fix: attempt to fix panic on decoding startup message

src/error.rs

@@ -13,6 +13,8 @@ pub enum PgWireError {
     InvalidMessageType(u8),
     #[error("Invalid target type, received {0}")]
     InvalidTargetType(u8),
+    #[error("Invalid startup message")]
+    InvalidStartupMessage,
     #[error(transparent)]
     IoError(#[from] std::io::Error),
     #[error("Portal not found for name: {0:?}")]

src/messages/startup.rs

@@ -29,6 +29,8 @@ impl Default for Startup {
 }
 
 impl Startup {
+    const MINIMUM_STARTUP_MESSAGE_LEN: usize = 8;
+
     fn is_protocol_version_supported(version: i32) -> bool {
         version == 196608
     }
@@ -64,7 +66,7 @@ impl Message for Startup {
     fn decode(buf: &mut BytesMut) -> PgWireResult<Option<Self>> {
         // packet len + protocol version
         // check if packet is valid
-        if buf.remaining() >= 8 {
+        if buf.remaining() >= Self::MINIMUM_STARTUP_MESSAGE_LEN {
             let packet_version = (&buf[4..8]).get_i32();
             if !Self::is_protocol_version_supported(packet_version) {
                 return Err(PgWireError::InvalidProtocolVersion(packet_version));
@@ -74,8 +76,17 @@ impl Message for Startup {
         codec::decode_packet(buf, 0, Self::decode_body)
     }
 
-    fn decode_body(buf: &mut BytesMut, _: usize) -> PgWireResult<Self> {
+    fn decode_body(buf: &mut BytesMut, msg_len: usize) -> PgWireResult<Self> {
+        // double check to ensure that the packet has more than 8 bytes
+        // `codec::decode_packet` has its validation to ensure buf remaining is
+        // larger than `msg_len`. So with both checks, we should not have issue
+        // with reading protocol numbers.
+        if msg_len <= Self::MINIMUM_STARTUP_MESSAGE_LEN {
+            return Err(PgWireError::InvalidStartupMessage);
+        }
+
         let mut msg = Startup::default();
+
         // parse
         msg.set_protocol_number_major(buf.get_u16());
         msg.set_protocol_number_minor(buf.get_u16());