Handle corrupt wallets gracefully.

Corrupt wallets used to cause a DB_RUNRECOVERY uncaught exception and a
crash. This commit does three things:

1) Runs a BDB verify early in the startup process, and if there is a
low-level problem with the database:
  + Moves the bad wallet.dat to wallet.timestamp.bak
  + Runs a 'salvage' operation to get key/value pairs, and
    writes them to a new wallet.dat
  + Continues with startup.

2) Much more tolerant of serialization errors. All errors in deserialization
are reported by tolerated EXCEPT for errors related to reading keypairs
or master key records-- those are reported and then shut down, so the user
can get help (or recover from a backup).

3) Adds a new -salvagewallet option, which:
 + Moves the wallet.dat to wallet.timestamp.bak
 + extracts ONLY keypairs and master keys into a new wallet.dat
 + soft-sets -rescan, to recreate transaction history

This was tested by randomly corrupting testnet wallets using a little
python script I wrote (https://gist.github.com/3812689)

src/db.cpp

@@ -136,6 +136,69 @@ void CDBEnv::MakeMock()
     fMockDb = true;
 }
 
+CDBEnv::VerifyResult CDBEnv::Verify(std::string strFile, bool (*recoverFunc)(CDBEnv& dbenv, std::string strFile))
+{
+    LOCK(cs_db);
+    assert(mapFileUseCount.count(strFile) == 0);
+
+    Db db(&dbenv, 0);
+    int result = db.verify(strFile.c_str(), NULL, NULL, 0);
+    if (result == 0)
+        return VERIFY_OK;
+    else if (recoverFunc == NULL)
+        return RECOVER_FAIL;
+
+    // Try to recover:
+    bool fRecovered = (*recoverFunc)(*this, strFile);
+    return (fRecovered ? RECOVER_OK : RECOVER_FAIL);
+}
+
+bool CDBEnv::Salvage(std::string strFile, bool fAggressive,
+                     std::vector<CDBEnv::KeyValPair >& vResult)
+{
+    LOCK(cs_db);
+    assert(mapFileUseCount.count(strFile) == 0);
+
+    u_int32_t flags = DB_SALVAGE;
+    if (fAggressive) flags |= DB_AGGRESSIVE;
+
+    stringstream strDump;
+
+    Db db(&dbenv, 0);
+    int result = db.verify(strFile.c_str(), NULL, &strDump, flags);
+    if (result != 0)
+    {
+        printf("ERROR: db salvage failed\n");
+        return false;
+    }
+
+    // Format of bdb dump is ascii lines:
+    // header lines...
+    // HEADER=END
+    // hexadecimal key
+    // hexadecimal value
+    // ... repeated
+    // DATA=END
+
+    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")
+        {
+            getline(strDump, valueHex);
+            vResult.push_back(make_pair(ParseHex(keyHex),ParseHex(valueHex)));
+        }
+    }
+
+    return (result == 0);
+}
+
+
 void CDBEnv::CheckpointLSN(std::string strFile)
 {
     dbenv.txn_checkpoint(0, 0, 0);
@@ -257,6 +320,15 @@ void CDBEnv::CloseDb(const string& strFile)
     }
 }
 
+bool CDBEnv::RemoveDb(const string& strFile)
+{
+    this->CloseDb(strFile);
+
+    LOCK(cs_db);
+    int rc = dbenv.dbremove(NULL, strFile.c_str(), NULL, DB_AUTO_COMMIT);
+    return (rc == 0);
+}
+
 bool CDB::Rewrite(const string& strFile, const char* pszSkip)
 {
     while (!fShutdown)

