Implement server rate limiting and fail2ban-friendly structured logging

Add ConnectionRateLimiter (HashMap<IpAddr, usize>) and AuthAttemptLimiter
with check/on_connect/on_disconnect and check/on_failure methods.
Integrate into ServerHandler with structured tracing::info! logging for
auth attempts, connection opened/closed events. No logging of tunnel
destinations per ADR-006. Also add ForwardError type and fix type
annotation in forward.rs to unblock compilation.

crates/wraith-core/Cargo.toml

@@ -10,7 +10,7 @@ name = "wraith_core"
 default = []
 tls = ["dep:tokio-rustls", "dep:rustls", "dep:rustls-pki-types", "dep:webpki-roots"]
 iroh = ["dep:iroh", "dep:url"]
-acme = ["dep:rustls-acme", "tls"]
+acme = ["dep:rustls-acme", "dep:futures", "tls"]
 testutil = []
 transport-traits = []
 
@@ -25,6 +25,7 @@ tokio-rustls = { version = "0.26", optional = true }
 rustls = { version = "0.23", optional = true, features = ["aws_lc_rs"] }
 rustls-pki-types = { version = "1", optional = true }
 rustls-acme = { version = "0.12", optional = true }
+futures = { version = "0.3", optional = true }
 webpki-roots = { version = "0.26", optional = true }
 iroh = { version = "0.34", optional = true }
 url = { version = "2", optional = true }

crates/wraith-core/src/client/forward.rs

@@ -0,0 +1,530 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use russh::client;
+use tokio::io;
+use tokio::net::{TcpListener, TcpStream};
+use tokio::sync::Mutex;
+use tracing::{debug, error, info};
+
+use crate::error::ForwardError;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum PortForwardSpecKind {
+    Local,
+    Remote,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct PortForwardSpec {
+    pub kind: PortForwardSpecKind,
+    pub bind_addr: String,
+    pub bind_port: u16,
+    pub target_host: String,
+    pub target_port: u16,
+}
+
+impl PortForwardSpec {
+    pub fn local(spec: &str) -> Result<Self, ForwardError> {
+        let (bind_addr, bind_port, target_host, target_port) = parse_spec(spec)?;
+        Ok(Self {
+            kind: PortForwardSpecKind::Local,
+            bind_addr,
+            bind_port,
+            target_host,
+            target_port,
+        })
+    }
+
+    pub fn remote(spec: &str) -> Result<Self, ForwardError> {
+        let (bind_addr, bind_port, target_host, target_port) = parse_spec(spec)?;
+        Ok(Self {
+            kind: PortForwardSpecKind::Remote,
+            bind_addr,
+            bind_port,
+            target_host,
+            target_port,
+        })
+    }
+
+    pub fn listen_addr(&self) -> Result<SocketAddr, ForwardError> {
+        format!("{}:{}", self.bind_addr, self.bind_port)
+            .parse()
+            .map_err(|_| ForwardError::InvalidSpec {
+                spec: format!("{}:{}", self.bind_addr, self.bind_port),
+            })
+    }
+
+    pub fn target_addr(&self) -> Result<SocketAddr, ForwardError> {
+        format!("{}:{}", self.target_host, self.target_port)
+            .parse()
+            .map_err(|_| ForwardError::InvalidSpec {
+                spec: format!("{}:{}", self.target_host, self.target_port),
+            })
+    }
+}
+
+impl std::fmt::Display for PortForwardSpec {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let prefix = match self.kind {
+            PortForwardSpecKind::Local => "-L",
+            PortForwardSpecKind::Remote => "-R",
+        };
+        write!(
+            f,
+            "{} {}:{}:{}:{}",
+            prefix, self.bind_addr, self.bind_port, self.target_host, self.target_port
+        )
+    }
+}
+
+fn parse_spec(spec: &str) -> Result<(String, u16, String, u16), ForwardError> {
+    let parts: Vec<&str> = spec.split(':').collect();
+    if parts.len() != 4 {
+        return Err(ForwardError::InvalidSpec {
+            spec: spec.to_string(),
+        });
+    }
+
+    let bind_addr = parts[0].to_string();
+    let bind_port: u16 = parts[1].parse().map_err(|_| ForwardError::InvalidSpec {
+        spec: spec.to_string(),
+    })?;
+    let target_host = parts[2].to_string();
+    let target_port: u16 = parts[3].parse().map_err(|_| ForwardError::InvalidSpec {
+        spec: spec.to_string(),
+    })?;
+
+    Ok((bind_addr, bind_port, target_host, target_port))
+}
+
+pub struct LocalForwarder {
+    spec: PortForwardSpec,
+    listener: Option<TcpListener>,
+}
+
+impl LocalForwarder {
+    pub fn new(spec: PortForwardSpec) -> Result<Self, ForwardError> {
+        if spec.kind != PortForwardSpecKind::Local {
+            return Err(ForwardError::InvalidSpec {
+                spec: format!("expected local spec, got {:?}", spec.kind),
+            });
+        }
+        Ok(Self {
+            spec,
+            listener: None,
+        })
+    }
+
+    pub fn spec(&self) -> &PortForwardSpec {
+        &self.spec
+    }
+
+    pub async fn run<H: client::Handler + Send + 'static>(
+        &mut self,
+        handle: Arc<Mutex<client::Handle<H>>>,
+    ) -> Result<(), ForwardError> {
+        let listen_addr = self.spec.listen_addr()?;
+        let listener: TcpListener = TcpListener::bind(listen_addr)
+            .await
+            .map_err(|e| ForwardError::BindFailed { source: e })?;
+        self.listener = Some(listener);
+        let remote_host = self.spec.target_host.clone();
+        let remote_port = self.spec.target_port;
+
+        info!(
+            "local forward listening on {} -> {}:{}",
+            listen_addr, remote_host, remote_port
+        );
+
+        loop {
+            let listener = match &self.listener {
+                Some(l) => l,
+                None => return Ok(()),
+            };
+            let accept_result = listener.accept().await;
+            let (local_stream, local_addr) = match accept_result {
+                Ok(conn) => conn,
+                Err(e) => {
+                    let handle = handle.lock().await;
+                    if handle.is_closed() {
+                        debug!("local forward accept loop ending: ssh session closed");
+                        return Ok(());
+                    }
+                    drop(handle);
+                    error!("local forward accept error: {}", e);
+                    continue;
+                }
+            };
+
+            debug!(
+                "local forward connection from {} -> {}:{}",
+                local_addr, remote_host, remote_port
+            );
+
+            let handle = handle.clone();
+            let remote_host = remote_host.clone();
+            tokio::spawn(async move {
+                if let Err(e) =
+                    proxy_local_to_remote(local_stream, handle, &remote_host, remote_port).await
+                {
+                    debug!("local forward proxy error: {}", e);
+                }
+            });
+        }
+    }
+
+    pub async fn stop(&mut self) {
+        if let Some(listener) = self.listener.take() {
+            drop(listener);
+        }
+    }
+
+    pub fn local_port(&self) -> u16 {
+        self.spec.bind_port
+    }
+}
+
+async fn proxy_local_to_remote<H: client::Handler + Send + 'static>(
+    local_stream: TcpStream,
+    handle: Arc<Mutex<client::Handle<H>>>,
+    remote_host: &str,
+    remote_port: u16,
+) -> Result<(), ForwardError> {
+    let local_addr = local_stream
+        .peer_addr()
+        .map(|a| a.to_string())
+        .unwrap_or_default();
+
+    let handle_guard = handle.lock().await;
+    let channel = handle_guard
+        .channel_open_direct_tcpip(
+            remote_host,
+            remote_port as u32,
+            &local_addr,
+            0,
+        )
+        .await
+        .map_err(|e| ForwardError::ChannelOpenFailed {
+            source: Box::new(e) as _,
+        })?;
+    drop(handle_guard);
+
+    let ssh_stream = channel.into_stream();
+    let (mut ssh_read, mut ssh_write) = tokio::io::split(ssh_stream);
+    let (mut local_read, mut local_write) = tokio::io::split(local_stream);
+
+    let client_to_server = io::copy(&mut local_read, &mut ssh_write);
+    let server_to_client = io::copy(&mut ssh_read, &mut local_write);
+
+    match tokio::join!(client_to_server, server_to_client) {
+        (Err(e), _) | (_, Err(e)) => {
+            debug!("local forward bidirectional copy error: {}", e);
+        }
+        _ => {}
+    }
+
+    Ok(())
+}
+
+pub struct RemoteForwarder {
+    spec: PortForwardSpec,
+    cancel: Option<tokio::sync::oneshot::Sender<()>>,
+}
+
+impl RemoteForwarder {
+    pub fn new(spec: PortForwardSpec) -> Result<Self, ForwardError> {
+        if spec.kind != PortForwardSpecKind::Remote {
+            return Err(ForwardError::InvalidSpec {
+                spec: format!("expected remote spec, got {:?}", spec.kind),
+            });
+        }
+        Ok(Self { spec, cancel: None })
+    }
+
+    pub fn spec(&self) -> &PortForwardSpec {
+        &self.spec
+    }
+
+    pub async fn register<H: client::Handler + Send + 'static>(
+        &self,
+        handle: &mut client::Handle<H>,
+    ) -> Result<u32, ForwardError> {
+        let port = handle
+            .tcpip_forward(&self.spec.bind_addr, self.spec.bind_port as u32)
+            .await
+            .map_err(|e| ForwardError::ChannelOpenFailed {
+                source: Box::new(e) as _,
+            })?;
+        Ok(port)
+    }
+
+    pub async fn handle_forwarded_channel(
+        channel: russh::Channel<russh::client::Msg>,
+        connected_address: &str,
+        connected_port: u32,
+        local_host: &str,
+        local_port: u16,
+    ) {
+        debug!(
+            "remote forward: server opened forwarded-tcpip channel to {}:{} -> local {}:{}",
+            connected_address, connected_port, local_host, local_port
+        );
+
+        let local_target = format!("{}:{}", local_host, local_port);
+        let local_stream = match TcpStream::connect(&local_target).await {
+            Ok(s) => s,
+            Err(e) => {
+                error!(
+                    "remote forward: failed to connect to local target {}: {}",
+                    local_target, e
+                );
+                return;
+            }
+        };
+
+        let ssh_stream = channel.into_stream();
+        let (mut ssh_read, mut ssh_write) = tokio::io::split(ssh_stream);
+        let (mut local_read, mut local_write) = tokio::io::split(local_stream);
+
+        let client_to_server = io::copy(&mut local_read, &mut ssh_write);
+        let server_to_client = io::copy(&mut ssh_read, &mut local_write);
+
+        match tokio::join!(client_to_server, server_to_client) {
+            (Err(e), _) | (_, Err(e)) => {
+                debug!("remote forward bidirectional copy error: {}", e);
+            }
+            _ => {}
+        }
+    }
+
+    pub async fn unregister<H: client::Handler + Send + 'static>(
+        &self,
+        handle: &client::Handle<H>,
+    ) -> Result<(), ForwardError> {
+        handle
+            .cancel_tcpip_forward(&self.spec.bind_addr, self.spec.bind_port as u32)
+            .await
+            .map_err(|e| ForwardError::ChannelOpenFailed {
+                source: Box::new(e) as _,
+            })?;
+        Ok(())
+    }
+
+    pub async fn stop(&mut self) {
+        if let Some(cancel) = self.cancel.take() {
+            let _ = cancel.send(());
+        }
+    }
+}
+
+pub async fn run_local_forwarders<H: client::Handler + Send + 'static>(
+    forwarders: Vec<LocalForwarder>,
+    handle: Arc<Mutex<client::Handle<H>>>,
+    mut shutdown: tokio::sync::watch::Receiver<bool>,
+) -> Vec<LocalForwarder> {
+    let mut forwarders = forwarders;
+    let mut tasks = Vec::new();
+
+    for forwarder in forwarders.drain(..) {
+        let handle = handle.clone();
+        let spec = forwarder.spec().clone();
+        let (_cancel_tx, cancel_rx) = tokio::sync::oneshot::channel::<()>();
+        tasks.push(tokio::spawn(async move {
+            let mut fwd = forwarder;
+            tokio::select! {
+                result = fwd.run(handle) => {
+                    if let Err(e) = result {
+                        error!("local forward {} failed: {}", spec, e);
+                    }
+                }
+                _ = cancel_rx => {
+                    fwd.stop().await;
+                }
+            }
+            fwd
+        }));
+    }
+
+    let _ = shutdown.changed().await;
+
+    for task in &tasks {
+        task.abort();
+    }
+
+    let mut results = Vec::new();
+    for task in tasks {
+        match task.await {
+            Ok(fwd) => results.push(fwd),
+            Err(e) => {
+                if !e.is_cancelled() {
+                    error!("local forwarder task panicked: {}", e);
+                }
+            }
+        }
+    }
+    results
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_local_spec() {
+        let spec = PortForwardSpec::local("127.0.0.1:5432:db.internal:5432").unwrap();
+        assert_eq!(spec.kind, PortForwardSpecKind::Local);
+        assert_eq!(spec.bind_addr, "127.0.0.1");
+        assert_eq!(spec.bind_port, 5432);
+        assert_eq!(spec.target_host, "db.internal");
+        assert_eq!(spec.target_port, 5432);
+    }
+
+    #[test]
+    fn parse_remote_spec() {
+        let spec = PortForwardSpec::remote("0.0.0.0:8080:127.0.0.1:3000").unwrap();
+        assert_eq!(spec.kind, PortForwardSpecKind::Remote);
+        assert_eq!(spec.bind_addr, "0.0.0.0");
+        assert_eq!(spec.bind_port, 8080);
+        assert_eq!(spec.target_host, "127.0.0.1");
+        assert_eq!(spec.target_port, 3000);
+    }
+
+    #[test]
+    fn parse_spec_invalid_few_parts() {
+        assert!(PortForwardSpec::local("127.0.0.1:5432:db").is_err());
+    }
+
+    #[test]
+    fn parse_spec_invalid_many_parts() {
+        assert!(PortForwardSpec::local("a:b:c:d:e").is_err());
+    }
+
+    #[test]
+    fn parse_spec_invalid_port() {
+        assert!(PortForwardSpec::local("127.0.0.1:abc:db:5432").is_err());
+    }
+
+    #[test]
+    fn parse_spec_invalid_target_port() {
+        assert!(PortForwardSpec::local("127.0.0.1:5432:db:abc").is_err());
+    }
+
+    #[test]
+    fn spec_display() {
+        let spec = PortForwardSpec::local("127.0.0.1:5432:db.internal:5432").unwrap();
+        assert_eq!(spec.to_string(), "-L 127.0.0.1:5432:db.internal:5432");
+    }
+
+    #[test]
+    fn spec_display_remote() {
+        let spec = PortForwardSpec::remote("0.0.0.0:8080:127.0.0.1:3000").unwrap();
+        assert_eq!(spec.to_string(), "-R 0.0.0.0:8080:127.0.0.1:3000");
+    }
+
+    #[test]
+    fn local_forwarder_rejects_remote_spec() {
+        let spec = PortForwardSpec::remote("0.0.0.0:8080:127.0.0.1:3000").unwrap();
+        assert!(LocalForwarder::new(spec).is_err());
+    }
+
+    #[test]
+    fn remote_forwarder_rejects_local_spec() {
+        let spec = PortForwardSpec::local("127.0.0.1:5432:db.internal:5432").unwrap();
+        assert!(RemoteForwarder::new(spec).is_err());
+    }
+
+    #[test]
+    fn listen_addr_valid() {
+        let spec = PortForwardSpec::local("127.0.0.1:5432:db.internal:5432").unwrap();
+        let addr = spec.listen_addr().unwrap();
+        assert_eq!(addr.port(), 5432);
+    }
+
+    #[test]
+    fn listen_addr_invalid_host() {
+        let spec = PortForwardSpec {
+            kind: PortForwardSpecKind::Local,
+            bind_addr: "!!!invalid".to_string(),
+            bind_port: 5432,
+            target_host: "db".to_string(),
+            target_port: 5432,
+        };
+        assert!(spec.listen_addr().is_err());
+    }
+
+    #[tokio::test]
+    async fn local_forward_bind_and_accept() {
+        let spec = PortForwardSpec::local(&format!("127.0.0.1:0:remote:5432")).unwrap();
+        let forwarder = LocalForwarder::new(spec).unwrap();
+
+        let listen_addr = forwarder.spec.listen_addr().unwrap();
+        let listener = TcpListener::bind(listen_addr).await.unwrap();
+        let bound_addr = listener.local_addr().unwrap();
+        drop(listener);
+
+        let spec = PortForwardSpec::local(&format!(
+            "127.0.0.1:{}:remote:5432",
+            bound_addr.port()
+        ))
+        .unwrap();
+        let forwarder = LocalForwarder::new(spec).unwrap();
+        assert_eq!(forwarder.local_port(), bound_addr.port());
+    }
+
+    #[tokio::test]
+    async fn remote_forward_proxy_bidirectional() {
+        use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
+        let echo_listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let _echo_addr = echo_listener.local_addr().unwrap();
+
+        let echo_server = tokio::spawn(async move {
+            let (mut stream, _) = echo_listener.accept().await.unwrap();
+            let mut buf = [0u8; 64];
+            loop {
+                let n = match stream.read(&mut buf).await {
+                    Ok(0) => break,
+                    Ok(n) => n,
+                    Err(_) => break,
+                };
+                if stream.write_all(&buf[..n]).await.is_err() {
+                    break;
+                }
+            }
+        });
+
+        let local_listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let local_addr = local_listener.local_addr().unwrap();
+
+        let proxy_task = tokio::spawn(async move {
+            let (stream, _) = local_listener.accept().await.unwrap();
+            let (mut read, mut write) = tokio::io::split(stream);
+            let _ = io::copy(&mut read, &mut write).await;
+        });
+
+        let mut local_conn = TcpStream::connect(local_addr).await.unwrap();
+        local_conn.write_all(b"hello").await.unwrap();
+        let mut buf = [0u8; 64];
+        let n = local_conn.read(&mut buf).await.unwrap();
+        assert_eq!(&buf[..n], b"hello");
+
+        echo_server.abort();
+        proxy_task.abort();
+    }
+
+    #[test]
+    fn forwarder_spec_access() {
+        let spec = PortForwardSpec::local("127.0.0.1:5432:db.internal:5432").unwrap();
+        let forwarder = LocalForwarder::new(spec.clone()).unwrap();
+        assert_eq!(forwarder.spec(), &spec);
+        assert_eq!(forwarder.local_port(), 5432);
+    }
+
+    #[test]
+    fn remote_forwarder_spec_access() {
+        let spec = PortForwardSpec::remote("0.0.0.0:8080:127.0.0.1:3000").unwrap();
+        let forwarder = RemoteForwarder::new(spec.clone()).unwrap();
+        assert_eq!(forwarder.spec(), &spec);
+    }
+}

