504 lines
20 KiB
Python
504 lines
20 KiB
Python
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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"""
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src/pyelliptic/ecc.py
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=====================
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"""
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# pylint: disable=protected-access
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# Copyright (C) 2011 Yann GUIBET <yannguibet@gmail.com>
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# See LICENSE for details.
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from hashlib import sha512
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from struct import pack, unpack
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from pyelliptic.cipher import Cipher
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from pyelliptic.hash import equals, hmac_sha256
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from pyelliptic.openssl import OpenSSL
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class ECC(object):
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"""
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Asymmetric encryption with Elliptic Curve Cryptography (ECC)
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ECDH, ECDSA and ECIES
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>>> import pyelliptic
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>>> alice = pyelliptic.ECC() # default curve: sect283r1
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>>> bob = pyelliptic.ECC(curve='sect571r1')
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>>> ciphertext = alice.encrypt("Hello Bob", bob.get_pubkey())
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>>> print bob.decrypt(ciphertext)
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>>> signature = bob.sign("Hello Alice")
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>>> # alice's job :
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>>> print pyelliptic.ECC(
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>>> pubkey=bob.get_pubkey()).verify(signature, "Hello Alice")
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>>> # ERROR !!!
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>>> try:
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>>> key = alice.get_ecdh_key(bob.get_pubkey())
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>>> except:
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>>> print("For ECDH key agreement, the keys must be defined on the same curve !")
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>>> alice = pyelliptic.ECC(curve='sect571r1')
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>>> print alice.get_ecdh_key(bob.get_pubkey()).encode('hex')
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>>> print bob.get_ecdh_key(alice.get_pubkey()).encode('hex')
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"""
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def __init__(
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self,
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pubkey=None,
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privkey=None,
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pubkey_x=None,
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pubkey_y=None,
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raw_privkey=None,
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curve='sect283r1',
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): # pylint: disable=too-many-arguments
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"""
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For a normal and High level use, specifie pubkey,
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privkey (if you need) and the curve
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"""
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if isinstance(curve, str):
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self.curve = OpenSSL.get_curve(curve)
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else:
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self.curve = curve
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if pubkey_x is not None and pubkey_y is not None:
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self._set_keys(pubkey_x, pubkey_y, raw_privkey)
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elif pubkey is not None:
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curve, pubkey_x, pubkey_y, _ = ECC._decode_pubkey(pubkey)
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if privkey is not None:
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curve2, raw_privkey, _ = ECC._decode_privkey(privkey)
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if curve != curve2:
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raise Exception("Bad ECC keys ...")
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self.curve = curve
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self._set_keys(pubkey_x, pubkey_y, raw_privkey)
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else:
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self.privkey, self.pubkey_x, self.pubkey_y = self._generate()
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def _set_keys(self, pubkey_x, pubkey_y, privkey):
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if self.raw_check_key(privkey, pubkey_x, pubkey_y) < 0:
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self.pubkey_x = None
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self.pubkey_y = None
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self.privkey = None
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raise Exception("Bad ECC keys ...")
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else:
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self.pubkey_x = pubkey_x
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self.pubkey_y = pubkey_y
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self.privkey = privkey
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@staticmethod
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def get_curves():
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"""
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static method, returns the list of all the curves available
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"""
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return OpenSSL.curves.keys()
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def get_curve(self):
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"""Encryption object from curve name"""
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return OpenSSL.get_curve_by_id(self.curve)
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def get_curve_id(self):
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"""Currently used curve"""
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return self.curve
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def get_pubkey(self):
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"""
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High level function which returns :
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curve(2) + len_of_pubkeyX(2) + pubkeyX + len_of_pubkeyY + pubkeyY
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"""
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return b''.join((
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pack('!H', self.curve),
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pack('!H', len(self.pubkey_x)),
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self.pubkey_x,
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pack('!H', len(self.pubkey_y)),
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self.pubkey_y,
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))
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def get_privkey(self):
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"""
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High level function which returns
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curve(2) + len_of_privkey(2) + privkey
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"""
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return b''.join((
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pack('!H', self.curve),
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pack('!H', len(self.privkey)),
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self.privkey,
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))
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@staticmethod
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def _decode_pubkey(pubkey):
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i = 0
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curve = unpack('!H', pubkey[i:i + 2])[0]
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i += 2
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tmplen = unpack('!H', pubkey[i:i + 2])[0]
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i += 2
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pubkey_x = pubkey[i:i + tmplen]
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i += tmplen
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tmplen = unpack('!H', pubkey[i:i + 2])[0]
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i += 2
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pubkey_y = pubkey[i:i + tmplen]
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i += tmplen
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return curve, pubkey_x, pubkey_y, i
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@staticmethod
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def _decode_privkey(privkey):
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i = 0
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curve = unpack('!H', privkey[i:i + 2])[0]
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i += 2
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tmplen = unpack('!H', privkey[i:i + 2])[0]
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i += 2
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privkey = privkey[i:i + tmplen]
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i += tmplen
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return curve, privkey, i
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def _generate(self):
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try:
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pub_key_x = OpenSSL.BN_new()
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pub_key_y = OpenSSL.BN_new()
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key = OpenSSL.EC_KEY_new_by_curve_name(self.curve)
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if key == 0:
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raise Exception("[OpenSSL] EC_KEY_new_by_curve_name FAIL ...")
