Fix panic on response larger than interchanges::SIZE or response::SIZE

src/dispatch.rs

@@ -22,6 +22,14 @@ use iso7816::{
     command::FromSliceError,
 };
 
+/// Maximum length of a data field of a response that can fit in an interchange message after
+/// concatenation of SW1SW2
+const MAX_INTERCHANGE_DATA: usize = if interchanges::SIZE < ResponseSize {
+    interchanges::SIZE
+} else {
+    ResponseSize
+} - 2;
+
 pub use iso7816::Interface;
 
 pub enum RequestType {
@@ -270,7 +278,7 @@ impl ApduDispatch
         // If the reader is using chaining, we will simply
         // reply 61XX, and put the response in a buffer.
         // It is up to the reader to then send GetResponse
-        // requests, to which we will return up to 256 bytes at a time.
+        // requests, to which we will return up to `Le` bytes at a time.
         let (new_state, response) = match &mut self.buffer.raw {
             RawApduBuffer::Request(_) | RawApduBuffer::None => {
                 info!("Unexpected GetResponse request.");
@@ -281,10 +289,10 @@ impl ApduDispatch
             }
             RawApduBuffer::Response(res) => {
 
-                if self.was_request_chained || res.len() > interchanges::SIZE {
+                if self.was_request_chained || res.len() > MAX_INTERCHANGE_DATA {
 
                     // Do not send more than the expected bytes
-                    let boundary = core::cmp::min(self.response_len_expected, res.len());
+                    let boundary = self.response_len_expected.min(res.len()).min(MAX_INTERCHANGE_DATA);
 
                     let to_send = &res[..boundary];
                     let remaining = &res[boundary..];
@@ -298,7 +306,7 @@ impl ApduDispatch
                         // Last chunk has success code
                         0x9000
                     };
-                    message.extend_from_slice(&return_code.to_be_bytes()).ok();
+                    message.extend_from_slice(&return_code.to_be_bytes()).expect("Failed add to status bytes");
                     if return_code == 0x9000 {
                         (
                             RawApduBuffer::None,
@@ -314,8 +322,8 @@ impl ApduDispatch
 
                 } else {
                     // Add success code
-                    res.extend_from_slice(&[0x90,00]).ok();
-                    (RawApduBuffer::None, interchanges::Data::from_slice(res.as_slice()).unwrap())
+                    res.extend_from_slice(&[0x90,00]).expect("Failed to add the status bytes");
+                    (RawApduBuffer::None, interchanges::Data::from_slice(&res.as_slice()).unwrap())
                 }
 
             }

tests/dispatch.rs

@@ -86,6 +86,24 @@ impl App< {apdu_dispatch::command::SIZE}, {apdu_dispatch::response::SIZE},> for
                 reply.extend_from_slice(&addr.to_be_bytes()).unwrap();
                 Ok(())
             }
+
+            // Testing a response larger than the interchange's size
+            0x21 => {
+                reply.extend_from_slice(&[10; interchanges::SIZE+1]).unwrap();
+                Ok(())
+            }
+            0x22 => {
+                reply.extend_from_slice(&[10; interchanges::SIZE-2]).unwrap();
+                Ok(())
+            }
+            0x23 => {
+                reply.extend_from_slice(&[10; interchanges::SIZE-1]).unwrap();
+                Ok(())
+            }
+            0x24 => {
+                reply.extend_from_slice(&[10; interchanges::SIZE]).unwrap();
+                Ok(())
+            }
             _ => 
                 Err(Status::InstructionNotSupportedOrInvalid)
         }
@@ -1029,6 +1047,51 @@ fn send_select_preceded_with_zero_chained_data(){
     )
 }
 
+#[test]
+#[serial]
+fn response_larger_than_interchange(){
+    // Sending a select after chaining 0 bytes should result in successful select operation
+    let mut response1 = vec![0x0A; interchanges::SIZE-2];
+    response1.extend_from_slice(&hex!("6103"));
+    let mut response2 = vec![0x0A; interchanges::SIZE-2];
+    response2.extend_from_slice(&hex!("9000"));
+    let mut response3 = vec![0x0A; interchanges::SIZE-2];
+    response3.extend_from_slice(&hex!("6101"));
+    let mut response4 = vec![0x0A; interchanges::SIZE-2];
+    response4.extend_from_slice(&hex!("6102"));
+    run_apdus(
+        &[
+            // Select 1
+            &hex!("00A40400 05 0A01000001"),
+            &hex!("9000"),
+
+            &hex!("00210000  00ffff"),
+            &response1,
+            
+            // Get Response
+            &hex!("00C00000 00"),
+            &hex!("0A0A0A 9000"),
+
+            &hex!("00220000  00ffff"),
+            &response2,
+
+            &hex!("00230000  00ffff"),
+            &response3,
+            
+            // Get Response
+            &hex!("00C00000 00"),
+            &hex!("0A 9000"),
+
+            &hex!("00240000  00ffff"),
+            &response4,
+
+            // Get Response
+            &hex!("00C00000 00"),
+            &hex!("0A0A 9000"),
+        ]
+    )
+}
+
 
 
 #[test]