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_cmd.h"
  44 #include "utils_base.h"
  45 #include <fcntl.h>
  46
  47 #ifdef HAVE_SYS_WAIT_H
  48 # include <sys/wait.h>
  49 #endif
  50
  51 /* used in _cmd_open to pass the environment to commands */
  52 extern char **environ;
  53
  54 /** macros **/
  55 #ifndef WEXITSTATUS
  56 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
  57 #endif
  58
  59 #ifndef WIFEXITED
  60 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  61 #endif
  62
  63 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
  64 #if defined(SIG_IGN) && !defined(SIG_ERR)
  65 # define SIG_ERR ((Sigfunc *)-1)
  66 #endif
  67
  68 /* This variable must be global, since there's no way the caller
  69  * can forcibly slay a dead or ungainly running program otherwise.
  70  * Multithreading apps and plugins can initialize it (via CMD_INIT)
  71  * in an async safe manner PRIOR to calling cmd_run() or cmd_run_array()
  72  * for the first time.
  73  *
  74  * The check for initialized values is atomic and can
  75  * occur in any number of threads simultaneously. */
  76 static pid_t *_cmd_pids = NULL;
  77
  78 /* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
  79  * If that fails and the macro isn't defined, we fall back to an educated
  80  * guess. There's no guarantee that our guess is adequate and the program
  81  * will die with SIGSEGV if it isn't and the upper boundary is breached. */
  82 #define DEFAULT_MAXFD  256   /* fallback value if no max open files value is set */
  83 #define MAXFD_LIMIT   8192   /* upper limit of open files */
  84 #ifdef _SC_OPEN_MAX
  85 static long maxfd = 0;
  86 #elif defined(OPEN_MAX)
  87 # define maxfd OPEN_MAX
  88 #else   /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
  89 # define maxfd DEFAULT_MAXFD
  90 #endif
  91
  92
  93 /** prototypes **/
  94 static int _cmd_open (char *const *, int *, int *)
  95         __attribute__ ((__nonnull__ (1, 2, 3)));
  96
  97 static int _cmd_fetch_output (int, output *, int)
  98         __attribute__ ((__nonnull__ (2)));
  99
 100 static int _cmd_close (int);
 101
 102 /* prototype imported from utils.h */
 103 extern void die (int, const char *, ...)
 104         __attribute__ ((__noreturn__, __format__ (__printf__, 2, 3)));
 105
 106
 107 /* this function is NOT async-safe. It is exported so multithreaded
 108  * plugins (or other apps) can call it prior to running any commands
 109  * through this api and thus achieve async-safeness throughout the api */
 110 void
 111 cmd_init (void)
 112 {
 113 #ifndef maxfd
 114         if (!maxfd && (maxfd = sysconf (_SC_OPEN_MAX)) < 0) {
 115                 /* possibly log or emit a warning here, since there's no
 116                  * guarantee that our guess at maxfd will be adequate */
 117                 maxfd = DEFAULT_MAXFD;
 118         }
 119 #endif
 120
 121         /* if maxfd is unnaturally high, we force it to a lower value
 122          * ( e.g. on SunOS, when ulimit is set to unlimited: 2147483647 this would cause
 123          * a segfault when following calloc is called ...  ) */
 124
 125         if ( maxfd > MAXFD_LIMIT ) {
 126                 maxfd = MAXFD_LIMIT;
 127         }
 128
 129         if (!_cmd_pids)
 130                 _cmd_pids = calloc (maxfd, sizeof (pid_t));
 131 }
 132
 133
 134 /* Start running a command, array style */
 135 static int
 136 _cmd_open (char *const *argv, int *pfd, int *pfderr)
 137 {
 138         pid_t pid;
 139 #ifdef RLIMIT_CORE
 140         struct rlimit limit;
 141 #endif
 142
 143         int i = 0;
 144
 145         /* if no command was passed, return with no error */
 146         if (argv == NULL)
 147                 return -1;
 148
 149         if (!_cmd_pids)
 150                 CMD_INIT;
 151
 152         setenv("LC_ALL", "C", 1);
 153
 154         if (pipe (pfd) < 0 || pipe (pfderr) < 0 || (pid = fork ()) < 0)
 155                 return -1;                                                                      /* errno set by the failing function */
 156
 157         /* child runs exceve() and _exit. */
 158         if (pid == 0) {
 159 #ifdef  RLIMIT_CORE
 160                 /* the program we execve shouldn't leave core files */
 161                 getrlimit (RLIMIT_CORE, &limit);
 162                 limit.rlim_cur = 0;
 163                 setrlimit (RLIMIT_CORE, &limit);
 164 #endif
 165                 close (pfd[0]);
