/mandos/trunk

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

/*

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

#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 <error.h>

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

				   dirent */

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

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

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

				   fprintf() */

#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(),

				   getenv() */

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

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

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

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

#include <argz.h>		/* argz_count(), argz_extract() */

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

sig_atomic_t interrupted_by_signal = 0;

int signal_received;

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

/* 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;

}

static bool usplash_write(int *fifo_fd_r,

			  const char *cmd, const char *arg){

  /* 

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

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

   * SEE ALSO

   *         usplash_write(8)

   */

  int ret;

  if(*fifo_fd_r == -1){

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

    if(ret == -1){

      return false;

    }

    *fifo_fd_r = ret;

  }

  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) + 1;

  } else {

    do {

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

      if(ret == -1){

	int e = errno;

	close(*fifo_fd_r);

	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(written < cmd_line_len){

    sret = write(*fifo_fd_r, cmd_line + written,

		 cmd_line_len - written);

    if(sret == -1){

      int e = errno;

      close(*fifo_fd_r);

      free(cmd_line_alloc);

      errno = e;

      return false;

    }

    written += (size_t)sret;

  }

  free(cmd_line_alloc);

  return true;

}

/* Create prompt string */

char *makeprompt(void){

  int ret = 0;

  char *prompt;

  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 NULL;

  }

  return prompt;

}

pid_t find_usplash(char **cmdline_r, size_t *cmdline_len_r){

  int ret = 0;

  ssize_t sret = 0;

  char *cmdline = NULL;

  size_t cmdline_len = 0;

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

  if(proc_dir == NULL){

    error_plus(0, errno, "opendir");

    return -1;

  }

  errno = 0;

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

      proc_ent != NULL;

      proc_ent = readdir(proc_dir)){

    pid_t pid;

    {

      intmax_t tmpmax;

      char *tmp;

      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 */

	errno = 0;

	continue;

      }

      pid = (pid_t)tmpmax;

    }

    /* 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){

	error_plus(0, errno, "asprintf");

	goto fail_find_usplash;

      }

      /* 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;

	}

	error_plus(0, errno, "lstat");

	free(exe_link);

	goto fail_find_usplash;

      }

      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);

    }

    /* Compare executable name */

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

       or (memcmp(usplash_name, exe_target,

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

      /* Not it */

      continue;

    }

    /* Found usplash */

    /* 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){

	  error_plus(0, errno, "asprintf");

	  goto fail_find_usplash;

	}

	cl_fd = open(cmdline_filename, O_RDONLY);

	free(cmdline_filename);

	if(cl_fd == -1){

	  error_plus(0, errno, "open");

	  goto fail_find_usplash;

	}

      }

      size_t cmdline_allocated = 0;

      char *tmp;

      const size_t blocksize = 1024;

      do {

	/* Allocate more space? */

	if(cmdline_len + blocksize > cmdline_allocated){

	  tmp = realloc(cmdline, cmdline_allocated + blocksize);

	  if(tmp == NULL){

	    error_plus(0, errno, "realloc");

	    close(cl_fd);

	    goto fail_find_usplash;

	  }

	  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");

	  close(cl_fd);

	  goto fail_find_usplash;

	}

	cmdline_len += (size_t)sret;

      } while(sret != 0);

      ret = close(cl_fd);

      if(ret == -1){

	error_plus(0, errno, "close");

	goto fail_find_usplash;

      }

    }

    /* Close directory */

    ret = closedir(proc_dir);

    if(ret == -1){

      error_plus(0, errno, "closedir");

      goto fail_find_usplash;

    }

    /* Success */

    *cmdline_r = cmdline;

    *cmdline_len_r = cmdline_len;

    return pid;

  }

 fail_find_usplash:

  free(cmdline);

  if(proc_dir != NULL){

    int e = errno;

    closedir(proc_dir);

    errno = e;

  }

  return 0;

}

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

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

  int ret = 0;

  ssize_t sret;

  int fifo_fd = -1;

  int outfifo_fd = -1;

  char *buf = NULL;

  size_t buf_len = 0;

  pid_t usplash_pid = -1;

  bool usplash_accessed = false;

  int status = EXIT_FAILURE;	/* Default failure exit status */

  char *prompt = makeprompt();

  if(prompt == NULL){

    status = EX_OSERR;

    goto failure;

  }

  /* Find usplash process */

  char *cmdline = NULL;

  size_t cmdline_len = 0;

  usplash_pid = find_usplash(&cmdline, &cmdline_len);

  if(usplash_pid == 0){

    status = 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");

      status = EX_OSERR;

      goto failure;

