[nsp] BGP TCP vulnerability - possible solution??

[Church, Chuck]

All,

	Been brainstorming a bit, came up with this.  How about setting
either the IP precedence or DSCP with a route map and local policy, and
allowing only BGP to and from your router with this particular
precedence set?  BGP defaults to precedence 6, so I used something else:

RTR1:
ip local policy route-map setprec
!
access-list 100 permit tcp any eq bgp host 192.168.0.1 range 11000 65525
access-list 100 permit tcp any range 11000 65535 host 192.168.0.1 eq bgp
access-list 120 permit tcp host 192.168.0.1 eq bgp host 192.168.0.11
range 11000 65535 precedence flash-override
access-list 120 permit tcp host 192.168.0.1 range 11000 65535 host
192.168.0.11 eq bgp precedence flash-override
access-list 120 deny   tcp host 192.168.0.1 eq bgp host 192.168.0.11
range 11000 65535
access-list 120 deny   tcp host 192.168.0.1 range 11000 65535 host
192.168.0.11 eq bgp
access-list 120 permit ip any any
!
route-map setprec permit 10
 match ip address 100
 set ip precedence flash-override

RTR2:
ip local policy route-map setdscp
!
access-list 100 permit tcp any range 11000 65525 host 192.168.0.11 eq
bgp
access-list 100 permit tcp any eq bgp host 192.168.0.11 range 11000
65535
access-list 120 permit tcp host 192.168.0.11 eq bgp host 192.168.0.1
range 11000 65535 precedence flash-override
access-list 120 permit tcp host 192.168.0.11 range 11000 65535 host
192.168.0.1 eq bgp precedence flash-override
access-list 120 deny   tcp host 192.168.0.11 eq bgp host 192.168.0.1
range 11000 65535
access-list 120 deny   tcp host 192.168.0.11 range 11000 65535 host
192.168.0.1 eq bgp
access-list 120 permit ip any any
route-map setdscp permit 10
 match ip address 100
 set ip precedence flash-override

With these two setup as eBGP peers, it works fine.  But if you disable
the local policy routing on one side, the access lists block the packets
as expected, which would block a rogue SYN/RST.  If you can take the
performance hit on an interface or on the control plane of a router,
this might help.  This example used precedence, but with DSCP, you've
got what, 64 different combinations?  Certainly makes it much harder for
a hacker to get it right.

Just a thought...

Chuck Church
Lead Design Engineer
CCIE #8776, MCNE, MCSE
Wam!Net Government Services - Design & Implementation Team
13665 Dulles Technology Dr. Ste 250
Herndon, VA 20171
Office: 703-480-2569
Cell: 703-819-3495
cchurch at wamnetgov.com
PGP key:
http://pgp.mit.edu:11371/pks/lookup?op=index&search=cchurch%40wamnetgov.
com