at first a happy new year to all our readers!
And, of course, to everybody else, too ;-). May 2013 bring good things for you all, in particular (but not only) in the infosec space.
At the recent ATSAC 2012 conference a guy from the CERT Insider Threat Center gave a talk on the exact topic. Given that the ENISA Cloud Computing Risk Assessment lists “Cloud Provider Malicious Insider” as one of the top eight risks (out of overall 35 risks evaluated) and we just had some discussion about this in a customer environment, this might be of interest for some readers.
Recommendations by the German Federal Office for Information Security (BSI – Bundesamt für Sicherheit in der Informationstechnik) are obligatory for German government agencies, civil services and authorities (like recommendations of the NIST are relevant to American government agencies and authorities). They are often used as references and security best practices in other countries as well. Hence it is hard to understand why the recommendations on how to harden Windows Server 2008 based systems were published only some weeks ago and only on a preliminary draft basis (which is, obviously, better than nothing ;-)).
We at ERNW, however, did an overall baseline security approach of Windows Server 2008 R2 and Active Directory for a large German authority last year. The aim was to fullfil the requirements of the German Federal Office for Information Security without having precise technical guidelines by the BSI itself (from our side we do have guidelines of course ;-)). The hardened Windows Server 2008 R2 environment was then approved at the end of 2011 by the German BSI. Now we published the results of our overall approach in our latest newsletter [German language].
Enjoy reading!
Friedwart Kuhn
PS: There’s also a digitally signed version of the newsletter. (Because it is signed with a qualified certificate, the validation requires an appropriate validation software, for example SecSigner from SecCommerce – which is free software).
As in 2011 we really liked the conference; there was a number of interesting talks and we met quite some fellows from the IPv6 security space. Btw: we plan to organize a dedicated IPv6 security summit in late 2012 (probably on 6th and 7th of November) in Heidelberg, similar to the Telco Sec Day at Troopers. We’ll annouce details as for this one in some weeks.
TROOPERS12 came to an end last week on Friday; needless to say it was an awesome event. 😉
The first two days offered workshops on various topics. On Monday Enno, Marc “Van Hauser” Heuse and I gave a one day workshop on “Advanced IPv6 Security”. I think attendees as well as trainers had a real good time during and after the workshop fiddling around with IPv6. Especially Marc had quite some fun as he discovered that we provided “global” IPv6 Connectivity for the conference network, and according to one of his tweets, TROOPERS12 was the first security conference he visited, offering this kind of connectivity.
So back to the topic
Our last posts on IPv6 Security go back to the first half of 2011. If you haven’t read them already, now it’s a good time to do so. You can find them here, here, here and here.
In the last post of the series Enno discussed how RA-Guard can be circumvented with clever use of extension headers. As a short reminder, the packet dump looks like this.
The Information of the upper-layer protocol is only present in the second fragment, so RA Guard does not kick in.
As we found out on the Heise IPv6 Kongress last year, this issue can be mitigated with the following parameter in an IPv6 ACL.
deny ipv6 any any undetermined-transport
As a reminder, this parameter drops all IPv6 packets where the upper-layer protocol information cannot be determined.
After the workshop was officially over, Marc and I played a little bit with this ACL Parameter to see if it is working as intended. So I configured the following IPv6 ACL on our beautiful Cisco 4948E:
4948E(config)#ipv6 access-list IPv6
4948E(config-ipv6-acl)#deny ipv6 any any undetermined-transport
4948E(config-ipv6-acl)#permit ipv6 any any
4948E(config)#interface g1/19
4948E(config-if)#ipv6 traffic-filter IPv6 in
We started the attack again with the following parameter:
Apparently nothing happened with my (IPv6 enabled) laptop (which is a good thing ;))
The corresponding packet dump looked quite unspectacular:
Only the STP packets could be seen, and the flooded router advertisements were dropped by the Switch.
So could this parameter solve the issue with the whole RA mess?
