[FIXED JENKINS-37032] Add a UI to allow controling the agent protocol enablement

core/src/main/java/hudson/TcpSlaveAgentListener.java

@@ -26,6 +26,7 @@ package hudson;
 import java.nio.charset.Charset;
 import java.security.interfaces.RSAPublicKey;
 import javax.annotation.Nullable;
+import jenkins.model.Jenkins;
 import jenkins.model.identity.InstanceIdentityProvider;
 import jenkins.util.SystemProperties;
 import hudson.slaves.OfflineCause;
@@ -50,6 +51,7 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 import org.apache.commons.codec.binary.Base64;
 import org.apache.commons.io.IOUtils;
+import org.apache.commons.lang.StringUtils;
 
 /**
  * Listens to incoming TCP connections from JNLP agents and CLI.
@@ -127,20 +129,7 @@ public final class TcpSlaveAgentListener extends Thread {
      * @since FIXME
      */
     public String getAgentProtocolNames() {
-        StringBuilder result = new StringBuilder();
-        boolean first = true;
-        for (AgentProtocol p : AgentProtocol.all()) {
-            String name = p.getName();
-            if (name != null) {
-                if (first) {
-                    first = false;
-                } else {
-                    result.append(", ");
-                }
-                result.append(name);
-            }
-        }
-        return result.toString();
+        return StringUtils.join(Jenkins.getInstance().getAgentProtocols(), ", ");
     }
 
     @Override
@@ -218,9 +207,13 @@ public final class TcpSlaveAgentListener extends Thread {
                 if(s.startsWith("Protocol:")) {
                     String protocol = s.substring(9);
                     AgentProtocol p = AgentProtocol.of(protocol);
-                    if (p!=null)
+                    if (p!=null) {
+                        if (Jenkins.getInstance().getAgentProtocols().contains(protocol)) {
                             p.handle(this.s);
-                    else
+                        } else {
+                            error(out, "Disabled protocol:" + s);
+                        }
+                    } else
                         error(out, "Unknown protocol:" + s);
                 } else {
                     error(out, "Unrecognized protocol: "+s);
@@ -268,6 +261,18 @@ public final class TcpSlaveAgentListener extends Thread {
             }
         }
 
+        /**
+         * Allow essential {@link AgentProtocol} implementations (basically {@link PingAgentProtocol})
+         * to be always enabled.
+         *
+         * @return {@code true} if the protocol can never be disbaled.
+         * @since FIXME
+         */
+        @Override
+        public boolean isRequired() {
+            return true;
+        }
+
         @Override
         public String getName() {
             return "Ping";

core/src/main/java/hudson/security/GlobalSecurityConfiguration.java

@@ -35,6 +35,8 @@ import hudson.model.ManagementLink;
 import hudson.util.FormApply;
 
 import java.io.IOException;
+import java.util.Set;
+import java.util.TreeSet;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -43,6 +45,7 @@ import javax.servlet.ServletException;
 import jenkins.model.GlobalConfigurationCategory;
 import jenkins.model.Jenkins;
 import jenkins.util.ServerTcpPort;
+import net.sf.json.JSONArray;
 import net.sf.json.JSONObject;
 
 import org.jenkinsci.Symbol;
@@ -69,6 +72,10 @@ public class GlobalSecurityConfiguration extends ManagementLink implements Descr
         return Jenkins.getInstance().getSlaveAgentPort();
     }
 
