Merge #10372: Add perf counter data to GetStrongRandBytes state in scheduler

888cce5 Add perf counter data to GetStrongRandBytes state in scheduler (Matt Corallo)
399fb8f Add internal method to add new random data to our internal RNG state (Matt Corallo)

Tree-SHA512: 9732a3804d015eaf48d56b60c73880014845fd17a098f1ac2eff6bd50a4beb8b8be65956ac1f0d641e96e3a53c17daddd919401edbf2e3797c3fb687730fb913

3 files changed, 46 insertions, 0 deletions

diff --git a/src/random.cpp b/src/random.cpp
index 3b9df3edaa..de7553c825 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -203,10 +203,43 @@ void GetRandBytes(unsigned char* buf, int num)
     }
 }
 
+static void AddDataToRng(void* data, size_t len);
+
+void RandAddSeedSleep()
+{
+    int64_t nPerfCounter1 = GetPerformanceCounter();
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    int64_t nPerfCounter2 = GetPerformanceCounter();
+
+    // Combine with and update state
+    AddDataToRng(&nPerfCounter1, sizeof(nPerfCounter1));
+    AddDataToRng(&nPerfCounter2, sizeof(nPerfCounter2));
+
+    memory_cleanse(&nPerfCounter1, sizeof(nPerfCounter1));
+    memory_cleanse(&nPerfCounter2, sizeof(nPerfCounter2));
+}
+
+
 static std::mutex cs_rng_state;
 static unsigned char rng_state[32] = {0};
 static uint64_t rng_counter = 0;
 
+static void AddDataToRng(void* data, size_t len) {
+    CSHA512 hasher;
+    hasher.Write((const unsigned char*)&len, sizeof(len));
+    hasher.Write((const unsigned char*)data, len);
+    unsigned char buf[64];
+    {
+        std::unique_lock<std::mutex> lock(cs_rng_state);
+        hasher.Write(rng_state, sizeof(rng_state));
+        hasher.Write((const unsigned char*)&rng_counter, sizeof(rng_counter));
+        ++rng_counter;
+        hasher.Finalize(buf);
+        memcpy(rng_state, buf + 32, 32);
+    }
+    memory_cleanse(buf, 64);
+}
+
 void GetStrongRandBytes(unsigned char* out, int num)
 {
     assert(num <= 32);
diff --git a/src/random.h b/src/random.h
index 9551e1c461..6a63d57429 100644
--- a/src/random.h
+++ b/src/random.h
@@ -24,6 +24,13 @@ int GetRandInt(int nMax);
 uint256 GetRandHash();
 
 /**
+ * Add a little bit of randomness to the output of GetStrongRangBytes.
+ * This sleeps for a millisecond, so should only be called when there is
+ * no other work to be done.
+ */
+void RandAddSeedSleep();
+
+/**
  * Function to gather random data from multiple sources, failing whenever any
  * of those source fail to provide a result.
  */
diff --git a/src/scheduler.cpp b/src/scheduler.cpp
index 0c1cfa2718..923ba2c231 100644
--- a/src/scheduler.cpp
+++ b/src/scheduler.cpp
@@ -4,6 +4,7 @@
 
 #include "scheduler.h"
 
+#include "random.h"
 #include "reverselock.h"
 
 #include <assert.h>
@@ -39,6 +40,11 @@ void CScheduler::serviceQueue()
     // is called.
     while (!shouldStop()) {
         try {
+            if (!shouldStop() && taskQueue.empty()) {
+                reverse_lock<boost::unique_lock<boost::mutex> > rlock(lock);
+                // Use this chance to get a tiny bit more entropy
+                RandAddSeedSleep();
+            }
             while (!shouldStop() && taskQueue.empty()) {
                 // Wait until there is something to do.
                 newTaskScheduled.wait(lock);