from asn1crypto.keys import PrivateKeyInfo, ECPrivateKey
from coincurve import PublicKey as cPublicKey, PrivateKey as cPrivateKey
from coincurve.utils import (
pem_to_der, lib as libsecp256k1, ffi as libsecp256k1_ffi
)
from coincurve.ecdsa import CDATA_SIG_LENGTH
from lbry.crypto.hash import hmac_sha512, hash160, double_sha256
from lbry.crypto.base58 import Base58
from .util import cachedproperty
class KeyPath:
RECEIVE = 0
CHANGE = 1
CHANNEL = 2
class DerivationError(Exception):
""" Raised when an invalid derivation occurs. """
class _KeyBase:
""" A BIP32 Key, public or private. """
def __init__(self, ledger, chain_code, n, depth, parent):
if not isinstance(chain_code, (bytes, bytearray)):
raise TypeError('chain code must be raw bytes')
if len(chain_code) != 32:
raise ValueError('invalid chain code')
if not 0 <= n < 1 << 32:
raise ValueError('invalid child number')
if not 0 <= depth < 256:
raise ValueError('invalid depth')
if parent is not None:
if not isinstance(parent, type(self)):
raise TypeError('parent key has bad type')
self.ledger = ledger
self.chain_code = chain_code
self.n = n
self.depth = depth
self.parent = parent
def _hmac_sha512(self, msg):
""" Use SHA-512 to provide an HMAC, returned as a pair of 32-byte objects. """
hmac = hmac_sha512(self.chain_code, msg)
return hmac[:32], hmac[32:]
def _extended_key(self, ver_bytes, raw_serkey):
""" Return the 78-byte extended key given prefix version bytes and serialized key bytes. """
if not isinstance(ver_bytes, (bytes, bytearray)):
raise TypeError('ver_bytes must be raw bytes')
if len(ver_bytes) != 4:
raise ValueError('ver_bytes must have length 4')
if not isinstance(raw_serkey, (bytes, bytearray)):
raise TypeError('raw_serkey must be raw bytes')
if len(raw_serkey) != 33:
raise ValueError('raw_serkey must have length 33')
return (
ver_bytes + bytes((self.depth,))
+ self.parent_fingerprint() + self.n.to_bytes(4, 'big')
+ self.chain_code + raw_serkey
)
def identifier(self):
raise NotImplementedError
def extended_key(self):
raise NotImplementedError
def fingerprint(self):
""" Return the key's fingerprint as 4 bytes. """
return self.identifier()[:4]
def parent_fingerprint(self):
""" Return the parent key's fingerprint as 4 bytes. """
return self.parent.fingerprint() if self.parent else bytes((0,)*4)
def extended_key_string(self):
""" Return an extended key as a base58 string. """
return Base58.encode_check(self.extended_key())
class PublicKey(_KeyBase):
""" A BIP32 public key. """
def __init__(self, ledger, pubkey, chain_code, n, depth, parent=None):
super().__init__(ledger, chain_code, n, depth, parent)
if isinstance(pubkey, cPublicKey):
self.verifying_key = pubkey
else:
self.verifying_key = self._verifying_key_from_pubkey(pubkey)
@classmethod
def from_compressed(cls, public_key_bytes, ledger=None) -> 'PublicKey':
return cls(ledger, public_key_bytes, bytes((0,)*32), 0, 0)
@classmethod
def _verifying_key_from_pubkey(cls, pubkey):
""" Converts a 33-byte compressed pubkey into an coincurve.PublicKey object. """
if not isinstance(pubkey, (bytes, bytearray)):
raise TypeError('pubkey must be raw bytes')
if len(pubkey) != 33:
raise ValueError('pubkey must be 33 bytes')
if pubkey[0] not in (2, 3):
raise ValueError('invalid pubkey prefix byte')
return cPublicKey(pubkey)
@cachedproperty
def pubkey_bytes(self):
""" Return the compressed public key as 33 bytes. """
return self.verifying_key.format(True)
@cachedproperty
def address(self):
""" The public key as a P2PKH address. """
return self.ledger.public_key_to_address(self.pubkey_bytes)
def ec_point(self):
return self.verifying_key.point()
def child(self, n: int) -> 'PublicKey':
""" Return the derived child extended pubkey at index N. """
if not 0 <= n < (1 << 31):
raise ValueError('invalid BIP32 public key child number')
msg = self.pubkey_bytes + n.to_bytes(4, 'big')
L_b, R_b = self._hmac_sha512(msg) # pylint: disable=invalid-name
derived_key = self.verifying_key.add(L_b)
return PublicKey(self.ledger, derived_key, R_b, n, self.depth + 1, self)
def identifier(self):
""" Return the key's identifier as 20 bytes. """
return hash160(self.pubkey_bytes)
def extended_key(self):
""" Return a raw extended public key. """
return self._extended_key(
self.ledger.extended_public_key_prefix,
self.pubkey_bytes
)
def verify(self, signature, digest) -> bool:
""" Verify that a signature is valid for a 32 byte digest. """
if len(signature) != 64:
raise ValueError('Signature must be 64 bytes long.')
