/mandos/trunk

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

/*

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

 * 

 * Copyright © 2008-2018 Teddy Hogeborn

 * Copyright © 2008-2018 Björn Påhlsson

 * 

 * This file is part of Mandos.

 * 

 * Mandos 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.

 * 

 * Mandos 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 Mandos.  If not, see <http://www.gnu.org/licenses/>.

 * 

 * Contact the authors at <mandos@recompile.se>.

 */

#define _GNU_SOURCE		/* getline(), asprintf() */

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

				   TCSAFLUSH, tcgetattr(), ECHO */

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

				   STDIN_FILENO, TCSAFLUSH,

				   tcgetattr(), ECHO, readlink() */

#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, struct dirent, pid_t,

				   ssize_t, open() */

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

				   getenv(), free() */

#include <dirent.h>		/* scandir(), alphasort() */

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

				   stdin, feof(), fputc(), vfprintf(),

				   vasprintf() */

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

				   EFAULT, EFBIG, EIO, ENOSPC, EINTR

				*/

#include <error.h>		/* error() */

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

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

#include <inttypes.h>		/* strtoumax() */

#include <sys/stat.h>		/* struct stat, lstat(), open() */

#include <string.h>		/* strlen, rindex, memcmp, strerror()

				 */

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

				   argp_state, struct argp,

				   argp_parse(), error_t,

				   ARGP_KEY_ARG, ARGP_KEY_END,

				   ARGP_ERR_UNKNOWN */

#include <sysexits.h>		/* EX_SOFTWARE, EX_OSERR,

				   EX_UNAVAILABLE, EX_IOERR, EX_OK */

#include <fcntl.h>		/* open() */

#include <stdarg.h>		/* va_list, va_start(), ... */

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@recompile.se>";

/* Needed for conflict resolution */

const char plymouth_name[] = "plymouthd";

/* Function to use when printing errors */

__attribute__((format (gnu_printf, 3, 4)))

void error_plus(int status, int errnum, const char *formatstring,

		...){

  va_list ap;

  char *text;

  int ret;

  va_start(ap, formatstring);

  ret = vasprintf(&text, formatstring, ap);

  if(ret == -1){

    fprintf(stderr, "Mandos plugin %s: ",

	    program_invocation_short_name);

    vfprintf(stderr, formatstring, ap);

    fprintf(stderr, ": %s\n", strerror(errnum));

    error(status, errno, "vasprintf while printing error");

    return;

  }

  fprintf(stderr, "Mandos plugin ");

  error(status, errnum, "%s", text);

  free(text);

}

static void termination_handler(int signum){

  if(quit_now){

    return;

  }

  quit_now = 1;

  signal_received = signum;

}

bool conflict_detection(void){

  /* plymouth conflicts with password-prompt since both want to read

     from the terminal.  Password-prompt will exit if it detects

     plymouth since plymouth performs the same functionality.

   */

  __attribute__((nonnull))

  int is_plymouth(const struct dirent *proc_entry){

    int ret;

    int cl_fd;

    {

      uintmax_t proc_id;

      char *tmp;

      errno = 0;

      proc_id = strtoumax(proc_entry->d_name, &tmp, 10);

      if(errno != 0 or *tmp != '\0'

	 or proc_id != (uintmax_t)((pid_t)proc_id)){

	return 0;

      }

    }

    char *cmdline_filename;

    ret = asprintf(&cmdline_filename, "/proc/%s/cmdline",

		   proc_entry->d_name);

    if(ret == -1){

      error_plus(0, errno, "asprintf");

      return 0;

    }

    /* Open /proc/<pid>/cmdline */

    cl_fd = open(cmdline_filename, O_RDONLY);

    free(cmdline_filename);

    if(cl_fd == -1){

      if(errno != ENOENT){

	error_plus(0, errno, "open");

      }

      return 0;

    }

    char *cmdline = NULL;

