iOS Application Security

PRATEEK GIANCHANDANI

1

iOS Application Penetration testing

Twitter:@prateekg147

EGOR TOLSTOY

Twitter:@igrekde

•  Intro to iOS applications •  Se6ing up an iOS pen testing environment •  Understanding the iOS filesystem •  Understanding the Objective-‐‑C runtime •  Runtime analysis and manipulation •  Insecure Data storage •  Side channel data leakage •  URL schemes •  Analyzing network traffic over HTTP/HTTPs/Cert pinning •  Jailbreak detection •  Broken cryptography •  Secure coding guidelines •  Patching iOS applications •  Automated testing

AGENDA

Intro to iOS applications

WHAT DO iOS apps look like ?

•  Developed using Apple’s SDK Xcode.

•  Distributed as .ipa files through the App store.

•  Compiled for ARM architecture.

•  Requires a provisioing profile to sign the application.

•  Encrypted with FairPlay DRM and signed with Apple’s signature.


Types of iOS applications

•  Native applications – Developed in Objective-‐‑C. Deliver much be6er performance than web applications.

•  Web applications – Developed in Html, CSS and javascript. Run using Webkit.

•  Hybrid applications – Combination of a web and native application.


iOS app specific terms •  AppDelegate

•  ViewController

•  UIView

•  Properties, instance variables

•  NSString, NSNumber, NSInteger etc

•  Categories, protocols


What is Objective-C ?

Objective-‐‑C is a general-‐‑purpose, object-‐‑oriented programming language that adds Smalltalk-‐‑style messaging to the C programming language. It is the main programming language used by Apple for the OS X and iOS operating systems, and their respective application programming interfaces (APIs), Cocoa and Cocoa Touch.

Source: Wikipedia

Intro to iOS applications Objective C continued

Instantiation

MyObject *o = [[MyObject alloc] init];

MyObject *o = [[MyObject alloc] initWithString:myString];

NSArray *myArray = [NSArray arrayWithObjects:object1,object2,object3,nil];

Calling Methods

[self doSomething];

[MainViewController performTaskWithID:[NSNumber numberWithInt:1]];


Header files have the extension .h while implementation files have the extension .m

A sample implementation file

Objective-C continued

Intro to iOS applications Simple Hello World !

•  Swift is a brand new native programming language for iOS, introduced at WWDC’14 for the first time.

•  Even when wri6en without a single line of Objective-‐‑C code, every Swift app executes inside the Objective-‐‑C runtime.

•  This may not always be the case – with the release of Swift-‐‑only system frameworks a full Swift runtime may appear.

Introduction to Swift

•  The important thing is that instead of objc_msgSend() method call, Swift classes operate with vtable (which contains the table of available methods).

•  vtables are created at compile time (when objc dispatch tables are generated dynamically).

•  This table contains functions pointers accessed by index, so it doesn’t need to bind selector to implementation.


•  Another interesting Swift feature is Name Mangling. Prepare to see something like __TFCCC4test1a1b1c1dfS2_FTS0_1xS1_1vFT1xSi_Si_OVS_1e1f when analysing Swift apps.

•  This string holds not only the exact function name, but also information about it’s type, parameters, nested classes etc. This is made for holding all the necessary method information in one string in the vtable.

•  The same thing goes for Class names.

•  You can use the function _stdlib_demangleName() for demangling.


Se6ing up an iOS pen testing environment

WHAT YOU NEED ?

•  A jailbroken iOS device (up to iOS 8.2)

•  Xcode installed on your system

•  Some tools that need to be installed on your jailbroken device

•  Jailbreak your device by downloading the pangu software from pangu.io

•  Click on “Start Jailbreak”and follow the process to jailbreak your device

•  For iOS 8.2 and iOS 8.3 you can make “Semi Jailbreak” using Safari – just visit the page h6p://pangu8.com/82.html

•  You’ll have to visit this page each time after rebooting your device

•  Big boss recommended tools from cydia •  Open SSH •  class-‐‑dump or class-‐‑dump-‐‑z (h6ps://code.google.com/p/

networkpx/wiki/class_dump_z) •  cycript (h6p://www.cycript.org/) •  clutch (h6ps://dl.dropboxusercontent.com/u/34557464/clutch) •  gdb (h6ps://dl.dropboxusercontent.com/u/34557464/gdb) •  For iOS 8, make sure you tap on Refresh the first time you

open up Cydia.

