用ModSecurity启动WAF的一次小试

CfgMgmtCamp 期间,我参加了FranziskaBühler(@bufrasch)主题为《 WAF——您的 DevOps pipeline 的朋友? 》的演讲。她谈到了Web应用程序防火墙(WAF)和 OWASP 的核心规则集(CRS)。

考虑到我自己经历的这类安全性事件,我决定尝试使用ModSecurity启动Web应用程序,并在我自己的测试环境中运行。

我的测试环境由一台NGINX的CentOS8设备组成,结果比我想象的要难一些。

ModSecurity模块是Apache Web服务器的标准可用模块,我本来应该选择它的。但是我喜欢挑战,所以就换成了CentOS8和NGINX。

在网络上搜索时,我发现了一些资源,虽然不是全部,但是对我有很大帮助,这里给大家参考一下。

在CentOS7上编译ModSecurity

NGINX的ModSecurity

核心规则集

owasp CRS

启用PowerTools存储库

由于所有配置均在CentOS8上进行,因此所有开发工具都必须可用,在此需要启用PowerTools存储库。

dnf config-manager --set-enabled PowerTools

并且需要很多开发工具

dnf -y install      \
    autoconf        \
    automake        \
    GeoIP-devel     \
    bison           \
    bison-devel     \
    curl            \
    curl-devel      \
    doxygen         \
    flex            \
    gcc             \
    gcc-c++         \
    git             \
    libcurl-devel   \
    libxml2-devel   \
    lmdb-devel      \
    lua-devel       \
    openssl-devel   \
    ssdeep-devel    \
    yajl            \
    yajl-devel      \
    zlib-devel

获取所有资源

现在所有软件都已安装到位,设置一个可以使用的环境。请注意,因为这是一个测试环境,所以没有sudo使用,一切都以root身份完成。

cd
mkdir owasp
cd owasp

然后下载所有资源。需要GeoIP2,因为GeoIP将很快被弃用,下载后并与NGINX一起安装。

wget https://nginx.org/download/nginx-1.17.8.tar.gz
wget https://github.com/SpiderLabs/ModSecurity/releases/download/v3.0.4/modsecurity-v3.0.4.tar.gz
wget https://github.com/SpiderLabs/owasp-modsecurity-crs/archive/v3.2.0.tar.gz -O CRS_v3.2.0.tar.gz
git clone --recursive https://github.com/maxmind/libmaxminddb
git clone             https://github.com/SpiderLabs/ModSecurity
git clone             https://github.com/SpiderLabs/ModSecurity-nginx
git clone             https://github.com/leev/ngx_http_geoip2_module

MaxMin library

ModSecurity库和ModSecurity模块都需要libmaxmin,因此首先

cd libmaxminddb
./bootstrap
./configure
make
make check
make install
cd ..

配置并安装modsecurity库

而之后libmaxmin的modsecurity库

tar -xvf modsecurity-v3.0.4.tar.gz
cd modsecurity-v3.0.4
./configure --with-lmdb --with-maxmind=/usr/local
make
make install
cd ..

配置并安装modsecurity模块

现在modsecurity库已可用,创建模块

cd ModSecurity
sh build.sh
git submodule init
git submodule update
./configure --with-lmdb --with-maxmind=/usr/local
make
make install
cd ..

棘手的一点

为了使NGINX能够接受并加载模块,必须使用与已安装的NGXINX完全相同的配置选项来编译它们。这些可以通过nginx -V命令确定。

但是不知何故我这里无法正常工作。我尝试了所有可能找到的选项,但一直会遇到binairy不兼容错误。因此,我决定也从头开始编译NGINX。当然,这具有以下缺点:NGINX无法再通过packagemanager进行升级,但是由于模块和nginx二进制文件之间的严格匹配,已经无法实现。我想确保自建nginx内容不会干扰系统的其余部分,因此我将所有内容都放入/usr/local/nginx。首先,我采用了配置选项,利用安装的NGINX,最后得到了:

