# vim: sts=4 sw=4 et
"""
M2Crypto wrapper for OpenSSL ENGINE API.

Pavel Shramov
IMEC MSU
"""

from M2Crypto import m2, EVP, X509, Err

class EngineError(Exception): pass

m2.engine_init_error(EngineError)

class Engine:
    """Wrapper for ENGINE object."""

    m2_engine_free = m2.engine_free
    
    def __init__(self, id = None, _ptr = None, _pyfree = 1):
        """Create new Engine from ENGINE pointer or obtain by id"""
        if not _ptr and not id:
            raise ValueError("No engine id specified")
        self._ptr = _ptr
        if not self._ptr:
            self._ptr = m2.engine_by_id(id)
            if not self._ptr:
                raise ValueError("Unknown engine: %s" % id)
        self._pyfree = _pyfree

    def __del__(self):
        if getattr(self, '_pyfree', 0):
            self.m2_engine_free(self._ptr)

    def init(self):
        """Obtain a functional reference to the engine.
        
        @return: 0 on error, non-zero on success."""
        return m2.engine_init(self._ptr)
        
    def finish(self):
        """Release a functional and structural reference to the engine."""
        return m2.engine_finish(self._ptr)

    def ctrl_cmd_string(self, cmd, arg, optional = 0):
        """Call ENGINE_ctrl_cmd_string"""
        if not m2.engine_ctrl_cmd_string(self._ptr, cmd, arg, optional):
            raise EngineError(Err.get_error())

    def get_name(self):
        """Return engine name"""
        return m2.engine_get_name(self._ptr)

    def get_id(self):
        """Return engine id"""
        return m2.engine_get_id(self._ptr)

    def set_default(self, methods = m2.ENGINE_METHOD_ALL):
        """Use this engine as default for methods specified in argument
        Possible values are bitwise OR of m2.ENGINE_METHOD_*"""
        return m2.engine_set_default(self._ptr, methods)

    def _engine_load_key(self, func, name, pin = None):
        """Helper function for loading keys"""
        ui = m2.ui_openssl()
        cbd = m2.engine_pkcs11_data_new(pin)
        try:
            kptr = func(self._ptr, name, ui, cbd)
            if not kptr:
                raise EngineError(Err.get_error())
            key = EVP.PKey(kptr, _pyfree = 1)
        finally:
            m2.engine_pkcs11_data_free(cbd)
        return key

    def load_private_key(self, name, pin = None):
        """Load private key with engine methods (e.g from smartcard).
            If pin is not set it will be asked
        """
        return self._engine_load_key(m2.engine_load_private_key, name, pin)

    def load_public_key(self, name, pin = None):
        """Load public key with engine methods (e.g from smartcard)."""
        return self._engine_load_key(m2.engine_load_public_key, name, pin)

    def load_certificate(self, name):
        """Load certificate from engine (e.g from smartcard).
        NOTE: This function may be not implemented by engine!"""
        cptr = m2.engine_load_certificate(self._ptr, name)
        if not cptr:
            raise EngineError("Certificate or card not found")
        return X509.X509(cptr, _pyfree = 1)


def load_dynamic_engine(id, sopath):
    """Load and return dymanic engine from sopath and assign id to it"""
    m2.engine_load_dynamic()
    e = Engine('dynamic')
    e.ctrl_cmd_string("SO_PATH", sopath)
    e.ctrl_cmd_string("ID", id)
    e.ctrl_cmd_string("LIST_ADD", "1")
    e.ctrl_cmd_string("LOAD", None)
    return e


def load_dynamic():
    """Load dynamic engine"""
    m2.engine_load_dynamic()


def load_openssl():
    """Load openssl engine"""
    m2.engine_load_openssl()


def cleanup():
    """If you load any engines, you need to clean up after your application
    is finished with the engines."""
    m2.engine_cleanup()
