// find or add a connect token entry
// intentional constant time worst case search
private bool findOrAddConnectToken(EndPoint address, byte[] mac, double time)
{
int matchingTokenIndex = -1;
int oldestTokenIndex = -1;
double oldestTokenTime = 0.0;
for (int i = 0; i < connectTokenHistory.Length; i++)
{
var token = connectTokenHistory[i];
if (MiscUtils.CompareHMACConstantTime(token.mac, mac))
{
matchingTokenIndex = i;
}
if (oldestTokenIndex == -1 || token.time < oldestTokenTime)
{
oldestTokenTime = token.time;
oldestTokenIndex = i;
}
}
// if no entry is found with the mac, this is a new connect token. replace the oldest token entry.
if (matchingTokenIndex == -1)
{
connectTokenHistory[oldestTokenIndex].time = time;
connectTokenHistory[oldestTokenIndex].endpoint = address;
Buffer.BlockCopy(mac, 0, connectTokenHistory[oldestTokenIndex].mac, 0, mac.Length);
return(true);
}
// allow connect tokens we have already seen from the same address
if (connectTokenHistory[matchingTokenIndex].endpoint.Equals(address))
{
return(true);
}
return(false);
}
