bitcoin/src/wallet/salvage.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <fs.h>
#include <streams.h>
#include <wallet/salvage.h>
#include <wallet/wallet.h>
#include <wallet/walletdb.h>

/* End of headers, beginning of key/value data */
static const char *HEADER_END = "HEADER=END";
/* End of key/value data */
static const char *DATA_END = "DATA=END";
typedef std::pair<std::vector<unsigned char>, std::vector<unsigned char> > KeyValPair;

bool RecoverDatabaseFile(const fs::path& file_path, void *callbackDataIn, bool (*recoverKVcallback)(void* callbackData, CDataStream ssKey, CDataStream ssValue), std::string& newFilename)
{
    std::string filename;
    std::shared_ptr<BerkeleyEnvironment> env = GetWalletEnv(file_path, filename);

    // Recovery procedure:
    // move wallet file to walletfilename.timestamp.bak
    // Call Salvage with fAggressive=true to
    // get as much data as possible.
    // Rewrite salvaged data to fresh wallet file
    // Set -rescan so any missing transactions will be
    // found.
    int64_t now = GetTime();
    newFilename = strprintf("%s.%d.bak", filename, now);

    int result = env->dbenv->dbrename(nullptr, filename.c_str(), nullptr,
                                       newFilename.c_str(), DB_AUTO_COMMIT);
    if (result == 0)
        LogPrintf("Renamed %s to %s\n", filename, newFilename);
    else
    {
        LogPrintf("Failed to rename %s to %s\n", filename, newFilename);
        return false;
    }

    /**
     * Salvage data from a file. The DB_AGGRESSIVE flag is being used (see berkeley DB->verify() method documentation).
     * key/value pairs are appended to salvagedData which are then written out to a new wallet file.
     * NOTE: reads the entire database into memory, so cannot be used
     * for huge databases.
     */
    std::vector<KeyValPair> salvagedData;

    std::stringstream strDump;

    Db db(env->dbenv.get(), 0);
    result = db.verify(newFilename.c_str(), nullptr, &strDump, DB_SALVAGE | DB_AGGRESSIVE);
    if (result == DB_VERIFY_BAD) {
        LogPrintf("Salvage: Database salvage found errors, all data may not be recoverable.\n");
    }
    if (result != 0 && result != DB_VERIFY_BAD) {
        LogPrintf("Salvage: Database salvage failed with result %d.\n", result);
        return false;
    }

    // Format of bdb dump is ascii lines:
    // header lines...
    // HEADER=END
    //  hexadecimal key
    //  hexadecimal value
    //  ... repeated
    // DATA=END

    std::string strLine;
    while (!strDump.eof() && strLine != HEADER_END)
        getline(strDump, strLine); // Skip past header

    std::string keyHex, valueHex;
    while (!strDump.eof() && keyHex != DATA_END) {
        getline(strDump, keyHex);
        if (keyHex != DATA_END) {
            if (strDump.eof())
                break;
            getline(strDump, valueHex);
            if (valueHex == DATA_END) {
                LogPrintf("Salvage: WARNING: Number of keys in data does not match number of values.\n");
                break;
            }
            salvagedData.push_back(make_pair(ParseHex(keyHex), ParseHex(valueHex)));
        }
    }

    bool fSuccess;
    if (keyHex != DATA_END) {
        LogPrintf("Salvage: WARNING: Unexpected end of file while reading salvage output.\n");
        fSuccess = false;
    } else {
        fSuccess = (result == 0);
    }

    if (salvagedData.empty())
    {
        LogPrintf("Salvage(aggressive) found no records in %s.\n", newFilename);
        return false;
    }
    LogPrintf("Salvage(aggressive) found %u records\n", salvagedData.size());

    std::unique_ptr<Db> pdbCopy = MakeUnique<Db>(env->dbenv.get(), 0);
    int ret = pdbCopy->open(nullptr,               // Txn pointer
                            filename.c_str(),   // Filename
                            "main",             // Logical db name
                            DB_BTREE,           // Database type
                            DB_CREATE,          // Flags
                            0);
    if (ret > 0) {
        LogPrintf("Cannot create database file %s\n", filename);
        pdbCopy->close(0);
        return false;
    }

    DbTxn* ptxn = env->TxnBegin();
    for (KeyValPair& row : salvagedData)
    {
        if (recoverKVcallback)
        {
            CDataStream ssKey(row.first, SER_DISK, CLIENT_VERSION);
            CDataStream ssValue(row.second, SER_DISK, CLIENT_VERSION);
            if (!(*recoverKVcallback)(callbackDataIn, ssKey, ssValue))
                continue;
        }
        Dbt datKey(&row.first[0], row.first.size());
        Dbt datValue(&row.second[0], row.second.size());
        int ret2 = pdbCopy->put(ptxn, &datKey, &datValue, DB_NOOVERWRITE);
        if (ret2 > 0)
            fSuccess = false;
    }
    ptxn->commit(0);
    pdbCopy->close(0);

    return fSuccess;
}

bool RecoverKeysOnlyFilter(void *callbackData, CDataStream ssKey, CDataStream ssValue)
{
    CWallet *dummyWallet = reinterpret_cast<CWallet*>(callbackData);
    std::string strType, strErr;
    bool fReadOK;
    {
        // Required in LoadKeyMetadata():
        LOCK(dummyWallet->cs_wallet);
        fReadOK = ReadKeyValue(dummyWallet, ssKey, ssValue, strType, strErr);
    }
    if (!WalletBatch::IsKeyType(strType) && strType != DBKeys::HDCHAIN) {
        return false;
    }
    if (!fReadOK)
    {
        LogPrintf("WARNING: WalletBatch::Recover skipping %s: %s\n", strType, strErr);
        return false;
    }

    return true;
}