unet.py

import base64
import hashlib
import hmac
import re
import struct
import logging
import aes
import ecdsa
from ecdsa import numbertheory, util
from ecdsa.curves import SECP256k1
from ecdsa.ecdsa import curve_secp256k1, generator_secp256k1
from ecdsa.ellipticcurve import Point
from ecdsa.util import number_to_string, string_to_number

from uwallet import msqr, version
from uwallet.base import base_decode, base_encode, EncodeBase58Check, DecodeBase58Check, __b58chars
from uwallet.util import print_error, rev_hex, var_int, int_to_hex
from uwallet.hashing import Hash, sha256, hash_160, hmac_sha_512
from uwallet.errors import InvalidPassword

log = logging.getLogger(__name__)

# address prefixes are set when the blockchain is initialized by blockchain.get_blockchain
# the default values are for unet_main
global PUBKEY_ADDRESS
global SCRIPT_ADDRESS
PUBKEY_ADDRESS = (0, 36)
SCRIPT_ADDRESS = (5, 204)

# AES encryption
EncodeAES = lambda secret, s: base64.b64encode(aes.encryptData(secret, s))
DecodeAES = lambda secret, e: aes.decryptData(secret, base64.b64decode(e))


# get the claim id hash from txid bytes and int n
def claim_id_hash(txid, n):
    return hash_160(txid + struct.pack('>I', n))


# deocde a claim_id hex string
def decode_claim_id_hex(claim_id_hex):
    return rev_hex(claim_id_hex).decode('hex')


# encode claim id bytes into hex string
def encode_claim_id_hex(claim_id):
    return rev_hex(claim_id.encode('hex'))


def strip_PKCS7_padding(s):
    """return s stripped of PKCS7 padding"""
    if len(s) % 16 or not s:
        raise ValueError("String of len %d can't be PCKS7-padded" % len(s))
    numpads = ord(s[-1])
    if numpads > 16:
        raise ValueError("String ending with %r can't be PCKS7-padded" % s[-1])
    if s[-numpads:] != numpads * chr(numpads):
        raise ValueError("Invalid PKCS7 padding")
    return s[:-numpads]


# backport padding fix to AES module
aes.strip_PKCS7_padding = strip_PKCS7_padding


def aes_encrypt_with_iv(key, iv, data):
    mode = aes.AESModeOfOperation.modeOfOperation["CBC"]
    key = map(ord, key)
    iv = map(ord, iv)
    data = aes.append_PKCS7_padding(data)
    keysize = len(key)
    assert keysize in aes.AES.keySize.values(), 'invalid key size: %s' % keysize
    moo = aes.AESModeOfOperation()
    (mode, length, ciph) = moo.encrypt(data, mode, key, keysize, iv)
    return ''.join(map(chr, ciph))


def aes_decrypt_with_iv(key, iv, data):
    mode = aes.AESModeOfOperation.modeOfOperation["CBC"]
    key = map(ord, key)
    iv = map(ord, iv)
    keysize = len(key)
    assert keysize in aes.AES.keySize.values(), 'invalid key size: %s' % keysize
    data = map(ord, data)
    moo = aes.AESModeOfOperation()
    decr = moo.decrypt(data, None, mode, key, keysize, iv)
    decr = strip_PKCS7_padding(decr)
    return decr


def pw_encode(s, password):
    if password:
        secret = Hash(password)
        return EncodeAES(secret, s.encode("utf8"))
    else:
        return s


def pw_decode(s, password):
    if password is not None:
        secret = Hash(password)
        try:
            d = DecodeAES(secret, s).decode("utf8")
        except Exception:
            raise InvalidPassword()
        return d
    else:
        return s


def op_push(i):
    if i < 0x4c:
        return int_to_hex(i)
    elif i < 0xff:
        return '4c' + int_to_hex(i)
    elif i < 0xffff:
        return '4d' + int_to_hex(i, 2)
    else:
        return '4e' + int_to_hex(i, 4)


def is_new_seed(x, prefix=version.SEED_PREFIX):
    import mnemonic
    x = mnemonic.prepare_seed(x)
    s = hmac_sha_512("Seed version", x.encode('utf8')).encode('hex')
    return s.startswith(prefix)


