Re: R: Linux kernel source archive vulnerable

Kyle Moffett
2006-09-12T05:06:49Z

On Sep 11, 2006, at 14:29:58, Jon Lewis wrote:
> On Fri, 8 Sep 2006, Perego Paolo Franco wrote:
>
>> Anyway just few considerations:
>> 2) a good sysadmin is aware that /usr/src is NOT supposed to be
>> world writable
>
> For some reason (bug in how they're being checked out of git, I
> assume), the latest kernel source tar files have all files and
> directories world writable. This is not how it's been in the past
> and is not how it should be.

-ENOBUG

Please see these threads and quit bringing up this topic like crazy:
http://marc.theaimsgroup.com/?l=linux-kernel&m=113304241100330&w=2
http://marc.theaimsgroup.com/?l=linux-kernel&m=114635639325551&w=2

To quote:
> Going over old ground again, any administrator a) compiling the
> kernel as root or b) relying on GNU tar to make
> _security_policy_decisions_ is completely insane.
>
> The only "trick" here is tar's decision not to apply umask, or root
> uid/gid, to files in a tar when extracted as root. This might make
> sense for tars that you created and want to extract again (say
> restoring a backup), but it certainly NEVER makes sense for files
> downloaded off the Internet.

So if you must cause a senseless hubbub on securityfocus.com, please
don't spill it over onto LKML. This sort of thing is at _worst_ a
bug in GNU tar that it's behavior is different when root. I run a
linux system with SELinux where user 0 is no different than any other
user and has no special permissions at all, and this kind of
stupidity bites me a lot. My user 0 is "kyle" when I want to chown
files I switch to the "sysadm" role, or if I absolutely need to
override security policy for some reason I jump through hoops to get
to the "root" role. In neither of those cases do I care what UID I am.

So either deal insecure permissions when you can't be bothered to use
GNU tar securely (easy), don't compile your kernel as root (easier)
or fix GNU tar not to assume UID 0 is God in the first place.

Cheers,
Kyle Moffett