private async Task <bool> InvokeCryptographyEndpointAsync()
        {
            // Metadata requests must be made via GET.
            // See http://openid.net/specs/openid-connect-discovery-1_0.html#ProviderConfigurationRequest
            if (!string.Equals(Request.Method, "GET", StringComparison.OrdinalIgnoreCase))
            {
                Logger.LogError("The discovery request was rejected because an invalid " +
                                "HTTP method was used: {Method}.", Request.Method);

                return(await SendCryptographyResponseAsync(new OpenIdConnectResponse {
                    Error = OpenIdConnectConstants.Errors.InvalidRequest,
                    ErrorDescription = "Invalid HTTP method: make sure to use GET."
                }));
            }

            var request = new OpenIdConnectRequest(Request.Query);

            // Note: set the message type before invoking the ExtractCryptographyRequest event.
            request.SetProperty(OpenIdConnectConstants.Properties.MessageType,
                                OpenIdConnectConstants.MessageTypes.Cryptography);

            // Store the discovery request in the ASP.NET context.
            Context.SetOpenIdConnectRequest(request);

            var @event = new ExtractCryptographyRequestContext(Context, Options, request);
            await Options.Provider.ExtractCryptographyRequest(@event);

            if (@event.HandledResponse)
            {
                return(true);
            }

            else if (@event.Skipped)
            {
                return(false);
            }

            else if (@event.IsRejected)
            {
                Logger.LogError("The discovery request was rejected with the following error: {Error} ; {Description}",
                                /* Error: */ @event.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                                /* Description: */ @event.ErrorDescription);

                return(await SendCryptographyResponseAsync(new OpenIdConnectResponse {
                    Error = @event.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                    ErrorDescription = @event.ErrorDescription,
                    ErrorUri = @event.ErrorUri
                }));
            }

            var context = new ValidateCryptographyRequestContext(Context, Options, request);
            await Options.Provider.ValidateCryptographyRequest(context);

            if (context.HandledResponse)
            {
                return(true);
            }

            else if (context.Skipped)
            {
                return(false);
            }

            else if (!context.IsValidated)
            {
                Logger.LogError("The discovery request was rejected with the following error: {Error} ; {Description}",
                                /* Error: */ context.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                                /* Description: */ context.ErrorDescription);

                return(await SendCryptographyResponseAsync(new OpenIdConnectResponse {
                    Error = context.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                    ErrorDescription = context.ErrorDescription,
                    ErrorUri = context.ErrorUri
                }));
            }

            var notification = new HandleCryptographyRequestContext(Context, Options, request);

            foreach (var credentials in Options.SigningCredentials)
            {
                // Ignore the key if it's not supported.
#if SUPPORTS_ECDSA
                if (!credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.RsaSha256Signature) &&
                    !credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.EcdsaSha256Signature) &&
                    !credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.EcdsaSha384Signature) &&
                    !credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.EcdsaSha512Signature))
                {
                    Logger.LogInformation("An unsupported signing key was ignored and excluded from the " +
                                          "key set: {Type}. Only RSA and ECDSA asymmetric security keys " +
                                          "can be exposed via the JWKS endpoint.", credentials.Key.GetType().Name);

                    continue;
                }
#else
                if (!credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.RsaSha256Signature))
                {
                    Logger.LogInformation("An unsupported signing key was ignored and excluded from the " +
                                          "key set: {Type}. Only RSA asymmetric security keys can be exposed " +
                                          "via the JWKS endpoint.", credentials.Key.GetType().Name);

                    continue;
                }
#endif

                var key = new JsonWebKey {
                    Use = JsonWebKeyUseNames.Sig,

                    // Resolve the JWA identifier from the algorithm specified in the credentials.
                    Alg = OpenIdConnectServerHelpers.GetJwtAlgorithm(credentials.Algorithm),

                    // Use the key identifier specified in the signing credentials.
                    Kid = credentials.Kid,
                };

                if (credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.RsaSha256Signature))
                {
                    RSA algorithm = null;

