lib/utils_cmd.c

   1 /*****************************************************************************
   2 *
   3 * Monitoring run command utilities
   4 *
   5 * License: GPL
   6 * Copyright (c) 2005-2006 Monitoring Plugins Development Team
   7 *
   8 * Description :
   9 *
  10 * A simple interface to executing programs from other programs, using an
  11 * optimized and safe popen()-like implementation. It is considered safe
  12 * in that no shell needs to be spawned and the environment passed to the
  13 * execve()'d program is essentially empty.
  14 *
  15 * The code in this file is a derivative of popen.c which in turn was taken
  16 * from "Advanced Programming for the Unix Environment" by W. Richard Stevens.
  17 *
  18 * Care has been taken to make sure the functions are async-safe. The one
  19 * function which isn't is cmd_init() which it doesn't make sense to
  20 * call twice anyway, so the api as a whole should be considered async-safe.
  21 *
  22 *
  23 * This program is free software: you can redistribute it and/or modify
  24 * it under the terms of the GNU General Public License as published by
  25 * the Free Software Foundation, either version 3 of the License, or
  26 * (at your option) any later version.
  27 *
  28 * This program is distributed in the hope that it will be useful,
  29 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  30 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  31 * GNU General Public License for more details.
  32 *
  33 * You should have received a copy of the GNU General Public License
  34 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  35 *
  36 *
  37 *****************************************************************************/
  38
  39 #define NAGIOSPLUG_API_C 1
  40
  41 /** includes **/
  42 #include "common.h"
  43 #include "utils.h"
  44 #include "utils_cmd.h"
  45 /* This variable must be global, since there's no way the caller
  46  * can forcibly slay a dead or ungainly running program otherwise.
  47  * Multithreading apps and plugins can initialize it (via CMD_INIT)
  48  * in an async safe manner PRIOR to calling cmd_run() or cmd_run_array()
  49  * for the first time.
  50  *
  51  * The check for initialized values is atomic and can
  52  * occur in any number of threads simultaneously. */
  53 static pid_t *_cmd_pids = NULL;
  54
  55 #include "utils_base.h"
  56
  57 #include "./maxfd.h"
  58
  59 #include <fcntl.h>
  60
  61 #ifdef HAVE_SYS_WAIT_H
  62 # include <sys/wait.h>
  63 #endif
  64
  65 /* used in _cmd_open to pass the environment to commands */
  66 extern char **environ;
  67
  68 /** macros **/
  69 #ifndef WEXITSTATUS
  70 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
  71 #endif
  72
  73 #ifndef WIFEXITED
  74 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  75 #endif
  76
  77 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
  78 #if defined(SIG_IGN) && !defined(SIG_ERR)
  79 # define SIG_ERR ((Sigfunc *)-1)
  80 #endif
  81
  82 /** prototypes **/
  83 static int _cmd_open (char *const *, int *, int *)
  84         __attribute__ ((__nonnull__ (1, 2, 3)));
  85
  86 static int _cmd_fetch_output (int, output *, int)
  87         __attribute__ ((__nonnull__ (2)));
  88
  89 static int _cmd_close (int);
  90
  91 /* prototype imported from utils.h */
  92 extern void die (int, const char *, ...)
  93         __attribute__ ((__noreturn__, __format__ (__printf__, 2, 3)));
  94
  95
  96 /* this function is NOT async-safe. It is exported so multithreaded
  97  * plugins (or other apps) can call it prior to running any commands
  98  * through this api and thus achieve async-safeness throughout the api */
  99 void
 100 cmd_init (void)
 101 {
 102         long maxfd = mp_open_max();
 103
 104         /* if maxfd is unnaturally high, we force it to a lower value
 105          * ( e.g. on SunOS, when ulimit is set to unlimited: 2147483647 this would cause
 106          * a segfault when following calloc is called ...  ) */
 107
 108         if ( maxfd > MAXFD_LIMIT ) {
 109                 maxfd = MAXFD_LIMIT;
 110         }
 111
 112         if (!_cmd_pids)
 113                 _cmd_pids = calloc (maxfd, sizeof (pid_t));
 114 }
 115
 116
 117 /* Start running a command, array style */
 118 static int
 119 _cmd_open (char *const *argv, int *pfd, int *pfderr)
 120 {
 121         pid_t pid;
 122 #ifdef RLIMIT_CORE
 123         struct rlimit limit;
 124 #endif
 125
 126         int i = 0;
 127
 128         if (!_cmd_pids)
 129                 CMD_INIT;
 130
 131         setenv("LC_ALL", "C", 1);
 132
 133         if (pipe (pfd) < 0 || pipe (pfderr) < 0 || (pid = fork ()) < 0)
 134                 return -1;                                                                      /* errno set by the failing function */
 135
 136         /* child runs exceve() and _exit. */
 137         if (pid == 0) {
