1 files changed, 59 insertions, 0 deletions

diff --git a/DNSKey.hs b/DNSKey.hs
new file mode 100644
index 0000000..38d336d
--- /dev/null
+++ b/DNSKey.hs
@@ -0,0 +1,59 @@
+module DNSKey where
+
+import           Data.Binary
+import           Data.Binary.Get
+import           Data.Binary.Put
+import           Data.Bits
+import qualified Data.ByteString      as B
+import qualified Data.ByteString.Lazy as L
+import           Data.Word
+
+-- RSA n e
+--  n = modulus
+--  e = exponent
+data RSA = RSA Integer Integer
+ deriving (Eq,Show)
+
+getRSA len = do
+    elen <- do
+        tog <- get
+        case tog :: Word8 of
+            0 -> get :: Get Word16
+            _ -> return $ fromIntegral tog
+    ebs <- getByteString (fromIntegral elen)
+    nlen <- fmap (fromIntegral . ((-) len)) bytesRead
+    nbs <- getByteString nlen
+    let e = snd $ B.foldl' (\(c,a) w8 -> (c-1, a + 256^c * fromIntegral w8)) (elen-1,0) ebs
+        n = snd $ B.foldl' (\(c,a) w8 -> (c-1, a + 256^c * fromIntegral w8)) (nlen-1,0) nbs
+    return $ RSA n e
+
+putRSA (RSA n e) = do
+    if elen > 255 || elen==0
+        then do
+            put (0 :: Word8)
+            put (fromIntegral elen :: Word16)
+        else do
+            put (fromIntegral elen :: Word8)
+    putByteString ebs
+    putByteString nbs
+ where
+    elen = B.length ebs
+    ebs = i2bs_unsized e
+    nbs = i2bs_unsized n
+
+-- |@i2bs_unsized i@ converts @i@ to a 'ByteString' of sufficient bytes to express the integer.
+-- The integer must be non-negative and a zero will be encoded in one byte.
+--
+-- Thanks: Thomas DuBuisson (crypto-api)
+i2bs_unsized :: Integer -> B.ByteString
+i2bs_unsized 0 = B.singleton 0
+i2bs_unsized i = B.reverse $ B.unfoldr (\i' -> if i' <= 0 then Nothing else Just (fromIntegral i', (i' `shiftR` 8))) i
+{-# INLINE i2bs_unsized #-}
+
+main = do
+    bs <- L.getContents
+    let rsa = runGet (getRSA (fromIntegral $ L.length bs)) bs
+        bs' = runPut (putRSA rsa)
+        rsa' = runGet (getRSA (fromIntegral $ L.length bs)) bs'
+    print rsa
+    print rsa'