Do a better job at faking simple challenge signatures.

chromeos/dbus/fake_cryptohome_client.h

Index: chromeos/dbus/fake_cryptohome_client.h
diff --git a/chromeos/dbus/fake_cryptohome_client.h b/chromeos/dbus/fake_cryptohome_client.h
index 02dece263f323ff5a71e36b183925ef21a9d9f0b..d6f1bd162d2fe6a3f6180009437028baf862d434 100644
--- a/chromeos/dbus/fake_cryptohome_client.h
+++ b/chromeos/dbus/fake_cryptohome_client.h
@@ -214,18 +214,29 @@ class CHROMEOS_EXPORT FakeCryptohomeClient : public CryptohomeClient {
   // format used by SystemSaltGetter::ConvertRawSaltToHexString()).
   static std::vector<uint8_t> GetStubSystemSalt();
 
+  // Signature nonces are twenty bytes. This matches the attestation code.
+  static const std::string kTwentyBytesNonce;
+  // Something symbolic as a signature.
+  static const std::string kSignature;

[Darren Krahn, 2016/09/02 17:32:12]

These constants can go in the cc file in an anonymous namespace (and then drop
the 'static'). Also, make these POD type.

https://engdoc.corp.google.com/eng/doc/devguide/cpp/styleguide.shtml?cl=head#...

[The one and only Dr. Crash, 2016/09/03 01:17:37]

Thanks for the pointer. And to think these were POD until Patchset 3 where I
thought I should promote them to std::string. I will also move them back to the
.cc file and have the unit tests only check for what matters, e.g. that the
original data is before the nonce and that the nonce is 20 bytes long (just to
avoid hard to debug issues later for those who hardcode 20 byes like our DM
server).

+
  private:
   void ReturnProtobufMethodCallback(
       const cryptohome::BaseReply& reply,
       const ProtobufMethodCallback& callback);
 
   // Posts tasks which return fake results to the UI thread.
-  void ReturnAsyncMethodResult(const AsyncMethodCallback& callback,
-                               bool returns_data);
+  void ReturnAsyncMethodResult(const AsyncMethodCallback& callback);
+
+  // Posts tasks which return fake data to the UI thread.
+  void ReturnAsyncMethodData(const AsyncMethodCallback& callback,
+                             const std::string& data);
+
+  // This method is used to implement ReturnAsyncMethodResult without data.
+  void ReturnAsyncMethodResultInternal(const AsyncMethodCallback& callback);
 
-  // This method is used to implement ReturnAsyncMethodResult.
-  void ReturnAsyncMethodResultInternal(const AsyncMethodCallback& callback,
-                                       bool returns_data);
+  // This method is used to implement ReturnAsyncMethodResult with data.
+  void ReturnAsyncMethodDataInternal(const AsyncMethodCallback& callback,
+                                     const std::string& data);
 
   bool service_is_available_;
   int async_call_id_;