[GH-539] Implement no-flow-control extension (fixes #539)

CHANGES.md

@@ -43,6 +43,7 @@
 ## New Features
 
 * New utility methods `SftpClient.put(Path localFile, String remoteFileName)` and `SftpClient.put(InputStream in, String remoteFileName)` facilitate SFTP file uploading.
+* [GH-539](https://github.com/apache/mina-sshd/issues/539) Implement no-flow-control extension 
 
 ## Potential compatibility issues
 

sshd-cli/src/main/java/org/apache/sshd/cli/client/ScpCommandMain.java

@@ -32,6 +32,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.EnumSet;
+import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
@@ -42,12 +43,14 @@
 import org.apache.sshd.client.auth.AuthenticationIdentitiesProvider;
 import org.apache.sshd.client.config.hosts.HostConfigEntry;
 import org.apache.sshd.client.session.ClientSession;
+import org.apache.sshd.common.PropertyResolver;
 import org.apache.sshd.common.SshConstants;
 import org.apache.sshd.common.session.Session;
 import org.apache.sshd.common.util.GenericUtils;
 import org.apache.sshd.common.util.ReflectionUtils;
 import org.apache.sshd.common.util.io.input.NoCloseInputStream;
 import org.apache.sshd.common.util.threads.ThreadUtils;
+import org.apache.sshd.core.CoreModuleProperties;
 import org.apache.sshd.scp.client.ScpClient;
 import org.apache.sshd.scp.client.ScpClient.Option;
 import org.apache.sshd.scp.client.ScpClientCreator;
@@ -61,6 +64,8 @@
 import org.apache.sshd.scp.common.helpers.ScpTimestampCommandDetails;
 import org.slf4j.Logger;
 
+import static org.apache.sshd.common.PropertyResolverUtils.toPropertyResolver;
+
 /**
  * @see    <A HREF="https://man7.org/linux/man-pages/man1/scp.1.html">SCP(1) - manual page</A>
  * @author <a href="mailto:[email protected]">Apache MINA SSHD Project</a>
@@ -151,7 +156,7 @@ public static String[] normalizeCommandArguments(PrintStream stdout, PrintStream
             return null;
         }
 
-        return effective.toArray(new String[effective.size()]);
+        return effective.toArray(new String[0]);
     }
 
     /* -------------------------------------------------------------------------------- */
@@ -248,11 +253,11 @@ public static void showUsageMessage(PrintStream stderr) {
     public static void xferLocalToRemote(
             BufferedReader stdin, PrintStream stdout, PrintStream stderr, String[] args,
             ScpLocation source, ScpLocation target, Collection<Option> options,
-            OutputStream logStream, Level level, boolean quiet)
+            OutputStream logStream, Level level, boolean quiet, PropertyResolver defaultOptions)
             throws Exception {
         ScpClientCreator creator = resolveScpClientCreator(stderr, args);
         ClientSession session = ((logStream == null) || (creator == null) || GenericUtils.isEmpty(args))
-                ? null : setupClientSession(SCP_PORT_OPTION, stdin, level, stdout, stderr, args);
+                ? null : setupClientSession(SCP_PORT_OPTION, stdin, level, stdout, stderr, args, defaultOptions);
         if (session == null) {
             showUsageMessage(stderr);
             System.exit(-1);
@@ -330,10 +335,10 @@ private void logEvent(
     public static void xferRemoteToRemote(
             BufferedReader stdin, PrintStream stdout, PrintStream stderr, String[] args,
             ScpLocation source, ScpLocation target, Collection<Option> options,
-            OutputStream logStream, Level level, boolean quiet)
+            OutputStream logStream, Level level, boolean quiet, PropertyResolver defaultOptions)
             throws Exception {
         ClientSession srcSession = ((logStream == null) || GenericUtils.isEmpty(args))
-                ? null : setupClientSession(SCP_PORT_OPTION, stdin, level, stdout, stderr, args);
+                ? null : setupClientSession(SCP_PORT_OPTION, stdin, level, stdout, stderr, args, defaultOptions);
         if (srcSession == null) {
             showUsageMessage(stderr);
             System.exit(-1);
@@ -444,6 +449,10 @@ public static void main(String[] args) throws Exception {
                 new InputStreamReader(new NoCloseInputStream(System.in), Charset.defaultCharset()))) {
             args = normalizeCommandArguments(stdout, stderr, args);
 
