qa: functional test Miniscript signing with key and timelocks

We'll need a better integration of the hash preimages PSBT fields to
satisfy Miniscript with such challenges from the RPC.

Thanks to Greg Sanders for his examples and suggestions to improve this
test.

Author: darosior

test/functional/wallet_miniscript.py

@@ -40,7 +40,90 @@
     # A Revault Unvault policy with the older() replaced by an after()
     f"andor(multi(2,{TPUBS[0]}/*,{TPUBS[1]}/*),and_v(v:multi(4,{PUBKEYS[0]},{PUBKEYS[1]},{PUBKEYS[2]},{PUBKEYS[3]}),after(424242)),thresh(4,pkh({TPUBS[2]}/*),a:pkh({TPUBS[3]}/*),a:pkh({TPUBS[4]}/*),a:pkh({TPUBS[5]}/*)))",
     # Liquid-like federated pegin with emergency recovery keys
-    "or_i(and_b(pk(029ffbe722b147f3035c87cb1c60b9a5947dd49c774cc31e94773478711a929ac0),a:and_b(pk(025f05815e3a1a8a83bfbb03ce016c9a2ee31066b98f567f6227df1d76ec4bd143),a:and_b(pk(025625f41e4a065efc06d5019cbbd56fe8c07595af1231e7cbc03fafb87ebb71ec),a:and_b(pk(02a27c8b850a00f67da3499b60562673dcf5fdfb82b7e17652a7ac54416812aefd),s:pk(03e618ec5f384d6e19ca9ebdb8e2119e5bef978285076828ce054e55c4daf473e2))))),and_v(v:thresh(2,pkh(tpubD6NzVbkrYhZ4YK67cd5fDe4fBVmGB2waTDrAt1q4ey9HPq9veHjWkw3VpbaCHCcWozjkhgAkWpFrxuPMUrmXVrLHMfEJ9auoZA6AS1g3grC/*),a:pkh(033841045a531e1adf9910a6ec279589a90b3b8a904ee64ffd692bd08a8996c1aa),a:pkh(02aebf2d10b040eb936a6f02f44ee82f8b34f5c1ccb20ff3949c2b28206b7c1068)),older(4209713)))",
+    f"or_i(and_b(pk({PUBKEYS[0]}),a:and_b(pk({PUBKEYS[1]}),a:and_b(pk({PUBKEYS[2]}),a:and_b(pk({PUBKEYS[3]}),s:pk({PUBKEYS[4]}))))),and_v(v:thresh(2,pkh({TPUBS[0]}/*),a:pkh({PUBKEYS[5]}),a:pkh({PUBKEYS[6]})),older(4209713)))",
+]
+
+MINISCRIPTS_PRIV = [
+    # One of two keys, of which one private key is known
+    {
+        "ms": f"or_i(pk({TPRVS[0]}/*),pk({TPUBS[0]}/*))",
+        "sequence": None,
+        "locktime": None,
+        "sigs_count": 1,
+        "stack_size": 3,
+    },
+    # A more complex policy, that can't be satisfied through the first branch (need for a preimage)
+    {
+        "ms": f"andor(ndv:older(2),and_v(v:pk({TPRVS[0]}),sha256(2a8ce30189b2ec3200b47aeb4feaac8fcad7c0ba170389729f4898b0b7933bcb)),and_v(v:pkh({TPRVS[1]}),pk({TPRVS[2]}/*)))",
+        "sequence": 2,
+        "locktime": None,
+        "sigs_count": 3,
+        "stack_size": 5,
+    },
+    # Signature with a relative timelock
+    {
+        "ms": f"and_v(v:older(2),pk({TPRVS[0]}/*))",
+        "sequence": 2,
+        "locktime": None,
+        "sigs_count": 1,
+        "stack_size": 2,
+    },
+    # Signature with an absolute timelock
+    {
+        "ms": f"and_v(v:after(20),pk({TPRVS[0]}/*))",
+        "sequence": None,
+        "locktime": 20,
+        "sigs_count": 1,
+        "stack_size": 2,
+    },
+    # Signature with both
+    {
+        "ms": f"and_v(v:older(4),and_v(v:after(30),pk({TPRVS[0]}/*)))",
+        "sequence": 4,
+        "locktime": 30,
+        "sigs_count": 1,
+        "stack_size": 2,
+    },
+    # We have one key on each branch; Core signs both (can't finalize)
+    {
+        "ms": f"c:andor(pk({TPRVS[0]}/*),pk_k({TPUBS[0]}),and_v(v:pk({TPRVS[1]}),pk_k({TPUBS[1]})))",
+        "sequence": None,
+        "locktime": None,
+        "sigs_count": 2,
+        "stack_size": None,
+    },
+    # We have all the keys, wallet selects the timeout path to sign since it's smaller and sequence is set
+    {
+        "ms": f"andor(pk({TPRVS[0]}/*),pk({TPRVS[2]}),and_v(v:pk({TPRVS[1]}),older(10)))",
+        "sequence": 10,
+        "locktime": None,
+        "sigs_count": 3,
+        "stack_size": 3,
+    },
+    # We have all the keys, wallet selects the primary path to sign unconditionally since nsequence wasn't set to be valid for timeout path
+    {
+        "ms": f"andor(pk({TPRVS[0]}/*),pk({TPRVS[2]}),and_v(v:pkh({TPRVS[1]}),older(10)))",
+        "sequence": None,
+        "locktime": None,
+        "sigs_count": 3,
+        "stack_size": 3,
+    },
+    # Finalizes to the smallest valid witness, regardless of sequence
+    {
+        "ms": f"or_d(pk({TPRVS[0]}/*),and_v(v:pk({TPRVS[1]}),and_v(v:pk({TPRVS[2]}),older(10))))",
+        "sequence": 12,
+        "locktime": None,
+        "sigs_count": 3,
+        "stack_size": 2,
+    },
+    # Liquid-like federated pegin with emergency recovery privkeys
+    {
+        "ms": f"or_i(and_b(pk({TPUBS[0]}/*),a:and_b(pk({TPUBS[1]}),a:and_b(pk({TPUBS[2]}),a:and_b(pk({TPUBS[3]}),s:pk({PUBKEYS[0]}))))),and_v(v:thresh(2,pkh({TPRVS[0]}),a:pkh({TPRVS[1]}),a:pkh({TPUBS[4]})),older(42)))",
+        "sequence": 42,
+        "locktime": None,
+        "sigs_count": 2,
+        "stack_size": 8,
+    },
 ]
 
