Handshake Ledger app

Hardware-wallet app for Handshake (HNS). Derives Handshake addresses and signs
Handshake transactions, including name-auction covenants, on Ledger Stax, Flex,
Nano S+, Nano X and Apex+.

The design premise is that the host computer is untrusted: every APDU byte is
attacker-controlled, and the device's job is to be correct when the host lies.
Two failures outrank all others, and the code is shaped around them.

Signing something other than what the user approved. Any field the signature
commits to and the host can vary has to appear on the review screen, and
anything the screen cannot represent honestly is refused rather than shown under
a label that does not describe it. So the device signs SIGHASH_ALL only,
checked per input rather than once for the session; it displays a TRANSFER
covenant's destination, which decides who ends up owning the name and appears
nowhere else in the output; it shows a covenant's name hash when the plaintext
name cannot be verified against it; and it refuses covenant kinds it cannot
name, outputs whose values exceed their inputs, and declared input totals that
would overflow the fee arithmetic.

Misusing key material. Derivation paths are constrained to
m/44'/{5353..5356}'/account'[/change/index] in the app itself, not only by the
install manifest, because BOLOS terminates the app on an out-of-whitelist path
instead of returning an error. One coin type per signing session, since the
review renders every address under a single HRP.

Panics count too: set_panic!(exiting_panic) means a panic kills the app and
strands the session, so nothing unwraps on host-derived data and the session
ceilings are sized to the configured heap.

Consensus follows shd, the Swift Handshake node, which is the reference for the
sighash preimage, covenant item layouts and address encoding.

SIGN_TX is a PSBT-style state machine driven by P1 (BEGIN / ADD_INPUT /
ADD_OUTPUT / REVIEW / SIGN_INPUT): the host streams the transaction as
structured records, the device accumulates its own view of the values, shows one
review, then signs each input on demand.

Tests run under speculos in a container (./scripts/test), 66 of them, green on
all five devices. test_sign_tx_policy.py covers each refusal above and needs no
golden snapshots because every case is rejected before anything is drawn; the
snapshots that do exist are the record of what the user sees before approving.
tests/application_client/handshake_sighash.py is a deliberately independent
reimplementation of the sighash, used to verify real signatures.

Status: v0.1, pre-audit. Not for mainnet keys. Signing has not yet been
exercised on physical hardware.

Forked from LedgerHQ/app-boilerplate-rust (Apache-2.0).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/application_client/handshake_command_sender.py

