der: add negative read_nested tests

der/src/asn1/sequence_of.rs

@@ -245,7 +245,9 @@ where
 #[cfg(test)]
 mod tests {
     use crate::asn1::SequenceOf;
-    use crate::ord::DerOrd;
+    use crate::{Decode, DerOrd, ErrorKind, Length};
+
+    use hex_literal::hex;
 
     #[test]
     fn sequenceof_valueord_value_cmp() {
@@ -265,4 +267,22 @@ mod tests {
         };
         assert_eq!(arr1.der_cmp(&arr2), Ok(Ordering::Greater));
     }
+
+    #[test]
+    fn sequenceof_data_too_short() {
+        let invalid_data = &hex!(
+            "3002" // SEQUENCE tag and length (shorter than actual data)
+                "0201" // INTEGER tag and length
+                    "05"
+        );
+        let err = SequenceOf::<u16, 5>::from_der(invalid_data)
+            .expect_err("read_nested should narrow down the data slice");
+        assert_eq!(
+            ErrorKind::Incomplete {
+                expected_len: Length::new(5),
+                actual_len: Length::new(4)
+            },
+            err.kind()
+        );
+    }
 }

der/src/asn1/set_of.rs

@@ -478,7 +478,9 @@ mod tests {
     use super::SetOf;
     #[cfg(feature = "alloc")]
     use super::SetOfVec;
-    use crate::{DerOrd, ErrorKind};
+    use crate::{Decode, DerOrd, ErrorKind, Length};
+
+    use hex_literal::hex;
 
     #[test]
     fn setof_tryfrom_array() {
@@ -505,6 +507,24 @@ mod tests {
         assert_eq!(set1.der_cmp(&set2), Ok(Ordering::Greater));
     }
 
+    #[test]
+    fn setof_data_too_short() {
+        let invalid_data = &hex!(
+            "3102" // SET tag and length (shorter than actual data)
+                "0201" // INTEGER tag and length
+                    "04"
+        );
+        let err = SetOf::<u16, 5>::from_der(invalid_data)
+            .expect_err("read_nested should narrow down the data slice");
+        assert_eq!(
+            ErrorKind::Incomplete {
+                expected_len: Length::new(5),
+                actual_len: Length::new(4)
+            },
+            err.kind()
+        );
+    }
+
     #[cfg(feature = "alloc")]
     #[test]
     fn setofvec_tryfrom_array() {

der/src/reader/slice.rs

@@ -222,4 +222,26 @@ mod tests {
             err.kind()
         );
     }
+
+    #[test]
+    fn read_nested_trailing_data() {
+        let len: Length = Length::new_usize(EXAMPLE_MSG.len()).expect("usize to be valid length");
+        let mut reader = SliceReader::new(EXAMPLE_MSG).expect("SliceReader to be created");
+
+        let nested_err: crate::Error = reader
+            .read_nested(len, |rdr| {
+                let x = i8::decode(rdr)?;
+                assert_eq!(42i8, x);
+                Ok(())
+            })
+            .unwrap_err();
+
+        assert_eq!(
+            ErrorKind::TrailingData {
+                decoded: 3u8.into(),
+                remaining: 1u8.into(),
+            },
+            nested_err.kind()
+        );
+    }
 }