lzoasym.hpp

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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_COMPRESS_LZOASYM_H
#define OPENVPN_COMPRESS_LZOASYM_H
 
#include <openvpn/buffer/buffer.hpp>
#include <openvpn/compress/lzoasym_impl.hpp>
 
// Implement asymmetrical LZO compression (only uncompress, don't compress)
// Should only be included by lzoselect.hpp
 
namespace openvpn {
 
class CompressLZOAsym : public Compress
{
  public:
    // magic number for LZO compression
    enum
    {
        LZO_COMPRESS = 0x66,
        LZO_COMPRESS_SWAP = 0x67,
    };
 
    OPENVPN_SIMPLE_EXCEPTION(lzo_init_failed);
 
    CompressLZOAsym(const Frame::Ptr &frame,
                    const SessionStats::Ptr &stats,
                    const bool support_swap_arg,
                    const bool asym_arg) // we are always asymmetrical, regardless of setting
        : Compress(frame, stats),
          support_swap(support_swap_arg)
    {
        OVPN_LOG_INFO("LZO-ASYM init swap=" << support_swap_arg << " asym=" << asym_arg);
    }
 
    static void init_static()
    {
    }
 
    const char *name() const override
    {
        return "lzo-asym";
    }
 
    void decompress_work(BufferAllocated &buf)
    {
        // initialize work buffer
        size_t zlen = frame->prepare(Frame::DECOMPRESS_WORK, work);
 
        // do uncompress
        const int err = lzo_asym_impl::lzo1x_decompress_safe(buf.c_data(), buf.size(), work.data(), &zlen);
        if (err != lzo_asym_impl::LZOASYM_E_OK)
        {
            error(buf);
            return;
        }
        OVPN_LOG_VERBOSE("LZO-ASYM uncompress " << buf.size() << " -> " << zlen);
        work.set_size(zlen);
        buf.swap(work);
    }
 
    void compress(BufferAllocated &buf, const bool hint) override
    {
        // skip null packets
        if (!buf.size())
            return;
 
        // indicate that we didn't compress
        if (support_swap)
            do_swap(buf, NO_COMPRESS_SWAP);
        else
            buf.push_front(NO_COMPRESS);
    }
 
    void decompress(BufferAllocated &buf) override
    {
        // skip null packets
        if (!buf.size())
            return;
 
        const unsigned char c = buf.pop_front();
        switch (c)
        {
        case NO_COMPRESS_SWAP:
            do_unswap(buf);
            [[fallthrough]];
        case NO_COMPRESS:
            break;
        case LZO_COMPRESS_SWAP:
            do_unswap(buf);
            [[fallthrough]];
        case LZO_COMPRESS:
            decompress_work(buf);
            break;
        default:
            error(buf); // unknown op
        }
    }
 
  private:
    const bool support_swap;
    BufferAllocated work;
};
 
} // namespace openvpn
 
#endif // OPENVPN_COMPRESS_LZOASYM_H