Prevent double authentication for the same public key

Openssh client sends two requests, one without a key signature to verify
that the public key is acceptable and the second one with the signature
after having loaded the private key and signed some data for actual
verification.

To prevent that the PublickeyAuthenticator#authenticate is called twice
cache the authentication status for session and public key.  Implement
SessionListener to clean up the cache entry when session is destroyed.

This is a workaround for SSHD bug [1].

Inspired-By: Guillaume Nodet <gnodet@apache.org>
[1] https://issues.apache.org/jira/browse/SSHD-300

5 files changed, 62 insertions, 23 deletions

diff --git a/src/main/java/com/gitblit/transport/ssh/PublicKeyAuthenticator.java b/src/main/java/com/gitblit/transport/ssh/CachingPublicKeyAuthenticator.java
index 84e7afa5..ee1de591 100644
--- a/src/main/java/com/gitblit/transport/ssh/PublicKeyAuthenticator.java
+++ b/src/main/java/com/gitblit/transport/ssh/CachingPublicKeyAuthenticator.java
@@ -16,9 +16,14 @@
 package com.gitblit.transport.ssh;
 
 import java.security.PublicKey;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
+import org.apache.sshd.common.Session;
+import org.apache.sshd.common.SessionListener;
 import org.apache.sshd.server.PublickeyAuthenticator;
 import org.apache.sshd.server.session.ServerSession;
 import org.slf4j.Logger;
@@ -26,13 +31,15 @@ import org.slf4j.LoggerFactory;
 
 import com.gitblit.manager.IAuthenticationManager;
 import com.gitblit.models.UserModel;
+import com.google.common.base.Preconditions;
 
 /**
- *
+ * 
  * @author Eric Myrhe
- *
+ * 
  */
-public class PublicKeyAuthenticator implements PublickeyAuthenticator {
+public class CachingPublicKeyAuthenticator implements PublickeyAuthenticator,
+		SessionListener {
 
 	protected final Logger log = LoggerFactory.getLogger(getClass());
 
@@ -40,26 +47,41 @@ public class PublicKeyAuthenticator implements PublickeyAuthenticator {
 
 	protected final IAuthenticationManager authManager;
 
-	public PublicKeyAuthenticator(IKeyManager keyManager, IAuthenticationManager authManager) {
+	private final Map<ServerSession, Map<PublicKey, Boolean>> cache =
+			new ConcurrentHashMap<ServerSession, Map<PublicKey, Boolean>>();
+
+	public CachingPublicKeyAuthenticator(IKeyManager keyManager,
+			IAuthenticationManager authManager) {
 		this.keyManager = keyManager;
 		this.authManager = authManager;
 	}
 
 	@Override
-	public boolean authenticate(String username, final PublicKey suppliedKey,
-			final ServerSession session) {
-		final SshDaemonClient client = session.getAttribute(SshDaemonClient.KEY);
-
-		if (client.getUser() != null) {
-			// TODO why do we re-authenticate?
-			log.info("{} has already authenticated!", username);
-			return true;
+	public boolean authenticate(String username, PublicKey key,
+			ServerSession session) {
+		Map<PublicKey, Boolean> map = cache.get(session);
+		if (map == null) {
+			map = new HashMap<PublicKey, Boolean>();
+			cache.put(session, map);
+			session.addListener(this);
 		}
+		if (map.containsKey(key)) {
+			return map.get(key);
+		}
+		boolean result = doAuthenticate(username, key, session);
+		map.put(key, result);
+		return result;
+	}
 
+	private boolean doAuthenticate(String username, PublicKey suppliedKey,
+			ServerSession session) {
+		SshDaemonClient client = session.getAttribute(SshDaemonClient.KEY);
+		Preconditions.checkState(client.getUser() == null);
 		username = username.toLowerCase(Locale.US);
 		List<PublicKey> keys = keyManager.getKeys(username);
 		if (keys == null || keys.isEmpty()) {
-			log.info("{} has not added any public keys for ssh authentication", username);
+			log.info("{} has not added any public keys for ssh authentication",
+					username);
 			return false;
 		}
 
@@ -73,11 +95,23 @@ public class PublicKeyAuthenticator implements PublickeyAuthenticator {
 			}
 		}
 
-		log.warn("could not authenticate {} for SSH using the supplied public key", username);
+		log.warn(
+				"could not authenticate {} for SSH using the supplied public key",
+				username);
 		return false;
 	}
 
 	public IKeyManager getKeyManager() {
 		return keyManager;
 	}
+
+	public void sessionCreated(Session session) {
+	}
+
+	public void sessionEvent(Session sesssion, Event event) {
+	}
+
+	public void sessionClosed(Session session) {
+		cache.remove(session);
+	}
 }
diff --git a/src/main/java/com/gitblit/transport/ssh/SshCommandFactory.java b/src/main/java/com/gitblit/transport/ssh/SshCommandFactory.java
index da57f76e..48e8869a 100644
--- a/src/main/java/com/gitblit/transport/ssh/SshCommandFactory.java
+++ b/src/main/java/com/gitblit/transport/ssh/SshCommandFactory.java
@@ -61,10 +61,12 @@ public class SshCommandFactory implements CommandFactory {
 	private static final Logger logger = LoggerFactory.getLogger(SshCommandFactory.class);
 
 	private final IGitblit gitblit;
-	private final PublicKeyAuthenticator keyAuthenticator;
+	private final CachingPublicKeyAuthenticator keyAuthenticator;
 	private final ScheduledExecutorService startExecutor;
 
