- Run test cases for EncryptedBlockStore with different ciphers

- Implement FakeAuthenticatedCipher for use with specific EncryptedBlockStoreTest
- Write skeleton for specific EncryptedBlockStoreTest
- Fix behavior of AES256_CFB when called with too small input
- Add testcase that all ciphers (also non-authenticating ones) have to handle too small input correctly

implementations/encrypted/ciphers/AES256_CFB.cpp

@@ -21,6 +21,10 @@ Data AES256_CFB::encrypt(const byte *plaintext, unsigned int plaintextSize, cons
 }
 
 boost::optional<Data> AES256_CFB::decrypt(const byte *ciphertext, unsigned int ciphertextSize, const EncryptionKey &encKey) {
+  if (ciphertextSize < IV_SIZE) {
+    return boost::none;
+  }
+
   const byte *ciphertextIV = ciphertext;
   const byte *ciphertextData = ciphertext + IV_SIZE;
   auto decryption = CFB_Mode<AES>::Decryption((byte*)encKey.data(), encKey.BINARY_LENGTH, ciphertextIV);

implementations/encrypted/ciphers/Cipher.h

@@ -4,6 +4,7 @@
 
 #include <boost/concept_check.hpp>
 #include <cstdint>
+#include <messmer/cpp-utils/data/Data.h>
 
 namespace blockstore {
 namespace encrypted {
@@ -15,8 +16,8 @@ public:
     same_type(UINT32_C(0), X::ciphertextSize(UINT32_C(5)));
     same_type(UINT32_C(0), X::plaintextSize(UINT32_C(5)));
     typename X::EncryptionKey key = X::EncryptionKey::CreateRandom();
-    same_type(cpputils::Data(0), X::encrypt((byte*)nullptr, UINT32_C(0), key));
-    same_type(boost::optional<cpputils::Data>(cpputils::Data(0)), X::decrypt((byte*)nullptr, UINT32_C(0), key));
+    same_type(cpputils::Data(0), X::encrypt((uint8_t*)nullptr, UINT32_C(0), key));
+    same_type(boost::optional<cpputils::Data>(cpputils::Data(0)), X::decrypt((uint8_t*)nullptr, UINT32_C(0), key));
   }
 
 private:

test/implementations/encrypted/CipherTest.cpp

@@ -1,7 +1,8 @@
 #include <google/gtest/gtest.h>
+#include "../../../implementations/encrypted/ciphers/Cipher.h"
 #include "../../../implementations/encrypted/ciphers/AES256_CFB.h"
 #include "../../../implementations/encrypted/ciphers/AES256_GCM.h"
-#include "../../../implementations/encrypted/ciphers/Cipher.h"
+#include "testutils/FakeAuthenticatedCipher.h"
 
 #include <messmer/cpp-utils/data/DataFixture.h>
 #include <messmer/cpp-utils/data/Data.h>
@@ -16,9 +17,9 @@ template<class Cipher>
 class CipherTest: public ::testing::Test {
 public:
   BOOST_CONCEPT_ASSERT((CipherConcept<Cipher>));
-  typename Cipher::EncryptionKey encKey = createRandomKey();
+  typename Cipher::EncryptionKey encKey = createKeyFixture();
 
-  static typename Cipher::EncryptionKey createRandomKey(int seed = 0) {
+  static typename Cipher::EncryptionKey createKeyFixture(int seed = 0) {
     Data data = DataFixture::generate(Cipher::EncryptionKey::BINARY_LENGTH, seed);
     return Cipher::EncryptionKey::FromBinary(data.data());
   }
@@ -40,6 +41,11 @@ public:
     EXPECT_EQ(Cipher::ciphertextSize(plaintext.size()), ciphertext.size());
   }
 
+  void ExpectDoesntDecrypt(const Data &ciphertext) {
+    auto decrypted = Cipher::decrypt((byte*)ciphertext.data(), ciphertext.size(), this->encKey);
+    EXPECT_FALSE(decrypted);
+  }
+
   Data Encrypt(const Data &plaintext) {
     return Cipher::encrypt((byte*)plaintext.data(), plaintext.size(), this->encKey);
   }
@@ -103,23 +109,38 @@ TYPED_TEST_P(CipherTest, EncryptedSize) {
   }
 }
 
