Category: Exploits

  • IKE VPNs Supporting Aggressive Mode

    In Raxis penetration tests, we often discover IKE VPNs that allow Aggressive Mode handshakes, even though this vulnerability was identified more than 16 years ago in 2002. In this post we’ll look at why Aggressive Mode continues to be a vulnerability, how it can be exploited, and how network administrators can mitigate this risk to protect their networks and remediate this finding on their penetration tests.

    What is an IKE VPN?

    Before we get into the security details, here are a few definitions:

    • Virtual Private Network (VPN) is a network used to securely connect remote users to a private, internal network.
    • Internet Protocol Security (IPSec) is a standard protocol used for VPN security.
    • Security Association (SA) is a security policy between entities to define communication. This relationship between the entities is represented by a key.
    • Internet Key Exchange (IKE) is an automatic process that negotiates an agreed IPSec Security Association between a remote user and a VPN.

    The IKE protocol ensures security for SA communication without the pre-configuration that would otherwise be required. This protocol used by a majority of VPNs including those manufactured by Cisco, Microsoft, Palo Alto, SonicWALL, WatchGuard, and Juniper. The IKE negotiation usually runs on UDP port 500 and can be detected by vulnerability scans.There are two versions of the IKE protocol:

    • IKEv2 was introduced in 2005 and can only be used with route-based VPNs.
    • IKEv1 was introduced in 1998 and continues to be used in situations where IKEv2 would not be feasible.
    Pre-Shared Keys (PSK)

    Many IKE VPNs use a pre-shared key (PSK) for authentication. The same PSK must be configured on every IPSec peer. The peers authenticate by computing and sending a keyed hash of data that includes the PSK. When the receiving peer (the VPN) is able to create the same hash independently using the PSK it has, confirming that the initiator (the client) has the same PSK, it authenticates the initiating peer.

    While PSKs are easy to configure, every peer must have the same PSK, weakening security.

    VPNs often offer other options that increase security but also increase the difficulty of client configuration.

    • RSA signatures are more secure because they use a Certificate Authority (CA) to generate a unique digital certificate. These certificates are used much like PSKs, but the peers’ RSA signatures are unique.
    • RSA encryption uses public and private keys on all peers so that each side of the transaction can deny the exchange if the encryption does not match.

    Cisco goes into details on these options in their VPN and VPN Technologies article. 

    Aggressive Mode vs. Main Mode

    In this post, we are discussing the first phase of IKEv1 transmissions. IKEv1 has two phases:

    1. Establish a secure communications channel. This is initiated by the client, and the VPN responds to the method the client requested based on the methods its configuration allows.
    2. Use the previously established channel to encrypt and transport data. All communication at this point is expected to be secure based on the authentication that occurred in the first phase. This phase is referred to as Quick Mode.

    There are two methods of key exchange available for use in the first IKEv1 phase:

    1. Main Mode uses a six-way handshake where parameters are exchanged in multiple rounds with encrypted authentication information.
    2. Aggressive Mode uses a three-way handshake where the VPN sends the hashed PSK to the client in a single unencrypted message. This is the method usually used for remote access VPNs or in situations where both peers have dynamic external IP addresses.

    The vulnerability we discuss in this article applies to weaknesses in Aggressive Mode. While Aggressive Mode is faster than Main Mode, it is less secure because it reveals the unencrypted authentication hash (the PSK). Aggressive Mode is used more often because Main Mode has the added complexity of requiring clients connecting to the VPN to have static IP addresses or to have certificates installed. 

    Exploiting Aggressive Mode
    ike-scan in Kali Linux

    Raxis considers Aggressive Mode a moderate risk finding, as it would take a great deal of effort to exploit the vulnerability to the point of gaining internal network access. However, exploitation has been proven possible in published examples. The NIST listing for CVE-2002-1623 describes the vulnerability in detail.A useful tool when testing for IKE Aggressive Mode vulnerabilities is ike-scan, a command-line tool developed by Roy Hills for discovering, fingerprinting, and testing IPSec VPN systems. When setting up an IKE VPN, ike-scan is a great tool to use to verify that everything is configured as expected. When Aggressive Mode is supported by the VPN, the tool can be used to obtain the PSK, often without a valid group name (ID), which can in turn be passed to a hash cracking tool.If you use Kali Linux, ike-scan is included in the build: We can use the following command to download the PSK from an IKE VPN that allows Aggressive Mode:

    ike-scan -A [IKE-IP-Address] --id=AnyID -PTestkey
    ike-scan
    psk-crack

    Here is an example of the command successfully retrieving a PSK:The tool also comes with psk-crack, a tool that allows various options for cracking the discovered PSK.Because Aggressive Mode allows us to download the PSK, we can attempt to crack it offline for extended periods without alerting the VPN owner. Hashcat also provides options for cracking IKE PSKs. This is an example Hashcat command for cracking an IKE PSK that uses an MD5 hash:

