Merge pull request #534 from gavinandresen/DoSorphans

Denial-of-service prevention: low-difficulty blocks

bitcoin-qt.pro

@@ -88,6 +88,7 @@ HEADERS += src/qt/bitcoingui.h \
     src/qt/bitcoinaddressvalidator.h \
     src/base58.h \
     src/bignum.h \
+    src/checkpoints.h \
     src/util.h \
     src/uint256.h \
     src/serialize.h \
@@ -152,6 +153,7 @@ SOURCES += src/qt/bitcoin.cpp src/qt/bitcoingui.cpp \
     src/init.cpp \
     src/net.cpp \
     src/irc.cpp \
+    src/checkpoints.cpp \
     src/db.cpp \
     src/json/json_spirit_writer.cpp \
     src/json/json_spirit_value.cpp \

src/checkpoints.cpp

@@ -0,0 +1,65 @@
+// Copyright (c) 2011 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file license.txt or http://www.opensource.org/licenses/mit-license.php.
+
+#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"))
+        ( 33333, uint256("0x000000002dd5588a74784eaa7ab0507a18ad16a236e7b1ce69f00d7ddfb5d0a6"))
+        ( 68555, uint256("0x00000000001e1b4903550a0b96e9a9405c8a95f387162e4944e8d9fbe501cd6a"))
+        ( 70567, uint256("0x00000000006a49b14bcf27462068f1264c961f11fa2e0eddd2be0791e1d4124a"))
+        ( 74000, uint256("0x0000000000573993a3c9e41ce34471c079dcf5f52a0e824a81e7f953b8661a20"))
+        (105000, uint256("0x00000000000291ce28027faea320c8d2b054b2e0fe44a773f3eefb151d6bdc97"))
+        (118000, uint256("0x000000000000774a7f8a7a12dc906ddb9e17e75d684f15e00f8767f9e8f36553"))
+        (134444, uint256("0x00000000000005b12ffd4cd315cd34ffd4a594f430ac814c91184a0d42d2b0fe"))
+        (140700, uint256("0x000000000000033b512028abb90e1626d8b346fd0ed598ac0a3c371138dce2bd"))
+        ;
+
+    bool CheckBlock(int nHeight, const uint256& hash)
+    {
+        if (fTestNet) return true; // Testnet has no checkpoints
+
+        MapCheckpoints::const_iterator i = mapCheckpoints.find(nHeight);
+        if (i == mapCheckpoints.end()) return true;
+        return hash == i->second;
+    }
+
+    int GetTotalBlocksEstimate()
+    {
+        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;
+    }
+}

src/checkpoints.h

@@ -0,0 +1,29 @@
+// Copyright (c) 2011 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file license.txt or http://www.opensource.org/licenses/mit-license.php.
+#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.
+// They are updated every release or three.
+//
+namespace Checkpoints
+{
+    // Returns true if block passes checkpoint checks
+    bool CheckBlock(int nHeight, const uint256& hash);
+
+    // 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

src/main.cpp

@@ -3,6 +3,7 @@
 // Distributed under the MIT/X11 software license, see the accompanying
 // file license.txt or http://www.opensource.org/licenses/mit-license.php.
 #include "headers.h"
+#include "checkpoints.h"
 #include "db.h"
 #include "net.h"
 #include "init.h"
@@ -29,7 +30,6 @@ map<COutPoint, CInPoint> mapNextTx;
 map<uint256, CBlockIndex*> mapBlockIndex;
 uint256 hashGenesisBlock("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f");
 static CBigNum bnProofOfWorkLimit(~uint256(0) >> 32);
-const int nTotalBlocksEstimate = 140700; // Conservative estimate of total nr of blocks on main chain
 const int nInitialBlockThreshold = 120; // Regard blocks up until N-threshold as "initial download"
 CBlockIndex* pindexGenesisBlock = NULL;
 int nBestHeight = -1;
@@ -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)
@@ -721,28 +742,15 @@ bool CheckProofOfWork(uint256 hash, unsigned int nBits)
     return true;
 }
 
