mirror of
https://github.com/OpenVPN/openvpn3.git
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16b10559f2
OpenVPN Technologies, Inc. change their name to OpenVPN Inc. during the autumn of 2017. Signed-off-by: David Sommerseth <davids@openvpn.net>
164 lines
5.1 KiB
C++
164 lines
5.1 KiB
C++
// OpenVPN -- An application to securely tunnel IP networks
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// over a single port, with support for SSL/TLS-based
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// session authentication and key exchange,
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// packet encryption, packet authentication, and
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// packet compression.
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//
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// Copyright (C) 2012-2017 OpenVPN Inc.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License Version 3
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// as published by the Free Software Foundation.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program in the COPYING file.
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// If not, see <http://www.gnu.org/licenses/>.
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#ifndef OPENVPN_TRANSPORT_PKTSTREAM_H
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#define OPENVPN_TRANSPORT_PKTSTREAM_H
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#include <algorithm> // for std::min
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#include <cstdint> // for std::uint16_t, etc.
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#include <openvpn/common/exception.hpp>
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#include <openvpn/buffer/buffer.hpp>
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#include <openvpn/frame/frame.hpp>
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namespace openvpn {
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// Used to encapsulate OpenVPN packets onto a stream transport such as TCP,
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// or extract them from the stream.
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class PacketStream
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{
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public:
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OPENVPN_SIMPLE_EXCEPTION(embedded_packet_size_error);
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OPENVPN_SIMPLE_EXCEPTION(packet_not_fully_formed);
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PacketStream() : declared_size_defined(false) {}
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// Add stream fragment to packet that we are building up.
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// Data will be read from buf. On return buf may still contain
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// residual data. If function is able to use all of buf, it may
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// grab ownership of it, replacing buf as returned to caller with
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// an empty (but possibly pre-allocated) BufferAllocated object.
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void put(BufferAllocated& buf, const Frame::Context& frame_context)
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{
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if (buf.defined())
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{
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if (!declared_size_defined && !buffer.defined())
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{
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if (size_defined(buf))
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{
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extract_size(buf, frame_context);
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if (buf.size() == declared_size) // packet is correctly sized
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buffer.swap(buf);
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else if (buf.size() < declared_size) // packet is undersized
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{
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if (buf.offset() + declared_size + frame_context.tailroom() <= buf.capacity())
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buffer.swap(buf);
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else
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{
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buffer.swap(buf);
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frame_context.realign(buffer);
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}
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}
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else // packet is oversized
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{
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frame_context.prepare(buffer);
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const unsigned char *data = buf.read_alloc(declared_size);
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buffer.write(data, declared_size);
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}
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}
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else // rare case where packet fragment is too small to contain embedded size
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{
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buffer.swap(buf);
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frame_context.realign(buffer);
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}
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}
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else
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{
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while (!declared_size_defined)
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{
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if (buf.empty())
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return;
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buffer.push_back(buf.pop_front());
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if (size_defined(buffer))
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extract_size(buffer, frame_context);
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}
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if (buffer.size() < declared_size)
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{
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const size_t needed = std::min(declared_size - buffer.size(), buf.size());
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const unsigned char *data = buf.read_alloc(needed);
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buffer.write(data, needed);
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}
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}
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}
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}
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// returns true if get() may be called to return fully formed packet
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bool ready() const
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{
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return declared_size_defined && buffer.size() >= declared_size;
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}
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// return fully formed packet as ret. ret, as passed to method, will
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// be grabbed, reset, and subsequently used internally.
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void get(BufferAllocated& ret)
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{
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if (declared_size_defined && buffer.size() == declared_size)
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{
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ret.swap(buffer);
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buffer.reset_content();
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declared_size_defined = false;
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}
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else
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throw packet_not_fully_formed();
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}
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// prepend uint16_t size to buffer
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static void prepend_size(Buffer& buf)
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{
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const std::uint16_t net_len = htons(buf.size());
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buf.prepend((const unsigned char *)&net_len, sizeof(net_len));
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}
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private:
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void extract_size(Buffer& buf, const Frame::Context& frame_context)
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{
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const size_t size = read_size(buf);
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validate_size(size, frame_context);
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declared_size = size;
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declared_size_defined = true;
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}
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static bool size_defined(const Buffer& buf)
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{
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return buf.size() >= sizeof(std::uint16_t);
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}
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static size_t read_size(Buffer& buf)
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{
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std::uint16_t net_len;
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buf.read((unsigned char *)&net_len, sizeof(net_len));
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return ntohs(net_len);
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}
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static void validate_size(const size_t size, const Frame::Context& frame_context)
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{
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if (!size || size > frame_context.payload())
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throw embedded_packet_size_error();
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}
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size_t declared_size; // declared size of packet in leading uint16_t prefix
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bool declared_size_defined; // true if declared_size is defined
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BufferAllocated buffer; // accumulated packet data
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};
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} // namespace openvpn
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#endif // OPENVPN_TRANSPORT_PKTSTREAM_H
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