Handle custom ALPNs in s2n impl of ALPN::to_wire_protocols()

pingora-core/src/listeners/mod.rs

@@ -118,11 +118,24 @@ pub trait TlsAccept {
 
 pub type TlsAcceptCallbacks = Box<dyn TlsAccept + Send + Sync>;
 
+/// Some protocols, such as the proxy protocol, must be inspected before the TLS
+/// handshake. The below trait provides access to the raw TCP stream right
+/// before TLS for these situations.
+#[async_trait]
+pub trait InspectPreTls: Send + Sync {
+    /// The implementation can read bytes from the stream (e.g., PROXY protocol header)
+    /// before the TLS handshake takes place.
+    ///
+    /// If this method returns an error, the connection will be dropped.
+    async fn inspect(&self, stream: &mut L4Stream) -> Result<()>;
+}
+
 struct TransportStackBuilder {
     l4: ServerAddress,
     tls: Option<TlsSettings>,
     #[cfg(feature = "connection_filter")]
     connection_filter: Option<Arc<dyn ConnectionFilter>>,
+    pre_tls_inspector: Option<Arc<dyn InspectPreTls>>,
 }
 
 impl TransportStackBuilder {
@@ -148,6 +161,7 @@ impl TransportStackBuilder {
         Ok(TransportStack {
             l4,
             tls: self.tls.take().map(|tls| Arc::new(tls.build())),
+            pre_tls_inspector: self.pre_tls_inspector.clone(),
         })
     }
 }
@@ -156,6 +170,7 @@ impl TransportStackBuilder {
 pub(crate) struct TransportStack {
     l4: ListenerEndpoint,
     tls: Option<Arc<Acceptor>>,
+    pre_tls_inspector: Option<Arc<dyn InspectPreTls>>,
 }
 
 impl TransportStack {
@@ -168,6 +183,7 @@ impl TransportStack {
         Ok(UninitializedStream {
             l4: stream,
             tls: self.tls.clone(),
+            pre_tls_inspector: self.pre_tls_inspector.clone(),
         })
     }
 
@@ -179,17 +195,27 @@ impl TransportStack {
 pub(crate) struct UninitializedStream {
     l4: L4Stream,
     tls: Option<Arc<Acceptor>>,
+    pre_tls_inspector: Option<Arc<dyn InspectPreTls>>,
 }
 
 impl UninitializedStream {
     pub async fn handshake(mut self) -> Result<Stream> {
         self.l4.set_buffer();
-        if let Some(tls) = self.tls {
+
+        // Expose raw l4 stream to any registered pre-TLS inspectors before
+        // handshaking.
+        if let Some(inspector) = self.pre_tls_inspector.as_ref() {
+            inspector.inspect(&mut self.l4).await?;
+        }
+
+        let res_with_stream: Result<Stream> = if let Some(tls) = self.tls {
             let tls_stream = tls.tls_handshake(self.l4).await?;
             Ok(Box::new(tls_stream))
         } else {
             Ok(Box::new(self.l4))
-        }
+        };
+
+        res_with_stream
     }
 
     /// Get the peer address of the connection if available
@@ -205,6 +231,7 @@ pub struct Listeners {
     stacks: Vec<TransportStackBuilder>,
     #[cfg(feature = "connection_filter")]
     connection_filter: Option<Arc<dyn ConnectionFilter>>,
+    pre_tls_inspector: Option<Arc<dyn InspectPreTls>>,
 }
 
 impl Listeners {
@@ -214,6 +241,7 @@ impl Listeners {
             stacks: vec![],
             #[cfg(feature = "connection_filter")]
             connection_filter: None,
+            pre_tls_inspector: None,
         }
     }
     /// Create a new [`Listeners`] with a TCP server endpoint from the given string.
@@ -294,13 +322,31 @@ impl Listeners {
         }
     }
 
+    /// Set a pre-TLS inspector for all endpoints in this listener collection.
+    ///
+    /// The inspector will be invoked after TCP accept but before the TLS handshake,
+    /// allowing the application to read and process data such as PROXY protocol
+    /// headers that arrive before TLS.
+    pub fn set_pre_tls_inspector(&mut self, inspector: Arc<dyn InspectPreTls>) {
+        log::debug!("Setting pre-TLS inspector on Listeners");
+
+        // Store the inspector for future endpoints
+        self.pre_tls_inspector = Some(inspector.clone());
+
+        // Apply to existing stacks
+        for stack in &mut self.stacks {
+            stack.pre_tls_inspector = Some(inspector.clone());
+        }
+    }
+
     /// Add the given [`ServerAddress`] to `self` with the given [`TlsSettings`] if provided
     pub fn add_endpoint(&mut self, l4: ServerAddress, tls: Option<TlsSettings>) {
         self.stacks.push(TransportStackBuilder {
             l4,
             tls,
             #[cfg(feature = "connection_filter")]
             connection_filter: self.connection_filter.clone(),
+            pre_tls_inspector: self.pre_tls_inspector.clone(),
         })
     }
 
