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/*
* TLS PRF
* (C) 2004-2006 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/prf_tls.h>
#include <botan/xor_buf.h>
#include <botan/hmac.h>
#include <botan/md5.h>
#include <botan/sha160.h>
namespace Botan {
namespace {
/*
* TLS PRF P_hash function
*/
SecureVector<byte> P_hash(MessageAuthenticationCode* mac,
u32bit len,
const byte secret[], u32bit secret_len,
const byte seed[], u32bit seed_len)
{
SecureVector<byte> out;
mac->set_key(secret, secret_len);
SecureVector<byte> A(seed, seed_len);
while(len)
{
const u32bit this_block_len = std::min(mac->OUTPUT_LENGTH, len);
A = mac->process(A);
mac->update(A);
mac->update(seed, seed_len);
SecureVector<byte> block = mac->final();
out.append(block, this_block_len);
len -= this_block_len;
}
return out;
}
}
/*
* TLS PRF Constructor and Destructor
*/
TLS_PRF::TLS_PRF()
{
hmac_md5 = new HMAC(new MD5);
hmac_sha1 = new HMAC(new SHA_160);
}
TLS_PRF::~TLS_PRF()
{
delete hmac_md5;
delete hmac_sha1;
}
/*
* TLS PRF
*/
SecureVector<byte> TLS_PRF::derive(u32bit key_len,
const byte secret[], u32bit secret_len,
const byte seed[], u32bit seed_len) const
{
u32bit S1_len = (secret_len + 1) / 2,
S2_len = (secret_len + 1) / 2;
const byte* S1 = secret;
const byte* S2 = secret + (secret_len - S2_len);
SecureVector<byte> key1, key2;
key1 = P_hash(hmac_md5, key_len, S1, S1_len, seed, seed_len);
key2 = P_hash(hmac_sha1, key_len, S2, S2_len, seed, seed_len);
xor_buf(key1.begin(), key2.begin(), key2.size());
return key1;
}
}
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