>No window will be big enough as experience shows some users have [clocks] that >are off by more than an hour and a half.
FWIW, I have seen users with clocks a year off (not at HP). They set their clocks wrong so they could run expired beta software. Any requirement for synchronizing clocks will be actively circumvented, occasionally. -----Original Message----- From: oauth-boun...@ietf.org [mailto:oauth-boun...@ietf.org] On Behalf Of Eran Hammer-Lahav Sent: Sunday, May 29, 2011 10:55 PM To: Peter Wolanin; Skylar Woodward Cc: OAuth WG Subject: Re: [OAUTH-WG] Fwd: issues with token age element - MAC token 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
