300 lines
9.9 KiB
Python
300 lines
9.9 KiB
Python
# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from __future__ import absolute_import, division, print_function
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from cryptography import utils
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from cryptography.exceptions import (
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InvalidSignature, UnsupportedAlgorithm, _Reasons
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)
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from cryptography.hazmat.backends.openssl.utils import _truncate_digest
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from cryptography.hazmat.primitives import hashes, serialization
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from cryptography.hazmat.primitives.asymmetric import (
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AsymmetricSignatureContext, AsymmetricVerificationContext, ec
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)
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def _truncate_digest_for_ecdsa(ec_key_cdata, digest, backend):
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"""
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This function truncates digests that are longer than a given elliptic
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curve key's length so they can be signed. Since elliptic curve keys are
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much shorter than RSA keys many digests (e.g. SHA-512) may require
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truncation.
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"""
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_lib = backend._lib
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_ffi = backend._ffi
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group = _lib.EC_KEY_get0_group(ec_key_cdata)
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with backend._tmp_bn_ctx() as bn_ctx:
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order = _lib.BN_CTX_get(bn_ctx)
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backend.openssl_assert(order != _ffi.NULL)
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res = _lib.EC_GROUP_get_order(group, order, bn_ctx)
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backend.openssl_assert(res == 1)
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order_bits = _lib.BN_num_bits(order)
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return _truncate_digest(digest, order_bits)
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def _ec_key_curve_sn(backend, ec_key):
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group = backend._lib.EC_KEY_get0_group(ec_key)
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backend.openssl_assert(group != backend._ffi.NULL)
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nid = backend._lib.EC_GROUP_get_curve_name(group)
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# The following check is to find EC keys with unnamed curves and raise
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# an error for now.
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if nid == backend._lib.NID_undef:
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raise NotImplementedError(
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"ECDSA certificates with unnamed curves are unsupported "
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"at this time"
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)
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curve_name = backend._lib.OBJ_nid2sn(nid)
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backend.openssl_assert(curve_name != backend._ffi.NULL)
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sn = backend._ffi.string(curve_name).decode('ascii')
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return sn
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def _mark_asn1_named_ec_curve(backend, ec_cdata):
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"""
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Set the named curve flag on the EC_KEY. This causes OpenSSL to
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serialize EC keys along with their curve OID which makes
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deserialization easier.
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"""
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backend._lib.EC_KEY_set_asn1_flag(
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ec_cdata, backend._lib.OPENSSL_EC_NAMED_CURVE
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)
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def _sn_to_elliptic_curve(backend, sn):
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try:
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return ec._CURVE_TYPES[sn]()
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except KeyError:
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raise UnsupportedAlgorithm(
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"{0} is not a supported elliptic curve".format(sn),
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_Reasons.UNSUPPORTED_ELLIPTIC_CURVE
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)
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@utils.register_interface(AsymmetricSignatureContext)
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class _ECDSASignatureContext(object):
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def __init__(self, backend, private_key, algorithm):
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self._backend = backend
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self._private_key = private_key
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self._digest = hashes.Hash(algorithm, backend)
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def update(self, data):
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self._digest.update(data)
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def finalize(self):
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ec_key = self._private_key._ec_key
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digest = self._digest.finalize()
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digest = _truncate_digest_for_ecdsa(ec_key, digest, self._backend)
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max_size = self._backend._lib.ECDSA_size(ec_key)
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self._backend.openssl_assert(max_size > 0)
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sigbuf = self._backend._ffi.new("char[]", max_size)
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siglen_ptr = self._backend._ffi.new("unsigned int[]", 1)
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res = self._backend._lib.ECDSA_sign(
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0,
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digest,
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len(digest),
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sigbuf,
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siglen_ptr,
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ec_key
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)
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self._backend.openssl_assert(res == 1)
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return self._backend._ffi.buffer(sigbuf)[:siglen_ptr[0]]
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@utils.register_interface(AsymmetricVerificationContext)
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class _ECDSAVerificationContext(object):
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def __init__(self, backend, public_key, signature, algorithm):
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self._backend = backend
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self._public_key = public_key
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self._signature = signature
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self._digest = hashes.Hash(algorithm, backend)
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def update(self, data):
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self._digest.update(data)
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def verify(self):
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ec_key = self._public_key._ec_key
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digest = self._digest.finalize()
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digest = _truncate_digest_for_ecdsa(ec_key, digest, self._backend)
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res = self._backend._lib.ECDSA_verify(
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0,
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digest,
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len(digest),
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self._signature,
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len(self._signature),
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ec_key
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)
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if res != 1:
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self._backend._consume_errors()
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raise InvalidSignature
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return True
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@utils.register_interface(ec.EllipticCurvePrivateKeyWithSerialization)
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class _EllipticCurvePrivateKey(object):
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def __init__(self, backend, ec_key_cdata, evp_pkey):
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self._backend = backend
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_mark_asn1_named_ec_curve(backend, ec_key_cdata)
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self._ec_key = ec_key_cdata
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self._evp_pkey = evp_pkey
