Sabato 16 Novembre 2013 il Mobile Security Lab ha partecipato al primo DevFest Rome 2013 con un talk sul Key Management fornito dalla piattaforma Android a partire dalla versione 4.3. I temi affrontati durante l’intervento sono disponibili qui, inoltre sono disponibili tutti gli esempi mostrati durante la sessione del Codelab. Molto interessante l’intervento tenuto da Alessandro Panconesi, Professore Dipartimento di Informatica dell’Università La Sapienza, sul tema Big Data dal titolo “BIG DATA in a small world”. Un grazie a tutto il gruppo del GDG Roma.
Dopo un lungo silenzio torniamo a pubblicare i risultati del nostro lavoro, che negli ultimi anni si è concentrato soprattutto su Android.
Il prossimo 16 novembre alcuni dei ricercatori del Mobile Security Lab terranno, nell’ambito del GDG DevFest Rome 2013, un CodeLab che tratterà alcuni aspetti relativi alle problematiche di sicurezza riguardanti il “Key Management” per le applicazioni Android.
Nella prima parte dell’intervento verranno introdotte le tematiche inerenti alla conservazione sicura e protetta del materiale crittografico utilizzato da un’applicazione (per il salvataggio cifrato dei dati, autenticazione con il backend, ecc).
Si proseguirà poi con la descrizione di alcune delle tecniche e delle metodologie di Key Management disponibili nelle varie versioni di Android.
Inoltre, si mostrerà come alcuni di questi meccanismi possano essere compromessi su dispositivi “rooted” o vulnerabili e come l’introduzione del nuovo “Android Key Store”, disponibile dalla versione 4.3 del sistema operativo, fornisca una maggiore resistenza a possibili attacchi.
Il CodeLab si svolgerà alternando sessioni teoriche a sessioni pratiche di coding, durante le quali si terrà una dimostrazione reale di come la compromissione del materiale crittografico sia possibile prima dell’introduzione dell’Android Key Store ma non successivamente.
Chi è interessato può iscriversi qui; i requisiti minimi per seguire il CodeLab sono:
- Eclipse con ADT Plugin 22.3.0
- SDK Android 4.4 ( API 19)
- Android SDK Tools 22.3
- Android SDK Build Tools 19
Thanks to the DeepSec team, the presentation of mseclab team “Hijacking Mobile Data Connections 2.0: Automated and Improved”, held in November 2009 in Vienna, has been published at vimeo website.
This presentation explains some techniques, effective still today, to hijack device originated Mobile Data Connections, on any phone equipped with OMA client. Furthermore, automated technique is shown to retrieve victim’s IMSI in order to select the right APN Mobile Operator Configuration; how to perform an SSLSTRIP attack has also been demonstrated.
We’ve just come back from HITB held in Amsterdam; we really had a good time there, and we would like to thank the whole staff for all the effort they put on it .
During our presentation “Hijacking Mobile Data Connections: State of Art” we discussed some relatively simple methods to extend the scope of the attack to iPhones/iPod/iPad and Android-based devices.
Regarding Apple products we suggested, as a countermeasure, to update the iPhone to iOS 4; we didn’t give any details to back up this, basically because iOS 4 had been released just a few days before and, apart from noticing some changes in the way it handles remote reconfiguration, we didn’t have time to perform full tests and report the results. In order to avoid any possible misinterpretation, we would like to point out a few additional details on this topic.
Apple’s iOS 4 features a new constraint when installing a Configuration Profile: if the user already has a Configuration Profile, previously installed, he can download a new one, but he cannot install it because an Error box like the one below is shown.
The only way around this is to manually remove the old one (if it’s not locked) and then proceed with the installation.
On the other hand, if the user has no installed Profile, he can download and install the new one in the usual way.
This mechanism protect all users that already have an installed profile; sadly, however, it does nothing to address the vulnerability of users that don’t have any installed profile.
