Two-Way Active Measurement Protocol (TWAMP) YANG Data Model
draft-ietf-ippm-twamp-yang-13
Yes
(Spencer Dawkins)
No Objection
(Alvaro Retana)
(Deborah Brungard)
(Martin Vigoureux)
Note: This ballot was opened for revision 10 and is now closed.
Spencer Dawkins Former IESG member
Yes
Yes
(for -10)
Unknown
Adam Roach Former IESG member
(was Discuss)
No Objection
No Objection
(2018-07-02)
Unknown
Thanks for addressing my discuss and comments
Alexey Melnikov Former IESG member
No Objection
No Objection
(2018-06-18 for -11)
Unknown
bit unauth-test-encrpyt-control { I think you probably mean "encrypt" above position 3; description "When using the Mixed Security Mode, the TWAMP-Test protocol follows the Unauthenticated mode and the TWAMP-Control protocol the Encrypted mode."; reference "RFC 5618: Mixed Security Mode for the Two-Way Active Measurement Protocol (TWAMP)"; } On pages 25-26: grouping key-management { list key-chain { key key-id; leaf key-id { type string { length 1..80; } description "KeyID used for a TWAMP-Control connection. As per Section 3.1 of RFC 4656, KeyID is 'a UTF-8 string, up to 80 octets in length' and is used to select which 'shared This makes me slightly uncomfortable about possibility of truncating a UTF-8 encoding of some Unicode characters, but this probably doesn't matter in reality. Are these likely to be used for display? shared secret the [Control-Client] wishes to use to authenticate or encrypt'.";
Alissa Cooper Former IESG member
No Objection
No Objection
(2018-06-21 for -11)
Unknown
I support Adam's DISCUSS. Section 1.1: I'm surprised to see the two references to the long-expired NFVRG drafts. If a reference to describe virtualized infrastructure using orchestration is really needed (I'm not convinced that it is), I would assume a better reference exists from outside the IETF/IRTF. Section 5.2: OLD "Encrypted mode 'makes it impossible to alter timestamps undetectably.' See also Section 4 of RFC 7717 and Section 6 of RFC 4656." NEW "Encrypted mode 'makes it impossible to alter timestamps undetectably' [Section 6 of RFC 4656]. See also Section 4 of RFC 7717." Process comment more for the AD: the YANG doctors reviewed a version of this more than a year ago. Is that typical or would they normally review again during IETF LC?
Alvaro Retana Former IESG member
No Objection
No Objection
(for -11)
Unknown
Ben Campbell Former IESG member
No Objection
No Objection
(2018-06-19 for -11)
Unknown
Substantive: §7: The security consideration lists a couple of examples of writeable nodes that might be vulnerable. I'd like to see an actual list of nodes thought to be vulnerable, along with a sentence or two describing the risks for each. Are there no nodes that are privacy (or otherwise) sensitive when just readable? Editorial: - Title/abstract: It seems like there's a bit more than a data model here; there some normative behavior as well. §3.3: - first bullet: s/ "identical with " / "identical to " - third bullet: "such as" and "for example" are redundant.
Benjamin Kaduk Former IESG member
No Objection
No Objection
(2018-06-18 for -11)
Unknown
Perhaps I am confused and/or misreading things, but the descriptions of the control-client and session-reflector include discussion of 'sid' session identifiers as if they were always used, but the mode bitmap includes a separate bit for negotiation of 'individual-session-control' for session identifier usage. Is there some conflict between this mandatory/negotiable distinction, or are they actually talking about different things? Comments below in document order, but please pay special note to the (potential) need for global uniqueness of key-ids, the PBKDF2 iteration count, and the list of sensitive nodes to call out in the security considerations. Section 3.1 o Authentication and encryption attributes such as KeyID, Token and the Client Initialization Vector (Client-IV); see also the last paragraph of Section 6 in OWAMP [RFC4656] and Randomness Requirements for Security [RFC4086]. I'm confused about what the RFC4656 reference is intended to call out -- the reliance on AES to be resistant to chosen plaintext, or the randomly generated challenge from the server, or the existential forgeries? o Information pertaining to the test packet stream, such as the test starting time, which performance metric is to be used Registry for Performance Metrics [I-D.ietf-ippm-metric-registry], or whether the test should be repeated. Is there something missing before or around "Registry for Performance Metrics"? The current text is hard to read. Section 3.4 Each Session-Reflector is associated with zero or more TWAMP-Test sessions. For each test session, the REFWAIT timeout parameter which determines whether to discontinue the session if no packets have been received (TWAMP [RFC5357], Section 4.2) can be configured. nit: I think this would be easier to read if "which determines...received" was offset by commas or parentheses. Read-only access to other data model parameters, such as the Sender IP address is foreseen. Each test session can be uniquely identified by the 