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+---
+labels:
+- Stage-Alpha
+rockspec:
+  build:
+    copy_directories:
+    - html
+summary: OAuth 2.0 Authorization Server API
+---
+
+## Introduction
+
+This module implements an [OAuth2](https://oauth.net/2/)/[OpenID Connect
+(OIDC)](https://openid.net/connect/) Authorization Server on top of
+Prosody's usual internal authentication backend.
+
+OAuth and OIDC are web standards that allow you to provide clients and
+third-party applications limited access to your account, without sharing your
+password with them.
+
+With this module deployed, software that supports OAuth can obtain
+"access tokens" from Prosody which can then be used to connect to XMPP
+accounts using the [OAUTHBEARER SASL mechanism][rfc7628] or via non-XMPP
+interfaces such as [mod_rest].
+
+Although this module has been around for some time, it has recently been
+significantly extended and largely rewritten to support OAuth/OIDC more fully.
+
+As of April 2023, it should be considered **alpha** stage. It works, we have
+tested it, but it has not yet seen wider review, testing and deployment. At
+this stage we recommend it for experimental and test deployments only. For
+specific information, see the [deployment notes section](#deployment-notes)
+below.
+
+Known client implementations:
+
+-   [example shell script for mod_rest](https://hg.prosody.im/prosody-modules/file/tip/mod_rest/example/rest.sh)
+-   *(we need you!)*
+
+Support for [OAUTHBEARER][rfc7628] has been added to the Lua XMPP
+library, [verse](https://code.matthewwild.co.uk/verse).  If you know of
+additional implementations, or are motivated to work on one, please let
+us know! We'd be happy to help (e.g. by providing a test server).
+
+## Standards support
+
+Notable supported standards:
+
+- [RFC 6749: The OAuth 2.0 Authorization Framework](https://www.rfc-editor.org/rfc/rfc6749)
+- [RFC 7009: OAuth 2.0 Token Revocation](https://www.rfc-editor.org/rfc/rfc7009)
+- [RFC 7591: OAuth 2.0 Dynamic Client Registration](https://www.rfc-editor.org/rfc/rfc7591.html)
+- [RFC 7628: A Set of Simple Authentication and Security Layer (SASL) Mechanisms for OAuth](https://www.rfc-editor.org/rfc/rfc7628)
+- [RFC 7636: Proof Key for Code Exchange by OAuth Public Clients](https://www.rfc-editor.org/rfc/rfc7636)
+- [RFC 7662: OAuth 2.0 Token Introspection](https://www.rfc-editor.org/rfc/rfc7662)
+- [RFC 8628: OAuth 2.0 Device Authorization Grant](https://www.rfc-editor.org/rfc/rfc8628)
+- [RFC 9207: OAuth 2.0 Authorization Server Issuer Identification](https://www.rfc-editor.org/rfc/rfc9207.html)
+- [OpenID Connect Core 1.0](https://openid.net/specs/openid-connect-core-1_0.html)
+- [OpenID Connect Discovery 1.0](https://openid.net/specs/openid-connect-discovery-1_0.html) (_partial, e.g. missing JWKS_)
+- [OpenID Connect Dynamic Client Registration 1.0](https://openid.net/specs/openid-connect-registration-1_0.html)
+
+## Configuration
+
+### Interface
+
+The module presents a web page to users to allow them to authenticate when
+a client requests access. Built-in pages are provided, but you may also theme
+or entirely override them.
+
+This module honours the `site_name` configuration option that is also used by
+a number of other modules:
+
+```lua
+site_name = "My XMPP Server"
+```
+
+To provide custom templates, specify the path to the template directory:
+
+```lua
+oauth2_template_path = "/etc/prosody/custom-oauth2-templates"
+```
+
+If you know what features your templates use use you can adjust the
+`Content-Security-Policy` header to only allow what is needed:
+
+```lua
+oauth2_security_policy = "default-src 'self'" -- this is the default
+```
+
+### Token parameters
+
+The following options configure the lifetime of tokens issued by the module.
+The defaults are recommended.
+
+```lua
+oauth2_access_token_ttl = 3600 -- one hour
+oauth2_refresh_token_ttl = 604800 -- one week
+```
+
+### Dynamic client registration
+
+To allow users to connect any compatible software, you should enable dynamic
+client registration.
+
+Dynamic client registration can be enabled by configuring a JWT key. Algorithm
+defaults to *HS256*, lifetime defaults to forever.
+
+```lua
+oauth2_registration_key = "securely generated JWT key here"
+oauth2_registration_algorithm = "HS256"
+oauth2_registration_ttl = nil -- unlimited by default
+```
+
+Registering a client is described in
+[RFC7591](https://www.rfc-editor.org/rfc/rfc7591.html).
+
+In addition to the requirements in the RFC, the following requirements
+are enforced:
+
+`client_name`
+:   **MUST** be present, is shown to users in consent screen.
+
+`client_uri`
+:   **MUST** be present and **MUST** be a `https://` URL.
+
+`redirect_uris`
+
+:   **MUST** contain at least one valid URI. Different rules apply
+    depending on the value of `application_type`, see below.
