From b63ecff0e0c4735a59c9ee0c8a2dbd70d7880daf Mon Sep 17 00:00:00 2001
From: Tom Deseyn <tom.deseyn@gmail.com>
Date: Wed, 1 Jul 2026 16:07:36 +0200
Subject: [PATCH 1/2] tls-uses-pqc: support running against OpenSSL 4.

---
 tls-uses-pqc/Program.cs | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/tls-uses-pqc/Program.cs b/tls-uses-pqc/Program.cs
index 5585079..2c5ac08 100644
--- a/tls-uses-pqc/Program.cs
+++ b/tls-uses-pqc/Program.cs
@@ -9,6 +9,8 @@
 using System.Security.Cryptography;
 using System.Security.Cryptography.X509Certificates;
 
+SetOpenSSLImportResolver();
+
 // Create a self-signed certificate.
 using var key = ECDsa.Create();
 var certReq = new CertificateRequest("CN=localhost", key, HashAlgorithmName.SHA256);
@@ -55,6 +57,23 @@
 return 1;
 
 // Use OpenSSL interop to get the negotiated key exchange group (SslStream doesn't expose this information).
+static void SetOpenSSLImportResolver()
+{
+    // Use the latest OpenSSL version on the system.
+    NativeLibrary.SetDllImportResolver(Assembly.GetExecutingAssembly(), (name, assembly, searchPath) =>
+    {
+        if (name == "libssl")
+        {
+            if (NativeLibrary.TryLoad("libssl.so.4", assembly, searchPath, out var h) ||
+                NativeLibrary.TryLoad("libssl.so.3", assembly, searchPath, out h))
+            {
+                return h;
+            }
+        }
+        return IntPtr.Zero;
+    });
+}
+
 static string? GetNegotiatedGroupName(SslStream sslStream)
 {
     var secCtxField = typeof(SslStream).GetField("_securityContext", BindingFlags.NonPublic | BindingFlags.Instance)!;
@@ -72,5 +91,5 @@
     }
 }
 
-[DllImport("libssl.so.3")]
+[DllImport("libssl")]
 static extern IntPtr SSL_get0_group_name(IntPtr ssl);

From 22f657a3fd98548a3ede0379bf505e9ab1173075 Mon Sep 17 00:00:00 2001
From: Tom Deseyn <tom.deseyn@gmail.com>
Date: Mon, 6 Jul 2026 14:15:34 +0200
Subject: [PATCH 2/2] Throw if we don't know how to map libssl.

---
 tls-uses-pqc/Program.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tls-uses-pqc/Program.cs b/tls-uses-pqc/Program.cs
index 2c5ac08..376a56e 100644
--- a/tls-uses-pqc/Program.cs
+++ b/tls-uses-pqc/Program.cs
@@ -69,8 +69,9 @@ static void SetOpenSSLImportResolver()
             {
                 return h;
             }
+            throw new NotSupportedException($"Cannot resolve {name}.");
         }
-        return IntPtr.Zero;
+        return IntPtr.Zero; // Use the default resolution logic.
     });
 }