I can't speak for Mozilla, but I can tell you that many folks don't have synchronized clocks, for a wide variety of reasons. I guess I don't really understand why you view age as problematic. You reference "fragility of using time-since-credentials-issued" but you don't say what exactly is fragile about it. There's nothing particularly complex about age, especially when using the monotonic clock provided by all modern operating systems.
Adam On Mon, May 30, 2011 at 12:03 AM, Skylar Woodward <sky...@kiva.org> wrote: > But see, now you are specializing the use of MAC token even more - now it's > becoming a service mainly for user-agents on home desktops? This is further > for the original goal of making MAC as flexible is possible. In this case you > should change the spec name to > MAC_TOKEN_FOR_BROWSER_COOKIE_REPLACEMENT_IN_AGENTS_LIKE_FIREFOX - or MTBCRLF > for short. > > Sarcasm aside, my point is that timestamp is just as good as your offset > technique and is more: reliable, straightforward, flexible. > > User agents that care about creating robust behavior for home desktops or > mobiles (presumably of users and OS not yet sophisticated enough to check > network time on their own) should be advised to do clock correction on their > own (by pinging a time service) and trusting the device clock alone. > > Please change the spec back to using timestamp rather than age. > > I'd also like to hear a convincing argument from the Mozilla co-authors about > why they think that age is more resilient than the above (I believe it is > not) and further more why they would find the above unattractive or difficult > to implement in a modern user-agent. > > Thanks, > skylar > > ... -.- -.-- .-.. .- .-. — .-- --- --- -.. .-- .- .-. -.. — ... -.- -.-- .-.. > .- .-. — .-- --- --- -.. .-- .- .-. -.. > skylar woodward > Kiva Developer Program / build.kiva.org / @buildkiva > > > On May 30, 2011, at 7:54 AM, Eran Hammer-Lahav wrote: > >> Any kind of clock sync requirement for user-agents (basically, home >> desktops) it completely impractical. The added complexity pales in >> comparison to the difficulty of trying to use timestamps and any kind of >> clock sync. No window will be big enough as experience shows some users have >> closes that are off by more than an hour and a half. >> >> The issue here is who is this being optimized for. Server-to-server >> communication should simply use TLS for privacy and MITM protection on top >> of MAC instead of using nonces to prevent replay. The whole point of this >> kind of replay protection is when TLS is not available. >> >> I think a better approach is to simply make checking the nonce optional when >> TLS is used. >> >> EHL >> >>> -----Original Message----- >>> From: oauth-boun...@ietf.org [mailto:oauth-boun...@ietf.org] On Behalf >>> Of Peter Wolanin >>> Sent: Sunday, May 29, 2011 6:53 PM >>> To: Skylar Woodward >>> Cc: OAuth WG >>> Subject: Re: [OAUTH-WG] Fwd: issues with token age element - MAC token >>> >>> I am also concerned by the fragility of using time-since-credentials-issued, >>> and also the added complexity of specifying this construction. >>> >>> I think it would be preferable to always require a timestamp as part of the >>> authorization header, and maybe even include in the spec a maximum time >>> difference between client and server (e.g. 900 seconds) that can be >>> tolerated. This makes generating the nonce easier also, since the value >>> need >>> to longer be unique over all time. >>> >>> We have such rules in place for an HMAC-based authentication system we >>> use. Once in a while a client has a local clock so far out of sync that >>> there is an >>> issue, but it's rare. >>> >>> -Peter >>> >>> On Mon, May 23, 2011 at 9:16 PM, Skylar Woodward <sky...@kiva.org> >>> wrote: >>>> Resending to the list from my subscribed account... >>>> >>>> Begin forwarded message: >>>> >>>>> From: Skylar Woodward <sky...@larw.com> >>>>> Date: May 23, 2011 6:14:00 PM PDT >>>>> To: Skylar Woodward <sky...@kiva.org> >>>>> Cc: Eran Hammer-Lahav <e...@hueniverse.com>, OAuth WG >>>>> <oauth@ietf.org> >>>>> Subject: Re: [OAUTH-WG] issues with token age element - MAC token >>>>> >>>>> So after discussing this today and reflecting on it a bit, I would >>>>> suggest that >>> nonce simply be the "unique value" (as it is so named) without further >>> requirements. It might be suggested that this be composed of an >>> random+timestamp (not age) value, but that seems more of a MAY or >>> "recommended" practice. If the expectation is that very few if any providers >>> would actually check the timestamp (or moreover, the nonce itself), why add >>> terminology in the draft that requires it? Developers are doing extra >>> housekeeping (and perhaps for a perceived benefit) but with no payoff or >>> added security. >>>>> >>>>> I'm sending this feedback based on having implemented the v3-5 changes >>> last night (for both client credentials and requests w/ access tokens). >>> After >>> the changes, the nonce creation is now the most complicated part of the >>> normalized request string and yet these changes offer the least benefit. >>> What's most important is that nonces are unique on each request for an ID. >>>>> >>>>> There are issues with age as well: >>>>> >>>>> - As Bill mentioned, if the client stores the issue time based on >>>>> receipt, then the internal clock changes (presumably w/o knowledge of >>>>> the software storing the dates) then time will also fail. Assuming >>>>> that a user with a