Fix folding of boundary lines

Ensure boundary lines are not folded with preceding decoded text.

2 files changed, 20 insertions, 1 deletions

diff --git a/src/normalize.rs b/src/normalize.rs
index 7c8487d..3774f73 100644
--- a/src/normalize.rs
+++ b/src/normalize.rs
@@ -350,7 +350,18 @@ fn decode_text_data_to_buf(
             _ => Err("unknown encoding".into()),
         };
 
-        if result.is_err() {
+        if result.is_ok() {
+            // During decoding the final CRLF/LF in the data may be dropped.
+            // Restore it to ensure that subsequent lines don't get folded
+            // with the decoded data.
+            const CRLF: &[u8] = &[b'\r', b'\n'];
+            const LF: &[u8] = &[b'\n'];
+            if data.ends_with(CRLF) && !out.ends_with(CRLF) {
+                out.extend(CRLF);
+            } else if data.ends_with(LF) && !out.ends_with(LF) {
+                out.extend(LF);
+            }
+        } else {
             out.resize(initial_len, 0);
             should_convert_charset = false;
         }
diff --git a/tests/test_encoding.rs b/tests/test_encoding.rs
index 1579449..9b339b5 100644
--- a/tests/test_encoding.rs
+++ b/tests/test_encoding.rs
@@ -106,6 +106,14 @@ fn base64_parts_are_decoded() {
 }
 
 #[test]
+fn base64_boundaries_remain_on_their_own_line() {
+    let email = Email::from_vec(TEST_EMAIL_MULTIPART.to_string().into_bytes()).unwrap();
+
+    assert!(!email.data().search(r"[^\n]--XtT01VFrJIenjlg\+ZCXSSWq4").unwrap());
+    assert!(!email.data().search(r"[^\n]--2c\+OeCbICgJrtINI5EFlsI6G").unwrap());
+}
+
+#[test]
 fn non_text_base64_is_not_decoded() {
     let email = Email::from_vec(TEST_EMAIL_MULTIPART.to_string().into_bytes()).unwrap();