auditd-plugin-clickhouse/logging.cpp

/*
 * This is an auditd plugin for sending auditd data
 * to clickhouse DB.
 * Copyright (C) 2020 Aleksei Nikiforov <darktemplar@basealt.ru>
 *
 * 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 <https://www.gnu.org/licenses/>.
 *
 */

#include "logging.hpp"

#include <boost/scope_exit.hpp>

std::mutex Logger::s_mutex;

Logger::Logger()
	: m_logfile(NULL)
{
}

Logger::~Logger()
{
	dump_impl();
	close_impl();
}

Logger& Logger::instance()
{
	static Logger s_instance;
	return s_instance;
}

void Logger::open(const char *filename)
{
	std::lock_guard<std::mutex> lock(s_mutex);
	instance().open_impl(filename);
}

void Logger::write(const char *format, ...)
{
	std::lock_guard<std::mutex> lock(s_mutex);

	va_list args;

	va_start(args, format);
	instance().write_impl(format, args);
	va_end(args);
}

void Logger::dump()
{
	std::lock_guard<std::mutex> lock(s_mutex);
	instance().dump_impl();
}

void Logger::open_impl(const char *filename)
{
	close_impl();

	FILE *f = fopen(filename, "at");
	if (f)
	{
		m_logfile = f;
		dump_impl();
	}
}

void Logger::write_impl(const char *format, va_list args)
{
	if (m_logfile)
	{
		vfprintf(m_logfile, format, args);

		fflush(m_logfile);
	}
	else
	{
		// save logged data for later use
		char *data = NULL;

		BOOST_SCOPE_EXIT(&data)
		{
			if (data != NULL)
			{
				free(data);
			}
		} BOOST_SCOPE_EXIT_END;

		int result = vasprintf(&data, format, args);

		if ((result >= 0) && (data != NULL))
		{
			m_lines.push_back(data);
		}
	}
}

void Logger::dump_impl()
{
	FILE *outfile = m_logfile ? m_logfile : stderr;

	for (auto iter = m_lines.begin(); iter != m_lines.end(); ++iter)
	{
		fwrite(iter->c_str(), 1, iter->length(), outfile);
	}

	fflush(outfile);
	m_lines.clear();
}

void Logger::close_impl()
{
	if (m_logfile)
	{
		fclose(m_logfile);
		m_logfile = NULL;
	}
}