-// Return conservative estimate of total number of blocks, 0 if unknown
-int GetTotalBlocksEstimate()
-{
-    if(fTestNet)
-    {
-        return 0;
-    }
-    else
-    {
-        return nTotalBlocksEstimate;
-    }
-}
-
 // Return maximum amount of blocks that other nodes claim to have
 int GetNumBlocksOfPeers()
 {
-    return std::max(cPeerBlockCounts.median(), GetTotalBlocksEstimate());
+    return std::max(cPeerBlockCounts.median(), Checkpoints::GetTotalBlocksEstimate());
 }
 
 bool IsInitialBlockDownload()
 {
-    if (pindexBest == NULL || nBestHeight < (GetTotalBlocksEstimate()-nInitialBlockThreshold))
+    if (pindexBest == NULL || nBestHeight < (Checkpoints::GetTotalBlocksEstimate()-nInitialBlockThreshold))
         return true;
     static int64 nLastUpdate;
     static CBlockIndex* pindexLastBest;
@@ -1317,17 +1325,8 @@ bool CBlock::AcceptBlock()
             return DoS(10, error("AcceptBlock() : contains a non-final transaction"));
 
     // Check that the block chain matches the known block chain up to a checkpoint
-    if (!fTestNet)
+    if (!Checkpoints::CheckBlock(nHeight, hash))
-        if ((nHeight ==  11111 && hash != uint256("0x0000000069e244f73d78e8fd29ba2fd2ed618bd6fa2ee92559f542fdb26e7c1d")) ||
+        return DoS(100, error("AcceptBlock() : rejected by checkpoint lockin at %d", nHeight));
-            (nHeight ==  33333 && hash != uint256("0x000000002dd5588a74784eaa7ab0507a18ad16a236e7b1ce69f00d7ddfb5d0a6")) ||
-            (nHeight ==  68555 && hash != uint256("0x00000000001e1b4903550a0b96e9a9405c8a95f387162e4944e8d9fbe501cd6a")) ||
-            (nHeight ==  70567 && hash != uint256("0x00000000006a49b14bcf27462068f1264c961f11fa2e0eddd2be0791e1d4124a")) ||
-            (nHeight ==  74000 && hash != uint256("0x0000000000573993a3c9e41ce34471c079dcf5f52a0e824a81e7f953b8661a20")) ||
-            (nHeight == 105000 && hash != uint256("0x00000000000291ce28027faea320c8d2b054b2e0fe44a773f3eefb151d6bdc97")) ||
-            (nHeight == 118000 && hash != uint256("0x000000000000774a7f8a7a12dc906ddb9e17e75d684f15e00f8767f9e8f36553")) ||
-            (nHeight == 134444 && hash != uint256("0x00000000000005b12ffd4cd315cd34ffd4a594f430ac814c91184a0d42d2b0fe")) ||
-            (nHeight == 140700 && hash != uint256("0x000000000000033b512028abb90e1626d8b346fd0ed598ac0a3c371138dce2bd")))
-            return DoS(100, error("AcceptBlock() : rejected by checkpoint lockin at %d", nHeight));
 
     // Write block to history file
     if (!CheckDiskSpace(::GetSerializeSize(*this, SER_DISK)))
@@ -1362,6 +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))
     {

src/main.h

@@ -99,7 +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);
-int GetTotalBlocksEstimate();
+unsigned int ComputeMinWork(unsigned int nBase, int64 nTime);
 int GetNumBlocksOfPeers();
 bool IsInitialBlockDownload();
 std::string GetWarnings(std::string strFor);

src/makefile.linux-mingw

@@ -32,6 +32,7 @@ CFLAGS=-O2 -w -Wno-invalid-offsetof -Wformat $(DEBUGFLAGS) $(DEFS) $(INCLUDEPATH
 HEADERS = \
     base58.h \
     bignum.h \
+    checkpoints.h \
     crypter.h \
     db.h \
     headers.h \
@@ -61,6 +62,7 @@ endif
 LIBS += -l mingwthrd -l kernel32 -l user32 -l gdi32 -l comdlg32 -l winspool -l winmm -l shell32 -l comctl32 -l ole32 -l oleaut32 -l uuid -l rpcrt4 -l advapi32 -l ws2_32 -l shlwapi
 
 OBJS= \
+    obj/checkpoints.o \
     obj/crypter.o \
     obj/db.o \
     obj/init.o \

src/makefile.mingw

@@ -29,6 +29,7 @@ CFLAGS=-mthreads -O2 -w -Wno-invalid-offsetof -Wformat $(DEBUGFLAGS) $(DEFS) $(I
 HEADERS = \
     base58.h \
     bignum.h \
+    checkpoints.h \
     crypter.h \
     db.h \
     headers.h \
@@ -58,6 +59,7 @@ endif
 LIBS += -l kernel32 -l user32 -l gdi32 -l comdlg32 -l winspool -l winmm -l shell32 -l comctl32 -l ole32 -l oleaut32 -l uuid -l rpcrt4 -l advapi32 -l ws2_32 -l shlwapi
 
