[Hipsec] Benjamin Kaduk's No Objection on draft-ietf-hip-rfc4423-bis-19: (with COMMENT)
Benjamin Kaduk <kaduk@mit.edu> Wed, 09 May 2018 20:58 UTC
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From: Benjamin Kaduk <kaduk@mit.edu>
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Date: Wed, 09 May 2018 13:58:25 -0700
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Subject: [Hipsec] Benjamin Kaduk's No Objection on draft-ietf-hip-rfc4423-bis-19: (with COMMENT)
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Benjamin Kaduk has entered the following ballot position for draft-ietf-hip-rfc4423-bis-19: No Objection 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/iesg/statement/discuss-criteria.html for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: https://datatracker.ietf.org/doc/draft-ietf-hip-rfc4423-bis/ ---------------------------------------------------------------------- COMMENT: ---------------------------------------------------------------------- I share Eric's concerns about the need for second-preimage-resistance from the hash, and in particular with the birthday bound, it's unclear that using a 128-bit hash leaves a very large margin for growth. Some other section-by-section notes follow. Section 1 [...] HIP provides for limited forms of trust between systems, enhance mobility, multi-homing and dynamic IP renumbering, aid in protocol translation / transition, and reduce certain types of denial-of-service (DoS) attacks. I think that something is weird here with singular vs. plural in the list elements. Section 4 I agree with the secdir reviewer's not about "SHOULD NOT [implement non-cryptographic HIP]" Section 5.1 At the client side, a host may have multiple Host Identities, for instance, for privacy purposes. Another reason can be that the person utilizing the host employs different identities for different administrative domains as an extra security measure. If a HIP-aware middlebox, such as a HIP-based firewall, is on the path between the client and server, the user or the underlying system should carefully choose the correct identity to avoid the firewall to unnecessarily drop HIP-based connectivity [komu-diss]. In addition to the firewall case, choosing the correct identifier can also impact the privacy considerations, as a given identifier would be trackable by on-path entities. Section 6.2 When a node moves while communication is already on-going, address changes are rather straightforward. The peer of the mobile node can just accept a HIP or an integrity protected ESP packet from any address and ignore the source address. However, as discussed in Section 12.2 below, a mobile node must send a HIP UPDATE packet to inform the peer of the new address(es), and the peer must verify that the mobile node is reachable through these addresses. Am I reading this right that from a technical perspective, the peer can just accept stuff from wherever, but from a policy/protocol perspective the UPDATE requirement is included? The text could probably be a bit more clear, potentially even without using RFC 2119 language. Section 10 There are a number of variables that influence the HIP exchange that each host must support. All HIP implementations should support at least 2 HIs, one to publish in DNS or similar directory service and an unpublished one for anonymous usage. Although unpublished HIs I suggest a parenthetical that the unpublished one should expect to be rotated frequently in order to disrupt linkability/trackability. will be rarely used as responder HIs, they are likely to be common for initiators. Support for multiple HIs is recommended. [...] If multiple means "more than two", it's probably better to say that. (If multiple means "more than one", this is just a weaker version of "should support at least 2", above.) And it's rather tempting to make it a MUST, anyway. Many initiators would want to use a different HI for different responders. The implementations should provide for a policy mapping of initiator HITs to responder HITs. This policy should also include preferred transforms and local lifetimes. "mapping of initiator to responder" is potentially confusing, in that in practice the procedure will be "I want to talk to responder A, so let me look up that I use HIT X to talk to responder A", which is the opposite direction from this text. Section 11.1 I'd consider replacing "is an attempt to" with "attempts to" -- for example, IPv6 tries to do a lot of things in addition to killing NAT! Section 11.3.1 [...]Second, a data plane component is needed. Most HIP implementations utilize the so called BEET mode of ESP that has been available since Linux kernel 2.6.27, but is included also as a userspace component in a few of the implementations. Nit: "but ESP is included", I think. Section 12.1 I don't understand the usage of "a-priori" in: The need to support multiple hashes for generating the HIT from the HI affords the MitM to mount a potentially powerful downgrade attack due to the a-priori need of the HIT in the HIP base exchange. In HIP, the Security Association for ESP is indexed by the SPI; the source address is always ignored, and the destination address may be ignored as well. Therefore, HIP-enabled Encapsulated Security Payload (ESP) is IP address independent. This might seem to make attacking easier, but ESP with replay protection is already as well protected as possible, and the removal of the IP address as a check should not increase the exposure of ESP to DoS attacks. It seems like there's still some potential incrased exposure, as validating the ESP crypto is presumably more expensive than validating source/destination IP addresses. Section 12.3 [...] At middleboxes, HIP-aware firewalls [lindqvist-enterprise] can use HITs or public keys to control both ingress and egress access to networks or individual hosts, even in the presence of mobile devices because the HITs and public keys are topologically independent. [...] Nit: I think that just "topology independent" is what's intended.
- [Hipsec] Benjamin Kaduk's No Objection on draft-i… Benjamin Kaduk
- Re: [Hipsec] Benjamin Kaduk's No Objection on dra… Miika Komu
- Re: [Hipsec] Benjamin Kaduk's No Objection on dra… Benjamin Kaduk