1 files changed, 30 insertions, 0 deletions
diff --git a/src/Sproxy/Application/State.hs b/src/Sproxy/Application/State.hs
new file mode 100644
index 0000000..29d9252
--- /dev/null
+++ b/src/Sproxy/Application/State.hs
@@ -0,0 +1,30 @@
+module Sproxy.Application.State (
+  decode
+, encode
+) where
+
+import Data.ByteString (ByteString)
+import Data.ByteString.Lazy (fromStrict, toStrict)
+import Data.Digest.Pure.SHA (hmacSha1, bytestringDigest)
+import qualified Data.ByteString.Base64 as Base64
+import qualified Data.Serialize as DS
+
+
+-- FIXME: Compress / decompress ?
+
+
+encode :: ByteString -> ByteString -> ByteString
+encode key payload = Base64.encode . DS.encode $ (payload, digest key payload)
+
+
+decode :: ByteString -> ByteString -> Either String ByteString
+decode key d = do
+  (payload, dgst) <- DS.decode =<< Base64.decode d
+  if dgst /= digest key payload
+  then Left "junk"
+  else Right payload
+  
+
+digest :: ByteString -> ByteString -> ByteString
+digest key payload = toStrict . bytestringDigest $ hmacSha1 (fromStrict key) (fromStrict payload)
+