HtmlWeb.GetExtensionForContentType throws an exception on .NET Framework 4.5.2

[alex-jitbit]

Exception

Exception message:

System.MethodAccessException: Attempt by security transparent method 'HtmlAgilityPack.PermissionHelper.GetIsRegistryAvailable()' to access security critical method 'System.AppDomain.get_PermissionSet()' failed.

Assembly 'HtmlAgilityPack, Version=1.11.0.0, Culture=neutral, PublicKeyToken=bd319b19eaf3b43a' is marked with the AllowPartiallyTrustedCallersAttribute, and uses the level 2 security transparency model.  Level 2 transparency causes all methods in AllowPartiallyTrustedCallers assemblies to become security transparent by default, which may be the cause of this exception.
   at HtmlAgilityPack.PermissionHelper.GetIsRegistryAvailable() in C:\Users\Jonathan\source\repos\HtmlAgilityPack\HtmlAgilityPack.Shared\HtmlWeb.cs:line 2570
   at HtmlAgilityPack.HtmlWeb.GetExtensionForContentType(String contentType, String def) in C:\Users\Jonathan\source\repos\HtmlAgilityPack\HtmlAgilityPack.Shared\HtmlWeb.cs:line 993

[JonathanMagnan]

Hello @alex-jitbit ,

A runnable project/solution or Fiddle is now required if you would like we look at it.

We now always ask for a project sample even if the issue is easy to reproduce. As a free product, we must find some way to save time to offer an overall better experience for everyone and release fixes faster.

You can send it to: info@zzzprojects.com if you need to keep the source private
Best Regards,

Jonathan

---

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Runtime Evaluation
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[alex-jitbit]

@JonathanMagnan here's a dotnetfiddle

https://dotnetfiddle.net/qjSYgD

[JonathanMagnan]

Hello @alex-jitbit ,

Thank you, my developer looked at it but there is not so much we can do.

This method requires additional permission to check in the key registry available mime type:

html-agility-pack/src/HtmlAgilityPack.Shared/HtmlWeb.cs

Lines 992 to 1017 in 3a6f0d2

	var helper = new PermissionHelper();
	if (!helper.GetIsRegistryAvailable())
	{
	//if (MimeTypes.ContainsValue(contentType))
	//{
	// foreach (KeyValuePair<string, string> pair in MimeTypes)
	// if (pair.Value == contentType)
	// return pair.Value;
	//}
	return def;
	}
	if (helper.GetIsRegistryAvailable())
	{
	try
	{
	RegistryKey reg = Registry.ClassesRoot;
	reg = reg.OpenSubKey(@"MIME\Database\Content Type\" + contentType, false);
	if (reg != null) ext = (string) reg.GetValue("Extension", def);
	}
	catch (Exception)
	{
	ext = def;
	}
	}

Honestly, I'm not really sure why it has been done like that as using registry key is mostly always a bad idea for a third party library.

What we could do on our side is doing a try/catch and in the catch using a dictionary of all common mime know mime type.

Is it something that will work for your scenario?

[alex-jitbit]

I'm not heavily dependent on this bug, just something I stumbled upon.

You can simply steal code from MS https://github.com/Microsoft/referencesource/blob/master/System.Web/MimeMapping.cs

Or even simply call their method (not sure its good idea since it would add System.Web dependency

[JonathanMagnan]

Hello @VBWebprofi ,

The v1.11.4 has been released.

Could you try it and let me know if everything is now working as expected?