From: James Bottomley <jejb@linux.ibm.com>
To: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Stefan Berger <stefanb@linux.ibm.com>,
linux-integrity@vger.kernel.org, zohar@linux.ibm.com,
christian.brauner@ubuntu.com, containers@lists.linux.dev,
dmitry.kasatkin@gmail.com, ebiederm@xmission.com,
krzysztof.struczynski@huawei.com, roberto.sassu@huawei.com,
mpeters@redhat.com, lhinds@redhat.com, lsturman@redhat.com,
puiterwi@redhat.com, jamjoom@us.ibm.com,
linux-kernel@vger.kernel.org, paul@paul-moore.com,
rgb@redhat.com, linux-security-module@vger.kernel.org,
jmorris@namei.org, Denis Semakin <denis.semakin@huawei.com>
Subject: Re: [PATCH v6 15/17] ima: Use mac_admin_ns_capable() to check corresponding capability
Date: Sat, 11 Dec 2021 15:12:57 -0500 [thread overview]
Message-ID: <15de0c8d4521aa7ab15ab34f642fd5b860b9b59f.camel@linux.ibm.com> (raw)
In-Reply-To: <20211211192222.GA27092@mail.hallyn.com>
On Sat, 2021-12-11 at 13:22 -0600, Serge E. Hallyn wrote:
> On Sat, Dec 11, 2021 at 11:05:10AM -0500, James Bottomley wrote:
> > On Sat, 2021-12-11 at 09:29 -0600, Serge E. Hallyn wrote:
> > > On Fri, Dec 10, 2021 at 02:47:34PM -0500, Stefan Berger wrote:
> > > > Use mac_admin_ns_capable() to check corresponding capability to
> > > > allow
> > > > read/write IMA policy without CAP_SYS_ADMIN but with
> > > > CAP_MAC_ADMIN.
> > > >
> > > > Signed-off-by: Denis Semakin <denis.semakin@huawei.com>
> > > > Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> > > > ---
> > > > include/linux/capability.h | 6 ++++++
> > > > security/integrity/ima/ima_fs.c | 2 +-
> > > > 2 files changed, 7 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/include/linux/capability.h
> > > > b/include/linux/capability.h
> > > > index 65efb74c3585..991579178f32 100644
> > > > --- a/include/linux/capability.h
> > > > +++ b/include/linux/capability.h
> > > > @@ -270,6 +270,12 @@ static inline bool
> > > > checkpoint_restore_ns_capable(struct user_namespace *ns)
> > > > ns_capable(ns, CAP_SYS_ADMIN);
> > > > }
> > > >
> > > > +static inline bool mac_admin_ns_capable(struct user_namespace
> > > > *ns)
> > > > +{
> > > > + return ns_capable(ns, CAP_MAC_ADMIN) ||
> > > > + ns_capable(ns, CAP_SYS_ADMIN);
> > > > +}
> > > > +
> > > > /* audit system wants to get cap info from files as well */
> > > > int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
> > > > const struct dentry *dentry,
> > > > diff --git a/security/integrity/ima/ima_fs.c
> > > > b/security/integrity/ima/ima_fs.c
> > > > index a136d14f29ec..090ee85bfa3a 100644
> > > > --- a/security/integrity/ima/ima_fs.c
> > > > +++ b/security/integrity/ima/ima_fs.c
> > > > @@ -440,7 +440,7 @@ static int ima_open_policy(struct inode
> > > > *inode,
> > > > struct file *filp)
> > > > #else
> > > > if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
> > > > return -EACCES;
> > > > - if (!capable(CAP_SYS_ADMIN))
> > > > + if (!mac_admin_ns_capable(user_ns))
> > >
> > > Sorry if I'm missing something. But I'm looking at your tree's
> > > version of ima_update_policy() and failing to see where it adds
> > > extra capability checks. Note that any unprivileged user can
> > > unshare a user namespace, map its hostuid to nsuid 0, and pass
> > > ns_capable(CAP_MAC_ADMIN).
> > >
> > > Likewise, a host uid 0 process which does not have CAP_MAC_ADMIN
> > > can create a new user namespace, map hostuid 0 to nsuid 0, and
> > > have CAP_MAC_ADMIN against the new userns.
> > >
> > > Somewhere you need to be checking for privilege against either
> > > the parent ns or the init_user_ns. I'm not seeing where that's
> > > being done. Can you point me to it?
