代码审计：躺在床上读代码之phpcms sql注射漏洞

 

$formguide_input = new formguide_input($formid);

$data = $formguide_input->get($_POST[‘info’]);

 

这里调用了一个class,formguide_input，然后get函数处理了$_POST过来的info，那么，我们看看这个get函数

 

 

function get($data,$isimport = 0) {

$this->data = $data;

$info = array();

foreach($this->fields as $field) {

…… 省略几行也不会死

$value = $data[$field[‘field’]];

//在这里的value使用了data的值，data就是$_POST[‘info’]

 

…… 省略几行也不会死

 

if($maxlength && $length > $maxlength) {

if($isimport) {

$value = str_cut($value,$maxlength,”);

//value使用了str_cut截取了字节

} else {

showmessage($name.’ ‘.L(‘not_more_than’).’ ‘.$maxlength.L(‘characters’));

}

} elseif($maxlength) {

$value = str_cut($value,$maxlength,”);

//又一次截取

}

 

省略……

return $info;

 

str_cut函数是phpcms自定义的截取函数，第三个参数是控制dot是不是…，所以这里截取的时候当value是123\’的时候，如果截取字段是4的话，将截取出一个反斜线\出来。

 

而后这部分的变量进入了insert

 

在phpcms/modules/formguide/index.php中的63行。

$dataid = $this->m_db->insert($data, true);

 

导致了SQL注射漏洞

 

以下为str_cut的代码

 

function str_cut($string, $length, $dot = ‘…’) {

$strlen = strlen($string);

if($strlen <= $length) return $string;

$string = str_replace(array(‘ ‘,’&nbsp;’, ‘&amp;’, ‘&quot;’, ‘&#039;’, ‘&ldquo;’, ‘&rdquo;’, ‘&mdash;’, ‘&lt;’, ‘&gt;’, ‘&middot;’, ‘&hellip;’), array(‘∵’,’ ‘, ‘&’, ‘”‘, “‘”, ‘“’, ‘”’, ‘—’, ‘<‘, ‘>’, ‘·’, ‘…’), $string);

$strcut = ”;

if(strtolower(CHARSET) == ‘utf-8’) {

$length = intval($length-strlen($dot)-$length/3);

$n = $tn = $noc = 0;

while($n < strlen($string)) {

$t = ord($string[$n]);

if($t == 9 || $t == 10 || (32 <= $t && $t <= 126)) {

$tn = 1; $n++; $noc++;

} elseif(194 <= $t && $t <= 223) {

$tn = 2; $n += 2; $noc += 2;

} elseif(224 <= $t && $t <= 239) {

$tn = 3; $n += 3; $noc += 2;

} elseif(240 <= $t && $t <= 247) {

$tn = 4; $n += 4; $noc += 2;

} elseif(248 <= $t && $t <= 251) {

$tn = 5; $n += 5; $noc += 2;

} elseif($t == 252 || $t == 253) {

$tn = 6; $n += 6; $noc += 2;

} else {

$n++;

}

if($noc >= $length) {

break;

}

}

if($noc > $length) {

$n -= $tn;

}

$strcut = substr($string, 0, $n);

$strcut = str_replace(array(‘∵’, ‘&’, ‘”‘, “‘”, ‘“’, ‘”’, ‘—’, ‘<‘, ‘>’, ‘·’, ‘…’), array(‘ ‘, ‘&amp;’, ‘&quot;’, ‘&#039;’, ‘&ldquo;’, ‘&rdquo;’, ‘&mdash;’, ‘&lt;’, ‘&gt;’, ‘&middot;’, ‘&hellip;’), $strcut);

} else {

$dotlen = strlen($dot);

$maxi = $length – $dotlen – 1;

$current_str = ”;

$search_arr = array(‘&’,’ ‘, ‘”‘, “‘”, ‘“’, ‘”’, ‘—’, ‘<‘, ‘>’, ‘·’, ‘…’,’∵’);

$replace_arr = array(‘&amp;’,’&nbsp;’, ‘&quot;’, ‘&#039;’, ‘&ldquo;’, ‘&rdquo;’, ‘&mdash;’, ‘&lt;’, ‘&gt;’, ‘&middot;’, ‘&hellip;’,’ ‘);

$search_flip = array_flip($search_arr);

for ($i = 0; $i < $maxi; $i++) {

$current_str = ord($string[$i]) > 127 ? $string[$i].$string[++$i] : $string[$i];

if (in_array($current_str, $search_arr)) {

$key = $search_flip[$current_str];

$current_str = str_replace($search_arr[$key], $replace_arr[$key], $current_str);

}

$strcut .= $current_str;

}

}

return $strcut.$dot;

}

 

我想证明一下，可是这个功能在我本地测试失败，该表不存在，但是漏洞步骤确实如上。

修复方案：进入数据库的东西不能随意取消dot的。