"""M2Crypto wrapper for OpenSSL DH API.

Copyright (c) 1999-2003 Ng Pheng Siong. All rights reserved."""

from util import genparam_callback

import BIO, Err, m2

class DHError(Exception): pass

m2.dh_init(DHError)

class DH:

"""

Object interface to the Diffie-Hellman key exchange

protocol.

"""

m2_dh_free = m2.dh_free

def __init__(self, dh, _pyfree=0):

assert m2.dh_type_check(dh)

self.dh = dh

self._pyfree = _pyfree

def __del__(self):

if getattr(self, '_pyfree', 0):

self.m2_dh_free(self.dh)

def __len__(self):

assert m2.dh_type_check(self.dh), "'dh' type error"

return m2.dh_size(self.dh)

def __getattr__(self, name):

if name in ('p', 'g', 'pub', 'priv'):

method = getattr(m2, 'dh_get_%s' % (name,))

assert m2.dh_type_check(self.dh), "'dh' type error"

return method(self.dh)

else:

raise AttributeError

def __setattr__(self, name, value):

if name in ('p', 'g'):

raise DHError, 'set (p, g) via set_params()'

elif name in ('pub','priv'):

raise DHError, 'generate (pub, priv) via gen_key()'

else:

self.__dict__[name] = value

def _ptr(self):

return self.dh

def check_params(self):

assert m2.dh_type_check(self.dh), "'dh' type error"

return m2.dh_check(self.dh)

def gen_key(self):

assert m2.dh_type_check(self.dh), "'dh' type error"

m2.dh_generate_key(self.dh)

def compute_key(self, pubkey):

assert m2.dh_type_check(self.dh), "'dh' type error"

return m2.dh_compute_key(self.dh, pubkey)

def print_params(self, bio):

assert m2.dh_type_check(self.dh), "'dh' type error"

return m2.dhparams_print(bio._ptr(), self.dh)

def gen_params(plen, g, callback=genparam_callback):

return DH(m2.dh_generate_parameters(plen, g, callback), 1)

def load_params(file):

bio = BIO.openfile(file)

return load_params_bio(bio)

def load_params_bio(bio):

return DH(m2.dh_read_parameters(bio._ptr()), 1)

def set_params(p, g):

dh = m2.dh_new()

m2.dh_set_p(dh, p)

m2.dh_set_g(dh, g)

return DH(dh, 1)

#def free_params(cptr):

# m2.dh_free(cptr)

DH_GENERATOR_2 = m2.DH_GENERATOR_2

DH_GENERATOR_5 = m2.DH_GENERATOR_5