+            PropertyResolver defaultOptions = toPropertyResolver(new HashMap<>());
+            CoreModuleProperties.NO_FLOW_CONTROL.set(defaultOptions, Boolean.TRUE);
+            CoreModuleProperties.WINDOW_SIZE.set(defaultOptions, 1024L * 1024L * 1024L);
+
             Level level = Level.SEVERE;
             int numArgs = GenericUtils.length(args);
             // see the way normalizeCommandArguments works...
@@ -472,9 +481,11 @@ public static void main(String[] args) throws Exception {
             }
 
             if (threeWay) {
-                xferRemoteToRemote(stdin, stdout, stderr, args, source, target, options, logStream, level, quiet);
+                xferRemoteToRemote(stdin, stdout, stderr, args, source, target, options, logStream, level, quiet,
+                        defaultOptions);
             } else {
-                xferLocalToRemote(stdin, stdout, stderr, args, source, target, options, logStream, level, quiet);
+                xferLocalToRemote(stdin, stdout, stderr, args, source, target, options, logStream, level, quiet,
+                        defaultOptions);
             }
         } finally {
             if ((logStream != stdout) && (logStream != stderr)) {

sshd-cli/src/main/java/org/apache/sshd/cli/client/SftpCommandMain.java

@@ -34,6 +34,7 @@
 import java.nio.file.Paths;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 import java.util.ServiceLoader;
@@ -47,6 +48,7 @@
 import org.apache.sshd.client.ClientFactoryManager;
 import org.apache.sshd.client.session.ClientSession;
 import org.apache.sshd.common.NamedResource;
+import org.apache.sshd.common.PropertyResolver;
 import org.apache.sshd.common.ServiceFactory;
 import org.apache.sshd.common.channel.ChannelFactory;
 import org.apache.sshd.common.cipher.CipherFactory;
@@ -71,6 +73,7 @@
 import org.apache.sshd.common.util.io.output.LineLevelAppenderStream;
 import org.apache.sshd.common.util.io.output.NullOutputStream;
 import org.apache.sshd.common.util.threads.ThreadUtils;
+import org.apache.sshd.core.CoreModuleProperties;
 import org.apache.sshd.server.config.SshServerConfigFileReader;
 import org.apache.sshd.sftp.client.SftpClient;
 import org.apache.sshd.sftp.client.SftpClient.Attributes;
@@ -91,6 +94,8 @@
 import org.apache.sshd.sftp.common.extensions.openssh.StatVfsExtensionParser;
 import org.slf4j.Logger;
 
+import static org.apache.sshd.common.PropertyResolverUtils.toPropertyResolver;
+
 /**
  * TODO Add javadoc
  *
@@ -366,9 +371,13 @@ public static void main(String[] args) throws Exception {
                 setupLogging(level, stdout, stderr, logStream);
             }
 
+            PropertyResolver defaultOptions = toPropertyResolver(new HashMap<>());
+            CoreModuleProperties.NO_FLOW_CONTROL.set(defaultOptions, Boolean.TRUE);
+            CoreModuleProperties.WINDOW_SIZE.set(defaultOptions, 1024L * 1024L * 1024L);
+
             ClientSession session = (logStream == null)
                     ? null
-                    : setupClientSession(SFTP_PORT_OPTION, stdin, level, stdout, stderr, args);
+                    : setupClientSession(SFTP_PORT_OPTION, stdin, level, stdout, stderr, args, defaultOptions);
             if (session == null) {
                 System.err.println("usage: sftp [-v[v][v]] [-E logoutput] [-i identity] [-io nio2|mina|netty]"
                                    + " [-J proxyJump] [-l login] [" + SFTP_PORT_OPTION + " port] [-o option=value]"

