Short iCloud Follow-Up

After the basic iCloud discussion in this post, I would like to add some more technical information. The following items are just a loose compilation of facts about the mentioned controls which allow the restriction of iCloud usage. The basic iCloud usage, consisting of backup, document sync, and photo stream, can be deactivated using the most recent version of the iPhone Configuration Utility:

Since there are no default settings for these values, it is necessary to include the disabled entries in existing configuration profiles.

Another new functionality which can be deactivated using configuration profiles is Siri. Even though this functionality is not directly related to the iCloud at first glance, it still bears a big threat potential. Looking at the SLAs of the iPhone 4s, the following paragraph gets relevant:
When you use Siri, the things you say will be recorded and sent to Apple to process your requests. Your device will also send Apple other information, such as your first name and nickname; the names, nicknames, and relationship with you (e.g., “my dad”) of your address book contacts; and song names in your collection (collectively, your “User Data”).

So Siri also uses cloud-based services in the background. The following screenshot shows the option to disallow the usage of Siri:

Thinking of this privacy relevant submission of data, another new option of the most recent tool version gets relevant: “Allow diagnostic data to be sent to Apple”. The two checked options in the following screenshots are also new features of the most recent version of the configuration utility:

That’s it for the short configuration option compilation of today, have a great week everybody,


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All Your Clouds are Belong to us

This is a _very_ interesting paper just published by some researchers (mainly) from RUB (Ruhr-University Bochum). Here’s the abstract:

“Cloud Computing resources are handled through control interfaces. It is through these interfaces that the new machine images can be added, existing ones can be modied, and instances can be started or ceased. Effectively, a successful attack on a Cloud control interface grants the attacker a complete power over the victim’s account, with all the stored data included.

In this paper, we provide a security analysis pertaining to the control interfaces of a large Public Cloud (Amazon) and a widely used Private Cloud software (Eucalyptus).

Our research results are alarming: in regards to the Amazon EC2 and S3 services, the control interfaces could be compromised via the novel signature wrapping and advanced XSS techniques. Similarly, the Eucalyptus control interfaces were vulnerable to classical signature wrapping attacks, and had nearly no protection against XSS. As a follow up to those discoveries, we additionally describe the countermeasures against these attacks, as well as introduce a novel ‘black box’ analysis methodology for public Cloud interfaces.”


While the actual described vulnerabilities have been fixed in the interim this stresses once more the point we made in this post: the overall security posture of the management (or “cloud control” as the authors of  the above paper call it) interfaces is crucial for potentially all the data that’s processed by/on your cloud based machines or applications.

Great research from those guys! This will help to drive the discussion and security efforts for a reasonable use of cloud based resources in the right direction…



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iTrust. Or not?

A few days ago (on 10/12/2011) Apple launched its new cloud offering which is called — who would have guessed 😉 — iCloud. Since we’re performing quite some research in the area of cloud security, we had a first look at the basic functionality and concepts of the iCloud. Its main features include the possibility to store full backups of Apple devices (at least, an iPhone, iPad or iPod touch running iOS 5 or a Mac running OS X Lion 10.7.2 is required), photos, music, or documents online. The data to be stored online is initially pushed to the cloud storage and then synchronized to any device which is using the same iCloud account. From this moment on, all changes on the cloudified data is immediately synchronized to the iCloud and then pushed to all participating devices. At this point, most infosec people might start to be worried a little bit: The common cloud concept of centralized data storage on premise of a third party does not cope well with the usual control focused approach of most technical infosec guys. The resulting concerns can be attributed to several main cloud computing related risks (which are proposed by ENISA and actually very valuable work:

