OpenResty(nginx扩展)实现防cc攻击

By | 2013 年 7 月 29 日

本文介绍使用openresty来实现防cc攻击的功能。openresty官网http://openresty.org/cn/index.html。下面是防cc攻击的流程图。
根据流程图,我们知道防cc攻击主要包括两部分,一是限制请求速度,二是给用户发送js跳转代码进行验证请求是否合法。
cc

一、安装依赖

centos:

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yum install readline-devel pcre-devel openssl-devel

ubuntu:

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apt-get install libreadline-dev libncurses5-dev libpcre3-dev libssl-dev perl

二、luajit安装

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cd /tmp/
git clone http://luajit.org/git/luajit-2.0.git
cd luajit-2.0/
make && make install
ln -sf luajit-2.0.0-beta10 /usr/local/bin/luajit
ln -sf /usr/local/lib/libluajit-5.1.so.2 /usr/lib/

三、openresty安装

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cd /tmp
wget http://agentzh.org/misc/nginx/ngx_openresty-1.2.4.13.tar.gz
tar xzf ngx_openresty-1.2.4.13.tar.gz
cd ngx_openresty-1.2.4.13/
./configure --prefix=/usr/local/openresty --with-luajit
make && make install

四、nginx配置

nginx.conf:

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http{
[......]
lua_shared_dict limit 10m;
lua_shared_dict jsjump 10m;
    server {
        #lua_code_cache off;
        listen       80;
        server_name  www.centos.bz;
        location / {
            default_type  text/html;
            content_by_lua_file "/usr/local/openresty/nginx/conf/lua";
        }
        location @cc {
            internal;
            root   html;
            index  index.html index.htm;
        }
    }
}

/usr/local/openresty/nginx/conf/lua文件:

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local ip = ngx.var.binary_remote_addr
local limit = ngx.shared.limit
local req,_=limit:get(ip)
if req then
        if req > 20 then
                ngx.exit(503)
        else
                limit:incr(ip,1)
        end
else
        limit:set(ip,1,10)
end
local jsjump = ngx.shared.jsjump
local uri = ngx.var.request_uri
local jspara,flags=jsjump:get(ip)
local args = ngx.req.get_uri_args()
if jspara then
    if flags then
        ngx.exec("@cc")
    else
                local p_jskey=''
                if args["jskey"] and type(args["jskey"])=='table' then
                         p_jskey=args["jskey"][table.getn(args["jskey"])]
                else
                         p_jskey=args["jskey"]
                end
        if p_jskey and p_jskey==tostring(jspara) then
                        jsjump:set(ip,jspara,3600,1)
                        ngx.exec("@cc")
        else
                        local url=''
                        if ngx.var.args then
                                url=ngx.var.scheme.."://"..ngx.var.host..uri.."&jskey="..jspara
                        else
                                url=ngx.var.scheme.."://"..ngx.var.host..uri.."?jskey="..jspara
                        end
                        local jscode="<script>window.location.href='"..url.."';</script>"
                        ngx.say(jscode)
        end
    end
else
    math.randomseed( os.time() );
    local random=math.random(100000,999999)
    jsjump:set(ip,random,60)
    local url=''
    if ngx.var.args then
        url=ngx.var.scheme.."://"..ngx.var.host..uri.."&jskey="..random
    else
        url=ngx.var.scheme.."://"..ngx.var.host..uri.."?jskey="..random
    end
    local jscode="<script>window.location.href='"..url.."';</script>"
    ngx.say(jscode)
end

lua代码部分解释:
1、1-12行是限速功能实现,第5和第10行表示10秒钟内容最多只能请求20次。
2、14-48行是验证部分,24行中的3600表示验证通过后,白名单时间为3600秒,即1小时。

update: 2013.5.26
1、修复JS无限跳转bug
2、增加随机种子

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