From: Tyler Hicks <tyhicks@linux.microsoft.com>
To: Mimi Zohar <zohar@linux.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
James Morris <jmorris@namei.org>,
"Serge E . Hallyn" <serge@hallyn.com>,
Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
Prakhar Srivastava <prsriva02@gmail.com>,
linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org,
Janne Karhunen <janne.karhunen@gmail.com>,
Eric Biederman <ebiederm@xmission.com>,
kexec@lists.infradead.org,
Casey Schaufler <casey@schaufler-ca.com>,
Nayna Jain <nayna@linux.ibm.com>
Subject: Re: [PATCH v3 00/12] ima: Fix rule parsing bugs and extend KEXEC_CMDLINE rule support
Date: Thu, 16 Jul 2020 23:34:21 -0500 [thread overview]
Message-ID: <20200717043421.GF3673@sequoia> (raw)
In-Reply-To: <1594960293.27397.2.camel@linux.ibm.com>
On 2020-07-17 00:31:33, Mimi Zohar wrote:
> On Thu, 2020-07-09 at 01:18 -0500, Tyler Hicks wrote:
> > This series ultimately extends the supported IMA rule conditionals for
> > the KEXEC_CMDLINE hook function. As of today, there's an imbalance in
> > IMA language conditional support for KEXEC_CMDLINE rules in comparison
> > to KEXEC_KERNEL_CHECK and KEXEC_INITRAMFS_CHECK rules. The KEXEC_CMDLINE
> > rules do not support *any* conditionals so you cannot have a sequence of
> > rules like this:
> >
> > dont_measure func=KEXEC_KERNEL_CHECK obj_type=foo_t
> > dont_measure func=KEXEC_INITRAMFS_CHECK obj_type=foo_t
> > dont_measure func=KEXEC_CMDLINE obj_type=foo_t
> > measure func=KEXEC_KERNEL_CHECK
> > measure func=KEXEC_INITRAMFS_CHECK
> > measure func=KEXEC_CMDLINE
> >
> > Instead, KEXEC_CMDLINE rules can only be measured or not measured and
> > there's no additional flexibility in today's implementation of the
> > KEXEC_CMDLINE hook function.
> >
> > With this series, the above sequence of rules becomes valid and any
> > calls to kexec_file_load() with a kernel and initramfs inode type of
> > foo_t will not be measured (that includes the kernel cmdline buffer)
> > while all other objects given to a kexec_file_load() syscall will be
> > measured. There's obviously not an inode directly associated with the
> > kernel cmdline buffer but this patch series ties the inode based
> > decision making for KEXEC_CMDLINE to the kernel's inode. I think this
> > will be intuitive to policy authors.
> >
> > While reading IMA code and preparing to make this change, I realized
> > that the buffer based hook functions (KEXEC_CMDLINE and KEY_CHECK) are
> > quite special in comparison to longer standing hook functions. These
> > buffer based hook functions can only support measure actions and there
> > are some restrictions on the conditionals that they support. However,
> > the rule parser isn't enforcing any of those restrictions and IMA policy
> > authors wouldn't have any immediate way of knowing that the policy that
> > they wrote is invalid. For example, the sequence of rules above parses
> > successfully in today's kernel but the
> > "dont_measure func=KEXEC_CMDLINE ..." rule is incorrectly handled in
> > ima_match_rules(). The dont_measure rule is *always* considered to be a
> > match so, surprisingly, no KEXEC_CMDLINE measurements are made.
> >
> > While making the rule parser more strict, I realized that the parser
> > does not correctly free all of the allocated memory associated with an
> > ima_rule_entry when going down some error paths. Invalid policy loaded
> > by the policy administrator could result in small memory leaks.
> >
> > I envision patches 1-7 going to stable. The series is ordered in a way
> > that has all the fixes up front, followed by cleanups, followed by the
> > feature patch. The breakdown of patches looks like so:
> >
> > Memory leak fixes: 1-3
> > Parser strictness fixes: 4-7
> > Code cleanups made possible by the fixes: 8-11
> > Extend KEXEC_CMDLINE rule support: 12
>
> Thanks, Tyler. This is a really nice patch set. The patches are now
> in the "next-integrity-testing" branch.
Thank you for all the helpful review comments. You know where to find me
if any bugs pop up during testing. :)
Tyler
>
> Mimi
next prev parent reply other threads:[~2020-07-17 4:34 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-09 6:18 [PATCH v3 00/12] ima: Fix rule parsing bugs and extend KEXEC_CMDLINE rule support Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 01/12] ima: Have the LSM free its audit rule Tyler Hicks
2020-07-17 19:20 ` Nayna
2020-07-17 19:24 ` Tyler Hicks
2020-07-19 11:02 ` Mimi Zohar
2020-07-09 6:19 ` [PATCH v3 02/12] ima: Free the entire rule when deleting a list of rules Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 03/12] ima: Free the entire rule if it fails to parse Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 04/12] ima: Fail rule parsing when buffer hook functions have an invalid action Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 05/12] ima: Fail rule parsing when the KEXEC_CMDLINE hook is combined with an invalid cond Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 06/12] ima: Fail rule parsing when the KEY_CHECK " Tyler Hicks
2020-07-17 18:56 ` Nayna
2020-07-17 19:18 ` Tyler Hicks
2020-07-17 23:39 ` Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 07/12] ima: Fail rule parsing when appraise_flag=blacklist is unsupportable Tyler Hicks
2020-07-16 18:14 ` Mimi Zohar
2020-07-16 18:20 ` Tyler Hicks
[not found] ` <76d2b27b-3b59-1852-046a-b1718c62b167@linux.vnet.ibm.com>
2020-07-17 18:11 ` Tyler Hicks
2020-07-20 17:02 ` Nayna
2020-07-09 6:19 ` [PATCH v3 08/12] ima: Shallow copy the args_p member of ima_rule_entry.lsm elements Tyler Hicks
2020-07-17 15:35 ` Konsta Karsisto
2020-07-17 16:51 ` Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 09/12] ima: Use correct type for " Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 10/12] ima: Move comprehensive rule validation checks out of the token parser Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 11/12] ima: Use the common function to detect LSM conditionals in a rule Tyler Hicks
2020-07-09 6:19 ` [PATCH v3 12/12] ima: Support additional conditionals in the KEXEC_CMDLINE hook function Tyler Hicks
2020-07-17 4:31 ` [PATCH v3 00/12] ima: Fix rule parsing bugs and extend KEXEC_CMDLINE rule support Mimi Zohar
2020-07-17 4:34 ` Tyler Hicks [this message]
2020-07-20 21:38 ` Mimi Zohar
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