Merge bitcoin/bitcoin#26184: test: p2p: check that headers message with invalid proof-of-work disconnects peer

7726712 test: p2p: check that headers message with invalid proof-of-work disconnects peer (Sebastian Falbesoner)

Pull request description:

  One of the earliest anti-DoS checks done after receiving and deserializing a `headers` message from a peer is verifying whether the proof-of-work is valid (called in method `PeerManagerImpl::ProcessHeadersMessage`):
  https://github.com/bitcoin/bitcoin/blob/f227e153e80c8c50c30d76e1ac638d7206c7ff61/src/net_processing.cpp#L2752-L2762
  The called method `PeerManagerImpl::CheckHeadersPoW` calls `Misbehaving` with a score of 100, i.e. leading to an immediate disconnect of the peer:
  https://github.com/bitcoin/bitcoin/blob/f227e153e80c8c50c30d76e1ac638d7206c7ff61/src/net_processing.cpp#L2368-L2372

  This PR adds a simple test for both the misbehaving log and the resulting disconnect. For creating a block header with invalid proof-of-work, we first create one that is accepted by the node (the difficulty field `nBits` is copied from the genesis block) and based on that the nonce is modified until we have block header hash prefix that is too high to fulfill even the minimum difficulty.

ACKs for top commit:
  Sjors:
    ACK 7726712
  achow101:
    ACK 7726712
  brunoerg:
    crACK 7726712
  furszy:
    Code review ACK 7726712 with a non-blocking speedup.

Tree-SHA512: 680aa7939158d1dc672b90aa6554ba2b3a92584b6d3bcb0227776035858429feb8bc66eed18b47de0fe56df7d9b3ddaee231aaeaa360136603b9ad4b19e6ac11

Author: achow101

test/functional/p2p_invalid_messages.py

@@ -13,11 +13,12 @@
     MAX_HEADERS_RESULTS,
     MAX_INV_SIZE,
     MAX_PROTOCOL_MESSAGE_LENGTH,
+    MSG_TX,
+    from_hex,
     msg_getdata,
     msg_headers,
     msg_inv,
     msg_ping,
-    MSG_TX,
     msg_version,
     ser_string,
 )
@@ -73,6 +74,7 @@ def run_test(self):
         self.test_oversized_inv_msg()
         self.test_oversized_getdata_msg()
         self.test_oversized_headers_msg()
+        self.test_invalid_pow_headers_msg()
         self.test_resource_exhaustion()
 
     def test_buffer(self):
@@ -248,6 +250,36 @@ def test_oversized_headers_msg(self):
         size = MAX_HEADERS_RESULTS + 1
         self.test_oversized_msg(msg_headers([CBlockHeader()] * size), size)
 
+    def test_invalid_pow_headers_msg(self):
+        self.log.info("Test headers message with invalid proof-of-work is logged as misbehaving and disconnects peer")
+        blockheader_tip_hash = self.nodes[0].getbestblockhash()
+        blockheader_tip = from_hex(CBlockHeader(), self.nodes[0].getblockheader(blockheader_tip_hash, False))
+
+        # send valid headers message first
+        assert_equal(self.nodes[0].getblockchaininfo()['headers'], 0)
+        blockheader = CBlockHeader()
+        blockheader.hashPrevBlock = int(blockheader_tip_hash, 16)
+        blockheader.nTime = int(time.time())
+        blockheader.nBits = blockheader_tip.nBits
+        blockheader.rehash()
+        while not blockheader.hash.startswith('0'):
+            blockheader.nNonce += 1
+            blockheader.rehash()
+        peer = self.nodes[0].add_p2p_connection(P2PInterface())
+        peer.send_and_ping(msg_headers([blockheader]))
+        assert_equal(self.nodes[0].getblockchaininfo()['headers'], 1)
+        chaintips = self.nodes[0].getchaintips()
+        assert_equal(chaintips[0]['status'], 'headers-only')
+        assert_equal(chaintips[0]['hash'], blockheader.hash)
+
+        # invalidate PoW
+        while not blockheader.hash.startswith('f'):
+            blockheader.nNonce += 1
+            blockheader.rehash()
+        with self.nodes[0].assert_debug_log(['Misbehaving', 'header with invalid proof of work']):
+            peer.send_message(msg_headers([blockheader]))
+            peer.wait_for_disconnect()
+
     def test_resource_exhaustion(self):
         self.log.info("Test node stays up despite many large junk messages")
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())