feat(tls): add shared TLS acceptor with SNI resolver and session resumption; prefer shared acceptor and fall back to per-connection when routes specify custom TLS versions

rust/crates/rustproxy-passthrough/src/tls_handler.rs

@@ -1,17 +1,99 @@
+use std::collections::HashMap;
 use std::io::BufReader;
 use std::sync::Arc;
 
 use rustls::pki_types::{CertificateDer, PrivateKeyDer};
+use rustls::server::ResolvesServerCert;
+use rustls::sign::CertifiedKey;
 use rustls::ServerConfig;
 use tokio::net::TcpStream;
 use tokio_rustls::{TlsAcceptor, TlsConnector, server::TlsStream as ServerTlsStream};
-use tracing::debug;
+use tracing::{debug, info};
+
+use crate::tcp_listener::TlsCertConfig;
 
 /// Ensure the default crypto provider is installed.
 fn ensure_crypto_provider() {
     let _ = rustls::crypto::ring::default_provider().install_default();
 }
 
+/// SNI-based certificate resolver with pre-parsed CertifiedKeys.
+/// Enables shared ServerConfig across connections — avoids per-connection PEM parsing
+/// and enables TLS session resumption.
+#[derive(Debug)]
+pub struct CertResolver {
+    certs: HashMap<String, Arc<CertifiedKey>>,
+    fallback: Option<Arc<CertifiedKey>>,
+}
+
+impl CertResolver {
+    /// Build a resolver from PEM-encoded cert/key configs.
+    /// Parses all PEM data upfront so connections only do a cheap HashMap lookup.
+    pub fn new(configs: &HashMap<String, TlsCertConfig>) -> Result<Self, Box<dyn std::error::Error + Send + Sync>> {
+        ensure_crypto_provider();
+        let provider = rustls::crypto::ring::default_provider();
+        let mut certs = HashMap::new();
+        let mut fallback = None;
+
+        for (domain, cfg) in configs {
+            let cert_chain = load_certs(&cfg.cert_pem)?;
+            let key = load_private_key(&cfg.key_pem)?;
+            let ck = Arc::new(CertifiedKey::from_der(cert_chain, key, &provider)
+                .map_err(|e| format!("CertifiedKey for {}: {}", domain, e))?);
+            if domain == "*" {
+                fallback = Some(Arc::clone(&ck));
+            }
+            certs.insert(domain.clone(), ck);
+        }
+
+        // If no explicit "*" fallback, use the first available cert
+        if fallback.is_none() {
+            fallback = certs.values().next().map(Arc::clone);
+        }
+
+        Ok(Self { certs, fallback })
+    }
+}
+
+impl ResolvesServerCert for CertResolver {
+    fn resolve(&self, client_hello: rustls::server::ClientHello<'_>) -> Option<Arc<CertifiedKey>> {
+        let domain = match client_hello.server_name() {
+            Some(name) => name,
+            None => return self.fallback.clone(),
+        };
+        // Exact match
+        if let Some(ck) = self.certs.get(domain) {
+            return Some(Arc::clone(ck));
+        }
+        // Wildcard: sub.example.com → *.example.com
+        if let Some(dot) = domain.find('.') {
+            let wc = format!("*.{}", &domain[dot + 1..]);
+            if let Some(ck) = self.certs.get(&wc) {
+                return Some(Arc::clone(ck));
+            }
+        }
+        self.fallback.clone()
+    }
+}
+
+/// Build a shared TLS acceptor with SNI resolution, session cache, and session tickets.
+/// The returned acceptor can be reused across all connections (cheap Arc clone).
+pub fn build_shared_tls_acceptor(resolver: CertResolver) -> Result<TlsAcceptor, Box<dyn std::error::Error + Send + Sync>> {
+    ensure_crypto_provider();
+    let mut config = ServerConfig::builder()
+        .with_no_client_auth()
+        .with_cert_resolver(Arc::new(resolver));
+
+    // Shared session cache — enables session ID resumption across connections
+    config.session_storage = rustls::server::ServerSessionMemoryCache::new(4096);
+    // Session ticket resumption (12-hour lifetime, Chacha20Poly1305 encrypted)
+    config.ticketer = rustls::crypto::ring::Ticketer::new()
+        .map_err(|e| format!("Ticketer: {}", e))?;
+
+    info!("Built shared TLS config with session cache (4096) and ticket support");
+    Ok(TlsAcceptor::from(Arc::new(config)))
+}
+
 /// Build a TLS acceptor from PEM-encoded cert and key data.
 pub fn build_tls_acceptor(cert_pem: &str, key_pem: &str) -> Result<TlsAcceptor, Box<dyn std::error::Error + Send + Sync>> {
     build_tls_acceptor_with_config(cert_pem, key_pem, None)