lib/utils_cmd.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 cmd_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 "common.h"
  43 #include "utils.h"
  44 #include "utils_cmd.h"
  45 /* This variable must be global, since there's no way the caller
  46  * can forcibly slay a dead or ungainly running program otherwise.
  47  * Multithreading apps and plugins can initialize it (via CMD_INIT)
  48  * in an async safe manner PRIOR to calling cmd_run() or cmd_run_array()
  49  * for the first time.
  50  *
  51  * The check for initialized values is atomic and can
  52  * occur in any number of threads simultaneously. */
  53 static pid_t *_cmd_pids = NULL;
  54
  55 #include "utils_base.h"
  56
  57 #include "./maxfd.h"
  58
  59 #include <fcntl.h>
  60
  61 #ifdef HAVE_SYS_WAIT_H
  62 #       include <sys/wait.h>
  63 #endif
  64
  65 /* used in _cmd_open to pass the environment to commands */
  66 extern char **environ;
  67
  68 /** macros **/
  69 #ifndef WEXITSTATUS
  70 #       define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
  71 #endif
  72
  73 #ifndef WIFEXITED
  74 #       define WIFEXITED(stat_val) (((stat_val)&255) == 0)
  75 #endif
  76
  77 /* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
  78 #if defined(SIG_IGN) && !defined(SIG_ERR)
  79 #       define SIG_ERR ((Sigfunc *)-1)
  80 #endif
  81
  82 /** prototypes **/
  83 static int _cmd_open(char *const *, int *, int *) __attribute__((__nonnull__(1, 2, 3)));
  84
  85 static int _cmd_fetch_output(int, output *, int) __attribute__((__nonnull__(2)));
  86
  87 static int _cmd_close(int);
  88
  89 /* prototype imported from utils.h */
  90 extern void die(int, const char *, ...) __attribute__((__noreturn__, __format__(__printf__, 2, 3)));
  91
  92 /* this function is NOT async-safe. It is exported so multithreaded
  93  * plugins (or other apps) can call it prior to running any commands
  94  * through this api and thus achieve async-safeness throughout the api */
  95 void cmd_init(void) {
  96         long maxfd = mp_open_max();
  97
  98         /* if maxfd is unnaturally high, we force it to a lower value
  99          * ( e.g. on SunOS, when ulimit is set to unlimited: 2147483647 this would cause
 100          * a segfault when following calloc is called ...  ) */
 101
 102         if (maxfd > MAXFD_LIMIT) {
 103                 maxfd = MAXFD_LIMIT;
 104         }
 105
 106         if (!_cmd_pids)
 107                 _cmd_pids = calloc(maxfd, sizeof(pid_t));
 108 }
 109
 110 /* Start running a command, array style */
 111 static int _cmd_open(char *const *argv, int *pfd, int *pfderr) {
 112         pid_t pid;
 113 #ifdef RLIMIT_CORE
 114         struct rlimit limit;
 115 #endif
 116
 117         int i = 0;
 118
 119         if (!_cmd_pids)
 120                 CMD_INIT;
 121
 122         setenv("LC_ALL", "C", 1);
 123
 124         if (pipe(pfd) < 0 || pipe(pfderr) < 0 || (pid = fork()) < 0)
 125                 return -1; /* errno set by the failing function */
 126
 127         /* child runs exceve() and _exit. */
 128         if (pid == 0) {
 129 #ifdef RLIMIT_CORE
 130                 /* the program we execve shouldn't leave core files */
 131                 getrlimit(RLIMIT_CORE, &limit);
 132                 limit.rlim_cur = 0;
 133                 setrlimit(RLIMIT_CORE, &limit);
 134 #endif
 135                 close(pfd[0]);
 136                 if (pfd[1] != STDOUT_FILENO) {
 137                         dup2(pfd[1], STDOUT_FILENO);
 138                         close(pfd[1]);
 139                 }
 140                 close(pfderr[0]);
 141                 if (pfderr[1] != STDERR_FILENO) {
 142                         dup2(pfderr[1], STDERR_FILENO);
 143                         close(pfderr[1]);
 144                 }
 145
 146                 /* close all descriptors in _cmd_pids[]
 147                  * This is executed in a separate address space (pure child),
 148                  * so we don't have to worry about async safety */
 149                 long maxfd = mp_open_max();
 150                 for (i = 0; i < maxfd; i++)
 151                         if (_cmd_pids[i] > 0)
 152                                 close(i);
 153
