/mandos/trunk

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

/*

 * Usplash - Read a password from usplash and output 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		/* asprintf() */

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

				   sigemptyset(), sigaddset(), SIGINT,

				   SIGHUP, SIGTERM, sigaction(),

				   SIG_IGN, kill(), SIGKILL */

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

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

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

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

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

				   dirent */

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

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

#include <stdio.h>		/* asprintf(), perror(), sscanf() */

#include <unistd.h>		/* close(), write(), readlink(),

				   read(), STDOUT_FILENO, sleep(),

				   fork(), setuid(), geteuid(),

				   setsid(), chdir(), dup2(),

				   STDERR_FILENO, execv() */

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

				   EXIT_SUCCESS, malloc(), _exit() */

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

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

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

sig_atomic_t interrupted_by_signal = 0;

static void termination_handler(__attribute__((unused))int signum){

  interrupted_by_signal = 1;

}

static bool usplash_write(const char *cmd, const char *arg){

  /* 

   * usplash_write("TIMEOUT", "15") will write "TIMEOUT 15\0"

   * usplash_write("PULSATE", NULL) will write "PULSATE\0"

   * SEE ALSO

   *         usplash_write(8)

   */

  int ret;

  int fifo_fd;

  do{

    fifo_fd = open("/dev/.initramfs/usplash_fifo", O_WRONLY);

    if(fifo_fd == -1 and (errno != EINTR or interrupted_by_signal)){

      return false;

    }

  }while(fifo_fd == -1);

  const char *cmd_line;

  size_t cmd_line_len;

  char *cmd_line_alloc = NULL;

  if(arg == NULL){

    cmd_line = cmd;

    cmd_line_len = strlen(cmd);

  }else{

    do{

      ret = asprintf(&cmd_line_alloc, "%s %s", cmd, arg);

      if(ret == -1 and (errno != EINTR or interrupted_by_signal)){

	int e = errno;

	close(fifo_fd);

	errno = e;

	return false;

      }

    }while(ret == -1);

    cmd_line = cmd_line_alloc;

    cmd_line_len = (size_t)ret + 1;

  }

  size_t written = 0;

  ssize_t sret = 0;

  while(not interrupted_by_signal and written < cmd_line_len){

    sret = write(fifo_fd, cmd_line + written,

		 cmd_line_len - written);

    if(sret == -1){

      if(errno != EINTR or interrupted_by_signal){

	int e = errno;

	close(fifo_fd);

	free(cmd_line_alloc);

	errno = e;

	return false;

      } else {

	continue;

      }

    }

    written += (size_t)sret;

  }

  free(cmd_line_alloc);

  do{

    ret = close(fifo_fd);

    if(ret == -1 and (errno != EINTR or interrupted_by_signal)){

      return false;

    }

  }while(ret == -1);

  if(interrupted_by_signal){

    return false;

  }

  return true;

}

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

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

  int ret = 0;

  ssize_t sret;

  bool an_error_occured = false;

  /* Create prompt string */

  char *prompt = NULL;

  {

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

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

    const char prompt_start[] = "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){

      return EXIT_FAILURE;

    }

  }

  /* Find usplash process */

  pid_t usplash_pid = 0;

  char *cmdline = NULL;

  size_t cmdline_len = 0;

  const char usplash_name[] = "/sbin/usplash";

  {

    DIR *proc_dir = opendir("/proc");

    if(proc_dir == NULL){

      free(prompt);

      perror("opendir");

      return EXIT_FAILURE;

    }

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

	proc_ent != NULL;

	proc_ent = readdir(proc_dir)){

      pid_t pid;

      /* In the GNU C library, pid_t is always int */

      ret = sscanf(proc_ent->d_name, "%d", &pid);

      if(ret != 1){

	/* Not a process */

	continue;

      }

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

	 /proc/<pid>/exe link */

      char exe_target[sizeof(usplash_name)];

      {

	/* create file name string */

	char *exe_link;

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

	if(ret == -1){

	  perror("asprintf");

	  free(prompt);

	  closedir(proc_dir);

	  return EXIT_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;

