Hails.HttpServer

This module exports the core of the Hails HTTP server. Specifically it defines basic types, such as HTTP Request and Response, used by the Hails web server and untrusted Hails Applications.

At a high level, a Hails Application, is a function from Request to Response in the DC monad. Every application response is sanitized and sanity checked with the secureApplication Middleware.

Hails uses Wai, and as such we provide two functions for converting Hails Applications to Wai Applicatoins: ' devHailsApplication used to execute Hails apps in development mode, and hailsApplicationToWai that should be used in production with an authentication service from Hails.HttpServer.Auth.

Documentation

module Hails.HttpServer.Types

Execute Hails application in development mode

devHailsApplication :: Application -> Application

A default Hails handler for development environments. Safely runs a Hails Application, using basic HTTP authentication for authenticating users. Note: authentication will accept any username/password pair, it is solely used to set the user-name.

Execute Hails application

hailsApplicationToWai :: Application -> Application

Safely wraps a Hails Application in a Wai Application that can be run by an application server. The application is executed with the secureApplication Middleware. The function returns status 500 if the Hails application throws an exception and the label of the exception flows to the browser label (see browserLabelGuard); if the label does not flow, it responds with a 403.

All applications serve static content from a "static" directory.

Middleware used by Hails

browserLabelGuard :: Middleware

Hails Middleware that ensures the Response from the application is readable by the client's browser (as determined by the result label of the app computation and the label of the browser). If the response is not readable by the browser, the middleware sends a 403 (unauthorized) response instead.

guardSensitiveResp :: Middleware

Adds the header X-Hails-Label to the response. If the label of the computation does not flow to the public label, dcPub, the JSON field isPublic is set to true, otherwise it is set to true and the JSON label is set to the secrecy component of the response label (if it is a disjunction of principals is added). An example may be:

 X-Hails-Label = { isPublic: true }

or

 X-Hails-Label = { isPublic: false, label : ["http://google.com:80", "alice"] }

sanitizeResp :: Middleware

Remove anything from the response that could cause inadvertant declasification. Currently this only removes the Set-Cookie header.

catchAllExceptions :: Middleware

Catch all exceptions thrown by middleware and return 500.

Network types

module Network.HTTP.Types