checkpoints.cpp

// Copyright (c) 2009-2012 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "checkpoints.h"
#include "main.h"
#include "txdb-leveldb.h"


namespace Checkpoints
{
    typedef std::map<int, std::pair<uint256, unsigned int> > MapCheckpoints;
    typedef std::list<uint256> ListBannedBlocks;

    //
    // 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 =
    {
        { 0,      {hashGenesisBlock, 1360105017} },
        { 13560,  {uint256("0xa1591a0fcbf11f282d671581edb9f0aadcd06fee69761081e0a3245914c13729"), 1364674052} },
        { 143990, {uint256("0x00000000001ff5c3940a9f73ad4a990f64955179bde0f743c76dbf0031429efc"), 1418953493} },
        { 149000, {uint256("0x7a24acfcadcf43054e7f7d9f273522c0dfc5791ba4006e0273e7521a8d36c525"), 1420872125} },
        { 160000, {uint256("0x000000000001cb1133043d38d077c0e93f66c8b2566779f10f182137d1e34a68"), 1425150237} },
        { 200000, {uint256("0x0000000000029f8bbf66e6ea6f3e5db55009404aae0fe395a53dd33142b2bff2"), 1441127233} },
        { 221047, {uint256("0xa28aef712e7aa0c285bfe29351ca21ed416689139e3063ef770fc826a8b9e9da"), 1449431646} },
        { 243100, {uint256("0x000000000006522d1ebc0734cb0e6b83f5d4da0c3cbc72bd91b82016f611c4f0"), 1458215793} },
        { 532000, {uint256("0x0000000000018b7eba5e189c41605780c8a855f74144fa837fa05fa4c67b6ba9"), 1569359486} },
        { 561108, {uint256("0x2f3cf523ae1022300b4f40073e506d15ef0d6e208f123aed5b93016f81a10e1e"), 1580943827} },
        { 712891, {uint256("0xaaafebcb23c1b8ab49f7517b7a34bcc420cc6f284d9ffc672c1f47b5af2b0088"), 1640557462} }
    };

    static ListBannedBlocks listBanned =
    {
        // Invalid block #221047 with future timestamp of 2016/02/23 09:24:17 UTC
        uint256("0x46223e5432ceffe650d5729b4bb8479dcdf0ca1e534fa8e69382dc87b42ea94b")
    };

    // TestNet has no checkpoints
    static MapCheckpoints mapCheckpointsTestnet =
    {
        { 0, { hashGenesisBlockTestNet, 1360105017 } }
    };

    bool CheckHardened(int nHeight, const uint256& hash)
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);

        MapCheckpoints::const_iterator i = checkpoints.find(nHeight);
        if (i == checkpoints.end()) return true;
        return hash == i->second.first;
    }

    bool CheckBanned(const uint256 &nHash)
    {
        if (fTestNet) // Testnet has no banned blocks
            return true;
        ListBannedBlocks::const_iterator it = std::find(listBanned.begin(), listBanned.end(), nHash);
        return it == listBanned.end();
    }

    int GetTotalBlocksEstimate()
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);

        return checkpoints.rbegin()->first;
    }

    unsigned int GetLastCheckpointTime()
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);

        return checkpoints.rbegin()->second.second;
    }

    CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex)
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);

        for(auto it = checkpoints.rbegin(); it != checkpoints.rend(); ++it)
        {
            const uint256& hash = it->second.first;
            auto t = mapBlockIndex.find(hash);
            if (t != mapBlockIndex.end())
                return t->second;
        }
        return NULL;
    }

    // ppcoin: synchronized checkpoint (centrally broadcasted)
    uint256 hashSyncCheckpoint = 0;
    uint256 hashPendingCheckpoint = 0;
    CSyncCheckpoint checkpointMessage;
    CSyncCheckpoint checkpointMessagePending;
    uint256 hashInvalidCheckpoint = 0;
    CCriticalSection cs_hashSyncCheckpoint;

    // ppcoin: get last synchronized checkpoint
    CBlockIndex* GetLastSyncCheckpoint()
    {
        LOCK(cs_hashSyncCheckpoint);
        if (!mapBlockIndex.count(hashSyncCheckpoint))
            error("GetSyncCheckpoint: block index missing for current sync-checkpoint %s", hashSyncCheckpoint.ToString().c_str());
        else
            return mapBlockIndex[hashSyncCheckpoint];
        return NULL;
    }

