embeddable-dll-service: add csharp example code

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/embeddable-dll-service/csharp/Keypair.cs b/embeddable-dll-service/csharp/Keypair.cs
new file mode 100644
index 00000000..98a00a30
--- /dev/null
+++ b/embeddable-dll-service/csharp/Keypair.cs
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+using System;
+using System.ComponentModel;
+using System.Runtime.InteropServices;
+
+namespace Tunnel
+{
+    public class Keypair
+    {
+        public readonly string Public;
+        public readonly string Private;
+
+        private Keypair(string pub, string priv)
+        {
+            Public = pub;
+            Private = priv;
+        }
+
+        public static Keypair Generate()
+        {
+            var algoHandle = new IntPtr();
+            var statusCode = Win32.BCryptOpenAlgorithmProvider(ref algoHandle, Win32.BCRYPT_ECDH_ALGORITHM, null, 0);
+            if (statusCode > 0)
+                throw new Win32Exception((int)statusCode);
+
+            try
+            {
+                var curveType = Win32.BCRYPT_ECC_CURVE_25519 + Char.MinValue;
+                statusCode = Win32.BCryptSetProperty(algoHandle, Win32.BCRYPT_ECC_CURVE_NAME, curveType, curveType.Length * sizeof(char), 0);
+                if (statusCode > 0)
+                    throw new Win32Exception((int)statusCode);
+                var key = new IntPtr();
+                statusCode = Win32.BCryptGenerateKeyPair(algoHandle, ref key, 255, 0);
+                if (statusCode > 0)
+                    throw new Win32Exception((int)statusCode);
+                try
+                {
+                    statusCode = Win32.BCryptFinalizeKeyPair(key, 0);
+                    if (statusCode > 0)
+                        throw new Win32Exception((int)statusCode);
+
+                    var keyBlob = new Win32.KeyBlob();
+                    int exportedKeySize = 0;
+                    statusCode = Win32.BCryptExportKey(key, IntPtr.Zero, Win32.BCRYPT_ECCPRIVATE_BLOB, keyBlob, Marshal.SizeOf(typeof(Win32.KeyBlob)), out exportedKeySize);
+                    if (statusCode > 0)
+                        throw new Win32Exception((int)statusCode);
+
+                    return new Keypair(Convert.ToBase64String(keyBlob.Public), Convert.ToBase64String(keyBlob.Private));
+                }
+                finally
+                {
+                    Win32.BCryptDestroyKey(key);
+                }
+            }
+            finally
+            {
+                Win32.BCryptCloseAlgorithmProvider(algoHandle, 0);
+            }
+        }
+    }
+}