Clean up an IPC error message. Contributed by Aaron T. Myers.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1494701 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -119,6 +119,9 @@ public class CommonConfigurationKeys extends CommonConfigurationKeysPublic {
       "hadoop.security.token.service.use_ip";
   public static final boolean HADOOP_SECURITY_TOKEN_SERVICE_USE_IP_DEFAULT =
       true;
+  
+  public static final String  IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY = "ipc.client.fallback-to-simple-auth-allowed";
+  public static final boolean IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_DEFAULT = false;
 
 }
 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java

@@ -86,6 +86,8 @@ public class Client {
 
   private SocketFactory socketFactory;           // how to create sockets
   private int refCount = 1;
+
+  private final boolean fallbackAllowed;
   
   final static int PING_CALL_ID = -1;
   
@@ -402,7 +404,8 @@ public class Client {
     private synchronized boolean setupSaslConnection(final InputStream in2, 
         final OutputStream out2) 
         throws IOException {
-      saslRpcClient = new SaslRpcClient(authMethod, token, serverPrincipal);
+      saslRpcClient = new SaslRpcClient(authMethod, token, serverPrincipal,
+          fallbackAllowed);
       return saslRpcClient.saslConnect(in2, out2);
     }
 
@@ -950,6 +953,9 @@ public class Client {
     this.valueClass = valueClass;
     this.conf = conf;
     this.socketFactory = factory;
+    this.fallbackAllowed = conf.getBoolean(CommonConfigurationKeys.IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY,
+        CommonConfigurationKeys.IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_DEFAULT);
+
   }
 
   /**

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

@@ -57,6 +57,7 @@ public class SaslRpcClient {
   public static final Log LOG = LogFactory.getLog(SaslRpcClient.class);
 
   private final SaslClient saslClient;
+  private final boolean fallbackAllowed;
 
   /**
    * Create a SaslRpcClient for an authentication method
@@ -67,8 +68,10 @@ public class SaslRpcClient {
    *          token to use if needed by the authentication method
    */
   public SaslRpcClient(AuthMethod method,
-      Token<? extends TokenIdentifier> token, String serverPrincipal)
+      Token<? extends TokenIdentifier> token, String serverPrincipal,
+      boolean fallbackAllowed)
       throws IOException {
+    this.fallbackAllowed = fallbackAllowed;
     switch (method) {
     case DIGEST:
       if (LOG.isDebugEnabled())
@@ -147,6 +150,11 @@ public class SaslRpcClient {
         readStatus(inStream);
         int len = inStream.readInt();
         if (len == SaslRpcServer.SWITCH_TO_SIMPLE_AUTH) {
+          if (!fallbackAllowed) {
+            throw new IOException("Server asks us to fall back to SIMPLE " +
+                "auth, but this client is configured to only allow secure " +
+                "connections.");
+          }
           if (LOG.isDebugEnabled())
             LOG.debug("Server asks us to fall back to simple auth.");
           saslClient.dispose();

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

@@ -873,4 +873,17 @@
   </description>
 </property>
 
+<property>
+  <name>ipc.client.fallback-to-simple-auth-allowed</name>
+  <value>false</value>
+  <description>
+    When a client is configured to attempt a secure connection, but attempts to
+    connect to an insecure server, that server may instruct the client to
+    switch to SASL SIMPLE (unsecure) authentication. This setting controls
+    whether or not the client will accept this instruction from the server.
+    When false (the default), the client will not allow the fallback to SIMPLE
+    authentication, and will abort the connection.
+  </description>
+</property>
+
 </configuration>