Merge branch 'twitter_oauth' into 'develop'

OAuth consumer (sign in / sign up with external provider)

See merge request pleroma/pleroma!923

24 files changed, 1047 insertions, 121 deletions

diff --git a/config/config.exs b/config/config.exs
index 5d959a859..900140797 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -395,6 +395,22 @@ config :pleroma, :ldap,
   base: System.get_env("LDAP_BASE") || "dc=example,dc=com",
   uid: System.get_env("LDAP_UID") || "cn"
 
+oauth_consumer_strategies = String.split(System.get_env("OAUTH_CONSUMER_STRATEGIES") || "")
+
+ueberauth_providers =
+  for strategy <- oauth_consumer_strategies do
+    strategy_module_name = "Elixir.Ueberauth.Strategy.#{String.capitalize(strategy)}"
+    strategy_module = String.to_atom(strategy_module_name)
+    {String.to_atom(strategy), {strategy_module, [callback_params: ["state"]]}}
+  end
+
+config :ueberauth,
+       Ueberauth,
+       base_path: "/oauth",
+       providers: ueberauth_providers
+
+config :pleroma, :auth, oauth_consumer_strategies: oauth_consumer_strategies
+
 config :pleroma, Pleroma.Mailer, adapter: Swoosh.Adapters.Sendmail
 
 config :prometheus, Pleroma.Web.Endpoint.MetricsExporter, path: "/api/pleroma/app_metrics"
diff --git a/config/dev.exs b/config/dev.exs
index f77bb9976..a7eb4b644 100644
--- a/config/dev.exs
+++ b/config/dev.exs
@@ -12,7 +12,6 @@ config :pleroma, Pleroma.Web.Endpoint,
     protocol_options: [max_request_line_length: 8192, max_header_value_length: 8192]
   ],
   protocol: "http",
-  secure_cookie_flag: false,
   debug_errors: true,
   code_reloader: true,
   check_origin: false,
diff --git a/docs/config.md b/docs/config.md
index ba0759e87..ed9b91363 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -391,6 +391,17 @@ config :auto_linker,
   ]
 ```
 
+## Pleroma.ScheduledActivity
+
+* `daily_user_limit`: the number of scheduled activities a user is allowed to create in a single day (Default: `25`)
+* `total_user_limit`: the number of scheduled activities a user is allowed to create in total (Default: `300`)
+* `enabled`: whether scheduled activities are sent to the job queue to be executed
+
+## Pleroma.Web.Auth.Authenticator
+
+* `Pleroma.Web.Auth.PleromaAuthenticator`: default database authenticator
+* `Pleroma.Web.Auth.LDAPAuthenticator`: LDAP authentication
+
 ## :ldap
 
 Use LDAP for user authentication.  When a user logs in to the Pleroma
@@ -409,13 +420,61 @@ Pleroma account will be created with the same name as the LDAP user name.
 * `base`: LDAP base, e.g. "dc=example,dc=com"
 * `uid`: LDAP attribute name to authenticate the user, e.g. when "cn", the filter will be "cn=username,base"
 
-## Pleroma.Web.Auth.Authenticator
+## :auth
 
-* `Pleroma.Web.Auth.PleromaAuthenticator`: default database authenticator
-* `Pleroma.Web.Auth.LDAPAuthenticator`: LDAP authentication
+Authentication / authorization settings.
 
-## Pleroma.ScheduledActivity
+* `auth_template`: authentication form template. By default it's `show.html` which corresponds to `lib/pleroma/web/templates/o_auth/o_auth/show.html.eex`. 
+* `oauth_consumer_template`: OAuth consumer mode authentication form template. By default it's `consumer.html` which corresponds to `lib/pleroma/web/templates/o_auth/o_auth/consumer.html.eex`.
+* `oauth_consumer_strategies`: the list of enabled OAuth consumer strategies; by default it's set by OAUTH_CONSUMER_STRATEGIES environment variable.
 
-* `daily_user_limit`: the number of scheduled activities a user is allowed to create in a single day (Default: `25`)
-* `total_user_limit`: the number of scheduled activities a user is allowed to create in total (Default: `300`)
-* `enabled`: whether scheduled activities are sent to the job queue to be executed
+# OAuth consumer mode
+
+OAuth consumer mode allows sign in / sign up via external OAuth providers (e.g. Twitter, Facebook, Google, Microsoft, etc.).
+Implementation is based on Ueberauth; see the list of [available strategies](https://github.com/ueberauth/ueberauth/wiki/List-of-Strategies).
+
+Note: each strategy is shipped as a separate dependency; in order to get the strategies, run `OAUTH_CONSUMER_STRATEGIES="..." mix deps.get`,
+e.g. `OAUTH_CONSUMER_STRATEGIES="twitter facebook google microsoft" mix deps.get`.
+The server should also be started with `OAUTH_CONSUMER_STRATEGIES="..." mix phx.server` in case you enable any strategies.
+
+Note: each strategy requires separate setup (on external provider side and Pleroma side). Below are the guidelines on setting up most popular strategies.  
+
+* For Twitter, [register an app](https://developer.twitter.com/en/apps), configure callback URL to https://<your_host>/oauth/twitter/callback
+
+* For Facebook, [register an app](https://developers.facebook.com/apps), configure callback URL to https://<your_host>/oauth/facebook/callback, enable Facebook Login service at https://developers.facebook.com/apps/<app_id>/fb-login/settings/
+
+* For Google, [register an app](https://console.developers.google.com), configure callback URL to https://<your_host>/oauth/google/callback
+
+* For Microsoft, [register an app](https://portal.azure.com), configure callback URL to https://<your_host>/oauth/microsoft/callback
+
+Once the app is configured on external OAuth provider side, add app's credentials and strategy-specific settings (if any — e.g. see Microsoft below) to `config/prod.secret.exs`,
+per strategy's documentation (e.g. [ueberauth_twitter](https://github.com/ueberauth/ueberauth_twitter)). Example config basing on environment variables:
+
+```
+# Twitter
+config :ueberauth, Ueberauth.Strategy.Twitter.OAuth,
+  consumer_key: System.get_env("TWITTER_CONSUMER_KEY"),
+  consumer_secret: System.get_env("TWITTER_CONSUMER_SECRET")
+
+# Facebook
+config :ueberauth, Ueberauth.Strategy.Facebook.OAuth,
+  client_id: System.get_env("FACEBOOK_APP_ID"),
+  client_secret: System.get_env("FACEBOOK_APP_SECRET"),
+  redirect_uri: System.get_env("FACEBOOK_REDIRECT_URI")
+
+# Google
+config :ueberauth, Ueberauth.Strategy.Google.OAuth,
+  client_id: System.get_env("GOOGLE_CLIENT_ID"),
+  client_secret: System.get_env("GOOGLE_CLIENT_SECRET"),
+  redirect_uri: System.get_env("GOOGLE_REDIRECT_URI")
+
+# Microsoft
+config :ueberauth, Ueberauth.Strategy.Microsoft.OAuth,
+  client_id: System.get_env("MICROSOFT_CLIENT_ID"),
+  client_secret: System.get_env("MICROSOFT_CLIENT_SECRET")
+  
+config :ueberauth, Ueberauth,
+  providers: [
+    microsoft: {Ueberauth.Strategy.Microsoft, [callback_params: []]}
+  ]
+```
diff --git a/lib/pleroma/config.ex b/lib/pleroma/config.ex
index 21507cd38..189faa15f 100644
--- a/lib/pleroma/config.ex
+++ b/lib/pleroma/config.ex
@@ -57,4 +57,8 @@ defmodule Pleroma.Config do
   def delete(key) do
     Application.delete_env(:pleroma, key)
   end
+
+  def oauth_consumer_strategies, do: get([:auth, :oauth_consumer_strategies], [])
+
+  def oauth_consumer_enabled?, do: oauth_consumer_strategies() != []
 end
diff --git a/lib/pleroma/registration.ex b/lib/pleroma/registration.ex
new file mode 100644
index 000000000..21fd1fc3f
--- /dev/null
+++ b/lib/pleroma/registration.ex
@@ -0,0 +1,57 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Registration do
+  use Ecto.Schema
+
+  import Ecto.Changeset
+
+  alias Pleroma.Registration
+  alias Pleroma.Repo
+  alias Pleroma.User
+
+  @primary_key {:id, Pleroma.FlakeId, autogenerate: true}
+
+  schema "registrations" do
+    belongs_to(:user, User, type: Pleroma.FlakeId)
+    field(:provider, :string)