src/db.h

@@ -50,6 +50,25 @@ public:
     ~CDBEnv();
     void MakeMock();
     bool IsMock() { return fMockDb; };
+
+    /*
+     * Verify that database file strFile is OK. If it is not,
+     * call the callback to try to recover.
+     * This must be called BEFORE strFile is opened.
+     * Returns true if strFile is OK.
+     */
+    enum VerifyResult { VERIFY_OK, RECOVER_OK, RECOVER_FAIL };
+    VerifyResult Verify(std::string strFile, bool (*recoverFunc)(CDBEnv& dbenv, std::string strFile));
+    /*
+     * Salvage data from a file that Verify says is bad.
+     * fAggressive sets the DB_AGGRESSIVE flag (see berkeley DB->verify() method documentation).
+     * Appends binary key/value pairs to vResult, returns true if successful.
+     * NOTE: reads the entire database into memory, so cannot be used
+     * for huge databases.
+     */
+    typedef std::pair<std::vector<unsigned char>, std::vector<unsigned char> > KeyValPair;
+    bool Salvage(std::string strFile, bool fAggressive, std::vector<KeyValPair>& vResult);
+
     bool Open(boost::filesystem::path pathEnv_);
     void Close();
     void Flush(bool fShutdown);
@@ -58,6 +77,7 @@ public:
     bool GetDetach() { return fDetachDB; }
 
     void CloseDb(const std::string& strFile);
+    bool RemoveDb(const std::string& strFile);
 
     DbTxn *TxnBegin(int flags=DB_TXN_WRITE_NOSYNC)
     {

src/init.cpp

@@ -279,6 +279,7 @@ std::string HelpMessage()
         "  -upgradewallet         " + _("Upgrade wallet to latest format") + "\n" +
         "  -keypool=<n>           " + _("Set key pool size to <n> (default: 100)") + "\n" +
         "  -rescan                " + _("Rescan the block chain for missing wallet transactions") + "\n" +
+        "  -salvagewallet         " + _("Attempt to recover private keys from a corrupt wallet.dat") + "\n" +
         "  -checkblocks=<n>       " + _("How many blocks to check at startup (default: 2500, 0 = all)") + "\n" +
         "  -checklevel=<n>        " + _("How thorough the block verification is (0-6, default: 1)") + "\n" +
         "  -loadblock=<file>      " + _("Imports blocks from external blk000?.dat file") + "\n" +
@@ -379,6 +380,11 @@ bool AppInit2()
         SoftSetBoolArg("-discover", false);
     }
 
+    if (GetBoolArg("-salvagewallet")) {
+        // Rewrite just private keys: rescan to find transactions
+        SoftSetBoolArg("-rescan", true);
+    }
+
     // ********************************************************* Step 3: parameter-to-internal-flags
 
     fDebug = GetBoolArg("-debug");
@@ -434,12 +440,13 @@ bool AppInit2()
 
     // ********************************************************* Step 4: application initialization: dir lock, daemonize, pidfile, debug log
 
+    const char* pszDataDir = GetDataDir().string().c_str();
+
     // Make sure only a single Bitcoin process is using the data directory.
     boost::filesystem::path pathLockFile = GetDataDir() / ".lock";
     FILE* file = fopen(pathLockFile.string().c_str(), "a"); // empty lock file; created if it doesn't exist.
     if (file) fclose(file);
     static boost::interprocess::file_lock lock(pathLockFile.string().c_str());
-    const char* pszDataDir = GetDataDir().string().c_str();
     if (!lock.try_lock())
         return InitError(strprintf(_("Cannot obtain a lock on data directory %s.  Bitcoin is probably already running."), pszDataDir));
 
@@ -481,7 +488,38 @@ bool AppInit2()
 
     int64 nStart;
 
-    // ********************************************************* Step 5: network initialization
+    // ********************************************************* Step 5: verify database integrity
+
+    uiInterface.InitMessage(_("Verifying database integrity..."));
+
+    if (!bitdb.Open(GetDataDir()))
+    {
+        string msg = strprintf(_("Error initializing database environment %s!"
+                                 " To recover, BACKUP THAT DIRECTORY, then remove"
+                                 " everything from it except for wallet.dat."), pszDataDir);
+        return InitError(msg);
+    }
+
+    if (GetBoolArg("-salvagewallet"))
+    {
+        // Recover readable keypairs:
+        if (!CWalletDB::Recover(bitdb, "wallet.dat", true))
+            return false;
+    }
+
+    CDBEnv::VerifyResult r = bitdb.Verify("wallet.dat", CWalletDB::Recover);
+    if (r == CDBEnv::RECOVER_OK)
+    {
+        string msg = strprintf(_("Warning: wallet.dat corrupt, data salvaged!"
+                                 " Original wallet.dat saved as wallet.{timestamp}.bak in %s; if"
+                                 " your balance or transactions are incorrect you should"
+                                 " restore from a backup."), pszDataDir);
+        uiInterface.ThreadSafeMessageBox(msg, _("Bitcoin"), CClientUIInterface::OK | CClientUIInterface::ICON_EXCLAMATION | CClientUIInterface::MODAL);
+    }
+    if (r == CDBEnv::RECOVER_FAIL)
+        return InitError(_("wallet.dat corrupt, salvage failed"));
+
+    // ********************************************************* Step 6: network initialization
 
