plugins/runcmd.c

   1 /*****************************************************************************
   2 *
   3 * Nagios run command utilities
   4 *
   5 * License: GPL
   6 * Copyright (c) 2005-2006 Nagios 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 np_runcmd_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 "runcmd.h"
  43 #ifdef HAVE_SYS_WAIT_H
  44 # include <sys/wait.h>
  45 #endif
  46
  47 /** macros **/
  48 #ifndef WEXITSTATUS
  49 # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
  50 #endif
  51
  52 #ifndef WIFEXITED
  53 # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
  54 #endif
  55
  56 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
  57 #if defined(SIG_IGN) && !defined(SIG_ERR)
  58 # define SIG_ERR ((Sigfunc *)-1)
  59 #endif
  60
  61 /* This variable must be global, since there's no way the caller
  62  * can forcibly slay a dead or ungainly running program otherwise.
  63  * Multithreading apps and plugins can initialize it (via NP_RUNCMD_INIT)
  64  * in an async safe manner PRIOR to calling np_runcmd() for the first time.
  65  *
  66  * The check for initialized values is atomic and can
  67  * occur in any number of threads simultaneously. */
  68 static pid_t *np_pids = NULL;
  69
  70 /* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
  71  * If that fails and the macro isn't defined, we fall back to an educated
  72  * guess. There's no guarantee that our guess is adequate and the program
  73  * will die with SIGSEGV if it isn't and the upper boundary is breached. */
  74 #ifdef _SC_OPEN_MAX
  75 static long maxfd = 0;
  76 #elif defined(OPEN_MAX)
  77 # define maxfd OPEN_MAX
  78 #else /* sysconf macro unavailable, so guess (may be wildly inaccurate) */
  79 # define maxfd 256
  80 #endif
  81
  82
  83 /** prototypes **/
  84 static int np_runcmd_open(const char *, int *, int *)
  85         __attribute__((__nonnull__(1, 2, 3)));
  86
  87 static int np_fetch_output(int, output *, int)
  88         __attribute__((__nonnull__(2)));
  89
  90 static int np_runcmd_close(int);
  91
  92 /* prototype imported from utils.h */
  93 extern void die (int, const char *, ...)
  94         __attribute__((__noreturn__,__format__(__printf__, 2, 3)));
  95
  96
  97 /* this function is NOT async-safe. It is exported so multithreaded
  98  * plugins (or other apps) can call it prior to running any commands
  99  * through this api and thus achieve async-safeness throughout the api */
 100 void np_runcmd_init(void)
 101 {
 102 #ifndef maxfd
 103         if(!maxfd && (maxfd = sysconf(_SC_OPEN_MAX)) < 0) {
 104                 /* possibly log or emit a warning here, since there's no
 105                  * guarantee that our guess at maxfd will be adequate */
 106                 maxfd = 256;
 107         }
 108 #endif
 109
 110         if(!np_pids) np_pids = calloc(maxfd, sizeof(pid_t));
 111 }
 112
 113
 114 /* Start running a command */
 115 static int
 116 np_runcmd_open(const char *cmdstring, int *pfd, int *pfderr)
 117 {
 118         char *env[2];
 119         char *cmd = NULL;
 120         char **argv = NULL;
 121         char *str;
 122         int argc;
 123         size_t cmdlen;
 124         pid_t pid;
 125 #ifdef RLIMIT_CORE
 126         struct rlimit limit;
 127 #endif
 128
 129         int i = 0;
 130
 131         if(!np_pids) NP_RUNCMD_INIT;
 132
 133         env[0] = strdup("LC_ALL=C");
 134         env[1] = '\0';
 135
 136         /* if no command was passed, return with no error */
 137         if (cmdstring == NULL)
 138                 return -1;
 139
 140         /* make copy of command string so strtok() doesn't silently modify it */
 141         /* (the calling program may want to access it later) */
 142         cmdlen = strlen(cmdstring);
 143         if((cmd = malloc(cmdlen + 1)) == NULL) return -1;
 144         memcpy(cmd, cmdstring, cmdlen);
 145         cmd[cmdlen] = '\0';
 146
