Re: [OAUTH-WG] draft-ietf-oauth-revocation-04

Torsten Lodderstedt <> Sun, 03 February 2013 12:20 UTC

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Subject: Re: [OAUTH-WG] draft-ietf-oauth-revocation-04
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Hi Donald,

Am 03.02.2013 12:57, schrieb Donald F Coffin:
> <snip>
> [Don] A typical Third Party application built to use the ESPI Standard 
> will interact with a Retail Customer and their energy provider.  The 
> nature of interaction with the Retail Customer will utilize short 
> interactive sessions. However, the interaction with their energy 
> provider will require the application obtain new energy information 
> for the previous 24-hours once a day.  Therefore, I anticipate 
> access_tokens will be granted for long periods of time as well as any 
> supporting refresh_tokens.  Because of the amount of data being 
> exchanged between the Third Party application and the energy provider, 
> both in number of retail customers and the amount of energy meter 
> data, it will be necessary to minimize the amount of “administrative” 
> traffic required in the exchange. Therefore, although I understand the 
> use case you described, I anticipate such an implementation would be 
> rare.
> The need to perform an audience style check to prevent exposure of the 
> AS to a denial of service attack, appears primarily due to the fact 
> the Revocation RFC requires an access_token and refresh_token to be 
> revoked independently.  Should a client need to revoke both Tokens the 
> sequence of the revocation request is extremely significant.  A simple 
> solution to this problem would be to provide a method that allows a 
> request to revoke both tokens simultaneously, as stated in one of the 
> responses you referenced in the archives.
> The example you gave in your response demonstrating how a denial of 
> service attack might occur is incorrect.  You said “if the AS revokes 
> the refresh_token when an access_token is revoked, I can steal an 
> access_token and send it to the revocation endpoint causing the real 
> client’s refresh_token to be revoked”.  I fail to see how that could 
> occur, since the AS revoked both the access_token and the 
> refresh_token when it received the request to revoke the 
> access_token.  Rather than explaining why a refresh_token shouldn’t be 
> revoked concurrently when an access_token is revoked, your example 
> does the exact opposite.  It shows why a refresh_token should be 
> revoked concurrently when an access_token is revoked.
> [Don] The focus of the *ESPI Standard* is to provide Retail Customer’s 
> with access to a single UsagePoint (i.e. their Smart Meter).  
> Therefore an access and refresh token will be tightly correlated with 
> the type and frequency of data the Smart Meter provides.  There are 
> only a few reasons defined within the *ESPI Standard* list of use 
> cases that will require the *Token Revocation* request to be issued.  
> The following summarizes the situations that require a *Token 
> Revocation *request:
> ·A Third Party application wishes to terminate their relationship with 
> a Retail Customer.
> ·A Third Party application wishes to terminate their relationship with 
> a Data Custodian.
> ·A Retail Customer wishes to terminate their relationship with a Third 
> Party application.
> ·A Retail Customer wishes to change the data (i.e. scope) a Third 
> Party application has permission to access.
> In none of the above situations will it be valid to retain a refresh 
> token, which I realize is implementation dependent, due to the nature 
> of the *ESPI Standard.*
> Perhaps the section on the *Server’s Revocation Policy* should address 
> a few of the reasons why a client may want or need to revoke a token.  
> The current description provides no consideration for the relationship 
> between tokens and scope, although there clearly is a relationship.
> I'm confident client or resource owner would revoke refresh (and not 
> access) tokens in all use cases you listed above. In my opinion, 
> access tokens are revoked only if the authorization server does not 
> support refresh tokens and therefore uses long term access tokens or 
> in high-security applications.
> [Don] Based on the above statement it would appear you assume an 
> access token is only valid for a short period of time. However, as I 
> explained in my last response, due to the nature of the access 
> required by the client and the manner in which the RS provides that 
> data, access token durations will typically be in days not minutes. 
>   Therefore, merely revoking a refresh_token will expose the data to 
> access that the resource owner meant to prevent unless the 
> access_token is also revoked.

I don't understand why access tokens need such a long duration in your 
scenario, even if the client needs to obtain energy data once a day. Any 
client can (potentially) obtain a new access token at any time if the 
access token expires if the authorization server issues corresponding 
refresh tokens. So even in your scenario, access tokens could have a 
short duration. If you want to issue long-living access tokens in order 
to minimize load on the authorization servers, then you have to consider 
the extra complexitity and load required to notify resource servers of 
access token revocation. It's a tradeoff decision, which we tried to 
describe in

> I would also like to hear the opinion of other WG members on this topic.
>     3. If the standard OAuth spec does not provide enough control,
>     your profile of OAuth2 for the ESPI can tighten it to provide the
>     protections desired.
>     [Don] I am aware we can provide additional parameters required to
>     integrate *OAuth 2.0 *with the *ESPI Standard* by submitting those
>     parameter values to the *OAuth Parameters* registry. I would
>     prefer not to do that, given the large amount of work being done
>     on RFC-drafts to resolve many of the issues we are facing to
>     integrate *OAuth 2.0* with the *ESPI Standard*, since the need to
>     use those extensions will most likely be short lived.
> Hmmm, if the need is only short lived, why do you want to make it part 
> of the long living revocation RFC?
> [Don] My response was to the suggestion that if the OAuth 
> specification does not provide enough control then the ESPI profile of 
> OAuth 2.0 could tighten it to provide the protections desired.  I 
> assumed George meant we could add additional “company” based 
> parameters, which requires us to register them with the “OAuth 
> Parameter Registry”.  I meant the usage of such “company” parameters 
> would be short termed.


