Re: [OAUTH-WG] I-D Action: draft-ietf-oauth-token-exchange-10.txt

Brian Campbell <> Sat, 09 December 2017 01:48 UTC

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From: Brian Campbell <>
Date: Fri, 8 Dec 2017 18:48:09 -0700
Message-ID: <>
To: Denis <>
Cc: Mike Jones <>, oauth <>, Rifaat Shekh-Yusef <>, Hannes Tschofenig <>
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Subject: Re: [OAUTH-WG] I-D Action: draft-ietf-oauth-token-exchange-10.txt
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The privacy matter is already mentioned. Despite your many messages to this
WG and others about the so called ABC attack, I do not believe it warrants
treatment in this document or others. And your continued proposals to have
it included in documents have not gotten support.

On Fri, Dec 8, 2017 at 2:46 PM, Denis <> wrote:

> RFC 3552 (Guidelines for Writing RFC Text on Security Considerations)
> states:
>    All RFCs are required by RFC 2223 to contain a Security
>    Considerations section.  The purpose of this is both to encourage
>    document authors to consider security in their designs and to inform
>    the reader of relevant security issues.  This memo is intended to
>    provide guidance to RFC authors in service of both ends.
> Section 5 (Writing Security Considerations Sections) of RFC 3552 states:
>    While it is not a requirement that any given protocol or system be
>    immune to all forms of attack, it is still necessary for authors to
>    consider as many forms as possible.  Part of the purpose of the
>    Security Considerations section is to explain what attacks are out of
>    scope and what countermeasures can be applied to defend against them
>    There should be a clear description of the kinds of threats on the
>    described protocol or technology.
> It is important to mention the threat related to collusion attacks. A
> different wording could be used,
> but the threat should be mentioned one way or another.
> RFC 6973 (Privacy Considerations for Internet Protocols) intends to
> provide a similar set of guidelines
> for considering privacy in protocol design. It is important to mention a
> current threat related to privacy. A different wording could be used,
> e.g. using the word "surveillance" as mentioned in 5.1.1 : "Surveillance
> is the observation or monitoring
> of an individual’s communications or activities", but the threat should be
> mentioned one way or another. Denis
> I believe the text would detract from the document.
> ------------------------------
> *From:* OAuth <> <> on behalf
> of Brian Campbell <>
> <>
> *Sent:* Friday, December 8, 2017 3:47:32 PM
> *To:* Denis
> *Cc:* oauth
> *Subject:* Re: [OAUTH-WG] I-D Action: draft-ietf-oauth-token-
> exchange-10.txt
> As an individual, I do not believe that the proposed text should be
> incorporated into the draft.
> As one of the document editors, my responsibility is for the document to
> be of reasonable quality and to reflect the rough consensus of this Working
> Group. So I should ask the list more explicitly - are there other WG
> remembers who are in favor of the proposed text here (the text would have
> to be fixed up some too)?
> On Fri, Dec 1, 2017 at 11:12 AM, Denis <> wrote:
>> Comments on draft-ietf-oauth-token-exchange-10
>> I propose the following rephrasing for sections 6 and 7:
>> 6 . Security Considerations
>> All of the normal security issues that are discussed in [JWT],especially
>> in relationship to comparing URIs
>> and dealing with unrecognized values, also apply here.  In addition, both
>> delegation and impersonation introduce
>> unique security issues. Any time one user receives a token, the potential
>> for abuse is a concern,
>> since that user might be willing to collude with another user so that
>> other user could use the token.
>> Techniques like the binding of an access token to a TLS channel described
>> elsewhere are ineffective since
>> the legitimate user would be able to perform all the cryptographic
>> computations that the other user would need
>> to demonstrate the ownership of the token. The use of the "scp" claim is
>> suggested to mitigate potential for
>> such abuse, as it restricts the contexts in which the token can be
>> exercised.  If the issued access token scope
>> allows to unambiguously identify the user, then that user is likely to be
>> reluctant to collude with another user.
>> However, if the issued access token scope only indicates that the user is
>> over 18, then there is no risk
>> for the original user to be discovered and in such a context a collusion
>> may easily take place.
>> This document does not specify techniques to prevent such a collusion to
>> be successful.
>> 7 . Privacy Considerations
>> Tokens typically carry personal information and their usage in Token
>> Exchange may reveal details of the target services
>> being accessed. The resource and the audience parameters allow
>> authorization servers to know where the issued access token
>> will be used.  This may be a privacy concern for some users. This
>> document does not specify techniques to prevent
>> authorization servers to know where the access tokens they issue will be
>> used.
>> Denis
>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>> This draft is a work item of the Web Authorization Protocol WG of the IETF.
>>         Title           : OAuth 2.0 Token Exchange
>>         Authors         : Michael B. Jones
>>                           Anthony Nadalin
>>                           Brian Campbell
>>                           John Bradley
>>                           Chuck Mortimore
>> 	Filename        : draft-ietf-oauth-token-exchange-10.txt
>> 	Pages           : 32
>> 	Date            : 2017-11-30
>> Abstract:
>>    This specification defines a protocol for an HTTP- and JSON- based
>>    Security Token Service (STS) by defining how to request and obtain
>>    security tokens from OAuth 2.0 authorization servers, including
>>    security tokens employing impersonation and delegation.
>> The IETF datatracker status page for this draft is:
>> There are also htmlized versions available at:
>> A diff from the previous version is available at:
>> Please note that it may take a couple of minutes from the time of submission
>> until the htmlized version and diff are available at
>> Internet-Drafts are also available by anonymous FTP at:
>> _______________________________________________
>> OAuth mailing listOAuth@ietf.org
>> _______________________________________________
>> OAuth mailing list
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