From 94d67ad86d73b1aacecf236f07824e620ed302e9 Mon Sep 17 00:00:00 2001
From: Parnell Springmeyer <parnell@digitalmentat.com>
Date: Tue, 2 May 2017 16:18:26 -0500
Subject: [PATCH] ed25519: Adding generateSecretKey and a unit test

---
 Crypto/PubKey/Ed25519.hs | 27 ++++++++++++++++++++++-----
 tests/KAT_Ed25519.hs     |  3 ++-
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/Crypto/PubKey/Ed25519.hs b/Crypto/PubKey/Ed25519.hs
index 6a80db8..094c929 100644
--- a/Crypto/PubKey/Ed25519.hs
+++ b/Crypto/PubKey/Ed25519.hs
@@ -7,12 +7,17 @@
 --
 -- Ed25519 support
 --
+{-# LANGUAGE BangPatterns               #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE ScopedTypeVariables        #-}
 module Crypto.PubKey.Ed25519
     ( SecretKey
     , PublicKey
     , Signature
+    -- * Size constants
+    , publicKeySize
+    , secretKeySize
+    , signatureSize
     -- * Smart constructors
     , signature
     , publicKey
@@ -21,17 +26,20 @@ module Crypto.PubKey.Ed25519
     , toPublic
     , sign
     , verify
+    , generateSecretKey
     ) where
 
 import           Data.Word
-import           Foreign.Ptr
 import           Foreign.C.Types
+import           Foreign.Ptr
 
+import           Crypto.Error
+import           Crypto.Internal.ByteArray (ByteArrayAccess, Bytes,
+                                            ScrubbedBytes, withByteArray)
+import qualified Crypto.Internal.ByteArray as B
 import           Crypto.Internal.Compat
 import           Crypto.Internal.Imports
-import           Crypto.Internal.ByteArray (ByteArrayAccess, withByteArray, ScrubbedBytes, Bytes)
-import qualified Crypto.Internal.ByteArray as B
-import           Crypto.Error
+import           Crypto.Random
 
 -- | An Ed25519 Secret key
 newtype SecretKey = SecretKey ScrubbedBytes
@@ -106,12 +114,21 @@ verify public message signatureVal = unsafeDoIO $
   where
     !msgLen = B.length message
 
+-- | Generate a secret key
+generateSecretKey :: MonadRandom m => m SecretKey
+generateSecretKey = do
+    ba :: ScrubbedBytes <- getRandomBytes secretKeySize
+    return (SecretKey $ B.copyAndFreeze ba (\_ -> return ()))
+
+-- | A public key is 32 bytes
 publicKeySize :: Int
 publicKeySize = 32
 
+-- | A secret key is 32 bytes
 secretKeySize :: Int
 secretKeySize = 32
 
+-- | A signature is 64 bytes
 signatureSize :: Int
 signatureSize = 64
 
diff --git a/tests/KAT_Ed25519.hs b/tests/KAT_Ed25519.hs
index 522f88f..62132f1 100644
--- a/tests/KAT_Ed25519.hs
+++ b/tests/KAT_Ed25519.hs
@@ -1,5 +1,5 @@
+{-# LANGUAGE BangPatterns      #-}
 {-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE BangPatterns #-}
 module KAT_Ed25519 ( tests ) where
 
 import           Crypto.Error
@@ -23,6 +23,7 @@ vec1 = Vec
 testVec :: String -> Vec -> [TestTree]
 testVec s vec =
     [ testCase (s ++ " gen publickey") (pub @=? Ed25519.toPublic sec)
+    , testCase (s ++ " gen secretkey") (Ed25519.generateSecretKey *> pure ())
     , testCase (s ++ " gen signature") (sig @=? Ed25519.sign sec pub (vecMsg vec))
     ]
   where