Unfortunately the answer is no. The ACL parameter does mitigate the issue with the fragmented router advertisement. However, the ACL parameter can be circumvented by using overlapping fragments. Unfortunately we couldn’t test this scenario because this wasn’t yet implemented in the THC Tool Suite, but this is just a matter of time…
The IPv6 Packet basically looks like this:
Fragment 1:
IPv6 Header
Fragmentation Header
Destination Header (8 bytes)
ICMPv6 with Echo Request
Fragment 2:
IPv6 Header
Fragmentation Header with offset == 1 (equals position of 8th byte ==
start of Echo Request in first fragment)
ICMPv6 with RA
In this case it depends on the operating system whether or not the packet is discarded when overlapping fragments are detected. RFC 5722 is very specific on how these should be handled:
“When reassembling an IPv6 datagram, if one or more its
constituent fragments is determined to be an overlapping
fragment,the entire datagram (and any constituent fragments,
including those not yet received) MUST be silently discarded.”
So it is up to the operating system to implement this behavior. We’ll see how things work out 😉
If you’re interested in more IPv6 issues, or simply wanna chat about this topic, meet Enno and me again at the Heise IPv6 Kongress this year in Frankfurt, where we will give a talk on IPv6 as well.
if you’re following this blog regularly or if you’ve ever attended an ERNW-led workshop which included an “architecture section” you will certainly remember the “Seven Sisters of Infrastructure Security” stuff (used for example in this post). These are a number of (well, more precisely, it’s seven ;-)) fundamental security principles which can be applied to any complex infrastructure, be that a network, a building, an airport or the like.
As part of our upcoming Black Hat and Troopers talks we will apply those principles to some VoIP networks we (security-) assessed and, given we won’t cover them in detail there, it might be helpful to perform a quick refresher of them, together with an initial application to VoIP deployments. Here we go; these are the “Seven Sisters of Infrastructure Security”:
Access Control
Isolation
Restriction
Encryption
Entity Protection
Secure Management
Visibility
Now, let me discuss them in a bit more detail and put them into a VoIP context.
Access Control (“try to keep the threats out of the environment containing the assets to be protected”)
This should pretty much always be an early consideration as limiting access to “some complex infrastructure” obviously provides a first layer of defense and does so in a preventative[1] way. Usually authentication plays a major role here. Please note that in computer networks the access control principle does not only encompass “access to the network [link]” (where unfortunately the most prevalent technology – Ethernet – does not include easy-to-use access control mechanisms. And, yes, I’m aware of 802.1X…) but can be applied to any kind of (“sub-level”) communication environment or exchange. Taking a “passive-interface” approach for routing protocols is a nice example here as this usually serves to prevent untrusted entities (“the access layer”) from participating in some critical protocol [exchange][2] at all.
In a VoIP scenario limiting who can participate in the various layers and communication exchanges, be it by authentication, be it by configuration of static communication peers for certain exchanges[3] (yes, we know this might not scale and usually has a bad operational feasibility) would be an implementation of the access control principle.
Isolation (“separate some elements of the environment from others, based on attributes like protection need, threat potential or trust/worthiness”)
In computer networks this one is usually implemented by network segmentation (with different technologies like VLANs or VRFs and many others) and it’s still one of the most important infrastructure security principles. I mean, can you imagine an airport or corporate headquarters without areas of differing protection needs, different threat exposure or separate layers and means of access? [You can’t? So why do you think about virtualizing all your corporate computer systems on one big unified “corporate cloud”? ;-)]
Again, it should be noted that “traditional network segmentation” is only one variant. Using RFC 1918 (or ULA, for that matter) addresses in some parts of your network without NATing them at some point, or refraining from route distribution at some demarcation point constitute other examples.
In the VoIP world the main realization of the isolation principle is the commonly found approach of “voice vs. data VLAN[s]”.
Restriction (“once [as of the above principle] isolated parts get connected try to limit the interaction between those parts at the intersection point”)
This is the one most people think of when it comes to network security as this is what the most widely deployed network security control, that is firewalls, is supposed to do.
Two points should be noted here, from our perspective:
In some network security architecture documents phrases going like “the different segments are [to be] separated by firewalls” can be found. Which, well, is a misconception: usually a firewall connects networks (which would be isolated otherwise), it does not separate them. It may (try to) limit the traffic passing the intersection point but it still is a connection element.
And it should be noted that the restriction it applies (by filtering traffic) always has an operational price tag. Which is the one of the reasons why firewalls nowadays tend to fail so miserably when it comes to their actual security benefit…
In VoIP networks using the restriction approach is considerably hard (and hence quite often simply doesn’t happen) given a number of protocols’ volatility when it comes to the (UDP/TCP) ports they use.
