xref: /aosp_15_r20/external/tink/cc/util/test_util.h (revision e7b1675dde1b92d52ec075b0a92829627f2c52a5)

// Copyright 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef TINK_UTIL_TEST_UTIL_H_
#define TINK_UTIL_TEST_UTIL_H_

#include <limits>
#include <memory>
#include <ostream>
#include <string>
#include <utility>

#include "absl/base/thread_annotations.h"
#include "absl/status/status.h"
#include "absl/strings/cord.h"
#include "absl/strings/match.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "absl/synchronization/mutex.h"
#include "tink/aead.h"
#include "tink/aead/cord_aead.h"
#include "tink/deterministic_aead.h"
#include "tink/hybrid_decrypt.h"
#include "tink/hybrid_encrypt.h"
#include "tink/input_stream.h"
#include "tink/keyset_handle.h"
#include "tink/kms_client.h"
#include "tink/mac.h"
#include "tink/output_stream.h"
#include "tink/public_key_sign.h"
#include "tink/public_key_verify.h"
#include "tink/random_access_stream.h"
#include "tink/streaming_aead.h"
#include "tink/subtle/common_enums.h"
#include "tink/subtle/mac/stateful_mac.h"
#include "tink/util/buffer.h"
#include "tink/util/constants.h"
#include "tink/util/protobuf_helper.h"
#include "tink/util/status.h"
#include "tink/util/statusor.h"
#include "proto/common.pb.h"
#include "proto/ecdsa.pb.h"
#include "proto/ecies_aead_hkdf.pb.h"
#include "proto/ed25519.pb.h"
#include "proto/tink.pb.h"

namespace crypto {
namespace tink {
namespace test {

// Various utilities for testing.
///////////////////////////////////////////////////////////////////////////////

// Reads the test file specified by `filename`, and returns its contents.
std::string ReadTestFile(absl::string_view filename);

// Converts a hexadecimal string into a string of bytes.
// Returns a status if the size of the input is odd or if the input contains
// characters that are not hexadecimal.
crypto::tink::util::StatusOr<std::string> HexDecode(absl::string_view hex);

// Converts a hexadecimal string into a string of bytes.
// Dies if the input is not a valid hexadecimal string.
std::string HexDecodeOrDie(absl::string_view hex);

// Converts a string of bytes into a hexadecimal string.
std::string HexEncode(absl::string_view bytes);

// Returns a temporary directory suitable for temporary testing files.
std::string TmpDir();

// Adds the given 'keyData' with specified status, key_id, and
// output_prefix_type to the keyset.
void AddKeyData(const google::crypto::tink::KeyData& key_data, uint32_t key_id,
                google::crypto::tink::OutputPrefixType output_prefix,
                google::crypto::tink::KeyStatusType key_status,
                google::crypto::tink::Keyset* keyset);

// Adds the given 'key' with specified parameters and output_prefix_type=TINK
// to the specified 'keyset'.
void AddTinkKey(const std::string& key_type, uint32_t key_id,
                const portable_proto::MessageLite& key,
                google::crypto::tink::KeyStatusType key_status,
                google::crypto::tink::KeyData::KeyMaterialType material_type,
                google::crypto::tink::Keyset* keyset);

// Adds the given 'key' with specified parameters and output_prefix_type=LEGACY
// to the specified 'keyset'.
void AddLegacyKey(const std::string& key_type, uint32_t key_id,
                  const portable_proto::MessageLite& key,
                  google::crypto::tink::KeyStatusType key_status,
                  google::crypto::tink::KeyData::KeyMaterialType material_type,
                  google::crypto::tink::Keyset* keyset);

// Adds the given 'key' with specified parameters and output_prefix_type=RAW
// to the specified 'keyset'.
void AddRawKey(const std::string& key_type, uint32_t key_id,
               const portable_proto::MessageLite& key,
               google::crypto::tink::KeyStatusType key_status,
               google::crypto::tink::KeyData::KeyMaterialType material_type,
               google::crypto::tink::Keyset* keyset);

// Generates a fresh test key for ECIES-AEAD-HKDF for the given curve,
// using AesGcm with the specified key size as AEAD, and HKDF with 'hash_type'.
google::crypto::tink::EciesAeadHkdfPrivateKey GetEciesAesGcmHkdfTestKey(
    subtle::EllipticCurveType curve_type, subtle::EcPointFormat ec_point_format,
    subtle::HashType hash_type, uint32_t aes_gcm_key_size);

// Generates a fresh test key for ECIES-AEAD-HKDF for the given curve,
// using AesGcm with the specified key size as AEAD, and HKDF with 'hash_type'.
google::crypto::tink::EciesAeadHkdfPrivateKey GetEciesAesGcmHkdfTestKey(
    google::crypto::tink::EllipticCurveType curve_type,
    google::crypto::tink::EcPointFormat ec_point_format,
    google::crypto::tink::HashType hash_type, uint32_t aes_gcm_key_size);

// Generates a fresh test key for ECIES-AEAD-HKDF for the given curve,
// using XChaCha20Poly1305 as AEAD, and HKDF with 'hash_type'.
google::crypto::tink::EciesAeadHkdfPrivateKey
GetEciesXChaCha20Poly1305HkdfTestKey(
    google::crypto::tink::EllipticCurveType curve_type,
    google::crypto::tink::EcPointFormat ec_point_format,
    google::crypto::tink::HashType hash_type);

// Generates a fresh test key for ECIES-AEAD-HKDF for the given curve,
// using AesCtrHmac with the specified AEAD params, and HKDF with 'hash_type'.
google::crypto::tink::EciesAeadHkdfPrivateKey GetEciesAesCtrHmacHkdfTestKey(
    google::crypto::tink::EllipticCurveType curve_type,
    google::crypto::tink::EcPointFormat ec_point_format,
    google::crypto::tink::HashType hash_type, uint32_t aes_ctr_key_size,
    uint32_t aes_ctr_iv_size, google::crypto::tink::HashType hmac_hash_type,
    uint32_t hmac_tag_size, uint32_t hmac_key_size);

// Generates a fresh test key for ECIES-AEAD-HKDF for the given curve,
// using AesSiv as the determinisitic AEAD, and HKDF with 'hash_type'.
google::crypto::tink::EciesAeadHkdfPrivateKey GetEciesAesSivHkdfTestKey(
    google::crypto::tink::EllipticCurveType curve_type,
    google::crypto::tink::EcPointFormat ec_point_format,
    google::crypto::tink::HashType hash_type);

// Generates a fresh test key for EC DSA for the given 'curve_type', 'hash_type'
// and 'encoding'.
google::crypto::tink::EcdsaPrivateKey GetEcdsaTestPrivateKey(
    subtle::EllipticCurveType curve_type, subtle::HashType hash_type,
    subtle::EcdsaSignatureEncoding encoding);

// Generates a fresh test key for EC DSA for the given 'curve_type', 'hash_type'
// and 'encoding'.
google::crypto::tink::EcdsaPrivateKey GetEcdsaTestPrivateKey(
    google::crypto::tink::EllipticCurveType curve_type,
    google::crypto::tink::HashType hash_type,
    google::crypto::tink::EcdsaSignatureEncoding encoding);

// TODO(ambrosin): Remove because it is unused.
// Generates a fresh test key for ED25519.
google::crypto::tink::Ed25519PrivateKey GetEd25519TestPrivateKey();

// Embeds the given Proto into a KeyData proto.
template <typename Proto>
google::crypto::tink::KeyData AsKeyData(
    const Proto& proto,
    google::crypto::tink::KeyData::KeyMaterialType key_material_type) {
  google::crypto::tink::KeyData result;
  result.set_value(proto.SerializeAsString());
  result.set_type_url(absl::StrCat(kTypeGoogleapisCom, proto.GetTypeName()));
  result.set_key_material_type(key_material_type);
  return result;
}