                    // Note: IdentityModel 5 doesn't expose a method allowing to retrieve the underlying algorithm
                    // from a generic asymmetric security key. To work around this limitation, try to cast
                    // the security key to the built-in IdentityModel types to extract the required RSA instance.
                    // See https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/issues/395
                    var x509SecurityKey = credentials.Key as X509SecurityKey;
                    if (x509SecurityKey != null)
                    {
                        algorithm = x509SecurityKey.PublicKey as RSA;
                    }

                    var rsaSecurityKey = credentials.Key as RsaSecurityKey;
                    if (rsaSecurityKey != null)
                    {
                        algorithm = rsaSecurityKey.Rsa;

                        // If no RSA instance can be found, create one using
                        // the RSA parameters attached to the security key.
                        if (algorithm == null)
                        {
                            var rsa = RSA.Create();
                            rsa.ImportParameters(rsaSecurityKey.Parameters);
                            algorithm = rsa;
                        }
                    }

                    // Skip the key if an algorithm instance cannot be extracted.
                    if (algorithm == null)
                    {
                        Logger.LogWarning("A signing key was ignored because it was unable " +
                                          "to provide the requested algorithm instance.");

                        continue;
                    }

                    // Export the RSA public key to create a new JSON Web Key
                    // exposing the exponent and the modulus parameters.
                    var parameters = algorithm.ExportParameters(includePrivateParameters: false);

                    Debug.Assert(parameters.Exponent != null &&
                                 parameters.Modulus != null,
                                 "RSA.ExportParameters() shouldn't return null parameters.");

                    key.Kty = JsonWebAlgorithmsKeyTypes.RSA;

                    // Note: both E and N must be base64url-encoded.
                    // See https://tools.ietf.org/html/rfc7518#section-6.3.1.1
                    key.E = Base64UrlEncoder.Encode(parameters.Exponent);
                    key.N = Base64UrlEncoder.Encode(parameters.Modulus);
                }

#if SUPPORTS_ECDSA
                else if (credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.EcdsaSha256Signature) ||
                         credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.EcdsaSha384Signature) ||
                         credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.EcdsaSha512Signature))
                {
                    ECDsa algorithm = null;

                    var x509SecurityKey = credentials.Key as X509SecurityKey;
                    if (x509SecurityKey != null)
                    {
                        algorithm = x509SecurityKey.PublicKey as ECDsa;
                    }

                    var ecdsaSecurityKey = credentials.Key as ECDsaSecurityKey;
                    if (ecdsaSecurityKey != null)
                    {
                        algorithm = ecdsaSecurityKey.ECDsa;
                    }

                    // Skip the key if an algorithm instance cannot be extracted.
                    if (algorithm == null)
                    {
                        Logger.LogWarning("A signing key was ignored because it was unable " +
                                          "to provide the requested algorithm instance.");

                        continue;
                    }

                    // Export the ECDsa public key to create a new JSON Web Key
                    // exposing the coordinates of the point on the curve.
                    var parameters = algorithm.ExportParameters(includePrivateParameters: false);

                    Debug.Assert(parameters.Q.X != null &&
                                 parameters.Q.Y != null,
                                 "ECDsa.ExportParameters() shouldn't return null coordinates.");

                    key.Kty = JsonWebAlgorithmsKeyTypes.EllipticCurve;
                    key.Crv = OpenIdConnectServerHelpers.GetJwtAlgorithmCurve(parameters.Curve);

                    // Note: both X and Y must be base64url-encoded.
                    // See https://tools.ietf.org/html/rfc7518#section-6.2.1.2
                    key.X = Base64UrlEncoder.Encode(parameters.Q.X);
                    key.Y = Base64UrlEncoder.Encode(parameters.Q.Y);
                }
#endif

                // If the signing key is embedded in a X.509 certificate, set
                // the x5t and x5c parameters using the certificate details.
                var certificate = (credentials.Key as X509SecurityKey)?.Certificate;
                if (certificate != null)
                {
                    // x5t must be base64url-encoded.
                    // See https://tools.ietf.org/html/rfc7517#section-4.8
                    key.X5t = Base64UrlEncoder.Encode(certificate.GetCertHash());

