From 9fea774b5d058c6885298e71da8235c25f24acb5 Mon Sep 17 00:00:00 2001 From: Hiroki Tokunaga Date: Tue, 10 Mar 2026 10:35:45 +0900 Subject: [PATCH] fix: restrict UDP forwarder upstream socket to server Connect the UDP socket to the configured upstream so packets from unexpected sources are ignored. Keep the regression test readable by extracting fixture helpers around the UDP packet flow. Made-with: Cursor --- .../packetproxy/common/UDPSocketEndpoint.java | 1 + .../common/UDPSocketEndpointTest.java | 182 ++++++++++++++++++ 2 files changed, 183 insertions(+) create mode 100644 src/test/java/packetproxy/common/UDPSocketEndpointTest.java diff --git a/src/main/java/core/packetproxy/common/UDPSocketEndpoint.java b/src/main/java/core/packetproxy/common/UDPSocketEndpoint.java index 8ec5efbe..63bab73b 100644 --- a/src/main/java/core/packetproxy/common/UDPSocketEndpoint.java +++ b/src/main/java/core/packetproxy/common/UDPSocketEndpoint.java @@ -33,6 +33,7 @@ public class UDPSocketEndpoint implements Endpoint { public UDPSocketEndpoint(InetSocketAddress addr) throws Exception { socket = new DatagramSocket(); + socket.connect(addr); serverAddr = addr; pipe = new PipeEndpoint(addr); loop(); diff --git a/src/test/java/packetproxy/common/UDPSocketEndpointTest.java b/src/test/java/packetproxy/common/UDPSocketEndpointTest.java new file mode 100644 index 00000000..2fa6a78f --- /dev/null +++ b/src/test/java/packetproxy/common/UDPSocketEndpointTest.java @@ -0,0 +1,182 @@ +/* + * Copyright 2026 DeNA Co., Ltd. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package packetproxy.common; + +import static org.junit.jupiter.api.Assertions.assertArrayEquals; +import static org.junit.jupiter.api.Assertions.assertThrows; + +import java.net.DatagramPacket; +import java.net.DatagramSocket; +import java.net.InetSocketAddress; +import java.nio.charset.StandardCharsets; +import java.util.Arrays; +import java.util.HashSet; +import java.util.Set; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import java.util.concurrent.Future; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.TimeoutException; +import org.junit.jupiter.api.Test; + +public class UDPSocketEndpointTest { + + @Test + public void testIgnorePacketFromUnexpectedSource() throws Exception { + try (var fixture = openFixture()) { + var request = ascii("request"); + var response = ascii("server-response"); + var intruderPayload = ascii("intruder-payload"); + + fixture.sendRequestFromEndpoint(request); + var serverReceivedPacket = fixture.receiveFromEndpoint(); + assertArrayEquals(request, getPayload(serverReceivedPacket)); + + var endpointResponse = fixture.readFromEndpointAsync(); + fixture.sendUnexpectedPacket(intruderPayload); + assertReadTimeout(endpointResponse); + + fixture.sendResponseToEndpoint(response, serverReceivedPacket); + assertArrayEquals(response, fixture.await(endpointResponse)); + } + } + + private TestFixture openFixture() throws Exception { + var existingThreads = new HashSet<>(Thread.getAllStackTraces().keySet()); + var serverSocket = new DatagramSocket(new InetSocketAddress("127.0.0.1", 0)); + serverSocket.setSoTimeout(1000); + var intruderSocket = new DatagramSocket(new InetSocketAddress("127.0.0.1", 0)); + var endpoint = new UDPSocketEndpoint(new InetSocketAddress("127.0.0.1", serverSocket.getLocalPort())); + var endpointThreads = getNewThreads(existingThreads); + var executor = Executors.newSingleThreadExecutor(); + return new TestFixture(serverSocket, intruderSocket, endpoint, endpointThreads, executor); + } + + private byte[] ascii(String value) { + return