[arin-ppml] implementing RPKI prefix validation actually increases risk

[Brad Gorman]

Hello everyone,

The arin-ppml list is open to the general public, and provides a forum to raise and discuss policy-related ideas and issues surrounding existing and proposed ARIN policies.  ARIN maintains another mailing list , arin-tech-discuss where those interested in providing feedback or seeking information from ARIN or other community members about ARIN's services on a more technical level. Information on all the mailing lists maintained by ARIN can be found on the ARIN website at the following link. (arin.net/participate/community/mailing_lists/#public-policy-mailing-list)

As stated deeper in this thread, the NANOG list is a location where participants will be better suited to provide more meaningful feedback on your comments and questions.

Best regards,

Brad Gorman
Sr Product Owner, Routing Security
American Registry for  Internet Numbers


From: ARIN-PPML <arin-ppml-bounces at arin.net> on behalf of Michel Py via ARIN-PPML <arin-ppml at arin.net>
Reply-To: Michel Py <michel at arneill-py.sacramento.ca.us>
Date: Monday, June 5, 2023 at 10:29 PM
To: PPML <arin-ppml at arin.net>
Subject: [arin-ppml] implementing RPKI prefix validation actually increases risk

Hi folks,

I am bumping into a dark side of RPKI prefix validation that actually increases risk to the network when deployed.

As many others here do, I use BGP blackhole feeds (RTBH). This technique has been around for a long time.
It is quite a common situation in some orgs to have the in-house SIEM/IDS redistribute blackhole prefixes via a BGP feed.
Also, there are numerous publicly available ones such as :
https://team-cymru.com/community-services/bogon-reference/bogon-reference-bgp/
https://www.spamhaus.org/bgpf/
http://arneill-py.sacramento.ca.us/cbbc/

When configuring RPKI validation, here is what happens. 152.89.196.0/24 is a real-world example of a prefix that has been blacklisted by three different RTBH feeds.
After implementing RPKI validation, it has generated some volume of firewall alarms for different type of attacks.

c4321-michel#sh ip bgp | beg 152.89.196.
BGP table version is 48156064, local router ID is 173.166.233.21
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
      Network          Next Hop            Metric LocPrf Weight Path
I*    152.89.196.0/24  192.0.2.1                0     90      0 21719 I              <== Trusted RTBH
N* i                   192.0.2.1                     100      1 i                    <== CBBC
I*                     192.0.2.1                0     40      0 65190 i              <== Spamhaus
V*>                    173.166.233.22                 30      0 1299 9002 57523 i    <== Prefix from full feed

The problem here is that RPKI validation is at the very top of the BGP bestpath decision process, before weight and local-preference, without any way to change that.
Therefore, the “Valid” status of the RPKI route affectively renders the RTBH feeds useless. No matter what manipulations of other parameters may be configured in route-maps, the RPKI status will override everything else.
Unsurprisingly, Cisco says that doing something about it is impossible.

Unfortunately, the “Valid” RPKI status presents no warranties whatsoever that the prefix is not used for rogue activities. Same as HTTPS certificates, crooks and spammers have realized that a ROA was a necessary part of doing their dirty business.
This particular prefix is a well-known source of attacks; there are very valid reasons it is present in multiple BGP blackholes. Unfortunately, RPKI validation, combined with Cisco’s implementation, as provided bad actors with a tool to disable a blacklisting method that plenty of orgs are currently using.

I am forced to disable RPKI prefix validation. To me, RPKI prefix validation does not bring enough value to compensate for the loss of the protection that the BGP blackhole feeds provide. Implementing RPKI validation has actually increased the volume of attacks on my network, attacks that were previously blocked right at the very edge. The risk increase is immediate : implementing RPKI validation is what made me look at these new firewall alarms. On the other hand, the gain is not immediately perceptible.

In terms of public policy and ARIN, I think that there is a consensus that deploying RPKI validation is good for everyone. I am posting this so that the community can build an understanding of why it may not be deployed universally. I am not deploying it because I don’t want it or don’t understand it, I am not deploying it because it simply does not work for me. I don’t think I will be the only one in that case. It looked like a good idea on paper, but the impossibility to accommodate currently implemented security measures is a no-go.

Michel

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