HADOOP-17159 Ability for forceful relogin in UserGroupInformation class (#2197)

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

@@ -1232,7 +1232,26 @@ public class UserGroupInformation {
     reloginFromKeytab(false);
   }
 
-  private void reloginFromKeytab(boolean checkTGT) throws IOException {
+  /**
+   * Force 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.
+   *
+   * @param ignoreTimeElapsed Force re-login irrespective of the time of last
+   *                          login
+   * @throws IOException
+   * @throws KerberosAuthException on a failure
+   */
+  @InterfaceAudience.Public
+  @InterfaceStability.Evolving
+  public void reloginFromKeytab(boolean ignoreTimeElapsed) throws IOException {
+    reloginFromKeytab(false, ignoreTimeElapsed);
+  }
+
+  private void reloginFromKeytab(boolean checkTGT, boolean ignoreTimeElapsed)
+      throws IOException {
     if (!shouldRelogin() || !isFromKeytab()) {
       return;
     }
@@ -1247,7 +1266,7 @@ public class UserGroupInformation {
         return;
       }
     }
-    relogin(login);
+    relogin(login, ignoreTimeElapsed);
   }
 
   /**
@@ -1268,25 +1287,27 @@ public class UserGroupInformation {
     if (login == null) {
       throw new KerberosAuthException(MUST_FIRST_LOGIN);
     }
-    relogin(login);
+    relogin(login, false);
   }
 
-  private void relogin(HadoopLoginContext login) throws IOException {
+  private void relogin(HadoopLoginContext login, boolean ignoreTimeElapsed)
+      throws IOException {
     // ensure the relogin is atomic to avoid leaving credentials in an
     // inconsistent state.  prevents other ugi instances, SASL, and SPNEGO
     // from accessing or altering credentials during the relogin.
     synchronized(login.getSubjectLock()) {
       // another racing thread may have beat us to the relogin.
       if (login == getLogin()) {
-        unprotectedRelogin(login);
+        unprotectedRelogin(login, ignoreTimeElapsed);
       }
     }
   }
 
-  private void unprotectedRelogin(HadoopLoginContext login) throws IOException {
+  private void unprotectedRelogin(HadoopLoginContext login,
+      boolean ignoreTimeElapsed) throws IOException {
     assert Thread.holdsLock(login.getSubjectLock());
     long now = Time.now();
-    if (!hasSufficientTimeElapsed(now)) {
+    if (!hasSufficientTimeElapsed(now) && !ignoreTimeElapsed) {
       return;
     }
     // register most recent relogin attempt

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

@@ -158,6 +158,42 @@ public class TestUGILoginFromKeytab {
     Assert.assertNotSame(login1, login2);
   }
 
+  /**
+   * 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 {
+    // Set this to false as we are testing force re-login anyways
+    UserGroupInformation.setShouldRenewImmediatelyForTests(false);
+    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 = getUser(ugi.getSubject());
+    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.reloginFromKeytab(true);
+    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);
+  }
+
   @Test
   public void testGetUGIFromKnownSubject() throws Exception {
     KerberosPrincipal principal = new KerberosPrincipal("user");