plugins/runcmd.c

   1 /*****************************************************************************
   2  *
   3  * Monitoring run command utilities
   4  *
   5  * License: GPL
   6  * Copyright (c) 2005-2024 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 #include "./utils.h"
  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 #include "../lib/maxfd.h"
  64
  65 /* This variable must be global, since there's no way the caller
  66  * can forcibly slay a dead or ungainly running program otherwise.
  67  * Multithreading apps and plugins can initialize it (via NP_RUNCMD_INIT)
  68  * in an async safe manner PRIOR to calling np_runcmd() for the first time.
  69  *
  70  * The check for initialized values is atomic and can
  71  * occur in any number of threads simultaneously. */
  72 static pid_t *np_pids = NULL;
  73
  74 /** prototypes **/
  75 static int np_runcmd_open(const char *, int *, int *) __attribute__((__nonnull__(1, 2, 3)));
  76
  77 static int np_fetch_output(int, output *, int) __attribute__((__nonnull__(2)));
  78
  79 static int np_runcmd_close(int);
  80
  81 /* prototype imported from utils.h */
  82 extern void die(int, const char *, ...) __attribute__((__noreturn__, __format__(__printf__, 2, 3)));
  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         long maxfd = mp_open_max();
  89         if (!np_pids)
  90                 np_pids = calloc(maxfd, sizeof(pid_t));
  91 }
  92
  93 /* Start running a command */
  94 static int np_runcmd_open(const char *cmdstring, int *pfd, int *pfderr) {
  95         char *env[2];
  96         char *cmd = NULL;
  97         char **argv = NULL;
  98         char *str;
  99         int argc;
 100         size_t cmdlen;
 101         pid_t pid;
 102 #ifdef RLIMIT_CORE
 103         struct rlimit limit;
 104 #endif
 105
 106         int i = 0;
 107
 108         if (!np_pids)
 109                 NP_RUNCMD_INIT;
 110
 111         env[0] = strdup("LC_ALL=C");
 112         env[1] = NULL;
 113
 114         /* make copy of command string so strtok() doesn't silently modify it */
 115         /* (the calling program may want to access it later) */
 116         cmdlen = strlen(cmdstring);
 117         if ((cmd = malloc(cmdlen + 1)) == NULL)
 118                 return -1;
 119         memcpy(cmd, cmdstring, cmdlen);
 120         cmd[cmdlen] = '\0';
 121
 122         /* This is not a shell, so we don't handle "???" */
 123         if (strstr(cmdstring, "\""))
 124                 return -1;
 125
 126         /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
 127         if (strstr(cmdstring, " ' ") || strstr(cmdstring, "'''"))
 128                 return -1;
 129
 130         /* each arg must be whitespace-separated, so args can be a maximum
 131          * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
 132         argc = (cmdlen >> 1) + 2;
 133         argv = calloc(argc, sizeof(char *));
 134
 135         if (argv == NULL) {
 136                 printf("%s\n", _("Could not malloc argv array in popen()"));
 137                 return -1;
 138         }
 139
 140         /* get command arguments (stupidly, but fairly quickly) */
 141         while (cmd) {
 142                 str = cmd;
 143                 str += strspn(str, " \t\r\n"); /* trim any leading whitespace */
 144
 145                 if (strstr(str, "'") == str) { /* handle SIMPLE quoted strings */
 146                         str++;
 147                         if (!strstr(str, "'"))
 148                                 return -1; /* balanced? */
 149                         cmd = 1 + strstr(str, "'");
 150                         str[strcspn(str, "'")] = 0;
 151                 } else {
 152                         if (strpbrk(str, " \t\r\n")) {
 153                                 cmd = 1 + strpbrk(str, " \t\r\n");
 154                                 str[strcspn(str, " \t\r\n")] = 0;
 155                         } else {
 156                                 cmd = NULL;
 157                         }
 158                 }
 159
 160                 if (cmd && strlen(cmd) == strspn(cmd, " \t\r\n"))
 161                         cmd = NULL;
 162
 163                 argv[i++] = str;
 164         }
 165
 166         if (pipe(pfd) < 0 || pipe(pfderr) < 0 || (pid = fork()) < 0)
 167                 return -1; /* errno set by the failing function */
 168
 169         /* child runs exceve() and _exit. */
 170         if (pid == 0) {
 171 #ifdef RLIMIT_CORE
 172                 /* the program we execve shouldn't leave core files */
 173                 getrlimit(RLIMIT_CORE, &limit);
 174                 limit.rlim_cur = 0;
 175                 setrlimit(RLIMIT_CORE, &limit);
 176 #endif
 177                 close(pfd[0]);
 178                 if (pfd[1] != STDOUT_FILENO) {
 179                         dup2(pfd[1], STDOUT_FILENO);
 180                         close(pfd[1]);
 181                 }
 182                 close(pfderr[0]);
 183                 if (pfderr[1] != STDERR_FILENO) {
 184                         dup2(pfderr[1], STDERR_FILENO);
 185                         close(pfderr[1]);
 186                 }
 187
 188                 /* close all descriptors in np_pids[]
 189                  * This is executed in a separate address space (pure child),
