trezor-firmware/trezorlib/stellar.py

import base64
import struct
import xdrlib

from . import messages as proto

# Memo types
MEMO_TYPE_TEXT = 0
MEMO_TYPE_ID = 1
MEMO_TYPE_HASH = 2
MEMO_TYPE_RETURN = 4

# Asset types
ASSET_TYPE_NATIVE = 0
ASSET_TYPE_ALPHA4 = 1
ASSET_TYPE_ALPHA12 = 2

# Operations
OP_CREATE_ACCOUNT = 0
OP_PAYMENT = 1
OP_PATH_PAYMENT = 2
OP_MANAGE_OFFER = 3
OP_CREATE_PASSIVE_OFFER = 4
OP_SET_OPTIONS = 5
OP_CHANGE_TRUST = 6
OP_ALLOW_TRUST = 7
OP_ACCOUNT_MERGE = 8
OP_INFLATION = 9  # Included for documentation purposes, not supported by Trezor
OP_MANAGE_DATA = 10
OP_BUMP_SEQUENCE = 11


DEFAULT_BIP32_PATH = "m/44h/148h/0h"


def address_from_public_key(pk_bytes):
    """Returns the base32-encoded version of pk_bytes (G...)
    """
    final_bytes = bytearray()

    # version
    final_bytes.append(6 << 3)
    # public key
    final_bytes.extend(pk_bytes)
    # checksum
    final_bytes.extend(struct.pack("<H", _crc16_checksum(final_bytes)))

    return base64.b32encode(final_bytes)


def address_to_public_key(address_str):
    """Returns the raw 32 bytes representing a public key by extracting
    it from the G... string
    """
    decoded = base64.b32decode(address_str)

    # skip 0th byte (version) and last two bytes (checksum)
    return decoded[1:-2]


def parse_transaction_bytes(tx_bytes):
    """Parses base64data into a map with the following keys:
        tx - a StellarSignTx describing the transaction header
        operations - an array of protobuf message objects for each operation
    """
    tx = proto.StellarSignTx(
        protocol_version=1
    )
    unpacker = xdrlib.Unpacker(tx_bytes)

    tx.source_account = _xdr_read_address(unpacker)
    tx.fee = unpacker.unpack_uint()
    tx.sequence_number = unpacker.unpack_uhyper()

    # Timebounds is an optional field
    if unpacker.unpack_bool():
        max_timebound = 2**32 - 1  # max unsigned 32-bit int (trezor does not support the full 64-bit time value)
        tx.timebounds_start = unpacker.unpack_uhyper()
        tx.timebounds_end = unpacker.unpack_uhyper()

        if tx.timebounds_start > max_timebound or tx.timebounds_start < 0:
            raise ValueError("Starting timebound out of range (must be between 0 and " + max_timebound)
        if tx.timebounds_end > max_timebound or tx.timebounds_end < 0:
            raise ValueError("Ending timebound out of range (must be between 0 and " + max_timebound)

    # memo type determines what optional fields are set
    tx.memo_type = unpacker.unpack_uint()

    # text
    if tx.memo_type == MEMO_TYPE_HASH:
        tx.memo_text = unpacker.unpack_string()
    # id (64-bit uint)
    if tx.memo_type == MEMO_TYPE_ID:
        tx.memo_id = unpacker.unpack_uhyper()
    # hash / return are the same structure (32 bytes representing a hash)
    if tx.memo_type == MEMO_TYPE_HASH or tx.memo_type == MEMO_TYPE_RETURN:
        tx.memo_hash = unpacker.unpack_fopaque(32)

    tx.num_operations = unpacker.unpack_uint()

    operations = []
    for i in range(tx.num_operations):
        operations.append(_parse_operation_bytes(unpacker))

    return tx, operations


def _parse_operation_bytes(unpacker):
    """Returns a protobuf message representing the next operation as read from
    the byte stream in unpacker
    """

    # Check for and parse optional source account field
    source_account = None
    if unpacker.unpack_bool():
        source_account = unpacker.unpack_fopaque(32)

    # Operation type (See OP_ constants)
    type = unpacker.unpack_uint()

    if type == OP_CREATE_ACCOUNT:
        return proto.StellarCreateAccountOp(
            source_account=source_account,
            new_account=_xdr_read_address(unpacker),
            starting_balance=unpacker.unpack_hyper()
        )

    if type == OP_PAYMENT:
        return proto.StellarPaymentOp(
            source_account=source_account,
            destination_account=_xdr_read_address(unpacker),
            asset=_xdr_read_asset(unpacker),
            amount=unpacker.unpack_hyper()
        )

    if type == OP_PATH_PAYMENT:
        op = proto.StellarPathPaymentOp(
            source_account=source_account,
            send_asset=_xdr_read_asset(unpacker),
            send_max=unpacker.unpack_hyper(),
            destination_account=_xdr_read_address(unpacker),
            destination_asset=_xdr_read_asset(unpacker),
            paths=[]
        )

        num_paths = unpacker.unpack_uint()
        for i in range(num_paths):
            op.paths.append(_xdr_read_asset(unpacker))