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if (OpenSSL.EC_KEY_generate_key(key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_generate_key FAIL ...")
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if (OpenSSL.EC_KEY_check_key(key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_check_key FAIL ...")
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priv_key = OpenSSL.EC_KEY_get0_private_key(key)
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group = OpenSSL.EC_KEY_get0_group(key)
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pub_key = OpenSSL.EC_KEY_get0_public_key(key)
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if OpenSSL.EC_POINT_get_affine_coordinates_GFp(
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group, pub_key, pub_key_x, pub_key_y, 0) == 0:
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raise Exception("[OpenSSL] EC_POINT_get_affine_coordinates_GFp FAIL ...")
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privkey = OpenSSL.malloc(0, OpenSSL.BN_num_bytes(priv_key))
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pubkeyx = OpenSSL.malloc(0, OpenSSL.BN_num_bytes(pub_key_x))
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pubkeyy = OpenSSL.malloc(0, OpenSSL.BN_num_bytes(pub_key_y))
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OpenSSL.BN_bn2bin(priv_key, privkey)
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privkey = privkey.raw
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OpenSSL.BN_bn2bin(pub_key_x, pubkeyx)
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pubkeyx = pubkeyx.raw
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OpenSSL.BN_bn2bin(pub_key_y, pubkeyy)
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pubkeyy = pubkeyy.raw
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self.raw_check_key(privkey, pubkeyx, pubkeyy)
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return privkey, pubkeyx, pubkeyy
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finally:
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OpenSSL.EC_KEY_free(key)
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OpenSSL.BN_free(pub_key_x)
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OpenSSL.BN_free(pub_key_y)
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def get_ecdh_key(self, pubkey):
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"""
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High level function. Compute public key with the local private key
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and returns a 512bits shared key
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"""
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curve, pubkey_x, pubkey_y, _ = ECC._decode_pubkey(pubkey)
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if curve != self.curve:
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raise Exception("ECC keys must be from the same curve !")
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return sha512(self.raw_get_ecdh_key(pubkey_x, pubkey_y)).digest()
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def raw_get_ecdh_key(self, pubkey_x, pubkey_y):
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"""ECDH key as binary data"""
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try:
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ecdh_keybuffer = OpenSSL.malloc(0, 32)
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other_key = OpenSSL.EC_KEY_new_by_curve_name(self.curve)
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if other_key == 0:
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raise Exception("[OpenSSL] EC_KEY_new_by_curve_name FAIL ...")
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other_pub_key_x = OpenSSL.BN_bin2bn(pubkey_x, len(pubkey_x), 0)
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other_pub_key_y = OpenSSL.BN_bin2bn(pubkey_y, len(pubkey_y), 0)
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other_group = OpenSSL.EC_KEY_get0_group(other_key)
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other_pub_key = OpenSSL.EC_POINT_new(other_group)
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if (OpenSSL.EC_POINT_set_affine_coordinates_GFp(other_group,
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other_pub_key,
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other_pub_key_x,
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other_pub_key_y,
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0)) == 0:
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raise Exception(
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"[OpenSSL] EC_POINT_set_affine_coordinates_GFp FAIL ...")
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if (OpenSSL.EC_KEY_set_public_key(other_key, other_pub_key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_set_public_key FAIL ...")
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if (OpenSSL.EC_KEY_check_key(other_key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_check_key FAIL ...")
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own_key = OpenSSL.EC_KEY_new_by_curve_name(self.curve)
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if own_key == 0:
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raise Exception("[OpenSSL] EC_KEY_new_by_curve_name FAIL ...")
