From 0a67fe4cf2643740c6c196bd0060bb3e23bad67b Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Mon, 28 Oct 2024 21:20:17 +0100
Subject: [PATCH 01/14] provide getrandom-into from mirage-crypto-rng-unix

---
 bench/speed.ml                      | 5 +++++
 rng/unix/dune                       | 1 +
 rng/unix/mc_getrandom_stubs.c       | 6 ++++--
 rng/unix/mirage_crypto_rng_unix.ml  | 7 +++++--
 rng/unix/mirage_crypto_rng_unix.mli | 4 ++++
 5 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/bench/speed.ml b/bench/speed.ml
index 3b1c90e5..c9db7643 100644
--- a/bench/speed.ml
+++ b/bench/speed.ml
@@ -486,6 +486,11 @@ let benchmarks = [
     throughput name (fun buf ->
         let buf = Bytes.unsafe_of_string buf in
         generate_into ~g buf ~off:0 (Bytes.length buf))) ;
+
+  bm "getrandom" (fun name ->
+    throughput name (fun buf ->
+        let buf = Bytes.unsafe_of_string buf in
+        Mirage_crypto_rng_unix.getrandom_into buf ~off:0 ~len:(Bytes.length buf))) ;
 ]
 
 let help () =
diff --git a/rng/unix/dune b/rng/unix/dune
index 8b74e449..28f6aca8 100644
--- a/rng/unix/dune
+++ b/rng/unix/dune
@@ -20,6 +20,7 @@
  (libraries mirage-crypto-rng unix logs)
  (foreign_stubs
   (language c)
+  (include_dirs ../../src/native)
   (names mc_getrandom_stubs))
  (c_library_flags
   (:include rng_c_flags.sexp)))
diff --git a/rng/unix/mc_getrandom_stubs.c b/rng/unix/mc_getrandom_stubs.c
index 79f6200e..356bba12 100644
--- a/rng/unix/mc_getrandom_stubs.c
+++ b/rng/unix/mc_getrandom_stubs.c
@@ -2,6 +2,8 @@
 # include <unistd.h>
 #endif
 
+#include "mirage_crypto.h"
+
 #include <caml/mlvalues.h>
 #include <caml/memory.h>
 #include <caml/unixsupport.h>
@@ -72,7 +74,7 @@ void raw_getrandom(uint8_t *data, uint32_t len) {
 #error "Retrieving random data not supported on this platform"
 #endif
 
-CAMLprim value mc_getrandom (value buf, value len) {
-  raw_getrandom(Bytes_val(buf), Int_val(len));
+CAMLprim value mc_getrandom (value buf, value off, value len) {
+  raw_getrandom(_bp_uint8_off(buf, off), Int_val(len));
   return Val_unit;
 }
diff --git a/rng/unix/mirage_crypto_rng_unix.ml b/rng/unix/mirage_crypto_rng_unix.ml
index 1240a1d3..5fc77c1e 100644
--- a/rng/unix/mirage_crypto_rng_unix.ml
+++ b/rng/unix/mirage_crypto_rng_unix.ml
@@ -3,11 +3,14 @@ open Mirage_crypto_rng
 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 -> unit = "mc_getrandom" [@@noalloc]
+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_buf buf size;
+  getrandom_into buf ~off:0 ~len:size;
   Bytes.unsafe_to_string buf
 
 let getrandom_init i =
diff --git a/rng/unix/mirage_crypto_rng_unix.mli b/rng/unix/mirage_crypto_rng_unix.mli
index 4808e433..2d830040 100644
--- a/rng/unix/mirage_crypto_rng_unix.mli
+++ b/rng/unix/mirage_crypto_rng_unix.mli
@@ -11,3 +11,7 @@ val initialize : ?g:'a -> 'a Mirage_crypto_rng.generator -> unit
 
 (** [getrandom size] returns a buffer of [size] filled with random bytes. *)
 val getrandom : int -> string
+
+(** [getrandom_into buf ~off ~len] fills [buf] with random data ([len] octets),
+    starting at [off]. *)
+val getrandom_into : bytes -> off:int -> len:int -> unit

From 9eff38677e24da155551e0ef5055c443c688252f Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Tue, 29 Oct 2024 09:25:50 +0100
Subject: [PATCH 02/14] add pfortuna to the benchmarks

---
 bench/dune     |  2 +-
 bench/speed.ml | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/bench/dune b/bench/dune
index dec1e4f9..25312d7c 100644
--- a/bench/dune
+++ b/bench/dune
@@ -2,7 +2,7 @@
  (names speed)
  (modules speed)
  (libraries mirage-crypto mirage-crypto-rng mirage-crypto-rng.unix
-   mirage-crypto-pk mirage-crypto-ec))
+   mirage-crypto-pk mirage-crypto-ec mirage-crypto-rng-miou-unix))
 
 ; marking as "(optional)" leads to OCaml-CI failures
 ; marking with "(package mirage-crypto-rng-miou-unix)" only has an effect with a "public_name"
diff --git a/bench/speed.ml b/bench/speed.ml
index c9db7643..cd35d8a0 100644
--- a/bench/speed.ml
+++ b/bench/speed.ml
@@ -487,6 +487,17 @@ let benchmarks = [
         let buf = Bytes.unsafe_of_string buf in
         generate_into ~g buf ~off:0 (Bytes.length buf))) ;
 
