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436 lines
14 KiB
436 lines
14 KiB
# This file is part of the Trezor project.
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#
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# Copyright (C) 2012-2018 SatoshiLabs and contributors
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#
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# This library is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License version 3
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# as published by the Free Software Foundation.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser General Public License for more details.
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#
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# You should have received a copy of the License along with this library.
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# If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
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import hashlib
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from enum import Enum
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from typing import Callable, List, NewType, Tuple
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import construct as c
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import ecdsa
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import pyblake2
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from . import cosi, messages, tools
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V1_SIGNATURE_SLOTS = 3
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V1_BOOTLOADER_KEYS = {
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1: "04d571b7f148c5e4232c3814f777d8faeaf1a84216c78d569b71041ffc768a5b2d810fc3bb134dd026b57e65005275aedef43e155f48fc11a32ec790a93312bd58",
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2: "0463279c0c0866e50c05c799d32bd6bab0188b6de06536d1109d2ed9ce76cb335c490e55aee10cc901215132e853097d5432eda06b792073bd7740c94ce4516cb1",
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3: "0443aedbb6f7e71c563f8ed2ef64ec9981482519e7ef4f4aa98b27854e8c49126d4956d300ab45fdc34cd26bc8710de0a31dbdf6de7435fd0b492be70ac75fde58",
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4: "04877c39fd7c62237e038235e9c075dab261630f78eeb8edb92487159fffedfdf6046c6f8b881fa407c4a4ce6c28de0b19c1f4e29f1fcbc5a58ffd1432a3e0938a",
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5: "047384c51ae81add0a523adbb186c91b906ffb64c2c765802bf26dbd13bdf12c319e80c2213a136c8ee03d7874fd22b70d68e7dee469decfbbb510ee9a460cda45",
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}
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V2_BOOTLOADER_KEYS = [
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bytes.fromhex("c2c87a49c5a3460977fbb2ec9dfe60f06bd694db8244bd4981fe3b7a26307f3f"),
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bytes.fromhex("80d036b08739b846f4cb77593078deb25dc9487aedcf52e30b4fb7cd7024178a"),
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bytes.fromhex("b8307a71f552c60a4cbb317ff48b82cdbf6b6bb5f04c920fec7badf017883751"),
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]
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V2_BOOTLOADER_M = 2
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V2_BOOTLOADER_N = 3
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ONEV2_CHUNK_SIZE = 1024 * 64
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V2_CHUNK_SIZE = 1024 * 128
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def _transform_vendor_trust(data: bytes) -> bytes:
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"""Byte-swap and bit-invert the VendorTrust field.
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Vendor trust is interpreted as a bitmask in a 16-bit little-endian integer,
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with the added twist that 0 means set and 1 means unset.
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We feed it to a `BitStruct` that expects a big-endian sequence where bits have
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the traditional meaning. We must therefore do a bitwise negation of each byte,
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and return them in reverse order. This is the same transformation both ways,
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fortunately, so we don't need two separate functions.