bad clock (of by hours or more) will never fix it >>>>> and actually encourages bad user behavior (don't fix your clock or >>>>> Twitterbot will stop working!). Though we say that timezones won't >>>>> bring about the situation of changed clock, I'd be to differ. Many >>>>> users aren't savvy enough to change time zone, but just adjust the >>>>> time to local time anyway. Users who are more likely to get it right >>>>> already have auto clock sync enabled (via web, mobile, etc.) >>>>> >>>>> - What if the token wasn't originally issued programmatically? In this >>>>> case, >>> the issue time has to be obtained from the server and stored on the client >>> then you have the same problem as with a timestamp - the client clock is not >>> sync'd to the server clock and there is no adjustment. You want this to >>> apply >>> to uses outside of just OAuth, but now requiring the client to be able to >>> determine an issue time based on when it receives an HTTP request >>> necessarily limits the types of token flows for which this can be used. >>>>> >>>>> - It's one more detail to store. Hardly an issue for a developer, but it >>>>> is >>> inelegant. It's like having a double ID. Yet it's not an ID, it is actually >>> more of a >>> recording of "my personal clock offset value" but obfuscated several times >>> over (one for each token) as issue_date. >>>>> >>>>> - This implementation assumes software programs use the computer >>> internal clock exclusively for timestamp. A robust program that is dependent >>> on accurate timestamps would ping the origin server (or similar trusted time >>> authority) to ask it the current time. Then it could store a "my device >>> clock >>> offset" value for the lifetime of the program execution. All requests >>> needing >>> timestamp would be adjusted accordingly. For age, if the clock is changed >>> since the stored issue_date, the problem can't be corrected in this manner. >>> Thus, a significant advantage for timestamp. >>>>> >>>>> All in all, this seems like a misguided but well-intentioned attempt to >>>>> get >>> around end-user issues of mis-set clocks. It feels like a hack and it >>> certainly >>> isn't a foolproof solution. The more I think about the implications of the >>> age >>> parameter, the less I like it. Timestamp has been used for many years in the >>> industry and with reasonable success in relevant applications. If we change >>> to >>> a new way of trying to sync on time I think we run a greater risk of >>> stumbling >>> upon unforeseen issues, such as those outlined above. >>>>> >>>>> I recommend the requirement of an age (or timestamp for that matter) >>> be dropped from the nonce construction. For providers that deem it >>> valuable, timestamp can be an optional value (either as part of the nonce or >>> the overall header, as before). >>>>> >>>>> skylar >>>>> >>>>> >>>>> >>>>> On May 23, 2011, at 2:11 AM, Skylar Woodward wrote: >>>>> >>>>>> You may have noticed, on page 8 the host is listed as "example.net" >>>>>> - should be example.com, I believe. (draft v5) >>>>>> >>>>>> All in all, I'm in support of the changes in v2. Certainly addresses my >>> hesitations from v2. >>>>>> >>>>>> skylar >>>>>> >>>>>> >>>>>> On May 9, 2011, at 12:36 PM, Eran Hammer-Lahav wrote: >>>>>> >>>>>>> (Please discuss this draft on the Apps-Discuss >>>>>>> <apps-disc...@ietf.org> mailing list) >>>>>>> >>>>>>> http://tools.ietf.org/html/draft-hammer-oauth-v2-mac-token >>>>>>> >>>>>>> While this document has moved to the Apps-Discuss mailing list for the >>> time being, I wanted to give a quick update to those who have been >>> following this draft which originated on this list. >>>>>>> >>>>>>> The major changes since -02 are: >>>>>>> >>>>>>> * Removed OAuth terminology and association. The draft is now a >>> general purpose HTTP authentication scheme. It does include an OAuth 2.0 >>> binding which is described in less than a page. One suggestion would be to >>> move section 5.1 into the OAuth specification and drop all the OAuth 2.0 >>> text >>> from the MAC draft. >>>>>>> >>>>>>> * Added 'Set-Cookie' extension for using MAC with session cookies. >>>>>>> >>>>>>> * Removed request URI query normalization. The new draft uses the >>> raw request URI unchanged. >>>>>>> >>>>>>> * Replaced timestamps with credentials age to remove the need for >>> clock sync. >>>>>>> >>>>>>> * Added a placeholder for extension, allowing random text to be >>> included in the request and MAC. >>>>>>> >>>>>>> * Added issuer attribute for identifying the source of the credentials >>>>>>> as >>> an additional protection. >>>>>>> >>>>>>> Draft -04 is not compatible with previous drafts. >>>>>>> >>>>>>> EHL >>>>>>> _______________________________________________ >>>>>>> OAuth mailing list >>>>>>> OAuth@ietf.org >>>>>>> https://www.ietf.org/mailman/listinfo/oauth >>>>>> >>>>> >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> >>> >>> >>> >>> -- >>> Peter M. Wolanin, Ph.D. : Momentum Specialist, Acquia. Inc. >>> peter.wola...@acquia.com : 978-296-5247 >>> >>> "Get a free, hosted Drupal 7 site: http://www.drupalgardens.com"; >>> _______________________________________________ >>> OAuth mailing list >>> OAuth@ietf.org >>> https://www.ietf.org/mailman/listinfo/oauth > > _______________________________________________ > OAuth mailing list > OAuth@ietf.org > https://www.ietf.org/mailman/listinfo/oauth > _______________________________________________ OAuth mailing list OAuth@ietf.org https://www.ietf.org/mailman/listinfo/oauth