# pywallet openssl private key implementation

def i2o_ECPublicKey(pubkey, compressed=False):
    # public keys are 65 bytes long (520 bits)
    # 0x04 + 32-byte X-coordinate + 32-byte Y-coordinate
    # 0x00 = point at infinity, 0x02 and 0x03 = compressed, 0x04 = uncompressed
    # compressed keys: <sign> <x> where <sign> is 0x02 if y is even and 0x03 if y is odd
    if compressed:
        if pubkey.point.y() & 1:
            key = '03' + '%064x' % pubkey.point.x()
        else:
            key = '02' + '%064x' % pubkey.point.x()
    else:
        key = '04' + \
              '%064x' % pubkey.point.x() + \
              '%064x' % pubkey.point.y()

    return key.decode('hex')


# end pywallet openssl private key implementation
# functions from pywallet


def public_key_to_bc_address(public_key):
    h160 = hash_160(public_key)
    return hash_160_to_bc_address(h160)


def hash_160_to_bc_address(h160, addrtype=0):
    if addrtype == PUBKEY_ADDRESS[0]:
        c = chr(PUBKEY_ADDRESS[1])
    elif addrtype == SCRIPT_ADDRESS[0]:
        c = chr(SCRIPT_ADDRESS[1])
    else:
        raise Exception("Invalid address prefix")

    vh160 = c + h160
    h = Hash(vh160)
    addr = vh160 + h[0:4]
    return base_encode(addr, base=58)


def bc_address_to_hash_160(addr):
    bytes = base_decode(addr, 25, base=58)
    addr_without_checksum, addr_checksum = bytes[:21], bytes[21:]
    if Hash(addr_without_checksum)[:4] != addr_checksum:
        raise Exception("Invalid address checksum")
    if bytes[0] == chr(PUBKEY_ADDRESS[1]):
        return PUBKEY_ADDRESS[0], bytes[1:21]
    elif bytes[0] == chr(SCRIPT_ADDRESS[1]):
        return SCRIPT_ADDRESS[0], bytes[1:21]
    else:
        raise Exception("Invalid address prefix")


def PrivKeyToSecret(privkey):
    return privkey[9:9 + 32]


def SecretToASecret(secret, compressed=False, addrtype=0):
    vchIn = chr((addrtype + 128) & 255) + secret
    if compressed:
        vchIn += '\01'
    return EncodeBase58Check(vchIn)


def ASecretToSecret(key, addrtype=0):
    vch = DecodeBase58Check(key)
    if vch and vch[0] == chr((addrtype + 128) & 255):
        return vch[1:]
    elif is_minikey(key):
        return minikey_to_private_key(key)
    else:
        return False


def regenerate_key(sec):
    b = ASecretToSecret(sec)
    if not b:
        return False
    b = b[0:32]
    return EC_KEY(b)


def GetPubKey(pubkey, compressed=False):
    return i2o_ECPublicKey(pubkey, compressed)


def GetSecret(pkey):
    return ('%064x' % pkey.secret).decode('hex')


def is_compressed(sec):
    b = ASecretToSecret(sec)
    return len(b) == 33


def public_key_from_private_key(sec):
    # rebuild public key from private key, compressed or uncompressed
    pkey = regenerate_key(sec)
    assert pkey
    compressed = is_compressed(sec)
    public_key = GetPubKey(pkey.pubkey, compressed)
    return public_key.encode('hex')


def address_from_private_key(sec):
    public_key = public_key_from_private_key(sec)
    address = public_key_to_bc_address(public_key.decode('hex'))
    return address


def is_valid(addr):
    return is_address(addr)


def is_address(addr):
    ADDRESS_RE = re.compile('[1-9A-HJ-NP-Za-km-z]{26,}\\Z')
    if not ADDRESS_RE.match(addr):
        return False
    try:
        addrtype, h = bc_address_to_hash_160(addr)
    except Exception:
        return False
    if addrtype not in [0, 5]:
        return False
    return addr == hash_160_to_bc_address(h, addrtype)


def is_private_key(key):
    try:
        k = ASecretToSecret(key)
        return k is not False
    except:
        return False