 166                 if (pfd[1] != STDOUT_FILENO) {
 167                         dup2 (pfd[1], STDOUT_FILENO);
 168                         close (pfd[1]);
 169                 }
 170                 close (pfderr[0]);
 171                 if (pfderr[1] != STDERR_FILENO) {
 172                         dup2 (pfderr[1], STDERR_FILENO);
 173                         close (pfderr[1]);
 174                 }
 175
 176                 /* close all descriptors in _cmd_pids[]
 177                  * This is executed in a separate address space (pure child),
 178                  * so we don't have to worry about async safety */
 179                 for (i = 0; i < maxfd; i++)
 180                         if (_cmd_pids[i] > 0)
 181                                 close (i);
 182
 183                 execve (argv[0], argv, environ);
 184                 _exit (STATE_UNKNOWN);
 185         }
 186
 187         /* parent picks up execution here */
 188         /* close childs descriptors in our address space */
 189         close (pfd[1]);
 190         close (pfderr[1]);
 191
 192         /* tag our file's entry in the pid-list and return it */
 193         _cmd_pids[pfd[0]] = pid;
 194
 195         return pfd[0];
 196 }
 197
 198 static int
 199 _cmd_close (int fd)
 200 {
 201         int status;
 202         pid_t pid;
 203
 204         /* make sure the provided fd was opened */
 205         if (fd < 0 || fd > maxfd || !_cmd_pids || (pid = _cmd_pids[fd]) == 0)
 206                 return -1;
 207
 208         _cmd_pids[fd] = 0;
 209         if (close (fd) == -1)
 210                 return -1;
 211
 212         /* EINTR is ok (sort of), everything else is bad */
 213         while (waitpid (pid, &status, 0) < 0)
 214                 if (errno != EINTR)
 215                         return -1;
 216
 217         /* return child's termination status */
 218         return (WIFEXITED (status)) ? WEXITSTATUS (status) : -1;
 219 }
 220
 221
 222 static int
 223 _cmd_fetch_output (int fd, output * op, int flags)
 224 {
 225         size_t len = 0, i = 0, lineno = 0;
 226         size_t rsf = 6, ary_size = 0;   /* rsf = right shift factor, dec'ed uncond once */
 227         char *buf = NULL;
 228         int ret;
 229         char tmpbuf[4096];
 230
 231         op->buf = NULL;
 232         op->buflen = 0;
 233         while ((ret = read (fd, tmpbuf, sizeof (tmpbuf))) > 0) {
 234                 len = (size_t) ret;
 235                 op->buf = realloc (op->buf, op->buflen + len + 1);
 236                 memcpy (op->buf + op->buflen, tmpbuf, len);
 237                 op->buflen += len;
 238                 i++;
 239         }
 240
 241         if (ret < 0) {
 242                 printf ("read() returned %d: %s\n", ret, strerror (errno));
 243                 return ret;
 244         }
 245
 246         /* some plugins may want to keep output unbroken, and some commands
 247          * will yield no output, so return here for those */
 248         if (flags & CMD_NO_ARRAYS || !op->buf || !op->buflen)
 249                 return op->buflen;
 250
 251         /* and some may want both */
 252         if (flags & CMD_NO_ASSOC) {
 253                 buf = malloc (op->buflen);
 254                 memcpy (buf, op->buf, op->buflen);
 255         }
 256         else
 257                 buf = op->buf;
 258
 259         op->line = NULL;
 260         op->lens = NULL;
 261         i = 0;
 262         while (i < op->buflen) {
 263                 /* make sure we have enough memory */
 264                 if (lineno >= ary_size) {
 265                         /* ary_size must never be zero */
 266                         do {
 267                                 ary_size = op->buflen >> --rsf;
 268                         } while (!ary_size);
 269
 270                         op->line = realloc (op->line, ary_size * sizeof (char *));
 271                         op->lens = realloc (op->lens, ary_size * sizeof (size_t));
 272                 }
 273
 274                 /* set the pointer to the string */
 275                 op->line[lineno] = &buf[i];
 276
 277                 /* hop to next newline or end of buffer */
 278                 while (buf[i] != '\n' && i < op->buflen)
 279                         i++;
 280                 buf[i] = '\0';
 281
 282                 /* calculate the string length using pointer difference */
 283                 op->lens[lineno] = (size_t) & buf[i] - (size_t) op->line[lineno];
