Kill insecure_random and associated global state

There are only a few uses of `insecure_random` outside the tests.
This PR replaces uses of insecure_random (and its accompanying global
state) in the core code with an FastRandomContext that is automatically
seeded on creation.

This is meant to be used for inner loops. The FastRandomContext
can be in the outer scope, or the class itself, then rand32() is used
inside the loop. Useful e.g. for pushing addresses in CNode or the fee
rounding, or randomization for coin selection.

As a context is created per purpose, thus it gets rid of
cross-thread unprotected shared usage of a single set of globals, this
should also get rid of the potential race conditions.

- I'd say TxMempool::check is not called enough to warrant using a special
  fast random context, this is switched to GetRand() (open for
  discussion...)

- The use of `insecure_rand` in ConnectThroughProxy has been replaced by
  an atomic integer counter. The only goal here is to have a different
  credentials pair for each connection to go on a different Tor circuit,
  it does not need to be random nor unpredictable.

- To avoid having a FastRandomContext on every CNode, the context is
  passed into PushAddress as appropriate.

There remains an insecure_random for test usage in `test_random.h`.

1 files changed, 9 insertions, 6 deletions

diff --git a/src/main.cpp b/src/main.cpp
index c92a38be98..ab0dc07529 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4758,6 +4758,7 @@ static void RelayAddress(const CAddress& addr, bool fReachable, CConnman& connma
     uint64_t hashAddr = addr.GetHash();
     std::multimap<uint64_t, CNode*> mapMix;
     const CSipHasher hasher = connman.GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY).Write(hashAddr << 32).Write((GetTime() + hashAddr) / (24*60*60));
+    FastRandomContext insecure_rand;
 
     auto sortfunc = [&mapMix, &hasher](CNode* pnode) {
         if (pnode->nVersion >= CADDR_TIME_VERSION) {
@@ -4766,9 +4767,9 @@ static void RelayAddress(const CAddress& addr, bool fReachable, CConnman& connma
         }
     };
 
-    auto pushfunc = [&addr, &mapMix, &nRelayNodes] {
+    auto pushfunc = [&addr, &mapMix, &nRelayNodes, &insecure_rand] {
         for (auto mi = mapMix.begin(); mi != mapMix.end() && nRelayNodes-- > 0; ++mi)
-            mi->second->PushAddress(addr);
+            mi->second->PushAddress(addr, insecure_rand);
     };
 
     connman.ForEachNodeThen(std::move(sortfunc), std::move(pushfunc));
@@ -5078,14 +5079,15 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             if (fListen && !IsInitialBlockDownload())
             {
                 CAddress addr = GetLocalAddress(&pfrom->addr, pfrom->GetLocalServices());
+                FastRandomContext insecure_rand;
                 if (addr.IsRoutable())
                 {
                     LogPrint("net", "ProcessMessages: advertising address %s\n", addr.ToString());
-                    pfrom->PushAddress(addr);
+                    pfrom->PushAddress(addr, insecure_rand);
                 } else if (IsPeerAddrLocalGood(pfrom)) {
                     addr.SetIP(pfrom->addrLocal);
                     LogPrint("net", "ProcessMessages: advertising address %s\n", addr.ToString());
-                    pfrom->PushAddress(addr);
+                    pfrom->PushAddress(addr, insecure_rand);
                 }
             }
 
@@ -6008,8 +6010,9 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
 
         pfrom->vAddrToSend.clear();
         vector<CAddress> vAddr = connman.GetAddresses();
+        FastRandomContext insecure_rand;
         BOOST_FOREACH(const CAddress &addr, vAddr)
-            pfrom->PushAddress(addr);
+            pfrom->PushAddress(addr, insecure_rand);
     }
 
 
@@ -6842,7 +6845,7 @@ bool SendMessages(CNode* pto, CConnman& connman)
             // until scheduled broadcast, then move the broadcast to within MAX_FEEFILTER_CHANGE_DELAY.
             else if (timeNow + MAX_FEEFILTER_CHANGE_DELAY * 1000000 < pto->nextSendTimeFeeFilter &&
                      (currentFilter < 3 * pto->lastSentFeeFilter / 4 || currentFilter > 4 * pto->lastSentFeeFilter / 3)) {
-                pto->nextSendTimeFeeFilter = timeNow + (insecure_rand() % MAX_FEEFILTER_CHANGE_DELAY) * 1000000;
+                pto->nextSendTimeFeeFilter = timeNow + GetRandInt(MAX_FEEFILTER_CHANGE_DELAY) * 1000000;
             }
         }
     }