Secure IM

21 11 2014

I know that this a deviation from my series on virtualisation security, however I feel it’s worth it.

I think that the latest new about WhatsApp/Facebook deciding to implement Moxie Marlinspike’s TextSecure by default, is a very big step for the future of secure communication. Instant messaging is sometimes snubbed among enterprises as a technology that is more designed for social interactions and teenagers, however IM is now doing what email has failed to do transparently for years. Sending anything securely over email in 2014 is still an additional process is not part of the protocol. I am not naive enough to discount that multi-client communication might change IM’s ‘transparentness’, but it’s still a positive step. I think that this will really see an increase in the use of these technologies, with hopefully others following suite.

There is also the idea that once public key cryptography is more widely adopted among end users, it would not be out of the question to see users public keys stored in address books alongside addresses and birthdays.

Maybe the future isn’t going to be as dark as we thought.

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Attacking management interfaces

29 09 2014

The management interfaces and everything that is incorporated into that software is, in the author’s opinion the most problematic area in virtualisation security today. There have been numerous attempts over the last few years to demonstrate how management interfaces can be breeched. The majority of these attacks are general attacks that use pre-existing attack methods such as brute forcing, MiTM (man-in-the-middle) and the numerous flaws with the PKI infrastructure. There are multiple proven attack methods available for exploiting management interfaces and below are descriptions of some of these attacks that have been discovered by researchers.

In an online blog (Mluft, 2011)  talks about how a brute force attack is achievable on the Amazon Web Services (AWS) portal by leveraging existing hacking software tools. In the attack (Mluft, 2011) demonstrated how it is possible to determine a successful logon using the exemplary payloads in the Burp Suite (Burp Suite, 2012). The use of the burp suite in this example is to simply automate the process of attempting logins to the interface. The payload in the software is also able to identify failed login attempts to the portal by returning a HTTP status code of 200 (Network Working Group , 1999). A correct password attempt is identified by a returned HTTP status code of 302. Using the documentation provided by Amazons services in relation to password policies (Mluft, 2011) created an appropriate wordlist and used the burp suite to attempt all the possible permutations. After 400,000 attempts the attack was paused and the results purged for the 302 status code. The code was found and also shown alongside was the value and the password attempted. This gave the attacker the username and password for the administration of all servers managed by that account. It should be noted that all of these attempts were originated from one IP address without the account being locked-out or subject to any account throttling.

As discussed earlier my earlier blog artical regarding the hypervisor, the Virtualization Assessment Toolkit (VASTO) has been developed to exploit multiple weaknesses, predominantly in the VMware family. As well as the identification module that returns the exact version of the server, it includes numerous attacks on virtual systems including a specific VMware brute forcing module, which mimics the attack on the AWS portal by (Mluft, 2011). One of the main contributors to the VASTO project (Criscione, 2010) demonstrated a number of the different functions found in VASTO at Blackhat USA 2010.  Although (Criscione, 2010) demonstrated how VASTO can be used at multiple layers of the virtual stack (Client, Hypervisor, Support, Management and internal), the majority concentrated on the management portion. (Criscione, 2010) confirms that although the (VMware, 2012) hardening guide recommends segmentation of management networks, these recommendations are often ignored and left situated on the same networks as traditional servers.

These servers that manage the entire fabric of the infrastructure have multiple attack vectors – from the operating systems they are installed on to the web services running the interfaces. Vulnerabilities in any one of these platforms can potentially jeopardise the security of an entire environment and should be taken very seriously.

The other element used in the VASTO modules which can target the management portion of the virtual infrastructure uses target flaws in the VMware components and implementation to expose threats in the infrastructure. One of the exploits that is included in the VASTO suite that best demonstrates how multiple components in these systems can be used for exploitation, originates via a flaw in the Jetty (Eclipse, 2012) web server that is used by vCenter Update manager. In the author’s opinion, this attack signifies how the complexity and code overhead that these management servers introduce, make securing virtual environments in an efficient manner, one that needs to be understood and prioritised. I will briefly give a breakdown of this attack to highlight the multiple elements that were used to complete the attack.

The Update Manager component of the vSphere suite is designed to secure the environment by automating the patching and updating process of hosts that fall under its management scope. However, (Criscione, 2010) recognised that the update manager requires a version of Jetty web server to operate. This is an additional component that is added to the total footprint of the management server. The version of Jetty installed prior to version 4.1 u1 (update 1) of the update manager was a version vulnerable to a directory traversal attack (Wilkins, 2009), which allowed attackers to view any files on a server that the Windows SYSTEM user has privileges. Consequentially vCenter stored a file on the server called “vpxd-profiler-*” which is a file used by administrators for debugging purposes. In this extensive file the, SOAP Session ID’s of all the users that have connected to that server are contained. With this ID the vmware_session_rider module, found in the VASTO toolkit, acts as a proxy server to allow the attacker to then connect through it into the vCenter server using the selected administrator SOAP ID. Once this is completed, the attacker is able to create a new admin credential within vCenter to ensure future access.

