It would be more a client having reached a non-MTLS endpoint and is 307'd
to an MTLS enabled endpoint.
On Fri, Feb 1, 2019 at 1:40 PM Phil Hunt <phil.h...@oracle.com> wrote:
> I was a bit confused by how the 307 would work.
>
> To confirm, Is the client having reached an MTLS optional endpoint being
> redirected to an MTLS mandatory endpoint if the AT (or a cookie) is
> detected to have a “cnf” claim in order to make the browser invoke MTLS?
>
> Phil
>
> Oracle Corporation, Cloud Security and Identity Architect
> @independentid
> www.independentid.com
> phil.h...@oracle.com
>
> On Feb 1, 2019, at 11:56 AM, Brian Campbell <
> bcampbell=40pingidentity....@dmarc.ietf.org> wrote:
>
> I'm finally getting around to working on the document updates (there's
> quite a few things that came out of AD review too). As far as the issue in
> this thread goes though, I'm leaning towards adding "mtls_endpoints" as a
> new metadata parameter. Maybe mention that a 307 might happen but it'd be
> more of a considerations type text.
>
> On Wed, Jan 16, 2019 at 5:52 AM Brian Campbell <bcampb...@pingidentity.com>
> wrote:
>
>> I guess I should have also said or been more straightforward in saying
>> that I don't particularly want to try and discuss/define the use of a 307
>> in the document.
>>
>> On Tue, Jan 15, 2019 at 6:59 AM Filip Skokan <panva...@gmail.com> wrote:
>>
>>> I don't know that the use of 307 would need to be discussed in the
>>>> document itself.
>>>
>>>
>>> If the clients are supposed to be ready for this, yeah. For instance, my
>>> client software by default doesn't follow redirects, in order for it to be
>>> ready for mtls client authentication i'd have to know 307 is a possibility
>>> and whitelist 307 as a valid code to be followed.
>>>
>>> S pozdravem,
>>> *Filip Skokan*
>>>
>>>
>>> On Tue, Jan 15, 2019 at 2:54 PM Brian Campbell <
>>> bcampb...@pingidentity.com> wrote:
>>>
>>>> I don't know that the use of 307 would need to be discussed in the
>>>> document itself.
>>>>
>>>> On Tue, Jan 15, 2019 at 2:30 AM Filip Skokan <panva...@gmail.com>
>>>> wrote:
>>>>
>>>>> I'm in favour of both 307 and metadata.
>>>>>
>>>>> - case 307 - I don't recall ever encountering an http client
>>>>> software that wouldn't have an option for following redirects, same
>>>>> for a
>>>>> server side frameworks not having the option to do a 307 response with
>>>>> a
>>>>> location header.
>>>>> - case 307 - Relying purely on a new metadata doesn't help in the
>>>>> scenario David put forth earlier about clients not being aware of using
>>>>> mtls, a device policy of sorts.
>>>>> - case metadata - no second request if the client knows there's an
>>>>> mtls endpoint it should use.
>>>>>
>>>>> Maybe we should specify both as optional for an AS to deploy and a
>>>>> client to be ready for?
>>>>>
>>>>> S pozdravem,
>>>>> *Filip Skokan*
>>>>>
>>>>>
>>>>> On Tue, Jan 15, 2019 at 10:05 AM Dave Tonge <
>>>>> dave.to...@momentumft.co.uk> wrote:
>>>>>
>>>>>> I'm in favour of the `mtls_endpoints` metadata parameter - although
>>>>>> it should be optional.
>>>>>> While a 307 redirect seems kind of elegant I worry, like you, that
>>>>>> not all clients would handle it appropriately.
>>>>>> There would probably need to be an error defined for clients who
>>>>>> attempt to use `tls_client_auth` at the regular endpoint.
>>>>>>
>>>>>> Dave
>>>>>>
>>>>>> On Mon, 14 Jan 2019 at 22:29, Brian Campbell <bcampbell=
>>>>>> 40pingidentity....@dmarc.ietf.org> wrote:
>>>>>>
>>>>>>> Trying to summarize things somewhat here and focus in hopefully
>>>>>>> towards some decision. There's basically an idea on the table to add an
>>>>>>> AS
>>>>>>> metadata parameter to the draft-ietf-oauth-mtls doc that would be a JSON
>>>>>>> object which contains endpoints that a client doing MTLS would use
>>>>>>> rather
>>>>>>> than the regular endpoints. A straw-man example might look like this
>>>>>>> (with
>>>>>>> mtls_endpoints being that new parameter).
