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Allow the client to initiate the key exchange #972

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Allow the client to initiate the key exchange #972

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f6d719f
Allow the client to initiate the key exchange
geoffstewart Jun 24, 2022
f5d680f
Merge branch 'develop' into initiateKeyExchange
geoffstewart Oct 11, 2023
565b7fb
Merge branch 'develop' into initiateKeyExchange
geoffstewart Oct 18, 2023
944f943
Merge branch 'develop' into initiateKeyExchange
geoffstewart Oct 31, 2023
8841805
Merge branch 'develop' into initiateKeyExchange
geoffstewart Nov 14, 2023
1f53cf0
Merge branch 'develop' into initiateKeyExchange
WojciechNagorski Nov 16, 2023
3779a09
Merge branch 'develop' into initiateKeyExchange
geoffstewart Nov 22, 2023
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9 changes: 9 additions & 0 deletions src/Renci.SshNet/ConnectionInfo.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -187,6 +187,14 @@ public class ConnectionInfo : IConnectionInfoInternal
/// </value>
public int MaxSessions { get; set; }

/// <summary>
/// For servers that wait for the Key Exchange message, send the SSH_MSG_KEXINIT explicitly on connect()
/// </summary>
/// <value>
/// True to initiate the key exchange on connect(). Default is false.
/// </value>
public bool InitiateKeyExchange { get; set; }

/// <summary>
/// Occurs when authentication banner is sent by the server.
/// </summary>
Expand Down Expand Up @@ -341,6 +349,7 @@ public ConnectionInfo(string host, int port, string username, ProxyTypes proxyTy
ChannelCloseTimeout = DefaultChannelCloseTimeout;
RetryAttempts = 10;
MaxSessions = 10;
InitiateKeyExchange = false;
Encoding = Encoding.UTF8;

KeyExchangeAlgorithms = new Dictionary<string, Type>
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5 changes: 5 additions & 0 deletions src/Renci.SshNet/Session.cs
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Expand Up @@ -650,6 +650,11 @@ public void Connect()
// ToDo: Make message pump async, to not consume a thread for every session
_ = ThreadAbstraction.ExecuteThreadLongRunning(MessageListener);

if (ConnectionInfo.InitiateKeyExchange)
{
SendMessage(ClientInitMessage);
}
Comment on lines +653 to +656
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So to summarise my thoughts here, we can

  1. make this unconditional
  2. add _keyExchangeInProgress = true before the SendMessage(ClientInitMessage); call
  3. move it above line 651 (_ = ThreadAbstraction.ExecuteThreadLongRunning(MessageListener);). This will ensure we have sent the client init before we continue the key exchange
  4. Add a parameter bool sendClientInitMessage to IKeyExchange.Start which guards SendMessage(session.ClientInitMessage); in KeyExchange.Start
  5. Add a private bool _initialKeyExchangeCompleted; (or similar) member to Session, which is used to decide the sendClientInitMessage parameter in Session.OnKeyExchangeInitReceived.

As for testing, if we make it unconditional then we are covered already 🙂


// Wait for key exchange to be completed
WaitOnHandle(_keyExchangeCompletedWaitHandle);

Expand Down