In case of an integrity violation, tell the user how they can reset integrity data.

src/blockstore/implementations/versioncounting/KnownBlockVersions.cpp

@@ -205,5 +205,9 @@ bool KnownBlockVersions::blockShouldExist(const Key &key) const {
     return found->second != CLIENT_ID_FOR_DELETED_BLOCK;
 }
 
+const bf::path &KnownBlockVersions::path() const {
+    return _stateFilePath;
+}
+
 }
 }

src/blockstore/implementations/versioncounting/KnownBlockVersions.h

@@ -32,6 +32,7 @@ namespace blockstore {
             uint64_t getBlockVersion(uint32_t clientId, const Key &key) const;
 
             uint32_t myClientId() const;
+            const boost::filesystem::path &path() const;
 
         private:
             std::unordered_map<ClientIdAndBlockKey, uint64_t> _knownVersions;

src/blockstore/implementations/versioncounting/VersionCountingBlockStore.cpp

@@ -43,7 +43,11 @@ namespace blockstore {
 
         void VersionCountingBlockStore::_checkNoPastIntegrityViolations() {
             if (_integrityViolationDetected) {
-                throw std::runtime_error("There was an integrity violation detected. Preventing any further access to the file system.");
+                throw std::runtime_error(string() +
+                                         "There was an integrity violation detected. Preventing any further access to the file system. " +
+                                         "If you want to reset the integrity data (i.e. accept changes made by a potential attacker), " +
+                                         "please unmount the file system and delete the following file before re-mounting it: " +
+                                         _knownBlockVersions.path().native());
             }
         }
 

test/blockstore/implementations/versioncounting/KnownBlockVersionsTest.cpp

@@ -335,3 +335,8 @@ TEST_F(KnownBlockVersionsTest, blockShouldExist_deletedBlock) {
     testobj.markBlockAsDeleted(key);
     EXPECT_FALSE(testobj.blockShouldExist(key));
 }
+
+TEST_F(KnownBlockVersionsTest, path) {
+    KnownBlockVersions obj(stateFile.path());
+    EXPECT_EQ(stateFile.path(), obj.path());
+}