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Date: Tue, 13 Jun 2017 22:59:59 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        keescook@...omium.org, matt@...tt.com
Cc: jason@...finion.com, linux-security-module@...r.kernel.org,
        Daniel Micay <danielmicay@...il.com>,
        kernel-hardening <kernel-hardening@...ts.openwall.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] shebang: restrict python interactive
 prompt/interpreter


On 12/06/2017 16:27, Mimi Zohar wrote:
> On Sun, 2017-06-11 at 22:32 -0400, Mimi Zohar wrote:
>> On Sun, 2017-06-11 at 13:44 +0200, Mickaël Salaün wrote:
>  
>>> Using filesystem xattr seems like a good idea for this kind of
>>> exceptions and instead of a hardcoded interpreter path. Something like
>>> "security.tpe.interpreter=1|2" (bitmask for interpreter-only and/or CLI)
>>> and "security.tpe.environment=HOME,LOGNAME" would be quite flexible to
>>> configure a security policy for some binaries. This could also be
>>> protected by IMA/EVM, if needed.
>>
>> Checking for the existence of an xattr without caching is relatively
>> slow.  I'm not sure that we would want to go this route.
>  
> For identifying interpreters, xattrs would be too slow (without
> caching results), but once identified, using xattrs as you suggested,
> for specifying how interpreters can be invoked and limiting
> environment variables, is a good idea.  Perhaps the two xattrs could
> be combined?

Yes, caching results is definitely interesting. I think using one
variable per usage is cleaner, though.



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