Also install the following on your device

iOS File system Ref: File system programming guide

•  Download a good file explorer utility like iExplorer or iFunbox

Understanding the iOS filesystem

•  Download a good file explorer utility like iExplorer.

Understanding the iOS filesystem

•  All the applications installed by Apple by default go inside the /Applications directory and run with the user root

•  All the applications downloaded from the app store go inside /var/mobile/applications and run with the user mobile (iOS 7)

•  Every application runs in its own environment known as the application sandbox, thereby preventing it to access resources from other applications. This is done to enforce additional security.

•  For iOS 8, the applications downloaded from App store reside in /var/mobile/Containers/Bundle/Application

•  Downloaded applications bundles reside in /var/mobile/Containers/Bundle/Application/<ID>/. Here you can find the *.app file with all the resources included.

•  Their /Documents and /Library data reside in /var/mobile/Containers/Data/Application/<ID>/. Here you can found writable application data, such as *.sqlite dbs or plist files.

•  Starting from iOS 8.0 many applications have different extensions (widgets). Their shared data can be found in /var/mobile/Containers/Shared/AppGroup/<ID>.

Here is how a typical application directory looks like The *.app folder contains the application binary.

Here is how a typical shared application directory looks like

Xcode

IDE for developing native iOS applications https://developer.apple.com/xcode/

Understanding the Objective-‐‑C runtime

•  All native iOS applications are Objective-‐‑C, which is a runtime oriented language.

•  Objective-‐‑C defers decisions from compile time and link time to the time when the code in the application is actually being executed.

•  Gives rise to a category of a6acks knows as runtime manipulation.

•  Variables and properties can be analyzed and modified at runtime.

•  Messages aren’t bound to method implementations until runtime, thereby allowing us to modify the method implementations.

•  The functions are implemented in the shared library found at /usr/lib/libobjc.A.dylib.

Usage: otool -l [binaryName]

•  Command line utility. Extremely helpful tool in iOS pentesting.

•  Extracts class information from unencrypted Mach-‐‑O binaries.

•  Helps in finding out the method names, properties, protocols being used in any class.

•  Tells a lot about the design of the application.

•  Information is presented in a readable format.

class-‐‑dump-‐‑z

Usage: class-dump-z [binaryName]

•  Application that are installed by default on iOS device won’t be encrypted, and hence class information can be dumped without any issues.

•  For applications downloaded from the App store, you must decrypt the application first using clutch.

class-‐‑dump-‐‑z

Usage: clutch [App Name]

•  Just using the clutch command will display a list of applications that can be decrypted.

•  Use “clutch [App Name]” to decrypt the application. The decrypted ipa file will be stored in the location as shown below.

{

•  Unzip the ipa file to a new folder.

•  Dump the class information from the binary inside this folder.

•  According to cycript.org -‐‑ Cycript allows developers to explore and modify running applications on either iOS or Mac OS X using a hybrid of Objective-‐‑C++ and JavaScript syntax through an interactive console that features syntax highlighting and tab completion.

•  Allows the user to hook into a running process during runtime and modify the values of instance variables, global variables, swizzle method implementations, call a particular method etc.

•  Complete documentation can be found at h6p://www.cycript.org/

Cycript

Setting up Cycript

Runtime analysis using Cycript

•  You can hook into the runtime of an application by using the command “cycript -‐‑p [PID]”

•  Some cool things that you can do with Cycript can be found here h6p://iphonedevwiki.net/index.php/Cycript_Tricks

•  For the case below, you can define a method named printMethods that takes input as a class and prints out all its methods.

•  This method has been taken from h6p://iphonedevwiki.net/index.php/Cycript_Tricks

•  For e.g, you can define your own methods.

•  You can also use the messages property of a class to print out all its messages, for e.g “AppDelegate.messages”. This will only print out the instance methods.

•  If you want to print out the class methods as well, use the isa pointer and print out its messages. The isa pointer for any object is a pointer to its class structure. For e.g “AppDelegate-‐‑>isa.messages”

•  This will print out the class methods as well.

