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/*************************************************
* SSLv3 PRF Source File *
* (C) 2004-2006 Jack Lloyd *
*************************************************/
#include <botan/prf_ssl3.h>
#include <botan/sha160.h>
#include <botan/md5.h>
#include <memory>
namespace Botan {
namespace {
/*************************************************
* Return the next inner hash *
*************************************************/
OctetString next_hash(u32bit where, u32bit want,
HashFunction& md5, HashFunction& sha1,
const byte secret[], u32bit secret_len,
const byte seed[], u32bit seed_len)
{
if(want > md5.OUTPUT_LENGTH)
throw Internal_Error("SSL3_PRF:next_hash: want is too big");
const byte ASCII_A_CHAR = 0x41;
for(u32bit j = 0; j != where + 1; j++)
sha1.update(ASCII_A_CHAR + where);
sha1.update(secret, secret_len);
sha1.update(seed, seed_len);
SecureVector<byte> sha1_hash = sha1.final();
md5.update(secret, secret_len);
md5.update(sha1_hash);
SecureVector<byte> md5_hash = md5.final();
return OctetString(md5_hash, want);
}
}
/*************************************************
* SSL3 PRF *
*************************************************/
SecureVector<byte> SSL3_PRF::derive(u32bit key_len,
const byte secret[], u32bit secret_len,
const byte seed[], u32bit seed_len) const
{
if(key_len > 416)
throw Internal_Error("SSL3_PRF: Requested key length is too large");
MD5 md5;
SHA_160 sha1;
OctetString output;
int counter = 0;
while(key_len)
{
const u32bit produce = std::min(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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