components/gcm_driver/crypto/gcm_message_cryptographer_unittest.cc

// Copyright 2015 The Chromium 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 "components/gcm_driver/crypto/gcm_message_cryptographer.h"

#include <memory>

#include "base/base64url.h"
#include "base/memory/ptr_util.h"
#include "base/strings/string_util.h"
#include "components/gcm_driver/crypto/p256_key_util.h"
#include "crypto/random.h"
#include "crypto/symmetric_key.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace gcm {

namespace {

// Example plaintext data to use in the tests.
const char kExamplePlaintext[] = "Example plaintext";

// The number of bits of the key in AEAD_AES_128_GCM.
const size_t kKeySizeBits = 128;

// Public keys of both the sender and the recipient as base64url-encoded
// uncompressed P-256 EC points, as well as an authentication secret used for
// the reference vectors. All used to create stable output.
const char kCommonRecipientPublicKey[] =
    "BIXzEKOFquzVlr_1tS1bhmobZU3IJq2bswDflMJsizixqd_HFSvCJaCAotNjBw6A-iKQk7FshA"
    "jdAA-T9Rh1a7U";
const char kCommonSenderPublicKey[] =
    "BAuzSrdIyKZsHnuOhqklkIKi6fl65V9OdPy6nFwI2SywL5-6I5SkkDtfIL9y7NkoEE345jv2Eo"
    "5n4NIbLJIBjTM";
const char kCommonAuthSecret[] = "MyAuthenticationSecret";

// Test vectors containing reference input for draft-ietf-webpush-encryption-03
// that was created using an separate JavaScript implementation of the draft.
struct TestVector {
  const char* const input;
  const char* const ecdh_shared_secret;
  const char* const salt;
  size_t record_size;
  const char* const output;
};

const TestVector kEncryptionTestVectorsDraft03[] = {
    // Simple message.
    {"Hello, world!", "AhA6n2oFYPWIh-cXwyv1m2C0JvmjHB4ZkXj8QylESXU",
     "tsJYqAGvFDk6lDEv7daecw", 4096,
     "FgWrrnZq79oI_N4ORkVLHx1jfVmjeiIk-xFX8PzVuA"},
    // Empty message.
    {"", "lMyvTong4VR053jfCpWmMDGW5dEDAqiTZUIU-inhTjU",
     "wH3uvZqcN6oey9whiGpn1A", 4096, "MTI9zZ8CJTUzbZ4qNDoQZs0k"},
    // Message with an invalid salt size.
    {
        "Hello, world!", "CcdxzkR6z1EY9vSrM7_IxYVxDxu46hV638EZQTPd7XI",
        "aRr1fI1YSGVi5XU", 4096,
        nullptr  // expected to fail
    }};

const TestVector kDecryptionTestVectorsDraft03[] = {
    // Simple message.
    {"ceiEu_YpmqLoakD4smdzvy2XKRQrJ9vBzB2aqYEfzw",
     "47ZytAw9qHlm-Q8g-7rH81rUPzaCgGcoFvlS1qxQtQk", "EuR7EVetcaWpndXd_dKeyA",
     4096, "Hello, world!"},
    // Simple message with 16 bytes of padding.
    {"WSf6fz1O0aIJyaPTCnvk83OqIQxsRKeFOvblPLsPpFB_1AV9ROk09TE1cGrB6zQ",
     "MYSsNybwrTzRIzQYUq_yFPc6ugcTrJdEZJDM4NswvUg", "8sEAMQYnufo2UkKl80cUGQ",
     4096, "Hello, world!"},
    // Empty message.
    {"Ur3vHedGDO5IPYDvbhHYjbjG", "S3-Ki_-XtzR66gUp_zR75CC5JXO62pyr5fWfneTYwFE",
     "4RM6s19jJHdmqiVEJDp9jg", 4096, ""},
    // Message with an invalid salt size.
    {
        "iGrOpmJC5XTTf7wtgdhZ_qT",
        "wW3Iy5ma803lLd-ysPdHUe2NB3HqXbY0XhCCdG5Y1Gw", "N7oMH_xohAhMhOY", 4096,
        nullptr  // expected to fail
    },
    // Message with an invalid record size.
    {
        "iGrOpmJC5XTTf7wtgdhZ_qT",
        "kR5BMfqMKOD1yrLKE2giObXHI7merrMtnoO2oqneqXA", "SQeJSPrqHvTdSfAMF8bBzQ",
        8,
        nullptr  // expected to fail
    },
    // Message with multiple (2) records.
    {
        "RqQVHRXlfYjzW9xhzh3V_KijLKjZiKzGXosqN_"
        "IaMzi0zI0tXXhC1urtrk3iWRoqttNXpkD2r"
        "UCgLy8A1FnTjw",
        "W3W4gx7sqcfmBnvNNdO9d4MBCC1bvJkvsNjZOGD-CCg", "xG0TPGi9aIcxjpXKmaYBBQ",
        7,
        nullptr  // expected to fail
    }};

}  // namespace

class GCMMessageCryptographerTest : public ::testing::Test {
 public:
  void SetUp() override {
    cryptographer_ = base::MakeUnique<GCMMessageCryptographer>(
        GCMMessageCryptographer::Version::DRAFT_03);

    ASSERT_TRUE(base::Base64UrlDecode(
        kCommonRecipientPublicKey, base::Base64UrlDecodePolicy::IGNORE_PADDING,
        &recipient_public_key_));
    ASSERT_TRUE(base::Base64UrlDecode(
        kCommonSenderPublicKey, base::Base64UrlDecodePolicy::IGNORE_PADDING,
        &sender_public_key_));

    std::unique_ptr<crypto::SymmetricKey> random_key(
        crypto::SymmetricKey::GenerateRandomKey(crypto::SymmetricKey::AES,
                                                kKeySizeBits));

    ASSERT_TRUE(random_key->GetRawKey(&ecdh_shared_secret_));
  }

 protected:
  // Generates a cryptographically secure random salt of 16-octets in size, the
  // required length as expected by the HKDF.
  std::string GenerateRandomSalt() {
    const size_t kSaltSize = 16;

    std::string salt;

    crypto::RandBytes(base::WriteInto(&salt, kSaltSize + 1), kSaltSize);
    return salt;
  }

  // Public keys of the recipient and sender as uncompressed P-256 EC points.
  std::string recipient_public_key_;
  std::string sender_public_key_;

  // Shared secret to use in transformations. Unrelated to the keys above.
  std::string ecdh_shared_secret_;

  // The GCMMessageCryptographer instance to use for the tests.
  std::unique_ptr<GCMMessageCryptographer> cryptographer_;
};

TEST_F(GCMMessageCryptographerTest, RoundTrip) {
  const std::string salt = GenerateRandomSalt();

  size_t record_size = 0;

  std::string ciphertext, plaintext;
  ASSERT_TRUE(cryptographer_->Encrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, kExamplePlaintext, &record_size, &ciphertext));

  EXPECT_GT(record_size, ciphertext.size() - 16);
  EXPECT_GT(ciphertext.size(), 0u);

  ASSERT_TRUE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, record_size, &plaintext));

  EXPECT_EQ(kExamplePlaintext, plaintext);
}

TEST_F(GCMMessageCryptographerTest, RoundTripEmptyMessage) {
  const std::string salt = GenerateRandomSalt();
  const std::string message = "";

  size_t record_size = 0;

  std::string ciphertext, plaintext;
  ASSERT_TRUE(cryptographer_->Encrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, message, &record_size, &ciphertext));

  EXPECT_GT(record_size, ciphertext.size() - 16);
  EXPECT_GT(ciphertext.size(), 0u);

  ASSERT_TRUE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, record_size, &plaintext));

  EXPECT_EQ(message, plaintext);
}

TEST_F(GCMMessageCryptographerTest, InvalidRecordSize) {
  const std::string salt = GenerateRandomSalt();

  size_t record_size = 0;

  std::string ciphertext, plaintext;
  ASSERT_TRUE(cryptographer_->Encrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, kExamplePlaintext, &record_size, &ciphertext));

  EXPECT_GT(record_size, ciphertext.size() - 16);

  EXPECT_FALSE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, 0 /* record_size */, &plaintext));

  EXPECT_FALSE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, ciphertext.size() - 17, &plaintext));

  EXPECT_TRUE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, ciphertext.size() - 16, &plaintext));
}

TEST_F(GCMMessageCryptographerTest, InvalidRecordPadding) {
  std::string message = std::string(sizeof(uint16_t), '\0') + kExamplePlaintext;

  const std::string salt = GenerateRandomSalt();

  const std::string prk =
      cryptographer_->encryption_scheme_->DerivePseudoRandomKey(
          ecdh_shared_secret_, kCommonAuthSecret);
  const std::string content_encryption_key =
      cryptographer_->DeriveContentEncryptionKey(recipient_public_key_,
                                                 sender_public_key_, prk, salt);
  const std::string nonce = cryptographer_->DeriveNonce(
      recipient_public_key_, sender_public_key_, prk, salt);