                    // Unlike E or N, the certificates contained in x5c
                    // must be base64-encoded and not base64url-encoded.
                    // See https://tools.ietf.org/html/rfc7517#section-4.7
                    key.X5c.Add(Convert.ToBase64String(certificate.RawData));
                }

                notification.Keys.Add(key);
            }

            await Options.Provider.HandleCryptographyRequest(notification);

            if (notification.HandledResponse)
            {
                return(true);
            }

            else if (notification.Skipped)
            {
                return(false);
            }

            else if (notification.IsRejected)
            {
                Logger.LogError("The discovery request was rejected with the following error: {Error} ; {Description}",
                                /* Error: */ notification.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                                /* Description: */ notification.ErrorDescription);

                return(await SendCryptographyResponseAsync(new OpenIdConnectResponse {
                    Error = notification.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                    ErrorDescription = notification.ErrorDescription,
                    ErrorUri = notification.ErrorUri
                }));
            }

            var keys = new JArray();

            foreach (var key in notification.Keys)
            {
                var item = new JObject();

                // Ensure a key type has been provided.
                // See https://tools.ietf.org/html/rfc7517#section-4.1
                if (string.IsNullOrEmpty(key.Kty))
                {
                    Logger.LogError("A JSON Web Key was excluded from the key set because " +
                                    "it didn't contain the mandatory 'kid' parameter.");

                    continue;
                }

                // Create a dictionary associating the
                // JsonWebKey components with their values.
                var parameters = new Dictionary <string, string> {
                    [JsonWebKeyParameterNames.Kid] = key.Kid,
                    [JsonWebKeyParameterNames.Use] = key.Use,
                    [JsonWebKeyParameterNames.Kty] = key.Kty,
                    [JsonWebKeyParameterNames.Alg] = key.Alg,
                    [JsonWebKeyParameterNames.Crv] = key.Crv,
                    [JsonWebKeyParameterNames.E]   = key.E,
                    [JsonWebKeyParameterNames.N]   = key.N,
                    [JsonWebKeyParameterNames.X]   = key.X,
                    [JsonWebKeyParameterNames.Y]   = key.Y,
                    [JsonWebKeyParameterNames.X5t] = key.X5t,
                    [JsonWebKeyParameterNames.X5u] = key.X5u
                };

                foreach (var parameter in parameters)
                {
                    if (!string.IsNullOrEmpty(parameter.Value))
                    {
                        item.Add(parameter.Key, parameter.Value);
                    }
                }

                if (key.KeyOps.Count != 0)
                {
                    item.Add(JsonWebKeyParameterNames.KeyOps, JArray.FromObject(key.KeyOps));
                }

                if (key.X5c.Count != 0)
                {
                    item.Add(JsonWebKeyParameterNames.X5c, JArray.FromObject(key.X5c));
                }

                keys.Add(item);
            }

            return(await SendCryptographyResponseAsync(new OpenIdConnectResponse {
                [OpenIdConnectConstants.Parameters.Keys] = keys
            }));
        }
示例#2
0
 /// <summary>
 /// Called by the client applications to retrieve the OpenID Connect JSON Web Key set associated with this instance.
 /// An application may implement this call in order to do any final modification to the keys set.
 /// </summary>
 /// <param name="context">The context of the event carries information in and results out.</param>
 /// <returns>Task to enable asynchronous execution</returns>
 public virtual Task HandleCryptographyRequest(HandleCryptographyRequestContext context) => OnHandleCryptographyRequest(context);
        private async Task <bool> InvokeCryptographyEndpointAsync()
        {
            // Metadata requests must be made via GET.
            // See http://openid.net/specs/openid-connect-discovery-1_0.html#ProviderConfigurationRequest
            if (!string.Equals(Request.Method, "GET", StringComparison.OrdinalIgnoreCase))
            {
                Logger.LogError("The discovery request was rejected because an invalid " +
                                "HTTP method was used: {Method}.", Request.Method);

                return(await SendErrorPayloadAsync(new OpenIdConnectMessage {
                    Error = OpenIdConnectConstants.Errors.InvalidRequest,
                    ErrorDescription = "Invalid HTTP method: make sure to use GET."
                }));
            }

            var validatingContext = new ValidateCryptographyRequestContext(Context, Options);
            await Options.Provider.ValidateCryptographyRequest(validatingContext);

            if (!validatingContext.IsValidated)
            {
                Logger.LogInformation("The discovery request was rejected by application code.");

                return(await SendErrorPayloadAsync(new OpenIdConnectMessage {
                    Error = validatingContext.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                    ErrorDescription = validatingContext.ErrorDescription,
                    ErrorUri = validatingContext.ErrorUri
                }));
            }

