zitadel/apps/login/readme.md

# ZITADEL Login UI

This is going to be our next UI for the hosted login. It's based on Next.js 13 and its introduced `app/` directory.

## Flow Diagram

> Back navigation or retrys are not displayed. The flows for reauthentication after registering Passkeys, OTP or U2F methods are not displayed either as these will be omitted in future UX.

```mermaid
    flowchart TD
    A[Start] --> register
    A[Start] --> accounts
    A[Start] --> loginname
    loginname -- signInWithIDP --> idp-success
    loginname -- signInWithIDP --> idp-failure
    idp-success --> B[signedin]
    loginname --> password
    loginname -- hasPasskey --> passkey
    loginname -- allowRegister --> register
    passkey-add --passwordAllowed --> password
    passkey -- hasPassword --> password
    passkey --> B[signedin]
    password -- hasMFA --> mfa
    password -- allowPasskeys --> passkey-add
    mfa --> otp
    otp --> B[signedin]
    mfa--> u2f
    u2f -->B[signedin]
    register --> passkey-add
    register --> password-set
    password-set --> B[signedin]
    passkey-add --> B[signedin]
    password --> B[signedin]
    password-- forceMFA -->mfaset
    mfaset --> u2fset
    mfaset --> otpset
    u2fset --> B[signedin]
    otpset --> B[signedin]
    accounts--> loginname
    password -- not verified yet -->verify
    register-- withpassword -->verify
    passkey-- notVerified --> verify
    verify --> B[signedin]
```

### /loginname

<img src="./screenshots/loginname.png" alt="/loginame" width="400px" />

This page shows a loginname field and Identity Providers to login or register.
If `loginSettings(org?).allowRegister` is `true`, if will also show a link to jump to /register

Requests to the APIs made:

- `getLoginSettings(org?)`
- `getLegalAndSupportSettings(org?)`
- `getIdentityProviders(org?)`
- `getBrandingSettings(org?)`
- `getActiveIdentityProviders(org?)`
- `startIdentityProviderFlow`
- `listUsers(org?)`
- `listAuthenticationMethodTypes`
- `getOrgsByDomain`
- `createSession()`
- `getSession()`

After a loginname is entered, a `listUsers` request is made using the loginName query to identify already registered users.

**USER FOUND:** If only one user is found, we query `listAuthenticationMethodTypes` to identify future steps.
If no authentication methods are found, we render an error stating: _User has no available authentication methods._ (exception see below.)
Now if only one method is found, we continue with the corresponding step (/password, /passkey).
If multiple methods are set, we prefer passkeys over any other method, so we redirect to /passkey, second option is IDP, and third is password.
If password is the next step, we check `loginSettings.passkeysType` for PasskeysType.ALLOWED, and prompt the user to setup passkeys afterwards.

**NO USER FOUND:** If no user is found, we check whether registering is allowed using `loginSettings.allowRegister`.
If `loginSettings?.allowUsernamePassword` is not allowed we continue to check for available IDPs. If a single IDP is available, we directly redirect the user to signup.

If no single IDP is set, we check for `loginSettings.allowUsernamePassword` and if no organization is set as context, we check whether we can discover a organization from the loginname of the user (using: `getOrgsByDomain`). Then if an organization is found, we check whether domainDiscovery is allowed on it and redirect the user to /register page including the discovered domain or without.

If no previous condition is met we throw an error stating the user was not found.

**EXCEPTIONS:** If the outcome after this order produces a no authentication methods found, or user not found, we check whether `loginSettings?.ignoreUnknownUsernames` is set to `true` as in this case we redirect to the /password page regardless (to not leak information about a registered user).

> NOTE: We ignore `loginSettings.allowExternalIdp` as the information whether IDPs are available comes as response from `getActiveIdentityProviders(org?)`. If a user has a cookie for the same loginname, a new session is created regardless and overwrites the old session. The old session is not deleted from the login as for now.

### /password

<img src="./screenshots/password.png" alt="/password" width="400px" />

This page shows a password field to hydrate the current session with password as a factor.
Below the password field, a reset password link is shown which allows to send a reset email.

Requests to the APIs made:

- `getLoginSettings(org?)`
- `getBrandingSettings(org?)`
- `listAuthenticationMethodTypes`
- `getSession()`
- `updateSession()`

**MFA AVAILABLE:** After the password has been submitted, additional authentication Methods are loaded.
If the user has set up an additional **single** second factor, it is redirected to add the next factor. Depending on the available method he is redirected to `/otp/time-based`,`/otp/sms?`, `/otp/email?` or `/u2f?`. If the user has multiple second factors, he is redirected to `/mfa` to select his preferred method to continue.

**NO MFA, FORCE MFA:** If no MFA method is available, and the settings force MFA, the user is sent to `/mfa/set` which prompts to setup a second factor.

**PROMPT PASSKEY** If the settings do not enforce MFA, we check if passkeys are allowed with `loginSettings?.passkeysType === PasskeysType.ALLOWED` and redirect the user to `/passkey/add` if no passkeys are setup. This step can be skipped.

If none of the previous conditions apply, we continue to sign in.

### /otp/[method]

<img src="./screenshots/otp.png" alt="/otp/[method]" width="400px" />

This page shows a code field to check an otp method. The session of the user is then hydrated with the respective factor. Supported methods are `time-based`, `sms` and `email`.

Requests to the APIs made:

- `getBrandingSettings(org?)`
- `getSession()`
- `updateSession()`

If `email` or `sms` is requested as method, the current session of the user is updated to request the challenge. This will trigger an email or sms which can be entered in the code field.
The `time-based` (TOTP) method does not require a trigger, therefore no `updateSession()` is performed and no resendLink under the code field is shown.

The submission of the code updates the session and continues to sign in the user.

### /u2f

<img src="./screenshots/u2f.png" alt="/u2f" width="400px" />

This page requests a webAuthN challenge for the user and updates the session afterwards.

Requests to the APIs made:

- `getBrandingSettings(org?)`
- `getSession()`
- `updateSession()`

When updating the session for the webAuthN challenge, we set `userVerificationRequirement` to `UserVerificationRequirement.DISCOURAGED` as this will request the webAuthN method as second factor and not as primary method.
After updating the session, the user is signed in.

### /passkey

<img src="./screenshots/passkey.png" alt="/passkey" width="400px" />

This page requests a webAuthN challenge for the user and updates the session afterwards.

Requests to the APIs made:

- `getBrandingSettings(org?)`
- `getSession()`
- `updateSession()`

When updating the session for the webAuthN challenge, we set `userVerificationRequirement` to `UserVerificationRequirement.REQUIRED` as this will request the webAuthN method as primary method to login.
After updating the session, the user is signed in.