HADOOP-12437. Allow SecurityUtil to lookup alternate hostnames. (Contributed by Arpit Agarwal)

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -638,6 +638,9 @@ Release 2.8.0 - UNRELEASED
     HADOOP-12438. Reset RawLocalFileSystem.useDeprecatedFileStatus in
     TestLocalFileSystem. (Chris Nauroth via wheat9)
 
+    HADOOP-12437. Allow SecurityUtil to lookup alternate hostnames.
+    (Arpit Agarwal)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeysPublic.java

@@ -299,6 +299,12 @@ public class CommonConfigurationKeysPublic {
   /** See <a href="{@docRoot}/../core-default.html">core-default.xml</a> */
   public static final String  HADOOP_SECURITY_AUTH_TO_LOCAL =
     "hadoop.security.auth_to_local";
+  /** See <a href="{@docRoot}/../core-default.html">core-default.xml</a> */
+  public static final String HADOOP_SECURITY_DNS_INTERFACE_KEY =
+    "hadoop.security.dns.interface";
+  /** See <a href="{@docRoot}/../core-default.html">core-default.xml</a> */
+  public static final String HADOOP_SECURITY_DNS_NAMESERVER_KEY =
+    "hadoop.security.dns.nameserver";
 
   @Deprecated
   /** Only used by HttpServer. */

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/DNS.java

@@ -18,6 +18,8 @@
 
 package org.apache.hadoop.net;
 
+import com.google.common.net.InetAddresses;
+import com.sun.istack.Nullable;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
@@ -27,9 +29,11 @@ import java.net.InetAddress;
 import java.net.NetworkInterface;
 import java.net.SocketException;
 import java.net.UnknownHostException;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Vector;
 
 import javax.naming.NamingException;
@@ -68,7 +72,7 @@ public class DNS {
    * @return The host name associated with the provided IP
    * @throws NamingException If a NamingException is encountered
    */
-  public static String reverseDns(InetAddress hostIp, String ns)
+  public static String reverseDns(InetAddress hostIp, @Nullable String ns)
     throws NamingException {
     //
     // Builds the reverse IP lookup form
@@ -228,28 +232,44 @@ public class DNS {
    *            (e.g. eth0 or eth0:0)
    * @param nameserver
    *            The DNS host name
+   * @param tryfallbackResolution
+   *            if true and if reverse DNS resolution fails then attempt to
+   *            resolve the hostname with
+   *            {@link InetAddress#getCanonicalHostName()} which includes
+   *            hosts file resolution.
    * @return A string vector of all host names associated with the IPs tied to
    *         the specified interface
    * @throws UnknownHostException if the given interface is invalid
    */
-  public static String[] getHosts(String strInterface, String nameserver)
+  public static String[] getHosts(String strInterface,
-    throws UnknownHostException {
+                                  @Nullable String nameserver,
-    String[] ips = getIPs(strInterface);
+                                  boolean tryfallbackResolution)
-    Vector<String> hosts = new Vector<String>();
+      throws UnknownHostException {
-    for (int ctr = 0; ctr < ips.length; ctr++) {
+    final List<String> hosts = new Vector<String>();
+    final List<InetAddress> addresses =
+        getIPsAsInetAddressList(strInterface, true);
+    for (InetAddress address : addresses) {
       try {
-        hosts.add(reverseDns(InetAddress.getByName(ips[ctr]),
+        hosts.add(reverseDns(address, nameserver));
-                             nameserver));
-      } catch (UnknownHostException ignored) {
       } catch (NamingException ignored) {
       }
     }
-    if (hosts.isEmpty()) {
+    if (hosts.isEmpty() && tryfallbackResolution) {
-      LOG.warn("Unable to determine hostname for interface " + strInterface);
+      for (InetAddress address : addresses) {
-      return new String[] { cachedHostname };
+        final String canonicalHostName = address.getCanonicalHostName();
-    } else {
+        // Don't use the result if it looks like an IP address.
-      return hosts.toArray(new String[hosts.size()]);
+        if (!InetAddresses.isInetAddress(canonicalHostName)) {
+          hosts.add(canonicalHostName);
+        }
+      }
     }
+
+    if (hosts.isEmpty()) {
+      LOG.warn("Unable to determine hostname for interface " +
+          strInterface);
+      hosts.add(cachedHostname);
+    }
+    return hosts.toArray(new String[hosts.size()]);
   }
 