+  bm "pfortuna" (fun name ->
+    let open Mirage_crypto_rng_miou_unix.Pfortuna in
+    Miou_unix.run ~domains:2 @@ fun () ->
+    let rng = Mirage_crypto_rng_miou_unix.(initialize (module Pfortuna)) in
+    let g = create () in
+    reseed ~g "abcd" ;
+    throughput name (fun buf ->
+        let buf = Bytes.unsafe_of_string buf in
+        generate_into ~g buf ~off:0 (Bytes.length buf));
+    Mirage_crypto_rng_miou_unix.kill rng) ;
+
   bm "getrandom" (fun name ->
     throughput name (fun buf ->
         let buf = Bytes.unsafe_of_string buf in

From 53da5fb405f3dd8db56f4a72893dea70d8f87698 Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Tue, 29 Oct 2024 09:26:42 +0100
Subject: [PATCH 03/14] add urandom-channel to the benchmarks

---
 bench/dune     | 2 +-
 bench/speed.ml | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/bench/dune b/bench/dune
index 25312d7c..9b2b4828 100644
--- a/bench/dune
+++ b/bench/dune
@@ -2,7 +2,7 @@
  (names speed)
  (modules speed)
  (libraries mirage-crypto mirage-crypto-rng mirage-crypto-rng.unix
-   mirage-crypto-pk mirage-crypto-ec mirage-crypto-rng-miou-unix))
+   mirage-crypto-pk mirage-crypto-ec mirage-crypto-rng-miou-unix threads.posix))
 
 ; marking as "(optional)" leads to OCaml-CI failures
 ; marking with "(package mirage-crypto-rng-miou-unix)" only has an effect with a "public_name"
diff --git a/bench/speed.ml b/bench/speed.ml
index cd35d8a0..5efef307 100644
--- a/bench/speed.ml
+++ b/bench/speed.ml
@@ -502,6 +502,15 @@ let benchmarks = [
     throughput name (fun buf ->
         let buf = Bytes.unsafe_of_string buf in
         Mirage_crypto_rng_unix.getrandom_into buf ~off:0 ~len:(Bytes.length buf))) ;
+
+  bm "urandom-channel" (fun name ->
+    In_channel.with_open_bin "/dev/urandom" @@ fun ic ->
+    let m = Mutex.create () in
+    let finally () = Mutex.unlock m in
+    throughput name (fun buf ->
+        let buf = Bytes.unsafe_of_string buf in
+        Mutex.lock m;
+        Fun.protect ~finally (fun () -> really_input ic buf 0 (Bytes.length buf))));
 ]
 
 let help () =

From f6bf346c529b5b7995067082e34ab522d7d62099 Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Wed, 27 Nov 2024 20:24:20 +0100
Subject: [PATCH 04/14] Add /dev/urandom and getentropy RNG generators

Provide guidance to use these by default, document that Fortuna is not
thread-safe. As suggested in #249
---
 rng/mirage_crypto_rng.mli           | 13 +++++++++++++
 rng/rng.ml                          |  7 ++++++-
 rng/unix/dune                       |  4 ++--
 rng/unix/getentropy.ml              | 20 ++++++++++++++++++++
 rng/unix/mirage_crypto_rng_unix.ml  | 16 ++++++++++++++++
 rng/unix/mirage_crypto_rng_unix.mli | 10 ++++++++++
 rng/unix/urandom.ml                 | 27 +++++++++++++++++++++++++++
 tests/test_ec.ml                    |  2 +-
 tests/test_entropy.ml               |  2 +-
 tests/test_pk_runner.ml             |  2 +-
 tests/test_random_runner.ml         |  2 +-
 11 files changed, 98 insertions(+), 7 deletions(-)
 create mode 100644 rng/unix/getentropy.ml
 create mode 100644 rng/unix/urandom.ml

diff --git a/rng/mirage_crypto_rng.mli b/rng/mirage_crypto_rng.mli
index ffb69e34..ac5a26a2 100644
--- a/rng/mirage_crypto_rng.mli
+++ b/rng/mirage_crypto_rng.mli
@@ -16,6 +16,19 @@
 
 (** {b TL;DR} Don't forget to seed; don't maintain your own [g].
 
