-- |
-- Module      : Crypto.PubKey.Rabin.OAEP
-- License     : BSD-style
-- Maintainer  : Carlos Rodriguez-Vega <crodveg@yahoo.es>
-- Stability   : experimental
-- Portability : unknown
--
-- OAEP padding scheme.
-- See <http://en.wikipedia.org/wiki/Optimal_asymmetric_encryption_padding>.
module Crypto.PubKey.Rabin.OAEP (
    OAEPParams (..),
    defaultOAEPParams,
    pad,
    unpad,
) where

import Data.Bits (complement, shiftR, xor, (.&.), (.|.))
import Data.ByteString (ByteString)
import qualified Data.ByteString as B
import qualified Data.List as L
import Data.Word (Word32)

import Crypto.Hash
import Crypto.Internal.ByteArray (ByteArray, ByteArrayAccess)
import qualified Crypto.Internal.ByteArray as B (constEq, convert)
import Crypto.PubKey.Internal (and')
import Crypto.PubKey.MaskGenFunction
import Crypto.PubKey.Rabin.Types

-- | Parameters for OAEP padding.
data OAEPParams hash seed output = OAEPParams
    { forall hash seed output. OAEPParams hash seed output -> hash
oaepHash :: hash
    -- ^ hash function to use
    , forall hash seed output.
OAEPParams hash seed output -> MaskGenAlgorithm seed output
oaepMaskGenAlg :: MaskGenAlgorithm seed output
    -- ^ mask Gen algorithm to use
    , forall hash seed output.
OAEPParams hash seed output -> Maybe ByteString
oaepLabel :: Maybe ByteString
    -- ^ optional label prepended to message
    }

-- | Default Params with a specified hash function.
defaultOAEPParams
    :: (ByteArrayAccess seed, ByteArray output, HashAlgorithm hash)
    => hash
    -> OAEPParams hash seed output
defaultOAEPParams :: forall seed output hash.
(ByteArrayAccess seed, ByteArray output, HashAlgorithm hash) =>
hash -> OAEPParams hash seed output
defaultOAEPParams hash
hashAlg =
    OAEPParams
        { oaepHash :: hash
oaepHash = hash
hashAlg
        , oaepMaskGenAlg :: MaskGenAlgorithm seed output
oaepMaskGenAlg = hash -> MaskGenAlgorithm seed output
forall seed output hashAlg.
(ByteArrayAccess seed, ByteArray output, HashAlgorithm hashAlg) =>
hashAlg -> seed -> Int -> output
mgf1 hash
hashAlg
        , oaepLabel :: Maybe ByteString
oaepLabel = Maybe ByteString
forall a. Maybe a
Nothing
        }