+TYPED_TEST_P(CipherTest, TryDecryptDataThatIsTooSmall) {
+  Data tooSmallCiphertext(TypeParam::ciphertextSize(0) - 1);
+  this->ExpectDoesntDecrypt(tooSmallCiphertext);
+}
+
+TYPED_TEST_P(CipherTest, TryDecryptDataThatIsMuchTooSmall_0) {
+  static_assert(TypeParam::ciphertextSize(0) > 0, "If this fails, the test case doesn't make sense.");
+  Data tooSmallCiphertext(0);
+  this->ExpectDoesntDecrypt(tooSmallCiphertext);
+}
+
+TYPED_TEST_P(CipherTest, TryDecryptDataThatIsMuchTooSmall_1) {
+  static_assert(TypeParam::ciphertextSize(0) > 1, "If this fails, the test case doesn't make sense.");
+  Data tooSmallCiphertext(1);
+  this->ExpectDoesntDecrypt(tooSmallCiphertext);
+}
+
 REGISTER_TYPED_TEST_CASE_P(CipherTest,
     Size,
     EncryptThenDecrypt_Zeroes,
     EncryptThenDecrypt_Data,
     EncryptIsIndeterministic_Zeroes,
     EncryptIsIndeterministic_Data,
-    EncryptedSize
+    EncryptedSize,
+    TryDecryptDataThatIsTooSmall,
+    TryDecryptDataThatIsMuchTooSmall_0,
+    TryDecryptDataThatIsMuchTooSmall_1
 );
 
 template<class Cipher>
 class AuthenticatedCipherTest: public CipherTest<Cipher> {
 public:
-  void ExpectDoesntDecrypt(const Data &ciphertext) {
-    auto decrypted = Cipher::decrypt((byte*)ciphertext.data(), ciphertext.size(), this->encKey);
-    EXPECT_FALSE(decrypted);
-  }
-
   Data zeroes1 = CipherTest<Cipher>::CreateZeroes(1);
   Data plaintext1 = CipherTest<Cipher>::CreateData(1);
   Data zeroes2 = CipherTest<Cipher>::CreateZeroes(100 * 1024);
@@ -184,23 +205,6 @@ TYPED_TEST_P(AuthenticatedCipherTest, TryDecryptRandomData) {
   this->ExpectDoesntDecrypt(this->plaintext2);
 }
 
-TYPED_TEST_P(AuthenticatedCipherTest, TryDecryptDataThatIsTooSmall) {
-  Data tooSmallCiphertext(TypeParam::ciphertextSize(0) - 1);
-  this->ExpectDoesntDecrypt(tooSmallCiphertext);
-}
-
-TYPED_TEST_P(AuthenticatedCipherTest, TryDecryptDataThatIsMuchTooSmall_0) {
-  static_assert(TypeParam::ciphertextSize(0) > 0, "If this fails, the test case doesn't make sense.");
-  Data tooSmallCiphertext(0);
-  this->ExpectDoesntDecrypt(tooSmallCiphertext);
-}
-
-TYPED_TEST_P(AuthenticatedCipherTest, TryDecryptDataThatIsMuchTooSmall_1) {
-  static_assert(TypeParam::ciphertextSize(0) > 1, "If this fails, the test case doesn't make sense.");
-  Data tooSmallCiphertext(1);
-  this->ExpectDoesntDecrypt(tooSmallCiphertext);
-}
-
 REGISTER_TYPED_TEST_CASE_P(AuthenticatedCipherTest,
   ModifyFirstByte_Zeroes_Size1,
   ModifyFirstByte_Zeroes,
@@ -211,13 +215,12 @@ REGISTER_TYPED_TEST_CASE_P(AuthenticatedCipherTest,
   ModifyMiddleByte_Zeroes,
   ModifyMiddleByte_Data,
   TryDecryptZeroesData,
-  TryDecryptRandomData,
-  TryDecryptDataThatIsTooSmall,
-  TryDecryptDataThatIsMuchTooSmall_0,
-  TryDecryptDataThatIsMuchTooSmall_1
+  TryDecryptRandomData
 );
 
 
-INSTANTIATE_TYPED_TEST_CASE_P(AES256_CFB, CipherTest, AES256_CFB);
+INSTANTIATE_TYPED_TEST_CASE_P(Fake, CipherTest, FakeAuthenticatedCipher);
+INSTANTIATE_TYPED_TEST_CASE_P(Fake, AuthenticatedCipherTest, FakeAuthenticatedCipher);
+INSTANTIATE_TYPED_TEST_CASE_P(AES256_CFB, CipherTest, AES256_CFB); //CFB mode is not authenticated
 INSTANTIATE_TYPED_TEST_CASE_P(AES256_GCM, CipherTest, AES256_GCM);
 INSTANTIATE_TYPED_TEST_CASE_P(AES256_GCM, AuthenticatedCipherTest, AES256_GCM);

