snap-0.9.0.1: Snap: A Haskell Web Framework: project starter executable and glue code library

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Snap.Snaplet.Auth

Contents

Description

This module contains all the central authentication functionality.

It exports a number of high-level functions to be used directly in your application handlers.

We also export a number of mid-level functions that should be helpful when you are integrating with another way of confirming the authentication of login requests.

Synopsis

Higher Level Handler Functions

createUser

Arguments

:: Text

Username

-> ByteString

Password

-> Handler b (AuthManager b) AuthUser 

Create a new user from just a username and password

May throw a DuplicateLogin if given username is not unique.

usernameExists

Arguments

:: Text

The username to be checked

-> Handler b (AuthManager b) Bool 

Check whether a user with the given username exists.

saveUser :: AuthUser -> Handler b (AuthManager b) AuthUser

Create or update a given user

May throw a BackendError if something goes wrong.

destroyUser :: AuthUser -> Handler b (AuthManager b) ()

Destroy the given user

May throw a BackendError if something goes wrong.

loginByUsername

Arguments

:: ByteString

Username/login for user

-> Password

Should be ClearText

-> Bool

Set remember token?

-> Handler b (AuthManager b) (Either AuthFailure AuthUser) 

Lookup a user by her username, check given password and perform login

loginByRememberToken :: Handler b (AuthManager b) (Maybe AuthUser)

Remember user from the remember token if possible and perform login

forceLogin

Arguments

:: AuthUser

An existing user, somehow looked up from db

-> Handler b (AuthManager b) (Either AuthFailure AuthUser) 

Login and persist the given AuthUser in the active session

Meant to be used if you have other means of being sure that the person is who she says she is.

logout :: Handler b (AuthManager b) ()

Logout the active user

currentUser :: Handler b (AuthManager b) (Maybe AuthUser)

Return the current user; trying to remember from cookie if possible.

isLoggedIn :: Handler b (AuthManager b) Bool

Convenience wrapper around rememberUser that returns a bool result

Lower Level Functions

markAuthSuccess :: AuthUser -> Handler b (AuthManager b) AuthUser

Mutate an AuthUser, marking successful authentication

This will save the user to the backend.

markAuthFail :: AuthUser -> Handler b (AuthManager b) AuthUser

Mutate an AuthUser, marking failed authentication

This will save the user to the backend.

checkPasswordAndLogin

Arguments

:: AuthUser

An existing user, somehow looked up from db

-> Password

A ClearText password

-> Handler b (AuthManager b) (Either AuthFailure AuthUser) 

Authenticate and log the user into the current session if successful.

This is a mid-level function exposed to allow roll-your-own ways of looking up a user from the database.

This function will:

  1. Check the password
  2. Login the user into the current session
  3. Mark success/failure of the authentication trial on the user record

Types

data AuthManager b

Abstract data type holding all necessary information for auth operation

Constructors

forall r . IAuthBackend r => AuthManager 

Fields

backend :: r

Storage back-end

session :: Lens b (Snaplet SessionManager)

A lens pointer to a SessionManager

activeUser :: Maybe AuthUser

A per-request logged-in user cache

minPasswdLen :: Int

Password length range

rememberCookieName :: ByteString

Cookie name for the remember token

rememberPeriod :: Maybe Int

Remember period in seconds. Defaults to 2 weeks.

siteKey :: Key

A unique encryption key used to encrypt remember cookie

lockout :: Maybe (Int, NominalDiffTime)

Lockout after x tries, re-allow entry after y seconds

randomNumberGenerator :: RNG

Random number generator

Instances

class IAuthBackend r where

All storage backends need to implement this typeclass

Backend operations may throw BackendErrors

Methods

save :: r -> AuthUser -> IO AuthUser

Create or update the given AuthUser record. If the userId in the AuthUser already exists in the database, then that user's information should be updated. If it does not exist, then a new user should be created.

lookupByUserId :: r -> UserId -> IO (Maybe AuthUser)

lookupByLogin :: r -> Text -> IO (Maybe AuthUser)

lookupByRememberToken :: r -> Text -> IO (Maybe AuthUser)

destroy :: r -> AuthUser -> IO ()

Instances

IAuthBackend JsonFileAuthManager 
IAuthBackend (AuthManager b) 

data AuthSettings

Authetication settings defined at initialization time

Constructors

AuthSettings 

Fields

asMinPasswdLen :: Int

Currently not used/checked

asRememberCookieName :: ByteString

Name of the desired remember cookie

asRememberPeriod :: Maybe Int

How long to remember when the option is used in rest of the API. Nothing means remember until end of session.

asLockout :: Maybe (Int, NominalDiffTime)

Lockout strategy: ([MaxAttempts], [LockoutDuration])

asSiteKey :: FilePath

Location of app's encryption key

defAuthSettings :: AuthSettings

Default settings for Auth.

 asMinPasswdLen = 8
 asRememberCookieName = "_remember"
 asRememberPeriod = Just (2*7*24*60*60) = 2 weeks
 asLockout = Nothing
 asSiteKey = "site_key.txt"

defAuthUser :: AuthUser

Default AuthUser that has all empty values.

newtype UserId

Internal representation of a User. By convention, we demand that the application is able to directly fetch a User using this identifier.