if len(digest) != 32:
raise ValueError('Digest must be 32 bytes long.')
key = self.verifying_key
raw_signature = libsecp256k1_ffi.new('secp256k1_ecdsa_signature *')
parsed = libsecp256k1.secp256k1_ecdsa_signature_parse_compact(
key.context.ctx, raw_signature, signature
)
assert parsed == 1
normalized_signature = libsecp256k1_ffi.new('secp256k1_ecdsa_signature *')
libsecp256k1.secp256k1_ecdsa_signature_normalize(
key.context.ctx, normalized_signature, raw_signature
)
verified = libsecp256k1.secp256k1_ecdsa_verify(
key.context.ctx, normalized_signature, digest, key.public_key
)
return bool(verified)
class PrivateKey(_KeyBase):
"""A BIP32 private key."""
HARDENED = 1 << 31
def __init__(self, ledger, privkey, chain_code, n, depth, parent=None):
super().__init__(ledger, chain_code, n, depth, parent)
if isinstance(privkey, cPrivateKey):
self.signing_key = privkey
else:
self.signing_key = self._signing_key_from_privkey(privkey)
@classmethod
def _signing_key_from_privkey(cls, private_key):
""" Converts a 32-byte private key into an coincurve.PrivateKey object. """
return cPrivateKey.from_int(PrivateKey._private_key_secret_exponent(private_key))
@classmethod
def _private_key_secret_exponent(cls, private_key):
""" Return the private key as a secret exponent if it is a valid private key. """
if not isinstance(private_key, (bytes, bytearray)):
raise TypeError('private key must be raw bytes')
if len(private_key) != 32:
raise ValueError('private key must be 32 bytes')
return int.from_bytes(private_key, 'big')
@classmethod
def from_seed(cls, ledger, seed) -> 'PrivateKey':
# This hard-coded message string seems to be coin-independent...
hmac = hmac_sha512(b'Bitcoin seed', seed)
privkey, chain_code = hmac[:32], hmac[32:]
return cls(ledger, privkey, chain_code, 0, 0)
@classmethod
def from_pem(cls, ledger, pem) -> 'PrivateKey':
der = pem_to_der(pem.encode())
try:
key_int = ECPrivateKey.load(der).native['private_key']
except ValueError:
key_int = PrivateKeyInfo.load(der).native['private_key']['private_key']
private_key = cPrivateKey.from_int(key_int)
return cls(ledger, private_key, bytes((0,)*32), 0, 0)
@classmethod
def from_bytes(cls, ledger, key_bytes) -> 'PrivateKey':
return cls(ledger, cPrivateKey(key_bytes), bytes((0,)*32), 0, 0)
@cachedproperty
def private_key_bytes(self):
""" Return the serialized private key (no leading zero byte). """
return self.signing_key.secret
@cachedproperty
def public_key(self) -> PublicKey:
""" Return the corresponding extended public key. """
verifying_key = self.signing_key.public_key
parent_pubkey = self.parent.public_key if self.parent else None
return PublicKey(
self.ledger, verifying_key, self.chain_code,
self.n, self.depth, parent_pubkey
)
def ec_point(self):
return self.public_key.ec_point()
def secret_exponent(self):
""" Return the private key as a secret exponent. """
return self.signing_key.to_int()
def wif(self):
""" Return the private key encoded in Wallet Import Format. """
return self.ledger.private_key_to_wif(self.private_key_bytes)
@property
def address(self):
""" The public key as a P2PKH address. """
return self.public_key.address
def child(self, n) -> 'PrivateKey':
""" Return the derived child extended private key at index N."""
