From dffda08fddf00889dd710ab704e9e99929be325a Mon Sep 17 00:00:00 2001
From: Scott Nadal <scott.nadal@gmail.com>
Date: Fri, 15 Jun 2012 16:32:28 +0100
Subject: [PATCH] PPCoin: Save sync-checkpoint to db and enforce sync-checkpoint

---
 src/checkpoints.cpp |   35 ++++++++++++++++++++++++++++++-----
 src/checkpoints.h   |    3 ++-
 src/main.cpp        |    6 +++++-
 3 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/src/checkpoints.cpp b/src/checkpoints.cpp
index 097dd87..d986b07 100644
--- a/src/checkpoints.cpp
+++ b/src/checkpoints.cpp
@@ -83,19 +83,22 @@ namespace Checkpoints
         return true;
     }
 
-    bool AcceptPendingSyncCheckpoint(uint256 hashAcceptedBlock)
+    bool AcceptPendingSyncCheckpoint()
     {
-        if (!mapBlockIndex.count(hashAcceptedBlock))
-            return false;
-
         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
-            if ((!checkpointMessagePending.IsNull()) && checkpointMessagePending.hashCheckpoint == hashAcceptedBlock)
+            if ((!checkpointMessagePending.IsNull()) && mapBlockIndex.count(checkpointMessagePending.hashCheckpoint))
             {
                 if (!ValidateSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
                 {
                     checkpointMessagePending.SetNull();
                     return false;
                 }
+
+                CTxDB txdb;
+                if (!txdb.WriteSyncCheckpoint(checkpointMessagePending.hashCheckpoint))
+                    return error("AcceptPendingSyncCheckpoint() : failed to write to db sync checkpoint %s\n", checkpointMessagePending.hashCheckpoint.ToString().c_str());
+                txdb.Close();
+
                 hashSyncCheckpoint = checkpointMessagePending.hashCheckpoint;
                 checkpointMessage = checkpointMessagePending;
                 checkpointMessagePending.SetNull();
@@ -118,6 +121,22 @@ namespace Checkpoints
         return pindex->GetBlockHash();
     }
 
+    // Check against synchronized checkpoint
+    bool CheckSync(int nHeight, const uint256& hashBlock)
+    {
+        if (fTestNet) return true; // Testnet has no checkpoints
+
+        CRITICAL_BLOCK(cs_hashSyncCheckpoint)
+        {
+            CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];
+            if (nHeight == pindexSync->nHeight && hashBlock != hashSyncCheckpoint)
+                return false; // same height with sync-checkpoint
+            if (nHeight < pindexSync->nHeight && !mapBlockIndex.count(hashBlock))
+                return false; // lower height than sync-checkpoint
+        }
+        return true;
+    }
+
     // ppcoin: automatic checkpoint (represented by height of checkpoint)
     int nAutoCheckpoint = 0;
     int nBranchPoint = 0;    // branch point to alternative branch
@@ -256,6 +275,12 @@ bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
         }
         if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
             return false;
+
+        CTxDB txdb;
+        if (!txdb.WriteSyncCheckpoint(this->hashCheckpoint))
+            return error("ProcessSyncCheckpoint() : failed to write to db sync checkpoint %s\n", this->hashCheckpoint.ToString().c_str());
+        txdb.Close();
+
         Checkpoints::hashSyncCheckpoint = this->hashCheckpoint;
         Checkpoints::checkpointMessage = *this;
         Checkpoints::checkpointMessagePending.SetNull();
diff --git a/src/checkpoints.h b/src/checkpoints.h
index e411c12..db3fe19 100644
--- a/src/checkpoints.h
+++ b/src/checkpoints.h
@@ -135,8 +135,9 @@ namespace Checkpoints
     extern CSyncCheckpoint checkpointMessage;
     extern CCriticalSection cs_hashSyncCheckpoint;
 
-    bool AcceptPendingSyncCheckpoint(uint256 hashAcceptedBlock);
+    bool AcceptPendingSyncCheckpoint();
     uint256 AutoSelectSyncCheckpoint();
+    bool CheckSync(int nHeight, const uint256& hashBlock);
 
     // ppcoin: automatic checkpoint
     extern int nAutoCheckpoint;
diff --git a/src/main.cpp b/src/main.cpp
index a8b65a8..4de69bf 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1578,6 +1578,10 @@ bool CBlock::AcceptBlock()
     if (!Checkpoints::CheckAuto(pindexPrev))
         return DoS(100, error("AcceptBlock() : rejected by automatic checkpoint at %d", Checkpoints::nAutoCheckpoint));
 
+    // ppcoin: check that the block satisfies synchronized checkpoint
+    if (!Checkpoints::CheckSync(nHeight, hash))
+        return DoS(100, error("AcceptBlock() : rejected by synchronized checkpoint"));
+
     // Write block to history file
     if (!CheckDiskSpace(::GetSerializeSize(*this, SER_DISK)))
         return error("AcceptBlock() : out of disk space");
@@ -1596,7 +1600,7 @@ bool CBlock::AcceptBlock()
                     pnode->PushInventory(CInv(MSG_BLOCK, hash));
 
     // ppcoin: check pending sync-checkpoint
-    Checkpoints::AcceptPendingSyncCheckpoint(hash);
+    Checkpoints::AcceptPendingSyncCheckpoint();
 
     return true;
 }
-- 
1.7.1