> >
> > I think you're thinking of my patches, which used a single ima log
> > for everything. With Stefan's patches, each namespace gets its own
> > log and starts out with and empty "do nothing" policy. However,
> > whatever policy was active in the parent namespace is still run for
> > activities in the child, so any activity the parent requires to be
> > measured/audited/appraised etc still happens, but all entries are
> > made in the parent.
>
> Oh. Stefan had previously said that one motivation was to do less
> logging in the hostns, so I assumed that a child ns policy could make
> it so the parent ns policy was no longer applied.
Well, the default policy even for the init_user_ns is don't log
anything, so you can keep that if you don't care. However, if you do
care you can log all the containers. If the containers install a
logging policy, that log will disappear when the namespace is reaped,
so if the hostns has a no log policy, all the log space the child used
will be freed.
James
> If that's not the case, and not planned, then that makes this a lot
> simpler.
>
next prev parent reply other threads:[~2021-12-11 20:13 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-10 19:47 [PATCH v6 00/17] ima: Namespace IMA with audit support in IMA-ns Stefan Berger
2021-12-10 19:47 ` [PATCH v6 01/17] ima: Add IMA namespace support Stefan Berger
2021-12-13 21:11 ` Stefan Berger
2021-12-15 19:41 ` Mimi Zohar
2021-12-15 21:10 ` Mimi Zohar
2021-12-16 2:34 ` Stefan Berger
2021-12-10 19:47 ` [PATCH v6 02/17] ima: Define ns_status for storing namespaced iint data Stefan Berger
2021-12-15 21:12 ` Mimi Zohar
2021-12-16 2:37 ` Stefan Berger
2021-12-16 3:53 ` Mimi Zohar
2021-12-16 4:00 ` Stefan Berger
2021-12-10 19:47 ` [PATCH v6 03/17] ima: Namespace audit status flags Stefan Berger
2021-12-15 21:15 ` Mimi Zohar
2021-12-16 2:38 ` Stefan Berger
2021-12-16 3:54 ` Mimi Zohar
2021-12-10 19:47 ` [PATCH v6 04/17] ima: Move delayed work queue and variables into ima_namespace Stefan Berger
2021-12-10 19:47 ` [PATCH v6 05/17] ima: Move IMA's keys queue related " Stefan Berger
2021-12-10 19:47 ` [PATCH v6 06/17] ima: Move policy " Stefan Berger
2021-12-13 21:15 ` Stefan Berger
2021-12-10 19:47 ` [PATCH v6 07/17] ima: Move ima_htable " Stefan Berger
2021-12-10 19:47 ` [PATCH v6 08/17] ima: Move measurement list related variables " Stefan Berger
2021-12-10 19:47 ` [PATCH v6 09/17] ima: Only accept AUDIT rules for IMA non-init_ima_ns namespaces for now Stefan Berger
2021-12-10 19:47 ` [PATCH v6 10/17] ima: Implement hierarchical processing of file accesses Stefan Berger
2021-12-10 19:47 ` [PATCH v6 11/17] securityfs: Only use simple_pin_fs/simple_release_fs for init_user_ns Stefan Berger
2021-12-10 19:47 ` [PATCH v6 12/17] securityfs: Extend securityfs with namespacing support Stefan Berger
2021-12-11 10:50 ` Christian Brauner
2021-12-11 22:31 ` Stefan Berger
2021-12-10 19:47 ` [PATCH v6 13/17] ima: Move some IMA policy and filesystem related variables into ima_namespace Stefan Berger
2021-12-10 19:47 ` [PATCH v6 14/17] ima: Tie opened SecurityFS files to the IMA namespace it belongs to Stefan Berger
2021-12-11 11:00 ` Christian Brauner
2021-12-11 22:33 ` Stefan Berger
2021-12-10 19:47 ` [PATCH v6 15/17] ima: Use mac_admin_ns_capable() to check corresponding capability Stefan Berger
2021-12-11 15:29 ` Serge E. Hallyn
2021-12-11 16:05 ` James Bottomley
2021-12-11 19:22 ` Serge E. Hallyn
2021-12-11 20:12 ` James Bottomley [this message]
2021-12-10 19:47 ` [PATCH v6 16/17] ima: Move dentry into ima_namespace and others onto stack Stefan Berger
2021-12-10 19:47 ` [PATCH v6 17/17] ima: Setup securityfs for IMA namespace Stefan Berger
2021-12-15 21:31 ` Mimi Zohar
2021-12-16 2:41 ` Stefan Berger
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