•  Similarly, you can also print out the instance methods of any view controller, class etc. In the example below, i am printing out the instance methods for the class RuntimeManipulationVC.

Runtime manipulation using Cycript

•  With cycript, you can manipulate the values of instance variables, global variables for a particular class.

•  You can also modify method implementations.

Runtime manipulation demo

•  In this case, we are manipulating the instance variable “urlToLoad” in the view controller RuntimeManipulationDetailsVC for DamnVulnerableiOSApp (h6p://damnvulnerableiosapp.com)

•  The first step is to get a reference to the view controller.

•  Once you get the reference, you can modify any of it’s variables.

•  For e.g UIApp.keyWindow.rootViewController.topViewController.topViewController.urlToLoad = [NSString stringWithFormat:@"ʺh6p://google.com"ʺ];

•  We can also swizzle method implementations and replace the method implementation with our own.

•  Let’s assume you find a method with the name isLoginValidated in a particular view controller that returns a YES or NO depending on whether the login information is correct or not.

•  To try this demo, download Damn Vulnerable iOS app from h6p://damnvulnerableiosapp.com

Runtime manipulation demo (Method Swizzling)

•  We can modify this method’s implementation to always return TRUE.

•  As you can see, the code on the R.H.S is actually Javascript, this is the beauty about Cycript, it can related both Objective-‐‑C and javascript syntax.

Runtime manipulation demo (Method Swizzling)

•  RuntimeManipulationDetailsVC.messages['ʹisLoginValidated'ʹ] = function() {return TRUE;}

•  Plist

•  NSUserDefaults

•  CoreData (Sqlite)

•  Keychain

Insecure Local Data Storage

There are many ways of storing data locally on an iOS device. Some of these techniques are …

•  Data stored in plist files is stored unencrypted in the application sandbox.

•  An a6acker doesn’t even need to have a jailbroken device to access the contents of the plist file. It can be accessed using simple file explorer utilities like iExplorer.

•  Most often, developers make the mistake of storing confidential data in Plist files.

Plist

Plist

•  Sample code for storing data in plist files.

Plist

•  These files can be easily found using any simple file explorer utility like iExplorer in the application folder.

Plist

•  On inspecting these files, you can find the information being saved in the plist file.

Plist

•  Do not use plist files to store confidential information like username/passwords.

•  Do not store session ID’s , important properties etc in a plist file.

•  Plist files should only be used to store information that is not important, for e.g, a list of image names, the last launch date of the application etc.

NSUserDefaults

•  Used for storing properties, objects that can persist even after an application restart.

•  Information is saved unencrypted inside the application sandbox in a plist file with the name [BUNDLE_ID].plist inside the folder Library -‐‑> preferences .

•  Developers make a common mistake of storing critical data using NSUserDefaults.

NSUserDefaults

•  All the information stored using NSUserDefaults can be found inside the file [BUNDLE_ID].plist inside the folder Library -‐‑> Preferences.

NSUserDefaults

•  All the key/value pairs stored using NSUserDefaults can be found in this file.

Core Data

•  Core Data framework is used to store persistent data, manage relationships between objects etc.

•  Information is again saved unencrypted on the device in .db or .sqlite files.

•  An a6acker can gather information about Core data objects by using a sqlite client.

•  Navigate to your application directory and look for files with the extension .db or .sqlite.

•  Use an sqlite client to access these files.

Core Data

•  Navigate to your application directory and look for files with the extension .db or .sqlite.

•  Use an sqlite client to access these files.

•  You can dump information from the tables in the database using the commands as shown in the image below.

Core Data

Core Data

Sqlite browser can be used for quick analysis of sqlite databases

Core Data

•  Core data framework should not be used to store confidential information as the information is stored unencrypted on the device.

•  If you want to use some confidential informaiton, encrypt it before saving locally or use some wrappers over core data that store encrypted information on the device.

Keychain

•  It is the most secure way of storing information locally on the device.

•  Used by most of the popular application like Gmail, Facebook to store confidential information like passwords, authentication tokens etc.

•  Common database for all apps. Data is stored outside of the application sandbox.

•  Currently, information stored in the keychain can only be dumped from a jailbroken device using a tool named Keychain Dumper.

