Merge pull request #89 from tweedegolf/extra-crc-collision-check

Add extra check to catch crc collisions

Author: diondokter

CHANGELOG.md

@@ -7,6 +7,7 @@
 - Added `Key` implementation for the unit type `()` for easy storage of a single value
 - *Breaking:* Changed API for map `fetch_all_items` such that the `Key` is captured in `MapItemIter`.
 - Fixed some logic so queue can be used on a single page. (It's still recommended to use at least 2 pages for both the queue and the map)
+- Add some extra logic to catch more crc collisions
 
 ## 4.0.3 18-06-25
 

src/item.rs

@@ -97,15 +97,27 @@ impl ItemHeader {
             break;
         }
 
-        Ok(Some(Self {
+        let header = Self {
             length: u16::from_le_bytes(header_slice[Self::LENGTH_FIELD].try_into().unwrap()),
             crc: {
                 match u32::from_le_bytes(header_slice[Self::DATA_CRC_FIELD].try_into().unwrap()) {
                     0 => None,
                     value => Some(NonZeroU32::new(value).unwrap()),
                 }
             },
-        }))
+        };
+
+        if header.next_item_address::<S>(address) > end_address {
+            // We have a header here that's claims it's larger than is possible
+            // This is never written. So either it's a bug or there's a CRC collision
+            // Let's assume the latter
+            return Err(Error::Corrupted {
+                #[cfg(feature = "_test")]
+                backtrace: std::backtrace::Backtrace::capture(),
+            });
+        }
+
+        Ok(Some(header))
     }
 
     pub async fn read_item<'d, S: NorFlash>(