GH-8797: Fix DefSftpSessionFactory.timeout logic

Fixes https://github.com/spring-projects/spring-integration/issues/8797

After migration to Apache MINA we have missed to fix `DefaultSftpSessionFactory.timeout`
to be `0` by default as it states in its Javadocs and reference manual
It is `null` by default which really means an infinite wait.

* Fix `DefaultSftpSessionFactory.timeout` to be a reasonable 30 seconds by default
* Fix `setTimeout()` Javadocs and respective `session-factory.adoc`
* Propagate this `timeout` down to the `SftpClient` for its commands interactions

spring-integration-sftp/src/main/java/org/springframework/integration/sftp/session/DefaultSftpSessionFactory.java

@@ -28,11 +28,13 @@ import java.util.concurrent.locks.ReentrantLock;
 import org.apache.sshd.client.SshClient;
 import org.apache.sshd.client.auth.keyboard.UserInteraction;
 import org.apache.sshd.client.auth.password.PasswordIdentityProvider;
+import org.apache.sshd.client.channel.ChannelSubsystem;
 import org.apache.sshd.client.config.hosts.HostConfigEntry;
 import org.apache.sshd.client.keyverifier.AcceptAllServerKeyVerifier;
 import org.apache.sshd.client.keyverifier.RejectAllServerKeyVerifier;
 import org.apache.sshd.client.keyverifier.ServerKeyVerifier;
 import org.apache.sshd.client.session.ClientSession;
+import org.apache.sshd.common.PropertyResolverUtils;
 import org.apache.sshd.common.SshConstants;
 import org.apache.sshd.common.config.keys.FilePasswordProvider;
 import org.apache.sshd.common.keyprovider.KeyIdentityProvider;
@@ -44,9 +46,11 @@ import org.apache.sshd.common.util.security.SecurityUtils;
 import org.apache.sshd.sftp.client.SftpClient;
 import org.apache.sshd.sftp.client.SftpErrorDataHandler;
 import org.apache.sshd.sftp.client.SftpVersionSelector;
+import org.apache.sshd.sftp.client.impl.AbstractSftpClient;
 import org.apache.sshd.sftp.client.impl.DefaultSftpClient;
 
 import org.springframework.core.io.Resource;
+import org.springframework.integration.context.IntegrationContextUtils;
 import org.springframework.integration.file.remote.session.SessionFactory;
 import org.springframework.integration.file.remote.session.SharedSessionCapable;
 import org.springframework.util.Assert;
@@ -107,7 +111,7 @@ public class DefaultSftpSessionFactory implements SessionFactory<SftpClient.DirE
 
 	private boolean allowUnknownKeys = false;
 
-	private Integer timeout;
+	private Integer timeout = (int) IntegrationContextUtils.DEFAULT_TIMEOUT;
 
 	private SftpVersionSelector sftpVersionSelector = SftpVersionSelector.CURRENT;
 
@@ -263,9 +267,9 @@ public class DefaultSftpSessionFactory implements SessionFactory<SftpClient.DirE
 
 	/**
 	 * The timeout property is used as the socket timeout parameter, as well as
-	 * the default connection timeout. Defaults to <code>0</code>, which means,
-	 * that no timeout will occur.
-	 * @param timeout The timeout.
+	 * the default connection timeout. Defaults to {@code 30 seconds}.
+	 * Setting to {@code 0} means no timeout; to {@code null} - infinite wait.
+	 * @param timeout the timeout.
 	 * @see org.apache.sshd.client.future.ConnectFuture#verify(Duration, org.apache.sshd.common.future.CancelOption...)
 	 */
 	public void setTimeout(Integer timeout) {
@@ -420,8 +424,10 @@ public class DefaultSftpSessionFactory implements SessionFactory<SftpClient.DirE
 	/**
 	 * The {@link DefaultSftpClient} extension to lock the {@link #send(int, Buffer)}
 	 * for concurrent interaction.
+	 * <p>
+	 * Also sets the provided {@link #timeout} as a {@link AbstractSftpClient#SFTP_CLIENT_CMD_TIMEOUT} property.
 	 */
-	protected static class ConcurrentSftpClient extends DefaultSftpClient {
+	protected class ConcurrentSftpClient extends DefaultSftpClient {
 
 		private final Lock sendLock = new ReentrantLock();
 
