path: root/lib/utils_cmd.c

/*****************************************************************************
 *
 * Monitoring run command utilities
 *
 * License: GPL
 * Copyright (c) 2005-2024 Monitoring Plugins Development Team
 *
 * Description :
 *
 * A simple interface to executing programs from other programs, using an
 * optimized and safe popen()-like implementation. It is considered safe
 * in that no shell needs to be spawned and the environment passed to the
 * execve()'d program is essentially empty.
 *
 * The code in this file is a derivative of popen.c which in turn was taken
 * from "Advanced Programming for the Unix Environment" by W. Richard Stevens.
 *
 * Care has been taken to make sure the functions are async-safe. The one
 * function which isn't is cmd_init() which it doesn't make sense to
 * call twice anyway, so the api as a whole should be considered async-safe.
 *
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 *****************************************************************************/

#define NAGIOSPLUG_API_C 1

/** includes **/
#include "common.h"
#include "utils.h"
#include "utils_cmd.h"
/* This variable must be global, since there's no way the caller
 * can forcibly slay a dead or ungainly running program otherwise.
 * Multithreading apps and plugins can initialize it (via CMD_INIT)
 * in an async safe manner PRIOR to calling cmd_run() or cmd_run_array()
 * for the first time.
 *
 * The check for initialized values is atomic and can
 * occur in any number of threads simultaneously. */
static pid_t *_cmd_pids = NULL;

#include "utils_base.h"

#include "./maxfd.h"

#include <fcntl.h>

#ifdef HAVE_SYS_WAIT_H
#	include <sys/wait.h>
#endif

/* used in _cmd_open to pass the environment to commands */
extern char **environ;

/** macros **/
#ifndef WEXITSTATUS
#	define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
#endif

#ifndef WIFEXITED
#	define WIFEXITED(stat_val) (((stat_val)&255) == 0)
#endif

/* 4.3BSD Reno <signal.h> doesn't define SIG_ERR */
#if defined(SIG_IGN) && !defined(SIG_ERR)
#	define SIG_ERR ((Sigfunc *)-1)
#endif

/** prototypes **/
static int _cmd_open(char *const *, int *, int *) __attribute__((__nonnull__(1, 2, 3)));

static int _cmd_fetch_output(int, output *, int) __attribute__((__nonnull__(2)));

static int _cmd_close(int);

/* prototype imported from utils.h */
extern void die(int, const char *, ...) __attribute__((__noreturn__, __format__(__printf__, 2, 3)));

/* this function is NOT async-safe. It is exported so multithreaded
 * plugins (or other apps) can call it prior to running any commands
 * through this api and thus achieve async-safeness throughout the api */
void cmd_init(void) {
	long maxfd = mp_open_max();

	/* if maxfd is unnaturally high, we force it to a lower value
	 * ( e.g. on SunOS, when ulimit is set to unlimited: 2147483647 this would cause
	 * a segfault when following calloc is called ...  ) */

	if (maxfd > MAXFD_LIMIT) {
		maxfd = MAXFD_LIMIT;
	}

	if (!_cmd_pids)
		_cmd_pids = calloc(maxfd, sizeof(pid_t));
}

/* Start running a command, array style */
static int _cmd_open(char *const *argv, int *pfd, int *pfderr) {
	pid_t pid;
#ifdef RLIMIT_CORE
	struct rlimit limit;
#endif

	int i = 0;

	if (!_cmd_pids)
		CMD_INIT;

	setenv("LC_ALL", "C", 1);

	if (pipe(pfd) < 0 || pipe(pfderr) < 0 || (pid = fork()) < 0)
		return -1; /* errno set by the failing function */

	/* child runs exceve() and _exit. */
	if (pid == 0) {
#ifdef RLIMIT_CORE
		/* the program we execve shouldn't leave core files */
		getrlimit(RLIMIT_CORE, &limit);
		limit.rlim_cur = 0;
		setrlimit(RLIMIT_CORE, &limit);
#endif
		close(pfd[0]);
		if (pfd[1] != STDOUT_FILENO) {
			dup2(pfd[1], STDOUT_FILENO);
			close(pfd[1]);
		}
		close(pfderr[0]);
		if (pfderr[1] != STDERR_FILENO) {
			dup2(pfderr[1], STDERR_FILENO);
			close(pfderr[1]);
		}

		/* close all descriptors in _cmd_pids[]
		 * This is executed in a separate address space (pure child),
		 * so we don't have to worry about async safety */
		long maxfd = mp_open_max();
		for (i = 0; i < maxfd; i++)
			if (_cmd_pids[i] > 0)
				close(i);

		execve(argv[0], argv, environ);
		_exit(STATE_UNKNOWN);
	}

	/* parent picks up execution here */
	/* close children descriptors in our address space */
	close(pfd[1]);
	close(pfderr[1]);

	/* tag our file's entry in the pid-list and return it */
	_cmd_pids[pfd[0]] = pid;

	return pfd[0];
}

static int _cmd_close(int fd) {
	int status;
	pid_t pid;

	/* make sure the provided fd was opened */
	long maxfd = mp_open_max();
	if (fd < 0 || fd > maxfd || !_cmd_pids || (pid = _cmd_pids[fd]) == 0)
		return -1;

	_cmd_pids[fd] = 0;
	if (close(fd) == -1)
		return -1;

	/* EINTR is ok (sort of), everything else is bad */
	while (waitpid(pid, &status, 0) < 0)
		if (errno != EINTR)
			return -1;

	/* return child's termination status */
	return (WIFEXITED(status)) ? WEXITSTATUS(status) : -1;
}

static int _cmd_fetch_output(int fd, output *op, int flags) {
	size_t len = 0, i = 0, lineno = 0;
	size_t rsf = 6, ary_size = 0; /* rsf = right shift factor, dec'ed uncond once */
	char *buf = NULL;
	int ret;
	char tmpbuf[4096];

	op->buf = NULL;
	op->buflen = 0;
	while ((ret = read(fd, tmpbuf, sizeof(tmpbuf))) > 0) {
		len = (size_t)ret;
		op->buf = realloc(op->buf, op->buflen + len + 1);
		memcpy(op->buf + op->buflen, tmpbuf, len);
		op->buflen += len;
		i++;
	}

	if (ret < 0) {
		printf("read() returned %d: %s\n", ret, strerror(errno));
		return ret;
	}

	/* some plugins may want to keep output unbroken, and some commands
	 * will yield no output, so return here for those */
	if (flags & CMD_NO_ARRAYS || !op->buf || !op->buflen)
		return op->buflen;

	/* and some may want both */
	if (flags & CMD_NO_ASSOC) {
		buf = malloc(op->buflen);
		memcpy(buf, op->buf, op->buflen);
	} else
		buf = op->buf;

	op->line = NULL;
	op->lens = NULL;
	i = 0;
	while (i < op->buflen) {
		/* make sure we have enough memory */
		if (lineno >= ary_size) {
			/* ary_size must never be zero */
			do {
				ary_size = op->buflen >> --rsf;
			} while (!ary_size);

			op->line = realloc(op->line, ary_size * sizeof(char *));
			op->lens = realloc(op->lens, ary_size * sizeof(size_t));
		}

		/* set the pointer to the string */
		op->line[lineno] = &buf[i];

		/* hop to next newline or end of buffer */
		while (buf[i] != '\n' && i < op->buflen)
			i++;
		buf[i] = '\0';

		/* calculate the string length using pointer difference */
		op->lens[lineno] = (size_t)&buf[i] - (size_t)op->line[lineno];

		lineno++;
		i++;
	}

	return lineno;
}

int cmd_run(const char *cmdstring, output *out, output *err, int flags) {
	int i = 0, argc;
	size_t cmdlen;
	char **argv = NULL;
	char *cmd = NULL;
	char *str = NULL;

	if (cmdstring == NULL)
		return -1;