     int nSocksVersion = GetArg("-socks", 5);
 
@@ -587,15 +625,7 @@ bool AppInit2()
     BOOST_FOREACH(string strDest, mapMultiArgs["-seednode"])
         AddOneShot(strDest);
 
-    // ********************************************************* Step 6: load blockchain
-
-    if (!bitdb.Open(GetDataDir()))
-    {
-        string msg = strprintf(_("Error initializing database environment %s!"
-                                 " To recover, BACKUP THAT DIRECTORY, then remove"
-                                 " everything from it except for wallet.dat."), pszDataDir);
-        return InitError(msg);
-    }
+    // ********************************************************* Step 7: load blockchain
 
     if (GetBoolArg("-loadblockindextest"))
     {
@@ -650,18 +680,24 @@ bool AppInit2()
         return false;
     }
 
-    // ********************************************************* Step 7: load wallet
+    // ********************************************************* Step 8: load wallet
 
     uiInterface.InitMessage(_("Loading wallet..."));
     printf("Loading wallet...\n");
     nStart = GetTimeMillis();
     bool fFirstRun = true;
     pwalletMain = new CWallet("wallet.dat");
-    int nLoadWalletRet = pwalletMain->LoadWallet(fFirstRun);
+    DBErrors nLoadWalletRet = pwalletMain->LoadWallet(fFirstRun);
     if (nLoadWalletRet != DB_LOAD_OK)
     {
         if (nLoadWalletRet == DB_CORRUPT)
             strErrors << _("Error loading wallet.dat: Wallet corrupted") << "\n";
+        else if (nLoadWalletRet == DB_NONCRITICAL_ERROR)
+        {
+            string msg(_("Warning: error reading wallet.dat! All keys read correctly, but transaction data"
+                         " or address book entries might be missing or incorrect."));
+            uiInterface.ThreadSafeMessageBox(msg, _("Bitcoin"), CClientUIInterface::OK | CClientUIInterface::ICON_EXCLAMATION | CClientUIInterface::MODAL);
+        }
         else if (nLoadWalletRet == DB_TOO_NEW)
             strErrors << _("Error loading wallet.dat: Wallet requires newer version of Bitcoin") << "\n";
         else if (nLoadWalletRet == DB_NEED_REWRITE)
@@ -727,7 +763,7 @@ bool AppInit2()
         printf(" rescan      %15"PRI64d"ms\n", GetTimeMillis() - nStart);
     }
 
-    // ********************************************************* Step 8: import blocks
+    // ********************************************************* Step 9: import blocks
 
     if (mapArgs.count("-loadblock"))
     {
@@ -753,7 +789,7 @@ bool AppInit2()
         }
     }
 
-    // ********************************************************* Step 9: load peers
+    // ********************************************************* Step 10: load peers
 
     uiInterface.InitMessage(_("Loading addresses..."));
     printf("Loading addresses...\n");
@@ -768,7 +804,7 @@ bool AppInit2()
     printf("Loaded %i addresses from peers.dat  %"PRI64d"ms\n",
            addrman.size(), GetTimeMillis() - nStart);
 
-    // ********************************************************* Step 10: start node
+    // ********************************************************* Step 11: start node
 
     if (!CheckDiskSpace())
         return false;
@@ -788,7 +824,7 @@ bool AppInit2()
     if (fServer)
         NewThread(ThreadRPCServer, NULL);
 
