Re: [lisp] Eric Rescorla's Discuss on draft-ietf-lisp-rfc6833bis-16: (with DISCUSS and COMMENT)
Eric Rescorla <ekr@rtfm.com> Sat, 29 September 2018 17:23 UTC
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From: Eric Rescorla <ekr@rtfm.com>
Date: Sat, 29 Sep 2018 10:22:41 -0700
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To: "Joel M. Halpern" <jmh@joelhalpern.com>
Cc: Dino Farinacci <farinacci@gmail.com>, IESG <iesg@ietf.org>, draft-ietf-lisp-rfc6833bis@ietf.org, Luigi Iannone <ggx@gigix.net>, lisp-chairs@ietf.org, "lisp@ietf.org list" <lisp@ietf.org>
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Subject: Re: [lisp] Eric Rescorla's Discuss on draft-ietf-lisp-rfc6833bis-16: (with DISCUSS and COMMENT)
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On Sat, Sep 29, 2018 at 10:18 AM Joel M. Halpern <jmh@joelhalpern.com> wrote: > With regard to the m-bit, I would prefer that this document leave the > bit reserved, Just trying to think through the interop implications of this. Would it be must be zero and must ignore? something else? -Ekr and the LISP mobile node document assign the bit fromthe > registry. That keeps a clean separation. > > Yours, > Joel > > On 9/29/18 1:05 PM, Eric Rescorla wrote: > > > > > > On Sat, Sep 29, 2018 at 9:30 AM Dino Farinacci <farinacci@gmail.com > > <mailto:farinacci@gmail.com>> wrote: > > > > Thanks Eric for your great comments. Like I said in previous emails, > > I’ll address the simple things here and then handle all the security > > related stuff separately next week. > > > > I will do the same with Benjamin’s comments as well. And in his > > reply, send a diff with changes that reflect both Eric and > > Benjamin’s comments. > > > > > On Sep 27, 2018, at 5:16 AM, Eric Rescorla <ekr@rtfm.com > > <mailto:ekr@rtfm.com>> wrote: > > > > > > Rich version of this review at: > > > https://mozphab-ietf.devsvcdev.mozaws.net/D4115 > > > > > > > > > IMPORTANT > > > S 5.2. > > >> s: This is the SMR-invoked bit. This bit is set to 1 when > > an xTR is > > >> sending a Map-Request in response to a received SMR-based > > Map- > > >> Request. > > >> > > >> m: This is the LISP mobile-node m-bit. This bit is set by > > xTRs that > > >> operate as a mobile node as defined in [I-D.ietf-lisp-mn]. > > > > > > This would appear to create a normative reference to this > > document. To > > > avoid that, you need to specify how I behave if I receive it but I > > > don't implement lisp-mn. > > > > I am find making it a normative reference but need the lisp-chairs > > to comment. I am not sure what the implications of that are. > > > > > > Me neither. Seems like it could go either way. My only interest is that > > the protocol be unambiguous. > > > > > > > > > S 5.5. > > >> is being mapped from a multicast destination EID. > > >> > > >> 5.5. EID-to-RLOC UDP Map-Reply Message > > >> > > >> A Map-Reply returns an EID-Prefix with a prefix length that > > is less > > >> than or equal to the EID being requested. The EID being > > requested is > > > > > > How do I behave if I receive an EID-Prefix that is less than any > > of my > > > mappings. So, I might have mappings for 10.1.0.0/16 > > <http://10.1.0.0/16> and 10.2.0.0/16 <http://10.2.0.0/16> > > > and someone asks me for 10.0.0.0/8 <http://10.0.0.0/8>? > > > > > > I think I'm still unclear on this point. > > > > Also, when you talk about prefix > > > length, I assume you mean the length fo the mask? > > > > Yes, this is explained later in this section. Was that not helpful?? > > > > > > I found it a bit confusing. It seems to me like there are two lengths > > involved here: > > > > - The length of the field (4 or 16) > > - The parts of the field that are significant (i.e., the mask) > > > > I had thought that "prefix length" referred to the former, but it seems > > like here it > > refers to the latter. > > > > > > > S 5.6. > > >> Authentication Data: This is the message digest used from > > the output > > >> of the MAC algorithm. The entire Map-Register payload is > > >> authenticated with this field preset to 0. After the MAC > is > > >> computed, it is placed in this field. Implementations of > > this > > >> specification MUST include support for HMAC-SHA-1-96 > > [RFC2404], > > >> and support for HMAC-SHA-256-128 [RFC4868] is RECOMMENDED. > > > > > > What prevents replay attacks here? I'm guessing it's the > Map-Version- > > > Number, but as I understand it, I can set this to 0. > > > > Well there are many. The nonce can change for each Map-Register > > sent. Same for Map-Version number as well as the key-id. > > > > > > I think you need to describe the precise process of replay prevention > here. > > > > > S 6.1. > > >> receives an SMR-based Map-Request and the source is not in > the > > >> Locator-Set for the stored Map-Cache entry, then the > > responding Map- > > >> Request MUST be sent with an EID destination to the mapping > > database > > >> system. Since the mapping database system is a more secure > > way to > > >> reach an authoritative ETR, it will deliver the Map-Request > > to the > > >> authoritative source of the mapping data. > > > > > > If I'm understanding this correctly, this allows an ETR to > prevent an > > > ITR from learning that it is no longer the appropriate ETR for a > > > prefix. The way this attack works is that before the topology > > shift, I > > > send SMRs, thus causing Map-Requests, which, because my entry is > > > cached, refresh the cache on the ITR past the topology shift. I > can > > > keep doing this indefinitely. Am I missing something > > > > Well if the ETR is being spoofed, then there is Map-Request load, > > but it won’t corrupt the ITR’s map-cache. The ITR always sends a > > verifying Map-Request to the mapping system to get the latest and > > authenticated RLOC-set for the mapping. Rate-limiting is necessary > > so each SMR received DOES NOT result in a Map-Requerst to the > > mapping system. > > > > > > I'm probably just confused here: SMRs go through the mapping system, not > > directly? If so, I agree