Powershell script to search in a folder of JARs for a given string inside those jars, also searches in nested jars (shaded)

README.md

SearchJars

Powershell script to search in a folder of JARs for a given string inside those jars. Also searches in nested jars (shaded).

Example usage:

.\SearchJars.ps1 -FolderPath "E:\.minecraft\mods" -SearchString "Search me!"

I initially did this to quickly search for unknown strings in Minecraft mods, though it can be used for anything else.

Warning

This is not a decompiler. It'll merely search for hardcoded strings, not actual code. It'll probably also match string constants that can be built at compile time (e.g. concatenated string literals) but I haven't tested that and have no guarantees of it.

SearchJars.ps1

param (
    [Parameter(Mandatory = $true)]
    [string]$FolderPath,
    [Parameter(Mandatory = $true)]
    [string]$SearchString
)

Add-Type -AssemblyName System.IO.Compression.FileSystem

$matchedPaths = [System.Collections.Generic.List[string]]::new()

function Search-Jar {
    param (
        [System.IO.Stream]$Stream,
        [string]$JarPath,
        [string]$SearchString
    )

    try {
        $zip = New-Object System.IO.Compression.ZipArchive($Stream, [System.IO.Compression.ZipArchiveMode]::Read)

        foreach ($entry in $zip.Entries) {
            if ([string]::IsNullOrWhiteSpace($entry.Name)) {
                continue
            }

            $entryFullPath = "$JarPath -> $($entry.FullName)"

            if ($entry.FullName -imatch '\.jar$') {
                Write-Output "Searching nested JAR: $entryFullPath"
                try {
                    $nestedStream = $entry.Open()
                    $memStream = New-Object System.IO.MemoryStream
                    $nestedStream.CopyTo($memStream)
                    $nestedStream.Close()
                    $memStream.Position = 0
                    Search-Jar -Stream $memStream -JarPath $entryFullPath -SearchString $SearchString
                    $memStream.Dispose()
                }
                catch {
                    Write-Warning "Failed to process nested JAR: $entryFullPath"
                }
                continue
            }

            # Search all other entries as text
            try {
                $entryStream = $entry.Open()
                $reader = New-Object System.IO.StreamReader($entryStream)
                $content = $reader.ReadToEnd()
                if ($content -imatch [regex]::Escape($SearchString)) {
                    Write-Host "Match found: $entryFullPath" -ForegroundColor Green
                    $matchedPaths.Add($entryFullPath)
                }
                $reader.Close()
                $entryStream.Close()
            }
            catch {
                continue
            }
        }

        $zip.Dispose()
    }
    catch {
        Write-Warning "Failed to read ZIP/JAR stream at: $JarPath"
    }
}

$jarFiles = Get-ChildItem -Path $FolderPath -Filter *.jar -File

foreach ($jar in $jarFiles) {
    Write-Output "Searching JAR: $($jar.Name)"
    try {
        $fileStream = [System.IO.File]::OpenRead($jar.FullName)
        Search-Jar -Stream $fileStream -JarPath $jar.Name -SearchString $SearchString
        $fileStream.Dispose()
    }
    catch {
        Write-Warning "Failed to open JAR: $($jar.FullName)"
    }
}

Write-Output ""
if ($matchedPaths.Count -eq 0) {
    Write-Output "No matches found in any scanned JAR."
} else {
    Write-Output "Found $($matchedPaths.Count) match(es):"
    foreach ($path in $matchedPaths) {
        Write-Host "  $path" -ForegroundColor Green
    }
}