Making Wickr Weaker

As part of Asterisk’s new mobile application security assessment service offering, we decided to use our acquired skills and research a high profile mobile app. Luckily, Malcom Turnbull helped us with the decision making process by confirming that he uses Wickr to keep his messages private.

For those who are not familiar with the app, it is a messaging platform that is prioritises privacy above all costs. The app has been through rigorous security assessments where the results are published on their website. Additionally, some of the research that was performed was presented at DEF CON 21.

This gave us an extra adrenaline boost knowing that the challenge was not going to be easy. To get to the juicy part, we reported two interesting vulnerabilities to Wickr that we found within version 2.5.2 (iOS) which was the most recent version at the time of initial contact (May 2015). It is important to note that we did not look at the Android version and so there may be applicable information or crossover to the Android app as well.

  • Vulnerability #1: Session Lock Authentication Bypass

Wickr has a built-in ‘Auto Lock’ feature that allows a user to set a time period before they are required to enter their password to the application. By default, the timeout value is 1 hour, however, a user can change that value to 5 seconds, which would appear to be an even more secure option. The screenshot below shows the ‘Auto Lock’ feature within Wickr’s settings view:

autolockOnce the app is moved into the background and then reopened (after the time set in the ‘Auto Lock’ functionality has exceeded), the user is required to re-enter their password to access the application. The ‘Session Lock’ view can be seen in the screenshot below:

sessionlock

‘SessionManager’ is the class that controls the session lock and implements various methods, for example:

• -(void)sucessfullyResumedSession
• -(BOOL)unlockSessionWithPass:(id)pass

It was observed that the ‘sucessfullyResumedSession’ method was called after the ‘unlockSessionWithPass’ method, under the condition that the password was confirmed to be correct. It was also observed that when ‘sucessfullyResumedSession’ is called, the ‘Session Lock’ view is removed and the user is granted normal access to the application including the sensitive data it holds.

With this in mind, if a reference to the current ‘SessionManager’ object is obtained, it is possible to invoke the ‘sucessfullyResumedSession’ method and therefore bypass the authentication requirement, gaining access to the user’s sensitive data.

The figure below demonstrates how the authentication can be bypassed, with the aid of Cycript on a jail broken device:

auth_bypass

The screenshot below shows the access gained from the steps above:

auth_bypass

  • Vulnerability #2: Persistent Sensitive Information Stored Unencrypted within the App’s Memory Space

Wickr’s authentication mechanism requires the user to input their password before gaining access to their sensitive information. It is assumed that once authentication is successful the password is no longer required for the application to function properly. This is thought to also be the case when the application enters the background as well as when the user is logged out completely.

While using the application it was observed that the password used for authentication remained in the application’s memory space in clear-text.
The authentication view is controlled by the ‘UserLogin’ class, which contains various properties, one of them, for example, is:

• UITextField* passBox

The ‘passBox’ property is used by the ‘UserLogin’ view controller to store the password entered by the user to authenticate. The following screenshot shows the ‘UserLogin’ view and the ‘passBox’ text field:

login

After the user authenticates successfully, the application seems to dereference the ‘UserLogin’ view controller, however, the data that the object holds was not overwritten. By writing the heap memory space of the application into a file and extracting strings from the file it is possible to recover the clear-text password. This process holds effective also when the user has explicitly logged off from the application with the application running inactive in the background.

The following figure shows the process of writing the heap memory into files by using heapdump on a jail broken device:

heapdump

For Proof-of-Concept purposes, a string that is known to be part of the password was searched within the written files. The highlighted portion is the legitimate password:

grep

For further details please refer to our advisories here and here.

Communication timeline:

  • 01/05/2015: Vulnerabilities were reported to Wickr
  • 08/05/2015: Asterisk requested reception to be confirmed
  • 08/05/2015: Wickr confirmed reception
  • 01/07/2015: Asterisk reminded Wickr of the disclosure date
  • 10/07/2015: Wickr confirmed the advisory reviewing process
  • 31/07/2015: Asterisk reminded Wickr of the disclosure date and offered additional week
  • 11/08/2015: Wickr confirmed that the advisory is still undergoing a review
  • 13/08/2015: Asterisk requested an update
  • 13/08/2015: Wickr acknowledged the bug  and offered $2000 reward
  • 13/08/2015: Asterisk sent banking details
  • 18/08/2015: Wickr requested to be given up to 6 more months to fix the issues
  • 18/08/2015: Asterisk asked to clarify the reasons for the requested additional time
  • 22/08/2015: Wickr responded with the reasons for the delay and clarified that only one bug (RAM) was acknowledged as the other one (authentication bypass) was already reported on the 16th of January, 2014
  • 24/08/2015: Asterisk notified Wickr that it forfeits the Bug Bounty Reward and will publish the advisories

 

Vulnerability Disclosure: Local Privilege Escalation through Trend Micro OfficeScan

Although we enjoy offensive work, we appreciate defensive work just as much. In this post we’ll discuss how we managed to escalate our privileges on a Windows host while performing a SOE assessment.

Focusing specifically on our assessment, we spotted that our client did not skip on the installation of an Anti-Virus program, in our case Trend Micro OfficeScan version 11.1. Normally these kind of programs run as a Windows service in the context of the most privileged user (SYSTEM). Looking closely at OfficeScan’s file permissions revealed that the executable file used to be loaded as the service upon system start-up was writeable by the ‘Everyone’ group.

The reason the file permissions were not secure is due to an installation feature. In short, during the installation process, administrators are asked if they want to install the Anti-Virus using a ‘normal’ or ‘high’ security setting. Administrators who chose the ‘normal’ setting unknowingly provide the option for normal users to escalate their privileges on the host.

