Tcl

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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Tcl


load ./chilkat.dll

set success 0

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

set tunnel [new_CkSshTunnel]

#  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.
CkSshTunnel_put_SocksVersion $tunnel 5
CkSshTunnel_put_SocksHostname $tunnel "socks.example.com"
CkSshTunnel_put_SocksPort $tunnel 1080

#  SOCKS4 supports only a username; SOCKS5 supports username and password.
CkSshTunnel_put_SocksUsername $tunnel "myProxyLogin"
CkSshTunnel_put_SocksPassword $tunnel "myProxyPassword"

CkSshTunnel_put_DestHostname $tunnel "db.internal.example.com"
CkSshTunnel_put_DestPort $tunnel 5432

#  Connect to the SSH server through the SOCKS proxy configured above.
set sshPort 22
set success [CkSshTunnel_Connect $tunnel "ssh.example.com" $sshPort]
if {$success == 0} then {
    puts [CkSshTunnel_lastErrorText $tunnel]
    delete_CkSshTunnel $tunnel
    exit
}

#  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.
set password "mySshPassword"

set success [CkSshTunnel_AuthenticatePw $tunnel "mySshLogin" $password]
if {$success == 0} then {
    puts [CkSshTunnel_lastErrorText $tunnel]
    delete_CkSshTunnel $tunnel
    exit
}

set listenPort 1080
set success [CkSshTunnel_BeginAccepting $tunnel $listenPort]
if {$success == 0} then {
    puts [CkSshTunnel_lastErrorText $tunnel]
    delete_CkSshTunnel $tunnel
    exit
}

puts "Tunnel established through the SOCKS proxy."

set waitForThreadExit 1
set success [CkSshTunnel_CloseTunnel $tunnel $waitForThreadExit]
if {$success == 0} then {
    puts [CkSshTunnel_lastErrorText $tunnel]
    delete_CkSshTunnel $tunnel
    exit
}


delete_CkSshTunnel $tunnel