Re: [OAUTH-WG] Phishing with Client Application Name Spoofing

Mark Mcgloin <> Fri, 16 December 2011 12:09 UTC

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Date: Fri, 16 Dec 2011 12:08:44 +0000
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Subject: Re: [OAUTH-WG] Phishing with Client Application Name Spoofing
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You are right that the threat model does not cover this kind of issue
related to client registration. Client registration is considered to be out
of scope in the oauth spec but it is worth drawing developers attention to
this.  I can add a threat entitled something like "Client Registration of
phishing clients". It kind of reminds me of the issues android market place
has seen recently with malware apps due to no vetting of those apps.

It is touched upon in the oauth 2 rfc:


On 3 Nov 2011 17:09:39, "Andre DeMarre" wrote:

You are right that they are similar, but there is a difference, and
only one of the six countermeasures is relevant to the threat I

seems to be about an attack where the malicious client impersonates a
different (valid) client that is registered with the authorization
server. In other words, the valid client is registered as client_id
123, and the malicious client does not have its own client_id but
tries to pose as client 123. This corresponds to

In the threat I described, there is no valid client. The malicious
client is properly registered with the authorization server and has
its own client_id and client credentials. It can authenticate with the
authorization server without trying to pose as a different client.

As an attacker you might reason, "Why would I try to impersonate a
valid client for which I don't know the client credentials and can't
pass the redirect URI test, when I can just register my own client
with my own redirect URI and be given my own credentials?"

Imagine the attacker wants to impersonate Google with a popular web
service called Foobar. The attacker registers his application with
Foobar's auth server. It does not matter if the real Google has
registered an authentic app with Foobar. The attacker has no reason to
be interested in stealing or guessing client credentials when he can
simply register his own app and call it "Google".

The information the auth server shows to end users when asking them to
grant authorization becomes very important.
Regards,Andre DeMarre
On Wed, Nov 2, 2011 at 2:27 PM, Torsten Lodderstedt
<torsten at> wrote:
> Hi Andre,
> how do you think differs the threat you descibed from
> regards,
> Torsten.