Teach the GCM Driver how to decrypt incoming messages.

components/gcm_driver/crypto/gcm_encryption_provider_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_encryption_provider.h"
+
+#include <sstream>
+#include <string>
+
+#include "base/base64.h"
+#include "base/bind.h"
+#include "base/files/scoped_temp_dir.h"
+#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "components/gcm_driver/common/gcm_messages.h"
+#include "components/gcm_driver/crypto/gcm_key_store.h"
+#include "components/gcm_driver/crypto/gcm_message_cryptographer.h"
+#include "crypto/curve25519.h"
+#include "crypto/random.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace gcm {
+namespace {
+
+const char kExampleAppId[] = "my-app-id";
+const char kExampleMessage[] = "Hello, world, this is the GCM Driver!";
+
+const char kValidEncryptionHeader[] =
+    "keyid=foo;salt=MTIzNDU2Nzg5MDEyMzQ1Ng;rs=1024";
+const char kInvalidEncryptionHeader[] = "keyid";
+
+const char kValidEncryptionKeyHeader[] =
+    "keyid=foo;dh=NjU0MzIxMDk4NzY1NDMyMTEyMzQ1Njc4OTAxMjM0NTY";
+const char kInvalidEncryptionKeyHeader[] = "keyid";
+
+// TODO(peter): Unify the Base64Url implementations. https://crbug.com/536745.
+void Base64UrlEncode(const std::string& decoded_input,
+                     std::string* encoded_output) {
+  base::Base64Encode(decoded_input, encoded_output);
+  base::ReplaceChars(*encoded_output, "+", "-", encoded_output);
+  base::ReplaceChars(*encoded_output, "/", "_", encoded_output);
+}
+
+}  // namespace
+
+class GCMEncryptionProviderTest : public ::testing::Test {
+ public:
+  void SetUp() override {
+    ASSERT_TRUE(scoped_temp_dir_.CreateUniqueTempDir());
+
+    encryption_provider_.reset(new GCMEncryptionProvider);
+    encryption_provider_->Init(scoped_temp_dir_.path(),
+                               message_loop_.task_runner());
+  }
+
+  void TearDown() override {
+    encryption_provider_.reset();
+
+    // |encryption_provider_| owns a ProtoDatabaseImpl whose destructor deletes
+    // the underlying LevelDB database on the task runner.
+    base::RunLoop().RunUntilIdle();
+  }
+
+  // To be used as a callback for GCMEncryptionProvider::GetPublicKey().
+  void DidGetPublicKey(std::string* key_out, const std::string& key) {
+    *key_out = key;
+  }
+
+  // To be used as a callback for GCMKeyStore::CreateKeys().
+  void DidCreateKeys(KeyPair* pair_out, const KeyPair& pair) {
+    *pair_out = pair;
+  }
+
+ protected:
+  // Tri-state enumaration listing whether the decryption operation is idle
+  // (hasn't started yet), succeeded or failed.
+  enum DecryptionResult {
+    DECRYPTION_IDLE,
+    DECRYPTION_SUCCEEDED,
+    DECRYPTION_FAILED
+  };
+
+  // Decrypts the |message| and then synchronously waits until either the
+  // success or failure callbacks has been invoked.
+  void Decrypt(const IncomingMessage& message) {
+    decryption_result_ = DECRYPTION_IDLE;
+    encryption_provider_->DecryptMessage(
+        kExampleAppId, message,
+        base::Bind(&GCMEncryptionProviderTest::OnDecryptionSucceeded,
+                   base::Unretained(this)),
+        base::Bind(&GCMEncryptionProviderTest::OnDecryptionFailed,
+                   base::Unretained(this)));
+
+    // The encryption keys will be read asynchronously.
+    base::RunLoop().RunUntilIdle();
+
+    ASSERT_NE(decryption_result_, DECRYPTION_IDLE);
+  }
+
+  DecryptionResult decryption_result() { return decryption_result_; }
+
+  const IncomingMessage& decrypted_message() { return decrypted_message_; }
+
+  GCMEncryptionProvider::DecryptionFailure failure_reason() {
+    return failure_reason_;
+  }
+
+  GCMEncryptionProvider* encryption_provider() {
+    return encryption_provider_.get();
+  }
+
+ private:
+  void OnDecryptionSucceeded(const IncomingMessage& message) {
+    decryption_result_ = DECRYPTION_SUCCEEDED;
+    decrypted_message_ = message;
+  }
+
+  void OnDecryptionFailed(GCMEncryptionProvider::DecryptionFailure reason) {
+    decryption_result_ = DECRYPTION_FAILED;
+    failure_reason_ = reason;
+  }
+
+  base::MessageLoop message_loop_;
+  base::ScopedTempDir scoped_temp_dir_;
+
+  scoped_ptr<GCMEncryptionProvider> encryption_provider_;
+
+  DecryptionResult decryption_result_ = DECRYPTION_IDLE;
+  GCMEncryptionProvider::DecryptionFailure failure_reason_ =
+      GCMEncryptionProvider::DECRYPTION_FAILURE_UNKNOWN;
+
+  IncomingMessage decrypted_message_;
+};
+
+TEST_F(GCMEncryptionProviderTest, IsEncryptedMessage) {
+  // Both the Encryption and Encryption-Key headers must be present, and the raw
+  // data must be non-empty for a message to be considered encrypted.
