On Sun, Nov 12, 2017 at 5:08 AM, Black, David <david.bl...@dell.com> wrote:
> Hi Ekr, > [writing as draft shepherd] > > Let's see if the two of us can find some time in Singapore to talk about > the two crypto algorithm Discuss points (encryption and secure hash), as > (IMHO) the authors' intentions are good: > Yep. - Encryption: The intent is - don't use anything weaker than AES-128, e.g., > don't even think about using 3DES. The concern is how to write that > requirement in a way that would survive hypothetical discovery of a > catastrophic cryptanalytic attack on AES-128. > Or even a small one. I mean, what does this say about Curve25519 or 4Q. - Secure Hash: The intent is - don't use vanity crypto. Does the Security > Area have some text that could just be copied to say that? > Not to my knowledge. I'm not sure this is really useful to say. > On URG handling, the Discuss point is: > > > IMPORTANT: This actually seems to be a bit confusing about how to > > handle URG. Consider TCP-use-TLS, you would just process URG in the > > normal way and then generate errors if URG causes reordering at the > > TLS layer. This seems like a reasonable procedure but is at least > > arguably prohibited by this text. > > I'm confused, as the only "MUST" requirement on URG handling is: > > o TEPs MUST prevent corrupted packets from causing urgent data to be > delivered when none has been sent. > > Surely TCP-use-TLS meets that requirement ;-). Beyond that, the list of > implementation techniques that follows uses "MAY" twice, and is not > intended to be comprehensive. Would stating that the list of > implementation techniques is not comprehensive suffice, or is something > else causing heartburn here? > Yep, that would be fine. I read those MAYs as exhaustive. -Ekr > > Thanks, --David > > > -----Original Message----- > > From: Eric Rescorla [mailto:e...@rtfm.com] > > Sent: Friday, November 10, 2017 9:04 PM > > To: The IESG <i...@ietf.org> > > Cc: draft-ietf-tcpinc-tcp...@ietf.org; Black, David <david.bl...@emc.com > >; > > tcpinc-cha...@ietf.org; Black, David <david.bl...@emc.com>; > tcpinc@ietf.org > > Subject: Eric Rescorla's Discuss on draft-ietf-tcpinc-tcpeno-13: (with > DISCUSS > > and COMMENT) > > > > Eric Rescorla has entered the following ballot position for > > draft-ietf-tcpinc-tcpeno-13: 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/iesg/stat > ement/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-tcpinc-tcpeno/ > > > > > > > > ---------------------------------------------------------------------- > > DISCUSS: > > ---------------------------------------------------------------------- > > > > o TEPs MUST NOT permit the negotiation of any encryption algorithms > > with significantly less than 128-bit security. > > IMPORTANT: I don't know what "significantly means". I wouldn't be > > making a point of this, but it's phrased as a normative requirement, > > so I don't know what conformance means. > > > > > > IMPORTANT: This actually seems to be a bit confusing about how to > > handle URG. Consider TCP-use-TLS, you would just process URG in the > > normal way and then generate errors if URG causes reordering at the > > TLS layer. This seems like a reasonable procedure but is at least > > arguably prohibited by this text. > > > > > > problems, TEPs MUST compute session IDs using only well-studied and > > conservative hash functions. That way, even if other parts of a TEP > > are vulnerable, it is still intractable for an attacker to induce > > > > IMPORTANT: this also does not seem to be unambiguous. > > > > > > ---------------------------------------------------------------------- > > COMMENT: > > ---------------------------------------------------------------------- > > > > > > > > 4. Provide a standard negotiation transcript through which TEPs can > > defend against tampering with TCP-ENO. > > > > This was unclear to me when I first read this. Maybe > > "Export a standard negotiation transcript to TEPs which they can use to > > defend > > against" > > > > opportunistically. It uses a new TCP option kind to negotiate one > > among multiple possible TCP encryption protocols or TEPs. The > > negotiation involves hosts exchanging sets of supported TEPs, where > > Nit: I would say "one TEP out of multiple" > > > > Also, "TCP encryption protocols or TEPs." is confusing. If you feel the > need to > > redefine, do "TCP encryption protocols (TEPs)" > > > > variable-length data. When "v = 0", the byte itself constitutes the > > entirety of the suboption. The 7-bit value "glt" expresses one of: > > I would say "the remaining 7-bit value, called "glt", may take on various > > meanings, as defined below" > > > > "b = 0" plays the "A" role. The host that sent "b = 1" plays the "B" > > role. > > This would be clearer if it (a) explained the reasoning and (b) appeared > before > > the packet formats. Perhaps something like > > > > "Because the passive opener MUST set b=1 and the active opener by default > > sets > > b=0, the normal cases is that the active opener is A and the passive > opener is > > B. Applications which depend on simultaneous open and have some other > > way of > > breaking the tie can set one side to b=1 (even though it is the active > opener) > > and thus arrange for correct role assignment. Otherwise, simultaneous > opens > > will fail" > > > > If both sides of a connection set "b = 1" (which can happen if the > > active opener misconfigures "b" before calling "connect"), or both > > sides set "b = 0" (which can happen with simultaneous open), then > > Why is this "misconfigures"? You allow them to do so. > > > > initial suboption byte (see Figure 4). By default, suboption data > > extends to the end of the TCP option. Hence, if only one suboption > > requires data, the most compact way to encode it is to place it last > > Why is this "by default"? It just seems like another setting of glt. > > > > connection or when there is any ambiguity over the meaning of the SYN > > data. This requirement applies to hosts that implement ENO even when > > ENO has been disabled by configuration. However, note that > > I think you may mean to say "when the last SYN TEP is not eventually > > negotiated" > > > > o TEPs MUST NOT depend on long-lived secrets for data > > confidentiality, as implementations SHOULD provide forward secrecy > > some bounded, short time after the close of a TCP connection. > > Maybe "depend solely" because one might want to use a DH mode where a > > static DH > > key is mixed in with an ephemeral. > > > > probability detect a FIN flag that was set or cleared in transit > > and does not match the sender's intent. A TEP MAY discard a > > segment with such a corrupted FIN bit, or may abort the connection > > What is "high probability" > > > > that disable urgent data by default. The exception is when > > applications and protocols are known never to send urgent data. > > > > (4) B -> A: SYN-ACK ENO<b=1,X,Y,Z> > > [rest of connection encrypted according to TEP Y] > > Can you show a=0 in line 1? > > > >
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