OutboundAgent test utility

pom.xml

@@ -83,6 +83,7 @@
     <jenkins.version>${jenkins.baseline}.3</jenkins.version>
     <hpi.compatibleSinceVersion>3.0.0</hpi.compatibleSinceVersion>
     <spotless.check.skip>false</spotless.check.skip>
+    <no-test-jar>false</no-test-jar>
   </properties>
 
   <dependencyManagement>

src/test/java/test/ssh_agent/OutboundAgent.java

@@ -0,0 +1,141 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2025 CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package test.ssh_agent;
+
+import com.cloudbees.jenkins.plugins.sshcredentials.impl.BasicSSHUserPrivateKey;
+import com.cloudbees.plugins.credentials.CredentialsProvider;
+import com.cloudbees.plugins.credentials.CredentialsScope;
+import com.cloudbees.plugins.credentials.domains.Domain;
+import hudson.Functions;
+import hudson.plugins.sshslaves.SSHLauncher;
+import hudson.slaves.DumbSlave;
+import java.io.ByteArrayOutputStream;
+import java.io.Serializable;
+import java.nio.charset.StandardCharsets;
+import org.apache.sshd.common.config.keys.KeyUtils;
+import org.apache.sshd.common.config.keys.writer.openssh.OpenSSHKeyPairResourceWriter;
+import org.apache.sshd.common.keyprovider.KeyPairProvider;
+import org.jvnet.hudson.test.JenkinsRule;
+import org.testcontainers.DockerClientFactory;
+import org.testcontainers.containers.GenericContainer;
+
+/**
+ * Test utility to create an outbound agent.
+ * Will use Docker when it is available (Testcontainers must be in your plugin classpath),
+ * which is preferable as it ensures that the process and filesystem namespace for the agent
+ * is distinct from that of the controller.
+ * Otherwise it falls back to running an agent process locally.
+ */
+public final class OutboundAgent implements AutoCloseable {
+
+    private String image = "jenkins/ssh-agent";
+
+    private SSHAgentContainer container;
+
+    public OutboundAgent() {}
+
+    /**
+     * Overrides the container image, by default {@code jenkins/ssh-agent} (latest).
+     */
+    public OutboundAgent withImage(String image) {
+        this.image = image;
+        return this;
+    }
+
+    private static final class SSHAgentContainer extends GenericContainer<SSHAgentContainer> {
+        final String privateKey;
+
+        SSHAgentContainer(String image) {
+            super(image);
+            try {
+                var kp = KeyUtils.generateKeyPair(KeyPairProvider.SSH_RSA, 2048);
+                var kprw = new OpenSSHKeyPairResourceWriter();
+                var baos = new ByteArrayOutputStream();
+                kprw.writePublicKey(kp, null, baos);
+                var pub = baos.toString(StandardCharsets.US_ASCII);
+                baos.reset();
+                kprw.writePrivateKey(kp, null, null, baos);
+                privateKey = baos.toString(StandardCharsets.US_ASCII);
+                withEnv("JENKINS_AGENT_SSH_PUBKEY", pub);
+                withExposedPorts(22);
+            } catch (Exception x) {
+                throw new AssertionError(x);
+            }
+        }
+    }
+
+    /**
+     * Start the container, if Docker is available.
+     * @return Docker connection details, or null if running locally; pass to {@link #createAgent}
+     */
+    public ConnectionDetails start() throws Exception {
+        if (!Functions.isWindows() && DockerClientFactory.instance().isDockerAvailable()) {
+            container = new SSHAgentContainer(image);
+            container.start();
+            return new ConnectionDetails(container.getHost(), container.getMappedPort(22), container.privateKey);
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Treat as opaque between {@link #start} and {@link #createAgent}.
+     */
+    public record ConnectionDetails(String host, int port, String privateKey) implements Serializable {}
+
+    /**
+     * Create an agent.
+     * @param rule this should run in the controller’s’ JVM, unlike {@link #start}
+     * @param name agent name
+     * @param connectionDetails connection details, or null to run a local agent
+     * @see JenkinsRule#waitOnline
+     */
+    public static void createAgent(JenkinsRule rule, String name, ConnectionDetails connectionDetails)
+            throws Exception {
+        if (connectionDetails != null) {
+            var creds = new BasicSSHUserPrivateKey(
+                    CredentialsScope.GLOBAL,
+                    null,
+                    "jenkins",
+                    new BasicSSHUserPrivateKey.DirectEntryPrivateKeySource(connectionDetails.privateKey),
+                    null,
+                    null);
+            CredentialsProvider.lookupStores(rule.jenkins).iterator().next().addCredentials(Domain.global(), creds);
+            rule.jenkins.addNode(new DumbSlave(
+                    name,
+                    "/home/jenkins/agent",
+                    new SSHLauncher(connectionDetails.host, connectionDetails.port, creds.getId())));
+        } else {
+            rule.createSlave(name, null, null);
+        }
+    }
+
+    @Override
+    public void close() throws Exception {
+        if (container != null) {
+            container.close();
+        }
+    }
+}

src/test/java/test/ssh_agent/OutboundAgentRJRTest.java

@@ -0,0 +1,50 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2025 CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package test.ssh_agent;
+
+import hudson.model.Slave;
+import org.junit.Rule;
+import org.junit.Test;
+import org.jvnet.hudson.test.RealJenkinsRule;
+
+public final class OutboundAgentRJRTest {
+
+    @Rule
+    public final RealJenkinsRule rr = new RealJenkinsRule();
+
+    @Test
+    public void smokes() throws Throwable {
+        rr.startJenkins();
+        try (var outbountAgent = new OutboundAgent()) {
+            rr.runRemotely(OutboundAgent::createAgent, "remote", outbountAgent.start());
+            rr.run(r -> {
+                var agent = (Slave) r.jenkins.getNode("remote");
+                r.waitOnline(agent);
+                System.err.println(
+                        "Running in " + agent.toComputer().getEnvironment().get("PWD"));
+            });
+        }
+    }
+}