diff --git a/changelogs/client_server/newsfragments/2150.feature b/changelogs/client_server/newsfragments/2150.feature new file mode 100644 index 000000000..6eff5607c --- /dev/null +++ b/changelogs/client_server/newsfragments/2150.feature @@ -0,0 +1 @@ +Add the OAuth 2.0 based authentication API, as per [MSC3861](https://github.com/matrix-org/matrix-spec-proposals/pull/3861) and its sub-proposals. diff --git a/content/client-server-api/_index.md b/content/client-server-api/_index.md index b9c4a7d5a..d1f9654de 100644 --- a/content/client-server-api/_index.md +++ b/content/client-server-api/_index.md @@ -1481,6 +1481,174 @@ MAY reject weak passwords with an error code `M_WEAK_PASSWORD`. ### OAuth 2.0 API +#### Login flow + +Logging in with the OAuth 2.0 API should be done with the [authorization code +grant](#authorization-code-grant). In the context of the Matrix specification, +this means requesting a [scope](#scope) including full client-server API +read/write access and allocating a device ID. + +Once the client has retrieved the [server metadata](#server-metadata-discovery), +it needs to generate the following values: + +- `device_id`: a unique identifier for this device; see the + [`urn:matrix:client:device:`](#device-id-allocation) scope token. +- `state`: a unique opaque identifier, like a [transaction ID](#transaction-identifiers), + that will allow the client to maintain state between the authorization request + and the callback. +- `code_verifier`: a cryptographically random value that will allow to make sure + that the client that makes the token request for a given `code` is the same + one that made the authorization request. + + It is defined in [RFC 7636](https://datatracker.ietf.org/doc/html/rfc7636) as + a high-entropy cryptographic random string using the characters `[A-Z]`, + `[a-z]`, `[0-9]`, `-`, `.`, `_` and `~` with a minimum length of 43 characters + and a maximum length of 128 characters. + +**Authorization request** + +The client then constructs the authorization request URL using the +`authorization_endpoint` value, with the following query parameters: + +| Parameter | Value | +|-------------------------|----------------------------------------------------| +| `response_type` | `code` | +| `client_id` | The client ID returned from client registration. | +| `redirect_uri` | The redirect URI that MUST match one of the values registered in the client metadata | +| `scope` | `urn:matrix:client:api:* urn:matrix:client:device:` with the `device_id` generated previously. | +| `state` | The `state` value generated previously. | +| `response_mode` | `fragment` or `query` (see "[Callback](#callback)" below). | +| `code_challenge` | Computed from the `code_verifier` value generated previously using the SHA-256 algorithm, as described in [RFC 7636](https://datatracker.ietf.org/doc/html/rfc7636). | +| `code_challenge_method` | `S256` | + +This authorization request URL must be opened in the user's browser: + +- For web-based clients, this can be done through a redirection or by opening + the URL in a new tab. +- For native clients, this can be done by opening the URL using the system + browser, or, when available, through platform-specific APIs such as + [`ASWebAuthenticationSession`](https://developer.apple.com/documentation/authenticationservices/aswebauthenticationsession) + on iOS or [Android Custom Tabs](https://developer.chrome.com/docs/android/custom-tabs). + +Sample authorization request, with extra whitespaces for readability: + +``` +https://account.example.com/oauth2/auth? + client_id = s6BhdRkqt3 & + response_type = code & + response_mode = fragment & + redirect_uri = https://app.example.com/oauth2-callback & + scope = urn:matrix:client:api:* urn:matrix:client:device:AAABBBCCCDDD & + state = ewubooN9weezeewah9fol4oothohroh3 & + code_challenge = 72xySjpngTcCxgbPfFmkPHjMvVDl2jW1aWP7-J6rmwU & + code_challenge_method = S256 +``` + + **Callback** + +Once completed, the user is redirected to the `redirect_uri`, with either a +successful or failed authorization in the URL fragment or query parameters. +Whether the parameters are in the URL fragment or query parameters is determined +by the `response_mode` value: + +- If set to `fragment`, the parameters will be placed in the URL fragment, like + `https://example.com/callback#param1=value1¶m2=value2`. +- If set to `query`, the parameters will be in placed the query string, like + `com.example.app:/callback?param1=value1¶m2=value2`. + +To avoid disclosing the parameters to the web server hosting the `redirect_uri`, +clients SHOULD use the `fragment` response mode if the `redirect_uri` is an +HTTPS URI with a remote host. + +In both success and failure cases, the parameters will include the `state` value +used in the authorization request. + +A successful authorization will have a `code` value, for example: + +``` +https://app.example.com/oauth2-callback#state=ewubooN9weezeewah9fol4oothohroh3&code=iuB7Eiz9heengah1joh2ioy9ahChuP6R +``` + +A failed authorization will have the following values: + +- `error`: the error code +- `error_description`: the error description (optional) +- `error_uri`: the URI where the user can find more information about the error (optional) + +For example: + +``` +https://app.example.com/oauth2-callback#state=ewubooN9weezeewah9fol4oothohroh3&error=access_denied&error_description=The+resource+owner+or+authorization+server+denied+the+request.