nfs: remote utility class to extract current user

Motivation:
the UnixUtils used by nfs client to extract curren user with the help of
reflection. As com.sun.security.auth.module.UnixSystem is a part of
official OpenJDK, there are no reasons to hide it usage.

Modification:
update nfs client to directly call
com.sun.security.auth.module.UnixSystem.

Result:
less magic in the code.

Acked-by: Paul Millar
Target: master

basic-client/src/main/java/org/dcache/nfs/v4/client/nfs4_prot_NFS4_PROGRAM_Client.java

@@ -21,8 +21,9 @@ package org.dcache.nfs.v4.client;
 import java.io.IOException;
 
 import java.net.InetAddress;
-import javax.security.auth.Subject;
-import org.dcache.auth.Subjects;
+import java.util.Arrays;
+
+import com.sun.security.auth.module.UnixSystem;
 
 import org.dcache.nfs.v4.xdr.COMPOUND4args;
 import org.dcache.nfs.v4.xdr.COMPOUND4res;
@@ -34,8 +35,6 @@ import org.dcache.oncrpc4j.rpc.RpcAuthTypeUnix;
 import org.dcache.oncrpc4j.rpc.RpcCall;
 import org.dcache.oncrpc4j.rpc.RpcTransport;
 import org.dcache.oncrpc4j.xdr.XdrVoid;
-import org.dcache.nfs.util.UnixUtils;
-
 
 /**
  * The class <code>nfs4_prot_NFS4_PROGRAM_Client</code> implements the client stub proxy
@@ -74,14 +73,11 @@ public class nfs4_prot_NFS4_PROGRAM_Client {
     public nfs4_prot_NFS4_PROGRAM_Client(InetAddress host, int port, int protocol)
            throws OncRpcException, IOException {
 
-        Subject currentUser = UnixUtils.getCurrentUser();
-        if (currentUser == null) {
-            throw new IllegalStateException("unable to determine current unix user. please provide uid/gid explicitly");
-        }
+        UnixSystem currentUser = new UnixSystem();
 
-        int uid = (int)Subjects.getUid(currentUser);
-        int gid = (int)Subjects.getPrimaryGid(currentUser);
-        int[] gids = UnixUtils.toIntArray(Subjects.getGids(currentUser));
+        int uid = (int)currentUser.getUid();
+        int gid = (int)currentUser.getGid();
+        int[] gids = Arrays.stream(currentUser.getGroups()).mapToInt(Math::toIntExact).toArray();
 
         rpcClient = new OncRpcClient(host, protocol, port);
         RpcTransport transport;

core/src/main/java/org/dcache/nfs/util/UnixUtils.java

-/*
- * Copyright (c) 2009 - 2020 Deutsches Elektronen-Synchroton,
- * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY
- *
- * This library is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Library General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public
- * License along with this program (see the file COPYING.LIB for more
- * details); if not, write to the Free Software Foundation, Inc.,
- * 675 Mass Ave, Cambridge, MA 02139, USA.
- */
-package org.dcache.nfs.util;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
-import javax.security.auth.Subject;
-import org.dcache.auth.GidPrincipal;
-import org.dcache.auth.UidPrincipal;
-
-public class UnixUtils {
-    private static final Logger _log = LoggerFactory.getLogger(UnixUtils.class);
-
-    /**
-     * attempts to get the current user, if running on a compatible OS/jre
-     * @return the current UnixUser, or null
-     */
-    public static Subject getCurrentUser() {
-        try {
-            Class<?> unixSystemClass = Class.forName("com.sun.security.auth.module.UnixSystem");
-            Object unixSystemInstance = unixSystemClass.getDeclaredConstructor().newInstance();
-            Method getUidMethod = unixSystemClass.getDeclaredMethod("getUid");
-            Method getGidMethod = unixSystemClass.getDeclaredMethod("getGid");
-            Method getGroupsMethod = unixSystemClass.getDeclaredMethod("getGroups");
-
-            Subject subject = new Subject();
-
-            subject.getPrincipals().add(new UidPrincipal((Long) getUidMethod.invoke(unixSystemInstance)) );
-            subject.getPrincipals().add(new GidPrincipal((Long) getGidMethod.invoke(unixSystemInstance), true));
-            long[] groups = (long[]) getGroupsMethod.invoke(unixSystemInstance);
-
-            for (long gid: groups) {
-                subject.getPrincipals().add(new GidPrincipal(gid, false));
-            }
-            return subject;
-
-        } catch (IllegalAccessException |
-                ClassNotFoundException | InvocationTargetException |
-                NoSuchMethodException | InstantiationException e) {
-            _log.debug("couldn't get current unix user",e);
-            return null;
-        }
-    }
-
-    public static int[] toIntArray(long[] longArray) {
-        int[] intArray = new int[longArray.length];
-        for (int i = 0; i < longArray.length; i++) {
-            intArray[i] = (int) longArray[i];
-        }
-        return intArray;
-    }
-}

core/src/test/java/org/dcache/nfs/util/UnixUtilsTest.java

-/*
- * Copyright (c) 2009 - 2020 Deutsches Elektronen-Synchroton,
- * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY
- *
- * This library is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Library General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public
- * License along with this program (see the file COPYING.LIB for more
- * details); if not, write to the Free Software Foundation, Inc.,
- * 675 Mass Ave, Cambridge, MA 02139, USA.
- */
-package org.dcache.nfs.util;
-
-import org.junit.Assert;
-import org.junit.Test;
-
-import java.util.Locale;
-import javax.security.auth.Subject;
-
-public class UnixUtilsTest {
-    @Test
-    public void testGetCurrentUser() {
-        String osName = System.getProperty("os.name");
-        boolean isWindows = osName.toLowerCase(Locale.ROOT).contains("windows");
-        Subject currentUser = UnixUtils.getCurrentUser();
-        if (isWindows) {
-            Assert.assertNull(currentUser);
-        } else {
-            Assert.assertNotNull(currentUser);
-        }
-    }
-}