public bool ExternalCertificateValidationCallback(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors, Logger log)
{
var senderHostname = RequestExecutor.ConvertSenderObjectToHostname(sender);
var cacheKey = new Key(senderHostname, certificate.GetCertHashString(), sslPolicyErrors);
Task<CachedValue> task;
if (_externalCertificateValidationCallbackCache.TryGetValue(cacheKey, out var existingTask) == false)
{
task = new Task<CachedValue>(() => CheckExternalCertificateValidation(senderHostname, certificate, chain, sslPolicyErrors, log));
existingTask = _externalCertificateValidationCallbackCache.GetOrAdd(cacheKey, task);
if (existingTask == task)
{
task.Start();
if (_externalCertificateValidationCallbackCache.Count > 50)
{
foreach (var item in _externalCertificateValidationCallbackCache.Where(x => x.Value.IsCompleted).OrderBy(x => x.Value.Result.Until).Take(25))
{
_externalCertificateValidationCallbackCache.TryRemove(item.Key, out _);
}
}
}
}
CachedValue cachedValue;
try
{
cachedValue = existingTask.Result;
}
catch
{
_externalCertificateValidationCallbackCache.TryRemove(cacheKey, out _);
throw;
}
if (_server.Time.GetUtcNow() < cachedValue.Until)
return cachedValue.Valid;
var cachedValueNext = cachedValue.Next;
if (cachedValueNext != null)
return ReturnTaskValue(cachedValueNext);
task = new Task<CachedValue>(() =>
CheckExternalCertificateValidation(senderHostname, certificate, chain, sslPolicyErrors, log));
var nextTask = Interlocked.CompareExchange(ref cachedValue.Next, task, null);
if (nextTask != null)
return ReturnTaskValue(nextTask);
task.ContinueWith(done =>
{
_externalCertificateValidationCallbackCache.TryUpdate(cacheKey, done, existingTask);
}, TaskContinuationOptions.OnlyOnRanToCompletion);
task.Start();
return cachedValue.Valid; // we are computing this, but may take some time, let's use cached value for now
bool ReturnTaskValue(Task<CachedValue> task)
{
if (task.IsCompletedSuccessfully)
return task.Result.Valid;
// not done yet? return the cached value
return cachedValue.Valid;
}
}