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own_priv_key = OpenSSL.BN_bin2bn(
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self.privkey, len(self.privkey), 0)
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if (OpenSSL.EC_KEY_set_private_key(own_key, own_priv_key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_set_private_key FAIL ...")
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if OpenSSL._hexversion > 0x10100000 and not OpenSSL._libreSSL:
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OpenSSL.EC_KEY_set_method(own_key, OpenSSL.EC_KEY_OpenSSL())
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else:
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OpenSSL.ECDH_set_method(own_key, OpenSSL.ECDH_OpenSSL())
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ecdh_keylen = OpenSSL.ECDH_compute_key(
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ecdh_keybuffer, 32, other_pub_key, own_key, 0)
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if ecdh_keylen != 32:
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raise Exception("[OpenSSL] ECDH keylen FAIL ...")
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return ecdh_keybuffer.raw
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finally:
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OpenSSL.EC_KEY_free(other_key)
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OpenSSL.BN_free(other_pub_key_x)
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OpenSSL.BN_free(other_pub_key_y)
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OpenSSL.EC_POINT_free(other_pub_key)
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OpenSSL.EC_KEY_free(own_key)
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OpenSSL.BN_free(own_priv_key)
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def check_key(self, privkey, pubkey):
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"""
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Check the public key and the private key.
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The private key is optional (replace by None)
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"""
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curve, pubkey_x, pubkey_y, _ = ECC._decode_pubkey(pubkey)
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if privkey is None:
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raw_privkey = None
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curve2 = curve
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else:
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curve2, raw_privkey, _ = ECC._decode_privkey(privkey)
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if curve != curve2:
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raise Exception("Bad public and private key")
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return self.raw_check_key(raw_privkey, pubkey_x, pubkey_y, curve)
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def raw_check_key(self, privkey, pubkey_x, pubkey_y, curve=None):
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"""Check key validity, key is supplied as binary data"""
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# pylint: disable=too-many-branches
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if curve is None:
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curve = self.curve
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elif isinstance(curve, str):
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curve = OpenSSL.get_curve(curve)
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else:
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curve = curve
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try:
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key = OpenSSL.EC_KEY_new_by_curve_name(curve)
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if key == 0:
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raise Exception("[OpenSSL] EC_KEY_new_by_curve_name FAIL ...")
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if privkey is not None:
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priv_key = OpenSSL.BN_bin2bn(privkey, len(privkey), 0)
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pub_key_x = OpenSSL.BN_bin2bn(pubkey_x, len(pubkey_x), 0)
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pub_key_y = OpenSSL.BN_bin2bn(pubkey_y, len(pubkey_y), 0)
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if privkey is not None:
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if (OpenSSL.EC_KEY_set_private_key(key, priv_key)) == 0:
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raise Exception(
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"[OpenSSL] EC_KEY_set_private_key FAIL ...")
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group = OpenSSL.EC_KEY_get0_group(key)
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pub_key = OpenSSL.EC_POINT_new(group)
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if (OpenSSL.EC_POINT_set_affine_coordinates_GFp(group, pub_key,
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pub_key_x,
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pub_key_y,
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0)) == 0:
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raise Exception(
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"[OpenSSL] EC_POINT_set_affine_coordinates_GFp FAIL ...")
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if (OpenSSL.EC_KEY_set_public_key(key, pub_key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_set_public_key FAIL ...")
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if (OpenSSL.EC_KEY_check_key(key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_check_key FAIL ...")
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return 0
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finally:
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OpenSSL.EC_KEY_free(key)
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OpenSSL.BN_free(pub_key_x)
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OpenSSL.BN_free(pub_key_y)
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OpenSSL.EC_POINT_free(pub_key)
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if privkey is not None:
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OpenSSL.BN_free(priv_key)
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def sign(self, inputb, digest_alg=OpenSSL.digest_ecdsa_sha1):
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"""
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Sign the input with ECDSA method and returns the signature
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"""
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# pylint: disable=too-many-branches,too-many-locals
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try:
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size = len(inputb)
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buff = OpenSSL.malloc(inputb, size)
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digest = OpenSSL.malloc(0, 64)
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if OpenSSL._hexversion > 0x10100000 and not OpenSSL._libreSSL:
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md_ctx = OpenSSL.EVP_MD_CTX_new()
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else:
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md_ctx = OpenSSL.EVP_MD_CTX_create()
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dgst_len = OpenSSL.pointer(OpenSSL.c_int(0))
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siglen = OpenSSL.pointer(OpenSSL.c_int(0))
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sig = OpenSSL.malloc(0, 151)
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key = OpenSSL.EC_KEY_new_by_curve_name(self.curve)
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if key == 0:
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raise Exception("[OpenSSL] EC_KEY_new_by_curve_name FAIL ...")
