unikernel/duniverse/mirage-crypto/rng/unix/mirage_crypto_rng_unix.ml

@@ -0,0 +1,57 @@
+open Mirage_crypto_rng
+
+module Urandom = Urandom
+
+module Getentropy = Getentropy
+
+let use_dev_urandom () =
+  let g = create (module Urandom) in
+  set_default_generator g
+
+let use_getentropy () =
+  let g = create (module Getentropy) in
+  set_default_generator g
+
+let use_default () = use_getentropy ()
+
+let src = Logs.Src.create "mirage-crypto-rng.unix" ~doc:"Mirage crypto RNG Unix"
+module Log = (val Logs.src_log src : Logs.LOG)
+
+external getrandom_buf : bytes -> int -> int -> unit = "mc_getrandom" [@@noalloc]
+
+let getrandom_into buf ~off ~len =
+  getrandom_buf buf off len
+
+let getrandom size =
+  let buf = Bytes.create size in
+  getrandom_into buf ~off:0 ~len:size;
+  Bytes.unsafe_to_string buf
+
+let getrandom_init i =
+  let data = getrandom 128 in
+  Entropy.header i data
+
+let running = Atomic.make false
+
+let initialize (type a) ?g (rng : a generator) =
+  if Atomic.get running then
+    Log.debug
+      (fun m -> m "Mirage_crypto_rng_unix.initialize has already been called, \
+                   ignoring this call.")
+  else begin
+    (try
+       let _ = default_generator () in
+       Log.warn (fun m -> m "Mirage_crypto_rng.default_generator has already \
+                             been set, check that this call is intentional");
+     with
+       No_default_generator -> ());
+    Atomic.set running true ;
+    let seed =
+      let init =
+        Entropy.[ bootstrap ; whirlwind_bootstrap ; bootstrap ; getrandom_init ]
+      in
+      List.mapi (fun i f -> f i) init |> String.concat ""
+    in
+    let _ = Entropy.register_source "getrandom" in
+    set_default_generator (create ?g ~seed rng)
+  end