示例#1
0
        /* TLS 1.3
         * 00 // opaque certificate_request_context
         * 00 2a // extension len
         * 00 0d 00 26 // SignatureAlgorithm extension len
         * 00 24 // SignatureAlgorithms len
         * 04 03 05 03 06 03 08 07 08 08 08 09 08 0a 08 0b 08 04 08 05 08 06 04 01 05 01 06 01 03 03 02 03 03 01 02 01
         */
        public CertificateRequest(byte[] cert_request_context, SignatureAlgorithm[] clientCertSAs = null) : base(null)
        {
            //https://tools.ietf.org/html/rfc8446#page-70
            //In addition, the signature algorithm MUST be compatible with the key in the sender's end-entity certificate.
            //RSA signatures MUST use an RSASSA - PSS algorithm, regardless of whether RSASSA-PKCS1 - v1_5 algorithms appear in "signature_algorithms".
            //The SHA - 1 algorithm MUST NOT be used in any signatures of CertificateVerify messages.
            CertificateTypes    = new ClientCertificateType[0];
            SignatureAlgorithms = clientCertSAs ?? new[]
            {
                SignatureAlgorithm.rsa_pss_rsae_sha256, SignatureAlgorithm.rsa_pss_rsae_sha384, SignatureAlgorithm.rsa_pss_rsae_sha512,
                SignatureAlgorithm.ecdsa_secp256r1_sha256, SignatureAlgorithm.ecdsa_secp384r1_sha384, SignatureAlgorithm.ecdsa_secp521r1_sha512,
            };

            var extBytes = new Extensions.SignatureAlgorithms(SignatureAlgorithms).Data;

            using (var ms = new System.IO.MemoryStream())
            {
                // certificate_request_context
                if (cert_request_context != null && cert_request_context.Length > 0)
                {
                    ms.WriteValue(cert_request_context, new[] { (byte)cert_request_context.Length });
                }
                else
                {
                    ms.WriteByte((byte)0);
                }
                // Extensions total length ushort
                ms.WriteValue((ushort)(extBytes.Length));
                // SignatureAlgorithms Extension
                ms.Write(extBytes, 0, extBytes.Length);

                Data = ms.ToArray();
            }
        }
		private void ProcessHandshakeMessage(HandshakeType type, byte[] buf)
		{
			MemoryStream inStr = new MemoryStream(buf, false);

			/*
			* Check the type.
			*/
			switch (type)
			{
				case HandshakeType.certificate:
				{
					switch (connection_state)
					{
						case CS_SERVER_HELLO_RECEIVED:
						{
							// Parse the Certificate message and send to cipher suite

							Certificate serverCertificate = Certificate.Parse(inStr);

							AssertEmpty(inStr);

							this.keyExchange.ProcessServerCertificate(serverCertificate);

							this.authentication = tlsClient.GetAuthentication();
							this.authentication.NotifyServerCertificate(serverCertificate);

							break;
						}
						default:
							this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
							break;
					}

					connection_state = CS_SERVER_CERTIFICATE_RECEIVED;
					break;
				}
				case HandshakeType.finished:
					switch (connection_state)
					{
						case CS_SERVER_CHANGE_CIPHER_SPEC_RECEIVED:
							/*
							 * Read the checksum from the finished message, it has always 12 bytes.
							 */
							byte[] serverVerifyData = new byte[12];
							TlsUtilities.ReadFully(serverVerifyData, inStr);

							AssertEmpty(inStr);

							/*
							 * Calculate our own checksum.
							 */
							byte[] expectedServerVerifyData = TlsUtilities.PRF(
								securityParameters.masterSecret, "server finished",
								rs.GetCurrentHash(), 12);

							/*
							 * Compare both checksums.
							 */
							if (!Arrays.ConstantTimeAreEqual(expectedServerVerifyData, serverVerifyData))
							{
								/*
								 * Wrong checksum in the finished message.
								 */
								this.FailWithError(AlertLevel.fatal, AlertDescription.handshake_failure);
							}

							connection_state = CS_DONE;

