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# Copyright (c) 2011 Sam Rushing
"""ECC secp256k1 OpenSSL wrapper.
WARNING: This module does not mlock() secrets; your private keys may end up on
disk in swap! Use with caution!
This file is modified from python-bitcoinlib.
"""
import ctypes
import ctypes.util
import hashlib
import sys
ssl = ctypes.cdll.LoadLibrary(ctypes.util.find_library ('ssl') or 'libeay32')
ssl.BN_new.restype = ctypes.c_void_p
ssl.BN_new.argtypes = []
ssl.BN_bin2bn.restype = ctypes.c_void_p
ssl.BN_bin2bn.argtypes = [ctypes.c_char_p, ctypes.c_int, ctypes.c_void_p]
ssl.BN_CTX_free.restype = None
ssl.BN_CTX_free.argtypes = [ctypes.c_void_p]
ssl.BN_CTX_new.restype = ctypes.c_void_p
ssl.BN_CTX_new.argtypes = []
ssl.ECDH_compute_key.restype = ctypes.c_int
ssl.ECDH_compute_key.argtypes = [ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p, ctypes.c_void_p]
ssl.ECDSA_sign.restype = ctypes.c_int
ssl.ECDSA_sign.argtypes = [ctypes.c_int, ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p]
ssl.ECDSA_verify.restype = ctypes.c_int
ssl.ECDSA_verify.argtypes = [ctypes.c_int, ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p]
ssl.EC_KEY_free.restype = None
ssl.EC_KEY_free.argtypes = [ctypes.c_void_p]
ssl.EC_KEY_new_by_curve_name.restype = ctypes.c_void_p
ssl.EC_KEY_new_by_curve_name.argtypes = [ctypes.c_int]
ssl.EC_KEY_get0_group.restype = ctypes.c_void_p
ssl.EC_KEY_get0_group.argtypes = [ctypes.c_void_p]
ssl.EC_KEY_get0_public_key.restype = ctypes.c_void_p
ssl.EC_KEY_get0_public_key.argtypes = [ctypes.c_void_p]
ssl.EC_KEY_set_private_key.restype = ctypes.c_int
ssl.EC_KEY_set_private_key.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
ssl.EC_KEY_set_conv_form.restype = None
ssl.EC_KEY_set_conv_form.argtypes = [ctypes.c_void_p, ctypes.c_int]
ssl.EC_KEY_set_public_key.restype = ctypes.c_int
ssl.EC_KEY_set_public_key.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
ssl.i2o_ECPublicKey.restype = ctypes.c_void_p
ssl.i2o_ECPublicKey.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
ssl.EC_POINT_new.restype = ctypes.c_void_p
ssl.EC_POINT_new.argtypes = [ctypes.c_void_p]
ssl.EC_POINT_free.restype = None
ssl.EC_POINT_free.argtypes = [ctypes.c_void_p]
ssl.EC_POINT_mul.restype = ctypes.c_int
ssl.EC_POINT_mul.argtypes = [ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p]
# this specifies the curve used with ECDSA.
NID_secp256k1 = 714 # from openssl/obj_mac.h
SECP256K1_ORDER = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141
SECP256K1_ORDER_HALF = SECP256K1_ORDER // 2
# Thx to Sam Devlin for the ctypes magic 64-bit fix.
def _check_result(val, func, args):
if val == 0:
raise ValueError
else:
return ctypes.c_void_p (val)
ssl.EC_KEY_new_by_curve_name.restype = ctypes.c_void_p
ssl.EC_KEY_new_by_curve_name.errcheck = _check_result
class CECKey(object):
"""Wrapper around OpenSSL's EC_KEY"""
POINT_CONVERSION_COMPRESSED = 2
POINT_CONVERSION_UNCOMPRESSED = 4
def __init__(self):
self.k = ssl.EC_KEY_new_by_curve_name(NID_secp256k1)
def __del__(self):
if ssl:
ssl.EC_KEY_free(self.k)
self.k = None
def set_secretbytes(self, secret):
priv_key = ssl.BN_bin2bn(secret, 32, ssl.BN_new())
group = ssl.EC_KEY_get0_group(self.k)
pub_key = ssl.EC_POINT_new(group)
ctx = ssl.BN_CTX_new()
if not ssl.EC_POINT_mul(group, pub_key, priv_key, None, None, ctx):
raise ValueError("Could not derive public key from the supplied secret.")
