RUST-713 Fix underflow on BSON array and binary deserialization (#244)

src/de/mod.rs

@@ -176,6 +176,17 @@ fn deserialize_array<R: Read + ?Sized>(reader: &mut R, utf8_lossy: bool) -> Resu
     let mut arr = Array::new();
     let length = read_i32(reader)?;
 
+    if !(MIN_BSON_DOCUMENT_SIZE..=MAX_BSON_SIZE).contains(&length) {
+        return Err(Error::invalid_length(
+            length as usize,
+            &format!(
+                "array length must be between {} and {}",
+                MIN_BSON_DOCUMENT_SIZE, MAX_BSON_SIZE
+            )
+            .as_str(),
+        ));
+    }
+
     ensure_read_exactly(
         reader,
         (length as usize) - 4,
@@ -224,6 +235,14 @@ pub(crate) fn deserialize_bson_kvp<R: Read + ?Sized>(
             if let BinarySubtype::BinaryOld = subtype {
                 let data_len = read_i32(reader)?;
 
+                if !(0..=(MAX_BSON_SIZE - 4)).contains(&data_len) {
+                    return Err(Error::invalid_length(
+                        data_len as usize,
+                        &format!("0x02 length must be between 0 and {}", MAX_BSON_SIZE - 4)
+                            .as_str(),
+                    ));
+                }
+
                 if data_len + 4 != len {
                     return Err(Error::invalid_length(
                         data_len as usize,

src/tests/modules/serializer_deserializer.rs

@@ -540,3 +540,25 @@ fn test_serialize_deserialize_document() {
     let bad_point: Result<Point, crate::de::Error> = from_document(bad_point);
     assert!(bad_point.is_err());
 }
+
+/// [RUST-713](https://jira.mongodb.org/browse/RUST-713)
+#[test]
+fn test_deserialize_invalid_array_length() {
+    let _guard = LOCK.run_concurrently();
+    let buffer = b"\n\x00\x00\x00\x04\x00\x00\x00\x00\x00";
+    Document::from_reader(&mut std::io::Cursor::new(buffer))
+        .expect_err("expected deserialization to fail");
+}
+
+/// [RUST-713](https://jira.mongodb.org/browse/RUST-713)
+#[test]
+fn test_deserialize_invalid_old_binary_length() {
+    let _guard = LOCK.run_concurrently();
+    let buffer = b"\x0F\x00\x00\x00\x05\x00\x00\x00\x00\x00\x02\xFC\xFF\xFF\xFF";
+    Document::from_reader(&mut std::io::Cursor::new(buffer))
+        .expect_err("expected deserialization to fail");
+
+    let buffer = b".\x00\x00\x00\x05\x01\x00\x00\x00\x00\x00\x02\xfc\xff\xff\xff\xff\xff\xff\xff\x00\x00*\x00h\x0e\x10++\x00h\x0e++\x00\x00\t\x00\x00\x00\x00\x00*\x0e\x10++";
+    Document::from_reader(&mut std::io::Cursor::new(buffer))
+        .expect_err("expected deserialization to fail");
+}