SPNEGO TLS verification

Signed-off-by: Akira Ajisaka <aajisaka@apache.org>
(cherry picked from commit 81d8a887b0406380e469c76ed2e41022a6372dd7)
(cherry picked from commit d73cdb1c8650241b0157c01ce1510e161ad1fe52)

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/WebHdfsFileSystem.java

@@ -152,6 +152,7 @@ public class WebHdfsFileSystem extends FileSystem
       + "/v" + VERSION;
   public static final String EZ_HEADER = "X-Hadoop-Accept-EZ";
   public static final String FEFINFO_HEADER = "X-Hadoop-feInfo";
+  public static final String DFS_HTTP_POLICY_KEY = "dfs.http.policy";
 
   /**
    * Default connection factory may be overridden in tests to use smaller
@@ -181,6 +182,7 @@ public class WebHdfsFileSystem extends FileSystem
 
   private DFSOpsCountStatistics storageStatistics;
   private KeyProvider testProvider;
+  private boolean isTLSKrb;
 
   /**
    * Return the protocol scheme for the FileSystem.
@@ -242,6 +244,7 @@ public class WebHdfsFileSystem extends FileSystem
           .newDefaultURLConnectionFactory(connectTimeout, readTimeout, conf);
     }
 
+    this.isTLSKrb = "HTTPS_ONLY".equals(conf.get(DFS_HTTP_POLICY_KEY));
 
     ugi = UserGroupInformation.getCurrentUser();
     this.uri = URI.create(uri.getScheme() + "://" + uri.getAuthority());
@@ -699,6 +702,11 @@ public class WebHdfsFileSystem extends FileSystem
       //redirect hostname and port
       redirectHost = null;
 
+      if (url.getProtocol().equals("http") &&
+        UserGroupInformation.isSecurityEnabled() &&
+        isTLSKrb) {
+        throw new IOException("Access denied: dfs.http.policy is HTTPS_ONLY.");
+      }
 
       // resolve redirects for a DN operation unless already resolved
       if (op.getRedirect() && !redirected) {