[PATCH v5 5/5] sidechannel: Linux Security Module for sidechannel
Casey Schaufler
casey at schaufler-ca.com
Thu Sep 27 22:39:54 UTC 2018
On 9/27/2018 2:45 PM, James Morris wrote:
> On Wed, 26 Sep 2018, Casey Schaufler wrote:
>
>> + /*
>> + * Namespace checks. Considered safe if:
>> + * cgroup namespace is the same
>> + * User namespace is the same
>> + * PID namespace is the same
>> + */
>> + if (current->nsproxy)
>> + ccgn = current->nsproxy->cgroup_ns;
>> + if (p->nsproxy)
>> + pcgn = p->nsproxy->cgroup_ns;
>> + if (ccgn != pcgn)
>> + return -EACCES;
>> + if (current->cred->user_ns != p->cred->user_ns)
>> + return -EACCES;
>> + if (task_active_pid_ns(current) != task_active_pid_ns(p))
>> + return -EACCES;
>> + return 0;
> I really don't like the idea of hard-coding namespace security semantics
> in an LSM. Also, I'm not sure if these semantics make any sense.
Checks on namespaces where explicitly requested. I think
these are the most sensible, but I'm willing to be educated.
I was also requested to check on potential issues between containers,
but as there is no kernel concept of containers this is the
best I see we can do.
> It least make it user configurable.
Would you have a suggested granularity? I could have a
configuration option for each of cgroups, user and pid
namespaces but that's getting to be a lot of knobs to
twist.
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