Mono: HttpWebRequest SSL Errors on non-SSL URI

I have a console application that I wrote for .NET/Windows that I suddenly had the need for on my unix system. Mono has, for the most part, been hugely successful at providing this for me.

There is however a small issue: The application issues many HttpWebRequests as it runs, and for a small portion of these, Mono is returning an error:

Error getting response stream (Write: The authentication or decryption has failed.): SendFailure

This error message seems to indicate an SSL error. However, this application does not issue any request to SSL-secured URIs (i.e. all URIs are http://).

The main code in question is as follows:

HttpWebRequest req = WebRequest.Create(url) as HttpWebRequest;
req.UserAgent = UserAgent;
req.AuthenticationLevel = AuthenticationLevel.None;
req.AllowAutoRedirect = true;
req.KeepAlive = true;
req.CachePolicy = new RequestCachePolicy(RequestCacheLevel.NoCacheNoStore);
req.Timeout = timeout;

if (useCompression) {
    req.Headers.Add(HttpRequestHeader.AcceptEncoding, "gzip,deflate");
}

Edit: For the purposes of running this code, you can define dummy variables as follows:

string url = "http://example.com";
string UserAgent = "WhateverBot";
int timeout = 5000;
bool useCompre开发者_运维知识库ssion = true;

It should be noted that the code works without any problem on Windows/.NET.

---

I also had this problem when running Mono in Windows even when the URL is not HTTPS. Let me say this loudly: ITS NOT REDIRECTED.

The solution has been to use the hack:

System.Net.ServicePointManager.ServerCertificateValidationCallback += delegate 
{ 
    return true; 
};  

My guess is that Mono does not look in the Windows keystore for certificates so does not find any so HTTPWebXXXX is not initialized correctly and then fails incorrectly.

My guess is that anyone taking the trouble to reproduce your error will know what they are doing with Mono (unlike me for example) and so have their environment set up correctly and be unable reproduce this real world problem.