openrc/src/rc/rc-plugin.c

/*
   librc-plugin.c
   Simple plugin handler
   */

/*
 * Copyright 2007-2008 Roy Marples <roy@marples.name>
 * All rights reserved

 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/wait.h>

#include <dirent.h>
#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "einfo.h"
#include "rc.h"
#include "rc-misc.h"
#include "rc-plugin.h"

#define RC_PLUGIN_HOOK "rc_plugin_hook"

bool rc_in_plugin = false;

typedef struct plugin
{
	char *name;
	void *handle;
	int (*hook)(RC_HOOK, const char *);
	STAILQ_ENTRY(plugin) entries;
} PLUGIN;
STAILQ_HEAD(, plugin) plugins;

#ifndef __FreeBSD__
dlfunc_t dlfunc(void * __restrict handle, const char * __restrict symbol)
{
	union {
		void *d;
		dlfunc_t f;
	} rv;

	rv.d = dlsym(handle, symbol);
	return rv.f;
}
#endif

void rc_plugin_load(void)
{
	DIR *dp;
	struct dirent *d;
	PLUGIN *plugin;
	char file[PATH_MAX];
	void *h;
	int (*fptr)(RC_HOOK, const char *);

	/* Don't load plugins if we're in one */
	if (rc_in_plugin)
		return;

	STAILQ_INIT(&plugins);

	if (! (dp = opendir(RC_PLUGINDIR)))
		return;

	while ((d = readdir(dp))) {
		if (d->d_name[0] == '.')
			continue;

		snprintf(file, sizeof(file), RC_PLUGINDIR "/%s",  d->d_name);
		h = dlopen(file, RTLD_LAZY);
		if (! h) {
			eerror("dlopen: %s", dlerror());
			continue;
		}

		fptr = (int (*)(RC_HOOK, const char*))dlfunc(h, RC_PLUGIN_HOOK);
		if (! fptr) {
			eerror("%s: cannot find symbol `%s'", d->d_name, RC_PLUGIN_HOOK);
			dlclose(h);
		} else {
			plugin = xmalloc(sizeof(*plugin));
			plugin->name = xstrdup(d->d_name);
			plugin->handle = h;
			plugin->hook = fptr;
			STAILQ_INSERT_TAIL(&plugins, plugin, entries);
		}
	}
	closedir(dp);
}

int rc_waitpid(pid_t pid)
{
	int status = 0;
	pid_t savedpid = pid;
	int retval = -1;

	errno = 0;
	while ((pid = waitpid(savedpid, &status, 0)) > 0) {
		if (pid == savedpid)
			retval = WIFEXITED(status) ? WEXITSTATUS(status) : EXIT_FAILURE;
	}

	return retval;
}

void rc_plugin_run(RC_HOOK hook, const char *value)
{
	PLUGIN *plugin;
	struct sigaction sa;
	sigset_t empty;
	sigset_t full;
	sigset_t old;
	int i;
	int flags;
	int pfd[2];
	pid_t pid;
	char *buffer;
	char *token;
	char *p;
	ssize_t nr;
	int retval;

	/* Don't run plugins if we're in one */
	if (rc_in_plugin)
		return;

	/* We need to block signals until we have forked */
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SIG_DFL;
	sigemptyset(&sa.sa_mask);
	sigemptyset(&empty);
	sigfillset(&full);

	STAILQ_FOREACH(plugin, &plugins, entries) {
		/* We create a pipe so that plugins can affect our environment
		 * vars, which in turn influence our scripts. */
		if (pipe(pfd) == -1) {
			eerror("pipe: %s", strerror(errno));
			return;
		}

		/* Stop any scripts from inheriting us.
		 * This is actually quite important as without this, the splash
		 * plugin will probably hang when running in silent mode. */
		for (i = 0; i < 2; i++)
			if ((flags = fcntl (pfd[i], F_GETFD, 0)) < 0 ||
			    fcntl (pfd[i], F_SETFD, flags | FD_CLOEXEC) < 0)
				eerror("fcntl: %s", strerror(errno));

		sigprocmask(SIG_SETMASK, &full, &old);

		/* We run the plugin in a new process so we never crash
		 * or otherwise affected by it */
		if ((pid = fork()) == -1) {
			eerror("fork: %s", strerror(errno));
			break;
		}

		if (pid == 0) {
			/* Restore default handlers */
			sigaction(SIGCHLD, &sa, NULL);
			sigaction(SIGHUP,  &sa, NULL);
			sigaction(SIGINT,  &sa, NULL);
			sigaction(SIGQUIT, &sa, NULL);
			sigaction(SIGTERM, &sa, NULL);
			sigaction(SIGUSR1, &sa, NULL);
			sigaction(SIGWINCH, &sa, NULL);
			sigprocmask(SIG_SETMASK, &old, NULL);
			
			rc_in_plugin = true;
			close(pfd[0]);
			rc_environ_fd = fdopen(pfd[1], "w");
			retval = plugin->hook(hook, value);
			fclose(rc_environ_fd);
			rc_environ_fd = NULL;

			/* Just in case the plugin sets this to false */
			rc_in_plugin = true;
			exit(retval);
		}

		sigprocmask(SIG_SETMASK, &old, NULL);
		close(pfd[1]);
		buffer = xmalloc(sizeof(char) * BUFSIZ);
		memset(buffer, 0, BUFSIZ);

		while ((nr = read(pfd[0], buffer, BUFSIZ)) > 0) {
			p = buffer;
			while (*p && p - buffer < nr) {
				token = strsep(&p, "=");
				if (token) {
					unsetenv(token);
					if (*p) {
						setenv(token, p, 1);
						p += strlen(p) + 1;
					} else
						p++;
				}
			}
		}

		free(buffer);
		close(pfd[0]);

		rc_waitpid(pid);
	}
}

void rc_plugin_unload(void)
{
	PLUGIN *plugin = STAILQ_FIRST(&plugins);
	PLUGIN *next;

	while (plugin) {
		next = STAILQ_NEXT(plugin, entries);
		dlclose(plugin->handle);
		free(plugin->name);
		free(plugin);
		plugin = next;
	}
	STAILQ_INIT(&plugins);
}