PureBasic

Connect an SSH Tunnel Through a Jump Host

Demonstrates the Chilkat SshTunnel.ConnectThroughSsh method, which connects to an SSH server through an already connected and authenticated Ssh object. The first argument is the jump-host Ssh object, and the second and third are the destination SSH hostname and port.

Background: This chains the tunnel through a "jump host" (bastion): the application reaches a gateway server, then tunnels onward to an SSH server that is only accessible from inside the network. Each hop authenticates separately with its own credentials. The result is a normal SshTunnel — still requiring its own authentication and BeginAccepting — whose transport is routed through the first connection.

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IncludeFile "CkSshTunnel.pb"
IncludeFile "CkSsh.pb"

Procedure ChilkatExample()

    success.i = 0

    ;  Demonstrates the SshTunnel.ConnectThroughSsh method, which connects to an SSH server through
    ;  an already connected and authenticated Ssh object (a jump host).  The 1st argument is the Ssh
    ;  object, and the 2nd and 3rd are the destination SSH hostname and port.

    sshJump.i = CkSsh::ckCreate()
    If sshJump.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ;  Connect and authenticate to the jump host first.
    sshPort.i = 22
    success = CkSsh::ckConnect(sshJump,"jump.example.com",sshPort)
    If success = 0
        Debug CkSsh::ckLastErrorText(sshJump)
        CkSsh::ckDispose(sshJump)
        ProcedureReturn
    EndIf

    ;  Normally you would not hard-code the password in source.  You should instead obtain it
    ;  from an interactive prompt, environment variable, or a secrets vault.
    password.s = "mySshPassword"

    success = CkSsh::ckAuthenticatePw(sshJump,"myJumpLogin",password)
    If success = 0
        Debug CkSsh::ckLastErrorText(sshJump)
        CkSsh::ckDispose(sshJump)
        ProcedureReturn
    EndIf

    ;  Set up the tunnel and connect to the target SSH server through the jump host.
    tunnel.i = CkSshTunnel::ckCreate()
    If tunnel.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkSshTunnel::setCkDestHostname(tunnel, "db.internal.example.com")
    CkSshTunnel::setCkDestPort(tunnel, 5432)

    success = CkSshTunnel::ckConnectThroughSsh(tunnel,sshJump,"ssh.internal.example.com",sshPort)
    If success = 0
        Debug CkSshTunnel::ckLastErrorText(tunnel)
        CkSsh::ckDispose(sshJump)
        CkSshTunnel::ckDispose(tunnel)
        ProcedureReturn
    EndIf

    ;  Authenticate to the target SSH server (its own credentials).
    success = CkSshTunnel::ckAuthenticatePw(tunnel,"mySshLogin",password)
    If success = 0
        Debug CkSshTunnel::ckLastErrorText(tunnel)
        CkSsh::ckDispose(sshJump)
        CkSshTunnel::ckDispose(tunnel)
        ProcedureReturn
    EndIf

    ;  After authenticating, call BeginAccepting to start listening for local connections to forward.

    waitForThreadExit.i = 1
    success = CkSshTunnel::ckCloseTunnel(tunnel,waitForThreadExit)
    If success = 0
        Debug CkSshTunnel::ckLastErrorText(tunnel)
        CkSsh::ckDispose(sshJump)
        CkSshTunnel::ckDispose(tunnel)
        ProcedureReturn
    EndIf

    CkSsh::ckDisconnect(sshJump)


    CkSsh::ckDispose(sshJump)
    CkSshTunnel::ckDispose(tunnel)


    ProcedureReturn
EndProcedure