Empty PHP SSH2 stream contents, even with stream_set_blocking?

Question

I am working on a tool that reads an iptables configuration from a remote host over SSH2 using the PECL SSH2 extension. I am able to successfully make the connection to the host, authenticate, and execute commands. The trouble I am having is sometimes the stream doesn't contain any data.

 /**
  * Load the current firewall configuration
  * @return bool
  */
 public function loadRules() {
  $stream = ssh2_exec($this->connection,"~/iptsave;");
  stream_set_blocking($stream,true);
  $iptablesSave = stream_get_contents($stream);
  if(empty($iptablesSave)) {
   return false;
   }
  parent::restore($iptablesSave);
  return true;
  }

About 25% of the time, loadRules() returns false, even when connecting to locahost instead of the remote system. I was able to work around the problem by changing the ssh2_exec call to

$stream = ssh2_exec($this->connection,"~/iptsave; sleep .5");

but I am concerned that something is wrong.

Did you ever get an answer to your question? – Kerry Jones Sep 16 '11 at 00:43 — Kerry Jones, Sep 16 '11 at 00:43

score 1 · Answer 1 · answered Dec 18 '09 at 18:05

1

phpSecLib may be able to help:

According to this post, it always returns the output, unlike ssh2.so.

answered Dec 18 '09 at 18:05

viewcopy

11
3

score 0 · Answer 2 · answered Nov 23 '09 at 15:59

0

I've got the same issue here. Somehow you need to set a delay for getting the result of the stream.

The way you've done it is possible, but you could also set a sleep(1) after the stream_set_block($stream, true) function. You could try the usleep() function. Haven't tried it yet

answered Nov 23 '09 at 15:59

Robert Cabri

3,821
1
20
17

I thought these solutions not working but I found my mistake. I appended to end of my command "2>&1" string in order to redirect stderr to stdout. Now it works :) Please checkout this link for more information: http://stackoverflow.com/questions/16665041/php-why-isnt-exec-returning-output – csonuryilmaz Oct 19 '16 at 10:43

score 0 · Answer 3 · answered Apr 27 '14 at 17:51

0

May be this will solve the issue:

$stream = ssh2_exec($this->connection,"~/iptsave;");
stream_set_blocking($stream,true);
$stream_out = ssh2_fetch_stream($stream, SSH2_STREAM_STDIO);
$iptablesSave = stream_get_contents($stream);

answered Apr 27 '14 at 17:51

Azraf

11

I thought these solutions not working but I found my mistake. I appended to end of my command "2>&1" string in order to redirect stderr to stdout. Now it works :) Please checkout this link for more information: http://stackoverflow.com/questions/16665041/php-why-isnt-exec-returning-output – csonuryilmaz Oct 19 '16 at 10:42

score 0 · Answer 4 · answered Sep 19 '21 at 11:51

With some severs you have to use 'interactive shell'. And sometimes you have to set the delay / sleep manually. A working example:

$connection = ssh2_connect($IP, 22);
$auth = ssh2_auth_password($connection, $User, $Pass);
$cmd = "help" . PHP_EOL;
if (!$auth) {
    echo "Login Failed;
    exit(1);
}

$shell = ssh2_shell($connection);

stream_set_blocking($shell, false); // we will use manual sleep
sleep(1); // This sleep to make sure that you get the prompt back

fwrite ($shell, $cmd . ";" . PHP_EOL);
sleep(1); // This to make sure that the command executes and we get the prompt back again!
while($output = fgets($shell)){
   echo $output;
}
fwrite ($shell, "exit;" . PHP_EOL); // If needed
sleep(1);

ssh2_disconnect($connection);
unset($shell);
unset($connection);

Empty PHP SSH2 stream contents, even with stream_set_blocking?

4 Answers4

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