Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt
René Hummen <hummen.committees@gmail.com> Sat, 22 October 2016 08:22 UTC
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From: René Hummen <hummen.committees@gmail.com>
Date: Sat, 22 Oct 2016 10:22:32 +0200
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To: Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.com>
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Cc: René Hummen <hummen.rwth@gmail.com>, hipsec@ietf.org
Subject: Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt
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Hi, I just uploaded draft version 04, where I addressed Miika's comments as discussed in the previous emails. >From my point of view, this document is ready to proceed. BR René 2016-10-21 9:13 GMT+02:00 Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.com> : > Hi Rene, > > do you intend to release a new version of the draft with this addition? > What is the current status of the draft otherwise? > > Thanks, > > Gonzalo > > On 26/09/2016 4:46 PM, Miika Komu wrote: > > Hi René, > > > > On 09/11/2016 11:06 PM, René Hummen wrote: > >> Hello Miika, > >> > >> going through your email again, I saw a total of four suggestions. > >> > >> Three of them refer to imprecisions in the text of RFC 7401 (which I > >> copy/pasted for HIP DEX). There, I understood that consistency with RFC > >> 7401 has a higher priority than only fixing your comments for HIP DEX, > >> but keeping the text as is for RFC 7401. This means, I will not modify > >> the text in the HIP DEX draft. Is this also your intention? > > > > yes, 7401 takes precedence over my comments. > > > >> The last remaining issue is related to the UPDATE message and the > >> rekeying procedure (Section 6.10.). Here, I added the following > >> paragraph for clarification purposes: > >> > >> [RFC7402] specifies the rekeying of an existing HIP SA using the > >> UPDATE message. This rekeying procedure can also be used with HIP > >> DEX. However, where rekeying involves a new Diffie-Hellman key > >> exchange, HIP DEX peers MUST establish a new connection in order to > >> create a new Pair-wise Key SA due to the use of static ECDH key-pairs > >> with HIP DEX. > >> > >> Does this fix your issue? > > > > Yes. I assume you mean a new HIP association with connection. > > > >> BR > >> René > >> > >> > >> > >> On Tue, Jun 7, 2016 at 3:11 PM, Miika Komu <miika.komu@ericsson.com > >> <mailto:miika.komu@ericsson.com>> wrote: > >> > >> Hi, > >> > >> On 06/03/2016 02:20 PM, René Hummen wrote: > >> > >> This is part 3 of 3. > >> > >> > >> I am fine with your fixes. Some comments below. > >> > >> On Mon, Mar 28, 2016 at 10:05 PM, Miika Komu > >> <miika.komu@ericsson.com <mailto:miika.komu@ericsson.com> > >> <mailto:miika.komu@ericsson.com > >> <mailto:miika.komu@ericsson.com>>> wrote: > >> > >> > [...] > >> > >> > 6.2.1. CMAC Calculation > >> > > >> > [...] > >> > > >> > > >> > 5. Set Checksum and Header Length fields in the HIP > >> header to > >> > original values. Note that the Checksum and Length > fields > >> > contain incorrect values after this step. > >> > >> I guess also the values following HIP_MAC should be restored > >> since > >> they were wiped in the step 2. > >> > >> > >> I also found this description a bit imprecise, but it is taken > >> from > >> RFC7401. Step 2 already hints at the fact that parameters > >> following > >> HIP_MAC may still be of interest: > >> "Remove the HIP_MAC parameter, as well as all other parameters > >> that follow it with greater Type value, saving the > >> contents if > >> they will be needed later." > >> > >> The question is whether we want to fix the description for HIP > >> DEX or to > >> keep things as they are for consistency reasons. In the former > >> case, I > >> would prefer to completely rewrite the verification procedure to > >> work on > >> the received packet without removing any parameters. However, we > >> should > >> then probably also post an errata to RFC7401. If there are no > >> stong > >> opinions about that, I would go for the latter option. > >> > >> > >> Latter option works for me too. > >> > >> > The CKDF-Extract function is the following operation: > >> > > >> > CKDF-Extract(I, IKM, info) -> PRK > >> > >> What does the arrow operator signify? I thought that it > >> produces PRK, > >> but PRK is actually defined below. > >> > >> > >> The arrow is part of a basic mathematical function definition. > >> So