Configure WinINET proxy server with PowerShell

Configure WinINET proxy server with PowerShell

A proxy server is used to allow applications and web browsers to communicate with the internet. There are multiple benefits. One of them is caching of the results. This is less important then it used to be. You also control what sites can be visited and that you have a log of where the traffic is going to. You can use a transparent proxy which means that you do not need to configure your hosts with proxy settings. The firewall sends all the internet bound traffic (HTTP/HTTPS) to the proxy server. With a standard proxy you need to tell the hosts and applications where to go and, optionally for what sites to bypass the proxy server. There are different options and libraries to configure the Windows proxy settings. Here we focus on how to Configure WinINET proxy server with PowerShell.

Why? Primarily because I wanted to automate this. Secondly, I needed a solution that was easy and fast in a non-domain joined / work group scenario.

How to configure proxy server settings

There are basically 3 ways to define proxy settings on a Windows host.I

  • Applications using the WinINET library.  WinINET, an API, is part of Internet Explorer and can also be used by other applications. Applications leveraging the WinINET API take over the proxy settings configured in Internet Explorer. You set these per user or per machine. In the latter case only a user with administrative rights can set or change the proxy server settings. We’ll look at PowerShell to configure this for us.
  • Applications using the WinHTTP library. WinHTTP is the best choice for non-interactive usage. Prime examples are windows services or custom applications. WinHTTP does not use the proxy settings from WinINET unless you import them. This is the one we need to configure for applications that do not use WinINET. If you do not do so you will run into issues when blocking direct internet access. Settings in WinINET are ignored. Which means the proxy is not by an application or service using WinHTTP. You set this via netsh winhttp set proxy <proxy>:<port>. You can reset this via netsh winhttp reset proxy. If you want to import the WinINET setting use netsh winhttp import proxy source=ie
  • Applications that have their own proxy settings. In this case you configure the settings in the application itself. Some applications like Firefox use the systems settings by default but you can also define Firefox specific proxy settings.

Where to configure the proxy settings

Bar the options to automatically detect the proxy setting or using a script (GPO or registry editing) you can manually configure the settings for WinINET.

I have stopped using Internet explorer and as such I avoid using it to configure the WinINET settings. For that I prefer to use the Windows, Settings, Network & Internet, Proxy. The result is the same and on modern OS versions I disable Internet Explorer.

Configure WinINET proxy server with PowerShell
Manual Proxy configuration

If you want to set them machine wide you can do so via a GPO or registry editing.

Via GPO: Computer Configuration\Administrative Templates\Windows Components\Internet Explorer\Make proxy settings per-machine (rather than per user)
Via Registry:HKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings
DWORD: ProxySettingsPerUser = 0

But bar using GPOs setting Proxy setting manually can be tedious, especially when you want to clean out old settings and have multiple profiles on the hosts. So I threw together a PowerShell solution to use in work group environments. This took some research and testing to get right.

$ProxyServer = "192.168.2.5:3128"
$ProxyBypassList = "192.168.2.3;192.168.2.4;192.168.2.5;192.168.2.72;<local>"
$TurnProxyOnOff = "On"
$ProxyPerMachine = $False

<#
$ProxyServer = ""
$ProxyBypassList = ""
$TurnProxyOnOff = "Off"
$ProxyPerMachine = $False
#/#>

#Example: Set-InternetProxy "mproxy:3128" "*.mysite.com;<local>"
function Set-InternetProxy($ProxyPerMachine, $TurnProxyOnOff, $proxy, $bypassUrls) {
    if ($TurnProxyOnOff -eq "Off") { $ProxyEnabled = '01'; $ProxyEnable = 0 } Else { $ProxyEnabled = '11'; $ProxyEnable = 1 }

