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/*
* Server Key Exchange Message
* (C) 2004-2010 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/pubkey.h>
#include <botan/dh.h>
#include <botan/loadstor.h>
#include <memory>
namespace Botan {
/**
* Create a new Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(Record_Writer& writer,
TLS_Handshake_State* state,
RandomNumberGenerator& rng,
const Private_Key* private_key)
{
const DH_PublicKey* dh_pub = dynamic_cast<const DH_PublicKey*>(state->kex_priv);
if(dh_pub)
{
params.push_back(dh_pub->get_domain().get_p());
params.push_back(dh_pub->get_domain().get_g());
params.push_back(BigInt::decode(dh_pub->public_value()));
}
else
throw Invalid_Argument("Unknown key type " + state->kex_priv->algo_name() +
" for TLS key exchange");
// FIXME: this should respect client's hash preferences
if(state->version >= TLS_V12)
hash_algo = TLS_ALGO_HASH_SHA256;
else
hash_algo = TLS_ALGO_NONE;
std::pair<std::string, Signature_Format> format =
state->choose_sig_format(private_key, hash_algo, false);
PK_Signer signer(*private_key, format.first, format.second);
signer.update(state->client_hello->random());
signer.update(state->server_hello->random());
signer.update(serialize_params());
signature = signer.signature(rng);
send(writer, state->hash);
}
/**
* Serialize a Server Key Exchange message
*/
MemoryVector<byte> Server_Key_Exchange::serialize() const
{
MemoryVector<byte> buf = serialize_params();
if(hash_algo != TLS_ALGO_NONE)
{}
append_tls_length_value(buf, signature, 2);
return buf;
}
/**
* Serialize the ServerParams structure
*/
MemoryVector<byte> Server_Key_Exchange::serialize_params() const
{
MemoryVector<byte> buf;
for(size_t i = 0; i != params.size(); ++i)
append_tls_length_value(buf, BigInt::encode(params[i]), 2);
return buf;
}
/**
* Deserialize a Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(const MemoryRegion<byte>& buf,
TLS_Ciphersuite_Algos kex_alg,
TLS_Ciphersuite_Algos sig_alg,
Version_Code version)
{
if(buf.size() < 6)
throw Decoding_Error("Server_Key_Exchange: Packet corrupted");
TLS_Data_Reader reader(buf);
if(kex_alg == TLS_ALGO_KEYEXCH_DH)
{
// 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));
params.push_back(v);
}
}
else
throw Decoding_Error("Unsupported server key exchange type");
if(sig_alg != TLS_ALGO_SIGNER_ANON)
{
if(version < TLS_V12)
hash_algo = TLS_ALGO_NONE; // use old defaults
else
hash_algo = Signature_Algorithms::hash_algo_code(reader.get_byte());
signature = reader.get_range<byte>(2, 0, 65535);
}
}
/**
* Return the public key
*/
Public_Key* Server_Key_Exchange::key() const
{
if(params.size() == 3)
return new DH_PublicKey(DL_Group(params[0], params[1]), params[2]);
else
throw Internal_Error("Server_Key_Exchange::key: No key set");
}
/**
* Verify a Server Key Exchange message
*/
bool Server_Key_Exchange::verify(const X509_Certificate& cert,
TLS_Handshake_State* state) const
{
std::auto_ptr<Public_Key> key(cert.subject_public_key());
std::pair<std::string, Signature_Format> format =
state->choose_sig_format(key.get(), hash_algo, false);
PK_Verifier verifier(*key, format.first, format.second);
verifier.update(state->client_hello->random());
verifier.update(state->server_hello->random());
verifier.update(serialize_params());
return verifier.check_signature(signature);
}
}
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