 154                 execve(argv[0], argv, environ);
 155                 _exit(STATE_UNKNOWN);
 156         }
 157
 158         /* parent picks up execution here */
 159         /* close children descriptors in our address space */
 160         close(pfd[1]);
 161         close(pfderr[1]);
 162
 163         /* tag our file's entry in the pid-list and return it */
 164         _cmd_pids[pfd[0]] = pid;
 165
 166         return pfd[0];
 167 }
 168
 169 static int _cmd_close(int fd) {
 170         int status;
 171         pid_t pid;
 172
 173         /* make sure the provided fd was opened */
 174         long maxfd = mp_open_max();
 175         if (fd < 0 || fd > maxfd || !_cmd_pids || (pid = _cmd_pids[fd]) == 0)
 176                 return -1;
 177
 178         _cmd_pids[fd] = 0;
 179         if (close(fd) == -1)
 180                 return -1;
 181
 182         /* EINTR is ok (sort of), everything else is bad */
 183         while (waitpid(pid, &status, 0) < 0)
 184                 if (errno != EINTR)
 185                         return -1;
 186
 187         /* return child's termination status */
 188         return (WIFEXITED(status)) ? WEXITSTATUS(status) : -1;
 189 }
 190
 191 static int _cmd_fetch_output(int fd, output *op, int flags) {
 192         size_t len = 0, i = 0, lineno = 0;
 193         size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
 194         char *buf = NULL;
 195         int ret;
 196         char tmpbuf[4096];
 197
 198         op->buf = NULL;
 199         op->buflen = 0;
 200         while ((ret = read(fd, tmpbuf, sizeof(tmpbuf))) > 0) {
 201                 len = (size_t)ret;
 202                 op->buf = realloc(op->buf, op->buflen + len + 1);
 203                 memcpy(op->buf + op->buflen, tmpbuf, len);
 204                 op->buflen += len;
 205                 i++;
 206         }
 207
 208         if (ret < 0) {
 209                 printf("read() returned %d: %s\n", ret, strerror(errno));
 210                 return ret;
 211         }
 212
 213         /* some plugins may want to keep output unbroken, and some commands
 214          * will yield no output, so return here for those */
 215         if (flags & CMD_NO_ARRAYS || !op->buf || !op->buflen)
 216                 return op->buflen;
 217
 218         /* and some may want both */
 219         if (flags & CMD_NO_ASSOC) {
 220                 buf = malloc(op->buflen);
 221                 memcpy(buf, op->buf, op->buflen);
 222         } else
 223                 buf = op->buf;
 224
 225         op->line = NULL;
 226         op->lens = NULL;
 227         i = 0;
 228         while (i < op->buflen) {
 229                 /* make sure we have enough memory */
 230                 if (lineno >= ary_size) {
 231                         /* ary_size must never be zero */
 232                         do {
 233                                 ary_size = op->buflen >> --rsf;
 234                         } while (!ary_size);
 235
 236                         op->line = realloc(op->line, ary_size * sizeof(char *));
 237                         op->lens = realloc(op->lens, ary_size * sizeof(size_t));
 238                 }
 239
 240                 /* set the pointer to the string */
 241                 op->line[lineno] = &buf[i];
 242
 243                 /* hop to next newline or end of buffer */
 244                 while (buf[i] != '\n' && i < op->buflen)
 245                         i++;
 246                 buf[i] = '\0';
 247
 248                 /* calculate the string length using pointer difference */
 249                 op->lens[lineno] = (size_t)&buf[i] - (size_t)op->line[lineno];
 250
 251                 lineno++;
 252                 i++;
 253         }
 254
 255         return lineno;
 256 }
 257
 258 int cmd_run(const char *cmdstring, output *out, output *err, int flags) {
 259         int i = 0, argc;
 260         size_t cmdlen;
 261         char **argv = NULL;
 262         char *cmd = NULL;
 263         char *str = NULL;
 264
 265         if (cmdstring == NULL)
 266                 return -1;
 267
 268         /* initialize the structs */
 269         if (out)
 270                 memset(out, 0, sizeof(output));
 271         if (err)
 272                 memset(err, 0, sizeof(output));
