public async Task <IActionResult> ExternalLoginCallback(string returnUrl)
{
// read external identity from the temporary cookie
var info = await HttpContext.Authentication.GetAuthenticateInfoAsync(IdentityServerConstants.ExternalCookieAuthenticationScheme);
var tempUser = info?.Principal;
if (tempUser == null)
{
throw new Exception("External authentication error");
}
// retrieve claims of the external user
var claims = tempUser.Claims.ToList();
// try to determine the unique id of the external user - the most common claim type for that are the sub claim and the NameIdentifier
// depending on the external provider, some other claim type might be used
var userIdClaim = claims.FirstOrDefault(x => x.Type == JwtClaimTypes.Subject);
if (userIdClaim == null)
{
userIdClaim = claims.FirstOrDefault(x => x.Type == ClaimTypes.NameIdentifier);
}
if (userIdClaim == null)
{
throw new Exception("Unknown userid");
}
// remove the user id claim from the claims collection and move to the userId property
// also set the name of the external authentication provider
claims.Remove(userIdClaim);
var provider = info.Properties.Items["scheme"];
var userId = userIdClaim.Value;
// check if the external user is already provisioned
var user = _repository.FindByExternalProvider(provider, userId);
if (user == null)
{
// this sample simply auto-provisions new external user
// another common approach is to start a registrations workflow first
user = _repository.AutoProvisionUser(provider, userId, claims);
}
var additionalClaims = new List <Claim>();
// if the external system sent a session id claim, copy it over
var sid = claims.FirstOrDefault(x => x.Type == JwtClaimTypes.SessionId);
if (sid != null)
{
additionalClaims.Add(new Claim(JwtClaimTypes.SessionId, sid.Value));
}
// if the external provider issued an id_token, we'll keep it for signout
AuthenticationProperties props = null;
var id_token = info.Properties.GetTokenValue("id_token");
if (id_token != null)
{
props = new AuthenticationProperties();
props.StoreTokens(new[] { new AuthenticationToken {
Name = "id_token", Value = id_token
} });
}
// issue authentication cookie for user
await HttpContext.Authentication.SignInAsync(user.Sid, user.Username, provider, props, additionalClaims.ToArray());
// delete temporary cookie used during external authentication
await HttpContext.Authentication.SignOutAsync(IdentityServerConstants.ExternalCookieAuthenticationScheme);
// validate return URL and redirect back to authorization endpoint
if (_interaction.IsValidReturnUrl(returnUrl))
{
return(Redirect(returnUrl));
}
return(Redirect("~/"));
}