112 lines
4.2 KiB
C++
112 lines
4.2 KiB
C++
/*************************************************************************/
|
|
/* Copyright (c) 2015 dx, http://kaimi.ru */
|
|
/* */
|
|
/* Permission is hereby granted, free of charge, to any person */
|
|
/* obtaining a copy of this software and associated documentation */
|
|
/* files (the "Software"), to deal in the Software without */
|
|
/* restriction, including without limitation the rights to use, */
|
|
/* copy, modify, merge, publish, distribute, sublicense, and/or */
|
|
/* sell copies of the Software, and to permit persons to whom the */
|
|
/* Software is furnished to do so, subject to the following conditions: */
|
|
/* The above copyright notice and this permission notice shall be */
|
|
/* included in all copies or substantial portions of the Software. */
|
|
/* */
|
|
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
|
|
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
|
|
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
|
|
/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
|
|
/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
|
|
/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
|
|
/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
|
|
/*************************************************************************/
|
|
#include <cmath>
|
|
#include "entropy.h"
|
|
#include "utils.h"
|
|
|
|
namespace pe_bliss
|
|
{
|
|
//Calculates entropy for PE image section
|
|
double entropy_calculator::calculate_entropy(const section& s)
|
|
{
|
|
if(s.get_raw_data().empty()) //Don't count entropy for empty sections
|
|
throw pe_exception("Section is empty", pe_exception::section_is_empty);
|
|
|
|
return calculate_entropy(s.get_raw_data().data(), s.get_raw_data().length());
|
|
}
|
|
|
|
//Calculates entropy for istream (from current position of stream)
|
|
double entropy_calculator::calculate_entropy(std::istream& file)
|
|
{
|
|
uint32_t byte_count[256] = {0}; //Byte count for each of 255 bytes
|
|
|
|
if(file.bad())
|
|
throw pe_exception("Stream is bad", pe_exception::stream_is_bad);
|
|
|
|
std::streamoff pos = file.tellg();
|
|
|
|
std::streamoff length = pe_utils::get_file_size(file);
|
|
length -= file.tellg();
|
|
|
|
if(!length) //Don't calculate entropy for empty buffers
|
|
throw pe_exception("Data length is zero", pe_exception::data_is_empty);
|
|
|
|
//Count bytes
|
|
for(std::streamoff i = 0; i != length; ++i)
|
|
++byte_count[static_cast<unsigned char>(file.get())];
|
|
|
|
file.seekg(pos);
|
|
|
|
return calculate_entropy(byte_count, length);
|
|
}
|
|
|
|
//Calculates entropy for data block
|
|
double entropy_calculator::calculate_entropy(const char* data, size_t length)
|
|
{
|
|
uint32_t byte_count[256] = {0}; //Byte count for each of 255 bytes
|
|
|
|
if(!length) //Don't calculate entropy for empty buffers
|
|
throw pe_exception("Data length is zero", pe_exception::data_is_empty);
|
|
|
|
//Count bytes
|
|
for(size_t i = 0; i != length; ++i)
|
|
++byte_count[static_cast<unsigned char>(data[i])];
|
|
|
|
return calculate_entropy(byte_count, length);
|
|
}
|
|
|
|
//Calculates entropy for this PE file (only section data)
|
|
double entropy_calculator::calculate_entropy(const pe_base& pe)
|
|
{
|
|
uint32_t byte_count[256] = {0}; //Byte count for each of 255 bytes
|
|
|
|
size_t total_data_length = 0;
|
|
|
|
//Count bytes for each section
|
|
for(section_list::const_iterator it = pe.get_image_sections().begin(); it != pe.get_image_sections().end(); ++it)
|
|
{
|
|
const std::string& data = (*it).get_raw_data();
|
|
size_t length = data.length();
|
|
total_data_length += length;
|
|
for(size_t i = 0; i != length; ++i)
|
|
++byte_count[static_cast<unsigned char>(data[i])];
|
|
}
|
|
|
|
return calculate_entropy(byte_count, total_data_length);
|
|
}
|
|
|
|
//Calculates entropy from bytes count
|
|
double entropy_calculator::calculate_entropy(const uint32_t byte_count[256], std::streamoff total_length)
|
|
{
|
|
double entropy = 0.; //Entropy result value
|
|
//Calculate entropy
|
|
for(uint32_t i = 0; i < 256; ++i)
|
|
{
|
|
double temp = static_cast<double>(byte_count[i]) / total_length;
|
|
if(temp > 0.)
|
|
entropy += std::abs(temp * (std::log(temp) * pe_utils::log_2));
|
|
}
|
|
|
|
return entropy;
|
|
}
|
|
}
|