Updating D2D protocol to v1 to support separate sequence numbers.

components/cryptauth/device_to_device_initiator_operations.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/cryptauth/device_to_device_initiator_operations.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
+#include "base/memory/ptr_util.h"
 #include "components/cryptauth/proto/cryptauth_api.pb.h"
 #include "components/cryptauth/proto/securemessage.pb.h"
 #include "components/cryptauth/secure_message_delegate.h"
+#include "components/cryptauth/session_keys.h"
 #include "components/proximity_auth/logging/logging.h"
 
 namespace cryptauth {
 
 namespace {
 
 // TODO(tengs): Due to a bug with the ChromeOS secure message daemon, we cannot
 // create SecureMessages with empty payloads. To workaround this bug, this value
 // is put into the payload if it would otherwise be empty.
 // See crbug.com/512894.
 const char kPayloadFiller[] = "\xae";
 
 // The version to put in the GcmMetadata field.
 const int kGcmMetadataVersion = 1;
 
+// The D2D protocol version.
+const int kD2DProtocolVersion = 1;
+
 // Callback for DeviceToDeviceInitiatorOperations::CreateInitiatorAuthMessage(),
 // after the inner message is created.
 void OnInnerMessageCreatedForInitiatorAuth(
-    const std::string& session_symmetric_key,
+    SessionKeys* session_keys,

[Tim Song, 2017/05/22 23:18:24]

I would just take the initiator_encode_key() here.

[sacomoto, 2017/05/23 09:50:13]

Done.

     SecureMessageDelegate* secure_message_delegate,
     const DeviceToDeviceInitiatorOperations::MessageCallback& callback,
     const std::string& inner_message) {
   if (inner_message.empty()) {
     PA_LOG(INFO) << "Failed to create inner message for [Initiator Auth].";
     callback.Run(std::string());
     return;
   }
 
   GcmMetadata gcm_metadata;
   gcm_metadata.set_type(DEVICE_TO_DEVICE_MESSAGE);
   gcm_metadata.set_version(kGcmMetadataVersion);
 
   // Store the inner message inside a DeviceToDeviceMessage proto.
   securemessage::DeviceToDeviceMessage device_to_device_message;
   device_to_device_message.set_message(inner_message);
-  device_to_device_message.set_sequence_number(2);
+  device_to_device_message.set_sequence_number(1);
 
   // Create and return the outer message, which wraps the inner message.
   SecureMessageDelegate::CreateOptions create_options;
   create_options.encryption_scheme = securemessage::AES_256_CBC;
   create_options.signature_scheme = securemessage::HMAC_SHA256;
   gcm_metadata.SerializeToString(&create_options.public_metadata);
   secure_message_delegate->CreateSecureMessage(
-      device_to_device_message.SerializeAsString(), session_symmetric_key,
-      create_options, callback);
+      device_to_device_message.SerializeAsString(),
+      session_keys->initiator_encode_key(), create_options, callback);
 }
 
 // Helper struct containing all the context needed to validate the
 // [Responder Auth] message.
 struct ValidateResponderAuthMessageContext {
   std::string responder_auth_message;
   std::string persistent_responder_public_key;
   std::string persistent_symmetric_key;
   std::string session_private_key;
   std::string hello_message;
@@ skipping 27 matching lines @@
 
 // Begins the [Responder Auth] validation flow by validating the header.
 void BeginResponderAuthValidation(ValidateResponderAuthMessageContext context) {
   // Parse the encrypted SecureMessage so we can get plaintext data from the
   // header. Note that the payload will be encrypted.
   securemessage::SecureMessage encrypted_message;
   securemessage::HeaderAndBody header_and_body;
   if (!encrypted_message.ParseFromString(context.responder_auth_message) ||
       !header_and_body.ParseFromString(encrypted_message.header_and_body())) {
     PA_LOG(WARNING) << "Failed to parse [Responder Hello] message";
-    context.callback.Run(false, std::string());
+    context.callback.Run(false, nullptr);
     return;
   }
 
   // Check that header public_metadata contains the correct metadata fields.
   securemessage::Header header = header_and_body.header();
   GcmMetadata gcm_metadata;
   if (!gcm_metadata.ParseFromString(header.public_metadata()) ||
       gcm_metadata.type() !=
           DEVICE_TO_DEVICE_RESPONDER_HELLO_PAYLOAD ||
       gcm_metadata.version() != kGcmMetadataVersion) {
     PA_LOG(WARNING) << "Failed to validate GcmMetadata in "
                     << "[Responder Auth] header.";
-    context.callback.Run(false, std::string());
+    context.callback.Run(false, nullptr);
     return;
   }
 