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priv_key = OpenSSL.BN_bin2bn(self.privkey, len(self.privkey), 0)
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pub_key_x = OpenSSL.BN_bin2bn(self.pubkey_x, len(self.pubkey_x), 0)
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pub_key_y = OpenSSL.BN_bin2bn(self.pubkey_y, len(self.pubkey_y), 0)
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if (OpenSSL.EC_KEY_set_private_key(key, priv_key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_set_private_key FAIL ...")
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group = OpenSSL.EC_KEY_get0_group(key)
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pub_key = OpenSSL.EC_POINT_new(group)
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if (OpenSSL.EC_POINT_set_affine_coordinates_GFp(group, pub_key,
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pub_key_x,
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pub_key_y,
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0)) == 0:
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raise Exception(
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"[OpenSSL] EC_POINT_set_affine_coordinates_GFp FAIL ...")
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if (OpenSSL.EC_KEY_set_public_key(key, pub_key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_set_public_key FAIL ...")
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if (OpenSSL.EC_KEY_check_key(key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_check_key FAIL ...")
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if OpenSSL._hexversion > 0x10100000 and not OpenSSL._libreSSL:
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OpenSSL.EVP_MD_CTX_new(md_ctx)
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else:
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OpenSSL.EVP_MD_CTX_init(md_ctx)
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OpenSSL.EVP_DigestInit_ex(md_ctx, digest_alg(), None)
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if (OpenSSL.EVP_DigestUpdate(md_ctx, buff, size)) == 0:
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raise Exception("[OpenSSL] EVP_DigestUpdate FAIL ...")
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OpenSSL.EVP_DigestFinal_ex(md_ctx, digest, dgst_len)
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OpenSSL.ECDSA_sign(0, digest, dgst_len.contents, sig, siglen, key)
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if (OpenSSL.ECDSA_verify(0, digest, dgst_len.contents, sig,
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siglen.contents, key)) != 1:
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raise Exception("[OpenSSL] ECDSA_verify FAIL ...")
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return sig.raw[:siglen.contents.value]
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finally:
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OpenSSL.EC_KEY_free(key)
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OpenSSL.BN_free(pub_key_x)
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OpenSSL.BN_free(pub_key_y)
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OpenSSL.BN_free(priv_key)
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OpenSSL.EC_POINT_free(pub_key)
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if OpenSSL._hexversion > 0x10100000 and not OpenSSL._libreSSL:
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OpenSSL.EVP_MD_CTX_free(md_ctx)
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else:
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OpenSSL.EVP_MD_CTX_destroy(md_ctx)
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def verify(self, sig, inputb, digest_alg=OpenSSL.digest_ecdsa_sha1):
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"""
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Verify the signature with the input and the local public key.
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Returns a boolean
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"""
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# pylint: disable=too-many-branches
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try:
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bsig = OpenSSL.malloc(sig, len(sig))
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binputb = OpenSSL.malloc(inputb, len(inputb))
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digest = OpenSSL.malloc(0, 64)
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dgst_len = OpenSSL.pointer(OpenSSL.c_int(0))
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if OpenSSL._hexversion > 0x10100000 and not OpenSSL._libreSSL:
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md_ctx = OpenSSL.EVP_MD_CTX_new()
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else:
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md_ctx = OpenSSL.EVP_MD_CTX_create()
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key = OpenSSL.EC_KEY_new_by_curve_name(self.curve)
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if key == 0:
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raise Exception("[OpenSSL] EC_KEY_new_by_curve_name FAIL ...")
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pub_key_x = OpenSSL.BN_bin2bn(self.pubkey_x, len(self.pubkey_x), 0)
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pub_key_y = OpenSSL.BN_bin2bn(self.pubkey_y, len(self.pubkey_y), 0)
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group = OpenSSL.EC_KEY_get0_group(key)
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pub_key = OpenSSL.EC_POINT_new(group)
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if (OpenSSL.EC_POINT_set_affine_coordinates_GFp(group, pub_key,
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pub_key_x,
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pub_key_y,
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0)) == 0:
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raise Exception(
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"[OpenSSL] EC_POINT_set_affine_coordinates_GFp FAIL ...")
