From 712ec68c1ba4f34e30a9259d65bc4d8391c8c7e5 Mon Sep 17 00:00:00 2001
From: Andrew Kozlik <andrew.kozlik@gmail.com>
Date: Mon, 15 Jun 2020 17:12:36 +0200
Subject: [PATCH] core/bitcoin: Add support for external inputs with proof of
 non-ownership.

---
 core/src/apps/bitcoin/keychain.py        |  2 ++
 core/src/apps/bitcoin/sign_tx/bitcoin.py | 28 +++++++++++++++---------
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/core/src/apps/bitcoin/keychain.py b/core/src/apps/bitcoin/keychain.py
index 587ecd959d..cf7484df79 100644
--- a/core/src/apps/bitcoin/keychain.py
+++ b/core/src/apps/bitcoin/keychain.py
@@ -32,6 +32,8 @@ def get_namespaces_for_coin(coin: coininfo.CoinInfo):
     # m/48'/slip44' (/account'/script_type'/change/addr)
     namespaces.append((curve, [48 | HARDENED, slip44_id]))
 
+    namespaces.append(("slip21", [b"SLIP-0019"]))
+
     if coin.segwit:
         # BIP-49 - p2sh segwit: m/49'/slip44' (/account'/change/addr)
         namespaces.append((curve, [49 | HARDENED, slip44_id]))
diff --git a/core/src/apps/bitcoin/sign_tx/bitcoin.py b/core/src/apps/bitcoin/sign_tx/bitcoin.py
index 0ed75990c3..e3a86f71b0 100644
--- a/core/src/apps/bitcoin/sign_tx/bitcoin.py
+++ b/core/src/apps/bitcoin/sign_tx/bitcoin.py
@@ -19,6 +19,7 @@ from apps.common.writers import write_bitcoin_varint
 
 from .. import addresses, common, multisig, scripts, writers
 from ..common import SIGHASH_ALL, ecdsa_sign
+from ..ownership import verify_nonownership
 from ..verification import SignatureVerifier
 from . import helpers, progress, tx_weight
 from .matchcheck import MultisigFingerprintChecker, WalletPathChecker
@@ -51,7 +52,8 @@ class Bitcoin:
         # Check fee, confirm lock_time and total.
         await self.step3_confirm_tx()
 
-        # Verify external inputs which have already been signed.
+        # Verify external inputs which have already been signed or which come with
+        # a proof of non-ownership.
         await self.step4_verify_external_inputs()
 
         # Check that inputs are unchanged. Serialize inputs and sign the non-segwit ones.
@@ -169,16 +171,22 @@ class Bitcoin:
             if prev_amount != txi.amount:
                 raise wire.DataError("Invalid amount specified")
 
-            verifier = SignatureVerifier(
-                script_pubkey, txi.script_sig, txi.witness, self.coin
-            )
+            if txi.ownership_proof:
+                if not verify_nonownership(
+                    txi.ownership_proof, script_pubkey, b"", self.keychain, self.coin
+                ):
+                    raise wire.DataError("Invalid external input")
+            else:
+                verifier = SignatureVerifier(
+                    script_pubkey, txi.script_sig, txi.witness, self.coin
+                )
 
-            verifier.ensure_hash_type(self.get_hash_type(txi))
+                verifier.ensure_hash_type(self.get_hash_type(txi))
 
-            tx_digest = await self.get_tx_digest(
-                i, txi, verifier.public_keys, verifier.threshold, script_pubkey
-            )
-            verifier.verify(tx_digest)
+                tx_digest = await self.get_tx_digest(
+                    i, txi, verifier.public_keys, verifier.threshold, script_pubkey
+                )
+                verifier.verify(tx_digest)
 
         # check that the inputs were the same as those streamed for confirmation
         if self.h_external.get_digest() != h_check.get_digest():
@@ -288,7 +296,7 @@ class Bitcoin:
         if not input_is_external(txi):
             raise wire.ProcessError("Transaction has changed during signing")
 
-        self.write_tx_input(self.serialized_tx, txi, txi.script_sig)
+        self.write_tx_input(self.serialized_tx, txi, txi.script_sig or bytes())
 
     async def serialize_segwit_input(self, i: int) -> None:
         # STAGE_REQUEST_SEGWIT_INPUT in legacy