    // ppcoin: only descendant of current sync-checkpoint is allowed
    bool ValidateSyncCheckpoint(uint256 hashCheckpoint)
    {
        if (!mapBlockIndex.count(hashSyncCheckpoint))
            return error("ValidateSyncCheckpoint: block index missing for current sync-checkpoint %s", hashSyncCheckpoint.ToString().c_str());
        if (!mapBlockIndex.count(hashCheckpoint))
            return error("ValidateSyncCheckpoint: block index missing for received sync-checkpoint %s", hashCheckpoint.ToString().c_str());

        CBlockIndex* pindexSyncCheckpoint = mapBlockIndex[hashSyncCheckpoint];
        CBlockIndex* pindexCheckpointRecv = mapBlockIndex[hashCheckpoint];

        if (pindexCheckpointRecv->nHeight <= pindexSyncCheckpoint->nHeight)
        {
            // Received an older checkpoint, trace back from current checkpoint
            // to the same height of the received checkpoint to verify
            // that current checkpoint should be a descendant block
            CBlockIndex* pindex = pindexSyncCheckpoint;
            while (pindex->nHeight > pindexCheckpointRecv->nHeight)
                if ((pindex = pindex->pprev) == NULL)
                    return error("ValidateSyncCheckpoint: pprev null - block index structure failure");
            if (pindex->GetBlockHash() != hashCheckpoint)
            {
                hashInvalidCheckpoint = hashCheckpoint;
                return error("ValidateSyncCheckpoint: new sync-checkpoint %s is conflicting with current sync-checkpoint %s", hashCheckpoint.ToString().c_str(), hashSyncCheckpoint.ToString().c_str());
            }
            return false; // ignore older checkpoint
        }

        // Received checkpoint should be a descendant block of the current
        // checkpoint. Trace back to the same height of current checkpoint
        // to verify.
        CBlockIndex* pindex = pindexCheckpointRecv;
        while (pindex->nHeight > pindexSyncCheckpoint->nHeight)
            if ((pindex = pindex->pprev) == NULL)
                return error("ValidateSyncCheckpoint: pprev2 null - block index structure failure");
        if (pindex->GetBlockHash() != hashSyncCheckpoint)
        {
            hashInvalidCheckpoint = hashCheckpoint;
            return error("ValidateSyncCheckpoint: new sync-checkpoint %s is not a descendant of current sync-checkpoint %s", hashCheckpoint.ToString().c_str(), hashSyncCheckpoint.ToString().c_str());
        }
        return true;
    }

    bool WriteSyncCheckpoint(const uint256& hashCheckpoint)
    {
        CTxDB txdb;
        txdb.TxnBegin();
        if (!txdb.WriteSyncCheckpoint(hashCheckpoint))
        {
            txdb.TxnAbort();
            return error("WriteSyncCheckpoint(): failed to write to db sync checkpoint %s", hashCheckpoint.ToString().c_str());
        }
        if (!txdb.TxnCommit())
            return error("WriteSyncCheckpoint(): failed to commit to db sync checkpoint %s", hashCheckpoint.ToString().c_str());

        Checkpoints::hashSyncCheckpoint = hashCheckpoint;
        return true;
    }

    bool AcceptPendingSyncCheckpoint()
    {
        LOCK(cs_hashSyncCheckpoint);
        if (hashPendingCheckpoint != 0 && mapBlockIndex.count(hashPendingCheckpoint))
        {
            if (!ValidateSyncCheckpoint(hashPendingCheckpoint))
            {
                hashPendingCheckpoint = 0;
                checkpointMessagePending.SetNull();
                return false;
            }

