Doorkeeper integration

1 files changed, 175 insertions, 0 deletions

diff --git a/lib/api/api_guard.rb b/lib/api/api_guard.rb
new file mode 100644
index 00000000000..23975518181
--- /dev/null
+++ b/lib/api/api_guard.rb
@@ -0,0 +1,175 @@
+# Guard API with OAuth 2.0 Access Token
+
+require 'rack/oauth2'
+
+module APIGuard
+  extend ActiveSupport::Concern
+
+  included do |base|
+    # OAuth2 Resource Server Authentication
+    use Rack::OAuth2::Server::Resource::Bearer, 'The API' do |request|
+      # The authenticator only fetches the raw token string
+
+      # Must yield access token to store it in the env
+      request.access_token
+    end
+
+    helpers HelperMethods
+
+    install_error_responders(base)
+  end
+
+  # Helper Methods for Grape Endpoint
+  module HelperMethods
+    # Invokes the doorkeeper guard.
+    #
+    # If token is presented and valid, then it sets @current_user.
+    #
+    # If the token does not have sufficient scopes to cover the requred scopes,
+    # then it raises InsufficientScopeError.
+    #
+    # If the token is expired, then it raises ExpiredError.
+    #
+    # If the token is revoked, then it raises RevokedError.
+    #
+    # If the token is not found (nil), then it raises TokenNotFoundError.
+    #
+    # Arguments:
+    #
+    #   scopes: (optional) scopes required for this guard.
+    #           Defaults to empty array.
+    #
+    def doorkeeper_guard!(scopes: [])
+      if (access_token = find_access_token).nil?
+        raise TokenNotFoundError
+
+      else
+        case validate_access_token(access_token, scopes)
+        when Oauth2::AccessTokenValidationService::INSUFFICIENT_SCOPE
+          raise InsufficientScopeError.new(scopes)
+
+        when Oauth2::AccessTokenValidationService::EXPIRED
+          raise ExpiredError
+
+        when Oauth2::AccessTokenValidationService::REVOKED
+          raise RevokedError
+
+        when Oauth2::AccessTokenValidationService::VALID
+          @current_user = User.find(access_token.resource_owner_id)
+
+        end
+      end
+    end
+
+    def doorkeeper_guard(scopes: [])
+      if access_token = find_access_token
+        case validate_access_token(access_token, scopes)
+        when Oauth2::AccessTokenValidationService::INSUFFICIENT_SCOPE
+          raise InsufficientScopeError.new(scopes)
+
+        when Oauth2::AccessTokenValidationService::EXPIRED
+          raise ExpiredError
+
+        when Oauth2::AccessTokenValidationService::REVOKED
+          raise RevokedError
+
+        when Oauth2::AccessTokenValidationService::VALID
+          @current_user = User.find(access_token.resource_owner_id)
+        end
+      end
+    end
+
+    def current_user
+      @current_user
+    end
+
+    private
+    def find_access_token
+      @access_token ||= Doorkeeper.authenticate(doorkeeper_request, Doorkeeper.configuration.access_token_methods)
+    end
+
+    def doorkeeper_request
+      @doorkeeper_request ||= ActionDispatch::Request.new(env)
+    end
+
+    def validate_access_token(access_token, scopes)
+      Oauth2::AccessTokenValidationService.validate(access_token, scopes: scopes)
+    end
+  end
+
+  module ClassMethods
+    # Installs the doorkeeper guard on the whole Grape API endpoint.
+    #
+    # Arguments:
+    #
+    #   scopes: (optional) scopes required for this guard.
+    #           Defaults to empty array.
+    #
+    def guard_all!(scopes: [])
+      before do
+        guard! scopes: scopes
+      end
+    end
+
+    private
+    def install_error_responders(base)
+      error_classes = [ MissingTokenError, TokenNotFoundError,
+                        ExpiredError, RevokedError, InsufficientScopeError]
+
+      base.send :rescue_from, *error_classes, oauth2_bearer_token_error_handler
+    end
+
+    def oauth2_bearer_token_error_handler
+      Proc.new {|e|
+        response = case e
+          when MissingTokenError
+            Rack::OAuth2::Server::Resource::Bearer::Unauthorized.new
+
+          when TokenNotFoundError
+            Rack::OAuth2::Server::Resource::Bearer::Unauthorized.new(
+              :invalid_token,
+              "Bad Access Token.")
+
+          when ExpiredError
+            Rack::OAuth2::Server::Resource::Bearer::Unauthorized.new(
+              :invalid_token,
+              "Token is expired. You can either do re-authorization or token refresh.")
+
+          when RevokedError
+            Rack::OAuth2::Server::Resource::Bearer::Unauthorized.new(
+              :invalid_token,
+              "Token was revoked. You have to re-authorize from the user.")
+
+          when InsufficientScopeError
+            # FIXME: ForbiddenError (inherited from Bearer::Forbidden of Rack::Oauth2)
+            # does not include WWW-Authenticate header, which breaks the standard.
+            Rack::OAuth2::Server::Resource::Bearer::Forbidden.new(
+              :insufficient_scope,
+              Rack::OAuth2::Server::Resource::ErrorMethods::DEFAULT_DESCRIPTION[:insufficient_scope],
+              { :scope => e.scopes})
+          end
+
+        response.finish
+      }
+    end
+  end
+
+  #
+  # Exceptions
+  #
+
+  class MissingTokenError < StandardError; end
+
+  class TokenNotFoundError < StandardError; end
+
+  class ExpiredError < StandardError; end
+
+  class RevokedError < StandardError; end
+
+  class InsufficientScopeError < StandardError
+    attr_reader :scopes
+    def initialize(scopes)
+      @scopes = scopes
+    end
+  end
+end
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