Remove header checks out of net_processing

This moves header size and netmagic checking out of net_processing and
into net.  This check now runs in ReadHeader, so that net can exit early
out of receiving bytes from the peer.  IsValid is now slimmed down, so
it no longer needs a MessageStartChars& parameter.

Additionally this removes the rest of the m_valid_* members from
CNetMessage.

8 files changed, 32 insertions, 62 deletions

diff --git a/src/net.cpp b/src/net.cpp
index 941ea3c4ac..633f9a2f7f 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -605,6 +605,7 @@ bool CNode::ReceiveMsgBytes(const char *pch, unsigned int nBytes, bool& complete
         // absorb network data
         int handled = m_deserializer->Read(pch, nBytes);
         if (handled < 0) {
+            // Serious header problem, disconnect from the peer.
             return false;
         }
 
@@ -616,6 +617,7 @@ bool CNode::ReceiveMsgBytes(const char *pch, unsigned int nBytes, bool& complete
             uint32_t out_err_raw_size{0};
             Optional<CNetMessage> result{m_deserializer->GetMessage(time, out_err_raw_size)};
             if (!result) {
+                // Message deserialization failed.  Drop the message but don't disconnect the peer.
                 // store the size of the corrupt message
                 mapRecvBytesPerMsgCmd.find(NET_MESSAGE_COMMAND_OTHER)->second += out_err_raw_size;
                 continue;
@@ -657,11 +659,19 @@ int V1TransportDeserializer::readHeader(const char *pch, unsigned int nBytes)
         hdrbuf >> hdr;
     }
     catch (const std::exception&) {
+        LogPrint(BCLog::NET, "HEADER ERROR - UNABLE TO DESERIALIZE, peer=%d\n", m_node_id);
+        return -1;
+    }
+
+    // Check start string, network magic
+    if (memcmp(hdr.pchMessageStart, m_chain_params.MessageStart(), CMessageHeader::MESSAGE_START_SIZE) != 0) {
+        LogPrint(BCLog::NET, "HEADER ERROR - MESSAGESTART (%s, %u bytes), received %s, peer=%d\n", hdr.GetCommand(), hdr.nMessageSize, HexStr(hdr.pchMessageStart), m_node_id);
         return -1;
     }
 
     // reject messages larger than MAX_SIZE or MAX_PROTOCOL_MESSAGE_LENGTH
     if (hdr.nMessageSize > MAX_SIZE || hdr.nMessageSize > MAX_PROTOCOL_MESSAGE_LENGTH) {
+        LogPrint(BCLog::NET, "HEADER ERROR - SIZE (%s, %u bytes), peer=%d\n", hdr.GetCommand(), hdr.nMessageSize, m_node_id);
         return -1;
     }
 
@@ -701,10 +711,6 @@ Optional<CNetMessage> V1TransportDeserializer::GetMessage(const std::chrono::mic
     // decompose a single CNetMessage from the TransportDeserializer
     Optional<CNetMessage> msg(std::move(vRecv));
 
-    // store state about valid header, netmagic and checksum
-    msg->m_valid_header = hdr.IsValid(m_chain_params.MessageStart());
-    msg->m_valid_netmagic = (memcmp(hdr.pchMessageStart, m_chain_params.MessageStart(), CMessageHeader::MESSAGE_START_SIZE) == 0);
-
     // store command string, time, and sizes
     msg->m_command = hdr.GetCommand();
     msg->m_time = time;
@@ -716,6 +722,7 @@ Optional<CNetMessage> V1TransportDeserializer::GetMessage(const std::chrono::mic
     // We just received a message off the wire, harvest entropy from the time (and the message checksum)
     RandAddEvent(ReadLE32(hash.begin()));
 
+    // Check checksum and header command string
     if (memcmp(hash.begin(), hdr.pchChecksum, CMessageHeader::CHECKSUM_SIZE) != 0) {
         LogPrint(BCLog::NET, "CHECKSUM ERROR (%s, %u bytes), expected %s was %s, peer=%d\n",
                  SanitizeString(msg->m_command), msg->m_message_size,
@@ -724,6 +731,11 @@ Optional<CNetMessage> V1TransportDeserializer::GetMessage(const std::chrono::mic
                  m_node_id);
         out_err_raw_size = msg->m_raw_message_size;
         msg = nullopt;
+    } else if (!hdr.IsCommandValid()) {
+        LogPrint(BCLog::NET, "HEADER ERROR - COMMAND (%s, %u bytes), peer=%d\n",
+                 hdr.GetCommand(), msg->m_message_size, m_node_id);
+        out_err_raw_size = msg->m_raw_message_size;
+        msg = nullopt;
     }
 
