From 15e794bdd83c4bf7ba37a2e83af6cd581fe37c20 Mon Sep 17 00:00:00 2001
From: Kittywhiskers Van Gogh <63189531+kwvg@users.noreply.github.com>
Date: Wed, 2 Feb 2022 15:35:26 +0100
Subject: [PATCH] merge bitcoin#24238: use arc4random on OpenBSD

---
 configure.ac   |  7 -------
 src/random.cpp | 20 ++++++++------------
 2 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/configure.ac b/configure.ac
index 7d0ebbc5bb..b1e8b7e11e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1171,13 +1171,6 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <unistd.h>
  [ AC_MSG_RESULT(no)]
 )
 
-AC_MSG_CHECKING(for getentropy)
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <unistd.h>]],
- [[ getentropy(nullptr, 32) ]])],
- [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_GETENTROPY, 1,[Define this symbol if the BSD getentropy system call is available]) ],
- [ AC_MSG_RESULT(no)]
-)
-
 AC_MSG_CHECKING(for getentropy via random.h)
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <unistd.h>
  #include <sys/random.h>]],
diff --git a/src/random.cpp b/src/random.cpp
index 3ccbe82c4a..21c56c106a 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -34,10 +34,8 @@
 #include <sys/syscall.h>
 #include <linux/random.h>
 #endif
-#if defined(HAVE_GETENTROPY) || (defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX))
-#include <unistd.h>
-#endif
 #if defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX)
+#include <unistd.h>
 #include <sys/random.h>
 #endif
 #ifdef HAVE_SYSCTL_ARND
@@ -307,16 +305,14 @@ void GetOSRand(unsigned char *ent32)
             RandFailure();
         }
     }
-#elif defined(HAVE_GETENTROPY) && defined(__OpenBSD__)
-    /* On OpenBSD this can return up to 256 bytes of entropy, will return an
-     * error if more are requested.
-     * The call cannot return less than the requested number of bytes.
-       getentropy is explicitly limited to openbsd here, as a similar (but not
-       the same) function may exist on other platforms via glibc.
+#elif defined(__OpenBSD__)
+    /* OpenBSD. From the arc4random(3) man page:
+       "Use of these functions is encouraged for almost all random number
+        consumption because the other interfaces are deficient in either
+        quality, portability, standardization, or availability."
+       The function call is always successful.
      */
-    if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) {
-        RandFailure();
-    }
+    arc4random_buf(ent32, NUM_OS_RANDOM_BYTES);
     // Silence a compiler warning about unused function.
     (void)GetDevURandom;
 #elif defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX)