Tcl

SSH Tunnel Authenticate with a SecureString Password

Demonstrates the Chilkat SshTunnel.AuthenticateSecPw method, which authenticates using SecureString login and password objects. The first argument is the login and the second is the password.

Background: Because a tunnel process is long-lived and holds its SSH credentials for its entire lifetime, protecting them in memory is worthwhile. A SecureString keeps the value encrypted under a randomly generated session key. Populate it from a value obtained at runtime rather than a hard-coded literal.

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Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the SshTunnel.AuthenticateSecPw method, which authenticates using SecureString
#  login and password objects.  The 1st argument is the login and the 2nd is the password.

set tunnel [new_CkSshTunnel]

#  The tunnel forwards accepted local connections to this destination through the SSH server.
CkSshTunnel_put_DestHostname $tunnel "db.internal.example.com"
CkSshTunnel_put_DestPort $tunnel 5432

#  Connect to the SSH server.  This performs the TCP/proxy connection and SSH handshake, but
#  does not authenticate yet.
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"

#  Place the login and password into SecureString objects.
set secureLogin [new_CkSecureString]

CkSecureString_Append $secureLogin "mySshLogin"
set securePassword [new_CkSecureString]

CkSecureString_Append $securePassword $password

set success [CkSshTunnel_AuthenticateSecPw $tunnel $secureLogin $securePassword]
if {$success == 0} then {
    puts [CkSshTunnel_lastErrorText $tunnel]
    delete_CkSshTunnel $tunnel
    delete_CkSecureString $secureLogin
    delete_CkSecureString $securePassword
    exit
}

puts "Authenticated with secure strings."

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

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


delete_CkSshTunnel $tunnel
delete_CkSecureString $secureLogin
delete_CkSecureString $securePassword