This document discusses security best practices for mobile development. It covers fundamental security principles like vulnerability, threat and mitigation. It details security measures in iOS like application sandboxing, permissions and encryption. It also discusses Android security concepts like application components and permissions. The document recommends practices like static analysis, encryption, jailbreak detection and the use of the Salesforce mobile SDK to help secure mobile apps and data.
Security Best Practices for Mobile Development @ Dreamforce 2013
1. Security Best Practices for Mobile
Development
Tom Gersic, Salesforce.com
Director, Mobile Services Delivery
@tomgersic
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4. Agenda
• Fundamental Principles
• What iOS and Android Share
• iOS Specific Characteristics
• Android Specific Characteristics
• Salesforce Mobile Offerings
19. Libtiff Image Exploit / Jailbreak
• iPhone 1 – patched in 1.1.2
• Tiff buffer overflow
• Nothing to prevent executing code on the heap
• Gained root access from viewing an image on the web
25. Concatenated SMS Exploit
• Takes 519 SMS messages – all but 1 is invisible
• Send message -1 of X to underflow the array buffer
• Can’t be stopped by the user
• Used to write an entire binary executable to the heap, and run
it, taking over the phone.
28. Data Security – Hardware Encryption
Requires PIN/Passcode on both iOS and Android
On iOS, apps opt-in
Supported on
iPhone 3GS w/ iOS v4+ (AES 256 bit)
Android Honeycomb+ (AES 128 bit)
• Some manufacturers increase to AES 256 bit (Samsung SAFE)
SD Card encryption on Android is manufacturer specific.
33. iOS Sandbox
• All apps (Apple’s and App Store) run as “mobile” user.
• Sandboxing is bolted on -- handled via XNU Sandbox
“Seatbelt” kernel extension.
• Applications run in separate subdirectories of
/private/var/mobile/Applications
• Any app in this directory is loaded with “container”
(sandboxed) profile.
34. Android Sandbox
• Uses underlying Linux security model
• Every app runs as a separate user
• Apps signed by the same developer can run as the same user, if
desired (not the default, though)
• Every app runs in its own instance of the Android Runtime (Dalvik
Virtual Machine)
• Like iOS, every app has its own directory structure
• SD Card, though, is generally public – accessible to all apps and
unencrypted unless manufacturer has added encryption (Samsung
SAFE)
51. Enable ASLR in your app
• ASLR: Address Space Layout Randomization
52. Stack Canaries
• AKA Stack Smashing Protection
• Protect against buffer overflows
• Places random known value (canary) before local variables
• Use Apple LLVM – won’t work with LLVM GCC
No system is perfectly secure
Security is all about managing risk
Something that allows an attack to take place.
To use credit cards, we frequently have to let them out of our sight
Someone we give our credit card to could skim it
Reduces the severity of one (or more) of the three
Laws and credit card company policies limit our liability to $50 (by law) or frequently $0 (by policy)
The vulnerability and threat still exist, but the consequence is nullified (for the consumer, anyway)
Separation of Concerns: Apps, modules, etc. are separated – each module has a specific function
Principle of Least Privilege – Each of these modules has only the permissions necessary to do its legitimate function
CIA applies to:
Application Security – Up to the developer
Operating System Security – Sandboxing, permissions
Device Security – PIN, Hardware Encryption
Infrastructure Security – Codesigning, app store reviews, etc.