•  h6ps://github.com/ptoomey3/Keychain-‐‑Dumper

Keychain

•  One line implementation.

•  Access group allows applications to share keychain data.

KeychainItemWrapper *wrapper = [[KeychainItemWrapper alloc] initWithIdentifier:@“Identifier” accessGroup:nil];

The same access group has to be given from both the apps and both the app ID’s have to be mentioned in the plist file for both the applications.

Storing Data in Keychain

•  Using Keychain is quite simple (especially with third-‐‑party wrappers). One of them is SSKeychain (h6ps://github.com/soffes/sskeychain):

•  [SSKeychain setPassword:@”secretkey” forService:@”DVIA” account:@”Admin”];

•  NSString *pass = [SSKeychain passwordForService:@”DVIA” account:@”Admin”];

Keychain dumper demo

Keychain dumper demo

•  Keychain information dumped for the application Damn Vulnerable iOS app can be clearly found in the image below.

•  Even though keychain is one of the most secure places to store information, consider adding an extra layer of encryption before saving data in the application to make the job for the a6acker more difficult.

Realm

•  Realm is a popular third-‐‑party cross-‐‑platform built on a custom C++ core.

•  Just like in all other cases information is stored unencrypted in the /Documents folder, in the *.realm files.

•  An a6acker can gather information using the default Realm Browser: h6ps://github.com/realm/realm-‐‑cocoa/tree/master/tools/RealmBrowser

Realm

Apple Watch

•  Apple Watch is the new wearable device from Apple.

•  All the Apple Watch apps are simply extensions of native iOS applications.

Apple Watch

•  The running app extension and containing app have no direct access to each other’s containers, so they use a shared data directory for data syncing.

•  Their shared data can be found in /var/mobile/Containers/Shared/AppGroup/<ID>.

•  So, all the Insecure Data Storage vulnerabilities can be applied to Apple Watch extensions.

Side Channel Data leakage

•  There are many different ways in which data can be leaked from the application without the awareness of the developer.

•  Device Logs

•  Application snapshots

•  Pasteboard

•  Keystroke logging

•  Cookies

Device Logs

•  Some developer use logs while debugging their applications but forget to remove them while releasing the application.

•  To see the device logs while you are running an application, make sure that the device is connected to your computer.

•  In Xcode, go to Window -‐‑> Organizer -‐‑> Device -‐‑> Your Device -‐‑> Console

Device Logs

•  Device logs should only be enabled for DEBUG mode in the application, this will ensure that the logs are disabled when the application is downloaded from the App store and run on a user’s device.

Application Snapshots

•  iOS by default takes a screenshot of your application when you take the application to background by pressing the home bu6on.

•  This screenshot is shown to the user when he opens the app again while the app is loaded in the background.

•  Provides a seamless experience.

•  The problem is that the screenshot is stored without any protection in the application folder.

•  Sometimes, these screenshots can contain confidential information that might be leaked to an a6acker.

Application Snapshots

•  The following image shows the application snapshot stored in the application folder

Pasteboard

•  Data copied using the cut/copy features in iOS goes inside a buffer known inside a pasteboard item.

•  It is possible for other applications to access the content of this pasteboard.

•  If the pasteboard item contains some confidential information, it might lead to information leakage.

Pasteboard

•  Data can be copied using the Copy feature in iOS.

•  Once it is copied, it remains in the buffer.

Pasteboard

•  Using the following command in Cycript or any other app can dump out the contents of the pasteboard.

!

[UIPasteboard generalPasteboard].items[0]

Pasteboard

•  For text fields that might contain secure information, make sure the Secure property is set.

•  Clear pasteboard contents when the application enters background.

[UIPasteboard generalPasteboard].items[0]!55544555555!

•  Use pasteboard with specific identifiers, this makes it difficult for other applications to fetch data from this pasteboard item.

Keystroke logging

•  iOS by default logs every input that you enter in any text field unless the secure flag is not set.

•  This helps in autocorrecting the user later.

•  All the keystroke logs can be easily fetched out from a device.

•  These logs might contain information that is important.

•  Logs remain stored on the device for a long time hence making it even more insecure.

•  Logs are stored in a file with the extension .dat in the location “/var/mobile/Library/Keyboard/“

[UIPasteboard generalPasteboard].items[0]!55544555555 !