  ASSERT_GT(message.size(), 1u);
  const size_t record_size = message.size() + 1;

  std::string ciphertext, plaintext;
  ASSERT_TRUE(cryptographer_->TransformRecord(
      GCMMessageCryptographer::Direction::ENCRYPT, message,
      content_encryption_key, nonce, &ciphertext));

  ASSERT_TRUE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, record_size, &plaintext));

  // Note that GCMMessageCryptographer::Decrypt removes the padding.
  EXPECT_EQ(kExamplePlaintext, plaintext);

  // Now run the same steps again, but say that there are four padding octets.
  // This should be rejected because the padding will not be all zeros.
  message[0] = 4;

  ASSERT_TRUE(cryptographer_->TransformRecord(
      GCMMessageCryptographer::Direction::ENCRYPT, message,
      content_encryption_key, nonce, &ciphertext));

  ASSERT_FALSE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, record_size, &plaintext));

  // Do the same but changing the second octet indicating padding size, leaving
  // the first octet at zero.
  message[0] = 0;
  message[1] = 4;

  ASSERT_TRUE(cryptographer_->TransformRecord(
      GCMMessageCryptographer::Direction::ENCRYPT, message,
      content_encryption_key, nonce, &ciphertext));

  ASSERT_FALSE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, record_size, &plaintext));

  // Run the same steps again, but say that there are more padding octets than
  // the length of the message.
  message[0] = 64;

  EXPECT_GT(static_cast<size_t>(message[0]), message.size());
  ASSERT_TRUE(cryptographer_->TransformRecord(
      GCMMessageCryptographer::Direction::ENCRYPT, message,
      content_encryption_key, nonce, &ciphertext));

  ASSERT_FALSE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_,
      kCommonAuthSecret, salt, ciphertext, record_size, &plaintext));
}

TEST_F(GCMMessageCryptographerTest, AuthSecretAffectsPRK) {
  ASSERT_NE(cryptographer_->encryption_scheme_->DerivePseudoRandomKey(
                ecdh_shared_secret_, "Hello"),
            cryptographer_->encryption_scheme_->DerivePseudoRandomKey(
                ecdh_shared_secret_, "World"));

  std::string salt = GenerateRandomSalt();

  // Verify that the IKM actually gets used by the transformations.
  size_t hello_record_size, world_record_size;
  std::string hello_ciphertext, world_ciphertext;

  ASSERT_TRUE(cryptographer_->Encrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_, "Hello",
      salt, kExamplePlaintext, &hello_record_size, &hello_ciphertext));

  ASSERT_TRUE(cryptographer_->Encrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_, "World",
      salt, kExamplePlaintext, &world_record_size, &world_ciphertext));

  // If the ciphertexts differ despite the same key and salt, it got used.
  ASSERT_NE(hello_ciphertext, world_ciphertext);
  EXPECT_EQ(hello_record_size, world_record_size);

  // Verify that the different ciphertexts can also be translated back to the
  // plaintext content. This will fail if the auth secret isn't considered.
  std::string hello_plaintext, world_plaintext;

  ASSERT_TRUE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_, "Hello",
      salt, hello_ciphertext, hello_record_size, &hello_plaintext));

  ASSERT_TRUE(cryptographer_->Decrypt(
      recipient_public_key_, sender_public_key_, ecdh_shared_secret_, "World",
      salt, world_ciphertext, world_record_size, &world_plaintext));

  EXPECT_EQ(kExamplePlaintext, hello_plaintext);
  EXPECT_EQ(kExamplePlaintext, world_plaintext);
}

class GCMMessageCryptographerTestVectorTest
    : public GCMMessageCryptographerTest {};

TEST_F(GCMMessageCryptographerTestVectorTest, EncryptionVectorsDraft03) {
  std::string ecdh_shared_secret, salt, output, ciphertext;
  size_t record_size = 0;

  for (size_t i = 0; i < arraysize(kEncryptionTestVectorsDraft03); ++i) {
    SCOPED_TRACE(i);

    ASSERT_TRUE(base::Base64UrlDecode(
        kEncryptionTestVectorsDraft03[i].ecdh_shared_secret,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &ecdh_shared_secret));
    ASSERT_TRUE(base::Base64UrlDecode(
        kEncryptionTestVectorsDraft03[i].salt,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &salt));

    const bool has_output = kEncryptionTestVectorsDraft03[i].output;
    const bool result = cryptographer_->Encrypt(
        recipient_public_key_, sender_public_key_, ecdh_shared_secret,
        kCommonAuthSecret, salt, kEncryptionTestVectorsDraft03[i].input,
        &record_size, &ciphertext);

    if (!has_output) {
      EXPECT_FALSE(result);
      continue;
    }

    EXPECT_TRUE(result);
    ASSERT_TRUE(base::Base64UrlDecode(
        kEncryptionTestVectorsDraft03[i].output,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &output));