+
+  IncomingMessage empty_message;
+  EXPECT_FALSE(encryption_provider()->IsEncryptedMessage(empty_message));
+
+  IncomingMessage single_header_message;
+  single_header_message.data["encryption"] = "";
+  EXPECT_FALSE(encryption_provider()->IsEncryptedMessage(
+                   single_header_message));
+
+  IncomingMessage double_header_message;
+  double_header_message.data["encryption"] = "";
+  double_header_message.data["encryption_key"] = "";
+  EXPECT_FALSE(encryption_provider()->IsEncryptedMessage(
+                   double_header_message));
+
+  IncomingMessage double_header_with_data_message;
+  double_header_with_data_message.data["encryption"] = "";
+  double_header_with_data_message.data["encryption_key"] = "";
+  double_header_with_data_message.raw_data = "foo";
+  EXPECT_TRUE(encryption_provider()->IsEncryptedMessage(
+                  double_header_with_data_message));
+}
+
+TEST_F(GCMEncryptionProviderTest, VerifiesEncryptionHeaderParsing) {
+  // The Encryption header must be parsable and contain valid values.
+  // Note that this is more extensively tested in EncryptionHeaderParsersTest.
+
+  IncomingMessage invalid_message;
+  invalid_message.data["encryption"] = kInvalidEncryptionHeader;
+  invalid_message.data["encryption_key"] = kValidEncryptionKeyHeader;
+
+  ASSERT_NO_FATAL_FAILURE(Decrypt(invalid_message));
+  ASSERT_EQ(DECRYPTION_FAILED, decryption_result());
+  EXPECT_EQ(GCMEncryptionProvider::DECRYPTION_FAILURE_INVALID_ENCRYPTION_HEADER,
+            failure_reason());
+
+  IncomingMessage valid_message;
+  valid_message.data["encryption"] = kValidEncryptionHeader;
+  valid_message.data["encryption_key"] = kInvalidEncryptionKeyHeader;
+
+  ASSERT_NO_FATAL_FAILURE(Decrypt(valid_message));
+  ASSERT_EQ(DECRYPTION_FAILED, decryption_result());
+  EXPECT_NE(GCMEncryptionProvider::DECRYPTION_FAILURE_INVALID_ENCRYPTION_HEADER,
+            failure_reason());
+}
+
+TEST_F(GCMEncryptionProviderTest, VerifiesEncryptionKeyHeaderParsing) {
+  // The Encryption-Key header must be parsable and contain valid values.
+  // Note that this is more extensively tested in EncryptionHeaderParsersTest.
+
+  IncomingMessage invalid_message;
+  invalid_message.data["encryption"] = kValidEncryptionHeader;
+  invalid_message.data["encryption_key"] = kInvalidEncryptionKeyHeader;
+
+  ASSERT_NO_FATAL_FAILURE(Decrypt(invalid_message));
+  ASSERT_EQ(DECRYPTION_FAILED, decryption_result());
+  EXPECT_EQ(
+      GCMEncryptionProvider::DECRYPTION_FAILURE_INVALID_ENCRYPTION_KEY_HEADER,
+      failure_reason());
+
+  IncomingMessage valid_message;
+  valid_message.data["encryption"] = kInvalidEncryptionHeader;
+  valid_message.data["encryption_key"] = kValidEncryptionKeyHeader;
+
+  ASSERT_NO_FATAL_FAILURE(Decrypt(valid_message));
+  ASSERT_EQ(DECRYPTION_FAILED, decryption_result());
+  EXPECT_NE(
+      GCMEncryptionProvider::DECRYPTION_FAILURE_INVALID_ENCRYPTION_KEY_HEADER,
+      failure_reason());
+}
+
+TEST_F(GCMEncryptionProviderTest, VerifiesExistingKeys) {
+  // When both headers are valid, the encryption keys still must be known to
+  // the GCM key store before the message can be decrypted.