 138 #ifdef  RLIMIT_CORE
 139                 /* the program we execve shouldn't leave core files */
 140                 getrlimit (RLIMIT_CORE, &limit);
 141                 limit.rlim_cur = 0;
 142                 setrlimit (RLIMIT_CORE, &limit);
 143 #endif
 144                 close (pfd[0]);
 145                 if (pfd[1] != STDOUT_FILENO) {
 146                         dup2 (pfd[1], STDOUT_FILENO);
 147                         close (pfd[1]);
 148                 }
 149                 close (pfderr[0]);
 150                 if (pfderr[1] != STDERR_FILENO) {
 151                         dup2 (pfderr[1], STDERR_FILENO);
 152                         close (pfderr[1]);
 153                 }
 154
 155                 /* close all descriptors in _cmd_pids[]
 156                  * This is executed in a separate address space (pure child),
 157                  * so we don't have to worry about async safety */
 158                 long maxfd = mp_open_max();
 159                 for (i = 0; i < maxfd; i++)
 160                         if (_cmd_pids[i] > 0)
 161                                 close (i);
 162
 163                 execve (argv[0], argv, environ);
 164                 _exit (STATE_UNKNOWN);
 165         }
 166
 167         /* parent picks up execution here */
 168         /* close children descriptors in our address space */
 169         close (pfd[1]);
 170         close (pfderr[1]);
 171
 172         /* tag our file's entry in the pid-list and return it */
 173         _cmd_pids[pfd[0]] = pid;
 174
 175         return pfd[0];
 176 }
 177
 178 static int
 179 _cmd_close (int fd)
 180 {
 181         int status;
 182         pid_t pid;
 183
 184         /* make sure the provided fd was opened */
 185         long maxfd = mp_open_max();
 186         if (fd < 0 || fd > maxfd || !_cmd_pids || (pid = _cmd_pids[fd]) == 0)
 187                 return -1;
 188
 189         _cmd_pids[fd] = 0;
 190         if (close (fd) == -1)
 191                 return -1;
 192
 193         /* EINTR is ok (sort of), everything else is bad */
 194         while (waitpid (pid, &status, 0) < 0)
 195                 if (errno != EINTR)
 196                         return -1;
 197
 198         /* return child's termination status */
 199         return (WIFEXITED (status)) ? WEXITSTATUS (status) : -1;
 200 }
 201
 202
 203 static int
 204 _cmd_fetch_output (int fd, output * op, int flags)
 205 {
 206         size_t len = 0, i = 0, lineno = 0;
 207         size_t rsf = 6, ary_size = 0;   /* rsf = right shift factor, dec'ed uncond once */
 208         char *buf = NULL;
 209         int ret;
 210         char tmpbuf[4096];
 211
 212         op->buf = NULL;
 213         op->buflen = 0;
 214         while ((ret = read (fd, tmpbuf, sizeof (tmpbuf))) > 0) {
 215                 len = (size_t) ret;
 216                 op->buf = realloc (op->buf, op->buflen + len + 1);
 217                 memcpy (op->buf + op->buflen, tmpbuf, len);
 218                 op->buflen += len;
 219                 i++;
 220         }
 221
 222         if (ret < 0) {
 223                 printf ("read() returned %d: %s\n", ret, strerror (errno));
 224                 return ret;
 225         }
 226
 227         /* some plugins may want to keep output unbroken, and some commands
 228          * will yield no output, so return here for those */
 229         if (flags & CMD_NO_ARRAYS || !op->buf || !op->buflen)
 230                 return op->buflen;
 231
 232         /* and some may want both */
 233         if (flags & CMD_NO_ASSOC) {
 234                 buf = malloc (op->buflen);
 235                 memcpy (buf, op->buf, op->buflen);
 236         }
 237         else
 238                 buf = op->buf;
 239
 240         op->line = NULL;
 241         op->lens = NULL;
 242         i = 0;
 243         while (i < op->buflen) {
 244                 /* make sure we have enough memory */
 245                 if (lineno >= ary_size) {
 246                         /* ary_size must never be zero */
 247                         do {
 248                                 ary_size = op->buflen >> --rsf;
 249                         } while (!ary_size);
 250
 251                         op->line = realloc (op->line, ary_size * sizeof (char *));
 252                         op->lens = realloc (op->lens, ary_size * sizeof (size_t));
 253                 }
 254
 255                 /* set the pointer to the string */
 256                 op->line[lineno] = &buf[i];
 257
 258                 /* hop to next newline or end of buffer */
 259                 while (buf[i] != '\n' && i < op->buflen)
 260                         i++;
 261                 buf[i] = '\0';
 262
 263                 /* calculate the string length using pointer difference */
 264                 op->lens[lineno] = (size_t) & buf[i] - (size_t) op->line[lineno];
 265
 266                 lineno++;
 267                 i++;
