How PyArmor Does It

Look at what happened after is obfuscated by PyArmor. Here are the files list in the output path dist:

pytransform/, or _pytransform.dll in Windows, _pytransform.dylib in MacOS

dist/ is obfuscated script, the content is:

from pytransform import pyarmor_runtime
__pyarmor__(__name__, __file__, b'\x06\x0f...')

There is an extra folder pytransform called Runtime Package, which are the only required to run or import obfuscated scripts. So long as this package is in any Python Path, the obfuscated script dist/ can be used as normal Python script. That is to say:

The original python scripts can be replaced with obfuscated scripts seamlessly.

How to Obfuscate Python Scripts

How to obfuscate python scripts by PyArmor?

First compile python script to code object:

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

Then change code object as the following way

  • 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
            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
  • Append function names __armor_enter, __armor_exit__ to co_consts

  • Increase co_stacksize by 2

  • Set CO_OBFUSCAED (0x80000000) flag in co_flags

  • Change all code objects in the co_consts recursively

Next serializing reformed code object and 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/", buf );

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

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

How to Deal With Plugins

In PyArmor, the plugin is used to inject python code into the obfuscted script before the script is obfuscated, thus the plugin code could be executed when the obfuscated script is running. For example, use a plugin to check internet time:

pyarmor obfuscate --plugin check_ntp_time

Why not insert the plugin code into the script directly? Because most of them must be called in the obufscated scripts. For example, get the license information of the obfuscated scripts.

Each plugin is a normal Python script, PyArmor searches it by this way:

  • If the plugin has absolute path, then find the corresponding .py file exactly.
  • If it has relative path, search the .py file in:
    • The current path
    • $HOME/.pyarmor/plugins
    • {pyarmor_folder}/plugins
  • Raise exception if not found

When there is plugin specified as obfuscating the script, each comment line will be scanned to find any plugin marker. There are 3 types of plugin marker:

  • Plugin Definition Marker
  • Plugin Inline Marker
  • Plugin Call Marker

The Plugin Definition Marker looks like this:

# {PyArmor Plugins}

Generally there is only one in a script, all the plugins will be injected here. It must be one leading comment line, no indentation. If there is no plugin definition marker, none of plugins will be injected.

The others are mainly used to call the function defined in the plugin scripts. There are 3 forms, any comment line with this prefix will be as a plugin marker:

# PyArmor Plugin:
# pyarmor_
# @pyarmor_

They could appear many times, in any indentation, generally should be behind plugin definition marker.

The first form called Plugin Inline Marker, PyArmor just removes this pattern and one following whitespace exactly, and leave the rest part as it is. For example, these are inline markers in the script

# PyArmor Plugin: check_ntp_time()
# PyArmor Plugin: print('This is plugin code')
# PyArmor Plugin: if sys.flags.debug:
# PyArmor Plugin:     check_something():

In the dist/, they’ll be replaced as:

print('This is plugin code')
if sys.flags.debug:

So long as there is any plugin specified in the command line, these replacements will be taken place. If there is no external plugin script, use special plugin name on in the command line. For example:

pyarmor obfuscate --plugin on

The second form called Plugin Call Marker, it’s only used to call function deinfed in the plugin script. Besides, if this function name is not specified as plugin name, PyArmor doesn’t touch this marker. For example, obufscate the script by this command:

pyarmor obfuscate --plugin check_ntp_time

In the, only the first marker will be handled, the second marker will be kept as it is, because there is no plugin name specified in the command line as the function name check_multi_mac:

# pyarmor_check_ntp_time()
# pyarmor_check_multi_mac()


# pyarmor_check_multi_mac()

The last form # @pyarmor_ is almost same as the second, but the comment prefix will be replaced with @, it’s mainly used to inject a decorator. For example:

# @pyarmor_assert_obfuscated(foo.connect)
def login(user, name):
    foo.connect(user, name)


def login(user, name):
    foo.connect(user, name)

If the plugin name have a leading @, it will be injected into the script only when it’s used in the script, otherwise it’s ignored. For example:

pyarmor obfuscate --plugin @check_ntp_time

The script must call plugin function check_ntp_time by one of Plugin Call Marker. For example:

# pyarmor_check_ntp_time()

The Plugin Inline Marker doesn’t work. For example:

# PyArmor Plugin: check_ntp_time()

Even this marker will be replaced with check_ntp_time(), but the plugin script will not be injected into the obfuscated script. When it runs, it will complain of no function check_ntp_name found.

Special Handling of Entry Script

There are 2 extra changes for entry script:

  • Before obfuscating, insert protection code to entry script.
  • After obfuscated, insert bootstrap code to obfuscated script.

Before obfuscating entry scipt, PyArmor will search the content line by line. If there is line like this:

# {PyArmor Protection Code}

PyArmor will replace this line with protection code.

If there is line like this:

# {No PyArmor Protection Code}

PyArmor will not patch this script.

If both of lines aren’t found, insert protection code before the line:

if __name__ == '__main__'

Do nothing if no __main__ line found.

