After "mix phx.gen.auth Accounts User users".

lib/beet_round_server/accounts.ex

@@ -0,0 +1,297 @@
+defmodule BeetRoundServer.Accounts do
+  @moduledoc """
+  The Accounts context.
+  """
+
+  import Ecto.Query, warn: false
+  alias BeetRoundServer.Repo
+
+  alias BeetRoundServer.Accounts.{User, UserToken, UserNotifier}
+
+  ## Database getters
+
+  @doc """
+  Gets a user by email.
+
+  ## Examples
+
+      iex> get_user_by_email("foo@example.com")
+      %User{}
+
+      iex> get_user_by_email("unknown@example.com")
+      nil
+
+  """
+  def get_user_by_email(email) when is_binary(email) do
+    Repo.get_by(User, email: email)
+  end
+
+  @doc """
+  Gets a user by email and password.
+
+  ## Examples
+
+      iex> get_user_by_email_and_password("foo@example.com", "correct_password")
+      %User{}
+
+      iex> get_user_by_email_and_password("foo@example.com", "invalid_password")
+      nil
+
+  """
+  def get_user_by_email_and_password(email, password)
+      when is_binary(email) and is_binary(password) do
+    user = Repo.get_by(User, email: email)
+    if User.valid_password?(user, password), do: user
+  end
+
+  @doc """
+  Gets a single user.
+
+  Raises `Ecto.NoResultsError` if the User does not exist.
+
+  ## Examples
+
+      iex> get_user!(123)
+      %User{}
+
+      iex> get_user!(456)
+      ** (Ecto.NoResultsError)
+
+  """
+  def get_user!(id), do: Repo.get!(User, id)
+
+  ## User registration
+
+  @doc """
+  Registers a user.
+
+  ## Examples
+
+      iex> register_user(%{field: value})
+      {:ok, %User{}}
+
+      iex> register_user(%{field: bad_value})
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def register_user(attrs) do
+    %User{}
+    |> User.email_changeset(attrs)
+    |> Repo.insert()
+  end
+
+  ## Settings
+
+  @doc """
+  Checks whether the user is in sudo mode.
+
+  The user is in sudo mode when the last authentication was done no further
+  than 20 minutes ago. The limit can be given as second argument in minutes.
+  """
+  def sudo_mode?(user, minutes \\ -20)
+
+  def sudo_mode?(%User{authenticated_at: ts}, minutes) when is_struct(ts, DateTime) do
+    DateTime.after?(ts, DateTime.utc_now() |> DateTime.add(minutes, :minute))
+  end
+
+  def sudo_mode?(_user, _minutes), do: false
+
+  @doc """
+  Returns an `%Ecto.Changeset{}` for changing the user email.
+
+  See `BeetRoundServer.Accounts.User.email_changeset/3` for a list of supported options.
+
+  ## Examples
+
+      iex> change_user_email(user)
+      %Ecto.Changeset{data: %User{}}
+
+  """
+  def change_user_email(user, attrs \\ %{}, opts \\ []) do
+    User.email_changeset(user, attrs, opts)
+  end
+
+  @doc """
+  Updates the user email using the given token.
+
+  If the token matches, the user email is updated and the token is deleted.
+  """
+  def update_user_email(user, token) do
+    context = "change:#{user.email}"
+
+    Repo.transact(fn ->
+      with {:ok, query} <- UserToken.verify_change_email_token_query(token, context),
+           %UserToken{sent_to: email} <- Repo.one(query),
+           {:ok, user} <- Repo.update(User.email_changeset(user, %{email: email})),
+           {_count, _result} <-
+             Repo.delete_all(from(UserToken, where: [user_id: ^user.id, context: ^context])) do
+        {:ok, user}
+      else
+        _ -> {:error, :transaction_aborted}
+      end
+    end)
+  end
+
+  @doc """
+  Returns an `%Ecto.Changeset{}` for changing the user password.
+
+  See `BeetRoundServer.Accounts.User.password_changeset/3` for a list of supported options.
+
+  ## Examples
+
+      iex> change_user_password(user)
+      %Ecto.Changeset{data: %User{}}
+
+  """
+  def change_user_password(user, attrs \\ %{}, opts \\ []) do
+    User.password_changeset(user, attrs, opts)
+  end
+
+  @doc """
+  Updates the user password.
+
+  Returns a tuple with the updated user, as well as a list of expired tokens.
+
+  ## Examples
+
+      iex> update_user_password(user, %{password: ...})
+      {:ok, {%User{}, [...]}}
+
+      iex> update_user_password(user, %{password: "too short"})
+      {:error, %Ecto.Changeset{}}
+
+  """
+  def update_user_password(user, attrs) do
+    user
+    |> User.password_changeset(attrs)
+    |> update_user_and_delete_all_tokens()
+  end