+
+`application_type`
+
+:   Optional, defaults to `web`. Determines further restrictions for
+    `redirect_uris`. The following values are supported:
+
+    `web` *(default)*
+    :   For web clients. With this, `redirect_uris` **MUST** be
+        `https://` URIs and **MUST** use the same hostname part as the
+        `client_uri`.
+
+    `native`
+    :   For native e.g. desktop clients etc. `redirect_uris` **MUST**
+        match one of:
+
+        -   Loopback HTTP URI, e.g. `http://127.0.0.1/` or
+            `http://[::1]`
+        -   Application-specific scheme, e.g. `com.example.app:/`
+        -   The special OOB URI `urn:ietf:wg:oauth:2.0:oob`
+
+`tos_uri`, `policy_uri`
+:   Informative URLs pointing to Terms of Service and Service Policy
+    document **MUST** use the same scheme (i.e. `https://`) and hostname
+    as the `client_uri`.
+
+#### Registration Examples
+
+In short registration works by POST-ing a JSON structure describing your
+client to an endpoint:
+
+``` bash
+curl -sSf https://xmpp.example.net/oauth2/register \
+    -H Content-Type:application/json \
+    -H Accept:application/json \
+    --data '
+{
+   "client_name" : "My Application",
+   "client_uri" : "https://app.example.com/",
+   "redirect_uris" : [
+      "https://app.example.com/redirect"
+   ]
+}
+'
+```
+
+Another example with more fields:
+
+``` bash
+curl -sSf https://xmpp.example.net/oauth2/register \
+    -H Content-Type:application/json \
+    -H Accept:application/json \
+    --data '
+{
+   "application_type" : "native",
+   "client_name" : "Desktop Chat App",
+   "client_uri" : "https://app.example.org/",
+   "contacts" : [
+      "support@example.org"
+   ],
+   "policy_uri" : "https://app.example.org/about/privacy",
+   "redirect_uris" : [
+      "http://localhost:8080/redirect",
+      "org.example.app:/redirect"
+   ],
+   "scope" : "xmpp",
+   "software_id" : "32a0a8f3-4016-5478-905a-c373156eca73",
+   "software_version" : "3.4.1",
+   "tos_uri" : "https://app.example.org/about/terms"
+}
+'
+```
+
+### Supported flows
+
+-   Authorization Code grant, optionally with Proof Key for Code Exchange
+-   Device Authorization Grant
+-   Resource owner password grant *(disabled by default)*
+-   Implicit flow *(disabled by default)*
+-   Refresh Token grants
+
+Various flows can be disabled and enabled with
+`allowed_oauth2_grant_types` and `allowed_oauth2_response_types`:
+
+```lua
+-- These examples reflect the defaults
+allowed_oauth2_grant_types = {
+	"authorization_code"; -- authorization code grant
+	"device_code";
+	-- "password"; -- resource owner password grant disabled by default
+}
+
+allowed_oauth2_response_types = {
+	"code"; -- authorization code flow
+    -- "token"; -- implicit flow disabled by default
+}
+```
+
+The [Proof Key for Code Exchange][RFC 7636] mitigation method is
+required by default but can be made optional:
+
+```lua
+oauth2_require_code_challenge = false -- default is true
+```
+
+Further, individual challenge methods can be enabled or disabled:
+
+```lua
+-- These reflects the default
+allowed_oauth2_code_challenge_methods = {
+    -- "plain"; -- insecure but backwards-compatible
+    "S256";
+}
+```
+
+### Policy documents
+
+Links to Terms of Service and Service Policy documents can be advertised
+for use by OAuth clients:
+
+```lua
+oauth2_terms_url = "https://example.com/terms-of-service.html"
+oauth2_policy_url = "https://example.com/service-policy.pdf"
+-- These are unset by default
+```
+
+## Deployment notes
+
+### Access management
+
+This module does not provide an interface for users to manage what they have
+granted access to their account! (e.g. to view and revoke clients they have
+previously authorized). It is recommended to join this module with
+[mod_client_management] to provide such access. However, at the time of writing,
+no XMPP clients currently support the protocol used by that module. We plan to
+work on additional interfaces in the future.
+
+### Scopes
+
+OAuth supports "scopes" as a way to grant clients limited access.
+
+There are currently no standard scopes defined for XMPP. This is
+something that we intend to change, e.g. by definitions provided in a
+future XEP. This means that clients you authorize currently have to
+choose between unrestricted access to your account (including the
+ability to change your password and lock you out!) and zero access. So,
+for now, while using OAuth clients can prevent leaking your password to
+them, it is not currently suitable for connecting untrusted clients to
+your account.
+
+As a first step, the `xmpp` scope is supported, and corresponds to
+whatever permissions the user would have when logged in over XMPP.
+
+Further, known Prosody roles can be used as scopes.
+
+OpenID scopes such as `openid` and `profile` can be used for "Login
+with XMPP" without granting access to more than limited profile details.
+
+## Compatibility
+
+Requires Prosody trunk (April 2023), **not** compatible with Prosody 0.12 or
+earlier.