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check_dns.c

/******************************************************************************

 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 2 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, write to the Free Software
 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 LIMITATION: nslookup on Solaris 7 can return output over 2 lines, which will not 
 be picked up by this plugin
 
 $Id: check_dns.c,v 1.47 2004/12/30 00:41:39 opensides Exp $

******************************************************************************/

const char *progname = "check_dns";
const char *revision = "$Revision: 1.47 $";
const char *copyright = "2000-2004";
const char *email = "nagiosplug-devel@lists.sourceforge.net";

#include "common.h"
#include "popen.h"
#include "utils.h"
#include "netutils.h"

int process_arguments (int, char **);
int validate_arguments (void);
int error_scan (char *);
void print_help (void);
void print_usage (void);

#define ADDRESS_LENGTH 256
char query_address[ADDRESS_LENGTH] = "";
char dns_server[ADDRESS_LENGTH] = "";
char ptr_server[ADDRESS_LENGTH] = "";
int verbose = FALSE;
char expected_address[ADDRESS_LENGTH] = "";
int match_expected_address = FALSE;
int expect_authority = FALSE;

int
main (int argc, char **argv)
{
      char *command_line = NULL;
      char input_buffer[MAX_INPUT_BUFFER];
      char *output = NULL;
      char *address = NULL;
      char *temp_buffer = NULL;
      int non_authoritative = FALSE;
      int result = STATE_UNKNOWN;
      double elapsed_time;
      long microsec;
      struct timeval tv;
      int multi_address;
      int parse_address = FALSE; /* This flag scans for Address: but only after Name: */

      setlocale (LC_ALL, "");
      bindtextdomain (PACKAGE, LOCALEDIR);
      textdomain (PACKAGE);

      /* Set signal handling and alarm */
      if (signal (SIGALRM, popen_timeout_alarm_handler) == SIG_ERR) {
            usage4 (_("Cannot catch SIGALRM"));
      }

      if (process_arguments (argc, argv) == ERROR) {
            usage4 (_("Could not parse arguments"));
      }

      /* get the command to run */
      asprintf (&command_line, "%s %s %s", NSLOOKUP_COMMAND, query_address, dns_server);

      alarm (timeout_interval);
      gettimeofday (&tv, NULL);

      if (verbose)
            printf ("%s\n", command_line);

      /* run the command */
      child_process = spopen (command_line);
      if (child_process == NULL) {
            printf (_("Could not open pipe: %s\n"), command_line);
            return STATE_UNKNOWN;
      }

      child_stderr = fdopen (child_stderr_array[fileno (child_process)], "r");
      if (child_stderr == NULL)
            printf (_("Could not open stderr for %s\n"), command_line);

      /* scan stdout */
      while (fgets (input_buffer, MAX_INPUT_BUFFER - 1, child_process)) {

            if (verbose)
                  printf ("%s", input_buffer);

            if (strstr (input_buffer, ".in-addr.arpa")) {
                  if ((temp_buffer = strstr (input_buffer, "name = ")))
                        address = strdup (temp_buffer + 7);
                  else {
                        output = strdup (_("Warning plugin error"));
                        result = STATE_WARNING;
                  }
            }

            /* the server is responding, we just got the host name... */
            if (strstr (input_buffer, "Name:"))
                  parse_address = TRUE;
            else if (parse_address == TRUE && (strstr (input_buffer, "Address:") ||
                     strstr (input_buffer, "Addresses:"))) {
                  temp_buffer = index (input_buffer, ':');
                  temp_buffer++;

                  /* Strip leading spaces */
                  for (; *temp_buffer != '\0' && *temp_buffer == ' '; temp_buffer++)
                        /* NOOP */;
                  
                  strip(temp_buffer);
                  if (temp_buffer==NULL || strlen(temp_buffer)==0) {
                        die (STATE_CRITICAL,
                             _("DNS CRITICAL - '%s' returned empty host name string\n"),
                             NSLOOKUP_COMMAND);
                  }

                  if (address == NULL)
                        address = strdup (temp_buffer);
                  else
                        asprintf(&address, "%s,%s", address, temp_buffer);
            }

            else if (strstr (input_buffer, _("Non-authoritative answer:"))) {
                  non_authoritative = TRUE;
            }

            result = error_scan (input_buffer);
            if (result != STATE_OK) {
                  output = strdup (1 + index (input_buffer, ':'));
                  strip (output);
                  break;
            }

      }

      /* scan stderr */
      while (fgets (input_buffer, MAX_INPUT_BUFFER - 1, child_stderr)) {

            if (verbose)
                  printf ("%s", input_buffer);

            if (error_scan (input_buffer) != STATE_OK) {
                  result = max_state (result, error_scan (input_buffer));
                  output = strdup (1 + index (input_buffer, ':'));
                  strip (output);
            }
      }

