JENKINS-74995 Add rootless support

src/main/java/org/jenkinsci/plugins/docker/workflow/WithContainerStep.java

@@ -197,7 +197,16 @@
             }
 
             String command = launcher.isUnix() ? "cat" : "cmd.exe";
-            container = dockerClient.run(env, step.image, step.args, ws, volumes, volumesFromContainers, envReduced, dockerClient.whoAmI(), /* expected to hang until killed */ command);
+            String whoAmI  = dockerClient.whoAmI();
+            if (dockerClient.isRootless()) {
+                listener.getLogger().println("Running in rootless mode.");
+                whoAmI = "";
+                if (dockerClient.getEngine().equals("podman")) {
+                    listener.getLogger().println("Podman detected.");
+                    step.args = step.args == null ? "--userns=keep-id" : "--userns=keep-id " + step.args;
+                }
+            }
+            container = dockerClient.run(env, step.image, step.args, ws, volumes, volumesFromContainers, envReduced, whoAmI, /* expected to hang until killed */ command);
             final List<String> ps = dockerClient.listProcess(env, container);
             if (!ps.contains(command)) {
                 listener.error(

src/main/java/org/jenkinsci/plugins/docker/workflow/client/DockerClient.java

@@ -31,6 +31,7 @@
 import hudson.FilePath;
 import hudson.Launcher;
 import hudson.model.Node;
+import hudson.model.TaskListener;
 import hudson.util.ArgumentListBuilder;
 import hudson.util.VersionNumber;
 import java.io.BufferedReader;
@@ -318,6 +319,12 @@
         return result;
     }
 
+    private String executeCommand(String... command) throws IOException, InterruptedException {
+        ByteArrayOutputStream output = new ByteArrayOutputStream();
+        launcher.launch().cmds(command).quiet(true).stdout(output).start().joinWithTimeout(CLIENT_TIMEOUT, TimeUnit.SECONDS, launcher.getListener());
+        return output.toString(Charset.defaultCharset()).trim();
+    }
+
     /**
      * Who is executing this {@link DockerClient} instance.
      *
@@ -328,15 +335,34 @@
             // Windows does not support username
             return "";
         }
-        ByteArrayOutputStream userId = new ByteArrayOutputStream();
-        launcher.launch().cmds("id", "-u").quiet(true).stdout(userId).start().joinWithTimeout(CLIENT_TIMEOUT, TimeUnit.SECONDS, launcher.getListener());
 
-        ByteArrayOutputStream groupId = new ByteArrayOutputStream();
-        launcher.launch().cmds("id", "-g").quiet(true).stdout(groupId).start().joinWithTimeout(CLIENT_TIMEOUT, TimeUnit.SECONDS, launcher.getListener());
+        String userId = executeCommand("id", "-u");
+        String groupId = executeCommand("id", "-g");
 
-        final String charsetName = Charset.defaultCharset().name();
-        return String.format("%s:%s", userId.toString(charsetName).trim(), groupId.toString(charsetName).trim());
+        return String.format("%s:%s", userId, groupId);
+    }
+
+    public String getEngine() throws IOException, InterruptedException {
+
+        String engine = "docker";
+
+        String cmd = executeCommand("docker", "--version");
+        if (cmd.toLowerCase().contains("podman")) {
+            engine = "podman";
+        }
+        else {
+            String rootless = executeCommand("docker", "info", "-f", "{{.SecurityOptions}}" );
+            if (rootless.toLowerCase().contains("rootless")) {
+                engine = "docker-rootless";
+            }
+        }
+
+        return engine;
+    }
 
+    public boolean isRootless() throws IOException, InterruptedException {
+        String engine = getEngine();
+        return engine.equals("docker-rootless") || engine.equals("podman");
     }
 
     private static final Pattern hostnameMount = Pattern.compile("/containers/([a-z0-9]{64})/hostname");