crates/wraith-core/src/client/mod.rs

@@ -1,3 +1,5 @@
 pub mod channel_manager;
+pub mod forward;
 
-pub use channel_manager::{ChannelManager, ForwardRequest};
+pub use channel_manager::{ChannelManager, ForwardRequest};
+pub use forward::{LocalForwarder, PortForwardSpec, PortForwardSpecKind, RemoteForwarder};

crates/wraith-core/src/error.rs

@@ -60,6 +60,22 @@ pub enum ConfigError {
     IncompatibleOptions,
 }
 
+#[derive(Debug, thiserror::Error)]
+pub enum ForwardError {
+    #[error("invalid forward spec: {spec}")]
+    InvalidSpec { spec: String },
+    #[error("bind failed")]
+    BindFailed {
+        #[source]
+        source: io::Error,
+    },
+    #[error("channel open failed")]
+    ChannelOpenFailed {
+        #[source]
+        source: Box<dyn std::error::Error + Send + Sync>,
+    },
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/wraith-core/src/lib.rs

@@ -8,6 +8,6 @@ pub mod error;
 #[cfg(feature = "testutil")]
 pub mod testutil;
 
-pub use error::{AuthError, ChannelError, ConfigError, TransportError};
+pub use error::{AuthError, ChannelError, ConfigError, ForwardError, TransportError};
 pub use transport::{Transport, TransportAcceptor, TransportInfo, TransportKind};
 pub use client::channel_manager::{ChannelManager, ForwardRequest};

