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Orphan block fill-up-memory attack prevention

pull/1/head
Gavin Andresen 11 years ago
parent
commit
10fd7f6689
  1. 32
      src/checkpoints.cpp
  2. 7
      src/checkpoints.h
  3. 49
      src/main.cpp
  4. 1
      src/main.h
  5. 51
      src/test/DoS_tests.cpp

32
src/checkpoints.cpp

@ -2,16 +2,23 @@ @@ -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 @@ -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;
}
}

7
src/checkpoints.h

@ -4,7 +4,11 @@ @@ -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 @@ -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

49
src/main.cpp

@ -659,11 +659,32 @@ int64 static GetBlockValue(int nHeight, int64 nFees) @@ -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) @@ -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))
{

1
src/main.h

@ -99,6 +99,7 @@ void IncrementExtraNonce(CBlock* pblock, CBlockIndex* pindexPrev, unsigned int& @@ -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);

51
src/test/DoS_tests.cpp

@ -1,6 +1,7 @@ @@ -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) @@ -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()

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