phantom sign-in with solana (server side issue)

[s-bilic]

Summary

Hi, I am trying out the new SIWS (https://github.com/phantom/sign-in-with-solana) in my next.js (app) application.
I followed the instructions/documentation. I got stuck at the last part verifying using the verifySIWS function.

I am posting the data to my nextjs API route (see below), it seems like 'output' is always empty, so the response will always return false. And for some reason 'input' actually does show the input data.

When I try to verify it without the server side, it works just fine. But I need it for the server side in my use case.

Not sure what the problem is, maybe I overlooked something?

Example

No response

Steps to Reproduce

const autoSignIn = useCallback(async (adapter: Adapter) => {
   // If the signIn feature is not available, return true
   if (!("signIn" in adapter)) return true;

   // Fetch the signInInput from the backend
   const createResponse = await fetch("api/sign");

   const input: SolanaSignInInput = await createResponse.json();

   // Send the signInInput to the wallet and trigger a sign-in request
   const output = await adapter.signIn(input);
   console.log(output);

   // Verify the sign-in output against the generated input server-side
   let strPayload = JSON.stringify({ input, output });
   const verifyResponse = await fetch("api/verify", {
     method: "POST",
     body: strPayload,
   });
   const success = await verifyResponse.json();

   // If verification fails, throw an error
   if (!success) throw new Error("Sign In verification failed!");

   return false;
 }, []);

// api/verify
import { NextResponse, NextRequest } from "next/server";
// function from the documentation
import { verifySIWS } from "@/components/verifySIWS";

export async function POST(req: NextRequest) {
  // input is empty data here for some reason
  const { input, output } = await req.json();

  const data = verifySIWS(input, output);

  return NextResponse.json(data);
}

empty data respone from 'output' on server side
{
account: { publicKey: Uint8Array(0) [] },
signature: Uint8Array(0) [],
signedMessage: Uint8Array(0) []
}

Phantom Version

23.13.1

Is there an existing discussion for this?

• I have searched the existing discussions

[s-bilic]

UPDATE:

Managed to solve the issue by scrolling through other discussions:
https://github.com/orgs/phantom/discussions/94#discussioncomment-7017833

1. The output object needs to be formatted first with Array.from() on the client side
2. When received on the server side you: reformat it back to a Uint8Array: