Issue 191: an internal name is served to the private network only

The first fix served the dropped route to anyone who sent its name. Record why in the issue, as a progressive insight on ADR 0138, and in the to-be connectivity design.
2026-10-02 01:10:13 +02:00
parent 496d136d72
commit 68650cda5f
4 changed files with 71 additions and 4 deletions
@@ -1,9 +1,9 @@
 ---
 status: located
 opened: 2026-10-01
-located-in: [mesh-controller examples/route-proxy/main.go (routesFrom requires a route's public `name` and treats `internal-name` only as an alias of it)]
+located-in: [mesh-controller examples/route-proxy/main.go (routesFrom requires a route's public `name` and treats `internal-name` only as an alias of it; the handler serves every routed name to any source), mesh-catalog modules/route-proxy/module.json (the proxy is not told the private network's range)]
 fixed-by:
-amended-design: []
+amended-design: [03-DESIGN/01-to-be/08-connectivity.md]
 ---

 # 191 — A route with only an internal name is dropped as naming nothing
@@ -23,9 +23,43 @@ mesh before ADR 0138, when both names were always composed. It has been wrong si
 The other half of the proxy already handles the case. Certificates for a host are split by whether it
 is in the public set: hosts outside it go to the internal authority, and only hosts inside it are
 eligible for ACME. A host that is only ever an internal name falls on the correct side of both checks
-without change. Only reading the route was wrong.
+without change. For certificates, only reading the route was wrong; who may reach the route is the next section.

 **The fix.** `routesFrom` takes a route that names either host, serves each name it carries, and
 marks only the public one as public. It still skips a route that names neither, with the same log line.
 A test proves an internal-only route is served, certified by the internal authority, and refused by
 the public one. That test fails against the code before the change.
+
+## The first fix would have made the name public — 2026-10-02, from review
+
+Serving the dropped route was not enough. The proxy picks a route from the name a request carries
+and never from where the request came from, and it answers public and internal names on the same
+listeners. Its public names resolve to an address the internet reaches. So once the internal-only
+route was served, any request from the internet carrying `unifi.home-server.internal` — a name of a
+fixed, guessable shape — would have reached an administration interface that reach `internal` was
+chosen to keep private. Before the fix the route was unreachable from everywhere. After it, it would
+have been reachable from everywhere. Two more leaks came with it: the proxy's answer for an unrouted
+name listed every name it serves, internal ones included, and the handshake handed a certificate
+naming the internal host to any client.
+
+Nothing showed this while every routed endpoint also had a public name: its internal name exposed
+nothing the public one did not. It is a gap in the decision's wording, not only in the proxy — ADR
+0138 says the proxy *serves* the internal name without saying to whom — so it is recorded there as a
+progressive insight and in the to-be connectivity design.
+
+**Where "inside" is decided.** The mesh's guard recognises the private network by the interface a
+packet arrives on, never by source address, because a source can be claimed. The proxy cannot see the
+interface, so it reads the source: the mesh's range, loopback, and the ranges of the machine's own
+container bridges, which are the same interfaces the guard names. A claimed source does not carry
+here, as a connection needs its replies, and replies to those addresses leave by the tunnel or a
+local bridge. The range reaches the proxy from the catalog as the machine's `mesh-range`, the way the
+intrusion filter already receives it. With none given, the proxy serves internal names to the machine
+alone: refused, not opened.
+
+**What changed with it.** The internal name of a route that also has a public one is now served to
+the private network only, like any other internal name. Outsiders have the public name, so nothing
+they could reach is lost.
+
+**Order of release.** The catalog change comes first. A proxy built from the change but started
+without the range would serve internal names to its own machine alone, and every other member of the
+mesh would lose them until the range arrived.