that "device" is an abstraction to the underlying OS PRNG.

In OpenBSD's case, we know it has optimal entropy properties,
so just say so.

okay mikeb@, "why not" deraadt@

1 files changed, 34 insertions, 2 deletions

diff --git a/lib/libcxx/src/random.cpp b/lib/libcxx/src/random.cpp
index 4ab424eaa6e..9efac7a66a7 100644
--- a/lib/libcxx/src/random.cpp
+++ b/lib/libcxx/src/random.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include <__config>
+
 #if defined(_LIBCPP_USING_WIN32_RANDOM)
 // Must be defined before including stdlib.h to enable rand_s().
 #define _CRT_RAND_S
@@ -23,17 +25,43 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-#if defined(_LIBCPP_USING_DEV_RANDOM)
+#if defined(_LIBCPP_USING_GETENTROPY)
+#include <sys/random.h>
+#elif defined(_LIBCPP_USING_DEV_RANDOM)
 #include <fcntl.h>
 #include <unistd.h>
 #elif defined(_LIBCPP_USING_NACL_RANDOM)
 #include <nacl/nacl_random.h>
 #endif
 
+#include <limits>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if defined(_LIBCPP_USING_ARC4_RANDOM)
+#if defined(_LIBCPP_USING_GETENTROPY)
+
+random_device::random_device(const string& __token)
+{
+    if (__token != "/dev/urandom")
+        __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
+}
+
+random_device::~random_device()
+{
+}
+
+unsigned
+random_device::operator()()
+{
+    unsigned r;
+    size_t n = sizeof(r);
+    int err = getentropy(&r, n);
+    if (err)
+        __throw_system_error(errno, "random_device getentropy failed");
+    return r;
+}
+
+#elif defined(_LIBCPP_USING_ARC4_RANDOM)
 
 random_device::random_device(const string& __token)
 {
@@ -146,7 +174,11 @@ random_device::operator()()
 double
 random_device::entropy() const _NOEXCEPT
 {
+#ifdef __OpenBSD__
+    return std::numeric_limits<unsigned int>::digits;
+#else
     return 0;
+#endif
 }
 
 _LIBCPP_END_NAMESPACE_STD