Re: [kitten] RFC2743 errata 4251
Nico Williams <nico@cryptonector.com> Mon, 15 December 2014 17:50 UTC
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Date: Mon, 15 Dec 2014 11:50:38 -0600
From: Nico Williams <nico@cryptonector.com>
To: Greg Hudson <ghudson@mit.edu>
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Subject: Re: [kitten] RFC2743 errata 4251
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On Mon, Dec 15, 2014 at 12:20:30PM -0500, Greg Hudson wrote: > On 12/10/2014 01:57 PM, Benjamin Kaduk wrote: > > Though future GSS-API extensions may add new uses of asynchronous > > security context tokens and ways to process them, applications > > using the GSS-API version 2, update 1, should generally call > > GSS_Delete_sec_context() after calling GSS_Process_context_token(), > > when the latter returns GSS_S_COMPLETE or GSS_S_FAILURE. > > I don't like the wording of this part. Encouraging applications to > assume that context tokens destroy the context essentially closes the > door to specifying context tokens which don't. > > (To be clear: saying that applications must eventually call > GSS_Delete_sec_context() is fine; saying that they should do so > immediately after a GSS_S_COMPLETE from GSS_Process_context_token() is > not fine.) GSS-APIv2u1 callers can still call GSS_Unwrap(), GSS_VerifyMIC(), and GSS_Pseudo_random()[*], and even GSS_Wrap() and GSS_GetMIC() before calling GSS_Delete_sec_context(), however, as it is today processing an async context token does mean that the other peer cannot continue. Therefore the caller of GSS_Process_context_token(), while they can continue to process per-msg tokens from the peer, has to get around to calling GSS_Delete_sec_context(). Sure, exiting, crashing, hanging around doing nothing -- these are also options, but not really desirable ones. In v2u1, the peer has indicated that it can't continue, so calling GSS_Wrap() and GSS_GetMIC() does the app no good[**]. Thus the word "generally". It's a bit of a weasel word that captures all of the above possibilities. Thus also the very specific reference to a GSS-API version (v2u1): it's quite true that a GSS-APIv2u1 application could not properly handle a v3 extension that uses async context tokens. What could a v2u1 application possibly do to properly handle such an extension? How could it interpret the major/minor status codes (other than GSS_S_DEFECTIVE_TOKEN) from GSS_Process_context_token() to determine whether the app should continue? If it can't, then how could it decide whether to keep going instead of getting around to calling GSS_Delete_sec_context()? I don't see how a GSS-APIv2u1 application could make that determination. A GSS-APIv2u1 app just has to end up calling GSS_Delete_sec_context() when GSS_Process_context_token() returns either GSS_S_COMPLETE or GSS_S_FAILURE -- and "soon" after, too. [*] Hmmm, should we consider GSS_Pseudo_random() to be part of a v2u2? [**] A vwu1 peer could have done GSS_Export_sec_context(), then imported it twice and then called GSS_Delete_sec_context() on one of them, producing a context deletion token, and sent it, while then continuing to use the second imported version. This would be rather tortured behavior! No app does this. Nico --
- [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Martin Rex
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Greg Hudson
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Greg Hudson
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Greg Hudson
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Martin Rex
- Re: [kitten] RFC2743 errata 4251 Martin Rex
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Martin Rex
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Stephen Farrell
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Martin Rex
- Re: [kitten] RFC2743 errata 4251 Stephen Farrell
- Re: [kitten] RFC2743 errata 4251 Greg Hudson
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Jeffrey Hutzelman
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Benjamin Kaduk
- Re: [kitten] RFC2743 errata 4251 Nico Williams
- Re: [kitten] RFC2743 errata 4251 Greg Hudson
- Re: [kitten] RFC2743 errata 4251 Jeffrey Hutzelman