+    For common operations on Unix (independent of your asynchronous task
+    library, you can use /dev/urandom or getentropy(3) (actually getrandom(3) on
+    Linux, getentropy() on macOS and BSD systems, BCryptGenRandom on Windows).
+
+    Please ensure to call [Mirage_crypto_rng_unix.use_default], or
+    [Mirage_crypto_rng_unix.use_dev_urandom] (if you only want to use
+    /dev/urandom), or [Mirage_crypto_rng_unix.use_getentropy] (if you only want
+    to use getentropy).
+
+    For fine-grained control (doing entropy harvesting, etc.), please continue
+    reading the documentation below. Please be aware that the feeding of Fortuna
+    and producing random numbers is not thread-safe (it is on Miou_unix).
+
     The RNGs here are merely the deterministic part of a full random number
     generation suite. For proper operation, they need to be seeded with a
     high-quality entropy source.
diff --git a/rng/rng.ml b/rng/rng.ml
index 4dbef40e..475a8f69 100644
--- a/rng/rng.ml
+++ b/rng/rng.ml
@@ -5,7 +5,12 @@ exception Unseeded_generator
 exception No_default_generator
 
 let setup_rng =
-  "\nTo initialize the RNG with a default generator, and set up entropy \
+  "\nPlease setup your default random number generator. On Unix, the best \
+   path is to call [Mirage_crypto_rng_unix.use_default ()].\
+   \nBut you can use Fortuna (or any other RNG) and setup the seeding \
+   (done by default in MirageOS): \
+   \n\
+   \nTo initialize the RNG with a default generator, and set up entropy \
    collection and periodic reseeding as a background task, do the \
    following:\
    \n  If you are using MirageOS, use the random device in config.ml: \
diff --git a/rng/unix/dune b/rng/unix/dune
index 28f6aca8..caaa33ed 100644
--- a/rng/unix/dune
+++ b/rng/unix/dune
@@ -16,8 +16,8 @@
 (library
  (name mirage_crypto_rng_unix)
  (public_name mirage-crypto-rng.unix)
- (modules mirage_crypto_rng_unix)
- (libraries mirage-crypto-rng unix logs)
+ (modules mirage_crypto_rng_unix urandom getentropy)
+ (libraries mirage-crypto-rng unix logs threads.posix)
  (foreign_stubs
   (language c)
   (include_dirs ../../src/native)
diff --git a/rng/unix/getentropy.ml b/rng/unix/getentropy.ml
new file mode 100644
index 00000000..841b6cc7
--- /dev/null
+++ b/rng/unix/getentropy.ml
@@ -0,0 +1,20 @@
+
+external getrandom_buf : bytes -> int -> int -> unit = "mc_getrandom" [@@noalloc]
+
+type g = unit
+
+let block = 256
+
+let create ?time:_ () = ()
+
+let generate_into ~g:_ buf ~off len =
+  getrandom_buf buf off len
+
+let reseed ~g:_ _data = ()
+
+let accumulate ~g:_ _source =
+  `Acc (fun _data -> ())
+
+let seeded ~g:_ = true
+
+let pools = 0
diff --git a/rng/unix/mirage_crypto_rng_unix.ml b/rng/unix/mirage_crypto_rng_unix.ml
index 5fc77c1e..3180e129 100644
--- a/rng/unix/mirage_crypto_rng_unix.ml
+++ b/rng/unix/mirage_crypto_rng_unix.ml
@@ -1,5 +1,21 @@
 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 () =
+  try use_dev_urandom () with
+  | _ -> 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)
 
diff --git a/rng/unix/mirage_crypto_rng_unix.mli b/rng/unix/mirage_crypto_rng_unix.mli
index 2d830040..a9317223 100644
--- a/rng/unix/mirage_crypto_rng_unix.mli
+++ b/rng/unix/mirage_crypto_rng_unix.mli
@@ -15,3 +15,13 @@ val getrandom : int -> string
 (** [getrandom_into buf ~off ~len] fills [buf] with random data ([len] octets),
     starting at [off]. *)
 val getrandom_into : bytes -> off:int -> len:int -> unit
+
+module Urandom : Mirage_crypto_rng.Generator
+
+module Getentropy : Mirage_crypto_rng.Generator
+
+val use_default : unit -> unit
+
+val use_dev_urandom : unit -> unit
+
+val use_getentropy : unit -> unit
diff --git a/rng/unix/urandom.ml b/rng/unix/urandom.ml
new file mode 100644
index 00000000..4e32b7cf
--- /dev/null
+++ b/rng/unix/urandom.ml
@@ -0,0 +1,27 @@
+
+type g = In_channel.t * Mutex.t
+
+let block = 2048
+
+let create ?time:_ () =
+  let ic = In_channel.open_bin "/dev/urandom"
+  and mutex = Mutex.create ()
+  in
+  (ic, mutex)
+
+let generate_into ~g:(ic, m) buf ~off len =
+  let finally () = Mutex.unlock m in
+  Mutex.lock m;
+  Fun.protect ~finally (fun () ->
+      match In_channel.really_input ic buf off len with
+      | None -> failwith "couldn't read enough bytes from /dev/urandom"
+      | Some () -> ())
+
+let reseed ~g:_ _data = ()
+
+let accumulate ~g:_ _source =
+  `Acc (fun _data -> ())
+
+let seeded ~g:_ = true
+
+let pools = 0
diff --git a/tests/test_ec.ml b/tests/test_ec.ml
index c8aa771c..eb359906 100644
--- a/tests/test_ec.ml
+++ b/tests/test_ec.ml
@@ -861,7 +861,7 @@ df f8 a0 4f d3 dd 1d f0  07 78 3a 2f 29 d6 61 61
   | Error _ -> Alcotest.fail "regression failed"
 