            var notification = new HandleCryptographyRequestContext(Context, Options);

            foreach (var credentials in Options.SigningCredentials)
            {
                // Ignore the key if it's not supported.
                if (!credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.RsaSha256Signature) &&
                    !credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.RsaSha384Signature) &&
                    !credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.RsaSha512Signature))
                {
                    Logger.LogInformation("An unsupported signing key was ignored and excluded " +
                                          "from the key set: {Type}. Only asymmetric security keys " +
                                          "supporting RS256, RS384 or RS512 can be exposed " +
                                          "via the JWKS endpoint.", credentials.Key.GetType().Name);

                    continue;
                }

                // Determine whether the security key is a RSA key embedded in a X.509 certificate.
                var x509SecurityKey = credentials.Key as X509SecurityKey;
                if (x509SecurityKey != null)
                {
                    // Create a new JSON Web Key exposing the
                    // certificate instead of its public RSA key.
                    notification.Keys.Add(new JsonWebKey {
                        Use = JsonWebKeyUseNames.Sig,
                        Kty = JsonWebAlgorithmsKeyTypes.RSA,

                        // Resolve the JWA identifier from the algorithm specified in the credentials.
                        Alg = OpenIdConnectServerHelpers.GetJwtAlgorithm(credentials.Algorithm),

                        // Use the key identifier specified
                        // in the signing credentials.
                        Kid = credentials.Kid,

                        // x5t must be base64url-encoded.
                        // See http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#section-4.8
                        X5t = Base64UrlEncoder.Encode(x509SecurityKey.Certificate.GetCertHash()),

                        // Unlike E or N, the certificates contained in x5c
                        // must be base64-encoded and not base64url-encoded.
                        // See http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#section-4.7
                        X5c = { Convert.ToBase64String(x509SecurityKey.Certificate.RawData) }
                    });
                }

                var rsaSecurityKey = credentials.Key as RsaSecurityKey;
                if (rsaSecurityKey != null)
                {
                    // Export the RSA public key.
                    notification.Keys.Add(new JsonWebKey {
                        Use = JsonWebKeyUseNames.Sig,
                        Kty = JsonWebAlgorithmsKeyTypes.RSA,

                        // Resolve the JWA identifier from the algorithm specified in the credentials.
                        Alg = OpenIdConnectServerHelpers.GetJwtAlgorithm(credentials.Algorithm),

                        // Use the key identifier specified
                        // in the signing credentials.
                        Kid = credentials.Kid,

                        // Both E and N must be base64url-encoded.
                        // See http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#appendix-A.1
                        E = Base64UrlEncoder.Encode(rsaSecurityKey.Parameters.Exponent),
                        N = Base64UrlEncoder.Encode(rsaSecurityKey.Parameters.Modulus)
                    });
                }
            }

            await Options.Provider.HandleCryptographyRequest(notification);

            if (notification.HandledResponse)
            {
                return(true);
            }

            else if (notification.Skipped)
            {
                return(false);
            }

            var payload = new JObject();
            var keys    = new JArray();

            foreach (var key in notification.Keys)
            {
                var item = new JObject();

                // Ensure a key type has been provided.
                // See http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#section-4.1
                if (string.IsNullOrEmpty(key.Kty))
                {
                    Logger.LogError("A JSON Web Key was excluded from the key set because " +
                                    "it didn't contain the mandatory 'kid' parameter.");

                    continue;
                }

                // Create a dictionary associating the
                // JsonWebKey components with their values.
                var parameters = new Dictionary <string, string> {
                    [JsonWebKeyParameterNames.Kid] = key.Kid,
                    [JsonWebKeyParameterNames.Use] = key.Use,
                    [JsonWebKeyParameterNames.Kty] = key.Kty,
                    [JsonWebKeyParameterNames.Alg] = key.Alg,
                    [JsonWebKeyParameterNames.X5t] = key.X5t,
                    [JsonWebKeyParameterNames.X5u] = key.X5u,
                    [JsonWebKeyParameterNames.E]   = key.E,
                    [JsonWebKeyParameterNames.N]   = key.N
                };

