About

Recursive Extractor is a Cross-Platform .NET Standard 2.0 Library and Command Line Program for parsing archive files and disk images, including nested archives and disk images.

Supported File Types

7zip+	ar	bzip2
deb	gzip	iso
rar^	tar	vhd
vhdx	vmdk	wim*
xzip	zip+

Details

* Windows only
+ Encryption Supported
^ Rar version 4 Encryption supported

Variants

Command Line

Installing

1. Ensure you have the latest .NET SDK.
2. run dotnet tool install -g Microsoft.CST.RecursiveExtractor.Cli

This adds RecursiveExtractor to your path so you can run it directly from the shell.

Running

Basic usage is: RecursiveExtractor --input archive.ext --output outputDirectory

Detailed Usage

• input: The path to the Archive to extract.
• output: The path a directory to extract into.
• passwords: A comma separated list of passwords to use for archives.
• allow-globs: A comma separated list of glob patterns to require each extracted file match.
• deny-globs: A comma separated list of glob patterns to require each extracted file not match.
• raw-extensions: A comma separated list of file extensions to not recurse into.
• no-recursion: Don't recurse into sub-archives.
• single-thread: Don't attempt to parallelize extraction.
• printnames: Output the name of each file extracted.

For example, to extract only ".cs" files:

RecursiveExtractor --input archive.ext --output outputDirectory --allow-globs **/*.cs

Run RecursiveExtractor --help for more details.

.NET Standard Library

Recursive Extractor is available on NuGet as Microsoft.CST.RecursiveExtractor. Recursive Extractor targets netstandard2.0+ and the latest .NET, currently .NET 6.0.

Usage

The most basic usage is to enumerate through all the files in the archive provided and do something with their contents as a Stream.

using Microsoft.CST.RecursiveExtractor;

var path = "path/to/file";
var extractor = new Extractor();
foreach(var file in extractor.Extract(path))
{
    doSomething(file.Content); //Do Something with the file contents (a Stream)
}

Extracting to Disk

This code adapted from the Cli extracts the contents of given archive located at `options.Input` to a directory located at `options.Output`, including extracting failed archives as themselves.

using Microsoft.CST.RecursiveExtractor;

var extractor = new Extractor();
var extractorOptions = new ExtractorOptions()
{
    ExtractSelfOnFail = true,
};
extractor.ExtractToDirectory(options.Output, options.Input, extractorOptions);

Async Usage

This example of using the async API prints out all the file names found from the archive located at the path.

var path = "/Path/To/Your/Archive"
var extractor = new Extractor();
try {
    IEnumerable<FileEntry> results = extractor.ExtractFileAsync(path);
    await foreach(var found in results)
    {
        Console.WriteLine(found.FullPath);
    }
}
catch(OverflowException)
{
    // This means Recursive Extractor has detected a Quine or Zip Bomb
}

The FileEntry Object

The Extractor returns `FileEntry` objects. These objects contain a `Content` Stream of the file contents.

public Stream Content { get; }
public string FullPath { get; }
public string Name { get; }
public FileEntry? Parent { get; }
public string? ParentPath { get; }
public DateTime CreateTime { get; }
public DateTime ModifyTime { get; }
public DateTime AccessTime { get; }

Extracting Encrypted Archives

You can provide passwords to use to decrypt archives, paired with a Regex that will operate against the Name of the Archive.

var path = "/Path/To/Your/Archive"
var directory
var extractor = new Extractor();
try {
    IEnumerable<FileEntry> results = extractor.ExtractFile(path, new ExtractorOptions()
    {
        Passwords = new Dictionary<Regex, List<string>>()
        {
            { new Regex("\.zip"), new List<string>(){ "PasswordForZipFiles" } },
            { new Regex("\.7z"), new List<string>(){ "PasswordFor7zFiles" } },
            { new Regex(".*"), new List<string>(){ "PasswordForAllFiles" } }

        }
    });
    foreach(var found in results)
    {
        Console.WriteLine(found.FullPath);
    }
}
catch(OverflowException)
{
    // This means Recursive Extractor has detected a Quine or Zip Bomb
}

Exceptions

RecursiveExtractor protects against ZipSlip, Quines, and Zip Bombs. Calls to Extract will throw an OverflowException when a Quine or Zip bomb is detected and a TimeOutException if EnableTiming is set and the specified time period has elapsed before completion.

Otherwise, invalid files found while crawling will emit a logger message and be skipped. RecursiveExtractor uses NLog for logging.

Notes on Enumeration

Multiple Enumeration

You should not iterate the Enumeration returned from the Extract and ExtractAsync interfaces multiple times, if you need to do so, convert the Enumeration to the collection of your choice first.

Parallel Enumeration

If you want to enumerate the output with parallelization you should use a batching mechanism, for example:

var extractedEnumeration = Extract(fileEntry, opts);
using var enumerator = extractedEnumeration.GetEnumerator();
ConcurrentBag<FileEntry> entryBatch = new();
bool moreAvailable = enumerator.MoveNext();
while (moreAvailable)
{
    entryBatch = new();
    for (int i = 0; i < BatchSize; i++)
    {
        entryBatch.Add(enumerator.Current);
        moreAvailable = enumerator.MoveNext();
        if (!moreAvailable)
        {
            break;
        }
    }

    if (entryBatch.Count == 0)
    {
        break;
    }

    // Run your parallel processing on the batch
    Parallel.ForEach(entryBatch, new ParallelOptions() { CancellationToken = cts.Token }, entry =>
    {
        // Do something with each FileEntry
    }
}

Disposing During Enumeration

If you are working with a very large archive or in particularly constrained environment you can reduce memory/file handle usage for the Content streams in each FileEntry by disposing as you iterate.

var results = extractor.Extract(path);
foreach(var file in results)
{
    using var theStream = file.Content;
    // Do something with the stream.
    _ = theStream.ReadByte();
}

Feedback

If you have any issues or feature requests (for example, supporting other formats) you can open a new Issue.

If you have an archive you are having trouble parsing a specific archive, it is helpful if you can include an archive that demonstrates the issue.

Dependencies

Recursive Extractor uses a number of libraries to parse archives.

• SharpZipLib
• SharpCompress
• DiscUtils

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.opensource.microsoft.com.

When you submit a pull request, a CLA bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., status check, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.