WebAuthN auth

lib/sso_bsn/accounts/user_token.ex

@@ -0,0 +1,83 @@
+defmodule SsoBsn.Accounts.UserToken do
+  use Ecto.Schema
+  import Ecto.Query
+  alias SsoBsn.Accounts.UserToken
+
+  @rand_size 32
+
+  @session_validity_in_days 60
+
+  schema "users_tokens" do
+    field :token, :binary
+    field :context, :string
+    field :sent_to, :string
+    belongs_to :user, SsoBsn.Accounts.User
+
+    timestamps(updated_at: false)
+  end
+
+  @doc """
+  Generates a token that will be stored in a signed place,
+  such as session or cookie. As they are signed, those
+  tokens do not need to be hashed.
+
+  The reason why we store session tokens in the database, even
+  though Phoenix already provides a session cookie, is because
+  Phoenix' default session cookies are not persisted, they are
+  simply signed and potentially encrypted. This means they are
+  valid indefinitely, unless you change the signing/encryption
+  salt.
+
+  Therefore, storing them allows individual user
+  sessions to be expired. The token system can also be extended
+  to store additional data, such as the device used for logging in.
+  You could then use this information to display all valid sessions
+  and devices in the UI and allow users to explicitly expire any
+  session they deem invalid.
+  """
+  def build_session_token(user) do
+    token = :crypto.strong_rand_bytes(@rand_size)
+     {token, %UserToken{token: token, context: "session", user_id: user.id}}
+  end
+
+  def build_login_token(user) do
+    token = Base.encode64(:crypto.strong_rand_bytes(@rand_size))
+    {token, %UserToken{token: token, context: "login", user_id: user.id}}
+  end
+
+  @doc """
+  Checks if the token is valid and returns its underlying lookup query.
+
+  The query returns the user found by the token, if any.
+
+  The token is valid if it matches the value in the database and it has
+  not expired (after @session_validity_in_days).
+  """
+  def verify_session_token_query(token) do
+    query =
+      from token in token_and_context_query(token, "session"),
+        join: user in assoc(token, :user),
+        where: token.inserted_at > ago(@session_validity_in_days, "day"),
+        select: user
+
+    {:ok, query}
+  end
+
+  @doc """
+  Returns the token struct for the given token value and context.
+  """
+  def token_and_context_query(token, context) do
+    from UserToken, where: [token: ^token, context: ^context]
+  end
+
+  @doc """
+  Gets all tokens for the given user for the given contexts.
+  """
+  def user_and_contexts_query(user, :all) do
+    from t in UserToken, where: t.user_id == ^user.id
+  end
+
+  def user_and_contexts_query(user, [_ | _] = contexts) do
+    from t in UserToken, where: t.user_id == ^user.id and t.context in ^contexts
+  end
+end