[docs](trx-rs): add safe deployment guide

Document deployment with a dedicated service account, restricted device access, authenticated network listeners, systemd user services, reverse proxying, verification, upgrades, and rollback.

Assisted-By: OpenAI Codex (GPT-5)
Signed-off-by: Stan Grams <sjg@haxx.space>

README.md

@@ -149,6 +149,11 @@ Serial (`/dev/ttyUSB*`) and audio access require your user to be in the
 `dialout` and `audio` groups. Remove everything with `script/uninstall.sh`
 (add `--purge` to also delete the config).
 
+For an unattended or remotely accessible installation, follow the
+[safe deployment guide](docs/Deployment.md). It covers a dedicated service
+account, device permissions, authentication, firewall and reverse-proxy
+boundaries, verification, upgrades, and rollback.
+
 ## How It Works
 
 ```mermaid

docs/Deployment.md

@@ -0,0 +1,287 @@
+# Safe deployment
+
+This guide deploys trx-rs on Linux as a dedicated, unprivileged user with
+systemd user services. It keeps radio-device access, configuration, and runtime
+data separate from an administrator's account.
+
+The examples use `trx-rs` as the account name and `/opt/trx-rs/bin` for
+root-owned executables. Adapt group names and firewall commands to your Linux
+distribution.
+
+## 1. Decide what must be reachable
+
+Only expose listeners that another machine actually needs:
+
+| Listener | Typical port | Recommended exposure |
+| --- | ---: | --- |
+| Server control | TCP 4530 | Loopback or trusted radio LAN only |
+| Server audio | TCP 4531 and per-rig ports | Trusted radio LAN only |
+| Client web UI | TCP 8080 or a chosen port | Loopback behind HTTPS proxy |
+| Client rigctl | Per-rig TCP ports | Loopback or trusted LAN only |
+| Client JSON | Configured TCP port | Loopback or trusted LAN only |
+
+`127.0.0.1` accepts connections only from the same host. Use a specific LAN
+address when possible, or `0.0.0.0` when the listener must accept connections
+on every IPv4 interface. Binding a socket does not configure the host firewall.
+
+Do not expose unauthenticated control, audio, rigctl, or JSON listeners to the
+public Internet. Prefer a VPN for links between radio sites. Put the web UI
+behind an HTTPS reverse proxy when it is remotely accessible.
+
+## 2. Create the service account
+
+Create a non-login service account with a home directory:
+
+```bash
+sudo useradd --create-home --shell /usr/sbin/nologin trx-rs
+sudo chmod 0750 /home/trx-rs
+```
+
+Add only the hardware groups required on this host. Common group names are
+`dialout` for serial devices and `audio` for sound devices:
+
+```bash
+sudo usermod -aG dialout,audio trx-rs
+```
+
+SDR USB access is distribution- and device-specific. Install the vendor's udev
+rules or add a narrowly scoped rule for the device's USB vendor/product IDs.
+Avoid making all USB devices world-writable. After reconnecting the device,
+verify access as the service account:
+
+```bash
+sudo -u trx-rs test -r /dev/ttyUSB0
+sudo -u trx-rs test -w /dev/ttyUSB0
+sudo -u trx-rs SoapySDRUtil --find
+```
+
+Run only the checks relevant to the configured hardware. Group membership and
+udev-rule changes normally require reconnecting the device or restarting the
+service.
+
+## 3. Build and install immutable binaries
+
+Build from a reviewed revision as a normal development user, not as root:
+
+```bash
+git clone https://github.com/stanislawgrams/trx-rs.git
+cd trx-rs
+git switch --detach <reviewed-tag-or-commit>
+cargo build --release -p trx-server -p trx-client -p trx-configurator
+```
+
+Install root-owned binaries into a directory the service user cannot modify:
+
+```bash
+sudo install -d -o root -g root -m 0755 /opt/trx-rs/bin
+sudo install -o root -g root -m 0755 \
+  target/release/trx-server \
+  target/release/trx-client \
+  target/release/trx-configurator \
+  /opt/trx-rs/bin/
+```
+
+If SDR support is not needed, build `trx-server` with
+`--no-default-features`. Keep the source revision and Rust toolchain used for
+the build in deployment records.
