/*

* TLS Callbacks

* (C) 2016 Jack Lloyd

*     2017 Harry Reimann, Rohde & Schwarz Cybersecurity

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/tls_callbacks.h>

#include <botan/tls_policy.h>

#include <botan/tls_algos.h>

#include <botan/x509path.h>

#include <botan/ocsp.h>

#include <botan/dh.h>

#include <botan/ecdh.h>

#include <botan/tls_exceptn.h>

#include <botan/internal/ct_utils.h>

#if defined(BOTAN_HAS_CURVE_25519)

  #include <botan/curve25519.h>

#endif

namespace Botan {

void TLS::Callbacks::tls_inspect_handshake_msg(const Handshake_Message&)

   {

   // default is no op

   }

std::string TLS::Callbacks::tls_server_choose_app_protocol(const std::vector<std::string>&)

   {

   return "";

   }

std::string TLS::Callbacks::tls_peer_network_identity()

   {

   return "";

   }

void TLS::Callbacks::tls_modify_extensions(Extensions&, Connection_Side)

   {

   }

void TLS::Callbacks::tls_examine_extensions(const Extensions&, Connection_Side)

   {

   }

std::string TLS::Callbacks::tls_decode_group_param(Group_Params group_param)

   {

   return group_param_to_string(group_param);

   }

void TLS::Callbacks::tls_verify_cert_chain(

   const std::vector<X509_Certificate>& cert_chain,

   const std::vector<std::shared_ptr<const OCSP::Response>>& ocsp_responses,

   const std::vector<Certificate_Store*>& trusted_roots,

   Usage_Type usage,

   const std::string& hostname,

   const TLS::Policy& policy)

   {

   if(cert_chain.empty())

      throw Invalid_Argument("Certificate chain was empty");

   Path_Validation_Restrictions restrictions(policy.require_cert_revocation_info(),

                                             policy.minimum_signature_strength());

   Path_Validation_Result result =

      x509_path_validate(cert_chain,

                         restrictions,

                         trusted_roots,

                         (usage == Usage_Type::TLS_SERVER_AUTH ? hostname : ""),

                         usage,

                         std::chrono::system_clock::now(),

                         tls_verify_cert_chain_ocsp_timeout(),

                         ocsp_responses);

   if(!result.successful_validation())

      {

      throw TLS_Exception(Alert::BAD_CERTIFICATE,

                          "Certificate validation failure: " + result.result_string());

      }

   }

std::vector<uint8_t> TLS::Callbacks::tls_sign_message(

   const Private_Key& key,

   RandomNumberGenerator& rng,

   const std::string& emsa,

   Signature_Format format,

   const std::vector<uint8_t>& msg)

   {

   PK_Signer signer(key, rng, emsa, format);

   return signer.sign_message(msg, rng);

   }

bool TLS::Callbacks::tls_verify_message(

   const Public_Key& key,

   const std::string& emsa,

   Signature_Format format,

   const std::vector<uint8_t>& msg,

   const std::vector<uint8_t>& sig)

   {

   PK_Verifier verifier(key, emsa, format);

   return verifier.verify_message(msg, sig);

   }

std::pair<secure_vector<uint8_t>, std::vector<uint8_t>> TLS::Callbacks::tls_dh_agree(

   const std::vector<uint8_t>& modulus,

   const std::vector<uint8_t>& generator,

   const std::vector<uint8_t>& peer_public_value,

   const Policy& policy,

   RandomNumberGenerator& rng)

   {

   BigInt p = BigInt::decode(modulus);

   BigInt g = BigInt::decode(generator);

   BigInt Y = BigInt::decode(peer_public_value);

   /*

    * A basic check for key validity. As we do not know q here we

    * cannot check that Y is in the right subgroup. However since

    * our key is ephemeral there does not seem to be any

    * advantage to bogus keys anyway.

    */

   if(Y <= 1 || Y >= p - 1)

      throw TLS_Exception(Alert::ILLEGAL_PARAMETER,

                          "Server sent bad DH key for DHE exchange");

   DL_Group group(p, g);

   if(!group.verify_group(rng, false))

      throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,

                          "DH group validation failed");

   DH_PublicKey peer_key(group, Y);

   policy.check_peer_key_acceptable(peer_key);

   DH_PrivateKey priv_key(rng, group);

   PK_Key_Agreement ka(priv_key, rng, "Raw");

   secure_vector<uint8_t> dh_secret = CT::strip_leading_zeros(

      ka.derive_key(0, peer_key.public_value()).bits_of());

   return std::make_pair(dh_secret, priv_key.public_value());

   }

std::pair<secure_vector<uint8_t>, std::vector<uint8_t>> TLS::Callbacks::tls_ecdh_agree(

   const std::string& curve_name,

   const std::vector<uint8_t>& peer_public_value,

   const Policy& policy,

   RandomNumberGenerator& rng,

   bool compressed)

   {

   secure_vector<uint8_t> ecdh_secret;

   std::vector<uint8_t> our_public_value;

   if(curve_name == "x25519")

      {

#if defined(BOTAN_HAS_CURVE_25519)

      if(peer_public_value.size() != 32)

         {

         throw TLS_Exception(Alert::HANDSHAKE_FAILURE, "Invalid X25519 key size");

         }

      Curve25519_PublicKey peer_key(peer_public_value);

      policy.check_peer_key_acceptable(peer_key);

      Curve25519_PrivateKey priv_key(rng);

      PK_Key_Agreement ka(priv_key, rng, "Raw");

      ecdh_secret = ka.derive_key(0, peer_key.public_value()).bits_of();

      // X25519 is always compressed but sent as "uncompressed" in TLS

      our_public_value = priv_key.public_value();

#else

      throw Internal_Error("Negotiated X25519 somehow, but it is disabled");

#endif

      }

   else

      {

      EC_Group group(OID::from_string(curve_name));

      ECDH_PublicKey peer_key(group, group.OS2ECP(peer_public_value));

      policy.check_peer_key_acceptable(peer_key);

      ECDH_PrivateKey priv_key(rng, group);

      PK_Key_Agreement ka(priv_key, rng, "Raw");

      ecdh_secret = ka.derive_key(0, peer_key.public_value()).bits_of();

      our_public_value = priv_key.public_value(compressed ? PointGFp::COMPRESSED : PointGFp::UNCOMPRESSED);

      }

   return std::make_pair(ecdh_secret, our_public_value);

   }

}