Additionally it must be considered that this raises another issue, having to do with how phone backups are managed. When the user backups his handset, configuration profile is stored in the backups itself, and is recovered when he later restores it; this also applies to locked profiles (PayloadRemovalDisallowed=true), that is, profiles that the user cannot modify or remove. In iPhone OS 3.x the user can work around this by installing a new profile and using it instead of the malicious one. In case of iOS 4, on the other hand, this is not possible anymore (for the reason explained above), so the user has no simple way, apart from reflashing the handset (and losing all his backup data) to restore it to a safe condition. The only solution, at this point, relies on the availability of an older backup, performed before the attack was carried out, and thus not including the malicious configuration profile.
Another point that deserves attention, as shown by the screenshots below, is related to the details of the new configuration that the handset shows to the mobile user before he accepts the it.
As opposed to the iPhone OS 3.1 behavior, iOS 4 presents to the user additional information about the Certificate used for signing the mobileconfig file, e.g. “Subject Name”, “Issuer Name”, “Signature Algorithm” (but also other useful information such as the email address which has been used when requesting the certificate itself), before the mobileconfig installation actually takes place.
By analyzing these information, the user should be able to decide if the configuration source is to be trusted or not. While this provides some useful information, it must be noted that only the first few characters of the strings are displayed.
Hence a smart attacker can forge a long enough common name and email address, to hide the suspect part of the strings.
Furthermore, the security flaws disclosed by Cryptopath blog still works, since a signature-only certificate is valid to sign a configuration profile and Safari root CAs list is used to validate the signature.
So, while iOS gives some degree of additional protection to (probably) most users, we must conclude that there is still an open vulnerability windows, that an attacker can exploit to perform the attack.
We are glad to take part, as speakers, to the first European edition of the “Hack In The Box” security conference, to be held from June 29th to July 2nd in Amsterdam – A big thank to all the HITB staff !
We are going to present our talk “Hijacking Mobile Data Connections: State of the Art”, where we’ll show how it’s possible to hijack “iPhone and Android” data connections. Further information are available at HITB web site.
See you in Amsterdam .
We’ve just come back from DeepSec, and we’re really glad to have attended the conference.
We’d like to thank Michael and the whole DeepSec staff for supporting us (and for their great tips!).
For everybody wishing to see the presentation, it is available here.
See you at next DeepSec conference ( and have a good Schnitzel )
SSL is the de-facto standard for securing communications between a user and a server against third parties. If someone is able to intercept, hijack, or have access in any other way to our network traffic, SSL provides an effective line of defense against eavesdropping.
Basically, all the devices have to do is check that the certificate protecting the connection to site “foo” carries a label (the CommonName Field) stating it belongs to site “foo”, and warn the user if it does not, something that is actually more complicated than it seems. At Black Hat USA 09, during the talk “More Tricks for Defeating SSL” given by Moxie Marlinspike, the “Null Prefix” attack was presented; the security researcher leveraged the fact that the string containing the domain name is represented using ASN.1 encoding as:
[domain_name length] domain_name
while many programs (browers, mail clients, and those used internally by CA’s) use the ‘C’ standard (null terminated-string) instead:
So he generated Certificate Requests for domain names containing a null character (\0 or \x00), for example “paypal.com\0.thoughtcrime.org”, and managed to get them signed by an official Certification Authority; several CAs verified that the request came from “thoughtcrime.org”, while the applications thought the certificate belonged to paypal.com.
The researcher discovered that the applications built with Mozilla NSS Library ( Network Security Services that support SSL/TLS standards) are vulnerable to wildcard certificates generated in the same way. From a certificate request for *\0.thoughtcrime.org, it is possible to obtain a certificate valid for every domain!
Another attack variation consists of generating a certificate for “sitekey.ba\0nkofamerica.com”: the sitekey.ba domain is used for requesting validation but the resulting certificate is valid for the domain “sitekey.bankofamerica.com” for SSL implementations that simply strip the “\0″ character.
The attack was fundamentally meant for desktop environments; we immediately wondered how it applies to mobile environments; so we’ve spent some time to test the attacks against some mobile devices. We’ve reported the results of our tests in the following table:
We’re glad to announce that we’ve been selected as speakers at DeepSec 2009 in Vienna, on November 17-20. We will present several intriguing enhancements of our “Hijacking Mobile Data Connections” attack. We are now working on the talk; its title will be “Hijacking Mobile Data Connections 2.0: Automated and Improved”, and it will include live demos of how the attack looks like from both user’s and attacker’s perspective, together with the latest findings of our research. Hereafter follows the abstract, also been published on DeepSec’s site.