tar -xvf nginx-1.17.8.tar.gz
cd nginx-1.17.8
./configure                                                     \
    --prefix=/usr/local/nginx                                   \
    --sbin-path=/usr/local/nginx/sbin/nginx                     \
    --modules-path=/usr/local/nginx/modules                     \
    --conf-path=/usr/local/nginx/etc/nginx.conf                 \
    --error-log-path=/var/log/nginx/error.log                   \
    --http-log-path=/var/log/nginx/access.log                   \
    --pid-path=/var/run/nginx.pid                               \
    --lock-path=/var/run/nginx.lock                             \
    --http-client-body-temp-path=/var/cache/nginx/client_temp   \
    --http-proxy-temp-path=/var/cache/nginx/proxy_temp          \
    --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp      \
    --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp          \
    --http-scgi-temp-path=/var/cache/nginx/scgi_temp            \
    --user=nginx                                                \
    --group=nginx                                               \
    --with-file-aio                                             \
    --with-threads                                              \
    --with-http_addition_module                                 \
    --with-http_auth_request_module                             \
    --with-http_dav_module                                      \
    --with-http_flv_module                                      \
    --with-http_gunzip_module                                   \
    --with-http_gzip_static_module                              \
    --with-http_mp4_module                                      \
    --with-http_random_index_module                             \
    --with-http_realip_module                                   \
    --with-http_secure_link_module                              \
    --with-http_slice_module                                    \
    --with-http_ssl_module                                      \
    --with-http_stub_status_module                              \
    --with-http_sub_module                                      \
    --with-mail                                                 \
    --with-mail_ssl_module                                      \
    --with-stream                                               \
    --with-stream_ssl_module                                    \
    --with-compat                                               \
    --with-cc-opt='-g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -DNGX_HTTP_HEADERS' \
    --with-ld-opt='-Wl,-Bsymbolic-functions -Wl,-z,relro -Wl,-z,now -Wl,--as-needed'i \
    --add-dynamic-module=../ModSecurity-nginx                   \
    --add-dynamic-module=../ngx_http_geoip2_module
make
make install
cd ..
useradd -m -c'nginx' nginx
mkdir -p /var/cache/nginx/client_temp
chown nginx:nginx /var/cache/nginx/client_temp

配置ModSecurity

nginx被编译并安装到modsec即可,ModSec(SpiderLabs)的创建者有提供下载默认配置,让我们着手行动。

mkdir -p /usr/local/nginx/etc/modsec
wget
https://raw.githubusercontent.com/SpiderLabs/ModSecurity/v3/master/modsecurity.conf-recommended \
    -O /usr/local/nginx/etc/modsec/modsecurity.conf
cp -p /root/owasp/modsecurity-v3.0.4/unicode.mapping /usr/local/nginx/etc/modsec/unicode.mapping
sed -i 's/^SecRuleEngine.*/SecRuleEngine On/' /usr/local/nginx/etc/modsec/modsecurity.conf
cat <<- '@EOF' > /usr/local/nginx/etc/modsec/main.conf
    Include "/usr/local/nginx/etc/modsec/modsecurity.conf"
    # Basic test rule
    SecRule ARGS:blogtest "@contains test" "id:1111,deny,status:403"
    SecRule REQUEST_URI "@beginsWith /admin"
    "phase:2,t:lowercase,id:2222,deny,msg:'block admin'"
@EOF

使用ModSec模块配置nginx。

worker_processes  1;
load_module modules/ngx_http_modsecurity_module.so;
load_module modules/ngx_http_geoip2_module.so;
load_module modules/ngx_stream_geoip2_module.so;
events {
    worker_connections  1024;
}
http {
    include            mime.types;
    default_type       application/octet-stream;
    sendfile           on;
    keepalive_timeout  65;
    server {
        listen         80;
        server_name    localhost;
        modsecurity    on;
        modsecurity_rules_file /usr/local/nginx/etc/modsec/main.conf;
        location / {
            root   html;
            index  index.html index.htm;
        }
        error_page  500 502 503 504 /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

要验证它是否全部损坏,请运行/usr/local/nginx/sbin/nginx -t并确保一切正常。检查ModЅecurity是否适用于:

curl http://localhost/adminaccess
<html>
<head><title>403 Forbidden</title></head>
<body>
<center><h1>403 Forbidden</h1></center>
<hr><center>nginx/1.17.8</center>
</body>
</html>