Exploitation of this configuration is fairly simple and straight forward. For all intents and purposes the following 3 steps were followed:

  1. Reboot the Windows system into Safe Mode so that the OfficeScan processes are not running.
  2. Overwrite the ntrtscan.exe (Real Time Scan Service) executable with a malicious executable of your choosing. In our instance, we used a windows service template file and added a few commands which will attempt to create a new local user account and added it to the Local Administrators group.
  3. Reboot the Windows system. During start-up, the Real Time Scan Service executable is started, executing the malicious payload.

For further details please see our advisory or Trend Micro’s advisory.

Communication timeline:

  • 16/04/2015: Vulnerabilities were reported to Trend Micro
  • 16/04/2015: Trend Micro confirmed reception of advisory
  • 30/04/2015: Trend Micro did not confirm vulnerability
  • 05/05/2015: Asterisk asked for disclosure permission
  • 05/05/2015: Trend Micro confirmed reviewing the advisory
  • 14/05/2015: Trend Micro confirmed vulnerability and requested to hold disclosure until July, 10
  • 14/05/2015: Asterisk confirmed disclosure date
  • 04/06/2015: Trend Micro requested a change of disclosure date to August, 4
  • 10/06/2015: Asterisk confirmed updated disclosure date
  • 03/08/2015: Asterisk reminded Trend Micro of the disclosure date
  • 04/08/2015: Trend Micro requested a change of disclosure date to August, 7
  • 04/08/2015: Asterisk confirmed the updated disclosure date
  • 07/08/2015: Disclosed by both parties

Vulnerability Disclosure: SQL Injection in ConnX ESP HR Management System (CVE-2015-4043)

During an engagement for one of our clients we came across ConnX‘s ESP HR Management System and found that it was vulnerable to SQL Injection. In line with our responsible disclosure policy, the vendor of ConnX was contacted to advise them of the issue and they were advised that this information would be published in 90 days.

We have received an acknowledgement from ConnX in regards to this issue stating:

… we are now releasing a version of ConnX where the issue that you brought to my attention has been addressed.

90 days have now passed from our initial disclosure to ConnX, and we are publishing details of the issue.

ConnX‘s ESP HR Management system is an application designed to aid payroll management of staff in organisations. We have identified that the input validation in the username parameter of the login page was not implemented correctly as noted below:

  • Location: /frmLogin.aspx
  • Parameter: ctl00$cphMainContent$txtUserName

Exploitation of this vulnerability would allow attackers to extract the data used by the ESP HR Management System. This information includes sensitive employee personal details.

The full advisory can be found here.

Communication timeline:

  • 2015-03-25: ConnX contacted with details of vulnerability
  • 2015-04-20: ConnX replied with details about mitigation
  • 2015-06-30: Publication of vulnerability

 

Information Security Root Causes

We do a lot of technical security testing at Asterisk, and this often brings up healthy discourse on the root cause of issues found. After thinking about this for a while I came up with a few themes which I think probably capture the majority of security issues. In fact, I think the following issues are possibly the root-cause problems that most information security professionals are trying to manage when protecting their organisation’s information. This management of issues is an important factor, as most people can’t manage threat agents. Unless you’re a government or other high-level entity, it’s unlikely you will be able to take action against attackers sitting somewhere on the other side of the world. These issues are not mutually-exclusive, but I do like the way it feels like a fairly manageable set of problems to solve.

Most of the issues we deal with as information security professionals come down to:

  1. Insecure software
  2. Misconfigured software
  3. People-related issues*
  4. Physical security issues

Surprised? Not really.

*nb: It’s important to note that these root-causes are often interrelated. Insecure or misconfigured software certainly relates to people-issues as well as other underlying issues. This interrelationship is important, but the distinction can be useful in breaking down how to address these problems.

Let us try and analyse these causes. Most of the layers of defence that organisations are applying to try and protect their assets are there to reduce attack surface area. In the case of web-based technology, we have firewalls, IDS / IPS, WAF and other related technical controls attempting to manage and reduce the likelihood that insecure or misconfigured software is exploited. If the layers of defence, and the system itself, have addressed insecure software issues, misconfiguration issues and was physically secure, it’s likely that any further exploitation is related to weak passwords, or passwords being disclosed through alternative system breaches (Take the LinkedIn breach for example).

Weak passwords are an example of a security issue that relates to both insecure software and people-related issues. More secure software may force users to use long, difficult to remember passwords. Unfortunately, if the credential is written down, or shared with someone else, then it doesn’t matter if it’s a strong password. In these particular instances, educating the user of better password practices may help.

Of the above issues, the people-related ones are often the more difficult to manage. Social engineering has proven itself an effective tool in an attacker’s arsenal over and over again, and even if you train your people, it’s difficult to reduce the exposure the same as you would with other issues. Whether this is due to the difficulty of educating the masses to social engineering, or that many information security professionals aren’t as good at addressing people-issues compared to technical-issues we can’t really say.

This list is not all that different from MITRE’s Common Attack Pattern Enumeration and Classification (CAPEC) ‘Domains of Attack’. Below is our root-causes, with the various CAPEC domains:

Root-cause CAPEC Domain
Insecure software Communications
Software
Supply Chain*
Misconfigured software Communications
Software
Supply Chain*
People-related issues Social Engineering
Supply Chain*
Physical security issues Communication (partially)
Hardware
Physical Security
Social Engineering
Supply Chain*

*nb: Supply chain relates to insecure or misconfigured software, people related issues or physical security weaknesses further up the supply chain.

Okay, so if we have these root causes, what can we do about them? Our subsequent blog posts will look at each of these root causes in further detail.