PamTest.java

/**
 * If you get a strange JVM crash on CentOS 6 in code related to JNA and PAM,
 * try uninstalling this RedHat package related to fingerprint scanners:
 *
 *    sudo yum remove fprintd-pam
 *
 * Run this program with 100-500 threads -- the jvm usually crashes with
 * a stack like below (from hs_error.log ). Probably related to issues like:
 * https://bugzilla.redhat.com/show_bug.cgi?id=1010844.
 * Probably also affected by machine resource limits.
 *
 * Download libpam4j and JNA jars (also reproducible with jna 3.5.2):
 * http://mvnrepository.com/artifact/org.kohsuke/libpam4j
 * https://github.com/twall/jna
 * BUILD: javac -classpath ./jna-4.0.0.jar:./libpam4j-1.7.jar:. PamTest.java
 * RUN:   java -classpath ./jna-4.0.0.jar:./libpam4j-1.7.jar:. PamTest 100
 */

// Stack: [0x00007f1136dee000,0x00007f1136eef000],  sp=0x00007f1136eebe40,  free space=1015k
//        Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
//        C  [libdbus-1.so.3+0x27eb4]  chmod+0x27eb4
//
// Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
//        j  com.sun.jna.Native.invokeInt(JI[Ljava/lang/Object;)I+0
//        j  com.sun.jna.Function.invoke([Ljava/lang/Object;Ljava/lang/Class;Z)Ljava/lang/Object;+225
//        j  com.sun.jna.Function.invoke(Ljava/lang/Class;[Ljava/lang/Object;Ljava/util/Map;)Ljava/lang/Object;+262
//        j  com.sun.jna.Library$Handler.invoke(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;+316
//        j  com.sun.proxy.$Proxy0.pam_authenticate(Lorg/jvnet/libpam/impl/PAMLibrary$pam_handle_t;I)I+23
//        j  org.jvnet.libpam.PAM.authenticate(Ljava/lang/String;Ljava/lang/String;)Lorg/jvnet/libpam/UnixUser;+34

import java.util.concurrent.*;

import org.jvnet.libpam.PAM;
import org.jvnet.libpam.UnixUser;

public class PamTest {

    private final static class PamTask implements Callable<String> {
        public String call(){
            try {
                PAM pam = new PAM("login");
                UnixUser u = pam.authenticate("gw-john", "password");
                System.out.println("User " + u.getUserName() + " " + u.getUID() + " " + u.getGID() + " " + u.getDir() + " " + u.getGecos() + " " + u.getShell() + " in " + u.getGroups());
                return u.getUserName();
            } catch (Exception e) {
                System.out.println("Exception: " + e);
                System.exit(1);
                return null;
            }
        }
    }
    public static void main(String[] argv) {
        try {
            int NUM_THREADS = 50;
            if (argv.length > 0) {
                NUM_THREADS = Integer.parseInt(argv[0]);
            }
            ExecutorService poolWorkers = Executors.newFixedThreadPool(NUM_THREADS);
            CompletionService<String> pool = new ExecutorCompletionService(poolWorkers);
            for(int i = 0; i < NUM_THREADS; i++){
                pool.submit(new PamTask());
            }
            for(int i = 0; i < NUM_THREADS; ++i){
                String result = pool.take().get();
                System.out.println(i + ". user: " + result);
            }
            poolWorkers.shutdown();
        } catch (Exception e) {
            System.out.println("Exception: " + e);
            e.printStackTrace();
            System.exit(1);
        }
        System.exit(0);
    }
}