Update HMACAuthenticationAttribute.cs

[vhatuncev]

var serverClock = TimeSpan.FromTicks(DateTime.UtcNow.Ticks);
var requestClock = TimeSpan.FromTicks(DateTime.UtcNow.AddSeconds(1).Ticks);

var serverTime = Convert.ToUInt64(serverClock.TotalSeconds);
var requestTime = Convert.ToUInt64(requestClock.TotalSeconds);

Console.WriteLine(serverTime - requestTime);

[vhatuncev]

need additional check for requestTotalSeconds variable
for example if requestTotalSeconds more on one second(because request host has different time),
result of statement serverTotalSeconds - requestTotalSeconds
will be very big value and not negative as expected so all request will treated as reply attack and rejected check code in comment for this file.
suggestion is - convert to signed integer, so even if request local time will be far away from server time it will

[saipuli]

I ran into the same issue, but used
Math.Abs((Int64)(serverTotalSeconds - requestTotalSeconds)) > requestMaxAgeInSeconds
I used Abs because I wanted to discourage clients with clocks that are way out of sync from calling my apis.

[vhatuncev]

Well, it can save you, but not more then requestMaxAgeInSeconds, if clients out of sync for hours you still get the error.
Another thing, it saves you only if clients have local time in future, relatively from server, if client clocks will be in the past, relatively from server, it won't help.