Try different TLS versions to allow download if TLS1.0 is disabled on…

… the server fixes luckyrat#20

KeePassFaviconDownloader.csproj

@@ -51,10 +51,13 @@
     <Reference Include="System" />
     <Reference Include="System.Data" />
     <Reference Include="System.Drawing" />
+    <Reference Include="System.Net" />
+    <Reference Include="System.Security" />
     <Reference Include="System.Windows.Forms" />
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="TlsExtensions.cs" />
     <Compile Include="KeePassFaviconDownloaderExt.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>

KeePassFaviconDownloaderExt.cs

@@ -46,6 +46,7 @@ public sealed class KeePassFaviconDownloaderExt : Plugin
 	{
 		// The plugin remembers its host in this variable.
 		private IPluginHost m_host = null;
+		private static SecurityProtocolType originalSecurityProtocol = System.Net.ServicePointManager.SecurityProtocol;
 
         public override string UpdateUrl
         {
@@ -439,13 +440,22 @@ private Uri getFromFaviconExplicitLocation(Uri fullURI, ref MemoryStream ms, ref
         /// <param name="message">Any error message is sent back through this string.</param>
         /// <returns></returns>
         private bool getFavicon(Uri uri, ref MemoryStream ms, ref string message)
+        {
+            return getFaviconWithSecurityProtocol(uri, ref ms, ref message, originalSecurityProtocol) || 
+                (originalSecurityProtocol != SecurityProtocolTypeExtensions.Tls12 && getFaviconWithSecurityProtocol(uri, ref ms, ref message, SecurityProtocolTypeExtensions.Tls12)) ||
+                (originalSecurityProtocol != SecurityProtocolTypeExtensions.Tls11 && getFaviconWithSecurityProtocol(uri, ref ms, ref message, SecurityProtocolTypeExtensions.Tls11));
+        }
+
+        private bool getFaviconWithSecurityProtocol(Uri uri, ref MemoryStream ms, ref string message, SecurityProtocolType securityProtocolType)
         {
             Stream s = null;
             Image img = null;
             MemoryStream memStream = new MemoryStream();
 
             try
             {
+                ServicePointManager.SecurityProtocol = securityProtocolType;
+
                 WebRequest webreq = WebRequest.Create(uri);
                 ((HttpWebRequest)webreq).UserAgent = "Mozilla/5.0 (Windows 6.1; rv:27.0) Gecko/20100101 Firefox/27.0";
                 ((HttpWebRequest)webreq).CookieContainer = new System.Net.CookieContainer();

TlsExtensions.cs

@@ -0,0 +1,26 @@
+using System.Security.Authentication;
+
+namespace System.Net
+{
+    /// <summary>
+    /// https://support.microsoft.com/en-gb/help/3154517/support-for-tls-system-default-versions-included-in-the-net-framework
+    /// </summary>
+    public static class SecurityProtocolTypeExtensions
+    {
+        public const SecurityProtocolType Tls12 = (SecurityProtocolType)SslProtocolsExtensions.Tls12;
+        public const SecurityProtocolType Tls11 = (SecurityProtocolType)SslProtocolsExtensions.Tls11;
+        public const SecurityProtocolType SystemDefault = (SecurityProtocolType)0;
+    }
+}
+
+namespace System.Security.Authentication
+{
+    /// <summary>
+    /// https://support.microsoft.com/en-gb/help/3154517/support-for-tls-system-default-versions-included-in-the-net-framework
+    /// </summary>
+    public static class SslProtocolsExtensions
+    {
+        public const SslProtocols Tls12 = (SslProtocols)0x00000C00;
+        public const SslProtocols Tls11 = (SslProtocols)0x00000300;
+    }
+}