Manually validating a JWT token in C#

Question

I am having some trouble manually validating a JWT token issued by Identity Server 4. Using the

ClientId: "CLIENT1" ClientSecret: "123456"

The exception I keep getting is: IDX10501: Signature validation failed. Unable to match keys: '[PII is hidden by default. Set the 'ShowPII' flag in IdentityModelEventSource.cs to true to reveal it.]'

Is anyone able to advise me where I am going wrong.

    private static void ValidateJwt(string jwt, DiscoveryResponse disco)
    {        

        var parameters = new TokenValidationParameters
        {

            ValidateIssuerSigningKey = true,
            ValidIssuer = disco.Issuer,
            IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("123456")),               
            ValidAudience = "CLIENT1",
            //IssuerSigningKeys = keys,
            // ValidateAudience = true,
            // ValidateLifetime = true,
        };

        SecurityToken validatedToken;
        var handler = new JwtSecurityTokenHandler();
        handler.InboundClaimTypeMap.Clear();

        try
        {
            var user = handler.ValidateToken(jwt, parameters, out validatedToken);
        }
        catch(Exception ex)
        {
            var error = ex.Message;
        }

    }

Answer 1

Check out ValidateJwt() in this sample:

https://github.com/IdentityServer/IdentityServer4/blob/master/samples/Clients/old/MvcManual/Controllers/HomeController.cs

The bit you're missing is loading the public key from the discovery document.