Encryption (“while in transit encrypt some asset to protect it from threats on its [transit] way”)
This is a very common infrastructure security control as well (alas, at times the only one people think of) and probably does not need further explanation here.
Still it should be noted – again – that it has an operational price tag (key management and the like). Which – again – is the very reason why it sometimes fails so miserably when it comes to providing actual security…
In the VoIP world (as this one is very much about “assets in transit”) it’s (nowadays) a quite common one, even though still a number of environments refrains from using it, mainly due to the mentioned “operational price tag”.
Entity Protection (“take care of the security exposure of the individual elements within the environment containing the assets to be protected”)
This encompasses all measures intended to increase the security of individual elements. It’s not limited to simple hardening though, but includes all other “security [posture] quality assurance” things like pentesting or code reviews (when the element looked at is an application).
Adding a comment again I’d like to state that, in times of virtualization and vaporizing security layers (deploying shiny apps pretty much directly connecting customers to your ERP systems, by means of fancy webservices) this one might become more and more important. In the past many security architectures relied on layers of isolation & restriction and thereby skipped the hardening/quality assurance step (“we don’t have to harden this Solaris box as there’s a firewall in front of it”). As the talks’ case studies will show this one is a fundamental (and overlooked) one in many VoIP deployments.
Secure Management (“manage the [infrastructure] elements in a secure way”)
Secure management usually can be broken down to:
Restrict the endpoints allowed to establish management connections.
Either use a trusted environment (network link) or use secure variants of mgmt. protocols instead of their less secure counterparts (SSH vs. Telnet, HTTPS vs. HTTP, SNMPv3 vs. community-based SNMP and the like).
Logging of security related events and potentially all management actions performed.
While this is (should be) an obvious security principle, daily assessment experience shows that failures/weaknesses in this space account for the majority of critical vulnerabilities when it comes to infrastructure security. This applies in particular to VoIP implementations (see the case studies for examples).
Visibility (“be able to assess the current security posture of your infrastructure and its elements with reasonable effort”)
This is where logging (+ analysis), monitoring etc. come into play. We’d like to note that while this is a valid infrastructure security principle, its actual security benefit is often overestimated given the “detection/reaction” nature of this principle and its subsequent bad operational feasibility.
This is a particularly interesting (and neglected) one in many VoIP environments. Usually the data generated in this space (for VoIP) can not be easily processed (by $SIEM you acquired two years ago, for a six-figure € number and which still has only a handful of use cases defined…), while on the other hand being heavily useful (or even required for legal follow-up) in one of those numerous billing fraudincidents.
How to Apply those Principles in a Generic Way
As the above application to VoIP shows, these fundamental security principles allow for tackling any type of “securing assets within a complex overall setting” by going through a simple (checklist-type) set of questions derived from them. These questions could look like
Can we limit who’s taking part in some network, protocol, technology, communication act?
Any need to isolate stuff due to different protection need, (threat) exposure or trust(worthiness)?
What can be done, filtering-wise, on intersection points?
Where to apply encryption in an operationally reasonable way?
What about the security of the overall system’s main elements?
How to manage the infrastructure elements in a secure way?
How to provide visibility as for security-related stuff, with reasonable effort?
In a sequel to this post I might cover the mentioned case studies in more detail. In case I miss doing so, the slides will be available after the respective events ;-).
Have a great Sunday,
Enno
[1] As it requires the usually most scarce resource of an organization, that is humans and their brains. The part that can not be easily substituted by technology…
[1] In general preventative controls have a better cost/benefit ratio than detective or reactive ones. And this is still true in the “you’ll get owned anyway that’s why you should spend lots of resources on detective/reactive controls” marketing hype age…
[2] To provide another example from the routing protocol space: the “inter-operator trust and TCP-” based nature of BGP (as opposed to the “multicast and UDP-“based nature of other routing protocols) certainly is one of the most fundamental stability contributing properties of the current Internet.
[3] Another simple example here. If the two VoIP gateways in the incident described here had used a host route for each other instead of their default route (which wasn’t needed given their only function was to talk to each other), presumably the whole thing wouldn’t have happened.
