From 1ff0da1841bd4c2b45ef13e3e8ffec26b65cd94f Mon Sep 17 00:00:00 2001
From: "Dylan M. Taylor" <dylan@dylanmtaylor.com>
Date: Tue, 3 Nov 2026 04:26:03 +0000
Subject: [PATCH] fix(figcraft): write the recovery copy's online note
 owner-only

The .online note beside a recovery copy holds the secret the client resumes
its identity with, but it was written with the default mode while the copy
itself was created 0600. Both now go through one owner-only writer, which
also narrows a note that already existed.
---
 apps/figcraft/src/recovery.rs | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/apps/figcraft/src/recovery.rs b/apps/figcraft/src/recovery.rs
index 750786d1c..92884e528 100644
--- a/apps/figcraft/src/recovery.rs
+++ b/apps/figcraft/src/recovery.rs
@@ -217,7 +217,8 @@ impl Recovery {
                     return false;
                 }
                 let _ = match online {
-                    Some(text) => std::fs::write(&note, text),
+                    // The note holds the secret the client resumes with: owner-only, as the copy.
+                    Some(text) => write_private(&note, text.as_bytes()),
                     None => std::fs::remove_file(&note),
                 };
                 true
@@ -326,24 +327,29 @@ fn rejoin_online(file: &Path, s: &mut Session) -> Option<u64> {
 fn write_atomic(path: &Path, doc: &figcraft_engine::doc::Document, versions: &[Version], branches: &[Branch]) -> bool {
     let Ok(bytes) = figcraft_format::save_bytes_with_history(doc, None, versions, branches) else { return false };
     let tmp = path.with_extension("tmp");
+    if write_private(&tmp, &bytes).is_err() {
+        let _ = std::fs::remove_file(&tmp);
+        return false;
+    }
+    std::fs::rename(&tmp, path).is_ok()
+}
+
+/// Write `bytes` to `path`, created (or cut back) readable by its owner only on Unix.
+fn write_private(path: &Path, bytes: &[u8]) -> std::io::Result<()> {
     #[cfg(unix)]
     {
-        use std::os::unix::fs::OpenOptionsExt;
+        use std::os::unix::fs::{OpenOptionsExt, PermissionsExt};
         let mut opts = std::fs::OpenOptions::new();
         opts.write(true).create(true).truncate(true).mode(0o600);
-        let Ok(mut f) = opts.open(&tmp) else { return false };
-        if std::io::Write::write_all(&mut f, &bytes).is_err() {
-            let _ = std::fs::remove_file(&tmp);
-            return false;
-        }
+        let mut f = opts.open(path)?;
+        // `mode` applies to a new file only: one that was there keeps its mode unless set.
+        f.set_permissions(std::fs::Permissions::from_mode(0o600))?;
+        std::io::Write::write_all(&mut f, bytes)
     }
     #[cfg(not(unix))]
     {
-        if std::fs::write(&tmp, bytes).is_err() {
-            return false;
-        }
+        std::fs::write(path, bytes)
     }
-    std::fs::rename(&tmp, path).is_ok()
 }
 
 /// [`recover_all`], for a start that keeps nothing waiting: how many documents came back as