MPLS VPN Security assessment C. Anselme-Moizan christophe.anselmemoizan@orange-ftgroup.com

Agenda MPLS VPN technology overview security concerns what to check ? how to check it ? conclusion MPLS VPN security assessment

MPLS VPN we consider here L3VPN (MPLS also supports L2VPN e.g. : EoMPLS, VPLS, …) network based VPN (vs. CE based VPN) any to any no ciphering VPN depends on whole core network configuration RFC 2547 -> RFC 4364 MPLS VPN security assessment

MPLS VPN vs. FR full mesh MPLS VPN security assessment

MPLS RFC 3031 Multi-protocol label switching Cisco : tag-switching (TDP -> LDP) MPLS header contains a (stack of) label(s) no CE participates to tag/label switching MPLS VPN security assessment

MPLS : label distribution (LDP) In Tag Prefix Out Iface 9 128.89 - ….. …. In Tag Prefix Out Iface 4 128.89 9 5 171.69 1 7 ….. …. In Tag Prefix Out Iface - 128.89 1 4 171.69 5 ….. …. 128.89 Label 9 for 128.89 PE CE 1 Label 4 for 128.89 Label 5 for 171.69 1 PE P Label 7 for 171.69 171.69 PE CE MPLS VPN security assessment

MPLS : label switching (no VPN) Tag Prefix Out Iface 9 128.89 - ….. …. In Tag Prefix Out Iface 4 128.89 9 5 171.69 1 7 ….. …. In Tag Prefix Out Iface - 128.89 1 4 171.69 5 ….. …. CE 128.89 PE 1 128.89.25.4 data 9 128.89.25.4 data 4 128.89.25.4 data 1 PE P 128.89.25.4 data CE 171.69 PE CE MPLS VPN security assessment

VRF Virtual Routing and Forwarding instance local to the PE, it contributes to the VPN but it is not the VPN Route Distinguisher RD (64 bits) => RD + @IPV4 = @VPN-IPV4 IPV4 addresses of two VPN can overlap, VPN-IPV4 addresses are distinct Interface to “red CE” is associated to “red VRF” : Interface does not accept labeled packets, only IPV4 Ingress traffic is routed through the associated VRF Egress traffic could be routed to an interface not associated with the VRF PE interface to the CE can be considered as “VPN edge” Using VRF, each VPN has its own routing table on PE. Now, how is the VPN built across the network ? MPLS VPN security assessment

MP-iBGP Part of Multiprotocol Extensions for BGP-4 (RFC 4760) Extension to BGP in order to advertise VPN-IPV4 routes A MP-iBGP update contains : VPN-IPV4 address Standard BGP attributes (loc.prf, MED, NH, AS path..) Site Of Origin (identifies the originating PE) Route Target (defines route propagation across VRFs) Route Origin (identifies the originating CE) Associated external label (set by originating PE) no CE participates to MPiBGP MPLS VPN security assessment

VRF configuration example VRF configuration determines : Route distinguisher Route Target (RT) attribute(s) to be added to route update Route Target (RT) to import i.e. a MP-iBGP update is accepted only if RT is imported by the VRF ip vrf I_SIMPLE320 rd 9999:13191001 route-target import 9999:13191000 route-target export 9999:13191000 maximum routes 1000 80 ! MPLS VPN security assessment

VRF configuration example RD identifies the VRF, RT identifies the VPN (simple case) VRF name could be different on each PE, it is only a convention to have the same name VRF of a same VPN on distant PE exchange routes using MPiBGP. Now, how is the VPN enforced in the MPLS core ? MPLS VPN security assessment

MPLS/VPN 2 levels of label : Internal label : to transport packet to egress PE in MPLS core External label : to identify the VRF on egress PE P routers only handle internal label, they don’t know VPNs On Ingress PE, the VRF determines which external label has to be added to the packet, and which egress PE is targeted. According to egress PE targeted, the internal label is added above the external one on label stack. On egress PE, internal label is discarded, external label determines by which VRF the packet must be forwarded, external label is discarded and packet is processed “by” the VRF MPLS VPN security assessment

Route Reflector RFC 4456 BGP route reflection avoid peering meshing RR knows RD, RT, but not each VRF content (VRF is local and depends on RT import in VRF) RR RR PE PE PE PE PE PE PE PE PE PE PE PE MPLS VPN security assessment

Extranet Extranet is when two VPN exchange routing information Use of route import/export between VRF For some customers, VPN is built with several VRFs exchanging routes (to reflect customer organization) A VRF can learn routes from another without exporting routes to this other VRF and vice versa i.e. main customer site may know routes to each branch but each branch does not know routes to other branches MPLS VPN security assessment

