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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13805) UGI.getCurrentUser() fails if user does not have a keytab associated
Date Tue, 15 Nov 2016 12:05:58 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13805?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15666971#comment-15666971

Alejandro Abdelnur commented on HADOOP-13805:


If you create a {{UGI}} from {{Subject}} externally, this can done only via the {{getUGIFromSubject(Subject)}}
method, and in that case the UGI should not relogin from keytab as we already discussed.

If you create a {{UGI}} from another {{UGI}}, ie via {{getCurrentUser()}}, the created {{UGI}}
should not relogin from keytab, the relogin should be done by the creator {{UGI}} if it has
a keytab.

My point is, any {{UGI}} created from a {{Subject}} (directly or via another {{UGI}}) should
never attempt to relogin, it is the creator of the responsibility to do so. 

The bug i'm hitting now is that {{UGI.getCurrentUser()}} creates a new UGI and this tries
to do relogin from keytab even if there is no keytab associated to the current UGI. This happens
when HDFS client is accessing encryption zones, specifically the HDFS client interacting with
the KMS client to get encryption keys.

> UGI.getCurrentUser() fails if user does not have a keytab associated
> --------------------------------------------------------------------
>                 Key: HADOOP-13805
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13805
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: security
>    Affects Versions: 2.8.0, 2.9.0, 3.0.0-alpha2
>            Reporter: Alejandro Abdelnur
>            Assignee: Xiao Chen
>            Priority: Blocker
> HADOOP-13558 intention was to avoid UGI from trying to renew the TGT when the UGI is
created from an existing Subject as in that case the keytab is not 'own' by UGI but by the
creator of the Subject.
> In HADOOP-13558 we introduced a new private UGI constructor {{UserGroupInformation(Subject
subject, final boolean externalKeyTab)}} and we use with TRUE only when doing a {{UGI.loginUserFromSubject()}}.
> The problem is, when we call {{UGI.getCurrentUser()}}, and UGI was created via a Subject
(via the {{UGI.loginUserFromSubject()}} method), we call {{new UserGroupInformation(subject)}}
which will delegate to {{UserGroupInformation(Subject subject, final boolean externalKeyTab)}}
 and that will use externalKeyTab == *FALSE*. 
> Then the UGI returned by {{UGI.getCurrentUser()}} will attempt to login using a non-existing
keytab if the TGT expired.
> This problem is experienced in {{KMSClientProvider}} when used by the HDFS filesystem
client accessing an an encryption zone.

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