// Uses a z test on the given byte string, expecting all bits to be uniformly
// set with probability 1/2. Returns non ok status if the z test fails by more
// than 10 standard deviations.
//
// With less statistics jargon: This counts the number of bits set and expects
// the number to be roughly half of the length of the string. The law of large
// numbers suggests that we can assume that the longer the string is, the more
// accurate that estimate becomes for a random string. This test is useful to
// detect things like strings that are entirely zero.
//
// Note: By itself, this is a very weak test for randomness.
util::Status ZTestUniformString(absl::string_view bytes);
// Tests that the crosscorrelation of two strings of equal length points to
// independent and uniformly distributed strings. Returns non ok status if the z
// test fails by more than 10 standard deviations.
//
// With less statistics jargon: This xors two strings and then performs the
// ZTestUniformString on the result. If the two strings are independent and
// uniformly distributed, the xor'ed string is as well. A cross correlation test
// will find whether two strings overlap more or less than it would be expected.
//
// Note: Having a correlation of zero is only a necessary but not sufficient
// condition for independence.
util::Status ZTestCrosscorrelationUniformStrings(absl::string_view bytes1,
                                                 absl::string_view bytes2);
// Tests that the autocorrelation of a string points to the bits being
// independent and uniformly distributed. Rotates the string in a cyclic
// fashion. Returns non ok status if the z test fails by more than 10 standard
// deviations.
//
// With less statistics jargon: This rotates the string bit by bit and performs
// ZTestCrosscorrelationUniformStrings on each of the rotated strings and the
// original. This will find self similarity of the input string, especially
// periodic self similarity. For example, it is a decent test to find English
// text (needs about 180 characters with the current settings).
//
// Note: Having a correlation of zero is only a necessary but not sufficient
// condition for independence.
util::Status ZTestAutocorrelationUniformString(absl::string_view bytes);

// A dummy implementation of Aead-interface.
// An instance of DummyAead can be identified by a name specified
// as a parameter of the constructor.
class DummyAead : public Aead {
 public:
  explicit DummyAead(absl::string_view aead_name) : aead_name_(aead_name) {}

  // Computes a dummy ciphertext, which is concatenation of provided 'plaintext'
  // with the name of this DummyAead.
  crypto::tink::util::StatusOr<std::string> Encrypt(
      absl::string_view plaintext,
      absl::string_view associated_data) const override {
    return absl::StrCat(aead_name_.size(), ":", associated_data.size(), ":",
                        aead_name_, associated_data, plaintext);
  }

  crypto::tink::util::StatusOr<std::string> Decrypt(
      absl::string_view ciphertext,
      absl::string_view associated_data) const override {
    std::string prefix =
        absl::StrCat(aead_name_.size(), ":", associated_data.size(), ":",
                     aead_name_, associated_data);
    if (!absl::StartsWith(ciphertext, prefix)) {
      return crypto::tink::util::Status(absl::StatusCode::kInvalidArgument,
                                        "Dummy operation failed.");
    }
    ciphertext.remove_prefix(prefix.size());
    return std::string(ciphertext);
  }

 private:
  std::string aead_name_;
};

// A dummy implementation of CordAead-interface.
// An instance of DummyCordAead can be identified by a name specified
// as a parameter of the constructor.
class DummyCordAead : public CordAead {
 public:
  explicit DummyCordAead(absl::string_view aead_name) : aead_(aead_name) {}

  // Computes a dummy ciphertext, which is concatenation of provided 'plaintext'
  // with the name of this DummyCordAead.
  crypto::tink::util::StatusOr<absl::Cord> Encrypt(
      absl::Cord plaintext, absl::Cord associated_data) const override {
    auto ciphertext =
        aead_.Encrypt(plaintext.Flatten(), associated_data.Flatten());

    if (!ciphertext.ok()) return ciphertext.status();

    absl::Cord ciphertext_cord;
    ciphertext_cord.Append(ciphertext.value());
    return ciphertext_cord;
  }

  crypto::tink::util::StatusOr<absl::Cord> Decrypt(
      absl::Cord ciphertext, absl::Cord associated_data) const override {
    auto plaintext =
        aead_.Decrypt(ciphertext.Flatten(), associated_data.Flatten());

    if (!plaintext.ok()) return plaintext.status();

    absl::Cord plaintext_cord;
    plaintext_cord.Append(plaintext.value());
    return plaintext_cord;
  }

 private:
  DummyAead aead_;
};

