tls: add opt-in pure-Rust rustls backend behind the TlsBackend trait (tls_backend = rustls; default stays openssl) — TLS1.3, CertFP via handshake-sig verify, SNI, REHASH reload; bump integration timeouts for loaded-host robustness

src/lib.rs

@@ -34,6 +34,7 @@ pub mod resolver;
 pub mod server;
 pub mod socketengine;
 pub mod tls;
+pub mod tls_rustls;
 pub mod users;
 pub mod watch;
 pub mod websocket;

src/main.rs

@@ -149,16 +149,46 @@ fn main() {
             })
             .unwrap_or_default();
         match (&cfg.tls_cert, &cfg.tls_key) {
-            (Some(cert), Some(key)) => match OpensslBackend::new(cert, key, sni) {
-                Ok(backend) => {
-                    let backend = Arc::new(backend);
-                    // publish for REHASH-triggered cert reload
-                    let _ = echoircd::tls::TLS_RELOAD.set(backend.clone());
-                    let backend: Arc<dyn TlsBackend> = backend;
+            (Some(cert), Some(key)) => {
+                // pick the TLS backend: pure-Rust rustls (opt-in via tls_backend =
+                // rustls) or openssl (the default). Both satisfy the same trait.
+                let use_rustls = cfg
+                    .raw
+                    .get("tls_backend")
+                    .and_then(|v| v.first())
+                    .is_some_and(|s| s.eq_ignore_ascii_case("rustls"));
+                let backend: Option<Arc<dyn TlsBackend>> = if use_rustls {
+                    match echoircd::tls_rustls::RustlsBackend::new(cert, key, sni) {
+                        Ok(b) => {
+                            let b = Arc::new(b);
+                            let _ = echoircd::tls::TLS_RELOAD.set(b.clone());
+                            eprintln!("echoircd TLS backend: rustls");
+                            Some(b as Arc<dyn TlsBackend>)
+                        }
+                        Err(e) => {
+                            eprintln!("echoircd: TLS disabled (rustls cert/key error): {e}");
+                            None
+                        }
+                    }
+                } else {
+                    match OpensslBackend::new(cert, key, sni) {
+                        Ok(b) => {
+                            let b = Arc::new(b);
+                            let _ = echoircd::tls::TLS_RELOAD.set(b.clone()); // REHASH cert reload
+                            eprintln!("echoircd TLS backend: openssl");
+                            Some(b as Arc<dyn TlsBackend>)
+                        }
+                        Err(e) => {
+                            eprintln!("echoircd: TLS disabled (cert/key error): {e}");
+                            None
+                        }
+                    }
+                };
+                if let Some(backend) = backend {
                     for bind_tls in &cfg.bind_tls {
                         match TcpListener::bind(bind_tls) {
                             Ok(tls_listener) => {
-                                eprintln!("echoircd TLS on {bind_tls} (openssl)");
+                                eprintln!("echoircd TLS on {bind_tls}");
                                 let tls_tx = tx.clone();
                                 let tls_counter = counter.clone();
                                 let tls_proxy_trust = proxy_trust.clone();
@@ -184,8 +214,7 @@ fn main() {
                         }
                     }
                 }
-                Err(e) => eprintln!("echoircd: TLS disabled (cert/key error): {e}"),
-            },
+            }
             _ => eprintln!("echoircd: bind_tls set but tls_cert/tls_key missing; TLS disabled"),
         }
     }

src/tls_rustls.rs

@@ -0,0 +1,321 @@
+//! Pure-Rust TLS backend (rustls), an alternative to the openssl backend behind the
+//! same [`TlsBackend`]/[`TlsConn`]/[`TlsSession`] traits. Opt in with
+//! `tls_backend = rustls` in the config; the default stays openssl. No C/FFI in the
+//! daemon itself — rustls keeps its `unsafe` internal like every other crate.
+//!