>>>>>>>
>>>>>>> {
>>>>>>> "issuer":"https://server.example.com";,
>>>>>>> "authorization_endpoint":"https://server.example.com/authz";,
>>>>>>> "token_endpoint":"https://server.example.com/token";,
>>>>>>> "token_endpoint_auth_methods_supported":[
>>>>>>> "client_secret_basic","tls_client_auth", "none"],
>>>>>>> "userinfo_endpoint":"https://server..example.com/userinfo
>>>>>>> <https://server.example.com/userinfo>",
>>>>>>> "revocation_endpoint":"https://server.example.com/revo";,
>>>>>>> "jwks_uri":"https://server.example.com/jwks.json";,
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> * "mtls_endpoints":{
>>>>>>> "token_endpoint":"https://mtls.example.com/token
>>>>>>> <https://mtls.example.com/token>", "userinfo_endpoint":"https://mtls
>>>>>>> <https://server.example.com/token>.example.com/userinfo
>>>>>>> <http://example.com/userinfo>", "revocation_endpoint":"https://mtls
>>>>>>> <https://server.example.com/token>..example.com/revo
>>>>>>> <http://example.com/revo>" }*
>>>>>>> }
>>>>>>>
>>>>>>> The idea behind this is that "regular" clients (those not doing
>>>>>>> MTLS) will use the regular endpoints. And only the host/port of the
>>>>>>> endpoints listed in mtls_endpoints will be set up to request TLS client
>>>>>>> certificates during handshake.. Thus any potential impact of the
>>>>>>> CertificateRequest message being sent in the TLS handshake can be
>>>>>>> avoided
>>>>>>> for all the other regular clients that are not going to do MTLS -
>>>>>>> including
>>>>>>> and most importantly in-browser javascript clients where there can be
>>>>>>> less
>>>>>>> than desirable UI presented to the end-user.
>>>>>>>
>>>>>>> The arguments in favor of that seem to be basically that it allows
>>>>>>> for AS deployments to support MTLS while still allowing for a "not
>>>>>>> broken"
>>>>>>> UX for end-users of clients (in-browser javascript clients) that aren't
>>>>>>> doing MTLS. And that it's not much in terms of adding to the spec and
>>>>>>> complexity of implementations.
>>>>>>>
>>>>>>> The arguments against it seem to be 1) the bad UX isn't really that
>>>>>>> bad and/or will only happen to a subset of users 2) there are other
>>>>>>> things
>>>>>>> that can be done, such as 307ing or renegotiation/post-handshake client
>>>>>>> auth, to avoid the bad UX.
>>>>>>>
>>>>>>> Speaking for myself, I'm kinda torn on it.
>>>>>>>
>>>>>>> I will say that, in addition to the folks that have pointed out that
>>>>>>> renegotiation just isn't possible in some cases, my experience trying
>>>>>>> to do
>>>>>>> something like that in the past was not particularly successful or
>>>>>>> encouraging. That could have been my fault, of course, but still seems a
>>>>>>> relevant data point. I also have my doubts about the actual difficulty
>>>>>>> of
>>>>>>> getting an AS to issue a 307 like response for requests based on the
>>>>>>> calling client and the likelihood that some/all OAuth client software
>>>>>>> would
>>>>>>> handle it appropriately.
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Jan 11, 2019 at 12:32 PM David Waite <
>>>>>>> da...@alkaline-solutions.com> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> > On Jan 11, 2019, at 3:32 AM, Neil Madden <
>>>>>>>> neil.mad...@forgerock.com> wrote:
>>>>>>>> >
>>>>>>>> > On 9 Jan 2019, at 05:54, David Waite <
>>>>>>>> da...@alkaline-solutions.com> wrote:
>>>>>>>> >>
>>>>>>>> >>> On Dec 28, 2018, at 3:55 PM, Brian Campbell <bcampbell=
>>>>>>>> 40pingidentity....@dmarc.ietf.org> wrote:
>>>>>>>> >>>
>>>>>>>> >> <snip>
>>>>>>>> >>
>>>>>>>> >>> All of that is meant as an explanation of sorts to say that I
>>>>>>>> think that things are actually okay enough as is and that I'd like to
>>>>>>>> retract the proposal I'd previously made about the MTLS draft
>>>>>>>> introducing a
>>>>>>>> new AS metadata parameter. It is admittedly interesting (ironic?) that
>>>>>>>> Neil
>>>>>>>> sent a message in support of the proposal as I was writing this. It did
>>>>>>>> give me pause but ultimately didn't change my opinion that it's not
>>>>>>>> worth
>>>>>>>> it to add this new AS metadata parameter.