// A dummy implementation of DeterministicAead-interface.
// An instance of DummyDeterministicAead can be identified by a name specified
// as a parameter of the constructor.
// The implementation is the same as DummyAead.
class DummyDeterministicAead : public DeterministicAead {
 public:
  explicit DummyDeterministicAead(absl::string_view daead_name)
      : aead_(daead_name) {}

  crypto::tink::util::StatusOr<std::string> EncryptDeterministically(
      absl::string_view plaintext,
      absl::string_view associated_data) const override {
    return aead_.Encrypt(plaintext, associated_data);
  }

  crypto::tink::util::StatusOr<std::string> DecryptDeterministically(
      absl::string_view ciphertext,
      absl::string_view associated_data) const override {
    return aead_.Decrypt(ciphertext, associated_data);
  }

 private:
  DummyAead aead_;
};

// A dummy implementation of StreamingAead-interface.  An instance of
// DummyStreamingAead can be identified by a name specified as a parameter of
// the constructor.  This name concatenated with 'associated_data' for a
// specific stream yields a header of an encrypted stream produced/consumed
// by DummyStreamingAead.
class DummyStreamingAead : public StreamingAead {
 public:
  explicit DummyStreamingAead(absl::string_view streaming_aead_name)
      : streaming_aead_name_(streaming_aead_name) {}

  crypto::tink::util::StatusOr<std::unique_ptr<crypto::tink::OutputStream>>
  NewEncryptingStream(
      std::unique_ptr<crypto::tink::OutputStream> ciphertext_destination,
      absl::string_view associated_data) const override {
    return {absl::make_unique<DummyEncryptingStream>(
        std::move(ciphertext_destination),
        absl::StrCat(streaming_aead_name_, associated_data))};
  }

  crypto::tink::util::StatusOr<std::unique_ptr<crypto::tink::InputStream>>
  NewDecryptingStream(
      std::unique_ptr<crypto::tink::InputStream> ciphertext_source,
      absl::string_view associated_data) const override {
    return {absl::make_unique<DummyDecryptingStream>(
        std::move(ciphertext_source),
        absl::StrCat(streaming_aead_name_, associated_data))};
  }

  crypto::tink::util::StatusOr<
      std::unique_ptr<crypto::tink::RandomAccessStream>>
  NewDecryptingRandomAccessStream(
      std::unique_ptr<crypto::tink::RandomAccessStream> ciphertext_source,
      absl::string_view associated_data) const override {
    return {absl::make_unique<DummyDecryptingRandomAccessStream>(
        std::move(ciphertext_source),
        absl::StrCat(streaming_aead_name_, associated_data))};
  }

  // Upon first call to Next() writes to 'ct_dest' the specifed 'header',
  // and subsequently forwards all methods calls to the corresponding
  // methods of 'cd_dest'.
  class DummyEncryptingStream : public crypto::tink::OutputStream {
   public:
    DummyEncryptingStream(std::unique_ptr<crypto::tink::OutputStream> ct_dest,
                          absl::string_view header)
        : ct_dest_(std::move(ct_dest)),
          header_(header),
          after_init_(false),
          status_(util::OkStatus()) {}

    crypto::tink::util::StatusOr<int> Next(void** data) override {
      if (!after_init_) {  // Try to initialize.
        after_init_ = true;
        auto next_result = ct_dest_->Next(data);
        if (!next_result.ok()) {
          status_ = next_result.status();
          return status_;
        }
        if (next_result.value() < header_.size()) {
          status_ =
              util::Status(absl::StatusCode::kInternal, "Buffer too small");
        } else {
          memcpy(*data, header_.data(), static_cast<int>(header_.size()));
          ct_dest_->BackUp(next_result.value() - header_.size());
        }
      }
      if (!status_.ok()) return status_;
      return ct_dest_->Next(data);
    }

    void BackUp(int count) override {
      if (after_init_ && status_.ok()) {
        ct_dest_->BackUp(count);
      }
    }

    int64_t Position() const override {
      if (after_init_ && status_.ok()) {
        return ct_dest_->Position() - header_.size();
      } else {
        return 0;
      }
    }
    util::Status Close() override {
      if (!after_init_) {  // Call Next() to write the header to ct_dest_.
        void* buf;
        auto next_result = Next(&buf);
        if (next_result.ok()) {
          BackUp(next_result.value());
        } else {
          status_ = next_result.status();
          return status_;
        }
      }
      return ct_dest_->Close();
    }

   private:
    std::unique_ptr<crypto::tink::OutputStream> ct_dest_;
    std::string header_;
    bool after_init_;
    util::Status status_;
  };  // class DummyEncryptingStream