# end pywallet functions


def is_minikey(text):
    # Minikeys are typically 22 or 30 characters, but this routine
    # permits any length of 20 or more provided the minikey is valid.
    # A valid minikey must begin with an 'S', be in base58, and when
    # suffixed with '?' have its SHA256 hash begin with a zero byte.
    # They are widely used in Casascius physical bitoins.
    return (len(text) >= 20 and text[0] == 'S'
            and all(c in __b58chars for c in text)
            and ord(sha256(text + '?')[0]) == 0)


def minikey_to_private_key(text):
    return sha256(text)


def msg_magic(message):
    varint = var_int(len(message))
    encoded_varint = "".join([chr(int(varint[i:i + 2], 16)) for i in xrange(0, len(varint), 2)])
    return "\x18Bitcoin Signed Message:\n" + encoded_varint + message


def verify_message(address, signature, message):
    try:
        EC_KEY.verify_message(address, signature, message)
        return True
    except Exception as e:
        print_error("Verification error: {0}".format(e))
        return False


def encrypt_message(message, pubkey):
    return EC_KEY.encrypt_message(message, pubkey.decode('hex'))


def chunks(l, n):
    return [l[i:i + n] for i in xrange(0, len(l), n)]


def ECC_YfromX(x, curved=curve_secp256k1, odd=True):
    _p = curved.p()
    _a = curved.a()
    _b = curved.b()
    for offset in range(128):
        Mx = x + offset
        My2 = pow(Mx, 3, _p) + _a * pow(Mx, 2, _p) + _b % _p
        My = pow(My2, (_p + 1) / 4, _p)

        if curved.contains_point(Mx, My):
            if odd == bool(My & 1):
                return [My, offset]
            return [_p - My, offset]
    raise Exception('ECC_YfromX: No Y found')


def negative_point(P):
    return Point(P.curve(), P.x(), -P.y(), P.order())


def point_to_ser(P, comp=True):
    if comp:
        return (('%02x' % (2 + (P.y() & 1))) + ('%064x' % P.x())).decode('hex')
    return ('04' + ('%064x' % P.x()) + ('%064x' % P.y())).decode('hex')


def ser_to_point(Aser):
    curve = curve_secp256k1
    generator = generator_secp256k1
    _r = generator.order()
    assert Aser[0] in ['\x02', '\x03', '\x04']
    if Aser[0] == '\x04':
        return Point(curve, string_to_number(Aser[1:33]), string_to_number(Aser[33:]), _r)
    Mx = string_to_number(Aser[1:])
    return Point(curve, Mx, ECC_YfromX(Mx, curve, Aser[0] == '\x03')[0], _r)


class MyVerifyingKey(ecdsa.VerifyingKey):
    @classmethod
    def from_signature(cls, sig, recid, h, curve):
        """ See http://www.secg.org/download/aid-780/sec1-v2.pdf, chapter 4.1.6 """
        curveFp = curve.curve
        G = curve.generator
        order = G.order()
        # extract r,s from signature
        r, s = util.sigdecode_string(sig, order)
        # 1.1
        x = r + (recid / 2) * order
        # 1.3
        alpha = (x * x * x + curveFp.a() * x + curveFp.b()) % curveFp.p()
        beta = msqr.modular_sqrt(alpha, curveFp.p())
        y = beta if (beta - recid) % 2 == 0 else curveFp.p() - beta
        # 1.4 the constructor checks that nR is at infinity
        R = Point(curveFp, x, y, order)
        # 1.5 compute e from message:
        e = string_to_number(h)
        minus_e = -e % order
        # 1.6 compute Q = r^-1 (sR - eG)
        inv_r = numbertheory.inverse_mod(r, order)
        Q = inv_r * (s * R + minus_e * G)
        return cls.from_public_point(Q, curve)


class MySigningKey(ecdsa.SigningKey):
    """Enforce low S values in signatures"""

    def sign_number(self, number, entropy=None, k=None):
        curve = SECP256k1
        G = curve.generator
        order = G.order()
        r, s = ecdsa.SigningKey.sign_number(self, number, entropy, k)
        if s > order / 2:
            s = order - s
        return r, s


