8373677: Clear text HttpServer connection could fail fast if receiving SSL ClientHello

src/jdk.httpserver/share/classes/sun/net/httpserver/Request.java

@@ -25,6 +25,7 @@
 
 package sun.net.httpserver;
 
+import java.net.ProtocolException;
 import java.nio.*;
 import java.io.*;
 import java.nio.channels.*;
@@ -39,15 +40,18 @@ class Request {
     static final int BUF_LEN = 2048;
     static final byte CR = 13;
     static final byte LF = 10;
+    static final byte FIRST_CHAR = 32;
 
     private String startLine;
     private SocketChannel chan;
     private InputStream is;
     private OutputStream os;
     private final int maxReqHeaderSize;
+    private final boolean firstClearRequest;
 
-    Request(InputStream rawInputStream, OutputStream rawout) throws IOException {
+    Request(InputStream rawInputStream, OutputStream rawout, boolean firstClearRequest) throws IOException {
         this.maxReqHeaderSize = ServerConfig.getMaxReqHeaderSize();
+        this.firstClearRequest = firstClearRequest;
         is = rawInputStream;
         os = rawout;
         do {
@@ -78,6 +82,25 @@ public String readLine() throws IOException {
         boolean gotCR = false, gotLF = false;
         pos = 0; lineBuf = new StringBuffer();
         long lsize = 32;
+
+        // For the first request that comes on a clear connection
+        // we will check that the first non CR/LF char on the
+        // request line is eligible. This should be the first char
+        // of a method name, so it should be at least greater or equal
+        // to 32 (FIRST_CHAR) which is the space character.
+        // The main goal here is to fail fast if we receive 0x16 (22) which
+        // happens to be the first byte of a TLS handshake record.
+        // This is typically what would be received if a TLS client opened
+        // a TLS connection on a non-TLS server.
+        // If we receive 0x16 we should close the connection immediately as
+        // it indicates we're receiving a ClientHello on a clear
+        // connection, and we will never receive the expected CRLF that
+        // terminates the first request line.
+        // Though we could check only for 0x16, any characters < 32
+        // (excluding CRLF) is not expected at this position in a
+        // request line, so we can still fail here early if any of
+        // those are detected.
+        int offset = 0;
         while (!gotLF) {
             int c = is.read();
             if (c == -1) {
@@ -89,13 +112,25 @@ public String readLine() throws IOException {
                 } else {
                     gotCR = false;
                     consume(CR);
+                    if (firstClearRequest && offset == 0) {
+                        if (c < FIRST_CHAR) {
+                            throw new ProtocolException("Unexpected start of request line");
+                        }
+                        offset++;
+                    }
                     consume(c);
                     lsize = lsize + 2;
                 }
             } else {
                 if (c == CR) {
                     gotCR = true;
                 } else {
+                    if (firstClearRequest && offset == 0) {
+                        if (c < FIRST_CHAR) {
+                            throw new ProtocolException("Unexpected start of request line");
+                        }
+                        offset++;
+                    }
                     consume(c);
                     lsize = lsize + 1;
                 }

src/jdk.httpserver/share/classes/sun/net/httpserver/ServerImpl.java

@@ -45,6 +45,7 @@
 import java.lang.System.Logger.Level;
 import java.net.BindException;
 import java.net.InetSocketAddress;
+import java.net.ProtocolException;
 import java.net.ServerSocket;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -733,7 +734,16 @@ public void run() {
                     connection.raw = rawin;
                     connection.rawout = rawout;
                 }
-                Request req = new Request(rawin, rawout);
+
+                Request req;
+                try {
+                    req = new Request(rawin, rawout, newconnection && !https);
+                } catch (ProtocolException pe) {
+                    logger.log(Level.DEBUG, "closing due to: " + pe);
+                    reject(Code.HTTP_BAD_REQUEST, "", pe.getMessage());
+                    return;
+                }
+
                 requestLine = req.requestLine();
                 if (requestLine == null) {
                     /* connection closed */

