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/*
* SSLv3 PRF
* (C) 2004-2006 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/prf_ssl3.h>
#include <botan/symkey.h>
#include <botan/exceptn.h>
#include <botan/sha160.h>
#include <botan/md5.h>
namespace Botan {
namespace {
/*
* Return the next inner hash
*/
OctetString next_hash(size_t where, size_t want,
HashFunction& md5, HashFunction& sha1,
const byte secret[], size_t secret_len,
const byte seed[], size_t seed_len)
{
BOTAN_ASSERT(want <= md5.output_length(),
"Output size producable by MD5");
const byte ASCII_A_CHAR = 0x41;
for(size_t j = 0; j != where + 1; j++)
sha1.update(static_cast<byte>(ASCII_A_CHAR + where));
sha1.update(secret, secret_len);
sha1.update(seed, seed_len);
secure_vector<byte> sha1_hash = sha1.final();
md5.update(secret, secret_len);
md5.update(sha1_hash);
secure_vector<byte> md5_hash = md5.final();
return OctetString(&md5_hash[0], want);
}
}
/*
* SSL3 PRF
*/
secure_vector<byte> SSL3_PRF::derive(size_t key_len,
const byte secret[], size_t secret_len,
const byte seed[], size_t seed_len) const
{
if(key_len > 416)
throw Invalid_Argument("SSL3_PRF: Requested key length is too large");
MD5 md5;
SHA_160 sha1;
OctetString output;
int counter = 0;
while(key_len)
{
const size_t produce = std::min<size_t>(key_len, md5.output_length());
output = output + next_hash(counter++, produce, md5, sha1,
secret, secret_len, seed, seed_len);
key_len -= produce;
}
return output.bits_of();
}
}
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