From a9ed131c8db7bcbf24f1764785aaea170c890ce9 Mon Sep 17 00:00:00 2001
From: kuyaya <alois.kuyaya@gmx.ch>
Date: Tue, 10 Nov 2020 13:26:45 +0100
Subject: [PATCH] Update Program.cs

---
 BadMorals/Program.cs | 42 ++++++++++++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/BadMorals/Program.cs b/BadMorals/Program.cs
index d9e49c8..439cc47 100644
--- a/BadMorals/Program.cs
+++ b/BadMorals/Program.cs
@@ -6,21 +6,35 @@ public class Program
     {
         static string s1 = "2SXFnY5yWMMHytNyzMM3uYFzzcZnuMNzzXXzzNMunZczzFYu3MMzyNtyHMMWy5YnFXS2";
         static string s2 = "fdmbxkHNsB3XGR1Q";
-        static string s3 = "::PNDlGpXpoR:7";
 
         static char[] a = s1.ToCharArray();
         static char[] b = s2.ToCharArray();
-        static char[] c = s3.ToCharArray();
+        static char[] c;
+
+        static string build;
         public static void Main(string[] args)
         {
+
+            //section 0: Read user input and possibly return the flag. The user input is currently: ":"
+            if (args.Length == 1)
+            {
+                build = args[0] + ":PNDlGpXpoR:7";
+                c = build.ToCharArray();
+            }
+            else
+            {
+                Console.Write("Usage: HV20.exe ARG");
+                Environment.Exit(1);
+            }
+
+
             // Section 1: Get every second char of s1
             string firstresult = "";
             for (int i = 0; i < a.Length; i++)
             {
                 if (i % 2 == 0)
                 {
-                    a[i] = a[i + 1];
-                    firstresult += a[i];
+                    firstresult += a[i+1];
                 }
             }
 
@@ -32,7 +46,7 @@ public static void Main(string[] args)
                 secondresult += b[u];
             }
 
-            // Section 3: XOR the string with a fixed byte
+            // Section 3: XOR the userinput + string with a fixed byte
             string thirdresult = "";
             byte q = 10;
             for (int z = 0; z < c.Length; z++)
@@ -43,13 +57,17 @@ public static void Main(string[] args)
             }
 
             // Final section: Convert the two strings from Base64 and print it out.
-            string final = firstresult + thirdresult;
-
-            byte[] bit = Convert.FromBase64String(final);
-
-            string flag = System.Text.Encoding.ASCII.GetString(bit);
-
-            Console.Write(flag);
+            try
+            {
+                string final = firstresult + thirdresult;
+                byte[] bit = Convert.FromBase64String(final);
+                string flag = System.Text.Encoding.ASCII.GetString(bit);
+                Console.Write(flag);
+            }
+            catch
+            {
+                Console.Write("Your input does not result in a valid Base64 string.");
+            }
         }
     }
 }