							/*
							* We are now ready to receive application data.
							*/
							this.appDataReady = true;
							break;
						default:
							this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
							break;
					}
					break;
				case HandshakeType.server_hello:
					switch (connection_state)
					{
						case CS_CLIENT_HELLO_SEND:
							/*
							 * Read the server hello message
							 */
							TlsUtilities.CheckVersion(inStr, this);

							/*
							 * Read the server random
							 */
							securityParameters.serverRandom = new byte[32];
							TlsUtilities.ReadFully(securityParameters.serverRandom, inStr);

							byte[] sessionID = TlsUtilities.ReadOpaque8(inStr);
							if (sessionID.Length > 32)
							{
								this.FailWithError(AlertLevel.fatal, AlertDescription.illegal_parameter);
							}

							this.tlsClient.NotifySessionID(sessionID);

							/*
							 * Find out which CipherSuite the server has chosen and check that
							 * it was one of the offered ones.
							 */
							CipherSuite selectedCipherSuite = (CipherSuite)TlsUtilities.ReadUint16(inStr);
							if (!ArrayContains(offeredCipherSuites, selectedCipherSuite)
								|| selectedCipherSuite == CipherSuite.TLS_EMPTY_RENEGOTIATION_INFO_SCSV)
							{
								this.FailWithError(AlertLevel.fatal, AlertDescription.illegal_parameter);
							}

							this.tlsClient.NotifySelectedCipherSuite(selectedCipherSuite);

                            /*
                             * Find out which CompressionMethod the server has chosen and check that
                             * it was one of the offered ones.
                             */
                            CompressionMethod selectedCompressionMethod = (CompressionMethod)TlsUtilities.ReadUint8(inStr);
							if (!ArrayContains(offeredCompressionMethods, selectedCompressionMethod))
							{
								this.FailWithError(AlertLevel.fatal, AlertDescription.illegal_parameter);
							}

                            this.tlsClient.NotifySelectedCompressionMethod(selectedCompressionMethod);

	                        /*
	                         * RFC3546 2.2 The extended server hello message format MAY be
	                         * sent in place of the server hello message when the client has
	                         * requested extended functionality via the extended client hello
	                         * message specified in Section 2.1.
							 * ...
							 * Note that the extended server hello message is only sent in response
							 * to an extended client hello message.  This prevents the possibility
							 * that the extended server hello message could "break" existing TLS 1.0
							 * clients.
	                         */

							/*
							 * TODO RFC 3546 2.3
							 * If [...] the older session is resumed, then the server MUST ignore
							 * extensions appearing in the client hello, and send a server hello
							 * containing no extensions.
							 */

							// ExtensionType -> byte[]
							IDictionary serverExtensions = Platform.CreateHashtable();

							if (inStr.Position < inStr.Length)
							{
								// Process extensions from extended server hello
                                byte[] extBytes = TlsUtilities.ReadOpaque16(inStr);

                                MemoryStream ext = new MemoryStream(extBytes, false);
                                while (ext.Position < ext.Length)
								{
                                    ExtensionType extType = (ExtensionType)TlsUtilities.ReadUint16(ext);
                                    byte[] extValue = TlsUtilities.ReadOpaque16(ext);

									// Note: RFC 5746 makes a special case for EXT_RenegotiationInfo
                                    if (extType != ExtensionType.renegotiation_info
										&& !clientExtensions.Contains(extType))
									{
										/*
										 * RFC 3546 2.3
										 * Note that for all extension types (including those defined in
										 * future), the extension type MUST NOT appear in the extended server
										 * hello unless the same extension type appeared in the corresponding
										 * client hello.  Thus clients MUST abort the handshake if they receive
										 * an extension type in the extended server hello that they did not
										 * request in the associated (extended) client hello.
										 */
										this.FailWithError(AlertLevel.fatal, AlertDescription.unsupported_extension);
									}

									if (serverExtensions.Contains(extType))
									{
										/*
										 * RFC 3546 2.3
										 * Also note that when multiple extensions of different types are
										 * present in the extended client hello or the extended server hello,
										 * the extensions may appear in any order. There MUST NOT be more than
										 * one extension of the same type.
										 */
										this.FailWithError(AlertLevel.fatal, AlertDescription.illegal_parameter);
									}

									serverExtensions.Add(extType, extValue);
								}
							}

							AssertEmpty(inStr);