+
+## 4. Install and validate configuration
+
+Create private configuration and state directories, then seed the example:
+
+```bash
+sudo install -d -o trx-rs -g trx-rs -m 0700 \
+  /home/trx-rs/.config/trx-rs \
+  /home/trx-rs/.config/systemd/user
+sudo install -o trx-rs -g trx-rs -m 0600 \
+  trx-rs.toml.example /home/trx-rs/.config/trx-rs/trx-rs.toml
+sudoedit /home/trx-rs/.config/trx-rs/trx-rs.toml
+```
+
+At minimum:
+
+- remove unused example rigs and remotes;
+- select the correct serial, TCP, or SDR device;
+- give every enabled rig a unique ID and audio port;
+- use `127.0.0.1` for same-host connections;
+- use a LAN address or `0.0.0.0` only for deliberately remote listeners;
+- enable authentication before exposing server control or the web UI;
+- replace every example password and token;
+- keep credential files mode `0600` and owned by `trx-rs`;
+- set `cookie_secure = true` when the web UI is served through HTTPS.
+
+For a remote server, control and each per-rig audio listener need an explicit
+non-loopback address:
+
+```toml
+[trx-server.listen]
+enabled = true
+listen = "0.0.0.0"
+port = 4530
+
+[trx-server.listen.auth]
+tokens_file = "/home/trx-rs/.config/trx-rs/server-tokens"
+
+[[trx-server.rigs]]
+id = "station-hf"
+
+[trx-server.rigs.audio]
+enabled = true
+listen = "0.0.0.0"
+port = 4531
+```
+
+When using several `[[trx-server.rigs]]` entries, configure audio under each
+`[trx-server.rigs.audio]` section. Do not rely on the legacy flat
+`[trx-server.audio]` section.
+
+For a web UI behind a reverse proxy, keep the backend on loopback and choose an
+unused port. The proxy upstream must use the same address and port:
+
+```toml
+[trx-client.frontends.http]
+enabled = true
+listen = "127.0.0.1"
+port = 7345
+
+[trx-client.frontends.http.auth]
+enabled = true
+users_file = "/home/trx-rs/.config/trx-rs/http-users.json"
+cookie_secure = true
+```
+
+Validate the configuration before starting either daemon:
+
+```bash
+sudo -u trx-rs /opt/trx-rs/bin/trx-server \
+  --check-config --config /home/trx-rs/.config/trx-rs/trx-rs.toml
+sudo -u trx-rs /opt/trx-rs/bin/trx-client \
+  --check-config --config /home/trx-rs/.config/trx-rs/trx-rs.toml
+```
+
+Treat unknown-key and deprecated-section warnings as deployment errors. They
+often mean a setting is not applied where expected.
+
+## 5. Install the systemd user services
+
+Render the packaged units with the immutable binary directory:
+
+```bash
+sed 's|@BINDIR@|/opt/trx-rs/bin|g' packaging/systemd/trx-server.service \
+  | sudo tee /home/trx-rs/.config/systemd/user/trx-server.service >/dev/null
+sed 's|@BINDIR@|/opt/trx-rs/bin|g' packaging/systemd/trx-client.service \
+  | sudo tee /home/trx-rs/.config/systemd/user/trx-client.service >/dev/null
+sudo chown trx-rs:trx-rs \
+  /home/trx-rs/.config/systemd/user/trx-server.service \
+  /home/trx-rs/.config/systemd/user/trx-client.service
+sudo chmod 0644 \
+  /home/trx-rs/.config/systemd/user/trx-server.service \
+  /home/trx-rs/.config/systemd/user/trx-client.service
+```
+
+Enable lingering so the user manager runs without an interactive login, then
+start it:
+
+```bash
+sudo loginctl enable-linger trx-rs
+trx_uid=$(id -u trx-rs)
+sudo systemctl start "user@${trx_uid}.service"
+```
+
+Manage the user services through that user's runtime directory:
+
+```bash
+trx_uid=$(id -u trx-rs)
+sudo -u trx-rs XDG_RUNTIME_DIR="/run/user/${trx_uid}" \
+  systemctl --user daemon-reload
+sudo -u trx-rs XDG_RUNTIME_DIR="/run/user/${trx_uid}" \
+  systemctl --user enable --now trx-server.service trx-client.service
+```
+
+The client unit has ordering, but not activation, on `trx-server.service`. If
+both are enabled locally, the client starts after the server process is
+started. If the local server is disabled because all remotes are external, the
+client does not start it. The client retries remote connections; systemd cannot
+order startup against a service on another host.
