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Date: Fri, 21 Sep 2012 12:37:00 +0200
From: Tomas Mraz <tmraz@...hat.com>
To: Matthias Weckbecker <mweckbecker@...e.de>
Cc: oss-security@...ts.openwall.com, vcizek@...e.de
Subject: Re: CVE request(?): gpg: improper file permssions set when
 en/de-crypting files

On Fri, 2012-09-21 at 12:20 +0200, Matthias Weckbecker wrote: 
> Hello Steve, Kurt, Vitezslav, Tomas, vendors,
> 
> we have recently been notified about a potential issue with gpg: When files
> are en/de-crypted the result is written world-readable by default.
> Short example (quote from [1]):
> 
>  # de-crypting
>  % gpg sikrit.gpg
>  % ll sikrit*
>    -rw-r--r-- 1 gp users  12 Sep 17 09:41 sikrit
>    -rw------- 1 gp users 480 Sep 17 09:40 sikrit.gpg
>  # en-crypting
>  % echo "my password" > sikrit
>  % chmod go= sikrit
>  % ll sikrit
>    -rw------- 1 gp users 12 Sep 17 09:38 sikrit
>  % gpg -e -r pfeifer sikrit
>  % wipe sikrit
>  % ll sikrit.gpg 
>    -rw-r--r-- 1 gp users 480 Sep 17 09:40 sikrit.gpg
> 
> [1] https://bugzilla.novell.com/show_bug.cgi?id=780943
> 
> Wouldn't one usually expect files that were previously encrypted to contain
> sensitive content (that's probably why content is encrypted at all)? And if
> so, shouldn't such files be only readable by certain users / group of users
> by default? Otherwise, a file that is e.g. decrypted in /tmp might leak due
> to the file permissions being too loose.
> 
> I'm not quite sure whether to assign a CVE for this, so I thought I'd just
> add a question mark behind the subject and let the list (and Kurt) decide.

I suppose the permissions respect the user's umask so I do not think
this is a real security issue in the gpg itself. Although using the
permissions of the original file when creating the decrypted/encrypted
one (still modified with the user's umask) would be more appropriate. So
in my opinion this does not warrant a CVE but improvement in the
upstream gnupg code would be appreciated I think.

-- 
Tomas Mraz
No matter how far down the wrong road you've gone, turn back.
                                              Turkish proverb

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