sshd-cli/src/main/java/org/apache/sshd/cli/client/SshClientCliSupport.java

@@ -119,7 +119,15 @@ public static boolean isArgumentedOption(String portOption, String argName) {
     // CHECKSTYLE:OFF
     public static ClientSession setupClientSession(
             String portOption, BufferedReader stdin, Level level,
-            PrintStream stdout, PrintStream stderr, String... args)
+            PrintStream stdout, PrintStream stderr, String[] args)
+            throws Exception {
+        return setupClientSession(portOption, stdin, level, stdout, stderr, args, null);
+    }
+
+    public static ClientSession setupClientSession(
+            String portOption, BufferedReader stdin, Level level,
+            PrintStream stdout, PrintStream stderr, String[] args,
+            PropertyResolver defaultOptions)
             throws Exception {
         int port = -1;
         String host = null;
@@ -240,7 +248,8 @@ public static ClientSession setupClientSession(
             return null;
         }
 
-        PropertyResolver resolver = PropertyResolverUtils.toPropertyResolver(options);
+        PropertyResolver resolver = PropertyResolverUtils.toPropertyResolver(options,
+                defaultOptions);
         SshClient client = setupClient(
                 resolver, ciphers, macs, compressions, identities,
                 stdin, stdout, stderr, level, args);

sshd-common/src/main/java/org/apache/sshd/common/kex/extension/parser/NoFlowControl.java

@@ -31,6 +31,9 @@
 public class NoFlowControl extends AbstractKexExtensionParser<String> {
     public static final String NAME = "no-flow-control";
 
+    public static final String SUPPORTED = "s";
+    public static final String PREFERRED = "p";
+
     public static final NoFlowControl INSTANCE = new NoFlowControl();
 
     public NoFlowControl() {

sshd-core/src/main/java/org/apache/sshd/common/channel/LocalWindow.java

@@ -70,6 +70,11 @@ public void consume(long len) throws IOException {
         BufferUtils.validateUint32Value(len, "Invalid consumption length: %d");
         checkInitialized("consume");
 
+        if (noFlowControl) {
+            // flow control is disabled, so just bail out
+            return;
+        }
+
         long remainLen;
         synchronized (lock) {
             remainLen = getSize() - len;

sshd-core/src/main/java/org/apache/sshd/common/channel/RemoteWindow.java

@@ -67,6 +67,11 @@ public void consume(long len) {
         BufferUtils.validateUint32Value(len, "Invalid consumption length: %d");
         checkInitialized("consume");
 
+        if (noFlowControl) {
+            // flow control is disabled, so just bail out
+            return;
+        }
+
         long remainLen;
         synchronized (lock) {
             remainLen = getSize() - len;

sshd-core/src/main/java/org/apache/sshd/common/channel/Window.java

@@ -25,6 +25,7 @@
 import java.util.function.Predicate;
 
 import org.apache.sshd.common.PropertyResolver;
+import org.apache.sshd.common.session.Session;
 import org.apache.sshd.common.util.ValidateUtils;
 import org.apache.sshd.common.util.buffer.BufferUtils;
 import org.apache.sshd.common.util.logging.AbstractLoggingBean;
@@ -46,6 +47,8 @@ public abstract class Window extends AbstractLoggingBean implements ChannelHolde
 
     protected final Object lock = new Object();
 
+    protected boolean noFlowControl;
+
     private final AtomicBoolean closed = new AtomicBoolean(false);
     private final AtomicBoolean initialized = new AtomicBoolean(false);
     private final Channel channelInstance;
@@ -94,6 +97,8 @@ protected void init(long size, long packetSize, PropertyResolver resolver) {
         }
 
         synchronized (lock) {
+            Session session = channelInstance.getSession(); // this should only be null during tests
+            this.noFlowControl = session != null && session.isNoFlowControl();
             this.maxSize = size;
             this.packetSize = packetSize;
             updateSize(size);

sshd-core/src/main/java/org/apache/sshd/common/kex/extension/DefaultClientKexExtensionHandler.java

