Merge bitcoin#23305: test: refactor: add script_util helper for creating bare multisig scripts

4718897 test: add script_util helper for creating bare multisig scripts (Sebastian Falbesoner)

Pull request description:

  This PR is a follow-up to bitcoin#22363 and bitcoin#23118 and introduces a helper `keys_to_multisig_script` for creating bare multisig outputs in the form of
  ```
  OP_K PubKey1 PubKey2 ... PubKeyN OP_N OP_CHECKMULTISIG
  ```
  The function takes a list of pubkeys (both hex- and byte-strings are accepted due to the `script_util.check_key` helper being used internally) and optionally a threshold _k_. If no threshold is passed, a n-of-n multisig output is created, with _n_ being the number of passed pubkeys.

ACKs for top commit:
  shaavan:
    utACK 4718897
  rajarshimaitra:
    tACK bitcoin@4718897

Tree-SHA512: b452d8a75b0d17316b66ac4ed4c6893fe59c7c417719931d4cd3955161f59afca43503cd09b83a35b5a252a122eb3f0fbb9da9f0e7c944cf8da572a02219ed9d

Author: MarcoFalke

test/functional/mempool_accept.py

@@ -24,13 +24,11 @@
 from test_framework.script import (
     CScript,
     OP_0,
-    OP_2,
-    OP_3,
-    OP_CHECKMULTISIG,
     OP_HASH160,
     OP_RETURN,
 )
 from test_framework.script_util import (
+    keys_to_multisig_script,
     script_to_p2sh_script,
 )
 from test_framework.util import (
@@ -275,7 +273,7 @@ def run_test(self):
         key = ECKey()
         key.generate()
         pubkey = key.get_pubkey().get_bytes()
-        tx.vout[0].scriptPubKey = CScript([OP_2, pubkey, pubkey, pubkey, OP_3, OP_CHECKMULTISIG])  # Some bare multisig script (2-of-3)
+        tx.vout[0].scriptPubKey = keys_to_multisig_script([pubkey] * 3, k=2)  # Some bare multisig script (2-of-3)
         self.check_mempool_result(
             result_expected=[{'txid': tx.rehash(), 'allowed': False, 'reject-reason': 'bare-multisig'}],
             rawtxs=[tx.serialize().hex()],

test/functional/test_framework/script_util.py

@@ -5,6 +5,8 @@
 """Useful Script constants and utils."""
 from test_framework.script import (
     CScript,
+    CScriptOp,
+    OP_CHECKMULTISIG,
     OP_CHECKSIG,
     OP_DUP,
     OP_EQUAL,
@@ -39,6 +41,17 @@ def key_to_p2pk_script(key):
     return CScript([key, OP_CHECKSIG])
 
 
+def keys_to_multisig_script(keys, *, k=None):
+    n = len(keys)
+    if k is None:  # n-of-n multisig by default
+        k = n
+    assert k <= n
+    op_k = CScriptOp.encode_op_n(k)
+    op_n = CScriptOp.encode_op_n(n)
+    checked_keys = [check_key(key) for key in keys]
+    return CScript([op_k] + checked_keys + [op_n, OP_CHECKMULTISIG])
+
+
 def keyhash_to_p2pkh_script(hash):
     assert len(hash) == 20
     return CScript([OP_DUP, OP_HASH160, hash, OP_EQUALVERIFY, OP_CHECKSIG])

test/functional/test_framework/wallet_util.py

@@ -11,14 +11,9 @@
     script_to_p2sh,
 )
 from test_framework.key import ECKey
-from test_framework.script import (
-    CScript,
-    OP_2,
-    OP_3,
-    OP_CHECKMULTISIG,
-)
 from test_framework.script_util import (
     key_to_p2pkh_script,
+    keys_to_multisig_script,
     script_to_p2sh_script,
 )
 
@@ -67,7 +62,7 @@ def get_multisig(node):
         addr = node.getaddressinfo(node.getnewaddress())
         addrs.append(addr['address'])
         pubkeys.append(addr['pubkey'])
-    script_code = CScript([OP_2] + [bytes.fromhex(pubkey) for pubkey in pubkeys] + [OP_3, OP_CHECKMULTISIG])
+    script_code = keys_to_multisig_script(pubkeys, k=2)
     return Multisig(privkeys=[node.dumpprivkey(addr) for addr in addrs],
                     pubkeys=pubkeys,
                     p2sh_script=script_to_p2sh_script(script_code).hex(),