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>

scripts/sign-tx

@@ -0,0 +1,218 @@
+#!/usr/bin/env python3
+"""End-to-end SIGN_TX driver for the PSBT-style state machine (INS 0x06).
+
+Streams an unsigned Handshake tx to the Ledger app as structured sub-ops
+(BEGIN / ADD_INPUT / ADD_OUTPUT / REVIEW / SIGN_INPUT), then assembles the
+signed tx with one witness per input.
+
+Usage:
+  ./scripts/sign-tx \
+    --path "44'/5353'/0'/0/0" \
+    --input 865d9e8011815fbfeb168bff83767f039cd6ac71bd75893d74fb89a3d932322d:0:10000000 \
+    --output hs1qdydhjsla4ahvy5tn6w44ax7y62mpsd5ny4jlej:9999000
+
+Amounts are in dollarydoos. 1 HNS = 1,000,000 dollarydoos.
+Exit code 0 = signed; nonzero = error or device rejection.
+"""
+import argparse
+import sys
+
+import bech32  # type: ignore[import-untyped]
+from ledgerwallet.transport import enumerate_devices
+
+CLA = 0xE0
+INS_GET_PUBKEY = 0x05
+INS_SIGN_TX = 0x06
+
+P1_BEGIN = 0x00
+P1_ADD_INPUT = 0x01
+P1_ADD_OUTPUT = 0x02
+P1_REVIEW = 0x03
+P1_SIGN_INPUT = 0x04
+
+P2_LAST = 0x00
+P2_MORE = 0x80
+
+SCRIPT_KIND_P2WPKH = 0x00
+MAX_DATA = 240
+
+HRP = {"main": "hs", "testnet": "ts", "regtest": "rs", "simnet": "ss"}
+
+
+def open_device():
+    devs = enumerate_devices()
+    if not devs:
+        print("no Ledger device found", file=sys.stderr)
+        sys.exit(1)
+    t = devs[0]
+    t.open()
+    return t
+
+
+def parse_path(s: str) -> bytes:
+    """`count(1) || components[count](BE u32, hardened bit set on quoted parts)`."""
+    parts = [p for p in s.lstrip("m/").split("/") if p]
+    out = bytearray([len(parts)])
+    for p in parts:
+        n = int(p.rstrip("'"))
+        if p.endswith("'"):
+            n |= 0x80000000
+        out.extend(n.to_bytes(4, "big"))
+    return bytes(out)
+
+
+def encode_varint(n: int) -> bytes:
+    if n < 0xFD:
+        return bytes([n])
+    if n <= 0xFFFF:
+        return b"\xfd" + n.to_bytes(2, "little")
+    if n <= 0xFFFFFFFF:
+        return b"\xfe" + n.to_bytes(4, "little")
+    return b"\xff" + n.to_bytes(8, "little")
+
+
+def apdu(ins: int, p1: int, p2: int, data: bytes) -> bytes:
+    if len(data) > 255:
+        raise RuntimeError(f"APDU data too long: {len(data)}")
+    return bytes([CLA, ins, p1, p2, len(data)]) + data
+
+
+def exchange(t, apdu_bytes: bytes, timeout_ms: int = 120000) -> bytes:
+    """Same convention as scripts/send-apdu: transport returns data || sw."""
+    print(f"-> {apdu_bytes.hex().upper()}", file=sys.stderr)
+    response = t.exchange(apdu_bytes, timeout=timeout_ms)
+    if len(response) < 2:
+        raise RuntimeError(f"short response: {response.hex()}")
+    sw = int.from_bytes(response[-2:], "big")
+    data = bytes(response[:-2])
+    print(f"<- sw={sw:04x} data={data.hex().upper()} ({len(data)} bytes)", file=sys.stderr)
+    if sw != 0x9000:
+        raise RuntimeError(f"APDU failed: sw={sw:04x}")
+    return data
+
+
+def get_compressed_pubkey(t, path_bytes: bytes) -> bytes:
+    """GET_PUBKEY (no display): pk_len(1)||pk||cc_len(1)||cc||addr_len(1)||addr."""
+    data = exchange(t, apdu(INS_GET_PUBKEY, 0, 0, path_bytes))
+    return data[1 : 1 + data[0]]
+
+
+def parse_input(s: str):
+    """`<txid_hex>:<vout>:<value_dollarydoos>`."""
+    txid_str, vout_str, value_str = s.split(":")
+    txid = bytes.fromhex(txid_str)
+    if len(txid) != 32:
+        raise ValueError(f"input txid must be 32 bytes, got {len(txid)}")
+    return txid, int(vout_str), int(value_str)
+
+
+def parse_output(s: str, hrp: str) -> bytes:
+    """`<bech32_addr>:<value>` -> value(8 LE)||ver(1)||len(1)||hash||cov(0x00)||varint(0)."""
