Merge bitcoin/bitcoin#25370: test: check for getblocktxn request with out-of-bounds tx index

5a8c321 test: check for `getblocktxn` request with out-of-bounds tx index (Sebastian Falbesoner)

Pull request description:

  This PR adds missing test coverage for the `getblocktxn` message handler, in the case that any of the contained indices is out-of-bounds:
  https://github.com/bitcoin/bitcoin/blob/a05876619a3307daefec0946de8e3cbbe5b0157f/src/net_processing.cpp#L2180-L2183

ACKs for top commit:
  dunxen:
    ACK 5a8c321

Tree-SHA512: 2743c2c6d8aed57b22f825aefd60ba3e670321b60625a42ea7248e7b0fc41c73e9a5945153567c02824ba3b5f0fce7f4125bffc974973fc608b6ffbe49e14b65

Author: MacroFake

test/functional/p2p_compactblocks.py

@@ -606,6 +606,15 @@ def test_getblocktxn_handler(self, test_node):
             assert_equal(test_node.last_message["block"].block.sha256, int(block_hash, 16))
             assert "blocktxn" not in test_node.last_message
 
+        # Request with out-of-bounds tx index results in disconnect
+        bad_peer = self.nodes[0].add_p2p_connection(TestP2PConn())
+        block_hash = node.getblockhash(chain_height)
+        block = from_hex(CBlock(), node.getblock(block_hash, False))
+        msg.block_txn_request = BlockTransactionsRequest(int(block_hash, 16), [len(block.vtx)])
+        with node.assert_debug_log(['getblocktxn with out-of-bounds tx indices']):
+            bad_peer.send_message(msg)
+        bad_peer.wait_for_disconnect()
+
     def test_compactblocks_not_at_tip(self, test_node):
         node = self.nodes[0]
         # Test that requesting old compactblocks doesn't work.