From 491b277ceedc1b9d60a7b7fdf021160d4af3cd6b Mon Sep 17 00:00:00 2001
From: Sebastian Messmer <messmer@cryfs.org>
Date: Sat, 25 Jun 2016 16:16:26 -0700
Subject: [PATCH] In case of an integrity violation, tell the user how they can
 reset integrity data.

---
 .../implementations/versioncounting/KnownBlockVersions.cpp  | 4 ++++
 .../implementations/versioncounting/KnownBlockVersions.h    | 1 +
 .../versioncounting/VersionCountingBlockStore.cpp           | 6 +++++-
 .../versioncounting/KnownBlockVersionsTest.cpp              | 5 +++++
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/blockstore/implementations/versioncounting/KnownBlockVersions.cpp b/src/blockstore/implementations/versioncounting/KnownBlockVersions.cpp
index 5f62e021..0f5a5e89 100644
--- a/src/blockstore/implementations/versioncounting/KnownBlockVersions.cpp
+++ b/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;
+}
+
 }
 }
diff --git a/src/blockstore/implementations/versioncounting/KnownBlockVersions.h b/src/blockstore/implementations/versioncounting/KnownBlockVersions.h
index b3edbbf2..4cc2243f 100644
--- a/src/blockstore/implementations/versioncounting/KnownBlockVersions.h
+++ b/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;
diff --git a/src/blockstore/implementations/versioncounting/VersionCountingBlockStore.cpp b/src/blockstore/implementations/versioncounting/VersionCountingBlockStore.cpp
index f73889f9..5dac818d 100644
--- a/src/blockstore/implementations/versioncounting/VersionCountingBlockStore.cpp
+++ b/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());
             }
         }
 
diff --git a/test/blockstore/implementations/versioncounting/KnownBlockVersionsTest.cpp b/test/blockstore/implementations/versioncounting/KnownBlockVersionsTest.cpp
index 877a125d..6c7ce192 100644
--- a/test/blockstore/implementations/versioncounting/KnownBlockVersionsTest.cpp
+++ b/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());
+}
\ No newline at end of file