Use checked sub

2020-12-10 21:26:44 -08:00
parent 9c9f9efcce
commit a7eb38aac8
1 changed files with 2 additions and 1 deletions
--- a/src/ctap/apdu.rs
+++ b/src/ctap/apdu.rs
@@ -174,7 +174,8 @@ impl TryFrom<&[u8]> for APDU {
                return Err(ApduStatusCode::SW_WRONG_LENGTH);
            }

-            let extended_apdu_le_len: usize = payload.len() - extended_apdu_lc - 3;
+            let extended_apdu_le_len: usize =
+                payload.len().checked_sub(extended_apdu_lc + 3).unwrap_or(0);
            if extended_apdu_le_len > 3 {
                return Err(ApduStatusCode::SW_WRONG_LENGTH);
            }