test/implementations/encrypted/EncryptedBlockStoreTest.cpp

@@ -1,28 +0,0 @@
-#include "../../../implementations/encrypted/ciphers/AES256_GCM.h"
-#include "../../../implementations/encrypted/EncryptedBlockStore.h"
-#include "../../../implementations/testfake/FakeBlockStore.h"
-#include "../../testutils/BlockStoreTest.h"
-#include "google/gtest/gtest.h"
-
-
-using blockstore::BlockStore;
-using blockstore::encrypted::EncryptedBlockStore;
-using blockstore::testfake::FakeBlockStore;
-using blockstore::encrypted::AES256_GCM;
-
-using std::unique_ptr;
-using std::make_unique;
-
-class EncryptedBlockStoreTestFixture: public BlockStoreTestFixture {
-public:
-  unique_ptr<BlockStore> createBlockStore() override {
-    return make_unique<EncryptedBlockStore<AES256_GCM>>(make_unique<FakeBlockStore>(), AES256_GCM::EncryptionKey::FromString("1491BB4932A389EE14BC7090A272EE5517627CFA147A971A8E6E747E0C772972"));
-  }
-};
-
-INSTANTIATE_TYPED_TEST_CASE_P(Encrypted, BlockStoreTest, EncryptedBlockStoreTestFixture);
-
-//TODO Add specific tests, for example
-// - loading it with a different encKey doesn't work
-// - loading it with a different blockstore::Key will fail (because it stores its key in a header)
-// - when using an authenticated cipher, loading a modified block will fail

test/implementations/encrypted/EncryptedBlockStoreTest_Generic.cpp

@@ -0,0 +1,40 @@
+#include "../../../implementations/encrypted/ciphers/AES256_GCM.h"
+#include "../../../implementations/encrypted/ciphers/AES256_CFB.h"
+#include "../../../implementations/encrypted/ciphers/Cipher.h"
+#include "../../../implementations/encrypted/EncryptedBlockStore.h"
+#include "../../../implementations/testfake/FakeBlockStore.h"
+#include "../../testutils/BlockStoreTest.h"
+#include "testutils/FakeAuthenticatedCipher.h"
+#include "google/gtest/gtest.h"
+
+using ::testing::Test;
+
+using blockstore::BlockStore;
+using blockstore::encrypted::EncryptedBlockStore;
+using blockstore::testfake::FakeBlockStore;
+using blockstore::encrypted::AES256_GCM;
+using blockstore::encrypted::AES256_CFB;
+
+using std::unique_ptr;
+using std::make_unique;
+
+using cpputils::Data;
+using cpputils::DataFixture;
+
+template<class Cipher>
+class EncryptedBlockStoreTestFixture: public BlockStoreTestFixture {
+public:
+  unique_ptr<BlockStore> createBlockStore() override {
+    return make_unique<EncryptedBlockStore<Cipher>>(make_unique<FakeBlockStore>(), createKeyFixture());
+  }
+
+private:
+  static typename Cipher::EncryptionKey createKeyFixture(int seed = 0) {
+    Data data = DataFixture::generate(Cipher::EncryptionKey::BINARY_LENGTH, seed);
+    return Cipher::EncryptionKey::FromBinary(data.data());
+  }
+};
+
+INSTANTIATE_TYPED_TEST_CASE_P(Encrypted_FakeCipher, BlockStoreTest, EncryptedBlockStoreTestFixture<FakeAuthenticatedCipher>);
+INSTANTIATE_TYPED_TEST_CASE_P(Encrypted_AES256_GCM, BlockStoreTest, EncryptedBlockStoreTestFixture<AES256_GCM>);
+INSTANTIATE_TYPED_TEST_CASE_P(Encrypted_AES256_CFB, BlockStoreTest, EncryptedBlockStoreTestFixture<AES256_CFB>);

test/implementations/encrypted/EncryptedBlockStoreTest_Specific.cpp

@@ -0,0 +1,35 @@
+#include <google/gtest/gtest.h>
+#include "testutils/FakeAuthenticatedCipher.h"
+#include "../../../implementations/encrypted/EncryptedBlockStore.h"
+#include "../../../implementations/testfake/FakeBlockStore.h"
+
+using ::testing::Test;
+
+using std::unique_ptr;
+using std::make_unique;
+
+using blockstore::testfake::FakeBlockStore;
+
+using namespace blockstore::encrypted;
+
+class EncryptedBlockStoreTest: public Test {
+public:
+  EncryptedBlockStoreTest(): blockStore(make_unique<EncryptedBlockStore<FakeAuthenticatedCipher>>(make_unique<FakeBlockStore>(), FakeAuthenticatedCipher::Key1())) {}
+  unique_ptr<EncryptedBlockStore<FakeAuthenticatedCipher>> blockStore;
+};
+
+TEST_F(EncryptedBlockStoreTest, LoadingWithSameKeyWorks) {
+  //TODO implement
+}
+
+TEST_F(EncryptedBlockStoreTest, LoadingWithDifferentKeyDoesntWork) {
+  //TODO Implement
+}
+
+TEST_F(EncryptedBlockStoreTest, LoadingModifiedBlockFails) {
+  //TODO Implement
+}
+
+TEST_F(EncryptedBlockStoreTest, LoadingWithDifferentBlockIdFails) {
+  //TODO loading it with a different blockstore::Key will fail (because it stores its key in a header)
+}