 OBJS= \
+    obj/checkpoints.o \
     obj/crypter.o \
     obj/db.o \
     obj/init.o \

src/makefile.osx

@@ -49,6 +49,7 @@ CFLAGS=-mmacosx-version-min=10.5 -arch i386 -O3 -Wno-invalid-offsetof -Wformat $
 HEADERS = \
     base58.h \
     bignum.h \
+    checkpoints.h \
     crypter.h \
     db.h \
     headers.h \
@@ -69,6 +70,7 @@ HEADERS = \
     wallet.h
 
 OBJS= \
+    obj/checkpoints.o \
     obj/crypter.o \
     obj/db.o \
     obj/init.o \

src/makefile.unix

@@ -87,6 +87,7 @@ xCXXFLAGS=-pthread -Wno-invalid-offsetof -Wformat $(DEBUGFLAGS) $(DEFS) $(HARDEN
 HEADERS = \
     base58.h \
     bignum.h \
+    checkpoints.h \
     crypter.h \
     db.h \
     headers.h \
@@ -107,6 +108,7 @@ HEADERS = \
     wallet.h
 
 OBJS= \
+    obj/checkpoints.o \
     obj/crypter.o \
     obj/db.o \
     obj/init.o \

src/makefile.vc

@@ -43,6 +43,7 @@ CFLAGS=/MD /c /nologo /EHsc /GR /Zm300 $(DEBUGFLAGS) $(DEFS) $(INCLUDEPATHS)
 HEADERS = \
     base58.h \
     bignum.h \
+    checkpoints.h \
     crypter.h \
     db.h \
     headers.h \
@@ -65,6 +66,7 @@ HEADERS = \
     wallet.h
 
 OBJS= \
+    obj\checkpoints.o \
     obj\crypter.o \
     obj\db.o \
     obj\init.o \
@@ -87,6 +89,8 @@ all: bitcoind.exe
 .cpp{obj}.obj:
     cl $(CFLAGS) /DGUI /Fo$@ %s
 
+obj\checkpoints.obj: $(HEADERS)
+
 obj\util.obj: $(HEADERS)
 
 obj\script.obj: $(HEADERS)
@@ -116,6 +120,8 @@ obj\uibase.obj: $(HEADERS)
 .cpp{obj\nogui}.obj:
     cl $(CFLAGS) /Fo$@ %s
 
+obj\nogui\checkpoints.obj: $(HEADERS)
+
 obj\nogui\util.obj: $(HEADERS)
 
 obj\nogui\script.obj: $(HEADERS)

src/test/Checkpoints_tests.cpp

@@ -0,0 +1,34 @@
+//
+// Unit tests for block-chain checkpoints
+//
+#include <boost/assign/list_of.hpp> // for 'map_list_of()'
+#include <boost/test/unit_test.hpp>
+#include <boost/foreach.hpp>
+
+#include "../checkpoints.h"
+#include "../util.h"
+
+using namespace std;
+
+BOOST_AUTO_TEST_SUITE(Checkpoints_tests)
+
+BOOST_AUTO_TEST_CASE(sanity)
+{
+    uint256 p11111 = uint256("0x0000000069e244f73d78e8fd29ba2fd2ed618bd6fa2ee92559f542fdb26e7c1d");
+    uint256 p140700 = uint256("0x000000000000033b512028abb90e1626d8b346fd0ed598ac0a3c371138dce2bd");
+    BOOST_CHECK(Checkpoints::CheckBlock(11111, p11111));
+    BOOST_CHECK(Checkpoints::CheckBlock(140700, p140700));
+
+    
+    // Wrong hashes at checkpoints should fail:
+    BOOST_CHECK(!Checkpoints::CheckBlock(11111, p140700));
+    BOOST_CHECK(!Checkpoints::CheckBlock(140700, p11111));
+
+    // ... but any hash not at a checkpoint should succeed:
+    BOOST_CHECK(Checkpoints::CheckBlock(11111+1, p140700));
+    BOOST_CHECK(Checkpoints::CheckBlock(140700+1, p11111));
+
+    BOOST_CHECK(Checkpoints::GetTotalBlocksEstimate() >= 140700);
+}    
+
+BOOST_AUTO_TEST_SUITE_END()

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>
 
@@ -64,5 +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()

src/test/test_bitcoin.cpp

@@ -13,6 +13,7 @@
 #include "util_tests.cpp"
 #include "base58_tests.cpp"
 #include "miner_tests.cpp"
+#include "Checkpoints_tests.cpp"
 
 CWallet* pwalletMain;