Explicitly call sodium_mlock

See jedisct1/libsodium#1237: sodium_malloc()
calls sodium_mlock() for us, but it ignores any failures reported from
there, so if we run out of our mlock quota, instead of failing loudly
and clearly, it will just give us non-mlocked memory instead, and when
we use it under the assumption that it will be mlocked, all sorts of
spurious / nondeterministic failures will result.

cardano-crypto-class/src/Cardano/Crypto/Libsodium/C.hs

@@ -9,6 +9,8 @@ module Cardano.Crypto.Libsodium.C (
     c_sodium_malloc,
     c_sodium_free,
     c_sodium_free_funptr,
+    c_sodium_mlock,
+    c_sodium_munlock,
 
     -- * Hashing
     -- ** SHA256
@@ -81,6 +83,16 @@ foreign import capi unsafe "sodium.h sodium_free" c_sodium_free :: Ptr a -> IO (
 -- <https://libsodium.gitbook.io/doc/memory_management>
 foreign import capi unsafe "sodium.h &sodium_free" c_sodium_free_funptr :: FunPtr (Ptr a -> IO ())
 
+-- | @void *sodium_mlock(void * const addr, size_t size);@
+--
+-- <https://libsodium.gitbook.io/doc/memory_management>
+foreign import capi unsafe "sodium.h sodium_mlock" c_sodium_mlock :: Ptr a -> CSize -> IO CInt
+
+-- | @void *sodium_munlock(void * const addr, size_t size);@
+--
+-- <https://libsodium.gitbook.io/doc/memory_management>
+foreign import capi unsafe "sodium.h sodium_munlock" c_sodium_munlock :: Ptr a  -> CSize-> IO CInt
+
 -------------------------------------------------------------------------------
 -- Hashing: SHA256
 -------------------------------------------------------------------------------

cardano-crypto-class/src/Cardano/Crypto/Libsodium/Memory/Internal.hs

@@ -66,7 +66,7 @@ makeMLockedPool = do
     (fromIntegral $ 4096 `div` (natVal (Proxy @n)) `div` 64)
     (\size -> mask_ $ do
       ptr <- sodiumMalloc (fromIntegral size)
-      newForeignPtr ptr (sodiumFree ptr)
+      newForeignPtr ptr (sodiumFree ptr (fromIntegral size))
     )
     (\ptr -> do
       eraseMem (Proxy @n) ptr
@@ -94,15 +94,24 @@ mlockedMalloc size = SFP <$> do
         mask_ $ do
           ptr <- sodiumMalloc size
           newForeignPtr ptr $ do
-            sodiumFree ptr
+            sodiumFree ptr size
 
 sodiumMalloc :: CSize -> IO (Ptr a)
 sodiumMalloc size = do
-    ptr <- c_sodium_malloc size
-    when (ptr == nullPtr) $ do
-        errno <- getErrno
-        ioException $ errnoToIOError "c_sodium_malloc" errno Nothing Nothing
-    return ptr
+  ptr <- c_sodium_malloc size
+  when (ptr == nullPtr) $ do
+      errno <- getErrno
+      ioException $ errnoToIOError "c_sodium_malloc" errno Nothing Nothing
+  res <- c_sodium_mlock ptr size
+  when (res /= 0) $ do
+      errno <- getErrno
+      ioException $ errnoToIOError "c_sodium_mlock" errno Nothing Nothing
+  return ptr
 
-sodiumFree :: Ptr a -> IO ()
-sodiumFree = c_sodium_free
+sodiumFree :: Ptr a -> CSize -> IO ()
+sodiumFree ptr size = do
+  res <- c_sodium_munlock ptr size
+  when (res /= 0) $ do
+    errno <- getErrno
+    ioException $ errnoToIOError "c_sodium_munlock" errno Nothing Nothing
+  c_sodium_free ptr