NIO: example for using secure connection (cert from string, adding metadata)

[ealymbaev]

Question Checklist

• Updated grpc-swift to the latest version
• I read the Contribution Guidelines
• I read README
• I searched for existing GitHub issues (especially, there are many resolved issues related to SSL)

Question Description

I am trying to use new nio branch of grpc-swift repo for communicating with LND and have encountered several issues:

• I could not find a way to set TLS certificate from a string (not from file). Apple Nio SSL has NIOSSLCertificate class, but is is able to init with file path and byte array only. In old implementation of grpc-swift we could init client with certificates string argument.

• In old implementation of grpc-swift I could also set Metadata to connection. I need it to set macaroons headers for authentication. In new nio branch I could not find a way to set metadata.

It would be great if you could provide some examples for setting options described above.

[glbrntt]

• I could not find a way to set TLS certificate from a string (not from file). Apple Nio SSL has NIOSSLCertificate class, but is is able to init with file path and byte array only. In old implementation of grpc-swift we could init client with certificates string argument.

You can use the bytes initializer for NIOSSLCertificate by taking the utf8 view of the string to get the bytes:

let certificateString: String = ...
let certificateBytes: [UInt8] = Array(certificateString.utf8)
let certificate = try NIOSSLCertificate(bytes: certificateBytes, ...)

• In old implementation of grpc-swift I could also set Metadata to connection. I need it to set macaroons headers for authentication. In new nio branch I could not find a way to set metadata.

The NaturalLanguage example shows how set metadata here. Note that you can set default callOptions on a generated clien, i.e. SomeGeneratedClient(connection: connection, defaultCallOptions: callOptions) or at the RPC level (as in the example).

I agree that we need to pad out the documentation here though.

[ealymbaev]

Thank you for your response. We were able to connect using NIO branch. The only issue left is that IP address host does not work yet, but we have created a PR:

#702