From 645bae8fb8065a353237d24aff274009f37d694e Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Sat, 7 Nov 2026 22:35:21 +0100
Subject: access: a node registers before it writes

Under a policy, a change by a node that isn't a member is refused with
all built on it: a node's registration is written before any write of
its own or through the API, not after (the registration itself
exempt).

Auth plan M6 (fix).
---
 src/swarm/members.rs | 49 +++++++++++++++++++++++++++++++------------------
 1 file changed, 31 insertions(+), 18 deletions(-)

(limited to 'src/swarm')

diff --git a/src/swarm/members.rs b/src/swarm/members.rs
index cbd970d..0cadb00 100644
--- a/src/swarm/members.rs
+++ b/src/swarm/members.rs
@@ -293,6 +293,34 @@ const RENEWAL_MOST_OFTEN: Duration = Duration::from_secs(3600);
 pub(crate) const MIN_ELECTORATE_WINDOW: Duration =
     Duration::from_secs(7 * RENEWAL_MOST_OFTEN.as_secs());
 
+/// Whether `node` is registered in `doc`'s member list.
+pub(crate) fn registered(doc: &impl ReadDoc, node: &str) -> bool {
+    store::read_path(doc, &member_path(node))
+        .ok()
+        .flatten()
+        .is_some()
+}
+
+/// This node's entry in the member list, as it registers (`ensure_registered`).
+pub(crate) fn entry(state: &AppState) -> JsonValue {
+    let now = state.clock.now_millis().as_u64();
+    let mut addresses = state.transport.local_addresses();
+    addresses.truncate(MAX_ADDRESSES);
+    let mut entry = json!({
+        "since": now,
+        "alive": now,
+        "addresses": addresses,
+        "window": state.electorate_window.as_millis() as u64,
+    });
+    if let Some(alias) = &state.alias {
+        entry["alias"] = json!(alias);
+    }
+    if let Some(url) = &state.dashboard_url {
+        entry["dashboard"] = json!(url);
+    }
+    entry
+}
+
 /// Registers this node if it is ready and its entry is missing, keeps its alias and its
 /// dashboard's URL as configured (set, changed or removed after a restart with another
 /// `--alias` or `--dashboard-url`) and its
@@ -315,12 +343,8 @@ pub(crate) async fn ensure_registered(state: &AppState) {
         shortest,
     ) = {
         let replica = state.doc.read().await;
-        let registered = store::read_path(&replica.doc, &own)
-            .ok()
-            .flatten()
-            .is_some();
         (
-            registered,
+            registered(&replica.doc, &local),
             alias(&replica.doc, &local),
             dashboard(&replica.doc, &local),
             addresses(&replica.doc, &local),
@@ -335,20 +359,9 @@ pub(crate) async fn ensure_registered(state: &AppState) {
     let now = state.clock.now_millis().as_u64();
 
     if !registered {
-        let mut entry = json!({
-            "since": now,
-            "alive": now,
-            "addresses": own_addresses,
-            "window": window,
-        });
-        if let Some(alias) = &wanted {
-            entry["alias"] = json!(alias);
-        }
-        if let Some(url) = &state.dashboard_url {
-            entry["dashboard"] = json!(url);
-        }
+        let entry = entry(state);
         match state
-            .mutate_doc(move |doc| store::write_path(doc, &own, &entry))
+            .mutate_doc_registering(move |doc| store::write_path(doc, &own, &entry))
             .await
         {
             Ok(()) => info!(
-- 
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