+    public Set<String> getAgentProtocols() {
+        return Jenkins.getInstance().getAgentProtocols();
+    }
+
     public boolean isDisableRememberMe() {
         return Jenkins.getInstance().isDisableRememberMe();
     }
@@ -100,6 +107,18 @@ public class GlobalSecurityConfiguration extends ManagementLink implements Descr
             } catch (IOException e) {
                 throw new hudson.model.Descriptor.FormException(e, "slaveAgentPortType");
             }
+            Set<String> agentProtocols = new TreeSet<>();
+            if (security.has("agentProtocol")) {
+                Object protocols = security.get("agentProtocol");
+                if (protocols instanceof JSONArray) {
+                    for (int i = 0; i < ((JSONArray) protocols).size(); i++) {
+                        agentProtocols.add(((JSONArray) protocols).getString(i));
+                    }
+                } else {
+                    agentProtocols.add(protocols.toString());
+                }
+            }
+            j.setAgentProtocols(agentProtocols);
         } else {
             j.disableSecurity();
         }

core/src/main/java/jenkins/AgentProtocol.java

@@ -21,6 +21,24 @@ import java.net.Socket;
  * @see TcpSlaveAgentListener
  */
 public abstract class AgentProtocol implements ExtensionPoint {
+    /**
+     * Allow experimental {@link AgentProtocol} implementations to declare being opt-in.
+     * @return {@code true} if the protocol requires explicit opt-in.
+     * @since FIXME
+     */
+    public boolean isOptIn() {
+        return false;
+    }
+    /**
+     * Allow essential {@link AgentProtocol} implementations (basically {@link TcpSlaveAgentListener.PingAgentProtocol})
+     * to be always enabled.
+     *
+     * @return {@code true} if the protocol can never be disbaled.
+     * @since FIXME
+     */
+    public boolean isRequired() {
+        return false;
+    }
     /**
      * Protocol name.
      *

core/src/main/java/jenkins/model/Jenkins.java

@@ -50,6 +50,7 @@ import hudson.Plugin;
 import hudson.PluginManager;
 import hudson.PluginWrapper;
 import hudson.ProxyConfiguration;
+import jenkins.AgentProtocol;
 import jenkins.util.SystemProperties;
 import hudson.TcpSlaveAgentListener;
 import hudson.UDPBroadcastThread;
@@ -224,6 +225,7 @@ import org.acegisecurity.providers.anonymous.AnonymousAuthenticationToken;
 import org.acegisecurity.ui.AbstractProcessingFilter;
 import org.apache.commons.jelly.JellyException;
 import org.apache.commons.jelly.Script;
+import org.apache.commons.lang.StringUtils;
 import org.apache.commons.logging.LogFactory;
 import org.jvnet.hudson.reactor.Executable;
 import org.jvnet.hudson.reactor.Milestone;
@@ -598,6 +600,28 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
      */
     private int slaveAgentPort = SystemProperties.getInteger(Jenkins.class.getName()+".slaveAgentPort",0);
 
+    /**
+     * The TCP agent protocols that are explicitly disabled (we store the disabled ones so that newer protocols
+     * are enabled by default).
+     *
+     * @since FIXME
+     */
+    private String disabledAgentProtocols;
+
+    /**
+     * The TCP agent protocols that are {@link AgentProtocol#isOptIn()} and explicitly enabled.
+     *
+     * @since FIXME
+     */
+    private String enabledAgentProtocols;
+
+    /**
+     * The TCP agent protocols that are enabled. Built from {@link #disabledAgentProtocols}.
+     *
+     * @since FIXME
+     */
+    private transient Set<String> agentProtocols;
+
     /**
      * Whitespace-separated labels assigned to the master as a {@link Node}.
      */
@@ -1060,6 +1084,65 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
         launchTcpSlaveAgentListener();
     }
 
