Subject: [secdir] SECDIR review of draft-ietf-oauth-jwsreq-09.txt

From: Steve KENT <[email-masked]>
Date: Mon, 16 Jan 2017 20:14:23 +0000

I generated this review of this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG.  These comments were written with the intent of improving security requirements and considerations in IETF drafts.  Comments not addressed in last call may be included in AD reviews during the IESG review.  Document editors and WG chairs should treat these comments just like any other last call comments.

This document proposes a mechanism to enable secure communication of OAuth 2.0 Authorization Requests using a JSON Web Token (JWT). This mechanism represents an improvement over the current way that OAuth Authorization Requests are transmitted, i.e., encoded as an (unprotected) URI.

The document notes that the current Authorization Request mechanism fails to provide integrity, authentic, or confidentiality. JSON is already used for OAuth responses, so using JWT to protect requests seems like an appropriate choice. (XML signatures and encryption were rejected as too complex.)

Section 4 defines the Request Object format and provides examples.

The text here is a bit confusing. It seems to state that only integrity and authenticity are mandated by this specification; confidentiality is an optional feature. However, when discussing the use of encryption that does not provide authentication, the text says that a signature “should” (not SHOULD””) be applied. The text then says that “In this case, it [the token] MUST be signed then encrypted …” This combination of sentences is confusing and OUGHT J to be revised.

Section 6 describes how to validate a received JWT request token. Section 6.1 appears to not mandate use of a signature for an encrypted token, suggesting that authentication and integrity need not be provided if the requestor encrypts the token (and does not employ an authenticated encryption algorithm).

Section 10 describes Security Considerations in addition to the ones already describes in RFC 6119 (OAuth 2.0). The wording of Section 10.1 is odd: “ …it MUST either be JWS signed with then considered appropriate algorithm or encrypted using [RFC7516].” Why is there no cite of 7515 for JWS algorithms here, to parallel the cite of JWE?

Section 10.2 indicates that a client and server might agree, a priori, to use the non-protected parameters transmitted in a request. It does not indicate how this might have been done (hopefully, in a secure fashion).

Section 10.3 finally mandates authentication of the request source, something that was ambiguous in earlier sections of this document. There are some ambiguous statement here, e.g. “Since Request Object URI can be replayed, the lifetime of the Request Object URI MUST be short and preferably one-time use.  The entropy of the Request Object URI MUST be sufficiently large.” The lack of guidance of what constitutes a “short” lifetime or a “sufficiently large” amount of entropy (in a short URI) is worrisome.  In (d) there is a typo: “The same requirements as (b) above applies.” -> “The same requirements as (b) above apply”.

Section 10.4 includes several typos:

“Although this specification does not require them, researchs such as …” -> “Although this specification does not require them, research such as …” This is the beginning of a run-on sentence.

“The endpoints that comes into question …” -> The endpoints that come into question …”

The wording in several places is awkward, e.g., missing articles.

This section ends with the statement “An extension specification should be created.” Presumably the intent here is to suggest that an extension is needed to remedy the vulnerability resulting from the lack of explicit endpoint identifiers. This should be more clearly stated.

Section 11 discusses Privacy Considerations an unusual element of an RFC. (The authors state that ISO/IEC 29100 is freely accessible. That seems to be true only if one follows the URL in the Informative References. A search for this ISO document tends to yield copies available for a non-trivial fee, i.e., ~ $150 USD.) Since there is standards language in this section (SHOULD and MUST) I think 29100 needs to be a Normative (not Informational) reference.

The text here raises some good privacy concerns and suggests some means by which these concerns might be addressed. However, the wording here needs to be significantly improved. There are extraneous articles and missing articles that make the text harder to read. The ambiguous comment about entropy that appeared in 10.3 appears here as well.

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---

From: John Bradley <[email-masked]>
Date: Mon, 16 Jan 2017 17:18:01 -0300

Thanks for the review. 

Nat and I will review and address your comments.

Regards
John B.