-- | Pad a message using OAEP.
pad
    :: HashAlgorithm hash
    => ByteString
    -- ^ Seed
    -> OAEPParams hash ByteString ByteString
    -- ^ OAEP params to use
    -> Int
    -- ^ size of public key in bytes
    -> ByteString
    -- ^ Message pad
    -> Either Error ByteString
pad :: forall hash.
HashAlgorithm hash =>
ByteString
-> OAEPParams hash ByteString ByteString
-> Int
-> ByteString
-> Either Error ByteString
pad ByteString
seed OAEPParams hash ByteString ByteString
oaep Int
k ByteString
msg
    | Int
k Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
< Int
2 Int -> Int -> Int
forall a. Num a => a -> a -> a
* Int
hashLen Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
2 = Error -> Either Error ByteString
forall a b. a -> Either a b
Left Error
InvalidParameters
    | ByteString -> Int
B.length ByteString
seed Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
/= Int
hashLen = Error -> Either Error ByteString
forall a b. a -> Either a b
Left Error
InvalidParameters
    | Int
mLen Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> Int
k Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
2 Int -> Int -> Int
forall a. Num a => a -> a -> a
* Int
hashLen Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
2 = Error -> Either Error ByteString
forall a b. a -> Either a b
Left Error
MessageTooLong
    | Bool
otherwise = ByteString -> Either Error ByteString
forall a b. b -> Either a b
Right ByteString
em
  where
    -- parameters
    mLen :: Int
mLen = ByteString -> Int
B.length ByteString
msg
    mgf :: MaskGenAlgorithm ByteString ByteString
mgf = OAEPParams hash ByteString ByteString
-> MaskGenAlgorithm ByteString ByteString
forall hash seed output.
OAEPParams hash seed output -> MaskGenAlgorithm seed output
oaepMaskGenAlg OAEPParams hash ByteString ByteString
oaep
    labelHash :: Digest hash
labelHash = hash -> ByteString -> Digest hash
forall ba alg.
(ByteArrayAccess ba, HashAlgorithm alg) =>
alg -> ba -> Digest alg
hashWith (OAEPParams hash ByteString ByteString -> hash
forall hash seed output. OAEPParams hash seed output -> hash
oaepHash OAEPParams hash ByteString ByteString
oaep) (ByteString
-> (ByteString -> ByteString) -> Maybe ByteString -> ByteString
forall b a. b -> (a -> b) -> Maybe a -> b
maybe ByteString
B.empty ByteString -> ByteString
forall a. a -> a
id (Maybe ByteString -> ByteString) -> Maybe ByteString -> ByteString
forall a b. (a -> b) -> a -> b
$ OAEPParams hash ByteString ByteString -> Maybe ByteString
forall hash seed output.
OAEPParams hash seed output -> Maybe ByteString
oaepLabel OAEPParams hash ByteString ByteString
oaep)
    hashLen :: Int
hashLen = hash -> Int
forall a. HashAlgorithm a => a -> Int
hashDigestSize (OAEPParams hash ByteString ByteString -> hash
forall hash seed output. OAEPParams hash seed output -> hash
oaepHash OAEPParams hash ByteString ByteString
oaep)
    -- put fields
    ps :: ByteString
ps = Int -> Word8 -> ByteString
B.replicate (Int
k Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
mLen Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
2 Int -> Int -> Int
forall a. Num a => a -> a -> a
* Int
hashLen Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
2) Word8
0
    db :: ByteString
db = [ByteString] -> ByteString
B.concat [Digest hash -> ByteString
forall bin bout.
(ByteArrayAccess bin, ByteArray bout) =>
bin -> bout
B.convert Digest hash
labelHash, ByteString
ps, Word8 -> ByteString
B.singleton Word8
0x1, ByteString
msg]
    dbmask :: ByteString
dbmask = MaskGenAlgorithm ByteString ByteString
mgf ByteString
seed (Int
k Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
hashLen Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
1)
    maskedDB :: ByteString
maskedDB = [Word8] -> ByteString
B.pack ([Word8] -> ByteString) -> [Word8] -> ByteString
forall a b. (a -> b) -> a -> b
$ (Word8 -> Word8 -> Word8) -> ByteString -> ByteString -> [Word8]
forall a. (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
B.zipWith Word8 -> Word8 -> Word8
forall a. Bits a => a -> a -> a
xor ByteString
db ByteString
dbmask
    seedMask :: ByteString
seedMask = MaskGenAlgorithm ByteString ByteString
mgf ByteString
maskedDB Int
hashLen
    maskedSeed :: ByteString
maskedSeed = [Word8] -> ByteString
B.pack ([Word8] -> ByteString) -> [Word8] -> ByteString
forall a b. (a -> b) -> a -> b
$ (Word8 -> Word8 -> Word8) -> ByteString -> ByteString -> [Word8]
forall a. (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
B.zipWith Word8 -> Word8 -> Word8
forall a. Bits a => a -> a -> a
xor ByteString
seed ByteString
seedMask
    em :: ByteString
em = [ByteString] -> ByteString
B.concat [Word8 -> ByteString
B.singleton Word8
0x0, ByteString
maskedSeed, ByteString
maskedDB]

