On Tue, Apr 23, 2019 at 11:01:36AM -0400, Brian Haley wrote:
On 4/23/19 9:57 AM, Ben Nemec wrote:
On 4/23/19 8:33 AM, Michael McCune wrote:
On Tue, Apr 23, 2019 at 3:19 AM Slawek Kaplonski <skaplons@redhat.com> wrote:
But in some corner case it might be even patched and defaults can be different in some specific cloud.
after replying to Nate last night, this was the only corner case i could think of as well. there /could/ exist a situation where an operator has modified the defaults such that they are not in the upstream source, in this case the "default hunting" could be seen as an exposure of information. whether that information is useful or not, i am still not sure about but it's worth noting. good observation =)
Chatting with amotoki on IRC I realized that "defaults" is a somewhat ambiguous term - there are the defaults set in code when we release OpenStack, and then there are the values that an operation defaults to while running, which can be influenced by the configuration of the running cloud. Just to be clear, I meant the latter when I referred to "defaults". In other words, if the sent value had not been sent, what would have been applied for that action? I.e. if I sent a create route request without "ha" specified, then is the resulting router created with ha=false? Then the value to pass through is ha=false. For example, anyone can create a port but only an admin or network owner can create a port with port security specified. Here is the result matrix for a create port request by a non-admin user that does not own the network in an environment where ports are created with port security enabled by default. | without proposal | with proposal | port_security | | | requested | | | ------------------|-----------------------|----------------------| enabled | Denied by policy | OK (same as default) | ------------------|-----------------------|----------------------| disabled | Denied by policy | Denied by policy | ------------------|-----------------------|----------------------|
Assuming you have permission to make the API call in the first place, wouldn't you be able to determine the defaults based on the results of the API call anyway? As in, I create a network and don't pass any value for the shared attribute, then I look at the created network and see that shared is False by default.
Maybe an example would make it clearer. If as an admin I want to enable DVR and L3-HA, I make some changes in neutron.conf to set that as the default. When a user creates a router there will be many objects created and extra daemons spawned, as opposed to the case when there is just centralized routing. An 'openstack router show routerX' won't return the distributed or ha values in the API response unless you are the admin user, so there isn't a way to determine the defaults.
Maybe there are defaults that aren't so easily observable, but in general I wouldn't consider them sensitive data. However, I am not a security guru so take my opinion for what it's worth.
In the above case, is knowledge of the router type sensitive data? Probably not, if I'm remembering correctly I think we kept them hidden since it's the admin that made the decision on the deployment, and users might get confused. But if you knew your router was distributed then you'd know there was something local to your hypervisor (router namespace), instead of only on a remote controller node. Again, probably not an issue, but it does let you know what additional agents might be running where your instance is.
I'm not sure how such knowledge would be usable without breaking the containment of the instance; if such knowledge is exploitable I think it would warrant a CVE.
Nate - I'm assuming your changes wouldn't allow users to figure something like this out based on making a series of API calls?
Yes, it would allow a user to determine the defaults. Since I scoped my proposal to boolean fields, in fact it would take at most two to check. As you mentioned before, my understanding is that we did not share some of the back-end implementation details for usability concerns - not confusing users - as opposed to a security/separation of concerns approach. If there are fields where the defaults should not be detectable by this kind of inspection then I definitely want to know, but I cannot think of any at this time. What does it benefit an attacker to know that ports are created with port security on by default, or that networks are created as not shared by default, or routers are or are not HA by default? I am hoping that by airing this in the community, perhaps others will see angles I cannot. Thanks, Nate