crates/wraith-core/src/server/handler.rs

@@ -0,0 +1,512 @@
+use std::net::{IpAddr, SocketAddr};
+use std::sync::Arc;
+use std::time::Instant;
+
+use async_trait::async_trait;
+use russh::keys::ssh_key::HashAlg;
+use russh::server::{Auth, Handler, Msg, Session};
+use russh::Channel;
+
+use crate::auth::ServerAuthConfig;
+use crate::server::rate_limit::{AuthAttemptLimiter, ConnectionRateLimiter};
+
+const WRAITH_PREFIX: &str = "wraith-";
+
+#[derive(Debug, Clone)]
+pub enum ProxyMode {
+    Direct,
+    Socks5(SocketAddr),
+    HttpConnect(SocketAddr),
+}
+
+#[derive(Debug, Clone)]
+pub struct ProxyConfig {
+    pub mode: ProxyMode,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum TransportKind {
+    Tcp,
+    Tls,
+    Iroh,
+}
+
+impl std::fmt::Display for TransportKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TransportKind::Tcp => write!(f, "tcp"),
+            TransportKind::Tls => write!(f, "tls"),
+            TransportKind::Iroh => write!(f, "iroh"),
+        }
+    }
+}
+
+pub struct ServerHandler {
+    auth_config: Arc<ServerAuthConfig>,
+    outbound_proxy: Option<ProxyConfig>,
+    remote_addr: Option<SocketAddr>,
+    transport: TransportKind,
+    connection_limiter: Arc<ConnectionRateLimiter>,
+    connection_allowed: bool,
+    auth_limiter: AuthAttemptLimiter,
+    connected_at: Instant,
+}
+
+impl ServerHandler {
+    pub fn new(
+        auth_config: Arc<ServerAuthConfig>,
+        outbound_proxy: Option<ProxyConfig>,
+        remote_addr: Option<SocketAddr>,
+        transport: TransportKind,
+        connection_limiter: Arc<ConnectionRateLimiter>,
+        max_auth_attempts: usize,
+    ) -> Self {
+        let allowed = if let Some(addr) = remote_addr {
+            let ip = addr.ip();
+            if connection_limiter.check(ip) {
+                connection_limiter.on_connect(ip);
+                tracing::info!(
+                    remote_addr = %addr,
+                    transport = %transport,
+                    "connection opened"
+                );
+                true
+            } else {
+                tracing::info!(
+                    remote_addr = %addr,
+                    transport = %transport,
+                    "connection rejected"
+                );
+                false
+            }
+        } else {
+            true
+        };
+
+        Self {
+            auth_config,
+            outbound_proxy,
+            remote_addr,
+            transport,
+            connection_limiter,
+            connection_allowed: allowed,
+            auth_limiter: AuthAttemptLimiter::new(max_auth_attempts),
+            connected_at: Instant::now(),
+        }
+    }
+
+    pub fn is_connection_allowed(&self) -> bool {
+        self.connection_allowed
+    }
+
+    pub fn remote_ip(&self) -> Option<IpAddr> {
+        self.remote_addr.map(|a| a.ip())
+    }
+}
+
+impl Drop for ServerHandler {
+    fn drop(&mut self) {
+        if let Some(addr) = self.remote_addr {
+            if self.connection_allowed {
+                self.connection_limiter.on_disconnect(addr.ip());
+            }
+            let duration = self.connected_at.elapsed();
+            tracing::info!(
+                remote_addr = %addr,
+                duration_secs = duration.as_secs_f64(),
+                "connection closed"
+            );
+        }
+    }
+}
+
+#[async_trait]
+impl Handler for ServerHandler {
+    type Error = russh::Error;
+
+    async fn auth_publickey(
+        &mut self,
+        user: &str,
+        public_key: &russh::keys::ssh_key::PublicKey,
+    ) -> Result<Auth, Self::Error> {
+        if !self.auth_limiter.check() {
+            let remote_addr_display = self
+                .remote_addr
+                .map_or("unknown".to_string(), |a| a.to_string());
+            let fingerprint = format!("{}", public_key.fingerprint(HashAlg::Sha256));
+            tracing::info!(
+                remote_addr = %remote_addr_display,
+                user = user,
+                key_fingerprint = %fingerprint,
+                result = "reject",
+                "auth attempt"
+            );
+            return Ok(Auth::Reject {
+                proceed_with_methods: None,
+            });
+        }
+
+        let fingerprint = format!("{}", public_key.fingerprint(HashAlg::Sha256));
+        let remote_addr_display = self
+            .remote_addr
+            .map_or("unknown".to_string(), |a| a.to_string());
+
+        let russh_pub = russh::keys::PublicKey::new(public_key.key_data().clone(), user);
+        let result = self.auth_config.authenticate_publickey(&russh_pub);
+
+        match result {
+            Ok(()) => {
+                tracing::info!(
+                    remote_addr = %remote_addr_display,
+                    user = user,
+                    key_fingerprint = %fingerprint,
+                    result = "accept",
+                    "auth attempt"
+                );
+                Ok(Auth::Accept)
+            }
+            Err(_) => {
+                self.auth_limiter.on_failure();
+                tracing::info!(
+                    remote_addr = %remote_addr_display,
+                    user = user,
+                    key_fingerprint = %fingerprint,
+                    result = "reject",
+                    "auth attempt"
+                );
+                Ok(Auth::Reject {
+                    proceed_with_methods: None,
+                })
+            }
+        }
+    }
+
+    async fn channel_open_direct_tcpip(
+        &mut self,
+        channel: Channel<Msg>,
+        host_to_connect: &str,
+        port_to_connect: u32,
+        originator_address: &str,
+        originator_port: u32,
+        _session: &mut Session,
+    ) -> Result<bool, Self::Error> {
+        if host_to_connect.starts_with(WRAITH_PREFIX) {
+            tracing::info!(
+                host = host_to_connect,
+                port = port_to_connect,
+                "routing to internal control channel handler"
+            );
+            return Ok(true);
+        }
+
+        let proxy_info = self
+            .outbound_proxy
+            .as_ref()
+            .map(|p| format!("{:?}", p.mode))
+            .unwrap_or_else(|| "direct".to_string());
+
+        tracing::info!(
+            host = host_to_connect,
+            port = port_to_connect,
+            originator_address = originator_address,
+            originator_port = originator_port,
+            proxy = %proxy_info,
+            "spawning tcp proxy task"
+        );
+
+        let _ = channel;
+        Ok(false)
+    }
+
+    async fn channel_open_session(
+        &mut self,
+        _channel: Channel<Msg>,
+        _session: &mut Session,
+    ) -> Result<bool, Self::Error> {
+        Ok(false)
+    }
+
+    async fn channel_open_x11(
+        &mut self,
+        _channel: Channel<Msg>,
+        _originator_address: &str,
+        _originator_port: u32,
+        _session: &mut Session,
+    ) -> Result<bool, Self::Error> {
+        Ok(false)
+    }
+
+    async fn channel_open_forwarded_tcpip(
+        &mut self,
+        _channel: Channel<Msg>,
+        _host_to_connect: &str,
+        _port_to_connect: u32,
+        _originator_address: &str,
+        _originator_port: u32,
+        _session: &mut Session,
+    ) -> Result<bool, Self::Error> {
+        Ok(false)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::auth::keys::KeySource;
+    use russh::keys::{decode_secret_key, PrivateKey};
+    use std::io::Write;
+
+    const ED25519_PRIVATE_KEY: &str = "-----BEGIN OPENSSH PRIVATE KEY-----\nb3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW\nQyNTUxOQAAACBOfInDyRS33JEeDNT8xd10qRdwFN8z/QukCOgEIkv01QAAAJiQ+NvMkPjb\nzAAAAAtzc2gtZWQyNTUxOQAAACBOfInDyRS33JEeDNT8xd10qRdwFN8z/QukCOgEIkv01Q\nAAAECIWwJf7+7MOuZAOOWmoQbE9i/5GxjKsFrtJHjZ34E/fk58icPJFLfckR4M1PzF3XSp\nF3AU3zP9C6QI6AQiS/TVAAAAD3VidW50dUBuczUyODA5NgECAwQFBg==\n-----END OPENSSH PRIVATE KEY-----\n";
+
+    const ED25519_PUBLIC_KEY: &str = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIE58icPJFLfckR4M1PzF3XSpF3AU3zP9C6QI6AQiS/TV ubuntu@ns528096";
+
+    fn make_authorized_keys_file(keys_content: &str) -> tempfile::NamedTempFile {
+        let mut f = tempfile::NamedTempFile::new().unwrap();
+        f.write_all(keys_content.as_bytes()).unwrap();
+        f.flush().unwrap();
+        f
+    }
+
+    fn load_key() -> PrivateKey {
+        decode_secret_key(ED25519_PRIVATE_KEY, None).unwrap()
+    }
+
+    fn make_auth_config(keys_content: &str) -> Arc<ServerAuthConfig> {
+        let f = make_authorized_keys_file(keys_content);
+        Arc::new(
+            ServerAuthConfig::from_keys_and_ca(
+                Some(KeySource::File(f.path().to_path_buf())),
+                None,
+            )
+            .unwrap(),
+        )
+    }
+
+    fn make_empty_auth_config() -> Arc<ServerAuthConfig> {
+        Arc::new(ServerAuthConfig::from_keys_and_ca(None, None).unwrap())
+    }
+
+    fn default_limiter() -> Arc<ConnectionRateLimiter> {
+        Arc::new(ConnectionRateLimiter::new(0))
+    }
+
+    fn make_handler(
+        auth_config: Arc<ServerAuthConfig>,
+        outbound_proxy: Option<ProxyConfig>,
+        remote_addr: Option<SocketAddr>,
+    ) -> ServerHandler {
+        ServerHandler::new(auth_config, outbound_proxy, remote_addr, TransportKind::Tcp, default_limiter(), 10)
+    }
+
+    #[tokio::test]
+    async fn auth_delegation_accepts_known_key() {
+        let auth_config = make_auth_config(ED25519_PUBLIC_KEY);
+        let mut handler = make_handler(auth_config, None, None);
+
+        let ssh_key = load_key().public_key().clone();
+        let result = handler.auth_publickey("testuser", &ssh_key).await.unwrap();
+        assert_eq!(result, Auth::Accept);
+    }
+
+    #[tokio::test]
+    async fn auth_delegation_rejects_unknown_key() {
+        let auth_config = make_auth_config(ED25519_PUBLIC_KEY);
+        let mut handler = make_handler(auth_config, None, None);
+
+        let other_key_text = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHeLC1lWiCYrXsf/85O/pkbUFZ6OGIt49PX3nw8iRoXE other@host";
+        let other_ssh_key = russh::keys::parse_public_key_base64(
+            other_key_text.split_whitespace().nth(1).unwrap(),
+        )
+        .unwrap();
+
+        let result = handler
+            .auth_publickey("testuser", &other_ssh_key)
+            .await
+            .unwrap();
+        assert_eq!(
+            result,
+            Auth::Reject {
+                proceed_with_methods: None
+            }
+        );
+    }
+
+    #[tokio::test]
+    async fn auth_delegation_empty_config_rejects_all() {
+        let auth_config = make_empty_auth_config();
+        let mut handler = make_handler(auth_config, None, None);
+
+        let ssh_key = load_key().public_key().clone();
+        let result = handler
+            .auth_publickey("testuser", &ssh_key)
+            .await
+            .unwrap();
+        assert_eq!(
+            result,
+            Auth::Reject {
+                proceed_with_methods: None
+            }
+        );
+    }
+
+    #[tokio::test]
+    async fn auth_logging_includes_remote_addr() {
+        let auth_config = make_auth_config(ED25519_PUBLIC_KEY);
+        let remote_addr: SocketAddr = "203.0.113.50:12345".parse().unwrap();
+        let mut handler = make_handler(auth_config, None, Some(remote_addr));
+
+        let ssh_key = load_key().public_key().clone();
+        let _ = handler.auth_publickey("root", &ssh_key).await.unwrap();
+    }
+
+    #[test]
+    fn reserved_wraith_destination_routing() {
+        assert!("wraith-control".starts_with(WRAITH_PREFIX));
+        assert!("wraith-status".starts_with(WRAITH_PREFIX));
+        assert!("wraith-events".starts_with(WRAITH_PREFIX));
+        assert!(!"example.com".starts_with(WRAITH_PREFIX));
+        assert!(!"localhost".starts_with(WRAITH_PREFIX));
+        assert!(!"wraith.example.com".starts_with(WRAITH_PREFIX));
+    }
+
+    #[test]
+    fn proxy_mode_variants() {
+        let direct = ProxyMode::Direct;
+        let socks5 = ProxyMode::Socks5("127.0.0.1:9050".parse().unwrap());
+        let http = ProxyMode::HttpConnect("127.0.0.1:8080".parse().unwrap());
+
+        match direct {
+            ProxyMode::Direct => {}
+            _ => panic!("expected Direct"),
+        }
+        match socks5 {
+            ProxyMode::Socks5(_) => {}
+            _ => panic!("expected Socks5"),
+        }
+        match http {
+            ProxyMode::HttpConnect(_) => {}
+            _ => panic!("expected HttpConnect"),
+        }
+    }
+
+    #[test]
+    fn server_handler_holds_config() {
+        let auth_config = make_empty_auth_config();
+        let proxy = Some(ProxyConfig {
+            mode: ProxyMode::Socks5("127.0.0.1:9050".parse().unwrap()),
+        });
+        let remote: Option<SocketAddr> = Some("10.0.0.1:22".parse().unwrap());
+
+        let handler = make_handler(auth_config, proxy.clone(), remote);
+        assert!(handler.outbound_proxy.is_some());
+        assert!(handler.remote_addr.is_some());
+    }
+
+    #[test]
+    fn one_handler_per_connection() {
+        let auth_config = make_empty_auth_config();
+        let handler1 = make_handler(auth_config.clone(), None, Some("10.0.0.1:22".parse().unwrap()));
+        let handler2 = make_handler(auth_config.clone(), None, Some("10.0.0.2:22".parse().unwrap()));
+
+        assert!(handler1.remote_addr != handler2.remote_addr);
+    }
+
+    #[tokio::test]
+    async fn auth_rate_limit_rejects_after_max_failures() {
+        let auth_config = make_empty_auth_config();
+        let limiter = Arc::new(ConnectionRateLimiter::new(0));
+        let mut handler = ServerHandler::new(
+            auth_config,
+            None,
+            Some("10.0.0.1:22".parse().unwrap()),
+            TransportKind::Tcp,
+            limiter,
+            2,
+        );
+
+        let ssh_key = load_key().public_key().clone();
+
+        let r1 = handler.auth_publickey("user", &ssh_key).await.unwrap();
+        assert_eq!(r1, Auth::Reject { proceed_with_methods: None });
+
+        let r2 = handler.auth_publickey("user", &ssh_key).await.unwrap();
+        assert_eq!(r2, Auth::Reject { proceed_with_methods: None });
+
+        assert!(!handler.auth_limiter.check());
+    }
+
+    #[test]
+    fn connection_rate_limit_blocks_over_limit() {
+        let limiter = Arc::new(ConnectionRateLimiter::new(1));
+        let auth_config = make_empty_auth_config();
+        let addr: SocketAddr = "10.0.0.1:22".parse().unwrap();
+
+        let h1 = ServerHandler::new(
+            auth_config.clone(),
+            None,
+            Some(addr),
+            TransportKind::Tcp,
+            limiter.clone(),
+            10,
+        );
+        assert!(h1.is_connection_allowed());
+
+        let h2 = ServerHandler::new(
+            auth_config.clone(),
+            None,
+            Some(addr),
+            TransportKind::Tcp,
+            limiter.clone(),
+            10,
+        );
+        assert!(!h2.is_connection_allowed());
+
+        drop(h1);
+
+        let h3 = ServerHandler::new(
+            auth_config,
+            None,
+            Some(addr),
+            TransportKind::Tcp,
+            limiter,
+            10,
+        );
+        assert!(h3.is_connection_allowed());
+    }
+
+    #[test]
+    fn transport_kind_display() {
+        assert_eq!(TransportKind::Tcp.to_string(), "tcp");
+        assert_eq!(TransportKind::Tls.to_string(), "tls");
+        assert_eq!(TransportKind::Iroh.to_string(), "iroh");
+    }
+
+    #[tokio::test]
+    async fn auth_log_includes_user_field() {
+        let auth_config = make_empty_auth_config();
+        let mut handler = ServerHandler::new(
+            auth_config,
+            None,
+            Some("203.0.113.50:12345".parse().unwrap()),
+            TransportKind::Tls,
+            Arc::new(ConnectionRateLimiter::new(0)),
+            10,
+        );
+
+        let ssh_key = load_key().public_key().clone();
+        let _ = handler.auth_publickey("root", &ssh_key).await.unwrap();
+    }
+
+    #[test]
+    fn connection_closed_logs_duration_on_drop() {
+        let auth_config = make_empty_auth_config();
+        let _handler = ServerHandler::new(
+            auth_config,
+            None,
+            Some("203.0.113.50:12345".parse().unwrap()),
+            TransportKind::Tcp,
+            Arc::new(ConnectionRateLimiter::new(0)),
+            10,
+        );
+    }
+}

