plugins/popen.c

   1 /*****************************************************************************
   2 *
   3 * Nagios plugins popen
   4 *
   5 * License: GPL
   6 * Copyright (c) 2005-2007 Nagios Plugins Development Team
   7 *
   8 * Description:
   9 *
  10 * A safe alternative to popen
  11 *
  12 * Provides spopen and spclose
  13 *
  14 * FILE * spopen(const char *);
  15 * int spclose(FILE *);
  16 *
  17 * Code taken with liitle modification from "Advanced Programming for the Unix
  18 * Environment" by W. Richard Stevens
  19 *
  20 * This is considered safe in that no shell is spawned, and the environment
  21 * and path passed to the exec'd program are essentially empty. (popen create
  22 * a shell and passes the environment to it).
  23 *
  24 *
  25 * This program is free software: you can redistribute it and/or modify
  26 * it under the terms of the GNU General Public License as published by
  27 * the Free Software Foundation, either version 3 of the License, or
  28 * (at your option) any later version.
  29 *
  30 * This program is distributed in the hope that it will be useful,
  31 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  32 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  33 * GNU General Public License for more details.
  34 *
  35 * You should have received a copy of the GNU General Public License
  36 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  37 *
  38 *
  39 *****************************************************************************/
  40
  41 #include "common.h"
  42
  43 /* extern so plugin has pid to kill exec'd process on timeouts */
  44 extern int timeout_interval;
  45 extern pid_t *childpid;
  46 extern int *child_stderr_array;
  47 extern FILE *child_process;
  48
  49 FILE *spopen (const char *);
  50 int spclose (FILE *);
  51 #ifdef REDHAT_SPOPEN_ERROR
  52 RETSIGTYPE popen_sigchld_handler (int);
  53 #endif
  54 RETSIGTYPE popen_timeout_alarm_handler (int);
  55
  56 #include <stdarg.h>                                                     /* ANSI C header file */
  57 #include <fcntl.h>
  58
  59 #include <limits.h>
  60 #include <sys/resource.h>
  61
  62 #ifdef HAVE_SYS_WAIT_H
  63 #include <sys/wait.h>
  64 #endif
  65
  66 #ifndef WEXITSTATUS
  67 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
  68 #endif
  69
  70 #ifndef WIFEXITED
  71 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  72 #endif
  73
  74 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
  75 #if defined(SIG_IGN) && !defined(SIG_ERR)
  76 #define SIG_ERR ((Sigfunc *)-1)
  77 #endif
  78
  79 #define min(a,b)        ((a) < (b) ? (a) : (b))
  80 #define max(a,b)        ((a) > (b) ? (a) : (b))
  81 int open_max (void);                                            /* {Prog openmax} */
  82 static void err_sys (const char *, ...) __attribute__((noreturn,format(printf, 1, 2)));
  83 char *rtrim (char *, const char *);
  84
  85 char *pname = NULL;                                                     /* caller can set this from argv[0] */
  86
  87 /*int *childerr = NULL;*//* ptr to array allocated at run-time */
  88 /*extern pid_t *childpid = NULL; *//* ptr to array allocated at run-time */
  89 static int maxfd;                                                               /* from our open_max(), {Prog openmax} */
  90
  91 #ifdef REDHAT_SPOPEN_ERROR
  92 static volatile int childtermd = 0;
  93 #endif
  94
  95 FILE *
  96 spopen (const char *cmdstring)
  97 {
  98         char *env[2];
  99         char *cmd = NULL;
 100         char **argv = NULL;
 101         char *str, *tmp;
 102         int argc;
 103
 104         int i = 0, pfd[2], pfderr[2];
 105         pid_t pid;
 106
 107 #ifdef  RLIMIT_CORE
 108         /* do not leave core files */
 109         struct rlimit limit;
 110         getrlimit (RLIMIT_CORE, &limit);
 111         limit.rlim_cur = 0;
 112         setrlimit (RLIMIT_CORE, &limit);
 113 #endif
 114
 115         env[0] = strdup("LC_ALL=C");
 116         env[1] = '\0';
 117
 118         /* if no command was passed, return with no error */
 119         if (cmdstring == NULL)
 120                 return (NULL);
 121
 122         /* make copy of command string so strtok() doesn't silently modify it */
 123         /* (the calling program may want to access it later) */
 124         cmd = malloc (strlen (cmdstring) + 1);
 125         if (cmd == NULL)
 126                 return NULL;
 127         strcpy (cmd, cmdstring);
 128
 129         /* This is not a shell, so we don't handle "???" */
 130         if (strstr (cmdstring, "\""))
 131                 return NULL;
 132
 133         /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
 134         if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
