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Asked: 2026-06-01T15:37:47+00:00

Here’s what I’m trying to achieve: open a shell (korn or bash, doesn’t matter),

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Here’s what I’m trying to achieve: open a shell (korn or bash, doesn’t matter), from that shell, I want to open a ssh connection (ssh user@host). At some point it is likely to happen I will be prompted for either a password or I might be asked whether or not I’m sure I want to connect (offending keys).

Before anyone asks: yes, I am aware there is a plugin for ssh2 exec calls, but the servers I’m working on don’t support it, and are unlikely to do so.

Here’s what I’ve tried so far: 

$desc = array(array('pipe','r'),array('pipe','w'));//used in all example code
$p = proc_open('ssh user@host',$desc,$pipes);
if(!is_resource($p)){ die('@!#$%');}//will omit this line from now on
sleep(1);//omitting this,too but it's there every time I need it

Then I tried to read console output (stream_get_contents($pipes[1])) to see what I have to pass next (either password, yes or return 'connection failed: '.stream_get_contents($pipes[1]) and proc_close $p.

This gave me the following error:

Pseudo-terminal will not be allocated because stdin is not a terminal.

So, I though ssh was called in the php:// io-stream context, seems a plausible explanation of the above error.

Next: I though about my first SO question and decided it might be a good idea to open a bash/ksh shell first:

$p = proc_open('bash',$desc,$pipes);

And take it from there, but I got the exact same error message, only this time, the script stopped running but ssh did run. So I got hopeful, then felt stupid and, eventually, desperate:

$p=proc_open('bash && ssh user@host',$desc,$pipes);

After a few seconds wait, I got the following error:

PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 133693440 bytes)

The Call Stack keeps bringing up the stream_get_contents line, even in my last desperate attempt:

#!/path/to/bin/php -n
<?php
    $p = proc_open('bash && ssh user@host',array(array('pipe','r'),array('pipe','w')),$ps);
    if (!is_resource($p))
    {
        die('FFS');
    }
    usleep(10);
    fwrite($ps[0],'yes'."\n");
    fflush($ps[0]);
    usleep(20);
    fwrite($ps[0],'password'."\n");
    fflush($ps[0]);
    usleep(20);
    fwrite($ps[0],'whoami'."\n");
    fflush($ps[0]);
    usleep(2);
    $msg = stream_get_contents($ps[1]);
    fwrite($ps[0],'exit'."\n");
    fclose($ps[0]);
    fclose($ps[1]);
    proc_close($p);
?>

I know, its a mess, a lot of fflush and redundancy, but the point is: I know this connection will first prompt me for offending keys, and then ask a password. My guess is the stream in $pipes[1] holds the ssh connection, hence it’s content is huge. what I need then, is a pipe inside a pipe… is this even possible? I must be missing something, what good is a pipe if this isn’t possible…
My guess is the proc_open command is wrong to begin with, (error: Broken pipe). But I really can’t see any other way around the first error… any thoughts? Or follow up questions if the above rant isn’t at all clear (which it probably isn’t).

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1 Answer

  1. Editorial Team

    Before anyone asks: yes, I am aware there is a plugin for ssh2 exec
    calls, but the servers I’m working on don’t support it, and are
    unlikely to do so.

    There are actually two. The PECL module, which is a PITA that most servers don’t have installed anyway and phpseclib, a pure PHP SSH2 implementation. An example of its use:

    <?php
include('Net/SSH2.php');

$ssh = new Net_SSH2('www.domain.tld');
if (!$ssh->login('username', 'password')) {
    exit('Login Failed');
}

echo $ssh->exec('pwd');
echo $ssh->exec('ls -la');
?>
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