crates/wraith-core/src/server/mod.rs

@@ -0,0 +1,5 @@
+pub mod handler;
+pub mod rate_limit;
+
+pub use handler::{ProxyConfig, ProxyMode, ServerHandler, TransportKind};
+pub use rate_limit::{AuthAttemptLimiter, ConnectionRateLimiter};

crates/wraith-core/src/server/rate_limit.rs

@@ -0,0 +1,193 @@
+use std::collections::HashMap;
+use std::net::IpAddr;
+use std::sync::Mutex;
+
+pub struct ConnectionRateLimiter {
+    max_per_ip: usize,
+    active: Mutex<HashMap<IpAddr, usize>>,
+}
+
+impl ConnectionRateLimiter {
+    pub fn new(max_per_ip: usize) -> Self {
+        Self {
+            max_per_ip,
+            active: Mutex::new(HashMap::new()),
+        }
+    }
+
+    pub fn check(&self, ip: IpAddr) -> bool {
+        if self.max_per_ip == 0 {
+            return true;
+        }
+        let active = self.active.lock().unwrap();
+        let count = active.get(&ip).copied().unwrap_or(0);
+        count < self.max_per_ip
+    }
+
+    pub fn on_connect(&self, ip: IpAddr) {
+        let mut active = self.active.lock().unwrap();
+        *active.entry(ip).or_insert(0) += 1;
+    }
+
+    pub fn on_disconnect(&self, ip: IpAddr) {
+        let mut active = self.active.lock().unwrap();
+        if let Some(count) = active.get_mut(&ip) {
+            if *count > 1 {
+                *count -= 1;
+            } else {
+                active.remove(&ip);
+            }
+        }
+    }
+}
+
+pub struct AuthAttemptLimiter {
+    max_attempts: usize,
+    failures: usize,
+}
+
+impl AuthAttemptLimiter {
+    pub fn new(max_attempts: usize) -> Self {
+        Self {
+            max_attempts,
+            failures: 0,
+        }
+    }
+
+    pub fn check(&self) -> bool {
+        if self.max_attempts == 0 {
+            return true;
+        }
+        self.failures < self.max_attempts
+    }
+
+    pub fn on_failure(&mut self) {
+        self.failures += 1;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
+
+    fn ip(n: u8) -> IpAddr {
+        IpAddr::V4(Ipv4Addr::new(192, 168, 1, n))
+    }
+
+    #[test]
+    fn connection_limiter_allows_when_under_limit() {
+        let limiter = ConnectionRateLimiter::new(3);
+        assert!(limiter.check(ip(1)));
+    }
+
+    #[test]
+    fn connection_limiter_blocks_when_at_limit() {
+        let limiter = ConnectionRateLimiter::new(2);
+        limiter.on_connect(ip(1));
+        limiter.on_connect(ip(1));
+        assert!(!limiter.check(ip(1)));
+    }
+
+    #[test]
+    fn connection_limiter_allows_after_disconnect() {
+        let limiter = ConnectionRateLimiter::new(2);
+        limiter.on_connect(ip(1));
+        limiter.on_connect(ip(1));
+        assert!(!limiter.check(ip(1)));
+        limiter.on_disconnect(ip(1));
+        assert!(limiter.check(ip(1)));
+    }
+
+    #[test]
+    fn connection_limiter_unlimited_when_zero() {
+        let limiter = ConnectionRateLimiter::new(0);
+        for _ in 0..100 {
+            limiter.on_connect(ip(1));
+        }
+        assert!(limiter.check(ip(1)));
+    }
+
+    #[test]
+    fn connection_limiter_tracks_per_ip_independently() {
+        let limiter = ConnectionRateLimiter::new(1);
+        limiter.on_connect(ip(1));
+        assert!(!limiter.check(ip(1)));
+        assert!(limiter.check(ip(2)));
+    }
+
+    #[test]
+    fn connection_limiter_ipv6() {
+        let limiter = ConnectionRateLimiter::new(1);
+        let ip6 = IpAddr::V6(Ipv6Addr::LOCALHOST);
+        limiter.on_connect(ip6);
+        assert!(!limiter.check(ip6));
+    }
+
+    #[test]
+    fn connection_limiter_disconnect_removes_zero_entry() {
+        let limiter = ConnectionRateLimiter::new(3);
+        limiter.on_connect(ip(1));
+        limiter.on_disconnect(ip(1));
+        {
+            let active = limiter.active.lock().unwrap();
+            assert!(!active.contains_key(&ip(1)));
+        }
+    }
+
+    #[test]
+    fn auth_limiter_allows_when_under_limit() {
+        let limiter = AuthAttemptLimiter::new(3);
+        assert!(limiter.check());
+    }
+
+    #[test]
+    fn auth_limiter_blocks_after_max_failures() {
+        let mut limiter = AuthAttemptLimiter::new(2);
+        limiter.on_failure();
+        limiter.on_failure();
+        assert!(!limiter.check());
+    }
+
+    #[test]
+    fn auth_limiter_unlimited_when_zero() {
+        let mut limiter = AuthAttemptLimiter::new(0);
+        for _ in 0..100 {
+            limiter.on_failure();
+        }
+        assert!(limiter.check());
+    }
+
+    #[test]
+    fn auth_limiter_still_allows_at_one_below_limit() {
+        let mut limiter = AuthAttemptLimiter::new(3);
+        limiter.on_failure();
+        limiter.on_failure();
+        assert!(limiter.check());
+        limiter.on_failure();
+        assert!(!limiter.check());
+    }
+
+    #[test]
+    fn connection_limiter_thread_safety() {
+        use std::sync::Arc;
+        use std::thread;
+
+        let limiter = Arc::new(ConnectionRateLimiter::new(100));
+        let mut handles = vec![];
+
+        for i in 0..10 {
+            let lim = Arc::clone(&limiter);
+            handles.push(thread::spawn(move || {
+                let ip_addr = ip((i % 3) as u8 + 1);
+                lim.on_connect(ip_addr);
+                assert!(lim.check(ip_addr));
+                lim.on_disconnect(ip_addr);
+            }));
+        }
+
+        for h in handles {
+            h.join().unwrap();
+        }
+    }
+}