yes, > >> PRK is the output (domain), but we still need to give it a > >> proper name. > >> I changed the artwork to clearly point out the inputs and > >> outputs. > >> > >> > >> Thanks, it is now better. > >> > >> Please check this section again in the updated version and get > >> back to > >> me if the above changes do not sufficiently help your > >> understanding. > >> > >> > >> It is good now, thanks! > >> > >> > L length of output keying material in octets > >> > (<= 255*RHASH_len/8) > >> > | denotes the concatenation > >> > > >> > The output keying material OKM is calculated as follows: > >> > > >> > N = ceil(L/RHASH_len/8) > >> > T = T(1) | T(2) | T(3) | ... | T(N) > >> > OKM = first L octets of T > >> > > >> > where > >> > > >> > T(0) = empty string (zero length) > >> > T(1) = CMAC(PRK, T(0) | info | 0x01) > >> > T(2) = CMAC(PRK, T(1) | info | 0x02) > >> > T(3) = CMAC(PRK, T(2) | info | 0x03) > >> > ... > >> > >> The Expand was a bit more clear, but still didn't understand > >> how to > >> get to the > >> Expanded key material due the arrow notation. > >> > >> > >> Ok, let's clarify this as several comments are related to the > >> arrow > >> notation. For the function definition we use the mathematical > >> arrow > >> notation (same as RFC 5869) and for the actual opertation we > >> use the > >> equals sign (same as RFC 5869). In the end, they denote the same > >> thing: > >> "assign X to Y". > >> > >> > >> Ok, this is what I guessed too. > >> > >> > (where the constant concatenated to the end of each > >> T(n) is a > >> > single octet.) > >> > >> Is there a max value? > >> > >> > >> I am not sure what you mean here. If you refer to the N in T(N) > >> then it > >> is defined above as N = ceil(L/RHASH_len/8). > >> > >> > >> Yes, I asked about the maximum value for N (which depends on L), but > >> never mind. > >> > >> > 8. The R1 packet may have the A-bit set - in this case, > >> the system > >> > MAY choose to refuse it by dropping the R1 packet and > >> returning > >> > to state UNASSOCIATED. The system SHOULD consider > >> dropping the > >> > R1 packet only if it used a NULL HIT in the I1 packet. > >> > >> I didn't understand the logic in the last sentence. > >> > >> > >> Someone must have had a reason for this recommendation, but that > >> someone > >> wasn't me. This is text from RFC7401. Any suggestions how to > >> proceed? > >> > >> > >> Fix similarly as the other RFC7401 issue in the beginning of this > >> email. > >> > >> > 6.7. Processing Incoming I2 Packets > >> > > >> > [...] > >> > > >> > 5. If the system's state machine is in the I2-SENT > >> state, the > >> > system MUST make a comparison between its local and > >> sender's > >> > HITs (similarly as in Section 6.3). If the local HIT is > >> smaller > >> > than the sender's HIT, it should drop the I2 packet, > >> use the > >> > peer Diffie-Hellman key, ENCRYPTED_KEY keying material > >> and nonce > >> > #I from the R1 packet received earlier, and get the local > >> > Diffie-Hellman key, ENCRYPTED_KEY keying material, and > >> nonce #J > >> > from the I2 packet sent to the peer earlier. > >> Otherwise, the > >> > system should process the received I2 packet and drop any > >> > previously derived Diffie-Hellman keying material Kij and > >> > ENCRYPTED_KEY keying material it might have generated > upon > >> > sending the I2 packet previously. The peer > >> Diffie-Hellman key, > >> > ENCRYPTED_KEY, and the nonce #J are taken from the just > >> arrived > >> > I2 packet. The local Diffie-Hellman key, ENCRYPTED_KEY > >> keying > >> > material, and the nonce #I are the ones that were sent > >> earlier > >> > in the R1 packet. > >> > >> Please replace "sender" with "peer" (or remote host) in this > >> section > >> for more symmetric terminology. > >> > >> get -> obtain > >> > >> > >> I can make these changes if you insist, but I was going for a > >> minimal > >> diff to RFC 7401. > >> > >> > >> Not insisting. > >> > >> > >> > 11. The implementation SHOULD also verify that the > >> Initiator's HIT > >> > in the I2 packet corresponds to the Host Identity sent in > >> the I2 > >> > packet. (Note: some middleboxes may not be able to > >> make this > >> > verification.) > >> > >> Why SHOULD? Why not MUST? I think we're talking about > >> end-hosts here > >> anyway. > >> > >> > >> It is defined this way in RFC 7401. Do you really want to > >> change the > >> packet processing behavior for HIP DEX only? > >> > >> > >> Fix similarly