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SSH Tunnel Set Allowed SSH Algorithms

Demonstrates the Chilkat SshTunnel.SetAllowedAlgorithms method, which restricts the SSH connection to a specific set of algorithms. A JsonObject supplies comma-separated allow-lists for the kex, hostKey, cipher, and mac categories. It must be called before Connect.

Important: You typically should not set allowed algorithms explicitly. By default Chilkat orders algorithms according to best practices and accounts for known vulnerabilities.

Background: SSH negotiates a mutually supported algorithm from each category at connection time, and pinning that choice makes an application brittle: if the server later drops a weak algorithm, the two sides may fail to agree and the tunnel stops working. The legitimate reasons to override are a security policy mandating specific algorithms or a compatibility problem with an old server; otherwise let the library's defaults evolve with current guidance.

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Local $bSuccess = False

;  Demonstrates the SshTunnel.SetAllowedAlgorithms method, which restricts the SSH connection to a
;  specific set of algorithms.  The only argument is a JsonObject.  It must be called before
;  Connect.
;  
;  Note: You typically should NOT set allowed algorithms explicitly.  By default Chilkat orders
;  algorithms according to best practices and accounts for known vulnerabilities.  Hard-coding
;  them can make an application brittle if a server later changes its allowed algorithms.

$oTunnel = ObjCreate("Chilkat.SshTunnel")

;  List the allowed algorithms for each category, in order of preference.
$oJson = ObjCreate("Chilkat.JsonObject")
$oJson.UpdateString("kex","curve25519-sha256@libssh.org,ecdh-sha2-nistp256")
$oJson.UpdateString("hostKey","ssh-ed25519,ecdsa-sha2-nistp256")
$oJson.UpdateString("cipher","chacha20-poly1305@openssh.com,aes256-ctr")
$oJson.UpdateString("mac","hmac-sha2-256,hmac-sha2-512")

;  Apply the allow-list before connecting.
$bSuccess = $oTunnel.SetAllowedAlgorithms($oJson)
If ($bSuccess = False) Then
    ConsoleWrite($oTunnel.LastErrorText & @CRLF)
    Exit
EndIf

$oTunnel.DestHostname = "db.internal.example.com"
$oTunnel.DestPort = 5432

Local $iSshPort = 22
$bSuccess = $oTunnel.Connect("ssh.example.com",$iSshPort)
If ($bSuccess = False) Then
    ConsoleWrite($oTunnel.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("Connected." & @CRLF)

Local $bWaitForThreadExit = True
$bSuccess = $oTunnel.CloseTunnel($bWaitForThreadExit)
If ($bSuccess = False) Then
    ConsoleWrite($oTunnel.LastErrorText & @CRLF)
    Exit
EndIf