# Authentication ```mermaid --- Authentication states --- stateDiagram-v2 [*] --> Unauthenticated Unauthenticated --> Authenticated : /api/auth/login Authenticated --> Unauthenticated : /api/auth/logout Authenticated --> Unauthenticated : Token expired ``` Authentication associates each authenticated request with a user. To create users, see [initial setup](./initial-setup.md) and [invitations](./invitations.md). ## Names The service handles user names using two separate forms. The first form is as given in the request used to create the user. This form of the use name is used throughout the API, and the service will preserve the name as entered (other than applying normalization), so that users' preferences around capitalization and accent marks are preserved. The second form is a "canonical" form, used internally by the service to control uniqueness and match names to users. The canonical form is both case-folded and normalized. The canonical form is not available to API clients, but its use has practical consequences: - Names that differ only by case or only by code point sequence are treated as the same name. If the name is in use, changing the capitalization or changing the sequence of combining marks will not allow the creation of a second "identical" user. - The login API accepts any name that canonicalizes to the form stored in the database, making user names effectively case-insensitive and composition-insensitive. ## Identity tokens A user is primarily authenticated using its username and password. However, passwords are a sensitive, long-lived credential, and are also operationally expensive to verify; for routine access, requests are authenticated using an identity token, instead. Tokens are issued by logging into the service, using the `/api/auth/login` endpoint. The `/api/auth/logout` endpoint immediately invalidates the token used to make a request to it. Tokens are also invalidated after seven days of inactivity. To authenticate a request, include `cookie: identity=TOKEN SECRET` header in the request. For browser-based clients, this may happen automatically. ## Authentication failures Unless the endpoint's documentation says otherwise, all endpoints require authentication. Making a request to any endpoint that requires authentication, either without a token, or with a token that is not valid or that has expired, causes the service to return a `401 Unauthorized` response, instead of the responses documented for the endpoint the request was intended for. The API will not take action on requests that fail authentication in this way. ## `POST /api/auth/login` Authenticates the user using their name and password. The user must exist before calling this endpoint. **This endpoint does not require an `identity` cookie.** ### Request ```json { "name": "example username", "password": "the plaintext password" } ``` The request must have the following fields: | Field | Type | Description | | :--------- | :----- | :----------------------------------- | | `name` | string | The login's name. | | `password` | string | The login's password, in plain text. | ### Success This endpoint will respond with a status of `204 No Content` when successful. The response will include a `Set-Cookie` header for the `identity` cookie, providing the client with a newly-minted identity token associated with the user identified in the request. This token's value must be kept confidential. The cookie will expire if it is not used regularly. ### Authentication failure This endpoint will respond with a status of `401 Unauthorized` if the login name and password do not correspond to an existing user. ## `POST /api/auth/logout` Invalidates the identity token used to make the request, logging the caller out. This terminates any [push subscriptions](push.md#receiving-web-push-messages) associated with the token. ### Request ```json {} ``` The request must be an empty JSON object. ### Success This endpoint will respond with a status of `204 No Content` when successful. The response will include a `Set-Cookie` header that clears the `identity` cookie. Regardless of whether the client clears the cookie, the service also invalidates the token. ## `POST /api/password` Changes the current user's password, and invalidates all outstanding identity tokens. This terminates any [push subscriptions](push.md#receiving-web-push-messages) associated with existing tokens. ### Authentication failure This endpoint will respond with a status of `401 Unauthorized` if the provided identity token is not valid. ### Request ```json { "password": "my-old-password", "to": "my-new-password" } ``` The request must have the following fields: | Field | Type | Description | | :--------- | :----- | :--------------------------------------------- | | `password` | string | The login's _current_ password, in plain text. | | `to` | string | The login's _new_ password, in plain text. | ### Success This endpoint will respond with a status of `204 No Content` when successful. The response will include a `Set-Cookie` header for the `identity` cookie, providing the client with a newly-minted identity token associated with the login identified in the request. This token's value must be kept confidential. All previously-created identity cookies will cease to be valid. The cookie will expire if it is not used regularly. ### Authentication failure This endpoint will respond with a status of `400 Bad Request` if the `password` does not match the login's current password.