/mandos/release

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

/*

 * Mandos plugin runner - Run Mandos plugins

 *

 * Copyright © 2007-2008 Teddy Hogeborn & 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 <mandos@fukt.bsnet.se>.

 */

#define _GNU_SOURCE		/* TEMP_FAILURE_RETRY() */

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

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

				   EXIT_SUCCESS, realloc() */

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

#include <stdio.h>		/* perror, popen(), fileno(),

				   fprintf(), stderr, STDOUT_FILENO */

#include <sys/types.h>	        /* DIR, opendir(), stat(), struct

				   stat, waitpid(), WIFEXITED(),

				   WEXITSTATUS(), wait(), pid_t,

				   uid_t, gid_t, getuid(), getgid(),

				   dirfd() */

#include <sys/select.h>		/* fd_set, select(), FD_ZERO(),

				   FD_SET(), FD_ISSET(), FD_CLR */

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

				   WEXITSTATUS() */

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

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

#include <dirent.h>		/* DIR, struct dirent, opendir(),

				   readdir(), closedir(), dirfd() */

#include <unistd.h>		/* struct stat, stat(), S_ISREG(),

				   fcntl(), setuid(), setgid(),

				   F_GETFD, F_SETFD, FD_CLOEXEC,

				   access(), pipe(), fork(), close()

				   dup2, STDOUT_FILENO, _exit(),

				   execv(), write(), read(),

				   close() */

#include <fcntl.h>		/* fcntl(), F_GETFD, F_SETFD,

				   FD_CLOEXEC */

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

				   strcat() */

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

#include <argp.h>		/* struct argp_option, struct

				   argp_state, struct argp,

				   argp_parse(), ARGP_ERR_UNKNOWN,

				   ARGP_KEY_END, ARGP_KEY_ARG, error_t */

#include <signal.h> 		/* struct sigaction, sigemptyset(),

				   sigaddset(), sigaction(),

				   sigprocmask(), SIG_BLOCK, SIGCHLD,

				   SIG_UNBLOCK, kill() */

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

#define BUFFER_SIZE 256

const char *argp_program_version = "plugbasedclient 1.0";

const char *argp_program_bug_address = "<mandos@fukt.bsnet.se>";

struct process;

typedef struct process{

  pid_t pid;

  int fd;

  char *buffer;

  size_t buffer_size;

  size_t buffer_length;

  bool eof;

  bool completed;

  int status;

  struct process *next;

} process;

typedef struct plugin{

  char *name;			/* can be NULL or any plugin name */

  char **argv;

  int argc;

  bool disabled;

  struct plugin *next;

} plugin;

static plugin *getplugin(char *name, plugin **plugin_list){

  for (plugin *p = *plugin_list; p != NULL; p = p->next){

    if ((p->name == name)

	or (p->name and name and (strcmp(p->name, name) == 0))){

      return p;

    }

  }

  /* Create a new plugin */

  plugin *new_plugin = malloc(sizeof(plugin));

  if (new_plugin == NULL){

    perror("malloc");

    exit(EXIT_FAILURE);

  }

  new_plugin->name = name;

  new_plugin->argv = malloc(sizeof(char *) * 2);

  if (new_plugin->argv == NULL){

    perror("malloc");

    exit(EXIT_FAILURE);

  }

  new_plugin->argv[0] = name;

  new_plugin->argv[1] = NULL;

  new_plugin->argc = 1;

  new_plugin->disabled = false;

  new_plugin->next = *plugin_list;

  /* Append the new plugin to the list */

  *plugin_list = new_plugin;

  return new_plugin;

}

static void addargument(plugin *p, char *arg){

  p->argv[p->argc] = arg;

  p->argv = realloc(p->argv, sizeof(char *) * (size_t)(p->argc + 2));

  if (p->argv == NULL){

    perror("malloc");

    exit(EXIT_FAILURE);

  }

  p->argc++;

  p->argv[p->argc] = NULL;

}

/*

 * Based on the example in the GNU LibC manual chapter 13.13 "File

 * Descriptor Flags".

 * *Note File Descriptor Flags:(libc)Descriptor Flags.