而/var/log/nginx/error.log文件显示:

2020/02/07 16:04:08 [error] 17871#17871: *3 [client 127.0.0.1]
ModSecurity: Access denied with code 403 (phase 2). Matched "Operator
`BeginsWith' with parameter `/admin' against variable `REQUEST_URI'
(Value: `/adminaccess' ) [file "/usr/local/nginx/etc/modsec/main.conf"]
[line "7"] [id "2222"] [rev ""] [msg "block admin"] [data ""] [severity
"0"] [ver ""] [maturity "0"] [accuracy "0"] [hostname "127.0.0.1"] [uri
"/adminaccess"] [unique_id "158108784890.091254"] [ref
"o0,6v4,12t:lowercase"], client: 127.0.0.1, server: localhost, request:
"GET /adminaccess HTTP/1.1", host: "localhost"

差不多好了

此时,ModSecurity正在NGINX上运行,因此所需的就是核心规则集(CRS)。一旦达到这一目标,接下来就轻而易举了。

cd /usr/local/nginx/etc
tar -xvf ~/owasp/CRS_v3.2.0.tar.gz
ln -s owasp-modsecurity-crs-3.2.0 owasp-crs
cp -p /usr/local/nginx/etc/owasp-crs/crs-setup.conf.example /usr/local/nginx/etc/owasp-crs/crs-setup.conf

将这些行添加到: /usr/local/nginx/etc/modsec/main.conf

Include "/usr/local/nginx/etc/owasp-crs/crs-setup.conf"
Include "/usr/local/nginx/etc/owasp-crs/rules/*.conf"

还要确保文件/usr/local/nginx/etc/owasp-crs/crs-setup.conf包含以下行

SecDefaultAction "phase:1,log,auditlog,deny,status:403"
SecDefaultAction "phase:2,log,auditlog,deny,status:403"

如果curl发出了正常状态,例如, curl http://localhost/trololo_singer.html 这不会触发任何安全规则,并且404会显示一个普通错误:

<html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>nginx/1.17.8</center>
</body>
</html>

但是,如果curl命令正在请求一个受保护的文件(如.htaccess文件),则将触发“核心规则集”并发出拒绝访问错误。

<html>
<head><title>403 Forbidden</title></head>
<body>
<center><h1>403 Forbidden</h1></center>
<hr><center>nginx/1.17.8</center>
</body>
</html>

而/var/log/nginx/error.log文件显示:

2020/02/07 16:17:28 [error] 2724#2724: *8 [client 127.0.0.1]
ModSecurity: Access denied with code 403 (phase 2). Matched "Operator
`PmFromFile' with parameter `restricted-files.data' against variable
`REQUEST_FILENAME' (Value: `/.htaccess' ) [file
"/usr/local/nginx/etc/owasp-crs/rules/REQUEST-930-APPLICATION-ATTACK-LFI.conf"]
[line "104"] [id "930130"] [rev ""] [msg "Restricted File Access
Attempt"] [data "Matched Data: .htaccess found within REQUEST_FILENAME:
/.htaccess"] [severity "2"] [ver "OWASP_CRS/3.2.0"] [maturity "0"]
[accuracy "0"] [tag "application-multi"] [tag "language-multi"] [tag
"platform-multi"] [tag "attack-lfi"] [tag "OWASP_CRS"] [tag
"OWASP_CRS/WEB_ATTACK/FILE_INJECTION"] [tag "WASCTC/WASC-33"] [tag
"OWASP_TOP_10/A4"] [tag "PCI/6.5.4"] [hostname "127.0.0.1"] [uri
"/.htaccess"] [unique_id "15813292242.837003"] [ref
"o1,9v4,10t:utf8toUnicode,t:urlDecodeUni,t:normalizePathWin,t:lowercase"],
client: 127.0.0.1, server: localhost, request: "GET /.htaccess
HTTP/1.1", host: "localhost"

*参考来源: tonkersten ,Sandra1432编译,转载请注明来自FreeBuf.COM

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