+    field(:uid, :string)
+    field(:info, :map, default: %{})
+
+    timestamps()
+  end
+
+  def nickname(registration, default \\ nil),
+    do: Map.get(registration.info, "nickname", default)
+
+  def email(registration, default \\ nil),
+    do: Map.get(registration.info, "email", default)
+
+  def name(registration, default \\ nil),
+    do: Map.get(registration.info, "name", default)
+
+  def description(registration, default \\ nil),
+    do: Map.get(registration.info, "description", default)
+
+  def changeset(registration, params \\ %{}) do
+    registration
+    |> cast(params, [:user_id, :provider, :uid, :info])
+    |> validate_required([:provider, :uid])
+    |> foreign_key_constraint(:user_id)
+    |> unique_constraint(:uid, name: :registrations_provider_uid_index)
+  end
+
+  def bind_to_user(registration, user) do
+    registration
+    |> changeset(%{user_id: (user && user.id) || nil})
+    |> Repo.update()
+  end
+
+  def get_by_provider_uid(provider, uid) do
+    Repo.get_by(Registration,
+      provider: to_string(provider),
+      uid: to_string(uid)
+    )
+  end
+end
diff --git a/lib/pleroma/user.ex b/lib/pleroma/user.ex
index 5012aef77..05f56c01e 100644
--- a/lib/pleroma/user.ex
+++ b/lib/pleroma/user.ex
@@ -13,6 +13,7 @@ defmodule Pleroma.User do
   alias Pleroma.Formatter
   alias Pleroma.Notification
   alias Pleroma.Object
+  alias Pleroma.Registration
   alias Pleroma.Repo
   alias Pleroma.User
   alias Pleroma.Web
@@ -55,6 +56,7 @@ defmodule Pleroma.User do
     field(:bookmarks, {:array, :string}, default: [])
     field(:last_refreshed_at, :naive_datetime_usec)
     has_many(:notifications, Notification)
+    has_many(:registrations, Registration)
     embeds_one(:info, Pleroma.User.Info)
 
     timestamps()
@@ -216,7 +218,7 @@ defmodule Pleroma.User do
     changeset =
       struct
       |> cast(params, [:bio, :email, :name, :nickname, :password, :password_confirmation])
-      |> validate_required([:email, :name, :nickname, :password, :password_confirmation])
+      |> validate_required([:name, :nickname, :password, :password_confirmation])
       |> validate_confirmation(:password)
       |> unique_constraint(:email)
       |> unique_constraint(:nickname)
@@ -227,6 +229,13 @@ defmodule Pleroma.User do
       |> validate_length(:name, min: 1, max: 100)
       |> put_change(:info, info_change)
 
+    changeset =
+      if opts[:external] do
+        changeset
+      else
+        validate_required(changeset, [:email])
+      end
+
     if changeset.valid? do
       hashed = Pbkdf2.hashpwsalt(changeset.changes[:password])
       ap_id = User.ap_id(%User{nickname: changeset.changes[:nickname]})
@@ -505,11 +514,10 @@ defmodule Pleroma.User do
       end
   end
 
+  def get_by_email(email), do: Repo.get_by(User, email: email)
+
   def get_by_nickname_or_email(nickname_or_email) do
-    case user = Repo.get_by(User, nickname: nickname_or_email) do
-      %User{} -> user
-      nil -> Repo.get_by(User, email: nickname_or_email)
-    end
+    get_by_nickname(nickname_or_email) || get_by_email(nickname_or_email)
   end
 
   def get_cached_user_info(user) do
diff --git a/lib/pleroma/web/auth/authenticator.ex b/lib/pleroma/web/auth/authenticator.ex
index 82267c595..89d88af32 100644
--- a/lib/pleroma/web/auth/authenticator.ex
+++ b/lib/pleroma/web/auth/authenticator.ex
@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.Auth.Authenticator do
+  alias Pleroma.Registration
   alias Pleroma.User
 
   def implementation do
@@ -12,14 +13,33 @@ defmodule Pleroma.Web.Auth.Authenticator do
     )
   end
 
-  @callback get_user(Plug.Conn.t()) :: {:ok, User.t()} | {:error, any()}
-  def get_user(plug), do: implementation().get_user(plug)
+  @callback get_user(Plug.Conn.t(), Map.t()) :: {:ok, User.t()} | {:error, any()}
+  def get_user(plug, params), do: implementation().get_user(plug, params)
+
+  @callback create_from_registration(Plug.Conn.t(), Map.t(), Registration.t()) ::
+              {:ok, User.t()} | {:error, any()}
+  def create_from_registration(plug, params, registration),
+    do: implementation().create_from_registration(plug, params, registration)
+
+  @callback get_registration(Plug.Conn.t(), Map.t()) ::
+              {:ok, Registration.t()} | {:error, any()}
+  def get_registration(plug, params),
+    do: implementation().get_registration(plug, params)
 
   @callback handle_error(Plug.Conn.t(), any()) :: any()
   def handle_error(plug, error), do: implementation().handle_error(plug, error)
 
   @callback auth_template() :: String.t() | nil
   def auth_template do
-    implementation().auth_template() || Pleroma.Config.get(:auth_template, "show.html")
+    # Note: `config :pleroma, :auth_template, "..."` support is deprecated
+    implementation().auth_template() ||
+      Pleroma.Config.get([:auth, :auth_template], Pleroma.Config.get(:auth_template)) ||
+      "show.html"
+  end
+
+  @callback oauth_consumer_template() :: String.t() | nil
+  def oauth_consumer_template do
+    implementation().oauth_consumer_template() ||
+      Pleroma.Config.get([:auth, :oauth_consumer_template], "consumer.html")
   end
 end
diff --git a/lib/pleroma/web/auth/ldap_authenticator.ex b/lib/pleroma/web/auth/ldap_authenticator.ex
index 88217aab8..8b6d5a77f 100644
--- a/lib/pleroma/web/auth/ldap_authenticator.ex
+++ b/lib/pleroma/web/auth/ldap_authenticator.ex
@@ -8,14 +8,19 @@ defmodule Pleroma.Web.Auth.LDAPAuthenticator do
   require Logger
 
   @behaviour Pleroma.Web.Auth.Authenticator
+  @base Pleroma.Web.Auth.PleromaAuthenticator
 
   @connection_timeout 10_000
   @search_timeout 10_000
 
-  def get_user(%Plug.Conn{} = conn) do
+  defdelegate get_registration(conn, params), to: @base
+
+  defdelegate create_from_registration(conn, params, registration), to: @base
+
+  def get_user(%Plug.Conn{} = conn, params) do
     if Pleroma.Config.get([:ldap, :enabled]) do
       {name, password} =
-        case conn.params do
+        case params do
           %{"authorization" => %{"name" => name, "password" => password}} ->
             {name, password}
 
@@ -29,14 +34,14 @@ defmodule Pleroma.Web.Auth.LDAPAuthenticator do
 
         {:error, {:ldap_connection_error, _}} ->
           # When LDAP is unavailable, try default authenticator
-          Pleroma.Web.Auth.PleromaAuthenticator.get_user(conn)
+          @base.get_user(conn, params)
 
         error ->
           error
       end
     else
       # Fall back to default authenticator
-      Pleroma.Web.Auth.PleromaAuthenticator.get_user(conn)
+      @base.get_user(conn, params)
     end
   end
 
@@ -46,6 +51,8 @@ defmodule Pleroma.Web.Auth.LDAPAuthenticator do
 
   def auth_template, do: nil
 
+  def oauth_consumer_template, do: nil
+
   defp ldap_user(name, password) do
     ldap = Pleroma.Config.get(:ldap, [])
     host = Keyword.get(ldap, :host, "localhost")
diff --git a/lib/pleroma/web/auth/pleroma_authenticator.ex b/lib/pleroma/web/auth/pleroma_authenticator.ex
index 94a19ad49..c826adb4c 100644
--- a/lib/pleroma/web/auth/pleroma_authenticator.ex
+++ b/lib/pleroma/web/auth/pleroma_authenticator.ex
@@ -4,13 +4,15 @@
 
 defmodule Pleroma.Web.Auth.PleromaAuthenticator do
   alias Comeonin.Pbkdf2
+  alias Pleroma.Registration
+  alias Pleroma.Repo
   alias Pleroma.User
 
   @behaviour Pleroma.Web.Auth.Authenticator
 
-  def get_user(%Plug.Conn{} = conn) do
+  def get_user(%Plug.Conn{} = _conn, params) do
     {name, password} =
-      case conn.params do
+      case params do
