AB#2432: Check for unsupported eclient import

[Nirusu]

Proposed changes

• Check based on ELF sections whether github.com/edgelesssys/ego/eclient was imported on sign or run
• Redirect user to github.com/edgelesssys/ego/enclave instead
• Move some other ELF functions both used by sign.go & bundle.go to elf.go & elf_test.go

The unit test is a bit heavy since it needs a go.mod & go.sum to function. Not sure whether we want to keep it as is or if there is a sleeker way.

Related issue

• AskForHelp: Can not run ego sign #138
• Discord support requests

[Nirusu]

Moved it from unit tests to integration tests.
However, my bash foo is not quite there to show the executed command with the pipe in there.

I would expect to show this in the output:
run test: ego sign unsupported-import |& grep "unsupported import"

But it's dropped. Any idea how to do handle this properly in bash?

[thomasten]

I'd guess that it cannot be done with our run function. But I'm not a bash expert either, so this is not a definite answer.
However, the test itself works and the output is meaningful enough for me.

[Nirusu]

Okay, I'll just keep it this way then.

I also had the idea that since we already have custom Open Enclave / Edgeless RT error handling for more user friendly error handling that we can also put everything in the same function handleErr(err). This should make everything a bit cleaner in terms of code and more consistent in terms of user output.

Only thing I am not super happy is that the

if err != nil {
   return err
}
return nil

block in sign.go is kinda pointless, but changing it to just

return err

is inconsistent with the other functions, even though it effectively also returns nil in case no error occurred.

Not sure what is the cleaner way here.

[thomasten]

LGTM. I have a slight preference for return err, but please do as you prefer.

[Nirusu]

I'll make it return err with a small comment next to it (in case it's not obvious).