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""" _curves.py
specify some additional curves that OpenSSL provides but cryptography doesn't explicitly expose
"""
from cryptography import utils
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.bindings.openssl.binding import Binding
__all__ = tuple()
# TODO: investigate defining additional curves using EC_GROUP_new_curve
# https://wiki.openssl.org/index.php/Elliptic_Curve_Cryptography#Defining_Curves
def _openssl_get_supported_curves():
if hasattr(_openssl_get_supported_curves, '_curves'):
return _openssl_get_supported_curves._curves
# use cryptography's cffi bindings to get an array of curve names
b = Binding()
cn = b.lib.EC_get_builtin_curves(b.ffi.NULL, 0)
cs = b.ffi.new('EC_builtin_curve[]', cn)
b.lib.EC_get_builtin_curves(cs, cn)
# store the result so we don't have to do all of this every time
curves = { b.ffi.string(b.lib.OBJ_nid2sn(c.nid)).decode('utf-8') for c in cs }
# Ed25519 and X25519 are always present in cryptography>=2.6
# The python cryptography lib provides a different interface for these curves,
# so they are handled differently in the ECDHPriv/Pub and EdDSAPriv/Pub classes
curves |= {'X25519', 'ed25519'}
_openssl_get_supported_curves._curves = curves
return curves
def use_legacy_cryptography_decorator():
"""
The decorator utils.register_interface was removed in version 38.0.0. Keep using it
if the decorator exists, inherit from `ec.EllipticCurve` otherwise.
"""
return hasattr(utils, "register_interface") and callable(utils.register_interface)
if use_legacy_cryptography_decorator():
@utils.register_interface(ec.EllipticCurve)
class BrainpoolP256R1(object):
name = 'brainpoolP256r1'
key_size = 256
@utils.register_interface(ec.EllipticCurve) # noqa: E303
class BrainpoolP384R1(object):
name = 'brainpoolP384r1'
key_size = 384
@utils.register_interface(ec.EllipticCurve) # noqa: E303
class BrainpoolP512R1(object):
name = 'brainpoolP512r1'
key_size = 512
@utils.register_interface(ec.EllipticCurve) # noqa: E303
class X25519(object):
name = 'X25519'
key_size = 256
@utils.register_interface(ec.EllipticCurve) # noqa: E303
class Ed25519(object):
name = 'ed25519'
key_size = 256
else:
class BrainpoolP256R1(ec.EllipticCurve):
name = 'brainpoolP256r1'
key_size = 256
class BrainpoolP384R1(ec.EllipticCurve): # noqa: E303
name = 'brainpoolP384r1'
key_size = 384
class BrainpoolP512R1(ec.EllipticCurve): # noqa: E303
name = 'brainpoolP512r1'
key_size = 512
class X25519(ec.EllipticCurve): # noqa: E303
name = 'X25519'
key_size = 256
class Ed25519(ec.EllipticCurve): # noqa: E303
name = 'ed25519'
key_size = 256
# add these curves to the _CURVE_TYPES list
for curve in [BrainpoolP256R1, BrainpoolP384R1, BrainpoolP512R1, X25519, Ed25519]:
if curve.name not in ec._CURVE_TYPES and curve.name in _openssl_get_supported_curves():
ec._CURVE_TYPES[curve.name] = curve
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