plugins/check_ssh.c

   1 /*****************************************************************************
   2  *
   3  * Monitoring check_ssh plugin
   4  *
   5  * License: GPL
   6  * Copyright (c) 2000-2024 Monitoring Plugins Development Team
   7  *
   8  * Description:
   9  *
  10  * This file contains the check_ssh plugin
  11  *
  12  * Try to connect to an SSH server at specified server and port
  13  *
  14  *
  15  * This program is free software: you can redistribute it and/or modify
  16  * it under the terms of the GNU General Public License as published by
  17  * the Free Software Foundation, either version 3 of the License, or
  18  * (at your option) any later version.
  19  *
  20  * This program is distributed in the hope that it will be useful,
  21  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  22  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23  * GNU General Public License for more details.
  24  *
  25  * You should have received a copy of the GNU General Public License
  26  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  27  *
  28  *
  29  *****************************************************************************/
  30
  31 const char *progname = "check_ssh";
  32 const char *copyright = "2000-2024";
  33 const char *email = "devel@monitoring-plugins.org";
  34
  35 #include "./common.h"
  36 #include "./netutils.h"
  37 #include "utils.h"
  38
  39 #ifndef MSG_DONTWAIT
  40 #       define MSG_DONTWAIT 0
  41 #endif
  42
  43 #define SSH_DFL_PORT 22
  44 #define BUFF_SZ      256
  45
  46 static int port = -1;
  47 static char *server_name = NULL;
  48 static char *remote_version = NULL;
  49 static char *remote_protocol = NULL;
  50 static bool verbose = false;
  51
  52 static int process_arguments(int /*argc*/, char ** /*argv*/);
  53 static int validate_arguments(void);
  54 static void print_help(void);
  55 void print_usage(void);
  56
  57 static int ssh_connect(char *haddr, int hport, char *remote_version, char *remote_protocol);
  58
  59 int main(int argc, char **argv) {
  60         setlocale(LC_ALL, "");
  61         bindtextdomain(PACKAGE, LOCALEDIR);
  62         textdomain(PACKAGE);
  63
  64         /* Parse extra opts if any */
  65         argv = np_extra_opts(&argc, argv, progname);
  66
  67         if (process_arguments(argc, argv) == ERROR)
  68                 usage4(_("Could not parse arguments"));
  69
  70         /* initialize alarm signal handling */
  71         signal(SIGALRM, socket_timeout_alarm_handler);
  72
  73         alarm(socket_timeout);
  74
  75         /* ssh_connect exits if error is found */
  76         int result = ssh_connect(server_name, port, remote_version, remote_protocol);
  77
  78         alarm(0);
  79
  80         return (result);
  81 }
  82
  83 /* process command-line arguments */
  84 int process_arguments(int argc, char **argv) {
  85         static struct option longopts[] = {{"help", no_argument, 0, 'h'},
  86                                                                            {"version", no_argument, 0, 'V'},
  87                                                                            {"host", required_argument, 0, 'H'}, /* backward compatibility */
  88                                                                            {"hostname", required_argument, 0, 'H'},
  89                                                                            {"port", required_argument, 0, 'p'},
  90                                                                            {"use-ipv4", no_argument, 0, '4'},
  91                                                                            {"use-ipv6", no_argument, 0, '6'},
  92                                                                            {"timeout", required_argument, 0, 't'},
  93                                                                            {"verbose", no_argument, 0, 'v'},
  94                                                                            {"remote-version", required_argument, 0, 'r'},
  95                                                                            {"remote-protocol", required_argument, 0, 'P'},
  96                                                                            {0, 0, 0, 0}};
  97
  98         if (argc < 2)
  99                 return ERROR;
 100
 101         for (int i = 1; i < argc; i++)
 102                 if (strcmp("-to", argv[i]) == 0)
 103                         strcpy(argv[i], "-t");
 104
 105         int option_char;
 106         while (true) {
 107                 int option = 0;
 108                 option_char = getopt_long(argc, argv, "+Vhv46t:r:H:p:P:", longopts, &option);
 109
 110                 if (option_char == -1 || option_char == EOF)
 111                         break;
 112
 113                 switch (option_char) {
 114                 case '?': /* help */
 115                         usage5();
 116                 case 'V': /* version */
 117                         print_revision(progname, NP_VERSION);
 118                         exit(STATE_UNKNOWN);
 119                 case 'h': /* help */
 120                         print_help();
 121                         exit(STATE_UNKNOWN);
 122                 case 'v': /* verbose */
 123                         verbose = true;
 124                         break;
 125                 case 't': /* timeout period */
 126                         if (!is_integer(optarg))
 127                                 usage2(_("Timeout interval must be a positive integer"), optarg);
 128                         else
 129                                 socket_timeout = atoi(optarg);
 130                         break;
 131                 case '4':
 132                         address_family = AF_INET;
 133                         break;
 134                 case '6':
 135 #ifdef USE_IPV6
 136                         address_family = AF_INET6;
 137 #else
 138                         usage4(_("IPv6 support not available"));
 139 #endif
 140                         break;
 141                 case 'r': /* remote version */
 142                         remote_version = optarg;
 143                         break;
 144                 case 'P': /* remote version */