    EXPECT_EQ(kEncryptionTestVectorsDraft03[i].record_size, record_size);
    EXPECT_EQ(output, ciphertext);
  }
}

TEST_F(GCMMessageCryptographerTestVectorTest, DecryptionVectorsDraft03) {
  std::string input, ecdh_shared_secret, salt, plaintext;
  for (size_t i = 0; i < arraysize(kDecryptionTestVectorsDraft03); ++i) {
    SCOPED_TRACE(i);

    ASSERT_TRUE(base::Base64UrlDecode(
        kDecryptionTestVectorsDraft03[i].input,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &input));
    ASSERT_TRUE(base::Base64UrlDecode(
        kDecryptionTestVectorsDraft03[i].ecdh_shared_secret,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &ecdh_shared_secret));
    ASSERT_TRUE(base::Base64UrlDecode(
        kDecryptionTestVectorsDraft03[i].salt,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &salt));

    const bool has_output = kDecryptionTestVectorsDraft03[i].output;
    const bool result = cryptographer_->Decrypt(
        recipient_public_key_, sender_public_key_, ecdh_shared_secret,
        kCommonAuthSecret, salt, input,
        kDecryptionTestVectorsDraft03[i].record_size, &plaintext);

    if (!has_output) {
      EXPECT_FALSE(result);
      continue;
    }

    EXPECT_TRUE(result);
    EXPECT_EQ(kDecryptionTestVectorsDraft03[i].output, plaintext);
  }
}

class GCMMessageCryptographerReferenceTest : public ::testing::Test {
 protected:
  // Computes the shared secret between the sender and the receiver. The sender
  // must have a key-pair containing a X.509 SubjectPublicKeyInfo block and a
  // ASN.1-encoded PKCS #8 EncryptedPrivateKeyInfo block, whereas the receiver
  // must have a public key in uncompressed EC point format.
  void ComputeSharedSecret(const char* encoded_sender_private_key,
                           const char* encoded_sender_public_key_x509,
                           const char* encoded_receiver_public_key,
                           std::string* shared_secret) const {
    std::string sender_private_key, sender_public_key_x509, receiver_public_key;
    ASSERT_TRUE(base::Base64UrlDecode(
        encoded_sender_private_key,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &sender_private_key));
    ASSERT_TRUE(base::Base64UrlDecode(
        encoded_sender_public_key_x509,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &sender_public_key_x509));
    ASSERT_TRUE(base::Base64UrlDecode(
        encoded_receiver_public_key,
        base::Base64UrlDecodePolicy::IGNORE_PADDING, &receiver_public_key));

    ASSERT_TRUE(ComputeSharedP256Secret(
        sender_private_key, sender_public_key_x509, receiver_public_key,
        shared_secret));
  }
};

// Reference test included for the Version::DRAFT_03 implementation.
// https://tools.ietf.org/html/draft-ietf-webpush-encryption-03
// https://tools.ietf.org/html/draft-ietf-httpbis-encryption-encoding-02
TEST_F(GCMMessageCryptographerReferenceTest, ReferenceDraft03) {
  // The 16-byte salt unique to the message.
  const char kSalt[] = "lngarbyKfMoi9Z75xYXmkg";

  // The 16-byte prearranged secret between the sender and receiver.
  const char kAuthSecret[] = "R29vIGdvbyBnJyBqb29iIQ";

  // The keying material used by the sender to encrypt the |kCiphertext|.
  const char kSenderPrivate[] =
      "MIGxMBwGCiqGSIb3DQEMAQMwDgQIh9aZ3UvuDloCAggABIGQZ-T8CJZe-no4mOTDgX1Gm986"
      "Gsbe3mjJeABhA4KOmut_qJh5kt_DLqdNShiQr-afk3AdkX-fxLZdrcHiW9aWvBjnMAY65zg5"
      "oHsuUaoEuG88Ksbku2u193OENWTQTsYaYE2O44qmRfsX773UNVcWXg_omwIbhbgf6tLZUZH_"
      "dTC3YjzuxjbSP89HPEJ-eBXA";
  const char kSenderPublicKeyUncompressed[] =
      "BNoRDbb84JGm8g5Z5CFxurSqsXWJ11ItfXEWYVLE85Y7CYkDjXsIEc4aqxYaQ1G8BqkXCJ6D"
      "PpDrWtdWj_mugHU";
  const char kSenderPublicX509[] =
      "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE2hENtvzgkabyDlnkIXG6tKqxdYnXUi19cRZh"
      "UsTzljsJiQONewgRzhqrFhpDUbwGqRcInoM-kOta11aP-a6AdQ";