     // Always reset the network deserializer (prepare for the next message)
diff --git a/src/net.h b/src/net.h
index 29941b9622..9a92f80511 100644
--- a/src/net.h
+++ b/src/net.h
@@ -706,10 +706,8 @@ class CNetMessage {
 public:
     CDataStream m_recv;                  //!< received message data
     std::chrono::microseconds m_time{0}; //!< time of message receipt
-    bool m_valid_netmagic = false;
-    bool m_valid_header = false;
-    uint32_t m_message_size{0};     //!< size of the payload
-    uint32_t m_raw_message_size{0}; //!< used wire size of the message (including header/checksum)
+    uint32_t m_message_size{0};          //!< size of the payload
+    uint32_t m_raw_message_size{0};      //!< used wire size of the message (including header/checksum)
     std::string m_command;
 
     CNetMessage(CDataStream&& recv_in) : m_recv(std::move(recv_in)) {}
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index d9d32cded6..920e7a1abf 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -3820,14 +3820,6 @@ bool PeerManager::MaybeDiscourageAndDisconnect(CNode& pnode)
 
 bool PeerManager::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgProc)
 {
-    //
-    // Message format
-    //  (4) message start
-    //  (12) command
-    //  (4) size
-    //  (4) checksum
-    //  (x) data
-    //
     bool fMoreWork = false;
 
     if (!pfrom->vRecvGetData.empty())
@@ -3868,19 +3860,6 @@ bool PeerManager::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgP
     CNetMessage& msg(msgs.front());
 
     msg.SetVersion(pfrom->GetCommonVersion());
-    // Check network magic
-    if (!msg.m_valid_netmagic) {
-        LogPrint(BCLog::NET, "PROCESSMESSAGE: INVALID MESSAGESTART %s peer=%d\n", SanitizeString(msg.m_command), pfrom->GetId());
-        pfrom->fDisconnect = true;
-        return false;
-    }
-
-    // Check header
-    if (!msg.m_valid_header)
-    {
-        LogPrint(BCLog::NET, "PROCESSMESSAGE: ERRORS IN HEADER %s peer=%d\n", SanitizeString(msg.m_command), pfrom->GetId());
-        return fMoreWork;
-    }
     const std::string& msg_type = msg.m_command;
 
     // Message size
diff --git a/src/protocol.cpp b/src/protocol.cpp
index 6b4de68ce9..84b6e96aee 100644
--- a/src/protocol.cpp
+++ b/src/protocol.cpp
@@ -111,31 +111,20 @@ std::string CMessageHeader::GetCommand() const
     return std::string(pchCommand, pchCommand + strnlen(pchCommand, COMMAND_SIZE));
 }
 
-bool CMessageHeader::IsValid(const MessageStartChars& pchMessageStartIn) const
+bool CMessageHeader::IsCommandValid() const
 {
-    // Check start string
-    if (memcmp(pchMessageStart, pchMessageStartIn, MESSAGE_START_SIZE) != 0)
-        return false;
-
     // Check the command string for errors
-    for (const char* p1 = pchCommand; p1 < pchCommand + COMMAND_SIZE; p1++)
-    {
-        if (*p1 == 0)
-        {
+    for (const char* p1 = pchCommand; p1 < pchCommand + COMMAND_SIZE; ++p1) {
+        if (*p1 == 0) {
             // Must be all zeros after the first zero
-            for (; p1 < pchCommand + COMMAND_SIZE; p1++)
-                if (*p1 != 0)
+            for (; p1 < pchCommand + COMMAND_SIZE; ++p1) {
+                if (*p1 != 0) {
                     return false;
-        }
-        else if (*p1 < ' ' || *p1 > 0x7E)
+                }
+            }
+        } else if (*p1 < ' ' || *p1 > 0x7E) {
             return false;
-    }
-
-    // Message size
-    if (nMessageSize > MAX_SIZE)
-    {
-        LogPrintf("CMessageHeader::IsValid(): (%s, %u bytes) nMessageSize > MAX_SIZE\n", GetCommand(), nMessageSize);
-        return false;
+        }
     }
 
     return true;
diff --git a/src/protocol.h b/src/protocol.h
index 3bf0797ca4..9a44a1626c 100644
--- a/src/protocol.h
+++ b/src/protocol.h
@@ -45,7 +45,7 @@ public:
     CMessageHeader(const MessageStartChars& pchMessageStartIn, const char* pszCommand, unsigned int nMessageSizeIn);
 
     std::string GetCommand() const;
-    bool IsValid(const MessageStartChars& messageStart) const;
+    bool IsCommandValid() const;
 
