PostLogoutRedirectUri always null in identity Server 4 with SPA (Angular 7 OIDC client) - asp.net

Question

Using the facebook login authentication in angular app with identity server 4. On logout method PostLogoutRedirectUri , ClientName, LogoutId is always null.
private async Task<LoggedOutViewModel> BuildLoggedOutViewModelAsync(string logoutId)
{
// get context information (client name, post logout redirect URI and iframe for federated signout)
var logout = await _interaction.GetLogoutContextAsync(logoutId);
var vm = new LoggedOutViewModel
{
AutomaticRedirectAfterSignOut = AccountOptions.AutomaticRedirectAfterSignOut,
PostLogoutRedirectUri = logout?.PostLogoutRedirectUri,
ClientName = string.IsNullOrEmpty(logout?.ClientName) ? logout?.ClientId : logout?.ClientName,
SignOutIframeUrl = logout?.SignOutIFrameUrl,
LogoutId = logoutId
};
if (User?.Identity.IsAuthenticated == true)
{
var idp = User.FindFirst(JwtClaimTypes.IdentityProvider)?.Value;
if (idp != null && idp != IdentityServer4.IdentityServerConstants.LocalIdentityProvider)
{
var providerSupportsSignout = await HttpContext.GetSchemeSupportsSignOutAsync(idp);
if (providerSupportsSignout)
{
if (vm.LogoutId == null)
{
// if there's no current logout context, we need to create one
// this captures necessary info from the current logged in user
// before we signout and redirect away to the external IdP for signout
vm.LogoutId = await _interaction.CreateLogoutContextAsync();
}
vm.ExternalAuthenticationScheme = idp;
}
}
}
return vm;
}
Angular oidc clident code
logout(): Promise<any> {
return this._userManager.signoutRedirect();
}
Client setup
public IEnumerable<Client> GetClients()
{
var client = new List<Client>
{
new Client
{
ClientId = ConstantValue.ClientId,
ClientName = ConstantValue.ClientName,
AllowedGrantTypes = GrantTypes.Implicit,
AllowAccessTokensViaBrowser = true,
RequireConsent = false,
RedirectUris = { string.Format("{0}/{1}", Configuration["IdentityServerUrls:ClientUrl"], "assets/oidc-login-redirect.html"), string.Format("{0}/{1}", Configuration["IdentityServerUrls:ClientUrl"], "assets/silent-redirect.html") },
PostLogoutRedirectUris = { string.Format("{0}?{1}", Configuration["IdentityServerUrls:ClientUrl"] , "postLogout=true") },
AllowedCorsOrigins = { Configuration["IdentityServerUrls: ClientUrl"] },
AllowedScopes =
{
IdentityServerConstants.StandardScopes.OpenId,
IdentityServerConstants.StandardScopes.Profile,
ConstantValue.ClientDashApi
},
IdentityTokenLifetime=120,
AccessTokenLifetime=120
},
};
return client;
}
logoutId is always null. I am successfully able to login to facebook return to the callback method. But redirect uri is always null.
Reference
IdentityServer4 PostLogoutRedirectUri null

Answer 1

This may not be your issue, but it was my issue when I got the same error as you so I am posting my own experience here.
I was following along in a Pluralsight video that was constructing an Angular app using IdentityServer4 as the STS Server, and it directed me to set the post_logout_redirect_uri in the configuration for my UserManager in the AuthService I was constructing, like so:
var config = {
authority: 'http://localhost:4242/',
client_id: 'spa-client',
redirect_uri: `${Constants.clientRoot}assets/oidc-login-redirect.html`,
scope: 'openid projects-api profile',
response_type: 'id_token token',
post_logout_redirect_uri: `${Constants.clientRoot}`,
userStore: new WebStorageStateStore({ store: window.localStorage })
}
this._userManager = new UserManager(config);
An old issue at the github repo https://github.com/IdentityServer/IdentityServer4/issues/396 discussed the fact that this is set automatically now and doesn't need to be set explicitly (see the end of the thread). Once I removed that from the configuration I no longer had the issue where logoutId was null in the AccountController's Logout method:
/// <summary>
/// Show logout page
/// </summary>
[HttpGet]
public async Task<IActionResult> Logout(string logoutId)
So this was the correct setup for the config for me:
var config = {
authority: 'http://localhost:4242/',
client_id: 'spa-client',
redirect_uri: `${Constants.clientRoot}assets/oidc-login-redirect.html`,
scope: 'openid projects-api profile',
response_type: 'id_token token',
userStore: new WebStorageStateStore({ store: window.localStorage })
}
this._userManager = new UserManager(config);

Answer 2

I had a similar issue and for a few hours I was lost. In my case the value/url I had in angular for post_logout_redirect_uri (in the UserManagerSettings) was different than the value/url I had in my IdentityServer4 in the field PostLogoutRedirectUris of the Client configuration. I messed up the routes. It's a silly mistake but sometimes you miss the simple things.