/mandos/trunk

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

/*

 * Plymouth - Read a password from Plymouth and output it

 * 

 * Copyright © 2010-2018 Teddy Hogeborn

 * Copyright © 2010-2018 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(),

				   kill(), SIG_IGN */

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

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

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

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

				   dirent, waitpid() */

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

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

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

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

				   fscanf(), vasprintf(), fprintf(),

				   vfprintf() */

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

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

				   STDERR_FILENO, execv(), access() */

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

				   EXIT_SUCCESS, malloc(), _exit(),

				   getenv() */

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

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

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

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

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

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

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

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

sig_atomic_t interrupted_by_signal = 0;

/* Used by Ubuntu 11.04 (Natty Narwahl) */

const char plymouth_old_old_pid[] = "/dev/.initramfs/plymouth.pid";

/* Used by Ubuntu 11.10 (Oneiric Ocelot) */

const char plymouth_old_pid[] = "/run/initramfs/plymouth.pid";

/* Used by Debian 9 (stretch) */

const char plymouth_pid[] = "/run/plymouth/pid";

const char plymouth_path[] = "/bin/plymouth";

const char plymouthd_path[] = "/sbin/plymouthd";

const char *plymouthd_default_argv[] = {"/sbin/plymouthd",

					"--mode=boot",

					"--attach-to-session",

					NULL };

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

  if(interrupted_by_signal){

    return;

  }

  interrupted_by_signal = 1;

}

/* 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);

}

/* 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[] = "Unlocking the disk";

  const char prompt_end[] = "Enter passphrase";

  if(cryptsource == NULL){

    if(crypttarget == NULL){

      ret = asprintf(&prompt, "%s\n%s", prompt_start, prompt_end);

    } else {

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

		     crypttarget, prompt_end);

    }

  } else {

    if(crypttarget == NULL){

      ret = asprintf(&prompt, "%s %s\n%s", prompt_start, cryptsource,

		     prompt_end);

    } else {

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

		     cryptsource, crypttarget, prompt_end);

    }

  }

  if(ret == -1){

    return NULL;

  }

  return prompt;

}

void kill_and_wait(pid_t pid){

  TEMP_FAILURE_RETRY(kill(pid, SIGTERM));

  TEMP_FAILURE_RETRY(waitpid(pid, NULL, 0));

}

bool become_a_daemon(void){

  int ret = setuid(geteuid());

  if(ret == -1){

    error_plus(0, errno, "setuid");

  }

  setsid();

  ret = chdir("/");

  if(ret == -1){

    error_plus(0, errno, "chdir");

    return false;

  }

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

  if(ret == -1){

    error_plus(0, errno, "dup2");

    return false;

  }

  return true;

}

__attribute__((nonnull (2, 3)))

bool exec_and_wait(pid_t *pid_return, const char *path,

		   const char * const *argv, bool interruptable,

		   bool daemonize){

  int status;

  int ret;

  pid_t pid;

  pid = fork();

  if(pid == -1){

    error_plus(0, errno, "fork");

    return false;

  }

  if(pid == 0){

    /* Child */

    if(daemonize){

      if(not become_a_daemon()){

	_exit(EX_OSERR);

      }

    }

    char **new_argv = malloc(sizeof(const char *));

    if(new_argv == NULL){

      error_plus(0, errno, "malloc");

      _exit(EX_OSERR);

    }

    char **tmp;

    int i = 0;

    for (; argv[i] != NULL; i++){

      tmp = realloc(new_argv, sizeof(const char *) * ((size_t)i + 2));

      if(tmp == NULL){

	error_plus(0, errno, "realloc");

	free(new_argv);

	_exit(EX_OSERR);

      }

      new_argv = tmp;

      new_argv[i] = strdup(argv[i]);

    }

    new_argv[i] = NULL;

    execv(path, (char *const *)new_argv);

    error_plus(0, errno, "execv");

    _exit(EXIT_FAILURE);

  }

  if(pid_return != NULL){

    *pid_return = pid;

