Merge bitcoin#28625: test: check that loading snapshot not matching AssumeUTXO parameters fails

2e31250 test: check that loading snapshot not matching AssumeUTXO parameters fails (Sebastian Falbesoner)

Pull request description:

  This PR adds test coverage for the failed loading of an AssumeUTXO snapshot in case the referenced block hash doesn't match the parameters in the chainparams. Right now, I expect this would be the most common error-case for `loadtxoutset` out in the wild, as for mainnet the `m_assumeutxo_data` map is empty and this error condition would obviously always be triggered for any (otherwise valid, correctly encoded) snapshot. Note that this test-case is the simplest scenario and doesn't cover any of the TODO ideas mentioned at the top of the functional test yet.

ACKs for top commit:
  jamesob:
    ACK bitcoin@2e31250
  Sjors:
    utACK 2e31250
  achow101:
    ACK 2e31250

Tree-SHA512: 8bcb2d525c95fbc95f87d3e978ad717d95bddb1ff67cbe7d3b06e4783f0f1ffba32b17ef451468c39c23bc1b3ef1150baa71148c145275c386f2d4822d790d39

Author: achow101

test/functional/feature_assumeutxo.py

@@ -36,7 +36,11 @@
 
 """
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal
+from test_framework.util import (
+    assert_equal,
+    assert_raises_rpc_error,
+)
+
 
 START_HEIGHT = 199
 SNAPSHOT_BASE_HEIGHT = 299
@@ -62,6 +66,25 @@ def setup_network(self):
         self.add_nodes(3)
         self.start_nodes(extra_args=self.extra_args)
 
+    def test_invalid_snapshot_scenarios(self, valid_snapshot_path):
+        self.log.info("Test different scenarios of loading invalid snapshot files")
+        self.log.info("  - snapshot file refering to a block that is not in the assumeutxo parameters")
+        with open(valid_snapshot_path, 'rb') as f:
+            valid_snapshot_contents = f.read()
+
+        # we can only test this with a block that is already known, as otherwise the `loadtxoutset` RPC
+        # would time out (waiting to see the hash in the headers chain), rather than error immediately
+        bad_snapshot_height = SNAPSHOT_BASE_HEIGHT - 1
+        bad_snapshot_path = valid_snapshot_path + '.mod'
+        with open(bad_snapshot_path, 'wb') as f:
+            bad_snapshot_block_hash = self.nodes[0].getblockhash(bad_snapshot_height)
+            # block hash of the snapshot base is stored right at the start (first 32 bytes)
+            f.write(bytes.fromhex(bad_snapshot_block_hash)[::-1] + valid_snapshot_contents[32:])
+
+        expected_log = f"assumeutxo height in snapshot metadata not recognized ({bad_snapshot_height}) - refusing to load snapshot"
+        with self.nodes[1].assert_debug_log(expected_log):
+            assert_raises_rpc_error(-32603, "Unable to load UTXO snapshot", self.nodes[1].loadtxoutset, bad_snapshot_path)
+
     def run_test(self):
         """
         Bring up two (disconnected) nodes, mine some new blocks on the first,
@@ -120,6 +143,8 @@ def run_test(self):
 
         assert_equal(n0.getblockchaininfo()["blocks"], FINAL_HEIGHT)
 
+        self.test_invalid_snapshot_scenarios(dump_output['path'])
+
         self.log.info(f"Loading snapshot into second node from {dump_output['path']}")
         loaded = n1.loadtxoutset(dump_output['path'])
         assert_equal(loaded['coins_loaded'], SNAPSHOT_BASE_HEIGHT)