ngx_lua模块学习示例之waf

转自：http://www.tuicool.com/articles/FbQ3ymB

WAF的主要功能为：

• ip黑白名单
• url黑白名单
• useragent黑白名单
• referer黑白名单
• 常见web漏洞防护，如xss，sql注入等
• cc攻击防护
• 扫描器简单防护
• 其他你想要的功能

WAF的总体检测思路：

• 当用户访问到nginx时，waf首先获取用户的ip，uri，referer，useragent，，cookie，args，post，method，header信息。
• 将获取到的信息依次传给上述功能的函数，如ip规则，在ip规则中，循环到所有的ip规则，如果匹配到ip则根据规则的处理方式来进行处理，匹配到之后不继续匹配后续规则。
• 需要开启的功能依次在主函数中调用即可，顺序也可根据实际场景来确定最合适的顺序。

config.lua

RulePath = "/data/mypro/ngx_lua/waf/wafconf/"
attacklog = "on"
logdir = "/usr/local/openresty/nginx/logs"
UrlDeny="on"
Redirect="on"
CookieMatch="on"
postMatch="on"
whiteModule="on"
ipWhitelist={}
ipBlocklist={"1.0.0.1"}
CCDeny="off"
CCrate="100/60"
html=[[Please go away~~ ]]

init.lua

require ‘config‘
local match = string.match
local ngxmatch=ngx.re.match
local unescape=ngx.unescape_uri
local get_headers = ngx.req.get_headers
local optionIsOn = function (options) return options == "on" and true or false end
logpath = logdir
rulepath = RulePath
UrlDeny = optionIsOn(UrlDeny)
PostCheck = optionIsOn(postMatch)
CookieCheck = optionIsOn(cookieMatch)
WhiteCheck = optionIsOn(whiteModule)
PathInfoFix = optionIsOn(PathInfoFix)
attacklog = optionIsOn(attacklog)
CCDeny = optionIsOn(CCDeny)
Redirect=optionIsOn(Redirect)
function getClientIp()
        IP = ngx.req.get_headers()["X-Real-IP"]
        if IP == nil then
                IP  = ngx.var.remote_addr
        end
        if IP == nil then
                IP  = "unknown"
        end
        return IP
end
function write(logfile,msg)
    local fd = io.open(logfile,"ab")
    if fd == nil then return end
    fd:write(msg)
    fd:flush()
    fd:close()
end
function log(method,url,data,ruletag)
    if attacklog then
        local realIp = getClientIp()
        local ua = ngx.var.http_user_agent
        local servername=ngx.var.server_name
        local time=ngx.localtime()
        if ua  then
            line = realIp.." ["..time.."] \""..method.." "..servername..url.."\" \""..data.."\"  \""..ua.."\" \""..ruletag.."\"\n"
        else
            line = realIp.." ["..time.."] \""..method.." "..servername..url.."\" \""..data.."\" - \""..ruletag.."\"\n"
        end
        local filename = logpath..‘/‘..servername.."_"..ngx.today().."_sec.log"
        write(filename,line)
    end
end
------------------------------------规则读取函数-------------------------------------------------------------------
function read_rule(var)
    file = io.open(rulepath..‘/‘..var,"r")
    if file==nil then
        return
    end
    t = {}
    for line in file:lines() do
        table.insert(t,line)
    end
    file:close()
    return(t)
end

local urlrules=read_rule(‘url‘)
  local argsrules=read_rule(‘args‘)
  local uarules=read_rule(‘user-agent‘)
  local wturlrules=read_rule(‘whiteurl‘)
  local postrules=read_rule(‘post‘)
  local ckrules=read_rule(‘cookie‘)

function say_html()
    if Redirect then
        ngx.header.content_type = "text/html"
        ngx.say(html)
        ngx.exit(200)
    end
end

function whiteurl()
    if WhiteCheck then
        if wturlrules ~=nil then
            for _,rule in pairs(wturlrules) do
                if ngxmatch(ngx.var.request_uri,rule,"imjo") then
                    return true
                 end
            end
        end
    end
    return false
end

function args()
    for _,rule in pairs(argsrules) do
        local args = ngx.req.get_uri_args()
        for key, val in pairs(args) do
            if type(val)==‘table‘ then
                if val == false then
                    data=table.concat(val, " ")
                end
            else
                data=val
            end
            if data and type(data) ~= "boolean" and rule ~="" and ngxmatch(unescape(data),rule,"imjo") then
                log(‘GET‘,ngx.var.request_uri,"-",rule)
                say_html()
                return true
            end
        end
    end
    return false
end