         %{"authorization" => %{"name" => name, "password" => password}} ->
           {name, password}
 
@@ -27,9 +29,69 @@ defmodule Pleroma.Web.Auth.PleromaAuthenticator do
     end
   end
 
+  def get_registration(
+        %Plug.Conn{assigns: %{ueberauth_auth: %{provider: provider, uid: uid} = auth}},
+        _params
+      ) do
+    registration = Registration.get_by_provider_uid(provider, uid)
+
+    if registration do
+      {:ok, registration}
+    else
+      info = auth.info
+
+      Registration.changeset(%Registration{}, %{
+        provider: to_string(provider),
+        uid: to_string(uid),
+        info: %{
+          "nickname" => info.nickname,
+          "email" => info.email,
+          "name" => info.name,
+          "description" => info.description
+        }
+      })
+      |> Repo.insert()
+    end
+  end
+
+  def get_registration(%Plug.Conn{} = _conn, _params), do: {:error, :missing_credentials}
+
+  def create_from_registration(_conn, params, registration) do
+    nickname = value([params["nickname"], Registration.nickname(registration)])
+    email = value([params["email"], Registration.email(registration)])
+    name = value([params["name"], Registration.name(registration)]) || nickname
+    bio = value([params["bio"], Registration.description(registration)])
+
+    random_password = :crypto.strong_rand_bytes(64) |> Base.encode64()
+
+    with {:ok, new_user} <-
+           User.register_changeset(
+             %User{},
+             %{
+               email: email,
+               nickname: nickname,
+               name: name,
+               bio: bio,
+               password: random_password,
+               password_confirmation: random_password
+             },
+             external: true,
+             confirmed: true
+           )
+           |> Repo.insert(),
+         {:ok, _} <-
+           Registration.changeset(registration, %{user_id: new_user.id}) |> Repo.update() do
+      {:ok, new_user}
+    end
+  end
+
+  defp value(list), do: Enum.find(list, &(to_string(&1) != ""))
+
   def handle_error(%Plug.Conn{} = _conn, error) do
     error
   end
 
   def auth_template, do: nil
+
+  def oauth_consumer_template, do: nil
 end
diff --git a/lib/pleroma/web/endpoint.ex b/lib/pleroma/web/endpoint.ex
index 6d9528c86..1633477c3 100644
--- a/lib/pleroma/web/endpoint.ex
+++ b/lib/pleroma/web/endpoint.ex
@@ -51,11 +51,22 @@ defmodule Pleroma.Web.Endpoint do
   plug(Plug.MethodOverride)
   plug(Plug.Head)
 
+  secure_cookies = Pleroma.Config.get([__MODULE__, :secure_cookie_flag])
+
   cookie_name =
-    if Application.get_env(:pleroma, Pleroma.Web.Endpoint) |> Keyword.get(:secure_cookie_flag),
+    if secure_cookies,
       do: "__Host-pleroma_key",
       else: "pleroma_key"
 
+  same_site =
+    if Pleroma.Config.oauth_consumer_enabled?() do
+      # Note: "SameSite=Strict" prevents sign in with external OAuth provider
+      #   (there would be no cookies during callback request from OAuth provider)
+      "SameSite=Lax"
+    else
+      "SameSite=Strict"
+    end
+
   # The session will be stored in the cookie and signed,
   # this means its contents can be read but not tampered with.
   # Set :encryption_salt if you would also like to encrypt it.
@@ -65,9 +76,8 @@ defmodule Pleroma.Web.Endpoint do
     key: cookie_name,
     signing_salt: {Pleroma.Config, :get, [[__MODULE__, :signing_salt], "CqaoopA2"]},
     http_only: true,
-    secure:
-      Application.get_env(:pleroma, Pleroma.Web.Endpoint) |> Keyword.get(:secure_cookie_flag),
-    extra: "SameSite=Strict"
+    secure: secure_cookies,
+    extra: same_site
   )
 
   # Note: the plug and its configuration is compile-time this can't be upstreamed yet
diff --git a/lib/pleroma/web/oauth/fallback_controller.ex b/lib/pleroma/web/oauth/fallback_controller.ex
index f0fe3b578..afaa00242 100644
--- a/lib/pleroma/web/oauth/fallback_controller.ex
+++ b/lib/pleroma/web/oauth/fallback_controller.ex
@@ -6,8 +6,21 @@ defmodule Pleroma.Web.OAuth.FallbackController do
   use Pleroma.Web, :controller
   alias Pleroma.Web.OAuth.OAuthController
 
-  # No user/password
-  def call(conn, _) do
+  def call(conn, {:register, :generic_error}) do
+    conn
+    |> put_status(:internal_server_error)
+    |> put_flash(:error, "Unknown error, please check the details and try again.")
+    |> OAuthController.registration_details(conn.params)
+  end
+
+  def call(conn, {:register, _error}) do
+    conn
+    |> put_status(:unauthorized)
+    |> put_flash(:error, "Invalid Username/Password")
+    |> OAuthController.registration_details(conn.params)
+  end
+
+  def call(conn, _error) do
     conn
     |> put_status(:unauthorized)
     |> put_flash(:error, "Invalid Username/Password")
diff --git a/lib/pleroma/web/oauth/oauth_controller.ex b/lib/pleroma/web/oauth/oauth_controller.ex
index aac8f97fc..bee7084ad 100644
--- a/lib/pleroma/web/oauth/oauth_controller.ex
+++ b/lib/pleroma/web/oauth/oauth_controller.ex
@@ -5,6 +5,7 @@
 defmodule Pleroma.Web.OAuth.OAuthController do
   use Pleroma.Web, :controller
 
+  alias Pleroma.Registration
   alias Pleroma.Repo
   alias Pleroma.User
   alias Pleroma.Web.Auth.Authenticator
@@ -15,6 +16,8 @@ defmodule Pleroma.Web.OAuth.OAuthController do
 
   import Pleroma.Web.ControllerHelper, only: [oauth_scopes: 2]
 
+  if Pleroma.Config.oauth_consumer_enabled?(), do: plug(Ueberauth)
+
   plug(:fetch_session)
   plug(:fetch_flash)
 
@@ -57,66 +60,65 @@ defmodule Pleroma.Web.OAuth.OAuthController do
     })
   end
 
-  def create_authorization(conn, %{
-        "authorization" =>
-          %{
-            "client_id" => client_id,
-            "redirect_uri" => redirect_uri
-          } = auth_params
-      }) do
-    with {_, {:ok, %User{} = user}} <- {:get_user, Authenticator.get_user(conn)},
-         %App{} = app <- Repo.get_by(App, client_id: client_id),
-         true <- redirect_uri in String.split(app.redirect_uris),
-         scopes <- oauth_scopes(auth_params, []),
-         {:unsupported_scopes, []} <- {:unsupported_scopes, scopes -- app.scopes},
-         # Note: `scope` param is intentionally not optional in this context
-         {:missing_scopes, false} <- {:missing_scopes, scopes == []},
-         {:auth_active, true} <- {:auth_active, User.auth_active?(user)},
-         {:ok, auth} <- Authorization.create_authorization(app, user, scopes) do
-      redirect_uri = redirect_uri(conn, redirect_uri)
+  def create_authorization(
+        conn,
+        %{"authorization" => auth_params} = params,
+        opts \\ []
+      ) do
+    with {:ok, auth} <- do_create_authorization(conn, params, opts[:user]) do
+      after_create_authorization(conn, auth, auth_params)
+    else
+      error ->
+        handle_create_authorization_error(conn, error, auth_params)
+    end
+  end
 
-      cond do
-        redirect_uri == "urn:ietf:wg:oauth:2.0:oob" ->
-          render(conn, "results.html", %{
-            auth: auth
-          })
+  def after_create_authorization(conn, auth, %{"redirect_uri" => redirect_uri} = auth_params) do
+    redirect_uri = redirect_uri(conn, redirect_uri)
 
-        true ->
-          connector = if String.contains?(redirect_uri, "?"), do: "&", else: "?"
-          url = "#{redirect_uri}#{connector}"
-          url_params = %{:code => auth.token}
+    if redirect_uri == "urn:ietf:wg:oauth:2.0:oob" do
+      render(conn, "results.html", %{
+        auth: auth
+      })
+    else
+      connector = if String.contains?(redirect_uri, "?"), do: "&", else: "?"