@@ -26,18 +26,23 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.TreeSet;
 import java.util.function.BiConsumer;
 
 import org.apache.sshd.common.AttributeRepository.AttributeKey;
 import org.apache.sshd.common.NamedFactory;
 import org.apache.sshd.common.kex.extension.parser.HostBoundPubkeyAuthentication;
+import org.apache.sshd.common.kex.extension.parser.NoFlowControl;
 import org.apache.sshd.common.kex.extension.parser.ServerSignatureAlgorithms;
 import org.apache.sshd.common.session.Session;
+import org.apache.sshd.common.session.helpers.AbstractSession;
 import org.apache.sshd.common.signature.Signature;
+import org.apache.sshd.common.util.ValidateUtils;
 import org.apache.sshd.common.util.buffer.Buffer;
 import org.apache.sshd.common.util.logging.AbstractLoggingBean;
+import org.apache.sshd.core.CoreModuleProperties;
 
 /**
  * Detects if the server sends a
@@ -92,6 +97,15 @@ public boolean handleKexExtensionRequest(
             } else {
                 session.setAttribute(HOSTBOUND_AUTHENTICATION, version);
             }
+        } else if (NoFlowControl.NAME.equals(name)) {
+            String o = NoFlowControl.INSTANCE.parseExtension(data);
+            Optional<Boolean> nfc = CoreModuleProperties.NO_FLOW_CONTROL.get(session);
+            if (NoFlowControl.PREFERRED.equals(o) && nfc.orElse(Boolean.TRUE)
+                    || NoFlowControl.SUPPORTED.equals(o) && nfc.orElse(Boolean.FALSE)) {
+                AbstractSession abstractSession
+                        = ValidateUtils.checkInstanceOf(session, AbstractSession.class, "Not a supported session: %s", session);
+                abstractSession.activateNoFlowControl();
+            }
         }
         return true;
     }
@@ -157,13 +171,19 @@ public void sendKexExtensions(Session session, KexPhase phase) throws Exception
      * Collects extension info records, handing them off to the given {@code marshaller} for writing into an
      * {@link KexExtensions#SSH_MSG_EXT_INFO} message.
      * <p>
-     * This default implementation does not marshal any extension.
+     * This default implementation marshals a {@link NoFlowControl} extension}.
      * </p>
      *
      * @param session    {@link Session} to send the KEX extension information for
      * @param phase      {@link KexPhase} of the SSH protocol
      * @param marshaller {@link BiConsumer} writing the extensions into an SSH message
      */
     public void collectExtensions(Session session, KexPhase phase, BiConsumer<String, Object> marshaller) {
+        // no-flow-control
+        Boolean nfc = CoreModuleProperties.NO_FLOW_CONTROL.get(session).orElse(null);
+        if (nfc == null || nfc) {
+            marshaller.accept(NoFlowControl.NAME,
+                    nfc != null ? NoFlowControl.PREFERRED : NoFlowControl.SUPPORTED);
+        }
     }
 }

sshd-core/src/main/java/org/apache/sshd/common/kex/extension/DefaultServerKexExtensionHandler.java

@@ -19,23 +19,29 @@
 
 package org.apache.sshd.common.kex.extension;
 
+import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.Optional;
 import java.util.function.BiConsumer;
 
 import org.apache.sshd.common.AttributeRepository.AttributeKey;
 import org.apache.sshd.common.kex.KexProposalOption;
+import org.apache.sshd.common.kex.extension.parser.NoFlowControl;
 import org.apache.sshd.common.kex.extension.parser.ServerSignatureAlgorithms;
 import org.apache.sshd.common.session.Session;
+import org.apache.sshd.common.session.helpers.AbstractSession;
 import org.apache.sshd.common.util.GenericUtils;
+import org.apache.sshd.common.util.ValidateUtils;
 import org.apache.sshd.common.util.buffer.Buffer;
 import org.apache.sshd.common.util.logging.AbstractLoggingBean;
+import org.apache.sshd.core.CoreModuleProperties;
 