-    // ********************************************************* Step 11: finished
+    // ********************************************************* Step 12: finished
 
     uiInterface.InitMessage(_("Done loading"));
     printf("Done loading\n");
@@ -808,4 +844,3 @@ bool AppInit2()
 
     return true;
 }
-

src/key.cpp

@@ -186,10 +186,24 @@ void CKey::MakeNewKey(bool fCompressed)
 bool CKey::SetPrivKey(const CPrivKey& vchPrivKey)
 {
     const unsigned char* pbegin = &vchPrivKey[0];
-    if (!d2i_ECPrivateKey(&pkey, &pbegin, vchPrivKey.size()))
-        return false;
+    if (d2i_ECPrivateKey(&pkey, &pbegin, vchPrivKey.size()))
+    {
+        // In testing, d2i_ECPrivateKey can return true
+        // but fill in pkey with a key that fails
+        // EC_KEY_check_key, so:
+        if (EC_KEY_check_key(pkey))
+        {
             fSet = true;
             return true;
+        }
+    }
+    // If vchPrivKey data is bad d2i_ECPrivateKey() can
+    // leave pkey in a state where calling EC_KEY_free()
+    // crashes. To avoid that, set pkey to NULL and
+    // leak the memory (a leak is better than a crash)
+    pkey = NULL;
+    Reset();
+    return false;
 }
 
 bool CKey::SetSecret(const CSecret& vchSecret, bool fCompressed)
@@ -245,12 +259,16 @@ CPrivKey CKey::GetPrivKey() const
 bool CKey::SetPubKey(const CPubKey& vchPubKey)
 {
     const unsigned char* pbegin = &vchPubKey.vchPubKey[0];
-    if (!o2i_ECPublicKey(&pkey, &pbegin, vchPubKey.vchPubKey.size()))
-        return false;
+    if (o2i_ECPublicKey(&pkey, &pbegin, vchPubKey.vchPubKey.size()))
+    {
         fSet = true;
         if (vchPubKey.vchPubKey.size() == 33)
             SetCompressedPubKey();
         return true;
+    }
+    pkey = NULL;
+    Reset();
+    return false;
 }
 
 CPubKey CKey::GetPubKey() const
@@ -377,6 +395,9 @@ bool CKey::IsValid()
     if (!fSet)
         return false;
 
+    if (!EC_KEY_check_key(pkey))
+        return false;
+
     bool fCompr;
     CSecret secret = GetSecret(fCompr);
     CKey key2;

src/wallet.cpp

@@ -335,7 +335,9 @@ void CWallet::WalletUpdateSpent(const CTransaction &tx)
             if (mi != mapWallet.end())
             {
                 CWalletTx& wtx = (*mi).second;
-                if (!wtx.IsSpent(txin.prevout.n) && IsMine(wtx.vout[txin.prevout.n]))
+                if (txin.prevout.n >= wtx.vout.size())
+                    printf("WalletUpdateSpent: bad wtx %s\n", wtx.GetHash().ToString().c_str());
+                else if (!wtx.IsSpent(txin.prevout.n) && IsMine(wtx.vout[txin.prevout.n]))
                 {
                     printf("WalletUpdateSpent found spent coin %sbc %s\n", FormatMoney(wtx.GetCredit()).c_str(), wtx.GetHash().ToString().c_str());
                     wtx.MarkSpent(txin.prevout.n);
@@ -1371,12 +1373,12 @@ string CWallet::SendMoneyToDestination(const CTxDestination& address, int64 nVal
 
 
 
-int CWallet::LoadWallet(bool& fFirstRunRet)
+DBErrors CWallet::LoadWallet(bool& fFirstRunRet)
 {
     if (!fFileBacked)
         return DB_LOAD_OK;
     fFirstRunRet = false;
-    int nLoadWalletRet = CWalletDB(strWalletFile,"cr+").LoadWallet(this);
+    DBErrors nLoadWalletRet = CWalletDB(strWalletFile,"cr+").LoadWallet(this);
     if (nLoadWalletRet == DB_NEED_REWRITE)
     {
         if (CDB::Rewrite(strWalletFile, "\x04pool"))

src/wallet.h

@@ -16,11 +16,11 @@
 #include "script.h"
 #include "ui_interface.h"
 #include "util.h"
+#include "walletdb.h"
 
 class CAccountingEntry;
 class CWalletTx;
 class CReserveKey;
-class CWalletDB;
 class COutput;
 