	/* initialize the structs */
	if (out)
		memset(out, 0, sizeof(output));
	if (err)
		memset(err, 0, sizeof(output));

	/* make copy of command string so strtok() doesn't silently modify it */
	/* (the calling program may want to access it later) */
	cmdlen = strlen(cmdstring);
	if ((cmd = malloc(cmdlen + 1)) == NULL)
		return -1;
	memcpy(cmd, cmdstring, cmdlen);
	cmd[cmdlen] = '\0';

	/* This is not a shell, so we don't handle "???" */
	if (strstr(cmdstring, "\""))
		return -1;

	/* allow single quotes, but only if non-whitesapce doesn't occur on both sides */
	if (strstr(cmdstring, " ' ") || strstr(cmdstring, "'''"))
		return -1;

	/* each arg must be whitespace-separated, so args can be a maximum
	 * of (len / 2) + 1. We add 1 extra to the mix for NULL termination */
	argc = (cmdlen >> 1) + 2;
	argv = calloc((size_t)argc, sizeof(char *));

	if (argv == NULL) {
		printf("%s\n", _("Could not malloc argv array in popen()"));
		return -1;
	}

	/* get command arguments (stupidly, but fairly quickly) */
	while (cmd) {
		str = cmd;
		str += strspn(str, " \t\r\n"); /* trim any leading whitespace */

		if (strstr(str, "'") == str) { /* handle SIMPLE quoted strings */
			str++;
			if (!strstr(str, "'"))
				return -1; /* balanced? */
			cmd = 1 + strstr(str, "'");
			str[strcspn(str, "'")] = 0;
		} else {
			if (strpbrk(str, " \t\r\n")) {
				cmd = 1 + strpbrk(str, " \t\r\n");
				str[strcspn(str, " \t\r\n")] = 0;
			} else {
				cmd = NULL;
			}
		}

		if (cmd && strlen(cmd) == strspn(cmd, " \t\r\n"))
			cmd = NULL;

		argv[i++] = str;
	}

	return cmd_run_array(argv, out, err, flags);
}

int cmd_run_array(char *const *argv, output *out, output *err, int flags) {
	int fd, pfd_out[2], pfd_err[2];

	/* initialize the structs */
	if (out)
		memset(out, 0, sizeof(output));
	if (err)
		memset(err, 0, sizeof(output));

	if ((fd = _cmd_open(argv, pfd_out, pfd_err)) == -1)
		die(STATE_UNKNOWN, _("Could not open pipe: %s\n"), argv[0]);

	if (out)
		out->lines = _cmd_fetch_output(pfd_out[0], out, flags);
	if (err)
		err->lines = _cmd_fetch_output(pfd_err[0], err, flags);

	return _cmd_close(fd);
}

int cmd_file_read(char *filename, output *out, int flags) {
	int fd;
	if (out)
		memset(out, 0, sizeof(output));

	if ((fd = open(filename, O_RDONLY)) == -1) {
		die(STATE_UNKNOWN, _("Error opening %s: %s"), filename, strerror(errno));
	}

	if (out)
		out->lines = _cmd_fetch_output(fd, out, flags);

	if (close(fd) == -1)
		die(STATE_UNKNOWN, _("Error closing %s: %s"), filename, strerror(errno));

	return 0;
}

void timeout_alarm_handler(int signo) {
	if (signo == SIGALRM) {
		printf(_("%s - Plugin timed out after %d seconds\n"), state_text(timeout_state), timeout_interval);

		long maxfd = mp_open_max();
		if (_cmd_pids)
			for (long int i = 0; i < maxfd; i++) {
				if (_cmd_pids[i] != 0)
					kill(_cmd_pids[i], SIGKILL);
			}

		exit(timeout_state);
	}
}