 
@@ -315,7 +335,7 @@ public class DNS {
    */
   public static String[] getHosts(String strInterface)
     throws UnknownHostException {
-    return getHosts(strInterface, null);
+    return getHosts(strInterface, null, false);
   }
 
   /**
@@ -331,17 +351,19 @@ public class DNS {
    * @throws UnknownHostException
    *             If one is encountered while querying the default interface
    */
-  public static String getDefaultHost(String strInterface, String nameserver)
+  public static String getDefaultHost(@Nullable String strInterface,
+                                      @Nullable String nameserver,
+                                      boolean tryfallbackResolution)
     throws UnknownHostException {
-    if ("default".equals(strInterface)) {
+    if (strInterface == null || "default".equals(strInterface)) {
       return cachedHostname;
     }
 
-    if ("default".equals(nameserver)) {
+    if (nameserver != null && "default".equals(nameserver)) {
-      return getDefaultHost(strInterface);
+      nameserver = null;
     }
 
-    String[] hosts = getHosts(strInterface, nameserver);
+    String[] hosts = getHosts(strInterface, nameserver, tryfallbackResolution);
     return hosts[0];
   }
 
@@ -357,9 +379,74 @@ public class DNS {
    * @throws UnknownHostException
    *             If one is encountered while querying the default interface
    */
-  public static String getDefaultHost(String strInterface)
+  public static String getDefaultHost(@Nullable String strInterface)
     throws UnknownHostException {
-    return getDefaultHost(strInterface, null);
+    return getDefaultHost(strInterface, null, false);
   }
 
+  /**
+   * Returns the default (first) host name associated by the provided
+   * nameserver with the address bound to the specified network interface.
+   *
+   * @param strInterface
+   *            The name of the network interface to query (e.g. eth0)
+   * @param nameserver
+   *            The DNS host name
+   * @throws UnknownHostException
+   *             If one is encountered while querying the default interface
+   */
+  public static String getDefaultHost(@Nullable String strInterface,
+                                      @Nullable String nameserver)
+      throws UnknownHostException {
+    return getDefaultHost(strInterface, nameserver, false);
+  }
+
+  /**
+   * Returns all the IPs associated with the provided interface, if any, as
+   * a list of InetAddress objects.
+   *
+   * @param strInterface
+   *            The name of the network interface or sub-interface to query
+   *            (eg eth0 or eth0:0) or the string "default"
+   * @param returnSubinterfaces
+   *            Whether to return IPs associated with subinterfaces of
+   *            the given interface
+   * @return A list of all the IPs associated with the provided
+   *         interface. The local host IP is returned if the interface
+   *         name "default" is specified or there is an I/O error looking
+   *         for the given interface.
+   * @throws UnknownHostException
+   *             If the given interface is invalid
+   *
+   */
+  public static List<InetAddress> getIPsAsInetAddressList(String strInterface,
+      boolean returnSubinterfaces) throws UnknownHostException {
+    if ("default".equals(strInterface)) {
+      return Arrays.asList(InetAddress.getByName(cachedHostAddress));
+    }
+    NetworkInterface netIf;
+    try {
+      netIf = NetworkInterface.getByName(strInterface);
+      if (netIf == null) {
+        netIf = getSubinterface(strInterface);
+      }
+    } catch (SocketException e) {
+      LOG.warn("I/O error finding interface " + strInterface +
+          ": " + e.getMessage());
+      return Arrays.asList(InetAddress.getByName(cachedHostAddress));
+    }
+    if (netIf == null) {
+      throw new UnknownHostException("No such interface " + strInterface);
+    }
+
+    // NB: Using a LinkedHashSet to preserve the order for callers
+    // that depend on a particular element being 1st in the array.
+    // For example, getDefaultIP always returns the first element.
+    LinkedHashSet<InetAddress> allAddrs = new LinkedHashSet<InetAddress>();
+    allAddrs.addAll(Collections.list(netIf.getInetAddresses()));
+    if (!returnSubinterfaces) {
+      allAddrs.removeAll(getSubinterfaceInetAddrs(netIf));
+    }
+    return new Vector<InetAddress>(allAddrs);
+  }
 }

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

@@ -17,6 +17,8 @@
 package org.apache.hadoop.security;
 
 import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.HADOOP_SECURITY_AUTHENTICATION;
+import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.HADOOP_SECURITY_DNS_INTERFACE_KEY;
+import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.HADOOP_SECURITY_DNS_NAMESERVER_KEY;
 
 import java.io.IOException;
 import java.net.InetAddress;
@@ -29,6 +31,7 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.ServiceLoader;
 
