Serve proxy auto-configuration file on Windows

pac-server.ps1

# Serve proxy auto-configuration file

Param(
    [int]$PacPort = 2694,
    [int]$SocksPort = 1080
)

# Write your pac file content here:
$pac = [System.Text.Encoding]::UTF8.GetBytes(@"
function FindProxyForURL(url, host) {
    var socks = 'SOCKS5 127.0.0.1:$SocksPort';

    if (
        dnsDomainIs(host, '.internal.exapmle.com') ||
        dnsDomainIs(host, '.internal.example.org')
    ) {
        return socks;
    }

    var hostIP = dnsResolve(host);
    if (
        isInNet(hostIP, '10.0.0.0', '255.0.0.0') ||
        isInNet(hostIP, '192.168.0.0', '255.255.0.0')
    ) {
        return socks;
    }

    return 'DIRECT';
}
"@)

$url = "http://127.0.0.1:$PacPort/"
$registryPath = 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings'
$registryName = 'AutoConfigURL'

# Refresh proxy settings.
# ref. https://web.archive.org/web/20170602213824/http://www.hsyntt.com/changing-proxy-server-settings-for-internet-explorer-using-powershell/
$WinInet = Add-Type -MemberDefinition @'
    [DllImport("wininet.dll")]
    public static extern bool InternetSetOption(IntPtr hInternet, uint dwOption, IntPtr lpBuffer, uint dwBufferLength);
'@ -Name Win32InternetSettings -PassThru
$INTERNET_OPTION_PROXY_SETTINGS_CHANGED = 95
$INTERNET_OPTION_REFRESH = 37

function Refresh-Proxy-Settings {
    $WinInet::InternetSetOption([System.IntPtr]::Zero, $INTERNET_OPTION_PROXY_SETTINGS_CHANGED, [System.IntPtr]::Zero, 0) | Out-Null
    $WinInet::InternetSetOption([System.IntPtr]::Zero, $INTERNET_OPTION_REFRESH, [System.IntPtr]::Zero, 0) | Out-Null
}

$listener = New-Object System.Net.HttpListener
$listener.Prefixes.Add($url)

try {
    $listener.Start()

    Set-ItemProperty -Path $registryPath -Name $registryName -Value $url
    Refresh-Proxy-Settings

    Write-Host "Serving Proxy Auto-Configuration File on $url"
    Write-Host "Please execute 'ssh -D $SocksPort <gateway-server>'"
    Write-Host ''
    Write-Host 'Press Ctrl+C to exit.'

    while ($True) {
        # Use async method to accept Ctrl+C while waiting a request.
        # ref. https://stackoverflow.com/questions/51218257/await-async-c-sharp-method-from-powershell
        $task = $listener.GetContextAsync()
        while (-not $task.AsyncWaitHandle.WaitOne(200)) { }
        $context = $task.GetAwaiter().GetResult()

        $response = $context.Response
        $response.ContentType = 'application/x-ns-proxy-autoconfig'
        $response.ContentLength64 = $pac.Length
        $response.Close($pac, $True)
    }
} finally {
    Remove-ItemProperty -Path $registryPath -Name $registryName
    Refresh-Proxy-Settings

    $listener.Close()
}

Hi. I have noticed that the Refresh-Proxy-Settings function has stopped working on windows 10 version 2004. I've test this on 3 computers running Windows 1909 and it's working on all of them. I've also tested on 3 computers running Windows 10 2004 and none of them work, so I think an update has broken this. Are you able to confirm on your side?

Thank you for your report! I'm afraid I don't have Windows 10 2004 computers.

Maybe we have to change proxy settings by calling the InternetSetOption function with the INTERNET_OPTION_PER_CONNECTION_OPTION flag as written in https://web.archive.org/web/20150110221907/http://support.microsoft.com/kb/226473/en-us , or we have to use some other API...

Thanks, I will look into this and let you know if I find anything useful.

Thanks, I will look into this and let you know if I find anything useful.

Did you fix is on windows 10 version 2004? @jay-99 @nanto

Hmm... I can't reproduce the issue. This script still works for me (enables proxy without restarting browsers) on Windows 11 Pro 23H2 and Firefox nightly 127.0a1, Chrome canary 126.0.6443.0, and Edge 124.0.2478.51.