    ./hc.bin -m 5300 md5-vpn.psk -a 3 ?a?a?a?a?a?a -u 1024 -n 800

    Another useful tool is IKEForce, which is a tool created specifically for enumerating group names and conducting XAUTH brute-force attacks. IKEForce includes specific features for attacking IKE VPNs that are configured with added protections. 

    What VPN Administrators Can Do to Protect Themselves

    As Aggressive Mode is an exploitable vulnerability, IKE VPNs that support Aggressive Mode will continue to appear as findings on penetration tests, and they continue to be a threat that possibly can be exploited by a determined attacker.We recommend that VPN administrators take one or more of the following actions to protect their networks. In addition, the above actions, when documented, should satisfy any remediation burden associated with a prior penetration test or other security assessment.

    1. Disable Aggressive Mode and only allow Main Mode when possible. Consider using certificates to authenticate clients that have dynamic IP addresses so that Main Mode can be used instead of Aggressive Mode.
    2. Use a very complex, unique PSK, and change it on a regular basis. A strong PSK, like a strong password, can protect the VPN by thwarting attackers from cracking the PSK.
    3. Change default or easily guessable group names (IDs) to complex group names that are not easily guessed. The more complex the group name, the more difficult of a time an attacker will have accessing the VPN.
    4. Keep your VPN fully updated and follow vendor security recommendations. Ensuring software is up to date is one of the best ways stay on top of vulnerability management.

    Also see our post on creating a secure password for more information on creating a strong PSK.

  • Aerial Drones – A New Frontier for Hackers

    Drones in the News

    Drones have been a hot news topic for a number of years. Individuals and businesses alike are scrambling to leverage these digital devices for everything from aerial photography to package delivery. Their inexpensive cost makes them readily accessible, and the uses are virtually unlimited – even for the malicious actor.Perhaps you saw in the news where a drone was used to get within range of a home and hack into the automation features to control the lights. While that stunt was simply annoying, it shines a spotlight (pun fully intended) on the bigger issue security professionals face when seeking to implement this new technology securely.

    Aerial Hacking

    Recently Raxis conducted a security assessment where we employed a drone to intercept aerial signals in transit between two locations. The drone was positioned in the line of sight of the transmission and intercepted the signal as it flew by.The drone relayed the data to our security engineer on the ground and the captured data was reviewed for exploitable content.Similarly, drones can be used for proximity attacks where they can get close enough to a target to intercept the radio signal. This information can be saved onboard or relayed to a remote location for analysis and use.Drones can be readily equipped to receive and transmit data across a myriad of transports. This creates an interesting array of attack vectors for the creative hacker.

    What Can You Do?

    Drones offer an entirely new attack vector for hackers. As a security engineer, you need a comprehensive plan that incorporates drone-related threat profiles:

    • Establish a no-fly zone and prepare countermeasures for safely landing a rouge drone (where legally available).
    • Maintain vigilant surveillance of critical areas.
    • Ensure that all data is highly encrypted and that no plain text passwords or other information is being transmitted through the air.
    • If a drone is spotted, consider ceasing all data traffic until the drone is no longer a threat.

    Beyond intercepting data, drones are employed for general surveillance with increasing frequency. An attacker preparing to infiltrate your physical property can gain a substantial amount of information by reviewing aerial footage obtained during overhead flights.Drones can be small, quiet, and hard to detect. It’s possible a drone could surveille your property without attracting undue attention. Even if the device is noticed, it’s likely that employees would simply assume its presence is recreational without considering the security implications regarding such a device in proximity to a given facility.Training and attentiveness are critical to maintaining a robust security posture against these aerial attacks. The old slogan from US Homeland Security, “If you see something, say something” applies here. Encourage your employees to report drone sightings and develop a legal and safe plan for handling drone flights in your area.Above all else, realize that drone-based attacks can pose a significant threat to your security posture and should be managed accordingly.

  • The Weakest Link in the Password Hash

    Your password is strong – but is everyone else’s?