 135                 return NULL;
 136
 137         /* there cannot be more args than characters */
 138         argc = strlen (cmdstring) + 1;  /* add 1 for NULL termination */
 139         argv = malloc (sizeof(char*)*argc);
 140
 141         if (argv == NULL) {
 142                 printf ("%s\n", _("Could not malloc argv array in popen()"));
 143                 return NULL;
 144         }
 145
 146         /* loop to get arguments to command */
 147         while (cmd) {
 148                 str = cmd;
 149                 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
 150
 151                 if (i >= argc - 2) {
 152                         printf ("%s\n",_("CRITICAL - You need more args!!!"));
 153                         return (NULL);
 154                 }
 155
 156                 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
 157                         str++;
 158                         if (!strstr (str, "'"))
 159                                 return NULL;                                            /* balanced? */
 160                         cmd = 1 + strstr (str, "'");
 161                         str[strcspn (str, "'")] = 0;
 162                 }
 163                 else if (strcspn(str,"'") < strcspn (str, " \t\r\n")) {
 164                                                                                 /* handle --option='foo bar' strings */
 165                         tmp = str + strcspn(str, "'") + 1;
 166                         if (!strstr (tmp, "'"))
 167                                 return NULL;                                            /* balanced? */
 168                         tmp += strcspn(tmp,"'") + 1;
 169                         *tmp = 0;
 170                         cmd = tmp + 1;
 171                 } else {
 172                         if (strpbrk (str, " \t\r\n")) {
 173                                 cmd = 1 + strpbrk (str, " \t\r\n");
 174                                 str[strcspn (str, " \t\r\n")] = 0;
 175                         }
 176                         else {
 177                                 cmd = NULL;
 178                         }
 179                 }
 180
 181                 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
 182                         cmd = NULL;
 183
 184                 argv[i++] = str;
 185
 186         }
 187         argv[i] = NULL;
 188
 189         if (childpid == NULL) {                         /* first time through */
 190                 maxfd = open_max ();                            /* allocate zeroed out array for child pids */
 191                 if ((childpid = calloc ((size_t)maxfd, sizeof (pid_t))) == NULL)
 192                         return (NULL);
 193         }
 194
 195         if (child_stderr_array == NULL) {       /* first time through */
 196                 maxfd = open_max ();                            /* allocate zeroed out array for child pids */
 197                 if ((child_stderr_array = calloc ((size_t)maxfd, sizeof (int))) == NULL)
 198                         return (NULL);
 199         }
 200
 201         if (pipe (pfd) < 0)
 202                 return (NULL);                                                  /* errno set by pipe() */
 203
 204         if (pipe (pfderr) < 0)
 205                 return (NULL);                                                  /* errno set by pipe() */
 206
 207 #ifdef REDHAT_SPOPEN_ERROR
 208         if (signal (SIGCHLD, popen_sigchld_handler) == SIG_ERR) {
 209                 usage4 (_("Cannot catch SIGCHLD"));
 210         }
 211 #endif
 212
 213         if ((pid = fork ()) < 0)
 214                 return (NULL);                                                  /* errno set by fork() */
 215         else if (pid == 0) {                                    /* child */
 216                 close (pfd[0]);
 217                 if (pfd[1] != STDOUT_FILENO) {
 218                         dup2 (pfd[1], STDOUT_FILENO);
 219                         close (pfd[1]);
 220                 }
 221                 close (pfderr[0]);
 222                 if (pfderr[1] != STDERR_FILENO) {
 223                         dup2 (pfderr[1], STDERR_FILENO);
 224                         close (pfderr[1]);
 225                 }
 226                 /* close all descriptors in childpid[] */
 227                 for (i = 0; i < maxfd; i++)
 228                         if (childpid[i] > 0)
 229                                 close (i);
 230
 231                 execve (argv[0], argv, env);
 232                 _exit (0);
 233         }
 234
 235         close (pfd[1]);                                                         /* parent */
 236         if ((child_process = fdopen (pfd[0], "r")) == NULL)
