x509: add utils to find certs by thumbprint

Author: mjcheetham

src/shared/Core/X509Utils.cs

@@ -0,0 +1,23 @@
+using System.Security.Cryptography.X509Certificates;
+
+namespace GitCredentialManager;
+
+public static class X509Utils
+{
+    public static X509Certificate2 GetCertificateByThumbprint(string thumbprint)
+    {
+        foreach (var location in new[]{StoreLocation.CurrentUser, StoreLocation.LocalMachine})
+        {
+            using var store = new X509Store(StoreName.My, location);
+            store.Open(OpenFlags.ReadOnly);
+
+            X509Certificate2Collection certs = store.Certificates.Find(X509FindType.FindByThumbprint, thumbprint, false);
+            if (certs.Count > 0)
+            {
+                return certs[0];
+            }
+        }
+
+        return null;
+    }
+}