protected virtual void SendServerHelloMessage()
{
HandshakeMessage message = new HandshakeMessage(HandshakeType.server_hello);
{
ProtocolVersion server_version = mTlsServer.GetServerVersion();
if (!server_version.IsEqualOrEarlierVersionOf(Context.ClientVersion))
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
mRecordStream.ReadVersion = server_version;
mRecordStream.SetWriteVersion(server_version);
mRecordStream.SetRestrictReadVersion(true);
ContextAdmin.SetServerVersion(server_version);
TlsUtilities.WriteVersion(server_version, message);
}
message.Write(this.mSecurityParameters.serverRandom);
/*
* The server may return an empty session_id to indicate that the session will not be cached
* and therefore cannot be resumed.
*/
TlsUtilities.WriteOpaque8(TlsUtilities.EmptyBytes, message);
int selectedCipherSuite = mTlsServer.GetSelectedCipherSuite();
if (!Arrays.Contains(mOfferedCipherSuites, selectedCipherSuite) ||
selectedCipherSuite == CipherSuite.TLS_NULL_WITH_NULL_NULL ||
CipherSuite.IsScsv(selectedCipherSuite) ||
!TlsUtilities.IsValidCipherSuiteForVersion(selectedCipherSuite, Context.ServerVersion))
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
mSecurityParameters.cipherSuite = selectedCipherSuite;
byte selectedCompressionMethod = mTlsServer.GetSelectedCompressionMethod();
if (!Arrays.Contains(mOfferedCompressionMethods, selectedCompressionMethod))
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
mSecurityParameters.compressionAlgorithm = selectedCompressionMethod;
TlsUtilities.WriteUint16(selectedCipherSuite, message);
TlsUtilities.WriteUint8(selectedCompressionMethod, message);
this.mServerExtensions = mTlsServer.GetServerExtensions();
/*
* RFC 5746 3.6. Server Behavior: Initial Handshake
*/
if (this.mSecureRenegotiation)
{
byte[] renegExtData = TlsUtilities.GetExtensionData(this.mServerExtensions, ExtensionType.renegotiation_info);
bool noRenegExt = (null == renegExtData);
if (noRenegExt)
{
/*
* Note that Sending a "renegotiation_info" extension in response to a ClientHello
* containing only the SCSV is an explicit exception to the prohibition in RFC 5246,
* Section 7.4.1.4, on the server Sending unsolicited extensions and is only allowed
* because the client is signaling its willingness to receive the extension via the
* TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV.
*/
/*
* If the secure_renegotiation flag is set to TRUE, the server MUST include an empty
* "renegotiation_info" extension in the ServerHello message.
*/
this.mServerExtensions = TlsExtensionsUtilities.EnsureExtensionsInitialised(mServerExtensions);
this.mServerExtensions[ExtensionType.renegotiation_info] = CreateRenegotiationInfo(TlsUtilities.EmptyBytes);
}
}
if (mSecurityParameters.extendedMasterSecret)
{
this.mServerExtensions = TlsExtensionsUtilities.EnsureExtensionsInitialised(mServerExtensions);
TlsExtensionsUtilities.AddExtendedMasterSecretExtension(mServerExtensions);
}
/*
* 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.
*/
if (this.mServerExtensions != null)
{
this.mSecurityParameters.encryptThenMac = TlsExtensionsUtilities.HasEncryptThenMacExtension(mServerExtensions);
this.mSecurityParameters.maxFragmentLength = ProcessMaxFragmentLengthExtension(mClientExtensions,
mServerExtensions, AlertDescription.internal_error);
this.mSecurityParameters.truncatedHMac = TlsExtensionsUtilities.HasTruncatedHMacExtension(mServerExtensions);
/*
* TODO It's surprising that there's no provision to allow a 'fresh' CertificateStatus to be sent in
* a session resumption handshake.
*/
this.mAllowCertificateStatus = !mResumedSession &&
TlsUtilities.HasExpectedEmptyExtensionData(mServerExtensions, ExtensionType.status_request,
AlertDescription.internal_error);
this.mExpectSessionTicket = !mResumedSession &&
TlsUtilities.HasExpectedEmptyExtensionData(mServerExtensions, ExtensionType.session_ticket,
AlertDescription.internal_error);
WriteExtensions(message, this.mServerExtensions);
}
mSecurityParameters.prfAlgorithm = GetPrfAlgorithm(Context, mSecurityParameters.CipherSuite);
/*
* RFC 5246 7.4.9. Any cipher suite which does not explicitly specify verify_data_length has
* a verify_data_length equal to 12. This includes all existing cipher suites.
*/
mSecurityParameters.verifyDataLength = 12;
ApplyMaxFragmentLengthExtension();
message.WriteToRecordStream(this);
}
protected virtual byte[] GenerateServerHello(ServerHandshakeState state)
{
SecurityParameters securityParameters = state.serverContext.SecurityParameters;
MemoryStream buf = new MemoryStream();
{
ProtocolVersion server_version = state.server.GetServerVersion();
if (!server_version.IsEqualOrEarlierVersionOf(state.serverContext.ClientVersion))
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
// TODO Read RFCs for guidance on the expected record layer version number
// recordStream.setReadVersion(server_version);
// recordStream.setWriteVersion(server_version);
// recordStream.setRestrictReadVersion(true);
state.serverContext.SetServerVersion(server_version);
TlsUtilities.WriteVersion(state.serverContext.ServerVersion, buf);
}
buf.Write(securityParameters.ServerRandom, 0, securityParameters.ServerRandom.Length);
/*
* The server may return an empty session_id to indicate that the session will not be cached
* and therefore cannot be resumed.
*/
TlsUtilities.WriteOpaque8(TlsUtilities.EmptyBytes, buf);
int selectedCipherSuite = state.server.GetSelectedCipherSuite();
if (!Arrays.Contains(state.offeredCipherSuites, selectedCipherSuite) ||
selectedCipherSuite == CipherSuite.TLS_NULL_WITH_NULL_NULL ||
CipherSuite.IsScsv(selectedCipherSuite) ||
!TlsUtilities.IsValidCipherSuiteForVersion(selectedCipherSuite, state.serverContext.ServerVersion))
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
ValidateSelectedCipherSuite(selectedCipherSuite, AlertDescription.internal_error);
securityParameters.cipherSuite = selectedCipherSuite;
byte selectedCompressionMethod = state.server.GetSelectedCompressionMethod();
if (!Arrays.Contains(state.offeredCompressionMethods, selectedCompressionMethod))
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
securityParameters.compressionAlgorithm = selectedCompressionMethod;
TlsUtilities.WriteUint16(selectedCipherSuite, buf);
TlsUtilities.WriteUint8(selectedCompressionMethod, buf);
state.serverExtensions = state.server.GetServerExtensions();
/*
* RFC 5746 3.6. Server Behavior: Initial Handshake
*/
if (state.secure_renegotiation)
{
byte[] renegExtData = TlsUtilities.GetExtensionData(state.serverExtensions, ExtensionType.renegotiation_info);
bool noRenegExt = (null == renegExtData);
if (noRenegExt)
{
/*
* Note that sending a "renegotiation_info" extension in response to a ClientHello
* containing only the SCSV is an explicit exception to the prohibition in RFC 5246,
* Section 7.4.1.4, on the server sending unsolicited extensions and is only allowed
* because the client is signaling its willingness to receive the extension via the
* TLS_EMPTY_RENEGOTIATION_INFO_SCSV SCSV.
*/
/*
* If the secure_renegotiation flag is set to TRUE, the server MUST include an empty
* "renegotiation_info" extension in the ServerHello message.
*/
state.serverExtensions = TlsExtensionsUtilities.EnsureExtensionsInitialised(state.serverExtensions);
state.serverExtensions[ExtensionType.renegotiation_info] = TlsProtocol.CreateRenegotiationInfo(TlsUtilities.EmptyBytes);
}
}
if (securityParameters.extendedMasterSecret)
{
state.serverExtensions = TlsExtensionsUtilities.EnsureExtensionsInitialised(state.serverExtensions);
TlsExtensionsUtilities.AddExtendedMasterSecretExtension(state.serverExtensions);
}
/*
* 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.
*/
if (state.serverExtensions != null)
{
securityParameters.encryptThenMac = TlsExtensionsUtilities.HasEncryptThenMacExtension(state.serverExtensions);
securityParameters.maxFragmentLength = EvaluateMaxFragmentLengthExtension(state.resumedSession,
state.clientExtensions, state.serverExtensions, AlertDescription.internal_error);
securityParameters.truncatedHMac = TlsExtensionsUtilities.HasTruncatedHMacExtension(state.serverExtensions);
/*
* TODO It's surprising that there's no provision to allow a 'fresh' CertificateStatus to be sent in
* a session resumption handshake.
*/
state.allowCertificateStatus = !state.resumedSession &&
TlsUtilities.HasExpectedEmptyExtensionData(state.serverExtensions, ExtensionType.status_request,
AlertDescription.internal_error);
state.expectSessionTicket = !state.resumedSession &&
TlsUtilities.HasExpectedEmptyExtensionData(state.serverExtensions, ExtensionType.session_ticket,
AlertDescription.internal_error);
TlsProtocol.WriteExtensions(buf, state.serverExtensions);
}
securityParameters.prfAlgorithm = TlsProtocol.GetPrfAlgorithm(state.serverContext,
securityParameters.CipherSuite);
/*
* RFC 5246 7.4.9. Any cipher suite which does not explicitly specify verify_data_length
* has a verify_data_length equal to 12. This includes all existing cipher suites.
*/
securityParameters.verifyDataLength = 12;
return(buf.ToArray());
}