src/lib/util/encrypted_message_util_test.cc

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/lib/util/encrypted_message_util.h"

#include <string>
#include <utility>

#include <gtest/gtest.h>

#include "src/pb/encrypted_message.pb.h"
#include "src/pb/envelope.pb.h"
#include "src/pb/key.pb.h"
#include "src/pb/observation.pb.h"
#include "third_party/tink/cc/cleartext_keyset_handle.h"
#include "third_party/tink/cc/hybrid_config.h"
#include "third_party/tink/cc/hybrid_decrypt_factory.h"
#include "third_party/tink/cc/hybrid_encrypt_factory.h"
#include "third_party/tink/cc/hybrid_key_templates.h"
#include "third_party/tink/cc/keyset_handle.h"
#include "third_party/tink/proto/tink.pb.h"

namespace cobalt::util {

constexpr char kShufflerContextInfo[] = "cobalt-1.0-shuffler";
constexpr char kAnalyzerContextInfo[] = "cobalt-1.0-analyzer";

std::string MakeCobaltEncryptionKeyBytes(const std::string& key_bytes, uint32_t key_index,
                                         CobaltEncryptionKey::KeyPurpose purpose) {
  CobaltEncryptionKey key;
  key.set_serialized_key(key_bytes);
  key.set_key_index(key_index);
  key.set_purpose(purpose);
  std::string cobalt_key_bytes;
  EXPECT_TRUE(key.SerializeToString(&cobalt_key_bytes));
  return cobalt_key_bytes;
}

// Tests the use of the no-encryption option.
TEST(EncryptedMessageUtilTest, NoEncryption) {
  // Make a dummy observation.
  std::string obs_id = "obs_id";
  Observation observation;
  observation.set_random_id(obs_id);

  // Make an EncryptedMessageMaker that outputs plaintext for testing purposes.
  util::PinnedUniquePtr<EncryptedMessageMaker> maker(EncryptedMessageMaker::MakeUnencrypted());
  // Encrypt the dummy observation.
  EncryptedMessage encrypted_message;
  EXPECT_TRUE(maker->Encrypt(observation, &encrypted_message));

  // Decrypt and check.
  observation.Clear();
  EXPECT_TRUE(observation.random_id().empty());
  EXPECT_TRUE(observation.ParseFromString(encrypted_message.ciphertext()));
  EXPECT_EQ(obs_id, observation.random_id());
}

class EncryptedMessageMakerTest : public ::testing::Test {
 public:
  // Get a serialized Keyset proto for a public key.
  [[nodiscard]] std::string GetPublicKeysetBytes() const {
    // Get the keyset protobuf message itself.
    const google::crypto::tink::Keyset public_keyset =
        ::crypto::tink::CleartextKeysetHandle::GetKeyset(*GetPublicKeysetHandle());
    EXPECT_EQ(1, public_keyset.key_size());

    // Serialize and encode the public keyset.
    std::string public_keyset_bytes;
    EXPECT_TRUE(public_keyset.SerializeToString(&public_keyset_bytes));
    return public_keyset_bytes;
  }

  // Decrypt the specified ciphertext.
  std::string Decrypt(const std::string& ciphertext, const std::string& context_info) {
    // Obtain a decrypter to be able to check the encrypted dummy observation.
    auto decrypter_result = keyset_handle_->GetPrimitive<::crypto::tink::HybridDecrypt>();
    EXPECT_TRUE(decrypter_result.ok());
    auto decrypter = std::move(decrypter_result.ValueOrDie());
    auto decrypted_result = decrypter->Decrypt(ciphertext, context_info);
    EXPECT_TRUE(decrypted_result.ok());
    return decrypted_result.ValueOrDie();
  }

 protected:
  void SetUp() override {
    auto status = ::crypto::tink::HybridConfig::Register();
    EXPECT_TRUE(status.ok());

    // Create a new key pair for testing.
    auto keyset_handle_result = ::crypto::tink::KeysetHandle::GenerateNew(
        ::crypto::tink::HybridKeyTemplates::EciesP256HkdfHmacSha256Aes128Gcm());
    EXPECT_TRUE(keyset_handle_result.ok());
    keyset_handle_ = std::move(keyset_handle_result.ValueOrDie());
  }

 private:
  [[nodiscard]] std::unique_ptr<::crypto::tink::KeysetHandle> GetPublicKeysetHandle() const {
    auto public_keyset_handle_result = keyset_handle_->GetPublicKeysetHandle();
    EXPECT_TRUE(public_keyset_handle_result.ok());
    return std::move(public_keyset_handle_result.ValueOrDie());
  }

  std::unique_ptr<::crypto::tink::KeysetHandle> keyset_handle_;
};

// Try to roundtrip an observation through a message encrypter.
TEST_F(EncryptedMessageMakerTest, EncryptObservation) {
  uint32_t key_index = 1;
  auto key_bytes = MakeCobaltEncryptionKeyBytes(GetPublicKeysetBytes(), key_index,
                                                CobaltEncryptionKey::ANALYZER);
  auto encrypted_message_maker_or_status = EncryptedMessageMaker::MakeForObservations(key_bytes);
  EXPECT_TRUE(encrypted_message_maker_or_status.ok());
  util::PinnedUniquePtr<EncryptedMessageMaker> maker(
      std::move(encrypted_message_maker_or_status).value());