crates/wraith-core/src/socks5/mod.rs

@@ -0,0 +1,490 @@
+mod protocol;
+
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt};
+use tokio::net::TcpListener;
+use tokio::sync::Mutex;
+use tracing::debug;
+
+use protocol::{Socks5Reply, Socks5Request, Socks5VersionMethod};
+
+pub use protocol::Socks5Address;
+
+const DEFAULT_SOCKS5_ADDR: &str = "127.0.0.1:1080";
+
+pub trait ChannelOpener: Send + Sync + 'static {
+    type Stream: AsyncRead + AsyncWrite + Unpin + Send + 'static;
+
+    fn open_channel(
+        &self,
+        host: String,
+        port: u16,
+    ) -> impl std::future::Future<Output = Result<Self::Stream, ChannelOpenError>> + Send;
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum ChannelOpenError {
+    #[error("session closed")]
+    SessionClosed,
+    #[error("channel open failed")]
+    ChannelOpenFailed,
+    #[error("connection refused")]
+    ConnectionRefused,
+}
+
+pub struct Socks5Server<C: ChannelOpener> {
+    listen_addr: SocketAddr,
+    channel_opener: Arc<C>,
+}
+
+impl<C: ChannelOpener> Socks5Server<C> {
+    pub fn new(channel_opener: C) -> Self {
+        Self::with_addr(channel_opener, DEFAULT_SOCKS5_ADDR)
+    }
+
+    pub fn with_addr(channel_opener: C, addr: &str) -> Self {
+        let listen_addr: SocketAddr = addr
+            .parse()
+            .expect("invalid SOCKS5 listen address");
+        Self {
+            listen_addr,
+            channel_opener: Arc::new(channel_opener),
+        }
+    }
+
+    pub fn listen_addr(&self) -> SocketAddr {
+        self.listen_addr
+    }
+
+    pub async fn run(self) -> Result<(), std::io::Error> {
+        let listener = TcpListener::bind(self.listen_addr).await?;
+        debug!("socks5 server listening on {}", self.listen_addr);
+        loop {
+            let (socket, _peer) = listener.accept().await?;
+            let opener = Arc::clone(&self.channel_opener);
+            tokio::spawn(async move {
+                if let Err(e) = handle_socks5_connection(socket, opener).await {
+                    debug!("socks5 connection error: {e}");
+                }
+            });
+        }
+    }
+}
+
+async fn handle_socks5_connection<S, C>(
+    mut socket: S,
+    opener: Arc<C>,
+) -> Result<(), Socks5Error>
+where
+    S: AsyncRead + AsyncWrite + Unpin,
+    C: ChannelOpener,
+{
+    let vm = Socks5VersionMethod::read_from(&mut socket).await?;
+    if vm.version != 0x05 {
+        return Err(Socks5Error::InvalidVersion(vm.version));
+    }
+    if !vm.methods.contains(&0x00) {
+        let reply = [0x05, 0xFF];
+        socket.write_all(&reply).await?;
+        socket.shutdown().await?;
+        return Err(Socks5Error::NoAcceptableAuth);
+    }
+    let reply = [0x05, 0x00];
+    socket.write_all(&reply).await?;
+
+    let request = Socks5Request::read_from(&mut socket).await?;
+    if request.version != 0x05 {
+        return Err(Socks5Error::InvalidVersion(request.version));
+    }
+    if request.command != 0x01 {
+        send_error_reply(&mut socket, Socks5Reply::command_not_supported()).await?;
+        return Err(Socks5Error::UnsupportedCommand(request.command));
+    }
+
+    let (host, port) = match &request.address {
+        Socks5Address::Ipv4(addr) => (addr.to_string(), request.port),
+        Socks5Address::Ipv6(addr) => (addr.to_string(), request.port),
+        Socks5Address::Domain(name) => (name.clone(), request.port),
+    };
+
+    match opener.open_channel(host, port).await {
+        Ok(mut ssh_stream) => {
+            let bind_addr = Socks5Address::Ipv4(std::net::Ipv4Addr::UNSPECIFIED);
+            let reply = Socks5Reply::success(bind_addr, 0);
+            reply.write_to(&mut socket).await?;
+            tokio::io::copy_bidirectional(&mut socket, &mut ssh_stream).await?;
+            Ok(())
+        }
+        Err(_) => {
+            send_error_reply(&mut socket, Socks5Reply::connection_refused()).await?;
+            Err(Socks5Error::ChannelOpenFailed)
+        }
+    }
+}
+
+async fn send_error_reply<S: AsyncRead + AsyncWrite + Unpin>(
+    socket: &mut S,
+    reply: Socks5Reply,
+) -> Result<(), Socks5Error> {
+    reply.write_to(socket).await?;
+    let _ = socket.shutdown().await;
+    Ok(())
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum Socks5Error {
+    #[error("invalid SOCKS version: {0}")]
+    InvalidVersion(u8),
+    #[error("no acceptable auth method")]
+    NoAcceptableAuth,
+    #[error("unsupported command: {0}")]
+    UnsupportedCommand(u8),
+    #[error("channel open failed")]
+    ChannelOpenFailed,
+    #[error("io error")]
+    Io(#[from] std::io::Error),
+}
+
+pub struct HandleChannelOpener<H: russh::client::Handler> {
+    handle: Arc<Mutex<russh::client::Handle<H>>>,
+}
+
+impl<H: russh::client::Handler> HandleChannelOpener<H> {
+    pub fn new(handle: russh::client::Handle<H>) -> Self {
+        Self {
+            handle: Arc::new(Mutex::new(handle)),
+        }
+    }
+
+    pub fn from_arc(handle: Arc<Mutex<russh::client::Handle<H>>>) -> Self {
+        Self { handle }
+    }
+}
+
+impl<H: russh::client::Handler + Send + Sync + 'static> ChannelOpener for HandleChannelOpener<H> {
+    type Stream = russh::ChannelStream<russh::client::Msg>;
+
+    async fn open_channel(&self, host: String, port: u16) -> Result<Self::Stream, ChannelOpenError> {
+        let handle = self.handle.lock().await;
+        if handle.is_closed() {
+            return Err(ChannelOpenError::SessionClosed);
+        }
+        let channel = handle
+            .channel_open_direct_tcpip(host, port as u32, "127.0.0.1", 0)
+            .await
+            .map_err(|_| ChannelOpenError::ChannelOpenFailed)?;
+        Ok(channel.into_stream())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tokio::io::{duplex, AsyncReadExt, AsyncWriteExt, DuplexStream};
+
+    struct MockChannelOpener {
+        fail: bool,
+    }
+
+    impl ChannelOpener for MockChannelOpener {
+        type Stream = DuplexStream;
+
+        async fn open_channel(
+            &self,
+            _host: String,
+            _port: u16,
+        ) -> Result<Self::Stream, ChannelOpenError> {
+            if self.fail {
+                Err(ChannelOpenError::ChannelOpenFailed)
+            } else {
+                let (client, _server) = duplex(4096);
+                Ok(client)
+            }
+        }
+    }
+
+    fn build_socks5_greeting(methods: &[u8]) -> Vec<u8> {
+        let mut buf = vec![0x05, methods.len() as u8];
+        buf.extend_from_slice(methods);
+        buf
+    }
+
+    fn build_socks5_connect_ipv4(addr: [u8; 4], port: u16) -> Vec<u8> {
+        let mut buf = vec![0x05, 0x01, 0x00, 0x01];
+        buf.extend_from_slice(&addr);
+        buf.extend_from_slice(&port.to_be_bytes());
+        buf
+    }
+
+    fn build_socks5_connect_domain(domain: &str, port: u16) -> Vec<u8> {
+        let mut buf = vec![0x05, 0x01, 0x00, 0x03];
+        buf.push(domain.len() as u8);
+        buf.extend_from_slice(domain.as_bytes());
+        buf.extend_from_slice(&port.to_be_bytes());
+        buf
+    }
+
+    fn build_socks5_connect_ipv6(addr: [u8; 16], port: u16) -> Vec<u8> {
+        let mut buf = vec![0x05, 0x01, 0x00, 0x04];
+        buf.extend_from_slice(&addr);
+        buf.extend_from_slice(&port.to_be_bytes());
+        buf
+    }
+
+    async fn do_handshake(client: &mut DuplexStream) -> [u8; 2] {
+        client.write_all(&build_socks5_greeting(&[0x00])).await.unwrap();
+        client.flush().await.unwrap();
+        let mut resp = [0u8; 2];
+        client.read_exact(&mut resp).await.unwrap();
+        resp
+    }
+
+    async fn do_connect_ipv4(client: &mut DuplexStream, addr: [u8; 4], port: u16) -> Vec<u8> {
+        client
+            .write_all(&build_socks5_connect_ipv4(addr, port))
+            .await
+            .unwrap();
+        client.flush().await.unwrap();
+        let mut reply_buf = [0u8; 10];
+        client.read_exact(&mut reply_buf).await.unwrap();
+        reply_buf.to_vec()
+    }
+
+    #[tokio::test]
+    async fn handshake_no_auth_method() {
+        let (mut client, server) = duplex(4096);
+        let opener = MockChannelOpener { fail: false };
+
+        let server_handle = tokio::spawn(async move {
+            handle_socks5_connection(server, Arc::new(opener)).await
+        });
+
+        let resp = do_handshake(&mut client).await;
+        assert_eq!(resp, [0x05, 0x00]);
+
+        let reply_buf = do_connect_ipv4(&mut client, [127, 0, 0, 1], 80).await;
+        assert_eq!(reply_buf[0], 0x05);
+        assert_eq!(reply_buf[1], 0x00);
+
+        drop(client);
+        let _ = server_handle.await;
+    }
+
+    #[tokio::test]
+    async fn handshake_rejects_no_acceptable_method() {
+        let (mut client, server) = duplex(4096);
+        let opener = MockChannelOpener { fail: false };
+
+        let server_handle = tokio::spawn(async move {
+            handle_socks5_connection(server, Arc::new(opener)).await
+        });
+
+        client
+            .write_all(&build_socks5_greeting(&[0x02]))
+            .await
+            .unwrap();
+        client.flush().await.unwrap();
+
+        let mut resp = [0u8; 2];
+        client.read_exact(&mut resp).await.unwrap();
+        assert_eq!(resp, [0x05, 0xFF]);
+
+        drop(client);
+        let result = server_handle.await.unwrap();
+        assert!(result.is_err());
+        assert!(matches!(
+            result.unwrap_err(),
+            Socks5Error::NoAcceptableAuth
+        ));
+    }
+
+    #[tokio::test]
+    async fn address_type_ipv4() {
+        let (mut client, server) = duplex(4096);
+        let opener = MockChannelOpener { fail: false };
+
+        let server_handle = tokio::spawn(async move {
+            handle_socks5_connection(server, Arc::new(opener)).await
+        });
+
+        do_handshake(&mut client).await;
+        let reply_buf = do_connect_ipv4(&mut client, [10, 0, 0, 1], 443).await;
+        assert_eq!(reply_buf[1], 0x00);
+
+        drop(client);
+        let _ = server_handle.await;
+    }
+
+    #[tokio::test]
+    async fn address_type_domain() {
+        let (mut client, server) = duplex(4096);
+        let opener = MockChannelOpener { fail: false };
+
+        let server_handle = tokio::spawn(async move {
+            handle_socks5_connection(server, Arc::new(opener)).await
+        });
+
+        do_handshake(&mut client).await;
+
+        client
+            .write_all(&build_socks5_connect_domain("example.com", 443))
+            .await
+            .unwrap();
+        client.flush().await.unwrap();
+
+        let mut reply_buf = [0u8; 10];
+        client.read_exact(&mut reply_buf).await.unwrap();
+        assert_eq!(reply_buf[1], 0x00);
+
+        drop(client);
+        let _ = server_handle.await;
+    }
+
+    #[tokio::test]
+    async fn address_type_ipv6() {
+        let (mut client, server) = duplex(4096);
+        let opener = MockChannelOpener { fail: false };
+
+        let server_handle = tokio::spawn(async move {
+            handle_socks5_connection(server, Arc::new(opener)).await
+        });
+
+        do_handshake(&mut client).await;
+
+        let ipv6_addr = [0x20, 0x01, 0x0d, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1];
+        client
+            .write_all(&build_socks5_connect_ipv6(ipv6_addr, 443))
+            .await
+            .unwrap();
+        client.flush().await.unwrap();
+
+        let mut reply_buf = [0u8; 10];
+        client.read_exact(&mut reply_buf).await.unwrap();
+        assert_eq!(reply_buf[0], 0x05);
+        assert_eq!(reply_buf[1], 0x00);
+
+        drop(client);
+        let _ = server_handle.await;
+    }
+
+    #[tokio::test]
+    async fn channel_open_failure_returns_socks5_error() {
+        let (mut client, server) = duplex(4096);
+        let opener = MockChannelOpener { fail: true };
+
+        let server_handle = tokio::spawn(async move {
+            handle_socks5_connection(server, Arc::new(opener)).await
+        });
+
+        do_handshake(&mut client).await;
+        let reply_buf = do_connect_ipv4(&mut client, [10, 0, 0, 1], 80).await;
+        assert_eq!(reply_buf[0], 0x05);
+        assert_eq!(reply_buf[1], 0x05);
+
+        drop(client);
+        let _ = server_handle.await;
+    }
+
+    #[tokio::test]
+    async fn unsupported_command_returns_error() {
+        let (mut client, server) = duplex(4096);
+        let opener = MockChannelOpener { fail: false };
+
+        let server_handle = tokio::spawn(async move {
+            handle_socks5_connection(server, Arc::new(opener)).await
+        });
+
+        do_handshake(&mut client).await;
+
+        let mut bind_req = vec![0x05, 0x02, 0x00, 0x01];
+        bind_req.extend_from_slice(&[127, 0, 0, 1]);
+        bind_req.extend_from_slice(&80u16.to_be_bytes());
+        client.write_all(&bind_req).await.unwrap();
+        client.flush().await.unwrap();
+
+        let mut reply_buf = [0u8; 10];
+        client.read_exact(&mut reply_buf).await.unwrap();
+        assert_eq!(reply_buf[1], 0x07);
+
+        drop(client);
+        let _ = server_handle.await;
+    }
+
+    #[tokio::test]
+    async fn bidirectional_proxy_flow() {
+        let (mut client_sock, server_sock) = duplex(4096);
+        let (ssh_client, mut ssh_server) = duplex(4096);
+
+        let ssh_stream = Arc::new(Mutex::new(Some(ssh_client)));
+
+        struct ProxyOpener {
+            stream: Arc<Mutex<Option<DuplexStream>>>,
+        }
+
+        impl ChannelOpener for ProxyOpener {
+            type Stream = DuplexStream;
+
+            async fn open_channel(
+                &self,
+                _host: String,
+                _port: u16,
+            ) -> Result<Self::Stream, ChannelOpenError> {
+                self.stream
+                    .lock()
+                    .await
+                    .take()
+                    .ok_or(ChannelOpenError::ChannelOpenFailed)
+            }
+        }
+
+        let opener = ProxyOpener {
+            stream: Arc::clone(&ssh_stream),
+        };
+
+        let server_handle = tokio::spawn(async move {
+            handle_socks5_connection(server_sock, Arc::new(opener)).await
+        });
+
+        do_handshake(&mut client_sock).await;
+        let reply_buf = do_connect_ipv4(&mut client_sock, [127, 0, 0, 1], 80).await;
+        assert_eq!(reply_buf[1], 0x00);
+
+        let test_data = b"hello through tunnel";
+        client_sock.write_all(test_data).await.unwrap();
+        client_sock.flush().await.unwrap();
+
+        let mut received = vec![0u8; test_data.len()];
+        AsyncReadExt::read_exact(&mut ssh_server, &mut received)
+            .await
+            .unwrap();
+        assert_eq!(&received, test_data);
+
+        let echo_data = b"response from tunnel";
+        ssh_server.write_all(echo_data).await.unwrap();
+        ssh_server.flush().await.unwrap();
+
+        let mut received_back = vec![0u8; echo_data.len()];
+        client_sock.read_exact(&mut received_back).await.unwrap();
+        assert_eq!(&received_back, echo_data);
+
+        drop(client_sock);
+        drop(ssh_server);
+        let _ = server_handle.await;
+    }
+
+    #[tokio::test]
+    async fn default_listen_address() {
+        let opener = MockChannelOpener { fail: false };
+        let server = Socks5Server::new(opener);
+        assert_eq!(server.listen_addr(), "127.0.0.1:1080".parse().unwrap());
+    }
+
+    #[tokio::test]
+    async fn custom_listen_address() {
+        let opener = MockChannelOpener { fail: false };
+        let server = Socks5Server::with_addr(opener, "127.0.0.1:9050");
+        assert_eq!(server.listen_addr(), "127.0.0.1:9050".parse().unwrap());
+    }
+}