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sn = _ec_key_curve_sn(backend, ec_key_cdata)
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self._curve = _sn_to_elliptic_curve(backend, sn)
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curve = utils.read_only_property("_curve")
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def signer(self, signature_algorithm):
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if isinstance(signature_algorithm, ec.ECDSA):
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return _ECDSASignatureContext(
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self._backend, self, signature_algorithm.algorithm
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)
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else:
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raise UnsupportedAlgorithm(
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"Unsupported elliptic curve signature algorithm.",
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_Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM)
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def exchange(self, algorithm, peer_public_key):
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if not (
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self._backend.elliptic_curve_exchange_algorithm_supported(
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algorithm, self.curve
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)
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):
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raise UnsupportedAlgorithm(
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"This backend does not support the ECDH algorithm.",
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_Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM
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)
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group = self._backend._lib.EC_KEY_get0_group(self._ec_key)
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z_len = (self._backend._lib.EC_GROUP_get_degree(group) + 7) // 8
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self._backend.openssl_assert(z_len > 0)
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z_buf = self._backend._ffi.new("uint8_t[]", z_len)
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peer_key = self._backend._lib.EC_KEY_get0_public_key(
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peer_public_key._ec_key
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)
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r = self._backend._lib.ECDH_compute_key(
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z_buf, z_len, peer_key, self._ec_key, self._backend._ffi.NULL
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)
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self._backend.openssl_assert(r > 0)
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return self._backend._ffi.buffer(z_buf)[:z_len]
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def public_key(self):
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group = self._backend._lib.EC_KEY_get0_group(self._ec_key)
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self._backend.openssl_assert(group != self._backend._ffi.NULL)
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curve_nid = self._backend._lib.EC_GROUP_get_curve_name(group)
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public_ec_key = self._backend._lib.EC_KEY_new_by_curve_name(curve_nid)
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self._backend.openssl_assert(public_ec_key != self._backend._ffi.NULL)
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public_ec_key = self._backend._ffi.gc(
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public_ec_key, self._backend._lib.EC_KEY_free
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)
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point = self._backend._lib.EC_KEY_get0_public_key(self._ec_key)
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self._backend.openssl_assert(point != self._backend._ffi.NULL)
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res = self._backend._lib.EC_KEY_set_public_key(public_ec_key, point)
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self._backend.openssl_assert(res == 1)
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evp_pkey = self._backend._ec_cdata_to_evp_pkey(public_ec_key)
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return _EllipticCurvePublicKey(self._backend, public_ec_key, evp_pkey)
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def private_numbers(self):
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bn = self._backend._lib.EC_KEY_get0_private_key(self._ec_key)
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private_value = self._backend._bn_to_int(bn)
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return ec.EllipticCurvePrivateNumbers(
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private_value=private_value,
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public_numbers=self.public_key().public_numbers()
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)
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def private_bytes(self, encoding, format, encryption_algorithm):
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return self._backend._private_key_bytes(
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encoding,
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format,
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encryption_algorithm,
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self._evp_pkey,
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self._ec_key
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)
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@utils.register_interface(ec.EllipticCurvePublicKeyWithSerialization)
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class _EllipticCurvePublicKey(object):
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def __init__(self, backend, ec_key_cdata, evp_pkey):
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self._backend = backend
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_mark_asn1_named_ec_curve(backend, ec_key_cdata)
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self._ec_key = ec_key_cdata
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self._evp_pkey = evp_pkey
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sn = _ec_key_curve_sn(backend, ec_key_cdata)
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self._curve = _sn_to_elliptic_curve(backend, sn)
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curve = utils.read_only_property("_curve")
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def verifier(self, signature, signature_algorithm):
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if not isinstance(signature, bytes):
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raise TypeError("signature must be bytes.")
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if isinstance(signature_algorithm, ec.ECDSA):
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return _ECDSAVerificationContext(
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self._backend, self, signature, signature_algorithm.algorithm
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)
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else:
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raise UnsupportedAlgorithm(
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"Unsupported elliptic curve signature algorithm.",
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_Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM)
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def public_numbers(self):
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set_func, get_func, group = (
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self._backend._ec_key_determine_group_get_set_funcs(self._ec_key)
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)
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point = self._backend._lib.EC_KEY_get0_public_key(self._ec_key)
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self._backend.openssl_assert(point != self._backend._ffi.NULL)
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with self._backend._tmp_bn_ctx() as bn_ctx:
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bn_x = self._backend._lib.BN_CTX_get(bn_ctx)
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bn_y = self._backend._lib.BN_CTX_get(bn_ctx)
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res = get_func(group, point, bn_x, bn_y, bn_ctx)
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self._backend.openssl_assert(res == 1)
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x = self._backend._bn_to_int(bn_x)
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y = self._backend._bn_to_int(bn_y)
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return ec.EllipticCurvePublicNumbers(
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x=x,
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y=y,
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curve=self._curve
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)
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def public_bytes(self, encoding, format):
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if format is serialization.PublicFormat.PKCS1:
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raise ValueError(
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"EC public keys do not support PKCS1 serialization"
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)
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return self._backend._public_key_bytes(
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encoding,
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format,
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self._evp_pkey,
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None
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)
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