  // Build an observation.
  std::string obs_id = "obs_id";
  Observation observation;
  observation.set_random_id(obs_id);

  // Encrypt the observation.
  EncryptedMessage encrypted_message;
  EXPECT_TRUE(maker->Encrypt(observation, &encrypted_message));

  EXPECT_EQ(key_index, encrypted_message.key_index());

  // Decrypt the observation.
  std::string decrypted = Decrypt(encrypted_message.ciphertext(), kAnalyzerContextInfo);
  observation.Clear();

  // Check that the observation was correctly round-tripped.
  EXPECT_TRUE(observation.random_id().empty());
  EXPECT_TRUE(observation.ParseFromString(decrypted));
  EXPECT_EQ(obs_id, observation.random_id());
}

// Try to roundtrip an envelope through a message encrypter.
TEST_F(EncryptedMessageMakerTest, EncryptEnvelope) {
  uint32_t key_index = 1;
  auto key_bytes = MakeCobaltEncryptionKeyBytes(GetPublicKeysetBytes(), key_index,
                                                CobaltEncryptionKey::SHUFFLER);
  auto encrypted_message_maker_or_status = EncryptedMessageMaker::MakeForEnvelopes(key_bytes);
  EXPECT_TRUE(encrypted_message_maker_or_status.ok());
  util::PinnedUniquePtr<EncryptedMessageMaker> maker(
      std::move(encrypted_message_maker_or_status).value());

  // Build an envelope proto.
  uint32_t metric_id = 25;
  Envelope envelope;
  envelope.add_batch()->mutable_meta_data()->set_metric_id(metric_id);

  // Encrypt the envelope.
  EncryptedMessage encrypted_message;
  EXPECT_TRUE(maker->Encrypt(envelope, &encrypted_message));
  EXPECT_EQ(key_index, encrypted_message.key_index());

  // Decrypt the envelope.
  std::string decrypted = Decrypt(encrypted_message.ciphertext(), kShufflerContextInfo);
  envelope.Clear();
  EXPECT_EQ(0, envelope.batch_size());
  EXPECT_TRUE(envelope.ParseFromString(decrypted));

  // Check to see that the envelope rountripped correctly.
  EXPECT_EQ(1, envelope.batch_size());
  EXPECT_EQ(metric_id, envelope.batch(0).meta_data().metric_id());
}

// Expect an error if the key_index field is set to 0 or unset.
TEST_F(EncryptedMessageMakerTest, ZeroKeyIndex) {
  auto key_bytes =
      MakeCobaltEncryptionKeyBytes(GetPublicKeysetBytes(), 0, CobaltEncryptionKey::SHUFFLER);
  auto result = EncryptedMessageMaker::MakeForEnvelopes(key_bytes);
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());

  key_bytes =
      MakeCobaltEncryptionKeyBytes(GetPublicKeysetBytes(), 0, CobaltEncryptionKey::ANALYZER);
  result = EncryptedMessageMaker::MakeForObservations(key_bytes);
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());
}

// Expect an error if the purpose field is unset.
TEST_F(EncryptedMessageMakerTest, PurposeUnset) {
  auto key_bytes =
      MakeCobaltEncryptionKeyBytes(GetPublicKeysetBytes(), 1, CobaltEncryptionKey::UNSET);
  auto result = EncryptedMessageMaker::MakeForEnvelopes(key_bytes);
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());

  key_bytes = MakeCobaltEncryptionKeyBytes(GetPublicKeysetBytes(), 1, CobaltEncryptionKey::UNSET);
  result = EncryptedMessageMaker::MakeForObservations(key_bytes);
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());
}

// Expect an error if trying to use an analyzer key to encrypt envelopes or
// trying to use a shuffler key to encrypt observations.
TEST_F(EncryptedMessageMakerTest, WrongPurpose) {
  auto key_bytes =
      MakeCobaltEncryptionKeyBytes(GetPublicKeysetBytes(), 1, CobaltEncryptionKey::ANALYZER);
  auto result = EncryptedMessageMaker::MakeForEnvelopes(key_bytes);
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());

  key_bytes =
      MakeCobaltEncryptionKeyBytes(GetPublicKeysetBytes(), 1, CobaltEncryptionKey::SHUFFLER);
  result = EncryptedMessageMaker::MakeForObservations(key_bytes);
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());
}

// Expect an error if the string purported to be a serialized
// CobaltEncryptionKey is actually not.
TEST_F(EncryptedMessageMakerTest, NotASerializedCobaltEncryptionKey) {
  auto result = EncryptedMessageMaker::MakeForEnvelopes("hello");
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());

  result = EncryptedMessageMaker::MakeForObservations("hello");
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());
}

// Expect an error if the serialized key is invalid.
TEST_F(EncryptedMessageMakerTest, NotRealSerializedKey) {
  auto key_bytes = MakeCobaltEncryptionKeyBytes("not key bytes", 1, CobaltEncryptionKey::SHUFFLER);
  auto result = EncryptedMessageMaker::MakeForEnvelopes(key_bytes);
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());

  key_bytes = MakeCobaltEncryptionKeyBytes("not key bytes", 1, CobaltEncryptionKey::ANALYZER);
  result = EncryptedMessageMaker::MakeForObservations(key_bytes);
  EXPECT_EQ(StatusCode::INVALID_ARGUMENT, result.status().error_code());
}

}  // namespace cobalt::util