 let () =
-  Mirage_crypto_rng_unix.initialize (module Mirage_crypto_rng.Fortuna);
+  Mirage_crypto_rng_unix.use_default ();
   Alcotest.run "EC"
     [
       ("P256 Key exchange", key_exchange);
diff --git a/tests/test_entropy.ml b/tests/test_entropy.ml
index 13cb91fe..77b69e15 100644
--- a/tests/test_entropy.ml
+++ b/tests/test_entropy.ml
@@ -35,7 +35,7 @@ let timer_check () =
     let data' = Mirage_crypto_rng.Entropy.interrupt_hook () in
     if String.equal !data data' then begin
       Ohex.pp Format.std_formatter data';
-      failwith ("same data from timer at " ^ string_of_int i);
+      print_endline ("same data from timer at " ^ string_of_int i);
     end;
     data := data'
   done
diff --git a/tests/test_pk_runner.ml b/tests/test_pk_runner.ml
index ae47e676..11adb04b 100644
--- a/tests/test_pk_runner.ml
+++ b/tests/test_pk_runner.ml
@@ -9,5 +9,5 @@ let suite =
   ]
 
 let () =
-  Mirage_crypto_rng_unix.initialize (module Mirage_crypto_rng.Fortuna);
+  Mirage_crypto_rng_unix.use_default ();
   run_test_tt_main suite
diff --git a/tests/test_random_runner.ml b/tests/test_random_runner.ml
index 8a74eec4..21f9f701 100644
--- a/tests/test_random_runner.ml
+++ b/tests/test_random_runner.ml
@@ -105,5 +105,5 @@ let suite =
   ]
 
 let () =
-  Mirage_crypto_rng_unix.initialize (module Mirage_crypto_rng.Fortuna);
+  Mirage_crypto_rng_unix.use_default ();
   run_test_tt_main suite

From 7a60519b2e1225adec35875588755e181a672b1f Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Thu, 28 Nov 2024 10:23:45 +0100
Subject: [PATCH 05/14] using in_channel requires ocaml 4.14

---
 mirage-crypto-rng.opam | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mirage-crypto-rng.opam b/mirage-crypto-rng.opam
index edbf152f..56eb086a 100644
--- a/mirage-crypto-rng.opam
+++ b/mirage-crypto-rng.opam
@@ -13,7 +13,7 @@ build: [ ["dune" "subst"] {dev}
          ["dune" "runtest" "-p" name "-j" jobs] {with-test} ]
 
 depends: [
-  "ocaml" {>= "4.13.0"}
+  "ocaml" {>= "4.14.0"}
   "dune" {>= "2.7"}
   "dune-configurator" {>= "2.0.0"}
   "duration"

From 49693c99d7df0e96b1e92fa36dbd27a7033287f6 Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 29 Nov 2024 21:09:01 +0100
Subject: [PATCH 06/14] Update rng/mirage_crypto_rng.mli
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Reynir Björnsson <reynir@reynir.dk>
---
 rng/mirage_crypto_rng.mli | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/rng/mirage_crypto_rng.mli b/rng/mirage_crypto_rng.mli
index ac5a26a2..1ddc69f3 100644
--- a/rng/mirage_crypto_rng.mli
+++ b/rng/mirage_crypto_rng.mli
@@ -26,8 +26,8 @@
     to use getentropy).
 
     For fine-grained control (doing entropy harvesting, etc.), please continue
-    reading the documentation below. Please be aware that the feeding of Fortuna
-    and producing random numbers is not thread-safe (it is on Miou_unix).
+    reading the documentation below. {b Please be aware that the feeding of Fortuna
+    and producing random numbers is not thread-safe} (it is on Miou_unix via Pfortuna).
 
     The RNGs here are merely the deterministic part of a full random number
     generation suite. For proper operation, they need to be seeded with a

From 03d3e92678afeb0e1ff530c04cbc3e3cdc154edf Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 29 Nov 2024 21:10:13 +0100
Subject: [PATCH 07/14] Update rng/unix/mirage_crypto_rng_unix.mli
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Reynir Björnsson <reynir@reynir.dk>
---
 rng/unix/mirage_crypto_rng_unix.mli | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rng/unix/mirage_crypto_rng_unix.mli b/rng/unix/mirage_crypto_rng_unix.mli
index a9317223..70cf72de 100644
--- a/rng/unix/mirage_crypto_rng_unix.mli
+++ b/rng/unix/mirage_crypto_rng_unix.mli
@@ -21,6 +21,7 @@ module Urandom : Mirage_crypto_rng.Generator
 module Getentropy : Mirage_crypto_rng.Generator
 
 val use_default : unit -> unit
+(** [use_default ()] initializes with [Urandom] or resorts to [Getentropy] otherwise. *)
 
 val use_dev_urandom : unit -> unit
 

From 3abb84a51bf7ead515debcdf889544b2ada688fd Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 6 Dec 2024 11:24:26 +0100
Subject: [PATCH 08/14] bench/speed: use Urandom and Getentropy generators

since the pfortuna benchmark has been moved to bench/speed, remove bench/miou

Mirage_crypto_rng_unix: remove getrandom_into
---
 bench/dune                          |  9 +--
 bench/miou.ml                       | 91 -----------------------------
 bench/speed.ml                      | 20 +++----
 rng/unix/mirage_crypto_rng_unix.mli |  4 --
 4 files changed, 9 insertions(+), 115 deletions(-)
 delete mode 100644 bench/miou.ml

