From: Mimi Zohar <firstname.lastname@example.org>
To: Roberto Sassu <email@example.com>,
Subject: Re: [PATCH v7 00/12] evm: Improve usability of portable signatures
Date: Fri, 21 May 2021 13:31:46 -0400 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On Fri, 2021-05-21 at 07:07 +0000, Roberto Sassu wrote:
> > From: Mimi Zohar [mailto:email@example.com]
> > Sent: Thursday, May 20, 2021 8:56 PM
> > On Fri, 2021-05-14 at 17:27 +0200, Roberto Sassu wrote:
> > > EVM portable signatures are particularly suitable for the protection of
> > > metadata of immutable files where metadata is signed by a software vendor.
> > > They can be used for example in conjunction with an IMA policy that
> > > appraises only executed and memory mapped files.
> > >
> > > However, until now portable signatures can be properly installed only if
> > > the EVM_ALLOW_METADATA_WRITES initialization flag is also set, which
> > > disables metadata verification until an HMAC key is loaded. This will cause
> > > metadata writes to be allowed even in the situations where they shouldn't
> > > (metadata protected by a portable signature is immutable).
> > >
> > > The main reason why setting the flag is necessary is that the operations
> > > necessary to install portable signatures and protected metadata would be
> > > otherwise denied, despite being legitimate, due to the fact that the
> > > decision logic has to avoid an unsafe recalculation of the HMAC that would
> > > make the unsuccessfully verified metadata valid. However, the decision
> > > logic is too coarse, and does not fully take into account all the possible
> > > situations where metadata operations could be allowed.
> > >
> > > For example, if the HMAC key is not loaded and it cannot be loaded in the
> > > future due the EVM_SETUP_COMPLETE flag being set, it wouldn't be a
> > problem
> > > to allow metadata operations, as they wouldn't result in an HMAC being
> > > recalculated.
> > >
> > > This patch set extends the decision logic and adds the necessary exceptions
> > > to use portable signatures without turning off metadata verification and
> > > deprecates the EVM_ALLOW_METADATA_WRITES flag.
> > Thanks, Roberto.
> > Applied to: git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-
> > integrity.git
> > next-integrity-testing
> Hi Mimi
> could you please take the newer version of patch 5/12, which also adds
> an exception for the INTEGRITY_UNKNOWN error (it occurs when xattrs
> are not supported)?
Thank you for catching it. I'd appreciate your checking once more.
FYI, get-lore-mbox.py moved "Cc: stable" to the end.
prev parent reply other threads:[~2021-05-21 17:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-14 15:27 [PATCH v7 00/12] evm: Improve usability of portable signatures Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 01/12] evm: Execute evm_inode_init_security() only when an HMAC key is loaded Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 02/12] evm: Load EVM key in ima_load_x509() to avoid appraisal Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 03/12] evm: Refuse EVM_ALLOW_METADATA_WRITES only if an HMAC key is loaded Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 04/12] evm: Introduce evm_revalidate_status() Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 05/12] evm: Introduce evm_hmac_disabled() to safely ignore verification errors Roberto Sassu
2021-05-20 8:48 ` [RESEND][PATCH " Roberto Sassu
2021-05-20 8:51 ` Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 06/12] evm: Allow xattr/attr operations for portable signatures Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 07/12] evm: Pass user namespace to set/remove xattr hooks Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 08/12] evm: Allow setxattr() and setattr() for unmodified metadata Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 09/12] evm: Deprecate EVM_ALLOW_METADATA_WRITES Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 10/12] ima: Allow imasig requirement to be satisfied by EVM portable signatures Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 11/12] ima: Introduce template field evmsig and write to field sig as fallback Roberto Sassu
2021-05-14 15:27 ` [PATCH v7 12/12] ima: Don't remove security.ima if file must not be appraised Roberto Sassu
2021-05-20 18:55 ` [PATCH v7 00/12] evm: Improve usability of portable signatures Mimi Zohar
2021-05-21 7:07 ` Roberto Sassu
2021-05-21 17:31 ` Mimi Zohar [this message]
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