+
+  ## Session
+
+  @doc """
+  Generates a session token.
+  """
+  def generate_user_session_token(user) do
+    {token, user_token} = UserToken.build_session_token(user)
+    Repo.insert!(user_token)
+    token
+  end
+
+  @doc """
+  Gets the user with the given signed token.
+
+  If the token is valid `{user, token_inserted_at}` is returned, otherwise `nil` is returned.
+  """
+  def get_user_by_session_token(token) do
+    {:ok, query} = UserToken.verify_session_token_query(token)
+    Repo.one(query)
+  end
+
+  @doc """
+  Gets the user with the given magic link token.
+  """
+  def get_user_by_magic_link_token(token) do
+    with {:ok, query} <- UserToken.verify_magic_link_token_query(token),
+         {user, _token} <- Repo.one(query) do
+      user
+    else
+      _ -> nil
+    end
+  end
+
+  @doc """
+  Logs the user in by magic link.
+
+  There are three cases to consider:
+
+  1. The user has already confirmed their email. They are logged in
+     and the magic link is expired.
+
+  2. The user has not confirmed their email and no password is set.
+     In this case, the user gets confirmed, logged in, and all tokens -
+     including session ones - are expired. In theory, no other tokens
+     exist but we delete all of them for best security practices.
+
+  3. The user has not confirmed their email but a password is set.
+     This cannot happen in the default implementation but may be the
+     source of security pitfalls. See the "Mixing magic link and password registration" section of
+     `mix help phx.gen.auth`.
+  """
+  def login_user_by_magic_link(token) do
+    {:ok, query} = UserToken.verify_magic_link_token_query(token)
+
+    case Repo.one(query) do
+      # Prevent session fixation attacks by disallowing magic links for unconfirmed users with password
+      {%User{confirmed_at: nil, hashed_password: hash}, _token} when not is_nil(hash) ->
+        raise """
+        magic link log in is not allowed for unconfirmed users with a password set!
+
+        This cannot happen with the default implementation, which indicates that you
+        might have adapted the code to a different use case. Please make sure to read the
+        "Mixing magic link and password registration" section of `mix help phx.gen.auth`.
+        """
+
+      {%User{confirmed_at: nil} = user, _token} ->
+        user
+        |> User.confirm_changeset()
+        |> update_user_and_delete_all_tokens()
+
+      {user, token} ->
+        Repo.delete!(token)
+        {:ok, {user, []}}
+
+      nil ->
+        {:error, :not_found}
+    end
+  end
+
+  @doc ~S"""
+  Delivers the update email instructions to the given user.
+
+  ## Examples
+
+      iex> deliver_user_update_email_instructions(user, current_email, &url(~p"/users/settings/confirm-email/#{&1}"))
+      {:ok, %{to: ..., body: ...}}
+
+  """
+  def deliver_user_update_email_instructions(%User{} = user, current_email, update_email_url_fun)
+      when is_function(update_email_url_fun, 1) do
+    {encoded_token, user_token} = UserToken.build_email_token(user, "change:#{current_email}")
+
+    Repo.insert!(user_token)
+    UserNotifier.deliver_update_email_instructions(user, update_email_url_fun.(encoded_token))
+  end
+
+  @doc """
+  Delivers the magic link login instructions to the given user.
+  """
+  def deliver_login_instructions(%User{} = user, magic_link_url_fun)
+      when is_function(magic_link_url_fun, 1) do
+    {encoded_token, user_token} = UserToken.build_email_token(user, "login")
+    Repo.insert!(user_token)
+    UserNotifier.deliver_login_instructions(user, magic_link_url_fun.(encoded_token))
+  end
+
+  @doc """
+  Deletes the signed token with the given context.
+  """
+  def delete_user_session_token(token) do
+    Repo.delete_all(from(UserToken, where: [token: ^token, context: "session"]))
+    :ok
+  end
+
+  ## Token helper
+
+  defp update_user_and_delete_all_tokens(changeset) do
+    Repo.transact(fn ->
+      with {:ok, user} <- Repo.update(changeset) do
+        tokens_to_expire = Repo.all_by(UserToken, user_id: user.id)
+
+        Repo.delete_all(from(t in UserToken, where: t.id in ^Enum.map(tokens_to_expire, & &1.id)))
+
+        {:ok, {user, tokens_to_expire}}
+      end
+    end)
+  end
+end

