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pkg-monitoring-plugins/plugins/check_dns.c

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/*****************************************************************************
*
* Monitoring check_dns plugin
*
* License: GPL
* Copyright (c) 2000-2008 Monitoring Plugins Development Team
*
* Description:
*
* This file contains the check_dns plugin
*
* LIMITATION: nslookup on Solaris 7 can return output over 2 lines, which
* will not be picked up by this plugin
*
*
* 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/>.
*
*
*****************************************************************************/
const char *progname = "check_dns";
const char *copyright = "2000-2008";
const char *email = "devel@monitoring-plugins.org";
#include "common.h"
#include "utils.h"
#include "utils_base.h"
#include "netutils.h"
#include "runcmd.h"
int process_arguments (int, char **);
int validate_arguments (void);
int error_scan (char *, bool *);
bool ip_match_cidr(const char *, const char *);
unsigned long ip2long(const 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] = "";
bool verbose = false;
char **expected_address = NULL;
int expected_address_cnt = 0;
bool expect_nxdomain = false;
bool expect_authority = false;
bool all_match = false;
thresholds *time_thresholds = NULL;
static int
qstrcmp(const void *p1, const void *p2)
{
/* The actual arguments to this function are "pointers to
pointers to char", but strcmp() arguments are "pointers
to char", hence the following cast plus dereference */
return strcmp(* (char * const *) p1, * (char * const *) p2);
}
int
main (int argc, char **argv)
{
char *command_line = NULL;
char input_buffer[MAX_INPUT_BUFFER];
char *address = NULL; /* comma separated str with addrs/ptrs (sorted) */
char **addresses = NULL;
int n_addresses = 0;
char *msg = NULL;
char *temp_buffer = NULL;
bool non_authoritative = false;
int result = STATE_UNKNOWN;
double elapsed_time;
long microsec;
struct timeval tv;
bool parse_address = false; /* This flag scans for Address: but only after Name: */
output chld_out, chld_err;
bool is_nxdomain = false;
setlocale (LC_ALL, "");
bindtextdomain (PACKAGE, LOCALEDIR);
textdomain (PACKAGE);
/* Set signal handling and alarm */
if (signal (SIGALRM, runcmd_timeout_alarm_handler) == SIG_ERR) {
usage_va(_("Cannot catch SIGALRM"));
}
/* Parse extra opts if any */
argv=np_extra_opts (&argc, argv, progname);
if (process_arguments (argc, argv) == ERROR) {
usage_va(_("Could not parse arguments"));
}
/* get the command to run */
xasprintf (&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 */
if((np_runcmd(command_line, &chld_out, &chld_err, 0)) != 0) {
msg = (char *)_("nslookup returned an error status");
result = STATE_WARNING;
}
/* scan stdout */
for(size_t i = 0; i < chld_out.lines; i++) {
if (addresses == NULL)
addresses = malloc(sizeof(*addresses)*10);
else if (!(n_addresses % 10))
addresses = realloc(addresses,sizeof(*addresses) * (n_addresses + 10));
if (verbose)
puts(chld_out.line[i]);
if (strcasestr (chld_out.line[i], ".in-addr.arpa") || strcasestr (chld_out.line[i], ".ip6.arpa")) {
if ((temp_buffer = strstr (chld_out.line[i], "name = ")))
addresses[n_addresses++] = strdup (temp_buffer + 7);
else {
msg = (char *)_("Warning plugin error");
result = STATE_WARNING;
}
}
/* bug ID: 2946553 - Older versions of bind will use all available dns
servers, we have to match the one specified */
if (strstr (chld_out.line[i], "Server:") && strlen(dns_server) > 0) {
