Pyarmor

Pyarmor is a command line tool used to obfuscate python scripts, bind obfuscated scripts to fixed machine or expire obfuscated scripts. It protects Python scripts by the following ways:

• Obfuscate code object to protect constants and literal strings.
• Obfuscate byte code of each code object.
• Clear f_locals of frame as soon as code object completed execution.
• Expired obfuscated scripts, or bind to fixed machine.

Look at what happened after foo.py is obfuscated by Pyarmor. Here are the files list in the output path dist

    foo.py

    pytransform.py
    _pytransform.so, or _pytransform.dll in Windows, _pytransform.dylib in MacOS

    pyshield.key
    pyshield.lic
    product.key
    license.lic

dist/foo.py is obfuscated script, the content is

   1     from pytransfrom import pyarmor_runtime
   2     pyarmor_runtime()
   3 
   4     __pyarmor__(__name__, __file__, b'\x06\x0f...')

All the other extra files called Runtime Files, which are required to run or import obfuscated scripts. So long as runtime files are in any Python path, obfuscated script dist/foo.py can be used as normal Python script. That is to say, the original python scripts can be replaced with obfuscated scripts seamlessly.

Obfuscate Scripts

How to obfuscate python scripts by Pyarmor?

First compile Python script to code object

    char *filename = "foo.py";
    char *source = read_file( filename );
    PyCodeObject *co = Py_CompileString( source, "<frozen foo>", Py_file_input );

Next change this code object as the following ways

• Wrap byte code co_code within a try...finally block

      wrap header:
  
              LOAD_GLOBALS    N (__armor_enter__)     N = length of co_consts
              CALL_FUNCTION   0
              POP_TOP
              SETUP_FINALLY   X (jump to wrap footer) X = size of original byte code
  
      changed original byte code:
  
              Increase oparg of each absolute jump instruction by the size of wrap header
  
              Obfuscate original byte code
  
              ...
  
      wrap footer:
  
              LOAD_GLOBALS    N + 1 (__armor_exit__)
              CALL_FUNCTION   0
              POP_TOP
              END_FINALLY

• Append function names __armor_enter, __armor_exit__ to co_consts

• Increase co_stacksize to 4 if it's less than 4

• Set CO_OBFUSCAED (0x80000000) flag in co_flags

• Change all code objects in the co_consts recursively

Then serialize this reformed code object, obfuscate it to protect constants and literal strings

    char *string_code = marshal.dumps( co );
    char *obfuscated_code = obfuscate_algorithm( string_code );

Finally generate obfuscated script

    sprintf( buf, "__pyarmor__(__name__, __file__, b'%s')", obfuscated_code );
    save_file( "dist/foo.py", buf );

The obfuscated script is a normal Python script, it looks like this

   1     __pyarmor__(__name__, __file__, b'\x01\x0a...')

Run Obfuscated Scripts

What happens to run obfuscated script dist/foo.py by Python Interpreter?

The first 2 lines, which called Bootstrap Code

   1     from pytransfrom import pyarmor_runtime
   2     pyarmor_runtime()

It will fulfil the following tasks

• Validate dist/license.lic, check whether it's expired or not etc.

• Add 3 functions to module builtins:

  • __pyarmor__

  • __armor_enter__

  • __armor_exit__

The next code line in dist/foo.py is

   1     ...
   2 
   3     __pyarmor__(__name__, __file__, b'\x01\x0a...')

__pyarmor__ is called, it will import original module from obfuscated code

    static PyObject *
    __pyarmor__(char *name, char *pathname, unsigned char *obfuscated_code)
    {
        char *string_code = restore_obfuscated_code( obfuscated_code );
        PyCodeObject *co = marshal.loads( string_code );
        return PyImport_ExecCodeModuleEx( name, co, pathname );
    }

After that, in the runtime of this python process

• __armor_enter__ is called as soon as any code object is executed, it will restore byte-code of this code object

      static PyObject *
      __armor_enter__(PyObject *self, PyObject *args)
      {
          // Got code object
          PyFrameObject *frame = PyEval_GetFrame();
          PyCodeObject *f_code = frame->f_code;
  
          // Increase refcalls of this code object
          // Borrow co_names->ob_refcnt as call counter
          // Generally it will not increased  by Python Interpreter
          PyObject *refcalls = f_code->co_names;
          refcalls->ob_refcnt ++;
  
          // Restore byte code if it's obfuscated
          if (IS_OBFUSCATED(f_code->co_flags)) {
              restore_byte_code(f_code->co_code);
              clear_obfuscated_flag(f_code);
          }
  
          Py_RETURN_NONE;
      }

• __armor_exit__ is called so long as code object completed execution, it will obfuscate byte-code again

      static PyObject *
      __armor_exit__(PyObject *self, PyObject *args)
      {
          // Got code object
          PyFrameObject *frame = PyEval_GetFrame();
          PyCodeObject *f_code = frame->f_code;
  
          // Decrease refcalls of this code object
          PyObject *refcalls = f_code->co_names;
          refcalls->ob_refcnt --;
  
          // Obfuscate byte code only if this code object isn't used by any function
          // In multi-threads or recursive call, one code object may be referenced
          // by many functions at the same time
          if (refcalls->ob_refcnt == 1) {
              obfuscate_byte_code(f_code->co_code);
              set_obfuscated_flag(f_code);
          }
  
          // Clear f_locals in this frame
          clear_frame_locals(frame);
  
          Py_RETURN_NONE;
      }

Usage

Install

    pip install pyarmor

Obfuscate Scripts

    cd /path/to/pyarmor
    python pyarmor.py obfuscate --src=examples/simple --entry=queens.py

Run Obfuscated Scripts

    cd dist
    python queens.py

Bind obfuscated scripts to fixed machine and expire it on some day. By default the obfuscated scripts can run in any machine and never expired, this behavior can be changed by replacing runtime file dist/license.lic

    cd /path/to/pyarmor
    python pyarmor.py licenses --expired "2018-12-31" --bind-mac "70:f1:a1:23:f0:94" Jondy
    cp licenses/Jondy/license.lic dist/

    cd dist
    python queens.py

Support Platforms

• Python 2.5, 2.6, 2.7 and Python3
• win32, win_amd64, linux_i386, linux_x86_64, macosx_intel
• Embedded Platform: Raspberry Pi, Banana Pi, TS-4600 / TS-7600

Besides, pyarmor works well with py2exe and PyInstaller. Here are some examples.

Other Links

• Homepage

• Source Code

• pypi

• User Guide

CategoryDistutilsCookbook