>>>>>>>> >>
>>>>>>>> >> Note that the AS could make a decision based on the token
>>>>>>>> endpoint request - such as a policy associated with the “client_id”,
>>>>>>>> or via
>>>>>>>> a parameter in the ilk of “client_assertion_type” indicating MTLS was
>>>>>>>> desired by this public client installation. The AS could then to TLS
>>>>>>>> 1.2
>>>>>>>> renegotiation, 1.3 post-handshake client authentication, or even use
>>>>>>>> 307
>>>>>>>> temporary redirects to another token endpoint to perform mutual
>>>>>>>> authentication.
>>>>>>>> >
>>>>>>>> > Renegotiation is an intriguing option, but it has some practical
>>>>>>>> difficulties. Our AS product runs in a Java servlet container, where
>>>>>>>> it is
>>>>>>>> pretty much impossible to dynamically trigger renegotiation without
>>>>>>>> accessing private internal APIs of the container. I also don’t know
>>>>>>>> how you
>>>>>>>> could coordinate this in the common scenario where TLS is terminated
>>>>>>>> at a
>>>>>>>> load balancer/reverse proxy?
>>>>>>>> >
>>>>>>>> > A 307 redirect could work though as the server will know if the
>>>>>>>> client either uses mTLS for client authentication or has indicated
>>>>>>>> that it
>>>>>>>> wants certificate-bound access tokens, so it can redirect to a
>>>>>>>> mTLS-specific endpoint in those cases.
>>>>>>>>
>>>>>>>> Agreed. There are trade-offs for both. As you say, I don’t know a
>>>>>>>> way to have say a custom error code or WWW-Authenticate challenge to
>>>>>>>> trigger renegotiation on the reverse proxy - usually this is just a
>>>>>>>> static,
>>>>>>>> location-based directive.
>>>>>>>>
>>>>>>>> >
>>>>>>>> >> Both the separate metadata url and a
>>>>>>>> “client_assertion_type”-like indicator imply that the client has
>>>>>>>> multiple
>>>>>>>> forms of authentication and is choosing to use MTLS. The URL in
>>>>>>>> particular
>>>>>>>> I’m reluctant to add support for, because I see it more likely a client
>>>>>>>> would use MTLS without knowing it (via a device-level policy being
>>>>>>>> applied
>>>>>>>> to a public web or native app) than the reverse, where a single client
>>>>>>>> (represented by a single client_id) is dynamically picking between
>>>>>>>> forms of
>>>>>>>> authentication.
>>>>>>>> >
>>>>>>>> > That’s an interesting observation. Can you elaborate on the sorts
>>>>>>>> of device policy you are talking about? I am aware of e.g. mobile
>>>>>>>> device
>>>>>>>> management being used to push client certificates to iOS devices, but I
>>>>>>>> think these are only available in Safari.
>>>>>>>>
>>>>>>>> The primary use is to set policy to rely on device level management
>>>>>>>> in controlled environments like enterprises when available. So an AS
>>>>>>>> may
>>>>>>>> try to detect a client certificate as an indicator of a managed
>>>>>>>> device, use
>>>>>>>> that to assume a device with certain device-level authentication,
>>>>>>>> single
>>>>>>>> user usage, remote wipe, etc. characteristics, and decide that it can
>>>>>>>> reduce user authentication requirements and/or expose additional
>>>>>>>> scopes.
>>>>>>>>
>>>>>>>> On more thought, this is typically done as part of the user agent
>>>>>>>> hitting the authorization endpoint, as a separate native application
>>>>>>>> may be
>>>>>>>> interacting with the token endpoint, and in some operating systems the
>>>>>>>> application’s network connections do not utilize (and may not have
>>>>>>>> access
>>>>>>>> to) the system certificate store.
>>>>>>>>
>>>>>>>> In terms of user agents, I believe you can perform similar behavior
>>>>>>>> (managed systems using client certificates on user agents
>>>>>>>> transparently) on
>>>>>>>> macOS, Windows, Chrome, and Android devices, Chrome (outside iOS)
>>>>>>>> typically
>>>>>>>> inherits device level policy. Firefox on desktop I assume you can do
>>>>>>>> that
>>>>>>>> in limited fashion as well.
>>>>>>>>
>>>>>>>> -DW
>>>>>>>
>>>>>>>
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>>>>>>
>>>>>>
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