[apparmor] [RFC][PATCH 0/7] File descriptor labeling

[Casey Schaufler]

On 5/4/2011 1:47 AM, Roberto Sassu wrote:
> On Wednesday, May 04, 2011 01:58:00 AM John Johansen wrote:
>> ....
>> I have to agree with Casey, Generally looping back through the vfs should
>> be using the user's credentials.  This doesn't even stop you opening the
>> lower file with a different set of permissions (eg.  rw while the upper
>> is opened with r).
> Hi Casey and John
>
> my patch set does not modify this behavior:  VFS calls on upper inodes
> made by user processes and VFS calls (read/write) made by eCryptfs
> on lower inodes still use the user's credentials.
>
> In addition, SELinux provide a model for file descriptors. They may be
> opened by another subject (which provided its own credentials) and
> other processes need the 'use' permission for those file descriptors
> other than permissions for related inodes.
>
> This means that, even if eCryptfs opens lower inodes with its own
> credentials, user processes still need permissions to read/write both
> upper and lower inodes.
>
> One benefit of allowing eCryptfs to provide its own credentials is that
> user processes must have granted only strictly required permissions.
>
> Roberto Sassu

My point is that you should be able to achieve all of what you
say you want to do without introducing the LSM changes you are
proposing.