RE: [RFC][PATCH 1/3] evm: Move hooks outside LSM infrastructure

[Roberto Sassu <roberto.sassu@huawei.com>]

> -----Original Message-----
> From: Mimi Zohar [mailto:zohar@linux.ibm.com]
> Sent: Wednesday, May 6, 2020 11:10 PM
> To: Roberto Sassu <roberto.sassu@huawei.com>; david.safford@gmail.com;
> viro@zeniv.linux.org.uk; jmorris@namei.org; John Johansen
> <john.johansen@canonical.com>
> Cc: linux-fsdevel@vger.kernel.org; linux-integrity@vger.kernel.org; linux-
> security-module@vger.kernel.org; linux-kernel@vger.kernel.org; Silviu
> Vlasceanu <Silviu.Vlasceanu@huawei.com>
> Subject: Re: [RFC][PATCH 1/3] evm: Move hooks outside LSM infrastructure
> 
> On Wed, 2020-05-06 at 15:44 -0400, Mimi Zohar wrote:
> > Since copying the EVM HMAC or original signature isn't applicable, I
> > would prefer exploring an EVM portable and immutable signature only
> > solution.
> 
> To prevent copying the EVM xattr, we added "security.evm" to
> /etc/xattr.conf.  To support copying just the EVM portable and
> immutable signatures will require a different solution.

This patch set removes the need for ignoring security.evm. It can be always
copied, even if it is an HMAC. EVM will update it only when verification in
the pre hook is successful. Combined with the ability of protecting a subset
of files without introducing an EVM policy, these advantages seem to
outweigh the effort necessary to make the switch.

Roberto

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