   // Extract responder session public key from |decryption_key_id| field.
   securemessage::ResponderHello responder_hello;
   if (!responder_hello.ParseFromString(header.decryption_key_id()) ||
       !responder_hello.public_dh_key().SerializeToString(
           &context.responder_session_public_key)) {
     PA_LOG(INFO) << "Failed to extract responder session public key in "
                  << "[Responder Auth] header.";
-    context.callback.Run(false, std::string());
+    context.callback.Run(false, nullptr);
     return;
   }
 
   // Perform a Diffie-Helmann key exchange to get the session symmetric key.
   context.secure_message_delegate->DeriveKey(
       context.session_private_key, context.responder_session_public_key,
       base::Bind(&OnSessionSymmetricKeyDerived, context));
 }
 
 // Called after the session symmetric key is derived, so now we can unwrap the
 // outer message of [Responder Auth].
 void OnSessionSymmetricKeyDerived(ValidateResponderAuthMessageContext context,
                                   const std::string& session_symmetric_key) {
   context.session_symmetric_key = session_symmetric_key;
 
   // Unwrap the outer message, using symmetric key encryption and signature.
   SecureMessageDelegate::UnwrapOptions unwrap_options;
   unwrap_options.encryption_scheme = securemessage::AES_256_CBC;
   unwrap_options.signature_scheme = securemessage::HMAC_SHA256;
   context.secure_message_delegate->UnwrapSecureMessage(
-      context.responder_auth_message, session_symmetric_key, unwrap_options,
+      context.responder_auth_message,
+      SessionKeys(session_symmetric_key).responder_encode_key(), unwrap_options,
       base::Bind(&OnOuterMessageUnwrappedForResponderAuth, context));
 }
 
 // Called after the outer-most layer of [Responder Auth] is unwrapped.
 void OnOuterMessageUnwrappedForResponderAuth(
     const ValidateResponderAuthMessageContext& context,
     bool verified,
     const std::string& payload,
     const securemessage::Header& header) {
   if (!verified) {
     PA_LOG(INFO) << "Failed to unwrap outer [Responder Auth] message.";
-    context.callback.Run(false, std::string());
+    context.callback.Run(false, nullptr);
     return;
   }
 
   // Parse the decrypted payload.
   securemessage::DeviceToDeviceMessage device_to_device_message;
   if (!device_to_device_message.ParseFromString(payload) ||
       device_to_device_message.sequence_number() != 1) {
     PA_LOG(INFO) << "Failed to validate DeviceToDeviceMessage payload.";
-    context.callback.Run(false, std::string());
+    context.callback.Run(false, nullptr);
     return;
   }
 
   // Unwrap the middle level SecureMessage, using symmetric key encryption and
   // signature.
   SecureMessageDelegate::UnwrapOptions unwrap_options;
   unwrap_options.encryption_scheme = securemessage::AES_256_CBC;
   unwrap_options.signature_scheme = securemessage::HMAC_SHA256;
   unwrap_options.associated_data = context.hello_message;
   context.secure_message_delegate->UnwrapSecureMessage(
       device_to_device_message.message(), context.persistent_symmetric_key,
       unwrap_options,
       base::Bind(&OnMiddleMessageUnwrappedForResponderAuth, context));
 }
 
 // Called after the middle layer of [Responder Auth] is unwrapped.
 void OnMiddleMessageUnwrappedForResponderAuth(
     const ValidateResponderAuthMessageContext& context,
     bool verified,
     const std::string& payload,
     const securemessage::Header& header) {
   if (!verified) {
     PA_LOG(INFO) << "Failed to unwrap middle [Responder Auth] message.";
-    context.callback.Run(false, std::string());
+    context.callback.Run(false, nullptr);
     return;
   }
 
   // Unwrap the inner-most SecureMessage, using no encryption and an asymmetric
   // key signature.
   SecureMessageDelegate::UnwrapOptions unwrap_options;
   unwrap_options.encryption_scheme = securemessage::NONE;
   unwrap_options.signature_scheme = securemessage::ECDSA_P256_SHA256;
   unwrap_options.associated_data = context.hello_message;
   context.secure_message_delegate->UnwrapSecureMessage(
@@ skipping 10 matching lines @@
   if (!verified)
     PA_LOG(INFO) << "Failed to unwrap inner [Responder Auth] message.";
 
