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/*
* Server Key Exchange Message
* (C) 2004-2010,2012 Jack Lloyd
*
* Released under the terms of the Botan license
*/
#include <botan/internal/tls_messages.h>
#include <botan/internal/tls_reader.h>
#include <botan/internal/tls_extensions.h>
#include <botan/tls_record.h>
#include <botan/internal/assert.h>
#include <botan/credentials_manager.h>
#include <botan/loadstor.h>
#include <botan/pubkey.h>
#include <botan/dh.h>
#include <botan/ecdh.h>
#include <botan/rsa.h>
#include <botan/oids.h>
#include <memory>
namespace Botan {
namespace TLS {
/**
* Create a new Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(Record_Writer& writer,
Handshake_State* state,
const Policy& policy,
Credentials_Manager& creds,
RandomNumberGenerator& rng,
const Private_Key* signing_key) :
m_kex_key(0)
{
const std::string kex_algo = state->suite.kex_algo();
if(kex_algo == "PSK" || kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
{
std::string identity_hint =
creds.psk_identity_hint("tls-server",
state->client_hello->sni_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, 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 = 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 = ecdh.release();
}
else if(kex_algo != "PSK")
throw Internal_Error("Server_Key_Exchange: Unknown kex type " + kex_algo);
if(state->suite.sig_algo() != "")
{
BOTAN_ASSERT(signing_key, "No signing key set");
std::pair<std::string, Signature_Format> format =
state->choose_sig_format(signing_key, m_hash_algo, m_sig_algo, false);
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(writer.send(*this));
}
/**
* Deserialize a Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(const MemoryRegion<byte>& buf,
const std::string& kex_algo,
const std::string& sig_algo,
Protocol_Version version) :
m_kex_key(0)
{
if(buf.size() < 6)
throw Decoding_Error("Server_Key_Exchange: Packet corrupted");
TLS_Data_Reader reader(buf);
/*
* We really are just serializing things back to what they were
* before, but unfortunately to know where the signature is we need
* to be able to parse the whole thing anyway.
*/
if(kex_algo == "PSK" || kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
{
const std::string identity_hint = reader.get_string(2, 0, 65535);
append_tls_length_value(m_params, identity_hint, 2);
}
if(kex_algo == "DH" || kex_algo == "DHE_PSK")
{
// 3 bigints, DH p, g, Y
for(size_t i = 0; i != 3; ++i)
{
BigInt v = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
append_tls_length_value(m_params, BigInt::encode(v), 2);
}
}
else if(kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
{
const byte curve_type = reader.get_byte();
if(curve_type != 3)
throw Decoding_Error("Server_Key_Exchange: Server sent non-named ECC curve");
const u16bit curve_id = reader.get_u16bit();
const std::string name = Supported_Elliptic_Curves::curve_id_to_name(curve_id);
MemoryVector<byte> ecdh_key = reader.get_range<byte>(1, 1, 255);
if(name == "")
throw Decoding_Error("Server_Key_Exchange: Server sent unknown named curve " +
std::to_string(curve_id));
m_params.push_back(curve_type);
m_params.push_back(get_byte(0, curve_id));
m_params.push_back(get_byte(1, curve_id));
append_tls_length_value(m_params, ecdh_key, 1);
}
else if(kex_algo != "PSK")
throw Decoding_Error("Server_Key_Exchange: Unsupported kex type " + kex_algo);
if(sig_algo != "")
{
if(version >= Protocol_Version::TLS_V12)
{
m_hash_algo = Signature_Algorithms::hash_algo_name(reader.get_byte());
m_sig_algo = Signature_Algorithms::sig_algo_name(reader.get_byte());
}
m_signature = reader.get_range<byte>(2, 0, 65535);
}
}
/**
* Serialize a Server Key Exchange message
*/
MemoryVector<byte> Server_Key_Exchange::serialize() const
{
MemoryVector<byte> buf = params();
if(m_signature.size())
{
// This should be an explicit version check
if(m_hash_algo != "" && m_sig_algo != "")
{
buf.push_back(Signature_Algorithms::hash_algo_code(m_hash_algo));
buf.push_back(Signature_Algorithms::sig_algo_code(m_sig_algo));
}
append_tls_length_value(buf, m_signature, 2);
}
return buf;
}
/**
* Verify a Server Key Exchange message
*/
bool Server_Key_Exchange::verify(const X509_Certificate& cert,
Handshake_State* state) const
{
std::unique_ptr<Public_Key> key(cert.subject_public_key());
std::pair<std::string, Signature_Format> format =
state->understand_sig_format(key.get(), m_hash_algo, m_sig_algo, false);
PK_Verifier verifier(*key, format.first, format.second);
verifier.update(state->client_hello->random());
verifier.update(state->server_hello->random());
verifier.update(params());
return verifier.check_signature(m_signature);
}
const Private_Key& Server_Key_Exchange::server_kex_key() const
{
BOTAN_ASSERT(m_kex_key, "Key is non-NULL");
return *m_kex_key;
}
}
}
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