6e54e0f411
Supports three packing modes: - append (default) — data after IEND marker - chunk — private pnZp PNG chunk - lsb — least significant bits of pixels Includes Python (pack.py/unpack.py) and PowerShell (pack.ps1/unpack.ps1) implementations with full cross-compatibility. Features: self-extract bootstrap, metadata one-liners (eXIf/tEXt), CRC32 integrity check, PNG clean mode.
91 lines
2.7 KiB
PowerShell
91 lines
2.7 KiB
PowerShell
# unpack.ps1 — Extract file(s) hidden inside a PNG image
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# Usage: powershell -File unpack.ps1 packed.png [-OutDir .] [-List]
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param(
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[Parameter(Mandatory, Position=0)][string]$Image,
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[string]$OutDir = ".",
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[switch]$List,
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[switch]$All
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)
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Add-Type -TypeDefinition @"
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using System;
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public static class PngZipHelper2 {
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static readonly uint[] crcTable;
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static PngZipHelper2() {
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crcTable = new uint[256];
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for (uint i = 0; i < 256; i++) {
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uint c = i;
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for (int j = 0; j < 8; j++)
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c = (c & 1) != 0 ? 0xEDB88320u ^ (c >> 1) : c >> 1;
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crcTable[i] = c;
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}
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}
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public static uint Crc32(byte[] data) {
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uint crc = 0xFFFFFFFF;
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foreach (byte b in data) crc = crcTable[(crc ^ b) & 0xFF] ^ (crc >> 8);
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return crc ^ 0xFFFFFFFF;
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}
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}
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"@
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$d = [IO.File]::ReadAllBytes((Resolve-Path $Image))
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$text = [Text.Encoding]::GetEncoding(28591).GetString($d)
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$sig = 'PNGZIP'
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$payloads = @()
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$offset = 0
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while ($true) {
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# Find next 'PNGZIP' and validate \x00\x01 suffix via byte array
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$i = $offset
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while (($i = $text.IndexOf($sig, $i, [StringComparison]::Ordinal)) -ge 0) {
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if ($d[$i+6] -eq 0 -and $d[$i+7] -eq 1) { break }
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$i++
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}
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if ($i -lt 0) { break }
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$p = $i + 8
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# name
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$nl = $d[$p] * 256 + $d[$p+1]; $p += 2
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$name = [Text.Encoding]::UTF8.GetString($d, $p, $nl); $p += $nl
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# compressed length (big-endian uint64)
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[uint64]$pl = 0
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for ($k = 0; $k -lt 8; $k++) { $pl = $pl * 256 + $d[$p+$k] }; $p += 8
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# decompress zlib: skip 2-byte header, exclude 4-byte adler32
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$ms = New-Object IO.MemoryStream
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$ms.Write($d, $p + 2, $pl - 6)
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[void]$ms.Seek(0, 0)
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$ds = New-Object IO.Compression.DeflateStream($ms, [IO.Compression.CompressionMode]::Decompress)
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$os = New-Object IO.MemoryStream
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$ds.CopyTo($os)
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$raw = $os.ToArray()
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$p += $pl
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# CRC check
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[uint32]$storedCrc = $d[$p]*16777216 + $d[$p+1]*65536 + $d[$p+2]*256 + $d[$p+3]
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$p += 4
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$actualCrc = [PngZipHelper2]::Crc32($raw)
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if ($actualCrc -ne $storedCrc) { Write-Warning "CRC mismatch for $name" }
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$payloads += @{ Name = $name; Data = $raw }
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$offset = $p
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}
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if ($payloads.Count -eq 0) { Write-Error "No payload found"; exit 3 }
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if ($List) {
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foreach ($p in $payloads) { Write-Host " $($p.Name) ($($p.Data.Length) bytes)" }
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return
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}
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$toExtract = if ($All) { $payloads } else { @($payloads[-1]) }
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$null = New-Item -ItemType Directory -Force -Path $OutDir
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foreach ($entry in $toExtract) {
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$safeName = [IO.Path]::GetFileName($entry.Name)
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$outPath = Join-Path $OutDir $safeName
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[IO.File]::WriteAllBytes($outPath, $entry.Data)
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Write-Host "Extracted: $outPath ($($entry.Data.Length) bytes)"
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}
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