[jira] Commented: (HADOOP-4490) Map and Reduce tasks should run as the user who submitted the job

["Hemanth Yamijala (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-4490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12661068#action_12661068 ] 

Hemanth Yamijala commented on HADOOP-4490:
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I attached a new patch that is more comprehensive. All changes from the previous patch still hold good. This one adds the correct permissions for all relevant files and directories, except distributed cache.

The previous patch only set relevant permissions on the task and log cache directories for all users, with the intent that tasks running as any user should be able to create and use other files and directories under them. This requirement still applies. However, there are other files and directories whose access needs to be adjusted too. The new patch addresses these changes:

- It sets permissions on the job related jar files and other directories allowing access to everyone.
- It sets read and execute permissions on directory paths until the task / job cache and log directories. For e.g. if a task cache directory is created under ${mapred.local.dir}/taskTracker/jobcache, all paths in this component are attempted to be given read and execute (and no write) access for all users. This is required for looking up paths and locating / reading files created by the tasktracker.

Both the changes above are required in future as well. Except then, the permission string would be more restrictive (disallowing access to group and others).

The previous patch was working because of a subtle behavior in setuid. On the systems where we tested, the umask was set such that read and execute permissions were provided to group by default. So, any of the job files created by the tasktracker had read and execute to the group to which the tasktracker user belonged. When the setuid executable switched users, it does not clear the supplementary group information of the launcher. Hence, the new process running as the job owner still had access to the groups to which the tasktracker belonged, and hence worked. Again, in HADOOP-4491, we propose to remove all access for the group ownership also, and hence this will not be an issue.

> Map and Reduce tasks should run as the user who submitted the job
> -----------------------------------------------------------------
>
>                 Key: HADOOP-4490
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4490
>             Project: Hadoop Core
>          Issue Type: Sub-task
>          Components: mapred, security
>            Reporter: Arun C Murthy
>            Assignee: Hemanth Yamijala
>         Attachments: hadoop-4490-design.pdf, HADOOP-4490.patch, HADOOP-4490.patch
>
>
> Currently the TaskTracker spawns the map/reduce tasks, resulting in them running as the user who started the TaskTracker.
> For security and accounting purposes the tasks should be run as the job-owner.

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