test/implementations/encrypted/testutils/FakeAuthenticatedCipher.cpp

@@ -0,0 +1,3 @@
+#include "FakeAuthenticatedCipher.h"
+
+constexpr unsigned int FakeKey::BINARY_LENGTH;

test/implementations/encrypted/testutils/FakeAuthenticatedCipher.h

@@ -0,0 +1,102 @@
+#pragma once
+#ifndef MESSMER_BLOCKSTORE_TEST_IMPLEMENTATIONS_ENCRYPTED_TESTUTILS_FAKEAUTHENTICATEDCIPHER_H_
+#define MESSMER_BLOCKSTORE_TEST_IMPLEMENTATIONS_ENCRYPTED_TESTUTILS_FAKEAUTHENTICATEDCIPHER_H_
+
+#include "../../../../implementations/encrypted/ciphers/Cipher.h"
+#include <messmer/cpp-utils/data/FixedSizeData.h>
+
+struct FakeKey {
+  FakeKey(uint8_t value_):value(value_) {}
+  static FakeKey CreateRandom() {
+    return FakeKey(rand());
+  }
+  static FakeKey FromBinary(const void *data) {
+    return FakeKey(*(uint8_t*)data);
+  }
+  static constexpr unsigned int BINARY_LENGTH = 1;
+
+  uint8_t value;
+};
+
+// This is a fake cipher that uses an indeterministic caesar chiffre and a 4-byte parity for a simple authentication mechanism
+class FakeAuthenticatedCipher {
+public:
+  BOOST_CONCEPT_ASSERT((blockstore::encrypted::CipherConcept<FakeAuthenticatedCipher>));
+
+  using EncryptionKey = FakeKey;
+
+  static EncryptionKey Key1() {
+    return FakeKey(5);
+  }
+  static EncryptionKey Key2() {
+    return FakeKey(63);
+  }
+
+  static constexpr unsigned int ciphertextSize(unsigned int plaintextBlockSize) {
+    return plaintextBlockSize + 5;
+  }
+
+  static constexpr unsigned int plaintextSize(unsigned int ciphertextBlockSize) {
+    return ciphertextBlockSize - 5;
+  }
+
+  static cpputils::Data encrypt(const byte *plaintext, unsigned int plaintextSize, const EncryptionKey &encKey) {
+    cpputils::Data result(ciphertextSize(plaintextSize));
+
+    //Add a random IV
+    uint8_t iv = rand();
+    std::memcpy(result.data(), &iv, 1);
+
+    //Use caesar chiffre on plaintext
+    _caesar((byte*)result.data() + 1, plaintext, plaintextSize, encKey.value + iv);
+
+    //Add parity information
+    int32_t parity = _parity((byte*)result.data(), plaintextSize + 1);
+    std::memcpy((byte*)result.data() + plaintextSize + 1, &parity, 4);
+
+    return result;
+  }
+
+  static boost::optional<cpputils::Data> decrypt(const byte *ciphertext, unsigned int ciphertextSize, const EncryptionKey &encKey) {
+    //We need at least 5 bytes (iv + parity)
+    if (ciphertextSize < 5) {
+      return boost::none;
+    }
+
+    //Check parity
+    int32_t expectedParity = _parity(ciphertext, plaintextSize(ciphertextSize) + 1);
+    int32_t actualParity = *(int32_t*)(ciphertext + plaintextSize(ciphertextSize) + 1);
+    if (expectedParity != actualParity) {
+      return boost::none;
+    }
+
+    //Decrypt caesar chiffre from ciphertext
+    int32_t iv = *(int32_t*)ciphertext;
+    cpputils::Data result(plaintextSize(ciphertextSize));
+    _caesar((byte*)result.data(), ciphertext + 1, plaintextSize(ciphertextSize), -(encKey.value+iv));
+    return std::move(result);
+  }
+
+private:
+  static int32_t _parity(const byte *data, unsigned int size) {
+    int32_t parity = 34343435; // some init value
+    int32_t *intData = (int32_t*)data;
+    unsigned int intSize = size / sizeof(int32_t);
+    for (unsigned int i = 0; i < intSize; ++i) {
+      parity += intData[i];
+    }
+    unsigned int remainingBytes = size - 4 * intSize;
+    for (unsigned int i = 0; i < remainingBytes; ++i) {
+      parity += (data[4*intSize + i] << (24 - 8*i));
+    }
+    return parity;
+  }
+
+  static void _caesar(byte *dst, const byte *src, unsigned int size, uint8_t key) {
+    for (int i = 0; i < size; ++i) {
+      dst[i] = src[i] + key;
+    }
+  }
+};
+
+#endif