Windows support for the Application Control for Business new CA handling logic

Introduction

The article outlines the new Application Control for Business (formerly known as Windows Defender Application Control (WDAC)) handling logic for signer rules where a TBS hash value for a Microsoft intermediate certificate authority (CA) is specified.

Microsoft Issuing CAs

Microsoft and Windows components are signed by leaf certificates mainly issued by six Microsoft Issuing CAs. Beginning in July 2025, these 15-year Issuing CAs begin to expire according to the following schedule.

121AF4B922A74247EA49DF50DE37609CC1451A1FE06B2CB7E1E079B492BD8195 

90C9669670E75989159E6EEF69625EB6AD17CBA6209ED56F5665D55450A05212

F6F717A43AD9ABDDC8CEFDDE1C505462535E7D1307E630F9544A2D14FE8BF26E

4E80BE107C860DE896384B3EFF50504DC2D76AC7151DF3102A4450637A032146

CEC1AFD0E310C55C1DCC601AB8E172917706AA32FB5EAF826813547FDF02DD46

C64CE3455898F871D11C14DA412AAC58FA2022D4213D8AC05F8DD6909B2FB0FCC76C19A1913DF5BC0CB1662229AD15D1

84A5BD1CCB7CD6509FF7214F4BA27D51CCF72BE2AC4AA7F0E97BC066FC804EBB635E8305D7D1108F89B4CF7BB2CAFED9

B52C1E712CF71D080614DDF95F8258BE0738C0722BD8A55F0AF4361BACEE35B6D73DCACB1B9DE10B5FD28508A3A50EAE

34EEC0CD7321C9C20309BEF31164D92B88E892341DE67FE2684D9E7FDA09C9E46B05498FB38E29B421E845FEB8C7A4CD

FFFA64ABBB400583B3F812A196A8AF7ABF329D4882F26221A142D734620B759D1E168537CC6DA74807C2E20C70DA7B78

While it is recommended, Application Control policies which have Signer rules with TBS hash values listed in the table above do not need to be updated to trust the components signed by the new 2023 and 2024 CAs. Application Control will automatically infer trust of the new 2023 and 2024 CAs, and their TBS hash values, if your policy has rules trusting the current CAs.

For example, if your policy trusts the Windows Production PCA 2011 using the following rule, trust for the new Windows Production PCA 2023 will be automatically inferred. Signer elements like CertEKU, CertPublisher, FileAttribRef and CertOemId are preserved in the inferencing logic. 

<Signer ID="ID_SIGNER_WINDOWS_CA_1" Name="Microsoft Windows Production PCA 2011"> 

  <CertRoot Type="TBS" Value="4E80BE107C860DE896384B3EFF50504DC2D76AC7151DF3102A4450637A032146" /> 

  <CertEKU ID="ID_EKU_WINDOWS" /> 

</Signer> 

<Signer ID="ID_SIGNER_WINDOWS_CA_2" Name=" Windows Production PCA 2023 "> 

  <CertRoot Type="TBS" Value=" 34EEC0CD7321C9C20309BEF31164D92B88E892341DE67FE2684D9E7FDA09C9E46B05498FB38E29B421E845FEB8C7A4CD " /> 

  <CertEKU ID="ID_EKU_WINDOWS" />     

</Signer> 

<Signer ID="ID_SIGNER_DENY_FOO_1" Name="Microsoft Code Signing PCA 2011”> 

  <CertRoot Type="TBS" Value=" F6F717A43AD9ABDDC8CEFDDE1C505462535E7D1307E630F9544A2D14FE8BF26E" /> 

  <CertPublisher Value="Microsoft Corporation" /> 

  <FileAttribRef RuleID="ID_FILEATTRIB_DENY_FOO" /> 

</Signer>

<Signer ID="ID_SIGNER_DENY_FOO_2" Name = “Microsoft Code Signing PCA 2024”> 

  <CertRoot Type="TBS" Value=" B52C1E712CF71D080614DDF95F8258BE0738C0722BD8A55F0AF4361BACEE35B6D73DCACB1B9DE10B5FD28508A3A50EAE" /> 

  <CertPublisher Value="Microsoft Corporation" /> 

  <FileAttribRef RuleID="ID_FILEATTRIB_DENY_FOO" /> 

</Signer>

Compatibility

Microsoft has serviced the TBS hash handling logic for the expiring CAs to all supported platforms where Application Control is supported according to the following table.

How to opt out

If you want to opt your systems out of the TBS hash inferencing logic performed by Application Control, set the following flag in policies: Disabled:Default Windows Certificate Remapping ​​​​​​​

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