    {

      size_t cmdline_len = 0;

      size_t cmdline_allocated = 0;

      char *tmp;

      const size_t blocksize = 1024;

      ssize_t sret;

      do {

	/* Allocate more space? */

	if(cmdline_len + blocksize + 1 > cmdline_allocated){

	  tmp = realloc(cmdline, cmdline_allocated + blocksize + 1);

	  if(tmp == NULL){

	    error_plus(0, errno, "realloc");

	    free(cmdline);

	    close(cl_fd);

	    return 0;

	  }

	  cmdline = tmp;

	  cmdline_allocated += blocksize;

	}

	/* Read data */

	sret = read(cl_fd, cmdline + cmdline_len,

		    cmdline_allocated - cmdline_len);

	if(sret == -1){

	  error_plus(0, errno, "read");

	  free(cmdline);

	  close(cl_fd);

	  return 0;

	}

	cmdline_len += (size_t)sret;

      } while(sret != 0);

      ret = close(cl_fd);

      if(ret == -1){

	error_plus(0, errno, "close");

	free(cmdline);

	return 0;

      }

      cmdline[cmdline_len] = '\0'; /* Make sure it is terminated */

    }

    /* we now have cmdline */

    /* get basename */

    char *cmdline_base = strrchr(cmdline, '/');

    if(cmdline_base != NULL){

      cmdline_base += 1;		/* skip the slash */

    } else {

      cmdline_base = cmdline;

    }

    if(strcmp(cmdline_base, plymouth_name) != 0){

      if(debug){

	fprintf(stderr, "\"%s\" is not \"%s\"\n", cmdline_base,

		plymouth_name);

      }

      free(cmdline);

      return 0;

    }

    if(debug){

      fprintf(stderr, "\"%s\" equals \"%s\"\n", cmdline_base,

	      plymouth_name);

    }

    free(cmdline);

    return 1;

  }

  struct dirent **direntries = NULL;

  int ret;

  ret = scandir("/proc", &direntries, is_plymouth, alphasort);

  if(ret == -1){

    error_plus(1, errno, "scandir");

  }

  {

    int i = ret;

    while(i--){

      free(direntries[i]);

    }

  }

  free(direntries);

  return ret > 0;

}

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

  ssize_t sret;

  int 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 },

      /*

       * These reproduce what we would get without ARGP_NO_HELP

       */

      { .name = "help", .key = '?',

	.doc = "Give this help list", .group = -1 },

      { .name = "usage", .key = -3,

	.doc = "Give a short usage message", .group = -1 },

      { .name = "version", .key = 'V',

	.doc = "Print program version", .group = -1 },

      { .name = NULL }

    };

    __attribute__((nonnull(3)))

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

      errno = 0;

      switch (key){

      case 'p':

	prefix = arg;

	break;

      case 128:

	debug = true;

	break;

	/*

	 * These reproduce what we would get without ARGP_NO_HELP

	 */

      case '?':			/* --help */

	argp_state_help(state, state->out_stream,

			(ARGP_HELP_STD_HELP | ARGP_HELP_EXIT_ERR)

			& ~(unsigned int)ARGP_HELP_EXIT_OK);

      case -3:			/* --usage */

	argp_state_help(state, state->out_stream,

			ARGP_HELP_USAGE | ARGP_HELP_EXIT_ERR);

      case 'V':			/* --version */

	fprintf(state->out_stream, "%s\n", argp_program_version);

	exit(argp_err_exit_status);

	break;

      default:

	return ARGP_ERR_UNKNOWN;

      }

      return errno;

    }

    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,

		     ARGP_IN_ORDER | ARGP_NO_HELP, NULL, NULL);

    switch(ret){

    case 0:

      break;

    case ENOMEM:

    default:

      errno = ret;

      error_plus(0, errno, "argp_parse");

      return EX_OSERR;

    case EINVAL:

      return EX_USAGE;

    }

  }

  if(debug){

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

  }

  if(conflict_detection()){

    if(debug){

      fprintf(stderr, "Stopping %s because of conflict\n", argv[0]);

    }

    return EXIT_FAILURE;

  }

  if(debug){

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

  }

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

    int e = errno;

    error_plus(0, errno, "tcgetattr");

    switch(e){

    case EBADF:

    case ENOTTY:

      return EX_UNAVAILABLE;

    default:

      return EX_OSERR;

