bugfix: 1of1 multisig

releases/Next-ChangeLog.md

@@ -41,6 +41,7 @@ This lists the new changes that have not yet been published in a normal release.
 - Bugfix: Handle malformed NDEF records robustly. Thanks, @Damir
 - Bugfix: Ignore `bkpw` if added to backup. Thanks [@dmonakhov](https://github.com/dmonakhov)
 - Bugfix: Keep NFC export tag live for repeated probes
+- Bugfix: Fix 1of1 multisig signing failure
 
 # Mk Specific Changes
 

shared/psbt.py

@@ -829,17 +829,20 @@ class psbtInputProxy(psbtProxy):
 
             self.scriptSig = redeem_script
 
-            # new cheat: psbt creator probably telling us exactly what key
-            # to use, by providing exactly one. This is ideal for p2sh wrapped p2pkh
-            if len(subpaths) == 1:
+            if not addr_is_segwit and len(redeem_script) == 22 and \
+                    redeem_script[0] == 0 and redeem_script[1] == 20:
+                # segwit p2pkh wrapped in p2sh: exactly one key, not multisig.
+                # psbt creator tells us the key by providing exactly one subpath.
+                self.addr_fmt = AF_P2WPKH_P2SH
+                addr = redeem_script[2:22]
+                self.is_segwit = True
+
+                assert len(subpaths) == 1, "p2sh-p2wpkh needs one key"
                 which_key, = subpaths.keys()
             else:
-                # Assume we'll be signing with any key we know
-                # - limitation: we cannot be two legs of a multisig (only if CCC feature used)
-                # - but if partial sig already in place, ignore that one
-                if not which_key:
-                    which_key = set()
+                self.is_multisig = True
 
+                which_key = set()
                 for pubkey, path in subpaths.items():
                     if self.part_sigs and (pubkey in self.part_sigs):
                         # pubkey has already signed, so ignore
@@ -850,20 +853,8 @@ class psbtInputProxy(psbtProxy):
                         which_key.add(pubkey)
 
                     elif pubkey in psbt.wif_store:
-                        # maybe sset some input value
                         which_key.add(pubkey)
 
-            if not addr_is_segwit and \
-                    len(redeem_script) == 22 and \
-                    redeem_script[0] == 0 and redeem_script[1] == 20:
-                # it's actually segwit p2pkh inside p2sh
-                self.addr_fmt = AF_P2WPKH_P2SH
-                addr = redeem_script[2:22]
-                self.is_segwit = True
-            else:
-                # multiple keys involved
-                self.is_multisig = True
-
             if self.witness_script and not self.is_segwit and self.is_multisig:
                 # bugfix
                 self.addr_fmt = AF_P2WSH_P2SH

testing/test_multisig.py

@@ -1510,6 +1510,24 @@ def test_ms_sign_simple(M_N, num_ins, dev, addr_fmt, clear_ms, incl_xpubs, impor
     else:
         try_sign(psbt)
 
+
+@pytest.mark.parametrize("finalize", [True, False])
+def test_1of1_multisig_sign(finalize, clear_ms, import_ms_wallet, fake_ms_txn, start_sign,
+                            end_sign, cap_story):
+    # Minimal 1-of-1 multisig: import the wallet, then sign a 1-in/1-out PSBT.
+    clear_ms()
+    M = N = 1
+    keys = import_ms_wallet(M, N, accept=True)
+
+    psbt = fake_ms_txn(1, 1, M, keys)
+
+    start_sign(psbt, finalize=finalize)
+    title, story = cap_story()
+    assert title == "OK TO SEND?"
+
+    end_sign(accept=True, finalize=finalize)
+
+
 @pytest.mark.unfinalized
 @pytest.mark.bitcoind
 @pytest.mark.parametrize('num_ins', [ 15 ])

testing/test_sign.py

@@ -1664,6 +1664,21 @@ def test_wrong_pubkey(dev, try_sign, fake_txn):
     msg = ee.value.args[0]
     assert ('pubkey vs. address wrong' in msg)
 
+
+def test_p2sh_p2wpkh_multiple_bip32_paths_rejected(fake_txn, start_sign, cap_story):
+    psbt = fake_txn(1, 1, segwit_in=True, wrapped=True)
+    po = BasicPSBT().parse(psbt)
+
+    other = BIP32Node.from_master_secret(os.urandom(32))
+    other_key = other.subkey_for_path("0/0")
+    po.inputs[0].bip32_paths[other_key.sec()] = other.fingerprint() + struct.pack('<II', 0, 0)
+
+    start_sign(po.as_bytes(), finalize=True)
+    title, story = cap_story()
+    assert title == "Failure"
+    assert "p2sh-p2wpkh needs one key" in story
+
+
 def test_incomplete_signing(dev, try_sign, fake_txn, cap_story):
     # psbt where we only sign one input
     # - must not allow finalization