leog/route.ts

The following piece of code works for me, however with some drawbacks:

import { NextResponse } from "next/server"
import type { NextRequest } from "next/server"
import { cookies } from "next/headers"
import { auth } from "../../../auth"
import { createHash } from "crypto";

export async function GET(request: NextRequest) {
     // check existing session to avoid redirecting to signin unnecessarily
    const { searchParams } = request.nextUrl;
    const referer = searchParams.get('redirect_uri'); 
    const session = await auth();
    if (session) return NextResponse.redirect(referer ?? '/');
        
    // getting cookies name in case we are in a secure environment
    const cookieStore = cookies()
    let csrfToken = cookieStore.get("authjs.csrf-token")?.value;
    const callbackUrl = referer //cookieStore.get("auth.callback-url")?.value;

    if (!csrfToken) {
        const csrfApiResponse = await fetch(`${process.env.AUTH_URL}/api/auth/csrf`).then((res) => res.json())
        console.log(`CsrfToken fetched: ${csrfApiResponse.csrfToken}`)
        csrfToken = csrfApiResponse.csrfToken
    }

    //Calculate csrfTokenHash
    const csrfTokenHash = createHash("sha256")
        .update(`${csrfToken}${process.env.AUTH_SECRET}`)
        .digest("hex");

    //Custom POST signin request
    const fetchRequest: RequestInit = {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
            'Cookie': `authjs.csrf-token=${csrfToken}|${csrfTokenHash};auth.callback-url=${callbackUrl}`
        },
        body: JSON.stringify({
            csrfToken: csrfToken?.split("|")[0],
            callbackUrl
        }),
        credentials: 'same-origin'
    };
    const fetchSignIn = await fetch(`${process.env.AUTH_URL}/api/auth/signin/[YOUR_PROVIDER]`, fetchRequest);

    return NextResponse.redirect(fetchSignIn.url ?? "/");
}

The drawbacks are:

• checks must set to none
• redirect_uri it seems it does not work properly