&error_uri=https%3A%2F%2Ferrors.example.com%2F +``` + +**Token request** + +The client then exchanges the authorization code to obtain an access token using +the token endpoint. + +This is done by making a POST request to the `token_endpoint` with the following +parameters, encoded as `application/x-www-form-urlencoded` in the body: + +| Parameter | Value | +|-----------------|------------------------------------------------------------| +| `grant_type` | `authorization_code` | +| `code` | The value of `code` obtained from the callback. | +| `redirect_uri` | The same `redirect_uri` used in the authorization request. | +| `client_id` | The client ID returned from client registration. | +| `code_verifier` | The value generated at the start of the authorization flow. | + +The server replies with a JSON object containing the access token, the token +type, the expiration time, and the refresh token. + +Sample token request: + +``` +POST /oauth2/token HTTP/1.1 +Host: account.example.com +Content-Type: application/x-www-form-urlencoded +Accept: application/json + +grant_type=authorization_code + &code=iuB7Eiz9heengah1joh2ioy9ahChuP6R + &redirect_uri=https://app.example.com/oauth2-callback + &client_id=s6BhdRkqt3 + &code_verifier=ogie4iVaeteeKeeLaid0aizuimairaCh +``` + +Sample response: + +```json +{ + "access_token": "2YotnFZFEjr1zCsicMWpAA", + "token_type": "Bearer", + "expires_in": 299, + "refresh_token": "tGz3JOkF0XG5Qx2TlKWIA", + "scope": "urn:matrix:client:api:* urn:matrix:client:device:AAABBBCCCDDD" +} +``` + +Finally, the client can call the [`/whoami`](#get_matrixclientv3accountwhoami) +endpoint to get the user ID that owns the access token. + +#### Token refresh flow + +Refreshing a token with the OAuth 2.0 API should be done with the [refresh token +grant](#refresh-token-grant). + +When the access token expires, the client must refresh it by making a `POST` +request to the `token_endpoint` with the following parameters, encoded as +`application/x-www-form-urlencoded` in the body: + +| Parameter | Value | +|-----------------|------------------------------------------------------------| +| `grant_type` | `refresh_token` | +| `refresh_token` | The `refresh_token` obtained from the token response during the last token request. | +| `client_id` | The client ID returned from client registration. | + +The server replies with a JSON object containing the new access token, the token +type, the expiration time, and a new refresh token, like in the authorization +flow. + #### Server metadata discovery {{% http-api spec="client-server" api="oauth_server_metadata" %}} @@ -1778,6 +1946,84 @@ This definition matches: - alphanumeric characters: `A-Z`, `a-z`, `0-9` - the following characters: ``! # $ % & ' ( ) * + , - . / : ; < = > ? @ [ ] ^ _ ` { | } ~`` +#### Grant types + +[RFC 6749](https://datatracker.ietf.org/doc/html/rfc6749) and other RFCs define +several "grant types": ways to obtain an ["access token"](#using-access-tokens). + +All these grants types require the client to know the following [authorization +server metadata](#server-metadata-discovery): +- `token_endpoint` +- `grant_types_supported` + +The client must also have obtained a `client_id` by [registering with the server](#client-registration). + +This specification supports the following grant types: +- [Authorization code grant](#authorization-code-grant) +- [Refresh token grant](#refresh-token-grant) + +##### Authorization code grant + +As per [RFC 6749 section 4.1](https://datatracker.ietf.org/doc/html/rfc6749#section-4.1), +the authorization code grant lets the client obtain an access token through a +browser redirect. + +This grant requires the client to know the following [authorization server +metadata](#server-metadata-discovery): +- `authorization_endpoint` +- `response_types_supported` +- `response_mode_supported` + +To use this grant, homeservers and clients MUST: + +- Support the authorization code grant as per [RFC 6749 section 4.1](https://datatracker.ietf.org/doc/html/rfc6749#section-4.1). +- Support the [refresh token grant](#refresh-token-grant). +- Support PKCE using the `S256` code challenge method as per [RFC 7636](https://datatracker.ietf.org/doc/html/rfc7636). +- Use [pre-registered](#client-registration), strict redirect URIs. +- Use the `fragment` response mode as per [OAuth 2.0 Multiple Response Type + Encoding Practices](https://openid.net/specs/oauth-v2-multiple-response-types-1_0.html) + for clients with an HTTPS redirect URI. + +###### User registration + +Clients can signal to the server that the user desires to register a new account +by initiating the authorization code grant with the `prompt=create` parameter +set in the authorization request as defined in [Initiating User Registration via +OpenID Connect 1.0](https://openid.net/specs/openid-connect-prompt-create-1_0.html). + +Whether the homeserver supports this parameter is advertised by the +`prompt_values_supported` authorization server metadata. + +Servers that support this parameter SHOULD show the account registration UI in +the browser. + +##### Refresh token grant + +As per [RFC 6749 section 6](https://datatracker.ietf.org/doc/html/rfc6749#section-6), +the refresh token grant lets the client exchange a refresh token for an access +token. + +When authorization is granted to a client, the homeserver MUST issue a refresh +token to the client in addition to the access token. + +The access token MUST be short-lived and SHOULD be refreshed using the +`refresh_token` when expired. + +The homeserver SHOULD issue a new refresh token each time an old one is used, +and invalidate the old one. However, it MUST ensure that the client is able to +retry the refresh request in the case that the response to the request is lost. + +The homeserver SHOULD consider that the session is compromised if an old, +invalidated refresh token is used, and SHOULD revoke the session. + +The client MUST handle access token refresh failures as follows: + + - If the refresh fails due to network issues or a `5xx` HTTP status code from + the server, the client should retry the request with the old refresh token + later. + - If the refresh fails due to a `4xx` HTTP status code from the server, the + client should consider the session logged out. + ### Account moderation #### Account locking