Web应用防护系统(也称:网站应用级入侵防御系统。英文:Web Application Firewall,简称: WAF)。利用国际上公认的一种说法:Web应用防火墙是通过执行一系列针对HTTP/HTTPS的安全策略来专门为Web应用提供保护的一款产品。本文介绍了常见的WAF指纹识别的一些技术,详见如下:
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一、WAF指纹
Cookie值
Citrix Netscaler
“Citrix Netscaler”会在HTTP返回头部Cookie位置加入“ns_af”的值,可以以此判断为Citrix Netscaler的WAF,国内此类WAF很少(这货居然是searchsecurity认定的2013最好的防火墙)。
一个恶意的请求示例:
GET / HTTP/1.1 Host: target.com User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:25.0) Gecko/20100101 Firefox/25.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate Cookie: ASPSESSIONIDAQQSDCSC=HGJHINLDNMNFHABGPPBNGFKC; ns_af=31+LrS3EeEOBbxBV7AWDFIEhrn8A000;ns_af_.target.br_%2F_wat=QVNQU0VTU0lPTklEQVFRU0RDU0Nf?6IgJizHRbTRNuNoOpbBOiKRET2gA& Connection: keep-alive Cache-Control: max-age=0
F5 BIG IP ASM
F5 BiG IP ASM会在Cookie中加入“TS+随机字符串”的Cookie信息,一个非恶意的请求如下: GET / HTTP/1.1 Host: www.target.com User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:25.0) Gecko/20100101 Firefox/25.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate Cookie: target_cem_tl=40FC2190D3B2D4E60AB22C0F9EF155D5; s_fid=77F8544DA30373AC-31AE8C79E13D7394; s_vnum=1388516400627%26vn%3D1; s_nr=1385938565978-New; s_nr2=1385938565979-New; s_lv=1385938565980; s_vi=[CS]v1|294DCEC0051D2761-40000143E003E9DC[CE]; fe_typo_user=7a64cc46ca253f9889675f9b9b79eb66; TSe3b54b=36f2896d9de8a61cf27aea24f35f8ee1abd1a43de557a25c529fe828; TS65374d=041365b3e678cba0e338668580430c26abd1a43de557a25c529fe8285a5ab5a8e5d0f299 Connection: keep-alive Cache-Control: max-age=0
HTTP响应
Mod_Security
Mod_Security是为Apache设计的开源Web防护模块,一个恶意的请求Mod_Security会在响应头返回“406 Not acceptable”的信息。
请求:
GET /HTTP/1.1 Host: www.target.com User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:25.0) Gecko/20100101 Firefox/25.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate Connection: keep-alive
响应:
HTTP/1.1 406 Not Acceptable Date: Thu, 05 Dec 2013 03:33:03 GMT Server: Apache Content-Length: 226 Keep-Alive: timeout=10, max=30 Connection: Keep-Alive Content-Type: text/html; charset=iso-8859-1Not Acceptable! Not Acceptable!
An appropriate representation of the requested resource could not be found on this server. This error was generated by Mod_Security.