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Subject: Re: [RFC PATCH V1 01/12] audit: add container id
To:     Richard Guy Briggs <rgb@redhat.com>
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From:   Stefan Berger <stefanb@linux.vnet.ibm.com>
Date:   Wed, 18 Apr 2018 15:39:21 -0400
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On 04/18/2018 03:23 PM, Richard Guy Briggs wrote:
> On 2018-04-18 14:45, Stefan Berger wrote:
>> On 03/15/2018 11:58 PM, Richard Guy Briggs wrote:
>>> On 2018-03-15 16:27, Stefan Berger wrote:
>>>> On 03/01/2018 02:41 PM, Richard Guy Briggs wrote:
>>>>> Implement the proc fs write to set the audit container ID of a process,
>>>>> emitting an AUDIT_CONTAINER record to document the event.
>>>>>
>>>>> This is a write from the container orchestrator task to a proc entry of
>>>>> the form /proc/PID/containerid where PID is the process ID of the newly
>>>>> created task that is to become the first task in a container, or an
>>>>> additional task added to a container.
>>>>>
>>>>> The write expects up to a u64 value (unset: 18446744073709551615).
>>>>>
>>>>> This will produce a record such as this:
>>>>> type=UNKNOWN[1333] msg=audit(1519903238.968:261): op=set pid=596 uid=0 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 auid=0 tty=pts0 ses=1 opid=596 old-contid=18446744073709551615 contid=123455 res=0
>>>>>
>>>>> The "op" field indicates an initial set.  The "pid" to "ses" fields are
>>>>> the orchestrator while the "opid" field is the object's PID, the process
>>>>> being "contained".  Old and new container ID values are given in the
>>>>> "contid" fields, while res indicates its success.
>>>>>
>>>>> It is not permitted to self-set, unset or re-set the container ID.  A
>>>>> child inherits its parent's container ID, but then can be set only once
>>>>> after.
>>>>>
>>>>> See: https://github.com/linux-audit/audit-kernel/issues/32
>>>>>
>>>>>
>>>>>     /* audit_rule_data supports filter rules with both integer and string
>>>>>      * fields.  It corresponds with AUDIT_ADD_RULE, AUDIT_DEL_RULE and
>>>>> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
>>>>> index 4e0a4ac..0ee1e59 100644
>>>>> --- a/kernel/auditsc.c
>>>>> +++ b/kernel/auditsc.c
>>>>> @@ -2073,6 +2073,92 @@ int audit_set_loginuid(kuid_t loginuid)
>>>>>     	return rc;
>>>>>     }
>>>>>
>>>>> +static int audit_set_containerid_perm(struct task_struct *task, u64 containerid)
>>>>> +{
>>>>> +	struct task_struct *parent;
>>>>> +	u64 pcontainerid, ccontainerid;
>>>>> +	pid_t ppid;
>>>>> +
>>>>> +	/* Don't allow to set our own containerid */
>>>>> +	if (current == task)
>>>>> +		return -EPERM;
>>>>> +	/* Don't allow the containerid to be unset */
>>>>> +	if (!cid_valid(containerid))
>>>>> +		return -EINVAL;
>>>>> +	/* if we don't have caps, reject */
>>>>> +	if (!capable(CAP_AUDIT_CONTROL))
>>>>> +		return -EPERM;
>>>>> +	/* if containerid is unset, allow */
>>>>> +	if (!audit_containerid_set(task))
>>>>> +		return 0;
>>>> I am wondering whether there should be a check for the target process that
>>>> will receive the containerid to not have CAP_SYS_ADMIN that would otherwise
>>>> allow it to arbitrarily unshare()/clone() and leave the set of namespaces
>>>> that may make up the container whose containerid we assign here?
>>> This is a reasonable question.  This has been debated and I understood
>>> the conclusion was that without a clear definition of a "container", the
>>> task still remains in that container that just now has more
>>> sub-namespaces (in the case of hierarchical namespaces), we don't want
>>> to restrict it in such a way and that allows it to create nested
>>> containers.  I see setns being more problematic if it could switch to
>>> another existing namespace that was set up by the orchestrator for a
>>> different container.  The coming v2 patchset acknowledges this situation
>>> with the network namespace being potentially shared by multiple
>>> containers.
>> Are you going to post v2 soon? We would like to build on top of it for IMA
>> namespacing and auditing inside of IMA namespaces.
> I don't know if it addresses your specific needs, but V2 was posted on
> March 16th along with userspace patches:
> 	https://www.redhat.com/archives/linux-audit/2018-March/msg00110.html
> 	https://www.redhat.com/archives/linux-audit/2018-March/msg00124.html
>
> V3 is pending.
Thanks. I hadn't actually looked at primarily due to the ghak and ghau 
in the title. Whatever these may mean.

Does V2 or will V3 prevent a privileged process to setns() to a whole 
different set of namespaces and still be audited with that initial 
container id ?