plugins/runcmd.c

   1 /****************************************************************************
   2  * Nagios run command utilities
   3  *
   4  * License: GPL
   5  * Copyright (c) 2005 nagios-plugins team
   6  *
   7  * $Id$
   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 np_runcmd_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 "runcmd.h"
  45 #ifdef HAVE_SYS_WAIT_H
  46 # include <sys/wait.h>
  47 #endif
  48
  49 /** macros **/
  50 #ifndef WEXITSTATUS
  51 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
  52 #endif
  53
  54 #ifndef WIFEXITED
  55 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  56 #endif
  57
  58 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
  59 #if defined(SIG_IGN) && !defined(SIG_ERR)
  60 # define SIG_ERR ((Sigfunc *)-1)
  61 #endif
  62
  63 /* This variable must be global, since there's no way the caller
  64  * can forcibly slay a dead or ungainly running program otherwise.
  65  * Multithreading apps and plugins can initialize it (via NP_RUNCMD_INIT)
  66  * in an async safe manner PRIOR to calling np_runcmd() for the first time.
  67  *
  68  * The check for initialized values is atomic and can
  69  * occur in any number of threads simultaneously. */
  70 static pid_t *np_pids = NULL;
  71
  72 /* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
  73  * If that fails and the macro isn't defined, we fall back to an educated
  74  * guess. There's no guarantee that our guess is adequate and the program
  75  * will die with SIGSEGV if it isn't and the upper boundary is breached. */
  76 #ifdef _SC_OPEN_MAX
  77 static long maxfd = 0;
  78 #elif defined(OPEN_MAX)
  79 # define maxfd OPEN_MAX
  80 #else /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
  81 # define maxfd 256
  82 #endif
  83
  84
  85 /** prototypes **/
  86 static int np_runcmd_open(const char *, int *, int *)
  87         __attribute__((__nonnull__(1, 2, 3)));
  88
  89 static int np_fetch_output(int, output *, int)
  90         __attribute__((__nonnull__(2)));
  91
  92 static int np_runcmd_close(int);
  93
  94 /* prototype imported from utils.h */
  95 extern void die (int, const char *, ...)
  96         __attribute__((__noreturn__,__format__(__printf__, 2, 3)));
  97
  98
  99 /* this function is NOT async-safe. It is exported so multithreaded
 100  * plugins (or other apps) can call it prior to running any commands
 101  * through this api and thus achieve async-safeness throughout the api */
 102 void np_runcmd_init(void)
 103 {
 104 #ifndef maxfd
 105         if(!maxfd && (maxfd = sysconf(_SC_OPEN_MAX)) < 0) {
 106                 /* possibly log or emit a warning here, since there's no
 107                  * guarantee that our guess at maxfd will be adequate */
 108                 maxfd = 256;
 109         }
 110 #endif
 111
 112         if(!np_pids) np_pids = calloc(maxfd, sizeof(pid_t));
 113 }
 114
 115
 116 /* Start running a command */
 117 static int
 118 np_runcmd_open(const char *cmdstring, int *pfd, int *pfderr)
 119 {
 120         char *env[2];
 121         char *cmd = NULL;
 122         char **argv = NULL;
 123         char *str;
 124         int argc;
 125         size_t cmdlen;
 126         pid_t pid;
 127 #ifdef RLIMIT_CORE
 128         struct rlimit limit;
 129 #endif
 130
 131         int i = 0;
 132
 133         if(!np_pids) NP_RUNCMD_INIT;
 134
 135         env[0] = strdup("LC_ALL=C");
 136         env[1] = '\0';
 137
 138         /* if no command was passed, return with no error */
 139         if (cmdstring == NULL)
 140                 return -1;
 141
 142         /* make copy of command string so strtok() doesn't silently modify it */
 143         /* (the calling program may want to access it later) */
 144         cmdlen = strlen(cmdstring);
 145         if((cmd = malloc(cmdlen + 1)) == NULL) return -1;
 146         memcpy(cmd, cmdstring, cmdlen);
 147         cmd[cmdlen] = '\0';
 148
 149         /* This is not a shell, so we don't handle "???" */
 150         if (strstr (cmdstring, "\"")) return -1;
 151
 152         /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
 153         if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
 154                 return -1;
 155
 156         /* each arg must be whitespace-separated, so args can be a maximum
 157          * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
 158         argc = (cmdlen >> 1) + 2;
 159         argv = calloc(sizeof(char *), argc);
 160
 161         if (argv == NULL) {
 162                 printf ("%s\n", _("Could not malloc argv array in popen()"));
 163                 return -1;
 164         }
 165
 166         /* get command arguments (stupidly, but fairly quickly) */
 167         while (cmd) {
 168                 str = cmd;
 169                 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
 170
 171                 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
 172                         str++;
 173                         if (!strstr (str, "'")) return -1;      /* balanced? */
 174                         cmd = 1 + strstr (str, "'");
 175                         str[strcspn (str, "'")] = 0;
 176                 }
 177                 else {
 178                         if (strpbrk (str, " \t\r\n")) {
 179                                 cmd = 1 + strpbrk (str, " \t\r\n");
 180                                 str[strcspn (str, " \t\r\n")] = 0;
 181                         }
 182                         else {
 183                                 cmd = NULL;
 184                         }
 185                 }
 186
 187                 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
 188                         cmd = NULL;
 189
 190                 argv[i++] = str;
 191         }
 192
 193         if (pipe(pfd) < 0 || pipe(pfderr) < 0 || (pid = fork()) < 0)
 194                 return -1; /* errno set by the failing function */
