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)

1 files changed, 5 insertions, 3 deletions

diff --git a/src/wallet.cpp b/src/wallet.cpp
index f3e71f59aa..1a6a1082b1 100644
--- a/src/wallet.cpp
+++ b/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"))