Z.Crypto.OTP

One time password schemes are a user authentication method that relies on a fixed secret key which is used to derive a sequence of short passwords, each of which is accepted only once. Commonly this is used to implement two-factor authentication (2FA), where the user authenticates using both a conventional password (or a public key signature) and an OTP generated by a small device such as a mobile phone.

Botan implements the HOTP and TOTP schemes from RFC 4226 and 6238.

Since the range of possible OTPs is quite small, applications must rate limit OTP authentication attempts to some small number per second. Otherwise an attacker could quickly try all 1000000 6-digit OTPs in a brief amount of time.

HOTP

data HOTP

HOTP generates OTPs that are a short numeric sequence, between 6 and 8 digits (most applications use 6 digits), created using the HMAC of a 64-bit counter value. If the counter ever repeats the OTP will also repeat, thus both parties must assure the counter only increments and is never repeated or decremented. Thus both client and server must keep track of the next counter expected. Anyone with access to the client-specific secret key can authenticate as that client, so it should be treated with the same security consideration as would be given to any other symmetric key or plaintext password.

Instances

Show HOTP

Defined in Z.Crypto.OTP

Methods

showsPrec :: Int -> HOTP -> ShowS

show :: HOTP -> String

showList :: [HOTP] -> ShowS

Generic HOTP

Defined in Z.Crypto.OTP

Associated Types

type Rep HOTP :: Type -> Type

Methods

from :: HOTP -> Rep HOTP x

to :: Rep HOTP x -> HOTP

Print HOTP

Defined in Z.Crypto.OTP

Methods

toUTF8BuilderP :: Int -> HOTP -> Builder ()

type Rep HOTP

Defined in Z.Crypto.OTP

type Rep HOTP = D1 ('MetaData "HOTP" "Z.Crypto.OTP" "Z-Botan-0.3.0.0-A7CYDOzUZjP9PeT4WTwYc" 'True) (C1 ('MetaCons "HOTP" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 BotanStruct)))

newHOTP :: HasCallStack => Bytes -> OTPAlgo -> OTPDigitLen -> IO HOTP

genHOTP

Arguments

:: HasCallStack

=> HOTP

the HOTP object

-> Word64

HOTP counter

-> IO Word32

Generate a HOTP code for the provided counter.

checkHOTP

Arguments

:: HasCallStack

=> HOTP

the HOTP object

-> Word32

the presented HOTP code

-> Word64

the HOTP counter

-> Int

resync range

-> IO (Bool, Word64)

Verify a HOTP code.

TOTP

data TOTP

TOTP is based on the same algorithm as HOTP, but instead of a counter a timestamp is used.

Instances

Show TOTP

Defined in Z.Crypto.OTP

Methods

showsPrec :: Int -> TOTP -> ShowS

show :: TOTP -> String

showList :: [TOTP] -> ShowS

Generic TOTP

Defined in Z.Crypto.OTP

Associated Types

type Rep TOTP :: Type -> Type

Methods

from :: TOTP -> Rep TOTP x

to :: Rep TOTP x -> TOTP

Print TOTP

Defined in Z.Crypto.OTP

Methods

toUTF8BuilderP :: Int -> TOTP -> Builder ()

type Rep TOTP

Defined in Z.Crypto.OTP

type Rep TOTP = D1 ('MetaData "TOTP" "Z.Crypto.OTP" "Z-Botan-0.3.0.0-A7CYDOzUZjP9PeT4WTwYc" 'True) (C1 ('MetaCons "TOTP" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 BotanStruct)))

newTOTP :: HasCallStack => Bytes -> OTPAlgo -> OTPDigitLen -> Int -> IO TOTP

genTOTP

Arguments

:: HasCallStack

=> TOTP

the TOTP object

-> Word64

the current local timestamp

-> IO Word32

Generate a TOTP code for the provided timestamp.

checkTOTP

Arguments

:: HasCallStack

=> TOTP

the TOTP object

-> Word32

the presented OTP

-> Word64

timestamp the current local timestamp

-> Int

specifies the acceptable amount of clock drift (in terms of time steps) between the two hosts.

-> IO Bool

Verify a TOTP code.

constants

type OTPAlgo = HashType

pattern OTP_SHA1 :: OTPAlgo

pattern OTP_SHA256 :: OTPAlgo

pattern OTP_SHA512 :: OTPAlgo

type OTPDigitLen = Int

pattern OTP_DIGIT_6 :: OTPDigitLen

pattern OTP_DIGIT_7 :: OTPDigitLen

pattern OTP_DIGIT_8 :: OTPDigitLen