+      url = "#{redirect_uri}#{connector}"
+      url_params = %{:code => auth.token}
 
-          url_params =
-            if auth_params["state"] do
-              Map.put(url_params, :state, auth_params["state"])
-            else
-              url_params
-            end
+      url_params =
+        if auth_params["state"] do
+          Map.put(url_params, :state, auth_params["state"])
+        else
+          url_params
+        end
 
-          url = "#{url}#{Plug.Conn.Query.encode(url_params)}"
+      url = "#{url}#{Plug.Conn.Query.encode(url_params)}"
 
-          redirect(conn, external: url)
-      end
-    else
-      {scopes_issue, _} when scopes_issue in [:unsupported_scopes, :missing_scopes] ->
-        # Per https://github.com/tootsuite/mastodon/blob/
-        #   51e154f5e87968d6bb115e053689767ab33e80cd/app/controllers/api/base_controller.rb#L39
-        conn
-        |> put_flash(:error, "This action is outside the authorized scopes")
-        |> put_status(:unauthorized)
-        |> authorize(auth_params)
+      redirect(conn, external: url)
+    end
+  end
 
-      {:auth_active, false} ->
-        # Per https://github.com/tootsuite/mastodon/blob/
-        #   51e154f5e87968d6bb115e053689767ab33e80cd/app/controllers/api/base_controller.rb#L76
-        conn
-        |> put_flash(:error, "Your login is missing a confirmed e-mail address")
-        |> put_status(:forbidden)
-        |> authorize(auth_params)
+  defp handle_create_authorization_error(conn, {scopes_issue, _}, auth_params)
+       when scopes_issue in [:unsupported_scopes, :missing_scopes] do
+    # Per https://github.com/tootsuite/mastodon/blob/
+    #   51e154f5e87968d6bb115e053689767ab33e80cd/app/controllers/api/base_controller.rb#L39
+    conn
+    |> put_flash(:error, "This action is outside the authorized scopes")
+    |> put_status(:unauthorized)
+    |> authorize(auth_params)
+  end
 
-      error ->
-        Authenticator.handle_error(conn, error)
-    end
+  defp handle_create_authorization_error(conn, {:auth_active, false}, auth_params) do
+    # Per https://github.com/tootsuite/mastodon/blob/
+    #   51e154f5e87968d6bb115e053689767ab33e80cd/app/controllers/api/base_controller.rb#L76
+    conn
+    |> put_flash(:error, "Your login is missing a confirmed e-mail address")
+    |> put_status(:forbidden)
+    |> authorize(auth_params)
+  end
+
+  defp handle_create_authorization_error(conn, error, _auth_params) do
+    Authenticator.handle_error(conn, error)
   end
 
   def token_exchange(conn, %{"grant_type" => "authorization_code"} = params) do
@@ -149,7 +151,7 @@ defmodule Pleroma.Web.OAuth.OAuthController do
         conn,
         %{"grant_type" => "password"} = params
       ) do
-    with {_, {:ok, %User{} = user}} <- {:get_user, Authenticator.get_user(conn)},
+    with {_, {:ok, %User{} = user}} <- {:get_user, Authenticator.get_user(conn, params)},
          %App{} = app <- get_app_from_request(conn, params),
          {:auth_active, true} <- {:auth_active, User.auth_active?(user)},
          {:user_active, true} <- {:user_active, !user.info.deactivated},
@@ -211,6 +213,184 @@ defmodule Pleroma.Web.OAuth.OAuthController do
     end
   end
 
+  @doc "Prepares OAuth request to provider for Ueberauth"
+  def prepare_request(conn, %{"provider" => provider} = params) do
+    scope =
+      oauth_scopes(params, [])
+      |> Enum.join(" ")
+
+    state =
+      params
+      |> Map.delete("scopes")
+      |> Map.put("scope", scope)
+      |> Poison.encode!()
+
+    params =
+      params
+      |> Map.drop(~w(scope scopes client_id redirect_uri))
+      |> Map.put("state", state)
+
+    # Handing the request to Ueberauth
+    redirect(conn, to: o_auth_path(conn, :request, provider, params))
+  end
+
+  def request(conn, params) do
+    message =
+      if params["provider"] do
+        "Unsupported OAuth provider: #{params["provider"]}."
+      else
+        "Bad OAuth request."
+      end
+
+    conn
+    |> put_flash(:error, message)
+    |> redirect(to: "/")
+  end
+
+  def callback(%{assigns: %{ueberauth_failure: failure}} = conn, params) do
+    params = callback_params(params)
+    messages = for e <- Map.get(failure, :errors, []), do: e.message
+    message = Enum.join(messages, "; ")
+
+    conn
+    |> put_flash(:error, "Failed to authenticate: #{message}.")
+    |> redirect(external: redirect_uri(conn, params["redirect_uri"]))
+  end
+
+  def callback(conn, params) do
+    params = callback_params(params)
+
+    with {:ok, registration} <- Authenticator.get_registration(conn, params) do
+      user = Repo.preload(registration, :user).user
+      auth_params = Map.take(params, ~w(client_id redirect_uri scope scopes state))
+
+      if user do
+        create_authorization(
+          conn,
+          %{"authorization" => auth_params},
+          user: user
+        )
+      else
+        registration_params =
+          Map.merge(auth_params, %{
+            "nickname" => Registration.nickname(registration),
+            "email" => Registration.email(registration)
+          })
+
+        conn
+        |> put_session(:registration_id, registration.id)
+        |> registration_details(registration_params)
+      end
+    else
+      _ ->
+        conn
+        |> put_flash(:error, "Failed to set up user account.")
+        |> redirect(external: redirect_uri(conn, params["redirect_uri"]))
+    end
+  end
+
+  defp callback_params(%{"state" => state} = params) do
+    Map.merge(params, Poison.decode!(state))
+  end
+
+  def registration_details(conn, params) do
+    render(conn, "register.html", %{
+      client_id: params["client_id"],
+      redirect_uri: params["redirect_uri"],
+      state: params["state"],
+      scopes: oauth_scopes(params, []),
+      nickname: params["nickname"],
+      email: params["email"]
+    })
+  end
+
+  def register(conn, %{"op" => "connect"} = params) do
+    authorization_params = Map.put(params, "name", params["auth_name"])
+    create_authorization_params = %{"authorization" => authorization_params}
+
+    with registration_id when not is_nil(registration_id) <- get_session_registration_id(conn),
+         %Registration{} = registration <- Repo.get(Registration, registration_id),
+         {_, {:ok, auth}} <-
+           {:create_authorization, do_create_authorization(conn, create_authorization_params)},
+         %User{} = user <- Repo.preload(auth, :user).user,
+         {:ok, _updated_registration} <- Registration.bind_to_user(registration, user) do
+      conn
+      |> put_session_registration_id(nil)
+      |> after_create_authorization(auth, authorization_params)
+    else
+      {:create_authorization, error} ->
+        {:register, handle_create_authorization_error(conn, error, create_authorization_params)}
+
+      _ ->
+        {:register, :generic_error}
+    end
+  end
+
+  def register(conn, %{"op" => "register"} = params) do
+    with registration_id when not is_nil(registration_id) <- get_session_registration_id(conn),
+         %Registration{} = registration <- Repo.get(Registration, registration_id),
+         {:ok, user} <- Authenticator.create_from_registration(conn, params, registration) do
+      conn
+      |> put_session_registration_id(nil)
+      |> create_authorization(
+        %{
+          "authorization" => %{
+            "client_id" => params["client_id"],
+            "redirect_uri" => params["redirect_uri"],
+            "scopes" => oauth_scopes(params, nil)
+          }
+        },
+        user: user
+      )
+    else
+      {:error, changeset} ->
+        message =
+          Enum.map(changeset.errors, fn {field, {error, _}} ->
+            "#{field} #{error}"
+          end)
+          |> Enum.join("; ")
+
+        message =
+          String.replace(
+            message,
+            "ap_id has already been taken",
+            "nickname has already been taken"
+          )
+
+        conn
+        |> put_status(:forbidden)
+        |> put_flash(:error, "Error: #{message}.")