temp_buffer = strchr (chld_out.line[i], ':');
temp_buffer++;
/* Strip leading tabs */
for (; *temp_buffer != '\0' && *temp_buffer == '\t'; temp_buffer++)
/* NOOP */;
strip(temp_buffer);
if (temp_buffer==NULL || strlen(temp_buffer)==0) {
die (STATE_CRITICAL,
_("DNS CRITICAL - '%s' returned empty server string\n"),
NSLOOKUP_COMMAND);
}
if (strcmp(temp_buffer, dns_server) != 0) {
die (STATE_CRITICAL, _("DNS CRITICAL - No response from DNS %s\n"), dns_server);
}
}
/* the server is responding, we just got the host name... */
if (strstr (chld_out.line[i], "Name:"))
parse_address = true;
else if (parse_address && (strstr (chld_out.line[i], "Address:") ||
strstr (chld_out.line[i], "Addresses:"))) {
temp_buffer = index (chld_out.line[i], ':');
temp_buffer++;
/* Strip leading spaces */
while (*temp_buffer == ' ')
temp_buffer++;
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);
}
addresses[n_addresses++] = strdup(temp_buffer);
}
else if (strstr (chld_out.line[i], _("Non-authoritative answer:"))) {
non_authoritative = true;
}
result = error_scan (chld_out.line[i], &is_nxdomain);
if (result != STATE_OK) {
msg = strchr (chld_out.line[i], ':');
if(msg) msg++;
break;
}
}
/* scan stderr */
for(size_t i = 0; i < chld_err.lines; i++) {
if (verbose)
puts(chld_err.line[i]);
if (error_scan (chld_err.line[i], &is_nxdomain) != STATE_OK) {
result = max_state (result, error_scan (chld_err.line[i], &is_nxdomain));
msg = strchr(input_buffer, ':');
if(msg)
msg++;
else
msg = input_buffer;
}
}
if (is_nxdomain && !expect_nxdomain) {
die (STATE_CRITICAL, _("Domain '%s' was not found by the server\n"), query_address);
}
if (addresses) {
int i,slen;
char *adrp;
qsort(addresses, n_addresses, sizeof(*addresses), qstrcmp);
for(i=0, slen=1; i < n_addresses; i++) {
slen += strlen(addresses[i])+1;
}
adrp = address = malloc(slen);
for(i=0; i < n_addresses; i++) {
if (i) *adrp++ = ',';
strcpy(adrp, addresses[i]);
adrp += strlen(addresses[i]);
}
*adrp = 0;
} else
die (STATE_CRITICAL,
_("DNS CRITICAL - '%s' msg parsing exited with no address\n"),
NSLOOKUP_COMMAND);
/* compare to expected address */
if (result == STATE_OK && expected_address_cnt > 0) {
result = STATE_CRITICAL;
temp_buffer = "";
unsigned long expect_match = (1 << expected_address_cnt) - 1;
unsigned long addr_match = (1 << n_addresses) - 1;
for (int i=0; i<expected_address_cnt; i++) {
int j;
/* check if we get a match on 'raw' ip or cidr */
for (j=0; j<n_addresses; j++) {
if ( strcmp(addresses[j], expected_address[i]) == 0
|| ip_match_cidr(addresses[j], expected_address[i]) ) {
result = STATE_OK;
addr_match &= ~(1 << j);
expect_match &= ~(1 << i);
}
}
/* prepare an error string */
xasprintf(&temp_buffer, "%s%s; ", temp_buffer, expected_address[i]);
}
/* check if expected_address must cover all in addresses and none may be missing */
if (all_match && (expect_match != 0 || addr_match != 0))
result = STATE_CRITICAL;
if (result == STATE_CRITICAL) {
/* Strip off last semicolon... */
temp_buffer[strlen(temp_buffer)-2] = '\0';
xasprintf(&msg, _("expected '%s' but got '%s'"), temp_buffer, address);
}
}
if (expect_nxdomain) {
if (!is_nxdomain) {
result = STATE_CRITICAL;
xasprintf(&msg, _("Domain '%s' was found by the server: '%s'\n"), query_address, address);
} else {
if (address != NULL) free(address);
address = "NXDOMAIN";
}
}
/* check if authoritative */
if (result == STATE_OK && expect_authority && non_authoritative) {
result = STATE_CRITICAL;
xasprintf(&msg, _("server %s is not authoritative for %s"), dns_server, query_address);