Admin/Service VPN How to reach customer devices from operator’s management network without exchanging routes between customers ? assymetric RT Hub and spoke topology 2 types of access to such a VPN : client : knows only routes to servers server : knows routes to clients and servers ip vrf I_SIMPLE320 ip vrf MGT rd 9999:13191001 rd 9999:20001 route-target import 9999:20000 route-target import 9999:30000 route-target import 9999:13191000 route-target export 9999:20000 route-target export 9999:30000 maximum routes 100000 80 route-target export 9999:13191000 ! maximum routes 1000 80 ! MPLS VPN security assessment

Admin/Service VPN Management 9999:30000 9999:30000 9999:20000 Red Green 9999:0001 9999:0002 MPLS VPN security assessment

Import map, Export map Not all import/export are declared statically Use of import and/or export map that define rules for setting route targets in routing updates For example : ip vrf I_SIMPLE320 rd 9999:13191001 export map VPN-export route-target import 9999:20000 route-target import 9999:13191000 route-target export 9999:13191000 maximum routes 1000 80 ! MPLS VPN security assessment

Import map, Export map route-map VPN-export permit 30 match tag 9000 set community 9999:20103 set extcommunity rt 9999:30000 ! ip route vrf I_SIMPLE320 10.10.99.2 255.255.255.255 ATM2/0/1.271 tag 9000 Allow to choose routes that are exported to management network (not all customer addresses, only management addresses) MPLS VPN security assessment

Security concerns MPLS/VPN security is reputed to be comparable to FR/ATM security assuming that : Attacker cannot gain access to the core Mistakes (or unwanted changes) in configurations are avoided a VPN configuration depends on whole network configuration (not only configuration of VRF on the access PE for that VPN) => to check one VPN, you must check the whole network MPLS VPN security assessment

Security concerns Then, following points are mandatory : PE and P are in operator premises and physically protected Each node (P/PE) is protected against intrusion Only PE and P participate in tag switching Only PE participate in MPiBGP (no CE) Each VPN configuration on each PE must be correct All the above points must be regularly checked It is important that provisioning process is fully reliable It is important to be able to check the whole network configuration for all VPN MPLS VPN security assessment

What to check about MPLS/VPN configuration ? VPN access points PE interfaces VRF configuration RD presence RD uniqueness Max route VPN connectivity RT Import/Export Routes/VRF consistency (do we route to an interface which do not belong to the VRF ?) Admin/Service VPN security RT use Routes use Compliance with provisioning/ressource allocation MPLS VPN security assessment

How to check SAFE (OBS security assessment tool) feature Collect periodically VPN related information in all VPN aware (PE) routers configurations : VRF name RD RT import/export Static Through route-map Interfaces in VRF Static routes MPLS VPN security assessment

How to check Get information from ressource allocation tool VRF name VPN id (RD and main RT are built from VPN id) Interfaces RT import RT export MPLS VPN security assessment

How to check Store information in order to be able to : Provide information on VPN perimeter Provide details where problems occur Check consistency (what is referenced is declared and vice-versa) Check compliancy of configuration data with allocation tool data Check service/admin RT use Check service/admin routes use Check RD presence and uniqueness Check static routes/interface consistency MPLS VPN security assessment

Results exploitation Even if we keep information for each PE, results are provided for the whole VPN. i.e. VPN A export to VPN B means that there is at least one PE where VRF A exports at least one route with a route target imported by VRF B on at least one PE. This does not mean that all routes known in VPN A are known in VPN B. Results are provided by VPN Two type of results : Obvious errors don’t depend on customer VPN architecture : ex: RD uniqueness, admin/service routes/RT use VPN perimeter problem : noncompliance with allocation tool Tool provides statistics MPLS VPN security assessment

Results exploitation Who may use the tool ? Depends on error type Backbone ops : operate the backbone (PE and P global configuration) VPN owner : is responsible for one (or more) VPN (Customer access Depends on error type Obvious errors : Can be identified by backbone ops All obvious errors are reported in dashboards (excel files) May require VPN owner action/validation VPN perimeter problem : can only be confirmed by VPN owner (knowledge of customer VPN architecture is needed) MPLS VPN security assessment

MPLS VPN security assessment

MPLS VPN security assessment

MPLS VPN security assessment

MPLS VPN security assessment

Conclusion A tool to keep an eye on VPN configurations Other tools may also contribute (production tools, routing supervision tools) But tool does not all the job, it is part of a whole set of security actions : provisioning tools are designed to minimize errors in configurations VPN owner checks his VPN perimeter (using his knowledge of customer network architecture) Network architects follow design rules (no CE involved in MPi-BGP, no PE out of AS) Backbone operators enforce PE and P protection against intrusion and check configurations for this protection periodically (also automated with a tool) MPLS VPN security assessment