+        |> registration_details(params)
+
+      _ ->
+        {:register, :generic_error}
+    end
+  end
+
+  defp do_create_authorization(
+         conn,
+         %{
+           "authorization" =>
+             %{
+               "client_id" => client_id,
+               "redirect_uri" => redirect_uri
+             } = auth_params
+         } = params,
+         user \\ nil
+       ) do
+    with {_, {:ok, %User{} = user}} <-
+           {:get_user, (user && {:ok, user}) || Authenticator.get_user(conn, params)},
+         %App{} = app <- Repo.get_by(App, client_id: client_id),
+         true <- redirect_uri in String.split(app.redirect_uris),
+         scopes <- oauth_scopes(auth_params, []),
+         {:unsupported_scopes, []} <- {:unsupported_scopes, scopes -- app.scopes},
+         # Note: `scope` param is intentionally not optional in this context
+         {:missing_scopes, false} <- {:missing_scopes, scopes == []},
+         {:auth_active, true} <- {:auth_active, User.auth_active?(user)} do
+      Authorization.create_authorization(app, user, scopes)
+    end
+  end
+
   # XXX - for whatever reason our token arrives urlencoded, but Plug.Conn should be
   # decoding it.  Investigate sometime.
   defp fix_padding(token) do
@@ -248,4 +428,9 @@ defmodule Pleroma.Web.OAuth.OAuthController do
   defp redirect_uri(conn, "."), do: mastodon_api_url(conn, :login)
 
   defp redirect_uri(_conn, redirect_uri), do: redirect_uri
+
+  defp get_session_registration_id(conn), do: get_session(conn, :registration_id)
+
+  defp put_session_registration_id(conn, registration_id),
+    do: put_session(conn, :registration_id, registration_id)
 end
diff --git a/lib/pleroma/web/router.ex b/lib/pleroma/web/router.ex
index 3b5ac6fdd..ef38fc34d 100644
--- a/lib/pleroma/web/router.ex
+++ b/lib/pleroma/web/router.ex
@@ -5,6 +5,11 @@
 defmodule Pleroma.Web.Router do
   use Pleroma.Web, :router
 
+  pipeline :browser do
+    plug(:accepts, ["html"])
+    plug(:fetch_session)
+  end
+
   pipeline :oauth do
     plug(:fetch_session)
     plug(Pleroma.Plugs.OAuthPlug)
@@ -213,6 +218,16 @@ defmodule Pleroma.Web.Router do
     post("/authorize", OAuthController, :create_authorization)
     post("/token", OAuthController, :token_exchange)
     post("/revoke", OAuthController, :token_revoke)
+    get("/registration_details", OAuthController, :registration_details)
+
+    scope [] do
+      pipe_through(:browser)
+
+      get("/prepare_request", OAuthController, :prepare_request)
+      get("/:provider", OAuthController, :request)
+      get("/:provider/callback", OAuthController, :callback)
+      post("/register", OAuthController, :register)
+    end
   end
 
   scope "/api/v1", Pleroma.Web.MastodonAPI do
diff --git a/lib/pleroma/web/templates/o_auth/o_auth/_scopes.html.eex b/lib/pleroma/web/templates/o_auth/o_auth/_scopes.html.eex
new file mode 100644
index 000000000..4b8fb5dae
--- /dev/null
+++ b/lib/pleroma/web/templates/o_auth/o_auth/_scopes.html.eex
@@ -0,0 +1,13 @@
+<div class="scopes-input">
+  <%= label @form, :scope, "Permissions" %>
+
+  <div class="scopes">
+    <%= for scope <- @available_scopes do %>
+      <%# Note: using hidden input with `unchecked_value` in order to distinguish user's empty selection from `scope` param being omitted %>
+      <div class="scope">
+        <%= checkbox @form, :"scope_#{scope}", value: scope in @scopes && scope, checked_value: scope, unchecked_value: "", name: assigns[:scope_param] || "scope[]" %>
+        <%= label @form, :"scope_#{scope}", String.capitalize(scope) %>
+      </div>
+    <% end %>
+  </div>
+</div>
diff --git a/lib/pleroma/web/templates/o_auth/o_auth/consumer.html.eex b/lib/pleroma/web/templates/o_auth/o_auth/consumer.html.eex
new file mode 100644
index 000000000..85f62ca64
--- /dev/null
+++ b/lib/pleroma/web/templates/o_auth/o_auth/consumer.html.eex
@@ -0,0 +1,13 @@
+<h2>Sign in with external provider</h2>
+
+<%= form_for @conn, o_auth_path(@conn, :prepare_request), [method: "get"], fn f -> %>
+  <%= render @view_module, "_scopes.html", Map.put(assigns, :form, f) %>
+
+  <%= hidden_input f, :client_id, value: @client_id %>
+  <%= hidden_input f, :redirect_uri, value: @redirect_uri %>
+  <%= hidden_input f, :state, value: @state %>
+
+    <%= for strategy <- Pleroma.Config.oauth_consumer_strategies() do %>
+      <%= submit "Sign in with #{String.capitalize(strategy)}", name: "provider", value: strategy %>
+    <% end %>
+<% end %>
diff --git a/lib/pleroma/web/templates/o_auth/o_auth/register.html.eex b/lib/pleroma/web/templates/o_auth/o_auth/register.html.eex
new file mode 100644
index 000000000..126390391
--- /dev/null
+++ b/lib/pleroma/web/templates/o_auth/o_auth/register.html.eex
@@ -0,0 +1,43 @@
+<%= if get_flash(@conn, :info) do %>
+  <p class="alert alert-info" role="alert"><%= get_flash(@conn, :info) %></p>
+<% end %>
+<%= if get_flash(@conn, :error) do %>
+  <p class="alert alert-danger" role="alert"><%= get_flash(@conn, :error) %></p>
+<% end %>
+
+<h2>Registration Details</h2>
+
+<p>If you'd like to register a new account, please provide the details below.</p>
+
+<%= form_for @conn, o_auth_path(@conn, :register), [], fn f -> %>
+
+<div class="input">
+  <%= label f, :nickname, "Nickname" %>
+  <%= text_input f, :nickname, value: @nickname %>
+</div>
+<div class="input">
+  <%= label f, :email, "Email" %>
+  <%= text_input f, :email, value: @email %>
+</div>
+
+<%= submit "Proceed as new user", name: "op", value: "register" %>
+
+<p>Alternatively, sign in to connect to existing account.</p>
+
+<div class="input">
+  <%= label f, :auth_name, "Name or email" %>
+  <%= text_input f, :auth_name %>
+</div>
+<div class="input">
+  <%= label f, :password, "Password" %>
+  <%= password_input f, :password %>
+</div>
+
+<%= submit "Proceed as existing user", name: "op", value: "connect" %>
+
+<%= hidden_input f, :client_id, value: @client_id %>
+<%= hidden_input f, :redirect_uri, value: @redirect_uri %>
+<%= hidden_input f, :scope, value: Enum.join(@scopes, " ") %>
+<%= hidden_input f, :state, value: @state %>
+
+<% end %>
diff --git a/lib/pleroma/web/templates/o_auth/o_auth/show.html.eex b/lib/pleroma/web/templates/o_auth/o_auth/show.html.eex
index 161333847..87278e636 100644
--- a/lib/pleroma/web/templates/o_auth/o_auth/show.html.eex
+++ b/lib/pleroma/web/templates/o_auth/o_auth/show.html.eex
@@ -4,7 +4,9 @@
 <%= if get_flash(@conn, :error) do %>
 <p class="alert alert-danger" role="alert"><%= get_flash(@conn, :error) %></p>
 <% end %>
+
 <h2>OAuth Authorization</h2>
+
 <%= form_for @conn, o_auth_path(@conn, :authorize), [as: "authorization"], fn f -> %>
 <div class="input">
   <%= label f, :name, "Name or email" %>
@@ -14,22 +16,16 @@
   <%= label f, :password, "Password" %>
   <%= password_input f, :password %>
 </div>
-<div class="scopes-input">
-<%= label f, :scope, "Permissions" %>
-  <div class="scopes">
-    <%= for scope <- @available_scopes do %>
-      <%# Note: using hidden input with `unchecked_value` in order to distinguish user's empty selection from `scope` param being omitted %>
-      <div class="scope">
-        <%= checkbox f, :"scope_#{scope}", value: scope in @scopes && scope, checked_value: scope, unchecked_value: "", name: "authorization[scope][]" %>
-        <%= label f, :"scope_#{scope}", String.capitalize(scope) %>
-      </div>
-    <% end %>
-  </div>
-</div>
+
+<%= render @view_module, "_scopes.html", Map.merge(assigns, %{form: f, scope_param: "authorization[scope][]"}) %>
 
 <%= hidden_input f, :client_id, value: @client_id %>
 <%= hidden_input f, :response_type, value: @response_type %>
 <%= hidden_input f, :redirect_uri, value: @redirect_uri %>
-<%= hidden_input f, :state, value: @state%>
+<%= hidden_input f, :state, value: @state %>
 <%= submit "Authorize" %>
 <% end %>
+
+<%= if Pleroma.Config.oauth_consumer_enabled?() do %>
+  <%= render @view_module, Pleroma.Web.Auth.Authenticator.oauth_consumer_template(), assigns %>