lib/beet_round_server/accounts/scope.ex

@@ -0,0 +1,33 @@
+defmodule BeetRoundServer.Accounts.Scope do
+  @moduledoc """
+  Defines the scope of the caller to be used throughout the app.
+
+  The `BeetRoundServer.Accounts.Scope` allows public interfaces to receive
+  information about the caller, such as if the call is initiated from an
+  end-user, and if so, which user. Additionally, such a scope can carry fields
+  such as "super user" or other privileges for use as authorization, or to
+  ensure specific code paths can only be access for a given scope.
+
+  It is useful for logging as well as for scoping pubsub subscriptions and
+  broadcasts when a caller subscribes to an interface or performs a particular
+  action.
+
+  Feel free to extend the fields on this struct to fit the needs of
+  growing application requirements.
+  """
+
+  alias BeetRoundServer.Accounts.User
+
+  defstruct user: nil
+
+  @doc """
+  Creates a scope for the given user.
+
+  Returns nil if no user is given.
+  """
+  def for_user(%User{} = user) do
+    %__MODULE__{user: user}
+  end
+
+  def for_user(nil), do: nil
+end

lib/beet_round_server/accounts/user.ex

@@ -0,0 +1,134 @@
+defmodule BeetRoundServer.Accounts.User do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @primary_key {:id, :binary_id, autogenerate: true}
+  @foreign_key_type :binary_id
+  schema "users" do
+    field :email, :string
+    field :password, :string, virtual: true, redact: true
+    field :hashed_password, :string, redact: true
+    field :confirmed_at, :utc_datetime
+    field :authenticated_at, :utc_datetime, virtual: true
+
+    timestamps(type: :utc_datetime)
+  end
+
+  @doc """
+  A user changeset for registering or changing the email.
+
+  It requires the email to change otherwise an error is added.
+
+  ## Options
+
+    * `:validate_unique` - Set to false if you don't want to validate the
+      uniqueness of the email, useful when displaying live validations.
+      Defaults to `true`.
+  """
+  def email_changeset(user, attrs, opts \\ []) do
+    user
+    |> cast(attrs, [:email])
+    |> validate_email(opts)
+  end
+
+  defp validate_email(changeset, opts) do
+    changeset =
+      changeset
+      |> validate_required([:email])
+      |> validate_format(:email, ~r/^[^@,;\s]+@[^@,;\s]+$/,
+        message: "must have the @ sign and no spaces"
+      )
+      |> validate_length(:email, max: 160)
+
+    if Keyword.get(opts, :validate_unique, true) do
+      changeset
+      |> unsafe_validate_unique(:email, BeetRoundServer.Repo)
+      |> unique_constraint(:email)
+      |> validate_email_changed()
+    else
+      changeset
+    end
+  end
+
+  defp validate_email_changed(changeset) do
+    if get_field(changeset, :email) && get_change(changeset, :email) == nil do
+      add_error(changeset, :email, "did not change")
+    else
+      changeset
+    end
+  end
+
+  @doc """
+  A user changeset for changing the password.
+
+  It is important to validate the length of the password, as long passwords may
+  be very expensive to hash for certain algorithms.
+
+  ## Options
+
+    * `:hash_password` - Hashes the password so it can be stored securely
+      in the database and ensures the password field is cleared to prevent
+      leaks in the logs. If password hashing is not needed and clearing the
+      password field is not desired (like when using this changeset for
+      validations on a LiveView form), this option can be set to `false`.
+      Defaults to `true`.
+  """
+  def password_changeset(user, attrs, opts \\ []) do
+    user
+    |> cast(attrs, [:password])
+    |> validate_confirmation(:password, message: "does not match password")
+    |> validate_password(opts)
+  end
+
+  defp validate_password(changeset, opts) do
+    changeset
+    |> validate_required([:password])
+    |> validate_length(:password, min: 12, max: 72)
+    # Examples of additional password validation:
+    # |> validate_format(:password, ~r/[a-z]/, message: "at least one lower case character")
+    # |> validate_format(:password, ~r/[A-Z]/, message: "at least one upper case character")
+    # |> validate_format(:password, ~r/[!?@#$%^&*_0-9]/, message: "at least one digit or punctuation character")
+    |> maybe_hash_password(opts)
+  end
+
+  defp maybe_hash_password(changeset, opts) do
+    hash_password? = Keyword.get(opts, :hash_password, true)
+    password = get_change(changeset, :password)
+
+    if hash_password? && password && changeset.valid? do
+      changeset
+      # If using Bcrypt, then further validate it is at most 72 bytes long
+      |> validate_length(:password, max: 72, count: :bytes)
+      # Hashing could be done with `Ecto.Changeset.prepare_changes/2`, but that
+      # would keep the database transaction open longer and hurt performance.
+      |> put_change(:hashed_password, Bcrypt.hash_pwd_salt(password))
+      |> delete_change(:password)
+    else
+      changeset
+    end
+  end
+
+  @doc """
+  Confirms the account by setting `confirmed_at`.
+  """
+  def confirm_changeset(user) do
+    now = DateTime.utc_now(:second)
+    change(user, confirmed_at: now)
+  end
+
+  @doc """
+  Verifies the password.
+
+  If there is no user or the user doesn't have a password, we call
+  `Bcrypt.no_user_verify/0` to avoid timing attacks.
+  """
+  def valid_password?(%BeetRoundServer.Accounts.User{hashed_password: hashed_password}, password)
+      when is_binary(hashed_password) and byte_size(password) > 0 do
+    Bcrypt.verify_pass(password, hashed_password)
+  end
+
+  def valid_password?(_, _) do
+    Bcrypt.no_user_verify()
+    false
+  end
+end