  // Upon first call to Next() tries to read from 'ct_source' a header
  // that is expected to be equal to 'expected_header'.  If this
  // header matching succeeds, all subsequent method calls are forwarded
  // to the corresponding methods of 'cd_source'.
  class DummyDecryptingStream : public crypto::tink::InputStream {
   public:
    DummyDecryptingStream(std::unique_ptr<crypto::tink::InputStream> ct_source,
                          absl::string_view expected_header)
        : ct_source_(std::move(ct_source)),
          exp_header_(expected_header),
          after_init_(false),
          status_(util::OkStatus()) {}

    crypto::tink::util::StatusOr<int> Next(const void** data) override {
      if (!after_init_) {  // Try to initialize.
        after_init_ = true;
        auto next_result = ct_source_->Next(data);
        if (!next_result.ok()) {
          status_ = next_result.status();
          if (status_.code() == absl::StatusCode::kOutOfRange) {
            status_ = util::Status(absl::StatusCode::kInvalidArgument,
                                   "Could not read header");
          }
          return status_;
        }
        if (next_result.value() < exp_header_.size()) {
          status_ =
              util::Status(absl::StatusCode::kInternal, "Buffer too small");
        } else if (memcmp((*data), exp_header_.data(),
                          static_cast<int>(exp_header_.size()))) {
          status_ = util::Status(absl::StatusCode::kInvalidArgument,
                                 "Corrupted header");
        }
        if (status_.ok()) {
          ct_source_->BackUp(next_result.value() - exp_header_.size());
        }
      }
      if (!status_.ok()) return status_;
      return ct_source_->Next(data);
    }

    void BackUp(int count) override {
      if (after_init_ && status_.ok()) {
        ct_source_->BackUp(count);
      }
    }

    int64_t Position() const override {
      if (after_init_ && status_.ok()) {
        return ct_source_->Position() - exp_header_.size();
      } else {
        return 0;
      }
    }

   private:
    std::unique_ptr<crypto::tink::InputStream> ct_source_;
    std::string exp_header_;
    bool after_init_;
    util::Status status_;
  };  // class DummyDecryptingStream

  // Upon first call to PRead() tries to read from `ct_source` a header
  // that is expected to be equal to `expected_header`.  If this
  // header matching succeeds, all subsequent method calls are forwarded
  // to `ct_source->PRead`.
  class DummyDecryptingRandomAccessStream
      : public crypto::tink::RandomAccessStream {
   public:
    DummyDecryptingRandomAccessStream(
        std::unique_ptr<crypto::tink::RandomAccessStream> ct_source,
        absl::string_view expected_header)
        : ct_source_(std::move(ct_source)), exp_header_(expected_header) {}

    crypto::tink::util::Status PRead(
        int64_t position, int count,
        crypto::tink::util::Buffer* dest_buffer) override {
      util::Status status = CheckHeader();
      if (!status.ok()) {
        return status;
      }
      status = dest_buffer->set_size(0);
      if (!status.ok()) return status;
      return ct_source_->PRead(position + exp_header_.size(), count,
                               dest_buffer);
    }

    util::StatusOr<int64_t> size() override {
      util::Status status = CheckHeader();
      if (!status.ok()) {
        return status;
      }
      auto ct_size_result = ct_source_->size();
      if (!ct_size_result.ok()) return ct_size_result.status();
      auto pt_size = ct_size_result.value() - exp_header_.size();
      if (pt_size >= 0) return pt_size;
      return util::Status(absl::StatusCode::kUnavailable, "size not available");
    }

