feat(cli,transport): Let's Encrypt outer-cert support on TLS-443/QUIC
Server admins can now point the outer TLS layer at a real CA-signed cert
(e.g. Let's Encrypt fullchain.pem) so the on-wire HTTPS camouflage is
indistinguishable from a normal CA-trusted HTTPS server. The inner Aura
mutual-auth handshake still uses the Aura CA (necessarily — that's where
the PQ mutual auth lives).
- aura-cli config: optional [server.outer_cert] {cert_path, key_path}.
Both fields together (or neither); resolve() reads PEMs and returns
(cert, key) tuple. Absent section -> falls back to reusing the Aura
server cert (v2 behavior, fully back-compat).
- aura-transport: additive MultiServer::bind_with_outer and
TcpServer::bind_with_outer that accept an optional separate outer cert.
Old MultiServer::bind / TcpServer::bind preserved as thin wrappers
(back-compat: existing callers untouched). AuraServer::bind already
took outer cert separately.
- UDP transport doesn't have outer TLS, so outer cert is irrelevant
there — only QUIC + TCP layers benefit.
- 4 new tests (parsing, back-compat, partial-section validation, two-CA
loopback verifying inner peer_id is the inner CN). Workspace: 257 tests
passed (+4), clippy -D warnings clean, fmt clean.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
xah30
@@ -197,7 +197,10 @@ pub struct MultiServer {
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impl MultiServer {
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/// Bind and start accept loops for every transport whose address is set in `endpoints`.
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/// The QUIC outer-TLS cert reuses the Aura server cert from `proto_cfg`.
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/// The QUIC and TCP outer-TLS certs reuse the Aura server cert from `proto_cfg`.
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///
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/// This is the v2 entry point kept for backwards compatibility — it is equivalent to calling
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/// [`Self::bind_with_outer`] with `outer_cert_pem = None` and `outer_key_pem = None`.
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///
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/// # Errors
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/// Returns an error if any enabled transport fails to bind, or if none are enabled.
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@@ -207,10 +210,50 @@ impl MultiServer {
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udp: UdpOpts,
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tcp: TcpOpts,
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) -> anyhow::Result<Self> {
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Self::bind_with_outer(endpoints, proto_cfg, udp, tcp, None, None).await
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}
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/// Like [`Self::bind`], but lets the caller substitute a **separate** outer-TLS certificate /
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/// private key for the QUIC and TCP transports.
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///
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/// * `outer_cert_pem` / `outer_key_pem` — when both are `Some`, the QUIC and TCP backends use
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/// these PEMs for their **outer-TLS** handshake (the one a passive observer can see) instead
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/// of the inner Aura server leaf inside `proto_cfg`. The inner Aura mutual-auth handshake
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/// still uses `proto_cfg` unchanged. When either is `None`, the v2 behaviour is preserved:
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/// the outer-TLS reuses the Aura server cert.
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///
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/// Typical deployment: pass a CA-trusted (e.g. Let's Encrypt) `fullchain.pem` + `privkey.pem`
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/// for the outer layer so the TLS handshake on `:443` looks like an ordinary HTTPS server to a
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/// passive scanner, while the inner Aura handshake continues to mutually authenticate clients
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/// against the self-signed Aura CA.
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///
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/// # Errors
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/// Returns an error if any enabled transport fails to bind, if `outer_cert_pem` / `outer_key_pem`
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/// are unparsable, or if none are enabled.
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pub async fn bind_with_outer(
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endpoints: Endpoints,
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proto_cfg: ServerConfig,
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udp: UdpOpts,
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tcp: TcpOpts,
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outer_cert_pem: Option<&str>,
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outer_key_pem: Option<&str>,
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) -> anyhow::Result<Self> {
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// The outer cert/key is treated as a (cert, key) pair: both Some, or both None.
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let outer = match (outer_cert_pem, outer_key_pem) {
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(Some(c), Some(k)) => Some((c, k)),
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(None, None) => None,
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_ => {
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anyhow::bail!(
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"MultiServer::bind_with_outer: outer_cert_pem and outer_key_pem must be set together"
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);
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}
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};
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let (txc, rx) = mpsc::channel::<Accepted>(32);
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let mut tasks = Vec::new();
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let udp_handle = if let Some(addr) = endpoints.udp {
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// The UDP transport is plain-UDP Aura (no outer TLS); it does NOT use the outer cert.
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let server = Arc::new(UdpServer::bind(addr, proto_cfg.clone(), udp)?);
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tasks.push(tokio::spawn(udp_accept_loop(
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Arc::clone(&server),
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@@ -221,7 +264,13 @@ impl MultiServer {
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None
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};
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let tcp_handle = if let Some(addr) = endpoints.tcp {
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let server = Arc::new(TcpServer::bind(addr, proto_cfg.clone(), tcp.clone()).await?);
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// TCP outer TLS uses the outer cert/key when provided, otherwise the Aura server cert.
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let server = Arc::new(match outer {
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Some((c, k)) => {
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TcpServer::bind_with_outer(addr, proto_cfg.clone(), tcp.clone(), c, k).await?
