CodeMash 2.0.1.5 - Practical iOS App Attack & Defense

Practical iOS App Attack and Defense – Seth Law © 2015
Practical iOS App Attack and
Defense
CodeMash 2.0.1.5

Introduction
• Seth Law
– Director of R&D @ nVisium
– Developer/Contributor to Swift.nV, SiRATool,
RAFT, Grails.nV
– Hacker, AppSec Architect, Security Consultant
– Soccer Hooligan

Disclaimer
Hacking of App Store apps is not condoned or encouraged in any way. What you do on your own time
is your responsibility. @sethlaw & nVisium take no responsibility if you use knowledge shared in this
presentation for unsavory acts.

Agenda
• Tools
• Application Anatomy
• Data Storage
• Network Communications
• Client Side Injection
• Privacy

Requirements
• Xcode (developer.apple.com)
– Command-line tools
– Xcode-select --install
– iOS Simulators
• Jailbroken iDevice (iPhone/iPad/iPod) *
– Cydia Tools
• Vulnerable App
– Swift.nV - https://github.com/nVisium/Swift.nV
* Only required to “test” apps from the App Store. **

Tools - idb
• idb - https://github.com/dmayer/idb

Tools - iFunBox
• https://www.i-funbox.com/ifunboxmac

Tools - Cydia Apps
• Cycript
• OpenSSH
• Erica Utilities
• Class Dump
• GNU Debugger
• network-cmds
• BigBoss Recommended Tools

Tools - Swift.nV
• INTENTIONALLY VULNERABLE
• Training Tool - Not for production use

Application Anatomy
• .app Directory
–Folder with distributed binary and artifacts
–iOS 8
•AppStore Apps - /var/mobile/Containers/Bundle/
Application/<APP GUID>/Application.app/
•Pre-installed Apps - /Applications/Application.app/
–iOS 7
•AppStore Apps - /var/mobile/Applications/<APP
GUID>/Application.app/
•Pre-installed Apps - /Applications/Application.app/

Application Anatomy
• Info.plist

Application Anatomy
• Deployed Application Data Directories
• iOS 8
• /var/mobile/Containers/Data/Application/<APP_GUID>/
• iOS 7
• /var/mobile/Applications/<APP_GUID>
Documents/
Library/
Caches/
Preferences/
...
tmp/

Application Anatomy
• Library/…
• Other folders may exist for specific purposes
• Files not exposed to the user
• SyncedPreferences/ - iCloud NSUserDefaults
• Cookies/ - Persistent cookie values
• Application Support/ - Other App files
• FlurryFiles/ - iAd files
• tmp/
• Scratch space
• Can be cleared by iOS when App not running

Data Storage
• M2 in OWASP Mobile Top 10
• Anything stored by the App on purpose
• Data at rest on a mobile device
• Majority of “mobile security” issues in the
news.
• Relevant functionality
• Core Data
• NSUserDefaults
• Keychain
• Documents
• Cache

Data Storage - Defense
• Databases – Defenses
• Encryption (SQLCipher)
• Rewrites crypto into database controller
• Don’t store sensitive data on the device.
• Weaknesses
• Key Storage

Data Storage - NSUserDefaults
• Property Lists - Code

Data Storage - Attack
• Property Lists

Data Storage - Attack
• Property Lists - idb

• Property List - Countermeasures
– Don’t store sensitive data using NSUserDefaults
– When ignoring rule #1, encrypt the data
– Use checksums or signatures to validate that
data returned from NSUserDefaults is appropriate
– iOS Keychain
– For quick Keychain conversion, use a library
– https://github.com/matthewpalmer/Locksmith

• Keychain
– Mac OS X/iOS Password Manager
– OS enforces security
– CAREFUL
• Keychain can be accessed by apps running on
jailbroken devices.
• idb
– Don’t assume Keychain is secure.
– Know your Keychain Attributes.
– Layered Security
• The application will be used under the worst possible
conditions, protect for THAT instance.

• Keychain Analysis – know your attributes
Attribute Data is...
kSecAttrAccessibleWhenUnlocked Only accessible when device is unlocked.
kSecAttrAccessibleAfterFirstUnlock Accessible while locked. But if the device is restarted it must
first be unlocked for data to be accessible again.
kSecAttrAccessibleAlways Always accessible.
kSecAttrAccessibleWhenUnlockedThis
DeviceOnly
Only accessible when device is unlocked. Data is not
migrated via backups.
kSecAttrAccessibleAfterFirstUnlockThis
DeviceOnly
Accessible while locked. But if the device is restarted it must
first be unlocked for data to be accessible again. Data is not
migrated via backups.
kSecAttrAccessibleAlwaysThisDeviceO
nly
Always accessible. Data is not migrated via backups.

Network Communications
• M3 - Insufficient Transport Layer
Protection
• Are network communications
secure?
• Encryption (or not)
• Key Handling
• Ciphers
• Proxy Communication

• LIVE DEMO
• Device: Jailbroken iPod Touch
• Proxy: Burp Suite Pro
• App: CodeMash Scanner

• Issues Exploited during demo
• Proxied Communications
• Do NOT require Jailbreak
• Corporations implement proxies all the time
• Accepting a proxy’s CA cert == full access to traffic
• Certificate Pinning
• App doesn’t insure traffic isn’t being messed with.
• Can be defeated with jailbroken device
• Web Service Vulnerabilities
• Missing Function Level Access Control
• Insecure Direct Object Reference

• Defense
– Good: Use an Internal Certificate Authority and
create certificates for all environments.
– Better: Buy actual certificates for all environments
– Best: Pin the Certificate within the application to
public certificate or CA.
continueWithoutCredentialForAuthenticatio
nChallenge == BAD

Client Side Injection
• M7 - Client Side Injection
• Fuzzing all application inputs
• Text Fields
• URLSchemes
• Stored Data (DBs, PLists, etc)
• Multiple Types
• XSS/HTML
• XML/JSON
• ...

Injection
• Text Field Injection
–Manually intensive

• URLScheme Injection
• Safari FTW!
• Still manual
• location bar
• Fuzz URL values
• Info.plist

• Demo - Injection with Swift.nV

• Defense
• Input Validation
• Don’t trust the user
• Output Encoding

Privacy
• Revealing of PII
• Location Information
• Shoulder surfing
• Physical Access
• Background screenshots
• Borrowed Phone attacks
• Backups/Logs

FRIENDS DON’T LET FRIENDS
LEAVE THEIR PHONE BEHIND

Privacy - Defense
• Mask mask mask
• No NSLog in production apps
• What is stored on the device is
also stored in the backup

Other Mobile Concerns
• Authentication
• Authorization
• Binary Protections
• Cryptography
• Unintended Functionality
• Untrusted Input

Conclusion
Security is hard.
Try harder.

Thanks
• Questions?
• Contact:
• Seth Law
• Email: seth@nvisium.com
• Twitter: @sethlaw

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