msg_hello_verify.cpp

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/*
* DTLS Hello Verify Request
* (C) 2012 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/tls_messages.h>
 
#include <botan/mac.h>
#include <botan/internal/tls_reader.h>
 
namespace Botan::TLS {
 
Hello_Verify_Request::Hello_Verify_Request(const std::vector<uint8_t>& buf) {
   if(buf.size() < 3) {
      throw Decoding_Error("Hello verify request too small");
   }
 
   const Protocol_Version version(buf[0], buf[1]);
 
   if(!version.is_datagram_protocol()) {
      throw Decoding_Error("Unknown version from server in hello verify request");
   }
 
   if(static_cast<size_t>(buf[2]) + 3 != buf.size()) {
      throw Decoding_Error("Bad length in hello verify request");
   }
 
   m_cookie.assign(buf.begin() + 3, buf.end());
}
 
Hello_Verify_Request::Hello_Verify_Request(const std::vector<uint8_t>& client_hello_bits,
                                           std::string_view client_identity,
                                           const SymmetricKey& secret_key) {
   auto hmac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
   hmac->set_key(secret_key);
 
   hmac->update_be(static_cast<uint64_t>(client_hello_bits.size()));
   hmac->update(client_hello_bits);
   hmac->update_be(static_cast<uint64_t>(client_identity.size()));
   hmac->update(client_identity);
 
   m_cookie.resize(hmac->output_length());
   hmac->final(m_cookie.data());
}
 
std::vector<uint8_t> Hello_Verify_Request::serialize() const {
   /* DTLS 1.2 server implementations SHOULD use DTLS version 1.0
      regardless of the version of TLS that is expected to be
      negotiated (RFC 6347, section 4.2.1)
   */
 
   const Protocol_Version format_version(254, 255);  // DTLS 1.0
 
   std::vector<uint8_t> bits;
   bits.push_back(format_version.major_version());
   bits.push_back(format_version.minor_version());
   append_tls_length_value(bits, m_cookie, 1);
   return bits;
}
 
}  // namespace Botan::TLS