Re: [OAUTH-WG] Token Chaining Use Case

Bill Mills <> Thu, 26 March 2015 23:02 UTC

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Date: Thu, 26 Mar 2015 23:02:23 +0000 (UTC)
From: Bill Mills <>
To: "Donald F. Coffin" <>, 'Phil Hunt' <>
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Subject: Re: [OAUTH-WG] Token Chaining Use Case
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AS already has the problem of checking requested scopes, this doesn't change that.
In fact an AS could issue a new "refresh token" in return for the presented one (which is the user/app AT) that's limited to be used by the RS as a client.
If one of the things we want is the ability to have the AS return N access tokens, one for each scope allowing the RS to make a single round trip request to the AS for all of the more limited scope tokens, then a new grant type is in fact needed.


     On Thursday, March 26, 2015 3:33 PM, Donald F. Coffin <> wrote:

 #yiv7149031579 #yiv7149031579 -- _filtered #yiv7149031579 {font-family:Helvetica;panose-1:2 11 6 4 2 2 2 2 2 4;} _filtered #yiv7149031579 {panose-1:2 4 5 3 5 4 6 3 2 4;} _filtered #yiv7149031579 {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;} _filtered #yiv7149031579 {font-family:Cambria;panose-1:2 4 5 3 5 4 6 3 2 4;} _filtered #yiv7149031579 {panose-1:3 6 8 2 4 4 6 7 3 4;}#yiv7149031579 #yiv7149031579 p.yiv7149031579MsoNormal, #yiv7149031579 li.yiv7149031579MsoNormal, #yiv7149031579 div.yiv7149031579MsoNormal {margin:0in;margin-bottom:.0001pt;font-size:12.0pt;}#yiv7149031579 a:link, #yiv7149031579 span.yiv7149031579MsoHyperlink {color:blue;text-decoration:underline;}#yiv7149031579 a:visited, #yiv7149031579 span.yiv7149031579MsoHyperlinkFollowed {color:purple;text-decoration:underline;}#yiv7149031579 p.yiv7149031579msonormal, #yiv7149031579 li.yiv7149031579msonormal, #yiv7149031579 div.yiv7149031579msonormal {margin-right:0in;margin-left:0in;font-size:12.0pt;}#yiv7149031579 p.yiv7149031579msolistparagraph, #yiv7149031579 li.yiv7149031579msolistparagraph, #yiv7149031579 div.yiv7149031579msolistparagraph {margin-right:0in;margin-left:0in;font-size:12.0pt;}#yiv7149031579 p.yiv7149031579msochpdefault, #yiv7149031579 li.yiv7149031579msochpdefault, #yiv7149031579 div.yiv7149031579msochpdefault {margin-right:0in;margin-left:0in;font-size:12.0pt;}#yiv7149031579 p.yiv7149031579msonormal1, #yiv7149031579 li.yiv7149031579msonormal1, #yiv7149031579 div.yiv7149031579msonormal1 {margin-right:0in;margin-left:0in;font-size:12.0pt;}#yiv7149031579 p.yiv7149031579msochpdefault1, #yiv7149031579 li.yiv7149031579msochpdefault1, #yiv7149031579 div.yiv7149031579msochpdefault1 {margin-right:0in;margin-left:0in;font-size:12.0pt;}#yiv7149031579 span.yiv7149031579msohyperlink {}#yiv7149031579 span.yiv7149031579msohyperlinkfollowed {}#yiv7149031579 span.yiv7149031579msohyperlink1 {}#yiv7149031579 span.yiv7149031579msohyperlinkfollowed1 {}#yiv7149031579 span.yiv7149031579emailstyle171 {}#yiv7149031579 span.yiv7149031579emailstyle27 {}#yiv7149031579 p.yiv7149031579msonormal2, #yiv7149031579 li.yiv7149031579msonormal2, #yiv7149031579 div.yiv7149031579msonormal2 {margin:0in;margin-bottom:.0001pt;font-size:12.0pt;}#yiv7149031579 span.yiv7149031579msohyperlink2 {color:blue;text-decoration:underline;}#yiv7149031579 span.yiv7149031579msohyperlinkfollowed2 {color:purple;text-decoration:underline;}#yiv7149031579 p.yiv7149031579msolistparagraph1, #yiv7149031579 li.yiv7149031579msolistparagraph1, #yiv7149031579 div.yiv7149031579msolistparagraph1 {margin-top:0in;margin-right:0in;margin-bottom:0in;margin-left:.5in;margin-bottom:.0001pt;font-size:12.0pt;}#yiv7149031579 p.yiv7149031579msochpdefault2, #yiv7149031579 li.yiv7149031579msochpdefault2, #yiv7149031579 div.yiv7149031579msochpdefault2 {margin-right:0in;margin-left:0in;font-size:12.0pt;}#yiv7149031579 p.yiv7149031579msonormal11, #yiv7149031579 li.yiv7149031579msonormal11, #yiv7149031579 div.yiv7149031579msonormal11 {margin:0in;margin-bottom:.0001pt;font-size:12.0pt;}#yiv7149031579 span.yiv7149031579msohyperlink11 {color:blue;text-decoration:underline;}#yiv7149031579 span.yiv7149031579msohyperlinkfollowed11 {color:purple;text-decoration:underline;}#yiv7149031579 span.yiv7149031579emailstyle1711 {color:windowtext;font-weight:normal;font-style:normal;text-decoration:none none;}#yiv7149031579 p.yiv7149031579msochpdefault11, #yiv7149031579 li.yiv7149031579msochpdefault11, #yiv7149031579 div.yiv7149031579msochpdefault11 {margin-right:0in;margin-left:0in;font-size:10.0pt;}#yiv7149031579 span.yiv7149031579emailstyle271 {color:windowtext;font-weight:normal;font-style:normal;text-decoration:none none;}#yiv7149031579 span.yiv7149031579EmailStyle39 {color:windowtext;font-weight:normal;font-style:normal;text-decoration:none none;}#yiv7149031579 .yiv7149031579MsoChpDefault {font-size:10.0pt;} _filtered #yiv7149031579 {margin:1.0in 1.0in 1.0in 1.0in;}#yiv7149031579 div.yiv7149031579WordSection1 {}#yiv7149031579 Bill,  Thanks for the clarification.  