From 654e2e5af3095c20930cffc399d1e4bba25bf956 Mon Sep 17 00:00:00 2001
From: oittaa <oittaa@users.noreply.github.com>
Date: Wed, 10 Oct 2018 03:36:26 +0300
Subject: [PATCH] Use getentropy() if available (#407)

* Check if getentropy exists in configure.ac

* Use getentropy in rand.c if available

* rand.c: try to fix broken osx

* Use /dev/urandom with broken operating systems

* Enable getentropy on macOS

* Don't include <sys/random.h> on Windows

* getentropy needs different header on old Linux versions

* Move getentropy check to different autoconf file
---
 config/ac_checks.m4 |  1 +
 src/common/rand.c   | 17 ++++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/config/ac_checks.m4 b/config/ac_checks.m4
index 393f251ee..f45376d86 100644
--- a/config/ac_checks.m4
+++ b/config/ac_checks.m4
@@ -21,5 +21,6 @@ AC_TYPE_UINT8_T
 AC_FUNC_MALLOC
 AC_CHECK_FUNCS([gettimeofday memmove memset pow sqrt strdup])
 AC_CHECK_SIZEOF([size_t])
+AC_CHECK_FUNCS(getentropy)
 ]
 )
diff --git a/src/common/rand.c b/src/common/rand.c
index 1ce8712ff..25f6f2471 100644
--- a/src/common/rand.c
+++ b/src/common/rand.c
@@ -8,6 +8,11 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <strings.h>
+#if defined(__APPLE__)
+#include <sys/random.h>
+#else
+#include <unistd.h>
+#endif
 #endif
 #include <fcntl.h>
 
@@ -51,12 +56,21 @@ void OQS_randombytes(uint8_t *random_array, size_t bytes_to_read) {
 	oqs_randombytes_algorithm(random_array, bytes_to_read);
 }
 
+#if !defined(_WIN32)
+#if defined(HAVE_GETENTROPY)
+void OQS_randombytes_system(uint8_t *random_array, size_t bytes_to_read) {
+
+	int rc;
+	do {
+		rc = getentropy(random_array, bytes_to_read);
+	} while (rc != 0);
+}
+#else
 static __inline void delay(unsigned int count) {
 	while (count--) {
 	}
 }
 
-#if !defined(_WIN32)
 void OQS_randombytes_system(uint8_t *random_array, size_t bytes_to_read) {
 
 	FILE *handle;
@@ -82,6 +96,7 @@ void OQS_randombytes_system(uint8_t *random_array, size_t bytes_to_read) {
 	}
 	fclose(handle);
 }
+#endif
 #else
 void OQS_randombytes_system(uint8_t *random_array, size_t bytes_to_read) {
 	HCRYPTPROV hCryptProv;