pysodium

[kentbull]

Package Details

This is a very simple wrapper around libsodium (written in C) masquerading as nacl.

Github: stef/pysodium
PyPi: pysodium

Important consideration:

Pysodium uses the system library installed to /usr/local/lib/libsodium.dylib, typically linked to /usr/local/lib/libsodium.23.dylib.

In order to pass MacOS Gatekeeper checks the libsodium.23.dylib file must be signed by the same Apple Account that signs all of the *.so files for a Flet build.

The request here is to include Pysodium as a statically linked binary, or if that is not possible, some standard way to tell Pysodium in a Flet app where the signed libsodium.23.dylib library file is.

Relevant issues and discussions

See this Flutter issue and this Flet issue discussing packaging that includes links to native libraries like this.

[kentbull]

I was able to get a workaround functional for pysodium by modifying the DYLD_LIBRARY_PATH and LD_LIBRARY_PATH variables as well as symlinking to the correct binary in a libsodium library directory in my repository.

This works because the entire app repo is copied to the app cache directory of ~/Library/Caches/myapp/app/ when running the app from the .dmg I build after making flet build macos.

Here's sample code of what I had to do to get pysodium to load my libsodium dynamic library from the libsodium/ directory in my repository.

################################# Custom Libsodium Loader ############################################
# This code has to be in the main module to avoid a partially initialized module error
# for the main app module.


def load_custom_libsodium(appdir):
    """
    Instruct the pysodium library to load a custom libsodium dylib from the appdir/libsodium
    """
    set_load_path_or_link(appdir)
    set_load_env_vars(appdir)

    custom_path = os.path.expanduser(f'{os.path.dirname(os.path.abspath(__file__))}/libsodium/libsodium.dylib')
    logger.info(f'Loading custom libsodium from {custom_path}')
    if os.path.exists(custom_path):
        logger.info(f'Found custom libsodium at {custom_path}')
        sodium = ctypes.cdll.LoadLibrary(custom_path)
    else:
        logger.info('Custom libsodium not found, loading from system')
        libsodium_path = find_library('sodium')
        if libsodium_path is not None:
            logger.info(f'Found libsodium at {libsodium_path}')
            sodium = ctypes.cdll.LoadLibrary(libsodium_path)
            logger.info(f'Loaded libsodium from {libsodium_path}')
        else:
            raise OSError('libsodium not found')


def set_load_path_or_link(appdir):
    """
    Symlinks the correct libsodium dylib based on the architecture of the system.
    """
    lib_home = f'{appdir}/libsodium'
    arch = platform.processor()

    if platform.system() == 'Windows':
        match arch:
            case 'x86' | 'i386' | 'i486' | 'i586' | 'i686':
                sodium_lib = 'libsodium.26.x32.dll'
            case 'AMD64' | 'x86_64':
                sodium_lib = 'libsodium.26.x64.dll'
            case _:
                raise OSError(f'Unsupported Windows architecture: {arch}')
    elif platform.system() == 'Darwin':
        match platform.processor():
            case 'x86_64':
                sodium_lib = 'libsodium.26.x86_64.dylib'
            case 'arm' | 'arm64' | 'aarch64':
                sodium_lib = 'libsodium.23.arm.dylib'
            # doesn't work
            case 'i386':
                sodium_lib = 'libsodium.23.i386.dylib'
            case _:
                raise OSError(f'Unsupported architecture: {platform.processor()}')
    else:
        # Linux and other Unix-like systems
        sodium_lib = 'libsodium.so.23'  # not yet supported
        raise OSError(f'Unsupported architecture: {platform.processor()}')

    lib_path = Path(os.path.join(lib_home, sodium_lib))

    logger.info(f'Arch: {platform.processor()} Linking libsodium lib: {sodium_lib} at path: {lib_path}')

    if platform.system() == 'Windows':  # if windows just set the PATH
        logger.info(f'Setting PATH to include {lib_path}')
        os.environ['PATH'] = f'{lib_path};{os.environ["PATH"]}'
    elif platform.system() == 'Darwin':  # if macOS, symlink the dylib
        if not lib_path.exists():
            logger.error(f'libsodium for architecture {platform.processor()} missing at {lib_path}, cannot link')
            raise FileNotFoundError(f'libsodium for architecture {platform.processor()} missing at {lib_path}')

        link_path = Path(os.path.join(lib_home, 'libsodium.dylib'))
        logger.info(f'Symlinking {lib_path} to {link_path}')
        try:
            os.symlink(f'{lib_path}', f'{link_path}')
        except FileExistsError:
            os.remove(f'{link_path}')
            os.symlink(f'{lib_path}', f'{link_path}')
        logger.info(f'Linked libsodium dylib: {link_path}')


def set_load_env_vars(appdir):
    """
    Sets the DYLD_LIBRARY_PATH and LD_LIBRARY_PATH that pysodium uses to find libsodium to the custom libsodium dylib.
    """
    if platform.system() == 'Windows':
        return  # Windows doesn't need this

    local_path = appdir

    logger.info(f'Setting DYLD_LIBRARY_PATH to {local_path}/libsodium')
    os.environ['DYLD_LIBRARY_PATH'] = f'{local_path}/libsodium'

    logger.info(f'Setting LD_LIBRARY_PATH to {local_path}/libsodium')
    os.environ['LD_LIBRARY_PATH'] = f'{local_path}/libsodium'


################################### End Custom Libsodium Loader ######################################

This is just for MacOS machines. I haven't tested the Windows support yet.

Static linking would completely remove the need to do this dynamic module loading.

[FeodorFitsner]

Thanks for sharing the solution! (I will add more comments in the similar issue).
Closing this one as this is a category for binary iOS and Android packages.

[kentbull]

Sounds reasonable to me.