Gyan, However what you say then raises additional concerns.
RFC8402 Section 8.2 explicitly prohibits sending SRv6 traffic beyond the borders of a domain and over the general internet. Making use of traffic destined for an address within the SRGB of another network isn’t permitted as per: SR domain boundary routers MUST filter any external traffic destined to an address within the SRGB of the trusted domain or the SRLB of the specific boundary router. External traffic is any traffic received from an interface connected to a node outside the domain of trust. As regards the BGP – it goes further still: From a network-protection standpoint, there is an assumed trust model such that any node adding an SRH to the packet is assumed to be allowed to do so. Therefore, by default, the explicit routing information MUST NOT be leaked through the boundaries of the administered domain. Now, I may be misunderstanding here – but – if at any point the announcements lead to traffic flowing towards a SID from outside the administered domain – that violates 8402. If the SID’s are in BGP prefix’s that are transitive and find their way onto the general internet – that also violates 8402. Now, this could be a misunderstanding on my part – so I’d welcome clarification if I am incorrect in what I am seeing here – which may also lead to text which is clearer (as a note, I ran this past several operators who had very similar readings to what I had – so – if it’s a matter of misunderstanding, we really do need to find a way to clarify it, if its not a misunderstanding, then we need to find a way to rectify it for security purposes and to bring it in-line with RFC8402. Thanks Andrew From: Gyan Mishra <hayabusa...@gmail.com> Sent: Saturday, February 12, 2022 10:18 PM To: Robert Raszuk <rob...@raszuk.net> Cc: Andrew - IETF <andrew-i...@liquid.tech>; BESS <bess@ietf.org>; Bocci, Matthew (Nokia - GB) <matthew.bo...@nokia.com>; The IESG <i...@ietf.org>; Warren Kumari <war...@kumari.net>; bess-cha...@ietf.org; draft-ietf-bess-srv6-servi...@ietf.org Subject: Re: [bess] Warren Kumari's Discuss on draft-ietf-bess-srv6-services-10: (with DISCUSS and COMMENT) Hi Robert / All For service providers and enterprises using GRT or VRF to carry the internet or intra internet routing table using MPLS today or SR-MPLS that would like to use SRv6 to provide the same service. Section. 5.1 and 5.2 cover the VPN case in which the customer traffic is in VRF overlay and the SRv6 transport layer is a closed domain. Section 5.3 and 5.4 cover GRT option and 5.3 using RFC 5549 next hop encoding. In this case using GRT transport underlay layer now carry’s the customer routes and that is what Warren and Andrew concern is as far as BGP leaks. So when GRT is used the same edge filtering protection mechanisms used today for MPLS and SR-MPLS would apply to SRv6 for GRT use case. I don’t think we are saying 5.3 or 5.4 should not be allowed but just to tighten up verbiage as far securing the domain. As far as the SRv6 domain is concerned even with GRT the domain is still closed at the PE ingress and egress points which is where the concern is for BGP leaks. The BGP Prefix SID encoding the SRv6 L3 service TLVs would, the encoding would only be present in the SRv6 SID Function field within the closed domain, and once you exit the SRv6 domain at the ingress or egress endpoints the SRv6 L3 service TLVs would now be carried natively in BGP and not in the SRv6 BGP prefix SID encoding. When an egress PE is enabled for BGP Services over SRv6 data-plane, it signals one or more SRv6 Service SIDs enclosed in SRv6 Service TLV(s) within the BGP Prefix-SID Attribute attached to MP-BGP NLRIs defined in [RFC4760<https://datatracker.ietf.org/doc/html/rfc4760>] [RFC4659<https://datatracker.ietf.org/doc/html/rfc4659>] [RFC8950<https://datatracker.ietf.org/doc/html/rfc8950>] [RFC7432<https://datatracker.ietf.org/doc/html/rfc7432>] [RFC4364<https://datatracker.ietf.org/doc/html/rfc4364>] [RFC9136<https://datatracker.ietf.org/doc/html/rfc9136>] where applicable as described in Section 5<https://datatracker.ietf.org/doc/html/draft-ietf-bess-srv6-services#section-5> and Section 6<https://datatracker.ietf.org/doc/html/draft-ietf-bess-srv6-services#section-6>. So as far as SRv6 SID leaking there would not be any leaking outside the SRv6 domain. However as the GRT carry internet or intranet BGP RIB the SP AS is of course transitive so entire table is propagated. That’s not a leak. I think we just need to maybe tighten up the verbiage on securing the PE edges of the SRv6 domain. Kind Regards Gyan On Sat, Feb 12, 2022 at 1:37 PM Robert Raszuk <rob...