/**
* Create a new Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(Handshake_IO& io,
Handshake_State& state,
const Policy& policy,
Credentials_Manager& creds,
RandomNumberGenerator& rng,
const Private_Key* signing_key)
{
const std::string hostname = state.client_hello()->sni_hostname();
const Kex_Algo kex_algo = state.ciphersuite().kex_method();
if(kex_algo == Kex_Algo::PSK || kex_algo == Kex_Algo::DHE_PSK || kex_algo == Kex_Algo::ECDHE_PSK)
{
std::string identity_hint =
creds.psk_identity_hint("tls-server", hostname);
append_tls_length_value(m_params, identity_hint, 2);
}
if(kex_algo == Kex_Algo::DH || kex_algo == Kex_Algo::DHE_PSK)
{
const std::vector<Group_Params> dh_groups = state.client_hello()->supported_dh_groups();
Group_Params shared_group = Group_Params::NONE;
/*
If the client does not send any DH groups in the supported groups
extension, but does offer DH ciphersuites, we select a group arbitrarily
*/
if(dh_groups.empty())
{
shared_group = policy.default_dh_group();
}
else
{
shared_group = policy.choose_key_exchange_group(dh_groups);
}
if(shared_group == Group_Params::NONE)
throw TLS_Exception(Alert::HANDSHAKE_FAILURE,
"Could not agree on a DH group with the client");
BOTAN_ASSERT(group_param_is_dh(shared_group), "DH groups for the DH ciphersuites god");
const std::string group_name = state.callbacks().tls_decode_group_param(shared_group);
std::unique_ptr<DH_PrivateKey> dh(new DH_PrivateKey(rng, DL_Group(group_name)));
append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_p()), 2);
append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_g()), 2);
append_tls_length_value(m_params, dh->public_value(), 2);
m_kex_key.reset(dh.release());
}
else if(kex_algo == Kex_Algo::ECDH || kex_algo == Kex_Algo::ECDHE_PSK)
{
const std::vector<Group_Params> ec_groups = state.client_hello()->supported_ecc_curves();
if(ec_groups.empty())
throw Internal_Error("Client sent no ECC extension but we negotiated ECDH");
Group_Params shared_group = policy.choose_key_exchange_group(ec_groups);
if(shared_group == Group_Params::NONE)
throw TLS_Exception(Alert::HANDSHAKE_FAILURE, "No shared ECC group with client");
std::vector<uint8_t> ecdh_public_val;
if(shared_group == Group_Params::X25519)
{
#if defined(BOTAN_HAS_CURVE_25519)
std::unique_ptr<Curve25519_PrivateKey> x25519(new Curve25519_PrivateKey(rng));
ecdh_public_val = x25519->public_value();
m_kex_key.reset(x25519.release());
#else
throw Internal_Error("Negotiated X25519 somehow, but it is disabled");
#endif
}
else
{
Group_Params curve = policy.choose_key_exchange_group(ec_groups);
const std::string curve_name = state.callbacks().tls_decode_group_param(curve);
EC_Group ec_group(curve_name);
std::unique_ptr<ECDH_PrivateKey> ecdh(new ECDH_PrivateKey(rng, ec_group));
// follow client's preference for point compression
ecdh_public_val = ecdh->public_value(
state.client_hello()->prefers_compressed_ec_points() ?
PointGFp::COMPRESSED : PointGFp::UNCOMPRESSED);
m_kex_key.reset(ecdh.release());
}
const uint16_t named_curve_id = static_cast<uint16_t>(shared_group);
m_params.push_back(3); // named curve
m_params.push_back(get_byte(0, named_curve_id));
m_params.push_back(get_byte(1, named_curve_id));
append_tls_length_value(m_params, ecdh_public_val, 1);
}
#if defined(BOTAN_HAS_SRP6)
else if(kex_algo == Kex_Algo::SRP_SHA)
{
const std::string srp_identifier = state.client_hello()->srp_identifier();
std::string group_id;
BigInt v;
std::vector<uint8_t> salt;
const bool found = creds.srp_verifier("tls-server", hostname,
srp_identifier,
group_id, v, salt,
policy.hide_unknown_users());
if(!found)
throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
"Unknown SRP user " + srp_identifier);
m_srp_params.reset(new SRP6_Server_Session);
BigInt B = m_srp_params->step1(v, group_id,
"SHA-1", rng);
DL_Group group(group_id);
append_tls_length_value(m_params, BigInt::encode(group.get_p()), 2);
append_tls_length_value(m_params, BigInt::encode(group.get_g()), 2);
append_tls_length_value(m_params, salt, 1);
append_tls_length_value(m_params, BigInt::encode(B), 2);
}
#endif
#if defined(BOTAN_HAS_CECPQ1)
else if(kex_algo == Kex_Algo::CECPQ1)
{
std::vector<uint8_t> cecpq1_offer(CECPQ1_OFFER_BYTES);
