module Codec.Encryption.OpenPGP.Internal (
countBits
, PktStreamContext(..)
, issuer
, emptyPSC
, pubkeyToMPIs
, multiplicativeInverse
, sigType
, sigPKA
, sigHA
, sigCT
, truncatingVerify
) where
import Crypto.Hash (hashWith)
import qualified Crypto.Hash.IO as CHI
import Crypto.Number.Basic (numBits)
import Crypto.Number.ModArithmetic (expFast, inverse)
import Crypto.Number.Serialize (os2ip)
import qualified Crypto.PubKey.DSA as DSA
import qualified Crypto.PubKey.RSA as RSA
import Data.Bits (testBit)
import Data.ByteArray (ByteArrayAccess)
import qualified Data.ByteArray as BA
import qualified Data.ByteString as B
import Data.ByteString.Lazy (ByteString)
import qualified Data.ByteString.Lazy as BL
import Data.List (find)
import Data.Maybe (fromJust)
import Data.Word (Word8, Word16)
import Codec.Encryption.OpenPGP.Types
import Codec.Encryption.OpenPGP.Ontology (isIssuerSSP, isSigCreationTime)
countBits :: ByteString -> Word16
countBits bs
| BL.null bs = 0
| otherwise = fromIntegral (BL.length bs * 8) fromIntegral (go (BL.head bs) 7)
where
go :: Word8 -> Int -> Word8
go _ 0 = 7
go n b = if testBit n b then 7 fromIntegral b else go n (b1)
data PktStreamContext = PktStreamContext { lastLD :: Pkt
, lastUIDorUAt :: Pkt
, lastSig :: Pkt
, lastPrimaryKey :: Pkt
, lastSubkey :: Pkt
}
emptyPSC :: PktStreamContext
emptyPSC = PktStreamContext (OtherPacketPkt 0 "lastLD placeholder") (OtherPacketPkt 0 "lastUIDorUAt placeholder") (OtherPacketPkt 0 "lastSig placeholder") (OtherPacketPkt 0 "lastPrimaryKey placeholder") (OtherPacketPkt 0 "lastSubkey placeholder")
issuer :: Pkt -> Maybe EightOctetKeyId
issuer (SignaturePkt (SigV4 _ _ _ _ usubs _ _)) = fmap (\(SigSubPacket _ (Issuer i)) -> i) (find isIssuerSSP usubs)
issuer _ = Nothing
pubkeyToMPIs :: PKey -> [MPI]
pubkeyToMPIs (RSAPubKey (RSA_PublicKey k)) = [MPI (RSA.public_n k), MPI (RSA.public_e k)]
pubkeyToMPIs (DSAPubKey (DSA_PublicKey k)) = [
pkParams DSA.params_p
, pkParams DSA.params_q
, pkParams DSA.params_g
, MPI . DSA.public_y $ k
]
where pkParams f = MPI . f . DSA.public_params $ k
pubkeyToMPIs (ElGamalPubKey k) = fmap MPI k
multiplicativeInverse :: Integral a => a -> a -> a
multiplicativeInverse _ 1 = 1
multiplicativeInverse q p = (n * q + 1) `div` p
where n = p multiplicativeInverse p (q `mod` p)
sigType :: SignaturePayload -> Maybe SigType
sigType (SigV3 st _ _ _ _ _ _) = Just st
sigType (SigV4 st _ _ _ _ _ _) = Just st
sigType _ = Nothing
sigPKA :: SignaturePayload -> Maybe PubKeyAlgorithm
sigPKA (SigV3 _ _ _ pka _ _ _) = Just pka
sigPKA (SigV4 _ pka _ _ _ _ _) = Just pka
sigPKA _ = Nothing
sigHA :: SignaturePayload -> Maybe HashAlgorithm
sigHA (SigV3 _ _ _ _ ha _ _) = Just ha
sigHA (SigV4 _ _ ha _ _ _ _) = Just ha
sigHA _ = Nothing
sigCT :: SignaturePayload -> Maybe ThirtyTwoBitTimeStamp
sigCT (SigV3 _ ct _ _ _ _ _) = Just ct
sigCT (SigV4 _ _ _ hsubs _ _ _) = fmap (\(SigSubPacket _ (SigCreationTime i)) -> i) (find isSigCreationTime hsubs)
sigCT _ = Nothing
truncatingVerify :: (ByteArrayAccess msg, CHI.HashAlgorithm hash) => hash -> DSA.PublicKey -> DSA.Signature -> msg -> Bool
truncatingVerify hashAlg pk (DSA.Signature r s) m
| r <= 0 || r >= q || s <= 0 || s >= q = False
| otherwise = v == r
where (DSA.Params p g q) = DSA.public_params pk
y = DSA.public_y pk
hm = os2ip . dsaTruncate . BA.convert $ hashWith hashAlg m
w = fromJust $ inverse s q
u1 = (hm*w) `mod` q
u2 = (r*w) `mod` q
v = (expFast g u1 p * expFast y u2 p) `mod` p `mod` q
dsaTruncate bs = let lbs = BL.fromStrict bs in if countBits lbs > fromIntegral dsaQLen then B.take (dsaQLen `div` 8) bs else bs
dsaQLen = numBits q