lib/utils_cmd.c

   1 /****************************************************************************
   2  * Nagios run command utilities
   3  *
   4  * License: GPL
   5  * Copyright (c) 2005 nagios-plugins team
   6  *
   7  * $Id: utils_cmd.c 1434 2006-06-18 19:36:48Z opensides $
   8  *
   9  * Description :
  10  *
  11  * A simple interface to executing programs from other programs, using an
  12  * optimized and safe popen()-like implementation. It is considered safe
  13  * in that no shell needs to be spawned and the environment passed to the
  14  * execve()'d program is essentially empty.
  15  *
  16  *
  17  * The code in this file is a derivative of popen.c which in turn was taken
  18  * from "Advanced Programming for the Unix Environment" by W. Richard Stevens.
  19  *
  20  * Care has been taken to make sure the functions are async-safe. The one
  21  * function which isn't is cmd_init() which it doesn't make sense to
  22  * call twice anyway, so the api as a whole should be considered async-safe.
  23  *
  24  * License Information:
  25  *
  26  * This program is free software; you can redistribute it and/or modify
  27  * it under the terms of the GNU General Public License as published by
  28  * the Free Software Foundation; either version 2 of the License, or
  29  * (at your option) any later version.
  30  *
  31  * This program is distributed in the hope that it will be useful,
  32  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  33  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  34  * GNU General Public License for more details.
  35  *
  36  * You should have received a copy of the GNU General Public License
  37  * along with this program; if not, write to the Free Software
  38  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  39  */
  40
  41 #define NAGIOSPLUG_API_C 1
  42
  43 /** includes **/
  44 #include "common.h"
  45 #include "utils_cmd.h"
  46 #include "utils_base.h"
  47
  48 #ifdef HAVE_SYS_WAIT_H
  49 # include <sys/wait.h>
  50 #endif
  51
  52 /** macros **/
  53 #ifndef WEXITSTATUS
  54 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
  55 #endif
  56
  57 #ifndef WIFEXITED
  58 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  59 #endif
  60
  61 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
  62 #if defined(SIG_IGN) && !defined(SIG_ERR)
  63 # define SIG_ERR ((Sigfunc *)-1)
  64 #endif
  65
  66 /* This variable must be global, since there's no way the caller
  67  * can forcibly slay a dead or ungainly running program otherwise.
  68  * Multithreading apps and plugins can initialize it (via CMD_INIT)
  69  * in an async safe manner PRIOR to calling cmd_run() or cmd_run_array()
  70  * for the first time.
  71  *
  72  * The check for initialized values is atomic and can
  73  * occur in any number of threads simultaneously. */
  74 static pid_t *_cmd_pids = NULL;
  75
  76 /* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
  77  * If that fails and the macro isn't defined, we fall back to an educated
  78  * guess. There's no guarantee that our guess is adequate and the program
  79  * will die with SIGSEGV if it isn't and the upper boundary is breached. */
  80 #ifdef _SC_OPEN_MAX
  81 static long maxfd = 0;
  82 #elif defined(OPEN_MAX)
  83 # define maxfd OPEN_MAX
  84 #else   /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
  85 # define maxfd 256
  86 #endif
  87
  88
  89 /** prototypes **/
  90 static int _cmd_open (char *const *, int *, int *)
  91         __attribute__ ((__nonnull__ (1, 2, 3)));
  92
  93 static int _cmd_fetch_output (int, output *, int)
  94         __attribute__ ((__nonnull__ (2)));
  95
  96 static int _cmd_close (int);
  97
  98 /* prototype imported from utils.h */
  99 extern void die (int, const char *, ...)