 
@@ -84,13 +167,77 @@ def watchonly_test(self, ms):
         utxo = self.ms_wo_wallet.listunspent(minconf=0, addresses=[addr])[0]
         assert utxo["txid"] == txid and utxo["solvable"]
 
+    def signing_test(self, ms, sequence, locktime, sigs_count, stack_size):
+        self.log.info(f"Importing private Miniscript '{ms}'")
+        desc = descsum_create(f"wsh({ms})")
+        res = self.ms_sig_wallet.importdescriptors(
+            [
+                {
+                    "desc": desc,
+                    "active": True,
+                    "range": 0,
+                    "next_index": 0,
+                    "timestamp": "now",
+                }
+            ]
+        )
+        assert res[0]["success"], res
+
+        self.log.info("Generating an address for it and testing it detects funds")
+        addr = self.ms_sig_wallet.getnewaddress()
+        txid = self.funder.sendtoaddress(addr, 0.01)
+        self.wait_until(lambda: txid in self.funder.getrawmempool())
+        self.funder.generatetoaddress(1, self.funder.getnewaddress())
+        utxo = self.ms_sig_wallet.listunspent(addresses=[addr])[0]
+        assert txid == utxo["txid"] and utxo["solvable"]
+
+        self.log.info("Creating a transaction spending these funds")
+        dest_addr = self.funder.getnewaddress()
+        seq = sequence if sequence is not None else 0xFFFFFFFF - 2
+        lt = locktime if locktime is not None else 0
+        psbt = self.ms_sig_wallet.createpsbt(
+            [
+                {
+                    "txid": txid,
+                    "vout": utxo["vout"],
+                    "sequence": seq,
+                }
+            ],
+            [{dest_addr: 0.009}],
+            lt,
+        )
+
+        self.log.info("Signing it and checking the satisfaction.")
+        res = self.ms_sig_wallet.walletprocesspsbt(psbt=psbt, finalize=False)
+        psbtin = self.nodes[0].rpc.decodepsbt(res["psbt"])["inputs"][0]
+        assert len(psbtin["partial_signatures"]) == sigs_count
+        res = self.ms_sig_wallet.finalizepsbt(res["psbt"])
+        assert res["complete"] == (stack_size is not None)
+
+        if stack_size is not None:
+            txin = self.nodes[0].rpc.decoderawtransaction(res["hex"])["vin"][0]
+            assert len(txin["txinwitness"]) == stack_size, txin["txinwitness"]
+            self.log.info("Broadcasting the transaction.")
+            # If necessary, satisfy a relative timelock
+            if sequence is not None:
+                self.funder.generatetoaddress(sequence, self.funder.getnewaddress())
+            # If necessary, satisfy an absolute timelock
+            height = self.funder.getblockcount()
+            if locktime is not None and height < locktime:
+                self.funder.generatetoaddress(
+                    locktime - height, self.funder.getnewaddress()
+                )
+            self.ms_sig_wallet.sendrawtransaction(res["hex"])
+
     def run_test(self):
         self.log.info("Making a descriptor wallet")
         self.funder = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
         self.nodes[0].createwallet(
             wallet_name="ms_wo", descriptors=True, disable_private_keys=True
         )
         self.ms_wo_wallet = self.nodes[0].get_wallet_rpc("ms_wo")
+        self.nodes[0].createwallet(wallet_name="ms_sig", descriptors=True)
+        self.ms_sig_wallet = self.nodes[0].get_wallet_rpc("ms_sig")
 
         # Sanity check we wouldn't let an insane Miniscript descriptor in
         res = self.ms_wo_wallet.importdescriptors(
@@ -111,6 +258,16 @@ def run_test(self):
         for ms in MINISCRIPTS:
             self.watchonly_test(ms)
 
+        # Test we can sign most Miniscript (all but ones requiring preimages, for now)
+        for ms in MINISCRIPTS_PRIV:
+            self.signing_test(
+                ms["ms"],
+                ms["sequence"],
+                ms["locktime"],
+                ms["sigs_count"],
+                ms["stack_size"],
+            )
+
 
 if __name__ == "__main__":
     WalletMiniscriptTest().main()