@@ -0,0 +1,150 @@
+"""APDU client for the Handshake Ledger app.
+
+Speaks the protocol the app actually implements: `SIGN_TX` is a state machine
+selected by P1 (BEGIN / ADD_INPUT / ADD_OUTPUT / REVIEW / SIGN_INPUT), not the
+chunked single-shot flow the Ledger boilerplate uses. See
+`src/handlers/sign_tx.rs` and `scripts/sign-tx`.
+"""
+
+from contextlib import contextmanager
+from enum import IntEnum
+from typing import Generator, List, Optional
+
+from ragger.backend.interface import BackendInterface, RAPDU
+from ragger.bip import pack_derivation_path
+
+CLA: int = 0xE0
+
+#: Data bytes per APDU. ADD_OUTPUT payloads above this are chunked with P2_MORE.
+MAX_APDU_DATA: int = 240
+
+
+class InsType(IntEnum):
+    GET_VERSION = 0x03
+    GET_APP_NAME = 0x04
+    GET_PUBLIC_KEY = 0x05
+    SIGN_TX = 0x06
+    SIGN_MESSAGE = 0x07
+
+
+class P1(IntEnum):
+    NONE = 0x00
+    #: GET_PUBLIC_KEY: show the address on-device before replying.
+    CONFIRM = 0x01
+    #: SIGN_TX sub-ops.
+    SIGN_BEGIN = 0x00
+    SIGN_ADD_INPUT = 0x01
+    SIGN_ADD_OUTPUT = 0x02
+    SIGN_REVIEW = 0x03
+    SIGN_INPUT = 0x04
+
+
+class P2(IntEnum):
+    LAST = 0x00
+    MORE = 0x80
+
+
+class Errors(IntEnum):
+    """Mirrors `AppSW` in src/main.rs."""
+
+    SW_DENY = 0x6985
+    SW_WRONG_P1P2 = 0x6A86
+    SW_WRONG_STATE = 0x6B00
+    SW_INS_NOT_SUPPORTED = 0x6D00
+    SW_CLA_NOT_SUPPORTED = 0x6E00
+    SW_COMM_ERROR = 0x6F00
+    SW_TX_DISPLAY_FAIL = 0xB001
+    SW_ADDR_DISPLAY_FAIL = 0xB002
+    SW_TX_WRONG_LENGTH = 0xB004
+    SW_TX_PARSING_FAIL = 0xB005
+    SW_TX_HASH_FAIL = 0xB006
+    SW_TX_SIGN_FAIL = 0xB008
+    SW_KEY_DERIVE_FAIL = 0xB009
+    SW_VERSION_PARSING_FAIL = 0xB00A
+    SW_BAD_DERIVATION_PATH = 0xB00B
+    SW_SWAP_FAIL = 0xC000
+
+
+def split_message(message: bytes, max_size: int) -> List[bytes]:
+    return [message[x:x + max_size] for x in range(0, len(message), max_size)]
+
+
+class HandshakeCommandSender:
+    def __init__(self, backend: BackendInterface) -> None:
+        self.backend = backend
+
+    # ── Simple queries ─────────────────────────────────────────────────────
+
+    def get_version(self) -> RAPDU:
+        return self.backend.exchange(cla=CLA, ins=InsType.GET_VERSION,
+                                     p1=P1.NONE, p2=P2.LAST, data=b"")
+
+    def get_app_name(self) -> RAPDU:
+        return self.backend.exchange(cla=CLA, ins=InsType.GET_APP_NAME,
+                                     p1=P1.NONE, p2=P2.LAST, data=b"")
+
+    def get_public_key(self, path: str) -> RAPDU:
+        return self.backend.exchange(cla=CLA, ins=InsType.GET_PUBLIC_KEY,
+                                     p1=P1.NONE, p2=P2.LAST,
+                                     data=pack_derivation_path(path))
+
+    @contextmanager
+    def get_public_key_with_confirmation(self, path: str) -> Generator[None, None, None]:
+        with self.backend.exchange_async(cla=CLA, ins=InsType.GET_PUBLIC_KEY,
+                                         p1=P1.CONFIRM, p2=P2.LAST,
+                                         data=pack_derivation_path(path)) as response:
+            yield response
+
+    # ── SIGN_TX state machine ──────────────────────────────────────────────
+
+    def sign_tx_begin(self, payload: bytes) -> RAPDU:
+        return self.backend.exchange(cla=CLA, ins=InsType.SIGN_TX,
+                                     p1=P1.SIGN_BEGIN, p2=P2.LAST, data=payload)
+
+    def sign_tx_add_input(self, payload: bytes) -> RAPDU:
+        return self.backend.exchange(cla=CLA, ins=InsType.SIGN_TX,
+                                     p1=P1.SIGN_ADD_INPUT, p2=P2.LAST, data=payload)
+
+    def sign_tx_add_output(self, payload: bytes) -> RAPDU:
+        """Send one output, chunking it across APDUs if needed."""
+        chunks = split_message(payload, MAX_APDU_DATA) or [b""]
+        rapdu = None
+        for i, chunk in enumerate(chunks):
+            p2 = P2.LAST if i == len(chunks) - 1 else P2.MORE
+            rapdu = self.backend.exchange(cla=CLA, ins=InsType.SIGN_TX,
+                                          p1=P1.SIGN_ADD_OUTPUT, p2=p2, data=chunk)
+        return rapdu
+
+    def sign_tx_review_sync(self) -> RAPDU:
+        """REVIEW without a navigator: only for cases the device rejects
+        before it puts anything on screen."""
+        return self.backend.exchange(cla=CLA, ins=InsType.SIGN_TX,
+                                     p1=P1.SIGN_REVIEW, p2=P2.LAST, data=b"")
+
+    @contextmanager
+    def sign_tx_review(self) -> Generator[None, None, None]:
+        """REVIEW: blocks on the user, so the caller drives the navigator."""
+        with self.backend.exchange_async(cla=CLA, ins=InsType.SIGN_TX,
+                                         p1=P1.SIGN_REVIEW, p2=P2.LAST,
+                                         data=b"") as response:
+            yield response
+
+    def sign_tx_input(self, index: int) -> RAPDU:
+        return self.backend.exchange(cla=CLA, ins=InsType.SIGN_TX,
+                                     p1=P1.SIGN_INPUT, p2=P2.LAST,
+                                     data=index.to_bytes(4, "big"))
+
+    # ── SIGN_MESSAGE ───────────────────────────────────────────────────────
+
+    @contextmanager
+    def sign_message(self, path: str, message: bytes) -> Generator[None, None, None]:
+        payload = (pack_derivation_path(path)
+                   + len(message).to_bytes(2, "little")
+                   + message)
+        with self.backend.exchange_async(cla=CLA, ins=InsType.SIGN_MESSAGE,
+                                         p1=P1.NONE, p2=P2.LAST,
+                                         data=payload) as response:
+            yield response
+
+    def get_async_response(self) -> Optional[RAPDU]:
+        return self.backend.last_async_response