HADOOP-17159. Make UGI support forceful relogin from keytab ignoring the last login time (#2245)

Contributed by Sandeep Guggilam.

Signed-off-by: Mingliang Liu <liuml07@apache.org>
Signed-off-by: Steve Loughran <stevel@apache.org>

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java

@@ -1215,15 +1215,37 @@ public class UserGroupInformation {
    * Re-Login a user in from a keytab file. Loads a user identity from a keytab
    * file and logs them in. They become the currently logged-in user. This
    * method assumes that {@link #loginUserFromKeytab(String, String)} had
-   * happened already.
-   * The Subject field of this UserGroupInformation object is updated to have
-   * the new credentials.
+   * happened already. The Subject field of this UserGroupInformation object is
+   * updated to have the new credentials.
+   *
    * @throws IOException
    * @throws KerberosAuthException on a failure
    */
   @InterfaceAudience.Public
   @InterfaceStability.Evolving
-  public synchronized void reloginFromKeytab() throws IOException {
+  public void reloginFromKeytab() throws IOException {
+    reloginFromKeytab(false);
+  }
+
+  /**
+   * Force re-Login a user in from a keytab file irrespective of the last login
+   * time. Loads a user identity from a keytab file and logs them in. They
+   * become the currently logged-in user. This method assumes that
+   * {@link #loginUserFromKeytab(String, String)} had happened already. The
+   * Subject field of this UserGroupInformation object is updated to have the
+   * new credentials.
+   *
+   * @throws IOException
+   * @throws KerberosAuthException on a failure
+   */
+  @InterfaceAudience.Public
+  @InterfaceStability.Evolving
+  public void forceReloginFromKeytab() throws IOException {
+    reloginFromKeytab(true);
+  }
+
+  private synchronized void reloginFromKeytab(boolean ignoreTimeElapsed)
+      throws IOException {
     if (!isSecurityEnabled()
         || user.getAuthenticationMethod() != AuthenticationMethod.KERBEROS
         || !isKeytab) {
@@ -1231,7 +1253,8 @@ public class UserGroupInformation {
     }
 
     long now = Time.now();
-    if (!shouldRenewImmediatelyForTests && !hasSufficientTimeElapsed(now)) {
+    if (!shouldRenewImmediatelyForTests && !ignoreTimeElapsed
+        && !hasSufficientTimeElapsed(now)) {
       return;
     }
 

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/security/TestUGILoginFromKeytab.java

@@ -31,6 +31,8 @@ import org.junit.rules.TemporaryFolder;
 
 import java.io.File;
 
+import javax.security.auth.login.LoginContext;
+
 /**
  * Verify UGI login from keytab. Check that the UGI is
  * configured to use keytab to catch regressions like
@@ -115,4 +117,39 @@ public class TestUGILoginFromKeytab {
         secondLogin > firstLogin);
   }
 
+  /**
+   * Force re-login from keytab using the MiniKDC and verify the UGI can
+   * successfully relogin from keytab as well.
+   */
+  @Test
+  public void testUGIForceReLoginFromKeytab() throws Exception {
+    UserGroupInformation.setShouldRenewImmediatelyForTests(true);
+    String principal = "foo";
+    File keytab = new File(workDir, "foo.keytab");
+    kdc.createPrincipal(keytab, principal);
+
+    UserGroupInformation.loginUserFromKeytab(principal, keytab.getPath());
+    UserGroupInformation ugi = UserGroupInformation.getLoginUser();
+    Assert.assertTrue("UGI should be configured to login from keytab",
+        ugi.isFromKeytab());
+
+    // Verify relogin from keytab.
+    User user = ugi.getSubject().getPrincipals(User.class).iterator().next();
+    final long firstLogin = user.getLastLogin();
+    final LoginContext login1 = user.getLogin();
+    Assert.assertNotNull(login1);
+
+    // Sleep for 2 secs to have a difference between first and second login
+    Thread.sleep(2000);
+
+    // Force relogin from keytab
+    ugi.forceReloginFromKeytab();
+    final long secondLogin = user.getLastLogin();
+    final LoginContext login2 = user.getLogin();
+    Assert.assertTrue("User should have been able to relogin from keytab",
+        secondLogin > firstLogin);
+    Assert.assertNotNull(login2);
+    Assert.assertNotSame(login1, login2);
+  }
+
 }