 145                         remote_protocol = optarg;
 146                         break;
 147                 case 'H': /* host */
 148                         if (!is_host(optarg))
 149                                 usage2(_("Invalid hostname/address"), optarg);
 150                         server_name = optarg;
 151                         break;
 152                 case 'p': /* port */
 153                         if (is_intpos(optarg)) {
 154                                 port = atoi(optarg);
 155                         } else {
 156                                 usage2(_("Port number must be a positive integer"), optarg);
 157                         }
 158                 }
 159         }
 160
 161         option_char = optind;
 162         if (server_name == NULL && option_char < argc) {
 163                 if (is_host(argv[option_char])) {
 164                         server_name = argv[option_char++];
 165                 }
 166         }
 167
 168         if (port == -1 && option_char < argc) {
 169                 if (is_intpos(argv[option_char])) {
 170                         port = atoi(argv[option_char++]);
 171                 } else {
 172                         print_usage();
 173                         exit(STATE_UNKNOWN);
 174                 }
 175         }
 176
 177         return validate_arguments();
 178 }
 179
 180 int validate_arguments(void) {
 181         if (server_name == NULL)
 182                 return ERROR;
 183         if (port == -1) /* funky, but allows -p to override stray integer in args */
 184                 port = SSH_DFL_PORT;
 185         return OK;
 186 }
 187
 188 /************************************************************************
 189  *
 190  * Try to connect to SSH server at specified server and port
 191  *
 192  *-----------------------------------------------------------------------*/
 193
 194 int ssh_connect(char *haddr, int hport, char *remote_version, char *remote_protocol) {
 195         struct timeval tv;
 196         gettimeofday(&tv, NULL);
 197
 198         int socket;
 199         int result = my_tcp_connect(haddr, hport, &socket);
 200
 201         if (result != STATE_OK)
 202                 return result;
 203
 204         char *output = (char *)calloc(BUFF_SZ + 1, sizeof(char));
 205         char *buffer = NULL;
 206         ssize_t recv_ret = 0;
 207         char *version_control_string = NULL;
 208         ssize_t byte_offset = 0;
 209         while ((version_control_string == NULL) && (recv_ret = recv(socket, output + byte_offset, BUFF_SZ - byte_offset, 0) > 0)) {
 210
 211                 if (strchr(output, '\n')) { /* we've got at least one full line, start parsing*/
 212                         byte_offset = 0;
 213
 214                         char *index = NULL;
 215                         int len = 0;
 216                         while ((index = strchr(output + byte_offset, '\n')) != NULL) {
 217                                 /*Partition the buffer so that this line is a separate string,
 218                                  * by replacing the newline with NUL*/
 219                                 output[(index - output)] = '\0';
 220                                 len = strlen(output + byte_offset);
 221
 222                                 if ((len >= 4) && (strncmp(output + byte_offset, "SSH-", 4) == 0)) {
 223                                         /*if the string starts with SSH-, this _should_ be a valid version control string*/
 224                                         version_control_string = output + byte_offset;
 225                                         break;
 226                                 }
 227
 228                                 /*the start of the next line (if one exists) will be after the current one (+ NUL)*/
 229                                 byte_offset += (len + 1);
 230                         }
 231
 232                         if (version_control_string == NULL) {
 233                                 /* move unconsumed data to beginning of buffer, null rest */
 234                                 memmove((void *)output, (void *)(output + byte_offset + 1), BUFF_SZ - len + 1);
 235                                 memset(output + byte_offset + 1, 0, BUFF_SZ - byte_offset + 1);
 236
 237                                 /*start reading from end of current line chunk on next recv*/
 238                                 byte_offset = strlen(output);
 239                         }
 240                 } else {
 241                         byte_offset += recv_ret;
 242                 }
 243         }
 244
 245         if (recv_ret < 0) {
 246                 printf("SSH CRITICAL - %s", strerror(errno));
 247                 exit(STATE_CRITICAL);
 248         }
 249
 250         if (version_control_string == NULL) {
 251                 printf("SSH CRITICAL - No version control string received");
 252                 exit(STATE_CRITICAL);
 253         }
 254         /*
 255          * "When the connection has been established, both sides MUST send an
 256          * identification string.  This identification string MUST be
 257          *
 258          * SSH-protoversion-softwareversion SP comments CR LF"
 259          *              - RFC 4253:4.2
 260          */
 261         strip(version_control_string);
 262         if (verbose)
 263                 printf("%s\n", version_control_string);
 264
 265         char *ssh_proto = version_control_string + 4;
 266
 267         /*
 268          * We assume the protoversion is of the form Major.Minor, although
 269          * this is not _strictly_ required. See
 270          *
 271          * "Both the 'protoversion' and 'softwareversion' strings MUST consist of
 272          * printable US-ASCII characters, with the exception of whitespace
 273          * characters and the minus sign (-)"
 274          *              - RFC 4253:4.2
 275          * and,
 276          *
 277          * "As stated earlier, the 'protoversion' specified for this protocol is
 278          * "2.0".  Earlier versions of this protocol have not been formally
 279          * documented, but it is widely known that they use 'protoversion' of
 280          * "1.x" (e.g., "1.5" or "1.3")."
