At least one byte needs to be present for successful C / b decodes

[malohtie]

Hello,
Sometimes we see this in our error logs when trying to login to some random servers we're using the last phpseclib 3 version

$this->sftp->login($this->server->username, $password)

"class": "LengthException",
"message": "At least one byte needs to be present for successful C / b decodes",
"files" : "/var/dms/vendor/phpseclib/phpseclib/phpseclib/Common/Functions/Strings.php:92",
"trace": [
    "/var/dms/vendor/phpseclib/phpseclib/phpseclib/Net/SSH2.php:2245",
    "/var/dms/vendor/phpseclib/phpseclib/phpseclib/Net/SSH2.php:2109",
    "/var/dms/vendor/phpseclib/phpseclib/phpseclib/Net/SSH2.php:2084",
    "/var/dms/vendor/phpseclib/phpseclib/phpseclib/Net/SFTP.php:441",
    ...
   ]

[terrafrost]

If the server isn't sending any bytes then the server isn't sending any bytes and idk that there's anything phpseclib can do about that.

But maybe the logs will provide more insight. Like maybe the server is sending an error message that's being picked up by filter() before it gets to that point.

Can you post the SSH logs? You can get them by doing define('NET_SSH2_LOGGING', 2) at the top and then echo $ssh->getLog() after the error.

Thanks!

[malohtie]

Hi,
Unfortunately i couldn't produce this bug locally in our servers, but it still occur in production server so i have no clue why it happening
thanks!

[simPod]

I've upgraded to v3 and it started occurring as well. Don't know why yet tho. Had similar issue with v2 (#1426) but that was fixed and no longer the case.

[terrafrost]

I've upgraded to v3 and it started occurring as well. Don't know why yet tho. Had similar issue with v2 (#1426) but that was fixed and no longer the case.

Can you post the SSH logs? You can get them by doing define('NET_SSH2_LOGGING', 2) at the top and echo $ssh->getLog() after the error. Since it's v3 you might actually need to do it in a try / catch block.

Thanks!

[simPod]

@terrafrost I have the log, can I send it to you somewhere privately?

[terrafrost]

You can email it to terrafrost@php.net.

Thanks!

[terrafrost]

@simPod - got the file. I'll try to take a look in the next few days.

Thanks!

[nateclonch]

I'm also seeing this issue. I hope it's okay to email you the log.

[insiderinside]

any update ?

[nateclonch]

I never quite figured out the problem. It usually works, but if the server takes too long to respond, then I may get the issue I asked you about.

[simPod]

@terrafrost asked me for another log though I have not get to it yet.

[malohtie]

reopening the issue

[terrafrost]

@malohtie / @insiderinside (and really @ just anyone having this issue)... get me logs! You can get them by doing define('NET_SSH2_LOGGING', 2) at the top and then echo $ssh->getLog() after the error.

Without logs, asking me for help is rather like asking some why their computer crashed. The reasons why a computer crashed are endless as are the reasons that this error could occur.

Ultimately, the server sends packets to phpseclib and phpseclib decrypts and then decodes them. If the server just decided to send the letter a repeated over and over again a bunch of times there's 99.999% chance that'd cause things to break. If the server sent over a malformed packet that'd cause things to break as well. Maybe the server doesn't implement the SSH / SFTP protocol very well. Or maybe there's a very specific packet that phpseclib isn't decoding correctly. In any event, the possibilities are endless and I really can't do much without the logs, so please, provide the logs.

Thank you.