durhelper.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_TIME_DURHELPER_H
#define OPENVPN_TIME_DURHELPER_H

#include <openvpn/common/options.hpp>
#include <openvpn/time/time.hpp>
#include <openvpn/random/randapi.hpp>

namespace openvpn {
inline void set_duration_parm(Time::Duration &dur,
                              const std::string &name,
                              const std::string &valstr,
                              const unsigned int min_value,
                              const bool x2, // multiply result by 2
                              const bool ms) // values are in milliseconds rather than seconds
{
    const unsigned int maxdur = ms ? 1000 * 60 * 60 * 24 : 60 * 60 * 24 * 7; // maximum duration -- milliseconds: 1 day, seconds: 7 days
    unsigned int value = 0;
    const bool status = parse_number<unsigned int>(valstr, value);
    if (!status)
        OPENVPN_THROW(option_error, name << ": error parsing number of " << (ms ? "milliseconds" : "seconds"));
    if (x2)
        value *= 2;
    if (value == 0 || value > maxdur)
        value = maxdur;
    if (value < min_value)
        value = min_value;
    dur = ms ? Time::Duration::milliseconds(value) : Time::Duration::seconds(value);
}

inline const Option *load_duration_parm(Time::Duration &dur,
                                        const std::string &name,
                                        const OptionList &opt,
                                        const unsigned int min_value,
                                        const bool x2,
                                        const bool allow_ms)
{
    // look for milliseconds given as <name>-ms
    if (allow_ms)
    {
        const Option *o = opt.get_ptr(name + "-ms");
        if (o)
        {
            set_duration_parm(dur, name, o->get(1, 16), min_value, x2, true);
            return o;
        }
    }

    // look for seconds given as <name>
    {
        const Option *o = opt.get_ptr(name);
        if (o)
            set_duration_parm(dur, name, o->get(1, 16), allow_ms ? 1 : min_value, x2, false);
        return o;
    }
}

inline Time::Duration load_duration_default(const std::string &name,
                                            const OptionList &opt,
                                            const Time::Duration &default_duration,
                                            const unsigned int min_value,
                                            const bool x2,
                                            const bool allow_ms)
{
    Time::Duration ret(default_duration);
    load_duration_parm(ret, name, opt, min_value, x2, allow_ms);
    return ret;
}

inline Time::Duration skew_duration(const Time::Duration &dur,
                                    const Time::Duration &min,
                                    const unsigned int flux_order,
                                    RandomAPI &rng)
{
    const unsigned int range = 1 << flux_order;
    const int delta = int(rng.rand_get<unsigned int>() & (range - 1)) - int(range >> 1);
    const Time::Duration ret = dur + delta;
    if (ret >= min)
        return ret;
    else
        return min;
}
} // namespace openvpn

#endif