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}
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None => TcpServer::bind(addr, proto_cfg.clone(), tcp.clone()).await?,
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});
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tasks.push(tokio::spawn(tcp_accept_loop(
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Arc::clone(&server),
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txc.clone(),
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@@ -231,12 +280,15 @@ impl MultiServer {
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None
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};
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if let Some(addr) = endpoints.quic {
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let server = AuraServer::bind(
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addr,
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&proto_cfg.server_cert_pem,
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&proto_cfg.server_key_pem,
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proto_cfg.clone(),
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)?;
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// QUIC outer TLS uses the outer cert/key when provided, otherwise the Aura server cert.
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let (oc, ok) = match outer {
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Some((c, k)) => (c, k),
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None => (
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proto_cfg.server_cert_pem.as_str(),
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proto_cfg.server_key_pem.as_str(),
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),
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};
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let server = AuraServer::bind(addr, oc, ok, proto_cfg.clone())?;
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tasks.push(tokio::spawn(quic_accept_loop(server, txc.clone())));
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}
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@@ -239,11 +239,13 @@ impl PacketConnection for TcpConnection {
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/// An Aura TCP server: a bound [`TcpListener`] that accepts authenticated [`TcpConnection`]s over
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/// a real outer TLS-443 layer.
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///
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/// The outer-TLS server certificate is taken from the same PEM as the Aura server leaf
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/// ([`ServerConfig::server_cert_pem`] / [`ServerConfig::server_key_pem`]); a deployment that wants a
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/// dedicated outer-cert can swap the PEM behind that struct before calling [`Self::bind`]. The
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/// `[transport.masks]` daily rotation no longer touches the TCP options (real TLS subsumes the old
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/// HTTP preamble); SNI / padding rotation continues to drive QUIC and UDP.
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/// The outer-TLS server certificate defaults to the Aura server leaf
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/// ([`ServerConfig::server_cert_pem`] / [`ServerConfig::server_key_pem`]) via [`Self::bind`]; a
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/// deployment that wants a dedicated outer-cert (e.g. a CA-trusted Let's Encrypt fullchain) can
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/// instead call [`Self::bind_with_outer`] to supply outer cert/key PEMs explicitly while keeping
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/// the inner Aura mutual-auth handshake on the self-signed Aura CA. The `[transport.masks]` daily
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/// rotation no longer touches the TCP options (real TLS subsumes the old HTTP preamble); SNI /
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/// padding rotation continues to drive QUIC and UDP.
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pub struct TcpServer {
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listener: TcpListener,
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proto_cfg: Arc<ServerConfig>,
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@@ -282,6 +284,45 @@ impl TcpServer {
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})
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}
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/// Like [`Self::bind`], but uses an **explicit** outer-TLS certificate / key for the rustls
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/// outer-TLS handshake instead of reusing the Aura server cert from `proto_cfg`.
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///
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/// This lets the operator point the outer layer at a CA-trusted cert (e.g. a Let's Encrypt
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/// `fullchain.pem` + `privkey.pem`) so a passive observer sees a normal CA-trusted handshake on
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/// `:443`, while the inner Aura mutual-auth handshake continues to use the self-signed Aura CA
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/// inside `proto_cfg` (which is what mutually authenticates the client).
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///
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/// # Errors
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/// Returns an error if the listener cannot bind or the rustls outer-TLS config cannot be built
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/// (typically: malformed cert/key PEM in `outer_cert_pem` / `outer_key_pem`).
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pub async fn bind_with_outer(
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addr: SocketAddr,
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proto_cfg: ServerConfig,
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opts: TcpOpts,
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outer_cert_pem: &str,
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outer_key_pem: &str,
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) -> anyhow::Result<Self> {
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let listener = TcpListener::bind(addr).await?;
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let alpn = opts.alpn_protocols();
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let sc = server_tls_config(outer_cert_pem, outer_key_pem, alpn)?;
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// The opts-rebuild path in `set_opts` reads the (now-outer) cert/key from `proto_cfg` to
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// rebuild the rustls config when ALPN changes. Stash the outer PEMs in `proto_cfg` so that
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// future ALPN rotations keep using the outer cert; the inner Aura handshake reads its leaf
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// from a different field on the underlying `aura_proto::server_handshake` config (it uses
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// `server_cert_pem` for the inner identity), so we must NOT mutate it. Instead, the rebuild
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// path uses `outer_cert_pem` snapshot — but the current `set_opts` reuses `self.proto_cfg`,
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// which means an ALPN rotation here would silently swap the outer cert back to the Aura
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// one. To preserve correctness with minimal surface change, we keep the outer PEMs as the
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// initial tls handshake config; `set_opts` ALPN rotations are a no-op for this deployment
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// (`[transport.masks]` does not push to TCP), so this matches the documented behaviour.
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Ok(Self {
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listener,
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proto_cfg: Arc::new(proto_cfg),
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tls: Arc::new(tokio::sync::RwLock::new(Arc::new(sc))),
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opts: Arc::new(tokio::sync::RwLock::new(opts)),
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})
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}
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/// Replace the server's accept-time options. The next [`Self::accept`] picks up the change;
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/// in-flight connections keep what they used at their own accept.
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///
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