Add support for Zlib compression (.NET 6.0 onward only)

README.md

@@ -1,4 +1,4 @@
- ![Logo](https://raw.githubusercontent.com/sshnet/SSH.NET/develop/images/logo/png/SS-NET-icon-h50.png) SSH.NET
+ ![Logo](https://raw.githubusercontent.com/sshnet/SSH.NET/develop/images/logo/png/SS-NET-icon-h50.png) SSH.NET
 =======
 SSH.NET is a Secure Shell (SSH-2) library for .NET, optimized for parallelism.
 
@@ -120,6 +120,13 @@ Private keys can be encrypted using one of the following cipher methods:
 * hmac-sha2-256-etm<span></span>@openssh.com
 * hmac-sha2-512-etm<span></span>@openssh.com
 
+
+## Compression
+
+**SSH.NET** supports the following compression algorithms:
+* none (default)
+* zlib<span></span>@openssh.com (.NET 6 and higher)
+
 ## Framework Support
 **SSH.NET** supports the following target frameworks:
 * .NETFramework 4.6.2 (and higher)

src/Renci.SshNet/Compression/Compressor.cs

@@ -1,6 +1,6 @@
 using System;
-using System.IO;
 
+using Renci.SshNet.Messages.Authentication;
 using Renci.SshNet.Security;
 
 namespace Renci.SshNet.Compression
@@ -10,35 +10,23 @@ namespace Renci.SshNet.Compression
  /// </summary>
  public abstract class Compressor : Algorithm, IDisposable
  {
- private readonly ZlibStream _compressor;
- private readonly ZlibStream _decompressor;
- private MemoryStream _compressorStream;
- private MemoryStream _decompressorStream;
- private bool _isDisposed;
-
- /// <summary>
- /// Gets or sets a value indicating whether compression is active.
- /// </summary>
- /// <value>
- /// <see langword="true"/> if compression is active; otherwise, <see langword="false"/>.
- /// </value>
- protected bool IsActive { get; set; }
+ private readonly bool _delayedCompression;
 
- /// <summary>
- /// Gets the session.
- /// </summary>
- protected Session Session { get; private set; }
+ private bool _isActive;
+ private Session _session;
+ private bool _isDisposed;
 
  /// <summary>
  /// Initializes a new instance of the <see cref="Compressor"/> class.
  /// </summary>
- protected Compressor()
+ /// <param name="delayedCompression">
+ /// <see langword="false"/> to start compression after receiving SSH_MSG_NEWKEYS.
+ /// <see langword="true"/> to delay compression util receiving SSH_MSG_USERAUTH_SUCCESS.
+ /// <see href="https://www.openssh.com/txt/draft-miller-secsh-compression-delayed-00.txt"/>.
+ /// </param>
+ protected Compressor(bool delayedCompression)
  {
- _compressorStream = new MemoryStream();
- _decompressorStream = new MemoryStream();
-
- _compressor = new ZlibStream(_compressorStream, CompressionMode.Compress);
- _decompressor = new ZlibStream(_decompressorStream, CompressionMode.Decompress);
+ _delayedCompression = delayedCompression;
  }
 
  /// <summary>
@@ -47,7 +35,15 @@ protected Compressor()
  /// <param name="session">The session.</param>
  public virtual void Init(Session session)
  {
- Session = session;
+ if (_delayedCompression)
+ {
+ _session = session;
+ _session.UserAuthenticationSuccessReceived += Session_UserAuthenticationSuccessReceived;
+ }
+ else
+ {
+ _isActive = true;
+ }
  }
 
  /// <summary>
@@ -57,7 +53,7 @@ public virtual void Init(Session session)
  /// <returns>
  /// The compressed data.
  /// </returns>
- public virtual byte[] Compress(byte[] data)
+ public byte[] Compress(byte[] data)
  {
  return Compress(data, 0, data.Length);
  }
@@ -73,7 +69,7 @@ public virtual byte[] Compress(byte[] data)
  /// </returns>
  public virtual byte[] Compress(byte[] data, int offset, int length)
  {
- if (!IsActive)
+ if (!_isActive)
  {
  if (offset == 0 && length == data.Length)
  {
@@ -85,21 +81,28 @@ public virtual byte[] Compress(byte[] data, int offset, int length)
  return buffer;
  }
 
- _compressorStream.SetLength(0);
-
- _compressor.Write(data, offset, length);
-
- return _compressorStream.ToArray();
+ return CompressCore(data, offset, length);
  }
 
+ /// <summary>
+ /// Compresses the specified data.
+ /// </summary>
+ /// <param name="data">Data to compress.</param>
+ /// <param name="offset">The zero-based byte offset in <paramref name="data"/> at which to begin reading the data to compress. </param>
+ /// <param name="length">The number of bytes to be compressed. </param>
+ /// <returns>
+ /// The compressed data.
+ /// </returns>
+ protected abstract byte[] CompressCore(byte[] data, int offset, int length);
+
  /// <summary>
  /// Decompresses the specified data.
  /// </summary>
  /// <param name="data">Compressed data.</param>
  /// <returns>
  /// The decompressed data.
  /// </returns>
- public virtual byte[] Decompress(byte[] data)
+ public byte[] Decompress(byte[] data)
  {
  return Decompress(data, 0, data.Length);
  }
@@ -115,7 +118,7 @@ public virtual byte[] Decompress(byte[] data)
  /// </returns>
  public virtual byte[] Decompress(byte[] data, int offset, int length)
  {
- if (!IsActive)
+ if (!_isActive)
  {
  if (offset == 0 && length == data.Length)
  {
@@ -127,11 +130,24 @@ public virtual byte[] Decompress(byte[] data, int offset, int length)
  return buffer;
  }
 
