Merge bitcoin#23142: Return false on corrupt tx rather than asserting

0ab4c3b Return false on corrupt tx rather than asserting (Samuel Dobson)

Pull request description:

  Takes up bitcoin#19793

  Rather than asserting, we log an error and return CORRUPT so that the user is informed. This type of error isn't critical so it isn't worth `assert`ing.

ACKs for top commit:
  achow101:
    ACK 0ab4c3b
  laanwj:
    Code review ACK 0ab4c3b
  ryanofsky:
    Code review ACK 0ab4c3b. There may be room for more improvements later like better error messages or easier recovery options, but changing from an assert to an error seems like a clear improvement, and this seems to avoid all the pitfalls of the last PR that tried this.

Tree-SHA512: 4a1a412e7c473d176c4e09123b85f390a6b0ea195e78d28ebd50b13814b7852f8225a172511a2efb6affb555b11bd4e667c19eb8c78b060c5444b62f0fae5f7a

Author: laanwj

src/wallet/walletdb.cpp

@@ -324,6 +324,7 @@ class CWalletScanState {
     std::map<uint256, DescriptorCache> m_descriptor_caches;
     std::map<std::pair<uint256, CKeyID>, CKey> m_descriptor_keys;
     std::map<std::pair<uint256, CKeyID>, std::pair<CPubKey, std::vector<unsigned char>>> m_descriptor_crypt_keys;
+    bool tx_corrupt{false};
 
     CWalletScanState() {
     }
@@ -358,7 +359,13 @@ ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue,
             // LoadToWallet call below creates a new CWalletTx that fill_wtx
             // callback fills with transaction metadata.
             auto fill_wtx = [&](CWalletTx& wtx, bool new_tx) {
-                assert(new_tx);
+                if(!new_tx) {
+                    // There's some corruption here since the tx we just tried to load was already in the wallet.
+                    // We don't consider this type of corruption critical, and can fix it by removing tx data and
+                    // rescanning.
+                    wss.tx_corrupt = true;
+                    return false;
+                }
                 ssValue >> wtx;
                 if (wtx.GetHash() != hash)
                     return false;
@@ -797,6 +804,11 @@ DBErrors WalletBatch::LoadWallet(CWallet* pwallet)
                 } else if (strType == DBKeys::FLAGS) {
                     // reading the wallet flags can only fail if unknown flags are present
                     result = DBErrors::TOO_NEW;
+                } else if (wss.tx_corrupt) {
+                    pwallet->WalletLogPrintf("Error: Corrupt transaction found. This can be fixed by removing transactions from wallet and rescanning.\n");
+                    // Set tx_corrupt back to false so that the error is only printed once (per corrupt tx)
+                    wss.tx_corrupt = false;
+                    result = DBErrors::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.