-- | Un-pad a OAEP encoded message.
--
-- The data block is scanned in full rather than up to the 01 octet separating
-- the padding from the message, and the label hash and the leading octet are
-- compared without an early exit, so neither the length of the padding nor
-- where a comparison first differs shows up in how long this takes.  This is
-- what "Crypto.PubKey.RSA.OAEP" does with the same block.
--
-- What remains visible is the result itself: whether the block was well formed,
-- and the length of the message when it was.  That is the signal Manger's
-- attack needs, so a caller that decrypts attacker-supplied ciphertext must not
-- pass the distinction on.
unpad
    :: HashAlgorithm hash
    => OAEPParams hash ByteString ByteString
    -- ^ OAEP params to use
    -> Int
    -- ^ size of public key in bytes
    -> ByteString
    -- ^ encoded message (not encrypted)
    -> Either Error ByteString
unpad :: forall hash.
HashAlgorithm hash =>
OAEPParams hash ByteString ByteString
-> Int -> ByteString -> Either Error ByteString
unpad OAEPParams hash ByteString ByteString
oaep Int
k ByteString
em
    | Bool
paddingSuccess = ByteString -> Either Error ByteString
forall a b. b -> Either a b
Right ByteString
msg
    | Bool
otherwise = Error -> Either Error ByteString
forall a b. a -> Either a b
Left Error
MessageNotRecognized
  where
    -- parameters
    mgf :: MaskGenAlgorithm ByteString ByteString
mgf = OAEPParams hash ByteString ByteString
-> MaskGenAlgorithm ByteString ByteString
forall hash seed output.
OAEPParams hash seed output -> MaskGenAlgorithm seed output
oaepMaskGenAlg OAEPParams hash ByteString ByteString
oaep
    labelHash :: ByteString
labelHash =
        Digest hash -> ByteString
forall bin bout.
(ByteArrayAccess bin, ByteArray bout) =>
bin -> bout
B.convert (Digest hash -> ByteString) -> Digest hash -> ByteString
forall a b. (a -> b) -> a -> b
$ hash -> ByteString -> Digest hash
forall ba alg.
(ByteArrayAccess ba, HashAlgorithm alg) =>
alg -> ba -> Digest alg
hashWith (OAEPParams hash ByteString ByteString -> hash
forall hash seed output. OAEPParams hash seed output -> hash
oaepHash OAEPParams hash ByteString ByteString
oaep) (ByteString
-> (ByteString -> ByteString) -> Maybe ByteString -> ByteString
forall b a. b -> (a -> b) -> Maybe a -> b
maybe ByteString
B.empty ByteString -> ByteString
forall a. a -> a
id (Maybe ByteString -> ByteString) -> Maybe ByteString -> ByteString
forall a b. (a -> b) -> a -> b
$ OAEPParams hash ByteString ByteString -> Maybe ByteString
forall hash seed output.
OAEPParams hash seed output -> Maybe ByteString
oaepLabel OAEPParams hash ByteString ByteString
oaep)
            :: ByteString
    hashLen :: Int
hashLen = hash -> Int
forall a. HashAlgorithm a => a -> Int
hashDigestSize (OAEPParams hash ByteString ByteString -> hash
forall hash seed output. OAEPParams hash seed output -> hash
oaepHash OAEPParams hash ByteString ByteString
oaep)
    -- getting em's fields
    (ByteString
pb, ByteString
em0) = Int -> ByteString -> (ByteString, ByteString)
B.splitAt Int
1 ByteString
em
    (ByteString
maskedSeed, ByteString
maskedDB) = Int -> ByteString -> (ByteString, ByteString)
B.splitAt Int
hashLen ByteString
em0
    seedMask :: ByteString
seedMask = MaskGenAlgorithm ByteString ByteString
mgf ByteString
maskedDB Int
hashLen
    seed :: ByteString
seed = [Word8] -> ByteString
B.pack ([Word8] -> ByteString) -> [Word8] -> ByteString
forall a b. (a -> b) -> a -> b
$ (Word8 -> Word8 -> Word8) -> ByteString -> ByteString -> [Word8]
forall a. (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
B.zipWith Word8 -> Word8 -> Word8
forall a. Bits a => a -> a -> a
xor ByteString
maskedSeed ByteString
seedMask
    dbmask :: ByteString
dbmask = MaskGenAlgorithm ByteString ByteString
mgf ByteString
seed (Int
k Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
hashLen Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
1)
    db :: ByteString
db = [Word8] -> ByteString
B.pack ([Word8] -> ByteString) -> [Word8] -> ByteString
forall a b. (a -> b) -> a -> b
$ (Word8 -> Word8 -> Word8) -> ByteString -> ByteString -> [Word8]
forall a. (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
B.zipWith Word8 -> Word8 -> Word8
forall a. Bits a => a -> a -> a
xor ByteString
maskedDB ByteString
dbmask
    -- getting db's fields
    (ByteString
labelHash', ByteString
db1) = Int -> ByteString -> (ByteString, ByteString)
B.splitAt Int
hashLen ByteString
db