crates/wraith-core/src/socks5/protocol.rs

@@ -0,0 +1,304 @@
+use std::net::{Ipv4Addr, Ipv6Addr};
+
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Socks5Address {
+    Ipv4(Ipv4Addr),
+    Ipv6(Ipv6Addr),
+    Domain(String),
+}
+
+#[derive(Debug)]
+pub struct Socks5VersionMethod {
+    pub version: u8,
+    pub methods: Vec<u8>,
+}
+
+impl Socks5VersionMethod {
+    pub async fn read_from<R: AsyncRead + Unpin>(reader: &mut R) -> std::io::Result<Self> {
+        let version = reader.read_u8().await?;
+        let nmethods = reader.read_u8().await?;
+        let mut methods = vec![0u8; nmethods as usize];
+        reader.read_exact(&mut methods).await?;
+        Ok(Self { version, methods })
+    }
+}
+
+#[derive(Debug)]
+pub struct Socks5Request {
+    pub version: u8,
+    pub command: u8,
+    pub address: Socks5Address,
+    pub port: u16,
+}
+
+impl Socks5Request {
+    pub async fn read_from<R: AsyncRead + Unpin>(reader: &mut R) -> std::io::Result<Self> {
+        let version = reader.read_u8().await?;
+        let command = reader.read_u8().await?;
+        let _rsv = reader.read_u8().await?;
+        let atyp = reader.read_u8().await?;
+
+        let address = match atyp {
+            0x01 => {
+                let mut octets = [0u8; 4];
+                reader.read_exact(&mut octets).await?;
+                Socks5Address::Ipv4(Ipv4Addr::from(octets))
+            }
+            0x04 => {
+                let mut octets = [0u8; 16];
+                reader.read_exact(&mut octets).await?;
+                Socks5Address::Ipv6(Ipv6Addr::from(octets))
+            }
+            0x03 => {
+                let len = reader.read_u8().await?;
+                let mut domain = vec![0u8; len as usize];
+                reader.read_exact(&mut domain).await?;
+                Socks5Address::Domain(String::from_utf8_lossy(&domain).into_owned())
+            }
+            _ => {
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::InvalidData,
+                    format!("unsupported address type: {atyp}"),
+                ))
+            }
+        };
+
+        let port = reader.read_u16().await?;
+
+        Ok(Self {
+            version,
+            command,
+            address,
+            port,
+        })
+    }
+}
+
+#[derive(Debug)]
+pub struct Socks5Reply {
+    pub version: u8,
+    pub reply: u8,
+    pub address: Socks5Address,
+    pub port: u16,
+}
+
+impl Socks5Reply {
+    pub fn success(address: Socks5Address, port: u16) -> Self {
+        Self {
+            version: 0x05,
+            reply: 0x00,
+            address,
+            port,
+        }
+    }
+
+    pub fn connection_refused() -> Self {
+        Self {
+            version: 0x05,
+            reply: 0x05,
+            address: Socks5Address::Ipv4(Ipv4Addr::UNSPECIFIED),
+            port: 0,
+        }
+    }
+
+    pub fn command_not_supported() -> Self {
+        Self {
+            version: 0x05,
+            reply: 0x07,
+            address: Socks5Address::Ipv4(Ipv4Addr::UNSPECIFIED),
+            port: 0,
+        }
+    }
+
+    pub async fn write_to<W: AsyncWrite + Unpin>(&self, writer: &mut W) -> std::io::Result<()> {
+        writer.write_u8(self.version).await?;
+        writer.write_u8(self.reply).await?;
+        writer.write_u8(0x00).await?;
+        match &self.address {
+            Socks5Address::Ipv4(addr) => {
+                writer.write_u8(0x01).await?;
+                writer.write_all(&addr.octets()).await?;
+            }
+            Socks5Address::Ipv6(addr) => {
+                writer.write_u8(0x04).await?;
+                writer.write_all(&addr.octets()).await?;
+            }
+            Socks5Address::Domain(name) => {
+                writer.write_u8(0x03).await?;
+                writer.write_u8(name.len() as u8).await?;
+                writer.write_all(name.as_bytes()).await?;
+            }
+        }
+        writer.write_u16(self.port).await?;
+        writer.flush().await?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Cursor;
+
+    #[tokio::test]
+    async fn parse_version_method_no_auth() {
+        let data = [0x05, 0x01, 0x00];
+        let mut cursor = Cursor::new(&data[..]);
+        let vm = Socks5VersionMethod::read_from(&mut cursor).await.unwrap();
+        assert_eq!(vm.version, 0x05);
+        assert_eq!(vm.methods, vec![0x00]);
+    }
+
+    #[tokio::test]
+    async fn parse_version_method_multiple() {
+        let data = [0x05, 0x02, 0x00, 0x02];
+        let mut cursor = Cursor::new(&data[..]);
+        let vm = Socks5VersionMethod::read_from(&mut cursor).await.unwrap();
+        assert_eq!(vm.version, 0x05);
+        assert_eq!(vm.methods, vec![0x00, 0x02]);
+    }
+
+    #[tokio::test]
+    async fn parse_request_ipv4() {
+        let mut data = vec![0x05, 0x01, 0x00, 0x01];
+        data.extend_from_slice(&[10, 0, 0, 1]);
+        data.extend_from_slice(&443u16.to_be_bytes());
+        let mut cursor = Cursor::new(&data[..]);
+        let req = Socks5Request::read_from(&mut cursor).await.unwrap();
+        assert_eq!(req.version, 0x05);
+        assert_eq!(req.command, 0x01);
+        assert_eq!(
+            req.address,
+            Socks5Address::Ipv4(Ipv4Addr::new(10, 0, 0, 1))
+        );
+        assert_eq!(req.port, 443);
+    }
+
+    #[tokio::test]
+    async fn parse_request_ipv6() {
+        let mut data = vec![0x05, 0x01, 0x00, 0x04];
+        let octets: [u8; 16] = [0x20, 0x01, 0x0d, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1];
+        data.extend_from_slice(&octets);
+        data.extend_from_slice(&443u16.to_be_bytes());
+        let mut cursor = Cursor::new(&data[..]);
+        let req = Socks5Request::read_from(&mut cursor).await.unwrap();
+        assert_eq!(req.version, 0x05);
+        assert_eq!(req.command, 0x01);
+        assert!(matches!(req.address, Socks5Address::Ipv6(_)));
+        assert_eq!(req.port, 443);
+    }
+
+    #[tokio::test]
+    async fn parse_request_domain() {
+        let domain = "example.com";
+        let mut data = vec![0x05, 0x01, 0x00, 0x03];
+        data.push(domain.len() as u8);
+        data.extend_from_slice(domain.as_bytes());
+        data.extend_from_slice(&443u16.to_be_bytes());
+        let mut cursor = Cursor::new(&data[..]);
+        let req = Socks5Request::read_from(&mut cursor).await.unwrap();
+        assert_eq!(req.version, 0x05);
+        assert_eq!(req.command, 0x01);
+        assert_eq!(req.address, Socks5Address::Domain("example.com".to_string()));
+        assert_eq!(req.port, 443);
+    }
+
+    #[tokio::test]
+    async fn parse_request_unsupported_address_type() {
+        let data = [0x05, 0x01, 0x00, 0x05];
+        let mut cursor = Cursor::new(&data[..]);
+        let result = Socks5Request::read_from(&mut cursor).await;
+        assert!(result.is_err());
+    }
+
+    #[tokio::test]
+    async fn reply_success_ipv4() {
+        let reply = Socks5Reply::success(Socks5Address::Ipv4(Ipv4Addr::UNSPECIFIED), 0);
+        let mut buf = Vec::new();
+        reply.write_to(&mut buf).await.unwrap();
+        assert_eq!(buf[0], 0x05);
+        assert_eq!(buf[1], 0x00);
+        assert_eq!(buf[2], 0x00);
+        assert_eq!(buf[3], 0x01);
+    }
+
+    #[tokio::test]
+    async fn reply_connection_refused() {
+        let reply = Socks5Reply::connection_refused();
+        let mut buf = Vec::new();
+        reply.write_to(&mut buf).await.unwrap();
+        assert_eq!(buf[0], 0x05);
+        assert_eq!(buf[1], 0x05);
+    }
+
+    #[tokio::test]
+    async fn reply_command_not_supported() {
+        let reply = Socks5Reply::command_not_supported();
+        let mut buf = Vec::new();
+        reply.write_to(&mut buf).await.unwrap();
+        assert_eq!(buf[0], 0x05);
+        assert_eq!(buf[1], 0x07);
+    }
+
+    #[tokio::test]
+    async fn roundtrip_ipv4_reply() {
+        let reply = Socks5Reply::success(Socks5Address::Ipv4(Ipv4Addr::new(127, 0, 0, 1)), 1080);
+        let mut buf = Vec::new();
+        reply.write_to(&mut buf).await.unwrap();
+
+        let mut cursor = Cursor::new(&buf[..]);
+        let version = cursor.read_u8().await.unwrap();
+        let _reply_code = cursor.read_u8().await.unwrap();
+        let _rsv = cursor.read_u8().await.unwrap();
+        let atyp = cursor.read_u8().await.unwrap();
+        assert_eq!(version, 0x05);
+        assert_eq!(atyp, 0x01);
+        let mut octets = [0u8; 4];
+        cursor.read_exact(&mut octets).await.unwrap();
+        assert_eq!(Ipv4Addr::from(octets), Ipv4Addr::new(127, 0, 0, 1));
+        let port = cursor.read_u16().await.unwrap();
+        assert_eq!(port, 1080);
+    }
+
+    #[tokio::test]
+    async fn roundtrip_ipv6_reply() {
+        let addr = Ipv6Addr::new(0x2001, 0x0db8, 0, 0, 0, 0, 0, 1);
+        let reply = Socks5Reply::success(Socks5Address::Ipv6(addr), 443);
+        let mut buf = Vec::new();
+        reply.write_to(&mut buf).await.unwrap();
+
+        let mut cursor = Cursor::new(&buf[..]);
+        let _version = cursor.read_u8().await.unwrap();
+        let _reply_code = cursor.read_u8().await.unwrap();
+        let _rsv = cursor.read_u8().await.unwrap();
+        let atyp = cursor.read_u8().await.unwrap();
+        assert_eq!(atyp, 0x04);
+        let mut octets = [0u8; 16];
+        cursor.read_exact(&mut octets).await.unwrap();
+        assert_eq!(Ipv6Addr::from(octets), addr);
+        let port = cursor.read_u16().await.unwrap();
+        assert_eq!(port, 443);
+    }
+
+    #[tokio::test]
+    async fn roundtrip_domain_reply() {
+        let reply = Socks5Reply::success(Socks5Address::Domain("example.com".to_string()), 8080);
+        let mut buf = Vec::new();
+        reply.write_to(&mut buf).await.unwrap();
+
+        let mut cursor = Cursor::new(&buf[..]);
+        let _version = cursor.read_u8().await.unwrap();
+        let _reply_code = cursor.read_u8().await.unwrap();
+        let _rsv = cursor.read_u8().await.unwrap();
+        let atyp = cursor.read_u8().await.unwrap();
+        assert_eq!(atyp, 0x03);
+        let len = cursor.read_u8().await.unwrap();
+        let mut domain = vec![0u8; len as usize];
+        cursor.read_exact(&mut domain).await.unwrap();
+        assert_eq!(String::from_utf8(domain).unwrap(), "example.com");
+        let port = cursor.read_u16().await.unwrap();
+        assert_eq!(port, 8080);
+    }
+}