  • Lock In: According to the way the cloud functionality is integrated into iOS and OS X , usage of the iCloud might result in strong lock in effects. There is neither the possibility to use different backend cloud storage for the functionality nor the possibility to develop a product which provides similar functionality (see later paragraphs for examples).
  • Isolation Failure: is probably the most present threat for many IT people, since it is highly related to technical implementation details. It includes, but is not limited to, breakout attacks from guest systems due to vulnerabilities in the hypervisor or to unauthorised data access due to insufficient permission models in backend storage. Thinking of the trust factor consistency, Apple’s history of cloud based services was not their “finest hour” (as Steve Jobs stated during his keynote on iCloud). Remembering this talk and the awkward MobileMe vulnerabilities, we would agree with that 😉
  • Loss of Governance: The loss of governance over data in the cloud is kind of an intrinsic risk to cloud computing (also refer to the proposed system operation life cycle and the motivation given here). Again, referring to explanations about the technical iCloud implementation in the later paragraphs, this loss might be even more relevant in the iCloud environment.
  • Data Protection Risks: Handing over responsibility for the storage of data to the cloud service provider, a customer also hands over the possibility to protect his valuable (or more concrete: personal) data by controls of his choice. Reviewing Apple’s terms of service for the iCloud, the following paragraphs are somewhat related to data protection issues: You understand that in order to provide the Service and make your Content available thereon, Apple may transmit your Content across various public networks, in various media, and modify or change your Content to comply with technical requirements of connecting networks or devices or computers. You agree that the license herein permits Apple to take any such actions. And in addition, the Apple Privacy Policy states the following: You further consent and agree that Apple may collect, use, transmit, process and maintain information related to your Account, and any devices or computers registered thereunder, for purposes of providing the Service, and any features therein, to you., which kind of reminds of the Dropbox Terms of service which even state that they are allowed to transfer your data to anybody if it is necessary in order to assure the quality of the offered service. Thinking of the trust factor components, all of these risks are getting even more relevant since Apple relies on third party cloud services (which are Amazon Web Services and Azure, according to several sources, including this one), which conclusively must also fulfill certain security requirements in order to lower the vulnerability factors for the presented risks.

There are some more risks according to the ENISA study, but those are beyond the scope of this post. If we do such rough assessments as sample exercises during our cloud security workshops, the participants usually ask what “they can do”. Possible controls can be divided into two groups: controls to reduce the risk to a reasonable level and controls which prohibit the usage of the particular service. When analyzing the cloud, the control always mentioned first is crypto. Speaking of cloud storage, crypto is a valid control to ensure that unauthorized access (e.g. due to isolation failure/physical access/subpoena) to data has no relevant impact. The only requirement is that the encryption is performed on client side (depending on the attacker model and whether you trust your cloud service provider). For example, Amazon provides a feature which is called Server Side Encryption which encrypts any file that is stored within S3. Additionally, Amazon allows the implementation of a custom encryption client which enables customers to perform transparent encryption of all files which are stored in S3. The analysis of the security benefits, attacker models, and operational feasibility of these controls will be the subject of yet-another blogpost, but at least Amazon offers these encryption features. The offered services of the iCloud differ a little bit in functionality (for example, the iCloud iTunes version is a kind-of music streaming platform), but basically there are two API functions which allow access to the iCloud backend. First, it is possible to store documents (where documents can be complete directory structures) in the iCloud, second, a so called key-value store can be accessed. The access is encapsulated in dedicated API calls which take care of the complete data transfer, synchronization, and pushing operations using an iCloud daemon. So any use of the iCloud is strictly connected to an app (I would have called it application ;-)) which has to use the introduced iCloud API calls. Even though I’m not that familiar with the iOS/OS X architecture, I would have guessed that it would have been easily possible to add client side encryption using the internal keychain and usual cryptographic mechanisms. Still, this is not the fact and it is questionable, regarding the user experience oriented focus of Apple, whether this feature will be implemented in the future. This lack of encryption possibility brings up the second class of controls, which shall restrict the iCloud usage. This is especially important in corporate context, where full backups of devices would potentially expose sensitive corporate data to third parties. Even though the usage might be restricted by acceptable use policies, this might not enough since the activation of this feature can happen accidentally: If a user logs in once into the iCloud frontend, which is possible using a regular apple ID, the data synchronization is enabled by default and starts immediately (refer also to the quoted terms of service above). Since most corporate environments use MDM solutions, it is possible to restrict the iCloud usage at least for iOS based devices. The corresponding configuration profiles offer several options to disable the functionality:

  • allowCloudBackup
  • allowCloudDocumentSync
  • allowPhotoStream

For today, this little introduction to iCloud and some of its security and trust aspects will be finished here. We will, however, continue to explore the attributes of iCloud more deeply in the near future (and we might even have a talk on it at Troopers ;-).