 237                 return (NULL);
 238         close (pfderr[1]);
 239
 240         childpid[fileno (child_process)] = pid; /* remember child pid for this fd */
 241         child_stderr_array[fileno (child_process)] = pfderr[0]; /* remember STDERR */
 242         return (child_process);
 243 }
 244
 245 int
 246 spclose (FILE * fp)
 247 {
 248         int fd, status;
 249         pid_t pid;
 250
 251         if (childpid == NULL)
 252                 return (1);                                                             /* popen() has never been called */
 253
 254         fd = fileno (fp);
 255         if ((pid = childpid[fd]) == 0)
 256                 return (1);                                                             /* fp wasn't opened by popen() */
 257
 258         childpid[fd] = 0;
 259         if (fclose (fp) == EOF)
 260                 return (1);
 261
 262 #ifdef REDHAT_SPOPEN_ERROR
 263         while (!childtermd);                                                            /* wait until SIGCHLD */
 264 #endif
 265
 266         while (waitpid (pid, &status, 0) < 0)
 267                 if (errno != EINTR)
 268                         return (1);                                                     /* error other than EINTR from waitpid() */
 269
 270         if (WIFEXITED (status))
 271                 return (WEXITSTATUS (status));  /* return child's termination status */
 272
 273         return (1);
 274 }
 275
 276 #ifdef  OPEN_MAX
 277 static int openmax = OPEN_MAX;
 278 #else
 279 static int openmax = 0;
 280 #endif
 281
 282 #define OPEN_MAX_GUESS  256                     /* if OPEN_MAX is indeterminate */
 283                                 /* no guarantee this is adequate */
 284
 285 #ifdef REDHAT_SPOPEN_ERROR
 286 RETSIGTYPE
 287 popen_sigchld_handler (int signo)
 288 {
 289         if (signo == SIGCHLD)
 290                 childtermd = 1;
 291 }
 292 #endif
 293
 294 RETSIGTYPE
 295 popen_timeout_alarm_handler (int signo)
 296 {
 297         int fh;
 298         if (signo == SIGALRM) {
 299                 if (child_process != NULL) {
 300                         fh=fileno (child_process);
 301                         if(fh >= 0){
 302                                 kill (childpid[fh], SIGKILL);
 303                         }
 304                         printf (_("CRITICAL - Plugin timed out after %d seconds\n"),
 305                                                 timeout_interval);
 306                 } else {
 307                         printf ("%s\n", _("CRITICAL - popen timeout received, but no child process"));
 308                 }
 309                 exit (STATE_CRITICAL);
 310         }
 311 }
 312
 313
 314 int
 315 open_max (void)
 316 {
 317         if (openmax == 0) {                                             /* first time through */
 318                 errno = 0;
 319                 if ((openmax = sysconf (_SC_OPEN_MAX)) < 0) {
 320                         if (errno == 0)
 321                                 openmax = OPEN_MAX_GUESS;       /* it's indeterminate */
 322                         else
 323                                 err_sys (_("sysconf error for _SC_OPEN_MAX"));
 324                 }
 325         }
 326         return (openmax);
 327 }
 328
 329
 330 /* Fatal error related to a system call.
 331  * Print a message and die. */
 332
 333 #define MAXLINE 2048
 334 static void
 335 err_sys (const char *fmt, ...)
 336 {
 337         int errnoflag = 1;
 338         int errno_save;
 339         char buf[MAXLINE];
 340
 341         va_list ap;
 342
 343         va_start (ap, fmt);
 344         /* err_doit (1, fmt, ap); */
 345         errno_save = errno;                                             /* value caller might want printed */
 346         vsprintf (buf, fmt, ap);
 347         if (errnoflag)
 348                 sprintf (buf + strlen (buf), ": %s", strerror (errno_save));
 349         strcat (buf, "\n");
 350         fflush (stdout);                                                        /* in case stdout and stderr are the same */
 351         fputs (buf, stderr);
 352         fflush (NULL);                                                          /* flushes all stdio output streams */
 353         va_end (ap);
 354         exit (1);
 355 }
 356
 357 char *
 358 rtrim (char *str, const char *tok)
 359 {
 360         int i = 0;
 361         int j = sizeof (str);
 362
 363         while (str != NULL && i < j) {
 364                 if (*(str + i) == *tok) {
 365                         sprintf (str + i, "%s", "\0");
 366                         return str;
 367                 }
 368                 i++;
 369         }
 370         return str;
 371 }