+import javax.annotation.Nullable;
 import javax.security.auth.kerberos.KerberosPrincipal;
 import javax.security.auth.kerberos.KerberosTicket;
 
@@ -39,6 +42,7 @@ import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.CommonConfigurationKeys;
 import org.apache.hadoop.io.Text;
+import org.apache.hadoop.net.DNS;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.security.UserGroupInformation.AuthenticationMethod;
 import org.apache.hadoop.security.token.Token;
@@ -180,13 +184,38 @@ public class SecurityUtil {
       throws IOException {
     String fqdn = hostname;
     if (fqdn == null || fqdn.isEmpty() || fqdn.equals("0.0.0.0")) {
-      fqdn = getLocalHostName();
+      fqdn = getLocalHostName(null);
     }
     return components[0] + "/" +
         StringUtils.toLowerCase(fqdn) + "@" + components[2];
   }
-  
+
-  static String getLocalHostName() throws UnknownHostException {
+  /**
+   * Retrieve the name of the current host. Multihomed hosts may restrict the
+   * hostname lookup to a specific interface and nameserver with {@link
+   * org.apache.hadoop.fs.CommonConfigurationKeysPublic#HADOOP_SECURITY_DNS_INTERFACE_KEY}
+   * and {@link org.apache.hadoop.fs.CommonConfigurationKeysPublic#HADOOP_SECURITY_DNS_NAMESERVER_KEY}
+   *
+   * @param conf Configuration object. May be null.
+   * @return
+   * @throws UnknownHostException
+   */
+  static String getLocalHostName(@Nullable Configuration conf)
+      throws UnknownHostException {
+    if (conf != null) {
+      String dnsInterface = conf.get(HADOOP_SECURITY_DNS_INTERFACE_KEY);
+      String nameServer = conf.get(HADOOP_SECURITY_DNS_NAMESERVER_KEY);
+
+      if (dnsInterface != null) {
+        return DNS.getDefaultHost(dnsInterface, nameServer, true);
+      } else if (nameServer != null) {
+        throw new IllegalArgumentException(HADOOP_SECURITY_DNS_NAMESERVER_KEY +
+            " requires " + HADOOP_SECURITY_DNS_INTERFACE_KEY + ". Check your" +
+            "configuration.");
+      }
+    }
+
+    // Fallback to querying the default hostname as we did before.
     return InetAddress.getLocalHost().getCanonicalHostName();
   }
 
@@ -207,7 +236,7 @@ public class SecurityUtil {
   @InterfaceStability.Evolving
   public static void login(final Configuration conf,
       final String keytabFileKey, final String userNameKey) throws IOException {
-    login(conf, keytabFileKey, userNameKey, getLocalHostName());
+    login(conf, keytabFileKey, userNameKey, getLocalHostName(conf));
   }
 
   /**

hadoop-common-project/hadoop-common/src/main/resources/core-default.xml

@@ -97,6 +97,31 @@
   </description>
 </property>
 
+<property>
+  <name>hadoop.security.dns.interface</name>
+  <description>
+    The name of the Network Interface from which the service should determine
+    its host name for Kerberos login. e.g. eth2. In a multi-homed environment,
+    the setting can be used to affect the _HOST subsitution in the service
+    Kerberos principal. If this configuration value is not set, the service
+    will use its default hostname as returned by
+    InetAddress.getLocalHost().getCanonicalHostName().
+
+    Most clusters will not require this setting.
+  </description>
+</property>
+
+<property>
+  <name>hadoop.security.dns.nameserver</name>
+  <description>
+    The host name or IP address of the name server (DNS) which a service Node
+    should use to determine its own host name for Kerberos Login. Requires
+    hadoop.security.dns.interface.
+
+    Most clusters will not require this setting.
+  </description>
+</property>
+
 <!-- 
 === Multiple group mapping providers configuration sample === 
   This sample illustrates a typical use case for CompositeGroupsMapping where

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/TestDNS.java

@@ -18,6 +18,10 @@
 
 package org.apache.hadoop.net;
 
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.net.NetworkInterface;
+import java.net.SocketException;
 import java.net.UnknownHostException;
 import java.net.InetAddress;
 
@@ -28,6 +32,9 @@ import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.util.Time;
 
 import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.not;
+import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.*;
 
