From mboxrd@z Thu Jan  1 00:00:00 1970
From: sds@tycho.nsa.gov (Stephen Smalley)
Date: Mon, 23 Oct 2017 08:57:39 -0400
Subject: [RFC PATCH 1/2] security, capabilities: Add CAP_SYS_MOUNT
In-Reply-To: <20171021134303.20685-1-nicolas@belouin.fr>
References: <20171021134303.20685-1-nicolas@belouin.fr>
Message-ID: <1508763459.24902.1.camel@tycho.nsa.gov>
To: linux-security-module@vger.kernel.org
List-Id: linux-security-module.vger.kernel.org

On Sat, 2017-10-21 at 15:43 +0200, Nicolas Belouin wrote:
> With CAP_SYS_ADMIN being bloated and inapropriate for actions such
> as mounting/unmounting filesystems, the creation of a new capability
> is needed.
> CAP_SYS_MOUNT is meant to give a process the ability to call for
> mount,
> umount and umount2 syscalls.

If adding a new capability isn't deemed acceptable, then another option
would be to introduce LSM hooks where there isn't already coverage and
implement finer-grained permission checks there.  In some cases, that
already occurs for mount and umount*.  That also offers the possibility
of taking the object of the operation into account, unlike capabilities
which are only subject/process-based.


> 
> Signed-off-by: Nicolas Belouin <nicolas@belouin.fr>
> ---
> ?include/uapi/linux/capability.h?????| 5 ++++-
> ?security/selinux/include/classmap.h | 4 ++--
> ?2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/include/uapi/linux/capability.h
> b/include/uapi/linux/capability.h
> index 230e05d35191..ce230aa6d928 100644
> --- a/include/uapi/linux/capability.h
> +++ b/include/uapi/linux/capability.h
> @@ -365,8 +365,11 @@ struct vfs_ns_cap_data {
> ?
> ?#define CAP_AUDIT_READ		37
> ?
> +/* Allow mounting, unmounting filesystems */
> ?
> -#define CAP_LAST_CAP?????????CAP_AUDIT_READ
> +#define CAP_SYS_MOUNT		38
> +
> +#define CAP_LAST_CAP?????????CAP_SYS_MOUNT
> ?
> ?#define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
> ?
> diff --git a/security/selinux/include/classmap.h
> b/security/selinux/include/classmap.h
> index 35ffb29a69cb..a873dce97fd5 100644
> --- a/security/selinux/include/classmap.h
> +++ b/security/selinux/include/classmap.h
> @@ -24,9 +24,9 @@
> ?	????"audit_control", "setfcap"
> ?
> ?#define COMMON_CAP2_PERMS??"mac_override", "mac_admin", "syslog", \
> -		"wake_alarm", "block_suspend", "audit_read"
> +		"wake_alarm", "block_suspend", "audit_read",
> "sys_mount"
> ?
> -#if CAP_LAST_CAP > CAP_AUDIT_READ
> +#if CAP_LAST_CAP > CAP_SYS_MOUNT
> ?#error New capability defined, please update COMMON_CAP2_PERMS.
> ?#endif
> ?
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