X-Git-Url: https://git.novaco.in/?a=blobdiff_plain;f=src%2Fmain.cpp;h=a7871fcc168747b4b8378dfaf69adba8649a2c0f;hb=10fd7f66893fd62ab65f9302115834c441eb571b;hp=832a0f9240265052de3543a9e95d5bf062f22ab0;hpb=eb5fff9e16b2c3e94835cd3a8897318472df2374;p=novacoin.git

diff --git a/src/main.cpp b/src/main.cpp
index 832a0f9..a7871fc 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -659,11 +659,32 @@ int64 static GetBlockValue(int nHeight, int64 nFees)
     return nSubsidy + nFees;
 }
 
+static const int64 nTargetTimespan = 14 * 24 * 60 * 60; // two weeks
+static const int64 nTargetSpacing = 10 * 60;
+static const int64 nInterval = nTargetTimespan / nTargetSpacing;
+
+//
+// minimum amount of work that could possibly be required nTime after
+// minimum work required was nBase
+//
+unsigned int ComputeMinWork(unsigned int nBase, int64 nTime)
+{
+    CBigNum bnResult;
+    bnResult.SetCompact(nBase);
+    while (nTime > 0 && bnResult < bnProofOfWorkLimit)
+    {
+        // Maximum 400% adjustment...
+        bnResult *= 4;
+        // ... in best-case exactly 4-times-normal target time
+        nTime -= nTargetTimespan*4;
+    }
+    if (bnResult > bnProofOfWorkLimit)
+        bnResult = bnProofOfWorkLimit;
+    return bnResult.GetCompact();
+}
+
 unsigned int static GetNextWorkRequired(const CBlockIndex* pindexLast)
 {
-    const int64 nTargetTimespan = 14 * 24 * 60 * 60; // two weeks
-    const int64 nTargetSpacing = 10 * 60;
-    const int64 nInterval = nTargetTimespan / nTargetSpacing;
 
     // Genesis block
     if (pindexLast == NULL)
@@ -1340,6 +1361,28 @@ bool ProcessBlock(CNode* pfrom, CBlock* pblock)
     if (!pblock->CheckBlock())
         return error("ProcessBlock() : CheckBlock FAILED");
 
+    CBlockIndex* pcheckpoint = Checkpoints::GetLastCheckpoint(mapBlockIndex);
+    if (pcheckpoint && pblock->hashPrevBlock != hashBestChain)
+    {
+        // Extra checks to prevent "fill up memory by spamming with bogus blocks"
+        int64 deltaTime = pblock->GetBlockTime() - pcheckpoint->nTime;
+        if (deltaTime < 0)
+        {
+            pfrom->Misbehaving(100);
+            return error("ProcessBlock() : block with timestamp before last checkpoint");
+        }
+        CBigNum bnNewBlock;
+        bnNewBlock.SetCompact(pblock->nBits);
+        CBigNum bnRequired;
+        bnRequired.SetCompact(ComputeMinWork(pcheckpoint->nBits, deltaTime));
+        if (bnNewBlock > bnRequired)
+        {
+            pfrom->Misbehaving(100);
+            return error("ProcessBlock() : block with too little proof-of-work");
+        }
+    }
+
+
     // If don't already have its previous block, shunt it off to holding area until we get it
     if (!mapBlockIndex.count(pblock->hashPrevBlock))
     {