X-Git-Url: https://www.bearssl.org/gitweb//home/git/?p=BearSSL;a=blobdiff_plain;f=src%2Finner.h;h=07e1d0a478e801a91580658918130fb8b595e407;hp=986220f0f5421ef11db5a7dd4c5c60e15043d7ab;hb=e4edfb84eda32c3b3aa548f975c4a13d406db989;hpb=924921d1be88f61b60bba54c48a4b9e81073528a

diff --git a/src/inner.h b/src/inner.h
index 986220f..07e1d0a 100644
--- a/src/inner.h
+++ b/src/inner.h
@@ -309,9 +309,20 @@
  * values are documented on:
  *    https://sourceforge.net/p/predef/wiki/OperatingSystems/
  *
- * TODO: enrich the list of detected system. Also add detection for
- * alternate system calls like getentropy(), which are usually
- * preferable when available.
+ * Win32's CryptGenRandom() should be available on Windows systems.
+ *
+ * /dev/urandom should work on all Unix-like systems (including macOS X).
+ *
+ * getentropy() is present on Linux (Glibc 2.25+), FreeBSD (12.0+) and
+ * OpenBSD (5.6+). For OpenBSD, there does not seem to be easy to use
+ * macros to test the minimum version, so we just assume that it is
+ * recent enough (last version without getentropy() has gone out of
+ * support in May 2015).
+ *
+ * Ideally we should use getentropy() on macOS (10.12+) too, but I don't
+ * know how to test the exact OS version with preprocessor macros.
+ *
+ * TODO: enrich the list of detected system.
  */
 
 #ifndef BR_USE_URANDOM
@@ -328,6 +339,15 @@
 #endif
 #endif
 
+#ifndef BR_USE_GETENTROPY
+#if (defined __linux__ \
+	&& (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 25))) \
+	|| (defined __FreeBSD__ && __FreeBSD__ >= 12) \
+	|| defined __OpenBSD__
+#define BR_USE_GETENTROPY   1
+#endif
+#endif
+
 #ifndef BR_USE_WIN32_RAND
 #if defined _WIN32 || defined _WIN64
 #define BR_USE_WIN32_RAND   1