MSBuild Wizardry: Detecting Signed Drivers and Preventing Re-Signing via Caching

Are you tired of resigned drivers clogging up your build process? Do you dream of a world where your builds are fast, efficient, and cache-friendly? Look no further! In this article, we’ll delve into the mystical realm of MSBuild and uncover the secrets of detecting signed drivers and preventing re-signing via caching.

The Problem: Signed Drivers and Build Performance

When building and signing drivers, it’s essential to ensure that the signed driver is identical to the previous non-signed build. Why? Because resigning the same driver multiple times can lead to:

• Slower build times due to unnecessary re-signing
• Increased risk of build failures and errors
• Potential issues with driver authenticity and trust

The solution lies in detecting whether the signed driver is identical to the previous non-signed build, and if so, skipping the re-signing process altogether. But how do we achieve this?

The Solution: Leveraging MSBuild and Hashing

The key to solving this puzzle lies in harnessing the power of MSBuild and hashing. By using MSBuild’s built-in hash functions and cleverly crafting our build script, we can detect whether the signed driver is identical to the previous non-signed build.

Here’s a high-level overview of the solution:

1. Calculate the hash of the non-signed driver binary during the build process
2. Store the hash value in a cache file or database
3. During subsequent builds, calculate the hash of the new non-signed driver binary
4. Compare the new hash value with the cached value
5. If the hashes match, skip resigning the driver and use the previously signed version

Step 1: Calculating the Hash of the Non-Signed Driver Binary

To calculate the hash of the non-signed driver binary, we’ll use MSBuild’s `` task. This task takes a file as input and returns the hash value as a string.

<Target Name="CalculateHash">
  <ComputeHash Files="@(DriverBinary)">
    <Output TaskParameter="Hash" PropertyName="DriverHash" />
  </ComputeHash>
</Target>

In this example, we’re using the `ComputeHash` task to calculate the hash of the `@(DriverBinary)` file, which represents the non-signed driver binary. The resulting hash value is stored in the `DriverHash` property.

Step 2: Storing the Hash Value in a Cache File

To store the hash value, we’ll create a cache file using MSBuild’s `` task. This task writes a list of strings to a file.

<Target Name="StoreHash">
  <WriteLinesToFile File="driver-hash.cache" Lines="@(DriverHash)" />
</Target>

In this example, we’re writing the `DriverHash` property value to a file named `driver-hash.cache`. This file will serve as our cache, storing the hash value for future builds to reference.

Step 3: Comparing the Hash Values

During subsequent builds, we’ll calculate the hash of the new non-signed driver binary and compare it with the cached hash value.

<Target Name="CompareHashes">
  <ComputeHash Files="@(DriverBinary)">
    <Output TaskParameter="Hash" PropertyName="NewDriverHash" />
  </ComputeHash>
  
  <ReadLinesFromFile File="driver-hash.cache">
    <Output TaskParameter="Lines" PropertyName="CachedDriverHash" />
  </ReadLinesFromFile>
  
  <Condition Condition="'@(NewDriverHash)' == '@(CachedDriverHash)'">
    <!-- Skip resigning the driver if hashes match -->
  </Condition>
</Target>

In this example, we’re calculating the hash of the new non-signed driver binary using the `ComputeHash` task, storing the result in the `NewDriverHash` property. We then read the cached hash value from the `driver-hash.cache` file using the `ReadLinesFromFile` task, storing the result in the `CachedDriverHash` property. Finally, we use a conditional statement to check if the new hash value matches the cached value. If they match, we skip resigning the driver.

Putting it all Together: The Complete MSBuild Script

Here’s the complete MSBuild script that detects whether the signed driver is identical to the previous non-signed build and prevents re-signing via caching:

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">

  <PropertyGroup>
    <DriverBinary>path/to/non-signed/driver.bin</DriverBinary>
  </PropertyGroup>

  <Target Name="CalculateHash">
    <ComputeHash Files="@(DriverBinary)">
      <Output TaskParameter="Hash" PropertyName="DriverHash" />
    </ComputeHash>
  </Target>

  <Target Name="StoreHash" DependsOnTargets="CalculateHash">
    <WriteLinesToFile File="driver-hash.cache" Lines="@(DriverHash)" />
  </Target>

  <Target Name="CompareHashes" DependsOnTargets="StoreHash">
    <ComputeHash Files="@(DriverBinary)">
      <Output TaskParameter="Hash" PropertyName="NewDriverHash" />
    </ComputeHash>
    
    <ReadLinesFromFile File="driver-hash.cache">
      <Output TaskParameter="Lines" PropertyName="CachedDriverHash" />
    </ReadLinesFromFile>
    
    <Condition Condition="'@(NewDriverHash)' == '@(CachedDriverHash)'">
      <!-- Skip resigning the driver if hashes match -->
    </Condition>
    
    <!-- Resign the driver if hashes don't match -->
    <Exec Command="signing-tool.exe @(DriverBinary)" />
  </Target>

</Project>

This script calculates the hash of the non-signed driver binary, stores the hash value in a cache file, and compares the hash values during subsequent builds. If the hashes match, it skips resigning the driver. If the hashes don’t match, it resigns the driver using the `signing-tool.exe` command.

Conclusion

By leveraging MSBuild’s built-in hash functions and cleverly crafting our build script, we’ve successfully detected whether the signed driver is identical to the previous non-signed build and prevented re-signing via caching. This solution not only improves build performance but also ensures the integrity and authenticity of our drivers.

Remember, a well-crafted MSBuild script is like a magic spell – it can make your build process faster, more efficient, and more reliable. So, the next time you’re building and signing drivers, don’t forget to add a dash of MSBuild wizardry to your build process!

Hashing Algorithm	Description
SHA-256	A widely used hashing algorithm that produces a 256-bit hash value
MD5	A commonly used hashing algorithm that produces a 128-bit hash value
SHA-1	A hashing algorithm that produces a 160-bit hash value, widely used in digital signatures

In this article, we’ve used the `ComputeHash` task to calculate the hash value of the non-signed driver binary. You can choose from a variety of hashing algorithms, such as SHA-256, MD5, or SHA-1, depending on your specific requirements.

I hope this article has cast a spell of understanding on the mystical realm of MSBuild and driver signing. Remember to bookmark this page and come back for more MSBuild wizardry!

Frequently Asked Question

Get the inside scoop on how MSBuild detects if a signed driver is the same as a previous built non-signed driver, and learn how to prevent re-signing via caching.