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When a client deletes a block, it will never again accept it as a valid block.

This commit is contained in:
Sebastian Messmer 2016-06-23 13:13:00 -07:00
parent 9c1a12c063
commit 577c697856
6 changed files with 61 additions and 17 deletions
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4
src/blockstore/implementations/versioncounting/KnownBlockVersions.cpp
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@ -175,5 +175,9 @@ uint32_t KnownBlockVersions::myClientId() const {
return _myClientId;
}
uint64_t KnownBlockVersions::getBlockVersion(uint32_t clientId, const Key &key) const {
return _knownVersions.at({clientId, key});
}
}
}

2
src/blockstore/implementations/versioncounting/KnownBlockVersions.h
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@ -25,6 +25,8 @@ namespace blockstore {
void updateVersion(const Key &key, uint64_t version);
uint64_t getBlockVersion(uint32_t clientId, const Key &key) const;
uint32_t myClientId() const;
private:

1
src/blockstore/implementations/versioncounting/VersionCountingBlock.cpp
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@ -7,5 +7,6 @@ namespace blockstore {
constexpr unsigned int VersionCountingBlock::HEADER_LENGTH;
constexpr uint16_t VersionCountingBlock::FORMAT_VERSION_HEADER;
constexpr uint64_t VersionCountingBlock::VERSION_ZERO;
constexpr uint64_t VersionCountingBlock::VERSION_DELETED;
}
}

49
src/blockstore/implementations/versioncounting/VersionCountingBlock.h
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@ -31,7 +31,7 @@ public:
static uint64_t blockSizeFromPhysicalBlockSize(uint64_t blockSize);
//TODO Storing key twice (in parent class and in object pointed to). Once would be enough.
VersionCountingBlock(cpputils::unique_ref<Block> baseBlock, cpputils::Data dataWithHeader, uint64_t version, KnownBlockVersions *knownBlockVersions);
VersionCountingBlock(cpputils::unique_ref<Block> baseBlock, cpputils::Data dataWithHeader, KnownBlockVersions *knownBlockVersions);
~VersionCountingBlock();
const void *data() const override;
@ -55,17 +55,18 @@ private:
static void _checkFormatHeader(const cpputils::Data &data);
static uint64_t _readVersion(const cpputils::Data &data);
static uint32_t _readClientId(const cpputils::Data &data);
static bool _versionIsNondecreasing(uint32_t clientId, const Key &key, uint64_t version, KnownBlockVersions *knownBlockVersions);
static bool _checkVersion(const cpputils::Data &data, const blockstore::Key &key, KnownBlockVersions *knownBlockVersions);
// This header is prepended to blocks to allow future versions to have compatibility.
static constexpr uint16_t FORMAT_VERSION_HEADER = 0;
static constexpr uint64_t VERSION_ZERO = 1; // lowest block version is '1', because that is required by class KnownBlockVersions.
std::mutex _mutex;
DISALLOW_COPY_AND_ASSIGN(VersionCountingBlock);
public:
static constexpr uint64_t VERSION_ZERO = 1; // lowest block version is '1', because that is required by class KnownBlockVersions.
static constexpr uint64_t VERSION_DELETED = std::numeric_limits<uint64_t>::max();
static constexpr unsigned int CLIENTID_HEADER_OFFSET = sizeof(FORMAT_VERSION_HEADER);
static constexpr unsigned int VERSION_HEADER_OFFSET = sizeof(FORMAT_VERSION_HEADER) + sizeof(uint32_t);
static constexpr unsigned int HEADER_LENGTH = sizeof(FORMAT_VERSION_HEADER) + sizeof(uint32_t) + sizeof(VERSION_ZERO);
@ -81,7 +82,7 @@ inline boost::optional<cpputils::unique_ref<VersionCountingBlock>> VersionCounti
}
knownBlockVersions->updateVersion(key, VERSION_ZERO);
return cpputils::make_unique_ref<VersionCountingBlock>(std::move(*baseBlock), std::move(dataWithHeader), VERSION_ZERO, knownBlockVersions);
return cpputils::make_unique_ref<VersionCountingBlock>(std::move(*baseBlock), std::move(dataWithHeader), knownBlockVersions);
}
inline cpputils::Data VersionCountingBlock::_prependHeaderToData(uint32_t myClientId, uint64_t version, cpputils::Data data) {
@ -98,14 +99,26 @@ inline boost::optional<cpputils::unique_ref<VersionCountingBlock>> VersionCounti
cpputils::Data data(baseBlock->size());
std::memcpy(data.data(), baseBlock->data(), data.size());
_checkFormatHeader(data);
uint32_t lastClientId = _readClientId(data);
uint64_t version = _readVersion(data);
if(!_versionIsNondecreasing(lastClientId, baseBlock->key(), version, knownBlockVersions)) {
//The stored key in the block data is incorrect - an attacker might have exchanged the contents with the encrypted data from a different block
cpputils::logging::LOG(cpputils::logging::WARN) << "Decrypting block " << baseBlock->key().ToString() << " failed due to wrong version number. Was the block rolled back by an attacker?";
if (!_checkVersion(data, baseBlock->key(), knownBlockVersions)) {
return boost::none;
}
return cpputils::make_unique_ref<VersionCountingBlock>(std::move(baseBlock), std::move(data), version, knownBlockVersions);
return cpputils::make_unique_ref<VersionCountingBlock>(std::move(baseBlock), std::move(data), knownBlockVersions);
}
inline bool VersionCountingBlock::_checkVersion(const cpputils::Data &data, const blockstore::Key &key, KnownBlockVersions *knownBlockVersions) {
uint32_t lastClientId = _readClientId(data);
uint64_t version = _readVersion(data);
if(!knownBlockVersions->checkAndUpdateVersion(lastClientId, key, version)) {
if (knownBlockVersions->getBlockVersion(lastClientId, key) == VERSION_DELETED) {
cpputils::logging::LOG(cpputils::logging::WARN) << "Decrypting block " << key.ToString() <<
" failed because it was marked as deleted. Was the block reintroduced by an attacker?";
} else {
cpputils::logging::LOG(cpputils::logging::WARN) << "Decrypting block " << key.ToString() <<
" failed due to decreasing version number. Was the block rolled back by an attacker?";
}
return false;
}
return true;
}
inline void VersionCountingBlock::_checkFormatHeader(const cpputils::Data &data) {
@ -126,18 +139,17 @@ inline uint64_t VersionCountingBlock::_readVersion(const cpputils::Data &data) {
return version;
}
inline bool VersionCountingBlock::_versionIsNondecreasing(uint32_t clientId, const Key &key, uint64_t version, KnownBlockVersions *knownBlockVersions) {
return knownBlockVersions->checkAndUpdateVersion(clientId, key, version);
}
inline VersionCountingBlock::VersionCountingBlock(cpputils::unique_ref<Block> baseBlock, cpputils::Data dataWithHeader, uint64_t version, KnownBlockVersions *knownBlockVersions)
inline VersionCountingBlock::VersionCountingBlock(cpputils::unique_ref<Block> baseBlock, cpputils::Data dataWithHeader, KnownBlockVersions *knownBlockVersions)
:Block(baseBlock->key()),
_knownBlockVersions(knownBlockVersions),
_baseBlock(std::move(baseBlock)),
_dataWithHeader(std::move(dataWithHeader)),
_version(version),
_version(_readVersion(_dataWithHeader)),
_dataChanged(false),
_mutex() {
if (_version == VERSION_DELETED) {
throw std::runtime_error("Loaded block is marked as deleted. This shouldn't happen because in case of a version number overflow, the block isn't stored at all.");
}
}
inline VersionCountingBlock::~VersionCountingBlock() {
@ -173,6 +185,11 @@ inline void VersionCountingBlock::resize(size_t newSize) {
inline void VersionCountingBlock::_storeToBaseBlock() {
if (_dataChanged) {
++_version;
if (_version == VERSION_DELETED) {
// It's *very* unlikely we ever run out of version numbers in 64bit...but just to be sure...
throw std::runtime_error("Version overflow");
static_assert(VERSION_DELETED == std::numeric_limits<uint64_t>::max(), "The check above assumes VERSION_DELETE to be an upper bound.");
}
uint32_t myClientId = _knownBlockVersions->myClientId();
std::memcpy(_dataWithHeader.dataOffset(CLIENTID_HEADER_OFFSET), &myClientId, sizeof(myClientId));
std::memcpy(_dataWithHeader.dataOffset(VERSION_HEADER_OFFSET), &_version, sizeof(_version));

