http://www.perlmonks.org?node_id=916535


in reply to Re: safely passing args through ssh
in thread safely passing args through ssh

I'm not sure this survives a double-ssh call: 
  print backticks('ssh', 'localhost', '--', 'ssh', 'localhost', '--', 
+'argcount', text_to_shell_lit('a b c'));

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This prints 3 for me.

As I mentioned in the original post, I was doubtful that backslash-escaping could solve the problem, but there still might be a way to do it.

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Re^3: safely passing args through ssh
by ikegami (Patriarch) on Jul 25, 2011 at 18:19 UTC

    That doesn't look anything like what I wrote. I showed how to contruct a shell command to pass to ssh but you passed 5 arguments after the target, none of which a shell command.

    If you call ssh twice, you have two shell commands to build. 

    sub text_to_shell_lit(_) {
   return $_[0] if $_[0] =~ /^[a-zA-Z0-9_\-]+\z/;
   my $s = $_[0];
   $s =~ s/'/'\\''/g;
   return "'$s'";
}

my $very_remote_cmd = join ' ', map text_to_shell_lit,
  argcount => ( 'a b c' );

my $remote_cmd = join ' ', map text_to_shell_lit,
  ssh => ( '--', $very_remote_target, $very_remote_cmd );

backticks(ssh => ( '--', $remote_target, $remote_cmd ));

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      Well, then I guess you didn't solve the problem that I stated.
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        The problem you stated: "what's a good way of encoding ... so that it will survive an ssh call?"

        Where "D" is the shell's literal parser and "s" is an arbitrary shell command, you want a function "E" that exhibits the following behaviour: 

        s = D(E(s)) = D(D(E(s))) = D(D(D(E(s)))) etc

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        but there is none.

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Re^3: safely passing args through ssh
by ikegami (Patriarch) on Jul 25, 2011 at 18:20 UTC
    		[reply]

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