+//! Client certs are requested but never chain-validated (services identify a user by
+//! the cert *fingerprint*, not a CA), mirroring the openssl backend's always-accept
+//! verify callback. The client's CertificateVerify signature IS still checked, so
+//! CertFP / SASL EXTERNAL keeps proving the client holds the matching private key.
+
+use std::io::{self, Read, Write};
+use std::net::{Shutdown, TcpStream};
+use std::sync::{Arc, RwLock};
+use std::time::Duration;
+
+use mio::net::TcpStream as MioStream;
+use openssl::hash::{hash, MessageDigest};
+
+use rustls::client::danger::HandshakeSignatureValid;
+use rustls::crypto::CryptoProvider;
+use rustls::pki_types::{CertificateDer, PrivateKeyDer, UnixTime};
+use rustls::server::danger::{ClientCertVerified, ClientCertVerifier};
+use rustls::server::{ClientHello, ResolvesServerCert};
+use rustls::sign::CertifiedKey;
+use rustls::{
+    DigitallySignedStruct, DistinguishedName, ServerConfig, ServerConnection, SignatureScheme,
+};
+
+use crate::map::HashMap;
+use crate::tls::{CertReload, TlsBackend, TlsConn, TlsSession};
+
+fn err<E: std::fmt::Display>(e: E) -> io::Error {
+    io::Error::other(e.to_string())
+}
+
+struct CertPaths {
+    cert: String,
+    key: String,
+}
+
+pub struct RustlsBackend {
+    // Swapped by `reload` on REHASH so renewed certs apply without a restart; read
+    // only at connection-accept time (infrequent), so the lock is never hot.
+    config: RwLock<Arc<ServerConfig>>,
+    primary: CertPaths,
+    sni: Vec<(String, CertPaths)>,
+    provider: Arc<CryptoProvider>,
+}
+
+/// Load a PEM chain + private key into a rustls `CertifiedKey`.
+fn load_key(cert: &str, key: &str, provider: &CryptoProvider) -> io::Result<Arc<CertifiedKey>> {
+    let cert_pem = std::fs::read(cert)?;
+    let certs: Vec<CertificateDer<'static>> = rustls_pemfile::certs(&mut &cert_pem[..])
+        .collect::<Result<_, _>>()
+        .map_err(err)?;
+    if certs.is_empty() {
+        return Err(err(format!("no certificates in {cert}")));
+    }
+    let key_pem = std::fs::read(key)?;
+    let key_der: PrivateKeyDer<'static> = rustls_pemfile::private_key(&mut &key_pem[..])
+        .map_err(err)?
+        .ok_or_else(|| err(format!("no private key in {key}")))?;
+    let signing_key = provider.key_provider.load_private_key(key_der).map_err(err)?;
+    Ok(Arc::new(CertifiedKey::new(certs, signing_key)))
+}
+
+/// Per-hostname cert selection: the SNI name's cert, else the primary. Mirrors the
+/// openssl backend's servername callback (no validation of the SNI cert here).
+#[derive(Debug)]
+struct SniResolver {
+    default: Arc<CertifiedKey>,
+    by_host: HashMap<String, Arc<CertifiedKey>>,
+}
+
+impl ResolvesServerCert for SniResolver {
+    fn resolve(&self, hello: ClientHello) -> Option<Arc<CertifiedKey>> {
+        if let Some(name) = hello.server_name() {
+            if let Some(ck) = self.by_host.get(&name.to_ascii_lowercase()) {
+                return Some(ck.clone());
+            }
+        }
+        Some(self.default.clone())
+    }
+}
+
+/// Accept any client certificate (we fingerprint, never chain-validate) but still
+/// verify the handshake signature so CertFP can't be spoofed without the key.
