From 77dc8fb9a1c04e124335ec3fe0015fd352d68dad Mon Sep 17 00:00:00 2001
From: Alex Barney <thealexbarney@gmail.com>
Date: Sat, 15 Sep 2018 15:55:50 -0500
Subject: [PATCH] Fix bug in updating the AES-CTR counter

---
 LibHac/Aes128CtrStream.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/LibHac/Aes128CtrStream.cs b/LibHac/Aes128CtrStream.cs
index 18a9e588..10402f89 100644
--- a/LibHac/Aes128CtrStream.cs
+++ b/LibHac/Aes128CtrStream.cs
@@ -85,11 +85,15 @@ namespace LibHac
         private void UpdateCounter(long offset)
         {
             ulong off = (ulong)offset >> 4;
-            for (uint j = 0; j < 0x8; j++)
+            for (uint j = 0; j < 0x7; j++)
             {
                 Counter[0x10 - j - 1] = (byte)(off & 0xFF);
                 off >>= 8;
             }
+
+            // Because the value stored in the counter is offset >> 4, the top 4 bits 
+            // of byte 8 need to have their original value preserved
+            Counter[8] = (byte)((Counter[8] & 0xF0) | (int)(off & 0x0F));
         }
 
         public override void Flush()