    }

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

    if(ret == -1){

      error_plus(0, errno, "sigaddset");

      status = EX_OSERR;

      goto failure;

    }

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

    if(ret == -1){

      error_plus(0, errno, "sigaddset");

      status = EX_OSERR;

      goto failure;

    }

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

    if(ret == -1){

      if(errno != EINTR){

	error_plus(0, errno, "sigaction");

	status = EX_OSERR;

      }

      goto failure;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	if(errno != EINTR){

	  error_plus(0, errno, "sigaction");

	  status = EX_OSERR;

	}

	goto failure;

      }

    }

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

    if(ret == -1){

      if(errno != EINTR){

	error_plus(0, errno, "sigaction");

	status = EX_OSERR;

      }

      goto failure;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	if(errno != EINTR){

	  error_plus(0, errno, "sigaction");

	  status = EX_OSERR;

	}

	goto failure;

      }

    }

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

    if(ret == -1){

      if(errno != EINTR){

	error_plus(0, errno, "sigaction");

	status = EX_OSERR;

      }

      goto failure;

    }

    if(old_action.sa_handler != SIG_IGN){

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

      if(ret == -1){

	if(errno != EINTR){

	  error_plus(0, errno, "sigaction");

	  status = EX_OSERR;

	}

	goto failure;

      }

    }

  }

  usplash_accessed = true;

  /* Write command to FIFO */

  if(not usplash_write(&fifo_fd, "TIMEOUT", "0")){

    if(errno != EINTR){

      error_plus(0, errno, "usplash_write");

      status = EX_OSERR;

    }

    goto failure;

  }

  if(interrupted_by_signal){

    goto failure;

  }

  if(not usplash_write(&fifo_fd, "INPUTQUIET", prompt)){

    if(errno != EINTR){

      error_plus(0, errno, "usplash_write");

      status = EX_OSERR;

    }

    goto failure;

  }

  if(interrupted_by_signal){

    goto failure;

  }

  free(prompt);

  prompt = NULL;

  /* Read reply from usplash */

  /* Open FIFO */

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

  if(outfifo_fd == -1){

    if(errno != EINTR){

      error_plus(0, errno, "open");

      status = EX_OSERR;

    }

    goto failure;

  }

  if(interrupted_by_signal){

    goto failure;

  }

  /* Read from FIFO */

  size_t buf_allocated = 0;

  const size_t blocksize = 1024;

  do {

    /* Allocate more space */

    if(buf_len + blocksize > buf_allocated){

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

      if(tmp == NULL){

	if(errno != EINTR){

	  error_plus(0, errno, "realloc");

	  status = EX_OSERR;

	}

	goto failure;

      }

      buf = tmp;

      buf_allocated += blocksize;

    }

    sret = read(outfifo_fd, buf + buf_len,

		buf_allocated - buf_len);

    if(sret == -1){

      if(errno != EINTR){

	error_plus(0, errno, "read");

	status = EX_OSERR;

      }

      close(outfifo_fd);

      goto failure;

    }

    if(interrupted_by_signal){

      break;

    }

    buf_len += (size_t)sret;

  } while(sret != 0);

  ret = close(outfifo_fd);

  if(ret == -1){

    if(errno != EINTR){

      error_plus(0, errno, "close");

      status = EX_OSERR;

    }

    goto failure;

  }

  outfifo_fd = -1;

  if(interrupted_by_signal){

    goto failure;

  }

  if(not usplash_write(&fifo_fd, "TIMEOUT", "15")){

    if(errno != EINTR){

      error_plus(0, errno, "usplash_write");

      status = EX_OSERR;

    }

    goto failure;

  }

  if(interrupted_by_signal){

    goto failure;

  }

  ret = close(fifo_fd);

  if(ret == -1){

    if(errno != EINTR){

      error_plus(0, errno, "close");

      status = EX_OSERR;

    }

    goto failure;

  }

  fifo_fd = -1;

  /* 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){

	  error_plus(0, errno, "write");

	  status = EX_OSERR;

	}

	goto failure;

      }

    } while(sret == -1);

    if(interrupted_by_signal){

      goto failure;

    }

    written += (size_t)sret;

  }

  free(buf);

  buf = NULL;

  if(interrupted_by_signal){

    goto failure;

  }

  free(cmdline);

  return EXIT_SUCCESS;

 failure:

  free(buf);

  free(prompt);

  /* If usplash was never accessed, we can stop now */