Snap.Snaplet.Auth

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.

Higher Level Handler Functions

createUser

Arguments

:: Text

Username

-> ByteString

Password

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

Create a new user from just a username and password

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) (Either AuthFailure AuthUser)

Create or update a given user

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

Destroy the given user

loginByUsername

Arguments

:: Text

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) (Either AuthFailure 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 ())

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) (Either AuthFailure AuthUser)

Mutate an AuthUser, marking successful authentication

This will save the user to the backend.

markAuthFail :: AuthUser -> Handler b (AuthManager b) (Either AuthFailure 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 :: SnapletLens b 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

IAuthBackend (AuthManager b)

class IAuthBackend r where

All storage backends need to implement this typeclass

Methods

save :: r -> AuthUser -> IO (Either AuthFailure AuthUser)

Create or update the given AuthUser record. A userId of Nothing indicates that a new user should be created, otherwise the user information for that userId should be updated.

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

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

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

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

Instances

IAuthBackend (AuthManager b)

data AuthSettings

Authentication 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"

data AuthUser

Type representing the concept of a User in your application.

Constructors

AuthUser

Fields

userId :: Maybe UserId

userLogin :: Text

userEmail :: Maybe Text

userPassword :: Maybe Password

userActivatedAt :: Maybe UTCTime

userSuspendedAt :: Maybe UTCTime

userRememberToken :: Maybe Text

userLoginCount :: Int

userFailedLoginCount :: Int

userLockedOutUntil :: Maybe UTCTime

userCurrentLoginAt :: Maybe UTCTime

userLastLoginAt :: Maybe UTCTime

userCurrentLoginIp :: Maybe ByteString

userLastLoginIp :: Maybe ByteString

userCreatedAt :: Maybe UTCTime

userUpdatedAt :: Maybe UTCTime

userResetToken :: Maybe Text

userResetRequestedAt :: Maybe UTCTime

userRoles :: [Role]

userMeta :: HashMap Text Value

Instances

Eq AuthUser

Show AuthUser

ToJSON AuthUser

FromJSON AuthUser

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

Instances

Eq UserId

Ord UserId

Read UserId

Show UserId

ToJSON UserId

FromJSON UserId

Hashable UserId

data Password

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

Constructors

ClearText ByteString

Encrypted ByteString

Instances

Eq Password

Ord Password

Read Password

Show Password

ToJSON Password

FromJSON Password

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

AuthError String

BackendError

DuplicateLogin

EncryptedPassword

IncorrectPassword

LockedOut UTCTime

Locked out until given time

PasswordMissing

UsernameMissing

UserNotFound

Instances

Eq AuthFailure

Ord AuthFailure

Read AuthFailure

Show AuthFailure

Typeable * AuthFailure

data Role

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

Constructors

Role ByteString

Instances

Eq Role

Ord Role

Read Role

Show Role

ToJSON Role

FromJSON Role

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.

checkPassword :: Password -> Password -> Bool

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) (Either AuthFailure 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

To make your users stay logged in for longer than the session replay prevention timeout, you must pass a field name as the third parameter and that field must be set to a value of "1" by the submitting form. This lets you use a user selectable check box. Or if you want user remembering always turned on, you can use a hidden form field.

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

:: SnapletLens b (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.

setPasswordResetToken :: Text -> Handler b (AuthManager b) (Maybe Text)

This function generates a random password reset token and stores it in the database for the user. Call this function when a user forgets their password. Then use the token to autogenerate a link that the user can visit to reset their password. This function also sets a timestamp so the reset token can be expired.

clearPasswordResetToken :: Text -> Handler b (AuthManager b) Bool

Clears a user's password reset token. Call this when the user successfully changes their password to ensure that the password reset link cannot be used again.

Splice helpers

addAuthSplices

Arguments

:: HasHeist b

=> Snaplet (Heist b)

-> SnapletLens b (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> <loggedInUser>

compiledAuthSplices :: SnapletLens b (AuthManager b) -> Splices (SnapletCSplice b)

List containing compiled splices for ifLoggedIn, ifLoggedOut, and loggedInUser.

userCSplices :: Monad m => Splices (RuntimeSplice m AuthUser -> Splice m)

Compiled splices for AuthUser.

userISplices :: Monad m => AuthUser -> Splices (Splice m)

Function to generate interpreted splices from an AuthUser.

ifLoggedIn :: SnapletLens b (AuthManager b) -> SnapletISplice b

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 :: SnapletLens b (AuthManager b) -> SnapletISplice b

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 :: SnapletLens b (AuthManager b) -> SnapletISplice b

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