Some TPKT packet could have less than 7 bytes as expected by specification

Author: citronneur

src/core/tpkt.rs

@@ -138,7 +138,7 @@ impl<S: Read + Write> Client<S> {
 
             // Minimal size must be 7
             // https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/18a27ef9-6f9a-4501-b000-94b1fe3c2c10
-            if size.inner() < 7 {
+            if size.inner() < 4 {
                 Err(Error::RdpError(RdpError::new(RdpErrorKind::InvalidSize, "Invalid minimal size for TPKT")))
             }
             else {
@@ -155,14 +155,14 @@ impl<S: Read + Write> Client<S> {
                 hi_length.read(&mut Cursor::new(self.transport.read(1)?))?;
                 let length: u16 = ((short_length & !0x80) as u16) << 8;
                 let length = length | hi_length as u16;
-                if length < 7 {
+                if length < 3 {
                     Err(Error::RdpError(RdpError::new(RdpErrorKind::InvalidSize, "Invalid minimal size for TPKT")))
                 } else {
                     Ok(Payload::FastPath(sec_flag, Cursor::new(self.transport.read(length as usize - 3)?)))
                 }
             }
             else {
-                if short_length < 7 {
+                if short_length < 2 {
                     Err(Error::RdpError(RdpError::new(RdpErrorKind::InvalidSize, "Invalid minimal size for TPKT")))
                 } else {
                     Ok(Payload::FastPath(sec_flag, Cursor::new(self.transport.read(short_length as usize - 2)?)))