B4X

SSH Tunnel Through an Outbound SOCKS Proxy

Demonstrates reaching the SSH server through an outbound SOCKS proxy using the SocksVersion, SocksHostname, SocksPort, SocksUsername, and SocksPassword properties.

Background: This is the reverse direction from dynamic forwarding: here a SOCKS proxy is used to reach the SSH server, for networks where outbound connections must pass through one. SocksVersion is the switch — 0 means no SOCKS, while 4 or 5 selects the protocol. SOCKS5 supports username/password authentication and remote DNS; SOCKS4 supports only a username.

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Dim success As Boolean = False

'  Demonstrates reaching the SSH server through an outbound SOCKS proxy using the SshTunnel
'  properties SocksVersion, SocksHostname, SocksPort, SocksUsername, and SocksPassword.

Dim tunnel As ChilkatSshTunnel
tunnel.Initialize("tunnel")

'  Set SocksVersion to 4 or 5 to route the outbound connection to the SSH server through a SOCKS
'  proxy.  A value of 0 (the default) means no SOCKS proxy.
tunnel.SocksVersion = 5
tunnel.SocksHostname = "socks.example.com"
tunnel.SocksPort = 1080

'  SOCKS4 supports only a username; SOCKS5 supports username and password.
tunnel.SocksUsername = "myProxyLogin"
tunnel.SocksPassword = "myProxyPassword"

tunnel.DestHostname = "db.internal.example.com"
tunnel.DestPort = 5432

'  Connect to the SSH server through the SOCKS proxy configured above.
Dim sshPort As Int = 22
success = tunnel.Connect("ssh.example.com", sshPort)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


'  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.
Dim password As String = "mySshPassword"

success = tunnel.AuthenticatePw("mySshLogin", password)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


Dim listenPort As Int = 1080
success = tunnel.BeginAccepting(listenPort)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If

Log("Tunnel established through the SOCKS proxy.")

Dim waitForThreadExit As Boolean = True
success = tunnel.CloseTunnel(waitForThreadExit)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If