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Modify 'anonymizer' example to rename a single function name

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This commit is contained in:
Serge Lamikhov-Center 2020-08-13 09:19:10 -07:00
parent 5cf544283b
commit c28402c5b6
1 changed files with 62 additions and 92 deletions
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126
examples/anonymizer/anonymizer.cpp
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@ -1,7 +1,8 @@
/*
anonymizer.cpp - Overwrites all data from an ELF file with random data.
anonymizer.cpp - Overwrites string table for a function name.
Copyright (C) 2017 by Martin Bickel
Copyright (C) 2020 by Serge Lamikhov-Center
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
@ -22,6 +23,20 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
/*
To run the example, you may use the following script:
#!/usr/bin/bash
make
cp anonymizer temp.elf
readelf -a temp.elf > before.txt
./anonymizer temp.elf
readelf -a temp.elf > after.txt
diff before.txt after.txt
*/
#ifdef _MSC_VER
#define _SCL_SECURE_NO_WARNINGS
#define ELFIO_NO_INTTYPES
@ -29,86 +44,41 @@ THE SOFTWARE.
#include <string>
#include <iostream>
#include <elfio/elfio.hpp>
#include <fstream>
#include <random>
#include <elfio/elfio.hpp>
using namespace ELFIO;
bool preserve_name( const std::string& name ) {
static std::vector<std::string> names_to_preserve = { ".shstrtab",
".rodata",
".bss",
".data",
".text",
".text_vle" };
for ( auto s = names_to_preserve.begin(); s != names_to_preserve.end(); ++s )
if ( *s == name)
return true;
return false;
}
std::default_random_engine generator(0xe1f);
std::uniform_int_distribution<int> distribution(0,255);
void randomize_data( const std::string& filename, long offset, long size ) {
void overwrite_data(const std::string &filename, long offset, std::string &str)
{
std::ofstream file(filename, std::ios::in | std::ios::out | std::ios::binary);
if (!file)
throw "error opening file" + filename;
file.seekp(offset);
for ( long i = 0; i < size; ++i ) {
const char value = distribution(generator);
file.write(&value, 1 );
}
}
void overwrite_data( const std::string& filename, long offset, const std::string& data ) {
std::ofstream file (filename, std::ios::in|std::ios::out|std::ios::binary);
if ( !file )
throw "error opening file" + filename;
throw "Error opening file" + filename;
std::string data(str.length(), '-');
file.seekp(offset);
file.write(data.c_str(), data.length() + 1);
}
std::string generate( int length ) {
static int counters[6] = { 0, 0, 10, 100, 1000, 10000 };
int counter = counters[length > 5 ? 5 : length ]++;
auto s = std::to_string(counter);
if ( s.length() > length ) {
throw "String length error at " + std::to_string( counter ) + "; expecting " + std::to_string( length ) + " bytes ";
}
while (s.length() < length)
s = "s" + s;
return s;
}
void processStringTable( const section* s, const std::string& filename ) {
void process_string_table(const section *s, const std::string &filename)
{
std::cout << "Info: processing string table section" << std::endl;
int counter = 0;
int index = 1;
while ( index < s->get_size() ) {
auto len = strlen( s->get_data()+index );
if ( len && !preserve_name( s->get_data()+index ))
overwrite_data( filename, s->get_offset() + index, generate( len ));
index += len + 1;
counter++;
while (index < s->get_size())
{
auto str = std::string(s->get_data() + index);
// For the example purpose, we rename main function name only
if (str == "main")
overwrite_data(filename, s->get_offset() + index, str);
index += str.length() + 1;
}
std::cout << counter << " strings found " << std::endl;
}
int main(int argc, char **argv)
{
try {
if ( argc != 2 ) {
try
{
if (argc != 2)
{
std::cout << "Usage: anonymizer <file_name>\n";
return 1;
}
@ -117,28 +87,28 @@ int main( int argc, char** argv )
elfio reader;
if ( !reader.load( filename ) ) {
if (!reader.load(filename))
{
std::cerr << "File " << filename << " is not found or it is not an ELF file\n";
return 1;
}
for ( auto sect = reader.sections.begin(); sect != reader.sections.end(); ++sect ) {
section* s = *sect;
if ( s->get_type() == SHT_STRTAB ) {
processStringTable(s, filename);
} else if ( s->get_type() == SHT_SYMTAB ) {
std::cout << "Skipping symbol table." << std::endl;
} else if ( s->get_type() == SHT_PROGBITS ) {
if ( s->get_size() > 0 ) {
randomize_data(filename, s->get_offset(), s->get_size());
std::cout << "Sanitized " << s->get_size() << " Bytes in section" << std::endl;
}
for (auto section = reader.sections.begin(); section != reader.sections.end(); ++section)
{
if ((*section)->get_type() == SHT_STRTAB &&
std::string((*section)->get_name()) == std::string(".strtab"))
{
process_string_table(*section, filename);
}
}
return 0;
} catch ( const std::string& s ) {
}
catch (const std::string &s)
{
std::cerr << s << std::endl;
} catch ( const char* s ) {
}
catch (const char *s)
{
std::cerr << s << std::endl;
}
return 1;