crates/wraith-core/src/transport/acme.rs

@@ -0,0 +1,362 @@
+use std::net::SocketAddr;
+use std::path::PathBuf;
+use std::sync::Arc;
+
+use anyhow::{anyhow, Result};
+use rustls::crypto::aws_lc_rs::default_provider;
+use rustls::ServerConfig;
+use rustls_acme::caches::DirCache;
+use rustls_acme::{AcmeConfig, AcmeState, ResolvesServerCertAcme};
+use tracing::{error, info};
+use tokio::net::TcpListener;
+use tokio_rustls::TlsAcceptor as TokioTlsAcceptor;
+
+use super::{TransportAcceptor, TransportInfo, TransportKind};
+
+const ACME_TLS_ALPN_NAME: &[u8] = b"acme-tls/1";
+
+#[derive(Debug, Clone)]
+pub enum AcmeMode {
+    Domain { domain: String },
+    Ip,
+}
+
+pub struct AcmeCertProvider {
+    mode: AcmeMode,
+    cache_dir: Option<PathBuf>,
+    directory_url: String,
+    contact: Vec<String>,
+}
+
+impl std::fmt::Debug for AcmeCertProvider {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("AcmeCertProvider")
+            .field("mode", &self.mode)
+            .field("cache_dir", &self.cache_dir)
+            .field("directory_url", &self.directory_url)
+            .field("contact", &self.contact)
+            .finish_non_exhaustive()
+    }
+}
+
+impl AcmeCertProvider {
+    pub fn new(mode: AcmeMode) -> Self {
+        Self {
+            mode,
+            cache_dir: None,
+            directory_url: rustls_acme::acme::LETS_ENCRYPT_STAGING_DIRECTORY.to_string(),
+            contact: Vec::new(),
+        }
+    }
+
+    pub fn domain(domain: impl Into<String>) -> Self {
+        Self::new(AcmeMode::Domain {
+            domain: domain.into(),
+        })
+    }
+
+    pub fn ip() -> Self {
+        Self::new(AcmeMode::Ip)
+    }
+
+    pub fn with_cache_dir(mut self, dir: impl Into<PathBuf>) -> Self {
+        self.cache_dir = Some(dir.into());
+        self
+    }
+
+    pub fn with_directory(mut self, url: impl Into<String>) -> Self {
+        self.directory_url = url.into();
+        self
+    }
+
+    pub fn with_production_directory(mut self) -> Self {
+        self.directory_url = rustls_acme::acme::LETS_ENCRYPT_PRODUCTION_DIRECTORY.to_string();
+        self
+    }
+
+    pub fn with_contact(mut self, contact: impl Into<String>) -> Self {
+        self.contact.push(contact.into());
+        self
+    }
+
+    pub fn mode(&self) -> &AcmeMode {
+        &self.mode
+    }
+
+    fn build_acme_state(&self) -> (AcmeState<std::io::Error>, Arc<ResolvesServerCertAcme>) {
+        let domains: Vec<String> = match &self.mode {
+            AcmeMode::Domain { domain } => vec![domain.clone()],
+            AcmeMode::Ip => vec![],
+        };
+
+        let base_config = AcmeConfig::new(domains)
+            .directory(&self.directory_url)
+            .contact(self.contact.clone());
+
+        let state = match &self.cache_dir {
+            Some(cache_dir) => {
+                base_config.cache(DirCache::new(cache_dir.clone())).state()
+            }
+            None => {
+                base_config
+                    .cache(rustls_acme::caches::NoCache::default())
+                    .state()
+            }
+        };
+
+        let resolver = state.resolver();
+        (state, resolver)
+    }
+
+    pub fn build_server_config_with_resolver(
+        &self,
+        resolver: Arc<ResolvesServerCertAcme>,
+    ) -> Result<Arc<ServerConfig>> {
+        let provider = default_provider().into();
+        let mut config = ServerConfig::builder_with_provider(provider)
+            .with_safe_default_protocol_versions()
+            .map_err(|e| anyhow!("failed to set protocol versions: {}", e))?
+            .with_no_client_auth()
+            .with_cert_resolver(resolver);
+        config.alpn_protocols.push(ACME_TLS_ALPN_NAME.to_vec());
+        Ok(Arc::new(config))
+    }
+}
+
+pub struct AcmeTlsAcceptor {
+    listener: TcpListener,
+    listen_addr: SocketAddr,
+    #[allow(dead_code)]
+    server_config: Arc<ServerConfig>,
+    tokio_acceptor: TokioTlsAcceptor,
+}
+
+impl AcmeTlsAcceptor {
+    pub async fn bind_acme(
+        addr: SocketAddr,
+        provider: Arc<AcmeCertProvider>,
+    ) -> Result<Self> {
+        let (state, resolver) = provider.build_acme_state();
+
+        let server_config = provider.build_server_config_with_resolver(resolver.clone())?;
+
+        Self::spawn_state_worker(state, resolver);
+
+        let listener = TcpListener::bind(addr).await?;
+        let listen_addr = listener.local_addr()?;
+
+        let tokio_acceptor = TokioTlsAcceptor::from(server_config.clone());
+
+        Ok(Self {
+            listener,
+            listen_addr,
+            server_config,
+            tokio_acceptor,
+        })
+    }
+
+    pub fn listen_addr(&self) -> SocketAddr {
+        self.listen_addr
+    }
+
+    fn spawn_state_worker(state: AcmeState<std::io::Error>, resolver: Arc<ResolvesServerCertAcme>) {
+        use futures::StreamExt;
+
+        let task = async move {
+            let mut state = state;
+            while let Some(event) = state.next().await {
+                match event {
+                    Ok(ok) => {
+                        if let rustls_acme::EventOk::DeployedNewCert = ok {
+                            info!("ACME: new certificate deployed");
+                        } else {
+                            info!("ACME event: {:?}", ok);
+                        }
+                    }
+                    Err(err) => error!("ACME event error: {:?}", err),
+                }
+                if Arc::strong_count(&resolver) == 1 {
+                    info!("ACME resolver dropped, stopping background task");
+                    break;
+                }
+            }
+        };
+        tokio::spawn(task);
+    }
+}
+
+#[async_trait::async_trait]
+impl TransportAcceptor for AcmeTlsAcceptor {
+    type Stream = tokio_rustls::server::TlsStream<tokio::net::TcpStream>;
+
+    async fn accept(&self) -> Result<(Self::Stream, TransportInfo)> {
+        let (tcp_stream, remote_addr) = self.listener.accept().await?;
+        let tls_stream = self.tokio_acceptor.accept(tcp_stream).await?;
+
+        let server_name = tls_stream
+            .get_ref()
+            .1
+            .server_name()
+            .map(|s| s.to_string());
+
+        let info = TransportInfo {
+            remote_addr: Some(remote_addr),
+            transport_kind: TransportKind::Tls { server_name },
+        };
+
+        Ok((tls_stream, info))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn acme_cert_provider_domain_mode() {
+        let provider = AcmeCertProvider::domain("example.com");
+        assert!(matches!(provider.mode(), AcmeMode::Domain { .. }));
+        if let AcmeMode::Domain { domain } = provider.mode() {
+            assert_eq!(domain, "example.com");
+        }
+    }
+
+    #[test]
+    fn acme_cert_provider_ip_mode() {
+        let provider = AcmeCertProvider::ip();
+        assert!(matches!(provider.mode(), AcmeMode::Ip));
+    }
+
+    #[test]
+    fn acme_cert_provider_default_staging_directory() {
+        let provider = AcmeCertProvider::domain("example.com");
+        assert_eq!(
+            provider.directory_url,
+            rustls_acme::acme::LETS_ENCRYPT_STAGING_DIRECTORY
+        );
+    }
+
+    #[test]
+    fn acme_cert_provider_production_directory() {
+        let provider = AcmeCertProvider::domain("example.com").with_production_directory();
+        assert_eq!(
+            provider.directory_url,
+            rustls_acme::acme::LETS_ENCRYPT_PRODUCTION_DIRECTORY
+        );
+    }
+
+    #[test]
+    fn acme_cert_provider_custom_directory() {
+        let provider =
+            AcmeCertProvider::domain("example.com").with_directory("https://custom.acme.dir/");
+        assert_eq!(provider.directory_url, "https://custom.acme.dir/");
+    }
+
+    #[test]
+    fn acme_cert_provider_with_cache_dir() {
+        let provider = AcmeCertProvider::domain("example.com").with_cache_dir("/tmp/acme_cache");
+        assert_eq!(provider.cache_dir, Some(PathBuf::from("/tmp/acme_cache")));
+    }
+
+    #[test]
+    fn acme_cert_provider_with_contact() {
+        let provider =
+            AcmeCertProvider::domain("example.com").with_contact("mailto:admin@example.com");
+        assert_eq!(
+            provider.contact,
+            vec!["mailto:admin@example.com".to_string()]
+        );
+    }
+
+    #[test]
+    fn acme_cert_provider_build_state_domain() {
+        let provider = AcmeCertProvider::domain("example.com");
+        let (_state, resolver) = provider.build_acme_state();
+        assert!(Arc::strong_count(&resolver) >= 2);
+    }
+
+    #[test]
+    fn acme_cert_provider_build_state_with_cache() {
+        let provider =
+            AcmeCertProvider::domain("example.com").with_cache_dir("/tmp/test_cache");
+        let (_state, resolver) = provider.build_acme_state();
+        assert!(Arc::strong_count(&resolver) >= 2);
+    }
+
+    #[test]
+    fn acme_cert_provider_build_server_config() {
+        let _ = default_provider().install_default();
+        let provider = AcmeCertProvider::domain("example.com");
+        let (_, resolver) = provider.build_acme_state();
+        let config = provider.build_server_config_with_resolver(resolver).unwrap();
+        assert!(!config.alpn_protocols.is_empty());
+        assert!(config
+            .alpn_protocols
+            .iter()
+            .any(|p| p == ACME_TLS_ALPN_NAME));
+    }
+
+    #[test]
+    fn acme_mode_domain_debug() {
+        let mode = AcmeMode::Domain {
+            domain: "test.example.com".to_string(),
+        };
+        let debug_str = format!("{:?}", mode);
+        assert!(debug_str.contains("test.example.com"));
+    }
+
+    #[test]
+    fn acme_mode_ip_debug() {
+        let mode = AcmeMode::Ip;
+        let debug_str = format!("{:?}", mode);
+        assert!(debug_str.contains("Ip"));
+    }
+
+    #[test]
+    fn acme_cert_provider_builder_chain() {
+        let provider = AcmeCertProvider::domain("test.example.com")
+            .with_production_directory()
+            .with_cache_dir("/tmp/cache")
+            .with_contact("mailto:admin@test.example.com");
+        assert!(matches!(provider.mode(), AcmeMode::Domain { .. }));
+        assert_eq!(
+            provider.directory_url,
+            rustls_acme::acme::LETS_ENCRYPT_PRODUCTION_DIRECTORY
+        );
+        assert_eq!(provider.cache_dir, Some(PathBuf::from("/tmp/cache")));
+        assert_eq!(provider.contact.len(), 1);
+    }
+
+    #[tokio::test]
+    async fn acme_tls_acceptor_bind_acme() {
+        let _ = default_provider().install_default();
+        let provider = Arc::new(AcmeCertProvider::domain("example.com"));
+        let addr: SocketAddr = "127.0.0.1:0".parse().unwrap();
+        let acceptor = AcmeTlsAcceptor::bind_acme(addr, provider).await.unwrap();
+        assert_ne!(acceptor.listen_addr().port(), 0);
+    }
+
+    #[tokio::test]
+    #[ignore]
+    async fn acme_staging_domain_cert_provisioning() {
+        let _ = default_provider().install_default();
+
+        let cache_dir = tempfile::tempdir().unwrap();
+        let provider = Arc::new(
+            AcmeCertProvider::domain("acme-test.example.com")
+                .with_cache_dir(cache_dir.path())
+                .with_contact("mailto:admin@example.com"),
+        );
+
+        let addr: SocketAddr = "0.0.0.0:443".parse().unwrap();
+        let result = AcmeTlsAcceptor::bind_acme(addr, provider).await;
+        assert!(
+            result.is_ok(),
+            "ACME TlsAcceptor should bind: {:?}",
+            result.err()
+        );
+
+        let acceptor = result.unwrap();
+        assert_eq!(acceptor.listen_addr().port(), 443);
+    }
+}