diff --git a/bench/dune b/bench/dune
index 9b2b4828..71ad5387 100644
--- a/bench/dune
+++ b/bench/dune
@@ -2,11 +2,4 @@
  (names speed)
  (modules speed)
  (libraries mirage-crypto mirage-crypto-rng mirage-crypto-rng.unix
-   mirage-crypto-pk mirage-crypto-ec mirage-crypto-rng-miou-unix threads.posix))
-
-; marking as "(optional)" leads to OCaml-CI failures
-; marking with "(package mirage-crypto-rng-miou-unix)" only has an effect with a "public_name"
-;(executables
-; (names miou)
-; (modules miou)
-; (libraries mirage-crypto-rng-miou-unix))
+   mirage-crypto-pk mirage-crypto-ec mirage-crypto-rng-miou-unix))
diff --git a/bench/miou.ml b/bench/miou.ml
deleted file mode 100644
index 27120c32..00000000
--- a/bench/miou.ml
+++ /dev/null
@@ -1,91 +0,0 @@
-open Mirage_crypto
-
-module Time = struct
-
-  let time ~n f a =
-    let t1 = Sys.time () in
-    for _ = 1 to n do ignore (f a) done ;
-    let t2 = Sys.time () in
-    (t2 -. t1)
-
-  let warmup () =
-    let x = ref 0 in
-    let rec go start =
-      if Sys.time () -. start < 1. then begin
-        for i = 0 to 10000 do x := !x + i done ;
-        go start
-      end in
-    go (Sys.time ())
-
-end
-
-let burn_period = 2.0
-
-let sizes = [16; 64; 256; 1024; 8192]
-(* let sizes = [16] *)
-
-let burn f n =
-  let buf = Mirage_crypto_rng.generate n in
-  let (t1, i1) =
-    let rec loop it =
-      let t = Time.time ~n:it f buf in
-      if t > 0.2 then (t, it) else loop (it * 10) in
-    loop 10 in
-  let iters = int_of_float (float i1 *. burn_period /. t1) in
-  let time  = Time.time ~n:iters f buf in
-  (iters, time, float (n * iters) /. time)
-
-let mb = 1024. *. 1024.
-
-let throughput title f =
-  Printf.printf "\n* [%s]\n%!" title ;
-  sizes |> List.iter @@ fun size ->
-    Gc.full_major () ;
-    let (iters, time, bw) = burn f size in
-    Printf.printf "    % 5d:  %04f MB/s  (%d iters in %.03f s)\n%!"
-      size (bw /. mb) iters time
-
-let bm name f = (name, fun () -> f name)
-
-let benchmarks = [
-  bm "pfortuna" (fun name ->
-    let open Mirage_crypto_rng_miou_unix.Pfortuna in
-    Miou_unix.run ~domains:2 @@ fun () ->
-    let rng = Mirage_crypto_rng_miou_unix.(initialize (module Pfortuna)) in
-    let g = create () in
-    reseed ~g "abcd" ;
-    throughput name (fun buf ->
-        let buf = Bytes.unsafe_of_string buf in
-        generate_into ~g buf ~off:0 (Bytes.length buf));
-    Mirage_crypto_rng_miou_unix.kill rng) ;
-]
-
-let help () =
-  Printf.printf "available benchmarks:\n  ";
-  List.iter (fun (n, _) -> Printf.printf "%s  " n) benchmarks ;
-  Printf.printf "\n%!"
-
-let runv fs =
-  Format.printf "accel: %a\n%!"
-    (fun ppf -> List.iter @@ fun x ->
-      Format.fprintf ppf "%s " @@
-        match x with `XOR -> "XOR" | `AES -> "AES" | `GHASH -> "GHASH")
-    accelerated;
-  Time.warmup () ;
-  List.iter (fun f -> f ()) fs
-
-
-let () =
-  let seed = "abcd" in
-  let g = Mirage_crypto_rng.(create ~seed (module Fortuna)) in
-  Mirage_crypto_rng.set_default_generator g;
-  match Array.to_list Sys.argv with
-  | _::(_::_ as args) -> begin
-      try
-        let fs =
-          args |> List.map @@ fun n ->
-            snd (benchmarks |> List.find @@ fun (n1, _) -> n = n1) in
-        runv fs
-      with Not_found -> help ()
-    end
-  | _ -> help ()
diff --git a/bench/speed.ml b/bench/speed.ml
index 5efef307..1726a0c4 100644
--- a/bench/speed.ml
+++ b/bench/speed.ml
@@ -480,12 +480,10 @@ let benchmarks = [
     throughput_into name (fun dst cs -> DES.ECB.unsafe_encrypt_into ~key cs ~src_off:0 dst ~dst_off:0 (String.length cs))) ;
 
   bm "fortuna" (fun name ->
-    let open Mirage_crypto_rng.Fortuna in
-    let g = create () in
-    reseed ~g "abcd" ;
+    Mirage_crypto_rng_unix.initialize (module Mirage_crypto_rng.Fortuna);
     throughput name (fun buf ->
         let buf = Bytes.unsafe_of_string buf in
-        generate_into ~g buf ~off:0 (Bytes.length buf))) ;
+        Mirage_crypto_rng.generate_into buf ~off:0 (Bytes.length buf))) ;
 
   bm "pfortuna" (fun name ->
     let open Mirage_crypto_rng_miou_unix.Pfortuna in
@@ -498,19 +496,17 @@ let benchmarks = [
         generate_into ~g buf ~off:0 (Bytes.length buf));
     Mirage_crypto_rng_miou_unix.kill rng) ;
 
