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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13558) UserGroupInformation created from a Subject incorrectly tries to renew the Kerberos ticket
Date Thu, 01 Sep 2016 08:02:22 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13558?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15454692#comment-15454692
] 

Steve Loughran commented on HADOOP-13558:
-----------------------------------------

LGTM; debug statement and cleanup of bug both improve code quality.

what do others think?

> UserGroupInformation created from a Subject incorrectly tries to renew the Kerberos ticket
> ------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-13558
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13558
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: security
>    Affects Versions: 2.7.2, 2.6.4, 3.0.0-alpha2
>            Reporter: Alejandro Abdelnur
>            Assignee: Xiao Chen
>         Attachments: HADOOP-13558.01.patch, HADOOP-13558.02.patch
>
>
> 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 do 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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