/mandos/trunk

/*  -*- coding: utf-8 -*- */

/*

 * Splashy - Read a password from splashy and output it

 * 

 * Copyright © 2008-2017 Teddy Hogeborn

 * Copyright © 2008-2017 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		/* TEMP_FAILURE_RETRY(), asprintf() */

#include <signal.h>		/* sig_atomic_t, struct sigaction,

				   sigemptyset(), sigaddset(), SIGINT,

				   SIGHUP, SIGTERM, sigaction,

				   SIG_IGN, kill(), SIGKILL */

#include <stddef.h>		/* NULL */

#include <stdlib.h>		/* getenv() */

#include <stdio.h>		/* asprintf(), vasprintf(), vprintf(),

				   fprintf() */

#include <stdlib.h>		/* EXIT_FAILURE, free(),

				   EXIT_SUCCESS */

#include <sys/types.h>		/* pid_t, DIR, struct dirent,

				   ssize_t */

#include <dirent.h>		/* opendir(), readdir(), closedir() */

#include <inttypes.h>		/* intmax_t, strtoimax() */

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

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

#include <unistd.h>		/* readlink(), fork(), execl(),

				   sleep(), dup2() STDERR_FILENO,

				   STDOUT_FILENO, _exit(),

				   pause() */

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

#include <errno.h>		/* errno, EACCES, ENOTDIR, ELOOP,

				   ENOENT, ENAMETOOLONG, EMFILE,

				   ENFILE, ENOMEM, ENOEXEC, EINVAL,

				   E2BIG, EFAULT, EIO, ETXTBSY,

				   EISDIR, ELIBBAD, EPERM, EINTR,

				   ECHILD */

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

#include <sys/wait.h>		/* waitpid(), WIFEXITED(),

				   WEXITSTATUS() */

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

				   EX_UNAVAILABLE */

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

sig_atomic_t interrupted_by_signal = 0;

int signal_received;

/* 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, ": ");

    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(interrupted_by_signal){

    return;

  }

  interrupted_by_signal = 1;

  signal_received = signum;

}

int main(__attribute__((unused))int argc,

	 __attribute__((unused))char **argv){

  int ret = 0;

  char *prompt = NULL;

  DIR *proc_dir = NULL;

  pid_t splashy_pid = 0;

  pid_t splashy_command_pid = 0;

  int exitstatus = EXIT_FAILURE;

  /* Create prompt string */

  {

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

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

    const char *const prompt_start = "getpass "

      "Enter passphrase to unlock the disk";

    if(cryptsource == NULL){

      if(crypttarget == NULL){

	ret = asprintf(&prompt, "%s: ", prompt_start);

      } else {

	ret = asprintf(&prompt, "%s (%s): ", prompt_start,

		       crypttarget);

      }

    } else {

      if(crypttarget == NULL){

	ret = asprintf(&prompt, "%s %s: ", prompt_start, cryptsource);

      } else {

	ret = asprintf(&prompt, "%s %s (%s): ", prompt_start,

		       cryptsource, crypttarget);

      }

    }

    if(ret == -1){

      prompt = NULL;

      exitstatus = EX_OSERR;

      goto failure;

    }

  }

  /* Find splashy process */

  {

    const char splashy_name[] = "/sbin/splashy";

    proc_dir = opendir("/proc");

    if(proc_dir == NULL){

      int e = errno;

      error_plus(0, errno, "opendir");

      switch(e){

      case EACCES:

      case ENOTDIR:

      case ELOOP:

      case ENOENT:

      default:

	exitstatus = EX_OSFILE;

	break;

      case ENAMETOOLONG:

      case EMFILE:

      case ENFILE:

      case ENOMEM:

	exitstatus = EX_OSERR;

	break;

      }

      goto failure;

    }

    for(struct dirent *proc_ent = readdir(proc_dir);

	proc_ent != NULL;

	proc_ent = readdir(proc_dir)){

      pid_t pid;