m_cecpq1_key.reset(new CECPQ1_key);
CECPQ1_offer(cecpq1_offer.data(), m_cecpq1_key.get(), rng);
append_tls_length_value(m_params, cecpq1_offer, 2);
}
#endif
else if(kex_algo != Kex_Algo::PSK)
{
throw Internal_Error("Server_Key_Exchange: Unknown kex type " +
kex_method_to_string(kex_algo));
}
if(state.ciphersuite().signature_used())
{
BOTAN_ASSERT(signing_key, "Signing key was set");
std::pair<std::string, Signature_Format> format =
state.choose_sig_format(*signing_key, m_scheme, false, policy);
std::vector<uint8_t> buf = state.client_hello()->random();
buf += state.server_hello()->random();
buf += params();
m_signature =
state.callbacks().tls_sign_message(*signing_key, rng,
format.first, format.second, buf);
}
state.hash().update(io.send(*this));
}
/**
* Create a new Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(Handshake_IO& io,
Handshake_State& state,
const Policy& policy,
Credentials_Manager& creds,
RandomNumberGenerator& rng,
const Private_Key* signing_key)
{
const std::string hostname = state.client_hello()->sni_hostname();
const std::string kex_algo = state.ciphersuite().kex_algo();
if(kex_algo == "PSK" || kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
{
std::string identity_hint =
creds.psk_identity_hint("tls-server", hostname);
append_tls_length_value(m_params, identity_hint, 2);
}
if(kex_algo == "DH" || kex_algo == "DHE_PSK")
{
std::unique_ptr<DH_PrivateKey> dh(new DH_PrivateKey(rng, DL_Group(policy.dh_group())));
append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_p()), 2);
append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_g()), 2);
append_tls_length_value(m_params, dh->public_value(), 2);
m_kex_key.reset(dh.release());
}
else if(kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
{
const std::vector<std::string>& curves =
state.client_hello()->supported_ecc_curves();
if(curves.empty())
throw Internal_Error("Client sent no ECC extension but we negotiated ECDH");
const std::string curve_name = policy.choose_curve(curves);
if(curve_name == "")
throw TLS_Exception(Alert::HANDSHAKE_FAILURE,
"Could not agree on an ECC curve with the client");
EC_Group ec_group(curve_name);
std::unique_ptr<ECDH_PrivateKey> ecdh(new ECDH_PrivateKey(rng, ec_group));
const std::string ecdh_domain_oid = ecdh->domain().get_oid();
const std::string domain = OIDS::lookup(OID(ecdh_domain_oid));
if(domain == "")
throw Internal_Error("Could not find name of ECDH domain " + ecdh_domain_oid);
const u16bit named_curve_id = Supported_Elliptic_Curves::name_to_curve_id(domain);
m_params.push_back(3); // named curve
m_params.push_back(get_byte(0, named_curve_id));
m_params.push_back(get_byte(1, named_curve_id));
append_tls_length_value(m_params, ecdh->public_value(), 1);
m_kex_key.reset(ecdh.release());
}
#if defined(BOTAN_HAS_SRP6)
else if(kex_algo == "SRP_SHA")
{
const std::string srp_identifier = state.client_hello()->srp_identifier();
std::string group_id;
BigInt v;
std::vector<byte> salt;
const bool found = creds.srp_verifier("tls-server", hostname,
srp_identifier,
group_id, v, salt,
policy.hide_unknown_users());
if(!found)
throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
"Unknown SRP user " + srp_identifier);
m_srp_params.reset(new SRP6_Server_Session);
BigInt B = m_srp_params->step1(v, group_id,
"SHA-1", rng);
DL_Group group(group_id);
append_tls_length_value(m_params, BigInt::encode(group.get_p()), 2);
append_tls_length_value(m_params, BigInt::encode(group.get_g()), 2);
append_tls_length_value(m_params, salt, 1);
append_tls_length_value(m_params, BigInt::encode(B), 2);
}
#endif
else if(kex_algo != "PSK")
throw Internal_Error("Server_Key_Exchange: Unknown kex type " + kex_algo);
if(state.ciphersuite().sig_algo() != "")
{
BOTAN_ASSERT(signing_key, "Signing key was set");
std::pair<std::string, Signature_Format> format =
state.choose_sig_format(*signing_key, m_hash_algo, m_sig_algo, false, policy);
PK_Signer signer(*signing_key, format.first, format.second);
signer.update(state.client_hello()->random());
signer.update(state.server_hello()->random());
signer.update(params());
m_signature = signer.signature(rng);
}
state.hash().update(io.send(*this));
}