    We spend considerable time trying to make sure our passwords are strong. But we also need to spend time educating our user base on why password strength is important.

    It is not uncommon for a hacker to establish his foothold in an environment by first compromising a weak or insecurely stored password. Once a base level of authenticated access is established, it becomes a matter of time before privilege escalation is achieved.

    So, while your password might be a strong 16 character, alphanumeric with symbols stronghold, your administrative assistant might still be using s0ftc@t1 (which, by the way, would crumble under a modest brute-force attack in less than 48 hours) as hers. If we can get that weak password we can extrapolate from there and gain access to other accounts.

    Important lessons to teach:
    • Use of symbols to recreate letters (i.e.: @ for a, ! for i, etc) is not that useful. Rule based brute-force attacks use dictionaries and account for common character substitution techniques.
    • Longer is better – an 8 character password is trivial for a skilled hacker regardless of it’s complexity. Currently, adding a single character and increasing the length to 9 characters, extends the time it takes to crack the password to a couple of months.
    • Use random letters and numbers.
    • Capital letters should be used along with non-capitals, but refrain from making the first character the capitalized letter (we expect that and hack for it).
    Consider multiple roots

    One trick is to use a 10 character base such as:yyT73p@55c

    Now remember that (see next section for tips).

    Now make it unique. By adding a “-” or a “+” or “_” and then a system identifier such as:

    yyT73p@55c-dr0p (say, for Dropbox)
    yyT73p@55c+f@cE (for Facebook)
    yyT73p@55c_BoA (for Bank of America)

    Now you have a super strong random root, followed by a symbol with a dictionary word including caps and symbols if you wish.

    Using this formulaic approach it’s possible to take a 10 character root and create a different password by creating an easy to remember tag. Now your passwords are 14+ characters long and easy to remember.

    Consider rhyme and pattern

    One trick I use for remembering that root is putting it in a rhythm and rhyme pattern that makes sense to me. This was a trick taught to me by a security engineer years ago and it’s worked. In the case of : yyT73p@55c every third letter (and 4th at  the end) rhymes, and I have a pace to it.

    Different root for types of systems

    Now. If you want to supercharge the geek (and help save your butt from mass hack password releases) consider having a small handful of root passwords. Perhaps one you use for social, one for finance, and one for work.

    Using that approach still only requires you to remember 3 base passwords, but, in doing so, you’ve strengthened your password repertoire considerably.

    Change the root

    Regardless of the strength of our passwords it’s still best practice to change them frequently. Using the root system all you need to do is periodically change the root and you’ve reset any exposure to compromise you may have had.

    BONUS ROUND.

    If you really care about security for a specific site (say, your bank), use a unique username. It doesn’t have to be crazy. If you tend to use “sally15” as your main username try using your last name “sanders15” for the bank. Use the same password root as above – but now you’ve got a unique username and a unique password that is associated with that one service.

    The Struggle is Real

    Getting your employees to use strong passwords is an uphill battle, but it’s a critical one. Remember – we are looking for the weakest link. Once we get a toe in the door it’s usually all we need before we spread like cancer in your system.

    By utilizing a simple system, such as the one suggested here, you can increase the chances of your employees maintaining difficult passwords and strengthening their online security.

  • HP iLO Password Cracking

    One of my favorite parts of information security is cracking password hashes. I have a dual nVidia GPU rig that I use to run hashcat on and sometimes my research leads me to crack hashes. 

    For those who don’t know, HP has a system for Integrated Lights Out, and it allows for remote management of systems. Usually these interfaces are located on a management network that is inaccessible unless you’re a systems admin.

    Well, I got my hands on some hashes using the Metasploit module called IPMI 2.0 RAKP Remote SHA1 Password Hash Retrieval. There’s a few blogs that talk about how to do that, so I’ll let you refer to them on the how. What I thought was interesting though is that a lot of the systems I was working with were left to the default password – which is a random 8 digit number.  

    With a dual GPU hashcat instance, that is fairly trivial.  I set a bruteforce attack using -a 3 ?d?d?d?d?d?d?d?d and the result below is what happened.

    1416515636048

    It took a mere 4 seconds to spin across 8 digits. If you’re a server admin, I hope you’re setting the administrator passwords on your iLO sessions to something other than digits. Also, and this goes without saying, keep your management network completely firewall off of the production network! There is no need to have the general user with any sort of access at all to these ports.  

    Still, a very strong password is your last line of defense in the event a breach occurs.