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Re: Subject: UMASK 002 or 022?




Paul Wise <pabs@xxxxxxxxxx> writes:

> On Wed, Jun 28, 2017 at 1:11 AM,  gwmfms6 wrote:
>
>> I'd like to know why giving the world (Other) read access is even under
>> consideration. If user wants a file to have Other readability this should be
>> on the user to set it, but it should not be the default.
>
> I expect for most Debian deployments this isn't that relevant, since
> most are either servers with no real users or single-user systems with
> no guest account.
>
>> What is the justification that every user be able to read everyone else's
>> documents?
>
> This decision was made in the mists of time and has never been questioned.
>
>> This discussion should be on whether to set a default UMASK of 077 or 027.
>
> I think the appropriate default umask is 077 due to the possibility of
> some sites not naming the primary group of each user after the user.

077 is poor choice of default given that we decided to have users in
their own dedicated group precisely to allow more generous group
permissions, and if someone decides to deviate from that policy they
need to take care of the consequences of their actions.

In case anyone is wondering why we have users in their own group is it
to allow one to create shared group directories, with the group s-bit
set, so that anyone in that group can create files in that directory.

If one has a 077 umask, that results in files in s-bit directories being
created that only the creator can read, which is almost certainly not
what you wanted.

To fix that, one sets a umask of something like 027 or 022 or 002
depending on your needs, but on traditional *nix systems all users would
generally be in a users or staff group, so you just gave
overly-permissive access to your home directory by doing that -- hence
the dedicated per-user groups.

> That said, 027 would probably be a reasonable default too since most
> sites do not do that.

I think 027 is much easier to justify, is seems likely that anyone that
prefers 022 over 027 is more likely to know why.

Cheers, Phil.
-- 
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