OpenID unable to get ID_token in .Net Core - .net-core

Question

I am using OpenID to get ID_token/ accesstoken. The problem is in OpenID workflow I am able to get authorization code from identity server but next step is to use the authorisation code and call the oauth/token endpoint to get the access token.
In order to call the Oauth/token endpoint , I need to pass the client ID and client secret as Request header(basic authentication) but it is getting passed in the request body, how do I get to pass it in the header instead of request body??
Here is the sample code from Startup.cs (.Net core 3.1)
public void ConfigureServices(IServiceCollection services)
{
services.AddAuthentication(options =>
{
options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
options.DefaultChallengeScheme = CookieAuthenticationDefaults.AuthenticationScheme;
})
.AddCookie(options =>
{
options.Events = new CookieAuthenticationEvents()
{
OnSigningIn = async context =>
{
var scheme = context.Properties.Items.Where(k => k.Key == ".AuthScheme").FirstOrDefault();
var claim = new Claim(scheme.Key, scheme.Value);
var claimsIdentity = context.Principal.Identity as ClaimsIdentity;
claimsIdentity.AddClaim(claim);
await Task.CompletedTask;
}
};
})
.AddOpenIdConnect("test",o => {
o.SignInScheme = "Cookies";
o.ClientId = "id";
o.ClientSecret = "08";
o.Authority = "https://ex.com";
o.ResponseType = "code";
o.MetadataAddress = "https://ex.com/.well-known/openid-configuration";
o.SaveTokens = true;
o.GetClaimsFromUserInfoEndpoint = true;
});
services.AddAuthorization(options =>
{
options.AddPolicy("BasicAuthentication", new AuthorizationPolicyBuilder("BasicAuthentication").RequireAuthenticatedUser().Build());
});
services.AddControllersWithViews();
services.AddRazorPages();
}

Answer 1

You don't need to try to get the ID/Access-token manually, it is all handled by the AddOpenIdConnect middleware. When the request comes back with the authorization code, then AddOpenIdConnect will automatically get the tokens for you.
In your code I would change to the following because the typical case is that you want to have the OpenIDConnect handler to handle the challenge part.
services.AddAuthentication(options =>
{
options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
options.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
})