test: check for false-positives in rpc_scanblocks.py

Author: theStack

test/functional/rpc_scanblocks.py

@@ -3,6 +3,10 @@
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test the scanblocks RPC call."""
+from test_framework.blockfilter import (
+    bip158_basic_element_hash,
+    bip158_relevant_scriptpubkeys,
+)
 from test_framework.messages import COIN
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
@@ -71,6 +75,28 @@ def run_test(self):
         assert(blockhash in node.scanblocks(
             "start", [{"desc": f"pkh({parent_key}/*)", "range": [0, 100]}], height)['relevant_blocks'])
 
+        # check that false-positives are included in the result now; note that
+        # finding a false-positive at runtime would take too long, hence we simply
+        # use a pre-calculated one that collides with the regtest genesis block's
+        # coinbase output and verify that their BIP158 ranged hashes match
+        genesis_blockhash = node.getblockhash(0)
+        genesis_spks = bip158_relevant_scriptpubkeys(node, genesis_blockhash)
+        assert_equal(len(genesis_spks), 1)
+        genesis_coinbase_spk = list(genesis_spks)[0]
+        false_positive_spk = bytes.fromhex("001400000000000000000000000000000000000cadcb")
+
+        genesis_coinbase_hash = bip158_basic_element_hash(genesis_coinbase_spk, 1, genesis_blockhash)
+        false_positive_hash = bip158_basic_element_hash(false_positive_spk, 1, genesis_blockhash)
+        assert_equal(genesis_coinbase_hash, false_positive_hash)
+
+        assert(genesis_blockhash in node.scanblocks(
+            "start", [{"desc": f"raw({genesis_coinbase_spk.hex()})"}], 0, 0)['relevant_blocks'])
+        assert(genesis_blockhash in node.scanblocks(
+            "start", [{"desc": f"raw({false_positive_spk.hex()})"}], 0, 0)['relevant_blocks'])
+
+        # TODO: after an "accurate" mode for scanblocks is implemented (e.g. PR #26325)
+        # check here that it filters out the false-positive
+
         # test node with disabled blockfilterindex
         assert_raises_rpc_error(-1, "Index is not enabled for filtertype basic",
                                 self.nodes[1].scanblocks, "start", [f"addr({addr_1})"])