Think of this type as a secure, authenticated user. You should normally never see this type unless a user has been authenticated.

Constructors

UserId 

Fields

unUid :: Text
 

data Password

Password is clear when supplied by the user and encrypted later when returned from the db.

data AuthFailure

Authentication failures indicate what went wrong during authentication. They may provide useful information to the developer, although it is generally not advisable to show the user the exact details about why login failed.

Constructors

UserNotFound 
IncorrectPassword 
PasswordMissing 
LockedOut UTCTime

Locked out until given time

AuthError String 

data Role

This will be replaced by a role-based permission system.

Constructors

Role ByteString 

Other Utilities

authSettingsFromConfig :: Initializer b v AuthSettings

Function to get auth settings from a config file. This function can be used by the authors of auth snaplet backends in the initializer to let the user configure the auth snaplet from a config file. All options are optional and default to what's in defAuthSettings if not supplied. Here's what the default options would look like in the config file:

 minPasswordLen = 8
 rememberCookie = "_remember"
 rememberPeriod = 1209600 # 2 weeks
 lockout = [5, 86400] # 5 attempts locks you out for 86400 seconds
 siteKey = "site_key.txt"

withBackend

Arguments

:: (forall r. IAuthBackend r => r -> Handler b (AuthManager v) a)

The function to run with the handler.

-> Handler b (AuthManager v) a 

Run a function on the backend, and return the result.

This uses an existential type so that the backend type doesn't escape AuthManager. The reason that the type is Handler b (AuthManager v) a and not a is because anything that uses the backend will return an IO something, which you can liftIO, or a Handler b (AuthManager v) a if it uses other handler things.

encryptPassword :: Password -> IO Password

Turn a ClearText password into an Encrypted password, ready to be stuffed into a database.

authenticatePassword

Arguments

:: AuthUser

Looked up from the back-end

-> Password

Check against this password

-> Maybe AuthFailure 

Check password for a given user.

Returns Nothing if check is successful and an IncorrectPassword error otherwise

setPassword :: AuthUser -> ByteString -> IO AuthUser

Set a new password for the given user. Given password should be clear-text; it will be encrypted into a Encrypted.

encrypt :: ByteString -> IO ByteString

The underlying encryption function, in case you need it for external processing.

verify

Arguments

:: ByteString

Cleartext

-> ByteString

Encrypted reference

-> Bool 

The underlying verify function, in case you need it for external processing.

Handlers

registerUser

Arguments

:: ByteString

Login field

-> ByteString

Password field

-> Handler b (AuthManager b) AuthUser 

Register a new user by specifying login and password Param fields

loginUser

Arguments

:: ByteString

Username field

-> ByteString

Password field

-> Maybe ByteString

Remember field; Nothing if you want no remember function.

-> (AuthFailure -> Handler b (AuthManager b) ())

Upon failure

-> Handler b (AuthManager b) ()

Upon success

-> Handler b (AuthManager b) () 

A MonadSnap handler that processes a login form.

The request paremeters are passed to performLogin

logoutUser

Arguments

:: Handler b (AuthManager b) ()

What to do after logging out

-> Handler b (AuthManager b) () 

Simple handler to log the user out. Deletes user from session.

requireUser

Arguments

:: Lens b (Snaplet (AuthManager b))

Lens reference to an AuthManager

-> Handler b v a

Do this if no authenticated user is present.

-> Handler b v a

Do this if an authenticated user is present.

-> Handler b v a 

Require that an authenticated AuthUser is present in the current session.

This function has no DB cost - only checks to see if a user_id is present in the current session.

Splice helpers

addAuthSplices

Arguments

:: HasHeist b 
=> Lens b (Snaplet (AuthManager b))

A lens reference to AuthManager

-> Initializer b v () 

Add all standard auth splices to a Heist-enabled application.

This adds the following splices: <ifLoggedIn> <ifLoggedOut>

ifLoggedIn :: Lens b (Snaplet (AuthManager b)) -> SnapletSplice b v

A splice that can be used to check for existence of a user. If a user is present, this will run the contents of the node.

 <ifLoggedIn> Show this when there is a logged in user </ifLoggedIn>

ifLoggedOut :: Lens b (Snaplet (AuthManager b)) -> SnapletSplice b v

A splice that can be used to check for absence of a user. If a user is not present, this will run the contents of the node.

 <ifLoggedOut> Show this when there is a logged in user </ifLoggedOut>

loggedInUser :: Lens b (Snaplet (AuthManager b)) -> SnapletSplice b v

A splice that will simply print the current user's login, if there is one.