Securing TLS in WAC (Windows Admin Center)

We had a need to publish WAC directly onto the web with a public IP address. We have internal security scanning tools that identified security threats according to Qualys scan. For reference, WAC will start out by attempting to communicate on TLS 1.3 and downgrade to TLS 1.2 and then TLS 1.1. These threats are part of the Windows operating system rather than the WAC services itself. We can remediate these threats by altering some registry settings for how the operating system handles these protocols by disabling them. These actions would be considered hardening the operating system.

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Issues

• Secure Sockets Layer/Transport Layer Security (SSL/TLS) Server supports Transport Layer Security (TLSv1.0)

• Secure Sockets Layer/Transport Layer Security (SSL/TLS) Server Supports Transport Layer Security (TLSv1.1)

• Birthday attacks against TLS ciphers with 64bit block size vulnerability (Sweet32)

WAC itself is built to attempt TLS 1.2 and downgrades to TLS 1.1. However, judging by the Qualys scan TLS 1.0 still responds also.

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TLS 1.0 & TLS 1.1

Microsoft offers some guidance here Transport Layer Security (TLS) registry settings | Microsoft Learn. If you’re doing this one off, open up regedit and head to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols and add create the keys TLS 1.0 and TLS 1.1, and Client and Server keys. Then add the following DWORD (32-bit) DisabledByDefault = 1 and Enabled = 0.

If you want to automate or run across more system you can user PowerShell

# TLS 1.0
New-Item 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Server' -Force
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Server' -PropertyType 'DWORD' -Name 'Enabled' -Value '0' 
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Server' -PropertyType 'DWORD' -Name 'DisabledByDefault' -Value '1' 
New-Item 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Client' -Force
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Client' -PropertyType 'DWORD' -Name 'Enabled' -Value '0'
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Client' -PropertyType 'DWORD' -Name 'DisabledByDefault' -Value '1' 

# TLS 1.1
New-Item 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server' -Force
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server' -PropertyType 'DWORD' -Name 'Enabled' -Value '0' 
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server' -PropertyType 'DWORD' -Name 'DisabledByDefault' -Value '1' 
New-Item 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Client' -Force
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Client' -PropertyType 'DWORD' -Name 'Enabled' -Value '0'
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Client' -PropertyType 'DWORD' -Name 'DisabledByDefault' -Value '1'

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Sweet32

Reference: How to disable 3DES and RC4 on Windows Server 2019? - Microsoft Q&A

get-tlsciphersuite -name '3DES'

will show what cihpers

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regedit, I deleted these and rebooted

TLS_RSA_WITH_3DES_EDE_CBC_SHA
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA
TLS_RSA_WITH_RC4_128_SHA
TLS_RSA_WITH_RC4_128_MD5

These steps provide a level-up in WAC front-end security.