Another example of how different elements of the management interface could be used to gain access to vCenter is through VMware’s use of Apache Tomcat technology (The Apache Software Foundation, 2012). When navigating to a vCenter server through a web browser one is presented with the standard vSphere “Getting started” screen as is shown in figure 1

Web browser connection to vCenter server

Web browser connection to vCenter server

Connection to that same servers IP address, but specifying the default tomcat Tomcats index page port of “8443” over an SSL connection shows further information, including a link to login as the “Tomcat manager”. This page is shown in figure 2

The web interface seen when you navigate to vCenter with a port of 8443

The web interface seen when you navigate to vCenter with a port of 8443

In VMware version 4.1 there is a user named “VMwareAdmin” that is automatically added to the Tomcat server, which has full admin rights to the Tomcat service. In the earlier versions of VMware, the password for this admin account was 5 characters long starting with 3 uppercase, 1 number and one lowercase. This leaves an attacker with a number of options for an attacking perspective. The most obvious is to brute force the credentials with a compatible tools or script such as the Apache tomcat brute force tool (Snipt, 2011). A second (and more sophisticated attack) would be to use the folder traversal vulnerability introduced by the Jetty service to gain read access to the server. From here the attacker could navigate to the “tomcat-users.xml” file (C:\Program Files\VMware\Infrastructure\tomcat\conf) as shown in Figure 3, which is an XML file found in VMware 4.1 and which shows the clear text credentials of the account.

(left) The tomcat-users.xml file showing the username and password of a default admin account (Right) tomcat manager login prompt

(left) The tomcat-users.xml file showing the username and password of a default admin account (Right) tomcat manager login prompt

Using this access, an attacker is able to control elements of the web service with admin rights. As shown in Figure 4, one is able to change a number of settings through the tomcat interface, including the ability to upload custom WAR files, which can be created using Metaspolit to upload meterpreter payloads to the server.

Logged in to the tomcat manager using the credentials found on server

Logged in to the tomcat manager using the credentials found on server

Although some of the attacks using the VASTO toolkit are specific and use vulnerabilities that have almost all been patched by VMware (at the time of writing), the management interfaces are still vulnerable to more general network attacks that are not as fundamental to secure as simply applying a patch or updating to the newest version. As is explained briefly in by post on hypervisors, access to these interfaces are vulnerable to MiTM attacks and the implementations dependence on a highly insecure certificate/PKI model. These vulnerabilities are not directly the responsibility of the vendors, but certainly nothing has been done by them to address this issue.

I will not be explaining the process of how MiTM attacks and flaws in the certificate infrastructure can be used to capture login credentials, as this a fundamental part of security and has been covered on numerous occasions by multiple sources (Irongeek, 2012) (Schneier, 2011). I have also written about the overarching problems with the certificate model and how it can be bypassed by in a blog post from 2011.

 

Mluft, 2011. The Key to your Datacenter. [Online] Available at: http://www.insinuator.net/2011/07/the-key-to-your-datacenter/

Criscione, C., 2010. Blackhat 2010 – Virtually Pwned. USA: Youtube.

Wilkins, G., 2009. Vulnerability in ResourceHandler and DefaultServlet with aliases. [Online] Available at: http://jira.codehaus.org/browse/JETTY-1004

Irongeek, 2012. Using Cain to do a “Man in the Middle” attack by ARP poisoning. [Online] Available at: http://www.irongeek.com/i.php?page=videos/using-cain-to-do-a-man-in-the-middle-attack-by-arp-poisoning

Schneier, B., 2011. Schneier on Security. [Online] Available at: http://www.schneier.com/blog/archives/2011/09/man-in-the-midd_4.html





Certificate weaknesses in SSL/TLS

31 07 2011

A major component that guarantees the authenticity of an SSL/TLS connection within the browser is done through the use of digital certificates. Root certificates are installed and updated independently by each browser vendor. A root cert is a self-signed certificate that can issue certificates to websites once they have proven their identity and ownership of the domain. As shown in Figure 1, Firefox has a number of root certificates installed as default, including the Japanese Government and the Hong Kong Post office.

