/mandos/trunk

/*  -*- coding: utf-8; mode: c; mode: orgtbl -*- */

/*

 * Password-prompt - Read a password from the terminal and print it

 * 

 * Copyright © 2008,2009 Teddy Hogeborn

 * Copyright © 2008,2009 Björn Påhlsson

 * 

 * 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/>.

 * 

 * Contact the authors at <https://www.fukt.bsnet.se/~belorn/> and

 * <https://www.fukt.bsnet.se/~teddy/>.

 */

#define _GNU_SOURCE		/* getline() */

#include <termios.h> 		/* struct termios, tcsetattr(),

				   TCSAFLUSH, tcgetattr(), ECHO */

#include <unistd.h>		/* struct termios, tcsetattr(),

				   STDIN_FILENO, TCSAFLUSH,

				   tcgetattr(), ECHO */

#include <signal.h>		/* sig_atomic_t, raise(), struct

				   sigaction, sigemptyset(),

				   sigaction(), sigaddset(), SIGINT,

				   SIGQUIT, SIGHUP, SIGTERM,

				   raise() */

#include <stddef.h>		/* NULL, size_t, ssize_t */

#include <sys/types.h>		/* ssize_t */

#include <stdlib.h>		/* EXIT_SUCCESS, EXIT_FAILURE,

				   getopt_long, getenv() */

#include <stdio.h>		/* fprintf(), stderr, getline(),

				   stdin, feof(), perror(), fputc(),

				   stdout, getopt_long */

#include <errno.h>		/* errno, EINVAL */

#include <iso646.h>		/* or, not */

#include <stdbool.h>		/* bool, false, true */

#include <string.h> 		/* strlen, rindex, strncmp, strcmp */

#include <argp.h>		/* struct argp_option, struct

				   argp_state, struct argp,

				   argp_parse(), error_t,

				   ARGP_KEY_ARG, ARGP_KEY_END,

				   ARGP_ERR_UNKNOWN */

volatile sig_atomic_t quit_now = 0;

int signal_received;

bool debug = false;

const char *argp_program_version = "password-prompt " VERSION;

const char *argp_program_bug_address = "<mandos@fukt.bsnet.se>";

static void termination_handler(int signum){

  if(quit_now){

    return;

  }

  quit_now = 1;

  signal_received = signum;

}

int main(int argc, char **argv){

  ssize_t ret;

  size_t n;

  struct termios t_new, t_old;

  char *buffer = NULL;

  char *prefix = NULL;

  int status = EXIT_SUCCESS;

  struct sigaction old_action,

    new_action = { .sa_handler = termination_handler,

		   .sa_flags = 0 };

  {

    struct argp_option options[] = {

      { .name = "prefix", .key = 'p',

	.arg = "PREFIX", .flags = 0,

	.doc = "Prefix shown before the prompt", .group = 2 },

      { .name = "debug", .key = 128,

	.doc = "Debug mode", .group = 3 },

      { .name = NULL }

    };

    error_t parse_opt (int key, char *arg, struct argp_state *state){

      switch (key){

      case 'p':

	prefix = arg;

	break;

      case 128:

	debug = true;

	break;

      case ARGP_KEY_ARG:

	argp_usage(state);

	break;

      case ARGP_KEY_END:

	break;

      default:

	return ARGP_ERR_UNKNOWN;

      }

      return 0;

    }

    struct argp argp = { .options = options, .parser = parse_opt,

			 .args_doc = "",

			 .doc = "Mandos password-prompt -- Read and"

			 " output a password" };

    ret = argp_parse(&argp, argc, argv, 0, 0, NULL);

    if(ret == ARGP_ERR_UNKNOWN){

      fprintf(stderr, "Unknown error while parsing arguments\n");

      return EXIT_FAILURE;

    }

  }

  if(debug){

    fprintf(stderr, "Starting %s\n", argv[0]);

  }

  if(debug){

    fprintf(stderr, "Storing current terminal attributes\n");

  }

  if(tcgetattr(STDIN_FILENO, &t_old) != 0){

    perror("tcgetattr");

    return EXIT_FAILURE;

  }

  sigemptyset(&new_action.sa_mask);

  ret = sigaddset(&new_action.sa_mask, SIGINT);

  if(ret == -1){

    perror("sigaddset");

    return EXIT_FAILURE;

  }

  ret = sigaddset(&new_action.sa_mask, SIGHUP);

  if(ret == -1){

    perror("sigaddset");

    return EXIT_FAILURE;

  }

  ret = sigaddset(&new_action.sa_mask, SIGTERM);

  if(ret == -1){

    perror("sigaddset");

    return EXIT_FAILURE;