4
src/blockstore/implementations/versioncounting/VersionCountingBlockStore.h
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@ -59,10 +59,12 @@ inline boost::optional<cpputils::unique_ref<Block>> VersionCountingBlockStore::l
}
inline void VersionCountingBlockStore::remove(cpputils::unique_ref<Block> block) {
Key key = block->key();
auto versionCountingBlock = cpputils::dynamic_pointer_move<VersionCountingBlock>(block);
ASSERT(versionCountingBlock != boost::none, "Block is not an VersionCountingBlock");
auto baseBlock = (*versionCountingBlock)->releaseBlock();
return _baseBlockStore->remove(std::move(baseBlock));
_baseBlockStore->remove(std::move(baseBlock));
_knownBlockVersions.updateVersion(key, VersionCountingBlock::VERSION_DELETED);
}
inline uint64_t VersionCountingBlockStore::numBlocks() const {

18
test/blockstore/implementations/versioncounting/VersionCountingBlockStoreTest_Specific.cpp
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@ -12,6 +12,7 @@ using cpputils::Data;
using cpputils::unique_ref;
using cpputils::make_unique_ref;
using cpputils::TempFile;
using boost::none;
using blockstore::testfake::FakeBlockStore;
@ -80,6 +81,14 @@ public:
baseBlock->write((char*)&clientId, VersionCountingBlock::CLIENTID_HEADER_OFFSET, sizeof(clientId));
}
void deleteBlock(const blockstore::Key &key) {
blockStore->remove(blockStore->load(key).value());
}
void insertBaseBlock(const blockstore::Key &key, Data data) {
EXPECT_NE(none, baseBlockStore->tryCreate(key, std::move(data)));
}
private:
DISALLOW_COPY_AND_ASSIGN(VersionCountingBlockStoreTest);
};
@ -127,6 +136,15 @@ TEST_F(VersionCountingBlockStoreTest, RollbackPrevention_DoesntAllowSameVersionN
EXPECT_EQ(boost::none, blockStore->load(key));
}
// Test that deleted blocks cannot be re-introduced
TEST_F(VersionCountingBlockStoreTest, RollbackPrevention_DoesntAllowReintroducingDeletedBlocks) {
auto key = CreateBlockReturnKey();
Data oldBaseBlock = loadBaseBlock(key);
deleteBlock(key);
insertBaseBlock(key, std::move(oldBaseBlock));
EXPECT_EQ(boost::none, blockStore->load(key));
}
TEST_F(VersionCountingBlockStoreTest, PhysicalBlockSize_zerophysical) {
EXPECT_EQ(0u, blockStore->blockSizeFromPhysicalBlockSize(0));
}