tcsetattr(STDIN_FILENO, TCSAFLUSH, &stty);
  /* This should be done as early and quickly as possible so as little
     as possible of the passphrase gets leaked to the output if the user
     begins entering the passphrase directly after the username. */
  
  /* Parse command line arguments */
  {
    char double_dashed = 0;
    char hostname_on_next = 0;
    for (i = 1; i < argc; i++)
      {
	char *arg = *(argv + i);
	char c;
	
	if (*arg == 0)
	  ;
	else if ((*arg == '-') && (double_dashed == 0))
	  while ((c = *(++arg)))
	    if ((c == 'V') || (c == 'H'))
	      ;
	    else if (c == 'p')
	      preserve_env = 1;
	    else if (c == 'h')
	      {
		if (*(arg + 1))
		  hostname = arg + 1;
		else
		  hostname_on_next = 1;
		break;
	      }
	    else if (c == 'f')
	      {
		if (*(arg + 1))
		  username = arg + 1;
		break;
	      }
	    else if (c == '-')
	      {
		double_dashed = 1;
		break;
	      }
	    else
	      fprintf(stderr, "%s: unrecognised options: -%c\n", *argv, c);
	else if (hostname_on_next)
	  {
	    hostname = arg;
	    hostname_on_next = 0;
	  }
	else
	  username = arg;
      }
  }
  
  printf("Passphrase: ");
  fflush(stdout);
  
  
  /* Reset terminal settings */
  tcsetattr(STDIN_FILENO, TCSAFLUSH, &saved_stty);
  
  return 0;
}