Alejandro Abdelnur created HADOOP-13558:
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Summary: UserGroupInformation created from a Subject incorrectly
tries to renew the Keberos ticket
Key: HADOOP-13558
URL: https://issues.apache.org/jira/browse/HADOOP-13558
Project: Hadoop Common
Issue Type: Bug
Components: security
Affects Versions: 2.6.4, 2.7.2, 3.0.0-alpha2
Reporter: Alejandro Abdelnur
The UGI {{checkTGTAndReloginFromKeytab()}} method checks certain conditions and
if they are met it invokes the {{reloginFromKeytab()}}. The
{{reloginFromKeytab()}} method then fails with an {{IOException}}
"loginUserFromKeyTab must be done first" because there is no keytab associated
with the UGI.
The {{checkTGTAndReloginFromKeytab()}} method checks if there is a keytab
({{isKeytab}} UGI instance variable) associated with the UGI, if there is one
it triggers a call to {{reloginFromKeytab()}}. The problem is that the
{{keytabFile}} UGI instance variable is NULL, and that triggers the mentioned
{{IOException}}.
The root of the problem seems to be when creating a UGI via the
{{UGI.loginUserFromSubject(Subject)}} method, this method uses the
{{UserGroupInformation(Subject)}} constructor, and this constructor does the
following to determine if there is a keytab or not.
{code}
this.isKeytab = KerberosUtil.hasKerberosKeyTab(subject);
{code}
If the {{Subject}} given had a keytab, then the UGI instance will have the
{{isKeytab}} set to TRUE.
It sets the UGI instance as it would have a keytab because the Subject has a
keytab. This has 2 problems:
First, it does not set the keytab file (and this, having the {{isKeytab}} set
to TRUE and the {{keytabFile}) set to NULL is what triggers the {{IOException}}
in the method {{reloginFromKeytab()}}.
Second (and even if the first problem is fixed, this still is a problem), it
assumes that because the subject has a keytab it is up to UGI to to the relogin
using the keytab. This is incorrect if the UGI was created using the
{{UGI.loginUserFromSubject(Subject)}} method. In such case, the owner of the
Subject is not the UGI, but the caller, so the caller is responsible for
renewing the Kerberos tickets and the UGI should not try to do so.
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