	  }

	  perror("lstat");

	  free(exe_link);

	  free(prompt);

	  closedir(proc_dir);

	  return EXIT_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(usplash_name, exe_target,

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

	usplash_pid = pid;

	/* Read and save the command line of usplash in "cmdline" */

	{

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

	  int cl_fd;

	  {

	    char *cmdline_filename;

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

			   proc_ent->d_name);

	    if(ret == -1){

	      perror("asprintf");

	      free(prompt);

	      closedir(proc_dir);

	      return EXIT_FAILURE;

	    }

	    cl_fd = open(cmdline_filename, O_RDONLY);

	    if(cl_fd == -1){

	      perror("open");

	      free(cmdline_filename);

	      free(prompt);

	      closedir(proc_dir);

	      return EXIT_FAILURE;

	    }

	    free(cmdline_filename);

	  }

	  size_t cmdline_allocated = 0;

	  char *tmp;

	  const size_t blocksize = 1024;

	  do{

	    if(cmdline_len + blocksize > cmdline_allocated){

	      tmp = realloc(cmdline, cmdline_allocated + blocksize);

	      if(tmp == NULL){

		perror("realloc");

		free(cmdline);

		free(prompt);

		closedir(proc_dir);

		return EXIT_FAILURE;

	      }

	      cmdline = tmp;

	      cmdline_allocated += blocksize;

	    }

	    sret = read(cl_fd, cmdline + cmdline_len,

			cmdline_allocated - cmdline_len);

	    if(sret == -1){

	      perror("read");

	      free(cmdline);

	      free(prompt);

	      closedir(proc_dir);

	      return EXIT_FAILURE;

	    }

	    cmdline_len += (size_t)sret;

	  } while(sret != 0);

	  close(cl_fd);

	}

	break;

      }

    }

    closedir(proc_dir);

  }

  if(usplash_pid == 0){

    free(prompt);

    return EXIT_FAILURE;

  }

  /* Set up the signal handler */

  {

    struct sigaction old_action,

      new_action = { .sa_handler = termination_handler,

		     .sa_flags = 0 };

    sigemptyset(&new_action.sa_mask);

    sigaddset(&new_action.sa_mask, SIGINT);

    sigaddset(&new_action.sa_mask, SIGHUP);

    sigaddset(&new_action.sa_mask, SIGTERM);

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

    if(ret == -1){

      perror("sigaction");

      free(prompt);

      return EXIT_FAILURE;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	perror("sigaction");

	free(prompt);

	return EXIT_FAILURE;

      }

    }

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

    if(ret == -1){

      perror("sigaction");

      free(prompt);

      return EXIT_FAILURE;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	perror("sigaction");

	free(prompt);

	return EXIT_FAILURE;

      }

    }

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

    if(ret == -1){

      perror("sigaction");

      free(prompt);

      return EXIT_FAILURE;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	perror("sigaction");

	free(prompt);

	return EXIT_FAILURE;

      }

    }

  }

  /* Write command to FIFO */

  if(not interrupted_by_signal){

    if(not usplash_write("TIMEOUT", "0")

       and (errno != EINTR)){

      perror("usplash_write");

      an_error_occured = true;

    }

  }

  if(not interrupted_by_signal and not an_error_occured){

    if(not usplash_write("INPUTQUIET", prompt)

       and (errno != EINTR)){

      perror("usplash_write");

      an_error_occured = true;

    }

  }

  free(prompt);

  /* This is not really a loop; while() is used to be able to "break"

     out of it; those breaks are marked "Big" */

  while(not interrupted_by_signal and not an_error_occured){

    char *buf = NULL;

    size_t buf_len = 0;

    /* Open FIFO */

    int fifo_fd;

    do{

      fifo_fd = open("/dev/.initramfs/usplash_outfifo", O_RDONLY);

      if(fifo_fd == -1){

	if(errno != EINTR){

	  perror("open");

	  an_error_occured = true;

	  break;