        return op

    if type == OP_MANAGE_OFFER:
        return proto.StellarManageOfferOp(
            source_account=source_account,
            selling_asset=_xdr_read_asset(unpacker),
            buying_asset=_xdr_read_asset(unpacker),
            amount=unpacker.unpack_hyper(),
            price_n=unpacker.unpack_uint(),
            price_d=unpacker.unpack_uint(),
            offer_id=unpacker.unpack_uhyper()
        )

    if type == OP_CREATE_PASSIVE_OFFER:
        return proto.StellarCreatePassiveOfferOp(
            source_account=source_account,
            selling_asset=_xdr_read_asset(unpacker),
            buying_asset=_xdr_read_asset(unpacker),
            amount=unpacker.unpack_hyper(),
            price_n=unpacker.unpack_uint(),
            price_d=unpacker.unpack_uint()
        )

    if type == OP_SET_OPTIONS:
        op = proto.StellarSetOptionsOp(
            source_account=source_account
        )

        # Inflation destination
        if unpacker.unpack_bool():
            op.inflation_destination_account = _xdr_read_address(unpacker)

        # clear flags
        if unpacker.unpack_bool():
            op.clear_flags = unpacker.unpack_uint()

        # set flags
        if unpacker.unpack_bool():
            op.set_flags = unpacker.unpack_uint()

        # master weight
        if unpacker.unpack_bool():
            op.master_weight = unpacker.unpack_uint()

        # low threshold
        if unpacker.unpack_bool():
            op.low_threshold = unpacker.unpack_uint()

        # medium threshold
        if unpacker.unpack_bool():
            op.medium_threshold = unpacker.unpack_uint()

        # high threshold
        if unpacker.unpack_bool():
            op.high_threshold = unpacker.unpack_uint()

        # home domain
        if unpacker.unpack_bool():
            op.home_domain = unpacker.unpack_string()

        # signer
        if unpacker.unpack_bool():
            op.signer_type = unpacker.unpack_uint()
            op.signer_key = unpacker.unpack_fopaque(32)
            op.signer_weight = unpacker.unpack_uint()

        return op

    if type == OP_CHANGE_TRUST:
        return proto.StellarChangeTrustOp(
            source_account=source_account,
            asset=_xdr_read_asset(unpacker),
            limit=unpacker.unpack_uhyper()
        )

    if type == OP_ALLOW_TRUST:
        op = proto.StellarAllowTrustOp(
            source_account=source_account,
            trusted_account=_xdr_read_address(unpacker),
            asset_type=unpacker.unpack_uint()
        )

        if op.asset_type == ASSET_TYPE_ALPHA4:
            op.asset_code = unpacker.unpack_fstring(4)
        if op.asset_type == ASSET_TYPE_ALPHA12:
            op.asset_code = unpacker.unpack_fstring(12)

        op.is_authorized = unpacker.unpack_bool()

        return op

    if type == OP_ACCOUNT_MERGE:
        return proto.StellarAccountMergeOp(
            source_account=source_account,
            destination_account=_xdr_read_address(unpacker)
        )

    # Inflation is not implemented since anyone can submit this operation to the network

    if type == OP_MANAGE_DATA:
        op = proto.StellarManageDataOp(
            source_account=source_account,
            key=unpacker.unpack_string(),
        )

        # Only set value if the field is present
        if unpacker.unpack_bool():
            op.value = unpacker.unpack_opaque()

        return op

    # Bump Sequence
    # see: https://github.com/stellar/stellar-core/blob/master/src/xdr/Stellar-transaction.x#L269
    if type == OP_BUMP_SEQUENCE:
        return proto.StellarBumpSequenceOp(
            source_account=source_account,
            bump_to=unpacker.unpack_uhyper()
        )

    raise ValueError("Unknown operation type: " + type)


def _xdr_read_asset(unpacker):
    """Reads a stellar Asset from unpacker"""
    asset = proto.StellarAssetType(
        type=unpacker.unpack_uint()
    )

    if asset.type == ASSET_TYPE_ALPHA4:
        asset.code = unpacker.unpack_fstring(4)
        asset.issuer = _xdr_read_address(unpacker)

    if asset.type == ASSET_TYPE_ALPHA12:
        asset.code = unpacker.unpack_fstring(12)
        asset.issuer = _xdr_read_address(unpacker)

    return asset


def _xdr_read_address(unpacker):
    """Reads a stellar address and returns the 32-byte
    data representing the address
    """
    # First 4 bytes are the address type
    address_type = unpacker.unpack_uint()
    if address_type != 0:
        raise ValueError("Unsupported address type")

    return unpacker.unpack_fopaque(32)


def _crc16_checksum(bytes):
    """Returns the CRC-16 checksum of bytearray bytes

    Ported from Java implementation at: http://introcs.cs.princeton.edu/java/61data/CRC16CCITT.java.html

    Initial value changed to 0x0000 to match Stellar configuration.
    """
    crc = 0x0000
    polynomial = 0x1021

    for byte in bytes:
        for i in range(8):
            bit = ((byte >> (7 - i) & 1) == 1)
            c15 = ((crc >> 15 & 1) == 1)
            crc <<= 1
            if c15 ^ bit:
                crc ^= polynomial

    return crc & 0xffff