Add an easy way to directly use the system PRNG.

4 files changed, 125 insertions, 0 deletions

diff --git a/src/cmd/rng.cpp b/src/cmd/rng.cpp
index 187fbad1e..0fdec2019 100644
--- a/src/cmd/rng.cpp
+++ b/src/cmd/rng.cpp
@@ -7,6 +7,10 @@
 #include "apps.h"
 #include <botan/libstate.h>
 
+#if defined(BOTAN_HAS_SYSTEM_RNG)
+  #include <botan/system_rng.h>
+#endif
+
 namespace {
 
 int rng(int argc, char* argv[])
@@ -22,6 +26,10 @@ int rng(int argc, char* argv[])
       const size_t amt = to_u32bit(argv[argc-1]);
       const bool raw = (argc == 3 && std::string(argv[1]) == "--raw-entropy");
 
+#if defined(BOTAN_HAS_SYSTEM_RNG)
+      std::cout << "System " << hex_encode(system_rng().random_vec(amt)) << "\n";
+#endif
+
       if(!raw)
          {
          AutoSeeded_RNG rng;
diff --git a/src/lib/rng/system_rng/info.txt b/src/lib/rng/system_rng/info.txt
new file mode 100644
index 000000000..387b7e1dd
--- /dev/null
+++ b/src/lib/rng/system_rng/info.txt
@@ -0,0 +1,19 @@
+define SYSTEM_RNG 20141202
+
+<os>
+aix
+cygwin
+darwin
+dragonfly
+freebsd
+haiku
+hpux
+hurd
+irix
+linux
+netbsd
+openbsd
+qnx
+solaris
+tru64
+</os>
diff --git a/src/lib/rng/system_rng/system_rng.cpp b/src/lib/rng/system_rng/system_rng.cpp
new file mode 100644
index 000000000..afffb69cc
--- /dev/null
+++ b/src/lib/rng/system_rng/system_rng.cpp
@@ -0,0 +1,79 @@
+/*
+* System RNG
+* (C) 2014 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/system_rng.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+
+namespace Botan {
+
+namespace {
+
+class System_RNG : public RandomNumberGenerator
+   {
+   public:
+      System_RNG();
+      ~System_RNG();
+
+      void randomize(byte buf[], size_t len);
+
+      bool is_seeded() const { return true; }
+      void clear() {}
+      std::string name() const { return "system"; }
+
+      void reseed(size_t) {}
+      void add_entropy(const byte[], size_t) {}
+   private:
+      int m_fd;
+   };
+
+System_RNG::System_RNG()
+   {
+   m_fd = ::open("/dev/urandom", O_RDONLY);
+   if(m_fd < 0)
+      throw std::runtime_error("System_RNG failed to open /dev/urandom");
+   }
+
+System_RNG::~System_RNG()
+   {
+   ::close(m_fd);
+   }
+
+void System_RNG::randomize(byte buf[], size_t len)
+   {
+   while(len)
+      {
+      ssize_t got = ::read(m_fd, buf, len);
+
+      if(got < 0)
+         {
+         if(errno == EINTR)
+            continue;
+         throw std::runtime_error("System_RNG read failed error " + std::to_string(errno));
+         }
+      if(got == 0)
+         throw std::runtime_error("System_RNG EOF on device"); // ?!?
+
+      buf += got;
+      len -= got;
+      }
+   }
+
+}
+
+RandomNumberGenerator& system_rng()
+   {
+   static System_RNG g_system_rng;
+   return g_system_rng;
+   }
+
+}
diff --git a/src/lib/rng/system_rng/system_rng.h b/src/lib/rng/system_rng/system_rng.h
new file mode 100644
index 000000000..6b4746a9c
--- /dev/null
+++ b/src/lib/rng/system_rng/system_rng.h
@@ -0,0 +1,19 @@
+/*
+* System RNG interface
+* (C) 2014 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_SYSTEM_RNG_H__
+#define BOTAN_SYSTEM_RNG_H__
+
+#include <botan/rng.h>
+
+namespace Botan {
+
+BOTAN_DLL RandomNumberGenerator& system_rng();
+
+}
+
+#endif