wallet: Be able to unlock the wallet for migration

Since migration reloads the wallet, the wallet will always be locked
unless the passphrase is given. migratewallet can now take the
passphrase in order to unlock the wallet for migration.

Author: achow101

src/wallet/rpc/wallet.cpp

@@ -724,6 +724,7 @@ static RPCHelpMan migratewallet()
         HELP_REQUIRING_PASSPHRASE,
         {
             {"wallet_name", RPCArg::Type::STR, RPCArg::DefaultHint{"the wallet name from the RPC endpoint"}, "The name of the wallet to migrate. If provided both here and in the RPC endpoint, the two must be identical."},
+            {"passphrase", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "The wallet passphrase"},
         },
         RPCResult{
             RPCResult::Type::OBJ, "", "",
@@ -752,15 +753,14 @@ static RPCHelpMan migratewallet()
                 wallet_name = request.params[0].get_str();
             }
 
-            WalletContext& context = EnsureWalletContext(request.context);
-            {
-                std::shared_ptr<CWallet> wallet = GetWallet(context, wallet_name);
-                if (wallet && wallet->IsCrypted()) {
-                    throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: migratewallet on encrypted wallets is currently unsupported.");
-                }
+            SecureString wallet_pass;
+            wallet_pass.reserve(100);
+            if (!request.params[1].isNull()) {
+                wallet_pass = std::string_view{request.params[1].get_str()};
             }
 
-            util::Result<MigrationResult> res = MigrateLegacyToDescriptor(wallet_name, context);
+            WalletContext& context = EnsureWalletContext(request.context);
+            util::Result<MigrationResult> res = MigrateLegacyToDescriptor(wallet_name, wallet_pass, context);
             if (!res) {
                 throw JSONRPCError(RPC_WALLET_ERROR, util::ErrorString(res).original);
             }

src/wallet/wallet.cpp

@@ -3875,7 +3875,7 @@ std::optional<MigrationData> CWallet::GetDescriptorsForLegacy(bilingual_str& err
 
     std::optional<MigrationData> res = legacy_spkm->MigrateToDescriptor();
     if (res == std::nullopt) {
-        error = _("Error: Unable to produce descriptors for this legacy wallet. Make sure the wallet is unlocked first");
+        error = _("Error: Unable to produce descriptors for this legacy wallet. Make sure to provide the wallet's passphrase if it is encrypted.");
         return std::nullopt;
     }
     return res;
@@ -4165,7 +4165,7 @@ bool DoMigration(CWallet& wallet, WalletContext& context, bilingual_str& error,
     return true;
 }
 
-util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& wallet_name, WalletContext& context)
+util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& wallet_name, const SecureString& passphrase, WalletContext& context)
 {
     MigrationResult res;
     bilingual_str error;
@@ -4215,6 +4215,19 @@ util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& walle
     {
         LOCK(local_wallet->cs_wallet);
 
+        // Unlock the wallet if needed
+        if (local_wallet->IsLocked() && !local_wallet->Unlock(passphrase)) {
+            if (passphrase.find('\0') == std::string::npos) {
+                return util::Error{Untranslated("Error: Wallet decryption failed, the wallet passphrase was not provided or was incorrect.")};
+            } else {
+                return util::Error{Untranslated("Error: Wallet decryption failed, the wallet passphrase entered was incorrect. "
+                                                "The passphrase contains a null character (ie - a zero byte). "
+                                                "If this passphrase was set with a version of this software prior to 25.0, "
+                                                "please try again with only the characters up to — but not including — "
+                                                "the first null character.")};
+            }
+        }
+
         // First change to using SQLite
         if (!local_wallet->MigrateToSQLite(error)) return util::Error{error};
 

src/wallet/wallet.h

@@ -1007,7 +1007,7 @@ struct MigrationResult {
 };
 
 //! Do all steps to migrate a legacy wallet to a descriptor wallet
-util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& wallet_name, WalletContext& context);
+util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& wallet_name, const SecureString& passphrase, WalletContext& context);
 } // namespace wallet
 
 #endif // BITCOIN_WALLET_WALLET_H

test/functional/wallet_migration.py

@@ -403,7 +403,6 @@ def test_encrypted(self):
 
         wallet.encryptwallet("pass")
 
-        assert_raises_rpc_error(-15, "Error: migratewallet on encrypted wallets is currently unsupported.", wallet.migratewallet)
         # TODO: Fix migratewallet so that we can actually migrate encrypted wallets
 
     def run_test(self):