I’m currently involved in creating an up to date approach to handling external connections (read: temporary/permanent connections with external parties like business partners) of a very large enterprise. Currently they have sth along the lines of: “there’s two types of external connections, trusted and untrusted. the untrusted ones have to be connected by means of a double staged firewall”.
Which – of course – doesn’t work at all in a VUCA world, for a number of reasons (the demarcation between trusted and untrusted is quite unclear – just think of mergers & acquisitions –; “business doesn’t like implementing 2-staged firewalls in some part of the world where they just signed the memorandum for a joint venture to build windmills in the desert”; firewalls might not be the appropriate control for quite some threats anyway – see for example slide 46 of this presentation– and so on). Not to mention that I personally think that the “double staged firewall” thing is based on an outdated threat model, in particular when implemented with two different vendors (for the simple reason that the added operational effort usually is not worth the added security benefit. see this post for some discussion of the concept of “operational feasibility”…).
Back to the initial point: the approach to be developed is meant to work on the basis of several types of remote connections which each determine associated security controls and other parameters. Which, at the first glance, does not seem overly complicated, but – as always – the devil is in the details.
What to base those categories on: the trust or security level of the other party (called “$OTHER_ORG” in the following) – or just assume they’re all untrusted? The protection needs of the data accessed by $OTHER_ORG? The (network) type of connection or number & type of users (unauthenticated vs. authenticated, many vs. few), the technical characteristics of the services involved (is an outbound Bloomberg link to be handled differently than an inbound connection to some published application, by means of a Citrix Access Gateway? if so, in what way?) etc.
As a start we put together a comprehensive list of questions as for the business partner, the characteristics of the connection and the data accessed and other stuff. These have to be answered by the (“business side”) requestor of an external connection. To give you an idea of the nature of questions here’s the first of those (~ 40 overall) questions:
Please provide details as for the company type and ownership of $OTHER_ORG.
More specifically: does $COMPANY hold shares of $OTHER_ORG?
Who currently manages the IT infrastructure of $OTHER_ORG?
Does $OTHER_ORG dispose of security relevant (e.g. ISO 27001) certifications or are they willing to provide SAS 70/ISAE 3402/SSAE 16 (“Type 2”) reports?
What is – from your perspective – $OTHER_ORG’s maturity level as for information security management, processes and overall posture?
How long will the connection be needed?
Which $COMPANY resources does $OTHER_ORG need to access?
Does a risk assessment for the mentioned ($COMPANY) resources exist?
What is the highest (data) classification level that $OTHER_ORG needs access to?
What is the highest (data) classification of data stored on systems that $OTHER_ORG accesses by some means (even if this data is not part of the planned access)?
Will data be accessed/processed that is covered by regulatory frameworks [e.g. Data Protection, PCI, SOX].
What would – from your perspective – be the impact for $COMPANY in case the data in question was disclosed to unauthorized 3rd parties?
What would – from your perspective – be the impact for $COMPANY in case the data in question was irreversibly destroyed?
What would – from your perspective – be the impact for $COMPANY in case the service(s) in question was/were rendered unavailable for a certain time?
We then defined an initial set of “types of connections” that dispose of different characteristics and might be handled with different measures (security controls being a subset of these). These connection types/categories included
“trusted business partners”/TBP (think of outsourcing partners, with strong mutual contractual controls in place etc.).
“external business partner”/EBP (this is the kind-of default, “traditional” case of an external connection).
“mergers & acquisitions [heritage]”/MA (including all those scenarios deriving from M & A, like “we legally own them but don’t really know the security posture of their IT landscape” or “somebody else now legally owns them, but they still need heavy access to our central systems, for the next 24-36 months”).
“business applications”/BusApp (think of Bloomberg access in finance or chemical databases in certain industry sectors).
“external associates”/ExtAss (“those three developers from that other organization we collaborate with on developing a new portal for some service, who need access to the project’s subversion system which happens to sit in our network”).
