addresses.py

"""
Operations with addresses
"""
# pylint: disable=inconsistent-return-statements

import logging
from binascii import hexlify, unhexlify
from struct import pack, unpack

try:
    from highlevelcrypto import double_sha512
except ImportError:
    from .highlevelcrypto import double_sha512


logger = logging.getLogger('default')

ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"


def encodeBase58(num):
    """Encode a number in Base X

    Args:
      num: The number to encode
      alphabet: The alphabet to use for encoding
    """
    if num < 0:
        return None
    if num == 0:
        return ALPHABET[0]
    arr = []
    base = len(ALPHABET)
    while num:
        num, rem = divmod(num, base)
        arr.append(ALPHABET[rem])
    arr.reverse()
    return ''.join(arr)


def decodeBase58(string):
    """Decode a Base X encoded string into the number

    Args:
      string: The encoded string
      alphabet: The alphabet to use for encoding
    """
    base = len(ALPHABET)
    num = 0

    try:
        for char in string:
            num *= base
            num += ALPHABET.index(char)
    except ValueError:
        # character not found (like a space character or a 0)
        return 0
    return num


class varintEncodeError(Exception):
    """Exception class for encoding varint"""
    pass


class varintDecodeError(Exception):
    """Exception class for decoding varint data"""
    pass


def encodeVarint(integer):
    """Convert integer into varint bytes"""
    if integer < 0:
        raise varintEncodeError('varint cannot be < 0')
    if integer < 253:
        return pack('>B', integer)
    if integer >= 253 and integer < 65536:
        return pack('>B', 253) + pack('>H', integer)
    if integer >= 65536 and integer < 4294967296:
        return pack('>B', 254) + pack('>I', integer)
    if integer >= 4294967296 and integer < 18446744073709551616:
        return pack('>B', 255) + pack('>Q', integer)
    if integer >= 18446744073709551616:
        raise varintEncodeError('varint cannot be >= 18446744073709551616')


def decodeVarint(data):
    """
    Decodes an encoded varint to an integer and returns it.
    Per protocol v3, the encoded value must be encoded with
    the minimum amount of data possible or else it is malformed.
    Returns a tuple: (theEncodedValue, theSizeOfTheVarintInBytes)
    """

    if not data:
        return (0, 0)
    firstByte, = unpack('>B', data[0:1])
    if firstByte < 253:
        # encodes 0 to 252
        return (firstByte, 1)  # the 1 is the length of the varint
    if firstByte == 253:
        # encodes 253 to 65535
        if len(data) < 3:
            raise varintDecodeError(
                'The first byte of this varint as an integer is %s'
                ' but the total length is only %s. It needs to be'
                ' at least 3.' % (firstByte, len(data)))
        encodedValue, = unpack('>H', data[1:3])
        if encodedValue < 253:
            raise varintDecodeError(
                'This varint does not encode the value with the lowest'
                ' possible number of bytes.')
        return (encodedValue, 3)
    if firstByte == 254:
        # encodes 65536 to 4294967295
        if len(data) < 5:
            raise varintDecodeError(
                'The first byte of this varint as an integer is %s'
                ' but the total length is only %s. It needs to be'
                ' at least 5.' % (firstByte, len(data)))
        encodedValue, = unpack('>I', data[1:5])
        if encodedValue < 65536:
            raise varintDecodeError(
                'This varint does not encode the value with the lowest'
                ' possible number of bytes.')
        return (encodedValue, 5)
    if firstByte == 255:
        # encodes 4294967296 to 18446744073709551615
        if len(data) < 9:
            raise varintDecodeError(
                'The first byte of this varint as an integer is %s'
                ' but the total length is only %s. It needs to be'
                ' at least 9.' % (firstByte, len(data)))
        encodedValue, = unpack('>Q', data[1:9])
        if encodedValue < 4294967296:
            raise varintDecodeError(
                'This varint does not encode the value with the lowest'
                ' possible number of bytes.')
        return (encodedValue, 9)


def encodeAddress(version, stream, ripe):
    """Convert ripe to address"""
    if version >= 2 and version < 4:
        if len(ripe) != 20:
            raise Exception(
                'Programming error in encodeAddress: The length of'
                ' a given ripe hash was not 20.'
            )