 /**
@@ -38,6 +45,11 @@ public class TestDNS {
   private static final Log LOG = LogFactory.getLog(TestDNS.class);
   private static final String DEFAULT = "default";
 
+  // This is not a legal hostname (starts with a hyphen). It will never
+  // be returned on any test machine.
+  private static final String DUMMY_HOSTNAME = "-DUMMY_HOSTNAME";
+  private static final String INVALID_DNS_SERVER = "0.0.0.0";
+
   /**
    * Test that asking for the default hostname works
    * @throws Exception if hostname lookups fail
@@ -89,12 +101,8 @@ public class TestDNS {
    */
   @Test
   public void testNullInterface() throws Exception {
-    try {
+    String host = DNS.getDefaultHost(null);  // should work.
-      String host = DNS.getDefaultHost(null);
+    assertThat(host, is(DNS.getDefaultHost(DEFAULT)));
-      fail("Expected a NullPointerException, got " + host);
-    } catch (NullPointerException npe) {
-      // Expected
-    }
     try {
       String ip = DNS.getDefaultIP(null);
       fail("Expected a NullPointerException, got " + ip);
@@ -103,6 +111,26 @@ public class TestDNS {
     }
   }
 
+  /**
+   * Test that 'null' DNS server gives the same result as if no DNS
+   * server was passed.
+   */
+  @Test
+  public void testNullDnsServer() throws Exception {
+    String host = DNS.getDefaultHost(getLoopbackInterface(), null);
+    assertThat(host, is(DNS.getDefaultHost(getLoopbackInterface())));
+  }
+
+  /**
+   * Test that "default" DNS server gives the same result as if no DNS
+   * server was passed.
+   */
+  @Test
+  public void testDefaultDnsServer() throws Exception {
+    String host = DNS.getDefaultHost(getLoopbackInterface(), DEFAULT);
+    assertThat(host, is(DNS.getDefaultHost(getLoopbackInterface())));
+  }
+
   /**
    * Get the IP addresses of an unknown interface
    */
@@ -147,10 +175,80 @@ public class TestDNS {
                 + " Loopback=" + localhost.isLoopbackAddress()
                 + " Linklocal=" + localhost.isLinkLocalAddress());
       }
-
     }
   }
 
+  /**
+   * Test that when using an invalid DNS server with hosts file fallback,
+   * we are able to get the hostname from the hosts file.
+   *
+   * This test may fail on some misconfigured test machines that don't have
+   * an entry for "localhost" in their hosts file. This entry is correctly
+   * configured out of the box on common Linux distributions, OS X and
+   * Windows.
+   *
+   * @throws Exception
+   */
+  @Test (timeout=60000)
+  public void testLookupWithHostsFallback() throws Exception {
+    final String oldHostname = changeDnsCachedHostname(DUMMY_HOSTNAME);
+
+    try {
+      String hostname = DNS.getDefaultHost(
+          getLoopbackInterface(), INVALID_DNS_SERVER, true);
+
+      // Expect to get back something other than the cached host name.
+      assertThat(hostname, not(DUMMY_HOSTNAME));
+    } finally {
+      // Restore DNS#cachedHostname for subsequent tests.
+      changeDnsCachedHostname(oldHostname);
+    }
+  }
+
+  /**
+   * Test that when using an invalid DNS server without hosts file
+   * fallback, we get back the cached host name.
+   *
+   * @throws Exception
+   */
+  @Test(timeout=60000)
+  public void testLookupWithoutHostsFallback() throws Exception {
+    final String oldHostname = changeDnsCachedHostname(DUMMY_HOSTNAME);
+
+    try {
+      String hostname = DNS.getDefaultHost(
+          getLoopbackInterface(), INVALID_DNS_SERVER, false);
+
+      // Expect to get back the cached host name since there was no hosts
+      // file lookup.
+      assertThat(hostname, is(DUMMY_HOSTNAME));
+    } finally {
+      // Restore DNS#cachedHostname for subsequent tests.
+      changeDnsCachedHostname(oldHostname);
+    }
+  }
+
+  private String getLoopbackInterface() throws SocketException {
+    return NetworkInterface.getByInetAddress(
+        InetAddress.getLoopbackAddress()).getDisplayName();
+  }
+
+  /**
+   * Change DNS#cachedHostName to something which cannot be a real
+   * host name. Uses reflection since it is a 'private final' field.
+   */
+  private String changeDnsCachedHostname(final String newHostname)
+      throws Exception {
+    final String oldCachedHostname = DNS.getDefaultHost(DEFAULT);
+    Field field = DNS.class.getDeclaredField("cachedHostname");
+    field.setAccessible(true);
+    Field modifiersField = Field.class.getDeclaredField("modifiers");
+    modifiersField.setAccessible(true);
+    modifiersField.set(field, field.getModifiers() & ~Modifier.FINAL);
+    field.set(null, newHostname);
+    return oldCachedHostname;
+  }
+
   /**
    * Test that the name "localhost" resolves to something.
    *

