issuer@oauth3.org (js)
======================

Implementation of server-side RESTful OAuth3 issuer APIs.

These are the OAuth3 APIs that allow for creation and retrieval of public keys
used for signing identity tokens.

"issuer" is somewhat of a misnomer from the OIDC breakdown of authentication /
authorization parties. What we mean by "issuer" here is actually more like
"notary" or "authorized verifier". However, since the "iss" field is already
standardized, we keep that name for consistency.

What's to be implemented:

Looking at <https://oauth3.org/.well-known/oauth3/directives.json>, the core
issuer components are these:

```
api:                    api.:hostname
create_jwk:             :scheme//:hostname/api/issuer@oauth3.org/jwks/:sub
jwks:                   :scheme//:hostname/api/issuer@oauth3.org/jwks/:thumbprint.json
grants:                 :scheme//:hostname/api/issuer@oauth3.org/grants/:sub/:azp?
credential_meta:        :scheme//:hostname/api/issuer@oauth3.org/logins/meta/:type/:id
credential_otp:         :scheme//:hostname/api/issuer@oauth3.org/otp
authorization_decision  :scheme//:hostname/api/issuer@oauth3.org/authorization_decision
authorization_dialog    :scheme//:hostname/api/issuer@oauth3.org/authorization_dialog
logout                  :scheme//:hostname/api/issuer@oauth3.org/#/logout
```

No `access_token` endpoint is strictly necessary. Since clients can create and
manage their identity, the can sign create their own tokens. If the identity is
stored on the issuer, then the issuer can also sign tokens. Doing so gives full
control of all resources owned by the subject "sub" to the issuer "iss".

```
create_sub:       :scheme//:hostname/api/issuer@oauth3.org/subs/:secret/:sub
```

And here are some others that are useful, but could be implemented differently
without breaking the protocol.

```
credential_create: :scheme//:hostname/api/issuer@oauth3.org/logins
credential_meta: :scheme//:hostname/api/issuer@oauth3.org/logins/meta/:type/:id
credential_otp: :scheme//:hostname/api/issuer@oauth3.org/otp
```

subject
-------

The `sub` field must be `sha256(secret + ':' + azp)`.

Example:

```js
var secret = '8f7acd369764df342d1581872ff5f70fcc261aa116b3c41dee7ca3474ee2020f' // cryto.randomBytes(32).toString('hex')
var sha256 = cryto.createHash('sha256');
sha256.update(new Buffer(secret, 'hex'));
sha256.update(':' + 'example.com');

var sub = sha256.digest('hex');
```

This way any issuer can transfer ownership of identity to any other issuer and
deterministically reproduce the ppid by virtue of the secret identity of the
subject and the public identity of the authorized party and the key is known to
be good if the issuer "iss" can supply the public key that verifies the token,
identified by its thumbprint "kid" (which the issuer knows without revealing
its ppid of the subject and without the authorized party needing to reveal its
ppid of the subject.

JWKs
----
We want the users to have the option of signing tokens using keys on their own
devices. This requires having a place to store the public half of those keys
on a server that can then server the public keys to resource providers for
signature verification.

### Saving a JWK ###
  * **URL** `:scheme//:hostname/api/issuer@oauth3.org/jwks/:sub`
  * **Method** `POST`
  * **Url Params**
    * `sub`: The [subject](#subject) using the issuer hostname as the `azp`
  * **Body Params**: The body should be a JSON object representing a
    [JWK](https://tools.ietf.org/html/rfc7517#section-4).

### Retrieving a JWK ###
  * **URL** `:scheme//:hostname/api/issuer@oauth3.org/jwks/:kid.json`
  * **Method** `GET`
  * **Url Params**
    * `kid`: The [JWK thumbprint](https://tools.ietf.org/html/rfc7638) of the key

Currently only `EC` and `RSA` key storage is supported. All provided parameters
will be stored in the database, but only generic JWK parameters and parameters
specified as part of the public key for the `kty` by the
[JWA](https://tools.ietf.org/html/rfc7518#section-6) will be given back by the
GET request. This is to avoid compromising a key if the private portion or any
other potentially sensitive fields are given to us.

TODO: we need to somehow associate a key with a particular user without needing
the issuer's subject. Resources providers will not have that subject but will
need to be able to retrieve only public keys that actually belong to the user
that are trying to validate.

Grants
------
Grants represent the list of resources the user has allowed a party to access.
We store those permissions on the server so that users will not have to grant
the same privileges multiple times on different machines.

### Saving/Modifying Grants ###
  * **URL** `:scheme//:hostname/api/issuer@oauth3.org/grants/:sub/:azp`
  * **Method** `POST`
  * **Url Params**
    * `sub`: The [subject](#subject) using the issuer hostname as the `azp`
    * `azp`: The authorized party the grants are for
  * **Body Params**
    * `scope`: A comma separated list of the permissions granted

### Retrieving Grants ###
  * **URL** `:scheme//:hostname/api/issuer@oauth3.org/grants/:sub/:azp`
  * **Method** `GET`
  * **Url Params**
    * `sub`: The [subject](#subject) using the issuer hostname as the `azp`
    * `azp`: The authorized party the grants are for
  * **Response**
    * `sub`: The same `sub` from the url
    * `azp`: The same `azp` from the url
    * `scope`: A comma separated list of the permissions granted
    * `updatedAt`: The timestamp for the most recent change to the grants