@@ -341,8 +387,8 @@ mod test {
 
     #[tokio::test]
     async fn test_listen_tcp() {
-        let addr1 = "127.0.0.1:7101";
-        let addr2 = "127.0.0.1:7102";
+        let addr1 = "127.0.0.1:7107";
+        let addr2 = "127.0.0.1:7108";
         let mut listeners = Listeners::tcp(addr1);
         listeners.add_tcp(addr2);
 
@@ -460,4 +506,87 @@ mod test {
             );
         }
     }
+
+    #[tokio::test]
+    #[cfg(any(feature = "openssl", feature = "boringssl"))]
+    async fn test_inspect_pre_tls() {
+        use pingora_error::{Error, Result};
+        use std::pin::Pin;
+        use std::sync::{Arc, Mutex};
+        use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
+        use crate::protocols::tls::SslStream;
+        use crate::tls::ssl;
+        struct HelloInspector {
+            stored_bytes: Arc<Mutex<Vec<u8>>>,
+        }
+
+        #[async_trait]
+        impl InspectPreTls for HelloInspector {
+            async fn inspect(&self, stream: &mut L4Stream) -> Result<()> {
+                let mut buf = [0u8; 5];
+                stream.read_exact(&mut buf).await.map_err(|e| {
+                    Error::new_str("failed to read pre-TLS bytes").more_context(format!("{e}"))
+                })?;
+                self.stored_bytes.lock().unwrap().extend_from_slice(&buf);
+                if &buf != b"hello" {
+                    return Err(Error::new_str("pre-TLS bytes did not match 'hello'"));
+                }
+                Ok(())
+            }
+        }
+
+        let stored = Arc::new(Mutex::new(Vec::new()));
+        let inspector = Arc::new(HelloInspector {
+            stored_bytes: stored.clone(),
+        });
+
+        let addr = "127.0.0.1:7109";
+        let cert_path = format!("{}/tests/keys/server.crt", env!("CARGO_MANIFEST_DIR"));
+        let key_path = format!("{}/tests/keys/key.pem", env!("CARGO_MANIFEST_DIR"));
+        let mut listeners = Listeners::tls(addr, &cert_path, &key_path).unwrap();
+
+        // Register HelloInspector on the listener so it fires before TLS handshaking.
+        listeners.set_pre_tls_inspector(inspector.clone());
+        let listener = listeners
+            .build(
+                #[cfg(unix)]
+                None,
+            )
+            .await
+            .unwrap()
+            .pop()
+            .unwrap();
+
+        let server_handle = tokio::spawn(async move {
+            // Acceptor thread should handshake, which will perform pre-TLS inspection
+            // and then the TLS handshake.
+            let stream = listener.accept().await.unwrap();
+            stream.handshake().await.unwrap();
+        });
+
+        // make sure the above starts before the lines below
+        sleep(Duration::from_millis(10)).await;
+
+        let client_handle = tokio::spawn(async move {
+            // Prepend the TLS handshake with the bytes "hello".
+            let mut tcp_stream = tokio::net::TcpStream::connect(addr).await.unwrap();
+            tcp_stream.write_all(b"hello").await.unwrap();
+
+            // Perform the TLS handshake with verification disabled because the
+            // certificates aren't actually valid.
+            let ssl_context = ssl::SslContext::builder(ssl::SslMethod::tls())
+                .unwrap()
+                .build();
+            let mut ssl_obj = ssl::Ssl::new(&ssl_context).unwrap();
+            ssl_obj.set_verify(ssl::SslVerifyMode::NONE);
+            let mut tls_stream = SslStream::new(ssl_obj, tcp_stream).unwrap();
+            Pin::new(&mut tls_stream).connect().await.unwrap();
+        });
+
+        server_handle.await.unwrap();
+        client_handle.await.unwrap();
+
+        assert_eq!(&*stored.lock().unwrap(), b"hello");
+    }
 }

pingora-core/src/protocols/l4/stream.rs

@@ -446,7 +446,10 @@ impl Stream {
     }
 
     /// Put Some data back to the head of the stream to be read again
-    pub(crate) fn rewind(&mut self, data: &[u8]) {
+    /// This can be used in cases where we "peek" at data only to find
+    /// it doesn't match what's expected, and so it needs to be put back
+    /// for a different protocol to potentially use it.
+    pub fn rewind(&mut self, data: &[u8]) {
         if !data.is_empty() {
             self.rewind_read_buf.push(data.to_vec());
         }

pingora-core/src/protocols/tls/mod.rs

@@ -190,6 +190,7 @@ impl ALPN {
             ALPN::H1 => vec![b"http/1.1".to_vec()],
             ALPN::H2 => vec![b"h2".to_vec()],
             ALPN::H2H1 => vec![b"h2".to_vec(), b"http/1.1".to_vec()],
+            ALPN::Custom(custom) => vec![custom.protocol().to_vec()],
         }
     }
 }