      /* close stderr */
      (void) fclose (child_stderr);

      /* close stdout */
      if (spclose (child_process)) {
            result = max_state (result, STATE_WARNING);
            if (output == NULL || !strcmp (output, ""))
                  output = strdup (_("nslookup returned error status"));
      }

      /* If we got here, we should have an address string, 
             and we can segfault if we do not */
      if (address==NULL || strlen(address)==0)
            die (STATE_CRITICAL,
                 _("DNS CRITICAL - '%s' output parsing exited with no address\n"),
                 NSLOOKUP_COMMAND);

      /* compare to expected address */
      if (result == STATE_OK && match_expected_address && strcmp(address, expected_address)) {
            result = STATE_CRITICAL;
            asprintf(&output, _("expected %s but got %s"), expected_address, address);
      }

      /* check if authoritative */
      if (result == STATE_OK && expect_authority && non_authoritative) {
            result = STATE_CRITICAL;
            asprintf(&output, _("server %s is not authoritative for %s"), dns_server, query_address);
      }

      microsec = deltime (tv);
      elapsed_time = (double)microsec / 1.0e6;

      if (result == STATE_OK) {
            if (strchr (address, ',') == NULL)
                  multi_address = FALSE;
            else
                  multi_address = TRUE;

            printf ("DNS %s: ", _("OK"));
            printf (ngettext("%.3f second response time ", "%.3f seconds response time ", elapsed_time), elapsed_time);
            printf (_("%s returns %s"), query_address, address);
            printf ("|%s\n", fperfdata ("time", elapsed_time, "s", FALSE, 0, FALSE, 0, TRUE, 0, FALSE, 0));
      }
      else if (result == STATE_WARNING)
            printf (_("DNS WARNING - %s\n"),
                    !strcmp (output, "") ? _(" Probably a non-existent host/domain") : output);
      else if (result == STATE_CRITICAL)
            printf (_("DNS CRITICAL - %s\n"),
                    !strcmp (output, "") ? _(" Probably a non-existent host/domain") : output);
      else
            printf (_("DNS UNKNOW - %s\n"),
                    !strcmp (output, "") ? _(" Probably a non-existent host/domain") : output);

      return result;
}



int
error_scan (char *input_buffer)
{

      /* the DNS lookup timed out */
      if (strstr (input_buffer, _("Note: nslookup is deprecated and may be removed from future releases.")) ||
          strstr (input_buffer, _("Consider using the `dig' or `host' programs instead.  Run nslookup with")) ||
          strstr (input_buffer, _("the `-sil[ent]' option to prevent this message from appearing.")))
            return STATE_OK;

      /* DNS server is not running... */
      else if (strstr (input_buffer, "No response from server"))
            die (STATE_CRITICAL, _("No response from DNS %s\n"), dns_server);

      /* Host name is valid, but server doesn't have records... */
      else if (strstr (input_buffer, "No records"))
            die (STATE_CRITICAL, _("DNS %s has no records\n"), dns_server);

      /* Connection was refused */
      else if (strstr (input_buffer, "Connection refused") ||
             strstr (input_buffer, "Couldn't find server") ||
               strstr (input_buffer, "Refused") ||
               (strstr (input_buffer, "** server can't find") &&
                strstr (input_buffer, ": REFUSED")))
            die (STATE_CRITICAL, _("Connection to DNS %s was refused\n"), dns_server);

      /* Query refused (usually by an ACL in the namserver) */ 
      else if (strstr (input_buffer, "Query refused"))
            die (STATE_CRITICAL, _("Query was refused by DNS server at %s\n"), dns_server);

      /* No information (e.g. nameserver IP has two PTR records) */
      else if (strstr (input_buffer, "No information"))
            die (STATE_CRITICAL, _("No information returned by DNS server at %s\n"), dns_server);

      /* Host or domain name does not exist */
      else if (strstr (input_buffer, "Non-existent") ||
               strstr (input_buffer, "** server can't find") ||
             strstr (input_buffer,"NXDOMAIN"))
            die (STATE_CRITICAL, _("Domain %s was not found by the server\n"), query_address);

      /* Network is unreachable */
      else if (strstr (input_buffer, "Network is unreachable"))
            die (STATE_CRITICAL, _("Network is unreachable\n"));

      /* Internal server failure */
      else if (strstr (input_buffer, "Server failure"))
            die (STATE_CRITICAL, _("DNS failure for %s\n"), dns_server);

      /* Request error or the DNS lookup timed out */
      else if (strstr (input_buffer, "Format error") ||
               strstr (input_buffer, "Timed out"))
            return STATE_WARNING;

      return STATE_OK;

