Microsoft Security Advisory (2728973)

What is the scope of the advisory? 
The purpose of this advisory is to notify customers that Microsoft is aware of Microsoft certificate authorities that are outside our recommended secure storage practices. Upon a routine review and out of an abundance of caution, we are placing these certificates in the Untrusted Certificate Store, and replacing them with new certificate authorities that meet our high standard of public-key infrastructure (PKI) management. We are unaware of any misuse of the certificate authorities, but are taking pre-emptive action to protect customers. This issue affects all supported releases of Microsoft Windows.

Microsoft has issued an update for all supported releases of Microsoft Windows that addresses the issue.

Does this update address any other unauthorized digital certificates? 
Yes, in addition to addressing the twenty-eight unauthorized certificates described in this advisory, this update is cumulative and addresses unauthorized digital certificates described in previous advisories: Microsoft Security Advisory 2524375, Microsoft Security Advisory 2607712, Microsoft Security Advisory 2641690, and Microsoft Security Advisory 2718704.

Note that although this update addresses certificates described in previous advisories, this update does not contain all the functionality introduced in previous advisories. For more information, see known issues in Microsoft Knowledge Base Article 2728973.

Is Windows 8 Release Preview or Windows Server 2012 Release Candidate affected by the issue addressed in this advisory? 
Yes. The update is available for Windows 8 Release Preview and Windows Server 2012 Release Candidate. Customers with Windows 8 Release Preview and Windows Server 2012 Release Candidate are encouraged to apply the updates to their systems. For information on how to apply the update for Windows 8 Release Preview and Windows Server 2012 Release Preview, see the Suggested Actions section of this advisory.

What is cryptography?
Cryptography is the science of securing information by converting it between its normal, readable state (called plaintext) and one in which the data is obscured (known as ciphertext).

In all forms of cryptography, a value known as a key is used in conjunction with a procedure called a crypto algorithm to transform plaintext data into ciphertext. In the most familiar type of cryptography, secret-key cryptography, the ciphertext is transformed back into plaintext using the same key. However, in a second type of cryptography, public-key cryptography, a different key is used to transform the ciphertext back into plaintext.

What is a digital certificate?
In public-key cryptography, one of the keys, known as the private key, must be kept secret. The other key, known as the public key, is intended to be shared with the world. However, there must be a way for the owner of the key to tell the world who the key belongs to. Digital certificates provide a way to do this. A digital certificate is a tamperproof piece of data that packages a public key together with information about it - who owns it, what it can be used for, when it expires, and so forth.

What are certificates used for?
Certificates are used primarily to verify the identity of a person or device, authenticate a service, or encrypt files. Normally you won’t have to think about certificates at all. You might, however, see a message telling you that a certificate is expired or invalid. In those cases you should follow the instructions in the message.

What is a certification authority (CA)?
Certification authorities are the organizations that issue certificates. They establish and verify the authenticity of public keys that belong to people or other certification authorities, and they verify the identity of a person or organization that asks for a certificate.

What is a Certificate Trust List (CTL)?
A trust must exist between the recipient of a signed message and the signer of the message. One method of establishing this trust is through a certificate, an electronic document verifying that entities or persons are who they claim to be. A certificate is issued to an entity by a third party that is trusted by both of the other parties. So, each recipient of a signed message decides if the issuer of the signer's certificate is trustworthy. CryptoAPI has implemented a methodology to allow application developers to create applications that automatically verify certificates against a predefined list of trusted certificates or roots. This list of trusted entities (called subjects) is called a certificate trust list (CTL). For more information, please see the MSDN article, Certificate Trust Verification.

What caused the issue?
Microsoft is aware of Microsoft certificate authorities that are outside our recommended secure storage practices. We are unaware of any misuse of the certificate authorities, but are taking pre-emptive action to protect customers.

What might an attacker use the issue to do? 
An attacker could use these certificates to spoof content, perform phishing attacks, or perform man-in-the-middle attacks.

What is a man-in-the-middle attack?
A man-in-the-middle attack occurs when an attacker reroutes communication between two users through the attacker’s computer without the knowledge of the two communicating users. Each user in the communication unknowingly sends traffic to and receives traffic from the attacker, all the while thinking they are communicating only with the intended user.

What is Microsoft doing to help with resolving this issue?
We have placed the affected Microsoft certification authorities in the Untrusted Certificate Store and replaced them with new certificate authorities that meet our high standard of public-key infrastructure (PKI) management.

After applying the update, how can I verify the certificates in the Microsoft Untrusted Certificates Store? 
For systems using the automatic updater of revoked certificates (see Microsoft Knowledge Base Article 2677070 for details), including Windows 8 Release Preview and Windows Server 2012 Release Candidate, you can check the Application log in the Event Viewer for an entry with the following values:

• Source: CAPI2
• Level: Information
• Event ID: 4112
• Description: Successful auto update of disallowed certificate list with effective date: Thursday, June 21, 2012 (or later).

For systems not using the automatic updater of revoked certificates, in the Certificates MMC snap-in, verify that the following certificates have been added to the Untrusted Certificates folder:

Note For information on how to view certificates with the MMC Snap-in, see the MSDN article, How to: View Certificates with the MMC Snap-in.

For supported editions of Windows XP and Windows Server 2003

The majority of customers have automatic updating enabled and will not need to take any action because the KB2728973 update will be downloaded and installed automatically. Customers who have not enabled automatic updating need to check for updates and install this update manually. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.

For administrators and enterprise installations, or end users who want to install the KB2728973 update manually, Microsoft recommends that customers apply the update immediately using update management software, or by checking for updates using the Microsoft Update service. For more information on how to manually apply the update, see Microsoft Knowledge Base Article 2728973.

For supported editions of Windows Vista, Windows Server 2008, Windows 7, Windows Server 2008 R2, Windows 8 Release Preview, and Windows Server 2012 Release Preview

The majority of customers have automatic updating enabled and will not need to take any action because an automatic updater of revoked certificates will address the issue by automatically adding the certificates to the Untrusted Certificate Store.

The automatic updater of revoked certificates is available for Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2 through the Microsoft Update service and is described in Microsoft Knowledge Base Article 2677070. The automatic updater of untrusted certificates is included in Windows 8 Release Preview and Windows Server 2012 Release Candidate.

For end users who do not have the automatic updater of revoked certificates (2677070) or for systems that are not connected to the Internet, Microsoft recommends that customers manually apply the KB2728973 update immediately. For more information on how to manually apply the update manually, see Microsoft Knowledge Base Article 2728973.

For administrators and enterprise installations, Microsoft recommends that customers apply the update immediately using update management software. For more information about the update, see Microsoft Knowledge Base Article 2728973.