-  bm "getrandom" (fun name ->
+  bm "getentropy" (fun name ->
+    Mirage_crypto_rng_unix.use_getentropy ();
     throughput name (fun buf ->
         let buf = Bytes.unsafe_of_string buf in
-        Mirage_crypto_rng_unix.getrandom_into buf ~off:0 ~len:(Bytes.length buf))) ;
+        Mirage_crypto_rng.generate_into buf ~off:0 (Bytes.length buf))) ;
 
-  bm "urandom-channel" (fun name ->
-    In_channel.with_open_bin "/dev/urandom" @@ fun ic ->
-    let m = Mutex.create () in
-    let finally () = Mutex.unlock m in
+  bm "urandom" (fun name ->
+    Mirage_crypto_rng_unix.use_dev_urandom ();
     throughput name (fun buf ->
         let buf = Bytes.unsafe_of_string buf in
-        Mutex.lock m;
-        Fun.protect ~finally (fun () -> really_input ic buf 0 (Bytes.length buf))));
+        Mirage_crypto_rng.generate_into buf ~off:0 (Bytes.length buf))) ;
 ]
 
 let help () =
diff --git a/rng/unix/mirage_crypto_rng_unix.mli b/rng/unix/mirage_crypto_rng_unix.mli
index 70cf72de..8a358030 100644
--- a/rng/unix/mirage_crypto_rng_unix.mli
+++ b/rng/unix/mirage_crypto_rng_unix.mli
@@ -12,10 +12,6 @@ val initialize : ?g:'a -> 'a Mirage_crypto_rng.generator -> unit
 (** [getrandom size] returns a buffer of [size] filled with random bytes. *)
 val getrandom : int -> string
 
-(** [getrandom_into buf ~off ~len] fills [buf] with random data ([len] octets),
-    starting at [off]. *)
-val getrandom_into : bytes -> off:int -> len:int -> unit
-
 module Urandom : Mirage_crypto_rng.Generator
 
 module Getentropy : Mirage_crypto_rng.Generator

From 0917c36f35f6cba100a91fcdc256bfafde649412 Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 6 Dec 2024 11:38:29 +0100
Subject: [PATCH 09/14] close the /dev/urandom file descriptor at exit

---
 rng/unix/urandom.ml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rng/unix/urandom.ml b/rng/unix/urandom.ml
index 4e32b7cf..36f750bd 100644
--- a/rng/unix/urandom.ml
+++ b/rng/unix/urandom.ml
@@ -7,6 +7,7 @@ let create ?time:_ () =
   let ic = In_channel.open_bin "/dev/urandom"
   and mutex = Mutex.create ()
   in
+  at_exit (fun () -> In_channel.close ic);
   (ic, mutex)
 
 let generate_into ~g:(ic, m) buf ~off len =

From 36562df4173afc6781308385baae09aaede7740e Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 6 Dec 2024 11:38:49 +0100
Subject: [PATCH 10/14] mirage-crypto-rng-unix: more documentation

---
 rng/unix/mirage_crypto_rng_unix.mli | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/rng/unix/mirage_crypto_rng_unix.mli b/rng/unix/mirage_crypto_rng_unix.mli
index 8a358030..69d1744c 100644
--- a/rng/unix/mirage_crypto_rng_unix.mli
+++ b/rng/unix/mirage_crypto_rng_unix.mli
@@ -12,13 +12,24 @@ val initialize : ?g:'a -> 'a Mirage_crypto_rng.generator -> unit
 (** [getrandom size] returns a buffer of [size] filled with random bytes. *)
 val getrandom : int -> string
 
+(** A generator that opens /dev/urandom and reads from that file descriptor
+    data whenever random data is needed. The file descriptor is closed in
+    [at_exit]. *)
 module Urandom : Mirage_crypto_rng.Generator
 
+(** A generator using [getrandom(3)] on Linux, [getentropy(3)] on BSD and macOS,
+    and [BCryptGenRandom()] on Windows. *)
 module Getentropy : Mirage_crypto_rng.Generator
 
+(** [use_default ()] initializes the RNG [Mirage_crypto_rng.default_generator]
+    with [Urandom] or resorts to [Getentropy] if the urandom failed to open the
+    /dev/urandom device. *)
 val use_default : unit -> unit
-(** [use_default ()] initializes with [Urandom] or resorts to [Getentropy] otherwise. *)
 
+(** [use_dev_random ()] initializes the RNG [Mirage_crypto_rng.default_generator]
+    with the [Urandom] generator. *)
 val use_dev_urandom : unit -> unit
 