   private:
    util::Status CheckHeader()
        ABSL_LOCKS_EXCLUDED(header_check_status_mutex_) {
      absl::MutexLock lock(&header_check_status_mutex_);
      if (header_check_status_.code() != absl::StatusCode::kUnavailable) {
        return header_check_status_;
      }
      auto buf = std::move(util::Buffer::New(exp_header_.size()).value());
      header_check_status_ =
          ct_source_->PRead(0, exp_header_.size(), buf.get());
      if (!header_check_status_.ok() &&
          header_check_status_.code() != absl::StatusCode::kOutOfRange) {
        return header_check_status_;
      }
      // EOF or Ok indicate a valid read has happened.
      header_check_status_ = util::OkStatus();
      // Invalid header.
      if (buf->size() < exp_header_.size()) {
        header_check_status_ = util::Status(absl::StatusCode::kInvalidArgument,
                               "Could not read header");
      } else if (memcmp(buf->get_mem_block(), exp_header_.data(),
                        static_cast<int>(exp_header_.size()))) {
        header_check_status_ = util::Status(absl::StatusCode::kInvalidArgument,
                               "Corrupted header");
      }
      return header_check_status_;
    }

    std::unique_ptr<crypto::tink::RandomAccessStream> ct_source_;
    std::string exp_header_;
    mutable absl::Mutex header_check_status_mutex_;
    util::Status header_check_status_
        ABSL_GUARDED_BY(header_check_status_mutex_) =
            util::Status(absl::StatusCode::kUnavailable, "Uninitialized");
  };  // class DummyDecryptingRandomAccessStream

 private:
  std::string streaming_aead_name_;
};  // class DummyStreamingAead

// A dummy implementation of HybridEncrypt-interface.
// An instance of DummyHybridEncrypt can be identified by a name specified
// as a parameter of the constructor.
class DummyHybridEncrypt : public HybridEncrypt {
 public:
  explicit DummyHybridEncrypt(absl::string_view hybrid_name)
      : dummy_aead_(absl::StrCat("DummyHybrid:", hybrid_name)) {}

  // Computes a dummy ciphertext, which is concatenation of provided 'plaintext'
  // with the name of this DummyHybridEncrypt.
  crypto::tink::util::StatusOr<std::string> Encrypt(
      absl::string_view plaintext,
      absl::string_view context_info) const override {
    return dummy_aead_.Encrypt(plaintext, context_info);
  }

 private:
  DummyAead dummy_aead_;
};

// A dummy implementation of HybridDecrypt-interface.
// An instance of DummyHybridDecrypt can be identified by a name specified
// as a parameter of the constructor.
class DummyHybridDecrypt : public HybridDecrypt {
 public:
  explicit DummyHybridDecrypt(absl::string_view hybrid_name)
      : dummy_aead_(absl::StrCat("DummyHybrid:", hybrid_name)) {}

  // Decrypts a dummy ciphertext, which should be a concatenation
  // of a plaintext with the name of this DummyHybridDecrypt.
  crypto::tink::util::StatusOr<std::string> Decrypt(
      absl::string_view ciphertext,
      absl::string_view context_info) const override {
    return dummy_aead_.Decrypt(ciphertext, context_info);
  }

 private:
  DummyAead dummy_aead_;
};

// A dummy implementation of PublicKeySign-interface.
// An instance of DummyPublicKeySign can be identified by a name specified
// as a parameter of the constructor.
class DummyPublicKeySign : public PublicKeySign {
 public:
  explicit DummyPublicKeySign(absl::string_view signature_name)
      : dummy_aead_(absl::StrCat("DummySign:", signature_name)) {}

  // Computes a dummy signature, which is a concatenation of 'data'
  // with the name of this DummyPublicKeySign.
  crypto::tink::util::StatusOr<std::string> Sign(
      absl::string_view data) const override {
    return dummy_aead_.Encrypt("", data);
  }

 private:
  DummyAead dummy_aead_;
};

// A dummy implementation of PublicKeyVerify-interface.
// An instance of DummyPublicKeyVerify can be identified by a name specified
// as a parameter of the constructor.
class DummyPublicKeyVerify : public PublicKeyVerify {
 public:
  explicit DummyPublicKeyVerify(absl::string_view signature_name)
      : dummy_aead_(absl::StrCat("DummySign:", signature_name)) {}