 100         __attribute__ ((__noreturn__, __format__ (__printf__, 2, 3)));
 101
 102
 103 /* this function is NOT async-safe. It is exported so multithreaded
 104  * plugins (or other apps) can call it prior to running any commands
 105  * through this api and thus achieve async-safeness throughout the api */
 106 void
 107 cmd_init (void)
 108 {
 109 #ifndef maxfd
 110         if (!maxfd && (maxfd = sysconf (_SC_OPEN_MAX)) < 0) {
 111                 /* possibly log or emit a warning here, since there's no
 112                  * guarantee that our guess at maxfd will be adequate */
 113                 maxfd = 256;
 114         }
 115 #endif
 116
 117         if (!_cmd_pids)
 118                 _cmd_pids = calloc (maxfd, sizeof (pid_t));
 119 }
 120
 121
 122 /* Start running a command, array style */
 123 static int
 124 _cmd_open (char *const *argv, int *pfd, int *pfderr)
 125 {
 126         char *env[2];
 127         pid_t pid;
 128 #ifdef RLIMIT_CORE
 129         struct rlimit limit;
 130 #endif
 131
 132         int i = 0;
 133
 134         /* if no command was passed, return with no error */
 135         if (argv == NULL)
 136                 return -1;
 137
 138         if (!_cmd_pids)
 139                 CMD_INIT;
 140
 141         env[0] = strdup ("LC_ALL=C");
 142         env[1] = '\0';
 143
 144         if (pipe (pfd) < 0 || pipe (pfderr) < 0 || (pid = fork ()) < 0)
 145                 return -1;                                                                      /* errno set by the failing function */
 146
 147         /* child runs exceve() and _exit. */
 148         if (pid == 0) {
 149 #ifdef  RLIMIT_CORE
 150                 /* the program we execve shouldn't leave core files */
 151                 getrlimit (RLIMIT_CORE, &limit);
 152                 limit.rlim_cur = 0;
 153                 setrlimit (RLIMIT_CORE, &limit);
 154 #endif
 155                 close (pfd[0]);
 156                 if (pfd[1] != STDOUT_FILENO) {
 157                         dup2 (pfd[1], STDOUT_FILENO);
 158                         close (pfd[1]);
 159                 }
 160                 close (pfderr[0]);
 161                 if (pfderr[1] != STDERR_FILENO) {
 162                         dup2 (pfderr[1], STDERR_FILENO);
 163                         close (pfderr[1]);
 164                 }
 165
 166                 /* close all descriptors in _cmd_pids[]
 167                  * This is executed in a separate address space (pure child),
 168                  * so we don't have to worry about async safety */
 169                 for (i = 0; i < maxfd; i++)
 170                         if (_cmd_pids[i] > 0)
 171                                 close (i);
 172
 173                 execve (argv[0], argv, env);
 174                 _exit (STATE_UNKNOWN);
 175         }
 176
 177         /* parent picks up execution here */
 178         /* close childs descriptors in our address space */
 179         close (pfd[1]);
 180         close (pfderr[1]);
 181
 182         /* tag our file's entry in the pid-list and return it */
 183         _cmd_pids[pfd[0]] = pid;
 184
 185         return pfd[0];
 186 }
 187
 188 static int
 189 _cmd_close (int fd)
 190 {
 191         int status;
 192         pid_t pid;
 193
 194         /* make sure the provided fd was opened */
 195         if (fd < 0 || fd > maxfd || !_cmd_pids || (pid = _cmd_pids[fd]) == 0)
 196                 return -1;
 197
 198         _cmd_pids[fd] = 0;
 199         if (close (fd) == -1)
 200                 return -1;
 201
 202         /* EINTR is ok (sort of), everything else is bad */
 203         while (waitpid (pid, &status, 0) < 0)
 204                 if (errno != EINTR)
 205                         return -1;
 206
 207         /* return child's termination status */
 208         return (WIFEXITED (status)) ? WEXITSTATUS (status) : -1;
 209 }
 210
 211
 212 static int
 213 _cmd_fetch_output (int fd, output * op, int flags)
 214 {
 215         size_t len = 0, i = 0, lineno = 0;
 216         size_t rsf = 6, ary_size = 0;   /* rsf = right shift factor, dec'ed uncond once */
 217         char *buf = NULL;
 218         int ret;
 219         char tmpbuf[4096];
 220
 221         op->buf = NULL;
 222         op->buflen = 0;
 223         while ((ret = read (fd, tmpbuf, sizeof (tmpbuf))) > 0) {
 224                 len = (size_t) ret;
 225                 op->buf = realloc (op->buf, op->buflen + len + 1);
 226                 memcpy (op->buf + op->buflen, tmpbuf, len);
 227                 op->buflen += len;
 228                 i++;
 229         }
 230
 231         if (ret < 0) {
 232                 printf ("read() returned %d: %s\n", ret, strerror (errno));
 233                 return ret;
 234         }
 235
 236         /* some plugins may want to keep output unbroken, and some commands
 237          * will yield no output, so return here for those */
 238         if (flags & CMD_NO_ARRAYS || !op->buf || !op->buflen)
 239                 return op->buflen;
 240
 241         /* and some may want both */
 242         if (flags & CMD_NO_ASSOC) {