 */

static int set_cloexec_flag(int fd)

{

  int ret = fcntl(fd, F_GETFD, 0);

  /* If reading the flags failed, return error indication now. */

  if(ret < 0){

    return ret;

  }

  /* Store modified flag word in the descriptor. */

  return fcntl(fd, F_SETFD, ret | FD_CLOEXEC);

}

process *process_list = NULL;

/* Mark a process as completed when it exits, and save its exit

   status. */

void handle_sigchld(__attribute__((unused)) int sig){

  process *proc = process_list;

  int status;

  pid_t pid = wait(&status);

  if(pid == -1){

    perror("wait");

    return;

  }

  while(proc != NULL and proc->pid != pid){

    proc = proc->next;

  }

  if(proc == NULL){

    /* Process not found in process list */

    return;

  }

  proc->status = status;

  proc->completed = true;

}

int main(int argc, char *argv[]){

  const char *plugindir = "/conf/conf.d/mandos/plugins.d";

  size_t d_name_len;

  DIR *dir = NULL;

  struct dirent *dirst;

  struct stat st;

  fd_set rfds_all;

  int ret, maxfd = 0;

  uid_t uid = 65534;

  gid_t gid = 65534;

  bool debug = false;

  int exitstatus = EXIT_SUCCESS;

  struct sigaction old_sigchld_action;

  struct sigaction sigchld_action = { .sa_handler = handle_sigchld,

				      .sa_flags = SA_NOCLDSTOP };

  char *plus_options = NULL;

  char **plus_argv = NULL;

  /* Establish a signal handler */

  sigemptyset(&sigchld_action.sa_mask);

  ret = sigaddset(&sigchld_action.sa_mask, SIGCHLD);

  if(ret < 0){

    perror("sigaddset");

    exit(EXIT_FAILURE);

  }

  ret = sigaction(SIGCHLD, &sigchld_action, &old_sigchld_action);

  if(ret < 0){

    perror("sigaction");

    exit(EXIT_FAILURE);

  }

  /* The options we understand. */

  struct argp_option options[] = {

    { .name = "global-options", .key = 'g',

      .arg = "OPTION[,OPTION[,...]]",

      .doc = "Options passed to all plugins" },

    { .name = "options-for", .key = 'o',

      .arg = "PLUGIN:OPTION[,OPTION[,...]]",

      .doc = "Options passed only to specified plugin" },

    { .name = "disable", .key = 'd',

      .arg = "PLUGIN",

      .doc = "Disable a specific plugin", .group = 1 },

    { .name = "plugin-dir", .key = 128,

      .arg = "DIRECTORY",

      .doc = "Specify a different plugin directory", .group = 2 },

    { .name = "userid", .key = 129,

      .arg = "ID", .flags = 0,

      .doc = "User ID the plugins will run as", .group = 2 },

    { .name = "groupid", .key = 130,

      .arg = "ID", .flags = 0,

      .doc = "Group ID the plugins will run as", .group = 2 },

    { .name = "debug", .key = 131,

      .doc = "Debug mode", .group = 3 },

    { .name = NULL }

  };

  error_t parse_opt (int key, char *arg, struct argp_state *state) {

    /* Get the INPUT argument from `argp_parse', which we know is a

       pointer to our plugin list pointer. */

    plugin **plugins = state->input;

    switch (key) {

    case 'g':

      if (arg != NULL){

	char *p = strtok(arg, ",");

	do{

	  addargument(getplugin(NULL, plugins), p);

	  p = strtok(NULL, ",");

	} while (p != NULL);

      }

      break;

    case 'o':

      if (arg != NULL){

	char *name = strtok(arg, ":");

	char *p = strtok(NULL, ":");

	if(p != NULL){

	  p = strtok(p, ",");

	  do{

	    addargument(getplugin(name, plugins), p);

	    p = strtok(NULL, ",");

	  } while (p != NULL);

	}

      }

      break;

    case 'd':

      if (arg != NULL){

	getplugin(arg, plugins)->disabled = true;

      }

      break;

    case 128:

      plugindir = arg;

      break;

    case 129:

      uid = (uid_t)strtol(arg, NULL, 10);

      break;

    case 130:

      gid = (gid_t)strtol(arg, NULL, 10);

      break;

    case 131:

      debug = true;

      break;

    case ARGP_KEY_ARG:

      if(plus_options != NULL or arg == NULL or arg[0] != '+'){

	argp_usage (state);

