[secdir] Re: Secdir telechat review of draft-ietf-httpbis-rfc6265bis-19

[Valery Smyslov <[e-mail]>]

[It seems that Steven responded to my review, but forgot to include CC:[e-mail]
and I didn't see the response until Deb has pointed me out to it:
https://mailarchive.ietf.org/arch/msg/httpbisa/BaKETLBU05ID_DOOl87ZCwqTZzE/ ]

Hi Steven,

thank you for addressing my concerns. I used the following two links from your message to evaluate
changes in the document (I don't know if new I-D is published):

https://github.com/httpwg/http-extensions/commit/4b5c5242984434dcbea153247ec7f7d9a509d0c9
https://github.com/httpwg/http-extensions/commit/f9881b3290e3edf7faeff933c8a49b0966285c55

I still have issue with the following sentence (In the Overview section of Security Considerations):

"In addition, by default, cookies do not provide confidentiality or integrity from network attackers, even when used in conjunction with HTTPS."

I think that it should either be elaborated (what "default" do you mean? does it mean that cookies are secure for "non-default" and how to reach it? 
"in addition" to what, given that previous text states basically the same - weak confidentiality and weak integrity of cookie?) or deleted.

My other concerns are either addressed or explained.

Regards,
Valery.


> -----Original Message-----
> From: Valery Smyslov via Datatracker <[e-mail]>
> Sent: Tuesday, February 11, 2025 4:32 PM
> To: [e-mail]
> Cc: [e-mail]; [e-mail]; [e-mail]
> Subject: [secdir] Secdir telechat review of draft-ietf-httpbis-rfc6265bis-19
> 
> Reviewer: Valery Smyslov
> Review result: Has Nits
> 
> I have reviewed this document as part of the security directorate's ongoing
> effort to review all IETF documents being processed by the IESG.  These
> comments were written primarily for the benefit of the security area directors.
> Document editors and WG chairs should treat these comments just like any other
> last call comments.
> 
> This document defines the HTTP cookie protocol. The document is well written
> and easy to read.
> 
> The Security Considerations section is mostly taken intact from RFC 6265
> (except that considerations for newly introduced SameSite cookies are added),
> and only overviews "a few of the more salient issues". This is a bit
> disappointing, I would have expected that more considerations are added based
> on 14 years experience since RFC 6265 was published. However, I understand that
> the list of security considerations would have been very long and still hardly
> complete. Since it seems to be next to impossible to accurately list all the
> possible cookie exploits, I wil mark the document as "Ready", but with a
> reservation, that the the Security Considerations section is intentionally not
> complete and this seems not possible to fix.
> 
> I still have some easy to address suggestions that I think would be helpful for
> readers.
> 
> 1. Please, make it more clear that the restrictions on the cookie use, that the
> server imposes via attributes, are not guaranteed to be honored even by a
> honest user agent. For example, if the clocks on the server and on the client
> are out of sync, then the user agent may innocently try to use cookie beyond
> its lifetime. Thus, the imposed restrictions for the received cookies MUST be
> checked by the server.
> 
> 2. Section 8.1 states that "by default, cookies do not provide confidentiality
> or integrity from network attackers, even when used in conjunction with HTTPS".
> In my reading this sounds like HTTPS is useless for cookies security. I think
> that this needs a clarification. While use of HTTPS cannot prevent network
> attacks using cookies mounted by other participants in HHTP communications
> (like cross-site attacks), it does prevent eavesdropping and manipulation of
> cookies by on-path entities that don't participate in these communications. I
> believe it should be emphisized that encrypted transport does reduce the attack
> surface using cookies.
> 
> 3. Section 8.3 lists security risks when cookies are sent in clear and clause 3
> states: "A malicious client could alter the Cookie header before transmission,
> with unpredictable results". I failed to understand how this is concerned with
> the use of TLS. In my understanding, malicious clients can do this in any case,
> regardless on whether TLS is used or not. Am I missing something?
> 
> 4. Section 7.1, last para states that "it is RECOMMENDED that user agents adopt
> a policy for third-party cookies that is as restrictive as compatibility
> constraints permit". This gives no concrete recommendations, and no examples,
> thus making this requirement vague and subjective. I think this requirement
> should be provided with more details how to deal with it.
> 
> Just out of curiosity - the draft adds a requirement that cookie SHOULD NOT be
> greater than 400 days. I wonder why this particular margin was chosen. Why not
> 365 days (a year) - it looks like a natural equivalet to "very long, but not
> infinite"?
> 
> 
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