lib/beet_round_server/accounts/user_notifier.ex

@@ -0,0 +1,84 @@
+defmodule BeetRoundServer.Accounts.UserNotifier do
+  import Swoosh.Email
+
+  alias BeetRoundServer.Mailer
+  alias BeetRoundServer.Accounts.User
+
+  # Delivers the email using the application mailer.
+  defp deliver(recipient, subject, body) do
+    email =
+      new()
+      |> to(recipient)
+      |> from({"BeetRoundServer", "contact@example.com"})
+      |> subject(subject)
+      |> text_body(body)
+
+    with {:ok, _metadata} <- Mailer.deliver(email) do
+      {:ok, email}
+    end
+  end
+
+  @doc """
+  Deliver instructions to update a user email.
+  """
+  def deliver_update_email_instructions(user, url) do
+    deliver(user.email, "Update email instructions", """
+
+    ==============================
+
+    Hi #{user.email},
+
+    You can change your email by visiting the URL below:
+
+    #{url}
+
+    If you didn't request this change, please ignore this.
+
+    ==============================
+    """)
+  end
+
+  @doc """
+  Deliver instructions to log in with a magic link.
+  """
+  def deliver_login_instructions(user, url) do
+    case user do
+      %User{confirmed_at: nil} -> deliver_confirmation_instructions(user, url)
+      _ -> deliver_magic_link_instructions(user, url)
+    end
+  end
+
+  defp deliver_magic_link_instructions(user, url) do
+    deliver(user.email, "Log in instructions", """
+
+    ==============================
+
+    Hi #{user.email},
+
+    You can log into your account by visiting the URL below:
+
+    #{url}
+
+    If you didn't request this email, please ignore this.
+
+    ==============================
+    """)
+  end
+
+  defp deliver_confirmation_instructions(user, url) do
+    deliver(user.email, "Confirmation instructions", """
+
+    ==============================
+
+    Hi #{user.email},
+
+    You can confirm your account by visiting the URL below:
+
+    #{url}
+
+    If you didn't create an account with us, please ignore this.
+
+    ==============================
+    """)
+  end
+end