+    addr, amount_str = s.rsplit(":", 1)
+    got_hrp, data = bech32.bech32_decode(addr)
+    if got_hrp != hrp:
+        raise ValueError(f"address HRP {got_hrp!r} != expected {hrp!r}")
+    if not data:
+        raise ValueError(f"invalid bech32 address: {addr}")
+    witver = data[0]
+    program = bech32.convertbits(data[1:], 5, 8, False)
+    if program is None:
+        raise ValueError(f"invalid bech32 program: {addr}")
+    return (
+        int(amount_str).to_bytes(8, "little")
+        + bytes([witver, len(program)])
+        + bytes(program)
+        + b"\x00"           # covenant kind NONE
+        + encode_varint(0)  # covenant item count
+    )
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(
+        description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter
+    )
+    ap.add_argument("--path", required=True, help="BIP-32 path, e.g. 44'/5353'/0'/0/0")
+    ap.add_argument("--input", action="append", required=True,
+                    help="`<txid>:<vout>:<value>` (repeat for multiple inputs)")
+    ap.add_argument("--output", action="append", default=[],
+                    help="`<bech32_addr>:<value>` (repeat for multiple outputs)")
+    ap.add_argument("--tx-version", type=int, default=0)
+    ap.add_argument("--locktime", type=int, default=0)
+    ap.add_argument("--sequence", type=lambda s: int(s, 0), default=0xFFFFFFFF)
+    ap.add_argument("--sighash-type", type=lambda s: int(s, 0), default=0x01)
+    ap.add_argument("--network", choices=list(HRP), default="main")
+    args = ap.parse_args()
+
+    hrp = HRP[args.network]
+    path_bytes = parse_path(args.path)
+    inputs = [parse_input(i) for i in args.input]
+    outputs = [parse_output(o, hrp) for o in args.output]
+
+    t = open_device()
+    try:
+        pubkey = get_compressed_pubkey(t, path_bytes)
+        print(f"# compressed pubkey: {pubkey.hex().upper()}", file=sys.stderr)
+
+        # BEGIN
+        exchange(t, apdu(INS_SIGN_TX, P1_BEGIN, 0,
+                         args.tx_version.to_bytes(4, "little")
+                         + encode_varint(len(inputs))
+                         + encode_varint(len(outputs))
+                         + args.locktime.to_bytes(4, "little")))
+
+        # ADD_INPUT (one APDU each)
+        for txid, vout, value in inputs:
+            exchange(t, apdu(INS_SIGN_TX, P1_ADD_INPUT, 0,
+                             txid
+                             + vout.to_bytes(4, "little")
+                             + args.sequence.to_bytes(4, "little")
+                             + value.to_bytes(8, "little")
+                             + bytes([args.sighash_type])
+                             + path_bytes
+                             + bytes([SCRIPT_KIND_P2WPKH])))
+
+        # ADD_OUTPUT (chunked; P2 = MORE until the last chunk of each output)
+        for payload in outputs:
+            chunks = [payload[i:i + MAX_DATA] for i in range(0, len(payload), MAX_DATA)]
+            for i, c in enumerate(chunks):
+                p2 = P2_LAST if i == len(chunks) - 1 else P2_MORE
+                exchange(t, apdu(INS_SIGN_TX, P1_ADD_OUTPUT, p2, c))
+
+        # REVIEW (blocks on the user)
+        exchange(t, apdu(INS_SIGN_TX, P1_REVIEW, 0, b""))
+
+        # SIGN_INPUT per input -> sig(64)||sighash(1)||pk_len(1)||pk
+        witnesses = []
+        for idx in range(len(inputs)):
+            r = exchange(t, apdu(INS_SIGN_TX, P1_SIGN_INPUT, 0, idx.to_bytes(4, "big")))
+            if len(r) < 66 or len(r) != 66 + r[65]:
+                raise RuntimeError(f"bad SIGN_INPUT response: {r.hex()}")
+            sig_with_sighash = r[:65]
+            pk = r[66:]
+            print(f"# input {idx} sig: {sig_with_sighash.hex().upper()}", file=sys.stderr)
+            witnesses.append(
+                encode_varint(2)
+                + encode_varint(len(sig_with_sighash)) + sig_with_sighash
+                + encode_varint(len(pk)) + pk
+            )
+
+        # version || inputs || outputs || locktime || witnesses (shd Transaction.write)
+        tx = bytearray(args.tx_version.to_bytes(4, "little"))
+        tx += encode_varint(len(inputs))
+        for txid, vout, _ in inputs:
+            tx += txid + vout.to_bytes(4, "little") + args.sequence.to_bytes(4, "little")
+        tx += encode_varint(len(outputs))
+        for payload in outputs:
+            tx += payload
+        tx += args.locktime.to_bytes(4, "little")
+        for w in witnesses:
+            tx += w
+
+        print(tx.hex())
+        return 0
+    finally:
+        t.close()
+
+
+if __name__ == "__main__":
+    sys.exit(main())