as the first RFC7401 issue in this email. > >> > >> > 6.10. Processing UPDATE, CLOSE, and CLOSE_ACK Packets > >> > >> > UPDATE, CLOSE, and CLOSE_ACK packets are handled > >> similarly in HIP DEX > >> > as in HIP BEX (see Sections 6.11, 6.12, 6.14, and 6.15 of > >> [RFC7401]). > >> > The only difference is the that the HIP_SIGNATURE is > >> never present > >> > and, therefore, is not required to be processed by the > >> receiving > >> > party. > >> > >> How does rekeying work with the extract and expand > functions? > >> > >> > >> Rekeying is not defined in this document, same as for RFC > >> 7401. That > >> being said, the rekeying procedure with reuse of the KEYMAT > >> from RFC > >> 7402 directly translates to HIP DEX. For new KEYMAT, the peers > >> need to > >> establish a new connection due to the use of static DH keys. > >> > >> > >> Maybe this should be explicitly stated in the draft. > >> > >> > >> > >> > 7. HIP Policies > >> > >> > There are a number of variables that will influence the > >> HIP exchanges > >> > that each host must support. All HIP DEX implementations > >> SHOULD > >> > provide for an ACL of Initiator's HI to Responder's HI. > >> This ACL > >> > SHOULD also include preferred transform and local > >> lifetimes. > >> > Wildcards SHOULD also be supported for this ACL. > >> > >> Why ACLs are mandatory? > >> > >> > >> It is not a MUST and considering that HIP DEX is primarly > >> targeted at > >> things, there is the need to do basic device authorizations > >> (based on > >> their identities) without a human in the loop. Of course you are > >> also > >> allowed to use more suffisticated authorization mechanisms. > >> > >> > >> Ok. > >> > >> ACL -> ACL consisting of > >> > >> > >> Changed to the following text that is closer to RFC 7401: > >> " All HIP DEX implementations SHOULD provide for an Access > >> Control List > >> (ACL), representing for which hosts they accept HIP diet > >> exchanges, > >> and the preferred transport format and local lifetimes. > >> Wildcarding > >> SHOULD be supported for such ACLs." > >> > >> > 8. Security Considerations > >> > >> > o The HIP DEX HIT generation may present new attack > >> opportunities. > >> > >> They cannot be used in ACLs. Maybe this could be mentioned. > >> Can this > >> be mitigated by always using full HIs? > >> > >> > >> I changed the bullet-point as follows: > >> "The HIP DEX HIT generation may present new attack > opportunities. > >> Hence, HIP DEX HITs should not be use as the only means > to > >> identify a peer in an ACL. Instead, the use of the > >> peer's HI is > >> recommended." > >> > >> > >> Ok. > >> > >> Note that I added a new Section 8 "Interoperability between HIP > >> DEX and > >> HIPv2" to satisfy your comment on HIP DEX and HIPv2 > >> compatibility. > >> > >> > >> Thanks! > >> > >> > >> _______________________________________________ > >> Hipsec mailing list > >> Hipsec@ietf.org <mailto:Hipsec@ietf.org> > >> https://www.ietf.org/mailman/listinfo/hipsec > >> <https://www.ietf.org/mailman/listinfo/hipsec> > >> > >> > > > > _______________________________________________ > Hipsec mailing list > Hipsec@ietf.org > https://www.ietf.org/mailman/listinfo/hipsec >
- [Hipsec] I-D Action: draft-ietf-hip-dex-02.txt internet-drafts
- Re: [Hipsec] I-D Action: draft-ietf-hip-dex-02.txt Robert Moskowitz
- [Hipsec] A review of draft-ietf-hip-dex-02.txt Miika Komu
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Gonzalo Camarillo
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Gonzalo Camarillo
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt René Hummen
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Miika Komu
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt René Hummen
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt René Hummen
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt René Hummen
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Miika Komu
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Miika Komu
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Gonzalo Camarillo
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt René Hummen
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Robert Moskowitz
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Miika Komu
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Gonzalo Camarillo
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt René Hummen
- Re: [Hipsec] A review of draft-ietf-hip-dex-02.txt Robert Moskowitz