if not 0 <= n < (1 << 32):
raise ValueError('invalid BIP32 private key child number')
if n >= self.HARDENED:
serkey = b'\0' + self.private_key_bytes
else:
serkey = self.public_key.pubkey_bytes
msg = serkey + n.to_bytes(4, 'big')
L_b, R_b = self._hmac_sha512(msg) # pylint: disable=invalid-name
derived_key = self.signing_key.add(L_b)
return PrivateKey(self.ledger, derived_key, R_b, n, self.depth + 1, self)
def sign(self, data):
""" Produce a signature for piece of data by double hashing it and signing the hash. """
return self.signing_key.sign(data, hasher=double_sha256)
def sign_compact(self, digest):
""" Produce a compact signature. """
key = self.signing_key
signature = libsecp256k1_ffi.new('secp256k1_ecdsa_signature *')
signed = libsecp256k1.secp256k1_ecdsa_sign(
key.context.ctx, signature, digest, key.secret,
libsecp256k1_ffi.NULL, libsecp256k1_ffi.NULL
)
if not signed:
raise ValueError('The private key was invalid.')
serialized = libsecp256k1_ffi.new('unsigned char[%d]' % CDATA_SIG_LENGTH)
compacted = libsecp256k1.secp256k1_ecdsa_signature_serialize_compact(
key.context.ctx, serialized, signature
)
if compacted != 1:
raise ValueError('The signature could not be compacted.')
return bytes(libsecp256k1_ffi.buffer(serialized, CDATA_SIG_LENGTH))
def identifier(self):
"""Return the key's identifier as 20 bytes."""
return self.public_key.identifier()
def extended_key(self):
"""Return a raw extended private key."""
return self._extended_key(
self.ledger.extended_private_key_prefix,
b'\0' + self.private_key_bytes
)
def to_pem(self):
return self.signing_key.to_pem()
def _from_extended_key(ledger, ekey):
"""Return a PublicKey or PrivateKey from an extended key raw bytes."""
if not isinstance(ekey, (bytes, bytearray)):
raise TypeError('extended key must be raw bytes')
if len(ekey) != 78:
raise ValueError('extended key must have length 78')
depth = ekey[4]
n = int.from_bytes(ekey[9:13], 'big')
chain_code = ekey[13:45]
if ekey[:4] == ledger.extended_public_key_prefix:
pubkey = ekey[45:]
key = PublicKey(ledger, pubkey, chain_code, n, depth)
elif ekey[:4] == ledger.extended_private_key_prefix:
if ekey[45] != 0:
raise ValueError('invalid extended private key prefix byte')
privkey = ekey[46:]
key = PrivateKey(ledger, privkey, chain_code, n, depth)
else:
raise ValueError('version bytes unrecognised')
return key
def from_extended_key_string(ledger, ekey_str):
"""Given an extended key string, such as
xpub6BsnM1W2Y7qLMiuhi7f7dbAwQZ5Cz5gYJCRzTNainXzQXYjFwtuQXHd
3qfi3t3KJtHxshXezfjft93w4UE7BGMtKwhqEHae3ZA7d823DVrL
return a PublicKey or PrivateKey.
"""
return _from_extended_key(ledger, Base58.decode_check(ekey_str))