add recursion limit

src/lib.rs

@@ -934,7 +934,7 @@ impl<'a> Iterator for PartsIterator<'a> {
 ///     assert_eq!(dateparse(parsed.headers.get_first_value("Date").unwrap().as_str()).unwrap(), 1475417182);
 /// ```
 pub fn parse_mail(raw_data: &[u8]) -> Result<ParsedMail, MailParseError> {
-    parse_mail_recursive(raw_data, false)
+    parse_mail_recursive(raw_data, false, u8::MAX)
 }
 
 /// Strips LF or CRLF if there is one at the end of the string raw_data[ix_start..ix].
@@ -954,6 +954,7 @@ fn strip_trailing_crlf(raw_data: &[u8], ix_start: usize, mut ix: usize) -> usize
 fn parse_mail_recursive(
     raw_data: &[u8],
     in_multipart_digest: bool,
+    depth: u8,
 ) -> Result<ParsedMail, MailParseError> {
     let (headers, ix_body) = parse_headers(raw_data)?;
     let ctype = headers
@@ -994,6 +995,9 @@ fn parse_mail_recursive(
                 result.subparts.push(parse_mail_recursive(
                     &raw_data[ix_part_start..ix_part_end],
                     in_multipart_digest,
+                    depth
+                        .checked_sub(1)
+                        .ok_or(MailParseError::Generic("Recursion limit reached"))?,
                 )?);
                 ix_boundary_end = ix_part_boundary_start
                     .map(|x| x + boundary.len())
@@ -1908,6 +1912,14 @@ mod tests {
         };
     }
 
+    #[test]
+    fn test_recursion_limit() {
+        let mail_filepath = "./tests/files/nested.eml";
+        let mail = std::fs::read(mail_filepath)
+            .expect(&format!("Unable to open the file [{}]", mail_filepath));
+        parse_mail(&mail).unwrap();
+    }
+
     #[test]
     fn test_body_content_encoding_with_multipart() {
         let mail_filepath = "./tests/files/test_email_01.txt";