  }

  /* Need to check if the handler is SIG_IGN before handling:

     | [[info:libc:Initial Signal Actions]] |

     | [[info:libc:Basic Signal Handling]]  |

  */

  ret = sigaction(SIGINT, NULL, &old_action);

  if(ret == -1){

    perror("sigaction");

    return EXIT_FAILURE;

  }

  if(old_action.sa_handler != SIG_IGN){

    ret = sigaction(SIGINT, &new_action, NULL);

    if(ret == -1){

      perror("sigaction");

      return EXIT_FAILURE;

    }

  }

  ret = sigaction(SIGHUP, NULL, &old_action);

  if(ret == -1){

    perror("sigaction");

    return EXIT_FAILURE;

  }

  if(old_action.sa_handler != SIG_IGN){

    ret = sigaction(SIGHUP, &new_action, NULL);

    if(ret == -1){

      perror("sigaction");

      return EXIT_FAILURE;

    }

  }

  ret = sigaction(SIGTERM, NULL, &old_action);

  if(ret == -1){

    perror("sigaction");

    return EXIT_FAILURE;

  }

  if(old_action.sa_handler != SIG_IGN){

    ret = sigaction(SIGTERM, &new_action, NULL);

    if(ret == -1){

      perror("sigaction");

      return EXIT_FAILURE;

    }

  }

  if(debug){

    fprintf(stderr, "Removing echo flag from terminal attributes\n");

  }

  t_new = t_old;

  t_new.c_lflag &= ~ECHO;

  if(tcsetattr(STDIN_FILENO, TCSAFLUSH, &t_new) != 0){

    perror("tcsetattr-echo");

    return EXIT_FAILURE;

  }

  if(debug){

    fprintf(stderr, "Waiting for input from stdin \n");

  }

  while(true){

    if(quit_now){

      if(debug){

	fprintf(stderr, "Interrupted by signal, exiting.\n");

      }

      status = EXIT_FAILURE;

      break;

    }

    if(prefix){

      fprintf(stderr, "%s ", prefix);

    }

    {

      const char *cryptsource = getenv("cryptsource");

      const char *crypttarget = getenv("crypttarget");

      const char *const prompt

	= "Enter passphrase to unlock the disk";

      if(cryptsource == NULL){

	if(crypttarget == NULL){

	  fprintf(stderr, "%s: ", prompt);

	} else {

	  fprintf(stderr, "%s (%s): ", prompt, crypttarget);

	}

      } else {

	if(crypttarget == NULL){

	  fprintf(stderr, "%s %s: ", prompt, cryptsource);

	} else {

	  fprintf(stderr, "%s %s (%s): ", prompt, cryptsource,

		  crypttarget);

	}

      }

    }

    ret = getline(&buffer, &n, stdin);

    if(ret > 0){

      status = EXIT_SUCCESS;

      /* Make n = data size instead of allocated buffer size */

      n = (size_t)ret;

      /* Strip final newline */

      if(n>0 and buffer[n-1] == '\n'){

	buffer[n-1] = '\0';	/* not strictly necessary */

	n--;

      }

      size_t written = 0;

      while(written < n){

	ret = write(STDOUT_FILENO, buffer + written, n - written);

	if(ret < 0){

	  perror("write");

	  status = EXIT_FAILURE;

	  break;

	}

	written += (size_t)ret;

      }

      break;

    }

    if(ret < 0){

      if(errno != EINTR and not feof(stdin)){

	perror("getline");

	status = EXIT_FAILURE;

	break;

      }

    }

    /* if(ret == 0), then the only sensible thing to do is to retry to

       read from stdin */

    fputc('\n', stderr);

    if(debug and not quit_now){

      /* If quit_now is nonzero, we were interrupted by a signal, and

	 will print that later, so no need to show this too. */

      fprintf(stderr, "getline() returned 0, retrying.\n");

    }

  }

  free(buffer);

  if(debug){

    fprintf(stderr, "Restoring terminal attributes\n");

  }

  if(tcsetattr(STDIN_FILENO, TCSAFLUSH, &t_old) != 0){

    perror("tcsetattr+echo");

  }

  if(quit_now){

    sigemptyset(&old_action.sa_mask);

    old_action.sa_handler = SIG_DFL;

    ret = sigaction(signal_received, &old_action, NULL);

    if(ret == -1){

      perror("sigaction");

    }

    raise(signal_received);

  }

  if(debug){

    fprintf(stderr, "%s is exiting with status %d\n", argv[0],

	    status);

  }

  if(status == EXIT_SUCCESS){

    fputc('\n', stderr);

  }

  return status;

}