							/*
							 * RFC 5746 3.4. When a ServerHello is received, the client MUST check if it
							 * includes the "renegotiation_info" extension:
							 */
							{
								bool secure_negotiation = serverExtensions.Contains(ExtensionType.renegotiation_info);

								/*
								 * If the extension is present, set the secure_renegotiation flag
								 * to TRUE.  The client MUST then verify that the length of the
								 * "renegotiated_connection" field is zero, and if it is not, MUST
								 * abort the handshake (by sending a fatal handshake_failure
								 * alert).
								 */
								if (secure_negotiation)
								{
                                    byte[] renegExtValue = (byte[])serverExtensions[ExtensionType.renegotiation_info];

                                    if (!Arrays.ConstantTimeAreEqual(renegExtValue,
                                        CreateRenegotiationInfo(emptybuf)))
									{
										this.FailWithError(AlertLevel.fatal, AlertDescription.handshake_failure);
									}
								}

								tlsClient.NotifySecureRenegotiation(secure_negotiation);
							}

							if (clientExtensions != null)
							{
								tlsClient.ProcessServerExtensions(serverExtensions);
							}

							this.keyExchange = tlsClient.GetKeyExchange();

	                        connection_state = CS_SERVER_HELLO_RECEIVED;
	                        break;
						default:
							this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
							break;
					}
					break;
				case HandshakeType.server_hello_done:
					switch (connection_state)
					{
						case CS_SERVER_CERTIFICATE_RECEIVED:
						case CS_SERVER_KEY_EXCHANGE_RECEIVED:
						case CS_CERTIFICATE_REQUEST_RECEIVED:

							// NB: Original code used case label fall-through
							if (connection_state == CS_SERVER_CERTIFICATE_RECEIVED)
							{
								// There was no server key exchange message; check it's OK
								this.keyExchange.SkipServerKeyExchange();
							}

							AssertEmpty(inStr);

							connection_state = CS_SERVER_HELLO_DONE_RECEIVED;

							TlsCredentials clientCreds = null;
							if (certificateRequest == null)
							{
								this.keyExchange.SkipClientCredentials();
							}
							else
							{
								clientCreds = this.authentication.GetClientCredentials(certificateRequest);

								Certificate clientCert;
								if (clientCreds == null)
								{
									this.keyExchange.SkipClientCredentials();
									clientCert = Certificate.EmptyChain;
								}
								else
								{
									this.keyExchange.ProcessClientCredentials(clientCreds);
									clientCert = clientCreds.Certificate;
								}

								SendClientCertificate(clientCert);
							}

							/*
							 * Send the client key exchange message, depending on the key
							 * exchange we are using in our CipherSuite.
							 */
							SendClientKeyExchange();

							connection_state = CS_CLIENT_KEY_EXCHANGE_SEND;

							if (clientCreds != null && clientCreds is TlsSignerCredentials)
							{
								TlsSignerCredentials signerCreds = (TlsSignerCredentials)clientCreds;
								byte[] md5andsha1 = rs.GetCurrentHash();
								byte[] clientCertificateSignature = signerCreds.GenerateCertificateSignature(
									md5andsha1);
								SendCertificateVerify(clientCertificateSignature);

								connection_state = CS_CERTIFICATE_VERIFY_SEND;
							}
					
							/*
							* Now, we send change cipher state
							*/
							byte[] cmessage = new byte[1];
							cmessage[0] = 1;
							rs.WriteMessage(ContentType.change_cipher_spec, cmessage, 0, cmessage.Length);

							connection_state = CS_CLIENT_CHANGE_CIPHER_SPEC_SEND;

