Allow customisation of alert sent for InvalidMessage

Use this to send the correct alert for InvalidMessage::PreSharedKeyIsNotFinalExtension

rustls/src/conn.rs

@@ -892,7 +892,7 @@ impl<Data> ConnectionCore<Data> {
             Err(err) => {
                 return Err(self
                     .common_state
-                    .send_fatal_alert(AlertDescription::DecodeError, err));
+                    .send_fatal_alert(err.into(), err));
             }
         };
 

rustls/src/error.rs

@@ -162,6 +162,15 @@ impl From<InvalidMessage> for Error {
     }
 }
 
+impl From<InvalidMessage> for AlertDescription {
+    fn from(e: InvalidMessage) -> Self {
+        match e {
+            InvalidMessage::PreSharedKeyIsNotFinalExtension => Self::IllegalParameter,
+            _ => Self::DecodeError,
+        }
+    }
+}
+
 #[non_exhaustive]
 #[allow(missing_docs)]
 #[derive(Debug, PartialEq, Clone)]

rustls/src/msgs/message/mod.rs

@@ -1,5 +1,5 @@
 use crate::enums::{AlertDescription, ContentType, HandshakeType, ProtocolVersion};
-use crate::error::{Error, InvalidMessage};
+use crate::error::InvalidMessage;
 use crate::msgs::alert::AlertMessagePayload;
 use crate::msgs::base::Payload;
 use crate::msgs::ccs::ChangeCipherSpecPayload;
@@ -190,7 +190,7 @@ impl Message<'_> {
 }
 
 impl TryFrom<PlainMessage> for Message<'static> {
-    type Error = Error;
+    type Error = InvalidMessage;
 
     fn try_from(plain: PlainMessage) -> Result<Self, Self::Error> {
         Ok(Self {
@@ -206,7 +206,7 @@ impl TryFrom<PlainMessage> for Message<'static> {
 /// A [`PlainMessage`] must contain plaintext content. Encrypted content should be stored in an
 /// [`InboundOpaqueMessage`] and decrypted before being stored into a [`PlainMessage`].
 impl<'a> TryFrom<InboundPlainMessage<'a>> for Message<'a> {
-    type Error = Error;
+    type Error = InvalidMessage;
 
     fn try_from(plain: InboundPlainMessage<'a>) -> Result<Self, Self::Error> {
         Ok(Self {