lib/beet_round_server/accounts/user_token.ex

@@ -0,0 +1,158 @@
+defmodule BeetRoundServer.Accounts.UserToken do
+  use Ecto.Schema
+  import Ecto.Query
+  alias BeetRoundServer.Accounts.UserToken
+
+  @hash_algorithm :sha256
+  @rand_size 32
+
+  # It is very important to keep the magic link token expiry short,
+  # since someone with access to the email may take over the account.
+  @magic_link_validity_in_minutes 15
+  @change_email_validity_in_days 7
+  @session_validity_in_days 14
+
+  @primary_key {:id, :binary_id, autogenerate: true}
+  @foreign_key_type :binary_id
+  schema "users_tokens" do
+    field :token, :binary
+    field :context, :string
+    field :sent_to, :string
+    field :authenticated_at, :utc_datetime
+    belongs_to :user, BeetRoundServer.Accounts.User
+
+    timestamps(type: :utc_datetime, 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's 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)
+    dt = user.authenticated_at || DateTime.utc_now(:second)
+    {token, %UserToken{token: token, context: "session", user_id: user.id, authenticated_at: dt}}
+  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, along with the token's creation time.
+
+  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 by_token_and_context_query(token, "session"),
+        join: user in assoc(token, :user),
+        where: token.inserted_at > ago(@session_validity_in_days, "day"),
+        select: {%{user | authenticated_at: token.authenticated_at}, token.inserted_at}
+
+    {:ok, query}
+  end
+
+  @doc """
+  Builds a token and its hash to be delivered to the user's email.
+
+  The non-hashed token is sent to the user email while the
+  hashed part is stored in the database. The original token cannot be reconstructed,
+  which means anyone with read-only access to the database cannot directly use
+  the token in the application to gain access. Furthermore, if the user changes
+  their email in the system, the tokens sent to the previous email are no longer
+  valid.
+
+  Users can easily adapt the existing code to provide other types of delivery methods,
+  for example, by phone numbers.
+  """
+  def build_email_token(user, context) do
+    build_hashed_token(user, context, user.email)
+  end
+
+  defp build_hashed_token(user, context, sent_to) do
+    token = :crypto.strong_rand_bytes(@rand_size)
+    hashed_token = :crypto.hash(@hash_algorithm, token)
+
+    {Base.url_encode64(token, padding: false),
+     %UserToken{
+       token: hashed_token,
+       context: context,
+       sent_to: sent_to,
+       user_id: user.id
+     }}
+  end
+
+  @doc """
+  Checks if the token is valid and returns its underlying lookup query.
+
+  If found, the query returns a tuple of the form `{user, token}`.
+
+  The given token is valid if it matches its hashed counterpart in the
+  database. This function also checks if the token is being used within
+  15 minutes. The context of a magic link token is always "login".
+  """
+  def verify_magic_link_token_query(token) do
+    case Base.url_decode64(token, padding: false) do
+      {:ok, decoded_token} ->
+        hashed_token = :crypto.hash(@hash_algorithm, decoded_token)
+
+        query =
+          from token in by_token_and_context_query(hashed_token, "login"),
+            join: user in assoc(token, :user),
+            where: token.inserted_at > ago(^@magic_link_validity_in_minutes, "minute"),
+            where: token.sent_to == user.email,
+            select: {user, token}
+
+        {:ok, query}
+
+      :error ->
+        :error
+    end
+  end
+
+  @doc """
+  Checks if the token is valid and returns its underlying lookup query.
+
+  The query returns the user_token found by the token, if any.
+
+  This is used to validate requests to change the user
+  email.
+  The given token is valid if it matches its hashed counterpart in the
+  database and if it has not expired (after @change_email_validity_in_days).
+  The context must always start with "change:".
+  """
+  def verify_change_email_token_query(token, "change:" <> _ = context) do
+    case Base.url_decode64(token, padding: false) do
+      {:ok, decoded_token} ->
+        hashed_token = :crypto.hash(@hash_algorithm, decoded_token)
+
+        query =
+          from token in by_token_and_context_query(hashed_token, context),
+            where: token.inserted_at > ago(@change_email_validity_in_days, "day")
+
+        {:ok, query}
+
+      :error ->
+        :error
+    end
+  end
+
+  defp by_token_and_context_query(token, context) do
+    from UserToken, where: [token: ^token, context: ^context]
+  end
+end