 268         }
 269
 270         return lineno;
 271 }
 272
 273
 274 int
 275 cmd_run (const char *cmdstring, output * out, output * err, int flags)
 276 {
 277         int i = 0, argc;
 278         size_t cmdlen;
 279         char **argv = NULL;
 280         char *cmd = NULL;
 281         char *str = NULL;
 282
 283         if (cmdstring == NULL)
 284                 return -1;
 285
 286         /* initialize the structs */
 287         if (out)
 288                 memset (out, 0, sizeof (output));
 289         if (err)
 290                 memset (err, 0, sizeof (output));
 291
 292         /* make copy of command string so strtok() doesn't silently modify it */
 293         /* (the calling program may want to access it later) */
 294         cmdlen = strlen (cmdstring);
 295         if ((cmd = malloc (cmdlen + 1)) == NULL)
 296                 return -1;
 297         memcpy (cmd, cmdstring, cmdlen);
 298         cmd[cmdlen] = '\0';
 299
 300         /* This is not a shell, so we don't handle "???" */
 301         if (strstr (cmdstring, "\"")) return -1;
 302
 303         /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
 304         if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
 305                 return -1;
 306
 307         /* each arg must be whitespace-separated, so args can be a maximum
 308          * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
 309         argc = (cmdlen >> 1) + 2;
 310         argv = calloc (sizeof (char *), argc);
 311
 312         if (argv == NULL) {
 313                 printf ("%s\n", _("Could not malloc argv array in popen()"));
 314                 return -1;
 315         }
 316
 317         /* get command arguments (stupidly, but fairly quickly) */
 318         while (cmd) {
 319                 str = cmd;
 320                 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
 321
 322                 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
 323                         str++;
 324                         if (!strstr (str, "'"))
 325                                 return -1;                                                      /* balanced? */
 326                         cmd = 1 + strstr (str, "'");
 327                         str[strcspn (str, "'")] = 0;
 328                 }
 329                 else {
 330                         if (strpbrk (str, " \t\r\n")) {
 331                                 cmd = 1 + strpbrk (str, " \t\r\n");
 332                                 str[strcspn (str, " \t\r\n")] = 0;
 333                         }
 334                         else {
 335                                 cmd = NULL;
 336                         }
 337                 }
 338
 339                 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
 340                         cmd = NULL;
 341
 342                 argv[i++] = str;
 343         }
 344
 345         return cmd_run_array (argv, out, err, flags);
 346 }
 347
 348 int
 349 cmd_run_array (char *const *argv, output * out, output * err, int flags)
 350 {
 351         int fd, pfd_out[2], pfd_err[2];
 352
 353         /* initialize the structs */
 354         if (out)
 355                 memset (out, 0, sizeof (output));
 356         if (err)
 357                 memset (err, 0, sizeof (output));
 358
 359         if ((fd = _cmd_open (argv, pfd_out, pfd_err)) == -1)
 360                 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), argv[0]);
 361
 362         if (out)
 363                 out->lines = _cmd_fetch_output (pfd_out[0], out, flags);
 364         if (err)
 365                 err->lines = _cmd_fetch_output (pfd_err[0], err, flags);
 366
 367         return _cmd_close (fd);
 368 }
 369
 370 int
 371 cmd_file_read ( char *filename, output *out, int flags)
 372 {
 373         int fd;
 374         if(out)
 375                 memset (out, 0, sizeof(output));
 376
 377         if ((fd = open(filename, O_RDONLY)) == -1) {
 378                 die( STATE_UNKNOWN, _("Error opening %s: %s"), filename, strerror(errno) );
 379         }
 380
 381         if(out)
 382                 out->lines = _cmd_fetch_output (fd, out, flags);
 383
 384         if (close(fd) == -1)
 385                 die( STATE_UNKNOWN, _("Error closing %s: %s"), filename, strerror(errno) );
 386
 387         return 0;
 388 }
 389
 390 void
 391 timeout_alarm_handler (int signo)
 392 {
 393         if (signo == SIGALRM) {
 394                 printf (_("%s - Plugin timed out after %d seconds\n"),
 395                                                 state_text(timeout_state), timeout_interval);
 396
 397                 long maxfd = mp_open_max();
 398                 if(_cmd_pids) for(long int i = 0; i < maxfd; i++) {
 399                         if(_cmd_pids[i] != 0) kill(_cmd_pids[i], SIGKILL);
 400                 }
 401
 402                 exit (timeout_state);
 403         }
 404 }