Re: Re: Re: CVE request(?): gpg: improper file permssions set when en/de-crypting files

[Tavis Ormandy <taviso () cmpxchg8b com>]

Michael Gilbert <mgilbert () debian org> wrote:

> On Mon, Sep 24, 2012 at 4:42 AM, Tavis Ormandy wrote:
> > I agree. Users do know how to use umask properly, but this isn't what
> > umask is for. The umask for the low order bits are only applied if the
> > program requested 0666, it's still the responsibility of the program to
> > choose the appropriate permissions.
> >
> > Creating sensitive files with 0666 and then saying "set your umask" is
> > just wrong.
>
> Think about the complexity potentially involved to solve these issues the
> right way.

What complexity?

> First of all, gpg is not the only application that would need to be
> "privacy-aware". Every single application that produces new files from
> existing ones to propagate permissions from those original files to the
> new ones, which would be pretty much everything.

I'm not sure what you're talking about, when you invoke open() with O_CREAT,
you need to put the correct value in the third parameter. I don't know what
that has to do with propogation.

>  In addition, piping
> would need to be permissions-aware to achieve the following:
>
> $ umask 077 $ touch sensitive-file $ umask 022 $ cat sensitive-file >
> sensitive-file2 $ ls -l sensitive-file* -rw------- 1 a a 0 Sep 24 13:09
> sensitive-file -rw------- 1 a a 0 Sep 24 13:09 sensitive-file2

I cannot parse this argument, but "piping" is a very high level concept, and
of little relevance. We're talking about the third parameter to open when
O_CREAT is specified.

> Also, in the gpg case, what should be done when starting with a 644,
> should the decrypted contents be 600 (acting more as a protective parent),
> or should it respect the original permissions (irrespective of the umask),
> or chose the more restrictive of both?

I think you mean 0666, which is what gpg is requesting. I'm pretty sure they
did not really intend for that, and so it should be updated to request what
they actually want. 


> I'm not saying that these problems couldn't (or shouldn't) be solved, but
> it seems like a daunting task.

I think you've misunderstood the problem, and it's trivial to solve.

Tavis.

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