-	public SshCommandFactory(IGitblit gitblit, PublicKeyAuthenticator keyAuthenticator, IdGenerator idGenerator) {
+	public SshCommandFactory(IGitblit gitblit,
+			CachingPublicKeyAuthenticator keyAuthenticator,
+			IdGenerator idGenerator) {
 		this.gitblit = gitblit;
 		this.keyAuthenticator = keyAuthenticator;
 
@@ -252,6 +254,7 @@ public class SshCommandFactory implements CommandFactory {
 			}
 		}
 
+		@SuppressWarnings("unused")
 		private void onDestroy() {
 			synchronized (this) {
 				if (cmd != null) {
diff --git a/src/main/java/com/gitblit/transport/ssh/SshDaemon.java b/src/main/java/com/gitblit/transport/ssh/SshDaemon.java
index c3d48600..c954b347 100644
--- a/src/main/java/com/gitblit/transport/ssh/SshDaemon.java
+++ b/src/main/java/com/gitblit/transport/ssh/SshDaemon.java
@@ -104,7 +104,8 @@ public class SshDaemon {
 			addr = new InetSocketAddress(bindInterface, port);
 		}
 
-		PublicKeyAuthenticator keyAuthenticator = new PublicKeyAuthenticator(keyManager, gitblit);
+		CachingPublicKeyAuthenticator keyAuthenticator = 
+				new CachingPublicKeyAuthenticator(keyManager, gitblit);
 
 		sshd = SshServer.setUpDefaultServer();
 		sshd.setPort(addr.getPort());
@@ -176,6 +177,7 @@ public class SshDaemon {
 		}
 	}
 
+	@SuppressWarnings("unchecked")
 	protected IKeyManager getKeyManager() {
 		IKeyManager keyManager = null;
 		IStoredSettings settings = gitblit.getSettings();
diff --git a/src/main/java/com/gitblit/transport/ssh/commands/BaseKeyCommand.java b/src/main/java/com/gitblit/transport/ssh/commands/BaseKeyCommand.java
index 36475244..f92ea6f9 100644
--- a/src/main/java/com/gitblit/transport/ssh/commands/BaseKeyCommand.java
+++ b/src/main/java/com/gitblit/transport/ssh/commands/BaseKeyCommand.java
@@ -21,7 +21,7 @@ import java.io.InputStreamReader;
 import java.io.UnsupportedEncodingException;
 import java.util.List;
 
-import com.gitblit.transport.ssh.PublicKeyAuthenticator;
+import com.gitblit.transport.ssh.CachingPublicKeyAuthenticator;
 import com.google.common.base.Charsets;
 
 /**
@@ -51,8 +51,8 @@ public abstract class BaseKeyCommand extends SshCommand {
 		return sshKeys;
 	}
 
-	protected PublicKeyAuthenticator authenticator;
-	public void setAuthenticator(PublicKeyAuthenticator authenticator) {
+	protected CachingPublicKeyAuthenticator authenticator;
+	public void setAuthenticator(CachingPublicKeyAuthenticator authenticator) {
 		this.authenticator = authenticator;
 	}
 }
diff --git a/src/main/java/com/gitblit/transport/ssh/commands/DispatchCommand.java b/src/main/java/com/gitblit/transport/ssh/commands/DispatchCommand.java
index 1e43e2f2..3c041af6 100644
--- a/src/main/java/com/gitblit/transport/ssh/commands/DispatchCommand.java
+++ b/src/main/java/com/gitblit/transport/ssh/commands/DispatchCommand.java
@@ -34,7 +34,7 @@ import com.gitblit.git.GitblitUploadPackFactory;
 import com.gitblit.git.RepositoryResolver;
 import com.gitblit.models.UserModel;
 import com.gitblit.transport.ssh.CommandMetaData;
-import com.gitblit.transport.ssh.PublicKeyAuthenticator;
+import com.gitblit.transport.ssh.CachingPublicKeyAuthenticator;
 import com.gitblit.transport.ssh.SshDaemonClient;
 import com.gitblit.utils.cli.SubcommandHandler;
 import com.google.common.base.Charsets;
@@ -237,9 +237,9 @@ public class DispatchCommand extends BaseCommand {
 		this.gitblitReceivePackFactory = gitblitReceivePackFactory;
 	}
 
-	private PublicKeyAuthenticator authenticator;
+	private CachingPublicKeyAuthenticator authenticator;
 
-	public void setAuthenticator(PublicKeyAuthenticator authenticator) {
+	public void setAuthenticator(CachingPublicKeyAuthenticator authenticator) {
 		this.authenticator = authenticator;
 	}
 }