Merge pull request #980 from IntersectMBO/use-wasi-for-randomness

Replace JS snippet with WASI call for random byte generation

Author: palas

cardano-wasm/cardano-wasm.cabal

@@ -42,14 +42,14 @@ executable cardano-wasm
     Cardano.Wasm.Internal.Api.GRPC
     Cardano.Wasm.Internal.Api.Info
     Cardano.Wasm.Internal.Api.InfoToTypeScript
+    Cardano.Wasm.Internal.Api.Random
     Cardano.Wasm.Internal.Api.Tx
     Cardano.Wasm.Internal.Api.TypeScriptDefs
     Cardano.Wasm.Internal.Api.Wallet
     Cardano.Wasm.Internal.ExceptionHandling
     Cardano.Wasm.Internal.JavaScript.Bridge
     Cardano.Wasm.Internal.JavaScript.GRPC
     Cardano.Wasm.Internal.JavaScript.GRPCTypes
-    Cardano.Wasm.Internal.JavaScript.Random
 
   build-depends:
     aeson,
@@ -74,6 +74,9 @@ executable cardano-wasm
       base16-bytestring,
       ghc-experimental,
       utf8-string,
+  else
+    build-depends:
+      crypton
 
 test-suite cardano-wasm-golden
   type: exitcode-stdio-1.0

cardano-wasm/src/Cardano/Wasm/Internal/Api/Random.hs

@@ -0,0 +1,59 @@
+{-# LANGUAGE CApiFFI #-}
+{-# LANGUAGE CPP #-}
+
+module Cardano.Wasm.Internal.Api.Random (getRandomBytes) where
+
+#if !defined(wasm32_HOST_ARCH)
+
+import Data.ByteString (ByteString)
+import Crypto.Random.Entropy (getEntropy)
+
+getRandomBytes :: Word -> IO ByteString
+getRandomBytes n = getEntropy (fromIntegral n)
+
+#else
+
+import Control.Exception (throwIO)
+import Data.ByteString (ByteString, packCStringLen)
+import Data.Word (Word8)
+import System.IO.Error (mkIOError, userErrorType)
+
+import Foreign.C.Types (CInt (..), CSize (..))
+import Foreign.Marshal.Alloc (allocaBytes)
+import Foreign.Ptr (Ptr, castPtr)
+
+-- | Import the 'random_get' function from wasi
+-- module provided by the WASI runtime.
+--
+-- It takes a raw pointer to a u8 buffer (Ptr Word8) and the buffer's
+-- length (CSize) and returns a CInt representing the error code number.
+-- A return value of 0 means success.
+foreign import ccall "__wasi_random_get"
+  wasi_random_get
+    :: Ptr Word8
+    -- ^ Pointer to the buffer to fill
+    -> CSize
+    -- ^ Number of bytes to write
+    -> IO CInt
+    -- ^ Returns 0 on success, or an errno code
+
+-- | A safe Haskell wrapper around 'random_get' function from wasi.
+-- It requests the given number of cryptographically secure random
+-- bytes and returns them as a ByteString.
+getRandomBytes :: Word -> IO ByteString
+getRandomBytes n =
+  allocaBytes (fromIntegral n) $ \ptr -> do
+    -- Get pointer to allocated buffer
+    errno <- wasi_random_get ptr (fromIntegral n)
+    if errno == 0
+      -- If successful, pack the bytes from the pointer into a Haskell managed ByteString
+      then packCStringLen (castPtr ptr, fromIntegral n)
+      else -- Otherwise, we throw
+        throwIO $
+          mkIOError
+            userErrorType
+            ("wasi_random_get failed with errno: " ++ show errno)
+            Nothing
+            Nothing
+
+#endif

cardano-wasm/src/Cardano/Wasm/Internal/Api/Wallet.hs

@@ -38,8 +38,8 @@ import Cardano.Api
   )
 
 import Cardano.Crypto.Seed (mkSeedFromBytes)
+import Cardano.Wasm.Internal.Api.Random (getRandomBytes)
 import Cardano.Wasm.Internal.ExceptionHandling (rightOrError, toMonadFail)
-import Cardano.Wasm.Internal.JavaScript.Random (getRandomBytes)
 
 import Data.Aeson ((.=))
 import Data.Aeson qualified as Aeson