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/*
* TLS v1.0 and v1.2 PRFs
* (C) 2004-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/prf_tls.h>
#include <botan/internal/xor_buf.h>
#include <botan/hmac.h>
#include <botan/md5.h>
#include <botan/sha160.h>
namespace Botan {
namespace {
/*
* TLS PRF P_hash function
*/
void P_hash(secure_vector<byte>& output,
MessageAuthenticationCode& mac,
const byte secret[], size_t secret_len,
const byte seed[], size_t seed_len)
{
try
{
mac.set_key(secret, secret_len);
}
catch(Invalid_Key_Length)
{
throw Internal_Error("The premaster secret of " +
std::to_string(secret_len) +
" bytes is too long for the PRF");
}
secure_vector<byte> A(seed, seed + seed_len);
size_t offset = 0;
while(offset != output.size())
{
const size_t this_block_len =
std::min<size_t>(mac.output_length(), output.size() - offset);
A = mac.process(A);
mac.update(A);
mac.update(seed, seed_len);
secure_vector<byte> block = mac.final();
xor_buf(&output[offset], &block[0], this_block_len);
offset += this_block_len;
}
}
}
/*
* TLS PRF Constructor and Destructor
*/
TLS_PRF::TLS_PRF()
{
hmac_md5.reset(new HMAC(new MD5));
hmac_sha1.reset(new HMAC(new SHA_160));
}
/*
* TLS PRF
*/
secure_vector<byte> TLS_PRF::derive(size_t key_len,
const byte secret[], size_t secret_len,
const byte seed[], size_t seed_len) const
{
secure_vector<byte> output(key_len);
size_t S1_len = (secret_len + 1) / 2,
S2_len = (secret_len + 1) / 2;
const byte* S1 = secret;
const byte* S2 = secret + (secret_len - S2_len);
P_hash(output, *hmac_md5, S1, S1_len, seed, seed_len);
P_hash(output, *hmac_sha1, S2, S2_len, seed, seed_len);
return output;
}
/*
* TLS v1.2 PRF Constructor and Destructor
*/
TLS_12_PRF::TLS_12_PRF(MessageAuthenticationCode* mac) : hmac(mac)
{
}
secure_vector<byte> TLS_12_PRF::derive(size_t key_len,
const byte secret[], size_t secret_len,
const byte seed[], size_t seed_len) const
{
secure_vector<byte> output(key_len);
P_hash(output, *hmac, secret, secret_len, seed, seed_len);
return output;
}
}
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