@@ -442,6 +448,14 @@ public class DefaultSftpSessionFactory implements SessionFactory<SftpClient.DirE
 			}
 		}
 
+		@Override
+		protected ChannelSubsystem createSftpChannelSubsystem(ClientSession clientSession) {
+			ChannelSubsystem sftpChannelSubsystem = super.createSftpChannelSubsystem(clientSession);
+			PropertyResolverUtils.updateProperty(sftpChannelSubsystem,
+					AbstractSftpClient.SFTP_CLIENT_CMD_TIMEOUT.getName(), DefaultSftpSessionFactory.this.timeout);
+			return sftpChannelSubsystem;
+		}
+
 	}
 
 }

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/session/SftpSessionFactoryTests.java

@@ -28,11 +28,13 @@ import java.util.stream.IntStream;
 
 import org.apache.sshd.client.SshClient;
 import org.apache.sshd.client.auth.password.PasswordIdentityProvider;
+import org.apache.sshd.client.channel.ClientChannel;
 import org.apache.sshd.client.keyverifier.AcceptAllServerKeyVerifier;
 import org.apache.sshd.common.SshException;
 import org.apache.sshd.server.SshServer;
 import org.apache.sshd.server.keyprovider.SimpleGeneratorHostKeyProvider;
 import org.apache.sshd.sftp.client.SftpClient;
+import org.apache.sshd.sftp.client.impl.AbstractSftpClient;
 import org.apache.sshd.sftp.server.SftpSubsystemFactory;
 import org.junit.jupiter.api.Test;
 
@@ -48,6 +50,7 @@ import static org.awaitility.Awaitility.await;
  * @author Gary Russell
  * @author Artem Bilan
  * @author Auke Zaaiman
+ *
  * @since 3.0.2
  */
 public class SftpSessionFactoryTests {
@@ -192,4 +195,27 @@ public class SftpSessionFactoryTests {
 		}
 	}
 
+	@Test
+	void customTimeoutIsApplied() throws IOException {
+		try (SshServer server = SshServer.setUpDefaultServer()) {
+			server.setPasswordAuthenticator((arg0, arg1, arg2) -> true);
+			server.setPort(0);
+			server.setKeyPairProvider(new SimpleGeneratorHostKeyProvider(new File("hostkey.ser").toPath()));
+			server.setSubsystemFactories(Collections.singletonList(new SftpSubsystemFactory()));
+			server.start();
+
+			DefaultSftpSessionFactory sftpSessionFactory = new DefaultSftpSessionFactory();
+			sftpSessionFactory.setHost("localhost");
+			sftpSessionFactory.setPort(server.getPort());
+			sftpSessionFactory.setUser("user");
+			sftpSessionFactory.setPassword("pass");
+			sftpSessionFactory.setAllowUnknownKeys(true);
+			sftpSessionFactory.setTimeout(15_000);
+
+			ClientChannel clientChannel = sftpSessionFactory.getSession().getClientInstance().getClientChannel();
+
+			assertThat(AbstractSftpClient.SFTP_CLIENT_CMD_TIMEOUT.getRequired(clientChannel)).hasSeconds(15);
+		}
+	}
+
 }

src/reference/antora/modules/ROOT/pages/sftp/session-factory.adoc

@@ -97,7 +97,8 @@ The passphrase is obtained from that object.
 Optional.
 
 `timeout`::The timeout property is used as the socket timeout parameter, as well as the default connection timeout.
-Defaults to `0`, which means, that no timeout will occur.
+Defaults to `30 seconds`.
+Setting to `0` means no timeout; to `null` - infinite wait.
 
 [[sftp-unk-keys]]
 `allowUnknownKeys`::Set to `true` to allow connections to hosts with unknown (or changed) keys.