src/docs/src/documentation/content/xdocs/Secure_Impersonation.xml - hadoop - Git at Google

 <?xml version="1.0"?>
 <!--
   Copyright 2002-2004 The Apache Software Foundation

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
 -->

 <!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V2.0//EN"
           "http://forrest.apache.org/dtd/document-v20.dtd">


 <document>

   <header>
     <title>
       Secure Impersonation using UserGroupInformation.doAs
     </title>
   </header>

   <body>
     <section>
       <title> Introduction </title>
       <p>
         This document describes how a superuser can submit jobs or access hdfs on behalf of another user in a secured way.
       </p>
     </section>

     <section>
       <title> Use Case  </title>
         <p>
           The code example described in the next section is applicable for the following use case.
         </p>
         <p>
           A superuser oozie wants to submit job and access hdfs on behalf of a user joe. The superuser has kerberos credentials but user joe doesn't have any. The tasks are required to run as user joe and any file accesses on namenode are required to be done as user joe. It is required that user joe can connect to the namenode or job tracker on a connection authenticated with oozie's kerberos credentials. In other words oozie is impersonating the user joe.
        </p>
      </section>


       <section>
         <title> Code example  </title>
         <p>
              In this example oozie's kerberos credentials are used for login and a proxy user ugi object is created for joe. The operations are performed within the doAs method of this proxy user ugi object.
         </p>
         <source>
              ...
              UserGroupInformation ugi =
                      UserGroupInformation.createProxyUser(user, UserGroupInformation.getLoginUser());
              ugi.doAs(new PrivilegedExceptionAction&lt;Void&gt;() {
                public Void run() throws Exception {
                  //Submit a job
                  JobClient jc = new JobClient(conf);
                  jc.submitJob(conf);
                  //OR access hdfs
                  FileSystem fs = FileSystem.get(conf);
                  fs.mkdir(someFilePath);
                }
              }
         </source>
       </section>

       <section>
         <title> Configurations </title>
         <p>
            The superuser must be configured on namenode and jobtracker to be allowed to impersonate another user. Following configurations are required.
         </p>
            <source>
              &lt;property&gt;
                &lt;name&gt;hadoop.proxyuser.oozie.groups&lt;/name&gt;
                &lt;value&gt;group1,group2&lt;/value&gt;
                &lt;description&gt;Allow the superuser oozie to impersonate any members of the group group1 and group2&lt;/description&gt;
              &lt;/property&gt;
              &lt;property&gt;
                &lt;name&gt;hadoop.proxyuser.oozie.hosts&lt;/name&gt;
                &lt;value&gt;host1,host2&lt;/value&gt;
                &lt;description&gt;The superuser can connect only from host1 and host2 to impersonate a user&lt;/description&gt;
              &lt;/property&gt;
            </source>
         <p>
            If these configurations are not present, impersonation will not be allowed and connection will fail.
         </p>
       </section>


       <section>
         <title> Caveats </title>
         <p>
            The superuser must have kerberos credentials to be able to impersonate another user. It cannot use delegation tokens for this feature. It would be wrong if superuser adds its own delegation token to the proxy user ugi, as it will allow the proxy user to connect to the service with the privileges of the superuser.
         </p>
         <p>
            However, if the superuser does want to give a delegation token to joe, it must first impersonate joe and get a delegation token for joe, in the same way as the code example above, and add it to the ugi of joe. In this way the delegation token will have the owner as joe.
         </p>
       </section>
   </body>
 </document>
	<?xml version="1.0"?>
	<!--
	Copyright 2002-2004 The Apache Software Foundation

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->

	<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V2.0//EN"
	"http://forrest.apache.org/dtd/document-v20.dtd">


	<document>

	<header>
	<title>
	Secure Impersonation using UserGroupInformation.doAs
	</title>
	</header>

	<body>
	<section>
	<title> Introduction </title>
	<p>
	This document describes how a superuser can submit jobs or access hdfs on behalf of another user in a secured way.
	</p>
	</section>

	<section>
	<title> Use Case </title>
	<p>
	The code example described in the next section is applicable for the following use case.
	</p>
	<p>
	A superuser oozie wants to submit job and access hdfs on behalf of a user joe. The superuser has kerberos credentials but user joe doesn't have any. The tasks are required to run as user joe and any file accesses on namenode are required to be done as user joe. It is required that user joe can connect to the namenode or job tracker on a connection authenticated with oozie's kerberos credentials. In other words oozie is impersonating the user joe.
	</p>
	</section>


	<section>
	<title> Code example </title>
	<p>
	In this example oozie's kerberos credentials are used for login and a proxy user ugi object is created for joe. The operations are performed within the doAs method of this proxy user ugi object.
	</p>
	<source>
	...
	UserGroupInformation ugi =
	UserGroupInformation.createProxyUser(user, UserGroupInformation.getLoginUser());
	ugi.doAs(new PrivilegedExceptionAction<Void>() {
	public Void run() throws Exception {
	//Submit a job
	JobClient jc = new JobClient(conf);
	jc.submitJob(conf);
	//OR access hdfs
	FileSystem fs = FileSystem.get(conf);
	fs.mkdir(someFilePath);
	}
	}
	</source>
	</section>

	<section>
	<title> Configurations </title>
	<p>
	The superuser must be configured on namenode and jobtracker to be allowed to impersonate another user. Following configurations are required.
	</p>
	<source>
	<property>
	<name>hadoop.proxyuser.oozie.groups</name>
	<value>group1,group2</value>
	<description>Allow the superuser oozie to impersonate any members of the group group1 and group2</description>
	</property>
	<property>
	<name>hadoop.proxyuser.oozie.hosts</name>
	<value>host1,host2</value>
	<description>The superuser can connect only from host1 and host2 to impersonate a user</description>
	</property>
	</source>
	<p>
	If these configurations are not present, impersonation will not be allowed and connection will fail.
	</p>
	</section>


	<section>
	<title> Caveats </title>
	<p>
	The superuser must have kerberos credentials to be able to impersonate another user. It cannot use delegation tokens for this feature. It would be wrong if superuser adds its own delegation token to the proxy user ugi, as it will allow the proxy user to connect to the service with the privileges of the superuser.
	</p>
	<p>
	However, if the superuser does want to give a delegation token to joe, it must first impersonate joe and get a delegation token for joe, in the same way as the code example above, and add it to the ugi of joe. In this way the delegation token will have the owner as joe.
	</p>
	</section>
	</body>
	</document>