1/*
2anonymizer.cpp - Overwrites string table for a function name.
3
4Copyright (C) 2017 by Martin Bickel
5Copyright (C) 2020 by Serge Lamikhov-Center
6
7Permission is hereby granted, free of charge, to any person obtaining a copy
8of this software and associated documentation files (the "Software"), to deal
9in the Software without restriction, including without limitation the rights
10to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11copies of the Software, and to permit persons to whom the Software is
12furnished to do so, subject to the following conditions:
13
14The above copyright notice and this permission notice shall be included in
15all copies or substantial portions of the Software.
16
17THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
20AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
23THE SOFTWARE.
24*/
25
26/*
27To run the example, you may use the following script:
28
29#!/usr/bin/bash
30
31make
32cp anonymizer temp.elf
33readelf -a temp.elf > before.txt
34./anonymizer temp.elf
35readelf -a temp.elf > after.txt
36diff before.txt after.txt
37
38*/
39
40#ifdef _MSC_VER
41#define _SCL_SECURE_NO_WARNINGS
42#define ELFIO_NO_INTTYPES
43#endif
44
45#include <string>
46#include <iostream>
47#include <fstream>
48#include <elfio/elfio.hpp>
49
50using namespace ELFIO;
51
52void overwrite_data( const std::string& filename,
53                     Elf64_Off          offset,
54                     const std::string& str )
55{
56    std::ofstream file( filename,
57                        std::ios::in | std::ios::out | std::ios::binary );
58    if ( !file )
59        throw "Error opening file" + filename;
60    std::string data( str.length(), '-' );
61    file.seekp( (std::streampos)offset );
62    file.write( data.c_str(), data.length() + 1 );
63}
64
65void process_string_table( const section* s, const std::string& filename )
66{
67    std::cout << "Info: processing string table section" << std::endl;
68    size_t index = 1;
69    while ( index < s->get_size() ) {
70        auto str = std::string( s->get_data() + index );
71        // For the example purpose, we rename main function name only
72        if ( str == "main" )
73            overwrite_data( filename, s->get_offset() + index, str );
74        index += str.length() + 1;
75    }
76}
77
78int main( int argc, char** argv )
79{
80    if ( argc != 2 ) {
81        std::cout << "Usage: anonymizer <file_name>\n";
82        return 1;
83    }
84
85    std::string filename = argv[1];
86
87    elfio reader;
88
89    if ( !reader.load( filename ) ) {
90        std::cerr << "File " << filename
91                  << " is not found or it is not an ELF file\n";
92        return 1;
93    }
94
95    for ( const auto& section : reader.sections ) {
96        if ( section->get_type() == SHT_STRTAB &&
97             std::string( section->get_name() ) == std::string( ".strtab" ) ) {
98            process_string_table( section.get(), filename );
99        }
100    }
101    return 0;
102}
103