+    /**
+     * Returns the enabled agent protocols.
+     *
+     * @return the enabled agent protocols.
+     * @since FIXME
+     */
+    public Set<String> getAgentProtocols() {
+        if (agentProtocols == null) {
+            // idempotent, so don't care if we do this concurrently, should all get same result
+            Set<String> result = new TreeSet<>();
+            Set<String> disabled = new TreeSet<>();
+            for (String p : StringUtils.split(StringUtils.defaultIfBlank(disabledAgentProtocols, ""), ",")) {
+                disabled.add(p.trim());
+            }
+            Set<String> enabled = new TreeSet<>();
+            for (String p : StringUtils.split(StringUtils.defaultIfBlank(enabledAgentProtocols, ""), ",")) {
+                enabled.add(p.trim());
+            }
+            for (AgentProtocol p : AgentProtocol.all()) {
+                String name = p.getName();
+                if (name != null && (p.isRequired()
+                        || (!disabled.contains(name) && (!p.isOptIn() || enabled.contains(name))))) {
+                    result.add(name);
+                }
+            }
+            agentProtocols = result;
+            return result;
+        }
+        return agentProtocols;
+    }
+
+    /**
+     * Sets the enabled agent protocols.
+     *
+     * @param protocols the enabled agent protocols.
+     * @since FIXME
+     */
+    public void setAgentProtocols(Set<String> protocols) {
+        Set<String> disabled = new TreeSet<>();
+        Set<String> enabled = new TreeSet<>();
+        for (AgentProtocol p : AgentProtocol.all()) {
+            String name = p.getName();
+            if (name != null && !p.isRequired()) {
+                if (p.isOptIn()) {
+                    if (protocols.contains(name)) {
+                        enabled.add(name);
+                    }
+                } else {
+                    if (!protocols.contains(name)) {
+                        disabled.add(name);
+                    }
+                }
+            }
+        }
+        disabledAgentProtocols = fixEmpty(StringUtils.join(disabled, ", "));
+        enabledAgentProtocols = fixEmpty(StringUtils.join(enabled, ", "));
+        agentProtocols = null;
+    }
+
     private void launchTcpSlaveAgentListener() throws IOException {
         synchronized(tcpSlaveAgentListenerLock) {
             // shutdown previous agent if the port has changed

core/src/main/resources/hudson/TcpSlaveAgentListener/index.jelly

@@ -23,7 +23,7 @@ THE SOFTWARE.
 -->
 
 <?jelly escape-by-default='true'?>
-<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form" xmlns:i="jelly:fmt">
+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form" xmlns:i="jelly:fmt" trim="true">
   <st:contentType value="text/plain;charset=UTF-8"/>
   <!--
     Publicize the TCP port number for JNLP agents so that they know where to conenct.

core/src/main/resources/hudson/security/GlobalSecurityConfiguration/help-agentProtocol.html

+<div>
+  Jenkins uses a TCP port to communicate with various remote agents. This option allows control
+  over which agent protocols are enabled.
+</div>
\ No newline at end of file

core/src/main/resources/hudson/security/GlobalSecurityConfiguration/index.groovy

@@ -3,6 +3,7 @@ package hudson.security.GlobalSecurityConfiguration
 import hudson.security.SecurityRealm
 import hudson.markup.MarkupFormatterDescriptor
 import hudson.security.AuthorizationStrategy
+import jenkins.AgentProtocol
 import jenkins.model.GlobalConfiguration
 import hudson.Functions
 import hudson.model.Descriptor
@@ -28,6 +29,20 @@ l.layout(norefresh:true, permission:app.ADMINISTER, title:my.displayName, csscla
                 f.entry (title:_("TCP port for JNLP agents"), field:"slaveAgentPort") {
                     f.serverTcpPort()
                 }
+                f.advanced(title: _("Agent protocols"), align:"left") {
+                    f.entry(title: _("Agent protocols")) {
+                        def agentProtocols = my.agentProtocols;
+                        for (AgentProtocol p: AgentProtocol.all()) {
+                            if (p.name != null && !p.required) {
+                                f.checkbox(name: "agentProtocol",
+                                        title: p.name,
+                                        checked:agentProtocols.contains(p.name),
+                                        json: p.name);
+                                br();
+                            }
+                        }
+                    }
+                }
 
                 f.entry (title:_("Disable remember me"), field: "disableRememberMe") {
                     f.checkbox()