A feed's credentials go to its own host alone (#327 #328)

feed::fetch already sent basic auth only to the feed's own host, but
two paths around it did not:

- download::download attached the feed's username and password to
  every enclosure, on whatever host the feed named: a CDN, or the
  measurement and ad-insertion prefixes podcasts route through (#328).
- subscriptions() and promote_kept() gave every feed an OPML or Patreon
  list derives the list's credentials, and fetch's same-host check then
  compared against the derived feed's own URL, so the list's password
  went to every host the OPML named, on every scan (#327).

config::Feed::auth_for and credentials_for compare hosts once, and
each of the three uses them.

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

crates/ipx/CHANGELOG.md

@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - HTTPS connections no longer trust certificates from emSign's distrusted intermediates, and certificate checks use constant-time comparisons: rustls-webpki, webpki-roots and ctutils are updated (#351).
 - A new install's `admin` gets a random password, written to `admin-password` beside config.toml and readable by iPX's user alone, or the one in `IPX_ADMIN_PASSWORD`. Every install began as admin / ipodderx, a password published in the README, and the log printed it (#321).
 - A show kept from a private OPML or Patreon list stays private, with the list's username and password, once the list is removed or left. It became public and was shared to the directory (#332).
+- A feed's username and password go to its own host alone: not to its episodes on other hosts, nor to the feeds an OPML lists on other hosts, which took the OPML's password on every check (#327, #328).
 
 ## [1.4.0] - 2026-10-19
 

crates/ipx/src/config.rs

@@ -300,6 +300,27 @@ impl Feed {
     pub fn auth(&self) -> Option<(&str, Option<String>)> {
         self.username.as_deref().map(|u| (u, self.password()))
     }
+
+    /// `auth()`, for a URL on the feed's own host only. The credential is for whoever issued it,
+    /// and an enclosure, or a feed an OPML lists, can be on any host its author names (#327, #328).
+    pub fn auth_for(&self, url: &str) -> Option<(&str, Option<String>)> {
+        same_host(&self.url, url).then(|| self.auth()).flatten()
+    }
+
+    /// The username, password and password_env a feed at `url` takes from this one, its OPML or
+    /// Patreon list: all of them on the list's own host, none elsewhere.
+    pub fn credentials_for(&self, url: &str) -> (Option<String>, Option<String>, Option<String>) {
+        if same_host(&self.url, url) {
+            (self.username.clone(), self.password.clone(), self.password_env.clone())
+        } else {
+            (None, None, None)
+        }
+    }
+}
+
+fn same_host(a: &str, b: &str) -> bool {
+    let host = |u: &str| url::Url::parse(u).ok().and_then(|u| u.host_str().map(str::to_ascii_lowercase));
+    host(a).is_some_and(|h| host(b).as_ref() == Some(&h))
 }
 
 impl Config {
@@ -529,6 +550,22 @@ fn expand_tilde(p: &Path) -> PathBuf {
 mod tests {
     use super::*;
 
+    #[test]
+    fn a_feeds_password_goes_to_its_own_host_alone() {
+        let paid = Feed {
+            url: "https://Members.example.com/feed.xml".into(),
+            username: Some("me".into()),
+            password: Some("pw".into()),
+            ..toml::from_str("url = 'x'").unwrap()
+        };
+        assert_eq!(paid.auth_for("https://members.example.com/ep1.mp3"), Some(("me", Some("pw".into()))));
+        assert_eq!(paid.auth_for("https://cdn.example.net/ep1.mp3"), None, "an enclosure elsewhere (#328)");
+        assert_eq!(paid.auth_for("https://members.example.com.evil.net/x"), None);
+        assert_eq!(paid.auth_for("not a url"), None);
+        assert_eq!(paid.credentials_for("https://members.example.com/other.xml").0.as_deref(), Some("me"));
+        assert_eq!(paid.credentials_for("https://elsewhere.org/feed.xml"), (None, None, None), "an OPML's feed (#327)");
+    }
+
     #[test]
     fn the_file_kept_beside_the_database_has_no_feeds_or_server_settings() {
         let cfg: Config = toml::from_str(

crates/ipx/src/download.rs

@@ -133,8 +133,8 @@ pub async fn download(
     mut on_progress: impl FnMut(u64, Option<u64>),
 ) -> Result<Downloaded> {
     let mut req = client.get(url);
-    if let Some(user) = &feed_cfg.username {
-        req = req.basic_auth(user, feed_cfg.password());
+    if let Some((user, password)) = feed_cfg.auth_for(url) {
+        req = req.basic_auth(user, password);
     }
     let resp = req.send().await.context("connecting")?;
     if !resp.status().is_success() {

crates/ipx/src/main.rs

@@ -1429,6 +1429,7 @@ pub async fn subscriptions(ctx: &Ctx) -> Result<Vec<Sub>> {
             }
         };
         let title = m.title.clone().unwrap_or_else(|| m.id.clone());
+        let (username, password, password_env) = parent.map(|p| p.credentials_for(&m.url)).unwrap_or_default();
         out.push(Sub {
             id: m.id.clone(),
             cfg: config::Feed {
@@ -1441,9 +1442,9 @@ pub async fn subscriptions(ctx: &Ctx) -> Result<Vec<Sub>> {
                 allow_explicit: parent.is_some_and(|p| p.allow_explicit),
                 auto_download: parent.is_none_or(|p| p.auto_download),
                 max_new_per_check: parent.and_then(|p| p.max_new_per_check),
-                username: parent.and_then(|p| p.username.clone()),
-                password: parent.and_then(|p| p.password.clone()),
-                password_env: parent.and_then(|p| p.password_env.clone()),
+                username,
+                password,
+                password_env,
                 category: None,
                 listed: false,
                 private: false,
@@ -1544,6 +1545,7 @@ async fn promote_kept(ctx: &Ctx, m: &db::Managed, base: Option<&config::Feed>) -
     }
     let mut cfg = ctx.edit_cfg().await;
     // The list's own settings carry over; its folder and group do not.
+    let (username, password, password_env) = base.map(|p| p.credentials_for(&m.url)).unwrap_or_default();
     cfg.feeds.entry(m.id.clone()).or_insert_with(|| config::Feed {
         url: m.url.clone(),
         folder: None,
@@ -1554,9 +1556,9 @@ async fn promote_kept(ctx: &Ctx, m: &db::Managed, base: Option<&config::Feed>) -
         allow_explicit: base.is_some_and(|p| p.allow_explicit),
         auto_download: base.is_none_or(|p| p.auto_download),
         max_new_per_check: base.and_then(|p| p.max_new_per_check),
-        username: base.and_then(|p| p.username.clone()),
-        password: base.and_then(|p| p.password.clone()),
-        password_env: base.and_then(|p| p.password_env.clone()),
+        username,
+        password,
+        password_env,
         category: None,
         listed: false,
         // Looked up after the list was removed, private was always false, and a private OPML's