 /**
  * A basic default implementation of a server-side {@link KexExtensionHandler} handling the
- * {@link ServerSignatureAlgorithms} KEX extension.
+ * {@link ServerSignatureAlgorithms} KEX extension along with the {@link NoFlowControl} extension.
  *
  * @see <a href="https://tools.ietf.org/html/rfc8308">RFC 8308</a>
  */
@@ -130,6 +136,23 @@ public void sendKexExtensions(Session session, KexPhase phase) throws Exception
         }
     }
 
+    @Override
+    public boolean handleKexExtensionRequest(
+            Session session, int index, int count, String name, byte[] data)
+            throws IOException {
+        if (NoFlowControl.NAME.equals(name)) {
+            String o = NoFlowControl.INSTANCE.parseExtension(data);
+            Optional<Boolean> nfc = CoreModuleProperties.NO_FLOW_CONTROL.get(session);
+            if (NoFlowControl.PREFERRED.equals(o) && nfc.orElse(Boolean.TRUE)
+                    || NoFlowControl.SUPPORTED.equals(o) && nfc.orElse(Boolean.FALSE)) {
+                AbstractSession abstractSession
+                        = ValidateUtils.checkInstanceOf(session, AbstractSession.class, "Not a supported session: %s", session);
+                abstractSession.activateNoFlowControl();
+            }
+        }
+        return true;
+    }
+
     /**
      * Collects extension info records, handing them off to the given {@code marshaller} for writing into an
      * {@link KexExtensions#SSH_MSG_EXT_INFO} message.
@@ -144,6 +167,7 @@ public void sendKexExtensions(Session session, KexPhase phase) throws Exception
      */
     @SuppressWarnings("javadoc")
     public void collectExtensions(Session session, KexPhase phase, BiConsumer<String, Object> marshaller) {
+        // server-sig-algs
         if (phase == KexPhase.NEWKEYS) {
             Collection<String> algorithms = session.getSignatureFactoriesNames();
             if (!GenericUtils.isEmpty(algorithms)) {
@@ -157,5 +181,11 @@ public void collectExtensions(Session session, KexPhase phase, BiConsumer<String
                         ServerSignatureAlgorithms.NAME);
             }
         }
+        // no-flow-control
+        Boolean nfc = CoreModuleProperties.NO_FLOW_CONTROL.get(session).orElse(null);
+        if (nfc != Boolean.FALSE) {
+            marshaller.accept(NoFlowControl.NAME,
+                    nfc != null ? NoFlowControl.PREFERRED : NoFlowControl.SUPPORTED);
+        }
     }
 }

sshd-core/src/main/java/org/apache/sshd/common/session/Session.java

@@ -382,4 +382,10 @@ static <T> T resolveAttribute(Session session, AttributeRepository.AttributeKey<
         T value = session.getAttribute(key);
         return (value != null) ? value : FactoryManager.resolveAttribute(session.getFactoryManager(), key);
     }
+
+    /**
+     * Check if the no-flow-control KEX extension has been activated.
+     */
+    boolean isNoFlowControl();
+
 }

sshd-core/src/main/java/org/apache/sshd/common/session/helpers/AbstractConnectionService.java

@@ -757,6 +757,13 @@ protected void channelOpen(Buffer buffer) throws Exception {
             return;
         }
 
+        if (getSession().isNoFlowControl() && !channels.isEmpty()) {
+            // TODO add language tag configurable control
+            sendChannelOpenFailure(buffer, sender, SshConstants.SSH_OPEN_CONNECT_FAILED,
+                    "Only a single channel can be opened when using no-flow-control", "");
+            return;
+        }
+
         Session session = getSession();
         FactoryManager manager = Objects.requireNonNull(session.getFactoryManager(), "No factory manager");
         Channel channel = ChannelFactory.createChannel(session, manager.getChannelFactories(), type);