            CTxDB txdb;
            CBlockIndex* pindexCheckpoint = mapBlockIndex[hashPendingCheckpoint];
            if (!pindexCheckpoint->IsInMainChain())
            {
                CBlock block;
                if (!block.ReadFromDisk(pindexCheckpoint))
                    return error("AcceptPendingSyncCheckpoint: ReadFromDisk failed for sync checkpoint %s", hashPendingCheckpoint.ToString().c_str());
                if (!block.SetBestChain(txdb, pindexCheckpoint))
                {
                    hashInvalidCheckpoint = hashPendingCheckpoint;
                    return error("AcceptPendingSyncCheckpoint: SetBestChain failed for sync checkpoint %s", hashPendingCheckpoint.ToString().c_str());
                }
            }

            if (!WriteSyncCheckpoint(hashPendingCheckpoint))
                return error("AcceptPendingSyncCheckpoint(): failed to write sync checkpoint %s", hashPendingCheckpoint.ToString().c_str());
            hashPendingCheckpoint = 0;
            checkpointMessage = checkpointMessagePending;
            checkpointMessagePending.SetNull();
            printf("AcceptPendingSyncCheckpoint : sync-checkpoint at %s\n", hashSyncCheckpoint.ToString().c_str());
            // relay the checkpoint
            if (!checkpointMessage.IsNull())
            {
                for (std::vector<CNode*>::iterator it = vNodes.begin(); it != vNodes.end(); ++it)
                    checkpointMessage.RelayTo(*it);
            }
            return true;
        }
        return false;
    }

    // Automatically select a suitable sync-checkpoint 
    uint256 AutoSelectSyncCheckpoint()
    {
        const CBlockIndex *pindex = pindexBest;
        // Search backward for a block within max span and maturity window
        while (pindex->pprev && (pindex->GetBlockTime() + CHECKPOINT_MAX_SPAN > pindexBest->GetBlockTime() || pindex->nHeight + 8 > pindexBest->nHeight))
            pindex = pindex->pprev;
        return pindex->GetBlockHash();
    }

    // Check against synchronized checkpoint
    bool CheckSync(const uint256& hashBlock, const CBlockIndex* pindexPrev)
    {
        if (fTestNet) return true; // Testnet has no checkpoints
        int nHeight = pindexPrev->nHeight + 1;

        LOCK(cs_hashSyncCheckpoint);
        // sync-checkpoint should always be accepted block
        assert(mapBlockIndex.count(hashSyncCheckpoint));
        const CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];

        if (nHeight > pindexSync->nHeight)
        {
            // trace back to same height as sync-checkpoint
            const CBlockIndex* pindex = pindexPrev;
            while (pindex->nHeight > pindexSync->nHeight)
                if ((pindex = pindex->pprev) == NULL)
                    return error("CheckSync: pprev null - block index structure failure");
            if (pindex->nHeight < pindexSync->nHeight || pindex->GetBlockHash() != hashSyncCheckpoint)
                return false; // only descendant of sync-checkpoint can pass check
        }
        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;
    }

    bool WantedByPendingSyncCheckpoint(uint256 hashBlock)
    {
        LOCK(cs_hashSyncCheckpoint);
        if (hashPendingCheckpoint == 0)
            return false;
        if (hashBlock == hashPendingCheckpoint)
            return true;
        if (mapOrphanBlocks.count(hashPendingCheckpoint) 
            && hashBlock == WantedByOrphan(mapOrphanBlocks[hashPendingCheckpoint]))
            return true;
        return false;
    }

    // ppcoin: reset synchronized checkpoint to last hardened checkpoint
    bool ResetSyncCheckpoint()
    {
        LOCK(cs_hashSyncCheckpoint);
        const uint256& hash = mapCheckpoints.rbegin()->second.first;
        if (mapBlockIndex.count(hash) && !mapBlockIndex[hash]->IsInMainChain())
        {
            // checkpoint block accepted but not yet in main chain
            printf("ResetSyncCheckpoint: SetBestChain to hardened checkpoint %s\n", hash.ToString().c_str());
            CTxDB txdb;
            CBlock block;
            if (!block.ReadFromDisk(mapBlockIndex[hash]))
                return error("ResetSyncCheckpoint: ReadFromDisk failed for hardened checkpoint %s", hash.ToString().c_str());
            if (!block.SetBestChain(txdb, mapBlockIndex[hash]))
            {
                return error("ResetSyncCheckpoint: SetBestChain failed for hardened checkpoint %s", hash.ToString().c_str());
            }
        }
        else if(!mapBlockIndex.count(hash))
        {
            // checkpoint block not yet accepted
            hashPendingCheckpoint = hash;
            checkpointMessagePending.SetNull();
            printf("ResetSyncCheckpoint: pending for sync-checkpoint %s\n", hashPendingCheckpoint.ToString().c_str());
        }

