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From: Mimi Zohar <>
To: Roberto Sassu <>,
Subject: Re: [PATCH 5/7] evm: Verify portable signatures against all protected xattrs
Date: Mon, 24 May 2021 14:21:43 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 2021-05-20 at 10:56 +0200, Roberto Sassu wrote:
> Currently, the evm_config_default_xattrnames array contains xattr names
> only related to LSMs which are enabled in the kernel configuration.
> However, EVM portable signatures do not depend on local information and a
> vendor might include in the signature calculation xattrs that are not
> enabled in the target platform.
> Just including all xattrs names in evm_config_default_xattrnames is not a
> safe approach, because a target system might have already calculated
> signatures or HMACs based only on the enabled xattrs. After applying this
> patch, EVM would verify those signatures and HMACs with all xattrs instead.
> The non-enabled ones, which could possibly exist, would cause a
> verification error.
> Thus, this patch adds a new field named enabled to the xattr_list
> structure, which is set to true if the LSM associated to a given xattr name
> is enabled in the kernel configuration. The non-enabled xattrs are taken
> into account in only evm_calc_hmac_or_hash(), if the passed security.evm
> The new function evm_protected_xattr_if_enabled() has been defined so that
> IMA can include all protected xattrs and not only the enabled ones in the
> measurement list, if the new template field evmxattrs has been included in
> the template format.
> Signed-off-by: Roberto Sassu <>

Nice, I really like this idea.


  reply	other threads:[~2021-05-24 18:22 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-20  8:56 [PATCH 0/7] ima: Add template fields to verify EVM portable signatures Roberto Sassu
2021-05-20  8:56 ` [PATCH 1/7] ima: Add ima_show_template_uint() template library function Roberto Sassu
2021-05-20  8:56 ` [PATCH 2/7] ima: Introduce template fields iuid and igid Roberto Sassu
2021-05-20  8:56 ` [PATCH 3/7] ima: Introduce template fields mntuidmap and mntgidmap Roberto Sassu
2021-05-20  9:36   ` Christian Brauner
2021-05-20  9:41     ` Christian Brauner
2021-05-20 11:54       ` Roberto Sassu
2021-05-20  8:56 ` [PATCH 4/7] ima: Introduce template field imode Roberto Sassu
2021-05-20  8:56 ` [PATCH 5/7] evm: Verify portable signatures against all protected xattrs Roberto Sassu
2021-05-24 18:21   ` Mimi Zohar [this message]
2021-05-20  8:57 ` [PATCH 6/7] ima: Introduce template field evmxattrs Roberto Sassu
2021-05-24 18:31   ` Mimi Zohar
2021-05-20  8:57 ` [PATCH 7/7] evm: Don't return an error in evm_write_xattrs() if audit is not enabled Roberto Sassu

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