Keystroke logging

•  The prefix of the file denotes the language in which the keystroke logs are stored.

•  Here is how a part of the logs file look like.

Cookies

•  Some applications create persistance cookies and store them in cookies.binarycookies file in application’s home directory.

•  The sample code for storing cookies:

•  [[NSHTTPCookieStorage sharedHTTPCookieStorage] setCookie:cookie];

•  The path to cookies is: /Library/Cookies/Cookies.binarycookies


Cookies

•  Revealing cookies is quite easy:

•  Download the python script BinaryCookieReader.py from h6p://securitylearn.net/wp-‐‑content/uploads/tools/iOS/BinaryCookieReader.py

•  Download the Cookies.binarycookies file from your device.

•  Run binarycookiereader.py /file-‐‑path-‐‑to-‐‑cookies

Cookies

•  This is the example from Aeroflot mobile application:

URL Schemes

•  Used for IPC between applications.

•  Every application can register for a particular URL scheme.

•  Any url starting with that particular URL scheme invokes the application that is registered to handle that url.

•  For e.g, the facebook iOS application registers for the URL scheme “}”

•  Url’s starting with }:// will invoke the facebook iOS application.

•  The Facebook iOS application will decide what to do with that particular url depending on its parameters.

•  For e.g }://chat_text?name=Prateek&message=Hello


URL Schemes

•  Any application can call a url starting with a particular url scheme and invoke the registered application.

•  A6acker can also embed the url inside an iframe in a malicious page, when the user visits the page, the url will execute and the registered application will be called.

•  These URL schemes can be used to execute important operations, for e.g FaceTime iOS app allows other apps to call user via URL scheme.

•  The problem happens when the operation is executed without any validation from the user.


•  A simple solution for this is to validate the action before performing it.

•  For critical apps, you can also set a list of whitelisted applications and only allow them to invoke an action. This can be checked by the sourceApplication property in the calling method.

•  Skype URL scheme vulnerability h6p://software-‐‑security.sans.org/blog/2010/11/08/insecure-‐‑handling-‐‑url-‐‑schemes-‐‑apples-‐‑ios/

URL Schemes

•  How to find out the URL scheme used by a particular application ?

•  This info can be found from the Info.plist file.

URL Schemes

•  Look for the property CFBundleURLSchemes inside CFBundleURLTypes -‐‑> Item 0

•  As we can see, the Facebook iOS app registers for quite a lot of URL schemes.

URL Schemes

•  Another important thing could be to find out the URL structure an application is expecting in order to perform a certain action.

•  This can be found by reverse engineering the application using tools like Hopper (hopperapp.com) and looking for strings that start with that particular URL scheme or looking at the disassembly of this method in the AppDelegate class.

•  Related article: h6p://highaltitudehacks.com/2014/03/07/ios-‐‑application-‐‑security-‐‑part-‐‑30-‐‑a6acking-‐‑url-‐‑schemes

URL Schemes

•  It is important to analyze the network traffic that flows between the client/server in an application.

•  Look for credentials, authentication tokens, API keys being transmi6ed over unsecured h6p channel.

•  Check for the entropy in Session ID’s.

•  Traffic can be analyzed using a simple proxy tool like Burp proxy.

•  Try to manipulate the request/response using Burp and see how the client side application responds to it.

Analyzing network traffic over HTTP/HTTPs

Analyzing traffic over HTTP

•  Configure Burp Proxy to start listening for traffic. Make sure it is listening on all interfaces.


•  Configure your iOS device to use your computer as a proxy.


•  You can now intercept the traffic as it goes to the server.

Analyzing traffic over HTTPs

•  This will require you to install Burp’s CA certificate as a trusted root on your device.

•  Configure your browser to relay traffic over Burp proxy.


You will get a warning, click on Add Exception.


•  Click on View.


•  Go to Details, select the topmost certificate, click on Export and save the file with extension as .crt


•  Send this file to your device via email, click on it and Install it. Accept all the instructions and click on Done.


•  Quit and restart the application you want to sniff traffic for. You will now be able to see the traffic even if it is over HTTPs

Certificate pinning

•  The server’s certificate is hardcoded in the application bundle and checked while exchanging data with the server.

•  Provides protection against MITM a6acks.

