Hello S-1-1-0! Today I would like to present a PowerShell script that allows you to add multiple files to a form and sign them using Authenticode signature.

As you already know, I’m using Software Restriction Policies and Applocker to prevent users (including myself) from running unauthorized applications and scripts. I’m using various options to allow certain applications and scripts in group policy. In certain cases I’m using hash rules, but mostly (as possible) I’m using digital signatures and publisher/certificate rules.

Since I’m writing a lot of PowerShell scripts I have to sign them in user-friendly way. Yes, there is Set-AuthenticodeSignature cmdlet, but I dislike to specify file path and signing certificate each time I want to sign something. Previously I used a nice function that adds a context menu to Windows Explorer and signs file: Подписывание скриптов PowerShell – практическая реализация (часть 2). However this script adds context menu only for PS1 files, while there are a lot of other file types that supports digital signatures. To address this question I wrote a little WinForms PowerShell script that allows me to perform file signing very easy. At first I start with screenshots.

Hi again! Recently I faced an issue with my Test-WebServerSSL function which is also available in my Powershell PKI module.

Issue

In certain cases, the function returns certificate chain errors, while Internet Explorer (as well as other web browsers) works normally and do not report anything wrong. For example, you can open https://www.nic.lv/ web site without any issues in your web browser. When you run Test-WebServerSSL function against this web site, you get the following:

Hello folks! If you are longing for CryptoAPI stuff here, then you are on the right page. Here you will see another bunch of CryptoAPI, PowerShell and p/invoke hardcore.

Today’s subject is to convert PFX file to PEM format. A time ago I wrote a function that does opposite — converts PEM to PFX: How to convert PEM file to a CryptoAPI compatible format. Read this post to get information about CryptoAPI structures and ASN modules for PKCS#1 and PKCS#8 structures.

The script below performs the following tasks:

1. Reads certificate or certificate file. If the file is not valid PFX or certificate hasn’t associated private key, an exception will be thrown.
2. Acquires private key (via unmanaged function calls) and attempts to export raw private key from CSP. If the private key is not marked as exportable or it is stored on smart card, an error will be thrown.
3. Inspects CryptoAPI private key blob as described here: RSA/Schannel Key BLOBs, removes header, reads raw private key and splits it to components (modulus, primes, exponents, coefficient). Each component is stored in separate variable.
4. Generates required ASN structures according to output type by using basic ASN encoder.
5. composes certificate and private key and saves them to file.

3 years ago a friend of mine asked me about how to enhance FCIV.exe utility functionality with PowerShell. Microsoft is not developing this tool anymore and you have to write your own tools or wrappers for fciv.exe to get required functionality.

I decided to write completely new tool from scratch by using only native PowerShell code. First version of PsFCIV was released about 3 years ago only for Russian-language audience. However there are many requests from English-language visitors. For example, users request new hashing algorithm support (SHA2 family) and other checking options, like file size and last modification timestamp checking. I made a lot of performance and reliability improvements, so new version works much faster than PsFCIV 1.0. Also I added support for SHA2 hashing algorithms. As the result, I was able to release a new updated PsFCIV 2.0 tool on TechNet Gallery:

Hello folks, CryptoGuy is here again. Today I’ll talk about the most common ways to violate default SRP configurations and how to protect SRP against them.

System folders with write access

It is generally correct that regular users haven’t write permissions on system folders and we can safely allow to run any program from these folders (C:\Windows). However this statement is not fully correct. This is because there are folders where regular users have write and execute permissions. There are at least two default folders:

1. System temp folder: C:\Windows\Temp
2. Print spooler folder.

Here is a screenshot of Temp folder ACL: