SYMPTOMS

Consider the following scenario. You configured Software Restriction Policies (SRP) to allow run all applications that are signed by the specific signer by creating a Certificate Rule against the signer certificate.

When the policy is refreshed on the client, user cannot run the application, because it is blocked by Software Restriction Policies.

CAUSE

This behavior occurs when the certificate is issued by a Certification Authority (CA) which do not include or provide incorrect issuer information in the Authority Information Access (AIA) extension in the signing certificate. In addition, intermediate CA certificate is not installed in the local store. SRP reads only signing certificate in the digital signature and ignores the rest certificates.

Today I want to present another useful CryptoAPI functions to use when working with PFX (PKCS#12) certificates.

1. Determine if the BLOB is PFX without having to pass a password;
2. Test PFX password.

Of course, you can try to use appropriate X509Certificate2 class constructor, but this approach is faster and do not require key import in cryptographic provider and other actions performed by X509Certificate2 constructor. This functionality is implemented in two CryptoAPI functions:

1. PFXIsPFXBlob
2. PFXVerifyPassword

And here is complete solution:

Point Of Interest

Yesterday I asked in Twitter, who can convert byte array to a formatted hex string in PowerShell in 5 minutes. I got one solution with the reference to Format-Hex function. Then I asked opposite question: can you convert formatted hex dump with address and ASCII panes back to byte array in PowerShell in 5 minutes? Didn’t get any response.

This subject is interesting and sometimes is necessary. Due to my specialization (cryptography), I have to deal with these formats often. And not only hex, Base64 with and without headers as well.

Common formatting examples

To make the subject clear, I provide some formatted examples:

Yesterday I released another version of PowerShell PKI module v3.1.

Though, this release is not that big like v3.0. Only 1 (one!) new command is added (Get-EnterprisePKIHealthStatus) and various bug fixes (as usually). On the other hand it includes very important things which are hidden behind the scene.

The project is growing and I have to battle hard with poor design decisions I made previously. Of course, I could break everything and make it as per all guidelines. However, it is too late, 3000 downloads for the past 7 months is not a joke and I can’t simply break it.

Next sections will cover some development details, so you can scroll down to the end of post to get the right link :)

Today I want to break my own rule (no more than 1 post per day). Today I want to announce two news:

Twitter

It’s a shame, but starting by March 3, 2015, I become a member of Twitter sect. My the only official account is @Crypt32. The purpose of this account is to promote my weblog, my open projects, talk about PKI-related and other topics I’m interesting in a twitter form.

Twitter: @Crypt32