    $regPath = "HKLM:\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings"
    $proxyBytes = [system.Text.Encoding]::ASCII.GetBytes($proxy)
    $bypassBytes = [system.Text.Encoding]::ASCII.GetBytes($bypassUrls)
    $defaultConnectionSettings = [byte[]]@(@(70, 0, 0, 0, 0, 0, 0, 0, $ProxyEnabled, 0, 0, 0, $proxyBytes.Length, 0, 0, 0) + $proxyBytes + @($bypassBytes.Length, 0, 0, 0) + $bypassBytes + @(1..36 | % { 0 }))
                       
    if ($ProxyPerMachine -eq $True) { #ProxySettingsPerMachine         

        New-ItemProperty -Path $regPath -Name 'ProxySettingsPerUser' -Value 0 -PropertyType DWORD -Force #-ErrorAction SilentlyContinue

        #Set the proxy settings per Machine
        SetProxySettingsPerMachine $Proxy $ProxyEnable $defaultConnectionSettings
                       
        #As we are using the per machine proxy settings clear the user settings, tidy up.
        #This is done for all profiles found on the host as well as the default profile.
        ClearProxySettingPerUser

    }
    Elseif ($ProxyPerMachine -eq $False) { #ProxySettingsPerUser
        New-ItemProperty -Path $regPath -Name 'ProxySettingsPerUser' -Value 1 -PropertyType DWORD -Force #-ErrorAction SilentlyContinue
        #write-Host "we  get here"

        #Set the proxy settings per user (this is done for all profiles found on the host as well as the default profile)
        SetProxySettingsPerUser $Proxy $ProxyEnable $defaultConnectionSettings
            
        #As we are using the per user proxy settings clear the machine settings, tidy up.
        ClearProxySettingsPerMachine

    }          
}

function SetProxySettingsPerUser($Proxy, $ProxyEnable, $defaultConnectionSettings) {
    
    # Get each user profile SID and Path to the profile
    $UserProfiles = Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList\*" | Where { $_.PSChildName -match "S-1-5-21-(\d+-?){4}$" } | Select-Object @{Name = "SID"; Expression = { $_.PSChildName } }, @{Name = "UserHive"; Expression = { "$($_.ProfileImagePath)\NTuser.dat" } }

    # We also grab the default user profile just in case the proxy settings have been changed in there, but they should not have been
    $DefaultProfile = "" | Select-Object SID, UserHive
    $DefaultProfile.SID = ".DEFAULT"
    $DefaultProfile.Userhive = "C:\Users\Public\NTuser.dat"

    $UserProfiles += $DefaultProfile

    # Loop through each profile we found on the host
    Foreach ($UserProfile in $UserProfiles) {
        # Load ntuser.dat if it's not already loaded
        If (($ProfileAlreadyLoaded = Test-Path Registry::HKEY_USERS\$($UserProfile.SID)) -eq $false) {
            Start-Process -FilePath "CMD.EXE" -ArgumentList "/C REG.EXE LOAD HKU\$($UserProfile.SID) $($UserProfile.UserHive)" -Wait -WindowStyle Hidden
            Write-Host -ForegroundColor Cyan "Loading hive" $UserProfile.UserHive "for user profile SID:" $UserProfile.SID
        }
        Else {
            Write-Host -ForegroundColor Cyan "Hive already loaded" $UserProfile.UserHive "for user profile SID:" $UserProfile.SID
        }                    
                    
                    
        $registryPath = "Registry::HKEY_USERS\$($UserProfile.SID)\Software\Microsoft\Windows\CurrentVersion\Internet Settings"
        #$registryPath = "HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings"
        Set-ItemProperty -Path $registryPath -Name ProxyServer -Value $proxy
        Set-ItemProperty -Path $registryPath -Name ProxyEnable -Value $ProxyEnable
        Set-ItemProperty -Path "$registryPath\Connections" -Name DefaultConnectionSettings -Value $defaultConnectionSettings   

        
        # Unload NTuser.dat if it wasen't loaded to begin with.  
        If ($ProfileAlreadyLoaded -eq $false) {
            [gc]::Collect() #Ckean up any open handles to the registry to avoid getting an "Access Denied" error.
            Start-Sleep -Seconds 5 #Give it some time
            #Unoad the user profile, but only if we loaded it our selves manually.
            Start-Process -FilePath "CMD.EXE" -ArgumentList "/C REG.EXE UNLOAD HKU\$($UserProfile.SID)" -Wait -WindowStyle Hidden | Out-Null
            Write-Host -ForegroundColor Cyan "Unloading hive" $UserProfile.UserHive "for user profile SID:" $UserProfile.SID
        } 
    }
        
