Security/chain request payload

main.py

@@ -258,6 +258,28 @@ async def handler(data):
         elif msg_type == "chain_request":
             start_index = payload.get("start_index", 0)
             limit = payload.get("limit", 500)
+            if (
+                not isinstance(start_index, int)
+                or isinstance(start_index, bool)
+                or start_index < 0
+            ):
+                logger.warning(
+                    "Malformed chain_request from %s: start_index is not a non-negative int (got %r). Ignoring.",
+                    peer_addr, start_index,
+                )
+                return ValidationStatus.MALFORMED
+
+            if (
+                not isinstance(limit, int)
+                or isinstance(limit, bool)
+                or limit < 0
+            ):
+                logger.warning(
+                    "Malformed chain_request from %s: limit is not a non-negative int (got %r). Ignoring.",
+                    peer_addr, limit,
+                )
+                return ValidationStatus.MALFORMED
+
             logger.info("📡 Peer requested blocks from %d (limit %d).", start_index, limit)
 
             if start_index < len(chain.chain):

tests/test_protocol_hardening.py

@@ -1,10 +1,12 @@
 import unittest
+from unittest.mock import AsyncMock, patch
 
 from nacl.encoding import HexEncoder
 from nacl.signing import SigningKey
 
 from minichain import Block, Mempool, P2PNetwork, State, Transaction, calculate_hash
 from minichain.serialization import canonical_json_dumps
+from minichain.validators import ValidationStatus
 
 
 class TestDeterministicConsensus(unittest.TestCase):
@@ -92,7 +94,6 @@ def test_remove_transactions_by_sender_nonce_when_tx_id_differs(self):
 
         self.assertEqual(len(mempool), 0)
 
-
 class TestP2PValidationAndDedup(unittest.IsolatedAsyncioTestCase):
     async def test_invalid_message_schema_is_rejected(self):
         invalid_payload = {"sender": "abc"}
@@ -162,3 +163,96 @@ async def test_duplicate_tx_and_block_detection(self):
         self.assertFalse(network._is_duplicate("block", block_message["data"]))
         network._mark_seen("block", block_message["data"])
         self.assertTrue(network._is_duplicate("block", block_message["data"]))
+
+class TestChainRequestValidation(unittest.IsolatedAsyncioTestCase):
+    """Verify that chain_request handler rejects malformed start_index/limit values."""
+
+    def _make_handler(self):
+        """Return (handler, network) so tests can mock network internals."""
+        from minichain import Blockchain, Mempool, P2PNetwork
+        from main import make_network_handler
+        chain = Blockchain()
+        mempool = Mempool()
+        network = P2PNetwork()
+        handler = make_network_handler(chain, mempool, network)
+        return handler, network
+
+    async def _call(self, handler_or_tuple, data):
+        """Wrap handler call to include required _peer_addr field.
+
+        Accepts either a bare handler or the (handler, network) tuple
+        returned by _make_handler.
+        """
+        handler = handler_or_tuple[0] if isinstance(handler_or_tuple, tuple) else handler_or_tuple
+        data.setdefault("_peer_addr", "test-peer")
+        return await handler(data)
+
+    async def test_string_start_index_is_rejected(self):
+        handler, _ = self._make_handler()
+        result = await self._call(handler, {
+            "type": "chain_request",
+            "data": {"start_index": "0", "limit": 10},
+        })
+        self.assertEqual(result, ValidationStatus.MALFORMED)
+
+    async def test_bool_start_index_is_rejected(self):
+        handler, _ = self._make_handler()
+        result = await self._call(handler, {
+            "type": "chain_request",
+            "data": {"start_index": True, "limit": 10},
+        })
+        self.assertEqual(result, ValidationStatus.MALFORMED)
+
+    async def test_negative_start_index_is_rejected(self):
+        handler, _ = self._make_handler()
+        result = await self._call(handler, {
+            "type": "chain_request",
+            "data": {"start_index": -1, "limit": 10},
+        })
+        self.assertEqual(result, ValidationStatus.MALFORMED)
+
+    async def test_string_limit_is_rejected(self):
+        handler, _ = self._make_handler()
+        result = await self._call(handler, {
+            "type": "chain_request",
+            "data": {"start_index": 0, "limit": "500"},
+        })
+        self.assertEqual(result, ValidationStatus.MALFORMED)
+
+    async def test_bool_limit_is_rejected(self):
+        handler, _ = self._make_handler()
+        result = await self._call(handler, {
+            "type": "chain_request",
+            "data": {"start_index": 0, "limit": False},
+        })
+        self.assertEqual(result, ValidationStatus.MALFORMED)
+
+    async def test_valid_chain_request_is_accepted(self):
+        """A valid request must dispatch a chain_response via _unicast_raw."""
+        handler, network = self._make_handler()
+        mock_unicast = AsyncMock()
+        network._unicast_raw = mock_unicast
+
+        await self._call(handler, {
+            "type": "chain_request",
+            "data": {"start_index": 0, "limit": 10},
+        })
+
+        mock_unicast.assert_awaited_once()
+        _, call_payload = mock_unicast.call_args.args
+        self.assertEqual(call_payload.get("type"), "chain_response")
+        self.assertIn("blocks", call_payload.get("data", {}))
+
+    async def test_negative_limit_is_rejected(self):
+        """limit: -1 must be rejected — handler returns None and sends no response."""
+        handler, network = self._make_handler()
+        mock_unicast = AsyncMock()
+        network._unicast_raw = mock_unicast
+
+        result = await self._call(handler, {
+            "type": "chain_request",
+            "data": {"start_index": 0, "limit": -1},
+        })
+
+        self.assertEqual(result, ValidationStatus.MALFORMED)
+        mock_unicast.assert_not_awaited()