 /** (client) version numbers for particular wallet features */
@@ -256,7 +256,7 @@ public:
     }
     void SetBestChain(const CBlockLocator& loc);
 
-    int LoadWallet(bool& fFirstRunRet);
+    DBErrors LoadWallet(bool& fFirstRunRet);
 
     bool SetAddressBookName(const CTxDestination& address, const std::string& strName);
 

src/walletdb.cpp

@@ -108,7 +108,7 @@ void CWalletDB::ListAccountCreditDebit(const string& strAccount, list<CAccountin
 }
 
 
-int
+DBErrors
 CWalletDB::ReorderTransactions(CWallet* pwallet)
 {
     LOCK(pwallet->cs_wallet);
@@ -181,51 +181,15 @@ CWalletDB::ReorderTransactions(CWallet* pwallet)
 }
 
 
-int CWalletDB::LoadWallet(CWallet* pwallet)
+bool
+ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue,
+             int& nFileVersion, vector<uint256>& vWalletUpgrade,
+             bool& fIsEncrypted,  bool& fAnyUnordered, string& strType, string& strErr)
 {
-    pwallet->vchDefaultKey = CPubKey();
-    int nFileVersion = 0;
-    vector<uint256> vWalletUpgrade;
-    bool fIsEncrypted = false;
-    bool fAnyUnordered = false;
-
-    //// todo: shouldn't we catch exceptions and try to recover and continue?
-    {
-        LOCK(pwallet->cs_wallet);
-        int nMinVersion = 0;
-        if (Read((string)"minversion", nMinVersion))
-        {
-            if (nMinVersion > CLIENT_VERSION)
-                return DB_TOO_NEW;
-            pwallet->LoadMinVersion(nMinVersion);
-        }
-
-        // Get cursor
-        Dbc* pcursor = GetCursor();
-        if (!pcursor)
-        {
-            printf("Error getting wallet database cursor\n");
-            return DB_CORRUPT;
-        }
-
-        loop
-        {
-            // Read next record
-            CDataStream ssKey(SER_DISK, CLIENT_VERSION);
-            CDataStream ssValue(SER_DISK, CLIENT_VERSION);
-            int ret = ReadAtCursor(pcursor, ssKey, ssValue);
-            if (ret == DB_NOTFOUND)
-                break;
-            else if (ret != 0)
-            {
-                printf("Error reading next record from wallet database\n");
-                return DB_CORRUPT;
-            }
-
+    try {
         // Unserialize
         // Taking advantage of the fact that pair serialization
         // is just the two items serialized one after the other
-            string strType;
         ssKey >> strType;
         if (strType == "name")
         {
@@ -239,10 +203,13 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
             ssKey >> hash;
             CWalletTx& wtx = pwallet->mapWallet[hash];
             ssValue >> wtx;
+            if (wtx.CheckTransaction() && (wtx.GetHash() == hash))
                 wtx.BindWallet(pwallet);
-
-                if (wtx.GetHash() != hash)
-                    printf("Error in wallet.dat, hash mismatch\n");
+            else
+            {
+                pwallet->mapWallet.erase(hash);
+                return false;
+            }
 