ssl.EC_POINT_mul(group, pub_key, priv_key, None, None, ctx)
ssl.EC_KEY_set_private_key(self.k, priv_key)
ssl.EC_KEY_set_public_key(self.k, pub_key)
ssl.EC_POINT_free(pub_key)
ssl.BN_CTX_free(ctx)
return self.k
def set_privkey(self, key):
self.mb = ctypes.create_string_buffer(key)
return ssl.d2i_ECPrivateKey(ctypes.byref(self.k), ctypes.byref(ctypes.pointer(self.mb)), len(key))
def set_pubkey(self, key):
self.mb = ctypes.create_string_buffer(key)
return ssl.o2i_ECPublicKey(ctypes.byref(self.k), ctypes.byref(ctypes.pointer(self.mb)), len(key))
def get_privkey(self):
size = ssl.i2d_ECPrivateKey(self.k, 0)
mb_pri = ctypes.create_string_buffer(size)
ssl.i2d_ECPrivateKey(self.k, ctypes.byref(ctypes.pointer(mb_pri)))
return mb_pri.raw
def get_pubkey(self):
size = ssl.i2o_ECPublicKey(self.k, 0)
mb = ctypes.create_string_buffer(size)
ssl.i2o_ECPublicKey(self.k, ctypes.byref(ctypes.pointer(mb)))
return mb.raw
def get_raw_ecdh_key(self, other_pubkey):
ecdh_keybuffer = ctypes.create_string_buffer(32)
r = ssl.ECDH_compute_key(ctypes.pointer(ecdh_keybuffer), 32,
ssl.EC_KEY_get0_public_key(other_pubkey.k),
self.k, 0)
if r != 32:
raise Exception('CKey.get_ecdh_key(): ECDH_compute_key() failed')
return ecdh_keybuffer.raw
def get_ecdh_key(self, other_pubkey, kdf=lambda k: hashlib.sha256(k).digest()):
# FIXME: be warned it's not clear what the kdf should be as a default
r = self.get_raw_ecdh_key(other_pubkey)
return kdf(r)
def sign(self, hash, low_s = True):
# FIXME: need unit tests for below cases
if not isinstance(hash, bytes):
raise TypeError('Hash must be bytes instance; got %r' % hash.__class__)
if len(hash) != 32:
raise ValueError('Hash must be exactly 32 bytes long')
sig_size0 = ctypes.c_uint32()
sig_size0.value = ssl.ECDSA_size(self.k)
mb_sig = ctypes.create_string_buffer(sig_size0.value)
result = ssl.ECDSA_sign(0, hash, len(hash), mb_sig, ctypes.byref(sig_size0), self.k)
assert 1 == result
assert mb_sig.raw[0] == 0x30
assert mb_sig.raw[1] == sig_size0.value - 2
total_size = mb_sig.raw[1]
assert mb_sig.raw[2] == 2
r_size = mb_sig.raw[3]
assert mb_sig.raw[4 + r_size] == 2
s_size = mb_sig.raw[5 + r_size]
s_value = int.from_bytes(mb_sig.raw[6+r_size:6+r_size+s_size], byteorder='big')
if (not low_s) or s_value <= SECP256K1_ORDER_HALF:
return mb_sig.raw[:sig_size0.value]
else:
low_s_value = SECP256K1_ORDER - s_value
low_s_bytes = (low_s_value).to_bytes(33, byteorder='big')
while len(low_s_bytes) > 1 and low_s_bytes[0] == 0 and low_s_bytes[1] < 0x80:
low_s_bytes = low_s_bytes[1:]
new_s_size = len(low_s_bytes)
new_total_size_byte = (total_size + new_s_size - s_size).to_bytes(1,byteorder='big')
new_s_size_byte = (new_s_size).to_bytes(1,byteorder='big')
return b'\x30' + new_total_size_byte + mb_sig.raw[2:5+r_size] + new_s_size_byte + low_s_bytes
def verify(self, hash, sig):
"""Verify a DER signature"""
return ssl.ECDSA_verify(0, hash, len(hash), sig, len(sig), self.k) == 1
def set_compressed(self, compressed):
if compressed:
form = self.POINT_CONVERSION_COMPRESSED
else:
form = self.POINT_CONVERSION_UNCOMPRESSED
ssl.EC_KEY_set_conv_form(self.k, form)
class CPubKey(bytes):
"""An encapsulated public key
Attributes:
is_valid - Corresponds to CPubKey.IsValid()
is_fullyvalid - Corresponds to CPubKey.IsFullyValid()
is_compressed - Corresponds to CPubKey.IsCompressed()
"""
def __new__(cls, buf, _cec_key=None):
self = super(CPubKey, cls).__new__(cls, buf)
if _cec_key is None:
_cec_key = CECKey()
self._cec_key = _cec_key
self.is_fullyvalid = _cec_key.set_pubkey(self) != 0
return self
@property
def is_valid(self):
return len(self) > 0
@property
def is_compressed(self):
return len(self) == 33
def verify(self, hash, sig):
return self._cec_key.verify(hash, sig)
def __str__(self):
return repr(self)
def __repr__(self):
# Always have represent as b'<secret>' so test cases don't have to
# change for py2/3
if sys.version > '3':
return '%s(%s)' % (self.__class__.__name__, super(CPubKey, self).__repr__())
else:
return '%s(b%s)' % (self.__class__.__name__, super(CPubKey, self).__repr__())
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