So stay tuned… Matthias

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Packetwars, Sun & Skills

During the last days, some of our guys (including me) had some great days in Dayton. Rene, Christopher, Hendrik, Sergej, and me flew in to give workshops and presentations at Day-Con as well as to compete in the infamous PacketWars game. While Day-Con is a one day event, the two days before the conference comprised workshops on secure iOS integration (given by Rene) and IPv6 security (given by Christopher). Since the overall topic of the conference was trust, Rene gave a keynote on broken trust which was based exemplary trust analysis, development of a trust metric, and different trust factors. Those trust factors were also used in my talk about evaluation methodologies for cloud service providers (regular followers will recognize some of the content of both talks from different posts 😉 ). There were also talks from Sergey Bratus, Graeme Neilson and Angus Blitter. While Sergey proposed a sound (not to say academic 😉 ) definition on the classification of vulnerabilities and their connection to turing complete input languages, Angus gave an introduction to PowerLine technologies and laid out, that these technologies still suffer from naive assumptions about trusted networks (he also refered to this). The day after the conference, the ERNW Allstars had to defend their championship title in PacketWars. Since the first battle was scheduled for 10AM, we had quite some time to tan in the sunny 30°C weather, recover from the conference and prepare the expected victory celebration (some of you might remember some “Champagne tradition” from Troopers). In face of this motivation, we rushed through the 3 battles and were able to score first place second year in a row. At this point, kudos to the two other participating teams who gave us a tough battle, especially during the reversing challenges.


Have a great week, Matthias

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Certificate Based Device Authentication with iOS Devices

We recently performed a Proof-of-Concept (PoC) implementation of certificate based auth with iPads in some large environment. So far the focus has been mainly on WLAN access; VPN and EAS authentication are going to follow in the next step.

As we figure that the topic might be of interest for some of you, we’ve extracted a certain, not-too-customer-specific part of the deliverable and converted it into an ERNW newsletter. Special thanks go to Rene Graf for leading the project! 😉

Of course, this stuff is going to be covered in much more detail in the Troopers12 edition of our “iOS Security Workshop” (see here for the agenda of this year or here for a German version of the current one).

Enjoy reading (& implementing)!



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Broken Trust, Part 2: Applying the Approach to… Dropbox

After having introduced the basic elements of our concept of trust, control and confidence in this post, today I’ll try to strengthen your (and maybe even my own as well ;-)) understanding of these ideas by applying them to another candidate, that is Dropbox. Hence this post is mainly about performing a certain analysis method to some object; conclusions as for the question if Dropbox is suited to be used in enterprise environments processing sensitive data are out of scope and are left entirely to you, the valued reader.

Two more preliminary remarks might be helpful to further understand the direction and intent of this post:

a) I don’t have any practical experience with Dropbox. I don’t use it personally and at ERNW using it for company-related data would require a risk acceptance, which – probably not too surprisingly – no company member has ever filed (and which would have a quite high likelihood of being turned down by the CEO anyway ;-)). In other words: I can’t imagine any occasion we’d use cloud based storage services for any of our data. It’s just that – given our idea of “highly skilled, thoughtful and responsible humans working here” – we don’t use terms like “xy is strictly forbidden” very often…

So feel free to jump in by PM or comment to this post if this stated lack of practical experience has lead to wrong conclusions or factual errors.

b) This post is not about blocking Dropbox in corporate networks by technical means (which – afaik – is relatively easy compared to, say, blocking Skype, as DB seems to operate mainly from a well-defined /24 network range). Doing so (technically blocking DB on corp firewalls) would not solve the underlying problem of potentially misplaced trust (or ignorance) and might just lead to yet-another-risk-acceptance popping up on the ISOs’ desks (I know, I know:  some of you would be happy if at least a risk acceptance existed for DB within your organization…). And, of course, the corp_fw way would not address the aggregate problem of running Dropbox on mobile devices (at least assumed that no cloud based proxy services are in use for those, which is currently the case in most networks I know).

However this post is about asking a certain set of questions and clarifying some company’s or service’s attributes to induce a reasonable discussion about the exact company’s/service’s suitability for processing sensitive assets. To us, such an approach is aligned with our understanding of an ISO as a trusted business advisor (as opposed to the “paranoid pitbull” or “unfortunately unheard master of governing guidelines” mission understanding of ancient times).


Now let’s have a look at the object of today’s trust exercise, that is Dropbox. Founded in 2007 and fueled by US$ 7.2 million venture capital (as of this Forbes article) the California-based company provides cloud-based file storage services with a simple GUI and some nice collaboration capabilities for groups of users sharing files. The description in the CrunchBase profile goes: “Always have your stuff, wherever you are”. A technical overview can be found in this paper recently presented at USENIX Security.