@raszuk.net<mailto:rob...@raszuk.net>> wrote: Hi Andrew, When I read Warren's note Iooked at this text from section 2 which says: - - - The SRv6 Service TLVs are defined as two new TLVs of the BGP Prefix- SID Attribute to achieve signaling of SRv6 SIDs for L3 and L2 services. o SRv6 L3 Service TLV: This TLV encodes Service SID information for SRv6 based L3 services. It corresponds to the equivalent functionality provided by an MPLS Label when received with a Layer 3 service route as defined in [RFC4364] [RFC4659] [RFC8950] [RFC9136]. Some SRv6 Endpoint behaviors which MAY be encoded, but not limited to, are End.DX4, End.DT4, End.DX6, End.DT6, etc. o SRv6 L2 Service TLV: This TLV encodes Service SID information for SRv6 based L2 services. It corresponds to the equivalent functionality provided by an MPLS Label1 for Ethernet VPN (EVPN) Route-Types as defined in [RFC7432]. Some SRv6 Endpoint behaviors which MAY be encoded, but not limited to, are End.DX2, End.DX2V, End.DT2U, End.DT2M etc. When an egress PE is enabled for BGP Services over SRv6 data-plane, it signals one or more SRv6 Service SIDs enclosed in SRv6 Service TLV(s) within the BGP Prefix-SID Attribute attached to MP-BGP NLRIs defined in [RFC4760] [RFC4659] [RFC8950] [RFC7432] [RFC4364] [RFC9136] where applicable as described in Section 5 and Section 6. The support for BGP Multicast VPN (MVPN) Services [RFC6513] with SRv6 is outside the scope of this document. - - - This limits the overlay signalling to non global SAFIs mainly SAFI 128 and SAFI 70. To your note SAFI 4 is private and never exchanged in the wild. Also SAFI 2 is multicast which is out of scope of this draft. The only thing which we need to sync on is indeed section 5.4 and use of global IPv6 AFI 2 & SAFI 1 Many thx, R. On Sat, Feb 12, 2022 at 7:11 PM Andrew - IETF <andrew-i...@liquid.tech> wrote: Robert, I have to say that I have very similar readings on parts of the draft. Let’s look at it – 5.1 uses the IPv4-VPN NLRI – That would seem to indicate AFI 1 / SAFI 4 5.2 – Uses AFI 2 / SAFI 4 from my reading 5.3 – According to RFC8950 – allows advertisement over SAFI 1, 2 or 4 5.4 – To my reading – very much refers to AFI 2 / SAFI 1. I would agree if this document limited itself to 5.1 and 5.2 – it doesn’t – and therefore I have to agree with the thoughts expressed in Warrens Discuss. If I am wrong about 5.3 and 5.4, let’s chat and help me understand this better, and then lets potentially see if we can work up some wording that would clarify this if that is what is required. Thanks Andrew From: iesg <iesg-boun...@ietf.org<mailto:iesg-boun...@ietf.org>> On Behalf Of Robert Raszuk Sent: Saturday, February 12, 2022 8:26 PM To: Warren Kumari <war...@kumari.net<mailto:war...@kumari.net>> Cc: Bocci, Matthew (Nokia - GB) <matthew.bo...@nokia.com<mailto:matthew.bo...@nokia.com>>; draft-ietf-bess-srv6-servi...@ietf.org<mailto:draft-ietf-bess-srv6-servi...@ietf.org>; bess-cha...@ietf.org<mailto:bess-cha...@ietf.org>; The IESG <i...@ietf.org<mailto:i...@ietf.org>>; BESS <bess@ietf.org<mailto:bess@ietf.org>> Subject: Re: Warren Kumari's Discuss on draft-ietf-bess-srv6-services-10: (with DISCUSS and COMMENT) Hi Warren, Thank you for your Discuss. But before we start discussing it perhaps it would be good to align on what this document really defines as I am sensing from your description there can be some disconnect (modulo some text may be indeed misleading in the draft). You said: > However, we all know that BGP leaks happen -- and when they do, the SID’s > contained in the leak will be logged by various systems and hence available to > the public into perpetuity. I think the term BGP is used here a bit too broadly. Leaks do happen but only within global AFI/SAFIs. This draft defines extensions for L3VPN and L2VPNs SAFIs which are not