From 6d4416ccb0bbe02105c4b9dfa1442b9198c0d923 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Thu, 26 May 2016 09:26:09 +0100
Subject: [PATCH] rand/noise.c (noise_devrandom): Use OpenBSD system call
 `getentropy'.

If it's available, it does the right thing.  I think.
---
 configure.ac |  1 +
 rand/noise.c | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/configure.ac b/configure.ac
index 631f7838..7887da32 100644
--- a/configure.ac
+++ b/configure.ac
@@ -222,6 +222,7 @@ AC_SUBST([limits])
 dnl Functions used for noise-gathering.
 AC_CHECK_FUNCS([setgroups])
 AC_CHECK_HEADERS([linux/random.h])
+AC_CHECK_FUNCS([getentropy])
 AC_CACHE_CHECK([whether the freewheel noise generator will work],
 	[catacomb_cv_freewheel],
 [AC_TRY_LINK(
diff --git a/rand/noise.c b/rand/noise.c
index b59fd8ad..2c30c13c 100644
--- a/rand/noise.c
+++ b/rand/noise.c
@@ -172,6 +172,9 @@ int noise_devrandom(rand_pool *r)
   fd_set infd;
   struct timeval tv = { 0, 0 };
 #endif
+#ifdef HAVE_GETENTROPY
+  size_t nn;
+#endif
 
 #if defined(HAVE_LINUX_RANDOM_H) &&					\
     defined(GRND_NONBLOCK) &&						\
@@ -189,6 +192,18 @@ int noise_devrandom(rand_pool *r)
   if (n == sizeof(buf)) goto win;
 #endif
 
+#ifdef HAVE_GETENTROPY
+  /* --- OpenBSD-flavoured shinies --- */
+
+  while (n < sizeof(buf)) {
+    nn = sizeof(buf) - nn;
+    if (nn > 256) nn = 256;
+    if (getentropy(buf + n, nn)) break;
+    n += nn;
+  }
+  if (n == sizeof(buf)) goto win;
+#endif
+
 #ifdef __linux__
   /* --- Don't take from `/dev/urandom' if `/dev/random' would block --- */
 
-- 
2.11.0