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From "Haohui Mai (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5923) Do not persist the ACL bit in the FsPermission
Date Tue, 11 Feb 2014 21:55:19 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5923?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13898370#comment-13898370
] 

Haohui Mai commented on HDFS-5923:
----------------------------------

The v0 patch takes a more aggressive approach, which removes the ACL bit completely. The rationale
is the following:

# Some applications might assume that {{FsPermission}} stay within the range of 0~0777. Changing
{{FsPermission}} might lead to unexpected issues.
# There are not many users care about whether the file has ACL except for ls. Since ls is
not in the critical path, ls can make a separate {{getAclStatus()}} call to calculate the
ACL bit.

> Do not persist the ACL bit in the FsPermission
> ----------------------------------------------
>
>                 Key: HDFS-5923
>                 URL: https://issues.apache.org/jira/browse/HDFS-5923
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client, namenode, security
>            Reporter: Haohui Mai
>            Assignee: Haohui Mai
>         Attachments: HDFS-5923.000.patch
>
>
> The current implementation persists and ACL bit in FSImage and editlogs. Moreover, the
security decisions also depend on whether the bit is set.
> The problem here is that we have to maintain the implicit invariant, which is the ACL
bit is set if and only if the the inode has AclFeature. The invariant has to be maintained
everywhere otherwise it can lead to a security vulnerability. In the worst case, an attacker
can toggle the bit and bypass the ACL checks.
> The jira proposes to treat the ACL bit as a transient bit. The bit should not be persisted
onto the disk, neither it should affect any security decisions.



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