							/*
							 * Calculate the master_secret
							 */
							byte[] pms = this.keyExchange.GeneratePremasterSecret();

							securityParameters.masterSecret = TlsUtilities.PRF(pms, "master secret",
								TlsUtilities.Concat(securityParameters.clientRandom, securityParameters.serverRandom),
								48);

							// TODO Is there a way to ensure the data is really overwritten?
							/*
							 * RFC 2246 8.1. The pre_master_secret should be deleted from
							 * memory once the master_secret has been computed.
							 */
							Array.Clear(pms, 0, pms.Length);

							/*
							 * Initialize our cipher suite
							 */
	                        rs.ClientCipherSpecDecided(tlsClient.GetCompression(), tlsClient.GetCipher());

							/*
							 * Send our finished message.
							 */
							byte[] clientVerifyData = TlsUtilities.PRF(securityParameters.masterSecret,
								"client finished", rs.GetCurrentHash(), 12);

							MemoryStream bos = new MemoryStream();
							TlsUtilities.WriteUint8((byte)HandshakeType.finished, bos);
							TlsUtilities.WriteOpaque24(clientVerifyData, bos);
							byte[] message = bos.ToArray();

							rs.WriteMessage(ContentType.handshake, message, 0, message.Length);

							this.connection_state = CS_CLIENT_FINISHED_SEND;
							break;
						default:
							this.FailWithError(AlertLevel.fatal, AlertDescription.handshake_failure);
							break;
					}
					break;
				case HandshakeType.server_key_exchange:
				{
					switch (connection_state)
					{
						case CS_SERVER_HELLO_RECEIVED:
						case CS_SERVER_CERTIFICATE_RECEIVED:
						{
							// NB: Original code used case label fall-through
							if (connection_state == CS_SERVER_HELLO_RECEIVED)
							{
								// There was no server certificate message; check it's OK
								this.keyExchange.SkipServerCertificate();
								this.authentication = null;
							}

    	                    this.keyExchange.ProcessServerKeyExchange(inStr);

	                        AssertEmpty(inStr);
							break;
						}
						default:
							this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
							break;
					}

					this.connection_state = CS_SERVER_KEY_EXCHANGE_RECEIVED;
					break;
				}
				case HandshakeType.certificate_request:
					switch (connection_state)
					{
						case CS_SERVER_CERTIFICATE_RECEIVED:
						case CS_SERVER_KEY_EXCHANGE_RECEIVED:
						{
							// NB: Original code used case label fall-through
							if (connection_state == CS_SERVER_CERTIFICATE_RECEIVED)
							{
								// There was no server key exchange message; check it's OK
								this.keyExchange.SkipServerKeyExchange();
							}

							if (this.authentication == null)
							{
								/*
								 * RFC 2246 7.4.4. It is a fatal handshake_failure alert
								 * for an anonymous server to request client identification.
								 */
								this.FailWithError(AlertLevel.fatal, AlertDescription.handshake_failure);
							}

                            int numTypes = TlsUtilities.ReadUint8(inStr);
                            ClientCertificateType[] certificateTypes = new ClientCertificateType[numTypes];
                            for (int i = 0; i < numTypes; ++i)
                            {
                                certificateTypes[i] = (ClientCertificateType)TlsUtilities.ReadUint8(inStr);
                            }

                            byte[] authorities = TlsUtilities.ReadOpaque16(inStr);

							AssertEmpty(inStr);

                            IList authorityDNs = Platform.CreateArrayList();

							MemoryStream bis = new MemoryStream(authorities, false);
							while (bis.Position < bis.Length)
							{
								byte[] dnBytes = TlsUtilities.ReadOpaque16(bis);
								// TODO Switch to X500Name when available
								authorityDNs.Add(X509Name.GetInstance(Asn1Object.FromByteArray(dnBytes)));
							}

							this.certificateRequest = new CertificateRequest(certificateTypes,
								authorityDNs);
							this.keyExchange.ValidateCertificateRequest(this.certificateRequest);

							break;
						}
						default:
							this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
							break;
					}

					this.connection_state = CS_CERTIFICATE_REQUEST_RECEIVED;
					break;
				case HandshakeType.hello_request:
					/*
					 * RFC 2246 7.4.1.1 Hello request
					 * This message will be ignored by the client if the client is currently
					 * negotiating a session. This message may be ignored by the client if it
					 * does not wish to renegotiate a session, or the client may, if it wishes,
					 * respond with a no_renegotiation alert.
					 */
					if (connection_state == CS_DONE)
					{
						// Renegotiation not supported yet
						SendAlert(AlertLevel.warning, AlertDescription.no_renegotiation);
					}
					break;
				case HandshakeType.client_key_exchange:
				case HandshakeType.certificate_verify:
				case HandshakeType.client_hello:
				default:
					// We do not support this!
					this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
					break;
			}
		}
示例#3
0
        private void ProcessHandshakeMessage(HandshakeType type, byte[] buf)
        {
            MemoryStream inStr = new MemoryStream(buf, false);

            /*
             * Check the type.
             */
            switch (type)
            {
            case HandshakeType.certificate:
            {
                switch (connection_state)
                {
                case CS_SERVER_HELLO_RECEIVED:
                {
                    // Parse the Certificate message and send to cipher suite

                    Certificate serverCertificate = Certificate.Parse(inStr);

                    AssertEmpty(inStr);

                    this.keyExchange.ProcessServerCertificate(serverCertificate);

                    this.authentication = tlsClient.GetAuthentication();
                    this.authentication.NotifyServerCertificate(serverCertificate);

                    break;
                }

                default:
                    this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
                    break;
                }

                connection_state = CS_SERVER_CERTIFICATE_RECEIVED;
                break;
            }

            case HandshakeType.finished:
                switch (connection_state)
                {
                case CS_SERVER_CHANGE_CIPHER_SPEC_RECEIVED:
                    /*
                     * Read the checksum from the finished message, it has always 12 bytes.
                     */
                    byte[] serverVerifyData = new byte[12];
                    TlsUtilities.ReadFully(serverVerifyData, inStr);

                    AssertEmpty(inStr);

                    /*
                     * Calculate our own checksum.
                     */
                    byte[] expectedServerVerifyData = TlsUtilities.PRF(
                        securityParameters.masterSecret, "server finished",
                        rs.GetCurrentHash(), 12);

                    /*
                     * Compare both checksums.
                     */
                    if (!Arrays.ConstantTimeAreEqual(expectedServerVerifyData, serverVerifyData))
                    {
                        /*
                         * Wrong checksum in the finished message.
                         */
                        this.FailWithError(AlertLevel.fatal, AlertDescription.handshake_failure);
                    }

                    connection_state = CS_DONE;

                    /*
                     * We are now ready to receive application data.
                     */
                    this.appDataReady = true;
                    break;

                default:
                    this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
                    break;
                }
                break;

            case HandshakeType.server_hello:
                switch (connection_state)
                {
                case CS_CLIENT_HELLO_SEND:
                    /*
                     * Read the server hello message
                     */
                    TlsUtilities.CheckVersion(inStr, this);

                    /*
                     * Read the server random
                     */
                    securityParameters.serverRandom = new byte[32];
                    TlsUtilities.ReadFully(securityParameters.serverRandom, inStr);

                    byte[] sessionID = TlsUtilities.ReadOpaque8(inStr);
                    if (sessionID.Length > 32)
                    {
                        this.FailWithError(AlertLevel.fatal, AlertDescription.illegal_parameter);
                    }

                    this.tlsClient.NotifySessionID(sessionID);

                    /*
                     * Find out which CipherSuite the server has chosen and check that
                     * it was one of the offered ones.
                     */
                    CipherSuite selectedCipherSuite = (CipherSuite)TlsUtilities.ReadUint16(inStr);
                    if (!ArrayContains(offeredCipherSuites, selectedCipherSuite) ||
                        selectedCipherSuite == CipherSuite.TLS_EMPTY_RENEGOTIATION_INFO_SCSV)
                    {
                        this.FailWithError(AlertLevel.fatal, AlertDescription.illegal_parameter);
                    }

                    this.tlsClient.NotifySelectedCipherSuite(selectedCipherSuite);

                    /*
                     * Find out which CompressionMethod the server has chosen and check that
                     * it was one of the offered ones.
                     */
                    CompressionMethod selectedCompressionMethod = (CompressionMethod)TlsUtilities.ReadUint8(inStr);
                    if (!ArrayContains(offeredCompressionMethods, selectedCompressionMethod))
                    {
                        this.FailWithError(AlertLevel.fatal, AlertDescription.illegal_parameter);
                    }

                    this.tlsClient.NotifySelectedCompressionMethod(selectedCompressionMethod);

                    /*
                     * RFC3546 2.2 The extended server hello message format MAY be
                     * sent in place of the server hello message when the client has
                     * requested extended functionality via the extended client hello
                     * message specified in Section 2.1.
                     * ...
                     * Note that the extended server hello message is only sent in response
                     * to an extended client hello message.  This prevents the possibility
                     * that the extended server hello message could "break" existing TLS 1.0
                     * clients.
                     */

                    /*
                     * TODO RFC 3546 2.3
                     * If [...] the older session is resumed, then the server MUST ignore
                     * extensions appearing in the client hello, and send a server hello
                     * containing no extensions.
                     */

                    // ExtensionType -> byte[]
                    IDictionary serverExtensions = Platform.CreateHashtable();

                    if (inStr.Position < inStr.Length)
                    {
                        // Process extensions from extended server hello
                        byte[] extBytes = TlsUtilities.ReadOpaque16(inStr);

                        MemoryStream ext = new MemoryStream(extBytes, false);
                        while (ext.Position < ext.Length)
                        {
                            ExtensionType extType  = (ExtensionType)TlsUtilities.ReadUint16(ext);
                            byte[]        extValue = TlsUtilities.ReadOpaque16(ext);

                            // Note: RFC 5746 makes a special case for EXT_RenegotiationInfo
                            if (extType != ExtensionType.renegotiation_info &&
                                !clientExtensions.Contains(extType))
                            {
                                /*
                                 * RFC 3546 2.3
                                 * Note that for all extension types (including those defined in
                                 * future), the extension type MUST NOT appear in the extended server
                                 * hello unless the same extension type appeared in the corresponding
                                 * client hello.  Thus clients MUST abort the handshake if they receive
                                 * an extension type in the extended server hello that they did not
                                 * request in the associated (extended) client hello.
                                 */
                                this.FailWithError(AlertLevel.fatal, AlertDescription.unsupported_extension);
                            }

                            if (serverExtensions.Contains(extType))
                            {
                                /*
                                 * RFC 3546 2.3
                                 * Also note that when multiple extensions of different types are
                                 * present in the extended client hello or the extended server hello,
                                 * the extensions may appear in any order. There MUST NOT be more than
                                 * one extension of the same type.
                                 */
                                this.FailWithError(AlertLevel.fatal, AlertDescription.illegal_parameter);
                            }

                            serverExtensions.Add(extType, extValue);
                        }
                    }

                    AssertEmpty(inStr);

                    /*
                     * RFC 5746 3.4. When a ServerHello is received, the client MUST check if it
                     * includes the "renegotiation_info" extension:
                     */
                    {
                        bool secure_negotiation = serverExtensions.Contains(ExtensionType.renegotiation_info);

                        /*
                         * If the extension is present, set the secure_renegotiation flag
                         * to TRUE.  The client MUST then verify that the length of the
                         * "renegotiated_connection" field is zero, and if it is not, MUST
                         * abort the handshake (by sending a fatal handshake_failure
                         * alert).
                         */
                        if (secure_negotiation)
                        {
                            byte[] renegExtValue = (byte[])serverExtensions[ExtensionType.renegotiation_info];

                            if (!Arrays.ConstantTimeAreEqual(renegExtValue,
                                                             CreateRenegotiationInfo(emptybuf)))
                            {
                                this.FailWithError(AlertLevel.fatal, AlertDescription.handshake_failure);
                            }
                        }

