Tcl

SSH Tunnel Authenticate with a SecureString Password and Private Key

Demonstrates the Chilkat SshTunnel.AuthenticateSecPwPk method, which authenticates using SecureString login and password objects together with a private key. The third argument is the SshKey private key.

Note: The private-key path is relative to the application's current working directory. Absolute paths may also be used. Supply the path to your own key file.

Background: This is the SecureString form of two-factor tunnel authentication: the password is held encrypted in memory and combined with a private key for servers that require both. It is the most protective option when a deployment mandates two-factor SSH and you also want to minimize plaintext credential exposure in a long-running process.

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Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the SshTunnel.AuthenticateSecPwPk method, which authenticates using SecureString
#  login and password objects together with a private key.  The 1st argument is the username, the
#  2nd is the password, and the 3rd is an SshKey private key.

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"

#  Load the SSH private key.  LoadText reads the file's text, which is then imported.
set privKey [new_CkSshKey]

set keyText [CkSshKey_loadText $privKey "qa_data/id_rsa"]
if {[CkSshKey_get_LastMethodSuccess $privKey] == 0} then {
    puts [CkSshKey_lastErrorText $privKey]
    delete_CkSshTunnel $tunnel
    delete_CkSshKey $privKey
    exit
}

set success [CkSshKey_FromOpenSshPrivateKey $privKey $keyText]
if {$success == 0} then {
    puts [CkSshKey_lastErrorText $privKey]
    delete_CkSshTunnel $tunnel
    delete_CkSshKey $privKey
    exit
}

#  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_AuthenticateSecPwPk $tunnel $secureLogin $securePassword $privKey]
if {$success == 0} then {
    puts [CkSshTunnel_lastErrorText $tunnel]
    delete_CkSshTunnel $tunnel
    delete_CkSshKey $privKey
    delete_CkSecureString $secureLogin
    delete_CkSecureString $securePassword
    exit
}

puts "Authenticated."

#  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_CkSshKey $privKey
    delete_CkSecureString $secureLogin
    delete_CkSecureString $securePassword
    exit
}


delete_CkSshTunnel $tunnel
delete_CkSshKey $privKey
delete_CkSecureString $secureLogin
delete_CkSecureString $securePassword