  }

  do {

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

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

	  and ((not interrupted_by_signal)

	       or (not interruptable)));

  if(interrupted_by_signal and interruptable){

    return false;

  }

  if(ret == -1){

    error_plus(0, errno, "waitpid");

    return false;

  }

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

    return true;

  }

  return false;

}

__attribute__((nonnull))

int is_plymouth(const struct dirent *proc_entry){

  int ret;

  {

    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 exe_target[sizeof(plymouthd_path)];

  char *exe_link;

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

  if(ret == -1){

    error_plus(0, errno, "asprintf");

    return 0;

  }

  struct stat exe_stat;

  ret = lstat(exe_link, &exe_stat);

  if(ret == -1){

    free(exe_link);

    if(errno != ENOENT){

      error_plus(0, errno, "lstat");

    }

    return 0;

  }

  if(not S_ISLNK(exe_stat.st_mode)

     or exe_stat.st_uid != 0

     or exe_stat.st_gid != 0){

    free(exe_link);

    return 0;

  }

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

  free(exe_link);

  if((sret != (ssize_t)sizeof(plymouthd_path)-1) or

      (memcmp(plymouthd_path, exe_target,

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

    return 0;

  }

  return 1;

}

pid_t get_pid(void){

  int ret;

  uintmax_t proc_id = 0;

  FILE *pidfile = fopen(plymouth_pid, "r");

  /* Try the new pid file location */

  if(pidfile != NULL){

    ret = fscanf(pidfile, "%" SCNuMAX, &proc_id);

    if(ret != 1){

      proc_id = 0;

    }

    fclose(pidfile);

  }

  /* Try the old pid file location */

  if(proc_id == 0){

    pidfile = fopen(plymouth_old_pid, "r");

    if(pidfile != NULL){

      ret = fscanf(pidfile, "%" SCNuMAX, &proc_id);

      if(ret != 1){

	proc_id = 0;

      }

      fclose(pidfile);

    }

  }

  /* Try the old old pid file location */

  if(proc_id == 0){

    pidfile = fopen(plymouth_old_old_pid, "r");

    if(pidfile != NULL){

      ret = fscanf(pidfile, "%" SCNuMAX, &proc_id);

      if(ret != 1){

	proc_id = 0;

      }

      fclose(pidfile);

    }

  }

  /* Look for a plymouth process */

  if(proc_id == 0){

    struct dirent **direntries = NULL;

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

    if(ret == -1){

      error_plus(0, errno, "scandir");

    }

    if(ret > 0){

      for(int i = ret-1; i >= 0; i--){

	if(proc_id == 0){

	  ret = sscanf(direntries[i]->d_name, "%" SCNuMAX, &proc_id);

	  if(ret < 0){

	    error_plus(0, errno, "sscanf");

	  }

	}

	free(direntries[i]);

      }

    }

    /* scandir might preallocate for this variable (man page unclear).

       even if ret == 0, therefore we need to free it. */

    free(direntries);

  }

  pid_t pid;

  pid = (pid_t)proc_id;

  if((uintmax_t)pid == proc_id){

    return pid;

  }

  return 0;

}

char **getargv(pid_t pid){

  int cl_fd;

  char *cmdline_filename;

  ssize_t sret;

  int ret;

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

		 (uintmax_t)pid);

  if(ret == -1){

    error_plus(0, errno, "asprintf");

    return NULL;

  }

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

  cl_fd = open(cmdline_filename, O_RDONLY);

  free(cmdline_filename);

  if(cl_fd == -1){

    error_plus(0, errno, "open");

    return NULL;

  }

  size_t cmdline_allocated = 0;

  size_t cmdline_len = 0;

  char *cmdline = NULL;

  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");

	free(cmdline);

	close(cl_fd);

	return NULL;

      }

      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 NULL;

    }

    cmdline_len += (size_t)sret;

  } while(sret != 0);

  ret = close(cl_fd);

  if(ret == -1){

    error_plus(0, errno, "close");

    free(cmdline);

    return NULL;

