Retain canonical WebDAV root href after alias redirects

src/lib.rs

@@ -23,6 +23,8 @@ const MAX_CHUNK: u32 = 1024 * 1024;
 
 struct Session {
   root: String,
+  /// The server's canonical href is only used to identify listing responses.
+  root_href: String,
   authorization: Option<String>,
 }
 
@@ -42,10 +44,20 @@ impl Session {
       dav::basic(&username, &lookup("password").unwrap_or_default())
     });
     Ok(Self {
+      root_href: root.clone(),
       root,
       authorization,
     })
   }
+
+  fn record_root(&mut self, found: &[dav::Found]) -> Result<(), ErrorCode> {
+    let root = found.first().ok_or(ErrorCode::NotFound)?;
+    if !root.collection || root.href.is_empty() {
+      return Err(ErrorCode::InvalidInput);
+    }
+    self.root_href.clone_from(&root.href);
+    Ok(())
+  }
 }
 
 thread_local! {
@@ -250,12 +262,13 @@ impl Guest for Webdav {
   ) -> Result<Capabilities, ErrorCode> {
     SESSION.set(None);
     SESSION.set(Some(Session::from_config(&config)?));
-    let probe = Self::stat(Locator::Path("/".to_owned())).and_then(|info| {
+    let probe = describe("/", "0").and_then(|found| {
-      if matches!(info.kind, EntryKind::Directory) {
+      SESSION.with_borrow_mut(|session| {
-        Ok(())
+        session
-      } else {
+          .as_mut()
-        Err(ErrorCode::InvalidInput)
+          .ok_or(ErrorCode::Internal)?
-      }
+          .record_root(&found)
+      })
     });
     if let Err(error) = probe {
       SESSION.set(None);
@@ -297,7 +310,7 @@ impl Guest for Webdav {
       None => 0,
     };
     let found = describe(&path, "1")?;
-    let url = session(|session| Ok(dav::url(&session.root, &path)))?;
+    let url = session(|session| Ok(dav::url(&session.root_href, &path)))?;
     let children: Vec<_> = dav::children(&found, &url)?
       .iter()
       .map(|entry| Entry {
@@ -417,7 +430,7 @@ impl Guest for Webdav {
   /// first and refused unless it is empty.
   fn remove(target: Locator) -> Result<(), ErrorCode> {
     let path = route(&target);
-    let url = session(|session| Ok(dav::url(&session.root, &path)))?;
+    let url = session(|session| Ok(dav::url(&session.root_href, &path)))?;
     dav::removable(&describe(&path, "1")?, &url)?;
     exchange(host::Method::Delete, &path, Vec::new(), &[])?;
     Ok(())
@@ -433,6 +446,7 @@ sdk::export!(Webdav with_types_in sdk);
 #[cfg(test)]
 mod tests {
   use super::{SESSION, Session, Webdav};
+  use crate::dav;
   use crate::sdk::{ErrorCode, Guest, Setting};
 
   #[tokio::test]
@@ -487,10 +501,90 @@ mod tests {
     Ok(())
   }
 
+  #[tokio::test]
+  async fn a_redirected_root_lists_its_canonical_directory()
+  -> Result<(), ErrorCode> {
+    let config = vec![(
+      "url".to_owned(),
+      Setting::Text("https://dav.example/webdav".to_owned()),
+    )];
+    let mut session = Session::from_config(&config)?;
+    let entries = [
+      dav::Found {
+        href: "/files/notes.md".to_owned(),
+        collection: false,
+        length: 12,
+        etag: None,
+      },
+      dav::Found {
+        href: "/files/".to_owned(),
+        collection: true,
+        length: 0,
+        etag: None,
+      },
+    ];
+    session.record_root(&entries[1..])?;
+    let expected_url = dav::url(&session.root_href, "/");
+    let listed = dav::children(&entries, &expected_url)?;
+    assert_eq!(listed.len(), 1);
+    assert_eq!(listed[0].href, "/files/notes.md");
+
+    let nested = [
+      dav::Found {
+        href: "/files/documents/child.md".to_owned(),
+        collection: false,
+        length: 7,
+        etag: None,
+      },
+      dav::Found {
+        href: "/files/documents/".to_owned(),
+        collection: true,
+        length: 0,
+        etag: None,
+      },
+    ];
+    let expected_url = dav::url(&session.root_href, "/documents");
+    let listed = dav::children(&nested, &expected_url)?;
+    assert_eq!(listed.len(), 1);
+    assert_eq!(listed[0].href, "/files/documents/child.md");
+    assert_eq!(
+      dav::removable(&nested, &expected_url),
+      Err(ErrorCode::Conflict)
+    );
+    Ok(())
+  }
+
+  #[tokio::test]
+  async fn a_canonical_href_does_not_change_the_authenticated_request_origin()
+  -> Result<(), ErrorCode> {
+    let config = vec![
+      (
+        "url".to_owned(),
+        Setting::Text("https://dav.example/webdav".to_owned()),
+      ),
+      ("username".to_owned(), Setting::Text("user".to_owned())),
+    ];
+    let mut session = Session::from_config(&config)?;
+    session.record_root(&[dav::Found {
+      href: "https://other.example/files/".to_owned(),
+      collection: true,
+      length: 0,
+      etag: None,
+    }])?;
+    assert_eq!(dav::url(&session.root, "/"), "https://dav.example/webdav");
+    assert_eq!(
+      dav::url(&session.root, "/documents/child.md"),
+      "https://dav.example/webdav/documents/child.md"
+    );
+    assert_eq!(session.authorization.as_deref(), Some("Basic dXNlcjo="));
+    Ok(())
+  }
+
   #[tokio::test]
   async fn a_failed_reopen_discards_the_previous_connection() {
     SESSION.set(Some(Session {
       root: "https://dav.example/files/".to_owned(),
+      root_href: "/files/".to_owned(),
       authorization: None,
     }));
     let result = Webdav::open("webdav".to_owned(), Vec::new());