[release/6.0] Fixing regression for AuthType.Anonymous which leads to a NullReferenceException be thrown. (#62824)

* Fixing regression for AuthType.Anonymous which leads to a NullReferenceException be thrown.

* Adding a unitTest to protect against a regression

* Ensure System.DirectoryServices.Protocols package gets built.

Co-authored-by: Jose Perez Rodriguez <joperezr@microsoft.com>

Author: github-actions[bot]

src/libraries/System.DirectoryServices.Protocols/src/System.DirectoryServices.Protocols.csproj

@@ -1,11 +1,13 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeDllSafeSearchPathAttribute>true</IncludeDllSafeSearchPathAttribute>
     <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent);netcoreapp3.1-windows;netcoreapp3.1-OSX;netcoreapp3.1-Linux;netcoreapp3.1;netstandard2.0</TargetFrameworks>
     <IsPackable>true</IsPackable>
     <AddNETFrameworkPlaceholderFileToPackage>true</AddNETFrameworkPlaceholderFileToPackage>
     <AddNETFrameworkAssemblyReferenceToPackage>true</AddNETFrameworkAssemblyReferenceToPackage>
+    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
+    <ServicingVersion>1</ServicingVersion>
     <PackageDescription>Provides the methods defined in the Lightweight Directory Access Protocol (LDAP) version 3 (V3) and Directory Services Markup Language (DSML) version 2.0 (V2) standards.</PackageDescription>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->

src/libraries/System.DirectoryServices.Protocols/src/System/DirectoryServices/Protocols/Interop/LdapPal.Linux.cs

@@ -111,7 +111,7 @@ internal static int BindToDirectory(ConnectionHandle ld, string who, string pass
                 passwordPtr = LdapPal.StringToPtr(passwd);
                 berval passwordBerval = new berval
                 {
-                    bv_len = passwd.Length,
+                    bv_len = passwd?.Length ?? 0,
                     bv_val = passwordPtr,
                 };
 

src/libraries/System.DirectoryServices.Protocols/tests/LdapConnectionTests.cs

@@ -112,6 +112,16 @@ public void AuthType_SetValid_GetReturnsExpected()
             Assert.Equal(AuthType.Basic, connection.AuthType);
         }
 
+        [Fact]
+        public void AuthType_Anonymous_DoesNotThrowNull()
+        {
+            var connection = new LdapConnection("server");
+            connection.AuthType = AuthType.Anonymous;
+            // When calling Bind we make sure that the exception thrown is not that there was a NullReferenceException
+            // trying to retrive a null password's lenght, but instead an LdapException given the server cannot be reached.
+            Assert.Throws<LdapException>(() => connection.Bind());
+        }
+
         [Theory]
         [InlineData(AuthType.Anonymous - 1)]
         [InlineData(AuthType.Kerberos + 1)]