    -- index of the first nonzero octet in db1, or its length when every octet
    -- is zero; all of them are looked at either way
    oneIndex :: Word32
oneIndex =
        (Word32, Word32) -> Word32
forall a b. (a, b) -> a
fst ((Word32, Word32) -> Word32) -> (Word32, Word32) -> Word32
forall a b. (a -> b) -> a -> b
$
            ((Word32, Word32) -> (Word32, Word8) -> (Word32, Word32))
-> (Word32, Word32) -> [(Word32, Word8)] -> (Word32, Word32)
forall b a. (b -> a -> b) -> b -> [a] -> b
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
L.foldl'
                (Word32, Word32) -> (Word32, Word8) -> (Word32, Word32)
forall {b}.
Integral b =>
(Word32, Word32) -> (Word32, b) -> (Word32, Word32)
step
                (Int -> Word32
forall a b. (Integral a, Num b) => a -> b
fromIntegral (ByteString -> Int
B.length ByteString
db1) :: Word32, Word32
1 :: Word32)
                ([Word32] -> [Word8] -> [(Word32, Word8)]
forall a b. [a] -> [b] -> [(a, b)]
zip [Word32
0 ..] (ByteString -> [Word8]
B.unpack ByteString
db1))
    step :: (Word32, Word32) -> (Word32, b) -> (Word32, Word32)
step (Word32
idx, Word32
unseen) (Word32
i, b
b) = (Word32 -> Word32 -> Word32 -> Word32
forall {a}. Bits a => a -> a -> a -> a
select Word32
found Word32
i Word32
idx, Word32
unseen Word32 -> Word32 -> Word32
forall a. Bits a => a -> a -> a
.&. Word32 -> Word32
forall a. Bits a => a -> a
complement Word32
found)
      where
        w :: Word32
w = b -> Word32
forall a b. (Integral a, Num b) => a -> b
fromIntegral b
b :: Word32
        -- 0 when b is zero, 1 otherwise
        nonZero :: Word32
nonZero = (Word32
w Word32 -> Word32 -> Word32
forall a. Bits a => a -> a -> a
.|. Word32 -> Word32
forall a. Num a => a -> a
negate Word32
w) Word32 -> Int -> Word32
forall a. Bits a => a -> Int -> a
`shiftR` Int
31
        -- all ones at the first nonzero octet only
        found :: Word32
found = Word32 -> Word32
forall a. Num a => a -> a
negate (Word32
unseen Word32 -> Word32 -> Word32
forall a. Bits a => a -> a -> a
.&. Word32
nonZero)
    select :: a -> a -> a -> a
select a
mask a
a a
b = (a
a a -> a -> a
forall a. Bits a => a -> a -> a
.&. a
mask) a -> a -> a
forall a. Bits a => a -> a -> a
.|. (a
b a -> a -> a
forall a. Bits a => a -> a -> a
.&. a -> a
forall a. Bits a => a -> a
complement a
mask)

    ps1 :: ByteString
ps1 = Int -> ByteString -> ByteString
B.take Int
1 (ByteString -> ByteString) -> ByteString -> ByteString
forall a b. (a -> b) -> a -> b
$ Int -> ByteString -> ByteString
B.drop (Word32 -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral Word32
oneIndex) ByteString
db1
    msg :: ByteString
msg = Int -> ByteString -> ByteString
B.drop (Word32 -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral Word32
oneIndex Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1) ByteString
db1

    paddingSuccess :: Bool
paddingSuccess =
        [Bool] -> Bool
and'
            [ ByteString
labelHash' ByteString -> ByteString -> Bool
forall bs1 bs2.
(ByteArrayAccess bs1, ByteArrayAccess bs2) =>
bs1 -> bs2 -> Bool
`B.constEq` ByteString
labelHash
            , ByteString
ps1 ByteString -> ByteString -> Bool
forall bs1 bs2.
(ByteArrayAccess bs1, ByteArrayAccess bs2) =>
bs1 -> bs2 -> Bool
`B.constEq` Int -> Word8 -> ByteString
B.replicate Int
1 Word8
0x1
            , ByteString
pb ByteString -> ByteString -> Bool
forall bs1 bs2.
(ByteArrayAccess bs1, ByteArrayAccess bs2) =>
bs1 -> bs2 -> Bool
`B.constEq` Int -> Word8 -> ByteString
B.replicate Int
1 Word8
0x0
            ]