 195
 196         /* child runs exceve() and _exit. */
 197         if (pid == 0) {
 198 #ifdef  RLIMIT_CORE
 199                 /* the program we execve shouldn't leave core files */
 200                 getrlimit (RLIMIT_CORE, &limit);
 201                 limit.rlim_cur = 0;
 202                 setrlimit (RLIMIT_CORE, &limit);
 203 #endif
 204                 close (pfd[0]);
 205                 if (pfd[1] != STDOUT_FILENO) {
 206                         dup2 (pfd[1], STDOUT_FILENO);
 207                         close (pfd[1]);
 208                 }
 209                 close (pfderr[0]);
 210                 if (pfderr[1] != STDERR_FILENO) {
 211                         dup2 (pfderr[1], STDERR_FILENO);
 212                         close (pfderr[1]);
 213                 }
 214
 215                 /* close all descriptors in np_pids[]
 216                  * This is executed in a separate address space (pure child),
 217                  * so we don't have to worry about async safety */
 218                 for (i = 0; i < maxfd; i++)
 219                         if(np_pids[i] > 0)
 220                                 close (i);
 221
 222                 execve (argv[0], argv, env);
 223                 _exit (STATE_UNKNOWN);
 224         }
 225
 226         /* parent picks up execution here */
 227         /* close childs descriptors in our address space */
 228         close(pfd[1]);
 229         close(pfderr[1]);
 230
 231         /* tag our file's entry in the pid-list and return it */
 232         np_pids[pfd[0]] = pid;
 233
 234         return pfd[0];
 235 }
 236
 237
 238 static int
 239 np_runcmd_close(int fd)
 240 {
 241         int status;
 242         pid_t pid;
 243
 244         /* make sure this fd was opened by popen() */
 245         if(fd < 0 || fd > maxfd || !np_pids || (pid = np_pids[fd]) == 0)
 246                 return -1;
 247
 248         np_pids[fd] = 0;
 249         if (close (fd) == -1) return -1;
 250
 251         /* EINTR is ok (sort of), everything else is bad */
 252         while (waitpid (pid, &status, 0) < 0)
 253                 if (errno != EINTR) return -1;
 254
 255         /* return child's termination status */
 256         return (WIFEXITED(status)) ? WEXITSTATUS(status) : -1;
 257 }
 258
 259
 260 void
 261 popen_timeout_alarm_handler (int signo)
 262 {
 263         size_t i;
 264
 265         if (signo == SIGALRM)
 266                 puts(_("CRITICAL - Plugin timed out while executing system call\n"));
 267
 268         if(np_pids) for(i = 0; i < maxfd; i++) {
 269                 if(np_pids[i] != 0) kill(np_pids[i], SIGKILL);
 270         }
 271
 272         exit (STATE_CRITICAL);
 273 }
 274
 275
 276 static int
 277 np_fetch_output(int fd, output *op, int flags)
 278 {
 279         size_t len = 0, i = 0, lineno = 0;
 280         size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
 281         char *buf = NULL;
 282         int ret;
 283         char tmpbuf[4096];
 284
 285         op->buf = NULL;
 286         op->buflen = 0;
 287         while((ret = read(fd, tmpbuf, sizeof(tmpbuf))) > 0) {
 288                 len = (size_t)ret;
 289                 op->buf = realloc(op->buf, op->buflen + len + 1);
 290                 memcpy(op->buf + op->buflen, tmpbuf, len);
 291                 op->buflen += len;
 292                 i++;
 293         }
 294
 295         if(ret < 0) {
 296                 printf("read() returned %d: %s\n", ret, strerror(errno));
 297                 return ret;
 298         }
 299
 300         /* some plugins may want to keep output unbroken, and some commands
 301          * will yield no output, so return here for those */
 302         if(flags & RUNCMD_NO_ARRAYS || !op->buf || !op->buflen)
 303                 return op->buflen;
 304
 305         /* and some may want both */
 306         if(flags & RUNCMD_NO_ASSOC) {
 307                 buf = malloc(op->buflen);
 308                 memcpy(buf, op->buf, op->buflen);
 309         }
 310         else buf = op->buf;
 311
 312         op->line = NULL;
 313         op->lens = NULL;
 314         i = 0;
 315         while(i < op->buflen) {
 316                 /* make sure we have enough memory */
 317                 if(lineno >= ary_size) {
 318                         /* ary_size must never be zero */
 319                         do {
 320                                 ary_size = op->buflen >> --rsf;
 321                         } while(!ary_size);
 322
 323                         op->line = realloc(op->line, ary_size * sizeof(char *));
 324                         op->lens = realloc(op->lens, ary_size * sizeof(size_t));
 325                 }
 326
 327                 /* set the pointer to the string */
 328                 op->line[lineno] = &buf[i];
 329
 330                 /* hop to next newline or end of buffer */
 331                 while(buf[i] != '\n' && i < op->buflen) i++;
 332                 buf[i] = '\0';
 333
 334                 /* calculate the string length using pointer difference */
 335                 op->lens[lineno] = (size_t)&buf[i] - (size_t)op->line[lineno];
 336
 337                 lineno++;
 338                 i++;
 339         }
 340
 341         return lineno;
 342 }
 343
 344
 345 int
 346 np_runcmd(const char *cmd, output *out, output *err, int flags)
 347 {
 348         int fd, pfd_out[2], pfd_err[2];
 349
 350         /* initialize the structs */
 351         if(out) memset(out, 0, sizeof(output));
 352         if(err) memset(err, 0, sizeof(output));
 353
 354         if((fd = np_runcmd_open(cmd, pfd_out, pfd_err)) == -1)
 355                 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), cmd);
 356
 357         if(out) out->lines = np_fetch_output(pfd_out[0], out, flags);
 358         if(err) err->lines = np_fetch_output(pfd_err[0], err, flags);
 359
 360         return np_runcmd_close(fd);
 361 }