So, see you in Vienna…
During the same days of our Hijacking attack presentation at BH EU ’09, we read of “a-sort-of” SMS hijacking attack performed on Windows Mobile phones. On the demonstrating video here a binary SMS is sent to a Windows mobile phone, and the browser suddenly pops up, opening an attacker specified URL. That’s the typical behaviour of an handset receiving a Service Load (SL) message, and actually this type of attack had already been discussed (here and here). We feel that this might still be a somewhat underestimated risk in the mobile environment, as Service Loading is supported by many platforms apart from Windows Mobile; but before going deeper into that, let’s explain what Service Loading messages are and what are they for.
Service Loading is a part of the WAP Push protocol suite for OTA (Over The Air) provisioning of mobile handset. It is often cited together with Service Indication: like Service Loading, Service Indication is used to carry URL addresses to the handset in a binary SMS message; but it is rather meant to notify the user of a certain URL in order to be, for instance, added to the bookmarks, and not necessarily to open it at once.
Let’s see the basic structure of a SL message:
As any other WAP protocol element, it uses an XML representation; the actual SL element have only two attributes: an URI (commonly said to be URL) and an action; the latter can be “execute-high”, meaning the content is executed in an user-obtrusive (visible) manner, “execute-low”, meaning the content is executed in a non user-obtrusive (invisible) manner, and “cache”, meaning that the content should simply be put in browser’s cache, not executed neither displayed. The default is execute-low. In order to be sent, this document must be converted to WBXML format (a compressed binary representation), then stuffed in an SMS message according to WSP protocol.
Upon receiving such a message, if the URI is an HTML page, the phone will load and show it with the default web browser; if it is an executable program, it will download and execute it, possibly in a silent way. The risk associated with this feature, especially without user’s awareness, should be obvious also for non tech savvy readers; that’s why most handsets come with some sort of security policy associated with WAP Push messages.
We have conducted a test on two largely used devices, a Nokia N95 and a Sony Ericsson C905, to check how they deal with Service Loading messages.
We hadn’t the chance to be at BH USA ’09, but we’ve seen there have been several talks about mobile security; and there seems to be a solid consensus in considering this as the new frontier of security. Mobile devices nowadays support many complex interfaces and protocols: GSM/UMTS network, IP network, Bluetooth, Smart cards…; this doesn’t only mean exposing more surface to attacks than traditional computers, but also that the mix of several small, unrelated security flaws could result in a much bigger one.
Black Hat USA 09 archives list a speech by Jesse Burns, of ISEC Partners, about Android’s security model, while Kevin Mahaffey, John Hering and Anthony Lineberry of Flexillis presented a non device-specific fuzzer for mobile platforms.
But the most impressive work was presented by Charlie Miller and Colin Mulliner; they managed to inject SMS messages past the radio section directly into phone’s processing chain. This technique has been applied to iPhone, Android and Windows Mobile; not having to rely on the network to send messages gets rid of the associated costs, and allows for a fast and thorough test (fuzzing) of SMS processing stack. The results were up to the expectations: actually, both Android and iPhone could be crashed by malformed binary messages, allowing for effective Denial of Service attack, while Windows Mobile is still under scrutiny. The vulnerability on iPhone was also found to potentially allow for remote code execution with full privileges, without any user advice nor any way to stop messages.
While Apple had to quickly release a security update, SMS is confirmed as one of the most investigated attack vectors.
However, other general issues could have a significant impact on mobile security; Moxie Marlinspike’s “More Tricks for Defeating SSL” is an effective attack against (almost any) popular web browsers, but it affects connections from mobile devices as well. As we pointed out, SSL is the last line of defense against the “Hijacking mobile data connection” attack we discovered, so knowing it can be attacked isn’t reassuring at all. We’ve began testing the attack on various mobile platforms, and we will post the result as soon as we can.