Implement getentropy for Cygwin

	* miscfuncs.cc (getentropy): Move fhandler_dev_random::crypt_gen_random
	here and rename to getentropy.  Fix type and return values to match
	getentropy requirements.
	* miscfuncs.h (getentropy): Add prototype.
	* fhandler.h (fhandler_dev_random::crypt_gen_random): Remove prototype.
	* fhandler_random.cc (fhandler_dev_random::crypt_gen_random): Drop.
	(fhandler_dev_random::write): Use getentropy instead.
	(fhandler_dev_random::read): Ditto.
	* fhandler_socket.cc (fhandler_socket::af_local_set_secret): Ditto.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

1 files changed, 19 insertions, 0 deletions

diff --git a/winsup/cygwin/miscfuncs.cc b/winsup/cygwin/miscfuncs.cc
index 796494132..54150f106 100644
--- a/winsup/cygwin/miscfuncs.cc
+++ b/winsup/cygwin/miscfuncs.cc
@@ -236,6 +236,25 @@ check_iovec (const struct iovec *iov, int iovcnt, bool forwrite)
   return -1;
 }
 
+/* There's a bug in ntsecapi.h (Mingw as well as MSFT).  SystemFunction036
+   is, in fact, a WINAPI function, but it's not defined as such.  Therefore
+   we have to do it correctly here. */
+#define RtlGenRandom SystemFunction036
+extern "C" BOOLEAN WINAPI RtlGenRandom (PVOID, ULONG);
+
+/* Used by arc2random, fhandler_socket and fhandler_random. */
+extern "C" int
+getentropy (void *ptr, size_t len)
+{
+  if (!RtlGenRandom (ptr, len))
+    {
+      debug_printf ("%E = RtlGenRandom()");
+      set_errno (EIO);
+      return -1;
+    }
+  return 0;
+}
+
 /* Try hard to schedule another thread.  
    Remember not to call this in a lock condition or you'll potentially
    suffer starvation.  */