From: Matthew Endsley <mendsley@gmail.com>
Date: Fri, 2 Apr 2021 01:10:37 +0000 (-0700)
Subject: Do not generate ClientRandom on ClientHello resend
X-Git-Tag: 1.0.0~9^2
X-Git-Url: https://git.deb.at/?a=commitdiff_plain;h=105f4b72e29eb999e3bbee5d1e6c2732f9d1e36f;p=rhonda%2Fimpostor.hazel.git

Do not generate ClientRandom on ClientHello resend

This buffer should only be generated at the start of the session.
Re-generating it on resend of ClientHello will desynchronize the session
between the client and server, resulting in the server refusing the
client's connection due to a hash mismatch in the Finished handshake
message.
---

diff --git a/Hazel/Dtls/DtlsUnityConnection.cs b/Hazel/Dtls/DtlsUnityConnection.cs
index 0c09e3d..eed6ba7 100644
--- a/Hazel/Dtls/DtlsUnityConnection.cs
+++ b/Hazel/Dtls/DtlsUnityConnection.cs
@@ -199,6 +199,7 @@ namespace Hazel.Dtls
             lock (this.syncRoot)
             {
                 this.ResetConnectionState();
+                this.nextEpoch.ClientRandom.FillWithRandom(this.random);
                 this.SendClientHello();
             }
 
@@ -577,6 +578,7 @@ namespace Hazel.Dtls
                         helloVerifyRequest.Cookie.CopyTo(this.nextEpoch.Cookie);
 
                         // Restart the handshake
+                        this.nextEpoch.ClientRandom.FillWithRandom(this.random);
                         this.SendClientHello();
                         break;
 
@@ -882,7 +884,6 @@ namespace Hazel.Dtls
         {
             // Reset our verification stream
             this.nextEpoch.VerificationStream.SetLength(0);
-            this.nextEpoch.ClientRandom.FillWithRandom(this.random);
 
             // Describe our ClientHello flight
             ClientHello clientHello = new ClientHello();