that this wont' work. > > > > > > > S 5. > > >> \ | UDP Length | UDP Checksum > > | > > >> > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > >> | > > | > > >> | LISP Message > > | > > >> | > > | > > >> > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > > > > What do these two diagrams correspond to? v4 and v6? This needs > > > explanation. > > > > It is th entire IP packet sent as a LISP control-message. The header > > before the diagrams indicate they are UDP packets. > > > > > > A caption would probably help. > > > > > S 5.2. > > >> P: This is the probe-bit, which indicates that a Map-Request > > SHOULD > > >> be treated as a Locator reachability probe. The receiver > > SHOULD > > >> respond with a Map-Reply with the probe-bit set, > > indicating that > > >> the Map-Reply is a Locator reachability probe reply, with > the > > >> nonce copied from the Map-Request. See RLOC-Probing > > Section 7.1 > > >> for more details. > > > > > > How am I supposed to handle this if I am a Map Server. > > > > It should be ignored. I will add text to reflect this point. Good > point. > > > > > > > > S 5.2. > > >> receipt. > > >> > > >> L: This is the local-xtr bit. It is used by an xTR in a > > LISP site to > > >> tell other xTRs in the same site that it is part of the > > RLOC-set > > >> for the LISP site. The L-bit is set to 1 when the RLOC > > is the > > >> sender's IP address. > > > > > > Is the xTR supposed to filter this on exiting the site. > > > > Nope. > > > > > > Won't this cause problems on ingress to another site? > > > > > S 5.3. > > >> originating Map-Request source. If the RLOC is not in the > > Locator- > > >> Set, then the ETR MUST send the "verifying Map-Request" to > the > > >> "piggybacked" EID. Doing this forces the "verifying > > Map-Request" to > > >> go through the mapping database system to reach the > > authoritative > > >> source of information about that EID, guarding against > > RLOC-spoofing > > >> in the "piggybacked" mapping data. > > > > > > This text here doesn't seem compatible with either of the two > cases > > > listed in "EID-prefix" above. > > > > I don’t understand the comment Eric. Maybe because I can’t find the > > exact reference to EID-prefix where you think there is a conflict. > > Please cite for me. Thanks. > > > > This does seem to have been assigned to the wrong text. > > > > I am referring to: > > > > " A Map-Reply returns an EID-Prefix with a prefix length that is less > > than or equal to the EID being requested. The EID being requested is > > either from the destination field of an IP header of a Data-Probe or > > the EID record of a Map-Request. The RLOCs in the Map-Reply are > > " > > > > versus > > > > " EID-Prefix: This prefix is 4 octets for an IPv4 address family and > > 16 octets for an IPv6 address family when the EID-Prefix-AFI is 1 > > or 2, respectively. For other AFIs [AFI], the length varies and > > for the LCAF AFI the format is defined in [RFC8060]. When a Map- > > " > > > > This is just the question of whether "prefix length" refers to the field > or > > the significant bits of the field. > > > > > > > > > > > > > > S 5.4. > > >> 'Nonce' field. > > >> > > >> Record TTL: This is the time in minutes the recipient of > > the Map- > > >> Reply will store the mapping. If the TTL is 0, the entry > > MUST be > > >> removed from the cache immediately. If the value is > > 0xffffffff, > > >> the recipient can decide locally how long to store the > > mapping. > > > > > > Am I supposed to merge this with previous mappings? REmove them? > > > > No replace it. There is text that says this that is not in the > > packet format description section. > > > > > > OK. > > > > > > > S 8.3. > > >> of the mapping database protocols. > > >> > > >> 8.3. Map-Server Processing > > >> > > >> Once a Map-Server has EID-Prefixes registered by its client > > ETRs, it > > >> can accept and process Map-Requests for them. > > > > > > This section is confusing because the introduction says that this > > > function is only performed by Map-Resolvers: > > > ' > > > "The LISP Mapping Service defines two new types of LISP-speaking > > > devices: the Map-Resolver, which accepts Map-Requests from an > > > Ingress > > > Tunnel Router (ITR) and "resolves" the EID-to-RLOC mapping > using a > > > mapping database; and the Map-Server, which learns authoritative > > > EID- > > > to-RLOC mappings from an Egress Tunnel Router (ETR) and > publishes > > > them in a database.” > > > > The document does cover the operation of a Map-Resolver and a > > Map-Server. Some functions are performed only by Map-Resolvers only > > and other different functions are performed by Map-Servers only. > > > > I am not sure what you don’t understand. > > > > > > Sure: As I understand it, Map Resolvers process Map Requests, and Map > > Servers do not (that's what the quoted text seems to say). However, this > > sentence talks about a Map Server processing a Map Request. That's > > where I am confused. > > > > -Ekr > > > > > > Thanks, > > Dino > > >
- [lisp] Eric Rescorla's Discuss on draft-ietf-lisp… Eric Rescorla
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Dino Farinacci
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Eric Rescorla
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Joel M. Halpern
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Eric Rescorla
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Joel M. Halpern
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Eric Rescorla
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Joel M. Halpern
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Eric Rescorla
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Dino Farinacci
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Eric Rescorla
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Dino Farinacci
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Eric Rescorla
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Dino Farinacci
- Re: [lisp] Eric Rescorla's Discuss on draft-ietf-… Benjamin Kaduk