}


/* process command-line arguments */
int
process_arguments (int argc, char **argv)
{
      int c;

      int opt_index = 0;
      static struct option long_opts[] = {
            {"help", no_argument, 0, 'h'},
            {"version", no_argument, 0, 'V'},
            {"verbose", no_argument, 0, 'v'},
            {"timeout", required_argument, 0, 't'},
            {"hostname", required_argument, 0, 'H'},
            {"server", required_argument, 0, 's'},
            {"reverse-server", required_argument, 0, 'r'},
            {"expected-address", required_argument, 0, 'a'},
            {"expect-authority", no_argument, 0, 'A'},
            {0, 0, 0, 0}
      };

      if (argc < 2)
            return ERROR;

      for (c = 1; c < argc; c++)
            if (strcmp ("-to", argv[c]) == 0)
                  strcpy (argv[c], "-t");

      while (1) {
            c = getopt_long (argc, argv, "hVvAt:H:s:r:a:", long_opts, &opt_index);

            if (c == -1 || c == EOF)
                  break;

            switch (c) {
            case '?': /* args not parsable */
                  usage2 (_("Unknown argument"), optarg);
            case 'h': /* help */
                  print_help ();
                  exit (STATE_OK);
            case 'V': /* version */
                  print_revision (progname, revision);
                  exit (STATE_OK);
            case 'v': /* version */
                  verbose = TRUE;
                  break;
            case 't': /* timeout period */
                  timeout_interval = atoi (optarg);
                  break;
            case 'H': /* hostname */
                  if (strlen (optarg) >= ADDRESS_LENGTH)
                        die (STATE_UNKNOWN, _("Input buffer overflow\n"));
                  strcpy (query_address, optarg);
                  break;
            case 's': /* server name */
                  /* TODO: this is_host check is probably unnecessary. */
                  /* Better to confirm nslookup response matches */
                  if (is_host (optarg) == FALSE) {
                        usage2 (_("Invalid hostname/address"), optarg);
                  }
                  if (strlen (optarg) >= ADDRESS_LENGTH)
                        die (STATE_UNKNOWN, _("Input buffer overflow\n"));
                  strcpy (dns_server, optarg);
                  break;
            case 'r': /* reverse server name */
                  /* TODO: Is this is_host necessary? */
                  if (is_host (optarg) == FALSE) {
                        usage2 (_("Invalid hostname/address"), optarg);
                  }
                  if (strlen (optarg) >= ADDRESS_LENGTH)
                        die (STATE_UNKNOWN, _("Input buffer overflow\n"));
                  strcpy (ptr_server, optarg);
                  break;
            case 'a': /* expected address */
                  if (strlen (optarg) >= ADDRESS_LENGTH)
                        die (STATE_UNKNOWN, _("Input buffer overflow\n"));
                  strcpy (expected_address, optarg);
                  match_expected_address = TRUE;
                  break;
            case 'A': /* expect authority */
                  expect_authority = TRUE;
                  break;
            }
      }

      c = optind;
      if (strlen(query_address)==0 && c<argc) {
            if (strlen(argv[c])>=ADDRESS_LENGTH)
                  die (STATE_UNKNOWN, _("Input buffer overflow\n"));
            strcpy (query_address, argv[c++]);
      }

      if (strlen(dns_server)==0 && c<argc) {
            /* TODO: See -s option */
            if (is_host(argv[c]) == FALSE) {
                  printf (_("Invalid hostname/address: %s\n\n"), argv[c]);
                  return ERROR;
            }
            if (strlen(argv[c]) >= ADDRESS_LENGTH)
                  die (STATE_UNKNOWN, _("Input buffer overflow\n"));
            strcpy (dns_server, argv[c++]);
      }

      return validate_arguments ();
}


int
validate_arguments ()
{
      if (query_address[0] == 0)
            return ERROR;
      else
            return OK;
}


void
print_help (void)
{
      print_revision (progname, revision);

      printf ("Copyright (c) 1999 Ethan Galstad <nagios@nagios.org>\n");
      printf (COPYRIGHT, copyright, email);

      printf (_("\
This plugin uses the nslookup program to obtain the IP address\n\
for the given host/domain query.  A optional DNS server to use may\n\
be specified.  If no DNS server is specified, the default server(s)\n\
specified in /etc/resolv.conf will be used.\n\n"));

      print_usage ();

      printf (_(UT_HELP_VRSN));

      printf (_("\
-H, --hostname=HOST\n\
   The name or address you want to query\n\
-s, --server=HOST\n\
   Optional DNS server you want to use for the lookup\n\
-a, --expected-address=IP-ADDRESS\n\
   Optional IP address you expect the DNS server to return\n\
-A, --expect-authority\n\
   Optionally expect the DNS server to be authoritative for the lookup\n"));

      printf (_(UT_TIMEOUT), DEFAULT_SOCKET_TIMEOUT);

      printf (_(UT_SUPPORT));
}


void
print_usage (void)
{
      printf ("\
Usage: %s -H host [-s server] [-a expected-address] [-A] [-t timeout]\n", progname);
}

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