Common: Add Random utilities

This makes it easier to generate random numbers or fill a buffer with
random data in a cryptographically secure way.

This also replaces existing usages of RNG functions in the codebase:

* <random> is pretty hard to use correctly, and std::random_device does
  not give enough guarantees about its results (it's
  implementation-defined, non cryptographically secure and could be
  deterministic on some platforms).
  Doing things correctly is error prone and verbose.

* rand() is terrible and should not be used especially in crypto code.

1 files changed, 2 insertions, 12 deletions

diff --git a/Source/Core/Common/TraversalClient.cpp b/Source/Core/Common/TraversalClient.cpp
index 4c415b2c64..36eb431c7f 100644
--- a/Source/Core/Common/TraversalClient.cpp
+++ b/Source/Core/Common/TraversalClient.cpp
@@ -4,22 +4,12 @@
 
 #include <cstddef>
 #include <cstring>
-#include <random>
 #include <string>
 
 #include "Common/CommonTypes.h"
 #include "Common/Logging/Log.h"
 #include "Common/MsgHandler.h"
-
-static void GetRandomishBytes(u8* buf, size_t size)
-{
-  // We don't need high quality random numbers (which might not be available),
-  // just non-repeating numbers!
-  static std::mt19937 prng(enet_time_get());
-  static std::uniform_int_distribution<unsigned int> u8_distribution(0, 255);
-  for (size_t i = 0; i < size; i++)
-    buf[i] = u8_distribution(prng);
-}
+#include "Common/Random.h"
 
 TraversalClient::TraversalClient(ENetHost* netHost, const std::string& server, const u16 port)
     : m_NetHost(netHost), m_Server(server), m_port(port)
@@ -280,7 +270,7 @@ TraversalRequestId TraversalClient::SendTraversalPacket(const TraversalPacket& p
 {
   OutgoingTraversalPacketInfo info;
   info.packet = packet;
-  GetRandomishBytes((u8*)&info.packet.requestId, sizeof(info.packet.requestId));
+  Common::Random::Generate(&info.packet.requestId, sizeof(info.packet.requestId));
   info.tries = 0;
   m_OutgoingTraversalPackets.push_back(info);
   ResendPacket(&m_OutgoingTraversalPackets.back());