How do you propose the AS deal with the following RFC6749 Section 6. Refreshing an Access Token requirement?  ScopeOPTIONAL.  The scope of the access request as described by Section 3.3.  The requested scope MUST NOT include any scope not originally granted by the resource owner, and if omitted is treated as equal to the scope originally granted by the resource owner.  The authorization server MAY issue a new refresh token, in which case the client MUST discard the old refresh token and replace it with the new refresh token.  The authorization server MAY revoke the old refresh token after issuing a new refresh token to the client.  If a new refresh token is issued, the refresh scope MUST be identical to that of the refresh token included by the client in the request.  Since the RS is attempting to obtain a new AT, what happens to the old AT that was submitted as a refresh_token, should the AS issue a new refresh_token, which it is allowed to do as stated above?  Since this was really an AT, doesn’t this mean the RS and issuing AS will be required to REVOKE the AT?  If the AS is not the AS that issued the original AT and there is no scope= value in the request, how does it ensure the request isn’t asking for more access than was granted by the granting AS?  Best regards,DonDonald F. CoffinFounder/CTO  REMI Networks2335 Dunwoody Crossing Suite EDunwoody, GA 30338-8221  Phone:      (949) 636-8571Email:  From: Bill Mills [] 
Sent: Thursday, March 26, 2015 6:04 PM
To: Bill Mills; Donald F. Coffin; 'Phil Hunt'
Subject: Re: [OAUTH-WG] Token Chaining Use Case    Again, I don't think requiring a call out to an internal token reissuer is a general solution.  That said...  The RS calls the token endpoint treating the AT as a refresh token in all cases and using the refresh_token grant type.  Desired scope is specified by the RS.  It's not in spec if there are derivative internal scopes not in the original scope list though.  This doesn't support internal scopes for partitioning that the AS doesn't know about.  An internal AS providing chaining would need to understand the AT just as the RS does, and treat it as a refresh token.  -bill  On Thursday, March 26, 2015 2:22 PM, Donald F. Coffin <> wrote:  Bill, Can you clarify your thoughts on the following: ·         What AS endpoint does the RS call and how does it present the AT he received?·         What is the grant_type value the RS use in the above endpoint request?·         What does the AS do if the AT was issued by another AS (which is possible using Justin’s use case)? Best regards,DonDonald F. CoffinFounder/CTO REMI Networks2335 Dunwoody Crossing Suite EDunwoody, GA 30338-8221 Phone:      (949) 636-8571Email: From: Bill Mills [] 
Sent: Thursday, March 26, 2015 5:13 PM
To: Donald F. Coffin; 'Phil Hunt'
Subject: Re: [OAUTH-WG] Token Chaining Use Case The RS calling back to the AS won't be confused, the token it gets would be it's refresh token.  I don't see any reason why the AS can't be smart enough to know that a token that looks like an access token it issued is usable as a refresh token for limited purposes or downscoping.    On Thursday, March 26, 2015 1:46 PM, Donald F. Coffin <> wrote: -1 Although  Justin’s point might be a bit pre-mature as far as a standards discussion, the more critical reason IMHO is calling the AS’s /Token endpoint with a grant_type of “refresh_token” but providing an issued AT rather than an issued refresh_token (RT) will definitely create a backwards compatibility issue for many implementations. Best regards,DonDonald F. CoffinFounder/CTO REMI Networks2335 Dunwoody Crossing Suite EDunwoody, GA 30338-8221 Phone:      (949) 636-8571Email: From: Phil Hunt [] 
Sent: Thursday, March 26, 2015 4:22 PM
To: Bill Mills
Cc: <>
Subject: Re: [OAUTH-WG] Token Chaining Use Case +1. We all have to change production code when non final specs evolve.  I particularly don't see this as a valid argument at the start of a standards discussion. 
On Mar 26, 2015, at 15:13, Bill Mills <> wrote:
By definition an access token is becoming a form of refresh token.    The "because my implementation didn't do it that way" isn't convincing me.  On Thursday, March 26, 2015 12:44 PM, Justin Richer <> wrote: Because many implementations (including mine which does support my old token chaining draft) treat access tokens and refresh tokens separately in terms of data store and structure. Additionally, the refresh token is tied to the client and presented by the client. But in this case it's someone downstream, an RS, presenting the token. So unlike a refresh token being presented by the one it was issued to, this token is being presented by someone it was presented to.  The feeling is close, but not quite the same in either development or assumptions. -- Justin / Sent from my phone /