        for(auto it = mapCheckpoints.rbegin(); it != mapCheckpoints.rend(); ++it)
        {
            const uint256& hash = it->second.first;
            if (mapBlockIndex.count(hash) && mapBlockIndex[hash]->IsInMainChain())
            {
                if (!WriteSyncCheckpoint(hash))
                    return error("ResetSyncCheckpoint: failed to write sync checkpoint %s", hash.ToString().c_str());
                printf("ResetSyncCheckpoint: sync-checkpoint reset to %s\n", hashSyncCheckpoint.ToString().c_str());
                return true;
            }
        }

        return false;
    }

    void AskForPendingSyncCheckpoint(CNode* pfrom)
    {
        LOCK(cs_hashSyncCheckpoint);
        if (pfrom && hashPendingCheckpoint != 0 && (!mapBlockIndex.count(hashPendingCheckpoint)) && (!mapOrphanBlocks.count(hashPendingCheckpoint)))
            pfrom->AskFor(CInv(MSG_BLOCK, hashPendingCheckpoint));
    }

    bool SetCheckpointPrivKey(std::string strPrivKey)
    {
        // Test signing a sync-checkpoint with genesis block
        CSyncCheckpoint checkpoint;
        checkpoint.hashCheckpoint = !fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet;
        CDataStream sMsg(SER_NETWORK, PROTOCOL_VERSION);
        sMsg << (CUnsignedSyncCheckpoint)checkpoint;
        checkpoint.vchMsg = std::vector<unsigned char>(sMsg.begin(), sMsg.end());

        std::vector<unsigned char> vchPrivKey = ParseHex(strPrivKey);
        CKey key;
        key.SetPrivKey(CPrivKey(vchPrivKey.begin(), vchPrivKey.end())); // if key is not correct openssl may crash
        if (!key.Sign(Hash(checkpoint.vchMsg.begin(), checkpoint.vchMsg.end()), checkpoint.vchSig))
            return false;

        // Test signing successful, proceed
        CSyncCheckpoint::strMasterPrivKey = strPrivKey;
        return true;
    }

    bool SendSyncCheckpoint(uint256 hashCheckpoint)
    {
        CSyncCheckpoint checkpoint;
        checkpoint.hashCheckpoint = hashCheckpoint;
        CDataStream sMsg(SER_NETWORK, PROTOCOL_VERSION);
        sMsg << (CUnsignedSyncCheckpoint)checkpoint;
        checkpoint.vchMsg = std::vector<unsigned char>(sMsg.begin(), sMsg.end());

        if (CSyncCheckpoint::strMasterPrivKey.empty())
            return error("SendSyncCheckpoint: Checkpoint master key unavailable.");
        std::vector<unsigned char> vchPrivKey = ParseHex(CSyncCheckpoint::strMasterPrivKey);
        CKey key;
        key.SetPrivKey(CPrivKey(vchPrivKey.begin(), vchPrivKey.end())); // if key is not correct openssl may crash
        if (!key.Sign(Hash(checkpoint.vchMsg.begin(), checkpoint.vchMsg.end()), checkpoint.vchSig))
            return error("SendSyncCheckpoint: Unable to sign checkpoint, check private key?");

        if(!checkpoint.ProcessSyncCheckpoint(NULL))
        {
            printf("WARNING: SendSyncCheckpoint: Failed to process checkpoint.\n");
            return false;
        }

        // Relay checkpoint
        {
            LOCK(cs_vNodes);
            for (std::vector<CNode*>::iterator it = vNodes.begin(); it != vNodes.end(); ++it)
                checkpoint.RelayTo(*it);
        }
        return true;
    }

    // Is the sync-checkpoint outside maturity window?
    bool IsMatureSyncCheckpoint()
    {
        LOCK(cs_hashSyncCheckpoint);
        // sync-checkpoint should always be accepted block
        assert(mapBlockIndex.count(hashSyncCheckpoint));
        const CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];
        return (nBestHeight >= pindexSync->nHeight + nCoinbaseMaturity ||
                pindexSync->GetBlockTime() + nStakeMinAge < GetAdjustedTime());
    }
}

