Torrents download into a folder of their own (#318 #331)

The recorded path was output_folder.join(handle.name()). The name is the
publisher's: librqbit checks it for traversal only when it chooses the
subfolder itself, and ipx passes output_folder, so a multi-file torrent
named "/config" or ".." pointed Delete, the reaper and /media at that
path. With output_folder set, librqbit also puts a multi-file torrent's
files straight into it, not under the name, so the joined path was not
where the files were even for an honest torrent.

Each enclosure now gets torrent-<id> inside its feed's folder, and that
folder is the path: playable() already picks the largest file under a
folder and remove() deletes one (#158). The same folder keeps
overwrite: true from replacing another enclosure's files of the same
name. A torrent half-downloaded before this restarts in its new folder.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ipx/CHANGELOG.md

@@ -20,6 +20,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - A WordPress.com site that answers its feed with a browser check (HTTP 403, "Checking your browser...") is read from WordPress.com's API instead, so Pelgrane Press's feed no longer fails for hours at a time. The items are the ones the feed gave: same ids (#317).
 
+### Security
+
+- An episode that comes as a torrent downloads into a folder of its own, `torrent-<id>` in its podcast's folder. A torrent could name a path anywhere on the server for Delete, the cleanup and playback to act on, and could overwrite other episodes' files of the same name (#318, #331).
+
 ## [1.4.0] - 2026-10-19
 
 ### Added

crates/ipx/src/main.rs

@@ -2401,7 +2401,7 @@ async fn torrent_one(
     let cfg = ctx.cfg();
     ctx.torrents()
         .await?
-        .fetch(&cfg, url, dest_dir, |done, total| {
+        .fetch(&cfg, url, &torrent::own_folder(dest_dir, enclosure), |done, total| {
             if let Some(pct) = (done * 100).checked_div(total).map(|p| p as i64)
                 && pct > last_pct
             {

crates/ipx/src/torrent.rs

@@ -39,7 +39,8 @@ impl Torrents {
     }
 
     /// Downloads a torrent (a .torrent URL or a magnet link) straight into `dest_dir`,
-    /// seeds it up to the configured limit, then stops.
+    /// seeds it up to the configured limit, then stops. `dest_dir` is the torrent's own
+    /// folder (`own_folder`), and it is the path returned: a file of several or one.
     ///
     /// Downloading in place rather than into a staging dir is deliberate: seeding serves
     /// the files it downloaded, so moving them first would break it.
@@ -103,8 +104,10 @@ impl Torrents {
             }
         }
 
-        let name = handle.name().unwrap_or_else(|| "torrent".to_owned());
-        let path = handle.output_folder().join(&name);
+        // The torrent's own name is the publisher's to choose, and librqbit checks it only when it
+        // picks the folder itself: joined on, "/config" or ".." pointed Delete, the reaper and
+        // /media at anything the daemon can reach (#318). The folder is ours, so it is the path.
+        let path = dest_dir.to_owned();
         let size = handle.stats().total_bytes;
 
         self.seed(cfg, &handle).await;
@@ -134,6 +137,13 @@ impl Torrents {
     }
 }
 
+/// The folder an enclosure's torrent downloads into, one per enclosure inside the feed's folder.
+/// With `overwrite` on, a torrent written straight into the feed's folder could replace another
+/// enclosure's files of the same name, another feed's too when they share a folder (#331).
+pub fn own_folder(feed_dir: &Path, enclosure: i64) -> PathBuf {
+    feed_dir.join(format!("torrent-{enclosure}"))
+}
+
 /// Uploaded over total. A zero-byte torrent counts as fully seeded rather than dividing by zero.
 pub fn ratio(uploaded: u64, total: u64) -> f64 {
     if total == 0 {
@@ -154,6 +164,15 @@ mod tests {
         assert!(ratio(0, 0).is_infinite(), "must not divide by zero or seed forever");
     }
 
+    #[test]
+    fn own_folder_is_one_folder_inside_the_feeds() {
+        let feed = Path::new("/downloads/Show");
+        let dir = own_folder(feed, 42);
+        assert_eq!(dir.parent(), Some(feed));
+        assert!(matches!(dir.components().next_back(), Some(std::path::Component::Normal(_))));
+        assert_ne!(own_folder(feed, 43), dir, "two enclosures never share a folder");
+    }
+
     #[test]
     fn stall_limit_is_never_zero() {
         let mut cfg = Config::default();