                        tlsClient.NotifySecureRenegotiation(secure_negotiation);
                    }

                    if (clientExtensions != null)
                    {
                        tlsClient.ProcessServerExtensions(serverExtensions);
                    }

                    this.keyExchange = tlsClient.GetKeyExchange();

                    connection_state = CS_SERVER_HELLO_RECEIVED;
                    break;

                default:
                    this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
                    break;
                }
                break;

            case HandshakeType.server_hello_done:
                switch (connection_state)
                {
                case CS_SERVER_CERTIFICATE_RECEIVED:
                case CS_SERVER_KEY_EXCHANGE_RECEIVED:
                case CS_CERTIFICATE_REQUEST_RECEIVED:

                    // NB: Original code used case label fall-through
                    if (connection_state == CS_SERVER_CERTIFICATE_RECEIVED)
                    {
                        // There was no server key exchange message; check it's OK
                        this.keyExchange.SkipServerKeyExchange();
                    }

                    AssertEmpty(inStr);

                    connection_state = CS_SERVER_HELLO_DONE_RECEIVED;

                    TlsCredentials clientCreds = null;
                    if (certificateRequest == null)
                    {
                        this.keyExchange.SkipClientCredentials();
                    }
                    else
                    {
                        clientCreds = this.authentication.GetClientCredentials(certificateRequest);

                        Certificate clientCert;
                        if (clientCreds == null)
                        {
                            this.keyExchange.SkipClientCredentials();
                            clientCert = Certificate.EmptyChain;
                        }
                        else
                        {
                            this.keyExchange.ProcessClientCredentials(clientCreds);
                            clientCert = clientCreds.Certificate;
                        }

                        SendClientCertificate(clientCert);
                    }

                    /*
                     * Send the client key exchange message, depending on the key
                     * exchange we are using in our CipherSuite.
                     */
                    SendClientKeyExchange();

                    connection_state = CS_CLIENT_KEY_EXCHANGE_SEND;

                    if (clientCreds != null && clientCreds is TlsSignerCredentials)
                    {
                        TlsSignerCredentials signerCreds = (TlsSignerCredentials)clientCreds;
                        byte[] md5andsha1 = rs.GetCurrentHash();
                        byte[] clientCertificateSignature = signerCreds.GenerateCertificateSignature(
                            md5andsha1);
                        SendCertificateVerify(clientCertificateSignature);

                        connection_state = CS_CERTIFICATE_VERIFY_SEND;
                    }

                    /*
                     * Now, we send change cipher state
                     */
                    byte[] cmessage = new byte[1];
                    cmessage[0] = 1;
                    rs.WriteMessage(ContentType.change_cipher_spec, cmessage, 0, cmessage.Length);

                    connection_state = CS_CLIENT_CHANGE_CIPHER_SPEC_SEND;

                    /*
                     * Calculate the master_secret
                     */
                    byte[] pms = this.keyExchange.GeneratePremasterSecret();

                    securityParameters.masterSecret = TlsUtilities.PRF(pms, "master secret",
                                                                       TlsUtilities.Concat(securityParameters.clientRandom, securityParameters.serverRandom),
                                                                       48);

                    // TODO Is there a way to ensure the data is really overwritten?

                    /*
                     * RFC 2246 8.1. The pre_master_secret should be deleted from
                     * memory once the master_secret has been computed.
                     */
                    Array.Clear(pms, 0, pms.Length);

                    /*
                     * Initialize our cipher suite
                     */
                    rs.ClientCipherSpecDecided(tlsClient.GetCompression(), tlsClient.GetCipher());

                    /*
                     * Send our finished message.
                     */
                    byte[] clientVerifyData = TlsUtilities.PRF(securityParameters.masterSecret,
                                                               "client finished", rs.GetCurrentHash(), 12);

