Add the Darwin_SecRandom entropy source

It uses the SecRandomCopyBytes function from the Security framework of
OS X and iOS. We need this because it is the official way to get
cryptographically secure random numbers on iOS, where /dev/random is not
accessible due to sandboxing.

1 files changed, 28 insertions, 0 deletions

diff --git a/src/lib/entropy/darwin_secrandom/darwin_secrandom.cpp b/src/lib/entropy/darwin_secrandom/darwin_secrandom.cpp
new file mode 100644
index 000000000..f04b75a12
--- /dev/null
+++ b/src/lib/entropy/darwin_secrandom/darwin_secrandom.cpp
@@ -0,0 +1,28 @@
+/*
+* Darwin SecRandomCopyBytes EntropySource
+* (C) 2015 Daniel Seither (Kullo GmbH)
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/internal/darwin_secrandom.h>
+#include <Security/Security.h>
+
+namespace Botan {
+
+/**
+* Gather entropy from SecRandomCopyBytes
+*/
+void Darwin_SecRandom::poll(Entropy_Accumulator& accum)
+   {
+   const size_t ENTROPY_BITS_PER_BYTE = 8;
+   const size_t BUF_SIZE = 256;
+
+   m_buf.resize(BUF_SIZE);
+   if (0 == SecRandomCopyBytes(kSecRandomDefault, m_buf.size(), m_buf.data()))
+      {
+      accum.add(m_buf.data(), m_buf.size(), ENTROPY_BITS_PER_BYTE);
+      }
+   }
+
+}