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List:       freebsd-current
Subject:    Re: Feature request: sticky bit inheritance
From:       Harald Schmalzbauer <h.schmalzbauer () omnilan ! de>
Date:       2013-11-28 8:27:07
Message-ID: 5296FE5B.6050208 () omnilan ! de
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 Bezüglich Julian Elischer's Nachricht vom 28.11.2013 01:05 (localtime):
> On 11/28/13, 12:17 AM, Harald Schmalzbauer wrote:
>>   Bezüglich Julian Elischer's Nachricht vom 27.11.2013 16:20
>> (localtime):
>>> On 11/27/13, 8:03 PM, Harald Schmalzbauer wrote:
>>>>    Hello,
>>>>
>>>> ever since I took a FreeBSD machine into production, acting as any
>>>> kind
>>>> of file server, I have to work arround the problem, that write
>>>> access to
>>>> a directory implies unlinking (deleting) directory contents.
>>> not sure I fully understand what you mean by that..
>>> Do you mean write access implies delete access? yes..
>>>
>>> This can be modified with the nounlink flag.
>> The uunlink flags also prohibits the owner to delete his files as far as
>> I know. I want to prohibt users from deleting "foreign" files, even if
>> the user has write access to the parent directory (and I wanted to
>> explain that I don't understand why anybody would want that a user with
>> write access to a directory can delete files on which the user doesn't
>> have write access).
>
> You can always unlink a file that is not yours if you own the directory.
> because the ability to unlink is purely dependent on the directory.
> You don't change the file, and it may in fact have other links

I have an idea why this kind of permission ist default: It's more
expensive to extra check the file permission copmpared to only check the
directory permission, the only part which will be altered any way. I
guess having the sticky bit set by default would cause extra I/O+check,
which might have been too expensive in the past… So the default was to
do as less work as needed?!?


...
>> I'd need every child directory of directories, who have the sticky bit
>> set, also to have the sticky bit. The same behaviour as with the gid –
>> it's the same as the parent has for new directories.
> "patches accepted" :-)

Besides horrible C skills, I have no idea where and how to start :-(
I hoped somebody else with deeper knowledge is also suffering badly and
someone could at least estimate the effort (in hours) needed to
implement a inhert-stickybit kernconf option, or even better, a sysctl.
Maybe I can pay for it.

Thanks,

-Harry


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