// ppcoin: sync-checkpoint master key
const std::string CSyncCheckpoint::strMasterPubKey = "04a51b735f816de4ec3f891d5b38bbc91e1f7245c7c08d17990760b86b4d8fc3910a850ffecf73bfa8886f01739a0c4c4322201282d07b6e48ce931cc92af94850";

std::string CSyncCheckpoint::strMasterPrivKey = "";

// ppcoin: verify signature of sync-checkpoint message
CSyncCheckpoint::CSyncCheckpoint()
{
    SetNull();
}

void CSyncCheckpoint::SetNull()
{
    CUnsignedSyncCheckpoint::SetNull();
    vchMsg.clear();
    vchSig.clear();
}

bool CSyncCheckpoint::IsNull() const
{
    return (hashCheckpoint == 0);
}

uint256 CSyncCheckpoint::GetHash() const
{
    return SerializeHash(*this);
}

bool CSyncCheckpoint::RelayTo(CNode *pnode) const
{
    // returns true if wasn't already sent
    if (pnode->hashCheckpointKnown != hashCheckpoint)
    {
        pnode->hashCheckpointKnown = hashCheckpoint;
        pnode->PushMessage("checkpoint", *this);
        return true;
    }
    return false;
}

bool CSyncCheckpoint::CheckSignature()
{
    CPubKey key(ParseHex(CSyncCheckpoint::strMasterPubKey));
    if (!key.Verify(Hash(vchMsg.begin(), vchMsg.end()), vchSig))
        return error("CSyncCheckpoint::CheckSignature() : verify signature failed");

    // Now unserialize the data
    CDataStream sMsg(vchMsg, SER_NETWORK, PROTOCOL_VERSION);
    sMsg >> *(CUnsignedSyncCheckpoint*)this;
    return true;
}

// process synchronized checkpoint
bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
{
    if (!CheckSignature())
        return false;

    LOCK(Checkpoints::cs_hashSyncCheckpoint);
    if (!mapBlockIndex.count(hashCheckpoint))
    {
        // We haven't received the checkpoint chain, keep the checkpoint as pending
        Checkpoints::hashPendingCheckpoint = hashCheckpoint;
        Checkpoints::checkpointMessagePending = *this;
        printf("ProcessSyncCheckpoint: pending for sync-checkpoint %s\n", hashCheckpoint.ToString().c_str());
        // Ask this guy to fill in what we're missing
        if (pfrom)
        {
            pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
            // ask directly as well in case rejected earlier by duplicate
            // proof-of-stake because getblocks may not get it this time
            pfrom->AskFor(CInv(MSG_BLOCK, mapOrphanBlocks.count(hashCheckpoint)? WantedByOrphan(mapOrphanBlocks[hashCheckpoint]) : hashCheckpoint));
        }
        return false;
    }

    if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
        return false;

    CTxDB txdb;
    CBlockIndex* pindexCheckpoint = mapBlockIndex[hashCheckpoint];
    if (!pindexCheckpoint->IsInMainChain())
    {
        // checkpoint chain received but not yet main chain
        CBlock block;
        if (!block.ReadFromDisk(pindexCheckpoint))
            return error("ProcessSyncCheckpoint: ReadFromDisk failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
        if (!block.SetBestChain(txdb, pindexCheckpoint))
        {
            Checkpoints::hashInvalidCheckpoint = hashCheckpoint;
            return error("ProcessSyncCheckpoint: SetBestChain failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
        }
    }

    if (!Checkpoints::WriteSyncCheckpoint(hashCheckpoint))
        return error("ProcessSyncCheckpoint(): failed to write sync checkpoint %s", hashCheckpoint.ToString().c_str());
    Checkpoints::checkpointMessage = *this;
    Checkpoints::hashPendingCheckpoint = 0;
    Checkpoints::checkpointMessagePending.SetNull();
    printf("ProcessSyncCheckpoint: sync-checkpoint at %s\n", hashCheckpoint.ToString().c_str());
    return true;
}