class EC_KEY(object):
    def __init__(self, k):
        secret = string_to_number(k)
        self.pubkey = ecdsa.ecdsa.Public_key(generator_secp256k1, generator_secp256k1 * secret)
        self.privkey = ecdsa.ecdsa.Private_key(self.pubkey, secret)
        self.secret = secret

    def get_public_key(self, compressed=True):
        return point_to_ser(self.pubkey.point, compressed).encode('hex')

    def sign(self, msg_hash):
        private_key = MySigningKey.from_secret_exponent(self.secret, curve=SECP256k1)
        public_key = private_key.get_verifying_key()
        signature = private_key.sign_digest_deterministic(msg_hash, hashfunc=hashlib.sha256,
                                                          sigencode=ecdsa.util.sigencode_string)
        assert public_key.verify_digest(signature, msg_hash, sigdecode=ecdsa.util.sigdecode_string)
        return signature

    def sign_message(self, message, compressed, address):
        signature = self.sign(Hash(msg_magic(message)))
        for i in range(4):
            sig = chr(27 + i + (4 if compressed else 0)) + signature
            try:
                self.verify_message(address, sig, message)
                return sig
            except Exception:
                log.exception("error: cannot sign message")
                continue
        raise Exception("error: cannot sign message")

    @classmethod
    def verify_message(cls, address, sig, message):
        if len(sig) != 65:
            raise Exception("Wrong encoding")
        nV = ord(sig[0])
        if nV < 27 or nV >= 35:
            raise Exception("Bad encoding")
        if nV >= 31:
            compressed = True
            nV -= 4
        else:
            compressed = False
        recid = nV - 27

        h = Hash(msg_magic(message))
        public_key = MyVerifyingKey.from_signature(sig[1:], recid, h, curve=SECP256k1)
        # check public key
        public_key.verify_digest(sig[1:], h, sigdecode=ecdsa.util.sigdecode_string)
        pubkey = point_to_ser(public_key.pubkey.point, compressed)
        # check that we get the original signing address
        addr = public_key_to_bc_address(pubkey)
        if address != addr:
            raise Exception("Bad signature")

    # ECIES encryption/decryption methods; AES-128-CBC with PKCS7 is used as the cipher;
    # hmac-sha256 is used as the mac

    @classmethod
    def encrypt_message(cls, message, pubkey):

        pk = ser_to_point(pubkey)
        if not ecdsa.ecdsa.point_is_valid(generator_secp256k1, pk.x(), pk.y()):
            raise Exception('invalid pubkey')

        ephemeral_exponent = number_to_string(ecdsa.util.randrange(pow(2, 256)),
                                              generator_secp256k1.order())
        ephemeral = EC_KEY(ephemeral_exponent)
        ecdh_key = point_to_ser(pk * ephemeral.privkey.secret_multiplier)
        key = hashlib.sha512(ecdh_key).digest()
        iv, key_e, key_m = key[0:16], key[16:32], key[32:]
        ciphertext = aes_encrypt_with_iv(key_e, iv, message)
        ephemeral_pubkey = ephemeral.get_public_key(compressed=True).decode('hex')
        encrypted = 'BIE1' + ephemeral_pubkey + ciphertext
        mac = hmac.new(key_m, encrypted, hashlib.sha256).digest()

        return base64.b64encode(encrypted + mac)

    def decrypt_message(self, encrypted):

        encrypted = base64.b64decode(encrypted)

        if len(encrypted) < 85:
            raise Exception('invalid ciphertext: length')

        magic = encrypted[:4]
        ephemeral_pubkey = encrypted[4:37]
        ciphertext = encrypted[37:-32]
        mac = encrypted[-32:]

        if magic != 'BIE1':
            raise Exception('invalid ciphertext: invalid magic bytes')

        try:
            ephemeral_pubkey = ser_to_point(ephemeral_pubkey)
        except AssertionError, e:
            raise Exception('invalid ciphertext: invalid ephemeral pubkey')

        if not ecdsa.ecdsa.point_is_valid(generator_secp256k1, ephemeral_pubkey.x(),
                                          ephemeral_pubkey.y()):
            raise Exception('invalid ciphertext: invalid ephemeral pubkey')

        ecdh_key = point_to_ser(ephemeral_pubkey * self.privkey.secret_multiplier)
        key = hashlib.sha512(ecdh_key).digest()
        iv, key_e, key_m = key[0:16], key[16:32], key[32:]
        if mac != hmac.new(key_m, encrypted[:-32], hashlib.sha256).digest():
            raise Exception('invalid ciphertext: invalid mac')

        return aes_decrypt_with_iv(key_e, iv, ciphertext)


