Revert "Test .NET Standard with no dependencies"

NetLicensingClient/NetLicensingClient.csproj

@@ -1,11 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>netstandard2.0</TargetFramework>
     <ReleaseVersion>2.x</ReleaseVersion>
     <PackOnBuild>true</PackOnBuild>
     <PackageId>NetLicensingClient-csharp</PackageId>
-    <PackageVersion>0.0.4</PackageVersion>
+    <PackageVersion>2.4.4</PackageVersion>
     <Authors>Labs64 NetLicensing</Authors>
     <Copyright>© 2010 Labs64 GmbH</Copyright>
     <PackageIconUrl>https://netlicensing.io/img/labs64-avatar-200x200.png</PackageIconUrl>
@@ -22,5 +22,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="System.Security.Cryptography.Xml" Version="4.7.0" />
+    <PackageReference Include="Portable.BouncyCastle" Version="1.8.6.7" />
   </ItemGroup>
 </Project>

NetLicensingClient/RestController/NetLicensingAPI.cs

@@ -8,6 +8,11 @@
 using System.Web;
 using NetLicensingClient.Entities;
 using NetLicensingClient.Exceptions;
+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.OpenSsl;
+using System.Security.Cryptography;
+using System.Security.Cryptography.Xml;
+using System.Xml;
 
 namespace NetLicensingClient.RestController
 {
@@ -132,6 +137,10 @@ public static netlicensing request(Context context, Method method, String path,
                                 using (StreamReader reader = new StreamReader(memoryStream))
                                 {
                                     var responseString = reader.ReadToEnd();
+                                    if (!VerifyXmlSignature(responseString, context.publicKey))
+                                    {
+                                        throw new NetLicensingException("XML signature could not be verified");
+                                    }
                                 }
                             }
                             memoryStream.Dispose();
@@ -198,6 +207,48 @@ private static netlicensing deserialize(Stream responseStream)
             return NetLicensingSerializer.Deserialize(responseStream) as netlicensing;
         }
 
+		private static bool VerifyXmlSignature(string xmlString, string publicKey)
+		{
+			using (var keyReader = new StringReader(publicKey))
+			{
+				var pemReader = new PemReader(keyReader);
+
+				RsaKeyParameters parameters = (RsaKeyParameters)pemReader.ReadObject();
+				RSAParameters rParams = new RSAParameters();
+				rParams.Modulus = parameters.Modulus.ToByteArray();
+				rParams.Exponent = parameters.Exponent.ToByteArray();
+
+                RSA rsaKey = RSA.Create();
+                rsaKey.ImportParameters(rParams);
+
+				XmlDocument xmlDoc = new XmlDocument();
+				xmlDoc.PreserveWhitespace = true;
+				xmlDoc.LoadXml(xmlString);
+
+                // Create a new SignedXml object and pass it the XML document class
+                SignedXml signedXml = new SignedXml(xmlDoc);
+                // Find the "Signature" node and create a new XmlNodeList object
+                XmlNodeList nodeList = xmlDoc.GetElementsByTagName("Signature");
+
+                // Throw an exception if no signature was found
+                if (nodeList.Count <= 0)
+				{
+					throw new CryptographicException("Verification failed: No Signature was found in the document.");
+				}
+
+				// Throw an exception if more than one signature was found
+				if (nodeList.Count >= 2)
+				{
+					throw new CryptographicException("Verification failed: More that one signature was found for the document.");
+				}
+
+                // Load the first <signature> node
+                signedXml.LoadXml((XmlElement)nodeList[0]);
+
+                // Check the signature and return the result
+                return signedXml.CheckSignature(rsaKey);
+			}
+		}
     }
 
 }