   // Note: The GMS Core implementation does not properly set the metadata
   // version, so we only check that the type is UNLOCK_KEY_SIGNED_CHALLENGE.
   GcmMetadata gcm_metadata;
   if (!gcm_metadata.ParseFromString(header.public_metadata()) ||
       gcm_metadata.type() != UNLOCK_KEY_SIGNED_CHALLENGE) {
     PA_LOG(WARNING) << "Failed to validate GcmMetadata in inner-most "
                     << "[Responder Auth] message.";
-    context.callback.Run(false, std::string());
+    context.callback.Run(false, nullptr);
     return;
   }
 
-  context.callback.Run(verified, context.session_symmetric_key);
+  context.callback.Run(
+      verified, base::MakeUnique<SessionKeys>(context.session_symmetric_key));
 }
 
 }  // namespace
 
 // static
 void DeviceToDeviceInitiatorOperations::CreateHelloMessage(
     const std::string& session_public_key,
     const std::string& persistent_symmetric_key,
     SecureMessageDelegate* secure_message_delegate,
     const MessageCallback& callback) {
   // Decode public key into the |initator_hello| proto.
-  securemessage::InitiatorHello initator_hello;
-  if (!initator_hello.mutable_public_dh_key()->ParseFromString(
+  securemessage::InitiatorHello initiator_hello;
+  if (!initiator_hello.mutable_public_dh_key()->ParseFromString(
           session_public_key)) {
     PA_LOG(ERROR) << "Unable to parse user's public key";
     callback.Run(std::string());
     return;
   }
+  initiator_hello.set_protocol_version(kD2DProtocolVersion);
 
   // The [Hello] message has the structure:
   // {
   //   header: <session_public_key>,
   //           Sig(<session_public_key>, persistent_symmetric_key)
   //   payload: ""
   // }
   SecureMessageDelegate::CreateOptions create_options;
   create_options.encryption_scheme = securemessage::NONE;
   create_options.signature_scheme = securemessage::HMAC_SHA256;
-  initator_hello.SerializeToString(&create_options.public_metadata);
+  initiator_hello.SerializeToString(&create_options.public_metadata);
   secure_message_delegate->CreateSecureMessage(
       kPayloadFiller, persistent_symmetric_key, create_options, callback);
 }
 
 // static
 void DeviceToDeviceInitiatorOperations::ValidateResponderAuthMessage(
     const std::string& responder_auth_message,
     const std::string& persistent_responder_public_key,
     const std::string& persistent_symmetric_key,
     const std::string& session_private_key,
@@ skipping 23 matching lines @@
       persistent_symmetric_key,
       session_private_key,
       hello_message,
       secure_message_delegate,
       callback};
   BeginResponderAuthValidation(context);
 }
 
 // static
 void DeviceToDeviceInitiatorOperations::CreateInitiatorAuthMessage(
-    const std::string& session_symmetric_key,
+    SessionKeys* session_keys,

[Tim Song, 2017/05/22 23:18:24]

And down here, we can then make this argument "const SessionKeys&" instead, so
we don't have to keep a raw pointer around.

[sacomoto, 2017/05/23 09:50:13]

Done.

     const std::string& persistent_symmetric_key,
     const std::string& responder_auth_message,
     SecureMessageDelegate* secure_message_delegate,
     const MessageCallback& callback) {
   // The [Initiator Auth] message has the structure:
   // {
   //   header: Sig(payload1, session_symmetric_key)
   //   payload1: Enc({
   //     sequence_number: 2,
   //     body: {
   //       header: Sig(payload2 + responder_auth_message,
   //                   persistent_symmetric_key)
   //       payload2: ""
   //     }
   //   }, session_symmetric_key)
   // }
   SecureMessageDelegate::CreateOptions create_options;
   create_options.encryption_scheme = securemessage::AES_256_CBC;
   create_options.signature_scheme = securemessage::HMAC_SHA256;
   create_options.associated_data = responder_auth_message;
   secure_message_delegate->CreateSecureMessage(
       kPayloadFiller, persistent_symmetric_key, create_options,
-      base::Bind(&OnInnerMessageCreatedForInitiatorAuth, session_symmetric_key,
+      base::Bind(&OnInnerMessageCreatedForInitiatorAuth, session_keys,
                  secure_message_delegate, callback));
 }
 
 }  // cryptauth