 281          *              - RFC 4253:5
 282          */
 283         char *ssh_server = ssh_proto + strspn(ssh_proto, "0123456789.") + 1; /* (+1 for the '-' separating protoversion from softwareversion) */
 284
 285         /* If there's a space in the version string, whatever's after the space is a comment
 286          * (which is NOT part of the server name/version)*/
 287         char *tmp = strchr(ssh_server, ' ');
 288         if (tmp) {
 289                 ssh_server[tmp - ssh_server] = '\0';
 290         }
 291         if (strlen(ssh_proto) == 0 || strlen(ssh_server) == 0) {
 292                 printf(_("SSH CRITICAL - Invalid protocol version control string %s\n"), version_control_string);
 293                 exit(STATE_CRITICAL);
 294         }
 295         ssh_proto[strspn(ssh_proto, "0123456789. ")] = 0;
 296
 297         static char *rev_no = VERSION;
 298         xasprintf(&buffer, "SSH-%s-check_ssh_%s\r\n", ssh_proto, rev_no);
 299         send(socket, buffer, strlen(buffer), MSG_DONTWAIT);
 300         if (verbose)
 301                 printf("%s\n", buffer);
 302
 303         if (remote_version && strcmp(remote_version, ssh_server)) {
 304                 printf(_("SSH CRITICAL - %s (protocol %s) version mismatch, expected '%s'\n"), ssh_server, ssh_proto, remote_version);
 305                 close(socket);
 306                 exit(STATE_CRITICAL);
 307         }
 308
 309         double elapsed_time = (double)deltime(tv) / 1.0e6;
 310         if (remote_protocol && strcmp(remote_protocol, ssh_proto)) {
 311                 printf(_("SSH CRITICAL - %s (protocol %s) protocol version mismatch, expected '%s' | %s\n"), ssh_server, ssh_proto, remote_protocol,
 312                            fperfdata("time", elapsed_time, "s", false, 0, false, 0, true, 0, true, (int)socket_timeout));
 313                 close(socket);
 314                 exit(STATE_CRITICAL);
 315         }
 316
 317         printf(_("SSH OK - %s (protocol %s) | %s\n"), ssh_server, ssh_proto,
 318                    fperfdata("time", elapsed_time, "s", false, 0, false, 0, true, 0, true, (int)socket_timeout));
 319         close(socket);
 320         exit(STATE_OK);
 321 }
 322
 323 void print_help(void) {
 324         char *myport;
 325         xasprintf(&myport, "%d", SSH_DFL_PORT);
 326
 327         print_revision(progname, NP_VERSION);
 328
 329         printf("Copyright (c) 1999 Remi Paulmier <remi@sinfomic.fr>\n");
 330         printf(COPYRIGHT, copyright, email);
 331
 332         printf("%s\n", _("Try to connect to an SSH server at specified server and port"));
 333
 334         printf("\n\n");
 335
 336         print_usage();
 337
 338         printf(UT_HELP_VRSN);
 339         printf(UT_EXTRA_OPTS);
 340
 341         printf(UT_HOST_PORT, 'p', myport);
 342
 343         printf(UT_IPv46);
 344
 345         printf(UT_CONN_TIMEOUT, DEFAULT_SOCKET_TIMEOUT);
 346
 347         printf(" %s\n", "-r, --remote-version=STRING");
 348         printf("    %s\n", _("Alert if string doesn't match expected server version (ex: OpenSSH_3.9p1)"));
 349
 350         printf(" %s\n", "-P, --remote-protocol=STRING");
 351         printf("    %s\n", _("Alert if protocol doesn't match expected protocol version (ex: 2.0)"));
 352
 353         printf(UT_VERBOSE);
 354
 355         printf(UT_SUPPORT);
 356 }
 357
 358 void print_usage(void) {
 359         printf("%s\n", _("Usage:"));
 360         printf("%s  [-4|-6] [-t <timeout>] [-r <remote version>] [-p <port>] <host>\n", progname);
 361 }