Would not be possible today because of DEP
ASLR: Address Space Layout Randomization
DEP: Data Execution Protection
Ref: http://books.google.com/books?id=1kDcjKcz9GwC&pg=PT10&lpg=PT10&dq=libtiff+iphone+dep&source=bl&ots=9KcFvBCd0n&sig=qjQdCSJWyWOnzsKmeVuw1psrCmU&hl=en&sa=X&ei=Yn8TUOiHLaeviQfvkICoBw&ved=0CFwQ6AEwAQ#v=onepage&q=libtiff%20iphone%20dep&f=false
Ref: http://365.rsaconference.com/servlet/JiveServlet/previewBody/3488-102-1-4589/MBS-402.pdf
Ref: http://en.wikipedia.org/wiki/Data_Execution_Prevention
Ref: http://en.wikipedia.org/wiki/Address_space_layout_randomization
iOS 4.3+, Android ICS (broken), Jelly Bean (fixed)
ASLR: Address Space Layout Randomization
DEP: Data Execution Protection
META-INF checksums – keep would-be hackers from modifying files in the APK after it’s been signed
Files of the same name
Checks first, installs last
http://nakedsecurity.sophos.com/2013/07/10/anatomy-of-a-security-hole-googles-android-master-key-debacle-explained/
http://bluebox.com/corporate-blog/bluebox-uncovers-android-master-key/
http://nakedsecurity.sophos.com/2013/08/09/android-master-key-vulnerability-more-malware-found-exploiting-code-verification-bypass/
2009
SMS is an excellent attack vector – no way to turn it off, no way to firewall it. It’s used to make the phone ring in addition to text messages, so it’s a wide open port on all phones
Attack exploited the fact that the start of a concatenated SMS message tells the phone how many individual 140 byte messages to expect – no messages are displayed until all are received
Ref: http://www.docstoc.com/docs/52434984/iPhone-SMS-Fuzzing-and-Exploitation
Ref: http://www.youtube.com/watch?gl=US&hl=en&client=mv-google&v=hUr4ilw0AeI&nomobile=1
Ref: https://community.rapid7.com/community/metasploit/blog/2007/10/11/cracking-the-iphone-part-1
Ref: https://community.rapid7.com/community/metasploit/blog/2007/10/14/cracking-the-iphone-part-2
Ref: https://community.rapid7.com/community/metasploit/blog/2007/10/16/cracking-the-iphone-part-21
Ref: https://community.rapid7.com/community/metasploit/blog/2007/10/21/cracking-the-iphone-part-3
Another Charlie Miller exploit – presented at Black Hat, July 25 2012
NFC tag can launch any URL in the browser – makes use of known WebKit exploit to take over the phone.
Doesn’t require user to give permission to launch the URL
Biggest threat is someone placing a rogue NFC tag on/near a legitimate NFC reader
http://www.forbes.com/sites/andygreenberg/2012/07/25/darpa-funded-researcher-can-take-over-android-and-nokia-phones-by-merely-waving-another-device-near-them/
But my phone’s encrypted!
128 bit / 256 bit really only makes a difference if password is greater than 16 characters (16*8=128)
With a PIN/Passcode, Email, Attachments, and some other system files are encrypted while device is locked
Any other app is storing the keys with the lock unless app specifies NSFileProtectionComplete
Sources:
http://source.android.com/tech/encryption/android_crypto_implementation.html
http://www.wilderssecurity.com/showthread.php?t=320996
http://www.ubergizmo.com/2012/06/samsungs-safe-initiative-will-make-the-galaxy-s3-enterprise-friendly/
on official App Store / Marketplace, all apps are digitally signed by the developer – ties malware back to an individual or company
-- With iOS, Apple is the Certificate Authority. With Android, self-signed certificates are acceptable.
applications are limited in what they can access with regards to other applications or system resources
limits damage that can be done by exploiting any one app
What’s new in iOS 7: https://developer.apple.com/library/ios/releasenotes/General/WhatsNewIniOS/Articles/iOS7.html
App States and Multitasking: https://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/ManagingYourApplicationsFlow/ManagingYourApplicationsFlow.html#//apple_ref/doc/uid/TP40007072-CH4
One of the biggest security concerns people have with Android is that they know apps can run in the background, and they can interact with other apps
Activities
Service
Content Provider
Broadcast Receiver
Intent
“Except passwords”?
Android apps need to specify which system resources they need access to
Users accept these when they install the app
Some things you can do, but none are 100% reliable.