daemon.hpp

//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2022 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    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 Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

#ifndef OPENVPN_COMMON_DAEMON_H
#define OPENVPN_COMMON_DAEMON_H

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

#include <string>

#include <openvpn/common/size.hpp>
#include <openvpn/common/exception.hpp>
#include <openvpn/common/to_string.hpp>
#include <openvpn/common/file.hpp>
#include <openvpn/common/logrotate.hpp>
#include <openvpn/common/redir.hpp>
#include <openvpn/common/usergroup.hpp>
#include <openvpn/common/logsetup.hpp>

namespace openvpn {

OPENVPN_EXCEPTION(daemon_err);

class LogReopen : public LogSetup
{
  public:
    LogReopen(const std::string &log_fn,
              const bool combine_out_err)
        : log_fn_(log_fn),
          combine_out_err_(combine_out_err)
    {
    }

    virtual void reopen() override
    {
        try
        {
            // open redirection log file, but don't redirect yet
            RedirectStd redir(std::string(),
                              log_fn_,
                              RedirectStd::FLAGS_APPEND,
                              RedirectStd::MODE_USER_GROUP,
                              combine_out_err_);

            // now do the redirect
            redir.redirect();
        }
        catch (const std::exception &e)
        {
            std::cerr << "LogReopen: " << e.what() << std::endl;
        }
    }

  private:
    const std::string log_fn_;
    const bool combine_out_err_;
};

inline LogSetup::Ptr log_setup(const std::string &log_fn,
                               const SetUserGroup *user_group,
                               const bool log_append,
                               const int log_versions,
                               const bool stdin_to_dev_null,
                               const bool combine_out_err)
{
    if (!log_append && log_versions >= 1)
        log_rotate(log_fn, log_versions);
    RedirectStd redir(stdin_to_dev_null ? "/dev/null" : "",
                      log_fn,
                      log_append ? RedirectStd::FLAGS_APPEND : RedirectStd::FLAGS_OVERWRITE,
                      RedirectStd::MODE_USER_GROUP,
                      combine_out_err);
    // if user_group specified, do chown on log file
    try
    {
        if (user_group && redir.out.defined())
            user_group->chown(redir.out(), log_fn);
    }
    catch (const std::exception &)
    {
    }
    redir.redirect();

    // possibly return a LogReopen object
    if (!log_versions)
        return LogSetup::Ptr(new LogReopen(log_fn, combine_out_err));
    else
        return LogSetup::Ptr();
}

inline void daemonize()
{
    // ignore daemon() deprecated on macOS
#if defined(__APPLE__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
#endif
    if (daemon(1, 1) < 0)
        throw daemon_err("daemon() failed");
#if defined(__APPLE__)
#pragma clang diagnostic pop
#endif
}

inline LogSetup::Ptr daemonize(const std::string &log_fn,
                               const SetUserGroup *user_group,
                               const bool log_append,
                               const int log_versions)
{
    LogSetup::Ptr ret = log_setup(log_fn, user_group, log_append, log_versions, true, true);
    daemonize();
    return ret;
}

inline void write_pid(const std::string &fn)
{
    write_string(fn, to_string(::getpid()) + '\n');
}

class WritePid
{
  public:
    WritePid(const char *pid_fn_arg) // must remain in scope for lifetime of object
        : pid_fn(pid_fn_arg)
    {
        if (pid_fn)
            write_pid(pid_fn);
    }

    ~WritePid()
    {
        if (pid_fn)
            ::unlink(pid_fn);
    }

  private:
    WritePid(const WritePid &) = delete;
    WritePid &operator=(const WritePid &) = delete;

    const char *const pid_fn;
};
} // namespace openvpn

#endif