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-rw-r--r--src/checkpoints.cpp32
-rw-r--r--src/checkpoints.h7
-rw-r--r--src/main.cpp49
-rw-r--r--src/main.h1
-rw-r--r--src/test/DoS_tests.cpp51
5 files changed, 132 insertions, 8 deletions
diff --git a/src/checkpoints.cpp b/src/checkpoints.cpp
index 4419a06c83..c7e054df37 100644
--- a/src/checkpoints.cpp
+++ b/src/checkpoints.cpp
@@ -2,16 +2,23 @@
// Distributed under the MIT/X11 software license, see the accompanying
// file license.txt or http://www.opensource.org/licenses/mit-license.php.
-#include "checkpoints.h"
-#include "uint256.h"
-#include "util.h"
-
#include <boost/assign/list_of.hpp> // for 'map_list_of()'
+#include <boost/foreach.hpp>
+
+#include "headers.h"
+#include "checkpoints.h"
namespace Checkpoints
{
typedef std::map<int, uint256> MapCheckpoints;
+ //
+ // What makes a good checkpoint block?
+ // + Is surrounded by blocks with reasonable timestamps
+ // (no blocks before with a timestamp after, none after with
+ // timestamp before)
+ // + Contains no strange transactions
+ //
static MapCheckpoints mapCheckpoints =
boost::assign::map_list_of
( 11111, uint256("0x0000000069e244f73d78e8fd29ba2fd2ed618bd6fa2ee92559f542fdb26e7c1d"))
@@ -36,8 +43,23 @@ namespace Checkpoints
int GetTotalBlocksEstimate()
{
- if (fTestNet) return 0; // Testnet has no checkpoints
+ if (fTestNet) return 0;
return mapCheckpoints.rbegin()->first;
}
+
+ CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex)
+ {
+ if (fTestNet) return NULL;
+
+ int64 nResult;
+ BOOST_REVERSE_FOREACH(const MapCheckpoints::value_type& i, mapCheckpoints)
+ {
+ const uint256& hash = i.second;
+ std::map<uint256, CBlockIndex*>::const_iterator t = mapBlockIndex.find(hash);
+ if (t != mapBlockIndex.end())
+ return t->second;
+ }
+ return NULL;
+ }
}
diff --git a/src/checkpoints.h b/src/checkpoints.h
index 32094fdde6..9d52da404f 100644
--- a/src/checkpoints.h
+++ b/src/checkpoints.h
@@ -4,7 +4,11 @@
#ifndef BITCOIN_CHECKPOINT_H
#define BITCOIN_CHECKPOINT_H
+#include <map>
+#include "util.h"
+
class uint256;
+class CBlockIndex;
//
// Block-chain checkpoints are compiled-in sanity checks.
@@ -17,6 +21,9 @@ namespace Checkpoints
// Return conservative estimate of total number of blocks, 0 if unknown
int GetTotalBlocksEstimate();
+
+ // Returns last CBlockIndex* in mapBlockIndex that is a checkpoint
+ CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex);
}
#endif
diff --git a/src/main.cpp b/src/main.cpp
index 832a0f9240..a7871fcc16 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))
{
diff --git a/src/main.h b/src/main.h
index f459d050ce..3870cee864 100644
--- a/src/main.h
+++ b/src/main.h
@@ -99,6 +99,7 @@ void IncrementExtraNonce(CBlock* pblock, CBlockIndex* pindexPrev, unsigned int&
void FormatHashBuffers(CBlock* pblock, char* pmidstate, char* pdata, char* phash1);
bool CheckWork(CBlock* pblock, CWallet& wallet, CReserveKey& reservekey);
bool CheckProofOfWork(uint256 hash, unsigned int nBits);
+unsigned int ComputeMinWork(unsigned int nBase, int64 nTime);
int GetNumBlocksOfPeers();
bool IsInitialBlockDownload();
std::string GetWarnings(std::string strFor);
diff --git a/src/test/DoS_tests.cpp b/src/test/DoS_tests.cpp
index 1093b73d80..01e6691254 100644
--- a/src/test/DoS_tests.cpp
+++ b/src/test/DoS_tests.cpp
@@ -1,6 +1,7 @@
//
// Unit tests for denial-of-service detection/prevention code
//
+#include <boost/assign/list_of.hpp> // for 'map_list_of()'
#include <boost/test/unit_test.hpp>
#include <boost/foreach.hpp>
@@ -64,4 +65,54 @@ BOOST_AUTO_TEST_CASE(DoS_bantime)
BOOST_CHECK(!CNode::IsBanned(addr.ip));
}
+static bool CheckNBits(unsigned int nbits1, int64 time1, unsigned int nbits2, int64 time2)
+{
+ if (time1 > time2)
+ return CheckNBits(nbits2, time2, nbits1, time1);
+ int64 deltaTime = time2-time1;
+
+ CBigNum required;
+ required.SetCompact(ComputeMinWork(nbits1, deltaTime));
+ CBigNum have;
+ have.SetCompact(nbits2);
+ return (have <= required);
+}
+
+BOOST_AUTO_TEST_CASE(DoS_checknbits)
+{
+ using namespace boost::assign; // for 'map_list_of()'
+
+ // Timestamps,nBits from the bitcoin blockchain.
+ // These are the block-chain checkpoint blocks
+ typedef std::map<int64, unsigned int> BlockData;
+ BlockData chainData =
+ map_list_of(1239852051,486604799)(1262749024,486594666)
+ (1279305360,469854461)(1280200847,469830746)(1281678674,469809688)
+ (1296207707,453179945)(1302624061,453036989)(1309640330,437004818)
+ (1313172719,436789733);
+
+ // Make sure CheckNBits considers every combination of block-chain-lock-in-points
+ // "sane":
+ BOOST_FOREACH(const BlockData::value_type& i, chainData)
+ {
+ BOOST_FOREACH(const BlockData::value_type& j, chainData)
+ {
+ BOOST_CHECK(CheckNBits(i.second, i.first, j.second, j.first));
+ }
+ }
+
+ // Test a couple of insane combinations:
+ BlockData::value_type firstcheck = *(chainData.begin());
+ BlockData::value_type lastcheck = *(chainData.rbegin());
+
+ // First checkpoint difficulty at or a while after the last checkpoint time should fail when
+ // compared to last checkpoint
+ BOOST_CHECK(!CheckNBits(firstcheck.second, lastcheck.first+60*10, lastcheck.second, lastcheck.first));
+ BOOST_CHECK(!CheckNBits(firstcheck.second, lastcheck.first+60*60*24*14, lastcheck.second, lastcheck.first));
+
+ // ... but OK if enough time passed for difficulty to adjust downward:
+ BOOST_CHECK(CheckNBits(firstcheck.second, lastcheck.first+60*60*24*365*4, lastcheck.second, lastcheck.first));
+
+}
+
BOOST_AUTO_TEST_SUITE_END()