enhancementhelp wanted
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Beschreibung
It seems like that Botan requires every new DTLS client hello be handled in a new TLS_Server. Therefore, DTLS session cookies only provide protection against amplification, but not against resource exhaustion attacks. An attacker can easily consume a few hundred megabytes of memory by creating many TLS servers, without actually responding to hello verify requests.
Finding no clue in the documentation, I end up writing a very ugly solution like this:
std::vector<uint8_t> msg_contents(record_buf.begin() + 12, record_buf.begin() + length + 8);
Client_Hello client_hello(msg_contents);
Hello_Verify_Request verify(client_hello.cookie_input_data(), client_identity, cookie_secret);
if (client_hello.cookie() == verify.cookie())
{
std::unique_ptr<Server> server(new Server(/* blablabla */));
// monkey-patch the sequence numbers in Handshake_IO here
}
else
{
std::unique_ptr<Datagram_Handshake_IO>
handshake_io(new Datagram_Handshake_IO(/* blablabla */));
handshake_io->send(verify);
}
Is there any facility in Botan to verify a DTLS cookie statelessly, like GnuTLS's gnutls_dtls_cookie_verify? If not, will there be any plan to add such an interface?