test/jdk/com/sun/net/httpserver/ClearTextServerSSL.java

@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8373677
+ * @summary Tests for verifying that a non-SSL server can detect
+ *          when a client attempts to use SSL.
+ * @library /test/lib
+ * @run junit/othervm ${test.main.class}
+ */
+
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpHandler;
+import com.sun.net.httpserver.HttpServer;
+import jdk.test.lib.net.SimpleSSLContext;
+import jdk.test.lib.net.URIBuilder;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.util.logging.ConsoleHandler;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import javax.net.ssl.SSLException;
+
+import static com.sun.net.httpserver.HttpExchange.RSPBODY_EMPTY;
+import static java.net.http.HttpClient.Builder.NO_PROXY;
+import static org.junit.jupiter.api.Assertions.*;
+
+public class ClearTextServerSSL {
+
+    static final InetAddress LOOPBACK_ADDR = InetAddress.getLoopbackAddress();
+    static final boolean ENABLE_LOGGING = true;
+    static final Logger logger = Logger.getLogger("com.sun.net.httpserver");
+
+    static final String CTXT_PATH = "/ClearTextServerSSL";
+
+    @BeforeAll
+    public static void setup() {
+        if (ENABLE_LOGGING) {
+            ConsoleHandler ch = new ConsoleHandler();
+            logger.setLevel(Level.ALL);
+            ch.setLevel(Level.ALL);
+            logger.addHandler(ch);
+        }
+    }
+
+    @Test
+    public void test() throws Exception {
+        var sslContext = new SimpleSSLContext().get();
+        var handler = new TestHandler();
+        var server = HttpServer.create(new InetSocketAddress(LOOPBACK_ADDR, 0), 0);
+        server.createContext(path(""), handler);
+        server.start();
+        try (var client = HttpClient.newBuilder()
+                    .sslContext(sslContext)
+                    .proxy(NO_PROXY)
+                    .build()) {
+            var request = HttpRequest.newBuilder()
+                    .uri(uri("http", server, path("/clear")))
+                    .build();
+            var response = client.send(request, HttpResponse.BodyHandlers.ofString());
+            assertEquals(200, response.statusCode());
+            var sslRequest = HttpRequest.newBuilder()
+                    .uri(uri("https", server, path("/ssl")))
+                    .build();
+            Assertions.assertThrows(SSLException.class, () -> {
+                client.send(sslRequest, HttpResponse.BodyHandlers.ofString());
+            });
+            try (var socket = new Socket()) {
+                socket.connect(server.getAddress());
+                byte[] badRequest = {
+                        22, 'B', 'A', 'D', ' ',
+                        '/', ' ' ,
+                        'H', 'T', 'T', 'P', '/', '1', '.', '1' };
+                socket.getOutputStream().write(badRequest);
+                socket.getOutputStream().flush();
+                var reader = new InputStreamReader(socket.getInputStream());
+                var line = reader.readAllLines();
+                Assertions.assertEquals("HTTP/1.1 400 Bad Request", line.get(0));
+                System.out.println("Got expected response:");
+                line.stream().map(l -> "\t" + l).forEach(System.out::println);
+            }
+
+        } finally {
+            server.stop(0);
+        }
+    }
+
+    // --- infra ---
+
+    static String path(String path) {
+        assert CTXT_PATH.startsWith("/");
+        assert !CTXT_PATH.endsWith("/");
+        if (path.startsWith("/")) {
+            return CTXT_PATH + path;
+        } else {
+            return CTXT_PATH + "/" + path;
+        }
+    }
+
+    static URI uri(String scheme, HttpServer server, String path) throws URISyntaxException {
+        return URIBuilder.newBuilder()
+                .scheme(scheme)
+                .loopback()
+                .port(server.getAddress().getPort())
+                .path(path)
+                .build();
+    }
+
+    /**
+     * A test handler that reads any request bytes and sends
+     * an empty 200 response
+     */
+    static class TestHandler implements HttpHandler {
+        @java.lang.Override
+        public void handle(HttpExchange exchange) throws IOException {
+            try (var reqBody = exchange.getRequestBody()) {
+                reqBody.readAllBytes();
+                exchange.sendResponseHeaders(200, RSPBODY_EMPTY);
+            } catch (Throwable t) {
+                t.printStackTrace();
+                exchange.sendResponseHeaders(500, RSPBODY_EMPTY);
+            }
+        }
+    }
+}