minimal webfinger (#5373)

* initial webfinger stub

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* add webfinger to proxy, return current host

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* some cleanup

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* allow passing multiple rel params

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* introduce interfaces

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* parse oidc auth token

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* add templating, drop chain, use map of relation providers

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* fix ocis url yaml

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* fix typos

Co-authored-by: Dominik Schmidt <dschmidt@owncloud.com>

* switch to userinfo claims

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* readme cleanup

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* add TODO.md with ideas

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* replace subject on authenticated request responses

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* Apply suggestions from code review

Co-authored-by: Martin <github@diemattels.at>

* markdown lint

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* return a 401 when bearer token expired, some more docs

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* Apply suggestions from code review

Co-authored-by: Martin <github@diemattels.at>

* fix docs

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* clarify env var

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* extract handler func

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* use correct service in reflex.conf

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* test relations

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

* Update services/webfinger/pkg/config/config.go

---------

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>
Co-authored-by: Dominik Schmidt <dschmidt@owncloud.com>
Co-authored-by: Martin <github@diemattels.at>

services/webfinger/README.md

@@ -0,0 +1,122 @@
+# Webfinger Service
+
+The webfinger service provides an RFC7033 WebFinger lookup of ownCloud instances relevant for a given user account.
+
+It is based on https://github.com/owncloud/lookup-webfinger-sciebo but also returns localized `titles` in addition to the `href` property.
+
+## OpenID Connect Discovery
+
+Clients can make an unauthenticated `GET https://drive.ocis.test/.well-known/webfinger?resource=https%3A%2F%2Fcloud.ocis.test` request to discover the OpenID Connect Issuer in the `http://openid.net/specs/connect/1.0/issuer` relation:
+```json
+{
+    "subject": "acct:einstein@drive.ocis.test",
+    "links": [
+        {
+            "rel": "http://openid.net/specs/connect/1.0/issuer",
+            "href": "https://sso.example.org/cas/oidc/"
+        }
+    ]
+}
+```
+
+Here, the `resource` takes the instance domain URI, but an `acct:` URI works as well. 
+
+## Authenticated Instance Discovery
+
+When using OpenID connect to authenticate requests, clients can look up the owncloud instances a user has access to.
+*   Authentication is necessary to prevent leaking information about existing users.
+*   Basic auth is not supported.
+
+The default configuration will simply return the `OCIS_URL` and direct clients to that domain:
+
+```json
+{
+    "subject": "acct:einstein@drive.ocis.test",
+    "links": [
+        {
+            "rel": "http://openid.net/specs/connect/1.0/issuer",
+            "href": "https://sso.example.org/cas/oidc/"
+        },
+        {
+            "rel": "http://webfinger.owncloud/rel/server-instance",
+            "href": "https://abc.drive.example.org",
+            "titles": {
+                "en": "oCIS Instance"
+            }
+        }
+    ]
+}
+```
+
+## Configure Different Instances Based on OpenidConnect UserInfo Claims
+
+A more complex example for configuring different instances could look like this:
+```yaml
+webfinger:
+  instances:
+  -  claim: email
+     regex: einstein@example\.org
+     href: "https://{{.preferred_username}}.cloud.ocis.test"
+     title: 
+       "en": "oCIS Instance for Einstein"
+       "de": "oCIS Instanz für Einstein"
+     break: true
+  -  claim: "email"
+     regex: marie@example\.org
+     href: "https://{{.preferred_username}}.cloud.ocis.test"
+     title: 
+       "en": "oCIS Instance for Marie"
+       "de": "oCIS Instanz für Marie"
+     break: false
+  -  claim: "email"
+     regex: .+@example\.org
+     href: "https://example-org.cloud.ocis.test"
+     title:
+       "en": "oCIS Instance for example.org"
+       "de": "oCIS Instanz für example.org"
+     break: true
+  -  claim: "email"
+     regex: .+@example\.com
+     href: "https://example-com.cloud.ocis.test"
+     title:
+       "en": "oCIS Instance for example.com"
+       "de": "oCIS Instanz für example.com"
+     break: true
+  -  claim: "email"
+     regex: .+@.+\..+
+     href: "https://cloud.ocis.test"
+     title:
+       "en": "oCIS Instance"
+       "de": "oCIS Instanz"
+     break: true
+```
+
+Now, an authenticated webfinger request for `acct:me@example.org` (when logged in as marie) would return two instances, based on her `email` claim, the regex matches and break flags:
+
+```json
+{
+    "subject": "acct:marie@example.org",
+    "links": [
+        {
+            "rel": "http://openid.net/specs/connect/1.0/issuer",
+            "href": "https://sso.example.org/cas/oidc/"
+        },
+        {
+            "rel": "http://webfinger.owncloud/rel/server-instance",
+            "href": "https://marie.cloud.ocis.test",
+            "titles": {
+                "en": "oCIS Instance for Marie",
+                "de": "oCIS Instanz für Marie"
+            }
+        },
+        {
+            "rel": "http://webfinger.owncloud/rel/server-instance",
+            "href": "https://xyz.drive.example.org",
+            "titles": {
+                "en": "oCIS Instance for example.org",
+                "de": "oCIS Instanz für example.org"
+            }
+        }
+    ]
+}
+```