+
+  IncomingMessage message;
+  message.data["encryption"] = kValidEncryptionHeader;
+  message.data["encryption_key"] = kValidEncryptionKeyHeader;
+
+  ASSERT_NO_FATAL_FAILURE(Decrypt(message));
+  ASSERT_EQ(DECRYPTION_FAILED, decryption_result());
+  EXPECT_EQ(GCMEncryptionProvider::DECRYPTION_FAILURE_NO_KEYS,
+            failure_reason());
+
+  std::string public_key;
+  encryption_provider()->GetPublicKey(
+      kExampleAppId,
+      base::Bind(&GCMEncryptionProviderTest::DidGetPublicKey,
+                 base::Unretained(this), &public_key));
+
+  // Getting (or creating) the public key will be done asynchronously.
+  base::RunLoop().RunUntilIdle();
+
+  ASSERT_EQ(crypto::curve25519::kBytes, public_key.size());
+
+  ASSERT_NO_FATAL_FAILURE(Decrypt(message));
+  ASSERT_EQ(DECRYPTION_FAILED, decryption_result());
+  EXPECT_NE(GCMEncryptionProvider::DECRYPTION_FAILURE_NO_KEYS,
+            failure_reason());
+}
+
+TEST_F(GCMEncryptionProviderTest, EncryptionRoundTrip) {
+  // Performs a full round-trip of the encryption feature, including getting a
+  // public/private key-pair and performing the cryptographic operations. This
+  // is more of an integration test than a unit test.
+
+  KeyPair pair;
+  KeyPair server_pair;
+
+  // Retrieve the public/private key-pair immediately from the key store, given
+  // that the GCMEncryptionProvider will only share the public key with users.
+  // Also create a second pair, which will act as the server's keys.
+  encryption_provider()->key_store_->CreateKeys(
+      kExampleAppId,
+      base::Bind(&GCMEncryptionProviderTest::DidCreateKeys,
+                 base::Unretained(this), &pair));
+
+  encryption_provider()->key_store_->CreateKeys(
+      std::string(kExampleAppId) + "-server",
+      base::Bind(&GCMEncryptionProviderTest::DidCreateKeys,
+                 base::Unretained(this), &server_pair));
+
+  // Creating the public keys will be done asynchronously.
+  base::RunLoop().RunUntilIdle();
+
+  ASSERT_EQ(crypto::curve25519::kScalarBytes, pair.private_key().size());
+  ASSERT_EQ(crypto::curve25519::kBytes, pair.public_key().size());
+
+  ASSERT_EQ(crypto::curve25519::kScalarBytes, server_pair.private_key().size());
+  ASSERT_EQ(crypto::curve25519::kBytes, server_pair.public_key().size());
+
+  std::string salt;
+
+  // Creates a cryptographically secure salt of |salt_size| octets in size, and
+  // calculate the shared secret for the message.
+  crypto::RandBytes(base::WriteInto(&salt, 16 + 1), 16);
+
+  uint8_t shared_key[crypto::curve25519::kBytes];
+  crypto::curve25519::ScalarMult(
+      reinterpret_cast<const unsigned char*>(server_pair.private_key().data()),
+      reinterpret_cast<const unsigned char*>(pair.public_key().data()),
+      shared_key);
+
+  base::StringPiece shared_key_string_piece(
+      reinterpret_cast<char*>(shared_key), crypto::curve25519::kBytes);
+
+  IncomingMessage message;
+  size_t record_size;
+
+  // Encrypts the |kExampleMessage| using the generated shared key and the
+  // random |salt|, storing the result in |record_size| and the message.
+  GCMMessageCryptographer cryptographer;
+  ASSERT_TRUE(cryptographer.Encrypt(kExampleMessage, shared_key_string_piece,
+                                    salt, &record_size, &message.raw_data));
+
+  std::string encoded_salt, encoded_key;
+
+  // Compile the incoming GCM message, including the required headers.
+  Base64UrlEncode(salt, &encoded_salt);
+  Base64UrlEncode(server_pair.public_key(), &encoded_key);
+
+  std::stringstream encryption_header;
+  encryption_header << "rs=" << base::SizeTToString(record_size) << ";";
+  encryption_header << "salt=" << encoded_salt;
+
+  message.data["encryption"] = encryption_header.str();
+  message.data["encryption_key"] = "dh=" + encoded_key;
+
+  ASSERT_TRUE(encryption_provider()->IsEncryptedMessage(message));
+
+  // Decrypt the message, and expect everything to go wonderfully well.
+  ASSERT_NO_FATAL_FAILURE(Decrypt(message));
+  ASSERT_EQ(DECRYPTION_SUCCEEDED, decryption_result());
+
+  EXPECT_TRUE(decrypted_message().decrypted);
+  EXPECT_EQ(kExampleMessage, decrypted_message().raw_data);
+}
+
+}  // namespace gcm