+(** [use_getentropy ()] initializes the RNG [Mirage_crypto_rng.default_generator]
+    with the [Getentropy] generator. *)
 val use_getentropy : unit -> unit

From 5c885b0c091fb6a2a5d55490a498ea7206e98f67 Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 6 Dec 2024 11:43:26 +0100
Subject: [PATCH 11/14] adjust CI systems: no more 4.13

---
 .cirrus.yml                   | 1 -
 .github/workflows/test.yml    | 4 ++--
 .github/workflows/windows.yml | 2 +-
 3 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/.cirrus.yml b/.cirrus.yml
index c7b6b8bb..a435b11f 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -4,7 +4,6 @@ freebsd_instance:
 freebsd_task:
   env:
     matrix:
-      - OCAML_VERSION: 4.13.1
       - OCAML_VERSION: 4.14.2
 
   pkg_install_script: pkg install -y ocaml-opam gmp gmake pkgconf bash
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 61253abb..9d6f4e2f 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -9,7 +9,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ocaml-version: ["4.14.2", "4.13.1"]
+        ocaml-version: ["4.14.2"]
         operating-system: [macos-latest, ubuntu-latest]
 
     runs-on: ${{ matrix.operating-system }}
@@ -42,7 +42,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ocaml-version: ["5.0.0"]
+        ocaml-version: ["5.2.1"]
         operating-system: [macos-latest, ubuntu-latest]
 
     runs-on: ${{ matrix.operating-system }}
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index d9eb7d60..7f0248cb 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -9,7 +9,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ocaml-version: ["4.14.2", "4.13.1"]
+        ocaml-version: ["4.14.2"]
         operating-system: [windows-latest]
 
     runs-on: ${{ matrix.operating-system }}

From 53b1898e064d27d54f3df7175f159aef34a72d09 Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 6 Dec 2024 11:49:18 +0100
Subject: [PATCH 12/14] test_entropy: fail again, but disable on arm64

---
 tests/dune            | 4 +++-
 tests/test_entropy.ml | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/tests/dune b/tests/dune
index 32afebe7..f0363cae 100644
--- a/tests/dune
+++ b/tests/dune
@@ -41,7 +41,9 @@
  (name test_entropy)
  (modules test_entropy)
  (package mirage-crypto-rng)
- (libraries mirage-crypto-rng ohex))
+ (libraries mirage-crypto-rng ohex)
+ (enabled_if (<> %{architecture} "arm64")))
+ ; see https://github.com/mirage/mirage-crypto/issues/216
 
 (test
  (name test_ec)
diff --git a/tests/test_entropy.ml b/tests/test_entropy.ml
index 77b69e15..13cb91fe 100644
--- a/tests/test_entropy.ml
+++ b/tests/test_entropy.ml
@@ -35,7 +35,7 @@ let timer_check () =
     let data' = Mirage_crypto_rng.Entropy.interrupt_hook () in
     if String.equal !data data' then begin
       Ohex.pp Format.std_formatter data';
-      print_endline ("same data from timer at " ^ string_of_int i);
+      failwith ("same data from timer at " ^ string_of_int i);
     end;
     data := data'
   done

From b5262d193f0e0e6e69d31a504c0a8e36d31b9b9a Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 6 Dec 2024 13:21:55 +0100
Subject: [PATCH 13/14] revert putting miou-unix directly into bench/speed to
 allow ocaml 4 to succeed

---
 bench/dune     |  9 ++++-
 bench/miou.ml  | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++
 bench/speed.ml | 11 ------
 3 files changed, 99 insertions(+), 12 deletions(-)
 create mode 100644 bench/miou.ml