}
microsec = deltime (tv);
elapsed_time = (double)microsec / 1.0e6;
if (result == STATE_OK) {
result = get_status(elapsed_time, time_thresholds);
if (result == STATE_OK) {
printf ("DNS %s: ", _("OK"));
} else if (result == STATE_WARNING) {
printf ("DNS %s: ", _("WARNING"));
} else if (result == STATE_CRITICAL) {
printf ("DNS %s: ", _("CRITICAL"));
}
printf (ngettext("%.3f second response time", "%.3f seconds response time", elapsed_time), elapsed_time);
printf (_(". %s returns %s"), query_address, address);
if ((time_thresholds->warning != NULL) && (time_thresholds->critical != NULL)) {
printf ("|%s\n", fperfdata ("time", elapsed_time, "s",
true, time_thresholds->warning->end,
true, time_thresholds->critical->end,
true, 0, false, 0));
} else if ((time_thresholds->warning == NULL) && (time_thresholds->critical != NULL)) {
printf ("|%s\n", fperfdata ("time", elapsed_time, "s",
false, 0,
true, time_thresholds->critical->end,
true, 0, false, 0));
} else if ((time_thresholds->warning != NULL) && (time_thresholds->critical == NULL)) {
printf ("|%s\n", fperfdata ("time", elapsed_time, "s",
true, time_thresholds->warning->end,
false, 0,
true, 0, false, 0));
} else
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 (msg, "") ? _(" Probably a non-existent host/domain") : msg);
else if (result == STATE_CRITICAL)
printf (_("DNS CRITICAL - %s\n"),
!strcmp (msg, "") ? _(" Probably a non-existent host/domain") : msg);
else
printf (_("DNS UNKNOWN - %s\n"),
!strcmp (msg, "") ? _(" Probably a non-existent host/domain") : msg);
return result;
}
bool ip_match_cidr(const char *addr, const char *cidr_ro) {
char *subnet, *mask_c, *cidr = strdup(cidr_ro);
int mask;
subnet = strtok(cidr, "/");
mask_c = strtok(NULL, "\0");
if (!subnet || !mask_c) {
return false;
}
mask = atoi(mask_c);
/* https://www.cryptobells.com/verifying-ips-in-a-subnet-in-php/ */
return (ip2long(addr) & ~((1 << (32 - mask)) - 1)) == (ip2long(subnet) >> (32 - mask)) << (32 - mask);
}
unsigned long
ip2long(const char* src) {
unsigned long ip[4];
/* http://computer-programming-forum.com/47-c-language/1376ffb92a12c471.htm */
return (sscanf(src, "%3lu.%3lu.%3lu.%3lu",
&ip[0], &ip[1], &ip[2], &ip[3]) == 4 &&
ip[0] < 256 && ip[1] < 256 &&
ip[2] < 256 && ip[3] < 256)
? ip[0] << 24 | ip[1] << 16 | ip[2] << 8 | ip[3]
: 0;
}
int
error_scan (char *input_buffer, bool *is_nxdomain)
{
const int nxdomain = strstr (input_buffer, "Non-existent") ||
strstr (input_buffer, "** server can't find") ||
strstr (input_buffer, "** Can't find") ||
strstr (input_buffer, "NXDOMAIN");
if (nxdomain) *is_nxdomain = true;
/* 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);
else if (strstr (input_buffer, "no servers could be reached"))
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);
/* 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;
char *warning = NULL;
char *critical = NULL;
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-nxdomain", no_argument, 0, 'n'},
{"expect-authority", no_argument, 0, 'A'},
{"all", no_argument, 0, 'L'},
{"warning", required_argument, 0, 'w'},
{"critical", required_argument, 0, 'c'},
{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, "hVvALnt:H:s:r:a:w:c:", long_opts, &opt_index);
if (c == -1 || c == EOF)
break;
switch (c) {
case 'h': /* help */
print_help ();
exit (STATE_UNKNOWN);
case 'V': /* version */
print_revision (progname, NP_VERSION);
exit (STATE_UNKNOWN);
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 host_or_die check is probably unnecessary.
