Re: [OAUTH-WG] Google's view on signatures in the core OAuth2 spec

["Richard L. Barnes" <[e-mail]>]

> I think that any signature method that we end up using needs to rely
> less on magic and anecdote and more on explicit declaration.

This is certainly correct ...


> I think
> that Brian Eaton's approach of sending the bare string that was  
> signed,
> which was also a JSON element that could be parsed and validated,  
> was an
> essential simplification.

... but this does not follow.  The signer can specify what was signed  
without sending the data...

> Even OpenID states which of the parameters on
> the request were signed, which makes it easier to validate.

... as in this pattern.  There are some other examples of elements of  
the signed object being conditionally included:
1. HTTP Digest authentication [1]
2. The IKEv2 key exchange messages [2]

As has been pointed out before, there is a security risk in sending  
the signed request data itself (as opposed to metadata that allows the  
recipient to reconstruct the data), because the recipient can choose  
not to verify the binding between the signed data and the request.

--Richard


[1] <http://tools.ietf.org/html/rfc2617#section-3.2.2>
[2] <http://tools.ietf.org/html/rfc4306#section-1.2>