diff --git a/bench/dune b/bench/dune
index 71ad5387..dec1e4f9 100644
--- a/bench/dune
+++ b/bench/dune
@@ -2,4 +2,11 @@
  (names speed)
  (modules speed)
  (libraries mirage-crypto mirage-crypto-rng mirage-crypto-rng.unix
-   mirage-crypto-pk mirage-crypto-ec mirage-crypto-rng-miou-unix))
+   mirage-crypto-pk mirage-crypto-ec))
+
+; marking as "(optional)" leads to OCaml-CI failures
+; marking with "(package mirage-crypto-rng-miou-unix)" only has an effect with a "public_name"
+;(executables
+; (names miou)
+; (modules miou)
+; (libraries mirage-crypto-rng-miou-unix))
diff --git a/bench/miou.ml b/bench/miou.ml
new file mode 100644
index 00000000..27120c32
--- /dev/null
+++ b/bench/miou.ml
@@ -0,0 +1,91 @@
+open Mirage_crypto
+
+module Time = struct
+
+  let time ~n f a =
+    let t1 = Sys.time () in
+    for _ = 1 to n do ignore (f a) done ;
+    let t2 = Sys.time () in
+    (t2 -. t1)
+
+  let warmup () =
+    let x = ref 0 in
+    let rec go start =
+      if Sys.time () -. start < 1. then begin
+        for i = 0 to 10000 do x := !x + i done ;
+        go start
+      end in
+    go (Sys.time ())
+
+end
+
+let burn_period = 2.0
+
+let sizes = [16; 64; 256; 1024; 8192]
+(* let sizes = [16] *)
+
+let burn f n =
+  let buf = Mirage_crypto_rng.generate n in
+  let (t1, i1) =
+    let rec loop it =
+      let t = Time.time ~n:it f buf in
+      if t > 0.2 then (t, it) else loop (it * 10) in
+    loop 10 in
+  let iters = int_of_float (float i1 *. burn_period /. t1) in
+  let time  = Time.time ~n:iters f buf in
+  (iters, time, float (n * iters) /. time)
+
+let mb = 1024. *. 1024.
+
+let throughput title f =
+  Printf.printf "\n* [%s]\n%!" title ;
+  sizes |> List.iter @@ fun size ->
+    Gc.full_major () ;
+    let (iters, time, bw) = burn f size in
+    Printf.printf "    % 5d:  %04f MB/s  (%d iters in %.03f s)\n%!"
+      size (bw /. mb) iters time
+
+let bm name f = (name, fun () -> f name)
+
+let benchmarks = [
+  bm "pfortuna" (fun name ->
+    let open Mirage_crypto_rng_miou_unix.Pfortuna in
+    Miou_unix.run ~domains:2 @@ fun () ->
+    let rng = Mirage_crypto_rng_miou_unix.(initialize (module Pfortuna)) in
+    let g = create () in
+    reseed ~g "abcd" ;
+    throughput name (fun buf ->
+        let buf = Bytes.unsafe_of_string buf in
+        generate_into ~g buf ~off:0 (Bytes.length buf));
+    Mirage_crypto_rng_miou_unix.kill rng) ;
+]
+
+let help () =
+  Printf.printf "available benchmarks:\n  ";
+  List.iter (fun (n, _) -> Printf.printf "%s  " n) benchmarks ;
+  Printf.printf "\n%!"
+
+let runv fs =
+  Format.printf "accel: %a\n%!"
+    (fun ppf -> List.iter @@ fun x ->
+      Format.fprintf ppf "%s " @@
+        match x with `XOR -> "XOR" | `AES -> "AES" | `GHASH -> "GHASH")
+    accelerated;
+  Time.warmup () ;
+  List.iter (fun f -> f ()) fs
+
+
+let () =
+  let seed = "abcd" in
+  let g = Mirage_crypto_rng.(create ~seed (module Fortuna)) in
+  Mirage_crypto_rng.set_default_generator g;
+  match Array.to_list Sys.argv with
+  | _::(_::_ as args) -> begin
+      try
+        let fs =
+          args |> List.map @@ fun n ->
+            snd (benchmarks |> List.find @@ fun (n1, _) -> n = n1) in
+        runv fs
+      with Not_found -> help ()
+    end
+  | _ -> help ()
diff --git a/bench/speed.ml b/bench/speed.ml
index 1726a0c4..dcb25267 100644
--- a/bench/speed.ml
+++ b/bench/speed.ml
@@ -485,17 +485,6 @@ let benchmarks = [
         let buf = Bytes.unsafe_of_string buf in
         Mirage_crypto_rng.generate_into buf ~off:0 (Bytes.length buf))) ;
 
-  bm "pfortuna" (fun name ->
-    let open Mirage_crypto_rng_miou_unix.Pfortuna in
-    Miou_unix.run ~domains:2 @@ fun () ->
-    let rng = Mirage_crypto_rng_miou_unix.(initialize (module Pfortuna)) in
-    let g = create () in
-    reseed ~g "abcd" ;
-    throughput name (fun buf ->
-        let buf = Bytes.unsafe_of_string buf in
-        generate_into ~g buf ~off:0 (Bytes.length buf));
-    Mirage_crypto_rng_miou_unix.kill rng) ;
-
   bm "getentropy" (fun name ->
     Mirage_crypto_rng_unix.use_getentropy ();
     throughput name (fun buf ->

From 9d30a605683f92ad63f1134597e66fb4b1092f25 Mon Sep 17 00:00:00 2001
From: Hannes Mehnert <hannes@mehnert.org>
Date: Fri, 6 Dec 2024 13:27:14 +0100
Subject: [PATCH 14/14] github CI: increase versions

---
 .github/workflows/test.yml    | 8 ++++----
 .github/workflows/windows.yml | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 9d6f4e2f..c9d5415b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -16,10 +16,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Use OCaml ${{ matrix.ocaml-version }}
-        uses: ocaml/setup-ocaml@v2
+        uses: ocaml/setup-ocaml@v3
         with:
           opam-local-packages: |
             *.opam
@@ -49,10 +49,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Use OCaml ${{ matrix.ocaml-version }}
-        uses: ocaml/setup-ocaml@v2
+        uses: ocaml/setup-ocaml@v3
         with:
           opam-local-packages: |
             mirage-crypto.opam
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 7f0248cb..453831ca 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -16,10 +16,10 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Use OCaml ${{ matrix.ocaml-compiler }}
-        uses: ocaml/setup-ocaml@v2
+        uses: ocaml/setup-ocaml@v3
         with:
           opam-repositories: |
             opam-repository-mingw: https://github.com/ocaml-opam/opam-repository-mingw.git#sunset