+#[derive(Debug)]
+struct AcceptAnyClientCert {
+    provider: Arc<CryptoProvider>,
+}
+
+impl ClientCertVerifier for AcceptAnyClientCert {
+    fn root_hint_subjects(&self) -> &[DistinguishedName] {
+        &[]
+    }
+    fn verify_client_cert(
+        &self,
+        _end: &CertificateDer,
+        _intermediates: &[CertificateDer],
+        _now: UnixTime,
+    ) -> Result<ClientCertVerified, rustls::Error> {
+        Ok(ClientCertVerified::assertion())
+    }
+    fn verify_tls12_signature(
+        &self,
+        message: &[u8],
+        cert: &CertificateDer,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, rustls::Error> {
+        rustls::crypto::verify_tls12_signature(
+            message,
+            cert,
+            dss,
+            &self.provider.signature_verification_algorithms,
+        )
+    }
+    fn verify_tls13_signature(
+        &self,
+        message: &[u8],
+        cert: &CertificateDer,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, rustls::Error> {
+        rustls::crypto::verify_tls13_signature(
+            message,
+            cert,
+            dss,
+            &self.provider.signature_verification_algorithms,
+        )
+    }
+    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
+        self.provider
+            .signature_verification_algorithms
+            .supported_schemes()
+    }
+    fn offer_client_auth(&self) -> bool {
+        true
+    }
+    fn client_auth_mandatory(&self) -> bool {
+        false
+    }
+}
+
+/// SHA-256 fingerprint (lowercase hex) of the peer's leaf certificate, matching the
+/// openssl backend's format so CertFP is identical across backends.
+fn fp_of(certs: Option<&[CertificateDer<'_>]>) -> Option<String> {
+    let cert = certs?.first()?;
+    let digest = hash(MessageDigest::sha256(), cert.as_ref()).ok()?;
+    Some(digest.iter().map(|b| format!("{b:02x}")).collect())
+}
+
+fn build_config(
+    primary: &CertPaths,
+    sni: &[(String, CertPaths)],
+    provider: &Arc<CryptoProvider>,
+) -> io::Result<Arc<ServerConfig>> {
+    let default = load_key(&primary.cert, &primary.key, provider)?;
+    let mut by_host: HashMap<String, Arc<CertifiedKey>> = HashMap::default();
+    for (h, cp) in sni {
+        by_host.insert(h.to_ascii_lowercase(), load_key(&cp.cert, &cp.key, provider)?);
+    }
+    let resolver = Arc::new(SniResolver { default, by_host });
+    let verifier = Arc::new(AcceptAnyClientCert {
+        provider: provider.clone(),
+    });
+    let cfg = ServerConfig::builder_with_provider(provider.clone())
+        .with_protocol_versions(rustls::ALL_VERSIONS)
+        .map_err(err)?
+        .with_client_cert_verifier(verifier)
+        .with_cert_resolver(resolver);
+    Ok(Arc::new(cfg))
+}
+
+impl RustlsBackend {
+    pub fn new(cert: &str, key: &str, sni: Vec<(String, String, String)>) -> io::Result<RustlsBackend> {
+        let provider = Arc::new(rustls::crypto::ring::default_provider());
+        let primary = CertPaths {
+            cert: cert.to_string(),
+            key: key.to_string(),
+        };
+        let sni: Vec<(String, CertPaths)> = sni
+            .into_iter()
+            .map(|(h, c, k)| (h, CertPaths { cert: c, key: k }))
+            .collect();
+        let config = build_config(&primary, &sni, &provider)?;
+        Ok(RustlsBackend {
+            config: RwLock::new(config),
+            primary,
+            sni,
+            provider,
+        })
+    }
+
+    pub fn reload(&self) -> io::Result<()> {
+        let fresh = build_config(&self.primary, &self.sni, &self.provider)?;
+        *self.config.write().unwrap() = fresh;
+        Ok(())
+    }
+
+    fn cfg(&self) -> Arc<ServerConfig> {
+        self.config.read().unwrap().clone()
+    }
+}
+
+impl CertReload for RustlsBackend {
+    fn reload(&self) -> io::Result<()> {
+        RustlsBackend::reload(self)
+    }
+}
+
+impl TlsBackend for RustlsBackend {
+    fn accept(&self, mut sock: TcpStream) -> io::Result<Box<dyn TlsConn>> {