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"""
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return bytes(~b & 0xFF for b in data)[::-1]
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class FirmwareIntegrityError(Exception):
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pass
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class InvalidSignatureError(FirmwareIntegrityError):
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pass
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class Unsigned(FirmwareIntegrityError):
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pass
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# fmt: off
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Toif = c.Struct(
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"magic" / c.Const(b"TOI"),
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"format" / c.Enum(c.Byte, full_color=b"f", grayscale=b"g"),
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"width" / c.Int16ul,
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"height" / c.Int16ul,
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"data" / c.Prefixed(c.Int32ul, c.GreedyBytes),
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)
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VendorTrust = c.Transformed(c.BitStruct(
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"reserved" / c.Default(c.BitsInteger(9), 0),
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"show_vendor_string" / c.Flag,
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"require_user_click" / c.Flag,
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"red_background" / c.Flag,
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"delay" / c.BitsInteger(4),
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), _transform_vendor_trust, 2, _transform_vendor_trust, 2)
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VendorHeader = c.Struct(
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"_start_offset" / c.Tell,
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"magic" / c.Const(b"TRZV"),
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"_header_len" / c.Padding(4),
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"expiry" / c.Int32ul,
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"version" / c.Struct(
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"major" / c.Int8ul,
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"minor" / c.Int8ul,
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),
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"vendor_sigs_required" / c.Int8ul,
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"vendor_sigs_n" / c.Rebuild(c.Int8ul, c.len_(c.this.pubkeys)),
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"vendor_trust" / VendorTrust,
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"reserved" / c.Padding(14),
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"pubkeys" / c.Bytes(32)[c.this.vendor_sigs_n],
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"vendor_string" / c.Aligned(4, c.PascalString(c.Int8ul, "utf-8")),
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"vendor_image" / Toif,
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"_data_end_offset" / c.Tell,
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c.Padding(-(c.this._data_end_offset + 65) % 512),
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"sigmask" / c.Byte,
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"signature" / c.Bytes(64),
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"_end_offset" / c.Tell,
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"header_len" / c.Pointer(
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c.this._start_offset + 4,
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c.Rebuild(c.Int32ul, c.this._end_offset - c.this._start_offset)
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),
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)
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VersionLong = c.Struct(
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"major" / c.Int8ul,
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"minor" / c.Int8ul,
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"patch" / c.Int8ul,
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"build" / c.Int8ul,
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)
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FirmwareHeader = c.Struct(
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"_start_offset" / c.Tell,
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"magic" / c.Const(b"TRZF"),
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"header_len" / c.Int32ul,
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"expiry" / c.Int32ul,
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"code_length" / c.Rebuild(
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c.Int32ul,
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lambda this:
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len(this._.code) if "code" in this._
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else (this.code_length or 0)
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),
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"version" / VersionLong,
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"fix_version" / VersionLong,
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"reserved" / c.Padding(8),
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"hashes" / c.Bytes(32)[16],
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"v1_signatures" / c.Bytes(64)[V1_SIGNATURE_SLOTS],
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"v1_key_indexes" / c.Int8ul[V1_SIGNATURE_SLOTS], # pylint: disable=E1136
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"reserved" / c.Padding(220),
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"sigmask" / c.Byte,
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"signature" / c.Bytes(64),
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"_end_offset" / c.Tell,
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"_rebuild_header_len" / c.If(
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c.this.version.major > 1,
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c.Pointer(
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c.this._start_offset + 4,
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c.Rebuild(c.Int32ul, c.this._end_offset - c.this._start_offset)
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),
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),
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)
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Firmware = c.Struct(
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"vendor_header" / VendorHeader,
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"firmware_header" / FirmwareHeader,
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"_code_offset" / c.Tell,
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"code" / c.Bytes(c.this.firmware_header.code_length),
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c.Terminated,
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)
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FirmwareOneV2 = c.Struct(
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"firmware_header" / FirmwareHeader,
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"_code_offset" / c.Tell,
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"code" / c.Bytes(c.this.firmware_header.code_length),
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c.Terminated,
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)
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FirmwareOne = c.Struct(
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"magic" / c.Const(b"TRZR"),
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"code_length" / c.Rebuild(c.Int32ul, c.len_(c.this.code)),
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"key_indexes" / c.Int8ul[V1_SIGNATURE_SLOTS], # pylint: disable=E1136
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"flags" / c.BitStruct(
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c.Padding(7),
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"restore_storage" / c.Flag,
