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/**
* Server Key Exchange Message
* (C) 2004-2010 Jack Lloyd
*
* Released under the terms of the Botan license
*/
#include <botan/tls_messages.h>
#include <botan/pubkey.h>
#include <botan/dh.h>
#include <botan/rsa.h>
#include <botan/dsa.h>
#include <botan/loadstor.h>
#include <memory>
namespace Botan {
/**
* Create a new Server Key Exchange message
*/
Server_Key_Exchange::Server_Key_Exchange(RandomNumberGenerator& rng,
Record_Writer& writer,
const Public_Key* kex_key,
const Private_Key* priv_key,
const MemoryRegion<byte>& c_random,
const MemoryRegion<byte>& s_random,
HandshakeHash& hash)
{
const DH_PublicKey* dh_pub = dynamic_cast<const DH_PublicKey*>(kex_key);
const RSA_PublicKey* rsa_pub = dynamic_cast<const RSA_PublicKey*>(kex_key);
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 if(rsa_pub)
{
params.push_back(rsa_pub->get_n());
params.push_back(rsa_pub->get_e());
}
else
throw Invalid_Argument("Bad key for TLS key exchange: not DH or RSA");
std::string padding = "";
Signature_Format format = IEEE_1363;
if(priv_key->algo_name() == "RSA")
padding = "EMSA3(TLS.Digest.0)";
else if(priv_key->algo_name() == "DSA")
{
padding == "EMSA1(SHA-1)";
format = DER_SEQUENCE;
}
else
throw Invalid_Argument(priv_key->algo_name() +
" is invalid/unknown for TLS signatures");
PK_Signer signer(*priv_key, padding, format);
signer.update(c_random);
signer.update(s_random);
signer.update(serialize_params());
signature = signer.signature(rng);
send(writer, hash);
}
/**
* Serialize a Server Key Exchange message
*/
SecureVector<byte> Server_Key_Exchange::serialize() const
{
SecureVector<byte> buf = serialize_params();
u16bit sig_len = signature.size();
buf.append(get_byte(0, sig_len));
buf.append(get_byte(1, sig_len));
buf.append(signature);
return buf;
}
/**
* Serialize the ServerParams structure
*/
SecureVector<byte> Server_Key_Exchange::serialize_params() const
{
SecureVector<byte> buf;
for(u32bit j = 0; j != params.size(); j++)
{
SecureVector<byte> param = BigInt::encode(params[j]);
u16bit param_size = param.size();
buf.append(get_byte(0, param_size));
buf.append(get_byte(1, param_size));
buf.append(param);
}
return buf;
}
/**
* Deserialize a Server Key Exchange message
*/
void Server_Key_Exchange::deserialize(const MemoryRegion<byte>& buf)
{
if(buf.size() < 6)
throw Decoding_Error("Server_Key_Exchange: Packet corrupted");
SecureVector<byte> values[4];
u32bit so_far = 0;
for(u32bit j = 0; j != 4; j++)
{
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[j].set(buf + so_far, len);
so_far += len;
if(j == 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() == 2)
return new RSA_PublicKey(params[0], params[1]);
else 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,
const MemoryRegion<byte>& c_random,
const MemoryRegion<byte>& s_random) const
{
std::unique_ptr<Public_Key> key(cert.subject_public_key());
std::string padding = "";
Signature_Format format = IEEE_1363;
if(key->algo_name() == "RSA")
padding = "EMSA3(TLS.Digest.0)";
else if(key->algo_name() == "DSA")
{
padding == "EMSA1(SHA-1)";
format = DER_SEQUENCE;
}
else
throw Invalid_Argument(key->algo_name() +
" is invalid/unknown for TLS signatures");
PK_Verifier verifier(*key, padding, format);
SecureVector<byte> params_got = serialize_params();
verifier.update(c_random);
verifier.update(s_random);
verifier.update(params_got);
return verifier.check_signature(signature, signature.size());
}
}
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