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

@@ -110,7 +110,7 @@ public class TestSecurityUtil {
 
   @Test
   public void testLocalHostNameForNullOrWild() throws Exception {
-    String local = StringUtils.toLowerCase(SecurityUtil.getLocalHostName());
+    String local = StringUtils.toLowerCase(SecurityUtil.getLocalHostName(null));
     assertEquals("hdfs/" + local + "@REALM",
                  SecurityUtil.getServerPrincipal("hdfs/_HOST@REALM", (String)null));
     assertEquals("hdfs/" + local + "@REALM",

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java

@@ -768,11 +768,24 @@ public class DataNode extends ReconfigurableBase
       throws UnknownHostException {
     String name = config.get(DFS_DATANODE_HOST_NAME_KEY);
     if (name == null) {
-      name = DNS.getDefaultHost(
+      String dnsInterface = config.get(
-          config.get(DFS_DATANODE_DNS_INTERFACE_KEY,
+          CommonConfigurationKeys.HADOOP_SECURITY_DNS_INTERFACE_KEY);
-                     DFS_DATANODE_DNS_INTERFACE_DEFAULT),
+      String nameServer = config.get(
-          config.get(DFS_DATANODE_DNS_NAMESERVER_KEY,
+          CommonConfigurationKeys.HADOOP_SECURITY_DNS_NAMESERVER_KEY);
-                     DFS_DATANODE_DNS_NAMESERVER_DEFAULT));
+      boolean fallbackToHosts = false;
+
+      if (dnsInterface == null) {
+        // Try the legacy configuration keys.
+        dnsInterface = config.get(DFS_DATANODE_DNS_INTERFACE_KEY);
+        nameServer = config.get(DFS_DATANODE_DNS_NAMESERVER_KEY);
+      } else {
+        // If HADOOP_SECURITY_DNS_* is set then also attempt hosts file
+        // resolution if DNS fails. We will not use hosts file resolution
+        // by default to avoid breaking existing clusters.
+        fallbackToHosts = true;
+      }
+
+      name = DNS.getDefaultHost(dnsInterface, nameServer, fallbackToHosts);
     }
     return name;
   }
@@ -2320,7 +2333,7 @@ public class DataNode extends ReconfigurableBase
     Collection<StorageLocation> dataLocations = getStorageLocations(conf);
     UserGroupInformation.setConfiguration(conf);
     SecurityUtil.login(conf, DFS_DATANODE_KEYTAB_FILE_KEY,
-        DFS_DATANODE_KERBEROS_PRINCIPAL_KEY);
+        DFS_DATANODE_KERBEROS_PRINCIPAL_KEY, getHostName(conf));
     return makeInstance(dataLocations, conf, resources);
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -225,19 +225,28 @@
 </property>
 
  <property>
-  <name>dfs.datanode.dns.interface</name>
+   <name>dfs.datanode.dns.interface</name>
-  <value>default</value>
+   <value>default</value>
-  <description>The name of the Network Interface from which a data node should 
+   <description>
-  report its IP address.
+     The name of the Network Interface from which a data node should
-  </description>
+     report its IP address. e.g. eth2. This setting may be required for some
+     multi-homed nodes where the DataNodes are assigned multiple hostnames
+     and it is desirable for the DataNodes to use a non-default hostname.
+
+     Prefer using hadoop.security.dns.interface over
+     dfs.datanode.dns.interface.
+   </description>
  </property>
  
 <property>
   <name>dfs.datanode.dns.nameserver</name>
   <value>default</value>
-  <description>The host name or IP address of the name server (DNS)
+  <description>
-  which a DataNode should use to determine the host name used by the
+    The host name or IP address of the name server (DNS) which a DataNode
-  NameNode for communication and display purposes.
+    should use to determine its own host name.
+
+    Prefer using hadoop.security.dns.nameserver over
+    dfs.datanode.dns.nameserver.
   </description>
  </property>