+        let mut conn = ServerConnection::new(self.cfg()).map_err(err)?;
+        // complete the handshake now, on the (blocking) socket, like openssl's accept
+        while conn.is_handshaking() {
+            conn.complete_io(&mut sock).map_err(err)?;
+        }
+        Ok(Box::new(RustlsConn { conn, sock }))
+    }
+
+    fn start(&self, sock: MioStream) -> io::Result<Box<dyn TlsSession>> {
+        let conn = ServerConnection::new(self.cfg()).map_err(err)?;
+        Ok(Box::new(RustlsSession { conn, sock }))
+    }
+}
+
+// --- blocking connection (thread-per-conn path) -----------------------------
+struct RustlsConn {
+    conn: ServerConnection,
+    sock: TcpStream,
+}
+
+impl TlsConn for RustlsConn {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        rustls::Stream::new(&mut self.conn, &mut self.sock).read(buf)
+    }
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        rustls::Stream::new(&mut self.conn, &mut self.sock).write_all(buf)
+    }
+    fn flush(&mut self) -> io::Result<()> {
+        rustls::Stream::new(&mut self.conn, &mut self.sock).flush()
+    }
+    fn set_read_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
+        self.sock.set_read_timeout(dur)
+    }
+    fn shutdown(&self) {
+        let _ = self.sock.shutdown(Shutdown::Both);
+    }
+    fn peer_cert_fp(&self) -> Option<String> {
+        fp_of(self.conn.peer_certificates())
+    }
+}
+
+// --- non-blocking session (reactor path) ------------------------------------
+struct RustlsSession {
+    conn: ServerConnection,
+    sock: MioStream,
+}
+
+impl RustlsSession {
+    /// Drain any decryptable TLS records the socket has for us, processing each.
+    /// `WouldBlock`/EOF just stop the loop — the caller checks state afterwards.
+    fn pump_read(&mut self) -> io::Result<()> {
+        loop {
+            match self.conn.read_tls(&mut self.sock) {
+                Ok(0) => return Ok(()), // socket EOF; reader() will report the close
+                Ok(_) => self.conn.process_new_packets().map_err(err)?,
+                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => return Ok(()),
+                Err(e) => return Err(e),
+            };
+        }
+    }
+    /// Flush rustls's pending outbound TLS bytes to the socket; a full socket
+    /// (`WouldBlock`) just leaves them buffered for the next writable event.
+    fn pump_write(&mut self) -> io::Result<()> {
+        while self.conn.wants_write() {
+            match self.conn.write_tls(&mut self.sock) {
+                Ok(0) => break,
+                Ok(_) => {}
+                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => break,
+                Err(e) => return Err(e),
+            }
+        }
+        Ok(())
+    }
+}
+
+impl TlsSession for RustlsSession {
+    fn accept(&mut self) -> io::Result<bool> {
+        self.pump_read()?;
+        self.pump_write()?; // handshake flight, and session tickets once it's done
+        Ok(!self.conn.is_handshaking())
+    }
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.pump_read()?;
+        self.pump_write()?; // process_new_packets can queue writes (alerts, key updates)
+        match self.conn.reader().read(buf) {
+            Ok(n) => Ok(n), // Ok(0) = clean close_notify, like a plaintext EOF
+            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+                Err(io::ErrorKind::WouldBlock.into())
+            }
+            Err(e) => Err(e),
+        }
+    }
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        let n = self.conn.writer().write(buf)?;
+        self.pump_write()?;
+        Ok(n)
+    }
+    fn source(&mut self) -> &mut MioStream {
+        &mut self.sock
+    }
+    fn peer_cert_fp(&self) -> Option<String> {
+        fp_of(self.conn.peer_certificates())
+    }
+    fn shutdown(&mut self) {
+        self.conn.send_close_notify();
+        let _ = self.pump_write();
+        let _ = self.sock.shutdown(Shutdown::Both);
+    }
+}