4-tuple mentioned in Section 3.2. Nit: comma after "Sender IP address". Section 4.1 [...] Specifically, mode-preference-chain lists the mode and its corresponding priority, expressed as a 16-bit unsigned integer, where zero is the highest priority and subsequent integers increase by one. I thought I remembered some discussion about this text being unclear and removing "and subsequent integers increase by one" being proposed. But I don't see that discussion in an obvious place, so maybe it was on a different document. Note that the list of preferred Modes may set bit position combinations when necessary, such as when referring to the extended [...] Maybe "may set multiple bits independently" would be more clear? But it seems that some bit combinations don't make any sense, like unauthenticated+authenticated -- is there need for more expository text here? [...] The secret-key is the shared secret, a sequence of octets of arbitrary length whose interpretation is unspecified. The key-id and secret-key encoding SHOULD follow Section 9.4 of YANG [RFC7950]. [...] Section 9.4 of YANG is for (printable) strings, but the secret-key is binary -- should this get a Section 9.8 reference as well? I'm also not sure that leaving it as "arbitrary length" is great -- if we're using it to derive 16-byte AES keys and 32-byte HMAC-SHA1 keys, we could at least say "SHOULD contain at least 128 bits of entropy". Section 4.2 [...] The Server, being prepared to conduct sessions with more than one Control-Client, uses KeyIDs to choose the appropriate secret-key; a Control-Client would typically have different secret keys for different Servers. key-id tells the Server which shared-secret the Control-Client wishes to use for authentication or encryption. Does this imply a global uniqueness requirement for key-ids? If so, that should be called out more clearly. Section 4.3 | name | | ctrl-connection-name {ro} | | fill-mode | | number-of-packets | | state {ro} | | sent-packets {ro} | | rcv-packets {ro} | | last-sent-seq {ro} | | last-rcv-seq {ro} | +---------------------------+ nit: should the "{ro}" on "state" be right-aligned with the others? Is there any privacy concern about exposing the parent-connection 4-tuple? Section 5.2 In the 'count' leaf, a default value of 10 (corresponding to an iteration count of 2^10 == 1024 for PBKDF2) is described. This seems quite low for a PBKDF2 iteration count, by modern standards. In "normal" cryptographic protocols we would generally be using a default closer to 32768 == 2^15 (which I see is the default *max* count value, and there is additional discussion of the issue in the leaf description for that leaf). Perhaps one could make an argument that this is just for test setups and the keys and data exchanged are "not very valuable", but there is always risk of key sharing across protocols, and my preference is to present the strong defaults and give users the option to reduce where appropriate. What are the authors' thoughts here? Section 7 There are probably more nodes that can get called out as particularly vulnerable, such as the count and max-count nodes that can cause a long time to be spent on PBKDF2 iterations, the dscp markings, the mode bitmask, etc. Appendix A The <secret-key> elements appear to be using base64-encoded values. Where is it specified that such encoding is used for the binary values? (I assume this is just my ignorance of a generic standard, so please enlighten me!) Am I reading it right that the <count>30</count> means 2^30 (one billion) PBKDF2 iterations? Has this actually been run in practice? It seems like it would be painfully slow.
Deborah Brungard Former IESG member
No Objection
No Objection
(for -11)
Unknown
Eric Rescorla Former IESG member
No Objection
No Objection
(2018-06-19 for -11)
Unknown
Rich version of this review at: https://mozphab-ietf.devsvcdev.mozaws.net/D3912 COMMENTS S 6.1. > Figure 8 shows a configuration example for a Control-Client with > client/admin-state enabled. In a real implementation following > Figure 2 this would permit the initiation of TWAMP-Control > connections and TWAMP-Test sessions. > > [note: '\' line wrapping is for formatting only] Most of these examples do not contain any line wrapping. S 7. > </twamp> > </data> > > 7. Security Considerations > > The YANG module specified in Section 5 this document defines a schema Some words about the threat model would be appreciated here. Is the assumption that the two sender and the reflector are owned by whoever runs the network and therefore they are not mounting an attack? If not, what is the model?
Ignas Bagdonas Former IESG member
(was Discuss)
No Objection
No Objection
(2018-06-26 for -11)
Unknown
Thank you for addressing DISCUSS comments.
Martin Vigoureux Former IESG member
No Objection
No Objection
(for -11)
Unknown
Mirja Kühlewind Former IESG member
No Objection
No Objection
(2018-06-18 for -11)
Unknown
High level question: How does this YANG model relate to the lmap YANG model (rfc8194)?
Suresh Krishnan Former IESG member
No Objection
No Objection
(2018-06-20 for -11)
Unknown