IdentityServer4发现文档URL含双反斜杠致客户端认证失败

I’ve run into this exact issue before—when your IdentityServer4 instance outputs well-known config URLs with an extra backslash in the schema (like \http://...), MVC clients choke trying to parse those invalid URLs. Let’s break down how to diagnose and fix this:

Common Causes & Step-by-Step Solutions #

1. Explicitly Set the IdentityServer Issuer URI #

The most frequent culprit is incorrect auto-generated issuer URI. IdentityServer sometimes guesses the base URL wrong (especially behind proxies or non-standard hosting). Force it explicitly in your Startup.cs to override auto-generation:

services.AddIdentityServer(options =>
{
    // Hardcode the valid public issuer URL to avoid formatting errors
    options.IssuerUri = "http://www.server.meetcorepoint.com";
})
.AddInMemoryClients(Config.Clients)
.AddInMemoryApiScopes(Config.ApiScopes)
// Add your identity store and other required services here

2. Validate MVC Client Configuration #

Double-check your MVC client’s setup to ensure the Authority value has no stray backslashes. It should be a clean, valid URL:

services.AddAuthentication(options =>
{
    options.DefaultScheme = "Cookies";
    options.DefaultChallengeScheme = "oidc";
})
.AddCookie("Cookies")
.AddOpenIdConnect("oidc", options =>
{
    options.Authority = "http://www.server.meetcorepoint.com"; // No backslashes allowed here!
    options.ClientId = "your-mvc-client-id";
    options.ClientSecret = "your-client-secret";
    options.ResponseType = "code";
    // Rest of your client configuration
});

3. Fix Proxy/Load Balancer Header Forwarding (If Applicable) #

If your IdentityServer is behind a reverse proxy or load balancer, missing or misconfigured forwarded headers can cause malformed URL generation. Add this middleware to your IdentityServer’s pipeline before UseIdentityServer:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // Forward headers so IdentityServer uses the public URL instead of internal container addresses
    app.UseForwardedHeaders(new ForwardedHeadersOptions
    {
        ForwardedHeaders = ForwardedHeaders.XForwardedProto | ForwardedHeaders.XForwardedHost
    });

    // Rest of your pipeline setup
    app.UseIdentityServer();
}

4. Verify the Well-Known Config Directly #

Visit http://www.server.meetcorepoint.com/.well-known/openid-configuration in your browser. If any endpoint URLs start with \http://, that confirms the formatting issue. After applying fixes, refresh this endpoint to ensure URLs are now valid (no leading backslashes).

Why This Error Occurs #

The "Unable to parse host name" exception happens because the client’s OpenID Connect handler can’t recognize URLs with a leading backslash in the schema. A URL like \http://www.server.meetcorepoint.com/connect/token isn’t a valid HTTP URL, so the handler fails to resolve the host.

内容的提问来源于stack exchange，提问作者Dejan Bogatinovski