This means that we, as users inherently trust any sites that are signed by these root authorities. The increase in the amount of root CA’s has resulted in certificates now being much easier to obtain then a number of years ago, with often very little validation being performed before being issue, (Hebbes, 2009) writes:

“the problem is that most Certification Authorities don’t do very much checking. Usually they check your domain name by sending you an email to an address that has the same domain name extension. All this says is that someone who has access to an email address on that domain wants to set up a secure web server. They don’t actually check who you are”

At Defcon 17, (Marlinspike, 2009) gave a talk on defeating SSL security by using a tool that he had developed called SSLSNIFF (http://www.thoughtcrime.org/software/sslsniff/) this tool uses multiple vulnerabilities in the certificate validation process and SSL/TLS implementation found in all the major browsers used today.

In the presentation (Marlinspike, 2009) explains that when completing a certificate signing request (CSR) (which is defined by the PKCS #10 standard) the subject attribute field, which is made up of several other sub attributes, requires the requester to enter the name of the site they wish to request the certificate for. As the SSL certificate process can now be completed purely online and also due to the different ways that strings can be formatted in the ‘commonName’ field according to X.509 (RFC2459), an attacker is able to use the null character string to separate the start of the commonName value from the end.

This way, only the end of the commonName attribute (the domain they own) is checked by the Root CA against the WHOIS database records. This means that they are able to add anything they want into the commonName attribute before the null value – such as http://www.paypal.com. A diagram of this process can be found below.

Armed with this certificate and SSLSNIFF an attacker is able to insert themselves into the middle of communication and act as Paypal.com – with what looks like a completely valid certificate. (Marlinspike, 2009) explains that this attack is possible not only in web browsers such as; Firefox, IE and Chrome, but also in mail clients like Thunderbird and Outlook and even SSL VPN solutions such as Citrix.

Finally (Marlinspike, 2009) demonstrated an attack base around the Network Security Services (NSS) libraries, which are implemented in Firefox and Chrome where an attacker is able to use the certificate wildcard function to gain a universal wildcard certificate using *.domain.com, which effectively gives an attacker a valid digital certificate for any website they wish.





Technical Implementation Attacks on SSL/TLS

11 07 2011

As shown in the introduction, since the original release of SSL 1.0 there have been a number of amendments required due to vulnerabilities found in the implementation or the protocol. While the latest version of the TLS protocol (1.2) currently appears to be fairly robust against external attacks – with the introduction of the SHA256 cipher suites, not all secure communication today takes advantage of this standard. As shown in Figure 1 – which is a screenshot taken of the supported transport protocols within Firefox 3.6.15, this shows that the Mozilla developers are yet to adopt the latest two versions of TLS, leaving users open to weakened ciphers and other vulnerabilities that have been addressed in newer versions.

The majority of attacks on SSL and TLS that occur are from within the same LAN, in the form of Man-in-the-middle attacks (MITM). These attacks work by an attacker placing themselves in-between the client and the server; this is done by using the address resolution protocol (ARP) to spoof the whereabouts of MAC addresses on the network. This works at layer 2 of the OSI model and is how machines communicate on all Ethernet LANs, this attack is explained in Appendix 1. In a white paper written by (Burkholder, 2002) he writes about how it was:

“In late 2000 security researcher Dug Song published an implementation of an SSL/TLS protocol MITM attack as part of his ‘dsniff’ package.”

Due to the processing overhead associated with the asymmetric algorithms that SSL/TLS use, sites have often only used these protocols where it is needed. It is not unusual for the majority of websites that actually use SSL to protect user’s information, to have them filled out their sensitive information on an unencrypted page first, before ‘bouncing’ the data through an SSL/TLS encrypted tunnel. This method of securing data is adequate against attackers that are not proactively sniffing network communications. However when using a tool like SSLStrip, as described by creator (Marlinspike, 2009) you are able to add yourself in as a bridge between the two lines of communication. As most users either encounter SSL/TLS through either a 302 redirection request, directing them from a HTTP page to a HTTPS page or in the way that shopping sites bounce you to HTTPS pages. This software intercepts the users request for the HTTPS page and strips the ‘S’ out of the request. It will do this so that all communication that takes place is over a non encrypted HTTP protocol. The software keeps track of changes it makes by adding each action it performs into a internal mapping buffer. The attacker is then able to sniff the information being sent in clear text.

The only way this attack can be spotted by a user is by checking that the address bar is showing HTTPS instead of HTTP and that the SSL padlock is also shown (location is dependent on individual browser), although there are ways to change the address icon from, say the Google logo to a padlock in transit.

Early in November 2009, in an article released by (Ray & Dispensa, 2009) information was disclosed of a flaw in the renegotiation portion of the TLS /SSL protocol. This attack affected all versions of TLS and also version 3 of SSL. Although this issue has now been patched by most individual vendors SSL/TLS implementations, an article written by (Pettersen, 2010) reports on research that suggests one year after the public disclosure of the flaw, only 37.3% of all SSL/TLS servers have been patched against the issue.