Monthly Archives: October 2017

WPA2 KRACK Vulnerability: What you need to know

Last Sunday, the early signs of a vulnerability disclosure affecting the extensively used Wi-Fi protected access (WPA2) protocol were evident. The next day, disclosure of the vulnerability lead to more details. The vulnerability was discovered by  two researchers Mathy Vanhoef and Frank Piessens of the Katholieke Universiteit Leuven (KU Leuven) while examining OpenBSD’s implementation of the WPA2 four way handshake.

Why should this vulnerability be considered important?
On Monday 16th October, the KRACK (key re-installation attacks) vulnerability was disclosed. This vulnerability was found within the implementation of the WPA2 protocol rather than any single device making it’s impact much more widespread. For example, vulnerable devices include Windows, OpenBSD (if not already patched against it), Linux, Apple iOS, Apple macOS and Google Android.

If exploited this vulnerability could allow decryption, packet replay, TCP connection hijacking and if WPA-TKIP (defined) or GCMP (explained) are used; the attacker can inject packets (defined) into a victim’s data, forging web traffic.

How can an attacker exploit this vulnerability?
To exploit the vulnerability an attacker must be within range of a vulnerable Wi-Fi network in order to perform a man in the middle attack (MiTM)(defined). This means that this vulnerability cannot be exploited over the Internet.

This vulnerability occurs since the initial four way handshake is used to generate a strong and unique key to encrypt the traffic between wireless devices. A handshake is used to authenticate two entities (in this example a wireless router and a wireless device wishing to connect to it) and to establish the a new key used to communicate.

The attacker needs to manipulate the key exchange (described below) by replaying cryptographic handshake messages (which blocks the message reaching the client device) causing it to be re-sent during the third step of the four way handshake. This is allowed since wireless communication is not 100% reliable e.g. a data packet could be lost or dropped and the router will re-send the third part of the handshake. This is allowed to occur multiple times if necessary. Each time the handshake is re-sent the attacker can use it to gather how cryptographic nonces (defined here and here) are created (since replay counters and nonces are reset) and use this to undermine the entire encryption scheme.

How can I protect myself from this vulnerability?
AS described in this CERT knowledge base article.; updates from vendors will be released in the coming days and weeks. Apple (currently a beta update) and Microsoft already have updates available. OpenBSD also resolved this issue before the disclosure this week.

Microsoft within the information they published for the vulnerability discusses how when a Windows device enters a low power state the vulnerable functionality of the wireless connection is passed to the underlying Wi-Fi hardware. For this reason they recommend contacting the vendor of that Wi-Fi hardware to request updated drivers (defined).

Links to affected hardware vendors are available from this ICASI Multi-Vendor Vulnerability Disclosure statement. Intel’ security advisory with relevant driver updates is here. The wireless vendor, Edimax also posted a statement with further updates to follow. A detailed but easy to use list of many vendors responses is here. Since I use an Asus router, the best response I could locate is here.

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Update: 21st October 2017:
Cisco have published a security advisory relating to the KRACK vulnerability for its wireless products. At the time of writing no patches were available but the advisory does contain a workaround for some of the affected products.
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The above updates are software fixes but updates will also be made available for devices in the form of firmware updates e.g. for wireless routers, smartphones and Internet of Things (IoT)(defined) devices. For any wireless devices you own, please check with the manufacturer/vendor for available updates with the above CERT article and vendor response list detailing many of the common vendors.

Thank you.

Infineon TPM Chips Patched Against Disclosed Vulnerability

With the release of Microsoft’s security updates last week; Infineon published a security advisory relating to a vulnerability discovered by security researchers in 2012.

Why should this vulnerability be considered important?
The vulnerable hardware is mostly to be found within corporate computers from manufacturers such as HP, Fujitsu and Lenovo. Google Chromebooks, routers and some Internet of Things (IoT)(defined). The vulnerability allows an attacker to determine a private (defined) encryption key when it has been generated by a vulnerable TPM (Trusted Platform Module) using only the public key (defined). Once the private key has been obtained it can be used by an attacker to decrypt the contents of a Microsoft BitLocker encrypted hard drive, to digitally sign fake software releases, to sign malware (making it appear more legitimate) as well impersonating the legitimate owner of the private key.

This vulnerability also affects cryptographic smart cards, security tokens and other secure hardware chips manufactured by Infineon. An estimate 760k devices are thought to be vulnerable while the true number could be up to three times that amount.

While the researchers were able to verify an attacker could derive the private key from 1024 and 2048 but public key, they were unable to do so for 4096 bit key since “a 4096-bit RSA key is not practically factorizable now, but “may become so, if the attack is improved.” For 1024 and 2048 bit keys, the factorisation can be easily parallelised by x number of CPUs, reducing the time taken by x times (where x is the number of cores a CPU has) allowing completion in hour or days.

