Pad generated vapid private key if required.

Author: Cory Thompson

WebPush/VapidHelper.cs

@@ -10,7 +10,6 @@ public static class VapidHelper
         /// <summary>
         ///     Generate vapid keys
         /// </summary>
-        /// <returns></returns>
         public static VapidDetails GenerateVapidKeys()
         {
             var results = new VapidDetails();
@@ -20,7 +19,7 @@ public static VapidDetails GenerateVapidKeys()
             var privateKey = ((ECPrivateKeyParameters) keys.Private).D.ToByteArrayUnsigned();
 
             results.PublicKey = UrlBase64.Encode(publicKey);
-            results.PrivateKey = UrlBase64.Encode(privateKey);
+            results.PrivateKey = UrlBase64.Encode(ByteArrayPadLeft(privateKey, 32));
 
             return results;
         }
@@ -146,5 +145,13 @@ private static long UnixTimeNow()
             var timeSpan = DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0);
             return (long) timeSpan.TotalSeconds;
         }
+
+        private static byte[] ByteArrayPadLeft(byte[] src, int size)
+        {
+            var dst = new byte[size];
+            var startAt = dst.Length - src.Length;
+            Array.Copy(src, 0, dst, startAt, src.Length);
+            return dst;
+        }
     }
 }

WebPush/WebPushClient.cs

@@ -331,7 +331,7 @@ public async Task SendNotificationAsync(PushSubscription subscription, string pa
         }
 
         /// <summary>
-        /// Handle Web Push responses.
+        ///     Handle Web Push responses.
         /// </summary>
         /// <param name="response"></param>
         /// <param name="subscription"></param>