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What is govm? ====================================================================== govm is an experimental/educational VM + compiler. I've written a small bytecode interpreter along with a custom bytecode for CIPHER 5 , originally based on an idea by Sascha Müller, who also wrote a little assembler for his vm, which I extended. When I tried to write bytecode with his assembler, I had to repeat the same instruction sequences over and over again. Because I hate to repeat myself more often than never, I decided I need to write a compiler. The idea of using the VM in a Capture the Flag contest was to force teams to write their own shellcode, to write their own buffer overflow protection, and to write their own disassembler. Thus, teams who cannot afford a commercial disassembler (or who are unwilling to buy one) are not at a disadvantage. The VM supports execution of arbitrary bytecode on its stack, provided the originally executed bytecode is vulnerable to stack overflows. The VM is written in C; the current version is implemented as a python module. It supports three syscalls: getc, putc and halt. getc and putc are redirected to python functions to allow for easy integration. COMPILING ====================================================================== You need: For compiling the compiler: sun java 1.5 sdk or later. For compiling the VM: python2.5, and python2.5 headers Simply issue 'make' to make both. The compiler will be stored in the project's root dir as govmc.jar. The VM can be invoked by doing cd pygovm && python rungovm.py $(BYTECODE) Some examples can be found in the examples/ directory. USAGE ====================================================================== The compiler is invoked like this: java -jar govmc.jar $INPUT $OUTPUT For a short language description, do man ./govmc.1 If invoked without arguments, the compiler is started up as a network service and can then subsequently be used over the net by doing: python cwrapper.py $INPUT $OUTPUT $HOST Check the pygovm/ subdirectory for the government vm, which interprets the generated bytecode. Why the government compiler? Because it is the reference implementation of the government bytecode, to be run on the government vm (govm). Why? Because it was originally written for CIPHER 5, and CIPHER 5's theme was "corrupt government". And a corrupt government needs its own vm. DOCUMENTATION ====================================================================== The original man page for the compiler is included. It can be a little confusing because the manpage is written with the assumption that the compiler is used over a web interface. QUESTIONS ====================================================================== firstname.lastname@example.org