-------- Original message --------
From: Bill Mills <> 
Date: 03/26/2015 2:24 PM (GMT-06:00) 
To: Justin Richer <jricher@MIT.EDU>DU>, "<>" <> 
Subject: Re: [OAUTH-WG] Token Chaining Use Case So why can't the access tokne simply be re-used as a refresh token?  Why would it need a new grant type at all?   On Thursday, March 26, 2015 11:31 AM, Justin Richer <jricher@MIT.EDU> wrote: As requested after last night’s informal meeting, here is the token chaining use case that I want to see represented in the token swap draft.

[ Client ]  ->  [ A ] -> [ B ] -> [ C ]

An OAuth client gets an access token AT1, just like it always would, with scopes [A, B, C] in order to call service A, which requires all three scopes. Service A (an RS) accepts this token since it has its scope, and then needs to call service B in turn, which requires scopes [B, C]. It could just re-send the token it got in, AT1, but that would give the downstream RS the ability to call services with scope [ A ] and it should not be allowed to do that. To limit exposure, service A calls a token swap at the AS to create AT2 with scopes [ B, C ], effectively acting as an OAuth client requesting a downscoped token based on AT1. Service A then acts as an OAuth client to call service B, now acting as an RS to service A’s client, and can fulfill the request. And it’s turtles all the way down: Service B can also call service C, and now B acts as a client, requesting AT3 with scope [ C ] based on AT2, and sending AT3 to service C. This prevents C from being able to call B or A, both of which would have been available if AT1 had been passed around. Note that service A or the Client can also request a downscoped token with [ C ] to call service C directly as well, and C doesn’t have to care how it got there.

In other words, it lets the client software be very, very dumb. It doesn’t have to do any special processing, doesn’t have to know what’s in the token, it just follows the recipe of “I got a token, I get another token based on this to call someone else”. It’s also analogous to the refresh token flow, but with access tokens going in and out. I’ve deployed this setup several times in different service deployments. Even though there is a performance hit in the additional round trips (as Phil brought up in another thread), in these cases the desire to have the tokens hold least privilege access rights (smallest set of scopes per service) outweighed any performance hit (which was shown to be rather small in practice).

What I want is for the token swap draft to define or use a mechanism that allows us to do this. I think we can do that pretty easily by adjusting the token swap syntax and language, and explicitly calling out the semantic processing portion (the current core of the document) for what it is: a way for a token issuer to communicate to a token service specific actions. At a high level, the spec would be something like:

1. How to swap a token at an AS
  1. Send a request to the token endpoint with a new grant type, and a token (of any type/format/flavor) on the way in
  2. Get back a new token in a token response
2. Communicating act as / on behalf of semantics via a JWT assertion
  1. How to create (as an AS/RS/client/other issuer) a JWT with act-as semantics
  2. What to do (as an AS/RS) with a JWT with act-as semantics
  3. How to create a JWT with on-behalf-of semeantics
  4. What to do with a JWT with on-behalf-of-semantics
  5. How to possibly represent these semantics with something other than a JWT

Section 2 uses the syntax from section 1. Other applications, like the one I laid out above, can use the syntax from section 1 as well. This works for structured, unstructured, self-generated, cross-domain, within-domain, and other tokens.

— Justin
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