+<% end %>
diff --git a/mix.exs b/mix.exs
index ec0865c4f..26a03b70b 100644
--- a/mix.exs
+++ b/mix.exs
@@ -54,6 +54,12 @@ defmodule Pleroma.Mixfile do
   #
   # Type `mix help deps` for examples and options.
   defp deps do
+    oauth_strategies = String.split(System.get_env("OAUTH_CONSUMER_STRATEGIES") || "")
+
+    oauth_deps =
+      for s <- oauth_strategies,
+          do: {String.to_atom("ueberauth_#{s}"), ">= 0.0.0"}
+
     [
       {:phoenix, "~> 1.4.1"},
       {:plug_cowboy, "~> 2.0"},
@@ -71,6 +77,7 @@ defmodule Pleroma.Mixfile do
       {:calendar, "~> 0.17.4"},
       {:cachex, "~> 3.0.2"},
       {:httpoison, "~> 1.2.0"},
+      {:poison, "~> 3.0", override: true},
       {:tesla, "~> 1.2"},
       {:jason, "~> 1.0"},
       {:mogrify, "~> 0.6.1"},
@@ -91,6 +98,7 @@ defmodule Pleroma.Mixfile do
       {:floki, "~> 0.20.0"},
       {:ex_syslogger, github: "slashmili/ex_syslogger", tag: "1.4.0"},
       {:timex, "~> 3.5"},
+      {:ueberauth, "~> 0.4"},
       {:auto_linker,
        git: "https://git.pleroma.social/pleroma/auto_linker.git",
        ref: "479dd343f4e563ff91215c8275f3b5c67e032850"},
@@ -103,7 +111,7 @@ defmodule Pleroma.Mixfile do
       {:prometheus_process_collector, "~> 1.4"},
       {:recon, github: "ferd/recon", tag: "2.4.0"},
       {:quack, "~> 0.1.1"}
-    ]
+    ] ++ oauth_deps
   end
 
   # Aliases are shortcuts or tasks specific to the current project.
diff --git a/mix.lock b/mix.lock
index 7c7e322de..bb40ebd48 100644
--- a/mix.lock
+++ b/mix.lock
@@ -5,7 +5,7 @@
   "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm"},
   "cachex": {:hex, :cachex, "3.0.2", "1351caa4e26e29f7d7ec1d29b53d6013f0447630bbf382b4fb5d5bad0209f203", [:mix], [{:eternal, "~> 1.2", [hex: :eternal, repo: "hexpm", optional: false]}, {:unsafe, "~> 1.0", [hex: :unsafe, repo: "hexpm", optional: false]}], "hexpm"},
   "calendar": {:hex, :calendar, "0.17.4", "22c5e8d98a4db9494396e5727108dffb820ee0d18fed4b0aa8ab76e4f5bc32f1", [:mix], [{:tzdata, "~> 0.5.8 or ~> 0.1.201603", [hex: :tzdata, repo: "hexpm", optional: false]}], "hexpm"},
-  "certifi": {:hex, :certifi, "2.4.2", "75424ff0f3baaccfd34b1214184b6ef616d89e420b258bb0a5ea7d7bc628f7f0", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm"},
+  "certifi": {:hex, :certifi, "2.5.1", "867ce347f7c7d78563450a18a6a28a8090331e77fa02380b4a21962a65d36ee5", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm"},
   "combine": {:hex, :combine, "0.10.0", "eff8224eeb56498a2af13011d142c5e7997a80c8f5b97c499f84c841032e429f", [:mix], [], "hexpm"},
   "comeonin": {:hex, :comeonin, "4.1.1", "c7304fc29b45b897b34142a91122bc72757bc0c295e9e824999d5179ffc08416", [:mix], [{:argon2_elixir, "~> 1.2", [hex: :argon2_elixir, repo: "hexpm", optional: true]}, {:bcrypt_elixir, "~> 0.12.1 or ~> 1.0", [hex: :bcrypt_elixir, repo: "hexpm", optional: true]}, {:pbkdf2_elixir, "~> 0.12", [hex: :pbkdf2_elixir, repo: "hexpm", optional: true]}], "hexpm"},
   "connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], [], "hexpm"},
@@ -28,7 +28,7 @@
   "floki": {:hex, :floki, "0.20.4", "be42ac911fece24b4c72f3b5846774b6e61b83fe685c2fc9d62093277fb3bc86", [:mix], [{:html_entities, "~> 0.4.0", [hex: :html_entities, repo: "hexpm", optional: false]}, {:mochiweb, "~> 2.15", [hex: :mochiweb, repo: "hexpm", optional: false]}], "hexpm"},
   "gen_smtp": {:hex, :gen_smtp, "0.13.0", "11f08504c4bdd831dc520b8f84a1dce5ce624474a797394e7aafd3c29f5dcd25", [:rebar3], [], "hexpm"},
   "gettext": {:hex, :gettext, "0.15.0", "40a2b8ce33a80ced7727e36768499fc9286881c43ebafccae6bab731e2b2b8ce", [:mix], [], "hexpm"},
-  "hackney": {:hex, :hackney, "1.14.3", "b5f6f5dcc4f1fba340762738759209e21914516df6be440d85772542d4a5e412", [:rebar3], [{:certifi, "2.4.2", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.4", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
+  "hackney": {:hex, :hackney, "1.15.1", "9f8f471c844b8ce395f7b6d8398139e26ddca9ebc171a8b91342ee15a19963f4", [:rebar3], [{:certifi, "2.5.1", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.4", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
   "html_entities": {:hex, :html_entities, "0.4.0", "f2fee876858cf6aaa9db608820a3209e45a087c5177332799592142b50e89a6b", [:mix], [], "hexpm"},
   "html_sanitize_ex": {:hex, :html_sanitize_ex, "1.3.0", "f005ad692b717691203f940c686208aa3d8ffd9dd4bb3699240096a51fa9564e", [:mix], [{:mochiweb, "~> 2.15", [hex: :mochiweb, repo: "hexpm", optional: false]}], "hexpm"},
   "httpoison": {:hex, :httpoison, "1.2.0", "2702ed3da5fd7a8130fc34b11965c8cfa21ade2f232c00b42d96d4967c39a3a3", [:mix], [{:hackney, "~> 1.8", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
@@ -40,7 +40,7 @@
   "meck": {:hex, :meck, "0.8.13", "ffedb39f99b0b99703b8601c6f17c7f76313ee12de6b646e671e3188401f7866", [:rebar3], [], "hexpm"},
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm"},
   "mime": {:hex, :mime, "1.3.1", "30ce04ab3175b6ad0bdce0035cba77bba68b813d523d1aac73d9781b4d193cf8", [:mix], [], "hexpm"},
-  "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [:rebar3], [], "hexpm"},
+  "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm"},
   "mochiweb": {:hex, :mochiweb, "2.15.0", "e1daac474df07651e5d17cc1e642c4069c7850dc4508d3db7263a0651330aacc", [:rebar3], [], "hexpm"},
   "mock": {:hex, :mock, "0.3.1", "994f00150f79a0ea50dc9d86134cd9ebd0d177ad60bd04d1e46336cdfdb98ff9", [:mix], [{:meck, "~> 0.8.8", [hex: :meck, repo: "hexpm", optional: false]}], "hexpm"},
   "mogrify": {:hex, :mogrify, "0.6.1", "de1b527514f2d95a7bbe9642eb556061afb337e220cf97adbf3a4e6438ed70af", [:mix], [], "hexpm"},
@@ -75,6 +75,7 @@
   "timex": {:hex, :timex, "3.5.0", "b0a23167da02d0fe4f1a4e104d1f929a00d348502b52432c05de875d0b9cffa5", [:mix], [{:combine, "~> 0.10", [hex: :combine, repo: "hexpm", optional: false]}, {:gettext, "~> 0.10", [hex: :gettext, repo: "hexpm", optional: false]}, {:tzdata, "~> 0.1.8 or ~> 0.5", [hex: :tzdata, repo: "hexpm", optional: false]}], "hexpm"},
   "trailing_format_plug": {:hex, :trailing_format_plug, "0.0.7", "64b877f912cf7273bed03379936df39894149e35137ac9509117e59866e10e45", [:mix], [{:plug, "> 0.12.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "tzdata": {:hex, :tzdata, "0.5.17", "50793e3d85af49736701da1a040c415c97dc1caf6464112fd9bd18f425d3053b", [:mix], [{:hackney, "~> 1.0", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
+  "ueberauth": {:hex, :ueberauth, "0.6.1", "9e90d3337dddf38b1ca2753aca9b1e53d8a52b890191cdc55240247c89230412", [:mix], [{:plug, "~> 1.5", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "unicode_util_compat": {:hex, :unicode_util_compat, "0.4.1", "d869e4c68901dd9531385bb0c8c40444ebf624e60b6962d95952775cac5e90cd", [:rebar3], [], "hexpm"},
   "unsafe": {:hex, :unsafe, "1.0.0", "7c21742cd05380c7875546b023481d3a26f52df8e5dfedcb9f958f322baae305", [:mix], [], "hexpm"},
   "web_push_encryption": {:hex, :web_push_encryption, "0.2.1", "d42cecf73420d9dc0053ba3299cc8c8d6ff2be2487d67ca2a57265868e4d9a98", [:mix], [{:httpoison, "~> 1.0", [hex: :httpoison, repo: "hexpm", optional: false]}, {:jose, "~> 1.8", [hex: :jose, repo: "hexpm", optional: false]}, {:poison, "~> 3.0", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
diff --git a/priv/repo/migrations/20190315101315_create_registrations.exs b/priv/repo/migrations/20190315101315_create_registrations.exs
new file mode 100644
index 000000000..6b28cbdd3
--- /dev/null
+++ b/priv/repo/migrations/20190315101315_create_registrations.exs
@@ -0,0 +1,18 @@
+defmodule Pleroma.Repo.Migrations.CreateRegistrations do
+  use Ecto.Migration
+
+  def change do
+    create table(:registrations, primary_key: false) do
+      add :id, :uuid, primary_key: true
+      add :user_id, references(:users, type: :uuid, on_delete: :delete_all)
+      add :provider, :string
+      add :uid, :string
+      add :info, :map, default: %{}
+
+      timestamps()
+    end
+
+    create unique_index(:registrations, [:provider, :uid])
+    create unique_index(:registrations, [:user_id, :provider, :uid])
+  end
+end
diff --git a/test/registration_test.exs b/test/registration_test.exs
new file mode 100644
index 000000000..6143b82c7
--- /dev/null
+++ b/test/registration_test.exs
@@ -0,0 +1,59 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.RegistrationTest do
+  use Pleroma.DataCase
+
+  import Pleroma.Factory
+
+  alias Pleroma.Registration
+  alias Pleroma.Repo
+
+  describe "generic changeset" do
+    test "requires :provider, :uid" do
+      registration = build(:registration, provider: nil, uid: nil)
+
+      cs = Registration.changeset(registration, %{})
+      refute cs.valid?