value.getBytes(StandardCharsets.US_ASCII); + } + + private byte[] getPayload(DatagramPacket packet) { + return Arrays.copyOf(packet.getData(), packet.getLength()); + } + + private void assertReadTimeout(Future future) { + assertThrows(TimeoutException.class, () -> future.get(200, TimeUnit.MILLISECONDS)); + } + + private Set getNewThreads(Set existingThreads) { + var currentThreads = Thread.getAllStackTraces().keySet(); + var newThreads = new HashSet(); + for (var thread : currentThreads) { + + if (!existingThreads.contains(thread)) { + newThreads.add(thread); + } + } + return newThreads; + } + + private void closeEndpoint(UDPSocketEndpoint endpoint, Set endpointThreads) throws Exception { + getSocket(endpoint).close(); + + var pipe = getPipe(endpoint); + pipe.getRawEndpoint().getInputStream().close(); + pipe.getRawEndpoint().getOutputStream().close(); + pipe.getProxyRawEndpoint().getInputStream().close(); + pipe.getProxyRawEndpoint().getOutputStream().close(); + + for (var thread : endpointThreads) { + + thread.interrupt(); + thread.join(1000); + } + } + + private DatagramSocket getSocket(UDPSocketEndpoint endpoint) throws Exception { + var socketField = UDPSocketEndpoint.class.getDeclaredField("socket"); + socketField.setAccessible(true); + return (DatagramSocket) socketField.get(endpoint); + } + + private PipeEndpoint getPipe(UDPSocketEndpoint endpoint) throws Exception { + var pipeField = UDPSocketEndpoint.class.getDeclaredField("pipe"); + pipeField.setAccessible(true); + return (PipeEndpoint) pipeField.get(endpoint); + } + + private class TestFixture implements AutoCloseable { + + private static final int BUFFER_SIZE = 4096; + private final DatagramSocket serverSocket; + private final DatagramSocket intruderSocket; + private final UDPSocketEndpoint endpoint; + private final Set endpointThreads; + private final ExecutorService executor; + + private TestFixture(DatagramSocket serverSocket, DatagramSocket intruderSocket, UDPSocketEndpoint endpoint, + Set endpointThreads, ExecutorService executor) { + this.serverSocket = serverSocket; + this.intruderSocket = intruderSocket; + this.endpoint = endpoint; + this.endpointThreads = endpointThreads; + this.executor = executor; + } + + private void sendRequestFromEndpoint(byte[] payload) throws Exception { + var endpointOutput = endpoint.getOutputStream(); + endpointOutput.write(payload); + endpointOutput.flush(); + } + + private DatagramPacket receiveFromEndpoint() throws Exception { + var packet = new DatagramPacket(new byte[BUFFER_SIZE], BUFFER_SIZE); + serverSocket.receive(packet); + return packet; + } + + private Future readFromEndpointAsync() { + return executor.submit(() -> { + var endpointInput = endpoint.getInputStream(); + var buf = new byte[BUFFER_SIZE]; + var len = endpointInput.read(buf); + return Arrays.copyOf(buf, len); + }); + } + + private void sendUnexpectedPacket(byte[] payload) throws Exception { + var packet = new DatagramPacket(payload, payload.length, + new InetSocketAddress("127.0.0.1", endpoint.getLocalPort())); + intruderSocket.send(packet); + } + + private void sendResponseToEndpoint(byte[] payload, DatagramPacket requestPacket) throws Exception { + var responsePacket = new DatagramPacket(payload, payload.length, requestPacket.getSocketAddress()); + serverSocket.send(responsePacket); + } + + private byte[] await(Future future) throws Exception { + return future.get(1, TimeUnit.SECONDS); + } + + @Override + public void close() throws Exception { + executor.shutdownNow(); + closeEndpoint(endpoint, endpointThreads); + intruderSocket.close(); + serverSocket.close(); + } + } +}