Tcl

Get SSH Server Authentication Methods

Demonstrates getting the authentication methods advertised by an SSH server. Connect first but do not authenticate, then call GetAuthMethods, which returns a lowercase, comma-separated list such as publickey,password,keyboard-interactive.

Important: Querying the authentication methods intentionally disconnects from the server, so reconnect before authenticating.

Background: Knowing what a server accepts lets a client choose the right authentication path rather than guessing — for example, falling back to keyboard-interactive when password authentication is not offered, or failing fast with a clear message when only public-key is allowed. It is also useful diagnostically when authentication fails for reasons that are not obvious from the error text.

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Tcl


load ./chilkat.dll

set success 0

#  This example requires the Chilkat API to have been previously unlocked.
#  See Global Unlock Sample for sample code.

#  Demonstrates getting the authentication methods advertised by an SSH server.

set ssh [new_CkSsh]

set port 22

#  The server must be connected, but not yet authenticated.
set success [CkSsh_Connect $ssh "ssh.example.com" $port]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  Returns a lowercase, comma-separated list, such as:
#      publickey,password,keyboard-interactive
set authMethods [CkSsh_getAuthMethods $ssh]
if {[CkSsh_get_LastMethodSuccess $ssh] == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

puts "Authentication methods supported by this server: $authMethods"

#  IMPORTANT: Querying the authentication methods intentionally disconnects from the server.
#  Reconnect before authenticating.
set success [CkSsh_Connect $ssh "ssh.example.com" $port]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    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 [CkSsh_AuthenticatePw $ssh "mySshLogin" $password]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

puts "SSH authentication successful."

CkSsh_Disconnect $ssh

delete_CkSsh $ssh