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From "Wei-Chiu Chuang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12468) Partial group resolution failure should not result in user lockout
Date Fri, 23 Oct 2015 15:03:27 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14971117#comment-14971117

Wei-Chiu Chuang commented on HADOOP-12468:

To [~yzhangal], to address your comment #1,
(1) I can not make an end-to-end test case, because the group resolution is the output from
shell command 'id'. To reproduce the scenario where the group id does not resolve, I must
manually tweak /etc/group to make it happen.

(2) Fortunately, by tweaking /etc/group, I was able to reproduce the scenario, such that part
of "id -Gn" output is numerical group id. In addition, the test case emulates the output from
the shell command. By piecing together the two parts, I can verify the fix is valid.

> Partial group resolution failure should not result in user lockout
> ------------------------------------------------------------------
>                 Key: HADOOP-12468
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12468
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: security
>    Affects Versions: 2.6.1
>         Environment: Linux
>            Reporter: Wei-Chiu Chuang
>            Assignee: Wei-Chiu Chuang
>            Priority: Minor
>         Attachments: HADOOP-12468.001.patch, HADOOP-12468.002.patch, HADOOP-12468.003.patch
> If a Hadoop cluster is configured to use ShellBasedUnixGroupsMapping for user/group name
mapping, occasionally some group names may become unresolvable (for example, using SSSD).

> ShellBasedUnixGroupsMapping uses shell command "id -Gn" to retrieve the group name of
a user; however, the existing logic assumes that if the exit code of the command is non-zero,
the user has no group name at all. The shell command in Linux returns non-zero exit code if
a group name is not resolvable. Unfortunately, it is possible that a user belongs to multiple
groups, and any partial failure in group name resolution would denied the user's access.
> On the other hand, the JNI implementation (JniBasedUnixGroupsMapping) is more resilient.
If any group name is unresolvable, it is simply ignored, and whatever are resolvable are returned.
> It is arguable that if the group name is not resolvable, the administrator should configure
their directory/authentication service correctly, and Hadoop is in no position to handle it,
but since the existing unit tests assume the output of JNI-based and shell-based implementation
are the same, we should improve the shell-based group name resolution, and make it as resilient
as the JNI-based one.

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