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if (OpenSSL.EC_KEY_set_public_key(key, pub_key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_set_public_key FAIL ...")
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if (OpenSSL.EC_KEY_check_key(key)) == 0:
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raise Exception("[OpenSSL] EC_KEY_check_key FAIL ...")
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if OpenSSL._hexversion > 0x10100000 and not OpenSSL._libreSSL:
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OpenSSL.EVP_MD_CTX_new(md_ctx)
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else:
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OpenSSL.EVP_MD_CTX_init(md_ctx)
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OpenSSL.EVP_DigestInit_ex(md_ctx, digest_alg(), None)
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if (OpenSSL.EVP_DigestUpdate(md_ctx, binputb, len(inputb))) == 0:
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raise Exception("[OpenSSL] EVP_DigestUpdate FAIL ...")
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OpenSSL.EVP_DigestFinal_ex(md_ctx, digest, dgst_len)
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ret = OpenSSL.ECDSA_verify(
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0, digest, dgst_len.contents, bsig, len(sig), key)
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if ret == -1:
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return False # Fail to Check
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if ret == 0:
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return False # Bad signature !
|
|
return True # Good
|
|
|
|
finally:
|
|
OpenSSL.EC_KEY_free(key)
|
|
OpenSSL.BN_free(pub_key_x)
|
|
OpenSSL.BN_free(pub_key_y)
|
|
OpenSSL.EC_POINT_free(pub_key)
|
|
if OpenSSL._hexversion > 0x10100000 and not OpenSSL._libreSSL:
|
|
OpenSSL.EVP_MD_CTX_free(md_ctx)
|
|
else:
|
|
OpenSSL.EVP_MD_CTX_destroy(md_ctx)
|
|
|
|
@staticmethod
|
|
def encrypt(data, pubkey, ephemcurve=None, ciphername='aes-256-cbc'):
|
|
"""
|
|
Encrypt data with ECIES method using the public key of the recipient.
|
|
"""
|
|
curve, pubkey_x, pubkey_y, _ = ECC._decode_pubkey(pubkey)
|
|
return ECC.raw_encrypt(data, pubkey_x, pubkey_y, curve=curve,
|
|
ephemcurve=ephemcurve, ciphername=ciphername)
|
|
|
|
@staticmethod
|
|
def raw_encrypt(
|
|
data,
|
|
pubkey_x,
|
|
pubkey_y,
|
|
curve='sect283r1',
|
|
ephemcurve=None,
|
|
ciphername='aes-256-cbc',
|
|
): # pylint: disable=too-many-arguments
|
|
"""ECHD encryption, keys supplied in binary data format"""
|
|
|
|
if ephemcurve is None:
|
|
ephemcurve = curve
|
|
ephem = ECC(curve=ephemcurve)
|
|
key = sha512(ephem.raw_get_ecdh_key(pubkey_x, pubkey_y)).digest()
|
|
key_e, key_m = key[:32], key[32:]
|
|
pubkey = ephem.get_pubkey()
|
|
iv = OpenSSL.rand(OpenSSL.get_cipher(ciphername).get_blocksize())
|
|
ctx = Cipher(key_e, iv, 1, ciphername)
|
|
ciphertext = iv + pubkey + ctx.ciphering(data)
|
|
mac = hmac_sha256(key_m, ciphertext)
|
|
return ciphertext + mac
|
|
|
|
def decrypt(self, data, ciphername='aes-256-cbc'):
|
|
"""
|
|
Decrypt data with ECIES method using the local private key
|
|
"""
|
|
# pylint: disable=too-many-locals
|
|
blocksize = OpenSSL.get_cipher(ciphername).get_blocksize()
|
|
iv = data[:blocksize]
|
|
i = blocksize
|
|
_, pubkey_x, pubkey_y, i2 = ECC._decode_pubkey(data[i:])
|
|
i += i2
|
|
ciphertext = data[i:len(data) - 32]
|
|
i += len(ciphertext)
|
|
mac = data[i:]
|
|
key = sha512(self.raw_get_ecdh_key(pubkey_x, pubkey_y)).digest()
|
|
key_e, key_m = key[:32], key[32:]
|
|
if not equals(hmac_sha256(key_m, data[:len(data) - 32]), mac):
|
|
raise RuntimeError("Fail to verify data")
|
|
ctx = Cipher(key_e, iv, 0, ciphername)
|
|
return ctx.ciphering(ciphertext)
|