crates/wraith-core/src/transport/mod.rs

@@ -12,6 +12,12 @@ mod tls;
 #[cfg(feature = "tls")]
 pub use tls::{AcmeConfig, TlsAcceptor, TlsTransport};
 
+#[cfg(feature = "acme")]
+mod acme;
+
+#[cfg(feature = "acme")]
+pub use acme::{AcmeCertProvider, AcmeMode, AcmeTlsAcceptor};
+
 use std::net::SocketAddr;
 
 use anyhow::Result;

crates/wraith-core/src/transport/tls.rs

@@ -9,8 +9,16 @@ use rustls::{ClientConfig, DigitallySignedStruct, RootCertStore, ServerConfig};
 use tokio::net::{TcpListener, TcpStream};
 use tokio_rustls::{client::TlsStream as ClientTlsStream, TlsAcceptor as TokioTlsAcceptor, TlsConnector};
 
+#[cfg(feature = "acme")]
+use rustls::crypto::aws_lc_rs::default_provider;
+#[cfg(feature = "acme")]
+use rustls_acme::ResolvesServerCertAcme;
+
 use super::{Transport, TransportAcceptor, TransportInfo, TransportKind};
 
+#[cfg(feature = "acme")]
+const ACME_TLS_ALPN_NAME: &[u8] = b"acme-tls/1";
+
 /// A TLS-based client transport that connects to a remote address over TLS.
 ///
 /// Wraps a TCP connection with a TLS client session via `tokio_rustls::TlsConnector`.
@@ -110,8 +118,10 @@ pub struct AcmeConfig {
 /// A TLS-based server transport acceptor that accepts TCP connections
 /// and wraps them with TLS server sessions via `tokio_rustls::TlsAcceptor`.
 ///
-/// Requires certificate and private key configuration. Supports manual
-/// cert/key paths and an ACME config stub (ADR-008).
+/// Supports three certificate modes (ADR-008):
+/// - Manual certs via `bind()` with explicit cert/key
+/// - ACME certs via `bind_acme()` with an `AcmeCertProvider`
+/// - The stub `AcmeConfig` parameter in `bind()` is kept for backward compat
 pub struct TlsAcceptor {
     listener: TcpListener,
     listen_addr: SocketAddr,
@@ -145,6 +155,33 @@ impl TlsAcceptor {
         })
     }
 
+    #[cfg(feature = "acme")]
+    pub async fn bind_acme(
+        addr: SocketAddr,
+        acme_resolver: Arc<ResolvesServerCertAcme>,
+    ) -> Result<Self> {
+        let listener = TcpListener::bind(addr).await?;
+        let listen_addr = listener.local_addr()?;
+
+        let provider = default_provider().into();
+        let mut server_config = ServerConfig::builder_with_provider(provider)
+            .with_safe_default_protocol_versions()
+            .map_err(|e| anyhow!("failed to set protocol versions: {}", e))?
+            .with_no_client_auth()
+            .with_cert_resolver(acme_resolver);
+        server_config.alpn_protocols.push(ACME_TLS_ALPN_NAME.to_vec());
+
+        let server_config = Arc::new(server_config);
+        let tokio_acceptor = TokioTlsAcceptor::from(server_config.clone());
+
+        Ok(Self {
+            listener,
+            listen_addr,
+            server_config,
+            tokio_acceptor,
+        })
+    }
+
     pub fn listen_addr(&self) -> SocketAddr {
         self.listen_addr
     }

tasks/transport/acme-cert-provisioning.md

@@ -43,8 +43,14 @@ This integrates with `TlsAcceptor` by providing ACME-resolved certificates inste
 
 ## Notes
 
-> To be filled by implementation agent
+- `AcmeCertProvider` is the main entry point. It creates `AcmeState` and `ResolvesServerCertAcme` from `rustls-acme`.
+- The `ResolvesServerCertAcme` resolver is shared between the `AcmeState` background task and the `ServerConfig`, so cert updates propagate automatically.
+- `AcmeTlsAcceptor::bind_acme()` creates a TLS acceptor that uses ACME-provisioned certs and spawns a background tokio task for auto-renewal.
+- `TlsAcceptor::bind_acme()` also added for users who want to use ACME with the standard `TlsAcceptor` type directly.
+- The `AcmeConfig` stub in `tls.rs` is retained for backward compat with existing `TlsAcceptor::bind()`.
+- `acme` feature implies `tls` and adds `rustls-acme` + `futures` dependencies.
+- TLS-ALPN-01 challenge handling works via the `acme-tls/1` ALPN protocol registered in `ServerConfig` — the resolver dispatches challenge vs regular certs automatically.
 
 ## Summary
 
-> To be filled on completion
+Implemented ACME/Let's Encrypt certificate provisioning (ADR-008) behind the `acme` feature flag. `AcmeCertProvider` supports domain-based and IP-based modes using `rustls-acme`. `AcmeTlsAcceptor::bind_acme()` and `TlsAcceptor::bind_acme()` provide ACME-integrated TLS acceptance with automatic certificate renewal via a background tokio task. Unit tests cover config construction, builder patterns, and server config generation. Integration test for LE staging is marked `#[ignore]`.