Descendent Hashes

This module is designed to generate hashes of all files in a directory and optionally its descendant directories. This module is compatible with Powershell 5 or later, and should work equally well on Powershell Core. There are no platform specific items in this module; Windows and Posix environments should work equally well.

These functions were written with bulk file transfers in mind; running Write-ChildItemHash on a path before transferring the entire directory structure to a remote endpoint and then validating that files transferred unmolested by executing Compare-ChildItemHash on the destination path once the transfer is complete. This process would not detect additional files, nor would it detect files that were not transferred at all, it would validate that files that were transferred match their transferred hashes.

Exported Cmdlets

• Descendent Hashes
  • Exported Cmdlets
    • Write-ChildItemHash
      • Parameters
    • Compare-ChildItemHash
      • Parameters

Write-ChildItemHash

This Cmdlet will find all child items of a specified path and write the hash of each child item to its own file. Calling Write-ChildItemHash -Path C:\foo where C:\foo contains bar1.txt, bar2.txt, and bar3.txt will result in new files C:\foo\bar1.txt.sha256, C:\foo\bar2.txt.sha256, and C:\foo\bar3.txt.sha256.

Write-ChildItemHash will skip hashing files for which there already exists a hash file; the Cmdlet will also skip hashing hash files for the targeted algorithm.

Parameters

• -Path Path to directory containing files to be hashed; defaults to .\
• -LogFile Path to log file to be written; default to automatically named file in directory specified in -Path
• -Algorithm Specifies the hashing algorithm to use; this supports any hashing function supported by Get-FileHash. Changing the algorithm will change the extension of the created files as well, using -Algorithm MD5 will create .md5 files when generating child hashes; defaults to sha256.
• -Recurse If passed specifies that Write-ChildItemHash should traverse all descendant directories and hash all files found.
• -Threads Number of threads to start when hashing items, if not explicitly set will default to the number of logical processors detected when run under Powershell for Windows or will default to 1 when run under Powershell Core.
• -Force Force hashing of files and over write any existing hash on disk.

Compare-ChildItemHash

Iterates through all children of a directory (and optionally recurses through child directories) validating that the current hash of a file matches the value stored in the associated hash file. Files that do not match their stored hash are written to the log file.

Compare-ChildItemHash is designed to validate that files previously hashed by Write-ChildItemHash still match their stored hash. This can be used to validate that transferred files have not been manipulated in transit. Files that do not have an associated hash file will be ignored. This will not detect missing files , nor will it detect extra files.

Parameters

• -Path Path to directory containing files to be validated; defaults to .\.
• -LogFile Path to log file to be written; default to automatically named file in directory specified in -Path. This log will contain all files that do not match their stored hash.
• -Algorithm Specifies the hashing algorithm to use; this supports any hashing function supported by Get-FileHash. Changing the algorithm will change the extension of the hash files as well, using -Algorithm MD5 will look for .md5 files when validating child hashes; defaults to sha256.
• -Recurse If passed specifies that Compare-ChildItemHash should traverse all descendant directories and validate all files found.