Next we tried to assign a category by analyzing the answers in a “point-based” manner (roughly going like: “in case we own them by 100% give a point for TBP”, “in case the connection is just outbound to a limited set of systems, give a point to BusApp”, “if it’s an inbound connection from less than 10 users, here’s a point for ExtAss” etc.), in an MS Excel sheet containing the questions together with drop-down response fields (plus comments where needed) and some calculation logic embedded in the sheet. This seemed a feasible approach, but reflecting on the actual points and assignment system, we realized that, in the end of the day, all these scenarios can be broken down to three relevant parameters which in turn determine the handling options. These parameters are
the trustworthiness of some entity (e.g. an organization, a network [segment], some users). pls note that _their trustworthiness_ is the basis for _our trust_ so both terms express sides of the same coin.
the (threat) exposure of systems and data contained in certain parts of some (own|external) network.
the protection needs of systems and data contained in certain parts of (usually the “own”/$COMPANY’s) network.
Interestingly enough every complex discussion about isolating/segmenting or – the other side of the story – connecting/consolidating (aka “virtualizing”) systems and networks can be reduced to those three fundamentals, see for example this presentation (and I might discuss, in another post, a datacenter project we’re currently involved in where this “reduction” turned out to be useful as well).
From this perspective a total of eight categories can be defined, with each of those mentioned parameters potentially being “high” or “low”. These would look like
Taking this route greatly facilitates the assignment of both individual connections to a category and sets of potential (generic) controls to the connection type categories, as each answer (to one of those questions) directly influences one of those three parameters (e.g. “we hold more than 50% of their shares” => increase trust; “$OTHER_ORG needs to access some of our systems with high privileges” => increase exposure; “data included that is subject to breach laws” => increase protection need etc.).
Which in turn allows a (potentially weighted) points based approach to identify those connections with many vs. few (trust|exposure|protection need) contributing factors.
More on this including details on the actual calculation approach and the final assignment of a category in the next part of this series which is to be published soon…
“This document was produced jointly with the OWASP mobile security project. It is also published as an ENISA deliverable in accordance with our work program 2011. It is written for developers of smartphone apps as a guide to developing secure apps. It may however also be of interest to project managers of smartphone development projects.
In writing the top 10 controls, we considered the top 10 most important risks for mobile users as described in (1) and (2). As a follow-up we are working on platform-specific guidance and code samples. We hope that these controls provide some simple rules to eliminate the most common vulnerabilities from your code.”
After having a first look at the document’s content I can, while not being a developer myself, state there’s a lot of valuable guidance in it. Which is particularly useful as our assessment experience shows that quite some things (examples to be discussed in this upcoming talk at Troopers) can go wrong as for application security on smartphones.
Currently there’s quite some discussion ongoing why it took Apple so long to fix a severe vulnerability in the update process of iTunes. A severe vulnerability which could easily be exploited by means of an automated tool called evilgrade which can be downloaded here (Hi Francisco!). Just one small note here: did you know that evilgrade was first shown and released at the 2008 edition of Troopers? We had a number of initial releases of tools in the last years (like wafw00f at the 2009 edition and VASTO at the 2010 edition) and we will continue this fine tradition in 2012. I can already promise that some nice code is going to be released for the first time at Troopers12…
The above is the exact title of a Gartner research note published some days ago. Its main thesis is that an increased convergence of carriers’ MPLS and Internet infrastructures onto shared IP infrastructures requires that enterprises re-evaluate their security and performance risks.
While I do not agree with the overall line of reasoning in the paper, it still highlights a number of interesting points when it comes to MPLS security. Which in turn reminds me of quite some stuff we’ve done in the past, mainly our Black Hat Europe 2009 talk “All your packets are belong to us – Attacking backbone technologies”. Today we’ll release an updated version of the accompanying whitepaper as a kind-of technical report. Its title is “Practical Attacks against MPLS or Carrier Ethernet Networks” and it can be found here.
Enjoy reading,
Enno
btw: for those of you who have actually read the Gartner paper… did you notice their repeated reference to customer RFIs/RFPs not covering a carrier’s separation between their public Internet and MPLS infrastructures? Here’s a document that describes how a given carrier’s trustworthiness might be evaluated and which furthermore contains an excerpt from an RFI (written back in 2006!) which, amongst others, ask for this very point…
As a follow-up to this post somebody pointed us to this interesting article on S/MIME support and associated certificate mgmt in iOS 5. Nice read which some of you may find worthwhile.
On a related note: if anyone is aware of an easy way/good (3rd party) solution for pushing certs to iOS devices (besides SCEP) we would be very interested in that one. In that case pls leave a comment or shoot us an email.