 190                  * so we don't have to worry about async safety */
 191                 long maxfd = mp_open_max();
 192                 for (i = 0; i < maxfd; i++)
 193                         if (np_pids[i] > 0)
 194                                 close(i);
 195
 196                 execve(argv[0], argv, env);
 197                 _exit(STATE_UNKNOWN);
 198         }
 199
 200         /* parent picks up execution here */
 201         /* close children descriptors in our address space */
 202         close(pfd[1]);
 203         close(pfderr[1]);
 204
 205         /* tag our file's entry in the pid-list and return it */
 206         np_pids[pfd[0]] = pid;
 207
 208         return pfd[0];
 209 }
 210
 211 static int np_runcmd_close(int fd) {
 212         int status;
 213         pid_t pid;
 214
 215         /* make sure this fd was opened by popen() */
 216         long maxfd = mp_open_max();
 217         if (fd < 0 || fd > maxfd || !np_pids || (pid = np_pids[fd]) == 0)
 218                 return -1;
 219
 220         np_pids[fd] = 0;
 221         if (close(fd) == -1)
 222                 return -1;
 223
 224         /* EINTR is ok (sort of), everything else is bad */
 225         while (waitpid(pid, &status, 0) < 0)
 226                 if (errno != EINTR)
 227                         return -1;
 228
 229         /* return child's termination status */
 230         return (WIFEXITED(status)) ? WEXITSTATUS(status) : -1;
 231 }
 232
 233 void runcmd_timeout_alarm_handler(int signo) {
 234
 235         if (signo == SIGALRM)
 236                 puts(_("CRITICAL - Plugin timed out while executing system call"));
 237
 238         long maxfd = mp_open_max();
 239         if (np_pids)
 240                 for (long int i = 0; i < maxfd; i++) {
 241                         if (np_pids[i] != 0)
 242                                 kill(np_pids[i], SIGKILL);
 243                 }
 244
 245         exit(STATE_CRITICAL);
 246 }
 247
 248 static int np_fetch_output(int fd, output *op, int flags) {
 249         size_t len = 0, i = 0, lineno = 0;
 250         size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
 251         char *buf = NULL;
 252         int ret;
 253         char tmpbuf[4096];
 254
 255         op->buf = NULL;
 256         op->buflen = 0;
 257         while ((ret = read(fd, tmpbuf, sizeof(tmpbuf))) > 0) {
 258                 len = (size_t)ret;
 259                 op->buf = realloc(op->buf, op->buflen + len + 1);
 260                 memcpy(op->buf + op->buflen, tmpbuf, len);
 261                 op->buflen += len;
 262                 i++;
 263         }
 264
 265         if (ret < 0) {
 266                 printf("read() returned %d: %s\n", ret, strerror(errno));
 267                 return ret;
 268         }
 269
 270         /* some plugins may want to keep output unbroken, and some commands
 271          * will yield no output, so return here for those */
 272         if (flags & RUNCMD_NO_ARRAYS || !op->buf || !op->buflen)
 273                 return op->buflen;
 274
 275         /* and some may want both */
 276         if (flags & RUNCMD_NO_ASSOC) {
 277                 buf = malloc(op->buflen);
 278                 memcpy(buf, op->buf, op->buflen);
 279         } else
 280                 buf = op->buf;
 281
 282         op->line = NULL;
 283         op->lens = NULL;
 284         i = 0;
 285         while (i < op->buflen) {
 286                 /* make sure we have enough memory */
 287                 if (lineno >= ary_size) {
 288                         /* ary_size must never be zero */
 289                         do {
 290                                 ary_size = op->buflen >> --rsf;
 291                         } while (!ary_size);
 292
 293                         op->line = realloc(op->line, ary_size * sizeof(char *));
 294                         op->lens = realloc(op->lens, ary_size * sizeof(size_t));
 295                 }
 296
 297                 /* set the pointer to the string */
 298                 op->line[lineno] = &buf[i];
 299
 300                 /* hop to next newline or end of buffer */
 301                 while (buf[i] != '\n' && i < op->buflen)
 302                         i++;
 303                 buf[i] = '\0';
 304
 305                 /* calculate the string length using pointer difference */
 306                 op->lens[lineno] = (size_t)&buf[i] - (size_t)op->line[lineno];
 307
 308                 lineno++;
 309                 i++;
 310         }
 311
 312         return lineno;
 313 }
 314
 315 int np_runcmd(const char *cmd, output *out, output *err, int flags) {
 316         int fd, pfd_out[2], pfd_err[2];
 317
 318         /* initialize the structs */
 319         if (out)
 320                 memset(out, 0, sizeof(output));
 321         if (err)
 322                 memset(err, 0, sizeof(output));
 323
 324         if ((fd = np_runcmd_open(cmd, pfd_out, pfd_err)) == -1)
 325                 die(STATE_UNKNOWN, _("Could not open pipe: %s\n"), cmd);
 326
 327         if (out)
 328                 out->lines = np_fetch_output(pfd_out[0], out, flags);
 329         if (err)
 330                 err->lines = np_fetch_output(pfd_err[0], err, flags);
 331
 332         return np_runcmd_close(fd);
 333 }