 243                 buf = malloc (op->buflen);
 244                 memcpy (buf, op->buf, op->buflen);
 245         }
 246         else
 247                 buf = op->buf;
 248
 249         op->line = NULL;
 250         op->lens = NULL;
 251         i = 0;
 252         while (i < op->buflen) {
 253                 /* make sure we have enough memory */
 254                 if (lineno >= ary_size) {
 255                         /* ary_size must never be zero */
 256                         do {
 257                                 ary_size = op->buflen >> --rsf;
 258                         } while (!ary_size);
 259
 260                         op->line = realloc (op->line, ary_size * sizeof (char *));
 261                         op->lens = realloc (op->lens, ary_size * sizeof (size_t));
 262                 }
 263
 264                 /* set the pointer to the string */
 265                 op->line[lineno] = &buf[i];
 266
 267                 /* hop to next newline or end of buffer */
 268                 while (buf[i] != '\n' && i < op->buflen)
 269                         i++;
 270                 buf[i] = '\0';
 271
 272                 /* calculate the string length using pointer difference */
 273                 op->lens[lineno] = (size_t) & buf[i] - (size_t) op->line[lineno];
 274
 275                 lineno++;
 276                 i++;
 277         }
 278
 279         return lineno;
 280 }
 281
 282
 283 int
 284 cmd_run (const char *cmdstring, output * out, output * err, int flags)
 285 {
 286         int fd, pfd_out[2], pfd_err[2];
 287         int i = 0, argc;
 288         size_t cmdlen;
 289         char **argv = NULL;
 290         char *cmd = NULL;
 291         char *str = NULL;
 292
 293         if (cmdstring == NULL)
 294                 return -1;
 295
 296         /* initialize the structs */
 297         if (out)
 298                 memset (out, 0, sizeof (output));
 299         if (err)
 300                 memset (err, 0, sizeof (output));
 301
 302         /* make copy of command string so strtok() doesn't silently modify it */
 303         /* (the calling program may want to access it later) */
 304         cmdlen = strlen (cmdstring);
 305         if ((cmd = malloc (cmdlen + 1)) == NULL)
 306                 return -1;
 307         memcpy (cmd, cmdstring, cmdlen);
 308         cmd[cmdlen] = '\0';
 309
 310         /* This is not a shell, so we don't handle "???" */
 311         if (strstr (cmdstring, "\"")) return -1;
 312
 313         /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
 314         if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
 315                 return -1;
 316
 317         /* each arg must be whitespace-separated, so args can be a maximum
 318          * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
 319         argc = (cmdlen >> 1) + 2;
 320         argv = calloc (sizeof (char *), argc);
 321
 322         if (argv == NULL) {
 323                 printf ("%s\n", _("Could not malloc argv array in popen()"));
 324                 return -1;
 325         }
 326
 327         /* get command arguments (stupidly, but fairly quickly) */
 328         while (cmd) {
 329                 str = cmd;
 330                 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
 331
 332                 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
 333                         str++;
 334                         if (!strstr (str, "'"))
 335                                 return -1;                                                      /* balanced? */
 336                         cmd = 1 + strstr (str, "'");
 337                         str[strcspn (str, "'")] = 0;
 338                 }
 339                 else {
 340                         if (strpbrk (str, " \t\r\n")) {
 341                                 cmd = 1 + strpbrk (str, " \t\r\n");
 342                                 str[strcspn (str, " \t\r\n")] = 0;
 343                         }
 344                         else {
 345                                 cmd = NULL;
 346                         }
 347                 }
 348
 349                 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
 350                         cmd = NULL;
 351
 352                 argv[i++] = str;
 353         }
 354
 355         return cmd_run_array (argv, out, err, flags);
 356 }
 357
 358 int
 359 cmd_run_array (char *const *argv, output * out, output * err, int flags)
 360 {
 361         int fd, pfd_out[2], pfd_err[2];
 362
 363         /* initialize the structs */
 364         if (out)
 365                 memset (out, 0, sizeof (output));
 366         if (err)
 367                 memset (err, 0, sizeof (output));
 368
 369         if ((fd = _cmd_open (argv, pfd_out, pfd_err)) == -1)
 370                 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), argv[0]);
 371
 372         if (out)
 373                 out->lines = _cmd_fetch_output (pfd_out[0], out, flags);
 374         if (err)
 375                 err->lines = _cmd_fetch_output (pfd_err[0], err, flags);
 376
 377         return _cmd_close (fd);
 378 }