From fff1db973096a893475f3ec96ee6f28e35c4a67c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C3=A9o=20Lam?= <leo@innovatetechnologi.es>
Date: Mon, 21 May 2018 15:48:17 +0200
Subject: 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.
---
 Source/Core/Common/TraversalServer.cpp | 31 +++----------------------------
 1 file changed, 3 insertions(+), 28 deletions(-)

(limited to 'Source/Core/Common/TraversalServer.cpp')

diff --git a/Source/Core/Common/TraversalServer.cpp b/Source/Core/Common/TraversalServer.cpp
index 5da45a05fe..097418b143 100644
--- a/Source/Core/Common/TraversalServer.cpp
+++ b/Source/Core/Common/TraversalServer.cpp
@@ -20,6 +20,7 @@
 #include <systemd/sd-daemon.h>
 #endif
 
+#include "Common/Random.h"
 #include "Common/TraversalProto.h"
 
 #define DEBUG 0
@@ -114,7 +115,6 @@ struct hash<TraversalHostId>
 }
 
 static int sock;
-static int urandomFd;
 static std::unordered_map<TraversalRequestId, OutgoingPacketInfo> outgoingPackets;
 static std::unordered_map<TraversalHostId, EvictEntry<TraversalInetAddress>> connectedClients;
 
@@ -166,28 +166,11 @@ static sockaddr_in6 MakeSinAddr(const TraversalInetAddress& addr)
   return result;
 }
 
-static void GetRandomBytes(void* output, size_t size)
-{
-  static u8 bytes[8192];
-  static size_t bytesLeft = 0;
-  if (bytesLeft < size)
-  {
-    ssize_t rv = read(urandomFd, bytes, sizeof(bytes));
-    if (rv != sizeof(bytes))
-    {
-      perror("read from /dev/urandom");
-      exit(1);
-    }
-    bytesLeft = sizeof(bytes);
-  }
-  memcpy(output, bytes + (bytesLeft -= size), size);
-}
-
 static void GetRandomHostId(TraversalHostId* hostId)
 {
   char buf[9];
   u32 num;
-  GetRandomBytes(&num, sizeof(num));
+  Common::Random::Generate(&num, sizeof(num));
   sprintf(buf, "%08x", num);
   memcpy(hostId->data(), buf, 8);
 }
@@ -215,7 +198,7 @@ static void TrySend(const void* buffer, size_t size, sockaddr_in6* addr)
 static TraversalPacket* AllocPacket(const sockaddr_in6& dest, TraversalRequestId misc = 0)
 {
   TraversalRequestId requestId;
-  GetRandomBytes(&requestId, sizeof(requestId));
+  Common::Random::Generate(&requestId, sizeof(requestId));
   OutgoingPacketInfo* info = &outgoingPackets[requestId];
   info->dest = dest;
   info->misc = misc;
@@ -376,14 +359,6 @@ static void HandlePacket(TraversalPacket* packet, sockaddr_in6* addr)
 int main()
 {
   int rv;
-
-  urandomFd = open("/dev/urandom", O_RDONLY);
-  if (urandomFd < 0)
-  {
-    perror("open /dev/urandom");
-    return 1;
-  }
-
   sock = socket(PF_INET6, SOCK_DGRAM, 0);
   if (sock == -1)
   {
-- 
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