# BIP32

def random_seed(n):
    return "%032x" % ecdsa.util.randrange(pow(2, n))


BIP32_PRIME = 0x80000000


def get_pubkeys_from_secret(secret):
    # public key
    private_key = ecdsa.SigningKey.from_string(secret, curve=SECP256k1)
    public_key = private_key.get_verifying_key()
    K = public_key.to_string()
    K_compressed = GetPubKey(public_key.pubkey, True)
    return K, K_compressed


# Child private key derivation function (from master private key)
# k = master private key (32 bytes)
# c = master chain code (extra entropy for key derivation) (32 bytes)
# n = the index of the key we want to derive. (only 32 bits will be used)
# If n is negative (i.e. the 32nd bit is set), the resulting private key's
#  corresponding public key can NOT be determined without the master private key.
# However, if n is positive, the resulting private key's corresponding
#  public key can be determined without the master private key.
def CKD_priv(k, c, n):
    is_prime = n & BIP32_PRIME
    return _CKD_priv(k, c, rev_hex(int_to_hex(n, 4)).decode('hex'), is_prime)


def _CKD_priv(k, c, s, is_prime):
    order = generator_secp256k1.order()
    keypair = EC_KEY(k)
    cK = GetPubKey(keypair.pubkey, True)
    data = chr(0) + k + s if is_prime else cK + s
    I = hmac.new(c, data, hashlib.sha512).digest()
    k_n = number_to_string((string_to_number(I[0:32]) + string_to_number(k)) % order, order)
    c_n = I[32:]
    return k_n, c_n


# Child public key derivation function (from public key only)
# K = master public key
# c = master chain code
# n = index of key we want to derive
# This function allows us to find the nth public key, as long as n is
#  non-negative. If n is negative, we need the master private key to find it.
def CKD_pub(cK, c, n):
    if n & BIP32_PRIME:
        raise Exception("CKD pub error")
    return _CKD_pub(cK, c, rev_hex(int_to_hex(n, 4)).decode('hex'))


# helper function, callable with arbitrary string
def _CKD_pub(cK, c, s):
    order = generator_secp256k1.order()
    I = hmac.new(c, cK + s, hashlib.sha512).digest()
    curve = SECP256k1
    pubkey_point = string_to_number(I[0:32]) * curve.generator + ser_to_point(cK)
    public_key = ecdsa.VerifyingKey.from_public_point(pubkey_point, curve=SECP256k1)
    c_n = I[32:]
    cK_n = GetPubKey(public_key.pubkey, True)
    return cK_n, c_n


BITCOIN_HEADER_PRIV = "0488ade4"
BITCOIN_HEADER_PUB = "0488b21e"

TESTNET_HEADER_PRIV = "04358394"
TESTNET_HEADER_PUB = "043587cf"

BITCOIN_HEADERS = (BITCOIN_HEADER_PUB, BITCOIN_HEADER_PRIV)
TESTNET_HEADERS = (TESTNET_HEADER_PUB, TESTNET_HEADER_PRIV)


def _get_headers(testnet):
    """Returns the correct headers for either testnet or bitcoin, in the form
    of a 2-tuple, like (public, private)."""
    if testnet:
        return TESTNET_HEADERS
    else:
        return BITCOIN_HEADERS


def deserialize_xkey(xkey):
    xkey = DecodeBase58Check(xkey)
    assert len(xkey) == 78

    xkey_header = xkey[0:4].encode('hex')
    # Determine if the key is a bitcoin key or a testnet key.
    if xkey_header in TESTNET_HEADERS:
        head = TESTNET_HEADER_PRIV
    elif xkey_header in BITCOIN_HEADERS:
        head = BITCOIN_HEADER_PRIV
    else:
        raise Exception("Unknown xkey header: '%s'" % xkey_header)

