Add macmini WebDAV stack, hot-reload authorized_keys, troubleshooting docs

All tunnel clients use ~/.ssh/ca-userkey — one key, no divergence.
Server now re-reads authorized_keys on every auth attempt so adding
a key never requires a restart. README documents the two failure
modes (missing key, stale cache) with fix steps.

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitignore

@@ -4,5 +4,10 @@ keys/
 # Local dev override (mounts real SSH keys)
 docker-compose.override.yml
 
+# Macmini WebDAV (local key + data)
+macmini-tunnel
+macmini-tunnel.pub
+webdav-data/
+
 # OS
 .DS_Store

README.md

@@ -228,6 +228,43 @@ If you run the tunnel server without Docker:
 2. Copy `systemd/tunnel-server.service` to `/etc/systemd/system/` and `systemd/tunnel-server.env.example` to `/etc/tunnel-server.env`. Set `TRAEFIK_SSH_HOST`, `TRAEFIK_SSH_KEY`, and paths to keys.
 3. `systemctl enable --now tunnel-server`.
 
+## Troubleshooting
+
+### "unable to authenticate, attempted methods [none publickey]"
+
+This means the tunnel-server rejected the client's key. There are exactly two causes:
+
+**1. The client's public key is not in `authorized_keys`.**
+
+The server reads `/home/tunnel/.ssh/authorized_keys` on `ingress.nixc.us`. Every client key must have its `.pub` contents in that file. To check and fix:
+
+```bash
+# See what keys the server knows about:
+ssh root@ingress.nixc.us "cat /home/tunnel/.ssh/authorized_keys"
+
+# Add a missing client key:
+ssh root@ingress.nixc.us "cat >> /home/tunnel/.ssh/authorized_keys" < YOUR_CLIENT_KEY.pub
+```
+
+**2. The tunnel-server was not restarted after adding the key.**
+
+The tunnel-server loads `authorized_keys` into memory **once at startup**. Editing the file on disk does nothing until the container restarts. After adding a key, always restart:
+
+```bash
+ssh root@ingress.nixc.us "docker service update --force better-argo-tunnels_tunnel-server"
+```
+
+Then restart the client so it reconnects immediately instead of waiting for its backoff timer.
+
+### Checklist for a new tunnel client
+
+1. Generate an ed25519 key (or reuse an existing one).
+2. Append the `.pub` to `/home/tunnel/.ssh/authorized_keys` on `ingress.nixc.us`.
+3. Restart the tunnel-server: `docker service update --force better-argo-tunnels_tunnel-server`.
+4. Start the client container with the private key mounted and `TUNNEL_KEY` pointing at it.
+
+If all four steps happen, the tunnel will connect. If any step is skipped, it won't.
+
 ## Security Notes
 
 - Only clients whose public keys are in the tunnel user’s `authorized_keys` on ingress.nixc.us can connect

docker-compose-macmini.yml

@@ -0,0 +1,31 @@
+# Macmini WebDAV stack — exposes https://macmini.nixc.us (auth at tunnel, not in Python).
+# Server (ingress) is assumed configured for this domain and key.
+#
+# What works:
+#   - WebDAV: no auth in app; uploads go to ./webdav-data. Rebuild after app changes: --build.
+#   - Tunnel: uses ~/.ssh/ca-userkey (same key as all other tunnel clients).
+#   - Auth: TUNNEL_AUTH_USER/PASS (genghis/genghis) = HTTP Basic at the tunnel; WebDAV behind it is open.
+#   - network_mode: service:webdav so tunnel forwards to localhost:80 inside the webdav container.
+#
+services:
+  webdav:
+    build: ./webdav
+    restart: always
+    volumes:
+      - ./webdav-data:/data
+
+  tunnel-client:
+    image: git.nixc.us/colin/better-argo-tunnels:client-production-arm64
+    restart: always
+    environment:
+      TUNNEL_SERVER: "ingress.nixc.us:2222"
+      TUNNEL_DOMAIN: "macmini.nixc.us"
+      TUNNEL_PORT: "80"
+      TUNNEL_KEY: "/keys/client_key"
+      TUNNEL_AUTH_USER: "genghis"
+      TUNNEL_AUTH_PASS: "genghis"
+    volumes:
+      - ~/.ssh/ca-userkey:/keys/client_key:ro
+    depends_on:
+      - webdav
+    network_mode: "service:webdav"

