Add ability to ignore certs for Splunk in sink

[merbla]

From #23

In a development environment it would be helpful to ignore sinks.

An implementation similar to the Seq sink may be appropriate.

[veccsolutions]

I too am in need of this. Is there any plan for it? Dotnet core doesn't seem to have a cert validation callback like the original dot net does.

[merbla]

@veccsolutions a new release is out with the HttpMessageHandler exposed. I will update the wiki however it may be of use to your situation.

[veccsolutions]

Thanks! I'll be checking this out in the next couple of days.

[veccsolutions]

@merbla Thanks for exposing it. However, I can't specify whether to ignore it or not through the config files. I was able to write my own sink configuration method to do it using the one you have already created as a template.

My custom configuration method is identical to yours except for the following changes.

1. In project.json I increased the netstandard framework to 1.6 (I didn't try earlier versions, but the ServerCertificateCustomValidationCallback property wasn't in the netstandard 1.1 framework)

2. I added an ignoreSsl parameter, and the following between your null checks and newing up the eventcollectorsink object:

           if (ignoreSsl)
           {
               //only ignore the certificates for correct host
               var uri = new Uri(splunkHost);
               var lowerHost = uri.Host?.ToLowerInvariant() ?? string.Empty;
   
   #if NET45
               ServicePointManager.ServerCertificateValidationCallback +=
                   (object sender, X509Certificate cert, X509Chain chain, SslPolicyErrors policyErrors) =>
                       ServerCertificateCallback((sender as WebRequest)?.RequestUri?.Host, lowerHost, policyErrors);
   #else
               HttpClientHandler client;
               //allow custom httpmessagehandlers
               if (messageHandler == null)
               {
                   client = new HttpClientHandler();
               }
               else
               {
                   client = messageHandler as HttpClientHandler;
               }
   
               //if the message handler is either HttpClientHandler or derived from it we can add to the callback
               if (client != null)
               {
                   client.ServerCertificateCustomValidationCallback +=
                       (HttpRequestMessage message, X509Certificate2 cert, X509Chain chain, SslPolicyErrors policyErrors) =>
                           ServerCertificateCallback(message?.RequestUri?.Host, lowerHost, policyErrors);
   
                   messageHandler = client;
               }
   #endif
           }

3. The ServerCertificateCallback method is:

       private static bool ServerCertificateCallback(string requestHost, string splunkHost, SslPolicyErrors policyErrors)
       {
           //quick check for no error
           if (policyErrors == SslPolicyErrors.None)
           {
               return true;
           }
   
           return requestHost.ToLowerInvariant() == splunkHost;
       }

[merbla]

@veccsolutions you are correct. The change was generally targeted at dotnet core and opening up the HttpMessageHandler for more than just the situation to ignore SSL certs.

We would have overload the config with an ignoreSSLValidation like param for the configuration from file to work. I am a little reluctant to implement however I know it can be a pain in development.

Generally what frameworks are you targeting?

[nblumhardt]

Just to add to @merbla's remarks about being reluctant to add this - I think we'd expose ourselves to some criticism by dealing with SSL certificate policy in the sink. (Even in the case of self-signed certificates, it's usually better to add the certificate to the list trusted by the client machine rather than disable validation entirely.)

[veccsolutions]

That's fine. I'll continue with my separate config method. I just need to be able to do it without managing the certs on the local system and still using the config file for different deployment targets like local development vs QA vs Production etc.

[merbla]

Closing this for now.