[tests] add first P256 test

cryptonite.cabal

@@ -254,6 +254,7 @@ Test-Suite test-cryptonite
                      KAT_PubKey.ECDSA
                      KAT_PubKey.OAEP
                      KAT_PubKey.PSS
+                     KAT_PubKey.P256
                      KAT_PubKey
                      KAT_RC4
                      KAT_Scrypt

tests/KAT_PubKey.hs

@@ -17,6 +17,7 @@ import KAT_PubKey.DSA
 import KAT_PubKey.ECC
 import KAT_PubKey.ECDSA
 import Utils
+import qualified KAT_PubKey.P256 as P256
 
 data VectorMgf = VectorMgf { seed :: ByteString
                            , dbMask :: ByteString
@@ -39,6 +40,7 @@ tests = testGroup "PubKey"
     , dsaTests
     , eccTests
     , ecdsaTests
+    , P256.tests
     ]
 
 --newKats = [ eccKatTests ]

tests/KAT_PubKey/P256.hs

@@ -0,0 +1,36 @@
+{-# LANGUAGE OverloadedStrings #-}
+module KAT_PubKey.P256 (tests) where
+
+import           Control.Arrow (second)
+
+import qualified Crypto.PubKey.ECC.Types as ECC
+import qualified Crypto.PubKey.ECC.Prim as ECC
+import qualified Crypto.PubKey.ECC.P256 as P256
+
+import           Test.Tasty.KAT
+import           Test.Tasty.KAT.FileLoader
+import           Data.ByteArray (Bytes)
+import           Crypto.Number.Serialize (i2ospOf)
+import           Crypto.Error
+
+import           Imports
+
+tests = testGroup "P256"
+    [ testGroup "scalar"
+        [ testProperty "marshalling" $ \(Positive r') ->
+            let r = r' `mod` curveN
+                rBytes = i2ospScalar r
+             in case P256.scalarFromBinary rBytes of
+                    CryptoFailed err    -> error (show err)
+                    CryptoPassed scalar -> rBytes `propertyEq` P256.scalarToBinary scalar
+        ]
+    ]
+  where
+    curve  = ECC.getCurveByName ECC.SEC_p256r1
+    curveN = ECC.ecc_n . ECC.common_curve $ curve
+
+    i2ospScalar :: Integer -> Bytes
+    i2ospScalar i =
+        case i2ospOf 32 i of
+            Nothing -> error "invalid size of P256 scalar"
+            Just b  -> b