•  Used by applications like Twi6er, Square etc.

Certificate pinning

•  The server’s certificate is hardcoded in the application bundle and checked while exchanging data with the server.

•  Provides protection against MITM a6acks.

•  Used by applications like Twi6er, Square etc.

Certificate pinning bypass

•  Certificate pinning can be bypassed by hooking into some low level methods during runtime.

•  iOS SSL kill switch was released in Blackhat to demonstrate this.

•  h6ps://github.com/iSECPartners/ios-‐‑ssl-‐‑kill-‐‑switch

Certificate pinning bypass

•  Once it is enabled, user can see the traffic through applications like Twi6er as well.

•  Most of modern applications use some third-‐‑party services for analytics, data storage, push-‐‑notifications, crash-‐‑reporting, social-‐‑auth and so on.

•  Besides different vulnerabilities in SDKs, this opens a couple of new a6ack vectors for penetration tester:

•  The unsecure storage of API keys,

•  The lack of security on the server-‐‑side.

Attacking Third-Party Services

•  Parse.com is a MBaaS which helps with se6ing up backend infrastructure for mobile applications. Some of its capabilities:

•  Cloud data storage

•  Push notifications

•  Cloud code hosting

•  Gathering usage statistics

Attacking Parse.com

•  All the data in Cloud Core is stored in Parse Classes (ordinary database tables).

Attacking Parse.com

•  There are different levels of access-‐‑permissions: class level and object level. We’re going to investigate CLA.

•  All of Class Level Access permissions are set to Public by default.

Attacking Parse.com

•  Using Hopper we can extract the API keys and Parse Classes names from target application:

Attacking Parse.com

•  Now you can query the Parse API using these keys:

•  [Parse setApplicationId:<APP_ID> clientKey:<CLIENT_KEY>]

•  PFQuery *query = [PFQuery queryWithClassName:@”Target”];

•  NSArray *data = [query findObjects];

•  You can perform all the CRUD operations on class with Public access permissions.

Attacking Parse.com

•  To simplify these tasks, you can use the Parse Revealer utility: h6ps://github.com/igrekde/ParseRevealer

•  It automates the analysis of access permissions and structure of provided classes.

Attacking Parse.com

•  Flurry.com is the most popular mobile analytics service.

•  It uses the single API key to identify the application. This key can be retrieved using Hopper app.

•  With this key an a6acker can build his own application, generating a large number of random events and pollute the target app’s statistics monitoring. It can lead to impossibility of statistics analysis, which is very crucial for popular applications.

Attacking Flurry.com

•  Starting session:

[Flurry startSession:@”API_KEY”];

•  Logging events:

[Flurry logEvent:@”EVENT_NAME” withParameters:params];

•  Logging page views:

[Flurry logPageView];

Attacking Flurry.com

•  For critical applications like banking applications etc, it is important that you ensure that the application doesn’t work on a jailbroken device.

•  With a copy of your app’s binary and tools like Cycript at his disposal, an a6acker is in complete control.

•  It is therefore important to check for a jailbroken device and disable certain features of the application or quit the application in order to protect it.

Jailbreak Detection

•  There are many ways to check for a jailbroken device.

•  Checking for specific files that exist on a jailbroken device is one of the most common techniques being used.

•  Another way is to check if the application is able to modify a file outside it’s own sandbox.

•  Most than 80% of the jailbroken devices have Cydia installed, so check if you can open a url that starts with Cydia’s URL scheme, i.e cydia://

•  It is important to note that no that there is no foolproof technique to detect a jailbroken device, however a combination of checks can make the job difficult for even a skilled hacker.

Jailbreak Detection

•  There are many ways to check for a jailbroken device.

•  Checking for specific files that exist on a jailbroken device is one of the most common techniques being used.

•  Another way is to check if the application is able to modify a file outside it’s own sandbox.

•  Most than 80% of the jailbroken devices have Cydia installed, so check if you can open a url that starts with Cydia’s URL scheme, i.e cydia://

•  It is important to note that no that there is no foolproof technique to detect a jailbroken device, however a combination of checks can make the job difficult for even a skilled hacker.