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),
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"reserved" / c.Padding(52),
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"signatures" / c.Bytes(64)[V1_SIGNATURE_SLOTS],
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"code" / c.Bytes(c.this.code_length),
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c.Terminated,
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"embedded_onev2" / c.RestreamData(c.this.code, c.Optional(FirmwareOneV2)),
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)
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# fmt: on
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class FirmwareFormat(Enum):
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TREZOR_ONE = 1
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TREZOR_T = 2
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TREZOR_ONE_V2 = 3
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FirmwareType = NewType("FirmwareType", c.Container)
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ParsedFirmware = Tuple[FirmwareFormat, FirmwareType]
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def parse(data: bytes) -> ParsedFirmware:
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if data[:4] == b"TRZR":
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version = FirmwareFormat.TREZOR_ONE
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cls = FirmwareOne
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elif data[:4] == b"TRZV":
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version = FirmwareFormat.TREZOR_T
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cls = Firmware
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elif data[:4] == b"TRZF":
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version = FirmwareFormat.TREZOR_ONE_V2
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cls = FirmwareOneV2
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else:
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raise ValueError("Unrecognized firmware image type")
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try:
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fw = cls.parse(data)
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except Exception as e:
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raise FirmwareIntegrityError("Invalid firmware image") from e
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return version, FirmwareType(fw)
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def digest_onev1(fw: FirmwareType) -> bytes:
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return hashlib.sha256(fw.code).digest()
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def check_sig_v1(
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digest: bytes, key_indexes: List[int], signatures: List[bytes]
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) -> None:
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distinct_key_indexes = set(i for i in key_indexes if i != 0)
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if not distinct_key_indexes:
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raise Unsigned
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if len(distinct_key_indexes) < len(key_indexes):
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raise InvalidSignatureError(
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"Not enough distinct signatures (found {}, need {})".format(
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len(distinct_key_indexes), len(key_indexes)
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)
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)
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for i in range(len(key_indexes)):
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key_idx = key_indexes[i]
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signature = signatures[i]
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if key_idx not in V1_BOOTLOADER_KEYS:
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# unknown pubkey
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raise InvalidSignatureError("Unknown key in slot {}".format(i))
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pubkey = bytes.fromhex(V1_BOOTLOADER_KEYS[key_idx])[1:]
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verify = ecdsa.VerifyingKey.from_string(pubkey, curve=ecdsa.curves.SECP256k1)
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try:
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verify.verify_digest(signature, digest)
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except ecdsa.BadSignatureError as e:
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raise InvalidSignatureError("Invalid signature in slot {}".format(i)) from e
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def _header_digest(
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header: c.Container,
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header_type: c.Construct,
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hash_function: Callable = pyblake2.blake2s,
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) -> bytes:
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stripped_header = header.copy()
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stripped_header.sigmask = 0
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stripped_header.signature = b"\0" * 64
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stripped_header.v1_key_indexes = [0, 0, 0]
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stripped_header.v1_signatures = [b"\0" * 64] * 3
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header_bytes = header_type.build(stripped_header)
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return hash_function(header_bytes).digest()
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def digest_v2(fw: FirmwareType) -> bytes:
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return _header_digest(fw.firmware_header, FirmwareHeader, pyblake2.blake2s)
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def digest_onev2(fw: FirmwareType) -> bytes:
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return _header_digest(fw.firmware_header, FirmwareHeader, hashlib.sha256)
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def validate_code_hashes(
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fw: FirmwareType,
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hash_function: Callable = pyblake2.blake2s,
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chunk_size: int = V2_CHUNK_SIZE,
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padding_byte: bytes = None,
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) -> None:
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for i, expected_hash in enumerate(fw.firmware_header.hashes):
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if i == 0:
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# Because first chunk is sent along with headers, there is less code in it.
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chunk = fw.code[: chunk_size - fw._code_offset]
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else:
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# Subsequent chunks are shifted by the "missing header" size.
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ptr = i * chunk_size - fw._code_offset
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chunk = fw.code[ptr : ptr + chunk_size]
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# padding for last chunk
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if padding_byte is not None and i > 1 and chunk and len(chunk) < chunk_size:
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chunk += padding_byte[0:1] * (chunk_size - len(chunk))
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if not chunk and expected_hash == b"\0" * 32:
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continue
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chunk_hash = hash_function(chunk).digest()
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if chunk_hash != expected_hash:
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raise FirmwareIntegrityError("Invalid firmware data.")