                    MemoryStream bos = new MemoryStream();
                    TlsUtilities.WriteUint8((byte)HandshakeType.finished, bos);
                    TlsUtilities.WriteOpaque24(clientVerifyData, bos);
                    byte[] message = bos.ToArray();

                    rs.WriteMessage(ContentType.handshake, message, 0, message.Length);

                    this.connection_state = CS_CLIENT_FINISHED_SEND;
                    break;

                default:
                    this.FailWithError(AlertLevel.fatal, AlertDescription.handshake_failure);
                    break;
                }
                break;

            case HandshakeType.server_key_exchange:
            {
                switch (connection_state)
                {
                case CS_SERVER_HELLO_RECEIVED:
                case CS_SERVER_CERTIFICATE_RECEIVED:
                {
                    // NB: Original code used case label fall-through
                    if (connection_state == CS_SERVER_HELLO_RECEIVED)
                    {
                        // There was no server certificate message; check it's OK
                        this.keyExchange.SkipServerCertificate();
                        this.authentication = null;
                    }

                    this.keyExchange.ProcessServerKeyExchange(inStr);

                    AssertEmpty(inStr);
                    break;
                }

                default:
                    this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
                    break;
                }

                this.connection_state = CS_SERVER_KEY_EXCHANGE_RECEIVED;
                break;
            }

            case HandshakeType.certificate_request:
                switch (connection_state)
                {
                case CS_SERVER_CERTIFICATE_RECEIVED:
                case CS_SERVER_KEY_EXCHANGE_RECEIVED:
                {
                    // NB: Original code used case label fall-through
                    if (connection_state == CS_SERVER_CERTIFICATE_RECEIVED)
                    {
                        // There was no server key exchange message; check it's OK
                        this.keyExchange.SkipServerKeyExchange();
                    }

                    if (this.authentication == null)
                    {
                        /*
                         * RFC 2246 7.4.4. It is a fatal handshake_failure alert
                         * for an anonymous server to request client identification.
                         */
                        this.FailWithError(AlertLevel.fatal, AlertDescription.handshake_failure);
                    }

                    int numTypes = TlsUtilities.ReadUint8(inStr);
                    ClientCertificateType[] certificateTypes = new ClientCertificateType[numTypes];
                    for (int i = 0; i < numTypes; ++i)
                    {
                        certificateTypes[i] = (ClientCertificateType)TlsUtilities.ReadUint8(inStr);
                    }

                    byte[] authorities = TlsUtilities.ReadOpaque16(inStr);

                    AssertEmpty(inStr);

                    IList authorityDNs = Platform.CreateArrayList();

                    MemoryStream bis = new MemoryStream(authorities, false);
                    while (bis.Position < bis.Length)
                    {
                        byte[] dnBytes = TlsUtilities.ReadOpaque16(bis);
                        // TODO Switch to X500Name when available
                        authorityDNs.Add(X509Name.GetInstance(Asn1Object.FromByteArray(dnBytes)));
                    }

                    this.certificateRequest = new CertificateRequest(certificateTypes,
                                                                     authorityDNs);
                    this.keyExchange.ValidateCertificateRequest(this.certificateRequest);

                    break;
                }

                default:
                    this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
                    break;
                }

                this.connection_state = CS_CERTIFICATE_REQUEST_RECEIVED;
                break;

            case HandshakeType.hello_request:
                /*
                 * RFC 2246 7.4.1.1 Hello request
                 * This message will be ignored by the client if the client is currently
                 * negotiating a session. This message may be ignored by the client if it
                 * does not wish to renegotiate a session, or the client may, if it wishes,
                 * respond with a no_renegotiation alert.
                 */
                if (connection_state == CS_DONE)
                {
                    // Renegotiation not supported yet
                    SendAlert(AlertLevel.warning, AlertDescription.no_renegotiation);
                }
                break;

            case HandshakeType.client_key_exchange:
            case HandshakeType.certificate_verify:
            case HandshakeType.client_hello:
            default:
                // We do not support this!
                this.FailWithError(AlertLevel.fatal, AlertDescription.unexpected_message);
                break;
            }
        }
		public CertificateRequest(ClientCertificateType[] certificateTypes, IList certificateAuthorities)
		{
			this.certificateTypes = certificateTypes;
			this.certificateAuthorities = certificateAuthorities;
		}