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Bug #46697 fread() fails for non-buffered streams in ssh2
Submitted: 2008-11-27 13:39 UTC Modified: 2008-11-27 13:45 UTC
From: borchinfolab at gmail dot com Assigned:
Status: Closed Package: Reproducible crash
PHP Version: 5.3CVS-2008-11-27 (snap) OS: FC9
Private report: No CVE-ID: None
 [2008-11-27 13:39 UTC] borchinfolab at gmail dot com
Description:
------------
When doing fread() from a ssh2 stream in unbuffered mode the program core dumps.

I believe the reason for this is ether a problem with fread() or a problem in php_ssh2_channel_stream_read(). I guess the reason for the crash is that libssh2_channel_read_ex() in libssh2 returns -37 when the buffer is empty -  this is handed over to fread() where I guess it expects a positive integer.

I made a small test in php_ssh2_channel_stream_read() to see if this is the case:

static size_t php_ssh2_channel_stream_read(php_stream *stream, char *buf, size_t count TSRMLS_DC)
{
   php_ssh2_channel_data *abstract = (php_ssh2_channel_data*)stream->abstract;

   stream->eof = libssh2_channel_eof(abstract->channel);
   libssh2_channel_set_blocking(abstract->channel, abstract->is_blocking);
   int res = libssh2_channel_read_ex(abstract->channel, abstract->streamid, buf, count);
   return(res < 0 ? 0 : res);
}

This fixed the problem for me. Perhaps the correct return value should be EOF?

Also ssh2 does not compile for php-5.3 (this has been reported in an other bug report) - managed to fix this by replacing statements with correct macros.

I guess the fix will work for php-5.2.* as well, but there has been corrections in stream_set_blocking() so it might not work after all.

This problem has been reported to php.net as well.


Reproduce code:
---------------
#!/usr/bin/php
<?php

$connection = ssh2_connect(HOSTNAME, 22, array('hostkey'=>'ssh-rsa'));
if(ssh2_auth_pubkey_file($connection, USERNAME, ID_RSA_PUB, ID_RSA, '')) {
   $stream = ssh2_exec($connection, "ps -elf");
   // stream_set_blocking($stream, false); THIS DOSN'T WORK
   stream_set_blocking($stream, true); // THIS WORKS

   while(!feof($stream)) {
      $buf = fread($stream, 1024);
      echo ">$buf\n";
   }
}

?>


Expected result:
----------------
Output from ps -elf

Actual result:
--------------
Core dump

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 [2008-11-27 13:45 UTC] borchinfolab at gmail dot com
Sorry, this one was for pecl...

Ignore this one
 
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