upx/src/filter.cpp

/* filter.cpp --

   This file is part of the UPX executable compressor.

   Copyright (C) 1996-2003 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996-2003 Laszlo Molnar
   All Rights Reserved.

   UPX and the UCL library are free software; you can redistribute them
   and/or modify them under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of
   the License, or (at your option) any later version.

   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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; see the file COPYING.
   If not, write to the Free Software Foundation, Inc.,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer              Laszlo Molnar
   <mfx@users.sourceforge.net>          <ml1050@users.sourceforge.net>
 */


#include "conf.h"
#include "filter.h"
#include "file.h"


/*************************************************************************
// util
**************************************************************************/

static //inline
void initFilter(Filter *f, upx_byte *buf, unsigned buf_len)
{
    f->buf = buf;
    f->buf_len = buf_len;
    // clear output parameters
    f->calls = f->wrongcalls = f->noncalls = f->firstcall = f->lastcall = 0;
}


/*************************************************************************
// get a FilterEntry
**************************************************************************/

const FilterImp::FilterEntry *FilterImp::getFilter(int id)
{
    static bool done = false;
    static unsigned char filter_map[256];

    if (!done)
    {
        // init the filter_map[]
        assert(n_filters <= 254);       // as 0xff means "empty slot"
        memset(filter_map, 0xff, sizeof(filter_map));
        for (int i = 0; i < n_filters; i++)
        {
            int fid = filters[i].id;
            assert(fid >= 0 && fid <= 255);
            assert(filter_map[fid] == 0xff);
            filter_map[fid] = (unsigned char) i;
        }
        done = true;
    }

    if (id < 0 || id > 255)
        return NULL;
    unsigned index = filter_map[id];
    if (index == 0xff)                  // empty slot
        return NULL;
    assert(filters[index].id == id);
    return &filters[index];
}


bool Filter::isValidFilter(int filter_id)
{
    const FilterImp::FilterEntry * const fe = FilterImp::getFilter(filter_id);
    return fe != NULL;
}


/*************************************************************************
// high level API
**************************************************************************/

void Filter::init(int id_, unsigned addvalue_)
{
    this->id = id_;
    initFilter(this, NULL, 0);
    // clear input parameters
    this->addvalue = addvalue_;
    this->preferred_ctos = NULL;
    // clear input/output parameters
    this->cto = 0;
    this->n_mru = 0;
}


bool Filter::filter(upx_byte *buf_, unsigned buf_len_)
{
    initFilter(this, buf_, buf_len_);

    const FilterImp::FilterEntry * const fe = FilterImp::getFilter(id);
    if (fe == NULL)
        throwInternalError("filter-1");
    if (fe->id == 0)
        return true;
    if (buf_len < fe->min_buf_len)
        return false;
    if (fe->max_buf_len && buf_len > fe->max_buf_len)
        return false;
    if (!fe->do_filter)
        throwInternalError("filter-2");

    // save checksum
    this->adler = 0;
    if (clevel != 1)
        this->adler = upx_adler32(this->buf, this->buf_len);

    //printf("filter: %02x %p %d\n", this->id, this->buf, this->buf_len);
    //OutputFile::dump("filter.dat", buf, buf_len);
    int r = (*fe->do_filter)(this);
    //printf("filter: %02x %d\n", fe->id, r);
    if (r > 0)
        throwFilterException();
    if (r == 0)
        return true;
    return false;
}


void Filter::unfilter(upx_byte *buf_, unsigned buf_len_, bool verify_checksum)
{
    initFilter(this, buf_, buf_len_);

    const FilterImp::FilterEntry * const fe = FilterImp::getFilter(id);
    if (fe == NULL)
        throwInternalError("unfilter-1");
    if (fe->id == 0)
        return;
    if (buf_len < fe->min_buf_len)
        return;
    if (fe->max_buf_len && buf_len > fe->max_buf_len)
        return;
    if (!fe->do_unfilter)
        throwInternalError("unfilter-2");

    //printf("unfilter: %02x %p %d\n", this->id, this->buf, this->buf_len);
    int r = (*fe->do_unfilter)(this);
    //printf("unfilter: %02x %d\n", fe->id, r);
    if (r != 0)
        throwInternalError("unfilter-3");
    //OutputFile::dump("unfilter.dat", buf, buf_len);

    // verify checksum
    if (verify_checksum && clevel != 1)
    {
        if (this->adler != upx_adler32(this->buf, this->buf_len))
            throwInternalError("unfilter-4");
    }
}


void Filter::verifyUnfilter()
{
    // Note:
    //   This verify is just because of complete paranoia that there
    //   could be a hidden bug in the filter implementation, and
    //   it should not be necessary at all.
    //   Maybe we will remove it at some future point.
    //
    // See also:
    //   Packer::verifyOverlappingDecompression()

    //printf("verifyUnfilter: %02x %p %d\n", this->id, this->buf, this->buf_len);
    if (clevel != 1)
        unfilter(this->buf, this->buf_len, true);
}


bool Filter::scan(const upx_byte *buf_, unsigned buf_len_)
{
    // Note: must use const_cast here. This is fine as the scan
    //   implementations (fe->do_scan) actually don't change the buffer.
    upx_byte *b = const_cast<upx_byte *>(buf_);
    initFilter(this, b, buf_len_);

    const FilterImp::FilterEntry * const fe = FilterImp::getFilter(id);
    if (fe == NULL)
        throwInternalError("scan-1");
    if (fe->id == 0)
        return true;
    if (buf_len < fe->min_buf_len)
        return false;
    if (fe->max_buf_len && buf_len > fe->max_buf_len)
        return false;
    if (!fe->do_scan)
        throwInternalError("scan-2");

    //printf("filter: %02x %p %d\n", this->id, this->buf, this->buf_len);
    int r = (*fe->do_scan)(this);
    //printf("filter: %02x %d\n", fe->id, r);
    if (r > 0)
        throwFilterException();
    if (r == 0)
        return true;
    return false;
}


/*
vi:ts=4:et
*/