From: Roberto Sassu <roberto.sassu@huawei.com>
To: Mimi Zohar <zohar@linux.ibm.com>, "mjg59@google.com" <mjg59@google.com>
Cc: "linux-integrity@vger.kernel.org"
<linux-integrity@vger.kernel.org>,
"linux-security-module@vger.kernel.org"
<linux-security-module@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Christian Brauner <christian.brauner@ubuntu.com>,
Andreas Gruenbacher <agruenba@redhat.com>,
kernel test robot <lkp@intel.com>
Subject: RE: [PATCH v6 08/11] evm: Allow setxattr() and setattr() for unmodified metadata
Date: Tue, 11 May 2021 14:21:28 +0000 [thread overview]
Message-ID: <c281b39bdbaa4b5ab921a2e9cece83b4@huawei.com> (raw)
In-Reply-To: <735bae46f0772b40ef6ecfb3c6fe0267b3ebbee8.camel@linux.ibm.com>
> From: Mimi Zohar [mailto:zohar@linux.ibm.com]
> Sent: Tuesday, May 11, 2021 4:12 PM
> Hi Roberto,
>
> On Wed, 2021-05-05 at 13:33 +0200, Roberto Sassu wrote:
> > With the patch to allow xattr/attr operations if a portable signature
> > verification fails, cp and tar can copy all xattrs/attrs so that at the
> > end of the process verification succeeds.
> >
> > However, it might happen that the xattrs/attrs are already set to the
> > correct value (taken at signing time) and signature verification succeeds
> > before the copy has completed. For example, an archive might contains files
> > owned by root and the archive is extracted by root.
> >
> > Then, since portable signatures are immutable, all subsequent operations
> > fail (e.g. fchown()), even if the operation is legitimate (does not alter
> > the current value).
> >
> > This patch avoids this problem by reporting successful operation to user
> > space when that operation does not alter the current value of xattrs/attrs.
>
> I must be missing something. If both the IMA and EVM status flags are
> reset after xattr or attr modification, do we really need to prevent
> any metadata - same or different - changes? Both evm_protect_xattr()
> and evm_inode_setattr() would need to be modified to allow
> INTEGRITY_PASS_IMMUTABLE.
Hi Mimi
yes, given that the IMA and EVM flags are reset, it should not be
a problem to allow changes. However, I think it is useful to keep
the current behavior. For example, it would prevent an accidental
change of the SELinux label during the relabeling process.
Roberto
HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Li Jian, Shi Yanli
> thanks,
>
> Mimi
next prev parent reply other threads:[~2021-05-11 14:21 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 11:29 [PATCH v6 00/11] evm: Improve usability of portable signatures Roberto Sassu
2021-05-05 11:29 ` [PATCH v6 01/11] evm: Execute evm_inode_init_security() only when an HMAC key is loaded Roberto Sassu
2021-05-05 11:29 ` [PATCH v6 02/11] evm: Load EVM key in ima_load_x509() to avoid appraisal Roberto Sassu
2021-05-05 11:29 ` [PATCH v6 03/11] evm: Refuse EVM_ALLOW_METADATA_WRITES only if an HMAC key is loaded Roberto Sassu
2021-05-11 13:41 ` Mimi Zohar
2021-05-11 14:12 ` Roberto Sassu
2021-05-11 19:53 ` Mimi Zohar
2021-05-05 11:29 ` [PATCH v6 04/11] evm: Introduce evm_status_revalidate() Roberto Sassu
2021-05-11 13:42 ` Mimi Zohar
2021-05-05 11:33 ` [PATCH v6 05/11] evm: Introduce evm_hmac_disabled() to safely ignore verification errors Roberto Sassu
2021-05-07 13:31 ` [RESEND][PATCH " Roberto Sassu
2021-05-11 13:42 ` Mimi Zohar
2021-05-05 11:33 ` [PATCH v6 06/11] evm: Allow xattr/attr operations for portable signatures Roberto Sassu
2021-05-05 11:33 ` [PATCH v6 07/11] evm: Pass user namespace to set/remove xattr hooks Roberto Sassu
2021-05-05 11:33 ` [PATCH v6 08/11] evm: Allow setxattr() and setattr() for unmodified metadata Roberto Sassu
2021-05-11 14:11 ` Mimi Zohar
2021-05-11 14:21 ` Roberto Sassu [this message]
2021-05-11 14:40 ` Mimi Zohar
2021-05-11 14:54 ` Roberto Sassu
2021-05-11 20:00 ` Mimi Zohar
2021-05-05 11:33 ` [PATCH v6 09/11] ima: Allow imasig requirement to be satisfied by EVM portable signatures Roberto Sassu
2021-05-05 11:33 ` [PATCH v6 10/11] ima: Introduce template field evmsig and write to field sig as fallback Roberto Sassu
2021-05-11 22:12 ` Mimi Zohar
2021-05-12 10:55 ` Roberto Sassu
2021-05-05 11:33 ` [PATCH v6 11/11] ima: Don't remove security.ima if file must not be appraised Roberto Sassu
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