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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/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");
std::pair<std::string, Signature_Format> format =
state->choose_sig_format(private_key, 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();
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)
{
if(buf.size() < 6)
throw Decoding_Error("Server_Key_Exchange: Packet corrupted");
MemoryVector<byte> values[4];
size_t so_far = 0;
for(size_t i = 0; i != 4; ++i)
{
const u16bit len = make_u16bit(buf[so_far], buf[so_far+1]);
so_far += 2;
if(len + so_far > buf.size())
throw Decoding_Error("Server_Key_Exchange: Packet corrupted");
values[i].resize(len);
copy_mem(&values[i][0], &buf[so_far], len);
so_far += len;
if(i == 2 && so_far == buf.size())
break;
}
params.push_back(BigInt::decode(values[0]));
params.push_back(BigInt::decode(values[1]));
if(values[3].size())
{
params.push_back(BigInt::decode(values[2]));
signature = values[3];
}
else
signature = values[2];
}
/**
* 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(), 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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