 147         /* This is not a shell, so we don't handle "???" */
 148         if (strstr (cmdstring, "\"")) return -1;
 149
 150         /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
 151         if (strstr (cmdstring, " ' ") || strstr (cmdstring, "'''"))
 152                 return -1;
 153
 154         /* each arg must be whitespace-separated, so args can be a maximum
 155          * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
 156         argc = (cmdlen >> 1) + 2;
 157         argv = calloc(sizeof(char *), argc);
 158
 159         if (argv == NULL) {
 160                 printf ("%s\n", _("Could not malloc argv array in popen()"));
 161                 return -1;
 162         }
 163
 164         /* get command arguments (stupidly, but fairly quickly) */
 165         while (cmd) {
 166                 str = cmd;
 167                 str += strspn (str, " \t\r\n"); /* trim any leading whitespace */
 168
 169                 if (strstr (str, "'") == str) { /* handle SIMPLE quoted strings */
 170                         str++;
 171                         if (!strstr (str, "'")) return -1;      /* balanced? */
 172                         cmd = 1 + strstr (str, "'");
 173                         str[strcspn (str, "'")] = 0;
 174                 }
 175                 else {
 176                         if (strpbrk (str, " \t\r\n")) {
 177                                 cmd = 1 + strpbrk (str, " \t\r\n");
 178                                 str[strcspn (str, " \t\r\n")] = 0;
 179                         }
 180                         else {
 181                                 cmd = NULL;
 182                         }
 183                 }
 184
 185                 if (cmd && strlen (cmd) == strspn (cmd, " \t\r\n"))
 186                         cmd = NULL;
 187
 188                 argv[i++] = str;
 189         }
 190
 191         if (pipe(pfd) < 0 || pipe(pfderr) < 0 || (pid = fork()) < 0)
 192                 return -1; /* errno set by the failing function */
 193
 194         /* child runs exceve() and _exit. */
 195         if (pid == 0) {
 196 #ifdef  RLIMIT_CORE
 197                 /* the program we execve shouldn't leave core files */
 198                 getrlimit (RLIMIT_CORE, &limit);
 199                 limit.rlim_cur = 0;
 200                 setrlimit (RLIMIT_CORE, &limit);
 201 #endif
 202                 close (pfd[0]);
 203                 if (pfd[1] != STDOUT_FILENO) {
 204                         dup2 (pfd[1], STDOUT_FILENO);
 205                         close (pfd[1]);
 206                 }
 207                 close (pfderr[0]);
 208                 if (pfderr[1] != STDERR_FILENO) {
 209                         dup2 (pfderr[1], STDERR_FILENO);
 210                         close (pfderr[1]);
 211                 }
 212
 213                 /* close all descriptors in np_pids[]
 214                  * This is executed in a separate address space (pure child),
 215                  * so we don't have to worry about async safety */
 216                 for (i = 0; i < maxfd; i++)
 217                         if(np_pids[i] > 0)
 218                                 close (i);
 219
 220                 execve (argv[0], argv, env);
 221                 _exit (STATE_UNKNOWN);
 222         }
 223
 224         /* parent picks up execution here */
 225         /* close childs descriptors in our address space */
 226         close(pfd[1]);
 227         close(pfderr[1]);
 228
 229         /* tag our file's entry in the pid-list and return it */
 230         np_pids[pfd[0]] = pid;
 231
 232         return pfd[0];
 233 }
 234
 235
 236 static int
 237 np_runcmd_close(int fd)
 238 {
 239         int status;
 240         pid_t pid;
 241
 242         /* make sure this fd was opened by popen() */
 243         if(fd < 0 || fd > maxfd || !np_pids || (pid = np_pids[fd]) == 0)
 244                 return -1;
 245
 246         np_pids[fd] = 0;