 284
 285                 lineno++;
 286                 i++;
 287         }
 288
 289         return lineno;
 290 }
 291
 292
 293 int
 294 cmd_run (const char *cmdstring, output * out, output * err, int flags)
 295 {
 296         int fd, pfd_out[2], pfd_err[2];
 297         int i = 0, argc;
 298         size_t cmdlen;
 299         char **argv = NULL;
 300         char *cmd = NULL;
 301         char *str = NULL;
 302
 303         if (cmdstring == NULL)
 304                 return -1;
 305
 306         /* initialize the structs */
 307         if (out)
 308                 memset (out, 0, sizeof (output));
 309         if (err)
 310                 memset (err, 0, sizeof (output));
 311
 312         /* make copy of command string so strtok() doesn't silently modify it */
 313         /* (the calling program may want to access it later) */
 314         cmdlen = strlen (cmdstring);
 315         if ((cmd = malloc (cmdlen + 1)) == NULL)
 316                 return -1;
 317         memcpy (cmd, cmdstring, cmdlen);
 318         cmd[cmdlen] = '\0';
 319
 320         /* This is not a shell, so we don't handle "???" */
 321         if (strstr (cmdstring, "\"")) return -1;
 322
 323         /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
 324         if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
 325                 return -1;
 326
 327         /* each arg must be whitespace-separated, so args can be a maximum
 328          * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
 329         argc = (cmdlen >> 1) + 2;
 330         argv = calloc (sizeof (char *), argc);
 331
 332         if (argv == NULL) {
 333                 printf ("%s\n", _("Could not malloc argv array in popen()"));
 334                 return -1;
 335         }
 336
 337         /* get command arguments (stupidly, but fairly quickly) */
 338         while (cmd) {
 339                 str = cmd;
 340                 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
 341
 342                 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
 343                         str++;
 344                         if (!strstr (str, "'"))
 345                                 return -1;                                                      /* balanced? */
 346                         cmd = 1 + strstr (str, "'");
 347                         str[strcspn (str, "'")] = 0;
 348                 }
 349                 else {
 350                         if (strpbrk (str, " \t\r\n")) {
 351                                 cmd = 1 + strpbrk (str, " \t\r\n");
 352                                 str[strcspn (str, " \t\r\n")] = 0;
 353                         }
 354                         else {
 355                                 cmd = NULL;
 356                         }
 357                 }
 358
 359                 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
 360                         cmd = NULL;
 361
 362                 argv[i++] = str;
 363         }
 364
 365         return cmd_run_array (argv, out, err, flags);
 366 }
 367
 368 int
 369 cmd_run_array (char *const *argv, output * out, output * err, int flags)
 370 {
 371         int fd, pfd_out[2], pfd_err[2];
 372
 373         /* initialize the structs */
 374         if (out)
 375                 memset (out, 0, sizeof (output));
 376         if (err)
 377                 memset (err, 0, sizeof (output));
 378
 379         if ((fd = _cmd_open (argv, pfd_out, pfd_err)) == -1)
 380                 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), argv[0]);
 381
 382         if (out)
 383                 out->lines = _cmd_fetch_output (pfd_out[0], out, flags);
 384         if (err)
 385                 err->lines = _cmd_fetch_output (pfd_err[0], err, flags);
 386
 387         return _cmd_close (fd);
 388 }
 389
 390 int
 391 cmd_file_read ( char *filename, output *out, int flags)
 392 {
 393         int fd;
 394         if(out)
 395                 memset (out, 0, sizeof(output));
 396
 397         if ((fd = open(filename, O_RDONLY)) == -1) {
 398                 die( STATE_UNKNOWN, _("Error opening %s: %s"), filename, strerror(errno) );
 399         }
 400
 401         if(out)
 402                 out->lines = _cmd_fetch_output (fd, out, flags);
 403
 404         if (close(fd) == -1)
 405                 die( STATE_UNKNOWN, _("Error closing %s: %s"), filename, strerror(errno) );
 406
 407         return 0;
 408 }