             // Undo serialize changes in 31600
             if (31404 <= wtx.fTimeReceivedIsTxTime && wtx.fTimeReceivedIsTxTime <= 31703)
@@ -252,12 +219,13 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
                     char fTmp;
                     char fUnused;
                     ssValue >> fTmp >> fUnused >> wtx.strFromAccount;
-                        printf("LoadWallet() upgrading tx ver=%d %d '%s' %s\n", wtx.fTimeReceivedIsTxTime, fTmp, wtx.strFromAccount.c_str(), hash.ToString().c_str());
+                    strErr = strprintf("LoadWallet() upgrading tx ver=%d %d '%s' %s",
+                                       wtx.fTimeReceivedIsTxTime, fTmp, wtx.strFromAccount.c_str(), hash.ToString().c_str());
                     wtx.fTimeReceivedIsTxTime = fTmp;
                 }
                 else
                 {
-                        printf("LoadWallet() repairing tx ver=%d %s\n", wtx.fTimeReceivedIsTxTime, hash.ToString().c_str());
+                    strErr = strprintf("LoadWallet() repairing tx ver=%d %s", wtx.fTimeReceivedIsTxTime, hash.ToString().c_str());
                     wtx.fTimeReceivedIsTxTime = 0;
                 }
                 vWalletUpgrade.push_back(hash);
@@ -301,16 +269,20 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
                 CPrivKey pkey;
                 ssValue >> pkey;
                 key.SetPubKey(vchPubKey);
-                    key.SetPrivKey(pkey);
+                if (!key.SetPrivKey(pkey))
+                {
+                    strErr = "Error reading wallet database: CPrivKey corrupt";
+                    return false;
+                }
                 if (key.GetPubKey() != vchPubKey)
                 {
-                        printf("Error reading wallet database: CPrivKey pubkey inconsistency\n");
-                        return DB_CORRUPT;
+                    strErr = "Error reading wallet database: CPrivKey pubkey inconsistency";
+                    return false;
                 }
                 if (!key.IsValid())
                 {
-                        printf("Error reading wallet database: invalid CPrivKey\n");
-                        return DB_CORRUPT;
+                    strErr = "Error reading wallet database: invalid CPrivKey";
+                    return false;
                 }
             }
             else
@@ -318,22 +290,26 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
                 CWalletKey wkey;
                 ssValue >> wkey;
                 key.SetPubKey(vchPubKey);
-                    key.SetPrivKey(wkey.vchPrivKey);
+                if (!key.SetPrivKey(wkey.vchPrivKey))
+                {
+                    strErr = "Error reading wallet database: CPrivKey corrupt";
+                    return false;
+                }
                 if (key.GetPubKey() != vchPubKey)
                 {
-                        printf("Error reading wallet database: CWalletKey pubkey inconsistency\n");
-                        return DB_CORRUPT;
+                    strErr = "Error reading wallet database: CWalletKey pubkey inconsistency";
+                    return false;
                 }
                 if (!key.IsValid())
                 {
-                        printf("Error reading wallet database: invalid CWalletKey\n");
-                        return DB_CORRUPT;
+                    strErr = "Error reading wallet database: invalid CWalletKey";
+                    return false;
                 }
             }
             if (!pwallet->LoadKey(key))
             {
-                    printf("Error reading wallet database: LoadKey failed\n");
-                    return DB_CORRUPT;
+                strErr = "Error reading wallet database: LoadKey failed";
+                return false;
             }
         }
         else if (strType == "mkey")
@@ -344,8 +320,8 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
             ssValue >> kMasterKey;
             if(pwallet->mapMasterKeys.count(nID) != 0)
             {