+
+## 6. Firewall and reverse proxy
+
+Allow only required ports and sources. For example, permit server control and
+audio only from the trusted radio subnet, not from every interface. Exact
+commands differ between nftables, firewalld, and ufw.
+
+For the web UI, terminate TLS in a maintained reverse proxy and send traffic to
+the loopback backend. Preserve WebSocket upgrade headers if the proxy requires
+them. Example nginx location:
+
+```nginx
+location / {
+    proxy_pass http://127.0.0.1:7345;
+    proxy_http_version 1.1;
+    proxy_set_header Host $host;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto $scheme;
+    proxy_set_header Upgrade $http_upgrade;
+    proxy_set_header Connection "upgrade";
+}
+```
+
+Test the backend directly before debugging a `502 Bad Gateway` response:
+
+```bash
+curl --fail --show-error http://127.0.0.1:7345/
+```
+
+A refused connection means nothing is listening at the proxy's configured
+address and port. Check for port conflicts with `ss -ltnp` and confirm the
+application log reports the same bind address as the proxy upstream.
+
+## 7. Verify the deployment
+
+```bash
+trx_uid=$(id -u trx-rs)
+sudo -u trx-rs XDG_RUNTIME_DIR="/run/user/${trx_uid}" \
+  systemctl --user status trx-server.service trx-client.service
+sudo journalctl _UID="${trx_uid}" \
+  -u trx-server.service -u trx-client.service --since today
+sudo ss -ltnp
+```
+
+Verify all of the following:
+
+- both required services remain active without a restart loop;
+- radio hardware opens successfully;
+- logs show the intended control, audio, and frontend bind addresses;
+- the client connects to every configured control and audio endpoint;
+- only intended interfaces expose listeners;
+- authentication works and anonymous access is rejected where configured;
+- the HTTPS proxy returns the UI and supports live updates;
+- the service account cannot write `/opt/trx-rs/bin`.
+
+Do not rely only on `systemctl` reporting `active`: individual frontend tasks
+can fail after the main client process starts. Always inspect startup logs and
+probe each required endpoint.
+
+## 8. Upgrade and roll back
+
+Build and validate a new revision before replacing the installed executables.
+Back up configuration and state first. Stop the services, install all binaries
+from the same build, and restart:
+
+```bash
+trx_uid=$(id -u trx-rs)
+sudo -u trx-rs XDG_RUNTIME_DIR="/run/user/${trx_uid}" \
+  systemctl --user stop trx-client.service trx-server.service
+sudo install -o root -g root -m 0755 \
+  target/release/trx-server \
+  target/release/trx-client \
+  target/release/trx-configurator \
+  /opt/trx-rs/bin/
+sudo -u trx-rs XDG_RUNTIME_DIR="/run/user/${trx_uid}" \
+  systemctl --user start trx-server.service trx-client.service
+```
+
+Keep the previous binaries or package revision available for rollback. If the
+new version fails, stop both services, restore the complete previous binary
+set, restore configuration only if its format changed, and start the services
+again.

