I think this threat is similar to clickjacking
(http://tools.ietf.org/html/draft-ietf-oauth-v2-20#section-10.13).
Could we incorporate it into this section (w/o delaying the spec's
release process)?
regards,
Torsten.
Am 26.07.2011 19:29, schrieb Niv Steingarten:
Would it be possible to consider adding this to the list of security
considerations?
Of course, the spec cannot cover all possible security threats, but
this appears to be a realistic one which could easily be exploited if
overlooked by developers (evident in the lack of scraping defense
mechanisms in many applications).
Is it too late to make such an amendment to the draft?
Thank you,
Niv
On Tue, Jul 26, 2011 at 02:40, Niv Steingarten<nivst...@gmail.com> wrote:
Yes, I believe the vast majority of user-agents would block this kind
of request if it originated from a JavaScript XMLHttpRequest or such.
However, there are still scenarios in which a user-agent based client
could manipulate this vulnerability.
For example, the client could launch the GET request to the
authorization server via an<img> HTML tag, taking the form of a CSRF.
Since it's a blind attack, the client would likely not receive the
contents of the web-page. However, this request is still necessary
from the client since it has the side-effect of creating an access
token (or other temporary token) on the authorization server. Since it
is highly likely that a malicious client has a priori knowledge of the
structure of the authorization page and form, it does not need the
response in order to advance to the next step, and can simply send the
fake request to 'Allow' itself to access the resource owner's
resources.
I believe this attack could be made very hard by either including a
CAPTCHA, as you suggested, or including some kind of token or nonce in
the submission of the form (which would still not prevent the attack
if the authorization server doesn't enforce same origin policy).
Niv
On Tue, Jul 26, 2011 at 02:10, Torsten Lodderstedt
<tors...@lodderstedt.net> wrote:
Hi Niv,
thank you for posting this to the list. I think you are right with your threat
description. One question: shouldn't the browser already prevent the request to
the authorization endpoint because of the same origin policy (or CORS
restrictions)?
Apart from that, a similar attack can be performed by a native applicication
(using an embedded browser). This kind of attack could not be prevented using
HTTP features but by enforcing a real user interaction (password input,
CAPTCHA).
regards,
Torsten.
Am 25.07.2011 18:27, schrieb Niv Steingarten:
Forwarded as per Eran's request.
A couple of corrections to my original email:
1. By AJAX, I mean, AJAX like techniques (if the user agent does not enforce
same origin policy).
2. When saying POST to '/authorize_callback' -- it may well be GET, if the
authorization server mishandles the request.
Thank you,
Niv
---------- Forwarded message ----------
From: Eran Hammer-Lahav<e...@hueniverse.com>
Date: Tue, Jul 26, 2011 at 01:21
Subject: RE: Several typos in -20 and a possible security consideration
To: Niv Steingarten<nivst...@gmail.com>
Please forward this message to the oauth list at oa...@ieft.org.
Thanks,
EHL
From: Niv Steingarten [mailto:nivst...@gmail.com]
Sent: Monday, July 25, 2011 2:52 PM
To: draft-ietf-oauth...@tools.ietf.org
Subject: Several typos in -20 and a possible security consideration
Hello,
I've noticed a couple of typos in -20:
Section 6 (page 41): Under 'The authorization server MUST', the second bullet should end
with the word "and", and the third bullet should end with a full-stop.
Section 10.2 (first paragraph): "...keep is client credentials confidential" should be
"...keep *its* client credentials confidential".
Regarding the security consideration --
I might be missing something, but I saw there are references to clickjacking
and to client impersonation, but I haven't seen any reference to possible
resource owner impersonation.
For example, in the implicit grant flow, a malicious client could send a
request to the authorization endpoint via, say, AJAX, and receive the markup of
the page asking the resource owner to authorize the client (assuming the
resource owner is signed in and no resource owner authentication is required).
Then, in a poorly designed authorization endpoint, the 'Allow' button might be
the submission button of a form whose target is '/authorize_callback' on the
authz server. Then, it may possible for the malicious client to simply POST to
'/authorize_callback' and authorize itself without any resource owner
intervention or knowledge that the process has even taken place. This, of
course, can be mitigated in most modern browsers if the authorization server
verifies the source of the request using the HTTP referrer header.
Thanks for your time and for the fantastic work on OAuth,
--
Niv Steingarten
T: +972-54-5828088
E: nivst...@gmail.com
W: http://nivstein.com
--
Niv Steingarten
T: +972-54-5828088
E: nivst...@gmail.com
W: http://nivstein.com
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