-                    printf("Error reading wallet database: duplicate CMasterKey id %u\n", nID);
-                    return DB_CORRUPT;
+                strErr = strprintf("Error reading wallet database: duplicate CMasterKey id %u", nID);
+                return false;
             }
             pwallet->mapMasterKeys[nID] = kMasterKey;
             if (pwallet->nMasterKeyMaxID < nID)
@@ -359,8 +335,8 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
             ssValue >> vchPrivKey;
             if (!pwallet->LoadCryptedKey(vchPubKey, vchPrivKey))
             {
-                    printf("Error reading wallet database: LoadCryptedKey failed\n");
-                    return DB_CORRUPT;
+                strErr = "Error reading wallet database: LoadCryptedKey failed";
+                return false;
             }
             fIsEncrypted = true;
         }
@@ -388,23 +364,109 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
             ssValue >> script;
             if (!pwallet->LoadCScript(script))
             {
-                    printf("Error reading wallet database: LoadCScript failed\n");
-                    return DB_CORRUPT;
+                strErr = "Error reading wallet database: LoadCScript failed";
+                return false;
             }
         }
         else if (strType == "orderposnext")
         {
             ssValue >> pwallet->nOrderPosNext;
         }
+    } catch (...)
+    {
+        return false;
+    }
+    return true;
+}
+
+static bool IsKeyType(string strType)
+{
+    return (strType== "key" || strType == "wkey" ||
+            strType == "mkey" || strType == "ckey");
+}
+
+DBErrors CWalletDB::LoadWallet(CWallet* pwallet)
+{
+    pwallet->vchDefaultKey = CPubKey();
+    int nFileVersion = 0;
+    vector<uint256> vWalletUpgrade;
+    bool fIsEncrypted = false;
+    bool fAnyUnordered = false;
+    bool fNoncriticalErrors = false;
+    DBErrors result = DB_LOAD_OK;
+
+    try {
+        LOCK(pwallet->cs_wallet);
+        int nMinVersion = 0;
+        if (Read((string)"minversion", nMinVersion))
+        {
+            if (nMinVersion > CLIENT_VERSION)
+                return DB_TOO_NEW;
+            pwallet->LoadMinVersion(nMinVersion);
+        }
+
+        // Get cursor
+        Dbc* pcursor = GetCursor();
+        if (!pcursor)
+        {
+            printf("Error getting wallet database cursor\n");
+            return DB_CORRUPT;
+        }
+
+        loop
+        {
+            // Read next record
+            CDataStream ssKey(SER_DISK, CLIENT_VERSION);
+            CDataStream ssValue(SER_DISK, CLIENT_VERSION);
+            int ret = ReadAtCursor(pcursor, ssKey, ssValue);
+            if (ret == DB_NOTFOUND)
+                break;
+            else if (ret != 0)
+            {
+                printf("Error reading next record from wallet database\n");
+                return DB_CORRUPT;
+            }
+
+            // Try to be tolerant of single corrupt records:
+            string strType, strErr;
+            if (!ReadKeyValue(pwallet, ssKey, ssValue, nFileVersion,
+                              vWalletUpgrade, fIsEncrypted, fAnyUnordered, strType, strErr))
+            {
+                // losing keys is considered a catastrophic error, anything else
+                // we assume the user can live with:
+                if (IsKeyType(strType))
+                    result = DB_CORRUPT;
+                else
+                {
+                    // Leave other errors alone, if we try to fix them we might make things worse.
+                    fNoncriticalErrors = true; // ... but do warn the user there is something wrong.
+                    if (strType == "tx")
+                        // Rescan if there is a bad transaction record:
+                        SoftSetBoolArg("-rescan", true);
+                }
+            }
+            if (!strErr.empty())
+                printf("%s\n", strErr.c_str());
         }
         pcursor->close();
     }
+    catch (...)
+    {
+        result = DB_CORRUPT;
+    }
 
