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, 31 insertions, 10 deletions

diff --git a/src/key.cpp b/src/key.cpp
index 76c45d0635..23f315203e 100644
--- a/src/key.cpp
+++ b/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;
-    fSet = true;
-    return true;
+    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;
-    fSet = true;
-    if (vchPubKey.vchPubKey.size() == 33)
-        SetCompressedPubKey();
-    return true;
+    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;