Re: [PATCH v10 12/27] ima: Define mac_admin_ns_capable() as a wrapper for ns_capable()

Stefan Berger
2022-02-07T18:45:13Z

On 2/6/22 12:20, Stefan Berger wrote:
>
> On 2/5/22 00:58, Serge E. Hallyn wrote:
>> On Tue, Feb 01, 2022 at 03:37:20PM -0500, Stefan Berger wrote:
>>> Define mac_admin_ns_capable() as a wrapper for the combined
>>> ns_capable()
>>> checks on CAP_MAC_ADMIN and CAP_SYS_ADMIN in a user namespace. Return
>>> true on the check if either capability or both are available.
>>>
>>> Use mac_admin_ns_capable() in place of capable(SYS_ADMIN). This will
>>> allow
>>> an IMA namespace to read the policy with only CAP_MAC_ADMIN, which has
>>> less privileges than CAP_SYS_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.h    | 6 ++++++
>>>   security/integrity/ima/ima_fs.c | 5 ++++-
>>>   3 files changed, 16 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);
>> Do you care about audit warnings?  If the task has CAP_SYS_ADMIN but
>> not CAP_MAC_ADMIN, is it desirable that selinux_capable() will audit the
>> CAP_MAC_ADMIN failure?
>
> Good point.  I will switch both to ns_capable_noaudit() so that the
> user cannot provoke unnecessary audit message.

Actually,  I will only change the MAC_ADMIN to not do auditing and not
change the auditing behavior related to SYS_ADMIN.

Stefan