[Openid-specs-ab] jku and x5u

Tim Bray tbray at textuality.com
Tue Apr 2 21:54:59 UTC 2013


>From where I sit, the most obvious thing to do is look at the issuer claim,
resolve ${issuer}/.well-known/openid-configuration, extract the jwk-url
claim, fetch the jwk, and validate using that.  For the kind of
consumer/internet stuff we do, wouldn't that nearly always be the right
choice?

-T


On Tue, Apr 2, 2013 at 11:48 AM, Hannes Tschofenig <
hannes.tschofenig at gmx.net> wrote:

> Hi Tim,
>
> There are three ways to shuffle keys around:
>
> * per value: you include the key in the message
> * per reference: you include a pointer to the key (e.g., a URL)
> * out-of-band: here you just give the key a name without telling where to
> find it.
>
> Needless to say that you have to be careful with all three mechanisms when
> it comes to security.
>
> You are already thinking about a complete use case that goes beyond what
> these header parameters by itself are able to answer.
>
> Ciao
> Hannes
>
>
>
> On 04/02/2013 09:35 PM, Tim Bray wrote:
>
>> Sorry, I’m probably failing to understand because I’m a crypto moron,
>> but if I want to use keys to validate a JWT allegedly from example.com
>> <http://example.com>, I’m not going to believe anything in the JWT until
>> I’ve checked using example.com <http://example.com>’s keys, so why
>>
>> should I believe the JWT’s assertion about where to get the keys to
>> validate it?  -T
>>
>>
>> On Tue, Apr 2, 2013 at 11:27 AM, Mike Jones <Michael.Jones at microsoft.com
>> <mailto:Michael.Jones@**microsoft.com <Michael.Jones at microsoft.com>>>
>> wrote:
>>
>>     Yes, that’s exactly it.  If you already know where the keys are or
>>     what they are (for instance, if you’ve established that information
>>     at registration time), there’s no need to use these parameters.  But
>>     for some use cases, this is valuable information that can be
>>     dynamically provided.  (The Key ID (“kid”) can also be dynamically
>>     provided, if appropriate to the use case.)____
>>
>>     __ __
>>
>>                                                                      --
>>     Mike____
>>
>>     __ __
>>
>>     *From:*openid-specs-ab-**bounces at lists.openid.net<openid-specs-ab-bounces at lists.openid.net>
>>     <mailto:openid-specs-ab-**bounces at lists.openid.net<openid-specs-ab-bounces at lists.openid.net>
>> >
>>     [mailto:openid-specs-ab-**bounces at lists.openid.net<openid-specs-ab-bounces at lists.openid.net>
>>     <mailto:openid-specs-ab-**bounces at lists.openid.net<openid-specs-ab-bounces at lists.openid.net>>]
>> *On Behalf Of
>>     *Tim Bray
>>     *Sent:* Tuesday, April 02, 2013 11:19 AM
>>     *To:* <openid-specs-ab at lists.openid.**net<openid-specs-ab at lists.openid.net>
>>     <mailto:openid-specs-ab at lists.**openid.net<openid-specs-ab at lists.openid.net>
>> >>
>>     *Subject:* [Openid-specs-ab] jku and x5u____
>>
>>     __ __
>>
>>
>>     Almost certainly I’m just missing something obvious, but I’m having
>>     trouble understanding why the jku and x5u header claims exist.  The
>>     idea is I get a message and believe the message’s assertion about
>>     where I should go to get the cert to validate the message?  -T____
>>
>>
>>
>>
>> ______________________________**_________________
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>>
>>
>
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