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