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Default SecurityProtocol in .NET 4.5


Question

What is the default security protocol for communicating with servers that support up to TLS 1.2? Will .NET by default, choose the highest security protocol supported on the server side or do I have to explicitly add this line of code:

System.Net.ServicePointManager.SecurityProtocol = 
SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

Is there a way to change this default, besides a code change?

Lastly, does .NET 4.0 only support up to TLS 1.0? i.e. I have to upgrade client projects to 4.5 to support TLS 1.2.

My motivation is to remove support for SSLv3 on the client side even if server supports it (I already have a powershell script to disable this in the machine registry) and to support the highest TLS protocol that the server supports.

Update: Looking at the ServicePointManager class in .NET 4.0 I see no enumerated values for TLS 1.0 and 1.1. In both .NET 4.0/4.5, the default is SecurityProtocolType.Tls|SecurityProtocolType.Ssl3. Hopefully this default won't break by disabling SSLv3 in the registry.

However, I've decided I have to upgrade all apps to .NET 4.5 and to explicitly add SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12; anyway to all bootstrapping code of all applications.

This will make outbound requests to various apis and services to not downgrade to SSLv3 and should select the highest level of TLS.

Does this approach sound reasonable or overkill? I have many applications to update, and I want to future proof them since I hear even TLS 1.0 may be deprecated in the near future by some providers.

As a client making outbound requests to APIs, does disabling SSL3 in the registry even have an effect in the .NET framework? I see by default, TLS 1.1 and 1.2 are not enabled, do we have to enable it via the registry? RE http://support.microsoft.com/kb/245030.

After a bit of investigation, I believe the registry settings will have no affect since they apply to IIS (server subkey) and browsers (client subkey).

Sorry this post turned into multiple questions, followed up with "maybe" answers.

2015/02/03
1
263
2/3/2015 7:16:47 PM

Accepted Answer

Some of the those leaving comments have noted that setting System.Net.ServicePointManager.SecurityProtocol to specific values means that your app won't be able to take advantage of future TLS versions that may become the default values in future updates to .NET. Instead of specifying a fixed list of protocols, you can instead turn on or off protocols you know and care about, leaving any others as they are.

To turn on TLS 1.1 and 1.2 without affecting other protocols:

System.Net.ServicePointManager.SecurityProtocol |= 
    SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

Notice the use of |= to turn on these flags without turning others off.

To turn off SSL3 without affecting other protocols:

System.Net.ServicePointManager.SecurityProtocol &= ~SecurityProtocolType.Ssl3;
2018/09/02
292
9/2/2018 9:54:21 PM


You can override the default behavior in following registry:

Key  : HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319 
Value: SchUseStrongCrypto
Type: REG_DWORD
Data : 1

and

Key  : HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\.NETFramework\v4.0.30319
Value: SchUseStrongCrypto
Type: REG_DWORD
Data : 1

For details, please see the implementation of ServicePointManager.

2018/09/20

Create a text file with a .reg extension and the following contents:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319]
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v4.0.30319]
"SchUseStrongCrypto"=dword:00000001

Or download it from the following source:

https://tls1test.salesforce.com/s/NET40-Enable-TLS-1_2.reg

Double-click to install...

2016/05/09

I have found that when I specify only TLS 1.2 that it will still down negotiate to 1.1. System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

I have specified this in the Global.asax startup method for my .net 4.5 web app.

2015/12/11

Following code will:

  • print enabled protocols
  • print available protocols
  • enable TLS1.2 if platform supports it and if it is not enabled to begin with
  • disable SSL3 if it is enabled
  • print end result

Constants:

  • 48 is SSL3
  • 192 is TLS1
  • 768 is TLS1.1
  • 3072 is TLS1.2

Other protocols will not be affected. This makes this compatible with future protocols (Tls1.3, etc).

Code

// print initial status
    Console.WriteLine("Runtime: " + System.Diagnostics.FileVersionInfo.GetVersionInfo(typeof(int).Assembly.Location).ProductVersion);
    Console.WriteLine("Enabled protocols:   " + ServicePointManager.SecurityProtocol);
    Console.WriteLine("Available protocols: ");
    Boolean platformSupportsTls12 = false;
    foreach (SecurityProtocolType protocol in Enum.GetValues(typeof(SecurityProtocolType))) {                
        Console.WriteLine(protocol.GetHashCode());
        if (protocol.GetHashCode() == 3072){
            platformSupportsTls12 = true;
        }
    }
    Console.WriteLine("Is Tls12 enabled: " + ServicePointManager.SecurityProtocol.HasFlag((SecurityProtocolType)3072));    


// enable Tls12, if possible
    if (!ServicePointManager.SecurityProtocol.HasFlag((SecurityProtocolType)3072)){
        if (platformSupportsTls12){
            Console.WriteLine("Platform supports Tls12, but it is not enabled. Enabling it now.");
            ServicePointManager.SecurityProtocol |= (SecurityProtocolType)3072;
        } else {
            Console.WriteLine("Platform does not supports Tls12.");
        }
    }

// disable ssl3
   if (ServicePointManager.SecurityProtocol.HasFlag(SecurityProtocolType.Ssl3)) { 
      Console.WriteLine("Ssl3SSL3 is enabled. Disabling it now.");
      // disable SSL3. Has no negative impact if SSL3 is already disabled. The enclosing "if" if just for illustration.
      System.Net.ServicePointManager.SecurityProtocol &= ~SecurityProtocolType.Ssl3;                      
   }
    Console.WriteLine("Enabled protocols:   " + ServicePointManager.SecurityProtocol);

Output

Runtime: 4.7.2114.0
Enabled protocols:   Ssl3, Tls
Available protocols: 
0
48
192
768
3072
Is Tls12 enabled: False
Platform supports Tls12, but it is not enabled. Enabling it now.
Ssl3 is enabled. Disabling it now.
Enabled protocols:   Tls, Tls12
2019/04/25

The registry change mechanism worked for me after a struggle. Actually my application was running as 32bit. So I had to change the value under path.

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft.NETFramework\v4.0.30319

The value type needs to be DWORD and value above 0 .Better use 1.Registry settings to get .Net 4.0 app use TLS 1.2 provided .Net 4.5 is installed in the machine.