> On Jan 16, 2017, at 5:14 PM, Steve KENT <[email-masked]> wrote:
> 
> 
> Section 10 describes Security Considerations in addition to the ones already describes in RFC 6119 (OAuth 2.0). The wording of Section 10.1 is odd: “ …it MUST either be JWS signed with then considered appropriate algorithm or encrypted using [RFC7516 <>].” Why is there no cite of 7515 for JWS algorithms here, to parallel the cite of JWE?
>  
> Section 10.3 finally mandates authentication of the request source, something that was ambiguous in earlier sections of this document. There are some ambiguous statement here, e.g. “Since Request Object URI can be replayed, the lifetime of the Request Object URI MUST be short and preferably one-time use.  The entropy of the Request Object URI MUST be sufficiently large.” The lack of guidance of what constitutes a “short” lifetime or a “sufficiently large” amount of entropy (in ashort URI) is worrisome.  In (d) there is a typo: “The same requirements as (b) above applies.” -> “The same requirements as (b) above apply”.
>

---

From: "Nat Sakimura" <[email-masked]>
Date: Mon, 30 Jan 2017 17:48:45 +0900

Hello. 

Sorry to have taken more than a week to reply. 

I have pushed -10 which hopefully has addressed all the issues raised. 

I have recorded all your comments into the issue tracker [1] of my working
repository and was recording the changes so you can see how I tried to
resolve them there as well. 

[1]  <https://bitbucket.org/Nat/oauth-jwsreq/issues?q=SECDIR>
https://bitbucket.org/Nat/oauth-jwsreq/issues?q=SECDIR

Best, 

Nat Sakimura

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From: Steve KENT [mailto:[email-masked]] 
Sent: Tuesday, January 17, 2017 5:14 AM
To: [email-masked]
Cc: [email-masked]; [email-masked]; [email-masked];
[email-masked]
Subject: SECDIR review of draft-ietf-oauth-jwsreq-09.txt

I generated this review of this document as part of the security
directorate's ongoing effort to review all IETF documents being processed by
the IESG.  These comments were written with the intent of improving security
requirements and considerations in IETF drafts.  Comments not addressed in
last call may be included in AD reviews during the IESG review.  Document
editors and WG chairs should treat these comments just like any other last
call comments.

This document proposes a mechanism to enable secure communication of OAuth
2.0 Authorization Requests using a JSON Web Token (JWT). This mechanism
represents an improvement over the current way that OAuth Authorization
Requests are transmitted, i.e., encoded as an (unprotected) URI. 

The document notes that the current Authorization Request mechanism fails to
provide integrity, authentic, or confidentiality. JSON is already used for
OAuth responses, so using JWT to protect requests seems like an appropriate
choice. (XML signatures and encryption were rejected as too complex.) 

The text here is a bit confusing. It seems to state that only integrity and
authenticity are mandated by this specification; confidentiality is an
optional feature. However, when discussing the use of encryption that does
not provide authentication, the text says that a signature "should" (not
SHOULD"") be applied. The text then says that "In this case, it [the token]
MUST be signed then encrypted ." This combination of sentences is confusing
and OUGHT :) to be revised. 

Section 6 describes how to validate a received JWT request token. Section
6.1 appears to not mandate use of a signature for an encrypted token,
suggesting that authentication and integrity need not be provided if the
requestor encrypts the token (and does not employ an authenticated
encryption algorithm). 

Section 10 describes Security Considerations in addition to the ones already
describes in RFC 6119 (OAuth 2.0). The wording of Section 10.1 is odd: " .it
MUST either be JWS signed with then considered appropriate algorithm or
encrypted using [RFC7516]." Why is there no cite of 7515 for JWS algorithms
here, to parallel the cite of JWE?

Section 10.2 indicates that a client and server might agree, a priori, to
use the non-protected parameters transmitted in a request. It does not
indicate how this might have been done (hopefully, in a secure fashion). 

Section 10.3 finally mandates authentication of the request source,
something that was ambiguous in earlier sections of this document. There are
some ambiguous statement here, e.g. "Since Request Object URI can be
replayed, the lifetime of the Request Object URI MUST be short and
preferably one-time use.  The entropy of the Request Object URI MUST be
sufficiently large." The lack of guidance of what constitutes a "short"
lifetime or a "sufficiently large" amount of entropy (in a short URI) is
worrisome.  In (d) there is a typo: "The same requirements as (b) above
applies." -> "The same requirements as (b) above apply".

"Although this specification does not require them, researchs such as ." ->
"Although this specification does not require them, research such as ." This
is the beginning of a run-on sentence. 

"The endpoints that comes into question ." -> The endpoints that come into
question ."