	}

	if(interrupted_by_signal){

	  break;

	}

      }

    }while(fifo_fd == -1);

    if(interrupted_by_signal or an_error_occured){

      break;			/* Big */

    }

    /* Read from FIFO */

    size_t buf_allocated = 0;

    const size_t blocksize = 1024;

    do{

      if(buf_len + blocksize > buf_allocated){

	char *tmp = realloc(buf, buf_allocated + blocksize);

	if(tmp == NULL){

	  perror("realloc");

	  an_error_occured = true;

	  break;

	}

	buf = tmp;

	buf_allocated += blocksize;

      }

      do{

	sret = read(fifo_fd, buf + buf_len, buf_allocated - buf_len);

	if(sret == -1){

	  if(errno != EINTR){

	    perror("read");

	    an_error_occured = true;

	    break;

	  }

	  if(interrupted_by_signal){

	    break;

	  }

	}

      }while(sret == -1);

      if(interrupted_by_signal or an_error_occured){

	break;

      }

      buf_len += (size_t)sret;

    }while(sret != 0);

    close(fifo_fd);

    if(interrupted_by_signal or an_error_occured){

      break;			/* Big */

    }

    if(not usplash_write("TIMEOUT", "15")

       and (errno != EINTR)){

	perror("usplash_write");

	an_error_occured = true;

    }

    if(interrupted_by_signal or an_error_occured){

      break;			/* Big */

    }

    /* Print password to stdout */

    size_t written = 0;

    while(written < buf_len){

      do{

	sret = write(STDOUT_FILENO, buf + written, buf_len - written);

	if(sret == -1){

	  if(errno != EINTR){

	    perror("write");

	    an_error_occured = true;

	    break;

	  }

	  if(interrupted_by_signal){

	    break;

	  }

	}

      }while(sret == -1);

      if(interrupted_by_signal or an_error_occured){

	break;

      }

      written += (size_t)sret;

    }

    free(buf);

    if(not interrupted_by_signal and not an_error_occured){

      free(cmdline);

      return EXIT_SUCCESS;

    }

    break;			/* Big */

  }				/* end of non-loop while() */

  /* If we got here, an error or interrupt must have happened */

  /* Create argc and argv for new usplash*/

  int cmdline_argc = 0;

  char **cmdline_argv = malloc(sizeof(char *));

  {

    size_t position = 0;

    while(position < cmdline_len){

      char **tmp = realloc(cmdline_argv,

			   (sizeof(char *)

			    * (size_t)(cmdline_argc + 2)));

      if(tmp == NULL){

	perror("realloc");

	free(cmdline_argv);

	return EXIT_FAILURE;

      }

      cmdline_argv = tmp;

      cmdline_argv[cmdline_argc] = cmdline + position;

      cmdline_argc++;

      position += strlen(cmdline + position) + 1;

    }

    cmdline_argv[cmdline_argc] = NULL;

  }

  /* Kill old usplash */

  kill(usplash_pid, SIGTERM);

  sleep(2);

  while(kill(usplash_pid, 0) == 0){

    kill(usplash_pid, SIGKILL);

    sleep(1);

  }

  pid_t new_usplash_pid = fork();

  if(new_usplash_pid == 0){

    /* Child; will become new usplash process */

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

       the real user ID (_mandos) */

    ret = setuid(geteuid());

    if(ret == -1){

      perror("setuid");

    }

    setsid();

    ret = chdir("/");

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

/*       _exit(EXIT_SUCCESS); */

/*     } */

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

    if(ret == -1){

      perror("dup2");

      _exit(EXIT_FAILURE);

    }

    execv(usplash_name, cmdline_argv);

    if(not interrupted_by_signal){

      perror("execv");

    }

    free(cmdline);

    free(cmdline_argv);

    _exit(EXIT_FAILURE);

  }

  free(cmdline);

  free(cmdline_argv);

  sleep(2);

  if(not usplash_write("PULSATE", NULL)

     and (errno != EINTR)){

    perror("usplash_write");

  }

  return EXIT_FAILURE;

}