      }

      plus_options = arg;

      break;

    case ARGP_KEY_END:

      break;

    default:

      return ARGP_ERR_UNKNOWN;

    }

    return 0;

  }

  plugin *plugin_list = NULL;

  struct argp argp = { .options = options, .parser = parse_opt,

		       .args_doc = "[+PLUS_SEPARATED_OPTIONS]",

		       .doc = "Mandos plugin runner -- Run plugins" };

  ret = argp_parse (&argp, argc, argv, 0, 0, &plugin_list);

  if (ret == ARGP_ERR_UNKNOWN){

    fprintf(stderr, "Unkown error while parsing arguments\n");

    exitstatus = EXIT_FAILURE;

    goto end;

  }

  if(plus_options){

    /* This is a mangled argument in the form of

     "+--option+--other-option=parameter+--yet-another-option", etc */

    /* Make new argc and argv vars, and call argp_parse() again. */

    plus_options++;		/* skip the first '+' character */

    const char delims[] = "+";

    char *arg;

    int new_argc = 1;

    plus_argv = malloc(sizeof(char*) * 2);

    if(plus_argv == NULL){

      perror("malloc");

      exitstatus = EXIT_FAILURE;

      goto end;

    }

    plus_argv[0] = argv[0];

    plus_argv[1] = NULL;

    arg = strtok(plus_options, delims); /* Get first argument */

    while(arg != NULL){

      new_argc++;

      plus_argv = realloc(plus_argv, sizeof(char *)

			 * ((unsigned int) new_argc + 1));

      if(plus_argv == NULL){

	perror("realloc");

	exitstatus = EXIT_FAILURE;

	goto end;

      }

      plus_argv[new_argc-1] = arg;

      plus_argv[new_argc] = NULL;

      arg = strtok(NULL, delims); /* Get next argument */

    }

    ret = argp_parse (&argp, new_argc, plus_argv, 0, 0, &plugin_list);

    if (ret == ARGP_ERR_UNKNOWN){

      fprintf(stderr, "Unkown error while parsing arguments\n");

      exitstatus = EXIT_FAILURE;

      goto end;

    }

  }

  if(debug){

    for(plugin *p = plugin_list; p != NULL; p=p->next){

      fprintf(stderr, "Plugin: %s has %d arguments\n",

	      p->name ? p->name : "Global", p->argc - 1);

      for(char **a = p->argv; *a != NULL; a++){

	fprintf(stderr, "\tArg: %s\n", *a);

      }

    }

  }

  ret = setuid(uid);

  if (ret == -1){

    perror("setuid");

  }

  setgid(gid);

  if (ret == -1){

    perror("setgid");

  }

  dir = opendir(plugindir);

  if(dir == NULL){

    perror("Could not open plugin dir");

    exitstatus = EXIT_FAILURE;

    goto end;

  }

  /* Set the FD_CLOEXEC flag on the directory, if possible */

  {

    int dir_fd = dirfd(dir);

    if(dir_fd >= 0){

      ret = set_cloexec_flag(dir_fd);

      if(ret < 0){

	perror("set_cloexec_flag");

	exitstatus = EXIT_FAILURE;

	goto end;

      }

    }

  }

  FD_ZERO(&rfds_all);

  while(true){

    dirst = readdir(dir);

    // All directory entries have been processed

    if(dirst == NULL){

      if (errno == EBADF){

	perror("readdir");

	exitstatus = EXIT_FAILURE;

	goto end;

      }

      break;

    }

    d_name_len = strlen(dirst->d_name);

    // Ignore dotfiles, backup files and other junk

    {

      bool bad_name = false;

      const char const *bad_prefixes[] = { ".", "#", NULL };

      const char const *bad_suffixes[] = { "~", "#", ".dpkg-new",

					   ".dpkg-old",

					   ".dpkg-divert", NULL };

      for(const char **pre = bad_prefixes; *pre != NULL; pre++){

	size_t pre_len = strlen(*pre);

	if((d_name_len >= pre_len)

	   and strncmp((dirst->d_name), *pre, pre_len) == 0){

	  if(debug){

	    fprintf(stderr, "Ignoring plugin dir entry \"%s\""

		    " with bad prefix %s\n", dirst->d_name, *pre);