+
+      assert [
+               provider: {"can't be blank", [validation: :required]},
+               uid: {"can't be blank", [validation: :required]}
+             ] == cs.errors
+    end
+
+    test "ensures uniqueness of [:provider, :uid]" do
+      registration = insert(:registration)
+      registration2 = build(:registration, provider: registration.provider, uid: registration.uid)
+
+      cs = Registration.changeset(registration2, %{})
+      assert cs.valid?
+
+      assert {:error,
+              %Ecto.Changeset{
+                errors: [
+                  uid:
+                    {"has already been taken",
+                     [constraint: :unique, constraint_name: "registrations_provider_uid_index"]}
+                ]
+              }} = Repo.insert(cs)
+
+      # Note: multiple :uid values per [:user_id, :provider] are intentionally allowed
+      cs2 = Registration.changeset(registration2, %{uid: "available.uid"})
+      assert cs2.valid?
+      assert {:ok, _} = Repo.insert(cs2)
+
+      cs3 = Registration.changeset(registration2, %{provider: "provider2"})
+      assert cs3.valid?
+      assert {:ok, _} = Repo.insert(cs3)
+    end
+
+    test "allows `nil` :user_id (user-unbound registration)" do
+      registration = build(:registration, user_id: nil)
+      cs = Registration.changeset(registration, %{})
+      assert cs.valid?
+      assert {:ok, _} = Repo.insert(cs)
+    end
+  end
+end
diff --git a/test/support/factory.ex b/test/support/factory.ex
index 608f8d46b..ea59912cf 100644
--- a/test/support/factory.ex
+++ b/test/support/factory.ex
@@ -275,4 +275,20 @@ defmodule Pleroma.Factory do
       params: build(:note) |> Map.from_struct() |> Map.get(:data)
     }
   end
+
+  def registration_factory do
+    user = insert(:user)
+
+    %Pleroma.Registration{
+      user: user,
+      provider: "twitter",
+      uid: "171799000",
+      info: %{
+        "name" => "John Doe",
+        "email" => "john@doe.com",
+        "nickname" => "johndoe",
+        "description" => "My bio"
+      }
+    }
+  end
 end
diff --git a/test/web/admin_api/admin_api_controller_test.exs b/test/web/admin_api/admin_api_controller_test.exs
index dd2fbfb15..ca6bd0e97 100644
--- a/test/web/admin_api/admin_api_controller_test.exs
+++ b/test/web/admin_api/admin_api_controller_test.exs
@@ -80,14 +80,13 @@ defmodule Pleroma.Web.AdminAPI.AdminAPIControllerTest do
       user = insert(:user)
       follower = insert(:user)
 
-      conn =
-        build_conn()
-        |> assign(:user, admin)
-        |> put_req_header("accept", "application/json")
-        |> post("/api/pleroma/admin/user/follow", %{
-          "follower" => follower.nickname,
-          "followed" => user.nickname
-        })
+      build_conn()
+      |> assign(:user, admin)
+      |> put_req_header("accept", "application/json")
+      |> post("/api/pleroma/admin/user/follow", %{
+        "follower" => follower.nickname,
+        "followed" => user.nickname
+      })
 
       user = User.get_by_id(user.id)
       follower = User.get_by_id(follower.id)
@@ -104,14 +103,13 @@ defmodule Pleroma.Web.AdminAPI.AdminAPIControllerTest do
 
       User.follow(follower, user)
 
-      conn =
-        build_conn()
-        |> assign(:user, admin)
-        |> put_req_header("accept", "application/json")
-        |> post("/api/pleroma/admin/user/unfollow", %{
-          "follower" => follower.nickname,
-          "followed" => user.nickname
-        })
+      build_conn()
+      |> assign(:user, admin)
+      |> put_req_header("accept", "application/json")
+      |> post("/api/pleroma/admin/user/unfollow", %{
+        "follower" => follower.nickname,
+        "followed" => user.nickname
+      })
 
       user = User.get_by_id(user.id)
       follower = User.get_by_id(follower.id)
diff --git a/test/web/oauth/oauth_controller_test.exs b/test/web/oauth/oauth_controller_test.exs
index a68528420..ac7843f9b 100644
--- a/test/web/oauth/oauth_controller_test.exs
+++ b/test/web/oauth/oauth_controller_test.exs
@@ -5,24 +5,330 @@
 defmodule Pleroma.Web.OAuth.OAuthControllerTest do
   use Pleroma.Web.ConnCase
   import Pleroma.Factory
+  import Mock
 
+  alias Pleroma.Registration
   alias Pleroma.Repo
   alias Pleroma.Web.OAuth.Authorization
   alias Pleroma.Web.OAuth.Token
 
-  describe "GET /oauth/authorize" do
+  @session_opts [
+    store: :cookie,
+    key: "_test",
+    signing_salt: "cooldude"
+  ]
+
+  describe "in OAuth consumer mode, " do
     setup do
-      session_opts = [
-        store: :cookie,
-        key: "_test",
-        signing_salt: "cooldude"
+      oauth_consumer_strategies_path = [:auth, :oauth_consumer_strategies]
+      oauth_consumer_strategies = Pleroma.Config.get(oauth_consumer_strategies_path)
+      Pleroma.Config.put(oauth_consumer_strategies_path, ~w(twitter facebook))
+
+      on_exit(fn ->
+        Pleroma.Config.put(oauth_consumer_strategies_path, oauth_consumer_strategies)
+      end)
+
+      [
+        app: insert(:oauth_app),
+        conn:
+          build_conn()
+          |> Plug.Session.call(Plug.Session.init(@session_opts))
+          |> fetch_session()
       ]
+    end
+
+    test "GET /oauth/authorize renders auth forms, including OAuth consumer form", %{
+      app: app,
+      conn: conn
+    } do
+      conn =
+        get(
+          conn,
+          "/oauth/authorize",
+          %{
+            "response_type" => "code",
+            "client_id" => app.client_id,
+            "redirect_uri" => app.redirect_uris,
+            "scope" => "read"
+          }
+        )
+
+      assert response = html_response(conn, 200)
+      assert response =~ "Sign in with Twitter"
+      assert response =~ o_auth_path(conn, :prepare_request)
+    end
 
+    test "GET /oauth/prepare_request encodes parameters as `state` and redirects", %{
+      app: app,
+      conn: conn
+    } do
+      conn =
+        get(
+          conn,
+          "/oauth/prepare_request",
+          %{
+            "provider" => "twitter",
+            "scope" => "read follow",
+            "client_id" => app.client_id,
+            "redirect_uri" => app.redirect_uris,
+            "state" => "a_state"
+          }
+        )
+
+      assert response = html_response(conn, 302)
+
+      redirect_query = URI.parse(redirected_to(conn)).query
+      assert %{"state" => state_param} = URI.decode_query(redirect_query)
+      assert {:ok, state_components} = Poison.decode(state_param)
+
+      expected_client_id = app.client_id
+      expected_redirect_uri = app.redirect_uris
+
+      assert %{
+               "scope" => "read follow",
+               "client_id" => ^expected_client_id,
+               "redirect_uri" => ^expected_redirect_uri,
+               "state" => "a_state"
+             } = state_components
+    end
+
+    test "with user-bound registration, GET /oauth/<provider>/callback redirects to `redirect_uri` with `code`",
+         %{app: app, conn: conn} do
+      registration = insert(:registration)
+
+      state_params = %{
+        "scope" => Enum.join(app.scopes, " "),
+        "client_id" => app.client_id,
+        "redirect_uri" => app.redirect_uris,
+        "state" => ""
+      }
+
+      with_mock Pleroma.Web.Auth.Authenticator,
+        get_registration: fn _, _ -> {:ok, registration} end do
+        conn =
+          get(
+            conn,
+            "/oauth/twitter/callback",
+            %{
