Ssh – Can we make ssh time out while waiting for a password

sshtimeout

I have written a script that is expected to get a bunch of host names from some place and run a command on each of those hosts:

ssh "$host" some command

I have the necessary configuration to make ssh connections without the need for a password. However, sometimes we encounter a host that does need a password and the script hangs.

Is there a way to make ssh time out while waiting for a password? I don't want to use the timeout command.

Best Answer

You are looking for LoginGraceTime in your sshd_config.

From sshd_config(5):

LoginGraceTime
             The server disconnects after this time if the user has not successfully logged in.  If the value is 0, there is no time
             limit.  The default is 120 seconds.

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SSH – Make Failed Forward a Fatal Error

There's an ssh configuration option for it (from ssh_config(5)):

ExitOnForwardFailure
Specifies whether ssh(1) should terminate the connection if it cannot set up all requested dynamic, tunnel, local, and remote port forwardings. The argument must be ``yes'' or ``no''. The default is ``no''.

So in your ssh configuration you can add:

ExitOnForwardFailure yes

Or from the command-line:

$ ssh -o ExitOnForwardFailure=yes blah

Linux – Exit All SSH Connections and Close PuTTY with One Command

Try using the ssh connection termination escape sequence.

In the ssh session, enter ~. (tilde dot). You won't see the characters when you type them, but the session will terminate immediately.

$ ~.
$ Connection to me.myhost.com closed.

From man 1 ssh

The supported escapes (assuming the default ‘~’) are:
 ~.      Disconnect.
 ~^Z     Background ssh.
 ~#      List forwarded connections.
 ~&      Background ssh at logout when waiting for forwarded 
         connection / X11 sessions to terminate.
 ~?      Display a list of escape characters.
 ~B      Send a BREAK to the remote system (only useful for SSH protocol
         version 2 and if the peer supports it).
 ~C      Open command line.  Currently this allows the addition of port 
         forwardings using the -L, -R and -D options (see above). It also
         allows the cancellation of existing remote port-forwardings using 
         -KR[bind_address:]port.  !command allows the user to execute a 
         local command if the PermitLocalCommand option is enabled in
         ssh_config(5).  Basic help is available, using the -h option.
 ~R      Request rekeying of the connection (only useful for SSH protocol 
         version 2 and if the peer supports it).

Best Answer

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SSH – Make Failed Forward a Fatal Error

Linux – Exit All SSH Connections and Close PuTTY with One Command

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