                foreach (var parameter in parameters)
                {
                    if (!string.IsNullOrEmpty(parameter.Value))
                    {
                        item.Add(parameter.Key, parameter.Value);
                    }
                }

                if (key.KeyOps.Any())
                {
                    item.Add(JsonWebKeyParameterNames.KeyOps, JArray.FromObject(key.KeyOps));
                }

                if (key.X5c.Any())
                {
                    item.Add(JsonWebKeyParameterNames.X5c, JArray.FromObject(key.X5c));
                }

                keys.Add(item);
            }

            payload.Add(JsonWebKeyParameterNames.Keys, keys);

            var context = new ApplyCryptographyResponseContext(Context, Options, payload);
            await Options.Provider.ApplyCryptographyResponse(context);

            if (context.HandledResponse)
            {
                return(true);
            }

            else if (context.Skipped)
            {
                return(false);
            }

            using (var buffer = new MemoryStream())
                using (var writer = new JsonTextWriter(new StreamWriter(buffer))) {
                    payload.WriteTo(writer);
                    writer.Flush();

                    Response.ContentLength = buffer.Length;
                    Response.ContentType   = "application/json;charset=UTF-8";

                    buffer.Seek(offset: 0, loc: SeekOrigin.Begin);
                    await buffer.CopyToAsync(Response.Body, 4096, Context.RequestAborted);

                    return(true);
                }
        }
示例#4
0
        private async Task <bool> InvokeCryptographyEndpointAsync()
        {
            // Metadata requests must be made via GET.
            // See http://openid.net/specs/openid-connect-discovery-1_0.html#ProviderConfigurationRequest
            if (!string.Equals(Request.Method, "GET", StringComparison.OrdinalIgnoreCase))
            {
                Logger.LogError("The discovery request was rejected because an invalid " +
                                "HTTP method was used: {Method}.", Request.Method);

                return(await SendCryptographyResponseAsync(null, new OpenIdConnectMessage {
                    Error = OpenIdConnectConstants.Errors.InvalidRequest,
                    ErrorDescription = "Invalid HTTP method: make sure to use GET."
                }));
            }

            var request = new OpenIdConnectMessage(Request.Query.ToDictionary());

            var context = new ValidateCryptographyRequestContext(Context, Options);
            await Options.Provider.ValidateCryptographyRequest(context);

            if (!context.IsValidated)
            {
                Logger.LogError("The discovery request was rejected with the following error: {Error} ; {Description}",
                                /* Error: */ context.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                                /* Description: */ context.ErrorDescription);

                return(await SendCryptographyResponseAsync(request, new OpenIdConnectMessage {
                    Error = context.Error ?? OpenIdConnectConstants.Errors.InvalidRequest,
                    ErrorDescription = context.ErrorDescription,
                    ErrorUri = context.ErrorUri
                }));
            }

            var notification = new HandleCryptographyRequestContext(Context, Options, request);

            foreach (var credentials in Options.SigningCredentials)
            {
                // Ignore the key if it's not supported.
                if (!(credentials.Key is AsymmetricSecurityKey) &&
                    !credentials.Key.IsSupportedAlgorithm(SecurityAlgorithms.RsaSha256Signature))
                {
                    Logger.LogInformation("An unsupported signing key was ignored and excluded " +
                                          "from the key set: {Type}. Only asymmetric security keys " +
                                          "supporting RS256, RS384 or RS512 can be exposed " +
                                          "via the JWKS endpoint.", credentials.Key.GetType().Name);

                    continue;
                }

                RSA algorithm = null;

                // Note: IdentityModel 5 doesn't expose a method allowing to retrieve the underlying algorithm
                // from a generic asymmetric security key. To work around this limitation, try to cast
                // the security key to the built-in IdentityModel types to extract the required RSA instance.
                // See https://github.com/AzureAD/azure-activedirectory-identitymodel-extensions-for-dotnet/issues/395
                var x509SecurityKey = credentials.Key as X509SecurityKey;
                if (x509SecurityKey != null)
                {
                    algorithm = (RSA)x509SecurityKey.PublicKey;
                }

                var rsaSecurityKey = credentials.Key as RsaSecurityKey;
                if (rsaSecurityKey != null)
                {
                    algorithm = rsaSecurityKey.Rsa;