* Better to confirm nslookup response matches */
host_or_die(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 host_or_die necessary? */
host_or_die(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"));
if (strchr(optarg, ',') != NULL) {
char *comma = strchr(optarg, ',');
while (comma != NULL) {
expected_address = (char **)realloc(expected_address, (expected_address_cnt+1) * sizeof(char**));
expected_address[expected_address_cnt] = strndup(optarg, comma - optarg);
expected_address_cnt++;
optarg = comma + 1;
comma = strchr(optarg, ',');
}
expected_address = (char **)realloc(expected_address, (expected_address_cnt+1) * sizeof(char**));
expected_address[expected_address_cnt] = strdup(optarg);
expected_address_cnt++;
} else {
expected_address = (char **)realloc(expected_address, (expected_address_cnt+1) * sizeof(char**));
expected_address[expected_address_cnt] = strdup(optarg);
expected_address_cnt++;
}
break;
case 'n': /* expect NXDOMAIN */
expect_nxdomain = true;
break;
case 'A': /* expect authority */
expect_authority = true;
break;
case 'L': /* all must match */
all_match = true;
break;
case 'w':
warning = optarg;
break;
case 'c':
critical = optarg;
break;
default: /* args not parsable */
usage5();
}
}
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 */
host_or_die(argv[c]);
if (strlen(argv[c]) >= ADDRESS_LENGTH)
die (STATE_UNKNOWN, _("Input buffer overflow\n"));
strcpy (dns_server, argv[c++]);
}
set_thresholds(&time_thresholds, warning, critical);
return validate_arguments ();
}
int
validate_arguments ()
{
if (query_address[0] == 0) {
printf ("missing --host argument\n");
return ERROR;
}
if (expected_address_cnt > 0 && expect_nxdomain) {
printf ("--expected-address and --expect-nxdomain cannot be combined\n");
return ERROR;
}
return OK;
}
void
print_help (void)
{
print_revision (progname, NP_VERSION);
printf ("Copyright (c) 1999 Ethan Galstad <nagios@nagios.org>\n");
printf (COPYRIGHT, copyright, email);
printf ("%s\n", _("This plugin uses the nslookup program to obtain the IP address for the given host/domain query."));
printf ("%s\n", _("An optional DNS server to use may be specified."));
printf ("%s\n", _("If no DNS server is specified, the default server(s) specified in /etc/resolv.conf will be used."));
printf ("\n\n");
print_usage ();
printf (UT_HELP_VRSN);
printf (UT_EXTRA_OPTS);
printf (" -H, --hostname=HOST\n");
printf (" %s\n", _("The name or address you want to query"));
printf (" -s, --server=HOST\n");
printf (" %s\n", _("Optional DNS server you want to use for the lookup"));
printf (" -a, --expected-address=IP-ADDRESS|CIDR|HOST\n");
printf (" %s\n", _("Optional IP-ADDRESS/CIDR you expect the DNS server to return. HOST must end"));
printf (" %s\n", _("with a dot (.). This option can be repeated multiple times (Returns OK if any"));
printf (" %s\n", _("value matches)."));
printf (" -n, --expect-nxdomain\n");
printf (" %s\n", _("Expect the DNS server to return NXDOMAIN (i.e. the domain was not found)"));
printf (" %s\n", _("Cannot be used together with -a"));
printf (" -A, --expect-authority\n");
printf (" %s\n", _("Optionally expect the DNS server to be authoritative for the lookup"));
printf (" -w, --warning=seconds\n");
printf (" %s\n", _("Return warning if elapsed time exceeds value. Default off"));
printf (" -c, --critical=seconds\n");
printf (" %s\n", _("Return critical if elapsed time exceeds value. Default off"));
printf (" -L, --all\n");
printf (" %s\n", _("Return critical if the list of expected addresses does not match all addresses"));
printf (" %s\n", _("returned. Default off"));
printf (UT_CONN_TIMEOUT, DEFAULT_SOCKET_TIMEOUT);
printf (UT_SUPPORT);
}
void
print_usage (void)
{
printf ("%s\n", _("Usage:"));
printf ("%s -H host [-s server] [-a expected-address] [-n] [-A] [-t timeout] [-w warn] [-c crit] [-L]\n", progname);
}
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