	  }

	  bad_name = true;

	  break;

	}

      }

      if(bad_name){

	continue;

      }

      for(const char **suf = bad_suffixes; *suf != NULL; suf++){

	size_t suf_len = strlen(*suf);

	if((d_name_len >= suf_len)

	   and (strcmp((dirst->d_name)+d_name_len-suf_len, *suf)

		== 0)){

	  if(debug){

	    fprintf(stderr, "Ignoring plugin dir entry \"%s\""

		    " with bad suffix %s\n", dirst->d_name, *suf);

	  }

	  bad_name = true;

	  break;

	}

      }

      if(bad_name){

	continue;

      }

    }

    char *filename = malloc(d_name_len + strlen(plugindir) + 2);

    if (filename == NULL){

      perror("malloc");

      exitstatus = EXIT_FAILURE;

      goto end;

    }

    strcpy(filename, plugindir); /* Spurious warning */

    strcat(filename, "/");	/* Spurious warning */

    strcat(filename, dirst->d_name); /* Spurious warning */

    ret = stat(filename, &st);

    if (ret == -1){

      perror("stat");

      exitstatus = EXIT_FAILURE;

      goto end;

    }

    if (not S_ISREG(st.st_mode)	or (access(filename, X_OK) != 0)){

      if(debug){

	fprintf(stderr, "Ignoring plugin dir entry \"%s\""

		" with bad type or mode\n", filename);

      }

      free(filename);

      continue;

    }

    if(getplugin(dirst->d_name, &plugin_list)->disabled){

      if(debug){

	fprintf(stderr, "Ignoring disabled plugin \"%s\"\n",

		dirst->d_name);

      }

      free(filename);

      continue;

    }

    plugin *p = getplugin(dirst->d_name, &plugin_list);

    {

      /* Add global arguments to argument list for this plugin */

      plugin *g = getplugin(NULL, &plugin_list);

      for(char **a = g->argv + 1; *a != NULL; a++){

	addargument(p, *a);

      }

    }

    int pipefd[2]; 

    ret = pipe(pipefd);

    if (ret == -1){

      perror("pipe");

      exitstatus = EXIT_FAILURE;

      goto end;

    }

    ret = set_cloexec_flag(pipefd[0]);

    if(ret < 0){

      perror("set_cloexec_flag");

      exitstatus = EXIT_FAILURE;

      goto end;

    }

    ret = set_cloexec_flag(pipefd[1]);

    if(ret < 0){

      perror("set_cloexec_flag");

      exitstatus = EXIT_FAILURE;

      goto end;

    }

    /* Block SIGCHLD until process is safely in process list */

    ret = sigprocmask (SIG_BLOCK, &sigchld_action.sa_mask, NULL);

    if(ret < 0){

      perror("sigprocmask");

      exitstatus = EXIT_FAILURE;

      goto end;

    }

    // Starting a new process to be watched

    pid_t pid = fork();

    if(pid == 0){

      /* this is the child process */

      ret = sigaction(SIGCHLD, &old_sigchld_action, NULL);

      if(ret < 0){

	perror("sigaction");

	_exit(EXIT_FAILURE);

      }

      ret = sigprocmask (SIG_UNBLOCK, &sigchld_action.sa_mask, NULL);

      if(ret < 0){

	perror("sigprocmask");

	_exit(EXIT_FAILURE);

      }

      ret = dup2(pipefd[1], STDOUT_FILENO); /* replace our stdout */

      if(ret == -1){

	perror("dup2");

	_exit(EXIT_FAILURE);

      }

      if(dirfd(dir) < 0){

	/* If dir has no file descriptor, we could not set FD_CLOEXEC

	   above and must now close it manually here. */

	closedir(dir);

      }

      if(execv(filename, p->argv) < 0){

	perror("execv");

	_exit(EXIT_FAILURE);

      }

      /* no return */

    }

    /* parent process */

    free(filename);

    close(pipefd[1]);		/* close unused write end of pipe */

    process *new_process = malloc(sizeof(process));

    if (new_process == NULL){

      perror("malloc");

      ret = sigprocmask (SIG_UNBLOCK, &sigchld_action.sa_mask, NULL);

      if(ret < 0){

	perror("sigprocmask");

      }

      exitstatus = EXIT_FAILURE;

      goto end;