/mandos/trunk

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

/*

 * Splashy - Read a password from splashy 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 <stddef.h>		/* NULL */

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

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

#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, SCNdMAX */

#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() */

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

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

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

				   WEXITSTATUS() */

sig_atomic_t interrupted_by_signal = 0;

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

  interrupted_by_signal = 1;

}

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

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

  int ret = 0;

  /* Create prompt string */

  char *prompt = NULL;

  {

    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){

      return EXIT_FAILURE;

    }

  }

  /* Find splashy process */

  pid_t splashy_pid = 0;

  {

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

    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;

      {

	intmax_t tmpmax;

	int numchars;

	ret = sscanf(proc_ent->d_name, "%" SCNdMAX "%n", &tmpmax,

		     &numchars);

	if(ret < 1 or tmpmax != (pid_t)tmpmax

	   or proc_ent->d_name[numchars] != '\0'){

	  /* 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){

	  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(splashy_name, exe_target,

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

	splashy_pid = pid;

	break;

      }

    }

    closedir(proc_dir);

  }

  if(splashy_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;

      }

    }

  }

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

  pid_t splashy_command_pid = 0;

  if(not interrupted_by_signal){

    splashy_command_pid = fork();

    if(splashy_command_pid == -1){

      if(not interrupted_by_signal){

	perror("fork");

      }

      return EXIT_FAILURE;

    }

    /* Child */

    if(splashy_command_pid == 0){

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

      ret = execl(splashy_command, splashy_command, prompt,

		  (char *)NULL);

      if(not interrupted_by_signal){

	perror("execl");

      }

      free(prompt);

      _exit(EXIT_FAILURE);

    }

  }

  /* Parent */

  free(prompt);

  /* Wait for command to complete */

  if(not interrupted_by_signal and splashy_command_pid != 0){

    int status;

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

    if(ret == -1){

      if(errno != EINTR){

	perror("waitpid");

      }

      if(errno == ECHILD){

	splashy_command_pid = 0;

      }

    } else {

      /* The child process has exited */

      splashy_command_pid = 0;

      if(not interrupted_by_signal and WIFEXITED(status)

	 and WEXITSTATUS(status)==0){

	return EXIT_SUCCESS;

      }

    }

  }

  kill(splashy_pid, SIGTERM);

  if(interrupted_by_signal and splashy_command_pid != 0){

    kill(splashy_command_pid, SIGTERM);

  }

  sleep(2);

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

    kill(splashy_pid, SIGKILL);

    sleep(1);

  }

  pid_t new_splashy_pid = 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){

      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);

    }

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

    if(not interrupted_by_signal){

      perror("execl");

    }

    _exit(EXIT_FAILURE);

  }

  return EXIT_FAILURE;

}