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Date: Thu, 11 Jul 2019 17:31:38 +0100
From: John Haxby <john.haxby@...cle.com>
To: oss-security@...ts.openwall.com
Cc: Malte Kraus <malte.kraus@...e.com>
Subject: Re: Privileged File Access from Desktop Applications
> On 11 Jul 2019, at 16:57, Bob Friesenhahn <bfriesen@...ple.dallas.tx.us> wrote:
>
> On Thu, 11 Jul 2019, Perry E. Metzger wrote:
>>
>> It seems like a bad idea.
>>
>> If one wants to have mechanisms by which the operating system can
>> allow unprivileged programs to temporarily assume privileges (which
>> is a frequent idea in security), then they should be carefully
>> designed and part of the OS, rather than creating an ad hoc facility
>> via a subsystem that isn't intended for it. There are good ways to do
>> that, like capabilities.
>
> I agree. It is rather common that more than one file needs to be modified at one time. If a more complex mechanism like a sqlite3 database needs to be updated, then the implementation of sqlite3 will expect to be able to access files in a normal way and it will expect to be use all the abilities it normally uses. It is rather common that atomic operations are required, locking is required, the ability to link/rename files is required, and that synchronization of file content and directories is required.
>
> In addition to the security concerns, it is difficult to see how a virtual filesystem intended for use by simplistic GUI file managers will satisfy common administrative requirements.
>
This bit us recently with a graphical application that needed to run as root (I forget what for). It also struck me that I often run gparted (don't ask why :)) which needs to dink with disks.
Obviously one could split the process into its graphical half and its messing-around-with-disks half but it's not clear to me how the graphical half would handle authentication[*] for the process that needs to run as root. There are any number of administrative tasks that will need to be redesigned to cope with this change.
jch
[*] Yes, you could, for example, use $SUDO_USER/UID/etc but you can bet that that will throw up all kinds of security problems that we don't have today.
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