    depth = ord(xkey[4])
    fingerprint = xkey[5:9]
    child_number = xkey[9:13]
    c = xkey[13:13 + 32]
    if xkey[0:4].encode('hex') == head:
        K_or_k = xkey[13 + 33:]
    else:
        K_or_k = xkey[13 + 32:]
    return depth, fingerprint, child_number, c, K_or_k


def get_xkey_name(xkey, testnet=False):
    depth, fingerprint, child_number, c, K = deserialize_xkey(xkey)
    n = int(child_number.encode('hex'), 16)
    if n & BIP32_PRIME:
        child_id = "%d'" % (n - BIP32_PRIME)
    else:
        child_id = "%d" % n
    if depth == 0:
        return ''
    elif depth == 1:
        return child_id
    else:
        raise BaseException("xpub depth error")


def xpub_from_xprv(xprv, testnet=False):
    depth, fingerprint, child_number, c, k = deserialize_xkey(xprv)
    K, cK = get_pubkeys_from_secret(k)
    header_pub, _ = _get_headers(testnet)
    xpub = header_pub.decode('hex') + chr(depth) + fingerprint + child_number + c + cK
    return EncodeBase58Check(xpub)


def bip32_root(seed, testnet=False):
    header_pub, header_priv = _get_headers(testnet)
    I = hmac.new("Bitcoin seed", seed, hashlib.sha512).digest()
    master_k = I[0:32]
    master_c = I[32:]
    K, cK = get_pubkeys_from_secret(master_k)
    xprv = (header_priv + "00" + "00000000" + "00000000").decode("hex") + master_c + chr(
        0) + master_k
    xpub = (header_pub + "00" + "00000000" + "00000000").decode("hex") + master_c + cK
    return EncodeBase58Check(xprv), EncodeBase58Check(xpub)


def xpub_from_pubkey(cK, testnet=False):
    header_pub, header_priv = _get_headers(testnet)
    assert cK[0] in ['\x02', '\x03']
    master_c = chr(0) * 32
    xpub = (header_pub + "00" + "00000000" + "00000000").decode("hex") + master_c + cK
    return EncodeBase58Check(xpub)


def bip32_private_derivation(xprv, branch, sequence, testnet=False):
    assert sequence.startswith(branch)
    if branch == sequence:
        return xprv, xpub_from_xprv(xprv, testnet)
    header_pub, header_priv = _get_headers(testnet)
    depth, fingerprint, child_number, c, k = deserialize_xkey(xprv)
    sequence = sequence[len(branch):]
    for n in sequence.split('/'):
        if n == '':
            continue
        i = int(n[:-1]) + BIP32_PRIME if n[-1] == "'" else int(n)
        parent_k = k
        k, c = CKD_priv(k, c, i)
        depth += 1

    _, parent_cK = get_pubkeys_from_secret(parent_k)
    fingerprint = hash_160(parent_cK)[0:4]
    child_number = ("%08X" % i).decode('hex')
    K, cK = get_pubkeys_from_secret(k)
    xprv = header_priv.decode('hex') + chr(depth) + fingerprint + child_number + c + chr(0) + k
    xpub = header_pub.decode('hex') + chr(depth) + fingerprint + child_number + c + cK
    return EncodeBase58Check(xprv), EncodeBase58Check(xpub)


def bip32_public_derivation(xpub, branch, sequence, testnet=False):
    header_pub, _ = _get_headers(testnet)
    depth, fingerprint, child_number, c, cK = deserialize_xkey(xpub)
    assert sequence.startswith(branch)
    sequence = sequence[len(branch):]
    for n in sequence.split('/'):
        if n == '':
            continue
        i = int(n)
        parent_cK = cK
        cK, c = CKD_pub(cK, c, i)
        depth += 1

    fingerprint = hash_160(parent_cK)[0:4]
    child_number = ("%08X" % i).decode('hex')
    xpub = header_pub.decode('hex') + chr(depth) + fingerprint + child_number + c + cK
    return EncodeBase58Check(xpub)


def bip32_private_key(sequence, k, chain):
    for i in sequence:
        k, chain = CKD_priv(k, chain, i)
    return SecretToASecret(k, True)