}    

    
function SetProxySettingsPerMachine ($Proxy, $ProxyEnable, $defaultConnectionSettings) {

    #Set the proxy settings per machine (this is done for both X64 and X86)
    $registryPath = "HKLM:\Software\Microsoft\Windows\CurrentVersion\Internet Settings"
    Set-ItemProperty -Path $registryPath -Name ProxyServer -Value $proxy
    Set-ItemProperty -Path $registryPath -Name ProxyEnable -Value $ProxyEnable
    Set-ItemProperty -Path "$registryPath\Connections" -Name DefaultConnectionSettings -Value $defaultConnectionSettings
            
    $registryPath = "HKLM:\Software\WOW6432Node\Microsoft\Windows\CurrentVersion\Internet Settings"
    Set-ItemProperty -Path $registryPath -Name ProxyServer -Value $proxy
    Set-ItemProperty -Path $registryPath -Name ProxyEnable -Value $ProxyEnable
    Set-ItemProperty -Path "$registryPath\Connections" -Name DefaultConnectionSettings -Value $defaultConnectionSettings
}

Function ClearProxySettingPerUser () {
    # Get each user profile SID and Path to the profile
    $UserProfiles = Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList\*" | Where { $_.PSChildName -match "S-1-5-21-(\d+-?){4}$" } | Select-Object @{Name = "SID"; Expression = { $_.PSChildName } }, @{Name = "UserHive"; Expression = { "$($_.ProfileImagePath)\NTuser.dat" } }

    # We also grab the default user profile just in case the proxy settings have been changed in there, but they should not have been
    $DefaultProfile = "" | Select-Object SID, UserHive
    $DefaultProfile.SID = ".DEFAULT"
    $DefaultProfile.Userhive = "C:\Users\Public\NTuser.dat"

    $UserProfiles += $DefaultProfile

    # Loop through each profile we found on the host
    Foreach ($UserProfile in $UserProfiles) {
        # Load ntuser.dat if it's not already loaded
        If (($ProfileAlreadyLoaded = Test-Path Registry::HKEY_USERS\$($UserProfile.SID)) -eq $false) {
            Start-Process -FilePath "CMD.EXE" -ArgumentList "/C REG.EXE LOAD HKU\$($UserProfile.SID) $($UserProfile.UserHive)" -Wait -WindowStyle Hidden
            Write-Host -ForegroundColor Cyan "Loading hive" $UserProfile.UserHive "for user profile SID:" $UserProfile.SID
        }
        Else {
            Write-Host -ForegroundColor Cyan "Hive already loaded" $UserProfile.UserHive "for user profile SID:" $UserProfile.SID
        }

        #As you are using per machine setttings erase any proxy setting for the current user.
        $proxyBytes = [system.Text.Encoding]::ASCII.GetBytes('')
        $bypassBytes = [system.Text.Encoding]::ASCII.GetBytes('')
        $defaultConnectionSettings = [byte[]]@(@(70, 0, 0, 0, 0, 0, 0, 0, 01, 0, 0, 0, $proxyBytes.Length, 0, 0, 0) + $proxyBytes + @($bypassBytes.Length, 0, 0, 0) + $bypassBytes + @(1..36 | % { 0 }))
           
        $registryPath = "Registry::HKEY_USERS\$($UserProfile.SID)\Software\Microsoft\Windows\CurrentVersion\Internet Settings"
        Set-ItemProperty -Path $registryPath -Name ProxyServer -Value ''
        Set-ItemProperty -Path $registryPath -Name ProxyEnable -Value 0
        Set-ItemProperty -Path "$registryPath\Connections" -Name DefaultConnectionSettings -Value $defaultConnectionSettings   
        
        # Unload NTuser.dat if it wasen't loaded to begin with.  
        If ($ProfileAlreadyLoaded -eq $false) {
            [gc]::Collect() #Clean up any open handles to the registry to avoid getting an "Access Denied" error.
            Start-Sleep -Seconds 2 #Give it some time
            #Unoad the user profile, but only if we loaded it our selves manually.
            Start-Process -FilePath "CMD.EXE" -ArgumentList "/C REG.EXE UNLOAD HKU\$($UserProfile.SID)" -Wait -WindowStyle Hidden | Out-Null
            Write-Host -ForegroundColor Cyan "Unloading hive" $UserProfile.UserHive "for user profile SID:" $UserProfile.SID
        } 
    }
}
    
Function ClearProxySettingsPerMachine () {
    #As you are using per user setttings erase any proxy setting per machine
    $proxyBytes = [system.Text.Encoding]::ASCII.GetBytes('')
    $bypassBytes = [system.Text.Encoding]::ASCII.GetBytes('')
    $defaultConnectionSettings = [byte[]]@(@(70, 0, 0, 0, 0, 0, 0, 0, 01, 0, 0, 0, $proxyBytes.Length, 0, 0, 0) + $proxyBytes + @($bypassBytes.Length, 0, 0, 0) + $bypassBytes + @(1..36 | % { 0 }))
            
    $registryPath = "HKLM:\Software\Microsoft\Windows\CurrentVersion\Internet Settings"
    Set-ItemProperty -Path $registryPath -Name ProxyServer -Value ''
    Set-ItemProperty -Path $registryPath -Name ProxyEnable -Value 0
    Set-ItemProperty -Path "$registryPath\Connections" -Name DefaultConnectionSettings -Value $defaultConnectionSettings
            
    $registryPath = "HKLM:\Software\WOW6432Node\Microsoft\Windows\CurrentVersion\Internet Settings"
    Set-ItemProperty -Path $registryPath -Name ProxyServer -Value ''
    Set-ItemProperty -Path $registryPath -Name ProxyEnable -Value 0
    Set-ItemProperty -Path "$registryPath\Connections" -Name DefaultConnectionSettings -Value $defaultConnectionSettings
}

Set-InternetProxy $ProxyPerMachine $TurnProxyOnOff $ProxyServer $ProxyBypassList

Test the above script to Configure WinINET proxy server with PowerShell.in a VM to verify its behaviour. I hope this help somebody and probably my future self as well.

7 thoughts on “Configure WinINET proxy server with PowerShell

  1. Pingback: Squid for Windows and Veeam - Working Hard In IT

  2. Thank you so much for this. Helped so much with an installer we were trying to deploy from a service account that ONLY would look at WinINET.

  3. Hi! Thanks for the excellent script. 🙂
    I ran into a couple of problems trying it on a new AWS server2016 machine.
    1) There was only one userprofile so the $userprofiles vafriable was cast as a single userprofile object and it does not support +=
    Fix was to add $userprofiles = @() to cast it as an array first and then use
    $userprofiles += get-itemproperty…(etc)
    for all subsequent additions.
    2) Our exception list is 752 characters long!
    I know, I know..
    Fix was
    [Uint32]$bypassBytesLenlow = $bypassBytes.length -band 0xff
    [Uint32]$bypassBytesLenHi = $bypassBytes.Length -shr 8

    then
    … + $proxyBytes + @($bypassBytesLenlow, $bypassBytesLenHi, 0, 0) +…

    This will handle exception strings up to 65535 characters in length but it looks as though the registry will support 4 hex numbers for this length which will be handy if your exception list is approaching 4,294,967,295 characters. 😉

  4. Thanks for the script and the info. 😀

    A tip to shorten the code though.
    You can load “HKEY_USERS” like this instead of looking for the datafiles:

    Map the HKEY_USERS registry to HKU:\

    New-PSDrive -PSProvider Registry -Name HKU -Root HKEY_USERS

    This gives you the posibility to navigate to all users registry hive without any more complex logic.
    Then you just need the SID to get the right user.
    Like this

    Get-ItemProperty “HKU:\$($UserProfile.SID)\Software\Microsoft\Windows\CurrentVersion\Internet Settings”

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