-    BOOST_FOREACH(uint256 hash, vWalletUpgrade)
-        WriteTx(hash, pwallet->mapWallet[hash]);
+    if (fNoncriticalErrors && result == DB_LOAD_OK)
+        result = DB_NONCRITICAL_ERROR;
+
+    // Any wallet corruption at all: skip any rewriting or
+    // upgrading, we don't want to make it worse.
+    if (result != DB_LOAD_OK)
+        return result;
 
     printf("nFileVersion = %d\n", nFileVersion);
 
+    BOOST_FOREACH(uint256 hash, vWalletUpgrade)
+        WriteTx(hash, pwallet->mapWallet[hash]);
 
     // Rewrite encrypted wallets of versions 0.4.0 and 0.5.0rc:
     if (fIsEncrypted && (nFileVersion == 40000 || nFileVersion == 50000))
@@ -414,10 +476,9 @@ int CWalletDB::LoadWallet(CWallet* pwallet)
         WriteVersion(CLIENT_VERSION);
 
     if (fAnyUnordered)
-        return ReorderTransactions(pwallet);
+        result = ReorderTransactions(pwallet);
 
-    // If you add anything else here... be sure to do it if ReorderTransactions returns DB_LOAD_OK too!
-    return DB_LOAD_OK;
+    return result;
 }
 
 void ThreadFlushWalletDB(void* parg)
@@ -521,3 +582,94 @@ bool BackupWallet(const CWallet& wallet, const string& strDest)
     }
     return false;
 }
+
+//
+// Try to (very carefully!) recover wallet.dat if there is a problem.
+//
+bool CWalletDB::Recover(CDBEnv& dbenv, std::string filename, bool fOnlyKeys)
+{
+    // Recovery procedure:
+    // move wallet.dat to wallet.timestamp.bak
+    // Call Salvage with fAggressive=true to
+    // get as much data as possible.
+    // Rewrite salvaged data to wallet.dat
+    // Set -rescan so any missing transactions will be
+    // found.
+    int64 now = GetTime();
+    std::string newFilename = strprintf("wallet.%"PRI64d".bak", now);
+
+    int result = dbenv.dbenv.dbrename(NULL, filename.c_str(), NULL,
+                                      newFilename.c_str(), DB_AUTO_COMMIT);
+    if (result == 0)
+        printf("Renamed %s to %s\n", filename.c_str(), newFilename.c_str());
+    else
+    {
+        printf("Failed to rename %s to %s\n", filename.c_str(), newFilename.c_str());
+        return false;
+    }
+
+    std::vector<CDBEnv::KeyValPair> salvagedData;
+    bool allOK = dbenv.Salvage(newFilename, true, salvagedData);
+    if (salvagedData.empty())
+    {
+        printf("Salvage(aggressive) found no records in %s.\n", newFilename.c_str());
+        return false;
+    }
+    printf("Salvage(aggressive) found %"PRIszu" records\n", salvagedData.size());
+
+    bool fSuccess = allOK;
+    Db* pdbCopy = new Db(&dbenv.dbenv, 0);
+    int ret = pdbCopy->open(NULL,                 // Txn pointer
+                            filename.c_str(),   // Filename
+                            "main",    // Logical db name
+                            DB_BTREE,  // Database type
+                            DB_CREATE,    // Flags
+                            0);
+    if (ret > 0)
+    {
+        printf("Cannot create database file %s\n", filename.c_str());
+        return false;
+    }
+    CWallet dummyWallet;
+    int nFileVersion = 0;
+    vector<uint256> vWalletUpgrade;
+    bool fIsEncrypted = false;
+    bool fAnyUnordered = false;
+
+    DbTxn* ptxn = dbenv.TxnBegin();
+    BOOST_FOREACH(CDBEnv::KeyValPair& row, salvagedData)
+    {
+        if (fOnlyKeys)
+        {
+            CDataStream ssKey(row.first, SER_DISK, CLIENT_VERSION);
+            CDataStream ssValue(row.second, SER_DISK, CLIENT_VERSION);
+            string strType, strErr;
+            bool fReadOK = ReadKeyValue(&dummyWallet, ssKey, ssValue,
+                                        nFileVersion, vWalletUpgrade,
+                                        fIsEncrypted, fAnyUnordered,
+                                        strType, strErr);
+            if (!IsKeyType(strType))
+                continue;
+            if (!fReadOK)
+            {
+                printf("WARNING: CWalletDB::Recover skipping %s: %s\n", strType.c_str(), strErr.c_str());
+                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);
+    delete pdbCopy;
+
+    return fSuccess;
+}
+
+bool CWalletDB::Recover(CDBEnv& dbenv, std::string filename)
+{
+    return CWalletDB::Recover(dbenv, filename, false);
+}

src/walletdb.h

@@ -17,6 +17,7 @@ enum DBErrors
 {
     DB_LOAD_OK,
     DB_CORRUPT,
+    DB_NONCRITICAL_ERROR,
     DB_TOO_NEW,
     DB_LOAD_FAIL,
     DB_NEED_REWRITE
@@ -153,8 +154,10 @@ public:
     int64 GetAccountCreditDebit(const std::string& strAccount);
     void ListAccountCreditDebit(const std::string& strAccount, std::list<CAccountingEntry>& acentries);
 
-    int ReorderTransactions(CWallet*);
-    int LoadWallet(CWallet* pwallet);
+    DBErrors ReorderTransactions(CWallet*);
+    DBErrors LoadWallet(CWallet* pwallet);
+    static bool Recover(CDBEnv& dbenv, std::string filename, bool fOnlyKeys);
+    static bool Recover(CDBEnv& dbenv, std::string filename);
 };
 
 #endif // BITCOIN_WALLETDB_H