This section ends with the statement "An extension specification should be
created." Presumably the intent here is to suggest that an extension is
needed to remedy the vulnerability resulting from the lack of explicit
endpoint identifiers. This should be more clearly stated.

Section 11 discusses Privacy Considerations an unusual element of an RFC.
(The authors state that ISO/IEC 29100 is freely accessible. That seems to be
true only if one follows the URL in the Informative References. A search for
this ISO document tends to yield copies available for a non-trivial fee,
i.e., ~ $150 USD.) Since there is standards language in this section (SHOULD
and MUST) I think 29100 needs to be a Normative (not Informational)
reference. 

The text here raises some good privacy concerns and suggests some means by
which these concerns might be addressed. However, the wording here needs to
be significantly improved. There are extraneous articles and missing
articles that make the text harder to read. The ambiguous comment about
entropy that appeared in 10.3 appears here as well.

---

From: Steve KENT <[email-masked]>
Date: Tue, 31 Jan 2017 15:08:02 +0000

Nat,

The revised text in the -11 version addressed my comments. There are still several places where the wording is rather awkward, but I'll defer to the RFC Editor to help you with these issues.

Steve

________________________________
From: Nat Sakimura <[email-masked]>
Sent: Monday, January 30, 2017 3:48:45 AM
To: Steve KENT; [email-masked]
Cc: [email-masked]; [email-masked]; [email-masked]
Subject: RE: SECDIR review of draft-ietf-oauth-jwsreq-09.txt

Hello.

I have recorded all your comments into the issue tracker [1] of my working repository and was recording the changes so you can see how I tried to resolve them there as well.

[1] https://bitbucket.org/Nat/oauth-jwsreq/issues?q=SECDIR

Best,

Nat Sakimura

From: Steve KENT [mailto:[email-masked]]
Sent: Tuesday, January 17, 2017 5:14 AM
To: [email-masked]
Cc: [email-masked]; [email-masked]; [email-masked]; [email-masked]
Subject: SECDIR review of draft-ietf-oauth-jwsreq-09.txt

The text here is a bit confusing. It seems to state that only integrity and authenticity are mandated by this specification; confidentiality is an optional feature. However, when discussing the use of encryption that does not provide authentication, the text says that a signature “should” (not SHOULD””) be applied. The text then says that “In this case, it [the token] MUST be signed then encrypted …” This combination of sentences is confusing and OUGHT :) to be revised.

---

From: "Nat Sakimura" <[email-masked]>
Date: Wed, 1 Feb 2017 16:11:21 +0900

Steve, 

Thanks very much. I am in the process of incorporating OpsDir comments. That
might solve some of your concerns re: awkward wordings. At the same time, if
you could send me the concrete text replacement for awkward phrases, I can
incorporate them in the process as well. 

Best, 

Nat Sakimura

--

From: Steve KENT [mailto:[email-masked]] 
Sent: Wednesday, February 1, 2017 12:08 AM
To: Nat Sakimura <[email-masked]>; [email-masked]
Cc: [email-masked]; [email-masked]; [email-masked]
Subject: Re: SECDIR review of draft-ietf-oauth-jwsreq-09.txt

Nat,

The revised text in the -11 version addressed my comments. There are still
several places where the wording is rather awkward, but I'll defer to the
RFC Editor to help you with these issues.

Steve

  _____  

From: Nat Sakimura <[email-masked] <mailto:[email-masked]> >
Sent: Monday, January 30, 2017 3:48:45 AM
To: Steve KENT; [email-masked] <mailto:[email-masked]> 
Cc: [email-masked] <mailto:[email-masked]> ; [email-masked]
<mailto:[email-masked]> ; [email-masked]
<mailto:[email-masked]> 
Subject: RE: SECDIR review of draft-ietf-oauth-jwsreq-09.txt 

Hello. 

Best, 

Nat Sakimura

--

From: Steve KENT [mailto:[email-masked]] 
Sent: Tuesday, January 17, 2017 5:14 AM
To: [email-masked] <mailto:[email-masked]> 
Cc: [email-masked] <mailto:[email-masked]> ; [email-masked]
<mailto:[email-masked]> ; [email-masked]
<mailto:[email-masked]> ; [email-masked]
<mailto:[email-masked]> 
Subject: SECDIR review of draft-ietf-oauth-jwsreq-09.txt