packaging/systemd/trx-client.service

@@ -33,9 +33,6 @@ RestartSec=2
 KillSignal=SIGINT
 TimeoutStopSec=15
 NoNewPrivileges=true
-# The client opens outbound TCP connections to remote servers and binds TCP
-# listeners for its configured HTTP, JSON, rigctl, and audio frontends.
-RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
 
 [Install]
 WantedBy=default.target

packaging/systemd/trx-server.service

@@ -33,9 +33,6 @@ RestartSec=2
 KillSignal=SIGINT
 TimeoutStopSec=15
 NoNewPrivileges=true
-# Permit local IPC plus IPv4/IPv6 listening and outbound connections.  Ports
-# are configuration-defined, so SocketBindAllow= cannot safely narrow them.
-RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
 
 [Install]
 WantedBy=default.target

src/trx-server/src/main.rs

@@ -922,11 +922,10 @@ fn bound_sockets(cli: &Cli, cfg: &ServerConfig, rigs: &[RigInstanceConfig]) -> V
             "[listen]",
         ));
     }
-    let audio_ip = cli.listen.unwrap_or(cfg.audio.listen);
     for rig in rigs {
         if rig.audio.enabled {
             sockets.push(BoundSocket::new(
-                audio_ip,
+                cli.listen.unwrap_or(rig.audio.listen),
                 rig.audio.port,
                 format!("rig \"{}\" [audio]", rig.id),
             ));
@@ -1276,9 +1275,9 @@ async fn main() -> DynResult<()> {
             }
         }));
 
-        // Spawn audio stack.
-        // listen_override priority: --listen CLI flag > global [audio].listen > per-rig default.
-        let audio_listen_override = cli.listen.or(Some(cfg.audio.listen));
+        // Spawn audio stack. --listen overrides every configured bind address;
+        // otherwise each rig keeps its own [rigs.audio].listen value.
+        let audio_listen_override = cli.listen;
         #[cfg(feature = "soapysdr")]
         let audio_vchan_manager = sdr_vchan_manager.clone();
         #[cfg(not(feature = "soapysdr"))]
@@ -1417,6 +1416,40 @@ mod tests {
         assert!(parse_serial_addr("   ").is_err());
     }
 
+    #[test]
+    fn bound_sockets_preserves_per_rig_audio_addresses() {
+        let cli = Cli::parse_from(["trx-server"]);
+        let cfg = ServerConfig::default();
+        let mut local = RigInstanceConfig::default();
+        local.id = "local".into();
+        local.audio.listen = "127.0.0.1".parse().unwrap();
+        local.audio.port = 4531;
+        let mut remote = RigInstanceConfig::default();
+        remote.id = "remote".into();
+        remote.audio.listen = "0.0.0.0".parse().unwrap();
+        remote.audio.port = 4532;
+
+        let sockets = bound_sockets(&cli, &cfg, &[local, remote]);
+        let local = sockets.iter().find(|s| s.port == 4531).unwrap();
+        let remote = sockets.iter().find(|s| s.port == 4532).unwrap();
+        assert_eq!(local.addr, "127.0.0.1".parse::<IpAddr>().unwrap());
+        assert_eq!(remote.addr, "0.0.0.0".parse::<IpAddr>().unwrap());
+    }
+
+    #[test]
+    fn bound_sockets_applies_cli_listen_to_every_audio_listener() {
+        let cli = Cli::parse_from(["trx-server", "--listen", "192.0.2.10"]);
+        let cfg = ServerConfig::default();
+        let mut rig = RigInstanceConfig::default();
+        rig.id = "remote".into();
+        rig.audio.listen = "127.0.0.1".parse().unwrap();
+        rig.audio.port = 4532;
+
+        let sockets = bound_sockets(&cli, &cfg, &[rig]);
+        let audio = sockets.iter().find(|s| s.port == 4532).unwrap();
+        assert_eq!(audio.addr, "192.0.2.10".parse::<IpAddr>().unwrap());
+    }
+
     #[test]
     fn default_audio_bandwidth_for_mode_table() {
         assert_eq!(default_audio_bandwidth_for_mode(&RigMode::USB), 3_000);