As you might recall from the first post of this series, there I laid out some trust contributing factors, which I took from the ISECOM “Mastering Trust” methodology that is taught in their Trust Analyst course (pls note that my interpretation of these may be wrong as I never attended that course. sorry, Pete ;-)).

These are:

  • Size – “Who exactly are you going to trust?”
  • Symmetry – “Do they trust us?”
  • Transparency – “How much do we know about $TRUSTEE?”
  • Consistency – “What happened in the past?”
  • Integrity – “[How] Do we notice if $TRUSTEE changes?”
  • Value of Reward – “What do we gain by trusting?” (that’s the one that Ponzi schemes are based on)
  • Components – “Which resources does $TRUSTEE rely on?”
  • Porosity – “How separated is $TRUSTEE from its environment?”


Applying all these to Dropbox might yield the following answers:

a) Size

While this might seem a simple one given Dropbox is a not-too-big company presumably held by their founders and some investors/venture capital providers (plus maybe employees holding stocks or options or sth) it should be noted that, more or less obviously, there’s more entities in the overall picture => see below at section “Components”.


b) Symmetry

Usually this one is hard to apply to B2C scenarios, so I’ll skip it here.


c) Transparency

Honestly, as I’m not a user of their service I don’t have a ultimate attitude here. However from a trust analyst point of view I just note there’s a number of people out there who think that DB failed severely in this regard. And there’s a (still pending?) complaint for injuctive relief filed to the FTC stating that Dropbox “continues to make deceptive statements to consumers regarding the extent to which it protects and encrypts their data.”

So overall this one (transparency) seems at least debatable; see also discussion on factor “Integrity” below.


d) Consistency: well, probably most of you know that three months ago DB suffered a breach which exposed all online storage lockers to anyone entering any password for ~ 4 hours.

Strictly taking the “consistency road” this does not contribute to their trustworthiness, from my humble evaluation.


e) Integrity

This post from the Hunton & Williams privacy blog provides an overview how Dropbox’ security statements (on its website) changed over time. I tend to assume the majority of users is/was not aware of those changes. In general it seems that one of their main communication channels is their blog. Which – given that most of you probably read a blogpost right now 😉 – might certainly be a valid channel… for B2C scenarios in modern times at least. Not sure if this is the right channel for the security properties of corporate information assets though.


f) Components

This is a particularly interesting one. As obvious as this may be, most users are probably not aware that DB does not operate the servers providing the service themselves. To the best of my knowledge the (Dropbox) service heavily relies on Amazon S3 and EC2 instances, in a certain setup that Mulazzani et.al., in their paper, comment on as follows: “However, the fact that encryption and storage is done at the same place seems questionable to us, as Amazon is most likely able to access decryption keys”.


g) Porosity

We can’t provide an evaluation here as we do not dispose of any information as for clear demarcation lines on the financial (e.g. who might potentially influence DB’s decisions due to simple ownership of shares ;-)) or organization/infrastructure (which 3rd parties actually provide which type of supporting service, e.g. do they share their office space with other parties in a business/office incubator etc.) sides of things.


So, once again, taking a structured approach when evaluating some party’s trustworthiness (to counter the fact that trust – by it’s very (Diego Gambetta’s) definition that we used in the initial post – is sth subjective) leads to – hopefully – interesting insight and results. Still, in this particular case, there’s another potential use of this way of looking at things: when dealing with (business’ desire to use) Dropbox in your organization, you might convert this points into a simple (one slide ;-)) checklist containing questions like
  • Do you know who owns the company Dropbox?
  • Do you know where their servers are located?
  • Do you know if they own the servers providing the service themselves or who else does this on their behalf? And where the servers of that “other party” are located? Which legislation applies there?
  • Do you know that they just suffered a breach temporarily allowing anyone in the world to access any one of its 25 million customers’ online storage lockers, simply by typing in any password?
  • Do you know who owns the keys necessary to decrypt data stored under your account?
[in case you like to promote your concerns the FUD way – which we do not like or recommend – you might add: “If you were a well-funded attacker, maybe from an emerging market, would Dropbox be an interesting target for you?”…]

If some people within your organization are still going to use DB for corporate data then, well, that’s an “educated decision by business” [no, no, the quotes are not put here to hint there might be a contradictio in adjecto ;-)].

Stay tuned for more stuff to come in this series & have a good week,



btw: we’ll probably have a talk about Dropbox at next year’s Troopers which takes place on 03/21 and 03/22 2012 in Heidelberg.

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