GH-891: Add a test against ProFTPd

Use docker container instantlinux/proftpd to run ProFTPd with SFTP
enabled (password auth since pubkey auth would be tedious to set up,
but that's OK for this test).

Configure the container to send ProFTPd logs to stderr, not to some
files inside the container. On stderr the test container's log consumer
will pick it up.

The test sets a low IGNORE_MESSAGE_FREQUENCY (every 20th message),
uploads a file, downloads it again, and compares the contents.

The test fails without the fix from commit e7f66e7 with the server
disconnecting midway through the upload and shows the expected
server-side log line "message format error: unable to read 2594667651
bytes of string data (buflen = 20)" (or similar numbers).

With the fix from commit e7f66e7 the test succeeds and the server-side
log shows several lines "client sent SSH_MSG_IGNORE message (X bytes)"
instead.

Author: tomaswolf

sshd-sftp/src/test/java/org/apache/sshd/sftp/client/ProFtpdTest.java

@@ -0,0 +1,122 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.sshd.sftp.client;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+import org.apache.sshd.client.SshClient;
+import org.apache.sshd.client.session.ClientSession;
+import org.apache.sshd.common.Factory;
+import org.apache.sshd.common.random.Random;
+import org.apache.sshd.common.util.io.IoUtils;
+import org.apache.sshd.core.CoreModuleProperties;
+import org.apache.sshd.util.test.JUnitTestSupport;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.testcontainers.containers.GenericContainer;
+import org.testcontainers.containers.output.Slf4jLogConsumer;
+import org.testcontainers.images.builder.ImageFromDockerfile;
+import org.testcontainers.junit.jupiter.Container;
+import org.testcontainers.junit.jupiter.Testcontainers;
+import org.testcontainers.utility.MountableFile;
+
+@Testcontainers(disabledWithoutDocker = true)
+class ProFtpdTest extends JUnitTestSupport {
+
+    private static final Logger LOG = LoggerFactory.getLogger(ProFtpdTest.class);
+
+    private static final String RESOURCES = "/" + ProFtpdTest.class.getPackage().getName().replace('.', '/');
+
+    @Container
+    static GenericContainer<?> server = new GenericContainer<>(
+            new ImageFromDockerfile().withDockerfileFromBuilder(builder -> builder.from("instantlinux/proftpd:latest") //
+                    // Get SFTP logs on stderr
+                    .run("sed -i -e 's:^WtmpLog:AllowLogSymLinks on\\nSystemLog /dev/stderr\\nSFTPLog /dev/stderr\\nWtmpLog:' /etc/proftpd/proftpd.conf") //
+                    .build())) //
+            .withEnv("PASV_ADDRESS", "127.0.0.1") //
+            .withEnv("FTPUSER_NAME", "test") //
+            .withEnv("SFTP_ENABLE", "on") //
+            // Set it up for password auth
+            .withCopyFileToContainer(MountableFile.forClasspathResource(RESOURCES + "/proftpd.pwd"),
+                    "/run/secrets/ftp-user-password-secret")
+            .withExposedPorts(2222) //
+            .withLogConsumer(new Slf4jLogConsumer(LOG));
+
+    private SshClient client;
+
+    @BeforeEach
+    void setUp() throws Exception {
+        client = SshClient.setUpDefaultClient();
+        client.setServerKeyVerifier((s, a, k) -> true);
+        client.start();
+    }
+
+    @AfterEach
+    void teardown() {
+        if (client != null) {
+            client.stop();
+        }
+    }
+
+    @Test // GH-891
+    void ignoreMesssage() throws Exception {
+        CoreModuleProperties.IGNORE_MESSAGE_FREQUENCY.set(client, 20L);
+        CoreModuleProperties.IGNORE_MESSAGE_VARIANCE.set(client, 0);
+        CoreModuleProperties.IGNORE_MESSAGE_SIZE.set(client, 16);
+        byte[] expected = new byte[8 * 1024 * 1024];
+
+        Factory<? extends Random> factory = client.getRandomFactory();
+        Random rnd = factory.create();
+        rnd.fill(expected);
+
+        try (ClientSession sshSession = client.connect("test", server.getHost(), server.getMappedPort(2222)).verify()
+                .getClientSession()) {
+            sshSession.addPasswordIdentity("test");
+            sshSession.auth().verify(2000);
+            try (SftpClient sftp = SftpClientFactory.instance().createSftpClient(sshSession)) {
+                // Copy some data onto the server
+                try (InputStream in = new ByteArrayInputStream(expected);
+                     OutputStream out = sftp.write("/home/test/file.bin", SftpClient.OpenMode.Create,
+                             SftpClient.OpenMode.Write)) {
+                    IoUtils.copy(in, out);
+                }
+                byte[] actual;
+                try (InputStream in = sftp.read("/home/test/file.bin");
+                     ByteArrayOutputStream buf = new ByteArrayOutputStream(expected.length)) {
+                    byte[] data = new byte[4096];
+                    for (int n = 0; n >= 0;) {
+                        n = in.read(data, 0, data.length);
+                        if (n > 0) {
+                            buf.write(data, 0, n);
+                        }
+                    }
+                    actual = buf.toByteArray();
+                }
+                assertArrayEquals(expected, actual);
+            }
+        }
+    }
+
+}

sshd-sftp/src/test/resources/org/apache/sshd/sftp/client/proftpd.pwd

@@ -0,0 +1 @@
+$6$Q7V2n3q2GRVv5YeQ$/AhLu07H76Asojy7bxGXMY1caKLAbp5Vt82LOZYMkD/8uDzyMAEXwk0c1Bdz1DkBsk2Vh/9SF130mOPavRGMo.