How can I protect myself from this vulnerability?
Microsoft’s advisory provides the recommended steps for systems using Windows or other Microsoft products e.g. Active Directory Certificate Services (ADCS), Active Directory Directory Services (ADDS) (among others). The updates they recommend are only a workaround for the vulnerability. The vulnerability must still be resolved by applying updates to the vulnerable TPM chips. This advice also includes clearing the TPM and re-generating the necessary keys only after applying the updates from Microsoft.

Similarly Google made available Chrome OS M60 to mitigate this vulnerability. Further links to other affected vendors are listed below:

Fujitsu

HP Customer Support

HP Enterprise Support

Lenovo

Toshiba

Thank you.

October 2017 Security Updates Summary

As scheduled Microsoft released their monthly security updates earlier today. They address 62 vulnerabilities; more formally known as CVEs (defined). These are detailed within Microsoft’s new Security Updates Guide.

This month there are 4 Known Issues (kb4041691, kb4042895 , kb4041676 and kb4041681) for this month’s Microsoft updates. 2 of these issues relate to an exception error dialog box appearing, with the others causing a black screen, updates not to install in express , a BSOD and changing of display languages. Microsoft states in each link above they are working on resolutions to these issues.

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Update: 18th October:

On the 16th of October Adobe released Flash Player v27.0.0.170 to address a critical zero day (defined) vulnerability being exploited in the wild (namely being exploited on computing devices used by the general public in their professional and personal lives)). The BlackOasis APT group are believed to operate in the Middle East. The group is using malicious Microsoft Office documents with embedded ActiveX controls which contain the necessary Flash exploit. This exploit later installs the FinSpy malware.

Please install this update as soon as possible for any device with Flash Player installed. Google Chrome has already automatically received the update while earlier today Windows 8.1 and Windows 10 began receiving it.

As always you can monitor the availability of security updates for most your software from the following websites (among others) or use Secunia PSI:
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US Computer Emergency Readiness Team (CERT) (please see the “Information on Security Updates” heading of the “Protecting Your PC” page):

https://www.us-cert.gov/

A further useful source of update related information is the Calendar of Updates. News/announcements of updates in the categories of General SoftwareSecurity Software and Utilities are available on their website. The news/announcements are very timely and (almost always) contain useful direct download links as well as the changes/improvements made by those updates (where possible).

If you like and use it, please also consider supporting that entirely volunteer run website by donating.

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If you use any of the above software, please install the appropriate updates as soon as possible. Steps for installing updates for Windows are provided on the “Protecting Your PC” page.

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For this month’s Microsoft updates, I will prioritize the order of installation for you below:
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Critical severity:

Microsoft Office Vulnerability : CVE-2017-11826 : While not critical severity since it is already being exploited by attackers namely a zero day (defined) vulnerability.

Windows DNS Vulnerabilities: Further details provided within this news article

Windows Search Service (CVE-11771): affects Windows 7 up to and including Windows 10

Windows Font Vulnerabilities: CVE-2017-11762 and CVE-2017-11763

Microsoft Edge and Internet Explorer (multiple versions of Edge and IE affected)

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Please install the remaining updates at your earliest convenience.

As usual; I would recommend backing up the data on any device for which you are installing updates to prevent data loss in the rare event that any update causes unexpected issues.

Thank you.

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Nvidia Geforce Drivers:
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This update (released in September 2017) applies to Linux, FreeBSD, Solaris and Windows and resolves up to 8 security vulnerabilities. The steps to install the drivers are detailed here. I detailed where Nvidia list their security advisories in a previous blog post.

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Google Chrome:
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Google Chrome: includes 35 security fixes.

Google Chrome updates automatically and will apply the update the next time Chrome is closed and then re-opened. Chrome can also be updated immediately by clicking the Options button (it looks like 3 stacked small horizontal lines, sometimes called a “hamburger” button) in the upper right corner of the window and choosing “About Google Chrome” from the menu. Follow the prompt to Re-launch Chrome for the update to take effect.
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Wireshark 2.4.2 and 2.2.10
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v2.4.2: 5 CVEs (defined) resolved

v2.2.10: 3 CVEs resolved

As per standard process Linux distributions can obtain this update using the operating systems standard package manager (if the latest version is not installed automatically using the package manager you can instead compile the source code (v2.4.2) or v2.2.10). This forum thread and this forum thread may also be helpful to you with installing Wireshark on your Linux based system.

For Mac OS X and Windows, the update is available within the downloads section of the Wireshark website. In addition, a detailed FAQ for Wireshark is available here.
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Oracle:
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This month Oracle resolved 250 vulnerabilities. Further details and installation steps are available here. Within the 250 vulnerabilities addressed, 22 vulnerabilities were addressed in the Java runtime.

If you use any of the Oracle products listed here, please install the appropriate security updates as soon as possible.
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