function url()
    if UrlDeny then
        for _,rule in pairs(urlrules) do
            if rule ~="" and ngxmatch(ngx.var.request_uri,rule,"imjo") then
                log(‘GET‘,ngx.var.request_uri,"-",rule)
                say_html()
                return true
            end
        end
    end
    return false
end

function ua()
    local ua = ngx.var.http_user_agent
    if ua ~= nil then
        for _,rule in pairs(uarules) do
            if rule ~="" and ngxmatch(ua,rule,"imjo") then
                log(‘UA‘,ngx.var.request_uri,"-",rule)
                say_html()
            return true
            end
        end
    end
    return false
end
function body(data)
    for _,rule in pairs(postrules) do
        if rule ~="" and data~="" and ngxmatch(unescape(data),rule,"imjo") then
            log(‘POST‘,ngx.var.request_uri,data,rule)
            say_html()
            return true
        end
    end
    return false
end
function cookie()
    local ck = ngx.var.http_cookie
    if CookieCheck and ck then
        for _,rule in pairs(ckrules) do
            if rule ~="" and ngxmatch(ck,rule,"imjo") then
                log(‘Cookie‘,ngx.var.request_uri,"-",rule)
                say_html()
            return true
            end
        end
    end
    return false
end

function denycc()
    if CCDeny then
        local uri=ngx.var.uri
        CCcount=tonumber(string.match(CCrate,‘(.*)/‘))
        CCseconds=tonumber(string.match(CCrate,‘/(.*)‘))
        local token = getClientIp()..uri
        local limit = ngx.shared.limit
        local req,_=limit:get(token)
        if req then
            if req > CCcount then
                 ngx.exit(503)
                return true
            else
                 limit:incr(token,1)
            end
        else
            limit:set(token,1,CCseconds)
        end
    end
    return false
end

function get_boundary()
    local header = get_headers()["content-type"]
    if not header then
        return nil
    end

    if type(header) == "table" then
        header = header[1]
    end

    local m = match(header, ";%s*boundary=\"([^\"]+)\"")
    if m then
        return m
    end

    return match(header, ";%s*boundary=([^\",;]+)")
end

function whiteip()
    if next(ipWhitelist) ~= nil then
        for _,ip in pairs(ipWhitelist) do
            if getClientIp()==ip then
                return true
            end
        end
    end
        return false
end

function blockip()
     if next(ipBlocklist) ~= nil then
         for _,ip in pairs(ipBlocklist) do
             if getClientIp()==ip then
                 ngx.exit(403)
                 return true
             end
         end
     end
         return false
end

waf.lua

local content_length=tonumber(ngx.req.get_headers()[‘content-length‘])
local method=ngx.req.get_method()
if whiteip() then
elseif blockip() then
elseif denycc() then
elseif ngx.var.http_Acunetix_Aspect then
    ngx.exit(444)
elseif ngx.var.http_X_Scan_Memo then
    ngx.exit(444)
elseif whiteurl() then
elseif ua() then
elseif url() then
elseif args() then
elseif cookie() then
elseif PostCheck then
    if method=="POST" then
        local boundary = get_boundary()
        if boundary then
            local len = string.len
            local sock, err = ngx.req.socket()
            if not sock then
                    return
            end
            ngx.req.init_body(128 * 1024)
            sock:settimeout(0)
            local content_length = nil
            content_length=tonumber(ngx.req.get_headers()[‘content-length‘])
            local chunk_size = 4096
            if content_length < chunk_size then
                chunk_size = content_length
            end
            local size = 0
            while size < content_length do
                local data, err, partial = sock:receive(chunk_size)
                data = data or partial
                if not data then
                    return
                end
                ngx.req.append_body(data)
                if body(data) then
                       return true
                end
                size = size + len(data)
                local less = content_length - size
                if less < chunk_size then
                    chunk_size = less
                end
             end
            ngx.req.finish_body()
        else
            ngx.req.read_body()
            local args = ngx.req.get_post_args()
            if not args then
                return
            end
            for key, val in pairs(args) do
                if type(val) == "table" or val == false then
                    data=table.concat(val, ", ")
                else
                    data=val
                end
                if data and type(data) ~= "boolean" and body(data) then
                    return true
                end
            end
        end
    end
else
    return
end

在nginx.conf的http段添加

    lua_package_path "/usr/local/nginx/conf/waf/?.lua";
    lua_shared_dict limit 10m;
    init_by_lua_file  /usr/local/nginx/conf/waf/init.lua;
    access_by_lua_file /usr/local/nginx/conf/waf/waf.lua;

重启nginx

部署完毕可以尝试如下命令：

curl http://xxxx/test.php?id=../etc/passwd
返回"Please go away~~"字样，说明规则生效。