Strategy for authentication using a one-time password (OTP).

In order to use OTP authentication your resource needs to meet the following minimum requirements:

1. Have a primary key.
2. A uniquely constrained identity field (eg username or email)
3. Have tokens enabled.

There are other options documented in the DSL.

Example

defmodule MyApp.Accounts.User do
  use Ash.Resource,
    extensions: [AshAuthentication],
    domain: MyApp.Accounts

  attributes do
    uuid_primary_key :id
    attribute :email, :ci_string, allow_nil?: false
  end

  authentication do
    tokens do
      enabled? true
      store_all_tokens? true
      token_resource MyApp.Accounts.Token
      signing_secret MyApp.Secrets
    end

    strategies do
      otp do
        identity_field :email
        brute_force_strategy :rate_limit
        otp_lifetime {10, :minutes}
        otp_length 6
        otp_characters :unambiguous_uppercase
        sender MyApp.OtpSender
      end
    end
  end

  identities do
    identity :unique_email, [:email]
  end
end

Actions

By default the OTP strategy will automatically generate the request and sign-in actions for you, however you're free to define them yourself. If you do, then the action will be validated to ensure that all the needed configuration is present.

If you wish to work with the actions directly from your code you can do so via the AshAuthentication.Strategy protocol.

Examples

Requesting that an OTP code is sent for a user:

iex> strategy = Info.strategy!(Example.UserWithOtp, :otp)
...> Strategy.action(strategy, :request, %{"email" => "user@example.com"})
:ok

Signing in using an OTP code:

iex> strategy = Info.strategy!(Example.UserWithOtp, :otp)
...> {:ok, user} = Strategy.action(strategy, :sign_in, %{"email" => "user@example.com", "otp" => "ABCDEF"})

Plugs

The OTP strategy provides plug endpoints for both request and sign-in actions.

If you wish to work with the plugs directly, you can do so via the AshAuthentication.Strategy protocol.