Re: [RFC PATCH v9 00/16] Integrity Policy Enforcement LSM (IPE)

Fan Wu <[email protected]> Tue, 31 Jan 2023 16:48:52 -0800

Newsgroups	com.redhat.linux-audit,dev.linux.lists.dm-devel,org.kernel.vger.linux-block,org.kernel.vger.linux-doc,org.kernel.vger.linux-fscrypt,org.kernel.vger.linux-integrity,org.kernel.vger.linux-kernel,org.kernel.vger.linux-security-module
Message-ID	<20230201004852.GB30104@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>

On Tue, Jan 31, 2023 at 03:22:05PM +0100, Roberto Sassu wrote:
> On Mon, 2023-01-30 at 14:57 -0800, Fan Wu wrote:
> > IPE has two known gaps:
> > 
> > 1. IPE cannot verify the integrity of anonymous executable memory, such as
> >   the trampolines created by gcc closures and libffi (<3.4.2), or JIT'd code.
> >   Unfortunately, as this is dynamically generated code, there is no way
> >   for IPE to ensure the integrity of this code to form a trust basis. In all
> >   cases, the return result for these operations will be whatever the admin
> >   configures the DEFAULT action for "EXECUTE".
> 
> I think it would be useful to handle special cases, for example you
> could allow a process that created a file with memfd to use it, at the
> condition that nobody else writes it.
> 
> This would be required during the boot, otherwise services could fail
> to start (depending on the policy).
> 
Thanks for the suggestion. I agree with your opinion and I think supporting
memfd is possible but restricting read/write needs more hooks. We would like
to avoid adding more complexity to this initial posting as necessary. 
We will consider this as a future work and will post follow-on patches
in the future.

-Fan

> > 2. IPE cannot verify the integrity of interpreted languages' programs when
> >   these scripts invoked via ``<interpreter> <file>``. This is because the
> >   way interpreters execute these files, the scripts themselves are not
> >   evaluated as executable code through one of IPE's hooks. Interpreters
> >   can be enlightened to the usage of IPE by trying to mmap a file into
> >   executable memory (+X), after opening the file and responding to the
> >   error code appropriately. This also applies to included files, or high
> >   value files, such as configuration files of critical system components.
> 
> Ok, it is a well known issue. Hopefully, it will be fixed soon.
> 
> Roberto
> 

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