 273
 274         /* make copy of command string so strtok() doesn't silently modify it */
 275         /* (the calling program may want to access it later) */
 276         cmdlen = strlen(cmdstring);
 277         if ((cmd = malloc(cmdlen + 1)) == NULL)
 278                 return -1;
 279         memcpy(cmd, cmdstring, cmdlen);
 280         cmd[cmdlen] = '\0';
 281
 282         /* This is not a shell, so we don't handle "???" */
 283         if (strstr(cmdstring, "\""))
 284                 return -1;
 285
 286         /* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
 287         if (strstr(cmdstring, " ' ") || strstr(cmdstring, "'''"))
 288                 return -1;
 289
 290         /* each arg must be whitespace-separated, so args can be a maximum
 291          * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
 292         argc = (cmdlen >> 1) + 2;
 293         argv = calloc((size_t)argc, sizeof(char *));
 294
 295         if (argv == NULL) {
 296                 printf("%s\n", _("Could not malloc argv array in popen()"));
 297                 return -1;
 298         }
 299
 300         /* get command arguments (stupidly, but fairly quickly) */
 301         while (cmd) {
 302                 str = cmd;
 303                 str += strspn(str, " \t\r\n"); /* trim any leading whitespace */
 304
 305                 if (strstr(str, "'") == str) { /* handle SIMPLE quoted strings */
 306                         str++;
 307                         if (!strstr(str, "'"))
 308                                 return -1; /* balanced? */
 309                         cmd = 1 + strstr(str, "'");
 310                         str[strcspn(str, "'")] = 0;
 311                 } else {
 312                         if (strpbrk(str, " \t\r\n")) {
 313                                 cmd = 1 + strpbrk(str, " \t\r\n");
 314                                 str[strcspn(str, " \t\r\n")] = 0;
 315                         } else {
 316                                 cmd = NULL;
 317                         }
 318                 }
 319
 320                 if (cmd && strlen(cmd) == strspn(cmd, " \t\r\n"))
 321                         cmd = NULL;
 322
 323                 argv[i++] = str;
 324         }
 325
 326         return cmd_run_array(argv, out, err, flags);
 327 }
 328
 329 int cmd_run_array(char *const *argv, output *out, output *err, int flags) {
 330         int fd, pfd_out[2], pfd_err[2];
 331
 332         /* initialize the structs */
 333         if (out)
 334                 memset(out, 0, sizeof(output));
 335         if (err)
 336                 memset(err, 0, sizeof(output));
 337
 338         if ((fd = _cmd_open(argv, pfd_out, pfd_err)) == -1)
 339                 die(STATE_UNKNOWN, _("Could not open pipe: %s\n"), argv[0]);
 340
 341         if (out)
 342                 out->lines = _cmd_fetch_output(pfd_out[0], out, flags);
 343         if (err)
 344                 err->lines = _cmd_fetch_output(pfd_err[0], err, flags);
 345
 346         return _cmd_close(fd);
 347 }
 348
 349 int cmd_file_read(char *filename, output *out, int flags) {
 350         int fd;
 351         if (out)
 352                 memset(out, 0, sizeof(output));
 353
 354         if ((fd = open(filename, O_RDONLY)) == -1) {
 355                 die(STATE_UNKNOWN, _("Error opening %s: %s"), filename, strerror(errno));
 356         }
 357
 358         if (out)
 359                 out->lines = _cmd_fetch_output(fd, out, flags);
 360
 361         if (close(fd) == -1)
 362                 die(STATE_UNKNOWN, _("Error closing %s: %s"), filename, strerror(errno));
 363
 364         return 0;
 365 }
 366
 367 void timeout_alarm_handler(int signo) {
 368         if (signo == SIGALRM) {
 369                 printf(_("%s - Plugin timed out after %d seconds\n"), state_text(timeout_state), timeout_interval);
 370
 371                 long maxfd = mp_open_max();
 372                 if (_cmd_pids)
 373                         for (long int i = 0; i < maxfd; i++) {
 374                                 if (_cmd_pids[i] != 0)
 375                                         kill(_cmd_pids[i], SIGKILL);
 376                         }
 377
 378                 exit(timeout_state);
 379         }
 380 }