      {

	intmax_t tmpmax;

	char *tmp;

	errno = 0;

	tmpmax = strtoimax(proc_ent->d_name, &tmp, 10);

	if(errno != 0 or tmp == proc_ent->d_name or *tmp != '\0'

	   or tmpmax != (pid_t)tmpmax){

	  /* Not a process */

	  continue;

	}

	pid = (pid_t)tmpmax;

      }

      /* Find the executable name by doing readlink() on the

	 /proc/<pid>/exe link */

      char exe_target[sizeof(splashy_name)];

      ssize_t sret;

      {

	char *exe_link;

	ret = asprintf(&exe_link, "/proc/%s/exe", proc_ent->d_name);

	if(ret == -1){

	  error_plus(0, errno, "asprintf");

	  exitstatus = EX_OSERR;

	  goto failure;

	}

	/* Check that it refers to a symlink owned by root:root */

	struct stat exe_stat;

	ret = lstat(exe_link, &exe_stat);

	if(ret == -1){

	  if(errno == ENOENT){

	    free(exe_link);

	    continue;

	  }

	  int e = errno;

	  error_plus(0, errno, "lstat");

	  free(exe_link);

	  switch(e){

	  case EACCES:

	  case ENOTDIR:

	  case ELOOP:

	  default:

	    exitstatus = EX_OSFILE;

	    break;

	  case ENAMETOOLONG:

	    exitstatus = EX_OSERR;

	    break;

	  }

	  goto failure;

	}

	if(not S_ISLNK(exe_stat.st_mode)

	   or exe_stat.st_uid != 0

	   or exe_stat.st_gid != 0){

	  free(exe_link);

	  continue;

	}

	sret = readlink(exe_link, exe_target, sizeof(exe_target));

	free(exe_link);

      }

      if((sret == ((ssize_t)sizeof(exe_target)-1))

	 and (memcmp(splashy_name, exe_target,

		     sizeof(exe_target)-1) == 0)){

	splashy_pid = pid;

	break;

      }

    }

    closedir(proc_dir);

    proc_dir = NULL;

  }

  if(splashy_pid == 0){

    exitstatus = EX_UNAVAILABLE;

    goto failure;

  }

  /* Set up the signal handler */

  {

    struct sigaction old_action,

      new_action = { .sa_handler = termination_handler,

		     .sa_flags = 0 };

    sigemptyset(&new_action.sa_mask);

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

    if(ret == -1){

      error_plus(0, errno, "sigaddset");

      exitstatus = EX_OSERR;

      goto failure;

    }

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

    if(ret == -1){

      error_plus(0, errno, "sigaddset");

      exitstatus = EX_OSERR;

      goto failure;

    }

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

    if(ret == -1){

      error_plus(0, errno, "sigaddset");

      exitstatus = EX_OSERR;

      goto failure;

    }

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

    if(ret == -1){

      error_plus(0, errno, "sigaction");

      exitstatus = EX_OSERR;

      goto failure;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	error_plus(0, errno, "sigaction");

	exitstatus = EX_OSERR;

	goto failure;

      }

    }

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

    if(ret == -1){

      error_plus(0, errno, "sigaction");

      exitstatus = EX_OSERR;

      goto failure;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	error_plus(0, errno, "sigaction");

	exitstatus = EX_OSERR;

	goto failure;

      }

    }

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

    if(ret == -1){

      error_plus(0, errno, "sigaction");

      exitstatus = EX_OSERR;

      goto failure;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	error_plus(0, errno, "sigaction");

	exitstatus = EX_OSERR;

	goto failure;

      }

    }

  }

  if(interrupted_by_signal){

    goto failure;

  }

  /* Fork off the splashy command to prompt for password */

  splashy_command_pid = fork();

  if(splashy_command_pid != 0 and interrupted_by_signal){

    goto failure;

  }

  if(splashy_command_pid == -1){

    error_plus(0, errno, "fork");

    exitstatus = EX_OSERR;

    goto failure;

  }

  /* Child */

  if(splashy_command_pid == 0){

    if(not interrupted_by_signal){

      const char splashy_command[] = "/sbin/splashy_update";

      execl(splashy_command, splashy_command, prompt, (char *)NULL);

      int e = errno;

      error_plus(0, errno, "execl");

      switch(e){

      case EACCES:

      case ENOENT:

      case ENOEXEC:

      case EINVAL:

	_exit(EX_UNAVAILABLE);

      case ENAMETOOLONG:

      case E2BIG:

      case ENOMEM:

      case EFAULT:

      case EIO:

      case EMFILE:

      case ENFILE:

      case ETXTBSY:

      default:

	_exit(EX_OSERR);

      case ENOTDIR:

      case ELOOP:

      case EISDIR:

#ifdef ELIBBAD

      case ELIBBAD:		/* Linux only */

#endif

      case EPERM:

	_exit(EX_OSFILE);

      }

    }

    free(prompt);

    _exit(EXIT_FAILURE);

  }

  /* Parent */

  free(prompt);

  prompt = NULL;

  if(interrupted_by_signal){

    goto failure;

  }

  /* Wait for command to complete */

  {

    int status;

    do {

      ret = waitpid(splashy_command_pid, &status, 0);

    } while(ret == -1 and errno == EINTR

	    and not interrupted_by_signal);

    if(interrupted_by_signal){

      goto failure;

    }

    if(ret == -1){

      error_plus(0, errno, "waitpid");

      if(errno == ECHILD){

	splashy_command_pid = 0;

      }

    } else {

      /* The child process has exited */

      splashy_command_pid = 0;

      if(WIFEXITED(status) and WEXITSTATUS(status) == 0){

	return EXIT_SUCCESS;

      }

    }

  }

 failure:

  free(prompt);

  if(proc_dir != NULL){

    TEMP_FAILURE_RETRY(closedir(proc_dir));

  }

  if(splashy_command_pid != 0){

    TEMP_FAILURE_RETRY(kill(splashy_command_pid, SIGTERM));

    TEMP_FAILURE_RETRY(kill(splashy_pid, SIGTERM));

    sleep(2);

    while(TEMP_FAILURE_RETRY(kill(splashy_pid, 0)) == 0){

      TEMP_FAILURE_RETRY(kill(splashy_pid, SIGKILL));

      sleep(1);

    }

    pid_t new_splashy_pid = (pid_t)TEMP_FAILURE_RETRY(fork());

    if(new_splashy_pid == 0){

      /* Child; will become new splashy process */

      /* Make the effective user ID (root) the only user ID instead of

	 the real user ID (_mandos) */

      ret = setuid(geteuid());

      if(ret == -1){

	error_plus(0, errno, "setuid");

      }

      setsid();

      ret = chdir("/");

      if(ret == -1){

	error_plus(0, errno, "chdir");

      }

/*       if(fork() != 0){ */

/* 	_exit(EXIT_SUCCESS); */

/*       } */

      ret = dup2(STDERR_FILENO, STDOUT_FILENO); /* replace stdout */

      if(ret == -1){

	error_plus(0, errno, "dup2");

	_exit(EX_OSERR);

      }

      execl("/sbin/splashy", "/sbin/splashy", "boot", (char *)NULL);

      {

	int e = errno;

	error_plus(0, errno, "execl");

	switch(e){

	case EACCES:

	case ENOENT:

	case ENOEXEC:

	default:

	  _exit(EX_UNAVAILABLE);

	case ENAMETOOLONG:

	case E2BIG:

	case ENOMEM:

	  _exit(EX_OSERR);

	case ENOTDIR:

	case ELOOP:

	  _exit(EX_OSFILE);

	}

      }

    }

  }

  if(interrupted_by_signal){

    struct sigaction signal_action;

    sigemptyset(&signal_action.sa_mask);

    signal_action.sa_handler = SIG_DFL;

    ret = (int)TEMP_FAILURE_RETRY(sigaction(signal_received,

					    &signal_action, NULL));

    if(ret == -1){

      error_plus(0, errno, "sigaction");

    }

    do {

      ret = raise(signal_received);

    } while(ret != 0 and errno == EINTR);

    if(ret != 0){

      error_plus(0, errno, "raise");

      abort();

    }

    TEMP_FAILURE_RETRY(pause());

  }

  return exitstatus;

}