Powershell : Decompiling – Compiled HTML Help (.CHM) files and Data Wrangling

WHAT IS COMPILED HTML HELP (.CHM)?

Microsoft Compiled HTML Help is a Microsoft proprietary online help format, consisting of a collection of HTML pages, an index and other navigation tools. The files are compressed and deployed in a binary format with the extension .CHM, for Compiled HTML. The format is often used for software documentation, like for Sysinternals tools.

APPROACH :

Today me and my friend were looking for a approach through which we can Decompile .chm files into HTML and then parse the HTML DOM to extract some information. After some googling I found that there is Windows command line utility HH.exe shipped with Windows operating system which can decompile the .CHM files to HTML using some command line options.

So I wrapped up the commands into a Powershell function, like below

	Function Get-DecompiledHTMLHelp
	{
	[cmdletbinding()]
	param(
	[String] $Destination, [String]$Filename
	)
	$EXE = 'C:\Windows\hh.exe'
	If(-not (Test-Path $destination))
	{
	"Destination folder doesn't exist"
	}
	elseIf(-not (Test-Path $Filename))
	{
	"Target .chm file not found, please make sure you're entering the full path and file name"
	}
	else
	{
	Start-Process -FilePath $EXE -ArgumentList "-decompile $Destination $Filename"
	$FilesAndFolder = Get-ChildItem $Destination -Recurse| group psiscontainer
	$FolderCount = ($Filesandfolder| ?{$_.name -eq $true}).count
	$FileCount = ($Filesandfolder| ?{$_.name -eq $False}).count
	Write-host "Decompiled into $(if($Foldercount -gt 0){$Foldercount}else{0}) Folders and $(if($FileCount){$FileCount}else{0}) Files to Destination $Destination" -ForegroundColor Yellow
	}
	}

view raw Get-DecompiledHTMLHelp.ps1 hosted with ❤ by GitHub

and then extracted the required information using following  piece of code

	Function Create-HTMLDOMFromFile
	{
	Param(
	[String] $FileName,
	[String] $TagName,
	[Int] $OuputCount = 11
	)
	$HTML = New-Object -Com "HTMLFile";
	$Content = Get-Content -Path $FileName -raw
	#To convert raw content to HTML DOM (Document object Model) and 2 stands for DOM level 2
	$HTML.IHTMLDocument2_write($Content)
	#Some data wrangling to extract the exact information
	$HTML.all.tags($TagName) | select innertext -ExpandProperty innertext -First $OuputCount
	}
	#Create-HTMLDOMFromFile -FileName 'C:\Temp\DecompiledHTML\Command_Line_Options.htm' -TagName 'P'

view raw Create-HTMLDOMFromFile.ps1 hosted with ❤ by GitHub

HOW TO RUN : 

Here I chose Compiled HTML Help file of  ProcMon.exe (Process Monitor – SysInternal Tool) as a sample .chm file.

	Function Create-HTMLDOMFromFile
	{
	Param(
	[String] $FileName,
	[String] $TagName,
	[Int] $OuputCount = 11
	)
	$HTML = New-Object -Com "HTMLFile";
	$Content = Get-Content -Path $FileName -raw
	#To convert raw content to HTML DOM (Document object Model) and 2 stands for DOM level 2
	$HTML.IHTMLDocument2_write($Content)
	#Some data wrangling to extract the exact information
	$HTML.all.tags($TagName) | select innertext -ExpandProperty innertext -First $OuputCount
	}
	#Create-HTMLDOMFromFile -FileName 'C:\Temp\DecompiledHTML\Command_Line_Options.htm' -TagName 'P'

view raw

Create-HTMLDOMFromFile.ps1

hosted with ❤ by GitHub

Hope you find it useful, happy learning 🙂

Prateek Singh  Follow @SinghPrateik