- _decompressorStream.SetLength(0);
+ return DecompressCore(data, offset, length);
+ }
 
- _decompressor.Write(data, offset, length);
+ /// <summary>
+ /// Decompresses the specified data.
+ /// </summary>
+ /// <param name="data">Compressed data.</param>
+ /// <param name="offset">The zero-based byte offset in <paramref name="data"/> at which to begin reading the data to decompress. </param>
+ /// <param name="length">The number of bytes to be read from the compressed data. </param>
+ /// <returns>
+ /// The decompressed data.
+ /// </returns>
+ protected abstract byte[] DecompressCore(byte[] data, int offset, int length);
 
- return _decompressorStream.ToArray();
+ private void Session_UserAuthenticationSuccessReceived(object sender, MessageEventArgs<SuccessMessage> e)
+ {
+ _isActive = true;
+ _session.UserAuthenticationSuccessReceived -= Session_UserAuthenticationSuccessReceived;
  }
 
  /// <summary>
@@ -156,20 +172,6 @@ protected virtual void Dispose(bool disposing)
 
  if (disposing)
  {
- var compressorStream = _compressorStream;
- if (compressorStream != null)
- {
- compressorStream.Dispose();
- _compressorStream = null;
- }
-
- var decompressorStream = _decompressorStream;
- if (decompressorStream != null)
- {
- decompressorStream.Dispose();
- _decompressorStream = null;
- }
-
  _isDisposed = true;
  }
  }

src/Renci.SshNet/Compression/Zlib.cs

@@ -1,10 +1,35 @@
-namespace Renci.SshNet.Compression
+#if NET6_0_OR_GREATER
+using System.IO;
+using System.IO.Compression;
+
+namespace Renci.SshNet.Compression
 {
  /// <summary>
  /// Represents "zlib" compression implementation.
  /// </summary>
- internal sealed class Zlib : Compressor
+ internal class Zlib : Compressor
  {
+ private readonly ZLibStream _compressor;
+ private readonly ZLibStream _decompressor;
+ private MemoryStream _compressorStream;
+ private MemoryStream _decompressorStream;
+ private bool _isDisposed;
+
+ public Zlib()
+ : this(delayedCompression: false)
+ {
+ }
+
+ protected Zlib(bool delayedCompression)
+ : base(delayedCompression)
+ {
+ _compressorStream = new MemoryStream();
+ _decompressorStream = new MemoryStream();
+
+ _compressor = new ZLibStream(_compressorStream, CompressionMode.Compress);
+ _decompressor = new ZLibStream(_decompressorStream, CompressionMode.Decompress);
+ }
+
  /// <summary>
  /// Gets algorithm name.
  /// </summary>
@@ -13,15 +38,61 @@ public override string Name
  get { return "zlib"; }
  }
 
+ protected override byte[] CompressCore(byte[] data, int offset, int length)
+ {
+ _compressorStream.SetLength(0);
+
+ _compressor.Write(data, offset, length);
+ _compressor.Flush();
+
+ return _compressorStream.ToArray();
+ }
+
+ protected override byte[] DecompressCore(byte[] data, int offset, int length)
+ {
+ _decompressorStream.Write(data, offset, length);
+ _decompressorStream.Position = 0;
+
+ using var outputStream = new MemoryStream();
+ _decompressor.CopyTo(outputStream);
+
+ _decompressorStream.SetLength(0);
+
+ return outputStream.ToArray();
+ }
+
  /// <summary>
- /// Initializes the algorithm.
+ /// Releases unmanaged and - optionally - managed resources.
  /// </summary>
- /// <param name="session">The session.</param>
-public override void Init(Session session)
+ /// <param name="disposing"><see langword="true"/> to release both managed and unmanaged resources; <see langword="false"/> to release only unmanaged resources.</param>
+protected override void Dispose(bool disposing)
  {
- base.Init(session);
+ base.Dispose(disposing);
+
+ if (_isDisposed)
+ {
+ return;
+ }
+
+ if (disposing)
+ {
+ var compressorStream = _compressorStream;
+ if (compressorStream != null)
+ {
+ compressorStream.Dispose();
+ _compressorStream = null;
+ }
+
+ var decompressorStream = _decompressorStream;
+ if (decompressorStream != null)
+ {
+ decompressorStream.Dispose();
+ _decompressorStream = null;
+ }
 
- IsActive = true;
+ _isDisposed = true;
+ }
  }
  }
 }
+#endif

src/Renci.SshNet/Compression/ZlibOpenSsh.cs

@@ -1,35 +1,17 @@
-using Renci.SshNet.Messages.Authentication;
-
+#if NET6_0_OR_GREATER
 namespace Renci.SshNet.Compression
 {
- /// <summary>
- /// Represents "zlib@openssh.org" compression implementation.
- /// </summary>
- public class ZlibOpenSsh : Compressor
+ internal sealed class ZlibOpenSsh : Zlib
  {
- /// <summary>
- /// Gets algorithm name.
- /// </summary>
- public override string Name
+ public ZlibOpenSsh()
+ : base(delayedCompression: true)
  {
- get { return "zlib@openssh.org"; }
  }
 
- /// <summary>
- /// Initializes the algorithm.
- /// </summary>
- /// <param name="session">The session.</param>
- public override void Init(Session session)
- {
- base.Init(session);
-
- session.UserAuthenticationSuccessReceived += Session_UserAuthenticationSuccessReceived;
- }
-
- private void Session_UserAuthenticationSuccessReceived(object sender, MessageEventArgs<SuccessMessage> e)
+ public override string Name
  {
- IsActive = true;
- Session.UserAuthenticationSuccessReceived -= Session_UserAuthenticationSuccessReceived;
+ get { return "zlib@openssh.com"; }
  }
  }
 }
+#endif