+              "oauth_token" => "G-5a3AAAAAAAwMH9AAABaektfSM",
+              "oauth_verifier" => "QZl8vUqNvXMTKpdmUnGejJxuHG75WWWs",
+              "provider" => "twitter",
+              "state" => Poison.encode!(state_params)
+            }
+          )
+
+        assert response = html_response(conn, 302)
+        assert redirected_to(conn) =~ ~r/#{app.redirect_uris}\?code=.+/
+      end
+    end
+
+    test "with user-unbound registration, GET /oauth/<provider>/callback renders registration_details page",
+         %{app: app, conn: conn} do
+      registration = insert(:registration, user: nil)
+
+      state_params = %{
+        "scope" => "read write",
+        "client_id" => app.client_id,
+        "redirect_uri" => app.redirect_uris,
+        "state" => "a_state"
+      }
+
+      with_mock Pleroma.Web.Auth.Authenticator,
+        get_registration: fn _, _ -> {:ok, registration} end do
+        conn =
+          get(
+            conn,
+            "/oauth/twitter/callback",
+            %{
+              "oauth_token" => "G-5a3AAAAAAAwMH9AAABaektfSM",
+              "oauth_verifier" => "QZl8vUqNvXMTKpdmUnGejJxuHG75WWWs",
+              "provider" => "twitter",
+              "state" => Poison.encode!(state_params)
+            }
+          )
+
+        assert response = html_response(conn, 200)
+        assert response =~ ~r/name="op" type="submit" value="register"/
+        assert response =~ ~r/name="op" type="submit" value="connect"/
+        assert response =~ Registration.email(registration)
+        assert response =~ Registration.nickname(registration)
+      end
+    end
+
+    test "on authentication error, GET /oauth/<provider>/callback redirects to `redirect_uri`", %{
+      app: app,
+      conn: conn
+    } do
+      state_params = %{
+        "scope" => Enum.join(app.scopes, " "),
+        "client_id" => app.client_id,
+        "redirect_uri" => app.redirect_uris,
+        "state" => ""
+      }
+
+      conn =
+        conn
+        |> assign(:ueberauth_failure, %{errors: [%{message: "(error description)"}]})
+        |> get(
+          "/oauth/twitter/callback",
+          %{
+            "oauth_token" => "G-5a3AAAAAAAwMH9AAABaektfSM",
+            "oauth_verifier" => "QZl8vUqNvXMTKpdmUnGejJxuHG75WWWs",
+            "provider" => "twitter",
+            "state" => Poison.encode!(state_params)
+          }
+        )
+
+      assert response = html_response(conn, 302)
+      assert redirected_to(conn) == app.redirect_uris
+      assert get_flash(conn, :error) == "Failed to authenticate: (error description)."
+    end
+
+    test "GET /oauth/registration_details renders registration details form", %{
+      app: app,
+      conn: conn
+    } do
+      conn =
+        get(
+          conn,
+          "/oauth/registration_details",
+          %{
+            "scopes" => app.scopes,
+            "client_id" => app.client_id,
+            "redirect_uri" => app.redirect_uris,
+            "state" => "a_state",
+            "nickname" => nil,
+            "email" => "john@doe.com"
+          }
+        )
+
+      assert response = html_response(conn, 200)
+      assert response =~ ~r/name="op" type="submit" value="register"/
+      assert response =~ ~r/name="op" type="submit" value="connect"/
+    end
+
+    test "with valid params, POST /oauth/register?op=register redirects to `redirect_uri` with `code`",
+         %{
+           app: app,
+           conn: conn
+         } do
+      registration = insert(:registration, user: nil, info: %{"nickname" => nil, "email" => nil})
+
+      conn =
+        conn
+        |> put_session(:registration_id, registration.id)
+        |> post(
+          "/oauth/register",
+          %{
+            "op" => "register",
+            "scopes" => app.scopes,
+            "client_id" => app.client_id,
+            "redirect_uri" => app.redirect_uris,
+            "state" => "a_state",
+            "nickname" => "availablenick",
+            "email" => "available@email.com"
+          }
+        )
+
+      assert response = html_response(conn, 302)
+      assert redirected_to(conn) =~ ~r/#{app.redirect_uris}\?code=.+/
+    end
+
+    test "with invalid params, POST /oauth/register?op=register renders registration_details page",
+         %{
+           app: app,
+           conn: conn
+         } do
+      another_user = insert(:user)
+      registration = insert(:registration, user: nil, info: %{"nickname" => nil, "email" => nil})
+
+      params = %{
+        "op" => "register",
+        "scopes" => app.scopes,
+        "client_id" => app.client_id,
+        "redirect_uri" => app.redirect_uris,
+        "state" => "a_state",
+        "nickname" => "availablenickname",
+        "email" => "available@email.com"
+      }
+
+      for {bad_param, bad_param_value} <-
+            [{"nickname", another_user.nickname}, {"email", another_user.email}] do
+        bad_params = Map.put(params, bad_param, bad_param_value)
+
+        conn =
+          conn
+          |> put_session(:registration_id, registration.id)
+          |> post("/oauth/register", bad_params)
+
+        assert html_response(conn, 403) =~ ~r/name="op" type="submit" value="register"/
+        assert get_flash(conn, :error) == "Error: #{bad_param} has already been taken."
+      end
+    end
+
+    test "with valid params, POST /oauth/register?op=connect redirects to `redirect_uri` with `code`",
+         %{
+           app: app,
+           conn: conn
+         } do
+      user = insert(:user, password_hash: Comeonin.Pbkdf2.hashpwsalt("testpassword"))
+      registration = insert(:registration, user: nil)
+
+      conn =
+        conn
+        |> put_session(:registration_id, registration.id)
+        |> post(
+          "/oauth/register",
+          %{
+            "op" => "connect",
+            "scopes" => app.scopes,
+            "client_id" => app.client_id,
+            "redirect_uri" => app.redirect_uris,
+            "state" => "a_state",
+            "auth_name" => user.nickname,
+            "password" => "testpassword"
+          }
+        )
+
+      assert response = html_response(conn, 302)
+      assert redirected_to(conn) =~ ~r/#{app.redirect_uris}\?code=.+/
+    end
+
+    test "with invalid params, POST /oauth/register?op=connect renders registration_details page",
+         %{
+           app: app,
+           conn: conn
+         } do
+      user = insert(:user)
+      registration = insert(:registration, user: nil)
+
+      params = %{
+        "op" => "connect",
+        "scopes" => app.scopes,
+        "client_id" => app.client_id,
+        "redirect_uri" => app.redirect_uris,
+        "state" => "a_state",
+        "auth_name" => user.nickname,
+        "password" => "wrong password"
+      }
+
+      conn =
+        conn
+        |> put_session(:registration_id, registration.id)
+        |> post("/oauth/register", params)
+
+      assert html_response(conn, 401) =~ ~r/name="op" type="submit" value="connect"/
+      assert get_flash(conn, :error) == "Invalid Username/Password"
+    end
+  end
+
+  describe "GET /oauth/authorize" do
+    setup do
       [
         app: insert(:oauth_app, redirect_uris: "https://redirect.url"),
         conn:
           build_conn()
-          |> Plug.Session.call(Plug.Session.init(session_opts))
+          |> Plug.Session.call(Plug.Session.init(@session_opts))
           |> fetch_session()
       ]
     end