  }

  /* we got cmdline and cmdline_len, ignore rest... */

  char **argv = malloc((argz_count(cmdline, cmdline_len) + 1)

		       * sizeof(char *)); /* Get number of args */

  if(argv == NULL){

    error_plus(0, errno, "argv = malloc()");

    free(cmdline);

    return NULL;

  }

  argz_extract(cmdline, cmdline_len, argv); /* Create argv */

  return argv;

}

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

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

  char *prompt;

  char *prompt_arg;

  pid_t plymouth_command_pid;

  int ret;

  bool bret;

  /* test -x /bin/plymouth */

  ret = access(plymouth_path, X_OK);

  if(ret == -1){

    /* Plymouth is probably not installed.  Don't print an error

       message, just exit. */

    exit(EX_UNAVAILABLE);

  }

  { /* Add signal handlers */

    struct sigaction old_action,

      new_action = { .sa_handler = termination_handler,

		     .sa_flags = 0 };

    sigemptyset(&new_action.sa_mask);

    for(int *sig = (int[]){ SIGINT, SIGHUP, SIGTERM, 0 };

	*sig != 0; sig++){

      ret = sigaddset(&new_action.sa_mask, *sig);

      if(ret == -1){

	error_plus(EX_OSERR, errno, "sigaddset");

      }

      ret = sigaction(*sig, NULL, &old_action);

      if(ret == -1){

	error_plus(EX_OSERR, errno, "sigaction");

      }

      if(old_action.sa_handler != SIG_IGN){

	ret = sigaction(*sig, &new_action, NULL);

	if(ret == -1){

	  error_plus(EX_OSERR, errno, "sigaction");

	}

      }

    }

  }

  /* plymouth --ping */

  bret = exec_and_wait(&plymouth_command_pid, plymouth_path,

		       (const char *[])

		       { plymouth_path, "--ping", NULL },

		       true, false);

  if(not bret){

    if(interrupted_by_signal){

      kill_and_wait(plymouth_command_pid);

      exit(EXIT_FAILURE);

    }

    /* Plymouth is probably not running.  Don't print an error

       message, just exit. */

    exit(EX_UNAVAILABLE);

  }

  prompt = makeprompt();

  ret = asprintf(&prompt_arg, "--prompt=%s", prompt);

  free(prompt);

  if(ret == -1){

    error_plus(EX_OSERR, errno, "asprintf");

  }

  /* plymouth ask-for-password --prompt="$prompt" */

  bret = exec_and_wait(&plymouth_command_pid,

		       plymouth_path, (const char *[])

		       { plymouth_path, "ask-for-password",

			   prompt_arg, NULL },

		       true, false);

  free(prompt_arg);

  if(bret){

    exit(EXIT_SUCCESS);

  }

  if(not interrupted_by_signal){

    /* exec_and_wait failed for some other reason */

    exit(EXIT_FAILURE);

  }

  kill_and_wait(plymouth_command_pid);

  char **plymouthd_argv = NULL;

  pid_t pid = get_pid();

  if(pid == 0){

    error_plus(0, 0, "plymouthd pid not found");

  } else {

    plymouthd_argv = getargv(pid);

  }

  bret = exec_and_wait(NULL, plymouth_path, (const char *[])

		       { plymouth_path, "quit", NULL },

		       false, false);

  if(not bret){

    if(plymouthd_argv != NULL){

      free(*plymouthd_argv);

      free(plymouthd_argv);

    }

    exit(EXIT_FAILURE);

  }

  bret = exec_and_wait(NULL, plymouthd_path,

		       (plymouthd_argv != NULL)

		       ? (const char * const *)plymouthd_argv

		       : plymouthd_default_argv,

		       false, true);

  if(plymouthd_argv != NULL){

    free(*plymouthd_argv);

    free(plymouthd_argv);

  }

  if(not bret){

    exit(EXIT_FAILURE);

  }

  exec_and_wait(NULL, plymouth_path, (const char *[])

		{ plymouth_path, "show-splash", NULL },

		false, false);

  exit(EXIT_FAILURE);

}