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|
// 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- OpenVPN Inc.
//
// SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
//
#ifndef OPENVPN_SSL_DATALIMIT_H
#define OPENVPN_SSL_DATALIMIT_H
#include <openvpn/common/exception.hpp>
namespace openvpn {
// Helper for handling keys which can have an upper limit
// on maximum amount of data encrypted/decrypted, such
// as Blowfish.
class DataLimit
{
public:
typedef unsigned int size_type;
enum Mode
{
Encrypt = 0,
Decrypt = 1,
};
enum State
{
None = 0,
Green = 1,
Red = 2,
};
struct Parameters
{
size_type encrypt_red_limit = 0;
size_type decrypt_red_limit = 0;
};
DataLimit(const Parameters &p)
: encrypt(p.encrypt_red_limit),
decrypt(p.decrypt_red_limit)
{
}
State update_state(const Mode mode, const State newstate)
{
return elgible(mode, component(mode).update_state(newstate));
}
State add(const Mode mode, const size_type n)
{
return elgible(mode, component(mode).add(n));
}
bool is_decrypt_green()
{
return decrypt.get_state() >= Green;
}
static const char *mode_str(const Mode m)
{
switch (m)
{
case Encrypt:
return "Encrypt";
case Decrypt:
return "Decrypt";
default:
return "Mode_???";
}
}
static const char *state_str(const State s)
{
switch (s)
{
case None:
return "None";
case Green:
return "Green";
case Red:
return "Red";
default:
return "State_???";
}
}
private:
// Don't return Encrypt-Red until Decrypt-Green
// has been received. This confirms that the peer
// is now transmitting on the key ID, making it
// eligible for renegotiation.
State elgible(const Mode mode, const State state)
{
// Bit positions for Encrypt/Decrypt and Green/Red
enum
{
EG = 1 << 0,
ER = 1 << 1,
DG = 1 << 2,
DR = 1 << 3,
};
if (state > None)
{
const unsigned int mask = 1 << ((int(state) - 1) + (int(mode) << 1));
if (!(flags & mask))
{
flags |= mask;
if ((mask & (ER | DG)) && ((flags & (ER | DG)) == (ER | DG)))
return Red;
else if (mask & ER)
return None;
else
return state;
}
}
return None;
}
class Component
{
public:
Component(const size_type red_limit_arg)
: red_limit(red_limit_arg)
{
}
State add(const size_type n)
{
bytes += n;
return update_state(transition(state));
}
State update_state(const State newstate)
{
State ret = None;
if (newstate > state)
state = ret = newstate;
return ret;
}
State get_state() const
{
return state;
}
private:
State transition(State s) const
{
switch (s)
{
case None:
if (bytes)
return Green;
else
return None;
case Green:
if (red_limit && bytes >= red_limit)
return Red;
else
return None;
case Red:
default:
return None;
}
}
const size_type red_limit;
size_type bytes = 0;
State state = None;
};
Component &component(const Mode m)
{
switch (m)
{
case Encrypt:
return encrypt;
case Decrypt:
return decrypt;
default:
throw Exception("DataLimit::Component: unknown mode");
}
}
Component encrypt;
Component decrypt;
unsigned int flags = 0;
};
} // namespace openvpn
#endif
|
