104 lines
3.5 KiB
C++
104 lines
3.5 KiB
C++
/*************************************************************************/
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/* Copyright (c) 2015 dx, http://kaimi.ru */
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/* */
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/* Permission is hereby granted, free of charge, to any person */
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/* obtaining a copy of this software and associated documentation */
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/* files (the "Software"), to deal in the Software without */
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/* restriction, including without limitation the rights to use, */
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/* copy, modify, merge, publish, distribute, sublicense, and/or */
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/* sell copies of the Software, and to permit persons to whom the */
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/* Software is furnished to do so, subject to the following conditions: */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/*************************************************************************/
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#include "pe_checksum.h"
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#include "pe_structures.h"
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#include "pe_base.h"
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namespace pe_bliss
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{
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using namespace pe_win;
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//Calculate checksum of image
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uint32_t calculate_checksum(std::istream& file)
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{
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//Save istream state
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std::ios_base::iostate state = file.exceptions();
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std::streamoff old_offset = file.tellg();
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//Checksum value
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unsigned long long checksum = 0;
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try
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{
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image_dos_header header;
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file.exceptions(std::ios::goodbit);
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//Read DOS header
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pe_base::read_dos_header(file, header);
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//Calculate PE checksum
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file.seekg(0);
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unsigned long long top = 0xFFFFFFFF;
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top++;
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//"CheckSum" field position in optional PE headers - it's always 64 for PE and PE+
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static const unsigned long checksum_pos_in_optional_headers = 64;
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//Calculate real PE headers "CheckSum" field position
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//Sum is safe here
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unsigned long pe_checksum_pos = header.e_lfanew + sizeof(image_file_header) + sizeof(uint32_t) + checksum_pos_in_optional_headers;
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//Calculate checksum for each byte of file
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std::streamoff filesize = pe_utils::get_file_size(file);
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for(long long i = 0; i < filesize; i += 4)
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{
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unsigned long dw = 0;
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//Read DWORD from file
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file.read(reinterpret_cast<char*>(&dw), sizeof(unsigned long));
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//Skip "CheckSum" DWORD
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if(i == pe_checksum_pos)
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continue;
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//Calculate checksum
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checksum = (checksum & 0xffffffff) + dw + (checksum >> 32);
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if(checksum > top)
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checksum = (checksum & 0xffffffff) + (checksum >> 32);
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}
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//Finish checksum
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checksum = (checksum & 0xffff) + (checksum >> 16);
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checksum = (checksum) + (checksum >> 16);
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checksum = checksum & 0xffff;
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checksum += static_cast<unsigned long>(filesize);
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}
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catch(const std::exception&)
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{
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//If something went wrong, restore istream state
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file.exceptions(state);
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file.seekg(old_offset);
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file.clear();
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//Rethrow
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throw;
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}
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//Restore istream state
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file.exceptions(state);
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file.seekg(old_offset);
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file.clear();
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//Return checksum
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return static_cast<uint32_t>(checksum);
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}
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}
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