Transcript rtgarea
Reshad Rahman, Editor Adrian Farrel Tony Li OldDog Consulting Ericsson David Ward Francois LeFaucheur Ashok Narayanan Cisco Perception that IP Router-Alert is a security threat RFC2113 just says “packets with this option must be examined further by the router” Efficient fast path implementation unclear Fast path punts all IP Options packets to RP High cost to routers which don’t need to process the packets received with IP RAO Attack vector against router CPU/backplane Some networks respond by dropping IP RAO packets at the edge Protocols using IP RAO are viewed as “dangerous” IP Router-Alert in E2E Applications IP Router-Alert in Networks Example router protection mechanisms Possible standards work to improve IP RAO Questions End-to-end application/protocol use of IP Router-Alert is questionable at best Delivery is not guaranteed end-to-end ◦ Intermediate routers could drop these, or turn off IP RAO Desired service unlikely to be received from SP routers Therefore, new application use of IP Router-Alert is currently considered harmful and strongly discouraged Existing applications… ◦ ◦ ◦ ◦ MUST NOT extend their use of IP RAO MUST NOT propose extensions that need IP RAO in an E2E manner SHOULD document RAO limitations for E2E use MAY investigate reduction or removal of IP RAO use “Walled-garden” networks can safely deploy applications with IP Router-Alert, if they can protect themselves against IP RAO attack from untrusted nodes. ◦ Existing applications MAY continue to use IP RAO in a walled-garden network Networks exposed to IP RAO attacks from untrusted nodes SHOULD take action to mitigate this attack. Systematic dropping of IP RAO packets is undesirable. Networks should protect themselves, in this order of preference: 1. Implement IP RAO protection mechanisms on routers 2. Encapsulate and transport IP RAO packets across network 3. Remove IP RAO option and forward packet 4. Drop packet Don’t automatically punt all packets with IP RAO option Unless protocol of interest is enabled, forward in fast path Configuration should be per-interface and/or global Don’t punt packets for unknown or unsupported protocols Rate-limit all punted & locally addressed packets Different queues for different IP-RAO protocols Ability to control rate-limiting per interface and box-wide For RAO option value 0, look at IP Protocol ID Keep table of matching IP PIDs of interest Don’t punt anything with a different PID Main weakness in IP RAO is lack of definition in determining packets of interest For Option Value 0, filter on IP PID only ◦ Compatible with RSVP, IGMP, PGM IP Protocol ID is scarce Use IP RAO 16-bit field as an IANA-registered selector Fast switching looks only at the IP RAO option value to determine whether they want the packet ◦ Legacy option values require additional IP PID lookup Is there a real issue with IP Router-Alert as currently defined and implemented? Applications: Should router protection implementation guidelines be BCP? Is there value in standards extension/clarification of IP RAO procedures to determine packets of interest? And finally, do these points apply to all IP Options? ◦ Is there a safe alternative to banning IP RAO use by new applications? ◦ Should we prevent any extensions to protocols that currently use IP RAO?