[Openstack-security] [Bug 1865036] Re: l3 agent metadata proxy allows access to metadata from any available network
Author: Brian Haley <bhaley at redhat.com>
Date: Thu Feb 27 17:33:28 2020 -0500
Remove extra header fields in proxied metadata requests
If a user specifies a header in their request for metadata,
it could override what the proxy would have inserted on their
behalf. Make sure to remove any headers we don't want, and
override something that might be present in the request.
If the agent somehow gets a request with both headers it will
silently drop it.
** Changed in: neutron
Status: In Progress => Fix Released
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l3 agent metadata proxy allows access to metadata from any available
Status in neutron:
Status in OpenStack Security Advisory:
Tested with Train release, by quick code check it affects also at
least Rocky, Stein and Ussuri (current master).
The security issue is than one can access metadata of an arbitrary other instance if the following conditions are met (let's call the "other instance" a "victim", it can be in any other project not normally available to the attacker):
1) Victim's port fixed IP address is known.
2) Victim's port network ID is known.
3) Attacker can use a network with access to l3 agent metadata proxy (i.e. can use routers) and deploy instances.
The scenario is as follows:
1) create a self-service network including the targeted address
2) create an instance with the same fixed IP address
3) create a router and wire it up with that network (other connections irrelevant)
4) boot up the instance (make sure to drop the potential route to dhcp agent metadata proxy if used)
5) run e.g.:
curl -H "X-Neutron-Network-ID: $VICTIM_NET_ID" 169.254.169.254/openstack/latest/meta_data.json
Normally-secret information disclosure.
Proxy ignores (removes) that extra header and proceeds as if nothing happened (most expected)
OR proxy returns an error (and logs it / sends a notification about it)
OR proxy blocks the request and calls the police as you are a bad boy :-) (least expected... but nice)
Initial code analysis:
1) the haproxy config is inadequate:
^ this should replace all current headers in the current trust model
2) the reason this works with l3 agent (and so far not with dhcp agent unless there is some other general header exploit in the stack) are the following lines:
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