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146 lines
4.2 KiB
Plaintext
146 lines
4.2 KiB
Plaintext
The UPX Hacker's Guide
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======================
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Foreword
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--------
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The precompiled UPX versions are linked against the NRV compression
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library instead of the UCL library. Using the same compression algorithms,
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NRV achieves a better compression ratio. NRV is not publicly
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available, though, and probably never will be.
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While you may be disappointed that you don't have access to the
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latest state-of-the-art compression technology this is actually
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a safe guard for all of us. The UPX source code release makes
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it very easy for any evil-minded person to do all sort of bad
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things. By not providing the very best compression ratio it is much
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more difficult to create fake or otherwise disguised UPX versions (or
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similar trojans), as any end user will notice when the compression
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has gotten worse with a new "version" or "product".
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Finally please be aware that you now have your hands on the source
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code of the most sophisticated executable packer ever.
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Let's join our forces to make it even better :-)
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Share and enjoy,
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Markus & Laszlo
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Introduction
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------------
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Welcome to the UPX source code release!
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UPX is not a toy for kids. Apart from basic knowledge about executables
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and data compression you will need to be firm in C++, assembler,
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Perl and Makefiles. Probably some other things as well.
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If you can't manage to compile it then the sources are
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probably not for you. Don't email us for help.
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The authors use Linux for development. You might want to as well.
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Short overview
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--------------
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The UPX source code consists of two mainly independent parts:
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1) The src/stub directory contains the decompression stubs that
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will get added to each compressed executable.
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The stubs are mainly written in assembler and get "compiled"
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into ordinary C header files.
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2) The src directory contains the actual packer sources. The stubs
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are #included by the individual executable format handlers.
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Prerequisites
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-------------
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- first of all you need to build the UCL compression library
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http://www.oberhumer.com/opensource/ucl/
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Use "CC=gcc -std=gnu89" especially with gcc-6.3 and gcc-7.1.
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To build for native aarch64 (64-bit ARM) the files config.guess
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and config.sub must be updated according to the recipe at
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https://www.gnu.org/software/gettext/manual/html_node/config_002eguess.html
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Tools needed to build/modify the UPX sources
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--------------------------------------------
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- A C++ compiler: gcc >= 3.3 or clang.
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- GNU make 3.81 or better
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- zlib and zlib-devel [or zlib-dev] software packages for your
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host environment
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- LZMA SDK from https://github.com/upx/upx-lzma-sdk
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When using git run 'git submodule update --init --recursive'.
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To compile the packer sources
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-----------------------------
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Set the environment variable UPX_UCLDIR to point to your
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UCL build directory, e.g.
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set UPX_UCLDIR=c:\src\ucl-1.03 (DOS / Windows)
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export UPX_UCLDIR=$HOME/local/src/ucl-1.03 (Unix)
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Finally type
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make
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If you want to modify the stub sources you'll also need
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-------------------------------------------------------
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- Perl & Python
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- upx-stubtools - a number of cross-assemblers and cross-compilers.
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Precompiled binaries for i386-linux hosts are available from
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https://github.com/upx/upx-stubtools/releases
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Misc. notes
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-----------
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As the docs say: UPX is a portable, extendable and endian neutral
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program, so if you want to add some new stuff, try not to break these
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nice properties.
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- Use the types LE16, LE32, BE16 and BE32 for fields in file headers.
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- Use [sg]et_[bl]e(16|32) for getting/setting values in the data
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stream.
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- Use gcc extensions and other compiler specific stuff only through
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macros.
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***
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Some conventions:
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- follow our coding style
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- indent level = 4
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- expand all tabulators
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- Use throwSomeException() functions instead of throw SomeException():
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this makes the code shorter if used often.
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***
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Patches/Contributions
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- Please send us bug fixes/contributions only using
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diff -u oldfile newfile
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or
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diff -uNr olddirectory newdirectory
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# vim:set ts=4 sw=4 et:
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