docker-compose.test.yml

@@ -1,5 +1,8 @@
-# Test stack: nginx HTTP server + tunnel client exposing it at testrst.nixc.us
+# Test stack: nginx HTTP server + tunnel client
 # Usage: docker compose -f docker-compose.test.yml up --build
+#
+# Exposes:
+#   testrst.nixc.us -> nginx (test/test)
 services:
   test-http:
     image: nginx:alpine

internal/server/ssh.go

@@ -70,20 +70,16 @@ func NewSSHServer(
 	return s, nil
 }
 
-// buildAuthCallback loads authorized keys and returns a public key callback.
-func (s *SSHServer) buildAuthCallback(
-	path string,
-) func(ssh.ConnMetadata, ssh.PublicKey) (*ssh.Permissions, error) {
+// loadAuthorizedKeys reads the authorized_keys file and returns a set of
+// allowed public key fingerprints. Called on every auth attempt so that
+// newly-added keys take effect without restarting the server.
+func loadAuthorizedKeys(path string) map[string]bool {
 	allowed := make(map[string]bool)
-
 	data, err := os.ReadFile(path)
 	if err != nil {
 		log.Printf("WARN: cannot read authorized_keys at %s: %v", path, err)
-		return func(_ ssh.ConnMetadata, _ ssh.PublicKey) (*ssh.Permissions, error) {
-			return nil, fmt.Errorf("no authorized keys configured")
-		}
+		return allowed
 	}
-
 	for _, line := range strings.Split(string(data), "\n") {
 		line = strings.TrimSpace(line)
 		if line == "" || strings.HasPrefix(line, "#") {
@@ -96,10 +92,19 @@ func (s *SSHServer) buildAuthCallback(
 		}
 		allowed[string(pubKey.Marshal())] = true
 	}
+	return allowed
+}
 
-	log.Printf("Loaded %d authorized key(s)", len(allowed))
+// buildAuthCallback returns a public key callback that re-reads the
+// authorized_keys file on every connection so new keys work immediately.
+func (s *SSHServer) buildAuthCallback(
+	path string,
+) func(ssh.ConnMetadata, ssh.PublicKey) (*ssh.Permissions, error) {
+	initial := loadAuthorizedKeys(path)
+	log.Printf("Loaded %d authorized key(s)", len(initial))
 
 	return func(_ ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
+		allowed := loadAuthorizedKeys(path)
 		if allowed[string(key.Marshal())] {
 			return &ssh.Permissions{}, nil
 		}

webdav/Dockerfile

@@ -0,0 +1,10 @@
+FROM python:3.12-slim
+
+WORKDIR /app
+RUN pip install --no-cache-dir wsgidav cheroot
+
+COPY app.py .
+RUN mkdir -p /data
+
+EXPOSE 80
+CMD ["python", "-u", "app.py"]

webdav/app.py

@@ -0,0 +1,25 @@
+"""Minimal WebDAV server. Serves /data for uploads. Auth handled at reverse tunnel."""
+from wsgidav.fs_dav_provider import FilesystemProvider
+from wsgidav.wsgidav_app import WsgiDAVApp
+from wsgidav.dir_browser import WsgiDavDirBrowser
+from wsgidav.error_printer import ErrorPrinter
+from wsgidav.request_resolver import RequestResolver
+from wsgidav.mw.cors import Cors
+from cheroot.wsgi import Server as WSGIServer
+
+ROOT = "/data"
+PORT = 80
+
+config = {
+    "host": "0.0.0.0",
+    "port": PORT,
+    "provider_mapping": {"/": FilesystemProvider(ROOT, readonly=False)},
+    "middleware_stack": [Cors, ErrorPrinter, WsgiDavDirBrowser, RequestResolver],
+    "verbose": 3,
+}
+
+app = WsgiDAVApp(config)
+
+if __name__ == "__main__":
+    server = WSGIServer((config["host"], config["port"]), app)
+    server.start()

webdav/requirements.txt

@@ -0,0 +1,2 @@
+wsgidav>=4.0.0
+cheroot>=10.0.0