                    // If no RSA instance can be found, create one using
                    // the RSA parameters attached to the security key.
                    if (algorithm == null)
                    {
                        algorithm = RSA.Create();
                        algorithm.ImportParameters(rsaSecurityKey.Parameters);
                    }
                }

                // Skip the key if a RSA instance cannot be retrieved.
                if (algorithm == null)
                {
                    Logger.LogError("A signing key was ignored because it was unable " +
                                    "to provide the requested RSA instance.");

                    continue;
                }

                // Export the RSA public key to create a new JSON Web Key
                // exposing the exponent and the modulus parameters.
                var parameters = algorithm.ExportParameters(includePrivateParameters: false);
                Debug.Assert(parameters.Exponent != null, "A null exponent was returned by RSA.ExportParameters()");
                Debug.Assert(parameters.Modulus != null, "A null modulus was returned by RSA.ExportParameters()");

                var key = new JsonWebKey {
                    Use = JsonWebKeyUseNames.Sig,
                    Kty = JsonWebAlgorithmsKeyTypes.RSA,

                    // Resolve the JWA identifier from the algorithm specified in the credentials.
                    Alg = OpenIdConnectServerHelpers.GetJwtAlgorithm(credentials.Algorithm),

                    // Use the key identifier specified
                    // in the signing credentials.
                    Kid = credentials.Kid,

                    // Both E and N must be base64url-encoded.
                    // See http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#appendix-A.1
                    E = Base64UrlEncoder.Encode(parameters.Exponent),
                    N = Base64UrlEncoder.Encode(parameters.Modulus)
                };

                // If the signing key is embedded in a X.509 certificate, set
                // the x5t and x5c parameters using the certificate details.
                var x509Certificate = x509SecurityKey?.Certificate;
                if (x509Certificate != null)
                {
                    // x5t must be base64url-encoded.
                    // See http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#section-4.8
                    key.X5t = Base64UrlEncoder.Encode(x509SecurityKey.Certificate.GetCertHash());

                    // Unlike E or N, the certificates contained in x5c
                    // must be base64-encoded and not base64url-encoded.
                    // See http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#section-4.7
                    key.X5c.Add(Convert.ToBase64String(x509SecurityKey.Certificate.RawData));
                }

                notification.Keys.Add(key);
            }

            await Options.Provider.HandleCryptographyRequest(notification);

            if (notification.HandledResponse)
            {
                return(true);
            }

            else if (notification.Skipped)
            {
                return(false);
            }

            var response = new JObject();
            var keys     = new JArray();

            foreach (var key in notification.Keys)
            {
                var item = new JObject();

                // Ensure a key type has been provided.
                // See http://tools.ietf.org/html/draft-ietf-jose-json-web-key-31#section-4.1
                if (string.IsNullOrEmpty(key.Kty))
                {
                    Logger.LogError("A JSON Web Key was excluded from the key set because " +
                                    "it didn't contain the mandatory 'kid' parameter.");

                    continue;
                }

                // Create a dictionary associating the
                // JsonWebKey components with their values.
                var parameters = new Dictionary <string, string> {
                    [JsonWebKeyParameterNames.Kid] = key.Kid,
                    [JsonWebKeyParameterNames.Use] = key.Use,
                    [JsonWebKeyParameterNames.Kty] = key.Kty,
                    [JsonWebKeyParameterNames.Alg] = key.Alg,
                    [JsonWebKeyParameterNames.E]   = key.E,
                    [JsonWebKeyParameterNames.N]   = key.N,
                    [JsonWebKeyParameterNames.X5t] = key.X5t,
                    [JsonWebKeyParameterNames.X5u] = key.X5u
                };

                foreach (var parameter in parameters)
                {
                    if (!string.IsNullOrEmpty(parameter.Value))
                    {
                        item.Add(parameter.Key, parameter.Value);
                    }
                }

                if (key.KeyOps.Count != 0)
                {
                    item.Add(JsonWebKeyParameterNames.KeyOps, JArray.FromObject(key.KeyOps));
                }

                if (key.X5c.Count != 0)
                {
                    item.Add(JsonWebKeyParameterNames.X5c, JArray.FromObject(key.X5c));
                }

                keys.Add(item);
            }

            response.Add(JsonWebKeyParameterNames.Keys, keys);

            return(await SendCryptographyResponseAsync(request, response));
        }