> I do not view the need to identify the type of token being revoked as 
> “short term”.  Even the previous exchanges on the topic within the WG 
> indicates it feels there may be a need to add an additional parameter 
> to the request.  However, because the draft is too far along, the WG 
> seems to prefer releasing an RFC they “suspect” will need to be 
> adjusted and let the implementers confirm their suspicions.   This 
> seems to be a very selfish and rather foolish attitude given we are 
> discussing a security protocol.  Not to mention it would seem easier 
> and faster to add an additional “optional” parameter now, rather than 
> requiring another RFC cycle.  A parameter I sensed in reading the 
> archives the WG feels will very likely need to be added in the future.

Since this is a WG item, it is up to the WG to decide.


> Thanks,
> George
> On 1/29/13 3:28 PM, Donald F Coffin wrote:
>     Hi Thorsten,
>     I am working with the OpenADE Task Force to document how the
>     “*/Energy Service Provider Interface (ESPI) Standard/* ” published
>     by the *North American Energy Standards Board* (NAESB) in October
>     of 2011 should be implemented.  The *ESPI Standard* defines how
>     Retail Customers, Third Party applications, and Data Custodians
>     (i.e. electrical, gas, or water utility) must interface to each
>     other and the data format used to exchange energy information. 
>      The interface between the Retail Customer and the Data Custodian
>     is known as “*Download My Data*”, which defines how a Retail
>     Customer receives their energy information in an XML file
>     downloaded to them by the Data Custodian.  The interface between
>     the Third Party application and the Data Custodian is known as
>     “*Connect My Data*”, which defines the message exchanges between
>     the Third Party application and the Data Custodian to allow the
>     Third Party to access data at the Data Custodian after a Retail
>     Customer has granted the Third Party application access.
>     It is my responsibility within the OpenADE Task Force to document
>     the integration of the *OAuth 2.0* protocol with the *ESPI
>     Standard.*  Since the *ESPI Standard* requires Retail Customers,
>     Third Party applications, and Data Custodians to revoke Tokens
>     (i.e. Access and Refresh Tokens) I am very interested in the
>     “*/Token Revocation (draft-ietf-oath-revocation-xx)/*” work being
>     done by you and your working group.
>     *_Token Revocation Request_*
>     The *Token Revocation* request has only the “token” parameter with
>     the description that the authorization server is supposed to
>     detect the token type automatically.  I would like to request that
>     an addition parameter “token_type” be added to the request.  The
>     “token_type” parameter could be optional and would define the type
>     of token being revoked (i.e. “access”, “refresh”, “registration
>     access”, etc.).
>     The *ESPI Standard* was developed to support the *Advanced Meter
>     Interface* *(AMI) *which is the interface used by “Smart Meters”
>     to provide automated energy usage collection and other operational
>     information about a Retail Customer’s residence to their Data
>     Custodian.  Third Party applications will be required to obtain
>     the approval if each Retail Customer that has had a “Smart Meter”
>     installed before they will be able to access the data provided by
>     their “Smart Meter”.  The number of “Smart Meters” currently
>     installed at the three largest California utilities (Pacific Gas &
>     Electric, Southern California Edison, and San Diego Gas &
>     Electric) is in excess of 10.0 M and growing.  The following table
>     indicates the number of “Smart Meters” each of the three utilities
>     had installed as of May 2012:
>     *Utility*
>     *“Smart Meters” Installed*
>     Pacific Gas & Electric (PG&E)
>     4,696,000
>     San Diego Gas & Electric (SDG&E)
>     1,364,000
>     Southern California Edison (SCE)
>     3,900,000
>     The numbers in the chart were taken from the “*/Utility-Scale
>     Smart Meter Deployments, Plans, & Proposals -- IEE Report/*”
>     published May 2012 by *The Edison Foundation Institute for
>     Electric Efficiency” *which I have attached.  The number of “Smart
>     Meters” currently installed are even larger than shown in the
>     report as I compose this email.  Assuming 10% of Pacific Gas &
>     Electric’s Retail Customers decide to utilize a Third Party
>     application (3 Third Party applications are currently supported
>     and are 3 more Third Party applications are preparing to be
>     supported) in order to support the ability to revoke a token they
>     would be required to track 500,000 access tokens and 500,000
>     refresh tokens.  Requiring PG&E’s authorization server to
>     “automatically” determine the type of Token being revoked begins
>     to negatively impact their processing capability.  If the *Token
>     Revocation* request was capable of indicating the type of Token to
>     be revoked, the amount of time it will take PG&E’s authorization
>     server would show a significant time savings to process the request.
>     *_Authorization Server Revocation Policy_*
>     6.Does the revocation of the access token also revoke the refresh
>     token (if it was provided) ? Or is this a revocation policy decision ?
>     - if the token passed to the request is a refresh token and the
>     server supports access token revocation, the server SHOULD also
>     revoke them.
>     - if the token passed to the request is an access token, the
>     server may decide to revoke the respective refresh token as well.
>     I believe that if the token passed in the request is an access
>     token, the server MUST revoke any respective refresh token. 
>     Otherwise, their exist a potential security risk of the respective
>     refresh token being used to gain access to the resources for which
>     the access token was issued. It also means the authorization
>     server will have potential “junk” in the refresh token file to
>     search through for any additional Token Revocation request.
>     I look forward to receiving your response.
>     Best regards,
>     Don
>     Donald F. Coffin
>     Founder/CTO
>     REMI Networks
>     22751 El Prado Suite 6216
>     Rancho Santa Margarita, CA  92688-3836
>     Phone: (949) 636-8571
>     Email:
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