The signature key was not found error when using IndentityServer4 with Angular, AspNet Core

Question

I've 3 projects in my solution one is Idp using IdentityServer4 with the following configuration. I'm using Implicit Flow

    public void ConfigureServices(IServiceCollection services)
{
    var cert = new X509Certificate2(Path.Combine(_environment.ContentRootPath, "damienbodserver.pfx"), "");


    // Add framework services.
    var connectionString = Configuration.GetConnectionString("PostgreSQLConnectionString");
    Console.WriteLine(connectionString);
    services.AddDbContext<ApplicationDbContext>(options =>
        options.UseNpgsql(connectionString));

    services.AddIdentity<ApplicationUser, IdentityRole>()
        .AddEntityFrameworkStores<ApplicationDbContext>()
        .AddDefaultTokenProviders();

    //NB added for implicit flow
    services.AddCors();

    services.AddMvc();

    // Add application services.
    services.AddTransient<IEmailSender, AuthMessageSender>();
    services.AddTransient<ISmsSender, AuthMessageSender>();

    services.AddScoped<IUserClaimsPrincipalFactory<ApplicationUser>, AppClaimsPrincipalFactory>();


    services.AddIdentityServer()
        //.AddTemporarySigningCredential()
        .AddSigningCredential(cert)
        .AddInMemoryPersistedGrants()
        .AddInMemoryIdentityResources(IdentityServerStatics.GetIdentityResources())
        .AddInMemoryApiResources(IdentityServerStatics.GetApiResources())
        .AddClientStore<CustomClientStore>() // Add the custom client store
        .AddAspNetIdentity<ApplicationUser>()
        .AddProfileService<CustomProfileService>(); // use custom profile service to pull in claims

    services.AddAuthorization(options =>
    {
        options.AddPolicy("MyUMD_User", policy => policy.RequireClaim("MyUMD:AccessLevel", "User", "Manage", "Support", "Admin"));
    });
    services.AddAuthorization(options =>
    {
        options.AddPolicy("MyUMD_Manage", policy => policy.RequireClaim("MyUMD:AccessLevel", "Manage", "Support", "Admin"));
    });
    services.AddAuthorization(options =>
    {
        options.AddPolicy("MyUMD_Support", policy => policy.RequireClaim("MyUMD:AccessLevel", "Support", "Admin"));
    });
    services.AddAuthorization(options =>
    {
        options.AddPolicy("MyUMD_Admin", policy => policy.RequireClaim("MyUMD:AccessLevel", "Admin"));
    });
}

and the resource server is configured as below.

NOTE this resource server is already working with custom JWT token generation and validation. Now I want to add additional capability to read the claims from the token generated by IdentityServer4

public void ConfigureJwtAuthService(IServiceCollection services)
    {
        var folderForKeyStore = Configuration["Production:KeyStoreFolderWhichIsBacked"];
        var cert = new X509Certificate2(Path.Combine(_env.ContentRootPath, "damienbodserver.pfx"), "");

        // Important The folderForKeyStore needs to be backed up.
        services.AddDataProtection()
            .SetApplicationName("vast_webapplication")
            .PersistKeysToFileSystem(new DirectoryInfo(_env.ContentRootPath))
            .ProtectKeysWithCertificate(cert);



        var symmetricKeyAsBase64 = "Y2F0Y2hlciUyMHdvbmclMjBsb3ZlJTIwLm5ldA==";
        var keyByteArray = Encoding.ASCII.GetBytes(symmetricKeyAsBase64);
        var signingKey = new SymmetricSecurityKey(keyByteArray);

        // JWT Token signing settings
        TokenAuthOptions tokenAuth = new TokenAuthOptions()
        {
            Audience = "vast-audience",
            Issuer = "vast-issuer",
            // this gets set later in Configure
            SigningCredentials = null,
            Key = signingKey
        };

        // add the auth options to the DI container
        services.AddSingleton(tokenAuth);

        var tokenValidationParameters = new TokenValidationParameters
        {
            // The signing key must match!
            ValidateIssuerSigningKey = true,
            IssuerSigningKey = signingKey,

            // Validate the JWT Issuer (iss) claim
            ValidateIssuer = true,
            ValidIssuer = "vast-issuer",

            // Validate the JWT Audience (aud) claim
            ValidateAudience = true,
            ValidAudience = "vast-audience",

            // Validate the token expiry
            ValidateLifetime = true,

            ClockSkew = TimeSpan.FromMinutes(60)
        };

        JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear();
        services.AddAuthentication(options =>
        {
            options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
            options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
        })
        .AddJwtBearer(o =>
        {
           o.TokenValidationParameters = tokenValidationParameters;
        });
        //.AddCookie(options=> options.Cookie.Domain="localhost:5000");


        services.AddAuthorization(options => {
            //options.DefaultPolicy= new AuthorizationPolicyBuilder(JwtBearerDefaults.AuthenticationScheme).RequireAuthenticatedUser().Build();

            options.AddPolicy(AuthorizationPolicies.TicketTypeRead, policy => {
                policy.AddAuthenticationSchemes(JwtBearerDefaults.AuthenticationScheme);
                policy.RequireClaim(CustomClaims.TicketTypRead);
            });


            string[] roles = new string[] { "User", "Management" };
            options.AddPolicy("Reporting_Managers", policy =>
            {
                policy.AddAuthenticationSchemes(JwtBearerDefaults.AuthenticationScheme);
                policy.RequireClaim("SkyBusReporting:Reporting", "Management");
            });

        });
    }

Angular app is also a .net project and it successfully calls the api (resource server function). In response I received a 401 Unauthorized status and in the header I can see this

www-authenticate →Bearer error="invalid_token", error_description="The signature key was not found"

What I'm doing wrong here?

Answer 1

thanks to aaronR i figured out the issue in my code. Now I'm not sure if this is the best way to implement the implicit flow

I changed my code is resource api to use the public key from the certificate to read the token which is missing in the above code.

In the ConfigureJwtAuthService function above I changed the code to get a key from the certificate as below

var cert = new X509Certificate2(Path.Combine(_env.ContentRootPath, "damienbodserver.pfx"), "");
        X509SecurityKey key = new X509SecurityKey(cert);
        SigningCredentials credentials = new SigningCredentials(key, "RS256");

than I used this key in TokenValidationParameters object as below

var tokenValidationParameters = new TokenValidationParameters
        {
            // The signing key must match!
            ValidateIssuerSigningKey = true,
            //IssuerSigningKey = signingKey,
            IssuerSigningKey = key,

            // Validate the JWT Issuer (iss) claim
            ValidateIssuer = false,
            ValidIssuer = "vast-issuer",

            // Validate the JWT Audience (aud) claim
            ValidateAudience = false,
            ValidAudience = "vast-audience",

            // Validate the token expiry
            ValidateLifetime = true,

            ClockSkew = TimeSpan.FromMinutes(60)
        };

I also changed the implementation of custom JWT Token generation to use the same key and credentials to generate the JWT Token.