fix: address argus review on matrix admin-room reset — ascii lowercase, tighter markers, unit tests

hive-c0re/src/matrix.rs

@@ -354,14 +354,20 @@ async fn discover_admin_room_id(
 /// Try to parse the new password from an admin-room bot response.
 /// Conduwuit/tuwunel responds with a message like:
 /// "Done: Password of user @user:server has been reset. The new password is: <password>"
+///
+/// Uses [`str::to_ascii_lowercase`] for case folding — unlike `to_lowercase`,
+/// ASCII lowercasing is guaranteed to produce a same-byte-length string, so the
+/// byte offset from `find` is always a valid index into the original `bot_message`
+/// and we never slice at a non-char boundary.
 fn extract_new_password(bot_message: &str) -> Option<String> {
-    // Look for "new password is:" (case-insensitive) followed by whitespace + the password.
-    let lower = bot_message.to_lowercase();
+    // ASCII lowercase: same byte length as the original, so positions from
+    // `lower.find(marker)` are valid byte indices into `bot_message`.
+    let lower = bot_message.to_ascii_lowercase();
     for marker in &[
         "new password is: ",
         "new password is:",
         "password is: ",
-        "password: ",
+        "password is:",
     ] {
         if let Some(pos) = lower.find(marker) {
             let rest = &bot_message[pos + marker.len()..];
@@ -378,6 +384,53 @@ fn extract_new_password(bot_message: &str) -> Option<String> {
     None
 }
 
+#[cfg(test)]
+mod extract_new_password_tests {
+    use super::extract_new_password;
+
+    #[test]
+    fn tuwunel_style_response() {
+        let msg = "Done: Password of user @atlas:pr1ma.darkest.space has been reset. The new password is: abc123XYZ!";
+        assert_eq!(extract_new_password(msg).as_deref(), Some("abc123XYZ!"));
+    }
+
+    #[test]
+    fn case_insensitive_marker() {
+        let msg = "Password reset complete. New Password Is: S3cr3tP@ss";
+        assert_eq!(extract_new_password(msg).as_deref(), Some("S3cr3tP@ss"));
+    }
+
+    #[test]
+    fn marker_without_trailing_space() {
+        let msg = "new password is:hunter2";
+        assert_eq!(extract_new_password(msg).as_deref(), Some("hunter2"));
+    }
+
+    #[test]
+    fn shorter_marker_variant() {
+        let msg = "Your password is: Tr0ub4dor&3";
+        assert_eq!(extract_new_password(msg).as_deref(), Some("Tr0ub4dor&3"));
+    }
+
+    #[test]
+    fn no_match_returns_none() {
+        let msg = "Command not recognised. Please try again.";
+        assert_eq!(extract_new_password(msg), None);
+    }
+
+    #[test]
+    fn empty_after_marker_returns_none() {
+        let msg = "new password is: ";
+        assert_eq!(extract_new_password(msg), None);
+    }
+
+    #[test]
+    fn password_stops_at_whitespace() {
+        let msg = "New password is: abc123 (save it now)";
+        assert_eq!(extract_new_password(msg).as_deref(), Some("abc123"));
+    }
+}
+
 /// Reset a user's password via the Matrix admin room as a fallback for
 /// homeservers that do not implement the Synapse admin REST API (e.g.
 /// tuwunel 1.6.x). Sends `reset-password @<localpart>:<server>` to