From fd79ed6b202ec872aa794ba6a23d4dfc373a98f1 Mon Sep 17 00:00:00 2001
From: Tomas van der Wansem <tomas@tomasvdw.nl>
Date: Thu, 21 Sep 2017 00:10:46 +0200
Subject: Ensure backupwallet fails when attempting to backup to source file

Previous behaviour was to destroy the wallet (to zero-length)

Github-Pull: #11376
Rebased-From: 5d465e396249a0e2cc60b16984a2bdbe4c8993c3
---
 src/wallet/db.cpp               |  5 +++++
 src/wallet/db.h                 |  2 +-
 test/functional/walletbackup.py | 10 ++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index d2fe4866fa..8c23d9c072 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -673,6 +673,11 @@ bool CWalletDBWrapper::Backup(const std::string& strDest)
                     pathDest /= strFile;
 
                 try {
+                    if (fs::equivalent(pathSrc, pathDest)) {
+                        LogPrintf("cannot backup to wallet source file %s\n", pathDest.string());
+                        return false;
+                    }
+
                     fs::copy_file(pathSrc, pathDest, fs::copy_option::overwrite_if_exists);
                     LogPrintf("copied %s to %s\n", strFile, pathDest.string());
                     return true;
diff --git a/src/wallet/db.h b/src/wallet/db.h
index 3614e34fbb..6f3cfe9557 100644
--- a/src/wallet/db.h
+++ b/src/wallet/db.h
@@ -45,7 +45,7 @@ public:
     void Reset();
 
     void MakeMock();
-    bool IsMock() { return fMockDb; }
+    bool IsMock() const { return fMockDb; }
 
     /**
      * Verify that database file strFile is OK. If it is not,
diff --git a/test/functional/walletbackup.py b/test/functional/walletbackup.py
index 15ea26afa1..85a149793e 100755
--- a/test/functional/walletbackup.py
+++ b/test/functional/walletbackup.py
@@ -190,6 +190,16 @@ class WalletBackupTest(BitcoinTestFramework):
         assert_equal(self.nodes[1].getbalance(), balance1)
         assert_equal(self.nodes[2].getbalance(), balance2)
 
+        # Backup to source wallet file must fail
+        sourcePaths = [
+            tmpdir + "/node0/regtest/wallet.dat",
+            tmpdir + "/node0/./regtest/wallet.dat",
+            tmpdir + "/node0/regtest/",
+            tmpdir + "/node0/regtest"]
+
+        for sourcePath in sourcePaths:
+            assert_raises_rpc_error(-4, "backup failed", self.nodes[0].backupwallet, sourcePath)
+
 
 if __name__ == '__main__':
     WalletBackupTest().main()
-- 
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