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def validate_onev2(fw: FirmwareType, allow_unsigned: bool = False) -> None:
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try:
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check_sig_v1(
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digest_onev2(fw),
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fw.firmware_header.v1_key_indexes,
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fw.firmware_header.v1_signatures,
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)
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except Unsigned:
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if not allow_unsigned:
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raise
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validate_code_hashes(
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fw,
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hash_function=hashlib.sha256,
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chunk_size=ONEV2_CHUNK_SIZE,
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padding_byte=b"\xFF",
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)
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def validate_onev1(fw: FirmwareType, allow_unsigned: bool = False) -> None:
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try:
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check_sig_v1(digest_onev1(fw), fw.key_indexes, fw.signatures)
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except Unsigned:
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if not allow_unsigned:
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raise
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if fw.embedded_onev2:
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validate_onev2(fw.embedded_onev2, allow_unsigned)
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def validate_v2(fw: FirmwareType, skip_vendor_header: bool = False) -> None:
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vendor_fingerprint = _header_digest(fw.vendor_header, VendorHeader)
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fingerprint = digest_v2(fw)
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if not skip_vendor_header:
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try:
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# if you want to validate a custom vendor header, you can modify
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# the global variables to match your keys and m-of-n scheme
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cosi.verify_m_of_n(
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fw.vendor_header.signature,
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vendor_fingerprint,
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V2_BOOTLOADER_M,
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V2_BOOTLOADER_N,
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fw.vendor_header.sigmask,
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V2_BOOTLOADER_KEYS,
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)
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except Exception:
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raise InvalidSignatureError("Invalid vendor header signature.")
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# XXX expiry is not used now
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# now = time.gmtime()
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# if time.gmtime(fw.vendor_header.expiry) < now:
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# raise ValueError("Vendor header expired.")
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try:
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cosi.verify_m_of_n(
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fw.firmware_header.signature,
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fingerprint,
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fw.vendor_header.vendor_sigs_required,
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fw.vendor_header.vendor_sigs_n,
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fw.firmware_header.sigmask,
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fw.vendor_header.pubkeys,
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)
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except Exception:
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raise InvalidSignatureError("Invalid firmware signature.")
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# XXX expiry is not used now
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# if time.gmtime(fw.firmware_header.expiry) < now:
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# raise ValueError("Firmware header expired.")
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validate_code_hashes(fw)
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def digest(version: FirmwareFormat, fw: FirmwareType) -> bytes:
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if version == FirmwareFormat.TREZOR_ONE:
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return digest_onev1(fw)
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elif version == FirmwareFormat.TREZOR_ONE_V2:
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return digest_onev2(fw)
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elif version == FirmwareFormat.TREZOR_T:
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return digest_v2(fw)
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else:
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raise ValueError("Unrecognized firmware version")
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def validate(
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version: FirmwareFormat, fw: FirmwareType, allow_unsigned: bool = False
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) -> None:
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if version == FirmwareFormat.TREZOR_ONE:
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return validate_onev1(fw, allow_unsigned)
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elif version == FirmwareFormat.TREZOR_ONE_V2:
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return validate_onev2(fw, allow_unsigned)
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elif version == FirmwareFormat.TREZOR_T:
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return validate_v2(fw)
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else:
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raise ValueError("Unrecognized firmware version")
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# ====== Client functions ====== #
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@tools.session
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def update(client, data):
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if client.features.bootloader_mode is False:
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raise RuntimeError("Device must be in bootloader mode")
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resp = client.call(messages.FirmwareErase(length=len(data)))
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# TREZORv1 method
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if isinstance(resp, messages.Success):
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resp = client.call(messages.FirmwareUpload(payload=data))
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if isinstance(resp, messages.Success):
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return
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else:
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raise RuntimeError("Unexpected result %s" % resp)
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# TREZORv2 method
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while isinstance(resp, messages.FirmwareRequest):
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payload = data[resp.offset : resp.offset + resp.length]
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digest = pyblake2.blake2s(payload).digest()
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resp = client.call(messages.FirmwareUpload(payload=payload, hash=digest))
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if isinstance(resp, messages.Success):
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return
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else:
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raise RuntimeError("Unexpected message %s" % resp)
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