  // Verifies a dummy signature, should be a concatenation of the name
  // of this DummyPublicKeyVerify with the provided 'data'.
  crypto::tink::util::Status Verify(absl::string_view signature,
                                    absl::string_view data) const override {
    return dummy_aead_.Decrypt(signature, data).status();
  }

 private:
  DummyAead dummy_aead_;
};

// A dummy implementation of Mac-interface.
// An instance of DummyMac can be identified by a name specified
// as a parameter of the constructor.
class DummyMac : public Mac {
 public:
  explicit DummyMac(const std::string& mac_name)
      : dummy_aead_(absl::StrCat("DummyMac:", mac_name)) {}

  // Computes a dummy MAC, which is concatenation of provided 'data'
  // with the name of this DummyMac.
  crypto::tink::util::StatusOr<std::string> ComputeMac(
      absl::string_view data) const override {
    return dummy_aead_.Encrypt("", data);
  }

  crypto::tink::util::Status VerifyMac(absl::string_view mac,
                                       absl::string_view data) const override {
    return dummy_aead_.Decrypt(mac, data).status();
  }

 private:
  DummyAead dummy_aead_;
};

// A dummy implementation of Stateful Mac interface.
// An instance of DummyStatefulMac can be identified by a name specified
// as a parameter of the constructor.
// Over the same inputs, the DummyStatefulMac and DummyMac should give the same
// output; DummyStatefulMac builds and internal_state_ and calls DummyMac.
class DummyStatefulMac : public subtle::StatefulMac {
 public:
  explicit DummyStatefulMac(const std::string& mac_name)
      : dummy_aead_(absl::StrCat("DummyMac:", mac_name)), buffer_("") {}

  util::Status Update(absl::string_view data) override {
    absl::StrAppend(&buffer_, data);
    return util::OkStatus();
  }
  util::StatusOr<std::string> Finalize() override {
    return dummy_aead_.Encrypt("", buffer_);
  }

 private:
  DummyAead dummy_aead_;
  std::string buffer_;
};

// A dummy implementation of KeysetWriter-interface.
class DummyKeysetWriter : public KeysetWriter {
 public:
  static crypto::tink::util::StatusOr<std::unique_ptr<DummyKeysetWriter>> New(
      std::unique_ptr<std::ostream> destination_stream) {
    std::unique_ptr<DummyKeysetWriter> writer(
        new DummyKeysetWriter(std::move(destination_stream)));
    return std::move(writer);
  }

  crypto::tink::util::Status Write(
      const google::crypto::tink::Keyset& keyset) override {
    return crypto::tink::util::OkStatus();
  }

  crypto::tink::util::Status Write(
      const google::crypto::tink::EncryptedKeyset& encrypted_keyset) override {
    return crypto::tink::util::OkStatus();
  }

 private:
  explicit DummyKeysetWriter(std::unique_ptr<std::ostream> destination_stream)
      : destination_stream_(std::move(destination_stream)) {}

  std::unique_ptr<std::ostream> destination_stream_;
};

// A dummy implementation of KmsClient-interface.
class DummyKmsClient : public KmsClient {
 public:
  DummyKmsClient(absl::string_view uri_prefix, absl::string_view key_uri)
      : uri_prefix_(uri_prefix), key_uri_(key_uri) {}

  bool DoesSupport(absl::string_view key_uri) const override {
    if (key_uri.empty()) return false;
    if (key_uri_.empty()) return absl::StartsWith(key_uri, uri_prefix_);
    return key_uri == key_uri_;
  }

  crypto::tink::util::StatusOr<std::unique_ptr<Aead>> GetAead(
      absl::string_view key_uri) const override {
    if (!DoesSupport(key_uri))
      return crypto::tink::util::Status(absl::StatusCode::kInvalidArgument,
                                        "key_uri not supported");
    return {absl::make_unique<DummyAead>(key_uri)};
  }

  ~DummyKmsClient() override = default;

 private:
  std::string uri_prefix_;
  std::string key_uri_;
};

}  // namespace test
}  // namespace tink
}  // namespace crypto

#endif  // TINK_UTIL_TEST_UTIL_H_