     SERIALIZE_METHODS(CMessageHeader, obj) { READWRITE(obj.pchMessageStart, obj.pchCommand, obj.nMessageSize, obj.pchChecksum); }
 
diff --git a/src/test/fuzz/deserialize.cpp b/src/test/fuzz/deserialize.cpp
index f87b7576a4..b799d3b43b 100644
--- a/src/test/fuzz/deserialize.cpp
+++ b/src/test/fuzz/deserialize.cpp
@@ -189,10 +189,9 @@ void test_one_input(const std::vector<uint8_t>& buffer)
         DeserializeFromFuzzingInput(buffer, s);
         AssertEqualAfterSerializeDeserialize(s);
 #elif MESSAGEHEADER_DESERIALIZE
-        const CMessageHeader::MessageStartChars pchMessageStart = {0x00, 0x00, 0x00, 0x00};
         CMessageHeader mh;
         DeserializeFromFuzzingInput(buffer, mh);
-        (void)mh.IsValid(pchMessageStart);
+        (void)mh.IsCommandValid();
 #elif ADDRESS_DESERIALIZE
         CAddress a;
         DeserializeFromFuzzingInput(buffer, a);
diff --git a/src/test/fuzz/p2p_transport_deserializer.cpp b/src/test/fuzz/p2p_transport_deserializer.cpp
index 6252b8e91b..7e216e16fe 100644
--- a/src/test/fuzz/p2p_transport_deserializer.cpp
+++ b/src/test/fuzz/p2p_transport_deserializer.cpp
@@ -39,12 +39,6 @@ void test_one_input(const std::vector<uint8_t>& buffer)
                 assert(result->m_raw_message_size <= buffer.size());
                 assert(result->m_raw_message_size == CMessageHeader::HEADER_SIZE + result->m_message_size);
                 assert(result->m_time == m_time);
-                if (result->m_valid_header) {
-                    assert(result->m_valid_netmagic);
-                }
-                if (!result->m_valid_netmagic) {
-                    assert(!result->m_valid_header);
-                }
             }
         }
     }
diff --git a/test/functional/p2p_invalid_messages.py b/test/functional/p2p_invalid_messages.py
index fe57057a83..78a9d2e852 100755
--- a/test/functional/p2p_invalid_messages.py
+++ b/test/functional/p2p_invalid_messages.py
@@ -81,7 +81,7 @@ class InvalidMessagesTest(BitcoinTestFramework):
     def test_magic_bytes(self):
         self.log.info("Test message with invalid magic bytes disconnects peer")
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())
-        with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: INVALID MESSAGESTART badmsg']):
+        with self.nodes[0].assert_debug_log(['HEADER ERROR - MESSAGESTART (badmsg, 2 bytes), received ffffffff']):
             msg = conn.build_message(msg_unrecognized(str_data="d"))
             # modify magic bytes
             msg = b'\xff' * 4 + msg[4:]
@@ -105,7 +105,7 @@ class InvalidMessagesTest(BitcoinTestFramework):
     def test_size(self):
         self.log.info("Test message with oversized payload disconnects peer")
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())
-        with self.nodes[0].assert_debug_log(['']):
+        with self.nodes[0].assert_debug_log(['HEADER ERROR - SIZE (badmsg, 4000001 bytes)']):
             msg = msg_unrecognized(str_data="d" * (VALID_DATA_LIMIT + 1))
             msg = conn.build_message(msg)
             conn.send_raw_message(msg)
@@ -115,9 +115,8 @@ class InvalidMessagesTest(BitcoinTestFramework):
     def test_msgtype(self):
         self.log.info("Test message with invalid message type logs an error")
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())
-        with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: ERRORS IN HEADER']):
+        with self.nodes[0].assert_debug_log(['HEADER ERROR - COMMAND']):
             msg = msg_unrecognized(str_data="d")
-            msg.msgtype = b'\xff' * 12
             msg = conn.build_message(msg)
             # Modify msgtype
             msg = msg[:7] + b'\x00' + msg[7 + 1:]