  // The keying material used by the recipient to decrypt the |kCiphertext|.
  const char kRecipientPrivate[] =
      "MIGxMBwGCiqGSIb3DQEMAQMwDgQIqMt4d7uJdt4CAggABIGQeikRHE3CqUeF-uUtJno9BL0g"
      "mNRyDihZe8P3nF_g-NYVzvdQowsXfYeza6OQOdDuMXxnGgNToVy2jsiWVN6rxCaSMTY622y8"
      "ajW5voSdqC2PakQ8ZNTPNHarLDMC9NpgGKrUh8hfRLhvb7vtbKIWmx-22rQB5yTYdqzN2m7A"
      "GHMWRnVk0mMzMsMjZqYFaa2D";
  const char kRecipientPublicKeyUncompressed[] =
      "BCEkBjzL8Z3C-oi2Q7oE5t2Np-p7osjGLg93qUP0wvqRT21EEWyf0cQDQcakQMqz4hQKYOQ3"
      "il2nNZct4HgAUQU";
  const char kRecipientPublicX509[] =
      "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEISQGPMvxncL6iLZDugTm3Y2n6nuiyMYuD3ep"
      "Q_TC-pFPbUQRbJ_RxANBxqRAyrPiFApg5DeKXac1ly3geABRBQ";

  // The ciphertext and associated plaintext of the message.
  const char kCiphertext[] = "6nqAQUME8hNqw5J3kl8cpVVJylXKYqZOeseZG8UueKpA";
  const char kPlaintext[] = "I am the walrus";

  std::string sender_shared_secret, receiver_shared_secret;

  // Compute the shared secrets between the sender and receiver's keys.
  ASSERT_NO_FATAL_FAILURE(ComputeSharedSecret(kSenderPrivate, kSenderPublicX509,
                                              kRecipientPublicKeyUncompressed,
                                              &sender_shared_secret));
  ASSERT_NO_FATAL_FAILURE(ComputeSharedSecret(
      kRecipientPrivate, kRecipientPublicX509, kSenderPublicKeyUncompressed,
      &receiver_shared_secret));

  ASSERT_GT(sender_shared_secret.size(), 0u);
  ASSERT_EQ(sender_shared_secret, receiver_shared_secret);

  // Decode the public keys of both parties, the auth secret and the salt.
  std::string recipient_public_key, sender_public_key, auth_secret, salt;
  ASSERT_TRUE(base::Base64UrlDecode(kRecipientPublicKeyUncompressed,
                                    base::Base64UrlDecodePolicy::IGNORE_PADDING,
                                    &recipient_public_key));
  ASSERT_TRUE(base::Base64UrlDecode(kSenderPublicKeyUncompressed,
                                    base::Base64UrlDecodePolicy::IGNORE_PADDING,
                                    &sender_public_key));
  ASSERT_TRUE(base::Base64UrlDecode(
      kAuthSecret, base::Base64UrlDecodePolicy::IGNORE_PADDING, &auth_secret));
  ASSERT_TRUE(base::Base64UrlDecode(
        kSalt, base::Base64UrlDecodePolicy::IGNORE_PADDING, &salt));

  std::string encoded_ciphertext, ciphertext, plaintext;
  size_t record_size = 0;

  // Now verify that encrypting a message with the given information yields the
  // expected ciphertext given the defined input.
  GCMMessageCryptographer cryptographer(
      GCMMessageCryptographer::Version::DRAFT_03);

  ASSERT_TRUE(cryptographer.Encrypt(recipient_public_key, sender_public_key,
                                    sender_shared_secret, auth_secret, salt,
                                    kPlaintext, &record_size, &ciphertext));

  base::Base64UrlEncode(ciphertext, base::Base64UrlEncodePolicy::OMIT_PADDING,
                        &encoded_ciphertext);
  ASSERT_EQ(kCiphertext, encoded_ciphertext);

  // And verify that decrypting the message yields the plaintext again.
  ASSERT_TRUE(cryptographer.Decrypt(recipient_public_key, sender_public_key,
                                    sender_shared_secret, auth_secret, salt,
                                    ciphertext, record_size, &plaintext));

  ASSERT_EQ(kPlaintext, plaintext);
}

}  // namespace gcm