used to peer outside of a domain, collection of domains under same administration + of course inter-as also could happen. With that being said I do not see risk that due to leaking there could be a situation where customer networks are exposed in any way externally - leaving alone that to even get at the transport level to the customer facing PE is also filtered and never allowed from outside. But this is out of scope of this document as here the focus is not on underlay but overlay. Now when I re-read this I see why there is a little piece perhaps misleading. The draft makes a claim that it is applicable to RFC8950 which defines use of NHv6 with both unicast and VPN AFs. That needs to be made clear that it is applicable to the latter only. If other co-authors believe this is applicable to the former your DISCUSS section would indeed be valid. Many thx, R. On Sat, Feb 12, 2022 at 12:05 AM Warren Kumari via Datatracker <nore...@ietf.org<mailto:nore...@ietf.org>> wrote: Warren Kumari has entered the following ballot position for draft-ietf-bess-srv6-services-10: Discuss When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to https://www.ietf.org/blog/handling-iesg-ballot-positions/<https://www.ietf.org/blog/handling-iesg-ballot-positions> for more information about how to handle DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: https://datatracker.ietf.org/doc/draft-ietf-bess-srv6-services/<https://datatracker.ietf.org/doc/draft-ietf-bess-srv6-services> ---------------------------------------------------------------------- DISCUSS: ---------------------------------------------------------------------- The Security Considerations section says: "The service flows between PE routers using SRv6 SIDs advertised via BGP are expected to be limited within the trusted SR domain (e.g., within a single AS or between multiple ASes within a single provider network). Precaution should be taken to ensure that the BGP service information (including associated SRv6 SID) advertised via BGP sessions are limited to peers within this trusted SR domain." This is related to (from RFC8402): "Therefore, by default, the explicit routing information MUST NOT be leaked through the boundaries of the administered domain." However, we all know that BGP leaks happen -- and when they do, the SID’s contained in the leak will be logged by various systems and hence available to the public into perpetuity. While the document states that border filtering should protect against traffic injection, this does not cover the case of internal compromise. Sure, there is the argument that once there is an internally compromised system, all bets are off -- but with this, an attacker that knows the SIDs in e.g inject traffic into a VPN. This seems to me to significantly expand the attack surface to include the customer's networks too. Not only does an operator have to ensure that BGP leaks never occur, they have to then ensure that at no point can there be any filter lapses at any border node, and be able to guarantee the security of every device, server and machine within the domain in order for a secure posture to be maintained. Simply saying that precautions should be taken to make sure that route leak don't occur, when the consequences of doing so are a: severe and b: hard to recover from seems to not really cover it. In addition, it seems that the blast radius from a missing ACL seems much larger if it allows injections. ---------------------------------------------------------------------- COMMENT: ---------------------------------------------------------------------- I'm still reviewing the document, but wanted to get an initial ballot in, so that we could start discussing it. Hopefully someone can help my understand how this doesn't expand the consequences of a BGP leak. _______________________________________________ BESS mailing list BESS@ietf.org<mailto:BESS@ietf.org> https://www.ietf.org/mailman/listinfo/bess<https://www.ietf.org/mailman/listinfo/bess> -- [Image removed by sender.]<http://www.verizon.com> Gyan Mishra Network Solutions Architect Email gyan.s.mis...@verizon.com<mailto:gyan.s.mis...@verizon.com> M 301 502-1347
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