From e6906fcf9e4d5692ead6c9bf5a2e11673315a1f5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Aur=C3=A8le=20Oul=C3=A8s?= <aurele@oules.com>
Date: Sun, 2 Oct 2022 18:21:11 +0200
Subject: [PATCH] rpc: Enable wallet import on pruned nodes
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: João Barbosa <joao.paulo.barbosa@gmail.com>
Co-authored-by: Ryan Ofsky <ryan@ofsky.org>
---
 src/wallet/rpc/backup.cpp | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/src/wallet/rpc/backup.cpp b/src/wallet/rpc/backup.cpp
index ddf10cae155..a85302c77d2 100644
--- a/src/wallet/rpc/backup.cpp
+++ b/src/wallet/rpc/backup.cpp
@@ -93,6 +93,22 @@ static void RescanWallet(CWallet& wallet, const WalletRescanReserver& reserver,
     }
 }
 
+static void EnsureBlockDataFromTime(const CWallet& wallet, int64_t timestamp)
+{
+    auto& chain{wallet.chain()};
+    if (!chain.havePruned()) {
+        return;
+    }
+
+    int height{0};
+    const bool found{chain.findFirstBlockWithTimeAndHeight(timestamp - TIMESTAMP_WINDOW, 0, FoundBlock().height(height))};
+
+    uint256 tip_hash{WITH_LOCK(wallet.cs_wallet, return wallet.GetLastBlockHash())};
+    if (found && !chain.hasBlocks(tip_hash, height)) {
+        throw JSONRPCError(RPC_WALLET_ERROR, strprintf("Pruned blocks from height %d required to import keys. Use RPC call getblockchaininfo to determine your pruned height.", height));
+    }
+}
+
 RPCHelpMan importprivkey()
 {
     return RPCHelpMan{"importprivkey",
@@ -504,13 +520,6 @@ RPCHelpMan importwallet()
 
     EnsureLegacyScriptPubKeyMan(*pwallet, true);
 
-    if (pwallet->chain().havePruned()) {
-        // Exit early and print an error.
-        // If a block is pruned after this check, we will import the key(s),
-        // but fail the rescan with a generic error.
-        throw JSONRPCError(RPC_WALLET_ERROR, "Importing wallets is disabled when blocks are pruned");
-    }
-
     WalletRescanReserver reserver(*pwallet);
     if (!reserver.reserve()) {
         throw JSONRPCError(RPC_WALLET_ERROR, "Wallet is currently rescanning. Abort existing rescan or wait.");
@@ -565,15 +574,18 @@ RPCHelpMan importwallet()
                         fLabel = true;
                     }
                 }
+                nTimeBegin = std::min(nTimeBegin, nTime);
                 keys.push_back(std::make_tuple(key, nTime, fLabel, strLabel));
             } else if(IsHex(vstr[0])) {
                 std::vector<unsigned char> vData(ParseHex(vstr[0]));
                 CScript script = CScript(vData.begin(), vData.end());
                 int64_t birth_time = ParseISO8601DateTime(vstr[1]);
+                if (birth_time > 0) nTimeBegin = std::min(nTimeBegin, birth_time);
                 scripts.push_back(std::pair<CScript, int64_t>(script, birth_time));
             }
         }
         file.close();
+        EnsureBlockDataFromTime(*pwallet, nTimeBegin);
         // We now know whether we are importing private keys, so we can error if private keys are disabled
         if (keys.size() > 0 && pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
             pwallet->chain().showProgress("", 100, false); // hide progress dialog in GUI
@@ -602,8 +614,6 @@ RPCHelpMan importwallet()
 
             if (has_label)
                 pwallet->SetAddressBook(PKHash(keyid), label, "receive");
-
-            nTimeBegin = std::min(nTimeBegin, time);
             progress++;
         }
         for (const auto& script_pair : scripts) {
@@ -616,9 +626,6 @@ RPCHelpMan importwallet()
                 fGood = false;
                 continue;
             }
-            if (time > 0) {
-                nTimeBegin = std::min(nTimeBegin, time);
-            }
 
             progress++;
         }