        if ripe[:2] == b'\x00\x00':
            ripe = ripe[2:]
        elif ripe[:1] == b'\x00':
            ripe = ripe[1:]
    elif version == 4:
        if len(ripe) != 20:
            raise Exception(
                'Programming error in encodeAddress: The length of'
                ' a given ripe hash was not 20.')
        ripe = ripe.lstrip(b'\x00')

    storedBinaryData = encodeVarint(version) + encodeVarint(stream) + ripe

    # Generate the checksum
    checksum = double_sha512(storedBinaryData)[0:4]

    # FIXME: encodeBase58 should take binary data, to reduce conversions
    # encodeBase58(storedBinaryData + checksum)
    asInt = int(hexlify(storedBinaryData) + hexlify(checksum), 16)
    # should it be str? If yes, it should be everywhere in the code
    return 'BM-' + encodeBase58(asInt)


def decodeAddress(address):
    """
    returns (status, address version number, stream number,
    data (almost certainly a ripe hash))
    """
    # pylint: disable=too-many-return-statements,too-many-statements
    # pylint: disable=too-many-branches

    address = str(address).strip()

    if address[:3] == 'BM-':
        integer = decodeBase58(address[3:])
    else:
        integer = decodeBase58(address)
    if integer == 0:
        status = 'invalidcharacters'
        return status, 0, 0, ''
    # after converting to hex, the string will be prepended
    # with a 0x and appended with a L in python2
    hexdata = hex(integer)[2:].rstrip('L')

    if len(hexdata) % 2 != 0:
        hexdata = '0' + hexdata

    data = unhexlify(hexdata)
    checksum = data[-4:]

    if checksum != double_sha512(data[:-4])[0:4]:
        status = 'checksumfailed'
        return status, 0, 0, ''

    try:
        addressVersionNumber, bytesUsedByVersionNumber = decodeVarint(data[:9])
    except varintDecodeError as e:
        logger.error(str(e))
        status = 'varintmalformed'
        return status, 0, 0, ''

    if addressVersionNumber > 4:
        logger.error('cannot decode address version numbers this high')
        status = 'versiontoohigh'
        return status, 0, 0, ''
    elif addressVersionNumber == 0:
        logger.error('cannot decode address version numbers of zero.')
        status = 'versiontoohigh'
        return status, 0, 0, ''

    try:
        streamNumber, bytesUsedByStreamNumber = \
            decodeVarint(data[bytesUsedByVersionNumber:])
    except varintDecodeError as e:
        logger.error(str(e))
        status = 'varintmalformed'
        return status, 0, 0, ''

    status = 'success'
    if addressVersionNumber == 1:
        return status, addressVersionNumber, streamNumber, data[-24:-4]
    elif addressVersionNumber == 2 or addressVersionNumber == 3:
        embeddedRipeData = \
            data[bytesUsedByVersionNumber + bytesUsedByStreamNumber:-4]
        if len(embeddedRipeData) == 19:
            return status, addressVersionNumber, streamNumber, \
                b'\x00' + embeddedRipeData
        elif len(embeddedRipeData) == 20:
            return status, addressVersionNumber, streamNumber, \
                embeddedRipeData
        elif len(embeddedRipeData) == 18:
            return status, addressVersionNumber, streamNumber, \
                b'\x00\x00' + embeddedRipeData
        elif len(embeddedRipeData) < 18:
            return 'ripetooshort', 0, 0, ''
        elif len(embeddedRipeData) > 20:
            return 'ripetoolong', 0, 0, ''
        return 'otherproblem', 0, 0, ''
    elif addressVersionNumber == 4:
        embeddedRipeData = \
            data[bytesUsedByVersionNumber + bytesUsedByStreamNumber:-4]
        if embeddedRipeData[0:1] == b'\x00':
            # In order to enforce address non-malleability, encoded
            # RIPE data must have NULL bytes removed from the front
            return 'encodingproblem', 0, 0, ''
        elif len(embeddedRipeData) > 20:
            return 'ripetoolong', 0, 0, ''
        elif len(embeddedRipeData) < 4:
            return 'ripetooshort', 0, 0, ''
        x00string = b'\x00' * (20 - len(embeddedRipeData))
        return status, addressVersionNumber, streamNumber, \
            x00string + embeddedRipeData


def addBMIfNotPresent(address):
    """Prepend BM- to an address if it doesn't already have it"""
    address = str(address).strip()
    return address if address[:3] == 'BM-' else 'BM-' + address