Tcl

SSH Tunnel Authenticate with a Private Key

Demonstrates the Chilkat SshTunnel.AuthenticatePk method, which authenticates the SSH connection using public-key authentication. The first argument is the username and the second is an SshKey private key. The matching public key must already be installed for the account on the SSH server.

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: Public-key authentication suits tunnels especially well because they typically run unattended for long periods: the private key stays on the client, the server trusts the corresponding public key, and no reusable password crosses the wire. The SshKey object imports several formats; for an encrypted key, set its Password before importing.

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Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the SshTunnel.AuthenticatePk method, which authenticates the SSH connection using
#  public-key authentication.  The 1st argument is the username and the 2nd is an SshKey private
#  key.  The matching public key must already be installed for the account on the SSH server.

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
}

#  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
}

set success [CkSshTunnel_AuthenticatePk $tunnel "mySshLogin" $privKey]
if {$success == 0} then {
    puts [CkSshTunnel_lastErrorText $tunnel]
    delete_CkSshTunnel $tunnel
    delete_CkSshKey $privKey
    exit
}

puts "Authenticated with a private key."

#  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
    exit
}


delete_CkSshTunnel $tunnel
delete_CkSshKey $privKey