 247         if (close (fd) == -1) return -1;
 248
 249         /* EINTR is ok (sort of), everything else is bad */
 250         while (waitpid (pid, &status, 0) < 0)
 251                 if (errno != EINTR) return -1;
 252
 253         /* return child's termination status */
 254         return (WIFEXITED(status)) ? WEXITSTATUS(status) : -1;
 255 }
 256
 257
 258 void
 259 popen_timeout_alarm_handler (int signo)
 260 {
 261         size_t i;
 262
 263         if (signo == SIGALRM)
 264                 puts(_("CRITICAL - Plugin timed out while executing system call\n"));
 265
 266         if(np_pids) for(i = 0; i < maxfd; i++) {
 267                 if(np_pids[i] != 0) kill(np_pids[i], SIGKILL);
 268         }
 269
 270         exit (STATE_CRITICAL);
 271 }
 272
 273
 274 static int
 275 np_fetch_output(int fd, output *op, int flags)
 276 {
 277         size_t len = 0, i = 0, lineno = 0;
 278         size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
 279         char *buf = NULL;
 280         int ret;
 281         char tmpbuf[4096];
 282
 283         op->buf = NULL;
 284         op->buflen = 0;
 285         while((ret = read(fd, tmpbuf, sizeof(tmpbuf))) > 0) {
 286                 len = (size_t)ret;
 287                 op->buf = realloc(op->buf, op->buflen + len + 1);
 288                 memcpy(op->buf + op->buflen, tmpbuf, len);
 289                 op->buflen += len;
 290                 i++;
 291         }
 292
 293         if(ret < 0) {
 294                 printf("read() returned %d: %s\n", ret, strerror(errno));
 295                 return ret;
 296         }
 297
 298         /* some plugins may want to keep output unbroken, and some commands
 299          * will yield no output, so return here for those */
 300         if(flags & RUNCMD_NO_ARRAYS || !op->buf || !op->buflen)
 301                 return op->buflen;
 302
 303         /* and some may want both */
 304         if(flags & RUNCMD_NO_ASSOC) {
 305                 buf = malloc(op->buflen);
 306                 memcpy(buf, op->buf, op->buflen);
 307         }
 308         else buf = op->buf;
 309
 310         op->line = NULL;
 311         op->lens = NULL;
 312         i = 0;
 313         while(i < op->buflen) {
 314                 /* make sure we have enough memory */
 315                 if(lineno >= ary_size) {
 316                         /* ary_size must never be zero */
 317                         do {
 318                                 ary_size = op->buflen >> --rsf;
 319                         } while(!ary_size);
 320
 321                         op->line = realloc(op->line, ary_size * sizeof(char *));
 322                         op->lens = realloc(op->lens, ary_size * sizeof(size_t));
 323                 }
 324
 325                 /* set the pointer to the string */
 326                 op->line[lineno] = &buf[i];
 327
 328                 /* hop to next newline or end of buffer */
 329                 while(buf[i] != '\n' && i < op->buflen) i++;
 330                 buf[i] = '\0';
 331
 332                 /* calculate the string length using pointer difference */
 333                 op->lens[lineno] = (size_t)&buf[i] - (size_t)op->line[lineno];
 334
 335                 lineno++;
 336                 i++;
 337         }
 338
 339         return lineno;
 340 }
 341
 342
 343 int
 344 np_runcmd(const char *cmd, output *out, output *err, int flags)
 345 {
 346         int fd, pfd_out[2], pfd_err[2];
 347
 348         /* initialize the structs */
 349         if(out) memset(out, 0, sizeof(output));
 350         if(err) memset(err, 0, sizeof(output));
 351
 352         if((fd = np_runcmd_open(cmd, pfd_out, pfd_err)) == -1)
 353                 die (STATE_UNKNOWN, _("Could not open pipe: %s\n"), cmd);
 354
 355         if(out) out->lines = np_fetch_output(pfd_out[0], out, flags);
 356         if(err) err->lines = np_fetch_output(pfd_err[0], err, flags);
 357
 358         return np_runcmd_close(fd);
 359 }