If a client attempts to force mtls would typical tls terminators accept it
enough to redirect?
My worry is how optionality works in browsers. It seems like they have to hit
an mtls required endpoint before they reliably use a client cert.
Phil
> On Feb 1, 2019, at 12:56 PM, Brian Campbell <bcampb...@pingidentity.com>
> wrote:
>
> 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";,
>>>>>>>>> "revocation_endpoint":"https://server.example.com/revo";,
>>>>>>>>> "jwks_uri":"https://server.example.com/jwks.json";,
>>>>>>>>> "mtls_endpoints":{
>>>>>>>>> "token_endpoint":"https://mtls.example.com/token";,
>>>>>>>>> "userinfo_endpoint":"https://mtls.example.com/userinfo";,
>>>>>>>>> "revocation_endpoint":"https://mtls..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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