From 4d2d6045a4784d576d56299244b9f76a5909904b Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Mon, 15 May 2017 09:11:03 -0400
Subject: Fix importmulti failure to return rescan errors

An off-by-one-block bug in importmulti rescan logic could cause it to return
success in an edge case even when a rescan was not successful. The case where
this would happen is if there were multiple blocks in a row with the same
GetBlockTimeMax() value, and the last block was scanned successfully, but one
or more of the earlier blocks was not readable.
---
 src/wallet/rpcdump.cpp | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

(limited to 'src/wallet/rpcdump.cpp')

diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 82708dab26..37cdaf121e 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -1121,13 +1121,13 @@ UniValue importmulti(const JSONRPCRequest& mainRequest)
 
     if (fRescan && fRunScan && requests.size()) {
         CBlockIndex* pindex = nLowestTimestamp > minimumTimestamp ? chainActive.FindEarliestAtLeast(std::max<int64_t>(nLowestTimestamp - TIMESTAMP_WINDOW, 0)) : chainActive.Genesis();
-        CBlockIndex* scannedRange = nullptr;
+        CBlockIndex* scanFailed = nullptr;
         if (pindex) {
-            scannedRange = pwallet->ScanForWalletTransactions(pindex, true);
+            scanFailed = pwallet->ScanForWalletTransactions(pindex, true);
             pwallet->ReacceptWalletTransactions();
         }
 
-        if (!scannedRange || scannedRange->nHeight > pindex->nHeight) {
+        if (scanFailed) {
             std::vector<UniValue> results = response.getValues();
             response.clear();
             response.setArray();
@@ -1137,12 +1137,23 @@ UniValue importmulti(const JSONRPCRequest& mainRequest)
                 // range, or if the import result already has an error set, let
                 // the result stand unmodified. Otherwise replace the result
                 // with an error message.
-                if (GetImportTimestamp(request, now) - TIMESTAMP_WINDOW >= scannedRange->GetBlockTimeMax() || results.at(i).exists("error")) {
+                if (GetImportTimestamp(request, now) - TIMESTAMP_WINDOW > scanFailed->GetBlockTimeMax() || results.at(i).exists("error")) {
                     response.push_back(results.at(i));
                 } else {
                     UniValue result = UniValue(UniValue::VOBJ);
                     result.pushKV("success", UniValue(false));
-                    result.pushKV("error", JSONRPCError(RPC_MISC_ERROR, strprintf("Failed to rescan before time %d, transactions may be missing.", scannedRange->GetBlockTimeMax())));
+                    result.pushKV(
+                        "error",
+                        JSONRPCError(
+                            RPC_MISC_ERROR,
+                            strprintf("Rescan failed for key with creation timestamp %d. There was an error reading a "
+                                      "block from time %d, which is after or within %d seconds of key creation, and "
+                                      "could contain transactions pertaining to the key. As a result, transactions "
+                                      "and coins using this key may not appear in the wallet. This error could be "
+                                      "caused by pruning or data corruption (see bitcoind log for details) and could "
+                                      "be dealt with by downloading and rescanning the relevant blocks (see -reindex "
+                                      "and -rescan options).",
+                                GetImportTimestamp(request, now), scanFailed->GetBlockTimeMax(), TIMESTAMP_WINDOW)));
                     response.push_back(std::move(result));
                 }
                 ++i;
-- 
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