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SubjectACLs (was: Ext3 filesystem info?)
On Sat, 18 Sep 1999, Michael Bacarella wrote:
>> While we're on the topic of ext3, is there any chance of seeing ACLs in
>> the near future? Or is ext3 destined to be simply ext2 + jfs?
>
> Could you clarify this for me? What does adding ACLs mean?
> I always thought that permission bits and file owner/group fell under
> the category of "access control lists".

Short answer: ACLs can be arbitrarily complex, and are defined by the user.

You can implement a lot of ACL functionality (but not all) in terms of Unix
users and groups, but to do so, you need to modify the system user and group
lists. ACLs are built in terms of existing security IDs. Example: Allow
just Fred to read a file in your home directory.

ACLs can grant rights to multiple security IDs. Example: Grant the
documentation folks read access to the source code directory, but the
programmers read+write.

ACLs can exclude security IDs as well as including them. Example: Grant all
members of accounting access to the payroll database, except for Bob.

ACLs can make another user a trustee (owner equivalence) of a resource.
Example: You are going on vacation for two weeks, so you allow Sam to modify
the security permissions of your project directory, in case someone else needs
access.

ACLs can generally be inherited by subdirectories and files. Example: You
can grant all programmers full rights to a shared source code directory. You
can do most of this with UNIX and the SGID bit, but files are still owned by
the creator, meaning other programmers cannot modify permissions (e.g., toggle
read-only or execute status).

There are probably other things that I am forgetting, but you get the idea.

Hope this helps! :-)

--
Benjamin Scott
dragonhawk@iname.com


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