    }

  }

  sigemptyset(&new_action.sa_mask);

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

  if(ret == -1){

    error_plus(0, errno, "sigaddset");

    return EX_OSERR;

  }

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

  if(ret == -1){

    error_plus(0, errno, "sigaddset");

    return EX_OSERR;

  }

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

  if(ret == -1){

    error_plus(0, errno, "sigaddset");

    return EX_OSERR;

  }

  /* 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){

    error_plus(0, errno, "sigaction");

    return EX_OSERR;

  }

  if(old_action.sa_handler != SIG_IGN){

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

    if(ret == -1){

      error_plus(0, errno, "sigaction");

      return EX_OSERR;

    }

  }

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

  if(ret == -1){

    error_plus(0, errno, "sigaction");

    return EX_OSERR;

  }

  if(old_action.sa_handler != SIG_IGN){

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

    if(ret == -1){

      error_plus(0, errno, "sigaction");

      return EX_OSERR;

    }

  }

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

  if(ret == -1){

    error_plus(0, errno, "sigaction");

    return EX_OSERR;

  }

  if(old_action.sa_handler != SIG_IGN){

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

    if(ret == -1){

      error_plus(0, errno, "sigaction");

      return EX_OSERR;

    }

  }

  if(debug){

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

  }

  t_new = t_old;

  t_new.c_lflag &= ~(tcflag_t)ECHO;

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

    int e = errno;

    error_plus(0, errno, "tcsetattr-echo");

    switch(e){

    case EBADF:

    case ENOTTY:

      return EX_UNAVAILABLE;

    case EINVAL:

    default:

      return EX_OSERR;

    }

  }

  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("CRYPTTAB_SOURCE");

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

      /* Before cryptsetup 1.1.0~rc2 */

      if(cryptsource == NULL){

	cryptsource = getenv("cryptsource");

      }

      if(crypttarget == NULL){

	crypttarget = getenv("crypttarget");

      }

      const char *const prompt1 = "Unlocking the disk";

      const char *const prompt2 = "Enter passphrase";

      if(cryptsource == NULL){

	if(crypttarget == NULL){

	  fprintf(stderr, "%s to unlock the disk: ", prompt2);

	} else {

	  fprintf(stderr, "%s (%s)\n%s: ", prompt1, crypttarget,

		  prompt2);

	}

      } else {

	if(crypttarget == NULL){

	  fprintf(stderr, "%s %s\n%s: ", prompt1, cryptsource,

		  prompt2);

	} else {

	  fprintf(stderr, "%s %s (%s)\n%s: ", prompt1, cryptsource,

		  crypttarget, prompt2);

	}

      }

    }

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

    if(sret > 0){

      status = EXIT_SUCCESS;

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

      n = (size_t)sret;

      /* 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){

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

	if(sret < 0){

	  int e = errno;

	  error_plus(0, errno, "write");

	  switch(e){

	  case EBADF:

	  case EFAULT:

	  case EINVAL:

	  case EFBIG:

	  case EIO:

	  case ENOSPC:

	  default:

	    status = EX_IOERR;

	    break;

	  case EINTR:

	    status = EXIT_FAILURE;

	    break;

	  }

	  break;

	}

	written += (size_t)sret;

      }

      sret = close(STDOUT_FILENO);

      if(sret == -1){

	int e = errno;

	error_plus(0, errno, "close");

	switch(e){

	case EBADF:

	  status = EX_OSFILE;

	  break;

	case EIO:

	default:

	  status = EX_IOERR;

	  break;

	}

      }

      break;

    }

    if(sret < 0){

      int e = errno;

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

	error_plus(0, errno, "getline");

	switch(e){

	case EBADF:

	  status = EX_UNAVAILABLE;

	  break;

	case EIO:

	case EINVAL:

	default:

	  status = EX_IOERR;

	  break;

	}

	break;

      }

    }

    /* if(sret == 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){

    error_plus(0, errno, "tcsetattr+echo");