Jailbreak Detection

+(BOOL)isJailbroken{ #if !(TARGET_IPHONE_SIMULATOR) if ([[NSFileManager defaultManager] fileExistsAtPath:@"ʺ/Applications/Cydia.app"ʺ]){ return YES; }else if([[NSFileManager defaultManager] fileExistsAtPath:@"ʺ/Library/MobileSubstrate/MobileSubstrate.dylib"ʺ]){ return YES; }else if([[NSFileManager defaultManager] fileExistsAtPath:@"ʺ/bin/bash"ʺ]){ return YES; }else if([[NSFileManager defaultManager] fileExistsAtPath:@"ʺ/usr/sbin/sshd"ʺ]){ return YES; }else if([[NSFileManager defaultManager] fileExistsAtPath:@"ʺ/etc/apt"ʺ]){ return YES; } NSError *error; NSString *stringToBeWri6en = @"ʺThis is a test."ʺ; [stringToBeWri6en writeToFile:@"ʺ/private/jailbreak.txt"ʺ atomically:YES encoding:NSUTF8StringEncoding error:&error]; if(error==nil){ //Device is jailbroken return YES; } else { [[NSFileManager defaultManager] removeItemAtPath:@"ʺ/private/jailbreak.txt"ʺ error:nil]; } if([[UIApplication sharedApplication] canOpenURL:[NSURL URLWithString:@"ʺcydia://package/com.example.package"ʺ]]){ //Device is jailbroken return YES; } #endif //All checks have failed. Most probably, the device is not jailbroken return NO; }

Jailbreak Detection

Combining all these techniques, we get this method.

Jailbreak Detection

•  The problem is that the signature of this method gives everything away.

•  A6acker can use Cycript to use bypass the check for jailbreak detection.

Jailbreak Detection

•  It is be6er to rename the method to something that doesn’t look important.

•  Something like +(BOOL)isDefaultColour

•  Yeah i know, we do ignore the coding guidelines, but in this case, the guidelines are something that gives everything away.

•  After analyzing the class-‐‑dump output of the application, the hacker is most likely to ignore this method.

•  He can always reverse engineer this method to see what’s going on inside, so this method is also not foolproof.

Broken Cryptography

•  Occurs when data stored on the device is not encrypted properly.

•  One of the most common vulnerabilities found in iOS applications.

•  Can occur by use of deprecated or weak algorithms.

•  Sometimes the key while encryption is hardcoded in the app thereby making it much easier for the a6acker to break the application.

•  Related article: h6p://www.andreas-‐‑kur�.de/2013/07/how-‐‑to-‐‑easily-‐‑spot-‐‑broken-‐‑cryptography.html

Secure coding guidelines

•  Do not store confidential data using NSUserDefaults, plist files or Core Data framework. Use keychain to store data like passwords, authentication tokens, API-‐‑keys etc.

•  Use proper encryption while storing data locally in any insecure place. Do not use hardcoded keys etc.

•  Validate incoming URLs using URL schemes and properly authorize the user before taking any action.

•  Add checks to detect jailbroken device for critical applications like banking applications etc.

•  Text fields that might contain important information should be marked Secure. This will prevent leaking of data via pasteboard, application snapshots etc.

•  Use libraries like SQLCipher to encrypt sqlite databases.

•  Clear pasteboard data when the application enters into background.

•  Add checks to prevent debuggers from hooking into your application. Add the highlighted lines of code in your application.

Secure coding guidelines

Patching iOS applications

•  Patching an application changes its login permanently.

•  This is be6er that making a change in cycript where you have to repeat the same process over and over again.

•  Often used to disable checks like Jailbreak detection, piracy check etc.

•  Tools used for patching iOS application: IDA Pro, Hexfiend and Hopper.

•  Once an application has been patched, it needs to be resigned using ldid before it can be deployed on the device.


•  Hopper is one of the best tools available for patching iOS applications.

•  Not free, but the value for money is very good.

•  Patching iOS applications with Hopper: h6p://highaltitudehacks.com/2014/01/17/ios-‐‑application-‐‑security-‐‑part-‐‑28-‐‑patching-‐‑ios-‐‑application-‐‑with-‐‑hopper/

•  Patching iOS applications with IDA Pro and Hex fiend:h6p://highaltitudehacks.com/2013/12/17/ios-‐‑application-‐‑security-‐‑part-‐‑26-‐‑patching-‐‑ios-‐‑applications-‐‑using-‐‑ida-‐‑pro-‐‑and-‐‑hex-‐‑fiend


•  To modify any instruction in Hopper, click on it and click on Modify -‐‑> Assemble Instruction.


