Second Life of a Hungarian SharePoint Geek

August 7, 2015

Computing Hash of SharePoint Files

Filed under: PowerShell, SP 2010 — Tags: , — Peter Holpar @ 10:46

Recently we had to compare master pages of hundreds of sites to find out, which ones contain customizations. Comparing the content of files means in practice typically to compare the hash values calculated based on the file content.

But how to compute the hash of a file stored in SharePoint?

If you had the SharePoint sites mapped to the Windows File System via WebDAV, you could use the Get-FileHash cmdlet from PowerShell 4.0 (or above). In PowerShell 5.0 the Get-FileHash cmdlet is able to compute the hash of input streams as well, so we could use SPFile.OpenBinaryStream method to access the file content, and then compute its hash value.

Since I have only PowerShell 2.0 on my SharePoint server, I had to create my own hashing solution, the Get-SPFileHash function:

function Get-SPFileHash($fileUrl) 

  $site = New-Object Microsoft.SharePoint.SPSite $fileUrl
  $web = $site.OpenWeb()
  $file = $web.GetFile($fileUrl)
  $bytes = $file.OpenBinary()
  $md5 = New-Object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
  $hash = [System.BitConverter]::ToString($md5.ComputeHash($bytes))
  return $hash
}

Having this method, it is easy to create a summary of all sites, their master pages, and the hash values of the master page content:

$siteUrl = "http://YourSharePointSite"

$site = Get-SPSite $siteUrl

$site.AllWebs | % {
  $obj = New-Object PSObject
  $obj | Add-Member NoteProperty Url($_.Url)
  $obj | Add-Member NoteProperty MasterUrl($_.MasterUrl)
  $obj | Add-Member NoteProperty FileHash(Get-SPFileHash ($siteUrl + $_.MasterUrl))
  Write-Output $obj
} | Export-CSV "C:\data\MasterPageHash.csv"

You can import the resulting CSV file into Excel and process its content as you wish.

Note: If you simply double-click on the CSV file created by the former script in Windows Explorer, it is not opened in the format you probably wish: values separated into columns. Instead of that, the first column would contain the entire line. You should first prepare the file: open it in Notepad, optionally remove the first header line, and save the file again, changing the encoding from ANSI to Unicode. Next, start Excel, and open the CSV file from Excel, setting the separator character to Comma on the second page of the Text Import Wizard.

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