Here it’s the default template of protection code:

def protect_pytransform():

    import pytransform

    def check_obfuscated_script():
        CO_SIZES = 49, 46, 38, 36
        CO_NAMES = set(['pytransform', 'pyarmor_runtime', '__pyarmor__',
                        '__name__', '__file__'])
        co = pytransform.sys._getframe(3).f_code
        if not ((set(co.co_names) <= CO_NAMES)
                and (len(co.co_code) in CO_SIZES)):
            raise RuntimeError('Unexpected obfuscated script')

    def check_mod_pytransform():
        def _check_co_key(co, v):
            return (len(co.co_names), len(co.co_consts), len(co.co_code)) == v
        for k, (v1, v2, v3) in {keylist}:
            co = getattr(pytransform, k).{code}
            if not _check_co_key(co, v1):
                raise RuntimeError('unexpected')
            if v2:
                if not _check_co_key(co.co_consts[1], v2):
                    raise RuntimeError('unexpected')
            if v3:
                if not _check_co_key(co.{closure}[0].cell_contents.{code}, v3):
                    raise RuntimeError('unexpected')

    def check_lib_pytransform():
        filename = pytransform.os.path.join({rpath}, {filename})
        size = {size}
        n = size >> 2
        with open(filename, 'rb') as f:
            buf =
        fmt = 'I' * n
        checksum = sum(pytransform.struct.unpack(fmt, buf)) & 0xFFFFFFFF
        if not checksum == {checksum}:
            raise RuntimeError("Unexpected %s" % filename)
    except Exception as e:
        print("Protection Fault: %s" % e)


All the string template {xxx} will be replaced with real value by PyArmor.

To prevent PyArmor from inserting this protection code, pass --no-cross-protection as obfuscating the scripts:

pyarmor obfuscate --no-cross-protection

After the entry script is obfuscated, the Bootstrap Code will be inserted at the beginning of the obfuscated script.

How to Run Obfuscated Script

How to run obfuscated script dist/ by Python Interpreter?

The first 2 lines, which called Bootstrap Code:

from pytransform import pyarmor_runtime

It will fulfil the following tasks

  • Load dynamic library _pytransform by ctypes
  • Check license.lic is valid or not
  • Add 3 cfunctions to module builtins: __pyarmor__, __armor_enter__, __armor_exit__

The next code line in dist/ is:

__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 interpreter

  • __armor_enter__ is called as soon as 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)) {
  • __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) {
        // Clear f_locals in this frame

How To Pack Obfuscated Scripts

The obfuscated scripts generated by PyArmor can replace Python scripts seamlessly, but there is an issue when packing them into one bundle by PyInstaller:

All the dependencies of obfuscated scripts CAN NOT be found at all

To solve this problem, the common solution is

  1. Find all the dependencies by original scripts.
  2. Add runtimes files required by obfuscated scripts to the bundle
  3. Replace original scripts with obfuscated in the bundle
  4. Replace entry script with obfuscated one

PyArmor provides command pack to achieve this. But in some cases maybe it doesn’t work. This document describes what the command pack does, and also could be as a guide to bundle the obfuscated scripts by yourself.

First install pyinstaller:

pip install pyinstaller

Then obfuscate scripts to dist/obf:

pyarmor obfuscate --output dist/obf --package-runtime 0

Next generate specfile, add runtime files required by obfuscated scripts:

pyi-makespec --add-data dist/obf/license.lic:. \
             --add-data dist/obf/pytransform.key:. \
             --add-data dist/obf/_pytransform.*:. \
             -p dist/obf --hidden-import pytransform \

If the scripts are obfuscated by super mode, generate specfile by this command:

pyi-makespec -p dist/obf --hidden-import pytransform
In windows, the : should be replace with ; in the command line.

And patch specfile hello.spec, insert the following lines after the Analysis object. The purpose is to replace all the original scripts with obfuscated ones:

src = os.path.abspath('.')
obf_src = os.path.abspath('dist/obf')

for i in range(len(a.scripts)):
    if a.scripts[i][1].startswith(src):
        x = a.scripts[i][1].replace(src, obf_src)
        if os.path.exists(x):
            a.scripts[i] = a.scripts[i][0], x, a.scripts[i][2]

for i in range(len(a.pure)):
    if a.pure[i][1].startswith(src):
        x = a.pure[i][1].replace(src, obf_src)
        if os.path.exists(x):
            if hasattr(a.pure, '_code_cache'):
                with open(x) as f:
                    a.pure._code_cache[a.pure[i][0]] = compile(, a.pure[i][1], 'exec')
            a.pure[i] = a.pure[i][0], x, a.pure[i][2]

Run patched specfile to build final distribution:

pyinstaller --clean -y hello.spec


Option --clean is required, otherwise the obfuscated scripts will not be replaced because the cached .pyz will be used.

Check obfuscated scripts work:

# It works

rm dist/hello/license.lic

# It should not work