•  Make the change and click on Assemble and Go Next


•  Once the change has been made, click on File -‐‑> Produce new executable and overwrite the existing one.


•  To deploy the application back to your device, resign the application binary first using ldid as shown in the image below.

Then copy the .app file to the /Applications directory on the device using Scp. You can also use sftp or the utility iExplorer to upload this application.


Now login as the mobile user, use the command su to get root privileges and give the binary executable permissions. Then use the exit command to go back as the mobile user, and use the command uicache to install the application. If this doesn’t work, you can reboot the device or try this method again.

You will see that the application has been successfully installed on your device.

Extracting Device Backups

•  It’s possible to extract the data from iOS device for further researches.

•  The first way is using libimobiledevice – a library to communicate with different services of iOS devices using native protocols.

•  You can download it from GitHub: h6ps://github.com/libimobiledevice/libimobiledevice


•  Run idevice_id –l for the list of connected devices

•  Run idevicebackup2 backup -‐‑-‐‑full -‐‑-‐‑source <UDID>~/Documents to make the full backup of the specified device.


•  Download iBackupBot: h6p://www.icopybot.com/itunes-‐‑backup-‐‑manager.htm

•  Drag the backup folder to iBackupBot and enjoy browsing.


•  The developer can mark files and directories to exclude them from backups.

•  The backup can be protected by the passcode.

Extracting iCloud Device Backups

•  The other way of extracting backups is from iCloud.

•  You need to know the AppleID and password, linked with the target device.

•  Use iLoot: h6ps://github.com/hackappcom/iloot

•  > python iloot.py [email protected] password

Automated testing

•  Automating tests while doing an iOS penetration test can help you save a lot of time.

•  Though not all tests can be automated, there are some tools that do a very good job at this.

•  Snoop-‐‑it -‐‑ h6ps://code.google.com/p/snoop-‐‑it/

•  iNalyzer -‐‑ h6ps://appsec-‐‑labs.com/iNalyzer

•  iRET -‐‑ h6ps://blog.veracode.com/2014/03/introducing-‐‑the-‐‑ios-‐‑reverse-‐‑engineering-‐‑toolkit/

•  idb -‐‑ h6p://www.idbtool.com/

•  iSpy -‐‑ h6ps://github.com/BishopFox/iSpy

Snoop-it

•  Source: h6ps://code.google.com/p/snoop-‐‑it/

•  For iOS 7, it currently supports only 32 bit devices.

•  Related article: h6p://highaltitudehacks.com/2013/08/20/ios-‐‑application-‐‑security-‐‑part-‐‑9-‐‑analyzing-‐‑security-‐‑of-‐‑ios-‐‑applications-‐‑using-‐‑snoop-‐‑it/

Snoop-it

•  Here is how the interface looks like.

iNalyzer

•  Related article: h6p://highaltitudehacks.com/2013/09/17/ios-‐‑application-‐‑security-‐‑part-‐‑15-‐‑static-‐‑analysis-‐‑of-‐‑ios-‐‑applications-‐‑using-‐‑inalyzer/

iRET

Source: h6ps://blog.veracode.com/2014/03/introducing-‐‑the-‐‑ios-‐‑reverse-‐‑engineering-‐‑toolkit/

•  Related article: h6ps://blog.veracode.com/2014/03/introducing-‐‑the-‐‑ios-‐‑reverse-‐‑engineering-‐‑toolkit/

idb

•  Related article: h6p://highaltitudehacks.com/2014/10/18/ios-‐‑application-‐‑security-‐‑part-‐‑35-‐‑auditing-‐‑ios-‐‑applications-‐‑with-‐‑idb/

iSpy

•  Related article: h6ps://github.com/BishopFox/iSpy/wiki/Setup-‐‑iSpy-‐‑from-‐‑Source

Further practice

Try out all the challenges in Damn Vulnerable iOS App (h6p://damnvulnerableiosapp.com)

THANK-‐‑YOU

Technology

iOS Application Security